Barnes Bend Acess Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Barnes Bend Acess Area clear sky chart from 2005-11-06 to 2025-05-11.

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% 6% 2 6% 4 4 4 4 6% 7% 44%	114780
	Night	13% 6% 2 6% 4 4 4 3 5% 7% 46%	114179
Transparency	Day	38% 3 10% 22% 20% 6%	118590
	Night	37% 3 9% 20% 22% 9%	118498
Seeing	Day	15% 8% 21% 25% 21% 11%	15414
	Night	15% 7% 21% 31% 22% 5%	24982

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	16% 9% 4 5% 3 3 3 3 4 5% 47%	4130
	11th to 20th	Day	12% 6% 4 5% 3 3 3 3 5% 6% 51%	4520
	21st to end	Day	21% 10% 2 6% 4 3 2 2 3 5% 41%	4972
February	1st to 10th	Day	18% 10% 2 7% 4 4 4 3 4 6% 40%	2000
	11th to 20th	Day	20% 8% 3 6% 4 4 4 3 4 4 41%	1948
	21st to end	Day	19% 8% 2 8% 5% 3 3 3 3 6% 41%	1650
March	1st to 10th	Day	20% 8% 3 7% 4 4 4 3 5% 6% 35%	4480
	11th to 20th	Day	12% 6% 2 6% 4 4 4 4 5% 7% 46%	4709
	21st to end	Day	15% 7% 3 7% 5% 4 4 3 5% 7% 40%	5967
April	1st to 10th	Day	12% 5% 2 5% 5% 4 5% 4 5% 6% 46%	2400
	11th to 20th	Day	13% 5% 2 6% 4 4 4 4 5% 6% 47%	2374
	21st to end	Day	9% 5% 1 5% 4 5% 4 3 6% 8% 51%	2400
May	1st to 10th	Day	11% 5% 2 6% 4 4 5% 4 6% 8% 46%	3908
	11th to 20th	Day	14% 5% 2 7% 5% 4 4 4 5% 9% 40%	4081
	21st to end	Day	8% 5% 2 6% 4 5% 5% 5% 7% 9% 43%	4476
June	1st to 10th	Day	9% 5% 2 6% 5% 6% 7% 6% 6% 10% 37%	2470
	11th to 20th	Day	6% 3 2 4 5% 6% 6% 5% 7% 10% 46%	2521
	21st to end	Day	6% 5% 2 6% 6% 5% 5% 5% 7% 10% 42%	2660
July	1st to 10th	Day	7% 5% 2 9% 6% 7% 7% 6% 9% 11% 29%	4440
	11th to 20th	Day	8% 4 2 6% 6% 6% 7% 6% 10% 11% 34%	4099
	21st to end	Day	9% 7% 3 10% 7% 8% 8% 5% 8% 9% 25%	4118
August	1st to 10th	Day	3 2 1 4 4 4 4 4 5% 8% 61%	3785
	11th to 20th	Day	5% 3 1 6% 5% 5% 6% 4 7% 10% 48%	3729
	21st to end	Day	7% 4 2 5% 4 5% 5% 4 7% 10% 47%	4180
September	1st to 10th	Day	10% 5% 3 7% 5% 5% 5% 4 5% 7% 44%	2280
	11th to 20th	Day	14% 6% 2 6% 4 5% 4 4 5% 7% 43%	2118
	21st to end	Day	10% 5% 2 5% 3 4 3 3 6% 6% 52%	2090
October	1st to 10th	Day	8% 4 2 5% 4 4 4 3 5% 5% 57%	2090
	11th to 20th	Day	8% 4 2 5% 3 2 3 3 5% 6% 58%	1991
	21st to end	Day	12% 6% 2 4 3 3 3 3 4 5% 56%	2063
November	1st to 10th	Day	11% 5% 1 5% 4 3 3 3 4 4 56%	1762
	11th to 20th	Day	13% 4 2 5% 4 4 4 3 4 6% 53%	1800
	21st to end	Day	14% 7% 2 6% 4 3 3 4 4 5% 49%	1800
December	1st to 10th	Day	17% 7% 2 6% 3 3 3 3 5% 6% 45%	2930
	11th to 20th	Day	14% 9% 3 6% 4 3 4 3 4 5% 44%	3373
	21st to end	Day	18% 7% 2 6% 3 4 3 3 4 5% 45%	4466
January	1st to 10th	Night	17% 9% 4 5% 3 3 2 2 3 4 47%	5797
	11th to 20th	Night	16% 7% 4 6% 3 3 3 3 4 5% 46%	5440
	21st to end	Night	20% 9% 2 6% 3 4 3 2 3 4 43%	5984
February	1st to 10th	Night	16% 8% 3 6% 4 3 4 3 5% 5% 43%	2400
	11th to 20th	Night	20% 7% 3 6% 4 4 3 3 3 5% 43%	2338
	21st to end	Night	18% 6% 2 6% 4 4 4 3 4 6% 42%	1980
March	1st to 10th	Night	21% 9% 2 7% 4 4 4 3 4 6% 36%	5373
	11th to 20th	Night	12% 6% 2 6% 4 4 4 3 4 6% 50%	5279
	21st to end	Night	17% 7% 3 6% 4 3 3 3 5% 5% 44%	4962
April	1st to 10th	Night	12% 5% 2 5% 4 4 4 3 6% 7% 48%	2000
	11th to 20th	Night	12% 4 2 5% 3 3 4 3 5% 8% 51%	1975
	21st to end	Night	9% 4 2 5% 3 4 4 4 6% 8% 51%	2000
May	1st to 10th	Night	11% 5% 2 6% 4 4 4 3 5% 8% 47%	3204
	11th to 20th	Night	17% 6% 2 6% 4 4 4 3 5% 7% 42%	2818
	21st to end	Night	7% 4 2 5% 4 5% 5% 5% 8% 10% 46%	3079
June	1st to 10th	Night	7% 5% 2 7% 6% 5% 5% 5% 8% 10% 40%	1710
	11th to 20th	Night	5% 4 1 3 4 3 4 4 8% 13% 50%	1648
	21st to end	Night	4 4 2 4 5% 6% 5% 6% 10% 11% 43%	1520
July	1st to 10th	Night	6% 6% 3 8% 6% 5% 5% 5% 9% 12% 35%	2530
	11th to 20th	Night	7% 4 2 6% 5% 4 6% 6% 10% 13% 38%	2850
	21st to end	Night	8% 8% 4 10% 7% 6% 6% 5% 9% 11% 27%	3435
August	1st to 10th	Night	2 2 1 4 3 3 5% 4 7% 10% 58%	3144
	11th to 20th	Night	4 3 2 5% 4 5% 5% 5% 7% 11% 51%	3100
	21st to end	Night	5% 4 1 6% 5% 5% 5% 5% 7% 9% 47%	3476
September	1st to 10th	Night	9% 5% 2 7% 5% 5% 4 4 7% 9% 43%	1900
	11th to 20th	Night	11% 7% 2 5% 4 4 5% 3 5% 9% 45%	2042
	21st to end	Night	7% 5% 2 6% 4 4 4 4 5% 6% 54%	2090
October	1st to 10th	Night	7% 4 1 4 3 3 3 3 5% 6% 61%	2090
	11th to 20th	Night	12% 5% 2 4 3 2 2 3 5% 7% 57%	2185
	21st to end	Night	14% 5% 2 4 3 2 2 2 3 5% 59%	2532
November	1st to 10th	Night	11% 4 2 4 3 4 5% 3 4 5% 55%	2536
	11th to 20th	Night	13% 5% 2 4 3 3 3 2 4 7% 53%	2600
	21st to end	Night	13% 5% 2 5% 3 4 4 4 5% 6% 49%	2600
December	1st to 10th	Night	19% 6% 2 5% 3 2 3 3 4 6% 49%	4250
	11th to 20th	Night	15% 9% 3 6% 4 4 4 2 4 4 46%	4822
	21st to end	Night	19% 8% 2 5% 3 3 3 3 4 6% 43%	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	42% 1 3 31% 19% 3	4131
	11th to 20th	Day	36% 2 6% 24% 28% 4	4520
	21st to end	Day	49% 2 5% 16% 18% 10%	4972
February	1st to 10th	Day	48% 2 5% 20% 18% 7%	2000
	11th to 20th	Day	48% 2 4 18% 20% 7%	1958
	21st to end	Day	48% 2 6% 16% 20% 8%	1650
March	1st to 10th	Day	52% 2 7% 13% 20% 7%	4480
	11th to 20th	Day	39% 3 6% 17% 21% 15%	4709
	21st to end	Day	46% 2 8% 18% 20% 7%	5969
April	1st to 10th	Day	38% 3 9% 22% 20% 8%	2400
	11th to 20th	Day	39% 2 7% 20% 24% 9%	2374
	21st to end	Day	33% 2 10% 26% 25% 4	2400
May	1st to 10th	Day	38% 2 11% 31% 16% 3	3943
	11th to 20th	Day	42% 2 13% 28% 14% 1	4085
	21st to end	Day	37% 3 14% 30% 16% 1	4489
June	1st to 10th	Day	42% 4 13% 24% 15% 2	2470
	11th to 20th	Day	31% 5% 16% 26% 19% 2	2521
	21st to end	Day	36% 5% 17% 24% 15% 3	2660
July	1st to 10th	Day	43% 10% 21% 20% 6% 1	4371
	11th to 20th	Day	37% 9% 25% 22% 6% 1	4028
	21st to end	Day	53% 8% 13% 19% 7%	3987
August	1st to 10th	Day	21% 4 13% 32% 29% 1	3773
	11th to 20th	Day	30% 7% 16% 30% 15% 2	3765
	21st to end	Day	31% 7% 16% 23% 19% 4	4179
September	1st to 10th	Day	38% 5% 12% 20% 19% 6%	2280
	11th to 20th	Day	41% 5% 11% 16% 22% 5%	2118
	21st to end	Day	32% 4 9% 24% 21% 9%	2090
October	1st to 10th	Day	21% 3 5% 14% 30% 27%	3480
	11th to 20th	Day	17% 2 4 17% 32% 29%	3283
	21st to end	Day	23% 2 4 18% 37% 16%	3377
November	1st to 10th	Day	33% 2 7% 21% 27% 10%	1762
	11th to 20th	Day	34% 3 6% 17% 29% 12%	1800
	21st to end	Day	39% 2 7% 18% 26% 8%	1800
December	1st to 10th	Day	41% 3 6% 22% 24% 3	2930
	11th to 20th	Day	45% 2 9% 18% 21% 5%	3370
	21st to end	Day	43% 1 5% 23% 25% 2	4466
January	1st to 10th	Night	44% 1 3 23% 25% 3	5797
	11th to 20th	Night	43% 2 3 19% 25% 8%	5440
	21st to end	Night	47% 2 2 16% 25% 7%	5984
February	1st to 10th	Night	44% 2 6% 18% 22% 9%	2400
	11th to 20th	Night	46% 3 4 17% 19% 11%	2339
	21st to end	Night	45% 2 6% 17% 19% 11%	1980
March	1st to 10th	Night	51% 2 5% 15% 18% 10%	5373
	11th to 20th	Night	36% 2 7% 17% 22% 16%	5279
	21st to end	Night	44% 2 6% 22% 18% 8%	4962
April	1st to 10th	Night	36% 3 10% 21% 19% 10%	2000
	11th to 20th	Night	33% 3 8% 20% 25% 11%	1975
	21st to end	Night	31% 4 10% 24% 25% 6%	2000
May	1st to 10th	Night	38% 2 11% 24% 21% 4	3234
	11th to 20th	Night	43% 2 10% 25% 17% 2	2819
	21st to end	Night	33% 3 13% 27% 20% 4	3087
June	1st to 10th	Night	38% 6% 14% 22% 17% 3	1710
	11th to 20th	Night	26% 4 18% 30% 18% 5%	1648
	21st to end	Night	31% 7% 20% 22% 18% 3	1520
July	1st to 10th	Night	39% 9% 26% 19% 6% 2	2490
	11th to 20th	Night	33% 9% 27% 24% 6% 1	2799
	21st to end	Night	48% 10% 20% 16% 6% 1	3325
August	1st to 10th	Night	18% 6% 16% 35% 23% 2	3132
	11th to 20th	Night	26% 7% 19% 31% 14% 3	3130
	21st to end	Night	31% 7% 16% 20% 21% 5%	3476
September	1st to 10th	Night	37% 5% 15% 19% 18% 6%	1900
	11th to 20th	Night	37% 5% 12% 18% 21% 7%	2042
	21st to end	Night	30% 4 7% 25% 23% 10%	2090
October	1st to 10th	Night	20% 3 7% 16% 24% 31%	3480
	11th to 20th	Night	18% 2 3 17% 28% 32%	3619
	21st to end	Night	21% 2 4 19% 35% 19%	4168
November	1st to 10th	Night	32% 3 7% 16% 28% 14%	2536
	11th to 20th	Night	33% 2 5% 20% 27% 13%	2600
	21st to end	Night	36% 2 6% 22% 22% 11%	2600
December	1st to 10th	Night	39% 2 7% 22% 26% 4	4250
	11th to 20th	Night	43% 3 7% 18% 24% 5%	4824
	21st to end	Night	44% 2 5% 21% 26% 2	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	25% 20% 32% 20% 4	300
	11th to 20th	Day	22% 20% 34% 15% 7% 1	300
	21st to end	Day	22% 21% 36% 16% 3 1	330
February	1st to 10th	Day	20% 18% 40% 15% 6% 1	300
	11th to 20th	Day	34% 14% 31% 17% 3	300
	21st to end	Day	25% 22% 36% 14% 3	249
March	1st to 10th	Day	24% 17% 37% 14% 8%	300
	11th to 20th	Day	21% 20% 35% 20% 4	325
	21st to end	Day	23% 14% 31% 23% 10%	550
April	1st to 10th	Day	18% 15% 31% 23% 10% 2	500
	11th to 20th	Day	17% 14% 29% 25% 12% 3	492
	21st to end	Day	13% 9% 30% 31% 15% 2	500
May	1st to 10th	Day	17% 8% 24% 31% 16% 5%	503
	11th to 20th	Day	10% 3 23% 34% 18% 12%	487
	21st to end	Day	9% 3 20% 31% 24% 14%	529
June	1st to 10th	Day	13% 2 12% 30% 30% 13%	490
	11th to 20th	Day	7% 1 14% 26% 32% 20%	541
	21st to end	Day	8% 4 10% 29% 32% 18%	680
July	1st to 10th	Day	7% 2 7% 29% 37% 18%	671
	11th to 20th	Day	9% 2 4 21% 33% 31%	520
	21st to end	Day	7% 2 7% 21% 36% 27%	532
August	1st to 10th	Day	7% 1 5% 22% 37% 29%	486
	11th to 20th	Day	7% 1 5% 22% 41% 24%	479
	21st to end	Day	15% 1 5% 19% 32% 27%	539
September	1st to 10th	Day	11% 2 7% 29% 35% 17%	490
	11th to 20th	Day	15% 3 8% 24% 36% 14%	490
	21st to end	Day	11% 4 10% 31% 31% 13%	490
October	1st to 10th	Day	11% 2 20% 33% 24% 10%	490
	11th to 20th	Day	9% 4 24% 37% 23% 3	391
	21st to end	Day	17% 10% 23% 32% 15% 3	330
November	1st to 10th	Day	17% 6% 30% 30% 12% 5%	300
	11th to 20th	Day	15% 11% 35% 26% 11% 1	300
	21st to end	Day	13% 16% 30% 25% 13% 3	300
December	1st to 10th	Day	25% 11% 35% 19% 8% 1	300
	11th to 20th	Day	24% 12% 34% 20% 9% 1	300
	21st to end	Day	27% 12% 33% 20% 6% 1	330
January	1st to 10th	Night	22% 13% 34% 25% 6%	800
	11th to 20th	Night	23% 14% 27% 28% 8%	800
	21st to end	Night	22% 13% 33% 29% 4	880
February	1st to 10th	Night	21% 12% 30% 32% 6%	800
	11th to 20th	Night	25% 14% 30% 26% 5%	783
	21st to end	Night	21% 15% 34% 27% 3	660
March	1st to 10th	Night	20% 13% 30% 29% 9%	800
	11th to 20th	Night	16% 12% 34% 30% 8%	769
	21st to end	Night	18% 9% 33% 28% 12%	660
April	1st to 10th	Night	15% 11% 32% 29% 12%	600
	11th to 20th	Night	14% 8% 34% 30% 13% 1	593
	21st to end	Night	9% 8% 30% 37% 15% 1	600
May	1st to 10th	Night	12% 4 25% 37% 19% 3	600
	11th to 20th	Night	13% 4 17% 36% 26% 4	563
	21st to end	Night	8% 3 12% 36% 33% 7%	617
June	1st to 10th	Night	8% 1 10% 39% 34% 8%	570
	11th to 20th	Night	5% 2 8% 31% 45% 9%	570
	21st to end	Night	5% 2 6% 32% 41% 14%	570
July	1st to 10th	Night	5% 2 4 26% 46% 17%	555
	11th to 20th	Night	5% 1 3 27% 43% 22%	552
	21st to end	Night	6% 2 5% 26% 45% 17%	624
August	1st to 10th	Night	6% 1 4 24% 46% 20%	567
	11th to 20th	Night	7% 1 2 26% 50% 13%	564
	21st to end	Night	12% 1 5% 24% 41% 17%	627
September	1st to 10th	Night	11% 2 7% 29% 41% 10%	570
	11th to 20th	Night	14% 3 10% 29% 38% 7%	712
	21st to end	Night	9% 2 11% 33% 39% 5%	760
October	1st to 10th	Night	9% 1 19% 34% 31% 6%	760
	11th to 20th	Night	14% 5% 19% 38% 21% 3	760
	21st to end	Night	16% 6% 16% 36% 23% 3	836
November	1st to 10th	Night	12% 6% 20% 35% 22% 3	780
	11th to 20th	Night	15% 7% 27% 34% 15% 1	800
	21st to end	Night	16% 8% 26% 36% 12% 2	800
December	1st to 10th	Night	22% 10% 25% 33% 10%	800
	11th to 20th	Night	23% 8% 29% 32% 9%	800
	21st to end	Night	25% 10% 28% 30% 6%	880

Page generated at 2025-05-08 08:33:54. Version ac07

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