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 2025-02-06.

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	18% 10% 3 8% 5% 5% 4 4 5% 7% 31%	107993
	Night	18% 11% 4 8% 5% 4 4 4 5% 6% 31%	110325
Transparency	Day	53% 5% 12% 20% 10% 1	111537
	Night	52% 5% 12% 20% 10% 1	114946
Seeing	Day	27% 14% 29% 20% 8% 2	16324
	Night	25% 13% 30% 24% 7%	24491

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	14% 21% 8% 12% 7% 4 4 2 3 4 20%	3201
	11th to 20th	Day	14% 14% 6% 16% 6% 4 4 3 4 5% 24%	3570
	21st to end	Day	8% 9% 4 11% 7% 7% 6% 4 6% 7% 32%	4070
February	1st to 10th	Day	14% 14% 4 10% 7% 6% 5% 4 5% 6% 27%	1755
	11th to 20th	Day	14% 13% 4 11% 7% 6% 5% 3 5% 5% 25%	1667
	21st to end	Day	12% 12% 4 8% 8% 5% 5% 4 6% 5% 31%	1570
March	1st to 10th	Day	22% 14% 4 8% 4 4 4 3 4 5% 28%	3206
	11th to 20th	Day	19% 20% 5% 11% 5% 5% 4 3 4 5% 19%	3480
	21st to end	Day	25% 15% 5% 8% 5% 4 3 3 4 7% 23%	3816
April	1st to 10th	Day	23% 13% 3 8% 5% 4 3 4 5% 6% 25%	2252
	11th to 20th	Day	21% 11% 3 7% 4 5% 3 4 5% 6% 33%	2442
	21st to end	Day	25% 9% 3 8% 4 4 4 3 4 4 32%	2470
May	1st to 10th	Day	20% 9% 3 8% 6% 5% 4 4 6% 7% 29%	4106
	11th to 20th	Day	21% 9% 3 8% 5% 4 4 3 5% 7% 30%	4225
	21st to end	Day	17% 7% 3 8% 6% 5% 6% 5% 6% 8% 31%	5149
June	1st to 10th	Day	26% 9% 3 7% 5% 4 4 4 6% 6% 27%	2850
	11th to 20th	Day	20% 8% 2 6% 4 4 4 4 6% 7% 35%	2850
	21st to end	Day	26% 9% 3 7% 5% 4 5% 4 5% 7% 25%	2850
July	1st to 10th	Day	14% 7% 3 7% 6% 5% 6% 5% 7% 8% 31%	4760
	11th to 20th	Day	16% 6% 2 6% 4 5% 6% 4 7% 8% 35%	4647
	21st to end	Day	15% 7% 3 7% 5% 5% 4 4 5% 8% 37%	4731
August	1st to 10th	Day	19% 7% 3 7% 5% 5% 5% 5% 6% 8% 31%	4105
	11th to 20th	Day	16% 8% 3 9% 5% 5% 5% 5% 7% 8% 30%	4045
	21st to end	Day	16% 6% 2 6% 5% 4 5% 4 6% 8% 37%	4532
September	1st to 10th	Day	13% 6% 2 6% 5% 4 5% 4 5% 6% 44%	2248
	11th to 20th	Day	17% 6% 2 6% 4 3 3 3 4 6% 46%	2090
	21st to end	Day	19% 6% 2 6% 4 4 4 3 5% 8% 40%	2090
October	1st to 10th	Day	19% 9% 3 6% 4 4 4 3 5% 6% 37%	1976
	11th to 20th	Day	24% 8% 2 6% 4 4 4 3 5% 6% 35%	1900
	21st to end	Day	23% 12% 3 7% 5% 4 4 3 4 6% 30%	1902
November	1st to 10th	Day	20% 10% 2 7% 5% 5% 5% 4 5% 6% 32%	1750
	11th to 20th	Day	20% 11% 4 7% 4 5% 4 4 5% 6% 31%	1600
	21st to end	Day	21% 12% 4 8% 5% 4 4 3 5% 6% 28%	1600
December	1st to 10th	Day	19% 12% 3 10% 5% 5% 4 4 6% 5% 27%	2394
	11th to 20th	Day	20% 11% 4 8% 5% 4 4 3 4 5% 32%	2618
	21st to end	Day	19% 14% 4 11% 6% 5% 3 3 3 5% 27%	3476
January	1st to 10th	Night	14% 17% 7% 14% 7% 4 4 3 5% 5% 20%	6747
	11th to 20th	Night	14% 13% 7% 13% 7% 5% 5% 4 5% 5% 24%	6315
	21st to end	Night	8% 11% 4 8% 5% 5% 5% 4 7% 8% 35%	6886
February	1st to 10th	Night	13% 15% 4 8% 6% 5% 5% 4 5% 6% 29%	2536
	11th to 20th	Night	15% 14% 5% 10% 7% 6% 5% 3 4 5% 25%	2394
	21st to end	Night	14% 14% 3 7% 8% 5% 5% 3 4 5% 33%	1884
March	1st to 10th	Night	23% 13% 3 7% 5% 5% 6% 3 4 4 26%	3634
	11th to 20th	Night	18% 19% 5% 9% 5% 5% 4 4 5% 5% 23%	3479
	21st to end	Night	28% 13% 4 6% 4 3 3 2 5% 6% 27%	3816
April	1st to 10th	Night	24% 13% 3 7% 4 3 4 3 4 6% 30%	1924
	11th to 20th	Night	23% 7% 3 6% 4 5% 4 2 4 7% 35%	1688
	21st to end	Night	26% 8% 2 6% 4 4 4 4 5% 4 33%	1710
May	1st to 10th	Night	21% 8% 2 5% 5% 4 5% 4 6% 8% 33%	2834
	11th to 20th	Night	20% 8% 3 7% 5% 5% 5% 4 6% 7% 31%	2674
	21st to end	Night	15% 7% 2 6% 5% 4 5% 4 7% 8% 37%	2464
June	1st to 10th	Night	23% 8% 3 7% 5% 5% 6% 3 5% 7% 29%	1330
	11th to 20th	Night	19% 6% 2 6% 5% 4 5% 5% 6% 7% 35%	1330
	21st to end	Night	25% 9% 3 7% 5% 4 4 3 5% 7% 30%	1330
July	1st to 10th	Night	14% 6% 2 6% 4 5% 5% 4 8% 7% 38%	2210
	11th to 20th	Night	18% 6% 2 6% 5% 4 4 4 6% 7% 38%	2303
	21st to end	Night	13% 6% 3 7% 5% 5% 4 4 6% 8% 40%	2789
August	1st to 10th	Night	18% 7% 3 8% 5% 5% 4 5% 7% 7% 30%	2825
	11th to 20th	Night	13% 8% 3 7% 4 6% 6% 4 7% 8% 34%	2782
	21st to end	Night	15% 6% 2 6% 4 4 4 3 5% 7% 44%	3124
September	1st to 10th	Night	15% 6% 2 5% 3 4 4 4 5% 7% 46%	1928
	11th to 20th	Night	17% 6% 2 5% 4 2 3 3 4 6% 49%	2090
	21st to end	Night	18% 5% 2 5% 4 4 4 4 5% 6% 43%	2090
October	1st to 10th	Night	20% 6% 3 5% 4 3 3 4 5% 7% 40%	2204
	11th to 20th	Night	19% 10% 3 6% 5% 3 4 3 6% 5% 36%	2280
	21st to end	Night	23% 10% 3 7% 4 4 3 3 4 6% 33%	2693
November	1st to 10th	Night	21% 9% 3 7% 4 4 5% 4 5% 6% 33%	2547
	11th to 20th	Night	20% 10% 3 7% 4 5% 4 3 5% 6% 34%	2800
	21st to end	Night	21% 11% 3 8% 5% 4 4 4 5% 6% 29%	2800
December	1st to 10th	Night	17% 12% 5% 10% 6% 5% 5% 3 5% 6% 26%	4792
	11th to 20th	Night	23% 10% 3 6% 5% 4 4 3 5% 5% 32%	5591
	21st to end	Night	19% 13% 4 11% 5% 4 4 3 5% 5% 26%	7502

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	69% 4 10% 13% 4	3202
	11th to 20th	Day	61% 6% 8% 18% 6%	3600
	21st to end	Day	50% 5% 9% 17% 18% 1	4070
February	1st to 10th	Day	58% 4 10% 18% 9% 2	1755
	11th to 20th	Day	60% 4 9% 16% 9% 1	1675
	21st to end	Day	52% 5% 10% 21% 9% 2	1570
March	1st to 10th	Day	60% 3 9% 14% 11% 4	3210
	11th to 20th	Day	68% 5% 8% 11% 7% 1	3480
	21st to end	Day	63% 3 6% 16% 11% 2	3816
April	1st to 10th	Day	59% 4 9% 17% 10% 2	2252
	11th to 20th	Day	52% 3 10% 22% 12% 1	2442
	21st to end	Day	55% 3 7% 18% 12% 4	2470
May	1st to 10th	Day	54% 5% 9% 23% 8% 1	4120
	11th to 20th	Day	54% 5% 13% 20% 8% 1	4229
	21st to end	Day	49% 7% 11% 19% 13% 1	5149
June	1st to 10th	Day	56% 5% 11% 17% 9% 1	2850
	11th to 20th	Day	47% 5% 13% 20% 13% 2	2850
	21st to end	Day	59% 5% 12% 16% 8% 1	2850
July	1st to 10th	Day	47% 7% 16% 20% 10%	4685
	11th to 20th	Day	45% 7% 15% 26% 7%	4566
	21st to end	Day	45% 6% 15% 27% 8%	4580
August	1st to 10th	Day	51% 7% 14% 24% 5%	4092
	11th to 20th	Day	50% 7% 14% 23% 5%	4084
	21st to end	Day	42% 6% 15% 24% 14%	4532
September	1st to 10th	Day	40% 5% 13% 28% 13%	2248
	11th to 20th	Day	41% 3 10% 30% 14% 1	2090
	21st to end	Day	43% 6% 9% 28% 14% 1	2090
October	1st to 10th	Day	51% 5% 11% 26% 6%	3288
	11th to 20th	Day	49% 4 12% 27% 8%	3140
	21st to end	Day	42% 4 17% 23% 15%	3114
November	1st to 10th	Day	53% 5% 12% 20% 10% 1	1750
	11th to 20th	Day	54% 4 11% 18% 11% 1	1600
	21st to end	Day	59% 4 14% 18% 4	1600
December	1st to 10th	Day	58% 6% 16% 13% 7%	2394
	11th to 20th	Day	55% 4 9% 18% 10% 4	2618
	21st to end	Day	62% 4 10% 12% 11% 1	3476
January	1st to 10th	Night	66% 5% 12% 12% 4	6747
	11th to 20th	Night	60% 6% 10% 18% 6%	6360
	21st to end	Night	45% 5% 9% 22% 17% 2	6886
February	1st to 10th	Night	55% 6% 10% 18% 10% 1	2536
	11th to 20th	Night	61% 4 8% 16% 9% 1	2397
	21st to end	Night	55% 4 9% 19% 11% 2	1884
March	1st to 10th	Night	62% 3 8% 18% 8% 1	3643
	11th to 20th	Night	62% 5% 9% 14% 8% 1	3480
	21st to end	Night	59% 2 6% 19% 11% 2	3816
April	1st to 10th	Night	57% 4 7% 16% 13% 3	1924
	11th to 20th	Night	51% 4 9% 20% 15% 2	1688
	21st to end	Night	54% 4 7% 18% 14% 2	1710
May	1st to 10th	Night	48% 4 15% 23% 9% 1	2840
	11th to 20th	Night	51% 7% 14% 21% 7% 1	2675
	21st to end	Night	43% 7% 16% 22% 11% 1	2465
June	1st to 10th	Night	55% 4 9% 21% 10% 1	1330
	11th to 20th	Night	47% 6% 13% 22% 11% 1	1330
	21st to end	Night	56% 5% 12% 16% 9% 2	1330
July	1st to 10th	Night	42% 7% 19% 22% 10%	2175
	11th to 20th	Night	45% 6% 15% 28% 6%	2261
	21st to end	Night	42% 7% 14% 28% 9%	2700
August	1st to 10th	Night	52% 7% 14% 21% 6%	2813
	11th to 20th	Night	46% 7% 19% 21% 7%	2809
	21st to end	Night	40% 5% 17% 22% 17%	3124
September	1st to 10th	Night	38% 5% 14% 30% 12% 1	1928
	11th to 20th	Night	38% 3 14% 31% 14%	2090
	21st to end	Night	42% 5% 12% 27% 13% 1	2090
October	1st to 10th	Night	48% 4 13% 25% 10%	3672
	11th to 20th	Night	46% 5% 11% 28% 10%	3779
	21st to end	Night	44% 4 18% 22% 12%	4431
November	1st to 10th	Night	50% 5% 13% 22% 9% 1	2547
	11th to 20th	Night	52% 4 13% 19% 11% 1	2800
	21st to end	Night	56% 6% 13% 17% 8% 1	2800
December	1st to 10th	Night	58% 5% 11% 20% 5%	4792
	11th to 20th	Night	54% 4 8% 20% 12% 1	5592
	21st to end	Night	59% 5% 8% 16% 11% 2	7502

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	34% 17% 32% 15% 3	200
	11th to 20th	Day	33% 21% 31% 9% 7% 1	200
	21st to end	Day	23% 20% 35% 14% 8% 1	265
February	1st to 10th	Day	29% 17% 32% 16% 5% 1	385
	11th to 20th	Day	24% 21% 36% 15% 3 1	368
	21st to end	Day	21% 23% 33% 19% 4	382
March	1st to 10th	Day	29% 19% 32% 17% 3	460
	11th to 20th	Day	27% 18% 32% 16% 6% 2	460
	21st to end	Day	32% 18% 26% 16% 7% 2	506
April	1st to 10th	Day	36% 21% 23% 14% 5% 1	460
	11th to 20th	Day	30% 19% 28% 17% 5% 1	452
	21st to end	Day	34% 14% 30% 17% 4 1	460
May	1st to 10th	Day	33% 16% 27% 19% 4 1	463
	11th to 20th	Day	30% 15% 27% 20% 7% 1	566
	21st to end	Day	26% 15% 35% 18% 7%	735
June	1st to 10th	Day	32% 12% 27% 20% 7% 2	680
	11th to 20th	Day	24% 13% 30% 23% 9% 1	680
	21st to end	Day	31% 9% 30% 20% 9% 1	680
July	1st to 10th	Day	20% 10% 32% 24% 11% 2	670
	11th to 20th	Day	20% 7% 31% 28% 14% 1	607
	21st to end	Day	17% 7% 32% 32% 10% 2	532
August	1st to 10th	Day	17% 9% 32% 27% 13% 2	486
	11th to 20th	Day	21% 10% 22% 32% 12% 3	479
	21st to end	Day	20% 13% 25% 25% 13% 4	539
September	1st to 10th	Day	16% 10% 35% 24% 11% 4	490
	11th to 20th	Day	22% 10% 28% 20% 14% 5%	490
	21st to end	Day	22% 12% 27% 26% 9% 4	490
October	1st to 10th	Day	23% 13% 24% 22% 14% 4	430
	11th to 20th	Day	33% 13% 27% 15% 10% 3	390
	21st to end	Day	32% 17% 28% 16% 7%	429
November	1st to 10th	Day	31% 15% 27% 19% 8% 1	395
	11th to 20th	Day	31% 18% 29% 15% 7% 1	400
	21st to end	Day	33% 16% 31% 16% 5%	400
December	1st to 10th	Day	31% 18% 29% 17% 4 1	275
	11th to 20th	Day	37% 22% 26% 13% 4	200
	21st to end	Day	32% 21% 31% 12% 3 1	220
January	1st to 10th	Night	26% 18% 31% 22% 3	888
	11th to 20th	Night	27% 17% 31% 21% 4	800
	21st to end	Night	20% 17% 36% 22% 5%	880
February	1st to 10th	Night	24% 20% 32% 19% 4	781
	11th to 20th	Night	25% 19% 37% 16% 3	743
	21st to end	Night	24% 19% 31% 21% 4	628
March	1st to 10th	Night	25% 14% 38% 22% 1	760
	11th to 20th	Night	28% 13% 33% 20% 6% 1	760
	21st to end	Night	27% 15% 29% 22% 6%	836
April	1st to 10th	Night	33% 15% 30% 18% 3	713
	11th to 20th	Night	29% 15% 33% 17% 6%	564
	21st to end	Night	33% 11% 32% 18% 6%	570
May	1st to 10th	Night	28% 14% 29% 23% 5%	570
	11th to 20th	Night	29% 12% 30% 23% 6%	562
	21st to end	Night	22% 11% 36% 25% 5%	448
June	1st to 10th	Night	27% 6% 31% 29% 8% 1	380
	11th to 20th	Night	21% 8% 30% 31% 9% 1	380
	21st to end	Night	29% 5% 29% 30% 6% 1	380
July	1st to 10th	Night	17% 3 38% 33% 9%	370
	11th to 20th	Night	15% 6% 27% 38% 13% 1	368
	21st to end	Night	19% 5% 26% 36% 13%	442
August	1st to 10th	Night	17% 4 28% 37% 14%	568
	11th to 20th	Night	17% 4 24% 39% 15% 1	562
	21st to end	Night	16% 6% 26% 35% 16% 1	627
September	1st to 10th	Night	19% 6% 35% 28% 12%	660
	11th to 20th	Night	19% 7% 24% 34% 14% 1	760
	21st to end	Night	21% 10% 26% 29% 12% 1	760
October	1st to 10th	Night	24% 9% 26% 28% 12% 1	760
	11th to 20th	Night	25% 12% 28% 25% 9% 1	760
	21st to end	Night	30% 17% 27% 22% 4	836
November	1st to 10th	Night	29% 16% 29% 21% 6%	785
	11th to 20th	Night	26% 18% 28% 21% 6% 1	900
	21st to end	Night	31% 16% 27% 22% 4	900
December	1st to 10th	Night	33% 13% 30% 19% 4 1	900
	11th to 20th	Night	31% 19% 29% 18% 3	900
	21st to end	Night	30% 18% 29% 18% 4 1	990

Page generated at 2025-02-03 04:05:51. Version ac07

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