President Bernie Zelazny called the meeting to order at 7:30 PM in Room 300 Lawrence Hall on the Sul Ross Campus.  There were 19 people present.
       Bernie reported on the recent launch of the Genesis Suncatcher Probe, a space craft designed to recover 10 to 20 micrograms of material from the solar wind.  The spacecraft will remain near the Earth's first Lagrangian point, 930,000 miles toward the Sun, where the pull of the Sun's and the Earth's gravity combine to keep a body "hovering" between them. 
       The minutes of the previous meeting were accepted as printed in the July Newsletter. 
       Jim Walker presented a program entitled Understanding the Seasons.

       Betty Grimm submitted the following treasurer's report:

       The Brewster County Commissioners voted unanimously on July 30 to adopt an outdoor lighting ordinance.  The ordinance will become effective 6 months from its adoption, a delay sufficient to allow local suppliers time to make acceptable light fixtures available.  Many thanks to Bill Wren, from McDonald Observatory, who was principally responsible for promoting the ordinance.

       On Saturday, August 18th, the 200 participants at the Saskatchewan Summer Star Party experienced an exciting moment as Canadian amateur astronomer Vance Petriew announced he had discovered a comet at the star party.  Petriew had been observing deep-sky sights with his new 20-inch Obsession reflector.  About 3:30 AM, he decided to swing over to M1, the Crab Nebula, but he never got there.  Star-hopping down from Beta Tauri, in the horns of Taurus, he stumbled upon a faint smudge that he suspected immediately was out of place.  Petriew checked his star charts to determine which galaxy he might be seeing.  Luckily, Richard Huziak of the Royal Astronomical Society of Canada's Saskatoon Centre happened to walk by for the first time that night, and Huziak knew there were none in that area of the sky.  The two observers plotted the object's position and continued to watch until dawn. Telltale motion through the stars certified that this was definitely a comet.

       Around 6:00 AM they called the Central Bureau for Astronomical Telegrams in Cambridge, Massachusetts. "With so many star parties going on the same weekend in the Northern Hemisphere I was sure someone else would have already discovered the comet," Petriew says, not to mention major sky-survey operations like LINEAR and NEAT.  But the discovery proved to be his alone, as he learned the next day.
       It is a rare event these days for any amateur to discover a comet visually.  But to do so at a star party with 200 other friends and fellow astronomers present to share the excitement was a rare moment for everyone.

       Does the sun rise in the east and set in the west?  The simple answer is yes, and indeed it does - exactly  twice every year.  On many of the other days, the sun may rise a long way from due east and set a long way from due west.  Figure 1 shows the directions of sunrise in the Alpine area on the two equinoxes and the two solstices.
       Notice that the sun rises directly in the east only on the two equinoxes, one marking the beginning of Spring and the other the beginning of Fall.  Literally, equinox means equal length of day and night.
       On the Summer solstice, which marks the northernmost excursion of the sun (in the northern hemisphere), the sun rises about 28 deg north of east in our area.  And on the Winter solstice, the sun rises a corresponding angular distance south of east.  The word solstice means standing still.  The sun isn't exactly stationary at the solstices, but it does move more slowly around those times.  Of course, it's the earth's motion - not the sun's - that causes these effects, but for our present purposes we'll talk as though the sun does the moving.
       You can use the above diagram to lay out a version of your own Stonehenge.  Barbara and I have built little cairns, piles of stone, in the locations shown by the pyramids in Figure 1.  We have also placed cairns to the west to mark the directions of the sunsets on these dates.  In the summer, the sun sets well north of west, and in the winter, well south of west.  Most people are aware of the movements of the sun in the course of a year, but many of our friends have been surprised at the actual extent of the movement. 
         The directions of sunrise and sunset also differ depending on your location, as Figure 2 shows (next page).  On the equator, as in Quito, Ecuador, the sun rises 23 1/2 deg N and S of east on the solstices (indeed, this 23 1/2 deg displacement is a kind of magic angle that enters into all sorts of things having great implications).
       Notice in Figure 2, that as we move northward from Quito through Alpine, Seattle, Fairbanks, and on to the arctic circle, the sun rises farther and farther to the north in the summer, and farther to the south in the winter. Anyone who thinks the sun always rises in the east will have problems navigating the bush country of northernCanada or Alaska.  Of course, there's always the compass.  Unfortunately, compasses become unreliable in many northern areas - exactly why is another story that would take us beyond our present concerns.  Notice how the sunrises move progressively farther to the north and to the south on the solstices.
       Figure 3, below, shows the directions of sunrise and sunset on a single diagram in the Alpine area. 
       If the diagram in Figure 3 were engraved on a metal disk, perhaps a foot or so in diameter, it could be mounted on a post or pedestal like a sundial.  Orienting the disk would then give the directions of sunrises and sunsets.
       A small version of the disk, above, might make an interesting refrigerator magnet.  Or if the figure were reproduced on porous ceramic, or printed on natural stone, it might make a nice coaster for your drink as you watch the sun go down.  Any other ideas???
       Figure 4 (below) shows the earth's orbit around the sun (size and distance are not to scale).  The earth's axis is tilted  23 1/2 deg with respect to the plane of our orbit.  It is this tilt that causes the different directions of sunrise and sunset throughout the year, as discussed above, and is also responsible for the seasons..
       The earth's orbit is very nearly circular, although I have shown it as an exaggerated ellipse to illustrate some points here.  During a single orbit, our axis remains essentially fixed in space, pointing close to Polaris, our current pole star for the northern hemisphere. 
       Notice that we are at aphelion, farthest from the sun, on July 4 - the hottest part of the year for the northern hemisphere.  At the same time, the southern hemisphere is in the dead of winter.
       We reach perihelion, our closest approach to the sun, on January 4, during our winter and the southern hemisphere's summer.  We northerners are roughly a couple of million miles closer to the sun during our winter, a trivial change in the sun's average distance of 93 million miles, not nearly enough to have any great effect on our temperature.  It is in fact the change in the angle of the sun's light that is principally responsible for our seasons.  In both hemispheres, the sun's rays a fall more nearly on the surface of the earth in the local summer.  A second factor is the longer days during the summer, which also result from the 23 1/2 deg tilt.
       If you have any question that a change in the angle of the sun's rays can produce great differences in temperature, then the highly scientific observations illustrated in Figure 5, below, should be convincing.
      As I was roofing our observatory on a sunny summer day, I stacked the asphalt shingles as shown.  The rather small difference in the slope of the east and west halves of the roof resulted in a huge difference in the heating of the shingles - proof positive that the sun angle makes a difference.  The difference in the angles here is only 28 deg, much less than the difference of 47 deg in the sun angle on the earth's surface between summer and winter.
        Figure 6, below left, explores the sun angles in the summer and winter a little more formally.  Angles are to scale, but not sizes and distances.  The stick figure represents a person standing upright in Alpine.  At the summer solstice, the sun is 83.5 deg above the horizon at noon, nearly overhead. 
       As we know, the noonday sun really beats down in the summer at our latitude.  At the winter solstice, the sun is low in the south at noon, only 36.5 deg above the horizon.  Some people have the impression that the winter sun is farther away than the summer sun, because some things low in the sky look closer than things that are higher.  Indeed, the Jamaican Travel Authority used to run ads encouraging people to get "closer to the sun."
       Notice that a person standing on the Tropic of Cancer on the summer solstice would find the sun directly overhead.  At all points between the Tropics of Cancer and Capricorn - in the tropics, that is - the sun is directly overhead twice each year, and fairly high at other times as well, compared with, say, Seattle or Fairbanks.  That's why the tropics are so tropical.
       We now reconsider Figure 4, showing the earth's orbit around the sun.  The orientation of the earth's axis is nearly constant over the course of a single year, but not quite.  In fact, our axis precesses slightly each year.  Over a period of about 26,000 years, the earth's axis rotates through an angle of 23 1/2 deg, rather like the axis of a spinning top.  This precession has many consequences.  Figure 7 (bottom left) illustrates the major factors in precession.
       One of the consequences of precession is the fact that the celestial poles do not stay in the same place in the sky.  Polaris has not always been our northern pole star, nor will it remain as such.  Indeed, it is nothing more than good luck that we have a fairly bright star near our celestial pole; the southern hemisphere doesn't have a bright pole star.
       Because of precession, the celestial equator and the ecliptic - the path of the sun through the sky - also move.  Since we measure celestial latitude in relation to the celestial equator and celestial longitude in hours of right ascension from the intersection of the equator and the ecliptic, the coordinates of objects are constantly changing.  How much?  Almost an arcminute each year, roughly 1/30 of our scope's field of view with a medium-power eyepiece.  Does that add up over a few years?  Sure does.  That's why star atlases are prepared for use at particular times, such as Epoch 1950, and Epoch 2000.  That's also why  Murray's 12" scope recomputes the positions of more than 63,000 objects every time we turn it on!  Even without telescopes, ancient astronomers were aware of precession by the second century AD.
       Figure 8 (bottom right) shows the path of the celestial pole through the heavens.  Thuban was the pole star when the ancient Egyptians were building the Pyramids.  In a little less than 13,000 years, Vega will be the closest bright star to the celestial north pole. 
       Actually, things are a little more complex than Figure 8 shows.  There is another kind of wobble in the earth's axis called nutation, a kind of nodding motion that adds a low-amplitude shorter-period component to the path of the celestial pole.  The gray circle in Figure 8 should actually be somewhat sinuous, or scalloped.
       And there are other complexities.  The tilt of the earth's axis does not remain constant, but may change cyclically from time to time, perhaps contributing to the great climatic changes that have brought on several ice ages.  Never a dull moment in the history of our planet!

If we have not yet received your dues, then please use the convenient envelope addressed to our treasurer that is included with this copy of your Newsletter.

Betty Lou Grimm, Treasurer
Big Bend Astronomical Society, Inc
1001 N 2nd Street, Apt F-22
Alpine, TX 79830