Originally posted by cheekygeek: Great thread and I appreciate the input from everyone, even thought I did not start this thread. I am not into Milky Way shots (at least not yet) but I have been using my Sigma EX 30mm f1.4 DG (old version) for aurora from Nebraska and was surprised when this last storm resulted in aurora that exceeded my FOV. A wider FOV would be nice for meteor images also (and I have a Vixen Polarie to try for pinpoint star images in meteor long exposures).
I'm on the fence about whether to get the Samyang/Rokinon 14mm f2.8 or the 16mm f/2. But I'm leaning toward the 16mm. I think the one-stop difference of the 16mm is a bigger deal than the extra (3mm equiv.) FOV. Northern Lights are in motion (for example) and what you get with a 10 second exposure vs a 20 exposure could be HUGE in terms of "freezing" the action (equiv. ISO). I also like that it is a 77mm filter size (like my 10-20mm). I rarely shoot with a filter, but it is nice to positively protect the front element with a screw-on filter rather than just a clip on lens cap in the camera bag.
If I thought I was going to shoot full frame then the 14mm would have an edge, but I'm probably an APS-C shooter for the foreseeable future.
Unfortunately, the Rokinon 16mm is a dedicated crop-sensor lens and it vignettes like crazy, while the 14mm f/2.8 is a full-frame lens and doesn't vignette as bad on a crop-sensor. Honestly, I'd call the 14 2.8 a better investment at the moment, considering Pentax' full-frame camera is on the horizon and it might be quite desirable for astro-landscape / nightscape photography.
Then again, the filter thread availability of the Rokinon 16mm is nice, and it is one heck of a sharp lens.