CSU-Pueblo Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the CSU-Pueblo Observatory clear sky chart from 2005-11-06 to 2026-08-30.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	4 4 1 4 3 3 4 4 6% 8% 59%	152503
	Night	5% 5% 2 5% 3 3 4 3 5% 7% 58%	147251
Transparency	Day	20% 5% 10% 23% 26% 16%	147502
	Night	24% 5% 10% 24% 25% 12%	143261
Seeing	Day	6% 6% 23% 33% 23% 9%	17997
	Night	6% 4 26% 45% 18% 1	27925

By Month

Percentage Cloud Cover SW (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	2 8% 2 5% 3 2 2 2 4 8% 61%	4720
	11th to 20th	Day	1 3 1 5% 4 3 3 3 4 6% 68%	5017
	21st to end	Day	3 6% 3 6% 4 3 3 2 4 6% 59%	5844
February	1st to 10th	Day	3 6% 2 5% 3 3 4 3 5% 7% 60%	1941
	11th to 20th	Day	1 5% 2 6% 4 3 5% 3 7% 9% 56%	2049
	21st to end	Day	2 5% 2 6% 3 4 4 4 4 5% 62%	1730
March	1st to 10th	Day	2 4 1 3 3 3 3 3 4 7% 67%	4600
	11th to 20th	Day	5% 6% 2 5% 4 3 4 3 5% 8% 54%	5005
	21st to end	Day	2 4 1 4 3 3 3 4 6% 8% 62%	5983
April	1st to 10th	Day	4 5% 2 3 3 3 4 4 5% 8% 59%	2520
	11th to 20th	Day	7% 6% 2 3 2 3 4 4 6% 8% 56%	2491
	21st to end	Day	8% 4 1 4 3 3 4 3 7% 8% 54%	2520
May	1st to 10th	Day	12% 6% 2 4 3 3 3 3 5% 7% 53%	7355
	11th to 20th	Day	5% 4 1 4 3 3 4 4 6% 8% 57%	7852
	21st to end	Day	6% 4 2 4 3 4 4 4 7% 10% 52%	9026
June	1st to 10th	Day	4 4 1 4 3 4 5% 5% 8% 11% 52%	2940
	11th to 20th	Day	4 2 1 3 2 3 4 4 7% 8% 62%	2940
	21st to end	Day	3 3 1 4 4 4 5% 5% 7% 10% 54%	2940
July	1st to 10th	Day	2 1 1 2 2 3 4 4 7% 9% 65%	8249
	11th to 20th	Day	2 2 1 3 3 3 4 4 7% 10% 62%	8250
	21st to end	Day	2 2 1 4 4 5% 6% 5% 9% 10% 50%	8664
August	1st to 10th	Day	4 3 1 4 4 4 6% 5% 10% 12% 47%	5739
	11th to 20th	Day	2 1 1 3 3 3 5% 5% 9% 11% 58%	5486
	21st to end	Day	5% 4 2 5% 4 5% 6% 5% 8% 10% 48%	6093
September	1st to 10th	Day	4 3 2 3 3 3 3 3 5% 7% 64%	2400
	11th to 20th	Day	4 2 1 3 2 3 4 3 5% 7% 65%	2354
	21st to end	Day	5% 3 1 3 3 2 3 3 4 6% 67%	2200
October	1st to 10th	Day	4 2 1 2 1 2 2 1 3 4 78%	3371
	11th to 20th	Day	4 3 1 4 2 2 3 3 4 7% 65%	3250
	21st to end	Day	4 3 1 2 2 2 2 2 3 4 75%	3437
November	1st to 10th	Day	3 3 1 2 2 2 2 3 5% 7% 70%	1853
	11th to 20th	Day	1 4 1 3 2 3 3 3 5% 6% 69%	1890
	21st to end	Day	3 5% 1 4 2 2 3 3 4 6% 65%	1890
December	1st to 10th	Day	1 5% 1 3 2 2 3 2 4 6% 71%	2706
	11th to 20th	Day	2 3 1 4 3 2 3 2 5% 8% 69%	3106
	21st to end	Day	2 5% 1 4 3 3 4 3 6% 7% 60%	4092
January	1st to 10th	Night	3 9% 3 6% 3 3 3 3 5% 7% 56%	8201
	11th to 20th	Night	1 4 1 5% 3 2 3 3 4 6% 67%	8029
	21st to end	Night	2 5% 2 6% 4 3 3 3 4 6% 63%	8370
February	1st to 10th	Night	3 7% 2 6% 3 3 3 2 4 7% 60%	2677
	11th to 20th	Night	3 9% 3 5% 3 3 4 3 5% 8% 54%	2458
	21st to end	Night	3 6% 2 5% 2 2 3 3 4 6% 63%	2076
March	1st to 10th	Night	4 8% 2 3 2 2 2 2 4 5% 66%	5494
	11th to 20th	Night	8% 7% 2 5% 3 3 3 3 4 5% 56%	5207
	21st to end	Night	4 5% 2 5% 3 3 4 4 5% 7% 58%	5202
April	1st to 10th	Night	4 5% 1 4 3 3 3 3 5% 6% 61%	2100
	11th to 20th	Night	9% 7% 2 4 2 2 3 3 5% 8% 55%	2077
	21st to end	Night	11% 6% 2 4 3 3 4 3 6% 7% 51%	2100
May	1st to 10th	Night	13% 5% 2 5% 3 3 3 3 5% 6% 52%	5578
	11th to 20th	Night	9% 4 2 4 2 3 3 3 5% 8% 56%	5023
	21st to end	Night	13% 7% 2 5% 3 3 3 3 4 6% 50%	5181
June	1st to 10th	Night	6% 3 1 4 3 4 4 4 8% 8% 56%	1680
	11th to 20th	Night	4 3 1 4 3 4 3 4 6% 7% 62%	1680
	21st to end	Night	4 4 2 4 4 4 5% 5% 7% 9% 51%	1680
July	1st to 10th	Night	5% 3 1 4 4 4 5% 4 7% 9% 54%	4740
	11th to 20th	Night	3 2 1 4 4 5% 6% 5% 8% 10% 52%	4740
	21st to end	Night	4 3 2 7% 6% 7% 7% 6% 10% 10% 38%	5441
August	1st to 10th	Night	8% 5% 2 6% 5% 5% 5% 5% 7% 8% 44%	4293
	11th to 20th	Night	4 3 2 5% 5% 5% 6% 5% 9% 11% 46%	4583
	21st to end	Night	8% 6% 2 6% 5% 5% 5% 5% 8% 10% 39%	5083
September	1st to 10th	Night	5% 4 2 5% 4 4 4 3 6% 9% 54%	2000
	11th to 20th	Night	6% 2 1 3 2 3 4 3 4 8% 63%	2045
	21st to end	Night	8% 3 1 4 2 3 3 3 4 6% 63%	2200
October	1st to 10th	Night	5% 2 1 3 2 2 2 2 3 4 74%	3812
	11th to 20th	Night	7% 3 1 4 2 2 3 3 5% 7% 63%	3898
	21st to end	Night	4 4 1 3 2 2 2 2 4 5% 71%	4329
November	1st to 10th	Night	3 4 1 2 2 2 2 2 4 7% 71%	2665
	11th to 20th	Night	2 5% 1 3 2 2 2 2 4 5% 71%	2730
	21st to end	Night	4 5% 2 4 2 2 3 3 4 6% 64%	2730
December	1st to 10th	Night	1 5% 2 4 2 2 3 2 3 6% 72%	4700
	11th to 20th	Night	2 4 1 4 3 3 3 2 5% 8% 66%	5321
	21st to end	Night	5% 6% 2 5% 3 4 4 3 5% 7% 57%	7128

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	22% 3 7% 33% 27% 8%	4723
	11th to 20th	Day	17% 4 8% 26% 30% 14%	5017
	21st to end	Day	26% 4 6% 22% 29% 13%	5844
February	1st to 10th	Day	22% 5% 9% 25% 26% 13%	1941
	11th to 20th	Day	23% 4 10% 25% 29% 9%	2059
	21st to end	Day	24% 4 5% 19% 26% 22%	1730
March	1st to 10th	Day	16% 4 6% 16% 31% 27%	4600
	11th to 20th	Day	26% 6% 7% 19% 29% 12%	5005
	21st to end	Day	18% 5% 10% 33% 27% 7%	5983
April	1st to 10th	Day	21% 5% 10% 23% 25% 16%	2520
	11th to 20th	Day	24% 6% 10% 23% 22% 15%	2494
	21st to end	Day	25% 6% 12% 23% 24% 11%	2520
May	1st to 10th	Day	29% 5% 9% 26% 22% 9%	7355
	11th to 20th	Day	21% 8% 9% 20% 26% 16%	7856
	21st to end	Day	24% 7% 14% 23% 17% 16%	9027
June	1st to 10th	Day	22% 8% 15% 23% 19% 13%	2940
	11th to 20th	Day	17% 6% 10% 18% 25% 24%	2940
	21st to end	Day	21% 7% 11% 20% 23% 18%	2940
July	1st to 10th	Day	14% 4 8% 18% 29% 27%	8181
	11th to 20th	Day	15% 5% 11% 23% 26% 20%	8175
	21st to end	Day	24% 7% 16% 24% 18% 12%	8471
August	1st to 10th	Day	28% 8% 18% 27% 12% 7%	4212
	11th to 20th	Day	19% 6% 15% 21% 22% 17%	4002
	21st to end	Day	22% 6% 14% 24% 23% 11%	4420
September	1st to 10th	Day	19% 5% 9% 22% 27% 17%	2400
	11th to 20th	Day	17% 5% 9% 18% 26% 25%	2354
	21st to end	Day	18% 4 7% 19% 32% 21%	2200
October	1st to 10th	Day	12% 3 6% 13% 33% 32%	3371
	11th to 20th	Day	19% 3 7% 22% 32% 16%	3250
	21st to end	Day	14% 2 3 18% 41% 22%	3437
November	1st to 10th	Day	14% 3 8% 23% 32% 21%	1853
	11th to 20th	Day	16% 3 7% 26% 34% 14%	1890
	21st to end	Day	20% 4 8% 17% 31% 20%	1890
December	1st to 10th	Day	15% 3 7% 28% 36% 10%	2706
	11th to 20th	Day	15% 3 8% 28% 34% 13%	3104
	21st to end	Day	20% 5% 9% 25% 30% 11%	4092
January	1st to 10th	Night	27% 3 6% 32% 27% 5%	8202
	11th to 20th	Night	17% 4 10% 28% 25% 15%	8029
	21st to end	Night	22% 4 9% 24% 31% 10%	8370
February	1st to 10th	Night	25% 4 9% 25% 26% 11%	2677
	11th to 20th	Night	27% 4 11% 26% 22% 10%	2458
	21st to end	Night	22% 3 7% 22% 31% 16%	2076
March	1st to 10th	Night	21% 3 5% 17% 35% 19%	5494
	11th to 20th	Night	28% 5% 9% 16% 27% 15%	5207
	21st to end	Night	23% 6% 11% 33% 23% 5%	5202
April	1st to 10th	Night	22% 5% 11% 23% 24% 16%	2100
	11th to 20th	Night	26% 5% 13% 21% 22% 14%	2077
	21st to end	Night	29% 5% 14% 21% 20% 9%	2100
May	1st to 10th	Night	32% 5% 12% 29% 15% 7%	5576
	11th to 20th	Night	24% 6% 11% 27% 17% 14%	5024
	21st to end	Night	34% 7% 14% 19% 13% 14%	5182
June	1st to 10th	Night	22% 8% 18% 24% 15% 12%	1680
	11th to 20th	Night	19% 6% 13% 20% 20% 22%	1680
	21st to end	Night	25% 8% 12% 19% 18% 17%	1680
July	1st to 10th	Night	25% 5% 10% 21% 25% 14%	4700
	11th to 20th	Night	24% 7% 16% 21% 22% 11%	4692
	21st to end	Night	37% 7% 17% 14% 17% 8%	5322
August	1st to 10th	Night	41% 8% 17% 17% 10% 7%	3144
	11th to 20th	Night	30% 9% 18% 17% 19% 6%	3343
	21st to end	Night	30% 8% 15% 26% 16% 5%	3687
September	1st to 10th	Night	26% 5% 12% 21% 24% 13%	2000
	11th to 20th	Night	17% 6% 11% 21% 24% 22%	2045
	21st to end	Night	22% 4 7% 18% 30% 20%	2200
October	1st to 10th	Night	15% 4 6% 17% 36% 23%	3812
	11th to 20th	Night	21% 3 6% 28% 27% 15%	3898
	21st to end	Night	16% 3 5% 22% 36% 18%	4329
November	1st to 10th	Night	15% 2 9% 25% 31% 18%	2665
	11th to 20th	Night	16% 2 6% 25% 37% 14%	2730
	21st to end	Night	21% 4 8% 22% 29% 16%	2730
December	1st to 10th	Night	16% 3 7% 37% 27% 10%	4700
	11th to 20th	Night	17% 3 7% 25% 38% 11%	5322
	21st to end	Night	25% 5% 9% 22% 29% 10%	7128

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	8% 5% 24% 40% 19% 4	330
	11th to 20th	Day	6% 7% 27% 43% 15% 2	330
	21st to end	Day	4 5% 26% 47% 14% 5%	363
February	1st to 10th	Day	4 7% 38% 38% 10% 4	330
	11th to 20th	Day	4 7% 33% 42% 14% 1	330
	21st to end	Day	5% 10% 27% 46% 13%	273
March	1st to 10th	Day	5% 9% 28% 36% 21% 2	330
	11th to 20th	Day	12% 10% 30% 32% 13% 3	487
	21st to end	Day	8% 17% 33% 29% 11% 1	594
April	1st to 10th	Day	7% 14% 37% 28% 12% 3	540
	11th to 20th	Day	9% 16% 36% 27% 10% 2	532
	21st to end	Day	14% 12% 28% 31% 12% 2	540
May	1st to 10th	Day	13% 10% 30% 31% 15% 3	648
	11th to 20th	Day	10% 8% 24% 31% 22% 6%	775
	21st to end	Day	7% 6% 24% 34% 22% 6%	844
June	1st to 10th	Day	5% 5% 21% 29% 30% 9%	780
	11th to 20th	Day	5% 4 24% 33% 27% 8%	780
	21st to end	Day	3 7% 22% 33% 27% 8%	780
July	1st to 10th	Day	5% 3 16% 26% 36% 13%	771
	11th to 20th	Day	3 1 13% 26% 40% 17%	768
	21st to end	Day	3 2 10% 27% 36% 22%	748
August	1st to 10th	Day	3 2 18% 30% 31% 15%	567
	11th to 20th	Day	3 2 16% 32% 27% 19%	557
	21st to end	Day	4 3 12% 35% 32% 15%	620
September	1st to 10th	Day	5% 2 18% 32% 27% 16%	530
	11th to 20th	Day	5% 3 19% 34% 27% 11%	484
	21st to end	Day	6% 5% 12% 28% 33% 16%	330
October	1st to 10th	Day	9% 2 21% 30% 21% 18%	330
	11th to 20th	Day	4 6% 18% 36% 25% 11%	330
	21st to end	Day	7% 4 19% 36% 26% 7%	363
November	1st to 10th	Day	5% 5% 21% 40% 23% 6%	330
	11th to 20th	Day	4 4 25% 40% 20% 7%	330
	21st to end	Day	8% 5% 19% 40% 23% 5%	330
December	1st to 10th	Day	3 6% 28% 41% 15% 7%	330
	11th to 20th	Day	4 6% 25% 44% 18% 2	330
	21st to end	Day	4 5% 35% 41% 12% 2	363
January	1st to 10th	Night	4 5% 28% 47% 13% 2	1050
	11th to 20th	Night	5% 3 35% 43% 13% 1	972
	21st to end	Night	5% 1 30% 50% 13% 1	924
February	1st to 10th	Night	5% 3 36% 47% 8% 1	840
	11th to 20th	Night	6% 4 37% 44% 9%	824
	21st to end	Night	7% 3 43% 42% 5%	692
March	1st to 10th	Night	5% 5% 35% 46% 8% 1	840
	11th to 20th	Night	10% 4 29% 44% 12% 1	840
	21st to end	Night	7% 5% 36% 46% 6%	749
April	1st to 10th	Night	7% 8% 41% 38% 7%	630
	11th to 20th	Night	12% 9% 32% 38% 9%	623
	21st to end	Night	12% 7% 30% 42% 9% 1	630
May	1st to 10th	Night	11% 6% 30% 42% 11%	630
	11th to 20th	Night	12% 5% 22% 42% 18% 1	621
	21st to end	Night	11% 5% 29% 39% 16% 1	683
June	1st to 10th	Night	5% 2 24% 44% 23% 2	630
	11th to 20th	Night	4 3 24% 50% 17% 1	630
	21st to end	Night	5% 4 20% 46% 25% 1	630
July	1st to 10th	Night	7% 2 13% 42% 34% 2	615
	11th to 20th	Night	4 1 11% 42% 38% 4	612
	21st to end	Night	7% 2 8% 35% 44% 4	690
August	1st to 10th	Night	8% 1 9% 38% 41% 2	627
	11th to 20th	Night	6% 2 12% 44% 34% 2	624
	21st to end	Night	5% 2 7% 43% 40% 3	687
September	1st to 10th	Night	5% 2 11% 46% 33% 4	600
	11th to 20th	Night	6% 3 14% 47% 27% 3	600
	21st to end	Night	8% 4 16% 47% 23% 2	600
October	1st to 10th	Night	10% 2 21% 45% 21% 2	731
	11th to 20th	Night	5% 2 22% 45% 23% 2	800
	21st to end	Night	7% 3 23% 44% 21% 2	921
November	1st to 10th	Night	4 2 24% 52% 17% 1	1025
	11th to 20th	Night	4 4 27% 50% 13% 2	1050
	21st to end	Night	6% 4 28% 43% 17% 1	1050
December	1st to 10th	Night	4 2 30% 49% 14% 1	1050
	11th to 20th	Night	5% 4 31% 48% 12% 1	1050
	21st to end	Night	5% 4 33% 48% 8%	1155

Page generated at 2026-08-27 02:07:09. Version ac07

Copyright © 2026 Attilla Danko.