[AZ-Observing] Re: Percent of Possible Sunshine (or maybe not)

You really don't want to get into the statistics of observing weather. I =
did
it last year after looking at Brian Skiff's historical photometric =
evening
data. It was sobering, and more than a bit depressing. So, in the spirit =
of
the recent weather posts, here goes:

All numbers are rounded up.

If I remember correctly, something less than 120 nights per year are =
truly
clear. Call that a 33% or 1/3 probability. Now, if you can only go out =
on
weekends, that gives a ~29% or 2/7 nights available in any week. Now =
factor
in new moon weekends . . . let's be generous and say every month has two
observing weekends (a stretch). So that's 50% or 1/2 the available =
weekends.

So we have .33 x .29 x .5 =3D .047, a little less than 5%

That's for the whole year, so .047 x 365 =3D ~17 nights on average of
photometric nights falling on a "new moon" weekend per year, or 8 =
weekends.

If you factor in whether the clear nights are consecutive (all factors =
in
this excerise are constrictive), the odds would take another hit, albeit =
a
small one. But I won't go there. This is enough of a bummer.

17 nights would be OK if everyone always went out for both nights, but =
that
is not possible for most people. So, divide by two again and we have ~8
nights.

And of course I can't/won't factor in life/family/job etc . . .

<insert happy face emoticon here>

In 2004 I made it out about five times. Due to my personal =
circumstances,
this year I probably won't be out at all until the fall (hopefully).

So what's a star-hugger to do? Seek councilling, dream of pristine =
nights
past, make telescopes (of course) and maybe buy a Planetarium:

http://antiqueradio.org/art/spitz01.jpg

<name withheld>


Tom uttered:
=20

-----Original Message-----
From: az-observing-bounce@xxxxxxxxxxxxx
[mailto:az-observing-bounce@xxxxxxxxxxxxx] On Behalf Of Tom Polakis
Sent: Tuesday, February 15, 2005 12:18 PM
To: AZ-Observing@xxxxxxxxxxxxx
Subject: [AZ-Observing] Percent of Possible Sunshine

In addition to not seeing a lot of starlight this Autumn/Winter, it =
seemed
like we're also not seeing a lot of sunlight.  Here is a table of the =
last
few months of data for percent of possible sunshine from the Phoenix NWS
office, with a comparison to the averages and lows since 1896.  The =
daytime
cloudiness has been bad, but not extremely so.


                     Percent of Possible Sunshine

         Oct      Nov     Dec      Jan      Feb (so far)

2004-5    88       75      72       64       53

1896-1995
Avg       88       84      78       78       80   =20
Low       65       62      47       54       47


Current weather and recent climate data is available at:
http://www.wrh.noaa.gov/Phoenix/

...and "The Climate of Phoenix" archived data is at:
http://geography.asu.edu/cerveny/phxwx.htm


I will resist saying that we are on track to set a new record low for
February sunshine, as that would be like saying that the Suns are on =
track
to win 70 games when they were midway through the season.

Tom

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