Milton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Milton clear sky chart from 2005-11-06 to 2024-01-14.

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% 5% 2 5% 5% 3 5% 5% 6% 8% 43%	74739
	Night	14% 6% 3 5% 5% 3 4 4 5% 7% 44%	75014
Transparency	Day	25% 38% 8% 16% 11% 2	74444
	Night	26% 37% 8% 15% 11% 2	74828
Seeing	Day	18% 13% 28% 24% 12% 4	13985
	Night	18% 11% 28% 30% 12% 1	23452

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	13% 8% 3 4 4 3 5% 5% 5% 7% 45%	1517
	11th to 20th	Day	16% 7% 2 5% 5% 3 4 4 4 6% 45%	1563
	21st to end	Day	15% 6% 3 5% 5% 3 4 3 4 6% 44%	1782
February	1st to 10th	Day	15% 7% 3 6% 5% 3 4 5% 7% 7% 38%	1620
	11th to 20th	Day	18% 5% 3 4 3 2 4 4 5% 5% 45%	1734
	21st to end	Day	18% 8% 3 6% 5% 2 5% 5% 4 5% 39%	1480
March	1st to 10th	Day	14% 5% 2 4 4 2 3 4 4 7% 49%	1813
	11th to 20th	Day	17% 4 2 5% 4 3 4 3 5% 6% 46%	1980
	21st to end	Day	17% 7% 2 5% 5% 3 6% 4 5% 6% 40%	2296
April	1st to 10th	Day	13% 8% 3 4 4 2 4 3 5% 7% 46%	2160
	11th to 20th	Day	12% 6% 2 4 4 3 5% 4 5% 8% 49%	2134
	21st to end	Day	16% 5% 2 5% 6% 3 4 4 6% 8% 42%	2160
May	1st to 10th	Day	16% 6% 3 5% 4 3 4 4 5% 8% 42%	2222
	11th to 20th	Day	18% 5% 3 5% 5% 3 4 5% 5% 8% 40%	2462
	21st to end	Day	14% 5% 2 4 5% 3 5% 5% 6% 8% 43%	2725
June	1st to 10th	Day	13% 5% 2 4 5% 3 5% 5% 7% 10% 41%	2520
	11th to 20th	Day	12% 5% 2 5% 5% 3 6% 5% 6% 9% 42%	2520
	21st to end	Day	10% 3 2 4 5% 3 5% 6% 8% 10% 43%	2520
July	1st to 10th	Day	9% 5% 3 6% 6% 3 5% 5% 6% 9% 43%	2520
	11th to 20th	Day	6% 3 2 5% 4 3 6% 7% 8% 12% 44%	2520
	21st to end	Day	10% 3 2 5% 6% 4 7% 8% 8% 12% 34%	2631
August	1st to 10th	Day	9% 5% 3 5% 6% 4 6% 6% 9% 10% 36%	2300
	11th to 20th	Day	9% 4 3 6% 6% 5% 6% 7% 7% 8% 39%	2126
	21st to end	Day	10% 5% 2 6% 7% 4 5% 7% 6% 8% 41%	2376
September	1st to 10th	Day	14% 4 2 4 5% 3 5% 5% 6% 9% 42%	2160
	11th to 20th	Day	11% 5% 2 6% 5% 3 3 5% 5% 7% 47%	2133
	21st to end	Day	19% 6% 2 5% 5% 3 4 4 5% 7% 39%	1980
October	1st to 10th	Day	17% 5% 2 5% 5% 4 4 4 5% 7% 43%	1806
	11th to 20th	Day	18% 5% 2 4 3 2 3 3 4 5% 50%	1800
	21st to end	Day	14% 6% 3 5% 5% 2 4 4 5% 6% 47%	1952
November	1st to 10th	Day	14% 5% 2 3 4 2 3 3 5% 6% 53%	1671
	11th to 20th	Day	13% 6% 2 5% 5% 2 4 4 4 6% 48%	1710
	21st to end	Day	15% 4 2 5% 4 2 3 4 4 8% 48%	1644
December	1st to 10th	Day	16% 6% 2 5% 4 3 6% 4 6% 8% 41%	1520
	11th to 20th	Day	15% 9% 3 5% 4 3 3 3 4 4 47%	1910
	21st to end	Day	15% 7% 2 5% 5% 2 4 5% 6% 7% 43%	2772
January	1st to 10th	Night	14% 7% 3 4 5% 3 3 4 5% 6% 46%	2649
	11th to 20th	Night	17% 6% 3 5% 5% 3 4 5% 6% 6% 42%	2465
	21st to end	Night	15% 6% 2 4 5% 2 4 4 4 5% 48%	2574
February	1st to 10th	Night	18% 6% 3 5% 4 3 4 4 5% 6% 42%	2340
	11th to 20th	Night	17% 7% 2 5% 5% 3 4 4 4 5% 43%	2111
	21st to end	Night	20% 6% 2 4 4 2 4 4 3 6% 45%	1776
March	1st to 10th	Night	14% 6% 3 4 4 2 3 3 4 6% 49%	2142
	11th to 20th	Night	18% 7% 2 4 4 3 4 5% 4 6% 43%	1980
	21st to end	Night	16% 9% 3 6% 4 2 4 3 5% 5% 41%	2058
April	1st to 10th	Night	17% 6% 3 6% 4 3 4 4 5% 6% 42%	1800
	11th to 20th	Night	12% 5% 3 6% 5% 3 4 4 6% 6% 47%	1775
	21st to end	Night	18% 5% 2 5% 4 3 5% 4 5% 8% 41%	1800
May	1st to 10th	Night	16% 7% 3 5% 5% 3 5% 5% 5% 7% 39%	1737
	11th to 20th	Night	18% 6% 4 5% 5% 2 4 6% 5% 7% 37%	1446
	21st to end	Night	13% 8% 3 5% 5% 4 5% 4 4 8% 40%	1550
June	1st to 10th	Night	14% 6% 2 4 4 3 4 6% 5% 7% 44%	1440
	11th to 20th	Night	11% 5% 2 6% 5% 3 5% 6% 6% 9% 41%	1440
	21st to end	Night	8% 4 3 6% 6% 4 5% 5% 7% 11% 41%	1440
July	1st to 10th	Night	8% 5% 3 6% 6% 4 6% 6% 6% 10% 42%	1440
	11th to 20th	Night	5% 4 3 6% 5% 4 5% 5% 7% 9% 46%	1440
	21st to end	Night	6% 3 3 5% 7% 4 7% 6% 6% 11% 41%	1683
August	1st to 10th	Night	7% 6% 3 5% 6% 4 5% 6% 7% 10% 41%	1619
	11th to 20th	Night	9% 4 2 6% 6% 4 5% 6% 6% 10% 42%	1774
	21st to end	Night	8% 7% 3 6% 6% 3 5% 5% 6% 9% 43%	1980
September	1st to 10th	Night	15% 6% 3 5% 4 3 4 4 6% 7% 44%	1800
	11th to 20th	Night	11% 5% 2 5% 4 2 4 5% 5% 8% 50%	1826
	21st to end	Night	20% 6% 2 5% 4 3 4 4 5% 7% 38%	1980
October	1st to 10th	Night	17% 6% 2 5% 4 2 3 4 4 6% 46%	2150
	11th to 20th	Night	18% 4 2 4 4 2 3 4 3 6% 51%	2160
	21st to end	Night	16% 6% 2 5% 4 2 3 4 4 6% 47%	2402
November	1st to 10th	Night	13% 5% 2 5% 4 2 3 4 4 5% 53%	2407
	11th to 20th	Night	15% 6% 3 5% 4 2 4 4 4 5% 48%	2470
	21st to end	Night	12% 5% 2 4 4 2 4 4 5% 7% 50%	2531
December	1st to 10th	Night	17% 8% 3 5% 4 2 4 3 5% 6% 42%	2660
	11th to 20th	Night	17% 5% 2 5% 5% 3 4 4 4 6% 44%	3285
	21st to end	Night	14% 7% 3 6% 5% 3 4 4 6% 8% 40%	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	24% 41% 7% 18% 9% 1	1518
	11th to 20th	Day	27% 41% 9% 11% 10% 1	1563
	21st to end	Day	27% 38% 6% 17% 11% 2	1782
February	1st to 10th	Day	27% 36% 9% 18% 9% 1	1620
	11th to 20th	Day	26% 37% 8% 17% 11% 1	1743
	21st to end	Day	30% 36% 8% 13% 9% 4	1480
March	1st to 10th	Day	23% 36% 8% 20% 12% 1	1813
	11th to 20th	Day	25% 37% 8% 15% 12% 3	1980
	21st to end	Day	30% 38% 5% 16% 10% 2	2296
April	1st to 10th	Day	24% 38% 10% 13% 12% 4	2160
	11th to 20th	Day	23% 36% 7% 16% 13% 5%	2134
	21st to end	Day	26% 38% 8% 13% 12% 4	2160
May	1st to 10th	Day	26% 38% 11% 14% 10% 1	2222
	11th to 20th	Day	27% 39% 8% 13% 10% 3	2466
	21st to end	Day	24% 39% 9% 18% 8% 1	2725
June	1st to 10th	Day	23% 39% 11% 16% 10% 1	2520
	11th to 20th	Day	26% 39% 11% 15% 8% 2	2520
	21st to end	Day	23% 41% 9% 16% 10% 1	2520
July	1st to 10th	Day	25% 40% 8% 16% 9% 2	2450
	11th to 20th	Day	20% 41% 10% 18% 8% 2	2445
	21st to end	Day	24% 43% 10% 14% 9%	2484
August	1st to 10th	Day	26% 39% 9% 19% 7%	2287
	11th to 20th	Day	28% 39% 8% 15% 9% 1	2126
	21st to end	Day	29% 40% 7% 14% 7% 3	2376
September	1st to 10th	Day	25% 39% 8% 12% 13% 3	2160
	11th to 20th	Day	22% 37% 6% 17% 15% 2	2133
	21st to end	Day	30% 37% 6% 10% 14% 3	1980
October	1st to 10th	Day	27% 37% 6% 14% 14% 3	1806
	11th to 20th	Day	26% 36% 6% 17% 13% 2	1800
	21st to end	Day	25% 38% 5% 16% 14% 1	1952
November	1st to 10th	Day	18% 41% 7% 20% 12% 1	1671
	11th to 20th	Day	24% 40% 7% 15% 12% 2	1710
	21st to end	Day	25% 39% 8% 15% 11% 1	1644
December	1st to 10th	Day	23% 41% 11% 16% 9%	1520
	11th to 20th	Day	30% 31% 6% 21% 9% 2	1906
	21st to end	Day	28% 27% 17% 17% 11%	2772
January	1st to 10th	Night	25% 39% 7% 16% 11% 1	2649
	11th to 20th	Night	27% 41% 7% 15% 9% 1	2465
	21st to end	Night	25% 37% 7% 18% 12% 2	2574
February	1st to 10th	Night	28% 36% 6% 16% 12% 1	2340
	11th to 20th	Night	28% 37% 6% 15% 10% 4	2113
	21st to end	Night	28% 37% 6% 14% 13% 2	1776
March	1st to 10th	Night	22% 36% 8% 18% 13% 2	2142
	11th to 20th	Night	29% 38% 7% 13% 11% 2	1980
	21st to end	Night	31% 37% 6% 12% 10% 4	2058
April	1st to 10th	Night	26% 37% 7% 13% 13% 4	1800
	11th to 20th	Night	25% 36% 8% 12% 14% 5%	1775
	21st to end	Night	27% 37% 6% 14% 12% 4	1800
May	1st to 10th	Night	29% 38% 7% 13% 11% 2	1737
	11th to 20th	Night	30% 38% 7% 10% 13% 2	1447
	21st to end	Night	26% 41% 10% 13% 9% 1	1551
June	1st to 10th	Night	25% 39% 10% 14% 11% 1	1440
	11th to 20th	Night	26% 40% 9% 14% 9% 2	1440
	21st to end	Night	25% 39% 11% 14% 8% 2	1440
July	1st to 10th	Night	25% 41% 9% 15% 8% 2	1400
	11th to 20th	Night	20% 42% 11% 18% 8% 2	1392
	21st to end	Night	23% 42% 9% 15% 10% 1	1589
August	1st to 10th	Night	25% 38% 13% 15% 8%	1608
	11th to 20th	Night	25% 39% 10% 14% 10% 1	1774
	21st to end	Night	28% 40% 11% 12% 7% 2	1980
September	1st to 10th	Night	26% 37% 8% 12% 13% 4	1800
	11th to 20th	Night	21% 37% 8% 17% 14% 2	1826
	21st to end	Night	29% 38% 7% 12% 12% 3	1980
October	1st to 10th	Night	25% 37% 5% 15% 15% 2	2150
	11th to 20th	Night	27% 37% 6% 16% 12% 2	2160
	21st to end	Night	25% 37% 7% 15% 14% 2	2402
November	1st to 10th	Night	20% 41% 6% 17% 13% 3	2407
	11th to 20th	Night	26% 40% 7% 13% 12% 2	2470
	21st to end	Night	23% 40% 8% 15% 12% 2	2531
December	1st to 10th	Night	24% 41% 7% 17% 10% 2	2660
	11th to 20th	Night	30% 32% 7% 14% 14% 2	3288
	21st to end	Night	32% 27% 14% 19% 8% 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	19% 25% 38% 14% 3 1	180
	11th to 20th	Day	21% 33% 28% 16% 3	210
	21st to end	Day	22% 27% 35% 11% 4	264
February	1st to 10th	Day	24% 26% 38% 9% 3	240
	11th to 20th	Day	27% 24% 38% 9% 3	402
	21st to end	Day	28% 21% 36% 12% 3	346
March	1st to 10th	Day	21% 26% 31% 19% 4	420
	11th to 20th	Day	23% 23% 34% 15% 3 2	420
	21st to end	Day	24% 19% 35% 16% 4 1	462
April	1st to 10th	Day	20% 24% 35% 15% 5% 2	420
	11th to 20th	Day	18% 14% 37% 24% 6% 1	412
	21st to end	Day	22% 16% 35% 20% 4 2	420
May	1st to 10th	Day	24% 15% 33% 20% 7% 1	423
	11th to 20th	Day	21% 13% 33% 23% 9% 1	447
	21st to end	Day	19% 7% 21% 32% 16% 5%	485
June	1st to 10th	Day	17% 7% 26% 30% 16% 3	450
	11th to 20th	Day	13% 7% 28% 32% 15% 5%	450
	21st to end	Day	12% 7% 23% 35% 19% 4	450
July	1st to 10th	Day	12% 4 19% 33% 24% 8%	445
	11th to 20th	Day	3 3 18% 39% 26% 9%	444
	21st to end	Day	10% 3 22% 35% 24% 7%	488
August	1st to 10th	Day	11% 3 21% 33% 23% 9%	446
	11th to 20th	Day	8% 4 16% 37% 26% 9%	439
	21st to end	Day	12% 4 19% 32% 21% 12%	495
September	1st to 10th	Day	16% 5% 21% 28% 16% 15%	450
	11th to 20th	Day	14% 4 23% 29% 20% 10%	450
	21st to end	Day	25% 8% 24% 27% 11% 5%	450
October	1st to 10th	Day	22% 7% 25% 24% 15% 7%	450
	11th to 20th	Day	18% 12% 25% 25% 18% 2	450
	21st to end	Day	19% 11% 35% 23% 10% 3	480
November	1st to 10th	Day	16% 13% 30% 21% 16% 4	365
	11th to 20th	Day	18% 21% 30% 22% 9% 1	370
	21st to end	Day	17% 19% 32% 20% 10% 2	304
December	1st to 10th	Day	19% 23% 39% 13% 6%	180
	11th to 20th	Day	24% 25% 31% 15% 6%	180
	21st to end	Day	25% 19% 30% 21% 6% 1	198
January	1st to 10th	Night	19% 22% 34% 22% 4	760
	11th to 20th	Night	20% 16% 35% 24% 4	735
	21st to end	Night	19% 18% 38% 23% 3	792
February	1st to 10th	Night	21% 15% 38% 24% 3	720
	11th to 20th	Night	23% 23% 34% 19% 1	703
	21st to end	Night	22% 20% 35% 20% 2	592
March	1st to 10th	Night	19% 19% 35% 22% 5%	720
	11th to 20th	Night	23% 16% 34% 19% 6% 1	720
	21st to end	Night	22% 12% 38% 22% 5% 1	792
April	1st to 10th	Night	22% 14% 39% 19% 6%	720
	11th to 20th	Night	14% 12% 34% 33% 6%	711
	21st to end	Night	21% 10% 35% 27% 8%	720
May	1st to 10th	Night	19% 10% 33% 30% 8%	657
	11th to 20th	Night	20% 8% 31% 32% 9%	385
	21st to end	Night	16% 3 20% 43% 16% 2	389
June	1st to 10th	Night	16% 3 23% 42% 14% 1	360
	11th to 20th	Night	11% 3 22% 43% 21% 1	360
	21st to end	Night	9% 4 18% 53% 16%	360
July	1st to 10th	Night	10% 2 18% 47% 22% 1	350
	11th to 20th	Night	5% 4 12% 44% 33% 2	348
	21st to end	Night	6% 2 18% 46% 26% 3	503
August	1st to 10th	Night	10% 1 12% 46% 30% 3	545
	11th to 20th	Night	10% 2 14% 43% 27% 3	710
	21st to end	Night	10% 3 14% 40% 29% 5%	792
September	1st to 10th	Night	18% 2 15% 34% 27% 4	720
	11th to 20th	Night	13% 3 16% 37% 27% 4	720
	21st to end	Night	23% 5% 20% 33% 18% 1	720
October	1st to 10th	Night	21% 6% 19% 32% 19% 4	720
	11th to 20th	Night	20% 8% 24% 31% 15% 1	720
	21st to end	Night	19% 8% 34% 26% 12% 2	792
November	1st to 10th	Night	14% 11% 33% 27% 13% 3	740
	11th to 20th	Night	19% 15% 29% 29% 8%	760
	21st to end	Night	14% 15% 31% 28% 11% 1	760
December	1st to 10th	Night	24% 14% 32% 20% 9% 1	760
	11th to 20th	Night	19% 16% 33% 26% 6%	760
	21st to end	Night	19% 13% 34% 31% 3	836

Page generated at 2024-01-11 04:22:43. Version ac07

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