Sky & Telescope - February 2025 - 24

Illuminated Clouds
4h 30m
4h 00m
ο
ζ
2
1
3
4
5
6
7
1432
+25°
η
M45
TAURUS
+20°
ε
Aldebaran
α
γ
+15°
SHIMMERING CLUSTER Head to northwestern Taurus for the Pleiades
and then scan north into Perseus for two delightful nebulae.
I see a small fan about 3′ wide that opens eastward. To the
west it falls off suddenly. A 12th-magnitude star lies near the
nebula's western side. Images of the nebula show a tiny, dark
blob on its western side, but I can't see it.
While it's only 3.5° to the north-northeast of NGC 2149
and 1.5° west of 4.0-magnitude Gamma (γ) Monocerotis,
1435
IC 348
+30°
3h 30m
1333
NGC 2170 inhabits the more distant Monoceros R2 molecular
cloud. It lies 2,900 light-years away, twice as far as NGC 2149.
At 92× and 150× I see it as a frosty and uniform circle about 2′
across with a partially obscured 10th-magnitude central star.
The Dusty Nebulosity of the Pleiades
Now, at last, let's turn our attention to the Pleiades (M45).
On nights of excellent transparency, faint nebulosity appears
around many of the cluster's bright stars. To ensure you're
not seeing the effect of condensation on your optics, nudge
your scope towards the neighboring Hyades star cluster. If you
see nebulosity there, too (where none exists), it might be time
to fire up a dew heater. Perhaps uniquely, the Pleiades' nebulosity
results from the cluster passing through an unrelated
cloud of interstellar dust.
The brightest nebulosity (where Slipher measured his
spectra more than a century ago) lies south of 4.2-magnitude
Merope in the form of NGC 1435. First seen by German
astronomer Wilhelm Tempel in 1859 with a 4-inch telescope,
this patch extends nearly 0.5o and is within reach of 10×50
binoculars in ideal conditions. I've seen it in a 66-mm refractor.
In my 10-inch at 50×, I detect a tapered fan of faint light
arcing southward from Merope with evidence of delicate structure
and striations. Unlike other reflection nebulae, this one
looks better to me with a wideband deep-sky filter, and I saw
more detail after placing Merope just outside the field of view.
Before you leave the Pleiades, try for NGC 1432 surrounding
the 3.9-magnitude star Maia. At 50×, the reflection
nebula appears round and largely featureless and less distinct
than its brighter, hazy neighbor.
Winter's Finest Reflection Nebulae
Object
M78
NGC 2071
NGC 1999
NGC 1788
NGC 2163
NGC 2261
NGC 2149
NGC 2170
M45
NGC 1435
NGC 1432
IC 348
NGC 1333
vdB 1
NGC 7023
Constellation
Orion
Orion
Orion
Orion
Orion
Monoceros
Monoceros
Monoceros
Taurus
Taurus
Taurus
Perseus
Perseus
Cassiopeia
Cepheus
Magnitude
8.0
8.3
9.5
-
~11
-
-
-
1.5
-
-
7.3
5.7
-
7.2
Size
RA
8′ × 6′
7′ × 5′
2′ × 2′
5′ × 3′
3′ × 2′
3′ × 1′
3′ × 2′
2′ × 2′
120′
30′ × 30′
26′ × 26′
10′
6′ × 3′
5′ × 5′
10′ × 8′
05h 46.7m
05h 47.1m
05h 36.4m
05h 06.9m
06h 07.8m
06h 39.2m
06h 03.5m
06h 07.5m
03h 47.5m
03h 46.2m
03h 45.8m
03h 44.6m
03h 29.3m
00h 11.0m
21h 01.6m
Dec.
+00° 05′
+00° 18′
-06° 43′
-03° 20′
+18° 39′
+08° 45′
-09° 44′
-06° 24′
+24° 06′
+23° 46′
+24° 22′
+32° 10′
+31° 25′
+58° 46′
+68° 10′
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.
24 FEBRUARY 2025 * SKY & TELESCOPE
Star magnitudes
Sky & Telescope - February 2025

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