NAME:
ADSTRING
PURPOSE:
Return RA and Dec as character string in sexigesimal format.
RA and Dec may be entered as either a 2 element vector or as
2 scalars. One can also specify the precision of the declination
in digits after the decimal point.
CALLING SEQUENCE
result = ADSTRING( ra_dec )
or
result = ADSTRING( ra,dec,[ precision ] )
INPUTS:
RA_DEC - 2 element vector giving the right ascension and declination
in decimal degrees.
or
RA - Right ascension in decimal degrees, numeric scalar
DEC - Declination in decimal degrees, numeric scalar
OPTIONAL INPUT:
PRECISION - The number of digits after the decimal of DEClination.
The RA is automatically 1 digit more. This parameter may
either be the third parameter after RA,DEC or the second
parameter after [RA,DEC]. It is not available for just DEC.
If no PRECISION parameter is passed, a precision of 1 for
both RA and DEC is returned to maintain compatibility with
past ADSTRING functions. A precision of 0 will result in
the below format, always claimed, but but never delivered by
ADSTRING.
OUTPUT:
RESULT - Character string containing HR,MIN,SEC,DEC,MIN,SEC formatted
as ( 2I3,F5.(p+1),2I3,F4.p ) where p is the PRECISION
parameter. If only a single scalar is supplied it is
converted to a sexigesimal string (2I3,F5.1).
EXAMPLE:
(1) Display CRVAL coordinates in a FITS header, H
IDL> crval = sxpar(h,'CRVAL*') ;Extract 2 element CRVAL vector (degs)
IDL> print, adstring(crval) ;Print CRVAL vector sexigesimal format
(2) print,adstring(30.42,-1.23,1) ==> ' 02 01 40.80 -01 13 48.0'
print,adstring(30.42,+0.23) ==> ' 02 01 40.8 +00 13 48.0'
print,adstring(+0.23) ==> '+00 13 48.0'
PROCEDURES CALLED:
RADEC, SIXTY, NINT
REVISION HISTORY:
Written W. Landsman June 1988
Addition of variable precision and DEC seconds precision fix.
ver. Aug. 1990 [E. Deutsch]
Output formatting spiffed up October 1991 [W. Landsman]
Remove ZPARCHECK call, accept 1 element vector April 1992 [W. Landsman]
(See /usr/local/idl/lib/zastron/astro/adstring.pro)
NAME: AIRTOVAC PURPOSE: Convert air wavelengths to vacuum wavelengths, i.e. correct for the index of refraction of air under standard conditions. Wavelength values below 2000 A will not be altered. Uses the IAU standard for conversion given in Morton (1991 Ap.J. Suppl. 77, 119) CALLING SEQUENCE: AIRTOVAC, WAVE INPUT/OUTPUT: WAVE - Wavelength in Angstroms, scalar or vector WAVE should be input as air wavelength(s), it will be returned as vacuum wavelength(s). WAVE is always converted to double precision upon return. EXAMPLE: If the air wavelength is W = 6056.125 (a Krypton line), then AIRTOVAC, W yields an vacuum wavelength of W = 6057.8019 METHOD: See Morton (Ap. J. Suppl. 77, 119) for the formula used REVISION HISTORY Written W. Landsman November 1991
(See /usr/local/idl/lib/zastron/astro/airtovac.pro)
NAME: AITOFF PURPOSE: Convert right ascension, declination to X,Y using an AITOFF equal-area projection. Often used to create an all-sky map in galactic coordinates. Output map coordinates are zero longitude centered. CALLING SEQUENCE: AITOFF, L, B, X, Y INPUTS: L - longitude - scalar or vector, in degrees B - latitude - same number of elements as L, in degrees OUTPUTS: X - X coordinate, same number of elements as L. X is normalized to be between -180 and 180 Y - Y coordinate, same number of elements as L. Y is normalized to be between -90 and 90. NOTES: See AIPS memo No. 46, page 4, for details of the algorithm. This version of AITOFF assumes the projection is centered at b=0 degrees. REVISION HISTORY: Written W.B. Landsman STX December 1989 Modified for Unix: J. Bloch LANL SST-9 5/16/91 1.1
(See /usr/local/idl/lib/zastron/astro/aitoff.pro)
NAME:
AITOFF_GRID
PURPOSE:
Produce an overlay of latitude and longitude lines over a plot or image
on the current graphics device. AITOFF_GRID assumes that the ouput plot
coordinates span the x-range of -180 to 180 and the y-range goes from
-90 to 90.
CALLING SEQUENCE:
AITOFF_GRID[,DLONG,DLAT,[LINESTYLE=N,/LABELS]
INPUTS:
DLONG = Optional input longitude line spacing in degrees. If left
out, defaults to 30.
DLAT = Optional input lattitude line spacing in degrees. If left
out, defaults to 30.
KEYWORDS:
LINESTYLE = Optional input integer specifying the linestyle to
use for drawing the grid lines.
LABELS = Optional keyword specifying that the lattitude and
longitude lines on the prime meridian and the
equator should be labeled in degrees. If LABELS is
given a value of 2, i.e. LABELS=2, then the longitude
labels will be in hours and minutes instead of
degrees.
OUTPUTS:
Draws grid lines on current graphics device.
CATAGORY:
SST-9 Graphics routine.
AUTHOR AND MODIFICATIONS:
J. Bloch 1.2 6/2/91
(See /usr/local/idl/lib/zastron/astro/aitoff_grid.pro)
NAME:
ARROWS
PURPOSE:
To display "weathervane" directional arrows on an astronomical image
showing orientation of North and East.
CALLING SEQUENCE:
arrows,h, [ xcen,ycen, THICK = , CHARSIZE = , ARROWLEN = , COLOR = ,
/NOTVERTEX ]
INPUTS:
h - FITS or STSDAS header array, must include astrometry
OPTIONAL INPUTS:
xcen,ycen - numeric scalars, specifying the center position of
arrows. Position in device units unless the /NORMALIZED
keyword is specified. If not supplied, then ARROWS
will prompt for xcen and ycen
OPTINAL KEYWORD INPUTS:
thick - line thickness, default = 1.0, floating point scalar
charsize - character size, default = 2.0, floating point scalar
arrowlen - length of arrows in terms of normal Y size of vector-drawn
character, default = 3.5, floating point scalar
color - color that the arrows and NE letters should be. Default
value is !P.COLOR
NotVertex - Normally (historically) the specified xcen,ycen indicated
the position of the vertex of the figure. If this
keyword is set, the xcen,ycen coordinates refer to a sort
of 'center of mass' of the figure. This allows the
figure to always appear with the area irregardless of
the rotation angle.
Normal - if this keyword is set and nonzero, the input center
(xcen,ycen) is taken to be in normalized coordinates. The
default is device coordinates.
OUTPUTS:
none
EXAMPLE:
Draw a weathervane at (400,100) on the currently active window,
showing the orientation of the image associated with a FITS header, hdr
IDL> arrows, hdr, 400, 100
METHOD:
Uses EXTAST to EXTract ASTrometry from the FITS header. The
directions of North and East are computed and the procedure
ONE_ARROW called to create the "weathervane".
REVISON HISTORY:
written by B. Boothman 2/5/86
Recoded with new procedures ONE_ARROW, ONE_RAY. R.S.Hill,HSTX,5/20/92
Added separate determination for N and E arrow to properly display
arrows irregardless of handedness or other peculiarities and added
/NotVertex keyword to improve positioning of figure. E.Deutsch 1/10/93
Added /DATA and /NORMAL keywords W. Landsman July 1993
(See /usr/local/idl/lib/zastron/astro/arrows.pro)
NAME:
ASTRO
PURPOSE:
Interactive astronomical utitlity for precession and coordinate
conversion.
CALLING SEQUENCE:
ASTRO, [ selection, EQUINOX = ]
OPTIONAL INPUT:
SELECTION - Scalar Integer (0-6) giving the the particular astronomical
utility to be used. (0) Precession, (1) RA, Dec to Galactic
coordinates, (2) Galactic to RA,Dec (3) RA,Dec to Ecliptic,
(4) Ecliptic to RA, Dec, (5) Ecliptic to Galactic, (6) Galactic
to Ecliptic. Program will prompt for SELECTION if this
parameter is omitted.
OPTIONAL KEYWORD INPUT:
EQUINOX - numeric scalar specifying the equinox to use when converting
between celestial and other coordinates. If not supplied,
then the RA and Dec will be assumed to be in EQUINOX 1950.
This keyword is ignored by the precession utility. For
example, to convert from RA and DEC (2000) to galactic
coordinates:
IDL> astro, 1, E=2000
METHOD:
ASTRO uses PRECESS to compute precession, and EULER to compute
coordinate conversions. The procedure GET_COORDS is used to
read the coordinates, and ADSTRING to format the RA,Dec output.
NOTES:
ASTRO temporarily sets !QUIET to suppress compilation messages and
keep a pretty screen display.
PROCEDURES USED:
Procedures: GET_COORDS, EULER Function: ADSTRING
REVISION HISTORY
Written, W. Landsman November 1987
Code cleaned up W. Landsman October 1991
Added Equinox keyword, call to GET_COORDS, W. Landsman April, 1992
(See /usr/local/idl/lib/zastron/astro/astro.pro)
NAME: A_b PURPOSE: Compute interstellar extinction in the B bandpass as a function of galactic position using the 21 parameter function given by deVaucoulers in the 2nd Reference Catalog of Galaxies (RC2). Note that this formula is no longer used in the RC3 and that reddenings are instead obtained from the Burstein-Heiles maps. CALLING SEQUENCE: result = A_b( l2, b2) INPUT PARAMETERS l2 = galactic longitude (degrees), scalar or vector b2 = galactic latitude (degrees), scalar or vector OUTPUT PARAMETERS RESULT - Interstellar extinction Ab in magnitudes, scalar NOTES: The controversial aspect of the deVaucoulers reddening curve is that it predicts an extinction of about 0.2 at the poles The parameters used here differ from the ones printed in the RC2 but are the ones actually used for entries in the catalog (see Rowan-Robinson 1985) REVISION HISTORY Written by R. Cornett and W. Landsman, STX October 1987 Vectorized code W. Landsman STX December 1992
(See /usr/local/idl/lib/zastron/astro/a_b.pro)
NAME:
BARYVEL
PURPOSE:
Calculates the heliocentric and barycentric velocity components of
the Earth. Takes into account the Earth-Moon motion. Useful for
radial velocity work to an accuracy of ~1 m/s.
CALLING SEQUENCE:
BARYVEL, dje, deq, dvelh, dvelb
INPUTS:
DJE - (scalar) julian ephemeris date.
DEQ - (scalar) epoch of mean equinox of dvelh and dvelb. If deq=0
then deq is assumed to be equal to dje.
OUTPUTS:
DVELH: (vector(3)) heliocentric velocity component. in km/s
DVELB: (vector(3)) barycentric velocity component. in km/s
The 3-vectors DVELH and DVELB are given in a right-handed coordinate
system with the +X axis toward the Vernal Equinox, and +Z axis
toward the celestial pole.
PROCEDURE CALLED:
Function PREMAT -- computes precession matrix
NOTES:
Algorithm taken from FORTRAN program of Stumpff (1980, A&A Suppl, 41,1)
Stumpf claimed an accuracy of 42 cm/s for the velocity. A
comparison with the JPL FORTRAN planetary ephemeris program PLEPH
found agreement to within about 65 cm/s between 1986 and 1994
EXAMPLE:
Compute the radial velocity of the Earth toward Altair on 15-Feb-1994
IDL> jdcnv, 1994, 2, 15, 0, jd ;==> JD = 2449398.5
IDL> ra = ten(19,50,46.77)/!RADEG ;RA in radians
IDL> dec = ten(08,52,3.5)/!RADEG ;Dec in radians
IDL> baryvel, jd, 2000, vh, vb
==> vh = [-17.07809, -22.80063, -9.885281] ;Heliocentric km/s
==> vb = [-17.08083, -22.80471, -9.886582] ;Barycentric km/s
IDL> v = vb(0)*cos(dec)*cos(ra) + $ ;Project velocity toward star
vb(1)*cos(dec)*sin(ra) + vb(2)*sin(dec)
REVISION HISTORY:
Jeff Valenti, U.C. Berkeley Translated BARVEL.FOR to IDL.
W. Landsman, Cleaned up program sent by Chris McCarthy (SfSU) June 1994
(See /usr/local/idl/lib/zastron/astro/baryvel.pro)
NAME BPRECESS PURPOSE: Calculate the mean place of a star at B1950.0 on the FK4 system from the mean place at J2000.0 on the FK5 system. CALLING SEQUENCE: bprecess, ra, dec, ra_1950, dec_1950, [ MU_RADEC = , PARALLAX = RAD_VEL = ] INPUTS: RA,DEC - Input J2000 right ascension and declination in *degrees*. Scalar or N element vector OUTPUTS: RA_1950, DEC_1950 - The corresponding B1950 right ascension and declination in *degrees*. Same number of elements as RA,DEC but always double precision. OPTIONAL INPUT-OUTPUT KEYWORDS MU_RADEC - 2xN element double precision vector containing the proper motion in seconds of arc per tropical *century* in right ascension and declination. PARALLAX - N_element vector giving stellar parallax (seconds of arc) RAD_VEL - N_element vector giving radial velocity in km/s The values of MU_RADEC, PARALLAX, and RADVEL will all be modified upon output to contain the values of these quantities in the B1950 system. The parallax and radial velocity will have a very minor influence on the B1950 position. NOTES: The algorithm is taken from the Astronomical Almanac 1990, page B42. Also see Aoki et al (1983), A&A, 128,263 The error in using the IDL procedure PRECESS for converting between B1950 and J1950 can be up to 1.5", mainly in right ascension. If better accuracy than this is needed then BPRECESS should be used. EXAMPLE: The SAO2000 catalogue gives the J2000 position and proper motion for the star HD 119288. Find the B1950 position. RA(2000) = 13h 42m 12.740s Dec(2000) = 8d 23' 17.69'' Mu(RA) = -.0257 s/yr Mu(Dec) = -.090 ''/yr IDL> mu_radec = 100D* [ -15D*.0257, -0.090 ] IDL> ra = ten(13, 42, 12.740)*15.D IDL> dec = ten(8, 23, 17.69) IDL> bprecess, ra, dec, ra1950, dec1950, mu_radec = mu_radec IDL> print, adstring(ra1950, dec1950,2) ===> 13h 39m 44.526s +08d 38' 28.63" REVISION HISTORY: Written, W. Landsman October, 1992 Vectorized, W. Landsman February, 1994
(See /usr/local/idl/lib/zastron/astro/bprecess.pro)
NAME: CCM_UNRED PURPOSE: Deredden a flux vector according to the parameterization of Cardelli, Clayton, and Mathis (1989 ApJ. 345, 245), including the update for the near-UV given by O'Donnell (1994, ApJ, 422, 158). Parameterization is valid from the IR to the far-UV (3.5 microns to 0.1 microns). CALLING SEQUENCE: CCM_UNRED, wave, flux, ebv, funred, [ R_V = ] INPUT: WAVE - wavelength vector (Angstroms) FLUX - calibrated flux vector, same number of elements as WAVE EBV - color excess E(B-V), scalar. If a negative EBV is supplied, then fluxes will be reddened rather than deredenned. OUTPUT: FUNRED - unreddened flux vector, same units and number of elements as FLUX OPTIONAL INPUT KEYWORD R_V - scalar specifying the ratio of total selective extinction R(V) = A(V) / E(B - V). If not specified, then R_V = 3.1 Extreme values of R(V) range from 2.75 to 5.3 EXAMPLE: Determine how a flat spectrum (in wavelength) between 1200 A and 3200 A is altered by a reddening of E(B-V) = 0.1. Assume an "average" reddening for the diffuse interstellar medium (R(V) = 3.1) IDL> w = 1200 + findgen(40)*50 ;Create a wavelength vector IDL> f = w*0 + 1 ;Create a "flat" flux vector IDL> ccm_unred, w, f, -0.1, fnew ;Redden (negative E(B-V)) flux vector IDL> plot,w,fnew NOTES: (1) The CCM curve shows good agreement with the Savage & Mathis (1979) ultraviolet curve shortward of 1400 A, but is probably preferable between 1200 and 1400 A. (2) Many sightlines with peculiar ultraviolet interstellar extinction can be represented with a CCM curve, if the proper value of R(V) is supplied. (3) Curve is extrapolated between 912 and 1000 A as suggested by Longo et al. (1989, ApJ, 339,474) REVISION HISTORY: Written W. Landsman Hughes/STX January, 1992 Extrapolate curve for wavelengths between 900 and 1000 A Dec. 1993 Use updated coefficients for near-UV from O'Donnell Feb 1994
(See /usr/local/idl/lib/zastron/astro/ccm_unred.pro)
NAME: CT2LST PURPOSE: To convert local civil time to local mean sidereal time. CALLING SEQUENCE: CT2LST, Lst, Lng, Tz, Time, [Day, Mon, Year] INPUTS: Lng The longitude in degrees of the place for which the local sidereal time is desired, scalar Tz The time zone of the site in hours. Use this to easily account for Daylight Savings time (e.g. 4=EDT, 5 = EST/CDT), scalar Tme If the optional parameters are specified then this is the time of day of the specified date in decimal hours. If the optional parameters are not specified then this is the Julian date of time in question, scalar or vector OPTIONAL INPUTS: Day The day of the month. Mon The month, in numerical format. Year The year. OUTPUTS: Lst The Local Sideral Time for the date/time specified in hours. RESTRICTIONS: If specified, the date should be in numerical form. The year should appear as yyyy. PROCEDURE: The Julian date of the day and time is question is used to determine the number of days to have passed since 0 Jan 1968. This is used in conjunction with the GST of that date to extrapolate to the current GST; this is then used to get the LST. MODIFICATION HISTORY: Adapted from the FORTRAN program GETSD by Michael R. Greason, STX, 27 October 1988.
(See /usr/local/idl/lib/zastron/astro/ct2lst.pro)
NAME:
DATE
PURPOSE:
DATE converts day-of-year to ordinary Gregorian date;
works on cumulative day from 1-JAN-1979 (for instance),
as well as more well-mannered days-of-year.
CALLING SEQUENCE:
D_STRING = DATE(Year, day )
INPUTS:
Year - Years after 1900 may either be written out in full
(e.g. 1986) or with just the last two digits (e.g. 86)
Day - number of days after Jan 1 of the specified year
OUTPUTS:
D_STRING - String giving date in format '13-MAR-1986'
RESTRICTIONS:
Will only work for years after 1900.
MODIFICATION HISTORY:
D.M. fecit 24 October,1983
(See /usr/local/idl/lib/zastron/astro/date.pro)
NAME:
DATE_CONV
PURPOSE:
Procedure to perform conversion of dates to one of three possible
formats.
format 1: real*8 scalar encoded as:
(year-1900)*1000 + day + hour/24. + min/24./60 + sec/24./60/60
where day is the day of year (1 to 366)
format 2: Vector encoded as:
date(0) = year (eg. 1987 or just 87)
date(1) = day of year (1 to 366)
date(2) = hour
date(3) = minute
date(4) = second
format 3: string (ascii text) encoded as
DD-MON-YEAR HH:MM:SS.SS
(eg. 14-JUL-1987 15:25:44.23)
format 4: three element vector giving spacecraft time words
from ST telemetry packet.
CALLING SEQUENCE
results = DATE_CONV( DATE, TYPE )
INPUTS:
DATE - input date in one of the three possible formats.
TYPE - type of output format desired. If not supplied then
format 3 (real*8 scalar) is used.
valid values:
'REAL' - format 1
'VECTOR' - format 2
'STRING' - format 3
TYPE can be abbreviated to the single character strings 'R',
'V', and 'S'.
Nobody wants to convert TO spacecraft time (I hope!)
OUTPUTS:
The converted date is returned as the function value.
HISTORY:
version 1 D. Lindler July, 1987
adapted for IDL version 2 J. Isensee May, 1990
(See /usr/local/idl/lib/zastron/astro/date_conv.pro)
NAME:
DAYCNV
PURPOSE:
Converts julian dates to gregorian calendar dates
CALLING SEQUENCE:
DAYCNV, XJD, YR, MN, DAY, HR
INPUTS:
XJD = Julian date, double precision scalar or vector
OUTPUTS:
YR = Year (Integer)
MN = Month (Integer)
DAY = Day (Integer)
HR = Hours and fractional hours (Real). If XJD is a vector,
then YR,MN,DAY and HR will be vectors of the same length.
EXAMPLE:
IDL> DAYCNV, 2440000.D, yr, mn, day, hr
yields yr = 1968, mn =5, day = 23, hr =12.
WARNING:
Be sure that the julian date is specified as double precision to
maintain accuracy at the fractional hour level.
REVISION HISTORY:
Converted to IDL from Yeoman's Comet Ephemeris Generator,
B. Pfarr, STX, 6/16/88
(See /usr/local/idl/lib/zastron/astro/daycnv.pro)
NAME:
DEREDD
PURPOSE:
Deredden then Stromgren parameters given for a value of E(b-y)
See the procedure UVBYBETA for more info.
CALLING SEQUENCE:
deredd, eby, by, m1, c1, ub, by0, m0, c0, ub0
INPUTS:
Eby - color index E(b-y),scalar
by - b-y color (observed)
m1 - Stromgren line blanketing parameter (observed)
c1 - Stromgren Balmer discontinuity parameter (observed)
ub - u-b color (observed)
OUTPUTS:
by0 - b-y color (dereddened)
m0 - Line blanketing index (dereddened)
c0 - Balmer discontinuity parameter (dereddened)
ub0 - u-b color (dereddened)
REVISION HISTORY:
Adapted from FORTRAN routine DEREDD by T.T. Moon
W. Landsman STX Co. April, 1988
(See /usr/local/idl/lib/zastron/astro/deredd.pro)
NAME: EQPOLE PURPOSE: Convert right ascension, declination to X,Y using an equal-area polar projection. The output X and Y coordinates are scaled to be between -90 and +90 to go from equator to pole to equator. Output map points can be centered on the north pole or south pole. CALLING SEQUENCE: EQPOLE, L, B, X, Y, [ /SOUTHPOLE ] INPUTS: L - longitude - scalar or vector, in degrees B - latitude - same number of elements as RA, in degrees OUTPUTS: X - X coordinate, same number of elements as RA. X is normalized to be between -90 and 90. Y - Y coordinate, same number of elements as DEC. Y is normalized to be between -90 and 90. KEYWORDS: /SOUTHPOLE - Keyword to indicate that the plot is to be centered on the south pole instead of the north pole. REVISION HISTORY: J. Bloch LANL, SST-9 1.1 5/16/91
(See /usr/local/idl/lib/zastron/astro/eqpole.pro)
NAME:
EQPOLE_GRID
PURPOSE:
Produce an overlay of latitude and longitude lines over a plot or image
on the current graphics device using the equal area polar projection.
EQPOLE_GRID assumes that the output plot coordinates span the
x and y ranges of -90 to 90 for a region that covers the equator to
the chosen pole. The grid is assumed to go from the equator to
the chosen pole.
CALLING SEQUENCE:
EQPOLE_GRID[,DLONG,DLAT,[/SOUTHPOLE,LINESTYLE=N,/LABEL]
INPUTS:
DLONG = Optional input longitude line spacing in degrees. If left
out, defaults to 30.
DLAT = Optional input lattitude line spacing in degrees. If left
out, defaults to 30.
KEYWORDS:
SOUTHPOLE = Optional flag indicating that the output plot is
to be centered on the south rather than the north
pole.
LINESTYLE = Optional input integer specifying the linestyle to
use for drawing the grid lines.
LABELS = Optional flag for creating labels on the output
grid on the prime meridian and the equator for
lattitude and longitude lines. If set =2, then
the longitude lines are labeled in hours and minutes.
OUTPUTS:
Draws grid lines on current graphics device.
CATAGORY:
SST-9 Graphics routine.
COPYRIGHT NOTICE:
Copyright 1992, The Regents of the University of California. This
software was produced under U.S. Government contract (W-7405-ENG-36)
by Los Alamos National Laboratory, which is operated by the
University of California for the U.S. Department of Energy.
The U.S. Government is licensed to use, reproduce, and distribute
this software. Neither the Government nor the University makes
any warranty, express or implied, or assumes any liability or
responsibility for the use of this software.
AUTHOR AND MODIFICATIONS:
J. Bloch 1.4 10/28/92
(See /usr/local/idl/lib/zastron/astro/eqpole_grid.pro)
NAME: EULER PURPOSE: Transform between galactic, celestial, and ecliptic coordinates. Use the procedure ASTRO to use this routine interactively CALLING SEQUENCE: EULER, AI, BI, AO, BO, [ SELECT ] INPUTS: AI - Input Longitude in DEGREES, scalar or vector. If only two parameters are supplied, then AI and BI will be modified to contain the output longitude and latitude. BI - Input Latitude in DEGREES OPTIONAL INPUT: SELECT - Integer (1-6) specifying type of coordinate transformation. SELECT From To | SELECT From To 1 RA-DEC(1950) GAL.(ii) | 4 ECLIPTIC RA-DEC 2 GAL.(ii) RA-DEC | 5 ECLIPTIC GAL.(ii) 3 RA-DEC ECLIPTIC | 6 GAL.(ii) ECLIPTIC If omitted, program will prompt for the value of SELECT OUTPUTS: AO - Output Longitude in DEGREES BO - Output Latitude in DEGREES REVISION HISTORY: Written W. Landsman, February 1987 Adapted from Fortran by Daryl Yentis NRL
(See /usr/local/idl/lib/zastron/astro/euler.pro)
NAME: FLAT PURPOSE: FLAT transforms the image of a galaxy so that the galaxy appears face-on. Either a nearest-neighbor approximations or a bilinear interpolation may be used. CALLING SEQUENCE: RESULT = FLAT( image, ang, inc, [, cen, /INTERP ] ) INPUTS: IMAGE - Image to be transformed ANG - Angle of major axis, counterclockwise from Y-axis, degrees For an image in standard orientation (North up, East left) this is the Position Angle INC - Angle of inclination of galaxy, degrees OPTIONAL INPUTS: CEN - Two element vector giving the X and Y position of galaxy center If not supplied, then the galaxy center is assumed to coincide with the image center INPUT KEYWORDS: INTERP - If present, and non-zero, then bilinear interpolation will be performed. Otherwise a nearest neighbor approximation is used. OUTPUTS: RESULT - the transformed image, same dimensions and type as IMAGE METHOD: A set of 4 equal spaced control points are corrected for inclination using the procedure POLYWARP. These control points are used by POLY_2D to correct the whole image. REVISION HISTORY: Written by R. S. Hill, SASC Technologies Inc., 4 December 1985 Code cleaned up a bit W. Landsman December 1992
(See /usr/local/idl/lib/zastron/astro/flat.pro)
NAME: FLUX2MAG PURPOSE: Convert from flux (ergs/s/cm^2/A) to magnitudes. Use MAG2FLUX for the opposite direction. CALLING SEQUENCE: mag = flux2mag( flux, [ zero_pt ] ) INPUTS: flux - scalar or vector flux vector OPTIONAL INPUT: zero_pt - scalar giving the zero point level of the magnitude. If not supplied then zero_pt = 21.1 (Code et al 1976) OUTPUT: mag - magnitude vector (mag = -2.5*alog10(flux) - zero_pt) REVISION HISTORY: Written J. Hill STX Co. 1988
(See /usr/local/idl/lib/zastron/astro/flux2mag.pro)
NAME: GCIRC PURPOSE: Computes rigorous great circle arc distances. CALLING SEQUENCE: GCIRC, U, RA1, DC1, RA2, DC2, DIS INPUTS: U -- Describes units of inputs and output: 0: everything radians 1: RAx in decimal hours, DCx in decimal degrees, DIS in arc seconds RA1 -- Right ascension of point 1 DC1 -- Declination of point 1 RA2 -- Right ascension of point 2 DC2 -- Declination of point 2 OUTPUTS: DIS -- Angular distance on the sky between points 1 and 2 See U above for units; double scalar PROCEDURE: Ordinary spherical trig formula. NOTES: Either RA1,DC1 or RA2,DC2 (but not both coordinates) can be vectors. In this case DIS is a vector giving the angular distance between each of the vector coordinates to the scalar coordinate MODIFICATION HISTORY: Written in Fortran by R. Hill -- SASC Technologies -- January 3, 1986 Translated from FORTRAN to IDL, RSH, STX, 2/6/87 Vector arguments allowed W. Landsman April 1989
(See /usr/local/idl/lib/zastron/astro/gcirc.pro)
NAME:
GET_COORDS
PURPOSE:
A general purpose routine that takes user input for angular
coordinates and returns floating-point values. The user may input as
floating point or sexigesimal. If user inputs RA then it is the
calling procedure's job to convert hours to degrees if needed.
Since the input string is parsed character-by-character, ANY character
that is not a digit, minus sign or decimal point may be used as a
delimiter, i.e. acceptable examples of user input are:
1:03:55 -10:15:31
1 3 55.0 -10 15 31
1*3 55 -10abcd15efghij31
1.065278 hello -10.25861
CALLING SEQUENCE:
GET_COORDS, Coords, [ PromptString, NumVals, INSTRING =, /QUIET ]
OPTIONAL INPUT:
PromptString - A string to inform the user what data are to be entered
InString - a keyword that, if set, is assumed to already contain the
input data string to be parsed. If this keyword is set, then
the user is not prompted for any input.
Quiet - if set the program won't printout any error messages, but bad
input is still flagged by Coords=[-999,-999].
OUTPUT:
Coords - a 2 element floating array containing the coordinates. The
vector [-999,-999] is returned if there has been an error.
OPTIONAL OUTPUT:
NumVals - the number of separate values entered by the user: 2 if the
user entered the coordinates as floating point numbers, 6 if
the user entered the coordinates as sexigesimal numbers. Some
calling procedures might find this information useful (e.g., to
to print some output in the same format as the user's input).
REVISION HISTORY
Written by Joel Parker, 5 MAR 90
Included InString and Quiet keywords. Cleaned up some of the code and
comments. JWmP, 16 Jun 94
*******************************************************************************
(See /usr/local/idl/lib/zastron/astro/get_coords.pro)
NAME:
GET_DATE
PURPOSE:
Return the current date in DD/MM/YY format. This is the format
required by the DATE and DATE-OBS keywords in a FITS header
CALLING SEQUENCE:
GET_DATE, dte
INPUTS:
None
OUTPUTS:
dte = An eight character scalar string specifying the current day
(0-31), current month (1-12), and last two digits of the
current year
EXAMPLE:
Add the current date to the DATE keyword in a FITS header,h
IDL> GET_DATE,dte
IDL> sxaddpar, h, 'DATE', dte
REVISION HISTORY:
Written W. Landsman March 1991
(See /usr/local/idl/lib/zastron/astro/get_date.pro)
NAME: GET_JULDATE PURPOSE: Return the current julian date CALLING SEQUENCE: GET_JULDATE,jd INPUTS: None OUTPUTS: jd = Current Julian Date, double precision scalar EXAMPLE: Return the current hour, day, month and year as integers IDL> GET_JULDATE, JD ;Get current julian date IDL> DAYCNV, JD, YR, MON, DAY, HOURS ;Convert to hour,day month & year METHOD: The systime(1) function is used to obtain the number of days after 1-JAN-1970. The offset to Julian days is then computed. WARNING! This procedure assumes that systime(1) returns the value of Universal Time (UT). This appears to be true for most Unix workstations and DOS machines, but not for VMS or Macintoshes, for which systime(1) returns the local time. Users may need to add the difference between UT and local time to the value of JD, depending on the particular installation. REVISION HISTORY: Written Wayne Landsman March, 1991
(See /usr/local/idl/lib/zastron/astro/get_juldate.pro)
NAME:
GLACTC
PURPOSE:
Program to convert right ascension (ra) and declination (dec) to
galactic longitude (gl) and latitude (gb) (j=1) or vice versa (j=2).
CALLING SEQUENCE:
glactc, ra, dec, year, gl, gb, j
INPUTS:
year equinox of ra and dec (input)
j direction of conversion (input)
1: ra,dec --> gl,gb
2: gl,gb --> ra,dec
INPUTS OR OUTPUTS ( depending on argument J )
ra right ascension, hours
dec declination, degrees
gl galactic longitude (system II), degrees
gb galactic latitude (system II), degrees
All results forced double precision floating.
COMMON BLOCKS:
gal See Side Effects.
SIDE EFFECTS:
Year and galaxy orientation saved in common to make repeated
computations more efficient.
HISTORY:
FORTRAN subroutine by T. A. Nagy, 21-MAR-78.
Conversion to IDL, R. S. Hill, STX, 19-OCT-87.
(See /usr/local/idl/lib/zastron/astro/glactc.pro)
NAME: HELIO PURPOSE: Compute (low-precision) Heliocentric coordinates for the planets. Adapted from the book Celestial Basic CALLING SEQUENCE: HELIO, JD, HMS, LIST, HRAD, HLONG, HLAT INPUTS: JD = Julian day to compute for, long scalar HMS = hours, minutes, seconds array: H, M, S. Universal time. LIST = List of planets array. May be a single number. 1 = merc, 2 = venus, ... 9 = pluto. OUTPUTS: HRAD = array of Heliocentric radii (A.U). HLONG = array of Heliocentric (ecliptic) longitudes (degrees). HLAT = array of Heliocentric latitudes (degrees). These values are scalars if LIST is a scalar. EXAMPLE: To find the heliocentric positions of Jupiter and Saturn on 1-Jan-1989 JDCNV,1989,1,1,0,JD ;Convert to Julian Date HELIO,JD,[0,0,0],[5,6],hrad,hlong,hlat ;Get radius, long, and lat COMMON BLOCKS: HELIOCOM --- stores parameters. ROUTINES USED: DATATYPE, ISARRAY, MODIFICATION HISTORY: R. Sterner. 20 Aug, 1986. Code cleaned up a bit W. Landsman December 1992
(See /usr/local/idl/lib/zastron/astro/helio.pro)
NAME:
HELIO_JD
PURPOSE:
Convert geocentric (reduced) Julian date to heliocentric julian date
(i.e. correct for extra light travel time between Earth and Sun)
CALLING SEQUENCE:
jdhelio = HELIO_JD( date, ra, dec)
INPUTS
date - reduced Julian date (= JD - 2400000), scalar or vector, MUST
be double precision
ra,dec - scalars giving right ascension and declination in DEGREES
OUTPUTS:
jdhelio - heliocentric julian date.
EXAMPLE:
What is heliocentric julian date of an observation of V402 Cygni
(RA = 20 7 15, Dec = 37 0.33) taken June 15, 1973 at 11:40 UT?
IDL> juldate, [1973,6,15,11,40], jd ;Get Geocentric julian date
IDL> hjd = helio_jd( jd, ten(20,7,15)*15., ten(37,0.33) )
==> hjd = 41848.9881
PROCEDURES CALLED:
zparcheck, xyz
REVISION HISTORY:
Algorithm from the book Astronomical Photometry by Henden, p. 114
Written, W. Landsman STX June, 1989
(See /usr/local/idl/lib/zastron/astro/helio_jd.pro)
NAME: IMCONTOUR PURPOSE: Contour plot labeled with astronomical coordinates. The type of coordinate display is controlled by the keyword TYPE Set TYPE=0 (default) to measure distances from the center of the image (IMCONTOUR will decide whether the plotting units will be in arc seconds, arc minutes, or degrees depending on image size.) Set TYPE=1 for standard RA and Dec labeling CALLING SEQUENCE: IMCONTOUR, im, hdr,[ TYPE=, PUTINFO=, XTITLE = , YTITLE = , NLEVELS= MAX_VALUE=, LEVELS=, TITLE =, SUBTITLE =, FOLLOW = , XMINOR =, YMINOR =, CHAN = ] INPUTS: IM - 2-dimensional image array HDR - FITS header associated with IM, string array, must include astrometry keywords. IMCONTOUR will also look for the OBJECT and IMAGE keywords, and print these if found and the PUTINFO keyword is set. OPTIONAL PLOTTING KEYWORDS: TYPE - the type of astronomical labeling to be displayed. Either set TYPE = 0 (default), distance to center of the image is marked in units of Arc seconds, arc minutes, or degrees TYPE = 1 astronomical labeling with Right ascension and declination. PUTINFO - If set then IMCONTOUR will add information about the image to the right of the contour plot. Information includes image name, object, image center, image center, contour levels, and date plot was made The other keywords XTITLE, YTITLE, NLEVELS, MAX_VALUE, LEVELS, TITLE, SUBTITLE, FOLLOW, XMINOR, and YMINOR have the same meaning as in the CONTOUR procedure. CHAN - On devices with multiple channels this specifies the output channel. On the IVAS and DeAnza image displays the default is the graphics overlay. NOTES: (1) The contour plot will have the same dimensional ratio as the input image array (2) To contour a subimage, use HEXTRACT before calling IMCONTOUR PROCEDURES USED: CHECK_FITS, EXTAST, GETROT, TICPOS, TICLABEL, TIC_ONE, TICS, XYAD CONS_RA, CONS_DEC, ADSTRING REVISION HISTORY: Written W. Landsman STX May, 1989 Fixed RA,Dec labeling W. Landsman November, 1991 Fix plottting keywords W.Landsman July, 1992
(See /usr/local/idl/lib/zastron/astro/imcontour.pro)
NAME:
IMF
PURPOSE:
Returns values of an N-component power-law logarithmic initial mass
function, normalized so that the total mass distribution equals one
solar mass.
CALLING SEQUENCE:
psi = IMF( mass, expon, mass_range )
INPUTS:
mass - mass in units of solar masses (scalar or vector)
Converted to floating point if necessary
expon - power law exponent, uusally negative, scalar or vector
The number of values in expon equals the number of different
power-law components in the IMF
A Saltpeter IMF has a scalar value of expon = -1.35
mass_range - vector containing the mass upper and lower limits of the
IMF and masses where the IMF exponent changes. The number
of values in mass_range should be one more than in expon.
The values in mass_range should be monotonically increasing.
OUTPUTS
psi - mass function, number of stars per unit logarithimic mass interval
evaluated for supplied masses
NOTES:
The mass spectrum f(m) giving the number of stars per unit mass
interval is related to psi(m) by m*f(m) = psi(m). The normalization
condition is that the integral of psi(m) between the upper and lower
mass limit is unity.
EXAMPLE:
(1) Print the number of stars per unit mass interval at 3 Msun
for a Salpeter (expon = -1.35) IMF, with a mass range from
0.1 MSun to 110 Msun.
IDL> print, imf(3, -1.35, [0.1, 110] ) / 3
(2) Lequex et al. (1981, A & A 103, 305) describes an IMF with an
exponent of -0.6 between 0.007 Msun and 1.8 Msun, and an
exponent of -1.7 between 1.8 Msun and 110 Msun. Plot
the mass spectrum f(m)
IDL> m = [0.01,0.1,indgen(110) + 1 ] ;Make a mass vector
IDL> expon = [-0.6, -1.7] ;Exponent Vector
IDL> mass_range = [ 0.007, 1.8, 110] ;Mass range
IDL> plot_oo, m, imf(m, expon, mass_range ) / m
METHOD
IMF first calculates the constants to multiply the power-law
components such that the IMF is continuous at the intermediate masses,
and that the total mass integral is one solar mass. The IMF is then
calculated for the supplied masses. Also see Scalo (1986)
REVISION HISTORY:
Written W. Landsman August, 1989
Set masses LE mass_u rather than LT mass_u August, 1992
Major rewrite to accept arbitary power-law components April 1993
(See /usr/local/idl/lib/zastron/astro/imf.pro)
NAME: JDCNV PURPOSE: Converts Gregorian dates to Julian days CALLING SEQUENCE: JDCNV, YR, MN, DAY, HR, JULIAN INPUTS: YR = Year (integer) MN = Month (integer 1-12) DAY = Day (integer 1-31) HR = Hours and fractions of hours of universal time (U.T.) OUTPUTS: JULIAN = Julian date (double precision) EXAMPLE: To find the Julian Date at 1978 January 1, 0h (U.T.) IDL> JDCNV, 1978, 1, 1, 0., JULIAN will give JULIAN = 2443509.5 NOTES: (1) JDCNV will accept vector arguments (2) JULDATE is an alternate procedure to perform the same function REVISON HISTORY: Converted to IDL from Don Yeomans Comet Ephemeris Generator, B. Pfarr, STX, 6/15/88
(See /usr/local/idl/lib/zastron/astro/jdcnv.pro)
NAME JPRECESS PURPOSE: Calculate the mean place of a star at J2000.0 on the FK5 system from the mean place at B1950.0 on the FK4 system. CALLING SEQUENCE: jprecess, ra, dec, ra_2000, dec_2000, [ MU_RADEC = , PARALLAX = RAD_VEL = ] INPUTS: RA,DEC - input B1950 right ascension and declination in *degrees*. Scalar or vector OUTPUTS: RA_2000, DEC_2000 - the corresponding J2000 right ascension and declination in *degrees*. Same number of elements as RA,DEC but always double precision. OPTIONAL INPUT-OUTPUT KEYWORDS MU_RADEC - 2xN element double precision vector containing the proper motion in seconds of arc per tropical *century* in right ascension and declination. PARALLAX - N_element vector giving stellar parallax (seconds of arc) RAD_VEL - N_element vector giving radial velocity in km/s The values of MU_RADEC, PARALLAX, and RADVEL will all be modified upon output to contain the values of these quantities in the J2000 system. Values will also be converted to double precision. The parallax and radial velocity will have a very minor influence on the J2000 position. NOTES: The algorithm is taken from the Astronomical Almanac 1990, page B42. Also see Aoki et al (1983), A&A, 128,263 The error in using the IDL procedure PRECESS for converting between B1950 and J2000 can be up to 1.5", mainly in right ascension. If better accuracy than this is needed then JPRECESS should be used. EXAMPLE: The SAO catalogue gives the B1950 position and proper motion for the star HD 119288. Find the J2000 position. RA(1950) = 13h 39m 44.526s Dec(1950) = 8d 38' 28.63'' Mu(RA) = -.0259 s/yr Mu(Dec) = -.093 ''/yr IDL> mu_radec = 100D* [ -15D*.0259, -0.093 ] IDL> ra = ten(13,39,44.526)*15.D IDL> dec = ten(8,38,28.63) IDL> jprecess, ra, dec, ra2000, dec2000, mu_radec = mu_radec IDL> print, adstring(ra2000, dec2000,2) ===> 13h 42m 12.740s +08d 23' 17.69" RESTRICTIONS: "When transferring individual observations, as opposed to catalog mean place, the safest method is to tranform the observations back to the epoch of the observation, on the FK4 system (or in the system that was used to to produce the observed mean place), convert to the FK5 system, and transform to the the epoch and equinox of J2000.0" -- from the Explanatory Supplement (1992), p. 180 REVISION HISTORY: Written, W. Landsman September, 1992 Corrected a couple of typos in M matrix October, 1992 Vectorized, W. Landsman February, 1994
(See /usr/local/idl/lib/zastron/astro/jprecess.pro)
NAME:
JULDATE
PURPOSE:
Convert from calender to Reduced Julian Date
CALLING SEQUENCE:
JULDATE, /PROMPT ;Prompt for Calender Date, print Julian Date
or
JULDATE, date, jd
INPUT:
DATE - 5-element array containing year,month (1-12),day,hour & minute
all specified as numbers (Universal Time). Year after 1900
can be specified 2 ways, either for example, as 83 or 1983.
Years B.C should be entered as negative numbers. If Hour or
Minute are not supplied, they will default to 0.
OUTPUT:
JD - reduced julian date, double precision scalar. To convert to
Julian Date, add 2400000. JULDATE will print the value of
JD at the terminal if less than 2 parameters are supplied, or
if the /PROMPT keyword is set
OPTIONAL INPUT KEYWORD:
PROMPT - If this keyword is set and non-zero, then JULDATE will prompt
for the calender date at the terminal.
RESTRICTIONS:
Will not work for years between 0 and 99 A.D. (since these are
interpreted as years 1900 - 1999). Will not work for year 1582.
The procedure HELIO_JD can be used after JULDATE, if a heliocentric
Julian date is required.
EXAMPLE:
A date of 25-DEC-1981 06:25 UT may be expressed as either
IDL> juldate, [81,12,25,6,25], jd
IDL> juldate, [1981,12,25.2673611], jd
In either case, one should obtain a reduced julian date of
JD = 44963.7673611
REVISION HISTORY
Adapted from IUE RDAF (S. Parsons) 8-31-87
Algorithm from Sky and Telescope April 1981
Added /PROMPT keyword, W. Landsman September 1992
(See /usr/local/idl/lib/zastron/astro/juldate.pro)
NAME: MAG2FLUX PURPOSE: Convert from magnitudes to flux (ergs/s/cm^2/A). Use FLUX2MAG for the opposite direction. CALLING SEQUENCE: flux = mag2flux( mag, [ zero_pt ] ) INPUTS: mag - scalar or vector of magnitudes OPTIONAL INPUT: zero_pt - scalar giving the zero point level of the magnitude. If not supplied then zero_pt = 21.1 (Code et al 1976) OUTPUT: flux - scalar or vector flux vector (flux = 10^(-0.4*(mag + zero_pt)) REVISION HISTORY: Written J. Hill STX Co. 1988
(See /usr/local/idl/lib/zastron/astro/mag2flux.pro)
NAME:
MOONPOS
PURPOSE:
To compute the RA and Dec of the Moon at a given date.
CALLING SEQUENCE:
MOONPOS, Dte, Ra, Dec
INPUTS:
Dte - The Julian date of the day (and time) in question.
OUTPUTS:
Ra - The right ascension of the moon at that date in radians.
Dec - The declination of the moon at that date in radians.
SIDE EFFECTS:
The user should be aware that the equations used are not highly
accurate. The error in right ascension will rarely exceed 0.3
degrees; the error in declination will rarely exceed 0.2 degrees.
PROCEDURE:
The lunar position is computed from the low precision formulae provided
in the Astronomical Almanac.
EXAMPLE:
IDL> juldate,[1982,4,6],jd ;Get reduced julian date
IDL> jd = jd + 2400000. ;Convert to full julian date
IDL> moonpos, jd, ra ,dec ;Get RA and Dec of moon
IDL> print,adstring(ra*!RADEG,dec*!RADEG)
==> 11 17 6.1 +09 17 56.0
This is about 5' from the position given in the Astronomical Almanac
MODIFICATION HISTORY:
Written by Michael R. Greason, STX, 31 October 1988.
(See /usr/local/idl/lib/zastron/astro/moonpos.pro)
NAME: PLANCK() PURPOSE: To calculate the Planck function in units ergs/cm2/s/a CALLING SEQUENCE: bbflux = PLANCK( wave, temp) INPUT PARAMETERS: WAVE Scalar or vector giving the wavelength(s) in **Angstroms** at which the planck function is to be evaluated. TEMP Scalar giving the temperature of the planck function in degree K OUTPUT PARAMETERS: BBFLUX - Scalar or vector giving the planck function at the specified wavelength points. EXAMPLES: To calculate the blackbody flux (i.e. PI*Intensity) in erg/cm^2/s/A for 30,000 K every 100 Angstroms between 2000A and 2900 A IDL> WAVE = 2000 + INDGEN(10)*100 IDL> BBFLUX = PLANCK(WAVE,30000) RESTRICTIONS: Values less than approximately 1E-24 are truncated to 0. PROCEDURE: The wavelength data are converted to cm, and the planck function is calculated for each wavelength point. See Allen (1973), Astrophysical Quantities, section 44 for more information. MODIFICATION HISTORY: Adapted from the IUE RDAF August, 1989
(See /usr/local/idl/lib/zastron/astro/planck.pro)
NAME:
PRECESS
PURPOSE:
Precess coordinates from EQUINOX1 to EQUINOX2. For interactive
display, one can use the procedure ASTRO which calls PRECESS or use
the /PRINT keyword. The default (RA,DEC) system is FK5 based on
epoch J2000.0 but FK4 based on B1950.0 is available via the FK4 keyword.
CALLING SEQUENCE:
PRECESS, ra, dec, [ equinox1, equinox2, /PRINT, /FK4 ]
INPUT - OUTPUT:
RA - Input right ascension in DEGREES (scalar or vector)
DEC - Input declination in DEGREES (scalar or vector)
NOTE: The input RA and DEC are modified by PRECESS to give the
values after precession.
OPTIONAL INPUTS:
EQUINOX1 - Original equinox of coordinates, numeric scalar. If
omitted, then PRECESS will query for EQUINOX1 and EQUINOX2.
EQUINOX2 - Equinox of precessed coordinates.
OPTIONAL INPUT KEYWORDS:
PRINT - If this keyword is set and non-zero, then the precessed
coordinates are displayed at the terminal.
FK4 - If this keyword is set, the FK4 (B1950.0) system
will be used otherwise FK5 (J2000.0) will be used instead.
RESTRICTIONS:
Accuracy of precession decreases for declination values near 90
degrees. PRECESS should not be used more than 2.5 centuries from
2000 on the FK5 system (1950.0 on the FK4 system).
EXAMPLES:
(1) The Pole Star has J2000.0 coordinates (2h, 31m, 46.3s,
89d 15' 50.6"); compute its coordinates at J1985.0
IDL> precess, ten(2,31,46.3)*15, ten(89,15,50.6), 2000, 1985, /PRINT
====> 2h 16m 22.73s, 89d 11' 47.3"
(2) Precess the B1950 coordinates of Eps Ind (RA = 21h 59m,33.053s,
DEC = (-56d, 59', 33.053") to equinox B1975.
IDL> ra = ten(21, 59, 33.053)*15
IDL> dec = ten(-56, 59, 33.053)
IDL> precess, ra, dec ,1950, 1975, /fk4
PROCEDURE:
Algorithm from Computational Spherical Astronomy by Taff (1983),
p. 24. (FK4). FK5 constants from "Astronomical Almanac Explanatory
Supplement 1992, page 104 Table 3.211.1.
PROCEDURE CALLED:
Function PREMAT - computes precession matrix
REVISION HISTORY
Written, Wayne Landsman, STI Corporation August 1986
Correct negative output RA values February 1989
Added /PRINT keyword W. Landsman November, 1991
Provided FK5 (J2000.0) I. Freedman January 1994
Precession Matrix computation now in PREMAT W. Landsman June 1994
(See /usr/local/idl/lib/zastron/astro/precess.pro)
NAME: PRECESS_CD PURPOSE: Precess CD (coordinate description) matrix from a FITS header from EPOCH1 to EPOCH2. Called by HPRECESS CALLING SEQUENCE: PRECESS_CD, cd, epoch1, epoch2, crval_old, crval_new INPUTS/OUTPUT: CD - 2 x 2 CD (coordinate description) matrix in any units (degrees or radians). CD will altered on output to contain precessed values in the same units. On output CD will always be double precision no matter how input. INPUTS: EPOCH1 - Original equinox of coordinates, scalar (e.g. 1950.0). EPOCH2 - Equinox of precessed coordinates, scalar (e.g. 2000.0) CRVAL_OLD - 2 element vector containing RA and DEC in DEGREES of the reference pixel in the original equinox CRVAL_NEW - 2 elements vector giving CRVAL in the new equinox INPUT KEYWORD: If this keyword is set, then the precession constants are taken in the FK4 reference frame. The default is the FK5 frame. RESTRICTIONS: PRECESS_CD should not be used more than 2.5 centuries from the year 1900. PROCEDURE: Adapted from the STSDAS program FMATPREC. Precession changes the location of the north pole, and thus changes the rotation of an image from north up. This is reflected in the precesion of the CD matrix. This is usually a very small change. REVISION HISTORY Written, Wayne Landsman, ST Systems February 1988 Fixed sign error in computation of SINRA March 1992 Added /FK4 keyword Feb 1994
(See /usr/local/idl/lib/zastron/astro/precess_cd.pro)
NAME:
PREMAT
PURPOSE:
Return the precession matrix from EQUINOX1 to EQUINOX2. This matrix
is used by the procedures PRECESS and BARVL to precess astronomical
coordinates
CALLING SEQUENCE:
matrix = PREMAT( equinox1, equinox2, [ /FK4 ] )
INPUTS:
EQUINOX1 - Original equinox of coordinates, numeric scalar.
EQUINOX2 - Equinox of precessed coordinates.
OUTPUT:
matrix - double precision 3 x 3 precession matrix, used to precess
equatorial rectangular coordinates
OPTIONAL INPUT KEYWORDS:
FK4 - If this keyword is set, the FK4 (B1950.0) system precession
angles are used to compute the precession matrix. The
default is to use FK5 (J2000.0) precession angles
EXAMPLES:
Return the precession matrix from 1950.0 to 1975.0 in the FK4 system
IDL> matrix = PREMAT( 1950.0, 1975.0, /FK4)
PROCEDURE:
FK4 constants from "Computational Spherical Astronomy" by Taff (1983),
p. 24. (FK4). FK5 constants from "Astronomical Almanac Explanatory
Supplement 1992, page 104 Table 3.211.1.
REVISION HISTORY
Written, Wayne Landsman, HSTX Corporation, June 1994
(See /usr/local/idl/lib/zastron/astro/premat.pro)
NAME: QDCB PURPOSE: Convert lattitude and longitude or right ascention and declination into quad cube data base coordinates. CATEGORY: Mapping Coordinate Conversion CALLING SEQUENCE: QDCB,RA,DEC,FACE,X,Y INPUT PARAMETERS: RA = Right ascention or longitude in degrees. May be a scaler or an array. DEC = Declination or lattitude in degrees. May be a scaler or an array but must have same number of elements as RA. OPTIONAL KEYWORD PARAMETERS: OUTPUT PARAMETERS: FACE = Output integer(s) from 0 to 5 identifying the cube face that the input coordinate(s) lie(s) on. Will have the same number of elements as RA and DEC. X = Output floaing point value between +1 and -1 for the X coordinate value(s) on the cube face(s). Will have the same number of elements as RA and DEC. Y = Output floaing point value between +1 and -1 for the Y coordinate value(s) on the cube face(s). Will have the same number of elements as RA and DEC. COMMON BLOCKS: NONE PROCEDURE: Transcribed the C routines from the EUVE quad cube library. COPYRIGHT NOTICE: Copyright 1991, The Regents of the University of California. This software was produced under U.S. Government contract (W-7405-ENG-36) by Los Alamos National Laboratory, which is operated by the University of California for the U.S. Department of Energy. The U.S. Government is licensed to use, reproduce, and distribute this software. Neither the Government nor the University makes any warranty, express or implied, or assumes any liability or responsibility for the use of this software. AUTHOR: Robert Langer MODIFICATIONS/REVISION LEVEL: 1.6 8/5/92
(See /usr/local/idl/lib/zastron/astro/qdcb.pro)
NAME: QDCB_GRID PURPOSE: Produce an overlay of latitude and longitude lines over a plot or image on the current graphics device assuming that the current plot is a map in the so called quad cube projection (see qdcb.pro). The output plot range is assumed to go from 7.0 to -1.0 on the X axis and -3.0 to 3.0 on the Y axis. Within this plotting space, the quad cube faces are laid out as follows (X=Empty, Astronomical Layout shown - X axis can be swapped for geographic maps): 3.0_ XXX0 4321 -3.0_XXX5 | | 7.0 -1.0 CATEGORY: Mapping Support Routine CALLING SEQUENCE: QDCB_GRID,[,DLONG,DLAT,[LINESTYLE=N,/LABELS] INPUT PARAMETERS: DLONG = Optional input longitude line spacing in degrees. If left out, defaults to 30. DLAT = Optional input lattitude line spacing in degrees. If left out, defaults to 30. OPTIONAL KEYWORD PARAMETERS: LINESTYLE = Optional input integer specifying the linestyle to use for drawing the grid lines. LABELS = Optional keyword specifying that the lattitude and longitude lines on the prime meridian and the equator should be labeled in degrees. If LABELS is given a value of 2, i.e. LABELS=2, then the longitude labels will be in hours and minutes instead of degrees. OUTPUT PARAMETERS: NONE COMMON BLOCKS: NONE PROCEDURE: Uses QDCB.PRO to compute positions of grid lines and labels. COPYRIGHT NOTICE: Copyright 1991, The Regents of the University of California. This software was produced under U.S. Government contract (W-7405-ENG-36) by Los Alamos National Laboratory, which is operated by the University of California for the U.S. Department of Energy. The U.S. Government is licensed to use, reproduce, and distribute this software. Neither the Government nor the University makes any warranty, express or implied, or assumes any liability or responsibility for the use of this software. AUTHOR: Jeff Bloch MODIFICATIONS/REVISION LEVEL: %I% %G%
(See /usr/local/idl/lib/zastron/astro/qdcb_grid.pro)
NAME: RADEC PURPOSE: To convert right ascension and declination from decimal degrees to sexigesimal hours (for R.A.) and degrees( for Dec.). CALLING SEQUENCE: radec, ra, dec, ihr, imin, xsec, ideg, imn, xsc INPUTS: ra - right ascension in decimal DEGREES, scalar or vector dec - declination in decimal DEGREES, scalar or vector, same number of elements as RA OUTPUTS: ihr - right ascension hours (INTEGER*2) imin - right ascension minutes (INTEGER*2) xsec - right ascension seconds (REAL*4 or REAL*8) ideg - declination degrees (INTEGER*2) imn - declination minutes (INTEGER*2) xsc - declination seconds (REAL*4 or REAL*8) RESTRICTIONS: RADEC does minimal parameter checking. REVISON HISTORY: Written by B. Pfarr, STX, 4/24/87
(See /usr/local/idl/lib/zastron/astro/radec.pro)
NAME: SIXTY() PURPOSE: Converts decimal number to sexigesimal. Reverse of TEN function. CALLING SEQUENCE: X = SIXTY( SCALAR ) INPUTS: SCALAR -- Decimal quantity. OUTPUTS: Function value returned = double real vector of three elements, sexigesimal equivalent of input decimal quantity. A negative number is signified by making the first non-zero element of the output vection negative. PROCEDURE: Mostly involves checking arguments and setting the sign. MODIFICATION HISTORY: Written by R. S. Hill, STX, 19-OCT-87 Output changed to single precision. RSH, STX, 1/26/88
(See /usr/local/idl/lib/zastron/astro/sixty.pro)
NAME: STRINGAD PURPOSE: Converts a string of sexigesimal coordinates to their decimal form. CALLING SEQUENCE: STRINGAD, COORDS, RA, DEC INPUT: COORDS A string of coordinates (e.g. '17 00 45.2 25 4 32.4') It should have six numbers delimited by spaces OUTPUT: RA Right Ascension, decimal degrees, scalar DEC Declination, decimal degrees, scalar PROCEDURES CALLED: Getopt Ten HISTORY: 09-AUG-90 Version 1 written Kerry McQuade 20-AUG-90 Put code to account for '-0' back in after it was cleverly removed before installation in the MOUSSE library. E. Deutsch
(See /usr/local/idl/lib/zastron/astro/stringad.pro)
NAME: SUNPOS PURPOSE: To compute the RA and Dec of the Sun at a given date. CALLING SEQUENCE: sunpos, jd, ra, dec, [elong] INPUTS: jd - The Julian date of the day (and time) in question, scalar or vector. OUTPUTS: ra - The right ascension of the sun at that date in RADIANS. dec - The declination of the sun at that date in RADIANS. OPTIONAL OUTPUT: elong - Ecliptic longitude of the sun at that date in DEGREES. KEYWORDS: DEGREES - If present and non-zero, all parameters that are returned in RADIANS are instead returned in DEGREES. ELNG - Returns the ecliptic longitude of the sun, in RADIANS. OBLIQUITY - Returns the obliquity of the ecliptic, in RADIANS. NOTES: The user should be aware that the equations used are not highly accurate. The error in right ascension and declination is 0.01 degrees. The Ra and Dec are in the given date's equinox. PROCEDURE: The solar position is computed using the low precision formulae given in the 1993 Astromonical Almanac. MODIFICATION HISTORY: Written by Michael R. Greason, STX, 28 October 1988. Accept vector arguments, W. Landsman April,1989 Eliminated negative right ascensions. MRG, Hughes STX, 6 May 1992. Rewritten using the 1993 Almanac. Keywords added. MRG, HSTX, 10 February 1994.
(See /usr/local/idl/lib/zastron/astro/sunpos.pro)
NAME: TEN() PURPOSE: Converts sexigesimal number to decimal. Inverse of SIXTY function. CALLING SEQUENCES: X = TEN( [ HOUR_OR_DEG, MIN, SEC ] ) X = TEN( HOUR_OR_DEG, MIN, SEC ) X = TEN( [ HOUR_OR_DEG, MIN ] ) X = TEN( HOUR_OR_DEG, MIN ) X = TEN( [ HOUR_OR_DEG ] ) <-- Trivial cases X = TEN( HOUR_OR_DEG ) <-- INPUTS: HOUR_OR_DEG,MIN,SEC -- Scalars giving sexigesimal quantity in in order from largest to smallest. OUTPUTS: Function value returned = double real scalar, decimal equivalent of input sexigesimal quantity. A minus sign on any element of the input vector causes all the elements to be taken as < 0. PROCEDURE: Mostly involves checking arguments and setting the sign. The procedure TENV can be used when dealing with a vector of sexigesimal quantities. MODIFICATION HISTORY: Written by R. S. Hill, STX, 21 April 87 Modified to allow non-vector arguments. RSH, STX, 19-OCT-87
(See /usr/local/idl/lib/zastron/astro/ten.pro)
NAME: TENV() PURPOSE: Converts sexigesimal number to decimal. Like TEN but allows vector input. CALLING SEQUENCES: Result = TENV( dd, mm ) ; result = dd + mm/60. Result = TENV( dd, mm, ss) ; result = dd + mm/60. + ss/3600. INPUTS: dd - Sexigesimal element(s) corresponding to hours or degrees mm - Sexigesimal element(s) corresponding to minutes ss - Sexigesimal element(s) corresponding to seconds (optional) The input parameters can be scalars or vectors. However, the number of elements in each parameter must be the same. OUTPUTS: Result - double, decimal equivalent of input sexigesimal quantities. Same number of elements as the input parameters. If the nth element in any of the input parameters is negative then the nth element in Result wil also be negative. EXAMPLE: If dd = [60,60,0], and mm = [30,-30,-30], then IDL> Result = TENV(dd,mm) ====> Result = [60.5,-60.5,-0.5] PROCEDURE: Mostly involves checking arguments and setting the sign. MODIFICATION HISTORY: Written by W.B. Landsman April, 1991
(See /usr/local/idl/lib/zastron/astro/tenv.pro)
NAME: TICLABELS PURPOSE: Used to display images with right ascension and declination axes. This routine creates labels for already determined tic marks (every other tic mark) CALLING SEQUENCE: ticlabels, minval, numtics, incr, ticlabs, [ RA = ,DELTA = ] INPUTS: minval - minimum value for labels (degrees) numtics - number of tic marks incr - increment in minutes for labels OUTPUTS: ticlabs - array of charater string labels OPTIONAL INPUT KEYWORDS: RA - if this keyword is set then the grid axis is assumed to be a Right Ascension. Otherwise a declination axis is assumed DELTA - Scalar specifying spacing of labels. The default is DELTA = 2 which means that a label is made or every other tic mark. Set DELTA=1 to create a label for every tic mark. NOTES: The following note applies to users of IDL version 2.4.0 or before. This bug mentioned was fixed in Version 3.0.0 If you are using the native Postscript fonts, you must first define your font with DEVICE,/TIMES,FONT_INDEX=3 where /TIMES is replaced with your font of choice. The default is Helvetica and therefore does not require the above DEVICE command. This patch is necessary if you are using IDL 2.4.0 or before, because the !X feature does not work properly using the PostScript Driver in this version. PROCEDURES USED: RADEC RESTRICTIONS: Invalid for wide field (> 2 degree) images since it assumes that a fixed interval in Y (or X) corresponds to a fixed interval in Dec (or RA) REVISON HISTORY: written by B. Pfarr, 4/15/87 Added DELTA keywrd for compatibility with IMCONTOUR W. Landsman Nov 1991 Added nicer hms and dms symbols when using native PS fonts Deutsch 11/92 Added Patch for bug in IDL <2.4.0 as explained in NOTES E. Deutsch 11/92 Fix when crossing 0 dec or 24h RA
(See /usr/local/idl/lib/zastron/astro/ticlabels.pro)
NAME: TICPOS PURPOSE: Procedure to specify distance between tic marks for astronomical coordinate overlays. User inputs number an approximate distance between tic marks, and the axis length in degrees. TICPOS will return a distance between tic marks such that the separation is a round multiple in arc seconds, arc minutes, or degrees CALLING SEQUENCE: ticpos, deglen, pixlen, ticsize, incr, units INPUTS: deglen - length of axis in DEGREES pixlen - length of axis in plotting units (pixels) ticsize - distance between tic marks (pixels). This value will be adjusted by TICPOS such that the distance corresponds to a round multiple in the astronomical coordinate. OUTPUTS: ticsize - distance between tic marks (pixels), positive scalar incr - incremental value for tic marks in round units given by the UNITS parameter units - string giving units of ticsize, either 'ARC SECONDS', 'ARC MINUTES', or 'DEGREES' EXAMPLE: Suppose a 512 x 512 image array corresponds to 0.2 x 0.2 degrees on the sky. A tic mark is desired in round angular units, approximately every 75 pixels. IDL> ticsize = 75 IDL> TICPOS,0.2,512,ticsize,incr,units ==> ticsize = 85.333, incr = 2. units = 'ARC MINUTES' i.e. a good tic mark spacing is every 2 arc minutes, corresponding to 85.333 pixels. REVISON HISTORY: written by W. Landsman November, 1988
(See /usr/local/idl/lib/zastron/astro/ticpos.pro)
NAME: TICS PURPOSE: For use in labelling a displayed image with right ascension and declination axes. An approximate distance between tic marks is input, and a new value is computed such that the distance between tic marks is in simple increments of the tic label values. CALLING SEQUENCE: tics, min, max, numx, ticsize, incr, [RA = ] INPUTS: min - minimum axis value (degrees) max - maximum axis value (degrees) numx - number of pixels in x direction INPUT/OUTPUT ticsize - distance between tic marks (pixels) OUTPUTS: incr - incremental value for tic labels (in minutes of time for R.A., minutes of arc for dec.) REVISON HISTORY: written by B. Pfarr, 4/14/87 Added some more tick precision (i.e. 1 & 2 seconds in case:) EWD May92
(See /usr/local/idl/lib/zastron/astro/tics.pro)
NAME: TIC_ONE PURPOSE: For use in labelling images with right ascension and declination axes. This routine determines the position in pixels of the first tic. CALLING SEQUENCE: tic_one, min, pixx, incr, min2, tic1, [RA = ] INPUTS: min - astronomical coordinate value at axis zero point (degrees or hours) pixx - distance in pixels between tic marks (usually obtained from TICS) incr - increment in minutes for labels (usually an even number obtained from the procedure TICS) OUTPUTS: min2 - astronomical coordinate value at first tic mark tic1 - position in pixels of first tic mark EXAMPLE: Suppose a declination axis has a value of 30.2345 degrees at its zero point. A tic mark is desired every 10 arc minutes, which corresponds to 12.74 pixels. Then IDL> TIC_ONE, 30.2345, 1, 12.74, min2, tic1 yields values of min2 = 30.333 and tic1 = 5.74, i.e. the first tic mark should be labeled 30 deg 20 minutes and be placed at pixel value 5.74 REVISION HISTORY: by B. Pfarr, 4/15/87
(See /usr/local/idl/lib/zastron/astro/tic_one.pro)
NAME: UNRED PURPOSE: Correct an (ultraviolet) flux vector for interstellar extinction. One can choose from 9 different extinction curves (or a user specified curve). Users may wish to consider the procedure CCM_UNRED as an alternative to UNRED. CALLING SEQUENCE: UNRED, wave, flux, ebv, funred, [ table, SILENT = ] INPUT: WAVE - wavelength vector (Angstroms) FLUX - calibrated flux vector, same number of elements as WAVE EBV - color excess E(B-V), scalar. If a negative EBV is supplied, then fluxes will be reddened rather than deredenned. OPTIONAL INPUT: TABLE - Scalar value describing the extinction curve to be used as described below. If not specified, UNRED will prompt for an extinction curve. UNRED assumes R = 3.1 for all curves except 2 (R=3.2) and 3 (R=3.0). Lambda Range Table 1000-34000A 1 Savage & Mathis (1979, Ann Rev) 1000-10000A 2 Seaton, M. "Interstellar Extinction in the UV," M.N.R.A.S. Vol. 187, No. 3 (June 1979) p. 73p-76p N.B. longward of 3700 A the data of Nandy, et al. 1373-10000A 3 Nandy "Studies of Ultraviolet Interstellar Extinction with the Sky-survey Telescope of the TD-1 Satellite," Astr. Ap., Vol. 44 No. 1 (Nov 1975) p. 195-203. 1000-3400 A 4 Theta 2B Orionis, Bohlin and Savage (1981) Ap. J. 249, 109. 1000-35000A 5 SMC Hutchings (1982) Ap. J. 255 p. 70 1184-3448A 6 LMC Nandy, et al. (1981) M.N.R.A.S. , 196, p. 955 1110-4400A 7 LMC Koornneef and Code (1981) Ap. J. 247, 860 1250-3448A 8 LMC 30 Dor Region Fitzpatrick (1985) Ap. J. 299, 219 1250-3448A 9 LMC non-30 Dor Fitzpatrick (1985) Ap. J. 99 User specified table OUTPUT: FUNRED - unreddened flux vector, same units and number of elements as FLUX OPTIONAL INPUT KEYWORD: SILENT - if this keyword is set and non-zero, then informational messages will not be printed. NOTES: If you wish to use a different extinction curve simply enter the name of the file containing the nonstandard extinction curve. Use record 1 for the wavelength and record 2 for the flux. The file must be floating point format. UNRED will assume R=3.1 in this case DATA FILES: The envrironment variable ASTRO_DATA (see first line of program) should point to the directory containing the data files. This line may need to be changed if UNRED is used outside of the LASP cluster. (See the procedure ASTROLIB). RESTRICTIONS: Unreddened fluxes will be very unreliable at wavelengths outside of the domain of the reddening curve (although no error message is printed) REVISION HISTORY: Adapted from the IUE RDAF November, 1988 Directory specifications generalized J. Offenberg July, 1991 Added Silent keyword W. Landsman January, 1992
(See /usr/local/idl/lib/zastron/astro/unred.pro)
NAME: UVBYBETA PURPOSE: Derive dereddened colors, metallicity, and effective temperature from Stromgren colors. Adapted from FORTRAN routine of same name published by T.T. Moon, Communications of University of London Observatory, No. 78. Can be used either interactively or called from a main procedure. CALLING SEQUENCE: uvbybeta ;Prompt for all parameters uvbybeta,by,m1,c1,beta,n ;Supply inputs, print outputs uvbybeta, by, m1, c1, beta, n, name, Te, Mv, Eby, delm0, radius, [ TEXTOUT= ] INPUTS: by - Stromgren b-y color, scalar m1 - Stromgren line-blanketing parameter, scalar c1 - Stromgren Balmer discontinuity parameter, scalar beta - H-beta line strength index. If beta is not know UVBYBETA will compute a value based on by, m1,and c1. n - Integer (1-8) giving approximate stellar classification (1) B0 - A0, classes III - V, 2.59 < BETA < 2.88,-0.20 < c0 < 1.00 (2) B0 - A0, class Ia , 2.52 < BETA < 2.59,-0.15 < c0 < 0.40 (3) B0 - A0, class Ib , 2.56 < BETA < 2.61,-0.10 < c0 < 0.50 (4) B0 - A0, class II , 2.58 < BETA < 2.63,-0.10 < c0 < 0.10 (5) A0 - A3, classes III - V, 2.87 < BETA < 2.93,-0.01 < (b-y)o< 0.06 (6) A3 - F0, classes III - V, 2.72 < BETA < 2.88, 0.05 < (b-y)o< 0.22 (7) F1 - G2, classes III - V, 2.60 < BETA < 2.72, 0.22 < (b-y)o< 0.39 (8) G2 - M2, classes IV _ V, 0.20 < m0 < 0.76, 0.39 < (b-y)o< 1.00 name - scalar string giving name of star. Used only when writing to disk for identification purposes. OPTIONAL INPUT KEYWORD: TEXTOUT Used to determine output device. If not present, the value of !TEXTOUT system variable is used (see TEXTOPEN) textout=1 Terminal with /MORE textout=2 Terminal without /MORE textout=3.PRT textout=4 Laser Printer textout=5 User must open file textout = filename (default extension of .prt) OPTIONAL OUTPUTS: Te - approximate effective temperature MV - absolute visible magnitude Eby - Color excess b-y delm0 - metallicity index, delta m0, may not be calculable for early B stars. radius - Stellar radius (R/R(solar)) SYSTEM VARIABLES: If keyword textout not used, the non-standard system variable !TEXTOUT becomes the output device indicator. Set !TEXTOUT =3 to have results directed to a file UVBYBETA.PRT If all output parameters were supplied, then type TEXTCLOSE to close this file REVISION HISTORY: W. Landsman IDL coding February, 1988 Keyword textout added, J. Isensee, July, 1990 Made some constants floating point. W. Landsman April, 1994
(See /usr/local/idl/lib/zastron/astro/uvbybeta.pro)
NAME: VACTOAIR PURPOSE: Convert vacuum wavelengths to air wavelengths, i.e. correct for the index of refraction of air under standard conditions. Wavelength values below 2000 A will not be altered. Accurate to about 0.005 A CALLING SEQUENCE: VACTOAIR, WAVE INPUT/OUTPUT: WAVE - Wavelength in Angstroms, scalar or vector WAVE should be input as vacuum wavelength(s), it will be returned as air wavelength(s). WAVE is always converted to double precision EXAMPLE: If the vacuum wavelength is W = 2000, then IDL> VACTOAIR, W yields an air wavelength of W = 1999.353 Angstroms METHOD: An approximation to the 4th power of inverse wavenumber is used See IUE Image Processing Manual Page 6-15. REVISION HISTORY Written, D. Lindler 1982 Documentation W. Landsman Feb. 1989
(See /usr/local/idl/lib/zastron/astro/vactoair.pro)
NAME:
WCSSPH2XY
PURPOSE:
To convert spherical (longitude and latitude -- sky) coordinates to x
and y (map) angular coordinates. This procedure is the inverse of
WCSXY2SPH. See WCS_DEMO for example of use.
CATEGORY:
Mapping and Auxilliary FITS Routine
CALLING SEQUENCE:
wcssph2xy, longitude, latitude, x, y, [ map_type , CTYPE = ,
FACE =,PROJP1 = , PROJP2= , CRVAL = , CRXY = , LONGPOLE = ,
NORTH_OFFSET =, SOUTH_OFFSET =, BADINDEX =]
INPUT PARAMETERS:
longitude - longitude of data, scalar or vector, in degrees
latitude - latitude of data, same number of elements as longitude,
in degrees
map_type - optional positional parameter, numeric scalar (0-25)
corresponding to a particular map projection. This is not a
FITS standard, it is simply put in to allow function similar
to that of less general map projection procedures (eg AITOFF).
The following list gives the map projection types and their
respective numbers.
FITS Number Name Comments
code code
---- ------ ----------------------- -----------------------------------
DEF 0 Default = Cartesian
AZP 1 Zenithal perspective projp1 required
TAN 2 Gnomic AZP w/ projp1 = 0
SIN 3 Orthographic AZP w/ projp1 = Infinity (>10^14)
STG 4 Stereographic AZP w/ projp1 = 1
ARC 5 Zenithal Equidistant
ZPN 6 Zenithal polynomial prop1-projp9 required, useless
ZEA 7 Zenithal equal area
AIR 8 Airy projp1 required
CYP 9 Cylindrical perspective projp1 and projp2 required
CAR 10 Cartesian
MER 11 Mercator
CEA 12 Cylindrical equal area projp1 required
COP 13 Conical perspective projp1 and projp2 required
COD 14 Conical equidistant projp1 and projp2 required
COE 15 Conical equal area projp1 and projp2 required
COO 16 Conical orthomorphic projp1 and projp2 required
BON 17 Bonne's equal area projp1 required
PCO 18 Polyconic
GLS 19 Sinusoidal
PAR 20 Parabolic
AIT 21 Hammer-Aitoff
MOL 22 Mollweide
CSC 23 Cobe Quadrilateralized convergence of inverse is poor
Spherical Cube
QSC 24 Quadrilateralized
Spherical Cube
TSC 25 Tangential Spherical Cube
OPTIONAL KEYWORD PARAMETERS:
CTYPE - One, two, or three element vector containing 8 character
strings corresponding to the CTYPE1, CTYPE2, and CTYPE3
FITS keywords:
CTYPE(0) - first four characters specify standard system
('RA--','GLON' or 'ELON' for right ascension, galactic
longitude or ecliptic longitude respectively), second four
letters specify the type of map projection (eg '-AIT' for
Aitoff projection)
CTYPE(1) - first four characters specify standard sytem
('DEC-','GLAT' or 'ELAT' for declination, galactic latitude
or ecliptic latitude respectively; these must match
the appropriate system of ctype1), second four letters of
ctype2 must match second four letters of ctype1.
CTYPE(2) - if present must be the 8 character string,'CUBEFACE',
only used for spherical cube projections to identify an axis
as containing the face on which each x and y pair of
coordinates lie.
FACE - a output variable used for spherical cube projections to
designate the face of the cube on which the x and y
coordinates lie. Will contain the same number of elements as
X and Y. Must contain at least 1 arbitary element on input
PROJP1 - scalar with first projection parameter, this may
or may not be necessary depending on the map projection used
PROJP2 - scalar with second projection parameter, this may
or may not be necessary depending on the map projection used
CRVAL - 2 element vector containing standard system coordinates (the
longitude and latitude) of the reference point
CRXY - 2 element vector giving the x and y coordinates of the
reference point, if this is not set the offset is [0,0]
This is not a FITS standard -- it is similar to CRPIX but in
angular X,Y coordinates (degrees) rather than pixel coordinates
LONGPOLE - native longitude of standard system's North Pole, default
is 180 degrees
NORTH_OFFSET - offset (radians) added to input points near north pole.
SOUTH_OFFSET - offset (radians) added to input points near south pole.
BADINDEX - vector, list of transformed points too close to poles.
OUTPUT PARAMETERS:
x - x coordinate of data, same number of elements as longitude, in
degrees; if CRXY is set, then x will be returned offset by
crxy(0). NOTE: x in all map projections increases to the
left, not the right.
y - y coordinate of data, same number of elements as longitude, in
degrees; if CRXY is set, y will be returned offset by crxy(1)
bad - vector returning index to transformed points close to pole.
NOTES:
The conventions followed here are described in more detail in
"Representations of Celestial Coordinates in FITS" by Eric Greisen
and Mark Calabretta (draft dated August 24, 1993). The general
scheme outlined in that article is to convert coordinates in one of
three standard systems (RA and DEC, galactic longitude and latitude
or ecliptic longitude and latitude) into a "native system" of
latitude and longitude. The latitude and longitude are then converted
into x and y coordinates which depend on the map projection which is
performed. Obviously, the rotation from standard to native coordinates
can be skipped if one so desires.
This procedure necessitates two basic sections. The first converts
"standard" coordinates to "native" coordinates while the second converts
"native" coordinates to x and y coordinates. The first section is
simply a procedure to rotate the coordinate systems while the second
contains the guts of the code in which all of the map projection is
done. This procedure can be called in a form similar to AITOFF, EQPOLE,
or QDCB by calling wcssph2xy with a fifth parameter specifying the map
projection by number and by not using any of the keywords related to the
map projection type (e.g. CTYPE).
PROCEDURE:
The first task of the procedure is to do general error-checking to
make sure the procedure was called correctly and none of the
parameters or keywords conflict. This is particularly important
because the procedure can be called in two ways (either using
FITS-type keywords or using a number corresponding to a map projection
type). All variables are converted into double precision values and
angular measurements are converted from degrees into radians.
If necessary, longitude values are converted into the range -pi to pi.
Any latitude points close to the of the poles are mapped to a specific
latitude of from the pole so that the map transformations become
completely invertible. The magnitude of this correction is given by
the keywords NORTH_OFFSET and SOUTH_OFFSET and a list of affected
points is optionally returned in the "badindex" output parameter.
The next task of the procedure is to convert the "standard"
coordinates to "native" coordinates by rotating the coordinate system.
This rotation is governed by the keywords CRVAL and LONGPOLE. The
transformation is a straightforward application of euler angles.
The final task of the procedure is to take "native" latitude and
longitude coordinates and convert them into x and y coordinates. Any
map specific error-checking is done at this time. All of the
equations were obtained from "Representations of Celestial
Coordinates in FITS" and cases needing special attention are handled
appropriately (see the comments with individual map projections for
more information on special cases).
Note that a further transformation (using the CD matrix) is required
to convert the (x,y) coordinates to pixel coordinates.
COMMON BLOCKS:
none
COPYRIGHT NOTICE:
Copyright 1993, The Regents of the University of California. This
software was produced under U.S. Government contract (W-7405-ENG-36)
by Los Alamos National Laboratory, which is operated by the
University of California for the U.S. Department of Energy.
The U.S. Government is licensed to use, reproduce, and distribute
this software. Neither the Government nor the University makes
any warranty, express or implied, or assumes any liability or
responsibility for the use of this software.
AUTHOR:
Rick Balsano
MODIFICATIONS/REVISION LEVEL:
1.1 8/31/93
2.3 9/15/93 W. Landsman (HSTX) Update quad cube coords, vectorize
keywords
2.4 12/29/93 I. Freedman (HSTX) Eliminated LU decomposition
2.5 1/5/93 I. Freedman (HSTX) Offset keywords / bad point index
(See /usr/local/idl/lib/zastron/astro/wcssph2xy.pro)
NAME: wcs_demo PURPOSE: To demonstrate the basic capabilities of the routines wcssph2xy.pro and wcsxy2sph.pro. CATEGORY: Mapping and Auxillary FITS Demo Routine CALLING SEQUENCE: .run wcs_demo: compiles wcs_demo and the supporting demo routines wcs_demo: run the demo INPUT PARAMETERS: none OUTPUT PARAMETERS: none PROCEDURE: This is a demo program which is meant to call the routines wcssph2xy.pro and wcsxy2sph.pro. Since the purpose of this routine is both to show what the routines can do and what the user has to do, a file is created with all of the commands needed to complete the desired operation. Wcs_demo actually executes this command file, so the user can exactly duplicate the results by simply re-executing this file. Also, this allows a user to edit an already existing file which calls wcssph2xy.pro and wcsxy2sph.pro properly and extend the file's usefulness. This demo program allows several possible tests. The first option is to simply draw a grid of evenly spaced latitude and longitude lines in a particular map transformation. Another possibility is to do a full loop, creating a Cartesian grid of latitude and longitude lines and calling wcssph2xy.pro to convert them to a particular map. Then, wcsxy2sph.pro is called to invert the process and the difference between the original and final latitudes and longitudes can be plotted. This allows one to assess the level of the numerical errors introduced by the mapping routines. A third possible option is to look at some of the map transformations and include rotations of the reference points so that a different perspective is given. COMMON BLOCKS: none PROCEDURES CALLED: SPHDIST, WCSXY2SPH, WCSSPH2XY COPYRIGHT NOTICE: Copyright 1991, The Regents of the University of California. This software was produced under U.S. Government contract (W-7405-ENG-36) by Los Alamos National Laboratory, which is operated by the University of California for the U.S. Department of Energy. The U.S. Government is licensed to use, reproduce, and distribute this software. Neither the Government nor the University makes any warranty, express or implied, or assumes any liability or responsibility for the use of this software. AUTHOR: Rick Balsano MODIFICATIONS/REVISION LEVEL: 1.1 8/31/93
(See /usr/local/idl/lib/zastron/astro/wcs_demo.pro)
NAME XYZ PURPOSE: Calculate heliocentric X,Y, and Z coordinates for 1950.0 (The positive X axis is directed towards the equinox, the y-axis towards the point on the equator at right ascension 6h, and the z axis toward the north pole of the equator. CALLING SEQUENCE: xyz, date, x, y, z INPUT: date - reduced julian date (=JD - 2400000), scalar or vector OUTPUT: X,Y,Z - scalars or vectors giving heliocentric rectangular coordinates (in A.U) for each date supplied. EXAMPLE: What were the rectangular coordinates of the sun on Jan 1, 1982 at 0h UT (= julian day 2444969.5) IDL> xyz,44969.5,x,y,z ==> x = 0.1494, y = -0.8915, z = -0.3867 within 0.001 A.U of the Astronomical Almanac position REVISION HISTORY Original algorithm from Almanac for Computers, Doggett et al. USNO 1978 Adapted from the book Astronomical Photometry by A. Henden Written W. Landsman STX June 1989
(See /usr/local/idl/lib/zastron/astro/xyz.pro)
NAME: ZANG() PURPOSE: Determine the angular size of an object as a function of redshift in a Friedmann cosmology (homogeneous, isotropic universe with zero cosmological constant) CALLING SEQUENCE: angsiz = zang( dl, [ z, h, omg ] ) INPUTS: dl - linear size of the object in kpc OPTIONAL INPUT User will be prompted for these parameters if not supplied. z - redshift of object h - Hubble constant in km/s/Mpc (usually 50 - 100) omega - Cosmological density parameter (twice the deceleration parameter q0), Omega =1 at the critical density OUTPUT: angsiz - Angular size of the object at the given redshift in arc seconds NOTES: One (and only one) of the input parameters may be supplied as a vector In this case, the output ANGSIZ will also be a vector. Be sure to supply the input linear size dl in units of kpc. REVISION HISTORY: Written J. Hill STX July, 1988
(See /usr/local/idl/lib/zastron/astro/zang.pro)
NAME: ZENPOS PURPOSE: To supply the zenith RA and Dec in radians corresponding to a supplied Julian date. CALLING SEQUENCE: ZENPOS, Date, Ra, Dec INPUT: Date The Julian date, in double precision, of the date and time for which the zenith position is desired, scalar or vector. OUTPUTS: Ra The right ascension in radians of the zenith. Dec The declination in radians of the zenith. PROCEDURE: The local sidereal time is computed; this is the RA of the zenith. It and the observatories latitude (corresponding to the Dec.) are converted to radians and returned as the zenith direction. PROMPTS: ZENPOS will prompt for the following 3 parameters if they are not defined in the common block SITE (see below) LAT,LNG - north latitude and west longitude of the desired location in DEGREES TZONE - Time Zone (in hours) of the desired location (e.g. 4 = EDT, 5 = EST) COMMON BLOCKS: SITE - This common block should contain the three scalars LAT, LNG and TZONE MODIFICATION HISTORY: Written by Michael R. Greason, STX, 14 October 1988.
(See /usr/local/idl/lib/zastron/astro/zenpos.pro)