Vale
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Vale clear sky chart from 2005-11-06 to 2024-11-08.

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	7% 6% 2 6% 4 4 4 3 5% 6% 53%	105210
	Night	9% 8% 3 6% 4 4 4 3 5% 6% 48%	102545
Transparency	Day	30% 7% 11% 19% 19% 14%	104954
	Night	35% 8% 12% 19% 16% 11%	102390
Seeing	Day	9% 6% 17% 28% 27% 13%	14488
	Night	11% 3 20% 39% 23% 3	23724

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	12% 17% 6% 11% 8% 6% 5% 4 6% 5% 21%	2539
	11th to 20th	Day	17% 19% 5% 11% 6% 6% 5% 3 4 5% 19%	2540
	21st to end	Day	20% 16% 6% 13% 6% 5% 5% 4 5% 6% 14%	2794
February	1st to 10th	Day	13% 14% 4 9% 6% 5% 5% 3 5% 6% 31%	1649
	11th to 20th	Day	10% 9% 4 10% 7% 5% 5% 4 6% 7% 33%	1850
	21st to end	Day	8% 9% 4 7% 6% 6% 5% 4 7% 9% 36%	1570
March	1st to 10th	Day	7% 13% 3 8% 5% 5% 6% 4 7% 9% 33%	3138
	11th to 20th	Day	6% 7% 2 5% 3 3 3 3 5% 5% 58%	3290
	21st to end	Day	8% 8% 3 9% 6% 6% 7% 5% 8% 9% 33%	4103
April	1st to 10th	Day	9% 8% 3 6% 5% 5% 5% 4 7% 7% 41%	2280
	11th to 20th	Day	6% 7% 3 7% 5% 4 5% 5% 6% 7% 46%	2253
	21st to end	Day	7% 6% 2 6% 4 3 5% 4 5% 8% 48%	2470
May	1st to 10th	Day	7% 7% 2 5% 4 5% 5% 4 5% 6% 50%	4110
	11th to 20th	Day	5% 3 2 3 2 3 3 3 5% 6% 66%	4341
	21st to end	Day	5% 4 2 5% 4 4 5% 4 6% 8% 53%	4813
June	1st to 10th	Day	7% 5% 2 5% 6% 5% 5% 5% 7% 8% 46%	2660
	11th to 20th	Day	6% 3 1 4 4 3 3 3 6% 8% 58%	2660
	21st to end	Day	3 3 1 3 3 2 3 3 4 6% 70%	2660
July	1st to 10th	Day	1 1 1 2 1 1 2 2 3 4 81%	4420
	11th to 20th	Day	2 2 1 2 2 2 2 2 3 4 80%	4420
	21st to end	Day	1 2 1 2 2 2 2 2 3 5% 78%	4790
August	1st to 10th	Day	4 4 2 4 3 3 3 3 5% 6% 65%	4344
	11th to 20th	Day	2 1 1 2 2 2 2 2 3 5% 79%	3946
	21st to end	Day	2 2 1 2 2 2 2 2 3 4 78%	4180
September	1st to 10th	Day	3 2 1 2 2 2 3 2 4 5% 75%	2280
	11th to 20th	Day	4 3 1 4 3 4 4 3 5% 7% 63%	2150
	21st to end	Day	5% 3 1 4 3 3 4 2 4 6% 65%	2090
October	1st to 10th	Day	5% 4 1 4 3 3 2 2 3 5% 68%	3442
	11th to 20th	Day	7% 6% 3 5% 4 3 3 3 4 7% 56%	3042
	21st to end	Day	9% 6% 2 6% 3 4 5% 4 6% 8% 46%	3101
November	1st to 10th	Day	13% 9% 3 6% 5% 4 4 4 6% 7% 39%	1737
	11th to 20th	Day	12% 9% 4 9% 5% 4 5% 5% 6% 6% 36%	1710
	21st to end	Day	10% 8% 5% 11% 6% 6% 5% 5% 6% 6% 32%	1596
December	1st to 10th	Day	18% 13% 3 8% 6% 5% 5% 4 6% 7% 26%	1520
	11th to 20th	Day	17% 13% 7% 17% 7% 5% 4 3 5% 5% 17%	1928
	21st to end	Day	12% 15% 5% 12% 7% 7% 6% 3 5% 5% 22%	2794
January	1st to 10th	Night	15% 17% 6% 12% 6% 6% 6% 4 5% 6% 18%	4406
	11th to 20th	Night	21% 14% 5% 11% 7% 5% 5% 3 4 5% 20%	4420
	21st to end	Night	22% 18% 5% 11% 5% 4 3 3 4 5% 21%	4862
February	1st to 10th	Night	12% 11% 4 9% 5% 4 5% 5% 6% 7% 32%	2525
	11th to 20th	Night	11% 10% 3 8% 4 4 5% 4 6% 7% 38%	2218
	21st to end	Night	9% 11% 3 9% 6% 5% 6% 5% 6% 7% 33%	1884
March	1st to 10th	Night	8% 11% 3 8% 6% 5% 6% 4 5% 8% 37%	3736
	11th to 20th	Night	7% 8% 2 5% 3 3 3 3 5% 6% 54%	3690
	21st to end	Night	8% 8% 3 9% 6% 6% 6% 5% 6% 10% 32%	3534
April	1st to 10th	Night	9% 8% 3 7% 5% 3 5% 4 5% 6% 45%	1900
	11th to 20th	Night	8% 7% 2 7% 5% 4 5% 4 5% 7% 46%	1874
	21st to end	Night	8% 5% 2 5% 3 3 4 4 6% 8% 51%	1710
May	1st to 10th	Night	9% 5% 2 6% 4 5% 5% 4 5% 7% 49%	2860
	11th to 20th	Night	4 3 1 5% 3 3 3 3 6% 7% 63%	2549
	21st to end	Night	7% 6% 2 6% 4 4 4 4 6% 7% 50%	2762
June	1st to 10th	Night	7% 4 2 7% 5% 5% 5% 4 6% 8% 47%	1520
	11th to 20th	Night	6% 4 2 4 4 3 4 3 5% 8% 58%	1520
	21st to end	Night	3 3 1 3 3 3 3 3 5% 7% 66%	1520
July	1st to 10th	Night	1 1 1 1 2 2 2 2 3 4 81%	2540
	11th to 20th	Night	1 1 1 2 2 3 4 4 81%	2540
	21st to end	Night	3 2 1 3 2 3 3 3 5% 5% 69%	2761
August	1st to 10th	Night	3 3 2 5% 4 4 4 4 5% 6% 60%	2587
	11th to 20th	Night	1 2 1 2 2 2 2 2 5% 5% 76%	2893
	21st to end	Night	3 3 1 2 2 2 2 1 3 4 77%	3498
September	1st to 10th	Night	4 2 1 2 2 2 2 2 4 5% 74%	1900
	11th to 20th	Night	5% 2 1 4 3 4 3 3 5% 6% 65%	2029
	21st to end	Night	6% 3 1 3 2 3 4 3 4 6% 65%	2090
October	1st to 10th	Night	5% 3 2 4 2 2 2 2 3 5% 70%	3521
	11th to 20th	Night	5% 4 1 4 4 3 4 3 5% 6% 62%	3890
	21st to end	Night	8% 6% 2 6% 4 4 4 4 6% 7% 49%	4457
November	1st to 10th	Night	12% 7% 3 6% 4 4 5% 4 5% 6% 44%	2502
	11th to 20th	Night	14% 8% 3 6% 4 5% 5% 4 6% 6% 39%	2470
	21st to end	Night	12% 9% 3 6% 5% 5% 5% 3 5% 6% 43%	2579
December	1st to 10th	Night	15% 13% 4 9% 5% 4 3 4 4 7% 32%	2660
	11th to 20th	Night	16% 12% 5% 10% 6% 5% 5% 4 6% 6% 24%	3276
	21st to end	Night	12% 15% 4 9% 5% 5% 6% 4 6% 7% 27%	4862

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	60% 13% 12% 12% 3	2539
	11th to 20th	Day	65% 11% 13% 10% 1	2540
	21st to end	Day	67% 14% 11% 7% 2	2794
February	1st to 10th	Day	51% 12% 19% 14% 4 1	1649
	11th to 20th	Day	45% 13% 16% 18% 7%	1860
	21st to end	Day	40% 11% 21% 19% 9% 1	1570
March	1st to 10th	Day	41% 12% 16% 20% 9% 1	3138
	11th to 20th	Day	27% 6% 14% 36% 16%	3290
	21st to end	Day	39% 13% 20% 19% 8% 2	4103
April	1st to 10th	Day	37% 9% 16% 23% 13% 2	2280
	11th to 20th	Day	33% 8% 14% 25% 16% 4	2256
	21st to end	Day	31% 7% 14% 27% 18% 3	2470
May	1st to 10th	Day	28% 7% 10% 26% 24% 5%	4110
	11th to 20th	Day	18% 5% 8% 26% 31% 13%	4344
	21st to end	Day	23% 9% 15% 31% 17% 3	4814
June	1st to 10th	Day	32% 9% 12% 24% 20% 2	2660
	11th to 20th	Day	23% 6% 10% 24% 26% 11%	2660
	21st to end	Day	15% 4 7% 20% 32% 21%	2660
July	1st to 10th	Day	9% 2 3 8% 20% 57%	4351
	11th to 20th	Day	11% 2 2 6% 19% 60%	4345
	21st to end	Day	10% 2 2 8% 29% 49%	4639
August	1st to 10th	Day	20% 3 4 9% 27% 36%	4328
	11th to 20th	Day	10% 2 3 15% 37% 32%	3985
	21st to end	Day	12% 2 4 22% 33% 26%	4179
September	1st to 10th	Day	13% 3 4 19% 32% 28%	2280
	11th to 20th	Day	20% 5% 10% 23% 28% 14%	2150
	21st to end	Day	20% 5% 9% 28% 30% 8%	2090
October	1st to 10th	Day	21% 4 7% 23% 37% 9%	3442
	11th to 20th	Day	29% 4 15% 29% 19% 4	3042
	21st to end	Day	34% 6% 13% 31% 15% 1	3101
November	1st to 10th	Day	41% 8% 18% 23% 9%	1737
	11th to 20th	Day	46% 10% 19% 19% 6% 1	1710
	21st to end	Day	48% 12% 18% 16% 6% 1	1596
December	1st to 10th	Day	55% 12% 17% 11% 5%	1520
	11th to 20th	Day	67% 11% 10% 8% 3	1928
	21st to end	Day	57% 13% 15% 11% 4	2794
January	1st to 10th	Night	60% 15% 15% 7% 2	4406
	11th to 20th	Night	63% 11% 14% 10% 2	4420
	21st to end	Night	64% 11% 14% 9% 2	4862
February	1st to 10th	Night	48% 12% 19% 17% 4	2525
	11th to 20th	Night	43% 10% 19% 19% 9%	2219
	21st to end	Night	43% 11% 18% 19% 7% 1	1884
March	1st to 10th	Night	39% 12% 16% 21% 10% 1	3736
	11th to 20th	Night	30% 6% 11% 35% 17%	3690
	21st to end	Night	39% 13% 18% 21% 8%	3534
April	1st to 10th	Night	37% 8% 15% 22% 16% 2	1900
	11th to 20th	Night	34% 8% 12% 26% 16% 4	1874
	21st to end	Night	28% 7% 13% 27% 22% 3	1710
May	1st to 10th	Night	28% 9% 12% 25% 23% 4	2860
	11th to 20th	Night	17% 6% 10% 25% 34% 8%	2549
	21st to end	Night	28% 9% 12% 32% 17% 2	2762
June	1st to 10th	Night	32% 8% 15% 23% 20% 2	1520
	11th to 20th	Night	25% 6% 10% 22% 28% 9%	1520
	21st to end	Night	18% 3 6% 21% 34% 18%	1520
July	1st to 10th	Night	8% 3 3 10% 19% 57%	2500
	11th to 20th	Night	8% 2 3 8% 20% 59%	2492
	21st to end	Night	18% 2 3 7% 27% 44%	2674
August	1st to 10th	Night	23% 3 5% 9% 25% 34%	2579
	11th to 20th	Night	12% 2 4 11% 31% 40%	2920
	21st to end	Night	14% 2 3 17% 33% 32%	3498
September	1st to 10th	Night	13% 2 5% 16% 29% 34%	1900
	11th to 20th	Night	20% 4 8% 20% 26% 22%	2029
	21st to end	Night	20% 4 6% 24% 31% 16%	2090
October	1st to 10th	Night	20% 2 6% 19% 33% 20%	3521
	11th to 20th	Night	24% 3 12% 29% 27% 4	3890
	21st to end	Night	33% 5% 12% 31% 18% 1	4457
November	1st to 10th	Night	39% 6% 14% 24% 14% 1	2502
	11th to 20th	Night	42% 10% 18% 22% 8%	2470
	21st to end	Night	40% 9% 19% 22% 9% 1	2579
December	1st to 10th	Night	50% 11% 16% 16% 6%	2660
	11th to 20th	Night	57% 13% 16% 12% 3	3276
	21st to end	Night	50% 15% 18% 11% 5%	4862

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	20% 6% 16% 32% 21% 6%	180
	11th to 20th	Day	21% 9% 12% 27% 22% 8%	180
	21st to end	Day	22% 3 15% 30% 24% 7%	198
February	1st to 10th	Day	18% 4 22% 30% 21% 4	294
	11th to 20th	Day	13% 6% 23% 35% 18% 5%	455
	21st to end	Day	10% 7% 30% 29% 18% 5%	382
March	1st to 10th	Day	14% 11% 24% 33% 17% 2	460
	11th to 20th	Day	12% 8% 22% 29% 22% 7%	460
	21st to end	Day	12% 12% 22% 29% 20% 4	506
April	1st to 10th	Day	12% 13% 22% 23% 21% 10%	460
	11th to 20th	Day	9% 13% 25% 27% 16% 9%	452
	21st to end	Day	8% 8% 27% 28% 21% 8%	460
May	1st to 10th	Day	6% 12% 23% 27% 22% 10%	463
	11th to 20th	Day	15% 8% 18% 26% 21% 12%	488
	21st to end	Day	7% 5% 15% 29% 25% 18%	529
June	1st to 10th	Day	7% 7% 18% 26% 26% 17%	490
	11th to 20th	Day	7% 8% 23% 29% 22% 10%	490
	21st to end	Day	3 2 18% 31% 30% 17%	490
July	1st to 10th	Day	3 1 12% 34% 34% 16%	486
	11th to 20th	Day	2 1 10% 36% 37% 14%	484
	21st to end	Day	2 1 9% 30% 39% 19%	531
August	1st to 10th	Day	6% 2 10% 29% 37% 17%	487
	11th to 20th	Day	1 1 11% 27% 35% 25%	477
	21st to end	Day	4 3 12% 28% 30% 24%	539
September	1st to 10th	Day	4 2 9% 23% 36% 26%	490
	11th to 20th	Day	4 3 12% 26% 33% 22%	490
	21st to end	Day	6% 3 13% 27% 33% 19%	490
October	1st to 10th	Day	7% 4 14% 22% 30% 22%	490
	11th to 20th	Day	8% 4 15% 27% 27% 18%	422
	21st to end	Day	10% 7% 16% 28% 28% 9%	330
November	1st to 10th	Day	14% 7% 17% 28% 28% 6%	291
	11th to 20th	Day	11% 6% 17% 29% 28% 9%	270
	21st to end	Day	15% 4 13% 27% 34% 7%	216
December	1st to 10th	Day	22% 4 17% 27% 18% 12%	180
	11th to 20th	Day	24% 6% 18% 29% 19% 3	180
	21st to end	Day	18% 5% 18% 31% 23% 6%	198
January	1st to 10th	Night	19% 5% 19% 34% 20% 4	760
	11th to 20th	Night	18% 5% 19% 33% 22% 4	760
	21st to end	Night	16% 2 19% 37% 22% 4	836
February	1st to 10th	Night	16% 4 23% 37% 18% 2	760
	11th to 20th	Night	14% 2 21% 41% 19% 2	744
	21st to end	Night	13% 3 26% 40% 16% 1	628
March	1st to 10th	Night	12% 4 26% 39% 16% 2	760
	11th to 20th	Night	11% 5% 21% 40% 19% 2	760
	21st to end	Night	13% 5% 27% 39% 14% 1	836
April	1st to 10th	Night	13% 6% 23% 36% 21% 1	760
	11th to 20th	Night	9% 6% 28% 37% 18% 2	746
	21st to end	Night	9% 5% 28% 39% 18% 1	570
May	1st to 10th	Night	7% 7% 29% 39% 17% 1	570
	11th to 20th	Night	8% 4 22% 36% 26% 4	394
	21st to end	Night	9% 5% 20% 39% 23% 4	411
June	1st to 10th	Night	7% 4 23% 39% 24% 2	380
	11th to 20th	Night	8% 7% 28% 36% 20% 2	380
	21st to end	Night	5% 4 24% 44% 23% 1	380
July	1st to 10th	Night	2 2 21% 53% 20% 1	370
	11th to 20th	Night	1 1 24% 59% 15%	368
	21st to end	Night	2 21% 51% 24% 1	416
August	1st to 10th	Night	4 1 20% 46% 28% 2	410
	11th to 20th	Night	2 2 14% 46% 34% 2	607
	21st to end	Night	4 2 14% 43% 33% 4	836
September	1st to 10th	Night	5% 2 12% 40% 37% 5%	760
	11th to 20th	Night	4 2 12% 38% 38% 6%	760
	21st to end	Night	8% 2 15% 36% 31% 8%	760
October	1st to 10th	Night	10% 3 16% 38% 28% 6%	760
	11th to 20th	Night	7% 3 18% 36% 30% 6%	760
	21st to end	Night	9% 3 19% 39% 26% 4	836
November	1st to 10th	Night	15% 3 17% 38% 25% 2	770
	11th to 20th	Night	16% 3 18% 40% 20% 3	760
	21st to end	Night	15% 3 21% 33% 24% 5%	760
December	1st to 10th	Night	20% 3 19% 37% 19% 3	760
	11th to 20th	Night	22% 3 15% 40% 19% 2	760
	21st to end	Night	22% 5% 22% 36% 13% 2	836

Page generated at 2024-11-05 06:15:50. Version ac07

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