Two tricks that might help you
First trick: use image crop as an alternative to zoom
Instead of using full zoom (i.e. 200mm on your K10D), try a lower value (e.g. 100mm) with less chromatic aberration, take the picture and then crop part of the image.
The 10 M pixels give you plenty of details: so picking 6 M or even 3 M out of the 10 M image is not a problem. I gave an example with the bird http://www.cameralabs.com/forum/viewtopic.php?p=3559#3559
By the way, which zoom are you using
Second trick: use RAW file and Pentax Laboratory
If you shoot in RAW mode, you can process that image with the Pentax Laboratory software, bundled with the K10D
. Pentax Laboratory software is pretty exhaustive and can address chromatic aberration.
Event better, if you're using a Pentax lens, let say, the 50-200mm zoom is registered in the Pentax Laboratory software, so image improvement is easier since parameters are known by the software.
Enjoy and keep discovering
Pentax K-5 + BG4 + DA* 16-50 + DA* 50-135 + DA* 60-250 + AF-540FGZreivilophotography.weebly.com