diff --git a/gemini_instruments/gmu.py b/gemini_instruments/gmu.py
index 3be8ef96a..8c812b02c 100644
--- a/gemini_instruments/gmu.py
+++ b/gemini_instruments/gmu.py
@@ -112,7 +112,9 @@ def return_requested_units(input_units='nm'):
     """
     Decorator that replaces the repeated code for asMicrometers,
     asNanometers, asAngstroms. Should be replaced by a "units='nm'"
-    parameter, but time is limited. Keeping current coding to avoid
+    parameter, but time is limited.
+
+    Returns as np.float32 values to avoid excessive precision
     """
     def inner_decorator(fn):
         @wraps(fn)
diff --git a/gemini_instruments/test/lut_descriptors.py b/gemini_instruments/test/lut_descriptors.py
index 07b2eba1f..4dbf765a3 100644
--- a/gemini_instruments/test/lut_descriptors.py
+++ b/gemini_instruments/test/lut_descriptors.py
@@ -510,7 +510,7 @@
         ('detector_x_bin', 1),
         ('detector_y_bin', 1),
         ('disperser', 'MIRROR'),
-        ('dispersion', [-3.8800000000000006e-10]),
+        ('dispersion', [-3.88e-10]),
         ('dispersion_axis', [2]),
         ('effective_wavelength', 1.25e-06),
         ('elevation', 60.1851833333),
diff --git a/gemini_instruments/test/test_astrodata_descriptors.py b/gemini_instruments/test/test_astrodata_descriptors.py
index ba28bd2f8..a423200ce 100644
--- a/gemini_instruments/test/test_astrodata_descriptors.py
+++ b/gemini_instruments/test/test_astrodata_descriptors.py
@@ -4,12 +4,19 @@
 import gemini_instruments
 import os
 
+import numpy as np
+
+
+FLOAT_TYPES = (float, np.float32, np.float64)
+
 THIS_DIR = os.path.dirname(__file__)
 
 from .lut_descriptors import fixture_data as descriptors_fixture_data
 # Keep separate because GHOST has non-raw files
 from .ghost_lut_descriptors import fixture_data as ghost_descriptors_fixture_data
 
+F
+
 
 @pytest.mark.parametrize("instr,filename,descriptor,value",
                          ([*k]+[*vv] for k, v in (list(descriptors_fixture_data.items()) +
@@ -40,7 +47,7 @@ def test_descriptor(instr, filename, descriptor, value):
         assert method() is None
     else:
         mvalue = method()
-        if float in (type(value), type(mvalue)):
+        if type(value) in FLOAT_TYPES or type(mvalue) in FLOAT_TYPES:
             assert abs(mvalue - value) < 0.0001
         else:
             assert value == mvalue