Re: [ATM] Forced Ventilation

[jeffmorgan@mindspring.com]

Pulling air down the tube is my arrangement also. I really like it, but never realized the advantage you mentioned about the diagonal mirror. Seems a heck of a lot better than picking up dust near the ground and flushing the mixed air back up the optical path.

At first I was concerned about the ability of my 20 cfm fan to actually pull against air warmed by the mirror. So I tested it by lighting a match and placing it over the top of the tube. The base of the flame was slightly elongated downward. When I blew the match out, all of the smoke went into the tube. (You can understand that with optics in place this is a test I don't want to repeat a great many times.) Also, when placing my hand over the front of the tube, the air movement can be plainly felt.

I can see where a square mirror box design may be too open for this application. But for a tubed scope I'd say it's a winner all the way around.

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