Sunday, May 18, 2008

Snakes on the brain

Around the dawn of time I promised to post occasional goodies from what may be the most wonderful book in the world, Gerald Wood's The Guinness Book of Animal Facts and Feats (this is also how I got to be a Google-recognized expert on headless butterflies). But I kept loaning the book out to people--forcing it on them like a pusher would be more accurate--and I never got around to it. Then just the other day I realized that I had the book back in the house so I picked it up and BANG! had my mind blown by the bit quoted below. Completely by coincidence, Darren decided to visit this overlooked branch of Tetrapoda this week as well. It's a strange world, and I can think of few pieces of information that better demonstrate that than this (from Wood 1982:112):

...the giant snakes are also great fasters and there are a number of records of individuals going 12 months or longer without food. One female reticulated python at Frankfurt Zoo fasted for 570 days, took food for a time and then fasted for another 415 days before eating, and a much larger example at the same zoo went 679 days without food although it drank regularly (Lederer, 1944).

All of these achievements, however, pale by comparison with the fasts carried out by the highly venomous Okinawa habu (Trimeresurus flavovirdes) of the Ryukyu Islands, W. Pacific. On 10 September 1977 the Amami Kanko Pit Viper Centre in Naze City, Kagoshima Prefecture, Japan started a fasting experiment with five of these snakes. Four of them died on the 207th, 696th, 1101st and 1184th days respectively, but the oldest individual aged c 12 years was still going strong--if approached it reared up in preparation for an attack--when the experiment was terminated on the 1189th day (12 December 1980), which is a record for a vertebrate animal. Although its weight decreased by 60.9 per cent during this period, its length actually increased much to the puzzlement of researchers. After is marathon fast the snake was given some milk and has since been restored to full physical health (Eiichi Nakamoto, pers. comm.).

If you are even remotely interested in animals, I strongly recommend tracking down a used copy of Wood's book. It's a shame that is has not been updated in 26 years, but it's still an awesome compendium of amazing stuff.

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Thursday, May 15, 2008

Shoot the moon II: Getting the most out of your binoculars

Part the First: Mount Up

The biggest pain in the butt about binoculars is that they shake. Or rather we do, no matter how we may try not to. If you can get rid of the shakes, using binoculars is awesome. But it ain't easy. Up until now I have done one of two things: steadied my binoculars against a nearby fence or wall, or steadied them against a monopod but without having them actually attached, just using the monopod as a sort of primitive mobile fencepost. But recently I came up with a better solution: I built a budget binocular bracket.

Lots of astronomy equipment companies sell dedicated binocular brackets, for mounting binoculars to monopods or tripods. The current issue of Sky & Telescope has a review of a premium model that costs $70. That's more than double the cost of my best pair of binoculars! Even the budget model from Orion costs $30.

Well, bump that. You can build your own for about $5. Go to the hardware store and pick up a steel angle bracket like the one shown in the photo above, some 1/4-20 nuts, and a 1-inch-long 1/4-20 thumbscrew. One of the holes in the bracket will fit over the 1/4-20 bolt on your monopod or tripod. Put on a nut and tighten 'er down. I used needle-nose pliers to get in there and get that nut nice and tight--you don't want your binoculars swinging in the breeze, no matter how cheap they were. Put a couple of nuts on the thumbscrew before you put it through the bracket--these act as spacers and keep the flat end of the thumbscrew from bumping up against the bracket when you tighten the rig. Then stick the thumbscrew through the bracket and screw it into the socket on the front of your binoculars. If the thumbscrew reaches the end of the socket before it's tight, pull it out and slip on one more nut as another spacer--that's what I had to do, and in the photo above you can just see the edge of the nut peeking out between the bracket and the socket on the binoculars.

Bang, you're done. Point the binoculars at something interesting and enjoy a completely shake-free view. I like running them up on my camera tripod and observing the moon without having to touch anything at all. I'm telling you, it's a qualitatively different experience from any binocular observing you've ever done in the past. And not just of astronomical targets--it's good for birds, landscapes, sunsets, your perverted neighbors, whatever.

And it's damn near free. If you use binoculars at all and own a tripod, there's no reason not to build one of these. And my tripod is not fancy--it's the absolute cheapest full-size model that Wal-Mart has to offer. It shakes and wobbles like crazy with a telescope on top, but it's plenty sturdy for a pair of binoculars or a camera.

Part the Second: Absolute basics of image processing

This is, no lie, the un-fiddled-with raw photo of the moon that I took through my Celestron 10x50 UpClose binoculars tonight. Well, okay, not completely un-fiddled-with. I did rotate and crop the image to get the moon in the middle and get rid of most of the empty field. But I didn't mess with any color or sharpness settings, so the moon itself is exactly as it came out of the camera.

I don't like to brag, but I was freaking amazed that I could get a picture that sharp using just binoculars. The 10x50s are quite a bit better than the Tasco 7x35s I used for my last attempt, but still. The image quality of the mounted binoculars is not far behind that of a small telescope, either visually or photographically (proof--compare these pictures to this one). The one advantage of even a small scope is that you can crank up the magnification if you want to see, for example, the rings of Saturn. On the other hand, binoculars are cheaper, lighter, easier to set up, and grab a lot more sky--all the reasons amateur astronomers use them in the first place.

Anyway, this part isn't about the binoculars. It's about what to do once you get a picture.

First thing, seriously, always, is Unsharp Mask. It looks like a gimmick but it's not. It can be overdone, like almost anything, but you should be able to play around with the settings minimally and find something that works. And it's available in just about every serious image processing program out there, including Photoshop and GIMP (the latter is free, BTW). The only difference between the photo immediately above and the one at the top of this section is that I applied Unsharp Mask in GIMP, using the default settings.

You'll notice some distracting color in both of the above images. The north edge of the moon is outlined in blue haze, and the southern end is an unwholesome-looking yellowish brown. That's chromatic aberration, and it's an unavoidable consequence of refracting light through glass. For telescopes you can buy anti-fringing filters, or super- or hyper-expensive apochromatic telescopes that use special kinds of glass to minimize CA, but even the best only knock it down to below the threshold of perception. It's impossible to completely get rid of. Physics is like that sometimes.

Let me amend that. It's impossible to completely get rid of in optical trains with refracting elements. A major advantage of reflecting telescopes is that they collect light with mirrors rather than lenses, so their views are blessedly free of CA.

Interestingly, I've never seen any CA on the moon through binoculars, and I've looked for it. Possibly the weak signal of color falling on my cones is just blown out by the intensity of light falling on my rods. Whatever the explanation, in my experience it is a strictly photographic problem.

This won't work for everything, but the moon is basically black and white in real life so it doesn't look weird if you convert the image to grayscale, as I've done here. And that's all I did--I didn't try to erase the dim halo around the northern regions, for example. It was always dim, and it only grabbed the eye because it was blue. Convert it to dark gray and it just disappears.

One last trick. I nudged up the contrast a little. It's really easy to overdo this, but if it's done right it certainly makes for a more interesting and pleasing image. The main problem with doing this on anything but a full moon is that the area near the terminator--the day/night line, where the lit part of the moon meets the unlit--drops off into blackness, and if you make the blacks blacker, the terminator appears to shift. Suddenly instead of describing a gentle curve or line from pole to pole, it zigs and zags as bright craters and dark maria pull it first one way and then the other. Which makes the photo look fake, because the real moon just doesn't look like that.

But there's an easy fix. Copy the image and paste it into a new layer. Bump up the contrast on that layer, and watch the terminator move. Once the contrast on everything else looks good, grab a big fuzzy eraser and erase the parts that got blackened out. The normally-lit terminator in the original image shows through. Flatten and save. You're done.

And so am I (UPDATE: no I'm not. Keep reading). Like I said, this is the bare bones of image processing. There's lots more here, and in many other places on the web. Have fun!


Hoo boy, what a dumbass I am. The picture above is actually how not to do contrast. I screwed up bigtime, but I'm leaving it in as a teaching tool. There are two big problems with that image, and somehow my poor addled brain didn't catch them until this morning. The first is that I only grabbed part of the image when I copied and pasted, so there is a distinct black box from the contrasty layer visible against the skyglow from the original background. Lesson 1: copy the entire image into the layer you're going to mess with. The second problem is that I colored outside the lines with the eraser, so next to the terminator there is a weird light-colored strip like a fuzzy caterpillar (if you can't see this, try tilting your monitor so the image looks lighter. Lesson 2: if you're going to up the contrast and then erase some of the contrasty layer, you have to be careful not to get off of your foreground target or the brighter background will show through. Both problems are fixed in this version:

I'd like to be able to say that I planned this little goof/save in advance, but I didn't. Just shouldn't process images in a dark room or blog when I'm tired. Sheesh. Keeps me humble.

Now I'm going to take Mike's advice and get back to work. No sarcastic commentary needed.

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Saturday, May 10, 2008

Shoot the moon: digiscoping 101

In a comment on a recent post, TheBrummell said, "Any advice on getting a couple of seconds exposure through 1/2 a pair of binoculars with a Nikon coolpix 5200?" Which may sound like a crazy question. Most of us own a pair of binoculars and a camera, but I'll reckon the fraction that have used the two in conjunction is vanishingly small.

I, however, am a member of this elite group. And I realized that although I have blogged the results of my digiscoping adventures here*, I haven't actually explained anything about the process, or given any instructions for doing it yourself. So here goes.

* A lot; possibly too much for those of you who came here hoping in vain for something paleo-related, but now that I have to feed SV-POW! regularly I send most of my paleo ramblings there.

What Digiscoping Is

Afocal projection photography, also known as digiscoping amongst birders and as white trash astrophotography by me, is the simplest and cheapest way of taking pictures using any kind of optical device: you just hold the camera up to the eyepiece and snap away. You can do it with just about anything. TheBrummell reports taking zillions of pictures through dissecting microscopes, my anatomy students take pictures of prepared slides through the compound microscopes in the teaching lab, birders and other nature lovers use spotting scopes or, less frequently, binoculars, and amateur astronomers use telescopes. The results can be striking--do a Google image search for 'digiscoped bird' and you'll see what I mean. The picture at the top of the post is my best image from 8 months of experimentation. Click on it for the full-size version, and check out the detail.

Okay, that's the what. What about the how?

Holding the Camera Steady

I use a Nikon Coolpix 4500, and for almost all of my pictures I really have just held the camera up to the eyepiece of whatever I'm shooting through. For steadier results you could put the camera on a tripod, or buy a dedicated adapter for mounting the camera behind the eyepiece, like the Steadypix from Orion (image from Orion's website).

I have also started experimenting with the camera on a monopod, which is what I used for the recent Earthshine photo. The monopod is nice because it's simple, lightweight, easily adjustable to any length, but sturdy enough to really damp out the little vibrations that you can't escape just because you're alive. (When I'm really trying to hold the camera still I can see my hands move ever so slightly in time with my pulse. Try it.) And mine was dirt cheap, something like $18.

An unexpected benefit of using a monopod is that it helps dampen out the shakes even when it's not on the ground, just by being long and heavy (relative to the camera). I discovered this when I was taking pictures in the OMNH last year and I wanted a tall-aspect photo, so I just picked up the camera plus monopod and flipped the whole rig on its side. The rig was easier to keep steady than the camera by itself, even when it wasn't propped against anything (you can sometimes prop a sideways monopod against a nearby wall, too).

Camera Settings

For settings I use macro mode, sometimes with a timer to eliminate the little bit of shake from manually pressing the shutter release. And I usually zoom in to eliminate vignetting, which is the "stopping down" of the image by the margins of the optical assembly (usually the field lens of the eyepiece). Here's what an unmodified vignetted image looks like:

Here's the same image rotated, cropped, and sharpened:

Vignetting is not a problem when I'm shooting at night, because the black margin does not show up against the dark sky. The settings I use to shoot the moon and planets don't usually show any stars anyway. If you want pictures of starfields, you'd be better off using a DSLR by itself--there are plenty of tutorials around that will explain how, and lots of camera-specific forums you can check out for advice and assistance.


Zooming in can also boost the magnification significantly. Magnification of any optical device is equal to the focal length of the objective divided by the focal length of the eyepiece. So a 25mm eyepiece will yield 40x in a telescope with a 1 meter focal length, but only 20x in a telescope with a 500 mm focal length. It is hard to get up to high magnifications with small refractors or Newtonian reflectors just because of that fact. Catadioptric telescopes like Schmidt-Cassegrains and Maksutovs have the opposite problem--their folded light paths mean that very small telescopes have very long focal lengths, and even fairly long-focal-length eyepieces still yield fairly high magnifications. For example, I have an Orion Apex 90 Maksutov-Cassegrain, and the tube is four inches in diameter and less than a foot long--which makes it a good travel telescope, because it fits in a carry-on bag with room to spare--but the focal length is 1250 mm, longer than my "big" telescope, a 6-inch Dob (see below).

So, two points. First, contrary to what most people think, the main point of a telescope is light collection, not magnification. A lot of astronomical objects are big but dim, like galaxies and nebulae. Some magnification is helpful, for sure, but the main benefit of the telescope is that it's light-collecting area is vast compared to that of the naked human eye. I've blogged about this before and I won't beat it to death here.

On the other hand, a good digital camera can pull more detail out of the scene than can your eye, thanks to the zoom. I took the photo at the top of the post at a telescopic magnification of 37x and a camera magnification between 2-3x. Which means my eye saw the moon magnified 37 times, and the camera saw it magnified somewhere between 74x and 111x, and recorded that. I have a 16x20 inch print of that image ($9.99 at Costco, and 12x18s are only $2.99!), and the detail holds up even at that size, which is waaay beyond what I can see with the naked eye at 37x.

Almost all of my moon photos have been taken at low telescopic magnification. The only exceptions are closeups of just part of the moon, like the second pic down here. I am usually forced to use low magnification for the whole-moon shots, just to get the whole moon into the field of view at once.

Exposure Time

Although my Coolpix autofocuses just fine, it's not so hot on figuring out exposure times for small bright objects in a sea of inky blackness. So I go over to manual for most stuff now. Here's why this matters--these photos were taken about a minute apart, but the one of the left is a two-second exposure and the one on the right is a 1/15 second exposure.

The moon varies in brightness a lot. If it's full or nearly full, I may use exposure times as short as 1/250 second or even 1/500 second. And obviously exposure time and camera steadiness are related--the shorter the exposure time, the less you have to worry about the shakes.

What To Shoot

Digiscopers with an astronomical bent have a limited choice of targets. Basically, the moon, the bright planets, and any evening or nighttime scenes you want to see really close up. Starfields are better imaged without a telescope, or with a long-exposure photo on a tracking mount, which is a whole 'nother kettle of (much more expensive) fish. Nebulas, clusters, and galaxies are too dim. You can image those things with simple webcams, but I'm not going to blog about that because I don't have any experience doing it. Yet. (My birthday is coming.)

Still, the moon and planets are pretty great. It is easy to forget that moon is an entire world. Yeah, airless and dead, but still: a whole world. And it's right there. Even cheap binoculars will show you tons of details that you can't see with the naked eye.

So far, the only planets I've shot are Saturn and Jupiter. The results are not going to make APOD, but you can make out cloud belts, rings, and the Great Red Spot, which is pretty amazing considering the entire operation consisted of holding the camera up to the eyepiece and pushing the button.

What To Shoot Through

Whatever you have. Seriously. Experimentation costs nothing, it's fun, and any result you get will probably be better than what your naked eye could have served up. So go nuts.

But if you want some advice, bigger is better. In the case of a large, bright target like the entire moon, the advantage of big optics is neither light-gathering nor magnification but resolving power. Compare these photos from similar phases but taken through scopes of different apertures:

Note that the middle photo was actually taken at slightly lower magnification than the one on the left, but the resolution is far superior. Here's what those scopes look like in real life:

The travelscope is the skeletal thing perched on the tripod. It's currently in its third incarnation, or fourth if you count its ignoble birth as a National Geographic toy (you can read my thoughts on the utility of the original product and the ethics of its marketing here). Previous evolutionary stages are here and here. The red ball-type scope on the table is my Edmund Astroscan, object of my desire since I was about 12 and my primary scope for car trips. The black howitzer-looking thing is my Orion SkyQuest XT6, a Newtonian reflector like the others, but on a Dobsonian or "Dob" mount. It's actually a lot more imposing in person--the tube is four feet long and seven inches in diameter, and the whole thing weighs 35 lbs. It just looks small next to me, which is an occupational hazard for us sasquatchi. And it does look suspiciously like a weapon, which often gets me weird looks from the neighbors and passersby when I set it up out front. So I invite them over to have a look through it, which is a great way to make someone's day.

I have done most of my digiscoping through the XT6, at first because it was my only telescope. I went through a phase this spring of shooting through the Astroscan, because it is so small and portable. I can sling it over one shoulder, put the camera over the other, stuff a couple of eyepieces in my pockets and be outside observing in about a minute and a half. But the images served up by the Astroscan are just a little mushy compared to those from the XT6, probably because of the fast optics--f/4.4 is a steep light cone. For a while it was kind of an enjoyable challenge to see how well I could do with the Astroscan, but pretty soon I got tired of really working for so-so images when I could get better ones for less effort through the XT6.

And by "so-so", I mean only by comparison to the images I'd already been getting through the XT6. I'm actually quite proud of some of my Astroscan photos, and I don't mean to knock the little scope at all. But Aperture Rules. I'm sure if I had a 10-inch scope to play with, I'd stop digiscoping with the XT6.

Which brings up the question of why I have so many telescopes (the Apex 90 I mentioned earlier in the post is not in the above photo, nor is the Explorascope I mention below). Partly it's because I'm a telescope nut, but partly it's because different scopes serve different purposes. The XT6 is both my default scope and my big gun. If I'm home and I want to do some serious observing or digiscoping, that's what I use. The Astroscan is my grab-n-go or quick look scope, my car travel scope, and the scope I share with my little boy. The travelscope, Apex 90, and Explorascope are all contenders in my quest for the perfect airline portable scope. And anyway, according to Ed Ting one really needs six scopes, so I'm still under the legal limit.

But wait, you say, why am I blabbing on about telescopes when TheBrummell specifically asked about


Yes, you can take pictures through binoculars. It takes some forethought. The first problem is mounting them. Almost all binoculars have a mounting socket at the front of the center column, usually covered by a plastic cap. Lots of astronomy and camera stores sell dedicated tripod adapters, which are L-shaped rigs with a 1/4-20 bolt on the vertical side to screw into the binoculars, and a 1/4-20 socket in the base for the tripod bolt to screw into. You could also make your own out of 1/4-20 thumbscrews and scrap lumber for about two dollars. UPDATE: a five-dollar solution is shown in the next post.

But that's not what I did. In my one adventure in binocular digiscoping, I used the Tasco 7x35s that I bought back in high school (or maybe even junior high). They have a mounting socket, but it's not a standard size, and I don't have a binocular adapter anyway. But I still got them mounted to the tripod. I used one of the struts from the travelscope, which has an inset 1/4-20 T-nut for tripod attachment, and simply lashed the binoculars to the strut with big rubber bands. It looked weird as hell:

How did it work out? Not too bad, actually. I had to squat down and put my head right next to the travelscope strut to sight the things in, but the focuser worked fine and I didn't have any problems taking pictures. I went a little nuts that night taking pictures of the same moon through several devices or none at all, in anticipation of writing this very post. Here's the comparison shot:

UPDATE: Gah! Better binocular photos now available, again in the next post.

The only real surprise in putting this together is how well the Coolpix did by itself, using maximum zoom and steadying the camera against one of the columns on the back porch.

To Shoot or Not To Shoot

I actually feel like kind of a weiner putting up the binocular shot here at the end, after having kicked off the post with a picture that is far better than you're ever going to get through binoculars. I'm not trying to discourage you--quite the contrary! The first time you get a nice, reasonably sharp photo of your own, it will feel pretty damn good. And it will hopefully make you want to do more.

I am always telling people that getting started in astronomy does not have to be prohibitively expensive. Even cheap binoculars will show you tons of stuff you can't see with the naked eye (especially if they're mounted on something), and not just on the moon. All of the Messier objects are visible in binoculars in dark skies, and most serious amateur astronomers spend at least part of their time observing with binoculars. Orion has several good beginner telescopes in the $100-250 range, a new Astroscan will run you $199 but used ones can be had for a little more than half that if you look around, and an XT6 is $269. But right now you can buy a workable telescope for about the same price as a modest pair of binoculars: Celestron's Explorascope, an 80 mm reflector, is on sale for under $40. Eighty mm is not much, and you won't get any XT6-worthy pictures through it, but the views will be closer to those through a six-inch scope than to those served up by binoculars (at least at higher magnifications; at low mag, maybe not). So if you've been reading and wondering if you'd get anything out of owning a telescope, now's a good time to find out without breaking the bank. I've got one in the mail, and I'll review it here once I get a chance to test it out.

Clear skies.

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Friday, May 09, 2008

Science you should know about: Homosexual necrophiliac duck rape

Moeliker (2002:fig. 2b): Wakka-cheeka-wakka-cheeka

Those funny guys at Zooillogix just covered the seal-brutalizes-penguin story that's been all over the news lately, which prompted me to post about my favorite scientific paper of all time:

Moeliker, C.W. 2001. The first case of homosexual necrophilia in the mallard Anas platyrhynchos (Aves: Anatidae). DEINSEA 8: 243-247.

Here's the entire text of the abstract:
"On 5 June 1995 an adult male mallard (Anas platyrhynchos) collided with the glass facade of the Natuurmuseum Rotterdam and died. An other drake mallard raped the corpse almost continuously for 75 minutes. Then the author disturbed the scene and secured the dead duck. Dissection showed that the rape-victim indeed was of the male sex. It is concluded that the mallards were engaged in an "Attempted Rape Flight" that resulted in the first described case of homosexual necrophilia in the mallard."

What the author doesn't mention in the abstract is that the 75-minute event ended prematurely when he separated the drake from the object of its perverted affection. Which makes me want to hit him (the author, not the drake). Because, why? Why would he end it? One minute was enough to document the behavior. After 75 minutes, surely any self-respecting scientist would want to know just how long this was going to continue, and watch until it was over. Now we'll never know. What a loss for science.

So if you see an animal doing something perverted--and they are, all the time, the unreconstructed little bastards--cowboy up and record the dad-blamed data. ALL OF IT.


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Tuesday, May 06, 2008

In for a penny, in for a pound

Aw, hell, here's the turtle. When I was growing up, with Herbert Zim's Golden Guide to Reptiles and Amphibians, this was Clemmys marmorata, but recent work shows that it is closer to Emys and the name Actinemys has been resurrected for it. And it really was just crawling across the driveway last week. I stuck him in a bucket, hauled him to school to show my ecology students, and then turned him loose in the creek towards which he was slogging when he was apprehended. And it is a him--check out that tail, and his plastron has a stronger arch than my feet ever have.

I'm pretty pumped to know that these things are around here. They're not doing great these days. For obvious reasons--show me a body of water west of the Sierras that isn't the center of a tourist trap, housing development, or agricultural or industrial outflow and I'll explain the optics of mirages for you.

I really just blog about this stuff to make Darren jealous.

Go, turtle, go.

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The moon by Earthlight

There's about a metric buttload of stuff I want to blog about, including the highlights of the Lick Observatory trip (now on my Flickr page) and some awesome predator/prey photos that one of my students took and the Western Pond Turtle that my wife caught crawling across our driveway last week, but it's the time of year when I've got finals to write and grade so all that stuff will have to wait.

In the meantime, this is what the moon looked like tonight. This fetching display is called "the old moon in the new moon's arms"; from the moon the Earth is nearly full and it bounces back enough light to dimly illuminate the shadowed regions of the moon. If you'd like to see it for yourself, you don't have to wait a month--the show should be almost as good for the next couple of nights.

For those who care, this was a two-second exposure with my Nikon Coolpix 4500, shooting through an Orion XT6 Dobsonian reflector with a 32mm Plossl eyepiece.

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