Wednesday, February 15, 2017

Lights in the Sky!

Always on the lookout for topics to blog, I watch certain websites, Heavens-Above among them. A few days ago I saw there was a good pass of the International Space Station (ISS) this evening, but promptly forgot about it! Thanks to the local weatherman at 5pm who mentioned it again, I was motivated to look it up again and set up a camera.

Now if you go to the website above, the first thing it wants to know is where you live - duh, it needs to know where you are located before it starts telling you where to look. Click the "change your location" button to tell it where you live, using the search box, or the google map to locate your city. The closer you can locate your observing location, the better! For some observations, like Iridium Flares, a mile or two off makes all the difference! Anyway, for tonight's ISS pass, I got the map at left. It is a map of the full sky with north at top and south at the bottom. You can see that Venus and Mars were bright in the west and Orion high in the southern sky. The path of ISS was to skim the three belt stars of Orion, and it ends before the bright star Sirius. What happens there? Well, since the ISS needs the sun to hit it to be visible, that is the sunset point - as the ISS continues to move eastwards, it moves into the earth's shadow!

I set up tripod and tracker so that the stars would look like points, working from the back yard. My sky glow from Midtown Tucson limits my exposures to 30 seconds or so before the orange glow from sodium lights starts to color the sky. For the exposure here, I used the Canon 6D and 85mm lens at F/3.5.  Seen is the streak of the moving ISS, just grazing under the 3 belt stars of Orion. Below the belt stars is the reddish glow of the Orion Nebula, and near the bottom are the 2 stars that make up the feet of Orion. I wasn't sure how long it would take to move through the field, so used 60 second on the intervalometer, planning to stop it when it blinked out to minimize skyglow.  This shot ended up being about 40 seconds, and I had to use Photoshop to neutralize and minimize the sky glow a little.

Surprisingly, the ISS didn't "blink out" once the sun net from its vantage. Just like it stays light right after sunset here on earth, the color of the ISS took on an orange-ish tint and faded out slowly - pretty cool!

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