Can you tell me how you did it?
First I made a very rough select with the Lasso that included all the sky, then I used Select->Color Range in Sampled Colors mode, clicking on lots of different places in the sky with the + eye dropper. I had the Fuzziness set to 45 and didn't bother to change it, which resulted in some blue edging around a few branches that I had to manually remove. I just repeated the selection with Fuzziness set to 70 and had better luck. (This is infinitely easier to do with a digital capture than a film one.)
focal plane of my clouds are at an upward angle - trying to miss all of those damn buildings
Perhaps a really tall tripod? ;) I maintain a large and growing collection of sky shots that I snap whenever I'm in a low horizon place with an interesting sky. I generally take several of the same sky at different focal lengths while I'm at it. Excuse to take a trip out to the sticks if you live in a big city? You can always add the smog afterwards in Photoshop... ;)
And yes, I have felt that Mother Nature is admonishing me for trying to fake it.
Actually, I have it from a reliable source that she very much appreciates our efforts and will try to do better in the future. It's just that right now she has to juggle all this global warming business, which apparently takes away from her ability to optimize for aesthetics.