On Saturday night, June 20, once again a clear night, good friends, and a 30-inch telescope combined to make a memorable observing session. Astronomy Editor David J. Eicher and I had been at developer Gene Turner’s Rancho Hidalgo in Animas, New Mexico, for 2 nights already, but both had been cloudy. (See my blog about why.)
See more pictures from Dave and Michael's trip to Rancho Hidalgo.
Earlier in the day, Turner proclaimed, “Tonight will be clear.” As the hours passed, it became apparent he was right, and Dave and I literally quivered with anticipation. Each of us had compiled an observing list full of the faint, the little-known, and the obscure.
We started with many objects on Dave’s list. I urge you to read his blog for a more complete picture of what we saw.
One of the first picks from my list was NGC 6000. This is a magnitude 12.2 spiral galaxy that measures 1.9' by 1.6'. So far, that’s pretty unremarkable, but it holds the distinction as the only NGC galaxy in the constellation Scorpius. That, and the fact that I hadn’t seen it in 32 years, made me want to revisit it. This galaxy also is one astronomers label “highly obscured,” meaning its light passes through a great deal of the Milky Way’s gas and dust.
The lack of entries in Scorpius from the New General Catalogue lies in the fact that the constellation’s position is nearly atop our galaxy’s center. Dust and gas in this region heavily obscure distant galaxies, dimming their apparent brightnesses. You'll find other galaxies here to be sure, but their magnitudes place them below the NGC's threshold for inclusion.
After a few more nice views, I requested that Turner point his leviathan at Seyfert’s Sextet in Serpens. Most observers rate this group of six dim galaxies (magnitude 13.8 and fainter) as a difficult object to spot. Through an eyepiece that yielded 135x, we immediately saw four of the sextet. Higher-power eyepieces revealed the other two, but we noted the seeing (the measure of atmospheric steadiness) was not as good as it had been on any of our previous trips. This was understandable given the amount of moisture and clouds that had just rolled through the whole Southwest.
Although many of our targets were faint “challenge” objects, we chose some bright ones based on different criteria. Some had interesting shapes. Others exhibited nice color. Some were deep-sky pairs or even threesomes.
To view one noteworthy pair, Turner targeted open cluster NGC 6520. This magnitude 7.6 cluster was dazzling. And it seemed even brighter by comparison because one of the sky’s great dark nebulae sits just to its west-northwest — Barnard 86. True, you don’t need a 30-inch telescope to observe this pair, but everyone agreed that this was one of the night’s great spectacles. One unusual thing that I noticed is that B86 wasn’t truly dark. The 30-inch telescope has enough light grasp to show more than a half dozen ultra-faint stars strewn across the face of this dark nebula. Instead of being distracting, these dim, twinkling points of light added a nearly three-dimensional quality to the scene.
Next, I chose a planetary nebula that exhibits some color through smaller scopes. My hope was that the 30-inch reflector would make it bright enough to fire our eyes’ color receptors and, well, knock our socks off. My first glance at the Emerald Nebula (NGC 6572) in the constellation Ophiuchus confirmed my hopes. Here was a vivid green object an observer didn’t need averted vision to view. It also had such high surface brightness that we could magnify it to our hearts’ content. Unfortunately, it shows scant detail, but it’s the color here that matters.
One other legendary challenge object we viewed was the Hercules Galaxy Cluster (Abell 2151). This object has been my favorite deep-sky treat since I was in 7th grade. At that time, I purchased a 35mm slide of Abell 2151 from the Mount Wilson and Palomar observatories. I recall marveling at the number, shapes, and interactions of galaxies that one slide showed. Back when the 200-inch Hale reflector took that picture, astronomers exposed a glass photographic plate for 13 hours over a 4-night period. What it revealed was a cluster of about 100 galaxies lying 650 million light-years away.
As I climbed Turner’s observing ladder, I remembered that the night’s seeing was soft, and that thought dampened my expectations. No worries, though — I immediately saw two dozen galaxies, and I wasn’t done counting. All were faint and shimmering slightly. To me, the view looked like someone had strewn a handful of rice grains across a black velvet blanket.
Funny. After all these years, looking at the object I first saw on a black-and-white slide 42 years ago still gives me chills. After all the astronomy lectures I’ve given, after all I’ve written for the magazine, after all the observing I’ve done through every imaginable telescope, I’ve retained my awe for the Hercules Galaxy Cluster. Maybe it’s the vast distance or that, in one view, I’m seeing roughly 100 trillion stars. More likely, it’s the magical feeling most observers get when standing under a dark sky.
As luck would have it, Steve Cullen, President of LightBuckets, shot an image with the LightBuckets Rodeo, New Mexico All-Sky Camera Saturday night. Rodeo sits right next to Animas, and Cullen thought our readers would like to see what the region’s sky looks like.
LightBuckets’ all-sky camera is an SBIG STL11000 CCD camera with a fast fisheye lens. It takes 120-second images, which Cullen says is definitely overkill for an all-sky, but it works great. He continued, “On both Saturday and Sunday we were seeing a sky darkness around the theoretical maximum of 22 magnitudes per square arcsecond or a naked-eye limiting magnitude of about 6.6 (per our Sky Quality Meter).”