It’s August, and so it’s time for some more dark skies at Oregon Star Party. As usual, a week of dry, dark skies at high elevation and some great times with about 600 or so friends in the Ochoco Forest in central Oregon. Unfortunately, as increasingly seems to be the new normal, the skies were heavily polluted this year with smoke from wildfires up and down the west coast. The skies were still clear enough to get some very good image data near the zenith, but anything below 30 degrees above the horizon was more-or-less completely obscured, and even at mid-altitudes my image data was seriously compromised. I was able to capture some really good data on Monday, Tuesday and Wednesday. My data from Thursday and Friday is more mixed; I’m still working on cleanup of some nasty gradients that appear to be smoke-related (I’m seeing gradients pretty much exclusively in the blue channel, and in a direction and at times that suggests lower altitude smoke effects).
One of my best image data sets was from Monday, and captures the large nebula complex in the constellation Cepheus known only as IC1396. This is an ionized gas cloud about 2,400 light years away from us. For scale, if you held a golf ball at arm’s length it would cover roughly the same area of sky as this object.
In the center at the bottom half of the image is a formation known as the Elephant’s Trunk nebula, which I’ve imaged before (including last year). Directly above that, and almost in the center of the image, is a bright white star. This is in fact a triple star, designated HD206267, and is a very bright and massive star that is responsible for illuminating the entire nebula complex. To the top right of the image is a bright, deep orange star known variously as Herschel’s Garnet Star or Erakis. This is much further away from us than the nebula at about 6,000 light years, and shines through the wispy outer limits of the gas cloud. It, and the previously mentioned HD206267 are the only things in this image visible to the naked eye.
All of this was captured over several hours on Monday night using the current iteration of my imaging setup, including a Takahashi FSQ-106 refractor telescope mounted on an Astro-Physics Mach 1 equatorial mount. New to my setup this year is an SBIG STL-11000M camera. This is a 12-year-old example that I bought from a listing at Astromart. The camera is now an obsolete model, introduced in 2004 and now replaced with the STXL-11002m. The image sensor chip (the KAI-11002, originally designed by Kodak and now part of On Semiconductor) is an old design but still current technology for this type of device, and the camera, although rather elderly for a high-end imager, is still functioning remarkably well.
The white bucket at bottom right of the picture is coolant water for the camera; I was running the camera at -10°C, which was a struggle given the very high temperatures at OSP this year, and water cooling assistance was very much required (the orange lines running to the camera are carrying water from a pump sitting in the bucket). We saw temperatures hitting 105°F during the daytime, and unusually for OSP, barely dropping below 70°F during the night. To deal with the typical conditions, I pack layers of clothes to deal with the expected brutal night-time temperature drop from baking hot to barely above freezing; this year I was walking around in a t-shirt at 4am.
Incidentally, the enormous telescope in the background at the right of the picture belongs to Howard Banich. I’m looking forward to seeing what he writes up from last week.
The data that comes directly from the camera is pretty messy for these type of images. I’m taking a sequence of exposures, all framed as close to identical as I can get them, or either 5 or 10 minutes dependent on the filter. The raw images are all monochrome, taken through one of a series of filters (red, green, blue and luminance) and composited in later processing to create a full-color image. This is what a single raw image looks like:
The data is very noisy, and contains many flaws that get removed as part of the calibration and compositing process, including multiple tracks from satellites that passed through the field of view during the exposure. I’m pretty sure that I have some meteors from the Perseid shower in this particular data set also. The diagonal track in this particular image, in the left hand side of the picture, looks like an upper stage rocket booster. These objects tend to stay in orbit for a year or two before burning up in the atmosphere, and tend to show up in images as dotted lines, because they are tumbling as they orbit; what we’re seeing is sunlight glinting off the booster fading in and out as it rotates. These are really common to see in images and range from the slow fade-in-and-out as seen here to short dotted lines.
Next up: I have more data from the Veil Nebula (Tuesday) and the heart of the Cygnus cloud (Wednesday) that I’ll be posting about shortly. Additional data from the Iris Nebula (Thursday) and the Cocoon Nebula (Friday) will take a little longer. I’m still scratching my head about how to clean up the smoke related gradients in the last two.