2 Attachment(s)
Object of the Week - October 13, 2013 - HICKSON 100
Object of the Week, October 13, 2013
Hickson 100
Pegasus
Position - NGC 7803
R.A.: 00h01m20.0s Dec.: +13°06'40" (2000)
I spent 4 days this last new moon at CalStar, an informal star party in northern California. The skies were dark but the transparency and seeing were about average, in my view, but the great friends in attendance more than made up for any deficiencies. More patience than usual was required to see details, we just needed to wait for those moments of improved seeing to tease out the faint stuff.
One night I spent 6 hours just cruising around in Pegasus, together with several friends, we started when it was half way up the eastern sky and ended when it was half way down the western sky, staying high on the ladder most of the night. There are 7 Hickson galaxy groups in Pegasus and we observed all of them. I thought that Hickson 100 was just a little better than any of the other groups, it just seemed to be more pleasing, somehow. Maybe the seeing improved during the time we observed it, or the transparency, but whatever the reason, it was a fine view.
HICKSON 100 is comprised of (4) components, as follows (magnitudes from SkyTools);
HCG 100A = NGC 7803 = PGC 101 = UGC 12906 = MCG +02-01-011 = CGCG 433-013, mag 14.1 B
HCG 100B = PGC 108 = Markarian 934 = MCG 2-1-12, mag 15.3 B
HCG 100C = PGC 89 = MCG 2-1-9, mag 15.9 B
HCG 100D = PGC 92 = MCG 2-1-10, mag 16.8 B
Attachment 925Attachment 924
My 25" Obsession has a new set of 10,000 tic encoders and the Argo Navis put Hickson 100 almost dead center in the FOV using my 13mm Ethos, my favorite eyepiece. The anchor galaxy of the group, NGC 7803 (HCG 100A), was obvious but small, presenting as slightly oval in the E-W direction, with an evenly illuminated disk and a brighter core. About 1' to the NW of this galaxy is a 16" pair of mag 14.3/15.2 stars, making a very pretty picture.
About 1.3 to the E is HCG 100B, more than a full magnitude fainter than component A, but still obvious with direct vision. I saw no structure whatsoever, it was just a hazy area near a mag 12 star to its east.
Just over 1' west of HCG 100A is HCG 100D, and although this guy is nearly 3 mags fainter than Component A, it has a high enough surface brightness due to its smaller area that it flickered in and out with regularity, and after a while it was resolved as a faint 4/1 elongated streak that pointed at the dimmer member of the previously mentioned wide double NW of NGC 7803.
The 4th and last member of Hickson 100, HCG 100C, is located 2.3' NW of NGC 7803, but it is not the dimmest member, being about a magnitude brighter than HCG 100D. With the effort required to see HCG 100D, HCG 100C was an easy score on this night.
All members of Hickson 100 fit easily into the FOV of the 13mm Ethos, and even fit in the FOV of the Meade 8.8mm UltraWide. The other labeled galaxy in the photo, PGC 97, was not seen, even though it has the same stated magnitude as component D, @ mag 16.8, its surface brightness was much lower, due to its extended surface... and none of the even fainter galaxies that are obvious in the photo were even considered :>)
“Give it a go and let us know!
Good luck and great viewing!”
