Canon 10D Crop Factor and Telescopes

SloopJohnE · Joined: 21 Jul 2004 Posts: 1 Location: Vienna, Virginia

I have a Canon 10D SLR digital body which I want to use to take astrophotos.

Because of the CMOS sensor's size, it crops off about 1/3 of a 35mm-size frame and turns my Canon Ef telephoto lenses into "longer" lenses. For example a 200mm lens "becomes" a 320mm lens, a 300mm lens "becomes" a 480mm lens, and so forth.

Therefore, which telescope in your inventory would make a good starter "telephoto lens" for astrophotography? I'd like to capture mostly the moon and some planets, but it would be nice to photograph some galaxies and nebulae also.

What are your recommendations? For example, would the B&L Discoverer spotting scope do the job? And what ISO and shutterspeed settings would give me the best results?

Stan @ Opticsplanet · Joined: 12 Jan 2004 Posts: 98 Location: Chicago, Illinois

Thank you for your interest in www.OpticsPlanet.com. Astrophotography is a very involved hobby. Exposure times on planetary objects can very on minutes or more, depending on how much detail you want to capture. A beginner telescope for this operation would need to be 5" diameter or more with tracking abilities. I would suggest something like the Meade ETX 125, http://www.opticsplanet.net/meade-ts-etx-125-at.html. You would also need the autostar imager for your computer, http://www.opticsplanet.net/meade-autostar-suite-and-lunar-planetary-imager-lpi-packag.html, so you can use your computer to follow the object.

Please let us know if there is anything else we can do for you.
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