diff --git a/airshower_beacon_simulation/ca_period_from_shower.py b/airshower_beacon_simulation/ca_period_from_shower.py
index e5d33f2..32185d3 100755
--- a/airshower_beacon_simulation/ca_period_from_shower.py
+++ b/airshower_beacon_simulation/ca_period_from_shower.py
@@ -68,6 +68,7 @@ def find_best_period_shifts_summing_at_location(test_loc, antennas, allowed_ks,
 
     t_sum = np.arange(t_min+max_neg_shift, t_max+max_pos_shift, dt)
     a_sum = np.zeros(len(t_sum))
+    a_first = np.zeros(len(t_sum))
 
     best_period_shifts = np.zeros( (len(antennas)) ,dtype=int)
     for i, (t_r, E_) in enumerate(zip(t_, a_)):
@@ -75,6 +76,7 @@ def find_best_period_shifts_summing_at_location(test_loc, antennas, allowed_ks,
 
         if i == 0:
             a_sum += f(t_sum)
+            a_first = a_sum
             best_period_shifts[i] = period_shift_first_trace
             continue
 
@@ -94,14 +96,14 @@ def find_best_period_shifts_summing_at_location(test_loc, antennas, allowed_ks,
             ax2.set_title("Maxima at {}; i={i}/{tot}".format(title_location, i=i, tot=N_ant))
             ax2.set_xlabel("$k$th Period")
             ax2.set_ylabel("Summed Amplitude")
-            ax2.plot(0, np.max(a_sum), marker='*', label='trace_sum', ls='none', ms=20)
+            ax2.plot(0, np.max(a_first), marker='*', label='strongest trace', ls='none', ms=20)
 
         # find the maxima for each period shift k
         shift_maxima = np.zeros( len(allowed_ks) )
         for j, k in enumerate(allowed_ks):
             augmented_a = f(t_sum + k*period)
 
-            shift_maxima[j] = np.max(augmented_a + a_sum)
+            shift_maxima[j] = np.max(augmented_a + a_first)
 
             if i in plot_iteration_with_shifted_trace and abs(k) <= 3:
                 ax.plot(t_sum, augmented_a, alpha=0.7, ls='dashed', label=f'{k:g}')