Aha! I take it this is same brother-out-law with the astronomy fetish and telescope on the way.
Obvious solution then. Wait for the next clear, starry night, perfect seeing, not a cloud in sight. Now: it takes a good half hour or more to set up a telescope properly, depending on the type of mount. So he lumps the whole works down to bottom of garden, sets up the mount, aligns everything properly, gets a good focus, settles down for a relaxing night's observing...
That's the precise moment at which your sis will yell from the house "It's starting, pet!"