The Darkest Skies
in Colorado

"Low extinction night, super bright zodical light, Gegenshein visible. Airglow visible beween 4-5. Earlier sets had bright zodiacal and gegenshein. 21.67 SQM. Bortle 2 possible without the direct glare."

"Excellent data with smooth atmosphere, no layered haze or directional anomolies, stable extinction coefficient, and no clouds. 5th set shows some signs of dewfall. 4th set used for measurement as Milky Way was least prominent during that set. Data shows remarkable zenith brightness of 22.14 despite substantial light pollution to west. Measured LM of 6.7 at 45 deg to NW and 7.0 at 60 deg to NE. Glimpsed one mag 7.4 star. Visual scene is substantially hampered by streetlights along highway and park lighting, visible in images (especially at azi 305 deg). These impede dark adaptation and result in Bortle Class 4 rating, when potentially site could be Bortle Class 3. SQM of 21.73 at 06:15."

"Sky quality measurements were recorded at Magnolia North in Piceance Basin on 3/29/2017. The site demonstrated a scientific darkness reading of 21.59 SQM."

"Simultaneous data collection with Kate Magargal. Sky is slightly brighter than previous data collection nights, but transparency was excellent allowing 7.0 limiting magnitude. Some haze to east and some very thin clouds retreating to the NE, but by second data set they appear to be diminished. Minor airglow present. Estes Park is not as bright or obvious this night due to better air clarity. Laramie, WY is barely visible to north."

"Excellent conditions for stargazing. Visibility is again possible to 100+ miles in all directions. Very stable atmosphere, with stars visible to less than 5 degrees above horizon. Nice detail throughout the Milky Way, which is visible almost to the horizon in the SW and down to 10 degrees in the NE. At sunset there were some low clouds to the south over Farmington area and some residual clouds to the NE over the San Juan Mtns. Would easily be a Bortle Class 2 sky if not for the the numerous distant light domes. Still this remote backcountry location is free from any local glare sources and provides the observer with a beautiful night sky. Durango easily visible to the east and brighter than Cortez."

"Transparency excellent, seeing good, in early evening sky looks very dark except light domes of Alamosa, Denver, Colorado Springs, and a broad glow toward the west that seems to parallel the highway 160/285 (headlights). Later, especially by 4th data set, sky in the east brightens considerably, north slightly, distant cities seem brighter behind the mountains. Gegenschien seen with a little difficulty, no zodiacal band, Milky Way in Sagittarius washed out by Alamosa, very nice in Cygnus. M33 easy averted vision but not seen direct. Light domes not bright but extend upward to 15 degrees (Alamosa and the band of light to the west), glare from farm lights the most obtrusive, interferes with night vision. SQM 21.55 first set, 21.48 last set"

"Sky quality measurements were recorded at Sunset View in Black Canyon of the Gunnison NP on 9/6/2004. The site demonstrated a scientific darkness reading of 21.49 SQM."

"Snowing at 6:00 pm but cleared out nicely by 9:00 pm. Very cold temps (27°) at start time and light winds. Transparency was excellent. The light dome of the greater Denver area easily visible to the NNE up to about 25° above horizon. Colorado Springs visible to the east and maybe a little brighter than Denver and light dome visible to the naked eye to almost 30°. The Milky Way rose later in the evening and the Prancing Horse was visible, though not vivid in detail, as the light dome of Colorado Springs was impacting that part of the sky. Naked eye limiting magnitude of 6.8 in the Big Dipper , which was near the zenith. Excellent night sky and great location for viewing and telescopes shielded from the highway. SQM reading of 21.67"

"Observing Condition: This observation was made during the Perseid meteor shower. Many meteors were captured in the images! There was some haze near the horizon; stars were visible only above 10 degrees in elevation. The Beaver Creek fire was going on but it did not cause an obvious observable effect at the time of the observation. In between the two datasets, the average wind speed and the relative humidity were measured to be 7 mph and 40%, both were higher compared to the condition at the beginning of the observation. During the acquisition of the second data set, a bright light from a car shined directly into the camera, causing a bright and wide saturated column in the 7th image in b filter. Naked-eye Sky: Light pollution from the nearby cities was apparent from the azimuthal angle of 75 degrees and 110 degrees (east). The light from the towns were directly visible. The view due east (90 degrees) was blocked by the nearby rock formation. Although faint, the light dome extends all the way to the zenith. The Milky Way with the dark lanes was visible from 10 degrees in elevation in the west to 45 degrees in elevation in the east; the rest is lost in the haze (west) or in the light dome (east). The darkest part of the sky is due west of the zenith at roughly 70 degrees in elevation. The zenith sky brightness is 21.62 mag."

"Sky quality measurements were recorded at Crater Rim in Capulin Volcano NM on 10/17/2004. The site demonstrated a scientific darkness reading of 21.45 SQM."