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 2026-09-29.

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% 10% 4 9% 5% 5% 5% 4 5% 7% 30%	149094
	Night	16% 11% 4 10% 5% 5% 4 3 5% 6% 31%	142318
Transparency	Day	53% 4 11% 21% 11% 1	152696
	Night	54% 3 10% 20% 11% 1	146787
Seeing	Day	24% 13% 27% 20% 11% 4	17145
	Night	23% 11% 26% 27% 11% 1	26733

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	17% 19% 9% 22% 6% 4 3 2 3 4 13%	5117
	11th to 20th	Day	11% 19% 9% 22% 9% 6% 3 2 3 3 13%	5280
	21st to end	Day	18% 17% 5% 13% 9% 7% 4 3 4 4 16%	5780
February	1st to 10th	Day	18% 17% 5% 11% 7% 5% 3 3 4 5% 21%	1890
	11th to 20th	Day	17% 15% 7% 14% 5% 5% 4 3 5% 5% 20%	1843
	21st to end	Day	19% 15% 5% 11% 6% 4 3 3 4 5% 24%	1719
March	1st to 10th	Day	17% 12% 5% 10% 5% 4 4 3 4 5% 32%	5045
	11th to 20th	Day	13% 9% 4 10% 5% 5% 5% 4 5% 6% 35%	5090
	21st to end	Day	16% 10% 4 9% 6% 5% 4 4 5% 6% 31%	5586
April	1st to 10th	Day	17% 12% 4 8% 4 5% 4 4 5% 6% 30%	2441
	11th to 20th	Day	16% 11% 3 8% 5% 5% 5% 4 4 6% 32%	2511
	21st to end	Day	21% 9% 2 7% 5% 4 4 3 4 6% 34%	2730
May	1st to 10th	Day	21% 9% 3 9% 5% 5% 5% 4 6% 7% 27%	7616
	11th to 20th	Day	17% 8% 3 8% 5% 5% 5% 4 6% 8% 31%	7626
	21st to end	Day	22% 8% 3 6% 4 4 4 4 5% 7% 33%	9041
June	1st to 10th	Day	14% 7% 2 7% 5% 5% 6% 4 6% 9% 35%	2940
	11th to 20th	Day	15% 7% 3 8% 5% 5% 5% 5% 7% 9% 33%	2940
	21st to end	Day	14% 7% 2 6% 5% 5% 4 4 7% 9% 36%	2940
July	1st to 10th	Day	11% 7% 3 7% 4 5% 5% 4 5% 8% 40%	8222
	11th to 20th	Day	9% 6% 3 8% 5% 5% 5% 4 7% 11% 37%	7680
	21st to end	Day	11% 7% 3 7% 5% 4 6% 5% 6% 8% 38%	8340
August	1st to 10th	Day	18% 9% 4 8% 5% 5% 5% 5% 6% 7% 28%	6014
	11th to 20th	Day	16% 8% 3 8% 5% 5% 5% 4 7% 8% 31%	5951
	21st to end	Day	7% 5% 2 7% 5% 5% 6% 6% 8% 11% 38%	6247
September	1st to 10th	Day	14% 7% 2 6% 4 4 5% 3 5% 7% 44%	2520
	11th to 20th	Day	11% 6% 2 6% 5% 4 5% 4 6% 8% 44%	2347
	21st to end	Day	21% 8% 4 6% 4 4 4 3 5% 6% 34%	2268
October	1st to 10th	Day	16% 6% 2 6% 4 4 4 4 6% 7% 41%	2000
	11th to 20th	Day	20% 7% 3 7% 4 5% 4 3 6% 6% 35%	2000
	21st to end	Day	22% 10% 3 8% 4 4 4 3 5% 7% 31%	2200
November	1st to 10th	Day	12% 8% 3 7% 6% 4 4 4 5% 6% 41%	1986
	11th to 20th	Day	19% 15% 3 8% 4 5% 4 3 4 5% 30%	1706
	21st to end	Day	19% 16% 5% 9% 6% 4 4 4 4 6% 23%	1680
December	1st to 10th	Day	19% 16% 8% 20% 6% 4 4 2 2 4 16%	2680
	11th to 20th	Day	23% 17% 7% 11% 4 3 3 2 3 5% 22%	3070
	21st to end	Day	22% 21% 6% 12% 5% 4 4 3 4 4 15%	4048
January	1st to 10th	Night	15% 18% 8% 21% 5% 4 4 3 3 4 14%	7773
	11th to 20th	Night	13% 16% 8% 20% 9% 7% 4 3 3 4 13%	7680
	21st to end	Night	19% 16% 5% 11% 8% 6% 5% 2 3 3 21%	8401
February	1st to 10th	Night	19% 14% 5% 11% 7% 5% 4 3 4 5% 24%	2730
	11th to 20th	Night	19% 13% 5% 13% 6% 5% 4 3 5% 5% 23%	2663
	21st to end	Night	19% 13% 4 13% 6% 4 4 3 5% 5% 25%	2081
March	1st to 10th	Night	20% 12% 5% 9% 5% 4 3 2 3 5% 31%	5028
	11th to 20th	Night	13% 10% 5% 7% 4 4 3 3 4 7% 40%	5090
	21st to end	Night	16% 10% 4 9% 5% 5% 4 3 4 6% 35%	5588
April	1st to 10th	Night	19% 13% 4 6% 4 5% 4 3 4 6% 33%	2179
	11th to 20th	Night	15% 9% 3 7% 4 4 5% 4 5% 7% 35%	2075
	21st to end	Night	15% 9% 4 8% 5% 4 4 3 6% 7% 35%	1890
May	1st to 10th	Night	23% 10% 3 8% 4 4 4 3 5% 7% 28%	5237
	11th to 20th	Night	16% 8% 3 7% 5% 4 4 4 5% 7% 36%	5234
	21st to end	Night	22% 7% 3 6% 3 4 4 3 5% 7% 35%	5112
June	1st to 10th	Night	11% 5% 2 7% 5% 4 4 3 6% 8% 44%	1680
	11th to 20th	Night	12% 5% 3 7% 4 4 5% 4 6% 9% 41%	1680
	21st to end	Night	10% 7% 2 6% 5% 4 5% 5% 6% 9% 40%	1680
July	1st to 10th	Night	12% 8% 3 8% 5% 4 4 3 6% 8% 39%	4731
	11th to 20th	Night	10% 7% 3 7% 5% 5% 5% 4 7% 9% 38%	5277
	21st to end	Night	10% 7% 3 8% 4 5% 4 4 6% 8% 42%	5736
August	1st to 10th	Night	17% 9% 4 8% 5% 5% 5% 4 5% 7% 31%	4135
	11th to 20th	Night	17% 9% 3 7% 5% 4 4 3 5% 6% 37%	4095
	21st to end	Night	7% 5% 2 7% 5% 5% 6% 5% 7% 9% 42%	4832
September	1st to 10th	Night	11% 6% 2 5% 4 4 4 4 6% 6% 49%	2100
	11th to 20th	Night	10% 5% 2 5% 3 3 4 2 6% 8% 52%	2268
	21st to end	Night	18% 8% 3 7% 5% 4 4 4 5% 6% 38%	2307
October	1st to 10th	Night	14% 6% 2 6% 4 4 4 3 5% 6% 45%	2400
	11th to 20th	Night	17% 6% 3 6% 4 5% 4 3 5% 7% 40%	2400
	21st to end	Night	21% 9% 3 6% 3 5% 3 3 4 7% 36%	2640
November	1st to 10th	Night	13% 9% 3 6% 4 3 4 4 5% 7% 42%	2529
	11th to 20th	Night	19% 11% 3 8% 5% 5% 5% 4 5% 6% 30%	2912
	21st to end	Night	20% 15% 3 8% 5% 5% 4 3 4 6% 28%	2940
December	1st to 10th	Night	17% 17% 10% 14% 5% 4 4 3 5% 5% 17%	4720
	11th to 20th	Night	22% 16% 7% 10% 5% 4 3 2 4 4 22%	5345
	21st to end	Night	22% 16% 6% 12% 5% 4 4 3 4 6% 17%	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	78% 2 7% 8% 5%	5118
	11th to 20th	Day	79% 2 5% 9% 4 1	5280
	21st to end	Day	73% 2 8% 13% 4	5780
February	1st to 10th	Day	67% 3 8% 15% 7%	1890
	11th to 20th	Day	66% 4 10% 14% 6%	1852
	21st to end	Day	62% 3 11% 16% 6% 1	1719
March	1st to 10th	Day	54% 4 10% 22% 8% 1	5045
	11th to 20th	Day	51% 3 13% 23% 8% 2	5090
	21st to end	Day	55% 3 8% 21% 12% 1	5586
April	1st to 10th	Day	55% 4 10% 18% 11% 2	2441
	11th to 20th	Day	52% 5% 10% 18% 13% 2	2511
	21st to end	Day	52% 4 10% 22% 11% 1	2730
May	1st to 10th	Day	56% 3 11% 20% 8% 2	7651
	11th to 20th	Day	50% 4 11% 23% 10% 1	7630
	21st to end	Day	50% 4 11% 19% 14% 2	9057
June	1st to 10th	Day	45% 6% 13% 22% 13% 1	2940
	11th to 20th	Day	46% 6% 15% 21% 12% 1	2940
	21st to end	Day	44% 5% 12% 26% 11% 1	2940
July	1st to 10th	Day	44% 4 10% 26% 14% 2	8152
	11th to 20th	Day	41% 3 11% 33% 11%	7611
	21st to end	Day	44% 3 10% 23% 19% 1	8156
August	1st to 10th	Day	55% 5% 11% 17% 10% 2	6001
	11th to 20th	Day	50% 4 13% 25% 8% 1	5990
	21st to end	Day	38% 5% 15% 28% 13% 1	6247
September	1st to 10th	Day	40% 6% 10% 23% 19% 3	2520
	11th to 20th	Day	38% 4 15% 26% 16% 1	2347
	21st to end	Day	50% 5% 10% 20% 14% 1	2268
October	1st to 10th	Day	36% 3 9% 32% 19% 1	3260
	11th to 20th	Day	45% 4 10% 24% 14% 4	3240
	21st to end	Day	39% 2 12% 29% 16% 1	3538
November	1st to 10th	Day	44% 4 12% 21% 17% 2	1986
	11th to 20th	Day	56% 4 10% 18% 9% 2	1706
	21st to end	Day	62% 3 12% 16% 5% 1	1680
December	1st to 10th	Day	75% 3 10% 9% 4	2680
	11th to 20th	Day	68% 2 11% 14% 4	3066
	21st to end	Day	74% 3 9% 11% 4	4048
January	1st to 10th	Night	75% 2 8% 11% 3	7774
	11th to 20th	Night	77% 3 7% 10% 3	7680
	21st to end	Night	69% 3 8% 14% 5% 1	8401
February	1st to 10th	Night	64% 3 9% 17% 7%	2730
	11th to 20th	Night	64% 3 10% 16% 7%	2665
	21st to end	Night	61% 4 9% 16% 9% 1	2081
March	1st to 10th	Night	57% 2 10% 21% 8%	5028
	11th to 20th	Night	46% 3 13% 27% 9% 3	5090
	21st to end	Night	51% 3 9% 18% 16% 1	5588
April	1st to 10th	Night	53% 4 9% 19% 13% 1	2179
	11th to 20th	Night	47% 6% 11% 19% 15% 3	2075
	21st to end	Night	48% 4 10% 24% 12% 3	1890
May	1st to 10th	Night	56% 4 10% 17% 11% 3	5264
	11th to 20th	Night	48% 4 9% 27% 10% 1	5235
	21st to end	Night	49% 4 11% 21% 13% 2	5119
June	1st to 10th	Night	38% 6% 14% 24% 17% 2	1680
	11th to 20th	Night	40% 5% 14% 25% 14% 2	1680
	21st to end	Night	39% 7% 14% 23% 16% 1	1680
July	1st to 10th	Night	45% 4 10% 23% 17% 2	4693
	11th to 20th	Night	43% 3 15% 27% 12% 1	5226
	21st to end	Night	41% 4 10% 19% 25% 1	5606
August	1st to 10th	Night	54% 4 11% 19% 10% 2	4124
	11th to 20th	Night	48% 3 12% 26% 10% 1	4122
	21st to end	Night	38% 4 14% 30% 12% 2	4832
September	1st to 10th	Night	34% 5% 12% 24% 20% 4	2100
	11th to 20th	Night	31% 4 14% 29% 22% 1	2268
	21st to end	Night	48% 4 10% 20% 16% 2	2307
October	1st to 10th	Night	37% 4 8% 27% 23% 1	3920
	11th to 20th	Night	39% 2 11% 25% 17% 6%	3899
	21st to end	Night	37% 3 10% 29% 20% 1	4252
November	1st to 10th	Night	41% 4 12% 23% 17% 3	2529
	11th to 20th	Night	54% 4 9% 21% 10% 3	2912
	21st to end	Night	59% 3 10% 21% 6% 1	2940
December	1st to 10th	Night	70% 3 11% 13% 3	4720
	11th to 20th	Night	67% 2 12% 15% 3	5348
	21st to end	Night	70% 4 10% 13% 3	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	31% 27% 26% 12% 3 1	303
	11th to 20th	Day	39% 28% 24% 6% 2 1	330
	21st to end	Day	34% 24% 31% 8% 3	363
February	1st to 10th	Day	35% 22% 34% 8% 2	330
	11th to 20th	Day	42% 24% 26% 7% 1	330
	21st to end	Day	36% 24% 32% 8% 1	320
March	1st to 10th	Day	32% 21% 29% 16% 3	540
	11th to 20th	Day	36% 19% 28% 12% 4 1	540
	21st to end	Day	33% 19% 29% 15% 3 1	594
April	1st to 10th	Day	33% 16% 28% 16% 5% 1	540
	11th to 20th	Day	29% 18% 28% 14% 8% 3	532
	21st to end	Day	30% 16% 31% 16% 5% 2	540
May	1st to 10th	Day	30% 16% 26% 18% 6% 3	543
	11th to 20th	Day	23% 11% 34% 20% 9% 4	567
	21st to end	Day	20% 9% 28% 24% 14% 5%	617
June	1st to 10th	Day	15% 13% 29% 26% 14% 3	570
	11th to 20th	Day	20% 13% 25% 25% 13% 4	570
	21st to end	Day	16% 9% 29% 26% 16% 3	570
July	1st to 10th	Day	15% 6% 18% 30% 22% 9%	565
	11th to 20th	Day	13% 6% 24% 31% 18% 8%	564
	21st to end	Day	14% 4 25% 32% 18% 7%	620
August	1st to 10th	Day	14% 6% 25% 27% 20% 9%	566
	11th to 20th	Day	16% 6% 23% 29% 17% 10%	559
	21st to end	Day	12% 5% 24% 27% 22% 10%	627
September	1st to 10th	Day	18% 6% 22% 26% 20% 8%	570
	11th to 20th	Day	12% 4 21% 30% 23% 10%	570
	21st to end	Day	28% 9% 22% 23% 13% 4	562
October	1st to 10th	Day	17% 9% 26% 22% 19% 6%	530
	11th to 20th	Day	24% 14% 29% 22% 9% 2	530
	21st to end	Day	31% 14% 30% 17% 8% 1	583
November	1st to 10th	Day	22% 17% 32% 18% 9% 2	464
	11th to 20th	Day	34% 16% 31% 13% 4 2	234
	21st to end	Day	28% 19% 40% 11% 1	220
December	1st to 10th	Day	35% 24% 26% 11% 3 1	220
	11th to 20th	Day	36% 21% 30% 11% 2	220
	21st to end	Day	38% 16% 31% 12% 3	242
January	1st to 10th	Night	29% 19% 34% 14% 3	840
	11th to 20th	Night	32% 20% 29% 16% 3	840
	21st to end	Night	31% 18% 30% 18% 3	924
February	1st to 10th	Night	30% 17% 26% 25% 2	840
	11th to 20th	Night	33% 18% 33% 15% 1	823
	21st to end	Night	30% 15% 34% 19% 2	692
March	1st to 10th	Night	28% 17% 31% 22% 3	840
	11th to 20th	Night	30% 17% 27% 20% 6% 1	840
	21st to end	Night	23% 18% 34% 20% 4 1	924
April	1st to 10th	Night	29% 15% 29% 22% 5%	840
	11th to 20th	Night	24% 13% 31% 22% 8% 1	831
	21st to end	Night	20% 10% 32% 32% 6%	630
May	1st to 10th	Night	24% 8% 25% 33% 8% 1	630
	11th to 20th	Night	21% 8% 26% 33% 11% 1	621
	21st to end	Night	15% 4 25% 33% 22% 2	460
June	1st to 10th	Night	13% 3 25% 42% 16% 1	420
	11th to 20th	Night	12% 7% 22% 40% 18% 1	420
	21st to end	Night	13% 3 28% 35% 20% 2	420
July	1st to 10th	Night	12% 2 18% 39% 24% 4	424
	11th to 20th	Night	12% 3 16% 35% 30% 5%	612
	21st to end	Night	12% 3 13% 45% 25% 1	690
August	1st to 10th	Night	12% 1 14% 43% 27% 3	627
	11th to 20th	Night	14% 5% 12% 36% 29% 4	624
	21st to end	Night	11% 4 18% 35% 28% 4	824
September	1st to 10th	Night	15% 3 20% 34% 24% 3	840
	11th to 20th	Night	12% 3 15% 37% 29% 3	840
	21st to end	Night	21% 7% 23% 27% 18% 4	833
October	1st to 10th	Night	17% 8% 21% 29% 23% 2	800
	11th to 20th	Night	21% 9% 31% 29% 10% 1	800
	21st to end	Night	27% 12% 26% 28% 7%	880
November	1st to 10th	Night	19% 11% 28% 30% 11%	820
	11th to 20th	Night	29% 13% 27% 23% 7% 1	840
	21st to end	Night	30% 13% 30% 20% 6%	840
December	1st to 10th	Night	33% 18% 27% 18% 5%	840
	11th to 20th	Night	30% 18% 29% 20% 3	840
	21st to end	Night	31% 16% 28% 22% 3	924

Page generated at 2026-09-26 04:18:41. Version ac07

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