Astronomy/constellations

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Question
Dear Courtney, I know this is probably a silly question, but could you please explain why some constellations appear upside down or on their side  some of the time? Thank you!

Answer
It's because as we move around the Earth, we look at the constellations from different angles. When you see a constellation rising in the East, North is on your left and West is on top. When you see it setting in the West, you have gone halfway round the Earth due to our rotation, and you have to turn around and look in the opposite direction to see the constellation, putting North on your right and West on the bottom. That makes the constellation look upside down compared to the way it looked when it was rising. (You can also see it the same way when it is rising in the East by turning your back to it, bending over and looking at it through your legs; that gives you the same view you have when standing normally and looking to the West half a day later.)

For in between positions, our angle of view is in between, so we see the constellations rotated by different amounts. This time of year a very good example is Orion. In the early evening it is rising in the East, "lying on its left side', with Betelgeuse on the left and Rigel on the right, and the belt rising vertically between them. In the pre-dawn hours, as it is getting ready to set, the constellation is starting to lie down on its right side, with Betelgeuse up to the right, Rigel down to the left, and the belt is tilted down and to the right between them. Near midnight, when Orion is in the south, it is "standing up", with Betelgeuse up and to the left at the top of the constellation, Rigel down and to the right at the bottom of the constellation, and the belt nearly horizontal between them. There's a terrific book about the stars and constellations, "The Stars" by the same H. A. Rey who did the Curious George books, that you should be able to browse through in any bookstore in the astronomy (or kids' astronomy) section. Partway through the book is a set of "seasonal" maps of the sky, showing the appearance of the constellations at different times of the night. You'll find that any constellation on the eastern horizon is upside down and backwards from the appearance it presents when setting on the western horizon, half a day later.

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Courtney Seligman

Expertise

I can answer almost any question about astronomy and related sciences, such as physics and geology. I will not answer questions about astrology and similar pseudo-scientific rubbish.

Experience

I have been a professor of astronomy for over 40 years, and am working on an online text/encyclopedia of astronomy, and an online catalog of NGC/IC objects.

Publications
Astronomical Journal, Publications of the Astronomical Society of the Pacific (too long ago to be really relevant, but you could search for Courtney Seligman on Google Scholar)

Education/Credentials
I received a BA in astronomy and physics and a MA in astronomy, both from UCLA. I was working on my doctoral dissertation when I started teaching, and discovered that I preferred teaching to research.

Awards and Honors
(too long ago to be relevant, but Phi Beta Kappa and Sigma Xi still keep trying to get me to become a paying member)

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