Barb's Ridge
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Barb's Ridge 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	14% 7% 3 7% 5% 5% 5% 4 6% 8% 38%	125957
	Night	14% 7% 3 6% 4 4 4 4 5% 7% 41%	123130
Transparency	Day	26% 39% 7% 14% 11% 2	129708
	Night	26% 38% 7% 14% 12% 3	127449
Seeing	Day	18% 11% 22% 22% 18% 9%	15797
	Night	17% 9% 19% 30% 21% 4	25761

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	18% 11% 4 5% 3 3 3 3 4 5% 40%	4056
	11th to 20th	Day	18% 5% 7% 8% 3 3 3 3 4 5% 43%	4060
	21st to end	Day	22% 9% 3 6% 3 3 3 3 5% 6% 37%	4809
February	1st to 10th	Day	19% 10% 3 7% 4 3 4 3 6% 6% 36%	2000
	11th to 20th	Day	24% 9% 3 6% 5% 3 4 4 4 5% 34%	1948
	21st to end	Day	21% 9% 3 6% 3 4 4 3 4 5% 38%	1650
March	1st to 10th	Day	20% 8% 3 8% 5% 4 4 3 5% 6% 33%	4480
	11th to 20th	Day	13% 7% 2 6% 3 4 3 3 4 6% 47%	4922
	21st to end	Day	14% 7% 2 7% 5% 4 4 4 5% 6% 42%	5504
April	1st to 10th	Day	13% 7% 3 6% 4 6% 5% 3 5% 7% 42%	2400
	11th to 20th	Day	13% 8% 2 6% 4 3 3 4 5% 7% 46%	2374
	21st to end	Day	13% 6% 2 6% 5% 5% 5% 3 6% 8% 41%	2487
May	1st to 10th	Day	17% 8% 2 8% 5% 5% 5% 5% 6% 8% 31%	5862
	11th to 20th	Day	16% 9% 3 9% 6% 7% 5% 4 6% 7% 28%	5861
	21st to end	Day	17% 7% 3 6% 4 4 4 4 6% 7% 37%	6433
June	1st to 10th	Day	9% 6% 2 7% 5% 6% 7% 5% 8% 10% 35%	2600
	11th to 20th	Day	5% 4 2 6% 5% 6% 6% 6% 8% 11% 41%	2600
	21st to end	Day	6% 5% 2 6% 6% 7% 6% 6% 8% 11% 36%	2600
July	1st to 10th	Day	6% 5% 2 7% 6% 6% 7% 6% 8% 11% 35%	5900
	11th to 20th	Day	8% 6% 3 7% 6% 6% 7% 5% 10% 13% 30%	5900
	21st to end	Day	10% 9% 4 9% 7% 7% 8% 6% 9% 11% 21%	6424
August	1st to 10th	Day	5% 4 1 5% 5% 6% 6% 5% 9% 11% 43%	4120
	11th to 20th	Day	6% 5% 2 6% 5% 5% 7% 6% 9% 11% 38%	3849
	21st to end	Day	7% 4 2 6% 5% 5% 5% 4 6% 7% 49%	4312
September	1st to 10th	Day	10% 6% 3 7% 5% 5% 6% 5% 7% 8% 38%	2300
	11th to 20th	Day	12% 6% 3 6% 5% 5% 5% 5% 6% 6% 41%	2178
	21st to end	Day	13% 5% 2 5% 5% 4 4 3 5% 6% 47%	2090
October	1st to 10th	Day	10% 5% 2 5% 4 3 4 3 4 5% 54%	2090
	11th to 20th	Day	10% 4 2 5% 4 3 4 3 4 6% 55%	2056
	21st to end	Day	15% 6% 2 4 3 4 2 3 4 5% 52%	1961
November	1st to 10th	Day	11% 6% 2 5% 4 3 3 2 4 5% 53%	1762
	11th to 20th	Day	13% 5% 2 6% 4 4 4 4 5% 6% 47%	1800
	21st to end	Day	17% 7% 2 4 3 4 4 3 5% 7% 44%	1800
December	1st to 10th	Day	19% 8% 2 5% 4 4 3 3 4 4 44%	2930
	11th to 20th	Day	22% 11% 4 7% 5% 5% 4 3 4 5% 32%	3373
	21st to end	Day	19% 9% 4 6% 4 4 4 3 5% 8% 33%	4466
January	1st to 10th	Night	16% 11% 3 8% 3 3 3 3 4 5% 41%	5889
	11th to 20th	Night	19% 8% 3 7% 3 2 3 3 4 5% 42%	5900
	21st to end	Night	19% 10% 3 5% 3 4 4 4 6% 5% 37%	6144
February	1st to 10th	Night	18% 9% 2 7% 5% 4 4 3 5% 5% 40%	2400
	11th to 20th	Night	22% 9% 3 7% 4 4 4 3 4 4 36%	2338
	21st to end	Night	24% 8% 3 5% 4 4 4 3 5% 5% 36%	1980
March	1st to 10th	Night	23% 10% 3 7% 5% 4 4 3 4 6% 30%	5373
	11th to 20th	Night	11% 6% 2 6% 4 4 4 3 5% 7% 48%	5036
	21st to end	Night	15% 7% 3 8% 5% 5% 4 3 4 5% 41%	5467
April	1st to 10th	Night	12% 6% 1 5% 4 4 5% 3 6% 7% 47%	2000
	11th to 20th	Night	13% 5% 2 5% 3 3 3 4 5% 7% 50%	1975
	21st to end	Night	12% 5% 2 6% 4 3 4 4 5% 8% 47%	1910
May	1st to 10th	Night	14% 8% 3 9% 6% 6% 6% 4 6% 8% 31%	4033
	11th to 20th	Night	18% 8% 4 9% 6% 5% 6% 4 5% 7% 28%	4032
	21st to end	Night	14% 7% 3 7% 5% 4 5% 4 7% 9% 37%	4421
June	1st to 10th	Night	6% 6% 3 7% 6% 6% 6% 4 7% 9% 39%	1800
	11th to 20th	Night	5% 3 1 4 4 3 6% 4 8% 10% 51%	1800
	21st to end	Night	5% 4 2 5% 5% 4 5% 5% 8% 12% 46%	1800
July	1st to 10th	Night	6% 5% 2 7% 5% 5% 6% 5% 8% 10% 39%	4058
	11th to 20th	Night	7% 6% 3 7% 4 5% 5% 5% 8% 13% 36%	4057
	21st to end	Night	8% 8% 3 9% 6% 6% 6% 5% 8% 12% 29%	4427
August	1st to 10th	Night	4 3 1 4 3 4 5% 5% 7% 11% 52%	3011
	11th to 20th	Night	6% 5% 2 6% 4 5% 5% 4 6% 9% 48%	3200
	21st to end	Night	6% 4 2 5% 4 4 5% 4 6% 9% 52%	3586
September	1st to 10th	Night	8% 5% 2 8% 4 5% 5% 5% 6% 9% 43%	2080
	11th to 20th	Night	13% 5% 2 6% 4 4 4 4 6% 6% 46%	2179
	21st to end	Night	11% 5% 2 4 4 3 4 4 5% 6% 51%	2090
October	1st to 10th	Night	10% 4 2 3 3 3 3 2 5% 6% 59%	2090
	11th to 20th	Night	12% 5% 2 6% 4 3 3 3 4 5% 52%	2123
	21st to end	Night	14% 6% 2 5% 3 3 3 3 4 5% 53%	2633
November	1st to 10th	Night	12% 6% 2 5% 4 3 3 3 6% 6% 49%	2536
	11th to 20th	Night	13% 7% 3 5% 4 3 2 3 5% 6% 50%	2600
	21st to end	Night	16% 9% 2 5% 4 3 4 3 4 6% 44%	2600
December	1st to 10th	Night	19% 8% 3 6% 3 3 3 3 5% 5% 42%	4250
	11th to 20th	Night	24% 9% 3 5% 3 3 3 3 4 5% 36%	4822
	21st to end	Night	21% 9% 4 7% 4 4 4 4 5% 6% 32%	6490

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	36% 26% 4 16% 18% 1	4057
	11th to 20th	Day	31% 25% 3 15% 23% 2	4060
	21st to end	Day	37% 27% 5% 14% 14% 2	4809
February	1st to 10th	Day	20% 62% 2 10% 6% 1	2000
	11th to 20th	Day	23% 60% 2 7% 7% 1	1958
	21st to end	Day	18% 61% 2 7% 9% 2	1650
March	1st to 10th	Day	41% 29% 5% 8% 11% 6%	4480
	11th to 20th	Day	25% 28% 2 15% 18% 11%	4922
	21st to end	Day	31% 28% 6% 21% 13% 2	5506
April	1st to 10th	Day	18% 62% 4 9% 6% 2	2400
	11th to 20th	Day	17% 62% 3 10% 6% 2	2374
	21st to end	Day	16% 62% 4 10% 6% 1	2487
May	1st to 10th	Day	35% 31% 10% 17% 7%	5897
	11th to 20th	Day	42% 30% 9% 14% 4	5865
	21st to end	Day	36% 29% 5% 16% 12% 2	6447
June	1st to 10th	Day	17% 62% 5% 9% 5% 1	2600
	11th to 20th	Day	14% 63% 8% 10% 5%	2600
	21st to end	Day	15% 62% 10% 8% 4	2600
July	1st to 10th	Day	24% 33% 15% 19% 8%	5835
	11th to 20th	Day	26% 35% 23% 15% 1	5831
	21st to end	Day	39% 31% 15% 11% 2	6240
August	1st to 10th	Day	16% 38% 10% 27% 9%	4107
	11th to 20th	Day	19% 39% 12% 19% 10% 1	3885
	21st to end	Day	14% 38% 9% 24% 16% 1	4311
September	1st to 10th	Day	15% 58% 6% 11% 8% 2	2300
	11th to 20th	Day	15% 59% 6% 13% 7%	2178
	21st to end	Day	15% 59% 6% 11% 7% 1	2090
October	1st to 10th	Day	13% 37% 4 10% 25% 10%	3480
	11th to 20th	Day	10% 36% 3 13% 25% 13%	3400
	21st to end	Day	14% 38% 6% 18% 18% 7%	3211
November	1st to 10th	Day	20% 55% 3 8% 10% 3	1762
	11th to 20th	Day	17% 56% 2 10% 12% 3	1800
	21st to end	Day	19% 56% 3 11% 10% 1	1800
December	1st to 10th	Day	28% 35% 2 14% 17% 4	2930
	11th to 20th	Day	40% 31% 2 12% 12% 2	3370
	21st to end	Day	38% 26% 6% 20% 9% 1	4466
January	1st to 10th	Night	37% 25% 4 15% 17% 2	5889
	11th to 20th	Night	32% 25% 4 15% 19% 5%	5900
	21st to end	Night	34% 28% 3 14% 16% 5%	6144
February	1st to 10th	Night	20% 62% 2 9% 6% 2	2400
	11th to 20th	Night	24% 60% 3 5% 6% 2	2339
	21st to end	Night	19% 61% 3 7% 8% 3	1980
March	1st to 10th	Night	44% 28% 5% 9% 12% 2	5373
	11th to 20th	Night	25% 28% 3 14% 17% 13%	5036
	21st to end	Night	35% 28% 4 17% 14% 3	5467
April	1st to 10th	Night	14% 62% 5% 8% 9% 2	2000
	11th to 20th	Night	17% 61% 3 9% 7% 2	1975
	21st to end	Night	15% 61% 4 10% 9% 1	1910
May	1st to 10th	Night	40% 30% 10% 14% 5%	4060
	11th to 20th	Night	46% 29% 8% 12% 5%	4033
	21st to end	Night	34% 29% 9% 18% 10%	4429
June	1st to 10th	Night	16% 63% 6% 8% 6% 1	1800
	11th to 20th	Night	10% 63% 8% 12% 7%	1800
	21st to end	Night	11% 63% 9% 13% 4 1	1800
July	1st to 10th	Night	25% 32% 17% 20% 6% 1	4015
	11th to 20th	Night	24% 34% 24% 16% 2 1	4006
	21st to end	Night	35% 32% 18% 12% 3 1	4297
August	1st to 10th	Night	15% 38% 9% 28% 10% 1	3000
	11th to 20th	Night	16% 38% 16% 20% 10% 1	3230
	21st to end	Night	12% 38% 9% 21% 20% 1	3586
September	1st to 10th	Night	15% 57% 7% 10% 9% 2	2080
	11th to 20th	Night	13% 58% 7% 13% 9% 1	2179
	21st to end	Night	15% 59% 6% 11% 8% 1	2090
October	1st to 10th	Night	13% 39% 5% 12% 18% 13%	3480
	11th to 20th	Night	9% 36% 2 12% 25% 16%	3518
	21st to end	Night	11% 37% 3 20% 20% 8%	4333
November	1st to 10th	Night	21% 56% 3 8% 10% 2	2536
	11th to 20th	Night	17% 56% 2 9% 12% 3	2600
	21st to end	Night	19% 56% 2 12% 10% 2	2600
December	1st to 10th	Night	29% 35% 3 12% 19% 1	4250
	11th to 20th	Night	36% 31% 3 13% 15% 2	4824
	21st to end	Night	42% 26% 5% 18% 10% 1	6490

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	34% 21% 30% 12% 3	300
	11th to 20th	Day	34% 23% 26% 11% 6% 1	300
	21st to end	Day	27% 24% 35% 11% 3	330
February	1st to 10th	Day	33% 20% 30% 14% 3	300
	11th to 20th	Day	44% 22% 26% 6% 1 1	300
	21st to end	Day	38% 24% 29% 7% 2	249
March	1st to 10th	Day	31% 22% 30% 12% 4 1	300
	11th to 20th	Day	28% 19% 26% 18% 6% 1	468
	21st to end	Day	27% 18% 31% 17% 7%	550
April	1st to 10th	Day	25% 17% 26% 19% 12% 2	500
	11th to 20th	Day	20% 16% 32% 20% 11% 1	492
	21st to end	Day	19% 12% 34% 20% 12% 3	500
May	1st to 10th	Day	19% 15% 27% 22% 13% 5%	503
	11th to 20th	Day	13% 11% 26% 25% 13% 11%	527
	21st to end	Day	14% 8% 21% 27% 18% 13%	573
June	1st to 10th	Day	11% 7% 18% 28% 21% 15%	530
	11th to 20th	Day	7% 5% 13% 30% 26% 19%	530
	21st to end	Day	8% 4 18% 26% 25% 19%	530
July	1st to 10th	Day	7% 3 12% 27% 28% 23%	525
	11th to 20th	Day	10% 4 11% 22% 28% 25%	524
	21st to end	Day	10% 5% 10% 24% 30% 23%	576
August	1st to 10th	Day	10% 3 13% 25% 29% 20%	526
	11th to 20th	Day	10% 4 11% 29% 30% 15%	519
	21st to end	Day	13% 4 8% 25% 31% 19%	583
September	1st to 10th	Day	11% 3 14% 28% 30% 14%	530
	11th to 20th	Day	11% 5% 12% 26% 33% 12%	522
	21st to end	Day	17% 5% 15% 25% 31% 7%	490
October	1st to 10th	Day	12% 4 20% 31% 24% 8%	490
	11th to 20th	Day	12% 10% 27% 31% 16% 4	490
	21st to end	Day	21% 9% 23% 27% 18% 2	410
November	1st to 10th	Day	19% 11% 32% 24% 13% 1	300
	11th to 20th	Day	16% 20% 35% 22% 7%	300
	21st to end	Day	21% 15% 36% 17% 10% 1	300
December	1st to 10th	Day	31% 18% 30% 16% 4 1	300
	11th to 20th	Day	30% 16% 33% 14% 6%	300
	21st to end	Day	31% 21% 28% 14% 5%	330
January	1st to 10th	Night	28% 15% 27% 26% 5%	800
	11th to 20th	Night	26% 18% 26% 24% 6%	800
	21st to end	Night	22% 15% 31% 28% 4	880
February	1st to 10th	Night	25% 11% 30% 29% 5%	800
	11th to 20th	Night	30% 17% 27% 24% 2	783
	21st to end	Night	30% 16% 27% 25% 2	660
March	1st to 10th	Night	23% 15% 27% 30% 5%	800
	11th to 20th	Night	21% 16% 26% 28% 9% 1	800
	21st to end	Night	21% 12% 28% 28% 11%	880
April	1st to 10th	Night	16% 13% 26% 32% 13%	600
	11th to 20th	Night	18% 10% 28% 30% 13% 1	593
	21st to end	Night	14% 8% 22% 40% 15% 2	600
May	1st to 10th	Night	13% 6% 22% 35% 21% 3	600
	11th to 20th	Night	14% 7% 16% 35% 23% 6%	591
	21st to end	Night	9% 3 12% 34% 34% 7%	650
June	1st to 10th	Night	8% 2 13% 35% 36% 6%	600
	11th to 20th	Night	5% 3 9% 34% 37% 13%	600
	21st to end	Night	6% 2 8% 28% 46% 10%	600
July	1st to 10th	Night	10% 2 6% 24% 46% 12%	585
	11th to 20th	Night	9% 3 6% 21% 44% 17%	582
	21st to end	Night	8% 2 6% 23% 46% 15%	657
August	1st to 10th	Night	7% 1 2 25% 50% 14%	597
	11th to 20th	Night	11% 2 7% 27% 44% 9%	594
	21st to end	Night	12% 2 6% 28% 44% 9%	660
September	1st to 10th	Night	10% 1 8% 30% 40% 10%	680
	11th to 20th	Night	15% 2 9% 29% 39% 7%	793
	21st to end	Night	12% 3 13% 31% 37% 3	760
October	1st to 10th	Night	12% 4 15% 33% 28% 8%	760
	11th to 20th	Night	15% 8% 18% 35% 23% 1	760
	21st to end	Night	16% 9% 17% 37% 18% 3	836
November	1st to 10th	Night	15% 8% 19% 35% 21% 2	780
	11th to 20th	Night	16% 11% 26% 32% 13% 1	800
	21st to end	Night	22% 10% 22% 33% 13% 1	800
December	1st to 10th	Night	25% 14% 24% 29% 8%	800
	11th to 20th	Night	23% 13% 23% 33% 9%	800
	21st to end	Night	27% 13% 24% 29% 6%	880

Page generated at 2025-09-16 00:49:16. Version ac07

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