FOCUS BREAKS (ACP users only):
  Enable focus breaks? (yes/no)                                       yes
  Interval between focus breaks (min):                                78.
  Duration of focus breaks (min):                                     3.5
  Filter to use when focusing:                                        clear

If you use a focuser which can be controlled by FocusMax, you may set the MU image acquisition script to automatically refocus the telescope at regular intervals. This section specifies the parameters related to the scheduling of these periodic focus breaks.

Note: In order to use FocusMax, you will also need to use ACP as your scripting system and MaxIm DL CCD as your camera control program.

• Enable focus breaks? If you answer yes, focus breaks will be scheduled at regular intervals during the observing run. The first focus break will always take place at the beginning of the observing run.

• Interval between focus breaks. Specify the interval (expressed in minutes) between successive focus breaks.

• Duration of focus breaks. Specify the duration (expressed in minutes) of a focus break. When you schedule your first observing run, you should make a reasonable guess about this duration. After you have executed your first scheduled run, you should examine the log file produced by the MU script to determine the average duration of a focus break. Note that if you change the parameters related to focus breaks in the MU script's configuration file, the average duration of a focus break will probably change, so you will need to adjust the value of this option of the scheduler configuration file.

• Filter to use when focusing. If you use an automated filter wheel, specify the filter to be used in the star observations during a focus break.

Aiming exposures

AIMING EXPOSURES (ACP users only):
  Enable aiming exposures? (yes/no)                                   no
  Minimum displacement which triggers an aiming exposure (deg):       35.
  Exposure time for aiming exposures (sec):                           15.
  Camera resolution for aiming exposures (High, Medium, Low):         Medium
  Frame size for aiming exposures (Full, Center):                     Full
  Filter to use during aiming exposures:                              clear
  Plate solving time (sec):                                           20.
  Duration of correction slews (sec):                                 2.3

This section may be skipped by all users except those ACP users who wish to use the so-called aiming exposures. These are special exposures taken before the actual imaging of some targets in order to correct for telescope pointing errors. If your telescope has pointing errors much smaller than your CCD field-of-view, you do not need to use aiming exposures. Users of Meade LX200 telescopes often use aiming exposures to improve their pointing accuracy.

• Enable aiming exposures? Choose yes or no depending on whether or not you wish to use aiming exposures.

• Minimum displacement which triggers an aiming exposure. The scheduler will insert an aiming exposure before the observation of a given target whenever the angular distance between that target and the previous target is larger than the minimum value (expressed in degrees) specified in this option. If this minimum displacement is set to a very large value, aiming exposures will very rarely be taken, and there is the possibility of getting large pointing errors in some images. If, on the other hand, this minimum displacement is set to a small value, pointing will probably be good on all images, but the aiming exposures will become so frequent that a sizable fraction of the telescope time will be spent on aiming exposures. Therefore, you should experiment with different values for this minimum displacement on your first scheduled runs until you find the largest value which still yields accurate pointing during the whole observing run.

• Exposure time for aiming exposures. This is the exposure time (expressed in seconds) to be used when taking aiming exposures. This should be chosen as short as possible while still allowing the detection of a sufficient number of reference stars for astrometric purposes.

• Camera resolution for aiming exposures. Aiming exposures are often taken at reduced resolution (Medium or Low) in order to minimize camera download times. You should make sure that the chosen resolution is not so low that automated astrometry using PinPoint becomes impossible.

• Frame size for aiming exposures. Users of large-format CCD detectors may wish to take aiming exposures using only the central portion of the detector (25% of the total detector area) in order to minimize download and processing times.

• Filter to use during aiming exposures If you use an automated filter wheel, specify the filter to be used when taking aiming exposures.

• Plate solving time This is a maximum (worst-case) estimated time (expressed in seconds) which will be required by the telescope control computer to perform an astrometric plate solution on an aiming exposure using PinPoint. In order to avoid introducing timing errors, when the control computer takes less than this maximum time to perform a plate solution, the MU image acquisition script will wait until this maximum time elapses before proceeding. When the control computer takes longer than the maximum estimated time to perform a plate solution, the image acquisition script will generally allow it to finish, provided PinPoint doesn't abort the plate solution due to excessive CPU time. When this (usually rare) event occurs, a small and usually harmless timing error is introduced in the scheduled run.

• Duration of correction slews. When an aiming exposure is successfully plate solved by PinPoint, the MU image acquisition script re-synchronizes the telescope with the celestial sphere based on the computed center coordinates of the aiming exposure, and then performs a short telescope slew in order to center the target in the field-of-view. On your first scheduled run, you may use a rough estimate for the duration of these correction slews. After the end of the first scheduled run, you may examine the log from the MU image acquisition script to obtain a better estimate.