diff --git a/optimal_mapping/optimal_mapping.py b/optimal_mapping/optimal_mapping.py
index 17b76c0..0580999 100644
--- a/optimal_mapping/optimal_mapping.py
+++ b/optimal_mapping/optimal_mapping.py
@@ -245,8 +245,10 @@ def set_a_mat(self, uvw_sign=1, apply_beam=True):
         
         Attribute:
         ------
-        .a_mat: 2d matrix (complex128)
+        ..a_mat: 2d matrix (complex128)
             a_matrix (Nvis X Npsf) from the given observation
+        .beam_mat: 2d matrix (complex128)
+            a_matrix with only the beam term considered (Nvis X Npsf)
         '''
         self.a_mat = np.zeros((len(self.data), len(self.idx_psf_in)), dtype='float64')
         self.beam_mat = np.zeros(self.a_mat.shape, dtype='float64')
@@ -357,7 +359,8 @@ def set_a_mat_ps(self, ps_radec, uvw_sign=1, apply_beam=True):
             a_matrix (Nvis X (Npsf+Nps)) from the given observation
         .a_mat: 2d matrix (complex128)
             a_matrix (Nvis X Npsf) from the given observation
-            
+        .beam_mat: 2d matrix (complex128)
+            a_matrix_ps with only the beam term considered (Nvis X (Npsf+Nps))
         '''
         self.a_mat_ps = np.zeros((len(self.data), len(self.idx_psf_in)+ps_radec.shape[0]), dtype='float64')
         self.beam_mat = np.zeros(self.a_mat_ps.shape, dtype='float64')