Canon EOS on SW ST-80?

[Apharov]

I'm planning to mount my Canon 70D on the ST-80 for tracked cluster/DSO imaging on HEQ-5. I'm aware that the image will have issues such as field curvature, chromatic aberration and vignetting, but I'd like to try it out anyway.

For this I suppose I'll need at least a T2-EOS adapter and probably also a T2 extension tube. Does anyone have experience or ideas on what would be the optimal extension tube length?

[RikM]

Something about 80mm I would expect. If you can get a t-thread extension, it will screw directly to the back of the draw tube rather than push fit. As you suggest, it won't be easy but it will be fun

[Alien 13]

Two inches is the normal length you can get the skywatcher photo adapter for this and the standard eos t ring.

Alan

[happy-kat]

My 1100d today did not need an extension tube to reach focus on the Orion ST80 but there was not a lot of focus tube travel left, not enough left to support using a barlow.

[RikM]

I found that without an extension the focuser draw tube sagged far enough to cause issues with focus. I actually use a dead Meade Barlow with the lens removed but the focuser is still racked out quite a way even with that.

[Apharov]

Thanks a lot for the quick replies! I have a couple of further questions though.

Two inches is the normal length you can get the skywatcher photo adapter for this and the standard eos t ring.

I assume the official photo adapter is designed to preserve some close (relatively speaking) focus capacity, so a 4cm would probably be enough for infinity focus?

My 1100d today did not need an extension tube to reach focus on the Orion ST80 but there was not a lot of focus tube travel left, not enough left to support using a barlow.

Are you using T2 extensions directly from the focuser threads or adapting from the 1.25" tubes at some point? If it's really possible to achieve focus with just a direct T2-camera adapter then a 4cm T2 extension would be nicely on the safe side of things

[happy-kat]

My camera has on it a T ring attached to that is a 1.25 eyepeice nose cone.

That I then inserted into the draw tube and I got focus with about 3/4 an inch to spare max on the focus tube. Admitedly I had not been able to focus on the moon but rather some trees equally not that far away but I think far enough to be a reasonable guide.

Whether our focus tubes are the same length I can't say.

I have this coupled with the T ring on my 1100d.

http://www.firstlightoptics.com/adaptors/flo-125-inch-t-mount-camera-adapter.html

[Apharov]

Thanks for the replies! I'll get the 4cm extension and report back (hopefully with images) when I get the chance to try it out.

[james_screech]

I have used a 50mm T extension with my ST80 and Canon 300D to take pictures at an air  show once. There was some vignette and some colour halos but considering the cost of the set up the pictures were reasonable.

James

[happy-kat]

I have a cropped sensor I wonder if that is why I didn't see vignette

[Apharov]

Just a quick update: the 4cm extension tube seems to have been a good length. Distant (500m or so) trees were in focus with (very) roughly 2cm focuser move. I'll let you know how it works out for actual imaging once a clear night comes by.

[Apharov]

..and the final report: imaging with the setup works better than I expected. The color fringing is rather horrible and the focuser + non-flat field makes pinpoint stars impossible, but for such a minimal scope I feel the results are pretty nice. Images can be seen in the following threads:

http://stargazerslounge.com/topic/210416-first-moon-with-sw-st-80-canon-70d/

and

http://stargazerslounge.com/topic/210417-m42-and-m81m82-with-sw-st-80-canon-70d/.