Fishing Battery Island
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fishing Battery Island clear sky chart from 2005-11-06 to 2025-10-04.

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	14% 6% 2 5% 4 4 4 4 6% 8% 42%	126475
	Night	15% 7% 2 6% 4 4 4 3 5% 7% 43%	122915
Transparency	Day	39% 6% 12% 23% 16% 3	130062
	Night	40% 5% 11% 23% 17% 4	127397
Seeing	Day	17% 12% 26% 25% 14% 5%	16184
	Night	18% 11% 29% 29% 12% 1	25521

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	13% 4 2 4 3 4 4 3 5% 6% 51%	3597
	11th to 20th	Day	13% 9% 3 7% 4 5% 4 3 4 5% 44%	3902
	21st to end	Day	17% 7% 2 5% 4 4 4 3 5% 6% 43%	4466
February	1st to 10th	Day	15% 7% 2 6% 4 5% 5% 5% 6% 6% 40%	1800
	11th to 20th	Day	17% 8% 3 5% 4 4 4 4 6% 6% 41%	1865
	21st to end	Day	18% 9% 3 6% 2 4 4 4 5% 5% 40%	1650
March	1st to 10th	Day	19% 4 1 4 3 3 4 3 5% 6% 48%	4652
	11th to 20th	Day	11% 6% 2 6% 4 4 4 3 5% 6% 48%	4980
	21st to end	Day	17% 6% 2 6% 4 4 4 4 5% 6% 43%	5689
April	1st to 10th	Day	15% 7% 2 5% 5% 4 5% 4 5% 7% 42%	2400
	11th to 20th	Day	13% 6% 2 5% 4 5% 4 4 6% 7% 44%	2374
	21st to end	Day	16% 5% 2 6% 4 4 4 4 6% 8% 43%	2400
May	1st to 10th	Day	23% 7% 2 6% 4 4 4 4 6% 9% 33%	5696
	11th to 20th	Day	22% 6% 2 6% 4 4 5% 4 6% 8% 32%	6318
	21st to end	Day	16% 6% 2 5% 3 4 5% 4 6% 9% 39%	6934
June	1st to 10th	Day	10% 5% 2 5% 4 5% 6% 4 7% 10% 40%	2800
	11th to 20th	Day	12% 5% 2 6% 5% 4 5% 5% 7% 9% 41%	2800
	21st to end	Day	9% 5% 1 4 4 4 5% 4 7% 10% 46%	2800
July	1st to 10th	Day	7% 4 2 6% 4 5% 5% 4 8% 11% 43%	6360
	11th to 20th	Day	10% 6% 3 7% 5% 5% 6% 6% 8% 12% 33%	6360
	21st to end	Day	8% 5% 2 6% 4 5% 5% 5% 8% 10% 42%	6564
August	1st to 10th	Day	16% 6% 2 5% 4 4 5% 4 8% 10% 36%	4234
	11th to 20th	Day	12% 5% 2 5% 4 4 5% 4 8% 10% 42%	3912
	21st to end	Day	8% 5% 2 5% 4 4 4 4 6% 8% 50%	4312
September	1st to 10th	Day	13% 5% 2 5% 4 3 5% 3 6% 7% 46%	2400
	11th to 20th	Day	12% 5% 1 5% 3 4 4 3 5% 8% 51%	2400
	21st to end	Day	18% 8% 3 6% 5% 4 4 3 5% 6% 38%	2143
October	1st to 10th	Day	16% 6% 2 5% 4 3 3 3 5% 7% 46%	1930
	11th to 20th	Day	15% 5% 1 4 3 3 4 3 5% 7% 49%	1900
	21st to end	Day	15% 5% 2 6% 4 4 4 3 4 5% 49%	2090
November	1st to 10th	Day	13% 5% 1 5% 3 3 3 3 5% 7% 52%	1761
	11th to 20th	Day	14% 6% 2 5% 4 3 4 4 6% 6% 48%	1800
	21st to end	Day	15% 6% 2 5% 5% 3 4 3 4 7% 47%	1636
December	1st to 10th	Day	13% 7% 2 5% 4 4 4 4 4 7% 46%	2600
	11th to 20th	Day	19% 9% 2 5% 3 4 4 3 4 6% 41%	2990
	21st to end	Day	14% 6% 2 7% 4 5% 4 4 6% 8% 40%	3960
January	1st to 10th	Night	14% 6% 2 5% 4 4 4 3 4 6% 48%	6349
	11th to 20th	Night	14% 7% 2 5% 4 3 3 3 4 5% 50%	6056
	21st to end	Night	17% 7% 2 6% 4 3 3 3 5% 5% 45%	6490
February	1st to 10th	Night	17% 8% 2 6% 4 4 4 3 5% 7% 40%	2600
	11th to 20th	Night	18% 8% 3 6% 3 3 4 3 4 5% 44%	2421
	21st to end	Night	16% 7% 3 7% 4 4 4 3 5% 6% 42%	1980
March	1st to 10th	Night	17% 7% 2 5% 3 3 3 3 4 6% 47%	5199
	11th to 20th	Night	10% 7% 2 5% 4 3 3 3 4 7% 51%	4980
	21st to end	Night	15% 7% 2 6% 4 4 4 3 5% 6% 44%	5241
April	1st to 10th	Night	17% 8% 3 6% 4 3 4 4 5% 6% 41%	2000
	11th to 20th	Night	14% 6% 3 6% 5% 4 4 3 5% 7% 44%	1975
	21st to end	Night	19% 6% 2 5% 3 3 3 3 6% 7% 44%	2000
May	1st to 10th	Night	21% 8% 3 7% 4 4 5% 4 6% 8% 28%	4213
	11th to 20th	Night	24% 8% 3 5% 4 4 4 3 6% 7% 31%	3575
	21st to end	Night	20% 6% 3 5% 3 4 4 3 6% 8% 38%	3920
June	1st to 10th	Night	13% 5% 3 6% 4 3 4 4 5% 8% 45%	1600
	11th to 20th	Night	11% 7% 3 7% 6% 4 4 4 7% 9% 40%	1600
	21st to end	Night	10% 5% 2 6% 4 5% 5% 5% 7% 11% 41%	1600
July	1st to 10th	Night	8% 7% 2 8% 5% 5% 5% 6% 7% 10% 38%	3598
	11th to 20th	Night	11% 9% 3 8% 5% 5% 6% 5% 8% 9% 30%	3597
	21st to end	Night	11% 6% 2 6% 4 5% 5% 4 7% 9% 42%	4283
August	1st to 10th	Night	18% 6% 2 6% 4 4 5% 4 7% 9% 34%	2915
	11th to 20th	Night	12% 7% 2 7% 5% 4 5% 5% 6% 7% 39%	3104
	21st to end	Night	10% 5% 2 5% 4 4 5% 3 5% 7% 49%	3586
September	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 6% 7% 45%	2000
	11th to 20th	Night	12% 6% 2 4 3 4 3 3 5% 7% 51%	2000
	21st to end	Night	19% 8% 2 7% 4 4 3 3 5% 7% 37%	2251
October	1st to 10th	Night	19% 7% 3 6% 4 3 4 3 4 5% 43%	2317
	11th to 20th	Night	15% 5% 2 5% 3 3 3 3 5% 7% 51%	2280
	21st to end	Night	16% 5% 1 4 3 4 4 3 5% 6% 50%	2508
November	1st to 10th	Night	12% 5% 2 4 3 3 4 3 5% 6% 53%	2536
	11th to 20th	Night	16% 6% 2 5% 4 3 3 3 5% 6% 48%	2600
	21st to end	Night	13% 5% 2 5% 4 4 4 3 5% 6% 47%	2760
December	1st to 10th	Night	12% 6% 2 6% 4 4 4 3 4 7% 48%	4580
	11th to 20th	Night	22% 5% 2 6% 3 4 4 3 5% 6% 40%	5205
	21st to end	Night	17% 7% 2 6% 4 4 5% 4 5% 7% 37%	6996

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	33% 4 9% 26% 23% 4	3598
	11th to 20th	Day	44% 4 8% 21% 16% 7%	3902
	21st to end	Day	42% 6% 11% 26% 13% 2	4466
February	1st to 10th	Day	43% 6% 13% 25% 12% 2	1800
	11th to 20th	Day	43% 4 9% 26% 15% 3	1874
	21st to end	Day	45% 5% 10% 22% 14% 4	1650
March	1st to 10th	Day	37% 5% 9% 25% 17% 7%	4652
	11th to 20th	Day	36% 5% 10% 27% 17% 6%	4980
	21st to end	Day	43% 4 8% 19% 20% 6%	5689
April	1st to 10th	Day	41% 7% 12% 19% 17% 5%	2400
	11th to 20th	Day	38% 5% 12% 22% 17% 5%	2374
	21st to end	Day	39% 5% 11% 20% 20% 4	2400
May	1st to 10th	Day	49% 7% 14% 18% 11% 2	5728
	11th to 20th	Day	48% 8% 11% 21% 11% 1	6322
	21st to end	Day	41% 7% 12% 23% 16% 2	6949
June	1st to 10th	Day	37% 9% 13% 24% 16% 2	2800
	11th to 20th	Day	38% 9% 13% 24% 13% 3	2800
	21st to end	Day	31% 9% 16% 24% 19% 1	2800
July	1st to 10th	Day	34% 9% 19% 18% 16% 4	6290
	11th to 20th	Day	42% 9% 19% 22% 8% 1	6285
	21st to end	Day	36% 7% 12% 22% 22% 1	6376
August	1st to 10th	Day	43% 8% 15% 25% 9% 1	4221
	11th to 20th	Day	36% 8% 12% 30% 13% 1	3950
	21st to end	Day	31% 6% 13% 30% 18% 2	4312
September	1st to 10th	Day	36% 7% 12% 21% 20% 4	2400
	11th to 20th	Day	32% 5% 11% 27% 21% 4	2400
	21st to end	Day	47% 5% 9% 19% 18% 2	2143
October	1st to 10th	Day	36% 4 8% 19% 28% 5%	3190
	11th to 20th	Day	25% 4 11% 25% 27% 9%	3140
	21st to end	Day	24% 2 10% 31% 28% 5%	3428
November	1st to 10th	Day	33% 4 13% 25% 20% 4	1761
	11th to 20th	Day	36% 5% 11% 24% 22% 3	1800
	21st to end	Day	38% 5% 12% 30% 13% 3	1636
December	1st to 10th	Day	39% 4 16% 26% 12% 3	2600
	11th to 20th	Day	45% 4 12% 28% 10% 2	2986
	21st to end	Day	41% 7% 14% 20% 16% 2	3960
January	1st to 10th	Night	36% 4 9% 24% 22% 5%	6349
	11th to 20th	Night	37% 3 10% 25% 19% 7%	6056
	21st to end	Night	41% 4 8% 27% 18% 2	6490
February	1st to 10th	Night	44% 5% 13% 23% 13% 1	2600
	11th to 20th	Night	44% 4 9% 21% 18% 4	2423
	21st to end	Night	44% 4 10% 20% 17% 5%	1980
March	1st to 10th	Night	40% 4 9% 25% 12% 10%	5199
	11th to 20th	Night	32% 6% 12% 28% 15% 6%	4980
	21st to end	Night	40% 5% 8% 18% 25% 4	5241
April	1st to 10th	Night	43% 5% 11% 18% 19% 4	2000
	11th to 20th	Night	39% 5% 11% 20% 19% 5%	1975
	21st to end	Night	39% 6% 10% 21% 19% 5%	2000
May	1st to 10th	Night	52% 6% 11% 17% 10% 3	4243
	11th to 20th	Night	51% 7% 11% 18% 11% 1	3576
	21st to end	Night	44% 7% 12% 23% 13% 3	3927
June	1st to 10th	Night	37% 7% 12% 23% 19% 2	1600
	11th to 20th	Night	40% 7% 14% 23% 15% 2	1600
	21st to end	Night	35% 8% 13% 25% 15% 3	1600
July	1st to 10th	Night	41% 9% 17% 17% 13% 3	3560
	11th to 20th	Night	47% 9% 19% 17% 7% 1	3552
	21st to end	Night	36% 8% 13% 23% 19%	4157
August	1st to 10th	Night	44% 8% 18% 20% 9% 1	2904
	11th to 20th	Night	41% 6% 12% 27% 13% 1	3132
	21st to end	Night	34% 6% 11% 29% 18% 2	3586
September	1st to 10th	Night	38% 7% 10% 22% 20% 5%	2000
	11th to 20th	Night	33% 6% 9% 25% 24% 4	2000
	21st to end	Night	46% 6% 9% 18% 18% 3	2251
October	1st to 10th	Night	45% 4 9% 20% 20% 3	3837
	11th to 20th	Night	25% 3 11% 26% 29% 6%	3779
	21st to end	Night	24% 4 11% 31% 24% 6%	4120
November	1st to 10th	Night	32% 5% 10% 26% 21% 6%	2536
	11th to 20th	Night	38% 4 9% 23% 20% 6%	2600
	21st to end	Night	36% 5% 11% 27% 18% 2	2760
December	1st to 10th	Night	37% 3 13% 29% 16% 2	4580
	11th to 20th	Night	45% 4 13% 19% 16% 4	5208
	21st to end	Night	44% 7% 12% 19% 17% 1	6996

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	23% 26% 31% 17% 3 1	200
	11th to 20th	Day	20% 32% 30% 15% 2	267
	21st to end	Day	19% 23% 35% 17% 5% 1	330
February	1st to 10th	Day	22% 21% 35% 17% 4	300
	11th to 20th	Day	26% 25% 34% 13% 1	413
	21st to end	Day	24% 21% 34% 18% 4	414
March	1st to 10th	Day	18% 25% 30% 21% 5%	500
	11th to 20th	Day	21% 22% 30% 20% 5% 1	500
	21st to end	Day	22% 17% 35% 20% 5% 2	550
April	1st to 10th	Day	23% 18% 37% 16% 7% 1	500
	11th to 20th	Day	19% 18% 29% 23% 8% 3	492
	21st to end	Day	21% 14% 33% 23% 8% 1	500
May	1st to 10th	Day	27% 13% 27% 21% 10% 2	503
	11th to 20th	Day	21% 8% 33% 24% 11% 3	527
	21st to end	Day	19% 4 21% 26% 21% 8%	573
June	1st to 10th	Day	14% 7% 27% 26% 18% 8%	530
	11th to 20th	Day	14% 9% 21% 32% 18% 5%	530
	21st to end	Day	12% 5% 23% 34% 18% 7%	530
July	1st to 10th	Day	12% 2 17% 33% 26% 11%	525
	11th to 20th	Day	4 3 16% 38% 28% 10%	524
	21st to end	Day	11% 4 19% 34% 26% 6%	576
August	1st to 10th	Day	12% 3 16% 34% 26% 9%	526
	11th to 20th	Day	11% 3 14% 33% 29% 9%	519
	21st to end	Day	10% 4 21% 32% 23% 11%	583
September	1st to 10th	Day	16% 7% 19% 25% 22% 11%	530
	11th to 20th	Day	14% 2 21% 33% 22% 10%	530
	21st to end	Day	25% 8% 22% 26% 16% 3	530
October	1st to 10th	Day	21% 8% 21% 26% 15% 9%	502
	11th to 20th	Day	15% 13% 28% 25% 16% 3	490
	21st to end	Day	17% 12% 30% 27% 12% 3	539
November	1st to 10th	Day	15% 12% 31% 25% 14% 3	395
	11th to 20th	Day	14% 19% 33% 23% 10% 1	400
	21st to end	Day	19% 21% 29% 22% 8%	236
December	1st to 10th	Day	22% 20% 35% 19% 5% 1	200
	11th to 20th	Day	24% 23% 29% 18% 7%	200
	21st to end	Day	22% 16% 33% 21% 8%	220
January	1st to 10th	Night	21% 18% 40% 18% 4	800
	11th to 20th	Night	24% 16% 31% 25% 4	800
	21st to end	Night	20% 16% 38% 24% 2	880
February	1st to 10th	Night	20% 15% 37% 25% 3	800
	11th to 20th	Night	23% 20% 38% 19% 1	783
	21st to end	Night	21% 18% 38% 19% 4	660
March	1st to 10th	Night	19% 17% 37% 23% 5%	800
	11th to 20th	Night	21% 15% 35% 23% 6% 1	800
	21st to end	Night	19% 11% 39% 24% 6%	880
April	1st to 10th	Night	21% 14% 37% 22% 6%	800
	11th to 20th	Night	16% 13% 32% 29% 9%	791
	21st to end	Night	21% 13% 27% 30% 9%	800
May	1st to 10th	Night	22% 8% 27% 34% 8% 1	692
	11th to 20th	Night	23% 7% 27% 31% 11%	394
	21st to end	Night	20% 4 18% 37% 19% 2	433
June	1st to 10th	Night	16% 5% 22% 38% 19% 1	400
	11th to 20th	Night	14% 5% 23% 39% 20% 1	400
	21st to end	Night	11% 3 22% 45% 19% 1	400
July	1st to 10th	Night	10% 3 18% 42% 23% 3	390
	11th to 20th	Night	8% 2 16% 40% 30% 4	388
	21st to end	Night	9% 2 16% 42% 28% 3	591
August	1st to 10th	Night	12% 2 15% 40% 29% 3	597
	11th to 20th	Night	13% 4 15% 34% 29% 5%	733
	21st to end	Night	14% 3 15% 37% 26% 4	880
September	1st to 10th	Night	16% 4 19% 33% 25% 4	800
	11th to 20th	Night	14% 3 17% 36% 26% 5%	800
	21st to end	Night	21% 6% 20% 32% 19% 2	800
October	1st to 10th	Night	21% 8% 22% 26% 18% 5%	773
	11th to 20th	Night	18% 9% 26% 33% 14% 1	760
	21st to end	Night	19% 10% 30% 26% 13% 1	836
November	1st to 10th	Night	16% 8% 35% 28% 12% 1	780
	11th to 20th	Night	20% 14% 31% 27% 8% 1	800
	21st to end	Night	16% 16% 34% 26% 7% 1	800
December	1st to 10th	Night	22% 16% 32% 22% 8% 1	800
	11th to 20th	Night	18% 13% 38% 25% 5%	800
	21st to end	Night	20% 14% 33% 31% 3	880

Page generated at 2025-10-01 01:39:08. Version ac07

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