If the filter is not specified in an observation request, the default filter specified in the user's profile would be used. Although this may be adequate for many requests, the user may wish to use a non-default filter for a given request. This is done using the filter keyword:

NGC4698; filter=R

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 R filter would be used. The names of the available filters are listed in a text file whose preparation has been previously discussed.

Specifying the number of images to take

If the number of images is not specified in an observation request, the default number of images specified in the user's profile would be used. Although this may be adequate for many requests, the user may wish to use a non-default number of images for a given request. This is done using the i keyword:

NGC4698; 6i

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 6 exposures would be taken.

The behavior of the scheduling algorithm varies with the number of requested images and the presence or absence of the timeseries keyword:

• If up to 4 exposures are requested and the timeseries keyword is absent, then either all of them will be scheduled, or, if that is not possible, none will be scheduled.

• If the timeseries keyword is present, then as many exposures as possible will be scheduled, up to the number requested. For example,

  NGC4698; 30i timeseries

  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 up to 30 exposures would be taken.

• If 5 or more exposures are requested and the timeseries is absent, the scheduler will behave as if the timeseries had been present.

Specifying the time interval between exposures of the same target

The time interval between exposures of a given target is determined by the keywords suc, mot (the meaning of these two keywords has been previously discussed) and int:

• If none of these keywords is present, the scheduler will use the keyword (either suc or mot) which is specified in the user's profile under "Type of image sequence".

• If one of these keywords is present, it will be used instead of the default keyword:
  • The suc keyword specifies exposures taken in direct succession. For example,

    2003 QF70; suc

    is a request for observations of asteroid 2003 QF70, made by the default user. The default number of exposures specified in the default user's profile is being requested, and they should be taken in direct succession. The other options for this request are all taken from the default user's profile.

  • The mot keyword specifies that the time interval between exposures be such that the target moves a specified number of pixels between exposures. Obviously, this keyword is only useful for moving targets. For example, the request

    2003 QF70; mot

    is identical to the previous example, except that the interval between exposures will be such that the motion of 2003 QF70 between exposures is approximately equal to the optimal number of pixels specified in the scheduler configuration file.

  • The int keyword serves to explicitly specify the interval (in minutes) between exposures. For example, the request

    2003 QF70; int=15

    is identical to the previous examples, except that the interval between exposures will be approximately 15 min.

Note: If the timeseries keyword is present in the observation request, the time interval between exposures may exceed the time interval specified by the keywords mot or int by more than the specified tolerance. Analogously, when the suc keyword is specified, some exposures belonging to the time series may not be taken in direct succession. This is intended to "soften" the constraints associated with the scheduling of long time series in crowded observing schedules.