Hi Mark, Why not 'KISS'? Just buy a large capacity 2nd car battery,(can get them 2nd hand from wreckers), install it in a convenient place & have the isolator wired up. Your laptop will happily run on one of the attached adjustable voltage converters. HTH.
L.
ps. Davo, Could this be a petrol driven 240 volt alternator set that you're actually recommending? Cost of petrol,oil,maintenance,spare parts,exhaust gases & CONSTANT NOISE at a quiet observing night! Worse than the Meade SCT's.......
L.
pps. & IMHO, Too many pieces of equipment needed for such a simple job.