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Thanks to all for the nice comments and I am very glad you like the image, what a spectacular piece of sky.
To answer the questions raised:
I use a Scoptronix ETX90 Piggyback adapter, I did try to make my own but it was not strong enough, the bought one cost $99 - a little high for a metal hoop and a thumb screw! If you have the tools and some basic metal working skill (that is me out by the way - I'm ok with a compiler though....) then I am sure you could make one for $20 or so.
I used F9 because the lens was the kit 18-55 F4-5.6 lens that came with the 20D. It is NOT a good lens for astro work, soft at best and with strong coma and sperical abberations. Come to think of it this is just not a good lens! The only way to use it for astro is to stop it down at least two stops, it would be better at f16 but then I would have to expose longer and my mount (ETX90 remeber) limits me to about 4 mins max at this focal length. This also dictates the ISO. This does not seem to be a problem as, so long as you are doing dark frame subtration and stacking, ISO is not so important as signal to noise ratio thus I always shoot at ISO 1600 to get to mid histogram and stack to average away the noise.
The acquired images were then processed in Registax 3 (stacking), Photoshop Elements (levels) and Neat Image (noise removal).
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