Fujinon 56 1.2 for astrophotography, focus problem

[fedevento]

Hello all, new member here . Last Saturday i went to do some astrophotos with my xt20 and my new 56 1.2. I would like to know if someone else have try to do some AP with this lens becouse i run in some issues with the focus. 

My idea was to use the intervalometer to take multiple shoots to stack the photos in post (typical for AP) so i tried to use manual focus but the focus by wire is not so trustworthy in this situations...it jumped a lot between small stars (close to focus) and big ones (far from it). In the end set to manual, back button focus and that seemed to work for bright stars...the problem was that after the first pic, all the others from the set were out of focus! even if the focus was set to manual it seemed to move it a bit, which for stars and 1.2 is terrible!! does anyone run to the same issue?? or know what would be the best strategy to do AP with this lens?? I have also the roki 85 1.4 and comparing pics (the ones in focus) im really happy with the results of the 56...but focusing the 85 it way easier!! If anyone can help me would be helpful!!! sorry about my english! Cheers from Argentina!

[bergat]

But .... seeing the line and cursor of focus and putting it at infinite, it is not coming the right picture?

[rzgp33]

Same issue here with the 90mm/f2  you just have to make separate exposures each time, and not use the intervalometer. Its a pain.

[Rob H]

I’ve used my 56mm for Astro before, the attached image is a single exposure straight out of camera, taken with my 56mm & XT-2. I tend to shoot at f2.8 as the vignetting at f1.2 makes Astro panos impossible. Also the chromatic abbreviation at f1.2 is less than ideal.  Focus wise I go by the hyperbolics & check with live view (back button to zoom right in on a bright star). Never had any issues with focus drifting but I have had condensation buildup on the from element making it look like the lens is of of focus. 
 

PS, which 56mm are you using as Fujifilm make two, an expensive one and an even more expensive one, mine is the former.

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