ArnaldoLopez Tonight the AMF didn’t fail! During calibration It ‘lost star’ maybe 2 or 3 times but after a while it settled and went on guiding. The only thing I don’t like is that the target isn’t in the middel anymore after all that… Not sure why… Maybe because of loosing stars? PS I lowered the aggression below 35 for both dec and ra,… that seems to work ;-)
Good to know that setting aggressiveness below 100% has removed the oscillations, as it should.
The fact that when you lose centering after you start to guide probably has to do with how much the centroid has to be corrected right after you start guiding -- i.e., take a look at your guide graph right after you start guiding, and you should see how it eventually settles down from a very large initial value. The mount is moving by that amount at the beginning of autoguiding.
As usual, check for is the backlash of the gears and any slippage in your mount.
Next, make sure that focus of the guide camera is tack sharp (don't listen to lazy people who say focusing can be sloppy). Check to see what the star size and shape is (the little inset at the top left of guide window). You want to focus until the star size is less than 3 pixels, if your guide optics can produce that. But as small as possible. I usually use a Bahtinov mask on my guide scope before each night. The smaller the star, the better signal-to-noise ratio there is (especially important for multi-star guiding).
When you start guiding, let it loop (take guide exposures) for a couple of cycles -- if guide exposure is 2 seconds, let it loop for 5 or 6 seconds before tapping on the guide button. Don't be impatient -- this is not a hobby for impatient people.
If you are using single star guiding, make sure that you pick a star that does not saturate (that little inset picture will show a flat top, with value shown at or over 255). That can move the centroid.
If you are using single star guiding, try to also pick a star whose intensity is over 90. With a number much lower than that, you could lose a star.
Try to also pick a star that is far away from hot or warm pixels.
If you use multi-star guiding, then ASIAIR will not pick a star that saturates or is a hot pixel. It typically don't even pick a star those intensity value is over 200. You still need to check the focus of your guide camera.
The guide camera plate scale can also affect everything. If you have small pixels and a short focal length guide scope, that too can affect things.
The next time there is a a large amount of de-centering right after you start to guide, just stop guiding, recenter the target in your main telescope by executing another goto, and restart guiding again (remember to start looping, and wait a bit before start guiding again). It can happen occasionally (clouds, passing airplane, the shadow of a tree branch sticking into the guide frame). But if it is consistently off centered, then you need to start checking everything, including the mount, since any problem will eventually re-surface as a guiding problem.
Chen