Return to the Coma Galaxy Cluster

​14 April 2021, 21:45 – 23:30 (BST)

Seeing: Average / Good

Transparency: Average

Chilly and windy (again). A few scattered clouds blowing south. The previous night’s attempt at astrophotography was blighted by polar alignment issues and a loose power cable. I did however manage to get a 120-second test shot of the Coma Galaxy Cluster, which showed a surprising amount of galaxies for a single unstacked image (see edited crop below). Bodes well for future imaging runs (if the wind ever drops again).

The galaxies near the centre of this image are over 300 million light years away.

Before diving into the galaxies I warmed up with a look at some double stars and a carbon star:

Izar (Epsilon Bootis)

Tight split at 171x. Pale yellow primary; blue-ish secondary NW. I say “blue-ish” because at times it looked vaguely purple (an impossible colour for a star).

Cor Caroli, Canes Venatici

171x. Brilliant bright double; wide separation. Icy white primary; pale yellow secondary.

Y Canum Venaticorum (La Superba), Canes Venatici

171x: Rusty red-hued star, though the colour is due to carbon, not iron.

NGC 3640, galaxy, Leo

171x. Follow up from previous session. As suspected, higher magnification made the difference. I could see a faint field star north of the galaxy, and a very faint, small fuzzy patch (NGC 3641) a similar distance to the south, only just visible with averted vision.

NGC 3705, galaxy, Leo

171x. Large oval haze. Star-like nucleus with averted vision, which also suggested mottling in the surrounding haze (possible s-spiral?). I missed this galaxy on Monday night and I’m not sure why, because it’s quite impressive – certainly not faint or inconspicuous.

 

NGC 4449 (Caldwell 21), galaxy, Canes Venatici

171x. Revisiting a favourite from the Caldwell list. Fascinating irregular galaxy, showing a lot of detail for a non-Messier object. Oblong haze with a bright bar running through it on a diagonal north-south axis. Averted vision showed a bright central spot on this bar flanked by two fainter ones. Averted vision also showed another spot or clump on the eastern corner (as noted in previous observations).

NGC 4889 (Caldwell 35), galaxy, Coma Berenices

171x. The powerhouse at the centre of the Coma Galaxy Cluster (see above). Faint but obvious, as was its slightly dimmer neighbour NGC 4874. Both galaxies appeared to swell in size with averted vision. As both the seeing and the transparency were relatively good I wanted to see if I could pick out any of NGC 4889’s companions (which I’m sure I’ve glimpsed on previous occasions). Once I got my eye in I could see a faint fuzzy spot (NGC 4886) just west of 4889, in line with the 7th magnitude “finder” star HD 112887. On the other side of 4889 and slightly south was a faint foreground star (no fuzziness), and then, a little farther east, another even fainter fuzzy spot (NGC 4898), forming a near right-angle triangle with two field stars to the south. All these galaxies were still visible when I dropped down to 133x, although it was a little more challenging with the comparatively bright HD 112887 in the field of view.

By now the clouds were getting larger, and reflecting a lot of light from the ground as they drifted southwest. With most of Coma Berenices obscured, I relocated to the constellation of Boötes.

NGC 5557, galaxy, Boötes

133x. Round blur; swelled with averted vision. Averted vision also showed a condensed, bright core with a star-like nucleus. Field star west, fainter one east.

SA 2000 plots a handful of other galaxies here, in addition to NGC 5557. I couldn’t see NGC 5529, but I did catch another one before the clouds got in the way.

NGC 5533, galaxy, Boötes

133x. Inconspicuous oval haze, fainter than NGC 5557. Gradually brighter towards the centre; star-like nucleus with averted vision.

The red light on my torch had been getting steadily dimmer throughout the session and now it was so dim I couldn’t see the star-charts or my notes, so it seemed like an appropriate point to call it a night. Though on the plus side, that dimness may well have helped me to see those faint galaxies in the Coma Cluster.