Mancave Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mancave Observatory clear sky chart from 2005-11-06 to 2026-01-02.

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	7% 5% 2 7% 5% 6% 6% 5% 7% 10% 40%	127079
	Night	8% 6% 2 7% 5% 5% 5% 4 7% 9% 43%	124289
Transparency	Day	36% 9% 16% 20% 14% 5%	130825
	Night	35% 8% 17% 21% 14% 5%	128598
Seeing	Day	7% 4 16% 25% 26% 21%	17102
	Night	8% 3 17% 34% 28% 9%	27167

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	7% 6% 2 6% 4 3 4 3 6% 9% 49%	4065
	11th to 20th	Day	18% 9% 3 8% 5% 5% 5% 3 5% 7% 32%	4060
	21st to end	Day	13% 5% 2 6% 4 3 4 3 6% 8% 45%	4862
February	1st to 10th	Day	10% 5% 2 6% 5% 4 4 4 7% 6% 46%	2000
	11th to 20th	Day	6% 4 2 5% 3 4 4 3 5% 8% 55%	1948
	21st to end	Day	7% 5% 1 5% 5% 5% 4 4 6% 7% 52%	1729
March	1st to 10th	Day	7% 5% 2 7% 5% 5% 5% 4 6% 7% 48%	4935
	11th to 20th	Day	4 3 2 4 3 4 3 3 5% 9% 61%	4980
	21st to end	Day	7% 4 2 5% 4 4 4 4 6% 9% 51%	5465
April	1st to 10th	Day	5% 4 1 5% 5% 4 5% 4 8% 10% 49%	2200
	11th to 20th	Day	6% 5% 2 6% 4 5% 6% 5% 7% 9% 47%	2176
	21st to end	Day	5% 3 2 5% 4 5% 6% 4 6% 8% 53%	2360
May	1st to 10th	Day	2 2 1 5% 4 5% 5% 5% 7% 11% 52%	5813
	11th to 20th	Day	8% 4 2 5% 4 4 4 4 6% 10% 49%	5861
	21st to end	Day	3 4 2 5% 5% 5% 6% 5% 8% 11% 46%	6433
June	1st to 10th	Day	11% 9% 3 9% 7% 8% 7% 6% 8% 9% 22%	2600
	11th to 20th	Day	7% 6% 3 10% 8% 8% 9% 7% 9% 9% 26%	2600
	21st to end	Day	7% 8% 3 9% 8% 8% 7% 7% 9% 9% 26%	2600
July	1st to 10th	Day	5% 6% 3 9% 8% 8% 9% 7% 10% 13% 22%	5900
	11th to 20th	Day	4 4 2 8% 7% 8% 10% 7% 10% 14% 26%	5900
	21st to end	Day	4 5% 3 8% 7% 8% 8% 7% 10% 12% 29%	6424
August	1st to 10th	Day	6% 6% 4 11% 8% 7% 7% 7% 8% 12% 25%	4204
	11th to 20th	Day	3 4 2 8% 7% 8% 8% 7% 8% 11% 34%	3791
	21st to end	Day	6% 5% 2 8% 7% 9% 8% 7% 10% 13% 24%	3949
September	1st to 10th	Day	7% 6% 3 10% 8% 8% 8% 7% 9% 11% 23%	2200
	11th to 20th	Day	7% 8% 3 10% 8% 8% 8% 6% 8% 10% 24%	2200
	21st to end	Day	7% 6% 3 10% 6% 6% 7% 6% 9% 9% 30%	2200
October	1st to 10th	Day	9% 6% 3 9% 6% 6% 6% 5% 7% 9% 35%	2200
	11th to 20th	Day	5% 6% 2 6% 4 5% 5% 4 5% 9% 48%	2037
	21st to end	Day	7% 5% 2 6% 5% 4 6% 4 6% 8% 49%	2200
November	1st to 10th	Day	7% 4 1 5% 5% 5% 5% 4 7% 8% 50%	2057
	11th to 20th	Day	7% 6% 2 6% 4 4 4 3 6% 8% 49%	2100
	21st to end	Day	7% 4 2 6% 4 5% 5% 4 5% 9% 49%	1982
December	1st to 10th	Day	4 3 1 4 4 3 4 3 5% 7% 61%	3020
	11th to 20th	Day	8% 6% 2 7% 4 4 5% 4 5% 9% 46%	3463
	21st to end	Day	10% 7% 3 8% 6% 6% 5% 5% 6% 8% 38%	4565
January	1st to 10th	Night	8% 5% 2 6% 4 4 4 4 6% 9% 47%	5903
	11th to 20th	Night	19% 11% 4 8% 5% 4 4 4 6% 7% 29%	5900
	21st to end	Night	14% 5% 2 6% 4 4 4 4 6% 8% 42%	6077
February	1st to 10th	Night	8% 6% 2 6% 4 4 4 4 5% 8% 47%	2400
	11th to 20th	Night	9% 5% 2 4 4 4 4 3 6% 7% 52%	2338
	21st to end	Night	6% 4 2 5% 4 4 5% 4 7% 8% 52%	1899
March	1st to 10th	Night	8% 5% 2 6% 4 4 4 4 6% 8% 49%	4918
	11th to 20th	Night	5% 3 1 4 3 3 4 4 6% 9% 58%	4980
	21st to end	Night	8% 5% 2 6% 4 4 3 4 5% 7% 51%	5467
April	1st to 10th	Night	5% 4 2 4 3 4 3 4 6% 10% 55%	2200
	11th to 20th	Night	5% 4 2 5% 3 4 4 4 7% 10% 53%	2173
	21st to end	Night	4 3 1 5% 4 5% 4 3 5% 8% 57%	2038
May	1st to 10th	Night	3 4 1 5% 4 4 5% 4 7% 9% 53%	4110
	11th to 20th	Night	7% 4 2 5% 4 3 4 3 5% 8% 54%	4032
	21st to end	Night	3 3 1 5% 4 4 4 4 6% 9% 55%	4421
June	1st to 10th	Night	10% 6% 2 7% 5% 5% 6% 5% 8% 10% 38%	1800
	11th to 20th	Night	5% 5% 2 7% 5% 5% 7% 5% 9% 13% 36%	1800
	21st to end	Night	6% 5% 2 7% 6% 6% 7% 6% 9% 15% 31%	1800
July	1st to 10th	Night	4 8% 4 10% 6% 7% 8% 7% 10% 12% 23%	4058
	11th to 20th	Night	4 6% 3 9% 7% 7% 8% 8% 10% 13% 26%	4057
	21st to end	Night	5% 6% 4 10% 8% 8% 8% 6% 10% 11% 24%	4427
August	1st to 10th	Night	5% 6% 3 9% 6% 6% 6% 5% 9% 13% 33%	2939
	11th to 20th	Night	4 4 2 5% 5% 7% 7% 6% 11% 14% 35%	3223
	21st to end	Night	5% 5% 2 9% 7% 7% 8% 7% 10% 13% 27%	3949
September	1st to 10th	Night	6% 7% 3 9% 6% 7% 6% 6% 10% 13% 29%	2200
	11th to 20th	Night	10% 7% 3 8% 7% 7% 7% 5% 8% 10% 29%	2200
	21st to end	Night	9% 7% 3 8% 6% 6% 7% 6% 9% 9% 32%	2200
October	1st to 10th	Night	9% 6% 2 7% 6% 5% 6% 5% 7% 8% 39%	2200
	11th to 20th	Night	6% 5% 3 5% 4 5% 4 3 6% 8% 50%	2360
	21st to end	Night	8% 5% 2 6% 4 3 5% 3 5% 8% 50%	2640
November	1st to 10th	Night	7% 5% 2 6% 4 4 4 5% 6% 7% 50%	2461
	11th to 20th	Night	8% 5% 2 5% 4 4 4 4 6% 7% 51%	2520
	21st to end	Night	7% 4 2 6% 5% 4 5% 3 7% 9% 49%	2634
December	1st to 10th	Night	4 3 1 4 3 4 3 3 5% 8% 61%	4380
	11th to 20th	Night	10% 6% 2 5% 4 3 4 4 5% 8% 49%	4952
	21st to end	Night	12% 8% 3 8% 5% 5% 5% 4 6% 8% 37%	6633

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	32% 5% 7% 20% 27% 9%	4066
	11th to 20th	Day	51% 4 6% 18% 16% 4	4060
	21st to end	Day	37% 5% 6% 28% 21% 5%	4862
February	1st to 10th	Day	35% 6% 9% 20% 20% 10%	2000
	11th to 20th	Day	26% 5% 9% 24% 25% 11%	1958
	21st to end	Day	30% 6% 10% 19% 24% 10%	1729
March	1st to 10th	Day	35% 5% 11% 20% 22% 8%	4935
	11th to 20th	Day	22% 4 10% 23% 22% 19%	4980
	21st to end	Day	30% 5% 8% 28% 21% 9%	5465
April	1st to 10th	Day	26% 7% 16% 25% 18% 7%	2200
	11th to 20th	Day	32% 7% 12% 18% 22% 9%	2176
	21st to end	Day	27% 7% 9% 24% 26% 8%	2360
May	1st to 10th	Day	22% 10% 19% 29% 16% 4	5847
	11th to 20th	Day	30% 6% 15% 32% 16% 1	5865
	21st to end	Day	26% 10% 18% 31% 13% 1	6447
June	1st to 10th	Day	52% 10% 18% 15% 4	2600
	11th to 20th	Day	47% 12% 22% 17% 3	2600
	21st to end	Day	48% 14% 23% 13% 2	2600
July	1st to 10th	Day	46% 15% 30% 7% 1	5835
	11th to 20th	Day	41% 16% 33% 10%	5831
	21st to end	Day	40% 16% 25% 18% 1	6240
August	1st to 10th	Day	47% 11% 31% 9% 2	4191
	11th to 20th	Day	38% 13% 27% 16% 5%	3827
	21st to end	Day	44% 15% 29% 11% 1	3949
September	1st to 10th	Day	50% 15% 24% 10% 1	2200
	11th to 20th	Day	49% 13% 20% 14% 4	2200
	21st to end	Day	45% 11% 16% 17% 9% 2	2200
October	1st to 10th	Day	52% 10% 16% 11% 8% 4	3590
	11th to 20th	Day	29% 6% 9% 23% 29% 5%	3290
	21st to end	Day	29% 5% 7% 26% 25% 8%	3538
November	1st to 10th	Day	30% 6% 12% 22% 19% 12%	2057
	11th to 20th	Day	32% 6% 8% 21% 22% 10%	2100
	21st to end	Day	32% 6% 10% 22% 20% 10%	1982
December	1st to 10th	Day	23% 5% 14% 28% 20% 10%	3020
	11th to 20th	Day	35% 5% 10% 20% 21% 9%	3460
	21st to end	Day	42% 6% 12% 21% 16% 3	4565
January	1st to 10th	Night	33% 4 8% 21% 25% 8%	5903
	11th to 20th	Night	54% 5% 9% 16% 12% 3	5900
	21st to end	Night	39% 6% 8% 24% 17% 6%	6077
February	1st to 10th	Night	35% 6% 10% 20% 21% 8%	2400
	11th to 20th	Night	30% 4 11% 23% 22% 10%	2339
	21st to end	Night	26% 7% 13% 21% 25% 7%	1899
March	1st to 10th	Night	33% 6% 13% 21% 19% 8%	4918
	11th to 20th	Night	22% 5% 16% 22% 18% 17%	4980
	21st to end	Night	32% 4 9% 28% 22% 6%	5467
April	1st to 10th	Night	23% 6% 19% 28% 17% 7%	2200
	11th to 20th	Night	24% 7% 17% 22% 23% 7%	2173
	21st to end	Night	25% 6% 14% 25% 26% 5%	2038
May	1st to 10th	Night	24% 10% 19% 29% 14% 4	4137
	11th to 20th	Night	27% 6% 18% 34% 14%	4033
	21st to end	Night	23% 9% 19% 32% 16% 1	4429
June	1st to 10th	Night	39% 10% 23% 22% 6%	1800
	11th to 20th	Night	35% 13% 29% 19% 4	1800
	21st to end	Night	38% 16% 26% 15% 5%	1800
July	1st to 10th	Night	48% 15% 29% 7%	4015
	11th to 20th	Night	44% 18% 30% 8%	4006
	21st to end	Night	49% 14% 23% 14%	4297
August	1st to 10th	Night	40% 14% 29% 10% 5%	2928
	11th to 20th	Night	35% 14% 34% 15% 3	3253
	21st to end	Night	44% 17% 31% 8% 1	3949
September	1st to 10th	Night	42% 17% 26% 13% 2	2200
	11th to 20th	Night	47% 13% 21% 16% 2	2200
	21st to end	Night	44% 12% 19% 16% 8% 1	2200
October	1st to 10th	Night	54% 9% 14% 11% 8% 4	3590
	11th to 20th	Night	28% 6% 10% 29% 25% 3	3833
	21st to end	Night	30% 5% 8% 28% 23% 6%	4252
November	1st to 10th	Night	31% 7% 11% 20% 20% 11%	2461
	11th to 20th	Night	30% 6% 10% 24% 21% 9%	2520
	21st to end	Night	31% 6% 10% 24% 21% 8%	2634
December	1st to 10th	Night	22% 4 16% 31% 15% 12%	4380
	11th to 20th	Night	33% 5% 12% 21% 20% 9%	4954
	21st to end	Night	43% 7% 15% 18% 14% 4	6633

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	9% 9% 41% 27% 12% 2	303
	11th to 20th	Day	8% 14% 35% 28% 13% 3	300
	21st to end	Day	12% 15% 39% 25% 7% 1	330
February	1st to 10th	Day	9% 9% 27% 32% 17% 6%	300
	11th to 20th	Day	6% 10% 31% 34% 15% 4	300
	21st to end	Day	5% 7% 27% 37% 19% 5%	328
March	1st to 10th	Day	5% 7% 35% 34% 17% 2	500
	11th to 20th	Day	7% 8% 27% 30% 25% 3	500
	21st to end	Day	6% 7% 27% 36% 21% 4	550
April	1st to 10th	Day	6% 7% 28% 36% 20% 3	500
	11th to 20th	Day	8% 6% 23% 36% 21% 7%	492
	21st to end	Day	6% 3 20% 31% 31% 9%	500
May	1st to 10th	Day	5% 2 15% 33% 33% 13%	503
	11th to 20th	Day	9% 5% 14% 26% 29% 18%	527
	21st to end	Day	6% 3 8% 22% 33% 28%	573
June	1st to 10th	Day	14% 4 7% 24% 25% 25%	530
	11th to 20th	Day	8% 2 7% 18% 29% 36%	530
	21st to end	Day	5% 2 4 12% 25% 52%	530
July	1st to 10th	Day	6% 2 3 9% 24% 57%	525
	11th to 20th	Day	5% 2 3 8% 30% 51%	524
	21st to end	Day	9% 2 5% 11% 25% 48%	576
August	1st to 10th	Day	8% 1 3 12% 27% 50%	526
	11th to 20th	Day	4 1 4 9% 29% 53%	519
	21st to end	Day	9% 3 4 16% 31% 37%	583
September	1st to 10th	Day	7% 3 5% 13% 33% 40%	530
	11th to 20th	Day	6% 3 5% 20% 34% 32%	530
	21st to end	Day	6% 2 4 20% 37% 31%	530
October	1st to 10th	Day	13% 2 12% 30% 33% 10%	530
	11th to 20th	Day	6% 2 16% 32% 33% 10%	530
	21st to end	Day	7% 3 18% 36% 29% 8%	583
November	1st to 10th	Day	9% 5% 19% 31% 29% 6%	535
	11th to 20th	Day	9% 4 21% 35% 25% 6%	540
	21st to end	Day	8% 5% 27% 29% 26% 6%	422
December	1st to 10th	Day	4 8% 33% 33% 16% 7%	330
	11th to 20th	Day	11% 5% 29% 32% 19% 3	330
	21st to end	Day	6% 7% 27% 36% 18% 6%	363
January	1st to 10th	Night	9% 6% 29% 41% 14% 1	805
	11th to 20th	Night	12% 6% 25% 41% 14% 1	800
	21st to end	Night	14% 7% 29% 38% 11%	880
February	1st to 10th	Night	11% 6% 29% 37% 17% 1	800
	11th to 20th	Night	10% 6% 27% 41% 16% 1	783
	21st to end	Night	8% 4 25% 48% 16%	660
March	1st to 10th	Night	5% 6% 33% 44% 12%	800
	11th to 20th	Night	7% 5% 26% 46% 16% 1	800
	21st to end	Night	6% 4 28% 45% 17% 1	880
April	1st to 10th	Night	6% 4 24% 47% 18% 1	800
	11th to 20th	Night	6% 3 28% 45% 18% 1	791
	21st to end	Night	4 3 23% 48% 21% 1	800
May	1st to 10th	Night	5% 1 12% 49% 31% 3	638
	11th to 20th	Night	7% 2 9% 46% 32% 4	591
	21st to end	Night	5% 2 7% 34% 44% 8%	650
June	1st to 10th	Night	10% 3 3 26% 46% 13%	600
	11th to 20th	Night	5% 1 5% 15% 49% 24%	600
	21st to end	Night	6% 1 3 10% 49% 32%	600
July	1st to 10th	Night	7% 2 3 7% 45% 37%	585
	11th to 20th	Night	5% 2 1 7% 44% 41%	582
	21st to end	Night	5% 2 2 8% 49% 34%	657
August	1st to 10th	Night	6% 1 3 8% 49% 33%	597
	11th to 20th	Night	6% 1 1 7% 41% 42%	604
	21st to end	Night	10% 3 4 18% 40% 25%	880
September	1st to 10th	Night	8% 2 4 18% 45% 24%	800
	11th to 20th	Night	11% 3 5% 23% 41% 18%	800
	21st to end	Night	12% 2 6% 25% 40% 15%	800
October	1st to 10th	Night	12% 2 12% 40% 30% 4	800
	11th to 20th	Night	7% 3 13% 36% 36% 3	800
	21st to end	Night	10% 3 17% 40% 27% 3	880
November	1st to 10th	Night	8% 4 22% 41% 23% 3	820
	11th to 20th	Night	7% 6% 20% 43% 22% 2	840
	21st to end	Night	8% 4 23% 43% 21% 1	840
December	1st to 10th	Night	8% 3 22% 41% 25% 1	840
	11th to 20th	Night	11% 3 22% 42% 20% 1	840
	21st to end	Night	10% 5% 23% 42% 20% 1	924

Page generated at 2025-12-30 01:14:07. Version ac07

Copyright © 2025 Attilla Danko.