Old 23-05-2006, 10:51 PM
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Entropy is offline
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Focsusing with a Newtonian

Hi all.
I own a Saxon 8inch Newt at f/5 and this camera
I seem to be having problems achieving focus. It seems that even when i turn the focuser all the way in, i still seem to be out of focus. Am i not being patient enough and have just missed the focal point ? or is this a probable problem with my setup ?

This was photographing at prime focus, i also own a variable length camera adapter. Could i use this with, say, a 20mm eyepiece to overcome this ? Any other ideas on what i can do to fix it (assuming it is a actual problem and not my fault)?

Thanks in advance
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Old 24-05-2006, 04:38 AM
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iceman (Mike)
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Which way is it out of focus?

ie: you haven't got enough out travel, or haven't got enough in travel?

If it's out-travel, then a spacer/extension tube might help. If it's in-focus, then you may have to move your mirror up the tube, which is common for prime focus photography with DSLR's and Newtonians.

You could use eyepiece projection using your camera adapter - it's worth a try.
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Old 24-05-2006, 07:19 AM
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Starcrazzy is offline
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Location: wollongong
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I own a saxon 8" newt.f6.I have the exact same problem with achiving focus, it seems that the focusser won't go in far enough..i have heard that moving the mirror up the tube would help but looking at my morrior i can't see how thats possible..I have orderd a lower profile focusser, the crayford one that andrew's sell..this may fix the problem, it may not..but the new focusser is a good upgrase anyway..
I hyave been able to get focus useing eyepiece projection..i used a 25 mm pl, and also a 10 mm pl worked quite well...good luck
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Old 29-05-2006, 02:29 PM
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gbeal is offline
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I would suspect that you need to get the camera closer to the primary. If you are able to hand-hold the camera and put it as close as you can to the focuser. Do this during the day, with the scope pointed at a distant object. If you physically move the camera in and out you should see the focus point. If not, point the scope at a closer object say a couple of hundred meters away, try it again. This time you may get it to focus. Superb focus is not required, just an indication that it is in focus or not.
If the closer object comes to focus, then see where this happens.For a distant (stellar) object the camera will need to move closer still to the primary/secondary. If this isn't possible with the current setup, trial it with the focuser removed. Measure how far from the tube to the camera lens mount. If this is less than the height of the focuser then you either need a shorter focuser, or the primary can be moved closer. It will need to be by the same amount. Moving the primary isn't impossible, but see which way you need to go first, and then by how much. Try and report back.
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Old 03-06-2006, 03:40 AM
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Entropy is offline
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I managed to achieve focus by taking off the eyepiece adaptor for the camera and fitting the 2" eyepiece adaptor to the focuser, it was VERY close to all the way in still, and i was pointing at jupiter with it.So i dont think it has far to go at all.

Does anyone know any links to a good low profiler crayford perhaps, or high quality R&P ?

Thanks for all your help so far guys
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