Alibates Flint Quarries Visitor Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Alibates Flint Quarries Visitor Center clear sky chart from 2005-11-06 to 2025-02-21.

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	5% 4 2 4 3 3 3 3 5% 7% 62%	113705
	Night	5% 4 1 4 3 3 4 3 5% 7% 60%	113489
Transparency	Day	22% 5% 9% 22% 28% 14%	113460
	Night	22% 5% 9% 21% 28% 15%	113324
Seeing	Day	7% 7% 29% 33% 19% 5%	15660
	Night	7% 8% 39% 36% 10%	25765

By Month

Percentage Cloud Cover SW (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	7% 9% 2 6% 4 3 3 2 4 5% 55%	3903
	11th to 20th	Day	4 5% 1 4 2 3 2 2 3 5% 69%	4080
	21st to end	Day	6% 5% 2 6% 3 3 3 3 4 6% 59%	4966
February	1st to 10th	Day	5% 7% 2 5% 3 3 3 3 5% 5% 59%	2000
	11th to 20th	Day	5% 7% 2 6% 4 3 3 3 5% 6% 57%	1949
	21st to end	Day	4 4 1 4 3 3 4 3 5% 6% 62%	1570
March	1st to 10th	Day	4 5% 1 3 2 2 3 3 4 7% 65%	3130
	11th to 20th	Day	7% 5% 2 6% 4 3 3 2 4 6% 59%	3343
	21st to end	Day	6% 6% 3 6% 4 4 4 3 6% 6% 52%	3991
April	1st to 10th	Day	6% 2 1 3 2 3 3 3 4 6% 66%	2280
	11th to 20th	Day	7% 5% 2 4 2 3 3 3 5% 6% 60%	2251
	21st to end	Day	7% 3 1 4 3 2 3 2 6% 7% 62%	2308
May	1st to 10th	Day	8% 4 1 3 3 3 4 3 4 6% 61%	4120
	11th to 20th	Day	7% 4 2 4 3 3 3 3 5% 6% 59%	4082
	21st to end	Day	6% 3 1 4 2 2 3 3 4 5% 66%	4489
June	1st to 10th	Day	5% 3 1 4 3 5% 4 4 7% 8% 55%	2470
	11th to 20th	Day	3 2 1 3 2 3 4 3 6% 7% 65%	2587
	21st to end	Day	2 3 1 3 3 3 4 4 7% 9% 60%	2660
July	1st to 10th	Day	7% 4 2 4 3 4 4 4 6% 8% 55%	4430
	11th to 20th	Day	3 2 1 4 3 4 4 4 6% 8% 61%	4223
	21st to end	Day	3 2 1 4 3 4 4 3 6% 9% 62%	4466
August	1st to 10th	Day	3 2 1 4 3 4 5% 4 6% 8% 57%	3862
	11th to 20th	Day	3 2 1 3 3 3 3 3 6% 9% 65%	3726
	21st to end	Day	5% 3 1 4 3 4 4 4 7% 10% 55%	4180
September	1st to 10th	Day	6% 4 2 4 4 4 4 3 6% 7% 58%	2263
	11th to 20th	Day	7% 4 1 4 3 3 3 3 4 7% 59%	2090
	21st to end	Day	6% 3 1 3 2 3 3 2 4 6% 67%	2090
October	1st to 10th	Day	6% 3 1 2 2 1 2 1 3 4 74%	3480
	11th to 20th	Day	7% 5% 2 5% 2 3 3 2 4 5% 63%	3412
	21st to end	Day	4 3 1 2 2 2 2 2 2 4 77%	3122
November	1st to 10th	Day	5% 4 1 3 2 3 2 2 4 6% 69%	1763
	11th to 20th	Day	2 4 1 3 2 3 2 2 4 6% 70%	1800
	21st to end	Day	8% 5% 2 4 2 3 2 3 3 6% 64%	1800
December	1st to 10th	Day	3 2 1 3 2 2 3 3 5% 6% 71%	2940
	11th to 20th	Day	4 4 1 3 3 4 4 3 4 6% 64%	3391
	21st to end	Day	5% 7% 3 6% 4 3 3 3 3 5% 58%	4488
January	1st to 10th	Night	5% 8% 3 6% 4 4 3 3 5% 6% 53%	5888
	11th to 20th	Night	2 3 1 5% 3 4 4 3 4 6% 65%	5900
	21st to end	Night	5% 5% 2 5% 4 3 3 3 5% 6% 58%	6053
February	1st to 10th	Night	5% 5% 2 5% 4 3 3 3 4 5% 60%	2400
	11th to 20th	Night	6% 6% 2 5% 5% 4 3 3 4 6% 56%	2338
	21st to end	Night	6% 3 1 4 3 4 4 3 5% 8% 60%	1884
March	1st to 10th	Night	3 6% 2 4 3 3 3 3 4 5% 66%	3734
	11th to 20th	Night	7% 4 2 5% 3 4 4 3 5% 7% 57%	3619
	21st to end	Night	4 4 2 4 4 4 4 3 5% 7% 58%	3642
April	1st to 10th	Night	5% 3 1 3 2 2 3 3 5% 8% 65%	1900
	11th to 20th	Night	8% 3 1 4 3 3 3 4 5% 6% 59%	1877
	21st to end	Night	7% 4 1 3 3 3 3 3 4 8% 60%	1872
May	1st to 10th	Night	8% 4 1 4 2 3 3 3 5% 6% 61%	2850
	11th to 20th	Night	8% 4 1 5% 4 4 4 4 5% 7% 55%	2823
	21st to end	Night	6% 4 2 4 3 3 3 3 4 6% 62%	3098
June	1st to 10th	Night	5% 2 1 3 3 3 4 4 8% 13% 54%	1710
	11th to 20th	Night	3 2 1 2 3 3 4 3 8% 9% 61%	1586
	21st to end	Night	4 2 1 4 3 4 5% 4 6% 8% 59%	1520
July	1st to 10th	Night	5% 3 2 5% 5% 5% 5% 4 7% 9% 51%	2540
	11th to 20th	Night	3 3 2 5% 5% 5% 5% 5% 7% 9% 50%	2739
	21st to end	Night	3 3 1 4 3 4 5% 4 9% 12% 53%	3097
August	1st to 10th	Night	4 3 1 5% 4 5% 6% 5% 8% 12% 46%	3059
	11th to 20th	Night	4 3 1 5% 4 5% 5% 5% 7% 12% 49%	3113
	21st to end	Night	4 3 1 4 3 5% 5% 5% 9% 12% 49%	3487
September	1st to 10th	Night	5% 3 1 4 3 3 4 3 6% 8% 59%	1915
	11th to 20th	Night	7% 4 2 4 4 3 4 3 5% 7% 58%	2090
	21st to end	Night	5% 2 1 3 2 2 3 3 5% 6% 68%	2090
October	1st to 10th	Night	4 2 1 3 1 2 2 2 3 4 75%	3480
	11th to 20th	Night	5% 4 1 5% 3 3 3 3 4 4 65%	3491
	21st to end	Night	5% 3 1 3 2 2 2 2 3 4 73%	4403
November	1st to 10th	Night	5% 3 1 2 2 2 2 2 4 7% 70%	2535
	11th to 20th	Night	3 2 1 3 3 3 3 2 3 5% 73%	2600
	21st to end	Night	6% 4 1 3 2 3 3 2 4 7% 64%	2600
December	1st to 10th	Night	3 3 1 3 2 2 3 2 4 6% 70%	4250
	11th to 20th	Night	3 3 1 4 3 2 3 2 5% 7% 67%	4816
	21st to end	Night	5% 5% 1 4 3 3 4 3 5% 7% 58%	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	32% 3 6% 25% 27% 6%	3904
	11th to 20th	Day	19% 3 7% 21% 33% 17%	4080
	21st to end	Day	26% 4 6% 21% 33% 10%	4966
February	1st to 10th	Day	26% 4 9% 23% 25% 14%	2000
	11th to 20th	Day	28% 4 7% 25% 24% 12%	1959
	21st to end	Day	22% 3 6% 19% 33% 17%	1570
March	1st to 10th	Day	20% 4 6% 17% 25% 29%	3130
	11th to 20th	Day	26% 5% 8% 23% 28% 10%	3343
	21st to end	Day	27% 9% 9% 20% 24% 11%	3991
April	1st to 10th	Day	20% 3 7% 19% 28% 22%	2280
	11th to 20th	Day	24% 5% 8% 19% 24% 19%	2254
	21st to end	Day	21% 5% 10% 24% 27% 11%	2308
May	1st to 10th	Day	22% 7% 9% 19% 22% 21%	4120
	11th to 20th	Day	23% 8% 10% 21% 26% 12%	4086
	21st to end	Day	20% 7% 10% 18% 21% 24%	4489
June	1st to 10th	Day	23% 9% 15% 27% 17% 10%	2470
	11th to 20th	Day	17% 6% 11% 20% 27% 18%	2587
	21st to end	Day	18% 7% 13% 28% 21% 13%	2660
July	1st to 10th	Day	26% 6% 11% 24% 26% 6%	4361
	11th to 20th	Day	19% 6% 12% 27% 29% 7%	4150
	21st to end	Day	19% 6% 12% 30% 26% 8%	4325
August	1st to 10th	Day	21% 7% 14% 28% 19% 11%	3849
	11th to 20th	Day	17% 6% 9% 23% 34% 11%	3762
	21st to end	Day	23% 6% 12% 29% 25% 6%	4179
September	1st to 10th	Day	26% 6% 11% 20% 24% 12%	2263
	11th to 20th	Day	26% 5% 9% 20% 31% 9%	2090
	21st to end	Day	20% 3 9% 22% 32% 14%	2090
October	1st to 10th	Day	16% 4 6% 13% 41% 21%	3480
	11th to 20th	Day	24% 4 8% 19% 29% 16%	3412
	21st to end	Day	14% 3 4 22% 38% 20%	3122
November	1st to 10th	Day	18% 3 8% 19% 35% 18%	1763
	11th to 20th	Day	17% 3 6% 26% 33% 15%	1800
	21st to end	Day	25% 3 6% 17% 32% 18%	1800
December	1st to 10th	Day	15% 4 7% 32% 30% 11%	2940
	11th to 20th	Day	22% 4 5% 18% 39% 13%	3389
	21st to end	Day	27% 6% 7% 23% 25% 12%	4488
January	1st to 10th	Night	31% 5% 7% 30% 23% 5%	5888
	11th to 20th	Night	18% 5% 9% 21% 30% 17%	5900
	21st to end	Night	24% 6% 9% 18% 32% 10%	6053
February	1st to 10th	Night	27% 3 7% 20% 27% 15%	2400
	11th to 20th	Night	30% 4 8% 18% 25% 15%	2338
	21st to end	Night	23% 3 5% 19% 29% 21%	1884
March	1st to 10th	Night	20% 5% 5% 16% 24% 30%	3734
	11th to 20th	Night	23% 8% 11% 21% 24% 14%	3619
	21st to end	Night	22% 8% 9% 25% 22% 14%	3642
April	1st to 10th	Night	17% 5% 9% 20% 25% 23%	1900
	11th to 20th	Night	24% 6% 9% 21% 23% 18%	1877
	21st to end	Night	22% 6% 11% 25% 22% 13%	1872
May	1st to 10th	Night	21% 8% 12% 17% 18% 24%	2850
	11th to 20th	Night	27% 10% 12% 17% 23% 12%	2824
	21st to end	Night	22% 8% 11% 15% 16% 28%	3099
June	1st to 10th	Night	20% 10% 18% 26% 16% 9%	1710
	11th to 20th	Night	16% 8% 14% 20% 24% 18%	1586
	21st to end	Night	20% 7% 15% 26% 19% 13%	1520
July	1st to 10th	Night	27% 8% 13% 30% 18% 4	2500
	11th to 20th	Night	27% 7% 13% 19% 28% 7%	2689
	21st to end	Night	21% 6% 12% 30% 25% 6%	2999
August	1st to 10th	Night	27% 6% 14% 21% 21% 10%	3049
	11th to 20th	Night	25% 7% 12% 22% 25% 9%	3143
	21st to end	Night	24% 7% 14% 28% 22% 6%	3487
September	1st to 10th	Night	22% 6% 12% 24% 23% 12%	1915
	11th to 20th	Night	26% 6% 10% 22% 26% 10%	2090
	21st to end	Night	16% 5% 9% 23% 30% 16%	2090
October	1st to 10th	Night	15% 3 5% 11% 38% 28%	3480
	11th to 20th	Night	21% 5% 8% 17% 29% 20%	3491
	21st to end	Night	17% 2 4 19% 40% 18%	4403
November	1st to 10th	Night	16% 4 8% 20% 33% 20%	2535
	11th to 20th	Night	15% 3 5% 24% 36% 17%	2600
	21st to end	Night	22% 3 5% 19% 31% 20%	2600
December	1st to 10th	Night	16% 3 7% 32% 35% 7%	4250
	11th to 20th	Night	18% 3 5% 18% 41% 16%	4817
	21st to end	Night	23% 5% 9% 22% 31% 11%	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	6% 13% 37% 34% 9% 1	300
	11th to 20th	Day	11% 15% 36% 27% 9% 1	300
	21st to end	Day	6% 9% 40% 32% 11% 2	330
February	1st to 10th	Day	8% 13% 35% 37% 7%	300
	11th to 20th	Day	11% 13% 43% 23% 8% 2	300
	21st to end	Day	12% 11% 53% 20% 5%	225
March	1st to 10th	Day	5% 10% 46% 31% 7% 1	270
	11th to 20th	Day	14% 14% 35% 24% 11% 1	270
	21st to end	Day	13% 16% 39% 22% 9% 1	397
April	1st to 10th	Day	10% 17% 42% 23% 7% 1	460
	11th to 20th	Day	10% 19% 41% 23% 7%	452
	21st to end	Day	10% 15% 39% 25% 10% 2	488
May	1st to 10th	Day	8% 11% 39% 32% 9% 1	653
	11th to 20th	Day	10% 8% 30% 34% 17% 2	675
	21st to end	Day	6% 9% 38% 32% 14% 1	734
June	1st to 10th	Day	6% 5% 26% 36% 21% 5%	680
	11th to 20th	Day	4 3 33% 40% 17% 4	680
	21st to end	Day	3 2 23% 44% 23% 5%	680
July	1st to 10th	Day	7% 1 15% 37% 27% 13%	671
	11th to 20th	Day	3 10% 44% 33% 10%	668
	21st to end	Day	4 1 11% 35% 38% 11%	739
August	1st to 10th	Day	3 1 13% 39% 35% 9%	539
	11th to 20th	Day	3 1 16% 38% 32% 10%	477
	21st to end	Day	7% 1 12% 39% 31% 9%	539
September	1st to 10th	Day	7% 1 14% 40% 29% 9%	473
	11th to 20th	Day	2 2 15% 46% 25% 10%	300
	21st to end	Day	7% 5% 22% 31% 27% 7%	300
October	1st to 10th	Day	11% 3 29% 30% 25% 3	300
	11th to 20th	Day	6% 7% 33% 32% 19% 3	300
	21st to end	Day	13% 8% 32% 28% 12% 5%	330
November	1st to 10th	Day	10% 7% 33% 33% 16% 2	300
	11th to 20th	Day	6% 11% 37% 31% 12% 3	300
	21st to end	Day	13% 12% 32% 28% 11% 4	300
December	1st to 10th	Day	5% 7% 39% 33% 14% 2	300
	11th to 20th	Day	9% 7% 36% 40% 8%	300
	21st to end	Day	13% 13% 45% 19% 9% 1	330
January	1st to 10th	Night	6% 10% 42% 36% 7%	1000
	11th to 20th	Night	8% 9% 40% 34% 9% 1	1000
	21st to end	Night	6% 6% 44% 35% 8%	910
February	1st to 10th	Night	7% 10% 45% 33% 5%	800
	11th to 20th	Night	9% 14% 45% 27% 4	784
	21st to end	Night	8% 14% 50% 25% 3	628
March	1st to 10th	Night	8% 11% 47% 30% 3	760
	11th to 20th	Night	9% 14% 42% 29% 6%	657
	21st to end	Night	7% 18% 51% 21% 2	627
April	1st to 10th	Night	7% 12% 56% 22% 2	570
	11th to 20th	Night	9% 12% 54% 23% 1	563
	21st to end	Night	8% 13% 49% 26% 3	570
May	1st to 10th	Night	8% 10% 48% 29% 4	570
	11th to 20th	Night	9% 8% 41% 35% 6% 1	561
	21st to end	Night	7% 7% 51% 28% 6%	617
June	1st to 10th	Night	5% 5% 44% 35% 10%	570
	11th to 20th	Night	4 6% 51% 34% 6%	570
	21st to end	Night	3 3 38% 44% 12%	570
July	1st to 10th	Night	4 2 26% 46% 21% 1	555
	11th to 20th	Night	3 1 20% 54% 22% 1	552
	21st to end	Night	3 19% 54% 21% 1	624
August	1st to 10th	Night	3 1 20% 51% 25% 1	567
	11th to 20th	Night	6% 2 20% 53% 18% 1	564
	21st to end	Night	4 1 21% 47% 26% 1	627
September	1st to 10th	Night	7% 1 22% 54% 16% 1	570
	11th to 20th	Night	8% 2 34% 42% 14%	570
	21st to end	Night	5% 3 34% 41% 16% 1	570
October	1st to 10th	Night	9% 4 37% 40% 9% 1	570
	11th to 20th	Night	7% 6% 42% 38% 6% 1	589
	21st to end	Night	8% 10% 34% 31% 16% 1	1005
November	1st to 10th	Night	6% 7% 38% 36% 11% 1	975
	11th to 20th	Night	4 11% 39% 37% 9%	1000
	21st to end	Night	8% 9% 36% 37% 11%	1000
December	1st to 10th	Night	8% 8% 38% 37% 9%	1000
	11th to 20th	Night	7% 10% 45% 33% 5%	1000
	21st to end	Night	10% 12% 39% 33% 6%	1100

Page generated at 2025-02-18 02:26:28. Version ac07

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