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Moonlit observing

David Levi

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On 25th March I was observing in the Brecon Beacons 3 days short of the new moon. My main target for the night was the Leo triplet of galaxies M65, M66 and NGC3628. After a little bit of searching below the star Chertan all three galaxies were in the eyepiece at 59x magnification. I haven't been able to observe any galaxies from my back garden except Andromeda and so it was quite exciting and spectacular to see three in the same view. A week later on 2nd April I went back to the same site to take advantage of another rare clear night. This time the moon was only a day short of first quarter. I was surprised the effect it had on the seeing. I could no longer see NGC3628 and M65 and M66 were a lot fainter. This night I also found M95, M96 and M105 working my way up from rho Leo. Not an impressive sight but luckily, so as not to deter further views or searches, I now know that this is probably due to the moonlight. Those two sessions together have been a good learning experience for me.

Often after observing away from home I dread going out in my back garden for some disappointing light polluted views. However, once I get started I enjoy it almost as much as with darker skies. It's just that when you first look up into the sky with your own eyes there just aren't that many stars to see compared with a dark site.

Anyway, last night armed with a positive attitude I went out into my back garden for another observing session. The moon, just past first quarter, was bright but I didn't curse it. As the months have passed and with the lack of clear night opportunities there are plenty of objects that I have missed the chance to see this year. So I thought that first up I would try for a couple of objects low in the west, namely the open clusters M46 and M47 in the constellation Puppis. Tracking across from Sirius I could see that it would become easy to get lost on the way to the clusters as this area of sky is fairly evenly scattered with tens of easily visible stars in the finderscope. Moving slowly though and with careful consultation with Stellarium I came to M47 without too much trouble. A pleasing open cluster with a pretty red star KQ Pup on it's outskirts. Moving across then to M46 once again you have to be careful not to miss it in the finderscope because although it's not far to the east of M47, it's a lot fainter. However, giving this cluster a bit more magnification 125x proved rewarding. A delicate and pretty cluster. Just south of M46, 140 Pup is another obviously red star. While I was in that part of the sky I decided to observe M48 as well. Starting at squiggle Monoceros, oops I mean zeta Monoceros, and then moving west to find a small collection of stars around C Hydra, M48 was quite easy to find working my way south west from C Hydra. Nothing startling about this open cluster with the stars quite spread.

While all this was going on I had Jupiter rising off to the east. Swinging the scope across to the gas giant revealed that the seeing conditions were very good. I could make out both north and south tropical belts and polar regions. My first time to do this. All four Galilean moons were spread out to the right hand side of the planet as seen in my eyepiece. Io was quite close to the planet and I discovered from Stellarium that it was about to transit the planet. I then spent the next two and a half hours (on and off of course) watching a small black dot move across the face of the planet. It was moving across an area somewhere between the north equatorial and tropical belts. While this was happening I popped up to the constellation Coma Berenices for a view of the globular cluster M53. Not far from alpha Berenices it's not hard to find. However, I was unable to make out any individual stars in the cluster. It was a dense patch of hazy light thinning out away from the centre. Not far away again is the gobular cluster NGC5053. I could not see it. Maybe the light pollution and moon put it out of the capability of my telescope on this particular night and from this particular location. I then observed the globular cluster M5 in the constellation Serpens. Starting at alpha Serpens (Unukalhai) and moving towards the right leg of Virgo an obvious pattern of stars (put your own shape here) including 4 and 6 Serpens gave away it's location. Quite an impressive globular cluster with many individual stars to be discerned. Very pleasing on the eye. I'll be going back to this one at the earliest opportunity when there is no moon. Finally the shadow of Io reached the western limb of Jupiter and slid into the darkness magically flipping from black to white. A pimple on the surface of Jupiter at first and then freedom.

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1 minute ago, David Levi said:

@wookie1965 there's certainly a lot of pleasure to be had observing doubles and clusters. They're not just a poor substitute if your skies don't permit galaxy and nebula viewing.

Yes I was forever having bad nights then went to a star party met my friend (Cotterless45) he said go for doubles and clusters, came home and the amount i have seen renewed my love of this hobby.

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14 hours ago, David Levi said:

Not far away again is the gobular cluster NGC5053. I could not see it. Maybe the light pollution and moon put it out of the capability of my telescope on this particular night and from this particular location. 

Although the magnitude of NGC 5053 is often given as around 9, this is very deceiving. 5053 is a very loose, open globular cluster, with a class of XI, where I is the most concentrated and XII is the least. The concentration of a globular cluster is more important than its magnitude. A couple of the Palomar globulars are around mag 10, and should be easily visible, but they are very loose, so extremely hard to see.

I have seen 5053 through my 12", just once. I had tried to see it before and failed. My notes say 'Quite large but very dim. A ghostly grey patch, not noticeably brighter in the middle. Three stars were seen clearly enough to plot, though others were glimpsed or suspected.'

It's a very difficult object, and with the combination of natural and artificial light pollution that you had, you'd have had no chance, so don't despair over that one!

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  • 2 weeks later...
On 04/05/2017 at 11:06, David Levi said:

right leg of Virgo an obvious pattern of stars (put your own shape here) including 4 and 6 Serpens gave away it's location

Nice! I also do the same mental tracking. In my mind the pattern is a horse.

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