40D + astrophotography ....

<p>Hi folks</p>

<p>Merry Christmas! I've had an 80mm refractor telescope for a few years now. It has an equatorial mount with an electronic drive. It's been very under-used almost since i bought it but now i'd really like to attatch my EOS 40D to it and give a bit of astrophotography a go .... I've got a T-ring for my 40D and a T-adaptor to connect to my telescope .... I'm not sure about doing long exposures for a while yet, even though i've got the motor drive, but i am really keen to try some lunar photography, maybe some planetary and bright star cluster imaging .... What i really am anxious to be re-assured about is the actual connecting of camera to telescope, i have read on the internet that you can get error readings because the camera isn't able to detect the apperture setting .... This issue (?) really puzzles me because i've seen so many astro images taken with a 40D, so i am accepting that a 40D can be connected to a telescope and can certainly take impressive images but am just wishing to be exactly sure as to how i properly connect my 40D to my refractor? </p>

<p>After that i just need advice about prime focus astrophotography with my 40D, eye-piece projection, shutter-speeds, moon filters and whether a Barlow lens will be of any use to me in conjuntion with a DSLR? </p>

<p>Hope someone can advise me in some way please .....</p>

<p>Kind regards<br>

Donaldo</p>

<p>You should just be able to snap it together, and set the 40D to Tv (or M) and set a proportional shutter speed (proportional to the FL of the telescope to minimize starfield (or lunar) movement to optimize your exposure). Aperture is ignored by the camera since there is no electrical connection. I'm not to familiar w/ the T-adaptors, (since I don't spend enough time doing astrophotography!) but the camera settings should be the same for virtually any manual setup.</p>

<p>The last time I shot the moon, I was @ ~1/10 second @ iso400 on the 5D2 (through a friend's 4" homebuilt reflector on an adaptor built out of an EOS body cap), and got decent results, but the specifics really are going to be dependent on a variety of conditions (the moon was pretty dim that night). </p>

You'll be fine and don't worry about any camera errors it just won't be able to control a aperture but you'll be in manual mode any way.

A few summers back I bought a used 1970's celestron C8(?) for $400 and coupled it to a 40d with a t-mount. Here is one of the first

shots:

Moon Photo w/40D: http://www.amazonbeach.com/PhotoVideo/AmazonBeachGallery/slides/20090602222448_40D_IMG_6724.html

The above shot is a full field of view, I wish the old C8 had been just a bit shorter to get all of the moon in one shot. So working with

camera directly coupled to a telescope, especially a crop body might be a bit confining for moon shots depending on the focal length

of the telescope. The other thing I remember is that the aperture of that telescope was like f10 so not much light getting through to

the camera. It was fun but not my cup of tea so I sold it again.

Some of the coolest images I've seen have been taken with the EF 135 f2 L. I think the camera and lens are piggybacked on a

refractor with a drive and tracking scope.

One thing I remember being especially difficult was focusing - even with live view! Actually, live view was awesome to have,

especially with the 10x view. But the the telescopes focusing mechanism just wasn't fine enough. Also, I don't think a reflector scope

was that good for planets so I think you'll be happy you have a refractor until you really want to start gathering some serious light and

need a really big mirror.

Another thing I remember reading about was drive types. I think the (german) equatorial mounts were the more recommended style

for long periods of precise tracking.

<p>I think you may be disappointed. Most 80mm refractors are inadequate for the kind of thing you propose. The f-number is just too large. Worse, the tripod, mount, and drive are awfully flimsy on all but the very high-end models. One thing that you might try is to rig a way to attach the 40D and an ordinary camera lens to the telescope tube. The telescope simply provides the pointing and drive. Any camera lens is superior to the simple doublet of you telescope. Pay particular care to balancing the camera on the telescope. If you can make that work you might get some wide-field images that you'll enjoy. Get the telescope polar-aligned and try exposures of several minutes. I don't mean to discourage you, but astro-photography is tough.</p>

<p>Joe</p>

<p>connecting a camera to the telescope optics is pretty dicey because the eyepieces slide into place and if they lock at all it's via a tiny screw.</p>

<p>There is a lot of info here on astrophotography:</p>

<p><a href="http://www.astropix.com/HTML/I_ASTROP/TOC_AP.HTM">http://www.astropix.com/HTML/I_ASTROP/TOC_AP.HTM</a></p>

<p>Joe, your comment makes no sense. You say the f ratio may be too large...yet this is precisely what he'd need for lunar work.</p>

<p>Donald, what is the focal length of your scope?</p>

<p>Hey Dave</p>

<p>Sorry, i haven't been back on Photo.net for a few days .... I've got a 600mm f7.5 telescope, an Orion optics ED80 ..... </p>

<p>Cheers<br>

Donaldo</p>