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Pinbout
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Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #5299538 - 07/02/12 05:56 PM

Quote:

That's a GREAT idea for getting the excess off the inside of the tube!

I'm going to try that next time I make one of these.

-Tim.




I thought you were going for the textured inside to help absorb the light.


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tim53
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Re: Delmarvascopics 8" f/9 OTA build new [Re: Pinbout]
      #5299697 - 07/02/12 07:44 PM

I did! (because I hadn't heard about taping the inside before I glued up this tube!)

-Tim.


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tim53
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Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #5299704 - 07/02/12 07:45 PM

So here's another idea I've been cogitating...

Instead of a sled focuser, why not something like a Clement focuser - only not under the eyepiece, but under the primary!

-Tim.


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tim53
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Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #5317860 - 07/14/12 06:07 PM Attachment (38 downloads)

Today, I squoze off some time to start sanding the tube:

Edited by tim53 (07/14/12 06:13 PM)


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tim53
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Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #5317867 - 07/14/12 06:14 PM Attachment (32 downloads)

Started with 100 grit in a rubber sanding block.

The final seam after I rolled it up had the most squeezout and needed the most sanding, but even that went fairly quickly:


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tim53
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Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #5317871 - 07/14/12 06:16 PM Attachment (27 downloads)

near the ends of the tube slats, my thickness planer tended to make shallow grooves in the slat, but they sanded out pretty quickly, too.

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tim53
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Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #5317874 - 07/14/12 06:18 PM Attachment (34 downloads)

and that is a knot on the left. I figure I'll cut a little off each end to make it nice and true on the ends, so this will probably be gone when I'm done.

All done with the 100 grit. Gonna switch to 220 in a tad.


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tim53
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Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #5317877 - 07/14/12 06:18 PM Attachment (34 downloads)

I love this grain!

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plyscope
Pooh-Bah


Reged: 11/23/06

Loc: Perth, West Australia
Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #5317954 - 07/14/12 07:19 PM

Me too!

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tim53
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Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #5318211 - 07/14/12 11:16 PM Attachment (33 downloads)

I decided I wanted to stain the tube and bring out the grain a bit more. I used a Brazilian Rosewood gel stain from Minwax. Oil based.

One coat. I might put another on tomorrow, depending on how I feel about it.


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tim53
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Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #5318213 - 07/14/12 11:16 PM Attachment (36 downloads)

Closeup, where the grain gets pretty wild!

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herrointment
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Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #5318268 - 07/15/12 12:05 AM

Great wood deserves your best efforts.

That's one big beautiful glue-up!


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Paul Drufva
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Reged: 06/26/11

Loc: Connecticut
Re: Delmarvascopics 8" f/9 OTA build new [Re: herrointment]
      #5319004 - 07/15/12 03:07 PM

I love it! Wonder if I could do a tube like that for a 12.5f 4.8. Might be a bit heavy. What's that tube weigh Tim? I love Circus canon Dobs, much easier to set up. Tubes have advantages. Beautiful work!

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tim53
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Re: Delmarvascopics 8" f/9 OTA build new [Re: Paul Drufva]
      #5319042 - 07/15/12 03:50 PM

Hi Paul.

I should weigh it! I don't know what it weighs, but it's lighter than a fiberglass tube. I still have to finish it and make tube rings for it, attach a focuser and make the primary and secondary holders. This tube a out
1/4" thick. For a 12.5" I think I'd go with 3/8" if made out of wood. Depending on the wood, it could still be fairly light.

I think I'll be lucky to get the finish close to done today. Then it could be quite a while before I can work on it again, since we'll be landing Curiosity on Mars on August 5th.

Tim


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tim53
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Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #5319283 - 07/15/12 07:34 PM Attachment (30 downloads)

I put a 2nd coat of stain on and wiped off the excess. I like the tone.

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tim53
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Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #5319285 - 07/15/12 07:35 PM Attachment (34 downloads)

I'm figurin' that the focuser needs to go here!

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tim53
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Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #5319293 - 07/15/12 07:40 PM

I had been planning on spraying a clear lacquer over it, but I can't get any that's not in a rattle can, and lacquer will dry so fast I won't be able to spray with out getting a very blotchy result.

So I bought a quart of oil-based spar polyurethane. The stain was oil based, so hopefully they'll live happily together. I'd like to spray it, but the can doesn't say anything about doing that. So I guess I'll try brushing a coat on, and see if it flows out well enough to hide brush strokes.

-Tim


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allardster
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Reged: 07/01/11

Loc: Toronto, Ontario, Canada
Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #5319436 - 07/15/12 09:29 PM

The wood is looking beautiful! Maybe try out the stain+poly on a piece of scrap first?

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Wes James
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Re: Delmarvascopics 8" f/9 OTA build new [Re: allardster]
      #5319445 - 07/15/12 09:36 PM

That tube's really looking great, Tim!!
If you thin the poly down a LOT (50%) with mineral spirits, you can wipe it on with a rag... wipe a heavy coat on- then scrub as much off as you can with that same rag.... let it sit for 24 hours, then lightly scuff it with 0000 steel wool... repeat... twice or 3 times, and you'll have a beautiful finish on the tube!


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Jeff Morgan
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Re: Delmarvascopics 8" f/9 OTA build new [Re: tim53]
      #5320138 - 07/16/12 11:24 AM

Love that grain, beautiful wood!

It makes me want to try this myself. My initial thought was to use bead & cove joints. You've obviously done this before (I never have) so I wanted to ask you about the advantages of using the "tape roll-up" method.


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