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View Full Version : Object of the Week, Hickson 90 (NGC’s 7172, 7173, 7174, 7176)



Paul Alsing
September 22nd, 2024, 09:34 PM
R.A.: 22 02 01.7 Dec.: -31 52 18 (NGC 7172 = HCG 90A)
Size: 2.5'x1.4', Magnitude: V 11.9
Piscis Austrinus

Alternate ID’s (for the triplet) KTS 66 = VV 698 = Klemola 34

It is a lot of fun the track down the 100 objects in the Hickson catalogue, and Hickson 90 yet another fun object. It is available to observe using telescopes both large and small.

Here is a labeled screenshot from Megastar with a RealSky overlay…


5545

There are several challenging galaxies in the area, give them a go, too!


The Big Dog in this group is NGC 7172. It is clearly the largest galaxy in the group, and the only one with any discernable structure in my own experience, and that only being a much brighter core.

The other 3 galaxies in the group, NGC 7173, NGC 7174 and NGC 7176 are also catalogued as KTS 66A, B and C, with the KTS being the “Karachentseva Southern Isolated Triplets of Galaxies”. They are in a small tight group, with 2 of them being in contact. All are fairly easy to see.

There is, however, a fly in the ointment regarding my picture. Megastar is a very old program and got its data from the RNGC, but the RNGC had it wrong, and in Steve Gottlieb’s own words… “The RNGC reverses the identifications of NGC 7173 and 7174, making NGC 7173 and 7176 the contact pair. This misidentification is listed in my RNGC Corrections #1”

As usual, I check Steve’s NGC and IC notes because I often learn something I did not previously know. Thanks, Steve!

As always, give it a go and let us know.

Raul Leon
September 22nd, 2024, 10:53 PM
Hi, here's my observation from 11/4/2013: four galaxies in Piscis Austrinus : ngc 7172 on bottom, brightest of the four, ngc 7174, ngc 7176 and ngc 7173. I used a 10mm Ethos at 198x with my 14.5 StarStructure f/4.35546

lamperti
September 23rd, 2024, 11:45 AM
Saw this grouping twice with an 18" at 256x and a 20" at 272x. Each was distinctively different.