Mancamp Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mancamp Observatory clear sky chart from 2005-11-06 to 2025-12-03.

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	18% 8% 3 7% 5% 4 5% 4 5% 7% 35%	126311
	Night	17% 9% 3 7% 4 4 4 4 5% 6% 36%	124377
Transparency	Day	47% 6% 11% 21% 13% 2	129818
	Night	47% 6% 12% 21% 13% 2	128958
Seeing	Day	25% 15% 30% 20% 9% 2	16591
	Night	23% 11% 31% 27% 8% 1	25283

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	13% 9% 3 9% 6% 5% 5% 4 6% 6% 33%	3597
	11th to 20th	Day	12% 8% 4 7% 5% 4 3 4 5% 8% 38%	3570
	21st to end	Day	10% 11% 3 7% 5% 5% 5% 3 5% 5% 42%	3960
February	1st to 10th	Day	16% 10% 3 7% 6% 5% 5% 3 6% 6% 34%	1740
	11th to 20th	Day	13% 10% 3 9% 7% 5% 5% 3 6% 5% 34%	1933
	21st to end	Day	14% 12% 4 7% 5% 6% 5% 4 5% 6% 34%	1650
March	1st to 10th	Day	21% 13% 4 9% 4 4 5% 3 4 4 29%	4476
	11th to 20th	Day	17% 12% 3 8% 5% 4 4 3 4 5% 35%	4882
	21st to end	Day	25% 9% 3 6% 4 3 3 3 5% 7% 32%	5618
April	1st to 10th	Day	19% 11% 3 8% 5% 3 3 3 4 6% 34%	2400
	11th to 20th	Day	18% 8% 2 6% 5% 4 5% 4 5% 6% 38%	2486
	21st to end	Day	22% 9% 3 7% 5% 4 4 3 4 5% 33%	2600
May	1st to 10th	Day	31% 10% 3 7% 5% 4 4 3 4 6% 23%	5886
	11th to 20th	Day	20% 8% 4 8% 5% 5% 5% 3 5% 6% 29%	6034
	21st to end	Day	19% 7% 3 6% 5% 5% 5% 4 6% 8% 31%	6949
June	1st to 10th	Day	23% 7% 2 6% 4 4 5% 4 7% 8% 29%	2875
	11th to 20th	Day	17% 6% 2 6% 5% 5% 5% 3 5% 7% 38%	3000
	21st to end	Day	23% 7% 3 6% 5% 4 4 4 6% 7% 32%	2857
July	1st to 10th	Day	16% 7% 3 7% 5% 5% 5% 5% 7% 9% 31%	6360
	11th to 20th	Day	15% 6% 2 6% 5% 4 5% 5% 6% 9% 37%	6360
	21st to end	Day	14% 6% 2 6% 4 4 4 4 6% 9% 41%	6926
August	1st to 10th	Day	15% 6% 3 7% 5% 5% 6% 4 7% 9% 33%	4303
	11th to 20th	Day	16% 9% 3 8% 4 5% 5% 4 6% 8% 33%	4175
	21st to end	Day	11% 5% 2 6% 4 4 5% 4 6% 9% 44%	4510
September	1st to 10th	Day	11% 5% 2 5% 5% 3 4 3 6% 8% 48%	2358
	11th to 20th	Day	12% 5% 1 4 3 3 4 4 5% 7% 52%	2200
	21st to end	Day	17% 5% 2 5% 4 4 3 4 6% 8% 44%	2200
October	1st to 10th	Day	18% 6% 3 6% 5% 4 4 4 4 6% 41%	2200
	11th to 20th	Day	18% 7% 3 5% 3 4 4 3 5% 7% 41%	1910
	21st to end	Day	23% 9% 3 7% 4 3 4 3 4 6% 34%	1980
November	1st to 10th	Day	16% 7% 3 6% 3 4 4 3 5% 6% 41%	1851
	11th to 20th	Day	19% 6% 2 6% 4 4 4 4 6% 7% 39%	1890
	21st to end	Day	21% 8% 2 6% 4 3 3 3 4 6% 39%	1795
December	1st to 10th	Day	18% 9% 3 7% 5% 5% 5% 4 5% 7% 33%	2294
	11th to 20th	Day	19% 8% 2 4 3 4 4 4 5% 7% 40%	2618
	21st to end	Day	20% 10% 2 7% 4 4 5% 4 6% 6% 32%	3868
January	1st to 10th	Night	13% 10% 4 9% 5% 4 5% 4 5% 6% 37%	6349
	11th to 20th	Night	12% 11% 5% 10% 5% 5% 6% 5% 7% 7% 27%	6315
	21st to end	Night	12% 9% 3 8% 5% 5% 5% 4 6% 6% 38%	6996
February	1st to 10th	Night	13% 10% 4 8% 6% 5% 4 5% 6% 6% 32%	2658
	11th to 20th	Night	11% 11% 3 7% 5% 5% 5% 4 5% 5% 39%	2348
	21st to end	Night	14% 10% 3 7% 4 5% 5% 4 5% 6% 37%	1980
March	1st to 10th	Night	25% 10% 3 8% 5% 5% 4 3 4 5% 28%	5364
	11th to 20th	Night	15% 11% 4 8% 4 5% 5% 4 5% 6% 33%	5076
	21st to end	Night	24% 10% 2 6% 4 4 4 4 6% 7% 29%	5298
April	1st to 10th	Night	20% 12% 3 7% 4 3 4 2 4 5% 35%	2000
	11th to 20th	Night	18% 7% 2 8% 5% 5% 4 5% 5% 6% 36%	1862
	21st to end	Night	24% 8% 2 7% 4 3 3 3 5% 6% 34%	1800
May	1st to 10th	Night	30% 11% 3 7% 4 4 4 3 5% 5% 25%	4054
	11th to 20th	Night	19% 9% 3 8% 5% 5% 5% 4 6% 6% 29%	3902
	21st to end	Night	17% 8% 2 7% 4 5% 5% 4 5% 7% 35%	3926
June	1st to 10th	Night	25% 7% 2 6% 4 4 4 3 5% 7% 33%	1515
	11th to 20th	Night	17% 7% 3 5% 4 3 4 5% 5% 8% 39%	1400
	21st to end	Night	23% 7% 3 5% 5% 3 4 4 6% 7% 33%	1532
July	1st to 10th	Night	12% 7% 3 6% 4 5% 6% 5% 7% 9% 36%	3600
	11th to 20th	Night	16% 7% 3 7% 5% 4 4 3 5% 8% 38%	3600
	21st to end	Night	10% 5% 2 5% 3 4 5% 4 7% 9% 47%	3926
August	1st to 10th	Night	20% 8% 3 7% 4 5% 5% 4 5% 6% 33%	2812
	11th to 20th	Night	14% 9% 3 7% 5% 4 5% 3 6% 7% 35%	2872
	21st to end	Night	11% 6% 2 6% 4 4 5% 3 6% 8% 45%	3385
September	1st to 10th	Night	13% 5% 2 5% 3 4 3 3 5% 7% 49%	2041
	11th to 20th	Night	15% 5% 2 4 3 3 4 3 5% 6% 52%	2200
	21st to end	Night	16% 6% 2 5% 3 4 3 3 5% 7% 45%	2200
October	1st to 10th	Night	17% 7% 2 6% 4 4 4 4 5% 6% 41%	2200
	11th to 20th	Night	17% 7% 2 5% 4 4 5% 3 5% 7% 41%	2488
	21st to end	Night	24% 9% 2 5% 4 3 4 4 5% 7% 34%	2860
November	1st to 10th	Night	18% 7% 2 6% 4 4 4 3 5% 6% 41%	2667
	11th to 20th	Night	17% 6% 2 6% 5% 4 4 3 5% 7% 41%	2730
	21st to end	Night	17% 8% 2 6% 4 4 5% 3 6% 7% 38%	2819
December	1st to 10th	Night	17% 11% 3 7% 5% 4 5% 4 6% 7% 32%	4941
	11th to 20th	Night	23% 8% 2 5% 4 4 4 3 5% 5% 36%	5591
	21st to end	Night	20% 10% 3 6% 4 3 4 3 5% 5% 37%	7070

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	49% 7% 9% 23% 12% 1	3598
	11th to 20th	Day	43% 7% 10% 27% 11% 3	3600
	21st to end	Day	43% 6% 10% 17% 18% 6%	3960
February	1st to 10th	Day	49% 6% 9% 19% 14% 4	1740
	11th to 20th	Day	50% 6% 11% 18% 13% 3	1942
	21st to end	Day	50% 6% 10% 17% 12% 5%	1650
March	1st to 10th	Day	58% 5% 7% 9% 14% 7%	4479
	11th to 20th	Day	51% 5% 12% 18% 11% 2	4882
	21st to end	Day	53% 4 5% 17% 18% 4	5618
April	1st to 10th	Day	53% 4 7% 17% 15% 4	2400
	11th to 20th	Day	46% 6% 9% 22% 15% 2	2486
	21st to end	Day	53% 5% 7% 18% 13% 4	2600
May	1st to 10th	Day	62% 7% 9% 15% 6% 1	5897
	11th to 20th	Day	53% 8% 12% 17% 7% 3	6038
	21st to end	Day	47% 8% 11% 20% 12% 1	6949
June	1st to 10th	Day	52% 7% 11% 20% 9% 1	2875
	11th to 20th	Day	44% 7% 11% 21% 15% 2	3000
	21st to end	Day	50% 9% 11% 18% 11% 1	2857
July	1st to 10th	Day	47% 6% 15% 21% 10%	6290
	11th to 20th	Day	42% 7% 14% 23% 13% 1	6285
	21st to end	Day	39% 6% 13% 27% 15%	6728
August	1st to 10th	Day	46% 8% 14% 26% 7%	4289
	11th to 20th	Day	48% 6% 15% 23% 7%	4214
	21st to end	Day	35% 7% 14% 25% 17% 2	4510
September	1st to 10th	Day	35% 7% 12% 27% 18% 1	2358
	11th to 20th	Day	32% 5% 9% 30% 21% 2	2200
	21st to end	Day	38% 6% 11% 28% 16% 1	2200
October	1st to 10th	Day	48% 6% 11% 21% 12% 1	3590
	11th to 20th	Day	37% 5% 11% 29% 17% 1	3087
	21st to end	Day	39% 4 14% 21% 19% 3	3180
November	1st to 10th	Day	43% 6% 13% 21% 15% 2	1851
	11th to 20th	Day	43% 6% 11% 20% 17% 3	1890
	21st to end	Day	47% 4 15% 22% 11% 1	1795
December	1st to 10th	Day	49% 6% 15% 18% 12% 1	2294
	11th to 20th	Day	43% 5% 11% 18% 17% 6%	2618
	21st to end	Day	51% 5% 10% 18% 13% 4	3868
January	1st to 10th	Night	47% 6% 11% 24% 11% 1	6349
	11th to 20th	Night	53% 7% 13% 17% 8% 2	6360
	21st to end	Night	46% 6% 7% 19% 17% 5%	6996
February	1st to 10th	Night	50% 6% 12% 17% 12% 3	2658
	11th to 20th	Night	46% 5% 11% 19% 15% 3	2350
	21st to end	Night	47% 5% 10% 20% 15% 4	1980
March	1st to 10th	Night	59% 4 8% 12% 13% 5%	5374
	11th to 20th	Night	50% 7% 15% 19% 8% 2	5077
	21st to end	Night	53% 4 7% 15% 18% 3	5298
April	1st to 10th	Night	53% 4 8% 18% 15% 3	2000
	11th to 20th	Night	48% 6% 9% 20% 17% 1	1862
	21st to end	Night	51% 5% 11% 17% 14% 3	1800
May	1st to 10th	Night	60% 7% 12% 13% 8% 1	4060
	11th to 20th	Night	53% 9% 10% 19% 8% 1	3903
	21st to end	Night	47% 7% 14% 21% 11% 1	3927
June	1st to 10th	Night	50% 7% 11% 21% 9% 1	1515
	11th to 20th	Night	43% 6% 14% 22% 13% 2	1400
	21st to end	Night	49% 8% 13% 19% 10% 1	1532
July	1st to 10th	Night	43% 6% 18% 23% 10%	3560
	11th to 20th	Night	46% 4 14% 25% 10%	3552
	21st to end	Night	33% 7% 17% 32% 11% 1	3809
August	1st to 10th	Night	51% 7% 14% 22% 6%	2802
	11th to 20th	Night	47% 6% 18% 19% 11%	2899
	21st to end	Night	37% 7% 15% 25% 15% 2	3385
September	1st to 10th	Night	34% 6% 13% 30% 16%	2041
	11th to 20th	Night	33% 5% 10% 32% 18% 2	2200
	21st to end	Night	39% 6% 10% 29% 14% 2	2200
October	1st to 10th	Night	45% 5% 13% 22% 14% 1	3590
	11th to 20th	Night	37% 5% 10% 29% 18% 1	4050
	21st to end	Night	41% 4 11% 27% 15% 2	4610
November	1st to 10th	Night	44% 5% 12% 24% 14% 1	2667
	11th to 20th	Night	43% 5% 10% 23% 15% 3	2730
	21st to end	Night	45% 5% 15% 20% 12% 2	2819
December	1st to 10th	Night	49% 6% 10% 27% 8% 1	4941
	11th to 20th	Night	49% 4 9% 17% 19% 2	5592
	21st to end	Night	50% 5% 10% 18% 17% 1	7070

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	31% 19% 33% 13% 5%	200
	11th to 20th	Day	30% 16% 34% 15% 4 2	200
	21st to end	Day	22% 20% 35% 19% 5%	220
February	1st to 10th	Day	30% 19% 29% 19% 4	340
	11th to 20th	Day	27% 24% 33% 15% 2	489
	21st to end	Day	23% 21% 33% 19% 3	414
March	1st to 10th	Day	28% 20% 33% 15% 4	500
	11th to 20th	Day	29% 21% 32% 15% 3 1	500
	21st to end	Day	29% 19% 30% 14% 6% 2	550
April	1st to 10th	Day	35% 20% 26% 12% 5% 1	500
	11th to 20th	Day	32% 18% 31% 12% 5% 2	492
	21st to end	Day	31% 20% 29% 13% 5% 2	500
May	1st to 10th	Day	35% 17% 25% 17% 4 1	503
	11th to 20th	Day	23% 17% 33% 18% 7% 1	527
	21st to end	Day	22% 17% 32% 21% 6% 1	573
June	1st to 10th	Day	24% 13% 32% 20% 8% 2	605
	11th to 20th	Day	22% 13% 27% 23% 12% 2	730
	21st to end	Day	25% 13% 29% 21% 11% 2	587
July	1st to 10th	Day	20% 12% 33% 23% 11% 2	525
	11th to 20th	Day	17% 7% 37% 24% 11% 3	524
	21st to end	Day	16% 9% 35% 26% 10% 4	576
August	1st to 10th	Day	13% 8% 29% 30% 15% 3	526
	11th to 20th	Day	16% 10% 27% 26% 14% 6%	519
	21st to end	Day	13% 13% 31% 26% 12% 5%	583
September	1st to 10th	Day	16% 11% 28% 25% 16% 4	530
	11th to 20th	Day	18% 8% 25% 23% 15% 10%	530
	21st to end	Day	18% 11% 29% 23% 14% 4	530
October	1st to 10th	Day	22% 15% 24% 22% 12% 5%	530
	11th to 20th	Day	27% 13% 28% 18% 12% 2	423
	21st to end	Day	33% 12% 27% 19% 8%	462
November	1st to 10th	Day	27% 14% 28% 22% 8% 1	425
	11th to 20th	Day	29% 15% 30% 17% 7% 1	430
	21st to end	Day	31% 19% 21% 21% 6% 1	424
December	1st to 10th	Day	31% 14% 34% 15% 6%	204
	11th to 20th	Day	34% 19% 35% 10% 4	200
	21st to end	Day	28% 19% 29% 19% 4 2	220
January	1st to 10th	Night	23% 14% 37% 24% 3	800
	11th to 20th	Night	25% 15% 31% 24% 4 1	800
	21st to end	Night	17% 17% 38% 24% 4	880
February	1st to 10th	Night	23% 17% 31% 27% 3	800
	11th to 20th	Night	21% 17% 39% 20% 2	783
	21st to end	Night	22% 12% 35% 27% 3	660
March	1st to 10th	Night	27% 14% 33% 24% 2	800
	11th to 20th	Night	23% 16% 32% 23% 6%	800
	21st to end	Night	26% 16% 31% 21% 6% 1	880
April	1st to 10th	Night	30% 16% 31% 21% 3	800
	11th to 20th	Night	23% 15% 35% 21% 5%	678
	21st to end	Night	31% 12% 33% 20% 4	600
May	1st to 10th	Night	28% 12% 29% 27% 5%	600
	11th to 20th	Night	24% 13% 32% 24% 7% 1	539
	21st to end	Night	20% 7% 33% 34% 5%	433
June	1st to 10th	Night	26% 6% 32% 30% 6%	400
	11th to 20th	Night	19% 6% 30% 35% 10%	400
	21st to end	Night	25% 4 30% 35% 7%	400
July	1st to 10th	Night	18% 3 29% 35% 14%	390
	11th to 20th	Night	19% 2 22% 41% 15% 1	388
	21st to end	Night	15% 3 26% 40% 15% 1	438
August	1st to 10th	Night	15% 4 23% 41% 16% 1	533
	11th to 20th	Night	16% 4 28% 36% 15% 1	592
	21st to end	Night	16% 7% 24% 36% 15% 2	757
September	1st to 10th	Night	14% 5% 32% 32% 16% 1	800
	11th to 20th	Night	18% 7% 24% 31% 17% 4	800
	21st to end	Night	20% 8% 29% 29% 14% 1	800
October	1st to 10th	Night	20% 9% 25% 31% 14% 1	800
	11th to 20th	Night	21% 11% 30% 26% 10% 1	800
	21st to end	Night	31% 11% 27% 25% 5%	880
November	1st to 10th	Night	25% 11% 30% 27% 7% 1	820
	11th to 20th	Night	23% 12% 31% 25% 8% 1	840
	21st to end	Night	25% 14% 29% 26% 6%	884
December	1st to 10th	Night	28% 10% 33% 23% 6%	911
	11th to 20th	Night	27% 14% 33% 21% 4	900
	21st to end	Night	29% 14% 30% 24% 4	897

Page generated at 2025-11-30 01:00:56. Version ac07

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