Texas Yard Canon Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Texas Yard Canon Observatory clear sky chart from 2005-11-06 to 2025-12-18.

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% 9% 3 8% 5% 4 5% 4 6% 7% 38%	127212
	Night	13% 10% 4 8% 5% 4 4 3 5% 6% 39%	124059
Transparency	Day	43% 7% 12% 24% 13% 1	130709
	Night	44% 6% 12% 22% 14% 2	128622
Seeing	Day	16% 12% 30% 25% 12% 5%	17401
	Night	17% 10% 31% 29% 12% 1	27277

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	8% 12% 6% 15% 6% 6% 6% 4 5% 6% 26%	3617
	11th to 20th	Day	8% 12% 7% 12% 4 3 4 6% 6% 6% 31%	3620
	21st to end	Day	12% 15% 7% 9% 4 3 3 3 4 6% 34%	4046
February	1st to 10th	Day	11% 14% 6% 10% 5% 5% 5% 4 4 7% 30%	1800
	11th to 20th	Day	12% 12% 3 7% 5% 5% 5% 4 5% 5% 36%	1945
	21st to end	Day	11% 15% 4 11% 5% 5% 4 4 5% 5% 30%	1650
March	1st to 10th	Day	14% 9% 3 7% 4 3 4 3 5% 6% 43%	4480
	11th to 20th	Day	11% 7% 2 7% 5% 4 5% 4 5% 7% 43%	4689
	21st to end	Day	20% 12% 5% 10% 5% 4 4 3 4 5% 27%	5967
April	1st to 10th	Day	17% 14% 3 7% 5% 5% 5% 4 6% 5% 30%	2400
	11th to 20th	Day	14% 11% 3 7% 5% 4 5% 4 6% 7% 34%	2374
	21st to end	Day	18% 10% 3 7% 4 4 4 4 5% 6% 34%	2521
May	1st to 10th	Day	14% 9% 2 7% 4 4 4 3 6% 7% 39%	5862
	11th to 20th	Day	13% 6% 3 6% 5% 5% 5% 4 6% 8% 40%	6319
	21st to end	Day	16% 7% 2 6% 4 4 5% 4 6% 9% 37%	6935
June	1st to 10th	Day	9% 6% 2 6% 5% 5% 5% 4 5% 9% 45%	2800
	11th to 20th	Day	11% 6% 2 6% 5% 4 4 4 7% 9% 43%	2800
	21st to end	Day	11% 6% 2 6% 5% 5% 4 5% 7% 8% 41%	2800
July	1st to 10th	Day	10% 8% 2 7% 5% 5% 5% 5% 7% 9% 37%	6360
	11th to 20th	Day	7% 5% 2 6% 4 5% 6% 5% 6% 9% 45%	6360
	21st to end	Day	8% 6% 2 7% 5% 5% 5% 4 6% 9% 42%	6924
August	1st to 10th	Day	9% 6% 2 6% 5% 4 6% 5% 7% 10% 41%	4544
	11th to 20th	Day	11% 5% 2 6% 4 4 5% 4 7% 8% 43%	3895
	21st to end	Day	8% 6% 3 7% 4 4 5% 3 6% 9% 46%	4312
September	1st to 10th	Day	11% 6% 2 7% 4 5% 5% 4 6% 8% 44%	2400
	11th to 20th	Day	11% 5% 2 5% 3 3 4 3 6% 9% 50%	2287
	21st to end	Day	12% 6% 2 7% 4 4 4 4 7% 6% 44%	2200
October	1st to 10th	Day	14% 6% 2 6% 4 3 4 3 6% 6% 47%	2119
	11th to 20th	Day	19% 8% 3 8% 5% 4 5% 4 5% 7% 33%	1980
	21st to end	Day	17% 9% 3 8% 4 5% 4 2 5% 6% 38%	1980
November	1st to 10th	Day	12% 10% 3 6% 5% 4 4 3 5% 6% 43%	1852
	11th to 20th	Day	12% 12% 5% 9% 6% 5% 4 4 5% 7% 32%	1890
	21st to end	Day	17% 12% 3 8% 5% 3 4 2 4 6% 35%	1748
December	1st to 10th	Day	8% 7% 4 10% 7% 6% 5% 4 6% 8% 37%	2690
	11th to 20th	Day	12% 15% 5% 11% 6% 5% 5% 4 7% 7% 25%	3064
	21st to end	Day	21% 22% 8% 11% 5% 4 4 3 4 4 15%	3982
January	1st to 10th	Night	10% 11% 7% 12% 6% 5% 4 3 4 5% 33%	6348
	11th to 20th	Night	10% 14% 6% 13% 7% 5% 6% 5% 6% 5% 23%	6360
	21st to end	Night	13% 14% 7% 10% 5% 4 4 3 4 5% 31%	6927
February	1st to 10th	Night	12% 14% 5% 10% 6% 5% 4 3 4 5% 33%	2600
	11th to 20th	Night	12% 11% 3 7% 5% 5% 4 4 6% 5% 39%	2340
	21st to end	Night	16% 11% 3 8% 4 4 4 4 5% 6% 35%	1980
March	1st to 10th	Night	16% 9% 3 6% 4 4 4 3 4 5% 43%	5373
	11th to 20th	Night	9% 7% 2 5% 4 4 4 4 5% 9% 47%	5314
	21st to end	Night	19% 12% 5% 10% 5% 4 4 3 4 5% 29%	4962
April	1st to 10th	Night	16% 10% 3 6% 4 4 5% 3 5% 7% 36%	2000
	11th to 20th	Night	19% 9% 3 7% 5% 4 4 4 4 5% 37%	1975
	21st to end	Night	18% 9% 3 5% 3 4 4 4 5% 6% 39%	1877
May	1st to 10th	Night	17% 8% 3 6% 4 4 4 4 5% 7% 38%	4016
	11th to 20th	Night	11% 6% 3 7% 5% 4 4 4 6% 6% 44%	3596
	21st to end	Night	15% 8% 3 6% 4 4 4 3 6% 6% 40%	3942
June	1st to 10th	Night	9% 5% 2 6% 5% 4 4 4 7% 7% 48%	1600
	11th to 20th	Night	11% 6% 2 6% 4 4 4 4 7% 8% 44%	1600
	21st to end	Night	9% 6% 2 6% 6% 4 4 4 6% 8% 45%	1600
July	1st to 10th	Night	10% 7% 3 6% 4 4 4 4 6% 8% 44%	3618
	11th to 20th	Night	6% 5% 2 5% 4 3 4 3 6% 9% 52%	3617
	21st to end	Night	6% 4 2 6% 4 5% 5% 4 7% 9% 49%	3947
August	1st to 10th	Night	9% 5% 2 5% 4 4 4 3 5% 9% 50%	2614
	11th to 20th	Night	10% 6% 2 6% 4 3 4 3 6% 8% 48%	3138
	21st to end	Night	8% 5% 2 5% 4 3 5% 3 6% 9% 51%	3586
September	1st to 10th	Night	7% 5% 2 6% 4 3 3 4 5% 6% 54%	2000
	11th to 20th	Night	10% 4 2 5% 3 3 4 3 5% 7% 53%	2092
	21st to end	Night	12% 6% 2 6% 4 5% 3 3 5% 6% 48%	2200
October	1st to 10th	Night	11% 6% 3 6% 4 3 4 3 5% 6% 50%	2279
	11th to 20th	Night	17% 7% 2 5% 4 4 4 3 4 6% 43%	2420
	21st to end	Night	18% 8% 2 6% 5% 3 4 3 5% 7% 37%	2860
November	1st to 10th	Night	13% 8% 3 6% 4 4 3 4 4 6% 46%	2666
	11th to 20th	Night	14% 10% 4 8% 5% 5% 5% 3 5% 6% 36%	2730
	21st to end	Night	16% 11% 4 7% 5% 4 4 4 5% 6% 35%	2868
December	1st to 10th	Night	9% 9% 3 7% 4 5% 4 4 5% 7% 41%	4720
	11th to 20th	Night	16% 15% 5% 10% 6% 5% 5% 3 5% 5% 27%	5298
	21st to end	Night	20% 20% 6% 11% 5% 5% 4 3 4 5% 18%	6996

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	57% 6% 12% 17% 7%	3618
	11th to 20th	Day	51% 6% 11% 13% 17% 2	3620
	21st to end	Day	52% 5% 9% 21% 13%	4046
February	1st to 10th	Day	54% 7% 12% 17% 10% 1	1800
	11th to 20th	Day	49% 6% 11% 23% 10% 2	1955
	21st to end	Day	54% 6% 10% 17% 10% 2	1650
March	1st to 10th	Day	41% 6% 10% 25% 12% 5%	4480
	11th to 20th	Day	39% 6% 14% 27% 13% 2	4689
	21st to end	Day	58% 7% 12% 13% 9% 1	5969
April	1st to 10th	Day	55% 7% 10% 18% 10%	2400
	11th to 20th	Day	48% 7% 11% 19% 12% 3	2374
	21st to end	Day	48% 9% 12% 18% 12% 1	2521
May	1st to 10th	Day	41% 8% 12% 23% 15% 1	5897
	11th to 20th	Day	39% 10% 12% 25% 14% 1	6323
	21st to end	Day	39% 9% 13% 25% 12% 2	6949
June	1st to 10th	Day	35% 8% 14% 25% 17% 2	2800
	11th to 20th	Day	35% 7% 15% 24% 17% 2	2800
	21st to end	Day	38% 9% 14% 22% 15% 2	2800
July	1st to 10th	Day	39% 7% 13% 29% 10% 1	6291
	11th to 20th	Day	33% 8% 15% 29% 15% 1	6285
	21st to end	Day	36% 9% 15% 22% 17% 1	6728
August	1st to 10th	Day	36% 9% 14% 29% 11% 1	4529
	11th to 20th	Day	34% 9% 14% 31% 12% 1	3932
	21st to end	Day	34% 7% 13% 25% 19% 1	4311
September	1st to 10th	Day	36% 8% 13% 26% 16% 2	2400
	11th to 20th	Day	31% 6% 14% 31% 17% 2	2287
	21st to end	Day	37% 7% 12% 29% 15% 1	2200
October	1st to 10th	Day	24% 4 7% 40% 24% 1	3444
	11th to 20th	Day	35% 5% 11% 27% 21% 1	3208
	21st to end	Day	41% 5% 10% 28% 13% 3	3180
November	1st to 10th	Day	41% 6% 13% 24% 14% 1	1852
	11th to 20th	Day	51% 7% 12% 20% 9% 1	1890
	21st to end	Day	51% 5% 13% 24% 7%	1748
December	1st to 10th	Day	43% 6% 21% 23% 6%	2690
	11th to 20th	Day	56% 6% 12% 17% 7% 1	3061
	21st to end	Day	72% 5% 7% 9% 6%	3982
January	1st to 10th	Night	52% 6% 8% 21% 12%	6348
	11th to 20th	Night	59% 6% 9% 9% 15% 1	6360
	21st to end	Night	54% 6% 13% 15% 11%	6927
February	1st to 10th	Night	52% 6% 11% 17% 12% 2	2600
	11th to 20th	Night	45% 6% 12% 21% 15% 1	2341
	21st to end	Night	49% 5% 12% 19% 11% 4	1980
March	1st to 10th	Night	44% 5% 12% 23% 12% 4	5373
	11th to 20th	Night	33% 6% 14% 30% 13% 4	5314
	21st to end	Night	57% 6% 9% 15% 11% 1	4962
April	1st to 10th	Night	45% 9% 10% 20% 15% 1	2000
	11th to 20th	Night	49% 5% 7% 19% 16% 3	1975
	21st to end	Night	43% 9% 13% 20% 15% 1	1877
May	1st to 10th	Night	43% 7% 13% 18% 17% 2	4043
	11th to 20th	Night	37% 8% 15% 21% 15% 3	3597
	21st to end	Night	42% 8% 10% 22% 13% 5%	3950
June	1st to 10th	Night	32% 8% 13% 27% 18% 2	1600
	11th to 20th	Night	36% 6% 13% 23% 21% 2	1600
	21st to end	Night	35% 8% 16% 22% 17% 3	1600
July	1st to 10th	Night	37% 6% 14% 30% 11% 3	3580
	11th to 20th	Night	27% 7% 15% 31% 19% 2	3572
	21st to end	Night	29% 9% 14% 24% 22% 2	3832
August	1st to 10th	Night	30% 8% 15% 28% 18% 1	2605
	11th to 20th	Night	32% 8% 13% 33% 14% 1	3166
	21st to end	Night	29% 7% 13% 28% 20% 3	3586
September	1st to 10th	Night	30% 7% 12% 27% 23% 2	2000
	11th to 20th	Night	30% 6% 10% 32% 20% 2	2092
	21st to end	Night	37% 5% 10% 30% 17% 1	2200
October	1st to 10th	Night	25% 5% 7% 38% 25% 1	3721
	11th to 20th	Night	35% 6% 11% 25% 22% 2	3931
	21st to end	Night	41% 5% 9% 26% 17% 2	4610
November	1st to 10th	Night	39% 6% 10% 26% 17% 2	2666
	11th to 20th	Night	48% 6% 13% 20% 11% 2	2730
	21st to end	Night	49% 6% 14% 21% 9% 1	2868
December	1st to 10th	Night	42% 6% 15% 26% 8% 3	4720
	11th to 20th	Night	58% 6% 9% 15% 10% 1	5300
	21st to end	Night	67% 5% 9% 13% 6%	6996

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	15% 19% 36% 23% 5% 1	300
	11th to 20th	Day	18% 20% 39% 19% 3 1	300
	21st to end	Day	21% 18% 39% 18% 4 1	330
February	1st to 10th	Day	15% 21% 43% 16% 5% 1	300
	11th to 20th	Day	22% 23% 37% 16% 3	300
	21st to end	Day	22% 24% 40% 12% 2	249
March	1st to 10th	Day	18% 24% 41% 14% 3	300
	11th to 20th	Day	24% 22% 31% 18% 4 1	315
	21st to end	Day	26% 16% 30% 20% 6% 2	550
April	1st to 10th	Day	25% 16% 34% 21% 4	500
	11th to 20th	Day	22% 22% 25% 19% 10% 2	492
	21st to end	Day	22% 14% 30% 21% 12% 1	500
May	1st to 10th	Day	20% 12% 33% 25% 8% 2	503
	11th to 20th	Day	21% 12% 30% 25% 10% 3	725
	21st to end	Day	17% 10% 30% 25% 12% 5%	789
June	1st to 10th	Day	9% 9% 33% 31% 14% 5%	730
	11th to 20th	Day	14% 8% 30% 31% 12% 5%	730
	21st to end	Day	14% 8% 32% 31% 12% 4	730
July	1st to 10th	Day	8% 4 22% 31% 25% 9%	721
	11th to 20th	Day	9% 6% 26% 34% 17% 7%	718
	21st to end	Day	6% 4 28% 38% 16% 8%	794
August	1st to 10th	Day	8% 3 22% 37% 19% 11%	720
	11th to 20th	Day	12% 5% 17% 30% 24% 12%	519
	21st to end	Day	8% 6% 22% 31% 25% 8%	583
September	1st to 10th	Day	13% 8% 22% 28% 20% 9%	530
	11th to 20th	Day	10% 4 20% 30% 25% 11%	530
	21st to end	Day	16% 10% 23% 26% 17% 8%	530
October	1st to 10th	Day	16% 10% 27% 26% 16% 5%	449
	11th to 20th	Day	22% 19% 31% 21% 8%	330
	21st to end	Day	25% 15% 35% 19% 4 1	363
November	1st to 10th	Day	18% 19% 33% 21% 8% 1	330
	11th to 20th	Day	22% 20% 34% 18% 6%	330
	21st to end	Day	24% 15% 40% 17% 4	330
December	1st to 10th	Day	18% 19% 41% 15% 6% 1	330
	11th to 20th	Day	17% 21% 37% 17% 7% 1	321
	21st to end	Day	27% 22% 33% 15% 2 2	330
January	1st to 10th	Night	18% 18% 36% 22% 6%	1000
	11th to 20th	Night	20% 15% 37% 22% 6% 1	1000
	21st to end	Night	19% 12% 39% 25% 6%	1100
February	1st to 10th	Night	21% 13% 37% 24% 5%	1000
	11th to 20th	Night	18% 17% 36% 24% 4	785
	21st to end	Night	24% 13% 40% 19% 4	660
March	1st to 10th	Night	21% 13% 36% 23% 7% 1	800
	11th to 20th	Night	16% 15% 37% 25% 7%	767
	21st to end	Night	22% 9% 32% 29% 7% 1	660
April	1st to 10th	Night	21% 12% 36% 25% 6%	600
	11th to 20th	Night	21% 14% 31% 25% 7% 1	593
	21st to end	Night	22% 10% 31% 27% 10% 1	600
May	1st to 10th	Night	19% 9% 34% 32% 6% 1	600
	11th to 20th	Night	18% 6% 31% 34% 12% 1	591
	21st to end	Night	14% 6% 27% 35% 18% 1	650
June	1st to 10th	Night	10% 5% 27% 43% 15% 1	600
	11th to 20th	Night	14% 4 33% 36% 14% 1	600
	21st to end	Night	10% 5% 28% 42% 15% 1	600
July	1st to 10th	Night	8% 2 18% 40% 29% 3	585
	11th to 20th	Night	9% 3 22% 40% 24% 3	582
	21st to end	Night	6% 3 18% 47% 25% 2	657
August	1st to 10th	Night	7% 2 15% 48% 26% 2	597
	11th to 20th	Night	10% 3 15% 39% 28% 5%	594
	21st to end	Night	10% 2 18% 39% 28% 3	660
September	1st to 10th	Night	8% 4 22% 36% 24% 6%	600
	11th to 20th	Night	11% 4 21% 30% 29% 4	692
	21st to end	Night	14% 7% 26% 30% 21% 3	800
October	1st to 10th	Night	14% 7% 28% 32% 18% 2	800
	11th to 20th	Night	21% 11% 32% 27% 9%	800
	21st to end	Night	23% 10% 31% 25% 10%	880
November	1st to 10th	Night	17% 12% 37% 24% 9% 1	820
	11th to 20th	Night	19% 16% 35% 23% 6%	840
	21st to end	Night	22% 15% 35% 22% 6%	978
December	1st to 10th	Night	20% 16% 39% 21% 4	1050
	11th to 20th	Night	23% 14% 36% 22% 5%	1036
	21st to end	Night	30% 14% 34% 20% 3	1100

Page generated at 2025-12-15 00:13:54. Version ac07

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