Sarles
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sarles clear sky chart from 2005-11-06 to 2026-08-15.

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	10% 8% 3 8% 5% 5% 5% 4 6% 8% 37%	153385
	Night	8% 9% 4 10% 6% 5% 5% 4 6% 7% 36%	145915
Transparency	Day	30% 34% 10% 18% 7%	147947
	Night	32% 35% 9% 17% 7%	142363
Seeing	Day	14% 9% 31% 29% 14% 3	18721
	Night	14% 8% 33% 32% 11% 1	28580

By Month

Percentage Cloud Cover SW (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	3 13% 5% 14% 9% 10% 8% 4 7% 6% 19%	4123
	11th to 20th	Day	3 9% 4 13% 10% 9% 13% 11% 10% 6% 12%	4602
	21st to end	Day	4 9% 4 13% 7% 7% 6% 4 7% 10% 28%	5188
February	1st to 10th	Day	8% 14% 6% 13% 7% 7% 6% 5% 7% 6% 21%	1727
	11th to 20th	Day	5% 11% 4 12% 9% 7% 8% 7% 9% 5% 23%	1876
	21st to end	Day	6% 10% 4 12% 8% 8% 8% 7% 5% 7% 24%	1730
March	1st to 10th	Day	9% 11% 4 12% 6% 6% 5% 4 7% 9% 28%	4600
	11th to 20th	Day	7% 12% 6% 14% 10% 6% 5% 4 6% 8% 23%	5040
	21st to end	Day	11% 12% 5% 15% 7% 7% 5% 4 5% 6% 23%	5649
April	1st to 10th	Day	9% 13% 4 9% 5% 4 4 4 6% 8% 35%	2541
	11th to 20th	Day	14% 11% 4 10% 6% 5% 4 4 6% 7% 31%	2699
	21st to end	Day	15% 11% 3 8% 5% 5% 4 3 6% 6% 34%	2730
May	1st to 10th	Day	11% 8% 3 5% 3 4 4 3 6% 8% 47%	7689
	11th to 20th	Day	19% 11% 3 7% 4 4 4 4 5% 7% 32%	8599
	21st to end	Day	12% 6% 2 6% 4 4 4 3 5% 7% 47%	9682
June	1st to 10th	Day	13% 7% 2 6% 4 4 5% 5% 7% 8% 40%	3150
	11th to 20th	Day	15% 6% 3 6% 5% 5% 5% 4 6% 9% 37%	3150
	21st to end	Day	13% 6% 2 7% 5% 5% 5% 4 6% 8% 38%	3150
July	1st to 10th	Day	9% 4 2 6% 5% 4 5% 4 7% 10% 43%	8849
	11th to 20th	Day	8% 5% 2 7% 4 4 5% 4 7% 9% 45%	8850
	21st to end	Day	7% 5% 2 5% 4 4 5% 5% 7% 10% 46%	8966
August	1st to 10th	Day	10% 7% 2 7% 4 4 5% 4 6% 9% 42%	6296
	11th to 20th	Day	12% 5% 2 5% 3 3 4 4 6% 9% 47%	5874
	21st to end	Day	8% 4 2 5% 3 3 4 4 6% 8% 53%	6490
September	1st to 10th	Day	11% 5% 1 5% 4 4 4 3 5% 7% 51%	2424
	11th to 20th	Day	16% 6% 2 5% 4 4 4 4 5% 7% 43%	2200
	21st to end	Day	12% 6% 2 5% 3 4 5% 3 6% 9% 45%	2200
October	1st to 10th	Day	10% 8% 2 6% 4 4 4 3 4 5% 51%	3458
	11th to 20th	Day	10% 9% 2 7% 4 3 4 3 5% 8% 44%	3034
	21st to end	Day	12% 12% 4 7% 4 4 4 3 6% 8% 35%	3190
November	1st to 10th	Day	14% 14% 5% 10% 5% 3 4 3 4 5% 32%	1815
	11th to 20th	Day	8% 15% 6% 15% 7% 5% 5% 4 4 4 28%	1680
	21st to end	Day	9% 13% 5% 12% 8% 6% 4 3 5% 5% 29%	1486
December	1st to 10th	Day	6% 13% 5% 16% 11% 9% 9% 5% 7% 6% 14%	2360
	11th to 20th	Day	9% 11% 5% 14% 10% 7% 6% 5% 6% 7% 19%	2713
	21st to end	Day	7% 10% 3 15% 8% 6% 5% 4 6% 5% 29%	3575
January	1st to 10th	Night	4 11% 5% 17% 9% 8% 7% 5% 6% 7% 19%	8799
	11th to 20th	Night	5% 10% 5% 13% 8% 8% 11% 7% 9% 7% 18%	8374
	21st to end	Night	4 10% 6% 13% 7% 5% 6% 5% 7% 9% 28%	9026
February	1st to 10th	Night	9% 12% 5% 12% 7% 7% 6% 5% 7% 6% 24%	2893
	11th to 20th	Night	6% 9% 3 11% 8% 6% 7% 5% 7% 6% 32%	2651
	21st to end	Night	6% 10% 4 9% 7% 7% 7% 5% 7% 7% 32%	2076
March	1st to 10th	Night	7% 11% 4 10% 6% 6% 6% 5% 7% 8% 30%	5494
	11th to 20th	Night	8% 11% 4 11% 7% 5% 4 4 6% 7% 32%	5142
	21st to end	Night	8% 13% 6% 15% 6% 5% 5% 4 6% 5% 28%	5512
April	1st to 10th	Night	8% 9% 3 8% 6% 5% 5% 4 6% 7% 39%	2079
	11th to 20th	Night	12% 12% 3 7% 6% 4 5% 4 5% 7% 35%	1869
	21st to end	Night	15% 9% 3 6% 5% 5% 4 4 6% 7% 37%	1890
May	1st to 10th	Night	11% 8% 2 7% 5% 4 4 4 5% 7% 41%	5245
	11th to 20th	Night	16% 9% 2 4 3 4 4 4 7% 8% 38%	4290
	21st to end	Night	12% 6% 2 5% 3 3 3 3 5% 8% 50%	4526
June	1st to 10th	Night	11% 4 2 4 4 3 4 4 6% 8% 50%	1470
	11th to 20th	Night	11% 6% 2 6% 6% 5% 5% 4 6% 7% 41%	1470
	21st to end	Night	10% 5% 2 5% 3 4 4 4 8% 9% 46%	1470
July	1st to 10th	Night	6% 4 1 5% 4 4 4 4 7% 9% 52%	4140
	11th to 20th	Night	6% 4 2 5% 4 4 4 4 6% 10% 52%	4140
	21st to end	Night	4 4 2 6% 4 4 5% 4 7% 8% 52%	5127
August	1st to 10th	Night	8% 6% 2 6% 4 4 4 3 5% 7% 51%	3735
	11th to 20th	Night	7% 5% 1 5% 4 3 4 4 6% 9% 52%	4064
	21st to end	Night	8% 3 2 4 3 3 4 3 5% 8% 57%	4487
September	1st to 10th	Night	7% 4 2 5% 4 4 4 3 6% 7% 54%	1972
	11th to 20th	Night	11% 6% 2 5% 4 4 3 3 5% 7% 49%	2200
	21st to end	Night	13% 6% 2 6% 4 4 4 4 5% 7% 47%	2200
October	1st to 10th	Night	10% 6% 3 6% 4 4 4 3 5% 7% 48%	3689
	11th to 20th	Night	10% 8% 2 7% 4 4 4 4 5% 8% 43%	4095
	21st to end	Night	8% 9% 3 8% 4 4 4 4 6% 7% 42%	4610
November	1st to 10th	Night	11% 10% 4 9% 5% 4 5% 4 6% 8% 34%	2702
	11th to 20th	Night	9% 14% 5% 13% 7% 5% 4 3 6% 6% 29%	2940
	21st to end	Night	10% 12% 4 12% 8% 6% 4 4 5% 6% 30%	3129
December	1st to 10th	Night	6% 12% 5% 14% 11% 8% 9% 5% 6% 6% 18%	5050
	11th to 20th	Night	8% 14% 5% 14% 9% 6% 6% 4 5% 7% 22%	5714
	21st to end	Night	7% 10% 4 14% 9% 7% 6% 5% 5% 6% 27%	7645

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	52% 21% 8% 13% 5%	4125
	11th to 20th	Day	51% 23% 8% 12% 5%	4602
	21st to end	Day	38% 23% 11% 19% 8%	5188
February	1st to 10th	Day	28% 59% 5% 4 4 1	1727
	11th to 20th	Day	24% 59% 4 10% 3	1885
	21st to end	Day	22% 60% 5% 9% 5%	1730
March	1st to 10th	Day	32% 30% 14% 16% 8%	4600
	11th to 20th	Day	45% 29% 10% 13% 3	5040
	21st to end	Day	46% 31% 7% 12% 4	5649
April	1st to 10th	Day	19% 60% 7% 11% 3	2541
	11th to 20th	Day	22% 59% 6% 8% 4	2702
	21st to end	Day	20% 59% 5% 10% 5% 1	2730
May	1st to 10th	Day	26% 24% 11% 28% 12%	7689
	11th to 20th	Day	42% 24% 7% 18% 7% 2	8603
	21st to end	Day	26% 23% 8% 23% 19%	9683
June	1st to 10th	Day	15% 59% 8% 12% 5% 1	3150
	11th to 20th	Day	20% 60% 6% 9% 4	3150
	21st to end	Day	20% 59% 7% 11% 3	3150
July	1st to 10th	Day	30% 22% 23% 23% 2	8776
	11th to 20th	Day	30% 20% 15% 29% 6%	8769
	21st to end	Day	28% 21% 16% 25% 10%	8767
August	1st to 10th	Day	23% 35% 13% 20% 9%	4622
	11th to 20th	Day	22% 36% 15% 24% 4	4263
	21st to end	Day	22% 36% 15% 24% 4	4674
September	1st to 10th	Day	14% 58% 8% 16% 4	2424
	11th to 20th	Day	20% 57% 8% 11% 3 1	2200
	21st to end	Day	19% 57% 7% 11% 5%	2200
October	1st to 10th	Day	22% 36% 5% 29% 7% 1	3458
	11th to 20th	Day	23% 36% 4 28% 9%	3034
	21st to end	Day	31% 35% 5% 20% 8%	3190
November	1st to 10th	Day	29% 53% 5% 10% 3	1815
	11th to 20th	Day	25% 54% 8% 8% 3 1	1680
	21st to end	Day	28% 55% 5% 8% 4	1486
December	1st to 10th	Day	47% 35% 7% 7% 4	2360
	11th to 20th	Day	42% 32% 9% 12% 4	2710
	21st to end	Day	38% 26% 7% 17% 11%	3575
January	1st to 10th	Night	52% 23% 8% 13% 5%	8800
	11th to 20th	Night	48% 22% 7% 17% 5%	8374
	21st to end	Night	39% 23% 8% 21% 8%	9026
February	1st to 10th	Night	27% 59% 6% 5% 3	2893
	11th to 20th	Night	19% 58% 6% 11% 5%	2652
	21st to end	Night	19% 60% 4 12% 5%	2076
March	1st to 10th	Night	32% 32% 12% 15% 9%	5494
	11th to 20th	Night	35% 32% 9% 15% 9%	5142
	21st to end	Night	43% 31% 6% 15% 5%	5512
April	1st to 10th	Night	17% 60% 6% 11% 5% 1	2079
	11th to 20th	Night	20% 59% 5% 11% 5% 1	1869
	21st to end	Night	19% 59% 3 11% 7% 1	1890
May	1st to 10th	Night	33% 24% 6% 24% 13%	5246
	11th to 20th	Night	35% 24% 8% 23% 9% 1	4291
	21st to end	Night	25% 24% 7% 22% 21% 1	4526
June	1st to 10th	Night	11% 59% 8% 16% 5% 1	1470
	11th to 20th	Night	20% 60% 5% 10% 6%	1470
	21st to end	Night	17% 58% 9% 13% 2	1470
July	1st to 10th	Night	25% 23% 23% 26% 4	4105
	11th to 20th	Night	25% 20% 12% 33% 7% 2	4098
	21st to end	Night	24% 21% 16% 27% 11% 1	5014
August	1st to 10th	Night	19% 35% 12% 23% 10% 1	2733
	11th to 20th	Night	20% 36% 15% 23% 6%	2951
	21st to end	Night	22% 35% 13% 23% 6%	3234
September	1st to 10th	Night	14% 56% 8% 16% 5% 1	1972
	11th to 20th	Night	18% 58% 10% 10% 4	2200
	21st to end	Night	17% 57% 5% 13% 7% 1	2200
October	1st to 10th	Night	23% 36% 8% 22% 11% 1	3689
	11th to 20th	Night	24% 36% 6% 21% 14%	4095
	21st to end	Night	25% 35% 7% 24% 8%	4610
November	1st to 10th	Night	25% 54% 7% 10% 3 1	2702
	11th to 20th	Night	24% 55% 8% 9% 4 1	2940
	21st to end	Night	28% 55% 6% 8% 3	3129
December	1st to 10th	Night	45% 36% 9% 8% 2	5050
	11th to 20th	Night	43% 31% 8% 13% 3 1	5716
	21st to end	Night	40% 27% 7% 15% 9% 1	7645

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	9% 10% 35% 32% 11% 4	330
	11th to 20th	Day	10% 15% 34% 31% 10% 1	330
	21st to end	Day	14% 9% 39% 26% 9% 2	363
February	1st to 10th	Day	12% 13% 38% 30% 5% 2	330
	11th to 20th	Day	11% 9% 38% 30% 11% 1	330
	21st to end	Day	5% 10% 37% 35% 11% 3	273
March	1st to 10th	Day	12% 12% 36% 30% 8% 1	330
	11th to 20th	Day	14% 12% 34% 28% 12% 2	330
	21st to end	Day	15% 11% 34% 25% 12% 3	389
April	1st to 10th	Day	14% 15% 32% 28% 10% 1	561
	11th to 20th	Day	19% 11% 33% 25% 11% 1	740
	21st to end	Day	17% 10% 32% 26% 13% 2	750
May	1st to 10th	Day	14% 10% 26% 30% 16% 2	753
	11th to 20th	Day	21% 8% 31% 25% 12% 3	775
	21st to end	Day	18% 8% 23% 30% 16% 5%	844
June	1st to 10th	Day	14% 11% 31% 26% 14% 5%	780
	11th to 20th	Day	14% 9% 35% 28% 10% 4	780
	21st to end	Day	14% 9% 30% 28% 15% 3	780
July	1st to 10th	Day	9% 5% 26% 32% 20% 8%	771
	11th to 20th	Day	11% 7% 30% 29% 18% 6%	768
	21st to end	Day	6% 4 27% 36% 20% 6%	849
August	1st to 10th	Day	10% 5% 24% 34% 21% 7%	776
	11th to 20th	Day	14% 5% 24% 30% 21% 7%	736
	21st to end	Day	11% 7% 26% 32% 21% 4	803
September	1st to 10th	Day	14% 8% 33% 27% 14% 4	554
	11th to 20th	Day	21% 9% 25% 32% 12% 1	330
	21st to end	Day	19% 9% 33% 26% 10% 2	330
October	1st to 10th	Day	21% 11% 28% 25% 12% 2	330
	11th to 20th	Day	21% 11% 36% 22% 8% 2	330
	21st to end	Day	25% 11% 35% 21% 6% 2	363
November	1st to 10th	Day	24% 12% 31% 23% 10%	330
	11th to 20th	Day	15% 12% 36% 28% 9%	330
	21st to end	Day	15% 12% 41% 24% 7% 2	330
December	1st to 10th	Day	12% 9% 37% 31% 9% 2	330
	11th to 20th	Day	17% 16% 38% 23% 4 1	330
	21st to end	Day	13% 9% 39% 28% 8% 3	363
January	1st to 10th	Night	11% 10% 39% 29% 11% 1	1050
	11th to 20th	Night	13% 11% 41% 27% 7% 1	1050
	21st to end	Night	11% 12% 39% 28% 9% 1	1155
February	1st to 10th	Night	12% 11% 35% 31% 9% 1	1050
	11th to 20th	Night	10% 9% 36% 32% 11% 2	1017
	21st to end	Night	10% 9% 35% 33% 10% 2	692
March	1st to 10th	Night	15% 9% 34% 29% 12% 2	840
	11th to 20th	Night	12% 9% 37% 32% 10% 1	656
	21st to end	Night	14% 7% 33% 30% 13% 2	693
April	1st to 10th	Night	13% 7% 35% 34% 10% 1	630
	11th to 20th	Night	17% 8% 31% 35% 8% 1	623
	21st to end	Night	17% 8% 30% 31% 14% 1	630
May	1st to 10th	Night	16% 8% 31% 31% 13% 1	630
	11th to 20th	Night	19% 7% 29% 33% 12%	621
	21st to end	Night	20% 7% 27% 33% 13% 1	683
June	1st to 10th	Night	12% 8% 33% 33% 12% 1	630
	11th to 20th	Night	14% 6% 33% 33% 13% 1	630
	21st to end	Night	12% 6% 26% 38% 17%	630
July	1st to 10th	Night	8% 1 24% 43% 22% 1	615
	11th to 20th	Night	8% 5% 26% 44% 15% 1	612
	21st to end	Night	6% 3 23% 48% 18% 2	690
August	1st to 10th	Night	8% 3 23% 45% 19% 2	627
	11th to 20th	Night	7% 3 24% 43% 20% 2	606
	21st to end	Night	11% 4 28% 40% 16% 1	660
September	1st to 10th	Night	10% 4 30% 36% 18% 3	600
	11th to 20th	Night	15% 7% 32% 36% 11% 1	600
	21st to end	Night	16% 9% 31% 30% 14% 1	600
October	1st to 10th	Night	17% 10% 32% 32% 8%	660
	11th to 20th	Night	20% 10% 32% 30% 8%	920
	21st to end	Night	17% 10% 37% 27% 8% 1	1100
November	1st to 10th	Night	16% 12% 37% 27% 7% 1	1025
	11th to 20th	Night	15% 11% 38% 25% 9% 2	1050
	21st to end	Night	16% 14% 39% 25% 5% 1	1050
December	1st to 10th	Night	11% 11% 39% 29% 9% 1	1050
	11th to 20th	Night	17% 13% 34% 28% 7% 1	1050
	21st to end	Night	19% 6% 35% 31% 9% 1	1155

Page generated at 2026-08-12 02:37:15. Version ac07

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