I have not posted anything recently, partly from inactivity and partly because I’ve been experimenting with new techniques and filters. I have been playing with observations of very specific spectral lines (called narrow-band observations) and then merging this information into RGB images. I have a preferred way to “merge” the images that is probably not kosher, but produces images that I prefer.
The image today is the California Nebula (NGC 1499/Sh2-220), an emission nebula located in the constellation Perseus that is supposed to look something like the geographical outline of the state of California. This was one of my first targets successfully imaged, and I remembered posting it on Facebook back in 2019. I later realized that the image had a lot of “features” that were the result of poor image processing techniques (manual intervention in fact). It looked cool but was really garbage. Subsequent images were of a much higher quality, but it still looked like a big blob of red colour. I started calling it the Sashimi nebula – a slice of red. This sashimi was missing the Wasabi – it was too bland.
This nebula is popular with astrophotographers because it is easy to observe. It is hard to observe visually because it spans a large area and is not bright enough. It was discovered by Barnard in 1884. It is a nebula in the Milky Way, close to us at only 1000 light-years. The nebula is quite big, at 2 ½ degrees long. Recall that the moon is roughly half a degree in diameter. This image cuts off some of the dimmer parts of the nebula.
The emission is almost completely at the red colour of the Hydrogen-Alpha line at 656.28 nm. I use a filter that allows this frequency through and virtually nothing else. In addition, I have used my “one shot colour” camera. Other emission lines seem so faint that it wasn’t worth trying to capture them.
This evening I looked at the images of this nebula in Wikipedia and on several astronomy sites. I prefer the image here to any and all images I've seen. I haven't seen a Hubble one, though.
Image captured on September 9 and October 2, 2022. Telescope RASA11, Cameras ZWO ASI6200 MC and MM. H-Alpha filter used with the Mono camera.
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