Abilene State Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Abilene State Park 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	7% 4 2 4 3 3 4 3 5% 7% 59%	148644
	Night	6% 4 1 4 3 3 3 3 5% 7% 61%	142889
Transparency	Day	26% 4 9% 22% 26% 13%	152475
	Night	24% 3 8% 22% 27% 15%	147125
Seeing	Day	9% 8% 27% 31% 20% 5%	17577
	Night	8% 8% 35% 36% 12% 1	27406

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	6% 4 3 5% 4 3 3 2 4 5% 60%	5289
	11th to 20th	Day	4 4 1 3 2 2 2 2 4 6% 69%	5310
	21st to end	Day	13% 6% 2 6% 4 3 3 3 5% 6% 50%	6422
February	1st to 10th	Day	9% 5% 2 4 2 2 3 3 5% 6% 58%	2100
	11th to 20th	Day	8% 8% 3 6% 4 4 3 3 4 5% 54%	2049
	21st to end	Day	10% 8% 1 4 2 2 2 3 3 5% 61%	1730
March	1st to 10th	Day	8% 5% 2 5% 3 3 3 3 5% 6% 58%	4682
	11th to 20th	Day	10% 5% 1 3 3 3 3 2 4 6% 59%	5090
	21st to end	Day	4 5% 2 4 3 3 4 3 5% 7% 58%	5583
April	1st to 10th	Day	7% 5% 1 4 4 3 4 4 5% 7% 57%	2383
	11th to 20th	Day	10% 5% 2 4 3 4 4 3 5% 6% 54%	2494
	21st to end	Day	7% 5% 1 5% 4 3 3 3 4 6% 58%	2594
May	1st to 10th	Day	10% 6% 2 6% 4 4 4 3 5% 6% 49%	7617
	11th to 20th	Day	10% 6% 2 5% 4 3 4 4 6% 6% 50%	7627
	21st to end	Day	9% 6% 2 7% 4 5% 5% 4 6% 8% 44%	8392
June	1st to 10th	Day	5% 3 1 4 3 3 3 4 6% 8% 60%	2730
	11th to 20th	Day	4 3 1 4 3 4 3 4 6% 8% 60%	2730
	21st to end	Day	5% 2 1 3 3 3 4 4 6% 8% 60%	2730
July	1st to 10th	Day	7% 4 2 5% 4 4 5% 4 7% 9% 48%	7680
	11th to 20th	Day	5% 4 2 5% 4 4 5% 4 5% 9% 55%	7680
	21st to end	Day	2 1 1 2 2 2 3 3 4 8% 71%	8337
August	1st to 10th	Day	1 1 2 2 2 3 3 4 7% 74%	5740
	11th to 20th	Day	3 2 1 2 2 2 2 3 4 8% 72%	5483
	21st to end	Day	2 2 1 4 3 4 4 4 5% 8% 63%	6079
September	1st to 10th	Day	10% 4 1 4 4 4 4 3 5% 7% 53%	2352
	11th to 20th	Day	9% 5% 2 6% 4 4 4 3 6% 7% 52%	2233
	21st to end	Day	9% 4 1 4 3 3 3 3 5% 6% 60%	2200
October	1st to 10th	Day	4 3 1 3 3 3 3 4 4 7% 66%	2200
	11th to 20th	Day	7% 3 2 4 3 3 3 2 3 4 67%	2156
	21st to end	Day	10% 4 1 4 2 2 2 3 4 3 66%	2200
November	1st to 10th	Day	7% 4 1 3 2 3 3 2 4 6% 63%	1874
	11th to 20th	Day	4 4 1 3 2 2 3 3 4 7% 66%	1890
	21st to end	Day	9% 5% 2 3 4 3 4 2 4 5% 58%	1890
December	1st to 10th	Day	10% 6% 2 7% 3 3 3 2 4 5% 53%	3030
	11th to 20th	Day	4 4 1 4 3 4 5% 4 6% 5% 59%	3481
	21st to end	Day	7% 6% 1 3 2 3 3 2 3 4 66%	4587
January	1st to 10th	Night	6% 4 2 6% 3 3 3 2 4 5% 61%	7634
	11th to 20th	Night	4 3 1 3 2 2 3 3 4 5% 72%	7680
	21st to end	Night	12% 7% 2 4 4 4 4 3 5% 6% 49%	7848
February	1st to 10th	Night	9% 5% 2 4 3 3 3 2 4 5% 59%	2520
	11th to 20th	Night	10% 6% 2 5% 4 3 3 3 5% 5% 54%	2458
	21st to end	Night	9% 5% 1 3 3 3 3 3 3 6% 62%	2076
March	1st to 10th	Night	5% 6% 3 5% 3 3 4 3 4 6% 59%	5405
	11th to 20th	Night	10% 5% 1 3 2 2 3 3 4 6% 61%	5090
	21st to end	Night	5% 5% 2 4 3 3 3 3 5% 6% 61%	5588
April	1st to 10th	Night	6% 5% 1 5% 4 3 3 3 5% 7% 59%	2231
	11th to 20th	Night	8% 5% 2 5% 3 3 3 3 5% 7% 55%	2077
	21st to end	Night	8% 4 1 4 3 3 3 4 4 6% 61%	2022
May	1st to 10th	Night	11% 6% 2 4 4 4 4 3 5% 6% 52%	5266
	11th to 20th	Night	6% 5% 1 4 3 3 4 3 5% 7% 57%	5265
	21st to end	Night	9% 6% 2 6% 4 4 5% 4 6% 9% 46%	5793
June	1st to 10th	Night	2 2 1 3 4 2 4 4 7% 10% 59%	1890
	11th to 20th	Night	3 2 1 3 3 3 4 3 7% 9% 62%	1890
	21st to end	Night	3 3 1 4 2 3 2 3 6% 9% 66%	1890
July	1st to 10th	Night	6% 5% 2 5% 3 3 4 3 6% 11% 53%	5308
	11th to 20th	Night	4 2 1 3 3 3 4 3 5% 9% 62%	5307
	21st to end	Night	1 1 2 1 2 2 3 5% 7% 75%	5770
August	1st to 10th	Night	1 1 2 1 2 2 2 4 6% 78%	4411
	11th to 20th	Night	2 1 1 2 1 2 2 2 4 8% 75%	4583
	21st to end	Night	2 2 1 3 2 3 3 3 5% 8% 68%	5069
September	1st to 10th	Night	7% 4 1 4 3 3 4 3 5% 8% 59%	2265
	11th to 20th	Night	8% 3 1 5% 3 4 4 4 7% 7% 53%	2233
	21st to end	Night	7% 3 1 4 3 3 3 3 5% 7% 61%	2200
October	1st to 10th	Night	3 3 1 3 3 3 3 3 5% 7% 67%	2200
	11th to 20th	Night	7% 4 1 2 2 2 3 2 3 5% 69%	2221
	21st to end	Night	7% 4 2 3 2 3 3 2 4 4 66%	2640
November	1st to 10th	Night	8% 4 1 3 2 2 3 3 3 5% 66%	2640
	11th to 20th	Night	4 3 1 4 2 3 3 3 4 6% 67%	2730
	21st to end	Night	10% 4 2 5% 3 3 3 3 5% 6% 55%	2730
December	1st to 10th	Night	10% 6% 3 6% 3 2 2 2 4 5% 56%	4380
	11th to 20th	Night	5% 4 1 5% 3 3 4 4 6% 6% 60%	4946
	21st to end	Night	7% 6% 2 5% 3 3 3 3 4 5% 61%	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	27% 2 5% 22% 32% 13%	5290
	11th to 20th	Day	19% 2 5% 23% 38% 15%	5310
	21st to end	Day	36% 3 4 16% 25% 15%	6422
February	1st to 10th	Day	28% 3 6% 16% 27% 20%	2100
	11th to 20th	Day	34% 3 5% 20% 24% 14%	2059
	21st to end	Day	28% 2 5% 12% 31% 22%	1730
March	1st to 10th	Day	28% 3 4 12% 23% 30%	4682
	11th to 20th	Day	28% 3 8% 9% 22% 30%	5090
	21st to end	Day	26% 4 7% 17% 28% 18%	5585
April	1st to 10th	Day	28% 4 9% 18% 22% 18%	2383
	11th to 20th	Day	32% 4 7% 15% 24% 17%	2494
	21st to end	Day	29% 4 8% 18% 27% 14%	2594
May	1st to 10th	Day	36% 4 8% 18% 21% 13%	7655
	11th to 20th	Day	34% 5% 6% 13% 30% 12%	7631
	21st to end	Day	37% 4 12% 25% 12% 10%	8405
June	1st to 10th	Day	23% 5% 15% 30% 22% 6%	2730
	11th to 20th	Day	22% 6% 11% 27% 26% 7%	2730
	21st to end	Day	22% 5% 13% 27% 24% 9%	2730
July	1st to 10th	Day	31% 5% 13% 30% 19% 2	7616
	11th to 20th	Day	28% 3 18% 30% 18% 2	7611
	21st to end	Day	12% 4 11% 37% 32% 3	8155
August	1st to 10th	Day	11% 3 10% 31% 34% 11%	5726
	11th to 20th	Day	13% 3 12% 38% 30% 3	5519
	21st to end	Day	19% 5% 14% 25% 31% 6%	6078
September	1st to 10th	Day	32% 5% 8% 21% 24% 10%	2352
	11th to 20th	Day	32% 6% 10% 22% 23% 6%	2233
	21st to end	Day	26% 5% 8% 20% 28% 14%	2200
October	1st to 10th	Day	13% 3 7% 14% 33% 30%	3590
	11th to 20th	Day	21% 2 5% 23% 24% 25%	3487
	21st to end	Day	16% 3 3 25% 39% 15%	3538
November	1st to 10th	Day	24% 4 7% 21% 28% 17%	1874
	11th to 20th	Day	19% 3 8% 22% 29% 19%	1890
	21st to end	Day	30% 3 5% 19% 28% 15%	1890
December	1st to 10th	Day	35% 3 4 19% 27% 11%	3030
	11th to 20th	Day	26% 5% 7% 15% 28% 18%	3479
	21st to end	Day	24% 3 3 22% 31% 18%	4587
January	1st to 10th	Night	26% 2 4 21% 34% 12%	7635
	11th to 20th	Night	17% 2 4 19% 36% 22%	7680
	21st to end	Night	36% 3 5% 15% 25% 16%	7848
February	1st to 10th	Night	28% 3 5% 15% 28% 21%	2520
	11th to 20th	Night	32% 3 8% 17% 23% 18%	2458
	21st to end	Night	25% 3 4 15% 27% 25%	2076
March	1st to 10th	Night	27% 3 3 14% 27% 26%	5405
	11th to 20th	Night	25% 3 8% 14% 16% 33%	5090
	21st to end	Night	24% 4 6% 20% 29% 17%	5588
April	1st to 10th	Night	26% 4 10% 20% 17% 22%	2231
	11th to 20th	Night	29% 5% 9% 17% 22% 18%	2077
	21st to end	Night	25% 4 11% 22% 26% 12%	2022
May	1st to 10th	Night	34% 4 10% 22% 19% 13%	5293
	11th to 20th	Night	26% 5% 8% 19% 28% 15%	5266
	21st to end	Night	35% 5% 15% 19% 14% 11%	5805
June	1st to 10th	Night	18% 8% 16% 31% 22% 4	1890
	11th to 20th	Night	17% 5% 13% 32% 25% 8%	1890
	21st to end	Night	18% 4 13% 30% 25% 10%	1890
July	1st to 10th	Night	27% 4 11% 36% 20% 2	5265
	11th to 20th	Night	21% 4 15% 33% 24% 3	5256
	21st to end	Night	10% 3 12% 37% 36% 2	5641
August	1st to 10th	Night	9% 2 8% 31% 39% 11%	4401
	11th to 20th	Night	10% 3 13% 39% 30% 5%	4613
	21st to end	Night	16% 4 15% 26% 32% 5%	5069
September	1st to 10th	Night	25% 5% 10% 23% 25% 12%	2265
	11th to 20th	Night	28% 6% 12% 24% 22% 7%	2233
	21st to end	Night	23% 4 8% 24% 25% 16%	2200
October	1st to 10th	Night	10% 3 7% 14% 32% 34%	3590
	11th to 20th	Night	17% 2 7% 19% 28% 26%	3616
	21st to end	Night	17% 3 4 23% 38% 15%	4252
November	1st to 10th	Night	24% 3 7% 20% 27% 20%	2640
	11th to 20th	Night	19% 4 7% 21% 30% 19%	2730
	21st to end	Night	30% 3 5% 16% 29% 15%	2730
December	1st to 10th	Night	32% 3 5% 21% 26% 14%	4380
	11th to 20th	Night	26% 4 6% 17% 28% 18%	4947
	21st to end	Night	27% 3 4 23% 25% 19%	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	10% 15% 43% 28% 4 1	330
	11th to 20th	Day	13% 17% 36% 25% 8% 2	330
	21st to end	Day	13% 16% 39% 24% 7%	363
February	1st to 10th	Day	15% 14% 41% 24% 6%	330
	11th to 20th	Day	17% 17% 42% 19% 4	330
	21st to end	Day	16% 17% 46% 16% 4	273
March	1st to 10th	Day	13% 18% 41% 24% 4	330
	11th to 20th	Day	17% 17% 37% 24% 5% 1	330
	21st to end	Day	11% 16% 45% 24% 4	363
April	1st to 10th	Day	12% 16% 45% 21% 6%	403
	11th to 20th	Day	14% 21% 46% 16% 3 1	532
	21st to end	Day	10% 17% 44% 22% 6%	614
May	1st to 10th	Day	9% 13% 41% 31% 5% 1	753
	11th to 20th	Day	12% 11% 34% 29% 12% 4	775
	21st to end	Day	9% 7% 37% 34% 13% 1	844
June	1st to 10th	Day	5% 4 26% 42% 20% 3	780
	11th to 20th	Day	4 2 26% 47% 17% 4	780
	21st to end	Day	3 2 16% 39% 33% 6%	780
July	1st to 10th	Day	7% 1 8% 38% 35% 10%	771
	11th to 20th	Day	4 1 7% 38% 40% 10%	768
	21st to end	Day	1 1 6% 34% 43% 15%	849
August	1st to 10th	Day	3 4 34% 44% 15%	658
	11th to 20th	Day	5% 2 6% 34% 40% 12%	557
	21st to end	Day	3 2 6% 37% 40% 13%	627
September	1st to 10th	Day	11% 1 7% 28% 36% 16%	402
	11th to 20th	Day	4 1 8% 36% 34% 17%	339
	21st to end	Day	13% 3 9% 29% 34% 12%	330
October	1st to 10th	Day	3 2 16% 39% 31% 9%	330
	11th to 20th	Day	8% 5% 35% 35% 14% 2	330
	21st to end	Day	16% 9% 26% 31% 15% 2	363
November	1st to 10th	Day	13% 7% 30% 34% 14% 2	330
	11th to 20th	Day	11% 12% 29% 31% 14% 3	330
	21st to end	Day	13% 17% 40% 18% 10% 2	330
December	1st to 10th	Day	15% 12% 37% 25% 8% 2	330
	11th to 20th	Day	7% 14% 44% 27% 7% 1	330
	21st to end	Day	14% 14% 37% 30% 4	363
January	1st to 10th	Night	10% 11% 41% 31% 7%	1050
	11th to 20th	Night	11% 12% 38% 32% 8%	1050
	21st to end	Night	10% 13% 42% 30% 5%	961
February	1st to 10th	Night	12% 9% 48% 26% 5%	840
	11th to 20th	Night	13% 16% 43% 25% 4	824
	21st to end	Night	11% 15% 50% 21% 3	692
March	1st to 10th	Night	11% 15% 45% 26% 4	803
	11th to 20th	Night	13% 15% 40% 27% 5%	630
	21st to end	Night	5% 16% 52% 25% 2	693
April	1st to 10th	Night	7% 14% 52% 23% 4	630
	11th to 20th	Night	10% 16% 52% 21% 2	623
	21st to end	Night	9% 12% 53% 22% 5%	630
May	1st to 10th	Night	6% 11% 52% 27% 4	630
	11th to 20th	Night	8% 8% 44% 29% 9% 1	621
	21st to end	Night	6% 7% 45% 34% 8%	683
June	1st to 10th	Night	3 3 36% 45% 12%	630
	11th to 20th	Night	3 2 41% 48% 5%	630
	21st to end	Night	3 2 27% 49% 18% 1	630
July	1st to 10th	Night	5% 2 15% 53% 24% 2	615
	11th to 20th	Night	3 1 12% 54% 29% 1	612
	21st to end	Night	1 7% 59% 31% 1	690
August	1st to 10th	Night	1 8% 58% 31% 1	627
	11th to 20th	Night	4 11% 49% 35% 2	624
	21st to end	Night	2 1 9% 47% 38% 3	693
September	1st to 10th	Night	8% 1 11% 48% 29% 3	630
	11th to 20th	Night	9% 1 13% 48% 28% 1	609
	21st to end	Night	9% 1 20% 44% 26% 1	600
October	1st to 10th	Night	4 3 26% 47% 19% 2	600
	11th to 20th	Night	8% 5% 34% 40% 13% 1	621
	21st to end	Night	10% 9% 31% 36% 13% 1	880
November	1st to 10th	Night	10% 6% 34% 36% 14% 1	1000
	11th to 20th	Night	5% 10% 37% 38% 10% 1	1050
	21st to end	Night	12% 11% 37% 30% 10%	1050
December	1st to 10th	Night	12% 10% 35% 37% 6%	1050
	11th to 20th	Night	10% 11% 41% 32% 6%	1050
	21st to end	Night	10% 10% 41% 32% 7%	1155

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

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