I've wondered how workable bakelite is, using machining techniques; it has fibers which might leave a rough surface. Let us know how this works out. --Peter
Subject: Russian 6x30
Did you or anybodyelse tried the Russian 6x30 wide engle binoculars? how is it compare with the 7x30 or 8x42? this 6x30 do not appear have the same long eye pieces. what interested me was the 12 degree view angle. did anybody compare with Sard 6x42? have u seen Russian military 8x30 wide angle binoculars? with fat eye pieces? look like a sister of Sard.
Lets us get this right. I suggest Smith, Modern Optical Engineering, McGraw-Hill. The denser glasses are desirable to avoid clipping, which occurs when some rays near the field edge fail to be totally internally reflected. Other rays in the cone from a point near the field edge will be totally internally reflected. The axis of this cone is not the optical axis. There are diagrams in Henson, Smith , Mil-Hndbk-141, etc . Vignetting is something else, an inverse function of prism size, and has been allowed in large amounts in prism binoculars . Clipping is the blue shading surrounding a bright square in the exit pupil . Vignetting is less obvious. Somebody in a SPIE publication called clipping an axial effect. Who was it, SPIE members? I call it erroneous. The right angle Fuji 25 x 150 used a pentaprism which was undersize relative to the normal Porro II which was downstream. Andy Toth noticed vignetting to be more than in his normal 25 x 150. The pentas came from a Japanese military rangefinder program of Fuji.
Re: prism glasses. The Fuji 25 x150 uses bk-7. Who needs BaK-4 at f/5., in a Porro II? Bk-7 has higher transmission, costs less, is lighter, and easier to work. A drawing and calculation will show if higher indices are needed in a particular case.
Subject: Large binocular Newtonian telescope
At this weekend's Oregon Star Party, I took pictures of Bruce Sayer's 22 inch binocular Newtonian.
A directory of 22 images is found at:
Binocular List #268: 08 September 2003
Subject: Carl Zeiss 7x30 Marineglas
I have a Carl Zeiss 7x30 Marineglas binoculars I have not been able to document in any source. The binoculars are marked "Carl Zeiss Jena" on the left prism housing and "Marineglas 523095 7X" on the right housing. The ocular glass measures 15mm diameter and the objectives measure 30mm. The prism top/bottoms are made from brass. There is an interocular lock at the bottom of