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Exposure Parameters

The next section concerns the exposure parameters:

# -speed used during slewing

slew_spd             25                          # speed relative to max. (in percent)

slew_spd_alert       100                         # speed when initiating alert response

# -definitions of exposure lengths in seconds:

tshort               5                           # short exposure length

tmedium              20                          # medium exposure length

tlong                60                          # long exposure length

max_moon             0.50                        # max moon fraction to run a tlong;

                                                 # otherwise tmedium is substituted

# -cuts on angular positions of frame, sun and moon

min_elev             20.0                        # min elev. for frame center (in deg.)

sun_elev             0.0                         # max elev. of sun (in deg.)

moon_dis             30.0                        # min distance to moon (in deg.)

First, the slew speeds are specified. For both normal slews and alert slews, the percentage of the maximum (as defined in schierd.conf) is given.

Next, the exposure length parameters. We have decided on standard values of 5 seconds, 20 seconds, and 60 seconds. Normal patrol operations use long (60s) exposures. However, when the moon is bright, the sky brightness can nearly saturate a long 60s exposure. Therefore, when the moon is up at its fraction is greater than max_moon, the exposure lengths are automatically stopped down to tmedium. Note, the system will not automatically take long exposures when the moon is brighter than that specified, either for regular sky patrols or for burst responses.

Finally, general cuts are made on what the telescope will image. A field must be at least a certain altitude above the horizon: an azimuthially-dependent number due to the elevation angle of the Declination limit switch on the mount yoke. Simply put, the telescope cannot swing too far opposite the pointing axis, or it will hit the yoke. In other directions, it can image closer to the horizon. The sun must of course be below a designated negative altitude, and the field must be at least 30${^\circ}$ from the moon. These cuts are usually only relevant for prompt burst responses. More stringent cuts can and should be used for normal schedule items.

next up previous contents index
Next: Sky Patrol Parameters Up: astrod.conf Previous: Daemon Parameters   Contents   Index
Rotse Pager 2003-05-20