Rocky Mountain Star Stare
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rocky Mountain Star Stare clear sky chart from 2005-11-06 to 2026-03-03.

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	2 4 2 4 4 4 5% 4 6% 8% 57%	139658
	Night	2 4 2 4 3 3 3 3 5% 8% 63%	139022
Transparency	Day	22% 6% 11% 23% 25% 13%	134652
	Night	20% 5% 11% 25% 28% 11%	135035
Seeing	Day	11% 17% 31% 25% 12% 3	17142
	Night	7% 13% 35% 30% 13% 2	27323

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	4 3 6% 3 2 3 2 4 7% 65%	4720
	11th to 20th	Day	1 1 3 3 3 3 3 3 5% 74%	5197
	21st to end	Day	6% 3 5% 3 3 4 3 5% 6% 62%	5844
February	1st to 10th	Day	4 3 6% 3 2 3 2 5% 8% 64%	1915
	11th to 20th	Day	1 3 2 4 3 3 4 3 6% 7% 64%	2049
	21st to end	Day	1 4 2 5% 2 4 3 3 5% 8% 62%	1730
March	1st to 10th	Day	4 3 5% 3 3 4 4 5% 7% 63%	4520
	11th to 20th	Day	2 11% 4 8% 5% 4 4 3 5% 8% 48%	4995
	21st to end	Day	1 4 2 5% 3 3 3 3 6% 9% 61%	5791
April	1st to 10th	Day	2 6% 2 5% 3 3 4 4 7% 8% 58%	2400
	11th to 20th	Day	2 6% 2 5% 4 4 4 3 5% 9% 54%	2371
	21st to end	Day	3 8% 3 5% 4 4 5% 5% 7% 8% 48%	2400
May	1st to 10th	Day	5% 8% 3 6% 3 4 5% 4 7% 9% 46%	5549
	11th to 20th	Day	3 4 1 5% 4 3 5% 4 6% 8% 55%	6095
	21st to end	Day	2 3 1 3 3 3 4 4 8% 10% 58%	6925
June	1st to 10th	Day	3 3 1 4 5% 5% 5% 5% 7% 11% 51%	2800
	11th to 20th	Day	2 3 1 2 3 4 5% 4 6% 8% 61%	2800
	21st to end	Day	2 3 2 5% 4 5% 6% 6% 9% 9% 50%	2800
July	1st to 10th	Day	2 2 1 3 3 4 5% 5% 8% 10% 57%	6339
	11th to 20th	Day	1 2 1 4 5% 8% 9% 7% 10% 10% 41%	6340
	21st to end	Day	3 3 2 6% 6% 6% 7% 6% 8% 10% 43%	6499
August	1st to 10th	Day	2 2 1 5% 5% 6% 8% 7% 10% 12% 40%	5656
	11th to 20th	Day	2 2 1 4 3 5% 6% 5% 9% 12% 50%	5366
	21st to end	Day	4 4 2 5% 4 5% 6% 6% 9% 12% 44%	5984
September	1st to 10th	Day	4 5% 2 5% 4 4 5% 5% 7% 8% 52%	2400
	11th to 20th	Day	4 2 2 4 3 3 4 3 6% 7% 62%	2379
	21st to end	Day	3 4 2 4 3 3 4 3 5% 6% 64%	2200
October	1st to 10th	Day	3 3 1 2 2 3 2 3 3 6% 72%	3304
	11th to 20th	Day	2 3 1 4 3 3 3 3 5% 8% 65%	3250
	21st to end	Day	2 3 1 2 2 2 2 2 3 6% 76%	3521
November	1st to 10th	Day	1 3 2 3 2 3 2 3 5% 8% 70%	1853
	11th to 20th	Day	3 2 4 2 2 3 2 4 8% 71%	1890
	21st to end	Day	1 4 2 5% 3 2 3 3 5% 6% 66%	1878
December	1st to 10th	Day	2 1 4 2 2 2 2 3 6% 76%	2700
	11th to 20th	Day	1 2 1 3 2 2 3 2 5% 8% 71%	3106
	21st to end	Day	3 2 6% 3 3 3 3 4 7% 65%	4092
January	1st to 10th	Night	3 3 7% 4 3 3 3 5% 8% 62%	8201
	11th to 20th	Night	2 1 3 2 3 3 2 4 5% 75%	7848
	21st to end	Night	1 3 2 5% 3 3 3 3 4 7% 68%	8370
February	1st to 10th	Night	1 4 2 6% 3 3 3 2 4 6% 67%	2704
	11th to 20th	Night	1 5% 2 7% 3 3 2 3 5% 6% 64%	2458
	21st to end	Night	4 2 5% 3 2 3 2 4 7% 68%	2076
March	1st to 10th	Night	1 6% 2 5% 2 3 3 2 4 6% 66%	5398
	11th to 20th	Night	1 8% 3 5% 3 3 3 3 5% 6% 59%	5000
	21st to end	Night	1 5% 2 4 2 3 3 3 4 7% 67%	5168
April	1st to 10th	Night	1 4 2 4 3 2 2 2 5% 7% 66%	2000
	11th to 20th	Night	3 7% 2 5% 2 3 3 3 5% 7% 60%	1977
	21st to end	Night	3 7% 2 5% 2 3 4 3 5% 8% 58%	2000
May	1st to 10th	Night	4 7% 2 5% 3 4 4 3 5% 7% 55%	4430
	11th to 20th	Night	6% 5% 1 3 3 2 2 3 4 7% 63%	3803
	21st to end	Night	4 5% 2 5% 3 4 3 3 5% 6% 60%	3972
June	1st to 10th	Night	3 4 2 4 3 3 4 5% 6% 9% 57%	1600
	11th to 20th	Night	2 2 1 3 3 3 3 4 6% 9% 65%	1600
	21st to end	Night	3 3 1 4 4 4 5% 5% 8% 10% 54%	1600
July	1st to 10th	Night	3 3 1 4 3 4 4 5% 7% 8% 57%	3640
	11th to 20th	Night	2 3 1 4 3 6% 6% 6% 10% 13% 45%	3640
	21st to end	Night	3 3 2 5% 4 5% 7% 6% 9% 11% 44%	4370
August	1st to 10th	Night	3 3 1 5% 4 5% 7% 5% 8% 10% 47%	4152
	11th to 20th	Night	2 2 1 3 4 5% 6% 5% 10% 14% 48%	4483
	21st to end	Night	4 5% 2 6% 4 5% 6% 6% 9% 12% 40%	4993
September	1st to 10th	Night	4 4 2 3 3 3 5% 4 7% 9% 54%	2000
	11th to 20th	Night	5% 4 1 3 2 3 3 4 5% 7% 64%	2020
	21st to end	Night	4 4 1 3 2 3 3 3 5% 6% 64%	2200
October	1st to 10th	Night	2 3 1 3 1 2 2 3 3 5% 75%	3881
	11th to 20th	Night	2 4 1 4 3 3 3 3 5% 7% 66%	3898
	21st to end	Night	2 3 1 3 2 2 2 2 3 5% 75%	4252
November	1st to 10th	Night	1 3 1 3 2 2 2 2 4 7% 73%	2659
	11th to 20th	Night	1 2 1 3 2 2 2 2 4 6% 74%	2730
	21st to end	Night	1 5% 1 4 2 2 2 3 5% 7% 68%	2740
December	1st to 10th	Night	1 2 1 4 2 2 2 2 3 5% 76%	4710
	11th to 20th	Night	1 3 1 3 2 2 2 2 5% 8% 72%	5321
	21st to end	Night	4 2 5% 3 3 3 3 5% 7% 64%	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	21% 4 8% 29% 31% 8%	4723
	11th to 20th	Day	14% 4 7% 24% 32% 18%	5197
	21st to end	Day	23% 5% 7% 22% 28% 16%	5844
February	1st to 10th	Day	20% 4 11% 29% 25% 11%	1915
	11th to 20th	Day	18% 5% 10% 27% 31% 9%	2059
	21st to end	Day	18% 5% 9% 19% 30% 18%	1730
March	1st to 10th	Day	17% 6% 6% 14% 36% 21%	4520
	11th to 20th	Day	32% 6% 7% 20% 27% 8%	4995
	21st to end	Day	19% 5% 8% 42% 23% 4	5791
April	1st to 10th	Day	22% 7% 11% 24% 23% 14%	2400
	11th to 20th	Day	25% 7% 9% 24% 21% 13%	2374
	21st to end	Day	29% 8% 11% 21% 24% 7%	2400
May	1st to 10th	Day	30% 6% 13% 22% 18% 11%	5549
	11th to 20th	Day	23% 8% 10% 19% 24% 16%	6099
	21st to end	Day	19% 7% 12% 20% 23% 19%	6926
June	1st to 10th	Day	24% 9% 15% 21% 21% 12%	2800
	11th to 20th	Day	17% 7% 11% 16% 24% 24%	2800
	21st to end	Day	24% 8% 14% 21% 21% 13%	2800
July	1st to 10th	Day	21% 6% 12% 17% 23% 22%	6271
	11th to 20th	Day	30% 8% 19% 27% 13% 3	6265
	21st to end	Day	32% 8% 19% 17% 15% 8%	6312
August	1st to 10th	Day	36% 11% 22% 17% 9% 5%	4118
	11th to 20th	Day	24% 7% 18% 20% 18% 14%	3882
	21st to end	Day	28% 7% 20% 21% 21% 4	4311
September	1st to 10th	Day	26% 8% 12% 23% 21% 10%	2400
	11th to 20th	Day	19% 6% 11% 19% 28% 17%	2379
	21st to end	Day	20% 6% 7% 21% 35% 12%	2200
October	1st to 10th	Day	14% 5% 6% 17% 36% 22%	3304
	11th to 20th	Day	20% 4 8% 24% 33% 11%	3250
	21st to end	Day	12% 3 5% 19% 43% 19%	3521
November	1st to 10th	Day	13% 4 8% 24% 35% 16%	1853
	11th to 20th	Day	14% 4 8% 31% 32% 12%	1890
	21st to end	Day	19% 5% 8% 22% 31% 16%	1878
December	1st to 10th	Day	12% 3 8% 29% 38% 10%	2700
	11th to 20th	Day	13% 3 10% 26% 37% 11%	3104
	21st to end	Day	17% 6% 8% 29% 26% 14%	4092
January	1st to 10th	Night	21% 4 7% 34% 27% 6%	8202
	11th to 20th	Night	13% 4 9% 28% 32% 14%	7848
	21st to end	Night	17% 6% 8% 24% 31% 14%	8370
February	1st to 10th	Night	20% 3 10% 29% 27% 11%	2704
	11th to 20th	Night	21% 5% 10% 29% 27% 8%	2458
	21st to end	Night	17% 3 7% 24% 35% 13%	2076
March	1st to 10th	Night	18% 4 6% 13% 43% 16%	5398
	11th to 20th	Night	25% 5% 7% 21% 33% 9%	5000
	21st to end	Night	18% 4 9% 43% 22% 4	5168
April	1st to 10th	Night	18% 4 11% 28% 27% 11%	2000
	11th to 20th	Night	23% 5% 11% 25% 26% 10%	1977
	21st to end	Night	25% 6% 14% 26% 22% 7%	2000
May	1st to 10th	Night	27% 5% 12% 27% 18% 10%	4427
	11th to 20th	Night	21% 5% 9% 29% 25% 11%	3804
	21st to end	Night	23% 6% 13% 16% 27% 15%	3972
June	1st to 10th	Night	21% 9% 15% 23% 18% 15%	1600
	11th to 20th	Night	15% 7% 11% 19% 26% 22%	1600
	21st to end	Night	24% 8% 14% 19% 21% 14%	1600
July	1st to 10th	Night	23% 8% 13% 18% 24% 15%	3600
	11th to 20th	Night	27% 7% 26% 27% 10% 3	3592
	21st to end	Night	30% 9% 20% 19% 17% 5%	4245
August	1st to 10th	Night	37% 11% 21% 17% 10% 4	3014
	11th to 20th	Night	27% 8% 25% 16% 16% 8%	3243
	21st to end	Night	29% 9% 22% 23% 14% 3	3597
September	1st to 10th	Night	24% 8% 15% 25% 21% 8%	2000
	11th to 20th	Night	19% 6% 11% 20% 26% 17%	2020
	21st to end	Night	20% 5% 9% 21% 34% 10%	2200
October	1st to 10th	Night	13% 4 8% 22% 35% 18%	3881
	11th to 20th	Night	20% 2 12% 24% 31% 11%	3898
	21st to end	Night	14% 3 5% 24% 40% 14%	4252
November	1st to 10th	Night	13% 4 8% 26% 34% 16%	2659
	11th to 20th	Night	13% 3 7% 32% 33% 13%	2730
	21st to end	Night	17% 4 9% 24% 34% 13%	2740
December	1st to 10th	Night	13% 4 7% 34% 32% 9%	4710
	11th to 20th	Night	12% 5% 8% 27% 40% 9%	5322
	21st to end	Night	19% 5% 12% 22% 30% 12%	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	18% 24% 30% 20% 6% 2	330
	11th to 20th	Day	15% 25% 39% 17% 3 1	330
	21st to end	Day	7% 25% 40% 20% 7% 1	363
February	1st to 10th	Day	16% 31% 35% 14% 2 2	330
	11th to 20th	Day	19% 28% 38% 13% 2 1	330
	21st to end	Day	24% 27% 33% 15% 2	273
March	1st to 10th	Day	21% 26% 26% 21% 6%	306
	11th to 20th	Day	20% 22% 37% 16% 4 1	495
	21st to end	Day	23% 32% 31% 10% 3	550
April	1st to 10th	Day	19% 29% 34% 13% 4 1	500
	11th to 20th	Day	22% 27% 36% 11% 3 1	492
	21st to end	Day	18% 28% 34% 15% 4 1	500
May	1st to 10th	Day	15% 24% 37% 17% 6% 1	547
	11th to 20th	Day	14% 15% 32% 28% 10% 2	725
	21st to end	Day	11% 17% 30% 28% 12% 2	789
June	1st to 10th	Day	6% 12% 28% 32% 18% 4	730
	11th to 20th	Day	8% 12% 32% 30% 15% 4	730
	21st to end	Day	5% 13% 31% 29% 18% 4	730
July	1st to 10th	Day	6% 5% 25% 37% 20% 7%	721
	11th to 20th	Day	4 4 17% 38% 29% 8%	718
	21st to end	Day	5% 3 17% 37% 28% 10%	621
August	1st to 10th	Day	5% 6% 26% 34% 21% 9%	527
	11th to 20th	Day	5% 4 27% 35% 22% 5%	517
	21st to end	Day	7% 6% 25% 38% 19% 5%	583
September	1st to 10th	Day	6% 9% 26% 34% 19% 6%	530
	11th to 20th	Day	5% 13% 39% 28% 13% 3	509
	21st to end	Day	8% 9% 28% 32% 18% 6%	330
October	1st to 10th	Day	10% 14% 28% 28% 15% 6%	330
	11th to 20th	Day	11% 23% 35% 18% 9% 4	330
	21st to end	Day	11% 18% 39% 20% 10% 2	363
November	1st to 10th	Day	13% 22% 35% 22% 7% 1	330
	11th to 20th	Day	12% 20% 35% 22% 10% 2	330
	21st to end	Day	10% 19% 36% 28% 5% 2	330
December	1st to 10th	Day	12% 29% 31% 18% 8% 1	330
	11th to 20th	Day	12% 32% 34% 15% 6% 2	330
	21st to end	Day	19% 25% 36% 16% 4 1	363
January	1st to 10th	Night	6% 22% 39% 24% 7% 1	1050
	11th to 20th	Night	7% 21% 42% 22% 6% 2	908
	21st to end	Night	4 16% 44% 27% 7% 1	924
February	1st to 10th	Night	4 20% 49% 22% 4 1	840
	11th to 20th	Night	6% 23% 48% 17% 6%	824
	21st to end	Night	5% 18% 54% 20% 3	692
March	1st to 10th	Night	7% 24% 44% 20% 5%	808
	11th to 20th	Night	8% 13% 41% 28% 8% 1	800
	21st to end	Night	9% 17% 45% 25% 4	740
April	1st to 10th	Night	12% 15% 46% 24% 3	600
	11th to 20th	Night	13% 11% 43% 25% 7%	593
	21st to end	Night	11% 16% 34% 31% 8% 1	600
May	1st to 10th	Night	10% 11% 39% 31% 8% 1	600
	11th to 20th	Night	13% 7% 32% 32% 14% 2	591
	21st to end	Night	10% 12% 30% 32% 13% 2	650
June	1st to 10th	Night	5% 9% 24% 42% 18% 2	600
	11th to 20th	Night	3 8% 32% 40% 16% 2	600
	21st to end	Night	4 3 25% 40% 25% 2	600
July	1st to 10th	Night	8% 2 14% 41% 30% 4	585
	11th to 20th	Night	4 2 11% 37% 38% 7%	582
	21st to end	Night	7% 2 6% 38% 41% 6%	657
August	1st to 10th	Night	6% 2 10% 41% 36% 5%	597
	11th to 20th	Night	5% 2 12% 46% 32% 3	594
	21st to end	Night	7% 3 12% 43% 31% 5%	660
September	1st to 10th	Night	5% 3 17% 44% 25% 6%	600
	11th to 20th	Night	8% 5% 23% 39% 21% 4	600
	21st to end	Night	7% 8% 25% 41% 16% 4	600
October	1st to 10th	Night	8% 8% 32% 37% 13% 2	774
	11th to 20th	Night	4 10% 40% 30% 13% 3	800
	21st to end	Night	7% 12% 37% 30% 12% 3	880
November	1st to 10th	Night	5% 14% 39% 31% 10% 1	1019
	11th to 20th	Night	7% 15% 42% 27% 8% 1	1050
	21st to end	Night	8% 15% 41% 29% 7% 1	1050
December	1st to 10th	Night	8% 18% 40% 26% 8%	1050
	11th to 20th	Night	6% 21% 44% 19% 9%	1050
	21st to end	Night	8% 22% 43% 22% 4 1	1155

Page generated at 2026-02-27 23:40:25. Version ac07

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