Originally posted by MrEarle I "think" I would want to set the ISO to 100 and mount on a tripod and automatically shoot on an interval for about 20 minutes, with enough time between shots to not lag on writing to SD card.
ISO 100 sounds about right (but 20 "minutes" - NO NO NO! - did you mean seconds?!):
Here are a couple of fireworks bursts shot with my K1 and D FA 28-105 lens (WR - great for when we rode around on the Maid of the Mist and at Cave of the WInds!) when we were at Niagara Falls back in September 2016. We were on the Canadian side and I rested my camera on a rock which was part of the railing system along (high above!) the river bank. A tripod would have been better, but it was not along for the trip.
I started out with 6-second exposures at ISO 400 and f 8. For the background, this is fine - the background is not overexposed. However, the bursts were generally overexposed.
As the show went on, I worked my way down to less and less exposure. The first two pictures here were taken at ISO 200 and f11. The first image is a cropped, downsized shot showing a launch and burst. The second image shows the center of the burst in the first frame at a 1-to-1 crop. The center of the bursts and the initial burst streamers are quite overexposed.
The last picture shows a downsized crop shot at ISO 100 and f 16, and this exposure seems about right for showing the intricate details at the center of a burst.
You will almost certainly want to experiment to find your own set of ISO and f-stop. Remember that underexposure can be pulled up in post processing, but blown out highlights are impossible to reconstruct.
These fireworks were coming fairly fast and furious. As I recall, I pretty much just kept shooting my 6 second exposures almost continually (by hand). Your exposure interval will depend on how rapidly the fireworks are launched. I would pick an interval such that you get only 1 or 2 or 3 bursts per frame. I think more bursts than that in a frame is overkill, but that’s your artistic call.