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 2024-03-18.

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% 9% 4 7% 6% 3 5% 5% 5% 7% 36%	78560
	Night	14% 10% 4 7% 5% 3 4 4 5% 6% 37%	81263
Transparency	Day	47% 6% 12% 21% 12% 1	78261
	Night	47% 6% 11% 22% 13% 2	81083
Seeing	Day	16% 11% 30% 25% 13% 5%	14862
	Night	18% 10% 31% 28% 12% 1	24939

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% 10% 11% 8% 3 4 4 3 5% 27%	2527
	11th to 20th	Day	12% 14% 6% 14% 6% 2 5% 9% 7% 5% 20%	2530
	21st to end	Day	17% 19% 10% 10% 5% 3 3 3 5% 6% 19%	2861
February	1st to 10th	Day	13% 13% 5% 8% 6% 5% 6% 5% 5% 6% 28%	1714
	11th to 20th	Day	14% 10% 4 7% 7% 3 5% 4 3 6% 37%	1848
	21st to end	Day	13% 13% 6% 9% 6% 3 4 4 4 7% 31%	1570
March	1st to 10th	Day	14% 10% 6% 8% 7% 3 4 4 4 5% 34%	1900
	11th to 20th	Day	13% 8% 3 7% 7% 3 4 4 6% 8% 38%	1932
	21st to end	Day	20% 10% 5% 7% 6% 3 5% 5% 5% 6% 27%	2376
April	1st to 10th	Day	17% 11% 5% 7% 7% 2 4 4 5% 5% 32%	2160
	11th to 20th	Day	16% 10% 3 6% 6% 4 5% 5% 6% 7% 34%	2134
	21st to end	Day	21% 8% 3 7% 6% 3 4 5% 5% 6% 32%	2250
May	1st to 10th	Day	17% 9% 3 7% 6% 4 5% 5% 6% 8% 31%	2340
	11th to 20th	Day	18% 8% 3 5% 5% 3 6% 5% 5% 7% 34%	2463
	21st to end	Day	13% 6% 4 6% 6% 3 6% 5% 7% 7% 37%	2725
June	1st to 10th	Day	10% 5% 2 6% 5% 3 5% 5% 6% 8% 45%	2520
	11th to 20th	Day	10% 6% 3 5% 4 3 4 5% 7% 10% 44%	2520
	21st to end	Day	11% 6% 4 6% 5% 3 6% 5% 6% 9% 39%	2520
July	1st to 10th	Day	7% 4 2 5% 5% 3 5% 6% 7% 10% 45%	2520
	11th to 20th	Day	9% 4 2 5% 5% 3 4 6% 6% 10% 45%	2520
	21st to end	Day	7% 4 3 5% 6% 4 6% 5% 6% 10% 45%	2743
August	1st to 10th	Day	8% 5% 2 5% 6% 4 5% 6% 8% 10% 42%	2492
	11th to 20th	Day	9% 6% 3 6% 6% 4 5% 5% 6% 8% 42%	2129
	21st to end	Day	9% 5% 2 5% 5% 3 5% 6% 6% 7% 48%	2376
September	1st to 10th	Day	12% 5% 2 6% 5% 3 4 4 6% 7% 46%	2160
	11th to 20th	Day	12% 4 2 4 3 3 4 4 4 8% 52%	2062
	21st to end	Day	11% 6% 3 6% 5% 3 4 4 6% 8% 44%	1980
October	1st to 10th	Day	13% 7% 2 6% 6% 3 4 5% 4 6% 45%	1904
	11th to 20th	Day	19% 9% 4 7% 6% 3 4 4 5% 8% 32%	1798
	21st to end	Day	21% 8% 4 6% 6% 3 3 3 5% 4 37%	1782
November	1st to 10th	Day	12% 7% 3 6% 4 2 4 5% 5% 6% 44%	1672
	11th to 20th	Day	14% 11% 5% 9% 6% 3 4 4 6% 5% 33%	1710
	21st to end	Day	18% 11% 4 6% 7% 3 4 4 4 5% 36%	1601
December	1st to 10th	Day	14% 11% 5% 8% 7% 4 5% 4 6% 5% 30%	1520
	11th to 20th	Day	12% 12% 5% 10% 6% 3 5% 6% 6% 8% 27%	1918
	21st to end	Day	20% 21% 10% 10% 7% 3 4 4 3 3 15%	2783
January	1st to 10th	Night	14% 13% 8% 10% 7% 3 4 3 3 4 30%	4428
	11th to 20th	Night	15% 16% 7% 13% 6% 3 4 7% 6% 4 20%	4440
	21st to end	Night	20% 17% 8% 10% 6% 2 4 3 4 5% 21%	4789
February	1st to 10th	Night	13% 14% 5% 8% 7% 4 4 4 4 6% 33%	2464
	11th to 20th	Night	13% 10% 4 7% 5% 3 5% 4 5% 6% 38%	2218
	21st to end	Night	18% 12% 4 5% 6% 3 3 4 5% 5% 36%	1884
March	1st to 10th	Night	17% 9% 4 6% 6% 4 4 4 5% 7% 35%	2280
	11th to 20th	Night	12% 8% 3 6% 5% 4 4 4 5% 8% 41%	2209
	21st to end	Night	19% 10% 4 7% 5% 4 5% 4 4 6% 32%	1980
April	1st to 10th	Night	16% 9% 4 6% 5% 3 6% 5% 4 6% 37%	1800
	11th to 20th	Night	19% 8% 4 6% 4 3 5% 4 4 5% 38%	1775
	21st to end	Night	19% 7% 3 6% 6% 3 4 3 5% 7% 38%	1710
May	1st to 10th	Night	15% 7% 3 7% 4 4 6% 5% 6% 8% 35%	1620
	11th to 20th	Night	17% 7% 2 5% 6% 3 3 5% 5% 9% 39%	1429
	21st to end	Night	11% 6% 3 6% 6% 3 4 4 5% 10% 41%	1551
June	1st to 10th	Night	9% 4 2 5% 4 4 5% 6% 6% 8% 48%	1440
	11th to 20th	Night	10% 5% 3 4 5% 3 5% 5% 5% 8% 47%	1440
	21st to end	Night	8% 5% 3 6% 5% 3 5% 5% 7% 9% 44%	1440
July	1st to 10th	Night	7% 4 2 3 4 3 4 5% 6% 11% 50%	1440
	11th to 20th	Night	7% 5% 1 4 5% 3 5% 4 6% 8% 52%	1440
	21st to end	Night	6% 4 2 4 4 3 4 6% 7% 10% 52%	1575
August	1st to 10th	Night	4 4 2 4 5% 3 4 5% 8% 11% 49%	1444
	11th to 20th	Night	9% 3 2 5% 4 2 3 5% 5% 8% 54%	1768
	21st to end	Night	8% 4 2 4 4 2 4 5% 6% 8% 54%	1980
September	1st to 10th	Night	10% 6% 2 4 5% 2 4 3 4 5% 54%	1800
	11th to 20th	Night	11% 4 2 5% 3 3 4 4 4 5% 55%	1880
	21st to end	Night	11% 5% 2 6% 5% 3 3 4 5% 6% 49%	1980
October	1st to 10th	Night	12% 6% 2 5% 4 3 4 4 4 6% 50%	2052
	11th to 20th	Night	18% 8% 3 5% 4 2 3 4 4 6% 43%	2160
	21st to end	Night	20% 9% 3 5% 5% 3 4 4 4 6% 38%	2574
November	1st to 10th	Night	11% 9% 3 5% 4 2 4 4 4 6% 48%	2406
	11th to 20th	Night	14% 11% 3 6% 6% 3 4 4 4 6% 37%	2470
	21st to end	Night	16% 10% 4 7% 5% 3 4 4 5% 6% 37%	2574
December	1st to 10th	Night	15% 10% 5% 8% 6% 3 5% 5% 4 7% 32%	2660
	11th to 20th	Night	15% 12% 5% 8% 6% 3 5% 4 5% 6% 31%	3279
	21st to end	Night	22% 17% 7% 9% 6% 3 4 5% 5% 5% 17%	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	61% 5% 11% 16% 7%	2528
	11th to 20th	Day	60% 6% 13% 13% 7%	2530
	21st to end	Day	67% 5% 8% 14% 6%	2861
February	1st to 10th	Day	56% 5% 12% 15% 10% 1	1714
	11th to 20th	Day	49% 5% 10% 23% 11% 2	1858
	21st to end	Day	54% 6% 9% 19% 11% 1	1570
March	1st to 10th	Day	53% 6% 11% 21% 8% 1	1900
	11th to 20th	Day	45% 6% 13% 24% 12% 2	1932
	21st to end	Day	58% 5% 12% 17% 6% 1	2376
April	1st to 10th	Day	54% 4 12% 19% 10%	2160
	11th to 20th	Day	49% 6% 10% 21% 12% 3	2134
	21st to end	Day	51% 6% 14% 16% 12% 1	2250
May	1st to 10th	Day	51% 7% 13% 22% 7%	2340
	11th to 20th	Day	48% 7% 13% 21% 10%	2467
	21st to end	Day	44% 8% 13% 18% 15% 2	2725
June	1st to 10th	Day	35% 7% 12% 27% 16% 2	2520
	11th to 20th	Day	35% 7% 13% 23% 19% 3	2520
	21st to end	Day	41% 8% 14% 21% 15% 2	2520
July	1st to 10th	Day	31% 8% 15% 29% 14% 3	2451
	11th to 20th	Day	32% 8% 16% 25% 17% 2	2445
	21st to end	Day	33% 8% 16% 26% 16% 3	2591
August	1st to 10th	Day	34% 9% 17% 27% 11% 2	2477
	11th to 20th	Day	38% 7% 15% 24% 14% 1	2129
	21st to end	Day	32% 7% 12% 25% 20% 3	2376
September	1st to 10th	Day	36% 7% 13% 24% 17% 3	2160
	11th to 20th	Day	31% 5% 12% 32% 18% 3	2062
	21st to end	Day	39% 5% 10% 29% 16% 1	1980
October	1st to 10th	Day	39% 7% 11% 26% 17% 1	1904
	11th to 20th	Day	51% 5% 12% 20% 12% 1	1798
	21st to end	Day	51% 4 10% 22% 10% 2	1782
November	1st to 10th	Day	40% 6% 13% 23% 16% 2	1672
	11th to 20th	Day	52% 5% 12% 21% 9% 1	1710
	21st to end	Day	51% 5% 11% 24% 8%	1601
December	1st to 10th	Day	54% 5% 14% 18% 8% 1	1520
	11th to 20th	Day	54% 7% 15% 16% 7% 2	1915
	21st to end	Day	76% 4 7% 9% 4	2783
January	1st to 10th	Night	58% 5% 9% 18% 9% 1	4428
	11th to 20th	Night	65% 5% 10% 12% 8%	4440
	21st to end	Night	67% 5% 9% 13% 6% 1	4789
February	1st to 10th	Night	54% 5% 9% 18% 13% 2	2464
	11th to 20th	Night	47% 5% 12% 21% 14% 1	2219
	21st to end	Night	51% 4 10% 21% 10% 4	1884
March	1st to 10th	Night	49% 6% 13% 21% 9% 2	2280
	11th to 20th	Night	41% 6% 13% 21% 15% 3	2209
	21st to end	Night	54% 5% 10% 19% 10% 2	1980
April	1st to 10th	Night	47% 7% 11% 21% 14% 2	1800
	11th to 20th	Night	49% 5% 6% 20% 16% 4	1775
	21st to end	Night	46% 5% 10% 23% 13% 2	1710
May	1st to 10th	Night	45% 9% 13% 21% 12%	1620
	11th to 20th	Night	43% 6% 12% 24% 14% 1	1430
	21st to end	Night	40% 7% 13% 22% 17% 2	1552
June	1st to 10th	Night	32% 8% 14% 25% 19% 3	1440
	11th to 20th	Night	35% 6% 10% 24% 23% 2	1440
	21st to end	Night	36% 7% 16% 22% 17% 2	1440
July	1st to 10th	Night	28% 8% 14% 31% 16% 4	1400
	11th to 20th	Night	29% 7% 14% 30% 18% 2	1392
	21st to end	Night	25% 7% 17% 27% 18% 5%	1487
August	1st to 10th	Night	26% 9% 17% 31% 14% 3	1435
	11th to 20th	Night	27% 7% 15% 31% 19% 1	1768
	21st to end	Night	27% 7% 13% 29% 20% 4	1980
September	1st to 10th	Night	33% 6% 9% 25% 24% 3	1800
	11th to 20th	Night	31% 4 9% 33% 21% 2	1880
	21st to end	Night	35% 5% 11% 31% 16% 2	1980
October	1st to 10th	Night	35% 5% 10% 29% 19% 2	2052
	11th to 20th	Night	42% 5% 10% 23% 18% 2	2160
	21st to end	Night	47% 5% 11% 24% 12% 1	2574
November	1st to 10th	Night	38% 5% 9% 26% 19% 3	2406
	11th to 20th	Night	49% 5% 12% 22% 12% 1	2470
	21st to end	Night	49% 4 12% 23% 11% 1	2574
December	1st to 10th	Night	52% 7% 11% 20% 9% 1	2660
	11th to 20th	Night	53% 6% 12% 19% 9% 1	3281
	21st to end	Night	68% 5% 10% 12% 5%	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	20% 16% 37% 21% 6%	270
	11th to 20th	Day	22% 16% 38% 20% 3 1	270
	21st to end	Day	21% 16% 39% 19% 4 1	297
February	1st to 10th	Day	16% 21% 41% 17% 4	270
	11th to 20th	Day	24% 21% 36% 15% 4	270
	21st to end	Day	23% 23% 39% 12% 3	225
March	1st to 10th	Day	19% 26% 38% 15% 3	270
	11th to 20th	Day	25% 17% 35% 14% 8%	269
	21st to end	Day	27% 13% 31% 19% 8% 2	462
April	1st to 10th	Day	23% 15% 33% 24% 4	420
	11th to 20th	Day	22% 19% 29% 19% 10% 2	412
	21st to end	Day	24% 12% 32% 19% 11% 2	420
May	1st to 10th	Day	21% 13% 31% 24% 8% 2	423
	11th to 20th	Day	22% 11% 31% 23% 10% 2	609
	21st to end	Day	17% 9% 28% 24% 16% 6%	679
June	1st to 10th	Day	10% 6% 32% 31% 16% 5%	630
	11th to 20th	Day	12% 9% 31% 29% 15% 5%	630
	21st to end	Day	13% 9% 27% 32% 14% 5%	630
July	1st to 10th	Day	8% 2 21% 31% 24% 14%	621
	11th to 20th	Day	9% 5% 28% 31% 19% 8%	618
	21st to end	Day	7% 5% 27% 38% 16% 7%	684
August	1st to 10th	Day	9% 2 22% 34% 21% 12%	611
	11th to 20th	Day	10% 5% 21% 25% 24% 15%	439
	21st to end	Day	9% 3 22% 32% 25% 9%	495
September	1st to 10th	Day	15% 7% 24% 25% 23% 6%	450
	11th to 20th	Day	10% 5% 20% 31% 22% 11%	450
	21st to end	Day	13% 11% 27% 24% 17% 7%	450
October	1st to 10th	Day	14% 10% 28% 27% 16% 5%	374
	11th to 20th	Day	26% 19% 32% 18% 6%	270
	21st to end	Day	31% 18% 31% 15% 5% 1	297
November	1st to 10th	Day	16% 16% 37% 21% 7% 2	270
	11th to 20th	Day	23% 18% 36% 16% 6% 1	270
	21st to end	Day	26% 11% 41% 18% 4	270
December	1st to 10th	Day	17% 21% 41% 16% 5%	270
	11th to 20th	Day	16% 19% 39% 20% 5% 1	270
	21st to end	Day	24% 24% 36% 14% 2	297
January	1st to 10th	Night	19% 16% 37% 23% 5%	950
	11th to 20th	Night	20% 17% 38% 20% 5% 1	950
	21st to end	Night	21% 12% 38% 25% 4	1045
February	1st to 10th	Night	22% 12% 38% 23% 5%	944
	11th to 20th	Night	19% 16% 37% 24% 4	743
	21st to end	Night	25% 13% 38% 20% 3	628
March	1st to 10th	Night	22% 13% 36% 22% 6% 1	760
	11th to 20th	Night	15% 13% 38% 27% 8% 1	713
	21st to end	Night	22% 10% 31% 28% 8% 1	594
April	1st to 10th	Night	21% 12% 37% 24% 6%	540
	11th to 20th	Night	23% 13% 31% 25% 8%	533
	21st to end	Night	23% 9% 30% 29% 9%	540
May	1st to 10th	Night	18% 11% 34% 29% 8% 1	540
	11th to 20th	Night	20% 8% 29% 30% 13%	531
	21st to end	Night	14% 6% 27% 33% 19% 1	584
June	1st to 10th	Night	9% 5% 27% 41% 18%	540
	11th to 20th	Night	13% 4 29% 39% 13% 1	540
	21st to end	Night	8% 5% 30% 39% 18% 1	540
July	1st to 10th	Night	8% 2 17% 39% 32% 2	525
	11th to 20th	Night	8% 3 26% 38% 23% 2	522
	21st to end	Night	5% 2 21% 46% 25% 1	591
August	1st to 10th	Night	5% 1 16% 49% 25% 4	537
	11th to 20th	Night	10% 4 14% 36% 32% 4	534
	21st to end	Night	9% 2 19% 40% 28% 3	594
September	1st to 10th	Night	11% 4 22% 35% 24% 4	540
	11th to 20th	Night	12% 4 21% 32% 27% 4	620
	21st to end	Night	13% 10% 24% 31% 19% 3	720
October	1st to 10th	Night	15% 6% 26% 32% 18% 2	720
	11th to 20th	Night	22% 13% 31% 24% 9% 1	720
	21st to end	Night	26% 11% 32% 23% 7%	792
November	1st to 10th	Night	17% 11% 37% 24% 10% 1	740
	11th to 20th	Night	21% 18% 33% 23% 6%	760
	21st to end	Night	21% 13% 38% 22% 6%	864
December	1st to 10th	Night	20% 14% 39% 21% 4	950
	11th to 20th	Night	23% 13% 38% 22% 5%	950
	21st to end	Night	28% 15% 36% 18% 3	1045

Page generated at 2024-03-15 13:01:39. Version ac07

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