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 2026-04-17.

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% 11% 4 10% 6% 5% 5% 4 5% 7% 30%	131821
	Night	14% 12% 4 10% 6% 5% 4 3 5% 6% 30%	130334
Transparency	Day	54% 2 10% 21% 11% 1	135395
	Night	55% 2 10% 20% 11% 1	134846
Seeing	Day	27% 16% 29% 17% 8% 3	16490
	Night	24% 15% 27% 23% 9% 1	25948

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	14% 16% 7% 18% 8% 4 4 3 4 4 18%	4661
	11th to 20th	Day	10% 14% 7% 21% 9% 7% 5% 3 4 5% 16%	4924
	21st to end	Day	13% 11% 7% 10% 8% 5% 5% 4 5% 6% 24%	5780
February	1st to 10th	Day	13% 14% 5% 13% 8% 6% 5% 3 4 4 24%	1890
	11th to 20th	Day	13% 14% 6% 14% 7% 4 5% 4 5% 5% 24%	1849
	21st to end	Day	16% 15% 4 11% 6% 3 3 3 5% 6% 27%	1730
March	1st to 10th	Day	17% 14% 6% 9% 5% 4 3 2 3 4 31%	4852
	11th to 20th	Day	11% 15% 5% 8% 5% 4 4 3 4 6% 36%	5090
	21st to end	Day	13% 11% 4 12% 6% 5% 5% 4 5% 5% 30%	5725
April	1st to 10th	Day	15% 15% 3 9% 6% 4 4 3 5% 7% 29%	2520
	11th to 20th	Day	16% 12% 4 6% 5% 5% 5% 5% 6% 6% 31%	2446
	21st to end	Day	18% 10% 3 7% 5% 4 3 3 6% 6% 35%	2450
May	1st to 10th	Day	26% 10% 3 7% 5% 4 4 3 5% 5% 27%	6041
	11th to 20th	Day	20% 11% 3 9% 5% 5% 5% 3 5% 7% 27%	6318
	21st to end	Day	19% 8% 3 8% 5% 5% 5% 4 6% 7% 31%	6949
June	1st to 10th	Day	15% 7% 2 8% 6% 5% 5% 4 6% 8% 33%	2800
	11th to 20th	Day	15% 7% 3 7% 6% 6% 5% 4 6% 8% 34%	2800
	21st to end	Day	13% 6% 2 7% 5% 5% 6% 5% 6% 9% 35%	2800
July	1st to 10th	Day	7% 6% 2 7% 6% 6% 6% 5% 7% 9% 37%	6360
	11th to 20th	Day	6% 6% 2 9% 6% 7% 7% 5% 8% 11% 32%	6360
	21st to end	Day	10% 6% 3 7% 5% 6% 5% 5% 6% 7% 40%	6663
August	1st to 10th	Day	17% 8% 3 7% 5% 4 5% 4 6% 8% 31%	4234
	11th to 20th	Day	14% 8% 3 8% 5% 6% 6% 4 7% 10% 29%	4090
	21st to end	Day	11% 8% 3 6% 5% 5% 4 3 6% 10% 37%	4312
September	1st to 10th	Day	16% 6% 2 7% 4 4 4 4 5% 7% 41%	2400
	11th to 20th	Day	14% 6% 2 6% 5% 4 5% 3 5% 7% 44%	2400
	21st to end	Day	20% 8% 2 7% 4 4 5% 4 5% 7% 33%	2105
October	1st to 10th	Day	16% 8% 2 8% 4 4 5% 4 6% 8% 36%	2000
	11th to 20th	Day	18% 9% 3 9% 5% 5% 4 4 5% 6% 33%	2000
	21st to end	Day	20% 12% 3 7% 6% 4 4 4 5% 6% 29%	2195
November	1st to 10th	Day	13% 12% 3 8% 5% 5% 4 2 4 5% 38%	1851
	11th to 20th	Day	14% 15% 4 10% 5% 4 5% 4 6% 6% 28%	1752
	21st to end	Day	15% 15% 5% 9% 6% 5% 4 3 5% 7% 25%	1680
December	1st to 10th	Day	14% 18% 10% 15% 6% 5% 5% 4 5% 4 16%	2680
	11th to 20th	Day	19% 14% 6% 11% 6% 4 4 3 4 5% 25%	3066
	21st to end	Day	16% 17% 6% 16% 7% 4 5% 3 4 6% 17%	4048
January	1st to 10th	Night	11% 15% 7% 20% 9% 5% 4 3 4 4 18%	8234
	11th to 20th	Night	9% 15% 7% 19% 7% 5% 5% 4 5% 6% 17%	7960
	21st to end	Night	12% 13% 6% 12% 8% 7% 6% 4 5% 5% 22%	8401
February	1st to 10th	Night	12% 13% 4 12% 7% 6% 5% 5% 5% 6% 25%	2730
	11th to 20th	Night	12% 14% 6% 12% 7% 5% 5% 3 4 5% 24%	2655
	21st to end	Night	14% 13% 4 14% 5% 6% 4 4 4 5% 26%	2076
March	1st to 10th	Night	15% 13% 5% 10% 7% 5% 4 3 4 4 30%	5206
	11th to 20th	Night	11% 15% 5% 8% 5% 3 4 3 4 6% 35%	5089
	21st to end	Night	14% 13% 4 10% 6% 4 4 3 4 5% 32%	5448
April	1st to 10th	Night	16% 14% 4 9% 6% 4 4 3 4 5% 29%	2100
	11th to 20th	Night	17% 11% 3 7% 5% 4 3 4 6% 6% 33%	2036
	21st to end	Night	16% 9% 3 7% 4 4 4 3 5% 6% 38%	1965
May	1st to 10th	Night	28% 11% 3 8% 4 4 3 3 4 5% 27%	3897
	11th to 20th	Night	22% 10% 3 8% 5% 4 4 3 5% 5% 31%	3575
	21st to end	Night	17% 10% 3 8% 5% 4 5% 3 6% 6% 33%	3926
June	1st to 10th	Night	13% 8% 2 7% 5% 4 4 4 6% 8% 38%	1600
	11th to 20th	Night	13% 7% 2 6% 5% 4 5% 4 7% 9% 39%	1600
	21st to end	Night	11% 5% 2 6% 5% 5% 5% 4 7% 8% 43%	1600
July	1st to 10th	Night	8% 9% 3 8% 5% 5% 4 3 6% 9% 40%	3600
	11th to 20th	Night	8% 5% 3 8% 5% 5% 6% 5% 8% 11% 38%	3600
	21st to end	Night	9% 6% 2 7% 5% 4 4 3 5% 7% 48%	4185
August	1st to 10th	Night	16% 9% 3 7% 5% 5% 5% 4 6% 6% 36%	2915
	11th to 20th	Night	14% 7% 3 8% 4 4 3 4 4 9% 40%	2926
	21st to end	Night	11% 7% 3 7% 5% 5% 5% 4 6% 8% 41%	3586
September	1st to 10th	Night	14% 6% 3 6% 3 4 4 3 5% 6% 46%	2000
	11th to 20th	Night	12% 6% 2 5% 3 3 3 3 5% 8% 50%	2000
	21st to end	Night	17% 7% 2 7% 5% 4 4 3 5% 6% 38%	2290
October	1st to 10th	Night	15% 8% 2 6% 4 3 5% 4 5% 6% 41%	2400
	11th to 20th	Night	17% 10% 3 5% 4 4 4 3 6% 8% 37%	2400
	21st to end	Night	21% 12% 2 8% 4 4 4 3 5% 6% 31%	2642
November	1st to 10th	Night	10% 13% 3 7% 4 4 4 3 5% 6% 41%	2667
	11th to 20th	Night	16% 13% 4 9% 5% 5% 5% 4 5% 6% 29%	2867
	21st to end	Night	14% 14% 4 10% 6% 5% 6% 4 5% 7% 26%	2940
December	1st to 10th	Night	10% 15% 9% 14% 8% 6% 6% 4 5% 6% 18%	4720
	11th to 20th	Night	18% 15% 5% 11% 5% 5% 4 3 3 4 26%	5348
	21st to end	Night	17% 17% 7% 13% 6% 4 4 3 4 5% 20%	7150

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	72% 1 7% 16% 4 1	4662
	11th to 20th	Day	73% 1 5% 11% 8% 1	4956
	21st to end	Day	62% 1 9% 18% 10%	5780
February	1st to 10th	Day	64% 2 9% 15% 9% 1	1890
	11th to 20th	Day	63% 3 6% 19% 9%	1858
	21st to end	Day	59% 2 8% 21% 9% 2	1730
March	1st to 10th	Day	60% 1 8% 19% 10% 2	4855
	11th to 20th	Day	51% 1 16% 20% 8% 4	5090
	21st to end	Day	57% 1 6% 18% 15% 3	5725
April	1st to 10th	Day	57% 2 7% 21% 11% 2	2520
	11th to 20th	Day	53% 3 10% 19% 14% 1	2446
	21st to end	Day	51% 3 7% 21% 15% 3	2450
May	1st to 10th	Day	61% 1 8% 18% 10% 1	6050
	11th to 20th	Day	58% 2 9% 21% 9% 1	6322
	21st to end	Day	54% 2 9% 22% 11% 1	6949
June	1st to 10th	Day	50% 3 10% 22% 14% 1	2800
	11th to 20th	Day	48% 3 13% 22% 12% 1	2800
	21st to end	Day	46% 4 11% 26% 13% 1	2800
July	1st to 10th	Day	43% 3 14% 27% 12% 1	6290
	11th to 20th	Day	45% 3 15% 26% 11%	6285
	21st to end	Day	43% 2 11% 26% 17% 1	6472
August	1st to 10th	Day	51% 3 13% 21% 11%	4221
	11th to 20th	Day	51% 3 13% 25% 8%	4129
	21st to end	Day	43% 2 9% 35% 10% 1	4312
September	1st to 10th	Day	43% 3 10% 28% 14% 2	2400
	11th to 20th	Day	41% 3 9% 28% 19% 1	2400
	21st to end	Day	51% 2 10% 20% 15% 1	2105
October	1st to 10th	Day	45% 2 9% 23% 20% 1	3260
	11th to 20th	Day	48% 1 8% 22% 17% 3	3240
	21st to end	Day	42% 2 14% 28% 14% 1	3521
November	1st to 10th	Day	50% 3 10% 21% 14% 2	1851
	11th to 20th	Day	57% 3 8% 21% 8% 3	1752
	21st to end	Day	60% 2 12% 19% 6% 1	1680
December	1st to 10th	Day	72% 1 7% 15% 5%	2680
	11th to 20th	Day	63% 1 11% 16% 9%	3066
	21st to end	Day	70% 2 10% 12% 6%	4048
January	1st to 10th	Night	71% 1 7% 14% 6% 1	8234
	11th to 20th	Night	69% 1 8% 12% 9% 1	8003
	21st to end	Night	65% 1 5% 16% 12% 1	8401
February	1st to 10th	Night	60% 3 10% 18% 9% 1	2730
	11th to 20th	Night	63% 2 8% 17% 9% 1	2657
	21st to end	Night	61% 1 8% 17% 10% 2	2076
March	1st to 10th	Night	60% 1 11% 17% 10% 2	5216
	11th to 20th	Night	52% 1 15% 21% 7% 4	5090
	21st to end	Night	56% 1 7% 17% 16% 3	5448
April	1st to 10th	Night	58% 3 8% 18% 12% 2	2100
	11th to 20th	Night	51% 3 12% 19% 14% 1	2036
	21st to end	Night	48% 2 10% 23% 15% 2	1965
May	1st to 10th	Night	63% 2 7% 19% 7% 2	3904
	11th to 20th	Night	57% 2 12% 18% 10% 1	3576
	21st to end	Night	54% 3 10% 20% 11% 2	3927
June	1st to 10th	Night	44% 3 10% 26% 16% 1	1600
	11th to 20th	Night	43% 3 15% 25% 13% 2	1600
	21st to end	Night	39% 4 13% 29% 14% 1	1600
July	1st to 10th	Night	43% 3 13% 27% 14% 1	3560
	11th to 20th	Night	41% 4 17% 26% 12%	3552
	21st to end	Night	37% 2 12% 26% 22% 1	4061
August	1st to 10th	Night	49% 4 14% 24% 9% 1	2904
	11th to 20th	Night	44% 2 15% 28% 11%	2953
	21st to end	Night	41% 3 12% 33% 10% 1	3586
September	1st to 10th	Night	41% 3 10% 29% 15% 2	2000
	11th to 20th	Night	34% 3 12% 32% 18% 2	2000
	21st to end	Night	47% 3 11% 24% 14% 1	2290
October	1st to 10th	Night	48% 2 8% 23% 17% 1	3920
	11th to 20th	Night	43% 2 10% 24% 17% 5%	3899
	21st to end	Night	42% 1 15% 28% 14% 1	4266
November	1st to 10th	Night	45% 3 11% 24% 14% 2	2667
	11th to 20th	Night	57% 2 9% 19% 11% 2	2867
	21st to end	Night	59% 2 12% 20% 6% 1	2940
December	1st to 10th	Night	68% 2 10% 16% 3	4720
	11th to 20th	Night	63% 1 10% 15% 10%	5348
	21st to end	Night	69% 2 7% 14% 8%	7150

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	40% 19% 30% 9% 2	220
	11th to 20th	Day	40% 29% 24% 5% 1	270
	21st to end	Day	35% 26% 31% 7% 2	363
February	1st to 10th	Day	36% 25% 31% 7% 1	330
	11th to 20th	Day	40% 26% 31% 2 1	336
	21st to end	Day	39% 22% 29% 9% 1	446
March	1st to 10th	Day	35% 22% 28% 12% 2	540
	11th to 20th	Day	36% 23% 25% 12% 3	540
	21st to end	Day	35% 25% 25% 10% 3 2	594
April	1st to 10th	Day	37% 20% 27% 11% 4 1	540
	11th to 20th	Day	32% 23% 27% 10% 5% 3	516
	21st to end	Day	32% 19% 29% 14% 5% 2	500
May	1st to 10th	Day	33% 17% 29% 11% 8% 3	503
	11th to 20th	Day	28% 16% 29% 16% 8% 3	527
	21st to end	Day	22% 11% 31% 22% 11% 4	573
June	1st to 10th	Day	20% 17% 31% 22% 9% 2	530
	11th to 20th	Day	22% 11% 30% 25% 11% 1	530
	21st to end	Day	18% 11% 37% 23% 10% 2	530
July	1st to 10th	Day	14% 5% 30% 30% 16% 4	525
	11th to 20th	Day	10% 9% 32% 29% 15% 6%	524
	21st to end	Day	14% 6% 37% 27% 12% 4	576
August	1st to 10th	Day	13% 7% 27% 30% 16% 7%	526
	11th to 20th	Day	17% 6% 27% 28% 16% 6%	519
	21st to end	Day	17% 8% 29% 23% 14% 9%	583
September	1st to 10th	Day	19% 10% 23% 25% 16% 8%	530
	11th to 20th	Day	15% 7% 26% 23% 19% 12%	530
	21st to end	Day	28% 11% 26% 19% 12% 3	530
October	1st to 10th	Day	24% 11% 24% 22% 15% 5%	530
	11th to 20th	Day	30% 15% 32% 16% 6% 2	530
	21st to end	Day	33% 19% 27% 17% 5%	580
November	1st to 10th	Day	27% 22% 26% 16% 9%	425
	11th to 20th	Day	37% 21% 26% 12% 3 1	292
	21st to end	Day	35% 28% 31% 5% 1	220
December	1st to 10th	Day	34% 28% 29% 5% 3 1	220
	11th to 20th	Day	38% 26% 29% 7% 1	220
	21st to end	Day	34% 28% 30% 7% 1	242
January	1st to 10th	Night	24% 25% 35% 13% 3	840
	11th to 20th	Night	28% 23% 29% 17% 3	840
	21st to end	Night	25% 25% 31% 17% 2	924
February	1st to 10th	Night	29% 21% 31% 18% 1	840
	11th to 20th	Night	31% 23% 33% 13% 1	823
	21st to end	Night	31% 20% 30% 17% 2	692
March	1st to 10th	Night	30% 23% 29% 16% 2	840
	11th to 20th	Night	32% 20% 28% 17% 3	840
	21st to end	Night	28% 21% 29% 16% 5% 1	924
April	1st to 10th	Night	29% 19% 31% 18% 3	840
	11th to 20th	Night	27% 16% 31% 18% 7%	816
	21st to end	Night	24% 14% 30% 26% 6%	765
May	1st to 10th	Night	30% 10% 21% 28% 9%	535
	11th to 20th	Night	21% 11% 29% 30% 8% 1	394
	21st to end	Night	14% 10% 28% 33% 14% 1	433
June	1st to 10th	Night	18% 7% 26% 33% 15% 1	400
	11th to 20th	Night	19% 8% 21% 39% 13%	400
	21st to end	Night	15% 5% 29% 39% 13% 1	400
July	1st to 10th	Night	11% 4 26% 37% 19% 2	390
	11th to 20th	Night	11% 2 22% 42% 21% 2	388
	21st to end	Night	14% 3 18% 43% 19% 2	544
August	1st to 10th	Night	11% 3 23% 38% 23% 2	597
	11th to 20th	Night	15% 3 17% 35% 26% 3	619
	21st to end	Night	15% 4 20% 37% 22% 3	880
September	1st to 10th	Night	18% 7% 22% 33% 17% 3	800
	11th to 20th	Night	15% 5% 19% 29% 27% 5%	800
	21st to end	Night	21% 9% 25% 26% 16% 3	800
October	1st to 10th	Night	21% 10% 24% 26% 17% 3	800
	11th to 20th	Night	26% 13% 28% 24% 7% 1	800
	21st to end	Night	30% 12% 29% 22% 6%	880
November	1st to 10th	Night	21% 17% 30% 24% 7%	820
	11th to 20th	Night	29% 19% 28% 18% 5% 2	840
	21st to end	Night	27% 19% 30% 20% 3 1	840
December	1st to 10th	Night	30% 23% 28% 14% 4	840
	11th to 20th	Night	30% 20% 30% 17% 2	840
	21st to end	Night	31% 20% 32% 16% 2	924

Page generated at 2026-04-14 02:44:25. Version ac07

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