>Ralph Seguin wrote:
>
>>I don't really anticipate much variation in seeing from one site to
>>another, but you never know.
>
>
>I think seeing conditions deserve much more attention than they
>usually get when choosing observing sites. The steadiness of the
>sky makes a huge difference in the amount of detail that can be seen
>in an observing session, and how faint you can go when pushing the
>limits for hard objects. Seeing often depends on local topology and
>is not well captured by light pollution maps or typical measures of
>sky darkness. I think there is a lot of variation in seeing from
>one site to another, and that some sites tend to have better steadier
>average skies because of a combination of altitude, topology, and
>proximity to other features that may disrupt laminar flow. My own
>experience has been that Bumpass Hell parking lot tends to have
>steadier skies than other sites around Mt. Lassen. In the Bay Area,
>both Mount Hamilton and Fremont Peak have had more consistently good
>seeing than the other sites I have tried.
>
>There was a pretty good example of this from just last Thursday night
>if you compare observing reports from observers at four different
>locations. (This is one of the reasons I enjoy reading observing
>reports on TAC- simultaneous experience collected from a range of
>locations).
>
>1) Henry Coe (4/22/2004):
>
>"Star images were not crisp. Jupiter was swimming, though it offered
>a wonderful sight as
>always with its satellites." ---- William Schultz
>
>2) Montebello (4/22/04):
>
>"The sky was good... seeing on the planets seemed good... I had saturn
>at about 240x mostly solid w/ occasional bluriness" ---Jeff Crilly
>
>3) Courtyard/driveway on the east side of Morgan Hill (4/22/04)
>
>"Jupiter was initially doing the backstroke, but was definitely
>looking better as time went on. Although the initial seeing was
>pretty soft, it was still far from the worst I've ever experienced."
>----Bob Czerwinski
>
>4) SW lot of Fremont Peak (4/22/04) Two reports
>
>"The seeing was remarkably sharp throughout the breezy period until it calmed
>down by 10pm. Planetary detail was very good on Jupiter with many whit ovals
>following the GRS at mid-disk. .... I was able to split doubles as
>tight as 0.5 arc-sec and
>tries alpha Coma B. at 0.4 arc-sec. It didn't split but was a clean oblong
>airy disk shape with nice diffraction all around. " ----Peter Natscher
>
>"The wind disappeared and the seeing only got better as the night progressed."
>---John Gleason
>
>
>That's just one night, but is a good example of how much seeing
>conditions can vary from site to site. It is also a good example of
>why I still often head to Fremont Peak when I am looking for
>altitude and steady skies in the Bay Area.
>
>--David Kingsley
Saturday, I was observing at Foothills Park, a site on Page Mill road
but quite a bit lower than Montebello. I didn't look closely at stars early
in the evening when, I think, the seeing was better. Near 1:00 am some
of us were trying to split some tight double stars. The seeing was not quite
good enough to show a first defraction ring when looking at Porrima using
high power.
On other nights with the same telescope (155mm f/7 APO) but up the road
more, a private site close to Montebello, Porrima would show a nice first
defraction ring and Airy disc.
Rich
Received on Mon Apr 26 16:33:08 2004