Fremont Peak was both warmer and damper Friday night than my trips in
January and February.
I arrived about 6:30 pm and set up my 14.5 inch Starmaster Dob on
one of the observing pads by the observatory. John Gleason arrived
just behind me, and set up for astrophotography on the flat area down
the hill from the observatory. Temps hovered around 45 degrees most
of the night. The humidity began around 70% and rose to 90% (enough
to make things damp but not soaking wet) There was an occasional
little breeze, but no problem at all with gusty wind. John and I
both noticed that there was hardly any naked eye twinkle to the
stars. The bright constellations of winter made a great sight
hanging steady in the sky. I was able to get in about five solid
hours of observing before the moon rose and bands of clouds started
building up on the eastern horizon after midnight
I headed over to M31 just after astronomical twilight began. When I
started my extragalactic globular cluster observing project last
fall, I could observe M31 for hours as the galaxy rose, transited
nearly directly overhead, and slowly began to fall again in the sky.
With spring nearly upon us, M31 is now already positioned lower than
45 degrees in the west before the sky even gets completely dark.
Still, I spent an enjoyable hour or so tracking down far away
globular clusters while M31 was still 30 degrees or so above the
horizon. I was able to find four more extragalactic globs in M31
last night, bringing my total to sixty M31 globular clusters since I
began hunting at LSA last October. Extragalactic fishing has been a
great way to extend a globular cluster observing project through the
winter, and I still have a few targets both in M31 and other local
group galaxies that should provide challenge targets for the future.
I also tracked down one of the fainter globs in our own Milky Way,
Palomar 1 in Cepheus. This is a sparse, faint cluster whose
metallicity and position far from the plane of the galaxy both
suggest it is more likely to be a globular than an open cluster.
However, the HR diagram and main sequence turn off point for Palomar
1 suggest it is only 6 to 7 billion years old. That is only about
half the age of a typical globular cluster in our Galaxy. Palomar 1
thus may have formed much more recently from the bulk of other
globular clusters in the Milky Way, and by a different mechanism (see
http://www.journals.uchicago.edu/AJ/journal/issues/v115n2/960336/960336.html).
I had tried to find Palomar 1 before from both Dino Point and LSA,
but had never been able to convince myself I had seen it. Last night
I had a much more detailed print out of faint field stars from a
SkyTools observing chart. With lots of quiet staring under a hood at
the eyepiece, I could just make out a small threshold glow with
averted vision at about the right location, though much smaller than
the circle indicated on the Sky Tools chart. Today I compared a
Digitized Sky Survey image of the region with the rough sketch I made
last night at the eyepiece. The threshold glow I saw last night is
located just at the core of the sparse globular, and its shape
matches the arc of the brightest individual stars near the core.This
is a much harder target than I thought it would be. Although Palomar
1 has integrated an visual magnitude of 13.6, it spread widely over
a circle of several arc minutes. Fortunately, the brightest
individual stars in Palomar 1 have visual magnitudes of about mag
16.3 ( the peak of the red giant branch). That brings the brightest
stars just within my visibility limit with a 14.5 inch scope from
sites near the Bay Area.
I tracked down a bunch of other targets last night as well, including
one much more typical NGC glob to add to my ongoing survey of Milky
Way globs with the 14.5 inch scope (NGC 4147)
a bright HII region in Perseus (NGC 1579),
a couple of planetaries with easy central stars, obvious halos, and
interesting detail (NGC 2346 in Moncerus and the Eskimo Nebula in
Gemini)
Hubble's variable nebula in Monocerus (NGC 2261, the bright star plus
fan shaped tail thing looks more like a comet than many comets I
have seen. Since the telescopic appearance of this nebular varies
substantially over time, it is worth checking again from time to
time, even if you have it before. Take a look at page 1204 in
Burnham volume 2 to get some idea of how much this object can change
from year to year).
a beautiful, "should have been a Messier" galaxy in Lynx (NGC 2683).
When the moon was going to come up, I also took a look at Jupiter.
The bright dot of Io was obvious against the edge of Jupiter's
surface. However, the views were no where near as steady as they had
been a couple of weeks ago at Fremont Peak. This surprised me
because the naked eye stars had much obvious twinkling last night
than on other recent trips, and many of the starfields that I had
chased down earlier during the night had looked pretty steady at
powers up to 400x. I stayed long enough to watch Io's shadow appear
on the edge of Jupiter, then packed up and headed for home about
12:30 am.
David Kingsley