Archive for November, 2010


Reading PDFs on the Kindle

November 29, 2010

About three weeks ago Vicki and I traded Kindles, as combination late anniversary/early Christmas presents. She’d gotten hooked on e-books using the free Kindle app on her Droid smartphone, and wanted to get something dedicated.

I’d been skeptical about e-readers for a long time. I’m a book guy; the second-best job I ever had was working in a used book store. I like curling up with books. I doubted that an another Damned Machine (the usual appellation for the electronic devices in my life) could offer the same cuddliness.

Well, I’m a believer now. The Kindle is lighter than hardbacks and even lighter than some paperbacks (I’m lookin’ at you, swollen fantasy epics), and a lot easier to read one-handed than either one. I topped up the charge when I got it, and it’s still at about a quarter of a tank three weeks later, so the promised month of battery life looks legit. I’ve taken it to the park and read in full sunlight, and it looked even better.

It is such a nice piece of kit that I have actually found myself reading more than I did before. At first I wondered if this was just infatuation with the new toy. But it’s been three weeks and I’m not only still reading more, period, but also more kinds of things. Right now on the Kindle I have:

  • about a dozen of my favorite essays, copied from the web into Word docs and sent to my Kindle wirelessly (and freely) using its dedicated e-mail address;
  • about 30 short stories, most of which I haven’t read, courtesy of and Cory Doctorow (also free);
  • a whole shedload of classic literature from the Kindle store, from the Bible to the Origin of Species (yes, I value them both) to G.K. Chesterton’s The Man Who Was Thursday to The Adventures of Sherlock Holmes to the first five novels in Edgar Rice Burroughs’ Barsoom series (also free);
  • and a handful of paid-for novels that I really desired.

The Kindle is so small that my default now is to just take it wherever I go, and then if the mood strikes, I have a whole range of things on hand to choose from. I don’t have to decide in advance whether to take a book along, or which book to take; to a first approximation, whatever I might want to read, I have with me just about all the time.

One thing I haven’t put much of on the Kindle yet is PDFs. As a scientist I both produce (a little) and consume (a LOT) of scientific literature, and almost all of it these days is in the form of PDFs. Unfortunately the Kindle is not going to replace the PDF vault on my hard drive, or even a good fraction of it. I have something like 20 gigs of paleontology papers in PDF form on my laptop, and the Kindle has about 3 gigs of user-available space, so if I want to take it all with me I’m going to have to wait a couple of hardware generations (at least). Taking it all with me is attractive because I never know when I’m going to be in a museum basement, looking at the vertebrae of some weird dinosaur, and have a sudden and quite desperate need for a paper on Apatosaurus or Dicraeosaurus or whatnot.

For this very reason, my friend, colleague, and frequent commenter Mike Taylor asked me to test-drive a PDF on my Kindle. Thanks to some dumb rules at Amazon, he has a shedload of credit that is useless at, and a Kindle would be a convenient and possibly useful way to dump some of it. So I loaded up the 2007 paper in which he and Darren Naish described the new dinosaur Xenoposeidon, and took it for a spin. The rest of this post is basically copied and pasted from what I reported back to Mike.

It works surprisingly well. Just opening the PDF gives one entire page per screen. At that scale I have no problem making out the text, but it’s too small to be comfortable. The screen is 6″ on the diagonal, so that’s no surprise, and I don’t regard it as being either a pro or a con. The device is what it is.

Adjacent to the space bar is a button with two capital As, one larger than the other, that controls page size, contrast, and screen rotation (for PDFs; with Kindle format docs you can also choose among 3 typesets, 3 line spacings, more or fewer words per line [independent of font size], and text-to-speech [wherein the device will read to you if you have headphones on]). Page size options include fit-to-screen (the default), 150%, 200%, 300%, and actual size. Going to 150% lets me get a bit over half a page on the screen at once, so I can see a whole page with four clicks in portrait view, or just two, I’d reckon, in landscape view.  I set it to ‘actual size’ which turns out not to be far off of 150% and had a good close look at the specimen photos. Resolution was fine. I noticed some pixellation so I opened up the PDF to compare, and the pixellation I noticed on the Kindle is just what’s present in the PDF, and nothing worse. The one downcheck here is that the Kindle screen background is not white but a very subdued gray. I imagine that this is deliberate, to prevent eyestrain during marathon reading sessions, but it does noticeably decrease the contrast range for photographs.

Final analysis: (1) using the clicker button to navigate around on a zoomed in page is slightly less invisible than using a mouse, but only slightly, and I’ve only done the former for about 30 seconds so the device might disappear more from my notice with longer use; and (2) the contrast range is reduced which sucks some of the life (and information) out of illustrations.

Other than that, based on my exhaustive 5-minute trial, the Kindle makes an acceptable PDF reader. You couldn’t tote your entire collection, but you could load it up with a gig or two of stuff you’d most likely need on any given trip.

Getting back to books–and to the stated purpose of this blog–the Kindle is kind of a dead end, astronomically speaking. Few astro books are available, and astronomy is a very visual thing but most Kindle versions (of everything) have the illustrations stripped out. There are a couple of compilations of star maps but these terrible reviews. I did find a handful of older astro books–as in, 19th and early 20th century–but I haven’t had the inclination to check them out yet. If anything good turns up, I’ll let you know.


Feanor & Sons

November 28, 2010

Feanor & Sons Silmaril Retrieval

Our commitment is second to none–we swear by it!

We also offer:

  • Slayings–ask about our family discount!
  • Hidden kingdoms sacked
  • Lands usurped (Beleriand only)
  • Dooms fulfilled

We use the latest Naugrim technology.

Going by sea? We have a fire sale on beautiful boats by Teleri! (sold as-is)

Special problems? Talk to Maglor in Coastal Operations, or Maedhros in Spelunking.

Family owned and operated since the First Age.

Genuine Noldorian service–don’t settle for Edain or Half-Elven, get screwed by those who have seen the light of the trees!

Actual descents into Angband by unpaid third party labor, so we can pass the savings on to you!

Feanor & Sons–get your curse’s worth, or we’ll stab you in the back!

Here’s what people are saying:

“They killed my dad!” –Elwing

“Honestly, Feanor & Sons did a lot of the work for me.” –Morgoth


There and back again

November 27, 2010

(I wrote this last July as the first and ultimately only post of a blog that I quickly abandoned. Now that I’m consolidating my bloggulation, I’m posting it here and killing the other blog. My comment exchange with Mike Taylor is now posted at the end of the original text.)

So I’m reading The Silmarillion again (i.e., for the first time all the way through–long story), and I’m about a third of the way through. Men have just awoken, and the Noldor have arrived back in Middle-Earth.

I was thinking about blogging it as I went, but (a) I don’t have time, and (2) in rereading Mike’s TRP posts, I found that he already said most of what I wanted to say. But I started writing a long message about it to Mike, and decided that it would make a decent blog post instead. So here I am, blogging about it after all. Truly, the mind boggles.

The Silmarillion really is a beautiful book, but the beauty comes at you in quick little flashes, and it always tainted by sorrow. I agree with Mike that Tolkien’s motivation was more than philology; the languages probably gave him a convenient mechanism for starting to build the world (and a metaphor, in the Ainulindale), but they don’t account for his motivation. I may be daring too greatly, but I think his motivation was probably in part to do what Lewis did with Narnia: to try to work out his ideas about God and man, life and death, suffering and redemption. At times during the opening sections I found myself wondering if our Creation was not something like the creation of Ea. It seems to be worthy speculation (Tolkien’s, not mine) into an aspect of existence that we can only read from frustratingly abstract and incomplete narratives–and by that I mean both Genesis and other creation myths, and the records of astronomy, geology, and paleontology. And obviously (to me, at least, although I am always puzzled that more religious folk don’t get this) we are fighting the long defeat in our mortal lives, and indeed the whole history of the world since the Fall is a long defeat, until the eventual remaking of the world. Tolkien wasn’t telling the factual story of our long defeat, but I think he hoped that by telling the fictional history of another long defeat, he might illuminate our condition and give us hope. After all, we have been disclosed more about our ultimate fate than the Eldar or even the Valar.

So my original plan was to:
1. Read The Silmarillion, without referring to LOTR;
2. Read LOTR in light of The Silmarillion, without watching the movies (I hadn’t seen them in years);
3. Watch the movies.

That plan is a bit wrecked now, because on the afternoon of the 4th of July I broke down and watched Fellowship (hey, it has fireworks). But I’m not too sad, because most of the music lodged in my head and now as I am reading The Silmarillion I have Howard Shore’s themes playing along, and I think they’re smashing. Whatever criticisms one might level against Jackson’s movies, I think the music is pretty much beyond reproach.

Also, I am thinking now that my Epic Rediscovery Of Tolkien’s Immense Canon of Art (henceforth EROTICA) should be expanded to include The Children of Hurin, which I read on its first release three years ago and loved, and The Hobbit, which I haven’t read since high school. So the new plan is to:
1. Finish The Silmarillion, still without referring to LOTR or any of the later books;
2. Read The Children of Hurin;
3. Read The Hobbit;
4. Read LOTR;
5. Watch the movies.

Incidentally, last weekend was my first LOTR movie watch in probably 5 years at least. I remembered the broad strokes of Fellowship (I can’t abide the acronym FOTR; it seems very coarse for such a beautiful work [OTOH, you may feel the same about EROTICA]), but I had pretty well forgotten the total effect of watching the movie. And I’m pleased to say that two impressions were extremely powerful, moreso than on any previous viewing.

The first was the depth of history behind the events of LOTR, and I think this is absolutely key to understanding not just LOTR (that’s obvious), but the success of LOTR. I think a lot of fantasy is sort of medieval escapism, and there’s probably nothing wrong with that (although I don’t particularly want to live in a place or time without antibiotics and cheap flouride toothpaste). But when you approach LOTR, you’re not just going back (and sideways) in time, you’re going back in time to somewhen that itself has loads of “back in time” behind it. Middle-Earth feels not just old, but positively ancient. I think now that much of the pleasure of the series derives from that. The heroes are not just legendary in our terms, they’re echoing the legends of their own world, and they’re not just fighting the Bad Guy of the Week (a Noldorian suicide bomber, perhaps), but saving the world from an ancient evil. All of this comes through very clearly in the movies, or at least in the first movie (I haven’t watched TTT or ROTK since the early oughts, so you’ll have to wait for my impressions on rewatching them).

The second impression was the palpable sense of evil and corruption emanating from the One Ring. I hadn’t really gotten that before. I mean, it’s stated plain as day in both the books and the movies, but I hadn’t grokked it. I suppose I had always thought of the Ring as something both beautiful and cool, which unfortunately happened to have this not-quite-dead dark lord’s spirit attached to it. Probably about what Boromir thought of it. But on this rewatch I finally really grokked how vile it is, not incidentally, but down to its core. From its conception it was an instrument of division, corruption, and enslavement, and I finally really got that.

Further bulletins as events warrant.

Discussion with Mike, from the original comment thread


“Truly, the mind boggles.”

In this case, it bloggles.


I meant to comment properly on this article, but got seduced by the cheap pun in my previous comment, so now I’m going to follow up my own comment with what I meant to say.

I may be daring too greatly, but I think his motivation was probably in part to do what Lewis did with Narnia: to try to work out his ideas about God and man, life and death, suffering and redemption.

I think that’s close to right; except that Lewis had been a Christian for longer when he started to write the Narnia books that Tolkien was when he started on what eventually became the Silmarillion, and so you might say the Lewis had already worked out his ideas and was merely laying them out in as comprehensible form as possible, whereas Tolkien was in the process of working out his idea, and laid them out in a largely incomprehensible form.

I like this idea because it neatly accounts for the fact that Middle-earth is much better art than Narnia, but Narnia is much better theology. And that in turn accounts for the fact that sophisticated adults almost always like Middle-earth more than Narnia, whereas children and others who have not yet raised barriers get a lot out of Narnia.

And obviously (to me, at least, although I am always puzzled that more religious folk don’t get this) we are fighting the long defeat in our mortal lives.

That’s not obvious to me. I’m not necessarily saying it isn’t true, but that it’s not obviously true. I certainly don’t get the impressions from the book of Acts that the early disciples felt themselves to be fighting a long defeat, nor from the letters of Paul. I think that may be something that Tolkien read into his religion from his personality rather than something that was already there — what Rilstone described in his Two Towers movie review as “Tolkien’s pessimistic, Catholic, view of morality”. If it seems obvious to you, too, then … could it be a shared derived character of Catholics?

I’m glad that the Fellowship movie worked so well for you this time around. For my part, I seem to get more out of them pretty much every time I watch. That’s not to say I don’t cringe in a lot of places (“No parent should have to bury their child”, indeed) but the essence of the films, their emotional core, is startlingly true to Tolkien — much more so than we had any right to expect or even to realistically hope.


Lewis had been a Christian for longer when he started to write the Narnia books that Tolkien was when he started on what eventually became the Silmarillion

Is that true? I thought Tolkien was a cradle Catholic, but 30 seconds of web search doesn’t turn up any support. Do you know that Tolkien converted as an adult, or is that an assumption?

That’s not obvious to me. I’m not necessarily saying it isn’t true, but that it’s not obviously true. I certainly don’t get the impressions from the book of Acts that the early disciples felt themselves to be fighting a long defeat, nor from the letters of Paul.

According to my understanding, to the Elves “the long defeat” means that they do not possess the power to save the world, that all that is wrought in Middle-Earth is impermanent and at least slightly tainted, but that it is better to struggle to achieve what happiness and beauty they can than to surrender to evil, or even apathy. At least, I meant it in that sense, and not the Nirnaeth Arenoediad/Doom of Mandos sense; the former seems to me to accord pretty well to our lot as mortals on Earth. Our ultimate victory and ultimate reward is elsewhere. That does not mean that there is not great beauty and much worthwhile work to be done in this life, it just means that our temporal efforts are, as the term implies, transient.

I think that may be something that Tolkien read into his religion from his personality rather than something that was already there — what Rilstone described in his Two Towers movie review as “Tolkien’s pessimistic, Catholic, view of morality”. If it seems obvious to you, too, then … could it be a shared derived character of Catholics?

Interesting. That is incorrect in the particulars, but might be true underneath. Any latent existential pessimism I harbor is a holdover from my nearly Puritanical (American) evangelical upbringing. Whatever its global and institutional failings–and those are many and vexing–the RCC has been in practice a font of peace and hope for me. But the broader point–that Tolkien and I are both projecting–is something I’ll have to think about.


Well, Tolkien wrote the very earliest parts of what ended up in the Silmarillion world at a very early age — in his late teens, IIRC. So even if he’d been raised Catholic, he would hardly have been thinking deeply about the implications for many years. By contrast, Lewis had been obsessively thinking through religion in general and Christianity in particular for many years before “gave in, and admitted that God was God” in 1929. And of course he hardly stopped thinking about it thereafter. It was fully 20 years later that he wrote The Lion, the Witch and the Wardrobe, the first of the Narnia books. So, yes, I do think it’s fair to say he would have written those books from a position of having worked out a much clearer theology than Tolkien had when he started out on his work. Then again, Tolkien was still tweaking that work when he died in his eighties, so I certainly don’t mean to imply that there was anything immature about his thinking. Just that his work probably reveals process much more the Lewis’s.



November 27, 2010

I have too many blogs, and I have discovered through experience that I am not going to feed them all. So I’m concatenating. From now on all my paleontology-related stuff is going on SV-POW!, and all my non-paleo stuff is going here, and my other blogs will languish. That will probably mean a lot more non-astronomy posts in the future, including the very near future. Stay tuned!


A Cheshire Cat on the moon

November 21, 2010

It’s been an interesting week.

I got a new scope…

That was sort of by accident. I really wanted the mount for my 5″ reflector, because it’s a bit too heavy for my current mount and tripod. Orion sells that mount as the VersaGo II for $199, but right now OPT has the SkyWatcher-branded version of that mount, the AZ4, and a nice 80mm refractor with finder and eyepieces for the same price. So by going through OPT I essentially got the scope and accessories for free. I originally planned on selling off the scope, but I keep hearing about people falling in love with the crisp views through refractors (which unlike reflectors and catadioptric scopes have no central obstruction), so I decided I’d give this one a fair shake before I got rid of it.

I’m glad I did. It’s a keeper–it has very sharp optics, gives a nice, clean, contrasty image, and is very fun and easy to use. It doesn’t pull down as much light as my bigger scopes, but it’s easier to handle and it cools down in no time, which is a big plus at this time of year. (One  of the biggest sources of image distortion at the eyepiece is heat waves coming off lenses and mirrors that haven’t reached ambient temperature.) Frequent commenter David DeLano has this scope as well, and he warned me that if I wanted to sell it, I shouldn’t look through it, because I’d get hooked. You called that one right, David!

I gave it a name, too. Some people name their scopes and some people don’t. I also talk to myself and to inanimate objects when I’m alone, and I suspect that those traits are highly correlated with naming scopes. Anyway, there’s a bit of back story behind this one. When I was a kid, my cousin Michael had a good friend, also named Michael, who was quite a bit taller than he was. They felt dumb calling each other by their own name, so my cousin Michael dubbed the taller one “Shorty Long”, and tall Michael retaliated by calling my cousin “Stubby Fats”. That’s never ceased to crack me up. And now I’ve got two shiny black SkyWatcher scopes that will be sharing a mount, one a long skinny refractor and the other a short fat reflector, so it made sense to name them Shorty Long and Stubby Fats.

With the moon and Jupiter both high and bright in the evenings this week, it didn’t pay to go after fainter fare, and I hadn’t put in any serious time on the moon in a long time.

Tuesday the moon was waxing gibbous. I got this shot through Shorty Long with my Coolpix 4500:

It doesn’t show everything there was to see. Sinus Iridium, the Bay of Rainbows, is the C-shape, open to the bottom, at the very top of the moon in the above picture; it’s an old impact basin mostly flooded by the later basalt flows that formed the maria or lunar seas. Just past Sinus Iridium I saw a couple of mountain peaks that the sunlight was just reaching, and they glowed like a pair of eyes staring at me from beyond the terminator. Here, I’ll show you:

Kinda spooky lookin’, eh?

It got better. As I stared back, the rising sun (from the perspective of those mountains) lit a couple of lower peaks, below and between the first two, and then a ridge running beneath all of them. It looked for all the world like the face of the Cheshire Cat, with two bright eyes, two nostrils, and a big wide smile. The nostril peaks and the smile ridge were too faint to show up in any of my photos, but a helpful guy on Cloudy Nights produced this image with the Lunar Terminator Visualization Tool (yay, more free astro software!) using my location and the time of the observation:

One of the nostril peaks was too dim to show up even in the LTVT shot, but other than that the face looks pretty much like what I saw Tuesday night. There is even a suggestion of eyebrows.

The peaks turn out to be the aptly named Harbinger Mountains. I asked around on Cloudy Nights and no one has reported seeing the Cheshire Cat “lunarism” before. I’m going to do a little more research on the features involved and report back.

That wasn’t the end of my weird moon adventures for the week. Last night I was back outside for the full moon:

I had basically just gotten set up when I saw a small, perfectly round object float by in front of the moon. I figured it was probably either a weather balloon or a satellite. Turns out that a CN user got video of the thing; the video is now on YouTube, here.

[Almost Immediate Update: the thing in the video is not the same thing I saw, or at least not the same pass, because that video was made about three hours before I made my observation. I just learned that in the CN thread, which is here.]

It’s probably a satellite; another CN user got video of a similar thing flying in front of the sun, and reports seeing them on a regular basis. So don’t get out your tinfoil hats just yet. But do get out and have a look at the moon when you get a chance. As this week has shown, you never know what you might find, even with this closest and most familiar of celestial objects.


Observing report: All-Arizona Star Party 2010

November 7, 2010

A few months ago I found a good deal on a used 12″ reflector. The guy selling the scope, Darrell Spencer, lives in Phoenix, and offered to drive part of the way for the handoff. We met at a diner on I-10 in Arizona and had a great conversation over breakfast. In particular, we talked about our favorite dark spots and the chances of meeting up to observe sometime. We parted fast friends, and both started scheming about how to meet up under dark skies.

With the new moon, pleasant temperatures, and clear skies over most of the southwest, this weekend was a big one for star parties. Through various clubs and friends I heard of at least four here in SoCal, and I’m sure I would have had a great time at any of them. But the one I ended up attending, thanks to an invite from Darrell, was the All-Arizona Star Party, out in the desert about 50 miles east of the California border. Darrell didn’t know I was going to take this picture until about half a second before I clicked the shutter, hence the expression.

The AASP was going on both Friday and Saturday nights, but I could only afford to do one night, and the forecasts called for Friday night to be a little bit better. I picked up London after kindergarten and we hit the road.


We rolled in about half an hour before sunset, and found a spot next to Darrell. Steve Coe and AJ Crayon were set up on either side, so I was hanging out with some truly legendary observers. They also turned out to be darned nice guys. Here’s AJ’s truss dob cooling down on the right, with my XT10 on the right.

There had been a few wisps of cloud in the sky when we pulled in, but as the sun set they evaporated, and by the time the first stars came out, the sky was clear except for a little fuzz over the Phoenix light dome, low on the eastern horizon. The last of the sunlight striped the western sky with some beautiful crepuscular rays.

I spent the couple of hours just surfing around the sky, hitting some seasonal favorites. London looked at a few things but spent most of his time watching for satellites and shooting stars. At 7:20 most people on the observing field stepped away from their scopes to watch the western horizon. There was supposed to be a rocket launch from Vandenberg, a Delta II putting up an Earth-observation satellite (here’s the story from the Vandenberg site). At 7:21 we saw a bright spark flying low over the western horizon. That’s what 100,000 lbs of thrust looks like from 300 miles away. It was the first time I’d ever seen a real rocket in flight. London was even more thrilled, if that’s possible. He also spotted a couple of satellites and shooting stars, so he got everything on his list. I had a list of my own to deal with.

Into the Deeps

London was dead asleep by 8:00 and I settled in for a nice long observing run. I was tracking down the last few objects I needed for the AL Caldwell Club, and starting on my next big observing project, the Herschel 400. A few of my favorite objects from the evening:

NGC 5982 and 5985 (H400): A nice pair of galaxies. At 92x, 5982 is a small bright round glow, like a miniature M32; 5985 is an elongate, dimmer smudge of light. Excellent pairing.

NGC 1023 (H400): Big, bright, beautiful edge-on spiral galaxy, with clearly delineated core and bits of detail in averted vision. A minor showpiece!

NGC 2261, Hubble’s Variable Nebula (Caldwell 46): Very cool V-shaped spray of bright nebulosity. Edges of ‘V’ are very sharp and crisp, and the middle of the fan fades out evenly. Not like anything else I’ve seen in the sky.

NGC 2362 (H400, Caldwell 64): Open cluster. At 37x, almost perfectly triangular scattering of about 20 equally bright stars around a much brighter central star. One of the prettiest open clusters I’ve seen–better than many Messiers.

NGC 2024 (H400): Big, detailed bright nebula adjacent to Alnitak in Orion. At 57x, looks like a ghostly version of its photographic appearance. Extremely cool.

I was using my XT10 for almost all of my observations. I also had 15×70 binoculars along and they came in handy for working out a couple of tough star-hops and for observing IC 342 (Caldwell 5)–this galaxy is so big and diffuse that it was difficult to make out in the telescope, even at low power, but it was a cinch in the binoculars.

But my favorite observation of the night, and one of my favorite observations of all time, was made with naked eyes. About 12:40 I leaned back from the eyepiece and just stared up. Right at the zenith, between the Pleiades and the constellation Aries, was a very large, faint, and diffuse patch of light. I called Darrell over to ask him if it was what I thought it was. He thought so, but wasn’t entirely sure, so we asked Steve Coe, and he confirmed it. We were looking at the gegenschein.

Gegenschein, Shine On

The solar system is full of dust. Very little if any of this dust is left over from the protoplanetary disk that gave rise to the planets; that should have spiraled into the sun long ago.  Most of what’s out there now is thought to have been “processed”: incorporated into planetesimals early in the formation of the solar system, and redistributed by meteor impacts, asteroid collisions, and the evaporation of comets. The planets do not revolve through empty space, but through a flat disk of dust that encircles the sun like a phonograph record.

Under very dark skies, this dust is visible, for the same reason that the planets are visible: reflected sunlight. The brighter manifestation of the reflected dust-light is the zodiacal light, which stands up like a pillar from the horizon. It’s called “zodiacal” because the dust, like the planets, orbits in the ecliptic plane, which is projected against the background stars that make up the constellations of the zodiac.

The gegenschein is another, dimmer reflection of sunlight off the interplanetary dust cloud. As the German term–“counter shine”–implies, the gegenschein is observed directly opposite the sun. Friday night the sun set a little after 6:00 PM, and Saturday morning it rose a little after 6:00 AM, so right after midnight the sun was directly behind us (as it always is midway between sunset and sunrise, wherever you happen to be). That meant that the dust grains right overhead were in full phase, the same way that the moon is full when it is opposite the sun in the sky.  Darrell, Steve, and I saw this full-phase portion of the sun’s dust cloud as that glowing patch of light directly overhead. I had read about the gegenschein, but I had never seen it before. It is so faint that even the smallest amount of moonlight, haze, or light pollution will make it invisible. Seeing the gegenschein is a sign that you’ve been under some of the darkest, clearest skies on Earth.

(There is one further step: some observers have seen the zodiacal light from both horizons extending up to the zenith, making a complete band of light crossing the entire sky, with the gegenschein in the center like a diamond on a ring. Those people have seen the entire disk of dust visible from Earth at that time. This is on my life list of things I most want to see.)

I pushed on to a little after 2:00 AM. I ended the night with 6 Caldwell objects, which pushed my total to 74, past the 70 required for the AL  club. I also observed 27 objects for the Herschel 400, and re-observed at least 21 Messier objects over the course of the evening. The Great Nebula in Orion looked better than I have ever seen it–the nebulosity just kept going on forever and ever, and the patch around the Trapezium was incredibly detailed. I saw a lot of amazing stuff Friday night, but the gegenschein easily takes the cake.


London and I have a deal on these camping trips: I observe all evening, and he takes me on a hike in the morning. He told me that yesterday’s hike would be a “bone hike”, and we’d be looking for bones, spiders, and scorpions in the desert.

There was a range of low hills about two miles to the west of camp. London was adamant that we were going to climb them. And so we did. The secondary summit of the hill on the left in this picture is the one we climbed. The entire hill was comprised of shattered rock and covered with cacti, and the farther we climbed, the worse it got, so we settled on the lower peak.

The round trip took three hours and with all the winding around we did we probably walked five miles. I would not have thought my little man would have the stamina, but he was a real trooper. He had even packed up the water we’d need for the hike in his backpack. Not bad for a five-year-old!

We saw plenty of cool stuff along the way: saguaro cacti, free-range cattle, a jackrabbit, ants of every imaginable size and shape, and lizards that zipped from bush to bush almost too quickly to see. London did find a spider–a baby tarantula that froze when we walked up–and a bone, the broken, sun-bleached tibia of a cow. So the walk was a success all around.

Fittingly, the Tuscon contingent at the star party had a bunch of specialized solar scopes set up on the sun. When London and I got back to camp, we went down to check out their setup. They invited us have a look. There was a bright active region and little spike-like prominences standing out from the edge of the sun like quills on a hedgehog. I say “little” prominences but the biggest were probably about as tall as the Earth is wide. It doesn’t pay to get too blase about anything up there, especially our closest star.

Until Next Time…

It’s funny, when I’m back in civilization I spent too much time mooning over gear (New Year’s resolution notwithstanding). But when I’m out under dark skies, gear is the last thing on my mind. The telescope just gets out of the way and I am alone with the stars. It’s easy to slip into a productive rhythm–checking the charts for the next object, working out the star-hop, trying different magnifications to see which will make a given object show up best, taking some time to really look for details, recording my observations…sitting back to look around and just exult in the majesty of the night sky. The time flies by, always faster than it should. Strange, how thoroughly I can lose myself finding things in the sky.

This weekend might have been the end of the fall star party season.
California’s rainy season is upon us.  There will be clear nights and plenty of good stuff to see for the next few months, but it will be catch as catch can. Still, I’ve had a great run this fall, and I can’t wait to see what’s next.


How to build a Dobsonian mount for a 5-inch telescope

November 2, 2010


By reader request, I am posting instructions on how to build the Dobsonian mount shown in photo above. The design was made up mostly on the fly to suit my particular needs and the materials I had on hand. Your requirements might be different, so I’ll also discuss the design decisions I made along the way, so that you can a build a mount that fits your telescope and your needs.

If  you have the freedom to design a telescope from the ground up, you’ll be much better served by the free instructions provided by the Sidewalk Astronomers, or in any of the several telescope-making books out there. I’m thinking here of Build Your Own Telescope by Richard Berry, The Dobsonian Telescope by David Kriege (yes, that David Kriege, founder of Obsession) and Richard Berry, Sam Brown’s aging but accessible compendium, All About Telescopes, and several others. There are also some awesome resources online, including the Cloudy Nights ATM (amateur telescope making) forum, and plenty of solo ATMers who have posted pictures and descriptions of their designs on their own blogs or webpages (I like these, these, and this one in particular).

But as Rich Hoover said in a comment,

Most everything on the net is catered to 6″ or 8″ OTAs, so finding some GOOD plans for a 130mm OTA is rather difficult. Those plans that I’ve seen also make some rather large assumptions on the user’s part. It’d be great if there were plans with a complete parts/price list.

So it seems there is a need here, and I will do my best to address it–although the emphasis on GOOD plans might mean I’m doomed from the start! I have zero experience with woodworking and anyone who knows what they’re doing will be appalled at the crimes against wood–and probably good taste–that I have committed. It is the height of ridiculosity for me to be instructing others in how to do this. Still, if you have some scrap wood, a saw, a drill/driver, no relevant experience and a desire to experiment, then you have everything I did when I started and you will probably do as well as I did, or, most likely, better.

Many thanks to David DeLano for much help along the way, and to Rich Hoover and Dan Walker for their continued interest in this project. Hope you find this useful!


The first thing to do is to get familiar with the basic parts of a Dob mount. In addition to the OTA (optical tube assembly), there are three basic assemblies: the altitude bearings, the rocker box, the ground board.

The altitude bearings are attached to the OTA and allow the telescope to rock up and down. The rocker box is really the main part of the mount, and the one that requires the most design decisions and the most work to build. At the top end it provides bearing surfaces for the alt bearings, and at the bottom it rotates on the ground board via the azimuth bearing (which is not listed as a separate part because it is created by the rocker box and ground board). The ground board is the simplest piece, the easiest to build, and the hardest to screw up.

When we get down to the actual building, there will be separate sections on how to make each of the three pieces, plus separate sections on bearing surfaces and finishing the mount.


If you’re building a Dob mount for an existing OTA, the tube dictates everything else. So the first steps are to measure the tube, find its balance point, and decide how tall you want your mount to be. Only with these measurements in hand will you be ready to start cutting wood.

In my case, the OTA came from a SkyWatcher 130N-EQ2 setup. I bought this last summer on the cheap, and they’re still pretty darned good deals. However, I didn’t want the EQ mount, so I sold it and started building a Dob mount.

Finding the width of the rocker box. The OTA on this particular scope is 33″ long and 6.5″ in diameter (blue arrows). I decided to attach the alt bearings to the tube rings, which have 1/4-20 sockets, for simplicity (if you don’t have tube rings, you’ll have to build a box around the tube, like this). The tube rings add an extra half an inch on either side, bringing the width of the thing which must be mounted to 7.5″ (red arrows). But that’s not all–I also knew that I would be using thin plates of wood as bearing retainers to keep the OTA and alt bearings from slipping off their supports on one side or the other. The bearing retainers are each 0.25″ thick, meaning that the rocker box had to enclose a space at least 8″ wide (yellow arrows).  I wanted a little breathing room on top of that; I was using wide bearings so if the rocker was a little too wide, no problem, but if it came out too narrow, I’d have to start all over. So I made mine with an internal width of 8.5″ (white arrows), although in retrospect 8.25″ would have been enough.

Finding the height of the rocker box. Here you have a lot more freedom. The length and balance point of the OTA set the minimum height of the rocker box, in that you want the bottom end of the OTA to be able to swing freely all the way to vertical without bumping into the bottom of the rocker. On the other hand, you can make the rocker box as tall as you want, within reason. I wanted to make the entire mount as small and light as possible, so I went with the minimum height, and I’ll explain how I got there in a moment.

One persuasive reason not to make the mount as small and light as possible is that such a short mount will require you to either get down on the ground to observe, or to set the mounted telescope on some kind of stool or table. Neither solution is optimal for most people; getting up and down off the ground can be tiring and dirty (although some people aren’t bothered by either thing), and few stools or tables are stable enough to serve as observing platforms. Tiny flexings and rockings that are completely unnoticeable during normal daily use can be annoying or intolerable when magnified 200 times, which is what they’ll be when you’re observing at 200x magnification. If you want a mount that will be comfortable to use when seated, then park yourself in a chair, sit up comfortably, measure the height of your eyeball off the ground, and go from there. Remember that your seated  eyeball height should correspond to the maximum height of the eyepiece; it’s easy to bend over a few inches if the eyepiece is  lower, and hard to stretch up those same few inches if it’s too high. From your eyeball-to-ground measurement, subtract the length of the OTA from the focuser to the balance point, and knock off a couple more inches for the ground board and azimuth bearing surfaces, and that’s how tall your rocker needs to be. For an excellent example of a DIY Dob mount meant for seated observing, see Rob Nabholz’s Kid Peek II.

To find the minimum height of the rocker box, you have to know the balance point of the OTA. Please don’t do it like I did in the above photo! Three things are wrong in that picture: first, it was ridiculously dangerous to balance the OTA on a <1″ surface suspended over concrete. Do it on thick carpet, and balance the tube on a paperback book or something. You don’t have to be exact, and inch or so of slop in either direction is unavoidable. Which brings us to the second thing that is wrong with that picture: the balance point is way too far back because the scope is lacking the finder and an eyepiece. But in practice you will have a finder, maybe more than one, and an eyepiece. So load up the front of the scope with whatever you will actually use on a night-to-night basis, and don’t forget to remove the dust cover from the front of the scope (the third thing I did wrong).

Finding the exact balance point down to the last micron is a lost cause, because eyepieces vary so much in weight. My lighest eyepieces only weigh 3 or 4 ounces, and my heaviest weigh over a pound. The entire OTA of this scope only weighs 10 lbs, so changing the weight at the front end by up to a pound is going to shift the balance point, bigtime. If you do as I did and attach the alt bearings to tube rings, no problem, you can just scoot that ring fore or aft on the tube to rebalance (that’s a capability you might want to retain if you have to build a box around your OTA). Other ATMers use springs or adjustable friction thingamabobs, but remember, here at 10MA you’re getting caveman-level engineering. Speaking of, you’ll notice that I put the extra tube ring down at the bottom of the OTA, to shift the balance point backward and allow a shorter rocker box.

In fact, with the finder in place and a middleweight eyepiece in the focuser, the balance point on the tube was just aft of the halfway point, so about 16.5″ of tube would hanging down into the rocker box. I made my rocker with a height of 18″ so that the OTA would clear it even if I had to shift the tube down in the rings to accommodate a heavier eyepiece. If you’re going for a minimum-height mount, it’s worth erring on the side of caution. If the mount is an inch too tall you’ll never notice, whereas if it’s an inch too short you won’t be able to balance your scope without hanging extra weights off the front end. IMHO, it’s kinda silly to design a minimal mount that requires you add extra, nonfunctional mass to the OTA, although some people deliberately do this when the mount absolutely has to be small (to fit in to luggage, for example).


Loads of other telescope-building resources, including many of those linked above, will show you how to make elegant alt bearings. I’m going to show you how to make easy, cheap alt bearings. My alt bearings are 4″ grated PVC endcaps, which you can get at any hardware store for two or three bucks apiece. They’re held on to the OTA with 1″ 1/4-20 thumbscrews threaded through washers. I also put on alt bearing retainers to keep the scope from slipping sideways off the alt bearing surfaces. The alt bearing retainers are 7″ squares of 1/4″ thick wood, that I cut from disposable fish cutting boards that I found at Big Lots, half a dozen for a dollar. Any reasonably stiff, reasonably thin material would work; if all else fails you could cut two circles of corrugated cardboard and poke holes in the middle. I drilled the center holes in the bearing retainers with a 3/8″ bit.

In case it’s not clear from the pictures, the thumbscrew on either side goes first through the washer, then through the middle slot in the PVC endcap, then through the center hole in the alt bearing retainer, and finally screws into the 1/4-20 socket in the tube ring.

Total parts  and price list:

2x 1″ long 1/4-20 thumbscrews (~$1.50 for a pack of four)

2x washers (~$1.00 for a pack of eight)

2x 4″ grated PVC endcaps (~$2.00 apiece)

2x 7″ square alt bearing retainers (made from disposable cutting boards, $1.00 for pack of six)

Total cost: about $7.50.


A rocker box minimally consists of four pieces: a front, two sides, and a bottom. You need the sides to support the alt bearing surfaces and thus hold up the OTA, the bottom to form part of the azimuth bearing, and the front to brace the whole thing and keep the sides from bowing or leaning under the weight of the OTA. So, at a minimum, all you have to do is build a four-sided box that matches the minimum internal height and width established above for your tube. Mine needed to have an internal width of 8.5″ and an internal height of 18″.

Rather than make a single front piece, I made three 8.5″-long braces. One connects the sides a little more than halfway up and sports a handle, and the other two sit at the bottom of the box  in front and in back. Whether you go with a single front piece or a series of braces, make sure that you don’t put them right at the top of the rocker, because you want the OTA to be able to swing down  to the horizon as well as up to vertical. I cut the braces from some 2.5″ wide x 7/8″ thick wooden bars left over from a broken futon, but just about anything would work.

The sides of my rocker box are 18″ lengths of an old wood shelf, 9 3/4″ wide x 5/8″ thick. Once you have cut the basic rectangle to length, the only necessary cuts are the V-cuts in the tops that will hold the alt bearings. I made these inboard of the corners a bit, to leave four flat surfaces on top. Partly because I didn’t want to stab myself if I fell on the mount, and partly because those flat surfaces made very handy supports when I turned the mount upside-down for finishing and for assembling the azimuth bearing (see below).

One thing I haven’t discussed yet is the effect of the V-cuts on the effective height of the rocker box. I made my V-cuts 4″ deep in the center, but obviously the alt bearing isn’t going to ride right down at the point of the V. It will ride higher up, at a point fixed by its diameter and the width of the V. By doing a little testing in advance I worked out that the 4″ PVC bearings sitting on some kind of bearing material (furniture sliders, as it turned out) would put the center of rotation back up at or near the top of the rocker box sides, and if you look closely at the top photo, you’ll see that that’s about where it ended up.

I had a 1.25″ spade bit that I was planning to make an eyepiece rack with, but in the end I used it to drill a bunch of holes in the side pieces of the rocker box. Mostly because I thought it would look cool. They probably help lighten the mount a little, although they also exposed more surface area for sealer and paint to bond to, so who knows. I’ll tell you this: if I had to do it over again, I’d leave out all the holes, because they made painting this thing a right sod.

The final piece of the rocker is the bottom, which on my mount is a 9″ by 9 3/4″ piece of 1/2″ plywood. It’s a little narrow, so the rest of the rocker partly overhangs it on either side. I could have gotten a bigger piece of plywood and cut a bottom that exactly matched the dimensions of my rocker (9 3/4″ long, fixed by the width of the shelf from which I made the sides, and 9 3/4″ wide,  fixed by the 8.5″ internal width plus 5/8″ on either side for the thickness of the rocker sides), but I already had an old plywood shelf that was 9″ wide. The bottom is screwed to the two lower braces anyway, and not to the sides of the rocker box; it’s really the braces that hold the whole thing together.

The rocker box is glued-and-screwed together. Get some long wood screws, drill pilot holes, do a test fit, put some wood glue on the surfaces to be bonded, and screw the thing together. If I can do it, anyone can.

Total parts and price list:

Braces: 2x 8 3/8″ long, 2 1/2″ tall, 7/8″ thick ($0)

Sides: 2x 18″ tall, 9 3/4″ long, 5/8″ thick ($0)

Bottom: 1x 9 3/4″ long, 9″ wide, 1/2″ thick ($0)

Wood screws (~$1.00 for a whole bunch)

Wood glue (~$4.00 for a good-sized bottle)

Total cost: for me, about $5.00, because I already had all the wood. If you don’t have scrap wood laying around, you could build a normal 4-sided rocker box (2 sides, 1 front, 1 bottom) entirely from 1/2″ or 3/4″ plywood. If you had worked out how big everything needed to be in advance, you could probably even get the hardware store to make the cuts for you. Or you could scavenge scraps from castoff bins and cut them yourself. Either way, it should still be possible to get out for under $10.


This one is dead easy. You need a piece of wood big enough to support the bottom of the rocker box. You can make it a circle if you want to be fancy, or a square if you want to be simple. I cut a 10″ length of my 9″ wide plywood shelf and drilled a hole in the middle. For feet I used four 1″ diameter screw-in type furniture feet, which I found for a buck at Big Lots. In theory, three would be more stable because a 4-footed structure can rock on uneven ground. In practice, however, I found that the 3-footed version tended to tip toward the unsupported corners. I could have avoided that problem by making the ground board larger than the minimum necessary to support the rocker, but that would have made the whole mount wider and heavier. Do whatever suits your needs. Don’t screw in the feet until you’re done finishing the mount (see next section)!

Total parts and price list:

1x 10″ long, 9″ wide piece of 1/2″ plywood ($0)

4x 1″ diameter screw-in furniture feet ($1)

Total cost: about a buck, since I had the wood. Again, this is something you could cut out of any spare board or sheet of plywood.


By finishing here I mean sealing, sanding, and painting, not completing. You can’t complete the mount without the bearing surfaces and so on, but you can’t put those on until after it’s painted. Painting is optional, but sealing is a good idea, because a working mount is going to dew up from time to time, maybe a lot depending on where you live.

Before sealing and painting I beveled off the top outside edge of the uppermost brace and put on a cheap drawer handle. The handle is a hollow U-shaped piece of plastic, like a very thick drinking straw folded back on itself. It’s threaded inside and the normal procedure would be to put bolts or screws through the thin front of  a wooden drawer and tighten them into the handle. I didn’t have that option, since I was going through a couple of inches of very hard wood. What I did instead was hammer in a couple of nails, liberally goop up the nails and the sockets in the handle with 5-minute epoxy, and then slide the handle down over the nails. Solid as a rock.

Also, I like nice smooth edges, so I sanded off all the sharp corners on the entire mount and ran little fillets of spackle along all of the joints. Totally optional.

At the suggestion of frequent commenter David DeLano, I sealed the mount with a mix of wood glue and water in equal measure, lightly sanding between coats. Then I gave it a couple of coats of water-based white primer, again with very light sanding between coats. I used Kilz2 latex primer, but anything would probably do. Since I was priming anyway, the sealing might have been overkill, but whatever. It was  cheap, didn’t take long, and if helps this thing last a little longer, great. Then two coats of black latex exterior house paint. I hate messing around with paint thinner so I did everything with water-based products.

Total parts and price list:

1x plastic drawer handle ($1.00)

Wood glue (same as above, for rocker box)

1 quart Kilz2 latex primer (~$6.00)

1 quart black latex exterior house paint (~$8.00)

sandpaper (~$2.00)

Total cost: about $17.00. Although I still have a lot of everything left over for future projects. If you count the fraction actually expended on this mount, it probably comes in under ten bucks.


Aye, there’s the rub: how much friction do you need or want on your bearing surfaces? Too much and the mount sticks or, worse, tips; too little and you can’t keep the scope pointed at anything long enough to see it.

The alt bearing surfaces were easy: I got four nail-in furniture sliders from Big Lots ($1.00 for the package) and, well, nailed ’em in. They’re the little white nubs in the V-cuts. David had kindly sent some Teflon tape, but it proved too slippery for this mount. I could have scuffed up either the tape or the PVC bearings but went for the simpler solution instead.

The azimuth bearing surfaces are also pretty simple. From Rob Nabholz I got the idea to use furniture sliders against an unwanted phonograph record. Here you almost certainly do want just three, because even minimal rocking at the azimuth bearing is going to wreck the motions of your scope. Another one-buck package of sliders from Big Lots covered this and I have one left over for something else. Pound these into the bottom of the rocker box, as far apart as you can get them. The LP I got from the local library book sale for a dollar, but you could probably get one even cheaper at a garage sale.

To hold the stack together you minimally need a 2″ long 1/4-20 bolt, a 1/4-20 wingnut, and a couple of washers. I also like to put in some milk-jug washers to keep things turning smoothly. Milk-jug washers are a cinch: cut out flat circles from the walls of plastic milk jugs, and cut or punch holes in the middles so they’ll fit over the azimuth bolt. If your Dob, of any size, has sticky azimuth friction, you can stack up some milk-jug washers and/or old CDs around the azimuth bolt, between the ground board and the rocker, to take some of the weight off the lateral pads. You want the stack just thick enough to free up the motion a little, but not so thick that it makes the rocker box rock back and forth on the ground board (the only rocking normally associated with the rocker box is the rocking up and down of the OTA).  For this scope and mount, I found that one old CD and two milk jug washers were perfect.

This photo shows mount upside down, read to thread the bolt through. From the bottom up (top down in the photo), the bolt goes through:

1 – flat metal washer
2 – 2″ milk jug washer
3 – ground board
4 – record (glued to ground board)
5 – 5″ milk jug washer
6 – old CD
7 – 5″ milk jug washer
8 – base of rocker
9 – 2″ milk jug washer
10 – flat metal washer
11 – wingnut

The reason the wingnut goes on top is so that you can adjust the azimuth friction by simply reaching into the bottom of the rocker box and tightening or loosening it.

Total parts and price list:

7x Teflon furniture sliders, 4 in the V-cuts for the alt-bearing surfaces, and 3 on the bottom of the rocker box for the azimuth bearing surfaces ($2.00; $1.00 each for two packs of four)

1x old phonograph record ($1.00)

2x flat metal washers (from the same package bought for the alt bearings, see above)

1x 2″ 1/4-20 bolt (~$1.00 for a pack of three or four)

1x 1/4-20 wingnut (~$1.00 for a pack of four or five)

milk jug washers ($0)

Total cost: about $5.00, less if you have some of the hardware already lying around.


That’s it, the whole shebang. If you can use a saw and a drill, you can build this mount, and probably just about anything else you put your mind to. If I forgot anything or if any of the steps are unclear, let me know in the comments and I’ll do my best to fix it.

Total cost of the entire project: for me, about $25, since I already had the wood. If you have to buy wood, add another $5-10. Remember that you can find scrap wood all over the place; heck, your neighbor probably some in the back of his garage that he’d be happy to give you.

If you find this writeup useful, you are welcome, but of course not expected, to help support the site, and you can do so at zero cost to yourself. Here’s how. Thanks and clear skies!