Thursday, April 14, 2011

ISS with Star Trails

My Canon Rebel 300D has some serious limitations though it beats the alternative which is to have nothing. Keeping this in mind, I headed out with the intent of pulling off a shot I have wanted for some time that is to shoot a star trails stack and have the International Space Station glide through. Besides having clear skies, a night off of work and an ideal pass angle, there were other factors I would need to consider if I wanted to be successful.

I've found with previous star trails projects that my 300D battery is good for 52 30 second shots before calling it quits. This equates to about 26 to 30 minutes worth of images when you also factor in buffer lag so for this endeavor I would need to do a little math. Rise time for the ISS was at 5:18 AM CDT (Orbital Tracking) so I figured if I started shooting at 5 AM then by 5:20 (or so) it should have completed its approaching pass giving me approximately 40 images to work with. I ended up with 32 30 second images in this time frame versus 40 due to the short lag between shots as the camera buffers itself. This equates to 16 minutes worth of trail shots. Buffer lag is also what creates the gaps in the line and is perhaps the biggest limitation of the 300D but anyways, per the image below, I at least nailed the timing.

Another limitation is that I don't have a true wide angle to get more of the sky thus I had better be spot on where I was pointing or else the shot was ruined. Using the compass on my iPhone, the distant light lined up pretty close with true NW so I used it as my focal point. I was in NE Macon County IL and the city light is of Maroa IL. The ISS would come in at 10 degrees above the horizon and arc across at 77 degrees. I knew it would likely bend to the left but not quite as much as you see. I thought the shot was a bust once I saw it rising but there was no sense in repositioning. The more I look at it though is the more I like it because it at least balances with the opposing star movement.

Keeping battery life in mind, I knew that I also wanted to quickly reposition once it was overhead and get the departing path. Today's pass was a full six minutes giving me just enough time when it was directly above and out of frame to hustle over to a new spot. With 32 images plus 6 test shots "in the tin" as Peter Lik would say, I knew I had at least 12 more left (factoring my 40 estimate) before she would cash in. I unknowingly had a few more than that available of course but with no time to switch out batteries, the following is comprised of 8 30 second shots equating to 4 minutes worth of star trails. I probably could have left the camera run itself down but was satisfied with the session and decided to nab a few parting shots illustrating the peacefulness despite my rush at the critical moment.

Looking NE

Looking SSW, Argenta at left, Decatur at right.

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