My little Schmidt-Cassegrain illuminated finder scope

[Omaroo (Chris Malikoff)]

Hi all

I've just purchased a 500mm Vivitar f/8 Schmidt-Cassegrain mirror lens from Lars (a member here on the forum). It had a Pentax threaded ring mount so I adapted a Nikon bayonet mount and attached the lens to it. Luckily the internal thread on the bayonet ring matched the lens thread. So - I have a 500mm lens for the camera. They're not brilliant lenses I've heard, but at 500mm anything is going to be tricky to get to perform well.

Anyway - I went a step further and adapted a spare Nikon extension tube that I had lying around to create a mountable body for the lens, and one that could also carry my Orion illuminated reticle.

Success! The unit works very well with the reticle, so I intend to mount it on my Celestron C8 and give it a go soon. Focus is a bit critical, but once I find infinity reliably I'll be OK I guess.

Good bit of fun. Thanks Lars!

Cheers
Chris

[montewilson (Monte)]

Thats really cool. I have fiddled around with this sort of thing and my Pentax 67 lenses and they worked well too.

[KG8]

That is cool! Nice work Omaroo.

[Terry B]

I also have an old 500mm mirror lens that I have also been playing with as a guider. It has fungus inside it but this hardly matters as a guider.
It works quite well but yes focus is crittical and if you bump it the lens turns very easily losing the focus. The main problem I have with it is that it foggs up really quickly as it has no dew shield. I suppose I could make one but haven't yet. This is the time I bump it-using a hairdryer to defog it.
The mount is a T thread so any eyepiece T adaptor will fit on it. I assume yours is the same as the nikon adaptor fits.
It is a very cheap and functional guide scope.
Good luck with yours.