Star Party in the Round


Recently, a friend has been making 360 degree by 180 degree panoramas of the night sky in various locations as part of a light pollution study.  As you can see, this is a pretty useful tool to document and demonstrate what light pollution looks like, but it also makes a pretty nice picture, so I asked him how to do it.  Mike was very helpful.  Not only did he show me how to do it, he loaned me his fancy tripod head to capture the frames, and did part of the processing that requires some software I don’t have (yet).

This image consists of 8 frames taken at a star party at SkyView Acres in Goldendale, WA last weekend.  Each frame covers more than 90 degrees vertically and 60 degrees horizontally, and they are captured at 45 degrees increments in azimuth.  Thus every frame contains the zenith (straight up) at the top and a wide swath of the horizon at the bottom.  Once “stitched” together, they can be projected in many different ways, but this is perhaps both the most accurate and the most interesting projection, especially for an astronomer.

The bottom of the image is looking due south, and the top is north.  It may seem counterintuitive, but the left side is to the east and the right side is west.  If you think about looking up at the sky instead of the usual looking down at a map, this does make sense.  The Milky Way stretches across most of the sky, but this southern end of it is most interesting – largely because it is looking toward the center of our galaxy, where it bulges and is more dense.  The bright red “line” in the lower left (southeast) is a multitude of red lights on the tops of wind turbines.  You can also see some red glow above the trees to the south from other turbines that are hidden by the trees.

Continuing around in a clockwise direction, there’s not much going on to the east, but as we get closer to the north the light pollution starts to increase.  Kennewick is ENE of Goldendale, and almost due north is Yakima.  Both of these areas contribute to the light pollution.

There is a slight hill to the west, which blocks some of the light from downtown Goldendale.  This city has strong regulations governing light pollution, but being so close it is still quite evident.

Below the horizon it is pretty dark, but you can make out a few vehicles and red lights of the astronomers.  One is using a red light at the bottom (south).  A little to the right of that is Mike’s truck, and the red glow on the very right (west) is my motorhome, illuminated by my laptop (with a red filter over the screen).  I couldn’t see this naked eye, but it shows up quite clearly in a 15 second exposure.  In the upper right is the larger motorhome of my friends, Tim and Chris, and even further north is our host, Phil, who owns this land and very generously lets us use it.

The photo could be made better, and I plan to attempt that.  In particular, you will notice that the sky is significantly darker near the top.  This is from vignetting, which is pretty much unavoidable in such a wide angle lens (14mm focal length on a full-frame camera).  But it can be calibrated out using “flat frames”.  This would also lighten the regions below the horizon, although that is less obvious.

I also captured some more conventional astro-photos at the star party, but haven’t had time to process them yet.  I had to do this one first because of the “fun factor”.  And I might not get a lot of good images out of this star party, since I was focused on trying to use my “big” scope to capture galaxies and globular clusters.  This never works unless the seeing is excellent.  But I do hope to have at least one more image to share with you soon.

 


About Greg Marshall

I am a retired electronics engineer and after a few months of enjoying my leisure I began to miss doing product development. My astronomy hobby always needed new solutions to unique problems, so I decided that whenever I came up with a good solution I would try to make it available to others.

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