Table Mountain is not much of a mountain: you can drive right to the top. Located in Washington state about 15 miles north of Ellensburg, this broad rise to an elevation of 6,500 feet features piney woods, lovely open meadows, and nice dark skies -- the kind of skies that the average east-coast observer would kill for. Westerners, of course, have their own favorite mountains with even better skies, well away from Ellensburg and several other towns 50 or 60 miles away. Nevertheless, Table Mountain is a good site, and it's the place where about 600 observers gather every year for the Table Mountain Star Party.
The trouble with Table Mountain is that it has no electricity. When I decided to go to the Table Mountain Star Party this year, I started to ponder how I would shoot CCD images from the mountaintop. Those of you who know me know that I shoot my images with a homebuilt Cookbook CCD camera, but what I have to say should apply to pretty much every type of CCD camera; only the details will vary. Those of you who know me also realize that 99.44% of the CCD imaging that I have done has been from civilized locations with electricpower, and when I imaged at home, I have done so from the small observatory pictured in The CCD Camera Cookbook, or nowadays from the shop building beside my house. In other words, I had never been a roving imager running on 12-volt batteries before.
One option was to take some eyepieces with my telescope and stick to visual observing. But a couple weeks before the event, people started to call and ask if I would be there with the Cookbook camera. Without really thinking, I said, "Certainly!" so I was trapped, not only by the technical challenge, but also by the expectations of people whom I did not even know!
Now the Cookbook camera was never designed for use on mountaintops. Veikko and John had electricity in their houses, as did I. Because it makes so much sense to operate computers and highly-sensitive digital cameras in a backyard observatory environment, we figured most people would observe from the back yard. We didn't even think about mountaintop observing until we encountered Californians. Only then did we seriously start thinking about portable observing with the Cookbook camera.
California amateur astronomers are different. Most people in the United States do most of their observing in their own back yard or within a few blocks or a few miles of home. Californians hardly ever observe at home or anywhere near it. They hop in a car and drive 100 or 150 miles to observe. This is the natural consequence of California's big, well-lit cities full of people an hour's drive from mountains and deserts with dark skies.
What is true of the Cookbook camera is true of most other CCD cameras: to shoot images, you need power for the CCD camera, power for the computer, and power for the telescope. The Cookbook camera normally uses 120-volt AC power, the computer I use needs 120-volt AC power, and my telescope normally uses 120-volt AC power. However, the Cookbook power supply sold by Coherent Systems will run from 12 volts DC and the antique Orion VFO for my Byers 812 will run from 12 volts DC, so (in theory) I was home free on two out of three. That left (in theory) only the computer, a 386/25MHz in a mini-tower and a 14-inch monitor, to power from batteries.
Here's how the options stacked up: For about $100 I could buy a heavy-duty deep-cycle marine battery that would run the power supply and the VFO. Cables would run about $20 more. The total drain on the battery would be about 7 amperes, so a fully charged battery would easily last the night. For $200, I could get an inverter to make 120 volts AC for the computer and monitor, but the draw would be over 10 amps, suggesting strongly a second battery for another $100. Or, for about $1,500 I could get a laptop computer that would draw only an ampere, and one battery would do the whole job.
At this point, I will admit to feeling somewhat defeated. People who buy their CCD cameras have already laid out several thousand smackeroos in cold hard cash, so spending another pile of cash to go portable is no big deal. As a Cookbook camera builder, my CCD imaging has been inexpensive and I wanted to keep it that way. The laptop option was attactive at the "nice new toy" level, but I really have no use for a laptop. For years I have used a NEC 8201 (Kyocera's other version of the Radio Shack's Model 100) for writing on the go, and a fancier laptop wouldn't capture keystrokes any better. The bottom line was that portable observing costs a minimum of $400 and as much more as your want to spend. No wonder folks get sticker shock when they think about CCDs!
At this point, I got lucky. Mel Bartels and I had done several joint observing sessions in my yard with his 20-inch f/5 computer-controlled Dobsonian. The results were promising, so we were thinking of teaming up at Table Mountain to shoot more images. Well, it turned out that Mel had a 650-watt generator that he was willing to bring.
To make a long story short, Mel's generator worked out wonderfully on Table Mountain. The generator is a Honda model 650 rated for 450 watts continuous and 650 watts peak. We put it 25 feet away from the telescope and ran its output through a line conditioner. On three quarts of unleaded gas it would run three hours, and the best thing was that this generator was QUIET. It purred along for hours while we observed and nobody minded its sound. Sadly, it was cold on Table Mountain this year (about 35 degrees F with a 20 knot wind) so we were all miserably cold, but Saturday night was beautifully clear and once we got going, a dozen other CCD enthusiasts and I shot several hundred CCD images.
The most important result of the imaging for me was making direct comparisons between images taken from the pretty good skies over my house (the Milky Way is clearly visible, but somewhat washed out) to the very good skies over Table Mountain (the Milky Way gleams). My conclusion is that good skies make for better CCD images. Although CCDs are relatively insensitive to the amount of sky background, when the sky is black, the images are better. If you can, do your CCD imaging under good skies.
There is no moral to this story. However, I have learned that it is entirely practical to rent, borrow, beg, or buy a generator to go CCD imaging in the boonies, and really great (quiet, easy to start) generators exist. Powering the CCD camera from batteries is expensive but not unduly so. The killer comes when you try to power a 120-volt computer and monitor from batteries or when you buy a low-power laptop you have no other use for. (If you already have a laptop computer, then lucky you!)
One month later, at the Oregon Star Party in the Ochoco Mountains 50
miles northeast of Bend, Oregon, I used Mel's generator again for two nights,
this time taking over 50 megabytes of wide-angle color images of the Milky
Way using a 5.5 millimeter aperture f/3.2 lens. It was great fun, and the
generator purred happily providing power for CCD imaging.
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