Pte. au Baril
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pte. au Baril clear sky chart from 2005-11-06 to 2025-10-19.

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% 10% 4 8% 5% 4 4 4 5% 7% 34%	126843
	Night	16% 13% 4 9% 5% 4 4 3 5% 6% 30%	122913
Transparency	Day	48% 7% 12% 22% 10% 1	130384
	Night	53% 6% 12% 19% 9% 1	127459
Seeing	Day	20% 13% 31% 24% 9% 2	16396
	Night	23% 12% 29% 25% 10% 1	25433

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	12% 19% 9% 11% 5% 4 3 3 5% 6% 24%	3158
	11th to 20th	Day	9% 19% 7% 17% 8% 6% 6% 4 5% 5% 13%	3495
	21st to end	Day	14% 17% 8% 15% 5% 6% 5% 4 4 4 18%	4466
February	1st to 10th	Day	13% 18% 5% 12% 7% 5% 5% 3 4 6% 23%	1800
	11th to 20th	Day	13% 15% 6% 10% 6% 4 5% 3 5% 5% 28%	1753
	21st to end	Day	14% 17% 5% 12% 5% 4 3 4 5% 5% 26%	1550
March	1st to 10th	Day	19% 12% 4 9% 4 4 4 3 4 5% 30%	4839
	11th to 20th	Day	13% 14% 5% 9% 5% 5% 5% 4 7% 7% 27%	4980
	21st to end	Day	17% 13% 4 9% 6% 4 3 3 4 5% 31%	5465
April	1st to 10th	Day	18% 12% 4 6% 5% 5% 4 4 5% 6% 31%	2335
	11th to 20th	Day	19% 9% 3 7% 5% 3 4 3 4 6% 37%	2552
	21st to end	Day	21% 9% 3 7% 4 3 4 3 4 6% 36%	2600
May	1st to 10th	Day	18% 7% 3 6% 5% 4 4 4 5% 8% 36%	5888
	11th to 20th	Day	13% 7% 2 6% 4 4 4 4 7% 8% 41%	6318
	21st to end	Day	21% 9% 2 6% 4 4 4 3 5% 7% 36%	6949
June	1st to 10th	Day	16% 7% 2 6% 5% 5% 4 4 5% 8% 38%	2952
	11th to 20th	Day	12% 5% 2 7% 5% 4 4 5% 6% 8% 41%	3000
	21st to end	Day	17% 7% 3 6% 5% 4 5% 4 6% 8% 36%	3000
July	1st to 10th	Day	14% 6% 2 7% 5% 4 4 4 6% 8% 38%	6819
	11th to 20th	Day	11% 5% 2 5% 4 4 4 3 5% 7% 50%	6787
	21st to end	Day	8% 5% 2 5% 4 4 4 4 6% 8% 52%	6566
August	1st to 10th	Day	9% 6% 2 7% 4 5% 5% 4 6% 9% 42%	4234
	11th to 20th	Day	15% 6% 2 5% 3 3 5% 4 7% 9% 41%	4174
	21st to end	Day	9% 5% 2 6% 5% 4 5% 4 6% 8% 47%	4614
September	1st to 10th	Day	13% 7% 2 6% 5% 4 5% 4 7% 7% 42%	2400
	11th to 20th	Day	14% 5% 2 4 3 4 4 4 6% 8% 47%	2233
	21st to end	Day	20% 7% 3 7% 5% 4 4 3 4 6% 38%	2191
October	1st to 10th	Day	18% 8% 2 7% 5% 4 5% 3 5% 7% 37%	2000
	11th to 20th	Day	24% 11% 3 8% 4 5% 5% 3 4 6% 27%	1980
	21st to end	Day	28% 12% 3 8% 5% 4 4 3 5% 5% 23%	2033
November	1st to 10th	Day	22% 13% 4 7% 5% 4 3 4 5% 7% 26%	1640
	11th to 20th	Day	19% 16% 5% 8% 6% 5% 5% 4 5% 6% 22%	1600
	21st to end	Day	24% 21% 5% 9% 5% 6% 4 3 4 5% 15%	1600
December	1st to 10th	Day	15% 23% 5% 11% 6% 6% 5% 4 5% 6% 14%	2600
	11th to 20th	Day	20% 19% 6% 13% 5% 4 4 3 3 4 18%	2796
	21st to end	Day	23% 20% 7% 13% 5% 4 3 2 3 5% 15%	3476
January	1st to 10th	Night	12% 18% 9% 13% 6% 5% 4 4 5% 5% 20%	6808
	11th to 20th	Night	12% 17% 7% 17% 7% 5% 4 4 5% 5% 17%	6385
	21st to end	Night	12% 19% 10% 15% 6% 5% 4 4 4 4 18%	6490
February	1st to 10th	Night	12% 18% 6% 12% 6% 5% 5% 3 6% 6% 23%	2600
	11th to 20th	Night	12% 16% 6% 12% 6% 6% 4 4 5% 6% 25%	2533
	21st to end	Night	15% 14% 5% 11% 7% 5% 4 4 5% 5% 24%	2079
March	1st to 10th	Night	16% 12% 4 8% 4 4 4 3 5% 6% 33%	5001
	11th to 20th	Night	13% 13% 5% 9% 4 5% 5% 4 6% 7% 30%	4979
	21st to end	Night	20% 11% 4 9% 5% 4 3 3 4 5% 33%	5467
April	1st to 10th	Night	21% 12% 4 7% 4 4 3 3 6% 5% 30%	2064
	11th to 20th	Night	19% 9% 3 8% 4 4 4 3 5% 6% 36%	1814
	21st to end	Night	20% 9% 3 10% 5% 4 4 4 5% 6% 30%	1800
May	1st to 10th	Night	15% 7% 3 7% 5% 5% 5% 5% 6% 7% 36%	4038
	11th to 20th	Night	10% 6% 3 7% 4 4 5% 4 6% 9% 43%	3575
	21st to end	Night	16% 8% 3 7% 5% 4 5% 4 5% 8% 35%	3926
June	1st to 10th	Night	13% 8% 2 7% 5% 4 4 5% 6% 8% 38%	1444
	11th to 20th	Night	12% 6% 1 5% 4 5% 5% 3 7% 10% 42%	1400
	21st to end	Night	13% 7% 2 6% 4 5% 5% 4 5% 8% 41%	1400
July	1st to 10th	Night	13% 7% 2 6% 4 3 4 3 6% 8% 43%	3160
	11th to 20th	Night	12% 5% 2 4 4 4 4 3 5% 7% 50%	3177
	21st to end	Night	10% 6% 2 5% 3 4 4 3 5% 8% 50%	4282
August	1st to 10th	Night	10% 6% 3 6% 3 4 5% 4 5% 9% 45%	2915
	11th to 20th	Night	12% 6% 3 7% 4 4 4 4 5% 7% 44%	2875
	21st to end	Night	12% 5% 2 5% 4 3 3 3 5% 7% 51%	3251
September	1st to 10th	Night	13% 5% 2 4 4 5% 4 4 7% 8% 46%	2000
	11th to 20th	Night	12% 6% 2 5% 3 4 4 3 4 7% 50%	2164
	21st to end	Night	17% 7% 2 7% 4 3 4 3 5% 7% 41%	2207
October	1st to 10th	Night	20% 8% 3 7% 4 4 4 3 4 6% 37%	2400
	11th to 20th	Night	25% 9% 3 8% 5% 4 4 4 5% 5% 27%	2377
	21st to end	Night	27% 12% 4 8% 4 5% 4 3 4 6% 24%	2562
November	1st to 10th	Night	23% 13% 4 7% 3 3 3 3 5% 6% 30%	2657
	11th to 20th	Night	18% 16% 4 9% 5% 5% 5% 4 5% 6% 23%	2800
	21st to end	Night	25% 20% 6% 8% 5% 5% 3 4 4 4 16%	2800
December	1st to 10th	Night	17% 23% 5% 10% 6% 5% 5% 4 5% 5% 15%	4580
	11th to 20th	Night	19% 20% 6% 14% 5% 4 4 3 4 4 15%	5401
	21st to end	Night	22% 20% 6% 12% 6% 5% 3 2 3 5% 15%	7502

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	62% 6% 8% 18% 5%	3159
	11th to 20th	Day	73% 5% 8% 9% 4	3525
	21st to end	Day	67% 7% 8% 11% 7% 1	4466
February	1st to 10th	Day	64% 6% 7% 18% 5%	1800
	11th to 20th	Day	57% 6% 12% 16% 8% 1	1762
	21st to end	Day	60% 6% 10% 18% 7%	1550
March	1st to 10th	Day	55% 6% 12% 10% 14% 2	4842
	11th to 20th	Day	52% 8% 15% 16% 8% 1	4980
	21st to end	Day	51% 8% 10% 20% 9% 1	5465
April	1st to 10th	Day	52% 7% 11% 18% 11% 1	2335
	11th to 20th	Day	47% 7% 7% 24% 14% 1	2552
	21st to end	Day	48% 6% 10% 19% 13% 3	2600
May	1st to 10th	Day	43% 9% 11% 22% 11% 4	5897
	11th to 20th	Day	38% 9% 13% 22% 16% 2	6322
	21st to end	Day	47% 6% 11% 20% 14% 2	6949
June	1st to 10th	Day	43% 7% 10% 26% 14% 1	2952
	11th to 20th	Day	38% 7% 12% 26% 16% 1	3000
	21st to end	Day	43% 9% 12% 23% 11% 1	3000
July	1st to 10th	Day	41% 8% 16% 25% 10% 1	6746
	11th to 20th	Day	31% 7% 14% 38% 10%	6706
	21st to end	Day	29% 7% 15% 32% 18% 1	6378
August	1st to 10th	Day	35% 8% 15% 31% 11%	4221
	11th to 20th	Day	38% 8% 16% 27% 11%	4213
	21st to end	Day	33% 7% 13% 35% 11%	4614
September	1st to 10th	Day	40% 8% 14% 27% 11% 1	2400
	11th to 20th	Day	34% 7% 14% 33% 11% 1	2233
	21st to end	Day	47% 8% 13% 23% 9%	2191
October	1st to 10th	Day	39% 6% 14% 27% 13%	3260
	11th to 20th	Day	47% 6% 17% 24% 6%	3220
	21st to end	Day	59% 7% 14% 15% 5%	3335
November	1st to 10th	Day	57% 7% 13% 18% 5%	1640
	11th to 20th	Day	63% 7% 14% 11% 5% 1	1600
	21st to end	Day	72% 6% 13% 7% 2	1600
December	1st to 10th	Day	69% 7% 15% 7% 1	2600
	11th to 20th	Day	69% 7% 10% 12% 3	2795
	21st to end	Day	73% 6% 7% 10% 4	3476
January	1st to 10th	Night	64% 8% 7% 15% 5%	6808
	11th to 20th	Night	69% 7% 9% 9% 6%	6430
	21st to end	Night	69% 5% 8% 9% 8% 1	6490
February	1st to 10th	Night	61% 6% 11% 16% 5% 1	2600
	11th to 20th	Night	60% 5% 13% 14% 7% 1	2535
	21st to end	Night	60% 6% 12% 16% 7%	2079
March	1st to 10th	Night	50% 6% 12% 14% 14% 4	5011
	11th to 20th	Night	51% 7% 16% 17% 8% 1	4980
	21st to end	Night	53% 5% 9% 19% 12% 2	5467
April	1st to 10th	Night	54% 5% 8% 20% 11% 2	2064
	11th to 20th	Night	49% 5% 8% 21% 16% 1	1814
	21st to end	Night	54% 5% 9% 15% 15% 2	1800
May	1st to 10th	Night	43% 8% 9% 23% 13% 4	4045
	11th to 20th	Night	37% 7% 12% 23% 19% 2	3576
	21st to end	Night	46% 7% 10% 23% 12% 3	3927
June	1st to 10th	Night	42% 6% 12% 23% 15% 3	1444
	11th to 20th	Night	35% 6% 14% 25% 19% 1	1400
	21st to end	Night	40% 6% 15% 25% 13% 1	1400
July	1st to 10th	Night	38% 5% 14% 29% 12% 2	3125
	11th to 20th	Night	33% 6% 12% 34% 14% 1	3135
	21st to end	Night	32% 6% 9% 33% 18% 1	4155
August	1st to 10th	Night	35% 6% 17% 26% 14% 1	2904
	11th to 20th	Night	37% 7% 19% 25% 11% 1	2902
	21st to end	Night	32% 6% 13% 36% 13% 1	3251
September	1st to 10th	Night	34% 7% 16% 29% 13% 2	2000
	11th to 20th	Night	34% 6% 16% 32% 12%	2164
	21st to end	Night	43% 6% 15% 25% 11%	2207
October	1st to 10th	Night	38% 6% 10% 29% 16%	3920
	11th to 20th	Night	46% 6% 16% 25% 6%	3876
	21st to end	Night	53% 6% 18% 17% 6%	4210
November	1st to 10th	Night	55% 7% 13% 20% 6%	2657
	11th to 20th	Night	62% 6% 15% 12% 4 1	2800
	21st to end	Night	71% 6% 12% 9% 1	2800
December	1st to 10th	Night	69% 8% 14% 8% 2	4580
	11th to 20th	Night	71% 6% 8% 10% 4	5401
	21st to end	Night	72% 5% 8% 10% 4	7502

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% 22% 32% 19% 5% 1	200
	11th to 20th	Day	22% 20% 31% 21% 5% 1	257
	21st to end	Day	28% 14% 34% 17% 7% 1	330
February	1st to 10th	Day	29% 25% 32% 11% 3	300
	11th to 20th	Day	21% 20% 45% 12% 1	300
	21st to end	Day	32% 24% 33% 10%	249
March	1st to 10th	Day	23% 20% 36% 17% 4	455
	11th to 20th	Day	20% 20% 36% 18% 4 1	500
	21st to end	Day	26% 18% 33% 18% 4 1	550
April	1st to 10th	Day	23% 18% 33% 18% 8%	500
	11th to 20th	Day	29% 18% 26% 16% 9% 3	492
	21st to end	Day	26% 16% 32% 18% 6% 1	500
May	1st to 10th	Day	22% 9% 37% 24% 7% 2	503
	11th to 20th	Day	17% 13% 30% 25% 12% 3	527
	21st to end	Day	18% 11% 29% 28% 12% 2	573
June	1st to 10th	Day	17% 10% 34% 31% 8% 1	682
	11th to 20th	Day	14% 11% 35% 28% 11% 2	730
	21st to end	Day	19% 11% 30% 31% 8% 2	730
July	1st to 10th	Day	11% 6% 32% 35% 14% 2	721
	11th to 20th	Day	12% 8% 31% 32% 14% 3	711
	21st to end	Day	11% 6% 32% 33% 14% 3	576
August	1st to 10th	Day	13% 6% 26% 34% 16% 6%	526
	11th to 20th	Day	13% 6% 24% 33% 17% 8%	519
	21st to end	Day	15% 10% 27% 28% 15% 4	583
September	1st to 10th	Day	16% 11% 27% 26% 14% 5%	530
	11th to 20th	Day	13% 7% 25% 28% 19% 7%	530
	21st to end	Day	24% 8% 24% 26% 16% 2	530
October	1st to 10th	Day	21% 15% 28% 23% 12% 2	530
	11th to 20th	Day	27% 15% 35% 19% 4	522
	21st to end	Day	34% 18% 29% 17% 1 1	482
November	1st to 10th	Day	32% 18% 33% 15% 3	238
	11th to 20th	Day	21% 26% 38% 14% 2 1	200
	21st to end	Day	34% 21% 29% 14% 3 1	200
December	1st to 10th	Day	30% 21% 30% 15% 5%	200
	11th to 20th	Day	33% 22% 31% 11% 4	200
	21st to end	Day	35% 20% 30% 12% 3	220
January	1st to 10th	Night	25% 17% 31% 21% 5% 1	1000
	11th to 20th	Night	27% 16% 31% 21% 5%	949
	21st to end	Night	21% 11% 33% 26% 8% 1	880
February	1st to 10th	Night	22% 19% 35% 20% 4	800
	11th to 20th	Night	21% 15% 34% 23% 6%	783
	21st to end	Night	22% 18% 31% 25% 3	660
March	1st to 10th	Night	19% 17% 35% 24% 5%	800
	11th to 20th	Night	21% 14% 35% 23% 6% 1	800
	21st to end	Night	20% 12% 33% 26% 9%	880
April	1st to 10th	Night	26% 13% 32% 24% 6%	800
	11th to 20th	Night	24% 11% 27% 26% 10% 1	630
	21st to end	Night	25% 11% 28% 23% 14%	600
May	1st to 10th	Night	19% 7% 26% 35% 12% 2	598
	11th to 20th	Night	15% 7% 29% 35% 13% 1	394
	21st to end	Night	14% 6% 30% 35% 15% 1	433
June	1st to 10th	Night	16% 6% 27% 38% 13% 1	400
	11th to 20th	Night	15% 9% 21% 36% 18% 1	400
	21st to end	Night	16% 5% 24% 35% 19% 2	400
July	1st to 10th	Night	10% 5% 18% 47% 19% 1	390
	11th to 20th	Night	13% 2 22% 37% 24% 2	388
	21st to end	Night	11% 7% 23% 35% 22% 2	589
August	1st to 10th	Night	12% 4 19% 39% 22% 4	597
	11th to 20th	Night	13% 6% 19% 33% 25% 4	594
	21st to end	Night	16% 7% 22% 31% 22% 2	675
September	1st to 10th	Night	15% 7% 26% 28% 20% 4	800
	11th to 20th	Night	14% 6% 23% 29% 22% 6%	800
	21st to end	Night	19% 7% 24% 30% 17% 3	800
October	1st to 10th	Night	23% 10% 28% 25% 12% 2	800
	11th to 20th	Night	31% 13% 26% 23% 8% 1	793
	21st to end	Night	32% 15% 30% 19% 4	836
November	1st to 10th	Night	32% 12% 27% 21% 8%	780
	11th to 20th	Night	28% 18% 30% 18% 6%	800
	21st to end	Night	36% 15% 28% 17% 3	800
December	1st to 10th	Night	33% 17% 31% 14% 4	800
	11th to 20th	Night	30% 19% 32% 15% 3 1	884
	21st to end	Night	33% 15% 31% 17% 4	1100

Page generated at 2025-10-16 01:50:24. Version ac07

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