### 360mm Nikkor Tele on Horseman FA

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I realize it`s a huge lens, but has anyone tried a 360mm Nikkor tele on a Horseman FA? I can`t seem to find the diameter and length of the rear element anywhere. Thanks, Steve Clark

-- Steve Clark (agno3@eesc.com), December 17, 2000

Steve: The rear mount diameter on the 360T Nikkor is 60mm... I think that will just fit the FA. Rear element length from flange is about 50mm... also no problem... but, the flange focal length at infinity is 261mm which is really near the 272mm limit of the FA (which includes maximum back extension). You will want to investigate one of Horseman's telephoto lensboards which protrude forward.

-- Glenn Kroeger (gkroeger@trinity.edu), December 17, 2000.

Glenn, I have both a 25mm and a 65mm extended tele board for the FA. I can get a total of about 335mm of extension, however the inside diameter of the boards is only about 58mm. Depending upon how that rear element is tapered it may or may not fit on the 25mm board if the rear element is indeed 50mm long. If the flange focal distance is 261mm on that lens, how close would it focus with 295mm of extension? Sorry the math fails me right now, do you know the formula for that? Thanks, Steve

-- Steve Clark (agno3@eesc.com), December 17, 2000.

Steve, my understanding from email communications I had with Horseman is that the 360 mm Nikkor will fit on the 25 mm extended board, but not on the 65 mm extended board. I believe that the 400 mm Fuji T will fit on BOTH boards, but because of the stability problems caused by the weight, Horseman only recommended using the 400 mm Fuji I on the 25 mm extended board. Hope that helps.

-- howard slavitt (info@naturelandscape.com), December 17, 2000.

Steve: If the rear opening in the boards is only 58mm, it looks like Howard is right, the 25mm board should work. As for focusing distance with 296mm of extension, I will calculate it exactly, but I am going to guess something like 20 feet.

-- Glenn Kroeger (gkroeger@trinity.edu), December 17, 2000.

That guess is based on the Toyo 45AX, which with 321mm of extension, can focus the 360 Nikkor to 8.3 feet.

-- Glenn Kroeger (gkroeger@trinity.edu), December 17, 2000.