What is a Night Sky Tour?
A night sky tour is a unique, often customized, educational, humorous, and very entertaining tour of your local night sky. A professional astronomer, in this case, me, begins with a panoramic view of your local night sky, description of various objects, definitions of some commonly used terms, and discussion of why the objects are important, what they are, and what to expect to see. After this introduction, a specialized, guided tour of the night sky will be given to you and your intimate group of friends or family using one or more telescopes or sets of astronomical binoculars. Although this night sky tour can be conducted anywhere, at any time, a dark sky site nearest New Moon provides the absolute best viewing. Especially for deep sky objects, the so-called “faint fuzzies,” you will want a location away from urban light pollution, to see galaxies millions and hundreds of millions of light years away, galaxy clusters, open and globular clusters, and faint nebulae. If the Moon and planets are what you want to view, an urban environment is just fine, and can provide a very rich evening of entertainment. Only a dark sky site, though, will enable you to see, with your very own eyes, things that the Hubble Space Telescope has taken images of.
Why would I want to have a Night Sky Tour?
In particular, why would I want to do this, if I can see Hubble Space Telescope pictures for free all day long on the internet?
I’m glad you asked. The answer to the question is the very same answer given when people ask why you might travel to Africa, or India, Antarctica, Paris, Ireland, England, the Grand Canyon, the Rocky Mountains, the Great Barrier Reef, Australia or any of the myriad other breathtaking places on this planet: it is one thing to look at pictures of them in a book, see them on TV, or watch videos or movies of them, it is entirely another thing to experience the place first hand, to interact with the culture, to be a part of it.
That is why you have a night sky tour. You want to experience these wonders of the universe first-hand. To be able to practically reach out and touch them. To look through an eyepiece and see with your very own eyes these objects that are millions and millions of light years away, whose light left, in many cases, long, long before the dinosaurs were killed here on Earth. To feel like you must strap a board to yourself to keep from falling into the telescope and touching this awe-inspiring object. That is why you have a night sky tour.
I can attend a Star Party through my local astronomy club. Why don’t I just want to do that?
A star party is a very different beast from a night sky tour. Star Parties usually comprise of a few things. Often, there are many telescopes set up, and, in some cases, you will be allowed to look through them. If so, what you will likely get is something along the lines of, “This is M31, isn’t this pretty?” And that is it. And you will have to move onto the next telescope, where you might see the same thing. In many cases, observers are conducting CCD imaging at their telescope and, thus, are unable or unwilling to show you anything. Also, the astronomers at star parties are almost entirely amateur astronomers. Many of them do not know the skies well, and few, if any, have formal education in the field. They cannot tell you anything about the object that you’re viewing, beyond what it is. They can’t tell you how far away it is, how we know that, methods for determining that, what kinds of stars are therein, how the object was formed, if it could possibly harbor an extrasolar planetary system, how long the object might live, how it will die, why this is important to us, and methods for learning the skies and comparing objects. In other words, a professional astronomer, with training in the fields of astronomy, space studies, or astrophysics, can provide you with a much, much richer experience than simply looking through the eyepiece and asking you, “Isn’t that pretty?”
Another disadvantage to a Star Party is that you will, often, see the same objects over and over and over again. And you will have to stand in a long line, in the cold, in order to do so. Astronomers who conduct star parties often show the most common objects. These are usually amongst the easiest to find. So, you may attend many star parties, and I have attended hundreds, and most of what I’ve seen at them is the Andromeda Galaxy, also known as M31, Saturn, Jupiter, and M13, and possibly the Great Orion Nebula. While these are all beautiful objects, there are thousands of other objects out there, harder to find, but with much, much richer stories associated with them. A night sky tour will enable you to see objects rarely, if ever, seen at a star party, and you will not have to stand in long lines in, often, very cold temperatures to do so.
Why do astronomers keep building bigger and bigger telescopes?
EXCELLENT question!!!! The short answer is, the bigger the telescope (the bigger the diameter of the telescope), the fainter the objects are that you will be able to see. For the objects that you can resolve, you will be able to see more detail in those objects. You will also be able to have more magnification of them, so you will be able to see them really up close, almost like you’re inside it.
Most of the really cool deep sky objects (galaxies, nebulae, and clusters) need a telescope of at least 10” in diameter to really make them stand out. An 8” is good, but just those two extra inches of diameter make an object just pop out of the eyepiece and make it feel like you are right there with it. Details inside the object, like individual stars, dust lanes, color contrasts, and nebulosity, that are not obvious in an 8” telescope become visible in a 10” or larger telescope, and become just absolutely AMAZING in the 28” telescope.
What is Magnification?
There is a formula for determining the magnification which an object is being viewed at, and that is something that is important for the astronomer to know. Many people think that more magnification is better. This is not true. More magnification only makes an object appear larger. If it is not a CLEAR (ie. well resolved) object, it is still a fuzzy object. A cotton ball under high magnification is still a cotton ball. Looking at it under high magnification will not make it appear more detailed. What people REALLY want when looking through a telescope is RESOLVING POWER. This is why astronomers keep building bigger and bigger telescopes.
What is Resolving Power, or Resolution?
The mirror, or lens, which forms the telescope is a circle. From basic math, we know that the area of a circle is pi times the radius of the circle, squared. So, for a 4” telescope, the radius is 2”, and the area of the circle is 4 times pi (4π). The ability of a telescope to resolve objects depends on the area of the mirror or lens. A mirror or lens with twice the diameter (astronomers use the term aperture for diameter) will have FOUR times the resolving power. So, an 8” telescope will have an area of 16 times pi (16π, the radius is 4”, squared = 16, times pi). 16 pi compared to 4 pi makes four times the resolving power. The greater the resolving power of a telescope, the greater the ability of it to separate distant objects into distinct items, and to show detail. See pictures below for examples.
What is Magnitude?
This is a term astronomers use to state how bright or faint an object is. Much like in golf, a higher score is “worse”. The more “negative” an object’s magnitude is, the brighter it is. The Sun is about magnitude minus 27 (-27), and the full moon is about magnitude minus 13 (-13). The Hubble Space Telescope has located objects down to about 30th magnitude, and MOST telescopes in use outside professional research facilities can only see down to around 12th magnitude. In general, the human eye, unaided, in perfect conditions can see objects down to about 6th magnitude. Some very dark sky sites that are designated in association with the International Dark Sky Association to be and maintain areas of low light pollution, in New Mexico, Arizona, and some parts of Texas, can show objects down to around the 7th magnitude with the unaided eye. Each step of magnitude is equal to 2.512 times fainter (it is a logarithmic scale).
What are “Conditions”?
Astronomers use a term called Seeing Conditions, which is specific to the amount of atmospheric turbulence encountered. That depends upon temperature changes and many other factors. There are no places in Southern California with perfect Seeing Conditions. There are places relatively near San Diego and Southern California with acceptable to very good seeing conditions. Other factors which should be taken into account for planning an astronomy event include cloud cover, light pollution, phase of the moon, humidity, wind, and temperature. Astronomers have a web site that helps them determine the location with the best combination of factors for the date and time that they wish to go observing. In general, the place with the most consistently reliable conditions near San Diego is Mt. Laguna. In Southern California, several places in the Anza-Borrego desert are good, and there are places nearer Los Angeles for people in those areas.
I have three places on Mt. Laguna that I often visit. The base of the mountain is at 4000 feet, and above some of the atmosphere. The top is at about 7000 feet, above the worst of the atmosphere, and even further from San Diego’s light pollution.
What do you mean by Horizon?
Many people think of going out camping and doing some observing while doing so. This is a fantastic idea, with one caveat: many, if not most, campers prefer campsites with a lot of trees. They provide a lot of privacy, and keep the campsite cooler on warm days. Unfortunately, no telescope has yet been invented that can see through tree bark or leaves. In other words, if viewing the heavens is one of your objectives, choose a campsite with as few trees as possible, for an unobstructed view of the horizon.
What else do I need to know?
For the best observing experience, you will want a place with as little white light as possible. It takes about 30 minutes for your eyes to “dark adapt”. This means that your eyes will be most sensitive, and best able to view faint celestial objects, about 30 minutes after dark. Any white light encountered after that will force open your pupils and make it harder to see faint objects. Astronomers forbid the use of white lights in and around observing locations, and only use flashlights that operate in red, or have red cellophane (or, in my case, red nail polish) on them. Choose a place where few, if any, people will be opening car doors, turning on car headlights, or where white lights from bathrooms or campfires could interfere or ruin your viewing plans.
How much Observing Time can I expect?
A night of observing usually begins around the time of astronomical twilight. This is when the Sun is 18 degrees below the horizon and when it no longer provides enough illumination to make a difference to observations. This happens about one hour after sundown. In the summer, 9 pm is a good number to work with. In the winter, 6 pm is a pretty good number to work with. The skies also darken after 11 pm, as a lot of people go to bed then, and turn off their outside porch lights. If you are near a larger city, like Palm Springs, Orange County, San Diego, or even Barstow or Palmdale, you will notice a difference in the darkness of the skies after 11 pm. So, in the summertime, the best observing begins two hours after astronomical twilight. For best results, I usually plan a night of observing to run until at least 1 am, but I am also a night owl, and I always pack coffee.
I keep hearing about Faint Fuzzies. What are Faint Fuzzies?
Faint fuzzies is an endearing term used by astronomers to describe the cornucopia of deep sky objects that appear as varying degrees of fuzziness in a telescope, depending directly on the amount of aperture available. In a small telescope, these objects either cannot be observed, or are just barely discernible. Most “faint fuzzies” have apparent magnitudes of at least 8, making them nearly impossible to see in the conditions of Southern California through a small telescope. Even when you can, the limited resolving power of a small telescope does not provide the level of detail sought by observers. This is, again, why astronomers keep building, and buying, bigger and bigger telescopes.