Double ISS Pass

First of all, if you’re in LA, I’m showing you this tonight because there’s an EXCELLENT pass of the ISS tomorrow!

Rise at 17:32 in the northwest, highest point at 19:35:58 in the southwest 62° above the horizon, sets at 19:37:54 in the south-southeast. (Map here on heavens-above.com)

Which brings us back to this evening.

The ISS goes around the Earth in about 90 minutes. If you happen to have a long twilight at a particular time of year and you get a pass early enough in the evening (but still after it’s dark enough to see the ISS in the dusk) you might get another one 90 minutes later before it’s full dark. That happened tonight in LA with passes at 18:48:35 and 20:24:56.

Here’s what I learned trying to photograph it (I’ve mentioned in the past that it’s a learning process):

(Image created using StarStaX 0.7)

For that early dusk pass, when it’s still fairly bright but you can see the ISS just fine with the naked eye, a one-second exposure isn’t going to work. The sky’s too bright and each frame will be way, way over-exposed. I had a feeling that might happen and was tempted to cut it to like 3/4 second – should have cut it to like 1/8 second or less and then just shot a LOT of frames to stack.

Secondly, when you realize the ISS is over there when you thought it was going to rise over there and you grab the tripod and scramble to reposition, take a second to make sure that the camera’s still in focus. (It probably isn’t any more – duh!)

For the second pass when it’s much later and darker, those 1-second exposures work well! The ISS here is the upper track, passing from the lower right to the upper left. The lower tracks are aircraft over the California coast on the long arc into LAX from Asia.

You’ll note that the ISS fades out in the top (upper left) of its arc. This was when it moved into shadow. Being the second pass of the night you’re probably not going to see it get too high or travel too far across the sky. It’ll still be there! But the Earth’s shadow will catch it, it will fly into orbital night, and you won’t see it any more. But watch for it – it will dim and turn red and orange as it goes through it’s ten-second orbital sunset.

Tasty!

Meanwhile:

In between the wires after the first pass there was a two-day old moon and Jupiter down on the western horizon. (They’ll be there tomorrow too when you go out to see that ISS pass that I told you about at the top – right?) This photo brought to you by the fact that I remembered to focus!

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Filed under Astronomy, Photography, Space

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