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 2024-02-15.

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% 5% 2 5% 5% 3 5% 5% 5% 8% 44%	78410
	Night	14% 6% 2 5% 5% 3 4 4 5% 7% 44%	80667
Transparency	Day	26% 37% 8% 15% 12% 2	78124
	Night	26% 36% 8% 15% 13% 3	80472
Seeing	Day	16% 10% 27% 26% 16% 5%	14173
	Night	16% 9% 29% 31% 13% 2	23911

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	17% 5% 2 3 4 2 3 3 4 5% 52%	2707
	11th to 20th	Day	13% 7% 2 5% 5% 3 3 4 5% 6% 47%	2840
	21st to end	Day	15% 10% 4 5% 5% 3 4 3 5% 5% 41%	3124
February	1st to 10th	Day	12% 8% 3 5% 5% 3 6% 5% 6% 7% 40%	1710
	11th to 20th	Day	21% 6% 2 3 4 2 3 3 5% 5% 46%	1722
	21st to end	Day	18% 6% 3 6% 5% 3 5% 5% 6% 7% 37%	1480
March	1st to 10th	Day	14% 6% 2 5% 4 2 3 3 3 6% 53%	1934
	11th to 20th	Day	17% 6% 2 4 5% 3 4 4 5% 6% 44%	1980
	21st to end	Day	16% 6% 3 5% 5% 3 4 4 5% 8% 40%	2223
April	1st to 10th	Day	12% 4 3 4 4 2 4 3 4 7% 52%	2160
	11th to 20th	Day	10% 5% 2 5% 4 2 4 5% 5% 7% 49%	2134
	21st to end	Day	14% 6% 2 4 5% 4 5% 4 5% 7% 44%	2160
May	1st to 10th	Day	14% 5% 2 5% 5% 4 5% 5% 5% 9% 42%	2186
	11th to 20th	Day	17% 6% 2 5% 6% 3 4 4 5% 8% 39%	2359
	21st to end	Day	13% 5% 2 5% 5% 2 5% 5% 5% 9% 44%	2725
June	1st to 10th	Day	12% 4 2 4 5% 4 5% 6% 7% 9% 43%	2520
	11th to 20th	Day	11% 5% 3 5% 5% 3 5% 6% 6% 10% 42%	2520
	21st to end	Day	7% 4 2 5% 5% 5% 7% 6% 6% 12% 39%	2520
July	1st to 10th	Day	8% 4 2 5% 6% 5% 6% 7% 8% 11% 39%	2520
	11th to 20th	Day	6% 4 2 4 5% 3 6% 8% 8% 12% 41%	2366
	21st to end	Day	7% 4 2 5% 6% 5% 7% 7% 9% 11% 37%	2547
August	1st to 10th	Day	10% 5% 3 5% 7% 4 7% 5% 8% 10% 35%	2327
	11th to 20th	Day	12% 5% 3 7% 6% 5% 6% 5% 6% 9% 35%	2137
	21st to end	Day	10% 5% 3 6% 7% 3 5% 5% 8% 10% 39%	2376
September	1st to 10th	Day	15% 4 2 5% 5% 3 4 6% 6% 10% 40%	2160
	11th to 20th	Day	13% 6% 3 6% 5% 3 5% 5% 5% 7% 42%	2160
	21st to end	Day	19% 7% 3 6% 5% 2 4 5% 5% 7% 36%	1913
October	1st to 10th	Day	17% 6% 2 6% 4 3 5% 4 4 7% 45%	1800
	11th to 20th	Day	16% 6% 2 4 4 2 4 4 4 5% 50%	1800
	21st to end	Day	13% 5% 2 5% 4 3 4 4 5% 5% 51%	1980
November	1st to 10th	Day	14% 5% 2 4 4 2 3 3 4 6% 52%	1791
	11th to 20th	Day	14% 6% 2 4 3 2 3 3 4 7% 52%	1710
	21st to end	Day	15% 4 2 4 4 3 3 3 4 6% 52%	1617
December	1st to 10th	Day	16% 7% 2 5% 5% 2 3 4 7% 7% 43%	1520
	11th to 20th	Day	15% 6% 2 5% 3 2 3 3 4 4 53%	1910
	21st to end	Day	17% 6% 2 5% 4 3 4 4 5% 6% 45%	2772
January	1st to 10th	Night	13% 7% 3 6% 5% 3 4 4 4 5% 47%	4237
	11th to 20th	Night	16% 8% 3 5% 5% 3 4 4 5% 5% 44%	4120
	21st to end	Night	19% 7% 2 6% 4 2 3 4 4 5% 43%	4532
February	1st to 10th	Night	16% 7% 3 5% 4 2 4 4 5% 7% 43%	2470
	11th to 20th	Night	20% 7% 3 5% 5% 3 3 3 4 6% 40%	2217
	21st to end	Night	17% 7% 3 4 4 2 3 3 4 6% 46%	1776
March	1st to 10th	Night	14% 5% 2 4 5% 3 4 4 4 5% 51%	2024
	11th to 20th	Night	17% 6% 2 4 5% 3 5% 4 6% 7% 41%	1980
	21st to end	Night	16% 5% 2 6% 5% 3 4 4 5% 6% 42%	2131
April	1st to 10th	Night	13% 6% 3 4 5% 2 5% 4 6% 7% 44%	1800
	11th to 20th	Night	14% 5% 2 4 4 3 4 3 5% 7% 50%	1775
	21st to end	Night	15% 5% 2 5% 4 3 4 4 5% 8% 45%	1800
May	1st to 10th	Night	14% 6% 3 5% 5% 4 5% 5% 6% 8% 40%	1788
	11th to 20th	Night	15% 6% 2 5% 5% 3 5% 6% 6% 8% 40%	1531
	21st to end	Night	14% 5% 3 5% 5% 2 5% 4 5% 8% 44%	1550
June	1st to 10th	Night	12% 4 2 4 5% 3 6% 5% 7% 11% 41%	1440
	11th to 20th	Night	10% 5% 2 5% 7% 3 6% 6% 7% 10% 40%	1440
	21st to end	Night	9% 5% 2 6% 6% 4 5% 7% 7% 10% 40%	1440
July	1st to 10th	Night	7% 4 2 5% 6% 4 5% 7% 5% 11% 43%	1440
	11th to 20th	Night	6% 5% 2 5% 5% 3 6% 7% 7% 11% 44%	1589
	21st to end	Night	8% 4 3 5% 6% 3 6% 6% 8% 12% 38%	1771
August	1st to 10th	Night	7% 6% 2 6% 6% 4 6% 7% 8% 11% 37%	1611
	11th to 20th	Night	10% 7% 3 6% 6% 4 6% 5% 7% 9% 38%	1744
	21st to end	Night	10% 4 2 5% 6% 4 5% 7% 7% 12% 39%	1980
September	1st to 10th	Night	12% 5% 2 4 5% 4 5% 4 6% 8% 44%	1800
	11th to 20th	Night	11% 5% 3 6% 6% 3 4 4 5% 7% 45%	1800
	21st to end	Night	20% 8% 3 5% 5% 3 4 5% 4 7% 38%	2042
October	1st to 10th	Night	15% 4 2 4 4 3 4 4 4 7% 48%	2160
	11th to 20th	Night	16% 5% 2 4 4 3 3 3 4 6% 49%	2160
	21st to end	Night	15% 4 2 3 4 3 4 4 5% 6% 51%	2376
November	1st to 10th	Night	15% 6% 2 4 4 2 4 3 5% 6% 50%	2284
	11th to 20th	Night	15% 5% 2 5% 4 2 3 3 4 6% 49%	2470
	21st to end	Night	13% 4 1 4 4 3 4 5% 5% 6% 50%	2560
December	1st to 10th	Night	17% 8% 3 6% 5% 3 4 4 5% 5% 41%	2660
	11th to 20th	Night	17% 6% 2 4 4 3 3 4 5% 6% 47%	3285
	21st to end	Night	14% 6% 3 5% 5% 3 4 4 5% 6% 45%	4884

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% 25% 6% 27% 16% 1	2708
	11th to 20th	Day	28% 26% 7% 15% 21% 4	2840
	21st to end	Day	37% 25% 8% 15% 13% 1	3124
February	1st to 10th	Day	28% 35% 7% 17% 11% 2	1710
	11th to 20th	Day	27% 36% 5% 14% 14% 4	1731
	21st to end	Day	30% 36% 7% 13% 12% 3	1480
March	1st to 10th	Day	21% 36% 7% 19% 14% 3	1934
	11th to 20th	Day	27% 37% 7% 14% 11% 4	1980
	21st to end	Day	30% 38% 8% 12% 10% 1	2223
April	1st to 10th	Day	22% 36% 8% 15% 14% 6%	2160
	11th to 20th	Day	23% 37% 8% 14% 14% 4	2134
	21st to end	Day	26% 38% 7% 14% 12% 4	2160
May	1st to 10th	Day	26% 39% 11% 13% 10% 1	2186
	11th to 20th	Day	30% 39% 8% 15% 6% 2	2363
	21st to end	Day	24% 40% 10% 16% 10%	2725
June	1st to 10th	Day	22% 40% 10% 18% 9% 1	2520
	11th to 20th	Day	25% 39% 11% 15% 8% 1	2520
	21st to end	Day	24% 41% 11% 14% 9% 2	2520
July	1st to 10th	Day	23% 42% 10% 15% 9% 2	2450
	11th to 20th	Day	21% 43% 13% 14% 6% 2	2295
	21st to end	Day	23% 44% 15% 12% 7%	2405
August	1st to 10th	Day	26% 40% 11% 17% 6% 1	2314
	11th to 20th	Day	30% 38% 9% 13% 9%	2137
	21st to end	Day	28% 41% 10% 12% 8% 2	2376
September	1st to 10th	Day	24% 39% 9% 10% 14% 4	2160
	11th to 20th	Day	25% 38% 6% 16% 13% 2	2160
	21st to end	Day	31% 38% 6% 11% 13% 2	1913
October	1st to 10th	Day	25% 36% 4 14% 17% 3	1800
	11th to 20th	Day	25% 37% 5% 16% 14% 3	1800
	21st to end	Day	24% 38% 5% 14% 15% 4	1980
November	1st to 10th	Day	18% 41% 6% 17% 16% 2	1791
	11th to 20th	Day	21% 39% 8% 15% 14% 3	1710
	21st to end	Day	21% 40% 6% 15% 14% 3	1617
December	1st to 10th	Day	21% 41% 8% 16% 13% 1	1520
	11th to 20th	Day	25% 32% 5% 20% 13% 6%	1906
	21st to end	Day	28% 26% 9% 24% 12% 1	2772
January	1st to 10th	Night	28% 27% 7% 19% 15% 3	4237
	11th to 20th	Night	32% 26% 6% 16% 18% 2	4120
	21st to end	Night	37% 24% 6% 15% 14% 4	4532
February	1st to 10th	Night	29% 34% 6% 16% 13% 3	2470
	11th to 20th	Night	30% 36% 4 14% 13% 4	2219
	21st to end	Night	28% 36% 6% 12% 14% 4	1776
March	1st to 10th	Night	22% 36% 7% 17% 16% 2	2024
	11th to 20th	Night	29% 37% 7% 14% 11% 3	1980
	21st to end	Night	29% 38% 6% 14% 11% 3	2131
April	1st to 10th	Night	25% 37% 7% 12% 14% 4	1800
	11th to 20th	Night	22% 36% 8% 15% 15% 5%	1775
	21st to end	Night	24% 38% 8% 17% 12% 3	1800
May	1st to 10th	Night	27% 40% 9% 14% 9% 2	1788
	11th to 20th	Night	29% 41% 8% 12% 9% 1	1532
	21st to end	Night	24% 41% 9% 17% 9%	1551
June	1st to 10th	Night	22% 40% 12% 16% 10%	1440
	11th to 20th	Night	26% 41% 11% 13% 8% 1	1440
	21st to end	Night	25% 42% 8% 15% 8% 2	1440
July	1st to 10th	Night	24% 43% 10% 14% 7% 2	1400
	11th to 20th	Night	19% 42% 14% 17% 7% 2	1537
	21st to end	Night	24% 43% 12% 15% 6%	1672
August	1st to 10th	Night	22% 43% 15% 15% 5%	1600
	11th to 20th	Night	28% 41% 9% 12% 9%	1744
	21st to end	Night	26% 43% 13% 12% 6% 1	1980
September	1st to 10th	Night	23% 38% 9% 14% 13% 4	1800
	11th to 20th	Night	24% 38% 7% 14% 15% 2	1800
	21st to end	Night	29% 38% 7% 10% 14% 3	2042
October	1st to 10th	Night	25% 38% 5% 13% 18% 3	2160
	11th to 20th	Night	27% 37% 6% 14% 14% 3	2160
	21st to end	Night	23% 38% 5% 15% 15% 4	2376
November	1st to 10th	Night	18% 41% 7% 15% 17% 3	2284
	11th to 20th	Night	23% 41% 6% 12% 14% 4	2470
	21st to end	Night	23% 40% 6% 15% 13% 3	2560
December	1st to 10th	Night	24% 40% 6% 14% 13% 2	2660
	11th to 20th	Night	28% 33% 7% 13% 15% 4	3288
	21st to end	Night	28% 27% 10% 20% 14% 1	4884

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	22% 18% 39% 15% 6%	234
	11th to 20th	Day	20% 27% 36% 15% 3	270
	21st to end	Day	16% 22% 39% 20% 3	297
February	1st to 10th	Day	14% 22% 41% 17% 5%	270
	11th to 20th	Day	29% 22% 34% 13% 3	366
	21st to end	Day	22% 21% 38% 17% 3	346
March	1st to 10th	Day	16% 20% 41% 18% 4	420
	11th to 20th	Day	23% 18% 34% 18% 6% 1	420
	21st to end	Day	19% 17% 36% 21% 5% 1	462
April	1st to 10th	Day	17% 21% 35% 18% 8% 1	420
	11th to 20th	Day	10% 15% 36% 25% 10% 4	412
	21st to end	Day	18% 12% 34% 26% 8% 1	420
May	1st to 10th	Day	13% 15% 38% 23% 8% 2	423
	11th to 20th	Day	20% 7% 28% 28% 15% 2	447
	21st to end	Day	21% 4 21% 27% 21% 7%	485
June	1st to 10th	Day	14% 3 22% 32% 24% 5%	450
	11th to 20th	Day	13% 5% 20% 31% 24% 7%	450
	21st to end	Day	9% 4 18% 38% 26% 5%	450
July	1st to 10th	Day	11% 1 13% 35% 31% 9%	445
	11th to 20th	Day	7% 2 11% 34% 34% 12%	444
	21st to end	Day	9% 2 16% 34% 30% 8%	488
August	1st to 10th	Day	12% 2 17% 33% 26% 9%	446
	11th to 20th	Day	13% 2 15% 29% 28% 12%	439
	21st to end	Day	9% 3 17% 28% 30% 13%	495
September	1st to 10th	Day	16% 2 17% 29% 22% 15%	450
	11th to 20th	Day	14% 4 16% 33% 20% 13%	450
	21st to end	Day	24% 7% 25% 25% 15% 4	450
October	1st to 10th	Day	20% 5% 20% 27% 20% 7%	450
	11th to 20th	Day	16% 10% 24% 28% 18% 3	450
	21st to end	Day	15% 11% 31% 27% 13% 4	495
November	1st to 10th	Day	17% 10% 28% 27% 14% 5%	424
	11th to 20th	Day	17% 16% 31% 25% 11% 1	370
	21st to end	Day	19% 15% 29% 23% 13% 1	277
December	1st to 10th	Day	23% 13% 38% 20% 5% 2	180
	11th to 20th	Day	21% 13% 34% 22% 10%	180
	21st to end	Day	21% 15% 34% 17% 13% 1	198
January	1st to 10th	Night	18% 18% 36% 24% 3 1	760
	11th to 20th	Night	19% 17% 34% 24% 5%	760
	21st to end	Night	20% 12% 40% 26% 2	836
February	1st to 10th	Night	21% 11% 40% 24% 3	760
	11th to 20th	Night	25% 18% 38% 17% 2	722
	21st to end	Night	20% 17% 38% 23% 2	592
March	1st to 10th	Night	16% 16% 37% 27% 5%	720
	11th to 20th	Night	21% 14% 38% 22% 6%	720
	21st to end	Night	18% 12% 40% 25% 5%	792
April	1st to 10th	Night	17% 16% 40% 23% 4	720
	11th to 20th	Night	15% 9% 39% 27% 10% 1	711
	21st to end	Night	17% 9% 33% 34% 7%	720
May	1st to 10th	Night	17% 11% 35% 30% 6% 1	708
	11th to 20th	Night	15% 6% 30% 37% 12%	470
	21st to end	Night	15% 2 20% 42% 18% 2	389
June	1st to 10th	Night	13% 2 20% 43% 20% 3	360
	11th to 20th	Night	8% 3 23% 45% 19% 2	360
	21st to end	Night	9% 2 19% 47% 21% 2	360
July	1st to 10th	Night	9% 2 15% 44% 27% 2	350
	11th to 20th	Night	6% 1 11% 42% 35% 5%	493
	21st to end	Night	9% 2 18% 42% 26% 3	591
August	1st to 10th	Night	10% 1 15% 41% 30% 4	537
	11th to 20th	Night	11% 2 16% 37% 30% 4	680
	21st to end	Night	11% 2 14% 35% 32% 6%	792
September	1st to 10th	Night	14% 3 14% 36% 29% 5%	720
	11th to 20th	Night	15% 3 15% 34% 28% 5%	720
	21st to end	Night	23% 4 18% 35% 17% 2	720
October	1st to 10th	Night	18% 6% 19% 28% 23% 5%	720
	11th to 20th	Night	19% 8% 25% 31% 15% 2	720
	21st to end	Night	17% 10% 29% 28% 15% 2	792
November	1st to 10th	Night	18% 8% 27% 30% 15% 2	740
	11th to 20th	Night	17% 10% 33% 30% 10% 1	760
	21st to end	Night	13% 13% 31% 30% 11% 1	760
December	1st to 10th	Night	20% 13% 33% 24% 9% 1	760
	11th to 20th	Night	19% 9% 38% 28% 6%	760
	21st to end	Night	19% 12% 31% 31% 6%	836

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