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ASTRO: Palomar 4



 
 
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Old January 24th 13, 02:31 PM posted to sci.astro.amateur
Steve
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Posts: 66
Default ASTRO: Palomar 4

In case anyone is interested in reading actual astronomy posts, there's
a fellow named Rick Johnson in alt.binaries.pictures.astro who regularly
posts not only images of NGC, Arp, and other distant objects, but also
includes an accompanying write up, which I personally find both
entertaining and informative.

In fact, he's pretty much the only traffic.

Here's an example of his work (write up):

Begin:
-----------
Palomar 4 is the most distant of the Palomar globulars. It is located
in Ursa Major some 356,000 light-years from earth. It was originally
discovered by Edwin Hubble in 1949 but before that was published A.G.
Wilson also found it in 1950. Wilson named it the Ursa Major Globular
Cluster and published it along with Palomar 3, 5 and 13 as well as two
galaxies. Wilson's classification as a globular was considered unsure
and it was cataloged in the UGCA Catalog as as a dwarf galaxy in our
local group. The UGCA is an appendix of 400 galaxies added to the UGC
catalog limited to late-type spirals, irregulars and dwarf systems --
and an occasional globular cluster it would seem. It was even given the
common name "The Ursa Major Dwarf."

I could find only one globular that is more distant than Palomar 4. That
is AM 1 but at declination -49.6 degrees it is always below my horizon.
Its distance is listed as just under 400 thousand light-years. It is
also the most distant from the core of our galaxy at just over 400
thousand light-years. Palomar 4 is the second most distant both from
the sun (354,400 light-years) and from the galaxy's center (362,500
light-years). I'm a bit confused about the orange stars seen against
the cluster. Most sources say the brightest star in the cluster is 18th
magnitude but 7 brightest orange stars are 16th to 17th magnitude by my
measurement. Some or all may not be cluster members. I just don't know.

While I was able to resolve quite a few stars in the globular seeing was
quite poor running about 3.7" FWHM. Under better seeing I'd likely pull
in a lot more stars in the cluster. It's on the reshoot list but it is
in a part of the sky with several hundred objects I've never imaged. I
might get to it if I live to be 100 so don't hold your breath.

Normally globulars are seen looking toward the core of our galaxy but
this one is almost opposite the galaxy's core which means it is in a
very unobscured part of the sky. For a change there are a lot of
galaxies in this globular image. They seem more common than foreground
stars. While NED lists a couple thousand galaxies in the field only a
few have redshift data. I annotated all of those. Nearly all have
catalog names that are just their position in the sky. I list those
only by type of object all of which are galaxies in this image. There
was one galaxy, a flat galaxy from the 2MASS survey, that is listed by
name and one galaxy group. It consists of 4 members, all of which are
easily seen in my image A line points to the center of the group as
defined by NED. Distances are noted in billions of light-years which
makes for a lot of leading zeros in the case of Palomar 4!

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

Rick
 




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