Chateau De Testa Stars
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chateau De Testa Stars clear sky chart from 2005-11-06 to 2025-05-26.

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	16% 11% 4 9% 5% 5% 4 4 5% 7% 30%	114110
	Night	16% 11% 5% 10% 5% 4 4 3 5% 6% 31%	115174
Transparency	Day	53% 4 11% 20% 10% 1	117755
	Night	54% 4 11% 20% 11% 1	119668
Seeing	Day	24% 14% 27% 20% 11% 4	15345
	Night	23% 12% 26% 27% 12% 1	25084

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	15% 19% 10% 22% 5% 3 2 2 3 4 16%	3941
	11th to 20th	Day	13% 21% 10% 20% 9% 6% 2 1 2 3 13%	4060
	21st to end	Day	20% 21% 6% 12% 7% 5% 4 3 4 4 16%	4466
February	1st to 10th	Day	19% 18% 5% 12% 7% 4 3 3 4 4 21%	1800
	11th to 20th	Day	17% 15% 6% 14% 6% 5% 4 4 5% 5% 20%	1753
	21st to end	Day	20% 14% 4 11% 7% 4 3 3 4 5% 24%	1640
March	1st to 10th	Day	17% 12% 5% 9% 5% 4 4 3 4 5% 32%	4935
	11th to 20th	Day	13% 9% 4 9% 5% 5% 5% 3 5% 6% 35%	4980
	21st to end	Day	16% 10% 4 9% 6% 5% 4 4 5% 6% 31%	5465
April	1st to 10th	Day	17% 12% 4 8% 4 5% 4 4 6% 6% 29%	2325
	11th to 20th	Day	17% 11% 3 8% 5% 4 5% 4 4 6% 32%	2390
	21st to end	Day	22% 9% 3 7% 5% 4 4 3 4 6% 34%	2600
May	1st to 10th	Day	24% 9% 3 8% 4 5% 4 3 6% 6% 28%	4212
	11th to 20th	Day	18% 9% 3 8% 5% 5% 5% 5% 6% 7% 29%	4211
	21st to end	Day	13% 6% 2 6% 5% 5% 5% 4 6% 10% 38%	4889
June	1st to 10th	Day	15% 7% 3 7% 6% 5% 6% 4 6% 9% 33%	2660
	11th to 20th	Day	14% 6% 2 7% 6% 5% 5% 5% 7% 9% 34%	2660
	21st to end	Day	14% 8% 2 6% 5% 5% 4 4 7% 8% 37%	2660
July	1st to 10th	Day	10% 6% 2 7% 5% 6% 5% 4 6% 9% 40%	4410
	11th to 20th	Day	10% 6% 2 7% 5% 4 5% 4 7% 9% 40%	4120
	21st to end	Day	11% 7% 3 8% 6% 4 6% 4 6% 8% 37%	4466
August	1st to 10th	Day	15% 8% 3 9% 6% 5% 5% 5% 6% 8% 30%	4104
	11th to 20th	Day	11% 7% 3 8% 5% 6% 6% 4 7% 8% 35%	4044
	21st to end	Day	9% 5% 3 6% 5% 5% 6% 5% 8% 9% 39%	4290
September	1st to 10th	Day	15% 7% 2 6% 4 4 5% 3 4 6% 43%	2280
	11th to 20th	Day	12% 6% 2 6% 4 4 4 4 6% 8% 44%	2123
	21st to end	Day	20% 8% 4 6% 4 4 4 3 5% 7% 35%	2071
October	1st to 10th	Day	17% 7% 2 6% 4 4 4 4 6% 7% 39%	1900
	11th to 20th	Day	20% 7% 3 7% 4 5% 4 3 6% 6% 34%	1900
	21st to end	Day	22% 10% 3 8% 4 4 4 3 5% 7% 31%	2090
November	1st to 10th	Day	12% 8% 3 7% 6% 4 4 4 5% 6% 41%	1890
	11th to 20th	Day	18% 14% 3 7% 4 5% 4 3 5% 5% 31%	1625
	21st to end	Day	19% 16% 5% 9% 6% 4 4 4 4 6% 23%	1600
December	1st to 10th	Day	19% 15% 8% 20% 6% 4 4 2 2 4 17%	2600
	11th to 20th	Day	23% 18% 7% 10% 4 3 3 2 3 5% 22%	2990
	21st to end	Day	22% 22% 6% 12% 5% 4 4 3 4 4 15%	3960
January	1st to 10th	Night	15% 17% 9% 24% 5% 4 3 3 3 3 15%	6001
	11th to 20th	Night	14% 17% 8% 18% 9% 6% 4 3 3 4 14%	5900
	21st to end	Night	22% 17% 6% 12% 6% 5% 5% 2 3 3 19%	6490
February	1st to 10th	Night	19% 14% 5% 11% 7% 5% 4 3 4 5% 23%	2600
	11th to 20th	Night	19% 13% 5% 12% 6% 5% 5% 3 5% 5% 23%	2533
	21st to end	Night	19% 13% 4 12% 6% 4 4 3 5% 5% 25%	1985
March	1st to 10th	Night	20% 12% 5% 9% 5% 4 3 2 3 5% 31%	4918
	11th to 20th	Night	13% 10% 5% 7% 4 4 3 3 4 7% 40%	4980
	21st to end	Night	16% 10% 4 9% 5% 5% 4 3 4 6% 35%	5467
April	1st to 10th	Night	19% 13% 4 6% 4 5% 4 3 4 6% 33%	2075
	11th to 20th	Night	15% 9% 3 7% 4 4 5% 4 5% 7% 36%	1975
	21st to end	Night	15% 9% 3 8% 5% 5% 4 3 6% 7% 36%	1800
May	1st to 10th	Night	27% 9% 3 7% 4 4 4 3 4 6% 28%	2903
	11th to 20th	Night	18% 9% 3 6% 5% 4 4 3 5% 7% 35%	2902
	21st to end	Night	12% 6% 2 6% 4 4 4 4 7% 10% 40%	2782
June	1st to 10th	Night	11% 5% 2 7% 5% 4 4 4 7% 8% 44%	1520
	11th to 20th	Night	12% 5% 3 7% 4 4 5% 4 6% 9% 41%	1520
	21st to end	Night	10% 6% 2 6% 5% 4 5% 5% 7% 10% 41%	1520
July	1st to 10th	Night	11% 8% 3 8% 5% 4 4 3 6% 8% 40%	2545
	11th to 20th	Night	10% 5% 2 6% 5% 4 5% 4 6% 9% 42%	2840
	21st to end	Night	9% 8% 3 9% 5% 5% 4 4 6% 7% 40%	3087
August	1st to 10th	Night	14% 8% 4 7% 5% 4 4 4 6% 7% 35%	2825
	11th to 20th	Night	12% 7% 3 6% 5% 4 4 4 5% 7% 41%	2785
	21st to end	Night	8% 5% 2 6% 4 4 6% 5% 7% 9% 44%	3334
September	1st to 10th	Night	12% 6% 2 5% 3 4 4 4 6% 6% 49%	1900
	11th to 20th	Night	9% 5% 2 5% 3 3 4 2 6% 8% 52%	2052
	21st to end	Night	17% 8% 3 6% 5% 4 4 4 5% 6% 40%	2107
October	1st to 10th	Night	14% 6% 2 7% 4 4 5% 3 5% 6% 44%	2280
	11th to 20th	Night	17% 7% 3 6% 4 5% 4 3 5% 7% 39%	2280
	21st to end	Night	21% 9% 2 6% 3 5% 3 3 4 7% 36%	2508
November	1st to 10th	Night	13% 9% 3 5% 4 3 4 4 5% 7% 42%	2406
	11th to 20th	Night	19% 11% 3 8% 5% 5% 5% 4 5% 6% 30%	2773
	21st to end	Night	19% 15% 3 8% 5% 5% 4 3 4 6% 29%	2800
December	1st to 10th	Night	17% 17% 10% 14% 5% 3 4 3 5% 5% 17%	4580
	11th to 20th	Night	22% 16% 7% 10% 5% 4 3 2 4 4 22%	5205
	21st to end	Night	22% 16% 6% 11% 5% 4 4 3 4 6% 17%	6996

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	76% 2 7% 9% 6%	3942
	11th to 20th	Day	80% 2 6% 8% 3 2	4060
	21st to end	Day	74% 2 8% 11% 5%	4466
February	1st to 10th	Day	68% 3 8% 14% 6%	1800
	11th to 20th	Day	66% 4 9% 15% 6%	1762
	21st to end	Day	63% 3 11% 15% 7% 1	1640
March	1st to 10th	Day	54% 4 10% 22% 8% 1	4935
	11th to 20th	Day	50% 3 13% 23% 9% 2	4980
	21st to end	Day	55% 3 8% 21% 12% 1	5465
April	1st to 10th	Day	55% 4 10% 17% 11% 2	2325
	11th to 20th	Day	52% 5% 10% 18% 13% 2	2390
	21st to end	Day	52% 4 9% 22% 12% 2	2600
May	1st to 10th	Day	56% 4 11% 20% 8% 1	4250
	11th to 20th	Day	53% 6% 12% 20% 8% 1	4215
	21st to end	Day	40% 7% 16% 23% 12% 3	4903
June	1st to 10th	Day	46% 6% 14% 22% 11% 1	2660
	11th to 20th	Day	45% 6% 15% 21% 12% 1	2660
	21st to end	Day	43% 6% 12% 27% 11% 1	2660
July	1st to 10th	Day	42% 5% 12% 24% 15% 3	4340
	11th to 20th	Day	39% 4 12% 30% 15%	4051
	21st to end	Day	45% 4 12% 20% 18% 1	4324
August	1st to 10th	Day	52% 5% 13% 22% 8%	4091
	11th to 20th	Day	44% 5% 12% 28% 11% 1	4083
	21st to end	Day	38% 5% 12% 29% 14% 2	4290
September	1st to 10th	Day	41% 6% 9% 22% 19% 3	2280
	11th to 20th	Day	38% 4 15% 26% 16% 1	2123
	21st to end	Day	49% 5% 10% 21% 14% 1	2071
October	1st to 10th	Day	36% 3 9% 31% 19% 1	3160
	11th to 20th	Day	45% 4 10% 24% 14% 4	3140
	21st to end	Day	39% 3 12% 30% 16% 1	3428
November	1st to 10th	Day	43% 5% 12% 21% 17% 2	1890
	11th to 20th	Day	55% 4 11% 19% 10% 2	1625
	21st to end	Day	62% 4 12% 16% 5% 1	1600
December	1st to 10th	Day	74% 3 10% 9% 4	2600
	11th to 20th	Day	68% 2 11% 14% 4	2986
	21st to end	Day	73% 3 9% 11% 4	3960
January	1st to 10th	Night	75% 3 7% 12% 3	6001
	11th to 20th	Night	75% 3 9% 10% 3	5900
	21st to end	Night	72% 3 8% 12% 5% 1	6490
February	1st to 10th	Night	65% 3 9% 16% 6%	2600
	11th to 20th	Night	63% 4 10% 16% 7%	2535
	21st to end	Night	61% 4 9% 15% 10% 1	1985
March	1st to 10th	Night	57% 3 10% 22% 8% 1	4918
	11th to 20th	Night	46% 3 13% 27% 9% 3	4980
	21st to end	Night	51% 4 9% 18% 17% 1	5467
April	1st to 10th	Night	53% 5% 9% 18% 14% 1	2075
	11th to 20th	Night	46% 6% 11% 19% 15% 3	1975
	21st to end	Night	47% 4 9% 24% 12% 3	1800
May	1st to 10th	Night	57% 4 9% 18% 10% 2	2930
	11th to 20th	Night	49% 5% 12% 23% 10% 1	2903
	21st to end	Night	37% 6% 16% 24% 13% 4	2789
June	1st to 10th	Night	37% 7% 15% 25% 15% 2	1520
	11th to 20th	Night	39% 6% 15% 25% 14% 2	1520
	21st to end	Night	38% 7% 14% 23% 16% 1	1520
July	1st to 10th	Night	44% 5% 9% 22% 17% 3	2505
	11th to 20th	Night	38% 5% 14% 26% 16% 1	2786
	21st to end	Night	43% 5% 10% 18% 22% 2	2988
August	1st to 10th	Night	48% 6% 13% 22% 11%	2814
	11th to 20th	Night	42% 4 10% 31% 12% 1	2812
	21st to end	Night	35% 5% 14% 31% 13% 2	3334
September	1st to 10th	Night	35% 6% 11% 24% 20% 4	1900
	11th to 20th	Night	30% 4 14% 28% 23% 1	2052
	21st to end	Night	46% 4 11% 22% 16% 1	2107
October	1st to 10th	Night	37% 4 8% 27% 23% 1	3800
	11th to 20th	Night	39% 2 11% 25% 16% 6%	3779
	21st to end	Night	37% 3 10% 29% 20% 1	4120
November	1st to 10th	Night	41% 4 12% 23% 17% 3	2406
	11th to 20th	Night	54% 4 9% 21% 10% 3	2773
	21st to end	Night	58% 4 11% 21% 6% 1	2800
December	1st to 10th	Night	70% 3 11% 13% 3	4580
	11th to 20th	Night	67% 2 12% 15% 3	5208
	21st to end	Night	70% 4 10% 13% 2	6996

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	31% 28% 25% 12% 4 1	275
	11th to 20th	Day	36% 28% 26% 6% 2 1	300
	21st to end	Day	33% 23% 32% 8% 3	330
February	1st to 10th	Day	37% 23% 33% 6% 1	300
	11th to 20th	Day	42% 25% 25% 7% 1	300
	21st to end	Day	38% 25% 28% 8% 1	294
March	1st to 10th	Day	31% 21% 29% 16% 3	500
	11th to 20th	Day	35% 19% 29% 13% 4 1	500
	21st to end	Day	33% 18% 29% 16% 3 1	550
April	1st to 10th	Day	33% 17% 27% 16% 6% 1	500
	11th to 20th	Day	29% 17% 28% 15% 8% 3	492
	21st to end	Day	30% 18% 29% 16% 5% 2	500
May	1st to 10th	Day	29% 16% 26% 19% 7% 3	503
	11th to 20th	Day	24% 10% 32% 20% 9% 4	527
	21st to end	Day	17% 10% 27% 26% 15% 5%	549
June	1st to 10th	Day	16% 12% 28% 26% 15% 3	490
	11th to 20th	Day	18% 12% 24% 27% 14% 5%	490
	21st to end	Day	16% 10% 30% 26% 14% 3	490
July	1st to 10th	Day	15% 6% 18% 29% 22% 9%	485
	11th to 20th	Day	13% 6% 26% 30% 17% 8%	484
	21st to end	Day	14% 4 26% 31% 18% 7%	532
August	1st to 10th	Day	13% 7% 22% 27% 21% 10%	486
	11th to 20th	Day	15% 6% 23% 29% 16% 11%	479
	21st to end	Day	13% 4 22% 27% 23% 10%	539
September	1st to 10th	Day	19% 6% 21% 26% 20% 8%	490
	11th to 20th	Day	13% 4 20% 30% 23% 10%	490
	21st to end	Day	27% 11% 22% 22% 14% 5%	490
October	1st to 10th	Day	18% 10% 27% 22% 18% 5%	490
	11th to 20th	Day	24% 14% 28% 23% 9% 2	490
	21st to end	Day	32% 13% 29% 17% 8% 1	539
November	1st to 10th	Day	21% 16% 32% 19% 10% 3	428
	11th to 20th	Day	31% 17% 33% 13% 4 2	213
	21st to end	Day	26% 20% 42% 11% 2 1	200
December	1st to 10th	Day	36% 23% 25% 13% 3 1	200
	11th to 20th	Day	37% 20% 29% 12% 3	200
	21st to end	Day	36% 17% 32% 12% 3	220
January	1st to 10th	Night	29% 20% 34% 14% 3	800
	11th to 20th	Night	32% 19% 29% 17% 3	800
	21st to end	Night	31% 18% 30% 19% 3	880
February	1st to 10th	Night	32% 17% 26% 23% 2	800
	11th to 20th	Night	33% 18% 33% 15% 1	783
	21st to end	Night	30% 15% 34% 19% 2	660
March	1st to 10th	Night	27% 18% 31% 22% 3	800
	11th to 20th	Night	29% 18% 26% 20% 6% 1	800
	21st to end	Night	23% 17% 34% 21% 4 1	880
April	1st to 10th	Night	29% 14% 29% 21% 5% 1	800
	11th to 20th	Night	24% 13% 31% 22% 8% 1	791
	21st to end	Night	21% 10% 33% 31% 6%	600
May	1st to 10th	Night	24% 9% 24% 34% 8% 1	600
	11th to 20th	Night	22% 8% 25% 32% 12% 1	591
	21st to end	Night	12% 4 24% 34% 23% 2	428
June	1st to 10th	Night	12% 3 26% 41% 16% 1	380
	11th to 20th	Night	11% 7% 21% 41% 19% 1	380
	21st to end	Night	12% 3 28% 36% 20% 1	380
July	1st to 10th	Night	12% 3 20% 38% 24% 4	382
	11th to 20th	Night	11% 3 17% 35% 29% 5%	552
	21st to end	Night	12% 3 13% 45% 26% 2	624
August	1st to 10th	Night	12% 1 14% 43% 27% 3	567
	11th to 20th	Night	13% 5% 12% 37% 29% 4	564
	21st to end	Night	11% 4 18% 34% 29% 5%	746
September	1st to 10th	Night	15% 3 20% 32% 26% 4	760
	11th to 20th	Night	11% 4 16% 37% 29% 4	760
	21st to end	Night	20% 7% 23% 27% 19% 4	760
October	1st to 10th	Night	18% 8% 22% 29% 22% 2	760
	11th to 20th	Night	22% 9% 30% 28% 10% 1	760
	21st to end	Night	27% 12% 26% 27% 8%	836
November	1st to 10th	Night	19% 11% 28% 31% 11%	780
	11th to 20th	Night	29% 13% 28% 23% 7% 1	800
	21st to end	Night	30% 14% 30% 20% 7%	800
December	1st to 10th	Night	33% 17% 27% 18% 5%	800
	11th to 20th	Night	30% 18% 29% 20% 3	800
	21st to end	Night	30% 16% 28% 23% 3	880

Page generated at 2025-05-23 09:21:02. Version ac07

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