I like taking astrophotography pics. To avoid star trails I'm limited in exposure time so I use the lens wide open to max the exposure. I'm currently using a Canon 28mm F2.8 at F2.8 on my 5DII. My question is: Which lens has the best relationship in price / sharpness wide open ? I'm open to all manufacturers and manual focusing lenses are fine, even with adaptors for Canon EOS.
Thanks for any recommendations you can give me!