Chippokes Plantation State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chippokes Plantation State Park clear sky chart from 2005-11-06 to 2026-07-31.

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	13% 6% 2 6% 4 4 4 4 6% 8% 43%	137906
	Night	14% 6% 2 6% 4 4 4 3 5% 7% 44%	135119
Transparency	Day	25% 37% 9% 15% 12% 3	141500
	Night	26% 36% 7% 15% 13% 3	139596
Seeing	Day	16% 11% 28% 25% 15% 4	17483
	Night	16% 10% 29% 30% 13% 2	27057

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% 4 2 5% 4 3 3 2 4 5% 55%	5019
	11th to 20th	Day	13% 6% 2 5% 3 3 2 2 4 5% 56%	5280
	21st to end	Day	13% 8% 3 6% 4 4 4 3 5% 5% 45%	5780
February	1st to 10th	Day	12% 9% 3 6% 4 4 5% 4 6% 7% 41%	1890
	11th to 20th	Day	21% 7% 2 4 3 3 3 3 5% 6% 44%	1976
	21st to end	Day	17% 7% 2 7% 4 4 4 3 6% 6% 39%	1730
March	1st to 10th	Day	18% 8% 3 7% 4 4 3 3 4 6% 40%	4943
	11th to 20th	Day	10% 6% 2 5% 4 3 3 3 5% 6% 52%	5090
	21st to end	Day	14% 6% 2 5% 4 4 4 3 5% 7% 45%	5717
April	1st to 10th	Day	12% 5% 2 5% 4 4 4 3 5% 7% 51%	2520
	11th to 20th	Day	10% 5% 2 6% 4 4 4 5% 5% 7% 49%	2494
	21st to end	Day	13% 6% 2 6% 5% 5% 4 3 6% 7% 44%	2520
May	1st to 10th	Day	14% 6% 2 6% 5% 5% 6% 4 6% 9% 39%	7116
	11th to 20th	Day	15% 6% 2 6% 4 4 5% 3 5% 8% 41%	7838
	21st to end	Day	18% 6% 2 6% 3 4 4 3 6% 8% 40%	9045
June	1st to 10th	Day	10% 4 2 5% 4 5% 5% 5% 7% 9% 43%	2940
	11th to 20th	Day	10% 5% 2 6% 5% 4 5% 5% 7% 10% 41%	2940
	21st to end	Day	7% 4 2 6% 5% 6% 6% 5% 7% 12% 41%	2940
July	1st to 10th	Day	7% 4 2 6% 5% 6% 6% 6% 7% 12% 39%	6500
	11th to 20th	Day	11% 7% 3 8% 6% 6% 6% 6% 8% 12% 29%	6085
	21st to end	Day	7% 5% 2 7% 5% 5% 7% 6% 9% 11% 36%	6554
August	1st to 10th	Day	15% 8% 3 8% 6% 6% 6% 5% 8% 10% 26%	4234
	11th to 20th	Day	11% 6% 3 8% 6% 6% 6% 5% 7% 10% 35%	3861
	21st to end	Day	8% 4 2 5% 4 4 4 4 8% 11% 46%	4312
September	1st to 10th	Day	15% 5% 2 6% 4 4 5% 5% 6% 9% 41%	2400
	11th to 20th	Day	15% 6% 2 7% 4 4 5% 3 5% 7% 41%	2400
	21st to end	Day	21% 8% 3 6% 4 3 4 4 5% 6% 35%	2124
October	1st to 10th	Day	16% 6% 2 6% 4 4 5% 3 4 6% 46%	2000
	11th to 20th	Day	15% 7% 2 5% 3 3 3 3 4 5% 52%	2000
	21st to end	Day	12% 5% 2 5% 3 4 3 3 5% 5% 53%	2200
November	1st to 10th	Day	13% 5% 2 4 3 3 4 2 4 6% 52%	1983
	11th to 20th	Day	14% 7% 2 5% 3 3 2 3 4 7% 52%	1890
	21st to end	Day	14% 5% 2 5% 3 3 3 3 4 7% 52%	1787
December	1st to 10th	Day	11% 5% 2 5% 3 3 3 3 5% 5% 54%	2680
	11th to 20th	Day	16% 7% 3 7% 3 3 3 3 4 5% 47%	3070
	21st to end	Day	13% 6% 2 5% 3 3 3 3 5% 7% 49%	4048
January	1st to 10th	Night	11% 6% 2 6% 4 4 4 3 4 6% 50%	7859
	11th to 20th	Night	12% 6% 2 5% 3 3 3 2 4 4 54%	7680
	21st to end	Night	16% 6% 2 6% 3 3 3 2 4 6% 49%	8401
February	1st to 10th	Night	17% 8% 2 6% 4 4 4 3 5% 6% 43%	2730
	11th to 20th	Night	20% 7% 2 5% 4 4 3 3 5% 6% 40%	2528
	21st to end	Night	16% 8% 2 5% 4 3 3 3 4 6% 46%	2076
March	1st to 10th	Night	18% 6% 2 6% 4 4 3 3 4 5% 44%	5127
	11th to 20th	Night	12% 6% 3 5% 4 4 3 3 5% 6% 50%	5090
	21st to end	Night	14% 6% 2 5% 4 4 4 3 5% 6% 48%	5455
April	1st to 10th	Night	13% 6% 3 5% 5% 4 5% 3 6% 7% 44%	2100
	11th to 20th	Night	13% 5% 2 5% 3 3 3 3 5% 8% 49%	2075
	21st to end	Night	13% 5% 2 5% 4 4 4 3 5% 8% 46%	2100
May	1st to 10th	Night	13% 6% 3 7% 5% 5% 6% 4 7% 9% 35%	5780
	11th to 20th	Night	16% 6% 2 6% 4 4 4 4 5% 7% 42%	5019
	21st to end	Night	21% 7% 3 7% 3 3 4 3 5% 8% 36%	5108
June	1st to 10th	Night	11% 4 2 5% 5% 5% 5% 5% 7% 10% 41%	1680
	11th to 20th	Night	10% 5% 2 6% 6% 5% 5% 5% 7% 10% 41%	1680
	21st to end	Night	8% 5% 2 6% 5% 5% 5% 6% 7% 10% 42%	1680
July	1st to 10th	Night	8% 4 2 6% 5% 5% 6% 6% 8% 11% 38%	3678
	11th to 20th	Night	10% 7% 3 8% 6% 5% 6% 6% 8% 12% 30%	4086
	21st to end	Night	9% 6% 3 8% 6% 5% 6% 5% 7% 10% 35%	4517
August	1st to 10th	Night	17% 8% 3 7% 5% 5% 5% 5% 7% 9% 29%	2915
	11th to 20th	Night	9% 7% 3 7% 5% 5% 5% 4 7% 9% 39%	3152
	21st to end	Night	9% 5% 2 5% 4 4 5% 4 6% 11% 46%	3586
September	1st to 10th	Night	12% 5% 2 5% 5% 4 4 3 6% 8% 45%	2000
	11th to 20th	Night	13% 6% 3 7% 5% 3 4 3 5% 6% 44%	2000
	21st to end	Night	20% 9% 3 6% 4 4 3 3 5% 7% 36%	2270
October	1st to 10th	Night	15% 5% 2 5% 4 4 4 3 4 6% 48%	2400
	11th to 20th	Night	16% 5% 2 5% 3 4 3 2 4 6% 50%	2400
	21st to end	Night	15% 4 2 4 3 4 4 3 4 6% 52%	2640
November	1st to 10th	Night	14% 6% 2 5% 3 2 4 2 5% 6% 50%	2532
	11th to 20th	Night	15% 6% 2 6% 3 3 4 3 4 7% 48%	2730
	21st to end	Night	12% 5% 1 5% 4 4 4 4 5% 6% 51%	2830
December	1st to 10th	Night	11% 5% 2 5% 4 3 4 3 5% 6% 54%	4720
	11th to 20th	Night	17% 7% 2 7% 5% 4 4 3 5% 5% 40%	5345
	21st to end	Night	12% 6% 2 6% 3 4 4 3 5% 6% 49%	7150

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	25% 21% 8% 20% 16% 9%	5020
	11th to 20th	Day	24% 21% 3 14% 28% 10%	5280
	21st to end	Day	33% 24% 6% 21% 13% 3	5780
February	1st to 10th	Day	17% 59% 5% 10% 6% 1	1890
	11th to 20th	Day	20% 59% 4 8% 7% 3	1985
	21st to end	Day	19% 60% 4 8% 7% 2	1730
March	1st to 10th	Day	35% 30% 6% 10% 14% 5%	4943
	11th to 20th	Day	22% 29% 7% 15% 19% 7%	5090
	21st to end	Day	26% 31% 10% 12% 15% 6%	5717
April	1st to 10th	Day	15% 60% 6% 10% 9% 2	2520
	11th to 20th	Day	13% 60% 6% 12% 7% 1	2494
	21st to end	Day	16% 60% 7% 10% 6% 2	2520
May	1st to 10th	Day	33% 27% 11% 16% 13% 1	7148
	11th to 20th	Day	30% 26% 11% 19% 13%	7842
	21st to end	Day	34% 26% 10% 15% 13% 3	9061
June	1st to 10th	Day	15% 61% 6% 9% 8% 1	2940
	11th to 20th	Day	13% 61% 7% 12% 7%	2940
	21st to end	Day	13% 59% 7% 14% 7%	2940
July	1st to 10th	Day	26% 31% 16% 16% 8% 2	6430
	11th to 20th	Day	38% 31% 19% 10% 2	6014
	21st to end	Day	28% 31% 10% 17% 13% 1	6370
August	1st to 10th	Day	36% 38% 12% 12% 2	4221
	11th to 20th	Day	26% 40% 10% 17% 7%	3897
	21st to end	Day	16% 38% 10% 21% 14% 1	4312
September	1st to 10th	Day	17% 60% 7% 9% 5% 2	2400
	11th to 20th	Day	20% 58% 6% 8% 7% 2	2400
	21st to end	Day	25% 58% 3 10% 3	2124
October	1st to 10th	Day	20% 37% 7% 15% 18% 3	3260
	11th to 20th	Day	12% 36% 4 13% 30% 7%	3240
	21st to end	Day	9% 36% 6% 19% 19% 11%	3538
November	1st to 10th	Day	18% 54% 4 13% 8% 2	1983
	11th to 20th	Day	16% 55% 4 10% 12% 3	1890
	21st to end	Day	16% 54% 4 13% 11% 2	1787
December	1st to 10th	Day	21% 35% 4 20% 14% 4	2680
	11th to 20th	Day	29% 31% 10% 13% 13% 4	3066
	21st to end	Day	25% 27% 11% 23% 13% 1	4048
January	1st to 10th	Night	29% 22% 8% 17% 17% 7%	7860
	11th to 20th	Night	26% 21% 3 17% 25% 8%	7680
	21st to end	Night	31% 23% 4 22% 16% 5%	8401
February	1st to 10th	Night	17% 59% 6% 10% 7% 1	2730
	11th to 20th	Night	21% 58% 3 9% 7% 2	2530
	21st to end	Night	17% 60% 3 10% 7% 4	2076
March	1st to 10th	Night	33% 30% 6% 12% 13% 7%	5127
	11th to 20th	Night	24% 29% 5% 14% 19% 9%	5090
	21st to end	Night	27% 29% 7% 18% 14% 5%	5455
April	1st to 10th	Night	16% 61% 5% 8% 9% 1	2100
	11th to 20th	Night	15% 60% 5% 11% 7% 1	2075
	21st to end	Night	16% 60% 6% 10% 7% 1	2100
May	1st to 10th	Night	34% 28% 12% 18% 8%	5810
	11th to 20th	Night	31% 25% 11% 21% 11%	5020
	21st to end	Night	39% 26% 9% 14% 11% 1	5115
June	1st to 10th	Night	17% 61% 6% 7% 9% 1	1680
	11th to 20th	Night	14% 61% 8% 10% 7%	1680
	21st to end	Night	13% 60% 5% 12% 9% 1	1680
July	1st to 10th	Night	30% 33% 13% 15% 9% 1	3640
	11th to 20th	Night	38% 33% 16% 12% 1	4037
	21st to end	Night	34% 29% 9% 16% 12%	4387
August	1st to 10th	Night	37% 38% 11% 12% 2	2904
	11th to 20th	Night	24% 40% 12% 17% 8%	3182
	21st to end	Night	18% 37% 6% 18% 19% 1	3586
September	1st to 10th	Night	16% 60% 9% 9% 5% 1	2000
	11th to 20th	Night	19% 58% 4 10% 8% 1	2000
	21st to end	Night	26% 59% 5% 8% 3	2270
October	1st to 10th	Night	23% 37% 8% 14% 15% 2	3920
	11th to 20th	Night	12% 35% 4 13% 25% 9%	3899
	21st to end	Night	9% 35% 4 24% 18% 10%	4252
November	1st to 10th	Night	20% 54% 4 11% 10% 2	2532
	11th to 20th	Night	17% 54% 3 9% 10% 6%	2730
	21st to end	Night	15% 55% 4 12% 12% 2	2830
December	1st to 10th	Night	20% 35% 5% 19% 17% 4	4720
	11th to 20th	Night	34% 32% 8% 12% 10% 5%	5348
	21st to end	Night	26% 28% 10% 22% 12% 1	7150

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	23% 22% 37% 13% 5%	286
	11th to 20th	Day	20% 28% 35% 14% 2	330
	21st to end	Day	17% 24% 40% 17% 2	363
February	1st to 10th	Day	16% 24% 39% 15% 4	330
	11th to 20th	Day	30% 22% 34% 13% 2	464
	21st to end	Day	22% 20% 38% 17% 4	446
March	1st to 10th	Day	18% 20% 39% 18% 5%	540
	11th to 20th	Day	22% 21% 33% 17% 6% 1	540
	21st to end	Day	19% 19% 38% 19% 5% 1	594
April	1st to 10th	Day	17% 20% 38% 17% 7% 1	540
	11th to 20th	Day	12% 17% 37% 24% 8% 3	532
	21st to end	Day	16% 13% 35% 27% 8% 1	540
May	1st to 10th	Day	14% 16% 38% 21% 9% 2	543
	11th to 20th	Day	19% 8% 29% 27% 14% 2	567
	21st to end	Day	21% 6% 24% 26% 18% 6%	617
June	1st to 10th	Day	12% 4 26% 30% 24% 5%	570
	11th to 20th	Day	12% 6% 23% 31% 21% 6%	570
	21st to end	Day	9% 4 20% 38% 26% 5%	570
July	1st to 10th	Day	10% 1 14% 36% 30% 8%	565
	11th to 20th	Day	9% 2 14% 33% 32% 10%	564
	21st to end	Day	9% 3 18% 34% 28% 8%	616
August	1st to 10th	Day	14% 3 19% 32% 24% 8%	526
	11th to 20th	Day	13% 3 18% 30% 25% 11%	519
	21st to end	Day	8% 3 19% 30% 27% 12%	583
September	1st to 10th	Day	16% 3 20% 28% 20% 13%	530
	11th to 20th	Day	17% 5% 17% 30% 19% 11%	530
	21st to end	Day	25% 8% 24% 25% 14% 4	530
October	1st to 10th	Day	18% 5% 22% 27% 19% 8%	530
	11th to 20th	Day	16% 13% 24% 27% 17% 3	530
	21st to end	Day	15% 12% 31% 26% 12% 5%	583
November	1st to 10th	Day	16% 11% 29% 28% 13% 4	496
	11th to 20th	Day	18% 16% 32% 25% 9% 1	430
	21st to end	Day	19% 17% 30% 22% 11% 1	327
December	1st to 10th	Day	24% 14% 39% 18% 4 1	220
	11th to 20th	Day	21% 14% 35% 21% 9%	220
	21st to end	Day	21% 14% 38% 15% 11%	242
January	1st to 10th	Night	18% 19% 36% 23% 3	840
	11th to 20th	Night	19% 18% 35% 23% 5%	840
	21st to end	Night	20% 14% 40% 25% 2	924
February	1st to 10th	Night	22% 11% 40% 23% 3	840
	11th to 20th	Night	26% 17% 38% 17% 2	823
	21st to end	Night	20% 18% 38% 22% 3	692
March	1st to 10th	Night	17% 16% 35% 26% 5%	840
	11th to 20th	Night	20% 15% 38% 22% 5%	840
	21st to end	Night	17% 14% 41% 23% 5%	924
April	1st to 10th	Night	16% 18% 40% 21% 4	840
	11th to 20th	Night	15% 10% 40% 26% 9%	831
	21st to end	Night	16% 10% 35% 33% 7%	840
May	1st to 10th	Night	16% 12% 35% 29% 6% 1	825
	11th to 20th	Night	15% 6% 30% 37% 11%	549
	21st to end	Night	17% 3 22% 40% 17% 2	455
June	1st to 10th	Night	12% 2 22% 43% 19% 2	420
	11th to 20th	Night	9% 2 25% 45% 17% 2	420
	21st to end	Night	9% 3 20% 46% 21% 2	420
July	1st to 10th	Night	9% 2 14% 46% 26% 2	410
	11th to 20th	Night	9% 1 13% 40% 32% 5%	579
	21st to end	Night	9% 3 19% 40% 26% 3	687
August	1st to 10th	Night	12% 1 16% 39% 28% 3	597
	11th to 20th	Night	11% 3 17% 37% 29% 4	757
	21st to end	Night	10% 2 15% 36% 31% 6%	880
September	1st to 10th	Night	14% 3 17% 36% 27% 4	800
	11th to 20th	Night	16% 3 16% 33% 27% 5%	800
	21st to end	Night	24% 5% 19% 35% 17% 2	800
October	1st to 10th	Night	18% 6% 20% 28% 23% 6%	800
	11th to 20th	Night	19% 9% 26% 30% 14% 2	800
	21st to end	Night	16% 10% 28% 28% 16% 2	880
November	1st to 10th	Night	17% 9% 27% 31% 14% 2	820
	11th to 20th	Night	17% 11% 34% 29% 9%	840
	21st to end	Night	12% 15% 31% 30% 11% 1	840
December	1st to 10th	Night	20% 14% 33% 25% 8% 1	840
	11th to 20th	Night	20% 9% 38% 27% 5%	840
	21st to end	Night	18% 12% 33% 31% 6%	924

Page generated at 2026-07-28 03:25:22. Version ac07

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