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
Received on Mon Apr 26 13:06:36 2004