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 2024-11-06.

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	15% 7% 2 6% 4 4 4 4 6% 7% 40%	101272
	Night	16% 7% 2 6% 4 4 4 3 5% 7% 42%	97801
Transparency	Day	41% 6% 12% 23% 16% 3	104831
	Night	40% 5% 11% 23% 17% 3	102331
Seeing	Day	19% 11% 29% 25% 12% 4	15088
	Night	18% 9% 30% 30% 11% 1	24323

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% 2 5% 3 3 3 4 4 5% 46%	2517
	11th to 20th	Day	15% 8% 3 8% 5% 5% 4 2 4 6% 41%	2553
	21st to end	Day	22% 11% 3 6% 5% 3 4 2 4 5% 36%	3124
February	1st to 10th	Day	14% 9% 2 7% 4 3 4 4 5% 6% 41%	1714
	11th to 20th	Day	17% 8% 2 5% 3 4 4 4 5% 6% 42%	1848
	21st to end	Day	17% 10% 2 7% 4 4 4 3 5% 6% 39%	1570
March	1st to 10th	Day	26% 7% 1 4 4 3 3 2 4 5% 40%	3116
	11th to 20th	Day	9% 5% 1 6% 4 4 4 4 6% 7% 50%	3411
	21st to end	Day	20% 7% 2 6% 4 4 3 3 3 5% 43%	4091
April	1st to 10th	Day	16% 7% 2 6% 4 4 4 4 5% 6% 41%	2280
	11th to 20th	Day	14% 6% 2 6% 4 4 4 4 6% 8% 43%	2254
	21st to end	Day	16% 7% 2 6% 4 4 4 4 6% 7% 40%	2280
May	1st to 10th	Day	25% 9% 3 8% 4 4 4 3 5% 7% 29%	4032
	11th to 20th	Day	27% 7% 3 7% 4 4 4 3 4 6% 30%	4355
	21st to end	Day	12% 5% 2 6% 4 4 4 4 6% 9% 44%	4837
June	1st to 10th	Day	12% 7% 2 7% 5% 4 5% 5% 6% 9% 39%	2660
	11th to 20th	Day	11% 5% 2 6% 5% 6% 5% 5% 7% 8% 40%	2660
	21st to end	Day	10% 5% 1 6% 6% 5% 5% 6% 7% 9% 41%	2660
July	1st to 10th	Day	7% 5% 2 6% 6% 5% 7% 6% 10% 11% 36%	4440
	11th to 20th	Day	10% 6% 2 6% 5% 5% 5% 5% 8% 10% 36%	4440
	21st to end	Day	10% 8% 3 8% 6% 6% 7% 5% 7% 10% 29%	4786
August	1st to 10th	Day	17% 6% 2 6% 5% 5% 6% 5% 6% 10% 30%	4020
	11th to 20th	Day	12% 7% 3 5% 5% 5% 6% 5% 7% 9% 37%	3730
	21st to end	Day	9% 5% 2 5% 4 4 5% 4 7% 10% 44%	4180
September	1st to 10th	Day	13% 7% 3 5% 5% 4 5% 3 6% 7% 42%	2280
	11th to 20th	Day	12% 5% 2 6% 4 4 4 3 5% 7% 48%	2221
	21st to end	Day	18% 7% 2 7% 4 4 4 3 4 7% 38%	2090
October	1st to 10th	Day	19% 6% 2 6% 3 4 3 3 6% 6% 43%	1952
	11th to 20th	Day	16% 6% 2 4 3 2 3 2 5% 6% 51%	1900
	21st to end	Day	16% 6% 2 5% 3 4 4 3 4 6% 47%	1997
November	1st to 10th	Day	14% 5% 2 4 4 4 3 3 3 6% 52%	1717
	11th to 20th	Day	15% 5% 2 5% 4 3 3 3 5% 6% 48%	1710
	21st to end	Day	14% 6% 2 4 4 5% 4 3 5% 7% 47%	1649
December	1st to 10th	Day	18% 7% 3 5% 3 4 4 4 5% 7% 40%	1520
	11th to 20th	Day	19% 7% 2 5% 3 3 3 3 4 4 45%	1906
	21st to end	Day	16% 7% 2 5% 4 4 5% 5% 6% 8% 38%	2772
January	1st to 10th	Night	17% 7% 2 5% 3 3 3 3 4 6% 46%	4429
	11th to 20th	Night	18% 9% 2 5% 4 3 3 2 4 4 44%	4404
	21st to end	Night	21% 9% 3 6% 4 4 4 3 4 5% 37%	4532
February	1st to 10th	Night	16% 9% 2 5% 4 3 4 4 5% 7% 41%	2464
	11th to 20th	Night	18% 9% 3 5% 3 3 4 3 5% 5% 42%	2218
	21st to end	Night	19% 7% 2 6% 3 4 3 3 4 6% 43%	1884
March	1st to 10th	Night	23% 11% 3 6% 3 3 2 3 4 5% 37%	3724
	11th to 20th	Night	12% 6% 2 6% 4 3 4 3 5% 5% 50%	3543
	21st to end	Night	18% 9% 3 6% 4 3 3 2 4 4 44%	3540
April	1st to 10th	Night	17% 8% 2 7% 4 3 4 3 5% 6% 41%	1900
	11th to 20th	Night	14% 7% 3 7% 5% 4 4 3 5% 7% 43%	1875
	21st to end	Night	18% 6% 2 5% 3 4 4 3 6% 7% 43%	1900
May	1st to 10th	Night	19% 11% 4 8% 5% 4 4 4 5% 8% 30%	2908
	11th to 20th	Night	26% 8% 2 6% 4 4 4 3 5% 6% 31%	2567
	21st to end	Night	14% 7% 2 6% 5% 4 4 3 5% 8% 42%	2738
June	1st to 10th	Night	14% 7% 2 5% 5% 4 4 3 6% 8% 42%	1520
	11th to 20th	Night	9% 6% 3 6% 6% 5% 5% 4 6% 9% 42%	1520
	21st to end	Night	8% 6% 2 6% 5% 5% 5% 5% 8% 10% 41%	1520
July	1st to 10th	Night	6% 7% 3 9% 6% 5% 7% 6% 7% 11% 34%	2520
	11th to 20th	Night	9% 7% 3 7% 5% 4 5% 5% 7% 11% 38%	2520
	21st to end	Night	14% 8% 3 8% 6% 4 5% 4 6% 9% 32%	2763
August	1st to 10th	Night	19% 7% 3 7% 4 4 5% 4 6% 8% 32%	2876
	11th to 20th	Night	11% 6% 2 7% 4 4 5% 3 6% 8% 43%	3097
	21st to end	Night	9% 5% 2 5% 4 3 4 3 5% 8% 51%	3476
September	1st to 10th	Night	14% 7% 2 6% 3 4 4 4 4 7% 46%	1900
	11th to 20th	Night	10% 5% 2 4 4 3 4 3 4 8% 53%	1958
	21st to end	Night	19% 7% 2 5% 4 4 4 3 5% 7% 39%	2090
October	1st to 10th	Night	18% 5% 2 7% 4 3 3 3 4 6% 44%	2225
	11th to 20th	Night	16% 4 1 5% 3 2 3 2 4 6% 52%	2280
	21st to end	Night	16% 7% 2 5% 3 3 3 3 5% 6% 48%	2598
November	1st to 10th	Night	12% 5% 2 5% 3 4 3 3 5% 6% 53%	2483
	11th to 20th	Night	16% 7% 2 5% 3 4 4 3 4 5% 47%	2470
	21st to end	Night	13% 6% 2 5% 4 3 4 4 5% 7% 47%	2527
December	1st to 10th	Night	19% 7% 3 5% 4 3 4 3 5% 5% 41%	2660
	11th to 20th	Night	17% 6% 2 7% 4 4 3 4 5% 8% 41%	3288
	21st to end	Night	15% 8% 3 6% 4 5% 4 4 6% 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	48% 4 8% 29% 10% 2	3119
	11th to 20th	Day	31% 6% 10% 32% 19% 3	3411
	21st to end	Day	45% 4 7% 18% 21% 5%	4091
April	1st to 10th	Day	42% 6% 10% 20% 16% 6%	2280
	11th to 20th	Day	38% 6% 13% 24% 17% 4	2254
	21st to end	Day	41% 5% 11% 19% 18% 5%	2280
May	1st to 10th	Day	54% 6% 11% 18% 9% 1	4046
	11th to 20th	Day	54% 6% 13% 18% 8% 1	4359
	21st to end	Day	34% 9% 13% 26% 17% 2	4837
June	1st to 10th	Day	39% 9% 13% 21% 15% 2	2660
	11th to 20th	Day	39% 9% 13% 25% 12% 3	2660
	21st to end	Day	37% 9% 13% 22% 17% 2	2660
July	1st to 10th	Day	38% 11% 18% 20% 12% 2	4370
	11th to 20th	Day	40% 8% 17% 23% 11% 1	4365
	21st to end	Day	47% 9% 11% 19% 13% 1	4633
August	1st to 10th	Day	46% 9% 16% 21% 9% 1	4007
	11th to 20th	Day	40% 7% 13% 26% 13% 1	3766
	21st to end	Day	32% 7% 12% 29% 18% 2	4180
September	1st to 10th	Day	39% 6% 13% 18% 21% 3	2280
	11th to 20th	Day	35% 5% 9% 24% 24% 3	2221
	21st to end	Day	47% 5% 8% 18% 19% 3	2090
October	1st to 10th	Day	37% 3 9% 19% 27% 5%	3238
	11th to 20th	Day	25% 3 8% 24% 31% 9%	3140
	21st to end	Day	26% 3 12% 27% 26% 6%	3274
November	1st to 10th	Day	35% 3 12% 27% 19% 4	1717
	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	50% 4 8% 23% 13% 2	3734
	11th to 20th	Night	35% 6% 12% 27% 16% 4	3544
	21st to end	Night	45% 4 7% 16% 22% 5%	3540
April	1st to 10th	Night	44% 4 9% 20% 18% 5%	1900
	11th to 20th	Night	41% 5% 10% 20% 20% 4	1875
	21st to end	Night	40% 7% 9% 20% 20% 5%	1900
May	1st to 10th	Night	52% 7% 9% 20% 10% 1	2914
	11th to 20th	Night	53% 7% 12% 17% 9% 2	2568
	21st to end	Night	40% 7% 14% 20% 17% 2	2739
June	1st to 10th	Night	39% 8% 11% 22% 19% 2	1520
	11th to 20th	Night	38% 9% 12% 26% 13% 2	1520
	21st to end	Night	35% 8% 16% 24% 16% 2	1520
July	1st to 10th	Night	43% 9% 17% 18% 10% 2	2480
	11th to 20th	Night	39% 7% 19% 25% 9% 1	2472
	21st to end	Night	46% 7% 13% 19% 14% 1	2675
August	1st to 10th	Night	49% 7% 18% 17% 9%	2865
	11th to 20th	Night	38% 6% 13% 31% 12% 1	3127
	21st to end	Night	31% 5% 11% 30% 21% 2	3476
September	1st to 10th	Night	38% 6% 13% 19% 20% 4	1900
	11th to 20th	Night	31% 5% 11% 25% 25% 4	1958
	21st to end	Night	44% 5% 8% 21% 19% 2	2090
October	1st to 10th	Night	37% 4 10% 23% 22% 3	3719
	11th to 20th	Night	24% 3 10% 25% 31% 7%	3779
	21st to end	Night	25% 4 11% 31% 25% 5%	4271
November	1st to 10th	Night	33% 4 11% 26% 20% 6%	2483
	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% 17% 35% 19% 4 1	506
April	1st to 10th	Day	24% 18% 33% 18% 6% 2	460
	11th to 20th	Day	18% 15% 36% 21% 7% 2	452
	21st to end	Day	25% 13% 34% 19% 7% 2	460
May	1st to 10th	Day	26% 15% 31% 17% 8% 3	463
	11th to 20th	Day	25% 9% 31% 24% 9% 2	487
	21st to end	Day	17% 8% 20% 32% 20% 4	529
June	1st to 10th	Day	14% 10% 29% 29% 14% 4	490
	11th to 20th	Day	14% 8% 30% 30% 12% 5%	490
	21st to end	Day	12% 7% 27% 34% 16% 5%	490
July	1st to 10th	Day	14% 2 21% 31% 24% 8%	485
	11th to 20th	Day	7% 3 21% 35% 25% 9%	484
	21st to end	Day	12% 4 24% 34% 20% 7%	532
August	1st to 10th	Day	13% 3 23% 30% 22% 8%	486
	11th to 20th	Day	13% 3 17% 34% 23% 9%	479
	21st to end	Day	13% 4 23% 29% 20% 11%	539
September	1st to 10th	Day	18% 5% 23% 25% 18% 11%	490
	11th to 20th	Day	13% 4 22% 32% 19% 10%	490
	21st to end	Day	25% 8% 27% 25% 11% 5%	490
October	1st to 10th	Day	24% 6% 23% 26% 13% 8%	490
	11th to 20th	Day	17% 11% 26% 28% 14% 4	490
	21st to end	Day	19% 10% 33% 22% 14% 2	489
November	1st to 10th	Day	15% 10% 32% 26% 13% 3	381
	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%	836
April	1st to 10th	Night	20% 16% 38% 21% 5%	760
	11th to 20th	Night	17% 13% 37% 27% 6%	751
	21st to end	Night	20% 9% 36% 29% 6%	760
May	1st to 10th	Night	21% 10% 34% 27% 8%	618
	11th to 20th	Night	22% 7% 33% 30% 7%	420
	21st to end	Night	19% 3 18% 42% 17% 1	411
June	1st to 10th	Night	18% 4 23% 41% 13% 1	380
	11th to 20th	Night	9% 3 26% 47% 16%	380
	21st to end	Night	10% 2 23% 48% 16%	380
July	1st to 10th	Night	11% 3 17% 49% 18% 2	370
	11th to 20th	Night	8% 4 15% 46% 24% 3	368
	21st to end	Night	9% 2 19% 47% 21% 1	428
August	1st to 10th	Night	12% 2 13% 46% 25% 2	592
	11th to 20th	Night	12% 3 16% 41% 26% 2	750
	21st to end	Night	14% 2 15% 41% 25% 4	836
September	1st to 10th	Night	16% 3 20% 38% 19% 4	760
	11th to 20th	Night	13% 4 16% 37% 26% 4	760
	21st to end	Night	23% 5% 21% 33% 17% 1	760
October	1st to 10th	Night	21% 5% 23% 29% 18% 4	760
	11th to 20th	Night	19% 7% 25% 34% 14% 1	760
	21st to end	Night	19% 7% 34% 29% 11% 1	836
November	1st to 10th	Night	15% 8% 34% 30% 12% 1	764
	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 2024-11-03 13:19:00. Version ac07

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