When I got my set up I had funny stars and was told this is normal and guiding is not affected. Well I am not so sure. In Maxim the autoguide picks the brightest star which is often distorted. My guide errors change when the star changes shape by a pixel or so due to atmospherics or the algorithm for binning pixels or antialiasing kicks in. The mount, an Atlas is very precisely polar aligned and a centered star hardly moves in 10 minutes. Any comments or best practices appreciated. I rechecked the focusing on the wheel tonight and it did not do any good. Please realize this is producing good image, just want to optimize.
If you are having overly-distorted images off-axis, you can set a subframe in the guider settings. Once you do that, the guider algorithms behave as if the chip was smaller, and it will never see the badly distorted stars.
Thanks for the reply. Is that using the attached control panel? I see that my autoguide image is 648x488 and the funny stars are sprinkled about.. I think they are just the bright ones. I do not see where I might reduce the exposure. The track box size is 32x32.. Is the track frame set in the attached box?
http://www.cyanogen.com/help/maximdl/HIDD_GUIDE.htm#bc-1 http://www.cyanogen.com/help/maximdl/Autoguider_Settings.htm
Well, I reread all the instructions. I was taking a guider image of 2s. I changed this to 1s and the guiding errors went down. I had to change this on my CCDComander scripts, which I believe then just pass along the settings to Maxim? Changing in Maxim did no good. I guess even shorter exposures would be better for me to avoid the spikes, but I do not think I need corrections every 1s or less. It seems I can reduce the amount of change with every frame to reduce chasing the fluctuations.
I am still working to optimize this and thought I would cross-post a note I just posted up on the CCDComander Yahoo Group. Anyone with ideas here, please respond. >>>>>>>>>>>>>>> Hi Matt, I have been plugging along but have been trying to improve the precision of my guiding. My polar alignment is very good.. tiny changes after 10m. But my Tak 180ED is very fast and when I use my OAG in my STT 8300M I will get distorted stars (spikes) if I use exposures longer than 1s... could use 0.5s and would probably be better (Tak is F 2.8). I notice that Maxim makes corrections every 1s also... for me I would prefer if it just waited 3-5s before making a correction... Not clear how I can do this while I set exposures to 1s. I notice that if I turn down the guiding aggressiveness to .35 it guides better... do not need big changes as scope is already tracking well. I am trying to find best settings to avoid guiding chasing atmospherics. I can see slight changes in guide star reflected in attempts by Maxim to follow... Ideas appreciated, JY
