[APML] Astrophotography from the ISS....again! pt. 2

Here is part 2

Don was especially thankful to me for my email support of the astrophotography he did and was very thankful for the Iridium satellite support that Rob Matson gave him and I relayed to him. He told me of the tale where Matson sent me a prediction for a dual Iridium flare that would happen the next day as seen from ISS. I sent it to the mail server that day and it was uploaded to ISS that night. Don read the email the next morning, looked at his watch and saw the flares were going to happen in about 50 seconds. He made for the window like Flash Gordon and slapped a camera with a 28 mm lens on the mount, aimed it by guesswork and opened the shutter....bang...bang... twin flares dead on time. The image shows the twin flares above the curved horizon that shows because of airglow and the stars rotating around an artificial polar axis created by the station then being in an attitude that rotates once per orbit. This particular attitude hold causes the stars to spin around a polar point that is offset from Polaris by about 30 degrees. They make a complete circle around the polar axis every orbit, so the sky does a Polaris star trail-like spin about 16 times a day while the earth seems to stay in the same spot and slowly roll around.

The other attitude hold they used fixes the station in relation to the stars and the earth then seems to rotate all the way around the station. This latter attitude hold worked really well for long exposures of stars. The station was inherently stable enough to make really respectable images with a fixed camera. The digital cameras were limited to 30-second exposures, but with film he did several minute shots with Fuji 800. They look great.

One film image that sticks in my mind showed the airglow over the horizon, the stars rotating around the artificial pole, and thunderstorms at night on earth drifting by through the image. The thunderstorms showed as a sequence of flashes illuminating the clouds like a strobe light, thus imaging the same cloud again and again as it moved through the field of view. This left multiple streams of cloud trails where the same cloud kept re-exposing itself with repeated flashes. Another image showed a thunderstorm at night as viewed from directly overhead and you can see high altitude cloud to cloud lightning bolts that can't bee seen from earth. I'm sure these it eventually be published in the future, but it was a thrill to see them now and have them explained by the guy who did the work up there.

More to follow...

Robert Reeves +29.484 98.440
reeves10@swbell.net San Antonio, Texas USA