Sky & Telescope - March 2025 - 27

A Splendid Surprise
I started with the 8-inch, which produced a view that was
brighter overall and showed more detail than the 30-inch
did the night before with just the O III filter. Before I started
sketching this marvelous sight, I slowly panned around
to see if there were any outer wisps I could see. And sure
enough, there were some off the northern quadrant of the
Rosette Nebula.
It quickly became apparent that these wisps were part of
an arc of nebulosity curving northward, and I soon found
myself admiring NGC 2264, and I could plainly see the Cone
Nebula at its southern tip. Wow! On the other hand, I could
not make out Hubble's Variable Nebula, probably because it
doesn't produce enough Hα emission. I also saw the Christmas
Tree Cluster well, and there was a less defined field of
nebulosity west of NGC 2264.
When I returned home, I wondered if I'd missed anything
in my eagerness to start sketching the Rosette in Hα with
the 30-inch. I searched online for Hα images to see what else
may have been in the area, and I found that I'd overlooked
a fainter arc of nebulosity that flows from the northeastern
edge of the Rosette, forming a huge circular feature with the
first arc I'd seen. The second arc doesn't quite make it to NGC
2264, and, to my amazement, both arcs form the Monoceros
Loop supernova remnant I mentioned earlier. I just had to try
and see this second arc, but cloudy weather at all my favorite
observing sites in central and eastern Oregon conspired to
keep me home in April.
Fortunately, much like in Hα astrophotography, Hα
observing works nearly as well under light-polluted conditions
as it does under a dark sky. Two weeks after returning home
the clouds parted for a few hours, and I set up my 8-inch in
the backyard. I now saw the nearly full circle of the Monoceros
Loop supernova remnant, with the Rosette hanging off
the southwestern end, and NGC 2264 and the other clusters
perched above the northern end! Wow, wow, wow! I added
this arc to my earlier sketch.
The Hα sketch I made of the Rosette with my 30-inch
became a challenge because of the incredible density of detail
I saw in the " eyepiece " of the night vision device and my
now-limited time to draw it. I would have needed many more
hours to do the Hα Rosette justice with my 30-inch instead
of the two hours I had left. (See the caption for the 30-inch
hydrogen-alpha sketch on page 26 for my workaround.)
I've found a similar abundance of detail in the Hα structure
in many of the nebulae I've observed, and the amazing
ability of a night vision device to so clearly show previously
invisible structure is something I'll never get tired of. Technology
that works this well, and with so little fuss, is a rare
and wonderful thing.
¢ As powerful as night vision devices and Hα filters are
together, Contributing Editor HOWARD BANICH is still a visual
observer 95% of the time. That seems to be gradually changing,
though.
RECOMMENDED To get an idea of what the Hα sky looks like
without buying anything, visit the MDW Hydrogen-Alpha Sky
Survey website at mdwskysurvey.org. This all-sky survey is
the brainchild of the late David Mittleman, along with Sky &
Telescope Associate Editor Sean Walker and Senior Contributing
Editor Dennis di Cicco.
In and Around the Rosette Nebula
Object
Type
NGC 2244
NGC 2237
NGC 2238
NGC 2246
Collinder 97
Collinder 104
Collinder 107
NGC 2252
NGC 2261
NGC 2264
12 Monocerotis
HD 46150
HD 46223
Open cluster
Emission nebula
Emission nebula
Emission nebula
Open cluster
Open cluster
Open cluster
Open cluster
Emission nebula
Emission nebula
Variable star
Young stellar object
Young stellar object
Mag(v)
4.8
-
-
-
5.4
9.6
5.1
-
-
4.1
5.8
6.7
7.3
Size
24′
RA
80′ × 50′
80′ × 60′
-
25′
20′
30′
-
3′
40′
-
-
-
06h 32.3m
06h 30.9m
06h 30.7m
06h 32.6m
06h 31.0m
06h 36.5m
06h 37.7m
06h 34.3m
06h 39.2m
06h 41.0m
06h 32.3m
06h 31.9m
06h 32.2m
Dec.
+04° 51′
+05° 03′
+05° 01′
+05° 08′
+05° 50′
+04° 50′
+04° 45′
+05° 19′
+08° 45′
+09° 54′
+04° 51′
+04° 57′
+04° 49′
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 * MARCH 2025 27

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Sky & Telescope - March 2025

Table of Contents for the Digital Edition of Sky & Telescope - March 2025