Arp 322

ARP 214+322 2017 Mar 20

Object:  ARP 322 (chain in Hickson 56) Date:          2017 March 20
Peculiarity:    Galaxy chain.
Constellation:           Ursa Major Time & altitude:   22.30 UT          80º
Catalogue data: Seeing (5 high):                                   5/5
            R.A:                11h 33m Transparency (5 high):                   5/5
            Dec:                52º 57 Telescope:     0.5m f4.1 Dob.
            Magnitudes:  see notes Eyepiece:      17mm Ethos    x120                                                                     8mm Ethos      x260

       Galaxy size (mins):

56B 1.1×0.6      56C 0.7×0.4      56D 0.4×0.3


With and without Lumicon Deep-Sky.


Awesome and rare viewing conditions behind a cold front clearing to the E. Arp 214 is 8 mins N of Arp 322. Both Arps in the zenith, seen easily with DV. In Arp 322 three components were seen without difficultly, namely Hickson 56B, 56C and 56D.  Components A and E were invisible.

Kanipe/Webb give 56D’s magnitude as 16.8. I can see it with DV, surely it is brighter than 16.8. However C Seligman’s website states similar magnitudes:

Hickson designation Seligman Kanipe/Webb
PGC35620 = 56B “15th mag” 14.7
PGC35631, 618 and 609 = 56A, C and E “16th mag” ?, 15.8 and 16.8
PGC35615 = 56D “17th mag” 16.8

56C & D are all core and no halo, looking like grains of rice end to end. 56B is larger and angles a little to the N, and is misty on the N side.

In view of the exceptional nature of the observation of Hickson 56D described above, I revisited the galaxy chain on 2017 March 25, observing for 20 minutes either side of 23.10UT. We are now under a stable high pressure area with transparency & seeing both say 4/5. Conditions unpleasant due to NE wind gusting to 25mph and Arp 322 right in the zenith where the telescope is tricky to manoeuvre.  In these less than perfect conditions I could not repeat the observation of five nights earlier.  At best Hickson 56 simply appeared as a slight curve of mist, not resolved into the components.