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Old 27-04-2007, 04:36 PM
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x-eyed focus

I,m looking to buy a canon 400D and believe that it will be okay with my scope(Maksutov-Cassegrain) to attach directly for prime-focus astrophotography. My query is: what is the best method for focusing accurately at high f-ratios? Should I have a matte screen fitted, or astrfocuser etc, and what are the costs? Any advice would be much appreciated.
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Old 27-04-2007, 05:07 PM
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Hmmmm...
Long time ago I had that dillema with my maksutov (MTO1000) and Practica VLC3... I solved it by matte glass and home built microscope (mag ~30x) which I placed into plug-in that I sacrificed for the purpose...
In your case, I think Hartmann mask and couple of test exposiures would solve the problem.. Or built-in focus indicator confirmation, but for this you have to have special adapter (a collegue of mine has it for his 350D, he bought it from a guy in Russia and this thing basically acts as a Canon lens, enabling manual focus confirmation functionality.
If you are interested I will ask him on Monday and let you know where he obtained this (it was $50 or so).
in the meantime, have a look at http://www.bobatkins.com/photography...g_adapter.html
or google a bit :-)
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Old 27-04-2007, 05:35 PM
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Thanks Bojan, I would be interested in any info., much appreciated.
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Old 27-04-2007, 06:33 PM
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Actually, now that I had a better look at the website I gave you, I realised this is what I was inteding to point you to :-) This adapter (dark little plastic thing with contacts ) is what he has, it is supposed to be glued to the lens adaptor that attaches to your maksutov.
Only, I think he paid less, because he dealt directly with this guy, and not via Rugift.com
Anyway, Monday 30th is not that far in the future..
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Old 30-04-2007, 09:32 AM
tuc_47 (Del)
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Details on obtaining the "dandelion" chip

You can get it directly from Viktor Lushnikov info@filmprocess.ru

It was US$50 for one plus postage. By the time I paid Western Union (the only payment method) it cost all up about A$90 and arrived within a week.

Here's an article.
http://www.digit-life.com/articles2/...ge/oduvan.html

btw - I haven't attached it to my T-ring yet.
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Old 30-04-2007, 03:54 PM
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Thanks, Tuc-47 and Bojan. I would have been googling all day without your help.
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Old 30-04-2007, 04:13 PM
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You are welcome :-)
Now, the only question to answer remains how good this feature is for our purpose... It probably works reasonably well on bright objects with a lot of contrast (Moon terminator, Sun on the edge or near sunspot (through sun filter of course)) and possibly on bright stars.. Perhaps you should experiment with afocal setup (50mm lens and low power eyepiece) to confirm the suitability before talking to your ministry of finance :-)
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Old 01-05-2007, 11:58 AM
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Bojan, I saw one website(ASSIGNobservatory) that discussed using t-adaptors that can accomodate an eyepiece, and radial guiders. Do all adaptors accept eye-pieces, and where does the radial guider fit? Presumably these still wont help with focussing! What about a Hartmann mask/Scheiner disc? Also, I've heard that the Canon400D doesn't yet have a matte screen option.
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Old 01-05-2007, 05:09 PM
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I do not know about that website...
T adaptors may or may not recive eyepieces, but I am not the right person to answer this, because I never bothered to buy one, my friend made it for me instead and of course it does :-)
Radial guiders, I think, can not help with focussing...
Hartmann mask is a standard item for the purpose, it works with bright stars and once you have focus, you leave it alone for the whole imaging session.
I am using it with my B/W quickcam.
Probably Canon does not use matte screen because it has autofocus (or manual focus, with confirmation ... ). I am also looking to buy that camera, so far it seems it is the best option for all purpose camera, including astro photography :-)
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Old 02-05-2007, 08:10 PM
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I agree, the canon 400d seems a good all-rounder, and to be honest I'll probably do more terrestial photography. Had a look at one at the local camera shop and I thought it was pretty good, and a reasonable price. I travel around the Swan Hill area a lot in my business, especially the back roads around the Mallee, and some of the wild life( Wedgetail's sitting on the side of the road-man are they big, goannas, roos, tawny frog-mouth owls) and some of the scenery and sunsets are awesome. Often go spot-lighting at night and the stars out in the Mallee seem to be right on top of you, they appear that bright and clear. Am planning to do some Winter overnight camping out there, and of course take my telescope, and hopefully a camera. The ministry of finance suffered a loss, my daughter bought a car and good old dad helped out.
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