Hill County Star Watch Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hill County Star Watch Observatory clear sky chart from 2005-11-06 to 2026-06-01.

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	10% 6% 2 5% 4 4 4 3 5% 7% 50%	132534
	Night	10% 6% 2 5% 3 3 3 3 5% 7% 53%	130967
Transparency	Day	33% 4 9% 21% 20% 12%	136365
	Night	31% 4 10% 20% 21% 14%	135200
Seeing	Day	13% 8% 25% 31% 18% 4	16866
	Night	13% 8% 29% 35% 13% 1	26867

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	9% 5% 3 5% 3 2 3 3 4 5% 58%	5289
	11th to 20th	Day	11% 7% 2 4 2 2 3 2 4 5% 58%	5370
	21st to end	Day	18% 6% 2 6% 3 4 3 2 4 6% 46%	6468
February	1st to 10th	Day	12% 7% 2 5% 3 3 3 3 4 6% 51%	2100
	11th to 20th	Day	11% 7% 2 5% 3 3 4 3 5% 6% 49%	2049
	21st to end	Day	12% 6% 2 4 3 3 3 3 5% 6% 54%	1730
March	1st to 10th	Day	10% 7% 2 4 3 3 3 2 4 6% 56%	4812
	11th to 20th	Day	11% 7% 2 5% 3 3 3 3 3 5% 55%	5090
	21st to end	Day	9% 7% 2 5% 3 4 4 3 5% 6% 52%	5583
April	1st to 10th	Day	11% 6% 3 6% 4 3 4 4 5% 7% 46%	2310
	11th to 20th	Day	15% 6% 2 6% 4 4 4 3 4 6% 45%	2441
	21st to end	Day	11% 7% 3 6% 5% 4 3 3 4 6% 49%	2584
May	1st to 10th	Day	14% 7% 3 7% 4 5% 5% 4 5% 7% 40%	5992
	11th to 20th	Day	9% 6% 2 6% 4 4 5% 4 6% 8% 46%	5992
	21st to end	Day	12% 7% 2 6% 5% 5% 5% 5% 6% 9% 38%	6577
June	1st to 10th	Day	4 5% 2 5% 4 4 5% 4 6% 9% 52%	2601
	11th to 20th	Day	5% 5% 1 5% 5% 4 5% 5% 6% 9% 51%	2600
	21st to end	Day	5% 5% 2 5% 6% 6% 6% 5% 8% 9% 45%	2600
July	1st to 10th	Day	13% 7% 2 7% 5% 5% 6% 4 6% 8% 37%	5900
	11th to 20th	Day	5% 5% 2 5% 4 5% 5% 4 7% 9% 49%	5900
	21st to end	Day	6% 5% 2 5% 4 4 5% 4 7% 10% 49%	6422
August	1st to 10th	Day	1 2 1 3 3 4 3 3 5% 8% 68%	3981
	11th to 20th	Day	4 2 1 3 4 4 4 3 6% 9% 61%	3846
	21st to end	Day	4 4 2 5% 5% 5% 6% 4 6% 10% 49%	4261
September	1st to 10th	Day	9% 6% 2 7% 5% 5% 5% 3 5% 8% 44%	2200
	11th to 20th	Day	8% 6% 3 7% 6% 5% 6% 4 6% 8% 42%	2200
	21st to end	Day	8% 4 2 6% 4 4 4 5% 5% 7% 50%	2200
October	1st to 10th	Day	5% 4 2 4 3 4 4 4 6% 7% 57%	2200
	11th to 20th	Day	10% 5% 2 5% 4 3 3 3 4 6% 56%	2150
	21st to end	Day	10% 5% 2 4 3 3 2 2 3 5% 60%	2200
November	1st to 10th	Day	12% 7% 2 5% 3 3 3 2 6% 6% 51%	2008
	11th to 20th	Day	8% 4 2 5% 3 4 4 3 5% 6% 56%	1890
	21st to end	Day	12% 7% 3 6% 4 3 3 2 4 6% 50%	1890
December	1st to 10th	Day	21% 9% 3 6% 3 2 3 2 4 5% 43%	3030
	11th to 20th	Day	11% 8% 2 7% 4 4 4 4 5% 6% 46%	3481
	21st to end	Day	10% 6% 2 4 2 2 3 2 3 4 62%	4587
January	1st to 10th	Night	10% 5% 2 6% 2 3 3 2 3 5% 59%	7634
	11th to 20th	Night	9% 4 1 3 2 2 2 2 5% 6% 66%	7662
	21st to end	Night	24% 7% 2 5% 3 3 3 2 3 5% 44%	7746
February	1st to 10th	Night	11% 6% 2 5% 3 3 3 3 5% 5% 54%	2520
	11th to 20th	Night	13% 6% 2 6% 3 3 3 3 5% 6% 51%	2458
	21st to end	Night	12% 6% 3 5% 3 3 3 3 4 5% 52%	2076
March	1st to 10th	Night	8% 8% 2 5% 3 3 3 4 6% 8% 50%	5270
	11th to 20th	Night	10% 8% 2 5% 3 3 3 3 4 4 54%	5090
	21st to end	Night	10% 10% 2 5% 3 3 3 2 5% 5% 51%	5588
April	1st to 10th	Night	8% 7% 2 6% 4 4 4 4 5% 6% 51%	2310
	11th to 20th	Night	13% 8% 3 6% 3 3 4 3 4 5% 47%	2123
	21st to end	Night	13% 8% 2 5% 4 3 3 3 4 6% 49%	2032
May	1st to 10th	Night	17% 10% 3 7% 4 3 3 3 4 5% 41%	4143
	11th to 20th	Night	6% 6% 2 6% 4 4 4 3 5% 8% 51%	4143
	21st to end	Night	12% 7% 2 6% 3 4 4 4 7% 10% 41%	4542
June	1st to 10th	Night	3 3 1 3 2 3 3 3 7% 11% 60%	1800
	11th to 20th	Night	4 3 2 4 3 3 4 4 5% 8% 61%	1800
	21st to end	Night	4 5% 2 4 4 4 4 3 5% 10% 54%	1800
July	1st to 10th	Night	11% 7% 2 6% 5% 4 4 3 6% 10% 43%	4078
	11th to 20th	Night	4 3 1 4 3 4 4 3 6% 9% 58%	4077
	21st to end	Night	6% 6% 2 5% 3 3 4 4 6% 10% 51%	4449
August	1st to 10th	Night	1 2 1 2 2 2 3 2 4 7% 74%	3174
	11th to 20th	Night	3 2 1 3 2 3 4 3 7% 10% 62%	3213
	21st to end	Night	4 5% 2 4 3 4 4 4 6% 10% 53%	3644
September	1st to 10th	Night	8% 5% 2 6% 4 4 4 4 5% 8% 51%	2200
	11th to 20th	Night	8% 6% 2 6% 4 4 5% 4 7% 8% 47%	2200
	21st to end	Night	7% 5% 2 5% 3 4 4 4 5% 7% 54%	2200
October	1st to 10th	Night	4 4 1 3 3 3 4 2 5% 6% 64%	2200
	11th to 20th	Night	9% 5% 2 4 3 3 3 2 4 5% 59%	2230
	21st to end	Night	12% 5% 1 4 3 2 2 2 3 4 63%	2640
November	1st to 10th	Night	11% 6% 2 5% 3 3 2 2 4 6% 57%	2506
	11th to 20th	Night	8% 6% 2 4 3 3 3 2 4 6% 59%	2730
	21st to end	Night	14% 6% 2 5% 3 3 3 3 4 6% 51%	2730
December	1st to 10th	Night	21% 6% 2 5% 3 3 3 3 4 5% 43%	4380
	11th to 20th	Night	16% 9% 2 5% 3 3 3 3 3 4 49%	4946
	21st to end	Night	12% 7% 2 4 2 2 2 2 3 4 60%	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	29% 3 5% 23% 26% 14%	5290
	11th to 20th	Day	31% 2 3 16% 27% 21%	5370
	21st to end	Day	41% 3 5% 14% 25% 13%	6468
February	1st to 10th	Day	35% 3 7% 13% 22% 20%	2100
	11th to 20th	Day	36% 3 7% 19% 19% 15%	2059
	21st to end	Day	32% 2 6% 16% 24% 18%	1730
March	1st to 10th	Day	31% 3 5% 17% 17% 27%	4812
	11th to 20th	Day	34% 3 5% 9% 15% 33%	5090
	21st to end	Day	33% 5% 7% 19% 21% 16%	5585
April	1st to 10th	Day	37% 5% 8% 18% 17% 15%	2310
	11th to 20th	Day	41% 4 7% 16% 20% 13%	2441
	21st to end	Day	38% 4 8% 21% 18% 11%	2584
May	1st to 10th	Day	42% 6% 9% 17% 19% 7%	6030
	11th to 20th	Day	34% 5% 10% 16% 22% 12%	5996
	21st to end	Day	41% 6% 11% 25% 14% 3	6590
June	1st to 10th	Day	28% 6% 12% 29% 21% 3	2601
	11th to 20th	Day	30% 6% 12% 26% 21% 6%	2600
	21st to end	Day	34% 8% 13% 24% 17% 5%	2600
July	1st to 10th	Day	43% 7% 16% 28% 6%	5836
	11th to 20th	Day	29% 7% 15% 33% 14% 2	5831
	21st to end	Day	28% 7% 19% 27% 18% 1	6240
August	1st to 10th	Day	14% 4 11% 39% 30% 1	3967
	11th to 20th	Day	20% 4 22% 38% 13% 2	3882
	21st to end	Day	28% 8% 17% 25% 19% 2	4260
September	1st to 10th	Day	40% 5% 10% 20% 18% 9%	2200
	11th to 20th	Day	38% 6% 11% 20% 19% 5%	2200
	21st to end	Day	33% 4 10% 22% 19% 13%	2200
October	1st to 10th	Day	16% 3 7% 14% 27% 33%	3590
	11th to 20th	Day	27% 3 6% 20% 23% 22%	3481
	21st to end	Day	25% 3 5% 17% 37% 13%	3538
November	1st to 10th	Day	35% 4 7% 19% 23% 13%	2008
	11th to 20th	Day	31% 4 6% 19% 22% 19%	1890
	21st to end	Day	38% 3 5% 17% 23% 14%	1890
December	1st to 10th	Day	46% 2 5% 17% 20% 10%	3030
	11th to 20th	Day	38% 5% 8% 11% 23% 15%	3479
	21st to end	Day	28% 2 4 17% 28% 21%	4587
January	1st to 10th	Night	30% 3 5% 17% 29% 15%	7635
	11th to 20th	Night	22% 2 3 17% 30% 26%	7662
	21st to end	Night	45% 3 3 10% 22% 17%	7746
February	1st to 10th	Night	33% 4 7% 13% 23% 21%	2520
	11th to 20th	Night	35% 4 6% 19% 20% 16%	2458
	21st to end	Night	35% 3 6% 13% 24% 19%	2076
March	1st to 10th	Night	32% 4 7% 18% 20% 19%	5270
	11th to 20th	Night	34% 4 5% 11% 17% 29%	5090
	21st to end	Night	36% 3 7% 19% 19% 17%	5588
April	1st to 10th	Night	34% 5% 10% 18% 15% 17%	2310
	11th to 20th	Night	39% 4 8% 15% 17% 16%	2123
	21st to end	Night	40% 3 9% 19% 18% 11%	2032
May	1st to 10th	Night	44% 6% 7% 18% 13% 11%	4170
	11th to 20th	Night	31% 6% 11% 20% 19% 14%	4144
	21st to end	Night	37% 6% 15% 25% 11% 4	4551
June	1st to 10th	Night	19% 6% 20% 34% 20% 2	1800
	11th to 20th	Night	23% 4 16% 28% 23% 5%	1800
	21st to end	Night	27% 5% 17% 28% 18% 4	1800
July	1st to 10th	Night	37% 8% 22% 29% 4	4035
	11th to 20th	Night	23% 7% 21% 34% 15% 1	4026
	21st to end	Night	29% 8% 20% 26% 15% 3	4320
August	1st to 10th	Night	12% 4 14% 44% 25% 1	3164
	11th to 20th	Night	17% 5% 28% 37% 11% 2	3243
	21st to end	Night	25% 10% 21% 25% 18% 2	3644
September	1st to 10th	Night	32% 6% 12% 23% 19% 8%	2200
	11th to 20th	Night	33% 7% 15% 23% 16% 6%	2200
	21st to end	Night	29% 5% 12% 22% 19% 13%	2200
October	1st to 10th	Night	14% 2 9% 16% 23% 36%	3590
	11th to 20th	Night	23% 3 8% 17% 29% 19%	3625
	21st to end	Night	25% 2 5% 19% 34% 15%	4252
November	1st to 10th	Night	31% 3 7% 20% 24% 15%	2506
	11th to 20th	Night	27% 4 7% 23% 21% 19%	2730
	21st to end	Night	37% 3 7% 16% 21% 16%	2730
December	1st to 10th	Night	45% 3 8% 15% 17% 13%	4380
	11th to 20th	Night	40% 3 5% 12% 21% 19%	4947
	21st to end	Night	31% 2 4 16% 29% 18%	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	19% 15% 42% 18% 5% 1	330
	11th to 20th	Day	22% 15% 35% 21% 6%	330
	21st to end	Day	20% 15% 40% 19% 5%	363
February	1st to 10th	Day	24% 12% 35% 22% 7%	330
	11th to 20th	Day	22% 17% 39% 18% 2 1	330
	21st to end	Day	19% 18% 42% 18% 3	273
March	1st to 10th	Day	22% 21% 40% 16% 2	330
	11th to 20th	Day	19% 20% 38% 18% 5%	330
	21st to end	Day	15% 17% 43% 20% 4 1	363
April	1st to 10th	Day	21% 19% 38% 19% 2	330
	11th to 20th	Day	21% 20% 39% 15% 5%	479
	21st to end	Day	18% 15% 44% 18% 5%	604
May	1st to 10th	Day	17% 10% 42% 25% 5%	753
	11th to 20th	Day	19% 9% 36% 26% 9% 1	775
	21st to end	Day	16% 7% 33% 33% 11%	844
June	1st to 10th	Day	6% 4 24% 44% 20% 3	731
	11th to 20th	Day	8% 3 23% 47% 17% 2	730
	21st to end	Day	6% 3 17% 40% 28% 5%	730
July	1st to 10th	Day	11% 4 9% 39% 29% 7%	721
	11th to 20th	Day	5% 2 7% 43% 37% 6%	718
	21st to end	Day	4 2 6% 41% 36% 10%	794
August	1st to 10th	Day	2 4 41% 42% 11%	577
	11th to 20th	Day	8% 1 4 37% 39% 12%	517
	21st to end	Day	5% 2 5% 34% 39% 14%	558
September	1st to 10th	Day	10% 1 8% 35% 33% 14%	330
	11th to 20th	Day	7% 1 4 35% 43% 10%	330
	21st to end	Day	10% 2 5% 37% 37% 9%	330
October	1st to 10th	Day	6% 2 14% 39% 31% 8%	330
	11th to 20th	Day	10% 2 26% 39% 19% 3	330
	21st to end	Day	16% 13% 29% 28% 12% 2	363
November	1st to 10th	Day	20% 5% 32% 30% 11% 3	330
	11th to 20th	Day	20% 9% 31% 26% 9% 5%	330
	21st to end	Day	23% 20% 30% 19% 7% 2	330
December	1st to 10th	Day	18% 10% 35% 28% 7% 2	330
	11th to 20th	Day	18% 15% 37% 21% 8% 1	330
	21st to end	Day	17% 13% 35% 26% 9%	363
January	1st to 10th	Night	16% 11% 35% 30% 8%	1050
	11th to 20th	Night	16% 12% 36% 30% 5%	1045
	21st to end	Night	20% 12% 33% 29% 6%	924
February	1st to 10th	Night	19% 13% 34% 28% 6%	840
	11th to 20th	Night	19% 14% 36% 27% 4	824
	21st to end	Night	18% 14% 46% 21% 1	692
March	1st to 10th	Night	20% 14% 38% 25% 3	746
	11th to 20th	Night	18% 12% 38% 29% 4	630
	21st to end	Night	14% 13% 47% 23% 3	693
April	1st to 10th	Night	11% 15% 48% 23% 3	630
	11th to 20th	Night	18% 17% 42% 21% 3	623
	21st to end	Night	19% 12% 43% 22% 4	630
May	1st to 10th	Night	16% 12% 44% 24% 3	630
	11th to 20th	Night	14% 7% 39% 32% 7%	621
	21st to end	Night	13% 6% 39% 32% 10% 1	683
June	1st to 10th	Night	5% 2 30% 47% 16% 1	600
	11th to 20th	Night	5% 4 37% 44% 9%	600
	21st to end	Night	7% 3 21% 49% 19% 2	600
July	1st to 10th	Night	9% 3 12% 48% 26% 2	585
	11th to 20th	Night	4 1 12% 54% 27% 2	582
	21st to end	Night	5% 1 9% 55% 26% 3	657
August	1st to 10th	Night	2 1 8% 54% 32% 3	597
	11th to 20th	Night	5% 1 8% 51% 32% 3	594
	21st to end	Night	5% 3 7% 45% 37% 4	660
September	1st to 10th	Night	10% 4 9% 40% 35% 3	600
	11th to 20th	Night	11% 2 7% 43% 35% 2	600
	21st to end	Night	9% 2 11% 45% 31% 2	600
October	1st to 10th	Night	6% 2 14% 47% 29% 2	600
	11th to 20th	Night	13% 4 24% 41% 17% 1	630
	21st to end	Night	16% 8% 27% 30% 17% 2	880
November	1st to 10th	Night	14% 7% 25% 39% 14% 1	866
	11th to 20th	Night	12% 7% 30% 36% 13% 2	1050
	21st to end	Night	20% 10% 30% 30% 11% 1	1050
December	1st to 10th	Night	16% 8% 31% 35% 8% 1	1050
	11th to 20th	Night	19% 10% 32% 31% 7%	1050
	21st to end	Night	16% 11% 32% 34% 7%	1155

Page generated at 2026-05-29 00:53:28. Version ac07

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