BNGC 3. Backpacking in the SMC
By Steve Mencinsky, 1992
This month's "Beyond the NGC" assumes major proportions, featuring objects within the largest NGC of all: NGC 292, the Small Magellanic Cloud.
In the Magellanic Clouds, we have galaxies close enough to see nebulae (of both the emission and reflection persuasion), open star clusters, globular star clusters, even the odd deep galaxy peering through, all through telescopes of moderate size. Indeed, quite a few of the emission nebulae and star associations in the Clouds are easily visible from Ilford with the unassisted eye. My interest in observing the Small Magellanic Cloud (SMC) started about a year ago when Mati Morel's detailed Large Magellanic Cloud (LMC) charts were first shown at Ilford. These seemed quite a daunting project but the SMC seemed as if it would be - to quote the legendary Goldilocks - "just right" so the chart and associated booklet were duly purchased and observing begun. (Regular readers of Universe would appreciate that Goldilocks and her friend Snow White are occasional observing companions of the equally legendary Mick McCullagh). One benefit of observing objects at these high southern declinations is that this far from the ecliptic, there are no planets (ptui!) to clutter up the sky...
The first observations were done from my backyard in Cremorne - at first glance, not the best environment in terms of light pollution. However, by about 3am on a workday, when most good citizens are asleep and only the odd possum is about, the level of outside lighting is therefore as low as it can ever be, the eyeball has been well and truly dark adapted by four hours sleep - the Small Cloud is barely but distinctly visible with the unassisted eye. If you've ever been in the author's previous suburb of Newtown, you'll understand why this was so exciting! Even in this environment, it was amazing what could be seen through the (then newly) super-aluminized Suchting 12" f4.8 telescope. A significant number of objects, either NGC or IC, were well visible. On reflection (if you pardon the pun!) this can probably be attributed to maps rather than any particular skill on my part.
Clearly, the chances of succeeding in observing faint objects are much higher if one knows exactly what to look for and where to look. With field stars down to 16th magnitude on the detailed Selected Area Charts, the precise location of the object in question can quickly be found in the star field to within tens of seconds of arc.
Observing the SMC from Ilford was even more of a thrill. It took a lot of star-hopping, and it took a full weekend - as in from evening twilight to morning twilight on both nights - to do it, but by Sunday manning EVERY OBJECT listed on Mati's charts was successfully observed, with only a few objects requiring assistance from the mighty Murrell 20" That Sunday night I went to bed feeling deliciously tired and with a marvellous satisfied sense of achievement : the best way to finish a weekend at Ilford!
(If you intend to observe the SMC for yourself, you should be aware of an error in the RNGC, which has flowed into Uranometr ia but fortunately not into Mati's charts. In the two former, NGC 460 is listed one degree too far north - presumably a typographic or transcription error. NGC 460 is in fact directly between NGC's 456 and 465.)
Not wishing to bore our readers with a blow-by-blow of these hundreds of individual objects within the SMC, here are a few highlights. Opinions are those of the author and are not necessarily those of anyone else.
The globular cluster NGC 362, while a foreground object and strictly speaking not associated with the Cloud, is always worth observing. This cluster is moderately large, bright, round, symmetrical, quite condensed. yet resolved to the core. This object is noteworthy enough to make Ted Lumley's Observation Officers report under its designation of Dunlop 62. The cluster is large and bright enough to appear nebulous in the 7x60 finder and forms the northernmost "entry point" to the objects in the northeastern part of the Cloud.
Due south of NGC 362 is NGC 361, which is a globular cluster actually in the Small Cloud. If one assumes that the two objects are of comparable actual size (not proven!) then moving from one to the other forms a nice "perspective" effect - the large, bright close object contrasted with the very small, very faint further one. This kind of "conceptual observing can be quite thought-provoking. (Walter Scott Houston mentioned this once - he was trying to visualise The spiral appearance of the bulk of Milky Way galaxy, attempting to ignore the foreground stars He would have found the going quite tough, since from his latitude the Galactic Centre barely clears the horizon!)
The area of NGC 371: This is a large, dense open cluster appearing as for example M46 might were it as far away (as NGC 371). However... again with the assistance of The OIII Filter, there is a reasonably bright emission nebula surrounding the cluster, well visible from the backyard. Since the brightest part of the nebula is the crescent rim on one side, while the brightest part of the cluster is the centre, and the filter enhanced the view, it was assumed that this is a real nebula and not simply light "bleeding" from the cluster. If you've tried to observe the nebula around M16 you'll be familiar with the challenge.
Joe Cauchi's magnificent photo of the SMC did not shed any light on this subject (another pun) since the cluster is quite dense and bright and therefore burned out on the photo - showing yet again that mere photographic film can't match the more photoelectric-like characteristics of the retina's rod cells. Maybe a colour Photo would do the trick? This was quite an exciting find - a nebula unlisted even on Mati's charts yet bright enough to be seen from a city backyard A few months later, this nebula was found while leafing through the ESO publication Observing the Southern Sky. charted as Henize 76 (N76).
On one side of 47 Tucanae (who amongst us is wordsmith enough to adequately describe this?) is the small faint globular NGC 121. On the other side, almost directly opposite and at the same angular distance away is the slightly larger but fainter globular Kron 3. With a 1.5 degree field. all these Globulars can be squeezed into the field - quite a remarkable sight From Kron 3, one can proceed to the western edge of the Cloud proper and then eastwards to the centre.
A number of small but moderately bright and well-condensed open clusters without NGC/IC designations were visible from the backyard. The brightest of these is Kron 42, near the area of IC 1611 and IC 1612. This object is certainly brighter and easier to see than for example, NGC 152. Similar could be said of Kron 50.
The open cluster NGC 346 and the emission nebula Henize 66 (N66) surrounding it. The cluster itself has the shape of a flattened triangle. The inner. brighter part of the nebula is "squarish", while the outer fainter nebula has an "S" shaped appearance. tapering at the edges giving it a combined appearance of a classical SBc barred spiral. This is the brightest nebula in the SMC (perhaps its equivalent of the Tarantula Nebula), Use combination being visible to the naked eye from Ilford. The three-level structure does not seem to photograph well perhaps due to the great range of brightness involved. Maybe unsharp masking could show this? Are any of our astro-photographers interested in this?
THE most exciting observation in the SMC? Well in its central core, in the thin triangle formed by NGC's 261, 267 and 290, there are some twelve distinct small emissions visible with the assistance of the OIII filter, each an individual in its own right with a different shape size and brightness - truly a wealth of detail In fact, one small area where there is no bright nebulosity appears at first glance to be a dark nebula! There is extensive but faint nebulosity surrounding the whole field here and there is the added benefit that there are no stars brighter than 10th magnitude to distract and cause glare. As a result, even with the OIII filter. the full circle of the Naglers' aperture stop could be seen in silhouette. How many other places - other than the very very select group of Eta Carinae the Tarantula Nebula and the Orion Nebula - can boast this? Even our ace reporter and editor, Greg Bryant was impressed by this sight. Perhaps he imagined it to be a cluster of comets!
For almost any size telescope, the Small Magellanic Cloud pays handsome dividends (always gladdening to the treasurer's heart) on any investment of time & effort - whether from a suburban backyard or from a dark sky such as Ilford (Wiruna). As always, the key is a god map, and plenty of patience.