Friday, March 13, 2009

Scout and about

The other evening, our neighbors Karen and Pete showed up for a beach bonfire with a Celestron SkyScout, a remarkable flashlight-sized device I had not seen before.

You hold the SkyScout in your hand and look through it along the long axis, as if you were looking through a paper tube or spotting scope. Point it at any object in the sky and press a button. The object is identified on the read-out screen, along with descriptive info. You can even have a voice speak the identification and info to you.

Want to find something in the sky? Just select any one of the tens of thousands of celestial objects in the data base -- the Andromeda Galaxy, say -- and peer through the device. Flashing LEDs will guide you across the sky until you are pointing at the selected object.

It's undeniably a cute toy, although I would be disinclined to pay $179 to have a little box tell me what I mostly know already. But how does it work? I lay awake half the night trying to work it out in my head.

Built-in GPS uses satellites to locate position on Earth and exact time. A gravity sensor detects the angle of the device's axis to the vertical (altitude). Magnetic sensors use the Earth's magnetic field to tell in what direction around the vertical the device is pointing (azimuth). This last can be tricky, since the magnetic field varies widely over the face of the globe and from year to year. I couldn't find confirmation on the internet, but I assume the SkyScout has a data base of thousands of point values for magnetic field, and interpolation algorithms to calculate the variation between points. (Help, anyone?)

What really interests me about this thing is that it exists at all -- a technological tour de force, a marvel of hardware, software and data bases packed into a box you can hold in your hand, continuously in touch with satellites in orbit around the Earth. In many respects, our little group of friends around a bonfire could have been any similar group of humans ten thousand years ago; human nature, presumably, has changed little, if at all, in that time. But the SkyScout represented a staggering and irreversible accumulation of knowledge, of the universe and how it works. Talk about the cosmic and the local! As I pointed the gizmo this way and that, and had it tell me exactly what I was looking at, I knew our bonfire was nowhere special in the universe -- and utterly central.

(By the way, for those who are interested, there is a lovely animation of magnetic declination during the past four centuries on the Wikipedia page for that subject. Scroll down to near bottom of page. One more thing the SkyScout must somehow take into account.)