Cohoctah Nightcrawler Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cohoctah Nightcrawler Observatory clear sky chart from 2005-11-06 to 2024-07-31.

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	14% 11% 4 8% 5% 5% 4 4 5% 7% 33%	89351
	Night	15% 12% 4 8% 5% 4 4 3 5% 6% 33%	90448
Transparency	Day	50% 6% 11% 20% 12% 1	89109
	Night	51% 6% 11% 20% 11% 1	90295
Seeing	Day	18% 12% 29% 23% 14% 6%	15194
	Night	19% 10% 30% 29% 11% 1	25216

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% 21% 6% 11% 5% 5% 4 4 4 4 20%	2527
	11th to 20th	Day	16% 19% 6% 14% 10% 9% 5% 3 3 4 12%	2530
	21st to end	Day	27% 21% 7% 11% 5% 3 3 2 3 4 13%	2965
February	1st to 10th	Day	14% 15% 6% 12% 8% 5% 5% 4 6% 6% 21%	1710
	11th to 20th	Day	14% 13% 6% 13% 8% 6% 4 3 4 5% 24%	1821
	21st to end	Day	14% 16% 6% 12% 6% 4 5% 4 4 5% 24%	1570
March	1st to 10th	Day	16% 16% 5% 8% 6% 4 4 4 4 6% 28%	3147
	11th to 20th	Day	12% 12% 5% 10% 6% 5% 5% 3 4 7% 30%	3480
	21st to end	Day	17% 15% 4 10% 5% 4 4 3 4 5% 28%	3815
April	1st to 10th	Day	17% 14% 3 8% 5% 5% 5% 3 5% 5% 30%	2251
	11th to 20th	Day	16% 10% 4 7% 4 4 4 4 5% 6% 35%	2384
	21st to end	Day	16% 9% 3 8% 5% 5% 4 4 5% 7% 34%	2470
May	1st to 10th	Day	18% 9% 3 6% 4 5% 5% 4 5% 7% 35%	4082
	11th to 20th	Day	16% 7% 2 6% 4 4 5% 4 6% 8% 37%	4081
	21st to end	Day	11% 6% 3 6% 4 4 4 3 5% 9% 45%	4586
June	1st to 10th	Day	10% 7% 2 6% 5% 4 5% 5% 6% 8% 43%	2660
	11th to 20th	Day	11% 5% 3 7% 5% 5% 5% 4 6% 8% 41%	2660
	21st to end	Day	10% 6% 2 6% 5% 5% 5% 6% 7% 9% 39%	2660
July	1st to 10th	Day	7% 5% 2 6% 4 5% 4 4 8% 10% 44%	2660
	11th to 20th	Day	10% 5% 2 6% 5% 4 5% 5% 7% 9% 44%	2660
	21st to end	Day	7% 6% 2 6% 5% 5% 5% 5% 9% 9% 42%	2785
August	1st to 10th	Day	10% 5% 3 6% 5% 5% 6% 5% 6% 9% 41%	2327
	11th to 20th	Day	10% 6% 3 7% 5% 5% 6% 4 6% 9% 39%	2303
	21st to end	Day	10% 7% 2 6% 5% 4 4 4 6% 8% 44%	2516
September	1st to 10th	Day	11% 8% 3 7% 5% 5% 4 4 7% 8% 39%	2062
	11th to 20th	Day	10% 6% 1 6% 4 4 4 4 5% 9% 46%	1980
	21st to end	Day	14% 7% 2 6% 4 5% 5% 5% 7% 7% 38%	1980
October	1st to 10th	Day	14% 7% 2 7% 6% 4 5% 3 5% 6% 40%	1954
	11th to 20th	Day	19% 10% 4 8% 4 5% 5% 3 5% 6% 31%	1800
	21st to end	Day	20% 11% 4 8% 6% 4 4 3 4 7% 29%	1796
November	1st to 10th	Day	13% 11% 3 6% 5% 4 4 4 5% 7% 37%	1672
	11th to 20th	Day	14% 14% 4 10% 5% 4 4 4 5% 7% 28%	1710
	21st to end	Day	18% 16% 6% 8% 5% 4 3 3 5% 6% 27%	1687
December	1st to 10th	Day	14% 18% 7% 12% 7% 5% 4 3 3 5% 21%	1520
	11th to 20th	Day	15% 18% 5% 11% 5% 5% 5% 4 6% 6% 21%	1757
	21st to end	Day	22% 23% 8% 13% 6% 4 4 3 4 4 10%	2783
January	1st to 10th	Night	16% 17% 7% 13% 6% 5% 4 3 4 5% 21%	4428
	11th to 20th	Night	14% 17% 7% 16% 6% 8% 6% 3 4 4 14%	4440
	21st to end	Night	23% 18% 8% 11% 5% 4 4 3 3 4 16%	4693
February	1st to 10th	Night	16% 17% 5% 10% 7% 5% 5% 4 4 4 22%	2470
	11th to 20th	Night	13% 14% 5% 12% 7% 6% 4 4 4 4 26%	2242
	21st to end	Night	16% 13% 4 10% 6% 4 5% 3 5% 6% 27%	1884
March	1st to 10th	Night	14% 13% 4 9% 4 4 4 3 4 7% 35%	3706
	11th to 20th	Night	9% 10% 3 7% 5% 4 5% 4 5% 7% 42%	3480
	21st to end	Night	16% 10% 4 9% 5% 4 5% 3 5% 5% 34%	3817
April	1st to 10th	Night	15% 13% 3 7% 4 3 4 4 5% 6% 36%	1945
	11th to 20th	Night	19% 9% 3 6% 4 4 4 3 6% 6% 36%	1744
	21st to end	Night	17% 8% 3 6% 4 4 5% 4 5% 6% 38%	1710
May	1st to 10th	Night	15% 9% 3 7% 5% 4 4 4 6% 7% 36%	2813
	11th to 20th	Night	16% 8% 3 6% 4 3 4 3 5% 7% 42%	2812
	21st to end	Night	10% 5% 2 7% 4 4 5% 3 5% 8% 47%	2969
June	1st to 10th	Night	11% 6% 2 6% 4 4 3 3 6% 9% 46%	1520
	11th to 20th	Night	11% 6% 3 6% 4 3 4 3 6% 9% 45%	1520
	21st to end	Night	9% 7% 2 6% 4 4 3 3 6% 9% 47%	1520
July	1st to 10th	Night	7% 3 2 5% 4 3 5% 3 6% 9% 52%	1520
	11th to 20th	Night	8% 5% 2 4 4 4 3 3 7% 8% 51%	1520
	21st to end	Night	6% 4 2 5% 4 4 4 4 7% 9% 51%	1763
August	1st to 10th	Night	8% 4 2 5% 4 4 5% 4 6% 10% 47%	1611
	11th to 20th	Night	8% 4 2 6% 4 5% 4 4 5% 9% 50%	1598
	21st to end	Night	9% 6% 2 6% 3 3 5% 3 5% 7% 51%	1838
September	1st to 10th	Night	10% 6% 2 6% 5% 4 4 4 5% 7% 47%	1880
	11th to 20th	Night	11% 6% 2 5% 3 3 4 3 4 6% 54%	1980
	21st to end	Night	14% 6% 2 6% 4 4 5% 3 5% 7% 44%	1980
October	1st to 10th	Night	15% 6% 3 6% 4 4 4 3 5% 6% 43%	2005
	11th to 20th	Night	19% 12% 4 7% 4 4 4 3 5% 5% 33%	2160
	21st to end	Night	22% 11% 3 7% 5% 4 4 4 5% 5% 31%	2558
November	1st to 10th	Night	15% 9% 3 6% 4 4 4 3 5% 7% 41%	2406
	11th to 20th	Night	15% 12% 4 8% 5% 5% 5% 5% 6% 6% 29%	2470
	21st to end	Night	19% 15% 4 7% 5% 4 4 3 5% 6% 28%	2487
December	1st to 10th	Night	17% 18% 6% 11% 6% 5% 4 4 4 5% 19%	2660
	11th to 20th	Night	14% 16% 6% 12% 7% 6% 4 4 5% 5% 21%	3415
	21st to end	Night	25% 24% 6% 10% 5% 4 3 2 4 5% 12%	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	66% 6% 9% 14% 4	2528
	11th to 20th	Day	75% 7% 9% 6% 3	2530
	21st to end	Day	77% 4 9% 7% 3 1	2965
February	1st to 10th	Day	62% 7% 8% 15% 7%	1710
	11th to 20th	Day	63% 4 8% 15% 9% 1	1831
	21st to end	Day	62% 4 10% 16% 6% 2	1570
March	1st to 10th	Day	58% 4 11% 19% 7% 1	3147
	11th to 20th	Day	53% 6% 12% 19% 9% 1	3480
	21st to end	Day	58% 5% 10% 15% 10% 2	3815
April	1st to 10th	Day	55% 5% 9% 19% 12%	2251
	11th to 20th	Day	49% 6% 11% 20% 13% 2	2384
	21st to end	Day	49% 6% 12% 17% 14% 2	2470
May	1st to 10th	Day	48% 6% 10% 22% 12% 2	4120
	11th to 20th	Day	43% 8% 14% 25% 10% 1	4085
	21st to end	Day	36% 6% 11% 20% 24% 3	4599
June	1st to 10th	Day	37% 7% 11% 28% 14% 2	2660
	11th to 20th	Day	39% 7% 11% 24% 17% 2	2660
	21st to end	Day	39% 8% 13% 22% 16% 2	2660
July	1st to 10th	Day	33% 8% 12% 26% 18% 3	2591
	11th to 20th	Day	34% 6% 13% 26% 18% 2	2585
	21st to end	Day	34% 9% 13% 24% 18% 3	2638
August	1st to 10th	Day	38% 8% 13% 26% 14% 2	2314
	11th to 20th	Day	40% 7% 13% 25% 14% 2	2303
	21st to end	Day	37% 7% 11% 26% 17% 2	2516
September	1st to 10th	Day	42% 6% 14% 23% 13% 2	2062
	11th to 20th	Day	35% 6% 11% 33% 14% 1	1980
	21st to end	Day	42% 7% 13% 25% 13%	1980
October	1st to 10th	Day	44% 5% 10% 25% 14% 2	1954
	11th to 20th	Day	53% 6% 12% 19% 10%	1800
	21st to end	Day	56% 5% 12% 18% 9%	1796
November	1st to 10th	Day	46% 5% 12% 23% 13% 1	1672
	11th to 20th	Day	55% 5% 13% 18% 8% 1	1710
	21st to end	Day	58% 5% 13% 17% 7% 1	1687
December	1st to 10th	Day	66% 5% 9% 16% 3	1520
	11th to 20th	Day	62% 7% 12% 15% 4	1753
	21st to end	Day	78% 5% 8% 6% 3	2783
January	1st to 10th	Night	65% 6% 9% 14% 5% 1	4428
	11th to 20th	Night	71% 6% 10% 9% 4	4440
	21st to end	Night	73% 4 9% 10% 3	4693
February	1st to 10th	Night	65% 5% 10% 13% 7% 1	2470
	11th to 20th	Night	60% 6% 8% 17% 8% 1	2243
	21st to end	Night	57% 5% 12% 16% 9% 2	1884
March	1st to 10th	Night	50% 5% 13% 25% 7% 1	3706
	11th to 20th	Night	39% 8% 13% 21% 18% 1	3480
	21st to end	Night	50% 7% 11% 21% 11% 1	3817
April	1st to 10th	Night	48% 5% 10% 21% 14% 2	1945
	11th to 20th	Night	47% 5% 10% 18% 17% 2	1744
	21st to end	Night	45% 6% 12% 19% 16% 2	1710
May	1st to 10th	Night	45% 7% 11% 22% 13% 3	2840
	11th to 20th	Night	41% 6% 9% 28% 13% 2	2813
	21st to end	Night	34% 6% 11% 22% 20% 6%	2977
June	1st to 10th	Night	35% 5% 10% 30% 18% 3	1520
	11th to 20th	Night	35% 6% 14% 25% 18% 2	1520
	21st to end	Night	33% 6% 13% 28% 19% 1	1520
July	1st to 10th	Night	28% 7% 12% 29% 20% 4	1480
	11th to 20th	Night	31% 5% 13% 29% 20% 3	1472
	21st to end	Night	28% 7% 16% 25% 21% 3	1670
August	1st to 10th	Night	30% 7% 15% 32% 15% 1	1600
	11th to 20th	Night	31% 8% 13% 32% 13% 3	1598
	21st to end	Night	32% 6% 12% 28% 21% 2	1838
September	1st to 10th	Night	35% 7% 12% 27% 17% 2	1880
	11th to 20th	Night	32% 6% 10% 31% 21% 1	1980
	21st to end	Night	39% 5% 13% 27% 15% 1	1980
October	1st to 10th	Night	41% 5% 10% 25% 18% 1	2005
	11th to 20th	Night	52% 5% 11% 20% 11% 1	2160
	21st to end	Night	54% 5% 11% 21% 9% 1	2558
November	1st to 10th	Night	44% 5% 10% 25% 15% 1	2406
	11th to 20th	Night	53% 6% 13% 19% 8% 1	2470
	21st to end	Night	58% 6% 11% 18% 6% 1	2487
December	1st to 10th	Night	67% 5% 10% 13% 5%	2660
	11th to 20th	Night	63% 6% 11% 14% 6% 1	3417
	21st to end	Night	76% 5% 10% 7% 2	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	21% 18% 37% 16% 6% 1	270
	11th to 20th	Day	20% 17% 45% 13% 4 1	270
	21st to end	Day	30% 17% 28% 18% 6%	297
February	1st to 10th	Day	26% 21% 36% 14% 3 1	270
	11th to 20th	Day	23% 21% 39% 16% 1	270
	21st to end	Day	25% 28% 35% 9% 3	225
March	1st to 10th	Day	23% 21% 38% 14% 3	284
	11th to 20th	Day	21% 13% 34% 23% 8% 1	460
	21st to end	Day	27% 13% 33% 20% 5% 1	506
April	1st to 10th	Day	20% 17% 34% 21% 7% 2	460
	11th to 20th	Day	25% 18% 32% 14% 6% 5%	452
	21st to end	Day	22% 13% 33% 20% 11% 1	460
May	1st to 10th	Day	22% 16% 28% 22% 10% 2	463
	11th to 20th	Day	21% 8% 29% 21% 15% 6%	487
	21st to end	Day	17% 7% 22% 26% 20% 8%	587
June	1st to 10th	Day	12% 10% 27% 30% 17% 5%	680
	11th to 20th	Day	14% 6% 31% 28% 17% 5%	680
	21st to end	Day	12% 8% 29% 30% 16% 6%	680
July	1st to 10th	Day	9% 6% 21% 29% 24% 11%	671
	11th to 20th	Day	12% 6% 26% 28% 18% 9%	668
	21st to end	Day	10% 5% 21% 31% 24% 9%	635
August	1st to 10th	Day	9% 2 22% 26% 23% 18%	446
	11th to 20th	Day	13% 5% 17% 26% 26% 14%	439
	21st to end	Day	11% 4 23% 26% 25% 11%	495
September	1st to 10th	Day	14% 7% 19% 26% 22% 12%	450
	11th to 20th	Day	10% 5% 20% 22% 30% 14%	450
	21st to end	Day	17% 10% 20% 23% 21% 9%	450
October	1st to 10th	Day	18% 8% 30% 21% 14% 8%	450
	11th to 20th	Day	20% 17% 27% 28% 7% 1	450
	21st to end	Day	30% 15% 37% 14% 4	311
November	1st to 10th	Day	19% 17% 35% 20% 9% 1	270
	11th to 20th	Day	22% 22% 33% 17% 5% 1	270
	21st to end	Day	26% 19% 39% 12% 4	259
December	1st to 10th	Day	27% 18% 32% 17% 7% 1	180
	11th to 20th	Day	21% 24% 40% 10% 3	202
	21st to end	Day	27% 24% 33% 15% 1	297
January	1st to 10th	Night	23% 15% 35% 21% 5% 1	950
	11th to 20th	Night	25% 15% 34% 22% 4 1	950
	21st to end	Night	19% 12% 36% 26% 6%	932
February	1st to 10th	Night	25% 13% 37% 23% 2	760
	11th to 20th	Night	23% 13% 36% 24% 3	743
	21st to end	Night	24% 18% 35% 20% 4	628
March	1st to 10th	Night	22% 13% 35% 23% 6%	760
	11th to 20th	Night	16% 15% 38% 25% 5% 1	760
	21st to end	Night	22% 11% 32% 27% 7% 1	836
April	1st to 10th	Night	20% 15% 36% 24% 4 1	615
	11th to 20th	Night	22% 10% 36% 25% 6% 1	563
	21st to end	Night	21% 8% 34% 29% 7% 1	570
May	1st to 10th	Night	19% 6% 33% 32% 8% 1	570
	11th to 20th	Night	22% 5% 29% 31% 12% 1	561
	21st to end	Night	12% 3 26% 39% 18% 2	617
June	1st to 10th	Night	11% 5% 26% 43% 14% 1	570
	11th to 20th	Night	13% 4 25% 41% 18%	570
	21st to end	Night	11% 4 23% 44% 17% 2	570
July	1st to 10th	Night	9% 2 18% 41% 28% 3	555
	11th to 20th	Night	10% 3 19% 40% 24% 3	552
	21st to end	Night	5% 2 20% 49% 22% 2	624
August	1st to 10th	Night	8% 2 14% 45% 27% 3	537
	11th to 20th	Night	11% 3 16% 38% 27% 5%	534
	21st to end	Night	11% 3 18% 36% 29% 4	594
September	1st to 10th	Night	12% 3 20% 35% 25% 4	620
	11th to 20th	Night	13% 3 18% 35% 27% 4	720
	21st to end	Night	16% 7% 22% 30% 21% 4	720
October	1st to 10th	Night	16% 8% 27% 30% 18% 2	720
	11th to 20th	Night	24% 13% 28% 27% 7% 1	720
	21st to end	Night	26% 11% 34% 23% 5%	792
November	1st to 10th	Night	20% 10% 31% 28% 9% 1	740
	11th to 20th	Night	22% 16% 34% 22% 6% 1	760
	21st to end	Night	25% 12% 34% 24% 5%	760
December	1st to 10th	Night	24% 16% 34% 20% 5%	760
	11th to 20th	Night	22% 13% 41% 20% 3 1	938
	21st to end	Night	31% 12% 37% 18% 2	1045

Page generated at 2024-07-28 09:52:11. Version ac07

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