Flying with the Eagles

Georgia has had a nice weather event lately; a passing cold front. A REAL cold front. The temperature has dropped about 20 degrees and the skies have cleared as much as I have seen them clear this summer. I have finally gotten a few good nights under the stars. No moon, Milky Way visible. Nice.

For the most part, the equipment has been working OK. I have imaged a few more things, most Messier objects. I got M17, M18, M69, M70, and M16. 

M18 is a open cluster. 

M18

It just looks like a bunch of stars to most folks. What's the big deal. Well, the deal has to do with the fact that all the stars are gravitationaly bound to each other and thus travel through space as a unit. Think of a school of fish in the ocean. I've read something that I currently can't remember about open clusters; something about their position is galactic evolution. I need to find that again, rather than giving out information that I'm not sure about. 

M69

M70

 M69 and M70 are both globular clusters. Same general idea as the open cluster, but obviously much more compact. They usually have many more stars, are usually much older, and generally orbit in the galactic halo, which means above and below the plane of the galaxy. At least that's what I remember about them. M69 and M70 are each only one photo, each a 1 minute exposure, and for the technically minded, only dark subtracted. They are interesting to image, since my eventual goal is to measure the light variance in variable stars. Imaging stars has it's own set of problems, compared to imaging nebulae and galaxies. Obviously, I hope, imaging variable stars will be more akin to imaging star clusters than nebulae.

M17 I've already processed.It's below.

 M16 I just finished, and is the longest exposure I've taken to date. 

M16

M16 is interesting for several reasons. First, it's an open cluster with an associated nebula. That makes the imaging harder, because the dynamic range is larger. What's dynamic range? It's the difference between the brightest object and dimmest object. Think of taking a picture of a flashlight with the sun in the same picture and trying to show the light coming from both. In this case, the stars to the upper right are fairly bright, but the nebula is really dim. There are several ways to solve this; mine was to set the exposure so that the stars did not reach saturation and then try to pull out the nebula in post processing. Since I consider myself a beginner at this, I was pleased with the result. Second, M16 contains the “Pillars of Creation.” See link. They are visible in my image, but the Hubble images in the link are the impressive ones.

Well, if we get some more clear nights, I'll see what else I can get. M31 is possible, but will be time consuming. It will have to be a mosaic; it won't fit on the sensor in one shot. It will be a multi-night imaging session and will probably be better later when it's higher in the sky. For now, I guess I had better go fix the leaky gutter. Yay.

PS. It just occurred to me to mention the "other" eagle; Aquila, the constellation. It contains the bright star Altair, one of the summer triangle stars. Aquila is not all that far from M16, relatively speaking, of course. They are both visible right now.