#1  
Old 02-10-2008, 09:26 PM
helioz (Erwin)
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Location: Wodonga, Australia
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DSLR Camera can't reach focus

This a probably a real silly question, but it's got me stumped.

I'm trying to take my first steps in astro photography using prime focus.
Got myself an adapter to fit my EOS450D, put it on, plug it into the focuser.
The problem appears to be that I can't get the focuser in close enough to reach focus.
Compared to with my SPC9000 webcam, it appears the focal plane of the EOS405D is 50mm further back, hence the problem.
I tried this on another telescope - same problem.

My questions relates to the adapter:
Are all camera adapters the same or do some adapters get the camera closer in to the focuser?
Has anyone else experienced the same problem? If so, how did you solve it?

I don't really want to make another tube for my newtonian with the focuser nearer the mirror - I'm hoping that the camera adapter is to blame.

Any help and comment would be appreciated.


Many Thanks
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Old 02-10-2008, 09:58 PM
Ian Robinson
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Move the primary mirror up a tad over 50mm

or

get a new (low profile) focusor that will allow you to rack in the required distance.

You didn't say how tall the focusor is when fully racked in.

Maybe you could post a picture of your focusor and the adapter so we can all see, the above are what I do. My 10" f4.66 newt is being rebuilt to take into account a new low profile crayford, and a Esyguider with a DSLR or SLR on the business end of it.
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Old 03-10-2008, 04:40 AM
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iceman (Mike)
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What telescope are you using?

If it's a newt, then yeh - Ian's right.
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Old 03-10-2008, 07:37 AM
helioz (Erwin)
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The scope is a 5" newt - we built them at our local Astronomical Society.
From memory, we positioned the focuser so the focal plane is in the middle of its adjustment range.
The focuser is only a plastic cheapy and its adjustment range would be something like 80mm.

Moving the primary is probably the quickest (and cheapest) way to fix my problem.

Thanks for your help
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