I'm running this on OS X Lion, and for some reason, the "Get Image URL's from Webapge" action was listing image links to external sites higher than apod.nasa.gov in its results.
Editing the following "Run Shell Script" step solves this:
If the page links to more than one image, we only want the first one.
Filter out non-APOD URL's.
cat - | grep 'apod' | head -n 1 }}}