Goethe Link Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Goethe Link Observatory clear sky chart from 2005-11-06 to 2024-11-06.

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% 9% 3 7% 4 4 4 4 6% 8% 38%	101047
	Night	14% 10% 3 7% 4 4 4 3 5% 6% 39%	98041
Transparency	Day	43% 6% 11% 23% 15% 2	104688
	Night	44% 5% 10% 22% 16% 2	102541
Seeing	Day	16% 10% 26% 25% 17% 7%	15571
	Night	17% 9% 27% 30% 15% 2	25374

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	15% 17% 8% 9% 4 4 3 3 4 5% 27%	2527
	11th to 20th	Day	16% 12% 5% 14% 6% 6% 6% 5% 5% 4 21%	2530
	21st to end	Day	26% 19% 7% 8% 5% 3 3 2 3 4 19%	2922
February	1st to 10th	Day	18% 13% 6% 9% 5% 4 4 4 4 5% 30%	1900
	11th to 20th	Day	15% 10% 4 11% 4 5% 4 3 5% 6% 32%	1848
	21st to end	Day	17% 15% 5% 9% 4 3 3 3 4 6% 32%	1570
March	1st to 10th	Day	22% 18% 3 7% 4 3 3 3 3 4 31%	3120
	11th to 20th	Day	14% 8% 2 6% 4 4 3 3 5% 7% 45%	3343
	21st to end	Day	15% 11% 3 8% 5% 5% 5% 4 6% 6% 32%	4005
April	1st to 10th	Day	13% 11% 3 8% 5% 4 4 3 6% 7% 36%	2280
	11th to 20th	Day	16% 10% 2 7% 4 4 4 3 6% 6% 39%	2254
	21st to end	Day	20% 8% 2 8% 5% 4 4 3 5% 7% 35%	2422
May	1st to 10th	Day	18% 9% 3 8% 5% 5% 5% 4 7% 9% 28%	4082
	11th to 20th	Day	20% 7% 2 6% 4 4 4 3 5% 7% 38%	4081
	21st to end	Day	9% 6% 3 7% 5% 5% 5% 5% 7% 9% 38%	4589
June	1st to 10th	Day	11% 7% 2 6% 5% 4 4 4 6% 8% 42%	2660
	11th to 20th	Day	9% 5% 2 5% 5% 5% 5% 4 7% 9% 45%	2660
	21st to end	Day	9% 6% 2 6% 5% 5% 5% 4 7% 10% 41%	2660
July	1st to 10th	Day	14% 6% 2 6% 4 5% 5% 4 7% 10% 38%	4440
	11th to 20th	Day	6% 4 2 5% 4 4 6% 4 7% 11% 46%	4440
	21st to end	Day	9% 7% 2 8% 5% 6% 6% 5% 8% 10% 34%	4688
August	1st to 10th	Day	7% 5% 2 5% 3 4 5% 4 7% 10% 47%	4104
	11th to 20th	Day	9% 5% 2 6% 4 4 6% 4 8% 11% 41%	3822
	21st to end	Day	6% 4 2 5% 4 4 4 3 6% 9% 54%	4180
September	1st to 10th	Day	12% 5% 2 5% 5% 4 5% 4 6% 8% 44%	2257
	11th to 20th	Day	10% 4 2 5% 4 4 5% 4 6% 8% 48%	2090
	21st to end	Day	13% 5% 2 6% 4 4 4 3 6% 6% 49%	2090
October	1st to 10th	Day	12% 5% 2 6% 4 3 4 3 5% 8% 49%	2090
	11th to 20th	Day	13% 6% 2 7% 4 4 5% 4 5% 7% 45%	1945
	21st to end	Day	18% 10% 2 8% 4 4 4 3 4 6% 37%	1881
November	1st to 10th	Day	9% 6% 3 6% 3 3 3 3 5% 6% 53%	1717
	11th to 20th	Day	15% 10% 3 7% 4 4 4 3 4 6% 39%	1710
	21st to end	Day	18% 12% 3 8% 4 4 3 2 4 6% 36%	1710
December	1st to 10th	Day	18% 15% 4 9% 5% 4 4 3 4 6% 30%	1710
	11th to 20th	Day	15% 16% 7% 9% 4 4 3 3 4 5% 30%	1937
	21st to end	Day	20% 21% 8% 10% 4 4 3 3 4 5% 18%	2783
January	1st to 10th	Night	18% 16% 7% 11% 5% 4 3 3 4 5% 24%	4428
	11th to 20th	Night	14% 19% 6% 14% 6% 5% 4 3 4 4 21%	4440
	21st to end	Night	25% 18% 6% 8% 5% 3 3 2 3 4 23%	4733
February	1st to 10th	Night	19% 11% 4 10% 6% 4 4 3 5% 5% 29%	2280
	11th to 20th	Night	14% 11% 4 10% 5% 5% 4 3 5% 6% 33%	2218
	21st to end	Night	19% 13% 4 8% 5% 3 4 2 4 5% 31%	1884
March	1st to 10th	Night	20% 16% 3 7% 4 3 3 2 4 5% 33%	3733
	11th to 20th	Night	13% 6% 2 6% 4 4 4 3 4 6% 47%	3616
	21st to end	Night	17% 8% 3 7% 5% 4 4 3 4 6% 39%	3640
April	1st to 10th	Night	14% 9% 3 6% 5% 4 4 4 5% 6% 39%	1900
	11th to 20th	Night	15% 9% 3 6% 4 4 4 3 4 7% 42%	1875
	21st to end	Night	16% 8% 2 7% 4 4 4 4 6% 7% 37%	1757
May	1st to 10th	Night	18% 11% 3 9% 5% 5% 4 4 5% 7% 29%	2813
	11th to 20th	Night	19% 6% 3 6% 4 3 3 3 5% 8% 40%	2812
	21st to end	Night	9% 6% 2 6% 5% 4 4 4 6% 9% 44%	2966
June	1st to 10th	Night	9% 5% 2 6% 4 4 4 3 5% 8% 49%	1520
	11th to 20th	Night	8% 5% 2 6% 4 4 4 3 5% 9% 49%	1520
	21st to end	Night	6% 4 2 5% 4 5% 5% 5% 8% 9% 46%	1520
July	1st to 10th	Night	10% 6% 2 5% 4 4 4 3 5% 9% 49%	2530
	11th to 20th	Night	5% 3 2 5% 3 4 4 4 6% 9% 55%	2530
	21st to end	Night	9% 7% 3 6% 5% 4 5% 4 7% 10% 40%	2869
August	1st to 10th	Night	9% 4 2 6% 4 4 4 3 4 9% 51%	2825
	11th to 20th	Night	7% 4 1 6% 5% 4 5% 5% 7% 9% 48%	3003
	21st to end	Night	4 3 1 5% 4 4 4 4 5% 8% 57%	3476
September	1st to 10th	Night	11% 6% 2 5% 4 4 4 2 5% 6% 50%	1902
	11th to 20th	Night	8% 5% 1 4 3 4 4 4 5% 8% 55%	2090
	21st to end	Night	12% 6% 2 6% 4 4 4 3 5% 6% 49%	2090
October	1st to 10th	Night	9% 3 2 5% 3 4 4 4 5% 6% 55%	2090
	11th to 20th	Night	16% 7% 2 5% 3 3 3 3 5% 5% 49%	2232
	21st to end	Night	17% 8% 3 6% 3 4 4 3 5% 6% 41%	2717
November	1st to 10th	Night	11% 7% 3 6% 4 3 3 4 5% 5% 50%	2483
	11th to 20th	Night	13% 9% 3 7% 4 4 4 3 6% 7% 40%	2470
	21st to end	Night	19% 12% 3 7% 4 4 4 3 4 5% 34%	2470
December	1st to 10th	Night	18% 12% 4 9% 6% 3 4 3 5% 7% 30%	2470
	11th to 20th	Night	18% 12% 4 9% 4 3 3 3 4 6% 33%	3255
	21st to end	Night	22% 20% 6% 9% 5% 5% 4 3 4 4 18%	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	59% 4 8% 20% 8% 1	2528
	11th to 20th	Day	61% 6% 12% 13% 7%	2530
	21st to end	Day	69% 5% 6% 16% 3 1	2922
February	1st to 10th	Day	57% 4 9% 18% 11% 1	1900
	11th to 20th	Day	53% 5% 10% 21% 10% 1	1858
	21st to end	Day	54% 5% 8% 21% 9% 2	1570
March	1st to 10th	Day	58% 4 6% 18% 12% 3	3120
	11th to 20th	Day	40% 5% 11% 29% 14% 1	3343
	21st to end	Day	50% 7% 13% 22% 7% 1	4005
April	1st to 10th	Day	47% 5% 12% 21% 15% 1	2280
	11th to 20th	Day	45% 5% 10% 24% 12% 3	2254
	21st to end	Day	49% 5% 10% 21% 11% 3	2422
May	1st to 10th	Day	51% 7% 13% 22% 6%	4120
	11th to 20th	Day	45% 7% 12% 25% 11%	4085
	21st to end	Day	38% 8% 13% 20% 19% 2	4602
June	1st to 10th	Day	38% 7% 11% 25% 16% 3	2660
	11th to 20th	Day	35% 7% 11% 24% 21% 3	2660
	21st to end	Day	37% 8% 15% 20% 16% 4	2660
July	1st to 10th	Day	40% 7% 12% 24% 16% 2	4371
	11th to 20th	Day	29% 8% 15% 29% 18% 1	4365
	21st to end	Day	41% 9% 15% 18% 14% 3	4540
August	1st to 10th	Day	28% 9% 16% 31% 15% 1	4091
	11th to 20th	Day	33% 8% 13% 31% 14% 1	3861
	21st to end	Day	26% 7% 15% 30% 18% 4	4179
September	1st to 10th	Day	37% 6% 11% 24% 18% 4	2257
	11th to 20th	Day	33% 5% 11% 26% 23% 3	2090
	21st to end	Day	34% 6% 10% 24% 23% 2	2090
October	1st to 10th	Day	23% 4 8% 30% 33% 2	3480
	11th to 20th	Day	32% 5% 8% 26% 28% 2	3200
	21st to end	Day	40% 3 9% 23% 23% 1	3081
November	1st to 10th	Day	33% 4 12% 29% 18% 4	1717
	11th to 20th	Day	46% 4 9% 22% 15% 4	1710
	21st to end	Day	50% 3 9% 22% 14% 1	1710
December	1st to 10th	Day	56% 4 10% 19% 11%	1710
	11th to 20th	Day	57% 4 6% 23% 9% 1	1934
	21st to end	Day	68% 5% 10% 11% 6%	2783
January	1st to 10th	Night	61% 5% 10% 16% 7%	4428
	11th to 20th	Night	68% 4 9% 13% 6%	4440
	21st to end	Night	67% 3 8% 14% 8% 1	4733
February	1st to 10th	Night	58% 4 11% 18% 7% 1	2280
	11th to 20th	Night	51% 5% 10% 20% 12% 1	2219
	21st to end	Night	56% 4 9% 18% 11% 2	1884
March	1st to 10th	Night	55% 4 7% 22% 11% 1	3733
	11th to 20th	Night	37% 6% 12% 23% 20% 2	3616
	21st to end	Night	46% 6% 10% 29% 8% 1	3640
April	1st to 10th	Night	45% 5% 11% 23% 13% 3	1900
	11th to 20th	Night	44% 5% 9% 20% 17% 5%	1875
	21st to end	Night	45% 6% 10% 22% 14% 3	1757
May	1st to 10th	Night	53% 8% 10% 20% 7% 1	2840
	11th to 20th	Night	42% 7% 13% 26% 11% 1	2813
	21st to end	Night	34% 8% 14% 24% 16% 4	2974
June	1st to 10th	Night	33% 6% 10% 26% 21% 3	1520
	11th to 20th	Night	32% 8% 10% 24% 21% 5%	1520
	21st to end	Night	31% 7% 15% 23% 19% 4	1520
July	1st to 10th	Night	33% 7% 11% 27% 19% 4	2490
	11th to 20th	Night	24% 7% 15% 31% 22% 2	2482
	21st to end	Night	37% 8% 16% 21% 14% 4	2778
August	1st to 10th	Night	31% 7% 14% 34% 13% 1	2814
	11th to 20th	Night	30% 8% 14% 28% 18% 1	3030
	21st to end	Night	25% 6% 13% 30% 22% 4	3476
September	1st to 10th	Night	35% 5% 10% 24% 20% 6%	1902
	11th to 20th	Night	27% 6% 9% 27% 27% 4	2090
	21st to end	Night	36% 5% 10% 22% 23% 4	2090
October	1st to 10th	Night	19% 5% 7% 24% 43% 3	3480
	11th to 20th	Night	27% 3 7% 26% 35% 3	3716
	21st to end	Night	34% 4 8% 24% 25% 5%	4467
November	1st to 10th	Night	36% 4 10% 25% 22% 4	2483
	11th to 20th	Night	43% 4 10% 22% 18% 3	2470
	21st to end	Night	53% 3 9% 22% 12% 1	2470
December	1st to 10th	Night	55% 4 10% 19% 11% 1	2470
	11th to 20th	Night	53% 3 10% 20% 13% 1	3257
	21st to end	Night	70% 5% 8% 10% 6%	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	25% 13% 35% 21% 5% 1	270
	11th to 20th	Day	26% 19% 33% 18% 3 1	270
	21st to end	Day	27% 20% 30% 19% 4	297
February	1st to 10th	Day	27% 16% 36% 17% 4	270
	11th to 20th	Day	22% 21% 34% 17% 5%	270
	21st to end	Day	25% 18% 41% 12% 4	225
March	1st to 10th	Day	25% 23% 32% 16% 4	270
	11th to 20th	Day	22% 19% 37% 16% 6% 1	375
	21st to end	Day	27% 16% 32% 18% 7%	506
April	1st to 10th	Day	18% 16% 32% 23% 9% 1	460
	11th to 20th	Day	21% 17% 25% 23% 12% 2	452
	21st to end	Day	24% 14% 32% 20% 8% 2	460
May	1st to 10th	Day	20% 12% 29% 26% 9% 3	463
	11th to 20th	Day	22% 7% 25% 25% 14% 7%	487
	21st to end	Day	11% 5% 26% 28% 20% 10%	590
June	1st to 10th	Day	12% 5% 26% 32% 19% 6%	680
	11th to 20th	Day	11% 5% 23% 32% 20% 8%	680
	21st to end	Day	12% 6% 27% 27% 20% 8%	680
July	1st to 10th	Day	12% 4 16% 27% 24% 18%	671
	11th to 20th	Day	6% 4 19% 34% 25% 12%	668
	21st to end	Day	11% 2 18% 29% 29% 12%	663
August	1st to 10th	Day	9% 3 13% 27% 31% 17%	486
	11th to 20th	Day	12% 4 18% 27% 28% 12%	479
	21st to end	Day	7% 2 13% 29% 34% 16%	539
September	1st to 10th	Day	10% 4 15% 30% 29% 12%	490
	11th to 20th	Day	10% 2 14% 27% 32% 15%	490
	21st to end	Day	16% 8% 21% 22% 23% 11%	490
October	1st to 10th	Day	11% 5% 24% 32% 21% 7%	490
	11th to 20th	Day	13% 13% 36% 22% 13% 2	408
	21st to end	Day	27% 12% 36% 23% 2	330
November	1st to 10th	Day	14% 14% 32% 26% 12% 3	285
	11th to 20th	Day	21% 17% 29% 20% 11% 1	270
	21st to end	Day	23% 13% 37% 21% 6%	270
December	1st to 10th	Day	15% 24% 34% 20% 5% 1	270
	11th to 20th	Day	24% 13% 37% 19% 5% 1	270
	21st to end	Day	29% 19% 31% 16% 4	297
January	1st to 10th	Night	21% 17% 33% 25% 4	950
	11th to 20th	Night	24% 17% 36% 20% 3	950
	21st to end	Night	21% 15% 37% 24% 3	974
February	1st to 10th	Night	24% 14% 36% 24% 2	760
	11th to 20th	Night	20% 16% 37% 24% 3	743
	21st to end	Night	25% 13% 39% 21% 2	628
March	1st to 10th	Night	23% 15% 32% 26% 4	760
	11th to 20th	Night	20% 12% 37% 25% 6% 1	760
	21st to end	Night	24% 10% 33% 28% 5% 1	736
April	1st to 10th	Night	15% 12% 36% 29% 7%	570
	11th to 20th	Night	18% 12% 29% 29% 11% 1	563
	21st to end	Night	19% 8% 40% 24% 9% 1	570
May	1st to 10th	Night	19% 6% 34% 30% 11% 1	570
	11th to 20th	Night	18% 4 23% 36% 16% 3	561
	21st to end	Night	9% 3 21% 40% 24% 3	617
June	1st to 10th	Night	10% 3 23% 42% 21% 1	570
	11th to 20th	Night	10% 3 18% 46% 21% 1	570
	21st to end	Night	7% 3 21% 39% 27% 2	570
July	1st to 10th	Night	9% 2 11% 37% 34% 7%	555
	11th to 20th	Night	5% 3 15% 37% 35% 4	552
	21st to end	Night	8% 3 10% 43% 32% 3	624
August	1st to 10th	Night	8% 2 10% 38% 38% 4	567
	11th to 20th	Night	7% 1 11% 42% 34% 4	564
	21st to end	Night	7% 2 12% 32% 41% 7%	627
September	1st to 10th	Night	12% 3 13% 37% 31% 4	572
	11th to 20th	Night	9% 2 14% 35% 36% 4	760
	21st to end	Night	13% 7% 18% 34% 25% 3	760
October	1st to 10th	Night	9% 4 22% 36% 23% 4	760
	11th to 20th	Night	19% 9% 26% 29% 15% 2	760
	21st to end	Night	21% 10% 34% 26% 8%	836
November	1st to 10th	Night	15% 9% 31% 33% 12% 1	764
	11th to 20th	Night	17% 14% 31% 29% 9%	760
	21st to end	Night	24% 12% 26% 30% 7%	760
December	1st to 10th	Night	23% 11% 37% 24% 5%	760
	11th to 20th	Night	24% 10% 33% 26% 6% 1	926
	21st to end	Night	31% 13% 32% 21% 4	1045

Page generated at 2024-11-03 13:19:03. Version ac07

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