Windsor Castle Park
Clear Sky Chart
History

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

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% 6% 2 6% 4 4 5% 4 6% 8% 42%	101064
	Night	14% 7% 2 6% 4 4 4 4 5% 7% 43%	98040
Transparency	Day	40% 4 12% 23% 17% 4	104701
	Night	41% 4 10% 23% 18% 4	102542
Seeing	Day	17% 11% 27% 25% 15% 5%	15271
	Night	17% 9% 28% 32% 14% 2	24865

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	16% 6% 2 4 3 3 3 3 4 5% 51%	2709
	11th to 20th	Day	13% 7% 2 5% 4 4 3 3 4 6% 48%	2840
	21st to end	Day	14% 10% 4 7% 4 4 4 3 5% 5% 41%	3124
February	1st to 10th	Day	12% 9% 3 6% 4 5% 5% 4 6% 7% 40%	1710
	11th to 20th	Day	19% 6% 2 5% 4 3 3 3 4 6% 45%	1792
	21st to end	Day	16% 9% 2 6% 4 4 5% 4 6% 6% 38%	1570
March	1st to 10th	Day	23% 9% 3 6% 4 3 3 3 4 6% 37%	3359
	11th to 20th	Day	10% 5% 2 4 4 3 4 2 5% 6% 54%	3480
	21st to end	Day	18% 8% 2 4 4 4 4 3 5% 7% 43%	3905
April	1st to 10th	Day	12% 5% 2 5% 3 3 4 3 5% 6% 51%	2280
	11th to 20th	Day	9% 6% 1 5% 4 4 5% 4 6% 7% 48%	2254
	21st to end	Day	13% 6% 2 6% 5% 4 4 3 6% 6% 45%	2280
May	1st to 10th	Day	13% 8% 3 8% 6% 5% 5% 4 6% 9% 33%	3790
	11th to 20th	Day	19% 7% 3 7% 5% 5% 5% 4 6% 8% 33%	4195
	21st to end	Day	9% 5% 2 5% 4 4 5% 4 7% 9% 48%	4823
June	1st to 10th	Day	10% 4 2 5% 4 6% 5% 4 8% 10% 42%	2660
	11th to 20th	Day	9% 6% 2 5% 4 5% 4 5% 8% 11% 41%	2660
	21st to end	Day	7% 5% 3 5% 6% 5% 6% 5% 7% 12% 39%	2660
July	1st to 10th	Day	6% 4 2 6% 5% 5% 6% 6% 8% 12% 39%	4440
	11th to 20th	Day	10% 7% 3 8% 5% 5% 5% 4 8% 10% 35%	4158
	21st to end	Day	7% 7% 3 9% 7% 7% 7% 6% 8% 10% 31%	4466
August	1st to 10th	Day	14% 9% 4 9% 6% 6% 6% 5% 8% 10% 25%	4104
	11th to 20th	Day	9% 6% 3 8% 6% 6% 6% 5% 7% 9% 35%	3730
	21st to end	Day	7% 5% 2 6% 4 5% 5% 5% 8% 11% 43%	4180
September	1st to 10th	Day	13% 5% 2 6% 4 5% 4 4 7% 11% 39%	2280
	11th to 20th	Day	14% 7% 2 8% 5% 4 4 4 5% 7% 41%	2280
	21st to end	Day	21% 8% 3 6% 5% 5% 4 3 5% 6% 37%	2023
October	1st to 10th	Day	17% 6% 2 6% 4 3 4 3 5% 6% 45%	1900
	11th to 20th	Day	14% 6% 2 5% 4 3 3 3 5% 5% 52%	1900
	21st to end	Day	11% 5% 2 5% 4 4 4 3 4 5% 52%	2090
November	1st to 10th	Day	14% 6% 2 5% 3 3 4 3 4 6% 50%	1877
	11th to 20th	Day	13% 7% 2 5% 3 3 3 2 4 7% 51%	1710
	21st to end	Day	15% 4 2 5% 3 3 3 3 4 6% 52%	1633
December	1st to 10th	Day	16% 6% 2 6% 4 4 3 4 6% 7% 42%	1520
	11th to 20th	Day	14% 6% 2 5% 4 3 3 2 5% 4 53%	1910
	21st to end	Day	16% 7% 2 5% 4 3 4 3 5% 7% 44%	2772
January	1st to 10th	Night	13% 7% 3 6% 3 4 4 3 4 6% 47%	4233
	11th to 20th	Night	16% 8% 3 6% 4 4 3 3 5% 5% 43%	4120
	21st to end	Night	17% 8% 2 7% 4 3 4 3 4 5% 43%	4532
February	1st to 10th	Night	16% 7% 3 5% 4 4 3 3 5% 7% 43%	2470
	11th to 20th	Night	20% 8% 2 5% 4 3 4 4 4 6% 41%	2271
	21st to end	Night	16% 8% 3 5% 4 3 3 3 4 5% 46%	1884
March	1st to 10th	Night	23% 8% 3 7% 5% 4 4 3 5% 5% 33%	3492
	11th to 20th	Night	14% 6% 2 5% 3 3 4 3 4 6% 51%	3480
	21st to end	Night	17% 7% 2 5% 4 3 3 2 4 5% 48%	3725
April	1st to 10th	Night	12% 7% 2 6% 4 4 5% 3 6% 7% 44%	1900
	11th to 20th	Night	12% 6% 3 5% 4 3 3 3 5% 6% 50%	1875
	21st to end	Night	14% 6% 2 5% 5% 4 3 3 5% 7% 46%	1900
May	1st to 10th	Night	15% 8% 3 9% 5% 5% 5% 4 6% 8% 33%	3130
	11th to 20th	Night	20% 6% 2 6% 5% 4 5% 3 6% 7% 36%	2698
	21st to end	Night	10% 6% 2 6% 4 4 5% 3 6% 9% 44%	2732
June	1st to 10th	Night	11% 5% 1 5% 4 4 5% 4 8% 11% 41%	1520
	11th to 20th	Night	8% 6% 2 7% 5% 4 5% 5% 7% 11% 41%	1520
	21st to end	Night	7% 5% 2 6% 6% 5% 5% 5% 8% 9% 42%	1520
July	1st to 10th	Night	7% 4 2 7% 6% 5% 7% 6% 7% 12% 38%	2520
	11th to 20th	Night	9% 7% 3 8% 5% 5% 5% 5% 8% 9% 36%	2797
	21st to end	Night	12% 9% 4 10% 6% 5% 5% 5% 6% 8% 30%	3087
August	1st to 10th	Night	17% 8% 3 8% 4 5% 5% 5% 7% 10% 28%	2825
	11th to 20th	Night	8% 8% 2 8% 5% 5% 5% 4 6% 9% 40%	3064
	21st to end	Night	8% 5% 2 6% 4 4 4 4 7% 11% 45%	3476
September	1st to 10th	Night	12% 5% 2 6% 4 4 3 4 6% 10% 44%	1900
	11th to 20th	Night	12% 7% 2 8% 4 4 5% 4 5% 6% 44%	1900
	21st to end	Night	20% 7% 2 7% 5% 4 4 3 5% 7% 36%	2152
October	1st to 10th	Night	15% 5% 2 6% 4 4 4 2 5% 6% 47%	2280
	11th to 20th	Night	15% 5% 2 5% 3 3 3 3 4 5% 51%	2280
	21st to end	Night	13% 5% 2 5% 3 3 3 4 5% 6% 53%	2508
November	1st to 10th	Night	14% 7% 2 5% 3 3 3 3 5% 5% 51%	2405
	11th to 20th	Night	15% 6% 2 5% 3 3 3 3 5% 6% 49%	2470
	21st to end	Night	12% 5% 2 5% 3 4 4 3 5% 6% 49%	2545
December	1st to 10th	Night	17% 6% 3 7% 4 4 4 4 5% 5% 41%	2660
	11th to 20th	Night	17% 6% 2 5% 3 4 4 3 5% 6% 47%	3285
	21st to end	Night	13% 7% 2 6% 4 4 4 4 5% 6% 45%	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	38% 1 4 30% 22% 4	2710
	11th to 20th	Day	39% 2 6% 20% 28% 5%	2840
	21st to end	Day	47% 2 8% 21% 19% 3	3124
February	1st to 10th	Day	43% 3 9% 25% 16% 4	1710
	11th to 20th	Day	43% 3 6% 22% 20% 6%	1801
	21st to end	Day	47% 3 11% 17% 18% 5%	1570
March	1st to 10th	Day	51% 2 9% 17% 15% 6%	3359
	11th to 20th	Day	33% 1 8% 23% 25% 9%	3480
	21st to end	Day	44% 2 14% 19% 19% 3	3905
April	1st to 10th	Day	35% 3 11% 23% 22% 7%	2280
	11th to 20th	Day	34% 2 11% 25% 20% 6%	2254
	21st to end	Day	41% 3 10% 24% 17% 5%	2280
May	1st to 10th	Day	48% 3 16% 21% 10% 2	3825
	11th to 20th	Day	51% 3 11% 25% 9% 1	4199
	21st to end	Day	35% 3 15% 26% 18% 2	4837
June	1st to 10th	Day	37% 5% 15% 26% 16% 1	2660
	11th to 20th	Day	36% 5% 16% 25% 16% 2	2660
	21st to end	Day	37% 5% 16% 25% 15% 2	2660
July	1st to 10th	Day	35% 10% 21% 20% 11% 3	4370
	11th to 20th	Day	44% 7% 22% 20% 5% 1	4087
	21st to end	Day	46% 8% 14% 17% 13% 1	4324
August	1st to 10th	Day	53% 6% 17% 19% 5%	4091
	11th to 20th	Day	42% 7% 15% 24% 12%	3766
	21st to end	Day	34% 5% 14% 29% 17% 2	4180
September	1st to 10th	Day	40% 6% 15% 17% 18% 5%	2280
	11th to 20th	Day	43% 4 10% 22% 19% 2	2280
	21st to end	Day	49% 4 7% 21% 16% 2	2023
October	1st to 10th	Day	32% 4 10% 24% 25% 4	3160
	11th to 20th	Day	25% 2 6% 20% 38% 9%	3140
	21st to end	Day	23% 3 7% 28% 26% 13%	3428
November	1st to 10th	Day	37% 3 8% 28% 21% 4	1877
	11th to 20th	Day	35% 3 10% 22% 23% 6%	1710
	21st to end	Day	36% 3 7% 27% 22% 5%	1633
December	1st to 10th	Day	43% 3 11% 22% 18% 4	1520
	11th to 20th	Day	36% 2 7% 29% 18% 8%	1906
	21st to end	Day	42% 2 9% 28% 17% 2	2772
January	1st to 10th	Night	41% 1 6% 24% 22% 6%	4233
	11th to 20th	Night	45% 2 7% 21% 22% 4	4120
	21st to end	Night	46% 2 6% 21% 19% 6%	4532
February	1st to 10th	Night	43% 2 9% 24% 18% 4	2470
	11th to 20th	Night	47% 2 5% 21% 19% 6%	2273
	21st to end	Night	42% 2 8% 22% 20% 7%	1884
March	1st to 10th	Night	54% 2 7% 19% 15% 3	3492
	11th to 20th	Night	37% 2 7% 20% 24% 10%	3480
	21st to end	Night	41% 2 7% 27% 18% 5%	3725
April	1st to 10th	Night	40% 4 11% 17% 23% 5%	1900
	11th to 20th	Night	36% 2 10% 24% 21% 6%	1875
	21st to end	Night	39% 2 10% 27% 18% 4	1900
May	1st to 10th	Night	50% 3 14% 21% 10% 1	3160
	11th to 20th	Night	49% 4 10% 27% 9% 1	2699
	21st to end	Night	39% 4 16% 26% 15% 1	2739
June	1st to 10th	Night	36% 7% 15% 25% 15% 1	1520
	11th to 20th	Night	37% 6% 18% 23% 15% 1	1520
	21st to end	Night	36% 6% 14% 25% 16% 3	1520
July	1st to 10th	Night	38% 11% 18% 21% 10% 2	2480
	11th to 20th	Night	41% 9% 21% 22% 5% 1	2745
	21st to end	Night	52% 7% 12% 17% 13%	2988
August	1st to 10th	Night	50% 6% 19% 20% 5%	2814
	11th to 20th	Night	40% 6% 18% 23% 13%	3094
	21st to end	Night	33% 5% 14% 26% 21% 1	3476
September	1st to 10th	Night	37% 6% 17% 21% 16% 4	1900
	11th to 20th	Night	40% 4 9% 23% 20% 3	1900
	21st to end	Night	49% 4 9% 18% 18% 2	2152
October	1st to 10th	Night	38% 4 9% 23% 23% 3	3800
	11th to 20th	Night	26% 3 6% 20% 33% 12%	3779
	21st to end	Night	22% 2 6% 31% 25% 14%	4120
November	1st to 10th	Night	37% 3 8% 22% 25% 4	2405
	11th to 20th	Night	38% 2 9% 20% 22% 10%	2470
	21st to end	Night	36% 2 8% 25% 23% 5%	2545
December	1st to 10th	Night	46% 3 8% 22% 17% 4	2660
	11th to 20th	Night	40% 2 9% 22% 21% 6%	3288
	21st to end	Night	42% 2 11% 24% 20% 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	25% 21% 37% 12% 6%	234
	11th to 20th	Day	26% 27% 33% 13% 1	270
	21st to end	Day	23% 23% 38% 14% 2	297
February	1st to 10th	Day	20% 23% 40% 12% 4	270
	11th to 20th	Day	28% 24% 32% 14% 3	400
	21st to end	Day	27% 19% 34% 18% 3	382
March	1st to 10th	Day	22% 19% 38% 17% 4 1	460
	11th to 20th	Day	23% 20% 32% 20% 4 1	460
	21st to end	Day	23% 17% 36% 17% 6% 1	506
April	1st to 10th	Day	21% 16% 39% 16% 7% 1	460
	11th to 20th	Day	14% 17% 36% 19% 10% 4	452
	21st to end	Day	18% 13% 36% 23% 8% 2	460
May	1st to 10th	Day	16% 16% 36% 21% 9% 3	463
	11th to 20th	Day	19% 8% 31% 26% 14% 2	487
	21st to end	Day	18% 5% 23% 25% 22% 6%	529
June	1st to 10th	Day	12% 5% 21% 32% 24% 5%	490
	11th to 20th	Day	10% 6% 21% 33% 21% 9%	490
	21st to end	Day	10% 6% 19% 34% 23% 8%	490
July	1st to 10th	Day	9% 3 13% 34% 32% 9%	485
	11th to 20th	Day	7% 2 12% 39% 29% 11%	484
	21st to end	Day	8% 2 19% 38% 25% 9%	532
August	1st to 10th	Day	14% 2 18% 32% 26% 8%	486
	11th to 20th	Day	12% 4 13% 30% 30% 11%	479
	21st to end	Day	10% 3 14% 32% 26% 14%	539
September	1st to 10th	Day	14% 3 19% 28% 21% 15%	490
	11th to 20th	Day	16% 4 18% 31% 18% 13%	490
	21st to end	Day	27% 8% 20% 25% 13% 7%	490
October	1st to 10th	Day	20% 5% 19% 24% 23% 8%	490
	11th to 20th	Day	15% 11% 28% 27% 18% 2	490
	21st to end	Day	14% 10% 31% 26% 13% 6%	539
November	1st to 10th	Day	18% 9% 32% 23% 15% 4	456
	11th to 20th	Day	18% 16% 31% 24% 11% 1	370
	21st to end	Day	20% 15% 25% 25% 13% 2	293
December	1st to 10th	Day	20% 21% 37% 14% 6% 1	180
	11th to 20th	Day	21% 14% 36% 22% 7%	180
	21st to end	Day	24% 17% 30% 18% 10% 2	198
January	1st to 10th	Night	18% 16% 38% 25% 4	760
	11th to 20th	Night	21% 13% 36% 25% 5%	760
	21st to end	Night	19% 13% 39% 28% 2	836
February	1st to 10th	Night	20% 12% 41% 23% 4	760
	11th to 20th	Night	24% 16% 40% 18% 1	743
	21st to end	Night	20% 17% 37% 22% 3	628
March	1st to 10th	Night	18% 15% 35% 27% 5%	760
	11th to 20th	Night	21% 15% 36% 22% 6%	760
	21st to end	Night	19% 14% 37% 24% 6%	836
April	1st to 10th	Night	18% 14% 41% 23% 4	760
	11th to 20th	Night	15% 11% 38% 25% 10% 1	751
	21st to end	Night	17% 9% 36% 32% 6% 1	760
May	1st to 10th	Night	17% 10% 34% 32% 7% 1	760
	11th to 20th	Night	17% 5% 28% 39% 9% 1	499
	21st to end	Night	14% 3 15% 45% 20% 2	411
June	1st to 10th	Night	12% 4 19% 44% 19% 2	380
	11th to 20th	Night	8% 3 17% 47% 22% 2	380
	21st to end	Night	7% 4 17% 47% 23% 1	380
July	1st to 10th	Night	9% 2 15% 47% 25% 2	370
	11th to 20th	Night	8% 2 8% 45% 32% 5%	524
	21st to end	Night	9% 4 15% 45% 25% 3	624
August	1st to 10th	Night	11% 2 11% 43% 29% 5%	567
	11th to 20th	Night	11% 3 10% 44% 27% 5%	729
	21st to end	Night	11% 3 11% 36% 32% 6%	836
September	1st to 10th	Night	14% 2 13% 40% 26% 6%	760
	11th to 20th	Night	16% 4 14% 34% 28% 4	760
	21st to end	Night	24% 5% 17% 33% 19% 2	760
October	1st to 10th	Night	18% 4 18% 32% 24% 5%	760
	11th to 20th	Night	18% 7% 25% 31% 16% 2	760
	21st to end	Night	15% 6% 28% 32% 17% 2	836
November	1st to 10th	Night	18% 6% 27% 30% 17% 2	779
	11th to 20th	Night	19% 10% 29% 31% 10% 1	760
	21st to end	Night	15% 9% 31% 32% 13% 1	760
December	1st to 10th	Night	21% 11% 34% 27% 8% 1	760
	11th to 20th	Night	18% 9% 36% 30% 7%	760
	21st to end	Night	18% 12% 33% 31% 6%	836

Page generated at 2024-11-07 06:55:49. Version ac07

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