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Carton f/13 Build

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#1 Rutilus

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Posted 25 November 2012 - 04:56 AM

Always been interested in Carton optics, and after picking up a 100mm f/13 lens, I went and did a scope build.

The tube is a soil pipe, and machined parts were from MDF and turned on my woodworking lathe.
I've been making parts out of MDF for the past 25 years and have found it very stable so long as you seal
the edges and waterproof it.

For the focus mount I went a bit retro and used a very nice Japanese made rack and pinion unit.

For a couple of years now I've been making small tubes from bonded sawdust and wood chips
(the waste material from the wood turning) I used this method for the dew shield.

Finally got the project finished, and here are the pictues.
First off, the lens and cell.

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#2 Rutilus

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Posted 25 November 2012 - 04:57 AM

Painted.

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#3 Rutilus

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Posted 25 November 2012 - 04:58 AM

Focus mount.

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#4 Rutilus

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Posted 25 November 2012 - 04:59 AM

baffles and tube cradle.

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#5 Rutilus

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Posted 25 November 2012 - 05:00 AM

Lens cap.

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#6 Rutilus

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Posted 25 November 2012 - 05:01 AM

Finished scope.

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#7 Rutilus

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Posted 25 November 2012 - 05:02 AM

last one.

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#8 Mirzam

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Posted 25 November 2012 - 07:19 AM

Nice job! Did you make that finder mounting ring?

JimC

#9 roscoe

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Posted 25 November 2012 - 07:53 AM

Nice work! That MDF works up surprisingly well! I like your idea of the focuser block and baffles all in one.

Russ

#10 Anil

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Posted 25 November 2012 - 07:54 AM

Beautiful looking scope!!
I like the cradle design & mount, nice work!

#11 glennnnnnn

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Posted 25 November 2012 - 09:42 AM

I like your idea of the focuser block and baffles all in one. -Russ

This would certainly make it easier to "tune" the baffles before installing them in the tube!
I agree, a good looking telescope, although I have no idea what MDF is. Using recycled products when possible is very cool, and making it yourself is something to be proud of.
-Glenn
EDIT: Medium Density Fiberboard. Oh. MDF sounds better. Don't they make that stuff with a waterproof resin?

#12 Pinbout

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Posted 25 November 2012 - 10:20 AM

that looks excellent!

I've been making parts out of MDF for the past 25 years



what do you use to seal the edges so you can get them as smooth as the faces?

#13 Rutilus

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Posted 25 November 2012 - 12:33 PM

Many thanks for the comments guys.

The finder scope is housed in a standard off the shelf tube holder, but the ring it is attached to was made from MDF on the lathe.

I think they do a waterprof resin MDF board, but it has always much more expensive on this side of the pond,
and besides I get my MDF extremely cheaply by buying off-cut pieces from local wood working shops in my area.

Danny - I use French polish. I apply it to the MDF and before it dries I spin the lathe up and buff it with paper kitchen roll.
Within about 15 seconds the polish is dry and if you get it right the edges are like glass.

The total cost of the build including the lens, finder scope and bracket, focus mount and materials came to
180 UK pounds.

Just about to take the scope out for first light observing.

#14 Jim Curry

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Posted 27 November 2012 - 10:25 PM

We have a winner! Nice job.

Jim

#15 Rutilus

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Posted 01 December 2012 - 06:58 AM

Many thanks Jim.

For the past week I have had excellent views with this scope. The Carton lens is a real stunner.
Side by side with a Tak 102mm APO, I had to call it a draw while observing the Double stars.
The only time I noticed a difference was on Alpha Gem, which showed a very tiny amount of C.A. with the Carton.
The Lens has excellent contrast and sharpness.

The PVC soil pipe and MDF lens cell have performed with noproblens at all. Taking the scope outside from a warm house and observing in falling
freezing temparatures have shown no side effects at all in the star image.

The other night the scope was out for 7 hours, at the end it was covered in a layer of ice, and yet the star test views seen were absolutely text book images.

#16 StarStuff1

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Posted 01 December 2012 - 12:08 PM

Excellent craftsmanship! I would be very interested in hearing more how you made small tubes from sawdust and wood chips. Perhaps there was an earlier thread?

#17 Rutilus

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Posted 02 December 2012 - 12:32 PM

Hi StarStuff1.

For the tubes, I machine a former for the lathe.
Onto the former I apply a thin sheet of card, then apply a thin coat of PVA glue then apply the wood chips.
I let this dry, spin the lathe and sand smooth.
Then I apply French polish, spin the lathe until polish is dry. Then I simply keep repeating the process for about
half a dozen times or until I am happy with the finish.

For larger tubes I apply another sheet of card half-way through the layering process.

Picture A shows a finished tube ready for painting.
B, shows a tube being made for a 6 inch refractor dewshield, on a larger tube I paint the tube black
near to the end of machining as this shows up any low spots, which can then be filled with a layer of PVA
and sawdust.

C, shows a special former I made for a 12 inch diameter tube.

The finished tubes are very strong. As a test I dropped one 40 feet out of a window onto concrete,
it simply bounced off leaving no damage at all to the tube.

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#18 glennnnnnn

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Posted 03 December 2012 - 10:52 AM

Impressive method! I had a Carton f/13 and it provided stunning views! A great lens, but I found the size of the telescope to be inconvenient. Now that I make folded refractors that seems like a pretty stupid excuse.
Anyway, I have been making paper for years and can get similar results but the drying time can be excessive for thick pieces. With pulp and resin glue I can also place nylon reinforcing/tensioning nets to increase strength.
But I mold everything, or hand surface it. One of these days a lathe will jump into my path and I'll take it home.
-Glenn

#19 StarStuff1

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Posted 03 December 2012 - 02:32 PM

Thanks, Rutilus. As Glen said, very impressive. It is amazing what creative solutions ATMers can come up with.






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