As a reference, the data provided for each object will at a minimum consist of its constellation of residence, the type of object, generally accepted visual magnitude (when applicable and/or known) and its typical angular size expressed in either degrees of arc ( ° ), minutes of arc ( ‘ ) or seconds of arc ( “ ). Additionally, for most objects I may include additional data per the following examples:
• Open Clusters will also include their Trumpler classification (see link for an explanation).
http://www.astrophoton.com/trumpler_class.htm
• Globular Clusters will also include their Shapley-Sawyer core concentration classification (see link for an explanation).
https://en.wikipedia.org/wiki/Shapley%E ... tion_Class
• Galaxies will also include their structural type as well as average surface brightness (SBr) expressed in magnitudes per square arc minutes.
• Planetary Nebulae will include an average surface brightness expressed in magnitudes per square arc minute and when known the magnitude of its central star.
• From time to time I may also add in some asterisms that I’ve found to be visually interesting. These will include designation of the brightest star and its magnitude, the group’s angular size, a rough count of the constituent stars and general description of the pattern they form.
For each object I will also provide a little of its history. Sometimes I may make a comment regarding the object’s appearance based on my own experience, though I do not wish to influence what you may or may not see through the eyepiece. What details we each pick up is influenced by many factors, such as localized conditions,
As a final comment, I will say this first edition leans heavily on the perennial favorite for this time of year – Orion. And because four of the objects come from that constellation alone, I have added in an extra challenge target for each side of the equator to add a wee bit of diversity. I also wanted to pay special homage to Charles
Northern Celestial Hemisphere:
This cluster is one of my personal favorites and a winter staple for many. Discovered by Phillippe De Chéseaux in the 1745-46 timeframe, it was independently recorded by Charles
This very small and dimmer cluster sits like a hidden treasure less than half a degree southwest of M35. Far overshadowed by its bright neighbor to the northeast, it can and is frequently overlooked by observers, particularly those with less experience. Discovered by William Herschel in 1764, he called it a very compressed cluster of very dim stars and very rich. I recommend you not overlook this little treasure, as it presents a marvelous counterpoise to the brightness and beauty of M35.
The brightest reflection nebula in the sky was discovered by Charles
In northern Orion, about a third of the way from the great hunter’s head toward his right shoulder, Betelgeuse, is this more challenging object for your pursuit. Discovered by William Herschel in 1785, visually it typically appears as a smooth disk until one starts getting into a bit larger
Southern Celestial Hemisphere:
When one thinks of Orion, thoughts automatically turn to the Great Orion Nebula complex. The vast structure is immersive and something that one could spend a great deal of time playing with both visually (and sketching) as well as through imaging. In our case we are given a twofer here, with
What we now know as
The smaller object later to be known as
Most of us observe this pair multiple times each year so we can marvel in their beauty and intricacy. Thus I wanted to include them in this first issue of the challenge.
We now head farther south into the celestial dove to pursue a beautiful globular cluster. James Dunlop discovered this fine object in 1826 using his 9 inch speculum mirror reflector during his time in Parramatta, New South Wales, Australia. As a class 2 core concentration cluster it exhibits a very tight and bright central core. Visually, at best it yields only slight resolution of some fringe member stars grudgingly, and typically only to larger apertures. Even in small apertures it is clearly a compact globular cluster with an intense core and quite a pretty sight. Give it a spin and see what you think.
Our final object for this month is an amazing emission nebula in Dorado the dolphinfish. This large nebula is actually in a Milky Way satellite galaxy, the Large Magellanic Cloud galaxy (ESO 56-115), thus it is an extragalactic object. Its listed magnitude is a bit difficult to pin down, as I’ve seen it listed from 5.0 up to the 8.3 that I use. I prefer to be more conservative, though it is bright, as I’ve easily seen it using 10x50 binoculars from a typical suburban sky in the southern hemisphere.
Known famously as the Tarantula Nebula, it was discovered by Nicolas-Louis de Lacaille in the 1751-1752 timeframe from the Cape of Good Hope using his famous 8x one-half inch refractor. So that gives you an idea of how bright it truly appears. It has extremely high luminosity and it is stated that were it as close to Earth as the Orion Nebula, it would cast visible shadows at night. So if it rises above your horizon, do take some time to observe, sketch and/or image it as that would be time well spent.
So there you have it, your first