Camera Lens As Telescopes

[winterlight]

Anyone tried to use long camera lenses as telescopes?

[winterlight]

Thinking of making one of this

Lens Diagonal

[Peter Drew]

I've tinkered with these in the past, some of them give excellent low power wide angle results. Most quality units are well corrected for CA and off axis aberrations in the interests of full frame coverage for terrestrial use. They don't usually perform well at high magnification although the longer focus Maksutov types like the Russian MTO 550 and 1100 were quite popular as a "double-up" astro scope.

[Aldebaran5]

In the early days I used a 400mm telephoto lens with a monocular convertor as a telescope, fixed on a tripod, it made do. It wasn't a good quality lens by any means but it gave me results.

Keith.

[badgerchap]

Yeah I played around with this last year. I used quite a large lens, and by all accounts the results were none too bad at low mag. I think provided there's no c£@p in the lens and you can find a descent way to attach the eyepiece (I used one of those hard aquafresh toothpaste tubes - the kind with the pump ) then you can actually get a useable refractor. Still trying to persuade my dad to give me his bad *** lens - primary diameter is about 70mm and focal length came out at about 400mm, so it'd make a short tube. Optics are pretty sweet too. My plan was to try to find a stable method of mounting it but I never got that far.

[Martyn_Bannister]

Older long lenses like this one on ebay here are quite often of respectable optical quality. They are relatively simple design and can usually be found for very low prices, especially if you can find one with a native mount that is un-popular, like this one, which is Canon FD. They perform very well on camera, so should be pretty good as a telescope. Their biggest problem is chromatic aberration, followed by their relatively small aperture.

As Peter Drew pointed out, the long mirror lenses can be very good too. I have 500mm and 1100mm russian mirrors and they also perform very well on camera. I have yet to try the 1100mm with a 2x tele-converter though

They usually exhibit very little CA, but are normally of smaller aperture than the refracting sort. The russian ones I have are a stop or so brighter than most.

It's an interesting thought to use them with a telescope eyepiece. I might try and pick up an eyepiece to experiment with.

[winterlight]

Most will need some sort of barlow to extend the back focus that increases the focal length. Anyone know of a 'lowest power' barlow, perhaps one that is used to a binoviewer?

[badgerchap]

Yeah, I had a bit of an issue with the back focus, hence my toothpaste tube device, which doubled nicely as a coupler and a back focus extension. So it was a bit like a 0x barlow lol

[blinky]

I think the main reason why lots of folks dont use camera lenses is the number of pieces of glass. A normal scope has either 2,3 or in some cases 4 lenses but these camera lenses can easily have 8 or 9 (so I am told) so that obviously leads to the possibility of internal reflections and also cuts down on the amount of light hitting your eye.

[Naz]

Nearly all the earlier cheap telephotos were usually only two elements, as most only used B&W, so colour correction wasn't an issue. These were commonly made by Soligor, other brands were sold by Dixons et al. Identified by the manual focus and the f stop ring. Should be very cheap!

I did a post on here some time ago, where I used a 500mm mirror and was very pleased with the results.

Archie