East Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the East Point clear sky chart from 2005-11-06 to 2026-03-18.

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	17% 12% 5% 11% 6% 5% 4 3 5% 6% 27%	131808
	Night	19% 14% 5% 13% 6% 5% 4 3 4 5% 22%	129876
Transparency	Day	57% 7% 12% 17% 6%	135305
	Night	62% 6% 11% 15% 6%	134473
Seeing	Day	23% 10% 24% 28% 14% 2	19422
	Night	25% 11% 26% 27% 10% 1	26853

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% 21% 9% 25% 6% 5% 3 2 2 3 10%	4690
	11th to 20th	Day	17% 16% 11% 19% 6% 5% 4 3 4 4 11%	4681
	21st to end	Day	9% 12% 7% 20% 10% 11% 6% 3 4 4 14%	5440
February	1st to 10th	Day	17% 15% 5% 15% 8% 7% 5% 3 4 4 16%	1890
	11th to 20th	Day	15% 16% 5% 12% 9% 6% 5% 4 4 5% 18%	1843
	21st to end	Day	10% 12% 5% 12% 9% 7% 5% 3 5% 7% 27%	1657
March	1st to 10th	Day	17% 13% 4 11% 9% 7% 3 3 4 4 24%	4712
	11th to 20th	Day	13% 12% 5% 14% 7% 6% 4 4 5% 6% 24%	5057
	21st to end	Day	20% 15% 7% 15% 6% 5% 4 3 4 5% 16%	5666
April	1st to 10th	Day	19% 12% 4 9% 6% 4 4 4 5% 5% 29%	2400
	11th to 20th	Day	19% 11% 3 7% 5% 4 4 3 5% 7% 32%	2374
	21st to end	Day	19% 12% 4 7% 5% 3 4 3 5% 6% 32%	2615
May	1st to 10th	Day	24% 14% 3 8% 4 4 3 3 4 5% 29%	6345
	11th to 20th	Day	18% 10% 2 8% 4 4 4 3 5% 7% 36%	6318
	21st to end	Day	16% 8% 3 7% 5% 4 5% 4 5% 8% 34%	6948
June	1st to 10th	Day	22% 12% 3 8% 5% 4 5% 4 6% 7% 24%	2800
	11th to 20th	Day	17% 7% 3 7% 5% 4 5% 4 5% 7% 36%	2800
	21st to end	Day	23% 9% 3 7% 5% 4 4 3 5% 7% 29%	2994
July	1st to 10th	Day	17% 10% 3 9% 5% 5% 5% 5% 6% 8% 27%	6365
	11th to 20th	Day	13% 6% 2 7% 4 4 5% 4 6% 8% 41%	6360
	21st to end	Day	11% 8% 3 8% 5% 5% 5% 4 6% 9% 38%	6927
August	1st to 10th	Day	16% 8% 3 9% 5% 6% 5% 4 6% 8% 29%	4440
	11th to 20th	Day	14% 7% 3 7% 4 4 4 4 6% 8% 38%	4175
	21st to end	Day	13% 7% 3 7% 5% 4 5% 4 5% 7% 41%	4388
September	1st to 10th	Day	16% 6% 2 6% 4 4 4 4 5% 8% 40%	2400
	11th to 20th	Day	18% 9% 3 7% 4 5% 5% 3 5% 7% 34%	2400
	21st to end	Day	18% 9% 3 6% 4 4 4 4 5% 8% 36%	2106
October	1st to 10th	Day	19% 9% 2 7% 5% 5% 4 4 5% 7% 32%	2000
	11th to 20th	Day	21% 13% 3 9% 5% 5% 5% 4 5% 7% 23%	2000
	21st to end	Day	23% 17% 4 8% 5% 5% 3 3 5% 6% 21%	2074
November	1st to 10th	Day	22% 21% 4 9% 6% 4 4 3 4 4 18%	1747
	11th to 20th	Day	23% 24% 6% 10% 6% 4 3 3 4 4 13%	1680
	21st to end	Day	19% 24% 8% 11% 5% 4 5% 3 5% 5% 11%	1680
December	1st to 10th	Day	17% 20% 12% 14% 7% 4 4 2 3 4 13%	2690
	11th to 20th	Day	23% 19% 8% 18% 5% 3 3 2 3 3 13%	3076
	21st to end	Day	18% 18% 11% 22% 5% 4 3 3 3 3 11%	4070
January	1st to 10th	Night	16% 21% 10% 20% 5% 4 4 3 3 3 11%	8234
	11th to 20th	Night	19% 16% 9% 24% 7% 5% 3 2 3 3 9%	8234
	21st to end	Night	10% 13% 6% 22% 10% 10% 5% 3 4 5% 13%	8757
February	1st to 10th	Night	19% 13% 4 14% 9% 6% 4 4 4 4 19%	2730
	11th to 20th	Night	16% 14% 5% 14% 9% 6% 4 3 5% 5% 20%	2663
	21st to end	Night	13% 13% 5% 13% 7% 5% 4 3 5% 5% 26%	2149
March	1st to 10th	Night	19% 14% 5% 11% 11% 5% 4 3 4 4 21%	5345
	11th to 20th	Night	17% 14% 5% 11% 6% 4 4 3 5% 5% 25%	5057
	21st to end	Night	23% 18% 5% 14% 5% 4 4 3 3 3 17%	5265
April	1st to 10th	Night	21% 13% 4 8% 5% 4 4 4 5% 5% 27%	2000
	11th to 20th	Night	19% 12% 4 8% 5% 4 4 3 5% 5% 32%	1976
	21st to end	Night	24% 11% 3 8% 5% 3 3 2 3 5% 32%	1780
May	1st to 10th	Night	28% 15% 4 7% 4 4 3 3 4 5% 23%	3615
	11th to 20th	Night	17% 9% 4 8% 4 5% 5% 4 6% 6% 33%	3596
	21st to end	Night	16% 9% 3 7% 5% 5% 4 5% 5% 8% 34%	3948
June	1st to 10th	Night	27% 9% 3 7% 4 5% 5% 4 5% 6% 25%	1600
	11th to 20th	Night	21% 6% 2 6% 5% 3 4 4 5% 6% 39%	1600
	21st to end	Night	23% 9% 4 8% 5% 5% 5% 4 5% 6% 27%	1411
July	1st to 10th	Night	16% 9% 4 10% 7% 7% 7% 5% 7% 6% 23%	3528
	11th to 20th	Night	12% 8% 3 7% 5% 4 5% 3 7% 9% 38%	3620
	21st to end	Night	17% 8% 2 6% 4 4 5% 4 6% 8% 36%	3948
August	1st to 10th	Night	17% 9% 3 8% 5% 4 5% 5% 7% 9% 29%	2713
	11th to 20th	Night	13% 8% 2 8% 5% 5% 5% 4 6% 7% 36%	2872
	21st to end	Night	12% 6% 2 6% 4 4 4 4 6% 8% 42%	3510
September	1st to 10th	Night	18% 6% 2 6% 4 4 5% 4 5% 7% 41%	2000
	11th to 20th	Night	19% 8% 3 6% 4 4 4 3 5% 5% 39%	2000
	21st to end	Night	19% 9% 2 7% 4 5% 4 3 4 6% 35%	2289
October	1st to 10th	Night	21% 8% 2 7% 5% 4 4 3 5% 6% 35%	2400
	11th to 20th	Night	22% 12% 3 8% 5% 5% 4 3 5% 7% 27%	2400
	21st to end	Night	27% 16% 4 8% 4 4 4 3 3 5% 21%	2765
November	1st to 10th	Night	21% 19% 4 10% 5% 4 4 3 4 5% 21%	2768
	11th to 20th	Night	26% 22% 5% 8% 5% 4 4 3 4 5% 13%	2940
	21st to end	Night	24% 23% 7% 10% 5% 5% 4 3 4 4 12%	2940
December	1st to 10th	Night	18% 16% 9% 16% 8% 6% 5% 3 4 5% 13%	4720
	11th to 20th	Night	23% 17% 8% 18% 5% 4 3 2 2 2 14%	5353
	21st to end	Night	23% 17% 8% 19% 5% 3 3 2 3 4 13%	7150

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	80% 6% 6% 6% 2	4691
	11th to 20th	Day	75% 5% 10% 6% 3	4710
	21st to end	Day	70% 6% 7% 13% 3	5440
February	1st to 10th	Day	71% 5% 10% 11% 3	1890
	11th to 20th	Day	66% 6% 11% 13% 3 1	1851
	21st to end	Day	56% 6% 12% 16% 9% 1	1657
March	1st to 10th	Day	63% 5% 8% 17% 8%	4716
	11th to 20th	Day	58% 8% 17% 12% 4 1	5057
	21st to end	Day	69% 6% 9% 11% 4 1	5666
April	1st to 10th	Day	55% 6% 11% 17% 10% 2	2400
	11th to 20th	Day	53% 5% 10% 20% 11% 1	2374
	21st to end	Day	53% 6% 12% 16% 10% 3	2615
May	1st to 10th	Day	58% 6% 11% 16% 8% 1	6357
	11th to 20th	Day	48% 7% 15% 23% 7%	6322
	21st to end	Day	46% 9% 12% 24% 8%	6948
June	1st to 10th	Day	58% 6% 13% 17% 6%	2800
	11th to 20th	Day	47% 7% 13% 24% 9% 1	2800
	21st to end	Day	54% 8% 12% 16% 10% 1	2994
July	1st to 10th	Day	52% 9% 15% 17% 7%	6295
	11th to 20th	Day	40% 8% 18% 28% 6%	6284
	21st to end	Day	41% 9% 20% 24% 6%	6730
August	1st to 10th	Day	52% 8% 15% 20% 5%	4426
	11th to 20th	Day	42% 8% 16% 26% 7%	4214
	21st to end	Day	41% 7% 13% 29% 10%	4388
September	1st to 10th	Day	41% 8% 15% 27% 9%	2400
	11th to 20th	Day	48% 8% 13% 23% 8%	2400
	21st to end	Day	45% 8% 13% 24% 11%	2106
October	1st to 10th	Day	51% 7% 14% 21% 7%	3260
	11th to 20th	Day	55% 7% 12% 21% 5%	3240
	21st to end	Day	55% 8% 15% 19% 3	3332
November	1st to 10th	Day	69% 7% 9% 12% 3	1747
	11th to 20th	Day	75% 6% 10% 9% 2	1680
	21st to end	Day	76% 6% 11% 6% 1	1680
December	1st to 10th	Day	72% 6% 7% 14% 1	2690
	11th to 20th	Day	79% 5% 6% 4 6%	3075
	21st to end	Day	79% 6% 7% 6% 2	4070
January	1st to 10th	Night	77% 6% 7% 8% 1	8234
	11th to 20th	Night	79% 5% 9% 6% 2	8280
	21st to end	Night	70% 5% 7% 12% 5%	8757
February	1st to 10th	Night	68% 5% 10% 11% 6% 1	2730
	11th to 20th	Night	65% 6% 10% 14% 5% 1	2666
	21st to end	Night	58% 6% 10% 16% 9% 1	2149
March	1st to 10th	Night	65% 4 7% 15% 8%	5354
	11th to 20th	Night	60% 7% 13% 13% 6% 1	5058
	21st to end	Night	71% 5% 6% 12% 5% 1	5265
April	1st to 10th	Night	58% 5% 11% 15% 11% 1	2000
	11th to 20th	Night	54% 5% 9% 20% 11% 2	1976
	21st to end	Night	56% 6% 9% 17% 11% 1	1780
May	1st to 10th	Night	65% 5% 7% 14% 9% 1	3620
	11th to 20th	Night	50% 8% 14% 20% 8%	3597
	21st to end	Night	47% 9% 15% 23% 6%	3949
June	1st to 10th	Night	58% 7% 10% 19% 6%	1600
	11th to 20th	Night	45% 7% 12% 20% 15%	1600
	21st to end	Night	56% 8% 13% 14% 8%	1411
July	1st to 10th	Night	57% 8% 13% 15% 6% 1	3489
	11th to 20th	Night	41% 8% 16% 23% 11%	3572
	21st to end	Night	44% 7% 17% 24% 8%	3831
August	1st to 10th	Night	50% 9% 17% 20% 4	2702
	11th to 20th	Night	44% 9% 18% 24% 5%	2899
	21st to end	Night	36% 9% 17% 30% 9%	3509
September	1st to 10th	Night	42% 8% 12% 28% 10%	2000
	11th to 20th	Night	46% 6% 12% 26% 10%	2000
	21st to end	Night	49% 7% 11% 25% 8%	2289
October	1st to 10th	Night	52% 7% 13% 20% 9%	3920
	11th to 20th	Night	53% 7% 12% 21% 6%	3899
	21st to end	Night	57% 6% 13% 18% 6%	4464
November	1st to 10th	Night	63% 8% 12% 12% 4	2768
	11th to 20th	Night	73% 6% 10% 9% 3	2940
	21st to end	Night	77% 7% 10% 5% 1	2940
December	1st to 10th	Night	67% 8% 9% 14% 1	4720
	11th to 20th	Night	77% 5% 7% 9% 2 1	5355
	21st to end	Night	75% 5% 9% 9% 1	7150

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% 21% 35% 17% 5%	430
	11th to 20th	Day	26% 16% 29% 20% 7%	430
	21st to end	Day	16% 16% 37% 25% 5%	473
February	1st to 10th	Day	27% 13% 31% 20% 6% 2	430
	11th to 20th	Day	23% 15% 31% 24% 5% 1	426
	21st to end	Day	14% 11% 33% 32% 8% 1	355
March	1st to 10th	Day	20% 11% 34% 26% 8% 1	463
	11th to 20th	Day	17% 12% 31% 28% 10% 1	528
	21st to end	Day	24% 12% 28% 27% 8% 1	550
April	1st to 10th	Day	25% 11% 33% 22% 9%	500
	11th to 20th	Day	25% 7% 32% 26% 10% 2	492
	21st to end	Day	22% 11% 20% 29% 15% 2	523
May	1st to 10th	Day	33% 5% 21% 27% 10% 4	703
	11th to 20th	Day	22% 5% 18% 34% 18% 4	724
	21st to end	Day	21% 5% 23% 36% 14% 1	790
June	1st to 10th	Day	28% 8% 15% 31% 15% 3	730
	11th to 20th	Day	18% 5% 18% 39% 19% 2	730
	21st to end	Day	25% 6% 14% 31% 20% 3	730
July	1st to 10th	Day	20% 3 15% 42% 19% 2	720
	11th to 20th	Day	16% 4 14% 38% 26% 2	718
	21st to end	Day	19% 5% 15% 34% 25% 2	795
August	1st to 10th	Day	14% 3 12% 39% 28% 4	653
	11th to 20th	Day	17% 6% 12% 34% 26% 6%	519
	21st to end	Day	16% 5% 18% 30% 26% 5%	583
September	1st to 10th	Day	14% 6% 22% 37% 17% 3	530
	11th to 20th	Day	22% 9% 19% 31% 17% 3	530
	21st to end	Day	19% 7% 27% 28% 14% 4	447
October	1st to 10th	Day	21% 7% 24% 30% 15% 3	420
	11th to 20th	Day	24% 10% 27% 23% 13% 3	420
	21st to end	Day	27% 13% 29% 22% 8% 1	462
November	1st to 10th	Day	31% 16% 28% 18% 6%	425
	11th to 20th	Day	33% 19% 26% 16% 5% 1	430
	21st to end	Day	33% 17% 30% 16% 4	430
December	1st to 10th	Day	33% 15% 31% 16% 4	430
	11th to 20th	Day	31% 22% 29% 16% 2	430
	21st to end	Day	23% 22% 31% 17% 6% 1	473
January	1st to 10th	Night	28% 17% 32% 19% 5%	950
	11th to 20th	Night	27% 14% 33% 20% 5%	950
	21st to end	Night	20% 19% 34% 20% 6%	990
February	1st to 10th	Night	26% 13% 31% 23% 7%	840
	11th to 20th	Night	23% 12% 36% 23% 5%	823
	21st to end	Night	19% 10% 33% 28% 9% 1	692
March	1st to 10th	Night	22% 10% 34% 28% 6%	840
	11th to 20th	Night	22% 10% 29% 27% 11% 1	829
	21st to end	Night	27% 10% 28% 25% 9% 1	795
April	1st to 10th	Night	24% 13% 25% 30% 7%	600
	11th to 20th	Night	24% 7% 28% 28% 12% 1	594
	21st to end	Night	28% 6% 25% 29% 10% 3	600
May	1st to 10th	Night	31% 4 22% 26% 13% 4	600
	11th to 20th	Night	22% 6% 18% 32% 18% 4	592
	21st to end	Night	22% 4 23% 38% 12% 2	649
June	1st to 10th	Night	29% 7% 18% 35% 11% 1	600
	11th to 20th	Night	22% 4 18% 40% 15% 1	600
	21st to end	Night	27% 3 16% 38% 14% 2	411
July	1st to 10th	Night	16% 4 15% 40% 23% 2	546
	11th to 20th	Night	18% 2 13% 44% 21% 2	582
	21st to end	Night	20% 3 14% 42% 19% 2	656
August	1st to 10th	Night	17% 2 15% 41% 23% 2	598
	11th to 20th	Night	19% 3 15% 37% 22% 4	592
	21st to end	Night	14% 5% 19% 33% 26% 2	660
September	1st to 10th	Night	20% 4 22% 34% 17% 2	600
	11th to 20th	Night	22% 6% 22% 32% 18% 2	600
	21st to end	Night	21% 8% 26% 32% 11% 2	740
October	1st to 10th	Night	24% 6% 29% 28% 12% 1	800
	11th to 20th	Night	26% 10% 25% 25% 11% 2	800
	21st to end	Night	33% 14% 27% 20% 6%	949
November	1st to 10th	Night	30% 17% 27% 21% 4 1	930
	11th to 20th	Night	34% 17% 27% 16% 6% 1	950
	21st to end	Night	34% 17% 28% 18% 3	950
December	1st to 10th	Night	31% 17% 31% 15% 5%	950
	11th to 20th	Night	30% 22% 29% 15% 3	950
	21st to end	Night	30% 18% 29% 18% 4 1	1045

Page generated at 2026-03-15 03:23:57. Version ac07

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