In the middle of the summer, I picked up a used Rokinon 85mm F/1.4 lens on Craigslist for $180. I know used Rokinons are iffy, but I didn't have an 85mm prime for my portrait photography and I was willing to take the risk at that price point. I've been trying to do a decent astro test ever since.
This is 58 minutes between Orion and Monoceros, captured over a 2-hour period between rain squalls. It's the only 58 minutes I've been able to capture since mid-August due to scheduling conflicts and bad weather (this monsoon season, while providing much needed moisture, won't seem to end). I had to throw out the other 62 minutes because of high-altitude clouds.
Captured on a stock Canon 6D and Rokinon 85mm F/1.4 @ F/2.8
29x120s lights @ ISO1600
10 bias frames
Calibrated/stacked with some home-brew code
Aligned using Hugin
Stretched/Curved in Lightroom 6
Thoughts on the lens
So ... this lens is great for portrait photography, but not so much for astro. Light falloff at F/2.8 isn't terrible, and coma is pretty good to the edges of APS-C, but it gets pretty bad in the FF corners. Chromatic Aberration is downright terrible. I may try this again with a UV cut filter to see if it helps, but I'm not getting my hopes up. I hope to do a more thorough test when the weather improves.
C&C welcome and appreciated!