Robber's Cave State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Robber's Cave State Park clear sky chart from 2005-11-06 to 2026-01-02.

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	11% 6% 2 6% 4 4 4 3 5% 7% 48%	127422
	Night	11% 6% 2 5% 3 3 3 3 5% 6% 53%	124204
Transparency	Day	35% 5% 10% 25% 20% 5%	131060
	Night	32% 4 9% 24% 23% 8%	128629
Seeing	Day	15% 12% 27% 27% 15% 3	16897
	Night	15% 12% 26% 31% 15% 2	26782

By Month

Percentage Cloud Cover SE (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	13% 12% 5% 6% 3 3 2 2 4 5% 46%	4086
	11th to 20th	Day	6% 6% 3 6% 4 3 3 3 4 5% 58%	4080
	21st to end	Day	20% 9% 2 4 2 2 2 2 3 4 48%	4488
February	1st to 10th	Day	18% 11% 3 6% 4 4 3 3 3 4 41%	1800
	11th to 20th	Day	14% 10% 3 7% 4 3 4 3 4 5% 42%	1880
	21st to end	Day	17% 10% 4 6% 3 3 3 2 4 5% 43%	1745
March	1st to 10th	Day	14% 8% 3 6% 3 3 4 3 3 4 50%	4936
	11th to 20th	Day	9% 6% 2 5% 4 4 4 3 4 6% 52%	4980
	21st to end	Day	14% 9% 3 6% 4 4 4 4 5% 7% 39%	5462
April	1st to 10th	Day	13% 6% 3 5% 4 4 5% 3 4 7% 46%	2230
	11th to 20th	Day	16% 7% 2 6% 4 4 4 2 5% 5% 46%	2374
	21st to end	Day	18% 8% 3 7% 5% 4 4 3 4 5% 40%	2463
May	1st to 10th	Day	17% 9% 3 7% 4 3 4 4 5% 6% 39%	5862
	11th to 20th	Day	12% 6% 2 7% 5% 5% 5% 3 5% 7% 42%	5862
	21st to end	Day	16% 7% 3 8% 5% 5% 4 4 5% 7% 36%	6434
June	1st to 10th	Day	9% 5% 2 6% 4 4 5% 5% 7% 8% 45%	2600
	11th to 20th	Day	7% 5% 2 6% 5% 3 5% 5% 6% 9% 47%	2600
	21st to end	Day	3 4 1 4 4 4 4 4 6% 9% 57%	2600
July	1st to 10th	Day	7% 5% 2 7% 5% 5% 6% 5% 8% 10% 41%	5900
	11th to 20th	Day	4 4 1 5% 4 3 4 4 6% 9% 57%	5900
	21st to end	Day	4 3 1 4 4 4 5% 4 8% 9% 52%	6422
August	1st to 10th	Day	3 3 2 5% 4 4 4 4 6% 8% 58%	4234
	11th to 20th	Day	8% 4 2 4 3 4 4 4 6% 9% 51%	4171
	21st to end	Day	5% 3 1 5% 4 5% 5% 4 7% 8% 52%	4330
September	1st to 10th	Day	10% 5% 2 5% 4 4 4 4 4 7% 52%	2292
	11th to 20th	Day	11% 4 2 5% 4 3 5% 4 5% 8% 48%	2200
	21st to end	Day	8% 3 2 4 4 4 5% 4 5% 7% 56%	2200
October	1st to 10th	Day	6% 4 1 5% 3 3 3 2 5% 6% 58%	2040
	11th to 20th	Day	11% 5% 2 5% 2 3 2 2 3 5% 61%	2000
	21st to end	Day	17% 7% 1 5% 3 3 3 2 3 5% 52%	2200
November	1st to 10th	Day	9% 6% 2 4 3 2 3 3 4 6% 57%	2058
	11th to 20th	Day	10% 5% 1 5% 2 3 3 2 3 5% 60%	2005
	21st to end	Day	14% 7% 3 4 4 3 3 2 5% 6% 50%	1890
December	1st to 10th	Day	14% 7% 3 5% 3 2 2 3 4 5% 52%	3030
	11th to 20th	Day	15% 8% 2 6% 4 3 3 3 4 6% 46%	3481
	21st to end	Day	17% 12% 4 8% 4 4 4 3 4 4 37%	4587
January	1st to 10th	Night	14% 7% 3 9% 4 3 3 3 4 6% 46%	5902
	11th to 20th	Night	7% 5% 2 5% 4 3 3 2 3 5% 61%	5900
	21st to end	Night	21% 9% 3 4 2 2 3 2 4 4 47%	6490
February	1st to 10th	Night	14% 10% 2 6% 3 3 3 3 5% 6% 46%	2600
	11th to 20th	Night	15% 8% 3 7% 4 4 3 3 4 5% 45%	2424
	21st to end	Night	13% 10% 3 6% 3 2 2 3 4 5% 49%	1883
March	1st to 10th	Night	18% 9% 2 6% 3 3 3 2 4 5% 47%	4919
	11th to 20th	Night	9% 7% 2 4 3 3 3 3 4 6% 57%	4980
	21st to end	Night	12% 7% 3 7% 4 4 4 3 5% 7% 44%	5467
April	1st to 10th	Night	12% 6% 2 5% 4 3 3 3 4 6% 50%	2170
	11th to 20th	Night	12% 7% 3 4 3 3 3 3 5% 7% 51%	1975
	21st to end	Night	14% 6% 2 5% 3 3 4 4 4 8% 47%	1932
May	1st to 10th	Night	14% 8% 3 6% 5% 3 3 3 5% 7% 43%	4053
	11th to 20th	Night	11% 5% 2 6% 4 4 5% 3 6% 8% 45%	4053
	21st to end	Night	14% 7% 2 5% 4 4 5% 3 5% 8% 44%	4443
June	1st to 10th	Night	5% 4 2 4 3 4 4 3 6% 10% 56%	1800
	11th to 20th	Night	5% 4 1 5% 3 3 3 4 6% 8% 59%	1800
	21st to end	Night	2 3 1 3 2 3 3 3 5% 9% 67%	1800
July	1st to 10th	Night	7% 4 2 6% 4 4 4 5% 7% 10% 46%	4078
	11th to 20th	Night	4 3 1 3 2 2 3 3 5% 8% 66%	4077
	21st to end	Night	3 2 1 4 3 3 4 4 6% 10% 61%	4449
August	1st to 10th	Night	1 2 1 3 3 3 4 3 6% 8% 65%	2926
	11th to 20th	Night	3 3 2 4 3 3 4 4 6% 8% 61%	2888
	21st to end	Night	3 3 1 4 3 3 4 4 6% 8% 61%	3554
September	1st to 10th	Night	8% 5% 2 4 3 3 3 3 5% 6% 58%	2103
	11th to 20th	Night	9% 5% 2 4 3 3 5% 4 6% 7% 52%	2200
	21st to end	Night	7% 4 2 4 3 4 3 3 5% 6% 59%	2200
October	1st to 10th	Night	5% 4 1 4 3 2 4 3 5% 6% 63%	2338
	11th to 20th	Night	11% 4 1 4 3 3 3 2 3 4 63%	2400
	21st to end	Night	17% 6% 2 4 3 3 2 2 3 4 55%	2640
November	1st to 10th	Night	11% 4 2 5% 3 2 3 3 3 5% 60%	2460
	11th to 20th	Night	8% 5% 2 5% 3 2 3 3 4 5% 60%	2611
	21st to end	Night	13% 7% 2 4 3 3 2 3 4 6% 53%	2730
December	1st to 10th	Night	10% 8% 3 6% 3 3 3 2 4 5% 53%	4380
	11th to 20th	Night	15% 7% 3 6% 3 3 2 2 3 4 52%	4946
	21st to end	Night	16% 11% 4 7% 3 3 3 2 4 4 43%	6633

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	43% 2 9% 24% 20% 2	4087
	11th to 20th	Day	29% 3 10% 25% 30% 4	4080
	21st to end	Day	41% 3 4 20% 25% 6%	4488
February	1st to 10th	Day	49% 3 8% 17% 19% 4	1800
	11th to 20th	Day	46% 3 7% 23% 17% 4	1889
	21st to end	Day	45% 3 5% 16% 23% 8%	1745
March	1st to 10th	Day	40% 3 6% 16% 18% 18%	4936
	11th to 20th	Day	33% 4 8% 18% 19% 17%	4980
	21st to end	Day	45% 4 9% 27% 14% 1	5464
April	1st to 10th	Day	39% 4 10% 20% 20% 6%	2230
	11th to 20th	Day	41% 4 9% 23% 18% 5%	2374
	21st to end	Day	47% 5% 8% 20% 18% 3	2463
May	1st to 10th	Day	46% 5% 10% 23% 15% 1	5900
	11th to 20th	Day	41% 6% 11% 21% 19% 3	5866
	21st to end	Day	47% 6% 11% 18% 16% 3	6447
June	1st to 10th	Day	34% 8% 15% 27% 14% 2	2600
	11th to 20th	Day	32% 7% 13% 27% 20% 2	2600
	21st to end	Day	24% 7% 14% 29% 22% 3	2600
July	1st to 10th	Day	35% 7% 16% 29% 11% 1	5836
	11th to 20th	Day	24% 6% 13% 36% 20% 1	5831
	21st to end	Day	24% 8% 15% 37% 16%	6240
August	1st to 10th	Day	23% 5% 13% 28% 27% 4	4220
	11th to 20th	Day	29% 6% 16% 32% 15% 2	4210
	21st to end	Day	27% 7% 13% 37% 14% 2	4329
September	1st to 10th	Day	33% 5% 8% 24% 21% 9%	2292
	11th to 20th	Day	32% 6% 11% 24% 20% 7%	2200
	21st to end	Day	28% 5% 8% 24% 29% 8%	2200
October	1st to 10th	Day	17% 3 7% 11% 39% 24%	3326
	11th to 20th	Day	19% 2 4 18% 39% 18%	3240
	21st to end	Day	30% 3 6% 29% 25% 7%	3538
November	1st to 10th	Day	29% 3 8% 25% 27% 7%	2058
	11th to 20th	Day	29% 3 8% 26% 25% 9%	2005
	21st to end	Day	36% 3 7% 23% 26% 5%	1890
December	1st to 10th	Day	37% 2 7% 34% 17% 3	3030
	11th to 20th	Day	40% 3 4 23% 25% 5%	3479
	21st to end	Day	49% 4 6% 21% 17% 3	4587
January	1st to 10th	Night	41% 3 8% 25% 20% 3	5902
	11th to 20th	Night	27% 3 11% 19% 33% 8%	5900
	21st to end	Night	42% 3 6% 16% 28% 6%	6490
February	1st to 10th	Night	40% 4 9% 23% 18% 6%	2600
	11th to 20th	Night	43% 3 5% 23% 20% 5%	2425
	21st to end	Night	38% 3 6% 19% 24% 10%	1883
March	1st to 10th	Night	42% 3 5% 16% 21% 13%	4919
	11th to 20th	Night	29% 3 7% 23% 19% 19%	4980
	21st to end	Night	40% 5% 10% 23% 19% 3	5467
April	1st to 10th	Night	36% 4 10% 20% 19% 11%	2170
	11th to 20th	Night	34% 4 8% 24% 20% 10%	1975
	21st to end	Night	37% 5% 10% 25% 21% 3	1932
May	1st to 10th	Night	41% 5% 13% 22% 15% 4	4080
	11th to 20th	Night	34% 7% 13% 23% 20% 4	4054
	21st to end	Night	38% 7% 15% 20% 16% 4	4452
June	1st to 10th	Night	24% 5% 15% 32% 20% 3	1800
	11th to 20th	Night	21% 6% 13% 31% 24% 4	1800
	21st to end	Night	16% 4 15% 31% 28% 5%	1800
July	1st to 10th	Night	31% 8% 17% 27% 14% 3	4035
	11th to 20th	Night	17% 5% 13% 35% 27% 2	4026
	21st to end	Night	18% 6% 18% 37% 19% 2	4320
August	1st to 10th	Night	16% 4 13% 27% 31% 8%	2916
	11th to 20th	Night	20% 5% 17% 35% 20% 3	2915
	21st to end	Night	20% 5% 13% 38% 21% 3	3554
September	1st to 10th	Night	26% 4 9% 27% 23% 11%	2103
	11th to 20th	Night	30% 6% 10% 24% 23% 8%	2200
	21st to end	Night	25% 5% 7% 24% 30% 10%	2200
October	1st to 10th	Night	14% 3 6% 14% 34% 30%	3819
	11th to 20th	Night	20% 2 4 14% 41% 19%	3899
	21st to end	Night	29% 2 4 29% 25% 11%	4252
November	1st to 10th	Night	29% 3 7% 24% 27% 10%	2460
	11th to 20th	Night	27% 3 8% 25% 26% 11%	2611
	21st to end	Night	34% 3 7% 21% 28% 7%	2730
December	1st to 10th	Night	35% 3 6% 31% 21% 4	4380
	11th to 20th	Night	39% 2 4 21% 23% 11%	4947
	21st to end	Night	45% 4 7% 20% 19% 5%	6633

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	25% 21% 33% 15% 5%	303
	11th to 20th	Day	24% 28% 35% 12% 2	300
	21st to end	Day	23% 25% 34% 13% 5%	330
February	1st to 10th	Day	28% 24% 36% 9% 4	300
	11th to 20th	Day	32% 26% 31% 7% 3	300
	21st to end	Day	35% 25% 25% 12% 2	249
March	1st to 10th	Day	23% 26% 34% 15% 2	300
	11th to 20th	Day	30% 29% 29% 10% 2	300
	21st to end	Day	28% 28% 33% 10% 2	330
April	1st to 10th	Day	22% 29% 35% 10% 4 1	330
	11th to 20th	Day	28% 21% 33% 14% 5%	492
	21st to end	Day	25% 20% 32% 16% 6% 1	563
May	1st to 10th	Day	18% 14% 42% 20% 5%	703
	11th to 20th	Day	17% 13% 34% 25% 10% 1	725
	21st to end	Day	14% 10% 36% 23% 13% 3	789
June	1st to 10th	Day	11% 5% 25% 35% 19% 5%	730
	11th to 20th	Day	9% 5% 26% 37% 19% 4	730
	21st to end	Day	3 4 28% 40% 21% 4	730
July	1st to 10th	Day	8% 3 18% 38% 26% 8%	721
	11th to 20th	Day	4 2 17% 42% 28% 7%	718
	21st to end	Day	4 1 11% 42% 32% 9%	794
August	1st to 10th	Day	6% 2 16% 44% 27% 5%	726
	11th to 20th	Day	10% 2 15% 41% 27% 5%	715
	21st to end	Day	8% 1 10% 36% 34% 11%	601
September	1st to 10th	Day	8% 3 11% 39% 31% 8%	422
	11th to 20th	Day	6% 2 23% 37% 25% 8%	330
	21st to end	Day	14% 6% 22% 32% 20% 6%	330
October	1st to 10th	Day	5% 8% 31% 36% 15% 4	330
	11th to 20th	Day	13% 13% 38% 28% 8% 1	330
	21st to end	Day	31% 13% 31% 20% 5% 1	363
November	1st to 10th	Day	16% 15% 40% 20% 7% 1	330
	11th to 20th	Day	17% 20% 37% 19% 5% 1	330
	21st to end	Day	25% 21% 37% 13% 4 1	330
December	1st to 10th	Day	24% 22% 32% 17% 4 1	330
	11th to 20th	Day	26% 20% 35% 14% 4	330
	21st to end	Day	25% 22% 35% 13% 5%	363
January	1st to 10th	Night	17% 19% 31% 26% 6%	1006
	11th to 20th	Night	19% 20% 32% 25% 4	1000
	21st to end	Night	17% 18% 31% 29% 4	1100
February	1st to 10th	Night	22% 19% 32% 23% 5%	1000
	11th to 20th	Night	23% 19% 33% 22% 3	870
	21st to end	Night	25% 18% 30% 25% 2	563
March	1st to 10th	Night	21% 16% 28% 31% 4	600
	11th to 20th	Night	22% 16% 34% 24% 5%	600
	21st to end	Night	19% 18% 33% 24% 6%	660
April	1st to 10th	Night	17% 21% 32% 26% 5%	600
	11th to 20th	Night	18% 17% 32% 25% 8%	593
	21st to end	Night	19% 12% 35% 24% 9% 1	600
May	1st to 10th	Night	12% 14% 32% 35% 8%	600
	11th to 20th	Night	14% 9% 27% 34% 15% 1	591
	21st to end	Night	13% 8% 30% 29% 19% 2	650
June	1st to 10th	Night	6% 4 17% 38% 32% 3	600
	11th to 20th	Night	7% 3 27% 41% 21% 1	600
	21st to end	Night	3 1 22% 41% 30% 5%	600
July	1st to 10th	Night	6% 1 12% 39% 37% 6%	585
	11th to 20th	Night	3 1 13% 42% 36% 5%	582
	21st to end	Night	3 2 9% 42% 39% 5%	657
August	1st to 10th	Night	3 1 15% 43% 35% 3	597
	11th to 20th	Night	5% 1 12% 39% 38% 5%	594
	21st to end	Night	6% 2 10% 37% 40% 5%	660
September	1st to 10th	Night	9% 1 12% 38% 36% 4	600
	11th to 20th	Night	11% 2 14% 33% 36% 4	600
	21st to end	Night	8% 4 21% 32% 31% 5%	600
October	1st to 10th	Night	8% 4 20% 37% 28% 4	738
	11th to 20th	Night	14% 10% 28% 34% 13% 1	800
	21st to end	Night	21% 11% 26% 28% 13% 1	880
November	1st to 10th	Night	13% 12% 32% 31% 11% 1	820
	11th to 20th	Night	13% 14% 32% 31% 10%	931
	21st to end	Night	20% 17% 30% 25% 8%	1050
December	1st to 10th	Night	19% 15% 31% 29% 6%	1050
	11th to 20th	Night	21% 13% 33% 28% 5%	1050
	21st to end	Night	17% 21% 31% 26% 5%	1155

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