20 - 24mm lens for nightscapes-astro imaging

Capt_Spaulding

Friends, I posted a related request sometime back but couldn't find it so I apologize for posting a new thread. The question is this. I'm interested in a wide, fast(ish) prime for nightscapes and astro imaging. Both Nikon and Sigma make primes in 20 and 24mm that are priced identically. The Sigma Arts are wider at 1.4, while this is the Nikon 1.8. Both are in the $700-800 range. Both get decent reviews, but I suspect both are somewhat plagued by coma. Any thoughts? Mnay thanks in advance for your expertise.

spraynpray

For sure the 20's are disappointing. I tried them and they had tangential and sagittal astigmatism levels that were too bad. I have the 24-35 Art which is f2 and good for aberrations - better than the primes. My dream is to get the 14/1.8 Art to pair with my D850 but that will have to wait. Until then, I am loving the 24-35 f2 which all the tests described as three primes in one.

spraynpray

I tried that lens and rejected it for terrible aberrations. I increasingly find a disparity between reviews and reality. Thankfully, good camera shops have a return policy that allows me to try a lens before I settle with it.

Another advantage of the 24-35 Art is that it is pretty handy for landscapes too.

spraynpray

We may have different expectations Betelgeuse. Firstly, you will not see significant aberrations at that image size. Secondly, your shutter speed is excessive (30 seconds) which means when you look closely all your stars are slotting. I always aim to print large which shows all the flaws. I see you shoot with a D750 so you could have taken that shot at ISO 3200 and 14 seconds and got the same result without slotting. If you want to avoid that, you are looking at using a tracking head and either blurring the foreground or creating a composite image.

That is what I see on facebook all the time, people cooing over others night shots which I know would not hold up to printing large or even viewing large on a monitor.

14mm is such a wide angle that it is pretty much impossible to take a shot that does not have the astronomical equator in it so the stars will be moving quickest there (and lets face it that is where the good stuff is) and so you just can't go over the 200 rule unless you are happy with looking at the images small.

All IMHO.

spraynpray

My point was that it is hard to determine the extent of aberrations when the stars are not round due to keeping the shutter open too long. I don't understand what you mean by 'deflecting'.

spraynpray

Looks good in those low res uploads, did you upload it 6000 x 4000?

spraynpray

Yes, in Lightroom, you don't resize at all then the jpeg comes out full size 6016 x 4016. You can upload whatever size you like to Flickr and people usually limit the image size if they keep a lot on Flickr so not to use all the capacity up, or if the image falls apart under close scrutiny like 99% of macro shots do.

spraynpray

You can disable downloads and still upload full res for critical viewing purposes. They are not mutually exclusive.

WestEndFoto

Try zooming in and taking a screen shot. Short of hacking your account, that is the most that they can do.