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Contrary to conventional wisdom, I observe variable stars during full
moon.
No, it's not my favorite time of the lunar cycle to observe due
to the sky brightness, but I think you should take advantage
of a
clear night regardless the phase of the moon. Once in a great while a
syzygy occurs and even full moon isn't such
a bad time. (A syzygy is
the alignment of three or more celestial bodies in the same
gravitational system along a straight
line. The word is usually used
in context with the Sun, Earth, and the Moon or a planet. Solar and
lunar eclipses occur
at times of syzygy.)
February 20th was the last total lunar eclipse for North America until
2010, and it happened
to be the first clear night here in 2008 that
wasn't -50C, so I headed out to the observatory as twilight ended. The
moon
was already well above the horizon in the east, parked slightly
NW of Saturn in Leo. Between the snow-covered ground and
the full moon
it was impossible to tell twilight had ended. It was bright enough
outside to read by. The snow underfoot
crunched sharply as I walked
out to the dome, a sign it was already pretty cold outside, but the
forecast low was for
-20C, seasonably cold for a Michigan night in
February, and bearable as long as there is no wind to speak of.
Orion
was just about due south, and neither the telescope nor I wanted
to move very far from our parked position, so I began
observing in and
around Orion first. The seeing was pretty steady and there was no haze
or cirrus. On a good night like
this I can easily see stars down to
about 14.5 from the celestial equator to about -20 declination with
the 12 inch.
Full moon's added charms had reduced that to around 13.8.
I checked off three stars in Eridanus and then moved on. Fortunately,
the
southernmost stars in Canis Major on my list were both fairly
bright, 10th magnitude, so making the estimates there was
easy. The
Moon was rising higher and the eclipse hadn't started yet, so the sky
was getting brighter as I moved into
Orion.
I find Orion to be a lot like Taurus for visual observing. There are
beautiful areas with bright blue and
white stars dotting the field of
view, and then there are those troublesome dull areas that seem to be
shrouded in a
haze and devoid of anything but a few dim guideposts to
find your way to the variables. Finding your way around during
full
moon is really difficult in these spots. I found myself getting
impatient for the eclipse to begin to eliminate
the moon-glow
polluting these star-poor fields. About the time the moon was half
covered by Earth's shadow, things started
getting better. Fainter
stars began popping out of the background and I was able to make 14th
magnitude estimates.
RR
Orionis is one of my favorite Miras in Orion. It spends a good deal
of time fainter than 13th magnitude and has a couple
14th magnitude
comparisons close by that can fool you into making a hasty
misidentification on a cold moonlit night.
Fortunately, its about as
far north as you can go in Orion, so if the moon isn't too bright I
can make out all the 13th
and 14th magnitude comp stars in the field
and sort it all out to make the call. RR Ori was in the mid 13's, so
it was
good that the earth's shadow was gobbling up the moon. I
finished the remaining LPVs in Orion and went inside to have some
coffee,
warm up and wait for totality.
About twenty minutes before the last bit of bright white Moon
disappeared I stepped
back outside and looked at the moon with
binoculars again. The back yard was noticeably darker and most naked
eye stars
visible on a moonless clear night were pretty easy to make
out. I headed to the observatory hoping to get dark-adapted
by the
time totality began, so I could take advantage of this 'bonus' dark
time in February.
I pointed the telescope
up towards Auriga. It looked like the darkest
part of the sky, was riding nice and high, and Auriga is chock full of
interesting
Miras. At this point the dogs in the area all seemed to
notice the moon was disappearing and began barking. One would start
barking
here, another one would answer him off in the distance, and
the racket grew louder and louder as all the dogs within earshot
started
sharing eclipse notes. As the moon turned completely dark
orange-red the coyotes began howling. This got all the dogs going
again.
As if that weren't enough to scare away whatever sky dragon was
eating the moon, the donkey on the horse farm north of
me started
braying as loudly as I've ever heard him. I found it somewhat
comforting to know I wasn't the only jackass
outside freezing my butt
off as the Moon slipped into the Earth's shadow.
The canine cacophony eventually subsided
and I enjoyed the hour of
totality observing Miras in Auriga. About the time the moon started to
escape the grip of
eclipse, both the telescope and I were pretty well
frozen. My fingers were starting to hurt and the corrector plate was
frosted
on the inside about an inch all the way around the central
obstruction. The dew heater can't keep up with pointing straight
up on
a -20C night for long. I packed it in, closed up the dome, took a last
quick tour of the moon in binoculars and
headed for the warmth of the
house.
In the morning I noticed the blue jays at the bird feeders seemed a
little
grumpier than usual. They probably didn't sleep very well with
all the racket from the dogs and the donkey the night before.
Me, I
slept like a frozen rock.
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