My final image from Oregon Star Party. I had quite a bit of difficulty just getting this image to upload to the blog, and tried many different strategies all of which broke WordPress. The difficulty arises because of the high resolution and large file size; the final image is 4713×3144 pixels and over 21MB, and I really didn’t want to compress it or downsample it. I finally resorted it to using FTP to upload the image to an accessible directory so I could just link to it directly. The full-resolution version is here.
The objects here, known, for obvious reasons, as the North America Nebula and Pelican Nebula, are parts of the same large cloud of mostly ionized hydrogen at a distance hypothesized to be about 1,800 light years. The apparent gap between the two us misleading; the black part isn’t a hole, it’s a cloud of interstellar dust between us and the nebula, obscuring parts of it. Although these objects are too faint to be naked eye visible, they appear several times the size of the full moon. The chart to the right shows their location; the constellation Cygnus, also known as the Northern Cross, will be close to dead overhead at mid-northern latitudes around 10pm at this time of year.
Due to the large apparent size of this object, I had to create a 2-panel mosaic to fit it all in. When I planned this out, I didn’t know if the weather (and smoke!) conditions would hold out to be able to capture everything, so I planned framings of the North America (NGC7000) and Pelican (IC5070) nebulas, each of which could work as a standalone image if I wasn’t able to capture all of the data for some reason. It happened to be possible to come up with a pair of positions and orientation of the camera that would both work as two separate images, as well as for the mosaic. To get an idea of the stitching process, to the left is one of the intermediate steps after performing the mosaic stitching of the luminance channel, clearly showing the two panels. Almost all of the processing was carried out using PixInsight, but I still don’t have a good handle on the mosaic tools in PixInsight, and reverted to using Maxim DL for that step.
The data was captured over Saturday night for the IC5070 panel and Sunday for the NGC7000 panel. Saturday was challenging due to low thin clouds that kept drifting overhead before midnight, and I ended up with a lot of images looking like the one on the right, with the thin clouds acting as a diffuser. I captured a total of 16 exposures using the luminance filter, each of 15 minutes, and ended up discarding all but 7 of them. (My exposures using red, green and blue filters, shot between 2am and 4am, were all fine). Nonetheless, I ended up with an interesting side effect that you can see in the final image: notice that the two bright stars on the right hand side seem to jump out of the image, and have a diffuse glow around them. That’s from the residual effects of the thin clouds when I was taking the images. It isn’t present on the left hand side of the image, because that was taken the following day with a much clearer sky.
This image still needs some work. I have a few escaped hot pixels from the pre-processing that show up as clusters of red, green and blue blotches that are visible at full magnification in the image. I’ll clean that up and do a full re-process at some point in the near future.
|Mount||Astro-Physics Mach1 GTO|
|Luminance||7 x 900s (IC5070) + 10 x 900s (NGC7000) @ 1×1|
|Red||6 x 300s (IC5070) + 6 x 300s (NGC7000) @ 2×2|
|Green||6 x 300s (IC5070) + 6 x 300s (NGC7000) @ 2×2|
|Blue||6 x 300s (IC5070) + 6 x 300s (NGC7000) @ 2×2|