there are two method for capturing lighting.
1st method is you set iso like 100 or 200, aperture 11 and maybe more. And shutter at 10 - 15 secs. If there is a lot of lightnings, then ju just release the shutter, drink your coffe, and release again
Prety wierd ?
Well you need a tripod, manual focus only, and mirroc lockup.
2nd method. this one is theoretical, but i'm tinking about making it.
You need a very sensible light sensor, and prety fast relay.
U set a light sensor, to the highest sensitivity, and connect to relay, that will trigger dslrts shutter
Scheme is prety easy, ~ 10 - 15 mins of work.
Such method was tried on microfone that releases shutter