Bremen
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bremen clear sky chart from 2005-11-06 to 2026-02-01.

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	14% 9% 4 8% 5% 5% 4 4 6% 7% 34%	127208
	Night	15% 11% 4 9% 5% 4 4 3 5% 6% 34%	125038
Transparency	Day	47% 5% 11% 22% 13% 1	130762
	Night	49% 5% 10% 21% 13% 1	129558
Seeing	Day	17% 11% 28% 24% 14% 5%	17370
	Night	19% 10% 30% 29% 12% 1	27310

By Month

Percentage Cloud Cover SE (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% 13% 10% 19% 7% 5% 4 3 5% 5% 17%	3697
	11th to 20th	Day	12% 14% 8% 14% 8% 8% 6% 5% 6% 5% 14%	3700
	21st to end	Day	21% 18% 7% 12% 5% 3 3 2 3 4 21%	4070
February	1st to 10th	Day	15% 17% 5% 11% 8% 5% 5% 3 5% 5% 22%	1943
	11th to 20th	Day	14% 13% 4 12% 9% 6% 5% 3 5% 6% 24%	1948
	21st to end	Day	16% 14% 6% 11% 5% 4 4 3 6% 6% 25%	1650
March	1st to 10th	Day	18% 12% 6% 11% 5% 4 3 3 4 4 30%	4480
	11th to 20th	Day	10% 9% 6% 7% 4 4 4 4 6% 8% 37%	4795
	21st to end	Day	18% 15% 5% 11% 6% 5% 5% 3 5% 5% 22%	5730
April	1st to 10th	Day	17% 13% 4 8% 5% 4 4 4 5% 6% 30%	2400
	11th to 20th	Day	17% 10% 2 7% 5% 4 4 3 4 7% 35%	2379
	21st to end	Day	19% 8% 3 7% 5% 3 4 4 5% 7% 34%	2600
May	1st to 10th	Day	19% 8% 3 8% 5% 5% 5% 3 6% 7% 31%	5862
	11th to 20th	Day	15% 7% 2 6% 5% 5% 5% 4 6% 8% 38%	5861
	21st to end	Day	14% 6% 2 6% 5% 4 4 4 6% 8% 41%	6835
June	1st to 10th	Day	11% 5% 2 6% 5% 4 4 4 7% 8% 44%	2800
	11th to 20th	Day	10% 6% 2 5% 5% 5% 5% 4 7% 8% 43%	2800
	21st to end	Day	10% 5% 2 6% 5% 6% 6% 4 7% 9% 40%	2800
July	1st to 10th	Day	10% 6% 2 7% 4 5% 5% 4 7% 10% 39%	6360
	11th to 20th	Day	9% 5% 2 6% 5% 5% 5% 5% 7% 10% 42%	6360
	21st to end	Day	10% 6% 3 7% 5% 5% 5% 4 6% 9% 40%	6907
August	1st to 10th	Day	8% 4 2 6% 5% 5% 5% 4 6% 8% 48%	4234
	11th to 20th	Day	10% 4 1 6% 4 5% 5% 4 6% 9% 46%	4085
	21st to end	Day	7% 4 2 6% 4 4 5% 4 6% 10% 48%	4312
September	1st to 10th	Day	10% 5% 2 6% 4 5% 4 4 5% 8% 47%	2380
	11th to 20th	Day	10% 5% 1 5% 4 4 4 4 6% 8% 49%	2200
	21st to end	Day	13% 6% 2 7% 5% 4 4 4 5% 7% 43%	2200
October	1st to 10th	Day	13% 6% 3 7% 4 4 4 4 5% 7% 44%	2200
	11th to 20th	Day	17% 9% 3 6% 4 4 4 4 5% 6% 38%	1985
	21st to end	Day	20% 10% 3 8% 5% 5% 5% 4 6% 6% 28%	1980
November	1st to 10th	Day	11% 10% 3 6% 4 4 4 4 5% 7% 41%	1852
	11th to 20th	Day	17% 14% 4 9% 6% 4 4 3 5% 6% 30%	1890
	21st to end	Day	19% 14% 5% 10% 6% 4 4 3 4 5% 25%	1890
December	1st to 10th	Day	11% 15% 5% 11% 6% 5% 4 3 5% 8% 27%	2865
	11th to 20th	Day	15% 17% 9% 13% 6% 5% 4 2 4 5% 20%	3088
	21st to end	Day	28% 20% 6% 13% 6% 5% 3 2 4 4 10%	4070
January	1st to 10th	Night	15% 16% 6% 17% 6% 5% 4 3 4 5% 18%	6488
	11th to 20th	Night	13% 18% 8% 15% 7% 5% 5% 4 5% 5% 16%	6500
	21st to end	Night	19% 15% 7% 9% 5% 4 4 3 4 4 25%	7150
February	1st to 10th	Night	18% 15% 5% 10% 7% 4 4 3 4 4 27%	2456
	11th to 20th	Night	14% 13% 4 9% 7% 4 6% 3 5% 6% 28%	2338
	21st to end	Night	20% 12% 4 11% 5% 4 3 3 4 6% 28%	1980
March	1st to 10th	Night	15% 10% 4 9% 5% 5% 4 3 4 6% 35%	5373
	11th to 20th	Night	12% 7% 3 7% 5% 4 4 3 5% 8% 42%	5164
	21st to end	Night	18% 10% 3 8% 5% 4 4 4 5% 6% 33%	5243
April	1st to 10th	Night	16% 10% 3 5% 4 5% 4 3 6% 7% 37%	2000
	11th to 20th	Night	19% 8% 3 6% 4 5% 4 4 5% 6% 38%	1968
	21st to end	Night	17% 9% 3 6% 5% 5% 4 4 6% 5% 37%	1800
May	1st to 10th	Night	19% 11% 3 8% 4 4 4 4 5% 6% 32%	4033
	11th to 20th	Night	17% 7% 2 6% 4 4 4 3 5% 9% 40%	4032
	21st to end	Night	16% 7% 3 7% 4 4 4 3 5% 7% 41%	4035
June	1st to 10th	Night	10% 4 2 5% 4 4 4 3 6% 10% 48%	1600
	11th to 20th	Night	9% 6% 2 7% 4 4 4 4 7% 8% 45%	1600
	21st to end	Night	10% 5% 2 6% 5% 4 4 5% 7% 9% 43%	1600
July	1st to 10th	Night	8% 5% 2 6% 4 4 4 4 7% 9% 46%	3618
	11th to 20th	Night	7% 5% 3 7% 4 4 5% 4 7% 8% 48%	3617
	21st to end	Night	10% 5% 2 7% 5% 4 4 4 7% 9% 43%	3961
August	1st to 10th	Night	9% 5% 3 5% 4 4 5% 4 6% 9% 46%	2915
	11th to 20th	Night	8% 5% 2 6% 3 4 4 4 6% 8% 50%	2959
	21st to end	Night	9% 5% 2 5% 4 4 4 4 5% 7% 51%	3586
September	1st to 10th	Night	11% 6% 1 6% 3 4 3 3 5% 7% 53%	2000
	11th to 20th	Night	9% 4 1 4 4 3 3 3 5% 7% 57%	2200
	21st to end	Night	13% 7% 2 6% 4 3 3 3 5% 7% 47%	2200
October	1st to 10th	Night	12% 7% 2 5% 4 4 3 3 5% 5% 51%	2200
	11th to 20th	Night	17% 8% 3 7% 4 3 4 3 5% 6% 41%	2410
	21st to end	Night	20% 9% 3 7% 4 3 3 3 4 6% 37%	2860
November	1st to 10th	Night	12% 10% 2 7% 5% 4 4 3 6% 5% 42%	2666
	11th to 20th	Night	14% 13% 3 8% 5% 4 5% 4 5% 7% 32%	2730
	21st to end	Night	20% 14% 5% 9% 5% 4 4 3 5% 6% 25%	2730
December	1st to 10th	Night	13% 11% 5% 10% 6% 5% 4 4 6% 7% 30%	4537
	11th to 20th	Night	16% 18% 8% 12% 5% 5% 4 4 4 5% 18%	5339
	21st to end	Night	25% 20% 7% 11% 5% 4 4 3 4 4 12%	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	67% 5% 11% 13% 4	3698
	11th to 20th	Day	69% 3 9% 9% 8% 1	3700
	21st to end	Day	68% 3 9% 14% 6%	4070
February	1st to 10th	Day	63% 4 12% 13% 7% 1	1943
	11th to 20th	Day	61% 4 9% 18% 7% 1	1958
	21st to end	Day	59% 4 12% 16% 8% 1	1650
March	1st to 10th	Day	57% 4 8% 21% 9%	4480
	11th to 20th	Day	44% 4 11% 33% 8% 1	4795
	21st to end	Day	64% 6% 11% 14% 5% 1	5732
April	1st to 10th	Day	54% 6% 9% 19% 12%	2400
	11th to 20th	Day	49% 5% 10% 22% 12% 2	2379
	21st to end	Day	48% 6% 12% 21% 11% 2	2600
May	1st to 10th	Day	50% 7% 10% 19% 12% 1	5897
	11th to 20th	Day	43% 7% 13% 23% 12% 1	5865
	21st to end	Day	39% 6% 10% 27% 17% 1	6849
June	1st to 10th	Day	36% 7% 12% 25% 18% 2	2800
	11th to 20th	Day	37% 6% 12% 25% 19% 2	2800
	21st to end	Day	38% 8% 14% 21% 16% 3	2800
July	1st to 10th	Day	38% 6% 11% 26% 17% 2	6291
	11th to 20th	Day	35% 7% 15% 27% 15% 1	6285
	21st to end	Day	39% 7% 12% 23% 17% 2	6711
August	1st to 10th	Day	33% 7% 14% 29% 16% 1	4221
	11th to 20th	Day	33% 8% 13% 27% 18% 1	4124
	21st to end	Day	32% 6% 13% 27% 20% 3	4311
September	1st to 10th	Day	35% 7% 13% 23% 19% 3	2380
	11th to 20th	Day	33% 6% 11% 27% 22% 2	2200
	21st to end	Day	40% 6% 9% 24% 19% 2	2200
October	1st to 10th	Day	29% 4 9% 34% 24% 1	3590
	11th to 20th	Day	37% 5% 10% 22% 26%	3201
	21st to end	Day	46% 5% 10% 25% 13% 2	3180
November	1st to 10th	Day	41% 5% 12% 25% 15% 1	1852
	11th to 20th	Day	56% 3 10% 20% 10% 1	1890
	21st to end	Day	60% 5% 11% 18% 6%	1890
December	1st to 10th	Day	55% 4 16% 21% 4	2865
	11th to 20th	Day	66% 4 10% 16% 4	3085
	21st to end	Day	80% 3 7% 7% 3	4070
January	1st to 10th	Night	68% 5% 8% 15% 4	6488
	11th to 20th	Night	71% 3 8% 9% 9%	6500
	21st to end	Night	62% 4 11% 15% 8%	7150
February	1st to 10th	Night	61% 4 10% 15% 8% 1	2456
	11th to 20th	Night	55% 5% 10% 20% 9% 1	2339
	21st to end	Night	58% 3 11% 17% 8% 2	1980
March	1st to 10th	Night	51% 4 9% 27% 8% 1	5373
	11th to 20th	Night	41% 5% 11% 29% 12% 2	5164
	21st to end	Night	52% 5% 11% 21% 10% 1	5243
April	1st to 10th	Night	46% 6% 12% 20% 15% 1	2000
	11th to 20th	Night	47% 5% 8% 21% 17% 3	1968
	21st to end	Night	46% 6% 10% 21% 14% 2	1800
May	1st to 10th	Night	52% 6% 8% 19% 13% 2	4060
	11th to 20th	Night	42% 6% 11% 26% 14% 1	4033
	21st to end	Night	43% 6% 10% 22% 18% 2	4043
June	1st to 10th	Night	32% 6% 11% 28% 19% 3	1600
	11th to 20th	Night	36% 6% 12% 25% 19% 2	1600
	21st to end	Night	35% 8% 17% 22% 16% 3	1600
July	1st to 10th	Night	34% 6% 11% 29% 16% 4	3580
	11th to 20th	Night	33% 7% 15% 23% 21% 2	3572
	21st to end	Night	36% 6% 14% 22% 19% 2	3846
August	1st to 10th	Night	34% 7% 13% 30% 15% 1	2904
	11th to 20th	Night	31% 7% 12% 30% 19% 1	2986
	21st to end	Night	32% 6% 10% 28% 22% 3	3586
September	1st to 10th	Night	32% 4 13% 25% 20% 5%	2000
	11th to 20th	Night	27% 4 8% 31% 27% 3	2200
	21st to end	Night	38% 5% 10% 25% 20% 2	2200
October	1st to 10th	Night	24% 4 8% 33% 30% 1	3590
	11th to 20th	Night	38% 3 8% 23% 27% 1	3933
	21st to end	Night	38% 3 9% 29% 20% 1	4610
November	1st to 10th	Night	42% 5% 11% 25% 16% 2	2666
	11th to 20th	Night	51% 4 12% 22% 10% 2	2730
	21st to end	Night	60% 3 12% 18% 7%	2730
December	1st to 10th	Night	52% 4 15% 24% 5%	4537
	11th to 20th	Night	67% 4 11% 11% 6%	5341
	21st to end	Night	76% 4 9% 8% 3	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% 19% 36% 20% 5% 1	330
	11th to 20th	Day	21% 19% 39% 16% 3 1	330
	21st to end	Day	27% 18% 32% 19% 4 1	363
February	1st to 10th	Day	24% 18% 37% 17% 3 1	300
	11th to 20th	Day	24% 20% 34% 18% 3	300
	21st to end	Day	25% 22% 39% 10% 4	249
March	1st to 10th	Day	23% 19% 41% 15% 2	300
	11th to 20th	Day	22% 18% 33% 21% 6%	419
	21st to end	Day	29% 17% 30% 18% 5% 1	550
April	1st to 10th	Day	25% 14% 33% 22% 5% 1	500
	11th to 20th	Day	21% 20% 29% 19% 8% 3	492
	21st to end	Day	26% 14% 29% 20% 9% 1	500
May	1st to 10th	Day	25% 14% 29% 21% 9% 3	503
	11th to 20th	Day	19% 10% 30% 22% 15% 4	527
	21st to end	Day	13% 8% 30% 26% 16% 7%	741
June	1st to 10th	Day	12% 8% 29% 28% 18% 5%	730
	11th to 20th	Day	13% 6% 29% 28% 18% 5%	730
	21st to end	Day	13% 6% 28% 29% 17% 6%	730
July	1st to 10th	Day	10% 4 20% 29% 23% 14%	721
	11th to 20th	Day	9% 3 27% 29% 19% 12%	718
	21st to end	Day	8% 4 22% 34% 24% 8%	789
August	1st to 10th	Day	7% 3 16% 30% 29% 16%	526
	11th to 20th	Day	10% 5% 19% 30% 27% 9%	519
	21st to end	Day	9% 3 15% 31% 30% 12%	583
September	1st to 10th	Day	12% 8% 18% 28% 23% 10%	530
	11th to 20th	Day	8% 6% 15% 25% 32% 16%	530
	21st to end	Day	14% 12% 20% 24% 22% 7%	530
October	1st to 10th	Day	13% 6% 26% 30% 19% 6%	530
	11th to 20th	Day	20% 16% 26% 29% 7% 1	424
	21st to end	Day	27% 15% 34% 20% 3 1	363
November	1st to 10th	Day	15% 15% 37% 22% 8% 2	330
	11th to 20th	Day	27% 19% 30% 17% 7%	330
	21st to end	Day	30% 15% 36% 16% 3	330
December	1st to 10th	Day	18% 21% 37% 17% 6%	330
	11th to 20th	Day	19% 22% 37% 15% 5% 1	330
	21st to end	Day	27% 22% 35% 14% 2	363
January	1st to 10th	Night	23% 15% 36% 21% 5%	1050
	11th to 20th	Night	24% 16% 37% 19% 3 1	1050
	21st to end	Night	21% 14% 37% 24% 4	1155
February	1st to 10th	Night	28% 11% 34% 24% 3	801
	11th to 20th	Night	21% 15% 38% 23% 3	783
	21st to end	Night	26% 14% 39% 18% 3	660
March	1st to 10th	Night	21% 12% 36% 25% 6% 1	800
	11th to 20th	Night	18% 13% 37% 27% 6%	800
	21st to end	Night	24% 12% 31% 29% 4	785
April	1st to 10th	Night	19% 15% 35% 25% 6% 1	600
	11th to 20th	Night	22% 12% 35% 24% 7% 1	593
	21st to end	Night	20% 11% 32% 27% 10% 1	600
May	1st to 10th	Night	20% 8% 32% 32% 8%	600
	11th to 20th	Night	19% 6% 28% 32% 15%	591
	21st to end	Night	13% 5% 24% 41% 16% 1	650
June	1st to 10th	Night	11% 4 26% 44% 16%	600
	11th to 20th	Night	11% 4 27% 40% 18% 1	600
	21st to end	Night	10% 5% 24% 36% 23% 1	600
July	1st to 10th	Night	7% 1 16% 44% 28% 4	585
	11th to 20th	Night	9% 3 19% 39% 27% 3	582
	21st to end	Night	7% 2 14% 43% 32% 2	657
August	1st to 10th	Night	7% 2 10% 48% 29% 4	597
	11th to 20th	Night	8% 1 15% 44% 28% 4	594
	21st to end	Night	10% 2 14% 39% 32% 3	660
September	1st to 10th	Night	13% 4 16% 37% 28% 3	600
	11th to 20th	Night	10% 4 15% 37% 31% 4	800
	21st to end	Night	16% 5% 24% 31% 21% 3	800
October	1st to 10th	Night	14% 6% 26% 34% 20% 2	800
	11th to 20th	Night	21% 13% 30% 27% 9% 1	800
	21st to end	Night	25% 12% 32% 25% 6%	880
November	1st to 10th	Night	17% 11% 36% 26% 10% 1	820
	11th to 20th	Night	22% 16% 35% 22% 5% 1	840
	21st to end	Night	27% 13% 32% 24% 5%	840
December	1st to 10th	Night	23% 16% 36% 20% 4	932
	11th to 20th	Night	24% 13% 37% 22% 4	1050
	21st to end	Night	31% 14% 33% 19% 3	1155

Page generated at 2026-01-29 01:21:44. Version ac07

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