TheDamObservatory-Lake Tschida
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the TheDamObservatory-Lake Tschida clear sky chart from 2005-11-06 to 2026-09-14.

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	8% 7% 3 7% 4 4 4 4 6% 8% 45%	157863
	Night	7% 7% 3 8% 5% 4 5% 4 6% 7% 44%	150701
Transparency	Day	37% 5% 13% 27% 15% 2	152509
	Night	38% 5% 15% 26% 14% 2	147067
Seeing	Day	13% 9% 31% 30% 15% 3	18712
	Night	11% 9% 33% 35% 11% 1	28551

By Month

Percentage Cloud Cover SW (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	3 10% 5% 11% 7% 6% 6% 4 6% 8% 33%	4720
	11th to 20th	Day	2 8% 4 15% 7% 6% 8% 5% 9% 9% 27%	4740
	21st to end	Day	3 8% 5% 11% 7% 6% 6% 4 5% 6% 39%	5188
February	1st to 10th	Day	8% 13% 5% 10% 7% 6% 5% 3 5% 6% 33%	1705
	11th to 20th	Day	5% 12% 5% 11% 6% 4 6% 5% 6% 7% 34%	2025
	21st to end	Day	5% 12% 4 11% 8% 5% 5% 4 5% 6% 36%	1730
March	1st to 10th	Day	5% 8% 4 8% 5% 4 5% 4 5% 8% 45%	4600
	11th to 20th	Day	5% 8% 4 8% 5% 5% 5% 4 8% 10% 38%	4816
	21st to end	Day	14% 16% 4 10% 6% 4 5% 4 5% 6% 26%	5960
April	1st to 10th	Day	10% 10% 3 8% 5% 4 5% 4 6% 8% 37%	2520
	11th to 20th	Day	13% 10% 4 9% 5% 5% 4 4 6% 6% 34%	2565
	21st to end	Day	16% 10% 3 7% 5% 3 4 4 5% 6% 37%	2730
May	1st to 10th	Day	9% 5% 2 5% 4 4 4 4 5% 7% 50%	7842
	11th to 20th	Day	18% 6% 2 5% 3 4 3 3 5% 7% 45%	8191
	21st to end	Day	12% 6% 2 5% 4 4 4 4 6% 8% 46%	9026
June	1st to 10th	Day	12% 5% 2 5% 5% 4 4 4 6% 8% 46%	3066
	11th to 20th	Day	11% 6% 2 5% 6% 5% 4 4 6% 9% 44%	3150
	21st to end	Day	8% 4 2 4 4 3 4 4 6% 8% 52%	3068
July	1st to 10th	Day	7% 5% 2 5% 5% 5% 5% 5% 7% 9% 46%	8249
	11th to 20th	Day	7% 3 2 4 2 3 3 3 5% 7% 60%	8250
	21st to end	Day	5% 4 2 6% 5% 5% 5% 4 6% 9% 48%	8957
August	1st to 10th	Day	10% 5% 2 5% 3 3 3 3 5% 7% 54%	8142
	11th to 20th	Day	10% 6% 2 6% 4 5% 5% 4 7% 8% 43%	7661
	21st to end	Day	6% 5% 2 5% 3 3 3 2 5% 6% 60%	7914
September	1st to 10th	Day	8% 4 2 3 3 4 4 3 5% 5% 59%	2520
	11th to 20th	Day	11% 6% 1 5% 3 3 3 3 5% 7% 53%	2297
	21st to end	Day	11% 5% 1 5% 3 3 2 2 4 6% 58%	2200
October	1st to 10th	Day	9% 4 1 4 2 2 3 3 5% 7% 60%	3531
	11th to 20th	Day	10% 6% 2 4 3 2 3 2 4 9% 54%	3003
	21st to end	Day	8% 9% 3 5% 3 4 4 3 6% 8% 47%	3190
November	1st to 10th	Day	10% 11% 3 6% 5% 4 4 4 6% 7% 41%	1853
	11th to 20th	Day	6% 8% 4 8% 6% 4 4 4 7% 8% 40%	1869
	21st to end	Day	6% 8% 4 9% 6% 5% 5% 4 6% 8% 39%	1590
December	1st to 10th	Day	5% 12% 6% 12% 6% 5% 4 3 5% 6% 37%	2360
	11th to 20th	Day	6% 12% 4 13% 7% 7% 7% 4 6% 7% 27%	2713
	21st to end	Day	6% 9% 4 10% 6% 5% 4 3 5% 6% 41%	3922
January	1st to 10th	Night	3 11% 5% 15% 9% 6% 5% 4 5% 6% 30%	8201
	11th to 20th	Night	3 8% 4 11% 6% 7% 9% 6% 9% 8% 29%	8250
	21st to end	Night	2 9% 5% 12% 6% 5% 6% 4 5% 7% 40%	9026
February	1st to 10th	Night	8% 12% 5% 9% 7% 6% 5% 5% 6% 7% 31%	2935
	11th to 20th	Night	5% 8% 4 10% 7% 5% 5% 4 6% 7% 40%	2480
	21st to end	Night	6% 10% 4 8% 5% 5% 4 4 6% 7% 42%	2076
March	1st to 10th	Night	6% 8% 3 8% 4 5% 5% 3 5% 7% 46%	5494
	11th to 20th	Night	6% 7% 2 7% 5% 4 5% 4 7% 10% 43%	5375
	21st to end	Night	13% 14% 5% 11% 6% 4 5% 4 5% 7% 27%	5212
April	1st to 10th	Night	8% 9% 3 7% 5% 4 6% 5% 7% 7% 39%	2100
	11th to 20th	Night	11% 9% 5% 8% 5% 4 4 4 7% 7% 36%	2002
	21st to end	Night	13% 6% 3 6% 5% 4 4 4 5% 7% 42%	1890
May	1st to 10th	Night	7% 4 2 5% 4 5% 4 4 7% 9% 48%	5088
	11th to 20th	Night	18% 7% 2 6% 4 3 4 3 5% 6% 41%	4701
	21st to end	Night	12% 6% 2 5% 4 3 4 3 5% 8% 48%	5181
June	1st to 10th	Night	8% 4 2 4 4 3 3 4 7% 10% 51%	1547
	11th to 20th	Night	10% 4 2 5% 4 5% 5% 4 7% 8% 46%	1470
	21st to end	Night	6% 4 2 4 3 3 4 3 7% 9% 56%	1545
July	1st to 10th	Night	6% 4 2 4 3 4 4 3 6% 10% 54%	4740
	11th to 20th	Night	3 2 1 3 2 2 3 4 6% 9% 63%	4740
	21st to end	Night	6% 4 2 6% 4 4 5% 4 6% 9% 51%	5152
August	1st to 10th	Night	5% 4 1 4 3 3 3 3 5% 7% 61%	4680
	11th to 20th	Night	7% 5% 2 6% 4 4 4 4 5% 8% 51%	5195
	21st to end	Night	6% 4 1 4 3 3 3 3 5% 7% 60%	6286
September	1st to 10th	Night	6% 3 1 4 2 2 3 3 5% 7% 63%	2100
	11th to 20th	Night	9% 5% 2 5% 3 4 3 3 6% 8% 52%	2168
	21st to end	Night	11% 4 2 4 3 3 3 3 4 7% 56%	2200
October	1st to 10th	Night	10% 4 1 3 2 3 3 3 4 7% 60%	3647
	11th to 20th	Night	8% 7% 2 5% 3 3 5% 4 6% 9% 48%	4113
	21st to end	Night	9% 8% 2 6% 4 3 4 3 5% 7% 48%	4610
November	1st to 10th	Night	7% 9% 3 7% 5% 4 4 4 7% 8% 42%	2665
	11th to 20th	Night	6% 8% 3 9% 6% 5% 5% 4 5% 7% 41%	2749
	21st to end	Night	6% 8% 4 8% 5% 5% 5% 4 6% 8% 42%	3027
December	1st to 10th	Night	5% 10% 5% 12% 7% 5% 6% 3 5% 6% 37%	5050
	11th to 20th	Night	6% 9% 4 10% 7% 6% 6% 4 6% 8% 33%	5714
	21st to end	Night	8% 10% 3 10% 6% 6% 5% 4 5% 6% 37%	7292

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	48% 5% 17% 22% 7%	4723
	11th to 20th	Day	50% 5% 15% 14% 15% 1	4740
	21st to end	Day	45% 5% 17% 23% 10%	5188
February	1st to 10th	Day	53% 4 12% 20% 10% 1	1705
	11th to 20th	Day	49% 4 12% 24% 10% 2	2035
	21st to end	Day	47% 5% 14% 23% 11% 1	1730
March	1st to 10th	Day	38% 5% 12% 31% 14%	4600
	11th to 20th	Day	39% 6% 16% 27% 12%	4816
	21st to end	Day	59% 5% 15% 15% 6%	5960
April	1st to 10th	Day	44% 5% 16% 23% 12% 2	2520
	11th to 20th	Day	48% 6% 12% 23% 11% 1	2568
	21st to end	Day	47% 5% 12% 24% 11% 1	2730
May	1st to 10th	Day	32% 4 10% 32% 20% 1	7842
	11th to 20th	Day	39% 4 9% 24% 18% 4	8195
	21st to end	Day	36% 5% 13% 30% 16% 1	9027
June	1st to 10th	Day	35% 5% 17% 30% 12% 1	3066
	11th to 20th	Day	37% 6% 16% 28% 12% 2	3150
	21st to end	Day	28% 6% 19% 31% 15% 1	3068
July	1st to 10th	Day	31% 8% 17% 31% 11% 1	8181
	11th to 20th	Day	23% 4 9% 31% 26% 7%	8175
	21st to end	Day	31% 7% 14% 29% 17% 2	8759
August	1st to 10th	Day	25% 4 11% 27% 25% 7%	6446
	11th to 20th	Day	38% 8% 19% 26% 8% 1	6038
	21st to end	Day	26% 4 13% 36% 19% 2	6202
September	1st to 10th	Day	27% 3 12% 34% 20% 3	2520
	11th to 20th	Day	32% 4 14% 31% 17% 2	2297
	21st to end	Day	30% 3 11% 33% 21% 3	2200
October	1st to 10th	Day	25% 3 10% 32% 23% 6%	3531
	11th to 20th	Day	30% 3 11% 37% 18% 1	3003
	21st to end	Day	36% 5% 12% 25% 21% 2	3190
November	1st to 10th	Day	41% 5% 14% 24% 15% 1	1853
	11th to 20th	Day	41% 5% 16% 26% 10% 2	1869
	21st to end	Day	43% 5% 18% 23% 10% 1	1590
December	1st to 10th	Day	49% 4 16% 23% 6% 1	2360
	11th to 20th	Day	55% 7% 15% 19% 5%	2710
	21st to end	Day	44% 4 10% 30% 11% 1	3922
January	1st to 10th	Night	55% 4 16% 19% 6%	8202
	11th to 20th	Night	48% 6% 16% 18% 12% 1	8250
	21st to end	Night	44% 5% 18% 23% 11%	9026
February	1st to 10th	Night	51% 5% 13% 19% 12% 1	2935
	11th to 20th	Night	43% 5% 12% 26% 12% 1	2480
	21st to end	Night	42% 4 14% 26% 13% 2	2076
March	1st to 10th	Night	37% 5% 12% 29% 15% 1	5494
	11th to 20th	Night	36% 6% 18% 29% 11%	5375
	21st to end	Night	55% 5% 15% 18% 6%	5212
April	1st to 10th	Night	41% 5% 12% 26% 13% 3	2100
	11th to 20th	Night	46% 5% 10% 23% 14% 2	2002
	21st to end	Night	40% 6% 12% 26% 15% 1	1890
May	1st to 10th	Night	30% 5% 11% 32% 20% 3	5089
	11th to 20th	Night	42% 5% 12% 21% 18% 2	4702
	21st to end	Night	34% 6% 15% 25% 18% 1	5182
June	1st to 10th	Night	28% 5% 17% 34% 13% 3	1547
	11th to 20th	Night	34% 8% 17% 26% 13% 2	1470
	21st to end	Night	24% 5% 20% 33% 16% 2	1545
July	1st to 10th	Night	25% 7% 18% 39% 10% 1	4700
	11th to 20th	Night	18% 5% 12% 33% 25% 8%	4692
	21st to end	Night	30% 6% 20% 27% 14% 3	5038
August	1st to 10th	Night	20% 4 12% 27% 31% 6%	3700
	11th to 20th	Night	35% 7% 20% 27% 9% 2	4094
	21st to end	Night	25% 5% 11% 34% 22% 3	4929
September	1st to 10th	Night	22% 4 11% 35% 24% 4	2100
	11th to 20th	Night	30% 5% 15% 30% 18% 2	2168
	21st to end	Night	29% 4 11% 32% 22% 2	2200
October	1st to 10th	Night	25% 3 8% 26% 31% 6%	3647
	11th to 20th	Night	33% 4 10% 36% 16% 1	4113
	21st to end	Night	36% 4 11% 29% 17% 2	4610
November	1st to 10th	Night	39% 5% 12% 25% 17% 2	2665
	11th to 20th	Night	42% 4 15% 24% 12% 2	2749
	21st to end	Night	40% 6% 18% 26% 10% 1	3027
December	1st to 10th	Night	48% 5% 20% 20% 6%	5050
	11th to 20th	Night	48% 7% 21% 19% 5%	5716
	21st to end	Night	49% 4 11% 23% 13% 1	7292

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	9% 10% 33% 31% 12% 4	330
	11th to 20th	Day	11% 15% 38% 25% 6% 4	330
	21st to end	Day	8% 15% 39% 23% 13% 2	363
February	1st to 10th	Day	11% 13% 40% 30% 6%	330
	11th to 20th	Day	12% 9% 42% 28% 9% 1	330
	21st to end	Day	12% 11% 36% 33% 7%	273
March	1st to 10th	Day	18% 10% 35% 26% 9% 2	330
	11th to 20th	Day	12% 12% 39% 28% 9% 2	330
	21st to end	Day	16% 10% 34% 27% 10% 3	531
April	1st to 10th	Day	17% 16% 35% 24% 8%	540
	11th to 20th	Day	18% 14% 35% 26% 6% 1	606
	21st to end	Day	22% 10% 27% 25% 14% 2	750
May	1st to 10th	Day	14% 9% 29% 31% 13% 3	753
	11th to 20th	Day	18% 10% 27% 29% 14% 3	775
	21st to end	Day	15% 9% 27% 26% 18% 5%	844
June	1st to 10th	Day	12% 9% 26% 29% 20% 4	780
	11th to 20th	Day	14% 10% 36% 26% 12% 2	780
	21st to end	Day	11% 10% 27% 33% 16% 3	780
July	1st to 10th	Day	6% 6% 25% 37% 22% 4	771
	11th to 20th	Day	6% 6% 28% 39% 18% 3	768
	21st to end	Day	6% 4 25% 42% 21% 3	849
August	1st to 10th	Day	9% 4 25% 35% 23% 4	776
	11th to 20th	Day	9% 4 24% 35% 23% 6%	765
	21st to end	Day	8% 6% 24% 34% 22% 5%	689
September	1st to 10th	Day	10% 8% 28% 30% 18% 5%	570
	11th to 20th	Day	13% 6% 28% 31% 17% 3	403
	21st to end	Day	16% 8% 30% 26% 16% 4	330
October	1st to 10th	Day	18% 8% 24% 27% 18% 5%	330
	11th to 20th	Day	16% 14% 36% 19% 13% 1	330
	21st to end	Day	17% 15% 36% 24% 6% 2	363
November	1st to 10th	Day	20% 9% 35% 22% 12% 2	330
	11th to 20th	Day	12% 13% 35% 26% 12% 2	330
	21st to end	Day	9% 16% 30% 32% 12% 1	330
December	1st to 10th	Day	13% 12% 40% 26% 8% 1	330
	11th to 20th	Day	15% 12% 43% 25% 4 1	330
	21st to end	Day	11% 10% 40% 27% 9% 2	363
January	1st to 10th	Night	9% 11% 39% 31% 10% 1	1050
	11th to 20th	Night	11% 16% 37% 28% 9% 1	1050
	21st to end	Night	9% 13% 37% 32% 8%	1155
February	1st to 10th	Night	12% 12% 36% 31% 7% 1	1045
	11th to 20th	Night	8% 8% 40% 33% 10% 1	824
	21st to end	Night	11% 6% 35% 37% 10% 1	692
March	1st to 10th	Night	12% 11% 37% 32% 8% 1	840
	11th to 20th	Night	14% 7% 36% 31% 10% 2	759
	21st to end	Night	18% 7% 34% 31% 10% 1	693
April	1st to 10th	Night	11% 10% 37% 34% 7%	630
	11th to 20th	Night	15% 9% 42% 25% 9%	623
	21st to end	Night	16% 10% 29% 34% 12%	630
May	1st to 10th	Night	12% 7% 29% 39% 13%	630
	11th to 20th	Night	15% 6% 29% 39% 10% 1	621
	21st to end	Night	17% 5% 29% 35% 13%	683
June	1st to 10th	Night	10% 7% 29% 39% 15%	630
	11th to 20th	Night	13% 7% 33% 35% 11%	630
	21st to end	Night	8% 6% 29% 45% 12%	630
July	1st to 10th	Night	7% 2 27% 48% 17%	615
	11th to 20th	Night	5% 3 31% 49% 12%	612
	21st to end	Night	5% 3 24% 52% 15% 1	690
August	1st to 10th	Night	6% 2 27% 50% 14% 1	627
	11th to 20th	Night	8% 2 26% 45% 17% 1	624
	21st to end	Night	6% 4 27% 46% 16% 1	693
September	1st to 10th	Night	8% 4 25% 45% 17% 1	630
	11th to 20th	Night	11% 4 29% 41% 14% 1	609
	21st to end	Night	14% 6% 31% 37% 12% 1	600
October	1st to 10th	Night	18% 7% 24% 39% 11%	631
	11th to 20th	Night	15% 10% 29% 34% 11% 1	925
	21st to end	Night	14% 12% 35% 29% 9% 1	1100
November	1st to 10th	Night	12% 10% 38% 32% 8%	1025
	11th to 20th	Night	10% 11% 39% 30% 10%	1050
	21st to end	Night	10% 12% 36% 34% 8%	1050
December	1st to 10th	Night	13% 10% 36% 33% 8% 1	1050
	11th to 20th	Night	12% 13% 35% 32% 7% 1	1050
	21st to end	Night	15% 10% 34% 31% 10%	1155

Page generated at 2026-09-11 02:11:57. Version ac07

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