Observatoire d'Astronomie Berrada
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Observatoire d'Astronomie Berrada 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% 11% 4 9% 5% 5% 5% 4 5% 6% 28%	149850
	Night	16% 13% 5% 11% 6% 5% 4 3 5% 6% 28%	141522
Transparency	Day	54% 6% 12% 18% 9% 1	153284
	Night	55% 6% 11% 17% 9% 1	146177
Seeing	Day	26% 19% 30% 17% 6% 2	16875
	Night	23% 16% 29% 23% 8% 1	25774

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	12% 17% 7% 18% 6% 6% 6% 3 4 5% 17%	4661
	11th to 20th	Day	8% 19% 8% 20% 12% 5% 3 2 3 4 17%	4650
	21st to end	Day	6% 12% 8% 19% 7% 7% 6% 4 5% 6% 21%	5124
February	1st to 10th	Day	8% 19% 6% 13% 9% 6% 3 3 5% 5% 23%	1855
	11th to 20th	Day	11% 17% 7% 14% 7% 5% 5% 2 4 6% 24%	1906
	21st to end	Day	13% 18% 6% 11% 7% 4 5% 3 5% 5% 22%	1730
March	1st to 10th	Day	16% 18% 5% 14% 7% 5% 4 2 3 4 22%	4576
	11th to 20th	Day	12% 16% 5% 12% 6% 4 4 3 4 6% 27%	4873
	21st to end	Day	16% 14% 4 10% 4 4 4 3 4 5% 31%	6047
April	1st to 10th	Day	18% 17% 5% 9% 4 3 3 3 4 6% 27%	2520
	11th to 20th	Day	23% 11% 4 8% 4 4 3 3 4 4 31%	2494
	21st to end	Day	20% 12% 4 8% 5% 4 4 3 4 5% 29%	2697
May	1st to 10th	Day	23% 12% 4 8% 5% 5% 5% 4 6% 6% 23%	8237
	11th to 20th	Day	21% 9% 3 7% 5% 5% 5% 4 6% 7% 27%	8221
	21st to end	Day	22% 10% 3 7% 5% 5% 4 4 5% 6% 29%	9060
June	1st to 10th	Day	24% 10% 2 7% 4 5% 5% 4 6% 5% 27%	2940
	11th to 20th	Day	18% 7% 3 8% 6% 5% 5% 5% 5% 7% 30%	2940
	21st to end	Day	24% 8% 3 7% 5% 5% 5% 4 6% 6% 26%	2940
July	1st to 10th	Day	16% 7% 3 7% 5% 5% 6% 4 6% 8% 33%	8280
	11th to 20th	Day	13% 5% 2 6% 5% 4 5% 4 7% 9% 40%	8280
	21st to end	Day	13% 6% 2 6% 5% 5% 5% 5% 6% 10% 36%	8993
August	1st to 10th	Day	18% 8% 3 8% 6% 6% 6% 4 6% 8% 30%	6483
	11th to 20th	Day	17% 7% 2 6% 4 4 5% 5% 7% 9% 33%	5955
	21st to end	Day	15% 7% 3 7% 5% 4 5% 5% 7% 9% 34%	6080
September	1st to 10th	Day	17% 7% 2 6% 4 5% 4 3 6% 7% 38%	2520
	11th to 20th	Day	15% 6% 2 6% 4 4 4 3 5% 7% 43%	2459
	21st to end	Day	20% 8% 2 6% 4 4 3 3 4 5% 40%	2288
October	1st to 10th	Day	24% 10% 3 6% 4 3 4 4 5% 6% 33%	2021
	11th to 20th	Day	23% 14% 4 8% 5% 4 4 3 5% 4 25%	1973
	21st to end	Day	26% 15% 4 7% 5% 3 4 3 4 5% 23%	1980
November	1st to 10th	Day	18% 16% 5% 8% 5% 3 4 3 4 5% 28%	1851
	11th to 20th	Day	19% 17% 6% 11% 6% 4 4 4 4 5% 21%	1742
	21st to end	Day	18% 21% 7% 13% 5% 5% 4 3 3 4 18%	1680
December	1st to 10th	Day	17% 19% 10% 16% 5% 4 4 3 3 4 14%	2680
	11th to 20th	Day	15% 20% 7% 14% 7% 4 4 3 4 4 19%	3066
	21st to end	Day	17% 16% 8% 11% 6% 4 4 3 4 5% 23%	4048
January	1st to 10th	Night	10% 20% 8% 17% 6% 5% 5% 3 4 4 17%	8234
	11th to 20th	Night	8% 16% 9% 22% 13% 7% 3 2 3 4 13%	8235
	21st to end	Night	5% 10% 8% 19% 9% 8% 7% 4 6% 5% 18%	9057
February	1st to 10th	Night	10% 16% 6% 13% 8% 6% 5% 4 4 6% 23%	2761
	11th to 20th	Night	10% 16% 7% 14% 7% 6% 5% 3 5% 4 24%	2599
	21st to end	Night	11% 16% 6% 12% 7% 4 5% 4 5% 6% 24%	2076
March	1st to 10th	Night	19% 15% 5% 12% 6% 4 4 3 4 4 24%	5484
	11th to 20th	Night	11% 15% 5% 11% 6% 4 5% 3 5% 7% 27%	5288
	21st to end	Night	16% 13% 5% 10% 6% 5% 4 3 5% 6% 28%	5125
April	1st to 10th	Night	21% 14% 3 8% 5% 3 3 3 4 6% 29%	2100
	11th to 20th	Night	18% 11% 4 7% 4 3 4 4 5% 6% 34%	2075
	21st to end	Night	20% 10% 4 8% 4 4 4 3 5% 5% 33%	1940
May	1st to 10th	Night	18% 12% 4 8% 5% 5% 5% 4 6% 6% 27%	4660
	11th to 20th	Night	21% 9% 3 7% 4 4 4 3 5% 7% 32%	4639
	21st to end	Night	22% 10% 3 7% 4 4 4 4 5% 7% 29%	5114
June	1st to 10th	Night	18% 9% 3 6% 5% 4 5% 4 6% 7% 32%	1680
	11th to 20th	Night	20% 8% 2 6% 4 4 4 3 6% 6% 37%	1680
	21st to end	Night	21% 7% 3 6% 4 5% 5% 3 5% 6% 36%	1680
July	1st to 10th	Night	16% 7% 2 7% 5% 5% 5% 4 7% 8% 34%	4680
	11th to 20th	Night	13% 7% 2 6% 4 4 3 4 5% 7% 44%	4680
	21st to end	Night	14% 5% 2 6% 5% 4 4 4 6% 8% 42%	5084
August	1st to 10th	Night	17% 7% 3 7% 4 4 4 4 6% 7% 36%	3666
	11th to 20th	Night	17% 8% 2 7% 4 4 4 3 5% 6% 38%	4029
	21st to end	Night	20% 8% 2 5% 3 4 4 3 5% 6% 40%	5045
September	1st to 10th	Night	15% 7% 2 6% 3 4 3 3 5% 7% 44%	2100
	11th to 20th	Night	16% 5% 2 5% 3 3 3 3 5% 6% 48%	2160
	21st to end	Night	18% 8% 2 5% 4 3 3 3 5% 7% 42%	2289
October	1st to 10th	Night	18% 9% 2 7% 5% 4 4 2 5% 5% 39%	2375
	11th to 20th	Night	22% 13% 3 8% 5% 4 4 3 4 5% 30%	2425
	21st to end	Night	24% 14% 4 9% 4 4 4 3 5% 6% 24%	2860
November	1st to 10th	Night	18% 13% 5% 9% 5% 4 4 4 5% 5% 27%	2667
	11th to 20th	Night	16% 15% 6% 12% 6% 5% 4 4 4 6% 22%	2877
	21st to end	Night	18% 20% 6% 12% 5% 4 5% 3 4 4 19%	2940
December	1st to 10th	Night	15% 15% 8% 18% 9% 6% 4 3 3 5% 14%	4720
	11th to 20th	Night	21% 17% 6% 12% 7% 4 3 2 3 4 20%	5348
	21st to end	Night	18% 21% 5% 10% 6% 4 3 2 3 4 24%	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	68% 5% 8% 14% 5%	4662
	11th to 20th	Day	73% 3 3 10% 9% 2	4680
	21st to end	Day	62% 6% 8% 11% 12% 1	5124
February	1st to 10th	Day	62% 4 7% 17% 8% 2	1855
	11th to 20th	Day	62% 3 9% 14% 10% 1	1915
	21st to end	Day	63% 4 8% 13% 10% 2	1730
March	1st to 10th	Day	65% 6% 6% 9% 11% 3	4579
	11th to 20th	Day	58% 5% 14% 11% 11% 2	4873
	21st to end	Day	54% 4 7% 15% 17% 2	6047
April	1st to 10th	Day	58% 4 9% 16% 11% 2	2520
	11th to 20th	Day	55% 5% 8% 19% 11% 2	2494
	21st to end	Day	56% 6% 8% 16% 12% 3	2697
May	1st to 10th	Day	58% 7% 9% 18% 8% 1	8249
	11th to 20th	Day	52% 8% 14% 18% 7% 1	8225
	21st to end	Day	53% 6% 10% 19% 11% 1	9061
June	1st to 10th	Day	55% 6% 10% 17% 10% 1	2940
	11th to 20th	Day	49% 7% 12% 20% 9% 2	2940
	21st to end	Day	56% 7% 10% 18% 8%	2940
July	1st to 10th	Day	46% 7% 14% 23% 10%	8210
	11th to 20th	Day	37% 8% 18% 29% 9%	8205
	21st to end	Day	40% 8% 18% 27% 7%	8795
August	1st to 10th	Day	51% 7% 16% 18% 7% 1	6469
	11th to 20th	Day	43% 9% 17% 24% 6%	5997
	21st to end	Day	44% 7% 17% 21% 10% 1	6080
September	1st to 10th	Day	43% 6% 15% 25% 12%	2520
	11th to 20th	Day	39% 7% 13% 30% 11% 1	2459
	21st to end	Day	45% 7% 11% 24% 13%	2288
October	1st to 10th	Day	48% 7% 11% 26% 7% 1	3294
	11th to 20th	Day	51% 7% 13% 21% 7% 1	3189
	21st to end	Day	54% 5% 20% 14% 7% 1	3180
November	1st to 10th	Day	56% 5% 12% 19% 7% 1	1851
	11th to 20th	Day	64% 5% 11% 12% 8% 1	1742
	21st to end	Day	69% 6% 9% 11% 4 1	1680
December	1st to 10th	Day	74% 4 8% 10% 4	2680
	11th to 20th	Day	68% 4 7% 14% 7%	3066
	21st to end	Day	64% 5% 8% 14% 9%	4048
January	1st to 10th	Night	67% 6% 9% 13% 4 1	8234
	11th to 20th	Night	73% 6% 7% 9% 5% 1	8280
	21st to end	Night	63% 6% 8% 10% 12% 1	9057
February	1st to 10th	Night	60% 5% 9% 17% 7% 1	2761
	11th to 20th	Night	60% 5% 10% 16% 9% 1	2601
	21st to end	Night	58% 5% 10% 16% 10% 2	2076
March	1st to 10th	Night	61% 6% 9% 10% 12% 3	5494
	11th to 20th	Night	55% 7% 12% 14% 10% 3	5289
	21st to end	Night	56% 5% 8% 19% 11% 3	5125
April	1st to 10th	Night	55% 5% 9% 18% 12% 2	2100
	11th to 20th	Night	49% 6% 10% 20% 13% 2	2075
	21st to end	Night	51% 5% 8% 19% 14% 2	1940
May	1st to 10th	Night	54% 8% 12% 18% 8% 1	4666
	11th to 20th	Night	50% 8% 13% 19% 9% 1	4640
	21st to end	Night	53% 6% 10% 18% 12% 1	5115
June	1st to 10th	Night	48% 7% 11% 22% 11% 1	1680
	11th to 20th	Night	46% 6% 13% 21% 12% 2	1680
	21st to end	Night	48% 8% 12% 20% 11% 1	1680
July	1st to 10th	Night	44% 8% 17% 21% 10%	4640
	11th to 20th	Night	38% 7% 19% 30% 6%	4632
	21st to end	Night	39% 8% 18% 27% 9%	4967
August	1st to 10th	Night	45% 7% 16% 22% 8% 1	3656
	11th to 20th	Night	44% 7% 20% 24% 6%	4053
	21st to end	Night	44% 7% 16% 23% 10% 1	5045
September	1st to 10th	Night	38% 6% 15% 27% 13% 1	2100
	11th to 20th	Night	36% 6% 16% 33% 10% 1	2160
	21st to end	Night	41% 7% 13% 26% 13%	2289
October	1st to 10th	Night	45% 7% 14% 22% 12% 1	3882
	11th to 20th	Night	49% 7% 12% 22% 9%	3948
	21st to end	Night	52% 5% 17% 15% 9% 2	4610
November	1st to 10th	Night	57% 6% 12% 18% 6% 1	2667
	11th to 20th	Night	60% 6% 11% 15% 7% 2	2877
	21st to end	Night	66% 6% 11% 12% 5%	2940
December	1st to 10th	Night	70% 7% 11% 8% 3	4720
	11th to 20th	Night	68% 4 6% 14% 8% 1	5348
	21st to end	Night	65% 4 5% 11% 14% 1	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	19% 25% 38% 16% 2	220
	11th to 20th	Day	30% 22% 33% 11% 4	220
	21st to end	Day	23% 20% 38% 15% 3 1	242
February	1st to 10th	Day	26% 33% 32% 7% 2	313
	11th to 20th	Day	27% 26% 38% 8%	393
	21st to end	Day	27% 26% 34% 12% 1	446
March	1st to 10th	Day	28% 24% 31% 14% 2	540
	11th to 20th	Day	29% 25% 31% 12% 2 1	540
	21st to end	Day	33% 23% 25% 13% 4 1	594
April	1st to 10th	Day	33% 20% 29% 12% 5% 1	540
	11th to 20th	Day	35% 20% 21% 14% 8% 1	532
	21st to end	Day	33% 22% 29% 12% 4 1	540
May	1st to 10th	Day	28% 22% 31% 14% 3 1	543
	11th to 20th	Day	27% 20% 29% 17% 5% 1	567
	21st to end	Day	28% 22% 28% 17% 4 1	617
June	1st to 10th	Day	28% 15% 35% 16% 6% 1	570
	11th to 20th	Day	22% 21% 30% 18% 8% 1	570
	21st to end	Day	25% 17% 33% 17% 7% 1	570
July	1st to 10th	Day	18% 13% 38% 23% 7% 2	565
	11th to 20th	Day	17% 14% 37% 25% 6% 1	564
	21st to end	Day	16% 13% 35% 26% 7% 2	620
August	1st to 10th	Day	18% 12% 30% 29% 10% 2	566
	11th to 20th	Day	17% 9% 32% 26% 10% 6%	559
	21st to end	Day	18% 18% 28% 19% 11% 6%	627
September	1st to 10th	Day	21% 15% 30% 20% 10% 4	570
	11th to 20th	Day	14% 15% 25% 25% 14% 8%	570
	21st to end	Day	21% 17% 26% 20% 11% 6%	562
October	1st to 10th	Day	27% 16% 26% 19% 9% 3	530
	11th to 20th	Day	31% 22% 25% 15% 6% 1	514
	21st to end	Day	35% 15% 29% 17% 4	462
November	1st to 10th	Day	35% 19% 27% 15% 3 1	425
	11th to 20th	Day	28% 22% 31% 13% 5%	282
	21st to end	Day	32% 30% 27% 10% 1	220
December	1st to 10th	Day	30% 20% 29% 16% 3 1	220
	11th to 20th	Day	28% 30% 31% 8% 2	220
	21st to end	Day	31% 24% 29% 12% 3 2	242
January	1st to 10th	Night	23% 23% 35% 15% 4	840
	11th to 20th	Night	25% 22% 29% 18% 6%	840
	21st to end	Night	16% 18% 38% 20% 6% 1	924
February	1st to 10th	Night	18% 24% 33% 20% 4 1	840
	11th to 20th	Night	21% 24% 37% 15% 3	823
	21st to end	Night	23% 19% 35% 21% 3	692
March	1st to 10th	Night	25% 19% 33% 19% 3	840
	11th to 20th	Night	26% 21% 30% 17% 4 1	840
	21st to end	Night	25% 17% 30% 21% 5% 1	924
April	1st to 10th	Night	30% 17% 27% 21% 4	840
	11th to 20th	Night	25% 18% 28% 22% 5% 1	831
	21st to end	Night	27% 15% 31% 19% 8%	680
May	1st to 10th	Night	23% 13% 31% 23% 8% 1	420
	11th to 20th	Night	21% 13% 29% 28% 7%	414
	21st to end	Night	21% 13% 36% 23% 7%	455
June	1st to 10th	Night	22% 10% 32% 28% 8%	420
	11th to 20th	Night	20% 12% 25% 31% 12% 1	420
	21st to end	Night	22% 7% 23% 34% 14%	420
July	1st to 10th	Night	15% 6% 28% 37% 13%	410
	11th to 20th	Night	14% 7% 26% 38% 16% 1	408
	21st to end	Night	14% 7% 27% 37% 14% 1	460
August	1st to 10th	Night	15% 5% 19% 43% 18%	418
	11th to 20th	Night	13% 6% 24% 34% 22% 1	594
	21st to end	Night	18% 9% 25% 28% 16% 2	924
September	1st to 10th	Night	17% 10% 28% 31% 13% 1	840
	11th to 20th	Night	17% 8% 22% 31% 20% 2	840
	21st to end	Night	20% 11% 26% 25% 17% 2	833
October	1st to 10th	Night	22% 13% 26% 24% 14% 1	800
	11th to 20th	Night	28% 14% 28% 21% 8% 1	800
	21st to end	Night	29% 18% 27% 22% 5%	880
November	1st to 10th	Night	28% 19% 28% 19% 5% 1	820
	11th to 20th	Night	25% 20% 30% 16% 8% 1	840
	21st to end	Night	30% 24% 25% 16% 4 1	840
December	1st to 10th	Night	28% 20% 29% 17% 5% 1	840
	11th to 20th	Night	29% 24% 26% 15% 5% 1	840
	21st to end	Night	33% 20% 26% 15% 5%	924

Page generated at 2026-09-26 04:18:39. Version ac07

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