Sunday, March 24, 2013
Astrophotography the Old Fashioned Way
If you entered the wonderful world of astrophotography over the last decade or so, hoo-boy are you lucky. With your auto-guider and your DSLR and your CCD, getting pretty pix of the deep sky is just as easy as falling off a log, ain’t it, muchachos? No, you say?
Imaging is and probably always will be the most demanding and frustrating pursuit in the broad range of pursuits we lump together under the heading “amateur astronomy.” It’s tough no matter how good your telescope, your mount, your computer program, and your camera. When it all gets to be too much, it might make you feel a smidge better to ruminate on what your forebears had to go through. Yeah, in addition to having to walk ten miles uphill (both ways) through the snow to the observing field, we had to deal with FILM and MANUAL GUIDING.
But there’s more to the old fashioned way than that. There’s nothing to say you can’t employ the same techniques today. Why would you do such a thing? To save money, mainly. I don’t consider DSLRs expensive, but a film SLR is much less expensive than any of ‘em. Camera stores are letting their old SLRs go for a song, and I don’t just mean K1000s. I mean all the way up to the Nikon thoroughbreds. A perfectly functional Nikon F3, which was once the top of the top of the line, can be had for 200 bucks or less.
The drawbacks? Film choices are few and processing chemicals and enlarging paper are hard(er) to get. But it’s still possible to shoot on film. Some astrophotographers and a sizeable number of terrestrial imagers are doing just that. You also need patience to take astro-pix the old fashioned way, but patience is the hallmark of every successful astrophotographer. So, what is The Old Fashioned Way like, and what the heck does Unk know about it anyhow?
I was there almost at the beginning, in the 1960s, right before the amateur astrophotography explosion of the 1970s. As I have often said, I am far from being the world’s best astrophotographer. Hell, I struggle to be lousy, but I’ve been at it off and on for a long, long time and have pretty much suffered every sling and arrow an astro-imager can suffer.
Why did I decide to take up deep sky astrophotography in the first place? Two reasons, I reckon. It was mainly an outgrowth of my fascination with Moon pictures. I’d had a high old time taking snapshots of Luna. Once I moved beyond the simplest of the simple, afocal images with my Argus twin-lens box camera and began to make some headway, the idea of capturing galaxies, nebulae, and star clusters began to seem not quite far-fetched.
The other motivator? I had wrapped my mind around the idea that no matter how large a telescope I was able to buy or use, M33 and the other distant wonders that fascinated me would never look like they did in photos. Even if I could get a peep through the guiding “microscope” in the prime focus cage of the mighty Hale 200-inch, it still wouldn’t be as good, not even close, to what was on the “plate.” Well, then, I’d shoot deep sky wonders myself.
I did a little experimenting with my Palomar Junior and my home-brew six inch Newtonians, but the Pal’s store-bought GEM and the pipe mount I built to hold my sixes were not even close to being up to the task. They were shaky and were bereft of clock drives or even slow motion controls. The best I was able to do was some trailed images of some of the stars of the Pleiades. I went back to the Moon; the deep sky would have to wait till I had a sturdy mount with a drive.
It took a few years for that to happen, but it finally did in the mid-seventies with a Cave Model “B” on what I thought was a Rock of Gibraltar mount. After giving my big 8-inch a sufficient visual try-out on the deep sky under the black skies of northern Arkansas, my mind turned to astrophotography. Did I have what I needed? I wasn’t sure exactly what I needed, but I did have a telescope, a mount and a camera. One evening I slapped my Base Exchange-bought Yashica FX SLR onto the scope via a prime focus adapter and let fly.
The result? I did get a picture of M42. Sorta. I could see a bright spot near the center of the frame that might be the nebula. But the stars? Hell, they were just as trailed as those in my non-driven snapshots of M45. What good was a clock drive? I didn’t know; I didn’t know much of anything when it came to celestial picture taking, it turned out. I’d assumed the clock drive was the key. Turn it on, the scope tracked, and you opened the camera’s shutter and wandered back inside to watch Three’s Company until the exposure was done.
I took my problems to a couple of the Jedi Masters in my club, “You did what, Padawan? You weren’t guiding? For 15-minutes? And how did you polar align?” I shamefacedly admitted that I didn’t have much idea of what “guiding” was, and that I’d polar aligned by nudging the mount in altitude and azimuth till Polaris was in the eyepiece with the telescope pointed north in declination.
Thus began my education in astrophotography. First thing I learned was you gotta guide. Few drives then were good enough to track unsupervised for 1-minute much less 15-minutes at 1400mm of focal length. Hell, you’ve got to put out major bucks these days to get a mount/drive combo that will do that.
How did we guide back then? In the days before DC powered drives, you plugged the mount’s AC cord into a drive corrector, one of them electronic widgets whose pictures in Sky and Telescope had so puzzled me when I first began getting The Magazine in 1965. You then watched a guide star in a crosshair eyepiece. The “hand paddle” of the drive corrector would have buttons you pushed to vary the scope’s speed in R.A. (and sometimes declination). It would adjust the frequency of the current enough to slow down or speed up the R.A. AC motor a bit, allowing you to keep that star centered in the eyepiece for the entire length of the exposure. But how did you watch a guide star with the camera mounted on the telescope’s focuser?
I next learned what the “guide scopes” they went on about in S&T were for. You mounted a smaller telescope, most often a long focal length refractor, to the main scope, usually via adjustable rings. You centered your target in the main telescope, adjusted the guide scope until a suitable (nearby) star was in the crosshairs, and began the exposure, trying as hard as you could to keep that pesky star centered.
So, I’d have to have a drive corrector, a guide scope, and guide scope rings before I could get off the ground, huh? I emptied my bank account and bought a Vogel drive corrector, scarfed up a mount-less Jason refractor at the Little Rock flea market one Saturday, purchased guide scope rings and a crosshair eyepiece from one of the ads in Sky and ‘Scope, and let ‘er rip.
How were the resulting pictures? They were much better, much better. Were they perfect? No, the stars were still elongated, but at least they were not trails. The prints weren’t overly attractive, either; some where too light and some were too dark, but I didn’t think that was my fault. I figgered it was asking a lot to expect Fotomat, those once crazy-popular little photo processing kiosks, to print astrophotos. But it was them or the drugstore unless I wanted to go back to black and white with Tri-X. I wanted color, so the solution would be to process color at home. Sigh. Someday.
The next quantum leaps in my imaging results came when I abandoned the Cave for an Orange Tube C8 and replaced the guide scope with an off axis guider. The SCT turned out to be better for imaging for a couple of reasons. Most significantly, its short tube was easier to balance and was less prone to vibration when winter winds began to blow. The moving mirror focuser of the SCT was also a Good Thing. The camera was securely mounted since it did not have to move to focus.
The off-axis-guider (OAG) also helped. Y’all know I like those things about as much as a case of the measles, but for long focal length, long exposure deep sky film astrophotography they were a godsend. When you had to expose each frame for at least 30 minutes, the chances of flexure—the guide scope moving independently of the telescope due to the rings not being sturdy enough—was a fact of life. Flexure caused trailed stars no matter how well you guided.
An OAG, which intercepts light from the main telescope via a small prism at the field edge, cured that. Sure, it was hard to find a decent candidate star when you were limited to scanning the edge of the field—the prism could only extend a little ways into the light cone or its shadow would show up in the pictures—but it was still easier to get round stars with one.
Further improvement in my photos was slower in coming. By the early 80s, I was finally able to develop and print color film thanks to Beseler’s (kinda) easy to use chemicals and “2-step” procedure. But I had to learn what a deep sky astrophoto should look like in the first place. I didn’t get far till an old hand explained to me that the backgrounds of my images should be dark gray, NOT BLACK. A rule that will serve you well even today. That seemingly simple thing allowed me to begin to understand how to print color astrophotos.
What came next? The Halley debacle. I got a few OK images of the comet with my Super C8 Plus when it was on its way in, but when Halley arrived and the big show began (or was supposed to have), I failed fairly miserably. The problems? There were many. The comet was even dimmer than I feared, it was low down in the sky, the Possum Swamp weather was its usual pitiful self, and I still didn’t like to polar align using the drift method. I snapped away at f/10, but conditions, my reluctance to piggyback a camera (real men shoot through the main scope), and my poor polar alignment meant I came out with smudges not much better than my first M42.
When Halley had fled back into the darkness, I was well and truly disgusted with celestial picture taking and gave up astrophotography for nearly five years. But the bite of the imaging bug is a lifetime infection they say, and by 1993 I was missing the smell of hypo and those odd Bessler soups, and was outside taking more Moon pictures. In 1995 I began accumulating the gear I’d need get back to the deep sky, including a modern SCT, a Celestron Ultima 8, and was soon ready for Comets Hyakutake and Hale Bopp. What helped me take some nice pix of the two comets, and especially the Boppster? Not just the more modern U8, but a book, and me (finally) embracing piggybacking.
Heretofore, the knowledge I’d gained of astrophotography had come from two sources: buddies and my own experience. Neither of which is a bad way to learn, but I lacked systematic knowledge. That was provided by Michael Covington’s Astrophotography for the Amateur. It had everything from tables that told you how long to expose the Moon during afocal imaging, to plans and a schematic diagram for a drive corrector. It was (and is) the best introductory book ever written for film astrophotography.
One of the most important things Mike Covington’s book did was convince me to piggyback, to mount my Pentax K1000 SLR on the tube of the C8 and shoot the sky in wide angle fashion through the camera’s lens. Piggybacking made sense for a comet. A comet was BIG. You needed the comparatively wide field of a telephoto lens to get the whole thing in. The biggest plus was that at 80 - 100mm of focal length or thereabout guiding and polar alignment were non-issues.
When my first Hale-Bopp pictures came out of the print tank I was some kinda happy. They were not perfect—I had not captured the delicate blue ion tail due to the short exposures necessary in the light polluted Swamp. But they looked damned good if I did say so myself. Astrophotography bumbler Rod didn’t get his pictures published in Sky and Telescope’s “Gallery,” but they did appear in The Possum Swamp Register.
In addition to piggybacking, one other thing improved my pix: better film. I had always used Kodak and nothing but Kodak. But then I heard there was More Better Gooder in the form of an emulsion from Fuji called “Super G 800.” It was fast and it worked well for astrophotography. The owner of the local pro camera store told me he thought it was the best color print film he had ever used—for its speed—and, while he didn’t know pea turkey about taking pictures of the sky, it was so good he betted it would do a bang up job on that, too.
It did. I still like the piggyback shots I did with Super G. Its reciprocity characteristics—its sensitivity decline over the course of a long exposure—were excellent, it was easy to color balance, and if there was grain in this ISO 800 film, I had a hard time seeing it. It worked so well that for a while I was flat out piggyback crazy. But in the back of my mind a little voice still whispered, “Unk, you will not be a REAL astrophotographer till you master through-the-scope picture taking.”
I resolved to get back on the prime focus wagon, but this time I would make things easier on myself. Y’all know I don’t like to spend money, but I ponied up 150 bucks to the folks behind the table at the (late, lamented) Pocono Mountain Optics booth at the 1997 Texas Star Party. For a Celestron f/6.3 reducer/corrector.
Celestron had introduced this widget some years before. What the thing did was speed up your telescope. At f/6.3, exposures could be 2-½ times shorter than at f/10. The field would be wider, too. But that was not all. Optics guru Jim Riffle, who designed the reducer/corrector for Celestron, added in the “corrector” part. The “r/c” would flatten the scope’s naturally curved field, making stars look better at the edge of the 35mm frame. Sounded too good to be true, but folks I trusted told me it worked like a champ.
It worked just great, both for imaging and visual use. Hell, I got some acceptable pictures of Omega Centauri that very night at the TSP despite haze, clouds, and high winds. The reducer wasn’t magic, of course. Making the SCT faster resulted in more “sky fog” from light pollution. I’d just have to do my picture taking from darker sites once I got back home.
So, when a new club member stood up at a meeting and said he’d arranged for us to use an astrophotography quality site only an hour from The Swamp, I was a happy little camper. Why don’t y’all join me in reliving that expedition? Not only will you see how it went, you will see how an astrophotography run worked in those days near the end of the film era.
Once upon a time the paper companies were the lifeblood of Possum Swamp. All the big ones, including Scott and International Paper, had huge plants here. They were stinky, yeah, but that was, we said, the smell of money. The paper plants with their jobs were our saviors when Brookley Air Force Base shut down for good in 1969. Even after the plants began to leave for Asia a decade later, their lingering memory remained in tracts of company-owned pine forest. When the newbie said he had connections that would allow us to observe from one of those forests, I was excited.
I figured the spot just might be good enough for serious astrophotography. Looking at the map, the area in question was almost equidistant between the Possum Swamp and Pensacola light domes. I didn’t expect “perfect,” just “good enough” for half-hour exposures of a Messier or three.
So it was that one Saturday night me, my buddy Pat, and several other Possum Swamp Astronomical Society members convoyed across the bay to a gas station where we met Joe Newmember who would lead us to the site. We drove. And we drove. And we drove. One thing was sure: we would need the dude to lead us out when we were done; there were countless twists and turns over miles of rutted dirt roads before we got to the spot. My reaction when we did? “Oh for god’s sake!”
I suppose what I had envisaged when Bubba told us there was a tree-free area on the land was a spot that had been clear cut. Uh-uh. The open area he’d found was tree-free because it was a clay pit. It hadn’t rained in a while, so at least our vehicles didn’t get stuck in the red dirt, but, almost as bad, the arrival of the cars stirred up a thick cloud of fine red dust that lingered.
I had my doubts, but we’d come all that way, me toting my full astrophotography kit, so why not give the place a chance? Also, I also gotta admit “full astrophotography kit” wasn’t anything like a CCD setup today. No computer. No cables. No five or six batteries. Just the telescope and tripod, the dew shield, the camera bag, the Star atlas, and the small battery for the Kendrick dew heater. I was set up in two-shakes. Shoulda brought a tarp to put the scope on and prevent me from having to kneel in the clay dust, but otherwise all was well.
Until I went to polar align. The fine latitude adjuster for the wedge tilt plate consisted of a threaded rod, a bracket, and four nuts, two threaded onto the rod on either side of the bracket. Somehow two of those nuts had come loose, were way down the shaft. And the bracket had worked itself loose from the wedge tilt plate. Basically, the whole cotton picking thing fell apart in my hands. With the coming of darkness pressuring me, I got fumble fingered and had a hard time figuring out how to put it back together. I said bunches of bad words, which were echoed from the other side of the field by Pat, who’d dropped something or other onto his 24-inch primary mirror.
By the time I had got the latitude adjuster back together, it was full dark. I could finally polar align, but I wasn’t in the mood to do a drift alignment. I’d just use the Ultima’s “polar” finder. The 7x50 had a reticle that, with the aid of a little round paper slide-rule like calculator, allowed you to do a decent polar alignment. You set the date and time on the slide rule, and placed Polaris on the spot on the reticle it indicated.
Worked pretty well, but only if the finder and the scope’s polar axis were parallel. You ensured they were by rotating the tube in right ascension, adjusting the finder, and re-centering Polaris till it stayed dead in the center when you moved in R.A. I was too antsy to get going to do that, and just put Polaris on the reticle where the slide rule said to put it.
I liked to start out on an easy one, and M42 was still visible on this early spring night. Screwed the f/6.3 r/c onto the rear cell, mounted the Meade (yes) off axis guider onto that, and attached the Ricoh KR-5 Super II (like an improved Pentax K1000) to the guider by means of a T-ring. That was the easy part. The hard part was finding a guide star.
I put a reticle eyepiece, a 12mm Meade, into the OAG’s focuser. Focused the camera on a bright star, and focused the same star in the OAG’s guiding eyepiece. Which was not easy. Even the brightest stars were dim in an SLR viewfinder. They were derned near as faint in the OAG eyepiece.
Focus achieved, it was on to M42. Centered it in the camera viewfinder and went back to the guiding eyepiece. I was lucky a useable star was in view. Often I had to loosen the ring attaching the guider to the scope and rotate the OAG around the back, “scanning” for a guide star on the field periphery. If I couldn’t locate a decent star, I’d have to move the scope till I could find one, which would result in the imaging target being off-center. It was a constant battle to keep the deep sky object in the camera frame while seeking a guide star.
Hokay, almost ready to roll. Next step was to attach the remote (cable) release to the camera and double check that the camera’s exposure was set to “B,” which would hold the shutter open when I depressed and locked the cable release. I am guessing I am not the only film astrophotographer who ever shot an entire roll of “long exposure” images with the shutter speed at 1/100-second.
Then the real work began. Using the hand-paddle, I centered the guide star on the reticle and opened the shutter. The work was keeping that rascal centered. If it drifted the slightest amount, I had to press the hand paddle button that would move it back where it belonged. Immediately. The slightest deviation would result in an off-round star. I had to be sure I pushed the correct button, too; the image would be ruined if fuzzy-headed me mashed the wrong direction button at 3 a.m.
The biggest challenge was doing that for the duration of a long exposure. No 2-minute “subs” in them days, younglings. For the brighter objects, you wanted 30-minutes at f/6.3. Dimmer stuff? You’d be sweating over that guide star for an hour. I was lucky in that my scope had PEC, “Periodic error correction,” the ancestor of today’s PERMANENT PEC. The difference was that I had to redo PEC every night—once the drive was turned off, the recording disappeared. I’d guide for one full rotation of the worm to record my corrections and then playback the PEC file for the rest of the night.
It was well worth it to spend a few minutes doing PEC “training,” since it meant that momentary distractions would not usually result in a ruined picture. I still had to guide, but I could take my eye from the guiding eyepiece for a few moments—to swat a mosquito, to scratch my nose, to see what Bubba next to me was hollering about—and still get a good shot.
I kept going until the kitchen timer that was one of my most important astrophotography accessories dinged at the end of 30-minutes. What then? Rested for a few minutes, had a swaller of coffee—no Monster Energy drinks in the Dark Ages—and did another shot of M42. I still like to take “insurance” shots of my subjects, but it was especially vital in The Day. Now, I can usually tell whether I’ve got an object “in the can” by looking at the finished CCD or DSLR exposure on my monitor. It will look rough, but I will be able to tell. In the film age, you wouldn’t have any idea whether you’d got a good one or not till the negatives came out of the soup the next day.
And so it went. I essayed three subjects that night before the combination of blowing red dust and weariness got to me. I did a little visual after that, had some looks through Pat’s big-dob, and then our new pal decided it was about time to call it a night. I can’t say I was sorry. If there is a worse observing location than a clay pit, I don’t know what it is. Best thing? Back then gear tear-down was quick and easy. In about an hour and a half I was once more within the comforting halls of Chaos Manor South. “Never again,” said I, and we never did go back to that fracking pit. Our friend moved away in a few months anyhow. His heart had been in the right place, but, gee whiz, A CLAY PIT?
My results when I developed and printed The Clay Pit Astrophotos a while later? As usual, then and now, “OK, pretty good. Some problems.” My impatient refusal to do a good polar alignment resulted in some trailing due to field rotation, and there were spurious reflections generated by the reducer/corrector I should have fixed in the darkroom. I could bear to look at the pix, though, and can still bear to look at ‘em.
Does film astrophotography sound like torture? It really wasn’t, muchachos. It sounds at least a little worse than it actually was, and once you got into the groove it could even be—dare I say it?—fun. It’s certainly possible to still practice the art today, with a few dodges and workarounds regarding film, paper, and chemicals, and I might have a little more to say on that some Sunday if’n y’all don’t mind.
Next Time: My Favorite Star Parties: TSP '97...
A very interesting installment about shooting film, Uncle Rod. But I am not certain about the opening statement, that photography is the most demanding pursuit within amateur astronomy. To most amateurs, the challenge of photography is primarily technological (getting the equipment to work); the challenge of visual observing is primarily personal (trying to see). Neither is inherently more difficult. Seeing a detailed galaxy as a featureless blob is not demanding; imaging the detailed galaxy as a featureless blob is not demanding either. Astrophotographers are just not as content with fuzzy blobs as visual observers tend to be. One reason is that it is the nature of man to be demanding of a machine.
The challenge in imaging is _getting everything to work right_ and it can be very tough. Yes, visual observing requires skill, but at least you don't have to worry about them dadgummed egg-shaped stars. ;-)Post a Comment