I do not see much halo effect here, but when it is really apparent, try using Layer Masks in Photoshop:
Take a good-looking darker sky from say a -2EV image, and the haloed HDR sky, and open both in PS.
- Drag the -2 EV image over the HDR image using the Move Tool while holding down the shift key to get an exact alignment.
- From the -2EV layer select the sky with the Magic Wand Tool. Uncheck the "Contiguous" and set "Tolerance" to around 20.
- Use Refine Edge to feather the selection **
- Click the Add Layer mask Button (a square with a circle in the center)
-check on and refine the feathered edge as needed
- Save the final image with a new file name, so you do not lose the old file!
Source: Complete Guide to HDR Digital Photography by Ferrell McCollough, Lark Books, pp. 88-89
** In CS5 Under Refine Edge you can choose View as Black and White to see the effect of feathering
BTW Go back and get rid of the blue rock. No excuses!