astro::delta_t::algo5 Namespace Reference

Functions
constexpr auto	compute (const double year) noexcept -> double
	Compute ΔT for a decimal Gregorian year using algorithm 5.

Variables
constexpr double	LAST_OBSERVATION_YEAR
	The decimal year of the last Bulletin A observation in the training data; also the boundary between the fitted and the extrapolated segments.

Function Documentation

compute()

auto astro::delta_t::algo5::compute ( const double year ) ->double

nodiscardconstexprnoexcept

Compute ΔT for a decimal Gregorian year using algorithm 5.

Parameters

year	The year, of double type.

Returns

ΔT in seconds.

Example

compute(2005.99999999....) returns ΔT for the last moment of year 2005.

Example

compute(1984.0) returns ΔT for the first moment of year 1984.

See also

IERS Bulletin A observations - https://www.iers.org/IERS/EN/Publications/Bulletins/bulletins.html

Morrison et al. 2021 addendum - https://doi.org/10.1098/rspa.2020.0776

Corrected HMNAO combined expression - https://web.archive.org/web/20230103030546id_/https://astro.ukho.gov.uk/nao/lvm/

Generation record - https://github.com/0xf3cd/AstroTime-Analysis/blob/ed1cdc2fd6c5122b391a82289aa2cc060340552d/DeltaT/algo5/record.json

Note

For year < 2005.0, algo2 is used instead (same delegation as algo4).

There is no upper bound: beyond the last observation, the anchored integrated-lod curve extrapolates smoothly for all future years.

noexcept (as is algo2), so a non-finite year propagates to a non-finite ΔT instead of throwing — IEEE propagation, not UB. The C ABI rejects non-finite years before calling; direct C++ callers get NaN back for NaN in (#86).

Variable Documentation

LAST_OBSERVATION_YEAR

double astro::delta_t::algo5::LAST_OBSERVATION_YEAR

inlineconstexpr

The decimal year of the last Bulletin A observation in the training data; also the boundary between the fitted and the extrapolated segments.