These last days I've been practising star trails photography. It's not complicated, but there's a problem that keeps me giving headaches: the white balance.
I know, for this type of situations, I have to choose color temperature close to blue or "cold". The problem start when I'm trying to configurate the white balance in order to get a precise color temperature in my Nikon D3200. This is how the color temperature grid looks like this:
It has no Kelvin temperature indicator. Instead, it has two text boxes, one labeled A-B and the other one G-M.
My question is: what are the closest values to the perfect white balance for star trail photography (using these both values)?
P.D.: What do both of them mean?