ASTRO: M41

Taking a short break from Arp galaxies.

M41 is a rather famous open star cluster below Sirius. But at -20
degrees it is down in the winter gunk for me. Still, being one of the
more famous M objects I had to give it a try on a really "good" night.
More on the imaging issues later.

M41 is thought to be about 2300 light-years away. It is a rather sparse
but bright star cluster covering about 38 minutes of arc which is larger
than my field's width of 33.7 minutes and a lot larger than its height
of 22.5 minutes. So I only capture the center of the cluster. It is
famous for the K3 orange star at its center though contains other
fainter K stars as well. They don't show their color visually in small
scopes however so are often overlooked. This is a rather young cluster,
thought to be about 190 to 240 million years old. This compares to our
sun's age of 4,500 million years. At about magnitude 4.5 it is visible
to the naked eye. There's weak evidence Aristotle saw it long before
the invention of the telescope. More certain is his discovery of
averted vision helping to see faint objects in the night sky.
http://www.seds.org/messier/more/m041_ari.html

Up here moisture in the air condenses out forming ice crystals our air
is so cold, -30C is typical on a good clear night and -40C/F not
uncommon. These crystals form a haze over the lake I live on. They
literally fall like fine snow out of a clear sky. Imaging low like this
means imaging through a lot of this ice crystal haze. Like atmospheric
particles these fine ice crystals scatter blue and green light. The
center of this image was in a fog of blue and some green light scattered
by the brighter stars of the cluster. GradientXterminator had to work
overtime but did a great job on this haze. I also forgot I was imaging a
cluster and used my normal 10 minute subs. This is way too long for
bright star clusters as the stars saturate making it difficult to
recover their true color. Fortunately there are techniques for finding
the color from the fringes of the star's bloated, overexposed image and
using that to color the star. I don't like to do that but did in this
case. Of course the over exposure also made the haze from the ice
crystals worse as well. Being so low stars distort due to atmospheric
refraction. I tried a technique used to reduce motion blur and finally
managed to sort of make it work. At least the stars looks somewhat
round but bloated. The haze I had hid most of the faint Milky Way
background stars. This helped the cluster stars to stand out but does
give a rather empty looking background compared to what I'd have
otherwise. Unfortunately there are many such Messier objects this low
in the sky making it next to impossible for me to image them from this
far north.

14" LX200R @ f/10, L=4x10' RGB=2x10'x3, STL-11000XM, Paramount ME

Rick
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Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".