NOTICE: CyberSky sales have stopped!

Due to my CyberSky astronomy software generating low revenue over the last year, Digital River MyCommerce, the company that has handled online sales and fulfillment for me for many years, has terminating my account.

The software business has changed dramatically since I first released CyberSky as shareware, a term I don’t think is used any more. I took the termination of my account as a sign I should retire, and have stopped sales of the program, effective May 3, 2024.

Thank you for your support, for sending me bug reports and a lot of suggestions to help me make CyberSky better, and especially for the many kind words you’ve sent me about my software over nearly three decades.


Frequently-asked questions

The most frequently-asked questions about using CyberSky are answered below. If you have a question that isn’t answered here or elsewhere on this website, please write to

Using CyberSky

How does CyberSky handle Julian and Gregorian calendar dates?

CyberSky uses the Julian calendar for all dates up to October 4, 1582, and the Gregorian calendar for all dates from October 15, 1582 onward. If you enter one of the ten dates that were eliminated by the introduction of the Gregorian calendar, it will be converted to a Gregorian calendar date for you. For example, if you enter October 5, 1582, the program will convert that date to October 15, 1582.

How does CyberSky handle daylight-saving time?

When you run CyberSky, the program checks your computer’s clock settings to see if daylight-saving time is currently in effect. If it is, the program automatically adjusts its calculations to take this into account. The rules governing the use of daylight-saving time are complicated—they vary from location to location, and even from year to year. CyberSky therefore doesn’t attempt to automatically adjust for daylight-saving time every time it draws a map. You may have to turn daylight-saving time on or off yourself if you change the viewing location or the time.

Why does CyberSky draw maps with east and west switched?

The reversal of east and west on maps drawn by CyberSky is not a mistake; it’s normal for maps of the sky. When you look at a map of the Earth’s surface, your viewpoint is far above the planet and you’re looking down at the ground. If you want to see the sky, you need to turn around and face the other direction, which causes east and west to switch places.

If you picture yourself outside looking south, east will be on your left and west will be on your right. This is exactly what you find on a map of the south horizon drawn by CyberSky; east is on the left side of the map, and west is on the right. This makes perfect sense, but we’re so used to seeing maps of the Earth’s surface, with west on the left and east on the right, that maps of the sky drawn by CyberSky can initially be confusing.

For a detailed explanation of the relationship between maps of the sky and your view of the real sky, see the topic “Understanding maps of the sky” in the program’s Help file.

Why does CyberSky show the Sun in the wrong place?

One of the most frequently-reported bugs in CyberSky is that the program shows the Sun in the wrong constellation on a specific date. For example, if you were born between July 23 and August 22, your astrological sign or “Sun sign” is Leo, which means that the Sun is in Leo on your birthday. Yet, CyberSky shows that the Sun is in Leo from about August 10 to about September 15, which doesn’t make sense. This confusion arises because astrological signs and astronomical constellations aren’t the same thing.

The area of the sky through which the Sun, Moon, and planets move is called the zodiac. It’s centered on the ecliptic, the Sun’s path across the sky. Several thousand years ago, the zodiac was divided into twelve parts, each exactly 30° wide, called signs. Although each of these signs corresponded to a group of stars at that time, the signs were fixed to the ecliptic rather than to those stars.

Since the time the astrological signs were invented, the gyration of the Earth’s axis of rotation has caused the ecliptic, and therefore the signs, to shift about 30° west with respect to the background stars. The positions of the astrological signs therefore no longer correspond to the groups of stars they were named after.

Another difference between signs and constellations is that the modern astronomical constellations have irregular boundaries and varying widths. They’re not each exactly 30° wide, so they can’t possibly correspond exactly to the ancient astrological signs. In fact, the astrological sign in which the Sun is located on a specific day of the year corresponds to the astronomical constellation of the same name only about one in seven times.

How accurate are the positions of the Sun, Moon, and planets?

The accuracy of the positions of the Sun, Moon, and planets calculated by CyberSky is discussed in the topic “Accuracy of calculated positions” in the program’s Help file.

Publishing and using maps created by CyberSky

Can I publish maps created by CyberSky or use them on my website?

You can use map images and printed maps created by the trial version of CyberSky only for evaluation and review of the software. You can use map images and printed maps created by the full version only for non-commercial purposes. You must clearly credit CyberSky as the source of any maps that you display or distribute to the public. A link to is appreciated.

Can I use maps created by CyberSky for commercial activity?

You can’t use map images or printed maps created by CyberSky for any commercial purpose without the prior explicit permission of Stephen Michael Schimpf, the program’s author. To inquire about using CyberSky for commercial activity, please write to