500mm Mirror Lens

Well this really is a camera lens. It is an old Accura screw mount 500mm (Maksutov) mirror lens I got from EBAY. (I have seen these old mirror lens sell for a little as $40 on Ebay). I wanted a upright correct image. I attached a eypiece adapter and Erecting diagonal to it. Unfortunately there was not enough adjustment to bring it into focus. I took the back off the Lens and put it on a small hobby lathe to remove the Screw mount. I then put the front tube of the diagonal on the lathe and shortened it to about 0.060 inches. I attached the diagonal to the lens back with Elmers Ultimate Glue. I have yet to find any material that this stuff does not work on. Lastly I removed the focusing stops. I now have this strange 500mm telescope. The second picture is a close up of the back of the lens where the modifications were made.
(Click on the image for a larger picture)

Shot with the Nikon 995 at full open (wide angle).
(Click on the image for a larger picture)

Shot with the Nikon 995 at full zoom (4X). (Click on the image for a larger picture)

Shot with the Nikon 995 and 500mm mirror lens at full open (Wide Angle).

(Click on the image for a larger picture)

Shot with the Nikon 995 and 500mm mirror lens at 50% zoom (2X).
br> (Click on the image for a larger picture)

Shot with the Nikon 995 and 500mm mirror lens at full zoom (4X).
(Click on the image for a larger picture)

Short of the full zoom this combination appears to work fairly well. Focusing is a bit touchy, but this might be a good combination when a "small" package is desired. I am not sure why full zoom came out so dark. I was shooting in the late afternoon but as soom as I zoomed in the camera went dark. Perhaps it has something to do with the mirror obstruction in front. I am going to have to with this combination a bit more.

22 March 2004:
I got home early enough to play a little this evening. I decide to try this scope on something a bit further away. So I picked a telephone pole in the next block (you may be able to make it out in the 1X photo between the two houses ... it is about 4 pixels wide). With the eyepiece the image looks razor sharp. So I attached the camera. Full wide angle still looks pretty good, but as soon as I zoom in the quality starts to decrease and very rapidly toward full full zoom. Just out of curosity I went back to the eyepiece and added a couple of 2X barlows. Sure enough the image had degraded as well ... but not as much as with the camera. The picture of the bird below shows the worst case senario (500mm at 4X). Then again without the scope he would be about 1 pixel.

23 March 2004:
Just got the prints back from useing a 35mm SLR at prime focus. They were scanned in on a HP4300C scanner. I am really suprised that the quality is not magnitudes better. Perhaps it was the quality of the drugstore processsing or the scanner or the three step process (negative, print, scan). Whatever: Film should be able to produce better results. I also note that there was some vigetting.

The second picture has crops from the 500mm-1x and the 500mm-SLR. You can judge for yourself.

Conclusion:
Cheap alternative but only useable up to 50% zoom. Much better at full wide angle.
Handy if one does not want to tote a heavy tripod and larger scope (i.e. might be good for the beach).