[AZ-Observing] Re: Mars-Moon Conjunction - Now Pickering Scale

Try this page for a reference as to the Pickering scale:

http://uk.geocities.com/dpeach_78/pickering.htm

I keep a copy of this animation on my laptop to use in the field but a
static version can be printed out too.  After a lot of practice I have
become pretty good estimating seeing based on this scale.  I am working on
comparing the Pickering scale method to Brian Skiff's equal double star
method of evaluating seeing.

The Pickering scale is based on a 5" refractor.  I haven't been able to do
side-by-side comparisons but in night-to-night comparisions there is a
significant difference between my 90mm f/5.6 refractor and my 128mm f/8.1
refractor.  The smaller the scope and/or shorter the f/l, the better the
seeing looks.  I don't know whether aperture or focal length is the more
important factor.  The difference is even more dramatic going from the 5"
refractor to a 10" f/12 D-K Cassegrain.  My ususal rating in the 10" is more
like 3/10.

Regards,

Bill Wood
Fountain Hills, AZ


> -----Original Message-----
> From: az-observing-bounce@xxxxxxxxxxxxx
> [mailto:az-observing-bounce@xxxxxxxxxxxxx]On Behalf Of Andrew Cooper
> Sent: Thursday, July 17, 2003 2:29 AM
> To: AZ-Observing mailing list
> Subject: [AZ-Observing] Mars-Moon Conjunction
>
>
> The seeing was poor to fair, a pickering 5 perhaps judging from the airy
> disk.  Need to print out a version of the Pickering Scale for the
> reference section of my observing notebook.  My refractor being similar
> to the instruments he designed the scale for.
>
>
> Good night,
>
> Andrew
>

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