# Fourier Analyst

Fourier Analysis is a mathematical tool which can do a number of things: separate out signals from noise; help identify patterns or trends in data; filter out all unwanted data and focus on a single signal; use approximations to make generalizations; make approximations of real world signals (think electronic music); combine harmonics to get a stronger signal. That's what I'll be trying to do here!! Won't you join me with your comments?

## Wednesday, July 18, 2007

### The Sky at Night (1)

At our backyard bar-b-que, some guests were having an argument, and I was asked to resolve it.

Guest 1, pointing to the south, "Okay, which planet is that one? I say Venus."
Guest 2, "It's not a planet, it's a star:"
Me, "Yes it's a planet, either Saturn or Jupiter."
Guest 1, "No, it's too bright, must be Venus."
Guest 3, "Oh, oh, you question the "professor"? You're gonna learn something now!"
Me (ignoring the teasing), "Okay, which planet is closer to the Sun, Venus or Earth?"
Guest 1, "Venus".
Me, "So, Venus will always be close to the Sun in the sky, either right after sundown or just before sunrise."
Guest 1, "Makes sense. So which planet is it?"
Me, "Not sure. Let me look it up." I go online to Tonight's Sky. "It's Jupiter."
Guest 2, "Are you sure it's not a star?"
Me, "It's not a star. I'll prove it to you." I get out the telescope (Meade ETX-70AT Autostar). The sun had gone down, the wind had subsided, it was clear at the moment, although not really dark. The object was just above the roof of a neighbor's house and I was able to get it in focus fairly quickly. "Take a look."
Guest 1, "Okay, I see a white dot. Why is this Jupiter?"
Me, "See the little dots on either side, along the middle of the big dot?"
Guest 1, "Yeah, there are two of them."
Me, "If you look closer, you should see 3, one is really close in. Those are some of Jupiter's moons."
Guest 2, "What are you looking at?"
Guest 1, "Yeah I see 3. Those are Jupiter's moons? How many does it have?"
Me, "Over 60 so far. But only a few are visible with a small telescope. Here, let me put in a stronger lens."
Guest 1, "Honey, come look at this. Jupiter's moons!"
Guest 3, "Told you you'd learn something!"

With the new lens we could actually see 4 moons, just like Gallileo did in 1610. All our guests and their kids got a chance to look through the telescope. And the kids brought their friends who were playing on the street. And we all talked about how amazing it was.

And it was. Though I've seen the same view many times, each time is still amazing and exciting. We were fortunate with the weather and the timing. Often you cannot see all 4 moons as they are in front of or behind the planet. Or the weather is not clear enough. Or Jupiter comes up too late or too early to make it easy to set up the scope. But we were lucky. Maybe you will be too. For the next 2 weeks or so, look a little to the south for the "first star", about 30 degrees above the horizon. With clear skies and a powerful pair of binoculars, or a small telescope, you should be able to see Jupiter and if you are lucky, one or more of its moons.

Happy viewing!

Rebecca said...

sounds SO exciting. I'd love to buy my husband a telescope for his birthday ...but they're all so expensive...and I bet it's not worth buying a cheap one?

And Jupiter has over 60 moons - I've certainly learnt something tonight.

Fourier Analyst said...

Don't know about your neck of the woods, but in the US and Europe you can get a pretty reasonable small scope (similar to mine) for about US\$100 or €100. What you want is about 100X magnification. There are a number of "off brands" that are actually made by the same factory that the name brands use. Here in Europe LIDL (a discount grocery chain) regularly has a special on two of the scopes similar to those I have, making me wish I had waited longer to buy mine! But I have advised friends who bought them as Christmas/birthday presents and they are very happy with their purchases. If you see such a special, do an online search of the brand and see what reviews you turn up. I have to admit, it is a really neat toy, but not one I get to use often enough because of the weather and light pollution here. Are you out in a dark-sky area? I would love to see some of the great objects that are only visible "down under"! Good Luck!

Jen said...

I'm certainly going to try this! How was Galileo able to see the moons? Was it a lack of light interference, or did he have a strong enough telescope?

I was an astronomy fanatic as a kid, and then a "helpful" math teacher told me I couldn't be an astronomer without being REALLY good at math, and I wasn't, and I hated her and hated math at the time, so I gave it all up. Stupid.

This was fascinating! Thanks!

Jenn in Holland said...

When can I come over and look in the telescope?

Real Life Drama Queen said...

Makes me wish I owned a telescope. Great blog today, per usual. :o)

FA - I fell in love with night skies early on, growing up on a farm in Northern New York State. The few glimpses I've had of the Aurora Borealis were breathtaking. At summer camp, there was a massive granite outcropping (almost 15 minute hike up from base camp) where we'd get to sleep out overnight on the bare face on New Moons. Without any light pollution, it was startling just how much you could see with the naked eye - and telescope! I miss those nights...

anno said...

This sounds like a discussion we have at our house quite frequently -- unfortunately, I can never hold onto the geometry of the planets and their orbits relative to the sun. Fortunately, M. never seems to tire of explaining it to me.

How wonderful to be able to see those moons! I never knew there were so many...

Worker Mommy said...

Can I come over and you can teach me a few things too ?

Mom not Mum said...

Way cool. Our neighbors had a telescope for about a week until buyers remorse set in and they didn't know how to use it. We were sad when they took it back.

Fourier Analyst said...

As this topic is close to my heart I will be posting more on the subject in the future. I've loved teaching astronomy to kids, but also know that some adults have never had the chance to see what fun it can be, especially when teachers emphasize the math and geometry aspects. Science does not always have to be hard and can also be really fun.

Galileo only had a small refractor telescope, about equivalent to some really good binoculars these days. Don't be afraid to go exploring the sky on your own!

Watch this space for more sky info!