fix: correct sidereal_day magnitude and standardize digit separators in astronomy.h (#787)

* fix: correct sidereal_day constant in astronomy.h (issue #786)

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* style: fix non-standard C++ digit separators in astronomy.h

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* Update astronomy_test.cpp content

* Restoring empty line separators

* Fix formatting in astronomy_test.cpp

* Refactor static assertions in astronomy_test.cpp

Updated static assertions for time and length units in astronomy tests.

* Fix static_assert syntax in astronomy_test.cpp

* Fix static_assert statements in astronomy_test.cpp

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: mpusz <506260+mpusz@users.noreply.github.com>
Co-authored-by: Mateusz Pusz <mateusz.pusz@gmail.com>

Author: Copilot

src/systems/include/mp-units/systems/astronomy.h

@@ -40,9 +40,9 @@ namespace mp_units::astronomy {
 // clang-format off
 // time
 inline constexpr struct day final : named_unit<"D", non_si::day> {} day;
-inline constexpr struct sidereal_day final : named_unit<"D_sid", mag_ratio<86'164'0905, 1'000'000> * si::second> {} sidereal_day;
-inline constexpr struct Julian_year final : named_unit<"a", mag_ratio<365'25, 100> * day> {} Julian_year;
-inline constexpr struct tropical_year final : named_unit<"a_trop", mag_ratio<365'242189, 1'000'000> * day> {} tropical_year;
+inline constexpr struct sidereal_day final : named_unit<"D_sid", mag_ratio<861'640'905, 10'000> * si::second> {} sidereal_day;
+inline constexpr struct Julian_year final : named_unit<"a", mag_ratio<36'525, 100> * day> {} Julian_year;
+inline constexpr struct tropical_year final : named_unit<"a_trop", mag_ratio<365'242'189, 1'000'000> * day> {} tropical_year;
 inline constexpr struct century final : named_unit<"c", mag<100> * Julian_year> {} century;
 inline constexpr struct millennium final : named_unit<"ka", mag<1000> * Julian_year> {} millennium;
 

test/static/astronomy_test.cpp

@@ -32,17 +32,17 @@ using namespace mp_units::si::unit_symbols;
 using mp_units::astronomy::unit_symbols::a;
 
 // time units
-static_assert(1. * D == 86'400. * s);
-static_assert(approx_equal(1. * D_sid, (86'164'0905. / 1'000'000.) * s));
-static_assert(approx_equal(1. * a, 365.25 * D));
-static_assert(approx_equal(1. * a, 31'557'600. * s));
+static_assert(1 * D == 86'400 * s);
+static_assert(10'000 * D_sid == 861'640'905 * s);
+static_assert(100 * a == 36525 * D);
+static_assert(1 * a == 31'557'600 * s);
 static_assert(approx_equal(1. * a_trop, 365.242189 * D));
-static_assert(1. * c == 100. * a);
-static_assert(1. * ka == 1000. * a);
+static_assert(1 * c == 100 * a);
+static_assert(1 * ka == 1000 * a);
 
 // length units
-static_assert(1. * LD == 384'399. * km);
-static_assert(1. * ly == 9'460'730'472'580'800. * m);
+static_assert(1 * LD == 384'399 * km);
+static_assert(1 * ly == 9'460'730'472'580'800 * m);
 
 // spectral flux density
 static_assert(approx_equal(1. * Jy, 1e-26 * W / m2 / Hz));