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Morag2 Aug 30, 2006 5:40 PM

Hey all, I have a question about telephoto lenses. I was wondering how much telephoto it is possible for a lens to have. I have seen 800mm lenses and heard of 1000mm ones, but never anything higher than that... so how much telephoto can you get?

Because if 1000 really is the highest... I'm not doing to bad with my P850 + Tcon giving me 750mm or so. (Although it's definatly not SLR quality).

Bob Nichol Aug 30, 2006 8:36 PM

Canon has an EF 1200mm f/5.6L USM "available" on request. Legend has it there are only ten in the world and Sports Illustrated magazine owns two of them! If you have to ask the price you can't afford it!;modelid=8178

Older lenses:

Canon 2000mm F/11 mirror lens

Reflex-Nikkor 2000mm f/11 mirror lens

While these lenses were in the catalogs, they were usually special order items and were neither cheap or common! These were about the limit in photographic lenses as it became cheaper to attach your camera to an astronomical telescope.

Morag2 Aug 30, 2006 9:27 PM

Hmm, interesting... so is it really possible to attach your camera to a telescope? And can the range on a telescope be converted into millimeters?

jacks Aug 30, 2006 9:39 PM

You could stack teleconverters on a lot of these too, though the resulting lens would be so slow you'd have to set it in concrete to keep it still enough.
I've seen shots of the moon on this forum of a sigma 800 with stacked teles which would give 800x2x1.4x1.6= nearly 3600mm on a crop body. No home telescopes have that native focal length though you can of course stick magnifying lense on them. More expensive telescopes tend to have a wider aperture instead of a long focal length as no focal length is enough to show a star as more than a point anyway. You want to make the stars brighter instead, which lets you see more of them.
Any really long lenses are likely to be reflectors. It's much easier to make a large mirror than a large set of lenses.
There is a sub forum here on digiscoping and I'm sure there are some knowledgeable people there if you are interested.

Sintares Aug 31, 2006 12:13 AM

Someone over at Dpreview took his Sigmonster (Sigma 300-800mm), added around x16 worth of tcs and attached the result to a Canon 350d !

Roughly equal to 20,488 mm(including the 1.6 crop factor of the 350d), full open f/90.51;changemode=1

jacks Aug 31, 2006 3:46 AM

lol, just read that thread.
Can see cracks on the blisters on the paint on the bracket on the support of a lid on a tank on a tower 60m away.
Not much chance of ever getting a clear shot at f90 though.
Someone suggested shooting the sun, the lens is so dark.

Red Royalty Aug 31, 2006 8:45 AM

lol looks funid love to bring that thing to an air port to shoot aircraft :cool:

Morag2 Aug 31, 2006 9:30 PM

That is quite possibly the coolest thing I've ever seen. I want one:blah: Just make the whole thing about 3 feet wider so you could get some decent light into it.

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