Goodwood
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Goodwood clear sky chart from 2005-11-06 to 2025-08-05.

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	15% 10% 4 9% 5% 5% 5% 4 5% 7% 32%	126017
	Night	14% 10% 4 9% 6% 5% 5% 4 5% 7% 32%	122006
Transparency	Day	49% 7% 12% 20% 11% 1	129607
	Night	48% 8% 12% 19% 12% 1	126502
Seeing	Day	21% 17% 30% 21% 9% 3	15334
	Night	20% 14% 32% 24% 9% 1	24679

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	13% 12% 4 11% 7% 6% 5% 4 5% 6% 27%	3597
	11th to 20th	Day	9% 17% 7% 19% 9% 7% 5% 3 4 5% 14%	3839
	21st to end	Day	16% 17% 7% 15% 6% 6% 5% 3 4 5% 16%	4466
February	1st to 10th	Day	15% 17% 5% 12% 7% 7% 5% 3 5% 5% 19%	1800
	11th to 20th	Day	12% 16% 7% 12% 7% 5% 4 3 5% 5% 23%	1753
	21st to end	Day	16% 17% 4 11% 6% 6% 5% 3 4 4 25%	1532
March	1st to 10th	Day	18% 11% 5% 9% 7% 4 4 3 5% 5% 30%	4932
	11th to 20th	Day	11% 13% 4 10% 6% 5% 5% 4 6% 7% 29%	4980
	21st to end	Day	18% 13% 3 9% 5% 4 4 3 4 5% 33%	5465
April	1st to 10th	Day	18% 14% 4 8% 5% 5% 4 3 5% 6% 27%	2375
	11th to 20th	Day	19% 11% 4 7% 4 3 4 3 5% 5% 34%	2439
	21st to end	Day	19% 10% 3 9% 5% 4 4 3 5% 6% 32%	2600
May	1st to 10th	Day	20% 8% 3 8% 4 5% 4 3 5% 7% 32%	5925
	11th to 20th	Day	15% 10% 3 9% 5% 4 4 3 5% 7% 34%	6318
	21st to end	Day	18% 6% 2 7% 4 4 5% 3 5% 7% 37%	6949
June	1st to 10th	Day	15% 8% 3 6% 5% 4 5% 4 6% 8% 35%	2800
	11th to 20th	Day	12% 6% 3 6% 5% 4 6% 4 6% 10% 37%	2800
	21st to end	Day	15% 6% 3 6% 5% 5% 5% 4 6% 9% 36%	2800
July	1st to 10th	Day	11% 6% 3 7% 5% 5% 6% 5% 6% 8% 38%	6360
	11th to 20th	Day	9% 5% 2 6% 4 5% 6% 4 7% 9% 43%	6360
	21st to end	Day	7% 4 2 7% 5% 5% 5% 5% 6% 8% 45%	6568
August	1st to 10th	Day	16% 8% 3 6% 5% 4 4 4 7% 8% 36%	4156
	11th to 20th	Day	12% 6% 3 8% 5% 4 5% 5% 7% 9% 35%	4044
	21st to end	Day	10% 6% 2 7% 4 4 5% 4 6% 8% 43%	4345
September	1st to 10th	Day	13% 6% 3 7% 5% 4 4 4 7% 6% 42%	2280
	11th to 20th	Day	12% 5% 2 6% 4 4 4 4 6% 8% 44%	2188
	21st to end	Day	15% 6% 3 8% 6% 5% 5% 4 5% 6% 38%	2038
October	1st to 10th	Day	18% 9% 4 8% 4 4 4 3 5% 7% 34%	1900
	11th to 20th	Day	19% 11% 3 10% 5% 4 4 4 5% 5% 29%	1900
	21st to end	Day	23% 14% 4 9% 5% 5% 4 3 5% 6% 22%	2090
November	1st to 10th	Day	15% 11% 4 9% 6% 4 5% 3 6% 7% 30%	1672
	11th to 20th	Day	16% 12% 4 11% 6% 6% 6% 4 6% 6% 23%	1600
	21st to end	Day	18% 16% 5% 12% 7% 5% 6% 3 4 5% 20%	1600
December	1st to 10th	Day	17% 20% 6% 14% 7% 7% 5% 4 5% 6% 10%	2600
	11th to 20th	Day	17% 19% 4 10% 6% 4 5% 3 4 6% 21%	2986
	21st to end	Day	23% 17% 6% 15% 6% 5% 5% 3 4 4 13%	3960
January	1st to 10th	Night	14% 12% 5% 11% 7% 6% 6% 5% 6% 7% 21%	6349
	11th to 20th	Night	12% 13% 6% 16% 9% 7% 6% 5% 6% 6% 16%	6042
	21st to end	Night	14% 14% 6% 13% 6% 6% 5% 4 6% 6% 21%	6490
February	1st to 10th	Night	12% 17% 4 10% 6% 7% 6% 5% 5% 5% 22%	2600
	11th to 20th	Night	13% 15% 5% 11% 6% 5% 5% 4 6% 6% 24%	2533
	21st to end	Night	13% 12% 4 11% 6% 6% 4 4 7% 6% 27%	2095
March	1st to 10th	Night	15% 11% 3 10% 6% 5% 5% 3 5% 6% 30%	4908
	11th to 20th	Night	9% 9% 3 8% 7% 5% 6% 5% 7% 8% 34%	4979
	21st to end	Night	19% 8% 3 9% 5% 4 4 3 4 6% 34%	5467
April	1st to 10th	Night	19% 11% 3 7% 6% 4 5% 4 5% 6% 30%	2024
	11th to 20th	Night	16% 8% 3 7% 5% 5% 4 4 5% 6% 37%	1927
	21st to end	Night	15% 8% 4 9% 6% 4 3 4 6% 8% 34%	1800
May	1st to 10th	Night	22% 8% 3 6% 4 4 4 3 5% 6% 34%	4012
	11th to 20th	Night	12% 8% 3 8% 4 5% 5% 3 6% 7% 40%	3575
	21st to end	Night	18% 6% 2 5% 4 4 4 3 5% 7% 42%	3926
June	1st to 10th	Night	12% 6% 2 7% 5% 4 4 4 6% 8% 41%	1600
	11th to 20th	Night	9% 5% 3 7% 5% 5% 5% 4 6% 8% 43%	1600
	21st to end	Night	12% 6% 2 7% 5% 4 4 4 5% 8% 42%	1573
July	1st to 10th	Night	8% 6% 2 6% 5% 5% 5% 4 5% 9% 46%	3600
	11th to 20th	Night	10% 5% 2 5% 4 4 4 4 5% 8% 49%	3600
	21st to end	Night	9% 4 2 5% 3 4 4 3 6% 8% 52%	4281
August	1st to 10th	Night	9% 6% 2 7% 4 4 4 4 6% 7% 48%	2861
	11th to 20th	Night	11% 5% 2 6% 4 3 4 3 5% 7% 49%	2785
	21st to end	Night	9% 6% 3 6% 4 4 4 3 5% 7% 48%	3278
September	1st to 10th	Night	9% 6% 2 6% 4 5% 5% 3 6% 7% 47%	1900
	11th to 20th	Night	11% 4 1 4 4 3 3 3 5% 7% 53%	1989
	21st to end	Night	16% 7% 3 6% 4 4 4 3 5% 8% 41%	2140
October	1st to 10th	Night	15% 7% 3 9% 4 5% 4 4 6% 6% 38%	2280
	11th to 20th	Night	18% 9% 3 8% 5% 6% 4 4 5% 6% 33%	2280
	21st to end	Night	21% 10% 3 7% 6% 5% 5% 3 5% 6% 28%	2508
November	1st to 10th	Night	18% 9% 3 7% 5% 4 4 4 5% 7% 35%	2620
	11th to 20th	Night	16% 11% 4 9% 6% 6% 5% 3 5% 7% 27%	2800
	21st to end	Night	18% 14% 3 9% 6% 6% 5% 4 6% 6% 22%	2800
December	1st to 10th	Night	17% 16% 5% 12% 8% 7% 6% 5% 5% 7% 14%	4580
	11th to 20th	Night	14% 19% 6% 11% 6% 6% 5% 4 5% 5% 20%	5208
	21st to end	Night	22% 15% 5% 15% 6% 5% 4 3 5% 5% 13%	6996

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	54% 8% 13% 14% 11%	3598
	11th to 20th	Day	71% 6% 10% 9% 4 1	3872
	21st to end	Day	68% 6% 10% 9% 7% 1	4466
February	1st to 10th	Day	65% 7% 9% 14% 5% 1	1800
	11th to 20th	Day	60% 8% 9% 15% 7% 1	1762
	21st to end	Day	61% 7% 9% 16% 7% 1	1532
March	1st to 10th	Day	53% 6% 14% 13% 14%	4935
	11th to 20th	Day	51% 7% 15% 18% 7% 2	4980
	21st to end	Day	51% 7% 8% 18% 15% 1	5465
April	1st to 10th	Day	55% 6% 10% 17% 11% 1	2375
	11th to 20th	Day	49% 6% 10% 20% 14% 1	2439
	21st to end	Day	50% 7% 11% 17% 13% 3	2600
May	1st to 10th	Day	50% 6% 12% 17% 10% 4	5934
	11th to 20th	Day	48% 8% 10% 16% 17% 1	6322
	21st to end	Day	44% 7% 12% 21% 13% 2	6949
June	1st to 10th	Day	43% 9% 12% 20% 15% 1	2800
	11th to 20th	Day	40% 8% 13% 24% 15% 1	2800
	21st to end	Day	43% 8% 13% 23% 13% 1	2800
July	1st to 10th	Day	39% 7% 15% 24% 14% 1	6290
	11th to 20th	Day	32% 9% 13% 32% 14% 1	6285
	21st to end	Day	32% 9% 14% 31% 14%	6380
August	1st to 10th	Day	44% 7% 14% 23% 12% 1	4143
	11th to 20th	Day	41% 8% 15% 27% 9%	4083
	21st to end	Day	36% 7% 14% 33% 10% 1	4345
September	1st to 10th	Day	39% 8% 14% 28% 10% 1	2280
	11th to 20th	Day	34% 9% 13% 28% 14%	2188
	21st to end	Day	45% 7% 13% 25% 9%	2038
October	1st to 10th	Day	38% 6% 15% 26% 14% 1	3160
	11th to 20th	Day	41% 7% 15% 23% 14%	3140
	21st to end	Day	52% 8% 15% 19% 6%	3428
November	1st to 10th	Day	50% 8% 14% 18% 8% 1	1672
	11th to 20th	Day	56% 10% 11% 13% 8% 1	1600
	21st to end	Day	63% 8% 10% 15% 3	1600
December	1st to 10th	Day	69% 9% 11% 7% 3	2600
	11th to 20th	Day	63% 9% 10% 10% 8%	2986
	21st to end	Day	73% 7% 6% 8% 6% 1	3960
January	1st to 10th	Night	55% 12% 11% 15% 7%	6349
	11th to 20th	Night	63% 8% 12% 11% 5% 1	6084
	21st to end	Night	60% 7% 13% 10% 10% 1	6490
February	1st to 10th	Night	59% 8% 10% 16% 5% 1	2600
	11th to 20th	Night	57% 8% 11% 16% 8%	2535
	21st to end	Night	53% 8% 13% 18% 8% 1	2095
March	1st to 10th	Night	52% 5% 12% 16% 12% 2	4918
	11th to 20th	Night	43% 7% 17% 22% 9% 2	4980
	21st to end	Night	46% 8% 10% 18% 16% 2	5467
April	1st to 10th	Night	53% 6% 10% 18% 12% 1	2024
	11th to 20th	Night	47% 6% 9% 20% 16% 2	1927
	21st to end	Night	47% 7% 12% 18% 16% 2	1800
May	1st to 10th	Night	50% 6% 11% 14% 14% 6%	4019
	11th to 20th	Night	42% 7% 14% 21% 14% 2	3576
	21st to end	Night	41% 7% 14% 23% 14% 2	3927
June	1st to 10th	Night	39% 8% 11% 24% 16% 2	1600
	11th to 20th	Night	37% 7% 12% 23% 20% 2	1600
	21st to end	Night	39% 7% 14% 24% 16% 1	1573
July	1st to 10th	Night	33% 7% 15% 25% 18% 2	3560
	11th to 20th	Night	30% 7% 14% 31% 17% 1	3552
	21st to end	Night	29% 7% 12% 32% 19% 1	4154
August	1st to 10th	Night	35% 5% 14% 29% 16% 2	2850
	11th to 20th	Night	33% 6% 17% 31% 12% 1	2812
	21st to end	Night	33% 7% 13% 33% 13% 1	3278
September	1st to 10th	Night	35% 8% 15% 27% 14% 1	1900
	11th to 20th	Night	30% 6% 12% 32% 18% 1	1989
	21st to end	Night	42% 6% 13% 27% 12%	2140
October	1st to 10th	Night	32% 6% 10% 28% 24% 1	3800
	11th to 20th	Night	41% 8% 14% 26% 12%	3779
	21st to end	Night	41% 8% 16% 26% 9%	4120
November	1st to 10th	Night	46% 8% 12% 21% 11% 1	2620
	11th to 20th	Night	54% 9% 12% 15% 9% 1	2800
	21st to end	Night	56% 11% 16% 13% 4	2800
December	1st to 10th	Night	64% 11% 13% 10% 3	4580
	11th to 20th	Night	62% 9% 9% 11% 9%	5208
	21st to end	Night	69% 8% 10% 7% 5%	6996

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% 26% 30% 17% 5%	200
	11th to 20th	Day	24% 30% 27% 14% 3 1	258
	21st to end	Day	25% 27% 33% 13% 2	330
February	1st to 10th	Day	30% 27% 29% 12% 2	300
	11th to 20th	Day	28% 28% 36% 7% 1	300
	21st to end	Day	35% 21% 36% 8%	278
March	1st to 10th	Day	26% 22% 35% 15% 3	500
	11th to 20th	Day	25% 23% 32% 16% 3 1	500
	21st to end	Day	32% 19% 30% 15% 4 1	550
April	1st to 10th	Day	29% 22% 32% 13% 5%	500
	11th to 20th	Day	31% 21% 25% 15% 6% 2	492
	21st to end	Day	27% 16% 35% 13% 7% 1	500
May	1st to 10th	Day	23% 16% 31% 18% 8% 4	503
	11th to 20th	Day	18% 16% 30% 24% 8% 3	527
	21st to end	Day	17% 13% 30% 26% 11% 3	573
June	1st to 10th	Day	17% 16% 31% 27% 8% 1	530
	11th to 20th	Day	15% 15% 31% 26% 11% 2	530
	21st to end	Day	22% 9% 32% 25% 10% 2	530
July	1st to 10th	Day	10% 9% 29% 33% 16% 3	525
	11th to 20th	Day	14% 8% 29% 30% 14% 6%	524
	21st to end	Day	8% 9% 36% 32% 10% 6%	576
August	1st to 10th	Day	13% 9% 26% 31% 14% 7%	502
	11th to 20th	Day	13% 9% 23% 28% 21% 6%	479
	21st to end	Day	13% 10% 29% 26% 15% 7%	539
September	1st to 10th	Day	13% 11% 27% 27% 15% 7%	490
	11th to 20th	Day	10% 8% 26% 25% 20% 12%	490
	21st to end	Day	17% 12% 29% 26% 12% 6%	490
October	1st to 10th	Day	21% 14% 30% 16% 16% 3	490
	11th to 20th	Day	22% 21% 32% 17% 7% 1	490
	21st to end	Day	28% 22% 28% 17% 5%	539
November	1st to 10th	Day	24% 24% 30% 16% 6% 1	279
	11th to 20th	Day	24% 27% 31% 15% 4 1	200
	21st to end	Day	25% 26% 38% 10% 2	200
December	1st to 10th	Day	27% 21% 35% 13% 5% 1	200
	11th to 20th	Day	33% 22% 31% 11% 3 1	200
	21st to end	Day	30% 20% 36% 12% 1	220
January	1st to 10th	Night	23% 24% 36% 12% 5%	800
	11th to 20th	Night	28% 17% 33% 17% 4 1	800
	21st to end	Night	20% 17% 37% 21% 6%	880
February	1st to 10th	Night	22% 22% 38% 17% 2	800
	11th to 20th	Night	24% 20% 35% 18% 3	783
	21st to end	Night	22% 22% 37% 15% 4	660
March	1st to 10th	Night	21% 21% 37% 18% 3	800
	11th to 20th	Night	21% 20% 37% 17% 4 1	800
	21st to end	Night	21% 17% 32% 24% 6%	880
April	1st to 10th	Night	26% 17% 33% 21% 3	800
	11th to 20th	Night	19% 18% 35% 20% 8% 1	743
	21st to end	Night	20% 14% 35% 23% 9%	600
May	1st to 10th	Night	21% 9% 28% 29% 11% 2	585
	11th to 20th	Night	17% 9% 32% 29% 12% 1	394
	21st to end	Night	12% 9% 27% 35% 16% 1	433
June	1st to 10th	Night	13% 9% 32% 35% 11%	400
	11th to 20th	Night	12% 10% 30% 35% 14% 1	400
	21st to end	Night	14% 6% 31% 36% 12% 1	400
July	1st to 10th	Night	7% 6% 28% 39% 19% 1	390
	11th to 20th	Night	12% 4 28% 36% 20% 1	388
	21st to end	Night	10% 3 27% 40% 18% 2	588
August	1st to 10th	Night	10% 4 21% 36% 27% 2	579
	11th to 20th	Night	8% 4 19% 41% 24% 3	564
	21st to end	Night	12% 5% 28% 34% 19% 3	716
September	1st to 10th	Night	12% 8% 25% 33% 18% 4	760
	11th to 20th	Night	12% 8% 22% 29% 23% 5%	760
	21st to end	Night	18% 9% 23% 31% 15% 4	760
October	1st to 10th	Night	19% 8% 30% 25% 16% 2	760
	11th to 20th	Night	23% 16% 31% 22% 8% 1	760
	21st to end	Night	28% 14% 32% 22% 3	836
November	1st to 10th	Night	24% 14% 31% 22% 8% 1	780
	11th to 20th	Night	22% 20% 32% 19% 6% 1	800
	21st to end	Night	26% 19% 30% 20% 5%	800
December	1st to 10th	Night	28% 18% 35% 15% 3	800
	11th to 20th	Night	22% 21% 37% 17% 3 1	800
	21st to end	Night	29% 18% 36% 15% 2	880

Page generated at 2025-08-02 01:32:22. Version ac07

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