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 2024-01-27.

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% 10% 4 8% 8% 4 6% 5% 5% 7% 28%	74874
	Night	12% 10% 5% 9% 8% 4 6% 5% 6% 7% 29%	75170
Transparency	Day	52% 6% 11% 19% 11% 1	74579
	Night	50% 6% 12% 19% 11% 1	74999
Seeing	Day	23% 23% 30% 16% 6% 2	13593
	Night	21% 22% 29% 20% 8% 1	22755

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	6% 13% 6% 14% 10% 5% 7% 7% 5% 8% 20%	1517
	11th to 20th	Day	8% 12% 7% 12% 11% 5% 5% 5% 6% 7% 23%	1520
	21st to end	Day	8% 9% 6% 13% 10% 5% 8% 7% 6% 6% 22%	1636
February	1st to 10th	Day	9% 12% 7% 12% 11% 5% 7% 6% 6% 6% 19%	1620
	11th to 20th	Day	6% 10% 6% 12% 11% 5% 7% 6% 5% 7% 24%	1689
	21st to end	Day	10% 15% 5% 11% 8% 4 6% 6% 6% 6% 23%	1480
March	1st to 10th	Day	10% 11% 6% 13% 10% 4 6% 5% 5% 5% 26%	1797
	11th to 20th	Day	11% 14% 6% 8% 10% 4 6% 4 4 6% 26%	1870
	21st to end	Day	13% 12% 5% 9% 7% 5% 5% 4 4 5% 31%	2370
April	1st to 10th	Day	15% 13% 5% 7% 8% 4 6% 5% 4 6% 28%	2160
	11th to 20th	Day	15% 11% 4 8% 7% 4 5% 4 4 5% 33%	2134
	21st to end	Day	20% 14% 4 8% 6% 3 4 3 5% 5% 27%	2275
May	1st to 10th	Day	18% 11% 4 8% 7% 4 4 5% 4 6% 29%	2441
	11th to 20th	Day	17% 9% 4 6% 6% 4 5% 4 5% 7% 33%	2478
	21st to end	Day	16% 7% 4 6% 7% 4 6% 5% 5% 9% 32%	2725
June	1st to 10th	Day	22% 9% 3 7% 6% 4 6% 5% 6% 7% 26%	2520
	11th to 20th	Day	16% 7% 3 7% 6% 3 5% 6% 6% 8% 32%	2520
	21st to end	Day	20% 8% 4 7% 7% 4 6% 5% 7% 6% 27%	2520
July	1st to 10th	Day	15% 7% 3 6% 6% 4 6% 6% 5% 8% 34%	2520
	11th to 20th	Day	14% 5% 4 7% 7% 5% 6% 7% 6% 9% 30%	2520
	21st to end	Day	14% 6% 3 7% 7% 4 7% 7% 7% 9% 29%	2744
August	1st to 10th	Day	12% 7% 3 8% 8% 5% 7% 7% 7% 8% 29%	2506
	11th to 20th	Day	11% 7% 4 8% 8% 4 6% 6% 6% 9% 31%	2209
	21st to end	Day	12% 7% 3 7% 7% 5% 7% 6% 7% 9% 32%	2376
September	1st to 10th	Day	14% 6% 2 6% 6% 3 5% 4 6% 8% 39%	2160
	11th to 20th	Day	13% 6% 3 6% 5% 4 4 4 6% 7% 43%	2084
	21st to end	Day	12% 8% 3 7% 6% 4 5% 6% 7% 7% 36%	1980
October	1st to 10th	Day	19% 11% 3 6% 7% 3 5% 4 6% 6% 29%	1866
	11th to 20th	Day	14% 12% 4 7% 7% 4 5% 6% 4 6% 30%	1782
	21st to end	Day	19% 12% 6% 10% 7% 3 4 4 4 6% 25%	1782
November	1st to 10th	Day	11% 11% 5% 10% 7% 4 7% 5% 6% 6% 29%	1671
	11th to 20th	Day	12% 11% 6% 9% 9% 5% 5% 5% 6% 5% 27%	1684
	21st to end	Day	12% 13% 5% 11% 8% 4 6% 6% 5% 6% 24%	1520
December	1st to 10th	Day	12% 17% 10% 13% 9% 3 5% 5% 5% 5% 16%	1520
	11th to 20th	Day	12% 14% 6% 12% 7% 4 6% 5% 7% 7% 22%	1906
	21st to end	Day	16% 15% 8% 9% 8% 4 5% 5% 4 5% 21%	2772
January	1st to 10th	Night	9% 12% 7% 12% 11% 6% 7% 7% 6% 7% 17%	2649
	11th to 20th	Night	8% 12% 5% 11% 10% 6% 8% 7% 6% 7% 19%	2660
	21st to end	Night	6% 8% 6% 12% 10% 6% 8% 7% 7% 7% 23%	2863
February	1st to 10th	Night	8% 12% 5% 11% 13% 6% 8% 6% 7% 6% 18%	2340
	11th to 20th	Night	7% 9% 6% 10% 12% 6% 9% 6% 7% 7% 22%	2156
	21st to end	Night	9% 11% 6% 11% 10% 4 6% 7% 5% 6% 25%	1776
March	1st to 10th	Night	11% 11% 5% 11% 9% 7% 7% 5% 4 5% 24%	2150
	11th to 20th	Night	11% 13% 5% 10% 9% 4 6% 3 6% 6% 28%	2087
	21st to end	Night	14% 12% 5% 8% 6% 3 5% 5% 5% 5% 33%	1985
April	1st to 10th	Night	14% 10% 4 9% 8% 4 6% 5% 5% 6% 28%	1800
	11th to 20th	Night	16% 10% 4 8% 7% 4 6% 4 6% 7% 28%	1775
	21st to end	Night	17% 11% 5% 8% 7% 3 4 5% 4 5% 31%	1684
May	1st to 10th	Night	19% 12% 3 7% 7% 3 4 4 5% 6% 29%	1535
	11th to 20th	Night	15% 9% 4 6% 6% 3 5% 5% 5% 7% 36%	1415
	21st to end	Night	12% 8% 3 7% 6% 3 5% 4 8% 8% 36%	1550
June	1st to 10th	Night	19% 7% 2 5% 7% 3 5% 6% 6% 7% 32%	1440
	11th to 20th	Night	16% 7% 2 5% 5% 3 5% 6% 7% 7% 38%	1440
	21st to end	Night	16% 6% 3 5% 6% 4 6% 5% 6% 8% 35%	1440
July	1st to 10th	Night	12% 5% 2 6% 5% 3 5% 5% 5% 9% 43%	1440
	11th to 20th	Night	9% 5% 3 5% 7% 3 6% 6% 6% 8% 42%	1440
	21st to end	Night	11% 5% 2 4 5% 4 5% 6% 7% 9% 42%	1574
August	1st to 10th	Night	11% 4 2 5% 6% 4 5% 5% 6% 10% 43%	1432
	11th to 20th	Night	9% 5% 3 7% 7% 4 5% 6% 6% 7% 40%	1669
	21st to end	Night	10% 7% 2 5% 6% 4 6% 5% 6% 9% 40%	1980
September	1st to 10th	Night	13% 6% 2 5% 6% 4 5% 5% 6% 6% 42%	1800
	11th to 20th	Night	12% 8% 3 5% 5% 3 4 4 4 6% 47%	1876
	21st to end	Night	15% 7% 2 6% 5% 3 4 4 6% 7% 40%	1980
October	1st to 10th	Night	18% 9% 4 6% 6% 4 6% 4 6% 8% 29%	2092
	11th to 20th	Night	16% 10% 3 7% 6% 5% 5% 5% 5% 7% 32%	2176
	21st to end	Night	19% 12% 6% 9% 7% 5% 6% 4 5% 5% 23%	2574
November	1st to 10th	Night	11% 13% 6% 8% 8% 4 6% 4 6% 6% 27%	2407
	11th to 20th	Night	12% 11% 5% 11% 8% 4 6% 5% 5% 6% 27%	2493
	21st to end	Night	11% 13% 6% 11% 8% 4 5% 5% 6% 7% 23%	2660
December	1st to 10th	Night	13% 14% 7% 15% 9% 4 6% 5% 5% 6% 15%	2660
	11th to 20th	Night	12% 13% 6% 13% 9% 5% 6% 5% 6% 5% 21%	3288
	21st to end	Night	15% 15% 6% 15% 7% 4 5% 4 5% 6% 18%	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	59% 5% 9% 18% 8% 1	1518
	11th to 20th	Day	58% 5% 10% 13% 11% 3	1520
	21st to end	Day	56% 6% 9% 15% 11% 2	1636
February	1st to 10th	Day	62% 5% 9% 15% 7% 2	1620
	11th to 20th	Day	55% 6% 11% 16% 10% 2	1698
	21st to end	Day	57% 4 11% 13% 12% 3	1480
March	1st to 10th	Day	57% 6% 10% 14% 10% 3	1800
	11th to 20th	Day	57% 4 10% 12% 13% 4	1870
	21st to end	Day	53% 5% 8% 15% 14% 5%	2370
April	1st to 10th	Day	54% 5% 10% 18% 12% 3	2160
	11th to 20th	Day	51% 6% 8% 19% 14% 2	2134
	21st to end	Day	58% 5% 8% 15% 11% 3	2275
May	1st to 10th	Day	54% 5% 7% 20% 13% 2	2441
	11th to 20th	Day	49% 5% 9% 20% 14% 2	2482
	21st to end	Day	49% 6% 13% 20% 11% 1	2725
June	1st to 10th	Day	55% 6% 13% 16% 10% 1	2520
	11th to 20th	Day	47% 6% 11% 23% 11% 2	2520
	21st to end	Day	55% 6% 11% 19% 9% 1	2520
July	1st to 10th	Day	45% 7% 12% 24% 11% 1	2450
	11th to 20th	Day	45% 8% 12% 27% 8%	2445
	21st to end	Day	46% 9% 13% 21% 10%	2591
August	1st to 10th	Day	46% 8% 14% 22% 10%	2492
	11th to 20th	Day	44% 9% 15% 24% 8%	2209
	21st to end	Day	44% 8% 12% 24% 11% 1	2376
September	1st to 10th	Day	39% 8% 11% 29% 13% 1	2160
	11th to 20th	Day	39% 6% 9% 28% 17% 1	2084
	21st to end	Day	43% 7% 14% 23% 11% 2	1980
October	1st to 10th	Day	53% 7% 9% 18% 13%	1866
	11th to 20th	Day	51% 6% 13% 21% 8% 1	1782
	21st to end	Day	58% 4 10% 18% 7% 2	1782
November	1st to 10th	Day	52% 6% 13% 17% 11% 1	1671
	11th to 20th	Day	54% 6% 10% 14% 13% 3	1684
	21st to end	Day	55% 5% 13% 18% 8% 1	1520
December	1st to 10th	Day	68% 5% 10% 12% 5%	1520
	11th to 20th	Day	59% 6% 11% 15% 8% 1	1906
	21st to end	Day	63% 4 10% 12% 11%	2772
January	1st to 10th	Night	59% 6% 11% 14% 9% 1	2649
	11th to 20th	Night	58% 7% 11% 14% 8% 2	2660
	21st to end	Night	51% 6% 9% 16% 14% 3	2863
February	1st to 10th	Night	59% 7% 10% 12% 9% 2	2340
	11th to 20th	Night	53% 7% 10% 17% 12% 1	2158
	21st to end	Night	54% 7% 10% 17% 10% 2	1776
March	1st to 10th	Night	56% 7% 10% 14% 11% 2	2160
	11th to 20th	Night	54% 4 8% 18% 12% 2	2088
	21st to end	Night	50% 5% 7% 19% 15% 4	1985
April	1st to 10th	Night	51% 6% 9% 18% 14% 2	1800
	11th to 20th	Night	51% 5% 12% 19% 12% 1	1775
	21st to end	Night	52% 6% 10% 17% 12% 3	1684
May	1st to 10th	Night	53% 5% 7% 18% 16% 2	1535
	11th to 20th	Night	45% 6% 10% 21% 16% 2	1416
	21st to end	Night	43% 6% 16% 22% 12% 2	1551
June	1st to 10th	Night	46% 7% 14% 22% 10% 1	1440
	11th to 20th	Night	42% 5% 15% 23% 13% 1	1440
	21st to end	Night	43% 6% 17% 25% 9%	1440
July	1st to 10th	Night	36% 7% 16% 27% 14% 1	1400
	11th to 20th	Night	35% 8% 15% 31% 10%	1392
	21st to end	Night	35% 8% 17% 28% 11% 1	1486
August	1st to 10th	Night	32% 8% 21% 29% 10%	1422
	11th to 20th	Night	38% 7% 15% 29% 11%	1669
	21st to end	Night	37% 6% 17% 28% 12% 1	1980
September	1st to 10th	Night	36% 8% 15% 28% 12% 1	1800
	11th to 20th	Night	37% 5% 13% 30% 15% 1	1876
	21st to end	Night	40% 7% 12% 27% 12% 2	1980
October	1st to 10th	Night	51% 7% 10% 18% 13% 1	2092
	11th to 20th	Night	48% 7% 13% 22% 9%	2176
	21st to end	Night	56% 7% 11% 14% 9% 2	2574
November	1st to 10th	Night	51% 9% 11% 16% 11% 2	2407
	11th to 20th	Night	52% 8% 10% 17% 10% 3	2493
	21st to end	Night	54% 7% 14% 17% 8% 1	2660
December	1st to 10th	Night	64% 6% 11% 13% 5%	2660
	11th to 20th	Night	58% 6% 10% 14% 11% 1	3288
	21st to end	Night	65% 4 9% 13% 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	16% 30% 31% 17% 6%	180
	11th to 20th	Day	23% 31% 36% 7% 2 1	180
	21st to end	Day	21% 29% 36% 11% 2 1	190
February	1st to 10th	Day	33% 43% 20% 3	240
	11th to 20th	Day	28% 31% 32% 7% 1	357
	21st to end	Day	32% 25% 30% 11% 2	346
March	1st to 10th	Day	26% 29% 31% 12% 2	420
	11th to 20th	Day	26% 30% 28% 11% 3 1	420
	21st to end	Day	31% 29% 22% 12% 5% 1	462
April	1st to 10th	Day	32% 23% 28% 13% 3 1	420
	11th to 20th	Day	31% 25% 24% 13% 4 3	412
	21st to end	Day	33% 25% 26% 10% 5% 1	420
May	1st to 10th	Day	30% 26% 27% 10% 5% 3	423
	11th to 20th	Day	22% 24% 32% 18% 3 1	447
	21st to end	Day	22% 21% 31% 20% 5% 2	485
June	1st to 10th	Day	29% 18% 32% 15% 5% 1	450
	11th to 20th	Day	18% 20% 35% 18% 7% 1	450
	21st to end	Day	22% 22% 30% 19% 6% 1	450
July	1st to 10th	Day	17% 13% 34% 24% 9% 2	445
	11th to 20th	Day	12% 16% 39% 23% 8% 2	444
	21st to end	Day	15% 14% 40% 23% 6% 2	488
August	1st to 10th	Day	12% 16% 33% 24% 11% 3	446
	11th to 20th	Day	13% 14% 34% 22% 12% 5%	439
	21st to end	Day	13% 18% 33% 21% 10% 5%	495
September	1st to 10th	Day	17% 14% 32% 19% 11% 7%	450
	11th to 20th	Day	15% 18% 26% 19% 13% 9%	450
	21st to end	Day	14% 20% 33% 18% 10% 5%	450
October	1st to 10th	Day	26% 21% 24% 16% 11% 2	450
	11th to 20th	Day	24% 27% 25% 18% 6% 1	441
	21st to end	Day	30% 20% 31% 16% 2	396
November	1st to 10th	Day	26% 21% 28% 17% 7%	365
	11th to 20th	Day	29% 31% 22% 13% 4 1	344
	21st to end	Day	28% 33% 25% 12% 2	180
December	1st to 10th	Day	24% 33% 26% 13% 4	180
	11th to 20th	Day	30% 36% 26% 9%	180
	21st to end	Day	29% 31% 30% 7% 2 1	198
January	1st to 10th	Night	20% 28% 34% 15% 3	760
	11th to 20th	Night	24% 24% 35% 13% 3	760
	21st to end	Night	12% 32% 34% 18% 4	820
February	1st to 10th	Night	20% 32% 33% 14% 2	720
	11th to 20th	Night	20% 30% 32% 16% 2	703
	21st to end	Night	21% 30% 29% 17% 3	592
March	1st to 10th	Night	25% 23% 32% 18% 2	720
	11th to 20th	Night	25% 29% 28% 13% 5% 1	720
	21st to end	Night	23% 25% 29% 17% 4 1	792
April	1st to 10th	Night	24% 24% 30% 18% 4	720
	11th to 20th	Night	25% 25% 24% 19% 6% 1	711
	21st to end	Night	26% 21% 27% 20% 5%	604
May	1st to 10th	Night	27% 18% 27% 21% 7%	455
	11th to 20th	Night	20% 20% 29% 24% 6% 1	354
	21st to end	Night	16% 16% 35% 21% 11%	389
June	1st to 10th	Night	22% 12% 32% 23% 11%	360
	11th to 20th	Night	19% 11% 26% 33% 11% 1	360
	21st to end	Night	18% 12% 29% 31% 9% 1	360
July	1st to 10th	Night	12% 11% 30% 31% 15% 1	350
	11th to 20th	Night	11% 7% 31% 33% 17% 2	348
	21st to end	Night	12% 9% 30% 36% 12% 1	394
August	1st to 10th	Night	10% 8% 27% 35% 17% 1	358
	11th to 20th	Night	10% 9% 28% 33% 17% 4	605
	21st to end	Night	14% 10% 28% 29% 19% 1	792
September	1st to 10th	Night	14% 13% 25% 31% 15% 3	720
	11th to 20th	Night	15% 14% 23% 24% 19% 4	720
	21st to end	Night	18% 15% 26% 22% 17% 2	720
October	1st to 10th	Night	23% 17% 25% 21% 13% 1	720
	11th to 20th	Night	24% 20% 24% 23% 9% 1	720
	21st to end	Night	28% 23% 25% 18% 5%	792
November	1st to 10th	Night	23% 23% 29% 18% 7% 1	740
	11th to 20th	Night	23% 27% 26% 14% 7% 2	760
	21st to end	Night	23% 28% 26% 16% 5% 1	760
December	1st to 10th	Night	23% 31% 28% 15% 3	760
	11th to 20th	Night	25% 25% 29% 17% 4 1	760
	21st to end	Night	25% 29% 31% 13% 2	836

Page generated at 2024-01-24 09:37:32. Version ac07

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