Saturday, December 10, 2011

Hunting Himalia - Part One

It was a super autumn here in the wild west, restorative you might say.

After the brutal spring winds that started unseasonably early in February and finished unseasonably late in May—accompanied by drifts of choking smoke from the catastrophic Wallow fire in Arizona—I was fall-to-my-knees grateful for clean, fresh fall air, accompanied only by fragrant drifts of roasting New Mexico green chile. After the blistering heat of our first summer on the mesa—and the challenges of trying to stay cool in a minimally insulated outbuilding masquerading as a residence—the crisp, cool autumn air was invigorating. After more than a few dark days of doubt, I am again filled with hope for my homesteading adventure.

Bolstering my restored optimism are systems that are finally beginning to work as envisioned. We sorted out the problems with our photovoltaic system and are now powered 24/7 by our nearest and dearest star, the Sun. We acquired a full-size propane refrigerator, so no more cooler runs to the ice machine in town, a 30-mile roundtrip. Even the cell phone service at our homestead miraculously and mysteriously returned this fall, after going AWOL for four months.

Our propane generator has been repaired and works like a top; we use it for our occasional heavy power loads. Such as, tada, pumping water! That’s right, we’ve fired up the well pump and filled our water tank. After having our H2O tested for E coli and nitrates (it passed with flying colors), we drank deep from the aquifer deep.

Water flows for the first time at the homestead

Nope, no flush toilet yet, but we’re almost there. The holes were dug, the tank acquired, the permit signed off on, and then the John Deere tractor broke down. Machines rule. We need it both to set the tank in the hole and to fill the leach field with river rock. We acquired the tractor second-hand, and although nothing runs like a Deere, the previous owner did only the minimum maintenance required to keep it running. It’s been in the shop for a month as the mechanics give it a complete overhaul, disassemble each system, revise and re-revise the initial estimate, and order in more parts. My foot is tapping compulsively. Can’t they work any faster? Don’t they know they’re standing between me and the realization of my flush toilet pipe dream?


Speaking of dreams realized, this enchanted autumn I fulfilled 50% of my 2011 New Year’s Stargazing Resolutions. Okay fine, there are only two items on the list, but they’re tough ones.

My first resolution was to observe Himalia, the so-called “fifth moon of Jupiter.” Anyone who’s looked at Jupiter with even a decent pair of binoculars has seen the four Galilean moons, the moons discovered by Galileo in the early 1600s: Ganymede, Io, Callisto, and Europa. The bright, star-like dots are easily apparent as they orbit the planet, arranging and re-arranging themselves in different configurations.

Well, Himalia is Number Five, reportedly the only other of Jupiter’s 60-plus moons that can be observed by amateur astronomers. It’s tiny, and recovering the faint speck would be a challenge requiring a bit of preparation and a substantial telescope. No one I knew, even veteran observers, had seen it, which made it irresistible as an observing target.

Like the Galilean moons, Himalia is named for one of the mythological Zeus’s (Jupiter’s) romantic conquests; the nymph Himalia, seduced by Zeus when he visited her native island of Rhodes, bore him three sons. The moon Himalia is about 100 miles in diameter; compare that to the smallest of the Galilean moons, Europa, which is 975 miles in diameter. I didn’t know if I had the observing chops to spot a 15th-magnitude (really really faint) flea-speck 400 million miles away in outer space, but I was on fire to try.

The highest resolution image available of Himalia
Image source: NASA, New Horizons mission to Pluto

When the stormy summer skies gave way to azure days and inky black nights, and Jupiter returned to the eastern sky after sunset, I knew my window of opportunity had arrived. I began my quest by reading amateur astronomer Rick Scott’s invaluable how-to article.

His six-step approach was a bit daunting, however, and involved the purchase of a couple software aps, so I only did Steps #1 and #2 in preparation. I figured I would see how far I could get, and re-group if unsuccessful.

Step #1
I went to the JPL Horizons site to generate an ephemeris. An ephemeris is a table showing the position of a celestial body for regular intervals. This data would tell me precisely where in the sky Himalia would be at specific times so I could target the telescope correctly. On the input screen, I changed Target Body to Himalia, and Observer Location to the closest town to my location.

For Time Span, I first had to determine what time I wanted to start looking for Himalia. I wanted Jupiter to be fairly high in the sky because observing conditions are generally best when an object is high in your sky (you’re looking through less of Earth’s murky atmosphere overhead). So for that night, I settled on midnight. Since all astronomical events are expressed in Universal Time (UT), you need to be familiar with how your time zone converts into UT, so you can interpret the ephemeris when it spits out.

I inputted the following day’s date for Start Time, and the next day’s date for Stop Time, and selected “1 hour” for Step Size. This would give me a 24-hour ephemeris at 1-hour increments, more than what I needed, but spanning my planned observing time. A click on the “Generate Ephemeris” button, and Bob’s your uncle. Here’s what it looked like:

Step #2
Next, off to the Digitized Sky Survey (DSS) site to pull an image of the piece of sky I’d be looking at. This would tell me what stars lie in the field of view where I’d be looking for Himalia. Since the moon would be in motion and just passing through the star field, I could expect to see a “star” that shouldn’t be in that field, once I began observing.

Astronomers use a celestial coordinate system—a sky-grid, if you will—to pinpoint the location of celestial objects, as seen from Earth. Each object has a Right Ascension (RA) coordinate and a Declination (DEC) coordinate. I had the RA and DEC for Himalia listed on my ephemeris, for each hour. I knew that 12 midnight in my local time converted to 6:00 UT, so I transferred the RA and DEC coordinates listed for the 6:00 time slot into the DSS search form. I selected HST Phase 2 (GSC 1) in the Retrieve From field. For File Format, I selected GIF. For Height and Width, I retained the default setting, to generate an image 15 arcminutes by 15 arcminutes. The image would be oriented with the RA and DEC for Himalia dead center. A click of the "Retrieve Image" button, and I was able to view and print this image of my hunting ground.

The starfield where I would hunt for Himalia

I had secured my two key pieces of supporting documentation to take to the observing field. Just two more important preparation tasks remained before lift-off. Stay tuned for the exciting conclusion, in my next post.