The Loose Rooster Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the The Loose Rooster Observatory clear sky chart from 2005-11-06 to 2025-09-19.

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	16% 10% 4 8% 5% 5% 5% 4 5% 7% 32%	126554
	Night	16% 11% 4 9% 5% 4 4 3 5% 6% 33%	122514
Transparency	Day	50% 5% 11% 21% 11% 1	130085
	Night	51% 5% 12% 20% 12% 1	127070
Seeing	Day	25% 18% 28% 18% 9% 3	15949
	Night	23% 17% 27% 24% 9% 1	25142

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	12% 13% 10% 19% 7% 3 3 2 3 4 24%	3597
	11th to 20th	Day	12% 15% 7% 17% 7% 5% 4 3 4 5% 21%	3593
	21st to end	Day	17% 14% 7% 9% 6% 4 4 3 4 4 30%	4466
February	1st to 10th	Day	15% 12% 4 10% 8% 6% 5% 4 5% 6% 25%	1800
	11th to 20th	Day	13% 12% 5% 10% 6% 5% 4 3 5% 7% 29%	1849
	21st to end	Day	17% 12% 3 11% 6% 4 4 4 4 6% 29%	1650
March	1st to 10th	Day	20% 14% 5% 9% 5% 4 3 2 3 4 31%	4518
	11th to 20th	Day	12% 12% 4 8% 5% 4 4 3 4 6% 39%	4980
	21st to end	Day	16% 9% 3 8% 5% 5% 5% 3 5% 6% 35%	5758
April	1st to 10th	Day	18% 13% 4 7% 5% 5% 4 3 4 5% 32%	2400
	11th to 20th	Day	15% 12% 3 7% 5% 5% 4 3 5% 6% 35%	2374
	21st to end	Day	16% 9% 3 7% 5% 4 4 4 6% 6% 35%	2400
May	1st to 10th	Day	26% 9% 3 7% 5% 4 4 3 5% 7% 26%	6074
	11th to 20th	Day	20% 10% 3 8% 5% 5% 5% 4 6% 6% 27%	6318
	21st to end	Day	21% 9% 2 6% 4 4 5% 5% 6% 8% 29%	6949
June	1st to 10th	Day	15% 7% 3 7% 5% 5% 5% 4 5% 10% 33%	2800
	11th to 20th	Day	15% 9% 3 7% 4 6% 5% 5% 6% 8% 32%	2800
	21st to end	Day	14% 7% 2 7% 5% 5% 5% 4 7% 9% 35%	2800
July	1st to 10th	Day	9% 7% 3 8% 6% 6% 6% 4 7% 9% 36%	6360
	11th to 20th	Day	9% 7% 3 8% 6% 6% 6% 5% 9% 11% 30%	6360
	21st to end	Day	13% 7% 3 7% 5% 5% 5% 4 6% 8% 38%	6891
August	1st to 10th	Day	19% 8% 3 8% 5% 5% 5% 4 6% 7% 29%	4234
	11th to 20th	Day	14% 7% 3 7% 5% 5% 6% 4 7% 8% 34%	3949
	21st to end	Day	15% 7% 2 6% 4 4 4 3 6% 8% 42%	4312
September	1st to 10th	Day	16% 6% 3 6% 5% 4 4 4 5% 8% 39%	2400
	11th to 20th	Day	13% 6% 2 5% 4 4 4 3 4 8% 46%	2366
	21st to end	Day	17% 8% 3 8% 4 4 5% 4 5% 7% 35%	2055
October	1st to 10th	Day	17% 8% 2 7% 4 3 5% 4 5% 7% 36%	1900
	11th to 20th	Day	16% 8% 3 7% 4 4 5% 3 5% 7% 37%	1900
	21st to end	Day	21% 10% 3 7% 4 5% 5% 3 5% 7% 31%	2014
November	1st to 10th	Day	13% 11% 3 6% 5% 3 3 3 4 6% 43%	1761
	11th to 20th	Day	14% 13% 3 8% 5% 4 4 3 4 6% 35%	1780
	21st to end	Day	17% 13% 4 8% 5% 4 4 4 5% 6% 30%	1600
December	1st to 10th	Day	14% 12% 7% 12% 7% 5% 4 4 5% 6% 24%	2600
	11th to 20th	Day	18% 14% 6% 10% 4 4 3 3 4 5% 29%	2986
	21st to end	Day	15% 15% 6% 13% 5% 4 4 4 5% 6% 23%	3960
January	1st to 10th	Night	11% 13% 7% 18% 8% 4 4 3 4 5% 23%	6349
	11th to 20th	Night	10% 14% 7% 19% 7% 4 4 3 4 5% 23%	6287
	21st to end	Night	16% 11% 4 10% 8% 5% 5% 4 5% 5% 27%	6490
February	1st to 10th	Night	16% 13% 4 9% 6% 4 4 3 5% 6% 30%	2600
	11th to 20th	Night	14% 12% 5% 10% 7% 5% 6% 4 5% 6% 27%	2436
	21st to end	Night	16% 13% 4 10% 6% 5% 4 3 4 5% 31%	1980
March	1st to 10th	Night	16% 13% 6% 8% 5% 4 3 3 4 5% 33%	5318
	11th to 20th	Night	10% 12% 5% 8% 5% 5% 4 3 4 5% 39%	4979
	21st to end	Night	15% 12% 3 8% 5% 5% 4 3 4 5% 34%	5174
April	1st to 10th	Night	17% 14% 4 8% 6% 5% 4 3 5% 6% 30%	2000
	11th to 20th	Night	18% 10% 3 7% 5% 3 4 4 4 7% 36%	1975
	21st to end	Night	18% 9% 3 7% 4 4 4 4 5% 6% 38%	2000
May	1st to 10th	Night	29% 10% 3 7% 5% 4 4 3 4 6% 26%	3908
	11th to 20th	Night	20% 10% 3 7% 5% 4 5% 3 5% 6% 32%	3575
	21st to end	Night	21% 11% 3 7% 4 4 4 4 6% 7% 29%	3926
June	1st to 10th	Night	16% 7% 3 5% 5% 4 5% 4 6% 7% 39%	1600
	11th to 20th	Night	14% 8% 3 7% 4 4 4 4 6% 8% 39%	1600
	21st to end	Night	13% 5% 1 5% 4 4 5% 4 6% 9% 44%	1600
July	1st to 10th	Night	12% 7% 3 7% 5% 5% 5% 4 5% 9% 39%	3600
	11th to 20th	Night	12% 7% 3 8% 6% 5% 6% 4 8% 9% 34%	3600
	21st to end	Night	12% 7% 2 5% 4 4 4 3 5% 7% 46%	3958
August	1st to 10th	Night	20% 9% 3 7% 4 5% 4 4 6% 8% 31%	2915
	11th to 20th	Night	16% 7% 3 7% 4 5% 4 3 5% 7% 41%	3066
	21st to end	Night	12% 7% 2 6% 4 4 4 3 5% 7% 47%	3586
September	1st to 10th	Night	14% 6% 2 5% 4 4 5% 4 5% 6% 44%	2000
	11th to 20th	Night	12% 7% 2 5% 4 3 4 2 5% 6% 50%	1990
	21st to end	Night	17% 8% 2 6% 4 4 4 3 6% 6% 40%	2122
October	1st to 10th	Night	19% 7% 3 6% 2 4 5% 3 5% 6% 40%	2280
	11th to 20th	Night	15% 8% 3 6% 4 4 4 3 5% 5% 43%	2280
	21st to end	Night	20% 10% 3 5% 4 4 4 3 5% 7% 35%	2584
November	1st to 10th	Night	12% 9% 3 7% 5% 4 4 2 5% 6% 44%	2537
	11th to 20th	Night	17% 11% 3 8% 4 4 4 3 5% 6% 35%	2615
	21st to end	Night	14% 13% 4 7% 5% 4 4 3 6% 6% 34%	2800
December	1st to 10th	Night	13% 14% 6% 11% 5% 5% 5% 3 5% 6% 27%	4580
	11th to 20th	Night	20% 15% 4 8% 4 3 3 3 4 4 32%	5208
	21st to end	Night	18% 16% 7% 10% 5% 4 4 2 4 5% 25%	6996

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	65% 3 7% 19% 4 1	3598
	11th to 20th	Day	66% 3 8% 14% 7% 2	3623
	21st to end	Day	58% 3 10% 20% 10%	4466
February	1st to 10th	Day	59% 5% 11% 16% 9% 1	1800
	11th to 20th	Day	55% 5% 8% 22% 10% 1	1858
	21st to end	Day	57% 4 9% 21% 7% 2	1650
March	1st to 10th	Day	57% 3 9% 17% 10% 4	4521
	11th to 20th	Day	46% 4 14% 25% 8% 3	4980
	21st to end	Day	50% 4 10% 13% 20% 3	5758
April	1st to 10th	Day	55% 4 7% 21% 10% 3	2400
	11th to 20th	Day	49% 5% 10% 22% 13% 2	2374
	21st to end	Day	49% 4 9% 22% 13% 3	2400
May	1st to 10th	Day	59% 5% 11% 16% 9% 1	6085
	11th to 20th	Day	56% 4 10% 19% 9% 1	6322
	21st to end	Day	51% 6% 11% 20% 11% 1	6949
June	1st to 10th	Day	47% 5% 13% 22% 13% 1	2800
	11th to 20th	Day	48% 5% 13% 21% 10% 1	2800
	21st to end	Day	44% 6% 13% 25% 11%	2800
July	1st to 10th	Day	44% 7% 13% 24% 12%	6290
	11th to 20th	Day	42% 9% 15% 23% 10%	6285
	21st to end	Day	42% 5% 12% 22% 17% 1	6693
August	1st to 10th	Day	53% 6% 13% 20% 8%	4221
	11th to 20th	Day	45% 6% 15% 26% 8%	3988
	21st to end	Day	40% 5% 10% 33% 11% 1	4312
September	1st to 10th	Day	43% 5% 12% 23% 16% 1	2400
	11th to 20th	Day	38% 4 11% 24% 22% 2	2366
	21st to end	Day	47% 5% 10% 22% 15% 2	2055
October	1st to 10th	Day	45% 5% 11% 21% 18% 1	3160
	11th to 20th	Day	41% 4 8% 25% 15% 7%	3140
	21st to end	Day	36% 3 17% 27% 16% 2	3304
November	1st to 10th	Day	43% 4 12% 24% 15% 2	1761
	11th to 20th	Day	51% 4 10% 21% 12% 2	1780
	21st to end	Day	54% 4 14% 21% 7% 1	1600
December	1st to 10th	Day	59% 6% 13% 16% 5% 1	2600
	11th to 20th	Day	58% 3 13% 15% 10%	2986
	21st to end	Day	62% 3 12% 13% 9% 1	3960
January	1st to 10th	Night	63% 4 9% 16% 7% 1	6349
	11th to 20th	Night	63% 4 11% 14% 6% 2	6332
	21st to end	Night	58% 4 10% 14% 13% 1	6490
February	1st to 10th	Night	54% 5% 12% 20% 9% 1	2600
	11th to 20th	Night	57% 5% 10% 17% 9% 1	2438
	21st to end	Night	55% 4 8% 19% 11% 2	1980
March	1st to 10th	Night	55% 2 12% 17% 12% 2	5328
	11th to 20th	Night	46% 5% 17% 21% 7% 4	4980
	21st to end	Night	51% 4 7% 15% 19% 2	5174
April	1st to 10th	Night	57% 3 9% 18% 11% 2	2000
	11th to 20th	Night	49% 5% 10% 21% 15% 1	1975
	21st to end	Night	46% 5% 10% 21% 15% 3	2000
May	1st to 10th	Night	60% 4 10% 17% 7% 2	3914
	11th to 20th	Night	52% 6% 13% 17% 10% 1	3576
	21st to end	Night	54% 5% 11% 19% 10% 1	3927
June	1st to 10th	Night	43% 5% 11% 26% 16%	1600
	11th to 20th	Night	42% 5% 15% 27% 10% 1	1600
	21st to end	Night	37% 6% 15% 27% 13% 1	1600
July	1st to 10th	Night	42% 7% 15% 20% 15% 1	3560
	11th to 20th	Night	43% 8% 15% 23% 10% 1	3552
	21st to end	Night	37% 6% 13% 27% 17% 1	3841
August	1st to 10th	Night	50% 6% 15% 20% 7%	2904
	11th to 20th	Night	43% 6% 16% 25% 11%	3093
	21st to end	Night	37% 5% 12% 32% 13% 1	3586
September	1st to 10th	Night	39% 6% 12% 25% 17% 1	2000
	11th to 20th	Night	36% 4 10% 27% 22% 2	1990
	21st to end	Night	44% 4 9% 24% 17% 1	2122
October	1st to 10th	Night	48% 4 10% 22% 15% 1	3800
	11th to 20th	Night	38% 4 12% 22% 18% 6%	3779
	21st to end	Night	36% 5% 17% 25% 17% 1	4244
November	1st to 10th	Night	42% 4 12% 23% 17% 3	2537
	11th to 20th	Night	49% 4 10% 21% 12% 2	2615
	21st to end	Night	50% 5% 14% 22% 9% 1	2800
December	1st to 10th	Night	57% 5% 12% 22% 4	4580
	11th to 20th	Night	57% 4 12% 16% 11% 1	5208
	21st to end	Night	63% 3 9% 15% 8% 1	6996

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	36% 26% 28% 8% 2 1	200
	11th to 20th	Day	42% 26% 24% 6% 1	205
	21st to end	Day	31% 32% 26% 8% 3 1	330
February	1st to 10th	Day	37% 30% 26% 7%	300
	11th to 20th	Day	39% 26% 28% 6% 1	396
	21st to end	Day	34% 28% 27% 8% 3	414
March	1st to 10th	Day	33% 24% 29% 11% 2	500
	11th to 20th	Day	32% 25% 27% 12% 4 1	500
	21st to end	Day	36% 23% 26% 10% 3 2	550
April	1st to 10th	Day	36% 24% 25% 11% 4	500
	11th to 20th	Day	30% 25% 27% 10% 6% 2	492
	21st to end	Day	27% 23% 32% 12% 4 2	500
May	1st to 10th	Day	35% 18% 28% 10% 7% 2	503
	11th to 20th	Day	26% 18% 32% 15% 7% 2	527
	21st to end	Day	20% 13% 31% 23% 11% 2	573
June	1st to 10th	Day	20% 15% 28% 24% 10% 2	530
	11th to 20th	Day	21% 17% 25% 25% 11% 1	530
	21st to end	Day	18% 13% 33% 28% 7% 1	530
July	1st to 10th	Day	14% 8% 30% 28% 15% 4	525
	11th to 20th	Day	9% 9% 31% 31% 17% 4	524
	21st to end	Day	15% 11% 33% 27% 10% 4	576
August	1st to 10th	Day	13% 9% 27% 26% 18% 7%	526
	11th to 20th	Day	15% 8% 25% 29% 17% 6%	519
	21st to end	Day	13% 12% 29% 25% 14% 7%	583
September	1st to 10th	Day	19% 12% 22% 22% 17% 8%	530
	11th to 20th	Day	14% 8% 25% 23% 19% 11%	522
	21st to end	Day	26% 13% 26% 20% 12% 4	490
October	1st to 10th	Day	26% 14% 24% 19% 13% 5%	490
	11th to 20th	Day	24% 17% 30% 21% 8% 1	490
	21st to end	Day	28% 18% 30% 17% 6% 1	499
November	1st to 10th	Day	24% 22% 23% 22% 8% 1	395
	11th to 20th	Day	30% 22% 28% 16% 4 1	380
	21st to end	Day	39% 23% 29% 8% 2	200
December	1st to 10th	Day	36% 28% 26% 8% 3 1	200
	11th to 20th	Day	40% 25% 25% 9% 2	200
	21st to end	Day	29% 30% 29% 10% 2	220
January	1st to 10th	Night	25% 27% 33% 12% 3	800
	11th to 20th	Night	28% 24% 29% 17% 2	800
	21st to end	Night	21% 29% 33% 15% 2	880
February	1st to 10th	Night	29% 22% 32% 16% 1	800
	11th to 20th	Night	30% 27% 32% 11% 1	783
	21st to end	Night	29% 25% 31% 14% 2	660
March	1st to 10th	Night	29% 23% 30% 16% 3	800
	11th to 20th	Night	28% 22% 29% 17% 4	800
	21st to end	Night	26% 22% 31% 15% 6%	880
April	1st to 10th	Night	26% 22% 31% 19% 2	800
	11th to 20th	Night	25% 21% 29% 18% 6%	791
	21st to end	Night	25% 17% 28% 25% 5%	800
May	1st to 10th	Night	28% 13% 27% 23% 9%	545
	11th to 20th	Night	18% 10% 35% 29% 6% 1	394
	21st to end	Night	15% 9% 26% 36% 14%	433
June	1st to 10th	Night	16% 9% 23% 39% 13%	400
	11th to 20th	Night	16% 8% 28% 38% 10%	400
	21st to end	Night	13% 6% 26% 43% 11% 1	400
July	1st to 10th	Night	13% 5% 21% 39% 21% 1	390
	11th to 20th	Night	12% 6% 19% 43% 18% 2	388
	21st to end	Night	14% 7% 19% 43% 16% 1	445
August	1st to 10th	Night	13% 3 19% 43% 20% 2	597
	11th to 20th	Night	16% 3 15% 37% 27% 2	707
	21st to end	Night	15% 6% 19% 36% 24% 1	880
September	1st to 10th	Night	17% 7% 22% 34% 18% 3	800
	11th to 20th	Night	15% 6% 20% 31% 23% 5%	793
	21st to end	Night	22% 9% 21% 29% 17% 2	760
October	1st to 10th	Night	24% 10% 22% 26% 17% 1	760
	11th to 20th	Night	19% 15% 28% 30% 8%	760
	21st to end	Night	27% 14% 30% 22% 6%	836
November	1st to 10th	Night	18% 18% 32% 24% 7% 1	780
	11th to 20th	Night	25% 21% 29% 19% 6% 1	800
	21st to end	Night	24% 22% 30% 19% 5% 1	800
December	1st to 10th	Night	28% 22% 30% 15% 4	800
	11th to 20th	Night	27% 24% 28% 18% 3	800
	21st to end	Night	27% 22% 32% 16% 3	880

Page generated at 2025-09-16 01:49:12. Version ac07

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