TAO - Image acquisition with the MU script

	File locations and telescope name
	Station data
	Basic parameters which determine script behavior
	Dome parameters
	Filter parameters
	Safe telescope position/parking option
	Image compression parameters
	CCD camera parameters
	Telescope slewing parameters
	Telescope slew limits
	Pointing corrections
	Timing tolerance/ waiting times
	Bias frame parameters
	Dark frame parameters
	Flat field parameters
	Image shifts for binned calibration files
	Weather station parameters
	Focus parameters Page 1 Page 2
	Aiming exposure parameters

Starting MU

Sequence of events
during an observing
run using MU

Timing Refinement

Collecting timing
data

Analyzing timing
data

Adjusting the
empirical timing
correction

Other Tools

Slew time
measurement script

Minor Planet Checker
query script

Etc.

Image acquisition with the MU script

Customizing the MU script (continued)

Focus parameters (continued)

minHFD, maxHFD. These two parameters define a range of acceptable half-flux diameters for an in-focus star image. minHFD should be positive to prevent the acceptance of spurious focus measurements with zero half-flux diameter; such spurious measurements have been produced on occasion by FocusMax.
useTempFocusRelation. Set this parameter to True if you wish to use a linear focus-temperature relationship defined by FocusIntercept and FocusSlope, otherwise set it to False. If useTempFocusRelation is set to True and focusSampleSize is greater than zero (so actual focus measurements will be performed during scheduled focus breaks), the focus-temperature relationship will be used to reject any focus measurement which deviates from the focuser position predicted by the relationship by more than FocusTol1 focuser steps. In this case, if all focus measurements fail or are rejected, the focuser position will be adjusted using the focus-temperature relationship. If useTempFocusRelation is set to True and focusSampleSize is zero (so that no actual focus measurements will be performed), the focuser position will be adjusted using the focus-temperature relationship. This provides the fastest way to focus the telescope.

FocusIntercept, FocusSlope. These two parameters are the coefficients A and B in the linear focus-temperature relationship

Focuser position (steps) = A + B x Temperature (degrees Celsius).

Here the temperature must be provided by a working weather station. To determine these coefficients, you should perform several observing runs on nights spanning a wide range of temperatures (ideally, the whole range of temperatures which occur at the observing site over a typical seasonal cycle). In these runs used to collect focus-temperature data, focusSampleSize should be set to a positive value, so that actual focus measurements are made by FocusMax. The focuser position and temperature for each focus measurement can be collected from the MU log files, as illustrated by the following section of a log file:

2004-07-03 04:45:29 Target: Focus Break (# 36 of 354)
2004-07-03 04:45:29   Starting image download...
2004-07-03 04:46:05   Download complete.
2004-07-03 04:46:10   Exposure saved to c:\users\PRH\040703_tel-1\images\PRH00034.fit
2004-07-03 04:46:10   Download/save time = 21.0 sec
2004-07-03 04:46:10   Camera temperature: -20.6 C.
2004-07-03 04:46:11   Using clear filter.
2004-07-03 04:46:11   Timing error: actual - scheduled = -36.2 sec.
2004-07-03 04:46:16   Temperature = 28.7 C
2004-07-03 04:46:16 Trying to focus telescope (2 measurements)...
2004-07-03 04:46:17   132 catalog stars found within search radius.
2004-07-03 04:46:23   Focus measurement #1
2004-07-03 04:46:28     Chosen focus star has magnitude 7.3
2004-07-03 04:46:28   Slewing to target: RA =  04.35211 h,    dec = -28.6209 deg,
2004-07-03 04:46:28                      az =  006.8583 deg,  alt =  82.4534 deg,
2004-07-03 04:46:28                      HA = -00.07703 h,    airmass = 1.009,
2004-07-03 04:46:28                      dHA = -01.84383 h,   dDec = +66.3456 deg,
2004-07-03 04:46:28                      dist = 071.1965 deg, MJD = 53189.19894
2004-07-03 04:46:30   Waiting for slew to end...
2004-07-03 04:47:35   Slew complete.
2004-07-03 04:47:35     Exposure time: .45 sec
2004-07-03 04:47:35     Starting automatic focusing...
2004-07-03 04:48:59     Automatic focusing successful. Half-flux diameter = 3.9
2004-07-03 04:48:59     Focus position = 2697.0
2004-07-03 04:49:00   Focus measurement #2
2004-07-03 04:49:04     Chosen focus star has magnitude 7.7
2004-07-03 04:49:04   Slewing to target: RA =  04.35791 h,    dec = -28.5342 deg,
2004-07-03 04:49:04                      az =  347.4309 deg,  alt =  82.2724 deg,
2004-07-03 04:49:04                      HA = +00.14383 h,    airmass = 1.009,
2004-07-03 04:49:04                      dHA = +00.18052 h,   dDec = +.0554 deg,
2004-07-03 04:49:04                      dist = 002.1062 deg, MJD = 53189.20074
2004-07-03 04:49:06   Waiting for slew to end...
2004-07-03 04:49:20   Slew complete.
2004-07-03 04:49:21     Exposure time: .52 sec
2004-07-03 04:49:21     Starting automatic focusing...
2004-07-03 04:50:45     Automatic focusing successful. Half-flux diameter = 3.5
2004-07-03 04:50:45     Focus position = 2704.0
2004-07-03 04:50:49 Set focuser position to 2700.5

All the focuser position and temperature data should be collected on a text file containing two numeric columns (temperature and focuser position):

28.7   2697.0
28.7   2704.0
...    ...

This data file would then be processed with program regress (or any other linear regression program) to produce the coefficients A and B in the above relationship.

FocusTol1. This parameter specifies the maximum acceptable deviation of a focus measurement from the focuser position computed using the focus-temperature relationship defined by FocusIntercept and FocusSlope. A focus measurement which deviates from the computed value by more than FocusTol1 focuser steps will be rejected. Note that this rejection process only takes place if useTempFocusRelation is set to True and focusSampleSize is greater than zero.
defaultFocus. This parameter specifies a default initial value for the focuser position. Some time after sunset (and before any calibration or science images are taken), the focuser is set to this default position provided that a (usually much more accurate) focus-temperature relationship is not enabled.
FocusTol2. This parameter specifies the maximum acceptable deviation of a focus measurement from the default focuser position defined by defaultFocus. A focus measurement which deviates from defaultFocus by more than FocusTol2 focuser steps will be rejected. Note that this rejection process will only apply if useTempFocusRelation is set to False or if useTempFocusRelation is set to True but a current temperature measurement is not available.
focusTimeOut. This parameter specifies the maximum time (in minutes) which FocusMax will be allowed to work on a focus measurement. If a measurement is still unfinished focusTimeOut minutes after it started, the script will abort it and consider it unsuccessful. This feature is useful to prevent certain situations when FocusMax will take a very long time to finish a focus measurement.
SetDefaultFocusAtStart. Set this parameter to True to focus the telescope before any calibration or science images are taken, otherwise set it to False. If useTempFocusRelation is set to True, the focuser position will be computed from the focus-temperature relationship. If useTempFocusRelation is set to False, the focuser position will be set to defaultFocus.
focusAtCurrentPosition. This parameter affects the sky position where the telescope will point at the time the focus is adjusted during a scheduled focus break. It has no effect unless focusSampleSize is set to 0. In this case, if focusAtCurrentPosition is set to False, the telescope will slew to the sky position defined by FocusHA and FocusDec before adjusting the focuser position. This is convenient when the telescope control software automatically compensates for focus changes due to altitude variations (as is the case with the SciTech telescope control software), so that focusing should be performed at a standard altitude (such as at zenith). If focusAtCurrentPosition is set to True, the focuser position will be adjusted with the telescope at whatever position it was pointed before the beginning of the focus break.
giveUpFocusIfFMGoesBad. This parameter affects the way the script will handle situations when FocusMax behaves unreasonably; such events, which have been observed on several occasions, may involve errors when creating or destroying focus control or focuser objects, setting exposure times, etc. When one of these events occurs, one may experience persistent problems in subsequent calls to FocusMax, which may be avoided by giving up all subsequent operations involving FocusMax (which may result in poor focus later in the observing run). If giveUpFocusIfFMGoesBad is set to True, all operations involving focus will be cancelled if the script notices signs that FocusMax is behaving unreasonably. If giveUpFocusIfFMGoesBad is set to False, the script will not cancel all focus operations even though FocusMax may give signs of unreasonable behavior.