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Rob Willett
Vendor (Degree Circles)
Reged: 02/07/05
Posts: 653
Loc: London, UK.
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Yet another 80mm short field refractor.
I made this with the three aims
1) The cheapest scope I could make. The CFO stopped me spending any money.
2) Learn a little more about refractor optics and design.
3) Something usable, it's no fun just as a test rig.
So far the scope has cost me $29 for the 80mm lens from Surplus Shed. I had the rest of the tubing (?) lying around from some plumbing work. A kind lady gave me an old 42mm telephoto lens to use as the focusor. I had a 42mm to 1.25" adaptor from a filter wheel which was pressed into service.
I chose to use metal rods as it was a real pain finding tubes the right side. This system also allows me to collimate the lens. I am unsure whether to put a diagonal on it, use it as is, or dedicate it as a webcam device. Comments welcomed.
Also if I had read the instructions from Surplus Shed I could have saved two weeks of pratting around trying to get it to come to focus. For those of you who don't know, what appears to me the right way to use the lens is actually back to front. This is clearly explained by SS, but I never bothered to read the page sent to me. .
I can't comment on star performance as the UK now has permanent cloud cover, but pointing it at my neighbours aerial looks OK.
Learnt a lot about refractor design (the mechanics, not the optics) so I think I've met all three targets.
One option is to see if I can make a pair of binoculars out of the second 80mm lens I have sitting around. Suggestions welcomed.
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Thanks,
Rob
Edited by Rob Willett (01/03/08 10:28 AM)
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APM America
Vendor - APM America
Reged: 11/07/05
Posts: 2767
Loc: Madison. NJ. USA
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A truss refractor 
The assembly looks like it might once have held a broken leg in place but all joking aside that is a fascinating piece of work and for less than 20 quid! Impressive Rob.
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Morris Bagnall
Sales Manager
www.apmamerica.com
A whole room full of APM refractors......
Seymor Rosin F/4.5 Astrograph in the making
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Rob Willett
Vendor (Degree Circles)
Reged: 02/07/05
Posts: 653
Loc: London, UK.
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Now you mention it, the tubing does have that 'medical' look about it. Never thought about it before.
Once it's tuned in, I may make a tube to fit.
The next problem is how to mount it. A little tricky at the moment as there's very little to mount a dovetail to.
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Thanks,
Rob
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Wes James
Post Laureate
Reged: 04/12/06
Posts: 3451
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Kewl scope!  (Like the acronym, too! If/when your scope has a full body, you ought to stencil that on it!)
Quote:
The next problem is how to mount it. A little tricky at the moment as there's very little to mount a dovetail to.
How about making a U-shaped channel out of wood- and attaching that to the scope with some nylon cable clamps (or metal) that will just fit the rods/screw onto the inside of the wood channel??
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Wes
Atlantic Beach, FL
Some bino’s from Miyauchi 5x32 Binon's up through Garrett 20x110 Signature's,
Some telescopes from a Stellarvue 80mm NHNG up through a couple of 8” reflectors…
And a wonderful 4.25" Delmarva Shiefspiegler!
Some good friends, made here on C/N.
Oh- several cats and a wonderful wife!
Anyone want a cat???? :-O
"When your work speaks for itself- Don't Interrupt" -Gamble Rogers
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Rob Willett
Vendor (Degree Circles)
Reged: 02/07/05
Posts: 653
Loc: London, UK.
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Wes,
Tried that already, the wood just rotates around the threaded rod. I can't get it tight enough.
I might try L-shaped pieces of metal with shakeproof washers. I might be able to really clamp it all together tight to see if that works.
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Thanks,
Rob
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Wes James
Post Laureate
Reged: 04/12/06
Posts: 3451
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You're not hearing what I'm a thinkin'! Take a look at www.mcmaster.com, search P/N 7572K12... some similar type of clamp (2) like this on each of 2 of the rods the inside diameter of the clamp would be the same size as your rod), then attached to the inside surface of the u-shaped channel of wood that's just slightly larger in inside width/height of the OTA. They're also known as pipe hangar clamps, or electrical clamps, meant for holding bundles of wires or conduit in place. Where I work we also have them in nylon as well as metal with channel rubber to protect whatever is clamped inside the clamp. You could find them at any Home Depot, Lowes or Ace Hardware in the pipe or electrical department. I didn't mean like a zip tie or tie wrap around the entire tube *BLEEP*'y...
Wes
edit- that was an abbreviation for the word ASSEMBLY, not a dirty word!!!
Edited by Wes James (01/03/08 01:10 PM)
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Rob Willett
Vendor (Degree Circles)
Reged: 02/07/05
Posts: 653
Loc: London, UK.
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Wes,
I think I visualise what you're saying.
I can see the Self-Closing Screw Mount Clips and can see that the curly bit might/would/should go around the threaded rod. However how would you keep it tight?
Mmm... I'll see if I can find something like this in the UK.
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Thanks,
Rob
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Wes James
Post Laureate
Reged: 04/12/06
Posts: 3451
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Quote:
I can see the Self-Closing Screw Mount Clips and can see that the curly bit might/would/should go around the threaded rod. However how would you keep it tight?
Rob- you would keep it tight by choosing the appropriate size clamp. These clamps are meant to hold whatever they're clamping when you tighten down the clamp. The normal kind we use in electronics are doubled over so they tighten down when you tighten down the mounting screw. You'd get a 1/4" dia. clamp for a 1/4" diameter rod; you might have to put a bit of sleeving to ensure the clamp tightens up on the rod, but I think you have the idea now.
Good luck- I liked your creativity of the way you built your A80MMSSSFR !
Wes
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Mert
Carpal Tunnel
Reged: 08/31/05
Posts: 1792
Loc: Spain, Pamplona
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Quote:
Now you mention it, the tubing does have that 'medical' look about it. Never thought about it before.
Once it's tuned in, I may make a tube to fit.
The next problem is how to mount it. A little tricky at the moment as there's very little to mount a dovetail to.
Rob, looks good, will work for sure!
Are these rods threaded? If so, it's quit easy
to get a grip on them, just use 2 nuts forced
against each other, maybe on 2 rods, 2 sets of
2 nuts.
On these, or between these you might mount some
metal plate or whatever you might have laying around.
Just my 2 cents 
Regards,
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Mert
42º49"N 1º38"W
3" Polarex refractor
6" F12 SW Maksutov,CS2-S
EQ6 + EQMOD 
SPC900NC/DFK21AU04.AS
My web-page don't laugh, I should make it better! 
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astroN00B
sage
Reged: 10/21/06
Posts: 389
Loc: Bakersfield, CA
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I was thinking of something like this as a travel scope that would break down. Fine work!
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100mm f/5 ATM achro refractor
WO 66mm SD APO
WO TR-188 tripod
Modified DS-2000 goto mount
AZ-3 for old-school viewing
Meade 5000 1.25" EPs, Telextender
GTO 7mm-22mm zoom
SV 80/9D 10:1 focuser (for sale, funding a dob)
Vixen Polaris (for sale, funding a dob)
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Rob Willett
Vendor (Degree Circles)
Reged: 02/07/05
Posts: 653
Loc: London, UK.
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What could easily be done is to remove the, ahem, focusor to reduce the length. That's pretty easy as it's just screwed on.
If I epoxied the inside nuts into place, once it's all collimated, and marked which ones go where, then it should go together quite easily. The collimation should hold up. I suppose this is a good test rig to try this out on.
That means it would breakdown into very tiny sections.
Food for thought. First thing though is to get a dovetail onto it somehow.
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Thanks,
Rob
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