Antique Airfield-IA27
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Antique Airfield-IA27 clear sky chart from 2005-11-06 to 2026-02-16.

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	12% 8% 3 8% 5% 4 4 4 5% 7% 40%	131267
	Night	12% 8% 3 8% 4 4 4 3 5% 6% 42%	129874
Transparency	Day	43% 3 12% 25% 15% 2	134867
	Night	43% 3 12% 25% 16% 2	134351
Seeing	Day	16% 10% 29% 26% 15% 4	17493
	Night	16% 10% 32% 30% 12% 1	27482

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	10% 12% 4 14% 6% 5% 5% 4 5% 7% 28%	4691
	11th to 20th	Day	6% 8% 3 10% 8% 7% 7% 4 5% 6% 37%	5223
	21st to end	Day	10% 13% 5% 12% 6% 5% 4 3 5% 6% 30%	5812
February	1st to 10th	Day	12% 11% 4 10% 7% 4 5% 4 6% 7% 29%	1890
	11th to 20th	Day	13% 11% 4 8% 5% 5% 5% 3 5% 7% 35%	1799
	21st to end	Day	15% 9% 3 8% 5% 4 4 3 6% 6% 38%	1645
March	1st to 10th	Day	17% 11% 3 6% 3 3 2 2 4 5% 44%	4847
	11th to 20th	Day	9% 6% 3 6% 4 4 5% 3 5% 8% 48%	4980
	21st to end	Day	19% 12% 4 8% 5% 4 4 4 5% 7% 28%	5543
April	1st to 10th	Day	17% 10% 3 7% 4 4 4 4 5% 6% 37%	2400
	11th to 20th	Day	16% 9% 3 7% 6% 4 4 3 5% 6% 37%	2374
	21st to end	Day	21% 7% 3 8% 5% 5% 4 3 5% 6% 33%	2440
May	1st to 10th	Day	14% 7% 3 7% 5% 5% 5% 4 6% 8% 37%	5862
	11th to 20th	Day	14% 6% 2 6% 4 4 4 3 5% 7% 44%	6310
	21st to end	Day	15% 7% 2 6% 5% 5% 5% 4 6% 7% 39%	6935
June	1st to 10th	Day	9% 4 2 6% 4 4 4 4 7% 9% 46%	2800
	11th to 20th	Day	9% 5% 2 5% 5% 4 5% 4 7% 9% 46%	2800
	21st to end	Day	10% 5% 2 6% 5% 5% 5% 5% 6% 8% 42%	2800
July	1st to 10th	Day	7% 6% 3 7% 5% 5% 5% 4 7% 9% 41%	6360
	11th to 20th	Day	8% 6% 2 7% 4 5% 6% 4 6% 9% 42%	6360
	21st to end	Day	9% 5% 2 6% 5% 5% 5% 5% 7% 11% 41%	6436
August	1st to 10th	Day	7% 5% 2 6% 4 4 5% 4 7% 11% 45%	4234
	11th to 20th	Day	12% 7% 2 7% 4 4 4 4 6% 8% 41%	4142
	21st to end	Day	8% 5% 2 5% 4 4 4 4 6% 9% 50%	4312
September	1st to 10th	Day	13% 4 2 4 3 3 4 2 5% 8% 52%	2400
	11th to 20th	Day	10% 4 2 5% 3 3 4 4 7% 9% 49%	2400
	21st to end	Day	10% 6% 2 5% 4 4 5% 3 4 8% 50%	2089
October	1st to 10th	Day	14% 6% 3 5% 3 3 3 2 4 6% 50%	2000
	11th to 20th	Day	14% 7% 3 7% 3 4 3 3 4 5% 48%	2000
	21st to end	Day	15% 10% 3 7% 4 3 3 2 5% 6% 43%	2200
November	1st to 10th	Day	10% 8% 2 4 3 5% 4 4 5% 8% 46%	1906
	11th to 20th	Day	14% 9% 3 7% 4 4 4 3 4 7% 41%	1749
	21st to end	Day	17% 9% 4 8% 4 4 4 2 4 6% 38%	1680
December	1st to 10th	Day	8% 8% 3 8% 4 3 3 2 4 6% 51%	2690
	11th to 20th	Day	13% 9% 4 15% 6% 4 6% 3 5% 7% 29%	3088
	21st to end	Day	21% 18% 7% 13% 5% 4 4 2 4 5% 17%	4070
January	1st to 10th	Night	11% 11% 5% 15% 6% 5% 4 3 4 5% 30%	8232
	11th to 20th	Night	7% 10% 4 11% 7% 5% 5% 4 6% 6% 34%	7763
	21st to end	Night	11% 13% 5% 11% 5% 4 4 3 4 5% 35%	8402
February	1st to 10th	Night	13% 11% 4 9% 5% 5% 4 3 5% 7% 34%	2730
	11th to 20th	Night	12% 10% 3 7% 5% 5% 4 3 5% 6% 40%	2599
	21st to end	Night	13% 10% 3 8% 5% 4 4 2 4 4 43%	1985
March	1st to 10th	Night	18% 9% 2 5% 3 3 3 3 3 5% 46%	5036
	11th to 20th	Night	10% 7% 2 5% 3 3 3 3 4 7% 51%	4980
	21st to end	Night	17% 12% 5% 9% 4 4 4 3 5% 6% 30%	5386
April	1st to 10th	Night	13% 9% 2 6% 4 3 4 3 5% 7% 43%	2000
	11th to 20th	Night	13% 8% 3 6% 5% 5% 5% 3 4 6% 42%	1975
	21st to end	Night	17% 7% 3 6% 4 3 4 5% 5% 6% 40%	1955
May	1st to 10th	Night	15% 7% 2 6% 4 4 4 3 6% 7% 41%	4053
	11th to 20th	Night	13% 4 2 5% 4 4 5% 4 5% 8% 46%	3602
	21st to end	Night	14% 7% 3 7% 4 4 4 3 4 6% 44%	3942
June	1st to 10th	Night	7% 5% 2 4 4 3 5% 4 8% 9% 50%	1600
	11th to 20th	Night	7% 5% 2 5% 3 4 5% 4 7% 11% 49%	1600
	21st to end	Night	7% 5% 1 5% 5% 3 4 5% 6% 9% 49%	1600
July	1st to 10th	Night	9% 4 2 6% 4 4 4 4 6% 9% 48%	3618
	11th to 20th	Night	6% 4 2 5% 4 4 4 4 6% 9% 52%	3617
	21st to end	Night	10% 6% 2 6% 4 4 4 4 6% 9% 47%	4418
August	1st to 10th	Night	3 3 1 4 4 4 4 4 6% 9% 58%	2926
	11th to 20th	Night	10% 4 2 5% 3 3 3 3 5% 7% 55%	2915
	21st to end	Night	6% 3 1 4 4 3 4 4 5% 9% 56%	3586
September	1st to 10th	Night	10% 4 2 4 2 3 3 3 5% 6% 57%	2000
	11th to 20th	Night	10% 4 2 6% 4 4 4 3 5% 6% 52%	2000
	21st to end	Night	9% 4 1 4 3 3 3 3 4 7% 58%	2287
October	1st to 10th	Night	12% 6% 2 5% 3 3 3 3 4 4 54%	2400
	11th to 20th	Night	14% 6% 3 5% 4 3 3 3 4 5% 52%	2400
	21st to end	Night	16% 7% 2 8% 4 4 3 3 4 6% 44%	2640
November	1st to 10th	Night	10% 6% 2 5% 3 2 3 3 5% 7% 55%	2611
	11th to 20th	Night	13% 9% 2 6% 4 4 3 4 5% 6% 44%	2867
	21st to end	Night	16% 10% 3 7% 4 3 3 3 4 5% 41%	2940
December	1st to 10th	Night	8% 9% 3 7% 4 4 4 3 4 6% 49%	4720
	11th to 20th	Night	13% 9% 4 10% 5% 4 4 3 4 6% 37%	5339
	21st to end	Night	21% 17% 7% 11% 5% 4 4 2 3 4 21%	7150

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	56% 2 14% 16% 11% 1	4692
	11th to 20th	Day	50% 1 8% 21% 17% 3	5223
	21st to end	Day	57% 2 10% 24% 7% 1	5812
February	1st to 10th	Day	54% 4 14% 18% 9% 1	1890
	11th to 20th	Day	50% 4 11% 23% 11% 1	1808
	21st to end	Day	47% 3 11% 24% 13% 2	1645
March	1st to 10th	Day	45% 2 8% 25% 19% 1	4847
	11th to 20th	Day	36% 2 9% 29% 21% 2	4980
	21st to end	Day	57% 2 17% 18% 4 1	5545
April	1st to 10th	Day	48% 4 11% 27% 10%	2400
	11th to 20th	Day	48% 4 10% 24% 12% 2	2374
	21st to end	Day	53% 3 11% 20% 12% 1	2440
May	1st to 10th	Day	46% 3 13% 20% 18% 1	5900
	11th to 20th	Day	41% 3 10% 28% 15% 3	6314
	21st to end	Day	45% 3 9% 26% 15% 1	6949
June	1st to 10th	Day	34% 5% 17% 28% 13% 2	2800
	11th to 20th	Day	34% 6% 12% 24% 20% 3	2800
	21st to end	Day	37% 6% 16% 24% 15% 2	2800
July	1st to 10th	Day	39% 3 14% 29% 14% 1	6291
	11th to 20th	Day	40% 3 13% 27% 16% 1	6285
	21st to end	Day	37% 4 18% 29% 12% 1	6253
August	1st to 10th	Day	32% 5% 16% 32% 14% 1	4220
	11th to 20th	Day	41% 3 13% 26% 16%	4181
	21st to end	Day	32% 3 16% 30% 16% 3	4311
September	1st to 10th	Day	32% 4 10% 28% 22% 4	2400
	11th to 20th	Day	32% 5% 10% 31% 19% 2	2400
	21st to end	Day	34% 3 10% 29% 21% 1	2089
October	1st to 10th	Day	24% 2 5% 19% 48% 3	3260
	11th to 20th	Day	27% 1 8% 26% 30% 8%	3240
	21st to end	Day	41% 2 9% 28% 18% 2	3538
November	1st to 10th	Day	36% 4 14% 25% 19% 3	1906
	11th to 20th	Day	43% 3 11% 25% 17% 1	1749
	21st to end	Day	48% 2 14% 23% 13%	1680
December	1st to 10th	Day	37% 2 16% 34% 11% 1	2690
	11th to 20th	Day	57% 2 11% 19% 11%	3085
	21st to end	Day	72% 2 9% 12% 4	4070
January	1st to 10th	Night	58% 2 14% 18% 7% 1	8233
	11th to 20th	Night	50% 2 10% 19% 17% 2	7763
	21st to end	Night	53% 1 12% 20% 12% 1	8402
February	1st to 10th	Night	51% 3 11% 23% 11% 1	2730
	11th to 20th	Night	46% 3 11% 25% 13% 2	2600
	21st to end	Night	46% 3 9% 23% 16% 4	1985
March	1st to 10th	Night	44% 2 6% 26% 21% 1	5036
	11th to 20th	Night	35% 2 7% 30% 20% 5%	4980
	21st to end	Night	56% 2 16% 16% 7% 2	5386
April	1st to 10th	Night	41% 4 11% 27% 16% 2	2000
	11th to 20th	Night	44% 3 10% 24% 16% 3	1975
	21st to end	Night	44% 4 13% 22% 14% 2	1955
May	1st to 10th	Night	44% 3 11% 24% 18% 2	4080
	11th to 20th	Night	37% 3 15% 25% 16% 4	3603
	21st to end	Night	43% 3 10% 22% 21% 2	3950
June	1st to 10th	Night	30% 5% 17% 28% 17% 3	1600
	11th to 20th	Night	29% 4 14% 28% 20% 4	1600
	21st to end	Night	32% 5% 16% 24% 20% 4	1600
July	1st to 10th	Night	34% 2 13% 31% 17% 3	3580
	11th to 20th	Night	31% 3 16% 29% 20% 1	3572
	21st to end	Night	34% 3 19% 28% 14% 1	4290
August	1st to 10th	Night	24% 4 17% 36% 17% 2	2916
	11th to 20th	Night	31% 3 14% 33% 19% 1	2942
	21st to end	Night	27% 3 14% 32% 18% 5%	3586
September	1st to 10th	Night	29% 4 9% 27% 26% 5%	2000
	11th to 20th	Night	34% 4 8% 31% 19% 4	2000
	21st to end	Night	28% 3 9% 30% 26% 3	2287
October	1st to 10th	Night	24% 2 5% 21% 44% 4	3920
	11th to 20th	Night	28% 2 8% 24% 29% 9%	3899
	21st to end	Night	43% 2 8% 24% 20% 3	4252
November	1st to 10th	Night	30% 4 16% 27% 19% 4	2611
	11th to 20th	Night	40% 3 11% 28% 15% 2	2867
	21st to end	Night	47% 2 11% 26% 13% 1	2940
December	1st to 10th	Night	38% 2 11% 38% 11% 1	4720
	11th to 20th	Night	50% 3 12% 25% 10% 1	5341
	21st to end	Night	70% 2 9% 14% 5% 1	7150

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	22% 13% 34% 22% 8% 1	330
	11th to 20th	Day	21% 17% 43% 17% 2	330
	21st to end	Day	20% 17% 41% 19% 2	363
February	1st to 10th	Day	19% 19% 37% 21% 3 1	330
	11th to 20th	Day	23% 15% 36% 20% 6%	315
	21st to end	Day	22% 14% 44% 15% 4 1	249
March	1st to 10th	Day	21% 14% 47% 14% 3	300
	11th to 20th	Day	23% 15% 35% 22% 6%	300
	21st to end	Day	34% 16% 32% 15% 3 1	360
April	1st to 10th	Day	23% 14% 36% 19% 6% 1	500
	11th to 20th	Day	22% 17% 34% 19% 8% 1	492
	21st to end	Day	24% 14% 34% 20% 6% 1	540
May	1st to 10th	Day	20% 14% 33% 22% 11%	703
	11th to 20th	Day	21% 12% 25% 25% 13% 3	725
	21st to end	Day	16% 8% 30% 27% 15% 4	789
June	1st to 10th	Day	8% 6% 25% 33% 22% 6%	730
	11th to 20th	Day	11% 4 26% 35% 20% 4	730
	21st to end	Day	11% 8% 33% 29% 16% 3	730
July	1st to 10th	Day	9% 3 16% 33% 27% 12%	721
	11th to 20th	Day	8% 4 22% 35% 24% 7%	718
	21st to end	Day	8% 3 20% 35% 28% 5%	794
August	1st to 10th	Day	9% 3 21% 36% 26% 6%	726
	11th to 20th	Day	11% 4 18% 31% 28% 8%	699
	21st to end	Day	9% 2 19% 33% 27% 9%	583
September	1st to 10th	Day	14% 5% 17% 31% 27% 5%	530
	11th to 20th	Day	10% 2 20% 36% 23% 9%	530
	21st to end	Day	12% 8% 27% 24% 23% 6%	340
October	1st to 10th	Day	20% 5% 30% 24% 14% 7%	330
	11th to 20th	Day	14% 23% 34% 21% 7% 1	330
	21st to end	Day	23% 17% 35% 18% 6% 1	363
November	1st to 10th	Day	16% 11% 41% 24% 7% 2	330
	11th to 20th	Day	21% 18% 34% 19% 7% 2	330
	21st to end	Day	25% 13% 38% 19% 5%	330
December	1st to 10th	Day	14% 15% 44% 19% 6% 3	330
	11th to 20th	Day	19% 17% 35% 20% 7% 1	330
	21st to end	Day	29% 20% 32% 17% 3	363
January	1st to 10th	Night	16% 13% 42% 21% 8%	1050
	11th to 20th	Night	16% 16% 40% 21% 6% 1	1050
	21st to end	Night	18% 14% 40% 24% 5%	1155
February	1st to 10th	Night	20% 12% 40% 24% 5%	1050
	11th to 20th	Night	18% 14% 38% 27% 3	1005
	21st to end	Night	19% 14% 40% 23% 4 1	665
March	1st to 10th	Night	18% 14% 38% 22% 7%	656
	11th to 20th	Night	18% 13% 37% 25% 7%	600
	21st to end	Night	26% 10% 37% 22% 5% 1	660
April	1st to 10th	Night	17% 13% 41% 25% 4	600
	11th to 20th	Night	19% 14% 34% 27% 5% 1	593
	21st to end	Night	20% 11% 33% 28% 8% 1	600
May	1st to 10th	Night	16% 8% 35% 33% 7% 1	600
	11th to 20th	Night	18% 8% 30% 30% 13% 1	591
	21st to end	Night	14% 6% 28% 35% 16% 1	650
June	1st to 10th	Night	9% 5% 23% 41% 20% 2	600
	11th to 20th	Night	9% 4 25% 43% 19% 1	600
	21st to end	Night	11% 4 29% 41% 16% 1	600
July	1st to 10th	Night	8% 2 13% 40% 35% 2	585
	11th to 20th	Night	6% 2 18% 44% 27% 3	582
	21st to end	Night	9% 2 15% 43% 29% 2	657
August	1st to 10th	Night	6% 3 15% 48% 26% 3	597
	11th to 20th	Night	8% 2 14% 43% 29% 4	594
	21st to end	Night	8% 2 13% 44% 30% 3	660
September	1st to 10th	Night	12% 3 20% 37% 25% 3	600
	11th to 20th	Night	12% 2 19% 38% 25% 4	600
	21st to end	Night	11% 5% 26% 34% 21% 3	700
October	1st to 10th	Night	14% 6% 29% 32% 17% 2	800
	11th to 20th	Night	16% 12% 33% 30% 8%	800
	21st to end	Night	19% 12% 34% 27% 7%	880
November	1st to 10th	Night	14% 10% 37% 31% 7%	820
	11th to 20th	Night	18% 14% 39% 23% 5%	977
	21st to end	Night	23% 12% 34% 24% 7%	1050
December	1st to 10th	Night	18% 14% 39% 23% 6% 1	1050
	11th to 20th	Night	20% 13% 36% 26% 5%	1050
	21st to end	Night	25% 14% 35% 23% 3	1155

Page generated at 2026-02-13 00:42:17. Version ac07

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