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 2024-04-10.

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	18% 8% 3 6% 6% 3 4 4 5% 7% 36%	82943
	Night	18% 9% 3 6% 5% 3 4 4 5% 6% 36%	85814
Transparency	Day	47% 6% 11% 21% 13% 2	82648
	Night	47% 6% 12% 21% 12% 2	85643
Seeing	Day	25% 18% 29% 18% 7% 2	14098
	Night	22% 17% 29% 24% 8% 1	23216

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	15% 9% 3 6% 5% 4 4 5% 5% 7% 38%	2517
	11th to 20th	Day	17% 9% 5% 8% 5% 4 5% 4 5% 6% 31%	2520
	21st to end	Day	19% 13% 5% 8% 5% 3 4 3 5% 5% 29%	2772
February	1st to 10th	Day	15% 11% 4 6% 5% 4 6% 6% 6% 7% 30%	1729
	11th to 20th	Day	13% 8% 4 9% 7% 4 5% 4 4 7% 34%	1848
	21st to end	Day	18% 10% 5% 8% 5% 4 4 4 4 5% 33%	1570
March	1st to 10th	Day	22% 14% 4 8% 7% 3 4 3 3 5% 27%	3116
	11th to 20th	Day	14% 11% 5% 6% 6% 3 4 4 5% 7% 35%	3270
	21st to end	Day	20% 9% 3 7% 5% 3 4 4 4 6% 34%	4132
April	1st to 10th	Day	20% 9% 4 7% 6% 3 3 3 5% 6% 34%	2270
	11th to 20th	Day	17% 7% 3 6% 4 4 5% 5% 5% 7% 37%	2134
	21st to end	Day	21% 9% 4 7% 6% 3 4 5% 4 5% 32%	2317
May	1st to 10th	Day	25% 9% 3 7% 5% 3 5% 4 3 5% 32%	2340
	11th to 20th	Day	18% 7% 3 5% 6% 3 4 4 5% 6% 39%	2428
	21st to end	Day	17% 6% 3 5% 5% 3 4 4 5% 8% 41%	2725
June	1st to 10th	Day	19% 6% 2 6% 7% 4 5% 5% 7% 8% 32%	2520
	11th to 20th	Day	18% 6% 2 6% 6% 3 5% 5% 5% 8% 36%	2520
	21st to end	Day	18% 6% 3 6% 7% 4 6% 5% 6% 8% 32%	2520
July	1st to 10th	Day	15% 5% 3 6% 5% 3 4 6% 6% 8% 39%	2520
	11th to 20th	Day	13% 6% 3 5% 6% 4 5% 6% 7% 9% 37%	2520
	21st to end	Day	14% 5% 3 5% 6% 4 6% 5% 6% 8% 38%	2744
August	1st to 10th	Day	12% 5% 3 5% 6% 3 6% 6% 7% 9% 39%	2430
	11th to 20th	Day	13% 5% 2 6% 5% 4 6% 5% 6% 9% 37%	2229
	21st to end	Day	12% 5% 2 5% 6% 3 5% 5% 6% 8% 43%	2376
September	1st to 10th	Day	13% 6% 2 4 5% 3 4 6% 5% 9% 42%	2160
	11th to 20th	Day	16% 5% 2 4 5% 2 3 4 4 6% 49%	2017
	21st to end	Day	17% 6% 2 5% 4 3 3 4 4 8% 44%	1980
October	1st to 10th	Day	23% 8% 3 5% 5% 3 5% 4 4 5% 36%	1972
	11th to 20th	Day	15% 7% 2 6% 5% 3 4 5% 5% 6% 41%	1737
	21st to end	Day	22% 9% 3 6% 6% 3 4 4 4 6% 31%	1782
November	1st to 10th	Day	14% 7% 3 5% 4 3 3 3 4 7% 45%	1671
	11th to 20th	Day	19% 9% 2 6% 4 2 4 4 4 6% 40%	1710
	21st to end	Day	20% 8% 3 6% 4 3 4 3 6% 7% 37%	1649
December	1st to 10th	Day	19% 10% 4 7% 6% 3 5% 4 5% 5% 31%	1520
	11th to 20th	Day	22% 12% 3 4 5% 3 4 3 4 4 37%	1906
	21st to end	Day	23% 12% 4 7% 7% 3 4 5% 4 5% 28%	2772
January	1st to 10th	Night	16% 9% 3 5% 5% 4 4 5% 4 6% 39%	4429
	11th to 20th	Night	14% 12% 4 8% 9% 4 6% 5% 4 6% 29%	4440
	21st to end	Night	21% 13% 4 7% 6% 4 4 4 4 5% 26%	4884
February	1st to 10th	Night	15% 9% 4 8% 6% 3 5% 5% 5% 6% 34%	2447
	11th to 20th	Night	11% 10% 4 6% 6% 4 5% 6% 6% 7% 35%	2218
	21st to end	Night	16% 10% 3 7% 5% 3 5% 5% 5% 6% 35%	1884
March	1st to 10th	Night	24% 11% 2 6% 6% 3 4 4 4 5% 30%	3724
	11th to 20th	Night	12% 11% 3 6% 7% 4 6% 5% 5% 5% 35%	3687
	21st to end	Night	23% 10% 4 6% 4 3 4 4 6% 5% 32%	3484
April	1st to 10th	Night	20% 8% 3 6% 5% 4 4 4 5% 6% 35%	1900
	11th to 20th	Night	20% 8% 3 4 4 2 4 4 5% 6% 39%	1775
	21st to end	Night	21% 8% 4 6% 5% 2 4 4 5% 6% 35%	1641
May	1st to 10th	Night	23% 10% 4 6% 5% 3 3 4 5% 5% 32%	1620
	11th to 20th	Night	20% 6% 3 5% 6% 3 5% 5% 6% 7% 35%	1481
	21st to end	Night	16% 6% 3 5% 5% 4 5% 5% 5% 8% 38%	1550
June	1st to 10th	Night	20% 7% 3 5% 5% 2 4 5% 5% 7% 36%	1440
	11th to 20th	Night	20% 6% 2 5% 4 3 5% 4 5% 8% 37%	1440
	21st to end	Night	15% 5% 3 5% 4 3 5% 6% 7% 8% 39%	1440
July	1st to 10th	Night	13% 4 3 5% 5% 3 4 6% 6% 8% 43%	1440
	11th to 20th	Night	13% 4 3 5% 5% 4 6% 6% 7% 9% 39%	1440
	21st to end	Night	12% 5% 2 4 5% 3 5% 5% 6% 8% 46%	1574
August	1st to 10th	Night	11% 6% 2 4 5% 3 4 5% 5% 9% 46%	1490
	11th to 20th	Night	14% 7% 3 6% 5% 3 5% 5% 6% 8% 39%	1668
	21st to end	Night	14% 6% 2 4 3 2 5% 3 5% 7% 49%	1980
September	1st to 10th	Night	13% 6% 2 4 4 3 3 5% 6% 7% 48%	1800
	11th to 20th	Night	15% 5% 1 4 3 2 4 4 4 6% 52%	1942
	21st to end	Night	16% 5% 2 4 5% 2 4 3 5% 6% 48%	1980
October	1st to 10th	Night	23% 7% 3 5% 5% 2 3 3 4 6% 39%	1984
	11th to 20th	Night	16% 7% 2 5% 5% 3 4 5% 6% 6% 41%	2222
	21st to end	Night	23% 9% 3 5% 5% 3 4 5% 5% 6% 33%	2574
November	1st to 10th	Night	17% 6% 2 5% 4 3 4 4 5% 5% 44%	2407
	11th to 20th	Night	18% 7% 3 6% 4 3 4 4 4 6% 41%	2470
	21st to end	Night	15% 9% 4 7% 4 3 4 4 5% 6% 39%	2527
December	1st to 10th	Night	20% 10% 3 5% 5% 3 4 4 5% 6% 32%	2660
	11th to 20th	Night	21% 10% 3 6% 4 3 4 4 4 6% 35%	3288
	21st to end	Night	22% 12% 5% 8% 5% 3 3 4 4 6% 27%	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	45% 5% 9% 31% 8% 1	2518
	11th to 20th	Day	51% 6% 12% 21% 8% 1	2520
	21st to end	Day	57% 5% 10% 19% 9% 2	2772
February	1st to 10th	Day	51% 7% 12% 19% 10% 1	1729
	11th to 20th	Day	50% 6% 9% 19% 14% 2	1857
	21st to end	Day	54% 4 9% 19% 12% 2	1570
March	1st to 10th	Day	61% 4 10% 12% 11% 2	3119
	11th to 20th	Day	45% 7% 14% 20% 11% 3	3270
	21st to end	Day	50% 4 6% 17% 19% 4	4132
April	1st to 10th	Day	51% 5% 9% 20% 13% 3	2270
	11th to 20th	Day	46% 6% 11% 19% 16% 2	2134
	21st to end	Day	53% 5% 8% 16% 14% 3	2317
May	1st to 10th	Day	55% 5% 7% 18% 12% 2	2340
	11th to 20th	Day	46% 5% 9% 22% 16% 3	2432
	21st to end	Day	42% 6% 15% 23% 12% 2	2725
June	1st to 10th	Day	49% 7% 13% 21% 10% 1	2520
	11th to 20th	Day	47% 6% 11% 19% 15% 2	2520
	21st to end	Day	49% 8% 12% 20% 11% 1	2520
July	1st to 10th	Day	41% 8% 12% 23% 15% 1	2450
	11th to 20th	Day	40% 8% 15% 26% 10% 1	2445
	21st to end	Day	41% 8% 13% 24% 13% 1	2591
August	1st to 10th	Day	40% 8% 16% 24% 12% 1	2416
	11th to 20th	Day	41% 8% 13% 25% 11% 1	2229
	21st to end	Day	38% 7% 12% 27% 15% 2	2376
September	1st to 10th	Day	39% 6% 13% 25% 16% 1	2160
	11th to 20th	Day	37% 6% 8% 25% 23% 2	2017
	21st to end	Day	39% 6% 10% 25% 17% 3	1980
October	1st to 10th	Day	52% 5% 8% 21% 12% 3	1972
	11th to 20th	Day	42% 5% 14% 28% 10% 1	1737
	21st to end	Day	53% 5% 10% 18% 10% 3	1782
November	1st to 10th	Day	40% 5% 15% 24% 14% 2	1671
	11th to 20th	Day	45% 5% 10% 21% 17% 3	1710
	21st to end	Day	47% 6% 15% 21% 10% 1	1649
December	1st to 10th	Day	55% 6% 13% 15% 11% 1	1520
	11th to 20th	Day	51% 5% 11% 17% 14% 1	1906
	21st to end	Day	58% 6% 10% 16% 9% 1	2772
January	1st to 10th	Night	44% 6% 13% 24% 10% 2	4429
	11th to 20th	Night	53% 7% 12% 17% 8% 2	4440
	21st to end	Night	59% 6% 9% 15% 9% 1	4884
February	1st to 10th	Night	49% 6% 14% 20% 10% 2	2447
	11th to 20th	Night	45% 7% 11% 21% 14% 2	2220
	21st to end	Night	47% 6% 11% 23% 10% 4	1884
March	1st to 10th	Night	55% 5% 9% 19% 10% 2	3734
	11th to 20th	Night	46% 8% 12% 20% 11% 2	3688
	21st to end	Night	50% 6% 7% 13% 19% 4	3484
April	1st to 10th	Night	49% 6% 10% 19% 14% 2	1900
	11th to 20th	Night	45% 7% 10% 21% 16% 2	1775
	21st to end	Night	49% 6% 10% 17% 13% 4	1641
May	1st to 10th	Night	54% 5% 8% 18% 13% 2	1620
	11th to 20th	Night	47% 6% 12% 17% 14% 3	1482
	21st to end	Night	45% 7% 13% 23% 11% 2	1551
June	1st to 10th	Night	46% 7% 12% 24% 10% 1	1440
	11th to 20th	Night	45% 7% 13% 21% 12% 1	1440
	21st to end	Night	40% 9% 16% 21% 13% 1	1440
July	1st to 10th	Night	38% 10% 14% 24% 13% 1	1400
	11th to 20th	Night	38% 9% 14% 27% 11%	1392
	21st to end	Night	34% 8% 16% 29% 11% 2	1486
August	1st to 10th	Night	34% 8% 17% 27% 13% 1	1480
	11th to 20th	Night	42% 7% 16% 23% 11%	1668
	21st to end	Night	36% 5% 12% 30% 16% 1	1980
September	1st to 10th	Night	36% 7% 13% 27% 18% 1	1800
	11th to 20th	Night	34% 6% 11% 27% 21% 2	1942
	21st to end	Night	37% 5% 10% 28% 17% 2	1980
October	1st to 10th	Night	48% 4 12% 22% 11% 2	1984
	11th to 20th	Night	42% 5% 14% 27% 11% 1	2222
	21st to end	Night	52% 6% 11% 20% 10% 2	2574
November	1st to 10th	Night	41% 5% 12% 22% 17% 3	2407
	11th to 20th	Night	43% 6% 11% 23% 15% 3	2470
	21st to end	Night	45% 6% 15% 23% 11% 1	2527
December	1st to 10th	Night	51% 6% 12% 21% 9% 1	2660
	11th to 20th	Night	49% 6% 13% 16% 14% 2	3288
	21st to end	Night	58% 5% 10% 19% 8%	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	28% 24% 29% 16% 3	180
	11th to 20th	Day	34% 22% 33% 8% 3 1	180
	21st to end	Day	22% 31% 32% 11% 4	198
February	1st to 10th	Day	32% 30% 26% 10% 1	309
	11th to 20th	Day	32% 26% 29% 12% 2	456
	21st to end	Day	33% 25% 28% 13% 2	382
March	1st to 10th	Day	30% 21% 34% 12% 3	460
	11th to 20th	Day	30% 28% 26% 11% 4 1	460
	21st to end	Day	31% 23% 29% 10% 5% 3	506
April	1st to 10th	Day	35% 22% 25% 11% 5% 2	457
	11th to 20th	Day	28% 27% 25% 12% 6% 2	412
	21st to end	Day	31% 17% 31% 14% 6% 1	420
May	1st to 10th	Day	34% 22% 23% 12% 7% 2	423
	11th to 20th	Day	21% 20% 37% 15% 5% 2	447
	21st to end	Day	21% 13% 33% 24% 7% 2	485
June	1st to 10th	Day	22% 15% 35% 18% 9% 2	450
	11th to 20th	Day	20% 16% 32% 23% 7% 2	450
	21st to end	Day	19% 16% 34% 20% 9% 2	450
July	1st to 10th	Day	18% 11% 28% 28% 13% 2	445
	11th to 20th	Day	17% 8% 31% 30% 11% 3	444
	21st to end	Day	15% 12% 35% 26% 9% 3	488
August	1st to 10th	Day	12% 13% 27% 31% 13% 5%	446
	11th to 20th	Day	14% 10% 28% 27% 15% 5%	439
	21st to end	Day	13% 13% 29% 27% 12% 6%	495
September	1st to 10th	Day	20% 12% 24% 26% 14% 6%	450
	11th to 20th	Day	18% 16% 26% 19% 13% 8%	450
	21st to end	Day	19% 14% 34% 18% 10% 6%	450
October	1st to 10th	Day	30% 15% 21% 20% 10% 4	450
	11th to 20th	Day	22% 16% 29% 22% 9% 2	418
	21st to end	Day	35% 12% 27% 20% 4 1	396
November	1st to 10th	Day	23% 18% 27% 20% 11% 1	365
	11th to 20th	Day	31% 21% 26% 18% 3 1	370
	21st to end	Day	32% 17% 29% 17% 4 1	309
December	1st to 10th	Day	27% 28% 29% 12% 3 1	180
	11th to 20th	Day	39% 24% 26% 10% 1	180
	21st to end	Day	33% 23% 30% 10% 5%	198
January	1st to 10th	Night	20% 24% 35% 18% 3	760
	11th to 20th	Night	27% 22% 31% 18% 2	760
	21st to end	Night	20% 23% 33% 21% 3	836
February	1st to 10th	Night	23% 23% 34% 19% 2	760
	11th to 20th	Night	23% 24% 35% 16% 1	743
	21st to end	Night	28% 24% 29% 18% 2	628
March	1st to 10th	Night	25% 21% 33% 19% 3	760
	11th to 20th	Night	23% 26% 29% 18% 4	760
	21st to end	Night	26% 20% 30% 18% 6%	836
April	1st to 10th	Night	27% 18% 30% 21% 4	760
	11th to 20th	Night	24% 20% 27% 22% 7%	711
	21st to end	Night	27% 18% 29% 21% 5%	561
May	1st to 10th	Night	29% 12% 31% 21% 6%	540
	11th to 20th	Night	20% 17% 33% 25% 5%	420
	21st to end	Night	20% 7% 27% 35% 10% 1	389
June	1st to 10th	Night	20% 8% 27% 33% 11% 1	360
	11th to 20th	Night	21% 10% 29% 31% 9% 1	360
	21st to end	Night	18% 7% 28% 39% 8% 1	360
July	1st to 10th	Night	14% 5% 29% 39% 12% 1	350
	11th to 20th	Night	14% 3 28% 38% 16% 2	348
	21st to end	Night	11% 5% 29% 39% 14% 1	394
August	1st to 10th	Night	13% 6% 25% 37% 19% 1	416
	11th to 20th	Night	16% 7% 25% 32% 18% 2	604
	21st to end	Night	16% 7% 22% 34% 19% 2	792
September	1st to 10th	Night	16% 7% 28% 31% 17% 1	720
	11th to 20th	Night	17% 9% 25% 29% 17% 3	720
	21st to end	Night	18% 9% 28% 28% 15% 2	720
October	1st to 10th	Night	27% 12% 21% 26% 12% 2	720
	11th to 20th	Night	20% 13% 31% 25% 10% 1	720
	21st to end	Night	29% 17% 27% 22% 6% 1	792
November	1st to 10th	Night	20% 18% 29% 25% 9%	740
	11th to 20th	Night	22% 24% 26% 21% 6% 1	760
	21st to end	Night	23% 20% 32% 18% 6% 1	760
December	1st to 10th	Night	27% 21% 30% 18% 4	760
	11th to 20th	Night	26% 21% 33% 17% 4	760
	21st to end	Night	27% 22% 33% 15% 3	836

Page generated at 2024-04-07 09:28:13. Version ac07

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