Was out last night with the 5DH and 24 to 105 F4L and took some shots at 24mm without any filters as they won't work much below 50mm FL. The larger angles change the transmission spectral position. Quite surprised how good this lens is for a zoom. I really only got it as good walkaround lens for terrestial.
Details
Canon 5DH, 24 to 105 F4L at 24mm at F4, 12 X 60sec ISO 1600, flat correction with ImagesPlus stacked with Registar adjusted with PS. The skyglow is due to light pollution. Center of picture is about at zenith.The field of view is 85x57 degrees.
This would be much better at a dark sky site.
Large pic 2.4MB
http://members.optusnet.com.au/~cheekyfish/MW03.jpg
Bert