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Old Mar 17, 2004, 11:38 PM   #1
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Default T-Rings, Vignetting and adapters oh my!

Pretty soon, I'm going to have a Canon EOS, D30 camera, and I'd like to use it with a Celestron Nexstar 8 GPS telescope.

The D30 takes Canon EF lenses.

Could somone please help me by telling me what I need and where I can find it?

-Thanks
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Old Mar 18, 2004, 11:41 AM   #2
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You will need the Celestron T-adapter 9333-A available from Celestron, and a Standard Canon EOS T- mount which is available from any Canon dealer.

The "T" adapter connects to the telescope and the "T" mount attaches to the camera. The two connect as if you were connecting a lens to your camera.

Once you have this combination, the telescope acts as a very large fixed focal length lens. You do all focusing with the telescope and must experiment to get proper ISO and shutter speed combinations for your subject. The aperture is fixed by the telescope.

Best regards,

Lin
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Old Mar 18, 2004, 11:44 AM   #3
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That there has to be the best answer ever! Thanks a heap! You obviously know your stuff!
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Old Mar 18, 2004, 11:50 AM   #4
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one more thing, I went to celeston's site, and I don't see a 9333A, but I see this:

Item #93633-A, T-Adapter, (C5, 8, 9 1/4, 11, 14)

is that what you meant?
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Old Mar 18, 2004, 7:35 PM   #5
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http://www.celestron.com/prod_pgs/tel/nx8gps.htm

Click on link above, then click on "recommended accessories" (top right of page) then scroll down to "T" mount..

Best regards,

Lin
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Old Mar 21, 2004, 6:43 PM   #6
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another question; do I need a focal reducer?
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Old Mar 21, 2004, 7:43 PM   #7
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It depends (focal reducer) on what you expect from the camera. The "effective" focal length will be the true focal length of the tube times the "crop factor" of your digicam.

For a Canon 10D, D60, D30, D300 (Digital Rebel) it's 1.6x. For a Nikon D1, D1H, D2H, D1X, Fuji S1, S2, it's 1.5x. For a Canon EOS-1D, EOS-1D Mark II, All Pro Kodak bodies except the 14n - 14x it's 1.3x. For the Contax 6 megapixel, Canon EOS-1D or Kodak 14 megapixel bodies it's 1.0.

So if your base focal length were 1250mm, with a Canon EOS-10D you would get 2000mm effective.

Figure your crop factor and native focal length and if it's too much for the intended job, the a focal length reducer is in order. Otherwise you don't need it.

Best regards,

Lin
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Old Sep 6, 2006, 11:41 AM   #8
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Dear Lin,
I have a Canon S1 IS. I need to icnrease the range to shoot birds. sould I go for tele converters or wiould a strong telephoto lens suffice.
regards
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Old Sep 8, 2006, 12:41 AM   #9
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Hi Nathan,

Since you can't change the lens, your only viable solution is to add a monocular type telephoto adapter. The problem is that with the long optical zoom, these don't work very well because of excessive vignetting. I really don't know of a good solution to get you much more focal length. Sorry....

Best regards,

Lin




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Old Sep 8, 2006, 1:39 AM   #10
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Hi Lin,
I am told the 2x / 3x tele converters work well only at the extreme zoom position. at lowe zoom elvels they give problems. If that is so, it is not a problem for me since I am to use it only at max zoom.
Alternately can u suggest a caemra - lens combination for birding, keeping in mind that I am a student.
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