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Equipment Discussions >> ATM, Optics and DIY Forum

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tim53
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Reged: 12/17/04

Loc: Highland Park, CA
Re: Round Wooden Tubes? new [Re: PhotoGazer]
      #4255378 - 12/17/10 10:12 PM

Mike:

They're 17" aluminum lazy susan bearings that I bought at Rockler. Cost ~$60 each, but that's cheap compared to Parks or Parallax rings for a 10" (really, probably a 12 or 14, since my tube isn't round). This thread has all the details!

-Tim.


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tim53
Postmaster
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Reged: 12/17/04

Loc: Highland Park, CA
Re: Round Wooden Tubes? new [Re: tim53]
      #4259363 - 12/19/10 09:12 PM Attachment (54 downloads)

An update on that small wooden tube I was working on a couple weeks ago...

I turned a couple end rings for it - one to hold the lens and cell of a 3" f/6 achromat, the source of which I don't know - the other end to support a Jaegers 1 1/4" focuser I had laying around.

Here are the parts, laid out:


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tim53
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Reged: 12/17/04

Loc: Highland Park, CA
Re: Round Wooden Tubes? new [Re: tim53]
      #4259367 - 12/19/10 09:13 PM Attachment (47 downloads)

And here are a couple of it drylabbed together.

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tim53
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Reged: 12/17/04

Loc: Highland Park, CA
Re: Round Wooden Tubes? new [Re: tim53]
      #4259369 - 12/19/10 09:14 PM Attachment (35 downloads)

2

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tim53
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Reged: 12/17/04

Loc: Highland Park, CA
Re: Round Wooden Tubes? new [Re: tim53]
      #4259374 - 12/19/10 09:17 PM

I have a couple things to do still...

The tube is about an inch too long to reach focus with the star diagonal, so I'll have to cut it shorter. The aluminum rings will be painted and the tube will be poly'd, maybe stained first.

I bought some "old brass" paint for the rings, but I wonder if that might be too much with the wrinkle black cell? Got a couple colors of hammertone paint - bronzish I think, that might work okay.

Will have to cogitate.

-Tim.


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slobeek
member


Reged: 02/15/10

Re: Round Wooden Tubes? new [Re: tim53]
      #4259805 - 12/20/10 03:36 AM

Guys help me out a little. If I want to make wooden tube (coopered) out of plywood...what is the minimum thickness of plywood for 8" tube?

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tim53
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Reged: 12/17/04

Loc: Highland Park, CA
Re: Round Wooden Tubes? new [Re: slobeek]
      #4260199 - 12/20/10 10:58 AM

I've made all my plywood tubes out of 1/4". You might want to reinforce it, particularly if you have a large number of sides.

-Tim.


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slobeek
member


Reged: 02/15/10

Re: Round Wooden Tubes? new [Re: tim53]
      #4260250 - 12/20/10 11:20 AM

Thanks Tim. 1/4" it is then

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plyscope
Pooh-Bah


Reged: 11/23/06

Loc: Perth, West Australia
Re: Round Wooden Tubes? new [Re: slobeek]
      #4261618 - 12/21/10 01:28 AM Attachment (56 downloads)

If you use the best quality marine ply you can go thinner, I used 4mm occoume marine ply for my octagonal tubes. They are built with ply ring frame/baffles. It is light and strong. My next project wil be a octagonal tube for a 5 inch refractor using 3mm marine ply. This picture shows an octagonal tube made 4 years ago for a 6 inch refractor with 4mm ply sides and baffles. 12mm ply is used at the ends. This scope is similar to Tims nonagonal 6 inch f15.

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PhotoGazer
super member
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Reged: 09/26/07

Re: Round Wooden Tubes? new [Re: plyscope]
      #4261670 - 12/21/10 02:18 AM

Very cool Andy. Does anyone have a program or equation that helps determine the size of the sections for the tube? In other words, if I wanted to have an 8" tube, and I wanted to use 8 slats for the tube, how wide would those slats have to be to make the 8" tube?

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DarkSkys
professor emeritus
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Reged: 10/11/10

Loc: In the dark desert of Eastern ...
Re: Round Wooden Tubes? new [Re: tim53]
      #4261755 - 12/21/10 03:30 AM

Quote:

Quote:

Holy Moly Tim! Some very nice work there.

Have you considered making a wood version of the telerad - then gutting the plastic one for its' parts?




Funny you should ask! I haven't done this, but I've been thinking about making veneer inserts for the sides where they're recessed inside that ridge edge?

-Tim.




Hmmmm. if i get a telrad, I might have to do that, to go along with the rest of the wood of my scope.


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txmnjim
sage


Reged: 03/31/09

Loc: Rochester, MN
Re: Round Wooden Tubes? new [Re: PhotoGazer]
      #4262003 - 12/21/10 08:34 AM

Quote:

Thanks for some really good ideas and links. I have several thought and ideas that I have developed from reading the comments here, and viewing the links. I plan to test some of them tomorrow in the wood shop. Just in case you don't know, I build guitars, but many of the techniques used in forming guitar bodies cannot be easily transferred over to the larger areas on wood used in telescope tubes. However, I have a large selection of beautiful and exotic woods at my disposal. Many of them were purchased in lots that contained the wood I wanted, but are not suitable for guitar tone woods. They are, however, terrific choices for telescope tubes. Since I started this thread, I am now more excited than ever about where I can go with this project. I plan to photograph the processes that I develop so others can take advantage of them, if they work out. Feel free to keep this thread going with more ideas and links if you have any. I think a lot of ATM'ers can take advantage of this info.



I would just advise choosing the *lightest* wood possible.
I built a nice 8" square tube newtonian and the major drawback was how heavy it was ;-)
Jim


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DL Sharp
member


Reged: 10/05/05

Loc: Cincinnati, Ohio
Re: Round Wooden Tubes? new [Re: ColoHank]
      #4280436 - 12/30/10 03:10 PM

Quote:

I've attached a picture of the wood-tubed Merz und Mahler scope, with Fraunhofer objective, which has been in regular service at the Cincinnati Observatory for almost 170 years. It's not only functional, but also a thing of beauty.




I agree - The 1843 Merz und Mahler 11" Refractor at the Cincinnati Observatory is a thing of beauty. I've had the opportunity to look through it on many occasions. They have a photo gallery of it on the observatory's website:

http://www.cincinnatiobservatory.org/merzundmahlerref.html

While you're there, you might as well check out the photo gallery for their "New" scope, a 1904 Alvan Clark & Sons 16" Refractor:

http://www.cincinnatiobservatory.org/alvanclarksonsre.html


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dan_h
Carpal Tunnel


Reged: 12/10/07

Re: Round Wooden Tubes? new [Re: PhotoGazer]
      #4280561 - 12/30/10 04:26 PM

Quote:

Very cool Andy. Does anyone have a program or equation that helps determine the size of the sections for the tube? In other words, if I wanted to have an 8" tube, and I wanted to use 8 slats for the tube, how wide would those slats have to be to make the 8" tube?




I use an on line circle calculator. It's amazing just how accurate this thing is. Certainly more accurate than I can cut wood.

http://www.1728.com/circsect.htm

Hope this helps,

dan


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ColoHank
Carpal Tunnel
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Reged: 06/07/07

Loc: western Colorado
Re: Round Wooden Tubes? new [Re: DL Sharp]
      #4280705 - 12/30/10 05:35 PM Attachment (34 downloads)

Quote:

I agree - The 1843 Merz und Mahler 11" Refractor at the Cincinnati Observatory is a thing of beauty. I've had the opportunity to look through it on many occasions.




I grew up in Mt. Lookout about 3/4 mile from the Observatory, a familiar neighborhood landmark. I first peeked through the Merz und Mahler when I was only about five or six years old. My parents were acting as chaperones one evening for a Girl Scout outing at the Observatory, and since I was too young to stay at home alone, I was dragged along. I have no recollection of what I viewed that night, but remember ascending a ladder or stairs of some kind to reach the eyepiece.

One evening in the autumn of 2008, after a lapse of sixty-one years, I was given the honor of removing the Merz und Mahler's lens cover (picture), after which I enjoyed my second peek through that scope -- this time at Jupiter.

My older sister was a classmate and friend of Marilyn Herget, whose father Paul was the Observatory's Director during my youth and beyond. Years later, while attending the University of Cincinnati, I was privileged to hear Dr. Herget speak at one of our regular geology department seminars about plotting minor planet and artificial satellite orbits and of his early adventures with the ENIAC computer.


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nytecam
Postmaster


Reged: 08/20/05

Loc: London UK
Re: Round Wooden Tubes? new [Re: PhotoGazer]
      #4282453 - 12/31/10 12:29 PM

Yep - twin-skinned diaphragm construction is exceptionally rigid but lightweight for 17.5" Newt then Dob



ps: some hereabouts confuse round wooden tubes with multi-faceted tubes


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tim53
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Reged: 12/17/04

Loc: Highland Park, CA
Re: Round Wooden Tubes? new [Re: nytecam]
      #4282499 - 12/31/10 12:49 PM Attachment (35 downloads)

LOL!

Well, *I* know the difference! Here's a few progress photos of my 3" f/6 Jaegers' tube. Here, I'm boring it out so it'll be round on the inside as well as the outside. Also, I needed to bore out the objective end quite a bit because it was so thick it was stopping down the lens to about 2 1/4"!

-Tim.


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tim53
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Reged: 12/17/04

Loc: Highland Park, CA
Re: Round Wooden Tubes? new [Re: tim53]
      #4282507 - 12/31/10 12:52 PM Attachment (31 downloads)

Here, I've mounted it in my wood lathe so I could turn it by hand easier and work on the sanding and finishing of the exterior:

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tim53
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Reged: 12/17/04

Loc: Highland Park, CA
Re: Round Wooden Tubes? new [Re: tim53]
      #4282514 - 12/31/10 12:54 PM Attachment (32 downloads)

And here it is with a second coat of poly/stain combo, waiting to dry:

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tim53
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Reged: 12/17/04

Loc: Highland Park, CA
Re: Round Wooden Tubes? new [Re: tim53]
      #4282522 - 12/31/10 12:59 PM

Still, it's taken me a LOT longer to make this round tube than it would to make a faceted tube. Part of that is because it's the first one I've tried, but most of it is in the turning from the glued-up staved tube. I may have been overly cautious in my cuts on the lathe, but I did have it bit and come out of the chuck a couple times, so it probably was a good idea to take it slow and easy.

It's also a very short tube. I'd like to make a matching tube for a 3" f/15 I have, but my lathe bed isn't long enough! (and I can't imagine boring something that deep - how would you support the tailstock end? Steady rest, I suppose. But my lathe doesn't have one).

-Tim.


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