Texas A&M University Teaching Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Texas A&M University Teaching 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	12% 6% 2 6% 4 4 4 4 6% 8% 44%	101079
	Night	13% 6% 2 5% 3 3 3 3 5% 7% 49%	98054
Transparency	Day	36% 7% 12% 20% 18% 7%	104809
	Night	33% 6% 12% 20% 19% 10%	102438
Seeing	Day	13% 6% 19% 26% 25% 10%	14909
	Night	14% 6% 24% 35% 18% 2	24765

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	16% 9% 2 4 3 3 3 4 5% 6% 45%	2847
	11th to 20th	Day	18% 6% 2 5% 2 2 2 2 4 6% 51%	2850
	21st to end	Day	22% 10% 3 6% 3 2 2 2 4 7% 38%	3135
February	1st to 10th	Day	22% 8% 3 7% 3 3 3 3 4 5% 39%	1862
	11th to 20th	Day	22% 7% 2 5% 5% 4 3 3 3 6% 41%	1849
	21st to end	Day	20% 7% 2 5% 4 3 3 3 4 5% 44%	1660
March	1st to 10th	Day	16% 8% 3 8% 5% 5% 4 4 5% 6% 35%	3436
	11th to 20th	Day	19% 8% 3 7% 5% 5% 5% 4 6% 6% 31%	3480
	21st to end	Day	16% 8% 3 6% 4 4 4 3 5% 6% 40%	3814
April	1st to 10th	Day	14% 8% 4 7% 5% 4 5% 3 5% 6% 39%	2090
	11th to 20th	Day	15% 8% 3 7% 5% 4 4 4 5% 7% 40%	2156
	21st to end	Day	13% 6% 2 6% 3 4 5% 3 5% 6% 45%	2280
May	1st to 10th	Day	18% 9% 3 8% 5% 4 5% 4 6% 7% 30%	4077
	11th to 20th	Day	14% 6% 2 7% 4 4 4 4 7% 7% 41%	4082
	21st to end	Day	9% 6% 2 7% 5% 6% 7% 5% 9% 10% 33%	4477
June	1st to 10th	Day	6% 4 2 4 5% 5% 5% 5% 9% 9% 44%	2470
	11th to 20th	Day	6% 4 2 5% 5% 5% 6% 5% 7% 9% 48%	2470
	21st to end	Day	6% 5% 2 6% 6% 6% 7% 6% 8% 10% 38%	2470
July	1st to 10th	Day	9% 4 1 5% 4 4 4 4 7% 11% 46%	4120
	11th to 20th	Day	5% 5% 2 6% 5% 5% 6% 5% 8% 11% 42%	4120
	21st to end	Day	13% 7% 3 6% 5% 5% 5% 5% 7% 10% 33%	4465
August	1st to 10th	Day	2 1 1 2 2 2 3 3 5% 8% 70%	4104
	11th to 20th	Day	3 2 1 3 3 4 5% 5% 7% 13% 55%	4021
	21st to end	Day	5% 4 2 5% 5% 6% 6% 5% 7% 11% 45%	3925
September	1st to 10th	Day	6% 5% 2 7% 5% 6% 6% 5% 6% 8% 45%	2090
	11th to 20th	Day	11% 6% 2 7% 5% 4 5% 5% 6% 7% 41%	2090
	21st to end	Day	6% 4 1 5% 4 5% 6% 5% 5% 6% 53%	2090
October	1st to 10th	Day	5% 4 1 5% 4 3 4 3 4 7% 60%	2030
	11th to 20th	Day	14% 4 2 4 3 3 3 3 4 6% 55%	1900
	21st to end	Day	13% 4 2 4 3 3 3 3 3 5% 58%	2090
November	1st to 10th	Day	11% 7% 2 5% 4 5% 5% 3 5% 7% 47%	1898
	11th to 20th	Day	11% 6% 2 6% 3 3 3 3 5% 6% 52%	1900
	21st to end	Day	18% 8% 2 5% 5% 3 4 3 5% 4 42%	1725
December	1st to 10th	Day	16% 7% 2 6% 3 3 3 3 4 6% 45%	1710
	11th to 20th	Day	18% 7% 2 6% 4 4 3 4 4 5% 43%	2161
	21st to end	Day	16% 8% 3 6% 3 3 3 3 3 4 47%	3135
January	1st to 10th	Night	18% 8% 2 4 2 3 3 3 3 5% 50%	4108
	11th to 20th	Night	18% 6% 1 4 2 2 2 2 2 4 56%	4120
	21st to end	Night	22% 8% 3 5% 4 3 3 3 4 6% 41%	4532
February	1st to 10th	Night	20% 7% 3 5% 4 3 3 2 4 5% 44%	2333
	11th to 20th	Night	21% 7% 3 4 3 3 3 2 3 4 47%	2218
	21st to end	Night	21% 6% 2 5% 3 3 4 3 4 5% 44%	1792
March	1st to 10th	Night	20% 8% 3 7% 4 4 4 3 5% 6% 36%	3419
	11th to 20th	Night	22% 8% 3 8% 5% 5% 3 3 5% 6% 33%	3480
	21st to end	Night	14% 7% 3 6% 5% 3 3 3 5% 5% 45%	3817
April	1st to 10th	Night	13% 5% 2 5% 4 4 4 4 5% 7% 47%	2090
	11th to 20th	Night	14% 6% 2 6% 4 4 3 3 5% 8% 45%	1970
	21st to end	Night	14% 7% 2 5% 4 3 3 3 5% 6% 48%	1900
May	1st to 10th	Night	20% 9% 3 8% 4 3 4 3 4 7% 35%	2823
	11th to 20th	Night	11% 6% 2 6% 5% 4 5% 3 5% 7% 46%	2823
	21st to end	Night	10% 6% 2 6% 5% 5% 5% 4 6% 10% 40%	3090
June	1st to 10th	Night	5% 3 2 4 3 3 4 3 8% 11% 56%	1710
	11th to 20th	Night	3 3 1 3 3 3 4 3 6% 10% 61%	1710
	21st to end	Night	4 4 1 5% 4 5% 5% 4 8% 11% 50%	1710
July	1st to 10th	Night	4 3 2 4 4 4 4 5% 7% 12% 50%	2850
	11th to 20th	Night	3 4 2 4 4 3 4 4 7% 11% 53%	2850
	21st to end	Night	10% 8% 2 6% 4 5% 4 4 7% 11% 39%	3098
August	1st to 10th	Night	1 1 2 2 2 2 2 5% 10% 74%	2836
	11th to 20th	Night	3 2 1 3 3 3 4 4 7% 12% 59%	2815
	21st to end	Night	3 3 2 4 3 4 5% 4 8% 12% 52%	3725
September	1st to 10th	Night	5% 5% 2 6% 4 4 4 4 6% 9% 50%	2090
	11th to 20th	Night	10% 5% 3 6% 4 5% 5% 4 6% 6% 47%	2090
	21st to end	Night	7% 4 1 4 3 3 4 3 6% 7% 58%	2090
October	1st to 10th	Night	4 3 1 4 3 3 3 3 4 7% 64%	2128
	11th to 20th	Night	11% 4 1 3 3 3 2 2 4 6% 61%	2280
	21st to end	Night	12% 5% 2 4 3 2 2 2 3 4 61%	2508
November	1st to 10th	Night	12% 5% 2 5% 3 3 3 3 4 6% 54%	2280
	11th to 20th	Night	11% 5% 2 4 4 4 4 3 4 6% 52%	2280
	21st to end	Night	16% 7% 2 5% 4 3 4 3 5% 6% 45%	2451
December	1st to 10th	Night	17% 8% 2 4 4 3 3 3 5% 6% 46%	2470
	11th to 20th	Night	17% 8% 3 6% 4 3 3 3 5% 5% 44%	3036
	21st to end	Night	16% 6% 3 5% 3 3 3 2 4 5% 51%	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	37% 6% 7% 17% 22% 10%	2848
	11th to 20th	Day	36% 3 7% 19% 28% 6%	2850
	21st to end	Day	48% 4 4 13% 20% 11%	3135
February	1st to 10th	Day	48% 5% 6% 12% 18% 11%	1862
	11th to 20th	Day	46% 3 7% 16% 18% 10%	1859
	21st to end	Day	43% 5% 8% 15% 17% 13%	1660
March	1st to 10th	Day	46% 9% 9% 13% 19% 5%	3436
	11th to 20th	Day	50% 9% 10% 11% 15% 6%	3480
	21st to end	Day	42% 6% 10% 16% 21% 5%	3814
April	1st to 10th	Day	45% 7% 6% 17% 14% 11%	2090
	11th to 20th	Day	44% 7% 9% 14% 18% 9%	2156
	21st to end	Day	38% 6% 10% 18% 21% 6%	2280
May	1st to 10th	Day	48% 11% 12% 14% 10% 5%	4115
	11th to 20th	Day	39% 9% 10% 17% 23% 3	4086
	21st to end	Day	38% 13% 14% 25% 10% 1	4489
June	1st to 10th	Day	31% 10% 15% 27% 15% 2	2470
	11th to 20th	Day	28% 9% 17% 24% 17% 4	2470
	21st to end	Day	37% 10% 15% 24% 12% 2	2470
July	1st to 10th	Day	30% 7% 27% 31% 5%	4056
	11th to 20th	Day	33% 8% 18% 25% 14% 1	4051
	21st to end	Day	44% 9% 18% 22% 6%	4325
August	1st to 10th	Day	14% 5% 14% 40% 26% 1	4090
	11th to 20th	Day	19% 7% 30% 34% 9% 2	4060
	21st to end	Day	31% 11% 20% 23% 13% 1	3924
September	1st to 10th	Day	35% 10% 12% 21% 15% 7%	2090
	11th to 20th	Day	40% 9% 13% 15% 17% 5%	2090
	21st to end	Day	30% 8% 11% 20% 17% 14%	2090
October	1st to 10th	Day	15% 4 7% 12% 21% 41%	3368
	11th to 20th	Day	20% 4 6% 16% 34% 20%	3140
	21st to end	Day	24% 5% 5% 21% 31% 15%	3428
November	1st to 10th	Day	35% 7% 10% 17% 21% 10%	1898
	11th to 20th	Day	33% 5% 10% 17% 22% 12%	1900
	21st to end	Day	45% 5% 7% 14% 19% 10%	1725
December	1st to 10th	Day	40% 5% 10% 17% 19% 8%	1710
	11th to 20th	Day	43% 6% 7% 13% 22% 10%	2159
	21st to end	Day	40% 4 6% 13% 26% 10%	3135
January	1st to 10th	Night	36% 5% 7% 18% 21% 13%	4108
	11th to 20th	Night	34% 3 6% 17% 28% 12%	4120
	21st to end	Night	45% 5% 5% 14% 21% 10%	4532
February	1st to 10th	Night	44% 4 5% 12% 19% 15%	2333
	11th to 20th	Night	42% 4 6% 15% 19% 13%	2218
	21st to end	Night	44% 4 8% 13% 16% 15%	1792
March	1st to 10th	Night	47% 7% 10% 12% 18% 6%	3419
	11th to 20th	Night	51% 7% 9% 15% 13% 6%	3480
	21st to end	Night	40% 7% 9% 14% 22% 8%	3817
April	1st to 10th	Night	36% 7% 10% 18% 17% 13%	2090
	11th to 20th	Night	37% 6% 11% 16% 17% 13%	1970
	21st to end	Night	36% 6% 10% 19% 22% 7%	1900
May	1st to 10th	Night	46% 9% 11% 18% 11% 5%	2850
	11th to 20th	Night	34% 8% 12% 20% 21% 4	2824
	21st to end	Night	35% 11% 15% 26% 12% 1	3099
June	1st to 10th	Night	21% 8% 20% 29% 21% 2	1710
	11th to 20th	Night	18% 8% 18% 32% 19% 5%	1710
	21st to end	Night	27% 7% 19% 29% 16% 2	1710
July	1st to 10th	Night	26% 8% 29% 32% 5%	2805
	11th to 20th	Night	24% 8% 21% 33% 13%	2796
	21st to end	Night	38% 9% 23% 23% 7%	2999
August	1st to 10th	Night	8% 5% 16% 41% 27% 2	2826
	11th to 20th	Night	17% 7% 30% 35% 11% 1	2842
	21st to end	Night	24% 11% 23% 28% 13% 2	3725
September	1st to 10th	Night	27% 10% 19% 22% 15% 7%	2090
	11th to 20th	Night	35% 9% 15% 19% 16% 7%	2090
	21st to end	Night	24% 6% 15% 20% 20% 14%	2090
October	1st to 10th	Night	13% 4 7% 15% 18% 42%	3544
	11th to 20th	Night	16% 3 4 20% 32% 25%	3779
	21st to end	Night	21% 3 5% 21% 32% 18%	4120
November	1st to 10th	Night	31% 6% 10% 21% 21% 12%	2280
	11th to 20th	Night	34% 5% 9% 19% 20% 13%	2280
	21st to end	Night	40% 4 9% 15% 19% 13%	2451
December	1st to 10th	Night	40% 5% 8% 20% 18% 10%	2470
	11th to 20th	Night	42% 5% 7% 11% 21% 14%	3037
	21st to end	Night	36% 5% 6% 14% 28% 10%	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	24% 11% 30% 26% 7% 2	270
	11th to 20th	Day	24% 10% 34% 24% 6% 1	270
	21st to end	Day	22% 13% 38% 17% 9% 1	297
February	1st to 10th	Day	30% 13% 30% 19% 7%	270
	11th to 20th	Day	29% 16% 31% 19% 6%	270
	21st to end	Day	27% 19% 36% 15% 3	225
March	1st to 10th	Day	23% 14% 37% 19% 8%	270
	11th to 20th	Day	20% 16% 38% 20% 4 2	270
	21st to end	Day	20% 12% 41% 18% 8% 1	297
April	1st to 10th	Day	19% 15% 40% 22% 3 1	270
	11th to 20th	Day	23% 15% 29% 21% 10% 2	354
	21st to end	Day	18% 9% 33% 27% 11% 2	460
May	1st to 10th	Day	16% 8% 35% 30% 10% 1	648
	11th to 20th	Day	14% 7% 26% 33% 16% 4	675
	21st to end	Day	11% 5% 23% 36% 20% 4	734
June	1st to 10th	Day	6% 2 13% 36% 32% 10%	680
	11th to 20th	Day	6% 2 11% 43% 31% 7%	680
	21st to end	Day	7% 2 10% 26% 39% 16%	680
July	1st to 10th	Day	7% 3 6% 28% 39% 17%	671
	11th to 20th	Day	3 4 29% 43% 21%	668
	21st to end	Day	6% 1 5% 24% 45% 19%	739
August	1st to 10th	Day	3 1 3 20% 53% 21%	676
	11th to 20th	Day	6% 2 21% 51% 20%	658
	21st to end	Day	8% 3 3 17% 38% 31%	388
September	1st to 10th	Day	5% 1 4 22% 37% 31%	300
	11th to 20th	Day	9% 5% 23% 37% 26%	300
	21st to end	Day	8% 2 8% 26% 37% 19%	300
October	1st to 10th	Day	4 1 12% 33% 37% 13%	300
	11th to 20th	Day	12% 3 20% 31% 23% 10%	300
	21st to end	Day	23% 8% 21% 20% 22% 6%	330
November	1st to 10th	Day	16% 5% 19% 35% 18% 7%	282
	11th to 20th	Day	16% 9% 24% 33% 14% 4	270
	21st to end	Day	24% 13% 29% 20% 11% 2	270
December	1st to 10th	Day	20% 5% 31% 23% 14% 6%	270
	11th to 20th	Day	26% 13% 31% 22% 7% 1	270
	21st to end	Day	23% 9% 34% 23% 9% 1	297
January	1st to 10th	Night	21% 8% 30% 33% 7%	950
	11th to 20th	Night	23% 10% 28% 30% 8%	950
	21st to end	Night	20% 9% 32% 32% 6%	1045
February	1st to 10th	Night	23% 12% 33% 27% 5%	813
	11th to 20th	Night	26% 10% 32% 28% 4	744
	21st to end	Night	26% 12% 40% 20% 2	536
March	1st to 10th	Night	22% 9% 40% 25% 4	570
	11th to 20th	Night	20% 9% 37% 28% 7%	570
	21st to end	Night	15% 9% 43% 28% 5%	627
April	1st to 10th	Night	15% 9% 41% 30% 4	570
	11th to 20th	Night	15% 11% 35% 32% 7%	563
	21st to end	Night	18% 8% 37% 28% 9%	570
May	1st to 10th	Night	14% 9% 40% 31% 6% 1	570
	11th to 20th	Night	12% 5% 30% 38% 13% 1	561
	21st to end	Night	9% 3 28% 42% 16% 1	617
June	1st to 10th	Night	6% 2 15% 47% 27% 3	570
	11th to 20th	Night	4 1 23% 48% 22% 2	570
	21st to end	Night	3 2 11% 46% 33% 5%	570
July	1st to 10th	Night	5% 2 6% 45% 37% 6%	555
	11th to 20th	Night	3 1 7% 48% 37% 4	552
	21st to end	Night	4 1 6% 49% 36% 4	624
August	1st to 10th	Night	2 5% 49% 40% 3	567
	11th to 20th	Night	5% 1 2 48% 39% 5%	564
	21st to end	Night	4 1 5% 35% 48% 7%	627
September	1st to 10th	Night	6% 2 8% 35% 42% 7%	570
	11th to 20th	Night	12% 2 5% 34% 42% 6%	570
	21st to end	Night	8% 1 10% 36% 39% 6%	570
October	1st to 10th	Night	5% 1 13% 43% 32% 6%	608
	11th to 20th	Night	12% 3 21% 42% 22% 1	760
	21st to end	Night	14% 6% 26% 32% 19% 3	836
November	1st to 10th	Night	14% 3 24% 38% 20% 2	760
	11th to 20th	Night	12% 8% 26% 39% 14% 1	760
	21st to end	Night	20% 9% 27% 29% 14% 1	931
December	1st to 10th	Night	21% 6% 27% 32% 12% 1	950
	11th to 20th	Night	24% 9% 27% 32% 7%	950
	21st to end	Night	21% 7% 30% 33% 9% 1	1045

Page generated at 2024-11-03 01:11:27. Version ac07

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