Flying South for the Winter

There was a plan to capture more data on this target, the Swan Nebula (Messier 17), from the observatory in Australia, but the Swan has now flown too far away and is no longer a viable target.  The good news is that I was able to make this pretty decent image with the data I do have.

By the way, don’t spend too much time trying to see a swan in this shape.  As is often the case, the photographic appearance of this nebula is very different from the visual appearance from which the name derives.  But if you really want to see it, it would probably help to turn this picture 180 degrees.  The Swan is upside down!

Also known as the Omega Nebula, the Swan is a very bright object in the constellation Sagittarius.  At apparent magnitude 6 it is on the threshold of naked eye visibility, meaning that under very good conditions an experienced observer (with younger eyes than mine) could spot this object, but for most of us a little help is needed, perhaps in the form of binoculars.  It is between 5,000 and 6,000 light-years from Earth, and is one of the largest star forming regions in the Milky Way (that we know of).

This image is constructed from RGB (natural color) data plus hydrogen-alpha (H-a) data.  The color is all defined by the RGB (no H-a was mixed into the color image), so this can be considered a natural color image.  The H-a data was used as a luminance layer, so it provides the sharpness and detailed texture.  In this case there is hydrogen throughout the nebula, so the H-a data works well in this role.  As is usually the case, combining narrowband and broadband data (the H-a and RGB data, respectively) results in strange colors around the stars because they are much brighter (and thus bigger) in the broadband image.  I solved this problem by removing the stars from the RGB image before applying the H-a luminance layer.

The total exposure time included here is 10.5 hours; 6 for the H-a and 4.5 for the RGB.  I got broadband luminance data as well, but did not use it because it was somewhat over-exposed.

I’ve been very busy working on several projects, including the 2019 Night Visions calendar, which should be available in a few weeks.  I’ll tell you more about that later.  Hopefully, I will have 1 or 2 other interesting announcements, but nothing is definite at this time.

I’m planning to go on a tour of the LIGO (Laser Interferometry Gravitational wave Observatory) facility in Hanford, WA this coming weekend, together with other members of the Rose City Astronomers.  If everything works out I’ll tell you about it next time.


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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