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 2026-04-17.

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% 9% 39%	131770
	Night	11% 6% 2 6% 4 4 4 4 6% 8% 44%	130426
Transparency	Day	39% 6% 13% 19% 16% 6%	135389
	Night	37% 6% 13% 19% 18% 7%	134877
Seeing	Day	14% 8% 24% 25% 20% 10%	17477
	Night	13% 5% 21% 33% 23% 4	27631

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	11% 4 2 5% 3 3 4 3 5% 8% 51%	5258
	11th to 20th	Day	13% 5% 2 5% 3 3 3 3 5% 7% 51%	5280
	21st to end	Day	15% 8% 3 6% 4 4 4 3 5% 7% 41%	5780
February	1st to 10th	Day	13% 6% 2 6% 5% 4 6% 5% 6% 6% 43%	1890
	11th to 20th	Day	18% 7% 2 6% 4 4 3 2 5% 5% 45%	2006
	21st to end	Day	14% 7% 2 6% 4 3 4 3 5% 6% 46%	1888
March	1st to 10th	Day	21% 9% 4 6% 4 3 3 3 5% 6% 37%	5045
	11th to 20th	Day	8% 4 2 5% 4 3 4 3 6% 7% 54%	5090
	21st to end	Day	12% 5% 2 6% 4 4 4 4 5% 5% 49%	5586
April	1st to 10th	Day	8% 5% 1 5% 4 4 5% 4 6% 7% 52%	2334
	11th to 20th	Day	9% 4 2 6% 4 3 4 4 6% 8% 51%	2446
	21st to end	Day	6% 4 1 4 3 4 5% 5% 6% 10% 52%	2400
May	1st to 10th	Day	9% 6% 3 7% 6% 5% 5% 4 7% 11% 37%	5806
	11th to 20th	Day	14% 6% 2 7% 5% 5% 6% 5% 7% 10% 33%	5861
	21st to end	Day	8% 5% 2 7% 5% 5% 6% 5% 8% 10% 41%	6433
June	1st to 10th	Day	9% 7% 3 7% 7% 7% 7% 6% 8% 11% 29%	2600
	11th to 20th	Day	8% 5% 2 6% 6% 6% 7% 6% 9% 12% 34%	2600
	21st to end	Day	6% 5% 2 6% 7% 7% 7% 6% 10% 13% 31%	2600
July	1st to 10th	Day	11% 8% 3 10% 7% 7% 8% 6% 9% 11% 20%	5900
	11th to 20th	Day	5% 4 2 8% 7% 7% 8% 7% 10% 15% 25%	5900
	21st to end	Day	6% 5% 3 9% 6% 8% 8% 7% 9% 14% 25%	6424
August	1st to 10th	Day	20% 9% 3 9% 5% 6% 6% 5% 8% 9% 19%	4234
	11th to 20th	Day	7% 6% 2 9% 7% 7% 8% 5% 9% 11% 28%	4054
	21st to end	Day	9% 7% 3 9% 6% 6% 7% 4 7% 10% 33%	4312
September	1st to 10th	Day	10% 6% 3 7% 5% 6% 7% 5% 8% 9% 35%	2287
	11th to 20th	Day	13% 7% 2 8% 5% 6% 7% 4 7% 8% 33%	2200
	21st to end	Day	15% 7% 2 7% 4 6% 5% 4 6% 7% 37%	2200
October	1st to 10th	Day	13% 6% 2 6% 4 6% 4 3 6% 7% 43%	2035
	11th to 20th	Day	9% 3 2 5% 4 3 3 3 5% 6% 57%	2000
	21st to end	Day	9% 5% 2 5% 4 4 4 3 4 5% 55%	2200
November	1st to 10th	Day	10% 6% 2 5% 3 3 3 3 4 6% 54%	2057
	11th to 20th	Day	12% 7% 2 6% 4 4 3 3 4 6% 51%	2100
	21st to end	Day	12% 5% 1 5% 4 3 4 3 5% 6% 51%	1916
December	1st to 10th	Day	9% 4 2 6% 4 4 4 4 5% 6% 51%	3020
	11th to 20th	Day	14% 6% 3 5% 3 3 4 3 4 6% 48%	3463
	21st to end	Day	18% 9% 3 5% 4 4 3 3 4 6% 42%	4565
January	1st to 10th	Night	9% 6% 2 6% 4 4 4 3 5% 6% 53%	7635
	11th to 20th	Night	11% 6% 2 6% 4 4 4 3 5% 6% 48%	7680
	21st to end	Night	14% 8% 3 7% 4 4 4 3 4 6% 43%	8401
February	1st to 10th	Night	14% 7% 2 6% 4 4 4 4 5% 6% 44%	2730
	11th to 20th	Night	16% 7% 3 6% 4 4 4 2 4 6% 42%	2495
	21st to end	Night	13% 7% 4 6% 4 3 4 4 5% 6% 43%	1916
March	1st to 10th	Night	17% 10% 4 7% 4 4 3 3 4 5% 40%	5028
	11th to 20th	Night	9% 5% 2 5% 3 3 3 3 6% 9% 52%	5090
	21st to end	Night	12% 5% 2 5% 4 3 4 3 5% 7% 50%	5588
April	1st to 10th	Night	10% 5% 2 5% 4 3 4 4 5% 8% 50%	2284
	11th to 20th	Night	10% 4 2 4 3 3 3 4 6% 7% 53%	2036
	21st to end	Night	7% 4 2 5% 4 4 3 4 6% 8% 53%	2000
May	1st to 10th	Night	5% 5% 2 7% 4 4 5% 4 7% 9% 46%	4131
	11th to 20th	Night	14% 7% 2 5% 3 4 5% 5% 6% 11% 38%	4032
	21st to end	Night	10% 5% 2 6% 4 5% 5% 5% 7% 9% 43%	4421
June	1st to 10th	Night	8% 6% 2 7% 6% 5% 6% 5% 8% 13% 35%	1800
	11th to 20th	Night	6% 5% 2 6% 5% 5% 7% 6% 9% 12% 38%	1800
	21st to end	Night	5% 5% 1 6% 6% 5% 6% 6% 10% 13% 37%	1800
July	1st to 10th	Night	10% 7% 3 8% 6% 6% 7% 6% 9% 10% 29%	4058
	11th to 20th	Night	6% 5% 3 7% 6% 5% 6% 6% 8% 14% 35%	4057
	21st to end	Night	7% 7% 3 7% 5% 6% 7% 5% 10% 12% 31%	4427
August	1st to 10th	Night	18% 8% 3 7% 5% 4 5% 5% 9% 12% 24%	2915
	11th to 20th	Night	8% 6% 2 7% 6% 5% 6% 6% 9% 11% 34%	2959
	21st to end	Night	6% 5% 2 8% 5% 5% 6% 4 6% 8% 45%	3586
September	1st to 10th	Night	8% 5% 2 7% 6% 6% 6% 5% 7% 9% 39%	2108
	11th to 20th	Night	9% 7% 2 8% 5% 6% 5% 4 8% 8% 38%	2200
	21st to end	Night	14% 8% 3 7% 4 4 4 4 6% 8% 39%	2200
October	1st to 10th	Night	12% 5% 2 5% 4 4 4 4 5% 6% 48%	2364
	11th to 20th	Night	10% 4 1 4 3 3 3 3 5% 6% 58%	2400
	21st to end	Night	9% 6% 2 5% 3 3 4 3 4 6% 55%	2640
November	1st to 10th	Night	11% 5% 2 5% 3 3 3 3 4 6% 55%	2461
	11th to 20th	Night	13% 7% 2 5% 3 3 3 3 4 6% 52%	2520
	21st to end	Night	10% 6% 2 6% 4 4 5% 3 6% 7% 47%	2699
December	1st to 10th	Night	11% 5% 2 6% 3 3 3 3 4 6% 55%	4380
	11th to 20th	Night	16% 8% 3 7% 4 4 4 3 3 4 44%	4952
	21st to end	Night	16% 7% 2 6% 4 4 4 3 5% 6% 44%	6633

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	33% 3 9% 22% 27% 7%	5259
	11th to 20th	Day	35% 2 5% 16% 30% 13%	5280
	21st to end	Day	44% 3 7% 18% 17% 11%	5780
February	1st to 10th	Day	40% 5% 8% 21% 20% 6%	1890
	11th to 20th	Day	42% 3 7% 17% 23% 8%	2016
	21st to end	Day	40% 4 8% 19% 18% 11%	1888
March	1st to 10th	Day	50% 2 7% 13% 18% 10%	5045
	11th to 20th	Day	29% 3 9% 17% 23% 18%	5090
	21st to end	Day	38% 4 9% 19% 21% 11%	5586
April	1st to 10th	Day	31% 4 12% 22% 21% 9%	2334
	11th to 20th	Day	31% 4 8% 25% 20% 12%	2446
	21st to end	Day	26% 6% 11% 30% 21% 5%	2400
May	1st to 10th	Day	39% 7% 16% 26% 10% 3	5840
	11th to 20th	Day	44% 7% 18% 21% 10% 1	5865
	21st to end	Day	36% 7% 14% 20% 21% 1	6447
June	1st to 10th	Day	45% 8% 17% 19% 11%	2600
	11th to 20th	Day	37% 9% 21% 24% 8% 1	2600
	21st to end	Day	39% 10% 22% 20% 8% 1	2600
July	1st to 10th	Day	51% 12% 19% 14% 3	5835
	11th to 20th	Day	41% 15% 32% 9% 2	5831
	21st to end	Day	43% 13% 20% 21% 3	6240
August	1st to 10th	Day	57% 9% 20% 12% 2	4221
	11th to 20th	Day	44% 11% 17% 20% 8%	4093
	21st to end	Day	44% 7% 15% 29% 4	4312
September	1st to 10th	Day	42% 9% 16% 16% 14% 3	2287
	11th to 20th	Day	46% 8% 12% 19% 12% 4	2200
	21st to end	Day	45% 6% 12% 20% 14% 4	2200
October	1st to 10th	Day	43% 4 9% 13% 26% 6%	3308
	11th to 20th	Day	18% 2 5% 14% 32% 28%	3240
	21st to end	Day	26% 3 6% 17% 38% 10%	3538
November	1st to 10th	Day	31% 3 9% 18% 26% 12%	2057
	11th to 20th	Day	36% 3 7% 18% 24% 12%	2100
	21st to end	Day	34% 3 9% 22% 23% 8%	1916
December	1st to 10th	Day	34% 3 8% 18% 22% 15%	3020
	11th to 20th	Day	38% 4 9% 20% 24% 5%	3460
	21st to end	Day	44% 3 6% 23% 21% 3	4565
January	1st to 10th	Night	33% 3 8% 19% 29% 7%	7636
	11th to 20th	Night	37% 3 5% 15% 29% 11%	7680
	21st to end	Night	44% 3 7% 13% 22% 10%	8401
February	1st to 10th	Night	40% 3 8% 20% 20% 8%	2730
	11th to 20th	Night	44% 4 8% 16% 19% 9%	2496
	21st to end	Night	42% 4 9% 18% 15% 12%	1916
March	1st to 10th	Night	48% 3 8% 13% 19% 9%	5028
	11th to 20th	Night	30% 4 9% 14% 26% 17%	5090
	21st to end	Night	33% 4 11% 20% 20% 11%	5588
April	1st to 10th	Night	33% 5% 14% 21% 19% 8%	2284
	11th to 20th	Night	30% 3 9% 26% 21% 11%	2036
	21st to end	Night	29% 4 13% 28% 21% 5%	2000
May	1st to 10th	Night	33% 6% 20% 29% 9% 2	4159
	11th to 20th	Night	39% 7% 21% 21% 11% 1	4033
	21st to end	Night	35% 7% 16% 24% 17% 1	4429
June	1st to 10th	Night	39% 7% 22% 21% 10%	1800
	11th to 20th	Night	34% 11% 23% 25% 8%	1800
	21st to end	Night	33% 12% 26% 23% 5% 1	1800
July	1st to 10th	Night	45% 11% 25% 16% 2 1	4015
	11th to 20th	Night	38% 14% 37% 9% 3	4006
	21st to end	Night	41% 12% 22% 22% 2	4297
August	1st to 10th	Night	49% 11% 26% 12% 2	2904
	11th to 20th	Night	38% 12% 22% 22% 6%	2986
	21st to end	Night	35% 8% 17% 35% 4	3586
September	1st to 10th	Night	38% 8% 19% 20% 11% 3	2108
	11th to 20th	Night	41% 8% 16% 19% 14% 2	2200
	21st to end	Night	42% 6% 16% 20% 14% 3	2200
October	1st to 10th	Night	36% 3 10% 18% 26% 6%	3871
	11th to 20th	Night	17% 3 5% 14% 26% 34%	3899
	21st to end	Night	26% 3 6% 19% 29% 16%	4252
November	1st to 10th	Night	32% 3 8% 18% 25% 13%	2461
	11th to 20th	Night	35% 3 7% 18% 25% 12%	2520
	21st to end	Night	36% 4 9% 18% 23% 10%	2699
December	1st to 10th	Night	33% 3 9% 14% 30% 12%	4380
	11th to 20th	Night	44% 4 9% 15% 20% 7%	4954
	21st to end	Night	41% 4 7% 22% 23% 3	6633

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% 18% 43% 20% 5%	330
	11th to 20th	Day	15% 17% 39% 19% 9% 1	330
	21st to end	Day	23% 21% 38% 15% 3	363
February	1st to 10th	Day	16% 16% 43% 20% 5%	330
	11th to 20th	Day	27% 13% 43% 14% 3	330
	21st to end	Day	19% 14% 37% 24% 5%	431
March	1st to 10th	Day	18% 14% 30% 27% 10% 1	540
	11th to 20th	Day	15% 13% 40% 22% 9% 1	540
	21st to end	Day	13% 12% 40% 22% 10% 2	594
April	1st to 10th	Day	14% 16% 32% 23% 11% 3	540
	11th to 20th	Day	8% 12% 30% 23% 19% 7%	516
	21st to end	Day	7% 9% 28% 27% 20% 10%	500
May	1st to 10th	Day	9% 11% 32% 25% 17% 7%	503
	11th to 20th	Day	13% 5% 21% 30% 21% 11%	527
	21st to end	Day	11% 4 17% 29% 23% 16%	573
June	1st to 10th	Day	11% 2 18% 29% 26% 14%	530
	11th to 20th	Day	9% 2 16% 27% 27% 19%	530
	21st to end	Day	7% 2 11% 31% 29% 21%	530
July	1st to 10th	Day	9% 2 6% 23% 37% 24%	525
	11th to 20th	Day	8% 1 5% 20% 40% 26%	524
	21st to end	Day	6% 2 9% 25% 37% 21%	576
August	1st to 10th	Day	16% 1 8% 24% 29% 22%	526
	11th to 20th	Day	9% 2 6% 23% 33% 26%	519
	21st to end	Day	16% 3 9% 21% 27% 24%	583
September	1st to 10th	Day	11% 3 10% 27% 30% 18%	530
	11th to 20th	Day	17% 2 13% 31% 26% 12%	530
	21st to end	Day	17% 3 13% 29% 25% 12%	530
October	1st to 10th	Day	17% 4 21% 32% 17% 9%	530
	11th to 20th	Day	11% 3 20% 34% 23% 8%	530
	21st to end	Day	11% 5% 24% 32% 22% 5%	583
November	1st to 10th	Day	14% 8% 26% 29% 19% 4	535
	11th to 20th	Day	18% 7% 34% 27% 13% 2	540
	21st to end	Day	12% 12% 33% 29% 12% 1	356
December	1st to 10th	Day	20% 11% 38% 23% 9%	330
	11th to 20th	Day	18% 13% 37% 19% 11% 2	330
	21st to end	Day	24% 12% 33% 22% 8% 1	363
January	1st to 10th	Night	14% 8% 36% 36% 6% 1	840
	11th to 20th	Night	14% 11% 30% 34% 10%	840
	21st to end	Night	18% 8% 39% 30% 4	924
February	1st to 10th	Night	17% 7% 34% 34% 8%	840
	11th to 20th	Night	21% 9% 33% 32% 5%	823
	21st to end	Night	15% 10% 36% 31% 7%	692
March	1st to 10th	Night	14% 10% 30% 36% 10%	840
	11th to 20th	Night	13% 9% 31% 37% 9%	840
	21st to end	Night	13% 7% 34% 35% 11% 1	924
April	1st to 10th	Night	12% 10% 30% 36% 11% 1	840
	11th to 20th	Night	11% 8% 27% 33% 19% 2	816
	21st to end	Night	11% 6% 25% 37% 20% 1	800
May	1st to 10th	Night	7% 5% 24% 40% 21% 2	647
	11th to 20th	Night	11% 3 19% 35% 28% 4	591
	21st to end	Night	10% 1 10% 35% 37% 7%	650
June	1st to 10th	Night	11% 2 9% 41% 31% 7%	600
	11th to 20th	Night	7% 2 7% 32% 40% 12%	600
	21st to end	Night	6% 2 7% 33% 44% 10%	600
July	1st to 10th	Night	8% 2 3 25% 52% 9%	585
	11th to 20th	Night	10% 1 2 24% 50% 14%	582
	21st to end	Night	6% 2 4 30% 49% 10%	657
August	1st to 10th	Night	12% 2 3 24% 48% 12%	597
	11th to 20th	Night	8% 2 4 25% 48% 12%	639
	21st to end	Night	12% 2 5% 27% 39% 14%	880
September	1st to 10th	Night	11% 2 6% 30% 44% 8%	800
	11th to 20th	Night	12% 2 7% 34% 38% 8%	800
	21st to end	Night	18% 2 9% 29% 35% 7%	800
October	1st to 10th	Night	15% 2 16% 34% 27% 6%	800
	11th to 20th	Night	12% 3 18% 36% 28% 4	800
	21st to end	Night	12% 5% 20% 35% 25% 3	880
November	1st to 10th	Night	13% 5% 21% 40% 20% 3	820
	11th to 20th	Night	16% 5% 25% 36% 16% 2	840
	21st to end	Night	12% 7% 26% 37% 18% 2	840
December	1st to 10th	Night	17% 6% 28% 36% 11% 2	840
	11th to 20th	Night	19% 6% 27% 31% 15% 1	840
	21st to end	Night	21% 7% 28% 33% 11%	924

Page generated at 2026-04-14 02:44:23. Version ac07

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