Nebulae in Monoceros

15 March 2021, 19:45 – 22:30

Seeing: Average / Poor

Transparency: Average (cloud permitting)

A cool evening (after a mild day) with bands of high, hazy cloud drifting across the sky. Very light condensation on the telescope tube. The gentle breeze was a welcome change after a run of very blustery weather over the last few days. 

With the nights getting shorter and a new lunar cycle already underway, this was probably my last opportunity for a while to explore the winter Milky Way, so I started at low power (50x) with the 24mm Panoptic, plus the OIII filter to pick out some nebulae. When using this filter you have to cup your hands around the eyepiece to get the best out of it, as it does tend to reflect stray light bouncing off your eyeball. (I’ve noticed this before, but tonight it was more prominent than usual, particularly on the right hand side of the field of view.)


NGC 2359, “Thor’s Helmet”, emission nebula, Canis Major

50x + OIII filter. The nebula showed up clearly with this eyepiece/filter combination, but only the brightest sections were visible tonight. Averted vision showed a bright spot on the northern part of the nebula.

The area northwest of NGC 2359 is rich in nebulae according to every chart I’ve seen, but nothing obvious jumped out at me when I scanned this region. Pushing on into Monoceros, I arrived at…

NGC 2237-9, Rosette Nebula, Monoceros

50x + OIII filter. Visible as a very large, structureless haze surrounding open cluster NGC 2244. The nebula appeared widest and brightest on the north and west sides.

After sweeping north, to the Christmas Tree cluster, and then west, I stumbled upon something I hadn’t seen before:

NGC 2245, reflection nebula, Monoceros

50x + OIII filter. Although catalogued as a reflection nebula (I didn’t know this at the time, as the chart doesn’t make a distinction between reflection and emission nebulae), it showed up very clearly as a small, fuzzy patch of light immediately southwest of a bright 8th magnitude star. Averted vision showed it to have a bright core. Increasing the magnification to 171x (no filter) improved the view considerably: now I could see an 11th magnitude star embedded in a wide, comet-shaped swathe of nebulosity fanning out to the southwest. Reminiscent of nearby NGC 2261 (Hubble’s Variable Nebula) but with a curved rather than a pointy apex. There was a hint of similar (albeit fainter) nebulosity corresponding with the position of nearby NGC 2247, but some hazy cloud pushed in before I could confirm it.

Relocating to a cloud-free (for now) part of the sky:

M97, Owl Nebula, Ursa Major

50x + OIII filter. Viewed at low power with an OIII filter, the Owl Nebula actually looked “bright” for once, appearing as a round, soft-edged disc of light. At 171x (no filter), it was faint, but the dark “eyes” were just about visible.

NGC 3893, galaxy, Ursa Major

171x. Follow-up from the previous session. At this magnification the companion galaxy (NGC 3896) was visible with averted vision as a small, faint patch of light roughly east of the main galaxy, and adjacent to a 13th magnitude field star. Together, the two galaxies resembled a subdued version of the Whirlpool Galaxy (M51) and its neighbour as seen through a small telescope. Magnification makes the difference on this one; NGC 3896 was much harder to distinguish from the 13th magnitude star when I dropped down to 92x.

NGC 3166 and 3169, interacting galaxies, Sextans

92x. Pair of small oval galaxies in same field of view, separated by a few arcminutes. Similar in size, but the western galaxy (NGC 3166) has a much brighter core. The other galaxy (NGC 3169) is just west of an 11th magnitude field star.

With more clouds pushing across the sky from the west, I called it a night.

The Tao of Tau Canis Majoris

28 January 2020, 21:30 – 23:30

A cold, breezy night. My feet felt frozen by the end of the session despite two layers of socks. Some hazy bands of cloud moving slowly from the south-west from about 23:15 onwards. But no condensation for a change.

Seeing: Average
Transparency: Good to Average

I started with a tour of some old favourites using the Panoptic 24mm (50x), before switching to higher magnification once the scope had cooled to ambient temperature and my eyes had dark-adjusted.

M42, The Orion Nebula
Viewed at 50x and 133x, both with and without the OIII filter. Not much I can add to previous descriptions; with the filter in place the nebulosity almost overwhelmed the Trapezium, particularly at the lower magnification. The OIII also imparted a strong green colour, more so than any other object I’ve used it on.

NGC 2392, Eskimo Nebula, Gemini
Showed up nicely at 92x (13mm Ethos). Bright shell and central star seen with direct vision; double shell with averted vision. Pale blue colour.

NGC 2420, open cluster, Gemini
At 92x appeared as a condensed fuzz of stars, about a dozen resolved with direct vision – more with averted vision. Lines of stars appear to curl out to four “corner” stars, giving the cluster a shape resembling a Mermaid’s Purse.

NGC 2355, open cluster, Gemini
92x. Another condensed group of faint stars. Brightest member on southern edge. Curving chain of stars leading north to brighter star. Pretty cluster!

NGC 2395, open cluster, Gemini
92x. Kite-shaped cluster of stars. Sparse, loose; not as good as 2355.

M50, open cluster, Monoceros
92x. As noted previously: rich, large. Prominent red star on southern edge of cluster.

NGC 2335, open cluster, Monoceros
92x. Small, sparse cluster, but there seemed to be an underlying haze of unresolved stars.

NGC 2343, open cluster, Monoceros
92x. Small and sparse again, but brighter stars than 2335. Roughly triangular in shape.

W Canis Majoris, carbon star, Canis Major
92x. Scarlet-hued star; distinctive, but not as vivid as Hind’s Crimson Star.

NGC 2353, open cluster, Monoceros
92x. Rich, if sprawling cluster, gathered around a bright 6th magnitude star (apparently a foreground star rather than a cluster member).

NGC 2362, Tau Canis Majoris cluster (Caldwell 64), Canis Major
92x. In a word: wow! I’ve never seen a cluster quite like this before. A stunning sight in the Ethos despite its very low altitude (declination -25 degrees). A brilliant 4-5 magnitude star (Tau) surrounded by a rich swarm of bright stars. Tau (which apparently is a member and not a foreground star) has a faint companion a few arcseconds east. The cluster has a roughly triangular shape, with another bright star further to the east. It almost looks too good to be true, like it was designed by a VFX artist for a sci-fi film. The highlight of the night.

NGC 2354, open cluster, Canis Major
92x. Loose, filmy mass of stars somewhat washed out by light pollution. Would no doubt be more impressive if it were higher in the sky (and not so near to NGC 2362).

NGC 2360, open cluster, Canis Major
(Caldwell 58) 92x. As previous description. Rich, straggly cluster of moderately bright stars.

NGC 2359, “Thor’s Helmet”, emission nebula, Canis Major
Ethos 13mm + OIII filter. I remember seeing a colour photo of this nebula in an astronomy book when I was a kid, and I was struck by how dramatic it looked: like a spectral demon charging headlong through the heavens. It’s an image that has stayed with me (particularly when I read the epigraph of JG Ballard’s story The Illuminated Man), but I never imagined I would get to see this nebula with my own eyes. For some reason I thought it was only visible from the southern hemisphere (curiously, O’Meara, in his book The Secret Deep, was under the same impression), but while planning my exploration of this part of the sky I realised that not only was its declination just -13 degrees, but also – crucially – it might be bright enough to see in the XT10.

I couldn’t see any nebulosity when I scanned the region unfiltered, but when I added the OIII it was immediately obvious, appearing as a bowl-shaped hemisphere of light with a short bright extension angling away from the southern end (one of the “horns” of the helmet). After staring at it (and to the side of it) for a little while I was able to see the other “horn” as a longer, fainter extension angling from the northern end, pointing west, as well as a bright spot on the northern edge of the bowl. Comparatively, NGC 2359 reminded me of a ghostlier version of the Crescent Nebula (NGC 6888 in Cygnus), another object which responds similarly well to filters, and is itself also powered by a Wolf-Rayet star.

It has to be said that telescopically NGC 2359 looked less like a spectral demon and more like a spectral cauliflower, but as nebulae go it was still very impressive. If NGC 2362 was the night’s highlight, this was a close second.

NGC 2438, planetary nebula, Puppis
With the OIII filter still in place I moved the scope across to NGC 2438, which would arguably be one of the winter’s best planetary nebulae even if it didn't share a telescopic field with M46. The OIII filter dimmed the surrounding starlight, thus making 2438 much more distinct, although it’s nowhere near as bright as the Eskimo Nebula in Gemini. On this occasion it looked a little like M57, appearing as a ring with a darker centre – although the dark core was smaller in size compared to the ring, giving the nebula a more donut-like appearance. Also the nebula seemed larger than it did on 17 January, though this was probably an illusory effect caused by the filter subduing M46.

NGC 2440, planetary nebula, Puppis
Small disc of light a few degrees south of 2438. A field star to the east helps confirm its status; otherwise I think it would be easy to overlook, particularly at low magnification. A close double star to the southeast can also distract the unwary observer. Very bright in the OIII filter; direct vision suggested a bright core and averted vision suggested a faint outer halo, but my eyes were getting very tired by this stage so it was hard to be sure. One to revisit at higher magnification.

Nature note
One frog in the pond (the usual long-stayer), plus lots of wriggling insect larvae.