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 2024-04-10.

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	18% 11% 5% 7% 6% 3 4 4 5% 7% 30%	83243
	Night	18% 12% 5% 7% 5% 3 4 4 4 6% 31%	85519
Transparency	Day	54% 6% 10% 19% 10% 1	82964
	Night	55% 5% 10% 19% 10% 2	85317
Seeing	Day	27% 14% 25% 19% 10% 4	13980
	Night	26% 13% 23% 25% 12% 1	23876

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	18% 20% 8% 12% 6% 3 3 2 4 4 18%	2836
	11th to 20th	Day	14% 22% 11% 15% 10% 3 3 2 3 3 15%	2840
	21st to end	Day	23% 19% 10% 9% 8% 3 4 3 3 4 15%	3124
February	1st to 10th	Day	21% 15% 6% 10% 7% 3 4 4 4 5% 21%	1710
	11th to 20th	Day	19% 14% 7% 12% 6% 4 4 3 4 5% 22%	1663
	21st to end	Day	22% 17% 6% 10% 5% 2 4 3 4 4 24%	1596
March	1st to 10th	Day	20% 15% 6% 6% 5% 2 3 3 4 7% 28%	3435
	11th to 20th	Day	16% 12% 5% 8% 5% 3 4 4 4 7% 33%	3480
	21st to end	Day	22% 12% 3 7% 5% 3 4 4 4 5% 31%	3815
April	1st to 10th	Day	18% 13% 4 7% 5% 3 5% 4 6% 6% 29%	2184
	11th to 20th	Day	17% 12% 3 6% 5% 3 4 5% 4 7% 34%	2134
	21st to end	Day	23% 10% 3 5% 5% 2 5% 5% 5% 6% 31%	2330
May	1st to 10th	Day	22% 10% 4 7% 6% 4 5% 5% 5% 6% 27%	2340
	11th to 20th	Day	23% 8% 3 8% 6% 4 5% 4 4 7% 28%	2301
	21st to end	Day	14% 6% 3 6% 6% 4 6% 5% 6% 9% 35%	2638
June	1st to 10th	Day	16% 6% 3 6% 5% 3 5% 6% 7% 9% 34%	2520
	11th to 20th	Day	16% 6% 3 6% 6% 4 6% 5% 6% 7% 33%	2520
	21st to end	Day	16% 5% 3 5% 6% 4 6% 6% 6% 10% 34%	2520
July	1st to 10th	Day	14% 6% 3 6% 7% 4 6% 6% 6% 8% 35%	2400
	11th to 20th	Day	14% 6% 3 6% 5% 4 6% 6% 5% 10% 37%	2340
	21st to end	Day	16% 8% 3 6% 6% 4 6% 6% 7% 8% 32%	2547
August	1st to 10th	Day	14% 7% 3 6% 6% 4 6% 6% 8% 10% 29%	2327
	11th to 20th	Day	15% 7% 3 6% 6% 3 5% 6% 7% 10% 34%	2303
	21st to end	Day	14% 5% 3 6% 6% 4 5% 5% 7% 9% 37%	2428
September	1st to 10th	Day	16% 6% 2 5% 5% 3 4 4 5% 6% 44%	2160
	11th to 20th	Day	14% 6% 3 5% 5% 3 4 4 5% 8% 43%	1998
	21st to end	Day	19% 8% 3 6% 6% 3 4 5% 4 7% 35%	1971
October	1st to 10th	Day	18% 7% 3 5% 5% 3 3 4 5% 7% 40%	1800
	11th to 20th	Day	21% 9% 2 6% 5% 3 4 4 4 5% 37%	1800
	21st to end	Day	26% 12% 3 4 3 2 4 3 3 5% 35%	1980
November	1st to 10th	Day	14% 10% 3 5% 4 3 4 3 4 7% 43%	1829
	11th to 20th	Day	17% 14% 6% 6% 4 2 4 4 6% 6% 31%	1606
	21st to end	Day	20% 17% 5% 7% 4 2 3 4 4 5% 27%	1520
December	1st to 10th	Day	23% 17% 9% 11% 5% 3 4 3 3 4 18%	1520
	11th to 20th	Day	20% 19% 7% 10% 5% 2 3 2 3 5% 23%	1910
	21st to end	Day	21% 21% 9% 8% 6% 3 4 3 4 5% 16%	2818
January	1st to 10th	Night	17% 23% 9% 11% 5% 4 4 4 3 4 17%	4109
	11th to 20th	Night	18% 18% 9% 13% 6% 5% 4 3 3 3 17%	4120
	21st to end	Night	27% 18% 9% 8% 8% 2 3 2 2 3 18%	4532
February	1st to 10th	Night	20% 14% 6% 9% 6% 3 3 4 4 4 26%	2470
	11th to 20th	Night	21% 16% 5% 11% 6% 4 4 3 3 5% 22%	2403
	21st to end	Night	22% 15% 5% 8% 5% 2 4 4 4 5% 25%	1851
March	1st to 10th	Night	23% 12% 5% 5% 5% 2 3 4 4 6% 29%	3418
	11th to 20th	Night	17% 17% 6% 6% 4 2 3 3 3 5% 31%	3480
	21st to end	Night	18% 12% 4 7% 5% 2 3 4 4 6% 37%	3817
April	1st to 10th	Night	20% 14% 5% 6% 5% 2 4 4 4 5% 32%	1984
	11th to 20th	Night	18% 9% 3 6% 4 3 5% 4 6% 7% 35%	1775
	21st to end	Night	16% 9% 4 7% 5% 3 4 4 5% 7% 37%	1646
May	1st to 10th	Night	21% 8% 3 5% 5% 3 5% 5% 6% 6% 32%	1620
	11th to 20th	Night	21% 6% 3 5% 6% 3 4 5% 5% 8% 33%	1592
	21st to end	Night	11% 6% 3 5% 5% 3 5% 5% 6% 10% 41%	1633
June	1st to 10th	Night	13% 6% 2 6% 6% 3 5% 4 6% 8% 43%	1440
	11th to 20th	Night	13% 7% 3 6% 6% 3 5% 6% 6% 9% 36%	1440
	21st to end	Night	14% 6% 2 4 4 3 5% 6% 7% 10% 39%	1440
July	1st to 10th	Night	13% 6% 2 5% 4 3 5% 5% 6% 9% 40%	1555
	11th to 20th	Night	12% 5% 2 5% 6% 2 3 7% 6% 9% 43%	1620
	21st to end	Night	15% 6% 3 4 4 3 6% 6% 7% 9% 38%	1771
August	1st to 10th	Night	9% 6% 3 6% 5% 4 6% 7% 8% 8% 38%	1611
	11th to 20th	Night	13% 6% 2 4 6% 3 5% 5% 6% 7% 42%	1598
	21st to end	Night	12% 6% 2 4 5% 2 4 5% 5% 8% 46%	1908
September	1st to 10th	Night	14% 6% 2 6% 4 3 4 4 6% 7% 43%	1800
	11th to 20th	Night	13% 5% 2 4 3 2 4 4 5% 7% 51%	1958
	21st to end	Night	16% 7% 3 5% 5% 3 4 5% 5% 6% 41%	1988
October	1st to 10th	Night	18% 6% 2 5% 4 3 4 5% 4 7% 43%	2160
	11th to 20th	Night	19% 8% 2 4 5% 3 4 4 6% 6% 39%	2160
	21st to end	Night	28% 8% 2 3 4 3 4 4 4 5% 36%	2376
November	1st to 10th	Night	15% 9% 3 6% 4 2 4 4 4 6% 44%	2247
	11th to 20th	Night	20% 14% 4 7% 5% 2 3 4 4 6% 31%	2572
	21st to end	Night	19% 15% 5% 8% 5% 3 4 4 4 5% 28%	2660
December	1st to 10th	Night	23% 18% 8% 10% 5% 2 4 3 3 4 19%	2660
	11th to 20th	Night	20% 18% 8% 9% 5% 2 3 3 4 4 22%	3285
	21st to end	Night	21% 20% 8% 8% 6% 3 4 3 4 5% 17%	4820

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	70% 4 9% 12% 4 1	2837
	11th to 20th	Day	77% 3 6% 9% 5%	2840
	21st to end	Day	74% 3 6% 13% 3	3124
February	1st to 10th	Day	66% 4 9% 15% 6%	1710
	11th to 20th	Day	66% 3 8% 13% 9%	1672
	21st to end	Day	64% 4 8% 13% 9% 2	1596
March	1st to 10th	Day	58% 4 9% 21% 8%	3435
	11th to 20th	Day	51% 6% 9% 25% 8% 1	3480
	21st to end	Day	56% 4 7% 20% 12% 1	3815
April	1st to 10th	Day	55% 6% 9% 17% 11% 2	2184
	11th to 20th	Day	51% 5% 10% 15% 17% 2	2134
	21st to end	Day	54% 5% 10% 20% 10% 2	2330
May	1st to 10th	Day	56% 6% 9% 17% 10% 1	2340
	11th to 20th	Day	56% 7% 11% 16% 9% 1	2305
	21st to end	Day	46% 8% 15% 22% 8% 1	2638
June	1st to 10th	Day	45% 9% 12% 22% 12% 1	2520
	11th to 20th	Day	48% 8% 12% 22% 9% 1	2520
	21st to end	Day	44% 9% 12% 23% 11% 1	2520
July	1st to 10th	Day	47% 7% 11% 20% 13% 3	2335
	11th to 20th	Day	41% 9% 12% 23% 14% 1	2271
	21st to end	Day	47% 8% 11% 21% 12% 1	2405
August	1st to 10th	Day	46% 9% 14% 22% 8% 1	2314
	11th to 20th	Day	45% 7% 12% 25% 11%	2303
	21st to end	Day	41% 8% 14% 22% 13% 3	2428
September	1st to 10th	Day	41% 6% 10% 21% 19% 3	2160
	11th to 20th	Day	39% 6% 11% 27% 14% 3	1998
	21st to end	Day	48% 5% 10% 19% 17% 1	1971
October	1st to 10th	Day	45% 6% 11% 23% 14% 2	1800
	11th to 20th	Day	50% 5% 9% 25% 12%	1800
	21st to end	Day	54% 3 9% 18% 14% 2	1980
November	1st to 10th	Day	43% 4 9% 23% 17% 4	1829
	11th to 20th	Day	53% 5% 10% 17% 14% 3	1606
	21st to end	Day	61% 3 10% 15% 11%	1520
December	1st to 10th	Day	72% 4 7% 12% 4 1	1520
	11th to 20th	Day	66% 3 7% 18% 5% 1	1906
	21st to end	Day	70% 5% 9% 11% 5%	2818
January	1st to 10th	Night	72% 3 6% 12% 5% 1	4109
	11th to 20th	Night	74% 3 9% 11% 2	4120
	21st to end	Night	75% 3 5% 13% 4 1	4532
February	1st to 10th	Night	62% 4 9% 16% 8%	2470
	11th to 20th	Night	67% 3 8% 14% 8%	2405
	21st to end	Night	62% 5% 8% 15% 9% 2	1851
March	1st to 10th	Night	57% 4 7% 24% 8% 1	3418
	11th to 20th	Night	56% 5% 7% 25% 6% 1	3480
	21st to end	Night	50% 4 7% 24% 13% 2	3817
April	1st to 10th	Night	56% 4 8% 16% 13% 2	1984
	11th to 20th	Night	47% 5% 11% 18% 15% 4	1775
	21st to end	Night	47% 5% 11% 23% 11% 3	1646
May	1st to 10th	Night	50% 7% 11% 18% 11% 3	1620
	11th to 20th	Night	49% 8% 12% 16% 13% 2	1593
	21st to end	Night	38% 7% 18% 26% 10% 1	1634
June	1st to 10th	Night	40% 8% 13% 25% 13% 1	1440
	11th to 20th	Night	42% 9% 13% 22% 12% 1	1440
	21st to end	Night	38% 9% 15% 23% 14% 1	1440
July	1st to 10th	Night	39% 9% 14% 22% 13% 3	1510
	11th to 20th	Night	35% 9% 12% 25% 17% 2	1566
	21st to end	Night	40% 8% 14% 23% 14% 1	1672
August	1st to 10th	Night	39% 9% 17% 22% 11% 1	1600
	11th to 20th	Night	39% 8% 14% 24% 14% 1	1598
	21st to end	Night	36% 7% 13% 27% 14% 3	1908
September	1st to 10th	Night	39% 7% 12% 22% 16% 5%	1800
	11th to 20th	Night	33% 5% 13% 26% 21% 2	1958
	21st to end	Night	43% 5% 11% 22% 18% 1	1988
October	1st to 10th	Night	42% 6% 10% 25% 14% 3	2160
	11th to 20th	Night	44% 5% 9% 26% 15% 1	2160
	21st to end	Night	52% 3 8% 22% 14% 2	2376
November	1st to 10th	Night	43% 4 11% 20% 17% 5%	2247
	11th to 20th	Night	55% 4 7% 17% 13% 2	2572
	21st to end	Night	59% 4 8% 18% 9% 2	2660
December	1st to 10th	Night	70% 4 7% 14% 4 1	2660
	11th to 20th	Night	66% 4 8% 15% 6% 1	3288
	21st to end	Night	70% 5% 9% 11% 5%	4820

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	38% 31% 17% 10% 4	270
	11th to 20th	Day	43% 26% 25% 6%	270
	21st to end	Day	39% 27% 27% 4 3	297
February	1st to 10th	Day	37% 28% 27% 7% 1	270
	11th to 20th	Day	46% 26% 23% 4	270
	21st to end	Day	45% 25% 23% 6% 1	280
March	1st to 10th	Day	35% 22% 28% 12% 4	460
	11th to 20th	Day	37% 20% 27% 11% 3 1	460
	21st to end	Day	37% 20% 26% 13% 4	506
April	1st to 10th	Day	35% 20% 23% 16% 5% 1	457
	11th to 20th	Day	26% 19% 28% 16% 7% 4	412
	21st to end	Day	35% 18% 26% 14% 5% 1	420
May	1st to 10th	Day	34% 16% 27% 12% 7% 4	423
	11th to 20th	Day	28% 15% 28% 18% 8% 4	447
	21st to end	Day	17% 11% 27% 23% 14% 8%	485
June	1st to 10th	Day	19% 9% 27% 26% 15% 5%	450
	11th to 20th	Day	22% 11% 22% 25% 16% 4	450
	21st to end	Day	18% 9% 27% 28% 15% 3	450
July	1st to 10th	Day	19% 4 21% 28% 16% 13%	445
	11th to 20th	Day	14% 6% 23% 32% 18% 8%	444
	21st to end	Day	19% 6% 24% 24% 19% 6%	488
August	1st to 10th	Day	15% 8% 20% 30% 19% 8%	446
	11th to 20th	Day	21% 2 20% 29% 19% 9%	439
	21st to end	Day	16% 5% 24% 26% 19% 11%	495
September	1st to 10th	Day	19% 7% 19% 27% 19% 9%	450
	11th to 20th	Day	16% 3 21% 28% 23% 9%	450
	21st to end	Day	25% 10% 25% 22% 14% 4	450
October	1st to 10th	Day	22% 9% 22% 27% 18% 3	450
	11th to 20th	Day	27% 12% 27% 26% 7% 1	450
	21st to end	Day	36% 16% 24% 16% 7%	495
November	1st to 10th	Day	22% 15% 28% 23% 9% 3	427
	11th to 20th	Day	34% 19% 26% 12% 7% 1	221
	21st to end	Day	33% 22% 31% 11% 2 1	180
December	1st to 10th	Day	33% 27% 28% 6% 3 2	180
	11th to 20th	Day	44% 21% 26% 7% 2	180
	21st to end	Day	40% 27% 17% 13% 3	213
January	1st to 10th	Night	35% 23% 25% 14% 3	760
	11th to 20th	Night	38% 19% 28% 14% 1	760
	21st to end	Night	34% 24% 25% 16% 1	836
February	1st to 10th	Night	30% 20% 28% 20% 2	760
	11th to 20th	Night	36% 25% 28% 11%	743
	21st to end	Night	33% 23% 27% 15% 1	628
March	1st to 10th	Night	29% 20% 28% 19% 3	760
	11th to 20th	Night	34% 17% 24% 18% 6%	760
	21st to end	Night	28% 19% 30% 19% 4	836
April	1st to 10th	Night	31% 16% 28% 19% 5%	760
	11th to 20th	Night	24% 12% 30% 22% 11% 1	711
	21st to end	Night	23% 11% 31% 26% 8%	566
May	1st to 10th	Night	26% 8% 26% 28% 10% 1	540
	11th to 20th	Night	24% 8% 25% 31% 12% 1	531
	21st to end	Night	14% 5% 20% 32% 27% 3	473
June	1st to 10th	Night	14% 4 21% 40% 21% 1	360
	11th to 20th	Night	13% 6% 21% 37% 21% 2	360
	21st to end	Night	15% 4 20% 42% 18% 1	360
July	1st to 10th	Night	16% 3 13% 36% 27% 4	460
	11th to 20th	Night	14% 3 12% 37% 29% 3	522
	21st to end	Night	17% 2 14% 36% 29% 2	591
August	1st to 10th	Night	12% 3 12% 43% 28% 3	537
	11th to 20th	Night	17% 4 9% 37% 30% 4	534
	21st to end	Night	14% 4 13% 37% 29% 3	720
September	1st to 10th	Night	18% 3 15% 32% 27% 4	720
	11th to 20th	Night	16% 3 18% 33% 26% 4	720
	21st to end	Night	20% 8% 18% 31% 20% 3	720
October	1st to 10th	Night	20% 8% 21% 29% 19% 3	720
	11th to 20th	Night	25% 10% 24% 30% 11% 1	720
	21st to end	Night	33% 11% 22% 26% 8% 1	792
November	1st to 10th	Night	22% 11% 22% 33% 11% 1	740
	11th to 20th	Night	31% 15% 24% 22% 6% 1	760
	21st to end	Night	29% 16% 28% 22% 4 1	760
December	1st to 10th	Night	37% 17% 24% 17% 4	760
	11th to 20th	Night	32% 21% 24% 19% 4	760
	21st to end	Night	33% 18% 28% 19% 1	836

Page generated at 2024-04-07 09:28:11. Version ac07

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