Interesting astrograph

anguslau

This should be an interesting astrograph:
http://www.dpreview.com/news/0801/08013101sigma250500.asp

oldfield

Fast!  Just wonder how it performs especially when it's a zoom

Raymond_Tse

Most tele photo lens suffers serious comas and field curvature at the corners. Some obvious chroma aberrations may appear too.

Their target group of buyers  is daytime shooters,  not astro imagers.

fatpang

For astro photography, you can also consider Tak E180 which is also around 500mm F2.8.