I may get a chance to tick off a "bucket-list" item within a month, that is, to see the aurora. Of course, I wouldn't mind getting some decent images too, and I'm prepared to spend some money on the project; hundreds, but not thousands.
I'll be using my 6D, but as for lenses, the most appropriate I have is the 24-105/4. I'm wondering if the Samyang 14/2.8 represents the best alternative without spending a small fortune.
I'm sorted for support with my Gitzo Explorer, and I can use my android phone for remote control to avoid shake.
So, will the 24-105 do the job, possibly by cranking up the ISO, or should I spring for the Samyang, or is there another option I should consider?
You can just use the 24-105 at F4. Unless you just want to buy an ultrawide. If you want an ultrawide, maybe look at the 14mm F2.8, a whole stop faster on the aperture which is a full stop advantage. And stops of light are what night astro/sky photography are all about. I'd start there. Otherwise, use the 24mm end of the 24-105 at F4. Even though it's F4, it's only 1 stop slower than F2.8. So you can make up for that with ISO on the 6D. The 6D handles ISO like a champion, so going from 1600 to 3200 or higher is not a big deal. You won't even notice the noise likely. You could even do this shot at 12800 ISO without too much worry. 15~25 seconds of exposure time, F4, ISO 1600~12800 depending on exposure that you want (do a test shot and see, add ISO until you get the range you want exposure wise).
So bottom line:
Zero money spent, add ISO for free. This is the 6D advantage.
$400 spent on a new lens. F2.8. One stop of light advantage. If you do this, you're just going down on ISO by 1 stop depending on which lens you select, for the same exposure basically. Or reducing shutter time 1 stop. And of course a wider angle.