Wahnsiedler Observatory
Clear Sky Chart
History

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

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	13% 8% 3 7% 4 4 4 4 6% 7% 39%	131800
	Night	15% 8% 3 7% 4 4 4 3 5% 7% 41%	131527
Transparency	Day	42% 5% 11% 24% 16% 2	135416
	Night	42% 5% 11% 23% 17% 3	135984
Seeing	Day	17% 9% 24% 24% 18% 8%	17559
	Night	17% 7% 25% 31% 16% 2	27415

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	14% 11% 6% 10% 5% 5% 5% 3 4 6% 30%	4691
	11th to 20th	Day	11% 10% 4 11% 6% 5% 4 3 5% 6% 35%	4710
	21st to end	Day	19% 12% 6% 9% 6% 4 4 3 4 5% 29%	5726
February	1st to 10th	Day	17% 11% 5% 7% 4 4 4 3 5% 6% 35%	2100
	11th to 20th	Day	17% 10% 4 9% 4 4 4 3 5% 6% 35%	2048
	21st to end	Day	15% 11% 4 9% 5% 4 4 3 6% 6% 34%	1730
March	1st to 10th	Day	18% 11% 4 7% 3 3 3 2 3 4 41%	4580
	11th to 20th	Day	12% 10% 3 6% 3 3 3 3 5% 7% 45%	4794
	21st to end	Day	14% 9% 3 8% 5% 4 4 4 6% 7% 38%	6042
April	1st to 10th	Day	14% 7% 2 6% 4 4 4 5% 6% 8% 39%	2520
	11th to 20th	Day	15% 8% 3 6% 4 4 4 4 5% 7% 40%	2494
	21st to end	Day	17% 6% 2 6% 4 4 4 4 5% 6% 41%	2583
May	1st to 10th	Day	19% 8% 3 7% 5% 5% 5% 4 7% 9% 26%	5992
	11th to 20th	Day	17% 7% 3 7% 4 5% 4 4 6% 7% 35%	5991
	21st to end	Day	14% 7% 3 7% 4 5% 5% 5% 7% 8% 35%	6733
June	1st to 10th	Day	11% 5% 3 5% 5% 4 4 3 6% 8% 45%	2801
	11th to 20th	Day	6% 5% 2 7% 5% 5% 6% 4 7% 8% 47%	2800
	21st to end	Day	8% 5% 2 5% 4 4 5% 5% 8% 10% 45%	2800
July	1st to 10th	Day	10% 6% 2 6% 4 5% 4 4 6% 9% 45%	6360
	11th to 20th	Day	8% 5% 2 7% 4 5% 6% 5% 8% 11% 40%	6360
	21st to end	Day	8% 6% 3 8% 6% 7% 7% 6% 8% 10% 31%	6754
August	1st to 10th	Day	6% 4 2 5% 3 4 4 4 7% 9% 53%	4106
	11th to 20th	Day	7% 4 2 7% 5% 5% 6% 4 8% 10% 41%	3849
	21st to end	Day	5% 4 2 5% 3 4 4 4 6% 9% 55%	4312
September	1st to 10th	Day	9% 6% 2 6% 4 4 4 4 6% 7% 48%	2400
	11th to 20th	Day	8% 4 2 6% 5% 4 3 4 6% 8% 50%	2215
	21st to end	Day	13% 5% 2 5% 4 4 4 2 5% 6% 52%	2200
October	1st to 10th	Day	10% 4 2 4 3 4 3 3 5% 6% 57%	2200
	11th to 20th	Day	12% 5% 2 5% 4 3 4 3 5% 7% 50%	2066
	21st to end	Day	18% 7% 3 6% 3 3 4 3 3 5% 45%	1990
November	1st to 10th	Day	9% 6% 2 5% 4 4 4 4 5% 7% 51%	1852
	11th to 20th	Day	15% 8% 3 6% 4 3 3 3 4 6% 43%	1890
	21st to end	Day	20% 10% 4 6% 3 3 4 3 4 5% 39%	1890
December	1st to 10th	Day	15% 10% 3 6% 3 3 3 2 4 5% 45%	3020
	11th to 20th	Day	16% 12% 5% 9% 4 5% 4 3 5% 6% 31%	3131
	21st to end	Day	27% 16% 5% 8% 5% 4 4 3 4 5% 20%	4070
January	1st to 10th	Night	17% 12% 5% 8% 4 4 4 3 4 6% 34%	8232
	11th to 20th	Night	13% 11% 4 9% 5% 6% 5% 3 4 5% 36%	8280
	21st to end	Night	19% 11% 4 7% 4 4 3 3 4 6% 37%	8446
February	1st to 10th	Night	20% 11% 4 8% 5% 4 4 4 5% 5% 31%	2520
	11th to 20th	Night	18% 9% 3 8% 5% 4 4 3 4 5% 38%	2458
	21st to end	Night	19% 10% 3 8% 3 3 2 3 5% 5% 37%	2076
March	1st to 10th	Night	21% 11% 3 6% 4 4 4 3 4 4 35%	5493
	11th to 20th	Night	12% 6% 2 6% 3 4 3 3 5% 6% 49%	5384
	21st to end	Night	18% 8% 3 8% 5% 4 4 3 5% 6% 36%	5171
April	1st to 10th	Night	13% 7% 2 6% 4 3 4 4 5% 7% 45%	2100
	11th to 20th	Night	16% 7% 2 7% 4 3 3 4 4 7% 43%	2075
	21st to end	Night	17% 7% 3 6% 5% 4 4 4 5% 8% 37%	2036
May	1st to 10th	Night	18% 9% 3 8% 5% 4 4 4 6% 9% 31%	4123
	11th to 20th	Night	15% 7% 3 7% 5% 5% 5% 4 6% 8% 35%	4122
	21st to end	Night	13% 7% 3 7% 4 5% 5% 4 7% 9% 36%	4353
June	1st to 10th	Night	10% 6% 2 5% 4 4 4 4 6% 7% 48%	1600
	11th to 20th	Night	6% 5% 1 5% 4 4 4 5% 7% 9% 49%	1600
	21st to end	Night	5% 4 1 4 4 4 4 5% 7% 11% 53%	1600
July	1st to 10th	Night	9% 5% 2 7% 5% 4 4 4 5% 8% 48%	3618
	11th to 20th	Night	7% 4 2 6% 4 4 5% 4 6% 10% 49%	3617
	21st to end	Night	7% 5% 3 7% 5% 5% 6% 6% 8% 11% 37%	4108
August	1st to 10th	Night	5% 4 1 5% 3 3 3 3 5% 9% 59%	3039
	11th to 20th	Night	6% 5% 2 6% 4 4 5% 4 6% 9% 51%	3200
	21st to end	Night	3 3 1 4 3 3 3 3 6% 9% 61%	3586
September	1st to 10th	Night	10% 4 2 6% 4 4 3 3 5% 7% 53%	2000
	11th to 20th	Night	7% 4 1 5% 3 4 4 4 6% 7% 55%	2165
	21st to end	Night	13% 5% 2 5% 3 3 4 3 5% 6% 51%	2200
October	1st to 10th	Night	8% 4 2 5% 3 3 3 3 4 6% 60%	2200
	11th to 20th	Night	14% 5% 2 5% 3 3 3 2 4 5% 54%	2330
	21st to end	Night	18% 7% 2 5% 3 4 4 2 4 5% 45%	2850
November	1st to 10th	Night	12% 6% 2 5% 4 3 4 3 5% 6% 52%	2666
	11th to 20th	Night	14% 6% 2 6% 3 4 4 3 4 6% 48%	2730
	21st to end	Night	19% 9% 3 5% 4 4 3 3 4 5% 42%	2730
December	1st to 10th	Night	18% 9% 3 7% 4 3 3 3 3 5% 43%	4380
	11th to 20th	Night	19% 9% 3 6% 4 4 4 3 5% 6% 38%	5289
	21st to end	Night	27% 15% 4 7% 5% 4 4 3 3 4 23%	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	56% 3 11% 22% 6% 1	4692
	11th to 20th	Day	51% 3 10% 23% 13% 1	4710
	21st to end	Day	59% 3 10% 16% 8% 4	5726
February	1st to 10th	Day	52% 3 11% 22% 11% 1	2100
	11th to 20th	Day	51% 4 9% 21% 12% 2	2058
	21st to end	Day	51% 4 9% 20% 13% 3	1730
March	1st to 10th	Day	49% 3 5% 19% 21% 4	4580
	11th to 20th	Day	40% 4 9% 28% 17% 3	4794
	21st to end	Day	45% 5% 12% 25% 12% 1	6044
April	1st to 10th	Day	41% 7% 13% 23% 16% 1	2520
	11th to 20th	Day	44% 5% 10% 23% 15% 3	2494
	21st to end	Day	42% 6% 12% 26% 12% 2	2583
May	1st to 10th	Day	51% 8% 13% 18% 10%	6027
	11th to 20th	Day	47% 6% 12% 24% 11% 1	5995
	21st to end	Day	43% 6% 12% 20% 17% 2	6747
June	1st to 10th	Day	36% 7% 11% 25% 19% 3	2801
	11th to 20th	Day	32% 9% 12% 25% 19% 3	2800
	21st to end	Day	32% 9% 13% 23% 18% 5%	2800
July	1st to 10th	Day	36% 6% 10% 27% 19% 2	6291
	11th to 20th	Day	36% 7% 17% 26% 12% 1	6285
	21st to end	Day	44% 8% 18% 21% 8% 1	6560
August	1st to 10th	Day	26% 7% 15% 35% 16% 1	4093
	11th to 20th	Day	35% 7% 14% 25% 17% 1	3885
	21st to end	Day	25% 5% 14% 35% 17% 3	4311
September	1st to 10th	Day	35% 5% 10% 25% 20% 5%	2400
	11th to 20th	Day	31% 6% 11% 27% 23% 3	2215
	21st to end	Day	34% 5% 7% 23% 27% 4	2200
October	1st to 10th	Day	19% 3 6% 25% 43% 4	3590
	11th to 20th	Day	24% 3 8% 26% 34% 5%	3345
	21st to end	Day	34% 3 7% 25% 26% 5%	3190
November	1st to 10th	Day	33% 6% 9% 30% 17% 6%	1852
	11th to 20th	Day	41% 4 8% 24% 18% 5%	1890
	21st to end	Day	48% 4 8% 22% 16% 2	1890
December	1st to 10th	Day	43% 3 12% 26% 16%	3020
	11th to 20th	Day	55% 3 10% 21% 10% 1	3128
	21st to end	Day	67% 4 11% 12% 5%	4070
January	1st to 10th	Night	52% 4 13% 23% 8% 1	8233
	11th to 20th	Night	51% 3 7% 19% 16% 3	8280
	21st to end	Night	50% 3 10% 21% 15% 1	8446
February	1st to 10th	Night	55% 5% 10% 20% 9% 1	2520
	11th to 20th	Night	49% 3 9% 23% 14% 2	2459
	21st to end	Night	48% 4 10% 22% 13% 3	2076
March	1st to 10th	Night	52% 4 6% 19% 16% 3	5493
	11th to 20th	Night	36% 4 10% 24% 22% 4	5384
	21st to end	Night	50% 5% 9% 24% 11% 1	5171
April	1st to 10th	Night	39% 5% 11% 27% 16% 3	2100
	11th to 20th	Night	41% 5% 10% 21% 19% 4	2075
	21st to end	Night	45% 6% 9% 22% 16% 2	2036
May	1st to 10th	Night	48% 8% 13% 22% 8% 1	4150
	11th to 20th	Night	46% 7% 10% 23% 12% 1	4123
	21st to end	Night	41% 7% 14% 21% 14% 2	4361
June	1st to 10th	Night	33% 6% 11% 25% 21% 4	1600
	11th to 20th	Night	29% 7% 13% 21% 24% 6%	1600
	21st to end	Night	23% 8% 17% 25% 20% 7%	1600
July	1st to 10th	Night	35% 6% 10% 25% 21% 3	3580
	11th to 20th	Night	31% 8% 17% 29% 13% 2	3572
	21st to end	Night	38% 8% 19% 23% 11% 1	3989
August	1st to 10th	Night	23% 6% 16% 39% 15% 2	3028
	11th to 20th	Night	29% 6% 14% 28% 21% 2	3230
	21st to end	Night	20% 6% 12% 32% 26% 3	3586
September	1st to 10th	Night	30% 6% 8% 26% 23% 6%	2000
	11th to 20th	Night	27% 6% 10% 26% 26% 5%	2165
	21st to end	Night	34% 5% 8% 22% 25% 7%	2200
October	1st to 10th	Night	18% 4 5% 15% 51% 6%	3590
	11th to 20th	Night	23% 2 6% 26% 37% 5%	3790
	21st to end	Night	32% 3 8% 23% 27% 8%	4600
November	1st to 10th	Night	34% 3 10% 24% 23% 5%	2666
	11th to 20th	Night	38% 4 8% 23% 21% 6%	2730
	21st to end	Night	45% 4 9% 24% 16% 2	2730
December	1st to 10th	Night	45% 3 11% 23% 16%	4380
	11th to 20th	Night	47% 3 13% 21% 15% 1	5291
	21st to end	Night	65% 4 9% 16% 6% 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	25% 18% 29% 21% 6% 1	330
	11th to 20th	Day	28% 21% 32% 16% 3	330
	21st to end	Day	26% 21% 35% 14% 4	363
February	1st to 10th	Day	24% 17% 38% 18% 2 1	330
	11th to 20th	Day	28% 21% 34% 13% 3 1	330
	21st to end	Day	26% 18% 35% 17% 4	273
March	1st to 10th	Day	26% 16% 37% 16% 5%	330
	11th to 20th	Day	27% 17% 36% 15% 5% 1	400
	21st to end	Day	26% 14% 36% 16% 7% 1	594
April	1st to 10th	Day	19% 15% 32% 25% 8% 1	540
	11th to 20th	Day	22% 17% 27% 20% 12% 2	532
	21st to end	Day	20% 13% 33% 23% 8% 4	540
May	1st to 10th	Day	20% 13% 29% 27% 8% 3	543
	11th to 20th	Day	20% 9% 24% 28% 12% 7%	567
	21st to end	Day	15% 6% 24% 28% 18% 11%	683
June	1st to 10th	Day	14% 5% 18% 26% 27% 11%	731
	11th to 20th	Day	7% 4 18% 33% 25% 12%	730
	21st to end	Day	11% 3 20% 33% 22% 11%	730
July	1st to 10th	Day	12% 3 13% 23% 27% 22%	721
	11th to 20th	Day	7% 4 14% 31% 29% 16%	718
	21st to end	Day	8% 2 12% 30% 34% 14%	724
August	1st to 10th	Day	11% 3 13% 27% 29% 18%	526
	11th to 20th	Day	12% 2 13% 27% 33% 13%	519
	21st to end	Day	7% 2 11% 25% 35% 19%	583
September	1st to 10th	Day	9% 3 15% 25% 33% 14%	530
	11th to 20th	Day	7% 3 9% 31% 32% 18%	530
	21st to end	Day	15% 6% 20% 22% 24% 13%	530
October	1st to 10th	Day	11% 3 19% 34% 24% 8%	530
	11th to 20th	Day	13% 9% 32% 26% 14% 6%	396
	21st to end	Day	27% 12% 28% 23% 9%	363
November	1st to 10th	Day	15% 9% 33% 25% 12% 5%	330
	11th to 20th	Day	18% 22% 28% 22% 9% 2	330
	21st to end	Day	29% 9% 31% 23% 8% 1	330
December	1st to 10th	Day	22% 20% 32% 16% 6% 3	330
	11th to 20th	Day	28% 14% 32% 18% 7% 1	330
	21st to end	Day	31% 20% 30% 16% 4	363
January	1st to 10th	Night	23% 12% 33% 28% 3	1050
	11th to 20th	Night	26% 14% 35% 21% 4	1050
	21st to end	Night	21% 12% 38% 26% 2	1095
February	1st to 10th	Night	26% 10% 36% 26% 2	840
	11th to 20th	Night	24% 13% 36% 26% 2	823
	21st to end	Night	26% 13% 37% 23% 2	692
March	1st to 10th	Night	23% 12% 32% 28% 5%	840
	11th to 20th	Night	22% 10% 35% 25% 6% 1	840
	21st to end	Night	24% 10% 28% 31% 7%	740
April	1st to 10th	Night	15% 12% 32% 34% 7%	630
	11th to 20th	Night	20% 9% 30% 27% 12% 1	623
	21st to end	Night	20% 6% 32% 32% 9% 1	630
May	1st to 10th	Night	17% 7% 27% 35% 13% 1	630
	11th to 20th	Night	15% 6% 20% 36% 21% 2	621
	21st to end	Night	9% 2 19% 40% 25% 4	683
June	1st to 10th	Night	12% 2 17% 40% 27% 3	600
	11th to 20th	Night	7% 2 17% 41% 31% 2	600
	21st to end	Night	5% 1 17% 41% 34% 3	600
July	1st to 10th	Night	11% 1 9% 32% 38% 9%	585
	11th to 20th	Night	6% 2 10% 35% 43% 5%	582
	21st to end	Night	8% 2 9% 36% 37% 7%	657
August	1st to 10th	Night	7% 2 8% 37% 41% 6%	597
	11th to 20th	Night	6% 2 8% 37% 41% 6%	594
	21st to end	Night	6% 1 7% 36% 42% 8%	660
September	1st to 10th	Night	11% 2 10% 35% 38% 5%	600
	11th to 20th	Night	7% 2 12% 36% 38% 5%	765
	21st to end	Night	14% 4 18% 30% 28% 6%	800
October	1st to 10th	Night	9% 5% 17% 37% 27% 5%	800
	11th to 20th	Night	16% 6% 25% 34% 18% 2	800
	21st to end	Night	21% 9% 31% 28% 11%	880
November	1st to 10th	Night	15% 7% 28% 36% 12% 1	820
	11th to 20th	Night	17% 10% 33% 29% 10%	840
	21st to end	Night	23% 10% 27% 30% 10%	840
December	1st to 10th	Night	23% 8% 33% 30% 6%	840
	11th to 20th	Night	26% 7% 32% 29% 6%	1013
	21st to end	Night	29% 12% 32% 23% 3	1155

Page generated at 2026-05-29 01:53:31. Version ac07

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