bicyclerepairman Loc: North Central Texas

Good one!

bicyclerepairman Loc: North Central Texas

Good one!

amfoto1 Loc: San Jose, Calif. USA

It looks similar to, but bigger than a Konica Hexanon 800mm f/8 I've got. Based on that, I'm guessing it's an old 1000mm f/8 or f/11 lens... but have no idea the brand.

The one in your photo appears to have a teleconverter added and be focused near it's minimum (which causes a LOT of extension of the barrel).

The Hexanon has a similar focusing ring. About four feet long w/ hood, around 8 to 9" (200mm) diameter and roughly 15 lb., it's also large enough that instead of the lens rotating on the tripod mount to switch back and forth between portrait and landscape orientation, the bayonet mount can be loosened to allow only the camera body to rotate. As you can see in the photo below, the Hexanon also has two folding "sights" to help you get closer to "on target" with it. It's a bit surprising that such a large lens only has two optical elements in a single group. It uses 55mm drop-in filters and has a minimum focus distance of about 20 meters (roughly 65 feet).

EDIT: I found reference to Asunama, Soligor and Vivitar 800mm lenses here: https://www.dpreview.com/forums/thread/3947231 There also was a similar Tokina 800mm, which could be split into two section to make it easier to transport... and might possibly have been usable with different heads to provide different focal lengths (400mm, 500mm, 600mm).

Below are several photos of a later version Hexanon 800mm (focused at infinity which shortens the lens considerably to it's minimum and without lens hood extended.... mine is the earlier version with a preset aperture, a screw-in lens hood and a different overall finish), photos courtesy of Camerawestwc:

(Download)

wdross Loc: Castle Rock, Colorado

It's a 21mm f2 wide angle!
Just kidding! It looks more like an older telescope telephoto design. Maybe 1500mm or 2000mm? If the light is not bent much by the glass lenses, maybe 1500mm or 2000mm? If the lens bends the light more, maybe 2000mm or 3000mm?

DaveC Loc: Illinois

With only a two element lens at the front it is not a ‘telephoto lens’ but rather a long focal length lens. Like a telescope without an eyepiece. Far less cost to design and manufacture but unwieldy long.

jerryc41 Loc: Catskill Mts of NY

And we have a winner!

amfoto1 Loc: San Jose, Calif. USA

THAT's an understatement!

DeanS Loc: Capital City area of North Carolina

I strongly disagree, it is a nifty-fifty 1.4 Super Takumat from Pentack and an extra long lens hood. I have the same lens, minus the hood, still on my ‘67 Pentack.

Alafoto Loc: Montgomery, AL

Is Pentack the Chinese reverse engineered version of the Pentax?

Longshadow Loc: Audubon, PA, United States

hassighedgehog Loc: Corona, CA

Call it an M31 for the galaxy it could see. (Or to give it's common name, the Andromeda Galaxy.)

kcaaron

Possibly they exchanged photography secrets before wireless signals
were invented between warships in Pre-World War One...those were the days my friends...😀😀😀

chippy65 Loc: Cambridge

perhaps it should have a "finderscope" on top. A severe case if penis envy ?

mniblick

Definitely less than 6 inches.

DeanS Loc: Capital City area of North Carolina

Can’t say, bought in Viet Nam, so could be. 😎