Keene
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Keene clear sky chart from 2005-11-06 to 2025-02-06.

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 10% 7% 6% 5% 4 6% 7% 28%	108400
	Night	11% 11% 5% 12% 7% 6% 5% 4 5% 6% 27%	109859
Transparency	Day	51% 6% 11% 20% 10% 1	111916
	Night	52% 6% 12% 18% 11% 1	114507
Seeing	Day	24% 23% 30% 16% 6% 2	14891
	Night	21% 22% 29% 20% 8% 1	24045

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	7% 13% 8% 17% 10% 8% 5% 4 4 6% 18%	3597
	11th to 20th	Day	5% 15% 6% 19% 14% 7% 5% 3 4 4 18%	3570
	21st to end	Day	9% 11% 5% 16% 8% 7% 7% 5% 5% 5% 22%	3978
February	1st to 10th	Day	9% 13% 6% 13% 10% 6% 6% 5% 6% 5% 21%	1755
	11th to 20th	Day	6% 10% 6% 14% 10% 8% 6% 5% 5% 6% 23%	1785
	21st to end	Day	9% 15% 5% 11% 8% 6% 5% 4 6% 6% 24%	1570
March	1st to 10th	Day	16% 16% 5% 12% 7% 5% 4 3 5% 5% 22%	3116
	11th to 20th	Day	8% 17% 7% 13% 9% 7% 6% 3 4 5% 22%	3286
	21st to end	Day	11% 11% 5% 10% 7% 6% 5% 3 4 5% 33%	4160
April	1st to 10th	Day	14% 16% 4 8% 7% 5% 5% 4 5% 6% 28%	2280
	11th to 20th	Day	14% 13% 4 9% 6% 5% 4 3 5% 5% 32%	2254
	21st to end	Day	19% 15% 4 9% 5% 4 4 3 5% 5% 28%	2402
May	1st to 10th	Day	18% 13% 4 10% 6% 5% 4 3 4 6% 26%	4291
	11th to 20th	Day	16% 10% 4 9% 6% 6% 5% 5% 6% 8% 26%	4398
	21st to end	Day	13% 7% 3 8% 6% 6% 5% 4 6% 9% 34%	4837
June	1st to 10th	Day	21% 10% 3 8% 5% 5% 6% 4 6% 6% 26%	2660
	11th to 20th	Day	16% 8% 3 8% 6% 5% 5% 6% 6% 7% 31%	2660
	21st to end	Day	20% 8% 3 9% 5% 6% 6% 5% 7% 6% 26%	2660
July	1st to 10th	Day	12% 6% 2 7% 6% 6% 6% 5% 7% 9% 32%	4440
	11th to 20th	Day	10% 5% 3 8% 5% 6% 7% 6% 8% 11% 32%	4440
	21st to end	Day	12% 6% 3 8% 6% 6% 6% 5% 7% 8% 33%	4814
August	1st to 10th	Day	14% 8% 3 8% 6% 6% 5% 5% 8% 8% 29%	4423
	11th to 20th	Day	12% 8% 3 10% 7% 6% 7% 6% 7% 8% 27%	3865
	21st to end	Day	13% 6% 2 7% 5% 5% 6% 3 7% 9% 35%	4180
September	1st to 10th	Day	14% 6% 2 6% 5% 5% 5% 3 6% 8% 40%	2280
	11th to 20th	Day	12% 6% 3 7% 5% 5% 4 3 6% 7% 43%	2199
	21st to end	Day	12% 8% 3 7% 5% 5% 5% 5% 7% 7% 36%	2090
October	1st to 10th	Day	18% 12% 3 7% 6% 4 5% 3 6% 6% 30%	1969
	11th to 20th	Day	14% 13% 4 9% 5% 5% 5% 4 5% 6% 31%	1881
	21st to end	Day	18% 13% 5% 10% 6% 4 4 3 4 6% 26%	1881
November	1st to 10th	Day	10% 12% 4 11% 6% 6% 6% 4 6% 6% 29%	1761
	11th to 20th	Day	11% 11% 6% 10% 8% 6% 6% 4 6% 5% 28%	1772
	21st to end	Day	12% 15% 5% 12% 7% 6% 5% 5% 5% 6% 23%	1600
December	1st to 10th	Day	8% 19% 8% 22% 9% 6% 5% 3 4 4 12%	2600
	11th to 20th	Day	11% 12% 6% 16% 6% 5% 5% 4 6% 6% 22%	2986
	21st to end	Day	12% 14% 6% 12% 6% 5% 5% 3 5% 6% 26%	3960
January	1st to 10th	Night	9% 15% 7% 18% 11% 9% 5% 3 4 5% 15%	6349
	11th to 20th	Night	5% 13% 8% 21% 14% 8% 6% 4 5% 5% 12%	6315
	21st to end	Night	9% 8% 6% 16% 9% 7% 8% 6% 7% 7% 18%	6977
February	1st to 10th	Night	7% 13% 5% 13% 11% 8% 7% 5% 7% 6% 19%	2536
	11th to 20th	Night	6% 10% 6% 13% 10% 8% 7% 5% 7% 6% 22%	2280
	21st to end	Night	8% 11% 5% 13% 8% 6% 5% 6% 5% 6% 26%	1884
March	1st to 10th	Night	15% 11% 4 10% 8% 7% 6% 4 5% 5% 24%	3724
	11th to 20th	Night	9% 14% 6% 14% 8% 6% 4 3 5% 6% 26%	3671
	21st to end	Night	11% 12% 6% 12% 6% 5% 4 3 4 4 32%	3471
April	1st to 10th	Night	13% 13% 4 11% 7% 6% 5% 4 5% 6% 28%	1900
	11th to 20th	Night	15% 12% 4 9% 6% 6% 5% 3 6% 7% 27%	1875
	21st to end	Night	17% 11% 5% 8% 7% 4 4 3 4 5% 32%	1777
May	1st to 10th	Night	18% 15% 4 9% 5% 4 5% 4 6% 6% 23%	2679
	11th to 20th	Night	16% 12% 4 9% 5% 5% 4 4 5% 6% 32%	2495
	21st to end	Night	12% 8% 2 8% 5% 4 5% 3 8% 8% 36%	2738
June	1st to 10th	Night	19% 8% 3 6% 5% 4 5% 4 6% 7% 32%	1520
	11th to 20th	Night	16% 7% 2 5% 5% 4 4 5% 6% 7% 38%	1520
	21st to end	Night	16% 8% 3 7% 5% 6% 4 5% 6% 7% 34%	1520
July	1st to 10th	Night	12% 6% 3 8% 6% 5% 5% 5% 5% 7% 37%	2520
	11th to 20th	Night	11% 5% 3 7% 5% 5% 5% 4 6% 8% 41%	2520
	21st to end	Night	10% 8% 2 7% 5% 5% 4 4 6% 7% 41%	2739
August	1st to 10th	Night	14% 8% 3 7% 5% 5% 4 4 5% 7% 37%	2506
	11th to 20th	Night	11% 7% 3 10% 6% 5% 5% 5% 7% 6% 36%	2927
	21st to end	Night	9% 8% 2 6% 5% 4 5% 4 6% 8% 43%	3476
September	1st to 10th	Night	12% 6% 2 6% 5% 5% 5% 4 5% 6% 43%	1900
	11th to 20th	Night	11% 8% 2 6% 4 4 4 3 4 6% 47%	1981
	21st to end	Night	15% 8% 2 7% 4 4 4 4 7% 7% 40%	2090
October	1st to 10th	Night	17% 10% 4 7% 5% 5% 5% 3 6% 8% 30%	2209
	11th to 20th	Night	15% 11% 3 8% 5% 6% 4 4 5% 6% 32%	2297
	21st to end	Night	17% 13% 5% 10% 6% 6% 5% 3 5% 5% 24%	2717
November	1st to 10th	Night	11% 14% 5% 9% 7% 6% 5% 3 6% 5% 27%	2537
	11th to 20th	Night	11% 12% 5% 12% 7% 5% 5% 4 5% 6% 28%	2625
	21st to end	Night	11% 14% 5% 12% 7% 6% 5% 4 6% 6% 22%	2800
December	1st to 10th	Night	9% 14% 7% 23% 12% 6% 5% 3 4 5% 12%	4580
	11th to 20th	Night	12% 14% 7% 14% 8% 6% 6% 4 5% 4 20%	5208
	21st to end	Night	11% 15% 5% 15% 6% 6% 6% 4 5% 6% 22%	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	58% 4 11% 20% 6% 1	3598
	11th to 20th	Day	67% 4 9% 9% 9% 3	3600
	21st to end	Day	57% 3 12% 15% 10% 2	3978
February	1st to 10th	Day	60% 5% 9% 16% 7% 2	1755
	11th to 20th	Day	55% 6% 10% 16% 11% 2	1794
	21st to end	Day	56% 4 11% 14% 12% 3	1570
March	1st to 10th	Day	63% 7% 8% 10% 9% 2	3119
	11th to 20th	Day	59% 5% 11% 13% 9% 3	3286
	21st to end	Day	50% 6% 7% 15% 20% 3	4160
April	1st to 10th	Day	54% 4 10% 17% 12% 3	2280
	11th to 20th	Day	52% 6% 8% 19% 14% 1	2254
	21st to end	Day	57% 5% 8% 15% 12% 3	2402
May	1st to 10th	Day	57% 5% 9% 20% 9% 1	4305
	11th to 20th	Day	52% 7% 15% 17% 8% 1	4402
	21st to end	Day	44% 6% 13% 25% 11% 1	4837
June	1st to 10th	Day	55% 6% 12% 16% 10% 1	2660
	11th to 20th	Day	47% 6% 11% 22% 11% 2	2660
	21st to end	Day	55% 6% 10% 19% 9% 1	2660
July	1st to 10th	Day	44% 7% 14% 25% 10%	4370
	11th to 20th	Day	41% 8% 15% 30% 7%	4365
	21st to end	Day	44% 8% 12% 28% 9%	4661
August	1st to 10th	Day	48% 7% 15% 20% 10% 1	4409
	11th to 20th	Day	47% 9% 16% 23% 5%	3905
	21st to end	Day	41% 8% 14% 25% 11% 1	4180
September	1st to 10th	Day	39% 7% 10% 30% 13% 1	2280
	11th to 20th	Day	38% 6% 10% 29% 16% 1	2199
	21st to end	Day	43% 7% 14% 23% 11% 2	2090
October	1st to 10th	Day	45% 5% 11% 25% 14%	3268
	11th to 20th	Day	44% 4 14% 22% 15% 1	3109
	21st to end	Day	44% 3 14% 30% 8% 1	3081
November	1st to 10th	Day	52% 6% 13% 17% 11% 1	1761
	11th to 20th	Day	53% 6% 10% 14% 15% 3	1772
	21st to end	Day	56% 5% 13% 17% 8% 1	1600
December	1st to 10th	Day	71% 4 8% 12% 4	2600
	11th to 20th	Day	57% 5% 11% 16% 10%	2986
	21st to end	Day	57% 5% 9% 13% 15% 1	3960
January	1st to 10th	Night	61% 4 12% 14% 8%	6349
	11th to 20th	Night	65% 7% 9% 10% 7% 1	6360
	21st to end	Night	57% 5% 11% 12% 13% 2	6977
February	1st to 10th	Night	58% 7% 10% 14% 9% 2	2536
	11th to 20th	Night	53% 7% 10% 17% 12% 1	2282
	21st to end	Night	53% 7% 10% 17% 10% 2	1884
March	1st to 10th	Night	57% 6% 9% 14% 12% 2	3734
	11th to 20th	Night	55% 4 12% 16% 10% 2	3672
	21st to end	Night	50% 7% 5% 18% 16% 4	3471
April	1st to 10th	Night	52% 6% 9% 17% 14% 2	1900
	11th to 20th	Night	53% 5% 12% 19% 12% 1	1875
	21st to end	Night	51% 6% 10% 18% 12% 3	1777
May	1st to 10th	Night	58% 5% 10% 17% 9% 1	2685
	11th to 20th	Night	51% 5% 13% 21% 9% 1	2496
	21st to end	Night	42% 5% 16% 21% 15% 1	2739
June	1st to 10th	Night	46% 7% 14% 21% 11% 1	1520
	11th to 20th	Night	42% 5% 16% 23% 13% 1	1520
	21st to end	Night	44% 6% 16% 24% 9%	1520
July	1st to 10th	Night	43% 6% 14% 24% 12% 1	2480
	11th to 20th	Night	35% 6% 17% 31% 10%	2472
	21st to end	Night	39% 8% 15% 27% 10% 1	2651
August	1st to 10th	Night	42% 8% 17% 24% 9%	2496
	11th to 20th	Night	42% 7% 18% 25% 9%	2953
	21st to end	Night	34% 6% 18% 31% 11% 1	3476
September	1st to 10th	Night	35% 7% 15% 29% 13% 1	1900
	11th to 20th	Night	36% 5% 13% 31% 14% 1	1981
	21st to end	Night	40% 7% 13% 26% 13% 2	2090
October	1st to 10th	Night	47% 7% 10% 25% 11% 1	3690
	11th to 20th	Night	42% 5% 13% 24% 11% 5%	3808
	21st to end	Night	47% 6% 14% 23% 8% 1	4467
November	1st to 10th	Night	51% 8% 11% 17% 11% 2	2537
	11th to 20th	Night	51% 7% 10% 17% 11% 3	2625
	21st to end	Night	54% 7% 14% 17% 8% 1	2800
December	1st to 10th	Night	67% 6% 11% 13% 3	4580
	11th to 20th	Night	61% 4 8% 13% 13% 1	5208
	21st to end	Night	61% 4 9% 11% 11% 3	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	17% 32% 31% 16% 6%	200
	11th to 20th	Day	24% 30% 35% 9% 2 1	200
	21st to end	Day	24% 29% 35% 9% 2 1	223
February	1st to 10th	Day	32% 42% 22% 3 1	285
	11th to 20th	Day	30% 31% 31% 7% 1	393
	21st to end	Day	32% 25% 30% 11% 2	382
March	1st to 10th	Day	27% 28% 30% 12% 2	460
	11th to 20th	Day	28% 30% 28% 10% 3 1	460
	21st to end	Day	33% 28% 22% 11% 5% 1	506
April	1st to 10th	Day	34% 23% 28% 12% 3 1	460
	11th to 20th	Day	34% 26% 22% 12% 3 3	452
	21st to end	Day	33% 26% 25% 10% 5% 1	460
May	1st to 10th	Day	30% 27% 26% 10% 5% 3	463
	11th to 20th	Day	21% 23% 32% 19% 3 1	487
	21st to end	Day	22% 22% 31% 19% 4 2	529
June	1st to 10th	Day	28% 19% 32% 15% 5% 1	490
	11th to 20th	Day	18% 20% 34% 19% 7% 1	490
	21st to end	Day	24% 23% 29% 17% 6% 1	490
July	1st to 10th	Day	17% 13% 36% 23% 9% 2	485
	11th to 20th	Day	12% 16% 41% 23% 7% 1	484
	21st to end	Day	15% 14% 40% 23% 6% 2	532
August	1st to 10th	Day	14% 16% 33% 24% 10% 3	486
	11th to 20th	Day	13% 15% 34% 22% 11% 4	479
	21st to end	Day	13% 17% 33% 22% 10% 5%	539
September	1st to 10th	Day	17% 16% 31% 19% 11% 7%	490
	11th to 20th	Day	13% 17% 26% 21% 14% 9%	490
	21st to end	Day	14% 20% 32% 18% 10% 5%	490
October	1st to 10th	Day	25% 21% 25% 16% 10% 2	490
	11th to 20th	Day	24% 26% 24% 18% 7% 1	480
	21st to end	Day	30% 21% 31% 16% 2	429
November	1st to 10th	Day	28% 21% 28% 16% 7%	395
	11th to 20th	Day	29% 30% 23% 14% 4 1	372
	21st to end	Day	31% 33% 24% 11% 2	200
December	1st to 10th	Day	24% 33% 27% 14% 4	200
	11th to 20th	Day	32% 34% 26% 9%	200
	21st to end	Day	28% 29% 30% 9% 3	220
January	1st to 10th	Night	20% 29% 33% 14% 3	800
	11th to 20th	Night	24% 25% 35% 14% 3	800
	21st to end	Night	12% 32% 35% 17% 3	880
February	1st to 10th	Night	20% 31% 33% 14% 2	781
	11th to 20th	Night	21% 30% 32% 15% 2	743
	21st to end	Night	21% 30% 29% 17% 3	628
March	1st to 10th	Night	26% 23% 31% 17% 3	760
	11th to 20th	Night	25% 29% 28% 13% 5% 1	760
	21st to end	Night	24% 26% 28% 17% 4 1	836
April	1st to 10th	Night	25% 24% 30% 17% 3	760
	11th to 20th	Night	26% 26% 25% 18% 6% 1	751
	21st to end	Night	26% 22% 27% 20% 5%	637
May	1st to 10th	Night	26% 18% 28% 21% 6%	480
	11th to 20th	Night	21% 20% 29% 24% 6% 1	374
	21st to end	Night	15% 17% 35% 21% 11%	411
June	1st to 10th	Night	21% 13% 32% 23% 11%	380
	11th to 20th	Night	19% 12% 26% 32% 11% 1	380
	21st to end	Night	18% 13% 29% 30% 9% 1	380
July	1st to 10th	Night	12% 11% 30% 32% 15% 1	370
	11th to 20th	Night	12% 7% 30% 33% 16% 2	368
	21st to end	Night	12% 9% 30% 37% 12% 1	416
August	1st to 10th	Night	11% 9% 27% 35% 16% 1	378
	11th to 20th	Night	11% 9% 28% 33% 16% 3	640
	21st to end	Night	13% 10% 28% 29% 18% 1	836
September	1st to 10th	Night	14% 14% 25% 30% 14% 3	760
	11th to 20th	Night	15% 13% 23% 25% 21% 4	760
	21st to end	Night	17% 14% 26% 23% 18% 2	760
October	1st to 10th	Night	22% 17% 25% 21% 14% 1	760
	11th to 20th	Night	24% 20% 24% 22% 9% 1	760
	21st to end	Night	27% 24% 26% 18% 5%	836
November	1st to 10th	Night	24% 24% 28% 18% 6% 1	780
	11th to 20th	Night	24% 27% 27% 14% 7% 2	800
	21st to end	Night	23% 29% 26% 16% 5% 1	800
December	1st to 10th	Night	23% 31% 29% 15% 3	800
	11th to 20th	Night	26% 25% 29% 17% 4 1	800
	21st to end	Night	25% 28% 31% 14% 3	880

Page generated at 2025-02-03 03:05:54. Version ac07

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