Sky & Telescope - April 2023 QR - 59

HCG 41
22′ × 22′
HD 86166
6.3
HCG 49
12′ × 12′
BD+68 623
10.3
HCG 52
12′ × 12′
b
a
b
c
d
a
c
BD+21 2319
10.0
a
b
c
d
d
HCG 41
360×, 10′
HCG 49
570×, 5′
of Alpha (α) Ursae Majoris, or Dubhe,
in the Big Dipper. A magnification of
360× readily showed me HCG 49A and
HCG 49B, as well as elongation in the
former. I could only detect HCG 49D
with effort, and HCG 49C not at all.
Upping the magnification to 570×
revealed elongation in B and the small,
round form of C next to it. HCG 49D,
however, remained small and amorphous
even at that magnification. I spotted
a 16th-magnitude star immediately
south of the group. The galaxies' visual
appearances are consistent with their
morphological classification: Components
A and B are evolved spirals, C is an
irregular galaxy, and D is an elliptical.
Let's end our excursion in Leo with
another fine example of a gathering of
galaxies, HCG 52. You'll find it a tad less
than 3° east-northeast of 2.5-magnitude
Delta (δ) Leonis, or Zosma. Three of the
four galaxies in the group are strongly
inclined to our line of sight. HCG 52A is
a barred spiral, and I observed only the
inner part of it at 190× and 310× with
our observatory telescope. I couldn't
resolve the features that are evident in
photographs, such as the bar and a surrounding
ring. HCG 52B appeared much
broader than the needlelike silhouette
that appears in images - a common
visual effect when observing edge-on
galaxies on the threshold of detection.
In these conditions, I only noted the
inner core of HCG 52C, with no hint of
its " garden sprinkler " arms. HCG 52D
is a round puff, barely larger than a star
image but lacking any sharp concentration
toward the middle. Indeed, if you
detect component D at all, you can
congratulate yourself on seeing about as
much as the best digital survey images
reveal in this tiny (a mere 20″ in diameter)
17th-magnitude galaxy.
Denser and better outlined than
typical galaxy clusters, compact galaxy
groups are among the largest cohesive
HCG 52
310×, 10′
structures that we can see with our
own eyes. Observing all the Hickson
groups has remained a challenging
undertaking for visual observers with
big telescopes. Once you start checking
Hicksons off your list, however, you
may not be able to put that list down.
¢ IVAN MALY is a biologist living in upstate
New York. His observing website is
at www.deepskyblog.net.
FURTHER READING: Hickson's original
1982 catalog is at https://is.gd/Hickson_
Catalog and his follow-up work at https://
is.gd/Hickson_Atlas_1993.
Hickson Compact Groups
Object
HCG 36
HCG 39
HCG 41
HCG 47
HCG 49
HCG 52
Anchor Galaxy Mag (Tot)
IC 528
UGC 5057
UGC 5345
UGC 5644
PGC 32899
PGC 35183
12.5
13.9
11.9
12.5
14.4
12.8
Size
1.9′
1.0′
4.1′
2.3′
0.9′
3.2′
RA
Dec
09h 09.4m
09h 29.5m
09h 57.7m
10h 25.8m
10h 56.6m
11h 26.3m
+15° 48′
-01° 21′
+45° 14′
+13° 44′
+67° 11′
+21° 05′
The magnitudes are total for each group. Angular sizes are from recent catalogs. Visually, an object's
size is often smaller than the cataloged value and varies according to the aperture and magnification of
the viewing instrument. Right ascension and declination are for equinox 2000.0.
sk yand tele scope .o r g * APRIL 2023 59

http://www.deepskyblog.net https://is.gd/Hickson_Catalog https://is.gd/Hickson_Catalog https://www.is.gd/Hickson_Atlas_1993 https://www.is.gd/Hickson_Atlas_1993 https://skyandtelescope.org/

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