Posts Made By: John Holt

Ask at Vixen?

Or perhaps somebody like these guys:http://www.preciseparts.com/ppmain/index.html

robert wikeen said:

Can someone explain the difference in views between a cooled down scope and one that isn't? Thanks!

Sometimes like atmospheric poor seeing.

In a solid tube newt one can defocus and see waves of turbulence sorta folding their way up the tube. Under other circumstances one can see (again defocussed) air chimneying out the top of the tube.

Optics of significant mass like primary mirrors and corrector plates can radiate heat for hours. This causes refractive air turbulence at the optical surfaces as well as tube currents. And reflectors of any flavor recieve their signal after two or more passed through this potential soup.

My largest scope is a 13" plate glass. Even after hours of cool down, long after the sonotube has shed it's thermal load and tube currents are undetectable, the mirror can still produce boundry layer thermals at the mirror surface. At this point they look a bit like the seeing is softening. Just a tad. Field stars at the limit of view will not sharpen. But when it is cooling issues, turning on the blower cleans up the image. Stars sharpen, tiny fuzzies don't. Planetary details sharpen also.

My first scope was a 4" newt. Not much thermal mass there. When I started using larger scopes I noticed how more seeing was an issue. Thought I was seeing much more of the atmospheric turbulence everybody was talking about. But a lot of it ultimatly turned out to be seeing conditions inside the scopes themselves.

If one looks down a solid tube newt, because of the heat sensitivity of our faces, heat coming up the tube can be easy to feel.

Casey Whalen said:

This is my first year stargazing. I have a 6" dob and i've noticed the few times i've taken it out this winter that after being outside for a while and then coming back in the house I have a fine mist or a kind of condensation on my scope. I'm mainly conserned about my primary and secondary mirrors. After bringing my dob in the house for a few minutes it disappears. Is this something I need to be concerned about?

Thanks.

Nope.
If it disappears you are good. You want to store it dry.

One can cover up the scope in an insulating covering. This will help prevent condensation from a cold scope meeting warm air. Blow drying the scope on the inside and out will work, with or without heat. Storing the scope with desiccant works. Storing the scope in an unheated area works. Or any combination of the above.

In general, dew, condensation and frost will not hurt as long as the scope is dried before storing it.

Worst case senario is to put away an ice cold dob into a warm house, in the vertical position. (Oh but it stored so much more conveniently that way!)
...I found the dried remains of the water puddles on the primary days later.

Ask Meade too. Due to the chemicals and abrassion factors.

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I'm with you!

For those just beginning and want a tool for at the eyepiece:

http://www.willbell.com/atlas/atlas1.htm


Highly recommended!

How about a home brew pipe mount? How heavy is a 66sd spotter? I've a 9 lbs short newt on a simple 90* elbow for a mount head. The tube rings on the newt mount right to a flange threaded on the elbow, for altitude. The elbow threads onto a vertical section for azimuth. Very simple and inexpensive.

Just not rating the other person is far better than nit-picking stars upon them. IMHO

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Sorta like fishing. No end at all.

The portabilty aspect is significant. It's much easier to get a portable scope out of town to darker sky. Which will make any scope into a whole different experience.

Another scope make over for the same sized scope is to use more detailed charts. Whether printed or electronic. Can't recommend this enough. Either format is more affordable, acurate and detailed than ever before.

How about an Orion Starblast?

It corrects coma, or astigmatism?