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tubes for 12" dob OTA 13-14" dia. 60" long where?

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#1 Sean Puett

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Posted 08 April 2013 - 09:37 AM

I have a protostar link but, their tubes only go to 12" diameter and 48" ling. I thought I remembered seeing larger tubes for sale somewhere. Can anyone point me in the right direction? :question:

#2 Pinbout

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Posted 08 April 2013 - 11:10 AM

shapes unlimited offer tubes 96" long.

the have stock shapes, that's what you want to buy. so if you have to move up or down an inch so be it.

aitwood has plywood cylinders

both places can custom veneer the tubes at extra cost.

#3 Mirzam

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Posted 08 April 2013 - 12:29 PM

Maybe you could try a welding/fabrication shop to see if they would roll an aluminum tube for your telescope. I've been thinking along these lines for a 20" tube but have not investigated the cost yet.

JimC

#4 Sean Puett

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Posted 08 April 2013 - 05:24 PM

That shapes unlimited place looks perfect. I'll check out the other one later

#5 Sean Puett

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Posted 08 April 2013 - 08:20 PM

Any more suggestions?

#6 Mirzam

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Posted 08 April 2013 - 08:57 PM

You could make a truss scope.

JimC

#7 StarDusty

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Posted 08 April 2013 - 09:11 PM

You might look here:

http://www.parksopti...glass Tubes ...

#8 Sky Captain

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Posted 08 April 2013 - 09:38 PM

Any more suggestions?

You could make a truss scope.

JimC


Sean, I'll second the truss scope build, unless you have a specific reason for a full tube design.
I'm sure you remember seeing mine at the last star party, much easier to travel with.

#9 Mirzam

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Posted 09 April 2013 - 06:48 AM

Parks Optical is defunct, unfortunately.

JimC

#10 Dick Jacobson

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Posted 09 April 2013 - 08:29 AM

If you don't want to make a truss, a two-piece solid tube is an excellent alternative that improves portability.

#11 Mirzam

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Posted 09 April 2013 - 10:01 AM

My first homebuilt scope was a split tube using two sections of sonotube held together by adjustable shelving rails. It was quite a bit lighter than a full sonotube style.

Sonotube, by the way, comes in 12 ft lengths, which should be plenty long enough for the OP's scope.

JimC

#12 Sean Puett

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Posted 09 April 2013 - 11:04 AM

I want a solid tube because it is easier for a first build, I can reuse most of my parts, there are less thermal issues, easier to hold collimation, and I like the alt clutch design that gso uses and I want to use it on the scope.
I may just lengthen my current tube a bit and remove the dents and dings from it. I could just make a dew shield like device to help block stray light. I don't know if I want a paper tube and the plywood tube is nearly $300.

#13 Pinbout

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Posted 09 April 2013 - 02:17 PM

I don't know if I want a paper tube



my 10in dia tube is fine, just soak the ends in expoy. fill the spiral seam with bondo.

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#14 planet earth

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Posted 09 April 2013 - 04:58 PM

Nice job, and purty too!..... :)
Sam

#15 Sean Puett

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Posted 09 April 2013 - 09:02 PM

That looks great. Maybe I could try that. There is one 62" long for $70. Much better than 300.

#16 Andrew123

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Posted 15 April 2013 - 08:47 AM

http://www.sonotube..../sizechart.aspx
I got my 12" tube at our local concrete outlet. Works great. Had to buy a 10' length.

#17 gmussman

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Posted 15 April 2013 - 12:43 PM

I want a solid tube because it is easier for a first build, I can reuse most of my parts, there are less thermal issues, easier to hold collimation, and I like the alt clutch design that gso uses and I want to use it on the scope.


Sean,
Just sharing my experience making a paper-tube scope a la stellafane's website and moving on to a 12" Truss.

Agree that the solid tube is easier to build, but there are some things the truss is just better at. My 2 cents:

1. Make sure the tube is stiff because placing the secondary sucks when the tube warps under tension. It is much easier on my truss because the rings are plywood.

2. Solid tube scope should have more thermal problems, because they hold the air current closer to the light path whereas trusses don't really have a tube to hold anything. Caveat: The mirror box has to be open at the bottom on the truss.
3. If you make your alt bearings large enough and balance your scope, you shouldn't have any need for a clutch. Personally, I hate the clutch on my 12" lightbridge (partly why I'm building the truss).

What I did is build a dob 4.5 from a $14 meade tube, then graduated to a 8 inch build with an 8 inch f5 mirror, now trying truss. I learned a ton, and made plenty of mistakes. I definitely benefitted from building the solid tube first -- mostly with regard to building the bearings.

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#18 kfiscus

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Posted 15 April 2013 - 06:10 PM

PM sent.

#19 Sean Puett

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Posted 15 April 2013 - 07:22 PM

The reason I like the clutches is that my eyepieces vary in size so much that balancing the scope for all of them is not quite possible in the current configuration. I am sure there is a better design, I am not sure I want to redo the whole design.

#20 Dick Parker

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Posted 15 April 2013 - 08:04 PM

Sean -

IMHO Sonotubes are underestimated. They are inexpensive, light for their size, and adequately strong. I used sonotube for the 16 inch Cassegrain shown here. The tube is 18 inches in diameter, came in a 12 foot length for --- oh probably $60. Very hard to beat. As said earlier, soak the ends in epoxy, fill the spiral with bondo, finish with epoxy and paint. They can be made to compete with the smoothess of aluminum tubes, or crudely painted with house paint for functionality or anything in between.

I suggest you get a tube from a cement contractor supply for consistent sizing. Typical home supply shops use what they call "nominal sizing". an 8 inch tube can be a variety of diameters. That is so they can slip three tubes inside one another for easier shipping.

Dick Parker

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#21 gmussman

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Posted 16 April 2013 - 08:14 AM

The reason I like the clutches is that my eyepieces vary in size so much that balancing the scope for all of them is not quite possible.


Oh, I see you have a paracorr. I've heard they are heavy and can make balancing a pain. I've been trying to avoid buying one because of $$. I'm at f5, so I'm getting by with lighter fare.

BTW, I didn't soak the end of my sonotube in epoxy as I see suggested here, so you may not run in to the "bendy" tube problem that I did when you try to place the secondary.

#22 Sean Puett

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Posted 16 April 2013 - 09:44 AM

If you don't start using a paracorr at f5, you should be fine. Once you do, you won't be able to tolerate the views without one. Very addictive.






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