Hi! Longtime Lurker Posting intro and lens mount question

Hi Everybody!

My name is Sean. Generally I have just been a reader of the forum for any tips y'all post and browsing other's work...every now and then posting a comment on something I think I know well enough to comment on.
My interests in photography are geared to more abstract with interests in recursive images and slitscan/rollout/perip​heral types of photography and video work.

My reason for posting is not so much to introduce myself but to ask for help identifying a lens mount so I may purchase an adaptor and use the lense on my canon EF bodies.
A while back a family member picked up a lens at a a thrift store. I haven't cleaned it but the optics look free from major issues, I just don't know the mount type to get the correct adaptor.
Its a Sigma Mirror Ultra-Telephoto 1:8 f=500mm
Made in Japan
Attached is a photo of the mount. It almost looks like a sigma sa mount or an EF but isn't as I have a sigma sa-9 and it doesn't fit.
Any ideas?
Thanks a bunch in advance!

Can you show the side of the mount? Many of the old mirror lenses are T mount, which adapt to just about anything. There may be an adapter on it already.

Heres another quick phone shot of the side.

Does the lens mount unscrew? Several ebay auctions that I see lead me to believe this is a T mount.

http://www.ebay.com …26sd%3D22179271​5676&rt=nc

http://www.ebay.com …26sd%3D22179271​5676&rt=nc

I agree, it's worth trying to unscrew it - if it comes off, it's a T-mount, and there are EOS T-mount adapters available. If it won't unscrew, take a look here for a representative selection of camera lens mounts.

It possibly could unscrew, the four black philips heads in the first picture, but one screw started stripping without budging so I stopped. The one screw I removed appeared to have glue/lock-tite upon it.
I tried it on an old nikon FM with no luck.
The only differences between those ebay items is the lens mount being not quite as chunky and having this sliding collar with some aperture number markings.
From the way the mount looks, the camera probably controlled the aperture.

I appreciate all the help you guys are putting forth.
Thanks again.

If it's a T-mount typoe lens, you wouldn't undo the Phillips screws; the whole lens mount would be screwed onto the back of the lens, looking something like a Pentax threaded mount. Try twisting the whole lens mount.

My apologies for the tardy reply,

The mount won't turn, twist, shimmy or shake and, unfortunately, it's not a T mount.
It does kinda look like a Pentax k mount, so i'll look more into that.

Thank you!

Looks like a Pentax k mount, except that the actual mount area looks small. I have a couple of pk mounts. Other than that I can only suggest Practikar from Practika.

It looks like an Olympus OM mount to me.

nvm. Olympus OM mount has 2 levers sticking out. One for aperture activation and one for aperture position

Pinquin87 wrote in post #17598053
It looks like an Olympus OM mount to me.

nvm. Olympus OM mount has 2 levers sticking out. One for aperture activation and one for aperture position

Wouldn't rule it out on that basis - the lens is a mirror tele, so doesn't have an aperture control; the lever would signal the aperture position is at f/8.