Is dslr too heavy

[allcart]

The only cameras I own are Canon 5DIII's. My plan was to use them piggybacked on my ST80 with my various lenses. Alternatively, I could also attach the dslr to the ED80 directly with a T- adapter.

Now I see that lots of folks are using 1000D's and 1100D's. The 1100D comes in at 495grams and the 5DIII comes in at 950grams, nearly twice the weight.

Does anyone see a problem with this, or do you think it will be ok.

It costs too much to have it drop on the floor.

Should I get a 1100D as well, just to be on the safe side.

[GlassWalker]

I don't know about piggyback, as that depends on how stable the fixture is. One thing to note is the 5D2 and 1xxxD have different sensor sizes, so you'll get different fields of view for a given optic. On that note, you might have difficulty getting high quality to the corners of the 5D3's sensor.

[allcart]

Piggyback is ok on the ST80, so will be ok on the ED80. I'm not worried about that as I have already tested it. It hanging the 5DIII on the end of the ED80 I'm not so sure about. And yes, the 5D's are full frame. Thats another thing I know nothing about until I try it.

So another question........What difference will a full frame sensor make when imaging through the scope.?

[GlassWalker]

Just like photography, the combination of focal length and sensor size will determine your field of view. For the same optics, a bigger sensor gives bigger field of view assuming it has sufficient coverage. And also like in photography, a bigger sensor is harder to "feed" to the corners, as optical performance tends to degrade away from the centre to varying degrees.

Again I'm unfamiliar with the ED80, but basically if the focuser can hold the camera without shifting under the weight, you're pretty good to go. I've used various Canons up to a 7D on various scopes using an 1.25" eyepiece adapter and haven't had any problems mechanically.

[allcart]

7D is 820grams on a 1.25" and 5D3 is 950grams on a 2". It might well be ok then.

I won't know what sensor coverage I'll get until I can get out and try it. Unless somebody has tried it with full frame and the ED80 and can shed some light.

[drmillrace]

I have an 1100D and a 7D. I always use the 1100D on the scope. The 7D seems very heavy hung off the back of my Vixen VMC200L especially as the focus tube needs to be quite a long way out for focus. Also the 1100D is lighter to handle in the dark and a lot less money down the drain if I drop it when I trip over the cables round the mount!

I don't see any difference in image quality ut I haven't got into pixel peeping

[brantuk]

"It costs too much to have it drop on the floor."

The weight won't be a problem so long as you have the scope well balanced on the mount it will be negligible - dslr's are very light. Most folks wrap the camera strap around the finder bracket or mounting gear just in case any of the couplings fail and the camera falls off. HTH

[Spikey]

The ED80 also has a stop on the focusser tube so it can't fall out of the scope easily. Mines holds the flattener/reducer/adapter/filterwheel/ccd on the stock focusser with no problems.

The stock focussers don't seem to come particularly well set up from the factory and require a bit of tweaking to get them to stop slipping. I adjusted mine over a year ago and haven't touched it since.

I would consider using a field flattener with the lager frame DSLR's.

[allcart]

Well I set up the ED80 this morning and had a quick test on a rooftop ariel. The scope held the camera without any problems but results were dissapointing. With the end cap off the scope it seems to focus in 2 planes. I can focus on vertical lines but horizontal lines are OOF, or I can focus on horizontal lines, but verticals are OOF. I replaced the large end cap and just removed the small centre cap and it seemed to relieve the problem, BUT I cannot achieve critical focus no matter how hard I try. Also vignetting is very evident and would require substantial cropping if flats did not rectify this.

I mounted my camera onto my ST80 (piggyback style) and took the same pics with my 400mm lens +1.4 extender to give the same approx FOV and the pics were crisp and clean as expected. In this short test it would seem that my lenses will outperform the optics of the scope so I am not sure I will gain anything by imaging through the scope as intended.

Maybe if I can find out how to achieve critical focus I may change my mind, but further testing is needed.

[GlassWalker]

Sounds like astigmatism there... like Spikey suggested a field flattener may help, I think for the focus, but probably not the vignetting.

As a further thought, the test subject is relatively close here, and the optics may only be better corrected for infinity. Can you try the same test on a more distant subject?

[allcart]

Not from home. I was hoping to use the moon this morning, but it went down too quick so I used the ariel. It may be that is will work better at infinity or at least as far as the moon. I may have to wait until tonight.

I think the vignetting will be a deal breaker. The only advantage the scope has over my lenses is the f ratio at a longer focal length, but if I have to crop a quarter of the frame, I might as well just use the camera at a shorter F/L. and get higher resolution.

I trust there is no significant vignetting with a 1.6 crop sensor.