The long exposure presents all kinds of interesting visuals, from simple Estes propellant grains showering down...
...to the errant path of an unstable rocket:
Here's another example of an unstable flight followed by the fiery forward spray of a motor closure failure under pressure:
And different propellant grains provide wonderful lighting:
And of course, all kinds of high jinks come out at night in the deep desert, like the washing machine tub full of scrap propellant:
Pyro bliss.