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NHRob
Carpal Tunnel
Reged: 08/27/04
Posts: 2544
Loc: New Hampshire
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I have a 8" f/6 Starsplitter dob with Zambuto optics which I am considering rebuilding. The construction is nice and solid but is kind of heavy and awkward for my bad back. The tube is thick sonotube and it is nit a lightweight design. I was thinking of a rebuild, going either truss or a different tube material .... aluminum or Blacklite tube from Protostar.
I'd love to hear feedback on Blacklite users and their experiences.
Thanks,
Rob
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Canon 12x36 IS binos
AP130EDT f/8 (for sale)
new 12.5" f/6 Royce conical mirror (for sale)
no free time ... lots of clouds !
" Life is what happens to you while you're busy making other plans" !!
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Mark Harry
Carpal Tunnel
Reged: 09/05/05
Posts: 2470
Loc: Northeast
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I have both Blacklight and metal-tubed 8" scopes. The Blacklight is a Dobster, F/4.72, with about 16" out front of the focuser acting like a glareshield. Works very well, and by itself, pretty light. It has to be checked for collimation evrry time it's used, on account of the focal ratio, and the slight dimensional change of the paper-phenolic material. For the little Dob, it's excellent.
I have had aluminum tube scopes, and they are dimensionally very stable in comparison, and quite reasonable in heft. The stability is better for maintaining collimation. The one I have -NOW- is a modified Orion 8"F/6, which hardly ever gets out of whack, but is sheet steel. (somewhat on the thin side.) The only downside to this scope, is the focuser height is way too tall, hence the tube is too short to make a simple mod to. And the diameter is a bit too small for my taste considering temp issues. Storage in the barn alleviates a lot of that problem.
Regards, Mark
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Scopes in the works-
Too many for putting down here! Favorites- 8" F/6, 8" F/4.72, 4.5" F/5.4, 14" F/4.455, all completed.
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Fiske
Carpal Tunnel
Reged: 03/14/04
Posts: 2057
Loc: Missouri / United States
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Mark:
Have you considered modifying the Orion with a flocked tube liner from ProtoStar? Bryan says they help resolve the thermal problem. He doesn't have a stock liner currently that fits the Orion tube diameter, but will have custom sizes for Orion (and Dobs from other manufacturers) later this year. His 10-inch Hastings liner can be modified (by slitting and retaping it) to fit the Orion 8-inch.
I haven't ordered one yet, but plan to do so.
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Fiske Miles
Nikon 8x42 LX / 12x50 SE Binos
Mini Borg 60ED, TV-101, AT80Ach, XT-8, C11/CI-700, 22-Inch Dob
Way too many Nagler eyepieces
http://www.fiskemiles.blogspot.com/
www.fiskemiles.com
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NHRob
Carpal Tunnel
Reged: 08/27/04
Posts: 2544
Loc: New Hampshire
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The alum. tube with liner sounds nice. I like the strength of the alum. tube. One problem I see with the sonotube is that it does not hold collimation well. I think there is some compliance or flex in the tube. I see that it does deform as I tighten the spider. Dimensional stability is important to me. I see no reason a properly built tube newt should have much drift in collimation.
Rob
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Canon 12x36 IS binos
AP130EDT f/8 (for sale)
new 12.5" f/6 Royce conical mirror (for sale)
no free time ... lots of clouds !
" Life is what happens to you while you're busy making other plans" !!
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Jeff Morgan
Carpal Tunnel
Reged: 09/28/03
Posts: 1509
Loc: Prescott, AZ
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Quote:
The alum. tube with liner sounds nice.
I did an 8" f/6 this way and was very pleased. On the surface it seems a bit pricey, but when you consider how difficult and tedious it is to properly line or paint the inside of a small tube, the liner is suddenly a great bargain. It also is the darkest tube treatment you will ever see.
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Jeff Morgan
Prescott, AZ
Wile E. Coyote School of Telescope Making
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Fiske
Carpal Tunnel
Reged: 03/14/04
Posts: 2057
Loc: Missouri / United States
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An additional advantage, according to Bryan, is that the gap between the liner and the tube wall acts as an insulator, significantly reducing thermal problems common to metal tube Newtonians. He feels the combination of the tube liner and a rear mounted fan are the two most important modifications to improve the optical performance of scopes like Orion's SkyQuests.
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Fiske Miles
Nikon 8x42 LX / 12x50 SE Binos
Mini Borg 60ED, TV-101, AT80Ach, XT-8, C11/CI-700, 22-Inch Dob
Way too many Nagler eyepieces
http://www.fiskemiles.blogspot.com/
www.fiskemiles.com
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Mark Harry
Carpal Tunnel
Reged: 09/05/05
Posts: 2470
Loc: Northeast
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Yeah, I have considered it; but if the tube's too short to begin with, it tends to put that on hold for the time being. I first want toget a smaller secondary to go with the primary. It's -VERY- accurately made, and does a nice job, but it could do significantly better with lower obstruction. But if I modified the tube size, it won't fit the XT8I base with locator....
Decisions.
Mark Thanks for the info, good to know !
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Scopes in the works-
Too many for putting down here! Favorites- 8" F/6, 8" F/4.72, 4.5" F/5.4, 14" F/4.455, all completed.
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Fiske
Carpal Tunnel
Reged: 03/14/04
Posts: 2057
Loc: Missouri / United States
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Mark:
Yeah. At some point it sort of starts becoming another telescope instead of a modification... 
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Fiske Miles
Nikon 8x42 LX / 12x50 SE Binos
Mini Borg 60ED, TV-101, AT80Ach, XT-8, C11/CI-700, 22-Inch Dob
Way too many Nagler eyepieces
http://www.fiskemiles.blogspot.com/
www.fiskemiles.com
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