Walker County Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Walker County Observatory clear sky chart from 2005-11-06 to 2024-10-25.

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% 7% 3 7% 5% 5% 5% 4 6% 7% 40%	100817
	Night	12% 6% 2 6% 4 4 4 4 6% 7% 43%	97959
Transparency	Day	40% 8% 11% 21% 16% 3	100626
	Night	39% 7% 11% 21% 18% 4	97819
Seeing	Day	17% 10% 23% 24% 18% 9%	14675
	Night	15% 8% 24% 30% 20% 3	24660

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	15% 10% 3 8% 5% 3 4 4 5% 5% 37%	2836
	11th to 20th	Day	17% 8% 3 8% 5% 5% 4 3 3 4 41%	2840
	21st to end	Day	23% 10% 2 5% 3 3 3 3 4 5% 39%	3321
February	1st to 10th	Day	17% 11% 3 6% 4 4 4 4 5% 5% 38%	1900
	11th to 20th	Day	18% 9% 3 7% 6% 3 5% 3 4 5% 37%	1848
	21st to end	Day	20% 7% 3 7% 4 4 4 3 5% 6% 36%	1570
March	1st to 10th	Day	23% 10% 4 8% 4 4 4 3 5% 5% 30%	3120
	11th to 20th	Day	13% 8% 3 6% 4 3 4 3 4 6% 48%	3470
	21st to end	Day	15% 7% 3 7% 6% 4 4 4 5% 6% 38%	3815
April	1st to 10th	Day	11% 5% 2 7% 5% 5% 6% 4 6% 7% 43%	2261
	11th to 20th	Day	12% 7% 3 6% 5% 4 3 3 6% 6% 44%	2254
	21st to end	Day	10% 6% 2 6% 5% 5% 4 4 6% 8% 45%	2382
May	1st to 10th	Day	11% 7% 3 7% 5% 5% 5% 4 7% 7% 40%	4082
	11th to 20th	Day	13% 8% 3 7% 4 5% 5% 4 6% 8% 36%	4081
	21st to end	Day	9% 5% 2 7% 5% 5% 4 5% 7% 9% 41%	4476
June	1st to 10th	Day	9% 6% 3 7% 6% 6% 6% 5% 8% 10% 36%	2470
	11th to 20th	Day	4 3 2 6% 5% 6% 6% 6% 8% 12% 42%	2470
	21st to end	Day	6% 4 2 7% 6% 6% 6% 6% 7% 12% 38%	2470
July	1st to 10th	Day	6% 5% 2 8% 7% 7% 8% 6% 9% 10% 31%	4120
	11th to 20th	Day	8% 6% 2 7% 6% 6% 7% 6% 8% 10% 34%	4120
	21st to end	Day	13% 10% 4 10% 8% 7% 7% 6% 8% 8% 19%	4466
August	1st to 10th	Day	4 4 1 6% 4 6% 6% 6% 8% 10% 44%	4049
	11th to 20th	Day	6% 4 2 6% 5% 5% 6% 5% 8% 11% 41%	3729
	21st to end	Day	8% 4 2 6% 5% 4 5% 5% 6% 8% 48%	4180
September	1st to 10th	Day	10% 6% 3 7% 5% 5% 6% 5% 7% 8% 39%	2164
	11th to 20th	Day	14% 6% 2 5% 5% 5% 5% 4 5% 7% 41%	2090
	21st to end	Day	13% 6% 2 7% 4 3 4 4 5% 6% 48%	2090
October	1st to 10th	Day	11% 5% 2 4 4 3 4 3 4 5% 54%	2090
	11th to 20th	Day	10% 5% 3 5% 3 3 4 2 5% 5% 56%	2037
	21st to end	Day	14% 4 2 4 3 3 4 3 5% 6% 52%	1937
November	1st to 10th	Day	11% 5% 2 5% 3 3 3 3 5% 5% 55%	1672
	11th to 20th	Day	12% 5% 2 6% 4 4 3 3 5% 6% 50%	1710
	21st to end	Day	16% 5% 2 5% 4 4 4 3 5% 7% 45%	1710
December	1st to 10th	Day	20% 9% 3 7% 4 5% 4 3 4 5% 36%	1710
	11th to 20th	Day	12% 7% 4 8% 6% 5% 4 3 4 6% 40%	2153
	21st to end	Day	18% 9% 4 7% 4 4 4 4 4 7% 34%	3124
January	1st to 10th	Night	17% 9% 3 7% 4 4 4 3 4 5% 40%	4109
	11th to 20th	Night	17% 8% 4 6% 4 3 3 3 4 5% 42%	4120
	21st to end	Night	20% 13% 2 6% 4 4 3 3 4 4 36%	4331
February	1st to 10th	Night	14% 8% 2 8% 4 4 4 3 5% 5% 43%	2280
	11th to 20th	Night	19% 7% 2 7% 5% 4 4 3 4 4 39%	2218
	21st to end	Night	20% 8% 3 6% 4 3 4 3 5% 6% 36%	1884
March	1st to 10th	Night	23% 11% 3 7% 4 4 3 3 5% 5% 31%	3733
	11th to 20th	Night	10% 7% 2 5% 4 4 4 4 6% 7% 47%	3490
	21st to end	Night	13% 8% 3 8% 5% 5% 4 4 4 5% 40%	3817
April	1st to 10th	Night	11% 5% 2 5% 4 4 4 4 5% 7% 48%	1934
	11th to 20th	Night	11% 6% 2 5% 4 3 3 4 4 8% 50%	1875
	21st to end	Night	10% 5% 2 5% 4 4 4 3 5% 8% 50%	1796
May	1st to 10th	Night	10% 7% 3 8% 6% 5% 5% 4 6% 8% 39%	2813
	11th to 20th	Night	13% 6% 2 6% 5% 5% 4 4 7% 9% 39%	2812
	21st to end	Night	7% 4 2 6% 4 5% 5% 5% 8% 11% 43%	3079
June	1st to 10th	Night	5% 5% 2 8% 6% 6% 6% 4 7% 11% 40%	1710
	11th to 20th	Night	4 3 2 4 3 5% 4 4 7% 13% 51%	1710
	21st to end	Night	5% 4 2 5% 5% 4 5% 6% 8% 12% 45%	1710
July	1st to 10th	Night	7% 5% 2 8% 7% 6% 6% 5% 8% 11% 33%	2840
	11th to 20th	Night	9% 5% 2 5% 5% 4 5% 5% 7% 11% 42%	2840
	21st to end	Night	11% 9% 4 10% 6% 7% 7% 5% 7% 10% 25%	3087
August	1st to 10th	Night	4 3 2 4 4 5% 5% 5% 9% 10% 49%	2876
	11th to 20th	Night	6% 4 2 5% 4 5% 4 4 7% 9% 50%	3100
	21st to end	Night	7% 3 2 4 4 4 4 4 6% 8% 56%	3476
September	1st to 10th	Night	8% 6% 2 7% 5% 5% 4 5% 6% 10% 41%	1995
	11th to 20th	Night	14% 6% 2 6% 4 4 4 4 6% 8% 43%	2090
	21st to end	Night	11% 5% 2 6% 4 4 3 4 5% 7% 50%	2090
October	1st to 10th	Night	11% 4 2 4 3 3 3 2 4 6% 59%	2090
	11th to 20th	Night	11% 4 1 7% 3 4 3 2 4 4 55%	2142
	21st to end	Night	13% 5% 2 4 3 3 3 3 4 5% 55%	2522
November	1st to 10th	Night	12% 5% 1 4 3 4 3 3 4 6% 54%	2406
	11th to 20th	Night	11% 7% 2 6% 4 3 3 3 5% 6% 52%	2470
	21st to end	Night	15% 6% 2 6% 5% 4 4 4 4 5% 46%	2470
December	1st to 10th	Night	18% 8% 3 7% 5% 5% 4 4 5% 6% 37%	2470
	11th to 20th	Night	15% 6% 2 6% 4 4 4 3 4 6% 46%	3042
	21st to end	Night	17% 7% 3 8% 5% 5% 5% 4 6% 7% 32%	4532

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	45% 7% 7% 18% 21% 2	2837
	11th to 20th	Day	46% 5% 7% 16% 24% 2	2840
	21st to end	Day	48% 3 9% 20% 18% 2	3321
February	1st to 10th	Day	47% 5% 7% 19% 17% 3	1900
	11th to 20th	Day	50% 5% 6% 19% 16% 5%	1858
	21st to end	Day	48% 5% 9% 14% 19% 5%	1570
March	1st to 10th	Day	54% 6% 8% 11% 13% 8%	3120
	11th to 20th	Day	38% 6% 7% 22% 21% 7%	3470
	21st to end	Day	45% 5% 11% 22% 15% 3	3815
April	1st to 10th	Day	39% 7% 10% 22% 17% 5%	2261
	11th to 20th	Day	39% 5% 8% 20% 22% 6%	2254
	21st to end	Day	36% 7% 10% 28% 16% 2	2382
May	1st to 10th	Day	40% 9% 13% 23% 14% 2	4120
	11th to 20th	Day	43% 9% 13% 23% 11% 1	4085
	21st to end	Day	36% 9% 11% 23% 19% 1	4489
June	1st to 10th	Day	39% 10% 16% 21% 12% 1	2470
	11th to 20th	Day	30% 11% 18% 25% 14% 2	2470
	21st to end	Day	36% 11% 17% 19% 13% 3	2470
July	1st to 10th	Day	40% 13% 20% 19% 7% 1	4055
	11th to 20th	Day	40% 11% 20% 20% 6% 2	4051
	21st to end	Day	58% 11% 12% 13% 5%	4324
August	1st to 10th	Day	30% 10% 13% 35% 11%	4036
	11th to 20th	Day	32% 9% 16% 25% 15% 2	3765
	21st to end	Day	31% 9% 11% 27% 20% 2	4179
September	1st to 10th	Day	39% 10% 13% 16% 16% 6%	2164
	11th to 20th	Day	41% 8% 10% 20% 18% 2	2090
	21st to end	Day	36% 6% 11% 19% 21% 7%	2090
October	1st to 10th	Day	32% 6% 8% 19% 27% 8%	2090
	11th to 20th	Day	30% 5% 8% 24% 24% 9%	2037
	21st to end	Day	33% 4 6% 22% 27% 7%	1937
November	1st to 10th	Day	32% 4 7% 19% 29% 8%	1672
	11th to 20th	Day	35% 4 7% 21% 26% 7%	1710
	21st to end	Day	40% 5% 7% 22% 23% 4	1710
December	1st to 10th	Day	50% 5% 7% 18% 17% 3	1710
	11th to 20th	Day	45% 5% 7% 19% 21% 3	2150
	21st to end	Day	48% 4 10% 21% 14% 3	3124
January	1st to 10th	Night	45% 5% 6% 20% 21% 2	4109
	11th to 20th	Night	43% 5% 7% 19% 18% 7%	4120
	21st to end	Night	51% 4 6% 18% 18% 3	4331
February	1st to 10th	Night	43% 5% 10% 19% 20% 4	2280
	11th to 20th	Night	49% 5% 7% 17% 16% 6%	2219
	21st to end	Night	49% 5% 8% 16% 17% 6%	1884
March	1st to 10th	Night	53% 6% 8% 13% 15% 5%	3733
	11th to 20th	Night	34% 6% 9% 22% 20% 10%	3490
	21st to end	Night	45% 5% 8% 21% 19% 2	3817
April	1st to 10th	Night	34% 6% 11% 23% 22% 5%	1934
	11th to 20th	Night	33% 4 7% 23% 22% 10%	1875
	21st to end	Night	33% 6% 11% 28% 20% 2	1796
May	1st to 10th	Night	39% 10% 14% 22% 14% 2	2840
	11th to 20th	Night	39% 10% 16% 23% 12% 1	2813
	21st to end	Night	29% 11% 16% 25% 16% 2	3087
June	1st to 10th	Night	36% 10% 17% 21% 14% 3	1710
	11th to 20th	Night	23% 9% 21% 30% 16% 2	1710
	21st to end	Night	29% 10% 20% 21% 14% 5%	1710
July	1st to 10th	Night	41% 12% 18% 20% 7% 2	2795
	11th to 20th	Night	33% 10% 24% 23% 7% 2	2786
	21st to end	Night	53% 11% 15% 15% 6% 1	2988
August	1st to 10th	Night	27% 10% 15% 35% 13% 1	2865
	11th to 20th	Night	28% 8% 21% 27% 14% 1	3130
	21st to end	Night	26% 8% 14% 24% 26% 2	3476
September	1st to 10th	Night	36% 9% 17% 18% 14% 5%	1995
	11th to 20th	Night	37% 9% 12% 19% 20% 2	2090
	21st to end	Night	33% 6% 10% 22% 21% 7%	2090
October	1st to 10th	Night	28% 4 8% 23% 26% 10%	2090
	11th to 20th	Night	33% 4 8% 20% 24% 11%	2142
	21st to end	Night	31% 4 6% 22% 27% 10%	2522
November	1st to 10th	Night	32% 5% 7% 22% 24% 10%	2406
	11th to 20th	Night	33% 4 7% 20% 27% 9%	2470
	21st to end	Night	40% 5% 6% 22% 22% 5%	2470
December	1st to 10th	Night	47% 6% 10% 17% 17% 3	2470
	11th to 20th	Night	39% 5% 8% 18% 27% 3	3044
	21st to end	Night	47% 6% 11% 21% 15% 2	4532

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	28% 24% 29% 17% 3	270
	11th to 20th	Day	29% 22% 31% 11% 6% 1	270
	21st to end	Day	22% 25% 37% 13% 3	297
February	1st to 10th	Day	28% 20% 35% 13% 4	270
	11th to 20th	Day	39% 21% 27% 11% 2	270
	21st to end	Day	36% 22% 32% 8% 1	225
March	1st to 10th	Day	28% 22% 30% 16% 3 1	270
	11th to 20th	Day	23% 19% 30% 21% 6% 1	450
	21st to end	Day	20% 17% 36% 19% 7%	506
April	1st to 10th	Day	18% 19% 31% 18% 12% 2	460
	11th to 20th	Day	16% 18% 31% 22% 12% 1	452
	21st to end	Day	17% 13% 33% 22% 14% 3	460
May	1st to 10th	Day	14% 11% 29% 26% 13% 6%	463
	11th to 20th	Day	13% 7% 23% 30% 18% 10%	487
	21st to end	Day	13% 5% 20% 27% 22% 13%	529
June	1st to 10th	Day	14% 4 18% 28% 22% 13%	490
	11th to 20th	Day	5% 3 13% 31% 27% 21%	490
	21st to end	Day	10% 3 18% 24% 25% 18%	490
July	1st to 10th	Day	10% 2 12% 25% 28% 23%	485
	11th to 20th	Day	11% 2 10% 24% 32% 21%	484
	21st to end	Day	9% 2 9% 28% 29% 23%	532
August	1st to 10th	Day	11% 3 12% 24% 32% 17%	486
	11th to 20th	Day	10% 2 15% 29% 29% 14%	479
	21st to end	Day	14% 3 10% 22% 32% 19%	539
September	1st to 10th	Day	9% 4 14% 29% 30% 15%	490
	11th to 20th	Day	18% 3 12% 23% 32% 13%	490
	21st to end	Day	17% 6% 16% 26% 30% 6%	490
October	1st to 10th	Day	14% 5% 20% 30% 22% 9%	490
	11th to 20th	Day	12% 11% 26% 30% 20% 2	490
	21st to end	Day	18% 9% 23% 29% 17% 4	424
November	1st to 10th	Day	21% 10% 26% 27% 12% 3	270
	11th to 20th	Day	17% 15% 34% 27% 6%	270
	21st to end	Day	15% 19% 35% 22% 8% 1	270
December	1st to 10th	Day	27% 18% 34% 17% 3 1	270
	11th to 20th	Day	19% 17% 38% 19% 7% 1	270
	21st to end	Day	29% 20% 30% 16% 4 1	297
January	1st to 10th	Night	23% 14% 35% 23% 5%	760
	11th to 20th	Night	20% 15% 32% 27% 6%	760
	21st to end	Night	19% 14% 35% 29% 3	836
February	1st to 10th	Night	19% 13% 35% 29% 4	760
	11th to 20th	Night	24% 15% 35% 24% 1	743
	21st to end	Night	27% 16% 35% 20% 2	628
March	1st to 10th	Night	19% 13% 34% 30% 5%	760
	11th to 20th	Night	18% 15% 34% 25% 8% 1	760
	21st to end	Night	18% 12% 33% 28% 9%	836
April	1st to 10th	Night	13% 13% 32% 31% 11%	604
	11th to 20th	Night	14% 10% 34% 31% 10% 1	563
	21st to end	Night	13% 8% 27% 40% 11% 1	570
May	1st to 10th	Night	10% 8% 27% 34% 20% 2	570
	11th to 20th	Night	14% 5% 21% 33% 23% 4	561
	21st to end	Night	10% 2 12% 39% 33% 4	617
June	1st to 10th	Night	8% 2 14% 38% 33% 5%	570
	11th to 20th	Night	4 2 11% 36% 37% 10%	570
	21st to end	Night	6% 2 10% 31% 43% 8%	570
July	1st to 10th	Night	10% 2 8% 27% 41% 11%	555
	11th to 20th	Night	9% 2 6% 27% 44% 12%	552
	21st to end	Night	8% 1 8% 26% 46% 10%	624
August	1st to 10th	Night	7% 2 5% 25% 50% 11%	567
	11th to 20th	Night	11% 1 11% 30% 41% 6%	564
	21st to end	Night	13% 1 8% 25% 43% 9%	627
September	1st to 10th	Night	10% 2 11% 31% 39% 7%	665
	11th to 20th	Night	15% 3 11% 30% 37% 4	760
	21st to end	Night	14% 2 15% 32% 34% 3	760
October	1st to 10th	Night	13% 4 18% 30% 29% 7%	760
	11th to 20th	Night	14% 5% 27% 32% 21% 1	760
	21st to end	Night	15% 6% 21% 37% 18% 2	812
November	1st to 10th	Night	14% 9% 21% 34% 20% 1	740
	11th to 20th	Night	13% 9% 34% 31% 12% 1	760
	21st to end	Night	18% 11% 28% 33% 10% 1	760
December	1st to 10th	Night	22% 13% 28% 29% 8%	760
	11th to 20th	Night	19% 11% 30% 31% 8% 1	760
	21st to end	Night	22% 11% 30% 30% 6%	836

Page generated at 2024-10-22 20:21:03. Version ac07

Copyright © 2024 Attilla Danko.