Karval Reservoir SWA
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Karval Reservoir SWA 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	4 4 1 4 3 3 4 3 5% 7% 60%	117871
	Night	5% 5% 2 5% 4 4 4 3 5% 7% 56%	120238
Transparency	Day	22% 5% 10% 24% 26% 12%	117612
	Night	26% 5% 10% 23% 24% 10%	120087
Seeing	Day	7% 7% 25% 32% 22% 7%	16252
	Night	7% 7% 30% 40% 15% 1	26333

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	2 7% 2 6% 4 4 4 3 5% 7% 56%	3638
	11th to 20th	Day	2 5% 2 6% 5% 4 4 3 5% 7% 59%	3640
	21st to end	Day	2 7% 2 5% 3 3 3 2 4 6% 63%	4482
February	1st to 10th	Day	3 7% 2 6% 3 4 4 3 5% 7% 56%	1924
	11th to 20th	Day	2 6% 2 6% 5% 4 4 4 5% 6% 56%	1949
	21st to end	Day	3 6% 2 7% 4 3 4 3 4 5% 59%	1650
March	1st to 10th	Day	2 3 1 4 3 3 3 3 5% 6% 67%	4500
	11th to 20th	Day	5% 6% 2 5% 3 4 4 3 5% 7% 58%	4698
	21st to end	Day	3 4 2 5% 4 3 4 4 6% 9% 56%	5969
April	1st to 10th	Day	5% 5% 2 4 3 3 4 3 6% 7% 59%	2400
	11th to 20th	Day	8% 5% 2 5% 4 3 4 4 5% 8% 53%	2371
	21st to end	Day	8% 4 2 5% 4 4 4 4 6% 7% 51%	2400
May	1st to 10th	Day	9% 5% 2 4 3 3 3 3 5% 6% 56%	4247
	11th to 20th	Day	7% 4 2 4 3 4 4 4 6% 9% 53%	4212
	21st to end	Day	6% 3 1 4 3 3 4 3 6% 8% 60%	4895
June	1st to 10th	Day	5% 2 1 4 3 3 3 4 6% 12% 57%	2660
	11th to 20th	Day	5% 3 1 4 3 4 3 4 5% 8% 60%	2660
	21st to end	Day	3 3 1 4 4 3 4 5% 6% 10% 56%	2660
July	1st to 10th	Day	3 2 1 5% 5% 5% 6% 5% 8% 8% 52%	4430
	11th to 20th	Day	2 2 1 4 3 4 5% 4 8% 11% 56%	4430
	21st to end	Day	3 2 1 4 3 3 4 4 7% 10% 58%	4802
August	1st to 10th	Day	9% 4 1 4 3 4 5% 4 7% 10% 49%	3907
	11th to 20th	Day	4 3 1 4 3 3 4 4 7% 9% 58%	3726
	21st to end	Day	3 3 1 4 3 4 4 4 7% 10% 57%	4180
September	1st to 10th	Day	4 4 1 4 3 3 3 4 5% 7% 62%	2280
	11th to 20th	Day	6% 2 1 3 3 3 3 3 4 7% 66%	2180
	21st to end	Day	6% 3 1 3 3 2 2 3 4 5% 68%	2090
October	1st to 10th	Day	5% 2 1 2 1 1 2 2 3 4 78%	3404
	11th to 20th	Day	5% 3 1 4 3 3 3 2 4 6% 66%	3150
	21st to end	Day	5% 4 1 3 2 2 2 2 3 5% 72%	3196
November	1st to 10th	Day	4 4 2 3 2 3 3 3 5% 6% 67%	1763
	11th to 20th	Day	3 4 1 4 3 2 3 3 4 5% 69%	1800
	21st to end	Day	4 4 2 4 2 3 2 3 5% 7% 65%	1800
December	1st to 10th	Day	2 7% 2 3 2 2 2 2 3 4 70%	2748
	11th to 20th	Day	2 4 1 3 2 3 3 3 5% 7% 66%	3026
	21st to end	Day	3 6% 2 5% 4 3 4 3 4 7% 58%	4004
January	1st to 10th	Night	3 8% 3 6% 4 4 4 3 5% 6% 55%	6327
	11th to 20th	Night	1 5% 2 6% 4 3 3 4 6% 7% 59%	6340
	21st to end	Night	2 6% 2 5% 3 3 3 3 4 5% 62%	6539
February	1st to 10th	Night	4 6% 2 5% 5% 4 4 3 5% 6% 56%	2475
	11th to 20th	Night	4 8% 3 6% 5% 4 5% 4 6% 7% 49%	2338
	21st to end	Night	4 5% 1 4 4 3 3 3 4 7% 61%	1980
March	1st to 10th	Night	3 5% 2 5% 3 3 4 3 5% 5% 62%	5374
	11th to 20th	Night	6% 7% 2 5% 3 3 4 3 5% 6% 55%	5279
	21st to end	Night	7% 6% 3 6% 4 4 5% 4 6% 7% 49%	4984
April	1st to 10th	Night	7% 6% 2 4 3 3 4 4 7% 6% 55%	2000
	11th to 20th	Night	9% 5% 2 5% 3 3 4 4 6% 7% 50%	1977
	21st to end	Night	11% 7% 2 7% 4 3 4 3 5% 7% 48%	2000
May	1st to 10th	Night	11% 8% 2 5% 3 4 4 4 4 6% 50%	2940
	11th to 20th	Night	10% 7% 3 6% 4 5% 4 4 5% 7% 46%	2900
	21st to end	Night	12% 5% 2 5% 4 5% 5% 4 6% 7% 45%	2806
June	1st to 10th	Night	4 3 1 4 3 4 5% 3 8% 11% 53%	1520
	11th to 20th	Night	5% 3 1 4 4 4 4 4 6% 10% 56%	1520
	21st to end	Night	6% 5% 1 5% 4 5% 5% 4 6% 10% 48%	1520
July	1st to 10th	Night	7% 4 2 6% 5% 5% 5% 5% 9% 9% 43%	2540
	11th to 20th	Night	4 3 1 5% 4 5% 6% 5% 7% 12% 48%	2540
	21st to end	Night	5% 4 2 5% 4 4 5% 4 7% 8% 52%	2761
August	1st to 10th	Night	12% 5% 2 9% 7% 6% 6% 5% 7% 9% 32%	3014
	11th to 20th	Night	6% 4 2 8% 5% 6% 6% 5% 7% 10% 41%	3113
	21st to end	Night	3 3 1 6% 5% 6% 7% 6% 10% 11% 43%	3487
September	1st to 10th	Night	7% 4 2 5% 3 4 3 3 6% 7% 56%	1900
	11th to 20th	Night	6% 3 1 3 2 3 3 4 6% 8% 62%	1998
	21st to end	Night	6% 4 1 4 3 2 3 3 4 5% 65%	2090
October	1st to 10th	Night	5% 3 1 3 3 3 3 2 4 5% 68%	3542
	11th to 20th	Night	6% 3 2 3 2 3 4 3 5% 6% 62%	3778
	21st to end	Night	4 4 1 4 2 3 3 3 4 5% 68%	4329
November	1st to 10th	Night	3 4 1 3 3 3 2 3 4 6% 68%	2535
	11th to 20th	Night	3 4 1 4 2 3 3 2 3 5% 70%	2600
	21st to end	Night	3 6% 2 5% 3 3 2 3 4 6% 64%	2600
December	1st to 10th	Night	1 3 1 3 3 3 3 2 4 5% 71%	4437
	11th to 20th	Night	2 5% 2 4 4 3 3 3 5% 7% 62%	5181
	21st to end	Night	3 6% 2 6% 4 4 4 4 6% 7% 54%	6974

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	27% 4 8% 33% 20% 9%	3639
	11th to 20th	Day	25% 5% 10% 22% 28% 10%	3640
	21st to end	Day	24% 3 9% 24% 29% 11%	4482
February	1st to 10th	Day	28% 4 10% 25% 23% 10%	1924
	11th to 20th	Day	28% 4 9% 25% 25% 8%	1959
	21st to end	Day	27% 4 8% 18% 25% 18%	1650
March	1st to 10th	Day	18% 4 6% 18% 34% 20%	4500
	11th to 20th	Day	25% 4 7% 21% 34% 10%	4698
	21st to end	Day	22% 5% 11% 38% 20% 4	5969
April	1st to 10th	Day	24% 5% 10% 25% 24% 12%	2400
	11th to 20th	Day	27% 5% 12% 25% 19% 11%	2374
	21st to end	Day	28% 6% 14% 24% 22% 7%	2400
May	1st to 10th	Day	26% 7% 12% 23% 19% 13%	4247
	11th to 20th	Day	23% 9% 15% 24% 23% 6%	4216
	21st to end	Day	19% 8% 15% 23% 23% 12%	4895
June	1st to 10th	Day	19% 7% 17% 29% 18% 10%	2660
	11th to 20th	Day	20% 6% 12% 20% 24% 19%	2660
	21st to end	Day	20% 7% 12% 23% 24% 14%	2660
July	1st to 10th	Day	26% 5% 10% 17% 30% 12%	4361
	11th to 20th	Day	20% 4 14% 24% 28% 10%	4355
	21st to end	Day	20% 5% 13% 22% 21% 19%	4651
August	1st to 10th	Day	28% 6% 16% 30% 14% 6%	3892
	11th to 20th	Day	22% 4 15% 23% 26% 8%	3762
	21st to end	Day	21% 4 11% 29% 23% 12%	4179
September	1st to 10th	Day	21% 5% 9% 23% 26% 16%	2280
	11th to 20th	Day	18% 4 9% 19% 29% 21%	2180
	21st to end	Day	19% 4 6% 19% 35% 17%	2090
October	1st to 10th	Day	13% 3 5% 16% 37% 27%	3404
	11th to 20th	Day	22% 2 7% 24% 34% 11%	3150
	21st to end	Day	18% 2 5% 22% 36% 17%	3196
November	1st to 10th	Day	17% 3 11% 24% 27% 17%	1763
	11th to 20th	Day	17% 3 7% 28% 33% 12%	1800
	21st to end	Day	21% 4 8% 21% 30% 18%	1800
December	1st to 10th	Day	19% 2 6% 28% 35% 9%	2748
	11th to 20th	Day	18% 3 8% 28% 36% 8%	3024
	21st to end	Day	26% 5% 9% 27% 26% 9%	4004
January	1st to 10th	Night	28% 4 8% 33% 21% 6%	6327
	11th to 20th	Night	23% 5% 11% 21% 26% 13%	6340
	21st to end	Night	24% 5% 9% 24% 27% 11%	6539
February	1st to 10th	Night	28% 5% 10% 24% 23% 10%	2475
	11th to 20th	Night	32% 5% 11% 25% 22% 6%	2338
	21st to end	Night	23% 4 8% 21% 29% 15%	1980
March	1st to 10th	Night	22% 4 7% 16% 33% 18%	5374
	11th to 20th	Night	28% 5% 11% 15% 25% 15%	5279
	21st to end	Night	30% 6% 12% 31% 17% 3	4984
April	1st to 10th	Night	27% 6% 10% 25% 22% 11%	2000
	11th to 20th	Night	28% 7% 13% 23% 19% 9%	1977
	21st to end	Night	35% 6% 13% 23% 18% 5%	2000
May	1st to 10th	Night	30% 11% 16% 20% 14% 8%	2940
	11th to 20th	Night	34% 9% 16% 23% 12% 7%	2901
	21st to end	Night	31% 11% 16% 20% 16% 6%	2806
June	1st to 10th	Night	23% 10% 22% 24% 15% 6%	1520
	11th to 20th	Night	22% 7% 15% 22% 20% 14%	1520
	21st to end	Night	28% 8% 12% 23% 19% 11%	1520
July	1st to 10th	Night	33% 6% 12% 22% 24% 3	2500
	11th to 20th	Night	28% 5% 17% 22% 24% 4	2492
	21st to end	Night	29% 6% 12% 19% 23% 11%	2674
August	1st to 10th	Night	47% 7% 14% 18% 8% 5%	3006
	11th to 20th	Night	37% 7% 14% 21% 16% 4	3143
	21st to end	Night	29% 7% 15% 26% 17% 6%	3487
September	1st to 10th	Night	25% 5% 12% 21% 23% 13%	1900
	11th to 20th	Night	19% 6% 11% 22% 25% 17%	1998
	21st to end	Night	22% 5% 8% 19% 33% 13%	2090
October	1st to 10th	Night	19% 5% 6% 18% 30% 22%	3542
	11th to 20th	Night	23% 3 7% 27% 27% 13%	3778
	21st to end	Night	20% 3 7% 24% 30% 16%	4329
November	1st to 10th	Night	17% 3 10% 25% 28% 16%	2535
	11th to 20th	Night	18% 3 7% 25% 34% 14%	2600
	21st to end	Night	23% 3 9% 21% 30% 15%	2600
December	1st to 10th	Night	17% 3 7% 33% 30% 10%	4437
	11th to 20th	Night	22% 3 5% 27% 35% 7%	5182
	21st to end	Night	28% 5% 9% 24% 26% 8%	6974

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	7% 5% 28% 40% 17% 4	300
	11th to 20th	Day	11% 9% 27% 36% 16% 1	300
	21st to end	Day	7% 8% 28% 36% 17% 4	330
February	1st to 10th	Day	5% 10% 40% 32% 11% 2	300
	11th to 20th	Day	5% 7% 48% 31% 9% 1	300
	21st to end	Day	5% 11% 40% 32% 10% 2	249
March	1st to 10th	Day	3 9% 31% 33% 21% 3	300
	11th to 20th	Day	11% 10% 27% 34% 15% 2	350
	21st to end	Day	11% 14% 37% 26% 11% 1	550
April	1st to 10th	Day	9% 14% 38% 24% 12% 3	500
	11th to 20th	Day	12% 16% 35% 26% 10% 2	492
	21st to end	Day	11% 15% 33% 27% 12% 2	500
May	1st to 10th	Day	12% 12% 29% 28% 16% 3	700
	11th to 20th	Day	12% 8% 28% 28% 20% 4	725
	21st to end	Day	9% 10% 29% 30% 18% 5%	760
June	1st to 10th	Day	6% 5% 21% 31% 26% 11%	680
	11th to 20th	Day	5% 5% 29% 34% 23% 5%	680
	21st to end	Day	4 6% 22% 35% 28% 6%	680
July	1st to 10th	Day	6% 3 16% 32% 32% 10%	671
	11th to 20th	Day	3 1 12% 32% 39% 13%	668
	21st to end	Day	5% 1 8% 33% 39% 14%	739
August	1st to 10th	Day	6% 2 14% 32% 31% 15%	522
	11th to 20th	Day	4 2 18% 34% 31% 10%	477
	21st to end	Day	4 2 14% 40% 27% 12%	539
September	1st to 10th	Day	5% 2 17% 35% 30% 12%	490
	11th to 20th	Day	3 3 19% 36% 27% 11%	390
	21st to end	Day	10% 4 19% 23% 28% 15%	300
October	1st to 10th	Day	9% 4 20% 23% 30% 14%	300
	11th to 20th	Day	5% 4 26% 34% 21% 10%	300
	21st to end	Day	11% 8% 26% 24% 23% 8%	330
November	1st to 10th	Day	8% 7% 27% 32% 20% 6%	300
	11th to 20th	Day	4 7% 29% 34% 22% 4	300
	21st to end	Day	8% 8% 26% 35% 20% 4	300
December	1st to 10th	Day	6% 7% 25% 41% 17% 4	300
	11th to 20th	Day	6% 7% 30% 36% 19% 2	300
	21st to end	Day	7% 11% 32% 38% 12% 1	330
January	1st to 10th	Night	6% 6% 30% 42% 14% 2	1000
	11th to 20th	Night	6% 7% 34% 39% 13% 1	1000
	21st to end	Night	5% 6% 31% 47% 10% 1	912
February	1st to 10th	Night	7% 6% 39% 40% 8%	800
	11th to 20th	Night	7% 7% 40% 38% 8% 1	784
	21st to end	Night	6% 8% 42% 37% 7%	660
March	1st to 10th	Night	6% 9% 36% 39% 10% 1	800
	11th to 20th	Night	9% 8% 33% 37% 11% 1	792
	21st to end	Night	10% 11% 42% 31% 7%	660
April	1st to 10th	Night	10% 12% 41% 32% 5%	600
	11th to 20th	Night	11% 13% 41% 30% 5%	593
	21st to end	Night	11% 17% 31% 32% 9%	600
May	1st to 10th	Night	13% 9% 37% 31% 10% 1	600
	11th to 20th	Night	13% 8% 30% 35% 13% 1	591
	21st to end	Night	12% 9% 39% 31% 9%	634
June	1st to 10th	Night	4 6% 30% 43% 15% 1	570
	11th to 20th	Night	5% 5% 36% 43% 11%	570
	21st to end	Night	6% 4 28% 45% 16% 1	570
July	1st to 10th	Night	7% 4 19% 46% 24% 1	555
	11th to 20th	Night	6% 1 13% 49% 29% 2	552
	21st to end	Night	9% 1 13% 40% 33% 2	624
August	1st to 10th	Night	9% 2 17% 41% 31% 1	567
	11th to 20th	Night	6% 1 19% 53% 20% 1	564
	21st to end	Night	5% 1 15% 48% 30% 2	627
September	1st to 10th	Night	8% 4 19% 48% 21% 1	570
	11th to 20th	Night	6% 3 21% 44% 24% 1	570
	21st to end	Night	7% 4 24% 39% 24% 1	570
October	1st to 10th	Night	11% 6% 28% 36% 17% 2	606
	11th to 20th	Night	5% 6% 27% 39% 21% 2	760
	21st to end	Night	6% 9% 26% 36% 20% 3	957
November	1st to 10th	Night	5% 5% 27% 43% 18% 1	975
	11th to 20th	Night	4 6% 32% 41% 16% 2	1000
	21st to end	Night	6% 8% 28% 40% 16% 3	1000
December	1st to 10th	Night	4 6% 33% 42% 13% 1	1000
	11th to 20th	Night	6% 6% 30% 42% 14% 1	1000
	21st to end	Night	7% 9% 33% 39% 11% 1	1100

Page generated at 2025-05-23 07:20:58. Version ac07

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