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Collimating cap

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#1 James Cunningham

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Posted 04 January 2013 - 04:51 PM

Where can I purchase a collimating cap? I tried to make one several times but the hole was never dead center. Thanks
Jim

#2 rguasto

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Posted 04 January 2013 - 05:01 PM

Rigel systems ALINE cap.

http://agenaastro.co...t-eyepiece.html

All I use in my 8" F8.

#3 James Cunningham

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Posted 04 January 2013 - 05:10 PM

I saw this cap but since it did not say "collimating" cap, I thought it was more like an auto collimator.
Jim

#4 KerryR

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Posted 04 January 2013 - 06:07 PM

When drilling holes in a focuser cap or 35mm film can, it's helpful to use the injection molding nipple as the centering guide. Slice it off flush, so that it can't deflect the drill bits. But, start with a pin, which you can place precisely. Then a thumb tack to enlarge the hole. Then your smallest drill bit, drilling on a piece of wood. Go up one size bit repeatedly 'til you reach your desired diameter, probably 1/8" or 3/16". This process does a good job of keeping things centered. With some 35mm film cans, a wrap or 2 of scotch or electrical tape can help take up slack around the barrel and further help keep things centered. If you can find the right size washer, you can stuff it into the film can or focuser cover, and simulate a Cats Eye style collimator.

Really, though, you'd be best served by something nicer and more functional-- you won't regret it. My favorite is the Cats Eye, followed by the cheap plastic cheshire from Celestron that came with my C6R, followed by Orion's cheshire.

#5 Nils Olof Carlin

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Posted 05 January 2013 - 05:16 AM

Probably easier to make a neat hole and placing it dead center later. It is easier, when you have the hole, to get the periphery accurate.
Nils Olof

#6 BDS316

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Posted 05 January 2013 - 07:43 AM

Where can I purchase a collimating cap? I tried to make one several times but the hole was never dead center. Thanks
Jim


Funny that you should mention this since the collimation cap that came with my XT8 has a hole that isn't exactly dead center either and these are useful for a quick confirmation but they are not precision instruments. One of the cheshire/sight tube combos would be better and I still like my Tectron tools even though they are going on 20 years old.

#7 precaud

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Posted 05 January 2013 - 08:49 AM

Spend a little extra and get the combined Cheshire / sight tube:
http://agenaastro.co...reflectors.html

I just got one, it's a nicely machined piece and much more accurate than a col cap for adjusting the secondary mirror.

#8 howard929

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Posted 05 January 2013 - 09:07 AM

Probably easier to make a neat hole and placing it dead center later. It is easier, when you have the hole, to get the periphery accurate.
Nils Olof


Come again Boss. How would one go about doing that?

#9 coopman

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Posted 05 January 2013 - 10:21 AM

I use the ALIGN too.

#10 UmaDog

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Posted 05 January 2013 - 10:31 AM

Why not just buy a combo tool?

#11 Nils Olof Carlin

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Posted 05 January 2013 - 03:19 PM

Come again Boss. How would one go about doing that?


Drill the hole (I think 1.5 mm or slightly larger would be good) in a piece of plastic or any material that drills cleanly. Then you carefully mark the material in 3-4 directions, 16 mm from the center of the hole - not difficult with some care. Then you put glue to the end of a 31.7 mm o.d. piece of tube, and put it down within the marks - just as easily done with quite reasonable precision. Let dry and trim.
Make the tube length/i.d equal to the f/ratio of the telescope, and you have a sight tube that is better than you can buy, for centering the secondary as well as tilting it - with better precision than with the crosshairs of common combination tools.
That is, more or less, how I have made sight tubes for my (few) telescopes of different f/ ratios, one for each. I use one Cheshire as well, but it is not dependent of f/ ratio.

Nils Olof






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