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Kopernik Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kopernik 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	16% 11% 4 8% 5% 5% 5% 4 6% 7% 30%	101499
	Night	16% 11% 4 9% 5% 4 4 3 5% 6% 31%	97568
Transparency	Day	52% 6% 11% 20% 10% 1	105047
	Night	52% 6% 12% 20% 10% 1	102108
Seeing	Day	25% 17% 28% 18% 9% 3	14767
	Night	23% 15% 28% 24% 9% 1	23986

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	13% 17% 10% 12% 5% 4 4 3 4 5% 23%	2517
	11th to 20th	Day	13% 16% 9% 16% 7% 6% 4 4 4 4 18%	2529
	21st to end	Day	17% 17% 10% 12% 9% 5% 4 3 3 4 17%	3124
February	1st to 10th	Day	16% 14% 5% 13% 8% 5% 5% 3 4 5% 20%	1710
	11th to 20th	Day	12% 15% 7% 13% 7% 6% 5% 3 5% 6% 22%	1720
	21st to end	Day	18% 13% 4 13% 8% 3 4 3 5% 5% 24%	1570
March	1st to 10th	Day	22% 16% 5% 10% 5% 3 3 2 3 4 25%	3180
	11th to 20th	Day	11% 17% 6% 10% 6% 4 4 3 4 6% 29%	3480
	21st to end	Day	17% 12% 4 10% 5% 4 4 4 4 5% 30%	3995
April	1st to 10th	Day	17% 15% 4 7% 5% 4 4 3 5% 6% 31%	2280
	11th to 20th	Day	16% 11% 3 8% 5% 5% 4 4 5% 6% 33%	2254
	21st to end	Day	18% 12% 3 7% 5% 4 4 3 5% 7% 33%	2280
May	1st to 10th	Day	25% 9% 2 6% 4 4 4 3 5% 6% 31%	4310
	11th to 20th	Day	20% 9% 3 8% 6% 6% 5% 4 7% 7% 26%	4398
	21st to end	Day	12% 6% 2 6% 5% 4 4 4 6% 9% 40%	4837
June	1st to 10th	Day	18% 7% 2 7% 5% 5% 5% 4 7% 9% 32%	2660
	11th to 20th	Day	15% 6% 3 7% 5% 5% 6% 5% 6% 9% 34%	2660
	21st to end	Day	13% 8% 3 6% 5% 5% 5% 4 8% 8% 35%	2660
July	1st to 10th	Day	9% 6% 2 7% 5% 5% 6% 5% 8% 12% 34%	4440
	11th to 20th	Day	8% 5% 3 8% 6% 5% 6% 6% 8% 11% 35%	4440
	21st to end	Day	12% 7% 3 7% 6% 6% 6% 5% 7% 8% 33%	4790
August	1st to 10th	Day	19% 8% 3 7% 5% 5% 6% 4 5% 8% 30%	4104
	11th to 20th	Day	16% 8% 3 7% 5% 6% 5% 4 7% 9% 30%	3888
	21st to end	Day	14% 8% 3 7% 4 4 5% 4 6% 7% 38%	4180
September	1st to 10th	Day	16% 7% 3 7% 3 4 5% 4 5% 8% 39%	2280
	11th to 20th	Day	14% 6% 2 6% 4 4 4 3 5% 7% 43%	2280
	21st to end	Day	20% 8% 3 6% 4 4 5% 3 6% 6% 35%	2032
October	1st to 10th	Day	16% 9% 3 8% 4 5% 4 3 5% 7% 34%	1900
	11th to 20th	Day	16% 10% 4 7% 5% 4 5% 4 5% 7% 33%	1900
	21st to end	Day	21% 14% 3 7% 5% 5% 4 3 5% 7% 27%	2023
November	1st to 10th	Day	14% 11% 2 8% 5% 4 4 3 5% 7% 38%	1717
	11th to 20th	Day	15% 15% 4 9% 5% 4 4 3 5% 4 31%	1643
	21st to end	Day	17% 16% 5% 9% 6% 4 4 3 5% 7% 24%	1520
December	1st to 10th	Day	17% 17% 6% 9% 6% 6% 5% 3 5% 5% 19%	1520
	11th to 20th	Day	21% 15% 8% 11% 4 3 3 2 3 5% 25%	1906
	21st to end	Day	22% 22% 6% 11% 6% 4 4 3 3 4 15%	2772
January	1st to 10th	Night	15% 14% 7% 14% 6% 5% 4 3 5% 6% 20%	4429
	11th to 20th	Night	12% 15% 7% 16% 7% 5% 4 3 5% 6% 20%	4427
	21st to end	Night	21% 16% 6% 15% 9% 5% 3 2 3 3 16%	4532
February	1st to 10th	Night	15% 13% 5% 11% 7% 5% 6% 4 5% 6% 24%	2470
	11th to 20th	Night	13% 14% 6% 13% 8% 6% 5% 4 5% 4 22%	2346
	21st to end	Night	18% 12% 3 12% 5% 5% 4 3 5% 6% 26%	1884
March	1st to 10th	Night	20% 14% 5% 10% 5% 4 4 3 4 4 28%	3643
	11th to 20th	Night	13% 17% 6% 10% 5% 4 4 3 5% 5% 28%	3479
	21st to end	Night	14% 14% 4 10% 5% 5% 4 4 4 5% 32%	3636
April	1st to 10th	Night	19% 12% 4 8% 6% 4 4 4 4 7% 30%	1900
	11th to 20th	Night	20% 10% 3 7% 4 3 4 3 5% 6% 35%	1875
	21st to end	Night	18% 9% 3 6% 4 5% 4 3 5% 6% 37%	1900
May	1st to 10th	Night	26% 9% 2 7% 4 3 4 3 4 6% 32%	2656
	11th to 20th	Night	17% 10% 4 7% 4 4 4 4 6% 7% 32%	2495
	21st to end	Night	11% 8% 3 7% 4 5% 5% 4 6% 8% 38%	2738
June	1st to 10th	Night	17% 7% 2 6% 5% 3 3 3 6% 9% 39%	1520
	11th to 20th	Night	14% 6% 2 5% 5% 5% 4 3 6% 9% 40%	1520
	21st to end	Night	11% 6% 2 6% 4 5% 5% 4 5% 8% 43%	1520
July	1st to 10th	Night	9% 7% 3 8% 6% 5% 4 4 6% 9% 40%	2520
	11th to 20th	Night	11% 5% 2 5% 4 4 5% 4 7% 9% 43%	2520
	21st to end	Night	14% 7% 3 7% 5% 5% 5% 4 5% 7% 39%	2760
August	1st to 10th	Night	18% 8% 3 8% 5% 4 4 3 5% 7% 35%	2825
	11th to 20th	Night	15% 7% 3 8% 4 5% 4 3 4 6% 41%	2908
	21st to end	Night	12% 8% 2 6% 4 4 5% 4 5% 8% 43%	3476
September	1st to 10th	Night	14% 7% 2 6% 4 4 4 3 6% 7% 44%	1900
	11th to 20th	Night	13% 5% 2 5% 4 3 4 3 4 7% 50%	1900
	21st to end	Night	16% 8% 2 6% 4 5% 5% 3 6% 7% 38%	2144
October	1st to 10th	Night	16% 9% 3 8% 5% 4 4 4 5% 6% 37%	2280
	11th to 20th	Night	18% 8% 3 6% 3 4 4 3 6% 7% 38%	2280
	21st to end	Night	22% 13% 3 8% 5% 3 3 3 5% 6% 29%	2574
November	1st to 10th	Night	12% 12% 3 8% 5% 4 4 3 5% 6% 39%	2483
	11th to 20th	Night	18% 11% 4 7% 5% 5% 5% 4 5% 5% 32%	2536
	21st to end	Night	14% 13% 4 8% 5% 4 5% 5% 6% 8% 28%	2660
December	1st to 10th	Night	17% 16% 6% 10% 6% 5% 4 4 6% 6% 21%	2660
	11th to 20th	Night	19% 15% 5% 10% 6% 4 5% 4 5% 4 24%	3288
	21st to end	Night	24% 16% 6% 10% 5% 4 4 3 4 5% 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	63% 3 12% 16% 4 1	2518
	11th to 20th	Day	69% 5% 7% 12% 5% 1	2529
	21st to end	Day	71% 4 10% 10% 4	3124
February	1st to 10th	Day	65% 6% 9% 13% 6% 1	1710
	11th to 20th	Day	62% 5% 8% 18% 7%	1729
	21st to end	Day	62% 4 10% 16% 7% 1	1570
March	1st to 10th	Day	64% 4 9% 17% 6% 1	3183
	11th to 20th	Day	55% 6% 11% 18% 8% 2	3480
	21st to end	Day	56% 4 7% 17% 14% 2	3995
April	1st to 10th	Day	54% 5% 7% 21% 10% 2	2280
	11th to 20th	Day	52% 5% 10% 19% 13% 2	2254
	21st to end	Day	52% 5% 8% 19% 12% 3	2280
May	1st to 10th	Day	53% 6% 9% 20% 10% 2	4323
	11th to 20th	Day	55% 8% 10% 20% 7% 1	4402
	21st to end	Day	39% 8% 12% 26% 15% 1	4837
June	1st to 10th	Day	48% 7% 11% 21% 13% 1	2660
	11th to 20th	Day	46% 8% 12% 22% 11% 1	2660
	21st to end	Day	44% 7% 13% 24% 11% 1	2660
July	1st to 10th	Day	40% 8% 18% 24% 9% 1	4370
	11th to 20th	Day	40% 8% 17% 25% 10%	4365
	21st to end	Day	45% 9% 14% 20% 11% 1	4637
August	1st to 10th	Day	52% 6% 14% 18% 10%	4091
	11th to 20th	Day	47% 9% 14% 24% 6%	3927
	21st to end	Day	43% 5% 11% 32% 8% 1	4180
September	1st to 10th	Day	44% 6% 11% 25% 13% 1	2280
	11th to 20th	Day	39% 6% 11% 23% 20% 1	2280
	21st to end	Day	49% 5% 11% 21% 13% 1	2032
October	1st to 10th	Day	46% 6% 11% 22% 14% 1	3160
	11th to 20th	Day	45% 5% 10% 23% 15% 3	3140
	21st to end	Day	41% 5% 16% 26% 11% 1	3313
November	1st to 10th	Day	46% 5% 13% 21% 13% 2	1717
	11th to 20th	Day	56% 4 12% 18% 9% 2	1643
	21st to end	Day	59% 5% 13% 16% 5% 1	1520
December	1st to 10th	Day	68% 4 12% 10% 5%	1520
	11th to 20th	Day	64% 4 13% 14% 4	1906
	21st to end	Day	74% 4 8% 10% 3	2772
January	1st to 10th	Night	63% 4 15% 13% 5% 1	4429
	11th to 20th	Night	64% 6% 11% 14% 4 1	4427
	21st to end	Night	74% 3 7% 11% 4	4532
February	1st to 10th	Night	60% 5% 12% 15% 8%	2470
	11th to 20th	Night	63% 4 11% 14% 7% 1	2348
	21st to end	Night	58% 4 11% 17% 9% 2	1884
March	1st to 10th	Night	60% 4 10% 17% 9%	3653
	11th to 20th	Night	57% 5% 12% 20% 6%	3480
	21st to end	Night	53% 5% 7% 21% 12% 2	3636
April	1st to 10th	Night	56% 5% 9% 18% 11% 2	1900
	11th to 20th	Night	50% 4 11% 19% 15% 1	1875
	21st to end	Night	48% 5% 10% 20% 14% 3	1900
May	1st to 10th	Night	55% 5% 8% 21% 9% 2	2662
	11th to 20th	Night	50% 8% 15% 18% 9% 1	2496
	21st to end	Night	42% 9% 12% 20% 16% 1	2739
June	1st to 10th	Night	43% 6% 11% 25% 14% 1	1520
	11th to 20th	Night	40% 8% 14% 26% 11% 2	1520
	21st to end	Night	39% 7% 13% 28% 13% 1	1520
July	1st to 10th	Night	42% 7% 15% 20% 15% 1	2480
	11th to 20th	Night	36% 8% 17% 25% 15%	2472
	21st to end	Night	44% 7% 12% 20% 16% 1	2672
August	1st to 10th	Night	50% 7% 15% 21% 7%	2814
	11th to 20th	Night	45% 6% 14% 25% 10%	2935
	21st to end	Night	40% 5% 12% 31% 11% 1	3476
September	1st to 10th	Night	41% 6% 12% 25% 15% 2	1900
	11th to 20th	Night	35% 5% 11% 29% 19% 1	1900
	21st to end	Night	45% 6% 10% 23% 15% 1	2144
October	1st to 10th	Night	51% 6% 10% 21% 11% 1	3800
	11th to 20th	Night	40% 5% 13% 22% 14% 5%	3779
	21st to end	Night	42% 5% 16% 26% 11% 1	4234
November	1st to 10th	Night	45% 6% 12% 20% 15% 2	2483
	11th to 20th	Night	53% 5% 11% 19% 10% 2	2536
	21st to end	Night	52% 8% 15% 19% 6%	2660
December	1st to 10th	Night	63% 7% 12% 14% 4	2660
	11th to 20th	Night	61% 6% 11% 16% 5%	3288
	21st to end	Night	68% 6% 11% 13% 2	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	29% 27% 31% 9% 4 1	180
	11th to 20th	Day	41% 26% 26% 5% 2 1	184
	21st to end	Day	28% 28% 30% 11% 2	297
February	1st to 10th	Day	34% 30% 29% 7%	270
	11th to 20th	Day	37% 29% 29% 5%	327
	21st to end	Day	37% 22% 29% 10% 2	382
March	1st to 10th	Day	34% 20% 31% 12% 4	460
	11th to 20th	Day	37% 20% 27% 12% 3 1	460
	21st to end	Day	34% 25% 25% 10% 3 2	506
April	1st to 10th	Day	34% 23% 27% 12% 4	460
	11th to 20th	Day	30% 24% 26% 11% 6% 3	452
	21st to end	Day	30% 23% 28% 12% 6% 1	460
May	1st to 10th	Day	33% 17% 28% 11% 9% 2	463
	11th to 20th	Day	22% 16% 32% 18% 8% 3	487
	21st to end	Day	20% 11% 31% 21% 12% 4	529
June	1st to 10th	Day	20% 16% 31% 19% 12% 1	490
	11th to 20th	Day	18% 13% 27% 28% 12% 1	490
	21st to end	Day	19% 14% 33% 23% 8% 3	490
July	1st to 10th	Day	13% 8% 31% 28% 14% 6%	485
	11th to 20th	Day	12% 8% 27% 31% 18% 4	484
	21st to end	Day	15% 9% 36% 26% 12% 3	532
August	1st to 10th	Day	15% 10% 27% 22% 19% 6%	486
	11th to 20th	Day	18% 8% 24% 29% 14% 8%	479
	21st to end	Day	13% 11% 26% 27% 13% 10%	539
September	1st to 10th	Day	18% 12% 25% 20% 17% 7%	490
	11th to 20th	Day	14% 9% 25% 22% 19% 10%	490
	21st to end	Day	23% 13% 29% 20% 10% 5%	490
October	1st to 10th	Day	25% 13% 24% 20% 13% 4	490
	11th to 20th	Day	23% 20% 28% 20% 7% 2	490
	21st to end	Day	32% 17% 28% 17% 7%	503
November	1st to 10th	Day	27% 16% 25% 22% 9% 2	381
	11th to 20th	Day	31% 22% 25% 14% 7%	303
	21st to end	Day	38% 19% 33% 7% 1 1	180
December	1st to 10th	Day	35% 21% 32% 8% 3 1	180
	11th to 20th	Day	36% 24% 26% 13% 1	180
	21st to end	Day	34% 28% 27% 11% 1	198
January	1st to 10th	Night	25% 25% 32% 15% 2	760
	11th to 20th	Night	27% 20% 29% 21% 3	760
	21st to end	Night	20% 24% 36% 17% 2	836
February	1st to 10th	Night	28% 20% 33% 17% 1	760
	11th to 20th	Night	27% 24% 36% 13% 1	743
	21st to end	Night	35% 18% 32% 14% 2	628
March	1st to 10th	Night	28% 23% 28% 18% 3	760
	11th to 20th	Night	28% 22% 30% 17% 4	760
	21st to end	Night	26% 21% 30% 17% 5% 1	836
April	1st to 10th	Night	28% 21% 31% 18% 3	760
	11th to 20th	Night	27% 19% 29% 17% 7%	751
	21st to end	Night	25% 15% 32% 23% 6%	760
May	1st to 10th	Night	28% 11% 25% 28% 8%	470
	11th to 20th	Night	17% 11% 35% 27% 8% 1	374
	21st to end	Night	13% 9% 30% 35% 12% 1	411
June	1st to 10th	Night	18% 8% 24% 36% 14%	380
	11th to 20th	Night	17% 8% 25% 34% 14% 1	380
	21st to end	Night	13% 6% 29% 42% 9%	380
July	1st to 10th	Night	9% 5% 22% 44% 17% 2	370
	11th to 20th	Night	12% 5% 20% 43% 19% 1	368
	21st to end	Night	16% 4 21% 44% 14% 1	425
August	1st to 10th	Night	11% 4 22% 38% 24% 2	567
	11th to 20th	Night	17% 4 15% 32% 29% 4	635
	21st to end	Night	15% 6% 19% 35% 24% 2	836
September	1st to 10th	Night	18% 6% 24% 33% 17% 3	760
	11th to 20th	Night	16% 6% 19% 32% 23% 5%	760
	21st to end	Night	20% 9% 25% 27% 16% 2	760
October	1st to 10th	Night	22% 10% 26% 24% 17% 2	760
	11th to 20th	Night	24% 14% 28% 26% 7% 1	760
	21st to end	Night	30% 15% 28% 21% 6%	836
November	1st to 10th	Night	20% 17% 30% 25% 7%	764
	11th to 20th	Night	27% 18% 32% 17% 5% 1	760
	21st to end	Night	24% 18% 32% 21% 4	760
December	1st to 10th	Night	28% 23% 29% 17% 3	760
	11th to 20th	Night	27% 22% 30% 18% 3	760
	21st to end	Night	29% 20% 33% 16% 2	836

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

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