Thanks Joe!
I'd only read a little on the Pentax star tracer but could still see it's benefits at times but quality lens, solid tripod and clean sensor are right at the top of my list. I still have an 80-200 ED f2.8 16 element -11 groups Nikkor lens I bought new (and far from a cheap lens at the time but I was working and had the money (tax return actually))when I bought a new Nikon SLR back in 90 or 91 (I still have both), it's a beautiful lens, unfortunately getting a little heavy now without a tripod but I got some sharp sports shots with it when I was younger. The trick with it as with a lot of photography was manual focus because it had a horrid reputation for seeking when focusing. The newer model came with a tripod foot but only 12 elements in less groups. This I know can be both a bonus and a curse because of extra reflections off the extra elements but in the right moments it's a very nice lens.
https://www.bhphotovideo.com/c/produ..._8D.html/specs
I tend to use the 500 rule (which I'm sure is what you were typing) then shorten it, with my 14mm Samyang while theoretically I can shoot around 30 seconds using the 500 rule I did some weird calculation I can not remember and came up with 16 seconds for sharper images but I'm very interested in seeing your formula.
I'm very keen on reading that thread and looking at the numbers!