Page History

...

The script normally stops if an acceptable star image is not available, either during acquisition or at any focus step, following retries. The conditioning flags setting causes all focus sweeps to run unconditionally to the end; however the focus setting is restored to focbase at the end regardless of results- this mode of operation merely updates the focus log.

Aborting a Focus Run

A focus run may be aborted with Stop Series  button.

1. Open LMI Control view.
2. Push the Stop Series button on the top row.
3. wait some seconds, and the LOIS log should indicate the script is aborting.
4. The script will set the focus back to the value of focbase.

The focus run can also be aborted as it has in the past, with ./abscript:

, which also allows a focus plot to be made. 

A Few Error Messages You Might Get (Lois Log, Level_11)

• Unknown flag xxxx  (bad flags argument)
• x: not a number (also for bad exptime, bin, focbase, focstep and y arguments)
• Focus script sees invalid inputs, returning ..   (result of bad numbers)
  
• Selected  x  (Y)  coordinate is off array or too near edge (could be a result of confusion about binning)
• Exposure time is out of range  (see longexp flag)
• Star very faint. near bias level, not adjusting etime (what you get for instance on a box with only background)
• Star too bright, could not adjust etime given adjustment limits (these limits are currently about a factor of 2- similar message if star is too faint)
•  Star too bright, maxpxl saturated (actual saturation, etime will not be recomputed- several variants on this message)
  
• Saturation of subframe (this is caused by bright background or a very bright star on the same row- related to ccd firmware bug)
  
• Try again, clouds may be involved (if a star that had been in brightness range is now out of range, unexpectedly)
•  Focus Script Stopped by User  (You hit the Stop Series button to abort the focus)

•  This parabolic fit focus is below the bottom of the range and rejected  (or above top of range- not a failure, but the focus was off center and a fit solution would be unreliable)
  

Aborting a Focus Run

A focus run may be aborted with Stop Series  button.

1. Open LMI Control view.
2. Push the Stop Series button on the top row.
3. wait some seconds, and the LOIS log should indicate the script is aborting.
4. The script will set the focus back to the value of focbase.

The focus run can also be aborted as it has in the past, with ./abscript:

1. Go to the home directory for obslemi in the console where you started LOIS.
2. type ./abscript
3. wait some seconds, and the LOIS log should indicate the script is aborting.
4. The script will set the focus back to the value of focbase.
5. now type ./abscript clear; if you fail to do this the focus and other scripts will abort immediately on startup.

...

Because of the save flag, there will be a subdirectory of the data directory called 05:13:12

with filesfiles

each of which is a subframe image for the corresponding focus step.

Bugs

• The script may still occasionally throw TCL errors (ugly multi-line error messages with UI popups). These should be reported with the time of occurrence.

• The script may still occasionally terminate without a clear indication that it has completed, or whether it succeeded or not.

• It would be extremely helpful if the LOIS analysis measured image ellipticity and this were logged and displayed during focus runs.

• The LMI version of focus can't adjust the filter (even though LMI LOIS can, now).

• The 'fom' ratio is peak/flux- it would be better to use peak/(flux*etime). This could only affect the focus outcome if the etime varied during the sweep, which is possible with the exposure time adjustment. In practice this rarely happens, because the adjustment is already done in acquisition.

• On LMI, the instrumental magnitude increases a bit at the wings of the focus sweep- almost certainly means the object apertures for photometry are too small.

• The acqtry parameter is not honored.

each of which is a subframe image for the corresponding focus step.

Bugs

• The script may still occasionally throw TCL errors (ugly multi-line error messages with UI popups). These should be reported with the time of occurrence.

• The script may still occasionally terminate without a clear indication that it has completed, or whether it succeeded or not.

• It would be extremely helpful if the LOIS analysis measured image ellipticity and this were logged and displayed during focus runs.

• The LMI version of focus can't adjust the filter (even though LMI LOIS can, now).

• The 'fom' ratio is peak/flux- it would be better to use peak/(flux*etime). This could only affect the focus outcome if the etime varied during the sweep, which is possible with the exposure time adjustment. In practice this rarely happens, because the adjustment is already done in acquisition.

• On LMI, the instrumental magnitude increases a bit at the wings of the focus sweep- almost certainly means the object apertures for photometry are too small.

• The acqtry parameter is not honored.

• Changing the focus takes too long, because it is being run open loop; defining when a focus offset move is complete turns out to be tricky.
  
  
• There is a bug in the CCD firmware that will cause anomalous saturation artifacts to appear on the left hand part of a subframe (given an A amplifier readout) either in a bright background situation (twilight or near the Moon) or if a star that is considerably brighter than the star being used for focus  is located to the left of the focus/acquisition subframe. If the pixels of the artifact intrude into the focus/acquisition analysis box, these will be picked up instead of the star and usually cause a focus failure. The size of the focus/acquisition subframe has recently been increased, without expanding the analysis box size, which has substantially mitigated the problem.  It's now possible to focus within a few degrees of the Full Moon.  Changing the focus takes too long, because it is being run open loop; defining when a focus offset move is complete turns out to be tricky.

LMI Definitions Applicable To The Focus Script

...