I just don't shoot enough astro or UWA, but the Sigma 14 mm Art could end up in my bag if I start doing either:

http://www.the-digital-picture.com/R...mp=2&APIComp=0

Sharper than the 11-24 (f/1.8 to f/4), vignetting looks well controlled (compared wide open here to the EF 16-35 III). I've also started to see reviews where the coma is well controlled (not perfect, but very good). This could be a dream lens for nightscapes.