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 2026-09-14.

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	11% 6% 2 6% 4 4 5% 4 6% 8% 42%	148963
	Night	13% 6% 2 6% 4 4 4 4 6% 8% 44%	142132
Transparency	Day	38% 5% 12% 22% 18% 5%	152735
	Night	37% 4 11% 21% 19% 7%	146425
Seeing	Day	14% 8% 21% 25% 21% 11%	17273
	Night	15% 7% 21% 31% 22% 5%	26641

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	19% 10% 4 5% 3 3 3 3 4 5% 42%	5360
	11th to 20th	Day	10% 5% 3 5% 3 3 3 3 5% 6% 55%	5880
	21st to end	Day	23% 10% 3 7% 5% 3 3 2 3 4 38%	6436
February	1st to 10th	Day	17% 9% 3 6% 4 4 4 3 4 6% 41%	2100
	11th to 20th	Day	19% 8% 3 6% 4 4 4 3 4 5% 41%	2048
	21st to end	Day	18% 7% 2 8% 5% 3 3 3 3 6% 42%	1730
March	1st to 10th	Day	20% 8% 3 7% 4 4 4 3 5% 6% 35%	4580
	11th to 20th	Day	12% 6% 2 6% 4 4 4 4 5% 7% 46%	4812
	21st to end	Day	14% 7% 3 7% 5% 4 4 3 5% 7% 40%	6099
April	1st to 10th	Day	12% 5% 2 5% 5% 4 5% 4 6% 7% 45%	2520
	11th to 20th	Day	13% 5% 2 6% 4 4 4 4 5% 7% 48%	2494
	21st to end	Day	9% 5% 2 6% 4 5% 4 3 6% 8% 49%	2520
May	1st to 10th	Day	16% 8% 3 8% 5% 4 5% 4 6% 7% 37%	7057
	11th to 20th	Day	10% 6% 2 8% 6% 5% 5% 5% 7% 9% 38%	7626
	21st to end	Day	13% 8% 3 8% 5% 5% 6% 5% 7% 8% 33%	8391
June	1st to 10th	Day	10% 6% 2 6% 5% 6% 7% 6% 6% 11% 37%	2730
	11th to 20th	Day	7% 4 2 5% 5% 5% 6% 5% 7% 10% 44%	2787
	21st to end	Day	6% 5% 2 6% 6% 5% 5% 5% 8% 11% 41%	2940
July	1st to 10th	Day	4 4 2 7% 5% 6% 7% 6% 9% 13% 35%	8280
	11th to 20th	Day	7% 4 2 6% 5% 6% 7% 6% 10% 14% 34%	7645
	21st to end	Day	6% 5% 2 8% 6% 7% 8% 6% 10% 13% 29%	7687
August	1st to 10th	Day	2 2 1 4 4 4 4 4 8% 12% 53%	5545
	11th to 20th	Day	4 3 1 5% 4 5% 5% 4 7% 12% 50%	5486
	21st to end	Day	6% 4 2 5% 4 5% 5% 4 9% 11% 45%	6080
September	1st to 10th	Day	9% 4 3 7% 5% 5% 5% 4 5% 8% 45%	2520
	11th to 20th	Day	13% 6% 2 6% 4 5% 4 4 5% 7% 44%	2263
	21st to end	Day	9% 5% 2 5% 3 4 3 3 6% 6% 53%	2200
October	1st to 10th	Day	8% 4 2 6% 4 4 4 3 5% 5% 56%	2200
	11th to 20th	Day	8% 4 2 4 3 2 3 3 5% 6% 60%	2096
	21st to end	Day	12% 6% 2 4 3 3 3 3 4 5% 55%	2171
November	1st to 10th	Day	11% 5% 2 5% 4 3 3 3 4 5% 57%	1852
	11th to 20th	Day	12% 4 2 4 4 4 4 3 4 6% 54%	1890
	21st to end	Day	14% 7% 2 5% 4 3 3 3 4 5% 49%	1890
December	1st to 10th	Day	17% 8% 2 6% 3 3 3 3 5% 6% 44%	3020
	11th to 20th	Day	14% 9% 3 6% 4 3 4 3 4 5% 44%	3463
	21st to end	Day	18% 7% 2 6% 3 4 4 2 4 5% 45%	4565
January	1st to 10th	Night	18% 9% 4 5% 3 4 3 3 3 5% 43%	7515
	11th to 20th	Night	15% 7% 4 6% 3 3 3 2 4 5% 49%	7080
	21st to end	Night	21% 9% 3 7% 4 3 3 2 3 4 41%	7745
February	1st to 10th	Night	16% 8% 2 6% 4 3 4 3 5% 5% 44%	2520
	11th to 20th	Night	20% 8% 2 6% 4 4 3 3 3 5% 43%	2458
	21st to end	Night	18% 7% 2 6% 4 4 4 3 4 6% 42%	2076
March	1st to 10th	Night	21% 9% 2 7% 3 4 4 3 4 6% 36%	5493
	11th to 20th	Night	12% 6% 2 6% 4 4 4 3 4 6% 50%	5396
	21st to end	Night	17% 7% 3 6% 4 3 3 3 5% 5% 45%	5072
April	1st to 10th	Night	12% 6% 2 5% 4 4 4 3 6% 7% 47%	2100
	11th to 20th	Night	12% 4 2 5% 3 3 4 3 5% 8% 52%	2075
	21st to end	Night	9% 5% 1 5% 3 4 4 4 6% 8% 50%	2100
May	1st to 10th	Night	17% 7% 2 6% 4 4 4 3 5% 7% 39%	5780
	11th to 20th	Night	14% 7% 3 7% 5% 4 5% 4 6% 8% 38%	5234
	21st to end	Night	12% 7% 3 8% 5% 5% 6% 5% 7% 9% 32%	5761
June	1st to 10th	Night	7% 5% 2 6% 6% 5% 5% 5% 8% 10% 41%	1890
	11th to 20th	Night	5% 4 1 4 4 4 5% 5% 8% 12% 48%	1822
	21st to end	Night	4 4 2 4 5% 5% 5% 6% 10% 11% 44%	1680
July	1st to 10th	Night	4 4 2 7% 5% 5% 5% 5% 9% 14% 39%	4708
	11th to 20th	Night	7% 4 2 6% 5% 4 5% 6% 10% 16% 35%	5291
	21st to end	Night	5% 5% 3 8% 6% 6% 6% 6% 9% 14% 32%	6389
August	1st to 10th	Night	2 3 2 5% 3 4 5% 5% 8% 12% 51%	4604
	11th to 20th	Night	3 2 2 4 4 5% 6% 5% 9% 14% 44%	4560
	21st to end	Night	4 3 1 6% 5% 5% 5% 5% 7% 11% 47%	5046
September	1st to 10th	Night	8% 5% 2 7% 5% 5% 4 4 7% 9% 44%	2100
	11th to 20th	Night	10% 7% 2 5% 3 4 5% 3 6% 9% 46%	2181
	21st to end	Night	7% 5% 2 6% 4 4 4 4 5% 7% 53%	2200
October	1st to 10th	Night	7% 4 1 4 3 3 4 3 5% 6% 60%	2200
	11th to 20th	Night	11% 4 1 4 2 2 2 3 5% 6% 58%	2300
	21st to end	Night	14% 6% 2 4 3 2 2 2 3 5% 58%	2665
November	1st to 10th	Night	11% 4 2 4 3 3 4 3 4 5% 56%	2666
	11th to 20th	Night	13% 5% 2 4 3 3 3 2 4 7% 55%	2730
	21st to end	Night	13% 5% 2 5% 3 4 4 4 5% 6% 49%	2730
December	1st to 10th	Night	19% 6% 2 5% 3 2 3 3 4 6% 48%	4380
	11th to 20th	Night	15% 9% 3 6% 4 4 3 2 4 4 46%	4952
	21st to end	Night	19% 8% 2 5% 3 3 3 3 4 6% 44%	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	48% 2 5% 28% 16% 2	5361
	11th to 20th	Day	31% 2 6% 24% 32% 5%	5880
	21st to end	Day	53% 2 5% 14% 18% 8%	6436
February	1st to 10th	Day	47% 2 5% 20% 19% 7%	2100
	11th to 20th	Day	48% 2 5% 18% 20% 7%	2058
	21st to end	Day	47% 2 6% 15% 20% 9%	1730
March	1st to 10th	Day	51% 2 7% 14% 19% 6%	4580
	11th to 20th	Day	39% 3 6% 17% 21% 15%	4812
	21st to end	Day	45% 2 8% 18% 20% 6%	6101
April	1st to 10th	Day	38% 3 9% 22% 20% 7%	2520
	11th to 20th	Day	37% 2 7% 21% 24% 8%	2494
	21st to end	Day	34% 2 10% 25% 25% 4	2520
May	1st to 10th	Day	48% 3 10% 23% 14% 2	7092
	11th to 20th	Day	41% 5% 17% 21% 14% 2	7630
	21st to end	Day	48% 6% 12% 20% 13% 1	8405
June	1st to 10th	Day	41% 4 13% 24% 16% 2	2730
	11th to 20th	Day	33% 6% 17% 24% 17% 2	2787
	21st to end	Day	35% 6% 17% 26% 14% 3	2940
July	1st to 10th	Day	34% 11% 24% 23% 7% 1	8211
	11th to 20th	Day	35% 12% 31% 19% 3	7574
	21st to end	Day	40% 11% 22% 23% 4	7517
August	1st to 10th	Day	22% 7% 17% 29% 24% 1	5533
	11th to 20th	Day	25% 7% 21% 33% 12% 2	5522
	21st to end	Day	29% 7% 17% 26% 17% 3	6079
September	1st to 10th	Day	36% 5% 13% 21% 19% 5%	2520
	11th to 20th	Day	40% 5% 11% 18% 22% 5%	2263
	21st to end	Day	31% 4 9% 24% 21% 9%	2200
October	1st to 10th	Day	22% 3 5% 14% 30% 26%	3590
	11th to 20th	Day	17% 2 4 17% 32% 29%	3388
	21st to end	Day	24% 2 4 18% 37% 15%	3485
November	1st to 10th	Day	32% 2 7% 21% 27% 11%	1852
	11th to 20th	Day	33% 3 7% 18% 28% 11%	1890
	21st to end	Day	39% 2 7% 19% 25% 8%	1890
December	1st to 10th	Day	42% 3 6% 22% 24% 3	3020
	11th to 20th	Day	44% 2 9% 18% 21% 6%	3460
	21st to end	Day	43% 1 5% 24% 25% 2	4565
January	1st to 10th	Night	47% 2 6% 22% 21% 2	7516
	11th to 20th	Night	40% 2 4 17% 28% 9%	7080
	21st to end	Night	50% 2 3 17% 22% 8%	7745
February	1st to 10th	Night	43% 2 6% 18% 23% 8%	2520
	11th to 20th	Night	47% 3 5% 17% 19% 10%	2459
	21st to end	Night	45% 2 6% 17% 19% 11%	2076
March	1st to 10th	Night	50% 2 5% 15% 18% 9%	5493
	11th to 20th	Night	36% 2 7% 17% 22% 16%	5396
	21st to end	Night	43% 2 6% 23% 18% 8%	5072
April	1st to 10th	Night	37% 3 10% 21% 19% 10%	2100
	11th to 20th	Night	32% 2 8% 21% 25% 11%	2075
	21st to end	Night	32% 4 11% 24% 24% 6%	2100
May	1st to 10th	Night	46% 4 12% 18% 16% 4	5810
	11th to 20th	Night	44% 4 13% 23% 15% 2	5235
	21st to end	Night	47% 7% 12% 18% 14% 2	5771
June	1st to 10th	Night	37% 6% 14% 23% 18% 2	1890
	11th to 20th	Night	28% 5% 18% 27% 17% 4	1822
	21st to end	Night	30% 7% 21% 22% 17% 3	1680
July	1st to 10th	Night	31% 10% 29% 23% 6% 1	4670
	11th to 20th	Night	33% 11% 33% 19% 3	5243
	21st to end	Night	38% 11% 25% 22% 4 1	6245
August	1st to 10th	Night	21% 7% 21% 30% 19% 2	4592
	11th to 20th	Night	25% 8% 21% 33% 11% 2	4590
	21st to end	Night	28% 7% 17% 26% 19% 4	5046
September	1st to 10th	Night	36% 5% 15% 19% 18% 6%	2100
	11th to 20th	Night	35% 5% 13% 20% 20% 7%	2181
	21st to end	Night	30% 4 8% 24% 23% 10%	2200
October	1st to 10th	Night	20% 3 7% 16% 24% 30%	3590
	11th to 20th	Night	18% 2 3 17% 28% 33%	3734
	21st to end	Night	22% 2 4 19% 34% 19%	4301
November	1st to 10th	Night	32% 3 7% 16% 29% 14%	2666
	11th to 20th	Night	31% 2 6% 21% 28% 13%	2730
	21st to end	Night	36% 2 6% 22% 22% 11%	2730
December	1st to 10th	Night	40% 2 7% 22% 26% 4	4380
	11th to 20th	Night	43% 2 7% 18% 25% 5%	4954
	21st to end	Night	44% 2 5% 22% 26% 2	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	25% 19% 31% 20% 4	330
	11th to 20th	Day	22% 20% 34% 15% 8% 1	330
	21st to end	Day	24% 21% 36% 15% 3 1	363
February	1st to 10th	Day	19% 19% 41% 15% 5% 1	330
	11th to 20th	Day	32% 16% 31% 17% 4	330
	21st to end	Day	26% 21% 36% 15% 3	273
March	1st to 10th	Day	22% 16% 39% 15% 8%	330
	11th to 20th	Day	20% 20% 36% 20% 4	356
	21st to end	Day	21% 13% 31% 25% 10%	594
April	1st to 10th	Day	18% 15% 31% 24% 10% 2	540
	11th to 20th	Day	16% 13% 30% 25% 13% 3	532
	21st to end	Day	14% 9% 29% 31% 15% 2	540
May	1st to 10th	Day	17% 10% 24% 30% 15% 4	543
	11th to 20th	Day	10% 5% 25% 33% 18% 10%	567
	21st to end	Day	11% 3 22% 30% 22% 12%	617
June	1st to 10th	Day	13% 2 14% 29% 29% 12%	570
	11th to 20th	Day	9% 1 14% 27% 31% 18%	627
	21st to end	Day	7% 3 10% 28% 33% 18%	780
July	1st to 10th	Day	6% 2 6% 30% 35% 20%	771
	11th to 20th	Day	8% 2 4 21% 35% 29%	604
	21st to end	Day	6% 3 7% 23% 36% 25%	620
August	1st to 10th	Day	7% 2 6% 22% 36% 28%	566
	11th to 20th	Day	6% 1 5% 21% 42% 25%	559
	21st to end	Day	14% 2 7% 21% 32% 24%	627
September	1st to 10th	Day	9% 2 8% 30% 34% 17%	570
	11th to 20th	Day	14% 3 8% 24% 36% 15%	542
	21st to end	Day	10% 4 11% 32% 31% 12%	530
October	1st to 10th	Day	11% 4 19% 33% 24% 9%	530
	11th to 20th	Day	8% 4 24% 37% 23% 3	426
	21st to end	Day	18% 12% 22% 31% 13% 3	363
November	1st to 10th	Day	17% 7% 30% 29% 12% 5%	330
	11th to 20th	Day	14% 10% 35% 28% 11% 1	330
	21st to end	Day	14% 17% 31% 24% 12% 2	330
December	1st to 10th	Day	27% 13% 33% 18% 8% 1	330
	11th to 20th	Day	23% 13% 34% 20% 9% 2	330
	21st to end	Day	27% 12% 32% 21% 7% 1	363
January	1st to 10th	Night	22% 13% 34% 25% 6%	840
	11th to 20th	Night	23% 15% 28% 28% 7%	840
	21st to end	Night	22% 12% 33% 29% 4	924
February	1st to 10th	Night	21% 12% 31% 32% 5%	840
	11th to 20th	Night	25% 14% 30% 26% 5%	823
	21st to end	Night	23% 15% 34% 27% 3	692
March	1st to 10th	Night	19% 13% 30% 30% 8%	840
	11th to 20th	Night	16% 12% 34% 30% 8%	807
	21st to end	Night	17% 9% 33% 29% 11%	693
April	1st to 10th	Night	15% 11% 32% 30% 12%	630
	11th to 20th	Night	14% 7% 34% 30% 14% 1	623
	21st to end	Night	10% 8% 29% 37% 15% 1	630
May	1st to 10th	Night	13% 5% 25% 36% 18% 3	630
	11th to 20th	Night	14% 4 18% 37% 24% 4	621
	21st to end	Night	9% 3 13% 37% 31% 7%	683
June	1st to 10th	Night	8% 2 11% 40% 33% 7%	630
	11th to 20th	Night	5% 3 9% 30% 44% 9%	630
	21st to end	Night	5% 2 6% 31% 43% 13%	630
July	1st to 10th	Night	5% 2 4 26% 48% 16%	615
	11th to 20th	Night	5% 1 3 25% 44% 21%	612
	21st to end	Night	6% 2 5% 26% 45% 16%	690
August	1st to 10th	Night	6% 1 5% 23% 47% 18%	627
	11th to 20th	Night	7% 1 3 25% 51% 13%	624
	21st to end	Night	11% 1 5% 25% 42% 16%	693
September	1st to 10th	Night	10% 2 8% 30% 41% 10%	630
	11th to 20th	Night	13% 3 10% 29% 39% 7%	760
	21st to end	Night	9% 3 11% 34% 39% 5%	800
October	1st to 10th	Night	9% 2 20% 34% 30% 6%	800
	11th to 20th	Night	14% 5% 19% 39% 22% 3	800
	21st to end	Night	17% 6% 17% 35% 22% 3	880
November	1st to 10th	Night	13% 6% 20% 35% 23% 3	820
	11th to 20th	Night	14% 7% 28% 35% 16% 1	840
	21st to end	Night	16% 8% 26% 36% 12% 2	840
December	1st to 10th	Night	23% 10% 25% 32% 10%	840
	11th to 20th	Night	22% 8% 28% 32% 10%	840
	21st to end	Night	24% 11% 28% 30% 7%	924

Page generated at 2026-09-11 03:11:51. Version ac07

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