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Autogiding needs to be tuned for a given setup. A guide scope would be one setup, an OAG another.
Assuming everything is tight and no looseness or flex and the camera is well secured etc etc (the basics are being done properly) then the next step is getting the settings right.
Can you post your exact procedures for setting up the OAG guide camera in software?
The usual problem with an OAG and I take it from your post you are past that is to get the stars in focus. I find if the stars are not close to being in focus they disappear off the screen and it looks like the OAG is not working. So assuming you have a focused guide star then it just leaves the autogudiing setup.
00. Polar alignment must be close to perfect. Autoguiding is not a substute for excellent polar alignment. Most autoguiding problems in my experience are actually not good enough polar alignment. So drift align or use software to achieve an accurate polar alignment before bothering with anything else. Same with balance and cable drag. Get your scope well balanced and sort cables so no drag.
0. Try to have your guide camera square to the scope ie not an angle so north on the image is straight up. That way the software does not need to correct for the camera being rotated.
1. You will need auto dark subtract with a Lodestar as it can have hot pixels that the software mistakes for the guide star. I think these software detect the brightest point in the framed image and it is assumed that is the guide star. Without a dark subtract the relatively noisy Lodestar needs a dark subtract, especially in summer now its getting hot. So setup a master dark for your Lodestar and set up Maxim to do a dark subtract on every image. If you don't you will get erratic guiding where the software will do massive moves to try to correct for a hot pixel instead of the guide star. I have seen it do this many times whenusing CCDSoft which will not do a library dark for autoguiders.
2. Callibrate the autoguider. The amount of a correction needed for the
mount to shift to correct for the guide star moving needs to be calculated as a scale. Also non squareness of the guide camera needs to be accounted for if its not done per the first step above.
3. Guide exposures vary with mounts. Well polar aligned and low PE mounts go better with longer exposures like 4 to 6 seconds but a mount with high PE needs fast corrections like 1 second guide exposures. Same with aggressiveness. I would start at about 7 and I reduce that to 5 or so when the mount is well polar aligned and PE is low.
4. Are you using PEC? This will help and you will see larger guide corrections because of it but the stars will be more round.
5. I set min/max move as I don't want a moment of bad seeing sending the mount into an overcorrect. I usually set mine to about min .1 and max 2.
6. Select a suitable guide star. Not too bright and fat and not a double star. Not a star with another star of similar brightness just outside the framing box. That could easily drift into the field of view and get confused with the guide star. Also it will mess up callibration where the mount moves, takes an image, moves again so stars just outside the framing box will move into the frame and mess things up.
7. I often recallibrate when on the other side of the meridian or have slewed a long way away from the last point of callibration. Not an important point but I think it reduces guide errors a tad.
8. The first thing I do if I get too large guide errors is to pick another guide star. Perhaps one a bit tighter. Often the errors drop enormously just doing that.
Greg.
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