fix skyback_level rescaling

ObservationSim/ObservationSim.py

@@ -439,14 +439,13 @@ class Observation(object):
                 pf_map = led_flat
         # whether to output zero, dark, flat calibration images.
         expTime = self.config["obs_setting"]["exp_time"]
-        skybg_unit = self.filter_param.param[sky_level_filt][5]
-        norm_scaler = skyback_level/expTime/skybg_unit
+        norm_scaler = skyback_level/expTime * self.filter_param.param[chip.filter_type][5] / self.filter_param.param[sky_level_filt][5]
 
         if skyback_level == 0:
             self.config["ins_effects"]["shutter_effect"] = False
 
         if chip.survey_type == "photometric":
-            sky_map = np.ones_like(chip.img.array) * skybg_unit * norm_scaler / self.tel.pupil_area
+            sky_map = np.ones_like(chip.img.array) * norm_scaler / self.tel.pupil_area
         elif chip.survey_type == "spectroscopic":
             flat_normal = np.ones_like(chip.img.array)
             if self.config["ins_effects"]["flat_fielding"] == True: