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 2024-11-01.

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	14% 10% 4 9% 5% 5% 5% 4 6% 7% 31%	101900
	Night	14% 10% 4 8% 5% 4 4 4 5% 7% 33%	97047
Transparency	Day	51% 6% 12% 19% 10% 1	101666
	Night	50% 6% 12% 20% 11% 1	96901
Seeing	Day	18% 11% 28% 24% 13% 5%	14905
	Night	19% 10% 29% 29% 12% 1	23955

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% 18% 7% 11% 6% 5% 5% 3 4 5% 20%	2643
	11th to 20th	Day	12% 20% 8% 20% 7% 4 3 3 5% 6% 12%	2840
	21st to end	Day	23% 20% 7% 13% 7% 5% 5% 3 4 4 11%	3124
February	1st to 10th	Day	14% 19% 4 12% 9% 6% 6% 4 4 5% 17%	1710
	11th to 20th	Day	13% 15% 6% 14% 9% 5% 5% 4 4 6% 20%	1663
	21st to end	Day	16% 14% 6% 12% 7% 5% 4 4 4 5% 23%	1536
March	1st to 10th	Day	19% 15% 5% 10% 6% 4 4 3 4 5% 25%	3388
	11th to 20th	Day	11% 14% 6% 10% 6% 5% 5% 4 5% 6% 29%	3480
	21st to end	Day	17% 11% 4 10% 5% 5% 4 3 5% 6% 31%	3815
April	1st to 10th	Day	15% 14% 4 8% 5% 4 5% 4 5% 7% 28%	2183
	11th to 20th	Day	18% 11% 3 8% 4 4 5% 3 5% 7% 33%	2394
	21st to end	Day	21% 10% 3 8% 4 4 4 3 3 6% 33%	2470
May	1st to 10th	Day	18% 8% 3 7% 4 4 4 4 6% 8% 33%	4108
	11th to 20th	Day	15% 10% 3 8% 5% 4 4 4 7% 9% 30%	4166
	21st to end	Day	12% 5% 2 5% 4 4 5% 4 6% 8% 45%	4837
June	1st to 10th	Day	13% 6% 3 7% 5% 5% 5% 4 7% 8% 38%	2660
	11th to 20th	Day	10% 6% 3 7% 5% 5% 6% 4 8% 10% 38%	2766
	21st to end	Day	12% 6% 2 6% 4 5% 5% 5% 7% 9% 39%	2850
July	1st to 10th	Day	10% 5% 3 6% 5% 5% 6% 5% 7% 9% 39%	4737
	11th to 20th	Day	9% 5% 2 5% 5% 5% 5% 5% 8% 10% 39%	4226
	21st to end	Day	7% 6% 3 7% 5% 6% 6% 5% 7% 8% 40%	4466
August	1st to 10th	Day	15% 7% 2 6% 4 5% 5% 5% 7% 8% 35%	4104
	11th to 20th	Day	10% 7% 3 7% 5% 5% 6% 5% 7% 10% 35%	4044
	21st to end	Day	8% 6% 2 7% 5% 5% 6% 4 7% 9% 39%	4441
September	1st to 10th	Day	12% 6% 2 7% 5% 5% 6% 5% 6% 8% 39%	2264
	11th to 20th	Day	11% 5% 2 6% 5% 4 6% 4 6% 7% 45%	2090
	21st to end	Day	14% 7% 2 8% 5% 5% 4 5% 6% 8% 35%	2090
October	1st to 10th	Day	16% 9% 4 7% 5% 5% 4 3 5% 7% 36%	1918
	11th to 20th	Day	19% 11% 3 7% 5% 5% 5% 3 6% 7% 30%	1900
	21st to end	Day	22% 12% 4 8% 6% 4 6% 5% 5% 7% 22%	2081
November	1st to 10th	Day	13% 11% 4 9% 6% 4 4 4 6% 8% 32%	1668
	11th to 20th	Day	15% 14% 4 8% 6% 5% 6% 3 7% 8% 24%	1520
	21st to end	Day	18% 16% 7% 9% 6% 4 5% 3 6% 6% 19%	1520
December	1st to 10th	Day	15% 18% 7% 13% 6% 4 5% 5% 5% 5% 18%	1520
	11th to 20th	Day	17% 18% 6% 13% 6% 6% 5% 5% 4 5% 16%	1906
	21st to end	Day	28% 19% 7% 14% 5% 4 3 3 4 4 8%	2772
January	1st to 10th	Night	17% 15% 7% 12% 7% 5% 5% 4 5% 6% 18%	4301
	11th to 20th	Night	14% 16% 7% 15% 7% 7% 7% 5% 6% 6% 12%	4120
	21st to end	Night	22% 15% 9% 13% 6% 5% 4 3 4 4 16%	4532
February	1st to 10th	Night	14% 16% 6% 11% 8% 6% 5% 3 5% 6% 21%	2470
	11th to 20th	Night	14% 13% 4 11% 7% 5% 5% 4 6% 7% 23%	2403
	21st to end	Night	15% 14% 4 12% 6% 5% 5% 4 5% 6% 23%	1916
March	1st to 10th	Night	15% 11% 4 8% 5% 4 4 3 5% 6% 34%	3452
	11th to 20th	Night	11% 9% 4 9% 5% 5% 5% 4 6% 7% 36%	3479
	21st to end	Night	16% 10% 4 7% 4 3 4 3 4 5% 40%	3817
April	1st to 10th	Night	18% 10% 3 8% 5% 4 4 4 5% 7% 32%	1996
	11th to 20th	Night	17% 9% 3 7% 5% 5% 4 3 4 7% 36%	1749
	21st to end	Night	14% 10% 2 7% 5% 5% 5% 4 7% 8% 33%	1710
May	1st to 10th	Night	18% 8% 3 6% 4 3 4 3 5% 7% 39%	2833
	11th to 20th	Night	11% 10% 3 8% 6% 5% 5% 4 6% 8% 35%	2723
	21st to end	Night	10% 4 2 5% 3 3 4 4 6% 7% 51%	2738
June	1st to 10th	Night	11% 6% 2 6% 4 4 4 4 7% 7% 45%	1520
	11th to 20th	Night	9% 6% 1 6% 4 4 5% 5% 7% 10% 44%	1406
	21st to end	Night	10% 5% 2 6% 4 5% 5% 4 6% 8% 46%	1330
July	1st to 10th	Night	6% 4 2 5% 4 4 4 3 5% 11% 52%	2227
	11th to 20th	Night	9% 4 2 5% 4 3 3 4 6% 8% 52%	2730
	21st to end	Night	5% 5% 2 5% 4 4 6% 5% 6% 8% 49%	3087
August	1st to 10th	Night	11% 5% 2 6% 4 5% 5% 4 6% 7% 45%	2825
	11th to 20th	Night	10% 6% 2 6% 3 4 4 4 5% 9% 46%	2785
	21st to end	Night	8% 5% 2 6% 4 4 4 4 7% 9% 47%	3183
September	1st to 10th	Night	10% 6% 2 7% 5% 4 4 3 5% 7% 47%	1913
	11th to 20th	Night	10% 5% 1 4 3 4 4 3 5% 7% 54%	2090
	21st to end	Night	16% 7% 3 7% 4 4 4 3 5% 7% 39%	2090
October	1st to 10th	Night	15% 8% 3 6% 4 4 4 3 5% 7% 42%	2261
	11th to 20th	Night	17% 9% 3 7% 5% 5% 4 4 5% 7% 35%	2280
	21st to end	Night	21% 9% 3 8% 5% 5% 4 4 6% 7% 29%	2514
November	1st to 10th	Night	14% 8% 3 7% 5% 4 4 5% 6% 7% 37%	2415
	11th to 20th	Night	15% 12% 4 9% 5% 5% 4 4 7% 7% 28%	2660
	21st to end	Night	19% 13% 5% 9% 6% 5% 4 4 5% 7% 23%	2660
December	1st to 10th	Night	17% 17% 5% 12% 6% 6% 4 5% 5% 5% 18%	2660
	11th to 20th	Night	13% 19% 6% 11% 6% 4 4 4 5% 7% 21%	3288
	21st to end	Night	26% 20% 7% 11% 6% 4 4 2 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	63% 5% 11% 13% 6% 1	1536
March	1st to 10th	Day	60% 5% 10% 20% 5% 1	3391
	11th to 20th	Day	54% 7% 14% 18% 6% 1	3480
	21st to end	Day	53% 5% 12% 18% 12% 1	3815
April	1st to 10th	Day	55% 5% 11% 17% 11% 1	2183
	11th to 20th	Day	51% 5% 11% 20% 11% 1	2394
	21st to end	Day	53% 6% 9% 19% 11% 2	2470
May	1st to 10th	Day	48% 7% 13% 19% 11% 3	4120
	11th to 20th	Day	47% 10% 14% 21% 7% 1	4170
	21st to end	Day	36% 8% 12% 20% 20% 4	4837
June	1st to 10th	Day	42% 7% 13% 24% 13% 2	2660
	11th to 20th	Day	41% 8% 12% 22% 16% 2	2766
	21st to end	Day	39% 7% 14% 24% 15%	2850
July	1st to 10th	Day	39% 5% 13% 26% 14% 2	4663
	11th to 20th	Day	37% 6% 13% 31% 12% 1	4153
	21st to end	Day	39% 6% 14% 21% 19% 1	4324
August	1st to 10th	Day	45% 6% 14% 21% 13% 1	4091
	11th to 20th	Day	43% 6% 15% 26% 9% 1	4083
	21st to end	Day	40% 5% 13% 30% 12% 1	4441
September	1st to 10th	Day	41% 7% 14% 24% 13% 1	2264
	11th to 20th	Day	36% 6% 14% 28% 16%	2090
	21st to end	Day	45% 7% 13% 24% 10% 1	2090
October	1st to 10th	Day	49% 5% 12% 20% 13% 1	1918
	11th to 20th	Day	52% 6% 13% 17% 11%	1900
	21st to end	Day	60% 6% 12% 15% 6%	2081
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	60% 6% 11% 16% 7%	1916
March	1st to 10th	Night	50% 6% 14% 23% 7% 1	3462
	11th to 20th	Night	43% 7% 17% 20% 12% 1	3480
	21st to end	Night	46% 5% 10% 21% 16% 2	3817
April	1st to 10th	Night	51% 5% 10% 19% 14% 1	1996
	11th to 20th	Night	48% 5% 10% 19% 17% 2	1749
	21st to end	Night	47% 5% 11% 20% 15% 3	1710
May	1st to 10th	Night	44% 6% 11% 19% 16% 4	2840
	11th to 20th	Night	43% 9% 14% 23% 9% 2	2724
	21st to end	Night	30% 8% 12% 23% 24% 3	2739
June	1st to 10th	Night	37% 7% 11% 26% 17% 2	1520
	11th to 20th	Night	34% 8% 13% 25% 17% 2	1406
	21st to end	Night	36% 7% 14% 23% 20% 1	1330
July	1st to 10th	Night	29% 5% 13% 27% 20% 6%	2192
	11th to 20th	Night	31% 4 14% 32% 17% 2	2680
	21st to end	Night	32% 6% 16% 24% 18% 3	2988
August	1st to 10th	Night	37% 5% 14% 26% 17% 1	2814
	11th to 20th	Night	36% 6% 16% 28% 13% 1	2812
	21st to end	Night	33% 5% 12% 32% 18% 1	3183
September	1st to 10th	Night	38% 6% 11% 26% 17% 2	1913
	11th to 20th	Night	29% 6% 12% 33% 19% 1	2090
	21st to end	Night	44% 7% 12% 25% 12% 1	2090
October	1st to 10th	Night	42% 6% 10% 25% 17% 1	2261
	11th to 20th	Night	48% 5% 13% 22% 11%	2280
	21st to end	Night	54% 6% 10% 18% 11% 1	2514
November	1st to 10th	Night	42% 6% 14% 23% 13% 1	2415
	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%	427
	11th to 20th	Day	23% 15% 37% 19% 5% 1	460
	21st to end	Day	28% 13% 29% 22% 7% 1	506
April	1st to 10th	Day	20% 18% 32% 22% 6% 2	460
	11th to 20th	Day	29% 14% 25% 17% 11% 4	452
	21st to end	Day	25% 13% 32% 22% 7% 3	460
May	1st to 10th	Day	24% 10% 25% 24% 13% 4	463
	11th to 20th	Day	17% 9% 29% 21% 19% 5%	487
	21st to end	Day	14% 7% 24% 30% 18% 7%	529
June	1st to 10th	Day	14% 9% 30% 30% 13% 4	490
	11th to 20th	Day	11% 9% 29% 32% 14% 4	596
	21st to end	Day	14% 9% 30% 31% 13% 4	680
July	1st to 10th	Day	9% 6% 24% 28% 25% 8%	661
	11th to 20th	Day	13% 4 25% 27% 21% 11%	484
	21st to end	Day	8% 4 23% 34% 23% 8%	532
August	1st to 10th	Day	9% 6% 20% 29% 21% 14%	486
	11th to 20th	Day	12% 5% 19% 27% 21% 15%	479
	21st to end	Day	11% 7% 20% 29% 22% 12%	539
September	1st to 10th	Day	13% 8% 22% 26% 21% 11%	490
	11th to 20th	Day	9% 4 18% 26% 29% 14%	490
	21st to end	Day	17% 10% 24% 27% 13% 8%	490
October	1st to 10th	Day	19% 9% 26% 23% 18% 6%	490
	11th to 20th	Day	19% 18% 30% 22% 8% 2	490
	21st to end	Day	27% 14% 32% 21% 6% 1	530
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	23% 17% 34% 23% 3	628
March	1st to 10th	Night	19% 14% 35% 26% 6%	760
	11th to 20th	Night	19% 15% 37% 22% 7% 1	760
	21st to end	Night	20% 12% 32% 25% 10%	836
April	1st to 10th	Night	22% 13% 31% 29% 5%	760
	11th to 20th	Night	21% 13% 30% 26% 9% 1	625
	21st to end	Night	18% 10% 31% 33% 8%	570
May	1st to 10th	Night	20% 6% 27% 31% 14% 1	570
	11th to 20th	Night	17% 4 26% 38% 14% 1	511
	21st to end	Night	10% 5% 27% 39% 18% 1	411
June	1st to 10th	Night	14% 4 27% 42% 11% 1	380
	11th to 20th	Night	9% 5% 30% 43% 12%	380
	21st to end	Night	13% 4 24% 44% 15%	380
July	1st to 10th	Night	5% 3 23% 45% 21% 2	370
	11th to 20th	Night	9% 3 20% 41% 25% 2	485
	21st to end	Night	10% 3 15% 47% 23% 2	624
August	1st to 10th	Night	9% 2 15% 43% 28% 2	567
	11th to 20th	Night	9% 3 13% 39% 30% 5%	564
	21st to end	Night	9% 3 21% 37% 27% 3	660
September	1st to 10th	Night	13% 5% 23% 31% 23% 5%	760
	11th to 20th	Night	12% 4 15% 38% 27% 5%	760
	21st to end	Night	19% 6% 19% 32% 19% 5%	760
October	1st to 10th	Night	18% 6% 25% 30% 18% 2	760
	11th to 20th	Night	21% 12% 29% 26% 11% 1	760
	21st to end	Night	26% 11% 31% 26% 5%	836
November	1st to 10th	Night	19% 12% 26% 30% 11% 2	743
	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 2024-10-29 11:20:49. Version ac07

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