Most accurate from mid-northern latitudes of approximately 36-40 degrees, north;
(e.g. San Francisco, U.S.A. ** Madrid, Spain ** Tokyo, Japan)
Copyright (c) 1995 Pete Harris; **Back to Star Facts Home Page**
Updated for the month of: September, 1995
San Francisco Throws Star Party for 80th Birthday of Inventor
of World's Most Popular TelescopeOn the evening of September 2,1995, at the Randall Museum in San Francisco the San Francisco Sidewalk Astronomers will hold a ceremony followed by a public star party in honor of John Dobson, one of its starters (in 1968), and the person responsible for the well known "Dobsonian" design telescope. The star party beginning after 8:00 p.m., provides a chance for any interested persons to see the stars through telescopes (weather permitting). Earlier in the day, beginning at 10:00 a.m., public activities will include mirror-grinding and telescope-making demonstrations, a portable planetarium, moon rocks, slide shows and a computer demonstration. The Randall Museum is located at 199 Museum Way (nearest cross street is Roosevelt) San Francisco.
The Dobsonian telescope is probably the world's most popular telescope, used by amateur astronomers everywhere. It has opened up astronomy to the masses with its simple and affordable design, yet powerful capacity. It is a design that can be made at home by an amateur or can be bought relatively inexpensively and easily used. Dobsonians are known as "light buckets" that allow excellent viewing of dim deep space objects such as galaxies, nebulae, and star clusters. The design is a variation of the famous Newtonian reflector telescope in which a large mirror sits at the bottom of a long open-top tube, focuses the image back up the tube to a small flat diagonally mounted mirror close to the top, which redirects the image out to a side hole for the eyepiece. The telescope swivels manually on a simple plywood base, up and down and left and right (called an altazimuth mount), and the tube can be made of inexpensive cardboard-like material. It is called the "user-friendly" telescope.
John Dobson's philosophy is that if you own a telscope it is your duty to share it with people who don't. The sole purpose of The San Francisco Sidewalk Astronomers has been to share the sky with the public. Call Barry Hirrell at 415-681-2565 for more information about the day's activities.
Andromeda, “the Great
Galaxy”,Andromeda, shown as M31 on star charts, and known as the "Great Galaxy", is a galaxy 2.2 million light years away from the Milky Way, made up of hundreds of billions of stars. It is the furthest object in the universe that can be seen with the unaided eye, although that is only possible from very dark, clear locations. It is quite visible with binoculars or a low power eyepiece on a telescope. (See Star Facts article for September, 1995, The Andromeda Galaxy - the Most Distant Thing Human Eyes Can See" for further description).
Andromeda is best seen beginning in late summer and throughout the autumn. It is found in the constellation that bears its name - Andromeda. The easiest way to find it is to face north and locate the constellation Cassiopeia, which looks like a giant and slightly squashed letter “M” in the sky. During early autumn evening hours the "M" is positioned sideways rather than right -side-up. Using the left half of the “M” as an imaginary arrowhead, go about 1 1/2 fist widths (the width of your clenched fist held up to the sky at arm’s length) in the direction the arrowhead points in. Scan this area with binoculars to find the fuzzy patch of light that is Andromeda. Sweep back and forth over the area until you begin seeing its dim outer regions that give it an oval shape. (See beautiful time-exposure Photo of Andromeda from Jason Ware's home page).
The "Great Square"
Dominates Autumn SkyFour moderately bright stars, called the "Great Square" dominate the evening sky during autumn. The Great Square is easily recognizable because it is surrounded by what appears to be mostly empty sky. During early autumn evening hours it is found a bit east of directly overhead, passing overhead at about midnight (daylight savings time), and moving west as the night goes on. During late autumn evening hours it is virtually overhead as darkness falls, and moves west as the night goes on.
There are several interesting facts about the Great Square:
- It is actually a rectangle, not a square; but the "Great Rectangle" just doesn't have the same ring to it.
- The Great Square is not actually considered a constellation. It is part of the larger constellation Pegasus (the "Winged Horse" - good luck trying to see a horse). The Great Square is considered an "asterism" - a recognizable pattern in the sky that is part of one or more constellations. (Another example of an asterism is the Big Dipper, which is part of the larger constellation Ursa Major - the Big Bear).
- One of the four stars of the Great Square, the northeast corner, is actually not in Pegasus at all, it is officially in the neighboring constellation Andromeda. So the Great Square of Pegasus, which is really a rectangle, probably should be called the Great Triangle of Pegasus. So much for the geometry discussion.
"The Teapot" - A Look Into
the Probably the best recognized and prettiest of the summer constellations is Sagittarius, better known as “the Teapot”. Early evening hours in September remain a good time to see it . From mid-northern latitudes it is found low in the south-southwestern sky as darkness begins. It clearly resembles an old teapot, tilted down toward the right, with its spout on the right side, its handle on the left side and a triangular top.
When we look at Sagittarius we are actually looking in the direction of the center of the Milky Way, the nucleus of our galaxy. This is the densest concentration of stars, gas and dust in the sky - it is an astronomical garden of rich star fields, beautiful nebulae, and sparkling star clusters. With binoculars or a low power eyepiece on a telescope, scan the areas above and on either side of the top of the Teapot. The glowing cloud-like areas are nebulae , places where new stars are being born from the gravitational collapse of interstellar dust and gas. The areas with tightly packed groupings of stars, known as open star clusters, are litters of young stars still “huddled” around one another before going off on their individual journeys through the galaxy. The dim fuzzy balls of light are ancient and distant groupings of thousands of stars, called globular star clusters, that date back to the beginnings of our galaxy, and travel in a ball-like shape in and out of the main disk of the Milky Way.
The "Summer Triangle" Marks
the Coming of Mid and Late SummerDuring evenings in mid and late summer, as the sun goes down, darkness begins to take over and the sounds of crickets begin, look overhead for the first stars that become visible. They will probably be 3 bright stars that form a distinctive triangular pattern. It is a landmark of summer called the Summer Triangle. The 3 stars which form this pattern are Vega, Deneb and Altair. Each of these stars is actually part of a different constellation. Vega is west-most of the three and is part of the small constellation Lyra. Deneb is north-most and is at the top of the “Northern Cross”, or officially called “Cygnus” (the Swan). Altair is south-most and part of the constellation Aquila.
Vega is not only the brightest of the 3 but it is the brightest of the summertime stars (don’t confuse it with the brighter planet Jupiter which is currently low in the southern sky, “passing through” Scorpius). Vega is “only” 26 light years away. It is so bright mostly because of its closeness. It is actually a relatively small star, about the size of our sun. Altair is even closer. It is “only” 17 light years away. Deneb, on the other hand, is a supergiant, with a diameter hundreds of times bigger than the other two. Deneb is 1800 light years away!. It is one of the furthest stars we can see with the unaided eye. Its size and brightness are so immense that even at its great distance, it appears to us almost as bright as Vega.
One more interesting fact about Vega. It has an important role in our future. In about 12,000 years the Earth will have changed its angle so that Vega will be virtually directly above our north pole. It will then be our North Star. (See Star Facts article for June, 1995, "There Will Come a Time When We No Longer Have a North Star" for further explanation)
The Moons of JupiterLike a string of pearls, the four largest moons of Jupiter appear in a diagonal line that crosses the giant planet. During September, 1995, these moons can just barely be seen with a good pair of binoculars. With a low to medium power eyepiece on a telescope, the moons and planet make a spectacular sight.(See Calvin Hamilton's "Views of the Solar System" for more details about Jupiter's moons). During September, Jupiter remains in the constellation Scorpius. As darkness falls it is low in the southwestern sky. Look at it shortly after dark, because it sets soon after. You can't miss it. It is very bright!
Not all of these moons are always visible. At various times only three or even two can be seen, as the moons circle behind or in front of the planet. Their positions change visibly from night to night. Make a diagram of the moons' positions one night, then look at them the next night. Notice the dramatic change in positions.
The Disappearing Rings of SaturnDuring September, 1995 Saturn is well up in the southeast by 9:00 p.m. daylight saving time. It's highest around midnight to 2:00 a.m. To find it, locate the Great Square of Pegasus (for help with finding it see entry above titled "The 'Great Square' dominates Autumn Sky"). The two stars with the widest spacing in the Great Square face south. Scan about 1 1/2 fist widths in a southerly direction from the middle of those two stars to find Saturn.
About seven years ago the planet Saturn reached its greatest tilt toward the Earth so that a good deal of the surface of its spectacular rings showed to us. Even small telescopes revealed a magnificent view of the rings. Since then, its angle relative to us has been straightening. In 1995 and 1996 the angle of the rings becomes edge-on to Earth on three separate occasions - May 22, 1995; Aug 10, 1995; and Feb 11, 1996. (See Hubble Space Telescope Image of Saturn Ring-Plane Crossing taken Aug. 10, 1995). Since the rings are believed to be only about 1 mile thick, the edge-on view causes them to disappear from view. Although this is not good for ring watching, it is good for viewing the moons and surface of Saturn. In about seven years from now Saturn will again reach its greatest tilt toward Earth and the rings will once again present a spectacular sight.
Full MoonThe next full moon occurs on the night of September 8-9, 1995. The moon is full when it is on the opposite side of the Earth from the sun, so that the part of the moon that faces us also faces the sun. Therefore, at the time of a full moon, the moon rises in the east at the same time that the sun sets in the west.
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