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 2026-05-02.

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	13% 11% 4 9% 5% 5% 5% 4 5% 7% 33%	130789
	Night	14% 12% 4 9% 5% 5% 4 3 5% 6% 33%	131849
Transparency	Day	49% 5% 11% 21% 12% 1	134344
	Night	50% 5% 11% 21% 12% 1	136365
Seeing	Day	18% 12% 29% 23% 14% 5%	17494
	Night	19% 10% 30% 29% 11% 1	27643

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	12% 19% 7% 17% 6% 5% 4 3 4 4 19%	4691
	11th to 20th	Day	13% 16% 8% 19% 10% 10% 5% 3 3 3 10%	4710
	21st to end	Day	18% 17% 6% 12% 10% 5% 7% 3 3 4 15%	5492
February	1st to 10th	Day	14% 15% 6% 12% 8% 5% 5% 3 6% 6% 21%	1890
	11th to 20th	Day	14% 13% 6% 13% 8% 6% 4 3 4 5% 23%	2019
	21st to end	Day	13% 17% 6% 12% 6% 4 5% 4 4 5% 24%	1730
March	1st to 10th	Day	14% 13% 4 10% 6% 4 4 4 4 6% 31%	4622
	11th to 20th	Day	12% 12% 4 9% 6% 4 4 3 5% 8% 33%	5090
	21st to end	Day	17% 16% 4 10% 5% 4 4 3 4 5% 28%	5586
April	1st to 10th	Day	17% 14% 3 8% 5% 4 5% 3 5% 5% 30%	2488
	11th to 20th	Day	16% 10% 4 8% 4 4 4 4 5% 6% 35%	2638
	21st to end	Day	16% 9% 3 8% 5% 5% 4 4 5% 7% 34%	2730
May	1st to 10th	Day	20% 10% 3 6% 4 4 4 3 5% 6% 34%	5875
	11th to 20th	Day	15% 8% 3 8% 5% 4 5% 4 6% 8% 35%	5861
	21st to end	Day	15% 7% 2 7% 4 4 4 3 5% 8% 41%	6585
June	1st to 10th	Day	10% 7% 2 6% 5% 4 5% 5% 6% 8% 43%	2800
	11th to 20th	Day	11% 6% 3 7% 5% 5% 5% 4 6% 8% 41%	2800
	21st to end	Day	10% 6% 2 6% 5% 5% 5% 6% 7% 9% 39%	2800
July	1st to 10th	Day	9% 6% 2 7% 5% 5% 5% 4 8% 10% 38%	6360
	11th to 20th	Day	8% 5% 2 6% 4 4 5% 4 6% 9% 47%	6360
	21st to end	Day	7% 6% 2 6% 4 4 5% 4 7% 9% 45%	6665
August	1st to 10th	Day	12% 5% 3 6% 4 5% 5% 4 6% 8% 42%	4234
	11th to 20th	Day	11% 7% 2 6% 5% 4 5% 4 6% 9% 41%	4174
	21st to end	Day	8% 6% 2 7% 5% 5% 5% 5% 7% 8% 42%	4557
September	1st to 10th	Day	10% 7% 2 7% 5% 5% 4 4 7% 8% 41%	2290
	11th to 20th	Day	9% 6% 1 6% 4 4 4 4 5% 9% 49%	2200
	21st to end	Day	15% 7% 3 7% 4 5% 5% 5% 7% 7% 37%	2200
October	1st to 10th	Day	14% 6% 2 7% 5% 4 5% 3 5% 6% 43%	2170
	11th to 20th	Day	18% 10% 4 8% 4 4 5% 4 5% 6% 33%	2000
	21st to end	Day	19% 11% 4 7% 5% 4 4 4 4 7% 30%	1994
November	1st to 10th	Day	12% 12% 3 7% 5% 4 4 4 5% 7% 37%	1852
	11th to 20th	Day	14% 15% 4 10% 5% 4 4 4 5% 7% 28%	1890
	21st to end	Day	17% 16% 6% 9% 5% 4 3 3 5% 6% 25%	1864
December	1st to 10th	Day	13% 17% 7% 13% 6% 5% 4 3 5% 6% 19%	2680
	11th to 20th	Day	16% 21% 7% 11% 6% 5% 4 3 4 5% 17%	2822
	21st to end	Day	24% 21% 8% 13% 5% 3 3 2 3 4 13%	4070
January	1st to 10th	Night	14% 16% 7% 15% 6% 5% 4 3 4 5% 22%	8232
	11th to 20th	Night	10% 17% 8% 16% 9% 9% 6% 4 5% 5% 14%	8280
	21st to end	Night	14% 16% 7% 12% 6% 6% 6% 4 4 5% 20%	8701
February	1st to 10th	Night	16% 16% 5% 11% 7% 5% 5% 3 4 4 23%	2730
	11th to 20th	Night	13% 14% 6% 12% 7% 6% 4 4 4 5% 27%	2484
	21st to end	Night	16% 13% 4 10% 6% 4 5% 4 5% 6% 27%	2076
March	1st to 10th	Night	14% 11% 4 9% 5% 4 4 3 5% 7% 35%	5451
	11th to 20th	Night	10% 10% 4 7% 4 4 4 4 5% 8% 41%	5090
	21st to end	Night	16% 11% 4 8% 5% 4 4 3 5% 5% 35%	5588
April	1st to 10th	Night	16% 13% 3 7% 5% 3 4 4 5% 6% 35%	2149
	11th to 20th	Night	18% 9% 3 6% 5% 4 4 3 6% 6% 36%	1930
	21st to end	Night	16% 8% 3 7% 4 4 5% 3 5% 7% 38%	1890
May	1st to 10th	Night	19% 10% 4 8% 5% 4 4 3 5% 6% 33%	4042
	11th to 20th	Night	16% 9% 3 7% 4 3 4 3 5% 6% 40%	4032
	21st to end	Night	13% 6% 2 7% 4 4 4 4 4 7% 44%	4272
June	1st to 10th	Night	11% 5% 2 6% 4 4 3 3 6% 9% 46%	1600
	11th to 20th	Night	11% 6% 3 6% 4 3 5% 4 6% 9% 45%	1600
	21st to end	Night	9% 6% 2 6% 4 4 3 4 6% 10% 47%	1600
July	1st to 10th	Night	8% 4 2 6% 4 4 5% 5% 7% 10% 47%	3618
	11th to 20th	Night	9% 5% 2 5% 4 4 4 4 6% 8% 50%	3617
	21st to end	Night	8% 6% 3 6% 4 4 3 4 5% 8% 48%	4182
August	1st to 10th	Night	10% 5% 2 5% 4 4 4 3 6% 8% 48%	2915
	11th to 20th	Night	11% 5% 2 5% 3 4 4 4 5% 8% 49%	2875
	21st to end	Night	8% 6% 2 7% 4 4 5% 3 5% 7% 48%	3338
September	1st to 10th	Night	9% 6% 2 5% 5% 4 4 4 4 7% 49%	2090
	11th to 20th	Night	9% 5% 1 5% 3 3 4 3 4 7% 57%	2200
	21st to end	Night	14% 7% 2 6% 4 4 5% 4 5% 7% 43%	2200
October	1st to 10th	Night	14% 6% 3 6% 4 4 4 3 5% 6% 47%	2229
	11th to 20th	Night	19% 11% 3 7% 4 4 4 3 5% 5% 35%	2400
	21st to end	Night	20% 10% 3 7% 5% 4 4 3 5% 5% 33%	2843
November	1st to 10th	Night	14% 9% 3 7% 4 4 4 3 5% 7% 41%	2666
	11th to 20th	Night	15% 12% 4 8% 5% 5% 5% 5% 6% 6% 29%	2730
	21st to end	Night	19% 16% 5% 8% 5% 4 4 3 5% 5% 26%	2749
December	1st to 10th	Night	12% 16% 7% 15% 6% 5% 4 3 5% 5% 21%	4720
	11th to 20th	Night	15% 20% 6% 13% 7% 5% 4 3 4 5% 18%	5580
	21st to end	Night	23% 22% 7% 11% 5% 4 3 2 3 4 14%	7150

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	68% 4 10% 13% 4	4692
	11th to 20th	Day	78% 4 8% 5% 4	4710
	21st to end	Day	73% 3 10% 8% 5%	5492
February	1st to 10th	Day	62% 6% 9% 16% 7%	1890
	11th to 20th	Day	64% 4 8% 14% 9% 1	2029
	21st to end	Day	62% 4 9% 16% 7% 2	1730
March	1st to 10th	Day	54% 3 13% 18% 9% 2	4622
	11th to 20th	Day	49% 5% 14% 21% 9% 1	5090
	21st to end	Day	58% 4 9% 16% 11% 2	5586
April	1st to 10th	Day	56% 5% 9% 19% 11% 1	2488
	11th to 20th	Day	49% 5% 10% 21% 13% 2	2638
	21st to end	Day	48% 5% 12% 19% 13% 1	2730
May	1st to 10th	Day	50% 5% 10% 19% 14% 3	5910
	11th to 20th	Day	46% 7% 12% 21% 13% 1	5865
	21st to end	Day	42% 5% 10% 22% 19% 3	6599
June	1st to 10th	Day	37% 7% 11% 28% 15% 2	2800
	11th to 20th	Day	39% 7% 12% 25% 16% 2	2800
	21st to end	Day	39% 8% 13% 22% 16% 2	2800
July	1st to 10th	Day	39% 6% 13% 25% 15% 1	6291
	11th to 20th	Day	32% 6% 13% 30% 18% 1	6285
	21st to end	Day	33% 7% 14% 24% 21% 1	6475
August	1st to 10th	Day	39% 6% 12% 24% 17% 1	4221
	11th to 20th	Day	38% 6% 11% 32% 12% 1	4213
	21st to end	Day	37% 7% 13% 29% 13% 1	4556
September	1st to 10th	Day	39% 6% 13% 27% 13% 2	2290
	11th to 20th	Day	33% 6% 12% 33% 16% 1	2200
	21st to end	Day	43% 7% 12% 24% 14%	2200
October	1st to 10th	Day	32% 4 9% 33% 20% 1	3534
	11th to 20th	Day	41% 4 10% 27% 18%	3240
	21st to end	Day	47% 4 12% 24% 12% 1	3194
November	1st to 10th	Day	46% 5% 12% 23% 12% 1	1852
	11th to 20th	Day	56% 4 13% 18% 8% 1	1890
	21st to end	Day	60% 5% 12% 17% 6% 1	1864
December	1st to 10th	Day	66% 5% 15% 11% 3	2680
	11th to 20th	Day	70% 5% 10% 12% 4	2818
	21st to end	Day	76% 4 7% 9% 4	4070
January	1st to 10th	Night	64% 4 9% 15% 6% 1	8233
	11th to 20th	Night	71% 5% 9% 9% 5%	8280
	21st to end	Night	66% 4 10% 14% 6%	8701
February	1st to 10th	Night	64% 5% 9% 14% 7% 1	2730
	11th to 20th	Night	60% 6% 8% 18% 8% 1	2485
	21st to end	Night	57% 5% 12% 16% 8% 1	2076
March	1st to 10th	Night	49% 4 13% 23% 10% 1	5451
	11th to 20th	Night	40% 6% 13% 25% 15% 1	5090
	21st to end	Night	50% 5% 11% 19% 13% 1	5588
April	1st to 10th	Night	50% 5% 10% 20% 13% 2	2149
	11th to 20th	Night	48% 5% 10% 18% 17% 2	1930
	21st to end	Night	44% 6% 13% 20% 16% 2	1890
May	1st to 10th	Night	51% 6% 10% 16% 13% 4	4069
	11th to 20th	Night	45% 6% 8% 26% 11% 4	4033
	21st to end	Night	39% 6% 10% 23% 18% 5%	4280
June	1st to 10th	Night	35% 5% 10% 29% 19% 2	1600
	11th to 20th	Night	36% 6% 13% 25% 17% 2	1600
	21st to end	Night	32% 6% 14% 28% 19% 1	1600
July	1st to 10th	Night	31% 6% 14% 28% 16% 5%	3580
	11th to 20th	Night	31% 6% 13% 29% 20% 1	3572
	21st to end	Night	34% 6% 13% 22% 24% 1	4060
August	1st to 10th	Night	33% 6% 15% 28% 18% 1	2904
	11th to 20th	Night	33% 7% 10% 37% 11% 2	2902
	21st to end	Night	35% 6% 11% 32% 14% 1	3338
September	1st to 10th	Night	34% 7% 11% 29% 17% 2	2090
	11th to 20th	Night	29% 5% 10% 32% 22% 2	2200
	21st to end	Night	41% 5% 13% 26% 15% 1	2200
October	1st to 10th	Night	26% 3 10% 33% 26% 1	3645
	11th to 20th	Night	44% 4 10% 23% 18% 1	3899
	21st to end	Night	41% 3 11% 31% 13% 1	4593
November	1st to 10th	Night	44% 5% 10% 26% 14% 1	2666
	11th to 20th	Night	53% 6% 13% 19% 8% 1	2730
	21st to end	Night	60% 5% 11% 18% 6% 1	2749
December	1st to 10th	Night	65% 5% 13% 13% 3	4720
	11th to 20th	Night	68% 5% 9% 12% 5% 1	5582
	21st to end	Night	75% 4 8% 7% 6%	7150

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	22% 17% 38% 16% 5% 1	330
	11th to 20th	Day	20% 21% 43% 11% 3 1	330
	21st to end	Day	29% 19% 28% 18% 5%	363
February	1st to 10th	Day	26% 21% 35% 13% 4 1	330
	11th to 20th	Day	24% 21% 38% 17% 1	330
	21st to end	Day	24% 29% 36% 9% 3	273
March	1st to 10th	Day	25% 20% 39% 14% 3	346
	11th to 20th	Day	23% 14% 34% 21% 7% 1	540
	21st to end	Day	26% 15% 35% 19% 4 1	594
April	1st to 10th	Day	21% 17% 36% 19% 6% 1	540
	11th to 20th	Day	25% 17% 33% 14% 7% 4	532
	21st to end	Day	21% 13% 32% 21% 11% 1	540
May	1st to 10th	Day	22% 15% 29% 22% 10% 2	507
	11th to 20th	Day	21% 8% 29% 21% 14% 6%	527
	21st to end	Day	17% 8% 23% 25% 19% 8%	634
June	1st to 10th	Day	12% 9% 28% 31% 16% 4	730
	11th to 20th	Day	14% 6% 30% 28% 17% 4	730
	21st to end	Day	12% 8% 28% 32% 15% 5%	730
July	1st to 10th	Day	9% 6% 21% 30% 24% 10%	721
	11th to 20th	Day	12% 6% 26% 28% 18% 9%	718
	21st to end	Day	10% 4 21% 32% 24% 9%	687
August	1st to 10th	Day	9% 2 21% 26% 25% 16%	526
	11th to 20th	Day	14% 5% 15% 27% 26% 12%	519
	21st to end	Day	11% 4 21% 27% 25% 11%	583
September	1st to 10th	Day	13% 8% 20% 25% 20% 14%	530
	11th to 20th	Day	8% 4 17% 22% 30% 18%	530
	21st to end	Day	19% 9% 19% 24% 20% 9%	530
October	1st to 10th	Day	16% 8% 29% 23% 16% 8%	530
	11th to 20th	Day	19% 14% 28% 29% 8% 1	530
	21st to end	Day	26% 16% 38% 16% 5%	377
November	1st to 10th	Day	20% 16% 35% 20% 8% 1	330
	11th to 20th	Day	25% 21% 32% 16% 5% 1	330
	21st to end	Day	26% 21% 38% 12% 4	316
December	1st to 10th	Day	25% 16% 33% 16% 8% 1	220
	11th to 20th	Day	24% 26% 36% 10% 3 1	248
	21st to end	Day	29% 22% 32% 15% 2	363
January	1st to 10th	Night	22% 16% 36% 21% 5% 1	1050
	11th to 20th	Night	23% 16% 35% 21% 4	1050
	21st to end	Night	19% 14% 37% 25% 5%	1030
February	1st to 10th	Night	24% 13% 37% 24% 2	840
	11th to 20th	Night	23% 14% 36% 24% 3	823
	21st to end	Night	23% 17% 36% 20% 3	692
March	1st to 10th	Night	22% 14% 35% 23% 6%	840
	11th to 20th	Night	18% 16% 37% 24% 5% 1	840
	21st to end	Night	22% 12% 33% 26% 6% 1	924
April	1st to 10th	Night	21% 15% 36% 22% 4 1	679
	11th to 20th	Night	22% 11% 35% 25% 7% 1	623
	21st to end	Night	19% 9% 34% 30% 7%	630
May	1st to 10th	Night	20% 6% 34% 32% 7% 1	603
	11th to 20th	Night	23% 5% 29% 30% 12% 1	591
	21st to end	Night	13% 3 26% 39% 17% 2	650
June	1st to 10th	Night	11% 5% 27% 43% 14% 1	600
	11th to 20th	Night	13% 4 24% 41% 18%	600
	21st to end	Night	11% 4 23% 44% 18% 2	600
July	1st to 10th	Night	9% 2 18% 41% 27% 3	585
	11th to 20th	Night	10% 3 18% 42% 24% 3	582
	21st to end	Night	6% 2 19% 49% 22% 2	657
August	1st to 10th	Night	8% 2 14% 45% 27% 3	597
	11th to 20th	Night	11% 3 17% 39% 26% 5%	594
	21st to end	Night	10% 3 17% 38% 28% 3	660
September	1st to 10th	Night	11% 4 21% 34% 25% 4	690
	11th to 20th	Night	12% 3 16% 35% 30% 4	800
	21st to end	Night	16% 6% 21% 31% 21% 4	800
October	1st to 10th	Night	15% 7% 27% 32% 18% 1	800
	11th to 20th	Night	23% 12% 28% 29% 8% 1	800
	21st to end	Night	24% 10% 35% 25% 6%	880
November	1st to 10th	Night	19% 11% 32% 28% 8% 1	820
	11th to 20th	Night	21% 16% 34% 23% 6% 1	840
	21st to end	Night	26% 12% 35% 23% 4	840
December	1st to 10th	Night	24% 16% 34% 21% 5%	840
	11th to 20th	Night	22% 14% 41% 20% 3 1	1038
	21st to end	Night	31% 13% 37% 17% 2	1155

Page generated at 2026-04-29 02:21:47. Version ac07

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