Caprock Canyons Trailway
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Caprock Canyons Trailway clear sky chart from 2005-11-06 to 2025-07-06.

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	7% 4 1 4 3 3 3 3 4 6% 61%	124103
	Night	6% 4 1 4 3 3 3 3 5% 7% 63%	123542
Transparency	Day	24% 4 7% 22% 27% 16%	123868
	Night	22% 4 8% 21% 27% 18%	123368
Seeing	Day	8% 7% 25% 33% 22% 6%	16144
	Night	8% 7% 30% 40% 14% 1	26087

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	7% 6% 3 6% 4 3 3 3 4 4 57%	4077
	11th to 20th	Day	4 3 1 3 2 3 2 2 3 5% 71%	4080
	21st to end	Day	10% 5% 1 3 3 3 3 3 4 6% 58%	4925
February	1st to 10th	Day	7% 6% 1 4 3 3 3 2 4 6% 62%	2000
	11th to 20th	Day	7% 6% 2 6% 3 3 3 2 4 7% 58%	1949
	21st to end	Day	6% 7% 2 4 3 2 3 3 3 5% 61%	1650
March	1st to 10th	Day	9% 4 2 5% 3 2 2 2 4 6% 62%	4500
	11th to 20th	Day	8% 4 2 4 2 3 2 3 5% 6% 61%	4891
	21st to end	Day	4 5% 2 4 3 3 4 3 5% 8% 59%	5501
April	1st to 10th	Day	7% 4 1 4 3 2 3 2 4 6% 64%	2400
	11th to 20th	Day	10% 4 2 4 3 3 3 3 4 5% 58%	2371
	21st to end	Day	9% 3 1 3 3 3 3 3 5% 6% 61%	2456
May	1st to 10th	Day	15% 5% 1 3 2 2 3 3 4 7% 55%	5900
	11th to 20th	Day	9% 4 2 4 3 2 3 2 4 5% 63%	5862
	21st to end	Day	10% 5% 2 5% 3 3 4 3 4 6% 55%	6446
June	1st to 10th	Day	6% 4 1 4 3 3 4 4 6% 9% 55%	2600
	11th to 20th	Day	6% 3 1 3 3 3 4 3 6% 8% 61%	2600
	21st to end	Day	3 3 1 4 3 4 4 4 6% 7% 62%	2600
July	1st to 10th	Day	8% 4 2 5% 4 4 5% 5% 6% 9% 49%	4186
	11th to 20th	Day	3 2 1 3 3 3 4 3 6% 9% 62%	4120
	21st to end	Day	2 2 1 3 3 3 4 3 5% 9% 62%	4466
August	1st to 10th	Day	3 2 1 3 3 3 4 4 6% 9% 64%	3918
	11th to 20th	Day	4 2 1 3 3 3 4 3 5% 8% 65%	3726
	21st to end	Day	6% 3 1 4 2 3 4 3 5% 8% 61%	4180
September	1st to 10th	Day	9% 4 2 4 3 3 3 3 5% 7% 57%	2209
	11th to 20th	Day	9% 4 1 5% 3 4 4 4 5% 8% 53%	2090
	21st to end	Day	8% 3 1 3 3 3 3 3 4 6% 64%	2090
October	1st to 10th	Day	5% 2 1 3 2 2 2 1 2 3 77%	3480
	11th to 20th	Day	10% 4 2 3 2 3 3 2 3 5% 64%	3434
	21st to end	Day	5% 3 1 2 1 2 2 2 3 5% 74%	3214
November	1st to 10th	Day	7% 3 1 3 2 2 3 2 4 6% 66%	1763
	11th to 20th	Day	4 3 1 2 2 2 3 3 4 5% 71%	1800
	21st to end	Day	9% 5% 1 4 2 2 3 2 4 6% 63%	1800
December	1st to 10th	Day	5% 4 2 5% 3 3 3 3 5% 6% 62%	2940
	11th to 20th	Day	5% 2 1 3 2 3 3 4 5% 5% 67%	3391
	21st to end	Day	7% 8% 3 5% 3 3 3 2 3 4 61%	4488
January	1st to 10th	Night	7% 7% 2 6% 3 3 3 3 4 6% 58%	5888
	11th to 20th	Night	3 2 2 4 3 2 3 3 4 5% 69%	5900
	21st to end	Night	8% 6% 3 5% 3 3 3 3 4 5% 56%	6094
February	1st to 10th	Night	7% 6% 1 5% 3 3 2 3 4 6% 61%	2400
	11th to 20th	Night	7% 6% 2 5% 4 3 3 3 4 6% 58%	2338
	21st to end	Night	6% 5% 1 3 3 3 3 3 5% 7% 61%	1980
March	1st to 10th	Night	5% 5% 2 4 3 3 3 3 4 5% 63%	5374
	11th to 20th	Night	5% 3 1 4 3 3 3 3 4 5% 67%	5072
	21st to end	Night	3 4 2 5% 3 3 4 3 5% 7% 60%	5428
April	1st to 10th	Night	6% 4 1 3 3 3 3 3 5% 6% 64%	2000
	11th to 20th	Night	8% 4 1 4 3 3 3 3 5% 7% 58%	1977
	21st to end	Night	9% 2 1 3 2 2 3 2 5% 6% 63%	1940
May	1st to 10th	Night	13% 4 1 4 3 2 2 2 3 6% 58%	4080
	11th to 20th	Night	7% 4 1 4 3 3 3 3 5% 6% 61%	4053
	21st to end	Night	10% 5% 2 5% 3 2 3 3 4 6% 58%	4451
June	1st to 10th	Night	5% 2 1 4 4 3 4 4 8% 11% 54%	1800
	11th to 20th	Night	3 2 1 2 3 4 3 4 8% 11% 59%	1800
	21st to end	Night	4 2 1 4 3 3 4 3 6% 9% 60%	1800
July	1st to 10th	Night	5% 3 1 6% 4 5% 4 4 7% 8% 52%	2895
	11th to 20th	Night	3 2 1 4 4 4 4 4 8% 11% 55%	2850
	21st to end	Night	2 2 1 3 3 3 4 3 6% 9% 63%	3097
August	1st to 10th	Night	2 1 1 3 3 3 3 4 6% 11% 64%	3017
	11th to 20th	Night	4 3 1 3 3 4 6% 4 6% 9% 56%	3113
	21st to end	Night	3 2 1 4 2 2 4 4 4 9% 65%	3487
September	1st to 10th	Night	7% 4 1 4 4 3 4 4 5% 6% 57%	1970
	11th to 20th	Night	10% 4 2 5% 4 3 4 4 6% 7% 52%	2090
	21st to end	Night	6% 2 1 3 2 2 3 3 5% 5% 66%	2090
October	1st to 10th	Night	5% 2 1 2 1 2 2 1 2 4 79%	3480
	11th to 20th	Night	8% 4 2 4 3 2 3 2 4 6% 63%	3460
	21st to end	Night	4 2 1 1 1 1 2 1 3 6% 77%	4327
November	1st to 10th	Night	7% 2 1 2 2 2 2 3 4 6% 70%	2535
	11th to 20th	Night	4 3 1 2 2 2 2 2 4 6% 72%	2600
	21st to end	Night	7% 4 1 4 3 3 3 3 4 5% 63%	2600
December	1st to 10th	Night	5% 3 1 4 3 3 4 2 4 6% 66%	4250
	11th to 20th	Night	4 3 1 2 3 2 3 2 4 7% 68%	4816
	21st to end	Night	5% 6% 2 4 3 3 3 3 5% 6% 61%	6490

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	30% 3 6% 25% 24% 12%	4078
	11th to 20th	Day	18% 2 5% 23% 33% 20%	4080
	21st to end	Day	28% 3 7% 19% 29% 15%	4925
February	1st to 10th	Day	25% 3 7% 24% 26% 16%	2000
	11th to 20th	Day	29% 3 6% 24% 23% 15%	1959
	21st to end	Day	27% 3 4 16% 31% 21%	1650
March	1st to 10th	Day	25% 3 4 10% 26% 32%	4500
	11th to 20th	Day	25% 2 5% 18% 26% 24%	4891
	21st to end	Day	23% 4 8% 25% 29% 11%	5501
April	1st to 10th	Day	23% 3 6% 18% 28% 22%	2400
	11th to 20th	Day	28% 4 6% 19% 23% 20%	2374
	21st to end	Day	23% 4 9% 23% 28% 13%	2456
May	1st to 10th	Day	31% 4 9% 22% 19% 15%	5900
	11th to 20th	Day	25% 3 6% 18% 21% 26%	5866
	21st to end	Day	30% 5% 9% 18% 18% 19%	6447
June	1st to 10th	Day	25% 6% 15% 28% 18% 8%	2600
	11th to 20th	Day	21% 6% 10% 23% 26% 14%	2600
	21st to end	Day	21% 5% 12% 28% 23% 12%	2600
July	1st to 10th	Day	30% 6% 10% 27% 21% 5%	4122
	11th to 20th	Day	18% 4 10% 31% 30% 7%	4051
	21st to end	Day	17% 6% 11% 28% 30% 8%	4325
August	1st to 10th	Day	17% 5% 12% 24% 28% 15%	3905
	11th to 20th	Day	18% 4 10% 24% 30% 13%	3762
	21st to end	Day	22% 5% 10% 25% 30% 9%	4179
September	1st to 10th	Day	27% 6% 9% 23% 22% 13%	2209
	11th to 20th	Day	29% 6% 10% 21% 28% 6%	2090
	21st to end	Day	21% 5% 7% 21% 33% 14%	2090
October	1st to 10th	Day	16% 3 5% 13% 34% 29%	3480
	11th to 20th	Day	25% 3 5% 22% 24% 21%	3434
	21st to end	Day	16% 2 3 25% 41% 13%	3214
November	1st to 10th	Day	20% 3 7% 18% 32% 20%	1763
	11th to 20th	Day	16% 4 5% 24% 34% 17%	1800
	21st to end	Day	25% 3 5% 16% 32% 20%	1800
December	1st to 10th	Day	23% 3 5% 32% 26% 12%	2940
	11th to 20th	Day	20% 3 6% 16% 38% 18%	3389
	21st to end	Day	29% 3 4 21% 31% 12%	4488
January	1st to 10th	Night	29% 3 6% 32% 23% 7%	5888
	11th to 20th	Night	17% 2 9% 19% 34% 19%	5900
	21st to end	Night	31% 4 6% 17% 29% 14%	6094
February	1st to 10th	Night	27% 3 7% 17% 29% 18%	2400
	11th to 20th	Night	28% 3 7% 21% 23% 17%	2338
	21st to end	Night	24% 3 5% 16% 26% 25%	1980
March	1st to 10th	Night	24% 3 3 13% 23% 34%	5374
	11th to 20th	Night	21% 3 6% 18% 17% 36%	5072
	21st to end	Night	23% 4 8% 22% 29% 15%	5428
April	1st to 10th	Night	21% 4 8% 18% 25% 24%	2000
	11th to 20th	Night	25% 5% 8% 17% 26% 19%	1977
	21st to end	Night	22% 4 10% 23% 26% 14%	1940
May	1st to 10th	Night	29% 4 10% 22% 18% 17%	4080
	11th to 20th	Night	22% 5% 7% 14% 24% 28%	4054
	21st to end	Night	29% 5% 10% 17% 15% 24%	4452
June	1st to 10th	Night	22% 6% 18% 29% 17% 8%	1800
	11th to 20th	Night	19% 6% 11% 25% 26% 13%	1800
	21st to end	Night	21% 4 12% 27% 21% 15%	1800
July	1st to 10th	Night	28% 6% 12% 32% 19% 4	2850
	11th to 20th	Night	20% 5% 11% 23% 32% 9%	2796
	21st to end	Night	18% 4 10% 24% 35% 10%	2999
August	1st to 10th	Night	15% 4 9% 26% 28% 19%	3007
	11th to 20th	Night	23% 5% 12% 20% 29% 11%	3143
	21st to end	Night	18% 5% 13% 26% 29% 10%	3487
September	1st to 10th	Night	26% 6% 10% 22% 23% 14%	1970
	11th to 20th	Night	31% 6% 11% 15% 28% 9%	2090
	21st to end	Night	19% 5% 7% 21% 30% 19%	2090
October	1st to 10th	Night	13% 2 6% 13% 31% 35%	3480
	11th to 20th	Night	24% 3 6% 17% 28% 22%	3460
	21st to end	Night	12% 2 4 22% 40% 20%	4327
November	1st to 10th	Night	17% 3 7% 22% 30% 22%	2535
	11th to 20th	Night	16% 2 5% 22% 35% 20%	2600
	21st to end	Night	23% 4 4 18% 31% 20%	2600
December	1st to 10th	Night	21% 2 6% 28% 32% 11%	4250
	11th to 20th	Night	18% 2 4 16% 41% 19%	4817
	21st to end	Night	25% 4 6% 25% 29% 12%	6490

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	10% 11% 33% 33% 11% 2	300
	11th to 20th	Day	13% 13% 28% 33% 12% 1	300
	21st to end	Day	7% 11% 37% 32% 12% 1	330
February	1st to 10th	Day	11% 12% 34% 33% 11%	300
	11th to 20th	Day	10% 10% 43% 24% 12% 1	300
	21st to end	Day	15% 15% 35% 28% 7% 1	249
March	1st to 10th	Day	11% 8% 42% 30% 9%	300
	11th to 20th	Day	16% 12% 36% 26% 7% 2	300
	21st to end	Day	11% 13% 35% 30% 10%	342
April	1st to 10th	Day	10% 17% 43% 22% 8%	500
	11th to 20th	Day	12% 16% 45% 22% 5%	492
	21st to end	Day	12% 16% 33% 28% 9% 2	556
May	1st to 10th	Day	11% 8% 37% 33% 10%	703
	11th to 20th	Day	12% 7% 29% 33% 16% 3	725
	21st to end	Day	9% 8% 32% 32% 17% 3	789
June	1st to 10th	Day	8% 4 21% 38% 25% 4	730
	11th to 20th	Day	6% 3 24% 40% 22% 4	730
	21st to end	Day	4 2 15% 40% 32% 7%	730
July	1st to 10th	Day	7% 1 7% 37% 34% 14%	697
	11th to 20th	Day	3 1 9% 34% 41% 13%	668
	21st to end	Day	2 4 34% 43% 16%	739
August	1st to 10th	Day	3 2 8% 37% 41% 9%	569
	11th to 20th	Day	4 1 9% 39% 31% 16%	477
	21st to end	Day	6% 1 8% 34% 37% 14%	539
September	1st to 10th	Day	7% 3 8% 35% 33% 14%	419
	11th to 20th	Day	5% 1 13% 38% 34% 10%	300
	21st to end	Day	11% 3 12% 28% 35% 11%	300
October	1st to 10th	Day	7% 2 24% 33% 26% 8%	300
	11th to 20th	Day	7% 5% 24% 34% 26% 4	300
	21st to end	Day	15% 6% 27% 26% 22% 4	330
November	1st to 10th	Day	14% 6% 30% 28% 17% 4	300
	11th to 20th	Day	7% 10% 28% 34% 16% 5%	300
	21st to end	Day	15% 11% 30% 23% 17% 4	300
December	1st to 10th	Day	8% 7% 40% 30% 15% 1	300
	11th to 20th	Day	6% 9% 32% 39% 13% 1	300
	21st to end	Day	14% 14% 36% 26% 8% 1	330
January	1st to 10th	Night	7% 8% 35% 40% 10%	1000
	11th to 20th	Night	9% 9% 34% 40% 9%	1000
	21st to end	Night	7% 9% 33% 43% 7% 1	925
February	1st to 10th	Night	10% 9% 35% 39% 7% 1	800
	11th to 20th	Night	9% 10% 40% 35% 5%	784
	21st to end	Night	11% 11% 38% 37% 4	660
March	1st to 10th	Night	9% 13% 41% 33% 5%	800
	11th to 20th	Night	12% 13% 37% 30% 8%	640
	21st to end	Night	6% 15% 45% 31% 4	660
April	1st to 10th	Night	7% 13% 43% 34% 3	600
	11th to 20th	Night	10% 11% 50% 27% 2	593
	21st to end	Night	10% 9% 43% 34% 4	600
May	1st to 10th	Night	11% 8% 43% 34% 5%	600
	11th to 20th	Night	10% 6% 32% 39% 11% 1	591
	21st to end	Night	8% 6% 37% 38% 10% 1	650
June	1st to 10th	Night	6% 3 29% 45% 17%	600
	11th to 20th	Night	4 3 39% 45% 10%	600
	21st to end	Night	5% 2 23% 48% 22% 1	600
July	1st to 10th	Night	5% 2 12% 46% 32% 2	570
	11th to 20th	Night	4 12% 48% 34% 1	552
	21st to end	Night	3 1 5% 47% 43% 2	624
August	1st to 10th	Night	3 1 8% 49% 38% 1	567
	11th to 20th	Night	7% 2 9% 45% 36% 1	564
	21st to end	Night	4 1 8% 42% 42% 2	627
September	1st to 10th	Night	6% 2 10% 46% 33% 2	570
	11th to 20th	Night	12% 2 14% 43% 28% 1	570
	21st to end	Night	6% 2 19% 44% 28% 2	570
October	1st to 10th	Night	10% 4 24% 42% 19% 1	570
	11th to 20th	Night	10% 4 31% 43% 12%	570
	21st to end	Night	8% 8% 30% 36% 18% 1	955
November	1st to 10th	Night	8% 6% 29% 43% 13% 1	975
	11th to 20th	Night	6% 8% 33% 40% 12% 1	1000
	21st to end	Night	9% 8% 33% 38% 12% 1	1000
December	1st to 10th	Night	10% 6% 31% 44% 9%	1000
	11th to 20th	Night	10% 8% 36% 39% 7%	1000
	21st to end	Night	11% 7% 35% 39% 7%	1100

Page generated at 2025-07-03 00:30:17. Version ac07

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