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Old 15-08-2006, 09:48 PM
davidpretorius's Avatar
davidpretorius
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Join Date: Jun 2005
Location: Launceston Tasmania
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2 types of seeing - boundary layer and atmospheric conditions

I know I have had it, that 8.5/10 night when the shadow of one of jupiter's moon is super still, or the CD of saturn is visible and super sharp.

On most occassions, this is not the case....

So, having viewed jupiter on my laptop screen heaps in less than ideal conditions, I am wondering what causes what in terms of atmospheric seeing and then boundary layer seeing.

There are those nights that when you look through the eyepiece and there appears to be a stream of hot air blasting across the planet.

Other times, jupiter appears to pulse in and out of focus on the laptop screen.

Jupiter will even bulge

In less than ideal seeing, turning on the cooling / fans will improve the image (maybe disperse the boundary layer), other times in better seeing, the focus is not near as sharp with fans on. Turn the fans off and aprox 2 mins later, the image sharpens up.

More tests are needed, but I find it amazing the different ways seeing buggas ya image.
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Old 16-08-2006, 05:54 AM
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iceman (Mike)
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Join Date: Sep 2004
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I know what you mean, Dave. I *think* that the waves of bulging distortion is caused by boundary layer, because on my "light bulb moment" night, where the mirror finally reached (within 0.3°) ambient temperature, that distortion stopped!

The image stood still.. still flickering from the atmospheric seeing, but not affected by the large pulsing waves.

I usually leave my fan running all the time, even while imaging at 7500mm FL.. I don't appear to get any vibrations from it, which is great.
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