Welcome once again to EbolaBooze’s Fortnightly Astro Corner, where the ride is astronomical. (I am so sorry, but it had to be said.)
The next stop is Messier 17, just a few degrees in the sky away from the Lagoon Nebula, our previous stop. This is an interesting one, in that it has many other names. Wikipedia lists its names as the Omega Nebula, Swan Nebula, Checkmark Nebula, Lobster Nebula, and the Horseshoe Nebula. To be honest, the names confuse me too, since I can’t see any of them in the nebula visually, all I get is very, very faint nebulosity and bright stars in my field of view, and that’s with a 254mm (10″) aperture telescope.
This is a target that is best viewed with a large aperture telescope (or photographed) for the best effect, you’ll get to see the bright L-shaped core and some extended nebulosity radiating from around it, and the open star cluster embedded in it that makes all the gas glow.
Here’s a picture that I took of M17 a little while back, reprocessed to bring out some finer details.
This data for this picture was captured in one night out the front of my house, comprised of 2×600+3x300s (2100s total) exposures each in Ha, OIII and SII for a total integration time of 105 minutes.
Now you may be wondering why this particular example is all green and golden, and that’s because it’s been processed in false colour. I’ve used the Hubble Space Telescope colour palette to colourise this image, as it has been captured by narrowband emission.
The filters I used in this particular example were hydrogen-alpha (Ha, colourised green), oxygen-three (OIII, colourised blue) and sulphur-two (SII, colourised red). These refer to different elements within the nebula complex which have been ionised by the energy released by the stars they surround. I won’t go into much more detail about the finer points of capturing emission nebulae in narrowband as there are much better researched, more comprehensive guides to the material out there. Instead, enjoy the picture!