Ultra Telephoto: Eyepiece [projection for 4x5

[Drew Bedo]

This thread may belong in the DIY forum.

I am thinking about trying to do some 4x5 photography with a mirror lens/telescope.

I have gotten an older Celestron C-90 with a few eyepieces and the T-adapter tube. I know that the direct view circle will only cover the 35mm format. Eyepiece projection will cover the 4x5 format. I was thinking of making a bracket to hold this telescope aligned with my Zone VI with a leaf shutter in between. I recognize that a top-hat shutter may be the way to go in the end.

If this can be made to work at any level of inconvenience, I will try to get a Wanderlust Travelwide body for reductions in weitht and complexity.

If that can be made to work effectively, I would look to get ahold of a larger telescope, C-5 or equivilant.

Any thoughts or suggestions?

[Dan Fromm]

How old is your C-90? I ask because I bought one in 1978 that was the worst lens I've ever owned. Terrible central hot spot, soft across the field. I returned it under warranty, Celestron sent me another. Turns out that the first one had been shipped without the necessary extension tubes. The second one with the necessary tubes was nearly as bad. Before you do anything else with the lens hang a 35 mm SLR behind it and find out whether it is usable. I never took a shot with either of mine that I was willing to show in public. My 700/8 Questar is much, much better.

The C-5 is much better, also much larger and heavier. Longer too.

While you're playing with the C-90, pay attention to how well you can stabilize the lens-camera combination. Long lenses penalize the least instablity.

[Drew Bedo]

Hi,

Thanks for sharing your experience.

Dunno how old. Haven't run the S/N. It is old enough to have an orange optical tube assembly that takes the 1.25" eyepieces. The newer models are black and take the 0.95" eyepieces.

If it needs adjusting (Collumination?) I think the folks here at Land-Sea&Sky in Houston can do it . . .they will probably be able to tell me the age too.

Yeah; stability will be an issue to address. I am hoping to set up a solid bracket or rail to hold both the telescope and camera . . .then put it all on a solid wooden tripod with a strong pan head.

[Dan Fromm]

Drew, my memory is failing, I think, but IIRC I had an orange beast. In those days Celestron was said to have major QC problems.

Good luck, have fun,

Dan

[Drew Bedo]

Thanks Dan. I am not confident of the new model c-90 scopes either. The 0.95" eyepiece spec is considered to be a low-end amature/kid standard . . .and they are made in China. There is a reason why the Questar instruments are much more expensive.

I will see what I can do and maybe post an image or two here. If it can be made to work at all, the next step will be to up-grade the optics when possible.

My aim is to get that telephoto stacking perspective on 4x5. I am sure that this effect can be had if we just max-out a (insert a high-end metal or color here) card.

Any suggestions or comments on this project are welcome.

[Jac@stafford.net]

I doubt you can project the image to cover 4x5", but I would appreciate correction.
Some astronomy fans use a Field Flattener in order to increase cover to a 24x36mm area.

[Drew Bedo]

I did something like this years ago with a Bausch & Lomb Discoverer scope and a beat up Spped Graphic. The bracket was a 2x4 with 1/4-20 all thread. Got a few interesting shots of a windmill with the sun setting behind. Had problems with stability and exposure. The scope was not the clearest optically either. . .all that glass and a 70s design zoom to boot.

Ultimately, I'd like to put a Wanderlust Travelwide body onto a larger modern scope on a solid tripod and go somewhere interesting.

[goodfood]

I remember at end 60's to early 70's Sky and Telescope mag. last page usually have Unitron telescope adv. either with a 4X5 camera at the end of eyepiece for eyepiece projection, or a six eye pieces turn-a-round.