Double Bubble, Toil and Trouble (well, open clusters anyway) - Wednesday night's session

[FenlandPaul]

I'd been working in Bavaria for a few days and was coming back to an empty house as it was half term. Flying back, the captain said that conditions were very smooth and, on landing, there were clear skies from horizon to horizon. All this coincided with an almost new moon. An opportunity awaited!!

Setting up in the back garden at about 20.30, Venus had almost set but Jupiter was taking over the night shift, just clear of the house. Even so close to the roof line, the image was fairly stable and the main belts and polar zones stood out wonderfully against the intensely bright Jovian disc. Io was only a few arc seconds from the edge of the disc as it headed towards an eclipse. Whilst this was the best view I've had of Jupiter with my own equipment, I know I can get a lot more out of this scope with better collimation, but as a taster this was great.

Onto the main focus of the evening: spending some time exploring just on constellation using my new Interstellarum atlas. As it was high in the sky, I plumped for Gemini.

M35 (open cluster) was first. This winter favourite was an easy spot in the finder - what a joy to have a quality finder! It almost filled the field at x47 in the 32mm and it was at first tricky to make it out as a cluster rather than just a field of stars. It was noticeable, though, that there was an orange hue to many of the brighter stars, a marked contrast to, say, the Pleiades.

To tease out some structure I squinted so that just the brighter members showed through. I acknowledge the apparent insanity in forking out for a large aperture scope and then stopping it down to a tiddler by almost closing my eyes, but it seemed to work. From the darkness emerged two brighter chains of stars, rather like splayed legs, bowing away from each other to the ENE and not quite coming to a point in the W. The northerly chain is tighter and curves more abruptly, ending in a bright orange star (and another bright star at the other end). The southerly chain was longer and looser but with a greater number of bright stars, curving more gently than the other "leg".

A fainter third chain starts where the other two would meet if they were a bit longer and extends a short distance to the north. There's an irregular hexagonal concentration of mostly unresolved starlight between the two main splays, closer to the northern, tighter, curvier leg. Dark lanes seem to run through the cluster either side of this milky hexagon.

Very clearly at the edge of same field, and patiently vying for attention, is NGC2158, another open cluster. In the 32mm at x47, 2158 was a milky smudge, unresolvable with direct vision save for one bright star. There was maybe a slight mottling with averted vision, but nothing definite. Alongside M35 this is a wonderful sight, contrasting sharply with its resolved, structured and almost sprawling bigger neighbour.. They're a great visual pair.

Hiking up the power to x75 in the 20mm led to around 5 brighter stars becoming resolvable on the western flank and with averted vision maybe a dozen stars flickered in and out of view in the main body. The cloudiness seemed to resemble a funnel, with the pointy end at the south; it was certainly brighter and more expansive towards the north.

The funnel shape was more emphasised in the 12mm at x125, reminding me of Coma Berenices. A few more stars were resolvable with averted vision and the structure became noticeably more mottled. The bright star at the NE occasionally seemed detached from the main cluster.

Not far from M35 and NGC2158 is the neat but easily overlooked pairing of IC2157 and IC2156, both open clusters in Gemini. In the 20mm at x75 around 10 stars were visible with direct vision in 2157. 2156 is in the same field of view to the north, with maybe 7 stars seen directly. 2157 is larger, with 2156 maybe two-thirds of the size. Neither has much structure to discern. 2157 is almost contained by an irregular pentagon of stars, like a lop-sided house drawn by a child. Adding the 2x Barlow resolved 15-20 stars with direct vision in 2157 and up to 10 stars in 2156.

Getting more obscure now and Koposov 53, an open cluster also in Gemini. I've never come across this catalogue before and had no idea what the "Kp" prefix meant in the star atlas. Some subsequent half-baked research and I'm still none the wiser; all I can say is it's about 2 degrees north of M35.

Kp53 might have been a challenge to find as it seems very compact, but credit goes to Interstellarum for making it reasonably easy. The 9mm at x167 showed 4 or 5 stars with direct vision; I kept wondering if it was indeed a cluster or just a complex multiple star system. There was no real shape, but it was a tight little object with a light grey glow between the resolvable stars. Not a whole lot to look at, but I enjoyed the challenge of locating it.

Final Gemini object of the evening was NGC 2371-2, the Double Bubble Nebula, a planetary nebula. This was a straightforward hop from a trio of stars that formed the apex of a triangle pointing west from Castor and Pollux. I was excited about the fantastic name! In the 32mm at x47 it was a distinct smudge, not unlike the Dumbell at low power although not as bright. In the 12mm at x125 it was still reasonably bright and acquired an apple core or egg-timer shape, sitting in a pleasant star field. It was elongated SW-NE, with lobes appearing at either end. Moving up to x250 via the Barlow the lobes became more pronounced. The lobe at the NE seemed bigger, with a fainter, concentric outer edge. The SW lobe had a brighter, more concentrated centre.

By now I was getting cold and rather tired. I dabbled for a while looking for some fainter galaxies but I shouldn't have bothered - I wasn't really concentrating. But I did manage to get short look at M41 in Canis Major once it cleared my log store. This was a first for me and I can't believe I've not looked at it before; I think I had in my mind that anything south of Sirius was practically unobservable from the UK - what nonsense! I'll come back to the Little Beehive another day I think.

A most enjoyable evening. I can't praise the beautifully produced Interstellarum Field Edition highly enough; it might be pricey, but it's an outstanding companion that gave me the most satisfying night's observing I can remember. I genuinely think I will use it and cherish it for decades - it will be a very good investment in the long run. As will my new observing chair, which was a pleasure to use for anything lower than 50 degrees altitude (for everything else I was standing but not hunched for once!).

Clear skies all, and thanks for reading.

Paul.

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[cotterless45]

Lovely report , wish more folk would delve into clusters. There are some lovely ones out there. The bi lobed planetary is one of my favourites. The atlas sounds great.

Have you tried the wanderer NGC 2419 ?

Nick.

[FenlandPaul]

Have you tried the wanderer NGC 2419 ?

Nick.

Thanks Nick. I haven't tried 2419, but I'm hoping to work my way through as many Caldwells as I can this year so I'll make sure it's one of the first. Just looked a few pictures and it looks very nicely situated in its field. Lynx is one of those constellations that I've neglected over the years - a few doubles but very little else.

Paul

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[cotterless45]

This might be useful, old Nick's hopeful list

[Qualia]

Lovely report, Paul. The clusters around Canis Major are stunning, so I look forward to hearing what you think Your atlas sounds a great joy and if you're interested there's a nice review here.