June 16th, 2020, 11:25 p.m. local time
Here is what I hope will be the return of an observation technique I have not done for a while – sketching. I am actually doing my most recent sketching posts in reverse. Over the past week, I was hunting for the galaxy M61, and have a small set of sketches that will be part of a larger post. But for now, last night I decided to have some fun and tried to observe and draw a star cluster for the first time.
My goal was to capture what I truly saw at the telescope. Yes, the cluster in question here, M3, really does look like just a gray smudge amongst a few dots of sparse stars. The smudge is actually the core of about a half million stars. All in all, I think that using a virtual charcoal pencil made a pretty accurate representation of what the cluster did look like to me, under very good viewing conditions for my location.
Using my 254mm (10-inch) Dobsonian, my best 2″ eyepiece along with a 2-times magnification Barlow lens, this was probably the best wide-field view of M3 that I can get. I could likely use my 1.25″ eyepieces, but finding this star cluster by star hopping would be extremely difficult with such a narrow view. While M3 is obvious when you find it in a telescope, there are no close guide stars. The closest bright star is Arcturus in the constellation Boötes. However, with my recent practice of trying to locate M61 (see future post), it wasn’t too hard to approximate the location between Boötes and Ursa Major (the Big Dipper), which is incredibly large and bright even in my light polluted skies.
How “large” is this star cluster? It is difficult to give an approximation because not all of the cluster is fully visible here. But for reference, it is officially listed at 18 arcminutes. The Moon is about 30 arcminutes. If I looked at the Full Moon with this eyepiece/lens setup, it would fill up a good portion of the view, but not entirely and with noticeable space to spare.
Using Stellarium, I looked up the surrounding stars and all their magnitudes. Remember that lower numbers are brighter. M3 was definitely the brightest object, magnitude 6.20, although the light was spread across the cluster, not concentrated to a single star. The next brightest star was to the right, named HIP 66890, at magnitude 8.40.
(Interestingly, Stellarium lists HIP 66890 as a double star. I may have to check it out again to see if I can gleam the second star.)
To the left of M3 are dimmer stars in the 10+ magnitude range. I have pointed out all of the key stars and M3 below:
I used Procreate on my iPad to draw this sketch, with a dark red background as the canvass and white pencil. I then removed all red afterward in PaintShop Pro, to give the black background you see here. I will discuss this setup and usage in more detail in upcoming post on M61.
