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  #101  
Old 26-04-2011, 07:36 AM
Alchemy (Clive)
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I also have come in late to the debate, given flexure was an issue I tried to sort for years I have had some experience in this.

Firstly a point perhaps missed is from exposure to exposure you have the AVERAGE for each exposure.... Ie your 10 min sub is the average for that 10 mins then the next sub is the AVERAGE for that next 10 mins, there is no magical jump.

Secondly so why do my stars appear round.... Again laws of averages, you have also to allow for atmospheric distortion, corrections within the guiding in fact any variability which will smear your image. IF the air was perfect and NO movement whatsoever and you had a perfect mount you would notice the trailing ( out of roundness) more.

Much of the elongation at times can be caused by overcorrecting in the guiding, ie overshooting left...right....left etc

So in conclusion, it's most likely flexure causing the drifting.... Try a 40 min sub to allow for more movement and this will be confirmed.

All you can do in the meantime is make all your connections as rigid as possible. Wherever you have a separate guidescope there is some flexure, it just comes down to how much.
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  #102  
Old 07-06-2011, 02:38 AM
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leinad
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..late post

Did you get past this hurdle Paul ?

I'm encountering similar issues that I believe is affected by a few things I need to eliminate and check again.

I know flexure has been mentioned with regards to the rigidity of your connections; but you have insured your cables are tied up properly ?

Cable management, cable weight and gravity may well be a factor.
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  #103  
Old 07-06-2011, 05:55 AM
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[1ponders] (Paul)
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Not entirely Dan, but its a hell of a lot better. Reducing anything that I could find that can induce flexure helped heaps and yes all the cables are bundled and secured. In some areas at times there is no noticeable movement. I still get a bit shooting to the SE at times, but very happy with the progress.
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  #104  
Old 07-06-2011, 10:29 AM
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RickS (Rick)
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I haven't noticed any movement between subs on my AP900, but I'm only at a 530mm focal length at present.

Cheers,
Rick.
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