Black Forest
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Black Forest clear sky chart from 2005-11-06 to 2025-02-21.

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	19% 13% 5% 9% 5% 4 4 3 5% 6% 27%	108664
	Night	19% 14% 5% 11% 5% 4 4 3 4 5% 25%	109895
Transparency	Day	58% 4 11% 18% 8% 1	112177
	Night	62% 4 9% 16% 8% 1	114546
Seeing	Day	29% 17% 28% 17% 7% 2	14943
	Night	27% 16% 27% 21% 7% 1	24202

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	11% 18% 10% 24% 10% 4 3 2 2 3 13%	3597
	11th to 20th	Day	12% 19% 9% 22% 11% 5% 2 2 2 3 12%	3570
	21st to end	Day	14% 18% 10% 15% 7% 7% 4 3 4 4 14%	4208
February	1st to 10th	Day	16% 21% 6% 15% 8% 5% 5% 3 3 4 15%	1800
	11th to 20th	Day	14% 19% 7% 16% 7% 4 3 3 3 4 20%	1838
	21st to end	Day	19% 18% 6% 13% 7% 4 4 3 3 4 19%	1570
March	1st to 10th	Day	22% 18% 7% 11% 4 3 2 2 3 4 23%	3116
	11th to 20th	Day	12% 24% 9% 9% 4 4 4 3 4 4 24%	3416
	21st to end	Day	18% 14% 5% 10% 5% 3 3 2 3 5% 31%	4070
April	1st to 10th	Day	22% 17% 4 7% 4 3 3 2 3 6% 30%	2280
	11th to 20th	Day	20% 14% 3 7% 5% 3 3 3 5% 5% 32%	2254
	21st to end	Day	22% 16% 3 7% 3 4 4 3 3 6% 29%	2323
May	1st to 10th	Day	26% 11% 3 6% 4 4 4 3 4 5% 29%	4380
	11th to 20th	Day	19% 10% 3 7% 5% 6% 6% 4 5% 8% 28%	4398
	21st to end	Day	18% 7% 2 6% 4 4 4 4 6% 8% 37%	4837
June	1st to 10th	Day	24% 8% 3 6% 5% 5% 4 3 6% 8% 28%	2660
	11th to 20th	Day	22% 7% 2 6% 4 5% 5% 4 7% 8% 30%	2660
	21st to end	Day	22% 8% 3 7% 4 5% 4 3 6% 8% 29%	2660
July	1st to 10th	Day	15% 6% 2 6% 4 4 5% 5% 7% 10% 34%	4440
	11th to 20th	Day	16% 7% 2 6% 5% 5% 6% 5% 7% 10% 31%	4440
	21st to end	Day	16% 6% 2 7% 5% 5% 6% 4 7% 7% 34%	4814
August	1st to 10th	Day	21% 7% 2 6% 4 5% 5% 4 6% 8% 32%	4310
	11th to 20th	Day	19% 9% 3 7% 5% 4 5% 4 6% 8% 30%	3858
	21st to end	Day	20% 6% 2 5% 4 4 4 4 6% 9% 36%	4180
September	1st to 10th	Day	19% 5% 2 5% 4 4 5% 4 6% 8% 36%	2280
	11th to 20th	Day	18% 7% 2 6% 3 4 3 3 5% 7% 42%	2247
	21st to end	Day	21% 8% 2 5% 5% 4 4 3 5% 7% 35%	2086
October	1st to 10th	Day	26% 10% 3 8% 5% 4 4 3 4 5% 29%	1900
	11th to 20th	Day	23% 12% 3 6% 4 4 4 4 5% 5% 29%	1900
	21st to end	Day	28% 13% 4 7% 4 4 3 4 4 5% 23%	1935
November	1st to 10th	Day	19% 14% 5% 8% 5% 5% 4 4 5% 5% 27%	1761
	11th to 20th	Day	19% 18% 4 8% 5% 3 4 3 4 5% 27%	1730
	21st to end	Day	20% 22% 7% 10% 4 5% 3 3 4 4 19%	1600
December	1st to 10th	Day	20% 27% 9% 16% 5% 3 2 3 3 3 9%	2600
	11th to 20th	Day	21% 21% 10% 16% 6% 3 3 2 3 3 14%	2986
	21st to end	Day	21% 19% 8% 12% 4 4 3 2 3 4 20%	3960
January	1st to 10th	Night	13% 19% 10% 22% 9% 5% 3 2 3 3 12%	6349
	11th to 20th	Night	10% 18% 9% 28% 12% 5% 3 2 2 2 8%	6315
	21st to end	Night	15% 16% 8% 19% 8% 7% 5% 3 4 4 13%	6747
February	1st to 10th	Night	17% 19% 7% 17% 8% 5% 4 2 4 4 15%	2600
	11th to 20th	Night	14% 15% 8% 16% 9% 5% 4 3 4 4 18%	2448
	21st to end	Night	17% 16% 6% 12% 7% 5% 4 3 4 6% 19%	1885
March	1st to 10th	Night	20% 16% 5% 12% 6% 4 3 2 4 4 24%	3724
	11th to 20th	Night	17% 23% 7% 8% 5% 4 3 3 4 4 24%	3527
	21st to end	Night	18% 14% 5% 12% 4 3 3 2 4 4 30%	3562
April	1st to 10th	Night	22% 16% 4 8% 3 4 3 3 5% 6% 27%	1900
	11th to 20th	Night	22% 13% 3 6% 5% 4 4 3 4 6% 31%	1875
	21st to end	Night	22% 12% 3 5% 3 4 4 3 5% 6% 33%	1857
May	1st to 10th	Night	27% 10% 3 6% 5% 4 4 3 5% 5% 28%	2589
	11th to 20th	Night	19% 11% 3 7% 4 4 4 3 5% 6% 33%	2495
	21st to end	Night	20% 7% 2 5% 4 4 5% 4 5% 8% 38%	2738
June	1st to 10th	Night	21% 5% 3 5% 4 5% 4 4 7% 7% 35%	1520
	11th to 20th	Night	22% 7% 2 4 3 3 3 4 5% 8% 38%	1520
	21st to end	Night	20% 7% 2 6% 4 4 4 5% 5% 7% 36%	1520
July	1st to 10th	Night	15% 7% 3 7% 5% 5% 5% 5% 6% 6% 36%	2520
	11th to 20th	Night	19% 7% 2 5% 3 3 4 3 6% 7% 40%	2520
	21st to end	Night	15% 9% 2 6% 4 3 3 4 6% 7% 42%	2739
August	1st to 10th	Night	24% 8% 2 6% 4 4 3 3 4 6% 36%	2601
	11th to 20th	Night	22% 8% 2 6% 4 3 3 3 4 6% 37%	2938
	21st to end	Night	16% 7% 2 5% 4 4 4 4 5% 7% 42%	3476
September	1st to 10th	Night	17% 7% 2 5% 4 4 4 4 5% 6% 42%	1900
	11th to 20th	Night	17% 6% 2 6% 3 3 3 3 4 6% 48%	1933
	21st to end	Night	21% 7% 2 5% 4 4 5% 3 5% 7% 38%	2090
October	1st to 10th	Night	26% 9% 3 7% 4 4 4 3 4 4 31%	2280
	11th to 20th	Night	24% 10% 3 6% 4 4 4 3 5% 6% 31%	2280
	21st to end	Night	27% 13% 4 8% 5% 3 4 3 5% 6% 22%	2661
November	1st to 10th	Night	19% 15% 4 8% 5% 3 4 3 4 6% 31%	2537
	11th to 20th	Night	21% 17% 4 6% 5% 4 3 3 4 5% 27%	2665
	21st to end	Night	19% 21% 6% 10% 4 3 4 3 5% 5% 19%	2800
December	1st to 10th	Night	19% 25% 11% 16% 4 3 3 2 3 3 10%	4580
	11th to 20th	Night	24% 21% 7% 15% 5% 3 3 2 2 3 15%	5208
	21st to end	Night	23% 20% 6% 12% 4 4 3 2 3 4 19%	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	79% 3 5% 10% 4	3598
	11th to 20th	Day	81% 2 4 6% 5% 2	3600
	21st to end	Day	74% 3 8% 8% 5% 1	4208
February	1st to 10th	Day	75% 3 6% 12% 4 1	1800
	11th to 20th	Day	70% 4 6% 12% 7% 1	1847
	21st to end	Day	70% 4 8% 11% 7%	1570
March	1st to 10th	Day	67% 2 9% 12% 8% 1	3119
	11th to 20th	Day	65% 3 13% 10% 7% 1	3416
	21st to end	Day	58% 3 6% 16% 15% 2	4070
April	1st to 10th	Day	58% 3 7% 19% 10% 2	2280
	11th to 20th	Day	55% 4 9% 20% 11% 1	2254
	21st to end	Day	58% 4 8% 16% 11% 3	2323
May	1st to 10th	Day	58% 3 9% 20% 9% 1	4394
	11th to 20th	Day	55% 4 11% 22% 6% 1	4402
	21st to end	Day	46% 4 13% 27% 10% 1	4837
June	1st to 10th	Day	55% 5% 12% 19% 9%	2660
	11th to 20th	Day	50% 5% 13% 22% 8% 1	2660
	21st to end	Day	53% 5% 14% 19% 8% 1	2660
July	1st to 10th	Day	43% 6% 16% 25% 10%	4370
	11th to 20th	Day	45% 7% 14% 26% 7%	4365
	21st to end	Day	46% 7% 13% 25% 8%	4661
August	1st to 10th	Day	48% 6% 15% 19% 11%	4296
	11th to 20th	Day	50% 6% 16% 22% 6%	3897
	21st to end	Day	44% 5% 15% 29% 6%	4180
September	1st to 10th	Day	44% 6% 11% 27% 11%	2280
	11th to 20th	Day	43% 4 10% 27% 15% 1	2247
	21st to end	Day	50% 5% 10% 23% 12% 1	2086
October	1st to 10th	Day	55% 4 9% 23% 9% 1	3160
	11th to 20th	Day	50% 3 12% 19% 15% 1	3140
	21st to end	Day	50% 4 15% 24% 6% 1	3160
November	1st to 10th	Day	58% 4 11% 17% 9%	1761
	11th to 20th	Day	59% 4 9% 15% 11% 2	1730
	21st to end	Day	68% 5% 12% 10% 5% 1	1600
December	1st to 10th	Day	82% 3 6% 6% 2	2600
	11th to 20th	Day	78% 3 5% 11% 3	2986
	21st to end	Day	71% 3 6% 8% 12% 1	3960
January	1st to 10th	Night	79% 2 6% 8% 4	6349
	11th to 20th	Night	84% 3 5% 4 3 1	6360
	21st to end	Night	77% 3 6% 8% 5% 1	6747
February	1st to 10th	Night	75% 2 7% 10% 5% 1	2600
	11th to 20th	Night	70% 4 7% 13% 6%	2450
	21st to end	Night	67% 4 9% 12% 7% 1	1885
March	1st to 10th	Night	66% 3 7% 16% 8% 1	3734
	11th to 20th	Night	65% 3 9% 16% 6% 1	3528
	21st to end	Night	59% 3 6% 19% 12% 2	3562
April	1st to 10th	Night	59% 4 9% 18% 7% 2	1900
	11th to 20th	Night	55% 5% 9% 19% 12%	1875
	21st to end	Night	54% 3 10% 18% 13% 3	1857
May	1st to 10th	Night	59% 4 9% 17% 10% 1	2595
	11th to 20th	Night	53% 5% 11% 22% 8% 1	2496
	21st to end	Night	46% 4 11% 23% 15% 1	2739
June	1st to 10th	Night	47% 5% 13% 22% 11% 1	1520
	11th to 20th	Night	44% 5% 15% 23% 11% 1	1520
	21st to end	Night	47% 6% 13% 23% 10% 1	1520
July	1st to 10th	Night	47% 6% 14% 19% 14% 1	2480
	11th to 20th	Night	44% 4 15% 26% 10%	2472
	21st to end	Night	42% 5% 12% 29% 11% 1	2651
August	1st to 10th	Night	51% 5% 13% 23% 8%	2591
	11th to 20th	Night	49% 4 13% 27% 7%	2965
	21st to end	Night	41% 5% 15% 31% 8%	3476
September	1st to 10th	Night	43% 5% 13% 26% 11% 1	1900
	11th to 20th	Night	39% 4 11% 30% 16% 1	1933
	21st to end	Night	45% 5% 12% 25% 11% 2	2090
October	1st to 10th	Night	57% 4 10% 20% 10%	3800
	11th to 20th	Night	48% 4 13% 20% 11% 5%	3779
	21st to end	Night	54% 5% 11% 24% 6% 1	4386
November	1st to 10th	Night	56% 5% 11% 16% 11% 2	2537
	11th to 20th	Night	60% 4 9% 16% 9% 3	2665
	21st to end	Night	66% 4 10% 15% 4 1	2800
December	1st to 10th	Night	81% 5% 7% 6% 2	4580
	11th to 20th	Night	77% 3 6% 11% 4	5208
	21st to end	Night	71% 2 7% 7% 11% 2	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	34% 20% 33% 12% 3	200
	11th to 20th	Day	36% 27% 30% 6% 2 1	200
	21st to end	Day	28% 26% 34% 9% 3	273
February	1st to 10th	Day	42% 29% 26% 3	300
	11th to 20th	Day	37% 29% 28% 5% 1	385
	21st to end	Day	36% 23% 32% 8% 1	382
March	1st to 10th	Day	32% 25% 28% 13% 2	460
	11th to 20th	Day	29% 27% 29% 10% 3	460
	21st to end	Day	35% 23% 25% 13% 3 1	506
April	1st to 10th	Day	37% 24% 23% 11% 5% 1	460
	11th to 20th	Day	37% 21% 21% 13% 7% 1	452
	21st to end	Day	35% 18% 28% 13% 4 2	460
May	1st to 10th	Day	35% 17% 27% 13% 6% 3	463
	11th to 20th	Day	25% 13% 32% 21% 7% 2	487
	21st to end	Day	24% 13% 30% 19% 11% 2	529
June	1st to 10th	Day	27% 17% 29% 19% 8% 2	490
	11th to 20th	Day	23% 13% 28% 26% 8% 2	490
	21st to end	Day	28% 13% 31% 18% 7% 2	490
July	1st to 10th	Day	20% 7% 30% 27% 13% 3	485
	11th to 20th	Day	19% 7% 30% 30% 11% 3	484
	21st to end	Day	20% 8% 36% 27% 8% 2	532
August	1st to 10th	Day	21% 8% 25% 27% 14% 5%	486
	11th to 20th	Day	24% 8% 24% 23% 14% 6%	479
	21st to end	Day	19% 14% 27% 21% 13% 6%	539
September	1st to 10th	Day	22% 10% 24% 23% 14% 6%	490
	11th to 20th	Day	19% 9% 26% 20% 17% 10%	490
	21st to end	Day	23% 10% 31% 21% 12% 3	490
October	1st to 10th	Day	32% 12% 24% 17% 13% 2	490
	11th to 20th	Day	30% 17% 31% 16% 6% 1	490
	21st to end	Day	36% 18% 24% 20% 4	456
November	1st to 10th	Day	35% 16% 25% 15% 8%	395
	11th to 20th	Day	33% 24% 26% 12% 3 1	330
	21st to end	Day	41% 24% 27% 8% 1	200
December	1st to 10th	Day	36% 23% 29% 9% 5%	200
	11th to 20th	Day	39% 26% 26% 7% 3	200
	21st to end	Day	36% 23% 29% 10% 2	220
January	1st to 10th	Night	31% 26% 30% 11% 1	800
	11th to 20th	Night	33% 23% 28% 14% 3	800
	21st to end	Night	22% 25% 34% 16% 3	880
February	1st to 10th	Night	29% 26% 33% 12% 1	800
	11th to 20th	Night	27% 27% 32% 12% 2	783
	21st to end	Night	30% 23% 32% 14% 2	629
March	1st to 10th	Night	25% 24% 33% 16% 2	760
	11th to 20th	Night	30% 21% 31% 15% 3	760
	21st to end	Night	27% 23% 29% 15% 6% 1	836
April	1st to 10th	Night	29% 19% 31% 19% 2	760
	11th to 20th	Night	30% 17% 30% 16% 7%	751
	21st to end	Night	32% 15% 26% 21% 6%	717
May	1st to 10th	Night	31% 9% 28% 24% 8% 1	429
	11th to 20th	Night	22% 14% 30% 27% 7% 1	374
	21st to end	Night	19% 5% 29% 35% 11% 1	411
June	1st to 10th	Night	24% 6% 23% 35% 11% 1	380
	11th to 20th	Night	23% 8% 24% 31% 14%	380
	21st to end	Night	24% 5% 28% 33% 11%	380
July	1st to 10th	Night	18% 4 21% 39% 17% 1	370
	11th to 20th	Night	15% 4 21% 39% 18% 2	368
	21st to end	Night	16% 6% 20% 43% 13% 1	416
August	1st to 10th	Night	21% 3 18% 39% 18% 1	434
	11th to 20th	Night	23% 4 19% 30% 21% 3	652
	21st to end	Night	19% 6% 21% 36% 17% 1	836
September	1st to 10th	Night	20% 8% 23% 31% 16% 2	760
	11th to 20th	Night	22% 6% 21% 28% 19% 4	760
	21st to end	Night	24% 8% 26% 27% 14% 2	760
October	1st to 10th	Night	30% 10% 24% 22% 13% 2	760
	11th to 20th	Night	30% 12% 28% 23% 6% 1	760
	21st to end	Night	35% 16% 28% 19% 3	836
November	1st to 10th	Night	26% 18% 29% 20% 7%	780
	11th to 20th	Night	32% 18% 30% 13% 6% 1	800
	21st to end	Night	30% 22% 29% 16% 3 1	800
December	1st to 10th	Night	35% 22% 27% 13% 3	800
	11th to 20th	Night	34% 24% 25% 14% 3 1	800
	21st to end	Night	35% 25% 25% 13% 2	880

Page generated at 2025-02-18 03:26:33. Version ac07

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