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 2025-01-07.

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% 5% 4 5% 7% 33%	104411
	Night	14% 12% 4 9% 5% 4 4 3 5% 6% 33%	104650
Transparency	Day	48% 6% 11% 21% 12% 1	108011
	Night	50% 5% 11% 21% 12% 1	109189
Seeing	Day	18% 12% 28% 23% 14% 6%	15736
	Night	19% 10% 30% 29% 11% 1	25844

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%	2575
	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	11% 6% 2 8% 5% 5% 5% 4 8% 9% 36%	4440
	11th to 20th	Day	8% 4 1 5% 4 4 5% 5% 7% 10% 48%	4440
	21st to end	Day	6% 6% 2 6% 5% 5% 6% 5% 8% 9% 41%	4637
August	1st to 10th	Day	12% 5% 3 6% 4 5% 5% 4 6% 8% 42%	4104
	11th to 20th	Day	11% 7% 2 6% 5% 4 5% 4 6% 9% 41%	4044
	21st to end	Day	8% 6% 2 7% 5% 5% 5% 5% 7% 8% 41%	4418
September	1st to 10th	Day	11% 7% 2 7% 5% 5% 4 4 6% 8% 40%	2176
	11th to 20th	Day	10% 6% 1 6% 4 4 4 4 5% 8% 48%	2090
	21st to end	Day	14% 7% 2 6% 4 5% 5% 5% 7% 7% 37%	2090
October	1st to 10th	Day	14% 7% 2 7% 5% 4 5% 3 5% 6% 41%	2062
	11th to 20th	Day	19% 10% 4 8% 4 4 5% 3 5% 6% 32%	1900
	21st to end	Day	20% 11% 4 7% 5% 4 4 4 4 7% 29%	1895
November	1st to 10th	Day	12% 12% 3 7% 5% 4 4 4 5% 7% 37%	1762
	11th to 20th	Day	15% 15% 4 10% 5% 4 4 4 5% 7% 27%	1800
	21st to end	Day	18% 16% 6% 9% 5% 4 3 3 5% 6% 26%	1775
December	1st to 10th	Day	13% 17% 7% 13% 6% 5% 4 3 5% 7% 20%	2600
	11th to 20th	Day	17% 22% 7% 11% 5% 5% 4 3 4 5% 17%	2749
	21st to end	Day	24% 21% 8% 13% 5% 3 3 3 3 4 13%	3982
January	1st to 10th	Night	16% 17% 7% 13% 6% 5% 4 3 4 5% 21%	4513
	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	8% 4 2 6% 4 4 5% 5% 7% 10% 45%	2530
	11th to 20th	Night	9% 4 2 4 3 4 3 3 6% 7% 54%	2530
	21st to end	Night	5% 5% 3 6% 5% 4 4 5% 7% 9% 48%	2920
August	1st to 10th	Night	10% 5% 2 5% 4 4 4 3 6% 8% 47%	2825
	11th to 20th	Night	11% 5% 2 5% 3 4 4 4 5% 8% 49%	2785
	21st to end	Night	9% 6% 2 7% 4 4 5% 3 5% 7% 48%	3236
September	1st to 10th	Night	9% 6% 2 6% 5% 4 4 4 5% 7% 48%	1985
	11th to 20th	Night	10% 5% 1 5% 3 3 4 3 4 6% 56%	2090
	21st to end	Night	14% 7% 2 6% 4 4 5% 4 5% 7% 42%	2090
October	1st to 10th	Night	15% 6% 3 6% 4 3 4 3 5% 6% 45%	2117
	11th to 20th	Night	19% 11% 3 7% 4 4 4 3 5% 5% 34%	2280
	21st to end	Night	21% 10% 3 7% 5% 4 4 4 5% 6% 32%	2701
November	1st to 10th	Night	15% 9% 3 6% 4 4 4 3 5% 6% 41%	2536
	11th to 20th	Night	15% 12% 4 9% 5% 5% 5% 5% 6% 6% 28%	2600
	21st to end	Night	19% 16% 5% 8% 5% 4 4 3 5% 5% 27%	2618
December	1st to 10th	Night	12% 16% 7% 15% 6% 5% 4 3 5% 5% 21%	4580
	11th to 20th	Night	15% 21% 7% 12% 7% 5% 4 3 4 5% 18%	5433
	21st to end	Night	23% 22% 7% 11% 5% 4 3 2 4 4 14%	6996

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% 10% 13% 4	2576
	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	42% 7% 14% 20% 16% 2	4371
	11th to 20th	Day	30% 6% 14% 33% 16% 1	4365
	21st to end	Day	36% 8% 14% 19% 21% 2	4490
August	1st to 10th	Day	39% 7% 12% 24% 17% 1	4091
	11th to 20th	Day	38% 6% 10% 32% 12% 1	4083
	21st to end	Day	37% 7% 13% 28% 13% 1	4417
September	1st to 10th	Day	40% 6% 13% 25% 13% 2	2176
	11th to 20th	Day	34% 6% 11% 32% 16% 1	2090
	21st to end	Day	43% 7% 12% 24% 13%	2090
October	1st to 10th	Day	33% 4 10% 32% 20% 1	3426
	11th to 20th	Day	41% 4 10% 26% 18%	3140
	21st to end	Day	47% 4 12% 25% 11% 1	3095
November	1st to 10th	Day	46% 5% 12% 23% 12% 1	1762
	11th to 20th	Day	56% 5% 13% 18% 8% 1	1800
	21st to end	Day	59% 5% 12% 16% 6% 1	1775
December	1st to 10th	Day	65% 6% 16% 11% 3	2600
	11th to 20th	Day	70% 5% 9% 12% 4	2745
	21st to end	Day	76% 4 7% 9% 4	3982
January	1st to 10th	Night	65% 6% 9% 14% 5% 1	4513
	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	32% 6% 13% 28% 14% 6%	2490
	11th to 20th	Night	28% 6% 12% 31% 21% 2	2482
	21st to end	Night	31% 7% 17% 19% 23% 2	2827
August	1st to 10th	Night	34% 5% 15% 28% 17% 1	2814
	11th to 20th	Night	33% 7% 10% 37% 12% 2	2812
	21st to end	Night	36% 6% 11% 32% 15% 1	3236
September	1st to 10th	Night	34% 7% 12% 27% 18% 2	1985
	11th to 20th	Night	30% 5% 10% 31% 22% 2	2090
	21st to end	Night	41% 5% 13% 26% 15% 1	2090
October	1st to 10th	Night	26% 3 11% 33% 26% 1	3533
	11th to 20th	Night	44% 4 11% 23% 18%	3779
	21st to end	Night	41% 3 11% 31% 13% 1	4451
November	1st to 10th	Night	44% 5% 10% 26% 14% 1	2536
	11th to 20th	Night	54% 6% 13% 18% 8% 1	2600
	21st to end	Night	59% 5% 11% 18% 6% 1	2618
December	1st to 10th	Night	65% 5% 14% 13% 3	4580
	11th to 20th	Night	69% 5% 9% 12% 5% 1	5435
	21st to end	Night	75% 4 8% 7% 6%	6996

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	20% 18% 39% 16% 6% 1	288
	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	9% 5% 21% 32% 24% 9%	638
August	1st to 10th	Day	10% 2 23% 26% 23% 16%	486
	11th to 20th	Day	14% 5% 16% 27% 25% 13%	479
	21st to end	Day	11% 4 22% 27% 26% 11%	539
September	1st to 10th	Day	13% 7% 20% 26% 21% 12%	490
	11th to 20th	Day	9% 5% 19% 22% 30% 16%	490
	21st to end	Day	19% 9% 20% 23% 20% 8%	490
October	1st to 10th	Day	17% 9% 29% 22% 15% 8%	490
	11th to 20th	Day	20% 16% 27% 29% 8% 1	490
	21st to end	Day	28% 15% 38% 14% 5%	344
November	1st to 10th	Day	19% 17% 36% 19% 8% 1	300
	11th to 20th	Day	24% 21% 32% 17% 4 1	300
	21st to end	Day	26% 19% 39% 13% 4	287
December	1st to 10th	Day	26% 17% 33% 17% 8% 1	200
	11th to 20th	Day	23% 25% 38% 11% 3	225
	21st to end	Day	28% 23% 31% 15% 2	330
January	1st to 10th	Night	23% 15% 35% 21% 5% 1	981
	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	567
	11th to 20th	Night	11% 3 17% 39% 26% 5%	564
	21st to end	Night	11% 3 17% 37% 28% 3	627
September	1st to 10th	Night	12% 4 21% 35% 25% 4	655
	11th to 20th	Night	12% 3 17% 36% 29% 4	760
	21st to end	Night	17% 7% 22% 31% 20% 4	760
October	1st to 10th	Night	16% 7% 28% 31% 18% 1	760
	11th to 20th	Night	24% 12% 28% 27% 8% 1	760
	21st to end	Night	25% 11% 35% 24% 6%	836
November	1st to 10th	Night	20% 11% 31% 28% 9% 1	780
	11th to 20th	Night	22% 16% 34% 22% 6% 1	800
	21st to end	Night	25% 12% 35% 23% 5%	800
December	1st to 10th	Night	24% 16% 34% 21% 5%	800
	11th to 20th	Night	23% 13% 40% 20% 3 1	988
	21st to end	Night	31% 12% 37% 18% 2	1100

Page generated at 2025-01-04 03:24:00. Version ac07

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