Connecting eyepiece to camera lens?

[big bedroom]

I've got a couple of old prime lenses with M42 fittings I'm gonna try out with my ccd camera, hopefully tonight if it stays clear!

I've got the spacing sorted for the camera. Ive tried putting my diagonal and eyepiece on but can't get it to focus.

Is there a way of calculating back focus for this? I was hoping to use my 25mm eyepiece just to help me align the mount without the need for my scope.

[Peter Drew]

I would have thought to try out your prime lenses and CCD camera would involve just that, the CCD camera and the lens. I'm not sure why you plan to add a diagonal and an eyepiece, doing so would need considerable extra IN focus. Unless I'm completely misunderstanding your plan. 

[big bedroom]

The eyepiece was just for for using the lens as a telescope, for aligning the mount and finding my target before I attatch the camera. I've got the lens mounted on a dovetail and thought I might be able to use it instead of a scope. I've never polar aligned just using the camera and would imagine it to be quite tricky.

[ronin]

The focal plane of the prime lens will be very close to the end of the actual lens the image plane of the eyepice has to coincide so a diagonal will hold the eyepiece too far away. You will almost exactly have to get the eyepiece at the same position as the camera/ccd sensor. If the optics are similar to a plossl then I think the barrel of the eyepiece will have to actually fit inside the rear opening of the prime lens.

Glad Peter asked this as I read the post hours ago and could not work out what you were trying.

[big bedroom]

I probably didn't explain it that well!

I'll try that tonight, cheers. Just trying to make an ultra portable set up while I'm saving for a small apo!

[D4N]

If you have the original camera you should be able to infer the focal point from that. The focal point will be where the sensor / film is. On my DSLR it is actually marked on the body of the camera with a small white line.

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