ASTRONOMY CLUB NEWSLETTER

LIGHT POLLUTION: S.A.F.E. Nights:

Come to our meeting Saturday October 24, at 8:30 where, in addition to views of the night sky, we will have the second of our two special programs on Light Pollution, entitled SAFE Nights. SAFE stands for "Stars Are for Everyone." It is an idea that addresses the concerns of amateur astronomers who want to preserve or resurrect a dark sky while also recognizing the general public's need to feel safe at night. The answer to meeting both of these goals is to encourage efficient, economical lighting that provides security where needed. In its September 1998 issue Sky & Telescope magazine, in association with the International Dark Sky Association (IDA), challenged amateur astronomers to "set one small, realistic lighting goal and accomplish it by year's end." What can you do? We will discuss this "challenge" at our meeting. We will also review the standards of good lighting, and the "Good Neighbor Outdoor Lighting" flyer that was distributed at our September meeting.

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Photon Torpedoes. Light pollution is light that is directed to places, including the sky, which are not intended to be illuminated by the light source. Laws to reduce the impact of light pollution have been adopted by New Jersey and Maine, the city .and county of San Diego, the cities of Los Angeles and San Jose, and the Arizona cities of Flagstaff, Tucson, and Tempe.

At one time light pollution addressed only the amount of light directed into the sky. But the topic has recently been broadened to include the notion of light trespass and nusiance glare from neighboring light fixtures. It also includes the efforts of improving visibility by reducing glare from strong lights ("glare bombs") when such glare is blinding, disabling or discomforting to others. Virtually all pollution problems with lighting can be reduced by using efficient lighting fixtures that are more efficient. Efficiency does not necessarily mean converting all outdoor lighting to orange, low-pressure sodium lamps. It means using sound lighting design practices and using "cutoff" fixtures to reduce stray lighting, reduce energy consumption and save money.

More information may be found in the September '98 issue of Sky and Telescope magazine. The IDA site itself is very thorough and it can be viewed at http://www.darksky.org/~ida/

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Major Meteor Activity Possible. Sky watchers should prepare for three potentially major events during the next 6 weeks as Earth passes near the orbits of 3 comets, whose dust produces meteor showers.

1. Thursday evening, October 8 could see an especially active return of the Giacobinid or Draconid meteor shower. These slow moving meteors appear anywhere in the sky, but if you trace their apparent path back to where they seem to be radiating from, the point will lie in the constellation Draco, which is in the general area of Polaris, the North Star.

2. From the last week of October through the first 10 days of November, bright, slow meteors may appear to be "radiating" (originating from) the area of Taurus, the Bull. Again, the meteors can appear anywhere in the sky.

3. Amateurs are hoping this is the year that the Leonid Shower puts on a grand show. Whatever you do, set your alarm clock for the pre-dawn hours of November 18th , if only to "check out" the sky. You wouldn't want to miss a storm that has produced as many as 150,000 meteors per hour in 1966,

NOTE: The Club will have a Leonid Meteor Shower Party at Fairfield School, west of Davis at 8:00 p.m. Tuesday November 17th!

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An Iridium flash opened our September 26 meeting at Explorit. The -1 magnitude flare lasted several seconds near the pole star, and appeared on schedule at 8:37. Our meeting featured a slide show from the IDA illustrating the effects of light pollution and how well-designed lighting improves safety and costs less while it preserves the dark sky. After the presentation, we adjourned to a partly cloudy summer sky to catch glimpses of Jupiter's moons, the Ring Nebula, Albireo, and other traditional summer favorites.

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That first telescope. The club's internet site* frequently attracts the attention of people who want to become amateur astronomers, and are looking for an appropriate "first" telescope for themselves or for a child. I believe that the best first "telescope" is a pair of binoculars. A "real" telescope or pair of binoculars should be purchased with the advice of a local member of an astronomy club. Contact your local club, find out if they have an appropriate meeting or activity you can attend, and take a look through telescopes and binoculars for yourself and find out from other amateur astronomers what they think is appropriate for your interest. I guarantee you will be suprised at what you can see and NOT see through telescopes and binoculars and you will be suprised by how expensive this hobby CAN become but doesn't need to be!

After the obligatory purchase of an inexpensive pair of binoculars or a telescope, get acquainted with the stars and constellations. Again, there is just no substitute to having someone familiar with the night sky point out where the stars and constellations are and where appropriate objects are in the sky that can be viewed with your new binocular or small telescope. A local club or science center is your best resource. That is how I started. Many people are surprised that there are MANY interesting and beautiful objects that can not be enjoyed through telescopes because telescopes do not view a large enough area of the sky to capture the complete object, such as a star cluster.

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From time to time Explorit receives questions on astronomy , usually from visitors at the Club's internet site. These are forwarded to me for answers. Finding the "right" answer can be tough. For instance, one correspondent asked: "How many light years and miles away is Polaris (The North Star) from earth and what color is it due to it's surface temperature?" Not knowing if the question was from a child or an adult, I offered two responses: a simple answer, and a longer answer.

1. Simple answer. The distance to the north star, Polaris is approximately 390 light years. To find out approximately how many miles that represents, multiply 6 times 390. That equals 2,340 but we're not finished yet. Now put 12 zeroes to the right of 2,340. That is the answer in miles (2,340,000,000,000,000 miles). You might call this "around 2 quadrillion miles." The color of Polaris is "white."

2. Longer answer. How did we get this answer of 390 light years? Because Polaris is a old, pulsating, star, its distance has been difficult to measure. Probably the most recent estimate is in Hartmut Frommert's description of Polaris. He says it is 390 light years. But in 1997 Dr. Stephen Odenwald, who works for NASA said it is 777 ly. My standard reference book, "Starlist 2000" by Richard Dibon-Smith, which appeared in 1992, gives the distance to Polaris as 690 light years. Probably the most accurate estimate would be in the data from the Hipparchos satellite, which is being published on CD ROM and which I do not have. However the Tycho catalogue is also a recent catalogue. It reports that Polaris has a parallax of "8.5," which I take to mean 0.0085 seconds of arc, or around 400 light years. So, I would favor the most recent data above by Frommert, which puts it around 390 light years. I should stress that star measurements at such distances are difficult, and it is not uncommon for data from the Hubble Space Telescope to disagree with data from the Hipparcos satellite and for both to disagree with ground based observations! Regarding the color of Polaris, it is classed fairly uniformly by all sources as an F7 spectral type with a temperature of 6000 to 7500 kelvins (that is 10,340 to 13,040 degrees Farenheit). In size, it is classified as a type "Ib" or supergiant, approximately 5,500 times brighter than the sun. (I hope these answers were "correct," and would enjoy hearing from you on this topic)

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Speaking of questions and answers, if the question and answer format appeals to you, I heartily recommend: The Astronomy Café: 365 Questions and Answers from "Ask the Astronomer" (1998) by Sten Odenwald, who is an astrophysicist and chief scientist with Raytheon STX Corporation at the NASA Goddard Space Flight Center. The book ($14.95) reprises some deceptively simple questions and terrific answers from the popular Astronomy Café.

The Astronomy Club is hosted by Dennis Smith with the assistance of Tim Feldman and other eager astronomy buffs. The club is for everyone - adults, children, knowledgeable or ignorant. Come to listen, look and learn, or to share your expertise or experience.