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Observing Report: LCROSS impact watch

October 13, 2009

Well, as you may have heard, the LCROSS impacts were successful in that both the Centaur upper stage and the LCROSS probe itself both hit the crater Cabeus at crazy high velocity. No one knows yet whether they were successful at detecting water–it will take some time to pore over the data from the mission to figure that out. And visually they were a complete dud. No flash, no mini-mushroom cloud, no plume of debris extending up into space.

For me, the impact watch was anticlimactic, but in the best sense; given how much fun I had last Thursday night, the impact probably would have been an anticlimax even if we had seen a debris plume.

For one thing, we were in a dark spot. I live about a mile from the eastern edge of LA county, which means that I am out of the worst of the LA light dome but still in a metropolitan area. The light pollution is not impossible but it’s easy to show people the constellations because usually the dark stars are the only ones showing. I’ve never seen the Milky Way from my driveway, and I doubt I ever will (barring a massive blackout, which I secretly wouldn’t mind so much).

Fortunately it’s easy to get to better skies. There are mountains to the north and east and deserts across the mountains, and you can get to really seriously dark skies in an hour or two. Acceptably dark skies are even closer–we went up Mount Baldy, which is the closest big peak and only about 20 miles from the house. With a little elevation to put us above the smog and a nice ring of mountains to block out most of the local light pollution, the sky is amazing. We still had the big LA light dome off to the southwest, but that really only knocked out about an eighth of the sky for serious observing, and the rest was just grand. The Milky Way was obvious, and I spotted the Andromeda galaxy with the naked eye for the first time in my life.

We also had just the right equipment. My friend brought along his 16-inch dob. Now, you know that I am a small scope afficionado, but even I got aperture fever around that thing. Tough objects looked good and average objects looked amazing. I have heard people claim that M11, the Wild Duck cluster, is their favorite deep sky object, but I never understood why–until now. It’s a cliche to describe a nice cluster as looking like a handful of diamonds scattered on black velvet. In the 16-inch dob, M11 looked like an armored car full of diamonds blew up over an oil spill. We had a look at the Cat’s Eye Nebula, and while it didn’t look as good as it did in the 60-inch at Mt. Wilson, it still looked awfully nice.  The spiral structure was obvious, it was a gorgeous flourescent green, and the central star was blazing.

I also took along my 15×70 binoculars. These are fairly recent acquisition. I had lusted after a pair for more than a year after seeing the excellent reviews on Amazon, and my night of binocular stargazing in Utah finally pushed me over the edge. I’m thrilled with them–the 70mm objectives each grab as much light as a small telescope, and they’re just so darn trivial to use. If I’m having company over I usually mount them so I can give people a rock-steady view, but on my own I free-hand them as often as not. They’re quite a bit heavier than my 10x50s, but the extra weight is more than worth it. The other night I laid out on the hood of the car and did a head-to-head comparison, and I think my 10x50s are going to be pretty lonely from now on. The 15x70s hit the sweet spot between magnification and field of view–I can see things well enough to feel that I’m really experiencing them and not just noting them, but the FOV is expansive enough that it easy to find my way around the sky. So far, they are my favorite tool for finding objects and just generally learning the sky.

And that’s just here in town. Out on the mountain, the 15x70s were spectacular. I saw the Double Cluster better than I ever have in any instrument, ever. Andromeda was awesome. I was sweeping up globular clusters left and right. I even bagged the Triangulum galaxy, which I’d never found before; it is a huge object with a very low surface brightness, so ideally you want dark skies (check) and an instrument with a wide enough FOV to separate it out from the background sky (double check).

Now, it may seem crazy that I am gushing about a 16-inch dob one minute and a pair of binoculars the next. But they’re for different and complementary modes of stargazing. The big scope will show incredible detail on objects–globular clusters like M22 showed so many stars that I felt like I needed to look several times to see them all. But it’s still a telescope; you don’t just pick it up and scan the sky until you find something interesting. Binoculars will let you do just that. I probably observed about three dozen different celestial objects with the binoculars the other night. With my sky atlas spread out on the hood of the truck, a red flashlight*, and the 15x70s, I could look ’em up, hunt ’em down, and take ’em in not much longer than it takes to write. On the flip side, most of those three dozen things, pretty as they were, were still just fuzzy blobs in the binoculars. It takes the light-gathering and magnifying abilities of a telescope to really bring out the best in most objects–hence the dob. If you ask me (or lots of other folks), that’s the yin and yang of optimal observing: binoculars for widefield scanning and locating objects, and a telescope for drinking in the details. Not on separate nights but at the same time, going back and forth to whichever tool best suits the job or your mood.

* For preserving night vision. You can buy custom jobs, but the traditional method is to get a compact flashlight (I have a mini-Maglite) and paint over the window with red nail polish. Cheap, easy, durable, reversible.

We got done setting up about 8:30 and observed pretty hard for about four hours. In the early morning we slowed down, spent more time jawing, and even hopped in the cab of the truck for a couple of hours to stay warm. Back out at 4:00 AM  to get set for the 4:31 impact, and we kept on observing until about 5:00 before packing it all up and coming home. As observing runs go, it was my own Apollo 13–I got everything I wanted except the moon.

I’m a week and a half away from being done with teaching for the fall. That means more nights on the mountain, and more regular updates here. Stay tuned!

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One comment

  1. […] was getting up to Mount Baldy with a friend from the PVAA in the fall of 2009 to try to catch the impact of the LCROSS mission on the moon. We didn’t see the impact fireball–no one on Earth did, not directly, although the […]



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