tommy2 Loc: Fort Worth, Texas

Since my 70 to 200 lens has not sold I want to convert/adapt it to be a spotting scope. I would like to add something to it to allow a telescope eyepiece to be attached. Any thoughts on this project would be appreciated. Thank you in advance, Tommy

CHG_CANON Loc: the Windy City

Sell the lens to KEH and use the proceeds to purchase an actual spotting scope, if that's what you desire.

tommy2 Loc: Fort Worth, Texas

That was my first thought but KEH will give me barely enough to buy a Penntax spotting scope. I borrowed a friend's and found they do not have the sharpest optics - compared to the canon lens. Also found this : Kenko Lens2Scope adapter but it does not allow the use of a telescope eyepiece - it has one built in and I want to use a quality lens I have left over from celestial bodies viewing. Thank You

Basil_O Loc: Minneapolis, MN

The Kenko Lens2Scope adapter is actually a pretty good option. I have one that I will add to a 500mm reflex (mirror) lens to view the moon. The detail is amazing. It has a 10x magnification factor, so it becomes the equivalent of a 5000mm viewing scope in a very compact package. It's worth giving it a go.

You may also wish to check out this page for another option:
https://www.bobatkins.com/photography/technical/Lens-scope-adapter.html

and this:
https://www.instructables.com/Turn-a-telephoto-lens-into-a-spotting-scope-or-tel/

tommy2 Loc: Fort Worth, Texas

Good idea - what Bob Atkins suggests. Just have to embolden myself and get a hacksaw - do have all the necessary parts. Thank you.

Basil_O Loc: Minneapolis, MN

I also added another link with a different option

tommy2 Loc: Fort Worth, Texas

Ok, the mention of a Barlow makes me feel better - have one plus an erecting lens. Don't know if one of the angled eyepiece holders might have the erecting prism built in or not but maybe the Barlow will fix that part's additional light path. Thank you again.

MJPerini

The issue with 'Telescope converters' is that they have to do a lot in a short space.
Any Camera lens is designed to form an image at the film plane, maybe 30-35mm.
So the image has to be inverted, and then magnified in a short space.
The Adapters do a pretty good job under those circumstances, but your scope will not be as sharp as you remember the lens being--- because there are a bunch of optics crammed into a small space.
This also depends a little on the optical compatibility of the lens to the adapter.
I have seen both good and bad reviews of the kenko & others so try before you buy

jamesl Loc: Pennsylvania

tommy2 Loc: Fort Worth, Texas

"The issue with 'Telescope converters' is..."

So I thought about your post and looked for an old Canon 40d body in the junk box, put the lens on it and mounted it on a tripod to have a very clear lens telescope. Now only need to find an angled adapter to look through the viewfinder. Actually makes a reasonably sized telescope with auto focus to boot. Thank you

TriX Loc: Raleigh, NC

or just connect the video out to an appropriate monitor with an NTSC (composite video) input, and use the camera in live view with the auto shut off disabled.

47greyfox Loc: on the edge of the Colorado front range

Personally, I’d sell the lens to KEH or MPB and use the money to buy something like a Celestron Regal M2 65ED spotting scope and a mount adapter for your camera. I bought the scope from Amazon last year for $425 plus $25 for the adapter. Excellent lower cost scope. Or, consider a Vortex Diamondback scope for slightly less. The Vortex Viper is nicer but quite a bit more expensive.

tommy2 Loc: Fort Worth, Texas

Good grief - UHH is a treasure trove of golden info!

so need to figure out what and how the suggested option works and look for ingredients to make that happen.

Where this is coming from is I live in an upstairs apartment in a downtown building and see all types of interesting happenings off my balconies...now using this set-up a few can be captured for printing. WOW

MJPerini

DIY projects are fun, and you can learn a lot while doing them. I'll make a couple of additional observations......
Optical quality, most camera lenses are very high quality, and quite sharp, they are sharp not just because of the fine lens elements, but also because of the extreme precision of mounting and centering those elements.
An all in one adaptor (Mount, erecting prism or optics and an ocular designed by an engineer who has considered the above) is probably your best shot.
You can also (as has been suggested) move the focal plane back with a barlow lens (good achromatic ones are not cheap, and cheap ones are not good) then assemble that with the hole in a plastic lens cap method, then add an erecting prism and then a telescope eyepiece. It can work, but consider alignment, additional air to glass surfaces (which degrade contrast) and you are pushing it.
Also most modern telephoto lenses already have a negative final element or group (essentially a barlow lens) as part of the lens design to keep them compact. So there is a fair amount of optical stacking going on.

I do not write this to discourage you from having fun with old lenses, but just to consider before you spend money on all the pieces. Because the KEH value plus whatever you would spend on the pieces, probably buys a better spotting scope than you are making.
If you happen to have all the stuff and just want to try it, Go for it

Basil_O Loc: Minneapolis, MN

Very few of
my dyi projects are as good as store bought alternatives. The fun is in the challenge to see I can make it work. This is coming from someone who once had the bolts holding a newly rebuilt alternator back themselves out.
I got it back together on the side of the road with bailing wire and duct tape. I drove it for the summer just to see how long it would last. The tape burned off, but the wire held. I was 16 and stupid, but smiled each time the car started and was charging the battery.

I digress. Enjoy playing with your scope/ lens.