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truss vs solid tube dob

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#1 paulr57

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Posted 02 May 2013 - 08:44 AM

I've been trying to find a comparison between a truss and solid tube dob. Other than weight considerations are there any advantages between the 2 designs?

#2 JimP

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Posted 02 May 2013 - 08:58 AM

A solid tube will keep the heat waves and extraneous light out of the optical path best.
From a stricktly aestheic point of view, and I am only speaking for me, I think a solid tube would look better and has the Potential to help transform the Dobsonianb into a far more professional looking telescope (if that even matters to you or anyone el;se). I did say For Me.
I awaiut the criticism and the points which favor open tubes with cloth shrouds.
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#3 DJCalma

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Posted 02 May 2013 - 09:50 AM

Solid tube: Hot water heater looking, heavy, bulky, ugly, unprofessional, heat wave trapping, inefficient, ancient cumbersome tube. :thumbsdown:

Truss: Sleek, professional, efficient, cool air flowing, practical, compact, versatile, modern, aesthetically attractive design. :waytogo:

#4 planet earth

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Posted 02 May 2013 - 09:56 AM

Solid tube: Hot water heater looking, heavy, bulky, ugly, unprofessional, heat wave trapping, inefficient, ancient cumbersome tube. :thumbsdown:


I don't know? the Cave Astrola telescopes look pretty fine to me.!
Sam

#5 okieav8r

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Posted 02 May 2013 - 09:57 AM

It's a size issue as much as anything. Once you start looking at telescopes 15" and bigger, tubes get massive. Big truss dobs break down for easier storage and transport. Discovery makes split-tube dobs in the 15"-17.5" sizes, and I think maybe a 12" too. A friend of mine has both 15" and 17.5" Discovery dobs, and in my opinion, they are way more of a hassle to deal with than my 20" Obsession. I just ramp it up into the bed of my pickup truck and go--no heavy or cumbersome lifting at all. But, that's just me--to each his own.

#6 dscarpa

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Posted 02 May 2013 - 10:32 AM

I ordered a Teeter 11" F/5 Solid Tube Series mainly because it will hold collimation better than a truss dob. 99% of the time the scope will be used in my back yard with lunar-planetary my number one interest though I do enjoy DSOs too, the STS will have Sky Commander. An 11" F/5 is the biggest tube dob I would want to deal with. David

#7 aatt

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Posted 02 May 2013 - 10:33 AM

I have the Discovery 15" split-tube. Despite careful measurements prior to purchasing I found it took me quite some time to figure out how to get it into my Honda Accord-after initially giving up in frustration. It will barely fit.Glad I did not get the 17.5" I would be stuck at home! The LTA is very awkward and heavy and the UTA is not bad. I have arrived at a system for moving it. Set-up is 6 minutes including collimation now (it holds collimation very well).Despite these issues, I am very very happy with it. Going bigger would not be advisable unless you have a van, are really tall (6+) and a have really strong lower back. The only reason I bought this one was money-truss designs were hundreds of dollars more.

#8 Mike B

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Posted 02 May 2013 - 10:35 AM

Once you start looking at telescopes 15" and bigger, tubes get massive.


I'm with Rex on this... tho i'd have to say "go look at the tuber before you BUY one!" A 12" tube-Dob is massive, and many cars can't easily fit the common 12-inch tube across the rear seat. Even a 10-incher is beyond most EQ mount's ability to hold one steady enough for serviceable views (if such a mounting issue matters?). You know this, as it sounds like you already have the 10.

The Dob mounting also gets big+heavy fast beyond 10-inches. Check the manuf. weights on 10 vs. 12 inchers. Everyone will have their own threshold of what they'd consider "too big" for tubers, but the threshold that matters is how it seems to YOU!

Solid tube: Hot water heater looking, heavy, bulky, ugly, unprofessional, heat wave trapping, inefficient, ancient cumbersome tube. :thumbsdown:

Truss: Sleek, professional, efficient, cool air flowing, practical, compact, versatile, modern, aesthetically attractive design. :waytogo:


:gotpopcorn:

#9 Achernar

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Posted 02 May 2013 - 10:40 AM

No tube currents, because of the open mirror box and thin fabric shroud. And you can set up a 20-inch or even larger truss-tube Dob yourself. I can get my 15-inch into a car, impossible to do with a solid tube of the same aperture and focal ratio.

Solid tubes are less expensive, less affected by dewing and heat waves getting into the light path, and they don't need to be collimated everytime you set them up. A truss tube requires that the collimation be touched up when it's set up, but that only takes a minute or two with the right collimation tool(s). A solid tube also allows you to put extra finders, digital setting circle computers, and the like where ever you want. In the 10-inch and under range, it makes more sense usually to opt for a solid tube, unless you require airline portability for the telescope.

Taras

#10 okieav8r

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Posted 02 May 2013 - 11:16 AM

One thing I'll say about truss dobs holding collimation: If it isn't holding it well, there is a weak link somewhere that needs to be looked at and can be fixed. Once I identified my weak links, my Obsession scopes hold collimation extremely well. One problem I had was that the nuts and bolts holding the miror cell in the rocker box would loosen over time, so I replaced the lock washers and check the tightness once or twice a year. I also replaced the original sling with a Glatter sling, which I feel was a very worthwhile investment. And, I made a few minor mods to the cam levers on the upper tube assembley, and now they hold rock solid. No issues.

Checking the mechanics of any telescope now and then is always a good idea.

#11 Jon Isaacs

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Posted 02 May 2013 - 12:17 PM

It's a size issue as much as anything. Once you start looking at telescopes 15" and bigger, tubes get massive. Big truss dobs break down for easier storage and transport. Discovery makes split-tube dobs in the 15"-17.5" sizes, and I think maybe a 12" too. A friend of mine has both 15" and 17.5" Discovery dobs, and in my opinion, they are way more of a hassle to deal with than my 20" Obsession. I just ramp it up into the bed of my pickup truck and go--no heavy or cumbersome lifting at all. But, that's just me--to each his own.


I agree, it's a size thing. I think once one is thinking of a 12 inch or larger, a truss style is definitely worthy of consideration.

I do think tube scopes have fewer thermal issues so if one is thinking of a planetary double-star scope, a solid tube scope is probably the best bet.

JOn

#12 paul hart

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Posted 02 May 2013 - 03:50 PM

I agree anything larger than 12" that will be car transportable should be a truss design.

#13 GeneT

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Posted 02 May 2013 - 03:54 PM

There are pros and cons for each. I like the rule of thumb--up to 10 inches, solid tubes are fine. At 12 inches and larger, it is better to go with a truss.

#14 paulr57

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Posted 02 May 2013 - 08:28 PM

Thank you for the responses! You've certainly clarified this for me. I was worried about stray light but it seems an easy fix with a shroud if needed. Fortunately for me I don't have much to worry much about this in my yard. I live fairly rurally and have no really close neighbors.

Again thanks for all the responses!

Paul

#15 JMW

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Posted 02 May 2013 - 09:01 PM

Even if you don't go huge a 12 - 16 inch well built truss dob will have a movement with steadiness at the eyepiece that exceeds any solid tube mass market scope. I enjoy the views in my Z12 tube but the solidness and settling time on our Obsession 20 F5 is way beyond the quality of experience on the dob I spent about $650 on.

I think a 12 inch water heater style tube dob is about the most bulk anyone will put up with. I think the dobstub kits are a good way up upgrading the experience if you are happy with the optics in your tube dob. Used truss dobs come up used all the time. If you are lucky something within driving distance will pop up. People hate to ship large dobs when selling used.

#16 Daniel Mounsey

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Posted 02 May 2013 - 10:47 PM

I've been trying to find a comparison between a truss and solid tube dob. Other than weight considerations are there any advantages between the 2 designs?


Paul,

I think there have been some serious misunderstandings on the pros & cons of a tube vs. truss, particularly regarding visual quality. From a portability aspect, a truss is certainly common among apertures larger than 10", and this is understandable, however, when it comes to visual accuracy, a solid tube is far superior than a truss for several reasons.

Regards

#17 JMW

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Posted 02 May 2013 - 11:09 PM

I agree that the rigidity of the optical system can be better on a quality solid tube dob. If the tube is giving much larger altitude bearings and a higher quality rocker box than you get with the particle board imports, the solid tube dob can give an excellent experience. I have no doubt that the Teeter 8 or 11 inch solid tube dobs are excellent. Notice that Teeter doesn't have solid tube dobs larger than 11 inches listed on his website.

With the proper mirror support a truss dob can maintain the collimation from horizon to zenith. Replacing a simple fabric sling with a Howie Glatter cable sling has made a major difference on our clubs' Obsession 20 inch f/5. You can put in a laser and move the scope from horizon to zenith and the laser stays on target. Faster f/3 to f/4.2 scopes also have shorter trusses which should reduce balance and sag on the UTA when close to the viewing the horizon.

#18 nicknacknock

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Posted 03 May 2013 - 01:45 AM

Thank you for the responses! You've certainly clarified this for me. I was worried about stray light but it seems an easy fix with a shroud if needed. Fortunately for me I don't have much to worry much about this in my yard. I live fairly rurally and have no really close neighbors.

Again thanks for all the responses!

Paul


Paul,

You night also want to get a night shield to place opposite the focuser. You want to reduce stray light as much as possible as it is a contrast killer.

CS,

Nicos

#19 dave brock

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Posted 03 May 2013 - 02:32 AM

The biggest advantage I've found with solid tube dobs (homemade at least) is the relative ease in making the tube rotatable to bring the eyepiece to a comfortable position. For that reason I went with solid tubes up to and including 16" F/5. 10" and larger scopes I make also have the tube break in half for easier transport. The tube not rotating is about the only thing I don't like with my 20" truss dob.

Dave

#20 okieav8r

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Posted 03 May 2013 - 05:56 AM

however, when it comes to visual accuracy, a solid tube is far superior than a truss for several reasons.


You'll have to elaborate on that Daniel. I've owned and used all kinds of telescopes, and speaking from practical experience, I don't agree with that.

#21 Pinbout

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Posted 03 May 2013 - 06:14 AM

The biggest advantage I've found with solid tube dobs (homemade at least) is the relative ease in making the tube rotatable to bring the eyepiece to a comfortable position. For that reason I went with solid tubes up to and including 16" F/5. 10" and larger scopes I make also have the tube break in half for easier transport. The tube not rotating is about the only thing I don't like with my 20" truss dob.

Dave


along with ease of rotation is the ease of rebalancing, when I put my binos on my truss dob I have to add weight, with my tube just slide it...

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#22 okieav8r

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Posted 03 May 2013 - 06:50 AM

that's a great looking telescope Danny. What is the tube made of?

#23 Mirzam

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Posted 03 May 2013 - 07:17 AM

Dave-

I'm curious how you made your large tube dob (16") rotatable. I'm also thinking to build one like this.

JimC

#24 MikeBOKC

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Posted 03 May 2013 - 07:52 AM

Agree with Rex. I've never seen any appreciable difference in the views through truss or solid tube scopes. The optical alignment/collimation principles are the same either way.

#25 Pinbout

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Posted 03 May 2013 - 07:55 AM

What is the tube made of?


its a cardboard tube from shapesunlimited.

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