Big Thicket Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Big Thicket Observatory clear sky chart from 2005-11-06 to 2024-11-05.

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	14% 6% 2 7% 5% 5% 5% 4 6% 7% 38%	100949
	Night	15% 6% 2 5% 4 3 4 3 5% 8% 44%	98164
Transparency	Day	42% 7% 11% 17% 16% 7%	104595
	Night	37% 6% 13% 19% 17% 8%	102645
Seeing	Day	14% 8% 20% 26% 22% 10%	14897
	Night	16% 6% 22% 32% 22% 3	24694

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	22% 9% 2 5% 3 3 3 3 4 5% 40%	2847
	11th to 20th	Day	19% 6% 2 5% 3 3 2 1 3 5% 51%	2850
	21st to end	Day	25% 7% 3 6% 4 3 3 2 5% 7% 35%	3135
February	1st to 10th	Day	23% 8% 3 6% 5% 4 3 3 5% 6% 35%	1710
	11th to 20th	Day	24% 8% 3 6% 3 3 3 2 4 4 38%	1922
	21st to end	Day	24% 8% 2 5% 5% 3 3 2 4 5% 37%	1727
March	1st to 10th	Day	23% 9% 4 8% 5% 5% 4 4 5% 5% 28%	3436
	11th to 20th	Day	20% 8% 3 8% 6% 5% 6% 4 6% 8% 29%	3480
	21st to end	Day	19% 7% 3 7% 5% 4 4 3 4 5% 40%	3814
April	1st to 10th	Day	16% 7% 3 7% 5% 6% 5% 4 5% 6% 38%	2133
	11th to 20th	Day	18% 7% 3 6% 5% 4 5% 4 5% 6% 37%	2254
	21st to end	Day	12% 6% 3 7% 5% 5% 4 4 6% 7% 42%	2280
May	1st to 10th	Day	19% 8% 3 8% 6% 5% 5% 5% 5% 7% 28%	3765
	11th to 20th	Day	15% 5% 2 6% 4 4 4 4 6% 7% 42%	3948
	21st to end	Day	10% 6% 2 7% 6% 6% 6% 5% 8% 9% 35%	4477
June	1st to 10th	Day	8% 5% 2 7% 6% 7% 7% 6% 8% 8% 35%	2470
	11th to 20th	Day	6% 6% 3 6% 6% 7% 9% 6% 9% 9% 35%	2470
	21st to end	Day	8% 7% 2 8% 7% 8% 8% 7% 9% 9% 28%	2470
July	1st to 10th	Day	9% 6% 3 7% 7% 7% 7% 6% 9% 12% 26%	4120
	11th to 20th	Day	8% 8% 4 10% 8% 7% 7% 6% 9% 10% 22%	4120
	21st to end	Day	17% 8% 3 8% 6% 6% 7% 5% 7% 9% 24%	4465
August	1st to 10th	Day	2 2 1 4 4 3 6% 3 7% 10% 56%	4104
	11th to 20th	Day	3 3 1 4 4 6% 7% 6% 9% 11% 45%	3738
	21st to end	Day	11% 6% 2 8% 6% 7% 7% 5% 7% 8% 36%	4180
September	1st to 10th	Day	10% 6% 2 8% 6% 6% 6% 5% 6% 9% 36%	2223
	11th to 20th	Day	15% 6% 3 7% 6% 5% 5% 5% 7% 8% 34%	2090
	21st to end	Day	11% 5% 1 6% 4 4 5% 4 6% 7% 45%	2087
October	1st to 10th	Day	7% 4 2 4 4 5% 4 4 5% 6% 55%	1900
	11th to 20th	Day	10% 5% 2 5% 4 4 4 4 6% 7% 52%	1900
	21st to end	Day	14% 5% 1 5% 3 3 3 3 4 6% 53%	2090
November	1st to 10th	Day	12% 6% 2 7% 5% 5% 4 3 6% 6% 45%	1898
	11th to 20th	Day	14% 5% 3 7% 3 4 3 4 4 5% 48%	1900
	21st to end	Day	17% 7% 2 7% 5% 4 3 2 4 4 44%	1900
December	1st to 10th	Day	17% 8% 2 6% 5% 4 4 3 4 6% 41%	1750
	11th to 20th	Day	17% 8% 3 7% 5% 4 4 3 4 6% 39%	2161
	21st to end	Day	18% 6% 2 6% 3 3 3 3 5% 7% 42%	3135
January	1st to 10th	Night	19% 8% 3 5% 3 3 3 2 4 7% 44%	4108
	11th to 20th	Night	21% 7% 2 5% 3 2 2 2 3 4 50%	4120
	21st to end	Night	25% 9% 2 5% 3 3 3 2 5% 7% 35%	4532
February	1st to 10th	Night	20% 9% 3 5% 4 4 3 3 4 6% 39%	2470
	11th to 20th	Night	23% 9% 3 4 3 2 3 2 3 5% 43%	2158
	21st to end	Night	24% 9% 3 5% 4 3 3 3 4 5% 37%	1727
March	1st to 10th	Night	26% 13% 3 7% 4 3 3 3 4 5% 29%	3419
	11th to 20th	Night	24% 8% 3 7% 5% 4 4 3 4 6% 31%	3480
	21st to end	Night	16% 6% 2 5% 4 5% 4 3 5% 6% 43%	3817
April	1st to 10th	Night	17% 7% 3 6% 4 4 4 3 5% 7% 40%	2047
	11th to 20th	Night	19% 5% 1 5% 4 3 3 3 6% 8% 43%	1875
	21st to end	Night	15% 7% 2 5% 4 3 4 3 5% 6% 44%	1900
May	1st to 10th	Night	27% 9% 2 6% 4 4 4 4 6% 7% 27%	3130
	11th to 20th	Night	16% 6% 2 7% 4 4 5% 3 5% 6% 43%	2947
	21st to end	Night	14% 7% 2 6% 4 4 4 5% 8% 10% 36%	3090
June	1st to 10th	Night	6% 5% 1 4 3 3 4 4 7% 10% 54%	1710
	11th to 20th	Night	5% 3 2 4 2 3 4 4 8% 13% 52%	1710
	21st to end	Night	8% 5% 2 5% 3 5% 5% 5% 9% 11% 42%	1710
July	1st to 10th	Night	6% 5% 2 6% 5% 4 4 5% 7% 14% 43%	2850
	11th to 20th	Night	4 4 3 7% 5% 5% 6% 5% 7% 11% 43%	2850
	21st to end	Night	10% 7% 3 7% 5% 4 5% 4 7% 10% 37%	3098
August	1st to 10th	Night	2 2 1 2 3 3 3 3 6% 11% 64%	2836
	11th to 20th	Night	2 2 1 2 2 3 4 3 7% 12% 62%	3091
	21st to end	Night	7% 4 2 5% 4 4 6% 5% 8% 11% 44%	3476
September	1st to 10th	Night	7% 5% 2 5% 4 4 5% 5% 7% 11% 47%	1950
	11th to 20th	Night	12% 5% 2 6% 5% 5% 5% 4 6% 8% 43%	2090
	21st to end	Night	9% 5% 2 4 3 3 4 3 4 7% 56%	2090
October	1st to 10th	Night	6% 3 1 4 3 3 3 4 5% 6% 61%	2261
	11th to 20th	Night	10% 4 1 4 2 3 3 3 5% 6% 60%	2280
	21st to end	Night	12% 6% 2 4 2 2 2 2 3 5% 60%	2508
November	1st to 10th	Night	12% 5% 1 5% 3 3 4 2 5% 6% 54%	2280
	11th to 20th	Night	12% 5% 1 4 3 3 4 3 5% 7% 52%	2280
	21st to end	Night	16% 7% 3 6% 4 3 3 3 5% 6% 44%	2280
December	1st to 10th	Night	19% 8% 2 5% 4 3 4 4 5% 6% 42%	2426
	11th to 20th	Night	18% 8% 3 6% 4 3 3 3 4 5% 43%	3036
	21st to end	Night	18% 7% 2 5% 4 4 4 3 5% 5% 42%	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	46% 4 5% 16% 19% 9%	2848
	11th to 20th	Day	38% 4 6% 17% 26% 9%	2850
	21st to end	Day	50% 3 4 16% 17% 10%	3135
February	1st to 10th	Day	52% 4 6% 13% 15% 10%	1710
	11th to 20th	Day	50% 5% 6% 13% 17% 10%	1932
	21st to end	Day	50% 5% 6% 13% 16% 9%	1727
March	1st to 10th	Day	55% 6% 10% 11% 13% 4	3436
	11th to 20th	Day	53% 5% 9% 13% 13% 6%	3480
	21st to end	Day	47% 4 7% 16% 22% 4	3814
April	1st to 10th	Day	46% 6% 8% 14% 15% 9%	2133
	11th to 20th	Day	46% 6% 9% 14% 15% 10%	2254
	21st to end	Day	40% 7% 9% 16% 23% 6%	2280
May	1st to 10th	Day	54% 8% 9% 16% 10% 4	3800
	11th to 20th	Day	39% 6% 8% 19% 24% 3	3952
	21st to end	Day	41% 10% 12% 26% 10% 1	4489
June	1st to 10th	Day	41% 11% 14% 19% 14% 1	2470
	11th to 20th	Day	38% 12% 13% 21% 14% 2	2470
	21st to end	Day	45% 13% 16% 17% 9%	2470
July	1st to 10th	Day	45% 12% 23% 17% 3	4056
	11th to 20th	Day	51% 12% 18% 14% 5%	4051
	21st to end	Day	53% 11% 16% 16% 3 1	4325
August	1st to 10th	Day	22% 8% 13% 34% 22%	4090
	11th to 20th	Day	27% 10% 30% 27% 4 1	3774
	21st to end	Day	44% 11% 13% 16% 15% 1	4179
September	1st to 10th	Day	42% 12% 13% 16% 13% 4	2223
	11th to 20th	Day	45% 9% 13% 14% 14% 5%	2090
	21st to end	Day	37% 7% 13% 18% 15% 11%	2087
October	1st to 10th	Day	22% 4 7% 12% 17% 37%	3160
	11th to 20th	Day	20% 3 5% 18% 34% 20%	3140
	21st to end	Day	27% 4 4 12% 40% 13%	3428
November	1st to 10th	Day	38% 6% 9% 17% 20% 10%	1898
	11th to 20th	Day	38% 5% 7% 16% 21% 13%	1900
	21st to end	Day	44% 4 6% 17% 19% 9%	1900
December	1st to 10th	Day	45% 5% 8% 18% 17% 7%	1750
	11th to 20th	Day	45% 5% 6% 14% 19% 10%	2159
	21st to end	Day	41% 5% 6% 15% 24% 9%	3135
January	1st to 10th	Night	42% 4 6% 17% 20% 10%	4108
	11th to 20th	Night	40% 3 5% 17% 26% 9%	4120
	21st to end	Night	51% 3 5% 15% 16% 9%	4532
February	1st to 10th	Night	47% 5% 7% 12% 18% 12%	2470
	11th to 20th	Night	46% 4 6% 15% 19% 10%	2158
	21st to end	Night	49% 5% 6% 13% 14% 12%	1727
March	1st to 10th	Night	58% 5% 7% 12% 12% 6%	3419
	11th to 20th	Night	54% 6% 9% 13% 13% 5%	3480
	21st to end	Night	41% 6% 10% 14% 23% 6%	3817
April	1st to 10th	Night	44% 6% 8% 18% 15% 10%	2047
	11th to 20th	Night	39% 6% 11% 16% 16% 12%	1875
	21st to end	Night	40% 5% 8% 20% 20% 6%	1900
May	1st to 10th	Night	56% 7% 10% 13% 10% 4	3160
	11th to 20th	Night	42% 6% 10% 17% 22% 4	2948
	21st to end	Night	38% 11% 19% 23% 8% 1	3099
June	1st to 10th	Night	24% 10% 20% 30% 16% 1	1710
	11th to 20th	Night	23% 9% 18% 32% 15% 3	1710
	21st to end	Night	31% 12% 21% 26% 10%	1710
July	1st to 10th	Night	32% 8% 37% 20% 3	2805
	11th to 20th	Night	33% 9% 31% 23% 5%	2796
	21st to end	Night	41% 12% 24% 20% 4	2999
August	1st to 10th	Night	14% 7% 20% 41% 18%	2826
	11th to 20th	Night	15% 8% 36% 34% 7%	3121
	21st to end	Night	33% 13% 20% 21% 13% 1	3476
September	1st to 10th	Night	29% 11% 22% 22% 13% 4	1950
	11th to 20th	Night	38% 8% 17% 18% 14% 5%	2090
	21st to end	Night	29% 6% 13% 23% 17% 12%	2090
October	1st to 10th	Night	18% 4 7% 16% 18% 37%	3768
	11th to 20th	Night	16% 4 4 24% 30% 22%	3779
	21st to end	Night	22% 2 5% 13% 40% 17%	4120
November	1st to 10th	Night	32% 4 12% 18% 23% 11%	2280
	11th to 20th	Night	32% 5% 10% 18% 24% 11%	2280
	21st to end	Night	40% 5% 9% 17% 18% 11%	2280
December	1st to 10th	Night	43% 4 9% 19% 15% 9%	2426
	11th to 20th	Night	44% 4 6% 11% 21% 14%	3037
	21st to end	Night	43% 5% 7% 13% 24% 7%	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	26% 14% 37% 16% 7% 1	270
	11th to 20th	Day	22% 14% 35% 21% 7% 1	270
	21st to end	Day	24% 21% 32% 17% 6%	297
February	1st to 10th	Day	28% 18% 33% 17% 4	270
	11th to 20th	Day	33% 16% 29% 20% 2	270
	21st to end	Day	29% 27% 32% 11% 2	225
March	1st to 10th	Day	26% 21% 31% 17% 6%	270
	11th to 20th	Day	18% 26% 40% 12% 4	270
	21st to end	Day	25% 15% 37% 18% 5%	297
April	1st to 10th	Day	19% 19% 33% 24% 5%	313
	11th to 20th	Day	24% 18% 25% 20% 12% 1	452
	21st to end	Day	17% 11% 32% 27% 13% 1	460
May	1st to 10th	Day	19% 13% 28% 27% 14% 1	463
	11th to 20th	Day	13% 6% 27% 34% 17% 3	593
	21st to end	Day	9% 6% 30% 32% 19% 5%	734
June	1st to 10th	Day	8% 3 14% 36% 28% 11%	680
	11th to 20th	Day	8% 3 16% 35% 29% 9%	680
	21st to end	Day	9% 3 14% 28% 29% 17%	680
July	1st to 10th	Day	8% 2 7% 27% 37% 19%	671
	11th to 20th	Day	7% 3 7% 25% 36% 23%	668
	21st to end	Day	10% 1 6% 26% 33% 24%	739
August	1st to 10th	Day	4 1 3 27% 42% 24%	676
	11th to 20th	Day	5% 1 4 14% 46% 30%	488
	21st to end	Day	12% 2 6% 21% 32% 27%	539
September	1st to 10th	Day	10% 2 9% 22% 36% 20%	433
	11th to 20th	Day	13% 2 7% 31% 31% 16%	300
	21st to end	Day	15% 2 10% 28% 35% 11%	300
October	1st to 10th	Day	6% 3 19% 42% 23% 7%	300
	11th to 20th	Day	12% 3 19% 39% 19% 8%	300
	21st to end	Day	19% 8% 25% 30% 14% 5%	330
November	1st to 10th	Day	14% 7% 25% 32% 20% 2	282
	11th to 20th	Day	16% 11% 33% 30% 9% 2	270
	21st to end	Day	23% 17% 30% 20% 8% 2	270
December	1st to 10th	Day	20% 9% 31% 24% 12% 3	270
	11th to 20th	Day	17% 15% 40% 23% 4 1	270
	21st to end	Day	21% 16% 38% 18% 5% 2	297
January	1st to 10th	Night	23% 10% 31% 28% 8%	950
	11th to 20th	Night	23% 9% 31% 29% 8%	950
	21st to end	Night	23% 11% 30% 31% 6%	1045
February	1st to 10th	Night	24% 12% 30% 30% 4	950
	11th to 20th	Night	29% 8% 31% 26% 6%	683
	21st to end	Night	27% 10% 37% 24% 2	471
March	1st to 10th	Night	26% 9% 30% 31% 4	570
	11th to 20th	Night	21% 10% 34% 29% 6%	570
	21st to end	Night	21% 8% 33% 28% 9%	627
April	1st to 10th	Night	17% 11% 36% 30% 6%	570
	11th to 20th	Night	22% 10% 27% 30% 11%	563
	21st to end	Night	18% 8% 33% 32% 10%	570
May	1st to 10th	Night	16% 8% 28% 38% 9%	570
	11th to 20th	Night	13% 5% 25% 40% 16% 1	561
	21st to end	Night	7% 5% 22% 38% 25% 2	617
June	1st to 10th	Night	6% 2 9% 40% 40% 3	570
	11th to 20th	Night	5% 1 11% 44% 36% 4	570
	21st to end	Night	8% 3 9% 30% 43% 7%	570
July	1st to 10th	Night	6% 2 5% 30% 47% 10%	555
	11th to 20th	Night	3 1 5% 31% 47% 13%	552
	21st to end	Night	5% 1 3 29% 49% 12%	624
August	1st to 10th	Night	3 2 29% 56% 10%	567
	11th to 20th	Night	4 3 23% 56% 14%	564
	21st to end	Night	7% 2 4 25% 50% 12%	627
September	1st to 10th	Night	8% 1 6% 25% 49% 10%	570
	11th to 20th	Night	11% 1 6% 25% 49% 8%	570
	21st to end	Night	10% 1 9% 32% 41% 8%	570
October	1st to 10th	Night	7% 2 12% 35% 39% 5%	741
	11th to 20th	Night	11% 3 19% 40% 23% 3	760
	21st to end	Night	13% 6% 21% 35% 22% 3	836
November	1st to 10th	Night	13% 3 21% 37% 24% 2	760
	11th to 20th	Night	14% 8% 24% 38% 16%	760
	21st to end	Night	18% 7% 30% 29% 14% 1	760
December	1st to 10th	Night	21% 8% 26% 31% 13% 1	906
	11th to 20th	Night	24% 9% 29% 31% 7%	950
	21st to end	Night	23% 10% 29% 30% 8%	1045

Page generated at 2024-11-03 01:11:18. Version ac07

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