Coral Key Village Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Coral Key Village Observatory clear sky chart from 2005-11-06 to 2026-02-01.

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	5% 4 2 5% 4 5% 5% 5% 8% 12% 45%	126881
	Night	5% 4 2 6% 5% 5% 5% 5% 8% 11% 44%	125151
Transparency	Day	29% 10% 23% 26% 11% 2	130586
	Night	31% 9% 20% 25% 12% 2	129515
Seeing	Day	6% 2 7% 22% 38% 25%	17689
	Night	7% 2 9% 26% 37% 19%	27845

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	5% 4 2 5% 4 4 5% 4 8% 14% 44%	4146
	11th to 20th	Day	11% 7% 3 8% 5% 5% 5% 5% 7% 9% 36%	4150
	21st to end	Day	6% 7% 3 7% 5% 5% 5% 5% 6% 8% 43%	4918
February	1st to 10th	Day	6% 4 2 5% 4 4 4 5% 7% 11% 50%	2000
	11th to 20th	Day	5% 3 2 4 3 4 4 4 6% 10% 56%	2048
	21st to end	Day	3 2 1 3 2 3 4 3 7% 10% 62%	1815
March	1st to 10th	Day	2 2 1 3 3 3 5% 5% 8% 10% 58%	4935
	11th to 20th	Day	2 2 1 2 2 3 4 3 6% 10% 65%	4980
	21st to end	Day	5% 3 2 5% 3 4 4 4 7% 10% 53%	5465
April	1st to 10th	Day	2 2 1 3 2 4 4 4 8% 12% 60%	2200
	11th to 20th	Day	3 3 1 3 3 3 4 3 6% 10% 60%	2196
	21st to end	Day	4 3 1 3 2 3 4 4 8% 10% 57%	2400
May	1st to 10th	Day	2 1 1 2 2 2 3 3 6% 13% 66%	5405
	11th to 20th	Day	5% 3 1 4 3 3 4 3 6% 10% 58%	5446
	21st to end	Day	3 3 1 3 3 3 3 3 6% 11% 61%	6433
June	1st to 10th	Day	10% 8% 3 9% 6% 6% 6% 6% 9% 13% 25%	2600
	11th to 20th	Day	6% 5% 3 7% 6% 5% 7% 5% 10% 16% 30%	2600
	21st to end	Day	4 5% 3 7% 5% 6% 7% 7% 10% 13% 33%	2600
July	1st to 10th	Day	3 3 2 6% 5% 6% 7% 6% 11% 17% 35%	5900
	11th to 20th	Day	3 4 2 6% 5% 6% 6% 7% 11% 16% 35%	5900
	21st to end	Day	2 2 1 4 3 4 6% 6% 9% 17% 46%	6424
August	1st to 10th	Day	2 3 2 7% 6% 7% 8% 7% 12% 16% 30%	4171
	11th to 20th	Day	2 4 2 8% 5% 5% 7% 6% 9% 15% 36%	3625
	21st to end	Day	3 2 1 6% 5% 7% 8% 8% 12% 17% 30%	3949
September	1st to 10th	Day	4 5% 2 6% 6% 6% 8% 8% 11% 17% 27%	2200
	11th to 20th	Day	5% 5% 2 7% 6% 7% 8% 7% 10% 15% 28%	2200
	21st to end	Day	6% 7% 3 8% 6% 7% 7% 6% 10% 13% 28%	2200
October	1st to 10th	Day	7% 5% 2 8% 6% 6% 7% 5% 9% 14% 30%	2160
	11th to 20th	Day	8% 5% 2 6% 6% 7% 6% 5% 9% 12% 34%	2000
	21st to end	Day	9% 5% 2 6% 5% 5% 5% 4 7% 10% 42%	2200
November	1st to 10th	Day	8% 4 2 5% 4 5% 5% 5% 7% 11% 46%	2057
	11th to 20th	Day	6% 5% 3 6% 5% 5% 5% 5% 7% 10% 44%	2100
	21st to end	Day	5% 4 2 5% 4 5% 5% 4 7% 9% 50%	2100
December	1st to 10th	Day	5% 3 1 4 3 4 4 3 6% 9% 58%	3330
	11th to 20th	Day	7% 5% 2 6% 4 5% 6% 5% 8% 11% 43%	3463
	21st to end	Day	10% 7% 3 9% 6% 5% 6% 5% 7% 9% 33%	4565
January	1st to 10th	Night	4 4 2 6% 5% 5% 5% 5% 8% 10% 45%	6019
	11th to 20th	Night	11% 7% 3 9% 5% 5% 6% 4 6% 8% 35%	6030
	21st to end	Night	8% 6% 3 7% 6% 6% 5% 4 7% 8% 41%	6275
February	1st to 10th	Night	6% 5% 2 5% 5% 6% 5% 5% 6% 9% 47%	2401
	11th to 20th	Night	5% 4 2 5% 4 3 4 4 6% 9% 54%	2234
	21st to end	Night	4 3 1 4 4 3 4 3 6% 8% 59%	1815
March	1st to 10th	Night	3 3 1 5% 4 5% 5% 5% 7% 8% 53%	4918
	11th to 20th	Night	3 2 1 4 3 3 4 3 5% 9% 63%	4980
	21st to end	Night	4 3 1 4 4 5% 5% 4 8% 11% 51%	5467
April	1st to 10th	Night	3 3 1 4 3 4 5% 4 7% 10% 56%	2200
	11th to 20th	Night	5% 3 2 5% 3 3 4 4 7% 9% 54%	2151
	21st to end	Night	4 3 2 4 3 4 5% 4 7% 9% 53%	2000
May	1st to 10th	Night	1 1 1 2 2 2 3 3 6% 11% 67%	4490
	11th to 20th	Night	5% 4 2 6% 4 4 4 4 5% 8% 53%	4474
	21st to end	Night	3 3 1 3 2 2 3 3 6% 10% 64%	4421
June	1st to 10th	Night	11% 10% 3 10% 7% 6% 5% 5% 9% 10% 24%	1800
	11th to 20th	Night	6% 5% 2 6% 5% 5% 7% 6% 9% 15% 34%	1800
	21st to end	Night	3 4 1 6% 7% 6% 8% 6% 10% 15% 33%	1800
July	1st to 10th	Night	2 2 2 5% 5% 6% 6% 6% 11% 18% 38%	4058
	11th to 20th	Night	2 3 2 5% 5% 6% 6% 6% 10% 14% 42%	4057
	21st to end	Night	1 2 1 3 4 3 5% 4 9% 16% 51%	4427
August	1st to 10th	Night	2 4 2 7% 5% 6% 8% 7% 11% 16% 33%	2943
	11th to 20th	Night	2 3 2 5% 6% 5% 6% 6% 9% 17% 40%	3415
	21st to end	Night	3 3 2 5% 5% 7% 8% 7% 13% 18% 28%	3949
September	1st to 10th	Night	4 5% 1 5% 6% 6% 8% 8% 11% 15% 32%	2200
	11th to 20th	Night	3 6% 3 9% 7% 8% 8% 7% 11% 11% 28%	2200
	21st to end	Night	7% 7% 3 8% 7% 7% 7% 6% 8% 12% 27%	2200
October	1st to 10th	Night	6% 6% 3 8% 7% 6% 7% 7% 10% 12% 29%	2237
	11th to 20th	Night	8% 6% 3 7% 6% 6% 6% 7% 9% 12% 31%	2400
	21st to end	Night	9% 6% 3 8% 6% 6% 6% 5% 7% 9% 36%	2640
November	1st to 10th	Night	9% 5% 2 5% 4 5% 5% 5% 9% 10% 40%	2461
	11th to 20th	Night	7% 7% 2 6% 5% 5% 5% 4 7% 11% 40%	2520
	21st to end	Night	7% 4 2 6% 4 5% 5% 4 8% 10% 45%	2520
December	1st to 10th	Night	5% 4 2 4 3 4 4 4 6% 9% 56%	4064
	11th to 20th	Night	7% 6% 2 6% 5% 5% 5% 5% 7% 10% 43%	4952
	21st to end	Night	9% 7% 3 10% 7% 7% 7% 5% 7% 9% 31%	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	27% 8% 15% 35% 12% 3	4147
	11th to 20th	Day	41% 9% 18% 24% 7% 2	4150
	21st to end	Day	36% 7% 9% 27% 17% 3	4918
February	1st to 10th	Day	27% 6% 14% 32% 18% 3	2000
	11th to 20th	Day	23% 5% 14% 31% 22% 5%	2058
	21st to end	Day	17% 5% 11% 30% 30% 6%	1815
March	1st to 10th	Day	18% 6% 19% 30% 24% 2	4935
	11th to 20th	Day	13% 6% 19% 32% 20% 10%	4980
	21st to end	Day	24% 6% 12% 34% 21% 3	5465
April	1st to 10th	Day	17% 6% 18% 41% 16% 3	2200
	11th to 20th	Day	19% 6% 19% 32% 19% 5%	2196
	21st to end	Day	19% 7% 16% 33% 22% 3	2400
May	1st to 10th	Day	10% 5% 19% 45% 19% 2	5437
	11th to 20th	Day	21% 6% 15% 50% 8%	5450
	21st to end	Day	17% 7% 19% 49% 8%	6447
June	1st to 10th	Day	47% 11% 23% 16% 3	2600
	11th to 20th	Day	37% 16% 31% 16% 1	2600
	21st to end	Day	35% 16% 36% 12%	2600
July	1st to 10th	Day	32% 14% 40% 13%	5835
	11th to 20th	Day	33% 13% 42% 11% 1	5831
	21st to end	Day	20% 13% 44% 21% 2	6240
August	1st to 10th	Day	33% 17% 35% 14% 1	4158
	11th to 20th	Day	30% 14% 40% 14% 2	3661
	21st to end	Day	32% 19% 40% 7% 1	3949
September	1st to 10th	Day	36% 20% 30% 13% 1	2200
	11th to 20th	Day	38% 17% 30% 13% 2	2200
	21st to end	Day	41% 16% 23% 15% 5%	2200
October	1st to 10th	Day	40% 12% 24% 18% 4 1	3524
	11th to 20th	Day	46% 14% 17% 15% 8% 1	3240
	21st to end	Day	36% 7% 12% 29% 14% 2	3538
November	1st to 10th	Day	31% 7% 15% 24% 19% 4	2057
	11th to 20th	Day	34% 8% 12% 22% 19% 4	2100
	21st to end	Day	29% 7% 14% 24% 23% 3	2100
December	1st to 10th	Day	22% 7% 11% 37% 22% 2	3330
	11th to 20th	Day	33% 8% 14% 26% 15% 4	3460
	21st to end	Day	44% 9% 14% 16% 15% 1	4565
January	1st to 10th	Night	30% 7% 13% 32% 15% 2	6019
	11th to 20th	Night	43% 8% 15% 23% 8% 1	6030
	21st to end	Night	38% 6% 10% 27% 17% 2	6275
February	1st to 10th	Night	31% 7% 13% 28% 18% 4	2401
	11th to 20th	Night	26% 6% 12% 26% 24% 7%	2235
	21st to end	Night	22% 6% 13% 23% 27% 9%	1815
March	1st to 10th	Night	25% 7% 13% 27% 24% 4	4918
	11th to 20th	Night	18% 6% 16% 30% 19% 11%	4980
	21st to end	Night	25% 6% 13% 29% 23% 4	5467
April	1st to 10th	Night	21% 7% 16% 37% 17% 3	2200
	11th to 20th	Night	25% 7% 17% 28% 20% 4	2151
	21st to end	Night	25% 7% 12% 32% 21% 2	2000
May	1st to 10th	Night	10% 6% 18% 49% 15% 2	4520
	11th to 20th	Night	28% 7% 13% 37% 15%	4475
	21st to end	Night	16% 5% 23% 44% 11%	4429
June	1st to 10th	Night	51% 11% 21% 14% 4	1800
	11th to 20th	Night	36% 16% 29% 16% 3	1800
	21st to end	Night	34% 16% 35% 15% 1	1800
July	1st to 10th	Night	27% 15% 44% 13%	4015
	11th to 20th	Night	30% 14% 46% 10%	4006
	21st to end	Night	19% 10% 42% 25% 4	4297
August	1st to 10th	Night	33% 14% 37% 14% 2	2932
	11th to 20th	Night	27% 13% 42% 16% 1	3445
	21st to end	Night	32% 21% 37% 9% 1	3949
September	1st to 10th	Night	33% 19% 34% 12% 1	2200
	11th to 20th	Night	42% 16% 28% 13% 2	2200
	21st to end	Night	44% 14% 24% 14% 5%	2200
October	1st to 10th	Night	41% 12% 22% 19% 5% 1	3653
	11th to 20th	Night	48% 13% 19% 12% 7% 1	3899
	21st to end	Night	42% 7% 11% 27% 12% 2	4252
November	1st to 10th	Night	34% 9% 13% 24% 16% 3	2461
	11th to 20th	Night	36% 7% 14% 23% 17% 3	2520
	21st to end	Night	32% 7% 12% 25% 20% 3	2520
December	1st to 10th	Night	24% 6% 12% 38% 17% 3	4064
	11th to 20th	Night	34% 8% 14% 26% 14% 4	4954
	21st to end	Night	46% 10% 13% 17% 13% 1	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	8% 3 16% 32% 35% 6%	330
	11th to 20th	Day	12% 4 15% 41% 23% 5%	330
	21st to end	Day	8% 6% 20% 38% 25% 3	363
February	1st to 10th	Day	4 3 11% 37% 40% 5%	300
	11th to 20th	Day	5% 2 11% 32% 45% 6%	400
	21st to end	Day	4 1 15% 31% 41% 7%	414
March	1st to 10th	Day	3 2 16% 43% 32% 4	500
	11th to 20th	Day	6% 1 13% 37% 39% 4	500
	21st to end	Day	3 1 13% 35% 42% 4	550
April	1st to 10th	Day	3 1 8% 41% 44% 3	500
	11th to 20th	Day	2 1 10% 45% 39% 4	492
	21st to end	Day	5% 2 4 38% 46% 4	500
May	1st to 10th	Day	4 1 4 30% 51% 11%	503
	11th to 20th	Day	9% 2 2 30% 45% 12%	527
	21st to end	Day	8% 1 4 13% 48% 26%	573
June	1st to 10th	Day	13% 1 4 14% 40% 28%	530
	11th to 20th	Day	7% 1 2 13% 34% 42%	530
	21st to end	Day	3 2 5% 31% 59%	530
July	1st to 10th	Day	3 1 1 3 30% 61%	525
	11th to 20th	Day	3 1 1 4 29% 61%	524
	21st to end	Day	5% 2 4 32% 58%	576
August	1st to 10th	Day	4 1 5% 37% 54%	526
	11th to 20th	Day	3 1 3 33% 60%	519
	21st to end	Day	6% 1 2 7% 34% 50%	583
September	1st to 10th	Day	6% 1 2 5% 30% 57%	530
	11th to 20th	Day	6% 1 2 5% 27% 58%	530
	21st to end	Day	7% 2 5% 9% 32% 45%	530
October	1st to 10th	Day	6% 1 4 16% 51% 22%	530
	11th to 20th	Day	10% 2 6% 21% 40% 22%	530
	21st to end	Day	8% 2 11% 25% 42% 12%	583
November	1st to 10th	Day	7% 2 11% 28% 42% 9%	535
	11th to 20th	Day	8% 3 12% 28% 39% 10%	540
	21st to end	Day	6% 2 13% 30% 39% 11%	540
December	1st to 10th	Day	9% 3 10% 28% 42% 9%	523
	11th to 20th	Day	7% 2 11% 28% 42% 9%	330
	21st to end	Day	8% 4 13% 29% 34% 11%	363
January	1st to 10th	Night	6% 3 15% 34% 36% 6%	840
	11th to 20th	Night	10% 3 18% 35% 30% 4	840
	21st to end	Night	7% 5% 21% 36% 28% 2	924
February	1st to 10th	Night	7% 3 14% 36% 36% 3	801
	11th to 20th	Night	5% 3 17% 35% 36% 4	783
	21st to end	Night	4 2 11% 36% 41% 6%	660
March	1st to 10th	Night	4 2 17% 43% 32% 3	800
	11th to 20th	Night	4 3 14% 39% 37% 4	800
	21st to end	Night	4 3 15% 40% 35% 4	880
April	1st to 10th	Night	3 2 9% 42% 43% 2	800
	11th to 20th	Night	6% 2 11% 40% 38% 3	791
	21st to end	Night	5% 2 9% 42% 40% 3	800
May	1st to 10th	Night	4 7% 34% 45% 10%	800
	11th to 20th	Night	9% 1 7% 30% 46% 8%	786
	21st to end	Night	8% 1 6% 16% 54% 16%	650
June	1st to 10th	Night	15% 3 6% 17% 41% 19%	600
	11th to 20th	Night	5% 2 4 11% 40% 39%	600
	21st to end	Night	4 1 1 7% 37% 51%	600
July	1st to 10th	Night	3 1 5% 32% 57%	585
	11th to 20th	Night	3 1 2 5% 35% 54%	582
	21st to end	Night	4 2 4 33% 57%	657
August	1st to 10th	Night	4 2 4 40% 50%	612
	11th to 20th	Night	3 2 6% 33% 55%	790
	21st to end	Night	7% 1 3 8% 35% 45%	880
September	1st to 10th	Night	6% 1 2 7% 33% 52%	800
	11th to 20th	Night	6% 1 3 9% 30% 52%	800
	21st to end	Night	10% 1 5% 10% 35% 39%	800
October	1st to 10th	Night	8% 1 6% 19% 46% 21%	800
	11th to 20th	Night	11% 1 6% 19% 42% 22%	800
	21st to end	Night	13% 2 9% 29% 35% 13%	880
November	1st to 10th	Night	11% 4 14% 29% 36% 7%	820
	11th to 20th	Night	9% 2 9% 30% 41% 8%	840
	21st to end	Night	7% 2 13% 34% 37% 7%	840
December	1st to 10th	Night	7% 4 10% 33% 39% 7%	840
	11th to 20th	Night	10% 3 11% 32% 37% 7%	840
	21st to end	Night	7% 3 13% 32% 34% 10%	924

Page generated at 2026-01-29 01:21:42. Version ac07

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