Don Shedrick

Dec, 2000

December DAS Focus

COMPUTERS IN ASTRONOMY by Don Shedrick

We have had some clear, crisp winter skies recently, and if you can brave the cold, some excellent observing can be had. This month we feature some observing aids to help you get the most from your observing sessions.

First, you will need to know when is the best time to observe. As most of us know, when the sun goes down, it is not necessarily going to be ideal for observing. We need dark skies, but an astronomer's criteria for darkness is dependent on twilight, moonshine (not the liquid type) and other factors such as smog and light pollution. While we can’t do much about the last two unless we change our location, we can deal with the first two by knowing at what time these criteria are optimal.

Dark Skies is a Windows freeware program available from the Internet at:

http://pages.sprint.ca/todd/dark_skies.html

This program calculates and displays the times of sunset, sunrise, moonset, moonrise, new moon and full moon, and end of twilight. Using Dark Skies you can determine which nights or weekends in the upcoming months (and years) will have moonless nights, and predict at what times during the night astronomical twilight ends in the evening and begins again in the morning. Dark Skies also predicts and displays the times that the moon will be above the horizon creating the dreaded moonshine effect.

If you have a telescope with a computerized GOTO capability to find celestial objects, you may need to enter the latitude and longitude of your observing location. A web site run by Etak, Inc. using their Eagle Geocoding Technology and U.S. Postal Service CASS-certified address standardization software provides exact coordinates to a thousandth of a second, as well as a map in case you are lost, for any address you enter on the web page:

http://www.geocode.com/eagle.html-ssi

If you must rely on finding the object of your observing desires the old fashioned way, there are some web sites to help you out. An amateur who labels himself "Astronomy Boy" has a clever constellation site with nice photos of the constellations on which the constellation outlines and labels for sky objects appear when you hold your cursor over the photo. This is a good way for a beginner to learn the constellations. This site can be found at:

http://www.astronomyboy.com/constellations/index.html

Binoculars are one of the best tools to start out learning the night sky, and are sometimes the best tool for observing wide scale objects. But a problem for binocular observers is that an object can appear so different from the telescopic photos found in books that it can be difficult to identify it. A web site developed by a professor at Fullerton College neatly solves this problem by providing images from the Digitized Sky Survey for a collection of celestial objects that are suitable and enjoyable for binocular observing. These are all reproduced at a consistent scale of 132 pixels per degree, which means that the magnification is about the same as your binoculars if you view the screen from 10 inches away. The starfields look very much like what you would actually see in binoculars, although the nebulous objects tend to look dimmer through binoculars than the DSS images would suggest, especially from light-polluted locations. The objects listed are fairly easy to find and are of sufficient size to appear as more than a small speck in binoculars. The objects clearly show some structure through binoculars when viewed under light-polluted skies, making the list rewarding for the beginner binocular user. The information on each object includes the photo, a corresponding detailed star chart with magnitudes, and a wider scale finder chart, and data on the object. The objects are listed by sky region and season, and by an alphabetical index. You can find this web site at:

http://www.lightandmatter.com/binosky/binosky.html

Before you set your sights on the stars, you will want to check the viewing conditions on the Intellicast STARcast web site, found at:

http://www.intellicast.com/Star/

This site has many useful features, including satellite and radar imagery, water vapor imagery (important for sky transparency), and to help you dress properly, temperature and wind chill forecasts. There is a section giving the expected highlights in tonight's sky, brought to you by EarthSky.com. An articles section will help clarify how weather affects our view of the night sky, and when to expect the best viewing conditions. How-To Articles give information that will help you get the most out of your sky watching, including frequently asked astronomy questions and the Question Of The Week, where you can ask your own astronomy question. The Aurora may be visible in unusual places now due to the active sun being near the peak in its 11-year sun spot cycle. The Aurora section of this web site features images of solar activity, and global maps showing where NASA tells us the Aurora is now and where computers forecast it will be tonight.

For our Cool Web Site of the Month, we stay with the theme of weather and the sun. The Space Environment Center of the National Oceanic and Atmospheric Administration runs the Space Weather Now web site at:

http://www.sec.noaa.gov/SWN/index.html

Space weather describes the conditions in space that effect Earth and its technological systems. Space weather originates on the sun. Activity on the surface of the sun, such as solar flares, can cause high levels of radiation in space. Space Weather is a consequence of the behavior of the sun, the nature of Earth's magnetic field and atmosphere, and our location in the solar system. This comprehensive web site features real time data and images of solar activity, latest alerts, bulletins, and watches, past solar activity reports, and estimates for future solar activity.