diff --git a/proseco/characteristics.py b/proseco/characteristics.py
index bff16185..71f2c287 100644
--- a/proseco/characteristics.py
+++ b/proseco/characteristics.py
@@ -31,7 +31,7 @@
 
 # ACA T_ccd penalty limit (degC).
 # Above this limit a temperature "penalty" is applied via get_effective_t_ccd()
-aca_t_ccd_penalty_limit = -8.8
+aca_t_ccd_penalty_limit = -8.1
 
 # Dark current that corresponds to a 5.0 mag star in a single pixel.  Apply
 # this value to the region specified by bad_pixels.