Myles Standish State Forest
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Myles Standish State Forest clear sky chart from 2005-11-06 to 2024-11-11.

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	17% 8% 2 6% 4 4 4 3 5% 7% 39%	101212
	Night	18% 9% 3 6% 4 4 4 3 5% 6% 38%	97957
Transparency	Day	43% 7% 13% 21% 14% 2	104792
	Night	45% 6% 12% 21% 14% 2	102467
Seeing	Day	19% 10% 30% 26% 12% 3	15196
	Night	20% 10% 31% 27% 9% 1	24053

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% 10% 2 6% 3 3 3 3 5% 5% 45%	2517
	11th to 20th	Day	18% 9% 3 6% 4 3 4 3 5% 5% 40%	2520
	21st to end	Day	21% 12% 4 8% 4 4 3 3 3 4 33%	2801
February	1st to 10th	Day	19% 9% 4 6% 4 4 4 3 5% 5% 36%	1805
	11th to 20th	Day	15% 7% 4 6% 3 4 4 4 5% 7% 43%	1848
	21st to end	Day	18% 11% 2 6% 4 3 4 3 5% 6% 38%	1570
March	1st to 10th	Day	24% 17% 3 7% 4 3 3 2 3 5% 30%	3116
	11th to 20th	Day	11% 7% 2 7% 4 4 4 4 5% 7% 44%	3384
	21st to end	Day	23% 10% 2 7% 4 4 3 3 4 4 36%	3942
April	1st to 10th	Day	20% 10% 2 5% 4 3 4 3 5% 6% 38%	2280
	11th to 20th	Day	18% 8% 2 6% 4 5% 4 4 4 6% 39%	2290
	21st to end	Day	19% 6% 3 6% 4 4 5% 3 5% 6% 39%	2470
May	1st to 10th	Day	24% 13% 4 7% 4 4 3 3 5% 6% 27%	4106
	11th to 20th	Day	23% 12% 3 6% 4 3 3 3 4 7% 31%	4081
	21st to end	Day	15% 6% 2 5% 4 3 4 3 5% 8% 45%	4766
June	1st to 10th	Day	20% 7% 3 5% 5% 4 4 4 6% 9% 35%	2660
	11th to 20th	Day	15% 6% 2 6% 4 4 4 5% 7% 9% 38%	2660
	21st to end	Day	14% 7% 3 6% 4 4 5% 4 7% 9% 38%	2660
July	1st to 10th	Day	13% 7% 3 6% 4 5% 5% 5% 7% 9% 36%	4440
	11th to 20th	Day	13% 7% 2 6% 4 4 5% 4 7% 9% 38%	4440
	21st to end	Day	19% 7% 2 6% 4 4 4 4 7% 8% 34%	4752
August	1st to 10th	Day	17% 7% 3 8% 5% 5% 6% 4 6% 8% 32%	4105
	11th to 20th	Day	12% 7% 3 7% 4 4 5% 5% 6% 8% 39%	4045
	21st to end	Day	8% 4 1 5% 4 5% 5% 5% 8% 10% 45%	4184
September	1st to 10th	Day	13% 6% 2 5% 4 4 4 3 5% 6% 47%	2242
	11th to 20th	Day	15% 6% 2 4 3 3 3 2 4 7% 51%	2090
	21st to end	Day	19% 7% 2 6% 3 3 4 3 5% 6% 42%	2090
October	1st to 10th	Day	22% 6% 2 5% 4 3 4 3 6% 5% 42%	2090
	11th to 20th	Day	16% 5% 2 5% 3 4 3 3 5% 7% 47%	1883
	21st to end	Day	18% 7% 2 6% 3 3 3 3 5% 6% 44%	1881
November	1st to 10th	Day	17% 7% 2 5% 3 3 4 3 5% 5% 46%	1761
	11th to 20th	Day	18% 8% 2 4 4 3 3 3 5% 7% 43%	1710
	21st to end	Day	17% 7% 2 5% 4 4 4 4 5% 6% 43%	1710
December	1st to 10th	Day	18% 8% 3 6% 4 4 4 3 4 6% 40%	1635
	11th to 20th	Day	20% 9% 3 6% 4 3 4 3 4 5% 42%	1906
	21st to end	Day	21% 11% 3 7% 5% 5% 4 3 5% 5% 34%	2772
January	1st to 10th	Night	18% 7% 2 5% 3 3 3 2 4 5% 48%	4429
	11th to 20th	Night	16% 12% 4 8% 3 3 3 2 4 4 40%	4440
	21st to end	Night	22% 13% 5% 9% 5% 4 4 3 3 3 29%	4853
February	1st to 10th	Night	17% 10% 3 7% 4 4 3 4 4 5% 39%	2375
	11th to 20th	Night	18% 9% 3 6% 5% 4 3 4 4 5% 40%	2218
	21st to end	Night	18% 8% 2 6% 5% 4 3 3 4 6% 42%	1884
March	1st to 10th	Night	31% 11% 2 4 3 2 3 3 4 5% 32%	3724
	11th to 20th	Night	10% 10% 3 7% 5% 4 4 4 5% 6% 40%	3575
	21st to end	Night	25% 9% 3 7% 5% 4 5% 3 4 4 32%	3674
April	1st to 10th	Night	18% 9% 3 6% 5% 3 5% 3 5% 6% 37%	1900
	11th to 20th	Night	18% 9% 2 5% 5% 4 4 4 5% 7% 37%	1838
	21st to end	Night	19% 8% 3 6% 5% 4 5% 2 5% 5% 38%	1710
May	1st to 10th	Night	24% 11% 4 8% 5% 4 4 3 5% 6% 25%	2834
	11th to 20th	Night	24% 12% 3 7% 5% 5% 4 4 6% 7% 23%	2813
	21st to end	Night	16% 8% 3 7% 4 5% 4 4 6% 7% 37%	2836
June	1st to 10th	Night	17% 8% 3 6% 4 4 5% 4 7% 7% 35%	1520
	11th to 20th	Night	18% 8% 2 6% 4 6% 4 3 5% 7% 38%	1520
	21st to end	Night	16% 9% 2 6% 4 3 4 4 6% 9% 36%	1520
July	1st to 10th	Night	15% 8% 3 7% 5% 4 5% 5% 7% 9% 32%	2520
	11th to 20th	Night	16% 7% 2 6% 4 4 5% 4 7% 8% 36%	2520
	21st to end	Night	17% 9% 3 8% 5% 5% 5% 4 6% 8% 31%	2768
August	1st to 10th	Night	21% 8% 2 7% 5% 5% 4 4 7% 8% 29%	2825
	11th to 20th	Night	9% 9% 3 8% 4 5% 6% 4 7% 8% 37%	2782
	21st to end	Night	8% 4 1 5% 3 3 4 3 6% 7% 54%	3468
September	1st to 10th	Night	13% 6% 3 6% 4 3 5% 3 5% 6% 46%	1937
	11th to 20th	Night	14% 6% 2 5% 3 3 4 2 5% 6% 51%	2090
	21st to end	Night	19% 7% 2 6% 5% 3 5% 4 5% 5% 41%	2090
October	1st to 10th	Night	21% 7% 2 6% 5% 4 3 3 4 6% 40%	2090
	11th to 20th	Night	15% 5% 2 6% 4 3 4 3 5% 7% 47%	2290
	21st to end	Night	19% 8% 3 6% 4 4 4 3 5% 6% 39%	2717
November	1st to 10th	Night	16% 6% 2 5% 3 4 3 4 5% 5% 46%	2537
	11th to 20th	Night	18% 8% 2 5% 3 3 3 3 4 6% 44%	2477
	21st to end	Night	16% 6% 2 5% 4 4 4 3 4 7% 45%	2470
December	1st to 10th	Night	20% 8% 2 7% 4 4 3 3 5% 5% 39%	2541
	11th to 20th	Night	18% 9% 2 5% 4 4 4 4 5% 6% 40%	3288
	21st to end	Night	19% 12% 4 8% 4 3 4 3 4 5% 36%	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	40% 5% 10% 28% 14% 2	2518
	11th to 20th	Day	45% 7% 11% 24% 10% 3	2520
	21st to end	Day	54% 6% 11% 20% 9% 1	2801
February	1st to 10th	Day	49% 6% 13% 17% 13% 3	1805
	11th to 20th	Day	42% 7% 13% 22% 15% 2	1857
	21st to end	Day	48% 5% 13% 19% 13% 3	1570
March	1st to 10th	Day	58% 4 12% 14% 10% 2	3119
	11th to 20th	Day	33% 9% 18% 24% 13% 2	3384
	21st to end	Day	52% 5% 8% 15% 14% 6%	3942
April	1st to 10th	Day	46% 6% 10% 19% 16% 3	2280
	11th to 20th	Day	44% 6% 11% 22% 15% 2	2290
	21st to end	Day	44% 7% 12% 19% 15% 4	2470
May	1st to 10th	Day	56% 10% 12% 13% 8% 1	4120
	11th to 20th	Day	51% 8% 16% 14% 10% 1	4085
	21st to end	Day	36% 9% 13% 22% 18% 1	4766
June	1st to 10th	Day	44% 8% 15% 21% 10%	2660
	11th to 20th	Day	41% 8% 15% 22% 14% 1	2660
	21st to end	Day	40% 9% 16% 22% 12% 1	2660
July	1st to 10th	Day	44% 9% 13% 20% 13% 1	4370
	11th to 20th	Day	41% 7% 17% 22% 12% 1	4365
	21st to end	Day	46% 7% 13% 20% 12% 1	4601
August	1st to 10th	Day	48% 8% 18% 20% 7%	4092
	11th to 20th	Day	41% 7% 16% 28% 8% 1	4084
	21st to end	Day	30% 7% 17% 27% 18% 1	4184
September	1st to 10th	Day	38% 6% 12% 24% 20% 1	2242
	11th to 20th	Day	34% 5% 11% 26% 21% 3	2090
	21st to end	Day	43% 6% 9% 21% 19% 2	2090
October	1st to 10th	Day	39% 5% 11% 27% 16% 3	3480
	11th to 20th	Day	31% 4 8% 29% 25% 3	3112
	21st to end	Day	30% 4 15% 32% 17% 2	3081
November	1st to 10th	Day	41% 6% 14% 21% 16% 2	1761
	11th to 20th	Day	40% 6% 13% 21% 17% 2	1710
	21st to end	Day	42% 7% 13% 25% 12% 2	1710
December	1st to 10th	Day	47% 5% 14% 16% 16% 1	1635
	11th to 20th	Day	45% 6% 15% 16% 14% 3	1906
	21st to end	Day	51% 7% 15% 18% 8% 1	2772
January	1st to 10th	Night	39% 4 13% 30% 11% 3	4429
	11th to 20th	Night	47% 5% 12% 23% 11% 2	4440
	21st to end	Night	58% 7% 9% 16% 9% 1	4853
February	1st to 10th	Night	47% 7% 13% 21% 11% 2	2375
	11th to 20th	Night	47% 5% 10% 21% 14% 3	2220
	21st to end	Night	44% 5% 12% 23% 14% 3	1884
March	1st to 10th	Night	55% 5% 10% 17% 11% 3	3734
	11th to 20th	Night	40% 9% 14% 19% 16% 2	3576
	21st to end	Night	55% 5% 7% 11% 15% 6%	3674
April	1st to 10th	Night	48% 6% 10% 17% 15% 3	1900
	11th to 20th	Night	46% 6% 10% 18% 17% 3	1838
	21st to end	Night	46% 6% 11% 19% 14% 4	1710
May	1st to 10th	Night	57% 9% 14% 12% 6% 1	2840
	11th to 20th	Night	56% 10% 15% 11% 6% 2	2814
	21st to end	Night	43% 11% 15% 19% 12%	2837
June	1st to 10th	Night	47% 9% 13% 20% 11% 1	1520
	11th to 20th	Night	44% 6% 12% 24% 14% 1	1520
	21st to end	Night	44% 7% 15% 21% 12% 1	1520
July	1st to 10th	Night	51% 8% 9% 17% 15%	2480
	11th to 20th	Night	45% 7% 16% 21% 10% 1	2472
	21st to end	Night	51% 7% 12% 17% 11% 2	2680
August	1st to 10th	Night	52% 8% 13% 17% 8% 1	2813
	11th to 20th	Night	42% 8% 15% 27% 8%	2809
	21st to end	Night	28% 6% 15% 27% 22% 1	3468
September	1st to 10th	Night	38% 7% 12% 23% 19% 1	1937
	11th to 20th	Night	35% 5% 11% 24% 22% 2	2090
	21st to end	Night	44% 7% 9% 19% 19% 3	2090
October	1st to 10th	Night	42% 4 11% 27% 14% 2	3480
	11th to 20th	Night	26% 4 9% 26% 32% 3	3800
	21st to end	Night	34% 4 11% 27% 21% 2	4467
November	1st to 10th	Night	40% 7% 12% 23% 16% 3	2537
	11th to 20th	Night	43% 5% 12% 21% 16% 3	2477
	21st to end	Night	39% 5% 15% 27% 12% 2	2470
December	1st to 10th	Night	48% 6% 14% 19% 13% 1	2541
	11th to 20th	Night	43% 6% 16% 17% 15% 2	3288
	21st to end	Night	49% 8% 13% 20% 9% 1	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	24% 19% 33% 17% 6%	180
	11th to 20th	Day	23% 19% 36% 17% 4	180
	21st to end	Day	19% 14% 43% 16% 6% 1	214
February	1st to 10th	Day	25% 14% 39% 19% 3	415
	11th to 20th	Day	22% 19% 42% 14% 2	456
	21st to end	Day	23% 17% 36% 19% 4 1	382
March	1st to 10th	Day	24% 15% 36% 19% 5%	460
	11th to 20th	Day	18% 18% 41% 19% 4	460
	21st to end	Day	23% 16% 35% 17% 7% 2	506
April	1st to 10th	Day	26% 15% 32% 20% 7% 1	460
	11th to 20th	Day	23% 12% 37% 23% 6%	452
	21st to end	Day	22% 11% 33% 24% 7% 2	460
May	1st to 10th	Day	28% 11% 31% 23% 6% 1	463
	11th to 20th	Day	20% 7% 33% 29% 9% 2	487
	21st to end	Day	18% 4 29% 30% 16% 3	529
June	1st to 10th	Day	19% 4 27% 34% 14% 2	490
	11th to 20th	Day	14% 7% 30% 33% 13% 3	490
	21st to end	Day	16% 5% 26% 37% 15% 2	490
July	1st to 10th	Day	15% 4 19% 38% 21% 4	485
	11th to 20th	Day	13% 4 20% 33% 26% 5%	484
	21st to end	Day	14% 5% 22% 39% 18% 3	532
August	1st to 10th	Day	13% 4 20% 39% 22% 3	486
	11th to 20th	Day	14% 5% 18% 35% 23% 5%	479
	21st to end	Day	13% 4 21% 31% 23% 8%	539
September	1st to 10th	Day	18% 3 23% 31% 19% 7%	490
	11th to 20th	Day	16% 6% 26% 25% 18% 9%	490
	21st to end	Day	23% 6% 26% 28% 12% 5%	490
October	1st to 10th	Day	25% 7% 23% 26% 14% 6%	490
	11th to 20th	Day	18% 8% 32% 24% 15% 3	420
	21st to end	Day	24% 8% 34% 21% 11% 3	429
November	1st to 10th	Day	14% 15% 31% 25% 13% 3	395
	11th to 20th	Day	21% 17% 35% 20% 7% 1	370
	21st to end	Day	18% 19% 30% 22% 9% 1	370
December	1st to 10th	Day	20% 14% 40% 19% 6%	295
	11th to 20th	Day	28% 19% 32% 18% 2 1	180
	21st to end	Day	22% 20% 37% 14% 6% 2	198
January	1st to 10th	Night	22% 14% 43% 18% 3	760
	11th to 20th	Night	26% 19% 36% 17% 3	760
	21st to end	Night	20% 17% 39% 20% 4	836
February	1st to 10th	Night	22% 15% 38% 24% 2	760
	11th to 20th	Night	24% 16% 44% 15% 1	743
	21st to end	Night	21% 16% 38% 21% 4	628
March	1st to 10th	Night	22% 15% 36% 24% 3	760
	11th to 20th	Night	20% 12% 40% 23% 4	760
	21st to end	Night	23% 12% 36% 22% 7%	836
April	1st to 10th	Night	22% 10% 36% 26% 5%	760
	11th to 20th	Night	22% 10% 34% 28% 5%	714
	21st to end	Night	21% 8% 35% 28% 9%	570
May	1st to 10th	Night	27% 6% 30% 26% 9% 1	570
	11th to 20th	Night	23% 7% 35% 27% 7% 1	562
	21st to end	Night	21% 5% 21% 41% 11% 1	470
June	1st to 10th	Night	18% 4 27% 35% 15% 1	380
	11th to 20th	Night	22% 3 20% 43% 11% 1	380
	21st to end	Night	21% 4 19% 43% 13%	380
July	1st to 10th	Night	14% 3 20% 46% 15% 2	370
	11th to 20th	Night	15% 4 18% 43% 18% 1	368
	21st to end	Night	16% 2 18% 49% 15% 1	433
August	1st to 10th	Night	11% 4 21% 46% 18% 1	568
	11th to 20th	Night	15% 2 18% 44% 19% 1	562
	21st to end	Night	15% 3 16% 40% 23% 4	828
September	1st to 10th	Night	15% 3 22% 37% 21% 2	760
	11th to 20th	Night	16% 4 21% 31% 22% 5%	760
	21st to end	Night	22% 4 24% 30% 17% 3	760
October	1st to 10th	Night	24% 7% 23% 26% 16% 4	760
	11th to 20th	Night	18% 9% 31% 26% 13% 2	760
	21st to end	Night	23% 9% 35% 23% 8% 1	836
November	1st to 10th	Night	19% 8% 33% 28% 12% 1	780
	11th to 20th	Night	21% 17% 34% 21% 7% 1	763
	21st to end	Night	18% 18% 33% 23% 6% 1	760
December	1st to 10th	Night	24% 15% 37% 18% 5% 1	760
	11th to 20th	Night	22% 18% 38% 19% 3	760
	21st to end	Night	23% 15% 40% 19% 3	836

Page generated at 2024-11-08 06:44:47. Version ac07

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