September 8, 2016: The DAS Dark Site and Messiers galore!

WHOOOOOOOOOOA!!!  This past Saturday, Digby, the DAS new member coordinator, drove me out to the DAS Edmund G. Kline Dark Site located near Deer Trail, CO, about 60 miles east of downtown Denver.  This is a well-equipped site, with fourteen concrete observing pads, each with access to electricity, and half of them with the ability to assemble pre-made windscreens to block the prevailing winds on the plains from the south.  It also has a warming hut and an outhouse, both of which are going to prove extremely handy as I plan to continue to travel out there as the weather gets colder.  Finally, there is a C14 onsite, enclosed in its own observing dome.

There are a bunch of reasons that I came out to Denver from Manhattan.  Having a dark sky observing location that is easily accessible from where I would be living was definitely one of them.  We reached the Site in about an hour or so.  That same amount of driving from Manhattan would barely get me to a dark orange site – big whoop.  The DAS Dark Site is located in a dark blue light pollution zone, easily the darkest skies I’ve ever seen.  Even with that, the light domes from Denver off to the west, and even from Colorado Springs towards the southwest, were clearly visible.  The Denver light dome rose a good 20 degrees into the western sky, but even so, it wasn’t that bad.  More importantly, I don’t care much about observing in the west; because all the good stuff is always either rising in the east or in the south.

We arrived while it was still very much light out.  It had been mostly cloudy all day, and there was a brief but violently windy rainstorm shortly after we arrived, but the forecast was for clearing skies as the night progressed.  As we waited for dark, I received an orientation from the Dark Site coordinator, Darrell, which would permit me to use the Dark Site whenever I wanted.  Oooh, baby!

The sun set around 7:30, and after an attack of killer mosquitoes from the nearby swamp (gotta remember the Off! for next time!), darkness crept in.  It was still very cloudy, but the sky continued to delight as the thunderstorms put on a continuous lightning show all night as the storms moved east toward Kansas.  Some sucker holes started appearing, first in the south around Antares and then to the north around the Big Dipper.  I got a quick glance at Mars and Saturn, and then went for M4, a giant and bright globular just over a degree away from Antares.

M4 had been a particular bugaboo of mine.  After all, at 6th magnitude, it’s plenty bright; at 26 minutes across, it’s almost as large as the full moon, and it’s so close to Antares, how could you ever miss it?  But that 6th magnitude is its integrated brightness, as if that brightness had squeezed down into an area the size of a single point light source – a star. That large size means that it has only very limited surface brightness. In New York, it is completely washed out by the light pollution.

But the famous M13 is about the same magnitude and 16 minutes across – why would that be so easily visible, while M4 is not?  I can only surmise that it’s due to three factors.  While the difference between 26 minutes and 16 minutes doesn’t sound like a whole lot, it is: M4 is about 264 percent larger than M13.  That alone accounts for much of the loss of surface brightness.  Additionally, the big differences in elevation over the horizon account for some brightness extinction as well, as M4’s light is coming through a lot more atmosphere than M13.  Finally, it would seem that there are globulars and there are globulars, and some globs (like M13) are more densely packed than others (like M4).  Concentrating most of the light into a tight core makes a big difference as well.  As a result, M4 is simply not as nice of a glob as others.

I moved on from the south to the north and all the galaxies in the Ursa Major area.  I had never been one much for galaxies in New York, mostly because I couldn’t hardly ever see any.  However, I figured my scope’s limiting magnitude would be at least mid-11th magnitude, if not deeper, as opposed to its usual 9.5 magnitude in Manhattan, and that I should give some galaxies a go.

I think I passed right by 11th magnitude and was somewhere close to my scope’s theoretical limit in the 12th.  M81 and M82 were glorious in the same field.  The differences in aspect between them was readily apparent.  Even through my modest 5-inch scope, M82 looked very much like the cigar it’s named after.  Monica Lewinsky would have been, um, pleased. I bounced all around that area of the sky, seeing M64, M106, M94, M63.  I also saw M51, the Whirlpool Galaxy, and M101, the Pinwheel Galaxy, but neither looked much like their nicknames.  None of the other galaxies even approached the detail I was seeing when I went back to M81 and 82.  While the others were just faint gray fuzzies, this pair was clearly a pair of galaxies.

All night long, I only used two eyepieces – my 32mm Plossl at 48x, and my 12.5mm Ortho at 123x.  I used the Ortho because it’s the sharpest EP I own.  But that Ortho has an AFOV of only about 42 degrees and doesn’t really place the DSO in the context of its surroundings.  As I don’t care for the views through my 15mm Luminos very much – 82 degrees is just too wide for me – perhaps I should get some other widefield eyepiece around the 12-13mm mark.  Yet another object on my “things to buy” list.

As the skies cleared more and more, Sagittarius finally came into view.  Wow!  Wowee wow wow wow!  This was the reason why I was here, and I was not disappointed.  The center of the galaxy is located down that way, and the Milky Way is at its densest and most beautiful there.  I saw just about everything in Sagittarius, and it was like seeing it all again for the first time.  Not only was I viewing everything at 48x with my Mak, but I was also viewing everything through the ST-80 at 16x and 3 1/4 degrees as the scope slewed from one object to the next.  In fact, just looking through the ST-80 all over the Milky Way was one of the highlights of the night.

M22 was ridiculous.  While I was panning between two other objects, I saw it passing by as this ginormous globular through the ST-80 first, and I had to stop whatever it was I was looking for to go immediately to it.  It was huge.  Granulated stars.  M17, the Omega Nebula, also known as the Swan Nebula, was also amazing.  I could see the swan shape – the upside-down “number two” – very clearly.  The dark lane was readily apparent in M8, the very bright Lagoon Nebula, but I could only just make out the dark lanes in the neighboring Trifid Nebula, M20.

I observed M11, the Wild Duck Cluster, through the scopes of a couple of guys observing near me, Leo, with his 12-inch Orion dob, and Fred, with his 11-inch Celestron SCT.  It was simply insane.  This was an open cluster that looked like a glob; it was that packed together, huge and bright.  It looks like I’m going to have to get over my collimation-phobia right quick and get me a 12-inch dob!  Okay, that won’t happen for a while yet, but hot damn!  I want aperture and I want it now.  I want it yesterday.  Yeah, not for a while.

M6 and M7 were glorious as well.  (Yeah, I know they’re in Scorpio, but I consider them part of Greater Sagitarrius.)  M7 was very easily naked eye, standing out even in the middle of the brilliant Milky Way arcing from horizon to horizon.  Both of them looked just sensational in the widefield ST-80.  And M6’s butterfly shape was very easy to see.

After fully touring the southern skies, I moved on to some of the old regulars – M13, M92, M57.  All were amazeballs.  As usual, M92 looked better than M13 because of the way it’s packed – it may be a bit dimmer than M13, but M92 is denser.  I even took a gander at M56, the little glob in little Lyra which I had never seen before.  As long as I was there, I swung over to the double-double, Epsilon Lyrae.  At 123x, one pair was just split; the other was elongated.

A little later, I moved onto the eastern sky, and went for M31.  It was stunning in the ST-80, stretching almost from side-to-side.  Beyond the bright core, I could clearly see a galactic shape.  And I finally saw the two satellite galaxies, M32 and M110.  M33, the Triangulum Galaxy was kind of a washout, though.  The Double Cluster was obviously a little more full of stars than usual, but didn’t look all that different from how I normally see it under LP.

As  we passed midnight, the Pleiades started rising significantly above the eastern horizon.  Of course, they looked nice through the ST-80.  But I had never seen any of the lovely nebulosity you see in all the pictures.  You know, this:

m45-pleiades

I tried to see the Merope nebula, the most prominent part of the nebulosity, first in the ST-80, and then in the Mak, when the Pleiades were about 20 degrees above the horizon, and no dice.  Then I got Fred to swing his big beast of an SCT over to the gals.  We were sure we were seeing some sort of faint bluish glow around Merope that we weren’t seeing around the other stars.

But we didn’t see the nebula at all.  We had fooled ourselves.  I thought Merope was at the bottom of the dipper furthest away from the handle; it’s the bottom star closest in to the handle.  We were seeing a “nebula” around Electra, where there pretty much ain’t none.

Of course, I asked the sages at Cloudy Nights about this.  It seems you need three things:  1) dark skies, 2) good dark adaptation, and 3) having the Pleiades at a high elevation.  Well, we definitely had the first one in spades.  But maybe at 20 degrees elevation, we didn’t have the last of the three.  And, come to think of it, maybe we didn’t have the second one, either:  that thunderstorm that had quickly moved on east towards Kansas put on a nice show all night long, as there was a constant lightning storm flailing away, getting lower and lower on the eastern horizon as it moved further and further away.  Even at midnight, it was still flashing away, just a couple of degrees above the eastern horizon, while we were trying to look at the nebula.  It didn’t effect the rest of the sky, though.

Is it possible that this “lack” of dark adaptation combined with the low elevation prevented us from seeing the nebula?  I would have thought that dark blue skies and 11 inches of aperture would certainly have been enough.  However, the answer appears to be all of the above, and that the nebula could be mistaken for dew on the scope.  After midnight, what had been a dry, clear night became filled with humidity and dew.  Fred’s scope had dewed over, and he was wiping off the corrector plate with a large piece of silk he had.

In total, I saw a baker’s dozen of new objects that night:  M4, M82, M101, M64, M63, M72, M51, M69, M70, M54, M32, M110, M56.  It was an astounding night.  I can’t wait to go back!

 

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