Return to the Cloudy Nights Telescope Reviews home pageAstronomics discounts for Cloudy Nights members
· Get a Cloudy Nights T-Shirt · Submit a Review / Article

Click here if you are having trouble logging into the forums

Privacy Policy | Please read our Terms of Service | Signup and Troubleshooting FAQ | Problems? PM a Red or a Green Gu… uh, User

Equipment Discussions >> Reflectors

Pages: 1 | 2 | 3 | 4 | (show all)
Pinbout
Postmaster
*****

Reged: 02/22/10

Loc: nj
Re: truss vs solid tube dob new [Re: dave brock]
      #5837721 - 05/03/13 07:14 AM

Quote:

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...



Post Extras: Print Post   Remind Me!   Notify Moderator  
okieav8rAdministrator
I'd rather be flying!
*****

Reged: 03/01/09

Loc: Oklahoma!
Re: truss vs solid tube dob new [Re: Pinbout]
      #5837755 - 05/03/13 07:50 AM

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

Post Extras: Print Post   Remind Me!   Notify Moderator  
Mirzam
Post Laureate
*****

Reged: 04/01/08

Loc: Lovettsville, VA
Re: truss vs solid tube dob new [Re: dave brock]
      #5837775 - 05/03/13 08:17 AM

Dave-

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

JimC


Post Extras: Print Post   Remind Me!   Notify Moderator  
MikeBOKC
Post Laureate
*****

Reged: 05/10/10

Loc: Oklahoma City, OK
Re: truss vs solid tube dob new [Re: okieav8r]
      #5837829 - 05/03/13 08:52 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.

Post Extras: Print Post   Remind Me!   Notify Moderator  
Pinbout
Postmaster
*****

Reged: 02/22/10

Loc: nj
Re: truss vs solid tube dob new [Re: okieav8r]
      #5837839 - 05/03/13 08:55 AM Attachment (14 downloads)

Quote:

What is the tube made of?




its a cardboard tube from shapesunlimited.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: truss vs solid tube dob new [Re: MikeBOKC]
      #5837913 - 05/03/13 09:37 AM

Quote:

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.




I think it has to do with the effect of body heat drifting across the optical path. Shrouds do not block breezes with the same effectiveness as a solid tube.

I have noticed that since I converted my 12.5 inch F/4.06 to a truss, it doesn't handle the high magnifications viewing double stars the way it used to. It's not a collimation issue, the collimation doesn't shift.

One of these days to test this, I am going to replace the cloth shroud with a sheet of 0.060" ABS wrapped around to make a tube, it would be captured by the truss poles.

Jon


Post Extras: Print Post   Remind Me!   Notify Moderator  
dave brock
professor emeritus


Reged: 06/06/08

Loc: Hamilton, New Zealand
Re: truss vs solid tube dob new [Re: Mirzam]
      #5837923 - 05/03/13 09:43 AM Attachment (23 downloads)

Quote:

Dave-

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

JimC




Hi Jim.
The Tube rides in an octagonal cradle that has ends which are lined on the inside (against the tube) with felt. At each end of the cradle is a tube ring with Teflon tabs that rub against the cradle. The upper ring takes all the weight of the scope while the lower ring keeps the cradle in place when the tube is horizontal or being carried.
The best pic I have showing the system is this one of a 12" I made. The 16" is in the background btw.

Dave


Post Extras: Print Post   Remind Me!   Notify Moderator  
dave brock
professor emeritus


Reged: 06/06/08

Loc: Hamilton, New Zealand
Re: truss vs solid tube dob new [Re: dave brock]
      #5837945 - 05/03/13 09:56 AM Attachment (25 downloads)

An 8" with the same rotating tube system.

Dave


Post Extras: Print Post   Remind Me!   Notify Moderator  
okieav8rAdministrator
I'd rather be flying!
*****

Reged: 03/01/09

Loc: Oklahoma!
Re: truss vs solid tube dob new [Re: Jon Isaacs]
      #5837987 - 05/03/13 10:17 AM

Quote:

Quote:

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.




I think it has to do with the effect of body heat drifting across the optical path. Shrouds do not block breezes with the same effectiveness as a solid tube.

I have noticed that since I converted my 12.5 inch F/4.06 to a truss, it doesn't handle the high magnifications viewing double stars the way it used to. It's not a collimation issue, the collimation doesn't shift.

One of these days to test this, I am going to replace the cloth shroud with a sheet of 0.060" ABS wrapped around to make a tube, it would be captured by the truss poles.

Jon




That would be an interesting experiment Jon. As for myself, I just don't see any real effect of body heat with my scope. I'm not much of a double star observer though, so it's hard to say.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: truss vs solid tube dob new [Re: okieav8r]
      #5837999 - 05/03/13 10:26 AM

Quote:

That would be an interesting experiment Jon. As for myself, I just don't see any real effect of body heat with my scope. I'm not much of a double star observer though, so it's hard to say.




I think Daniel is a serious planetary/double star guy and observes with a group of LA "whackos" (as opposed to San Diego or Oklahoma whackos) who are really into it. They often have the good seeing and it's a constant shootout between some pretty awesome planetary scopes.

Jon


Post Extras: Print Post   Remind Me!   Notify Moderator  
Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: truss vs solid tube dob new [Re: Jon Isaacs]
      #5838123 - 05/03/13 11:15 AM

There are advantages to a truss--many actually:
1) lower center of gravity--more stable
2) much shorter rocker box--less shimmy and vibration
3) lower weight--OTA easier to pick up and move in a pinch.
4) easier to transport in a car--smaller and lighter segments
5) easier to remove primary mirror for cleaning
6) easier to create baffles above the primary to enhance contrast
7) larger altitude trunnions for less sensitivity to balance and superior altitude movement.
8) Better looking--more like a professional telescope. Often made of finely-finished wood.
9) easier to collimate accurately because you can get closer to the primary and secondary mirror surfaces or focuser to see a laser dot or shadow of the centermarker.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: truss vs solid tube dob new [Re: Starman1]
      #5838148 - 05/03/13 11:25 AM

Quote:

There are advantages to a truss--many actually:
1) lower center of gravity--more stable
2) much shorter rocker box--less shimmy and vibration
3) lower weight--OTA easier to pick up and move in a pinch.
4) easier to transport in a car--smaller and lighter segments
5) easier to remove primary mirror for cleaning
6) easier to create baffles above the primary to enhance contrast
7) larger altitude trunnions for less sensitivity to balance and superior altitude movement.
8) Better looking--more like a professional telescope. Often made of finely-finished wood.
9) easier to collimate accurately because you can get closer to the primary and secondary mirror surfaces or focuser to see a laser dot or shadow of the centermarker.




There is no doubt there are many advantages to a truss scope... But thermal management does not seem to be one of them.

Jon


Post Extras: Print Post   Remind Me!   Notify Moderator  
okieav8rAdministrator
I'd rather be flying!
*****

Reged: 03/01/09

Loc: Oklahoma!
Re: truss vs solid tube dob new [Re: Jon Isaacs]
      #5838167 - 05/03/13 11:40 AM

Quote:


I think Daniel is a serious planetary/double star guy and observes with a group of LA "whackos" (as opposed to San Diego or Oklahoma whackos) who are really into it. They often have the good seeing and it's a constant shootout between some pretty awesome planetary scopes.

Jon




What's "good seeing"?


Post Extras: Print Post   Remind Me!   Notify Moderator  
okieav8rAdministrator
I'd rather be flying!
*****

Reged: 03/01/09

Loc: Oklahoma!
Re: truss vs solid tube dob new [Re: Starman1]
      #5838178 - 05/03/13 11:44 AM

Quote:

There are advantages to a truss--many actually:
1) lower center of gravity--more stable
2) much shorter rocker box--less shimmy and vibration
3) lower weight--OTA easier to pick up and move in a pinch.
4) easier to transport in a car--smaller and lighter segments
5) easier to remove primary mirror for cleaning
6) easier to create baffles above the primary to enhance contrast
7) larger altitude trunnions for less sensitivity to balance and superior altitude movement.
8) Better looking--more like a professional telescope. Often made of finely-finished wood.
9) easier to collimate accurately because you can get closer to the primary and secondary mirror surfaces or focuser to see a laser dot or shadow of the centermarker.




Good points Don. My whole thing with the Truss vs. tube thing is that I just don't see a difference visually. My preference for truss scopes is simply that for large sizes, they are easier to deal with logistically, as your points well show.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: truss vs solid tube dob new [Re: okieav8r]
      #5838215 - 05/03/13 12:05 PM

Quote:

Quote:


I think Daniel is a serious planetary/double star guy and observes with a group of LA "whackos" (as opposed to San Diego or Oklahoma whackos) who are really into it. They often have the good seeing and it's a constant shootout between some pretty awesome planetary scopes.

Jon




What's "good seeing"?




Half arcsecond or better? Don knows more about Daniel than I do. I agree that in the larger sizes, trusses are far more practical than Tube Dobs... No doubt about that...

Jon


Post Extras: Print Post   Remind Me!   Notify Moderator  
Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: truss vs solid tube dob new [Re: Jon Isaacs]
      #5838260 - 05/03/13 12:21 PM

There's no question that enhancing seeing conditions is a worthy thing for lunar/planetary/double star observers.

You can only do so much about the atmosphere (maybe by picking a site with good seeing), and the rest is in the scope. Thermal management is critical, which includes the ground under the scope as well as the scope. Even how you observe and where your body is relative to the scope matters.

For every other kind of observing, though, seeing can be less than perfect and still be OK. I've seen seeing so good the 12.5" was aperture-limited, but that's rare. It's less rare for my 5" Mak.
I've always paid attention to collimation and thermal issues in my scopes, so I get satisfactory performance from them just about all of the time.
That doesn't mean superb seeing isn't appreciated, though. Even we hard-core deep-sky observers see more details when seeing is superb.

So, pay attention to collimation and thermal issues and you will see better seeing more of the time. What side of the scope you stand on, or whether the scope is a full-tube or truss seems to be somewhat, uh, lower on the list of important issues.


Post Extras: Print Post   Remind Me!   Notify Moderator  
okieav8rAdministrator
I'd rather be flying!
*****

Reged: 03/01/09

Loc: Oklahoma!
Re: truss vs solid tube dob new [Re: Jon Isaacs]
      #5838649 - 05/03/13 03:58 PM

Quote:

Quote:



What's "good seeing"?




Half arcsecond or better? Don knows more about Daniel than I do. I agree that in the larger sizes, trusses are far more practical than Tube Dobs... No doubt about that...

Jon




Thanks Jon. My comment was more of a jab at the generally mediocre seeing I have to deal with in eastern Oklahoma. I have to get out into the western part of the state for better seeing conditions. I envy you for where you live and the much better seeing conditions that you have access to.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Scanning4Comets
Markus
*****

Reged: 12/26/04

Loc: Ontario, Canada
Re: truss vs solid tube dob new [Re: okieav8r]
      #5838687 - 05/03/13 04:17 PM

Those scopes are a gorgeous work of art.



Cheers,


Post Extras: Print Post   Remind Me!   Notify Moderator  
Mike B
Starstruck
*****

Reged: 04/06/05

Loc: shake, rattle, & roll, CA
Re: truss vs solid tube dob new [Re: okieav8r]
      #5838719 - 05/03/13 04:36 PM

Quote:

My comment was more of a jab at the generally mediocre seeing I have to deal with in eastern Oklahoma.



Ayup, that was clear enough.


Quote:

One of these days to test this, I am going to replace the cloth shroud with a sheet of 0.060" ABS wrapped around to make a tube, it would be captured by the truss poles.



Have thot 'bout this myself... shouldn't be too hard? Maybe even just at the upper half or third of the assembly, nearer the UTA. At least as a temporary set-up, to evaluate whether it was really worth pursuing...

For some folks, where their truss-Dob set-up for viewing planets has the prevailing winds blowing their heat back AWAY from the scope, perhaps it's not such an issue?

Last nite i was out, warm nite still from a hot (~92*F) day, thermals profoundly visible in the defocus (= "bright platter of squiggling worms" )... i could hold my hand up in front of the UTA & see the shadow of my hand+fingers in the "platter"- heat was pouring off like crazy & wafting upwards like "smoke"!

Yet- within mere seconds of removing my hand, the "smokey" thermals were gone. Entirely. Then, breathing forcibly thru the Dob's fabric shroud, i looked into the "platter" and saw a gradual waviness waft across the platter... then it, too, was gone. I can hardly imagine how "normal" breathing would even show up here... ... to say nothing of radiating body-heat.

Perhaps these "body-heat" effects are more pronounced (& of reasonable concern ) during winter months & greater delta-T's?... 99* human versus 33* ambient 12-inches away?... and/or combined with breezes pushing it into the lite-path? But 99* to ~80* over 12-inches... i remain not so much unconvinced, as unconcerned.

I'll take the 15" trusser over the tuber, ANY day! Thanks.


Post Extras: Print Post   Remind Me!   Notify Moderator  
Achernar
Postmaster
*****

Reged: 02/25/06

Loc: Mobile, Alabama, USA
Re: truss vs solid tube dob [Re: Jon Isaacs]
      #5839049 - 05/03/13 08:59 PM

When you reach 15 or 16-inches, a truss is really the only practical option if you have to transport it. As for thermal issues, I don't see any disavantages at all, indeed my mirror cools off quite rapidly and I have an Obssession pattern mirror cell. I have a variable speed fan that I leave running all the time at low speed, without vibration problems and turning it off or on does not seem to affect the views. It's no worse or better than my 10-inch solid tube, also with a cooling fan.

Taras


Post Extras: Print Post   Remind Me!   Notify Moderator  
Pages: 1 | 2 | 3 | 4 | (show all)


Extra information
4 registered and 7 anonymous users are browsing this forum.

Moderator:  ausastronomer, Knuklhdastrnmr, Phillip Creed, JayinUT 

Print Thread

Forum Permissions
      You cannot start new topics
      You cannot reply to topics
      HTML is disabled
      UBBCode is enabled


Thread views: 2939

Jump to

CN Forums Home


Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics