Baltic Corners
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Baltic Corners clear sky chart from 2005-11-06 to 2024-03-23.

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% 10% 4 7% 6% 3 5% 5% 5% 7% 32%	78512
	Night	18% 11% 4 8% 6% 3 4 4 5% 6% 31%	81367
Transparency	Day	52% 7% 12% 19% 10% 1	78217
	Night	54% 6% 12% 18% 9% 1	81196
Seeing	Day	22% 16% 29% 21% 9% 2	13641
	Night	23% 12% 30% 25% 9% 1	22855

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% 17% 5% 11% 7% 3 4 4 4 4 23%	2517
	11th to 20th	Day	14% 14% 7% 10% 9% 3 6% 5% 4 5% 23%	2520
	21st to end	Day	15% 18% 6% 9% 7% 5% 5% 5% 5% 5% 18%	2804
February	1st to 10th	Day	15% 16% 5% 11% 6% 3 4 4 5% 6% 25%	1710
	11th to 20th	Day	15% 14% 5% 11% 7% 3 4 4 4 6% 27%	1715
	21st to end	Day	20% 13% 6% 8% 6% 3 5% 4 4 5% 26%	1570
March	1st to 10th	Day	17% 12% 5% 9% 8% 4 4 4 3 5% 29%	1897
	11th to 20th	Day	17% 12% 4 8% 5% 4 5% 4 5% 6% 31%	2028
	21st to end	Day	20% 10% 4 6% 5% 3 4 5% 4 5% 36%	2354
April	1st to 10th	Day	23% 12% 3 5% 5% 3 4 3 3 5% 33%	2160
	11th to 20th	Day	21% 9% 3 7% 5% 3 3 3 4 6% 35%	2134
	21st to end	Day	24% 9% 4 7% 5% 3 4 4 5% 5% 30%	2272
May	1st to 10th	Day	21% 8% 3 7% 5% 3 5% 4 4 6% 34%	2520
	11th to 20th	Day	18% 7% 3 6% 6% 3 4 4 5% 6% 39%	2478
	21st to end	Day	17% 6% 3 6% 5% 3 5% 5% 5% 8% 36%	2725
June	1st to 10th	Day	24% 8% 3 6% 6% 3 4 5% 5% 7% 29%	2520
	11th to 20th	Day	15% 6% 3 5% 5% 5% 5% 5% 6% 8% 37%	2520
	21st to end	Day	20% 7% 3 6% 4 3 5% 5% 6% 9% 30%	2520
July	1st to 10th	Day	12% 6% 3 5% 6% 3 5% 4 6% 9% 40%	2520
	11th to 20th	Day	13% 5% 2 6% 5% 3 6% 6% 7% 9% 37%	2520
	21st to end	Day	13% 6% 3 5% 5% 4 6% 5% 7% 10% 38%	2744
August	1st to 10th	Day	13% 7% 3 6% 6% 3 5% 5% 5% 8% 39%	2506
	11th to 20th	Day	12% 6% 2 6% 5% 4 5% 5% 7% 8% 40%	2255
	21st to end	Day	13% 6% 3 6% 5% 3 5% 5% 5% 8% 40%	2376
September	1st to 10th	Day	14% 6% 2 4 4 3 5% 6% 6% 8% 42%	2160
	11th to 20th	Day	15% 4 2 5% 4 3 3 5% 5% 7% 47%	2124
	21st to end	Day	19% 6% 3 5% 4 3 3 4 6% 7% 41%	1980
October	1st to 10th	Day	22% 6% 2 6% 5% 2 4 5% 5% 7% 36%	1800
	11th to 20th	Day	22% 10% 4 8% 6% 3 4 4 4 7% 29%	1800
	21st to end	Day	27% 10% 3 6% 5% 3 4 5% 5% 5% 27%	1792
November	1st to 10th	Day	17% 8% 5% 7% 5% 3 4 6% 5% 6% 33%	1671
	11th to 20th	Day	18% 13% 4 7% 7% 2 4 5% 5% 7% 28%	1582
	21st to end	Day	22% 13% 4 9% 6% 4 6% 4 5% 6% 22%	1520
December	1st to 10th	Day	25% 14% 7% 9% 6% 4 5% 5% 4 4 17%	1520
	11th to 20th	Day	23% 14% 6% 9% 5% 4 4 4 3 6% 23%	1906
	21st to end	Day	27% 18% 6% 9% 6% 3 3 3 3 3 20%	2772
January	1st to 10th	Night	18% 16% 7% 10% 7% 3 5% 4 4 5% 21%	4429
	11th to 20th	Night	13% 14% 6% 12% 9% 5% 6% 5% 5% 5% 19%	4440
	21st to end	Night	17% 18% 7% 10% 8% 4 4 3 3 5% 21%	4848
February	1st to 10th	Night	15% 13% 6% 11% 7% 5% 5% 5% 5% 5% 23%	2470
	11th to 20th	Night	15% 12% 5% 10% 8% 4 5% 5% 4 5% 28%	2350
	21st to end	Night	16% 14% 5% 9% 6% 3 5% 4 4 5% 30%	1884
March	1st to 10th	Night	17% 13% 6% 9% 6% 3 5% 4 4 5% 29%	2270
	11th to 20th	Night	18% 13% 4 7% 7% 3 4 3 4 5% 32%	2146
	21st to end	Night	18% 10% 3 7% 5% 2 4 3 4 5% 38%	2046
April	1st to 10th	Night	23% 10% 3 6% 5% 4 4 4 4 7% 31%	1800
	11th to 20th	Night	22% 8% 3 6% 5% 3 4 4 4 6% 36%	1775
	21st to end	Night	22% 9% 4 6% 5% 3 4 4 4 7% 33%	1703
May	1st to 10th	Night	22% 8% 2 6% 5% 2 5% 5% 5% 5% 35%	1440
	11th to 20th	Night	19% 7% 3 5% 5% 2 4 5% 4 6% 41%	1415
	21st to end	Night	15% 7% 2 5% 5% 3 5% 4 5% 7% 42%	1550
June	1st to 10th	Night	19% 7% 3 5% 6% 3 6% 6% 6% 10% 29%	1440
	11th to 20th	Night	17% 6% 2 6% 5% 3 5% 5% 5% 7% 40%	1440
	21st to end	Night	17% 7% 4 5% 5% 4 4 5% 6% 8% 36%	1440
July	1st to 10th	Night	10% 4 2 5% 5% 3 6% 5% 6% 9% 44%	1440
	11th to 20th	Night	11% 5% 2 6% 5% 3 5% 5% 7% 9% 41%	1440
	21st to end	Night	11% 6% 2 5% 6% 2 6% 5% 6% 9% 42%	1574
August	1st to 10th	Night	11% 6% 2 5% 5% 3 4 5% 7% 9% 43%	1432
	11th to 20th	Night	12% 6% 3 6% 5% 3 5% 5% 5% 8% 43%	1624
	21st to end	Night	12% 6% 3 6% 5% 3 5% 5% 6% 8% 42%	1980
September	1st to 10th	Night	12% 6% 2 6% 6% 3 5% 5% 6% 6% 43%	1800
	11th to 20th	Night	15% 6% 2 4 4 2 3 4 4 8% 48%	1836
	21st to end	Night	17% 5% 2 5% 4 3 5% 4 4 7% 42%	1980
October	1st to 10th	Night	21% 7% 3 5% 5% 3 5% 4 4 7% 37%	2159
	11th to 20th	Night	21% 9% 4 6% 6% 3 5% 5% 4 6% 32%	2160
	21st to end	Night	25% 9% 4 7% 5% 3 4 4 5% 5% 28%	2564
November	1st to 10th	Night	21% 10% 3 7% 5% 2 4 3 5% 6% 34%	2407
	11th to 20th	Night	19% 10% 4 7% 6% 3 5% 5% 4 6% 31%	2593
	21st to end	Night	22% 12% 5% 9% 6% 3 4 4 4 6% 24%	2660
December	1st to 10th	Night	21% 16% 7% 9% 7% 4 5% 4 5% 5% 18%	2660
	11th to 20th	Night	23% 14% 5% 8% 6% 4 4 4 4 4 25%	3288
	21st to end	Night	30% 18% 4 9% 5% 2 3 4 3 3 19%	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	64% 7% 13% 10% 5% 1	2518
	11th to 20th	Day	61% 7% 13% 12% 7% 1	2520
	21st to end	Day	66% 8% 13% 9% 5%	2804
February	1st to 10th	Day	62% 5% 9% 19% 4 2	1710
	11th to 20th	Day	58% 6% 12% 16% 7% 1	1724
	21st to end	Day	61% 4 12% 13% 9% 1	1570
March	1st to 10th	Day	58% 5% 10% 16% 9% 1	1900
	11th to 20th	Day	55% 5% 12% 15% 11% 2	2028
	21st to end	Day	52% 4 9% 16% 14% 4	2354
April	1st to 10th	Day	54% 5% 8% 19% 12% 3	2160
	11th to 20th	Day	51% 4 7% 21% 15% 2	2134
	21st to end	Day	55% 6% 8% 15% 12% 4	2272
May	1st to 10th	Day	51% 6% 8% 19% 14% 3	2520
	11th to 20th	Day	46% 5% 11% 20% 16% 3	2482
	21st to end	Day	45% 7% 13% 19% 13% 2	2725
June	1st to 10th	Day	53% 6% 11% 17% 11% 1	2520
	11th to 20th	Day	43% 7% 13% 22% 13% 2	2520
	21st to end	Day	49% 9% 13% 18% 9% 1	2520
July	1st to 10th	Day	40% 7% 14% 25% 14% 1	2450
	11th to 20th	Day	40% 8% 16% 27% 9%	2445
	21st to end	Day	40% 8% 17% 24% 10%	2591
August	1st to 10th	Day	41% 8% 18% 24% 9%	2492
	11th to 20th	Day	38% 9% 19% 24% 10%	2255
	21st to end	Day	41% 7% 15% 25% 12% 1	2376
September	1st to 10th	Day	38% 8% 15% 26% 13%	2160
	11th to 20th	Day	36% 6% 13% 31% 14% 1	2124
	21st to end	Day	42% 8% 14% 27% 9%	1980
October	1st to 10th	Day	48% 7% 11% 23% 11%	1800
	11th to 20th	Day	57% 6% 13% 17% 6%	1800
	21st to end	Day	58% 7% 11% 16% 7% 1	1792
November	1st to 10th	Day	50% 8% 14% 20% 7% 1	1671
	11th to 20th	Day	55% 6% 13% 15% 9%	1582
	21st to end	Day	63% 6% 15% 11% 5%	1520
December	1st to 10th	Day	69% 7% 11% 10% 3	1520
	11th to 20th	Day	64% 8% 12% 13% 4	1906
	21st to end	Day	70% 5% 8% 13% 4	2772
January	1st to 10th	Night	65% 6% 15% 10% 3	4429
	11th to 20th	Night	63% 9% 14% 9% 4	4440
	21st to end	Night	66% 6% 12% 10% 6% 1	4848
February	1st to 10th	Night	63% 6% 10% 15% 6% 1	2470
	11th to 20th	Night	57% 6% 11% 18% 7%	2352
	21st to end	Night	57% 4 9% 18% 11% 1	1884
March	1st to 10th	Night	59% 4 9% 16% 10% 2	2280
	11th to 20th	Night	55% 5% 10% 17% 10% 3	2147
	21st to end	Night	51% 4 7% 19% 15% 4	2046
April	1st to 10th	Night	54% 5% 8% 18% 13% 2	1800
	11th to 20th	Night	50% 6% 8% 19% 15% 2	1775
	21st to end	Night	51% 5% 9% 17% 14% 4	1703
May	1st to 10th	Night	49% 6% 8% 17% 16% 5%	1440
	11th to 20th	Night	44% 6% 8% 19% 19% 3	1416
	21st to end	Night	39% 9% 13% 19% 17% 3	1551
June	1st to 10th	Night	48% 8% 14% 18% 10% 1	1440
	11th to 20th	Night	42% 7% 12% 21% 17% 2	1440
	21st to end	Night	45% 8% 14% 19% 13%	1440
July	1st to 10th	Night	34% 9% 13% 25% 18% 1	1400
	11th to 20th	Night	37% 8% 13% 30% 12%	1392
	21st to end	Night	37% 9% 17% 24% 13%	1486
August	1st to 10th	Night	36% 9% 19% 25% 11%	1422
	11th to 20th	Night	39% 7% 16% 26% 11% 1	1624
	21st to end	Night	38% 8% 16% 27% 11% 1	1980
September	1st to 10th	Night	40% 7% 12% 26% 15% 1	1800
	11th to 20th	Night	36% 6% 13% 33% 11% 1	1836
	21st to end	Night	41% 7% 12% 28% 11%	1980
October	1st to 10th	Night	48% 7% 10% 22% 12% 1	2159
	11th to 20th	Night	53% 7% 12% 20% 8%	2160
	21st to end	Night	57% 6% 13% 15% 8% 1	2564
November	1st to 10th	Night	51% 5% 15% 21% 8% 1	2407
	11th to 20th	Night	53% 8% 13% 17% 8% 1	2593
	21st to end	Night	62% 6% 12% 15% 5%	2660
December	1st to 10th	Night	68% 6% 10% 13% 3	2660
	11th to 20th	Night	64% 5% 9% 16% 6% 1	3288
	21st to end	Night	70% 5% 9% 13% 4	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	27% 20% 30% 21% 3	180
	11th to 20th	Day	27% 27% 29% 13% 4 1	180
	21st to end	Day	16% 20% 40% 19% 5%	207
February	1st to 10th	Day	29% 30% 28% 11% 2	270
	11th to 20th	Day	25% 25% 39% 10% 1	322
	21st to end	Day	30% 19% 31% 18% 1	382
March	1st to 10th	Day	24% 20% 32% 19% 5%	460
	11th to 20th	Day	23% 25% 33% 16% 2 1	460
	21st to end	Day	32% 19% 22% 17% 8% 1	470
April	1st to 10th	Day	29% 18% 31% 16% 5%	420
	11th to 20th	Day	30% 19% 25% 16% 8% 2	412
	21st to end	Day	30% 19% 26% 16% 9% 1	420
May	1st to 10th	Day	26% 16% 33% 16% 7% 2	423
	11th to 20th	Day	19% 17% 33% 20% 9% 2	447
	21st to end	Day	18% 18% 33% 21% 9% 1	485
June	1st to 10th	Day	28% 11% 28% 23% 7% 2	450
	11th to 20th	Day	16% 14% 30% 28% 11% 2	450
	21st to end	Day	23% 10% 30% 22% 12% 3	450
July	1st to 10th	Day	14% 9% 29% 29% 17% 3	445
	11th to 20th	Day	13% 9% 31% 29% 15% 3	444
	21st to end	Day	15% 8% 31% 31% 12% 2	488
August	1st to 10th	Day	15% 7% 27% 30% 16% 4	446
	11th to 20th	Day	14% 7% 23% 32% 16% 8%	439
	21st to end	Day	14% 12% 27% 26% 15% 7%	495
September	1st to 10th	Day	15% 12% 28% 21% 16% 8%	450
	11th to 20th	Day	13% 11% 23% 24% 18% 10%	450
	21st to end	Day	18% 13% 30% 19% 15% 5%	450
October	1st to 10th	Day	24% 15% 26% 20% 12% 4	450
	11th to 20th	Day	25% 19% 29% 18% 9% 1	450
	21st to end	Day	32% 12% 30% 19% 5%	401
November	1st to 10th	Day	26% 18% 27% 21% 7% 1	365
	11th to 20th	Day	26% 21% 33% 15% 5%	242
	21st to end	Day	28% 22% 28% 16% 5% 1	180
December	1st to 10th	Day	29% 18% 33% 16% 4	180
	11th to 20th	Day	28% 24% 33% 12% 1 1	180
	21st to end	Day	32% 24% 29% 13% 3	198
January	1st to 10th	Night	27% 17% 35% 17% 4	760
	11th to 20th	Night	28% 14% 33% 20% 5% 1	760
	21st to end	Night	20% 14% 35% 26% 5%	836
February	1st to 10th	Night	21% 16% 37% 22% 3	760
	11th to 20th	Night	22% 18% 37% 20% 4	743
	21st to end	Night	24% 15% 33% 25% 3	628
March	1st to 10th	Night	23% 16% 34% 23% 4	760
	11th to 20th	Night	25% 18% 32% 21% 3	760
	21st to end	Night	23% 15% 28% 26% 7%	801
April	1st to 10th	Night	29% 12% 29% 25% 3	720
	11th to 20th	Night	25% 14% 32% 22% 6%	711
	21st to end	Night	29% 12% 29% 22% 8%	623
May	1st to 10th	Night	26% 8% 31% 24% 8% 2	360
	11th to 20th	Night	22% 9% 32% 27% 9% 1	354
	21st to end	Night	16% 7% 37% 30% 10%	389
June	1st to 10th	Night	20% 6% 30% 36% 7% 1	360
	11th to 20th	Night	19% 6% 28% 33% 12% 1	360
	21st to end	Night	17% 5% 30% 31% 17% 1	360
July	1st to 10th	Night	10% 7% 28% 37% 17% 1	350
	11th to 20th	Night	12% 4 29% 40% 15%	348
	21st to end	Night	14% 4 30% 37% 13% 1	394
August	1st to 10th	Night	13% 3 24% 40% 20% 1	358
	11th to 20th	Night	14% 4 22% 36% 22% 2	560
	21st to end	Night	15% 5% 27% 34% 17% 2	792
September	1st to 10th	Night	15% 5% 28% 36% 16% 1	720
	11th to 20th	Night	18% 7% 22% 32% 19% 3	720
	21st to end	Night	19% 7% 28% 25% 19% 2	720
October	1st to 10th	Night	24% 8% 30% 26% 12% 1	720
	11th to 20th	Night	24% 12% 30% 25% 10%	720
	21st to end	Night	27% 13% 31% 24% 5%	792
November	1st to 10th	Night	26% 14% 27% 25% 8% 1	740
	11th to 20th	Night	23% 17% 33% 17% 9%	760
	21st to end	Night	27% 16% 29% 21% 7%	760
December	1st to 10th	Night	29% 15% 32% 19% 4	760
	11th to 20th	Night	30% 18% 28% 18% 4 1	760
	21st to end	Night	35% 17% 29% 16% 3	836

Page generated at 2024-03-19 23:31:05. Version ac07

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