Sky & Telescope - November 2022 - 32

Sideways Spiral
experiences with the 12.5-inch and 8-inch apertures show
that this almost perfectly edge-on galaxy can be seen well in
more modest apertures.
Something I enjoy thinking about when observing
NGC 891 is that any of its astronomically minded residents
would have a similar view of our Milky Way - but wouldn't
see our galaxy quite as edge-on. Look at NGC 891's position
on a star chart and you'll see that it's less than 20° from
the galactic equator - this means that the Milky Way would
appear approximately 20° from being exactly edge-on as seen
from NGC 891. Cool stuff to ponder while at the eyepiece.
A Galaxy Group
Like most galaxies, NGC 891 isn't alone in the void. It's part
of the NGC 1023 Group, which includes a dozen other
galaxies (six of which are NGC targets). On average, they're
about 20 million light-years away, which puts NGC 891 on
the far side of this collection. You can spend a lovely evening
observing just the brighter targets in this collection.
A member of the group, the 15th-magnitude, gas-rich
satellite galaxy UGC 1807, lies about ½° northwest of
NGC 891. It seems to be a good candidate for the interacting
object creating the stellar streams that loop around NGC
891, but its stellar population makes it a poor fit. We'll need
to wait for future research to settle this.
A Galaxy Cluster
On the other hand, the galaxy cluster ACO 347 has no
physical relationship to NGC 891 and is merely along the
line of sight. It's a real treat of a cluster as it's loaded with
nine galaxies with NGC numbers. Its brightest member,
NGC 898, is less than ½° southeast of NGC 891. At a
distance of 252 million light-years, NGC 898 is more than
eight times farther away than NGC 891. If you can see both
galaxies in the same field of view, you'll have a depth of field
that's hard to match anywhere in the sky.
Even better, consider the Milky Way field stars you're seeing
all this through. They range from a few hundred to a little
more than a thousand light-years away, making the depth
of field even more pronounced - the universe can click into
startling 3D if you think about all this while peering through
the eyepiece of your telescope. Wow!
At magnitude 13.7, NGC 898 is a well-defined but small
edge-on galaxy that's bright enough to detect without giant
optics:
I can just see it in the 8-inch with averted vision as a faint
smudge, slightly elongated. 127×, 21.47 SQM.
But it's much more interesting through a 28-inch:
This is the brightest galaxy in ACO 347 and is surprisingly
long. [It has] a bright but not quite stellar core, and there
appears to be a small, faint background galaxy nearby (PGC
212965). 408×, 21.47 SQM.
Making this distant object even more intriguing,
NGC 898 likely sports a nifty bisecting dust lane just like
NGC 891 does. I couldn't see this feature with the 28-inch,
but just knowing it's there is cool, especially when both galaxies
are in the same field of view.
There's more to ACO 347 than NGC 898, though. The
rest of the cluster is full of accessible NGC galaxies, some of
which are nestled among foreground Milky Way stars. I first
observed the brighter members of the galaxy group without
initially knowing where they all were, and then, armed with
Other Members of the NGC 1023 Group
Object
NGC 1023
NGC 925
NGC 949
NGC 959
NGC 1003
NGC 1058
UGC 1865
UGC 2014
UGC 2023
UGC 2034
UGC 2259
Constellation
Perseus
Triangulum
Triangulum
Triangulum
Perseus
Perseus
Triangulum
Andromeda
Triangulum
Andromeda
Perseus
Surface Brightness
12.8
14.4
12.9
13.6
13.8
13.4
15.9
15.8
15.3
14.8
14.8
Mag(v)
10.4
10.1
11.8
12.4
11.5
11.2
13.8
15.3
13.3
13.2
13.2
Size/Sep
7.4′ × 2.5′
10.5′ × 5.9′
3.0′ × 1.6′
2.3′ × 1.4′
4.3′ × 1.3′
2.5′ × 2.5′
3.2′ × 2.6′
1.9′ × 0.9′
2.8′ × 2.6′
2.5′ × 1.9′
2.6′ × 2.0′
RA
Dec.
02h 40.4m
02h 27.3m
02h 30.8m
02h 32.4m
02h 39.3m
02h 43.5m
02h 25.0m
02h 32.9m
02h 33.3m
02h 33.7m
02h 47.9m
+39° 04′
+33° 35′
+37° 08′
+35° 30′
+40° 52′
+37° 20′
+36° 02′
+38° 41′
+33° 29′
+40° 32′
+37° 32′
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.
32 NOVEMBER 2022 * SKY & TELESCOPE

Sky & Telescope - November 2022

Table of Contents for the Digital Edition of Sky & Telescope - November 2022