Sidewalk astronomy introduces the public to the world of astronomy by holding star parties in public places. Hopefully, by introducing the public to astronomy in the comfort of their local neighborhood , they will be able to experience something that would normally entail late nights at remote locations! While serious astronomy usually occurs in remote places with few lights, many objects in the night sky are visible from urban areas.

The heavens are filled with wondrous objects such as planets, galaxies and star clusters that can be easily viewed with the help of an experienced astronomer to point the way. Many objects you view tonight can be easily viewed from your backyard with a pair of 7x50 binoculars. You only have to look in the right spot to see them!

What is Amateur Astronomy?

"Considered as a collector or rare and precious things, the amateur astronomer has a great advantage over amateurs in all other fields, who must usually content themselves with second and third rate specimens. For example, only a few of the world's mineralogists could hope to own such a specimen as the Hope diamond, and I have yet to meet the amateur fossil collector who displays a complete tyrannosaurus skeleton in his cabinet. In contrast, the amateur astronomer has access at all times to the original objects of his study; the masterworks of the heavens belong to him/her as much as to the great observatories of the world. And there is no privilege like that of being allowed to stand in the presence of the original."

There are many different types of astronomy and many different related activities.. A few examples are:

• Visual nighttime astronomy
• Solar Astronomy
• Radio Astronomy
• Cosmology

Other pursuits that astronomers can become involved in are:

• Celestial photography either with film or CCD's , light receiving chips that are then processed by a computer.
• Telescope making - Make your own instead of buying!
• Mirror fabrication
• Mythology - study of the constellations and the stories about them.

What will you see tonight?

"We are beginning a journey. It will be a journey both strange and wonderful. In our tour of the Universe we shall travel the vast empty pathways of limitless space and explore the uncharted wilderness of creation. Here, in the dark unknown immensity of the heavens, we shall meet with the glories beyond description and witness scenes of inexpressible splendor. In the great black gulfs of space and in the realm of the innumerable stars, we shall find mysteries and wonders undreamed of. And when we return to Earth, we shall try to remember something of that we have learned about the incredible Universe which is our home."

The different types of objects you may see tonight include:

Solar System -Planets, their moons, asteroids and comets.

Photo Courtesy Jack Newton

Galaxies - Like our own Milky Way

Photo Courtesy of William McLaughlin

Nebula - These are often remnants of stars that have ended their life in a fiery death. They expel gasses that form ethereal shapes that are sometimes filled with many different colors.

Photo Courtesy of William McLaughlin

Double Stars - Two stars that orbit each other and come in many different sizes, colors

Clusters - These are groups of stars in the same physical location, but are small in size compared to a galaxy.

Photo Courtesy of Dennis Luse

Constellations - See if you can remember 3 when you go home tonight.

Telescopes

Binoculars

These are perhaps the most overlooked type of "telescope". A good pair of binoculars is a cost-effective way of introducing yourself to the night sky. They are especially useful in light polluted areas such as suburban or city locations. Many books have been written detailing the different types of objects easily viewed by most binoculars. In fact, over 50 of the Messier objects can be viewed with a pair of 10x50 binoculars. To be effective, binoculars should be at least 7x50, with 10x50 being a good starting pair. The "7" and "10" refer to power while the "50" refers to the diameter (in millimeters) of the lens. Binoculars with a diameter of less than 50 are not suitable for astronomy because they simply cannot gather enough light to be effective.

Department Store

These are normally sold in department stores or other variety stores. They are technically a "refractor" but the quality of the construction is usually so poor that people buying these can have a bad experience, forever dimming their goal of looking at the night sky. If a telescope costs less than $300, it falls within this category and should be avoided at all costs. In fact, a decent pair of binoculars, in the $150-200 range will give you much more viewing pleasure and fewer headaches than these mass-produced thingamabobs.

Reflectors

Also called "Dobs" or "Newtonian", these are by far the most common telescope today and are excellent entry level telescopes.

They are characterized by a long tube with a mirror at the bottom end and the eyepiece at the top. They start out with a mirror diameter of 4.5 inches and go all the way up to 40 inches in diameter. A good starting telescope has a 8" diameter mirror, and will give countless hours of enjoyment viewing the night sky. While smaller diameters will still allow you to view many of the same objects, an 8" or larger telescope will give you much more detail. These type of telescopes are manual in nature, with the operator having to physically move the telescope to point at an object and unless mounted to an equatorial mount, are not able to "track" a star so that it stays within the field of view at all times. An 8" Dob costs around $400-500, but can be as high as $1,000 if mounted equatorially.

Schmidt Cassegrains

Also called the SCT, these telescopes are a "stubby" version of the telescope, in that they fold the light twice from the time it hits the main mirror to the time the light exits at the eyepiece.

They are normally mounted in on either a fork-mounted or german equatorial, which allow the telescope to be oriented in such a way that it is in the same "plane" as the night sky. These types of telescopes are normally equipped with a clock drive, giving the ability to track an object for hours at a time. They are also capable of doing long-exposure photography and are more portable than their dobsonian counterpart for sizes greater than 8" in diameter. It is important to note, however, that they offer no better viewing than the same size dobsonian telescope. They just come with more bells and whistles. An 8" SCT costs between $1,200 and $3,000, depending on the sophistication of the computer and tracking hardware.

Refractors

This is your "typical" telescope in that this is what most people picture when thinking of a telescope. These use lenses to focus the light instead of a mirror which is used by both Dobs and SCTs.

Refractors will give much better views than their SCT or Dob counterparts at smaller sizes.

They are normally better suited for planetary viewing and usually are mounted on a german equatorial mount or what is called an "alt-azimuth" mount, allowing the telescope to track stars. An entry level 4" refractor without tracking hardware will cost around $1,000, but can go upwards of $2,000 to $3,000 depending upon the quality of the lenses, mount, and tracking hardware.

Note: Drawings not to scale. Dotted lines represent the path of light from when it enters the scope to where it exits at the eyepiece

Astronomy Resources

If you think you might be interested in pursuing astronomy as a hobby, you should refrain from purchasing until you have researched the different types of telescopes. Resources which can help you in this endeavor are:

• Magazines such as Astronomy or Sky and Telescope
• Books such as "The Backyard Astronomers Guide" or "StarWare" ,"Burnhams Celestial Handbook", "Nightwatch" and others will help you with the night sky.
• Joining a astronomy club such as Rose City Astronomers and going to monthly meetings
• Your local science center, such as OMSI, occasionally have programs or special days dedicated to astronomy.
• Planispheres are a plastic disk containing the constellations that rotates within a "window" allowing you to match what you are seeing in the sky to what is on the planisphere. It helps with identifying the constellations and their stars.
• Going to "Star Parties" where hundreds of different type of telescopes will be. Astronomers are friendly and love to share their equipment. However, if you are not careful, you may end up talking until dawn as they are a passionate group of people who love to discuss astronomy! Astronomy clubs put on about 5-10 star parties a year, but many "impromptu" parties will form on weekends when the clouds are away!

Interesting Facts

Messier Objects

In the 1700's, many astronomers were looking for comets as they were perceived to be good luck. One French astronomer named Charles Messier published a catalog comprised of objects which he and others of his time had found but were not comets - The catalog grew to over one hundred different objects that looked like comets, but since they didn't move in relation to the other stars, were not comets. Today, these are some the most fabulous objects in the night sky including galaxies, nebula, clusters and others. A amateur world-wide club called the Messier Club is full of thousands of people who have viewed them all!

The Herschel 400

Herschel objects. In the 1800's, a much more complete survey of the sky was completed and the Herschell objects, while numbering several thousand, includes many objects that Messier missed and are just as wondrous. Their list was popularized by the "best" 400 of these, giving foundation for another club for finding these objects, many of which are very faint and elusive, but are very rewarding once viewed!

Distances to objects

Astronomical distances are normally measured in light years: the distance light will travel in a single year or 5.88 trillion miles. For another perspective, if you were to turn on a flashlight and point it over the horizon, the light would circumnavigate the earth 7 times in a single second! Another point of reference is that Pluto is about 6 light hours from Earth. One of the most impressive galaxies, Andromeda, is over 2 million light years away and is around 180,000 light years in diameter. It is a "naked eye" object, meaning that you can see it without the aid of binoculars or telescopes. This means that the light we are now seeing today is over 2 million years old!

Stars & The Milky Way

While there are "gazillions" of stars in our universe, you can actually only see around 2,700 with the unaided eye. Our own galaxy "The Milky way" is around 100,000 light years in diameter, containing approximately 1 trillion stars. Our solar system is out about 10,000 light years from the center, on a spiral arm where the density of stars is approximately 1 in every 4 cubic light years. Near the center of our galaxy, there are about 50 stars for each cubic light year. If you were to live on a planet circling one of these stars, you would be in perpetual daylight and would most likely not see any stars further than a few light years away because you would never experience "night" as we know it.

Our Solar System

Saturn, Jupiter, Neptune and Uranus are composed almost entirely of gas. There is no "surface" as we have on earth. Saturn "tilts" actively on 12 year cycles, with the rings tilting in various angles. 1995 was a "ring-plane crossing" year in that the rings were not visible from Earth. Over the next six years they will tilt more an more until they start to tilt back towards being edge on and then continues the cycle. Our "Sun" was formed approximately 4 billion years ago. Approximately 4 billion years from now, it will become a red-giant - a process that stars similar to our sun go through in it's latter stages of life - whereby our sun will slowly expand in size and it is accepted that it will grow so large that it will eventually consume the Earth. Popular theory has it that our "Moon" was actually formed when another large planet or asteroid collided with the earth when it was first forming and is actually made from the earth!

Meteors or Falling stars

Contrary to popular belief, meteors are actually very small in size, with the majority being no larger than a grain of sand. The "streak" of light you see is actually this grain of sand burning up in our atmosphere. Meteor showers are usually from remnants of comets that passed through our galaxy a long time ago and are named after the constellation they appear to be coming from.

Mythology

Stories about the stars are as old as mankind. Throughout the ages, in all lands around the earth, the ancients had devised glorious stories about the heavens. It is surprising that people thousands of miles apart looked up and the night sky and saw the same thing. They had different stories, but many of the shapes are common across races and ages.

One such story is that of Ursa Major, "The Great Bear". Many people know it by its popular name "The Big Dipper". Somehow that doesn't conjure up images of fancy!

Following is an excerpt from a heartily recommended book "The Constellations: An Enthusiast's Guide to the Night Sky" By Lloyd Motz and Carol Nathanson, Published by DoubleDay, 1987.

"Artemis (known as Diana), moon goddess and mistress of the hunt, surrounded herself with a band of beautiful nymphs who always accompanied her on the chase. Among these hunting companions was an especially lovely maiden named Callisto; like the others, she took a vow of chastity on joining Artemis' band.

Zeus, or Jupiter, king of all the gods and husband of Hera (Juno), had a weakness for mortal women that often aroused the jealous ire of his queenly wife. On one of his frequent visits to the Earth, he happened to pass the woodland cove where the lissome Callisto, having put off her huntress' garb, lay soundly asleep. Falling instantly in love with the beatuful girl, Zeus disguised himself as Artemis' brother, Apollo, and then overwhelmed the unsuspecting Callisto, becoming her lover. She bore him a son, named Arcas (after the Greeek arktos, or "bear").

Zeus, now perceiving that he would have to protect Callisto from the wrath of his slighted wife, Hera, as well as from the vengeful rage of Artemis, who brooked no desertion from her ranks, let alone a violation of the sacred vows of chastity which bound her followers together, turned his sweetheart Callisto into a bear.

One day, when Callisto's son Arcas had grown to manhood and mastered the skill of bow and arrow, he saw a great bear in the forest. The creature was in fact his unhappy mother, constantly forced to flee other beasts, with which she felt no affinity, and pursued by the very hunters in whose company she was once included. At the sight of her son she paused in joy, but Arcas, ignorant of his mother's transformation, drew his bow and took aim at her. At this moment, Zeus intervened and changed Arcas into a little bear, so that he could recognize Callisto. The godly source of all their troubles then transported mother and son to the heavens, allowing them a happier residence in the region of the north pole. Thenceforth, they have been known as the Greater and Lesser Bears.

Hera, though, was far from satisfied with this turn of events; for in their new stellar domain the Bears brightened the heavens and, it was said, lit up the very pole that they now guarded. In protest against this unexpected honor to the "miscreants" (however innocent) who symbolized the indignity she had endured from her unfaithful husband, Zeus, and resentful of the Bears' rivalry of her own brilliance, Hera pleaded with the ocean god never to permit Callisto and Carcas to bathe themselves in its immortal waters. The proud goddess' unkind wish was granted, and mother and son were forever fated to circle the north celestial pole, never descending to join the other constellations in a pleasant ocean bath. In more recent times, this stern dictum has apparently suffered a slight violation; for points of observation south of the 41st parallel of declination, the Great Bear, at least, is allowed a partial dip into the waters."

Theft of the Night

Text of a December 1989 National Academy of Sciences Op-Ed Press Release by David L. Crawford

A priceless part of our human heritage is fading into the night sky.

Most Americans are growing up unable to see the stars their grandparents knew so well. They see the night sky only in pictures or at planetariums. This is true not only in cities, but also in many suburbs where street lamps and other sources of "light pollution" have obscured our view of constellations, meteor showers, and planets. Indeed, many youngsters may now say, after viewing the night sky in a rural area for the first time, that "it looks just like the planetarium".

Light pollution is not a matter of life and death. Yet it is important nonetheless, profoundly so. We human beings lose something of ourselves when we can no longer look up ad see our place in the universe. It is like never again hearing the laughter of children; we give up part of what we are. Such a loss might be acceptable if light pollution were the inevitable price of progress, but it's not. Most sky glow, as scientist call it, is unnecessary. The light that obscures our view of the night sky comes mainly from inefficient lighting sources that do little to increase nighttime safety, utility or security. It produces only glare and clutter. costing more than $1 billion annually in wasted energy in the United States alone.

For science, the impact has been even more tangible and adverse. Astronomers require observations of extremely faint objects that can be made only with large telescopes at sites free of air pollution and urban sky glow. For example, scientists interested n how the universe was formed may study the light of galaxies and quasars at incredibly vast distances from Earth. These images offer information about faraway corners of the universe, helping us understand how our own world was formed. Yet, after traveling countless light years, the light from these objects can be lost at the end of its journey in the glare of our own sky.

Space-based telescopes, such as the Hubble Space Telescope launched by the shuttle in April 1990, offer one way around the problem. However, large telescopes on Earth will always be used, if only because they are accessible, cost much less that orbiting devices, and can do many jobs more cheaply.

In fact, our experience over the past two decades has shown that space--based astronomy, far from reducing the need for ground-based observations, actually increases the demand for these facilities. new telescopes now planned or under construction on Earth will complement the knowledge we gain from telescopes in space -- but only if they are not compromised by encroaching light pollution, as has occurred at Mount Wilson, near Los Angeles, and several other older observatories.

Reducing light pollution is not difficult, but it does require public officials and ordinary citizens be aware of the problem and act to counter it. Low pressure sodium light, for example, can replace existing fixtures for most streets, parking lots, and other locations. They reduce glare and save money.

Another fairly painless way to reduce light pollution is with outdoor lighting control ordinances, over 50 of which have been enacted throughout Arizona and in several key cities and counties in California and Hawaii. These measures typically require communities to prohibit inefficient, low-quality lighting. Not only do they help preserve dark skies, but they also enhance energy efficiency. an outdoor light system recently installed at a prison in Arizona, for example, improved security and reduced light pollution while cutting energy costs by 50 percent. There is no reason that all communities should not have such efficient lighting.

On an individual level, people can help reduce sky glow by using night lighting only when necessary, choosing well shielded fixtures and turning off lights when they are not needed.

Curing light pollution saves money while reducing glare. Unlike other issues involving pollution, it presents us with a rare case where we should strive to be kept in the dark. The stars above us are a priceless heritage -- not only for scientific knowledge, but also for our identity as human beings.

More of our children -- and their children -- should be able to look up at night and see the Milky Way isn't only a candy bar.

National Academy of Sciences

For more information, contact the International Dark Sky Association http://www.darksky.org/

Author's Notes: This document has many references that are specific to the Portland, Oregon area. As such, it may be reproduced or adapted free of charge providing the person/persons reproducing are associated with the Astronomical League or are a recognized member at large or get prior authorization from the author, Thurman Miller and all references are kept intact for quotations and pictures and this "Author Notes" section remains intact.

Return to top