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Autoguider settings
I thought I'd pass on some testing I did last night with CCDsoft autoguiding.
I was using an ST402ME on a MMOAG through my 2939mm focal length Planewave CDK17. So accurate autoguiding becomes critical over about 600mm in focal length and harder longer than about 2 metres.
The mount is a Paramount ME.
I used Pempro's polar alignment wizard and I found it quite use friendly and not too complex. It got the mount very accurately polar aligned. It has a nice drift alignment feature where it plots the autoguider errors in real time and projects forward a long channel that shows the trend of the errors and how far off from perfect it is. You then adjust your mount in real time and it then replots and reprojects the trend of the errors (they move around a bit due to PE and seeing etc) and after 10 minutes of this you can get the adjustments really close.
So my polar alignment was very close, not 100% but very close.
I then did a new PEC run and that helped lower errors.
I tried various exposure times for the guider, aggressiveness settings and min/max move allowed.
In the end what seemed to be ideal and got the lowest errors most consistently was:
Seeing was quite good so this may vary in poorer seeing, probably by needing slightly longer exposures to let the seeing settle before corrections:
3 second guide exposures at 2x2 binning (1x1 binning may give slightly better results but only with a bright guide star)
aggressiveness set to 8
min move .01
max move .60
range of errors was from 0.00 to .80.
It also helped by updating the time. My computer was about 15-20 seconds off. Amazing but it did make a difference.
The idea of min/max move was watching the errors the usual typical error in X was more like about .05 to about .4 with a median probably about .25. So anything about .5 or larger then must be a blip in the seeing or a bit of PE that got through or some other factor like tube flexure. I didn't want the mount correcting for a false error as that would be overcorrecting for something that was a one off brief error that had already occurred.
When I use my Tak NJP though I find 1 second exposures always got the best results unless the seeing was really poor and even then 2 seconds was best. Aggressiveness I would turn down to 5 but I needed a good polar alignment for this to work.
Autoguiding at 330mm focal length of the guide scope in 2x binning and the ST402 then I would get errors from .00 to about .4 with the median about .2.
I thought I would pass this on as autoguiding data is hard to find.
Greg.
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