diff --git a/script/test/FindCenter.py b/script/test/FindCenter.py
index d46cf3f7..6be36f43 100644
--- a/script/test/FindCenter.py
+++ b/script/test/FindCenter.py
@@ -25,7 +25,7 @@ print "scienta time: ", scienta_time
 
 STEP = 0.2
 SPEED = STEP / scienta_time
-fly_time = (RANGE[1] - RANGE[0]) / SPEED
+fly_time = abs(RANGE[1] - RANGE[0]) / SPEED
 STEPS = int(fly_time / scienta_time) + 1
 
 print "coarse scan"
@@ -51,7 +51,7 @@ print "lower edge, upper edge: ", lo_edge, ", ", hi_edge
 RANGE = (lo_edge - 0.4, lo_edge + 0.4)
 STEP = 0.01
 SPEED = STEP / scienta_time
-fly_time = (RANGE[1] - RANGE[0]) / SPEED
+fly_time = abs(RANGE[1] - RANGE[0]) / SPEED
 STEPS = int(fly_time / scienta_time) + 1
 
 print "lower edge scan"
@@ -64,7 +64,7 @@ cscan(MOTORS, SENSORS, RANGE[0], RANGE[1], STEPS, time=fly_time, before_read=bef
 RANGE = (hi_edge - 0.4, hi_edge + 0.4)
 STEP = 0.01
 SPEED = STEP / scienta_time
-fly_time = (RANGE[1] - RANGE[0]) / SPEED
+fly_time = abs(RANGE[1] - RANGE[0]) / SPEED
 STEPS = int(fly_time / scienta_time) + 1
 
 print "upper edge scan"