Goose Creek
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Goose Creek clear sky chart from 2005-11-06 to 2024-12-24.

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	11% 6% 2 7% 5% 5% 5% 4 7% 8% 39%	101585
	Night	11% 6% 2 6% 4 4 5% 4 6% 8% 43%	98495
Transparency	Day	40% 6% 12% 19% 16% 6%	105248
	Night	37% 6% 13% 19% 17% 7%	102971
Seeing	Day	13% 7% 23% 26% 21% 11%	15711
	Night	13% 5% 20% 33% 24% 4	25825

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	13% 5% 1 5% 4 4 5% 4 7% 9% 43%	2836
	11th to 20th	Day	12% 6% 2 6% 4 3 4 4 5% 8% 47%	2840
	21st to end	Day	13% 9% 3 7% 4 3 4 3 5% 5% 44%	3124
February	1st to 10th	Day	14% 6% 2 6% 5% 4 6% 5% 6% 6% 40%	1710
	11th to 20th	Day	17% 7% 2 6% 4 4 3 3 5% 5% 46%	1810
	21st to end	Day	14% 7% 3 6% 4 3 4 3 5% 6% 45%	1712
March	1st to 10th	Day	22% 10% 4 6% 4 3 3 3 5% 6% 34%	3435
	11th to 20th	Day	8% 4 2 5% 4 4 4 3 6% 8% 53%	3480
	21st to end	Day	17% 6% 2 6% 4 3 3 4 5% 6% 44%	3815
April	1st to 10th	Day	8% 5% 1 5% 4 4 4 4 5% 6% 53%	2112
	11th to 20th	Day	10% 4 2 6% 4 4 4 4 6% 8% 49%	2254
	21st to end	Day	6% 4 1 4 3 4 5% 5% 6% 10% 53%	2280
May	1st to 10th	Day	7% 5% 2 7% 5% 5% 6% 5% 8% 10% 40%	4040
	11th to 20th	Day	13% 7% 3 7% 5% 5% 5% 4 6% 8% 36%	4081
	21st to end	Day	6% 4 2 5% 4 5% 6% 5% 8% 10% 44%	4476
June	1st to 10th	Day	9% 7% 3 7% 7% 7% 7% 6% 8% 10% 29%	2470
	11th to 20th	Day	8% 5% 2 6% 6% 6% 7% 6% 9% 12% 34%	2470
	21st to end	Day	6% 5% 2 6% 7% 7% 7% 7% 10% 13% 29%	2470
July	1st to 10th	Day	13% 8% 2 9% 7% 7% 8% 6% 8% 11% 23%	4120
	11th to 20th	Day	6% 5% 3 9% 7% 7% 8% 7% 10% 14% 24%	4120
	21st to end	Day	6% 6% 3 10% 7% 8% 8% 8% 10% 12% 20%	4466
August	1st to 10th	Day	20% 8% 3 8% 5% 6% 6% 5% 8% 10% 19%	4104
	11th to 20th	Day	7% 6% 2 9% 7% 7% 8% 5% 9% 11% 29%	3928
	21st to end	Day	8% 7% 3 9% 6% 6% 7% 4 7% 10% 33%	4180
September	1st to 10th	Day	10% 6% 3 7% 5% 6% 7% 5% 8% 9% 34%	2173
	11th to 20th	Day	13% 7% 2 8% 5% 7% 7% 4 7% 8% 32%	2090
	21st to end	Day	14% 7% 2 7% 4 6% 5% 3 6% 7% 37%	2090
October	1st to 10th	Day	12% 7% 2 6% 4 5% 4 3 6% 7% 44%	1933
	11th to 20th	Day	8% 3 2 5% 4 3 3 3 5% 6% 57%	1900
	21st to end	Day	9% 5% 2 5% 4 4 4 3 4 6% 55%	2090
November	1st to 10th	Day	10% 6% 2 5% 4 3 3 3 4 6% 54%	1957
	11th to 20th	Day	12% 7% 2 6% 4 4 3 3 4 6% 49%	2000
	21st to end	Day	13% 5% 1 5% 4 3 3 3 5% 6% 51%	1825
December	1st to 10th	Day	12% 6% 3 7% 5% 5% 4 5% 5% 7% 42%	1800
	11th to 20th	Day	15% 6% 2 4 2 2 3 2 4 6% 53%	2243
	21st to end	Day	17% 9% 3 5% 4 4 4 3 4 5% 44%	3151
January	1st to 10th	Night	13% 7% 2 6% 4 4 5% 4 6% 6% 43%	4109
	11th to 20th	Night	10% 7% 3 6% 5% 5% 5% 4 6% 8% 41%	4120
	21st to end	Night	13% 8% 3 7% 4 4 4 3 5% 6% 43%	4532
February	1st to 10th	Night	14% 7% 2 6% 4 4 4 4 5% 6% 43%	2470
	11th to 20th	Night	16% 7% 3 5% 4 4 4 2 4 6% 43%	2252
	21st to end	Night	13% 7% 4 6% 4 3 5% 4 5% 6% 43%	1740
March	1st to 10th	Night	20% 13% 4 8% 4 3 3 3 4 5% 33%	3418
	11th to 20th	Night	10% 6% 2 6% 3 4 4 3 5% 8% 50%	3480
	21st to end	Night	15% 5% 2 5% 4 4 4 3 6% 8% 45%	3817
April	1st to 10th	Night	9% 5% 2 6% 4 3 4 4 5% 7% 50%	2066
	11th to 20th	Night	11% 5% 2 5% 4 4 3 4 6% 8% 50%	1875
	21st to end	Night	7% 4 2 5% 4 4 3 4 6% 8% 53%	1900
May	1st to 10th	Night	5% 5% 2 6% 4 4 4 4 8% 10% 49%	2883
	11th to 20th	Night	11% 7% 2 6% 4 3 5% 4 5% 9% 45%	2812
	21st to end	Night	6% 3 2 6% 4 4 5% 5% 7% 9% 50%	3079
June	1st to 10th	Night	8% 6% 2 6% 6% 5% 6% 5% 8% 13% 35%	1710
	11th to 20th	Night	6% 5% 2 5% 5% 5% 7% 6% 9% 11% 39%	1710
	21st to end	Night	5% 5% 1 7% 6% 5% 7% 6% 10% 13% 35%	1710
July	1st to 10th	Night	10% 7% 3 8% 6% 6% 7% 6% 9% 10% 30%	2840
	11th to 20th	Night	7% 6% 3 7% 6% 6% 6% 6% 8% 13% 32%	2840
	21st to end	Night	7% 7% 3 7% 6% 6% 7% 6% 10% 13% 26%	3087
August	1st to 10th	Night	17% 7% 3 7% 5% 4 5% 5% 9% 12% 25%	2825
	11th to 20th	Night	7% 6% 2 7% 6% 5% 6% 6% 9% 11% 35%	2867
	21st to end	Night	5% 5% 2 8% 5% 5% 5% 4 6% 8% 46%	3476
September	1st to 10th	Night	8% 5% 2 7% 6% 6% 6% 5% 7% 10% 38%	2002
	11th to 20th	Night	9% 8% 3 8% 5% 6% 5% 4 8% 8% 37%	2090
	21st to end	Night	13% 8% 3 7% 4 4 4 4 6% 8% 39%	2090
October	1st to 10th	Night	12% 5% 2 5% 4 4 3 4 6% 6% 49%	2246
	11th to 20th	Night	9% 4 1 4 3 3 3 4 5% 6% 59%	2280
	21st to end	Night	8% 6% 2 5% 3 3 4 3 5% 6% 55%	2508
November	1st to 10th	Night	11% 5% 2 5% 3 4 3 3 4 6% 54%	2341
	11th to 20th	Night	13% 7% 2 5% 3 3 3 3 4 6% 51%	2400
	21st to end	Night	10% 6% 2 6% 4 4 5% 3 6% 6% 47%	2570
December	1st to 10th	Night	14% 6% 2 7% 4 4 4 4 5% 7% 43%	2600
	11th to 20th	Night	17% 6% 2 4 3 3 3 3 4 5% 48%	3172
	21st to end	Night	18% 7% 2 6% 4 4 4 4 5% 6% 41%	4578

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	37% 4 8% 20% 23% 8%	2837
	11th to 20th	Day	36% 3 6% 19% 26% 10%	2840
	21st to end	Day	42% 5% 6% 17% 20% 11%	3124
February	1st to 10th	Day	42% 5% 8% 19% 19% 6%	1710
	11th to 20th	Day	41% 3 8% 16% 23% 9%	1820
	21st to end	Day	40% 4 8% 19% 17% 11%	1712
March	1st to 10th	Day	53% 3 7% 15% 14% 8%	3435
	11th to 20th	Day	30% 4 10% 18% 24% 14%	3480
	21st to end	Day	41% 4 8% 18% 23% 6%	3815
April	1st to 10th	Day	31% 4 12% 21% 21% 10%	2112
	11th to 20th	Day	33% 4 8% 23% 19% 12%	2254
	21st to end	Day	26% 6% 11% 30% 22% 5%	2280
May	1st to 10th	Day	36% 8% 14% 26% 12% 4	4077
	11th to 20th	Day	44% 7% 12% 23% 13% 1	4085
	21st to end	Day	31% 7% 16% 24% 20% 2	4489
June	1st to 10th	Day	46% 8% 17% 18% 11%	2470
	11th to 20th	Day	38% 9% 19% 25% 9% 1	2470
	21st to end	Day	40% 10% 21% 19% 8% 1	2470
July	1st to 10th	Day	50% 11% 16% 18% 4 1	4055
	11th to 20th	Day	45% 14% 28% 10% 3	4051
	21st to end	Day	47% 15% 20% 16% 2	4324
August	1st to 10th	Day	56% 10% 20% 12% 2	4091
	11th to 20th	Day	44% 11% 17% 20% 8%	3967
	21st to end	Day	44% 7% 15% 30% 4	4180
September	1st to 10th	Day	43% 9% 17% 15% 13% 3	2173
	11th to 20th	Day	48% 8% 12% 17% 12% 4	2090
	21st to end	Day	45% 5% 12% 20% 14% 4	2090
October	1st to 10th	Day	42% 3 8% 13% 27% 6%	3206
	11th to 20th	Day	18% 2 5% 14% 32% 28%	3140
	21st to end	Day	25% 3 6% 18% 38% 10%	3428
November	1st to 10th	Day	32% 3 9% 18% 26% 12%	1957
	11th to 20th	Day	38% 3 7% 17% 23% 12%	2000
	21st to end	Day	35% 3 8% 23% 23% 9%	1825
December	1st to 10th	Day	41% 5% 10% 19% 16% 8%	1800
	11th to 20th	Day	35% 3 7% 21% 28% 6%	2240
	21st to end	Day	43% 3 6% 19% 24% 4	3151
January	1st to 10th	Night	39% 5% 8% 16% 23% 10%	4109
	11th to 20th	Night	40% 4 6% 18% 25% 6%	4120
	21st to end	Night	42% 4 7% 12% 23% 11%	4532
February	1st to 10th	Night	41% 4 8% 19% 20% 8%	2470
	11th to 20th	Night	43% 4 8% 15% 20% 10%	2253
	21st to end	Night	41% 4 10% 19% 15% 11%	1740
March	1st to 10th	Night	54% 4 10% 12% 12% 7%	3418
	11th to 20th	Night	33% 4 10% 16% 23% 14%	3480
	21st to end	Night	37% 5% 11% 20% 18% 8%	3817
April	1st to 10th	Night	33% 5% 13% 20% 21% 9%	2066
	11th to 20th	Night	32% 3 9% 24% 20% 11%	1875
	21st to end	Night	29% 4 13% 28% 22% 5%	1900
May	1st to 10th	Night	29% 7% 20% 28% 12% 3	2911
	11th to 20th	Night	36% 7% 15% 25% 16% 1	2813
	21st to end	Night	27% 8% 17% 28% 18% 1	3087
June	1st to 10th	Night	39% 7% 23% 21% 10%	1710
	11th to 20th	Night	33% 10% 22% 26% 8%	1710
	21st to end	Night	34% 13% 26% 22% 5% 1	1710
July	1st to 10th	Night	45% 10% 19% 22% 3 1	2795
	11th to 20th	Night	41% 13% 32% 10% 4	2786
	21st to end	Night	43% 15% 22% 17% 2	2988
August	1st to 10th	Night	48% 11% 27% 12% 2	2814
	11th to 20th	Night	38% 11% 22% 22% 6%	2894
	21st to end	Night	34% 8% 17% 36% 5%	3476
September	1st to 10th	Night	39% 8% 20% 18% 11% 3	2002
	11th to 20th	Night	42% 8% 16% 18% 14% 2	2090
	21st to end	Night	42% 6% 15% 19% 14% 3	2090
October	1st to 10th	Night	36% 3 10% 18% 27% 6%	3753
	11th to 20th	Night	16% 3 6% 14% 26% 35%	3779
	21st to end	Night	26% 3 6% 20% 29% 16%	4120
November	1st to 10th	Night	32% 3 9% 18% 25% 13%	2341
	11th to 20th	Night	36% 3 7% 18% 25% 12%	2400
	21st to end	Night	36% 3 9% 18% 23% 10%	2570
December	1st to 10th	Night	40% 4 14% 17% 18% 7%	2600
	11th to 20th	Night	38% 4 8% 16% 27% 7%	3174
	21st to end	Night	44% 4 6% 20% 22% 4	4578

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	14% 19% 41% 20% 5%	270
	11th to 20th	Day	13% 16% 40% 20% 10% 1	270
	21st to end	Day	23% 21% 37% 16% 3	297
February	1st to 10th	Day	16% 16% 42% 21% 5%	270
	11th to 20th	Day	25% 12% 44% 16% 3	270
	21st to end	Day	17% 14% 40% 23% 6% 1	367
March	1st to 10th	Day	18% 14% 31% 28% 9% 1	460
	11th to 20th	Day	14% 12% 40% 22% 9% 2	460
	21st to end	Day	15% 12% 39% 22% 10% 2	506
April	1st to 10th	Day	15% 17% 32% 22% 12% 2	460
	11th to 20th	Day	9% 13% 30% 21% 19% 7%	452
	21st to end	Day	7% 9% 28% 26% 19% 10%	460
May	1st to 10th	Day	9% 11% 31% 24% 18% 7%	463
	11th to 20th	Day	13% 5% 19% 31% 22% 11%	487
	21st to end	Day	11% 3 14% 30% 24% 17%	529
June	1st to 10th	Day	11% 2 16% 29% 27% 15%	490
	11th to 20th	Day	10% 3 16% 26% 27% 19%	490
	21st to end	Day	7% 2 12% 31% 28% 20%	490
July	1st to 10th	Day	9% 2 5% 22% 38% 24%	485
	11th to 20th	Day	8% 1 5% 20% 40% 25%	484
	21st to end	Day	6% 2 9% 26% 37% 20%	532
August	1st to 10th	Day	15% 1 7% 23% 30% 24%	486
	11th to 20th	Day	9% 2 5% 24% 34% 25%	479
	21st to end	Day	15% 3 8% 20% 28% 26%	539
September	1st to 10th	Day	12% 2 9% 27% 31% 19%	490
	11th to 20th	Day	18% 2 12% 30% 27% 11%	490
	21st to end	Day	16% 3 13% 30% 26% 13%	490
October	1st to 10th	Day	17% 3 21% 32% 18% 10%	490
	11th to 20th	Day	9% 3 21% 34% 23% 9%	490
	21st to end	Day	10% 5% 23% 32% 24% 6%	539
November	1st to 10th	Day	15% 7% 26% 29% 19% 4	495
	11th to 20th	Day	19% 7% 33% 26% 13% 2	500
	21st to end	Day	13% 11% 34% 28% 12% 1	325
December	1st to 10th	Day	17% 11% 38% 24% 10%	300
	11th to 20th	Day	18% 14% 38% 17% 12% 1	300
	21st to end	Day	24% 12% 32% 23% 8% 2	306
January	1st to 10th	Night	14% 8% 35% 36% 7% 1	760
	11th to 20th	Night	14% 11% 28% 36% 11%	760
	21st to end	Night	18% 8% 39% 30% 5%	836
February	1st to 10th	Night	18% 7% 34% 34% 9%	760
	11th to 20th	Night	21% 8% 34% 32% 6%	743
	21st to end	Night	15% 9% 36% 32% 7%	628
March	1st to 10th	Night	14% 9% 30% 37% 9%	760
	11th to 20th	Night	13% 8% 31% 37% 10% 1	760
	21st to end	Night	14% 7% 33% 35% 11% 1	836
April	1st to 10th	Night	12% 10% 31% 35% 11% 1	760
	11th to 20th	Night	12% 8% 26% 32% 18% 2	751
	21st to end	Night	11% 6% 25% 37% 20% 1	760
May	1st to 10th	Night	7% 5% 25% 39% 22% 2	615
	11th to 20th	Night	11% 3 17% 35% 29% 4	561
	21st to end	Night	9% 1 9% 35% 38% 8%	617
June	1st to 10th	Night	11% 2 8% 41% 31% 7%	570
	11th to 20th	Night	8% 2 7% 30% 41% 12%	570
	21st to end	Night	6% 2 7% 33% 43% 10%	570
July	1st to 10th	Night	8% 2 3 25% 53% 9%	555
	11th to 20th	Night	10% 1 2 24% 49% 14%	552
	21st to end	Night	6% 1 3 32% 48% 9%	624
August	1st to 10th	Night	11% 1 2 23% 50% 12%	567
	11th to 20th	Night	8% 2 4 26% 48% 11%	607
	21st to end	Night	11% 2 5% 26% 41% 15%	836
September	1st to 10th	Night	11% 2 5% 29% 45% 8%	760
	11th to 20th	Night	12% 2 7% 33% 38% 7%	760
	21st to end	Night	18% 2 10% 29% 35% 7%	760
October	1st to 10th	Night	15% 2 15% 34% 28% 6%	760
	11th to 20th	Night	11% 3 19% 36% 28% 4	760
	21st to end	Night	11% 4 19% 35% 26% 4	836
November	1st to 10th	Night	13% 4 20% 39% 20% 3	780
	11th to 20th	Night	17% 5% 25% 35% 16% 2	800
	21st to end	Night	12% 7% 25% 37% 18% 2	800
December	1st to 10th	Night	16% 6% 28% 37% 12% 2	800
	11th to 20th	Night	20% 5% 27% 31% 16% 1	800
	21st to end	Night	22% 7% 28% 32% 11%	851

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