ULTRA WIDE LENS ASTROPHOTOGRAPHY BATTLE! Sigma Vs. IRIX Vs. Rokinon

I went to my favorite light house on the west side of Michigan to test out the IRIX 15mm 2.4 lens.
My Sigma 14mm is in for repair so I wanted to see what some other much cheaper ultra wide angle lenses have to offer.
I still have my 14mm 2.8 AF Rokinon lenses to test and is currently the main Ultra wide angle lens I use.
I compare all 3 lenses for the following
over all sharpness
Comatic aberrations
Stigmatisms
Vignetting
Over all i think this is a really solid lens but not one I'm keeping because of the issues wide open at 2.4 and I'm looking for a really good fast lens I can use at 1-4 seconds for aurora photography

[@dw.in.michigan]

I bought the Irix 15mm to replace my Rokinon 14mm fully manual lens. My Canon version of the Rokinon was really good, but when I switched to Nikon, the lens I got was terrible. I bought the Irix, based on a reading several reviews, and it is really good, and mine is a refurbished unit. I'm sure it isn't as good as the Sigma Art. I think both Irix and Rokinon, at their price point, have a problem of consistency, so some are going to be bad copies.
If you have the full user's manual, they describe how to calibrate the lens, so you might want to check that out, if you haven't done so already.

[@JMNaturescapes]

Hmm interesting!

[@ig25]

What do you mean by tracker?

[@JMNaturescapes]

A star tracker. It's a device used to take long exposure of the sky without trails. It tracks with the Earth's rotation so the stars don't appear to steak.