From f376314249241d89fa4a8d04a275b6e2cc35fe0b Mon Sep 17 00:00:00 2001
From: "Adam R. Jensen" <39184289+AdamRJensen@users.noreply.github.com>
Date: Fri, 1 Aug 2025 15:51:35 +0200
Subject: [PATCH 1/2] Change refraction correction limit in ephemeris solar
 position algorithm

---
 pvlib/solarposition.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pvlib/solarposition.py b/pvlib/solarposition.py
index 7284191d68..07005c298f 100644
--- a/pvlib/solarposition.py
+++ b/pvlib/solarposition.py
@@ -828,7 +828,7 @@ def ephemeris(time, latitude, longitude, pressure=101325.0, temperature=12.0):
     TanEl = pd.Series(np.tan(np.radians(Elevation)), index=time_utc)
     Refract = pd.Series(0., index=time_utc)
 
-    Refract[(Elevation > 5) & (Elevation <= 85)] = (
+    Refract[(Elevation > 5) & (Elevation <= 90)] = (
         58.1/TanEl - 0.07/(TanEl**3) + 8.6e-05/(TanEl**5))
 
     Refract[(Elevation > -0.575) & (Elevation <= 5)] = (

From 068b02ba8380b4cd8f3a5a41626c561942869626 Mon Sep 17 00:00:00 2001
From: "Adam R. Jensen" <39184289+AdamRJensen@users.noreply.github.com>
Date: Sat, 2 Aug 2025 15:05:20 +0200
Subject: [PATCH 2/2] Add testing and whatsnew

---
 docs/sphinx/source/whatsnew/v0.13.1.rst |  3 +++
 tests/test_solarposition.py             | 12 ++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/docs/sphinx/source/whatsnew/v0.13.1.rst b/docs/sphinx/source/whatsnew/v0.13.1.rst
index d83667b302..2029b7596b 100644
--- a/docs/sphinx/source/whatsnew/v0.13.1.rst
+++ b/docs/sphinx/source/whatsnew/v0.13.1.rst
@@ -6,6 +6,9 @@ v0.13.1 (Anticipated September, 2025)
 
 Breaking Changes
 ~~~~~~~~~~~~~~~~
+* Change refraction for solar elevation angles between 85 and 90
+  degrees to be calculated rather than set to 0 in
+  :py:func:`~pvlib.solarposition.ephemeris`. (:pull:`2524`)
 
 
 Deprecations
diff --git a/tests/test_solarposition.py b/tests/test_solarposition.py
index 88093e05f9..5be76ec42c 100644
--- a/tests/test_solarposition.py
+++ b/tests/test_solarposition.py
@@ -964,3 +964,15 @@ def test_spa_python_numba_physical_dst(expected_solpos, golden):
                                               temperature=11, delta_t=67,
                                               atmos_refract=0.5667,
                                               how='numpy', numthreads=1)
+
+
+def test_ephmeris_refraction_85_90_degrees():
+    # Test that refraction is calculated rather than set to zero
+    # for solar elevatoin angles between 85 and 90 degrees
+    # PR#2524
+    # The below example has a solar elevation angle of 87.9
+    result = solarposition.ephemeris(
+        time=pd.date_range('2020-03-23 12', periods=1, tz='UTC'),
+        latitude=0, longitude=0)
+    refraction = (result['apparent_zenith'] - result['zenith']).iloc[0]
+    assert refraction == -0.0005818446332597205