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I was wondering if anyone here could chime in on what type of lens elements this could be? A friend of mine gave this to me the other day for free. I looked up on the web and it is a Bell Howell 36" F/8 Type I (914mm FL) Objective. It was used in U2 Spy Planes back in the day. Now this is just the Objective part. The full version as seen in the photos has a shutter fixed to it and some type of rear element Lens. Well I don't have them and thinking why can't I make a refractor of it. Since those two parts were for making Very Large Photos I think.
Also, the rear glass of the objective is somewhat curved as shown in the photos. I can take more photos if needed.
Now for my questions.
- Does anyone know what type of Lens Elelement it could be? Acro, APO, Doublet etc... Ad if so, could it be Airspaced or Oil used in it?
- Can I use this to make a refractor or do I need that Rear Element which could be a corrector of some sort or to aid in the Camera that was used, I think they were Ultra Wide Format?
- If I can make it a refractor, would the focal length be (914mm) or different since I don't have the Rear Element?
The Blue Part is the Glass Objective
Rear Hole
Thanks in Advanced
Telescopes:Apertura AD12 Dob : iOptron CEM70 without TripodBarlows:GSO 2x Shorty Focuser: Rigel nStep
ahh it must be 36'' focal length ,''camera lense specs'' .
Is the glass itself about 5.5 inches in diameter? so the second element must be some sort of barlow lense . f8 at 36" (914mm) fl = 114 mm front objective lense diameter which isn't correct shown in your measurement . so it looks like you will definitely need another element to get the lense to a usable focal length
edit: so let say ahh the lense is 5.5'' that's 139x8 = 1112mm , so the second lense is a focal reducer ?
scopes :gso/bintel f4 12"truss tube, bresser messier ar127s /skywatcher 10'' dob,meade 12'' f10 lx200 sct
cameras : asi 1600mm-c/asi1600mm-c,asi120mc,prostar lp guidecam, nikkon d60, sony a7,asi 290 mm
mounts : eq6 pro/eq8/mesu 200 v2
filters : 2'' astronomik lp/badder lrgb h-a,sII,oIII,h-b,Baader Solar Continuum, chroma 3nm ha,sii,oiii,nii,rgb,lowglow,uv/ir,Thousand Oaks Solar Filter,1.25'' #47 violet,pro planet 742 ir,pro planet 807 ir,pro planet 642 bp ir.
extras : skywatcher f4 aplanatic cc, Baader MPCC MKIII Coma Corrector,Orion Field Flattener,zwo 1.25''adc.starlight maxi 2" 9x filter wheel,tele vue 2x barlow .
yobbo89 wrote: Tue Aug 29, 2023 1:13 pm
ahh it must be 36'' focal length ,''camera lense specs'' .
Is the glass itself about 5.5 inches in diameter? so the second element must be some sort of barlow lense . f8 at 36" (914mm) fl = 114 mm front objective lense diameter which isn't correct shown in your measurement. so it looks like you will definitely need another element to get the lense to a usable focal length
edit: so let say ahh the lense is 5.5'' that's 139x8 = 1112mm , so the second lens is a focal reducer ?
Thanks Rob, I was thinking the rear lens was a corrector/reducer of some sort lol. I think the objective is around 6.5"-7" When I get back home I will check it out more.
Now the X factor in the rear lens, could that be a corrector/reducer that is specifically made for Ultra Large Format Camera? If so , then could I get someone to make a corrector of some sort? It is kind of gona be a work in progress over the next few years. I want to machine the tube ect... Even if it is not the sharpest, I think it is kind of cool to say this was taken from a U2 Bommber spyplane Lens lol. I read that the same lens was shownin the movie" The Courier" which was made in 2020 and about the Cold War with hte Russians.
Thanks Again Rob and soon enough I should be back up imaging,
Brian
Telescopes:Apertura AD12 Dob : iOptron CEM70 without TripodBarlows:GSO 2x Shorty Focuser: Rigel nStep
yobbo89 wrote: Tue Aug 29, 2023 5:16 pm
i had a look on ebay, there's a few complete ones, they go for about $500+ , big image circle
Yeah, I kind of wish I had it complete, but Free is better lol So correct me if I am wrong. If that rear element was used for an Ultra Large Format Cameras, Could I find another corrector or have one made and put it in the imaging train specific for today's Astro cams like the ZWO6200mm or 2600mm? I know I would probably have to have the rear element custom-made.
Also what kind of a guess do you think the Len elements are in the Objective? I know I won't find out until it is taken apart and cleaned. And by the way the objective weighs 10lbs lol
Telescopes:Apertura AD12 Dob : iOptron CEM70 without TripodBarlows:GSO 2x Shorty Focuser: Rigel nStep
Hi @TheButcher
These aerial survey lenses were designed for 4x5in 5x7in or 8x10in. The rear element is a corrector/flattener for the large image circle. If you are going to put a smaller digital sensor behind it, you might get away with nothing (try it) or a modern field flattener.
My astronomy mentor, Arthur Page, had a Wray astrograph, a 9" diameter f4 lens that could shoot onto 4x5 in or 5x7 in glass plates. He also had two Ross lenses, perhaps 4" diam @ f10. The picture shows the mount. The main instrument was a Coulter 12" f15 classical cassegrain with a large photoelectric photometer hanging off the back. Arthur is looking through a 4"f15 Unitron Refractor finder/guidescope. The Wray is sitting between the forks. The Wray weighed about 40kg. The mount is a custom made fork mount. The Fork base plate was a 1 metre diameter circular 1 inch steel plate with massive forks and a worm drive that from memory was 24-30 inch diameter.
You can't see the two Ross 4" astrographs, they are hidden behind the instrument from this angle. Having two, he could image two plates with R & B filters simultaneously.
.
Your lens will be an achromat on anastigmat definitely not an APO. These are probably at least 50 -80 years old lens designs and predate ED and APO glasses that only began to be used in the 1980's/90's.
Remember that the principle was that the focal length was long and the large format was only contact printed or very slightly enlarged. A 2 X enlargement of an 8x10in plate produces a 16x20in print. The lenses are not really good enough for high enlargement used with modern small sensors.
I would suggest that the results will be less than optimal unless you get the original corrector and shoot large format film. The project will cost a fair bit. The point of all the talk of my mentors scopes is to show that you will end up with a very heavy OTA that will require a very expensive solid mount to support it.
In my opinion, you are probably wasting money and you'd get better results with an small Chinese APO refractor (ED80?) and a flattener.
Cheers
Joe
Joe Cali (OzEclipse)
34 South - The Hilltops Observatory
Hilltops region, Young, New South Wales, Australia. [148E, 34S]
Amateur astronomer since 1978.....Web site :http://joe-cali.com/.....Total & Annular Eclipses Observed:18 Scopes: ATM 18" Dob, Vixen VC200L, Hand Made 6"f7, Stellarvue 102ED, Saxon ED80, WO M70 ED, Orion 102 Maksutov, Coronado PST Binoculars: Celestron Skymaster Pro 15x70, SV Bony SV202 10x42ED Mounts: Takahashi EM-200, iOptron iEQ45, Push Dobsonian with Nexus DSC, 3 ATM EQ mounts. ..............Losmandy Starlapse, Vixen Polarie and Skywatcher Star Adventurer compact trackers. Eyepieces: TV Naglers 31, 17, 12, 7; Denkmeier D21 & D14; Pentax XW10, XW5. Cameras : ZWO ASI2600MC, Pentax K1, K5, K01, K10D / VIDEO CAMS : TacosBD, Lihmsec. Cam/guider/controllers: Lacerta MGEN 3, SW Synguider, Simulation Curriculum SkyFi 3+Sky safari Memberships The Sky Searchers (moderator); Astronomical Association of Queensland; RASNZ Occultations Section.
Thanks for all that info Joe, very interesting Now, I think I may end up making it some kind of showpiece or something or selling it rather than spending the money to try to make it a scope and take your advice and just go for a modern APO again. Hopefully, I will be back up and running again this year imaging.
And Thanks Again for giving such detailed info about the lens and your explaining your Mentor's setup.
Brian
Telescopes:Apertura AD12 Dob : iOptron CEM70 without TripodBarlows:GSO 2x Shorty Focuser: Rigel nStep