Woodstock
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Woodstock clear sky chart from 2005-11-06 to 2024-03-01.

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	15% 10% 5% 8% 6% 3 5% 5% 5% 7% 30%	78940
	Night	15% 10% 5% 8% 6% 3 5% 5% 5% 7% 31%	80446
Transparency	Day	52% 7% 12% 18% 10% 1	78655
	Night	52% 6% 12% 19% 10% 1	80266
Seeing	Day	19% 11% 28% 24% 13% 5%	13902
	Night	19% 10% 29% 29% 12% 1	23170

By Month

Percentage Cloud Cover NE (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	16% 17% 8% 9% 8% 4 5% 4 4 5% 20%	2643
	11th to 20th	Day	12% 19% 9% 18% 8% 4 4 4 5% 6% 12%	2840
	21st to end	Day	23% 19% 7% 12% 8% 3 5% 4 4 4 11%	3124
February	1st to 10th	Day	15% 17% 5% 10% 10% 5% 6% 5% 4 6% 17%	1710
	11th to 20th	Day	13% 14% 7% 12% 10% 3 5% 6% 4 6% 20%	1663
	21st to end	Day	17% 13% 6% 10% 8% 4 6% 4 4 5% 23%	1536
March	1st to 10th	Day	15% 12% 5% 10% 8% 4 5% 5% 5% 6% 26%	1945
	11th to 20th	Day	14% 12% 7% 9% 7% 3 4 4 4 7% 30%	1980
	21st to end	Day	18% 11% 6% 7% 7% 3 4 3 5% 5% 30%	2178
April	1st to 10th	Day	16% 12% 6% 7% 6% 3 5% 5% 5% 7% 28%	2068
	11th to 20th	Day	17% 10% 4 7% 5% 3 5% 4 5% 8% 33%	2266
	21st to end	Day	22% 9% 4 7% 5% 3 4 4 3 7% 32%	2340
May	1st to 10th	Day	17% 8% 4 7% 5% 3 4 5% 5% 8% 33%	2340
	11th to 20th	Day	16% 8% 3 6% 5% 3 4 4 6% 7% 36%	2344
	21st to end	Day	12% 5% 2 5% 5% 3 6% 6% 6% 9% 41%	2725
June	1st to 10th	Day	13% 5% 3 6% 5% 4 5% 5% 6% 8% 39%	2520
	11th to 20th	Day	11% 6% 3 6% 5% 3 6% 5% 7% 10% 39%	2620
	21st to end	Day	12% 5% 2 5% 5% 3 5% 6% 7% 9% 41%	2700
July	1st to 10th	Day	8% 4 2 5% 6% 3 6% 6% 6% 9% 45%	2691
	11th to 20th	Day	10% 6% 3 6% 7% 4 5% 6% 7% 10% 37%	2404
	21st to end	Day	8% 6% 3 7% 6% 4 6% 6% 7% 10% 38%	2547
August	1st to 10th	Day	8% 5% 3 6% 6% 4 6% 6% 7% 10% 38%	2327
	11th to 20th	Day	9% 5% 3 6% 6% 4 6% 7% 8% 9% 37%	2303
	21st to end	Day	11% 7% 3 6% 6% 3 5% 5% 6% 9% 40%	2525
September	1st to 10th	Day	12% 6% 3 6% 6% 3 6% 5% 6% 8% 38%	2145
	11th to 20th	Day	11% 4 3 5% 5% 3 5% 5% 6% 8% 44%	1980
	21st to end	Day	15% 6% 2 7% 6% 4 5% 6% 6% 8% 36%	1980
October	1st to 10th	Day	16% 9% 4 6% 6% 4 5% 4 4 7% 35%	1818
	11th to 20th	Day	20% 11% 4 6% 7% 3 5% 5% 5% 7% 28%	1800
	21st to end	Day	23% 11% 4 7% 7% 3 5% 6% 5% 6% 22%	1972
November	1st to 10th	Day	13% 10% 4 8% 7% 3 4 4 6% 8% 32%	1668
	11th to 20th	Day	15% 13% 5% 7% 6% 4 6% 5% 7% 9% 25%	1520
	21st to end	Day	18% 15% 8% 9% 6% 3 5% 5% 5% 6% 19%	1520
December	1st to 10th	Day	15% 18% 8% 11% 7% 3 5% 5% 5% 5% 18%	1520
	11th to 20th	Day	18% 16% 7% 11% 7% 4 6% 6% 4 5% 16%	1906
	21st to end	Day	29% 18% 8% 13% 6% 3 4 3 4 4 8%	2772
January	1st to 10th	Night	17% 14% 7% 11% 8% 4 5% 5% 5% 6% 18%	4301
	11th to 20th	Night	14% 15% 7% 13% 9% 6% 7% 6% 6% 6% 12%	4120
	21st to end	Night	22% 14% 9% 12% 7% 4 4 4 4 4 16%	4532
February	1st to 10th	Night	15% 14% 7% 10% 9% 4 5% 4 5% 6% 21%	2470
	11th to 20th	Night	14% 12% 5% 10% 8% 4 5% 6% 6% 7% 24%	2403
	21st to end	Night	16% 13% 5% 10% 7% 4 5% 5% 5% 6% 23%	1916
March	1st to 10th	Night	13% 9% 3 8% 7% 4 5% 5% 6% 7% 33%	2009
	11th to 20th	Night	14% 10% 4 8% 6% 4 5% 5% 5% 6% 34%	1979
	21st to end	Night	17% 10% 4 7% 6% 2 4 5% 4 4 36%	2178
April	1st to 10th	Night	18% 8% 4 7% 5% 3 4 5% 5% 7% 33%	1891
	11th to 20th	Night	17% 8% 3 6% 6% 3 5% 4 4 7% 37%	1656
	21st to end	Night	14% 10% 3 6% 6% 3 5% 5% 7% 8% 33%	1620
May	1st to 10th	Night	17% 7% 3 5% 5% 3 4 5% 6% 8% 36%	1620
	11th to 20th	Night	13% 6% 3 6% 6% 3 4 5% 6% 8% 40%	1545
	21st to end	Night	9% 4 2 4 3 3 4 5% 6% 7% 52%	1550
June	1st to 10th	Night	10% 4 3 5% 5% 3 4 5% 6% 7% 46%	1440
	11th to 20th	Night	9% 6% 2 5% 5% 3 5% 5% 6% 10% 44%	1332
	21st to end	Night	10% 5% 2 5% 4 3 5% 5% 6% 8% 47%	1260
July	1st to 10th	Night	5% 2 2 4 5% 3 3 4 6% 9% 56%	1264
	11th to 20th	Night	9% 4 2 5% 5% 2 4 5% 6% 9% 50%	1552
	21st to end	Night	7% 5% 2 5% 5% 3 6% 6% 7% 8% 48%	1771
August	1st to 10th	Night	7% 4 3 5% 5% 3 5% 5% 7% 8% 48%	1611
	11th to 20th	Night	7% 4 2 5% 5% 3 4 5% 6% 10% 49%	1598
	21st to end	Night	8% 5% 2 5% 4 3 4 4 6% 10% 48%	1813
September	1st to 10th	Night	11% 6% 3 6% 6% 3 5% 4 4 7% 46%	1812
	11th to 20th	Night	10% 5% 1 4 4 3 4 4 6% 7% 53%	1980
	21st to end	Night	16% 6% 3 5% 5% 3 4 4 5% 7% 41%	1980
October	1st to 10th	Night	15% 8% 3 5% 4 3 4 4 5% 7% 41%	2142
	11th to 20th	Night	18% 8% 4 7% 5% 3 4 5% 5% 7% 34%	2160
	21st to end	Night	23% 8% 3 7% 6% 4 4 5% 5% 6% 28%	2381
November	1st to 10th	Night	14% 8% 3 6% 6% 3 4 5% 6% 7% 37%	2408
	11th to 20th	Night	15% 11% 4 8% 6% 4 5% 5% 6% 7% 28%	2660
	21st to end	Night	19% 12% 5% 8% 6% 3 5% 5% 5% 7% 24%	2660
December	1st to 10th	Night	18% 16% 6% 11% 7% 3 6% 6% 4 6% 18%	2660
	11th to 20th	Night	14% 18% 7% 10% 6% 3 4 4 5% 6% 22%	3288
	21st to end	Night	26% 19% 8% 10% 7% 3 4 3 4 4 11%	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	64% 9% 10% 10% 6%	2644
	11th to 20th	Day	73% 5% 11% 7% 4	2840
	21st to end	Day	77% 6% 7% 6% 3	3124
February	1st to 10th	Day	68% 6% 10% 12% 4 1	1710
	11th to 20th	Day	65% 5% 10% 13% 7%	1672
	21st to end	Day	64% 5% 11% 13% 6% 1	1536
March	1st to 10th	Day	58% 6% 13% 16% 6% 1	1948
	11th to 20th	Day	55% 6% 9% 18% 10% 2	1980
	21st to end	Day	57% 4 10% 17% 11% 2	2178
April	1st to 10th	Day	56% 5% 11% 17% 11% 1	2068
	11th to 20th	Day	51% 5% 12% 20% 12% 2	2266
	21st to end	Day	53% 5% 10% 19% 11% 2	2340
May	1st to 10th	Day	49% 6% 11% 21% 12% 1	2340
	11th to 20th	Day	47% 6% 12% 21% 12% 2	2348
	21st to end	Day	39% 8% 13% 22% 15% 2	2725
June	1st to 10th	Day	41% 7% 13% 24% 13% 2	2520
	11th to 20th	Day	41% 8% 12% 22% 15% 2	2620
	21st to end	Day	38% 8% 14% 24% 16%	2700
July	1st to 10th	Day	34% 8% 13% 26% 17% 3	2617
	11th to 20th	Day	39% 9% 15% 24% 12% 1	2331
	21st to end	Day	40% 9% 14% 22% 13% 2	2405
August	1st to 10th	Day	38% 9% 17% 25% 11% 1	2314
	11th to 20th	Day	41% 9% 16% 22% 11% 1	2303
	21st to end	Day	39% 8% 13% 25% 13% 2	2525
September	1st to 10th	Day	42% 8% 14% 23% 12% 1	2145
	11th to 20th	Day	36% 7% 14% 28% 15%	1980
	21st to end	Day	44% 8% 13% 24% 10% 1	1980
October	1st to 10th	Day	50% 5% 12% 19% 12% 1	1818
	11th to 20th	Day	54% 7% 13% 16% 9% 1	1800
	21st to end	Day	62% 6% 12% 14% 6% 1	1972
November	1st to 10th	Day	49% 7% 12% 23% 8% 2	1668
	11th to 20th	Day	54% 7% 17% 14% 8% 1	1520
	21st to end	Day	64% 6% 14% 12% 4	1520
December	1st to 10th	Day	65% 8% 13% 10% 4	1520
	11th to 20th	Day	69% 6% 12% 9% 4	1906
	21st to end	Day	79% 6% 8% 6% 1	2772
January	1st to 10th	Night	63% 7% 14% 10% 5% 1	4301
	11th to 20th	Night	69% 8% 11% 9% 3	4120
	21st to end	Night	72% 6% 8% 11% 3 1	4532
February	1st to 10th	Night	64% 6% 10% 15% 5%	2470
	11th to 20th	Night	59% 6% 12% 15% 8%	2405
	21st to end	Night	61% 6% 11% 16% 7%	1916
March	1st to 10th	Night	49% 6% 13% 21% 10% 1	2019
	11th to 20th	Night	50% 6% 10% 22% 11% 2	1980
	21st to end	Night	51% 5% 9% 19% 13% 3	2178
April	1st to 10th	Night	50% 5% 10% 19% 14% 1	1891
	11th to 20th	Night	47% 5% 10% 19% 18% 2	1656
	21st to end	Night	47% 5% 11% 20% 15% 3	1620
May	1st to 10th	Night	45% 6% 10% 22% 15% 3	1620
	11th to 20th	Night	42% 6% 11% 24% 14% 4	1546
	21st to end	Night	31% 7% 14% 26% 19% 3	1551
June	1st to 10th	Night	36% 7% 12% 27% 17% 3	1440
	11th to 20th	Night	35% 8% 12% 25% 18% 2	1332
	21st to end	Night	35% 7% 14% 23% 20% 1	1260
July	1st to 10th	Night	25% 7% 11% 28% 24% 4	1229
	11th to 20th	Night	32% 6% 14% 29% 17% 3	1502
	21st to end	Night	32% 9% 14% 25% 17% 3	1672
August	1st to 10th	Night	32% 8% 15% 31% 13% 1	1600
	11th to 20th	Night	30% 9% 15% 30% 14% 2	1598
	21st to end	Night	32% 7% 13% 30% 16% 2	1813
September	1st to 10th	Night	39% 7% 11% 25% 16% 2	1812
	11th to 20th	Night	30% 6% 13% 32% 18% 1	1980
	21st to end	Night	42% 7% 12% 26% 13% 1	1980
October	1st to 10th	Night	43% 6% 11% 24% 15% 1	2142
	11th to 20th	Night	49% 6% 13% 21% 11%	2160
	21st to end	Night	56% 7% 10% 17% 11% 1	2381
November	1st to 10th	Night	42% 6% 14% 23% 13% 1	2408
	11th to 20th	Night	52% 7% 13% 18% 9% 1	2660
	21st to end	Night	59% 6% 16% 13% 5% 1	2660
December	1st to 10th	Night	65% 7% 12% 12% 4	2660
	11th to 20th	Night	61% 5% 15% 14% 4	3288
	21st to end	Night	76% 5% 10% 7% 2	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% 19% 34% 19% 5% 1	216
	11th to 20th	Day	23% 19% 40% 13% 4 1	270
	21st to end	Day	28% 14% 33% 22% 2 1	297
February	1st to 10th	Day	24% 18% 39% 15% 3 1	270
	11th to 20th	Day	24% 21% 40% 12% 3	270
	21st to end	Day	28% 28% 30% 13% 1	225
March	1st to 10th	Day	25% 14% 35% 20% 5% 1	388
	11th to 20th	Day	23% 13% 38% 19% 6% 1	420
	21st to end	Day	29% 13% 29% 22% 7% 1	462
April	1st to 10th	Day	20% 18% 32% 22% 6% 2	420
	11th to 20th	Day	28% 13% 25% 18% 12% 4	412
	21st to end	Day	25% 12% 31% 22% 7% 3	420
May	1st to 10th	Day	25% 10% 26% 24% 12% 4	423
	11th to 20th	Day	17% 10% 29% 21% 17% 5%	447
	21st to end	Day	14% 7% 22% 30% 18% 8%	485
June	1st to 10th	Day	14% 9% 29% 31% 12% 4	450
	11th to 20th	Day	12% 9% 28% 32% 15% 5%	550
	21st to end	Day	13% 7% 30% 32% 13% 4	630
July	1st to 10th	Day	9% 6% 22% 28% 26% 9%	612
	11th to 20th	Day	14% 3 23% 28% 21% 11%	444
	21st to end	Day	8% 4 24% 34% 23% 7%	488
August	1st to 10th	Day	8% 4 20% 30% 23% 15%	446
	11th to 20th	Day	12% 5% 17% 29% 22% 16%	439
	21st to end	Day	12% 7% 20% 27% 22% 12%	495
September	1st to 10th	Day	13% 7% 21% 27% 21% 11%	450
	11th to 20th	Day	10% 4 19% 27% 28% 12%	450
	21st to end	Day	17% 10% 24% 26% 14% 9%	450
October	1st to 10th	Day	20% 9% 25% 22% 19% 6%	450
	11th to 20th	Day	19% 19% 31% 22% 8% 2	450
	21st to end	Day	28% 13% 32% 20% 6% 1	487
November	1st to 10th	Day	21% 21% 32% 17% 8% 2	268
	11th to 20th	Day	25% 18% 33% 14% 7% 3	180
	21st to end	Day	25% 17% 39% 16% 3	180
December	1st to 10th	Day	29% 19% 33% 13% 5% 1	180
	11th to 20th	Day	26% 24% 32% 16% 2	180
	21st to end	Day	30% 19% 36% 11% 3	198
January	1st to 10th	Night	22% 18% 36% 17% 6% 1	760
	11th to 20th	Night	28% 15% 32% 21% 3	760
	21st to end	Night	19% 12% 35% 28% 6%	836
February	1st to 10th	Night	22% 16% 36% 24% 2	760
	11th to 20th	Night	22% 15% 34% 24% 5%	743
	21st to end	Night	24% 17% 34% 23% 3	628
March	1st to 10th	Night	19% 14% 35% 26% 6%	723
	11th to 20th	Night	19% 14% 37% 22% 7% 1	720
	21st to end	Night	21% 12% 32% 25% 10% 1	792
April	1st to 10th	Night	22% 13% 31% 29% 5%	720
	11th to 20th	Night	20% 13% 30% 27% 10% 1	592
	21st to end	Night	18% 10% 31% 32% 8%	540
May	1st to 10th	Night	20% 6% 27% 31% 15% 1	540
	11th to 20th	Night	18% 4 27% 37% 13% 1	484
	21st to end	Night	10% 5% 28% 38% 18% 1	389
June	1st to 10th	Night	14% 4 27% 43% 11% 1	360
	11th to 20th	Night	10% 5% 31% 42% 13%	360
	21st to end	Night	13% 4 23% 45% 15%	360
July	1st to 10th	Night	5% 3 22% 46% 21% 2	350
	11th to 20th	Night	10% 2 20% 41% 24% 2	458
	21st to end	Night	10% 3 15% 47% 22% 2	591
August	1st to 10th	Night	9% 2 14% 44% 29% 2	537
	11th to 20th	Night	9% 2 13% 40% 31% 5%	534
	21st to end	Night	9% 3 20% 37% 27% 4	625
September	1st to 10th	Night	13% 5% 22% 32% 23% 5%	720
	11th to 20th	Night	13% 4 15% 38% 26% 4	720
	21st to end	Night	18% 7% 20% 31% 20% 5%	720
October	1st to 10th	Night	18% 7% 24% 30% 18% 2	720
	11th to 20th	Night	21% 12% 30% 26% 10% 1	720
	21st to end	Night	27% 11% 31% 26% 5%	792
November	1st to 10th	Night	19% 12% 26% 30% 11% 2	740
	11th to 20th	Night	20% 16% 35% 21% 8% 1	760
	21st to end	Night	25% 12% 33% 23% 6%	760
December	1st to 10th	Night	27% 16% 33% 19% 5%	760
	11th to 20th	Night	23% 19% 36% 18% 5%	760
	21st to end	Night	30% 14% 34% 19% 3	836

Page generated at 2024-02-27 06:30:15. Version ac07

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