Long lens to telescope

Started Feb 17, 2006 | Discussions
LightMagician
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Long lens to telescope
Feb 17, 2006

A telescope can be used for astrophotography using an adaptor to mount a camera. Now I have a reverse situation: I would like to convert my long lens (500mm/4) to make it a telescope, meaning using an adaptor so that I can insert a eye piece for viewing the heavenly bodies.

I have talked to a local dealer and a guy from Adorama(where many telescopes are sold), no one had an idea how to make it happen.
Any idea is appreciated.
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nickleback
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Re: Long lens to telescope
In reply to LightMagician, Feb 17, 2006

LightMagician wrote:

I would like to
convert my long lens (500mm/4) to make it a telescope

Search around eBay, they come up often enough. Most people don't know what to name them so they can be tricky to find. Try seaching for scope and the name of the lens mount you are interested in. Don't let the price of the first link below scare you! Third party manufacturers made these, too, including Kenko/Tokina.

http://cgi.ebay.com/NIKON-LENS-SCOPE-CONVERTER-ADAPTER_W0QQitemZ7591571446QQcategoryZ48556QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

http://cgi.ebay.com/Diastone-Scope-Adapter_W0QQitemZ7591731131QQcategoryZ3636QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

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nickoly
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Re: Long lens to telescope
In reply to LightMagician, Feb 17, 2006

LightMagician wrote:

Adorama(where many> telescopes are sold), no one had an idea how to make it happen.

They may sell a lot but this clearly indicates it is not a good place to buy one.

There is some place on the Internet that sells M42 eyepiece adapters at a very reasonable price. It is made for the Ruibinar lens and thus probably Russian. You should be able to trawl it up. I believe they also sell surplus lenses. If your lens is not M42, there is a raft of cheap adapters for whatever lens you have and you should be able to cobble up a satisfactory piece of gear.

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nickleback
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Re: Long lens to telescope
In reply to nickoly, Feb 17, 2006

nickoly wrote:

If your lens is not M42,
there is a raft of cheap adapters for whatever lens you have and
you should be able to cobble up a satisfactory piece of gear.

The raft of cheap adapters are for hooking up an m42 lens to a non-m42 body, which is the inverse of what you'd need to hook up an m42 adapter to a non-m42 lens.

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LightMagician
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Re: Long lens to telescope
In reply to nickleback, Feb 17, 2006

Thanks for the links. That is good to know there is an adaptor out there.The guy from a big camera/telescope store looked at as if I was from the moon. BTW, what is M34?
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nickleback
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Re: Long lens to telescope
In reply to LightMagician, Feb 18, 2006

LightMagician wrote:

Thanks for the links. That is good to know there is an adaptor out
there.The guy from a big camera/telescope store looked at as if I
was from the moon. BTW, what is M34?

If you mean m42, that is the old 35mm SLR screw-mount, aka universal/praktika/pentax screw mount. 42mm diameter, 1mm thread pitch. Many lenses in the '50s and '60s had this mount. Some still do. Adapters to mount m42 lenses on practically any modern camera mount are a dime a dozen, but if you want to go the other way around (which you'd need to with an M42 scope adapter to a non-m42 lens) it isn't so easy.

It you need to hack things together, easiest would probably be Minolta MD (manual focus), as it has among the shortest registration distances, giving you room to fit an adapter to almost anything. If MD-> your mount isn't available, you could cobble something together by cutting the lens mount side off either an extension tube or rear lens cap and epoxying it to the front of a Minolta-mount scope adapter.

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nickoly
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lens mount.
In reply to LightMagician, Feb 18, 2006

LightMagician wrote:

The guy from a big camera/telescope store looked at as if I> was from the moon. BTW, what is M34?

I was (cryptically) alluding to the M42 Practika srew mount, used by a great swag of film SLRs. It is a 42mm thread.

Further to this, it can't be hard to make one. All you need is an extension tube, a back lens cap, a short length of tube with 1 1/4" i.d., and a telescope eyepiece.

My telescope was originally a camera lens. It was converted simply by glueing a tube in the mount and removing the infinity stop. The M42 mount is still in place and it can serve as both.

Here you can see the aluminium tube in the back of the lens. Removing the infinity stop meant an angle finder could be used and no extension tube is needed. I think the tube is a better idea. The boxlike object is the mount for a finderscope.

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nickoly
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Re: lens mount. oops
In reply to nickoly, Feb 18, 2006

I forgot to say that the tube is cut into the back lens cap. You can determine the dimensions by holding the eyepiece up to the lens.
I guess you worked all that out already!!

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LightMagician
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Re: lens mount. oops
In reply to nickoly, Feb 18, 2006

This may be a problem. My lens is practically new (2 years old) 500mm/4 IS. I don't want to make it a full time telescope. I am a wildlife photographer, only occasionally wanting to see the heavenly bodies. The 5oomm/f4 has more light gathering power than many refractory telescopes I have seen. Well, it cost me $5600.00 2 years ago. I am thinking of using it as a telescope as well, but it seems this isn't done so often and not so easy. From what I read, for this purpose of conversion to telescope, people use the lenses that are old, really old lenses, that is not good for photography any longer. Just for fun kiind of! I may have to spend another $ 6000.00 to buy a decent telescope?!!:)) there is no end to it.
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ScottyNV
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Re: Long lens to telescope
In reply to LightMagician, Feb 18, 2006

Interesting that you ask.. I went doing the same investigative process that you are a few months ago.. I wanted to use my Sigma 600/8 mirror lens (EOS mount) as the telescope.. I got the same strange looks as you did, and the same kinds of trouble finding such a thing... I have come to the conclusion that I'll have to construct something.. I have purchased the CAMERA SIDE mounting ring and now just have to get myself down to the telescope store to buy a M42 standard eyepiece mount and figure out a way to mate the two.. in this situation, the short registration distance that Canon uses with the EOS system is a hinderance rather than a help.. I may need to add an intermediary lens to maintain infinity focus.. I do not wish to compromise my lens as a photographic tool just to get a 'scope... time and money....

Cheers,
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DougJGreen
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Re: Long lens to telescope
In reply to LightMagician, Feb 18, 2006

Look for a lens to scope adapter.

Basically, what it is, is a female lens mount, and an eyepiece. I bought one on ebay that was made by Tokina, for Minolta MC mount, and it cost me something like $20. I have also seen them in M42, Nikon F, and Canon FD mounts. I use it with a 500mm T-mount Mirror lens, which I can make into a Minolta mount by putting a Minolta t-mount on it.

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nickoly
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None of what you say is true
In reply to LightMagician, Feb 18, 2006

LightMagician wrote:

This may be a problem. My lens is practically new (2 years old)> 500mm/4 IS. I don't want to make it a full time telescope. I am a> wildlife photographer, only occasionally wanting to see the> heavenly bodies. The 5oomm/f4 has more light gathering power than> many refractory telescopes I have seen. Well, it cost me $5600.00 2> years ago.

In astronomical terms, your lens is nothing more complex than the front end of a potentially useful short focus 125mm refractor. The light gathering power is reflected (no pun) by that dimension. The $5600 has nothing to do with it. Its age has nothing to do with it either.

I am thinking of using it as a telescope as well, but it> seems this isn't done so often and not so easy. From what I read,> for this purpose of conversion to telescope, people use the lenses> that are old, really old lenses, that is not good for photography> any longer.

This is baloney.

Putting an eyepiece adapter on a tele lens involves the same effort and measure of intellect, as putting a camera on it. The same applies to its removal.

Other than abuse and/or fungus, or being bad from the start, there isn't much that makes a lens no good for photography. The shot below was taken recently with a 1936 Leitz f2 on a 1955 FED, with reasonable confidence it would come out OK.

If an old lens actually deteriorates to the point where it is no good for photography, it's no good for anything else. Indeed quite the opposite. If fungus gets round the edges, the usual starting point, the lens deteriortates as a telescope but may have long service, if only at reduced aperture, on a camera.

I suppose the reason why you don't see it done too often may only be because everybody you see has a spare $6000 for a telescope. You may find in other circles it is different, most particularly in astronomy circles, where a 500mm f4 camera lens would be seen as the makings great finderscope for something serious, and far to good to be confined merely to shooting wildlife. The physics are there for us all.

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nickleback
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Re: lens mount. oops
In reply to LightMagician, Feb 18, 2006

LightMagician wrote:

This may be a problem. My lens is practically new (2 years old)
500mm/4 IS. I don't want to make it a full time telescope.

You don't have to. Mounting a scope adapter is not any different than mounting a teleconverter or extension tube. It is temporary.

Kenko used to make a scope adapter in EF mount. That would be your best bet. If you can find one on eBay, it'll cost you $20. 2nd best would be Canon FD or Minolta MD adapter with original mount trimmed off and hollowed-out EF rear lens cap glued on. Just make sure your len-cap mod don't add more than 2mm in overall length so you can preserve infinity focus. Also would cost $20 and probably an hour of your time. I even posted a link to one currently on eBay.

It would be really nice if Canon were to make an EF scope adapter that enabled and powered the IS. That plus the 70-300mmDO would make a very nice, compact and stabilized 30x zoom scope. If they could make it for about the same price as their teleconverters (i.e. around $300) they could sell a bunch.

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nickoly
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Not necessary?
In reply to ScottyNV, Feb 18, 2006

ScottyNV wrote:

in this situation, the short registration distance that Canon> uses with the EOS system is a hinderance rather than a help.. I may> need to add an intermediary lens to maintain infinity focus.. I do> not wish to compromise my lens as a photographic tool just to get a> 'scope... time and money....

There should be no need for that sort of complication. The reason my lens was modified (by removing a screw) is that this was necessary to accommodate the right angle eyepiece prism. I don't think the EOS makes things difficult. The film-to-mount distance is much the same as any other SLR, isn't it? I don't think the proprietory adapters Nickleback alludes to would require lens modification and a more compact prism may not demand it either.

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ScottyNV
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Re: Not necessary?
In reply to nickoly, Feb 18, 2006

Actually, I remember seeing a list of mount registration distances a while ago.. the EF is the shortest, by a couple of mm... also, both the OP and myself do not want to modify the lens/focus mechanism at all because we still want to use the lens as a photographic tool, with the ability to use it as a telescope once in a while.. not to turn it into a telescope full time!

The short registration of the EF mount is the largest impediment to using EF lenses on older FD bodies.. you lose infinity focus just as if you had an extension tube in place..

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nickoly
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No, not necessary
In reply to ScottyNV, Feb 19, 2006

So what difference does a couple of mm make? The only time I can see this being a bit of a problem is when the lens mount is behind the film plane. As I said in my previous, I'm sure you will find the adapter makers don't require any modification to the camera lens. The tube and lens cap cobble I alluded to would make no demand on the camera lens either.

The 1100mm Maksutov I showed was modified so that it could use the standard astro gear shown and it wasn't intended to go on a camera again. Actually, it serves regularly on a camera by the simple expedient of spacing it out with a 12.5mm extension tube so that the mirror clears the new tube.

The Nikon adapter flagged by Nickelback actually includes its own eyepiece. This is probably makes a Galilean telescope, which is less demanding on space than mine. I'm sure Nikon have a fair idea of what they are doing when it comes to lens design.

I don't know what an EF is. I don't know what lens the OP has either. It doesn't matter.

ScottyNV wrote:

Actually, I remember seeing a list of mount registration distances> a while ago.. the EF is the shortest, by a couple of mm... also,> both the OP and myself do not want to modify the lens/focus> mechanism at all because we still want to use the lens as a> photographic tool, with the ability to use it as a telescope once> in a while.. not to turn it into a telescope full time!

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nickleback
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Re: Not necessary?
In reply to nickoly, Feb 19, 2006

nickoly wrote:

The film-to-mount distance is
much the same as any other SLR, isn't it?

EF (Canon EOS) film-to-lens mount distance is shorter than any other current 35mm SLR.

I don't think the
proprietory adapters Nickleback alludes to would require lens
modification and a more compact prism may not demand it either.

The proprietary adapters I alluded to were either designed for EF mount, or for an even shorter mount (Minolta MD, Canon FD). Adapting these to EF should be relatively straightforward. But adapting m42 to EF would be more difficult. You'd nee to paste on an EF mount and shorten it a few mm from its original size (i.e. before pasting on the EF mount). Depending on the design of the scope adapter, you may have your work cut out for you (pun intended).

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nickleback
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Re: No, not necessary
In reply to nickoly, Feb 19, 2006

nickoly wrote:

So what difference does a couple of mm make?

Infinity focus or not. A scope without infinity focus is pretty useless. You can of course readjust or remove the infinity stop to fix this and hope the focusing mechanism has enough travel to still get to infinity. This is something I'd do without pause on a $20 lens, but not something I'd attempt on a $5k plus lens.

I'm sure Nikon have a fair idea
of what they are doing when it comes to lens design.

I'm certain they do. But I'm also certain the Nikon F mount distance is 2.5mm deeper than EF, so stacking a custom F-> EF adapter on top of that wonderful Nikon piece will put the lens about 5mm further from imaging plane that it was designed. So to retain infinity focus you are left with 3 options:

1. hacking (literally) the beautiful Nikon scope adapter down 5mm or so.
2. Incorporating optics in a custom F-EF adapter.
3. performing a focusstopectomy on the $5k Canon lens.

None of these options are particularly appealing.

I don't know what an EF is.

Canon EOS lens mount.

I don't know what lens the OP has either.

He already said. Canon EF 500mm f/4L IS.

It doesn't matter.

The particular lens doesn't usually matter (unless it is one of the older big EF lenses with electonic manual focusing), but the mount does.

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cpw
cpw
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Re: Long lens to telescope
In reply to LightMagician, Feb 19, 2006

Hello,

Awhile back, I found this cool idea in the December 2004 issue of Sky & Telescope, p. 137, entitled 'Cheap Converter.' You simply make your adapter out of two parts: the dust cap that fits on your lens's bayonet mount, and a 1 1/4 inch compression fitting from the plumbing section of the hardware store. You cut a hole in the dust cap, and glue to the fitting with ABS plumbing cement. The compression fitting clamps down and holds a 1 1/4 inch eyepiece in place, and the modified dust cap then gets attached to the lens. I just took the eyepiece to the hardware store and found out what works. You may need to cut down these plastic parts to the right sizes so as to achieve infinity focus, also taking care that the eyepiece doesn't bottom out on any optics from the lens; but if you like to tinker, it's a whole lot easier and less stressful to be modifying these plastic parts than the lens itself! I made one for my Nikon F mount a while ago, and it works well. Now I just need some longer focal length lenses than the 100 mm that I have so far!

Take care,

Chris

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brandrx
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I bought 4 of these adapters...
In reply to LightMagician, Feb 19, 2006

The Bower telephoto lens adapter is the cheapest I have found so far. I buy them alsong with cheap lenses to make simple telescopes/spotting scopes to give to grandkids as gifts. Kids love these things. I found them for the Minolta, Canon FD, Pentax, and Olympus so far. The Bower will make your 500mm lens into a 50X telescope. Here is a link for a Canon adapter:

http://cgi.ebay.com/New-in-Box-Bower-Tele-Photo-Lens-Adapter-Canon_W0QQitemZ7557994619QQcategoryZ79000QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

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