In reply to Beardyman:
Yeah I do quite a lot of this,
The best apature is around large, off centre ie f/4 to f/8 depending on the lens you are using. A lot of middling lenses have soft edges and drop off in the corners and you will find that A. This get worse towards the extremes of the large apatures and B. The event is normally bigger than your field of view so you want the full extent of you lens. I shoot with both a Nikkor 16 mm f/2.8 full frame fish eye MF and a 24 mm f/2.8 on a D800 and the 24 is not always wide enough. This means that cheap to middling glass can ruin your result quite easily if you are pushing the wide end.
You shutter speed is determined in part by the max ISO that your camera will take a good photo with, I'm happy around 640 but I don't know about your rig, the time of night the show happens and or the moon cycle (ie how dark is the sky?) and the rule of 600 or what ever applies to your sensor size. Many a good photo has been ruined by stars that are almost moving......
The best shots I have are always foreground inclusive so it helps to know the ground before the event. "Normally" UK events happen in complete darkness but sometime they are early ie the night of the 20th Dec which had a gibbous moon allowing for fore ground illumination and an azure sky with stars.
Have fun and wish her luck hunting.
Post edited at 21:59