Digi-scoping

[hregor]

Hi Ian
I've got a Celestron C90 scope which has a focal length of 1000mm and an aperture of 90mm. I use it with my camera and a T2 adapter with limited success. It's a wonderful telescope but it's got a few limitations on a camera. Although the C90 uses a mirror, I think the same problems will apply to your scope.

Presumably you can focus on objects OK through the viewfinder. If not, the camera isn't at the right distance from the telescope. Mine has got quite a long extension tube between the scope and camera.

The major limitation is that the aperture is fixed. mine is f11, f= focal length divided by aperture, 1000/90.

You've got an aperture of 80 mm and a focal length of 480mm so it's 480/80= f6

So the only way you can control the amount of light through the camera is by varying the shutter speed and the ISO. The depth of field is very sharp on mine and will be worse on yours. Also the auto-focus won't work so you have to be very careful when focusing.

I was disappointed with the limitations on the camera and haven't stood over it to really get to grips with it, photography is a minor interest to me.

I've noticed on telescopes you can use a lens cover with a smaller hole cut in it to reduce the aperture when viewing bright objects but I've never tried it myself. This would increase the depth of field but I'm not sure about image quality.

Not a lot of help I'm afraid but I thought I'd give you my experiences in view of the lack of a response from the photographers on FC. In their defence, they probably wouldn't go near a setup like this because they realise the limitations.

Roger

Edit PS I did find this site which might be of interest http://www.forum.rnavspotters.pl/viewfo ... 2bf70fbe62 Cut and paste into Google Translate if your Polish is as good as mine, ie very bad.