RE: [APML] PLEASE - what is the clearity rating scale?

[leakeysg@netscape.net]

Mark,

One source of information on the seeing rating is the Wallis and Provin book, ("A manual of advanced celestial photography", Brad D. Wallis and Robert W. Provin).  They provide a table developed by J.B. Sidgwick in "Amateur Astronomers Handbook."  It is based on the appearance of the spurious disk and diffraction rings of a relatively bright star at high power (60 times or more the aperture in inches).  The rating was based on a telescope with an aperture of about 5 inches.  It varies from a seeing of:

1.  Disk and rings undifferentiated; image usually about twice the size of the true diffraction pattern

to

5.  Disk always visible; short arcs of the rings visible for about half the time

to

10.  Disk always sharply defined; all rings virtually stationary

Lee Dodge


>
>What is the 1 - 10 clarity (seeing) rating scale and how do you use it?
>I know someone on this list must know because I see it used from time to 
>time (Tony)...
>
>Mark Park
>Mark_park@hotmail.com
>AstroPhoto Page:http://www.wilkes.net/~tspark/astrphts.htm
>Home Page: http://www.wilkes.net/~tspark/
>
>
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