Yes, I agree. Stopping down fast primes a stop or two is the norm. The 50 Macro Planner is quite good in that respect probably due to being a slower lens design.

For astrophotography with DSLRs the problem for me is the lack of 'red' which is filtered out by the IR filter. Canon have a partial solution to this with their D60a. Of course serious astrophotographers use dedicated monochrome astro CCD cameras and filters.

I have a permanently mounted telescope on a large equatorial mount and living down here dont really have the light pollution issues. Plenty of cloud though.