Well, mine would have to be my first look through my ( any ) telescope a Tasco 10x-50x X 40mm of the moon, seeing all those craters and mountains.
It was 1968 and I was 12 years old and full of the wonderment of the space age and the forthcoming lunar landings.
Second would have to be very recently looking through my 12" Lightbridge, all those old favourites have taken on a new lease of life. WOW!!!