I am working with this post from an old post from oct 2017 giving the following formula for calculating moon refining yield:
Refining Yield Modifier * (1 + (Structure Bonus/100) * Structure Security Modifier * (1+ (Refining Skill level * .03)) * (1+ (Reprocessing Efficiency skill level * * (1+(Ore specific/ice processing skill level * .02)) * (1 + (Processing Implant Percentage/100))

But no matter how I apply that formula I get all the wrong results. So is there a better formula or am I just using this one wrong?

Here are some test cases.
Skills Processing 5 (x1.15), Reprocessing Efficiency 5 (x1.1), all Moon ores 4 (x1.04). no implants.
Tatara T1 reprocessing rig in nullsec
50% base, +4% for being tatara, +1% from rig shoudl be 55% base. in game it shows 59%. If I factor in the 1.12 bonus for nullsec into the base then I get (50+4+1)*1.12=61.6
So right now I cannot even determine how the base yield is figured.

But assuming I take the in game value of 59% and I apply my skills I get 591.151.1*1.08=80.6 but game says 81.2

I get similar results when testing on an unrigged athanor I also own and several other structures of various sizes and rig configurations some of which I own or have verified their rigs with the owners.

so I am totally lost here. been at this since Saturday and been asking in game but everyone who has looked at this cant make any more sense of it then I can.

Can someone point me int he right direction here with the right formula or point out the error in how I am using this formula? I am sure its some stupid mistake on I my part I just cant seem to figure it out.

Your problem in this formula is that you’re missing some parentheses, try this:

BaseYield = 50 (%), 51 if T1 rig and 53 if T2 rig. or if you will (50 + 1 or 3)
SecurityModifier = 1x in HS, 1.06 in LS and 1.12 in Null/WH.
RefineryMod = 1.02x if Athanor or 1.04 if Tatara.
ImplantMod = 1.01x, 1.02x or 1.04x
SkillA (Reprocessing) = 1.03x - 1.15x
SkillB (ReprocessEfficiency) = 1.02x - 1.1x
SkillC (OreReprocess) = 1.02x - 1.1x

This is because the yield is calculated multiplicative not additive as you have assumed. (50+1) * 1.04 = 53.04% * 1.12 = 59.405%

In regards to how the Base yields is done, excluding all the various bonuses, with no rig it is 50%, then the rig(s) simply replaces that with it’s own corresponding base yield 51% or 53% for Tech 1 and Tech 2 respectively. Hence why you can just do a simple calculation like this 50 + RigMod, where RigMod = 0, 1 or 3.

ok here is what I come up with:
T0 athanor, so no rig, same skills as I listed above:
50% (base) * 1 .02 (athanor) * 1 (no sec bonus since that comes form rig) * 1.15 (reprocessing V) * 1.1 (reprocessing efficiency V) * 1.08 (exceptional moon processing 4) * 1 (no implant) = 69.68%
ok so that comes close as the actual in game is 69.70%. so rounded up to nearest tenth here

Now on to the tatara case which I know to be t1 rigged:
51% (base+rig) * 1 .04 (tatara) * 1.12 (nullsec) * 1.15 (reprocessing V) * 1.1 (reprocessing efficiency V) * 1.08 (exceptional moon processing 4) * 1 (no implant) = 81.16%
in game it shows 81.20% so rounding up again.

OK this seems to work a lot better now that I am doing it this way. Thanks. Now to apply this to other structures and see if I get the correct numbers but it looks promising.

followup: my spreadsheet is now accurate across all structures that I can confirm rigs for and now I can also tell what rigs are on any other stations by looking up the numbers in this spreadsheet
Thanks for pointing out my mistake!