Conditions for this past Thursday's observation started off okay, even though seeing left something to be desired. Hoping the downpour today cleans things up and steadies things down. But got two good observations in before the sky went to mush around 9 or so. The Sculptor galaxy, or the Silver Coin - NGC 253 has been on my list for some time but just never got around to it, so I put it at the head of the line and followed with the pair in Pisces as that was their highest placement for the session.
NGC 253, the Sculptor Galaxy, or Sliver Coin in Sculptor:
Finally got around to this one! It's around 11.5 million ly distant and I was surprised at how big it was in the eyepiece. Only M31 is bigger in my experience. 253 is an intermediate spiral, with dust making it hard to make out any arm structure, even with really big telescopes. It’s also a starburst galaxy undergoing a lot of star formation. Caroline Herschel, not William this time, discovered it while looking for comets in 1783.
Observing: Started out with the 21mm at 145x and at first it didn’t seem that impressive. I’m going to blame the run of poor transparency we’ve had. But over time more details began to show themselves, and I went through the 13mm @ 235x and the 8mm @ 381x to see if I could pull out more. Things got a bit mushy at 381x, but at least it helped to confirm the detail that showed up in the 13mm. However, the galaxy was too big for that eyepiece even with the Ethos’s 100˚ view. So, for the sketch I went with the 21mm view, including the details picked up or confirmed with higher powered EPs.
There are a number of threshold stars that helped to define the limits of the halo. It just seemed to keep growing, first in AV and then direct. The halo was rather mottled but did show a bit of streaking particularly to the north, but there was also a bit of that to the south near the halo’s edge and to the west of the bright foreground star. There is a dust lane just outside the core on the northern side which gets wider as it curls around to the west (left in this view) and then south. There are also suggestions of it extending somewhat to the east, and perhaps a segment of an additional one as well in that direction.
The core itself is not uniform in shape nor in brightness. It’s elongated and has an odd curve to the south where it also seems a bit brighter. There is mottling in the core area as well. It’s not as distinct as say M31’s or M104’s, but it does stand out from the halo in its irregular way.
The two brightest stars in the field clearly mark the galaxy to the south of the core, and along with them, a rather dimmer pair forms the other side of a trapezoid to do the same for the northeastern side.
Even though 253 did not grab me at first look, it grew clearer with time and displayed an intriguing character. Why did it take me this long?
Sketching: white pastel pencils and white pastel powder on Bachmore 92 lb. black multimedia paper. Big targets use a lot of brushes, and 253 was no exception. The overall extent of the halo was laid down with a #12 Filbert, with #8 and #2 Filberts defining the edges of the halo and creating the core. Details in both were handled by the #5 pointed brush and the 12/0 mini angular, including the #5’s ability as an eraser. The dust lanes were created with the kneaded eraser and partially filled back in with the pointed and mini angular brushes. The mini angular did the streaking with other brushes blending them out.
NGC 7541 and 7537 – interacting spiral galaxies in Pisces:
At 104 million ly and 127 million ly distance respectively, NGC 7541 and 7537 show signs of interaction, primarily due to two tidal tails extending from 7541. That galaxy also has an Active Galactic Nucleus (AGN) that is partially dust obscured. Both are barred spirals, and the significant star formation lends to the theory that bar structures channel dust and molecular clouds in to form stellar nurseries. 7541’s rate of formation is well above the average. It was discovered in 1785 by Willliam Herschel. Guess his sister was still looking for comets.
Observing: A fairly distinct star field surrounds this pair, with a fairly bright equilateral triangle to the east-southeast (up in this view). A shallow curve of stars is off the western ends of the galaxies.
7541 is clearly the larger of the two and has a somewhat brighter halo than its smaller companion, even though it's rather diffuse especially at the ends, but not a brighter core. Both the halo and core are highly elongated. The core does stand out from the halo in shape and brightness, but not distinctly so. There is a threshold star at the eastern tip of the halo. The tidal tails were not seen.
7537 is smaller and fainter, but its core is the brighter of the two, and also more concentrated. Elongated, though not as much as 7541’s, the core of 7537 is distinct from the halo and at first was seen without it. Over time the halo’s size displays itself, but is still best appreciated in AV. The galaxy lies at an angle to its larger companion, appearing to point toward its eastern tip. It also has a faint threshold star at its western tip.
Sketching: white pastel pencils and white pastel powder on Bachmore 92 lb. black multimedia paper. The halo of 7541 was drawn with a #6 Filbert brush, with its ends, its core, and the halo of 7537 placed by a #2 Filbert. A #5 pointed brush drew 7537’s core.
Thanks for looking. Clear skies and dry paper everyone!