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My Spiratone spotting scope

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#1 snorkler

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Posted 30 October 2013 - 12:28 PM

Old-timers may remember Spiratone, a discount own-label distributor of camera and darkroom accessories ~50 years ago. One of Spiratone's optics was a Japanese-made Minitel-M 500 mm./8 catadioptric telephoto lens. The lens wasn't great optically, but it was impressively compact.

I got my 50 year-old cat out of mothballs, and used the 35 mm. extension tube off my Lunt LS60T solar scope and the scope ring from my Canon "L" 100-400 mm. IS zoom telephoto lens to make a compact spotting scope.

The Spiratone cat is threaded for a T-mount. The Lunt 35 mm. extension tube is also T-mount threaded, and is the 1.25" eyepiece adapter for my solar scope. The cat was always a macro lens, focusing down to 1.7 m. The resultant hybrid spotting scope maintains that focusing range.

The cat performs better as a spotting scope than as a lens, perhaps because my visual standards are lower. With a nominal 62.5 mm. aperture and large central obstruction, the scope still easily surpasses the views through the standard Bushnell Spacemaster of the 1960s.

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#2 snorkler

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Posted 30 October 2013 - 12:31 PM

For comparison, here's my 80 mm. spotting scope hanging from the tripod.

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#3 KennyJ

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Posted 30 October 2013 - 01:38 PM

Very interesting and certainly compact!

Just the kind of thing I may have come up with, had I the components at my disposal!

Kenny

#4 sarastro

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Posted 30 October 2013 - 05:19 PM

I like that as well. :bow:
How much does it weigh?
I'll have to keep an eye out for an old catadioptric lens.

#5 snorkler

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Posted 30 October 2013 - 09:23 PM

I don't have a scale capable of measuring the lens accurately, but I'm guessing the whole scope (lens, ring, adapter, and eyepiece) total slightly less than a pound (.4536 kg).

I paid $60 for the lens. I had the extension tube and eyepiece laying around the house, but similar eyepiece holding extension tubes are available for $15-$20.

#6 sarastro

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Posted 31 October 2013 - 10:44 AM

Could make a nifty little travel scope.
Have you tried it for astronomy?

#7 snorkler

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Posted 31 October 2013 - 07:03 PM

No, I haven't tried it for astronomy. Mounting a Rigel Quickfinder or Telrad would be a problem. It would be a hoot getting the Messier list with it, wouldn't it?

I was going to the post office, so I took the scope along. It weighs more than I thought - 1 lb., 10 oz.

#8 Mark9473

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Posted 01 November 2013 - 04:55 AM

That's a very nifty device, Darrell. What do you think (or know?) the magnification is?

#9 snorkler

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Posted 01 November 2013 - 11:57 AM

Mark,

Magnification varies with the eyepiece, according to the formula magnif=f.l./ep. Since the Spiratone is a 500mm lens, a 25mm ep gives 500/25 = 20x magnification. A 20mm ep = 25x, and a 10mm ep = 50x. The working range for terrestrial spotting scopes is usually 20-60x.

#10 snorkler

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Posted 04 November 2013 - 04:26 PM

There's a Tokina 500 mm. cat lens for auction here, going for $11 at the moment. Unfortunately, the Tokina TM500 wasn't sold as a T-Mount lens, so anyone wanting to make this into a spotting scope will have to do some modifications coupling a telescope eyepiece adapter to a rear lens cap, a body flange, or something similar.






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