Originally Posted by: Jolly McJollysonG-A-B-C-D-E-F-G is G mixolydian, which is a diatonic mode.

G-A-B-C-D-E-F#-G is G ionian, which is another diatonic mode.

Being diatonic has nothing to do with accidentals. Diatonic just means "in key."

I have done alot of investigation into accidentals, and the most basic definition I have come across is " a wrong note ". Now thats certainly not the way I look at them because no matter what scale I am playing their is always cool sounds to be explored by sampling notes outside the scale.
But threw my studys I have always found the diatonic scale patterns to be the blueprint , or basis for most scale variations. And I just cant see an accidental, or wrong note in a basic diatonic scale.
So if you could show me a diatonic scale with an accidental in it, and explain why the note that your pointing out as an accidental, that would leave much thankful.