Sky & Telescope - April 2023 QR - 57
Going Deep by Ivan Maly
The Hickson Catalog's Deep End
These compact galaxy groups make for pleasing, but challenging, views in the eyepiece.
W
hen Canadian astronomer Paul
Hickson published his survey of
compact galaxy groups in 1982, he was
driven by his interest in their dynamical
peculiarities and their role in galaxy
evolution. Before the century was out,
however, he found himself a soughtafter
guest and lecturer among amateur
astronomers who gathered with their
telescopes under dark skies to observe
his groups visually. Amateurs' interest
in Hickson's catalog was emblematic of
the new direction the hobby was taking
as scientific information and largeaperture
telescopes were becoming more
accessible.
Visual observers have since pursued
other galaxy groups, such as those in
catalogs that American astronomer
James Rose or Armenian astronomer
Romelia Shakhbazian assembled. Yet
the 100 Hickson groups remain the
most popular. The more frequently
observed Hicksons comprise, or at least
are anchored by, galaxies from the New
General Catalogue of Nebulae and Clusters
of Stars, which are comparatively
bright. We have previously highlighted
some of these brighter groups (see,
e.g., S&T: Nov. 2017, p. 34). The typical
Hickson group, however, contains no
NGC galaxies at all.
As I'm completing my visual survey
of the Hickson catalog, the faintest
members of quite a few groups still
elude me, even though I have access to
very dark mountain skies and a 20-inch
scope. To decide if you are up for jumping
into this catalog's deep end, try
the following selection of targets well
placed in the April sky and see if they
whet your appetite for further pursuit.
Dipping Our Toes
Transiting near the zenith in the early
evening is Hickson Compact Group
36 in Cancer. Look for HCG 36 some
6.3° east-southeast of Delta (δ) Cancri.
This group is anchored by the
relatively large and bright 14.1-magnitude,
1.5′-long galaxy IC 528. The
companions, however, are from the
Catalogue of Principal Galaxies. The
galaxies of HCG 36 are all spirals, and
each displays a different inclination to
our line of sight. After tracking down
this group with the 20-inch telescope
of the Buffalo Astronomical Association
observatory under rural skies, I
detected all four members at 450×.
Components of a Hickson group are
referred to by letter designations, which
usually run from A through D in order
of brightness. HCG 36's easternmost
component, HCG 36D, displayed its
elongated form, as did the dominant
central galaxy, HCG 36A (IC 528). The
latter, however, appeared to terminate
south of HCG 36C, indicating that I was
only seeing its inner core. In the case
of the southernmost component, HCG
36B, which is a nearly edge-on spiral,
I only noted the compact central core.
Subsequently, observing with my own
20-inch from a much darker location, I
GRACEFUL GROUPINGS You'll need a big telescope and dark skies to observe the galaxy groups outlined here. But if you succeed, you'll be well
rewarded by having stepped up to the challenge. We've used Hickson's original lowercase labeling for the components in the images presented here.
HCG 47
40′ × 15′
b
c
d
a
HD 90445
7.3
HCG 47
450×, 10′
sk yand tele scope .o r g * APRIL 2023 57
ALL IMAGES POSS-II / STSCI / CALTECH / PALOMAR
OBSERVATORY; ALL SKETCHES IVAN MALY
https://skyandtelescope.org/
Sky & Telescope - April 2023 QR
Table of Contents for the Digital Edition of Sky & Telescope - April 2023 QR
Contents
Sky & Telescope - April 2023 QR - Cover1
Sky & Telescope - April 2023 QR - Cover2
Sky & Telescope - April 2023 QR - 1
Sky & Telescope - April 2023 QR - Contents
Sky & Telescope - April 2023 QR - 3
Sky & Telescope - April 2023 QR - 4
Sky & Telescope - April 2023 QR - 5
Sky & Telescope - April 2023 QR - 6
Sky & Telescope - April 2023 QR - 7
Sky & Telescope - April 2023 QR - 8
Sky & Telescope - April 2023 QR - 9
Sky & Telescope - April 2023 QR - 10
Sky & Telescope - April 2023 QR - 11
Sky & Telescope - April 2023 QR - 12
Sky & Telescope - April 2023 QR - 13
Sky & Telescope - April 2023 QR - 14
Sky & Telescope - April 2023 QR - 15
Sky & Telescope - April 2023 QR - 16
Sky & Telescope - April 2023 QR - 17
Sky & Telescope - April 2023 QR - 18
Sky & Telescope - April 2023 QR - 19
Sky & Telescope - April 2023 QR - 20
Sky & Telescope - April 2023 QR - 21
Sky & Telescope - April 2023 QR - 22
Sky & Telescope - April 2023 QR - 23
Sky & Telescope - April 2023 QR - 24
Sky & Telescope - April 2023 QR - 25
Sky & Telescope - April 2023 QR - 26
Sky & Telescope - April 2023 QR - 27
Sky & Telescope - April 2023 QR - 28
Sky & Telescope - April 2023 QR - 29
Sky & Telescope - April 2023 QR - 30
Sky & Telescope - April 2023 QR - 31
Sky & Telescope - April 2023 QR - 32
Sky & Telescope - April 2023 QR - 33
Sky & Telescope - April 2023 QR - 34
Sky & Telescope - April 2023 QR - 35
Sky & Telescope - April 2023 QR - 36
Sky & Telescope - April 2023 QR - 37
Sky & Telescope - April 2023 QR - 38
Sky & Telescope - April 2023 QR - 39
Sky & Telescope - April 2023 QR - 40
Sky & Telescope - April 2023 QR - 41
Sky & Telescope - April 2023 QR - 42
Sky & Telescope - April 2023 QR - 43
Sky & Telescope - April 2023 QR - 44
Sky & Telescope - April 2023 QR - 45
Sky & Telescope - April 2023 QR - 46
Sky & Telescope - April 2023 QR - 47
Sky & Telescope - April 2023 QR - 48
Sky & Telescope - April 2023 QR - 49
Sky & Telescope - April 2023 QR - 50
Sky & Telescope - April 2023 QR - 51
Sky & Telescope - April 2023 QR - 52
Sky & Telescope - April 2023 QR - 53
Sky & Telescope - April 2023 QR - 54
Sky & Telescope - April 2023 QR - 55
Sky & Telescope - April 2023 QR - 56
Sky & Telescope - April 2023 QR - 57
Sky & Telescope - April 2023 QR - 58
Sky & Telescope - April 2023 QR - 59
Sky & Telescope - April 2023 QR - 60
Sky & Telescope - April 2023 QR - 61
Sky & Telescope - April 2023 QR - 62
Sky & Telescope - April 2023 QR - 63
Sky & Telescope - April 2023 QR - 64
Sky & Telescope - April 2023 QR - 65
Sky & Telescope - April 2023 QR - 66
Sky & Telescope - April 2023 QR - 67
Sky & Telescope - April 2023 QR - 68
Sky & Telescope - April 2023 QR - 69
Sky & Telescope - April 2023 QR - 70
Sky & Telescope - April 2023 QR - 71
Sky & Telescope - April 2023 QR - 72
Sky & Telescope - April 2023 QR - 73
Sky & Telescope - April 2023 QR - 74
Sky & Telescope - April 2023 QR - 75
Sky & Telescope - April 2023 QR - 76
Sky & Telescope - April 2023 QR - 77
Sky & Telescope - April 2023 QR - 78
Sky & Telescope - April 2023 QR - 79
Sky & Telescope - April 2023 QR - 80
Sky & Telescope - April 2023 QR - 81
Sky & Telescope - April 2023 QR - 82
Sky & Telescope - April 2023 QR - 83
Sky & Telescope - April 2023 QR - 84
Sky & Telescope - April 2023 QR - Cover3
Sky & Telescope - April 2023 QR - Cover4
https://www.nxtbook.com/nxtbooks/aas/st_202410
https://www.nxtbook.com/nxtbooks/aas/st_202409
https://www.nxtbook.com/nxtbooks/aas/st_202408
https://www.nxtbook.com/nxtbooks/aas/st_202407
https://www.nxtbook.com/nxtbooks/aas/st_202406
https://www.nxtbook.com/nxtbooks/aas/st_202405
https://www.nxtbook.com/nxtbooks/aas/st_202404_qr
https://www.nxtbook.com/nxtbooks/aas/st_202404
https://www.nxtbook.com/nxtbooks/aas/st_202403
https://www.nxtbook.com/nxtbooks/aas/st_202402
https://www.nxtbook.com/nxtbooks/aas/st_202401_aus
https://www.nxtbook.com/nxtbooks/aas/st_202401
https://www.nxtbook.com/nxtbooks/aas/st_202312_aus
https://www.nxtbook.com/nxtbooks/aas/st_202312
https://www.nxtbook.com/nxtbooks/aas/st_202311
https://www.nxtbook.com/nxtbooks/aas/st_202310
https://www.nxtbook.com/nxtbooks/aas/st_202309
https://www.nxtbook.com/nxtbooks/aas/st_202308
https://www.nxtbook.com/nxtbooks/aas/st_202307
https://www.nxtbook.com/nxtbooks/aas/st_202306
https://www.nxtbook.com/nxtbooks/aas/st_202305
https://www.nxtbook.com/nxtbooks/aas/st_202304
https://www.nxtbook.com/nxtbooks/aas/st_202304_qr
https://www.nxtbook.com/nxtbooks/aas/st_202303
https://www.nxtbook.com/nxtbooks/aas/st_202302
https://www.nxtbook.com/nxtbooks/aas/st_202301
https://www.nxtbook.com/nxtbooks/aas/st_202212
https://www.nxtbook.com/nxtbooks/aas/st_202211
https://www.nxtbook.com/nxtbooks/aas/st_202210
https://www.nxtbook.com/nxtbooks/aas/st_202209
https://www.nxtbook.com/nxtbooks/aas/st_202208
https://www.nxtbook.com/nxtbooks/aas/st_202207
https://www.nxtbook.com/nxtbooks/aas/st_202206
https://www.nxtbook.com/nxtbooks/aas/st_202205
https://www.nxtbook.com/nxtbooks/aas/st_202204
https://www.nxtbook.com/nxtbooks/aas/st_202203
https://www.nxtbook.com/nxtbooks/aas/st_202202
https://www.nxtbook.com/nxtbooks/aas/st_202201
https://www.nxtbook.com/nxtbooks/aas/st_202112
https://www.nxtbook.com/nxtbooks/aas/st_202111
https://www.nxtbook.com/nxtbooks/aas/st_202110
https://www.nxtbook.com/nxtbooks/aas/st_202109
https://www.nxtbook.com/nxtbooks/aas/st_202108
https://www.nxtbook.com/nxtbooks/aas/st_202107
https://www.nxtbook.com/nxtbooks/aas/st_202106
https://www.nxtbook.com/nxtbooks/aas/st_202105
https://www.nxtbook.com/nxtbooks/aas/st_202104
https://www.nxtbook.com/nxtbooks/aas/st_202103
https://www.nxtbook.com/nxtbooks/aas/st_202102
https://www.nxtbook.com/nxtbooks/aas/st_202101
https://www.nxtbook.com/nxtbooks/aas/skywatch_2021
https://www.nxtbook.com/nxtbooks/aas/st_202012
https://www.nxtbook.com/nxtbooks/aas/st_202011
https://www.nxtbook.com/nxtbooks/aas/st_202010
https://www.nxtbook.com/nxtbooks/aas/st_202009
https://www.nxtbook.com/nxtbooks/aas/st_202008
https://www.nxtbook.com/nxtbooks/aas/st_202007
https://www.nxtbook.com/nxtbooks/aas/st_202006
https://www.nxtbook.com/nxtbooks/aas/st_202005
https://www.nxtbook.com/nxtbooks/aas/st_202004
https://www.nxtbook.com/nxtbooks/aas/st_202003
https://www.nxtbook.com/nxtbooks/aas/st_202002
https://www.nxtbook.com/nxtbooks/aas/st_202001
https://www.nxtbook.com/nxtbooks/aas/st_201912
https://www.nxtbook.com/nxtbooks/aas/st_201911
https://www.nxtbook.com/nxtbooks/aas/st_201910
https://www.nxtbook.com/nxtbooks/aas/st_201909
https://www.nxtbook.com/nxtbooks/aas/st_201908
https://www.nxtbook.com/nxtbooks/aas/st_201907
https://www.nxtbook.com/nxtbooks/aas/st_201906
https://www.nxtbook.com/nxtbooks/aas/st_201905
https://www.nxtbook.com/nxtbooks/aas/st_201904
https://www.nxtbook.com/nxtbooks/aas/st_201903
https://www.nxtbook.com/nxtbooks/aas/st_201902
https://www.nxtbook.com/nxtbooks/aas/st_201901
https://www.nxtbook.com/nxtbooks/aas/st_201812
https://www.nxtbook.com/nxtbooks/aas/st_201811
https://www.nxtbook.com/nxtbooks/aas/st_201810
https://www.nxtbook.com/nxtbooks/aas/st_201809
https://www.nxtbook.com/nxtbooks/aas/st_201808
https://www.nxtbook.com/nxtbooks/aas/st_201807
https://www.nxtbook.com/nxtbooks/aas/st_201806
https://www.nxtbook.com/nxtbooks/aas/st_201805
https://www.nxtbook.com/nxtbooks/aas/st_201804
https://www.nxtbook.com/nxtbooks/aas/st_201803
https://www.nxtbook.com/nxtbooks/aas/st_201802
https://www.nxtbook.com/nxtbooks/aas/st_201801
https://www.nxtbook.com/nxtbooks/aas/st_201712
https://www.nxtbook.com/nxtbooks/aas/st_201711
https://www.nxtbook.com/nxtbooks/aas/st_201710
https://www.nxtbook.com/nxtbooks/aas/st_201709
https://www.nxtbook.com/nxtbooks/aas/st_201708
https://www.nxtbook.com/nxtbooks/aas/st_201707
https://www.nxtbook.com/nxtbooks/aas/st_201706
https://www.nxtbook.com/nxtbooks/aas/st_201705
https://www.nxtbook.com/nxtbooks/aas/st_201704
https://www.nxtbook.com/nxtbooks/aas/st_201703
https://www.nxtbook.com/nxtbooks/aas/st_201702
https://www.nxtbook.com/nxtbooks/aas/st_201701
https://www.nxtbook.com/nxtbooks/aas/st_201612
https://www.nxtbook.com/nxtbooks/aas/st_201611
https://www.nxtbook.com/nxtbooks/aas/st_201610
https://www.nxtbook.com/nxtbooks/aas/st_201609
https://www.nxtbook.com/nxtbooks/aas/st_201608
https://www.nxtbook.com/nxtbooks/aas/st_201607
https://www.nxtbook.com/nxtbooks/aas/st_201606
https://www.nxtbook.com/nxtbooks/aas/st_201605
https://www.nxtbook.com/nxtbooks/aas/st_201604
https://www.nxtbook.com/nxtbooks/aas/st_201603
https://www.nxtbook.com/nxtbooks/aas/st_201602
https://www.nxtbook.com/nxtbooks/aas/st_201601
https://www.nxtbook.com/nxtbooks/aas/st_201512
https://www.nxtbook.com/nxtbooks/aas/st_201511
https://www.nxtbook.com/nxtbooks/aas/st_201510
https://www.nxtbook.com/nxtbooks/aas/st_201509
https://www.nxtbook.com/nxtbooks/aas/st_201508
https://www.nxtbook.com/nxtbooks/aas/st_201507
https://www.nxtbook.com/nxtbooks/aas/st_201506
https://www.nxtbook.com/nxtbooks/aas/st_201505
https://www.nxtbook.com/nxtbooks/aas/st_201504
https://www.nxtbook.com/nxtbooks/aas/st_201503
https://www.nxtbook.com/nxtbooks/aas/st_201502
https://www.nxtbook.com/nxtbooks/aas/st_201501
https://www.nxtbook.com/nxtbooks/aas/st_201412
https://www.nxtbook.com/nxtbooks/aas/st_201411
https://www.nxtbook.com/nxtbooks/aas/st_201410
https://www.nxtbook.com/nxtbooks/aas/st_201409
https://www.nxtbook.com/nxtbooks/aas/st_201408
https://www.nxtbook.com/nxtbooks/aas/st_201407
https://www.nxtbook.com/nxtbooks/aas/st_201406
https://www.nxtbook.com/nxtbooks/aas/st_mars
https://www.nxtbook.com/nxtbooks/aas/st_201405
https://www.nxtbook.com/nxtbooks/aas/st_201404
https://www.nxtbook.com/nxtbooks/aas/st_201403
https://www.nxtbook.com/nxtbooks/aas/st_201402
https://www.nxtbook.com/nxtbooks/aas/st_201401
https://www.nxtbook.com/nxtbooks/aas/st_201312
https://www.nxtbook.com/nxtbooks/aas/st_201311
https://www.nxtbook.com/nxtbooks/aas/st_201310
https://www.nxtbook.com/nxtbooks/aas/st_201309
https://www.nxtbook.com/nxtbooks/aas/st_201308
https://www.nxtbook.com/nxtbooks/aas/st_201307
https://www.nxtbook.com/nxtbooks/aas/st_201306
https://www.nxtbook.com/nxtbooks/aas/st_201305
https://www.nxtbook.com/nxtbooks/aas/st_201304
https://www.nxtbook.com/nxtbooks/aas/st_201303
https://www.nxtbook.com/nxtbooks/aas/st_201302
https://www.nxtbook.com/nxtbooks/aas/st_201301
https://www.nxtbook.com/nxtbooks/aas/st_201212
https://www.nxtbook.com/nxtbooks/aas/st_201211
https://www.nxtbook.com/nxtbooks/aas/st_201210
https://www.nxtbook.com/nxtbooks/aas/st_201209
https://www.nxtbook.com/nxtbooks/aas/st_201208
https://www.nxtbook.com/nxtbooks/aas/st_201207
https://www.nxtbook.com/nxtbooks/aas/st_201206
https://www.nxtbook.com/nxtbooks/aas/st_201205
https://www.nxtbook.com/nxtbooks/aas/st_201204
https://www.nxtbook.com/nxtbooks/aas/st_201203
https://www.nxtbook.com/nxtbooks/aas/st_201202
https://www.nxtbook.com/nxtbooks/aas/st_201201
https://www.nxtbook.com/nxtbooks/aas/st_201112
https://www.nxtbook.com/nxtbooks/aas/st_201111
https://www.nxtbook.com/nxtbooks/aas/st_201110
https://www.nxtbook.com/nxtbooks/aas/st_201109
https://www.nxtbook.com/nxtbooks/aas/st_201108
https://www.nxtbook.com/nxtbooks/aas/st_201107
https://www.nxtbook.com/nxtbooks/aas/st_201106
https://www.nxtbook.com/nxtbooks/aas/st_201105
https://www.nxtbook.com/nxtbooks/aas/st_201104
https://www.nxtbook.com/nxtbooks/aas/st_201103
https://www.nxtbook.com/nxtbooks/aas/st_201102
https://www.nxtbook.com/nxtbooks/aas/st_201101
https://www.nxtbook.com/nxtbooks/aas/st_201012
https://www.nxtbook.com/nxtbooks/aas/st_201011
https://www.nxtbook.com/nxtbooks/aas/st_201010
https://www.nxtbook.com/nxtbooks/aas/st_201009
https://www.nxtbook.com/nxtbooks/aas/st_201008
https://www.nxtbook.com/nxtbooks/aas/st_201007
https://www.nxtbook.com/nxtbooks/aas/st_201006
https://www.nxtbook.com/nxtbooks/aas/st_201005
https://www.nxtbook.com/nxtbooks/aas/st_201004
https://www.nxtbook.com/nxtbooks/aas/st_201003
https://www.nxtbook.com/nxtbooks/aas/st_201002
https://www.nxtbook.com/nxtbooks/aas/st_201001
https://www.nxtbookmedia.com