FreeLists / az-observing / [AZ-Observing] Re: Recording Seeing Conditions (was WOW!)

[Andrew Cooper <acooper@xxxxxxxxx>]

I have been following this thread for a while now and just have to weigh 
in with my disagreement.  Arbitrary, unscientific, crude seeing and 
transparency scales certainly do have a role for the visual observer!  I 
keep notes of my impressions of the conditions for my observations. This 
gives me something to go on when reviewing my notes later, sometimes 
years later.  Was the night good or bad?  Why did I not see the dust 
lane in NGCxxxx or did see the central star in PNxxxx? Do I need to 
re-observe ICxxxx under darker skies to properly appreciate it?

I use something like Pickering's scale for seeing and a visual estimate 
of the dimmest stars I can see near zenith for my notes. (I don't use 
the pole because I am so often south of Tucson or Phoenix)  It's not 
very calibrated, it isn't rigorously controlled, but it gives me some 
sort of scale when looking back to put my notes into perspective.

I generally don't share my numbers with others beyond it was a good 
night, or transparency was great but seeing looked like we were viewing 
from the bottom of Old Faithful, every few minutes the stars turned into 
beachballs.  I usually give an average SE Arizona night a 6 or 7 for 
seeing and a 5.5 to 6.5 for transparency.  Consider a little standard 
distribution statistics and this makes perfect sense.  I have seen a 10 
for seeing precisely two times.

We need something, I am not always going to hook in a CCD camera and do 
a measurement of the FWHM to figure out the seeing in arcseconds.  Such 
data has it's place and I appreciate it when available.  But when 
standing by a telescope I need something, and it needs to be quick, 
simple and need not be horribly accurate.  The only  important thing 
that it be reasonably consistent.  Looking at a star at high mag and 
looking at zenith with a star chart in hand fits the bill.

Andrew

Andrew Cooper
----------------------------------------------------
http://www.siowl.com



Brian Skiff wrote:

> <>
> That's why you avoid these arbitrary scales altogether, and use
> physical units you can actually measure, specifically arcseconds.
>
> Brian
>
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