Chestnut Ridge Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chestnut Ridge Park 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	17% 11% 4 8% 5% 4 4 4 5% 7% 30%	126188
	Night	18% 12% 4 9% 5% 4 4 3 5% 6% 30%	123495
Transparency	Day	52% 5% 10% 21% 11% 1	129794
	Night	54% 5% 9% 19% 11% 2	127958
Seeing	Day	27% 15% 25% 19% 10% 4	16053
	Night	26% 13% 23% 26% 11% 1	25773

By Month

Percentage Cloud Cover SE (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% 20% 7% 20% 8% 4 3 2 3 3 15%	4056
	11th to 20th	Day	13% 22% 11% 16% 11% 5% 3 2 2 2 13%	4060
	21st to end	Day	19% 18% 8% 9% 7% 4 4 3 4 4 20%	4466
February	1st to 10th	Day	20% 17% 5% 11% 6% 4 4 3 4 5% 21%	1800
	11th to 20th	Day	20% 16% 7% 12% 5% 5% 3 3 4 5% 22%	1753
	21st to end	Day	21% 18% 5% 10% 4 3 3 2 4 4 24%	1678
March	1st to 10th	Day	16% 18% 7% 6% 4 3 3 2 4 6% 32%	4935
	11th to 20th	Day	14% 11% 4 8% 4 4 4 4 4 7% 37%	4980
	21st to end	Day	20% 13% 4 9% 5% 4 4 3 4 5% 30%	5465
April	1st to 10th	Day	19% 15% 3 7% 4 4 4 3 6% 6% 28%	2310
	11th to 20th	Day	16% 13% 3 7% 4 4 5% 3 4 7% 33%	2374
	21st to end	Day	22% 10% 3 6% 4 4 4 4 5% 6% 32%	2590
May	1st to 10th	Day	21% 10% 3 8% 5% 5% 5% 4 6% 7% 25%	5862
	11th to 20th	Day	20% 9% 3 8% 5% 5% 5% 5% 6% 8% 27%	5861
	21st to end	Day	21% 8% 3 6% 5% 5% 5% 4 6% 8% 29%	6707
June	1st to 10th	Day	15% 7% 3 7% 5% 4 5% 5% 7% 9% 34%	2800
	11th to 20th	Day	16% 7% 3 7% 6% 6% 6% 4 7% 8% 33%	2800
	21st to end	Day	15% 5% 2 6% 5% 5% 6% 4 7% 9% 35%	2800
July	1st to 10th	Day	12% 6% 2 7% 5% 5% 5% 4 6% 8% 40%	6044
	11th to 20th	Day	15% 7% 2 7% 5% 5% 6% 5% 6% 10% 31%	5900
	21st to end	Day	16% 8% 2 7% 4 4 5% 4 6% 8% 35%	6424
August	1st to 10th	Day	15% 8% 3 8% 5% 5% 6% 5% 7% 9% 30%	4234
	11th to 20th	Day	15% 6% 3 6% 5% 4 5% 5% 6% 9% 37%	4174
	21st to end	Day	9% 4 2 5% 4 4 5% 4 7% 10% 46%	4395
September	1st to 10th	Day	16% 6% 2 6% 4 3 3 3 5% 6% 47%	2400
	11th to 20th	Day	13% 7% 2 6% 4 4 4 4 5% 8% 44%	2220
	21st to end	Day	20% 8% 3 7% 5% 4 4 4 4 7% 33%	2189
October	1st to 10th	Day	17% 7% 3 6% 4 3 3 3 5% 7% 43%	2000
	11th to 20th	Day	19% 9% 2 7% 4 4 4 3 4 5% 38%	1980
	21st to end	Day	24% 12% 3 5% 3 3 3 2 3 5% 36%	2090
November	1st to 10th	Day	13% 11% 2 6% 4 4 3 3 4 6% 43%	1927
	11th to 20th	Day	16% 16% 4 7% 4 3 4 4 6% 6% 30%	1690
	21st to end	Day	19% 19% 5% 9% 4 3 3 3 4 5% 26%	1600
December	1st to 10th	Day	18% 14% 7% 22% 4 4 3 2 4 3 19%	2600
	11th to 20th	Day	23% 19% 6% 10% 4 3 3 2 3 5% 22%	2990
	21st to end	Day	19% 20% 7% 11% 5% 4 4 3 4 6% 17%	4034
January	1st to 10th	Night	15% 20% 8% 21% 7% 4 3 2 3 3 14%	5889
	11th to 20th	Night	15% 18% 9% 17% 8% 6% 3 2 2 3 17%	5900
	21st to end	Night	21% 15% 7% 11% 7% 4 3 2 3 3 23%	6490
February	1st to 10th	Night	19% 16% 6% 10% 5% 3 4 3 4 5% 25%	2600
	11th to 20th	Night	20% 17% 5% 12% 5% 5% 4 2 4 4 22%	2533
	21st to end	Night	21% 16% 4 10% 4 3 4 3 4 5% 25%	1945
March	1st to 10th	Night	21% 13% 6% 8% 5% 3 3 3 3 5% 31%	4918
	11th to 20th	Night	14% 14% 5% 6% 3 3 3 2 4 6% 39%	4980
	21st to end	Night	16% 14% 3 8% 5% 4 4 3 4 6% 33%	5467
April	1st to 10th	Night	20% 16% 4 7% 4 3 4 2 4 5% 31%	2088
	11th to 20th	Night	18% 10% 3 6% 3 4 4 3 6% 7% 35%	1975
	21st to end	Night	16% 9% 4 7% 5% 3 4 3 5% 8% 37%	1828
May	1st to 10th	Night	27% 11% 3 8% 5% 4 4 3 5% 6% 24%	4033
	11th to 20th	Night	18% 8% 3 8% 5% 5% 4 4 6% 8% 31%	4032
	21st to end	Night	23% 11% 3 7% 4 4 4 3 5% 7% 29%	4129
June	1st to 10th	Night	13% 7% 2 7% 5% 4 4 3 6% 7% 42%	1600
	11th to 20th	Night	12% 7% 3 7% 5% 5% 4 5% 7% 9% 36%	1600
	21st to end	Night	14% 6% 2 5% 4 4 5% 5% 7% 10% 38%	1600
July	1st to 10th	Night	14% 8% 3 7% 4 4 4 4 5% 8% 38%	3909
	11th to 20th	Night	18% 8% 3 7% 5% 4 4 5% 6% 9% 32%	4057
	21st to end	Night	15% 8% 3 6% 4 4 5% 4 6% 9% 37%	4427
August	1st to 10th	Night	14% 8% 3 8% 5% 5% 5% 4 7% 9% 32%	2915
	11th to 20th	Night	17% 7% 2 6% 5% 3 4 4 5% 6% 41%	2875
	21st to end	Night	8% 5% 2 5% 4 4 5% 5% 7% 10% 45%	3468
September	1st to 10th	Night	14% 6% 2 6% 3 4 4 3 6% 6% 45%	2000
	11th to 20th	Night	12% 5% 2 5% 3 3 4 3 6% 7% 52%	2176
	21st to end	Night	16% 8% 3 7% 4 4 5% 3 5% 6% 39%	2210
October	1st to 10th	Night	17% 6% 2 5% 3 3 4 4 4 7% 45%	2400
	11th to 20th	Night	17% 8% 2 5% 4 4 4 3 6% 6% 41%	2377
	21st to end	Night	26% 9% 2 4 3 3 3 3 4 5% 37%	2508
November	1st to 10th	Night	15% 10% 3 6% 3 3 4 3 4 6% 45%	2369
	11th to 20th	Night	20% 15% 4 8% 4 3 3 4 4 5% 30%	2708
	21st to end	Night	19% 17% 5% 9% 5% 3 4 3 4 4 28%	2800
December	1st to 10th	Night	19% 16% 6% 20% 4 3 3 2 4 4 19%	4580
	11th to 20th	Night	23% 17% 8% 10% 4 3 3 3 4 4 22%	5205
	21st to end	Night	19% 21% 7% 10% 5% 4 4 3 4 5% 18%	6904

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	76% 3 7% 9% 3 1	4057
	11th to 20th	Day	80% 2 5% 8% 5% 1	4060
	21st to end	Day	68% 4 7% 13% 7%	4466
February	1st to 10th	Day	66% 4 9% 15% 6%	1800
	11th to 20th	Day	67% 3 8% 13% 9%	1762
	21st to end	Day	64% 4 9% 13% 9% 2	1678
March	1st to 10th	Day	55% 3 7% 22% 9% 3	4935
	11th to 20th	Day	47% 5% 9% 27% 9% 3	4980
	21st to end	Day	57% 4 6% 19% 13% 1	5465
April	1st to 10th	Day	56% 5% 9% 17% 11% 2	2310
	11th to 20th	Day	51% 5% 11% 15% 16% 2	2374
	21st to end	Day	52% 5% 10% 22% 10% 2	2590
May	1st to 10th	Day	56% 6% 9% 19% 7% 2	5897
	11th to 20th	Day	52% 9% 9% 22% 7% 1	5865
	21st to end	Day	51% 7% 13% 18% 10% 2	6722
June	1st to 10th	Day	44% 9% 12% 23% 12% 1	2800
	11th to 20th	Day	48% 8% 12% 22% 10% 1	2800
	21st to end	Day	43% 9% 12% 23% 12% 1	2800
July	1st to 10th	Day	41% 7% 10% 25% 15% 2	5979
	11th to 20th	Day	45% 8% 13% 24% 9% 1	5831
	21st to end	Day	45% 6% 9% 23% 16% 1	6240
August	1st to 10th	Day	47% 8% 13% 24% 7%	4221
	11th to 20th	Day	42% 6% 10% 31% 11%	4213
	21st to end	Day	31% 8% 15% 29% 15% 1	4395
September	1st to 10th	Day	39% 5% 10% 22% 21% 3	2400
	11th to 20th	Day	38% 6% 11% 27% 16% 3	2220
	21st to end	Day	51% 5% 10% 18% 16% 1	2189
October	1st to 10th	Day	34% 4 8% 29% 22% 3	3260
	11th to 20th	Day	44% 5% 9% 22% 14% 7%	3220
	21st to end	Day	37% 3 9% 28% 22% 1	3428
November	1st to 10th	Day	43% 4 8% 23% 17% 4	1927
	11th to 20th	Day	53% 4 9% 16% 14% 3	1690
	21st to end	Day	62% 3 9% 15% 11%	1600
December	1st to 10th	Day	72% 3 12% 10% 2 1	2600
	11th to 20th	Day	67% 3 10% 16% 5% 1	2986
	21st to end	Day	69% 4 8% 14% 5%	4034
January	1st to 10th	Night	77% 2 5% 10% 4 1	5889
	11th to 20th	Night	75% 3 7% 10% 4 2	5900
	21st to end	Night	68% 3 7% 14% 7% 1	6490
February	1st to 10th	Night	62% 4 9% 16% 8%	2600
	11th to 20th	Night	68% 3 8% 14% 8%	2535
	21st to end	Night	62% 4 7% 15% 9% 2	1945
March	1st to 10th	Night	58% 3 6% 23% 9% 1	4918
	11th to 20th	Night	47% 4 8% 29% 8% 3	4980
	21st to end	Night	52% 4 9% 20% 13% 2	5467
April	1st to 10th	Night	57% 4 8% 16% 13% 2	2088
	11th to 20th	Night	48% 5% 11% 18% 14% 4	1975
	21st to end	Night	45% 5% 11% 24% 11% 3	1828
May	1st to 10th	Night	61% 6% 10% 13% 8% 2	4060
	11th to 20th	Night	49% 8% 10% 25% 7% 1	4033
	21st to end	Night	53% 6% 12% 20% 6% 3	4136
June	1st to 10th	Night	41% 7% 12% 24% 14% 2	1600
	11th to 20th	Night	42% 9% 13% 22% 12% 1	1600
	21st to end	Night	39% 8% 14% 23% 15% 1	1600
July	1st to 10th	Night	45% 7% 10% 23% 14% 2	3866
	11th to 20th	Night	47% 8% 14% 20% 9% 1	4006
	21st to end	Night	43% 7% 10% 21% 18% 1	4297
August	1st to 10th	Night	46% 8% 18% 20% 7%	2904
	11th to 20th	Night	44% 5% 9% 24% 17% 1	2902
	21st to end	Night	32% 8% 12% 33% 13% 2	3468
September	1st to 10th	Night	38% 6% 11% 22% 18% 5%	2000
	11th to 20th	Night	32% 5% 13% 27% 22% 2	2176
	21st to end	Night	46% 5% 10% 21% 17% 1	2210
October	1st to 10th	Night	35% 4 8% 28% 20% 4	3920
	11th to 20th	Night	39% 4 8% 23% 17% 8%	3876
	21st to end	Night	38% 3 7% 27% 24% 2	4120
November	1st to 10th	Night	42% 4 11% 21% 18% 5%	2369
	11th to 20th	Night	56% 4 7% 17% 13% 3	2708
	21st to end	Night	60% 4 8% 18% 9% 1	2800
December	1st to 10th	Night	70% 3 9% 14% 3 1	4580
	11th to 20th	Night	67% 3 11% 15% 4	5208
	21st to end	Night	69% 4 10% 12% 6%	6904

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	41% 30% 16% 9% 4	300
	11th to 20th	Day	44% 26% 23% 6%	300
	21st to end	Day	39% 28% 25% 5% 3	330
February	1st to 10th	Day	39% 28% 25% 6% 1	300
	11th to 20th	Day	49% 26% 21% 3	300
	21st to end	Day	44% 26% 25% 5% 1	307
March	1st to 10th	Day	36% 21% 28% 11% 3	500
	11th to 20th	Day	37% 20% 27% 11% 3 1	500
	21st to end	Day	37% 20% 26% 13% 4	550
April	1st to 10th	Day	38% 20% 23% 15% 5% 1	500
	11th to 20th	Day	29% 19% 27% 15% 6% 3	492
	21st to end	Day	33% 18% 27% 16% 5% 1	500
May	1st to 10th	Day	32% 18% 28% 13% 6% 4	503
	11th to 20th	Day	28% 15% 28% 17% 9% 3	527
	21st to end	Day	20% 12% 27% 22% 13% 6%	573
June	1st to 10th	Day	19% 11% 27% 25% 15% 4	530
	11th to 20th	Day	21% 10% 23% 25% 15% 4	530
	21st to end	Day	16% 9% 27% 28% 16% 4	530
July	1st to 10th	Day	17% 5% 23% 29% 15% 11%	525
	11th to 20th	Day	14% 7% 23% 31% 17% 7%	524
	21st to end	Day	20% 7% 24% 24% 20% 5%	576
August	1st to 10th	Day	14% 9% 21% 30% 18% 7%	526
	11th to 20th	Day	20% 3 21% 29% 19% 8%	519
	21st to end	Day	14% 6% 23% 28% 19% 10%	583
September	1st to 10th	Day	18% 8% 20% 26% 19% 8%	530
	11th to 20th	Day	14% 4 22% 30% 22% 9%	530
	21st to end	Day	28% 10% 25% 22% 12% 3	530
October	1st to 10th	Day	20% 9% 22% 27% 18% 4	530
	11th to 20th	Day	26% 12% 28% 25% 7% 1	522
	21st to end	Day	33% 15% 27% 17% 8%	539
November	1st to 10th	Day	22% 15% 29% 22% 9% 3	465
	11th to 20th	Day	33% 21% 27% 11% 6% 1	245
	21st to end	Day	36% 22% 30% 10% 2 1	200
December	1st to 10th	Day	33% 28% 28% 7% 3 2	200
	11th to 20th	Day	45% 22% 26% 6% 2	200
	21st to end	Day	41% 25% 18% 13% 3	237
January	1st to 10th	Night	36% 23% 25% 13% 3	800
	11th to 20th	Night	38% 20% 27% 14% 1	800
	21st to end	Night	33% 25% 26% 15% 1	880
February	1st to 10th	Night	31% 20% 27% 19% 2	800
	11th to 20th	Night	37% 25% 27% 11%	783
	21st to end	Night	33% 23% 28% 15% 1	660
March	1st to 10th	Night	30% 19% 28% 19% 3	800
	11th to 20th	Night	34% 17% 25% 18% 6%	800
	21st to end	Night	29% 19% 30% 18% 4	880
April	1st to 10th	Night	32% 17% 27% 19% 5%	800
	11th to 20th	Night	26% 13% 30% 22% 9% 1	791
	21st to end	Night	23% 12% 32% 26% 8%	628
May	1st to 10th	Night	26% 9% 26% 28% 10% 1	600
	11th to 20th	Night	25% 8% 25% 31% 11% 1	591
	21st to end	Night	16% 6% 20% 31% 25% 2	526
June	1st to 10th	Night	15% 5% 21% 40% 19% 1	400
	11th to 20th	Night	12% 7% 22% 38% 20% 2	400
	21st to end	Night	15% 5% 21% 41% 19% 1	400
July	1st to 10th	Night	16% 3 15% 37% 26% 4	514
	11th to 20th	Night	14% 4 13% 37% 28% 3	582
	21st to end	Night	16% 3 14% 37% 28% 2	657
August	1st to 10th	Night	13% 3 13% 43% 25% 3	597
	11th to 20th	Night	17% 4 10% 39% 27% 3	594
	21st to end	Night	13% 4 14% 39% 27% 3	801
September	1st to 10th	Night	18% 3 18% 33% 25% 4	800
	11th to 20th	Night	15% 3 18% 34% 26% 4	800
	21st to end	Night	21% 9% 20% 30% 18% 2	800
October	1st to 10th	Night	19% 8% 21% 31% 19% 3	800
	11th to 20th	Night	24% 10% 24% 30% 11% 1	793
	21st to end	Night	31% 11% 22% 26% 8%	836
November	1st to 10th	Night	22% 11% 23% 33% 11% 1	780
	11th to 20th	Night	32% 15% 25% 22% 6% 1	800
	21st to end	Night	30% 16% 28% 22% 4 1	800
December	1st to 10th	Night	37% 18% 24% 17% 4	800
	11th to 20th	Night	33% 21% 23% 19% 4	800
	21st to end	Night	33% 18% 29% 19% 1	880

Page generated at 2025-10-16 01:50:26. Version ac07

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