diff --git a/openmc/filter.py b/openmc/filter.py
index 36053ec46..e63d72412 100644
--- a/openmc/filter.py
+++ b/openmc/filter.py
@@ -22,7 +22,7 @@ _FILTER_TYPES = (
     'universe', 'material', 'cell', 'cellborn', 'surface', 'mesh', 'energy',
     'energyout', 'mu', 'polar', 'azimuthal', 'distribcell', 'delayedgroup',
     'energyfunction', 'cellfrom', 'legendre', 'spatiallegendre',
-    'sphericalharmonics', 'zernike', 'particle', 'zernikeradial'
+    'sphericalharmonics', 'zernike', 'zernikeradial', 'particle'
 )
 
 _CURRENT_NAMES = (
diff --git a/src/constants.F90 b/src/constants.F90
index 1bdcec74f..4de52322e 100644
--- a/src/constants.F90
+++ b/src/constants.F90
@@ -379,8 +379,9 @@ module constants
        FILTER_SPH_HARMONICS  = 18, &
        FILTER_SPTL_LEGENDRE  = 19, &
        FILTER_ZERNIKE        = 20, &
-       FILTER_PARTICLE       = 21, &
-       FILTER_ZERNIKE_RADIAL = 22
+       FILTER_ZERNIKE_RADIAL = 21, &
+       FILTER_PARTICLE       = 22
+
 
   ! Mesh types
   integer, parameter :: &
diff --git a/src/math_functions.h b/src/math_functions.h
index e0ecad60e..7ef39c446 100644
--- a/src/math_functions.h
+++ b/src/math_functions.h
@@ -92,18 +92,13 @@ extern "C" void calc_rn_c(int n, const double uvw[3], double rn[]);
 extern "C" void calc_zn_c(int n, double rho, double phi, double zn[]);
 
 //==============================================================================
-//! Calculate only the even radial components of n-th order modified Zernike 
-//! polynomial moment with azimuthal dependency m = 0 for a given angle 
-//! (rho, theta) location on the unit disk.
+//! Calculate only the even order components of n-th order modified Zernike 
+//! polynomial moment with azimuthal dependency m = 0 for a given radial (rho)
+//! location on the unit disk.
 //!
 //! Since m = 0, n could only be even orders. Z_q0 = R_q0
 //!
-//! This procedure uses the modified Kintner's method for calculating Zernike
-//! polynomials as outlined in Chong, C. W., Raveendran, P., & Mukundan,
-//! R. (2003). A comparative analysis of algorithms for fast computation of
-//! Zernike moments. Pattern Recognition, 36(3), 731-742.
-//! The normalization of the polynomials is such that the integral of Z_pq^2
-//! over the unit disk is exactly pi.
+//! See calc_zn_c for methodology.
 //!
 //! @param n       The maximum order requested
 //! @param rho     The radial parameter to specify location on the unit disk