Wednesday, November 19, 2008

I Thought Space Was Supposed To Be Empty!

We finally got out of town to see some real stars last night, but for various reasons we didn't get out of Tucson until nearly sunset (afternoon doctor's appt, massive rush hour traffic with massive interstate construction, inability to buy gas from Circle K at the pump). So we missed the pretty good pass of the space station nearly overhead, and instead of getting to a higher elevation, we set up at the base of Kitt Peak National Observatory, just off the main road. I took a number of images comparing my "new" (from June, but first time under a dark sky) Canon XSi to the now 3 year old Canon 20Da. One thing I'll tell you - using the 3" screen of the former compared to the 1.6" screen of the later just about brings tears to your eyes! Four times the area makes like a picture window in comparison!

Anyway, I am just getting those images downloaded, but one interesting sequence I took as we were shutting down was almost a "throwaway" shot. As we disassembled gear, I put the XSi on a tripod and shot at about 55 degrees off the southern horizon. From our latitude that is where the geosynchronous satellites hang out and sure enough, they were easily visible. No tracking to follow the stars, so the stars are horizontal streaks in these shots.

Arthur C. Clarke came up with the idea back in the '40s to have a satellite with an orbital period of 24 hours. As seen from the earth, the point of light (when visible) would not appear to move, but be stationary in the sky. This point is about 22,000 miles off the earths surface, and that orbit is now FULL of communications, weather, and TV satellites. Although I couldn't see any last night (they sometimes can be visible to the naked eye), they show up easily with these 4 minute exposures (with 85mm lens at F/4, so about 20 degree field). The geostationary satellites show up as points of light - they truly are fixed with respect to my tripod firmly on the ground. What might be even more interesting is that there is other detritus consisting of rocket boosters and non-operational satellites that are moved out of this magic orbit, but they are still geosynchronous, but have up-down movement through this orbital plane. These objects show up as up-down trails in the images. I counted 19 geostationaries and 14 geosynchronous in the full image - so a lot of hardware out there. Of course, the modern world would be a different place without these, from our phone calls to Internet to cable and broadcast TV all use them.

1 comment:

Andrew Cooper said...

Those pesky geosynchronous satellites! From southern Arizona they were always the correct latitude to go right through the Orion Nebula region. When taking photos of this beautiful nebula there would always be the streaks of satellites in nearly every image.

From here in Hawai'i the latitude difference means that the geosynchronous satellites go right through the Horsehead Nebula instead. Took a sequence of shots a few weeks ago and more than half the frames have one or more streaks through them.