Truss or closed tube ??

[alexandre]

Hello !
I am has the research for information about the comparisons of different type of telescope (truss or closed tube)!
My project is to pass is one diameter 360 mm (Astrosib 360 for example).
But my sky is transparent, but with a lot of turbulence, that recommend to me you?

Thank you in advance!;)
@lex.

[gregbradley]

Truss would outperform tube every time. Tubes have trouble with thermal currents reducing resolution. If your seeing is already difficult then you don't want to worsen performance with tube currents.

Truss design usually costs more though.

Greg.

[Paul Haese]

Yep I would have thought a truss would be better at handling cooling and tube currents.

[Allan]

A tube offers better contrast and more stable collimation.

Without an active cooling system a truss mounted mirror might track the ambient temp closer than a tube.

It is easy to install a good fan system in a tube to scrub the mirror boundary layer and create a laminar airflow through the tube. Not so easy in a truss with the fabric shroud.

[coldknights]

https://www.facebook.com/photo.php?fbid=684338981585729&set=a.469212383098391.115502.362933 397059624&type=1&theater

Thought people may enjoy this !!!!!:D
Bintel's New Truss scope coming soon.

[jase]

+1 what Allan notes. Truss will allow the optics to cool faster to ambient but a tube isn't that far behind. The laminar airflow down a tube is extremely effective at cooling. Tube currents are a thing of the past with active cooling. With a tube, you will not need to clean the optics as much.

If you are using the scope in an open area, truss wins as it has a low surface cross section thus not challenged by the wind. Obviously a truss with a latex sock for contrast will experience problems with the wind.

[alexandre]

Thank you for your answers!!
I see that it will be difficult to make to me an idea, because impresions is very different!!
Not easy for me!!

bye;)
@lex.

[John K]

And don't forget that something like a 12"+ telescope in a tube will feel even the slightest touch of breeze. Even a truss with a shroud creates this effect.

Truss wins hands down unless you can fully actively cool something like a carbon fibre tube.

The other issue is weight vs cost. I think this is the reason why there has been a big shift to truss tubes as well to keep the weight down and easier to break down and transport.

Obviously depends on the mount you get and I notice that some of the premium RC telescope makes still offer tube designs.

John K.

[gregbradley]

Absolutely John.

Tubes suck.

I don't know how many times my RCOS 12.5 inch closed tube scope sat in the car at my dark site because as you say the slightest breeze and it was impossible to guide.

Greg.

[SkyViking]

I vote for truss too, the design offers increased stability and reduced weight.
And dew control and cooling is beneficial regardless of weather you use a tube or truss design.

[jase]

Really? Sounds like your mount couldn't handle it. My 12.5" RCOS tube on a PME will guide without issue up to 15km/h winds - hardly a slight breeze. Beyond this it gets a little sketchy. Obviously it comes down to how well sheltered the system is. If you put the system in a dome, who cares?