Oleo Acres Double Barrel Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Oleo Acres Double Barrel Observatory 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 5% 4 4 4 3 5% 7% 49%	148985
	Night	11% 5% 2 5% 3 3 3 3 5% 7% 54%	142478
Transparency	Day	34% 5% 10% 25% 21% 5%	152637
	Night	31% 4 9% 24% 24% 8%	146893
Seeing	Day	17% 11% 29% 27% 14% 3	17877
	Night	16% 12% 30% 29% 12% 1	27603

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	10% 8% 3 6% 4 3 3 3 4 5% 50%	5289
	11th to 20th	Day	5% 5% 2 5% 3 3 3 3 4 5% 64%	5310
	21st to end	Day	18% 9% 3 5% 2 2 3 2 4 5% 47%	5812
February	1st to 10th	Day	19% 8% 2 7% 5% 4 3 2 3 5% 42%	1890
	11th to 20th	Day	16% 8% 3 6% 4 4 3 3 5% 6% 43%	2028
	21st to end	Day	19% 8% 2 6% 3 3 3 3 3 5% 46%	1805
March	1st to 10th	Day	18% 8% 2 6% 3 3 3 2 4 4 48%	5046
	11th to 20th	Day	11% 6% 2 6% 3 4 3 3 4 6% 52%	5090
	21st to end	Day	15% 9% 3 6% 4 4 4 3 5% 7% 40%	5583
April	1st to 10th	Day	15% 7% 3 7% 4 3 3 3 4 7% 45%	2310
	11th to 20th	Day	18% 5% 2 6% 4 4 4 3 5% 6% 44%	2489
	21st to end	Day	20% 8% 3 6% 4 4 3 3 4 6% 39%	2617
May	1st to 10th	Day	18% 8% 3 7% 4 3 4 3 4 6% 40%	7617
	11th to 20th	Day	13% 6% 3 7% 5% 4 4 4 5% 7% 42%	7627
	21st to end	Day	17% 8% 3 7% 5% 5% 5% 4 6% 7% 34%	8392
June	1st to 10th	Day	10% 5% 2 5% 5% 4 6% 4 7% 8% 44%	2730
	11th to 20th	Day	9% 5% 2 6% 4 5% 5% 4 6% 9% 43%	2730
	21st to end	Day	5% 3 2 4 4 5% 4 4 7% 9% 53%	2730
July	1st to 10th	Day	5% 4 2 5% 5% 4 6% 5% 8% 11% 45%	7680
	11th to 20th	Day	4 4 1 5% 4 4 5% 4 7% 10% 52%	7680
	21st to end	Day	4 3 1 4 4 4 4 5% 7% 9% 55%	8337
August	1st to 10th	Day	2 2 1 3 3 3 4 3 5% 7% 68%	6014
	11th to 20th	Day	5% 2 1 3 2 3 3 3 5% 9% 64%	5948
	21st to end	Day	3 3 1 4 4 4 5% 4 7% 9% 55%	6158
September	1st to 10th	Day	10% 5% 1 4 4 4 5% 4 5% 6% 52%	2340
	11th to 20th	Day	9% 4 2 7% 5% 4 5% 3 5% 7% 47%	2233
	21st to end	Day	8% 4 1 4 3 4 5% 4 5% 6% 57%	2200
October	1st to 10th	Day	8% 4 1 4 4 4 4 3 4 5% 59%	2070
	11th to 20th	Day	13% 4 1 4 3 2 2 2 3 4 61%	2000
	21st to end	Day	18% 7% 2 4 3 2 3 2 3 4 52%	2200
November	1st to 10th	Day	12% 5% 2 6% 3 2 3 3 4 6% 54%	2058
	11th to 20th	Day	11% 5% 2 4 3 3 3 2 3 5% 59%	1984
	21st to end	Day	16% 7% 2 5% 3 3 3 2 4 5% 52%	1890
December	1st to 10th	Day	17% 7% 2 4 2 3 2 2 4 5% 52%	3030
	11th to 20th	Day	18% 9% 2 5% 3 3 3 2 4 5% 46%	3481
	21st to end	Day	21% 10% 2 5% 3 3 3 3 4 5% 41%	4587
January	1st to 10th	Night	12% 6% 2 7% 4 3 4 3 4 6% 49%	7634
	11th to 20th	Night	5% 4 2 3 2 2 2 2 4 5% 69%	7680
	21st to end	Night	21% 8% 3 5% 3 3 3 3 4 4 43%	8402
February	1st to 10th	Night	14% 8% 3 6% 3 3 4 3 4 5% 47%	2730
	11th to 20th	Night	15% 9% 3 6% 4 3 3 3 4 5% 45%	2495
	21st to end	Night	14% 8% 3 4 4 3 2 2 3 5% 52%	1998
March	1st to 10th	Night	18% 8% 2 5% 3 3 3 3 4 5% 46%	5029
	11th to 20th	Night	11% 5% 2 4 3 3 3 3 4 6% 57%	5090
	21st to end	Night	14% 7% 3 6% 3 3 3 3 5% 6% 46%	5588
April	1st to 10th	Night	14% 6% 2 6% 3 3 3 3 4 7% 48%	2310
	11th to 20th	Night	14% 6% 2 5% 3 3 4 3 5% 6% 50%	2079
	21st to end	Night	16% 7% 2 5% 3 4 3 3 5% 7% 46%	1998
May	1st to 10th	Night	16% 8% 2 6% 4 4 4 3 6% 7% 40%	5266
	11th to 20th	Night	12% 5% 2 5% 4 4 4 4 6% 8% 45%	5265
	21st to end	Night	15% 6% 2 6% 4 4 4 4 6% 9% 39%	5793
June	1st to 10th	Night	7% 4 1 4 3 2 4 3 7% 9% 55%	1890
	11th to 20th	Night	6% 4 2 4 3 3 3 3 7% 9% 56%	1890
	21st to end	Night	4 2 1 3 3 2 3 3 6% 9% 65%	1890
July	1st to 10th	Night	5% 4 2 6% 4 4 4 4 6% 12% 51%	5308
	11th to 20th	Night	3 3 1 3 3 3 4 3 6% 9% 62%	5307
	21st to end	Night	2 2 1 3 3 3 3 4 6% 9% 65%	5770
August	1st to 10th	Night	1 1 2 2 2 3 4 5% 7% 71%	4156
	11th to 20th	Night	3 2 1 2 2 2 3 3 5% 7% 71%	4118
	21st to end	Night	2 2 1 4 3 4 3 3 5% 9% 63%	4958
September	1st to 10th	Night	7% 5% 1 4 3 3 4 3 5% 7% 58%	2274
	11th to 20th	Night	9% 4 1 6% 4 3 5% 3 6% 8% 52%	2233
	21st to end	Night	6% 3 1 5% 2 3 3 3 5% 7% 61%	2200
October	1st to 10th	Night	6% 4 1 4 3 2 3 3 4 6% 63%	2308
	11th to 20th	Night	11% 3 2 4 2 2 3 2 4 5% 61%	2400
	21st to end	Night	17% 5% 2 4 2 2 2 2 3 4 56%	2640
November	1st to 10th	Night	12% 4 2 4 3 3 3 3 4 5% 59%	2460
	11th to 20th	Night	8% 5% 2 4 3 3 3 3 3 5% 60%	2630
	21st to end	Night	16% 6% 2 3 2 2 3 2 4 6% 53%	2730
December	1st to 10th	Night	11% 8% 2 6% 3 3 3 3 3 5% 53%	4380
	11th to 20th	Night	16% 7% 3 6% 3 3 3 2 3 4 51%	4946
	21st to end	Night	18% 11% 3 5% 2 2 2 2 3 5% 47%	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	37% 3 9% 25% 23% 2	5290
	11th to 20th	Day	24% 2 9% 22% 38% 5%	5310
	21st to end	Day	42% 3 4 19% 24% 8%	5812
February	1st to 10th	Day	46% 4 7% 17% 21% 5%	1890
	11th to 20th	Day	43% 4 7% 22% 19% 5%	2038
	21st to end	Day	43% 3 5% 14% 26% 9%	1805
March	1st to 10th	Day	41% 3 6% 15% 18% 17%	5046
	11th to 20th	Day	35% 3 7% 18% 18% 18%	5090
	21st to end	Day	44% 4 9% 25% 16% 1	5585
April	1st to 10th	Day	42% 3 10% 20% 19% 7%	2310
	11th to 20th	Day	42% 4 9% 21% 19% 6%	2489
	21st to end	Day	47% 5% 8% 20% 17% 3	2617
May	1st to 10th	Day	46% 4 9% 21% 18% 2	7655
	11th to 20th	Day	41% 6% 11% 22% 18% 2	7631
	21st to end	Day	48% 7% 12% 17% 13% 3	8405
June	1st to 10th	Day	34% 8% 15% 27% 14% 2	2730
	11th to 20th	Day	35% 7% 13% 26% 17% 2	2730
	21st to end	Day	26% 7% 15% 28% 21% 3	2730
July	1st to 10th	Day	30% 7% 18% 31% 12% 1	7616
	11th to 20th	Day	25% 8% 17% 33% 16% 1	7611
	21st to end	Day	23% 7% 13% 39% 17% 1	8155
August	1st to 10th	Day	16% 5% 10% 29% 32% 8%	6000
	11th to 20th	Day	19% 4 13% 38% 23% 2	5987
	21st to end	Day	23% 6% 15% 35% 17% 3	6157
September	1st to 10th	Day	31% 5% 8% 25% 21% 9%	2340
	11th to 20th	Day	34% 6% 10% 23% 20% 7%	2233
	21st to end	Day	28% 5% 8% 22% 28% 9%	2200
October	1st to 10th	Day	18% 3 6% 11% 38% 25%	3369
	11th to 20th	Day	21% 2 4 18% 36% 19%	3240
	21st to end	Day	30% 3 6% 28% 26% 7%	3538
November	1st to 10th	Day	33% 3 7% 24% 26% 7%	2058
	11th to 20th	Day	30% 3 7% 26% 26% 9%	1984
	21st to end	Day	37% 2 7% 21% 26% 7%	1890
December	1st to 10th	Day	36% 3 7% 33% 17% 3	3030
	11th to 20th	Day	42% 2 5% 19% 26% 6%	3479
	21st to end	Day	45% 4 6% 22% 20% 4	4587
January	1st to 10th	Night	37% 3 7% 26% 24% 3	7635
	11th to 20th	Night	19% 3 9% 18% 38% 12%	7680
	21st to end	Night	46% 3 5% 14% 25% 7%	8402
February	1st to 10th	Night	40% 4 8% 20% 21% 7%	2730
	11th to 20th	Night	42% 3 6% 21% 21% 6%	2495
	21st to end	Night	38% 3 6% 18% 24% 12%	1998
March	1st to 10th	Night	42% 3 6% 14% 20% 15%	5029
	11th to 20th	Night	30% 3 6% 22% 17% 22%	5090
	21st to end	Night	39% 4 10% 21% 23% 3	5588
April	1st to 10th	Night	37% 4 9% 20% 19% 11%	2310
	11th to 20th	Night	35% 5% 8% 23% 19% 11%	2079
	21st to end	Night	38% 5% 9% 25% 21% 3	1998
May	1st to 10th	Night	43% 5% 11% 20% 16% 4	5293
	11th to 20th	Night	35% 6% 12% 23% 20% 4	5266
	21st to end	Night	41% 8% 17% 18% 12% 5%	5805
June	1st to 10th	Night	23% 8% 16% 30% 19% 3	1890
	11th to 20th	Night	25% 5% 13% 32% 23% 3	1890
	21st to end	Night	17% 5% 15% 30% 27% 6%	1890
July	1st to 10th	Night	27% 6% 18% 30% 17% 2	5265
	11th to 20th	Night	19% 7% 17% 34% 22% 2	5256
	21st to end	Night	16% 6% 14% 42% 20% 2	5641
August	1st to 10th	Night	12% 4 10% 30% 34% 10%	4146
	11th to 20th	Night	14% 3 12% 38% 29% 4	4145
	21st to end	Night	19% 4 13% 37% 23% 3	4958
September	1st to 10th	Night	24% 6% 10% 25% 26% 10%	2274
	11th to 20th	Night	30% 6% 10% 24% 22% 9%	2233
	21st to end	Night	23% 3 9% 25% 30% 11%	2200
October	1st to 10th	Night	14% 3 6% 14% 35% 29%	3776
	11th to 20th	Night	18% 2 4 14% 41% 20%	3899
	21st to end	Night	30% 3 4 29% 24% 11%	4252
November	1st to 10th	Night	30% 3 7% 23% 28% 10%	2460
	11th to 20th	Night	29% 3 7% 23% 27% 11%	2630
	21st to end	Night	35% 2 7% 21% 27% 7%	2730
December	1st to 10th	Night	34% 4 7% 27% 23% 5%	4380
	11th to 20th	Night	40% 2 4 18% 25% 11%	4947
	21st to end	Night	42% 3 6% 22% 21% 5%	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	24% 25% 35% 13% 3	330
	11th to 20th	Day	23% 27% 38% 8% 2 1	330
	21st to end	Day	25% 26% 32% 13% 3	363
February	1st to 10th	Day	34% 18% 37% 10% 2	330
	11th to 20th	Day	36% 25% 32% 6% 1	330
	21st to end	Day	36% 28% 27% 7% 3	273
March	1st to 10th	Day	34% 19% 33% 12% 1	330
	11th to 20th	Day	35% 22% 33% 7% 2	330
	21st to end	Day	25% 28% 38% 7% 1	363
April	1st to 10th	Day	29% 21% 36% 11% 3	330
	11th to 20th	Day	31% 19% 35% 11% 3	527
	21st to end	Day	27% 21% 33% 14% 4 1	637
May	1st to 10th	Day	20% 16% 42% 18% 3	753
	11th to 20th	Day	18% 12% 39% 21% 9% 1	775
	21st to end	Day	17% 9% 37% 23% 12% 2	844
June	1st to 10th	Day	12% 5% 26% 35% 17% 4	780
	11th to 20th	Day	11% 5% 31% 35% 15% 3	780
	21st to end	Day	5% 4 27% 40% 20% 4	780
July	1st to 10th	Day	8% 2 18% 40% 25% 7%	771
	11th to 20th	Day	4 2 17% 40% 31% 5%	768
	21st to end	Day	4 2 15% 41% 30% 8%	849
August	1st to 10th	Day	5% 2 14% 48% 27% 4	776
	11th to 20th	Day	8% 1 16% 45% 26% 4	765
	21st to end	Day	7% 2 12% 40% 31% 7%	668
September	1st to 10th	Day	8% 2 12% 41% 30% 7%	390
	11th to 20th	Day	5% 2 22% 43% 23% 4	339
	21st to end	Day	13% 7% 21% 38% 18% 3	330
October	1st to 10th	Day	6% 8% 32% 38% 13% 3	330
	11th to 20th	Day	17% 12% 39% 26% 6%	330
	21st to end	Day	31% 12% 29% 22% 5%	363
November	1st to 10th	Day	16% 16% 41% 20% 5% 2	330
	11th to 20th	Day	19% 19% 37% 21% 3 2	330
	21st to end	Day	26% 21% 36% 14% 2	330
December	1st to 10th	Day	28% 15% 36% 16% 4 1	330
	11th to 20th	Day	30% 20% 37% 9% 4	330
	21st to end	Day	29% 20% 36% 13% 2	363
January	1st to 10th	Night	19% 18% 35% 23% 5%	1050
	11th to 20th	Night	22% 18% 34% 22% 4	1050
	21st to end	Night	20% 18% 32% 25% 4	1155
February	1st to 10th	Night	24% 20% 35% 18% 3	1050
	11th to 20th	Night	26% 22% 33% 16% 2	861
	21st to end	Night	26% 20% 34% 18% 2	614
March	1st to 10th	Night	24% 15% 35% 22% 3	630
	11th to 20th	Night	23% 17% 39% 18% 4	630
	21st to end	Night	18% 19% 38% 20% 4 1	693
April	1st to 10th	Night	20% 18% 36% 21% 5%	630
	11th to 20th	Night	21% 18% 35% 22% 5%	623
	21st to end	Night	19% 16% 36% 20% 7% 1	630
May	1st to 10th	Night	14% 12% 37% 29% 7%	630
	11th to 20th	Night	14% 9% 37% 27% 12% 1	621
	21st to end	Night	11% 7% 33% 31% 16% 1	683
June	1st to 10th	Night	9% 4 25% 40% 21% 3	630
	11th to 20th	Night	8% 3 33% 41% 14%	630
	21st to end	Night	4 1 27% 42% 23% 3	630
July	1st to 10th	Night	6% 1 16% 44% 29% 4	615
	11th to 20th	Night	3 1 16% 49% 28% 3	612
	21st to end	Night	3 1 14% 45% 33% 5%	690
August	1st to 10th	Night	4 1 15% 48% 29% 3	627
	11th to 20th	Night	6% 15% 45% 29% 4	624
	21st to end	Night	5% 1 15% 44% 31% 4	693
September	1st to 10th	Night	9% 2 14% 44% 29% 3	630
	11th to 20th	Night	10% 2 19% 38% 28% 3	609
	21st to end	Night	7% 3 26% 37% 25% 3	600
October	1st to 10th	Night	8% 5% 30% 34% 20% 2	708
	11th to 20th	Night	14% 10% 32% 31% 13% 1	800
	21st to end	Night	22% 12% 30% 25% 11% 1	880
November	1st to 10th	Night	14% 13% 37% 28% 8% 1	820
	11th to 20th	Night	14% 15% 36% 27% 8%	950
	21st to end	Night	24% 15% 33% 21% 7%	1050
December	1st to 10th	Night	20% 15% 35% 26% 4	1050
	11th to 20th	Night	23% 15% 35% 22% 4	1050
	21st to end	Night	24% 19% 32% 21% 4	1155

Page generated at 2026-09-11 03:11:55. Version ac07

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