I do this all the time. The only play I've actually SEEN and gotten an autograph at was Mr. and Mrs. Fitch starring John Lithgow

Go for it!
I've done it before when I couldn't make the show/couldn't afford it. If you're a fan of someone, I think they wouldn't mind that you didn't see the show.I think they'd be grateful for the admiration

I have done it before and have no issues with it, so long as there isn't a huge number of people waiting. If there are, I feel bad about taking the place of someone who paid to see the show, you know? Alternatively, turn up about 2hrs before the show and wait for him to turn up (actors typically turn up to the theatre about 1.5hrs before the show, but it does vary - especially if there was a matinee that day). That way, he knows you've not seen the show and you can be on your merry once he's gone inside.

Can I ask who the person is & where they're performing?

I would have no problem with asking for an autograph without seeing the show. I have had several successes from local theatres writing a normal sort of LOR but adding that I'm gutted to not be able to come to see the show. Nothing to stop you doing both, obviously.

I'm in a bit of a quandary and wondered what your guys thoughts on this were. Basically there is a theatre near me that has a play on at the moment starring someone who's autograph I have wanted for ages!!! However, the play he is in doesn't particularly interest me nor is it that cheap either. £30 quid for ticket, which might not sound much but I don't really have that sort of money. However, I am happy to drive to the theatre and wait around the stage door afterwards to get his autograph. There aren't many theatres near me - I don't live in London and so it is unlikely he will ever come back near me again - nor is he a particularly big name.

Now is this rude to ask for an autograph and a picture from someone you aren't going to see in the show he is in? Has anyone else done this before?