Thread: Guiding woes
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Old 27-03-2012, 12:03 PM
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gregbradley
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Join Date: Feb 2006
Location: Sydney
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4 pixel guiding errors is atrocious and would never give round stars with any scope.

It needs to be more like .2 to .4. With my PME recently at 3 metres focal length I was getting errors
up to 1.5 (very high) and still getting round stars with PEC on. It surprised me. But once it settled down
it was more like .1 to .5.

If in fact your PA is good (double check with drift aligning if any doubt) then next most likely error is imbalance.

If your scope is heavily out of balance you will get that or if there is bad cable drag.

If you are getting 4 pixel errors and your max move is 1 then your autoguider is effectively never going to do a correction as you are always outside the maximum move before it corrects.

Here is the list of guide errors:

1. Guiding is only as good as your polar alignment. So check your alignment is in fact good. Your guide errors are telling you otherwise than T-point.

2 You have bad flexure - something is very loose, guide camera, the camera itself. Is it a solid screwed adapter fixing to the scope or is it a slide in eyepiece holder type arrangement?
Is your OAG tight and no loose parts?

3. Balance. Scope must be very evenly balanced at the angle you are going to be imaging at. If the centre of gravity is badly skewed it can be
nicely balanced horizontally yet badly imbalanced at 35 degree angle. Check this.

4. Cable drag. Power cables, USB cables, can get tangled up and pull on the guide camera and cause it to be off.

5. I take it your mount is relatively level.

6. Turn PEC off in case that is not setup properly. Turn Protrack off as well.

7. Make sure your Sky X is running on the correct time and location.

8. Sometimes selecting a different star can get guide errors down heavily.

9. Are your image frames from the STi clear of artifacts? Lodestar can get a white line or a hot pixel down one side
and CCDsoft does not autodark from libraries (as far as I can tell and I have tried several times) when autoguiding.
Click on the auto button in the Autoguiding tab and see what it selects with the white square. Maybe its chosing
a hot pixel. The clue to that is the guide error does not change (being the same distance in the image every time)
and often a large error like 8 or 15.

Greg.
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