Sky & Telescope - February 2024 - 58

ADAM BLOCK
FEBRUARY 2024 OBSERVING
Going Deep by Al Lamperti and Frank Colosimo
COSMIC COMPANIONS NGC 125, in southern
Pisces, travels through space accompanied
by multiple " friends. " East of NGC 125 lies a
grouping of galaxies centered on 12th-magnitude
NGC 128. In addition, two stars south of
the ringed galaxy handily point to your quarry.
Let's review a dozen of the more
accessible ring galaxies visible in winter
and spring skies.
Sampling
Some Ring
Galaxies
A duo teams up to observe
and image a selection of
interacting galaxies.
G
alactic interactions can manifest
in many shapes, forms, and
classifications, details which Halton
Arp's classic Atlas of Peculiar Galaxies
distinctly illustrates. A subset of
peculiar galaxies is the " ring galaxies. "
In an S&T article, Dave Tosteson
covered four categories of ring galaxies:
polar, collisional, accretion, and those
resulting from secular evolution (S&T:
May 2020, p. 57; the classifications are
from a 2017 journal article authored
by Burçin Mutlu-Pakdil of the University
of Minnesota and her colleagues).
Both amateur and professional images
show the exquisite dynamism of these
galactic interactions. However, for
visual observers, these unique objects
can be quite challenging. Nevertheless,
we decided to take a whirl through a
sampling of them.
58 FEBRUARY 2024 * SKY & TELESCOPE
Our starting point was Observing
Ring Galaxies by renowned amateurs
Alvin Huey and Jimi Lowrey (https://
is.gd/RingGalaxies), from which we
culled a selection of 51 ring galaxies
brighter than magnitude 14.8 and farther
north than -9° declination. We set
those parameters so as to narrow our
subset down to targets that we could
snag visually as well as image advantageously
from our observing sites in
Pennsylvania.
My (Lamperti) primary telescope was
a 22-inch f/4.2 Obsession Ultra Compact
reflector, equipped with a Paracorr, Argo
Navis, and ServoCAT. Unless otherwise
noted, I used a magnification of 450×.
Of the targets I observed visually,
I could only detect rings in half of
them. For the most part, I observed the
rings as an extended glow around the
brighter core of the galaxy. Moreover,
the average altitude of the object for my
detections was 48.4°, and the average
Sky Quality Meter reading was 20.6
magnitudes per square arcescond.
Altitude turned out to be a decisive
factor in my observations. I couldn't
detect any evidence of a ring in five galaxies
when they were at an average altitude
of 29°. However, when I reobserved
them at an altitude of around 57° (with
the same telescope and magnification), I
definitely noted haze around the bright
core with direct vision.
Ring Galaxies for Winter
Nights
Look for 13.2-magnitude UGC 1840
near the Perseus-Andromeda border,
about 3.7° east-southeast of Gamma
(γ) Andromedae. To snag my quarry,
I had to place the 5.8-magnitude star
HD 14622 outside the field of view. This
way, I could just tease out an arc of haze
adjacent to a close pair of 13th-magnitude
stars. I also detected the galaxy
that together with UGC 1840 makes up
Arp 145, one of hundreds of peculiar
galaxies Halton Arp listed in his seminal
1966 catalog.
Now let's slide over to Pisces for
our next four targets. Our first stop
is NGC 7428, which is fairly bright
at magnitude 12.5. You'll locate it
in westernmost Pisces, about 6½°
southwest of 3.7-magnitude Gamma
Piscium and less than ½° northwest
of 6.4-magnitude HD 217131. I could
easily detect the galaxy's core at 337×,
but its ring remained elusive. However,
upping the magnification to 450× and
using averted vision, I saw an oval glow
(that I'm taking to be the ring) that was
larger than the core.
Next, we'll visit NGC 38, a
13.3-magnitude spiral, which is in
southern Pisces about ¾° north of
the border with Cetus. The galaxy is
a bit more than 1½° east of 4.6-magnitude
33 Piscium and ½° southeast
of 5.8-magnitude HD 587. With my
standard setup, I noted that NGC 38
has a brighter core with a misty patch
surrounding it. This was one of the
targets that - to detect the ring - I had
to observe when it was at an altitude
greater than 24°.
From NGC 38 slew a little less
than 9½° north-northeast to arrive at
12.1-magnitude NGC 125. Four NGC
http://is.gd/RingGalaxies http://is.gd/RingGalaxies
Sky & Telescope - February 2024

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