Tired of SCT tube currents, then get rid of the tube

Removing the tube has advantages. Normally accurate baffles are both strictly required to avoid undesired lights. Expensive carbon fiber materials from RCOS and A&M OTAs are used to get the tube rigid enough, but in such cases the scopes are very hard to be quickly cooled down because of the insulating tube.

When a tube is removed, heat plumes are no longer seen even when the telescope has been outdoor for just half an hour or even less, provided the temperature gap isn't too large , no external reflections are seen because the air surrounding optics cannot reflect light which means a very short wait to get the scope ready to start.

Environmental lights aren't an issue because only the in-axis light path, no off-axis light can disturb the view at the eyepiece. The background sky level is as black as seen with the naked eye or even better if some external light is disturbing the view. This performance is improved if special black velvet wrapped around any critical surface along the light path. This is the most effective material known for light blocking, no painting can give better results because heavy moisture sooner or later will make painted surfaces shiny. Velvet absorbs moisture.

Under average humidity conditions , mirrors get wet only after a long time, expecially the primary mirror because due to its thermal inertia, keeps the glass slightly warmer than the air. An optional dewshield or heater belt helps to keep mirrors dry over the whole night.

So I like the approach he has taken, but he could have got rid of this truss design altogether to obtain slightly better results by using a single rigid platform.

The imaging results would be superior than a tube.

Eamonn A

Scary!

Another interesting way to cool your SCT.
I'd be worried about dust getting in though.

www.starcrwzr.com/cooler.htm

T

I met Scott a few years back, nice guy, the cooler was another one of those things I was going to build, the dome removed the need for it.