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Building a telescope from a telephoto camera lens

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#1 tekcajder

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Posted 24 March 2011 - 12:44 PM

Hello everyone,

About a year ago, I came across an article about how one could make a telescope using a telephoto lens and the eyepiece from a telescope. At the time, I didn't have a telescope and I was really chomping at the bit to get my hands on something, anything really.

So I set out to see if I could make this work, I know this is a terribly simple project compared to most of the endeavors of the ATM community, but it gave me a taste and I've already moved on to building a refractor (I'm not grinding my own lenses yet, but small steps!)

I thought I could detail the process for anyone who's browsing the ATM forums, looking for a starting place.

You'll need:

- Telephoto lens
- 1.25" telescope eye piece
- 1.25" drill bit
- Rear Cover cap for lens
- some additional material to help shore up the fitting(a small scrap piece of wood, plastic, etc)
- super glue

1.) The first step was to locate the center of the rear cover cap, fortunately for me, the exact center was marked with an injection point from the plastic cap being manufactured. (you probably can't see it in this picture, but it's right in the middle of the "k".)

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2.) Using a 1.25" drill bit, I slowly and carefully drilled out the center of the lens cap.

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3.) ... till I had something that looked like this (The other cap is there for comparison)

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4.) From there, I cut and drilled out two small pieces of masonite to help create a tube to hold the eyepiece. This helped keep the eyepiece correctly aligned with the lens as well as holding it firmly in place.

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5.) I used a small amount of super glue to adhere the masonite and the lens cap together. While it dried, I inserted the eyepiece so it wouldn't shift out of alignment and dry permanently in place.

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6.) Once the glue had set, it was just a matter of putting the cap back on and inserting the eyepiece.

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It worked, better than I'd hoped, and I had a telescope, built out a second hand camera lens and an inexpensive plossl eyepiece. I could comfortably view the Orion Nebula as well as Saturn and one of it's moons.

Considering up until this point, I'd never seen either close up with my own eyes, it felt incredible!

I made a short video right after mounting the eyepiece for the first time. You'll have to excuse the shot through the scope, my camera doesn't quite come close enough to the eyepiece and it gives the impression you're looking through a key-hole.

Video Link @ Youtube

#2 WillCarney

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Posted 24 March 2011 - 01:55 PM

That works well. I cheated on mine. I bought a t-mount to 1.25" adapter. I just screw it into any of my t-mount camera lenses and I have a telescope. Of course it won't work on non t-mount lenses. But most of my telephoto's are t-mount so that's not a problem.

William

#3 Gary Fuchs

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Posted 24 March 2011 - 03:18 PM

Nice ATMing!

Gary

#4 Tak North

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Posted 24 March 2011 - 03:35 PM

Yes, this works very well given the flat, well corrected image produced by a good camera lens. Its just too bad that most camera lenses don't have enough back focus to allow the use of a diagonal. Really a shame given that I probably have more invested in camera lenses than in telescopes! :(

#5 1stScope

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Posted 24 March 2011 - 03:41 PM

I built a similar eyepiece holder also using a lens cap but a friend machined a bushing to attach to it for holding an eyepiece. Camera lenses are corrected differently than telescope objectives so the 50mm and 60mm Tasco telescopes that have been given to me perform much, much better than my 300mm ED Nikkor lens. I did make a couple of finders from the lens barrels of 200mm f4 lenses, which fit nicely into PVC tubing allowing PVC fittings to be used as eyepiece holders. Such lenses were in the 'junk pile' of a couple of camera shops and were almost free. A 50mm lens barrel and the focusing mechanism cobbled into some PVC tubing makes a nice loupe.

#6 Wes James

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Posted 24 March 2011 - 03:42 PM

Neat idea, and inexpensive execution! ;)
Welcome to Cloudy Nights- and the ATM forum!

#7 Dick Jacobson

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Posted 25 March 2011 - 07:27 AM

Another possibility is to use an extension tube that fits the lens. The extension tube gives you a cheap lens mount. Modify the tube as needed to hold an eyepiece.

#8 ccs_hello

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Posted 25 March 2011 - 07:34 AM

Just FYI...

... Its just too bad that most camera lenses don't have enough back focus to allow the use of a diagonal. Really a shame given that I probably have more invested in camera lenses than in telescopes! :(


It doing serious surgery is an option, this and this old CN post might help.

Clear Skies!

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#9 ccs_hello

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Posted 25 March 2011 - 07:48 AM

James,

Welcome to Cloudy Nights!

Nice mod.
What's the mechanism to make the eyepiece tight to the assembly?

Clear Skies!

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#10 ed_turco

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Posted 25 March 2011 - 11:51 AM

Nice job!

#11 WaterMaster

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Posted 25 March 2011 - 02:03 PM

Welcome to CN James! Nice job.

You've found a place full of folks that appreciate projects like this.

#12 Ed Holland

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Posted 25 March 2011 - 02:23 PM

Great project....

It got me hunting fleabay for used Telephoto's - it seems there are all manner of inexpensive options that could be turned into telescopes. Food for thought indeed, thanks for sharing your ideas.

Ed

#13 SilentLight

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Posted 25 March 2011 - 05:46 PM

The one in my avatar is the first scope I biult using a Sigma APO 50-500mm ("Bigma") camera lens and an Orion camera holder (the type that holds the camera to eyepiece - I just made it work backwards!)

And then I tried a permanent mount using a PVC reducer and a lens cap (PVC reducer shortened by 0.25"). Works fine on my many Canon FD/FL lenses. Flat field or curvature depends on eyepiece you use.

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#14 geezer88

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Posted 26 March 2011 - 09:39 AM

Nice job on your conversion. I love the creativity of this site.

Here's another option for folks that are not so handy or don't have the time:

http://img27.imagesh...572/page17y.jpg

Look down to the bottom right corner for the "Wide Field Tele-View Adapter" made by Tamron. I don't think they are available any more, but you can find them now and then on the auction sites. They can with a range of adapter for different manufacturer of lenses, and optically they are quite good. I've got two of them that will some day become a large binocular. Even with the wrong mount, you could modify the adapter and/or the lens to make it work. It is nice to have an erect image as well as the right angle.

tom

#15 Jobryant

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Posted 17 May 2011 - 06:58 PM

The one in my avatar is the first scope I biult using a Sigma APO 50-500mm ("Bigma") camera lens and an Orion camera holder (the type that holds the camera to eyepiece - I just made it work backwards!)


I know I'm a bit late but I just found this thread anyways how did you like the Bigma as a telescope SilentLight? Is the image any good?

#16 TONGKW

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Posted 17 May 2011 - 10:15 PM

Yes, this works very well given the flat, well corrected image produced by a good camera lens. Its just too bad that most camera lenses don't have enough back focus to allow the use of a diagonal. Really a shame given that I probably have more invested in camera lenses than in telescopes! :(


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Yes, you can add a 2x Barlow between the lens and the diagonal and then infinity focus can be reached.

K W TONG
C8+CG5 GT, TSA102+HEQ5 PRO, MK67+Voyager, NexStar 6SE, C5+Mizar K, WO ZS80FD+Kenko NES, Megrez 72FD+Kenko KDS, Mini Borg 50, PST

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  • 4587868-Lens Scope 400f5.6 -002.jpg


#17 rkayakr

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Posted 18 May 2011 - 09:03 AM

In the same vein Surplus Shed sells a telescope / finder kit that includes a 105-150 zoom lens, a 1 1/4" diagonal, an eyepiece, some plastic tube sections and includes a padded case. I got mine during the last sale for ~ $40.

http://www.surplussh...item/k3001.html

#18 tekcajder

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Posted 19 May 2011 - 09:39 AM

Thanks for all the feedback, sorry about the lapse - I've been really busy and haven't had a chance to post anything for a while.

What's the mechanism to make the eyepiece tight to the assembly?


The tolerance between the 1-1/4 eyepiece and the 1-1/4 hole cut through the two pieces of masonite are pretty close. Also having three holes (one in the lens cap, and two in masonite) that were hand-aligned, helps keep the eyepiece nice and snug in the tube.

#19 oso

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Posted 18 March 2012 - 11:18 AM

has any built a scope just using the lenses


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