July 26, 2017: A Stellar Night at the Dark Site

Sorry for the bad pun.  Ahem.  Well, actually sorry, not sorry.

This past Sunday night, Digby took me out to the Denver Astronomical Society’s dark site, about 60 miles east of town.  (I am still carless, but this will be remedied in just over two months when my Jeopardy money finally comes in!)  This had to be my first time out there in about 8 months or so, with clouds and/or snow messing up all the dark site weekends in between.  That’s a lotta missed observing opportunities!

The dark site weekend is scheduled each month for the “dark of the moon” – the weekend around when the new moon occurs, so that there is no light pollution from the moon, to make the dark skies truly as dark as possible.  But the dark site itself is open to members to go whenever they want – and as soon as I get my car (I’m looking at getting a used Honda CR-V, rated very highly by Consumer Reports), I’ll be out there a lot more often.

The skies were pretty dang dark on Sunday.  Stupendously dark.  Magnificently dark.  As I said, the skies were stellar.  As it was when I was there before, the Denver and Colorado Springs light domes were visible in the west and southwest respectively, and lit up some horizon-hugging clouds that seemed to hang out there for most of the night.  But again, the dome didn’t extend very far up the horizon – only about 15 degrees or so, and above that it was as dark as any other part of the sky.

The rest of the sky was really something – at times I couldn’t tell the difference between the high, thin clouds that passed over sometimes, and the Milky Way itself.  Nice!

The most important part of the summer sky is THE SOUTH.  The summer triangle is nice and all, but give me the south anyday of the week, and twice on Sundays.  The summer is my absolute favorite time to observe, because of what I like to call the Greater Sagittarius area = Sagittarius/Scorpius/Scutum.  Basically, the trail of the great southern part of the Milky Way.  There are so many Messiers packed in that one area of the sky that if you threw a rock, you’d hit one.  Plus, even beyond that, the Milky Way itself in that area is simply glorious.

Sagittarius is the greatest constellation (well, at least for my money) because the center of the Milky Way galaxy is right there – the brightly glowing central bulge at the core of the galaxy.  So even the Milky Way in the sky is at its brightest down there.

Early in the evening, as everyone was still settling into observing, the ISS made a fantastic appearance.  Screaming by for a full minute or more almost directly overhead, it was about the brightest I’ve ever seen anything other than the sun and moon – definitely brighter than the brightest I’ve seen Venus, for sure.

Speaking of planets, Jupiter and Saturn were up and beautiful early in the evening as dusk retreated into darkness.  Plus, as a nice bonus, the seeing was very steady – I took them to 193x with the 8mm Plossl without any problem.  Jupiter’s belts showed fine detail, and the Cassini Division was easy to split.  But the night was not about planetary observing.

A few of my favorite objects of all time are down Sagittarius way – M11, the Wild Duck Cluster; M22, one of the best globular clusters up there; M17, the Omega Nebula, also known as the Swan; and M6 and M7, known as the Butterfly and Ptolemy Clusters respectively, two large and bright open clusters.

M11, the Wild Duck Cluster.

If you’re thinking M11 looks a lot like a globular cluster, you’re right, and you’re also wrong.  M11 is simply a regular open cluster – but one with 2900 stars packed tightly together.  Globs will typically have tens of thousands or even hundreds of thousands of stars.  In even greater contrast with globs, M11 is “only” 250 million years old, while globs are about as old as the galaxy itself – billions of years.  But as you look at it through the scope, it sure looks like a beautiful glob indeed.

M22 is a stunning 5th magnitude glob, one of the brightest in the sky.  The reason why I like it so much is that even in my 5-inch Mak, I can see the granulation – individual stars – to a small extent.  I can’t really say that about too many globs.

M22.  Yeah, this one is actually a glob.

Then there’s the Omega or Swan Nebula.  It looks like an upside-down number 2, with a very long base to stand on.  But even in my little 5″ scope, the shape is unmistakable.

The Omega or Swan Nebula, M17.  The Swan shape is very prominent and easily visible.

M6 and M7 are highlights of observing the southern sky in summer.  These are two beautiful open clusters right near each other in Scorpius.

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M6, the Butterfly Cluster.
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M7, the Ptolemy Cluster

M6 really does show a butterfly-like shape, and M7 is huge, and showed itself well in the ST-80.

Even beyond observing through the scope, just sitting back in my camping chair and looking up was incredible.  I brought my binoculars, as always, and I just sat there from time-to-time during the night, scanning the Milky Way, up and down and all over.  As the night went on, it went from horizon to horizon, from Sagittarius, up through Aquila, on to Cygnus, and then down to Cassiopeia.  I could even see the split in the Milky Way up by Aquila and Scutum.

On the same observing pad as me was a new member, Jake (not from State Farm), who was using one of the club’s loaner scopes, an 8-inch dob.  It was a real pleasure helping him out and showing him things in the sky through my scope so that he could then try to find them manually with his.  I always find that when you help a beginner, you get to see the sky through their eyes – and it’s like seeing it all over again for the first time.

In addition to all the wonderful Messiers down south, (M4, M80, M16-25, M8, M10, M12, M14), and some old standards (M57, M13, M3, the Double Cluster late in the evening) I also tried for some new ones.  I was just able to see M107, a 9th magnitude globular in Ophiuchus.  It amazes me that Messier himself was able to pick it out with a less than perfect 4-inch refractor 250 years ago, but I guess when your entire existence is as a professional astronomer, you do tend to pick up on these things.  I also saw M9, another faint glob, magnitude 8.4, nearby.

And by see, I do just mean see, as opposed to observe.  M107 for one was just barely there in the Mak, on the edge of visibility.  I was only just able to see it by moving the scope slowly with the handset, and noticing the “cloud” moving across the field of view.  M9, being half a magnitude brighter, was easier to view directly.  However, I could make both of them out a little better in the ST-80 due to the fact that all of their brightness was compressed down into a much smaller area – as a result of the lower magnification.  I can’t wait until I get the C9.25 to be able to see more out of objects like these.

I also observed M23, an open cluster that I must have missed somehow in my southerly travels, and M24, the Sagittarius Star Cloud, both of them for the first time.  So that’s four new Messiers in one night!  My total is now an even 60.

I also turned towards the northwest and saw a few galaxies.  M81 and 82, of course, but also M106, M63 (Sunflower Galaxy), and M51 (Whirpool Galaxy).  There was nothing really remarkable about these; just one gray fuzz patch after another.  However, I was able to detect the two bright cores of the Whirlpool – which was pretty impressive!  Because M51 is face-on to us, with some more aperture, I think I’d be able to make out some of the spiral structure.

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This was pretty much my view of M51, but without being able to see the faint spiral structure you can make out in the photo.  (Credit: Kerry-Ann Lecky Hepburn)

Another DAS member, Zach, arrived late to the dark site and set up his 12″ dob for some real deep space action.  The Cat’s Eye Nebula, Caldwell 6, didn’t look anything like a Cat’s Eye, but it was a bright, round little ball.  The Dumbbell Nebula, M27 really looked like a dumbbell, or more to the point, an apple with two bites taken out of it on opposite sides.

Then, late in the night as Digby and I were packing up and leaving, Zach turned to Andromeda.  Andromeda’s two satellite galaxies, M32 and M110, were easily visible, as was the overall oval shape of M31.  Unlike how it looks in my scope, a gray smudge that overwhelms the entire field of view because it’s so much larger than it, in Zach’s 12-inch, there was definitely some definition to the edge.

Then Zach put his scope on NGC 7331, also known as Caldwell 30, a nice 10th magnitude spiral galaxy in Pegasus, which had risen in the east.  It was a cigar-shaped gray blob, like most galaxies.  But NGC 7331 wasn’t the point of the view.  Next to it was NGC 7335, one of a group of four 13-14th magnitude little specks of galaxies just nearby.

NGC 7331, at right, with what’s called the Deer Lick Group on the left:  NGCs 7535, 7536, 7537, and 7540.  7335 is the slightly larger elongated little spiral galaxy just above the center.

NGC 7331 is a spiral galaxy that is very similar to the Milky Way, about 40 million light years away.  But 7335, the brightest of the little group at magnitude 13.3, is much further than that – 330 m.l.y. away!  Wow!  This would be the oldest light I’d ever seen – if I could only see it.

However, we were looking at it right after me and Digby had just finished packing up.   Since there was nobody else left at the dark site but Zach, we used plenty of white light, and to search our observing pad for anything we might have dropped.  We had completely blown our dark adaptation.  Zach said we had to use averted vision, and possibly averted imagination, to be able to see 7335.  I wasn’t so sure if I actually saw it or not, so my record for oldest light ever seen will have to remain at 35 million years.  For now, anyway.

 

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