Woodbridge
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Woodbridge clear sky chart from 2005-11-06 to 2024-10-25.

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% 9% 3 8% 5% 5% 5% 4 6% 7% 33%	101587
	Night	15% 10% 3 8% 5% 5% 5% 4 5% 7% 35%	97173
Transparency	Day	47% 8% 14% 20% 10% 1	101354
	Night	47% 8% 13% 20% 11% 1	97026
Seeing	Day	18% 13% 30% 24% 11% 4	14599
	Night	19% 10% 31% 28% 11% 1	23782

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	17% 12% 5% 10% 5% 5% 5% 4 5% 6% 26%	2517
	11th to 20th	Day	11% 18% 7% 16% 9% 6% 4 3 4 5% 18%	2772
	21st to end	Day	20% 20% 6% 10% 6% 4 5% 3 4 5% 16%	3124
February	1st to 10th	Day	14% 17% 4 13% 6% 5% 5% 4 5% 5% 21%	1710
	11th to 20th	Day	12% 14% 6% 12% 7% 5% 5% 3 5% 6% 24%	1663
	21st to end	Day	17% 15% 5% 10% 5% 4 5% 4 4 6% 25%	1467
March	1st to 10th	Day	19% 12% 5% 8% 5% 4 4 3 4 5% 30%	3432
	11th to 20th	Day	11% 15% 5% 9% 5% 5% 5% 4 6% 6% 29%	3480
	21st to end	Day	16% 9% 3 8% 5% 4 4 3 5% 6% 36%	3815
April	1st to 10th	Day	16% 13% 3 9% 6% 4 5% 3 5% 7% 29%	2237
	11th to 20th	Day	19% 9% 3 7% 4 4 4 4 6% 5% 35%	2335
	21st to end	Day	20% 8% 3 8% 5% 4 4 3 5% 6% 33%	2470
May	1st to 10th	Day	18% 8% 3 7% 5% 4 4 4 6% 8% 33%	4108
	11th to 20th	Day	16% 9% 3 9% 5% 5% 4 4 5% 8% 32%	4360
	21st to end	Day	11% 6% 2 6% 4 4 5% 4 5% 8% 46%	4837
June	1st to 10th	Day	13% 8% 2 7% 6% 4 5% 5% 6% 8% 37%	2660
	11th to 20th	Day	12% 6% 2 6% 5% 4 4 4 7% 11% 39%	2660
	21st to end	Day	13% 6% 2 6% 5% 5% 5% 5% 7% 9% 38%	2822
July	1st to 10th	Day	9% 5% 2 6% 4 5% 6% 5% 8% 11% 39%	4509
	11th to 20th	Day	9% 4 2 5% 4 4 5% 5% 8% 10% 44%	4440
	21st to end	Day	7% 5% 2 7% 5% 5% 6% 5% 8% 9% 40%	4483
August	1st to 10th	Day	16% 7% 2 6% 4 4 5% 4 7% 9% 36%	4104
	11th to 20th	Day	9% 7% 3 9% 5% 5% 6% 5% 8% 10% 34%	4044
	21st to end	Day	8% 5% 3 7% 5% 5% 5% 5% 7% 10% 41%	4372
September	1st to 10th	Day	12% 6% 2 7% 5% 5% 4 4 6% 7% 41%	2280
	11th to 20th	Day	11% 5% 2 6% 4 5% 4 3 6% 8% 45%	2159
	21st to end	Day	13% 7% 3 7% 6% 5% 6% 4 6% 9% 35%	2057
October	1st to 10th	Day	18% 8% 3 7% 4 4 5% 4 6% 6% 35%	1900
	11th to 20th	Day	19% 8% 3 9% 5% 6% 5% 3 6% 7% 29%	1900
	21st to end	Day	23% 12% 4 8% 6% 5% 5% 4 5% 6% 22%	2027
November	1st to 10th	Day	13% 10% 3 8% 6% 4 4 4 6% 8% 32%	1605
	11th to 20th	Day	14% 12% 4 10% 6% 5% 6% 5% 6% 7% 25%	1520
	21st to end	Day	17% 15% 4 9% 6% 6% 5% 4 6% 7% 21%	1520
December	1st to 10th	Day	16% 17% 5% 13% 6% 6% 6% 4 5% 6% 16%	1520
	11th to 20th	Day	19% 14% 4 11% 6% 5% 5% 4 6% 6% 21%	1906
	21st to end	Day	28% 18% 6% 12% 5% 4 4 3 4 4 12%	2772
January	1st to 10th	Night	17% 14% 6% 11% 6% 6% 5% 3 5% 6% 22%	4429
	11th to 20th	Night	14% 14% 6% 12% 10% 7% 6% 4 5% 5% 17%	4184
	21st to end	Night	21% 12% 6% 10% 8% 6% 5% 3 5% 5% 19%	4532
February	1st to 10th	Night	13% 16% 4 10% 7% 5% 5% 4 5% 6% 25%	2470
	11th to 20th	Night	13% 14% 5% 9% 8% 5% 5% 4 5% 5% 27%	2403
	21st to end	Night	13% 13% 4 10% 7% 5% 4 4 6% 6% 29%	1982
March	1st to 10th	Night	18% 9% 4 8% 6% 6% 4 4 5% 5% 31%	3408
	11th to 20th	Night	12% 11% 3 8% 5% 5% 4 4 5% 7% 36%	3479
	21st to end	Night	16% 8% 3 5% 3 3 4 3 4 6% 44%	3817
April	1st to 10th	Night	18% 11% 3 8% 5% 4 4 4 5% 6% 32%	1942
	11th to 20th	Night	15% 8% 3 7% 5% 4 4 4 5% 6% 38%	1811
	21st to end	Night	16% 9% 4 6% 4 5% 4 4 6% 8% 36%	1710
May	1st to 10th	Night	18% 7% 2 6% 4 4 5% 4 5% 6% 39%	2833
	11th to 20th	Night	15% 9% 3 6% 4 4 4 4 6% 7% 38%	2532
	21st to end	Night	10% 4 2 5% 4 4 4 3 6% 8% 51%	2738
June	1st to 10th	Night	12% 5% 2 5% 6% 5% 5% 4 6% 8% 42%	1520
	11th to 20th	Night	8% 6% 3 6% 4 5% 5% 4 7% 9% 43%	1520
	21st to end	Night	10% 6% 2 6% 5% 5% 4 4 6% 7% 46%	1343
July	1st to 10th	Night	6% 4 2 5% 4 4 4 4 5% 10% 51%	2427
	11th to 20th	Night	11% 4 2 4 3 3 4 4 6% 8% 51%	2520
	21st to end	Night	7% 4 2 6% 4 4 5% 4 6% 9% 51%	3053
August	1st to 10th	Night	9% 6% 2 7% 4 5% 4 3 6% 7% 48%	2825
	11th to 20th	Night	10% 5% 1 6% 4 3 4 3 5% 8% 50%	2785
	21st to end	Night	10% 5% 2 6% 4 4 4 4 6% 8% 47%	3252
September	1st to 10th	Night	8% 5% 2 6% 5% 4 4 4 7% 7% 48%	1900
	11th to 20th	Night	10% 5% 1 4 3 3 4 4 5% 8% 53%	2019
	21st to end	Night	15% 7% 3 7% 4 4 4 3 6% 6% 41%	2123
October	1st to 10th	Night	16% 7% 3 7% 4 4 5% 4 5% 6% 39%	2280
	11th to 20th	Night	17% 8% 2 8% 6% 4 5% 3 5% 6% 35%	2280
	21st to end	Night	20% 10% 3 9% 4 5% 5% 4 5% 7% 28%	2435
November	1st to 10th	Night	16% 8% 2 6% 5% 4 4 3 6% 6% 38%	2469
	11th to 20th	Night	16% 11% 3 8% 6% 5% 5% 4 5% 7% 30%	2660
	21st to end	Night	19% 11% 4 9% 6% 5% 5% 4 6% 7% 25%	2660
December	1st to 10th	Night	20% 15% 4 8% 6% 5% 4 4 6% 6% 22%	2660
	11th to 20th	Night	15% 17% 4 11% 6% 5% 5% 4 5% 6% 21%	3288
	21st to end	Night	29% 16% 4 10% 5% 5% 4 4 4 5% 13%	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	56% 9% 17% 10% 7%	2518
	11th to 20th	Day	69% 6% 12% 10% 3	2772
	21st to end	Day	70% 7% 10% 8% 4 1	3124
February	1st to 10th	Day	62% 8% 11% 14% 3 1	1710
	11th to 20th	Day	58% 8% 13% 14% 7% 1	1672
	21st to end	Day	58% 7% 12% 14% 7% 1	1467
March	1st to 10th	Day	54% 7% 14% 16% 8% 1	3435
	11th to 20th	Day	51% 9% 12% 18% 9% 1	3480
	21st to end	Day	46% 7% 12% 20% 13% 2	3815
April	1st to 10th	Day	54% 6% 11% 17% 10% 1	2237
	11th to 20th	Day	48% 6% 11% 20% 14% 1	2335
	21st to end	Day	51% 7% 11% 18% 12% 2	2470
May	1st to 10th	Day	44% 8% 15% 18% 13% 1	4120
	11th to 20th	Day	47% 11% 15% 19% 8% 1	4364
	21st to end	Day	34% 8% 14% 23% 17% 3	4837
June	1st to 10th	Day	42% 8% 13% 21% 14% 1	2660
	11th to 20th	Day	38% 8% 15% 23% 15% 1	2660
	21st to end	Day	39% 8% 15% 23% 14% 1	2822
July	1st to 10th	Day	36% 6% 17% 25% 15% 2	4439
	11th to 20th	Day	31% 7% 14% 36% 11% 1	4365
	21st to end	Day	35% 9% 15% 21% 18% 1	4340
August	1st to 10th	Day	42% 8% 15% 21% 14% 1	4091
	11th to 20th	Day	41% 9% 17% 23% 10%	4083
	21st to end	Day	35% 7% 13% 33% 10% 1	4372
September	1st to 10th	Day	39% 9% 15% 26% 11% 1	2280
	11th to 20th	Day	35% 7% 15% 29% 14%	2159
	21st to end	Day	43% 9% 14% 25% 8%	2057
October	1st to 10th	Day	46% 9% 15% 19% 11% 1	1900
	11th to 20th	Day	52% 7% 15% 19% 7% 1	1900
	21st to end	Day	59% 8% 12% 15% 5%	2027
November	1st to 10th	Day	47% 8% 17% 20% 8% 1	1605
	11th to 20th	Day	53% 10% 14% 14% 8%	1520
	21st to end	Day	59% 10% 16% 14% 3	1520
December	1st to 10th	Day	66% 9% 12% 11% 3	1520
	11th to 20th	Day	60% 11% 14% 11% 4	1906
	21st to end	Day	73% 9% 9% 8% 1	2772
January	1st to 10th	Night	60% 10% 13% 13% 4	4429
	11th to 20th	Night	63% 12% 13% 9% 3 1	4184
	21st to end	Night	64% 9% 13% 10% 4 1	4532
February	1st to 10th	Night	57% 7% 11% 19% 5% 1	2470
	11th to 20th	Night	56% 8% 13% 16% 8%	2405
	21st to end	Night	53% 7% 15% 17% 8%	1982
March	1st to 10th	Night	50% 8% 14% 20% 7% 1	3418
	11th to 20th	Night	42% 9% 16% 20% 11% 2	3480
	21st to end	Night	39% 7% 10% 24% 18% 2	3817
April	1st to 10th	Night	51% 6% 11% 17% 13% 1	1942
	11th to 20th	Night	46% 6% 10% 21% 15% 2	1811
	21st to end	Night	44% 8% 12% 17% 16% 2	1710
May	1st to 10th	Night	42% 8% 13% 17% 16% 3	2840
	11th to 20th	Night	42% 11% 16% 18% 11% 2	2533
	21st to end	Night	28% 8% 15% 23% 22% 3	2739
June	1st to 10th	Night	37% 7% 13% 23% 18% 2	1520
	11th to 20th	Night	35% 7% 13% 23% 21% 2	1520
	21st to end	Night	36% 7% 13% 25% 17% 1	1343
July	1st to 10th	Night	28% 6% 15% 25% 22% 4	2387
	11th to 20th	Night	30% 6% 14% 33% 16% 1	2472
	21st to end	Night	29% 8% 15% 30% 16% 2	2956
August	1st to 10th	Night	35% 6% 13% 28% 15% 2	2814
	11th to 20th	Night	33% 6% 16% 32% 12% 1	2812
	21st to end	Night	34% 7% 13% 31% 14% 1	3252
September	1st to 10th	Night	32% 8% 16% 28% 15% 1	1900
	11th to 20th	Night	29% 7% 12% 34% 18%	2019
	21st to end	Night	41% 7% 13% 27% 11%	2123
October	1st to 10th	Night	43% 7% 13% 21% 16% 1	2280
	11th to 20th	Night	48% 7% 14% 23% 8%	2280
	21st to end	Night	53% 8% 12% 17% 9% 1	2435
November	1st to 10th	Night	45% 6% 15% 22% 11% 1	2469
	11th to 20th	Night	50% 9% 14% 17% 8% 1	2660
	21st to end	Night	55% 8% 19% 14% 3	2660
December	1st to 10th	Night	60% 9% 14% 14% 4	2660
	11th to 20th	Night	60% 8% 15% 13% 3	3288
	21st to end	Night	71% 9% 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	23% 17% 32% 22% 6% 1	180
	11th to 20th	Day	23% 25% 32% 13% 6% 1	250
	21st to end	Day	25% 20% 32% 20% 4	297
February	1st to 10th	Day	25% 22% 39% 11% 3	270
	11th to 20th	Day	22% 22% 41% 11% 3	270
	21st to end	Day	31% 24% 33% 11%	236
March	1st to 10th	Day	21% 17% 35% 21% 6%	460
	11th to 20th	Day	22% 17% 38% 17% 5% 1	460
	21st to end	Day	25% 18% 31% 19% 6% 1	506
April	1st to 10th	Day	21% 20% 34% 18% 7%	460
	11th to 20th	Day	27% 18% 28% 16% 8% 3	452
	21st to end	Day	24% 13% 36% 18% 7% 2	460
May	1st to 10th	Day	21% 12% 30% 22% 10% 5%	463
	11th to 20th	Day	17% 10% 30% 26% 13% 5%	487
	21st to end	Day	15% 7% 28% 28% 15% 5%	529
June	1st to 10th	Day	14% 13% 29% 32% 11% 2	490
	11th to 20th	Day	14% 9% 28% 31% 16% 2	490
	21st to end	Day	16% 8% 31% 31% 11% 4	652
July	1st to 10th	Day	9% 6% 26% 34% 20% 6%	528
	11th to 20th	Day	13% 5% 24% 33% 17% 8%	484
	21st to end	Day	8% 4 27% 39% 16% 7%	532
August	1st to 10th	Day	13% 6% 21% 29% 22% 9%	486
	11th to 20th	Day	10% 5% 25% 28% 21% 11%	479
	21st to end	Day	10% 7% 27% 28% 20% 9%	539
September	1st to 10th	Day	13% 8% 25% 28% 15% 10%	490
	11th to 20th	Day	10% 6% 22% 25% 22% 15%	490
	21st to end	Day	15% 10% 30% 24% 16% 6%	490
October	1st to 10th	Day	19% 13% 27% 22% 13% 5%	490
	11th to 20th	Day	18% 17% 36% 19% 8% 2	490
	21st to end	Day	29% 14% 28% 22% 6%	514
November	1st to 10th	Day	19% 23% 26% 22% 9% 1	257
	11th to 20th	Day	21% 24% 31% 19% 3 2	180
	21st to end	Day	24% 15% 42% 17% 2	180
December	1st to 10th	Day	26% 19% 36% 15% 4	180
	11th to 20th	Day	24% 24% 32% 16% 4	180
	21st to end	Day	26% 20% 40% 12% 2	198
January	1st to 10th	Night	23% 16% 37% 20% 4	760
	11th to 20th	Night	26% 17% 31% 24% 3	760
	21st to end	Night	19% 10% 40% 23% 7%	836
February	1st to 10th	Night	21% 16% 40% 21% 3	760
	11th to 20th	Night	22% 15% 38% 22% 3	743
	21st to end	Night	20% 16% 39% 21% 3	628
March	1st to 10th	Night	18% 15% 38% 24% 5%	760
	11th to 20th	Night	20% 17% 35% 22% 6%	760
	21st to end	Night	20% 11% 35% 26% 8%	836
April	1st to 10th	Night	23% 11% 37% 26% 4	760
	11th to 20th	Night	17% 13% 38% 22% 9% 1	687
	21st to end	Night	19% 9% 32% 30% 9%	570
May	1st to 10th	Night	17% 6% 30% 32% 13% 2	570
	11th to 20th	Night	16% 4 31% 36% 12% 1	398
	21st to end	Night	10% 4 29% 36% 20%	411
June	1st to 10th	Night	15% 4 29% 36% 16% 1	380
	11th to 20th	Night	10% 6% 28% 41% 15% 1	380
	21st to end	Night	11% 6% 23% 44% 16%	380
July	1st to 10th	Night	6% 4 24% 44% 22% 1	370
	11th to 20th	Night	11% 2 24% 41% 20% 2	368
	21st to end	Night	7% 3 20% 45% 23% 2	603
August	1st to 10th	Night	9% 1 17% 43% 28% 2	567
	11th to 20th	Night	8% 2 17% 44% 27% 2	564
	21st to end	Night	11% 3 23% 35% 25% 3	703
September	1st to 10th	Night	11% 6% 24% 34% 21% 4	760
	11th to 20th	Night	12% 4 20% 32% 28% 5%	760
	21st to end	Night	17% 6% 22% 31% 20% 4	760
October	1st to 10th	Night	18% 6% 28% 27% 18% 3	760
	11th to 20th	Night	20% 12% 31% 27% 10% 1	760
	21st to end	Night	26% 11% 32% 26% 5%	812
November	1st to 10th	Night	21% 10% 30% 28% 10% 1	740
	11th to 20th	Night	20% 14% 35% 23% 7% 2	760
	21st to end	Night	25% 12% 33% 24% 5%	760
December	1st to 10th	Night	28% 13% 37% 17% 4	760
	11th to 20th	Night	23% 15% 40% 19% 3	760
	21st to end	Night	31% 14% 33% 20% 2	836

Page generated at 2024-10-22 20:21:05. Version ac07

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