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 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	17% 12% 4 10% 6% 5% 4 4 5% 6% 28%	114031
	Night	16% 13% 5% 11% 6% 5% 4 3 4 5% 27%	115219
Transparency	Day	55% 6% 11% 18% 9% 1	117511
	Night	56% 6% 11% 16% 9% 1	119903
Seeing	Day	26% 19% 30% 17% 6% 2	15113
	Night	23% 16% 29% 22% 8% 1	24199

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% 20% 8% 16% 6% 6% 6% 3 4 4 15%	3597
	11th to 20th	Day	10% 17% 7% 19% 13% 6% 2 2 3 4 18%	3570
	21st to end	Day	7% 13% 8% 19% 6% 5% 5% 4 5% 5% 22%	3960
February	1st to 10th	Day	8% 20% 6% 13% 9% 6% 3 3 4 5% 22%	1766
	11th to 20th	Day	11% 17% 7% 14% 7% 5% 5% 2 4 5% 23%	1813
	21st to end	Day	14% 19% 6% 11% 7% 4 5% 3 5% 5% 23%	1650
March	1st to 10th	Day	16% 18% 5% 14% 7% 5% 4 2 3 4 22%	4476
	11th to 20th	Day	12% 16% 5% 12% 6% 4 4 2 4 6% 27%	4768
	21st to end	Day	17% 14% 4 9% 4 4 4 3 4 5% 32%	5916
April	1st to 10th	Day	18% 17% 5% 9% 4 3 3 3 4 6% 28%	2400
	11th to 20th	Day	23% 11% 4 8% 4 4 3 3 4 4 31%	2374
	21st to end	Day	20% 12% 4 8% 5% 4 4 4 4 5% 29%	2569
May	1st to 10th	Day	21% 11% 3 8% 5% 4 5% 4 5% 6% 27%	4566
	11th to 20th	Day	19% 8% 3 7% 5% 5% 5% 4 7% 8% 29%	4538
	21st to end	Day	19% 8% 3 8% 5% 5% 4 4 5% 6% 32%	4907
June	1st to 10th	Day	24% 10% 2 7% 4 5% 6% 4 6% 5% 26%	2660
	11th to 20th	Day	18% 7% 3 7% 6% 5% 5% 5% 5% 7% 31%	2660
	21st to end	Day	25% 9% 3 7% 6% 6% 5% 4 6% 6% 25%	2660
July	1st to 10th	Day	15% 8% 3 9% 6% 5% 6% 5% 6% 8% 29%	4440
	11th to 20th	Day	16% 7% 3 7% 6% 5% 5% 4 7% 8% 33%	4440
	21st to end	Day	14% 6% 2 6% 4 4 5% 4 5% 7% 42%	4814
August	1st to 10th	Day	16% 7% 2 8% 6% 6% 6% 5% 6% 8% 29%	4423
	11th to 20th	Day	18% 7% 3 7% 4 4 5% 5% 6% 7% 33%	4047
	21st to end	Day	16% 6% 3 7% 5% 5% 5% 4 7% 8% 35%	4180
September	1st to 10th	Day	18% 7% 2 6% 4 5% 4 3 5% 7% 39%	2280
	11th to 20th	Day	16% 7% 2 6% 4 4 4 3 5% 7% 42%	2225
	21st to end	Day	21% 9% 2 6% 3 4 4 3 4 6% 38%	2090
October	1st to 10th	Day	24% 10% 3 6% 4 3 4 4 5% 5% 31%	1920
	11th to 20th	Day	24% 14% 4 8% 5% 4 4 3 5% 4 24%	1875
	21st to end	Day	26% 15% 4 7% 5% 3 4 3 4 5% 23%	1881
November	1st to 10th	Day	17% 16% 4 8% 5% 3 4 3 5% 5% 29%	1761
	11th to 20th	Day	19% 16% 6% 11% 6% 4 4 4 4 5% 21%	1659
	21st to end	Day	18% 21% 7% 12% 5% 5% 4 3 3 4 19%	1600
December	1st to 10th	Day	17% 20% 10% 16% 5% 5% 4 3 3 4 13%	2600
	11th to 20th	Day	16% 20% 7% 13% 6% 4 4 3 4 4 19%	2986
	21st to end	Day	18% 16% 8% 10% 6% 4 4 3 4 5% 23%	3960
January	1st to 10th	Night	11% 23% 10% 16% 5% 5% 4 3 4 4 16%	6349
	11th to 20th	Night	8% 14% 8% 20% 13% 7% 3 3 4 5% 15%	6315
	21st to end	Night	6% 12% 8% 20% 9% 7% 6% 4 5% 5% 19%	6996
February	1st to 10th	Night	10% 16% 6% 13% 8% 6% 5% 4 4 6% 23%	2630
	11th to 20th	Night	10% 16% 7% 14% 7% 6% 5% 3 5% 4 24%	2472
	21st to end	Night	12% 17% 6% 12% 7% 4 5% 4 5% 6% 24%	1980
March	1st to 10th	Night	19% 15% 5% 12% 6% 4 4 3 4 4 24%	5364
	11th to 20th	Night	11% 15% 5% 11% 6% 4 5% 3 5% 7% 28%	5173
	21st to end	Night	16% 13% 5% 10% 6% 5% 4 3 5% 6% 28%	5014
April	1st to 10th	Night	21% 14% 3 8% 5% 4 3 3 4 6% 29%	2000
	11th to 20th	Night	18% 11% 4 7% 4 3 4 4 5% 6% 34%	1975
	21st to end	Night	20% 10% 4 8% 4 4 4 3 5% 5% 32%	1847
May	1st to 10th	Night	19% 11% 4 8% 5% 4 5% 4 5% 6% 29%	2594
	11th to 20th	Night	20% 8% 2 6% 4 4 4 3 4 7% 37%	2575
	21st to end	Night	20% 7% 3 7% 6% 5% 5% 4 5% 7% 32%	2784
June	1st to 10th	Night	19% 9% 3 7% 5% 5% 5% 4 6% 7% 30%	1520
	11th to 20th	Night	19% 8% 2 6% 4 4 4 3 6% 7% 38%	1520
	21st to end	Night	21% 7% 3 6% 4 5% 4 3 6% 6% 35%	1520
July	1st to 10th	Night	16% 6% 3 8% 6% 5% 5% 4 6% 7% 33%	2520
	11th to 20th	Night	17% 7% 3 6% 5% 4 4 4 6% 7% 38%	2520
	21st to end	Night	12% 4 2 5% 4 4 4 4 6% 8% 46%	2739
August	1st to 10th	Night	14% 7% 3 8% 5% 4 4 4 6% 7% 38%	2506
	11th to 20th	Night	19% 9% 2 7% 4 4 4 3 5% 5% 38%	2748
	21st to end	Night	19% 6% 2 6% 4 5% 4 3 5% 6% 39%	3476
September	1st to 10th	Night	15% 7% 2 6% 4 4 3 3 5% 7% 44%	1900
	11th to 20th	Night	17% 5% 2 5% 3 3 3 3 5% 6% 47%	1954
	21st to end	Night	18% 8% 2 5% 5% 2 3 3 5% 7% 42%	2090
October	1st to 10th	Night	19% 9% 2 7% 5% 5% 4 2 5% 5% 37%	2256
	11th to 20th	Night	23% 13% 3 8% 5% 4 4 3 4 5% 29%	2304
	21st to end	Night	24% 14% 4 9% 4 4 4 3 5% 6% 24%	2717
November	1st to 10th	Night	18% 13% 5% 9% 5% 5% 4 4 5% 5% 27%	2537
	11th to 20th	Night	16% 15% 5% 12% 6% 5% 4 4 5% 6% 23%	2740
	21st to end	Night	18% 20% 6% 12% 5% 4 5% 4 4 4 19%	2800
December	1st to 10th	Night	16% 16% 8% 18% 9% 6% 4 3 3 5% 13%	4580
	11th to 20th	Night	21% 17% 6% 12% 7% 4 3 2 3 4 20%	5208
	21st to end	Night	19% 21% 5% 10% 5% 4 3 2 3 4 24%	6996

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	71% 6% 7% 12% 4	3598
	11th to 20th	Day	71% 4 4 12% 7% 2	3600
	21st to end	Day	62% 6% 8% 12% 11% 1	3960
February	1st to 10th	Day	64% 4 7% 15% 8% 2	1766
	11th to 20th	Day	63% 4 9% 13% 9% 1	1822
	21st to end	Day	64% 4 8% 13% 10% 2	1650
March	1st to 10th	Day	66% 6% 5% 9% 11% 3	4479
	11th to 20th	Day	57% 5% 14% 11% 11% 2	4768
	21st to end	Day	54% 4 7% 15% 17% 2	5916
April	1st to 10th	Day	57% 4 9% 16% 11% 2	2400
	11th to 20th	Day	54% 5% 8% 19% 12% 2	2374
	21st to end	Day	57% 6% 8% 15% 12% 3	2569
May	1st to 10th	Day	54% 7% 9% 20% 8% 1	4580
	11th to 20th	Day	49% 9% 17% 16% 8% 1	4542
	21st to end	Day	50% 7% 10% 19% 13% 1	4907
June	1st to 10th	Day	56% 6% 11% 16% 10% 1	2660
	11th to 20th	Day	49% 7% 12% 19% 10% 3	2660
	21st to end	Day	58% 7% 10% 16% 8%	2660
July	1st to 10th	Day	48% 8% 15% 21% 7%	4370
	11th to 20th	Day	44% 8% 19% 23% 6%	4365
	21st to end	Day	40% 7% 15% 29% 9%	4661
August	1st to 10th	Day	50% 8% 16% 20% 5%	4409
	11th to 20th	Day	46% 9% 16% 25% 5%	4089
	21st to end	Day	44% 7% 16% 20% 12% 1	4180
September	1st to 10th	Day	44% 6% 14% 24% 12%	2280
	11th to 20th	Day	41% 7% 13% 28% 10% 1	2225
	21st to end	Day	47% 7% 11% 25% 10%	2090
October	1st to 10th	Day	50% 7% 11% 26% 6% 1	3193
	11th to 20th	Day	52% 8% 13% 21% 6%	3091
	21st to end	Day	54% 5% 20% 13% 7% 1	3081
November	1st to 10th	Day	55% 5% 13% 19% 7% 1	1761
	11th to 20th	Day	63% 5% 11% 12% 8% 1	1659
	21st to end	Day	68% 6% 9% 11% 4 1	1600
December	1st to 10th	Day	74% 4 8% 10% 3	2600
	11th to 20th	Day	67% 5% 7% 14% 7%	2986
	21st to end	Day	64% 5% 8% 14% 9%	3960
January	1st to 10th	Night	69% 7% 9% 11% 3	6349
	11th to 20th	Night	68% 7% 8% 11% 4 1	6360
	21st to end	Night	65% 6% 8% 8% 12% 1	6996
February	1st to 10th	Night	61% 5% 10% 17% 7% 1	2630
	11th to 20th	Night	61% 5% 10% 16% 8% 1	2474
	21st to end	Night	57% 5% 10% 16% 10% 2	1980
March	1st to 10th	Night	62% 6% 8% 10% 12% 3	5374
	11th to 20th	Night	54% 7% 12% 15% 10% 3	5174
	21st to end	Night	55% 5% 8% 19% 11% 3	5014
April	1st to 10th	Night	55% 4 9% 18% 12% 2	2000
	11th to 20th	Night	49% 6% 10% 20% 13% 2	1975
	21st to end	Night	52% 5% 9% 19% 13% 2	1847
May	1st to 10th	Night	52% 9% 13% 17% 8% 2	2600
	11th to 20th	Night	45% 9% 16% 16% 12% 2	2576
	21st to end	Night	50% 7% 11% 18% 12% 2	2785
June	1st to 10th	Night	49% 8% 12% 21% 9%	1520
	11th to 20th	Night	45% 7% 13% 21% 12% 2	1520
	21st to end	Night	49% 8% 12% 19% 12% 1	1520
July	1st to 10th	Night	48% 7% 17% 19% 9%	2480
	11th to 20th	Night	42% 8% 20% 24% 5%	2472
	21st to end	Night	34% 8% 20% 26% 11%	2651
August	1st to 10th	Night	43% 8% 16% 26% 7%	2496
	11th to 20th	Night	45% 7% 20% 22% 6%	2772
	21st to end	Night	43% 8% 15% 23% 10% 2	3476
September	1st to 10th	Night	39% 6% 15% 26% 13% 1	1900
	11th to 20th	Night	37% 6% 16% 31% 9% 1	1954
	21st to end	Night	41% 7% 13% 28% 11%	2090
October	1st to 10th	Night	46% 7% 14% 22% 11%	3763
	11th to 20th	Night	50% 7% 12% 22% 8%	3827
	21st to end	Night	53% 5% 17% 15% 9% 2	4467
November	1st to 10th	Night	56% 7% 12% 18% 6% 1	2537
	11th to 20th	Night	59% 6% 11% 15% 7% 2	2740
	21st to end	Night	65% 6% 11% 12% 5%	2800
December	1st to 10th	Night	70% 7% 12% 8% 3	4580
	11th to 20th	Night	68% 4 5% 14% 8% 1	5208
	21st to end	Night	65% 4 5% 11% 14% 1	6996

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% 25% 39% 16% 2	200
	11th to 20th	Day	28% 22% 33% 13% 5% 1	200
	21st to end	Day	23% 21% 39% 14% 3 1	220
February	1st to 10th	Day	29% 35% 30% 5% 2	284
	11th to 20th	Day	28% 27% 38% 7%	360
	21st to end	Day	28% 27% 32% 12% 1	414
March	1st to 10th	Day	28% 23% 31% 15% 2	500
	11th to 20th	Day	26% 27% 31% 13% 2 1	500
	21st to end	Day	33% 22% 25% 14% 5% 1	550
April	1st to 10th	Day	33% 19% 29% 12% 5% 1	500
	11th to 20th	Day	34% 21% 22% 14% 8% 1	492
	21st to end	Day	31% 23% 30% 12% 3 1	500
May	1st to 10th	Day	28% 22% 31% 14% 3 1	503
	11th to 20th	Day	26% 20% 29% 18% 6% 2	527
	21st to end	Day	26% 20% 30% 18% 5% 1	549
June	1st to 10th	Day	28% 16% 34% 16% 6% 1	490
	11th to 20th	Day	20% 21% 30% 19% 8% 2	490
	21st to end	Day	28% 17% 31% 17% 7% 1	490
July	1st to 10th	Day	17% 11% 39% 24% 7% 2	485
	11th to 20th	Day	16% 13% 38% 26% 6% 1	484
	21st to end	Day	17% 11% 36% 27% 7% 2	532
August	1st to 10th	Day	19% 12% 30% 27% 11% 1	486
	11th to 20th	Day	18% 9% 30% 26% 11% 6%	479
	21st to end	Day	17% 19% 28% 19% 10% 6%	539
September	1st to 10th	Day	20% 15% 30% 20% 10% 5%	490
	11th to 20th	Day	14% 14% 26% 25% 14% 8%	490
	21st to end	Day	22% 17% 24% 20% 11% 6%	490
October	1st to 10th	Day	29% 17% 25% 18% 9% 3	490
	11th to 20th	Day	32% 23% 23% 15% 6% 1	476
	21st to end	Day	35% 15% 29% 17% 4	429
November	1st to 10th	Day	35% 19% 27% 16% 4 1	395
	11th to 20th	Day	29% 23% 31% 13% 5%	259
	21st to end	Day	31% 30% 29% 10% 2	200
December	1st to 10th	Day	33% 19% 28% 16% 4 1	200
	11th to 20th	Day	28% 31% 30% 9% 2 1	200
	21st to end	Day	32% 24% 27% 12% 3 2	220
January	1st to 10th	Night	23% 23% 35% 15% 4	800
	11th to 20th	Night	25% 21% 29% 19% 6%	800
	21st to end	Night	15% 18% 39% 21% 6% 1	880
February	1st to 10th	Night	19% 25% 33% 19% 4	800
	11th to 20th	Night	21% 23% 38% 15% 3	783
	21st to end	Night	23% 19% 35% 20% 3	660
March	1st to 10th	Night	25% 19% 33% 20% 4	800
	11th to 20th	Night	25% 21% 31% 18% 4 1	800
	21st to end	Night	25% 17% 30% 22% 5% 1	880
April	1st to 10th	Night	30% 17% 27% 22% 5%	800
	11th to 20th	Night	25% 18% 28% 22% 6% 1	791
	21st to end	Night	27% 14% 31% 19% 8%	647
May	1st to 10th	Night	24% 13% 31% 23% 8% 2	400
	11th to 20th	Night	21% 13% 28% 29% 8% 1	394
	21st to end	Night	20% 13% 37% 23% 8%	423
June	1st to 10th	Night	23% 9% 32% 29% 8%	380
	11th to 20th	Night	20% 10% 25% 31% 13% 1	380
	21st to end	Night	23% 6% 23% 33% 14% 1	380
July	1st to 10th	Night	16% 6% 27% 36% 15%	370
	11th to 20th	Night	13% 6% 27% 36% 17% 1	368
	21st to end	Night	14% 7% 26% 38% 14% 1	416
August	1st to 10th	Night	15% 5% 19% 43% 17%	378
	11th to 20th	Night	13% 6% 23% 33% 23% 1	537
	21st to end	Night	17% 9% 26% 28% 17% 3	836
September	1st to 10th	Night	16% 10% 29% 31% 14% 1	760
	11th to 20th	Night	18% 8% 22% 31% 20% 2	760
	21st to end	Night	21% 12% 25% 24% 17% 2	760
October	1st to 10th	Night	23% 14% 25% 23% 14% 1	760
	11th to 20th	Night	28% 14% 28% 21% 8% 1	760
	21st to end	Night	29% 18% 27% 21% 5%	836
November	1st to 10th	Night	27% 19% 28% 19% 6% 1	780
	11th to 20th	Night	24% 20% 30% 17% 8% 1	800
	21st to end	Night	30% 24% 25% 16% 4 1	800
December	1st to 10th	Night	29% 20% 28% 16% 6% 1	800
	11th to 20th	Night	30% 23% 26% 15% 5% 1	800
	21st to end	Night	32% 20% 26% 16% 5%	880

Page generated at 2025-05-23 09:20:57. Version ac07

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