Tales from Santa Luce, Tuscany, Episode VII: First of the Summer Galaxies

[michael.h.f.wilkinson]

August 2, the day after the planetary hunt, I set off after some galaxies in Libra and Serpens. I often forget about these, because from home they are highest just when the "grey nights" set in, whereas during my summer holidays they are generally setting early (and so many goodies in our own galaxy are beckoning).

Using the C8, I set out from Grafias, and an easy star hop lead to the location on NGC 5903 and NGC 5895. I had not looked up their magnitudes in the Revised Shapley-Ames Catalogue, so was chancing it a it, but two very faint, roughly circular fuzzy patches could be made out. After consulting the catalogue, I was pleasantly surprised that I had found two mag 12.5 galaxies, despite their low altitude. I have seen similar galaxies at such an altitude before, but it did indicate that the skies were pretty transparent. I had noted the daytime skies were more intensely blue than they were on any other day during our stay, so that does suggest a very transparent atmosphere.

I then tried NGC 5885 near Zubeneschamali, but despite prolonged efforts failed to spot it conclusively (some tantalizing hints, but nothing solid).

By contrast, NGC 5915 and NGC 5916 did show up, although they were very difficult to make out. Whenever I nudged the scope a bit, two extremely faint blobs seemed to be moving with the stars, the top slightly elongated, and the bottom more distinctly elongated. At first I had my doubts, but I managed to repeat this a could of times. NGC 5915 is listed at 12.9 in the S-A catalogue, and NGC 5916 isn't even listed. One source lists it at 13.3, which makes this the faintest galaxy I have seen through my scope to date. I wonder if the fact that they are a pair makes them easier (or rather: less difficult) to pick up. A single blotch moving in the FOV could much more easily be mistaken for some reflection, whereas two blotches moving together are more evidence to the brain. One might argue that a close mag 12.5 pair like the first one has the same integrated brightness as a single mag 11.75 galaxy (a factor of 2 in brightness is 0.75 mag difference). On the other hand, galaxies are fickle, and nearby NGC 5878 stubbornly refused to show itself.

Likewise, NGC 6118 only dropped tantalizing hints of its existence, but not enough to be sure, and bag it. Moving further into Serpens, NGC 6070 was easy by comparison, whereas NGC 6010 could just be picked out in averted vision.

I then moved to M13 and its neighbour in the sky NGC 6207, as a starting point for a hunt for NGC 6166. This proved very hard indeed, but after a prolonged effort I noted a faint patch of fuzz popping in and out of averted vision at the correct coordinates. Not much to look at visually, but one of the more distant galaxies I have observed at 490 million light years. It is the primary galaxy in the Abel 2199 supercluster in Hercules

Leaving galaxies aside, I picked up NGC 6058, as a small, faint, but resolved (at 120x in the 17T4) planetary nebula. It keeps its brightness when a UHC filter is inserted, while a nearby, similar magnitude star grows distinctly fainter.

To summarize, a nice, somewhat unexpected catch of new galaxies, along with a couple of failures, but among the latter, several that gave subtle hints that merit a revisit (perhaps starting earlier than I managed tonight, so they are higher in the sky).

Next episode: More Galaxies in Summer.

[KevUU]

"one of the more distant galaxies I have observed at 490 million light years"

This stuff still gets me. Say it out loud then give yourself a second to realise what it means. 490 million light-years! 1AU is 8 light-minutes ... dear god my head just exploded.

[michael.h.f.wilkinson]

"one of the more distant galaxies I have observed at 490 million light years"

This stuff still gets me. Say it out loud then give yourself a second to realise what it means. 490 million light-years! 1AU is 8 light-minutes ... dear god my head just exploded.

Precisely. The photons I spotted must have left the galaxy somewhere on the boundary of the Cambrian and Ordovician periods. It gets even worse with quasars. My most distant object is OJ at 3,500 million light years. The photons reaching your eyes today were emitted when the earth was less than a quarter of its current age.

[KevUU]

Precisely. The photons I spotted must have left the galaxy somewhere on the boundary of the Cambrian and Ordovician periods. It gets even worse with quasars. My most distant object is OJ at 3,500 million light years. The photons reaching your eyes today were emitted when the earth was less than a quarter of its current age.

BOOM! There goes my head again