How dark is the sky in Ontario?
Sky darkness for 57 towns and parks in Ontario, worked out from NASA satellite images of light at night (2025). 21 of them have skies of Bortle 4 or darker, where the Milky Way shows overhead. The darkest is Polar Bear Provincial Park (21.95, Bortle 2), the brightest Toronto (17.40, Bortle 8).
19
Bortle class, 1 pristine to 9 city center
park or dark-sky place
city
Numbers like 21.95 or 16.97 are the brightness of the sky overhead on a clear, moonless night, in mag/arcsec². The scale runs backwards: a lower number means a brighter sky, from about 22 for a natural sky to about 17 in a city center.
How the readings are made
Darkest skies in Ontario
- Polar Bear Provincial ParkBortle 221.95
- Wabakimi Provincial ParkBortle 221.95
- Lake Superior Provincial ParkBortle 221.92
- Woodland Caribou Provincial ParkBortle 221.92
- Quetico Provincial ParkBortle 221.91
Among the places on this site. Plenty of land between them is just as dark, with no town or park to name it by.
Brightest city skies in Ontario
All 57 places in Ontario
Amber names are parks and certified dark-sky places. The figure is the Bortle class: 1 darkest, 9 city center.
Ajax8Algonquin Provincial Park3Barrie7Belleville7Bon Echo Provincial Park4Brampton8Brantford8Bruce Peninsula National Park3Burlington8Caledon6Cambridge8Georgian Bay Islands National Park4Guelph8Halton Hills7Hamilton8Kakabeka Falls Provincial Park4Kawartha Highlands Provincial Park4Killarney Provincial Park3Kingston7Kitchener8Lake Superior Provincial Park2London8Markham8Marten River Provincial Park3Milton8Mississauga8Newmarket8Niagara Falls8Norfolk County5North Bay7North Frontenac4Oakville8Oshawa8Ottawa8Peterborough7Petroglyphs Provincial Park4Pickering7Point Pelee National Park5Polar Bear Provincial Park2Presqu'ile Provincial Park4Quetico Provincial Park2Rondeau Provincial Park4Sandbanks Provincial Park4Sarnia8Sault Ste. Marie8St. Catharines8Sudbury7The Pinery Provincial Park4Thousand Islands National Park4Thunder Bay7Toronto8Torrance Barrens4Vaughan8Wabakimi Provincial Park2Welland7Windsor8Woodland Caribou Provincial Park2