Pine Islands
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pine Islands clear sky chart from 2005-11-06 to 2025-08-05.

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	16% 10% 4 8% 5% 4 4 4 5% 7% 34%	126203
	Night	17% 13% 5% 10% 5% 4 4 3 5% 6% 27%	121839
Transparency	Day	31% 40% 8% 14% 7% 1	129761
	Night	35% 40% 7% 11% 6% 1	126357
Seeing	Day	21% 12% 29% 24% 11% 3	15977
	Night	23% 12% 28% 25% 11% 1	24987

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	13% 17% 12% 13% 5% 5% 8% 5% 4 4 15%	3158
	11th to 20th	Day	11% 19% 9% 21% 9% 6% 5% 4 4 4 9%	3754
	21st to end	Day	14% 20% 8% 14% 8% 6% 4 3 5% 4 14%	4466
February	1st to 10th	Day	14% 19% 6% 17% 7% 4 4 3 3 4 19%	1800
	11th to 20th	Day	13% 15% 5% 12% 7% 5% 4 3 5% 6% 25%	1753
	21st to end	Day	16% 17% 7% 9% 5% 5% 4 4 4 5% 24%	1537
March	1st to 10th	Day	19% 11% 4 8% 4 5% 4 3 4 5% 33%	4884
	11th to 20th	Day	12% 12% 5% 8% 6% 6% 5% 4 5% 8% 29%	4980
	21st to end	Day	18% 10% 3 7% 5% 4 5% 4 5% 6% 33%	5465
April	1st to 10th	Day	19% 11% 3 7% 5% 4 4 3 5% 5% 33%	2346
	11th to 20th	Day	21% 8% 3 5% 3 4 4 3 4 6% 37%	2517
	21st to end	Day	21% 8% 3 6% 5% 4 4 3 5% 6% 36%	2600
May	1st to 10th	Day	17% 7% 2 7% 4 4 4 3 5% 7% 39%	5888
	11th to 20th	Day	12% 8% 2 7% 4 5% 4 4 6% 7% 41%	6318
	21st to end	Day	20% 8% 2 6% 4 4 4 3 5% 7% 35%	6949
June	1st to 10th	Day	16% 7% 2 5% 4 4 4 4 6% 7% 39%	2860
	11th to 20th	Day	12% 5% 2 5% 5% 4 5% 4 6% 9% 43%	3000
	21st to end	Day	16% 8% 3 6% 3 4 4 4 6% 8% 39%	3000
July	1st to 10th	Day	13% 6% 2 7% 5% 4 5% 4 6% 9% 39%	6819
	11th to 20th	Day	11% 5% 2 5% 4 3 4 3 5% 7% 52%	6600
	21st to end	Day	9% 5% 2 6% 3 3 4 3 5% 8% 52%	6547
August	1st to 10th	Day	12% 6% 2 6% 4 4 4 4 6% 9% 42%	4156
	11th to 20th	Day	15% 6% 2 5% 3 3 4 3 6% 9% 43%	4044
	21st to end	Day	9% 4 2 6% 4 4 4 4 6% 9% 48%	4436
September	1st to 10th	Day	14% 6% 2 6% 5% 4 4 3 6% 7% 44%	2280
	11th to 20th	Day	13% 6% 2 6% 4 4 3 4 5% 7% 46%	2139
	21st to end	Day	18% 8% 3 7% 5% 5% 4 3 5% 6% 37%	2071
October	1st to 10th	Day	22% 8% 2 6% 4 4 4 3 4 6% 36%	1900
	11th to 20th	Day	26% 10% 4 9% 5% 4 4 4 3 7% 24%	1900
	21st to end	Day	31% 12% 4 9% 4 4 4 3 4 5% 19%	2066
November	1st to 10th	Day	21% 16% 4 8% 6% 5% 3 2 5% 6% 24%	1637
	11th to 20th	Day	21% 16% 5% 10% 6% 5% 5% 4 4 6% 17%	1600
	21st to end	Day	24% 22% 5% 10% 8% 6% 4 4 4 4 10%	1600
December	1st to 10th	Day	19% 28% 6% 9% 6% 5% 5% 3 5% 5% 10%	2600
	11th to 20th	Day	19% 24% 9% 15% 5% 4 3 2 3 4 12%	2986
	21st to end	Day	26% 18% 5% 11% 5% 5% 4 5% 4 4 13%	3547
January	1st to 10th	Night	13% 21% 11% 16% 6% 5% 5% 4 4 4 12%	6808
	11th to 20th	Night	13% 18% 9% 21% 7% 5% 4 3 4 4 11%	6100
	21st to end	Night	13% 18% 8% 14% 9% 6% 4 3 4 5% 14%	6490
February	1st to 10th	Night	13% 20% 6% 13% 8% 6% 4 3 5% 5% 18%	2600
	11th to 20th	Night	14% 16% 6% 13% 7% 5% 4 3 4 6% 22%	2533
	21st to end	Night	17% 14% 5% 11% 6% 5% 5% 4 5% 5% 24%	2090
March	1st to 10th	Night	17% 12% 4 9% 5% 3 4 3 5% 6% 30%	4955
	11th to 20th	Night	11% 12% 4 9% 6% 5% 5% 4 6% 7% 30%	4979
	21st to end	Night	21% 11% 4 7% 5% 5% 5% 4 4 4 30%	5467
April	1st to 10th	Night	21% 12% 3 7% 6% 4 4 3 5% 4 31%	2053
	11th to 20th	Night	19% 10% 3 7% 4 4 4 3 5% 7% 35%	1847
	21st to end	Night	20% 8% 4 9% 5% 5% 4 3 5% 6% 32%	1800
May	1st to 10th	Night	16% 7% 3 8% 5% 5% 5% 4 5% 6% 35%	4053
	11th to 20th	Night	12% 7% 3 7% 5% 4 5% 3 5% 8% 42%	3575
	21st to end	Night	17% 7% 2 7% 5% 4 4 4 4 7% 37%	3926
June	1st to 10th	Night	15% 8% 3 5% 6% 4 5% 4 6% 7% 39%	1535
	11th to 20th	Night	12% 6% 2 5% 4 5% 4 4 7% 9% 43%	1400
	21st to end	Night	15% 6% 3 5% 4 5% 4 3 7% 6% 41%	1400
July	1st to 10th	Night	14% 7% 2 7% 5% 3 3 3 5% 8% 42%	3160
	11th to 20th	Night	14% 5% 2 5% 4 4 4 3 5% 7% 48%	3353
	21st to end	Night	11% 5% 2 5% 3 4 4 3 5% 8% 50%	4289
August	1st to 10th	Night	11% 6% 2 6% 4 4 4 4 6% 7% 46%	2861
	11th to 20th	Night	15% 6% 3 6% 4 4 4 3 5% 7% 44%	2785
	21st to end	Night	15% 5% 2 5% 4 3 4 3 5% 7% 47%	3188
September	1st to 10th	Night	12% 5% 2 6% 4 4 4 4 5% 7% 46%	1900
	11th to 20th	Night	13% 5% 2 6% 5% 3 5% 3 6% 7% 45%	2038
	21st to end	Night	20% 6% 2 6% 5% 4 4 3 6% 7% 37%	2109
October	1st to 10th	Night	21% 9% 3 8% 4 4 4 3 4 6% 34%	2280
	11th to 20th	Night	28% 11% 3 8% 5% 4 4 3 5% 6% 23%	2280
	21st to end	Night	29% 14% 4 9% 5% 3 4 3 5% 5% 19%	2527
November	1st to 10th	Night	23% 15% 3 8% 5% 3 4 2 5% 5% 26%	2660
	11th to 20th	Night	19% 21% 5% 10% 5% 5% 5% 3 5% 4 19%	2800
	21st to end	Night	25% 23% 6% 10% 6% 4 4 3 4 4 11%	2800
December	1st to 10th	Night	21% 29% 6% 12% 5% 4 3 3 3 4 9%	4580
	11th to 20th	Night	18% 24% 9% 16% 6% 4 4 3 3 4 9%	5208
	21st to end	Night	24% 20% 6% 13% 6% 5% 4 3 4 4 10%	7410

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	44% 29% 7% 14% 6%	3159
	11th to 20th	Day	60% 29% 3 5% 2	3787
	21st to end	Day	53% 31% 5% 6% 5%	4466
February	1st to 10th	Day	28% 63% 3 5% 2	1800
	11th to 20th	Day	23% 62% 4 7% 4	1762
	21st to end	Day	25% 62% 3 7% 2	1537
March	1st to 10th	Day	41% 31% 9% 5% 13% 1	4887
	11th to 20th	Day	39% 32% 12% 11% 5% 1	4980
	21st to end	Day	37% 33% 9% 15% 5% 1	5465
April	1st to 10th	Day	22% 62% 3 8% 5%	2346
	11th to 20th	Day	20% 62% 3 10% 5% 1	2517
	21st to end	Day	20% 63% 4 7% 6% 1	2600
May	1st to 10th	Day	32% 33% 10% 14% 8% 4	5897
	11th to 20th	Day	30% 33% 11% 12% 14% 1	6322
	21st to end	Day	37% 31% 8% 12% 9% 2	6949
June	1st to 10th	Day	16% 63% 3 11% 7%	2860
	11th to 20th	Day	17% 63% 4 10% 6% 1	3000
	21st to end	Day	17% 61% 5% 9% 7% 1	3000
July	1st to 10th	Day	32% 28% 12% 20% 8%	6746
	11th to 20th	Day	25% 27% 9% 28% 10%	6519
	21st to end	Day	21% 27% 11% 28% 13%	6360
August	1st to 10th	Day	24% 39% 11% 18% 7%	4143
	11th to 20th	Day	28% 40% 11% 16% 5%	4083
	21st to end	Day	19% 39% 8% 27% 7%	4436
September	1st to 10th	Day	16% 62% 6% 11% 5%	2280
	11th to 20th	Day	13% 61% 4 15% 7%	2139
	21st to end	Day	17% 62% 5% 11% 5%	2071
October	1st to 10th	Day	26% 39% 10% 18% 7%	3160
	11th to 20th	Day	24% 40% 11% 21% 4	3140
	21st to end	Day	37% 38% 9% 13% 3	3380
November	1st to 10th	Day	31% 57% 5% 5% 3	1637
	11th to 20th	Day	29% 58% 6% 6% 1	1600
	21st to end	Day	31% 58% 5% 4 2 1	1600
December	1st to 10th	Day	45% 37% 12% 5% 1	2600
	11th to 20th	Day	53% 33% 7% 8% 1	2986
	21st to end	Day	53% 29% 5% 8% 6%	3547
January	1st to 10th	Night	51% 28% 6% 10% 5%	6808
	11th to 20th	Night	55% 30% 5% 5% 5%	6141
	21st to end	Night	52% 32% 7% 3 5% 1	6490
February	1st to 10th	Night	26% 63% 4 5% 2	2600
	11th to 20th	Night	23% 61% 4 9% 4	2535
	21st to end	Night	25% 63% 4 4 3	2090
March	1st to 10th	Night	39% 32% 7% 9% 10% 3	4965
	11th to 20th	Night	38% 32% 13% 11% 5% 1	4980
	21st to end	Night	40% 33% 7% 11% 7% 1	5467
April	1st to 10th	Night	25% 62% 3 6% 4	2053
	11th to 20th	Night	19% 63% 2 8% 7% 1	1847
	21st to end	Night	22% 62% 5% 5% 5% 1	1800
May	1st to 10th	Night	34% 33% 7% 14% 8% 4	4060
	11th to 20th	Night	28% 33% 9% 15% 14% 1	3576
	21st to end	Night	36% 31% 7% 17% 8% 1	3927
June	1st to 10th	Night	14% 62% 3 11% 9% 2	1535
	11th to 20th	Night	14% 61% 5% 11% 9%	1400
	21st to end	Night	16% 61% 4 12% 7% 1	1400
July	1st to 10th	Night	34% 27% 10% 19% 9% 1	3125
	11th to 20th	Night	26% 27% 9% 28% 10%	3311
	21st to end	Night	25% 27% 6% 27% 14% 1	4162
August	1st to 10th	Night	24% 37% 11% 15% 12% 1	2850
	11th to 20th	Night	29% 39% 11% 15% 6%	2812
	21st to end	Night	21% 38% 7% 26% 9%	3188
September	1st to 10th	Night	11% 63% 7% 13% 6%	1900
	11th to 20th	Night	13% 61% 5% 13% 9%	2038
	21st to end	Night	17% 61% 5% 11% 6%	2109
October	1st to 10th	Night	22% 39% 6% 20% 12%	3800
	11th to 20th	Night	26% 39% 12% 19% 5%	3779
	21st to end	Night	31% 40% 14% 13% 3	4151
November	1st to 10th	Night	30% 57% 5% 6% 2	2660
	11th to 20th	Night	27% 58% 6% 6% 3	2800
	21st to end	Night	32% 58% 4 3 2	2800
December	1st to 10th	Night	47% 37% 10% 5% 1	4580
	11th to 20th	Night	55% 34% 5% 4 2	5208
	21st to end	Night	56% 28% 5% 7% 4	7410

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	18% 25% 36% 14% 7% 1	200
	11th to 20th	Day	22% 22% 33% 17% 5% 1	260
	21st to end	Day	29% 15% 30% 20% 5%	330
February	1st to 10th	Day	31% 21% 32% 12% 3 1	300
	11th to 20th	Day	21% 24% 40% 14% 1	300
	21st to end	Day	33% 20% 34% 12% 1	249
March	1st to 10th	Day	23% 17% 35% 20% 4	476
	11th to 20th	Day	23% 17% 34% 21% 5% 1	500
	21st to end	Day	28% 15% 29% 22% 5% 1	550
April	1st to 10th	Day	24% 17% 30% 21% 8%	500
	11th to 20th	Day	31% 16% 25% 17% 9% 3	492
	21st to end	Day	27% 17% 30% 17% 7% 1	500
May	1st to 10th	Day	20% 10% 37% 23% 8% 3	503
	11th to 20th	Day	18% 9% 29% 28% 14% 3	527
	21st to end	Day	17% 9% 29% 28% 14% 4	573
June	1st to 10th	Day	19% 10% 28% 29% 12% 1	590
	11th to 20th	Day	15% 8% 29% 33% 12% 4	730
	21st to end	Day	20% 7% 28% 30% 13% 2	730
July	1st to 10th	Day	11% 7% 27% 32% 20% 3	721
	11th to 20th	Day	14% 7% 24% 33% 17% 5%	628
	21st to end	Day	13% 6% 28% 33% 16% 4	576
August	1st to 10th	Day	14% 6% 21% 34% 18% 7%	502
	11th to 20th	Day	15% 5% 19% 33% 20% 9%	479
	21st to end	Day	16% 7% 24% 30% 17% 6%	539
September	1st to 10th	Day	15% 9% 24% 28% 18% 7%	490
	11th to 20th	Day	13% 7% 23% 26% 23% 9%	490
	21st to end	Day	21% 8% 23% 26% 20% 3	490
October	1st to 10th	Day	27% 13% 26% 17% 14% 4	490
	11th to 20th	Day	25% 19% 31% 18% 7% 1	490
	21st to end	Day	36% 16% 30% 14% 4	515
November	1st to 10th	Day	30% 20% 29% 18% 4	237
	11th to 20th	Day	25% 24% 34% 15% 3	200
	21st to end	Day	31% 20% 35% 15%	200
December	1st to 10th	Day	31% 21% 30% 14% 4 1	200
	11th to 20th	Day	36% 24% 28% 11% 2 1	200
	21st to end	Day	35% 20% 30% 14% 2	220
January	1st to 10th	Night	27% 18% 32% 18% 5% 1	1000
	11th to 20th	Night	30% 15% 31% 18% 5%	836
	21st to end	Night	22% 11% 32% 26% 8% 1	880
February	1st to 10th	Night	23% 18% 33% 21% 4	800
	11th to 20th	Night	22% 14% 34% 23% 6%	783
	21st to end	Night	24% 17% 32% 22% 6%	660
March	1st to 10th	Night	21% 15% 36% 24% 5%	800
	11th to 20th	Night	18% 17% 34% 25% 6% 1	800
	21st to end	Night	23% 9% 32% 26% 10%	880
April	1st to 10th	Night	27% 12% 30% 25% 5%	800
	11th to 20th	Night	24% 11% 27% 25% 11% 1	663
	21st to end	Night	24% 10% 28% 26% 13%	600
May	1st to 10th	Night	21% 6% 23% 36% 12% 2	600
	11th to 20th	Night	17% 6% 27% 37% 12% 1	394
	21st to end	Night	14% 5% 25% 38% 18%	433
June	1st to 10th	Night	17% 6% 26% 37% 14% 1	400
	11th to 20th	Night	15% 8% 20% 42% 15% 1	400
	21st to end	Night	19% 5% 22% 33% 21% 1	400
July	1st to 10th	Night	10% 5% 18% 40% 24% 3	390
	11th to 20th	Night	13% 5% 23% 32% 26% 2	388
	21st to end	Night	12% 4 23% 36% 23% 2	596
August	1st to 10th	Night	11% 5% 17% 36% 27% 3	579
	11th to 20th	Night	12% 3 18% 35% 26% 5%	564
	21st to end	Night	16% 5% 23% 28% 24% 4	665
September	1st to 10th	Night	14% 6% 23% 30% 21% 5%	760
	11th to 20th	Night	14% 6% 21% 31% 22% 5%	760
	21st to end	Night	20% 9% 19% 30% 18% 4	760
October	1st to 10th	Night	23% 12% 26% 23% 15% 1	760
	11th to 20th	Night	32% 13% 24% 22% 8% 2	760
	21st to end	Night	33% 16% 29% 19% 3	836
November	1st to 10th	Night	32% 13% 27% 19% 9%	780
	11th to 20th	Night	29% 20% 30% 16% 5%	800
	21st to end	Night	38% 14% 31% 15% 3	800
December	1st to 10th	Night	36% 20% 27% 14% 4	800
	11th to 20th	Night	29% 21% 34% 13% 4	800
	21st to end	Night	33% 14% 31% 19% 3	1060

Page generated at 2025-08-02 01:32:27. Version ac07

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