Friday, June 1, 2012

The Silver Coin galaxy

Just a quick image posting today... I don't have as much time as I'd like to write about this object.

I was going through some files the other day, and I realized I had this image of NGC 253, the `Silver Coin' galaxy, sitting on my hard drive. Might as well add it to Photon Shot Noise!

At the moment, I don't have a lot of information about the details of how I acquired it and processed it. I definitely used my Orion ED80 refractor, and I was using a camera with the Kodak 8300 monochrome chip, shooting through a Luminance filter. I think the subexposures were 15 minutes long. I was using my Orion Sirius mount (which has since been retired for solar-observing duty at school), and I was pleasantly surprised that my polar alignment and autoguiding were good enough for 15-minute subs. I seem to recall acquiring the data on one or more cold nights at a Bay Area hilltop observing site, sometime in the last year or two.

As with the acquisition, the details of processing are a bit hazy at the moment. I'm fairly sure I processed this in Pixinsight, and I recall being pleased at how much detail I was able to bring out. This is due to the reasonably good SNR, which came from taking lots of relatively long subexposures over one or two nights. I either used Deconvolution for sharpening, or perhaps an ATWT-based sharpening and noise-reduction workflow.

If I recall correctly, one of the nice things about NGC 253 is its relatively sharp `edge'. It doesn't have much of an extended, low-surface-brightness halo around it, at least not in my subexposures. As a result, I wasn't tormented by the desire to bring out lots of surrounding faint stuff. Such faint stuff around a galaxy is often hard to make look decent, since it requires either a mountain of exposure time, or a miraculous touch with the noise-reduction routines. I seem to recall that NGC 253 pretty much ends where you see it ending here, and so I didn't have any significant `halo struggles'.

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