Osservatorio Aucello
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Osservatorio Aucello clear sky chart from 2005-11-06 to 2026-03-03.

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% 7% 3 6% 4 4 4 3 5% 7% 46%	130864
	Night	11% 7% 3 6% 4 4 4 3 5% 6% 48%	130557
Transparency	Day	38% 4 12% 27% 17% 3	134476
	Night	37% 3 11% 26% 19% 4	135022
Seeing	Day	14% 11% 30% 27% 14% 3	17394
	Night	14% 10% 33% 31% 11% 1	27394

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	14% 11% 3 9% 4 4 3 3 4 5% 41%	5289
	11th to 20th	Day	5% 7% 3 10% 7% 6% 6% 3 4 6% 43%	5310
	21st to end	Day	12% 13% 4 8% 4 4 4 3 3 5% 40%	5812
February	1st to 10th	Day	14% 10% 4 7% 5% 5% 3 3 4 6% 39%	1890
	11th to 20th	Day	12% 10% 3 7% 5% 4 4 3 5% 6% 41%	1844
	21st to end	Day	10% 8% 3 6% 4 4 4 3 5% 6% 46%	1791
March	1st to 10th	Day	12% 9% 2 6% 3 3 3 3 3 5% 51%	4958
	11th to 20th	Day	10% 6% 1 5% 3 3 4 3 4 6% 56%	4980
	21st to end	Day	12% 10% 4 7% 5% 5% 5% 4 5% 7% 35%	5462
April	1st to 10th	Day	14% 8% 3 6% 4 3 4 3 4 6% 45%	2307
	11th to 20th	Day	15% 8% 3 7% 4 5% 4 4 5% 6% 41%	2374
	21st to end	Day	19% 8% 2 7% 5% 5% 4 3 4 6% 36%	2540
May	1st to 10th	Day	15% 8% 2 6% 4 3 4 3 5% 6% 43%	5862
	11th to 20th	Day	14% 6% 2 6% 3 4 4 3 5% 7% 45%	5862
	21st to end	Day	19% 6% 2 5% 4 3 4 4 5% 7% 41%	6543
June	1st to 10th	Day	7% 4 2 4 4 5% 5% 5% 7% 9% 49%	2800
	11th to 20th	Day	7% 5% 3 6% 4 5% 5% 4 7% 9% 47%	2800
	21st to end	Day	7% 3 2 5% 4 4 5% 4 6% 8% 52%	2771
July	1st to 10th	Day	8% 6% 2 6% 4 4 5% 4 6% 9% 46%	5900
	11th to 20th	Day	8% 5% 2 6% 4 4 4 4 7% 9% 48%	5900
	21st to end	Day	7% 5% 2 6% 4 5% 6% 5% 8% 10% 43%	6422
August	1st to 10th	Day	5% 4 2 5% 4 4 5% 4 6% 9% 53%	4234
	11th to 20th	Day	10% 6% 2 6% 4 4 4 3 5% 8% 48%	4171
	21st to end	Day	6% 4 2 5% 3 3 5% 3 6% 8% 56%	4397
September	1st to 10th	Day	12% 5% 2 5% 3 3 3 4 5% 6% 53%	2400
	11th to 20th	Day	8% 5% 2 5% 5% 5% 4 4 5% 7% 49%	2214
	21st to end	Day	9% 4 2 6% 3 3 3 4 5% 6% 54%	2189
October	1st to 10th	Day	11% 5% 2 5% 3 3 3 2 5% 7% 53%	2000
	11th to 20th	Day	12% 6% 2 4 2 3 3 2 4 5% 56%	2000
	21st to end	Day	16% 7% 3 6% 3 3 3 2 4 5% 48%	2200
November	1st to 10th	Day	10% 5% 2 5% 3 3 4 3 4 6% 55%	2058
	11th to 20th	Day	14% 6% 2 4 4 3 3 3 4 7% 51%	1821
	21st to end	Day	15% 8% 2 7% 3 4 3 3 3 5% 47%	1680
December	1st to 10th	Day	6% 6% 2 5% 5% 4 3 3 5% 7% 54%	2690
	11th to 20th	Day	10% 7% 3 8% 3 4 3 3 4 6% 49%	3088
	21st to end	Day	18% 16% 7% 11% 4 3 4 3 4 5% 26%	4305
January	1st to 10th	Night	12% 10% 3 12% 5% 4 3 3 3 4 39%	7634
	11th to 20th	Night	7% 7% 3 8% 5% 6% 4 3 4 5% 49%	7680
	21st to end	Night	13% 10% 4 9% 4 5% 4 3 4 5% 40%	8402
February	1st to 10th	Night	11% 10% 3 7% 5% 4 4 3 5% 7% 40%	2730
	11th to 20th	Night	12% 9% 3 7% 5% 4 4 3 4 6% 42%	2663
	21st to end	Night	12% 7% 3 6% 5% 4 3 3 5% 5% 48%	2029
March	1st to 10th	Night	13% 9% 3 4 3 3 3 3 4 5% 50%	4941
	11th to 20th	Night	8% 7% 1 4 2 3 3 3 6% 7% 56%	4980
	21st to end	Night	13% 8% 4 7% 4 4 4 4 5% 7% 39%	5467
April	1st to 10th	Night	11% 7% 2 6% 4 3 3 3 6% 6% 49%	2091
	11th to 20th	Night	13% 7% 3 6% 4 3 3 3 5% 6% 47%	1975
	21st to end	Night	17% 7% 3 7% 4 3 4 4 4 5% 42%	1855
May	1st to 10th	Night	15% 7% 2 5% 4 4 3 3 5% 6% 45%	4053
	11th to 20th	Night	14% 6% 2 5% 3 3 3 3 4 6% 51%	4053
	21st to end	Night	17% 5% 2 4 3 3 3 3 4 6% 50%	4316
June	1st to 10th	Night	6% 3 1 4 3 5% 4 5% 6% 9% 55%	1600
	11th to 20th	Night	6% 4 2 4 3 4 4 5% 7% 10% 52%	1600
	21st to end	Night	5% 3 1 3 3 3 3 4 6% 9% 60%	1621
July	1st to 10th	Night	8% 5% 2 6% 4 3 4 3 6% 8% 50%	4078
	11th to 20th	Night	5% 5% 2 5% 3 4 5% 4 6% 9% 53%	4077
	21st to end	Night	7% 4 2 5% 4 4 5% 5% 8% 12% 45%	4449
August	1st to 10th	Night	2 1 1 3 3 4 5% 5% 6% 10% 61%	2926
	11th to 20th	Night	10% 7% 2 5% 3 3 4 3 4 6% 53%	2888
	21st to end	Night	4 3 1 5% 4 3 4 3 5% 8% 60%	3490
September	1st to 10th	Night	10% 4 2 5% 3 3 3 3 4 5% 57%	2000
	11th to 20th	Night	8% 5% 2 4 4 4 4 4 6% 8% 53%	2182
	21st to end	Night	6% 4 2 5% 4 4 3 3 5% 5% 59%	2200
October	1st to 10th	Night	9% 4 1 5% 3 3 3 3 4 5% 58%	2390
	11th to 20th	Night	12% 5% 2 5% 3 3 3 3 4 5% 57%	2400
	21st to end	Night	16% 7% 2 5% 3 3 3 2 4 4 51%	2640
November	1st to 10th	Night	9% 5% 2 4 3 3 3 2 4 5% 61%	2460
	11th to 20th	Night	10% 6% 2 4 3 3 3 3 5% 7% 54%	2791
	21st to end	Night	15% 7% 2 5% 3 3 3 3 3 5% 51%	2940
December	1st to 10th	Night	7% 6% 2 5% 4 3 3 3 5% 6% 56%	4720
	11th to 20th	Night	11% 8% 4 6% 4 4 4 3 5% 6% 46%	5339
	21st to end	Night	18% 16% 5% 9% 4 4 3 3 3 4 31%	6897

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	47% 3 10% 26% 12% 2	5290
	11th to 20th	Day	44% 2 9% 25% 15% 4	5310
	21st to end	Day	49% 2 11% 18% 17% 3	5812
February	1st to 10th	Day	48% 3 12% 23% 11% 3	1890
	11th to 20th	Day	45% 5% 11% 22% 15% 3	1853
	21st to end	Day	39% 3 10% 25% 18% 4	1791
March	1st to 10th	Day	38% 3 8% 21% 22% 7%	4958
	11th to 20th	Day	31% 3 9% 22% 28% 7%	4980
	21st to end	Day	48% 3 16% 26% 6% 1	5464
April	1st to 10th	Day	41% 4 12% 24% 17% 2	2307
	11th to 20th	Day	44% 5% 12% 23% 16% 1	2374
	21st to end	Day	51% 4 11% 23% 10% 1	2540
May	1st to 10th	Day	43% 5% 11% 25% 15% 1	5900
	11th to 20th	Day	39% 4 12% 24% 18% 3	5866
	21st to end	Day	43% 4 10% 30% 12% 1	6557
June	1st to 10th	Day	29% 8% 17% 29% 15% 2	2800
	11th to 20th	Day	33% 5% 15% 30% 16% 2	2800
	21st to end	Day	29% 6% 15% 30% 16% 4	2771
July	1st to 10th	Day	36% 3 13% 26% 19% 2	5836
	11th to 20th	Day	32% 4 15% 31% 16% 1	5831
	21st to end	Day	34% 4 17% 35% 9% 1	6240
August	1st to 10th	Day	28% 5% 15% 30% 21% 2	4220
	11th to 20th	Day	36% 4 18% 27% 15% 1	4210
	21st to end	Day	27% 4 15% 35% 14% 4	4396
September	1st to 10th	Day	32% 5% 13% 25% 20% 6%	2400
	11th to 20th	Day	33% 6% 11% 26% 22% 2	2214
	21st to end	Day	30% 4 9% 29% 24% 3	2189
October	1st to 10th	Day	19% 2 7% 23% 41% 8%	3260
	11th to 20th	Day	20% 2 5% 25% 39% 9%	3240
	21st to end	Day	34% 2 10% 25% 25% 3	3538
November	1st to 10th	Day	32% 4 12% 30% 19% 5%	2058
	11th to 20th	Day	36% 2 10% 27% 21% 4	1821
	21st to end	Day	42% 3 9% 27% 18% 1	1680
December	1st to 10th	Day	32% 2 12% 36% 17% 1	2690
	11th to 20th	Day	38% 2 12% 33% 13% 1	3085
	21st to end	Day	62% 3 11% 17% 6% 1	4305
January	1st to 10th	Night	50% 3 11% 24% 11% 1	7635
	11th to 20th	Night	41% 2 8% 27% 19% 4	7680
	21st to end	Night	48% 2 11% 18% 16% 4	8402
February	1st to 10th	Night	44% 4 11% 23% 14% 3	2730
	11th to 20th	Night	43% 4 12% 23% 16% 3	2664
	21st to end	Night	39% 3 8% 23% 20% 6%	2029
March	1st to 10th	Night	38% 3 8% 22% 25% 4	4941
	11th to 20th	Night	28% 3 7% 22% 32% 8%	4980
	21st to end	Night	45% 4 16% 24% 10% 2	5467
April	1st to 10th	Night	35% 4 11% 23% 22% 4	2091
	11th to 20th	Night	38% 3 9% 28% 17% 4	1975
	21st to end	Night	44% 4 11% 25% 14% 1	1855
May	1st to 10th	Night	41% 4 13% 25% 16% 1	4080
	11th to 20th	Night	36% 4 12% 24% 18% 6%	4054
	21st to end	Night	37% 4 9% 29% 21% 1	4324
June	1st to 10th	Night	24% 7% 18% 32% 16% 3	1600
	11th to 20th	Night	27% 6% 14% 33% 19% 2	1600
	21st to end	Night	21% 4 14% 34% 23% 4	1621
July	1st to 10th	Night	32% 3 15% 25% 22% 3	4035
	11th to 20th	Night	28% 4 15% 34% 17% 2	4026
	21st to end	Night	31% 3 17% 38% 10% 1	4320
August	1st to 10th	Night	19% 3 21% 29% 22% 6%	2916
	11th to 20th	Night	34% 3 12% 30% 19% 2	2915
	21st to end	Night	25% 3 12% 38% 17% 5%	3490
September	1st to 10th	Night	30% 4 11% 27% 21% 8%	2000
	11th to 20th	Night	29% 5% 11% 27% 24% 4	2182
	21st to end	Night	27% 4 8% 27% 30% 5%	2200
October	1st to 10th	Night	18% 3 5% 21% 45% 8%	3910
	11th to 20th	Night	23% 2 6% 26% 30% 14%	3899
	21st to end	Night	35% 2 6% 30% 24% 3	4252
November	1st to 10th	Night	28% 3 12% 28% 23% 6%	2460
	11th to 20th	Night	31% 3 10% 28% 23% 5%	2791
	21st to end	Night	38% 3 10% 29% 18% 3	2940
December	1st to 10th	Night	31% 3 14% 34% 18% 1	4720
	11th to 20th	Night	39% 3 12% 27% 17% 2	5341
	21st to end	Night	59% 3 9% 20% 7% 1	6897

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% 15% 40% 17% 5%	330
	11th to 20th	Day	23% 20% 40% 15% 2	330
	21st to end	Day	16% 15% 48% 17% 3	363
February	1st to 10th	Day	22% 20% 43% 12% 3	330
	11th to 20th	Day	20% 22% 40% 15% 3 1	330
	21st to end	Day	13% 30% 41% 12% 3	273
March	1st to 10th	Day	19% 19% 44% 15% 3	306
	11th to 20th	Day	28% 15% 36% 17% 4	300
	21st to end	Day	29% 24% 31% 13% 3	330
April	1st to 10th	Day	24% 20% 35% 15% 6%	407
	11th to 20th	Day	20% 18% 39% 17% 4 1	492
	21st to end	Day	22% 17% 35% 19% 8%	640
May	1st to 10th	Day	18% 14% 38% 21% 8% 1	703
	11th to 20th	Day	19% 11% 28% 25% 13% 3	725
	21st to end	Day	17% 10% 31% 24% 14% 4	789
June	1st to 10th	Day	7% 6% 23% 33% 25% 6%	730
	11th to 20th	Day	9% 4 29% 35% 18% 4	730
	21st to end	Day	6% 7% 35% 36% 15% 2	730
July	1st to 10th	Day	10% 4 15% 34% 27% 10%	721
	11th to 20th	Day	5% 3 18% 42% 25% 6%	718
	21st to end	Day	8% 3 16% 38% 27% 7%	794
August	1st to 10th	Day	6% 3 21% 39% 27% 4	726
	11th to 20th	Day	8% 3 19% 39% 25% 6%	715
	21st to end	Day	9% 2 17% 32% 31% 9%	642
September	1st to 10th	Day	12% 3 17% 40% 23% 6%	530
	11th to 20th	Day	7% 2 20% 43% 22% 6%	344
	21st to end	Day	11% 5% 28% 33% 18% 5%	330
October	1st to 10th	Day	12% 6% 33% 27% 15% 5%	330
	11th to 20th	Day	12% 16% 42% 23% 6% 1	330
	21st to end	Day	24% 15% 37% 20% 3 1	363
November	1st to 10th	Day	15% 18% 36% 24% 6% 1	330
	11th to 20th	Day	18% 17% 35% 21% 8% 1	330
	21st to end	Day	23% 17% 32% 22% 5%	330
December	1st to 10th	Day	11% 19% 42% 22% 3 3	330
	11th to 20th	Day	18% 20% 40% 15% 6% 1	330
	21st to end	Day	22% 26% 34% 18% 1	363
January	1st to 10th	Night	15% 15% 39% 25% 5%	1050
	11th to 20th	Night	15% 16% 40% 24% 4 1	1050
	21st to end	Night	14% 15% 43% 26% 3	1155
February	1st to 10th	Night	17% 14% 42% 24% 3	1050
	11th to 20th	Night	18% 16% 40% 24% 3	1029
	21st to end	Night	16% 16% 45% 20% 3	645
March	1st to 10th	Night	15% 15% 42% 24% 4	606
	11th to 20th	Night	20% 13% 36% 26% 6% 1	600
	21st to end	Night	25% 14% 35% 23% 3	660
April	1st to 10th	Night	14% 15% 39% 26% 6%	600
	11th to 20th	Night	19% 14% 35% 28% 5%	593
	21st to end	Night	20% 12% 38% 23% 6%	600
May	1st to 10th	Night	17% 9% 37% 31% 7%	600
	11th to 20th	Night	15% 8% 28% 35% 13% 1	591
	21st to end	Night	13% 7% 29% 35% 14% 2	650
June	1st to 10th	Night	7% 3 21% 45% 23% 2	600
	11th to 20th	Night	6% 3 29% 43% 18% 1	600
	21st to end	Night	5% 3 34% 46% 12% 1	600
July	1st to 10th	Night	8% 2 13% 46% 28% 3	585
	11th to 20th	Night	3 2 18% 47% 27% 2	582
	21st to end	Night	7% 2 14% 45% 30% 2	657
August	1st to 10th	Night	3 2 17% 47% 29% 1	597
	11th to 20th	Night	8% 3 13% 45% 28% 3	594
	21st to end	Night	6% 2 15% 42% 33% 2	660
September	1st to 10th	Night	12% 3 20% 40% 21% 3	600
	11th to 20th	Night	10% 2 21% 40% 23% 4	600
	21st to end	Night	8% 5% 23% 42% 18% 4	600
October	1st to 10th	Night	10% 6% 29% 35% 18% 2	790
	11th to 20th	Night	13% 10% 40% 30% 7%	800
	21st to end	Night	21% 11% 34% 26% 8%	880
November	1st to 10th	Night	11% 11% 38% 30% 9% 1	820
	11th to 20th	Night	13% 14% 39% 26% 8%	1045
	21st to end	Night	21% 13% 36% 26% 5%	1050
December	1st to 10th	Night	17% 12% 40% 26% 5% 1	1050
	11th to 20th	Night	18% 12% 41% 25% 4	1050
	21st to end	Night	19% 16% 37% 24% 3	1155

Page generated at 2026-02-28 00:40:26. Version ac07

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