Reader Don McCrady sent a bunch of gorgeous astronomy photos. His notes are indented, and further technical and astronomical notes are at the links. Click to enlarge.
Now that the weather in Seattle has turned back to being typical Seattle weather, I’ve finally had a chance to process some of the images I took during August. There’s 6 of them, so I thought I’d just drop them all into one big post. After this batch, you might not hear from me for a while given the crappy weather I can look forward to for the next 7 months.
First, a batch of emission nebulae. My astro-imaging system [JAC: have a look!] is optimized for these targets because I shoot from my highly light-polluted backyard, under the glare of 3 street lights. Emission nebulae such as these respond well to narrow-band filters because they block out all light, including light pollution, except for a 3 nanometer wide strip of the spectrum corresponding to the emissions of ionized hydrogen (Hydrogen-α) and oxygen (Oxygen-III). Since Hα sits in the red portion of the spectrum, I map it to “red” in the image; and since Oxygen-III lies very close to the blue-green boundary of the spectrum, I use it for both blue and green, thus making a 3-colour final image from only 2 source colours. (I do add about 10% of the Hα to the blue channel since that element does shine weakly in that part of the spectrum.) The result is a sort-of-close-to-true-colour image.
Here are 5 such emission nebulae.
M27 – the Dumbbell Nebula: This planetary nebula offers a vision of what our own sun might look like when it has run its course and puffed off its shell of heavy elements formed in its furnace the preceding 10 billion years. It lies about 1300 light years distant in the constellation of Vulpecula (the Fox), and is an easy visual target for amateur astronomers.
The Elephant’s Trunk Nebula: This is a portion of a much larger nebula known non-poetically as IC1396, which lies 3000 light years distant in the constellation Cepheus. The bright blue star near the left edge of the image is HD 206267, and is responsible for the energizing the dust and glass in the area. The stellar winds compress the molecular cloud into thin edges, and the intense radiation ionizes it forming bright filaments and fascinating structures.
The Pacman Nebula: A whimsical name for a nebula more formally known as NGC281, which lies approximately 9500 light years away, toward the constellation Cassiopeia.
Sharpless 2-188: Sorry, but as far as I know there is no well-known whimsical name for this nebula, which is the 188th entry in the 2nd edition of Steward Sharpless’s catalog of emission nebulae. It is a planetary nebula — the remains of a dying star — in the constellation Cassiopeia. It is unusual because of its asymmetry, and is thought to be much brighter in one segment because the central star is moving rapidly in that direction.
The Eastern Veil and the Western Veil nebulae: These two images are the eastern and western portions (respectively) of the Veil Nebula, a complex remnant of a powerful supernova explosion which occurred thousands of years ago. The bright star in the Western Veil (also called the Witch’s Broom Nebula) is 52 Cygni.
The Triangulum Galaxy: Finally, something that is not a nebula, although I worked hard to bring out the nebulae within this nearby galaxy, Messier 33. This image was taken through wide-band red, green, and blue filters and thus is rendered here in “true colour”. However, I did also take separate Hydrogen-α, which augments and highlights the active emission nebulae that are scattered throughout the galaxy. Some of these nebulae have their own NGC designations such as the very bright NGC604 on the left edge of the galaxy. Both the galaxy and some of its bright nebulae are easily seen through amateur telescopes, and although it has a low surface brightness, M33 can be seen with the naked eye from a dark location.