As an aside, another gem of wisdom (or not
) is to let the sky (The Earth's rotation) dither for you, by stacking (
short*) exposures from a fixed mount/tripod, with a
generous gap between exposures, of between 2 to 3 times the exposure length. Somewhat off-topic, but useful if you're on holidays without all your gear/EQ-mount.
*Short as in
sufficiently "short" exposures such as not to cause
obvious star trailing, as defined by using typical 600 exposure rule, except that I prefer to use 300.
Best
JA