[AZ-Observing] Re: 2003 Flagstaff nighttime cloudiness
- From: Jeff Hopkins <phxjeff@xxxxxxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Thu, 1 Jan 2004 14:55:23 -0700
At 13:48 -0700 01/01/2004, Brian Skiff wrote in part:
>We don't get that kind of weather around here! When I started
>this 25 years ago, I decided that rather than trying to distinguish
>various levels of cloudy nights, the thing of real interest were
>the genuinely clear nights from start to finish. So for instance,
>if a snowstorm clears out an hour after dusk, that night is not what
>I call a 'photometric' night, but a 'partial' one, though the remaining
>hours go into the total clear-hours tally.
Thanks Brian,
Back in the early 80's I had a request for observations of 22
VULPECULAE. The window for making measurements was narrow. I believe
it was during the summer months (August in particular). Almost every
night was clouded with lots of thunderstorms around. What I did was
just waited until I had an opening between clouds. I found the
readings amazingly steady. In fact I got more than one set of good
observations with lightning flashing all around me.
I have found the thin cirrus, sometimes not even visible, can defeat
photometric observations as the extinction varies greatly over a
short period and even differential measurements become worthless.
Perhaps CCD photometry that had the comparison and program stars in
the same field would still work as the data would have been taken at
the same time. For single channel photometry, it's time for bed.
>This is obviously a
>conservative reckoning, but in order to do this indefinitely the
>amount of work involved has to be minimal---I can't be around recording
>the state of sky hourly every night.
>
>\Brian
I figured you had this automated. Coming up with that information
manually is a significant job. My only thought were regarding the
photometric nights. As even you noted some of those non-photometric
nights are indeed very photometric.
Jeff
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