My observing circle is filled with people with far more
observing experience than I, people who have been amateur astronomers since
adolescence, people who have forgotten more about astronomy than I’ll ever
know. Q: What can I possibly bring to the table? A: Enthusiasm!
When I read or hear about an object that intrigues me, and I
then find out it’s accessible to amateurs, suddenly I have to see it. I’m on fire
to see it—and make sure others see it too. I do like to instigate.
I’ll mention the object casually to observing pals, talk it
up, drop hints. In the process, I’ll sometimes discover that, amazingly, few to
none of the seasoned veterans have seen it. That’s all I need to hear to put
that object firmly in my crosshairs. In the case of Himalia, even the ΓΌber-observers of my club hadn’t seen
it. Here was an irresistible challenge: pursue an object even they hadn’t seen!
I knew the Fall 2011-Spring 2012 apparition of Jupiter would
be ripe for a Himalia quest. Jupiter was rising around 10 p.m. in September,
and so would be high enough to begin Himalia hunting around midnight. It’s
always a plus when you don’t have to stay up bleary-eyed until 4 a.m. to acquire
your target. Another big plus would be the warm late-September night; no clothing
layers required. Yup, this was gonna be great.
Final Prep Step #1: Assemble the Equipment
With the promise of good weather and clear skies as the appointed evening approached, the mate decided to retrieve his 24-inch reflector from storage, where it had been safely stowed since our move to the mesa. Although that may sound like mosquito hunting with an elephant gun, all that glass can help tremendously when trying to recover a 14.8 magnitude speck.
Since it’s not a tracking telescope—a motorized telescope
that keeps acquired targets in the field of view by compensating for Earth’s
rotation—we decided to place it on an equatorial platform, which turns a
non-tracking scope into a tracking one. Although the platform is heavy and must
be manually re-set every half hour or so, not having to worry about constantly
nudging the scope to keep your target centered is a huge plus when you need all
your concentration just to spot it.
Equipment Checklist
- 24-inch f3.9 home-made reflector (aka “The Cannon”)
- Osypowski equatorial platform
- 13mm Nagler eyepiece
- 4.5-inch Starblast with 24mm eyepiece (used as a finder scope on the 24-inch)
- Ladder
- Jellybeans
"The Cannon"
Equatorial Platform
Final Prep Step #2:
Assemble the Experts
With the mate—a more seasoned observer—at my side, I had substantially
increased my odds of success. While setting up at our astronomy club’s
observing site, we pooled resources by reeling in Kevin, a very accomplished
observer who also had Himalia on his life list and was keen to try for it. Kevin was familiar with the
motions of Jupiter and its moons, which proved extremely valuable in our shared
quest.
The Main Event
At the appointed hour, the mate re-set the equatorial
platform to get a full 30 minutes of accurate tracking, and then aligned his telescope
using his NGC-MAX (a computer controller that aids in locating objects). I read
off the RA and DEC coordinates for Himalia from my ephemeris (see Part One)
and he tapped them into the NGC-MAX. He inserted a 13mm eyepiece
in the focuser, as we had determined that the field of view produced would be a
good match to the field shown in the DSS image.
After pushing the cannon-like scope to the coordinates, he
climbed the ladder to the eyepiece clutching the piece of paper with the DSS
star field image. After rotating the paper once to the right, the image matched
what was in the eyepiece. A few bright stars in a triangle pattern and a
three-star arc within the target field helped. Piece of pie!
He then set out comparing the DSS image to the eyepiece
view, star by star. Finally, he was left with one star in the center of the
field of view that was not represented on the DSS image. It had to be Himalia,
didn’t it?
I climbed the ladder next, and using the DSS image, was
easily able to tick off the brighter stars in the field, including the triangle.
I made my way incrementally to each dimmer star in the field, but was only able
to see the top star of the three-star arc. I couldn’t see the two dimmer stars
below it. I waited to let more light integrate on my retinas. And then using
averted vision, I saw the central speck that wasn’t on the DSS image. The mate
confirmed that it was dimmer than the top arc star but brighter than the two
lower arc stars, which explained why I could see Himalia, but not the lower arc
stars.
Himalia was seen at tip of arrow
We huddled to confer. It couldn’t be just another star in
the field that was too dim to be represented on the DSS image, because it was
brighter than the two lower arc stars, which were on the image. It had to be
Himalia, didn’t it?
Kevin mounted the ladder next. He easily spotted the
“interloper” star in the field. We discussed whether we could see it move that
night. Observed movement against the background stars would be verification
that it was no star. Based on how much the RA & DEC coordinates on my
ephemeris changed over time, it seemed likely. In fact, Kevin predicted that,
if we waited about an hour, we would be able to see motion. With his knowledge
of the current motions of Jupiter & Company, he also predicted in which
direction we would see the Himalia candidate move.
I kept thinking: can it really be this easy? Rick Scott’s
article (see Part One) had made this target sound so daunting. As it turned
out, what we had—that the author didn’t—was aperture, 24 inches compared to his
10 inches. It made all the difference.
We waited about an hour to see if the suspected moon moved
against the background stars. Sure enough, it had shifted westward, moving in
the direction Kevin had predicted. Eureka! Himalia was ours!
I was only able to see Himalia with averted vision, that is, by using my peripheral vision and looking
at a spot in the black sky right above it, rather than directly at it. My two
observing partners were able to see it with direct vision, the second time they looked at it. This is
because 1) Himalia was then a little
higher in the sky and less obscured by Earth’s atmosphere, and 2) their eyes are annoyingly better than
mine. Given Himalia’s faintness, I was suitably impressed with Rick Scott’s
accomplishment, spotting it with far less aperture. How did he do it?
Although it was exciting to observe such a tiny fleck of
reflected light, one of the best views of the night, for me, was when I looked
at Himalia and couldn’t see it. Let me explain.
Starblast (little blue scope) riding piggyback as a finder scope
We were using a 4.5-inch Starblast, a nice little telescope
in its own right, as a finder scope (targeting tool), riding piggyback on the
24-inch scope and aligned with it. The view through the finder provided a much
wider field of view and much less magnification than the big scope. I could
therefore see Jupiter and all four Galilean moons, with a lot of black space
around them. Himalia was centered in the big scope—and staying centered because
it was tracking. So when I looked through the finder, I knew that Himalia,
although I couldn’t see it with such low magnification, was dead center in the
field of view. That allowed me to see the big picture, where Himalia was in
relation to its host planet.
I knew Himalia was considered a “far-ranging” moon; indeed,
most moons in Jupiter’s large harem have far-ranging orbits. Himalia floats
through space about seven million miles from Jupiter. Compare that to the orbit
of Earth’s Moon, a mere quarter of a million miles from its parent planet. The
view through the finder confirmed Himalia’s lonely orbit: it was more than one
degree from Jupiter, far from the mother ship and its four famous satellites. A
degree in the sky is two times the
width of a Full Moon as observed from Earth.
Four other seasoned observers on the field that night—Dave,
Bob, Ed, and Vance—came over for their first look at Himalia. This is what I
call “giving back”: for all the fabulous views of remarkable objects offered to
me over the years and for the unfailing generosity of the amateur astronomy
community.
Hunting Himalia was team astronomy at its best, and we seven
could now say we had “been to Himalia”!
