Archive for September, 2010

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Stargazer’s bookshelf: Nightwatch

September 30, 2010

NightWatch: A Practical Guide to Viewing the Universe
by Terence Dickinson

If ever there was a book to buy before you buy anything else, this is it.

It covers pretty much everything: not just types of telescopes, but what kinds specifically are good for different purposes, and which to consider as good first telescopes. And setting up a telescope, if it’s the day after Christmas and you or a young relative are looking at a new telescope and feeling lost. And not just telescopes, but also binoculars for stargazing, and naked eye observing. And plenty of observing basics, like what makes a good observing site, whether it’s in your driveway or on the other end of an airplane ride, what to take out with you when you observe, and lots of the tips and tricks for seeing more while you’re observing. Also, sections not just on where and how to observe, but also what to observe, from atmospheric phenomena to meteor showers, the sun and moon, planets, comets, and other solar system targets, to deep sky objects like nebulae, star clusters, and galaxies.

This is going to be one of those “and…and…and” reviews because the book does so much. There are seasonal all-sky maps that show the bright stars so you can learn your way around the sky and quickly get your bearings. Better still, there are twenty or so maps of selected regions of the sky showing prominent constellations, bright stars, and the best and brightest deep sky objects. The book was designed to be used in the field–it’s spiral-bound to lay flat in your lap or some other surface, hardbound for durability and to make a smooth and stable platform for the maps, and the maps are clean and uncluttered and easy to read with a red flashlight.

One of my most memorable nights of stargazing was back in the fall of 2007, when I was just getting started. I spent the whole evening in a lawn chair in my back yard, with this book in my lap and my binoculars around my neck, surfing my way through almost the entire sky. If you think “spiral bound” and instantly picture bent wires and torn pages, fear not: the spiral is enclosed in the hard binding and it’s very sturdy, and the paper is thick, glossy, and durable. My copy is still like new despite three years of regular use, both by me and by all the folks to whom I’ve loaned it.

I don’t know when the first edition of Nightwatch came out, but the current edition is the fourth, published in 2006, and it includes tables for planetary positions, meteor showers, and so on through 2018. Even after 2018, I’m sure I’ll keep coming back to this book to look into little nooks and crannies of the hobby that I haven’t explored yet (observing aurorae, perhaps, or building a barn-door tracking mount for astrophotography), and simply for the joy of reading Terence Dickinson’s prose. There are books that are easy to read, and then there are books that are so easy to read that the pages just fly by, and afterward you know a lot more but hardly remember how all the information got into your head. This is one of the latter. It’s also copiously illustrated with full-color photos, so it’s an attractive book to simply flip through.

Nightwatch has a sort of “big brother”, which is The Backyard Astronomers Guide, by Terence Dickinson and Alan Dyer. If Nightwatch is a working lunch, The Backyard Astronomer’s Guide is a seven course meal with brandy and cigars afterward. It covers all the same stuff as Nightwatch and then some, and covers everything in a lot more detail, going into things like what specific brands and models of telescopes the authors prefer (and between them, they’ve used about everything). All the extra material comes at a price, literally and figuratively: The Backyard Astronomer’s Guide is about twice as thick as Nightwatch, weighs about twice as much, and costs about twice as much. It’s too thick to be effectively spiral bound–it has a very high quality sewn binding–and too clunky to take in the field, so it includes no observing charts. On the other hand, it has an extremely useful supplementary website with a blog. If you’re already planning to get a separate star atlas or observing guide, and you want encyclopedic coverage, and you don’t mind paying more, get The Backyard Astronomer’s Guide. But if you’re just getting into amateur astronomy, or if you just got your first telescope and you’re thinking, “Now what?”, and you’re looking for a good all-around introduction to stargazing, get Nightwatch.

Pros:

  • very broad introduction to amateur astronomy, covers almost everything you really need
  • includes sections on just about every conceivable type of observing
  • all-sky charts and maps of selected regions are very intuitive
  • spiral bound to lay flat in the field, and tough enough to be used that way
  • high production quality, with nice paper and lots of color photos, but plenty of meat as well
  • updated regularly

Cons:

  • Covers almost everything adequately enough for beginners, but almost everything is covered in more depth somewhere else. That’s not really a con, more like an inevitable trade-off. No book can be a good introduction AND a exhaustively thorough at the same time, not and remain inexpensive and approachable (although The Backyard Astronomer’s Guide comes close, and fails mainly in being the heaviest and most expensive astronomy book on my shelf).
  • Sky maps don’t show many stars, which can make it tough to get to some of the objects. As a field resource, most people who stay in the hobby will outgrow it fairly quickly. But the maps are only a small portion of the book, and the rest of the material will be interesting and useful indefinitely.

Recommended? Heck yes. Enough to make it my first loaner to people who are thinking about getting into astronomy (unless it’s already loaned out, in which case I fall back on The Backyard Astronomer’s Guide), and enough that if anything ever happens to my copy, I’ll replace it in a heartbeat.

If you’re getting started in astronomy, or thinking about getting started in astronomy, and you only get one book, this is the one. The list price is $35, but you can usually get it for $25 or less at Amazon. Here are the product links again:

NightWatch: A Practical Guide to Viewing the Universe
The Backyard Astronomer’s Guide

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Notes from the underground

September 25, 2010

This is my teaching time of year, and between that and attending a conference in England the week before last, I have had precious little time for observing. But I did get out this week for half an hour to take some pictures of the full moon. Not nearly as detailed and sharp as some of the others I’ve taken in the past, but most of those were taken with 6-10″ scopes, and this was taken with my 2″ SV50.

Now that moon is on the wane, every night will be better and better for observing comet Harley 2, which is cruising through Cassiopeia right now. S&T has a nice page with info on the comet and finder charts. I haven’t looked for it yet, but it’s on my to-do list.

Finally, the fourth installment in my series on the world’s largest telescopes appeared in this month’s PVAA newsletter. This link will be good for the next three months, after which it will be available on the Nightwatch archive site.

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Observing Report: Saturday night at Owl Canyon

September 6, 2010

Owl Canyon Campground is a few miles north of Barstow, in the Mojave Desert on BLM land. There are picnic tables, shelters, fire pits, and restrooms but no running water, and if you spend the night you’re supposed to leave your camping fee–all of six bucks–in a metal can on a post near the entrance. It’s almost exactly 90 miles from my house, on the other side of the San Gabriel Mountains. Although the Dark  Sky Finder puts the campground on the border between the green and blue zones, to my light-pollution-conditioned eyes, it is pretty darned dark out there. I was there observing from a little before 9:00 PM Saturday night until about 5:00 AM Sunday morning.

I set up my 10″ scope and took a quick turn around the sky, hitting the best and brightest clusters, nebulae, and galaxies. M51, the Whirlpool Galaxy, showed spiral structure. I saw not one but two dark lanes in M31, the Andromeda Galaxy. M27, the Dumbbell Nebula, looked more like a football wearing a bowtie, so extended was the nebulosity.

I had seen some of these things before, in larger telescopes, but they were all first-time observations for me, using my own telescope. And the night was just beginning.

Taking a break from the telescope, I pulled out my 15×70 binoculars just to see what I could see. And what I could see was incredible. The Milky Way was a wide, detailed arch of pale light stretching across the sky, so rich that I found star clusters and nebulae far faster than I could log or identify or even count them. I saw the North American Nebula, which really does look strikingly like North America, for the first time. Buoyed by that success, I went after the Veil Nebula, a double arc of wispy light expanding out from an ancient supernova. It was there, not bright, but unmistakably present. Later, using the telescope, I saw in the Veil the riffles of detail that I had previously seen only in long-exposure astrophotos.

I didn’t see all this at once, of course. After about 5 minutes of cruising the sky with binoculars, I realized that I was going to need a more extended, more comfortable look. I put a blanket and pillow on an empty picnic table, stretched supine, and spent the next two hours just looking up in wonder, much of the time with my naked eyes alone.

Lying up on the picnic table, my immediate surroundings were out of even my peripheral vision. The dome of the sky came down on all sides to the mountains, bluffs, and buttes that ring the campground on all sides. I was, therefore, alone beneath the cosmos, on a rocky world of my own.

There are about two dozen campsites at Owl Canyon. Saturday night, only three others were occupied, and none of them were close to me. But as usual when observing at a public campground, after setting up I had walked to the two inhabited sites I could conveniently reach (the third was across a minor canyon) and let the people there know that I had set up a telescope and that they were welcome, but certainly not obligated, to drop by for some stargazing. For the first time ever, I got no takers.

To be out there in that fantastic place, seeing such spectacularly evocative and beautiful things, and to have no one with whom to share them, was almost unbearable. I felt embarrassingly wealthy, like someone devouring a feast while his neighbors on either side go hungry.

About midnight I got down off the table, went back to the scope, and started on my planned observing program. Whether this reflects dedication, more focused curiosity, or a species of retreat from the terrible immensity which I had recently been contemplating, even I am not sure. You are welcome to perform the experiment yourself and report back. In fact, I strongly recommend it.

At some point I knocked off to take some photos of Jupiter, which by the early morning hours was almost halfway across the sky and the brightest single source of light I could see. I got some pictures, but the Great Red Spot was not in evidence. Fortunately Jupiter rotates quickly, once every 9 hours, so I had a feeling that I would catch the spot if only I was patient. I went back to the deep sky.

About 4:00 AM I was working the northern sky when I saw a most arresting site: an immense pale dome rising like a puffball mushroom behind a mountain to the east. This was of course the moon, but I had never before watched the waning crescent moon rise, and certainly not from a site as dark as this. The waning crescent moon leads the sun; the illuminated part is of course sun-wards, so the “dark” part is to the west and rises first. And this is what I saw coming up over the mountain: not the thin sliver of the moon illuminated by the sun, but the rest of the disc lit only by Earthshine. By the time I got the scope pointed in the right direction and the camera properly set, the bright “horns” of the sunlit moon were over the horizon, but the summit of the mountain still took a bite out of the disc.

By this point I had been awake for almost 20 hours and observing for more than 7, and I was starting to wind down. But I went back to Jupiter for one last look, and sure enough, the Great Red Spot was there. And above the GRS was a little black BB: the shadow of a moon crossing the face of the King of Planets. The visible moons from left to right in this shot are Europa, Ganymede, and Callisto. Io is invisible in front of Jupiter, at least through my telescope, but it is the one casting the shadow.

After Jupiter I crawled into the car, slept for 3 hours, and then drove into Barstow to the hotel where Vicki  and London were staying. The next night I drove them a couple of miles out of town and showed them the Milky Way. And now… now all I want is for the next few weeks to pass quickly, and for the next dark of the moon to find me once again in the desert, under beautifully dark skies, staring up in wonder.

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The unrestrained Jupiter worship has got to stop

September 3, 2010

In a comment on the recent Jupiter impact post, Mike asked,

Uh. If this [i.e., big things slamming into Jupiter] is happening to Jupiter three times in thirteen months, what does that tell us about the odds of it happening to us?

The answer is that Jupiter giveth, and Jupiter taketh away.

In my experience, about 99% of the popular sources out there only mention the second, positive part: Jupiter is the solar system’s vacuum cleaner, hoovering up tons of wayward comets and other “small bodies” (all the way down to mere dinosaur killers) that would otherwise bomb us back into the Paleocene. The spate of recent impacts would tend to confirm that. Three cheers for Jupiter! Our hero! Let’s have a ticker tape parade!

Barf.

Can we all take the Jupiter worship down a couple thousand percent? Because that ain’t the whole simple story. Jupiter also giveth, and what it giveth, we don’t wanteth.

Ever wonder why there are so many Earth-crossing asteroids?  I mean, the solar system has been here for close to 5 billion years. Shouldn’t the space rocks have hit something or gotten shot out of the system by now? In fact, the vast majority of them have. Earth-crossing asteroids have orbits that are stable on multi-million year timescales… which means that on the multi-billion year timescale of the solar system, they should be history. But they’re not, because new ones keep migrating in from the asteroid belt all the time, to replenish the ones that either get flung elsewhere or (gulp) hit us. And why do new asteroids keep coming in from the belt? Because of orbital resonances with stinkin’ Jupiter. That big bully keeps throwing rocks at us!

Now, it’s true that most near-Earth asteroids are destined to either spiral on it toward the Sun or get flung out of the inner solar system, and that only a very small fraction actually hit the Earth. And it’s also true that Jupiter sucks up a lot of comets and asteroids that might otherwise come in and hit us, and that the occasional impact damage from Earth-crossing asteroids is probably preferable to getting creamed by an unfettered rain of comets barreling in from the outer solar system. So on the balance, we’re better off with Jupiter than without. Jupiter is like that one tough guy among your childhood friends, who would keep other groups of kids from hassling your group, but might punch you really hard in the shoulder once a while, for no apparent reason.

So let’s lay off with the fawning science news coverage and virgin sacrifices. Jupiter is nice to have around, but it is nowhere near 100% cool.

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In other news, I took the shot at the top from my driveway the other night, shooting with a Nikon Coolpix 4500 through an Orion XT12i telescope and 13mm Stratus eyepiece. The moons from left to right are Ganymede, Io, and Europa. I could see Callisto off to the right as well, but it was out of this shot.