Thread: Ic 498
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Old July 27th 15, 09:00 PM posted to
Stefan Lilge
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Posts: 2,269
Default Ic 498


I hope this spiral can cope with it's one heavy arm. It certainly looks so
in your image :-)


"WA0CKY" schrieb im Newsbeitrag ...

IC 0498 is a spiral galaxy that fits Arp's category for spirals with one
heavy arm. Its arm seems odd in that the heavy part spirals in to the
end of a much finer arm that spiral in to the eastern side of the core.
A similar arm comes off the western side and ends in what appears to be
a bunch of star clusters or is it debris from something the galaxy is
digesting? NED lists one of these, up by where the heavy arm meets the
much finer arm coming from the eastern side of the core, as a separate
galaxy but with the same redshift. Even on the Sloan image I can't see
it as anything different than many other such star clouds in the area.
The galaxy is in southeastern Canis Minor about 470 million light-years

The UGC says of it: "Strongly deformed spiral pattern, bright arc in
northwest, eccentric nuclear region, no disturbing object visible." The
bright arc being the heavy arm in Arp's terminology. While there is no
"disturbing object" in the area the galaxy is part of ZwCl 0806.8+0514,
a cluster of 220 galaxies in a medium compact cluster some 73 minutes of
arc across according to NED. The cluster is centered about 5 minutes
south of my image's southern edge. That means my image is well within
its boundaries covering only part of its northern region. With that
many galaxies it wouldn't surprise me if one wasn't the cause of IC
498's apparent indigestion from eating it.

IC 498 was discovered by Rudolf Spitaler on November 11, 1888 apparently
using the 27" refractor at Wein University in Vienna on November 11,
1888. He found 64 IC objects while at the university, most of them from
1891 to 1892. Though 54 are galaxies, one, IC 1470, is an emission
nebula. The rest are dubious at best. One is a single star, four
double stars, two triple stars, yet another a quadruple star and the
last can't be identified with anything in the sky. Seems he was a bit
over anxious to find objects. In fact it was a race between astronomers
of that era to find these objects. IC 1440, his only emission nebula,
was discovered by Barnard only one day later. In the pressure to find
one before someone else it seems on nights of less than ideal seeing
stars became deep sky objects, especially when in tight groups of two to
four. A single star at the magnitude limit for the night can also
create the illusion of an extended object. Even today's photographic
searches make mistakes, just not as obvious as those of the days of
visual astronomy.

Speaking of conditions they were awful for this one. I tried on three
different nights, all of which were of 3.5" seeing or worse. While the
third night was better for seeing transparency was awful. I ended up
including 9 of the luminance images taken as including just the 4 from
the best seeing night didn't go very deep at all. By including even
those down to 4" seeing I managed to get my usual depth but at the cost
of resolution. I used the three best of 6 color frames taken those
nights for each color. I threw out those of such poor quality they added
only noise to the final result when included.

14" LX200R @ f/10, L=9x10' RGB=3x10', STL-11000XM, Paramount ME