The moon avoidance radius is a parameter used to prevent observations from being made too close to the moon, which could result in unusable images. If the moon avoidance radius is not specified in an observation request, it is computed from the default moon avoidance radius at full moon specified in the user's profile, using an algorithm which has been previously discussed.

The moon avoidance radius may also be explicitly specified using the keyword moondist:

NGC4698; moondist>35

This would be interpreted as a request for observations of NGC4698, made by the default user. The observations would be carried out using the default options specified in the default user's profile, except that the moon avoidance radius would be 35 deg.

Notes:

1. The moon avoidance radius specified using with keyword moondist refers to the night when the observations will take place, not to the full moon (as is the case for the default moon avoidance radius at full moon specified in the user profiles).

2. The avoidance radius only takes effect when the moon is at an altitude greater than -5 deg. This allows certain observations to be made at distances from the moon which are smaller than the avoidance radius, if they can be carried out while the moon is below altitude -5 deg.

Specifying a request identifier

It is possible to "label" an observation request using an identifier up to 8 characters long. This makes it easier to identify which scheduled images are part of the same observation request. For example, the request

NGC4698; #0035A

would be labeled with the identifier 0035A.

Notes:

1. Request identifiers should start right after the #character and should not contain blank spaces.

2. If you use ACP and the MU image acquisition script, the request identifiers will be written to the REQUEST keyword in the FITS headers of the resulting images.

Specifying an observing window

Although in general it is best to leave to the scheduler all the decisions about when to carry out an observation, there are situations when the observations should be performed during a specified time window, which may not correspond to the time when the target is best placed for observation. For example, if one wishes to observe the eclipse of a binary star system whose start and end times are approximately known, it would make sense to specify the observing window explicitly.

The observing window may be specified using the keyword t. For example, the request

NGC4698; t>030517-19:37 t<030517-20:39

specifies an observing window extending from 19:37 UT to 20:39 UT on 2003 May 17. It is also possible to specify only the start or only the end of the observing window, as in

NGC4698; t>030517-19:37
NGC2537; t<030517-16:00

The first request specifies that observations of NGC4698 be made between 2003 May 17, 19:37 UT and the end of the scheduled run at the observing station. The second request specifies that observations of NGC2537 be made between the beginning of the scheduled run and 2003 May 17, 16:00 UT. The start and end times of a scheduled observing run may be either automatically computed using the maximum sun altitude parameters in the scheduler configuration file, or specified by the user when the scheduler is run.