The following is the October article I wrote for Aurora, the newsletter for the Windsor, Ontario branch of the RASC. The entire newsletter (and all the older ones) can be downloaded from our website (RASC Windsor).
My idea of what constitutes a great night of observing varies with the seasons, and which projects are on my clipboard for the next clear night. Sometimes it might be a long list of double stars, and sometimes a clump of NGC objects. Usually I prefer to work in detail in one area of the sky at one time, so I will have a list for early night and a list for later in the night. For a few nights recently, and lasting throughout October, I have a suggestion for viewers who can access a dark sky sight, preferably near the lake to get good southern sky exposure.
There are currently five outer planets available to viewers this month, with Mars being the main attraction. I have enjoyed several superb views of its surface in October with the 12” Dob, the best I have ever seen, including my first opposition experience in 1971. I like to use a red filter at 166x, which really brings out the dark areas strongly, and then switch to a yellow filter at 231x, which makes the detail stand out clearer and brighter. Since Mars is currently best observed after 11 PM, I have been starting with Jupiter and Saturn lately. Again I prefer a yellow filter with both planets, which are really too bright in my 12” mirror otherwise. Over the summer I have kept a steady watch and have enjoyed many clear and incredible views of both planets and their moons.
Uranus and Neptune are visible, too. Neptune is easy to find after 9 PM, nestled into an area near 96 Aquarii. I have been watching its slow progress through the sky over several nights recently, and on my last visit (Oct. 14th) I was able to easily see Triton, the first time I have had such luck. The moon is about mag. 13.5, moving between 12” and 17” of arc from the planet. Deborah and I both saw it clearly, and it was quite a chill and a thrill to do so at the eyepiece (231x). I find that the chart in the Astronomical handbook is next to useless to finding Neptune, so I went on-line and found a better one. It isn’t far from eg 7585, a prominent galaxy in Aquarius, and is an easy star hop from there.
Uranus is best seen later, after around 11 pm. It is in Aries, in the middle of nowhere. The Handbook chart is helpful, and I was able to plot the planet on Uranometria beforehand. It is much brighter than Neptune (which is bluish-green and pretty bright in the 12” scope), and stands out as the brightest object in its area of sky. It appears blue in colour. At 231x it does show a tiny disc, but on the night I found it the seeing was quite bad, and the planet shimmered away. I will return on a better night. Over the course of one evening we were able to observe Saturn, Jupiter, Neptune, Mars, and Uranus, in that order, with Deb’s 6” scope and my 12”. It was a fun way to spend an evening. But wait, there’s more!
Aquarius is home to two very different planetary nebula, both well known to amateurs. One of these objects resembles a planet closely enough to deserve the name planetary nebula. NGC 7009 is called the Saturn Nebula. It is mag. 8, being 35” in size, and has a bright central star. It has a remarkable colour, a very strong blue that is fun to compare with that of Neptune and Uranus. This nebula takes magnification well, and I enjoyed good views at 333x. No filter is required to see this object at its best. At first its two extremities, or ansae, appear as tiny dots, or stars, preceding and following the object. After a few moments, and at reasonably high magnifications, they appear attached to the main body. These can be seen in an 8”, with patience. The overall impression of NGC 7009 is of a cartoon drawing of Saturn. At high power with 12” it also appears to have a fuzzy or mottled texture, as of many fine lines engraved across its surface.
Not too far away is another showpiece planetary nebula, The Helix (NGC 7293). This very large and faint nebula sits at 21 degrees of declination. From Hallam this is in a very poor area of the southern sky. Ideally, Point Pelee would serve well, or a dark place along the lake. The visual magnitude of the overall object is a bright 7.3. However, due do its enormous size (1054”), expect a shock when you see it for the first time, especially in a smaller scope. It might appear very faint and ghostly. Under good conditions and with the right equipment, this is one of the major wonders of the heavens. I like to observe the nebula at low to medium magnifications, starting at 86x, then moving up to 107x and finally 120x. Without a filter there is a veritable open cluster of stars to be seen through the haze, but finding the central star, mag. 13.5, is not difficult. I really like the view using my old Orion Skyglow filter. The nebula brightens a lot, and areas of varying brightness can be easily distinguished, especially towards the edges. However, the OIII filter (Celestron), while giving darker views, also provides a more 3D immersive experience, showing plenty of detail and giving the impression of great turbulence and churning. I pushed as high as 166x, filling my eyepiece with this amazing object, using the Skyglow filter. As far as seeing detail goes, this object rates as highly as Jupiter, Saturn, or Mars at opposition. It is a mini-universe unto itself!
Messier of the Month
Since we are already in the area of Aquarius, I will now discuss two of its Messier objects, one of which is almost a showpiece, and one of which is certainly a dud. Let’s begin with the showpiece. My first official logging of Messier 72, or gc 6981, was the night of July 28th, 1994, using my Edmund 8” reflector. While located easily at 59x, and observed up to 200x, it was basically a round ball of light, not that bright, and showing no resolution worth mentioning. Switch to September 18th of 2020, when I first came after M 72 with the 12”. Looking much like a comet at 86x, the cluster is unresolved. Lying at -12.5 degrees south, it was in a good enough sky from my Kent County location. At 120x it takes on a granular quality. Finally, at 166x, the globular cluster begins to resolve into very tiny stars, all across the bright central area. 231X achieves fair resolution, with tiny pinpricks of light dancing across the background haze of unresolved stars. 333X provides decent resolution for well seasoned eyes, though M 72 is far from a showpiece cluster for untrained eyes. It does provide a good challenge for a 12” scope from our latitude and sky conditions. The outer, much fainter haze surrounding the central area is not very large.
While M 72 was claimed by Mechain, and does resemble a comet-like object, Messier himself must shoulder the blame for M 73. I remember being quite disgusted and disappointed the first time I saw it, and wondering how such a sight had ever made it to the list. Messier used a 3.5” refractor, yet he still added this to his list of objects that could be mistaken for a comet. Perhaps his lens was fogged. But all there is to see is a 4-star asterism of mag. 9 stars. Nothing else. I’m not the only person who finds it odd that M 73 and M 72 (which Messier does not mention) are at roughly the same declination, and separated by 1 hour of right ascension. Was there a mix up of some kind, and he really meant to log M 72? We’ll never know, but after seeing how many such mistakes were made in the original NGC catalogue, it is not an impossible thing to imagine.
Messier 72 (NGC 6981): Size 6’.6; Vis. Mag. 9.2; Brightest star mag. 14.2.
Messier 73 (NGC 6994): Size 1’.4; 4 stars; Vis. mag. 8.9.
Mapman Mike wishes you clear skies!
