Archive for February, 2016


Observing report: Dark nights at Anza-Borrego Desert State Park

February 18, 2016

Anza-Borrego Nov 2014 6 - crescent moon

Back in November, 2014, London and I visited the Palomar observatory and then went camping at Anza-Borrego Desert State Park. At the end of my Palomar post, I teased, “Next up: crazy-dark skies at Anza-Borrego. Stay tuned.”

Obviously, that never happened. I find that with my observing reports, I need to get them done and out quickly or they never happen.

I was back at ABDSP this past weekend and I got in some very enjoyable stargazing, so now I’m going to try to kill two birds with one stone.

Anza-Borrego Nov 2014 1 - camp Wedel

When London and I stayed there together back in 2014, we camped at the Palm Canyon campground, which is basically the headquarters campground of the park. It’s a nice developed campground down on the desert floor, right next to the town of Borrego Springs. The state park is a pretty isolated patch of SoCal, in terms of light pollution, and Borrego Springs is the only International Dark Sky Community in California. There are no stoplights in town (there is one roundabout, and enough stop signs), and all of the businesses use low (but sufficient!) outdoor lighting, and mostly turn the lights off when they’re not needed. As a result, I can see more stars in town in Borrego Springs than I can in some rural areas elsewhere. Happily, the locals are aware of how much of a draw the dark skies are, and they actively promote Borrego Springs as a place to come stargaze (for example).

So the skies are pretty dark even in town, and once you get outside of the town they get very dark. One of the highlights of the November 2014 trip for me was getting my first really good look at NGC 2371 and 2372, two halves of a planetary nebula in northern Gemini. Always before the nebula had just looked like a dim blob, but that night I could see both halves very clearly as separate arcs of nebulosity.

Anza-Borrego Nov 2014 4 - finder

London was rolling that night with his XT4.5, which he’d just gotten a couple of weeks earlier for his 10th birthday. In the gift shop at Palomar he spent some of his birthday money to get a planisphere and a constellation guide. At the campground he drove his scope by himself, and found Andromeda, the Double Cluster, the Pleiades, and Orion without any help from me. It was a milestone observing session for him.

I spent a lot of time in Orion that night myself. Orion always looks pretty good – the total object – but under very dark skies it looks amazing. There was so much detail in the nebula, swirls and knots of gas and fine gradations in the sheets of light that you just don’t see in even minimally light-polluted skies. I got a special treat around midnight – I saw a satellite drifting through the field of view as I nudged the scope along to follow the nebula.

To be visible that long after dark, a satellite has to be far enough above Earth to not fall into the planet’s shadow, so I knew right away that this was a geosynchronous satellite. I stopped pushing the scope and sure enough, the satellite just sat there, rock solid, while the nebula and starfield drifted past. I’d seen exactly one of these before – Steve Coe had shown one to Darrell Spencer and me at my first All-Arizona Star Party back in 2010 – but this was my first time catching one on my own. What’s particularly cool about geosynchronous satellites is that you don’t have to do anything to track them. Just leave your scope pointed in the same place and they’ll be visible until you decide to look at something else. So you can swap eyepieces without worrying about losing the object, you can take a break to get a snack and go to the bathroom – I did all of these things – and when you come back, the satellite will still be there, serenely sitting as Earth’s rotation carries the background stars past in an endless parade.


I was back at Anza-Borrego this past weekend for the Western Association of Vertebrate Paleontologists annual meeting. It was a one-day regional conference held on Saturday, February 13. I gave a talk and I wanted to look presentable, so instead of camping the night before I got a hotel room. But I planned to camp Saturday night, after the conference – there was a banquet after the meeting and I didn’t want to drive home in the middle of the night. Especially if by staying out I could get in some good dark-sky time.

I had originally planned to drive around to one of the Salton Sea campgrounds – Borrego Springs is on the western side of the sea. I preferred to stay in the state park, as it’s 600 feet above sea level instead of 200 feet below, like the seashore campgrounds, and those 800 feet mean thinner air, less humidity, and darker skies. But I figured that with the holiday weekend all of the campsites would be taken.

I was wrong! In the State Park visitor center – which is awesome and has some cool fossils from the park on display – I learned that the many undeveloped campgrounds in the park do not require reservations and that not all of them were likely to fill up. In particular, the ranger recommended Culp Valley Campground, which is about 8 miles west of Borrego Springs and at an elevation of 3000 feet. I drove up Friday night after dinner to hike it out and do a quick binocular tour of the winter best and brightest. One of the fun spin-off benefits of having written the Canis Major and Puppis binocular tour for the December Sky & Telescope is that now I am compelled to run through those objects anytime I am out observing. It only takes a couple of minutes if I’m in a hurry and it’s always rewarding.

The conference on Saturday was great, my talk went well and I had a great time talking to colleagues old and new. After the banquet I drove up to Culp Valley, found a spot, and got settled in. My plan was to go right to bed and get up in the morning for dawn patrol, but – predictably – I was not able to pass up another quick turn around the sky, which evolved into half an hour of fun binocular observing. I did manage to get up at 4:30 for another productive half-hour run. The sky was so dark that I when I got up off my cot and looked to the east, I saw a bright cloud and said to myself, “What the heck is that?” It was the Scutum Star Cloud, and in binoculars it glittered with hundreds of barely resolved stars and the combined glow of thousands more. It wasn’t even that far above the horizon – I can’t wait to see what it looks like from there this summer, when it’s riding high in the south.


Did I mention that all of the undeveloped campgrounds in Anza-Borrego Desert State Park are free to camp in? You don’t need a park pass or a day use fee or anything. Totally, completely, free. I had to have the ranger explain it to me twice. I have nothing against supporting our state and national parks – quite the contrary – I’m just not used to having any of them be free. That said, if you go stay at one I encourage you to stop by the park visitor center and leave a few bucks in the donation box – even undeveloped campgrounds require some upkeep.


We’ve been through this Pluto thing before

February 17, 2016

Pluto and other former planets

Mike Taylor sent me a link to this post on Quora about why Pluto should still be called a planet. Here’s the response I sent back after reading that piece, only lightly edited and with some links added:

I am unmoved. If we go back to the classical definition of planets as “wanderers” then there are 7: the sun, moon, Mercury, Venus, Mars, Jupiter, and Saturn. Clearly we have the ability to redefine the term from “naked-eye visible objects that move against the background stars as seen from Earth” to “big round things that orbit the sun”.

As for the idea that Pluto was a planet for 70-odd years before being demoted, so what? Ceres and Vesta were planets for half a century, and Juno and Vesta were planets for more than 40 years. Eventually people decided that it was unworkable to classify everything in the rocky belt between Mars and Jupiter as a planet – asteroids are a different class of objects, and referring to them as planets conflates two very different phenomena. Recently many people – an acting majority – have decided that it is equally unworkable to classify everything in the icy belt beyond Neptune as a planet, for the same reason. Kuiper Belt objects are a fundamentally different kind of thing from either the rocky planets or the gas giants. We’ve been through all of this before. We can have 8 planets, or hundreds.

Finally, I am completely opposed to this essentialist idea that terms have to keep their meaning forever and aren’t available for revision as we learn more. I think it’s a harmful doctrine, not least because it’s strongly at odds with the reality of how people actually use language – in science, and in all other areas of life.

That said, thanks for the link. I haven’t seen the pro-Pluto argument couched quite that way before. I disagree with almost all of it, but it’s still useful to know that people think that way.

To which Mike replied:

I’d agree with pretty much all of that, for what it’s worth. I thought it was interesting to see the strongest case made for Pluto’s planetary status by someone with a stake and some expertise, and then to see how far short of being persuasive that was.

What do you think?