A super dark spot in Latvia

This time I follow a recommendation by Oliver Lindecke a PhD student from the Leibniz Institute for Zoo and Wildlife Research in Berlin. He is working (among other stuff) on effects of artificial light on bats (recent paper here).

Oli studies bats in Pape Village in Latvia and he told me that the bat research station is in a very dark spot. Checking the world atlas data shows that indeed across the Courland peninsula many sites are almost free of light pollution.

So I pack an SQM, the camera with fisheye and fly to Riga. The plan is to go around the peninsula in the first night, do some measurements at the Northern tip, record night sky brightness wit an SQM roadrunner system along the travel and meet up with the bat researchers in the morning.

Its a long drive from Riga and I arrive at Kolka Village at the northern tip just after sunset. Due to some technical problems I have to improvise and run the SQM and GPS with separate programs. But it finally works and the weather is completely overcast.

At around 11 p.m. I start measurements and it is very dark. I get readings of 22.9 mags/arcsec² with the SQM, which is around 0.074 mcd/m² actually more than 3 times darker than a historical clear night at 0.250 mcd/m².

With the camera I am able to capture some very dark images near the village of Saunags within Slītere National Park. The values confirm the SQM readings giving 22.9 mags/arcsec² and a horizontal illuminance of 220 µlx (thats micro lux!).

This is the darkest I have ever recorded with both SQM and camera. See our latest preprint for data from Lake Stechlin and South Africa explaining the background of why it is importnat to know ow dark it can get at night.

RGB all-sky image recorded at the beach of Saunags, Latvia

Luminance map calculated from all-sky imgae shown above using Sky Quality Camera Software