New Boston
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the New Boston 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	13% 5% 2 5% 5% 3 4 4 5% 7% 46%	75115
	Night	12% 5% 2 4 4 2 4 4 5% 7% 52%	74964
Transparency	Day	37% 6% 10% 22% 20% 5%	74839
	Night	33% 5% 9% 21% 23% 8%	74760
Seeing	Day	13% 6% 20% 26% 25% 10%	14124
	Night	14% 6% 23% 34% 21% 2	24099

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	17% 8% 2 3 5% 2 4 2 4 5% 49%	1707
	11th to 20th	Day	19% 6% 2 3 4 2 4 4 4 4 48%	1710
	21st to end	Day	19% 6% 2 4 4 2 3 3 3 5% 48%	1836
February	1st to 10th	Day	21% 8% 4 6% 5% 2 4 3 3 4 40%	1620
	11th to 20th	Day	20% 8% 3 5% 4 3 3 4 4 5% 40%	1677
	21st to end	Day	25% 7% 2 5% 5% 2 3 3 3 4 41%	1628
March	1st to 10th	Day	18% 6% 3 5% 4 2 4 3 5% 6% 43%	1980
	11th to 20th	Day	20% 6% 3 5% 5% 2 3 4 3 5% 43%	1980
	21st to end	Day	17% 7% 4 6% 5% 3 4 3 3 5% 42%	2178
April	1st to 10th	Day	14% 5% 3 5% 5% 3 4 5% 4 7% 44%	2041
	11th to 20th	Day	16% 6% 3 4 4 3 4 4 5% 6% 46%	2134
	21st to end	Day	14% 6% 3 4 5% 3 5% 4 5% 7% 45%	2160
May	1st to 10th	Day	16% 5% 3 4 5% 3 4 3 5% 7% 44%	2254
	11th to 20th	Day	12% 6% 2 5% 5% 3 5% 5% 6% 8% 42%	2302
	21st to end	Day	11% 5% 3 6% 5% 3 6% 5% 6% 9% 40%	2531
June	1st to 10th	Day	7% 4 2 5% 5% 3 5% 7% 6% 10% 46%	2340
	11th to 20th	Day	6% 4 2 4 6% 4 7% 6% 6% 9% 45%	2340
	21st to end	Day	6% 3 2 4 4 3 5% 7% 7% 10% 51%	2340
July	1st to 10th	Day	8% 5% 3 6% 6% 4 7% 7% 7% 10% 36%	2340
	11th to 20th	Day	6% 3 2 4 5% 2 6% 7% 7% 10% 49%	2340
	21st to end	Day	7% 4 2 4 6% 4 5% 6% 8% 10% 45%	2546
August	1st to 10th	Day	4 3 1 4 5% 4 6% 6% 7% 11% 49%	2328
	11th to 20th	Day	10% 3 2 4 6% 2 5% 6% 6% 8% 48%	2230
	21st to end	Day	7% 4 3 5% 5% 4 6% 7% 7% 9% 43%	2376
September	1st to 10th	Day	9% 6% 2 4 4 3 4 5% 5% 7% 51%	2134
	11th to 20th	Day	12% 4 2 4 5% 3 5% 5% 6% 7% 47%	1980
	21st to end	Day	9% 3 1 4 4 2 4 4 5% 6% 57%	1976
October	1st to 10th	Day	7% 4 2 3 4 2 4 4 5% 7% 58%	1800
	11th to 20th	Day	15% 4 2 3 3 3 3 3 3 4 56%	1800
	21st to end	Day	16% 6% 2 4 4 2 4 3 3 5% 53%	1980
November	1st to 10th	Day	13% 4 3 3 4 2 3 4 4 7% 53%	1858
	11th to 20th	Day	10% 5% 2 5% 4 2 3 3 4 7% 54%	1900
	21st to end	Day	19% 6% 3 4 4 3 2 3 3 4 49%	1763
December	1st to 10th	Day	17% 7% 2 4 3 2 3 3 4 5% 48%	1710
	11th to 20th	Day	16% 9% 3 5% 4 3 4 4 4 6% 42%	2161
	21st to end	Day	18% 8% 3 6% 5% 2 4 3 3 6% 43%	3135
January	1st to 10th	Night	17% 6% 2 4 3 2 3 3 4 5% 52%	2458
	11th to 20th	Night	19% 6% 1 4 4 2 3 2 4 6% 49%	2470
	21st to end	Night	18% 6% 2 4 4 2 3 3 4 4 50%	2665
February	1st to 10th	Night	18% 6% 2 4 4 2 3 3 4 5% 48%	2340
	11th to 20th	Night	20% 6% 2 5% 4 2 3 4 4 6% 44%	2184
	21st to end	Night	21% 6% 2 4 4 2 2 3 3 5% 48%	1628
March	1st to 10th	Night	18% 6% 2 4 4 2 4 4 5% 6% 45%	1980
	11th to 20th	Night	17% 6% 3 5% 5% 3 4 3 4 6% 46%	1980
	21st to end	Night	15% 5% 3 6% 5% 2 4 3 4 6% 48%	2178
April	1st to 10th	Night	11% 5% 2 4 4 3 4 4 5% 6% 52%	1918
	11th to 20th	Night	12% 6% 2 4 4 2 4 4 5% 7% 50%	1775
	21st to end	Night	11% 5% 2 4 4 2 3 3 4 9% 53%	1800
May	1st to 10th	Night	10% 4 2 5% 5% 2 4 4 5% 9% 50%	1702
	11th to 20th	Night	10% 6% 2 5% 4 3 4 4 5% 7% 49%	1593
	21st to end	Night	9% 5% 3 5% 4 3 3 5% 6% 8% 49%	1745
June	1st to 10th	Night	4 3 2 4 4 3 4 5% 5% 9% 55%	1620
	11th to 20th	Night	4 3 2 3 3 2 3 4 5% 9% 61%	1620
	21st to end	Night	4 3 1 3 3 3 4 4 7% 9% 60%	1620
July	1st to 10th	Night	4 3 2 5% 5% 3 5% 5% 8% 13% 47%	1620
	11th to 20th	Night	3 2 1 2 4 2 4 5% 6% 11% 61%	1620
	21st to end	Night	3 2 1 3 4 3 6% 6% 8% 12% 52%	1772
August	1st to 10th	Night	3 2 1 1 4 2 3 5% 7% 11% 60%	1611
	11th to 20th	Night	7% 4 2 5% 4 3 4 5% 5% 11% 51%	1671
	21st to end	Night	5% 3 2 4 5% 3 5% 6% 7% 10% 49%	1980
September	1st to 10th	Night	7% 4 2 4 3 3 4 4 5% 7% 58%	1822
	11th to 20th	Night	10% 4 2 4 5% 3 4 5% 6% 8% 51%	1980
	21st to end	Night	7% 3 2 3 3 2 3 3 5% 7% 63%	1980
October	1st to 10th	Night	7% 3 2 3 3 2 3 3 4 7% 63%	2145
	11th to 20th	Night	11% 4 2 3 3 2 3 3 4 5% 61%	2160
	21st to end	Night	17% 5% 2 3 3 2 2 2 3 4 57%	2376
November	1st to 10th	Night	12% 4 2 4 4 1 2 3 3 5% 59%	2220
	11th to 20th	Night	10% 5% 2 4 4 2 3 3 4 5% 57%	2280
	21st to end	Night	15% 6% 2 5% 4 2 4 3 3 5% 51%	2413
December	1st to 10th	Night	16% 5% 3 5% 4 2 3 3 4 6% 49%	2470
	11th to 20th	Night	15% 6% 2 5% 5% 3 4 4 3 5% 48%	3036
	21st to end	Night	17% 7% 2 4 3 2 3 3 4 4 48%	4532

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	40% 3 9% 20% 23% 5%	1708
	11th to 20th	Day	39% 4 6% 24% 22% 5%	1710
	21st to end	Day	42% 3 5% 18% 25% 7%	1836
February	1st to 10th	Day	50% 3 6% 17% 18% 6%	1620
	11th to 20th	Day	48% 3 6% 19% 18% 6%	1686
	21st to end	Day	50% 4 4 12% 22% 8%	1628
March	1st to 10th	Day	43% 4 7% 17% 20% 10%	1980
	11th to 20th	Day	46% 4 7% 20% 18% 5%	1980
	21st to end	Day	46% 3 7% 20% 20% 4	2178
April	1st to 10th	Day	39% 5% 9% 23% 17% 7%	2041
	11th to 20th	Day	40% 5% 8% 21% 20% 7%	2134
	21st to end	Day	39% 6% 9% 21% 22% 3	2160
May	1st to 10th	Day	41% 5% 8% 23% 19% 4	2254
	11th to 20th	Day	39% 8% 13% 23% 16% 1	2306
	21st to end	Day	41% 9% 12% 23% 15% 1	2531
June	1st to 10th	Day	32% 8% 14% 28% 15% 2	2340
	11th to 20th	Day	34% 7% 15% 24% 18% 2	2340
	21st to end	Day	28% 8% 13% 28% 21% 2	2340
July	1st to 10th	Day	40% 10% 16% 23% 11% 1	2276
	11th to 20th	Day	26% 8% 18% 27% 19% 2	2271
	21st to end	Day	31% 8% 18% 32% 11%	2405
August	1st to 10th	Day	27% 9% 15% 31% 16% 1	2314
	11th to 20th	Day	33% 8% 13% 28% 16% 3	2230
	21st to end	Day	35% 8% 15% 26% 14% 3	2376
September	1st to 10th	Day	33% 6% 11% 20% 22% 8%	2134
	11th to 20th	Day	35% 7% 11% 20% 20% 7%	1980
	21st to end	Day	28% 6% 9% 22% 25% 11%	1976
October	1st to 10th	Day	26% 4 12% 21% 24% 13%	1800
	11th to 20th	Day	33% 4 5% 17% 27% 14%	1800
	21st to end	Day	37% 3 6% 18% 25% 11%	1980
November	1st to 10th	Day	33% 4 8% 20% 25% 9%	1858
	11th to 20th	Day	33% 3 8% 19% 28% 9%	1900
	21st to end	Day	42% 3 5% 17% 26% 7%	1763
December	1st to 10th	Day	40% 3 8% 21% 20% 7%	1710
	11th to 20th	Day	43% 3 6% 17% 23% 7%	2159
	21st to end	Day	44% 3 6% 17% 23% 6%	3135
January	1st to 10th	Night	37% 4 6% 16% 29% 8%	2458
	11th to 20th	Night	39% 4 8% 18% 24% 7%	2470
	21st to end	Night	40% 2 5% 16% 27% 10%	2665
February	1st to 10th	Night	40% 3 7% 20% 21% 9%	2340
	11th to 20th	Night	44% 3 6% 18% 21% 8%	2185
	21st to end	Night	42% 4 6% 14% 22% 12%	1628
March	1st to 10th	Night	41% 4 8% 15% 20% 13%	1980
	11th to 20th	Night	42% 4 7% 17% 22% 8%	1980
	21st to end	Night	39% 5% 8% 21% 22% 5%	2178
April	1st to 10th	Night	34% 4 10% 22% 19% 11%	1918
	11th to 20th	Night	34% 5% 9% 20% 21% 11%	1775
	21st to end	Night	32% 5% 9% 24% 26% 5%	1800
May	1st to 10th	Night	33% 7% 9% 24% 17% 10%	1702
	11th to 20th	Night	34% 6% 13% 26% 17% 3	1594
	21st to end	Night	33% 7% 13% 26% 19% 2	1746
June	1st to 10th	Night	24% 8% 13% 31% 20% 4	1620
	11th to 20th	Night	21% 7% 13% 31% 24% 5%	1620
	21st to end	Night	20% 8% 13% 27% 27% 5%	1620
July	1st to 10th	Night	26% 9% 20% 29% 14% 2	1575
	11th to 20th	Night	17% 6% 18% 34% 22% 3	1566
	21st to end	Night	21% 9% 17% 34% 18% 1	1673
August	1st to 10th	Night	17% 7% 18% 34% 22% 2	1601
	11th to 20th	Night	29% 6% 13% 27% 21% 4	1671
	21st to end	Night	28% 8% 14% 27% 19% 3	1980
September	1st to 10th	Night	27% 5% 13% 22% 24% 10%	1822
	11th to 20th	Night	32% 6% 10% 22% 22% 9%	1980
	21st to end	Night	21% 5% 9% 23% 28% 14%	1980
October	1st to 10th	Night	23% 4 10% 24% 23% 17%	2145
	11th to 20th	Night	27% 4 7% 15% 27% 19%	2160
	21st to end	Night	33% 3 6% 18% 25% 15%	2376
November	1st to 10th	Night	30% 4 8% 18% 28% 13%	2220
	11th to 20th	Night	30% 4 8% 17% 28% 12%	2280
	21st to end	Night	38% 4 5% 18% 26% 9%	2413
December	1st to 10th	Night	37% 5% 9% 18% 22% 9%	2470
	11th to 20th	Night	42% 3 5% 15% 24% 11%	3037
	21st to end	Night	40% 3 7% 20% 24% 6%	4532

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	24% 11% 35% 23% 7%	270
	11th to 20th	Day	23% 16% 36% 19% 6%	270
	21st to end	Day	23% 19% 33% 20% 5%	282
February	1st to 10th	Day	26% 12% 40% 16% 5% 1	240
	11th to 20th	Day	26% 16% 40% 13% 5%	240
	21st to end	Day	32% 18% 36% 11% 4	198
March	1st to 10th	Day	24% 13% 34% 22% 6% 1	240
	11th to 20th	Day	20% 23% 32% 19% 5% 1	240
	21st to end	Day	19% 17% 38% 20% 5%	264
April	1st to 10th	Day	18% 9% 40% 24% 9% 1	301
	11th to 20th	Day	23% 12% 31% 23% 10% 1	412
	21st to end	Day	16% 10% 32% 27% 12% 2	420
May	1st to 10th	Day	16% 9% 30% 32% 12% 1	517
	11th to 20th	Day	14% 5% 24% 33% 20% 4	625
	21st to end	Day	12% 3 19% 36% 23% 7%	679
June	1st to 10th	Day	9% 1 13% 28% 37% 11%	630
	11th to 20th	Day	5% 2 11% 35% 37% 10%	630
	21st to end	Day	6% 1 13% 30% 35% 16%	630
July	1st to 10th	Day	7% 1 9% 28% 38% 16%	621
	11th to 20th	Day	5% 2 5% 26% 40% 23%	618
	21st to end	Day	6% 1 4 25% 43% 22%	684
August	1st to 10th	Day	4 1 7% 21% 45% 22%	626
	11th to 20th	Day	11% 1 4 26% 42% 16%	544
	21st to end	Day	9% 1 4 17% 44% 26%	495
September	1st to 10th	Day	8% 2 4 20% 42% 23%	424
	11th to 20th	Day	6% 2 7% 26% 37% 22%	270
	21st to end	Day	13% 3 10% 27% 30% 18%	270
October	1st to 10th	Day	3 17% 43% 28% 8%	270
	11th to 20th	Day	13% 6% 27% 31% 17% 6%	270
	21st to end	Day	22% 11% 27% 23% 14% 3	297
November	1st to 10th	Day	16% 8% 29% 25% 20% 3	270
	11th to 20th	Day	13% 7% 35% 34% 9% 2	270
	21st to end	Day	22% 16% 25% 22% 12% 3	270
December	1st to 10th	Day	20% 11% 35% 22% 9% 4	270
	11th to 20th	Day	25% 11% 34% 21% 8% 1	270
	21st to end	Day	23% 14% 39% 16% 5% 1	297
January	1st to 10th	Night	21% 9% 31% 32% 7%	950
	11th to 20th	Night	22% 9% 32% 28% 7% 1	950
	21st to end	Night	21% 8% 36% 30% 5%	1025
February	1st to 10th	Night	22% 9% 35% 28% 6%	900
	11th to 20th	Night	24% 10% 35% 26% 4	790
	21st to end	Night	26% 11% 35% 25% 3	444
March	1st to 10th	Night	23% 7% 34% 31% 5%	540
	11th to 20th	Night	19% 8% 31% 34% 7% 1	540
	21st to end	Night	17% 8% 36% 33% 7%	594
April	1st to 10th	Night	13% 8% 37% 34% 9%	540
	11th to 20th	Night	13% 8% 36% 30% 13%	533
	21st to end	Night	14% 6% 36% 33% 11% 1	540
May	1st to 10th	Night	11% 6% 30% 41% 12% 1	540
	11th to 20th	Night	12% 3 27% 37% 19% 2	531
	21st to end	Night	9% 4 17% 43% 23% 4	584
June	1st to 10th	Night	6% 1 11% 36% 43% 3	540
	11th to 20th	Night	4 2 10% 44% 37% 3	540
	21st to end	Night	4 1 9% 38% 41% 8%	540
July	1st to 10th	Night	3 1 4 32% 52% 7%	525
	11th to 20th	Night	3 4 29% 55% 8%	522
	21st to end	Night	3 5% 27% 55% 9%	591
August	1st to 10th	Night	4 1 4 32% 52% 8%	537
	11th to 20th	Night	7% 1 4 35% 46% 6%	534
	21st to end	Night	6% 1 4 30% 52% 8%	594
September	1st to 10th	Night	9% 1 4 32% 47% 7%	540
	11th to 20th	Night	11% 1 7% 33% 44% 4	540
	21st to end	Night	9% 1 8% 38% 39% 5%	540
October	1st to 10th	Night	7% 2 10% 44% 32% 5%	705
	11th to 20th	Night	15% 4 21% 39% 20% 2	720
	21st to end	Night	17% 7% 24% 31% 18% 3	792
November	1st to 10th	Night	13% 4 24% 41% 18% 1	740
	11th to 20th	Night	13% 7% 27% 40% 13% 1	760
	21st to end	Night	18% 9% 30% 29% 13% 1	893
December	1st to 10th	Night	19% 8% 29% 36% 8%	950
	11th to 20th	Night	22% 8% 28% 35% 7%	950
	21st to end	Night	20% 9% 32% 31% 7%	1045

Page generated at 2024-01-24 08:37:30. Version ac07

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