Searching the Sky: circumpolar constellations

David Baumgartner writes about routes of constellations and how we can use them to navigate.

This column was provided by San Benito County resident and amateur astronomer David Baumgartner as part of a local series on astronomy.

In April we saw the Big Dipper floating around in the eastern part of the sky. In May it is swinging over nearer to the western part of the sky and beginning to slope downward toward the horizon. 

This is part of the same turning motion which makes Orion, Leo and all the constellations move toward the west. When they reach the horizon they set—that is, they disappear from our view—and don’t grace us with their presence again until the end of the year.

But the Big Dipper is too far north to disappear from us. Instead, it will move in a circle around the polestar headed for the horizon, but still above it and in full sight.

The same pattern applies to the other constellations: Draco, Ursa Minor, Cepheus, and Cassiopeia. They are called circumpolar constellations, which means “around the pole.” The circumpolar constellations never set, they keep circling around the pole, like numbers drawn on a huge clock. But this clock’s hands turn counterclockwise. The stars seem to be rolling from right to left in the sky if you are facing north.

The closer a star is to the polestar the smaller the circle it moves in, and the slower it moves. If you put a spot of paint halfway down the hand of a clock, it will move more slowly than the tip of the hand and make a smaller circle, though they both go around in the same time.

Wow, this is heavy stuff. You may want to reread that last paragraph. I sure hope you are having a hard time understanding all this. I wouldn’t want to be the only one.

There is one star that I have left out here, and it may be the most important star in the circumpolar region, if not the whole sky, and that would be the polestar. This star can go by many other names, such as: the North Star, or the north polestar, the north celestial pole, and the most popular, Polaris (“Polar” in Latin). This bright star is so close to the middle of the clock that it makes only a tiny circle. Many people say it doesn’t move at all. This isn’t quite true, but for most purposes it is true enough.

Polaris can be very useful because it shows you where north is. So, if you are lost, just look up and find this north star, and now you can walk straight ahead at Polaris to go north, or left to go west, or right to go east. Now of course this method only works at night. 

During daylight hours you can always use the sun to show you the way, such as the sun rising in the east and setting in the west, or the moss growing on the north side of trees, and the trees growing on the north side of mountains. But there is a better way of getting around in situations like this. You will need to learn how to use it properly, but try investing in a small compass.

But these methods don’t always work everywhere on Earth. While in the Air Force, I had the pleasure of spending a year up in Thule Air Base at the northern tip of Greenland, just 700 miles from the North Pole. 

Pleasure might not be the proper word for it, but we can go into that another time. In Thule, looking up at Polaris you would notice it was almost straight up in the sky, unlike 37 degrees here in Central California pointing us to the north. You would also notice the lack of mountains, therefore the lack of trees and growing moss. Even the compass didn’t work properly. 

The only thing you had left was the Sun to count on and it disappeared completely for the three winter months of the year. What a beautiful tour it was. The best part of it all was the temperature: we never had to worry about getting too hot, for it never got above 32 degrees the whole year I was there. Now if any of you young people out there are interested in joining the Air Force and touring Thule, I still have connections.

I hope you don’t get into the situation of having to test this wisdom to find your direction at night. However, it should come in handy if you do get lost. But what the heck are you doing getting lost at night anyway?

Don’t forget your compass.  

Clear skies . . .



What’s up in May

May 16: Full Moon

May 17: Moon is at perigee (223,879 miles from Earth)

May 17: Mars passes 0.6° south of Neptune

May 22: Moon passes 4° south of Saturn

May 22: Last Quarter Moon

May 24: Moon passes 4° south of Neptune

May 24: Moon passes 3° south of Mars

May 24: Moon passes 3° south of Jupiter

May 26: Moon passes 0.2° south of Venus

May 28: Moon passes 0.3° south of Uranus

May 28: Moon passes 0.6° south of Jupiter

May 30: New Moon


David Baumgartner

I am a local fella. Local schools from Fremont, Sacred Heart, Santa Anita, Hollister High, to San Benito Jr. College (Now Gavilan). Then joined the US Air Force where I specialized in Airborne Radar. Married my high school sweetheart JoAnne., shortly after three children arrived; Cindi, Michael, and Lisa. Somehow we ended up with nine Grandchildren.  Went on to San Luis Obispo, Questa, Colleges, and on to Univ. of New Mexico. Came back to Hollister. Opened up Three Pet Stores; Dave's Aquarium Pets & Supplies in SLO, Watsonville, and Hollister. The family spent two and a half years running a ranch up in Oregon. Made our way back to Hollister.  Got my Real Estate License in 1982, opened my own office in 93'. In the mean time raised Swans and revitalized my old hobby of Astronomy.  In 2001 I was named Chamber of Commence Man of the Year. I think I was the only one nominated. I don't care, I'm taking it. In December of 2018 I retired. Not sure if I was forced out or not. None the less, I am retired and I think it was time. Now the last thing I have to do is buy a coffin. I hear COSCO sells them now. But the only drawback is; you have to buy them in lots of six.  I guess I could buy them for the whole family. Not that funny, but thrifty.