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 2024-01-17.

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% 10% 4 7% 6% 3 5% 5% 5% 7% 33%	74537
	Night	15% 10% 4 7% 6% 3 5% 4 5% 6% 34%	75284
Transparency	Day	49% 6% 11% 20% 12% 1	74244
	Night	50% 6% 11% 20% 12% 1	75097
Seeing	Day	18% 11% 28% 23% 14% 6%	14403
	Night	19% 10% 30% 29% 11% 1	24544

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	16% 15% 7% 11% 7% 4 5% 6% 5% 5% 19%	1517
	11th to 20th	Day	15% 17% 8% 11% 9% 6% 5% 5% 4 5% 16%	1488
	21st to end	Day	16% 19% 9% 11% 9% 3 4 3 3 5% 17%	1688
February	1st to 10th	Day	15% 14% 7% 11% 10% 3 5% 5% 5% 6% 19%	1620
	11th to 20th	Day	15% 12% 6% 13% 9% 5% 4 4 3 5% 23%	1723
	21st to end	Day	15% 16% 7% 11% 7% 3 4 5% 4 5% 23%	1480
March	1st to 10th	Day	14% 12% 5% 8% 9% 4 5% 5% 4 6% 29%	1813
	11th to 20th	Day	13% 12% 6% 9% 7% 3 4 4 4 7% 32%	1980
	21st to end	Day	18% 14% 3 8% 6% 4 4 3 4 6% 29%	2178
April	1st to 10th	Day	17% 13% 4 7% 6% 3 5% 4 5% 6% 30%	2132
	11th to 20th	Day	17% 9% 4 7% 5% 3 5% 5% 5% 6% 35%	2257
	21st to end	Day	17% 8% 4 7% 7% 3 5% 4 5% 7% 34%	2340
May	1st to 10th	Day	17% 9% 4 5% 6% 4 5% 5% 6% 6% 33%	2340
	11th to 20th	Day	19% 7% 3 6% 5% 3 5% 4 5% 7% 37%	2301
	21st to end	Day	13% 6% 3 5% 5% 4 4 5% 6% 10% 39%	2585
June	1st to 10th	Day	10% 6% 3 5% 6% 3 4 6% 6% 8% 43%	2520
	11th to 20th	Day	12% 5% 3 6% 6% 4 5% 5% 6% 8% 41%	2520
	21st to end	Day	10% 6% 2 5% 6% 4 5% 6% 7% 10% 40%	2520
July	1st to 10th	Day	7% 4 2 5% 5% 3 5% 5% 7% 10% 46%	2520
	11th to 20th	Day	10% 5% 2 5% 6% 3 5% 5% 7% 8% 44%	2520
	21st to end	Day	7% 5% 2 5% 6% 4 5% 6% 9% 9% 42%	2648
August	1st to 10th	Day	10% 4 3 6% 6% 4 6% 6% 6% 9% 41%	2327
	11th to 20th	Day	10% 6% 3 6% 6% 4 5% 6% 6% 9% 39%	2303
	21st to end	Day	10% 6% 3 5% 5% 4 4 6% 6% 8% 44%	2516
September	1st to 10th	Day	11% 7% 3 6% 6% 4 4 5% 7% 8% 39%	2062
	11th to 20th	Day	11% 6% 2 6% 4 3 4 5% 5% 9% 46%	1980
	21st to end	Day	14% 6% 3 5% 5% 4 5% 6% 7% 8% 38%	1980
October	1st to 10th	Day	14% 6% 3 6% 7% 3 4 4 5% 6% 40%	1954
	11th to 20th	Day	19% 9% 4 7% 6% 3 4 5% 5% 6% 31%	1800
	21st to end	Day	21% 11% 4 7% 7% 4 4 4 4 7% 29%	1796
November	1st to 10th	Day	13% 11% 4 6% 6% 3 5% 5% 5% 7% 38%	1672
	11th to 20th	Day	15% 13% 5% 9% 6% 3 4 5% 5% 7% 29%	1710
	21st to end	Day	18% 15% 6% 7% 5% 3 4 4 5% 6% 27%	1687
December	1st to 10th	Day	15% 16% 8% 11% 8% 4 4 4 3 6% 21%	1520
	11th to 20th	Day	15% 16% 6% 10% 6% 4 5% 6% 5% 7% 21%	1757
	21st to end	Day	23% 22% 9% 11% 7% 3 4 4 3 4 10%	2783
January	1st to 10th	Night	18% 13% 6% 11% 7% 4 5% 4 4 5% 22%	2648
	11th to 20th	Night	18% 16% 8% 11% 7% 3 5% 4 5% 5% 19%	2617
	21st to end	Night	13% 15% 8% 12% 8% 4 6% 4 4 6% 20%	2665
February	1st to 10th	Night	18% 16% 6% 9% 8% 4 6% 4 4 4 21%	2340
	11th to 20th	Night	14% 13% 6% 10% 9% 4 5% 5% 4 4 26%	2120
	21st to end	Night	18% 13% 4 9% 7% 3 5% 4 4 6% 27%	1776
March	1st to 10th	Night	15% 11% 5% 8% 6% 3 5% 4 5% 6% 33%	2147
	11th to 20th	Night	12% 11% 4 6% 5% 3 5% 5% 5% 6% 38%	1980
	21st to end	Night	20% 9% 3 7% 6% 3 5% 4 4 6% 33%	2178
April	1st to 10th	Night	15% 11% 4 6% 5% 2 5% 5% 5% 6% 36%	1843
	11th to 20th	Night	19% 8% 3 6% 4 3 4 4 5% 6% 37%	1651
	21st to end	Night	18% 8% 3 6% 4 2 5% 5% 4 7% 38%	1620
May	1st to 10th	Night	17% 8% 4 6% 6% 3 4 5% 6% 7% 34%	1620
	11th to 20th	Night	20% 6% 3 5% 4 2 4 4 6% 7% 39%	1592
	21st to end	Night	10% 4 2 6% 6% 4 5% 5% 5% 9% 45%	1686
June	1st to 10th	Night	12% 5% 2 5% 5% 3 4 3 6% 9% 46%	1440
	11th to 20th	Night	11% 5% 3 5% 4 2 4 4 6% 9% 46%	1440
	21st to end	Night	9% 6% 3 5% 4 3 4 4 5% 10% 47%	1440
July	1st to 10th	Night	7% 3 2 4 5% 2 4 5% 6% 9% 53%	1440
	11th to 20th	Night	9% 5% 2 4 4 3 4 4 6% 8% 51%	1440
	21st to end	Night	6% 4 3 4 4 3 5% 4 6% 9% 52%	1669
August	1st to 10th	Night	8% 4 2 4 5% 3 5% 5% 6% 10% 47%	1611
	11th to 20th	Night	8% 4 2 5% 4 4 4 5% 5% 9% 50%	1598
	21st to end	Night	9% 5% 2 5% 4 3 4 4 5% 7% 51%	1838
September	1st to 10th	Night	10% 6% 2 5% 5% 3 4 5% 5% 7% 47%	1880
	11th to 20th	Night	11% 5% 2 4 4 3 4 4 4 6% 54%	1980
	21st to end	Night	14% 6% 3 5% 5% 3 5% 4 5% 7% 44%	1980
October	1st to 10th	Night	15% 6% 3 6% 5% 3 4 4 5% 6% 44%	2005
	11th to 20th	Night	19% 11% 4 6% 5% 3 4 4 5% 5% 33%	2160
	21st to end	Night	22% 10% 3 6% 6% 3 4 5% 4 5% 31%	2558
November	1st to 10th	Night	15% 8% 3 6% 5% 3 4 4 4 7% 41%	2406
	11th to 20th	Night	16% 11% 4 7% 6% 4 5% 6% 6% 6% 29%	2470
	21st to end	Night	20% 14% 5% 7% 5% 3 4 4 5% 6% 28%	2487
December	1st to 10th	Night	17% 16% 7% 11% 7% 4 5% 5% 4 5% 19%	2660
	11th to 20th	Night	14% 15% 7% 11% 8% 4 5% 5% 5% 6% 21%	3415
	21st to end	Night	25% 23% 7% 9% 6% 3 4 3 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% 5% 9% 14% 5%	1518
	11th to 20th	Day	70% 6% 11% 8% 5%	1488
	21st to end	Day	72% 4 6% 12% 6% 1	1688
February	1st to 10th	Day	65% 7% 8% 14% 6%	1620
	11th to 20th	Day	64% 4 8% 14% 8% 1	1733
	21st to end	Day	63% 4 9% 15% 6% 2	1480
March	1st to 10th	Day	55% 5% 12% 18% 9% 1	1813
	11th to 20th	Day	52% 5% 10% 18% 13% 2	1980
	21st to end	Day	57% 4 9% 19% 9% 1	2178
April	1st to 10th	Day	56% 5% 10% 18% 11%	2132
	11th to 20th	Day	49% 6% 11% 19% 14% 2	2257
	21st to end	Day	50% 5% 13% 16% 14% 2	2340
May	1st to 10th	Day	50% 6% 11% 21% 10% 2	2340
	11th to 20th	Day	47% 6% 11% 20% 14% 2	2305
	21st to end	Day	41% 6% 14% 24% 14% 2	2585
June	1st to 10th	Day	37% 7% 12% 28% 14% 2	2520
	11th to 20th	Day	39% 7% 11% 24% 17% 2	2520
	21st to end	Day	38% 8% 13% 22% 16% 2	2520
July	1st to 10th	Day	32% 8% 11% 27% 19% 4	2451
	11th to 20th	Day	35% 6% 13% 26% 18% 2	2445
	21st to end	Day	34% 9% 12% 24% 18% 3	2501
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	64% 5% 9% 16% 6%	2648
	11th to 20th	Night	67% 5% 12% 10% 5%	2617
	21st to end	Night	66% 5% 11% 13% 6% 1	2665
February	1st to 10th	Night	67% 5% 10% 12% 6% 1	2340
	11th to 20th	Night	61% 6% 7% 16% 9% 1	2121
	21st to end	Night	58% 5% 11% 16% 9% 2	1776
March	1st to 10th	Night	52% 5% 10% 22% 10% 1	2147
	11th to 20th	Night	46% 6% 10% 22% 14% 2	1980
	21st to end	Night	53% 5% 9% 21% 11% 2	2178
April	1st to 10th	Night	48% 5% 10% 21% 14% 1	1843
	11th to 20th	Night	47% 5% 11% 18% 17% 2	1651
	21st to end	Night	46% 5% 12% 19% 16% 3	1620
May	1st to 10th	Night	49% 6% 11% 21% 11% 2	1620
	11th to 20th	Night	44% 6% 9% 20% 18% 4	1593
	21st to end	Night	37% 6% 14% 25% 15% 3	1687
June	1st to 10th	Night	35% 5% 10% 30% 18% 3	1440
	11th to 20th	Night	35% 6% 14% 25% 18% 2	1440
	21st to end	Night	33% 6% 13% 28% 19% 1	1440
July	1st to 10th	Night	27% 7% 12% 29% 21% 4	1400
	11th to 20th	Night	31% 6% 13% 29% 20% 3	1392
	21st to end	Night	28% 7% 15% 25% 21% 3	1576
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	19% 18% 45% 12% 4 1	258
	21st to end	Day	29% 17% 30% 17% 6%	264
February	1st to 10th	Day	28% 21% 37% 13% 2	240
	11th to 20th	Day	25% 22% 39% 14% 1	240
	21st to end	Day	27% 30% 32% 9% 2	198
March	1st to 10th	Day	23% 22% 38% 13% 3	253
	11th to 20th	Day	20% 14% 33% 24% 8% 1	420
	21st to end	Day	28% 13% 33% 20% 5% 1	462
April	1st to 10th	Day	20% 15% 33% 22% 8% 2	420
	11th to 20th	Day	25% 17% 31% 14% 7% 5%	412
	21st to end	Day	23% 12% 33% 20% 11% 1	420
May	1st to 10th	Day	24% 14% 28% 22% 11% 2	423
	11th to 20th	Day	21% 8% 30% 21% 13% 6%	447
	21st to end	Day	17% 6% 21% 26% 20% 9%	539
June	1st to 10th	Day	11% 8% 27% 31% 18% 5%	630
	11th to 20th	Day	14% 7% 30% 27% 18% 5%	630
	21st to end	Day	11% 8% 28% 30% 17% 6%	630
July	1st to 10th	Day	8% 5% 20% 29% 26% 12%	621
	11th to 20th	Day	12% 6% 26% 28% 19% 9%	618
	21st to end	Day	10% 5% 22% 32% 23% 9%	589
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% 21% 4 1	935
	21st to end	Night	18% 12% 37% 27% 6%	883
February	1st to 10th	Night	26% 14% 37% 22% 2	720
	11th to 20th	Night	23% 13% 36% 24% 3	703
	21st to end	Night	24% 17% 35% 20% 4	592
March	1st to 10th	Night	22% 13% 35% 23% 7%	720
	11th to 20th	Night	17% 14% 37% 25% 6% 1	720
	21st to end	Night	23% 11% 32% 27% 7% 1	792
April	1st to 10th	Night	19% 15% 36% 25% 4 1	583
	11th to 20th	Night	22% 9% 35% 26% 6% 1	533
	21st to end	Night	21% 8% 34% 29% 8% 1	540
May	1st to 10th	Night	20% 6% 33% 32% 8% 1	540
	11th to 20th	Night	23% 5% 29% 30% 13% 1	531
	21st to end	Night	12% 3 25% 39% 19% 2	584
June	1st to 10th	Night	11% 4 26% 44% 15% 1	540
	11th to 20th	Night	13% 4 24% 41% 18%	540
	21st to end	Night	11% 3 22% 44% 18% 2	540
July	1st to 10th	Night	9% 2 17% 40% 29% 3	525
	11th to 20th	Night	11% 4 18% 41% 24% 3	522
	21st to end	Night	5% 2 21% 48% 21% 2	591
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

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