Cobleskill
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cobleskill clear sky chart from 2005-11-06 to 2025-10-19.

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	15% 10% 4 9% 5% 5% 5% 4 6% 7% 31%	126818
	Night	15% 11% 4 10% 5% 4 4 4 5% 6% 31%	122914
Transparency	Day	50% 7% 12% 20% 10% 1	130307
	Night	52% 7% 12% 18% 10% 1	127512
Seeing	Day	25% 18% 28% 18% 9% 3	16014
	Night	23% 18% 27% 23% 8% 1	25067

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	9% 14% 9% 21% 8% 4 3 3 4 4 20%	3597
	11th to 20th	Day	11% 17% 6% 15% 8% 4 5% 3 5% 5% 20%	3570
	21st to end	Day	15% 15% 6% 10% 5% 5% 4 4 5% 6% 25%	4208
February	1st to 10th	Day	14% 14% 6% 12% 8% 6% 5% 4 5% 5% 21%	1800
	11th to 20th	Day	10% 13% 6% 15% 8% 5% 5% 4 5% 5% 24%	1882
	21st to end	Day	16% 15% 4 10% 8% 4 4 4 4 6% 25%	1650
March	1st to 10th	Day	18% 15% 6% 10% 4 5% 4 3 4 5% 27%	4476
	11th to 20th	Day	13% 14% 5% 9% 4 4 4 3 4 5% 35%	4832
	21st to end	Day	17% 10% 4 10% 5% 5% 4 3 5% 5% 33%	5892
April	1st to 10th	Day	16% 15% 3 8% 5% 5% 5% 3 5% 5% 31%	2400
	11th to 20th	Day	16% 11% 4 7% 5% 5% 4 3 4 6% 35%	2374
	21st to end	Day	19% 12% 4 8% 4 4 4 4 4 6% 32%	2450
May	1st to 10th	Day	31% 9% 3 7% 4 4 4 4 5% 6% 24%	6111
	11th to 20th	Day	17% 9% 3 8% 6% 5% 5% 4 6% 6% 30%	6318
	21st to end	Day	18% 9% 3 8% 5% 5% 4 4 6% 8% 29%	6949
June	1st to 10th	Day	18% 7% 2 8% 5% 5% 5% 5% 6% 7% 33%	2800
	11th to 20th	Day	16% 7% 2 7% 5% 5% 5% 5% 7% 11% 30%	2800
	21st to end	Day	16% 6% 3 8% 6% 5% 5% 5% 6% 8% 33%	2800
July	1st to 10th	Day	9% 6% 3 8% 6% 5% 6% 5% 7% 9% 35%	6360
	11th to 20th	Day	8% 5% 2 7% 6% 6% 7% 5% 8% 11% 35%	6360
	21st to end	Day	13% 6% 2 7% 5% 5% 5% 4 6% 7% 41%	6926
August	1st to 10th	Day	17% 6% 3 7% 5% 5% 5% 4 5% 8% 34%	4465
	11th to 20th	Day	13% 7% 3 8% 5% 6% 6% 4 8% 9% 32%	3895
	21st to end	Day	12% 6% 2 8% 4 5% 5% 4 7% 9% 37%	4312
September	1st to 10th	Day	14% 6% 2 6% 4 4 5% 4 6% 7% 42%	2400
	11th to 20th	Day	12% 6% 2 6% 4 4 4 3 4 7% 47%	2339
	21st to end	Day	14% 7% 2 5% 4 5% 4 5% 7% 8% 37%	2200
October	1st to 10th	Day	18% 8% 3 7% 5% 5% 5% 4 6% 5% 36%	2040
	11th to 20th	Day	14% 9% 2 7% 5% 4 4 4 6% 8% 37%	1980
	21st to end	Day	21% 13% 2 7% 5% 3 5% 4 6% 6% 28%	1925
November	1st to 10th	Day	13% 12% 3 6% 4 4 4 3 5% 6% 39%	1761
	11th to 20th	Day	13% 15% 3 7% 5% 5% 5% 4 5% 6% 32%	1800
	21st to end	Day	15% 15% 4 8% 6% 4 5% 4 5% 6% 28%	1600
December	1st to 10th	Day	11% 17% 10% 14% 7% 5% 5% 4 6% 5% 16%	2600
	11th to 20th	Day	16% 16% 7% 10% 5% 4 4 3 4 6% 25%	2986
	21st to end	Day	16% 16% 7% 10% 6% 4 4 3 6% 6% 22%	3960
January	1st to 10th	Night	12% 12% 7% 21% 7% 4 5% 3 5% 5% 18%	6349
	11th to 20th	Night	9% 15% 5% 20% 8% 6% 5% 4 6% 5% 18%	6315
	21st to end	Night	13% 13% 5% 11% 7% 6% 5% 4 5% 7% 25%	6747
February	1st to 10th	Night	14% 13% 5% 11% 7% 5% 5% 5% 5% 6% 22%	2600
	11th to 20th	Night	11% 12% 6% 13% 8% 6% 5% 5% 6% 7% 22%	2402
	21st to end	Night	15% 12% 5% 12% 7% 5% 5% 4 5% 5% 24%	1980
March	1st to 10th	Night	16% 9% 4 11% 8% 5% 4 4 6% 7% 26%	5364
	11th to 20th	Night	14% 14% 5% 7% 5% 4 4 3 4 6% 34%	5125
	21st to end	Night	17% 13% 4 11% 5% 4 4 3 5% 5% 30%	5039
April	1st to 10th	Night	17% 13% 4 8% 6% 5% 5% 4 5% 6% 28%	2000
	11th to 20th	Night	18% 11% 3 6% 4 4 4 3 5% 6% 35%	1975
	21st to end	Night	18% 12% 3 6% 4 4 4 3 4 5% 36%	1949
May	1st to 10th	Night	32% 11% 2 6% 4 4 4 3 4 5% 24%	3871
	11th to 20th	Night	17% 11% 3 8% 4 5% 5% 4 5% 7% 32%	3575
	21st to end	Night	19% 9% 4 8% 5% 4 5% 4 6% 7% 29%	3926
June	1st to 10th	Night	14% 8% 2 7% 4 4 3 4 7% 8% 39%	1600
	11th to 20th	Night	16% 5% 2 6% 4 3 4 4 6% 9% 40%	1600
	21st to end	Night	12% 5% 2 6% 5% 5% 6% 4 7% 8% 42%	1600
July	1st to 10th	Night	8% 6% 3 7% 6% 5% 6% 5% 6% 8% 41%	3600
	11th to 20th	Night	11% 5% 2 7% 5% 5% 6% 4 6% 8% 40%	3600
	21st to end	Night	10% 6% 2 6% 4 4 5% 4 5% 7% 48%	3926
August	1st to 10th	Night	18% 6% 2 6% 4 5% 4 4 6% 8% 37%	2680
	11th to 20th	Night	13% 7% 3 7% 5% 4 4 4 5% 7% 42%	3121
	21st to end	Night	13% 6% 2 5% 4 4 4 4 6% 7% 46%	3586
September	1st to 10th	Night	13% 6% 2 5% 4 4 4 3 5% 8% 46%	2000
	11th to 20th	Night	13% 5% 2 4 3 3 4 3 4 6% 53%	2060
	21st to end	Night	15% 6% 1 7% 4 4 4 3 5% 7% 42%	2200
October	1st to 10th	Night	17% 7% 3 7% 5% 4 4 3 5% 6% 39%	2357
	11th to 20th	Night	17% 8% 3 7% 4 4 4 4 5% 7% 38%	2377
	21st to end	Night	21% 11% 3 7% 4 4 4 3 6% 6% 30%	2672
November	1st to 10th	Night	13% 10% 3 7% 4 4 5% 3 5% 6% 39%	2537
	11th to 20th	Night	14% 13% 4 7% 5% 4 5% 4 5% 7% 32%	2600
	21st to end	Night	13% 13% 5% 8% 6% 5% 5% 4 5% 6% 29%	2797
December	1st to 10th	Night	14% 15% 6% 12% 5% 5% 5% 4 6% 7% 20%	4580
	11th to 20th	Night	19% 13% 5% 10% 5% 4 4 3 4 5% 27%	5208
	21st to end	Night	19% 15% 8% 10% 6% 4 4 3 4 5% 24%	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	67% 5% 10% 13% 4	3598
	11th to 20th	Day	63% 7% 10% 12% 6% 2	3600
	21st to end	Day	59% 6% 9% 17% 8% 1	4208
February	1st to 10th	Day	65% 5% 10% 14% 6% 1	1800
	11th to 20th	Day	61% 6% 9% 16% 7% 1	1891
	21st to end	Day	60% 6% 10% 14% 10%	1650
March	1st to 10th	Day	59% 6% 9% 14% 10% 3	4479
	11th to 20th	Day	51% 5% 16% 18% 7% 4	4832
	21st to end	Day	53% 6% 7% 14% 18% 2	5892
April	1st to 10th	Day	55% 5% 8% 20% 10% 2	2400
	11th to 20th	Day	50% 6% 11% 18% 13% 1	2374
	21st to end	Day	52% 6% 9% 18% 12% 3	2450
May	1st to 10th	Day	61% 7% 8% 15% 9% 1	6122
	11th to 20th	Day	51% 8% 12% 20% 8% 1	6322
	21st to end	Day	50% 8% 12% 22% 8% 1	6949
June	1st to 10th	Day	47% 8% 13% 20% 11% 1	2800
	11th to 20th	Day	47% 8% 14% 20% 10% 1	2800
	21st to end	Day	47% 8% 14% 20% 10% 1	2800
July	1st to 10th	Day	42% 9% 13% 24% 11%	6290
	11th to 20th	Day	38% 10% 16% 24% 12% 1	6285
	21st to end	Day	40% 6% 12% 29% 12%	6728
August	1st to 10th	Day	47% 8% 13% 20% 11%	4451
	11th to 20th	Day	45% 8% 17% 24% 5%	3932
	21st to end	Day	40% 8% 13% 31% 8%	4312
September	1st to 10th	Day	40% 7% 11% 27% 14% 1	2400
	11th to 20th	Day	37% 5% 11% 27% 18% 1	2339
	21st to end	Day	41% 8% 13% 24% 12% 2	2200
October	1st to 10th	Day	45% 7% 9% 23% 15% 1	3326
	11th to 20th	Day	41% 4 12% 24% 17% 2	3220
	21st to end	Day	40% 6% 14% 26% 11% 2	3150
November	1st to 10th	Day	43% 6% 14% 23% 12% 1	1761
	11th to 20th	Day	52% 5% 12% 18% 11% 1	1800
	21st to end	Day	55% 7% 16% 16% 6% 1	1600
December	1st to 10th	Day	67% 8% 10% 11% 3	2600
	11th to 20th	Day	61% 5% 13% 14% 6%	2986
	21st to end	Day	62% 5% 9% 15% 8% 1	3960
January	1st to 10th	Night	66% 6% 11% 12% 5%	6349
	11th to 20th	Night	66% 7% 11% 10% 6% 1	6360
	21st to end	Night	57% 6% 11% 11% 12% 2	6747
February	1st to 10th	Night	60% 7% 12% 14% 6% 1	2600
	11th to 20th	Night	59% 7% 12% 15% 6% 1	2404
	21st to end	Night	58% 7% 13% 13% 7% 1	1980
March	1st to 10th	Night	56% 7% 14% 14% 9% 1	5374
	11th to 20th	Night	51% 5% 19% 16% 7% 2	5126
	21st to end	Night	55% 7% 6% 17% 14% 1	5039
April	1st to 10th	Night	56% 6% 11% 17% 8% 1	2000
	11th to 20th	Night	50% 6% 11% 18% 14% 1	1975
	21st to end	Night	49% 6% 12% 18% 13% 3	1949
May	1st to 10th	Night	61% 7% 9% 13% 9% 1	3877
	11th to 20th	Night	50% 8% 13% 20% 8% 1	3576
	21st to end	Night	53% 8% 12% 17% 9% 1	3927
June	1st to 10th	Night	42% 7% 11% 25% 13% 2	1600
	11th to 20th	Night	40% 7% 16% 25% 11% 1	1600
	21st to end	Night	38% 8% 16% 25% 12% 1	1600
July	1st to 10th	Night	39% 9% 16% 22% 14% 1	3560
	11th to 20th	Night	41% 8% 15% 22% 14%	3552
	21st to end	Night	35% 7% 12% 33% 12% 1	3809
August	1st to 10th	Night	44% 9% 14% 24% 9%	2670
	11th to 20th	Night	41% 7% 17% 26% 9%	3150
	21st to end	Night	36% 6% 13% 34% 10% 1	3586
September	1st to 10th	Night	36% 7% 15% 28% 14% 1	2000
	11th to 20th	Night	32% 6% 12% 29% 20% 1	2060
	21st to end	Night	42% 6% 13% 23% 15% 2	2200
October	1st to 10th	Night	48% 6% 12% 24% 11% 1	3851
	11th to 20th	Night	38% 5% 14% 23% 17% 3	3876
	21st to end	Night	43% 6% 14% 27% 9% 1	4397
November	1st to 10th	Night	46% 6% 12% 20% 15% 2	2537
	11th to 20th	Night	51% 7% 12% 18% 11% 2	2600
	21st to end	Night	53% 7% 16% 18% 5% 1	2797
December	1st to 10th	Night	61% 7% 13% 17% 2	4580
	11th to 20th	Night	59% 7% 10% 14% 10%	5208
	21st to end	Night	64% 6% 9% 11% 9% 2	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	31% 29% 29% 9% 3 1	200
	11th to 20th	Day	42% 22% 29% 6% 2 1	200
	21st to end	Day	30% 25% 34% 7% 3	273
February	1st to 10th	Day	37% 29% 26% 7% 1	300
	11th to 20th	Day	38% 31% 21% 9% 1	430
	21st to end	Day	34% 25% 29% 10% 2	414
March	1st to 10th	Day	33% 25% 29% 10% 3	500
	11th to 20th	Day	34% 22% 28% 12% 3 1	500
	21st to end	Day	36% 25% 22% 11% 5% 1	550
April	1st to 10th	Day	36% 25% 21% 11% 5% 1	500
	11th to 20th	Day	31% 25% 23% 12% 6% 2	492
	21st to end	Day	34% 19% 28% 12% 4 3	500
May	1st to 10th	Day	36% 18% 25% 11% 6% 3	503
	11th to 20th	Day	23% 20% 31% 17% 8% 2	527
	21st to end	Day	21% 12% 32% 21% 11% 3	573
June	1st to 10th	Day	20% 17% 33% 20% 9% 2	530
	11th to 20th	Day	19% 16% 29% 22% 11% 2	530
	21st to end	Day	21% 16% 30% 22% 9% 1	530
July	1st to 10th	Day	13% 10% 33% 26% 13% 3	525
	11th to 20th	Day	11% 7% 35% 30% 13% 3	524
	21st to end	Day	14% 10% 36% 27% 10% 3	576
August	1st to 10th	Day	12% 9% 29% 26% 19% 6%	526
	11th to 20th	Day	16% 9% 27% 27% 14% 7%	519
	21st to end	Day	13% 14% 30% 23% 14% 6%	583
September	1st to 10th	Day	17% 11% 25% 24% 15% 8%	530
	11th to 20th	Day	13% 9% 26% 22% 19% 11%	530
	21st to end	Day	17% 12% 30% 21% 13% 5%	530
October	1st to 10th	Day	22% 13% 26% 19% 15% 5%	530
	11th to 20th	Day	25% 18% 27% 19% 10% 2	522
	21st to end	Day	29% 18% 29% 17% 7%	452
November	1st to 10th	Day	26% 20% 23% 18% 12% 1	395
	11th to 20th	Day	31% 24% 23% 16% 6% 1	400
	21st to end	Day	36% 24% 27% 12% 1 1	200
December	1st to 10th	Day	35% 24% 24% 13% 4	200
	11th to 20th	Day	40% 22% 26% 11% 1	200
	21st to end	Day	31% 18% 34% 12% 4	220
January	1st to 10th	Night	27% 28% 31% 12% 2	800
	11th to 20th	Night	28% 25% 29% 16% 2 1	800
	21st to end	Night	22% 29% 31% 17% 2	880
February	1st to 10th	Night	29% 22% 32% 16% 2	800
	11th to 20th	Night	28% 28% 30% 13% 2	783
	21st to end	Night	30% 25% 28% 15% 2	660
March	1st to 10th	Night	29% 23% 31% 15% 3	800
	11th to 20th	Night	27% 25% 29% 16% 3	800
	21st to end	Night	27% 22% 27% 19% 6%	880
April	1st to 10th	Night	29% 21% 29% 18% 3	800
	11th to 20th	Night	25% 22% 28% 19% 6%	791
	21st to end	Night	27% 19% 26% 22% 6%	749
May	1st to 10th	Night	31% 13% 27% 20% 7% 1	521
	11th to 20th	Night	20% 15% 26% 31% 7% 1	394
	21st to end	Night	17% 8% 30% 31% 12% 1	433
June	1st to 10th	Night	17% 12% 25% 34% 11% 1	400
	11th to 20th	Night	17% 12% 22% 35% 14%	400
	21st to end	Night	14% 8% 27% 38% 12% 1	400
July	1st to 10th	Night	10% 6% 24% 42% 17% 2	390
	11th to 20th	Night	13% 5% 23% 41% 16% 2	388
	21st to end	Night	9% 7% 26% 44% 12% 2	438
August	1st to 10th	Night	10% 3 28% 35% 22% 1	453
	11th to 20th	Night	14% 5% 20% 38% 20% 4	738
	21st to end	Night	16% 7% 22% 34% 19% 1	880
September	1st to 10th	Night	15% 8% 24% 33% 19% 2	800
	11th to 20th	Night	15% 8% 22% 29% 22% 5%	800
	21st to end	Night	18% 10% 23% 30% 17% 2	800
October	1st to 10th	Night	23% 14% 20% 24% 16% 2	800
	11th to 20th	Night	21% 16% 26% 27% 9% 1	793
	21st to end	Night	28% 18% 27% 22% 5%	836
November	1st to 10th	Night	22% 18% 27% 25% 7%	780
	11th to 20th	Night	28% 19% 27% 18% 7% 2	800
	21st to end	Night	26% 24% 26% 20% 5% 1	800
December	1st to 10th	Night	26% 27% 27% 15% 4	800
	11th to 20th	Night	33% 20% 28% 16% 3	800
	21st to end	Night	30% 26% 26% 16% 3	880

Page generated at 2025-10-16 01:50:29. Version ac07

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