West Point(PE)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the West Point(PE) clear sky chart from 2005-11-06 to 2024-12-24.

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% 10% 3 8% 5% 4 4 4 5% 7% 33%	102117
	Night	18% 11% 4 9% 5% 4 4 3 5% 6% 30%	98075
Transparency	Day	48% 8% 14% 20% 9% 1	105668
	Night	52% 7% 13% 19% 8% 1	102614
Seeing	Day	21% 8% 26% 30% 14% 2	16994
	Night	23% 9% 30% 28% 9% 1	24579

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	15% 14% 4 12% 8% 5% 6% 3 5% 5% 22%	2207
	11th to 20th	Day	12% 12% 5% 10% 6% 5% 5% 3 5% 6% 32%	2308
	21st to end	Day	10% 10% 4 9% 7% 4 4 3 5% 6% 37%	3124
February	1st to 10th	Day	16% 13% 3 8% 5% 5% 4 4 5% 6% 32%	1710
	11th to 20th	Day	15% 14% 4 9% 5% 6% 4 3 5% 6% 29%	1663
	21st to end	Day	11% 13% 3 8% 5% 5% 5% 3 6% 6% 35%	1413
March	1st to 10th	Day	20% 13% 5% 8% 4 5% 4 3 4 7% 27%	3406
	11th to 20th	Day	14% 14% 5% 12% 7% 6% 5% 4 5% 6% 22%	3480
	21st to end	Day	25% 14% 4 7% 5% 3 4 3 4 6% 24%	3816
April	1st to 10th	Day	19% 11% 2 7% 5% 5% 4 4 5% 6% 31%	2267
	11th to 20th	Day	19% 10% 2 6% 4 3 3 3 5% 8% 35%	2384
	21st to end	Day	22% 9% 3 7% 4 4 4 3 5% 7% 31%	2470
May	1st to 10th	Day	20% 13% 3 7% 5% 4 4 3 5% 8% 28%	4282
	11th to 20th	Day	15% 9% 3 6% 4 4 4 4 5% 7% 40%	4398
	21st to end	Day	15% 8% 3 8% 5% 5% 5% 4 6% 8% 32%	4836
June	1st to 10th	Day	22% 9% 3 7% 5% 4 4 4 5% 7% 28%	2821
	11th to 20th	Day	18% 7% 2 6% 5% 4 4 5% 5% 7% 37%	2850
	21st to end	Day	24% 7% 3 6% 5% 4 5% 3 5% 7% 31%	2850
July	1st to 10th	Day	13% 7% 3 7% 5% 6% 6% 4 7% 8% 34%	4760
	11th to 20th	Day	15% 5% 2 7% 5% 5% 5% 4 6% 8% 38%	4701
	21st to end	Day	12% 7% 3 6% 4 4 4 4 7% 8% 41%	4769
August	1st to 10th	Day	16% 7% 3 8% 5% 5% 5% 4 6% 7% 34%	4105
	11th to 20th	Day	13% 5% 2 7% 5% 5% 5% 4 6% 8% 40%	4045
	21st to end	Day	13% 5% 2 5% 3 3 4 4 5% 8% 48%	4418
September	1st to 10th	Day	15% 5% 2 6% 4 3 4 4 6% 8% 44%	2280
	11th to 20th	Day	17% 7% 2 5% 4 4 4 3 4 5% 44%	2194
	21st to end	Day	16% 6% 2 6% 4 4 4 3 5% 7% 43%	2040
October	1st to 10th	Day	17% 10% 3 6% 4 3 3 3 5% 7% 39%	1900
	11th to 20th	Day	19% 9% 3 9% 5% 4 4 3 5% 7% 32%	1900
	21st to end	Day	20% 11% 3 8% 5% 4 4 4 4 7% 30%	2051
November	1st to 10th	Day	20% 12% 4 7% 5% 5% 4 3 5% 5% 30%	1565
	11th to 20th	Day	21% 14% 6% 8% 5% 5% 4 3 4 6% 24%	1600
	21st to end	Day	17% 18% 5% 11% 6% 5% 4 3 5% 5% 21%	1600
December	1st to 10th	Day	22% 16% 7% 12% 6% 3 3 3 4 3 20%	1600
	11th to 20th	Day	17% 19% 6% 13% 7% 5% 4 3 3 3 21%	1852
	21st to end	Day	18% 13% 5% 15% 7% 5% 4 3 4 5% 22%	2452
January	1st to 10th	Night	11% 13% 5% 12% 7% 5% 5% 3 5% 6% 28%	4748
	11th to 20th	Night	17% 12% 4 9% 6% 5% 5% 3 4 6% 29%	4655
	21st to end	Night	12% 14% 4 8% 8% 4 4 3 5% 6% 32%	4532
February	1st to 10th	Night	15% 13% 4 8% 5% 4 5% 4 6% 6% 29%	2470
	11th to 20th	Night	17% 15% 4 9% 7% 5% 4 3 5% 5% 27%	2403
	21st to end	Night	13% 15% 3 7% 6% 5% 4 3 5% 5% 35%	2041
March	1st to 10th	Night	20% 14% 4 12% 5% 5% 4 3 4 4 25%	3432
	11th to 20th	Night	22% 18% 5% 10% 5% 5% 4 3 3 4 21%	3479
	21st to end	Night	28% 13% 4 8% 5% 4 3 3 5% 5% 23%	3816
April	1st to 10th	Night	22% 14% 3 8% 5% 4 4 3 5% 4 27%	1912
	11th to 20th	Night	21% 11% 3 7% 5% 3 4 4 5% 6% 31%	1744
	21st to end	Night	22% 11% 3 8% 4 4 3 3 4 5% 31%	1710
May	1st to 10th	Night	26% 11% 3 7% 5% 4 4 3 5% 5% 27%	2662
	11th to 20th	Night	15% 8% 2 7% 5% 4 4 3 5% 7% 40%	2506
	21st to end	Night	16% 9% 4 9% 6% 6% 5% 4 6% 8% 28%	2749
June	1st to 10th	Night	23% 11% 3 8% 4 4 3 3 5% 7% 29%	1374
	11th to 20th	Night	19% 7% 3 6% 5% 3 5% 4 6% 6% 36%	1330
	21st to end	Night	22% 8% 2 6% 6% 6% 5% 5% 5% 6% 29%	1330
July	1st to 10th	Night	14% 8% 2 8% 5% 6% 5% 5% 6% 7% 34%	2210
	11th to 20th	Night	15% 7% 2 8% 6% 5% 5% 5% 6% 8% 33%	2237
	21st to end	Night	13% 6% 2 6% 4 4 4 4 5% 9% 43%	2780
August	1st to 10th	Night	17% 7% 3 9% 6% 6% 6% 4 6% 8% 28%	2825
	11th to 20th	Night	11% 6% 3 8% 5% 6% 5% 4 5% 8% 39%	2782
	21st to end	Night	11% 4 2 7% 5% 4 4 4 6% 7% 46%	3237
September	1st to 10th	Night	15% 7% 2 6% 4 3 4 4 5% 7% 43%	1900
	11th to 20th	Night	16% 6% 2 6% 4 3 3 3 5% 5% 45%	1984
	21st to end	Night	16% 6% 2 6% 3 4 4 3 5% 6% 44%	2139
October	1st to 10th	Night	19% 8% 3 6% 4 3 4 3 5% 7% 39%	2280
	11th to 20th	Night	18% 9% 3 8% 5% 4 4 2 5% 7% 35%	2280
	21st to end	Night	24% 12% 3 7% 4 3 5% 3 3 5% 30%	2545
November	1st to 10th	Night	21% 13% 4 7% 5% 4 4 3 5% 6% 30%	2733
	11th to 20th	Night	21% 14% 4 9% 6% 4 4 3 4 6% 25%	2800
	21st to end	Night	24% 15% 4 10% 5% 4 4 3 4 5% 22%	2800
December	1st to 10th	Night	23% 15% 6% 11% 6% 4 3 3 5% 5% 20%	2800
	11th to 20th	Night	21% 18% 5% 12% 7% 4 3 2 4 5% 20%	3562
	21st to end	Night	23% 13% 6% 13% 4 4 3 3 4 5% 22%	5288

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	57% 12% 13% 13% 5%	2208
	11th to 20th	Day	49% 6% 10% 22% 12% 1	2308
	21st to end	Day	46% 7% 16% 17% 13% 1	3124
February	1st to 10th	Day	52% 6% 13% 17% 11% 1	1710
	11th to 20th	Day	55% 6% 10% 18% 9% 2	1671
	21st to end	Day	46% 6% 14% 19% 12% 3	1413
March	1st to 10th	Day	54% 7% 12% 20% 5% 2	3410
	11th to 20th	Day	58% 10% 12% 13% 6% 1	3480
	21st to end	Day	61% 5% 8% 16% 8% 2	3816
April	1st to 10th	Day	52% 6% 10% 17% 11% 3	2267
	11th to 20th	Day	48% 7% 11% 21% 13% 1	2384
	21st to end	Day	50% 7% 12% 15% 12% 3	2470
May	1st to 10th	Day	53% 9% 12% 18% 7% 1	4296
	11th to 20th	Day	43% 8% 16% 25% 8% 1	4402
	21st to end	Day	45% 13% 15% 18% 10%	4836
June	1st to 10th	Day	53% 9% 13% 18% 6%	2821
	11th to 20th	Day	45% 8% 14% 23% 9% 1	2850
	21st to end	Day	52% 9% 13% 17% 9% 1	2850
July	1st to 10th	Day	44% 9% 19% 17% 10%	4685
	11th to 20th	Day	42% 8% 17% 25% 7%	4620
	21st to end	Day	38% 9% 20% 25% 7%	4617
August	1st to 10th	Day	48% 7% 14% 25% 6%	4092
	11th to 20th	Day	38% 10% 15% 24% 11% 1	4084
	21st to end	Day	33% 7% 17% 27% 15% 1	4418
September	1st to 10th	Day	36% 8% 18% 25% 12%	2280
	11th to 20th	Day	42% 6% 13% 24% 13% 1	2194
	21st to end	Day	41% 7% 12% 25% 14% 1	2040
October	1st to 10th	Day	42% 7% 15% 27% 8% 1	3160
	11th to 20th	Day	50% 6% 12% 25% 8%	3140
	21st to end	Day	43% 8% 17% 20% 12%	3354
November	1st to 10th	Day	55% 8% 11% 19% 7% 1	1565
	11th to 20th	Day	60% 7% 14% 12% 8%	1600
	21st to end	Day	64% 8% 15% 11% 3	1600
December	1st to 10th	Day	68% 6% 10% 11% 5%	1600
	11th to 20th	Day	70% 4 8% 11% 6% 1	1851
	21st to end	Day	63% 7% 15% 9% 5% 1	2452
January	1st to 10th	Night	50% 11% 16% 19% 3	4748
	11th to 20th	Night	51% 8% 12% 20% 9% 1	4655
	21st to end	Night	51% 6% 12% 21% 9% 1	4532
February	1st to 10th	Night	54% 6% 11% 16% 11% 2	2470
	11th to 20th	Night	59% 5% 10% 15% 10% 2	2406
	21st to end	Night	50% 6% 10% 20% 11% 3	2041
March	1st to 10th	Night	61% 7% 8% 15% 7% 2	3441
	11th to 20th	Night	64% 7% 9% 13% 6% 1	3480
	21st to end	Night	62% 5% 6% 16% 9% 1	3816
April	1st to 10th	Night	59% 5% 9% 13% 11% 2	1912
	11th to 20th	Night	53% 6% 9% 19% 12% 1	1744
	21st to end	Night	55% 6% 9% 14% 15% 1	1710
May	1st to 10th	Night	57% 8% 12% 15% 8% 1	2668
	11th to 20th	Night	41% 9% 17% 25% 7% 1	2507
	21st to end	Night	49% 13% 15% 16% 6%	2750
June	1st to 10th	Night	54% 8% 14% 15% 8%	1374
	11th to 20th	Night	47% 8% 12% 23% 9% 1	1330
	21st to end	Night	55% 8% 13% 16% 8%	1330
July	1st to 10th	Night	47% 7% 16% 18% 10%	2175
	11th to 20th	Night	46% 8% 18% 21% 6%	2195
	21st to end	Night	37% 9% 20% 22% 11%	2692
August	1st to 10th	Night	54% 8% 14% 19% 5%	2813
	11th to 20th	Night	41% 9% 19% 21% 10%	2809
	21st to end	Night	36% 8% 16% 26% 15% 1	3236
September	1st to 10th	Night	39% 8% 12% 29% 12%	1900
	11th to 20th	Night	41% 5% 14% 28% 12%	1984
	21st to end	Night	41% 6% 12% 28% 12% 1	2139
October	1st to 10th	Night	48% 6% 13% 25% 8%	3800
	11th to 20th	Night	44% 7% 13% 27% 9%	3779
	21st to end	Night	49% 6% 14% 20% 11%	4193
November	1st to 10th	Night	55% 7% 13% 17% 7% 1	2733
	11th to 20th	Night	58% 7% 12% 15% 7% 1	2800
	21st to end	Night	63% 7% 12% 13% 4	2800
December	1st to 10th	Night	66% 6% 10% 13% 5%	2800
	11th to 20th	Night	68% 5% 9% 13% 5%	3564
	21st to end	Night	64% 6% 13% 12% 4	5288

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	27% 17% 27% 24% 6%	180
	11th to 20th	Day	23% 11% 42% 18% 5% 1	239
	21st to end	Day	17% 7% 36% 30% 10%	407
February	1st to 10th	Day	25% 10% 33% 24% 7% 1	370
	11th to 20th	Day	20% 9% 40% 26% 5%	366
	21st to end	Day	15% 10% 30% 33% 11% 1	307
March	1st to 10th	Day	20% 11% 34% 27% 6% 1	456
	11th to 20th	Day	16% 13% 30% 30% 11% 2	460
	21st to end	Day	26% 10% 29% 25% 8% 2	506
April	1st to 10th	Day	25% 11% 32% 24% 8%	460
	11th to 20th	Day	22% 8% 31% 27% 10% 2	452
	21st to end	Day	24% 9% 24% 28% 13% 2	460
May	1st to 10th	Day	28% 6% 28% 25% 12% 2	561
	11th to 20th	Day	20% 6% 23% 31% 18% 3	674
	21st to end	Day	21% 6% 26% 35% 10% 1	735
June	1st to 10th	Day	27% 7% 21% 32% 11% 2	680
	11th to 20th	Day	20% 5% 19% 35% 17% 3	680
	21st to end	Day	24% 5% 18% 33% 18% 3	680
July	1st to 10th	Day	15% 3 19% 38% 21% 3	670
	11th to 20th	Day	15% 4 17% 37% 23% 4	668
	21st to end	Day	14% 3 15% 42% 23% 4	718
August	1st to 10th	Day	12% 5% 12% 42% 25% 5%	486
	11th to 20th	Day	16% 4 16% 30% 28% 7%	479
	21st to end	Day	14% 5% 18% 34% 23% 6%	539
September	1st to 10th	Day	12% 5% 24% 37% 18% 3	490
	11th to 20th	Day	20% 9% 21% 29% 16% 6%	490
	21st to end	Day	19% 6% 27% 28% 15% 5%	463
October	1st to 10th	Day	20% 10% 20% 30% 16% 3	390
	11th to 20th	Day	24% 8% 27% 26% 13% 1	390
	21st to end	Day	23% 10% 36% 23% 7% 1	429
November	1st to 10th	Day	23% 13% 33% 23% 7% 1	395
	11th to 20th	Day	26% 16% 34% 19% 5% 1	400
	21st to end	Day	30% 13% 34% 22% 2 1	400
December	1st to 10th	Day	27% 14% 33% 22% 4	400
	11th to 20th	Day	25% 25% 31% 15% 3	310
	21st to end	Day	17% 19% 38% 23% 4	204
January	1st to 10th	Night	23% 11% 36% 24% 6%	850
	11th to 20th	Night	23% 10% 37% 24% 6%	848
	21st to end	Night	19% 8% 37% 27% 8% 1	836
February	1st to 10th	Night	24% 8% 36% 24% 7% 1	760
	11th to 20th	Night	25% 8% 38% 26% 3 1	743
	21st to end	Night	19% 8% 32% 31% 9%	628
March	1st to 10th	Night	22% 9% 33% 32% 5%	760
	11th to 20th	Night	24% 7% 32% 27% 9% 1	760
	21st to end	Night	25% 10% 29% 26% 9% 1	836
April	1st to 10th	Night	27% 9% 28% 30% 6%	582
	11th to 20th	Night	26% 5% 29% 29% 10%	564
	21st to end	Night	26% 7% 29% 27% 10% 1	570
May	1st to 10th	Night	28% 5% 26% 29% 10% 2	570
	11th to 20th	Night	23% 4 25% 30% 16% 2	562
	21st to end	Night	17% 7% 31% 37% 8%	616
June	1st to 10th	Night	27% 4 22% 37% 10%	424
	11th to 20th	Night	21% 4 20% 38% 15% 2	380
	21st to end	Night	24% 2 18% 41% 13% 2	380
July	1st to 10th	Night	16% 3 21% 40% 18% 1	370
	11th to 20th	Night	16% 2 21% 42% 18% 1	382
	21st to end	Night	17% 3 19% 44% 16% 1	623
August	1st to 10th	Night	16% 2 21% 42% 19% 1	568
	11th to 20th	Night	16% 2 19% 38% 22% 2	562
	21st to end	Night	14% 4 22% 36% 22% 2	627
September	1st to 10th	Night	18% 5% 27% 35% 14% 1	570
	11th to 20th	Night	17% 8% 23% 34% 17% 1	654
	21st to end	Night	18% 7% 27% 34% 12% 1	760
October	1st to 10th	Night	23% 6% 28% 30% 12% 1	760
	11th to 20th	Night	22% 10% 32% 25% 10% 1	760
	21st to end	Night	28% 14% 31% 22% 4	841
November	1st to 10th	Night	26% 13% 34% 22% 5%	880
	11th to 20th	Night	26% 15% 31% 21% 6% 1	900
	21st to end	Night	31% 15% 29% 21% 4	900
December	1st to 10th	Night	27% 13% 37% 19% 4	900
	11th to 20th	Night	26% 20% 35% 15% 4	900
	21st to end	Night	27% 13% 35% 20% 4 1	953

Page generated at 2024-12-21 05:13:53. Version ac07

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