Celestron C-90: Can I use it on a 4x5?

[Drew Bedo]

I have acquired a Celestron C-90 spotting scope. This is a mirror optic with T mount threads on the back. When used with a 35mm SLR it should be a 1200mm/f-11 lens. Is there a way to use this on a 4x5 using eye-piece projection?

[philip964]

Not counting optics, just getting a tripod to hold both the lens and the camera will be tricky as both are very heavy and the tripod mount for one will not hold the other.

[Drew Wiley]

Ironically, you might be able to adapt a 4X5 film holder made for a microscope, though it would allow no movements except focus.

[George Stewart]

I used to own a C90. While I'm sure something could be rigged up, I doubt it would be usable. The f-stop would be very high, and curvature of field might be a problem. If your goal is astrophotography, then the moon and sun would be the only subjects that might lend themselves to LF eyepiece projection. Since both are effectively static subjects, it would be better to use modern technology and stitch images together using a DSLR.

[Dan Fromm]

Horrible lens, Drew, run away from it. I used to own one, never got a shot with it that I was willing to show in public.

If you need a long lens, look for long process lenses.

[Drew Bedo]

Thanks everyone.

Advice here and elsewhere seems to be that this is not a good optic. Is this also true for the mirror lenses by Tameron, Sigma and others too?

[Dan Fromm]

Drew, mirror lenses have their uses but ones made for 35 mm barely cover 24 x 36. If you want to use larger format film to take small circular images, go for it.

I have no idea how any of the bon-bons you mentioned will work as a taking lens when fitted with a projection eyepiece. Since you have a C-90, why don't you ask Celestron which of their eyepieces they recommend for the application you have in mind? This is probably the least expensive way to do what you want.

FWIW, the best of this class of lenses are the 700/8 Questar 700 and, believe it or not, the 1250/10 Celestron. This last is not the same design as the C-90. Q-700s are uncommon and expensive, I've never shopped for the big Celestron ... I have a Q-700, find it hard to use in front of a Nikon but capable of outstanding results.

If you want a not too expensive long lens to use on LF, get a process lens, shell out for a Polaroid MP-4 Copal #1 Press shutter and an adapter to hold the lens in front of it, and go shoot. The adapter will cost more than the lens.

Cheers,

Dan

[Joseph O'Neil]

Well I am going to disagree - I ahve one, but an older one,a nd very good optics. Mine is an old "astro C-90".

What happened is during comet Halley, circa 1986, Celestron and Meade started pumping out telescopes like the end of the world, and quality went tot he crapper on many scopes. Some Q/C recovered, ont eh c90, it never did. But older ones - very good.

However - the bad news - I get vignetting on my 35mm camera, and it barely covers the sensor on my D40 Nikon Digital SLR. 4x5? Hmmm

[Dan Fromm]

Joe, you miserable old grump, I got my C-90 at the end of '78 to use in Costa Rica in early '79. I eventually discovered, after seeing another one in a store, that mine had been shipped with bits missing. Even after the entire lens, including the missing bits, had been replaced under warranty it was god-awful. That larger Celestrons were any good boggles the mind.

So much for your belief that "older ones -- very good."

My C-90's poor quality -- build and image -- didn't, as it turned out, interfere with the purpose I got it for. The subjects I got it for -- my idea was to shoot at 10', its close focusing limit and about as close an approach as the subjects would allow, with flash -- weren't in evidence. Trees had been chopped down, ground-level microclimate had changed ... Economic development, they say. So we don't have photographic documentation of Rivulus isthmensis sitting out of water. Saw lots in '76, didn't then have a long enough lens or a powerful enough flash ...

[Joseph O'Neil]

So much for your belief that "older ones -- very good."

Hi Dan;
Well not kidding, mine is actually pretty darned good. Maybe there was a difference, as I remember there were orignally two models -the "astro" version - which is what i have - single fork arm, wedge, etc, and the "spotting scope" model, which was made for years.

The "astro" version was rather expensive , and at that time, the closest alternative was the 3.5" Questar. I've heard of and read other reviews that he old "astro" C90 was not a bad scope too, so just speculation here, all I can guess is they maybe sorted the optics (quality control?) or made the two scopes differently somehow.

I have seen bad C90s myself, spotting scope versions, but in those C90s, even the focus feels different than in mine.

Ah well, good or bad, neither will cover even 35mm .