14mm 2.8L or the 24 1.4L?

I'm off to Tenerife to shoot some stars by the Observatory there and it's my third time.

Usually I rely on the 16-35 on the 1DX, But I'm after a cleaner image with less vignetting wide open.

For those in the know, would the 14mm be a better choice than the 24mm prime even though the latter is faster?

As a secondary question, can anyone recommend a simple, lightweight idiot proof tracking system to avoid trailing please?

Thanks!

I'd go for the 14mm. But that's because I like the wider FOV. You should always shoot at f/4 or higher to reduce star bloat. The Astrotac or Polarie are good portable trackers

I don't own 24mm L and have no experience with it but I can swear by my Rokinon 14mm F2.8 or my Tokina 11-16 F2.8 for astrophotography.

BTW are you shooting on a cropped or FF body? I am asking this because you are concern with Vignette but let me tell you if you think Vignetting is getting worse with Wide open F, you are totally mistaking.

As for Tracker, what is your payload? If you are considering a small ultra wide angle as said and a normal weight body, 2 good choices:

1- iOptron 3302B
2- Vixen Optics 35505

Both are good. Both are the lightest weight mounts. First one comes with illuminated polar scope in the basic package and should cost you well under $400. Second one is more expensive (Not necessarily better) is just under $400 but has only a simple hole for rough polar alignment. If you are to buy accessory Polar scope, that will cost you an additional $130 to 150 to make it equivalent of the first one so its about $150 more.
Amazon has both but if you find my advice useful, please do NOT buy from Adorama. I hate them.

Samsen, it's going on a 1DX.

Trying to obtain an Astrotrac too.

1DX is heavy.
You need to look into something stable.
I would personally piggyback that on my large autostar glass but there are many users here with hand on experience on exactly what you need to know. Let see what else Mo, Wes,
Madweasel and others are having to say.