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Astronomycast, episode 170 from one day December 28, 2009. Coordinate Systems.

Welcome to Astronomycast, our weekly facts-based journey through the cosmos, where we help you understand not only what we know, but how we know what we know.

My name is Fraser Cane, I'm the publisher of University Day and with me is Dr. Pamela Gaia Professor at Southern Illinois University.

Hello Pamela.

Hey Fraser, how's it going?

Good, so I've got to admit, this is a show for me today.

This is my show. The rest of you can listen in if you want, but this is sort of designed to help me get over a bit of a mental block that I've got.

This is going to be one of those weeks where we tackle something you're mentally avoiding and by you and me.

You all know those astronomical terms, like alt-azimuth, right ascension, declination, arc seconds, arc minutes.

Of course not, your mind is blocked them out, but today we're going to explain them so you don't need to avoid them anymore.

Soon you'll be ready to find anything in the cosmos.

I will readily admit that if you give me the alt-azimuth numbers or the right ascension, declination, and say go find that thing with your telescope, I will just give you a blank stare.

If you say show me how big something is in arc minutes, I would just kind of draw a circle and show you and kind of hope I was right.

I know that the moon is half a degree across. I've used that in enough articles now that I know that, but honestly.

I have this mental block, I just passed right past it.

Today we deal with my mental block and maybe everybody else's as well.

So coordinate systems. Pamela, what are the different coordinate systems that astronomers use to find something in the sky?

There's basically three different coordinate systems that we use most.

The first is the one that you learn when you're learning how to use an amateur telescope.

And that's the altitude asmuth or alt-az system, which just tells you where something is relative to the horizon.

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