The skies unexpectedly (for me, anyway) cleared last night, but late enough that I didn't want to pack everything in the car and drive to the clubs "dark" site. Recently, I had picked up a used Astronomik CLS light pollution filter from someone at Cloudy Nights, and this would be a perfect opportunity to test it out from smack dab in the middle of Bloomington-Normal's light dome. This filter uses the EOS Clip Filter System that has the filter sit between the lens and CCD chip, instead of in front of the lens. This way, you can use the same filter for a range of lenses instead of just ones that have the same front aperture.

As for the filter itself, it claims to block something like 99% percent of the light wavelengths that make up light pollution and make it so difficult to observe or photograph astronomical objects from within a city's light dome. Considering that I have to set up my scope in the shadow of my garage because of a sodium vapor glare bomb behind my house, that certainly sounds like what I need. And indeed, it did seem to do the trick.

Today's target was Messier 13, a large globular star cluster in the constellation of Hercules. It is one of the brightest and biggest globluars in the northern hemisphere, and quite popular to observe because it is so well-placed in the sky. I, personally, much prefer Messier 22 in Sagittarius. M-22 is situated amongst the central Milky Way star clouds which provides a much richer-looking field of view as opposed to Hercules' somewhat sparse patch of sky.

But, I digress again.

Here are the fruits of my staying up till 3am last night:

Messier 13
Instrument: Astro Tech AT106LE, 106mm f/6.5 Triplet w/Astro Tech Field Flattener
Camera: Canon XSi (Unmodified), ISO 400
Filter: Astronimik CLS EOS Clip
Mount: Celestron CGE
Guider: Orion ST-80, w/ StarShoot Autoguider
Exposures: 60 X 60 seconds (1 hour total integration time)
Calibration: 30 Darks, no flats, no bias
Software: Image acquisition: Canon EOS Utility (RAW mode)
Stacking: Deep-Sky Stacker
Post-Processing: Photoshop CS4