Observation Windows

insgen then determines following windows (time spans).

• UP window: the time during which the entire group of targets observed in the request are above the requested airmass and are with the telescope limits.
• BEST window: the time in which the midpoint of the observation occurs when the object group transits and lasting as long as the observation.
• NIGHT window: the time when the sun is below the specified twilight value.

There are two exceptions to the above: If UTStart is present in the Request table, the BEST and UP windows begin at the specified Universal time and last the length of the observation only. If SunStart is present in the Request table, the observation BEST and UP windows begin when the sun sets to the requested altitude and last the length of the observation only.

Finally insgen calculates a VISIBLE window which is the intersection of the UP and NIGHT windows. If this intersection is NULL, an entry is made in the Skipped table stating that the request is not up tonight.