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 2024-01-16.

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	19% 11% 5% 8% 6% 3 5% 4 5% 6% 27%	74931
	Night	21% 13% 5% 9% 6% 3 4 4 4 5% 24%	74861
Transparency	Day	57% 7% 12% 17% 7% 1	74634
	Night	62% 6% 11% 15% 6%	74693
Seeing	Day	23% 9% 24% 28% 14% 2	16440
	Night	26% 10% 26% 27% 10% 1	23875

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	20% 16% 10% 16% 8% 5% 4 4 3 3 10%	1516
	11th to 20th	Day	21% 14% 9% 17% 10% 4 4 4 4 5% 8%	1481
	21st to end	Day	12% 12% 9% 17% 12% 6% 5% 5% 4 5% 12%	1673
February	1st to 10th	Day	18% 13% 5% 12% 11% 5% 7% 4 4 5% 16%	1620
	11th to 20th	Day	17% 14% 5% 11% 10% 5% 6% 5% 5% 6% 19%	1573
	21st to end	Day	9% 10% 5% 10% 11% 5% 5% 4 4 7% 28%	1417
March	1st to 10th	Day	13% 13% 5% 10% 7% 3 5% 4 5% 6% 27%	1847
	11th to 20th	Day	14% 9% 6% 10% 9% 4 5% 5% 5% 6% 26%	1980
	21st to end	Day	18% 12% 7% 8% 6% 3 4 3 3 5% 29%	2253
April	1st to 10th	Day	18% 11% 4 8% 6% 4 4 5% 5% 6% 30%	2160
	11th to 20th	Day	20% 10% 3 6% 5% 3 4 3 5% 7% 34%	2134
	21st to end	Day	20% 11% 5% 7% 5% 2 4 5% 5% 6% 31%	2352
May	1st to 10th	Day	25% 9% 3 6% 5% 3 4 4 5% 6% 28%	2520
	11th to 20th	Day	20% 9% 3 6% 5% 2 4 3 4 7% 36%	2478
	21st to end	Day	20% 7% 3 6% 5% 3 5% 4 6% 8% 33%	2724
June	1st to 10th	Day	24% 11% 4 7% 5% 3 5% 5% 6% 6% 24%	2520
	11th to 20th	Day	18% 7% 4 6% 6% 3 5% 4 5% 7% 36%	2520
	21st to end	Day	23% 9% 3 6% 5% 3 4 4 5% 7% 30%	2694
July	1st to 10th	Day	15% 7% 3 5% 5% 3 5% 4 6% 8% 37%	2525
	11th to 20th	Day	13% 7% 2 6% 5% 4 6% 6% 6% 9% 36%	2520
	21st to end	Day	17% 9% 3 8% 6% 3 6% 5% 5% 7% 30%	2745
August	1st to 10th	Day	16% 5% 3 6% 5% 4 5% 5% 7% 9% 36%	2442
	11th to 20th	Day	18% 7% 3 6% 5% 3 4 5% 6% 8% 36%	2304
	21st to end	Day	16% 6% 3 5% 5% 4 5% 5% 5% 8% 37%	2422
September	1st to 10th	Day	17% 6% 2 5% 5% 3 4 5% 5% 8% 39%	2160
	11th to 20th	Day	19% 9% 3 6% 5% 3 5% 4 4 7% 33%	2160
	21st to end	Day	19% 9% 3 5% 4 3 4 4 5% 7% 36%	1897
October	1st to 10th	Day	20% 9% 2 6% 6% 3 5% 5% 5% 8% 32%	1800
	11th to 20th	Day	21% 13% 3 8% 6% 4 5% 5% 6% 7% 23%	1800
	21st to end	Day	24% 17% 4 7% 6% 3 4 4 4 6% 20%	1868
November	1st to 10th	Day	22% 20% 4 8% 7% 2 6% 3 4 4 20%	1577
	11th to 20th	Day	21% 21% 7% 10% 6% 3 5% 4 4 5% 14%	1520
	21st to end	Day	19% 23% 9% 10% 6% 3 5% 4 4 5% 11%	1520
December	1st to 10th	Day	24% 21% 11% 13% 6% 3 4 3 2 4 8%	1520
	11th to 20th	Day	25% 21% 12% 14% 8% 2 4 3 3 3 5%	1906
	21st to end	Day	20% 20% 11% 14% 6% 3 3 4 3 3 12%	2783
January	1st to 10th	Night	20% 18% 10% 15% 8% 4 4 3 4 4 11%	2649
	11th to 20th	Night	20% 14% 8% 18% 10% 4 4 4 4 5% 12%	2601
	21st to end	Night	16% 13% 9% 15% 10% 4 4 4 3 4 17%	2682
February	1st to 10th	Night	19% 12% 4 12% 9% 4 5% 4 4 5% 19%	2340
	11th to 20th	Night	18% 13% 5% 12% 10% 5% 5% 4 4 5% 19%	2273
	21st to end	Night	12% 13% 5% 11% 8% 4 5% 4 5% 6% 27%	1839
March	1st to 10th	Night	15% 13% 6% 11% 7% 4 5% 4 5% 5% 26%	2097
	11th to 20th	Night	18% 11% 5% 9% 8% 3 5% 4 5% 6% 27%	1979
	21st to end	Night	19% 14% 5% 9% 5% 3 4 4 4 4 29%	2102
April	1st to 10th	Night	22% 11% 5% 7% 6% 3 5% 4 5% 6% 26%	1800
	11th to 20th	Night	20% 11% 3 7% 6% 3 4 4 5% 5% 33%	1776
	21st to end	Night	24% 11% 3 7% 5% 2 3 3 3 5% 33%	1603
May	1st to 10th	Night	28% 9% 3 4 4 3 4 4 4 6% 31%	1440
	11th to 20th	Night	22% 7% 3 6% 5% 3 4 4 4 6% 35%	1416
	21st to end	Night	19% 8% 4 6% 6% 3 4 5% 6% 7% 33%	1550
June	1st to 10th	Night	29% 8% 3 6% 5% 3 5% 5% 5% 6% 25%	1440
	11th to 20th	Night	22% 6% 3 6% 5% 2 4 4 5% 6% 38%	1440
	21st to end	Night	24% 9% 4 7% 6% 3 5% 4 4 6% 28%	1271
July	1st to 10th	Night	17% 6% 3 5% 7% 4 6% 6% 6% 7% 34%	1404
	11th to 20th	Night	15% 7% 3 6% 6% 3 6% 5% 7% 9% 35%	1440
	21st to end	Night	18% 10% 3 6% 5% 4 6% 5% 6% 8% 30%	1573
August	1st to 10th	Night	16% 5% 1 5% 5% 3 5% 6% 8% 10% 36%	1494
	11th to 20th	Night	17% 9% 3 7% 6% 4 5% 4 6% 6% 35%	1596
	21st to end	Night	14% 5% 3 5% 5% 4 4 5% 6% 9% 40%	1934
September	1st to 10th	Night	18% 6% 2 5% 5% 3 5% 5% 5% 7% 40%	1800
	11th to 20th	Night	21% 8% 3 6% 5% 3 4 4 4 5% 38%	1800
	21st to end	Night	20% 8% 3 7% 5% 4 3 4 4 6% 36%	2059
October	1st to 10th	Night	21% 8% 2 6% 6% 3 4 4 5% 6% 35%	2160
	11th to 20th	Night	23% 12% 3 6% 5% 3 4 4 5% 7% 27%	2160
	21st to end	Night	29% 16% 4 7% 5% 3 4 4 3 5% 20%	2488
November	1st to 10th	Night	22% 17% 4 8% 6% 2 5% 4 4 5% 22%	2498
	11th to 20th	Night	24% 21% 6% 8% 6% 4 4 4 4 5% 14%	2660
	21st to end	Night	24% 21% 8% 9% 6% 3 5% 3 4 4 12%	2660
December	1st to 10th	Night	26% 20% 9% 12% 6% 3 5% 3 3 4 9%	2660
	11th to 20th	Night	27% 19% 10% 16% 6% 3 3 2 2 2 10%	3293
	21st to end	Night	28% 18% 8% 15% 6% 2 2 3 3 3 13%	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	79% 6% 6% 6% 3	1517
	11th to 20th	Day	79% 6% 8% 5% 2	1481
	21st to end	Day	73% 5% 9% 9% 3	1673
February	1st to 10th	Day	71% 5% 10% 11% 3	1620
	11th to 20th	Day	66% 6% 11% 13% 4 1	1581
	21st to end	Day	56% 6% 13% 15% 9% 2	1417
March	1st to 10th	Day	57% 5% 10% 20% 8%	1851
	11th to 20th	Day	58% 6% 11% 17% 6% 1	1980
	21st to end	Day	59% 4 11% 16% 8% 2	2253
April	1st to 10th	Day	55% 6% 11% 17% 10% 2	2160
	11th to 20th	Day	52% 5% 10% 20% 11% 1	2134
	21st to end	Day	53% 6% 12% 17% 10% 2	2352
May	1st to 10th	Day	57% 6% 10% 16% 10% 2	2520
	11th to 20th	Day	49% 6% 11% 23% 11%	2482
	21st to end	Day	49% 9% 13% 20% 10%	2724
June	1st to 10th	Day	59% 6% 13% 17% 5%	2520
	11th to 20th	Day	49% 6% 12% 24% 9% 1	2520
	21st to end	Day	54% 8% 12% 16% 9% 1	2694
July	1st to 10th	Day	41% 10% 18% 24% 6%	2455
	11th to 20th	Day	42% 10% 16% 22% 9% 1	2444
	21st to end	Day	53% 8% 15% 17% 7%	2592
August	1st to 10th	Day	43% 9% 17% 25% 5%	2428
	11th to 20th	Day	46% 9% 16% 23% 6%	2304
	21st to end	Day	43% 9% 16% 24% 8%	2422
September	1st to 10th	Day	41% 8% 16% 25% 8%	2160
	11th to 20th	Day	51% 7% 11% 21% 9%	2160
	21st to end	Day	46% 7% 13% 23% 10%	1897
October	1st to 10th	Day	52% 5% 13% 21% 8%	1800
	11th to 20th	Day	59% 7% 14% 15% 5%	1800
	21st to end	Day	65% 8% 10% 13% 4	1868
November	1st to 10th	Day	68% 7% 10% 13% 3	1577
	11th to 20th	Day	74% 6% 10% 8% 2	1520
	21st to end	Day	76% 6% 11% 6% 1	1520
December	1st to 10th	Day	82% 6% 7% 4 1	1520
	11th to 20th	Day	87% 5% 4 2 1	1905
	21st to end	Day	78% 6% 10% 4 2	2783
January	1st to 10th	Night	78% 7% 7% 6% 2	2649
	11th to 20th	Night	77% 6% 9% 7% 2	2601
	21st to end	Night	71% 5% 9% 10% 5%	2682
February	1st to 10th	Night	67% 5% 11% 11% 6% 1	2340
	11th to 20th	Night	67% 6% 10% 13% 4 1	2276
	21st to end	Night	57% 6% 11% 16% 9% 1	1839
March	1st to 10th	Night	60% 5% 10% 16% 8% 1	2106
	11th to 20th	Night	58% 6% 10% 17% 8% 2	1980
	21st to end	Night	60% 5% 9% 15% 10% 1	2102
April	1st to 10th	Night	59% 5% 11% 14% 10% 1	1800
	11th to 20th	Night	53% 5% 9% 20% 11% 2	1776
	21st to end	Night	56% 5% 10% 17% 11% 1	1603
May	1st to 10th	Night	56% 5% 9% 19% 9% 1	1440
	11th to 20th	Night	50% 6% 10% 21% 12% 1	1417
	21st to end	Night	50% 7% 13% 21% 9% 1	1551
June	1st to 10th	Night	59% 6% 11% 18% 5%	1440
	11th to 20th	Night	47% 7% 12% 19% 15%	1440
	21st to end	Night	57% 8% 13% 14% 8%	1271
July	1st to 10th	Night	45% 9% 18% 22% 6%	1365
	11th to 20th	Night	44% 9% 16% 21% 9% 1	1392
	21st to end	Night	50% 9% 15% 19% 7%	1486
August	1st to 10th	Night	40% 11% 19% 25% 5%	1483
	11th to 20th	Night	48% 8% 18% 19% 6%	1596
	21st to end	Night	40% 10% 18% 27% 6%	1934
September	1st to 10th	Night	43% 8% 13% 27% 9%	1800
	11th to 20th	Night	47% 6% 11% 25% 11%	1800
	21st to end	Night	49% 6% 11% 25% 8%	2059
October	1st to 10th	Night	49% 6% 14% 22% 9%	2160
	11th to 20th	Night	57% 5% 16% 19% 3	2160
	21st to end	Night	66% 5% 9% 14% 5%	2488
November	1st to 10th	Night	63% 8% 12% 13% 4	2498
	11th to 20th	Night	72% 7% 11% 8% 3	2660
	21st to end	Night	77% 7% 11% 4 1	2660
December	1st to 10th	Night	80% 6% 8% 5% 1	2660
	11th to 20th	Night	83% 4 6% 5% 1	3295
	21st to end	Night	78% 4 9% 7% 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% 21% 36% 15% 5%	370
	11th to 20th	Day	26% 14% 32% 22% 5%	356
	21st to end	Day	18% 13% 39% 25% 5%	374
February	1st to 10th	Day	29% 14% 33% 20% 4	340
	11th to 20th	Day	24% 15% 32% 24% 4 1	336
	21st to end	Day	13% 12% 35% 31% 9% 1	280
March	1st to 10th	Day	19% 10% 33% 28% 9% 1	364
	11th to 20th	Day	16% 12% 30% 30% 10% 1	420
	21st to end	Day	24% 10% 27% 27% 9% 1	462
April	1st to 10th	Day	24% 10% 33% 22% 10%	420
	11th to 20th	Day	25% 6% 31% 26% 9% 2	412
	21st to end	Day	24% 8% 21% 29% 16% 3	440
May	1st to 10th	Day	33% 4 22% 27% 10% 4	603
	11th to 20th	Day	23% 4 18% 35% 17% 3	624
	21st to end	Day	23% 5% 24% 34% 13% 1	680
June	1st to 10th	Day	30% 7% 15% 30% 15% 4	630
	11th to 20th	Day	20% 5% 18% 37% 19% 3	630
	21st to end	Day	26% 6% 11% 32% 22% 3	630
July	1st to 10th	Day	20% 2 15% 41% 20% 2	620
	11th to 20th	Day	17% 4 14% 38% 24% 3	618
	21st to end	Day	21% 4 15% 34% 24% 2	685
August	1st to 10th	Day	15% 2 12% 38% 29% 4	561
	11th to 20th	Day	20% 5% 12% 33% 23% 7%	439
	21st to end	Day	17% 4 18% 28% 28% 5%	495
September	1st to 10th	Day	14% 6% 23% 36% 17% 4	450
	11th to 20th	Day	25% 8% 21% 30% 14% 2	450
	21st to end	Day	21% 7% 27% 28% 13% 4	383
October	1st to 10th	Day	23% 6% 24% 30% 13% 4	360
	11th to 20th	Day	24% 9% 28% 23% 13% 2	360
	21st to end	Day	29% 13% 30% 19% 8% 2	396
November	1st to 10th	Day	29% 15% 28% 20% 7% 1	365
	11th to 20th	Day	31% 19% 28% 16% 5% 1	370
	21st to end	Day	32% 18% 29% 17% 3	370
December	1st to 10th	Day	34% 14% 34% 15% 4	370
	11th to 20th	Day	32% 21% 29% 16% 2	370
	21st to end	Day	25% 22% 32% 15% 6% 1	407
January	1st to 10th	Night	28% 17% 32% 19% 5%	850
	11th to 20th	Night	27% 14% 34% 20% 5%	829
	21st to end	Night	22% 17% 34% 21% 6%	840
February	1st to 10th	Night	26% 13% 32% 24% 5%	720
	11th to 20th	Night	24% 12% 38% 21% 5%	703
	21st to end	Night	18% 9% 33% 29% 10% 1	592
March	1st to 10th	Night	21% 8% 35% 29% 7%	720
	11th to 20th	Night	22% 9% 28% 27% 12% 1	720
	21st to end	Night	26% 8% 29% 26% 9% 2	716
April	1st to 10th	Night	24% 12% 25% 31% 8%	540
	11th to 20th	Night	24% 7% 27% 29% 12% 1	534
	21st to end	Night	28% 5% 25% 29% 10% 3	540
May	1st to 10th	Night	31% 4 22% 25% 13% 5%	540
	11th to 20th	Night	23% 5% 19% 32% 17% 4	532
	21st to end	Night	23% 4 24% 37% 11% 1	583
June	1st to 10th	Night	30% 6% 17% 34% 10% 1	540
	11th to 20th	Night	24% 3 18% 39% 15% 1	540
	21st to end	Night	28% 3 15% 37% 15% 2	371
July	1st to 10th	Night	17% 3 15% 40% 22% 3	490
	11th to 20th	Night	18% 2 13% 43% 21% 2	522
	21st to end	Night	21% 3 14% 41% 20% 2	590
August	1st to 10th	Night	17% 1 15% 42% 23% 1	538
	11th to 20th	Night	20% 2 15% 36% 22% 4	532
	21st to end	Night	14% 5% 18% 33% 28% 2	594
September	1st to 10th	Night	20% 4 22% 34% 18% 2	540
	11th to 20th	Night	23% 6% 21% 31% 17% 1	540
	21st to end	Night	21% 8% 27% 32% 10% 2	666
October	1st to 10th	Night	25% 5% 29% 27% 12% 1	720
	11th to 20th	Night	27% 9% 26% 25% 11% 2	720
	21st to end	Night	34% 14% 27% 19% 5%	848
November	1st to 10th	Night	30% 16% 27% 21% 4 1	830
	11th to 20th	Night	32% 17% 28% 17% 6% 1	850
	21st to end	Night	35% 16% 28% 18% 3	850
December	1st to 10th	Night	32% 17% 32% 14% 6%	850
	11th to 20th	Night	30% 22% 29% 15% 4	850
	21st to end	Night	31% 17% 30% 16% 4 1	935

Page generated at 2024-01-13 10:37:52. Version ac07

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