Clarence Fahnestock Memorial State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Clarence Fahnestock Memorial State Park clear sky chart from 2005-11-06 to 2024-12-06.

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	16% 7% 3 6% 4 4 4 4 5% 7% 38%	101595
	Night	17% 8% 3 6% 4 4 4 3 5% 7% 39%	98125
Transparency	Day	44% 5% 12% 23% 15% 2	105127
	Night	43% 4 12% 24% 15% 2	102682
Seeing	Day	23% 16% 29% 21% 9% 2	15036
	Night	21% 14% 30% 26% 8% 1	24167

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% 8% 3 6% 4 4 3 3 5% 5% 44%	2517
	11th to 20th	Day	15% 10% 3 8% 6% 5% 5% 3 4 5% 35%	2520
	21st to end	Day	20% 13% 5% 8% 4 4 3 3 4 4 31%	2941
February	1st to 10th	Day	17% 10% 3 7% 5% 5% 4 4 5% 7% 34%	1715
	11th to 20th	Day	15% 8% 3 7% 4 4 4 4 5% 6% 40%	1848
	21st to end	Day	19% 9% 3 6% 5% 4 4 3 5% 6% 36%	1570
March	1st to 10th	Day	26% 10% 3 7% 5% 3 3 3 3 5% 33%	3116
	11th to 20th	Day	10% 7% 2 7% 5% 5% 5% 5% 6% 7% 41%	3307
	21st to end	Day	20% 9% 2 6% 4 3 3 3 5% 5% 39%	4156
April	1st to 10th	Day	18% 10% 3 8% 4 4 4 3 5% 6% 36%	2280
	11th to 20th	Day	17% 7% 2 7% 4 4 4 3 5% 7% 40%	2254
	21st to end	Day	20% 7% 2 5% 4 4 5% 4 5% 6% 38%	2332
May	1st to 10th	Day	26% 8% 3 6% 4 3 3 3 5% 7% 31%	4106
	11th to 20th	Day	21% 9% 2 8% 5% 4 5% 3 6% 6% 31%	4388
	21st to end	Day	13% 6% 2 5% 3 4 5% 4 6% 9% 44%	4837
June	1st to 10th	Day	17% 5% 2 5% 4 5% 5% 4 7% 8% 37%	2660
	11th to 20th	Day	14% 7% 3 7% 5% 4 5% 5% 7% 8% 36%	2660
	21st to end	Day	13% 6% 2 7% 5% 5% 5% 5% 6% 9% 38%	2660
July	1st to 10th	Day	9% 7% 3 8% 6% 6% 7% 4 7% 9% 35%	4440
	11th to 20th	Day	10% 6% 3 7% 5% 5% 6% 5% 7% 10% 37%	4440
	21st to end	Day	14% 8% 3 8% 5% 5% 5% 5% 6% 7% 34%	4814
August	1st to 10th	Day	20% 7% 2 6% 5% 5% 5% 4 6% 7% 32%	4251
	11th to 20th	Day	12% 7% 2 6% 4 4 5% 4 6% 9% 41%	3730
	21st to end	Day	10% 6% 2 6% 4 4 4 4 6% 9% 46%	4180
September	1st to 10th	Day	14% 6% 2 6% 4 5% 4 5% 6% 6% 43%	2280
	11th to 20th	Day	12% 5% 2 5% 4 4 3 3 5% 7% 49%	2190
	21st to end	Day	17% 6% 2 7% 4 4 4 3 5% 7% 40%	2090
October	1st to 10th	Day	21% 7% 3 6% 4 3 4 3 4 5% 41%	1995
	11th to 20th	Day	14% 5% 2 6% 3 4 4 3 5% 8% 45%	1900
	21st to end	Day	21% 6% 3 5% 4 4 4 3 6% 5% 38%	1914
November	1st to 10th	Day	14% 6% 2 4 4 4 3 2 5% 6% 50%	1761
	11th to 20th	Day	17% 6% 2 5% 4 3 3 3 5% 7% 45%	1800
	21st to end	Day	17% 7% 3 5% 4 4 4 4 5% 6% 41%	1705
December	1st to 10th	Day	18% 8% 4 8% 5% 4 5% 3 5% 6% 35%	1560
	11th to 20th	Day	21% 7% 2 5% 3 3 4 3 5% 6% 41%	1906
	21st to end	Day	19% 11% 4 8% 6% 4 5% 4 5% 6% 29%	2772
January	1st to 10th	Night	17% 6% 2 6% 4 3 4 3 5% 6% 43%	4429
	11th to 20th	Night	15% 9% 3 9% 5% 4 4 4 5% 5% 37%	4440
	21st to end	Night	23% 11% 4 7% 4 4 3 2 4 5% 32%	4710
February	1st to 10th	Night	16% 10% 3 7% 4 4 4 3 4 5% 39%	2463
	11th to 20th	Night	15% 8% 3 7% 5% 4 5% 4 6% 5% 38%	2218
	21st to end	Night	18% 7% 3 7% 4 3 4 3 6% 5% 40%	1884
March	1st to 10th	Night	23% 11% 3 6% 3 4 3 3 4 5% 34%	3724
	11th to 20th	Night	11% 6% 3 7% 5% 5% 4 4 6% 7% 42%	3649
	21st to end	Night	18% 9% 3 6% 3 4 4 3 4 5% 41%	3475
April	1st to 10th	Night	17% 9% 3 7% 5% 6% 5% 4 5% 6% 34%	1900
	11th to 20th	Night	19% 7% 3 7% 4 4 4 4 4 6% 37%	1875
	21st to end	Night	20% 8% 2 6% 4 3 4 3 5% 5% 40%	1847
May	1st to 10th	Night	25% 8% 2 7% 5% 3 4 4 5% 8% 28%	2834
	11th to 20th	Night	21% 9% 4 8% 4 4 4 3 5% 6% 32%	2534
	21st to end	Night	14% 6% 2 5% 4 4 4 3 6% 9% 42%	2738
June	1st to 10th	Night	16% 6% 3 6% 5% 3 4 4 6% 8% 40%	1520
	11th to 20th	Night	13% 6% 2 6% 5% 4 5% 3 7% 9% 40%	1520
	21st to end	Night	11% 5% 2 6% 4 4 4 4 7% 10% 41%	1520
July	1st to 10th	Night	10% 7% 3 6% 5% 5% 5% 5% 8% 8% 38%	2520
	11th to 20th	Night	11% 7% 3 8% 5% 4 5% 4 7% 9% 37%	2520
	21st to end	Night	15% 10% 3 6% 4 4 4 4 6% 6% 38%	2739
August	1st to 10th	Night	20% 7% 2 9% 4 5% 5% 3 6% 7% 32%	2630
	11th to 20th	Night	14% 8% 2 7% 4 4 4 4 5% 7% 39%	3097
	21st to end	Night	12% 5% 2 5% 3 3 4 3 5% 7% 52%	3476
September	1st to 10th	Night	15% 6% 2 6% 4 4 4 3 4 6% 46%	1900
	11th to 20th	Night	13% 5% 1 4 3 3 3 3 5% 7% 53%	1990
	21st to end	Night	17% 7% 2 5% 3 4 3 3 5% 7% 44%	2090
October	1st to 10th	Night	19% 8% 3 5% 3 3 4 3 4 5% 42%	2181
	11th to 20th	Night	14% 6% 2 6% 4 4 3 3 5% 7% 47%	2280
	21st to end	Night	21% 7% 2 6% 4 4 4 3 5% 6% 38%	2684
November	1st to 10th	Night	12% 7% 2 5% 4 4 4 3 5% 7% 47%	2537
	11th to 20th	Night	18% 8% 2 5% 4 3 3 3 4 6% 45%	2600
	21st to end	Night	15% 7% 2 5% 5% 4 3 3 6% 7% 43%	2692
December	1st to 10th	Night	19% 8% 2 6% 4 4 4 3 5% 6% 38%	2737
	11th to 20th	Night	19% 8% 2 6% 4 4 4 4 5% 6% 36%	3288
	21st to end	Night	21% 10% 3 7% 4 4 4 3 5% 6% 33%	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	39% 5% 9% 34% 10% 2	2518
	11th to 20th	Day	51% 4 10% 24% 10% 1	2520
	21st to end	Day	56% 3 9% 21% 10% 1	2941
February	1st to 10th	Day	48% 4 11% 21% 14% 1	1715
	11th to 20th	Day	44% 4 9% 24% 16% 2	1857
	21st to end	Day	49% 3 11% 22% 13% 2	1570
March	1st to 10th	Day	54% 3 11% 19% 10% 2	3119
	11th to 20th	Day	36% 6% 13% 31% 12% 2	3307
	21st to end	Day	47% 3 6% 17% 22% 5%	4156
April	1st to 10th	Day	48% 4 9% 22% 14% 4	2280
	11th to 20th	Day	44% 4 11% 21% 17% 3	2254
	21st to end	Day	45% 5% 9% 22% 16% 3	2332
May	1st to 10th	Day	53% 5% 13% 16% 12% 1	4120
	11th to 20th	Day	52% 5% 12% 20% 9% 1	4392
	21st to end	Day	35% 7% 12% 26% 17% 2	4837
June	1st to 10th	Day	42% 6% 14% 23% 14% 1	2660
	11th to 20th	Day	44% 6% 13% 25% 11% 2	2660
	21st to end	Day	41% 7% 13% 24% 13% 1	2660
July	1st to 10th	Day	44% 7% 11% 22% 15% 1	4370
	11th to 20th	Day	41% 6% 17% 23% 13% 1	4365
	21st to end	Day	48% 5% 11% 18% 15% 2	4661
August	1st to 10th	Day	50% 6% 13% 22% 9%	4237
	11th to 20th	Day	39% 5% 17% 29% 10%	3766
	21st to end	Day	35% 5% 11% 32% 16% 1	4180
September	1st to 10th	Day	40% 6% 10% 24% 18% 1	2280
	11th to 20th	Day	35% 5% 8% 26% 24% 2	2190
	21st to end	Day	44% 5% 9% 23% 16% 3	2090
October	1st to 10th	Day	41% 4 8% 19% 24% 4	3320
	11th to 20th	Day	30% 4 8% 28% 25% 5%	3140
	21st to end	Day	31% 3 16% 26% 21% 4	3126
November	1st to 10th	Day	36% 3 13% 26% 19% 3	1761
	11th to 20th	Day	40% 4 10% 24% 19% 3	1800
	21st to end	Day	42% 4 14% 29% 10% 2	1705
December	1st to 10th	Day	50% 4 14% 19% 13% 1	1560
	11th to 20th	Day	44% 2 16% 22% 13% 2	1906
	21st to end	Day	54% 5% 11% 22% 8% 1	2772
January	1st to 10th	Night	40% 3 12% 30% 12% 3	4429
	11th to 20th	Night	46% 4 12% 24% 11% 3	4440
	21st to end	Night	55% 3 9% 22% 11% 2	4710
February	1st to 10th	Night	46% 4 14% 23% 12% 2	2463
	11th to 20th	Night	44% 4 11% 20% 18% 4	2220
	21st to end	Night	45% 3 8% 24% 16% 4	1884
March	1st to 10th	Night	52% 3 11% 20% 12% 2	3734
	11th to 20th	Night	38% 4 14% 27% 14% 2	3650
	21st to end	Night	46% 3 7% 16% 23% 5%	3475
April	1st to 10th	Night	48% 3 11% 21% 14% 3	1900
	11th to 20th	Night	46% 5% 9% 20% 19% 1	1875
	21st to end	Night	45% 4 8% 23% 17% 4	1847
May	1st to 10th	Night	54% 6% 11% 18% 9% 1	2840
	11th to 20th	Night	53% 5% 13% 18% 10% 1	2535
	21st to end	Night	39% 6% 15% 25% 13% 2	2739
June	1st to 10th	Night	41% 7% 10% 23% 17% 2	1520
	11th to 20th	Night	39% 7% 17% 26% 10% 1	1520
	21st to end	Night	36% 6% 16% 26% 15% 1	1520
July	1st to 10th	Night	41% 7% 16% 20% 15% 2	2480
	11th to 20th	Night	43% 6% 14% 25% 12% 1	2472
	21st to end	Night	45% 5% 14% 15% 18% 2	2651
August	1st to 10th	Night	51% 6% 15% 18% 9% 1	2620
	11th to 20th	Night	44% 5% 14% 28% 9% 1	3127
	21st to end	Night	31% 5% 11% 36% 16% 1	3476
September	1st to 10th	Night	39% 5% 10% 27% 17% 1	1900
	11th to 20th	Night	32% 4 11% 26% 25% 2	1990
	21st to end	Night	40% 5% 9% 22% 22% 1	2090
October	1st to 10th	Night	42% 4 10% 22% 20% 2	3636
	11th to 20th	Night	27% 3 10% 29% 27% 4	3779
	21st to end	Night	35% 3 13% 30% 17% 2	4422
November	1st to 10th	Night	36% 4 12% 24% 21% 3	2537
	11th to 20th	Night	41% 3 9% 24% 20% 4	2600
	21st to end	Night	40% 3 14% 30% 12% 1	2692
December	1st to 10th	Night	46% 4 11% 25% 13% 1	2737
	11th to 20th	Night	46% 4 13% 20% 15% 3	3288
	21st to end	Night	51% 3 12% 22% 12%	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	26% 27% 29% 13% 4	180
	11th to 20th	Day	33% 25% 27% 13% 2	180
	21st to end	Day	21% 27% 35% 13% 3 2	247
February	1st to 10th	Day	34% 25% 31% 9% 1	275
	11th to 20th	Day	29% 26% 32% 13%	456
	21st to end	Day	32% 20% 31% 14% 3	382
March	1st to 10th	Day	30% 20% 30% 16% 3	460
	11th to 20th	Day	27% 27% 29% 14% 2 1	460
	21st to end	Day	31% 21% 30% 12% 4 2	506
April	1st to 10th	Day	31% 22% 27% 13% 6% 1	460
	11th to 20th	Day	25% 25% 28% 14% 7% 1	452
	21st to end	Day	30% 16% 32% 16% 5% 1	460
May	1st to 10th	Day	33% 18% 27% 14% 6% 1	463
	11th to 20th	Day	24% 12% 36% 21% 7% 1	487
	21st to end	Day	19% 12% 27% 27% 13% 2	529
June	1st to 10th	Day	21% 11% 30% 24% 11% 2	490
	11th to 20th	Day	16% 16% 29% 25% 13% 1	490
	21st to end	Day	15% 14% 27% 27% 13% 3	490
July	1st to 10th	Day	14% 8% 29% 27% 16% 5%	485
	11th to 20th	Day	13% 7% 29% 31% 16% 3	484
	21st to end	Day	14% 8% 30% 33% 13% 2	532
August	1st to 10th	Day	16% 8% 24% 31% 16% 5%	486
	11th to 20th	Day	15% 7% 24% 33% 15% 6%	479
	21st to end	Day	13% 10% 28% 27% 15% 7%	539
September	1st to 10th	Day	17% 13% 25% 23% 16% 7%	490
	11th to 20th	Day	14% 8% 29% 25% 13% 10%	490
	21st to end	Day	23% 11% 28% 23% 10% 6%	490
October	1st to 10th	Day	28% 9% 25% 21% 14% 3	490
	11th to 20th	Day	20% 16% 30% 21% 10% 1	490
	21st to end	Day	28% 13% 29% 21% 9%	446
November	1st to 10th	Day	19% 15% 30% 23% 10% 3	395
	11th to 20th	Day	27% 23% 27% 17% 5% 1	400
	21st to end	Day	25% 22% 29% 19% 4 1	305
December	1st to 10th	Day	24% 23% 34% 14% 5%	190
	11th to 20th	Day	36% 21% 31% 11% 2	180
	21st to end	Day	25% 26% 28% 15% 5%	198
January	1st to 10th	Night	21% 17% 39% 20% 3	760
	11th to 20th	Night	25% 19% 30% 23% 2	760
	21st to end	Night	20% 22% 34% 21% 3	836
February	1st to 10th	Night	23% 18% 36% 21% 2	760
	11th to 20th	Night	23% 21% 40% 15% 1	743
	21st to end	Night	26% 19% 34% 19% 3	628
March	1st to 10th	Night	24% 21% 32% 19% 3	760
	11th to 20th	Night	23% 23% 31% 19% 3	760
	21st to end	Night	24% 21% 33% 18% 4 1	836
April	1st to 10th	Night	23% 20% 34% 19% 4	760
	11th to 20th	Night	25% 15% 33% 22% 4	751
	21st to end	Night	24% 16% 34% 21% 5%	707
May	1st to 10th	Night	25% 15% 32% 22% 5%	570
	11th to 20th	Night	24% 12% 34% 25% 6%	400
	21st to end	Night	19% 8% 24% 37% 11% 1	411
June	1st to 10th	Night	19% 7% 29% 34% 11%	380
	11th to 20th	Night	15% 5% 31% 33% 14% 1	380
	21st to end	Night	14% 3 28% 43% 12%	380
July	1st to 10th	Night	16% 5% 20% 39% 19% 1	370
	11th to 20th	Night	14% 2 24% 41% 17% 2	368
	21st to end	Night	15% 3 22% 41% 18% 1	416
August	1st to 10th	Night	13% 4 21% 43% 18% 2	450
	11th to 20th	Night	16% 4 20% 36% 22% 2	750
	21st to end	Night	18% 5% 18% 36% 22% 2	836
September	1st to 10th	Night	18% 6% 25% 35% 15% 2	760
	11th to 20th	Night	17% 5% 24% 32% 18% 4	760
	21st to end	Night	21% 7% 25% 30% 15% 2	760
October	1st to 10th	Night	23% 9% 26% 26% 14% 2	760
	11th to 20th	Night	19% 13% 30% 28% 10%	760
	21st to end	Night	27% 11% 32% 22% 8%	836
November	1st to 10th	Night	16% 12% 34% 27% 9% 1	780
	11th to 20th	Night	24% 17% 31% 22% 7% 1	800
	21st to end	Night	20% 19% 30% 24% 7%	800
December	1st to 10th	Night	28% 16% 32% 19% 5%	783
	11th to 20th	Night	25% 16% 32% 23% 3	760
	21st to end	Night	25% 16% 36% 19% 2	836

Page generated at 2024-12-03 06:45:14. Version ac07

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