Multi-star Guiding MaximDL Plugin

Triggered by some threads on the MaximDL yahoo group discussing whether guiding based on the average error of several guide stars would be better than relying on a single star measurement, I decided to put together a plugin to try it out.

This plugin allows the user to select the number of stars in the guider image to guide on, performing an average of the measured errors and using that average error to determine the mount correction movements. This should hopefully reduce the effects of scintillation on the guide inputs.

Jim McMillan was one of the proponents of the idea on the discussion thread and he trialed the plugin in the field and posted some results and analysis to the MaximDL Yahoo group.

Usage:
An image must be open in MaximDL in order to activate the plugins menu. Once the multiguide plugin is launched, the user selects an initial exposure duration, then an exposure is taken through the guider.

Once the user has examined the initial exposure and decided which stars will be used to guide on, the config options are completed and guiding starts.

In order to abort guiding, spin the aggressiveness settings for both the X and Y axis down to zero – the plugin will then exit.

The plugin maintains a log file, recording the individual star errors along with the mount corrections, in the file c:\multiguide.csv which is in comma separated value format for easy import to a spreadsheet like Excel for graphing and analysis.

Config options:

         Initial exposure duration = Duration of exposure used to select stars, can be longer to aid identification

         Number of guide stars = The number of stars which will be selected for averaging

         Min S/N ratio = Not currently used

         Min stars to average = Not currently used

         Subframe border in pixels = Not currently used

         Min move = Errors below this threshold are ignored

         Max move = the max move in one guide cycle

If the guide camera does not have fast full-frame downloads, it’s possible to use sub-frames:

1) Take a full frame guider exposure
2) Guider Tab, Options, Guider Settings
3) Draw a box around the stars you want to use
4) Close Guider Settings
5) Start Multistar Guider plug-in

Version history:
v1.0 - Initial release
v1.1 - Fixed signing error in star offset calculation (star runaway)
v1.2 - Correct method of detecting end of guider slew (changed to GuiderMoving from GuiderRunning)
v1.3 - Corrected declination compensation algorithm
v1.4 - Fixed declination compensation.
v1.5 - Change defaults to integer values to work better with non-English Windows.
v1.6 - Fix selection box left after star selection.

Multi-star Guider v1.6

If you download this to give it a go, please post feedback on the Yahoo group, or email me directly at: winfij_AT_gmail_DOT_com
One final note - if you have any errors, please note the exact error messages and let me know!

Regards,
John

 

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