Venetie
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Venetie clear sky chart from 2005-11-06 to 2024-11-30.

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	9% 10% 4 10% 6% 6% 6% 5% 7% 8% 30%	108880
	Night	7% 12% 5% 12% 7% 6% 5% 4 6% 6% 30%	101448
Transparency	Day	49% 7% 19% 20% 5%	108498
	Night	53% 6% 15% 17% 8% 1	101479
Seeing	Day	11% 4 12% 27% 28% 17%	19420
	Night	12% 3 13% 32% 30% 10%	22638

By Month

Percentage Cloud Cover NW (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 8% 4 9% 4 8% 5% 3 4 7% 46%	336
	11th to 20th	Day	4 9% 5% 14% 4 5% 6% 6% 6% 7% 34%	776
	21st to end	Day	4 7% 3 11% 7% 5% 7% 7% 9% 8% 33%	1397
February	1st to 10th	Day	2 8% 4 13% 9% 7% 7% 3 6% 8% 33%	1100
	11th to 20th	Day	3 10% 5% 14% 9% 6% 7% 5% 7% 7% 28%	1268
	21st to end	Day	3 8% 6% 11% 7% 6% 7% 6% 8% 7% 30%	1256
March	1st to 10th	Day	2 7% 5% 19% 10% 8% 7% 5% 6% 6% 25%	2933
	11th to 20th	Day	3 13% 5% 15% 8% 7% 7% 5% 6% 6% 25%	3254
	21st to end	Day	4 15% 6% 10% 7% 6% 6% 4 6% 7% 27%	4128
April	1st to 10th	Day	3 12% 5% 12% 7% 6% 5% 5% 6% 9% 30%	2494
	11th to 20th	Day	3 8% 3 11% 7% 5% 5% 4 5% 8% 41%	2702
	21st to end	Day	3 6% 2 8% 6% 6% 6% 4 7% 9% 43%	2959
May	1st to 10th	Day	14% 17% 4 10% 6% 5% 5% 3 5% 6% 24%	5392
	11th to 20th	Day	4 5% 2 6% 6% 6% 6% 5% 8% 10% 41%	5821
	21st to end	Day	14% 11% 4 9% 6% 5% 6% 5% 7% 6% 27%	6895
June	1st to 10th	Day	7% 7% 3 8% 8% 6% 7% 6% 7% 8% 33%	4291
	11th to 20th	Day	8% 7% 3 8% 5% 6% 6% 5% 9% 10% 34%	4560
	21st to end	Day	9% 5% 2 7% 7% 6% 6% 6% 8% 9% 35%	4560
July	1st to 10th	Day	12% 9% 3 9% 7% 6% 6% 6% 8% 9% 26%	7243
	11th to 20th	Day	10% 7% 3 8% 5% 6% 6% 6% 7% 10% 33%	6400
	21st to end	Day	13% 8% 3 9% 6% 6% 6% 5% 6% 8% 30%	6362
August	1st to 10th	Day	11% 8% 3 8% 6% 6% 6% 5% 8% 9% 29%	5432
	11th to 20th	Day	17% 8% 3 10% 5% 6% 6% 5% 6% 8% 26%	4920
	21st to end	Day	14% 9% 4 9% 6% 5% 6% 5% 6% 7% 30%	5018
September	1st to 10th	Day	11% 9% 4 9% 5% 6% 6% 4 6% 7% 31%	2521
	11th to 20th	Day	15% 13% 4 9% 5% 6% 4 4 6% 8% 26%	2255
	21st to end	Day	14% 13% 4 9% 6% 5% 4 4 5% 7% 30%	2074
October	1st to 10th	Day	10% 13% 5% 12% 7% 6% 5% 4 6% 5% 27%	2922
	11th to 20th	Day	11% 17% 5% 13% 7% 5% 5% 3 4 7% 22%	2634
	21st to end	Day	7% 16% 6% 15% 10% 6% 4 3 5% 6% 22%	2407
November	1st to 10th	Day	8% 22% 6% 14% 8% 5% 5% 3 5% 5% 20%	1030
	11th to 20th	Day	3 12% 7% 13% 9% 7% 7% 4 4 6% 29%	810
	21st to end	Day	8% 16% 4 12% 7% 6% 5% 6% 7% 6% 23%	554
December	1st to 10th	Day	7% 15% 4 8% 7% 6% 7% 4 5% 8% 28%	176
	January	1st to 10th	Night	3 11% 5% 11% 6% 5% 5% 3 5% 5% 40%	6616
11th to 20th		Night	5% 11% 4 10% 6% 4 4 4 5% 7% 39%	6163
21st to end		Night	5% 8% 3 11% 7% 5% 5% 5% 9% 8% 33%	6270
February	1st to 10th	Night	2 9% 3 12% 8% 6% 6% 5% 8% 9% 32%	3079
	11th to 20th	Night	4 10% 6% 12% 6% 5% 6% 5% 6% 8% 32%	2797
	21st to end	Night	4 10% 4 11% 7% 5% 5% 4 6% 8% 36%	2198
March	1st to 10th	Night	2 7% 5% 17% 7% 6% 7% 4 5% 6% 34%	3924
	11th to 20th	Night	3 10% 6% 15% 7% 6% 5% 3 5% 6% 34%	3704
	21st to end	Night	5% 17% 5% 11% 5% 5% 5% 4 6% 6% 31%	3503
April	1st to 10th	Night	4 10% 4 13% 8% 6% 5% 4 7% 8% 32%	1683
	11th to 20th	Night	3 10% 4 10% 5% 4 6% 5% 6% 7% 40%	1427
	21st to end	Night	4 6% 3 7% 6% 6% 6% 5% 8% 8% 42%	1220
May	1st to 10th	Night	16% 15% 4 9% 6% 4 4 4 4 5% 29%	1567
	11th to 20th	Night	3 6% 2 6% 4 6% 6% 5% 11% 13% 38%	1084
	21st to end	Night	16% 11% 3 6% 6% 4 5% 4 6% 7% 31%	677
June	1st to 10th	Night	12% 6% 12% 10% 6% 6% 10% 12% 6% 23%	52
	July	1st to 10th	Night	25% 13% 25% 21% 4 4 4 4	24
11th to 20th		Night	10% 7% 2 10% 5% 5% 5% 4 6% 11% 35%	568
21st to end		Night	15% 9% 3 10% 7% 6% 5% 5% 7% 9% 24%	1202
August	1st to 10th	Night	10% 8% 4 10% 5% 5% 6% 4 8% 10% 29%	1501
	11th to 20th	Night	20% 10% 4 9% 6% 4 5% 4 7% 8% 22%	1918
	21st to end	Night	13% 9% 3 8% 6% 6% 6% 6% 7% 6% 30%	2647
September	1st to 10th	Night	11% 9% 3 9% 4 4 5% 4 7% 7% 36%	1659
	11th to 20th	Night	19% 11% 4 8% 6% 5% 4 4 6% 6% 27%	1923
	21st to end	Night	14% 18% 5% 9% 5% 5% 4 4 4 5% 28%	2104
October	1st to 10th	Night	9% 15% 5% 10% 5% 4 4 4 6% 8% 30%	4046
	11th to 20th	Night	11% 16% 8% 15% 6% 4 4 3 3 5% 27%	4292
	21st to end	Night	8% 13% 6% 18% 8% 6% 5% 3 4 5% 23%	5152
November	1st to 10th	Night	9% 20% 5% 13% 7% 6% 5% 4 4 4 22%	3265
	11th to 20th	Night	5% 12% 5% 13% 9% 8% 7% 4 5% 6% 26%	3568
	21st to end	Night	7% 14% 6% 13% 8% 6% 7% 4 5% 6% 23%	3840
December	1st to 10th	Night	7% 15% 5% 13% 7% 6% 5% 3 7% 6% 25%	4004
	11th to 20th	Night	5% 14% 6% 16% 9% 7% 6% 4 6% 5% 21%	5599
	21st to end	Night	4 13% 6% 17% 9% 7% 6% 4 5% 6% 23%	8172

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	38% 7% 11% 21% 15% 8%	336
	11th to 20th	Day	48% 5% 9% 21% 16% 2	782
	21st to end	Day	47% 5% 8% 16% 24%	1397
February	1st to 10th	Day	49% 7% 8% 21% 12% 3	1100
	11th to 20th	Day	53% 7% 14% 19% 6% 1	1274
	21st to end	Day	49% 8% 15% 21% 7%	1256
March	1st to 10th	Day	58% 5% 11% 20% 5%	2933
	11th to 20th	Day	58% 5% 12% 18% 7%	3254
	21st to end	Day	53% 7% 18% 14% 6% 1	4128
April	1st to 10th	Day	49% 5% 18% 20% 6% 1	2494
	11th to 20th	Day	39% 5% 22% 25% 9%	2702
	21st to end	Day	34% 7% 22% 28% 8%	2959
May	1st to 10th	Day	59% 6% 12% 18% 4	5392
	11th to 20th	Day	35% 6% 20% 32% 7%	5825
	21st to end	Day	51% 7% 15% 20% 8%	6896
June	1st to 10th	Day	43% 7% 17% 23% 9%	4291
	11th to 20th	Day	40% 7% 16% 29% 8%	4560
	21st to end	Day	40% 9% 18% 27% 6%	4560
July	1st to 10th	Day	49% 9% 21% 17% 4	7134
	11th to 20th	Day	41% 8% 25% 23% 2	6286
	21st to end	Day	48% 9% 21% 22%	6160
August	1st to 10th	Day	46% 9% 29% 15% 1	5411
	11th to 20th	Day	53% 9% 26% 12%	4968
	21st to end	Day	51% 8% 23% 18%	5017
September	1st to 10th	Day	48% 10% 25% 13% 3	2521
	11th to 20th	Day	55% 6% 25% 13% 1	2255
	21st to end	Day	54% 6% 21% 18% 1	2074
October	1st to 10th	Day	57% 6% 18% 17% 2	2922
	11th to 20th	Day	60% 7% 18% 13% 1	2634
	21st to end	Day	62% 5% 17% 15% 1	2407
November	1st to 10th	Day	68% 7% 11% 12% 2	1030
	11th to 20th	Day	59% 5% 19% 13% 5%	810
	21st to end	Day	60% 6% 13% 16% 5%	554
December	1st to 10th	Day	56% 5% 15% 17% 7%	176
	January	1st to 10th	Night	46% 7% 11% 17% 17% 3	6616
11th to 20th		Night	45% 4 9% 20% 14% 7%	6219
21st to end		Night	45% 4 7% 14% 29%	6270
February	1st to 10th	Night	47% 6% 13% 20% 12% 3	3079
	11th to 20th	Night	49% 7% 15% 20% 9% 1	2802
	21st to end	Night	45% 7% 15% 24% 10%	2198
March	1st to 10th	Night	49% 4 14% 24% 8%	3924
	11th to 20th	Night	52% 3 14% 20% 11%	3706
	21st to end	Night	53% 5% 19% 15% 8% 1	3503
April	1st to 10th	Night	48% 6% 18% 21% 7% 2	1683
	11th to 20th	Night	41% 6% 21% 24% 7% 1	1427
	21st to end	Night	35% 7% 22% 27% 8%	1220
May	1st to 10th	Night	55% 6% 13% 22% 3	1567
	11th to 20th	Night	29% 7% 24% 34% 6%	1084
	21st to end	Night	50% 5% 14% 26% 5%	677
June	1st to 10th	Night	48% 12% 13% 15% 12%	52
	July	1st to 10th	Night	88% 4 4 4	24
11th to 20th		Night	39% 7% 23% 30% 2	559
21st to end		Night	54% 9% 19% 16% 1	1165
August	1st to 10th	Night	49% 7% 25% 17% 2	1497
	11th to 20th	Night	57% 7% 25% 11% 1	1936
	21st to end	Night	50% 8% 23% 18% 1	2647
September	1st to 10th	Night	45% 9% 28% 15% 3	1659
	11th to 20th	Night	55% 6% 23% 15% 1	1923
	21st to end	Night	58% 7% 18% 16% 2	2104
October	1st to 10th	Night	52% 6% 21% 20% 2	4046
	11th to 20th	Night	61% 5% 18% 15% 1	4292
	21st to end	Night	62% 6% 17% 12% 1	5152
November	1st to 10th	Night	66% 6% 13% 14% 2	3265
	11th to 20th	Night	59% 6% 18% 13% 3	3568
	21st to end	Night	63% 5% 13% 16% 4	3840
December	1st to 10th	Night	59% 6% 14% 15% 6%	4004
	11th to 20th	Night	63% 7% 11% 13% 5%	5599
	21st to end	Night	61% 6% 9% 14% 10%	8172

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	3 5% 12% 35% 37% 8%	65
	11th to 20th	Day	9% 4 16% 32% 28% 11%	90
	21st to end	Day	8% 1 14% 35% 34% 7%	99
February	1st to 10th	Day	4 4 10% 33% 27% 23%	249
	11th to 20th	Day	7% 2 12% 33% 27% 19%	317
	21st to end	Day	5% 2 11% 29% 33% 21%	307
March	1st to 10th	Day	5% 2 9% 28% 33% 23%	370
	11th to 20th	Day	8% 3 11% 30% 30% 19%	370
	21st to end	Day	7% 4 15% 29% 29% 17%	592
April	1st to 10th	Day	7% 2 12% 31% 33% 14%	641
	11th to 20th	Day	5% 3 14% 29% 31% 17%	640
	21st to end	Day	4 2 10% 25% 34% 25%	650
May	1st to 10th	Day	10% 4 16% 25% 25% 19%	662
	11th to 20th	Day	9% 4 17% 30% 27% 13%	958
	21st to end	Day	10% 4 14% 29% 30% 13%	1145
June	1st to 10th	Day	9% 3 15% 30% 29% 14%	1141
	11th to 20th	Day	9% 4 11% 28% 33% 15%	1250
	21st to end	Day	9% 1 8% 32% 33% 16%	1250
July	1st to 10th	Day	10% 4 8% 26% 32% 21%	1136
	11th to 20th	Day	13% 3 11% 26% 27% 20%	1036
	21st to end	Day	11% 4 12% 23% 28% 23%	1036
August	1st to 10th	Day	15% 5% 13% 28% 23% 16%	758
	11th to 20th	Day	19% 5% 13% 24% 22% 16%	665
	21st to end	Day	22% 3 12% 20% 24% 19%	748
September	1st to 10th	Day	14% 4 12% 23% 25% 22%	680
	11th to 20th	Day	21% 3 13% 26% 25% 14%	544
	21st to end	Day	20% 5% 11% 23% 19% 22%	390
October	1st to 10th	Day	21% 6% 14% 26% 19% 15%	390
	11th to 20th	Day	20% 5% 15% 23% 20% 17%	390
	21st to end	Day	19% 5% 10% 20% 27% 20%	429
November	1st to 10th	Day	16% 7% 13% 24% 27% 13%	139
	11th to 20th	Day	6% 6% 17% 23% 26% 22%	100
	21st to end	Day	15% 5% 10% 30% 24% 15%	99
December	1st to 10th	Day	11% 5% 11% 35% 35% 5%	84
	January	1st to 10th	Night	7% 4 15% 30% 32% 13%	1130
11th to 20th		Night	12% 3 13% 34% 31% 8%	1116
21st to end		Night	8% 2 15% 38% 28% 10%	1034
February	1st to 10th	Night	5% 3 15% 29% 33% 15%	855
	11th to 20th	Night	9% 3 14% 36% 31% 7%	834
	21st to end	Night	8% 1 14% 34% 35% 7%	703
March	1st to 10th	Night	5% 3 10% 39% 30% 12%	736
	11th to 20th	Night	7% 2 16% 36% 30% 10%	633
	21st to end	Night	6% 4 14% 35% 30% 12%	627
April	1st to 10th	Night	10% 1 15% 32% 34% 8%	570
	11th to 20th	Night	8% 2 12% 41% 32% 6%	563
	21st to end	Night	5% 2 16% 35% 36% 6%	460
May	1st to 10th	Night	11% 3 16% 36% 31% 4	200
	11th to 20th	Night	5% 6% 20% 38% 29% 2	187
	21st to end	Night	12% 4 21% 29% 33% 2	206
June	1st to 10th	Night	12% 2 17% 37% 23% 10%	52
	July	1st to 10th	Night	18% 9% 55% 18%	11
11th to 20th		Night	14% 2 17% 24% 35% 8%	184
21st to end		Night	11% 3 11% 35% 33% 7%	208
August	1st to 10th	Night	16% 6% 12% 34% 24% 7%	219
	11th to 20th	Night	19% 3 15% 30% 27% 6%	398
	21st to end	Night	16% 3 11% 27% 31% 11%	627
September	1st to 10th	Night	13% 3 13% 28% 33% 10%	570
	11th to 20th	Night	24% 2 11% 31% 26% 6%	570
	21st to end	Night	24% 4 12% 31% 24% 5%	577
October	1st to 10th	Night	19% 5% 16% 30% 22% 7%	812
	11th to 20th	Night	21% 4 10% 30% 27% 7%	860
	21st to end	Night	19% 5% 9% 26% 30% 10%	946
November	1st to 10th	Night	19% 5% 17% 28% 24% 7%	880
	11th to 20th	Night	11% 4 11% 24% 32% 19%	1022
	21st to end	Night	13% 2 11% 29% 32% 13%	1200
December	1st to 10th	Night	14% 5% 12% 34% 28% 6%	1130
	11th to 20th	Night	12% 5% 13% 27% 31% 12%	1202
	21st to end	Night	8% 4 14% 33% 29% 13%	1316

Page generated at 2024-11-27 13:30:54. Version ac07

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