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 2025-03-27.

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%	108884
	Night	14% 6% 2 6% 4 4 4 3 5% 7% 45%	110456
Transparency	Day	21% 45% 7% 13% 10% 3	112521
	Night	22% 43% 6% 14% 12% 3	114958
Seeing	Day	16% 11% 27% 26% 15% 5%	15658
	Night	16% 9% 29% 30% 13% 2	25385

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	15% 4 1 4 3 3 3 2 4 5% 57%	3871
	11th to 20th	Day	12% 7% 2 5% 3 3 3 2 4 5% 53%	4060
	21st to end	Day	12% 8% 3 6% 4 4 4 3 5% 5% 45%	4466
February	1st to 10th	Day	12% 9% 3 6% 4 5% 5% 4 6% 7% 40%	1800
	11th to 20th	Day	21% 6% 2 4 3 3 3 3 5% 5% 44%	1879
	21st to end	Day	17% 6% 2 6% 4 4 4 4 6% 6% 40%	1650
March	1st to 10th	Day	21% 10% 3 6% 4 3 3 3 4 6% 37%	3472
	11th to 20th	Day	11% 5% 2 4 4 3 3 3 5% 6% 54%	3590
	21st to end	Day	18% 7% 2 6% 4 3 4 3 5% 6% 42%	3967
April	1st to 10th	Day	12% 5% 2 5% 4 4 3 3 5% 6% 51%	2280
	11th to 20th	Day	10% 5% 2 6% 4 4 4 4 5% 7% 49%	2254
	21st to end	Day	14% 6% 2 5% 5% 5% 4 3 6% 6% 44%	2280
May	1st to 10th	Day	15% 7% 2 8% 5% 5% 6% 4 6% 9% 33%	3819
	11th to 20th	Day	20% 7% 2 6% 5% 5% 5% 4 6% 8% 32%	4195
	21st to end	Day	9% 4 2 5% 3 4 4 4 6% 10% 48%	4823
June	1st to 10th	Day	11% 4 2 5% 4 5% 5% 5% 7% 9% 42%	2660
	11th to 20th	Day	10% 5% 2 6% 5% 4 5% 5% 7% 10% 42%	2660
	21st to end	Day	7% 5% 2 6% 5% 6% 6% 5% 7% 12% 40%	2660
July	1st to 10th	Day	6% 4 2 6% 5% 6% 6% 6% 8% 12% 40%	4440
	11th to 20th	Day	12% 6% 3 7% 5% 5% 5% 5% 7% 10% 35%	4160
	21st to end	Day	9% 6% 3 8% 6% 6% 7% 6% 8% 9% 32%	4466
August	1st to 10th	Day	14% 8% 3 8% 6% 6% 6% 5% 8% 10% 26%	4104
	11th to 20th	Day	11% 5% 3 8% 6% 6% 6% 5% 7% 9% 35%	3741
	21st to end	Day	8% 4 2 5% 4 4 4 4 8% 11% 45%	4180
September	1st to 10th	Day	14% 5% 2 5% 4 4 5% 5% 6% 9% 41%	2280
	11th to 20th	Day	14% 6% 2 7% 4 4 5% 3 5% 7% 41%	2280
	21st to end	Day	20% 7% 3 7% 4 3 4 4 5% 6% 36%	2018
October	1st to 10th	Day	16% 6% 2 6% 3 4 5% 3 4 7% 45%	1900
	11th to 20th	Day	15% 6% 2 5% 3 3 3 3 4 5% 52%	1900
	21st to end	Day	12% 5% 2 5% 4 4 4 3 5% 5% 53%	2090
November	1st to 10th	Day	13% 5% 2 4 4 3 4 2 4 6% 52%	1887
	11th to 20th	Day	14% 7% 2 5% 3 3 3 3 4 7% 51%	1800
	21st to end	Day	14% 5% 1 5% 3 3 3 3 4 7% 52%	1702
December	1st to 10th	Day	10% 5% 2 5% 4 3 3 3 5% 5% 55%	2600
	11th to 20th	Day	16% 7% 3 7% 3 3 3 3 4 5% 47%	2990
	21st to end	Day	13% 6% 2 5% 3 3 3 3 5% 7% 49%	3960
January	1st to 10th	Night	12% 6% 2 5% 3 3 3 3 4 5% 53%	6059
	11th to 20th	Night	13% 7% 2 5% 3 3 3 3 4 4 54%	5900
	21st to end	Night	16% 7% 2 6% 3 3 3 3 4 5% 50%	6490
February	1st to 10th	Night	17% 8% 2 5% 4 4 4 3 5% 7% 42%	2600
	11th to 20th	Night	20% 7% 2 6% 4 4 3 3 5% 6% 40%	2405
	21st to end	Night	16% 8% 2 5% 4 3 3 2 4 6% 47%	1980
March	1st to 10th	Night	23% 7% 3 7% 4 4 3 3 4 5% 36%	3599
	11th to 20th	Night	14% 5% 2 4 4 4 3 3 5% 6% 51%	3590
	21st to end	Night	18% 7% 2 5% 3 3 3 2 4 4 48%	3802
April	1st to 10th	Night	13% 6% 3 5% 5% 4 5% 4 6% 7% 43%	1900
	11th to 20th	Night	13% 6% 2 5% 4 3 3 3 5% 7% 49%	1875
	21st to end	Night	14% 6% 2 5% 4 4 4 3 5% 7% 46%	1900
May	1st to 10th	Night	17% 8% 3 7% 5% 5% 5% 4 6% 7% 34%	3104
	11th to 20th	Night	21% 7% 2 6% 5% 4 4 4 5% 7% 36%	2695
	21st to end	Night	12% 5% 2 6% 4 4 5% 3 5% 9% 45%	2732
June	1st to 10th	Night	12% 4 2 5% 5% 4 5% 5% 7% 11% 40%	1520
	11th to 20th	Night	9% 5% 2 6% 6% 5% 5% 5% 7% 10% 41%	1520
	21st to end	Night	8% 5% 2 7% 5% 5% 5% 6% 7% 9% 41%	1520
July	1st to 10th	Night	8% 4 2 6% 5% 5% 6% 6% 8% 11% 40%	2520
	11th to 20th	Night	10% 7% 3 7% 5% 4 5% 5% 7% 10% 36%	2795
	21st to end	Night	13% 8% 3 9% 7% 5% 6% 5% 7% 8% 30%	3087
August	1st to 10th	Night	17% 8% 3 7% 5% 5% 5% 5% 7% 9% 29%	2825
	11th to 20th	Night	9% 7% 2 7% 5% 5% 5% 4 7% 9% 40%	3054
	21st to end	Night	9% 5% 2 5% 4 4 5% 4 6% 11% 46%	3476
September	1st to 10th	Night	12% 5% 2 5% 5% 5% 4 3 6% 8% 45%	1900
	11th to 20th	Night	12% 6% 3 7% 5% 3 4 3 6% 7% 44%	1900
	21st to end	Night	20% 9% 3 6% 4 4 3 3 5% 7% 37%	2156
October	1st to 10th	Night	15% 5% 2 5% 4 4 4 3 4 6% 47%	2280
	11th to 20th	Night	15% 5% 2 5% 3 4 3 3 4 6% 50%	2280
	21st to end	Night	14% 4 2 4 3 4 4 3 4 6% 52%	2508
November	1st to 10th	Night	14% 6% 2 5% 4 2 4 3 5% 6% 50%	2408
	11th to 20th	Night	16% 6% 2 5% 3 3 3 3 4 6% 49%	2600
	21st to end	Night	12% 5% 1 5% 4 4 4 4 5% 6% 50%	2695
December	1st to 10th	Night	10% 5% 2 5% 4 3 4 3 5% 5% 55%	4580
	11th to 20th	Night	17% 8% 2 7% 5% 5% 4 3 5% 5% 39%	5205
	21st to end	Night	12% 6% 2 6% 3 4 4 3 5% 6% 48%	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	22% 26% 2 20% 18% 12%	3872
	11th to 20th	Day	23% 27% 4 14% 25% 7%	4060
	21st to end	Day	31% 30% 6% 20% 11% 2	4466
February	1st to 10th	Day	17% 62% 5% 10% 5% 1	1800
	11th to 20th	Day	18% 62% 3 7% 6% 3	1888
	21st to end	Day	17% 63% 4 7% 7% 2	1650
March	1st to 10th	Day	35% 42% 6% 6% 8% 3	3472
	11th to 20th	Day	15% 40% 6% 15% 19% 6%	3590
	21st to end	Day	24% 42% 8% 11% 13% 3	3967
April	1st to 10th	Day	13% 66% 4 8% 8% 2	2280
	11th to 20th	Day	12% 66% 5% 9% 6% 1	2254
	21st to end	Day	14% 65% 6% 8% 5% 2	2280
May	1st to 10th	Day	30% 45% 8% 12% 3 1	3854
	11th to 20th	Day	28% 45% 9% 13% 4	4199
	21st to end	Day	15% 44% 11% 16% 12% 2	4837
June	1st to 10th	Day	13% 67% 5% 8% 6%	2660
	11th to 20th	Day	11% 67% 6% 10% 7%	2660
	21st to end	Day	11% 65% 6% 11% 7%	2660
July	1st to 10th	Day	21% 42% 17% 11% 6% 2	4370
	11th to 20th	Day	31% 39% 16% 11% 2	4089
	21st to end	Day	31% 40% 7% 10% 10% 1	4324
August	1st to 10th	Day	35% 40% 12% 12% 2	4091
	11th to 20th	Day	25% 41% 9% 18% 7%	3777
	21st to end	Day	15% 39% 10% 21% 14% 1	4180
September	1st to 10th	Day	16% 63% 7% 7% 5% 2	2280
	11th to 20th	Day	18% 61% 6% 8% 6% 2	2280
	21st to end	Day	24% 60% 2 10% 3	2018
October	1st to 10th	Day	20% 38% 8% 15% 17% 3	3160
	11th to 20th	Day	11% 37% 4 12% 30% 7%	3140
	21st to end	Day	9% 37% 6% 20% 19% 11%	3428
November	1st to 10th	Day	18% 56% 4 12% 8% 2	1887
	11th to 20th	Day	16% 57% 4 8% 12% 3	1800
	21st to end	Day	15% 57% 3 12% 11% 2	1702
December	1st to 10th	Day	20% 36% 4 20% 14% 5%	2600
	11th to 20th	Day	29% 32% 10% 13% 12% 4	2986
	21st to end	Day	25% 28% 11% 23% 13% 1	3960
January	1st to 10th	Night	25% 27% 3 14% 21% 9%	6059
	11th to 20th	Night	24% 26% 3 17% 24% 5%	5900
	21st to end	Night	28% 29% 4 21% 16% 3	6490
February	1st to 10th	Night	16% 62% 6% 9% 5% 1	2600
	11th to 20th	Night	19% 61% 3 8% 7% 2	2407
	21st to end	Night	15% 62% 3 9% 7% 4	1980
March	1st to 10th	Night	37% 41% 5% 9% 7% 1	3599
	11th to 20th	Night	18% 40% 4 13% 18% 8%	3590
	21st to end	Night	24% 40% 4 16% 13% 3	3802
April	1st to 10th	Night	14% 67% 4 6% 9% 1	1900
	11th to 20th	Night	13% 66% 4 9% 6% 1	1875
	21st to end	Night	14% 66% 5% 8% 6% 1	1900
May	1st to 10th	Night	31% 45% 8% 11% 5%	3134
	11th to 20th	Night	29% 44% 8% 16% 3	2696
	21st to end	Night	19% 45% 12% 14% 10%	2739
June	1st to 10th	Night	15% 67% 5% 7% 6% 1	1520
	11th to 20th	Night	10% 67% 7% 9% 7%	1520
	21st to end	Night	12% 66% 5% 9% 8% 1	1520
July	1st to 10th	Night	25% 44% 12% 12% 6% 1	2480
	11th to 20th	Night	29% 40% 14% 15% 1	2743
	21st to end	Night	37% 38% 7% 9% 9%	2988
August	1st to 10th	Night	36% 40% 11% 11% 2	2814
	11th to 20th	Night	22% 41% 12% 17% 8%	3084
	21st to end	Night	18% 38% 6% 18% 19% 1	3476
September	1st to 10th	Night	15% 63% 9% 7% 4 1	1900
	11th to 20th	Night	17% 61% 4 9% 7% 1	1900
	21st to end	Night	23% 61% 4 8% 3	2156
October	1st to 10th	Night	23% 38% 8% 14% 14% 2	3800
	11th to 20th	Night	11% 36% 4 13% 25% 10%	3779
	21st to end	Night	8% 37% 4 24% 18% 10%	4120
November	1st to 10th	Night	19% 57% 4 10% 8% 2	2408
	11th to 20th	Night	16% 57% 3 9% 9% 6%	2600
	21st to end	Night	14% 57% 4 12% 12% 2	2695
December	1st to 10th	Night	19% 36% 4 19% 17% 4	4580
	11th to 20th	Night	34% 32% 7% 12% 9% 5%	5208
	21st to end	Night	26% 29% 10% 22% 12% 1	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	24% 21% 37% 13% 5%	260
	11th to 20th	Day	19% 28% 36% 15% 2	300
	21st to end	Day	16% 23% 40% 19% 2	330
February	1st to 10th	Day	16% 24% 39% 16% 4	300
	11th to 20th	Day	29% 22% 34% 13% 2	427
	21st to end	Day	21% 19% 39% 18% 3	414
March	1st to 10th	Day	18% 20% 39% 18% 4	500
	11th to 20th	Day	22% 19% 34% 18% 6% 1	500
	21st to end	Day	20% 18% 36% 21% 5% 1	530
April	1st to 10th	Day	17% 21% 37% 17% 7% 1	460
	11th to 20th	Day	11% 15% 36% 25% 9% 3	452
	21st to end	Day	17% 12% 35% 27% 8% 1	460
May	1st to 10th	Day	13% 14% 38% 23% 10% 2	463
	11th to 20th	Day	20% 8% 27% 28% 14% 2	487
	21st to end	Day	19% 4 22% 28% 20% 7%	529
June	1st to 10th	Day	13% 3 23% 31% 24% 5%	490
	11th to 20th	Day	12% 5% 21% 32% 23% 7%	490
	21st to end	Day	9% 4 19% 37% 25% 5%	490
July	1st to 10th	Day	10% 1 13% 36% 31% 8%	485
	11th to 20th	Day	9% 2 13% 34% 32% 11%	484
	21st to end	Day	9% 2 18% 34% 29% 8%	532
August	1st to 10th	Day	13% 3 18% 33% 25% 8%	486
	11th to 20th	Day	13% 2 19% 29% 26% 11%	479
	21st to end	Day	8% 3 17% 30% 29% 13%	539
September	1st to 10th	Day	15% 3 18% 28% 21% 14%	490
	11th to 20th	Day	16% 5% 17% 31% 20% 12%	490
	21st to end	Day	25% 8% 24% 24% 15% 4	490
October	1st to 10th	Day	19% 5% 21% 27% 20% 7%	490
	11th to 20th	Day	15% 11% 24% 29% 18% 3	490
	21st to end	Day	14% 10% 31% 27% 13% 5%	539
November	1st to 10th	Day	16% 10% 28% 28% 14% 4	460
	11th to 20th	Day	17% 16% 32% 25% 10% 1	400
	21st to end	Day	19% 17% 29% 22% 12% 1	302
December	1st to 10th	Day	22% 15% 39% 19% 5% 2	200
	11th to 20th	Day	22% 13% 35% 21% 10%	200
	21st to end	Day	20% 15% 36% 16% 12%	220
January	1st to 10th	Night	18% 19% 36% 23% 3 1	800
	11th to 20th	Night	20% 17% 35% 24% 5%	800
	21st to end	Night	20% 13% 40% 26% 2	880
February	1st to 10th	Night	22% 11% 41% 23% 3	800
	11th to 20th	Night	26% 18% 38% 17% 2	783
	21st to end	Night	20% 17% 38% 22% 3	660
March	1st to 10th	Night	17% 17% 35% 26% 5%	800
	11th to 20th	Night	20% 15% 38% 22% 6%	800
	21st to end	Night	17% 13% 41% 24% 5%	863
April	1st to 10th	Night	16% 18% 40% 22% 4	760
	11th to 20th	Night	15% 9% 39% 26% 9% 1	751
	21st to end	Night	16% 9% 34% 34% 6%	760
May	1st to 10th	Night	17% 11% 34% 31% 6% 1	747
	11th to 20th	Night	15% 6% 30% 37% 11%	496
	21st to end	Night	14% 2 20% 43% 18% 2	411
June	1st to 10th	Night	12% 2 21% 43% 20% 3	380
	11th to 20th	Night	8% 2 22% 47% 18% 2	380
	21st to end	Night	9% 3 19% 47% 20% 2	380
July	1st to 10th	Night	9% 2 15% 45% 27% 2	370
	11th to 20th	Night	8% 1 12% 41% 34% 4	522
	21st to end	Night	9% 2 19% 41% 25% 3	624
August	1st to 10th	Night	11% 1 15% 40% 29% 3	567
	11th to 20th	Night	10% 2 16% 38% 29% 4	719
	21st to end	Night	11% 2 14% 36% 32% 6%	836
September	1st to 10th	Night	13% 3 15% 36% 28% 5%	760
	11th to 20th	Night	15% 3 16% 33% 28% 5%	760
	21st to end	Night	24% 4 18% 35% 17% 2	760
October	1st to 10th	Night	18% 6% 20% 28% 23% 5%	760
	11th to 20th	Night	18% 9% 26% 31% 15% 2	760
	21st to end	Night	16% 9% 28% 28% 17% 2	836
November	1st to 10th	Night	18% 7% 27% 31% 15% 2	780
	11th to 20th	Night	17% 10% 33% 30% 9% 1	800
	21st to end	Night	13% 14% 31% 30% 11% 1	800
December	1st to 10th	Night	20% 13% 34% 24% 8% 1	800
	11th to 20th	Night	20% 9% 38% 28% 6%	800
	21st to end	Night	19% 12% 32% 31% 7%	880

Page generated at 2025-03-24 09:04:33. Version ac07

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