Univerciel
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Univerciel 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	17% 9% 3 8% 5% 5% 5% 4 5% 7% 33%	149888
	Night	17% 11% 4 9% 5% 5% 4 4 5% 6% 32%	141466
Transparency	Day	50% 6% 12% 21% 10% 1	153355
	Night	53% 6% 11% 19% 10% 1	146088
Seeing	Day	22% 15% 30% 22% 10% 3	16862
	Night	22% 11% 28% 28% 10% 1	25858

By Month

Percentage Cloud Cover NE (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	14% 15% 7% 15% 5% 5% 5% 3 5% 5% 21%	4661
	11th to 20th	Day	12% 20% 6% 14% 6% 5% 4 3 4 6% 20%	4650
	21st to end	Day	8% 15% 6% 15% 8% 7% 5% 4 5% 5% 21%	5304
February	1st to 10th	Day	12% 15% 4 13% 7% 5% 4 4 5% 6% 25%	1890
	11th to 20th	Day	13% 15% 6% 10% 6% 5% 4 3 5% 6% 27%	1854
	21st to end	Day	18% 14% 4 11% 7% 5% 4 4 5% 5% 24%	1730
March	1st to 10th	Day	20% 13% 4 10% 5% 5% 4 4 5% 5% 25%	4576
	11th to 20th	Day	14% 11% 4 9% 5% 5% 5% 3 6% 7% 30%	5061
	21st to end	Day	18% 11% 3 8% 5% 4 4 3 4 4 35%	5911
April	1st to 10th	Day	22% 11% 3 7% 5% 4 4 3 4 6% 32%	2520
	11th to 20th	Day	23% 9% 3 7% 4 4 4 3 4 5% 35%	2494
	21st to end	Day	22% 9% 4 7% 5% 5% 4 3 4 4 32%	2673
May	1st to 10th	Day	22% 9% 3 7% 5% 4 5% 4 6% 7% 28%	8237
	11th to 20th	Day	18% 7% 3 8% 6% 5% 5% 3 5% 7% 33%	8221
	21st to end	Day	22% 8% 2 6% 4 4 4 4 5% 6% 35%	9060
June	1st to 10th	Day	22% 7% 2 7% 5% 5% 4 4 6% 7% 31%	2940
	11th to 20th	Day	14% 6% 2 6% 5% 5% 5% 4 7% 7% 38%	2940
	21st to end	Day	20% 6% 2 6% 5% 5% 6% 5% 7% 7% 33%	2940
July	1st to 10th	Day	13% 5% 2 6% 5% 5% 5% 4 7% 10% 38%	8280
	11th to 20th	Day	11% 4 1 5% 4 4 5% 4 6% 9% 47%	8280
	21st to end	Day	12% 5% 2 5% 4 4 5% 4 7% 10% 42%	8993
August	1st to 10th	Day	16% 6% 3 8% 5% 5% 5% 4 6% 7% 36%	6421
	11th to 20th	Day	15% 4 2 6% 4 4 5% 5% 7% 9% 40%	5864
	21st to end	Day	15% 5% 2 6% 4 5% 5% 4 7% 10% 37%	6080
September	1st to 10th	Day	15% 5% 2 6% 4 4 5% 4 5% 8% 43%	2520
	11th to 20th	Day	12% 4 2 6% 4 4 4 3 5% 7% 50%	2515
	21st to end	Day	19% 5% 2 5% 4 4 4 3 5% 8% 41%	2231
October	1st to 10th	Day	21% 6% 2 7% 3 4 4 4 5% 6% 37%	2000
	11th to 20th	Day	24% 8% 2 7% 5% 5% 5% 4 5% 6% 30%	2000
	21st to end	Day	25% 10% 3 6% 5% 5% 5% 3 4 5% 29%	2027
November	1st to 10th	Day	16% 10% 3 7% 5% 4 4 5% 5% 6% 34%	1851
	11th to 20th	Day	19% 12% 4 8% 4 5% 5% 4 5% 6% 27%	1690
	21st to end	Day	23% 15% 4 8% 5% 5% 5% 4 4 6% 20%	1680
December	1st to 10th	Day	21% 20% 6% 9% 5% 4 5% 4 6% 6% 15%	2680
	11th to 20th	Day	18% 16% 4 11% 6% 5% 4 3 4 3 27%	3066
	21st to end	Day	23% 18% 4 9% 5% 4 5% 3 3 4 21%	4048
January	1st to 10th	Night	14% 20% 8% 14% 6% 4 3 3 4 5% 21%	8234
	11th to 20th	Night	12% 18% 6% 15% 7% 6% 5% 3 4 4 19%	8235
	21st to end	Night	11% 17% 5% 12% 7% 7% 6% 4 5% 6% 22%	8859
February	1st to 10th	Night	13% 14% 5% 12% 6% 5% 5% 4 5% 5% 26%	2730
	11th to 20th	Night	13% 13% 5% 11% 7% 5% 4 3 4 5% 29%	2652
	21st to end	Night	16% 13% 4 9% 6% 4 4 4 5% 5% 29%	2076
March	1st to 10th	Night	23% 13% 4 9% 5% 4 4 3 3 4 29%	5484
	11th to 20th	Night	13% 13% 3 10% 5% 5% 5% 4 6% 8% 30%	5100
	21st to end	Night	19% 10% 4 8% 5% 4 4 3 5% 6% 34%	5262
April	1st to 10th	Night	21% 10% 3 8% 5% 3 3 3 5% 6% 33%	2100
	11th to 20th	Night	20% 8% 3 6% 5% 4 4 4 5% 5% 36%	2075
	21st to end	Night	22% 9% 3 6% 3 4 3 3 5% 6% 36%	1961
May	1st to 10th	Night	21% 9% 3 9% 5% 5% 5% 4 6% 7% 26%	4660
	11th to 20th	Night	18% 7% 2 7% 5% 4 5% 4 5% 6% 37%	4639
	21st to end	Night	21% 7% 3 7% 5% 4 5% 4 5% 6% 34%	5114
June	1st to 10th	Night	16% 6% 2 7% 5% 5% 4 5% 6% 8% 36%	1680
	11th to 20th	Night	15% 6% 3 6% 4 4 4 4 5% 6% 43%	1680
	21st to end	Night	18% 7% 2 5% 5% 5% 4 4 6% 7% 36%	1680
July	1st to 10th	Night	13% 5% 2 7% 5% 6% 5% 5% 7% 9% 38%	4680
	11th to 20th	Night	12% 5% 2 5% 4 4 4 4 6% 7% 49%	4680
	21st to end	Night	13% 5% 2 7% 5% 4 5% 4 6% 6% 43%	5084
August	1st to 10th	Night	15% 6% 3 7% 5% 4 6% 4 6% 8% 36%	3712
	11th to 20th	Night	15% 4 2 6% 4 4 4 4 5% 7% 45%	4134
	21st to end	Night	14% 5% 2 7% 5% 5% 5% 4 6% 7% 41%	5045
September	1st to 10th	Night	12% 5% 1 6% 5% 4 4 3 5% 6% 47%	2100
	11th to 20th	Night	14% 5% 1 4 4 3 3 3 5% 6% 52%	2105
	21st to end	Night	18% 5% 2 6% 5% 3 4 3 4 6% 45%	2343
October	1st to 10th	Night	19% 7% 2 5% 4 4 5% 4 4 6% 42%	2400
	11th to 20th	Night	21% 6% 2 7% 6% 5% 5% 3 5% 6% 33%	2400
	21st to end	Night	22% 10% 3 7% 5% 4 4 4 4 6% 30%	2812
November	1st to 10th	Night	20% 9% 3 6% 4 4 4 4 5% 6% 34%	2667
	11th to 20th	Night	19% 10% 3 9% 5% 4 5% 3 5% 6% 30%	2925
	21st to end	Night	21% 12% 4 9% 5% 5% 4 4 5% 6% 25%	2940
December	1st to 10th	Night	19% 17% 5% 10% 6% 5% 5% 4 5% 6% 18%	4720
	11th to 20th	Night	23% 14% 4 8% 5% 4 4 3 4 4 27%	5348
	21st to end	Night	27% 17% 4 9% 4 4 4 3 4 4 22%	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	66% 6% 9% 15% 4	4662
	11th to 20th	Day	66% 4 9% 11% 9%	4680
	21st to end	Day	64% 6% 11% 10% 8% 1	5304
February	1st to 10th	Day	60% 5% 10% 18% 6% 1	1890
	11th to 20th	Day	58% 4 12% 16% 8% 1	1863
	21st to end	Day	61% 5% 10% 13% 10% 1	1730
March	1st to 10th	Day	61% 5% 9% 12% 11% 3	4579
	11th to 20th	Day	52% 6% 17% 15% 10% 1	5061
	21st to end	Day	52% 4 6% 18% 17% 2	5911
April	1st to 10th	Day	54% 4 8% 18% 12% 3	2520
	11th to 20th	Day	52% 4 6% 21% 15% 2	2494
	21st to end	Day	56% 4 8% 16% 14% 3	2673
May	1st to 10th	Day	53% 6% 8% 22% 10% 1	8249
	11th to 20th	Day	49% 7% 13% 21% 9% 1	8225
	21st to end	Day	49% 5% 10% 22% 12% 1	9061
June	1st to 10th	Day	52% 6% 10% 19% 12% 1	2940
	11th to 20th	Day	43% 7% 12% 24% 12% 2	2940
	21st to end	Day	47% 8% 13% 21% 10% 1	2940
July	1st to 10th	Day	41% 7% 15% 26% 12%	8210
	11th to 20th	Day	33% 6% 14% 34% 12% 1	8205
	21st to end	Day	36% 7% 16% 31% 9%	8795
August	1st to 10th	Day	48% 6% 15% 19% 10% 1	6407
	11th to 20th	Day	39% 7% 17% 29% 7% 1	5903
	21st to end	Day	41% 7% 20% 23% 9%	6080
September	1st to 10th	Day	39% 7% 14% 29% 11%	2520
	11th to 20th	Day	35% 6% 13% 33% 13% 1	2515
	21st to end	Day	42% 7% 13% 25% 13%	2231
October	1st to 10th	Day	46% 6% 11% 28% 8%	3260
	11th to 20th	Day	46% 7% 15% 24% 7% 1	3240
	21st to end	Day	49% 5% 19% 21% 7%	3252
November	1st to 10th	Day	49% 7% 13% 22% 7% 1	1851
	11th to 20th	Day	57% 6% 13% 15% 8% 1	1690
	21st to end	Day	64% 7% 12% 10% 6% 1	1680
December	1st to 10th	Day	69% 6% 13% 10% 2	2680
	11th to 20th	Day	64% 4 10% 15% 7%	3066
	21st to end	Day	67% 5% 8% 15% 5%	4048
January	1st to 10th	Night	67% 5% 10% 13% 5%	8234
	11th to 20th	Night	68% 6% 9% 12% 6%	8280
	21st to end	Night	62% 5% 8% 12% 11% 1	8859
February	1st to 10th	Night	60% 5% 11% 16% 7% 1	2730
	11th to 20th	Night	59% 4 9% 20% 7%	2654
	21st to end	Night	56% 6% 9% 19% 10% 1	2076
March	1st to 10th	Night	61% 4 7% 15% 12% 3	5494
	11th to 20th	Night	52% 7% 15% 15% 8% 3	5101
	21st to end	Night	52% 4 7% 21% 13% 2	5262
April	1st to 10th	Night	53% 5% 9% 17% 14% 2	2100
	11th to 20th	Night	50% 6% 7% 20% 15% 1	2075
	21st to end	Night	50% 4 8% 17% 17% 3	1961
May	1st to 10th	Night	55% 8% 9% 19% 8% 2	4666
	11th to 20th	Night	46% 7% 12% 21% 13% 1	4640
	21st to end	Night	49% 5% 10% 19% 15% 1	5115
June	1st to 10th	Night	45% 7% 11% 24% 11% 2	1680
	11th to 20th	Night	40% 7% 10% 25% 15% 2	1680
	21st to end	Night	46% 9% 11% 20% 13% 1	1680
July	1st to 10th	Night	41% 8% 17% 21% 13% 1	4640
	11th to 20th	Night	33% 6% 13% 33% 13%	4632
	21st to end	Night	41% 7% 12% 27% 13%	4967
August	1st to 10th	Night	45% 7% 15% 20% 10% 2	3702
	11th to 20th	Night	38% 6% 15% 33% 7%	4161
	21st to end	Night	42% 8% 15% 25% 10% 1	5045
September	1st to 10th	Night	37% 8% 11% 30% 14% 1	2100
	11th to 20th	Night	33% 8% 12% 35% 11% 1	2105
	21st to end	Night	42% 4 11% 28% 14%	2343
October	1st to 10th	Night	39% 8% 13% 28% 12% 1	3920
	11th to 20th	Night	43% 7% 14% 26% 9%	3899
	21st to end	Night	46% 6% 17% 21% 9%	4537
November	1st to 10th	Night	51% 6% 15% 20% 8%	2667
	11th to 20th	Night	55% 6% 12% 17% 10% 1	2925
	21st to end	Night	61% 6% 12% 15% 5%	2940
December	1st to 10th	Night	66% 6% 13% 12% 3	4720
	11th to 20th	Night	62% 4 7% 15% 11% 1	5348
	21st to end	Night	67% 4 7% 13% 9%	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	24% 15% 33% 23% 4	220
	11th to 20th	Day	24% 18% 38% 14% 5% 1	220
	21st to end	Day	20% 15% 37% 23% 5%	275
February	1st to 10th	Day	29% 21% 32% 15% 3	330
	11th to 20th	Day	26% 25% 35% 13% 1	341
	21st to end	Day	27% 18% 33% 19% 3	446
March	1st to 10th	Day	25% 18% 33% 19% 6%	540
	11th to 20th	Day	27% 19% 31% 19% 4 1	540
	21st to end	Day	28% 21% 29% 14% 7% 1	594
April	1st to 10th	Day	28% 23% 29% 14% 6%	540
	11th to 20th	Day	31% 19% 23% 16% 9% 1	532
	21st to end	Day	28% 20% 32% 13% 6% 1	540
May	1st to 10th	Day	24% 16% 31% 20% 7% 2	543
	11th to 20th	Day	19% 17% 32% 19% 10% 2	567
	21st to end	Day	21% 15% 30% 23% 9% 2	617
June	1st to 10th	Day	24% 11% 29% 24% 10% 2	570
	11th to 20th	Day	16% 15% 31% 25% 12% 2	570
	21st to end	Day	21% 12% 30% 23% 11% 2	570
July	1st to 10th	Day	12% 8% 28% 34% 13% 4	565
	11th to 20th	Day	13% 9% 32% 27% 15% 3	564
	21st to end	Day	12% 8% 30% 31% 15% 4	620
August	1st to 10th	Day	14% 8% 25% 32% 18% 3	566
	11th to 20th	Day	14% 9% 23% 29% 18% 7%	559
	21st to end	Day	14% 10% 28% 26% 15% 7%	627
September	1st to 10th	Day	17% 11% 27% 22% 15% 8%	570
	11th to 20th	Day	11% 8% 23% 25% 21% 13%	570
	21st to end	Day	19% 12% 27% 23% 14% 6%	562
October	1st to 10th	Day	23% 12% 26% 22% 14% 5%	530
	11th to 20th	Day	26% 15% 32% 18% 8% 1	530
	21st to end	Day	29% 14% 28% 24% 5% 1	487
November	1st to 10th	Day	26% 17% 29% 18% 9% 1	425
	11th to 20th	Day	24% 18% 37% 15% 6% 1	230
	21st to end	Day	31% 19% 30% 15% 3 1	220
December	1st to 10th	Day	26% 15% 35% 20% 4	220
	11th to 20th	Day	25% 22% 36% 15% 2	220
	21st to end	Day	32% 19% 31% 13% 4 1	242
January	1st to 10th	Night	27% 13% 34% 23% 3	840
	11th to 20th	Night	28% 16% 28% 22% 6%	840
	21st to end	Night	19% 10% 35% 28% 7% 1	924
February	1st to 10th	Night	21% 13% 34% 27% 4	840
	11th to 20th	Night	19% 17% 37% 22% 4	823
	21st to end	Night	23% 15% 29% 29% 4	692
March	1st to 10th	Night	25% 15% 33% 23% 4	840
	11th to 20th	Night	24% 17% 33% 22% 4	840
	21st to end	Night	24% 15% 29% 24% 7%	924
April	1st to 10th	Night	28% 12% 30% 25% 5%	840
	11th to 20th	Night	23% 16% 31% 22% 8%	831
	21st to end	Night	27% 12% 28% 25% 8% 1	701
May	1st to 10th	Night	24% 7% 28% 30% 9% 2	420
	11th to 20th	Night	22% 9% 26% 33% 9%	414
	21st to end	Night	16% 8% 38% 27% 10%	455
June	1st to 10th	Night	18% 5% 28% 39% 11%	420
	11th to 20th	Night	16% 7% 27% 35% 13% 1	420
	21st to end	Night	19% 6% 26% 34% 14% 1	420
July	1st to 10th	Night	9% 4 27% 45% 16%	410
	11th to 20th	Night	12% 4 22% 45% 17%	408
	21st to end	Night	10% 3 26% 41% 17% 2	460
August	1st to 10th	Night	12% 4 20% 41% 23%	438
	11th to 20th	Night	14% 3 18% 37% 25% 3	637
	21st to end	Night	14% 7% 21% 36% 20% 2	924
September	1st to 10th	Night	13% 7% 26% 34% 19% 1	840
	11th to 20th	Night	16% 6% 19% 32% 24% 4	840
	21st to end	Night	21% 7% 23% 27% 21% 2	833
October	1st to 10th	Night	22% 8% 26% 25% 17% 2	800
	11th to 20th	Night	24% 11% 29% 27% 9% 1	800
	21st to end	Night	27% 12% 27% 28% 6%	880
November	1st to 10th	Night	27% 12% 25% 27% 8% 1	820
	11th to 20th	Night	24% 14% 33% 19% 9%	840
	21st to end	Night	28% 16% 28% 23% 5%	840
December	1st to 10th	Night	29% 14% 29% 23% 4	840
	11th to 20th	Night	29% 14% 31% 20% 5% 1	840
	21st to end	Night	34% 13% 29% 19% 4	924

Page generated at 2026-09-26 04:18:40. Version ac07

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