Castle Rock
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Castle Rock clear sky chart from 2005-11-06 to 2024-12-24.

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 5% 2 5% 4 4 4 4 6% 8% 53%	105544
	Night	4 6% 2 5% 3 3 4 3 5% 7% 56%	103281
Transparency	Day	25% 8% 12% 22% 23% 11%	105288
	Night	24% 7% 12% 24% 24% 9%	103127
Seeing	Day	7% 9% 28% 31% 19% 6%	15714
	Night	6% 4 32% 43% 14% 1	25808

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	1 4 2 7% 3 3 3 2 6% 8% 61%	2538
	11th to 20th	Day	2 8% 3 7% 4 4 4 3 5% 6% 53%	2613
	21st to end	Day	2 6% 3 5% 4 3 3 3 5% 7% 58%	3146
February	1st to 10th	Day	2 9% 3 7% 3 4 4 2 5% 7% 55%	1710
	11th to 20th	Day	1 4 2 5% 3 4 4 4 6% 8% 59%	1849
	21st to end	Day	1 8% 3 5% 3 3 3 4 5% 5% 59%	1570
March	1st to 10th	Day	2 10% 3 6% 4 3 3 3 5% 6% 56%	3130
	11th to 20th	Day	4 12% 3 6% 4 4 4 4 5% 6% 48%	3421
	21st to end	Day	3 8% 2 4 4 4 4 4 6% 8% 53%	4072
April	1st to 10th	Day	6% 8% 2 5% 4 3 4 4 6% 6% 53%	2280
	11th to 20th	Day	7% 9% 3 6% 4 4 4 4 5% 7% 46%	2251
	21st to end	Day	8% 8% 2 6% 4 3 5% 5% 6% 9% 44%	2280
May	1st to 10th	Day	8% 7% 3 7% 5% 5% 5% 5% 7% 8% 42%	4010
	11th to 20th	Day	10% 7% 2 5% 4 5% 5% 5% 7% 9% 42%	4320
	21st to end	Day	5% 5% 2 5% 4 4 5% 5% 8% 9% 49%	4825
June	1st to 10th	Day	5% 4 2 4 4 4 5% 5% 8% 10% 50%	2660
	11th to 20th	Day	5% 4 1 4 3 5% 5% 6% 8% 9% 51%	2660
	21st to end	Day	4 4 2 4 4 5% 6% 6% 8% 10% 48%	2660
July	1st to 10th	Day	5% 4 1 4 3 4 5% 4 6% 8% 56%	4430
	11th to 20th	Day	3 3 1 5% 4 5% 6% 5% 9% 11% 48%	4430
	21st to end	Day	5% 4 1 5% 4 5% 5% 5% 7% 8% 52%	4718
August	1st to 10th	Day	8% 5% 2 6% 5% 6% 7% 5% 8% 9% 39%	4045
	11th to 20th	Day	3 3 1 5% 4 6% 6% 5% 9% 8% 49%	3726
	21st to end	Day	4 4 2 5% 4 5% 6% 5% 8% 10% 50%	4180
September	1st to 10th	Day	4 4 1 4 3 4 4 4 5% 8% 58%	2280
	11th to 20th	Day	6% 4 1 3 3 3 4 3 6% 7% 59%	2247
	21st to end	Day	5% 3 1 4 2 2 3 3 4 6% 65%	2090
October	1st to 10th	Day	3 3 1 3 2 2 2 2 3 5% 74%	3218
	11th to 20th	Day	3 4 2 4 3 3 3 3 4 8% 61%	3150
	21st to end	Day	4 6% 1 3 2 2 3 2 4 5% 67%	3314
November	1st to 10th	Day	2 5% 2 3 2 3 3 2 6% 8% 64%	1763
	11th to 20th	Day	2 6% 2 4 3 3 3 3 4 7% 64%	1800
	21st to end	Day	3 6% 2 5% 3 3 2 3 4 7% 63%	1734
December	1st to 10th	Day	1 7% 2 5% 3 3 3 3 6% 8% 60%	1600
	11th to 20th	Day	2 4 2 5% 4 3 3 3 5% 8% 59%	2006
	21st to end	Day	1 7% 4 8% 4 4 4 4 5% 6% 53%	2818
January	1st to 10th	Night	1 8% 4 7% 3 3 3 3 5% 8% 55%	4417
	11th to 20th	Night	1 4 2 6% 4 4 3 3 5% 8% 60%	4384
	21st to end	Night	2 6% 3 7% 4 4 3 4 4 6% 58%	4521
February	1st to 10th	Night	1 7% 3 7% 4 3 4 3 5% 7% 56%	2468
	11th to 20th	Night	1 8% 3 7% 5% 3 3 3 5% 7% 54%	2218
	21st to end	Night	2 7% 2 6% 4 3 2 2 4 6% 62%	1884
March	1st to 10th	Night	3 8% 3 4 3 3 3 3 5% 6% 60%	3734
	11th to 20th	Night	7% 11% 3 5% 3 3 3 2 5% 6% 52%	3552
	21st to end	Night	3 8% 2 5% 3 4 4 3 6% 8% 52%	3573
April	1st to 10th	Night	5% 9% 2 4 3 3 3 3 5% 7% 56%	1900
	11th to 20th	Night	10% 10% 3 4 3 3 4 3 5% 5% 51%	1877
	21st to end	Night	11% 10% 2 5% 3 3 4 3 5% 6% 49%	1900
May	1st to 10th	Night	10% 8% 3 5% 4 4 3 4 5% 7% 47%	2956
	11th to 20th	Night	10% 6% 2 6% 4 3 4 3 6% 8% 46%	2581
	21st to end	Night	7% 5% 1 4 3 3 4 4 6% 8% 55%	2762
June	1st to 10th	Night	5% 2 1 4 3 3 4 4 7% 10% 57%	1520
	11th to 20th	Night	5% 3 1 3 3 3 2 4 6% 10% 59%	1520
	21st to end	Night	4 3 2 4 4 4 4 4 8% 10% 54%	1520
July	1st to 10th	Night	4 5% 2 4 4 4 4 4 6% 7% 56%	2540
	11th to 20th	Night	2 3 1 5% 4 4 4 5% 8% 11% 53%	2540
	21st to end	Night	4 3 1 4 4 4 4 4 8% 9% 55%	2842
August	1st to 10th	Night	6% 5% 3 6% 5% 5% 7% 6% 8% 9% 40%	2894
	11th to 20th	Night	4 4 2 5% 4 4 6% 5% 8% 11% 48%	3113
	21st to end	Night	3 4 1 4 4 4 5% 5% 8% 10% 50%	3487
September	1st to 10th	Night	6% 4 1 4 4 3 4 5% 6% 8% 54%	1900
	11th to 20th	Night	5% 2 1 4 3 3 4 3 5% 7% 63%	1932
	21st to end	Night	6% 3 1 4 3 3 3 2 4 7% 63%	2090
October	1st to 10th	Night	4 4 1 3 2 3 3 2 4 5% 69%	3734
	11th to 20th	Night	7% 4 2 5% 3 2 3 3 5% 8% 58%	3778
	21st to end	Night	3 7% 2 4 2 2 3 2 3 5% 67%	4211
November	1st to 10th	Night	2 4 2 4 4 3 3 3 5% 6% 66%	2535
	11th to 20th	Night	2 5% 1 4 3 3 3 2 4 6% 66%	2600
	21st to end	Night	3 7% 2 5% 3 3 3 2 4 7% 61%	2665
December	1st to 10th	Night	1 5% 2 5% 3 3 3 3 5% 7% 63%	2800
	11th to 20th	Night	1 6% 2 5% 3 3 4 3 5% 8% 59%	3411
	21st to end	Night	3 8% 3 7% 4 4 4 3 5% 7% 53%	4922

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	19% 6% 12% 31% 24% 8%	2539
	11th to 20th	Day	25% 8% 13% 29% 18% 6%	2613
	21st to end	Day	23% 7% 12% 29% 24% 6%	3146
February	1st to 10th	Day	29% 5% 11% 27% 19% 9%	1710
	11th to 20th	Day	21% 7% 10% 26% 28% 7%	1859
	21st to end	Day	25% 5% 9% 21% 26% 14%	1570
March	1st to 10th	Day	24% 7% 8% 20% 28% 13%	3130
	11th to 20th	Day	29% 11% 14% 27% 15% 4	3421
	21st to end	Day	25% 9% 14% 27% 21% 4	4072
April	1st to 10th	Day	28% 7% 13% 22% 21% 9%	2280
	11th to 20th	Day	33% 8% 12% 20% 18% 8%	2254
	21st to end	Day	33% 9% 13% 22% 20% 3	2280
May	1st to 10th	Day	31% 11% 12% 25% 15% 7%	4010
	11th to 20th	Day	32% 11% 14% 23% 17% 3	4324
	21st to end	Day	23% 13% 13% 22% 20% 8%	4825
June	1st to 10th	Day	26% 10% 16% 22% 17% 10%	2660
	11th to 20th	Day	25% 9% 12% 17% 21% 16%	2660
	21st to end	Day	26% 9% 13% 18% 22% 13%	2660
July	1st to 10th	Day	23% 9% 10% 14% 29% 17%	4361
	11th to 20th	Day	24% 9% 11% 21% 22% 12%	4355
	21st to end	Day	26% 9% 12% 18% 18% 18%	4569
August	1st to 10th	Day	35% 11% 16% 20% 12% 5%	4031
	11th to 20th	Day	26% 8% 14% 17% 20% 14%	3762
	21st to end	Day	25% 9% 13% 18% 24% 11%	4179
September	1st to 10th	Day	23% 6% 9% 21% 23% 17%	2280
	11th to 20th	Day	22% 6% 11% 17% 27% 17%	2247
	21st to end	Day	20% 5% 8% 20% 34% 13%	2090
October	1st to 10th	Day	14% 4 6% 15% 36% 24%	3218
	11th to 20th	Day	22% 4 8% 24% 34% 8%	3150
	21st to end	Day	19% 3 7% 20% 38% 13%	3314
November	1st to 10th	Day	18% 5% 10% 23% 28% 16%	1763
	11th to 20th	Day	20% 5% 8% 24% 33% 11%	1800
	21st to end	Day	22% 4 9% 22% 29% 15%	1734
December	1st to 10th	Day	22% 6% 12% 28% 23% 9%	1600
	11th to 20th	Day	22% 6% 12% 22% 29% 9%	2004
	21st to end	Day	26% 9% 11% 23% 23% 9%	2818
January	1st to 10th	Night	24% 7% 11% 26% 28% 4	4417
	11th to 20th	Night	18% 8% 14% 26% 22% 10%	4384
	21st to end	Night	25% 8% 11% 32% 19% 6%	4521
February	1st to 10th	Night	27% 5% 11% 27% 23% 8%	2468
	11th to 20th	Night	28% 5% 11% 27% 22% 8%	2218
	21st to end	Night	23% 4 7% 25% 27% 13%	1884
March	1st to 10th	Night	22% 6% 8% 20% 33% 10%	3734
	11th to 20th	Night	31% 8% 14% 20% 24% 4	3552
	21st to end	Night	25% 10% 13% 30% 20% 3	3573
April	1st to 10th	Night	27% 7% 11% 22% 22% 10%	1900
	11th to 20th	Night	33% 7% 11% 25% 18% 7%	1877
	21st to end	Night	35% 7% 12% 24% 18% 4	1900
May	1st to 10th	Night	31% 10% 14% 24% 13% 9%	2956
	11th to 20th	Night	32% 11% 16% 25% 12% 5%	2582
	21st to end	Night	22% 11% 20% 23% 17% 6%	2762
June	1st to 10th	Night	20% 9% 20% 28% 15% 8%	1520
	11th to 20th	Night	19% 7% 15% 21% 22% 15%	1520
	21st to end	Night	22% 9% 12% 23% 23% 9%	1520
July	1st to 10th	Night	25% 9% 13% 17% 29% 7%	2500
	11th to 20th	Night	21% 9% 17% 28% 19% 6%	2492
	21st to end	Night	21% 9% 16% 23% 18% 14%	2753
August	1st to 10th	Night	36% 10% 17% 23% 11% 3	2885
	11th to 20th	Night	27% 11% 18% 19% 17% 7%	3143
	21st to end	Night	24% 9% 16% 26% 21% 4	3487
September	1st to 10th	Night	24% 7% 11% 22% 24% 12%	1900
	11th to 20th	Night	19% 6% 12% 23% 25% 15%	1932
	21st to end	Night	21% 5% 9% 23% 31% 11%	2090
October	1st to 10th	Night	16% 6% 7% 20% 32% 18%	3734
	11th to 20th	Night	23% 6% 10% 26% 26% 9%	3778
	21st to end	Night	21% 3 7% 25% 31% 14%	4211
November	1st to 10th	Night	18% 4 10% 23% 29% 15%	2535
	11th to 20th	Night	19% 4 9% 26% 31% 12%	2600
	21st to end	Night	24% 4 8% 22% 30% 11%	2665
December	1st to 10th	Night	21% 6% 12% 27% 26% 9%	2800
	11th to 20th	Night	22% 6% 11% 23% 31% 7%	3412
	21st to end	Night	28% 7% 11% 23% 23% 8%	4922

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	5% 7% 33% 34% 18% 3	270
	11th to 20th	Day	7% 10% 33% 40% 9% 1	270
	21st to end	Day	4 10% 36% 36% 12% 2	297
February	1st to 10th	Day	3 11% 49% 29% 7% 1	270
	11th to 20th	Day	2 10% 46% 32% 10% 1	270
	21st to end	Day	3 18% 43% 28% 8% 1	225
March	1st to 10th	Day	4 10% 38% 31% 14% 3	270
	11th to 20th	Day	10% 17% 35% 25% 10% 3	417
	21st to end	Day	12% 23% 32% 23% 9% 1	506
April	1st to 10th	Day	11% 17% 37% 23% 10% 2	460
	11th to 20th	Day	12% 26% 31% 21% 8% 2	452
	21st to end	Day	16% 14% 34% 23% 12% 1	460
May	1st to 10th	Day	13% 15% 34% 25% 10% 2	582
	11th to 20th	Day	14% 10% 26% 29% 17% 4	675
	21st to end	Day	9% 12% 28% 28% 17% 6%	734
June	1st to 10th	Day	6% 6% 23% 32% 24% 9%	680
	11th to 20th	Day	6% 9% 27% 34% 21% 4	680
	21st to end	Day	5% 5% 27% 34% 23% 6%	680
July	1st to 10th	Day	7% 3 17% 31% 34% 9%	671
	11th to 20th	Day	4 2 15% 31% 38% 10%	668
	21st to end	Day	6% 2 15% 28% 37% 12%	691
August	1st to 10th	Day	9% 3 19% 32% 25% 12%	487
	11th to 20th	Day	4 4 21% 34% 26% 11%	477
	21st to end	Day	6% 3 24% 33% 27% 7%	539
September	1st to 10th	Day	6% 4 23% 33% 24% 10%	490
	11th to 20th	Day	6% 5% 25% 31% 25% 8%	457
	21st to end	Day	5% 8% 20% 30% 24% 14%	300
October	1st to 10th	Day	8% 9% 19% 27% 24% 13%	300
	11th to 20th	Day	2 8% 28% 35% 20% 7%	300
	21st to end	Day	8% 11% 28% 35% 14% 4	330
November	1st to 10th	Day	5% 12% 29% 33% 17% 4	300
	11th to 20th	Day	5% 8% 27% 45% 13% 3	300
	21st to end	Day	7% 9% 33% 38% 11% 3	300
December	1st to 10th	Day	4 10% 36% 31% 16% 3	300
	11th to 20th	Day	6% 7% 40% 36% 11%	300
	21st to end	Day	4 10% 38% 36% 10% 2	306
January	1st to 10th	Night	3 5% 37% 43% 11% 2	950
	11th to 20th	Night	3 4 41% 42% 8% 2	917
	21st to end	Night	3 2 37% 47% 10% 1	836
February	1st to 10th	Night	4 5% 46% 40% 6% 1	760
	11th to 20th	Night	5% 6% 42% 40% 7%	744
	21st to end	Night	5% 6% 48% 39% 3	628
March	1st to 10th	Night	5% 5% 44% 38% 7%	760
	11th to 20th	Night	9% 5% 32% 43% 9% 1	760
	21st to end	Night	8% 6% 40% 39% 6%	684
April	1st to 10th	Night	9% 7% 44% 35% 4	570
	11th to 20th	Night	15% 10% 34% 33% 8%	563
	21st to end	Night	15% 9% 32% 35% 8%	570
May	1st to 10th	Night	13% 8% 30% 39% 9% 1	570
	11th to 20th	Night	16% 4 22% 42% 14% 1	561
	21st to end	Night	9% 5% 30% 40% 14% 1	617
June	1st to 10th	Night	5% 4 22% 47% 20% 2	570
	11th to 20th	Night	6% 3 27% 48% 15% 1	570
	21st to end	Night	4 2 23% 49% 21% 1	570
July	1st to 10th	Night	6% 1 16% 45% 29% 3	555
	11th to 20th	Night	3 1 17% 43% 33% 4	552
	21st to end	Night	6% 1 11% 45% 35% 1	624
August	1st to 10th	Night	7% 1 13% 46% 30% 2	567
	11th to 20th	Night	5% 3 17% 53% 21% 2	564
	21st to end	Night	6% 2 17% 48% 25% 2	627
September	1st to 10th	Night	7% 2 18% 45% 25% 3	570
	11th to 20th	Night	6% 2 22% 45% 23% 2	570
	21st to end	Night	7% 2 23% 47% 18% 2	570
October	1st to 10th	Night	9% 3 28% 42% 16% 2	720
	11th to 20th	Night	4 3 31% 45% 16% 2	760
	21st to end	Night	8% 4 29% 42% 15% 2	891
November	1st to 10th	Night	3 5% 33% 45% 14% 1	975
	11th to 20th	Night	4 6% 36% 45% 9% 1	1000
	21st to end	Night	6% 6% 32% 43% 12% 1	1000
December	1st to 10th	Night	3 3 39% 45% 10%	1000
	11th to 20th	Night	5% 4 41% 39% 11% 1	1000
	21st to end	Night	6% 5% 40% 42% 6% 1	1063

Page generated at 2024-12-21 02:13:50. Version ac07

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