Nice image there (the first one
). You can't use Registax's auto-balance feature for planets that are predominantly one colour (eg Mars, Uranus, Neptune and probably Saturn), as it tries to "correct" the image to make the colours roughly equal. Jupiter works well, the other planets not so much.
Remember, Mars is red, here is a "true colour" image from the Rosetta spacecraft.
http://www.damianpeach.com/marscolour.htm
Oh, and you only need to capture the planets in 8 bit mode.