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View Full Version : f/2.5 7in. 5x5 HCO 022 lens



Pat Kearns
26-Apr-2012, 20:41
I acquired a f/2.5 7in. Harvard College Observatory lens recently along with a Kodak Aero Ektar f/2.5 lens. I appears to my eyes these two lenses are the same? Okay all you lens Guru's out there what is this HCO lens? This is one serious hunk of glass.

RawheaD
26-Apr-2012, 20:46
Ah, you got it from Ebay. I had my eyes on the listing. Yes, it looks the same as the Aero Ektar.

Pat Kearns
26-Apr-2012, 21:18
Ah, you got it from Ebay. I had my eyes on the listing. Yes, it looks the same as the Aero Ektar.
No, I got it locally and it with an Aero Ektar was in a couple of boxes of treasures and trash. I'm picking through them to see what to keep and dispose. I knew about the Aero but this stumped me. When I googled Harvard College Observatory I figured it might be a telescope lens but it has an aperture whereas the Aero didn't. I guess the aperture will increase the DOF a little more. Just click stops no f/stop markings.

Dan Fromm
27-Apr-2012, 06:26
Pat, whatever it is the fourth image shows Newton's rings, so at least one pair of cemented elements is separated.

Most 7"/2.5 Aero Ektars have diaphragms. Few 6"/2.5 Aero Ektars (and the same made by, IIRC, B&H) have diaphragms.

Can you check to see whether it is radioactive? All 7" Aero Ektars are.

It seems to be an aerial camera lens. Like many lenses for aerial cameras it has three radial pins at the front for attaching a spring-loaded filter holder.

frybros
21-Apr-2014, 23:42
Post seems a bit old but I just picked up one of these lenses from ebay and I love it!
I put it on my graflex and took my first few photos over the weekend. It was an aerial lens commissioned for the Victory Lens Project.
This is what I found.. http://www.osa.org/en-us/about_osa/newsroom/obituaries/obit/

Dan Fromm
22-Apr-2014, 06:17
All very odd. G. H. Aklin, a Kodak lens designer, filed for a patent on the f/2.5 Aero-Ektar design on Oct. 8, 1941. The patent (USP 2,343,627) was granted Mar. 7, 1944.

The OSA obituary says "Goddard's "Victory Lens" project began on May 20, 1942 when he visited Dr. Baker's office at Harvard Observatory and described the need for a lens of f/2.5 covering a 5x5 plate to be made in huge quantities from rolled optical glass."

I think the person who wrote the obit got things slightly wrong.

EdSawyer
22-Apr-2014, 18:56
I saw the one on ebay, it's definitely a normal 7" aero ektar. Why harvard bothered to "rebrand" those, one will never know. Seems like an inane thing to do. Agreed re: that obit being pretty imaginative and far off in more than a couple respects.

launiek
27-Apr-2014, 19:57
I saw the one on ebay, it's definitely a normal 7" aero ektar. Why harvard bothered to "rebrand" those, one will never know. Seems like an inane thing to do. Agreed re: that obit being pretty imaginative and far off in more than a couple respects.


I saw the one on ebay, it's definitely a normal 7" aero ektar. Why harvard bothered to "rebrand" those, one will never know. Seems like an inane thing to do. Agreed re: that obit being pretty imaginative and far off in more than a couple respects.

No, in fact the WW 2 Harvard Observatory Optical Project Baker-designed 7" f/2.5 lenses are of a different design made at around the same time to satisfy similar requirements using more readily available and cheaper thick opthalmic sheet glass instead of the rare earth glasses used in the Kodak Aero Ektar design. I don't believe it worked quite as well as the Aero Ektar, but since I knew some of the people involved with the project much later on I'd still love to have one of them myself, should anyone have one they'd part with. I have the 6, 7 and 12" f/2.5 Aero Ektars, and they do show the amber tint of the rare earth glass. Rudolph Kingslake, head of optical design at Kodak for many years mentioned Harvard's design in a 1946 report on recent developments in aerial lenses, and it's documented in other reports, too. There even was yet another design done by Baker in conjunction with Polaroid in the 1940's that had one or more plastic elements. During the war the Harvard Optical Project was moved off-campus and grew to design and build prototype quantities of 80 different aerial (and other) lenses for the war effort. Among the lenses and cameras built by Baker's group was what is probably still the largest camera ever built and flown. It had a 32 inch aperture lens and a huge negative size, and occupied a large part of a B-36. I think it's now on display at Wright Patterson AFB. Many of James Baker's lens designs such as the distortionless 40" f/5 and the 36-inch f/8 were manufactured during the war in quantity by Kodak, Bausch and Lomb, Fairchild and Curtiss.

Baker is credited with being the first person to use a computer for optical design (Harvard's Mark 1 computer) in the 1940's. That Optical Society obituary of him mentioned above is in fact accurate, and doesn't list many of his accomplishments. Here's a link to an Air Force Space Command bio of him when he was inducted into their Hall of Fame in 2002: http://www.afspc.af.mil/shared/media/document/AFD-100405-071.pdf