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by Jay Reynolds Freeman
Saturday evening, 19 June 1999, Lick Observatory held one of its public programs, atop Mount Hamilton, near San Jose, California. These fun events are much sought after by astronomically minded folks all over northern California. Lick is a small facility with few personnel, however, so when 250 people show up at once, the staff gets desperate enough to enlist the aid of local amateur astronomers. Many of the volunteers simply act as ushers, taking tickets and guiding guests up and down stairs into the domes of the 36-inch refractor and 40-inch reflector, but a few bring their own telescopes, to provide the visitors with variety. Such was my own mission for the evening.
I stuffed my 1987 model 6-inch Astro-Physics refractor into my Geo Metro, and secured it well, for the long, twisty drive up Mount Hamilton Road. My Losmandy G-11 mounting breaks into many manageable pieces, and fits unobtrusively into the cargo area of the Geo, which is quite roomy with the rear seats folded forward. But the rectangular pine box for the optical tube assembly is over four feet long, and I can only get it aboard by reclining the passenger seat and setting the box lengthwise on top, so that it overlaps the headrest and protrudes into the cargo area. It looks rather like a small coffin, or perhaps a large gun carrier. I often wonder what passers-by think I am carrying.
So close to summer solstice, the Sun set late. Guests were lining up while Sol was still blazing. Someone on the west side of the observatory had an ETX with a Sun filter, but the rest of us had set up in the courtyard on the other side of the main building, and were already in shadow. Fortunately, the first-quarter Moon was well-placed, and Venus stood high enough to be visible above the roof line. Our other telescopes included a 5-inch Takahashi fluorite and two C-8s.
Conditions were comfortable. I have a portable thermometer and relative humidity meter: In the shade, before sunset, the temperature was about 20 C and the percent relative humidity in the low 30s. Seeing was good as well, though at 124x, I was not pushing it. Venus showed a crisp fat crescent, by coincidence nearly the same shape and size through my telescope as was the Moon to the naked eye, surrounded by a mere trace of violet glow left over from the color correction of the pre-ED-glass Christen triplet. An interesting lunar feature was suitably illuminated for scrutiny -- I called many viewers' attentions to the crater Posidonius, with its arcs of interior walls.
The pellucid sky was so clear and transparent that it did not seem remarkable to be seeing Venus easily with the naked eye in daylight. When it finally registered that this experience was noteworthy, I mentioned it, too, to folks in line at my telescope. Later, immediately after sunset, I pointed out the dark gray band of the shadow of the world, rising from the far eastern horizon, in sharp contrast with the salmon-pink layer of air above it, still illuminated by the Sun. Over the next several minutes the dark band rose rapidly and started to cross the heavens, becoming more diffuse and less sharply demarked as the sky above it also darkened. Lick's view is sufficiently unobstructed that we could easily see that the shadow band sloped downward, to meet the south horizon ninety degrees from the point where the Sun had set.
As Mars emerged from twilight, I switched the telescope to it, and increased magnification to 248x. I had brought some Vixen Lanthanum LV eyepieces. Their uniform 20 mm eye relief makes it easy for beginners to enjoy high-magnification views. That is space enough for glasses, too, which further simplifies conducting a public star party -- I can focus the telescope with my own glasses on, then tell folks in line to leave theirs on, too, and expect the image to be sharp. I do have to be sure to remind users of bifocals or of "progressive" lenses, to look through the part that is best corrected for distant vision.
One common problem of newcomers to observing is not getting their eye in the right place to intercept the exit pupil. I kept reminding people to try to look straight down the axis of the eyepiece, and that if all they saw was blackness, to bob their head up and down and move it from side to side until they saw the luminous gray sky background, with stars and other objects within it, like a porthole on the heavens.
Mars showed considerable detail at 248x. The meridian at the center of the disc was about 60 degrees at the time of observation. Alas, the lines were too long for me to take more than a brief look, but the telescope was manifestly doing a good job. Mars can be disappointing to newcomers, because the features are so low in contrast. I warned folks in line that viewing Mars through a small telescope was rather like viewing the face of a person using makeup artfully and well. A casual glance may reveal nothing, but look closely and you will see where eye shadow has been blended in, or how a trace of rouge has enhanced a contour. Since much of Mars's color is due to iron oxide -- the classic rouge -- this description was useful chemically as well as visually.
I had put on my furry hat, of the type called an "ushanka", to keep from getting chilled. The temperature had fallen to the middle teens (Celsius). I noted happily that the relative humidity had fallen as well. In this area, that combination often indicates a developing inversion layer, which usually means good seeing. Several people commented that I was wearing a "Russian hat", which was twice true: Not only is the style Russian, but I bought the garment imported -- it is Soviet military surplus. "But of course, comrade," I quipped. "Red Planet, red hat!" I suppose I will have to dig up some garment associated with the "green" environmentalist movement, if I ever show Uranus at a public star party -- or maybe dress as someone from Oz.
Presently I switched to Messier 5. At 248x, this spectacular globular cluster was showing resolved stars against its background glow, all the way to the core. Most visitors agreed with my description of it as a "swarm of fireflies". Then we looked at M57. Experimentally, I kept the high magnification. A little less might possibly have been best for the Ring Nebula, but I believe everyone had a good view at 248x, and that magnification made the elongation of the ring, and its slow decline in brightness at the "long ends", more evident to many.
I took advantage of a lull to look at objects of personal interest. I am working on the usual Messier survey, that I do with all my telescopes, and ran through most of the ones in the south summer Milky Way. For this purpose, I put in a Vixen 8-24 mm zoom lanthanum eyepiece, to make it easy to find things at low magnification, then adjust power up for best viewing. The Moon was still up, so it was particularly important to use the best magnification for diffuse objects. The zoom eyepiece worked nicely and usefully -- to my eye, for each object, there was a range of a few mm in focal length that was noticeably better than other focal lengths. A decent zoom eyepiece does the work of six to ten ordinary eyepieces, not merely two or three.
There were no surprises in this work. Everything looked nice, many of the globulars were resolved, particularly at the upper end of the zoom's 52-155x range, and -- even with the Moon still up -- there was nebulosity in all the places we usually expect it.
I ended up with M8 in the field, and showed it to another line of people. "Stars in swaddling clothes", was my metaphor for this young cluster, surrounded by remnants of the gas it condensed from, now made fluorescent by the hot, newborn suns.
Later, I worked my way up the Milky Way Messier objects, all the way to M39. The little refractor (I cannot call it "big" when the 36-inch dome loomed over it) was loafing when I looked at Messier objects. As I have said before, a modern six-inch refractor is quite a lot more telescope than a six-inch Newtonian or Maksutov, both in ability to see subtle detail and in light-gathering. The latter advantage stems from two additional reflections in the other instrument types, off coatings that are usually less than perfect, plus light blocked by the secondary or diagonal. Refractors also tend to be extremely well baffled against stray light, which matters considerably when observing deep-sky objects. On the other hand, an Astro-Physics refractor -- even an old one -- costs a good deal more than most other instruments of the same aperture.
A few stragglers requested specific objects. Someone asked for M23, and I was pleased to be able to chase it down quickly. Someone else asked about M51, so I located this popular face-on spiral galaxy. At 52x, using the zoom eyepiece at its lowest setting, the central regions of both main galaxy and NGC 5195, the companion, were clearly visible, but then came the hard part, for a couple of the viewers were inexperienced. I carefully explained averted vision, and talked them through to where they could see the fainter, round disc of light that surrounded the central region of the main galaxy. Then I asked if it appeared at all inhomogeneous, and everyone could see that it did: They were beginning to detect spiral structure. Not bad for a six-inch telescope with a first-quarter Moon still an hour from the horizon.
After the guests had all left, I offered to watch the telescopes while the rest of the volunteers went inside for a little observing with the 36-inch. But when someone came to tell me it was my turn, I had my own telescope half apart, and did not want to leave it. So I did not get to look through the Great Refractor that evening. But no matter, my own teeny weeny one had done pretty well, and I am booked for several more nights as a volunteer this summer.