After a blustery start, Monday, April 9, segued into a beautiful sunset. Behind a line of clouds were clear skies, a gap long enough to get some night observations after astronomical twilight. Darkness essentially began at 10 pm.
When I arrived at the eastern edge of the development area, I turned north off Rt. 20 onto Hamilton Road. At a road bumpout I pulled over, listened to the radio, and waited for the cloudline to move sufficiently east. It had already cleared overhead.
North, Zone B
At 10:20 pm conditions were acceptable and I started Sky Quality Meter (SQM) readings. Meter 733 averaged 19.93 magnitudes per square arcsecond. Meter 9896 averaged 20.18.
The next SQM readings were from Hamilton Trail just south of the toll road overpass. Meter 733 averaged 20.34 magnitudes per square arcsecond. Meter 9896 averaged 20.46. The Dark Sky Meter (DSM) varied more, averaging 20.5. Also, the naked eye could discern down to limiting magnitude 4.6 using the Leo star chart. The four labeled stars above the lion's hind quarters gave it away.
Central, Zone A
Along Filmore St. in the central zone, meter 733 averaged 19.84; meter 9896 averaged 20.01. The DSM gave 20.06. It was 11:20 pm.
South, Zone C
Near the intersection of Gordon and Strawberry meter 733 averaged 20.23; meter 9896 averaged 20.38. The DSM was 20.50. It was 11:28 pm.
On Tamarack north of Johnson and the railroad line, meter 733 averaged 20.26; meter 9896 averaged 20.53. The DSM was 20.52. It was 11:55 pm.