diff --git a/src/droplet_growth/register.py b/src/droplet_growth/register.py
index e8f0dca8c97ef27ed372b8a76abb36e6f993fc60..fe866b03b6ee7024cb2a758e00ceb81d78e0ff8e 100644
--- a/src/droplet_growth/register.py
+++ b/src/droplet_growth/register.py
@@ -26,6 +26,13 @@ META_ALIGNED = {'ImageJ': '1.53c',
  'LUTs': [grey, green, blue]
  }
 
+constraints={
+    "scale": [1, 0.1],
+    "tx": [0, 150],
+    "ty": [0, 150],
+    "angle": [0, 10],
+}
+
 def align_stack(data_or_path, template16, mask2, plot=False, path_to_save=None, binnings=(1,16,2), suffix='.aligned.tif'):
     '''
     stack should contain two channels: bright field and fluorescence.
@@ -280,7 +287,7 @@ def register(image, template):
     '''
     assert np.array_equal(image.shape, template.shape), \
         f'unequal shapes {(image.shape, template.shape)}'
-    return reg.similarity(template, image, constraints={'scale': [1,0.2], 'tx': [0, 500], 'ty': [0, 500], 'angle': [0, 30]})
+    return reg.similarity(template, image, constraints=constraints)
 
 
 def filter_by_fft(