Friday, October 13, 2006

Andromeda Galaxy Through Big Bertha

Through 70mm binoculars, the Andromeda Galaxy (M31) is a smudge. Even in an 8" reflector, it's not much to look at--you can see why there was serious debate, even into the beginning of the 20th century, whether this was a gas cloud in our galaxy (admittedly, one with a lot of stars in between us and them), or another large collection of stars--an "island universe" to use the picturesque expression first used to describe another galaxy.

Our word "galaxy," by the way, comes from the Greek "galactos" for milk. The Milky Way, of course, is our galaxy. And yes, there is a dwarf satellite galaxy named Snickers, although there is some dispute about whether it is a galaxy or simply a hydrogen cloud--but it is the ultimate form of product placement, I suppose, for Mars Corporation, the maker of Snickers candy bars.

Anyway, back from the etymological/peanuts/chocolate tangent. I dragged Big Bertha out this evening, and after a little hunting with the 70mm binoculars, I was able to find the Andromeda Galaxy--and then I was able to aim Big Bertha at it well enough.

Picking the right eyepiece for a deep sky object is always an interesting challenge. As the magnification increases, all other things being equal, contrast drops. For an object with low surface brightness, such as a galaxy, it helps to keep magnification low. At the same time, if the magnification is too low, you have a high contrast object surrounded by blackness.

Of course, I was using 2" eyepieces for this. The Russell Optics 85mm eyepiece was a bit low a magnification (23.5x); the 18mm University Optics orthoscopic (111x) gave just the bright core of the galaxy and a little bit of surrounding haze of stars. There's a weird military surplus eyepiece that came with Big Bertha that, while a pretty poor eyepiece in some abstract sense, turned out to be close to perfect for this application. I think it may be about 60mm (33.3x). The bright core was plenty visible, but enough of the surrounding halo of stars was visible that you could see where the long exposure photographs of Andromeda give that spectacular image that most of you know:

Anyway, it inclines me to want to find some way to make Big Bertha equatorially mounted, so that I can do some long exposure astrophotography.

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