Re: a twinkle question

Chris L Peterson wrote:
On Thu, 06 Apr 2006 15:26:30 GMT, Phil Wheeler <w6tuh-ng7@xxxxxxxxx>
wrote:


Probably high mag more than large aperture. The two can go together, but need not.


No, I think it is aperture that matters primarily. The wider the column
of air the rays are passing through, the more complex the image
distortion can become.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Yes, that's true and the measure of this is the ratio of the diameter of the aperture to the size of the coherent patch or D/r0.

For D/r0 less than 3 most of the seeing is tip/tilt and a star appears to move around as a single image.

For example typical seeing of 2 arc seconds is about a 5 cm r0 so D/r0 of 3 correspond to a diameter 15 cm or about 6 inches.

As D/r0 gets larger the single image breaks up in to speckles and the over all "center of mass" of the image moves less.

dan
.

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