A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Antoine Couëtte
Date: 2018 Sep 10, 04:51 -0700
RE : Astronomy-DLL-for-NET-SofaJpl-212-released-Hirose-sep-2018-g42680
You indicate that " There's a major increase in computational complexity since the [IAU2000]'A' [Nutation] model evaluates about 1400 trigonometric terms. I can't imagine you'd notice a difference in a "one shot" run like the demo program, but nevertheless I see no need for such elaboration. The default 'B' model is accurate to "only" 1 mas, which is enough for me. And it's even smaller than the old IAU 1980 nutation model. "
Regarding Nutation, and since the Planetary Terms effects come to play only at the sub-milli arc second level, and given the 0.001" accuracy you are claiming with your "B" Model, I would surmise that this "B" Model of yours encompasses / includes / computes all Luni-Solar Terms, and none of the Planetary Terms. True ?
It is already impressive to see that - while being "shorter" in term of Series number and lenght - such "B" Model is definitely more accurate - both now and mostly in the long term - against VLBI measurements than the IAU1976 Nutation Model.
This is also quite surprising that an authoritative Software such as Horizons keeps using the IAU1976 Nutation Model which has quite a few shortcomings (mainly because it was too hastily derived) and which is definitely less accurate than your Default "B Model" excerpted from the IAU2000A Nutation Model.
Best Regards, and again congratulations for your ongoing superb achievements,
Antoine M. "Kermit" Couëtte