Rocky Gap State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rocky Gap State Park clear sky chart from 2005-11-06 to 2025-06-10.

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	14% 8% 3 7% 5% 5% 5% 4 6% 7% 37%	119579
	Night	14% 8% 3 7% 5% 4 4 4 5% 7% 39%	118643
Transparency	Day	43% 8% 13% 22% 13% 2	123221
	Night	42% 7% 13% 23% 13% 2	123138
Seeing	Day	23% 15% 26% 20% 11% 4	15560
	Night	20% 14% 25% 28% 12% 1	25238

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% 13% 5% 14% 6% 4 3 3 4 4 30%	3891
	11th to 20th	Day	11% 13% 6% 12% 6% 6% 5% 4 5% 6% 26%	4060
	21st to end	Day	15% 11% 4 10% 5% 4 4 3 4 6% 34%	4466
February	1st to 10th	Day	14% 13% 3 9% 5% 4 5% 3 5% 6% 33%	1800
	11th to 20th	Day	14% 9% 4 10% 5% 6% 5% 4 5% 6% 32%	1753
	21st to end	Day	16% 8% 4 11% 5% 4 3 3 4 5% 36%	1660
March	1st to 10th	Day	16% 11% 3 7% 4 4 4 3 4 5% 39%	4935
	11th to 20th	Day	12% 7% 3 6% 4 4 4 3 6% 8% 43%	4980
	21st to end	Day	13% 10% 3 8% 5% 4 5% 4 5% 6% 38%	5465
April	1st to 10th	Day	14% 10% 3 8% 6% 4 5% 3 5% 7% 35%	2369
	11th to 20th	Day	13% 8% 3 6% 6% 5% 5% 3 5% 7% 40%	2374
	21st to end	Day	19% 7% 2 6% 4 4 5% 4 6% 6% 37%	2500
May	1st to 10th	Day	20% 7% 3 7% 5% 5% 5% 4 7% 8% 29%	5862
	11th to 20th	Day	23% 8% 2 6% 4 5% 5% 4 6% 8% 29%	5942
	21st to end	Day	17% 6% 2 6% 5% 5% 6% 4 7% 9% 33%	6934
June	1st to 10th	Day	13% 5% 2 5% 5% 4 5% 5% 7% 9% 40%	2786
	11th to 20th	Day	10% 5% 2 7% 5% 5% 7% 6% 7% 9% 37%	2660
	21st to end	Day	9% 5% 2 6% 5% 5% 5% 5% 8% 11% 40%	2660
July	1st to 10th	Day	6% 4 2 6% 5% 5% 6% 5% 7% 9% 44%	4440
	11th to 20th	Day	7% 5% 2 6% 5% 5% 6% 5% 7% 11% 41%	4132
	21st to end	Day	12% 8% 3 7% 6% 5% 5% 4 6% 8% 37%	4466
August	1st to 10th	Day	16% 6% 3 7% 5% 5% 6% 4 7% 9% 33%	4104
	11th to 20th	Day	10% 5% 2 6% 5% 5% 6% 4 7% 9% 41%	4026
	21st to end	Day	11% 4 1 5% 4 5% 5% 4 7% 8% 46%	4180
September	1st to 10th	Day	15% 5% 2 5% 4 4 4 3 6% 7% 45%	2280
	11th to 20th	Day	13% 5% 2 6% 3 4 4 4 5% 6% 49%	2200
	21st to end	Day	20% 7% 2 6% 4 4 5% 4 6% 6% 36%	2027
October	1st to 10th	Day	17% 6% 2 5% 3 4 4 3 6% 6% 45%	1900
	11th to 20th	Day	16% 7% 2 7% 5% 4 4 3 5% 6% 42%	1900
	21st to end	Day	14% 6% 3 6% 4 5% 4 4 5% 6% 43%	2090
November	1st to 10th	Day	10% 6% 2 5% 3 4 4 3 5% 7% 50%	1942
	11th to 20th	Day	14% 10% 2 6% 4 4 4 4 6% 6% 40%	1645
	21st to end	Day	15% 10% 2 7% 5% 4 4 3 6% 6% 37%	1600
December	1st to 10th	Day	13% 8% 4 10% 6% 5% 5% 4 5% 6% 35%	2600
	11th to 20th	Day	21% 12% 3 7% 4 3 3 3 5% 5% 33%	2990
	21st to end	Day	17% 11% 5% 10% 5% 6% 6% 4 6% 7% 23%	3960
January	1st to 10th	Night	11% 10% 5% 14% 6% 5% 5% 4 4 5% 32%	6050
	11th to 20th	Night	11% 11% 5% 12% 5% 4 4 3 5% 6% 34%	5900
	21st to end	Night	15% 10% 3 8% 4 4 4 3 5% 6% 39%	6490
February	1st to 10th	Night	14% 9% 3 7% 5% 6% 4 4 6% 6% 37%	2600
	11th to 20th	Night	14% 10% 4 8% 5% 5% 5% 4 6% 6% 33%	2533
	21st to end	Night	15% 9% 4 8% 6% 5% 4 4 6% 7% 32%	1964
March	1st to 10th	Night	17% 9% 2 6% 4 3 3 3 5% 6% 41%	4918
	11th to 20th	Night	10% 8% 2 6% 4 3 3 3 4 7% 49%	4980
	21st to end	Night	12% 8% 3 8% 5% 4 4 3 5% 5% 45%	5467
April	1st to 10th	Night	17% 9% 3 7% 5% 4 4 3 6% 5% 36%	2030
	11th to 20th	Night	14% 7% 2 5% 5% 4 5% 4 6% 8% 41%	1975
	21st to end	Night	17% 5% 2 5% 4 4 4 4 5% 8% 43%	1916
May	1st to 10th	Night	23% 9% 3 7% 4 4 5% 3 5% 7% 27%	4033
	11th to 20th	Night	25% 8% 3 6% 4 4 4 3 6% 7% 30%	3947
	21st to end	Night	19% 7% 3 6% 4 4 5% 4 6% 8% 36%	3920
June	1st to 10th	Night	12% 5% 2 4 4 3 6% 5% 5% 8% 47%	1598
	11th to 20th	Night	11% 4 2 6% 5% 5% 5% 4 7% 9% 42%	1520
	21st to end	Night	8% 5% 2 5% 5% 4 4 4 9% 10% 44%	1520
July	1st to 10th	Night	7% 4 2 5% 5% 5% 6% 5% 8% 9% 44%	2520
	11th to 20th	Night	6% 5% 3 6% 5% 5% 6% 4 7% 10% 43%	2823
	21st to end	Night	10% 6% 2 6% 6% 5% 5% 5% 7% 9% 39%	3087
August	1st to 10th	Night	15% 5% 2 7% 5% 5% 5% 4 7% 9% 35%	2825
	11th to 20th	Night	10% 5% 2 6% 5% 5% 5% 5% 6% 8% 44%	2785
	21st to end	Night	14% 5% 2 5% 3 4 5% 3 5% 8% 47%	3460
September	1st to 10th	Night	15% 5% 2 5% 4 4 3 3 4 7% 48%	1900
	11th to 20th	Night	11% 6% 2 5% 3 4 3 4 5% 6% 51%	1976
	21st to end	Night	21% 6% 2 5% 3 4 4 3 5% 6% 41%	2152
October	1st to 10th	Night	18% 5% 2 5% 4 4 3 3 5% 6% 44%	2280
	11th to 20th	Night	14% 6% 1 5% 3 4 4 3 4 8% 48%	2280
	21st to end	Night	16% 5% 1 6% 4 4 4 4 5% 6% 45%	2508
November	1st to 10th	Night	9% 7% 3 6% 4 4 4 3 4 6% 51%	2355
	11th to 20th	Night	14% 10% 2 6% 5% 4 4 4 5% 6% 40%	2750
	21st to end	Night	14% 8% 3 8% 5% 5% 5% 4 5% 7% 38%	2800
December	1st to 10th	Night	11% 9% 4 10% 4 5% 5% 3 5% 6% 38%	4580
	11th to 20th	Night	18% 10% 3 8% 5% 5% 4 4 5% 5% 32%	5205
	21st to end	Night	16% 11% 4 10% 6% 6% 5% 4 6% 7% 25%	6996

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	54% 7% 10% 20% 6% 3	3892
	11th to 20th	Day	55% 7% 10% 13% 13% 3	4060
	21st to end	Day	49% 8% 11% 20% 10% 1	4466
February	1st to 10th	Day	51% 7% 13% 19% 9% 1	1800
	11th to 20th	Day	51% 6% 14% 19% 10% 1	1762
	21st to end	Day	50% 5% 14% 17% 12% 2	1660
March	1st to 10th	Day	45% 7% 10% 21% 12% 5%	4935
	11th to 20th	Day	36% 6% 14% 27% 13% 3	4980
	21st to end	Day	45% 7% 9% 20% 16% 3	5465
April	1st to 10th	Day	48% 8% 12% 16% 13% 3	2369
	11th to 20th	Day	42% 7% 11% 19% 16% 3	2374
	21st to end	Day	45% 7% 11% 23% 12% 2	2500
May	1st to 10th	Day	50% 9% 12% 18% 9% 2	5897
	11th to 20th	Day	50% 8% 11% 23% 7% 1	5946
	21st to end	Day	43% 10% 13% 19% 13% 2	6949
June	1st to 10th	Day	39% 10% 14% 22% 15% 1	2786
	11th to 20th	Day	38% 13% 15% 20% 13% 1	2660
	21st to end	Day	35% 11% 17% 23% 13% 1	2660
July	1st to 10th	Day	35% 9% 16% 26% 10% 4	4370
	11th to 20th	Day	34% 9% 18% 25% 13% 1	4062
	21st to end	Day	44% 7% 10% 22% 16% 1	4324
August	1st to 10th	Day	45% 9% 17% 21% 8%	4091
	11th to 20th	Day	38% 8% 12% 27% 15%	4065
	21st to end	Day	34% 8% 15% 27% 14% 2	4180
September	1st to 10th	Day	38% 8% 12% 18% 19% 4	2280
	11th to 20th	Day	35% 7% 11% 27% 18% 2	2200
	21st to end	Day	46% 9% 12% 17% 16% 1	2027
October	1st to 10th	Day	33% 6% 10% 25% 22% 5%	3160
	11th to 20th	Day	35% 5% 12% 26% 16% 6%	3140
	21st to end	Day	26% 5% 14% 30% 22% 2	3428
November	1st to 10th	Day	34% 6% 13% 23% 19% 4	1942
	11th to 20th	Day	42% 7% 13% 19% 17% 2	1645
	21st to end	Day	45% 8% 14% 22% 10% 1	1600
December	1st to 10th	Day	49% 6% 14% 23% 5% 3	2600
	11th to 20th	Day	52% 5% 15% 20% 8% 1	2986
	21st to end	Day	56% 9% 14% 11% 9%	3960
January	1st to 10th	Night	50% 9% 8% 20% 12% 1	6050
	11th to 20th	Night	48% 6% 11% 18% 12% 5%	5900
	21st to end	Night	43% 7% 12% 25% 11% 2	6490
February	1st to 10th	Night	44% 9% 14% 22% 10% 1	2600
	11th to 20th	Night	50% 7% 11% 19% 12% 1	2535
	21st to end	Night	48% 8% 11% 19% 10% 3	1964
March	1st to 10th	Night	41% 7% 11% 24% 11% 5%	4918
	11th to 20th	Night	33% 8% 14% 31% 10% 4	4980
	21st to end	Night	40% 7% 12% 21% 16% 3	5467
April	1st to 10th	Night	47% 8% 11% 16% 15% 3	2030
	11th to 20th	Night	40% 8% 13% 20% 15% 4	1975
	21st to end	Night	38% 8% 12% 26% 12% 3	1916
May	1st to 10th	Night	54% 8% 11% 15% 9% 4	4060
	11th to 20th	Night	49% 8% 12% 21% 9% 1	3948
	21st to end	Night	44% 9% 15% 23% 7% 2	3927
June	1st to 10th	Night	34% 9% 12% 27% 16% 2	1598
	11th to 20th	Night	36% 10% 15% 26% 12% 1	1520
	21st to end	Night	32% 8% 18% 24% 16% 2	1520
July	1st to 10th	Night	34% 9% 18% 21% 12% 6%	2480
	11th to 20th	Night	34% 9% 17% 24% 14% 1	2770
	21st to end	Night	39% 9% 14% 20% 16% 1	2988
August	1st to 10th	Night	43% 9% 18% 22% 9%	2814
	11th to 20th	Night	36% 8% 12% 25% 18% 1	2812
	21st to end	Night	35% 7% 14% 30% 13% 2	3460
September	1st to 10th	Night	36% 7% 13% 21% 19% 4	1900
	11th to 20th	Night	32% 6% 12% 27% 21% 2	1976
	21st to end	Night	42% 8% 12% 21% 16% 1	2152
October	1st to 10th	Night	36% 5% 10% 27% 22% 1	3800
	11th to 20th	Night	28% 5% 11% 25% 25% 6%	3779
	21st to end	Night	27% 4 12% 31% 24% 2	4120
November	1st to 10th	Night	34% 6% 13% 23% 20% 4	2355
	11th to 20th	Night	42% 7% 10% 23% 14% 4	2750
	21st to end	Night	45% 7% 14% 21% 12% 2	2800
December	1st to 10th	Night	46% 5% 15% 27% 7%	4580
	11th to 20th	Night	51% 6% 14% 19% 9%	5208
	21st to end	Night	54% 10% 14% 15% 7%	6996

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	34% 26% 25% 10% 3	263
	11th to 20th	Day	39% 24% 27% 8% 2	300
	21st to end	Day	32% 28% 26% 12% 3	330
February	1st to 10th	Day	32% 26% 32% 9% 2	300
	11th to 20th	Day	40% 28% 26% 4 1	300
	21st to end	Day	32% 25% 29% 12% 2	369
March	1st to 10th	Day	30% 22% 28% 17% 3	500
	11th to 20th	Day	30% 26% 26% 13% 4 1	500
	21st to end	Day	29% 22% 29% 13% 4 1	550
April	1st to 10th	Day	32% 22% 23% 17% 4 1	500
	11th to 20th	Day	23% 23% 26% 17% 8% 4	492
	21st to end	Day	30% 18% 27% 15% 7% 2	500
May	1st to 10th	Day	29% 17% 27% 15% 8% 3	503
	11th to 20th	Day	26% 16% 27% 17% 9% 4	527
	21st to end	Day	23% 11% 23% 23% 13% 8%	573
June	1st to 10th	Day	18% 13% 29% 21% 15% 4	526
	11th to 20th	Day	17% 10% 29% 25% 13% 6%	490
	21st to end	Day	13% 12% 30% 24% 17% 4	490
July	1st to 10th	Day	12% 6% 25% 27% 18% 10%	485
	11th to 20th	Day	7% 6% 28% 32% 19% 8%	484
	21st to end	Day	15% 6% 27% 29% 18% 5%	532
August	1st to 10th	Day	14% 8% 22% 27% 20% 9%	486
	11th to 20th	Day	15% 4 25% 27% 20% 9%	479
	21st to end	Day	14% 4 25% 23% 22% 11%	539
September	1st to 10th	Day	19% 8% 20% 22% 21% 9%	490
	11th to 20th	Day	17% 5% 18% 31% 22% 9%	490
	21st to end	Day	29% 10% 23% 20% 14% 4	490
October	1st to 10th	Day	21% 9% 24% 23% 18% 4	490
	11th to 20th	Day	20% 16% 27% 24% 11% 2	490
	21st to end	Day	20% 19% 28% 22% 10% 2	539
November	1st to 10th	Day	16% 16% 31% 25% 11% 2	488
	11th to 20th	Day	24% 20% 29% 21% 5%	245
	21st to end	Day	28% 22% 30% 17% 4 1	200
December	1st to 10th	Day	29% 27% 28% 12% 5% 1	200
	11th to 20th	Day	30% 24% 23% 20% 4	200
	21st to end	Day	30% 18% 25% 22% 4	220
January	1st to 10th	Night	23% 25% 31% 18% 4	800
	11th to 20th	Night	25% 21% 30% 22% 2	800
	21st to end	Night	22% 24% 32% 20% 2	880
February	1st to 10th	Night	23% 21% 31% 24% 2	800
	11th to 20th	Night	27% 26% 31% 15% 1	783
	21st to end	Night	26% 20% 31% 22% 2	660
March	1st to 10th	Night	24% 19% 33% 21% 4	800
	11th to 20th	Night	26% 22% 26% 21% 5% 1	800
	21st to end	Night	23% 18% 33% 20% 5% 1	880
April	1st to 10th	Night	26% 20% 28% 21% 5%	800
	11th to 20th	Night	20% 17% 27% 27% 8%	791
	21st to end	Night	20% 14% 26% 31% 9%	716
May	1st to 10th	Night	22% 12% 24% 29% 13% 1	600
	11th to 20th	Night	25% 9% 22% 32% 11%	558
	21st to end	Night	16% 8% 18% 32% 24% 2	433
June	1st to 10th	Night	15% 5% 23% 35% 22%	400
	11th to 20th	Night	13% 6% 22% 38% 21% 1	380
	21st to end	Night	10% 3 22% 42% 22% 1	380
July	1st to 10th	Night	11% 4 16% 39% 26% 4	370
	11th to 20th	Night	7% 3 13% 38% 35% 4	536
	21st to end	Night	9% 3 18% 37% 30% 2	624
August	1st to 10th	Night	10% 2 15% 40% 29% 3	567
	11th to 20th	Night	10% 4 13% 40% 28% 5%	564
	21st to end	Night	14% 3 16% 34% 29% 4	820
September	1st to 10th	Night	18% 4 17% 32% 25% 4	760
	11th to 20th	Night	15% 5% 14% 32% 30% 4	760
	21st to end	Night	26% 7% 17% 28% 19% 3	760
October	1st to 10th	Night	21% 7% 21% 28% 22% 2	760
	11th to 20th	Night	18% 14% 25% 30% 12% 1	760
	21st to end	Night	21% 14% 24% 29% 11% 1	836
November	1st to 10th	Night	14% 12% 27% 35% 12% 1	780
	11th to 20th	Night	21% 19% 24% 28% 8% 1	800
	21st to end	Night	22% 17% 27% 27% 7%	800
December	1st to 10th	Night	25% 19% 28% 23% 5%	800
	11th to 20th	Night	23% 18% 30% 26% 3	800
	21st to end	Night	22% 18% 27% 30% 3	880

Page generated at 2025-06-07 10:28:18. Version ac07

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