Sioux Falls Stargazing & Astronomy Report

Key Sky Quality Metrics

SQM (mag/arcsec²)

17.74

Bortle class

Class 9 (Class 9)

Darkness Quotient

21%

Dataset

March 2026

Inner city sky

Sioux Falls: The Practical Verdict

Sioux Falls is the largest city in South Dakota, a regional urban centre on the northern Great Plains with a broad, open-sky setting and a growing metropolitan feel.

The city generally experiences High Light Pollution, with a Darkness Quotient of 21% — placing it among the more light-polluted urban skies in the region, even if it is not quite at the very worst extreme.

For practical observing from within the city, the most reliable targets are the Moon, planets, double stars and the brightest open clusters. Fainter deep-sky objects are heavily washed out by the urban glow, with only a few showpiece objects managing to push through.

The encouraging news is that a worthwhile improvement does not require a huge journey. Around 40 kilometres to the south-east, near 40 km SE, skies improve to a genuinely useful level, and even darker conditions appear farther out to the east and south-south-west.

The map shows Sioux Falls as a concentrated bright core surrounded by a broad halo of skyglow, with the city standing out clearly against the darker prairie around it. The central urban area appears in the hottest colours, then fades through brighter surrounding tones into cooler blues as you move away from town.

What is especially noticeable is how quickly the western side of the map falls away into darker territory. To the west and south-west, the background becomes much darker and less continuous, suggesting a cleaner break from the city's light dome than on the eastern side.

By contrast, the east and north-east look busier and more illuminated overall, with many smaller bright patches and a more persistent blue-green glow across the landscape. In other words, Sioux Falls is much brighter than its immediate surroundings, but the wider region still offers several promising escape routes once you leave the urban halo behind.

What the sky overhead is like

Looking straight up from Sioux Falls, the sky is bright enough that the urban glow remains obvious even overhead rather than staying confined to the horizon. The zenith sits in an inner-city regime, so contrast is poor and the background sky never takes on a truly dark appearance.

Familiar constellations are still visible, but they tend to look thinned out, with many of the fainter linking stars missing. The brightest stars, planets and the Moon remain easy targets, while subtler naked-eye sights are much harder to appreciate.

For telescope users, this means high-contrast objects fare best. Wide, faint structures and delicate low-surface-brightness targets are where the city sky becomes most limiting.

• 105 km SSW

  Direction

  SSW

  Distance (km)

  105.2

  SQM

  21.40

  Bortle

  3

  Milky Way visible, broadband DSO imaging

• 55 km E

  Direction

  E

  Distance (km)

  55.2

  SQM

  21.29

  Bortle

  4

  Bright nebulae, galaxies, narrowband imaging

• 40 km SE

  Direction

  SE

  Distance (km)

  40.2

  SQM

  21.01

  Bortle

  4

  Bright nebulae, galaxies, narrowband imaging

Historical Light Pollution Trends

Across the long run, Sioux Falls appears broadly stable rather than dramatically changing. The recorded sky brightness shifts only slightly from 17.63 SQM in the earliest data to 17.74 SQM in the latest, which points to little overall movement in practical terms.

There is some variation within the record, with readings ranging from 17.3 to 22 SQM, but the average sits at 17.9 SQM. The trend slope is very small, so observers in the city are unlikely to feel that the night sky has either markedly improved or sharply deteriorated based on this dataset alone.

In everyday use, that means the city remains a bright urban observing environment where local conditions may fluctuate, but the overall experience is still dominated by strong artificial skyglow.