Questar, leather and alcohol

You learn the darndest things in backyard astromony. After 40 years of
waiting, I finally broke down and bought a Questar telescope. It's an oldie
from the 60s, but a real goodie. The problem was that the leather cases were
a mess, especially the outer "dust cover". However, some alcohol took all
the tape residue right off, so I then applied it to the black goo on the
inner case. Big mistake. The leather of the inner case is dyed, and the
alcohol took the pigment right off. Left a big blotch right on the front
cover. So, a word to the wise: always test solvents on a spot that doesn't
show!

PS: the Questar is everything I ever hoped and believed it would be.