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Mike Lang
member
Reged: 07/25/09
Posts: 15
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Howdy:
I have an old Zeiss Apochromat Tessar 64mm diameter, f10. Apparently was used in a large format camera as it has an iris. Has very faint coatings, no scratches on the elements, clean glass. Wondering if anyone has tried building up one of these lenses in a telescope for visual imaging or astrophotography, and if so, do you think it's worth the effort ?
thanks !
MRL
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tommyhawk13
professor emeritus
Reged: 09/28/07
Posts: 693
Loc: Jacksonville, Fl
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I think those large format f/9 and f/10 lenses are copy lenses, meant to reproduce print where everything has to be perfectly flat and tack sharp from a close distance. I don't think they do so well when focused at infinity, at least for photography.
Do you have a large format camera?
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Meade Starfinder 8,Meade SN-8 OTA, Orion Atlas, and a handfull of film cameras
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ZachK
professor emeritus
Reged: 08/21/05
Posts: 709
Loc: Israel
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I have something similar, a F5.6 300mm fl lens, was thinking about trying to build something around it. It may become a LF sky camera.
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Zach Kessin
Ariel Israel
Meade ETX 127 Mak-Cass
15x70 Celestron Skymaster Binoculars
Sinar F 4x5 view camera
Rolliflex Camera 80mm F2.8
Pentax K-1000 Camera 35,50 and 60--300mm zoom
4 kids
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Vincent Becker
super member
Reged: 09/16/08
Posts: 198
Loc: France
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The Tessar (four lenses it three groups, Tessar coming from the greek word for "four") was an excellent design when it came out... in 1910. At that time films where orthochromatic, i.e. insentitive to red. So the lenses are usually not very well color-corrected. But as yours is f/10 it might be OK. Tessars begin to get quite good à f/3.5 and very good at f/8. For astrophotography color correction might become a problem with H-alpha as it is quite far in the red. I have the problem with a Leitz Macro-Elmar 65mm f/3.5 of essentially the same design (though very different FL and apreture).
If you have a hint of coatings (I guess it is bluish) then it is a Post-WWII lens. Don't expect wonders from it regarding flare and transmission, though it is better than nothing.
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Vincent Becker
10" dobsonian on EQ platform (home-made by my father)
8" string newtonian as travelscope (home-made by myself  )
Orion 80ED and GSO 200/1000 on Atlas EQ-G for astro-imaging
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Mike Lang
member
Reged: 07/25/09
Posts: 15
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Thanks for the responses.
I disassembled the lens last night to perform a light cleaning (there was some dust on the internal elements, and a slight haze on them). All the surfaces are coated - light blue. I read on line that some of the older coatings could be damaged by water, so I used an alcohol based lens cleaner that we use in the lab to clean microsope lenses. The lenses all cleaned up very nice, and they are still coated. When I got it apart, I did find that there were a few faint scratches (apparently from an earlier overzealous cleaning). Most interestingly, there is a very tiny bubble inside two of the lenses, and the center lens coating has a very nice deep blue coating on both surfaces. I cleaned up the iris so that it operates nice and smooth now. Reassembled the lens and maintained the clocking between the elements (not that the earlier "disassembler" did). Next step will be to machine a threaded flange to attach it to a piece of thin wall aluminum tubing. Because it was designed to focus onto a flat film surface of a large format camera, I would think that it should do well for a tiny CCD. Of course, I'm most interested in the "APOCHROMAT" aspect of the lens, but I suspect, that term has a different meaning to us today than it did 60 to 100 years ago.
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Vincent Becker
super member
Reged: 09/16/08
Posts: 198
Loc: France
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I think like you that the Apochromat name can't be translated into today's APO.
Tiny bubbles are perfectly normal for lenses of this era. Optical glass was very expensive to make and, as a tiny bubble won't affect the image at all (no more than the few scratches) they were tolerated to some extent.
I don't think that the clocking between the elemnts matters much, the distance between them being more critical.
Is there an integrated shutter or is it a bare lens with an iris? BTW, NEVER apply any lubricant to the iris. It would kill it.
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Vincent Becker
10" dobsonian on EQ platform (home-made by my father)
8" string newtonian as travelscope (home-made by myself )
Orion 80ED and GSO 200/1000 on Atlas EQ-G for astro-imaging
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Mike Lang
member
Reged: 07/25/09
Posts: 15
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The lens only has an iris - no shutter. And when I had it apart, I pondered oiling the iris because it was a little stiff, but decided against it, exercised it a few times and gave it a few puffs of air from my lens-cleaning bulb. It works nice and smooth now. We had a spectacular blue-sky day this weekend, so I sat the elements out in direct sun around noon for 15 minutes, just in case there were some nasty fungus spores. I think I will assembly the lens into a wood box for a quick check - to help me decide how involved I will (or not) get into it. If it checks out okay, I'm thinking an all-brass tube and an old Sky Giant microfocuser would match the "ambiance" of the lens. Anybody have a source for 2.75 to 3 inch diameter brass tubing ?
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