The spectrum of a reflection nebula shall be obtained over the whole wavelength range of PHT-S. Therefore, the parameter RANGE SELECT is set to BOTH. The observation is performed in staring mode because the object is too extended for the available chopper throws. A second staring observation for the determination of the background spectrum may be executed, if spectrophotometry shall be performed and features or the shape of the background are unknown.
MAXIMUM UNSATURATED SOURCE FLUX 2.5 TO 5 
m:
20 
DETECTION LIMIT 2.5 TO 5 
:
5
MAXIMUM BACKGROUND FLUX 2.5 TO 5 m: 1.1
MAXIMUM UNSATURATED SOURCE FLUX 6 TO 12 m:
40
DETECTION LIMIT 6 TO 12 : 10
MAXIMUM BACKGROUND FLUX 6 TO 12 m: 4.2
Using Tab. 13 the following exemplary S/N ratios for integration times of 2048sec can be calculated:
2.54 to 2.83:
3.46 to 3.75:
4.70 to 4.98:
5.93 to 6.63:
8.13 to 8.87:
11.12 to 11.81:
The following overheads have to be added to derive the total observing time:
time for target acquisition and slewing : 180 sec
time for instrument set-up : 15 sec
time for memory effect check dark exposure : 32 sec
time for wheel positioning (1 wheel): 10 sec
The total is 2285sec.