Foxboro Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Foxboro Park clear sky chart from 2005-11-06 to 2026-02-01.

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	5% 4 2 4 3 3 3 3 5% 7% 62%	136055
	Night	7% 5% 2 5% 4 4 4 3 5% 7% 54%	133388
Transparency	Day	23% 4 8% 19% 25% 20%	130975
	Night	28% 5% 10% 18% 21% 17%	129455
Seeing	Day	9% 10% 29% 34% 15% 3	16921
	Night	11% 5% 19% 37% 24% 4	26327

By Month

Percentage Cloud Cover SW (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	12% 7% 3 6% 4 4 5% 4 6% 7% 42%	3936
	11th to 20th	Day	10% 7% 3 7% 4 3 3 3 3 5% 50%	4190
	21st to end	Day	14% 8% 3 8% 4 4 4 3 4 6% 40%	4609
February	1st to 10th	Day	15% 7% 2 6% 4 3 4 4 4 6% 44%	1801
	11th to 20th	Day	11% 8% 3 6% 5% 5% 3 4 7% 8% 40%	1830
	21st to end	Day	11% 7% 2 7% 4 4 4 3 4 7% 48%	1650
March	1st to 10th	Day	9% 8% 3 10% 6% 6% 5% 4 7% 8% 36%	4868
	11th to 20th	Day	8% 5% 2 6% 4 4 5% 4 5% 8% 49%	5000
	21st to end	Day	9% 6% 2 6% 5% 6% 6% 5% 8% 10% 37%	5563
April	1st to 10th	Day	10% 8% 2 5% 4 4 4 4 6% 8% 45%	2400
	11th to 20th	Day	7% 5% 2 4 3 3 4 3 5% 7% 57%	2369
	21st to end	Day	3 4 2 4 3 3 3 3 5% 10% 60%	2400
May	1st to 10th	Day	4 2 1 2 2 1 2 2 3 5% 78%	5660
	11th to 20th	Day	2 1 1 2 1 2 2 2 4 6% 77%	6002
	21st to end	Day	1 2 1 2 1 1 1 1 3 6% 79%	6902
June	1st to 10th	Day	3 4 2 3 3 3 3 3 5% 7% 64%	2800
	11th to 20th	Day	1 2 1 2 2 2 2 3 4 8% 75%	2800
	21st to end	Day	1 2 1 2 2 2 2 3 4 6% 76%	2800
July	1st to 10th	Day	1 1 2 2 2 2 2 3 5% 83%	6319
	11th to 20th	Day	1 1 3 2 2 3 2 4 6% 76%	5936
	21st to end	Day	2 1 4 3 2 3 2 3 5% 74%	6402
August	1st to 10th	Day	1 1 1 2 2 2 3 3 4 7% 75%	5777
	11th to 20th	Day	1 1 3 2 2 2 2 3 5% 81%	5543
	21st to end	Day	1 1 1 2 2 2 3 3 4 8% 73%	5984
September	1st to 10th	Day	2 1 4 2 2 2 2 3 7% 75%	2400
	11th to 20th	Day	2 4 2 4 3 3 3 3 4 7% 65%	2400
	21st to end	Day	2 3 1 2 2 2 2 2 3 6% 74%	2115
October	1st to 10th	Day	2 2 1 4 2 2 3 2 5% 7% 71%	3280
	11th to 20th	Day	4 4 1 4 3 3 3 3 4 6% 65%	3261
	21st to end	Day	4 3 2 5% 4 4 4 4 5% 8% 58%	3558
November	1st to 10th	Day	7% 5% 2 4 3 3 4 4 6% 7% 57%	2014
	11th to 20th	Day	9% 6% 3 8% 4 4 5% 3 6% 7% 44%	1890
	21st to end	Day	10% 6% 1 5% 3 3 3 4 6% 7% 52%	1696
December	1st to 10th	Day	7% 5% 2 4 3 2 4 4 7% 11% 52%	2700
	11th to 20th	Day	17% 10% 3 9% 5% 6% 7% 5% 6% 7% 24%	3108
	21st to end	Day	17% 13% 4 9% 5% 4 4 4 6% 8% 26%	4092
January	1st to 10th	Night	9% 6% 3 6% 4 4 5% 5% 6% 8% 44%	6222
	11th to 20th	Night	10% 6% 3 8% 4 4 4 4 5% 6% 45%	6010
	21st to end	Night	13% 8% 3 8% 4 4 4 3 4 6% 43%	6611
February	1st to 10th	Night	14% 6% 3 5% 4 3 3 3 4 6% 48%	2600
	11th to 20th	Night	11% 6% 3 7% 4 4 4 3 5% 8% 46%	2455
	21st to end	Night	10% 7% 2 4 4 4 5% 3 6% 7% 51%	1980
March	1st to 10th	Night	10% 8% 3 9% 5% 4 4 4 5% 8% 40%	5011
	11th to 20th	Night	12% 6% 2 5% 4 3 3 3 5% 7% 51%	5000
	21st to end	Night	11% 9% 2 7% 4 4 4 3 5% 8% 43%	5411
April	1st to 10th	Night	7% 6% 3 6% 5% 4 3 4 6% 8% 50%	2000
	11th to 20th	Night	6% 5% 2 5% 3 3 3 3 4 6% 58%	1979
	21st to end	Night	4 3 2 3 3 2 4 3 6% 8% 61%	2000
May	1st to 10th	Night	3 3 1 3 2 2 2 1 4 5% 75%	4312
	11th to 20th	Night	1 2 1 3 3 4 4 3 5% 7% 66%	3900
	21st to end	Night	1 1 1 2 2 2 2 2 3 5% 78%	3972
June	1st to 10th	Night	3 4 1 5% 3 4 3 3 7% 11% 57%	1600
	11th to 20th	Night	1 2 3 2 3 2 3 5% 8% 70%	1600
	21st to end	Night	1 3 1 3 3 2 3 2 5% 8% 69%	1600
July	1st to 10th	Night	1 1 2 3 3 2 2 4 6% 75%	3640
	11th to 20th	Night	1 3 2 6% 6% 6% 5% 3 6% 8% 55%	4024
	21st to end	Night	1 5% 2 7% 7% 5% 4 4 7% 10% 47%	4472
August	1st to 10th	Night	2 2 1 3 3 4 3 3 6% 8% 65%	4035
	11th to 20th	Night	1 1 3 3 3 3 2 4 8% 71%	4317
	21st to end	Night	1 2 1 4 3 3 3 3 5% 11% 64%	5015
September	1st to 10th	Night	2 1 3 3 3 3 3 5% 8% 69%	2000
	11th to 20th	Night	2 5% 2 5% 5% 3 3 3 5% 8% 59%	2000
	21st to end	Night	2 3 1 4 3 3 3 2 4 7% 68%	2279
October	1st to 10th	Night	3 3 1 3 3 2 3 2 4 6% 70%	3920
	11th to 20th	Night	3 6% 2 5% 4 3 3 2 4 7% 61%	3897
	21st to end	Night	4 4 2 5% 3 3 4 4 6% 7% 59%	4253
November	1st to 10th	Night	5% 6% 2 5% 4 4 3 3 5% 9% 54%	2502
	11th to 20th	Night	10% 6% 2 6% 4 3 4 3 6% 7% 49%	2730
	21st to end	Night	8% 5% 1 4 5% 4 3 3 6% 7% 53%	2919
December	1st to 10th	Night	7% 4 2 5% 3 4 4 3 5% 7% 54%	4700
	11th to 20th	Night	18% 10% 4 8% 5% 5% 5% 4 8% 8% 25%	5316
	21st to end	Night	19% 9% 4 9% 5% 4 5% 4 5% 6% 29%	7106

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	39% 6% 16% 20% 15% 4	3936
	11th to 20th	Day	38% 4 7% 15% 21% 15%	4190
	21st to end	Day	45% 6% 6% 12% 14% 16%	4609
February	1st to 10th	Day	40% 6% 7% 19% 20% 8%	1801
	11th to 20th	Day	39% 7% 9% 18% 21% 6%	1839
	21st to end	Day	37% 4 9% 23% 20% 8%	1650
March	1st to 10th	Day	45% 6% 7% 20% 20% 2	4868
	11th to 20th	Day	33% 4 15% 29% 11% 8%	5000
	21st to end	Day	38% 8% 15% 27% 10% 2	5563
April	1st to 10th	Day	37% 6% 13% 21% 20% 4	2400
	11th to 20th	Day	28% 6% 14% 24% 21% 7%	2372
	21st to end	Day	21% 7% 13% 30% 25% 4	2400
May	1st to 10th	Day	12% 3 7% 27% 31% 19%	5660
	11th to 20th	Day	11% 3 6% 31% 39% 9%	6005
	21st to end	Day	9% 6% 7% 29% 44% 4	6904
June	1st to 10th	Day	20% 7% 10% 27% 28% 8%	2800
	11th to 20th	Day	9% 6% 8% 21% 37% 19%	2800
	21st to end	Day	11% 3 6% 13% 33% 34%	2800
July	1st to 10th	Day	6% 2 3 6% 23% 61%	6251
	11th to 20th	Day	8% 2 3 5% 12% 70%	5865
	21st to end	Day	11% 2 4 16% 28% 40%	6217
August	1st to 10th	Day	13% 3 4 9% 26% 45%	4206
	11th to 20th	Day	7% 2 3 9% 41% 37%	4014
	21st to end	Day	10% 2 5% 13% 36% 35%	4311
September	1st to 10th	Day	11% 3 4 11% 31% 41%	2400
	11th to 20th	Day	19% 5% 6% 21% 33% 15%	2400
	21st to end	Day	14% 3 5% 20% 34% 24%	2115
October	1st to 10th	Day	14% 3 4 12% 28% 39%	3280
	11th to 20th	Day	18% 2 6% 25% 30% 19%	3261
	21st to end	Day	23% 3 7% 25% 30% 14%	3558
November	1st to 10th	Day	26% 4 11% 27% 21% 11%	2014
	11th to 20th	Day	38% 6% 10% 22% 20% 6%	1890
	21st to end	Day	31% 4 11% 20% 24% 10%	1696
December	1st to 10th	Day	27% 3 7% 31% 26% 6%	2700
	11th to 20th	Day	58% 5% 8% 15% 12% 3	3108
	21st to end	Day	54% 6% 11% 18% 10% 2	4092
January	1st to 10th	Night	34% 7% 21% 20% 14% 4	6222
	11th to 20th	Night	37% 6% 8% 16% 21% 13%	6010
	21st to end	Night	43% 5% 7% 11% 19% 15%	6611
February	1st to 10th	Night	38% 5% 8% 19% 20% 10%	2600
	11th to 20th	Night	37% 6% 11% 18% 20% 8%	2457
	21st to end	Night	32% 5% 11% 27% 19% 6%	1980
March	1st to 10th	Night	42% 9% 9% 18% 20% 3	5011
	11th to 20th	Night	33% 6% 13% 24% 15% 8%	5000
	21st to end	Night	40% 8% 14% 24% 12% 2	5411
April	1st to 10th	Night	33% 6% 14% 22% 21% 5%	2000
	11th to 20th	Night	28% 7% 12% 25% 19% 9%	1979
	21st to end	Night	20% 6% 14% 31% 23% 6%	2000
May	1st to 10th	Night	14% 4 8% 25% 30% 18%	4309
	11th to 20th	Night	17% 4 17% 26% 27% 10%	3901
	21st to end	Night	10% 6% 14% 25% 40% 5%	3972
June	1st to 10th	Night	21% 9% 12% 22% 27% 9%	1600
	11th to 20th	Night	11% 6% 9% 19% 35% 19%	1600
	21st to end	Night	13% 4 12% 14% 28% 30%	1600
July	1st to 10th	Night	6% 2 4 5% 21% 62%	3600
	11th to 20th	Night	14% 3 6% 5% 10% 63%	3972
	21st to end	Night	19% 2 6% 14% 24% 35%	4345
August	1st to 10th	Night	19% 3 7% 8% 23% 39%	2929
	11th to 20th	Night	10% 4 8% 7% 36% 36%	3116
	21st to end	Night	13% 3 8% 11% 32% 32%	3608
September	1st to 10th	Night	12% 3 9% 11% 25% 40%	2000
	11th to 20th	Night	23% 6% 11% 19% 25% 15%	2000
	21st to end	Night	15% 3 7% 18% 29% 26%	2279
October	1st to 10th	Night	16% 3 6% 11% 18% 46%	3920
	11th to 20th	Night	21% 3 7% 26% 22% 22%	3897
	21st to end	Night	24% 3 6% 23% 25% 19%	4253
November	1st to 10th	Night	27% 6% 11% 25% 18% 13%	2502
	11th to 20th	Night	33% 5% 12% 24% 19% 7%	2730
	21st to end	Night	30% 5% 10% 20% 22% 12%	2919
December	1st to 10th	Night	29% 4 6% 25% 26% 10%	4700
	11th to 20th	Night	54% 5% 9% 15% 15% 3	5316
	21st to end	Night	53% 7% 12% 16% 9% 3	7106

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% 31% 19% 13% 2	320
	11th to 20th	Day	17% 10% 26% 33% 12% 2	430
	21st to end	Day	14% 9% 30% 31% 15% 2	473
February	1st to 10th	Day	23% 11% 18% 29% 17% 2	401
	11th to 20th	Day	18% 17% 25% 25% 13% 1	432
	21st to end	Day	12% 15% 27% 30% 14% 2	414
March	1st to 10th	Day	20% 16% 31% 20% 10% 3	500
	11th to 20th	Day	18% 17% 26% 20% 14% 4	500
	21st to end	Day	14% 18% 32% 25% 10% 1	550
April	1st to 10th	Day	17% 14% 32% 25% 10% 3	500
	11th to 20th	Day	13% 16% 32% 25% 9% 4	492
	21st to end	Day	6% 19% 30% 29% 11% 5%	500
May	1st to 10th	Day	9% 16% 33% 31% 11% 1	503
	11th to 20th	Day	9% 13% 33% 31% 13% 1	528
	21st to end	Day	6% 12% 33% 35% 12% 2	573
June	1st to 10th	Day	7% 11% 36% 33% 12% 2	530
	11th to 20th	Day	4 12% 37% 36% 9% 2	530
	21st to end	Day	1 7% 35% 43% 14% 1	530
July	1st to 10th	Day	2 4 33% 47% 12% 1	526
	11th to 20th	Day	1 2 24% 54% 17% 2	524
	21st to end	Day	2 2 31% 48% 15% 2	575
August	1st to 10th	Day	2 5% 31% 46% 13% 3	527
	11th to 20th	Day	2 4 30% 44% 16% 4	517
	21st to end	Day	2 3 24% 48% 20% 4	583
September	1st to 10th	Day	2 5% 24% 44% 18% 7%	530
	11th to 20th	Day	4 11% 28% 36% 16% 6%	530
	21st to end	Day	4 9% 26% 32% 25% 5%	530
October	1st to 10th	Day	5% 7% 27% 31% 22% 8%	530
	11th to 20th	Day	7% 9% 22% 30% 26% 7%	530
	21st to end	Day	9% 7% 24% 30% 24% 6%	583
November	1st to 10th	Day	11% 9% 19% 26% 30% 6%	490
	11th to 20th	Day	10% 12% 19% 34% 21% 4	330
	21st to end	Day	13% 7% 30% 34% 15% 2	228
December	1st to 10th	Day	14% 11% 27% 30% 14% 4	220
	11th to 20th	Day	18% 13% 25% 31% 13% 1	220
	21st to end	Day	24% 11% 29% 26% 10%	242
January	1st to 10th	Night	20% 6% 16% 32% 22% 4	840
	11th to 20th	Night	13% 6% 16% 38% 22% 4	840
	21st to end	Night	17% 5% 14% 38% 23% 3	924
February	1st to 10th	Night	19% 6% 15% 37% 21% 3	800
	11th to 20th	Night	14% 9% 18% 34% 21% 4	784
	21st to end	Night	14% 8% 20% 34% 21% 2	660
March	1st to 10th	Night	19% 9% 22% 29% 19% 3	800
	11th to 20th	Night	17% 8% 21% 30% 21% 3	800
	21st to end	Night	16% 8% 27% 32% 17% 1	880
April	1st to 10th	Night	12% 8% 26% 35% 17% 2	800
	11th to 20th	Night	10% 13% 25% 31% 18% 3	791
	21st to end	Night	7% 9% 29% 33% 20% 3	800
May	1st to 10th	Night	6% 5% 28% 40% 19% 2	695
	11th to 20th	Night	6% 3 24% 41% 23% 3	522
	21st to end	Night	5% 7% 30% 39% 17% 2	433
June	1st to 10th	Night	4 4 32% 44% 16% 1	400
	11th to 20th	Night	1 4 27% 52% 15% 1	400
	21st to end	Night	3 3 23% 45% 24% 1	400
July	1st to 10th	Night	3 19% 52% 25% 1	390
	11th to 20th	Night	3 1 14% 53% 25% 4	547
	21st to end	Night	3 2 18% 45% 30% 3	657
August	1st to 10th	Night	6% 3 20% 43% 26% 3	597
	11th to 20th	Night	3 1 21% 46% 26% 4	703
	21st to end	Night	5% 1 14% 47% 29% 4	880
September	1st to 10th	Night	2 1 15% 42% 33% 7%	800
	11th to 20th	Night	6% 2 18% 41% 28% 4	800
	21st to end	Night	5% 4 16% 37% 33% 6%	800
October	1st to 10th	Night	7% 3 16% 36% 31% 7%	800
	11th to 20th	Night	8% 5% 14% 33% 33% 7%	800
	21st to end	Night	9% 4 12% 32% 34% 10%	880
November	1st to 10th	Night	8% 5% 14% 30% 35% 7%	820
	11th to 20th	Night	13% 4 15% 36% 27% 5%	840
	21st to end	Night	11% 5% 14% 40% 26% 5%	840
December	1st to 10th	Night	15% 5% 16% 35% 24% 5%	840
	11th to 20th	Night	23% 5% 16% 33% 20% 3	840
	21st to end	Night	22% 8% 22% 29% 17% 1	924

Page generated at 2026-01-28 22:21:45. Version ac07

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