Every few months, the IDA Oregon Chapter puts out their most recent report about how the previous few months have progressed from a light pollution perspective regarding Oregon dark skies. We previously covered the 7th report, therefore, with the 8th report, this will be covering some of the big changes in the work and Oregon Dark skies. Please note that all quotes and figures come from the report, they are not our own original work. We will add in some unique context at the end.

As the data shows and the report says. “The processed data show increases of 4% to 6% per year for SQM sites in expanding cities in central Oregon. Other peripheral SQM sites show increases of 2% to 4% per year, while most remote sites tend to show little to no change in zenith skyglow per year. However, percentage changes are deceptive. Compared to nearby sites that show little change over the last few years, light pollution over the cities of Central Oregon is increasing faster by 10x to 20x.”

Box plot showing the clear sky measurements of the sites as of the November 2023 deadline
for this report

The table above showing the change for the 27 long-term SQM sites.

The table above shows Milky Way visibility at the various SQM sites, with greater visibility at the bottom.

Our notes:

It is great that this information is available and being collected, plus tracked. Our concern is that there are places such as Cottonwood Canyon, which are wonderful places to go stargazing have increased light pollution. Although 3.2% might not be much, over time, this will compound and cause wonderful places to become less ideal places to go stargazing. An example of this is Stub Stewart State Park, which is moving its average closer to the limit of a Dark Sky Park or Reserve marker.

Important Note: Cottonwood Canyon looks to have similar or darker skies than Prineville Reservoir, but increasing light pollution from the collector means this wont stay this way for long. However, the limitation of this is that the SQM may not move and reflect the entire area for a larger state park such as Cottonwood Canyon. Cottonwood Canyon state park has a size of 8,000+ acres, whereas Prineville Reservoir State Parks is 4.734 mi². Therefore, it would be easier to have the sky meter readings for Prineville Reservoir to be more accurate of the entire park; whereas, the Cottonwood Canyon sky meter is less likely to reflect the entire park reading.

To check out the full report, check out the darkskyoregon.org website. Make sure to follow us on Twitter and Instagram, and make sure to view our other unique astronomy sites such as this one for more places to view astronomy in the Pacific Northwest.