At that altitude a UV filter may do more good than a CPL.

Canon's SX30 had 16MP, when Canon brought out the SX40 they wisely reduced the MPs to reduce noise. You just can't put16MP on a small format sensor and not get excessive noise. The 10MP SX10 was in some respects the best camera in the series. Low noise.

The SX40 most certainly does shoot raw as does the SX20 and most other small Canons. But you must install CHDK in order to do so. There are a number of other advantages to doing so.

Just checked the chdk site, the SX30 is included. RDH

The Canon SX40 can shot raw, but you need to install the Canon Hack Developer's Kit to do so. I have been using CHDK with a Canon SX20 for several years and would not be with out it. For full information see: http://chdk.wikia.com/wiki/CHDK_in_Brief. The "Hack" is installed on the CD card and does not affect the Camera.