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Telescope eyepieces on telephoto lenses

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Has anyone tried putting a good eyepiece on a long telephoto lens (500mm) to make a refractor telescope? Is it worth even trying? How would you physically fit them together?

Edited by vulcan
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I did that several years ago with a cheap 500mm mirror lens by drilling a hole in a plastic end cap, worked OK. You would just have to use the focus on the lens to move the lens far enough forward to achieve focus.

Jessops used to sell an adaptor with an ep fitted, not seen one for years. It would make a reasonable cheap grab and go.

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I've put a camera on a good eyepiece and put the eyepiece into a refractor telescope, but not sure if that's what you're asking here?

Are you trying to make a telephoto lens into a refractor telescope? If so I guess it would need careful measurement/matching and tailored fittings :D

(edit - naz beat me to it lol)

Edited by brantuk
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Easily done... works reasonably well.

You can use a Mogg adaptor (google) which fits your lens and has a end attachment for 1.25" eyepieces and/or cameras.

I used a x2 camera extender and removed the guts; replaced them with a small piece of 1.25" tube. Now I can use any eyepiece on any of my old Zuiko lenses.

Watch the back clearance on the lens! The backfocus is 50mm but some lens have a rear element which slides back into this space during focusing...one of my 50mm lens only allows 30mm clearance.

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This is why I love SGL :D

I would never have even thought to ask. I have an old M42 Prinzgalaxy 500mm f8 lens that I was given when I first started slr photography sitting in a cupboard. I've just got it out and it seems to be an m42 adaptor on a t thread :D (same diameter, narrower pitch than m42). It also has a built in tripod connector.

Held up an eyepiece to the back and whaddaya know? upside down image of the house opposite/horizon, nice and clear.

Looks like i've got me a 60mm frac - just need an adaptor/focusser to give me a 2-3 inches of outfocus.

Cheers peeps:icon_salut:

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come on people, it's not like it hasn't been done few dozens times before... :D

i tried that already and i have to tell you, it works great!

now, sure, depending on your specific focal ratio, you get better or worse images, but you can't ask for more from an old lens; and by "old" i'm not being disrespectful, i only mean that the glass is made by old recepies, and there's no special correction for visual use, not at current standards at least - it's not what it was initially designed for.


Real stuff :: Visual Tair picture by saiph_ro - Photobucket

my Tair works great as a grab & go, but its 300/4.5 comes nowhere near the C80 ED which produces sublime views of almost anything (limited to its aperture, of course). the barlow lens cell can be attached directly to the diagonal mirror and get wider true field of view. three or four eyepieces are more than enough.

too bad it's quite considerably heavy and can't be used as a finder for my Alter M603 on EQ5. but even so, the soviets intuitively knew what their tele lens might look like and made it bulky and sturdy, so you can use it for almost anything from visual, to prime, to afocal photo (btw, the sun and moon look so nice, and eclipses are much easier to frame, even with a barlow lens cell inserted in a specially designed adapter for dslr photo).

by the way, when you are talking about converting tele lenses to anything else, it's all about adapters - don't live home without them, and think of any possible combination before going to the lathe workshop with your sketches. use the M42/1 thread to attach any other piece you might want. i sincerely don't recommend plastic/PVC improvisations or worse (duct tape), if you don't want to be disappointed from first shot.

all in all, converting tele photo lenses for visual observations is lots of fun, you get a compact package that can yield in anything you want (bird watching, wild-life, neighbor spying, night time surveillance, wide-field astrophoto, moon- or sunsets / rises, eclipses, landscapes), provided the right adapter/filter is used.

good luck and clear skies!


Edited by saiph
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  • 1 month later...

I use an Intes M42x0.75 to 1.25" adapter with compression ring to use eyepieces on my Russian lenses. It works superbly, even although it would be better if the thread was the proper M42x1.

I've hung my Speers 5-8 zoom off the end of my LZOS MC 3M-5CA Mak lens. Looks weird but it works !


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  • 9 years later...

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