Just spotted the earlier thread about using a 70-200 Tele lens for astrophotography. It's given me another project to keep me amused as I have a nice KM 70-300 f4.5 which gets little use these days.
When I did use it ( motorsports photography ) I ALWAYS had a good HOYA UV filter screwed onto the front, partially for the UV sheilding and partially for the anti rock protection which on Rally events was always a possiblity. Cheaper to replace a whacked filter than a whacked lens !!
Question is should this be removed for Astrophotography ? Goes against my grain as a Photog to do so protection wise.
... and yes, I did have to replace two over the years for rock damage. You can get pretty close to the action in Motorsports, especially Rallies.