Yet more globular clusters.

[xilman]

Originally Posted by xilman

More globular cluster images --- eight of them this time. All are in M31; the brightest is catalogued at m_V = 17.34 and the faintest at 18.80. Image taken with a 0.4m Cassegrain with an unfiltered 10 minute exposure.

After that I had to try for something more challenging. M81 is outside the local group of galaxies and five times further away than M31. Accordingly its globulars will be about 25 times fainter. The attached image was built from 239 30-second subs for a total exposure time of 7170 seconds. The gory details are on my BAA web page but the summary is that 49 globulars are marked, ranging in brightness from mag 17.5 to 20.9.

Next up will be M87, which has recently been in the news for another reason. That galaxy, the largest in the Virgo group, is another factor of four further away than M81 but I'm hoping it won't be too much of a challenge. Not only is the galaxy bright and enormous, so are some of its approximately twenty thousand globular clusters. Our galaxy, M31 and M81 each have around 1% of that number.

[ewmayer]

Very nice! My first thought on viewing the image was "given that many of the (alleged) clusters are barely distinguishable from noise, how does one reliably identify them?" Your BAA page answers that.

[Spherical Cow]

Outstanding! And an excellent description of the process in the linked BAA page. Thanks!

Norm