Manning
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Manning clear sky chart from 2005-11-06 to 2026-02-16.

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	12% 8% 3 8% 5% 4 4 3 5% 7% 41%	131136
	Night	10% 8% 3 8% 4 4 4 3 5% 6% 44%	129997
Transparency	Day	42% 5% 12% 25% 14% 2	134741
	Night	39% 5% 12% 26% 16% 2	134470
Seeing	Day	15% 11% 32% 27% 13% 3	17550
	Night	14% 10% 35% 30% 10% 1	27567

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	8% 12% 4 17% 9% 6% 5% 3 4 5% 27%	5009
	11th to 20th	Day	5% 9% 4 11% 7% 6% 7% 5% 5% 6% 34%	5310
	21st to end	Day	7% 10% 5% 14% 6% 6% 5% 3 5% 6% 33%	5812
February	1st to 10th	Day	10% 12% 5% 11% 7% 6% 4 4 5% 8% 28%	1890
	11th to 20th	Day	10% 11% 4 10% 5% 4 5% 3 5% 5% 38%	1799
	21st to end	Day	12% 11% 3 9% 6% 5% 3 4 5% 7% 36%	1609
March	1st to 10th	Day	15% 9% 3 7% 3 3 3 2 4 4 48%	4936
	11th to 20th	Day	12% 7% 2 6% 4 3 4 3 5% 8% 46%	4980
	21st to end	Day	22% 12% 5% 9% 5% 4 4 4 5% 5% 25%	5462
April	1st to 10th	Day	15% 11% 3 6% 5% 4 4 3 5% 6% 38%	2319
	11th to 20th	Day	17% 10% 2 7% 5% 4 4 3 4 6% 37%	2426
	21st to end	Day	22% 8% 2 6% 4 4 5% 4 4 6% 35%	2600
May	1st to 10th	Day	15% 7% 2 6% 5% 4 4 3 5% 6% 42%	5862
	11th to 20th	Day	16% 6% 2 5% 3 4 4 3 4 5% 49%	5948
	21st to end	Day	17% 8% 3 7% 4 5% 4 4 6% 7% 35%	6935
June	1st to 10th	Day	12% 5% 2 5% 5% 4 5% 3 6% 8% 45%	2800
	11th to 20th	Day	9% 4 1 5% 5% 4 5% 4 7% 9% 46%	2800
	21st to end	Day	8% 5% 3 5% 5% 5% 6% 5% 6% 6% 47%	2800
July	1st to 10th	Day	10% 5% 2 6% 4 4 5% 4 6% 8% 44%	6360
	11th to 20th	Day	9% 4 2 5% 4 4 4 4 5% 7% 52%	5992
	21st to end	Day	6% 4 2 6% 4 4 5% 4 8% 10% 47%	6422
August	1st to 10th	Day	8% 5% 2 6% 4 4 5% 5% 6% 10% 44%	4234
	11th to 20th	Day	15% 7% 2 6% 4 4 4 4 6% 7% 41%	4171
	21st to end	Day	8% 5% 2 6% 4 4 4 4 7% 8% 47%	4520
September	1st to 10th	Day	12% 5% 2 5% 3 3 4 3 5% 6% 53%	2400
	11th to 20th	Day	10% 5% 1 5% 3 4 4 3 4 8% 52%	2220
	21st to end	Day	11% 4 2 4 3 3 3 3 6% 7% 54%	2191
October	1st to 10th	Day	13% 6% 2 4 3 3 4 2 4 7% 51%	2000
	11th to 20th	Day	13% 7% 2 5% 4 3 3 2 4 6% 51%	2000
	21st to end	Day	15% 8% 3 7% 4 3 4 3 5% 6% 42%	2200
November	1st to 10th	Day	11% 7% 2 6% 4 3 4 3 5% 7% 48%	1921
	11th to 20th	Day	11% 8% 3 9% 5% 4 4 3 5% 7% 41%	1680
	21st to end	Day	13% 10% 4 7% 5% 4 3 3 6% 6% 42%	1680
December	1st to 10th	Day	6% 6% 3 9% 6% 4 4 4 4 6% 49%	2690
	11th to 20th	Day	11% 10% 3 9% 6% 5% 5% 4 5% 7% 35%	3088
	21st to end	Day	17% 11% 4 18% 6% 4 4 3 4 5% 24%	4070
January	1st to 10th	Night	9% 11% 4 17% 9% 5% 4 3 5% 5% 28%	7899
	11th to 20th	Night	5% 8% 3 9% 6% 5% 7% 4 7% 7% 38%	7680
	21st to end	Night	6% 10% 5% 13% 6% 5% 5% 3 5% 5% 37%	8402
February	1st to 10th	Night	10% 11% 4 11% 7% 5% 5% 3 5% 5% 35%	2730
	11th to 20th	Night	11% 10% 4 7% 5% 5% 5% 3 5% 6% 40%	2599
	21st to end	Night	9% 8% 3 9% 5% 4 4 2 4 6% 45%	2035
March	1st to 10th	Night	15% 7% 2 6% 2 3 3 2 4 5% 52%	4919
	11th to 20th	Night	10% 7% 2 5% 3 3 3 3 5% 8% 52%	4980
	21st to end	Night	17% 10% 4 10% 5% 4 5% 4 5% 6% 31%	5467
April	1st to 10th	Night	12% 9% 2 6% 4 3 3 4 5% 6% 44%	2080
	11th to 20th	Night	12% 9% 2 7% 5% 4 4 3 5% 6% 43%	1921
	21st to end	Night	17% 9% 3 6% 4 4 4 3 5% 7% 38%	1800
May	1st to 10th	Night	15% 6% 2 5% 3 3 3 3 5% 6% 49%	4053
	11th to 20th	Night	13% 5% 2 5% 3 3 3 3 4 7% 52%	3962
	21st to end	Night	18% 8% 2 6% 4 3 4 3 5% 6% 41%	3942
June	1st to 10th	Night	7% 4 2 5% 4 3 5% 4 7% 7% 52%	1600
	11th to 20th	Night	6% 4 2 5% 4 4 4 5% 6% 10% 50%	1600
	21st to end	Night	6% 4 2 4 4 4 4 4 6% 8% 55%	1600
July	1st to 10th	Night	7% 5% 2 5% 4 4 4 3 6% 9% 52%	3618
	11th to 20th	Night	8% 5% 1 4 3 3 3 3 5% 8% 58%	3980
	21st to end	Night	5% 4 2 5% 4 4 5% 4 7% 10% 51%	4449
August	1st to 10th	Night	5% 4 2 6% 3 4 4 3 7% 9% 54%	2926
	11th to 20th	Night	10% 7% 2 4 3 3 2 3 5% 8% 53%	2888
	21st to end	Night	8% 5% 2 5% 3 2 3 4 5% 7% 56%	3383
September	1st to 10th	Night	8% 4 1 4 3 3 3 2 5% 7% 59%	2000
	11th to 20th	Night	10% 4 2 4 3 3 4 3 5% 7% 55%	2177
	21st to end	Night	9% 5% 2 5% 3 3 3 3 4 6% 58%	2200
October	1st to 10th	Night	14% 6% 1 5% 3 3 3 3 4 6% 53%	2387
	11th to 20th	Night	15% 7% 2 5% 3 2 2 2 3 6% 52%	2400
	21st to end	Night	16% 8% 2 6% 3 3 3 2 3 5% 49%	2640
November	1st to 10th	Night	9% 5% 2 5% 4 3 4 3 5% 6% 54%	2591
	11th to 20th	Night	10% 7% 2 8% 4 3 4 3 6% 6% 46%	2940
	21st to end	Night	11% 10% 3 8% 3 3 4 3 5% 6% 44%	2940
December	1st to 10th	Night	5% 8% 3 9% 5% 4 4 3 5% 6% 47%	4720
	11th to 20th	Night	10% 9% 4 12% 6% 5% 5% 4 5% 6% 36%	5339
	21st to end	Night	17% 14% 4 14% 5% 4 4 3 4 5% 27%	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	61% 4 10% 14% 10% 1	5010
	11th to 20th	Day	51% 3 9% 21% 14% 3	5310
	21st to end	Day	53% 5% 13% 21% 8%	5812
February	1st to 10th	Day	54% 5% 12% 18% 9% 1	1890
	11th to 20th	Day	49% 4 11% 21% 14% 2	1808
	21st to end	Day	48% 5% 12% 21% 11% 4	1609
March	1st to 10th	Day	42% 3 8% 29% 17% 3	4936
	11th to 20th	Day	37% 5% 8% 27% 21% 3	4980
	21st to end	Day	60% 6% 14% 15% 4 1	5464
April	1st to 10th	Day	47% 5% 11% 26% 9% 1	2319
	11th to 20th	Day	48% 4 12% 22% 12% 2	2426
	21st to end	Day	50% 5% 10% 22% 12% 1	2600
May	1st to 10th	Day	43% 6% 10% 26% 16% 1	5900
	11th to 20th	Day	38% 5% 7% 27% 20% 3	5952
	21st to end	Day	47% 6% 11% 22% 14% 1	6949
June	1st to 10th	Day	36% 7% 16% 26% 13% 2	2800
	11th to 20th	Day	33% 7% 15% 29% 16% 1	2800
	21st to end	Day	34% 8% 15% 27% 13% 3	2800
July	1st to 10th	Day	36% 6% 13% 33% 10% 1	6291
	11th to 20th	Day	32% 6% 13% 30% 17% 2	5921
	21st to end	Day	29% 8% 19% 28% 14% 1	6240
August	1st to 10th	Day	35% 7% 14% 28% 15% 1	4220
	11th to 20th	Day	43% 5% 10% 30% 11% 1	4210
	21st to end	Day	33% 7% 14% 25% 17% 3	4519
September	1st to 10th	Day	31% 5% 12% 30% 18% 4	2400
	11th to 20th	Day	31% 6% 12% 31% 17% 1	2220
	21st to end	Day	29% 5% 11% 30% 24% 1	2191
October	1st to 10th	Day	21% 3 6% 27% 41% 2	3260
	11th to 20th	Day	25% 3 12% 31% 22% 6%	3240
	21st to end	Day	39% 4 8% 28% 19% 4	3538
November	1st to 10th	Day	36% 4 15% 24% 18% 2	1921
	11th to 20th	Day	43% 4 12% 23% 16% 1	1680
	21st to end	Day	44% 3 14% 25% 13% 1	1680
December	1st to 10th	Day	37% 4 16% 30% 11% 1	2690
	11th to 20th	Day	49% 5% 16% 21% 9%	3085
	21st to end	Day	63% 4 10% 16% 6% 1	4070
January	1st to 10th	Night	59% 4 11% 16% 8% 1	7900
	11th to 20th	Night	42% 4 12% 21% 19% 3	7680
	21st to end	Night	49% 4 12% 20% 13% 1	8402
February	1st to 10th	Night	51% 5% 11% 20% 11% 2	2730
	11th to 20th	Night	45% 4 11% 23% 14% 3	2600
	21st to end	Night	42% 3 11% 22% 19% 3	2035
March	1st to 10th	Night	36% 2 7% 33% 19% 3	4919
	11th to 20th	Night	32% 3 8% 34% 18% 5%	4980
	21st to end	Night	53% 7% 14% 19% 5% 2	5467
April	1st to 10th	Night	39% 5% 12% 26% 16% 2	2080
	11th to 20th	Night	41% 6% 10% 24% 16% 3	1921
	21st to end	Night	45% 5% 12% 22% 14% 1	1800
May	1st to 10th	Night	36% 5% 9% 28% 21% 1	4080
	11th to 20th	Night	33% 5% 11% 23% 22% 6%	3963
	21st to end	Night	44% 5% 11% 23% 14% 2	3950
June	1st to 10th	Night	29% 7% 14% 32% 15% 4	1600
	11th to 20th	Night	27% 9% 14% 26% 21% 4	1600
	21st to end	Night	26% 6% 16% 29% 19% 3	1600
July	1st to 10th	Night	29% 5% 15% 33% 16% 2	3580
	11th to 20th	Night	27% 5% 15% 33% 19% 2	3932
	21st to end	Night	28% 8% 18% 31% 15% 1	4320
August	1st to 10th	Night	27% 6% 17% 32% 17% 2	2916
	11th to 20th	Night	31% 6% 14% 30% 16% 2	2915
	21st to end	Night	28% 5% 15% 26% 18% 6%	3383
September	1st to 10th	Night	26% 6% 12% 30% 22% 4	2000
	11th to 20th	Night	29% 4 12% 33% 19% 2	2177
	21st to end	Night	28% 5% 9% 30% 25% 4	2200
October	1st to 10th	Night	22% 3 6% 22% 45% 3	3907
	11th to 20th	Night	27% 3 10% 26% 27% 6%	3899
	21st to end	Night	38% 3 10% 29% 19% 1	4252
November	1st to 10th	Night	31% 5% 16% 25% 20% 3	2591
	11th to 20th	Night	38% 4 14% 26% 16% 2	2940
	21st to end	Night	41% 4 11% 27% 15% 2	2940
December	1st to 10th	Night	38% 3 12% 36% 10% 1	4720
	11th to 20th	Night	49% 4 13% 26% 7%	5341
	21st to end	Night	61% 4 10% 18% 7%	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	16% 15% 39% 22% 7% 1	330
	11th to 20th	Day	17% 17% 42% 19% 4 1	330
	21st to end	Day	15% 13% 45% 21% 5% 1	363
February	1st to 10th	Day	15% 20% 41% 20% 4	330
	11th to 20th	Day	14% 16% 43% 22% 4 1	315
	21st to end	Day	18% 18% 45% 16% 3	249
March	1st to 10th	Day	19% 17% 41% 19% 3 1	300
	11th to 20th	Day	24% 14% 35% 22% 4	300
	21st to end	Day	32% 17% 32% 16% 2	330
April	1st to 10th	Day	23% 16% 37% 19% 4	419
	11th to 20th	Day	24% 17% 33% 19% 7%	544
	21st to end	Day	23% 16% 33% 20% 6% 2	700
May	1st to 10th	Day	22% 14% 30% 23% 9% 2	703
	11th to 20th	Day	19% 14% 30% 22% 12% 3	725
	21st to end	Day	19% 8% 31% 26% 14% 2	789
June	1st to 10th	Day	9% 7% 27% 32% 22% 3	730
	11th to 20th	Day	9% 7% 35% 32% 15% 3	730
	21st to end	Day	9% 8% 37% 30% 14% 3	730
July	1st to 10th	Day	8% 3 21% 35% 26% 7%	721
	11th to 20th	Day	6% 5% 29% 35% 20% 6%	718
	21st to end	Day	6% 3 24% 38% 25% 5%	794
August	1st to 10th	Day	9% 3 24% 36% 24% 5%	726
	11th to 20th	Day	11% 4 20% 38% 21% 4	715
	21st to end	Day	10% 4 22% 40% 19% 5%	713
September	1st to 10th	Day	13% 5% 25% 34% 18% 5%	530
	11th to 20th	Day	8% 5% 38% 28% 18% 3	350
	21st to end	Day	13% 8% 32% 30% 15% 2	330
October	1st to 10th	Day	18% 9% 30% 24% 15% 3	330
	11th to 20th	Day	16% 19% 37% 21% 7% 1	330
	21st to end	Day	21% 15% 39% 17% 7% 1	363
November	1st to 10th	Day	18% 14% 42% 19% 6% 2	330
	11th to 20th	Day	17% 20% 38% 20% 4	330
	21st to end	Day	22% 18% 36% 20% 4 1	330
December	1st to 10th	Day	11% 16% 44% 23% 5% 1	330
	11th to 20th	Day	13% 22% 38% 19% 7%	330
	21st to end	Day	23% 17% 44% 14% 3	363
January	1st to 10th	Night	13% 15% 39% 28% 5%	1050
	11th to 20th	Night	13% 17% 42% 22% 6%	1050
	21st to end	Night	17% 12% 42% 24% 5%	1155
February	1st to 10th	Night	15% 13% 43% 24% 4	1050
	11th to 20th	Night	16% 13% 44% 23% 5%	1005
	21st to end	Night	14% 15% 46% 20% 5% 1	715
March	1st to 10th	Night	17% 11% 38% 27% 6% 1	600
	11th to 20th	Night	19% 11% 39% 24% 8%	600
	21st to end	Night	22% 14% 36% 22% 5% 1	660
April	1st to 10th	Night	18% 16% 39% 23% 4	600
	11th to 20th	Night	18% 12% 40% 26% 5%	593
	21st to end	Night	20% 12% 35% 25% 8% 1	600
May	1st to 10th	Night	18% 8% 35% 31% 8% 1	600
	11th to 20th	Night	16% 10% 29% 35% 10% 1	591
	21st to end	Night	14% 8% 30% 36% 12%	650
June	1st to 10th	Night	8% 4 27% 46% 16%	600
	11th to 20th	Night	7% 5% 34% 41% 12%	600
	21st to end	Night	6% 5% 35% 40% 14%	600
July	1st to 10th	Night	5% 2 19% 44% 28% 1	585
	11th to 20th	Night	5% 2 20% 50% 20% 2	582
	21st to end	Night	4 2 18% 51% 24% 1	657
August	1st to 10th	Night	7% 3 22% 44% 23% 2	597
	11th to 20th	Night	9% 4 19% 44% 23% 2	594
	21st to end	Night	8% 3 23% 43% 20% 2	660
September	1st to 10th	Night	9% 5% 24% 38% 21% 3	600
	11th to 20th	Night	11% 3 31% 39% 15% 2	600
	21st to end	Night	11% 6% 33% 34% 15% 1	600
October	1st to 10th	Night	15% 9% 32% 31% 11% 2	787
	11th to 20th	Night	17% 12% 39% 26% 6%	800
	21st to end	Night	20% 13% 33% 26% 8%	880
November	1st to 10th	Night	12% 13% 38% 29% 8%	951
	11th to 20th	Night	14% 17% 41% 22% 5%	1050
	21st to end	Night	17% 13% 38% 25% 7%	1050
December	1st to 10th	Night	14% 13% 43% 25% 5%	1050
	11th to 20th	Night	16% 12% 42% 25% 5%	1050
	21st to end	Night	19% 14% 40% 24% 3	1155

Page generated at 2026-02-13 00:42:10. Version ac07

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