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Surplus Shed 127/700mm RFT/Spotter

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#1 BillB9430

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Posted 10 September 2008 - 03:09 PM

Hello folks,
I’ve been away from Internet and CN access for this past summer. Somewhat belatedly, I can now share photos and information about my Surplus Shed 127/700 mm RFT prismatic spotting scope that was completed last May. Looking back at the ATM Forum archives, it seems that not much has been posted on scopes built with this lens. Surplus Shed now lists this objective as temporarily out of stock, so hopefully more of these excellent lenses will be available soon. I was also lucky enough to buy two pairs of 50 mm Porro-Abbe prisms here on CN classifieds. (Thanks again, Howard!) Two of the prisms were cemented together to make an oversized erecting system for the scope. Focusing is accomplished using a homemade helical focuser made from thick wall aluminum tubing and UHMW polyethylene. The components were assembled in a 5” aluminum tube, with a short length of 6” aluminum tubing serving as a glare/dew hood. The scope is a joy to use, and provides high contrast, sharp, wide field images. Used with a military surplus 38 mm Erfle eyepiece, it gives 18 x and a 3.5 degree field – a space walk feeling for astronomical viewing. It also gives good images with the Garrett SWA eyepieces down to 20 mm focal length (35x). In bright sunlight (for terrestrial use) and excellent seeing, one can even get away with Barlowing the 20 mm SWA to give 70x. I was pleasantly surprised to find that although the glare stops were cut to allow illumination for 2” wide field eyepieces, there does not seem to be much contrast loss when using 1.25” eyepieces with a smaller field stop. The complete scope with large military surplus eyepiece weighs 13.5 lb. (6 kg).
Used terrestrially, the instrument is kind of a “spotting scope on steroids”. It provides bright images in the evening; long after my 3” spotting scope is out of business. Dozens of visitors used this scope to get good (and safe) views of grizzly bears and other wildlife in Glacier National Park this summer.
I have other photos of construction details and will be glad to post more if there are questions. Five photos follow. – Bill Blunk

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  • 2635297-Erecting prism assembly.jpg


#2 BillB9430

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Posted 10 September 2008 - 03:13 PM

Final assembly of the 127/700

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  • 2635301-Final Assembly.jpg


#3 BillB9430

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Posted 10 September 2008 - 03:15 PM

Finished scope

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  • 2635308-Finished scope.jpg


#4 BillB9430

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Posted 10 September 2008 - 03:17 PM

Focuser w/38 mm Erfle

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  • 2635310-Focuser w:38mm Erfle.jpg


#5 BillB9430

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Posted 10 September 2008 - 03:19 PM

Viewing griz with the 5" scope

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  • 2635316-Viewing griz.jpg


#6 Wes James

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Posted 10 September 2008 - 03:27 PM

Nice looking scope, nice looking execution! Rare to see a scope here with an erecting prism incorporated into the design! Welcome back!

#7 Lynnrb

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Posted 10 September 2008 - 08:14 PM

This my version of the Surplus Shed 127/700 lens. It is a straight RFT astro scope. It has a 5" tube, 2.7" R&P focuser and 1 baffle just ahead of the draw tube. Lynn

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  • 2635776-059.JPG


#8 mattyfatz

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Posted 11 September 2008 - 02:58 AM

Bill
What an excellent project. I would be interested in the full report about the construction of this scope. I can't stay of that SS website, thinking about all of the fun scope projects I could crate from their stock.

#9 mattyfatz

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Posted 11 September 2008 - 03:00 AM

Lynn
Great looking scope. Is the mount home made as well? how about that focuser? Is the tube made from PVC pipe?

#10 Glenhuon

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Posted 11 September 2008 - 04:48 AM

Nice jobs guys.
I've made 3 so far. The 80x 400, 70 x 500 (guide scope) and the 102 x 600. All were good except the 80, had to change the objective cell for an adjustable one to get rid of coma. But that might have been misalignment in the assembly as it was the first one I made.

Bill

#11 StarStuff1

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Posted 11 September 2008 - 10:36 AM

Lynn, how sharp are the images in the astro RFT? Maximum useful magnification? I would expect noticeable CA on bright objects. I had been thinking about an Orion 120 f/5 but might wait until SS gets these lenses back in stock if they are at least as good as the Orion.

Anybody want to report on how their 120 f/5 Chinese scope performs?

#12 Lynnrb

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Posted 11 September 2008 - 01:10 PM

The scope is all aluminum except for the lens cell(lens came with a plastic cell). The 2.7" focuser is from a Meade ED refractor. The mount is aluminum also, it was designed to be a GEM but I mounted the south end of the polar axis vertically to the tripod so now it is an alt/az.
The CA is not very noticable at the low power that I use with this scope. It is an f/5.5 achromat so the CA will be there at higher power. I use my 5" Meade refractor for higher power observing.
I see nice sharp views at the 30X with this scope. I use it to sweep the Milky Way and large objects like M45 ect. Lynn


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