Mansfield
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mansfield clear sky chart from 2005-11-06 to 2024-01-16.

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	15% 10% 4 8% 7% 4 5% 5% 5% 7% 31%	74727
	Night	14% 10% 4 8% 6% 4 5% 5% 5% 6% 32%	75075
Transparency	Day	54% 3 10% 21% 11% 1	74438
	Night	53% 3 11% 21% 11% 1	74898
Seeing	Day	26% 16% 29% 18% 9% 3	13590
	Night	24% 15% 28% 23% 9% 1	23047

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	11% 14% 8% 11% 9% 4 5% 4 5% 6% 22%	1517
	11th to 20th	Day	13% 14% 6% 13% 9% 5% 5% 4 5% 6% 20%	1566
	21st to end	Day	11% 13% 7% 13% 11% 4 5% 6% 5% 5% 20%	1782
February	1st to 10th	Day	14% 13% 7% 11% 10% 5% 5% 4 4 4 22%	1620
	11th to 20th	Day	14% 12% 6% 12% 9% 3 6% 5% 4 5% 25%	1577
	21st to end	Day	18% 13% 4 11% 8% 3 4 4 5% 6% 25%	1480
March	1st to 10th	Day	14% 12% 7% 10% 7% 3 4 3 4 6% 29%	1899
	11th to 20th	Day	15% 13% 5% 8% 7% 3 4 4 4 6% 30%	1980
	21st to end	Day	18% 12% 4 8% 6% 3 5% 4 4 6% 29%	2231
April	1st to 10th	Day	14% 13% 5% 8% 6% 3 4 4 4 7% 31%	2160
	11th to 20th	Day	17% 11% 4 5% 5% 3 4 6% 5% 7% 32%	2134
	21st to end	Day	20% 9% 4 5% 6% 3 4 4 5% 6% 33%	2204
May	1st to 10th	Day	17% 10% 3 7% 6% 4 5% 4 6% 6% 32%	2395
	11th to 20th	Day	20% 8% 3 6% 6% 4 5% 5% 5% 7% 32%	2478
	21st to end	Day	13% 7% 3 6% 5% 4 5% 5% 5% 7% 38%	2725
June	1st to 10th	Day	16% 6% 3 7% 6% 4 5% 6% 5% 8% 34%	2520
	11th to 20th	Day	14% 6% 3 6% 6% 5% 5% 5% 6% 9% 34%	2520
	21st to end	Day	13% 6% 2 6% 6% 4 6% 6% 6% 9% 35%	2520
July	1st to 10th	Day	10% 6% 3 6% 7% 5% 6% 7% 6% 9% 36%	2520
	11th to 20th	Day	9% 6% 2 6% 6% 4 7% 6% 7% 10% 37%	2520
	21st to end	Day	12% 6% 3 6% 6% 4 6% 6% 6% 7% 37%	2646
August	1st to 10th	Day	10% 5% 4 5% 7% 4 6% 7% 8% 10% 35%	2327
	11th to 20th	Day	14% 6% 3 6% 6% 5% 6% 6% 7% 9% 31%	2263
	21st to end	Day	14% 6% 3 6% 7% 4 6% 5% 6% 10% 33%	2376
September	1st to 10th	Day	17% 7% 3 7% 5% 3 4 5% 5% 7% 39%	2160
	11th to 20th	Day	15% 6% 2 5% 6% 3 5% 4 5% 7% 43%	2160
	21st to end	Day	18% 8% 2 6% 5% 3 5% 5% 5% 7% 36%	1896
October	1st to 10th	Day	17% 8% 2 7% 5% 3 5% 5% 6% 8% 34%	1800
	11th to 20th	Day	19% 8% 4 8% 6% 3 5% 4 5% 6% 32%	1800
	21st to end	Day	22% 12% 4 6% 7% 3 3 5% 5% 5% 27%	1976
November	1st to 10th	Day	13% 11% 3 7% 6% 4 5% 3 4 5% 38%	1671
	11th to 20th	Day	15% 13% 4 9% 6% 3 5% 5% 5% 6% 28%	1586
	21st to end	Day	15% 13% 5% 8% 7% 3 5% 4 5% 7% 27%	1520
December	1st to 10th	Day	17% 17% 7% 10% 7% 3 5% 4 5% 5% 19%	1520
	11th to 20th	Day	18% 14% 6% 11% 6% 3 4 3 5% 6% 24%	1906
	21st to end	Day	21% 19% 6% 11% 7% 3 5% 5% 4 5% 15%	2772
January	1st to 10th	Night	12% 12% 6% 12% 7% 4 7% 5% 5% 6% 24%	2649
	11th to 20th	Night	13% 13% 6% 12% 8% 5% 6% 5% 6% 7% 20%	2521
	21st to end	Night	10% 12% 6% 11% 10% 5% 7% 6% 6% 6% 21%	2574
February	1st to 10th	Night	13% 12% 5% 10% 9% 4 5% 6% 4 6% 24%	2340
	11th to 20th	Night	12% 13% 7% 10% 8% 4 6% 5% 4 6% 26%	2267
	21st to end	Night	15% 11% 5% 12% 7% 4 5% 5% 4 5% 26%	1776
March	1st to 10th	Night	11% 13% 6% 11% 7% 4 5% 4 5% 5% 29%	2046
	11th to 20th	Night	16% 12% 5% 8% 8% 3 4 4 4 5% 32%	1979
	21st to end	Night	15% 13% 5% 8% 6% 3 4 3 4 6% 33%	2124
April	1st to 10th	Night	16% 12% 5% 9% 6% 3 4 4 4 6% 31%	1800
	11th to 20th	Night	18% 9% 3 6% 6% 3 4 4 6% 6% 35%	1775
	21st to end	Night	16% 9% 4 6% 5% 4 4 4 5% 6% 37%	1769
May	1st to 10th	Night	21% 11% 2 6% 5% 3 4 4 5% 5% 34%	1562
	11th to 20th	Night	14% 7% 2 6% 7% 4 6% 6% 6% 7% 36%	1415
	21st to end	Night	11% 6% 3 6% 6% 3 5% 4 6% 7% 43%	1550
June	1st to 10th	Night	13% 7% 3 6% 6% 3 4 5% 5% 9% 39%	1440
	11th to 20th	Night	12% 7% 2 6% 5% 3 6% 5% 7% 9% 39%	1440
	21st to end	Night	11% 4 2 5% 6% 3 5% 6% 6% 8% 44%	1440
July	1st to 10th	Night	9% 6% 3 6% 5% 4 4 4 6% 8% 45%	1440
	11th to 20th	Night	8% 3 2 4 4 3 5% 5% 6% 10% 48%	1440
	21st to end	Night	11% 6% 2 6% 5% 4 4 5% 6% 8% 43%	1668
August	1st to 10th	Night	8% 6% 2 5% 5% 3 5% 6% 7% 7% 46%	1611
	11th to 20th	Night	11% 6% 3 6% 6% 4 4 6% 5% 9% 40%	1620
	21st to end	Night	11% 5% 2 5% 5% 3 6% 6% 7% 8% 43%	1980
September	1st to 10th	Night	15% 6% 3 5% 4 3 4 4 5% 6% 45%	1800
	11th to 20th	Night	14% 6% 2 5% 4 2 3 3 5% 8% 49%	1800
	21st to end	Night	15% 6% 2 6% 6% 3 5% 4 5% 7% 41%	2060
October	1st to 10th	Night	16% 8% 2 5% 6% 3 4 5% 5% 6% 39%	2160
	11th to 20th	Night	18% 9% 3 5% 5% 3 5% 4 6% 8% 36%	2160
	21st to end	Night	23% 11% 3 7% 5% 3 4 4 5% 6% 29%	2377
November	1st to 10th	Night	11% 12% 3 6% 5% 3 4 4 5% 6% 41%	2407
	11th to 20th	Night	17% 11% 5% 8% 5% 3 6% 5% 5% 6% 30%	2593
	21st to end	Night	14% 12% 4 8% 6% 3 6% 5% 5% 7% 28%	2660
December	1st to 10th	Night	15% 15% 6% 10% 7% 4 5% 5% 5% 6% 20%	2660
	11th to 20th	Night	17% 15% 5% 10% 7% 3 6% 4 4 4 24%	3288
	21st to end	Night	21% 15% 8% 10% 7% 4 5% 4 4 6% 16%	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	63% 2 9% 19% 7% 1	1518
	11th to 20th	Day	68% 3 8% 13% 7% 1	1566
	21st to end	Day	66% 2 9% 13% 8% 1	1782
February	1st to 10th	Day	67% 2 10% 12% 9% 1	1620
	11th to 20th	Day	62% 3 6% 19% 9% 1	1586
	21st to end	Day	61% 3 7% 19% 9% 2	1480
March	1st to 10th	Day	58% 2 10% 20% 8% 2	1902
	11th to 20th	Day	56% 2 8% 20% 11% 3	1980
	21st to end	Day	58% 2 6% 19% 12% 2	2231
April	1st to 10th	Day	55% 2 7% 22% 11% 2	2160
	11th to 20th	Day	52% 4 9% 19% 15% 1	2134
	21st to end	Day	52% 3 7% 20% 14% 3	2204
May	1st to 10th	Day	55% 2 8% 21% 12% 2	2395
	11th to 20th	Day	53% 3 9% 20% 13% 2	2482
	21st to end	Day	45% 4 14% 23% 12% 1	2725
June	1st to 10th	Day	50% 4 10% 22% 14% 1	2520
	11th to 20th	Day	48% 3 13% 23% 12% 2	2520
	21st to end	Day	46% 4 10% 27% 12% 1	2520
July	1st to 10th	Day	46% 4 11% 24% 13% 1	2450
	11th to 20th	Day	42% 3 14% 27% 13% 1	2445
	21st to end	Day	46% 4 12% 24% 14% 1	2498
August	1st to 10th	Day	43% 4 14% 26% 13%	2314
	11th to 20th	Day	49% 4 12% 24% 10% 1	2263
	21st to end	Day	47% 4 9% 24% 14% 2	2376
September	1st to 10th	Day	45% 4 10% 26% 13% 2	2160
	11th to 20th	Day	42% 3 9% 26% 19% 1	2160
	21st to end	Day	49% 2 10% 22% 16% 1	1896
October	1st to 10th	Day	50% 3 10% 22% 14% 1	1800
	11th to 20th	Day	54% 2 9% 23% 10% 1	1800
	21st to end	Day	60% 2 11% 17% 9% 1	1976
November	1st to 10th	Day	49% 3 10% 20% 14% 3	1671
	11th to 20th	Day	57% 3 9% 21% 8% 2	1586
	21st to end	Day	59% 2 12% 20% 7% 1	1520
December	1st to 10th	Day	68% 2 10% 13% 7%	1520
	11th to 20th	Day	63% 2 14% 16% 5%	1906
	21st to end	Day	73% 2 8% 14% 3	2772
January	1st to 10th	Night	61% 3 9% 17% 9% 1	2649
	11th to 20th	Night	63% 4 12% 15% 5% 1	2521
	21st to end	Night	63% 3 7% 17% 9% 1	2574
February	1st to 10th	Night	60% 3 11% 17% 8% 1	2340
	11th to 20th	Night	61% 3 8% 18% 10% 1	2269
	21st to end	Night	61% 1 8% 17% 10% 2	1776
March	1st to 10th	Night	58% 2 9% 21% 9% 2	2056
	11th to 20th	Night	57% 2 9% 20% 11% 1	1980
	21st to end	Night	55% 2 9% 17% 14% 3	2124
April	1st to 10th	Night	56% 3 9% 19% 12% 1	1800
	11th to 20th	Night	50% 3 12% 19% 15% 2	1775
	21st to end	Night	49% 2 10% 22% 15% 2	1769
May	1st to 10th	Night	53% 2 10% 21% 11% 2	1562
	11th to 20th	Night	48% 3 10% 22% 15% 1	1416
	21st to end	Night	41% 5% 15% 24% 13% 2	1551
June	1st to 10th	Night	44% 3 11% 26% 15% 1	1440
	11th to 20th	Night	43% 3 15% 25% 13% 2	1440
	21st to end	Night	38% 5% 13% 31% 14% 1	1440
July	1st to 10th	Night	38% 5% 13% 28% 14% 2	1400
	11th to 20th	Night	33% 4 17% 27% 18% 1	1392
	21st to end	Night	38% 4 16% 24% 16% 2	1575
August	1st to 10th	Night	36% 4 17% 30% 12% 1	1600
	11th to 20th	Night	42% 4 15% 27% 12%	1620
	21st to end	Night	39% 5% 14% 26% 15% 2	1980
September	1st to 10th	Night	42% 3 10% 29% 13% 2	1800
	11th to 20th	Night	35% 3 12% 29% 19% 2	1800
	21st to end	Night	44% 3 11% 26% 15% 1	2060
October	1st to 10th	Night	45% 4 13% 23% 14% 1	2160
	11th to 20th	Night	48% 3 13% 23% 12% 1	2160
	21st to end	Night	56% 2 11% 20% 10% 1	2377
November	1st to 10th	Night	45% 3 11% 24% 14% 3	2407
	11th to 20th	Night	56% 2 10% 19% 11% 2	2593
	21st to end	Night	56% 3 13% 21% 6% 1	2660
December	1st to 10th	Night	66% 3 10% 16% 5%	2660
	11th to 20th	Night	64% 2 9% 17% 7%	3288
	21st to end	Night	71% 2 9% 15% 3	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	39% 18% 30% 9% 3 1	180
	11th to 20th	Day	38% 29% 25% 6% 1	208
	21st to end	Day	31% 26% 34% 7% 2	264
February	1st to 10th	Day	36% 28% 32% 4	240
	11th to 20th	Day	39% 27% 32% 2	244
	21st to end	Day	42% 21% 25% 11% 1	346
March	1st to 10th	Day	33% 23% 29% 13% 2	420
	11th to 20th	Day	34% 23% 26% 13% 4	420
	21st to end	Day	35% 22% 26% 11% 3 3	462
April	1st to 10th	Day	34% 20% 29% 12% 4 1	420
	11th to 20th	Day	31% 22% 26% 11% 7% 4	412
	21st to end	Day	34% 19% 27% 14% 5% 2	420
May	1st to 10th	Day	31% 18% 28% 12% 8% 3	423
	11th to 20th	Day	28% 16% 29% 17% 7% 3	447
	21st to end	Day	20% 10% 31% 23% 12% 5%	485
June	1st to 10th	Day	19% 17% 31% 22% 10% 1	450
	11th to 20th	Day	21% 11% 31% 24% 12% 1	450
	21st to end	Day	17% 11% 38% 22% 10% 2	450
July	1st to 10th	Day	15% 5% 29% 29% 17% 5%	445
	11th to 20th	Day	10% 9% 30% 32% 15% 5%	444
	21st to end	Day	14% 6% 39% 26% 10% 5%	488
August	1st to 10th	Day	12% 7% 27% 30% 16% 7%	446
	11th to 20th	Day	15% 7% 26% 29% 15% 7%	439
	21st to end	Day	18% 8% 29% 23% 13% 9%	495
September	1st to 10th	Day	20% 10% 22% 25% 16% 7%	450
	11th to 20th	Day	16% 8% 28% 21% 18% 9%	450
	21st to end	Day	24% 12% 27% 19% 13% 4	450
October	1st to 10th	Day	26% 10% 24% 20% 14% 5%	450
	11th to 20th	Day	28% 15% 32% 16% 6% 2	450
	21st to end	Day	35% 18% 25% 17% 4	493
November	1st to 10th	Day	27% 19% 25% 17% 11% 1	365
	11th to 20th	Day	36% 21% 27% 12% 4 1	246
	21st to end	Day	30% 29% 34% 6% 2	180
December	1st to 10th	Day	33% 26% 31% 6% 3 1	180
	11th to 20th	Day	38% 26% 28% 8% 1	180
	21st to end	Day	37% 26% 30% 7% 1	198
January	1st to 10th	Night	24% 25% 35% 13% 3	760
	11th to 20th	Night	27% 22% 30% 18% 3	744
	21st to end	Night	24% 24% 32% 17% 3	792
February	1st to 10th	Night	30% 22% 31% 16% 1	720
	11th to 20th	Night	30% 24% 33% 12% 1	703
	21st to end	Night	32% 20% 30% 17% 2	592
March	1st to 10th	Night	29% 24% 29% 16% 2	720
	11th to 20th	Night	31% 21% 27% 17% 3	720
	21st to end	Night	27% 20% 30% 16% 5% 2	792
April	1st to 10th	Night	28% 20% 31% 18% 3	720
	11th to 20th	Night	26% 16% 31% 18% 8% 1	711
	21st to end	Night	24% 14% 31% 25% 6%	689
May	1st to 10th	Night	29% 10% 22% 29% 10%	482
	11th to 20th	Night	19% 11% 31% 31% 7% 1	354
	21st to end	Night	13% 10% 28% 33% 15% 1	389
June	1st to 10th	Night	16% 8% 26% 34% 16% 1	360
	11th to 20th	Night	19% 8% 21% 39% 13%	360
	21st to end	Night	14% 4 30% 40% 12%	360
July	1st to 10th	Night	10% 5% 27% 36% 20% 3	350
	11th to 20th	Night	11% 1 22% 41% 22% 3	348
	21st to end	Night	15% 4 19% 42% 19% 3	488
August	1st to 10th	Night	10% 3 24% 38% 23% 2	537
	11th to 20th	Night	14% 3 17% 35% 26% 4	556
	21st to end	Night	14% 4 20% 36% 22% 3	792
September	1st to 10th	Night	19% 8% 21% 33% 16% 3	720
	11th to 20th	Night	16% 6% 21% 29% 24% 4	720
	21st to end	Night	19% 10% 26% 26% 16% 3	720
October	1st to 10th	Night	21% 10% 25% 25% 16% 3	720
	11th to 20th	Night	26% 14% 28% 24% 7% 1	720
	21st to end	Night	32% 13% 29% 21% 5%	792
November	1st to 10th	Night	20% 18% 30% 24% 8%	740
	11th to 20th	Night	28% 19% 28% 17% 6% 2	760
	21st to end	Night	26% 19% 31% 20% 3 1	760
December	1st to 10th	Night	31% 23% 28% 14% 4	760
	11th to 20th	Night	29% 20% 31% 18% 3	760
	21st to end	Night	30% 21% 32% 15% 1	836

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