Batsto
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Batsto clear sky chart from 2005-11-06 to 2024-03-28.

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	15% 6% 2 5% 5% 3 5% 5% 5% 7% 42%	78733
	Night	15% 7% 3 5% 5% 3 4 4 5% 7% 43%	81248
Transparency	Day	41% 6% 12% 23% 16% 3	78439
	Night	41% 5% 11% 23% 17% 3	81076
Seeing	Day	19% 11% 29% 24% 12% 4	14205
	Night	18% 10% 30% 30% 11% 1	23605

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	15% 10% 3 4 4 2 3 4 4 5% 47%	2517
	11th to 20th	Day	15% 7% 3 7% 6% 4 4 3 4 5% 41%	2553
	21st to end	Day	22% 10% 3 5% 5% 3 4 3 4 5% 36%	3124
February	1st to 10th	Day	15% 8% 2 6% 4 2 5% 5% 5% 6% 41%	1714
	11th to 20th	Day	17% 8% 3 5% 4 3 4 4 5% 6% 42%	1848
	21st to end	Day	17% 9% 3 6% 5% 3 4 4 4 6% 39%	1570
March	1st to 10th	Day	15% 6% 2 4 5% 3 4 4 4 5% 48%	1897
	11th to 20th	Day	15% 6% 2 5% 5% 2 4 5% 6% 6% 43%	2047
	21st to end	Day	19% 6% 3 5% 5% 3 4 5% 3 6% 40%	2411
April	1st to 10th	Day	16% 7% 3 5% 4 3 4 5% 5% 6% 43%	2160
	11th to 20th	Day	14% 5% 3 5% 4 2 4 5% 6% 8% 44%	2134
	21st to end	Day	16% 6% 3 5% 4 3 5% 5% 6% 7% 40%	2160
May	1st to 10th	Day	18% 7% 3 5% 4 3 4 5% 5% 7% 38%	2294
	11th to 20th	Day	17% 6% 3 5% 4 3 5% 4 5% 8% 38%	2449
	21st to end	Day	14% 6% 2 5% 4 3 4 5% 6% 9% 43%	2725
June	1st to 10th	Day	12% 7% 2 6% 5% 3 5% 6% 6% 9% 39%	2520
	11th to 20th	Day	12% 5% 3 6% 5% 4 6% 5% 7% 8% 39%	2520
	21st to end	Day	10% 5% 2 5% 6% 4 6% 7% 7% 9% 41%	2520
July	1st to 10th	Day	9% 5% 2 6% 7% 4 6% 5% 8% 8% 39%	2520
	11th to 20th	Day	6% 4 2 5% 6% 4 6% 6% 9% 12% 41%	2520
	21st to end	Day	9% 6% 2 7% 7% 4 7% 6% 7% 10% 35%	2729
August	1st to 10th	Day	10% 6% 2 5% 7% 5% 6% 7% 5% 9% 39%	2284
	11th to 20th	Day	12% 5% 2 4 6% 5% 5% 6% 7% 10% 38%	2126
	21st to end	Day	12% 5% 3 5% 5% 3 6% 6% 7% 9% 39%	2376
September	1st to 10th	Day	13% 7% 3 4 5% 3 5% 4 6% 8% 41%	2160
	11th to 20th	Day	12% 5% 3 5% 4 3 4 4 5% 7% 49%	2105
	21st to end	Day	17% 7% 3 6% 5% 3 4 4 4 8% 40%	1980
October	1st to 10th	Day	19% 6% 2 5% 4 3 4 4 5% 6% 42%	1850
	11th to 20th	Day	16% 6% 2 4 4 2 3 3 5% 6% 50%	1800
	21st to end	Day	17% 6% 2 4 4 4 4 4 4 6% 46%	1892
November	1st to 10th	Day	14% 5% 2 4 4 3 3 4 3 6% 52%	1671
	11th to 20th	Day	15% 5% 2 5% 5% 2 3 4 5% 7% 48%	1710
	21st to end	Day	14% 5% 2 4 4 4 5% 4 5% 7% 47%	1649
December	1st to 10th	Day	18% 7% 3 4 4 3 4 5% 5% 7% 40%	1520
	11th to 20th	Day	20% 6% 2 5% 4 2 3 4 3 5% 46%	1906
	21st to end	Day	16% 7% 2 4 5% 3 5% 6% 6% 8% 38%	2772
January	1st to 10th	Night	17% 6% 2 4 4 3 3 4 4 6% 47%	4429
	11th to 20th	Night	18% 9% 3 4 4 2 3 3 4 4 44%	4404
	21st to end	Night	21% 9% 3 5% 4 3 4 4 4 5% 37%	4532
February	1st to 10th	Night	17% 8% 3 5% 4 2 4 4 5% 7% 41%	2464
	11th to 20th	Night	18% 8% 3 4 4 2 4 4 5% 6% 42%	2218
	21st to end	Night	19% 6% 2 5% 4 3 3 4 4 6% 43%	1884
March	1st to 10th	Night	16% 5% 2 5% 4 3 3 4 5% 7% 47%	2270
	11th to 20th	Night	17% 6% 3 5% 5% 2 4 4 4 6% 45%	2127
	21st to end	Night	17% 7% 3 6% 4 3 4 3 4 5% 44%	2099
April	1st to 10th	Night	17% 7% 3 6% 4 3 4 4 5% 6% 41%	1800
	11th to 20th	Night	14% 6% 3 5% 6% 3 4 4 5% 7% 44%	1775
	21st to end	Night	19% 6% 2 4 4 3 4 4 6% 8% 42%	1800
May	1st to 10th	Night	17% 8% 3 6% 6% 3 4 5% 5% 7% 35%	1666
	11th to 20th	Night	18% 7% 2 5% 5% 2 4 5% 6% 7% 38%	1459
	21st to end	Night	16% 8% 3 6% 6% 3 5% 4 4 7% 39%	1550
June	1st to 10th	Night	14% 6% 3 5% 6% 3 4 4 6% 8% 42%	1440
	11th to 20th	Night	10% 6% 4 5% 7% 4 5% 5% 6% 9% 40%	1440
	21st to end	Night	9% 5% 1 6% 5% 3 5% 5% 8% 11% 42%	1440
July	1st to 10th	Night	8% 7% 3 7% 6% 4 6% 6% 5% 10% 37%	1440
	11th to 20th	Night	6% 5% 3 5% 6% 3 6% 7% 6% 11% 43%	1440
	21st to end	Night	7% 6% 2 6% 6% 3 5% 6% 6% 11% 42%	1585
August	1st to 10th	Night	8% 5% 3 5% 5% 4 7% 6% 6% 9% 42%	1634
	11th to 20th	Night	10% 5% 3 7% 6% 3 5% 5% 6% 10% 41%	1774
	21st to end	Night	12% 5% 2 5% 6% 2 5% 5% 6% 9% 43%	1980
September	1st to 10th	Night	14% 7% 2 6% 4 3 4 4 4 7% 45%	1800
	11th to 20th	Night	10% 5% 2 4 4 2 4 4 4 8% 53%	1854
	21st to end	Night	18% 7% 2 4 4 3 4 4 5% 7% 41%	1980
October	1st to 10th	Night	19% 5% 2 5% 5% 3 3 4 4 6% 44%	2107
	11th to 20th	Night	17% 4 2 4 4 2 3 3 4 6% 51%	2160
	21st to end	Night	16% 7% 2 4 3 3 3 4 5% 6% 47%	2461
November	1st to 10th	Night	12% 5% 2 4 3 2 4 4 5% 6% 53%	2407
	11th to 20th	Night	16% 6% 2 5% 4 3 4 3 4 5% 47%	2470
	21st to end	Night	13% 5% 2 4 5% 3 4 5% 6% 7% 47%	2527
December	1st to 10th	Night	19% 6% 3 5% 5% 2 4 4 5% 5% 41%	2660
	11th to 20th	Night	17% 6% 2 6% 5% 3 3 4 5% 8% 42%	3288
	21st to end	Night	15% 8% 3 5% 5% 4 4 5% 5% 7% 38%	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	40% 4 10% 26% 17% 4	2518
	11th to 20th	Day	46% 4 10% 23% 14% 4	2553
	21st to end	Day	52% 4 10% 21% 11% 2	3124
February	1st to 10th	Day	43% 4 13% 26% 13% 2	1714
	11th to 20th	Day	43% 5% 8% 25% 16% 3	1857
	21st to end	Day	46% 5% 8% 21% 14% 5%	1570
March	1st to 10th	Day	40% 4 11% 28% 15% 3	1900
	11th to 20th	Day	39% 5% 11% 24% 16% 4	2047
	21st to end	Day	46% 4 8% 20% 18% 4	2411
April	1st to 10th	Day	42% 6% 10% 21% 16% 6%	2160
	11th to 20th	Day	37% 5% 12% 25% 17% 4	2134
	21st to end	Day	42% 6% 11% 19% 18% 5%	2160
May	1st to 10th	Day	45% 6% 10% 22% 15% 3	2294
	11th to 20th	Day	44% 6% 13% 22% 13% 2	2453
	21st to end	Day	38% 7% 16% 24% 12% 2	2725
June	1st to 10th	Day	40% 9% 13% 22% 14% 2	2520
	11th to 20th	Day	40% 9% 13% 23% 12% 2	2520
	21st to end	Day	37% 9% 13% 22% 17% 1	2520
July	1st to 10th	Day	39% 9% 14% 21% 14% 2	2450
	11th to 20th	Day	32% 9% 16% 28% 13% 2	2445
	21st to end	Day	40% 10% 12% 22% 14% 2	2576
August	1st to 10th	Day	39% 9% 15% 23% 13% 1	2271
	11th to 20th	Day	39% 9% 16% 20% 15% 2	2126
	21st to end	Day	38% 8% 14% 21% 16% 3	2376
September	1st to 10th	Day	39% 6% 14% 18% 19% 3	2160
	11th to 20th	Day	35% 5% 9% 24% 24% 4	2105
	21st to end	Day	45% 5% 9% 18% 20% 3	1980
October	1st to 10th	Day	43% 4 11% 22% 18% 2	1850
	11th to 20th	Day	36% 4 9% 25% 23% 3	1800
	21st to end	Day	40% 4 10% 24% 20% 3	1892
November	1st to 10th	Day	35% 3 12% 28% 19% 4	1671
	11th to 20th	Day	37% 4 10% 22% 24% 3	1710
	21st to end	Day	38% 4 10% 31% 14% 3	1649
December	1st to 10th	Day	42% 6% 15% 22% 14% 1	1520
	11th to 20th	Day	42% 3 11% 27% 13% 3	1906
	21st to end	Day	41% 7% 13% 24% 14% 1	2772
January	1st to 10th	Night	39% 4 9% 29% 14% 4	4429
	11th to 20th	Night	44% 4 10% 24% 15% 3	4404
	21st to end	Night	49% 4 8% 24% 14% 2	4532
February	1st to 10th	Night	42% 4 14% 23% 14% 2	2464
	11th to 20th	Night	44% 5% 8% 20% 18% 6%	2220
	21st to end	Night	43% 3 9% 22% 17% 6%	1884
March	1st to 10th	Night	39% 4 11% 25% 18% 4	2280
	11th to 20th	Night	41% 5% 9% 22% 18% 4	2128
	21st to end	Night	44% 4 9% 18% 19% 6%	2099
April	1st to 10th	Night	43% 4 9% 20% 18% 5%	1800
	11th to 20th	Night	41% 5% 10% 20% 20% 4	1775
	21st to end	Night	41% 6% 9% 19% 19% 5%	1800
May	1st to 10th	Night	47% 6% 9% 19% 16% 2	1666
	11th to 20th	Night	45% 6% 12% 17% 17% 3	1460
	21st to end	Night	46% 7% 15% 18% 13% 2	1551
June	1st to 10th	Night	40% 8% 11% 21% 19% 2	1440
	11th to 20th	Night	40% 9% 12% 23% 14% 2	1440
	21st to end	Night	35% 7% 16% 24% 17% 2	1440
July	1st to 10th	Night	42% 9% 16% 20% 12% 3	1400
	11th to 20th	Night	35% 8% 16% 25% 14% 2	1392
	21st to end	Night	34% 8% 14% 27% 15% 1	1497
August	1st to 10th	Night	37% 8% 17% 23% 15% 1	1623
	11th to 20th	Night	39% 8% 15% 21% 15% 2	1774
	21st to end	Night	37% 7% 15% 19% 18% 3	1980
September	1st to 10th	Night	39% 6% 13% 20% 18% 4	1800
	11th to 20th	Night	31% 5% 11% 24% 25% 4	1854
	21st to end	Night	42% 5% 8% 22% 20% 2	1980
October	1st to 10th	Night	41% 5% 12% 21% 17% 3	2107
	11th to 20th	Night	35% 5% 11% 28% 19% 3	2160
	21st to end	Night	39% 5% 9% 25% 20% 3	2461
November	1st to 10th	Night	33% 4 11% 26% 20% 6%	2407
	11th to 20th	Night	40% 4 9% 20% 22% 5%	2470
	21st to end	Night	36% 4 12% 27% 19% 2	2527
December	1st to 10th	Night	45% 4 11% 24% 15% 2	2660
	11th to 20th	Night	42% 4 13% 19% 19% 4	3288
	21st to end	Night	43% 7% 13% 25% 11% 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	22% 20% 33% 18% 4 2	180
	11th to 20th	Day	26% 27% 28% 16% 3	190
	21st to end	Day	26% 21% 33% 14% 5% 2	297
February	1st to 10th	Day	24% 22% 36% 14% 4 1	274
	11th to 20th	Day	25% 22% 38% 14% 2	456
	21st to end	Day	27% 20% 32% 17% 4	382
March	1st to 10th	Day	23% 19% 32% 22% 4	460
	11th to 20th	Day	20% 22% 37% 14% 5% 2	460
	21st to end	Day	24% 18% 34% 19% 4 1	490
April	1st to 10th	Day	23% 19% 32% 17% 6% 2	420
	11th to 20th	Day	18% 15% 36% 22% 7% 2	412
	21st to end	Day	27% 13% 35% 18% 6% 1	420
May	1st to 10th	Day	26% 15% 33% 17% 8% 3	423
	11th to 20th	Day	24% 10% 32% 23% 9% 2	447
	21st to end	Day	18% 8% 19% 31% 20% 4	485
June	1st to 10th	Day	15% 10% 29% 28% 15% 4	450
	11th to 20th	Day	15% 9% 30% 30% 12% 4	450
	21st to end	Day	12% 6% 26% 34% 16% 5%	450
July	1st to 10th	Day	15% 2 21% 30% 24% 8%	445
	11th to 20th	Day	6% 3 21% 35% 26% 10%	444
	21st to end	Day	12% 4 23% 34% 21% 7%	488
August	1st to 10th	Day	13% 2 24% 30% 23% 8%	446
	11th to 20th	Day	14% 3 17% 33% 25% 9%	439
	21st to end	Day	13% 3 23% 30% 20% 11%	495
September	1st to 10th	Day	19% 4 23% 23% 19% 12%	450
	11th to 20th	Day	14% 4 22% 31% 18% 10%	450
	21st to end	Day	23% 8% 27% 25% 12% 6%	450
October	1st to 10th	Day	25% 5% 22% 27% 14% 7%	450
	11th to 20th	Day	18% 11% 25% 28% 15% 3	450
	21st to end	Day	20% 10% 34% 21% 13% 2	450
November	1st to 10th	Day	16% 10% 32% 25% 14% 3	365
	11th to 20th	Day	19% 18% 30% 24% 9%	370
	21st to end	Day	18% 15% 32% 23% 10% 2	309
December	1st to 10th	Day	26% 17% 38% 12% 7% 1	180
	11th to 20th	Day	28% 17% 33% 18% 3 1	180
	21st to end	Day	27% 13% 30% 21% 7% 2	198
January	1st to 10th	Night	20% 16% 36% 24% 4 1	760
	11th to 20th	Night	24% 15% 33% 25% 4	760
	21st to end	Night	19% 14% 39% 25% 2	836
February	1st to 10th	Night	22% 13% 37% 25% 2	760
	11th to 20th	Night	22% 20% 41% 15% 1	743
	21st to end	Night	24% 16% 34% 22% 3	628
March	1st to 10th	Night	21% 15% 36% 24% 4	760
	11th to 20th	Night	22% 15% 36% 22% 4 1	760
	21st to end	Night	21% 11% 40% 22% 6%	821
April	1st to 10th	Night	20% 16% 37% 21% 5%	720
	11th to 20th	Night	16% 13% 37% 28% 6%	711
	21st to end	Night	21% 10% 36% 28% 6%	720
May	1st to 10th	Night	21% 10% 35% 26% 8%	586
	11th to 20th	Night	21% 7% 34% 30% 8%	398
	21st to end	Night	20% 3 17% 42% 16% 2	389
June	1st to 10th	Night	18% 4 24% 40% 14% 1	360
	11th to 20th	Night	9% 3 26% 46% 15%	360
	21st to end	Night	11% 2 23% 48% 17%	360
July	1st to 10th	Night	11% 3 17% 48% 17% 3	350
	11th to 20th	Night	8% 3 14% 47% 25% 2	348
	21st to end	Night	9% 2 20% 47% 22% 1	405
August	1st to 10th	Night	10% 2 13% 46% 26% 3	560
	11th to 20th	Night	12% 3 15% 41% 26% 2	710
	21st to end	Night	14% 2 15% 41% 25% 4	792
September	1st to 10th	Night	16% 3 19% 37% 19% 5%	720
	11th to 20th	Night	13% 4 17% 37% 25% 5%	720
	21st to end	Night	22% 5% 22% 33% 17% 1	720
October	1st to 10th	Night	21% 5% 23% 30% 18% 4	720
	11th to 20th	Night	20% 7% 24% 34% 14% 1	720
	21st to end	Night	20% 7% 35% 27% 10% 1	792
November	1st to 10th	Night	15% 8% 34% 30% 13% 1	740
	11th to 20th	Night	19% 12% 31% 30% 8% 1	760
	21st to end	Night	15% 12% 36% 28% 9% 1	760
December	1st to 10th	Night	23% 13% 34% 21% 7% 1	760
	11th to 20th	Night	19% 12% 38% 26% 6%	760
	21st to end	Night	19% 13% 38% 27% 3	836

Page generated at 2024-03-24 23:37:01. Version ac07

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