Potsdam
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Potsdam clear sky chart from 2005-11-06 to 2024-12-09.

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	18% 11% 4 8% 5% 4 4 4 5% 6% 30%	101841
	Night	19% 13% 4 9% 5% 4 4 3 4 5% 28%	97946
Transparency	Day	53% 8% 12% 20% 8% 1	105311
	Night	56% 7% 11% 17% 8% 1	102565
Seeing	Day	26% 17% 29% 18% 7% 2	14659
	Night	26% 16% 29% 21% 7% 1	23762

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	17% 22% 6% 14% 7% 5% 4 3 3 4 14%	2517
	11th to 20th	Day	14% 20% 8% 18% 8% 6% 3 3 3 4 14%	2520
	21st to end	Day	16% 23% 8% 12% 6% 8% 4 3 4 4 13%	2864
February	1st to 10th	Day	17% 17% 5% 15% 7% 5% 3 3 4 5% 19%	1710
	11th to 20th	Day	15% 17% 8% 12% 7% 5% 4 2 4 4 21%	1720
	21st to end	Day	19% 18% 5% 10% 7% 5% 3 3 4 4 21%	1570
March	1st to 10th	Day	22% 16% 5% 9% 5% 4 3 3 4 5% 26%	3116
	11th to 20th	Day	15% 22% 4 10% 6% 4 4 3 4 4 25%	3406
	21st to end	Day	16% 11% 3 9% 5% 4 3 3 4 5% 36%	4086
April	1st to 10th	Day	22% 14% 4 7% 4 4 4 3 4 5% 30%	2280
	11th to 20th	Day	22% 11% 3 7% 4 4 3 3 4 4 35%	2254
	21st to end	Day	24% 11% 3 6% 4 4 4 3 5% 5% 31%	2362
May	1st to 10th	Day	22% 10% 3 8% 5% 5% 4 3 5% 6% 29%	4426
	11th to 20th	Day	18% 10% 3 8% 5% 5% 5% 3 5% 6% 31%	4398
	21st to end	Day	16% 7% 2 6% 5% 4 5% 4 7% 8% 36%	4837
June	1st to 10th	Day	25% 7% 2 7% 5% 4 4 4 6% 7% 29%	2660
	11th to 20th	Day	19% 5% 2 6% 5% 4 4 6% 5% 8% 35%	2660
	21st to end	Day	22% 7% 2 6% 4 5% 4 5% 5% 7% 32%	2660
July	1st to 10th	Day	14% 6% 2 6% 4 4 5% 5% 7% 10% 37%	4440
	11th to 20th	Day	14% 6% 3 6% 4 5% 5% 5% 6% 8% 38%	4440
	21st to end	Day	13% 6% 2 6% 4 5% 5% 5% 7% 9% 39%	4814
August	1st to 10th	Day	18% 7% 3 7% 4 5% 4 4 6% 8% 34%	4399
	11th to 20th	Day	17% 6% 3 6% 4 4 4 4 6% 7% 37%	3898
	21st to end	Day	18% 6% 2 6% 3 4 4 4 6% 8% 38%	4180
September	1st to 10th	Day	17% 6% 2 6% 3 4 4 4 5% 7% 41%	2280
	11th to 20th	Day	15% 6% 2 5% 4 3 4 4 5% 7% 45%	2247
	21st to end	Day	19% 6% 2 6% 4 5% 5% 3 6% 6% 38%	2081
October	1st to 10th	Day	21% 9% 3 8% 4 4 4 4 5% 6% 32%	1900
	11th to 20th	Day	21% 13% 3 8% 5% 4 5% 3 4 5% 27%	1900
	21st to end	Day	27% 13% 3 7% 5% 4 4 3 4 5% 25%	1911
November	1st to 10th	Day	16% 12% 4 9% 6% 5% 4 4 5% 6% 29%	1761
	11th to 20th	Day	17% 15% 4 8% 5% 5% 6% 3 4 5% 28%	1682
	21st to end	Day	21% 20% 5% 10% 5% 4 4 3 4 4 20%	1600
December	1st to 10th	Day	24% 22% 5% 12% 7% 4 3 3 3 4 12%	1584
	11th to 20th	Day	21% 20% 7% 10% 6% 4 3 3 3 4 20%	1906
	21st to end	Day	25% 20% 5% 12% 4 4 4 3 3 3 16%	2772
January	1st to 10th	Night	18% 23% 7% 13% 5% 4 3 3 3 4 17%	4429
	11th to 20th	Night	15% 20% 8% 18% 7% 5% 5% 3 3 3 13%	4440
	21st to end	Night	20% 21% 7% 13% 6% 5% 3 2 3 3 15%	4788
February	1st to 10th	Night	18% 20% 6% 13% 8% 4 3 3 4 5% 17%	2470
	11th to 20th	Night	15% 16% 6% 12% 6% 5% 4 3 4 5% 23%	2346
	21st to end	Night	17% 17% 5% 11% 7% 3 3 3 4 4 25%	1884
March	1st to 10th	Night	20% 14% 4 8% 5% 3 3 2 3 5% 31%	3724
	11th to 20th	Night	20% 22% 5% 8% 4 3 3 2 3 4 25%	3548
	21st to end	Night	17% 15% 4 8% 5% 4 3 3 3 4 36%	3545
April	1st to 10th	Night	22% 13% 4 8% 5% 3 3 3 4 5% 30%	1900
	11th to 20th	Night	23% 11% 3 7% 4 4 4 2 3 6% 33%	1875
	21st to end	Night	23% 12% 2 6% 4 4 4 2 4 5% 33%	1825
May	1st to 10th	Night	25% 11% 3 6% 4 4 5% 4 6% 7% 26%	2522
	11th to 20th	Night	21% 10% 3 7% 4 4 4 3 5% 6% 33%	2495
	21st to end	Night	16% 7% 3 7% 5% 4 4 3 6% 9% 39%	2738
June	1st to 10th	Night	22% 6% 3 6% 6% 5% 6% 4 6% 7% 30%	1520
	11th to 20th	Night	18% 6% 2 7% 4 4 4 5% 4 9% 38%	1520
	21st to end	Night	21% 7% 3 6% 5% 5% 6% 5% 4 7% 31%	1520
July	1st to 10th	Night	17% 7% 3 6% 5% 5% 4 4 5% 7% 37%	2520
	11th to 20th	Night	14% 7% 3 6% 4 4 4 4 6% 8% 41%	2520
	21st to end	Night	13% 7% 3 7% 4 5% 5% 3 6% 7% 39%	2739
August	1st to 10th	Night	18% 8% 2 7% 5% 4 4 3 5% 7% 37%	2528
	11th to 20th	Night	17% 8% 3 8% 5% 4 4 3 5% 7% 36%	2899
	21st to end	Night	14% 6% 3 7% 5% 4 5% 3 6% 8% 40%	3476
September	1st to 10th	Night	16% 7% 2 6% 4 4 4 3 4 6% 44%	1900
	11th to 20th	Night	16% 5% 2 5% 4 3 3 3 4 7% 50%	1932
	21st to end	Night	17% 8% 2 6% 4 4 4 4 5% 8% 38%	2095
October	1st to 10th	Night	22% 8% 2 6% 4 4 4 4 4 7% 33%	2280
	11th to 20th	Night	21% 9% 3 7% 5% 5% 5% 3 5% 6% 32%	2280
	21st to end	Night	27% 12% 3 7% 5% 5% 4 3 4 6% 25%	2685
November	1st to 10th	Night	20% 13% 3 7% 4 4 4 4 4 6% 32%	2537
	11th to 20th	Night	19% 13% 4 9% 5% 5% 4 3 4 5% 30%	2715
	21st to end	Night	23% 17% 6% 8% 5% 4 4 3 4 4 22%	2800
December	1st to 10th	Night	22% 22% 6% 12% 6% 4 4 3 3 4 13%	2779
	11th to 20th	Night	23% 19% 5% 10% 5% 4 3 2 3 3 23%	3288
	21st to end	Night	29% 19% 5% 12% 5% 3 3 2 3 4 14%	4884

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	72% 11% 8% 7% 2	2518
	11th to 20th	Day	73% 8% 8% 6% 4 1	2520
	21st to end	Day	76% 7% 8% 6% 3 1	2864
February	1st to 10th	Day	69% 6% 7% 15% 3 1	1710
	11th to 20th	Day	66% 7% 9% 12% 6% 1	1729
	21st to end	Day	66% 7% 8% 11% 6% 1	1570
March	1st to 10th	Day	60% 7% 10% 16% 7% 1	3119
	11th to 20th	Day	60% 8% 12% 11% 7% 1	3406
	21st to end	Day	48% 8% 8% 19% 14% 2	4086
April	1st to 10th	Day	57% 5% 7% 19% 10% 2	2280
	11th to 20th	Day	52% 5% 8% 18% 14% 2	2254
	21st to end	Day	54% 5% 10% 15% 13% 3	2362
May	1st to 10th	Day	54% 8% 10% 19% 8% 1	4440
	11th to 20th	Day	51% 10% 11% 19% 8% 1	4402
	21st to end	Day	42% 10% 12% 24% 12% 1	4837
June	1st to 10th	Day	52% 9% 12% 17% 10% 1	2660
	11th to 20th	Day	45% 8% 12% 23% 10% 2	2660
	21st to end	Day	51% 8% 11% 19% 10% 1	2660
July	1st to 10th	Day	41% 7% 14% 28% 10%	4370
	11th to 20th	Day	41% 8% 15% 29% 7%	4365
	21st to end	Day	40% 9% 13% 31% 7%	4661
August	1st to 10th	Day	47% 7% 15% 22% 9%	4385
	11th to 20th	Day	45% 8% 16% 25% 6%	3937
	21st to end	Day	42% 7% 17% 23% 10%	4180
September	1st to 10th	Day	41% 8% 14% 25% 12%	2280
	11th to 20th	Day	38% 7% 12% 29% 14% 1	2247
	21st to end	Day	44% 8% 13% 25% 9%	2081
October	1st to 10th	Day	48% 6% 12% 26% 9%	3160
	11th to 20th	Day	51% 5% 14% 23% 6%	3140
	21st to end	Day	49% 5% 17% 22% 6% 1	3123
November	1st to 10th	Day	54% 8% 12% 19% 6% 1	1761
	11th to 20th	Day	58% 7% 11% 14% 9% 2	1682
	21st to end	Day	67% 9% 11% 9% 4	1600
December	1st to 10th	Day	75% 6% 9% 7% 2	1584
	11th to 20th	Day	69% 9% 10% 10% 2	1906
	21st to end	Day	74% 6% 6% 12% 2	2772
January	1st to 10th	Night	70% 10% 10% 8% 3	4429
	11th to 20th	Night	73% 10% 7% 6% 3	4440
	21st to end	Night	74% 6% 7% 8% 3 1	4788
February	1st to 10th	Night	71% 6% 9% 9% 5%	2470
	11th to 20th	Night	64% 6% 9% 16% 5%	2348
	21st to end	Night	62% 7% 9% 15% 7%	1884
March	1st to 10th	Night	55% 6% 9% 21% 8% 1	3734
	11th to 20th	Night	61% 7% 13% 12% 5% 1	3549
	21st to end	Night	52% 6% 6% 21% 13% 2	3545
April	1st to 10th	Night	57% 5% 8% 18% 10% 1	1900
	11th to 20th	Night	54% 5% 9% 18% 12% 1	1875
	21st to end	Night	54% 5% 8% 17% 12% 3	1825
May	1st to 10th	Night	54% 10% 11% 14% 9% 2	2528
	11th to 20th	Night	49% 10% 12% 19% 9% 1	2496
	21st to end	Night	41% 7% 13% 21% 17% 1	2739
June	1st to 10th	Night	49% 10% 14% 17% 9% 1	1520
	11th to 20th	Night	43% 7% 14% 20% 15% 1	1520
	21st to end	Night	51% 8% 12% 18% 11%	1520
July	1st to 10th	Night	45% 6% 12% 22% 13% 1	2480
	11th to 20th	Night	39% 7% 16% 30% 8%	2472
	21st to end	Night	43% 9% 13% 24% 12%	2651
August	1st to 10th	Night	47% 7% 14% 23% 8%	2518
	11th to 20th	Night	46% 7% 15% 23% 8% 1	2926
	21st to end	Night	41% 6% 15% 26% 10% 1	3476
September	1st to 10th	Night	41% 7% 13% 25% 12% 1	1900
	11th to 20th	Night	35% 7% 15% 30% 13%	1932
	21st to end	Night	43% 7% 12% 26% 11% 1	2095
October	1st to 10th	Night	47% 6% 12% 25% 9% 1	3800
	11th to 20th	Night	47% 6% 15% 21% 10%	3779
	21st to end	Night	52% 6% 16% 19% 6% 1	4423
November	1st to 10th	Night	53% 7% 13% 17% 8% 1	2537
	11th to 20th	Night	56% 8% 12% 15% 7% 3	2715
	21st to end	Night	66% 7% 11% 12% 4	2800
December	1st to 10th	Night	76% 7% 8% 8% 2	2779
	11th to 20th	Night	68% 7% 9% 13% 4	3288
	21st to end	Night	74% 7% 7% 10% 1	4884

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	35% 16% 31% 14% 4	180
	11th to 20th	Day	33% 24% 28% 12% 3 1	180
	21st to end	Day	25% 24% 33% 18% 1	223
February	1st to 10th	Day	38% 29% 27% 6%	270
	11th to 20th	Day	30% 32% 33% 5%	327
	21st to end	Day	36% 23% 31% 9% 1	382
March	1st to 10th	Day	32% 21% 30% 14% 3	460
	11th to 20th	Day	34% 22% 29% 12% 3	460
	21st to end	Day	36% 22% 24% 11% 6%	506
April	1st to 10th	Day	37% 19% 28% 12% 4	460
	11th to 20th	Day	35% 20% 24% 15% 4 2	452
	21st to end	Day	36% 20% 25% 12% 6% 2	460
May	1st to 10th	Day	28% 19% 28% 18% 7% 1	463
	11th to 20th	Day	22% 19% 30% 19% 9% 1	487
	21st to end	Day	21% 17% 28% 25% 9%	529
June	1st to 10th	Day	30% 15% 30% 19% 6% 1	490
	11th to 20th	Day	19% 15% 36% 21% 7% 2	490
	21st to end	Day	27% 16% 32% 15% 9% 1	490
July	1st to 10th	Day	16% 11% 33% 26% 12% 2	485
	11th to 20th	Day	15% 13% 32% 28% 10% 2	484
	21st to end	Day	16% 11% 34% 29% 9% 1	532
August	1st to 10th	Day	17% 11% 29% 28% 12% 2	486
	11th to 20th	Day	18% 9% 27% 29% 12% 4	479
	21st to end	Day	16% 12% 35% 23% 10% 4	539
September	1st to 10th	Day	19% 13% 30% 22% 11% 6%	490
	11th to 20th	Day	14% 11% 24% 25% 16% 9%	490
	21st to end	Day	19% 13% 29% 25% 11% 3	490
October	1st to 10th	Day	27% 17% 24% 18% 10% 4	490
	11th to 20th	Day	29% 20% 29% 14% 6% 1	490
	21st to end	Day	37% 16% 26% 17% 4	444
November	1st to 10th	Day	30% 19% 29% 17% 5% 1	395
	11th to 20th	Day	28% 24% 28% 13% 5% 1	282
	21st to end	Day	35% 23% 31% 9% 4	200
December	1st to 10th	Day	38% 13% 28% 18% 3	196
	11th to 20th	Day	34% 30% 27% 7% 1 1	180
	21st to end	Day	39% 20% 27% 11% 2	198
January	1st to 10th	Night	33% 20% 31% 14% 2	760
	11th to 20th	Night	29% 24% 27% 15% 4	760
	21st to end	Night	23% 21% 32% 20% 4	836
February	1st to 10th	Night	29% 23% 32% 15% 1	760
	11th to 20th	Night	26% 21% 37% 14% 2	743
	21st to end	Night	28% 20% 33% 16% 3	628
March	1st to 10th	Night	29% 19% 30% 20% 2	760
	11th to 20th	Night	31% 19% 31% 16% 4	760
	21st to end	Night	29% 17% 28% 19% 5% 1	836
April	1st to 10th	Night	30% 18% 30% 20% 3	760
	11th to 20th	Night	31% 19% 27% 16% 7%	751
	21st to end	Night	32% 14% 30% 19% 6%	685
May	1st to 10th	Night	28% 12% 32% 22% 5% 1	388
	11th to 20th	Night	21% 11% 35% 28% 5% 1	374
	21st to end	Night	17% 11% 36% 27% 9%	411
June	1st to 10th	Night	23% 10% 28% 33% 6%	380
	11th to 20th	Night	20% 10% 29% 29% 11% 1	380
	21st to end	Night	20% 9% 33% 28% 9% 1	380
July	1st to 10th	Night	13% 7% 32% 40% 8% 1	370
	11th to 20th	Night	12% 6% 33% 36% 13%	368
	21st to end	Night	13% 7% 35% 37% 7% 1	416
August	1st to 10th	Night	17% 6% 27% 36% 14%	387
	11th to 20th	Night	20% 6% 22% 35% 16% 1	626
	21st to end	Night	16% 6% 33% 30% 13% 2	836
September	1st to 10th	Night	19% 9% 28% 30% 13% 1	760
	11th to 20th	Night	17% 9% 23% 30% 18% 3	760
	21st to end	Night	19% 13% 25% 25% 17% 1	760
October	1st to 10th	Night	27% 12% 28% 20% 12% 1	760
	11th to 20th	Night	28% 16% 27% 22% 7%	760
	21st to end	Night	35% 16% 26% 21% 3	836
November	1st to 10th	Night	30% 18% 29% 17% 6% 1	780
	11th to 20th	Night	29% 20% 27% 15% 8% 1	800
	21st to end	Night	34% 21% 25% 15% 5%	800
December	1st to 10th	Night	35% 21% 25% 16% 3	795
	11th to 20th	Night	32% 22% 30% 13% 3 1	760
	21st to end	Night	37% 18% 28% 14% 3	836

Page generated at 2024-12-06 03:54:50. Version ac07

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