Peter Alway's Astrophotography Page

The Solar System

I'll start with images of our solar system, working out from the sun.  Some astronomical phenomena actually happen in the earth's atmosphere--so meteors and auroras will go with the earth, between Venus and Mars.

The Sun

Usually, the problem with astrophotography is insufficient light. A simple constellation photo requires at least a 15-second exposure, and galaxies and nebulae require many minutes to get an interesting image. Even the moon, in broad daylight at our distance from the sun, can require exposures longer than the few milliseconds of a terrestrial snapshot when you spread its light out with lots of magnification.

But the sun is an embarrassment of riches. I actually have one slide in my collection, labeled "Sun, 50 mm lens" that is completely transparent (overexposed white) with a little melted spot in the middle. I've photographed images of the sun projected on paper, but for this photo, I used an aluminized mylar solar filter to photograph our star.

Using solar filters can be tricky, by the way. A glass eyepiece filter, placed where the telescope's objective lens or primary mirror focuses, can overheat and crack if used on too large an instrument. A plastic filter at the same location would quickly melt or burn. You need a full-aperture filter that covers the front end of the telescope. Such filters can blur the image if they are not of sufficient optical quality. I borrowed the filter I used to take this photo back in 1982.

Colors in solar photos can be deceptive. Some of the neatest solar pictures, showing all sorts of detail, as well as solar prominences protruding from the limb of the sun, are taken in Hydrogen Alpha light, a spectral line of hydrogegn off in the red. Such images are often presented in deep red. The aluminized filter I used for this image actually made the sun look bluish. I've corrected the color to match the off-white color of the sun that I see when I project it onto white paper.

It's funny how common wisdom makes the sun yellow. If you think about it, though, our default outdoor light source pretty much defines white. Why does it appear yellow in every kid's drawing? Well, I'm not trained in the subtleties of color perception, but I do know a thing or two about optics, and it's all about scattering. Short wavelength (blue) light is scattered both by gas molecules and by dust in the atmosphere to give us a blue sky. That leaves the unscattered direct sunlight deficient in blue. When the sun is high in the sky, a slight loss of blue makes sunlight look slightly yellowish. As the sun gets lower in the sky, the light passes through more air, and the color shift increases, turning the sun more yellow, orange, or even red.

When the sun is high in the sky, though, it's just a touch on the yellow side. Scattered light from the blue sky partially compensates for that, giving us a landscape that is illuminated by light that is a little bluer than the sun as we see it, making the sun look a little yellowish.  If you look at a snowy landscape, you will notice that the snow looks bluish in shadow, where it is illuminated by scattered light, and yellowish in direct sunlight.

I could have skipped the whole color issue by turning the image into a greyscale picture, but I like that little tint. One last color issue--why is the sky black in this shot? Well, if you filter the sunlight enough to see detail on the sun, the light of the daytime sky is diminished in proportion--to black.

This picture shows the photosphere, the level of the sun that radiates almost all the sunlight we see. Below the photosphere (in the convective zone), the sun is opaque, dense, ionized gas; light can't escape. Above the photosphere--in the chromosphere and corona--the sun glows so dimly that it is is completely overwhelmed by the brilliant photosphere.  To see the outer layerschromosphere, you need either a total solar eclipse or a Hydrogen Alpha filter.  To see the Corona, you need a total solar eclipse or a space-based X-ray telescope.

Notice that the sun is dimmer around the edges--that's real, not a photographic defect. It's called limb darkening. The photosphere is not a well--defined surface, after all, the sun is a mass of incandescent gas (there's a fun song about that here). The higher levels aren't as hot and don't glow as brightly. At the center of the disk we can see deeper into the photosphere where it is hotter; toward the limb, we are looking through more of the higher, cooler gas.

The flyspecks--earth-sized flyspecks--in this image are sunspots. When I took my students out to look at the sun on August 30, 2006, we spotted one tiny sunspot. But the sun was a lot more active in 1982. I have never gotten a decent explanation of the root cause of sunspots--there are all sorts of complicated and chaotic things going on in the sun, what with turbulence as the hottest gas in the outer layers of the sun rises to the surface, radiates sunlight, cools, and sinks down again, the sun's constantly-shifting magnetic field, which constrains the flow of the ionized gas, the and the charges in the ionized gas that affect the magnetic field. The bottom line is that the sunspots are slightly cooler regions of gas that last for days or weeks.

You will note that many of the spots come in pairs. Typically the spots in a pair represent opposite magnetic poles. Larger sunspots comprise a darker core, or "umbra" and a not-so-dark "penumbra" around it. You can see hints of that in some of the larger spots toward the lower left, but at this resolution you might just see it as blurriness.

Mercury

Mercury was known to the ancients--it looks like a bright naked eye star. Except that it never ventures far from the sun in the sky (seeing as how it never ventures far from the sun in space). So unless there's a total solar eclipse going on, you'll only see it low in the east during morning twilight, or low in the west during evening twilight. For naked-eye viewing, twilight overwhelms Mercury's brilliance, scattering and absorption dim the planet, and often trees and buildings block our veiw. It's been reported that Johannes Kepler, the man who first calculated the elliptical orbits of planets never even saw Mercury with his own eyes.

For telescopic observing, the fact that you can only spot Mercury when it is low in the sky means that turbulence in the air--bad seeing--spoils the view. And Mercury is just plain small. Now that Pluto has been booted out of the club, it's the smallest planet in the solar system. A bit smaller than Mars, but while Mars can get to within 35 million miles of Earth, we only catch Mercury when its orbit takes it wide to the side of the sun, putting it close to the sun's distance of 93 million miles.

Before Mariner 10 visited Mercury in 1974, astronomers thought they had seen markings on Mercury, but they didn't see them clearly enough to even chart Mercury's rotation correctly.

You can kind of see that it's flat on the leftish-upperish side. That's because this was a half-mercury, illuminated by the sun to the lower right. The yellowish tint is because the planet was low in the sky. The red at the bottom an the blueish fringe toward the top-leftish is due to refraction of light by the atmosphere--if you watch the sunset with a telescope (with correct filters or projection) you will notice a reddish fringe at the bottom and a blueish or even green fringe along the top.

Venus

The Copernican Revolution is at the heart of science's creation myth. By this I mean the story of the origins of science, not of the world. We see ourselves as rebellious free thinkers, who follow reason and the evidence of nature, political or religious orthodoxy be damned. Even the crackpots love the story of Copernicus, Galileo, and Kepler. "They laughed at Galileo," says the self-styled revolutionary genius.

Galileo saw a lot of things with his little refracting telescope. Craters on the moon, proving that celestial bodies have pits, sunspots showing that even the face of the sun had zits. Jupiter's moons were a microcosm of the solar system. But for me, the nail in the coffin for the old Ptolemaic, earth-centered worldview would be the phases of Venus. If Venus is a crescent, it's on this side of the sun. If Venus is full or gibbous, and in the same part of sky as the sun, it has to be on the far side of the sun.

I took these three photographs months apart. Each was taken with the 24-inch telescope at the cassegrain focus, so the image size is proportional to the apparent size. I added a little glow to the lower-right corner, because that is the direction of the sun when you see Venus in the evening.

You can see Venus on our side of the sun, looking big and crescent shaped, and Venus on the far side looking small and gibbous. Galileo saw this with his own eyes, and recognized that he was watching Venus orbit the sun.

The sulfuric acid clouds of Venus obscure its surface completely. The planet looks like a brilliant white star to the naked eye, and is even visible during the day as a chalky-white point of light, if you know exactly when and where to look. The colors in these images are entirely due to the earth's atmosphere--the red fringe at the bottom and the blue fringe at the top are from refraction, and the yellowish tint is from scattering.

Aurora Borealis

In the summer of 1983 I had borrowed my parents van to move from one student abode to another.
I took advantage of the van to drive out to Peach Mountain, my refuge, alone. An old 24" research telescope had been left to the local amateur astronomers at the site, a hill to the northwest of Dexter, Michigan. The University Lowbrow Astronomers, a group of students and a couple of townies (now it's been taken over by townies and there is separate student astronomy club), were given keys, took over the telescope, restoring it to usable condition. The club still uses the scope, and opens it to the public on clear Saturday nights close to the new moon.

I had been the passenger on many trips out there, and had access to keys to the gate and to the building. This was, I think, the only time I went out alone. Well, not completely alone. There was a guy camping out in a sleeping bag near the site. Spooked me, but he seemed harmless enough. I rolled open the observatory roof, and pointed the telescope at something. I have no record of  what. But the sky was hazy. I was quite disappointed by the haze, until I noticed a pattern of vertical streamers.

This was an Aurora Borealis--the Northern Lights. Particles from the sun--essentially protons and electrons from hydrogen atoms--are continuously trapped by the Earth's magnetic field. The live invisibly over our heads in the Van Allen radiation belts, named for James Van Allen, who discovered them in 1958 with an instrument he built for the first US Satellite, Explorer 1. Van Allen is still alive and kicking--I just read in August of 2006 that he had published a new paper in some journal.

But when the sun is active--and it can happen unexpectedly at any time in its 11-year cycle of activity--it can send out more particles that distort the Earth's magnetic field and dump particles into the Earth's atmosphere at Michigan's latitude. The field constrains the particles to move along field lines--the bright vertical lines in the aurora trace the earth's magnetic field lines. Your pocket compass picks up the horizontal component of the magnetic field, but here in Michigan, the field is actually mostly vertical, so the streamers are vertical.

As the protons and electrons of the solar wind/Van Allen Belts hit the upper air, they knock electrons loose in the atoms and excite them to radiate light. With Oxygen, nitrogen, and hydrogen available, shades of green, blue, and red can appear in the auroras. The glow happens high up--hundreds of miles. As the particles get farther down, the atmosphere gets denser, so that the glow is brighter lower, until the air is too dense for the particles to make it through, so that the aurora stops something like 100 miles up--the bottom of the shimmering curtains, flickering spikes, shining pillars, or vague glow that characterizes the aurora on the night you are lucky enough to spot it.

In my photo, you can see the vertical spires tilted slightly to the left, fading out at the top and reaching a peak intensity near the bottom. Those spires are the Earth's magnetic field lines rendered visible. The glow running from the center of the right edge to the center bottom edge (hypothetically, as your view is blocked) comes from altitude where the most particles are absorbed and the glow peaks--the sky is dark below that level.

The black frame is the 24" telescope. The auroral glow is reflected in the cassegrain secondary mirror. The dome is illuminated by red lights that allow observers to navigate the dome without losing their night vision.  Casseopeia is to the right, Arcturus is to the right, the Big Dipper is partially covered by the telescope--you can see part of the "cup" of the dipper through the frame. I took this shot with a fisheye lens.  I don't know the exact date of this photo, but the slide was processed in August of 1983.

Meteor

Sometimes an astronomical photo is a matter of luck--but just as serendipity favors the prepared mind, it also favors the open shutter. This is one of my earliest astrophotos, dating to December of 1979. That fall, Joe Patterson, a postdoc at the University of Michigan had heard rumors that the U had a 24-inch telescope "lost in the woods" somewhere. (publicly using the words "lost in the woods" or "abandoned" would get people a stern talking-to later.  In fact, I will add a disclaimer in case anyone from the U of M Astronomy Department sees this--I am not claiming the University lost or abandoned the instrument, but rather that those are the words Joe heard when he started asking after the 24"). Joe was able to locate the instrument, and get an amateur astronomy club going. As a 19-year-old student, I attended the first meeting of the University Lowbrow Astronomers, named in contrast to the highbrow PhD astronomers in the department.  The club is going strong today, thought the membership has changed from students to local folk.

Even before the telescope was up and running, the student members recognized the value of a dark observing site. When the annual Geminid meteor shower rolled around, on or about December 13, a bunch of us rolled out to Peach Mountain, maybe 15 miles northwest of town.

The best way to observe meteors is with the naked eye. Lie back comfortably somewhere with a broad view of a dark sky and wait. During a shower, you might see as many as one or two meteors per minute (there have been exceptional cases, like the intense Leonid "meteor storms" that have hit roughly every thirty-some years, where there are dozens of meteors per minute). It's a slow, easygoing affair, best combined with friendly chatter and generic constellation gazing.

Meteor showers happen when the earth crosses the orbit of a comet, and plows into the debris shed by its nucleus. Though I just learned from the link above that the Geminids come from a weird comet-like asteroid.

Shower meteors appear to radiate from a point in the sky (called the radiant) that depends on the combination of the earth's motion, and the orbit of the debris stream. Imagine driving through a heavy snowfall at night. The snowflakes are coming straight down, while you are driving straight forward, and they appear to come from a point above and ahead. If there is a crosswind, they come from a little off to the side, which can be very disorienting. The Geminid meteors appear to come from Gemini, hence the name.

Because they come from comets, shower meteors tend to be made of fluffy stuff that doesn't make it to the surface of the earth--last I heard, there have been no meteorites recovered from a meteor shower.

I brought a little 35-mm rangefinder camera that my dad had lent me, a tripod, and a cable release. I pointed the thing vaguely up, and left the shutter open for 5-10 minute intervals. I figured that if I didn't catch any meteors, at least I'd get constellation shots. Today's photo is about a five minute exposure of the constellations Auriga (pentagon filling roughly the lower left quarter of the frame), Perseus (along the right side), and Camelopardus (the Camel-Leopard, now called the Giraffe, in the top-left) I captured a meteor zinging through Camelopardus--it's the long streak near the top of the image.

The radiant in Gemini is off to the lower left of this image, so the meteor would have been travelling from left to right.

I know it was a five-minute exposure by the trailing of all the star images. They trace the rotation of the earth, and checking against my trusty old Norton's Star Atlas, I see that they cover 5 minutes of right ascension. So this image has a thousand star trails and one meteor trail. (My spiffy Milky Way and Andromeda shots don't show the trails because I attached the camera to a telescope with a clock drive that compensated for the earth's rotation.)

The meteor doesn't look so bright compared to the stars in this image, but keep in mind that each star trail represents five minutes of light spread across a little short trail, while the meteor flashed for no more than a second. It was probably as bright as the brightest stars in the field. Not bad for a pea-sized clump of dust vaporizing a hundred miles up, zinging by at tens of thousands of miles per hour.

The Crescent Moon:  Earthshine

The moon always keeps one side facing the earth, more or less. The moon rotates on its axis at the same average rate it revolves around the earth. The moon spins at a very uniform rate, but its motion around the earth isn't quite constant as it follows its eccentric orbit. Technicalities aside, there is a side of the moon we never see from earth, the far side. One of my pet peeves is people who call the far side the dark side, when, of course, the far side gets as much sunlight as the near side. The dark side of the moon is the half of the moon that happens to be pointed away from the sun tonight.

Today's photo shows the dark side of the moon. whatever the moon's phase as seen from earth, the earth appears to have the opposite phase as seen from the moon. At new moon, the moon sees a full earth, at the full moon, the moon sees a new earth. Just as the full moon illuminates our landscape, the full earth illuminates the moonscape. Only moreso. Not only is the earth's diameter nearly four times that of the moon, (meaning it fills a patch of the sky close to 16 times bigger), but our white clouds reflect more light than the moon's dark grey dust. One of my favorite sights is the lunar landscape illuminated by a bright earth in the sky. This is best seen on a thin crescent moon, when the moon sees us as a nearly-full gibbous moon, though I've been able to catch a glimps of it at first quarter. Thin crescent moons are highest in the sky on spring evenings and fall mornings.

I took this picture with my old 6-inch Criterion Dynascope, a Newtonian Reflector with a clock drive. I was borrowing one of my Dad's Canon SLR's, with an adapter that replaced the lens on the camera and the eyepiece on the telescope--this was prime focus photography, where the telescope's mirror functioned as an f/8, 1200 mm telephoto lens.

The bright side of the moon is in direct sunlight, so I usually would expose a shot like this for some reasonable fraction of a second--1/60 of a second or whatever I worked out to be appropriate for the film I was using, but to get the earthshine, I grossly overexposed the illuminated side of the moon, and exposed for, I'm guessing, 2 to 15 seconds.

You can see some of the maria on the dark side of the moon, and you can imagine what it would be like to cross the lunar landscape at night, your way dimly illuminated by the glow of the big blue and white planet overhead.

Lunar Eclipses

A theme of my astronomy class is "how do we know what we know." Specifically how do we know how far away and how big things are in space. Historically, the earliest quantitative astronomical measurements of size were made by the Greek Aristarchus vaguely around 300 BC. He recognized that the dragon that ate the moon during a lunar eclipse was nothing more than the earth's shadow. By noting that the edge of the shadow--our silhouette--was always a circular arc of the same radius, he proved the earth is spherical, roughly 1800 years before a confused Columbus thought he had proved the earth's circumference was smaller around the equator than pole-to-pole.

In my astronomy class, I have my students measure the curvature in the shadow of some of my old eclipse photos, and we measure that the earth's diameter is a little under four times the diameter of the moon's. Aristarchus did the same thing with the naked eye (I think he actually timed an eclipse, but it's the same idea of measuring the size of the earth's shadow compared to the moon).

Rather than post one of those photos here, I thought it would be fun to post a composite of several photos, all taken with my 6" Newtonian telescope.

The photo at the top is of the partial lunar eclipse of July 25, 1981, when the moon just skimmed across the northern edge of the earth's shadow. This image is particularly bright, because I overexposed it to show the dimly lit Umbra, or deep shadow. I took this picture out at Peach Mountain on a trip with my roommates--I know this because I also have a slide of them mugging for the camera with the partially eclipsed moon in the background.

Photos at the left, right, and center date back to the total lunar eclipse of July 6, 1982. That night, the moon passed near the center of the earth's shadow. The moon moves from right to left in its orbit, so that I took the shot on the right first. That first photo is exposed to show the penumbra, the fuzzy outer shadow of the earth that completely covers the moon in all these photos. This is the same as the fuzzy outline of your own shadow. An astronaut in the penumbra would see the sun partly covered by the earth.

The photo in the middle shows the totally eclipsed moon. If I had exposed it like the previous shot, it would appear totally black--I actually opened the shutter for 30 seconds to get this image. The totally eclipsed moon is illuminated by sneaky light that is refracted through the earth's atmosphere. A person on the moon would see the earth as a dark ball surrounded by a brilliant red ring of sunset. The light is red for the same reason a sunset is red--the atmosphere scatters the blue light (causing blue skies on earth), leaving the red to reach the moon.

You will notice that the north side of the moon is darker than the south side. That was a freak occurrence for that particular eclipse--there had been a major volcanic eruption (I think it was El Chichon in Mexico) in the northern hemisphere earlier that year, which absorbed more sunlight in the earth's atmosphere in the North.

The final 1982 image, on the left, was also overexposed to get the first re-emergence of the moon from the earth's deep shadow. This was a long eclipse, it was late, so I packed up and went to bed before the whole thing was over. I took these shots at a late-night public observing session on the roof of Angell Hall on the University of Michigan campus.

The bottom image was taken during a partial eclipse on June 25, 1983. This time, the moon skimmed the southern edge of the Earth's shadow. This photo is also exposed to show the gentle gradient of the earth's penumbra, or outer fuzzy shadow.

Taken together, these images show the the shape of the earth's silhouette--this is the closest I will ever get to taking a picture of the earth from space.

The Moon in Closeup:  Hadley Rille

I'm not sure when I took this photo, but it was probably in the early 1980's, just ten years after Apollo 15 landed not far from the center of the field of view.

Crossing the photo from the bottom left to just past the center of the image are the Apennine mountains. Like most lunar mountain ranges, they are really just part of a large crater rim--in this case, Mare Imbrium, the huge, lava-filled impact basin that dominates the northwest quadrant of the near side of the moon. Astronomy lecturer Jim Loudon always said that the impact that made the crater nearly broke the moon apart.

It was Loudon's lectures that turned me into a total space geek, and gave me a feel for the individual Apollo missions. What I remembered about Apollo 15 was that it landed near Hadley Rille, the remains of a river of lava or a collapsed lava tube from the time when the Imbrium Basin was inundated with liquid rock. The Apollo 15 astronauts came quite close to the gaping chasm, which was something like a mile wide where they visited it.

The 24-inch telescope at Peach Mountain has an effective focal length of about 50 feet--a remarkably long focal length making for extremely high magnifications--this image is about 700 miles (1100 km) wide (close to a mile per pixel), as wide an image as the instrument allows. The theoretical resolution of the scope would be about a sixth of a second of arc, or a sixth of a mile at the range of the moon, making Hadley Rille easy to see. But thanks to atmospheric turbulence, anything better than a mile resolution would be exceptional. Occasionally, however, when the sun angle was right and the seeing was good, one could make out Hadley Rille. This slide barely shows the wider part of the rille south of the Apollo 15 site. I've labeled a closeup of that part of the image. The two arrows point to the ends of the part of the rille visible in this photo. Apollo 15 landed in the plain to the northeast of the crater at the northeast end of the part of the rille you can see. I'm not sure I ever saw that part of the rille--I know I never photographed it.

Mars

The planet Mars has probably captured the imaginations of earthlings more than any other celestial body. Named for the god of war, Mars varies in intensity from an inconspicuous reddish star in the east before dawn, to a brilliant red-orange point of light, outshining even Jupiter, at opposition, back down to a dim star in the west in the evening, all in a roughly two-year cycle. Astrologers loved this foreboding planet, and as their telescopes grew large, so did astronomers.

In 1877, during a favorable opposition of Mars (a close approach. Technically, opposition means the time in the cycle that Mars appears directly opposite the sun in our sky, which actually means that Earth and Mars are on the same side of the sun. Favorable oppositions are when Mares is near perihelion, when it is closest to the sun, and thus the earth) Italian astronomer Giovanni Schiaparelli reported seeing fine lines on Mars, which he called "canali," or channels.

The filthy rich American astronomer Percival Lowell read "canali" as "canals." Lowell was convinced that these canals, thousand-mile-long straight lines that he also saw on Mars, had to be created by intelligent beings. He threw his share of his family fortune into creating the Lowell Observatory in Flagstaff, Arizona, where he could study these canals in detail.

Eventually he wrote three books about Mars: Mars, Mars and its Canals, and finally Mars as an Abode of Life. Lowells theories captured the imagination, even if they didn't persuade the astronomical community, and they inspired War of the Worlds, by H. G. Wells. This, in turn, inspired Robert H. Goddard to make advances in rocket science.

When I visited Lowell Observatory, I was impressed to see his big 24" telescope, now used exclusively for public observing (alas, it was cloudy the night we were in town, so we visited in the day). That's the same aperture of the telescope I used to take these two shots.

For all that Mars has captured the imagination, it is a disappointment in a telescope. While it does approach the Earth closely, more closely than any planet except Venus, it is a small world, a bit over half the size of earth. Its markings are faint and tought to make out, and its close approaches are few and far between. I consider myself lucky that I got any features on the planet at all in these pictures--each is a composite of three slides, I might add.

You can find my more detailed sketches of Mars dating to its 2003 opposition elsewhere on my site.

Jupiter

I really could have used Photoshop in 1981. Having access to a 24-inch telescope (that's diameter, for you non-astronomers) was great, and I took a lot of slides with the thing, but it was hit and miss. The problem is that the earth's atmosphere is a mix of warm and cold air. It stirs and churns and refracts the light coming through it like the surface of the water above you when you are diving. Of course, a clear sky looks placid above you, but at high magnifications, the churning of the atmosphere is a constant nuisance. You watch and wait for a moment when things smooth out enough for your telescope to resolve detail to its full potential. I took at least 17 shots of Jupiter on the morning of March 7, 1981, but I ended up throwing away all but five slides. One was a long exposure showing a couple of moons, and four were attempts to capture details in Jupiter's cloud tops.

I was hoping to get Jupiter's Great Red Spot, but some time during the 1970's, it turned elusive. Years before, it had been a dark red oval in one of Jupiter's whitish cloud bands, an easy sight in a small telescope. But it had tucked itself under one of the brownish-tan dark bands in the 70's, and also faded to a  subtle storm three times the size of Earth.

My memory is fading, but I'm certain that I would have shown these slides at an astronomy club meeting, and my fellow geeks might have walked up to the screen to try to make out more details. But the shots weren't great--the color balance was off--kind of bluish--when Jupiter is a warm tannish color to the eye. The contrast was low, and there was film grain, to boot.

Nowadays, amateur astronomers use a different set of techniques to photograph planets. Where I attached a single lens reflex, they attach a webcam to the telescope. They take a couple minutes of video, capturing thousands of individual images as the shimmering atmosphere alternately blurs and sharpens. They feed the video into their computer, where special software sifts through all the frames, picking the sharpest. Then it superimposes the images, kicks up the contrast with edge-sharpening filters, and generates an image that rivals the spacecraft images of the 1970's

When I found the four surviving cloud-top images of Jupiter, I scanned each, and superimposed them in Photoshop. The composite image was far less grainy than the originals, so I could kick up the contrast with the "Levels" function in Photoshop. Finally, I tweaked the color balance--not enhancing the color, but changing it from the false blue tint of the old slides to a more realistic tan-and-white impression.

I'm pleased to present my 25-year-old photo of Jupiter, looking far better than it did in 1981.
The Great Red Spot is the pale pinkish interruption in the dark cloud band immediately below the center of the planet's disk.

For scale, Jupiter is roughly ten times the diameter of Earth.

Saturn

Saturn is the most fun object to show students in a telescope. Most years the rings are easy to see, and when the seeing is good, you can see enough detail to get good sense of three dimensions. Saturn is small in angular size, and so it is not so easy to photograph well. In spite of about 60 slides of Saturn in my collection, none are really clear. In fact, before the Voyager spacecraft flew by Saturn in the 1970's even the best observatory shots of Saturn were grainy and blurry. Most of us learned to love Saturn from paintings.

Each of these photos is a composite of three horribly grainy shots taken on the same night. The nights were years apart--in 1981, 1984, and 1986. Each shot shows the rings facing more toward the Earth. At Saturn's equinoxes, the rings nearly disappear from view as we see them edge on. At the solstices the rings are more face-on. Saturn's 30-year period means that the seasons between those points are roughly 7 1/2 years apart. These photos show spring in the northern hemisphere as the rings open up for us earthlings,

I took these shots less than one Saturnian year ago. By the time I am posting this, it is late in northern winter.  Not too many years until the Saturnian equinox, when the rings will go edge-on again.

Uranus

Composer William Herschel discovered Uranus in 1781. While he's far better known as an astronomer than as a composer, I found a CD of some of his symphonies at a record store, and they are actually kind of nice.

While Uranus is just barely visible to the naked eye of someone with superb vision, Herschel found it with a six-inch telescope. I photographed it here with the 24" telescope (same for Mercury).

While Uranus is big--four times the diameter of Earth--it's far enough away that it's not much to look at. Astronomers reported coud bands on the planet long before Voyager flew by in 1986 (just a day before the Challenger disaster, so that hardly anyone noticed), but again, it's pretty much a blank, greenish planet.

The green color of the dot in this image is the only real information it contains. The original slide was actually underexposed, so when I lightened up the image, I got this really saturated color.

Comet Hyakutake

The mid 1990's was a good time for comets. In 1994, the nucleus of Comet Shoemaker-Levi 9 broke into a train of fragments and crashed into Jupiter as astronomers watched. Comet Hale-Bopp cut through light pollution to be an easy sight even from urban locations in 1997. Between them was a comet that was just as remarkable as sight, though it didn't get the same press--Comet Hyakutake. I took a number of photos of the comet; here is a scan of a big print of my nicest shot, taken on March 26, 1996.

I present two scans here, in hopes that one will look good on your screen. The top one looks best on my bright new monitor, but most of the comet's tail disappears on  dimmer old monitor. So I added the smaller B&W version that's quite a bit brighter, in hopes that everyone can see the full length of the tail.

And I should add that it was the length of the tail, or at least the apparent length as seen from earth, that made this comet remarkable. It wasn't all that bright--I don't know if I could see it at all from my home in Ann Arbor--but when I got out to the dark skies of Peach Mountain, I was amazed to see how far this comet stretched across the sky. I recall measuring it out with my hands (a fist at arm's length subtends about 10 degrees); Hyakutake's ghostly tail covered 60 degrees, or a third of the sky. Some sharp-eyed observers made out a 100-degree tail.  This photo is not a telephoto shot; it shows roughly thirty degrees of sky from top to bottom. The bright star to the bottom right is Polaris, the North Star, and a few stars of the Little Dipper run along the right edge of the shot.

While the nucleus of a comet is a "dirty snowball" just a few miles across, the tail--comprised of vaporized ice and the dust it carries with it--is typically millions or tens of millions of miles long--on the order of magnitude of the distances between planets in the inner solar system. So when the comet came within 10 million miles of the earth, the tail looked huge.

One cool thing that made photography easy was that the head of the comet passed nearly over the the the earth's north pole. To observers on earth, it passed very near the north celestial pole, where the sky's motion is the slowest. That meant it was possible to take a fairly long exposure--something like 1-2 minutes here--without blurring.

Aside from a few "short-period" examples, like Halley's, Comets are random. We haven't gotten any great naked-eye comets since 1997, but one could be discovered tomorrow and amaze us all in a few weeks or months. Or there may not be another good one in my lifetime.

Comet Hale-Bopp

Looking at what charts I could find online, and the position of the moon, I believe the photo was taken on April 9, 1997. The moon was actually a thin crescent, but it's overexposed into a general glowing blob. The big dish is the Universiy of Michigan's 85-foot radio telescope on Peach Mountain, near Dexter, Michigan, west of Ann Arbor.

Beyond the Solar System:  Deep Sky Objects

Amateur astronomers call stuff beyond the solar system "deep sky."  Usually deep sky objects are faint fuzzy things like galaxies, clusters, and nebulae, but they also include just plain stars.

The Constellation Orion

Orion is the king of the winter sky.  The three stars in a row in the center of the constellation, Orion's Belt, are a starting point for identifying a whole family of bright stars, constellations, and star clusters.  I'm particularly fond of the slide here. In manipulating it in Photoshop, I decided to emphasize the colors of the stars. I actually did a little Gaussian blur on the image to make the stars appear as little disks that show the colors of the stars. I think this image looks more like a star chart than a photograph, and I kind of like it that way.  I'll add that I did not "enhance" or intensify the colors beyond what the original film did.

At the top-left corner of the constellation is the red giant Betelguese, and you can clearly see its orangish tint, compared to the bluer stars in the rest of Orion.

Below the belt at the center, you can see the three stars in a vertical line that make up Orion's sword. Note the pink color of the middle star. That is M-42, the Great Nebula in Orion, birthplace of stars, and everyone's favorite deep sky object. The pink comes from the glow of the hydrogen gas that makes up most of the nebula, and in fact, most of the universe.

Orion Nebula, M-42

The top star in Orion's sword is actually two or three stars clumped together at the top of this image. The bottom star is barely in the bottom of this frame. The middle star is the Orion Nebula, glowing in pink at the center of this image.

I took this picture by attaching my 6" telescope to the frame of the 24" telescope at Peach Mountain. It was a precarious attachment, and I only took one slide with that setup. I was either too cold, too tired, or having too much trouble reaching the camera to take multiple shots, Or there were other people wanting to use the telescope. There are better pictures out there, but you can still see some neat stuff here.

First, the pink color is from glowing hydrogen--the most abundant element in the cosmos. The hydrogen is glowing because it is being illuminated by a group of stars in the nebula called "the trapesium" for the four brightest stars. They appear as a white blob just to the right of the little dark indentation in the nebula. That dark indentation is part of a dark cloud of dust that covers much of the nebula. You can see a little pink peeking out around the other side of that cloud above that dark indentation.

The Orion Nebula is the site of current star formation. The trapesium stars are new stars that formed in the nebula, and their radiation has blown a bubble in the cloud--the bright pink we see is the inside of that bubble. The combination of gas and dust provides the hydrogen that makes up the bulk of the new stars, and acts as fusion fuel, as well as the solid mater of planets. The dark dust is collapsing into disks around some of the protostars--Hubble space telescope images actually show the disks--which will eventually become planets.

The Orion Nebula is nice in binoculars, fascinating in a small telescope, and amazing in a big one. You just need to get somewhere with dark skies. You can't really see the color, though. With a very big scope the pink hydrogen glow has just the faintest tint, which my eye reads as "warm" or "brownish." The brightest part of the nebula actually has a greenish glow, from oxygen. Unfortunately, color film (or at least the color film of the 1980's) has a spectral blind spot--it doesn't register the wavelength of green light that oxygen produces. But with a huge telescope, your eye can actually can get a little hint of the green in contrast to the red of the dimmer parts of the nebula.  Now that astronomical photography is done with electronic detectors, the full colors of nebulas are more familiar.

The Milky Way Galaxy in and near Sagittarius

In his public TV series Cosmos, aired on public television circa 1980, Carl Sagan challenged viewers to imagine what it would be like to live on a planet just outside a galaxy, with a view of the great spiral filling the sky. You'd be able to see all kinds of nebulae, star clusters, and clouds of interstellar dust.

My reaction was that we already live in the outskirts of a great galaxy that we can see edge on. If you can get into a place with dark skies, you can see it spanning across the sky. But there are only a few images that show our Milky Way as an edge on galaxy--you really nead to make a composite of many photos for it to work. This photo would go near the center of the composite. It shows the heart of the Milky Way galaxy, in Sagittarius, as well as points north.

I took this slide in the summer of 1980 using Ektachrome film in a camera with a normal (50 mm) lens. I mounted the camera piggyback on a telescope--I'm guessing the 24-inch at peach mountain, and exposed for anywhere from five to twenty minutes.

The fun part, though, was sharing it with my fellow amateur astronomers, because it is full of dozens of obscure celestial bodies. I present two versions of the image here, one plain, and one with labels added for some of the deep sky objects.

That's the horizon at the bottom-right corner of the image--I've done some manipulation of this picture in Photoshop to subtract distracting sky glow, and that process sort of masked out the horizon as well.. Remember that this is not a telescopic view--it's the same sort of area you'd see in a normal snapshot. You can even see some thin clouds above the horizon. They are are tilted because this photo was tilted--I had to mount the camera on the telescope however I could, and since there is no up or down in space, I didn't worry so much about it.

The "teapot" is the most recognizable feature of Sagittarius. The whole centaur-archer configuration you see in the illustrated charts is, well, a stretch. Notice how the Milky Way rises like steam out of the cosmic teapot. Or is that a teakettle? I never drink tea myself.

M-6 and M-7 are two of the many not-comets discovered by Charles Messier, who catalogued about a hundred faint fuzzy objects that might throw off his efforts to discover comets. They are open clusters--clusters of stars orbiting within the Milky Way that formed together and are more or less holding together through mutual gravitational attraction.

M-8 is the Lagoon Nebula. It's a nice little haze around a cluster of stars that's easy to see in binoculars. One of my favorite summer objects. Its pink color indicates that it is a cloud of glowing Hydrogen gas.

M-20, the Triffid Nebula is an old favorite for 1960's science fiction shows showing the eerie and mysterious realm of outer space. I think it was on one of the overhead panel displays on the bridge of the original Starship Enterprise. It was named for the three dark dust lanes that split the pink hydrogen nebula into three pie slices.

M-17, the Omega Nebula is another pretty cloud of hydrogen that looks nice in a small telescope.

M-16, the Eagle Nebula, isn't all that great in a small telescope--It's another of those pink hydrogen nebulae where stars are being born. But it's very dramatic-looking in the old 1960's era images--another favorite cosmic backdrop. But the Hubble Space Telescope made it much more famous. Do a google search on "Pillars of Creation" to find some spiffy images of this nebula.

At the top, I have pointed out a few clouds of interstellar dust. You will see that there are a lot of those clouds throughout the Milky way. They give the impression of splitting our galaxy in two, as the dust has collapsed into a flatter disk than the milky way as a whole. The center of our galaxy is in the field of this image, roughly between M-6 and M-8, but interstellar dust blots it out in visible light. We can only detect it in longer wavelengths of electromagnetic radiation--infrared and radio--that ignore the tiny dust particles, whose size is closer to smoke particles than household grit.

The Andromeda Galaxy

To an amateur astronomer, fall brings to mind the most distant object most of us can see with the naked eye--the Great Galaxy in Andromeda, M-31.

M stands for Charles Messier, a French astronomer whose passion was discovering comets. To him, galaxies, nebulae, and star clusters were nuisances--the fools' gold of the sky. So he assembled a directory of fuzzy things that aren't comets, giving a number to each. Professional astronomers use the Messier numbers as a way of sounding objective and precise when speaking of those galaxies, clusters, and nebulae. Amateur astronomers use the Messier list the way birders use the appendix to their Peterson's Guides--as a checklist and test of their ocular acumen.

But the Andromeda Galaxy is often know to the masses as just "Andromeda." Technically, "Andromeda" is a constellation--a patch of the celestial sphere, signifying the general direction to a patch of stars that ancient Greeks fancied looked like a princess chained to a rock. The term "Galaxy" originally referred to our own milky way, which, in the light-pollution free nights of the past, lactated its way across the summer sky. Only ninety or so years ago did it dawn on astronomers that certain nebulae (clouds) in the night sky were Milky Ways--Galaxies--to themselves.

The Andromeda galaxy Is roughly 2-3 million light years from us, and something like 100,000 light years across, so it actually fills a respecable patch of the sky--much bigger than the full moon, actually But like our galaxy, its hundreds of billions of stars (wikipedia says it's been recently put at a trillion) are so widely dispersed that it shines with the faintest milky haze. You can see it with your naked eye from a dark site only if you know exactly where to look. A nice pair of binoculars is best for the purpose.

This month's Sky and Telescope magazine has a cover story on M-31's impending collision with our own milky way--a crisis that will come to a head in as few as 3 billion years--consequences, could include a close encounter with a star that could throw one of our nine eight planets out of its orbit.

M-33 is another nearby galaxy in our local group, not far from the Andromeda Galaxy. Some claim it to be a naked eye object, but I've never spotted it without binoculars.

In 1983, I bolted my camera piggyback to the 24-inch telescope at Peach Mountain, and pointed it midway between M-31 and M-33. I left the shutter open for somewhere between 5 and 30 minutes while the telescope guided it. I didn't shoot through the telescope--I took the picture with a 50 mm normal lens. The photo is not magnified beyond an ordinary snapshot. Long exposures like this pick up an ugly green background, from a combination of light pollution, sky glow, a faint natural aurora that is always present, and a quirk of chemical photography, called "reciprocity failure" where the sensitivity of the film goes nonlinear at low light levels.

Thanks to Photoshop, I was able to mostly fix that this evening, by grossly blurring a copy of the image such that all you could see was the green background, and subtracting the background from the original picture I also kicked up the contrast, so you can now see one of my 20-year-old photos far better than I could when it was new.

The Andromeda Galaxy is the elongated fuzzy blob near the top of the image. There is a fainter fuzzy patch about the same distance from the bottom of the image--that's M-33 in Triangulum.

Observatories

As a member of a couple of astronomy clubs, I've had the opportunity to visit, and occasionally use, a few observatories.  I've taken photos of a few of them in their natural habitat, under the night sky.

The Detroit Observatory, Ann Arbor, Michigan

The Detroit Observatory is located in Ann Arbor, on the campus of the University of Michigan, on Observatory street. It was named for the wealthy Detroiters who funded its construction in 1854. Those of you who are familiar with Ann Arbor geography might be amused to know that the entire U of M medical complex is built on land that was donated to the University specifically for use in astronomical research--the hospital really should be paying rent to the astronomers.

The 12-inch refractor was one of the largest telescopes, if not the largest telescope, in the US at the time it was built. It was used in the discovery of 21 asteroids and two comets

There was a second dome at the site, housing a larger telescope, but that was shipped out, and the dome torn down. The university now offers regular public programs at the site, but at the time these photos were taken in the early 1980's, opportunities to look through the telescope were rare.

The first slide shows the outside of the building on the night of a special tour in 1983. A dormatory is visible to the left. The clouds overhead are steam from the campus heating plant--a block away where I believe a shiny new biomedical research facility now stands.

If you look at the narrow window on the front side of the wing toward the camera, you will notice it reaches the roof, and even takes a slice out of the decorative element along the edge of the roof. That is a slit for the transit telescope. That's a smaller scope that only moves north and south along the meridian, used to time when a star transits--crosses from the eastern to the western sky. They used that scope to get the first accurate measurement of Ann Arbor's longitude. The instrument also maintained accurate time for Detroit. The far wing of the building houses a small classroom where the Lowbrows met for a few years. The masonry walls in the room gave it perfect acoustics for renaissance music, and the University's music school held a number of early music concerts in that room back in the 1980's They may still be doing so.

The second photo shows Dr. Orren Mohler showing off the 12-inch reflector to a crowd of amateur astronomers. He was an elderly professor emeritus at the time (1984), and he died many years ago. I recall a couple of his stories--for instance, before they installed wheels for the dome to turn on, it rolled on cannonballs distributed around the rim. The problem is that over time, all the cannonballs would work their way over to one side of the dome, so the thing would get stuck.

You can google "detroit observatory" and find a few relevant pages. Here is one put up by the Lowbrows:

http://www.umich.edu/~lowbrows/reflections/1998/dsnyder.13.html

Peach Mountain Radio Observatory

If you go to a library with bound back issues of Astronomy Magazine, dating back twenty-two years, find the January, 1984 issue, and flip to page 37. There you will find my first published photograph. The article is "Add Drama and Interest to your Astrophotos" by Kevin Moan. Basically it's about what I used to call "artsy nightime photos," where instead of straight astronomical photos that might well have been taken from orbit, the goal is to link the terrestrial and celestial in one frame.

The caption for my photo reads:

"Venus and the Pleiades shine behind an 84-foot radio telescope. Peter Alway used light from a full Moon to help illuminate the scene and color the sky blue; the equipment was a 50 mm lens and 400 ASA film."

That's a microwave radio telescope, by the way. The University of Michigan owns and operates it at Peach Mountain, northwest of town. I recall that they used it for systematic observations of quasars. I also recall that it was automated--there was a little support building on the grounds, but nobody worked there nights or weekends, but from time to time, you would here the motors grind and the bearings creak as it pointed from one object to the next. The scope still functions night and day. I recall going inside the building once when I was a student taking an observational astronomy class. In the radio astronomy unit, the prof did a series of scans across the sun in microwaves as we watched. I think we did some sort of calculations with the data, but I don't recall anymore.

In any case, the dish was big, and looked all sciency, and was located maybe a quarter mile from the 24" reflector where we spent our nights out. So it was a favorite to photograph, which is how it got into my astronomy icon. This particular shot was processed in March of 1983, and was taken when there was snow on the ground that winter--reflected moonlight from the snow illuminated the underside of the dish.

This was one of six to ten slides I submitted to Astronomy Magazine in 1983. They published this one and two others a couple of years later. It was kind of exciting to get published at the time--they paid $10 per photo, which was nice, too.