debug: dark in overscan

observation_sim/sim_steps/readout_output.py

@@ -20,7 +20,7 @@ def add_prescan_overscan(self, chip, filt, tel, pointing, catalog, obs_param):
     if obs_param["add_dark"] is True:
         ny = int(chip.npix_y/2)
         base_dark = (ny-1)*(chip.readout_time/ny)*chip.dark_noise
-        chip.img.array[(chip.prescan_y+ny):-(chip.prescan_y+ny), :] = base_dark
+        chip.img.array[(chip.prescan_y+ny):-(chip.prescan_y+ny), :] += base_dark
     return chip, filt, tel, pointing