Hi Andrew
I don’t have any direct experience of the set up your will be using, but I have some experience in connecting a consumer (stills) ccd camera to my ‘scope for afocal astrophotography. The camera used was Minolta DiMage 7Hi which had a fixed 28-200mm zoom lens, i.e. the lens does not come off the camera, unlike a DSLR that has interchangeable lenses. I suspect your video camera also has a fixed zoom lens. Here is what I learned:
With the optical train of ccd camera -> fixed lens -> slim adapter ring -> 40mm 1 ¼ inch eyepiece -> telescope focuser I experienced significant vignetting (see attached image). That is, it was like looking down a tunnel, the image frame was a dark rectangle with a circular image in the middle.
- The vignetting becomes less the closer you get the camera lens to the front lens (eye lens) of the eyepiece.
- I used a Scopetronix MaxView 40mm eyepiece and thin adapter to get the camera lens and eye lens as close as possible. This is probably the best it can get.
- The vignetting was least at the 200mm end of the lens and worse at 28mm.
- The weight of the camera/lens attached to the 40mm eyepiece made the focuser sag.
- If you are imaging planets, then the vignetting is not as big an issue as you can easily fit the disc of the planet in the circular image.
- The telescope is usually focused for infinity, so that the image forming light rays exiting from the eyepiece are parallel when intercepted by the camera lens. Hence the term afocal, meaning that the ‘scope is not focusing the image, the camera is doing the work.
- Focusing was a little tricky and had to be switched to manual focusing to stop the camera from hunting or missing focus completely.
Hope that my experience is of some help.
Cheers
Dennis
