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 2024-11-01.

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	9% 7% 3 7% 5% 4 4 4 6% 8% 44%	101328
	Night	8% 8% 3 7% 5% 4 5% 4 6% 7% 44%	97790
Transparency	Day	38% 5% 14% 28% 13% 2	101071
	Night	38% 5% 14% 27% 13% 2	97637
Seeing	Day	12% 9% 30% 30% 15% 3	16060
	Night	11% 9% 33% 35% 11% 1	25993

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 8% 4 12% 7% 6% 5% 4 6% 8% 36%	2538
	11th to 20th	Day	2 7% 3 12% 7% 6% 9% 6% 10% 12% 25%	2540
	21st to end	Day	3 10% 6% 11% 6% 6% 6% 4 5% 6% 37%	2794
February	1st to 10th	Day	8% 12% 4 10% 7% 6% 5% 3 5% 6% 33%	1542
	11th to 20th	Day	5% 12% 5% 11% 6% 4 6% 5% 6% 6% 33%	1827
	21st to end	Day	5% 12% 5% 11% 8% 5% 5% 4 5% 6% 34%	1570
March	1st to 10th	Day	6% 9% 4 10% 6% 5% 4 3 5% 7% 40%	3130
	11th to 20th	Day	6% 7% 3 9% 5% 5% 6% 4 7% 10% 38%	3290
	21st to end	Day	17% 17% 4 9% 6% 4 4 3 4 6% 24%	4069
April	1st to 10th	Day	9% 10% 3 8% 5% 5% 5% 4 7% 8% 36%	2280
	11th to 20th	Day	15% 11% 4 9% 5% 4 4 4 6% 6% 33%	2317
	21st to end	Day	15% 10% 3 7% 5% 4 4 4 5% 6% 37%	2470
May	1st to 10th	Day	15% 8% 2 6% 4 4 4 4 6% 7% 40%	4230
	11th to 20th	Day	10% 6% 2 6% 4 5% 4 4 6% 8% 44%	4388
	21st to end	Day	12% 7% 2 6% 5% 5% 5% 4 6% 8% 41%	4825
June	1st to 10th	Day	13% 5% 2 5% 5% 4 4 4 6% 8% 45%	2774
	11th to 20th	Day	10% 5% 2 5% 6% 5% 4 4 6% 9% 45%	2850
	21st to end	Day	7% 4 2 4 4 3 4 4 6% 8% 53%	2776
July	1st to 10th	Day	6% 4 1 5% 5% 5% 5% 5% 8% 10% 46%	4430
	11th to 20th	Day	4 3 1 3 3 3 3 3 5% 8% 63%	4430
	21st to end	Day	4 3 1 5% 4 4 5% 4 6% 8% 55%	4802
August	1st to 10th	Day	10% 5% 2 5% 3 4 3 3 5% 7% 53%	4411
	11th to 20th	Day	10% 5% 2 6% 5% 5% 5% 4 7% 7% 44%	4078
	21st to end	Day	7% 4 2 4 3 3 3 3 5% 7% 59%	4262
September	1st to 10th	Day	9% 4 2 4 3 4 4 3 5% 5% 58%	2280
	11th to 20th	Day	9% 5% 1 5% 3 3 3 3 5% 7% 55%	2148
	21st to end	Day	11% 6% 1 5% 3 3 2 2 4 6% 56%	2090
October	1st to 10th	Day	13% 6% 2 6% 4 3 3 2 5% 6% 48%	2057
	11th to 20th	Day	11% 9% 2 6% 4 2 4 3 5% 8% 45%	1762
	21st to end	Day	9% 10% 3 6% 4 4 4 3 6% 8% 42%	1881
November	1st to 10th	Day	10% 11% 2 6% 4 4 5% 4 6% 7% 42%	1673
	11th to 20th	Day	6% 8% 4 8% 7% 4 4 4 6% 8% 40%	1691
	21st to end	Day	5% 8% 4 9% 6% 5% 5% 4 6% 9% 39%	1440
December	1st to 10th	Day	6% 11% 4 9% 6% 5% 5% 4 6% 8% 35%	1330
	11th to 20th	Day	5% 12% 4 10% 5% 4 6% 4 6% 9% 36%	1683
	21st to end	Day	8% 10% 3 9% 6% 5% 4 3 5% 6% 41%	2670
January	1st to 10th	Night	4 10% 4 11% 9% 5% 5% 4 6% 6% 37%	4417
	11th to 20th	Night	3 8% 3 9% 6% 7% 12% 7% 9% 9% 27%	4430
	21st to end	Night	3 10% 4 10% 5% 5% 5% 5% 7% 8% 37%	4873
February	1st to 10th	Night	7% 11% 5% 9% 7% 6% 5% 5% 6% 7% 31%	2656
	11th to 20th	Night	5% 9% 4 10% 7% 5% 5% 4 6% 7% 39%	2238
	21st to end	Night	6% 11% 4 8% 6% 6% 4 4 5% 6% 40%	1884
March	1st to 10th	Night	7% 9% 4 8% 5% 5% 5% 3 5% 5% 45%	3734
	11th to 20th	Night	6% 7% 3 6% 4 4 4 4 6% 9% 47%	3675
	21st to end	Night	16% 16% 5% 10% 5% 3 4 3 5% 5% 27%	3553
April	1st to 10th	Night	7% 8% 3 7% 5% 4 6% 5% 8% 8% 39%	1900
	11th to 20th	Night	11% 9% 5% 8% 5% 4 5% 4 7% 7% 35%	1810
	21st to end	Night	13% 6% 3 5% 5% 5% 4 4 5% 7% 42%	1710
May	1st to 10th	Night	13% 6% 2 5% 5% 5% 4 4 6% 7% 45%	2736
	11th to 20th	Night	11% 6% 2 7% 5% 4 5% 4 7% 7% 42%	2517
	21st to end	Night	14% 6% 2 4 4 3 5% 4 7% 9% 45%	2762
June	1st to 10th	Night	9% 4 2 4 4 3 4 4 8% 10% 50%	1400
	11th to 20th	Night	10% 4 2 6% 4 5% 5% 4 7% 7% 46%	1330
	21st to end	Night	5% 4 2 4 3 3 4 3 8% 9% 57%	1397
July	1st to 10th	Night	5% 3 2 5% 4 4 4 4 8% 11% 52%	2540
	11th to 20th	Night	2 3 1 4 3 3 4 4 6% 8% 63%	2540
	21st to end	Night	4 3 2 4 3 3 4 4 6% 9% 59%	2761
August	1st to 10th	Night	6% 4 1 4 3 4 4 3 6% 6% 59%	2528
	11th to 20th	Night	7% 5% 2 5% 4 4 4 4 5% 8% 53%	2761
	21st to end	Night	7% 4 1 4 3 3 3 3 6% 7% 59%	3389
September	1st to 10th	Night	7% 3 1 4 2 2 3 3 5% 7% 63%	1900
	11th to 20th	Night	8% 5% 2 5% 3 3 3 3 5% 8% 55%	2031
	21st to end	Night	12% 5% 2 4 3 3 3 3 4 7% 55%	2090
October	1st to 10th	Night	15% 6% 1 5% 3 4 3 3 5% 7% 47%	2119
	11th to 20th	Night	9% 9% 2 6% 4 3 6% 4 5% 7% 46%	2399
	21st to end	Night	10% 8% 3 7% 5% 3 4 3 5% 8% 45%	2717
November	1st to 10th	Night	7% 9% 4 7% 4 4 4 4 6% 8% 43%	2412
	11th to 20th	Night	6% 8% 3 9% 6% 5% 5% 4 5% 8% 41%	2487
	21st to end	Night	6% 8% 3 8% 5% 4 5% 4 6% 8% 44%	2738
December	1st to 10th	Night	7% 11% 4 10% 7% 5% 6% 4 5% 7% 35%	2850
	11th to 20th	Night	6% 9% 4 9% 6% 5% 5% 3 6% 8% 40%	3514
	21st to end	Night	10% 11% 4 8% 6% 5% 4 4 4 5% 38%	4992

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	46% 5% 19% 23% 6%	2539
	11th to 20th	Day	49% 5% 14% 17% 14% 1	2540
	21st to end	Day	47% 5% 14% 27% 6%	2794
February	1st to 10th	Day	53% 4 13% 20% 10% 1	1542
	11th to 20th	Day	50% 4 12% 23% 9% 1	1837
	21st to end	Day	49% 5% 13% 22% 10% 1	1570
March	1st to 10th	Day	43% 5% 12% 29% 10%	3130
	11th to 20th	Day	40% 6% 19% 29% 7%	3290
	21st to end	Day	61% 4 14% 14% 6%	4069
April	1st to 10th	Day	44% 5% 15% 23% 11% 2	2280
	11th to 20th	Day	51% 5% 11% 22% 10% 1	2320
	21st to end	Day	47% 5% 13% 24% 10% 1	2470
May	1st to 10th	Day	42% 4 12% 27% 13% 1	4230
	11th to 20th	Day	35% 6% 13% 30% 14% 1	4392
	21st to end	Day	40% 6% 17% 30% 7%	4825
June	1st to 10th	Day	36% 5% 17% 29% 11% 1	2774
	11th to 20th	Day	36% 6% 16% 28% 12% 2	2850
	21st to end	Day	27% 6% 19% 30% 15% 1	2776
July	1st to 10th	Day	28% 8% 18% 32% 10% 2	4361
	11th to 20th	Day	19% 5% 11% 33% 27% 5%	4355
	21st to end	Day	24% 6% 14% 34% 19% 2	4651
August	1st to 10th	Day	31% 5% 12% 31% 16% 5%	4396
	11th to 20th	Day	37% 6% 16% 28% 12% 1	4117
	21st to end	Day	25% 4 13% 33% 22% 2	4261
September	1st to 10th	Day	28% 3 11% 34% 21% 3	2280
	11th to 20th	Day	30% 4 14% 32% 18% 2	2148
	21st to end	Day	31% 3 11% 33% 20% 3	2090
October	1st to 10th	Day	37% 4 15% 27% 15% 2	2057
	11th to 20th	Day	38% 4 11% 31% 14% 2	1762
	21st to end	Day	40% 5% 14% 24% 14% 2	1881
November	1st to 10th	Day	41% 6% 14% 23% 15% 2	1673
	11th to 20th	Day	41% 5% 16% 26% 10% 2	1691
	21st to end	Day	42% 6% 18% 23% 11% 1	1440
December	1st to 10th	Day	47% 5% 14% 25% 9% 1	1330
	11th to 20th	Day	45% 5% 19% 24% 7%	1680
	21st to end	Day	45% 4 10% 29% 12% 1	2670
January	1st to 10th	Night	48% 4 16% 23% 9% 1	4417
	11th to 20th	Night	49% 6% 15% 20% 8% 1	4430
	21st to end	Night	44% 6% 16% 26% 7%	4873
February	1st to 10th	Night	50% 5% 13% 19% 12%	2656
	11th to 20th	Night	44% 5% 13% 26% 11% 2	2238
	21st to end	Night	44% 3 13% 24% 13% 2	1884
March	1st to 10th	Night	41% 5% 10% 29% 15%	3734
	11th to 20th	Night	33% 6% 18% 32% 11%	3675
	21st to end	Night	59% 4 14% 15% 7% 1	3553
April	1st to 10th	Night	40% 5% 13% 25% 14% 2	1900
	11th to 20th	Night	47% 6% 10% 23% 14% 2	1810
	21st to end	Night	40% 6% 13% 25% 15% 1	1710
May	1st to 10th	Night	37% 5% 12% 28% 13% 4	2736
	11th to 20th	Night	36% 7% 17% 26% 13%	2518
	21st to end	Night	34% 7% 20% 27% 11% 1	2762
June	1st to 10th	Night	28% 6% 18% 33% 13% 3	1400
	11th to 20th	Night	34% 8% 18% 25% 13% 2	1330
	21st to end	Night	22% 5% 20% 34% 17% 2	1397
July	1st to 10th	Night	26% 7% 18% 36% 11% 3	2500
	11th to 20th	Night	18% 6% 13% 34% 25% 4	2492
	21st to end	Night	22% 5% 18% 32% 19% 4	2674
August	1st to 10th	Night	25% 5% 13% 29% 21% 7%	2520
	11th to 20th	Night	30% 5% 19% 31% 13% 2	2788
	21st to end	Night	25% 5% 10% 34% 22% 4	3389
September	1st to 10th	Night	22% 4 10% 35% 25% 5%	1900
	11th to 20th	Night	28% 4 15% 31% 19% 2	2031
	21st to end	Night	30% 4 11% 32% 20% 2	2090
October	1st to 10th	Night	36% 4 13% 26% 19% 2	2119
	11th to 20th	Night	37% 4 10% 32% 15% 2	2399
	21st to end	Night	38% 4 14% 27% 15% 2	2717
November	1st to 10th	Night	39% 5% 12% 24% 18% 2	2412
	11th to 20th	Night	42% 5% 14% 25% 12% 2	2487
	21st to end	Night	38% 6% 18% 27% 11% 1	2738
December	1st to 10th	Night	48% 5% 15% 22% 8% 1	2850
	11th to 20th	Night	42% 5% 21% 24% 8%	3516
	21st to end	Night	48% 3 10% 24% 13% 1	4992

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% 11% 34% 30% 11% 5%	270
	11th to 20th	Day	10% 13% 39% 26% 7% 5%	270
	21st to end	Day	8% 13% 39% 23% 15% 2	297
February	1st to 10th	Day	10% 13% 41% 30% 6%	270
	11th to 20th	Day	13% 9% 44% 26% 7% 1	270
	21st to end	Day	13% 10% 35% 33% 8%	225
March	1st to 10th	Day	19% 10% 36% 26% 7% 3	270
	11th to 20th	Day	11% 11% 39% 27% 10% 2	270
	21st to end	Day	16% 10% 31% 28% 11% 3	449
April	1st to 10th	Day	15% 17% 34% 25% 8%	460
	11th to 20th	Day	19% 14% 36% 25% 5% 1	518
	21st to end	Day	22% 10% 27% 26% 14% 2	650
May	1st to 10th	Day	16% 9% 30% 30% 13% 3	653
	11th to 20th	Day	16% 9% 27% 30% 15% 3	675
	21st to end	Day	15% 10% 28% 25% 18% 5%	734
June	1st to 10th	Day	12% 9% 24% 29% 21% 5%	680
	11th to 20th	Day	13% 9% 36% 28% 12% 3	680
	21st to end	Day	10% 9% 25% 34% 18% 3	680
July	1st to 10th	Day	6% 6% 25% 37% 21% 4	671
	11th to 20th	Day	6% 6% 28% 39% 19% 3	668
	21st to end	Day	5% 4 25% 42% 22% 3	739
August	1st to 10th	Day	8% 4 25% 35% 23% 5%	676
	11th to 20th	Day	9% 4 23% 35% 23% 6%	665
	21st to end	Day	9% 6% 23% 35% 22% 5%	595
September	1st to 10th	Day	11% 8% 28% 29% 19% 6%	490
	11th to 20th	Day	11% 6% 29% 33% 18% 4	358
	21st to end	Day	18% 8% 31% 25% 14% 3	300
October	1st to 10th	Day	20% 9% 23% 26% 17% 5%	300
	11th to 20th	Day	14% 14% 37% 20% 15% 1	300
	21st to end	Day	18% 15% 35% 24% 5% 2	330
November	1st to 10th	Day	21% 9% 33% 21% 13% 3	270
	11th to 20th	Day	12% 14% 35% 26% 11% 2	270
	21st to end	Day	10% 16% 30% 33% 10% 1	270
December	1st to 10th	Day	12% 11% 39% 26% 10% 1	270
	11th to 20th	Day	13% 11% 44% 27% 4 1	270
	21st to end	Day	11% 12% 41% 24% 10% 3	297
January	1st to 10th	Night	9% 11% 39% 30% 10% 1	950
	11th to 20th	Night	11% 15% 36% 29% 9% 1	950
	21st to end	Night	9% 13% 37% 32% 8%	1045
February	1st to 10th	Night	12% 11% 36% 32% 8% 1	946
	11th to 20th	Night	8% 9% 42% 31% 9% 1	744
	21st to end	Night	11% 6% 34% 37% 11% 1	628
March	1st to 10th	Night	12% 12% 36% 31% 8% 2	760
	11th to 20th	Night	14% 7% 36% 30% 10% 2	687
	21st to end	Night	18% 6% 33% 31% 11% 1	627
April	1st to 10th	Night	10% 10% 38% 34% 7%	570
	11th to 20th	Night	15% 9% 42% 25% 9% 1	563
	21st to end	Night	16% 9% 28% 33% 13% 1	570
May	1st to 10th	Night	13% 7% 28% 38% 14%	570
	11th to 20th	Night	14% 5% 29% 41% 11% 1	561
	21st to end	Night	17% 5% 31% 34% 13%	617
June	1st to 10th	Night	10% 7% 28% 40% 15%	570
	11th to 20th	Night	13% 7% 34% 34% 12%	570
	21st to end	Night	6% 5% 28% 46% 13%	570
July	1st to 10th	Night	6% 2 27% 47% 17%	555
	11th to 20th	Night	5% 3 29% 50% 13%	552
	21st to end	Night	4 4 22% 53% 16% 1	624
August	1st to 10th	Night	6% 2 25% 51% 15% 1	567
	11th to 20th	Night	8% 2 26% 45% 17% 2	564
	21st to end	Night	6% 3 28% 44% 17% 1	627
September	1st to 10th	Night	9% 3 24% 45% 17% 1	570
	11th to 20th	Night	9% 5% 29% 41% 15% 1	570
	21st to end	Night	14% 6% 32% 36% 11% 1	570
October	1st to 10th	Night	18% 8% 25% 38% 11% 1	599
	11th to 20th	Night	14% 10% 28% 35% 12% 1	879
	21st to end	Night	14% 12% 35% 29% 9% 1	1045
November	1st to 10th	Night	12% 11% 38% 32% 8%	928
	11th to 20th	Night	10% 11% 39% 29% 11%	950
	21st to end	Night	10% 12% 37% 33% 7%	950
December	1st to 10th	Night	13% 10% 36% 32% 9% 1	950
	11th to 20th	Night	12% 12% 35% 33% 8% 1	950
	21st to end	Night	16% 11% 33% 29% 10%	1045

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