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Old 29-03-2012, 06:22 PM
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bmitchell82 (Brendan)
Newtonian power! Love it!

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This is flexure at its best and how to fix it!

http://brendanmitchell.net/?p=365

This is my take on the situation regarding polar alignment and guiding

http://brendanmitchell.net/?p=386

I think also to add to what James has already said, with guiding though a On axis Guide scope, when you pick a star it is X distance away from the imaging plane and hence pulls a different star. if you put a pin though a piece of paper the pin does not move the rest of the paper around the pin moves.

By default as the telescope tracks across the sky the image rotates with it and hence keeping it in the same spot and orientation. If your polar alignment is out the scope is on a different arc across the night sky to the star and eventually will get pulled away while your guide star stay's realitive to the guide scope!
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  #22  
Old 29-03-2012, 10:24 PM
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alistairsam
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Hi Brendan,
I agree an OAG is superior, but for backyard imaging, I might need a camera that's more sensitive than a qhy5 or ssag, so i'll have to make do with what I have at the moment.
I didn't really understand your explanation, but as you'll pointed out, my polar alignment could be the root cause here.
skies are clouded up tonight, so will try again later, this time using my main scope for polar alignment.
thanks
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  #23  
Old 29-03-2012, 11:18 PM
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bmitchell82 (Brendan)
Newtonian power! Love it!

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It took me ages too to figure it out because i had the same issue for ages My guide star stayed still like a lizard on a rock. my image looked like it had drank a bottle of Jack daniels!!!!!

Also you don't need a super sensitive camera for it to work my dear friend! an Orion Starshoot auto guider works for a friend of mine with a 120mm refractor, My DSI II works on my scope no problems.

OAG's Are not hard, they aren't magical, but you do need to think about what you are doing! Also you need to have an idea about what the light/light path is doing! Paper and a pen/pencil are amazing things for figuring it out quickly.
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