Since there seemed to be a few people here interested in barn-door trackers and other 'on-the-cheap' astro-hacks, I thought I'd share another experiment: How to use standard 1.25" telescope eyepiece filters (e.g., UHC nebula filters) with a normal DSLR/lens combination (no telescope). I haven't seen this done anywhere else.
http://www.zenadsl6044.zen.co.uk/UHC/
Summary: There's a risk of camera damage (caveat emptor and all that), but the result are quite impressive, much better than with a didymium filter (which was the best option up to now). I have managed to hack the filter fairly easily into all the lenses I've tried, but of course there's no guarantee that it'll work with any other camera/lens combinations.
Oh, and the Samyang 135mm f2 is a cracking (albeit manual focus) lens!
