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Stauchy Blog » Blog Archive » Star Tracks, Friday, July 20, 2007 (JRS)

Star Tracks, Friday, July 20, 2007 (JRS)

No, not Star Trek.  Being at the South Pole of the Earth can be quite a mind game sometimes.  The passing of days is a bit hard to imagine until you’ve experienced it.  There are a few things that help it sink in that we’re actually at the Pole of the Earth (i.e. the Earth is rotating around us, as opposed to us rotating around on the Earth).  One of these things is watching the start over a long period of time.  Unlike in the ”real world”, where stars journey overhead from one horizon to the other throughout the night, here the stars just continuously circle around our head.  Just by seeing where the stars are, you can figure out what time of day it is.  For instance, when I walk out to ARO in the afternoons, I see Jupiter (the brightest object in the sky) to my right.  The later in the afternoon it is, the further it is to my right.  So, I decided to get a visual representation of this via long-exposure photography.  Ideally, in a 24-hour exposure, each star would make a perfect circle.

Here’s my best Star Track picture, I’ll explain how I got to this point in this blog:

4hours.JPG

This is something that’s been done many times, so I can’t take the credit for the idea.  But, our friend Emrys (who is also an avid amature photographer) and I set out to get our own.  The biggest problem is how to get the shutter to stay open for a long period of time.  The longest shutter time you can set is 30 seconds.  There are remote switches that you can buy that will allow you to open the shutter for as long as the switch is on, but obviously, we can’t get those here.  So, Emrys got creative and built a switch himself.  A little solder and a little duct tape here and we were in business.  The next problem is to set the aperature and ISO settings correctly to get the lighting just right.  If you open it up too wide, you’ll get too much light, and the ambient light and the light from the Milky Way will wash out everything.  If you don’t open it enough, you won’t even be able to see the stars.  So, we set up the camera and took a couple of practice shots over 15-30 minutes.

The first shot was far too dark.  Here’s the second test shot, which is also too dark.  It was about a 33-minute exposure (F-16, ISO-250.

toodark_33min.JPG

Our third attempt turned out to be exactly the brightness we wanted.  This is a about a 23-minute exposure (F-6.3, ISO-400).

justright_23min.JPG

The first thing that you probably notice is the green light.  This is a laser that is being shined straight up that helps determine the cloud content in the sky.  It makes for a nice reference.  Since it is pointed straight up, if you were to follow it to inifinity, it represents the point about which the stars are rotating.  It’s almost like having an extension of the Earth’s pole, out into space and the star field.  This becomes more apparent in the longer-exposures coming up.

This next one is our last attempt for the first day.  This is about a 150-minute exposure (F-9, ISO-400).  I’m not sure why, but I decided to open up the aperature, which caused the picture to turn out a bit too bright.  There is a lot of ambient noise, which is combination of scattered light from blowing snow and from the “stardust” from the disk of the Milky Way.

toolight_150min.JPG 

I decided to stop for the day because I was concerned about the light from the laser damaging the CCD of my camera.  After talking to several people, I became convinced that it wouldn’t.  The next day was a bit clearer, so we had to test our aperature and ISO settings again.  Here’s about a 45-minute exposure (F-10, ISO-400).  This one illustrates the Milky Way “stardust” very well: the white blur to the left and below center.

justright_45min.JPG

 This next one is the final picture that I took.  I was hoping to get a 24-hour exposure with this one, but it turns out that the battery doesn’t last that long.  Since it was a much longer exposure, I closed up the aperature a bit (F-13, ISO-400), then I let it rip.  I left and came back the next morning to find that it had died, which means that it did not record how long the shutter was open.  But, we can make an approximation by how far the starts traveled.  They travel 360 degrees in 24 hours, so 90 degrees in 6 hours.  So, given that the stars traveled about 60 degrees, we estimate that the exposure was about 4 hours.  This is the best I’ll be able to do without an external battery pack, which I don’t have.

4hours.JPG

Doing this long-exposure made me realize the limitations of my camera.  For instance, the horizontal streaks across the middle of the picture are a feature of the lense or CCD, probably the CCD.  There are also a ton of red, white and blue spots throughout the picture (you have to look very closely).  I later learned that these are “hot spots” in my CCD, and are common in long-exposure digital images.  I’m hoping to clean up the pictures and get rid of these features with Photoshop, but I wanted to post these pictures now.

-JRS

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2 Responses to “Star Tracks, Friday, July 20, 2007 (JRS)”

  1. shaun Says:

    Hi Jason - greetings from a complete stranger. I just wanted to introduce myself and say thanks for sharing your adventures on the ice. I came across your blog in a random browsing of antarctic sites that someone put together - so I hope you don’t mind the intrustion.

    My wife and I are hoping to get down there for the 2008-09 season. We seem to share a reasonable amount of similarities with the two of you (age, background, etc) - so I’d love to pick your brain about the experience and read whatever advice you’ve got about getting onto the ice if/when you have time. I’ve attached our blog link and my email address in the WP profile. Cheers.

  2. stauchy Says:

    Hi Shaun,

    No intrusion at all! We love to get new readers, complete strangers or not. I checked out your blog really quick, and a couple of your flickr sets. I look forward to reading/seeing more. We’re (my wife and I) are planing a month-long trip to Australia, so we could probably all benefit from eachother’s experiences. I’ll drop you an email.

    Thanks for the comment!

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