Great images H! Mark - I'm no astrophotographer, but I noticed JJJ uses a Tammy 90mm, which is a very sharp and great value lens for general photography, so that might be worth a shot if you find your 50 is too wide for some things. Seen some great wide fields with a cheap 50mm. Also there's the Canon 100mm which is a little pricier than the 90mm Tammy, but still great. If you wanted something in the 200mm focal length range I'm not sure if there's much better on offer than the 200mm L that you're already eying. (and wow, looking at H's image I might be in for one of those soon too

)
Again, these opinions are not coming from an astrophotography background