TAMUK Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the TAMUK Observatory clear sky chart from 2005-11-06 to 2024-03-18.

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	11% 5% 2 5% 5% 3 5% 5% 6% 8% 44%	79181
	Night	12% 5% 2 4 4 2 4 4 5% 7% 50%	80678
Transparency	Day	35% 8% 13% 21% 16% 7%	78906
	Night	33% 7% 14% 22% 15% 9%	80473
Seeing	Day	11% 5% 22% 33% 23% 7%	13577
	Night	14% 4 23% 37% 20% 2	23724

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% 7% 3 5% 4 3 4 4 5% 6% 45%	2847
	11th to 20th	Day	14% 5% 2 4 4 2 4 4 4 7% 50%	2859
	21st to end	Day	22% 6% 3 5% 5% 3 4 5% 6% 6% 36%	3487
February	1st to 10th	Day	20% 7% 3 5% 5% 3 4 4 5% 5% 39%	1900
	11th to 20th	Day	18% 6% 3 5% 4 2 3 3 5% 6% 45%	1849
	21st to end	Day	16% 7% 3 5% 5% 2 4 3 4 5% 46%	1594
March	1st to 10th	Day	20% 6% 2 5% 5% 3 4 5% 6% 9% 36%	2090
	11th to 20th	Day	18% 7% 3 6% 5% 3 4 4 5% 7% 38%	2057
	21st to end	Day	11% 6% 3 4 5% 3 5% 4 4 7% 48%	2178
April	1st to 10th	Day	11% 6% 3 6% 5% 3 5% 5% 6% 7% 44%	1980
	11th to 20th	Day	14% 7% 3 5% 5% 3 4 4 6% 7% 42%	1956
	21st to end	Day	11% 5% 2 5% 5% 3 5% 5% 6% 7% 45%	2128
May	1st to 10th	Day	8% 6% 2 7% 6% 4 5% 5% 6% 8% 43%	2340
	11th to 20th	Day	9% 6% 3 7% 5% 3 5% 5% 6% 8% 43%	2302
	21st to end	Day	7% 4 2 5% 5% 4 7% 7% 8% 10% 41%	2531
June	1st to 10th	Day	4 3 1 4 4 3 6% 6% 7% 11% 51%	2340
	11th to 20th	Day	4 3 1 5% 6% 4 5% 6% 6% 12% 49%	2340
	21st to end	Day	7% 4 2 5% 5% 4 7% 7% 8% 10% 40%	2340
July	1st to 10th	Day	8% 5% 3 7% 6% 3 8% 6% 7% 9% 37%	2340
	11th to 20th	Day	4 2 1 4 5% 4 6% 6% 8% 11% 50%	2340
	21st to end	Day	4 3 2 4 5% 3 6% 6% 8% 10% 48%	2546
August	1st to 10th	Day	1 2 2 2 4 3 5% 6% 6% 12% 57%	2233
	11th to 20th	Day	4 3 1 3 5% 3 5% 6% 8% 12% 50%	2123
	21st to end	Day	5% 4 2 6% 6% 4 6% 6% 8% 11% 41%	2217
September	1st to 10th	Day	9% 6% 2 7% 9% 5% 6% 6% 7% 9% 34%	1980
	11th to 20th	Day	10% 6% 3 8% 6% 4 6% 6% 6% 9% 35%	1980
	21st to end	Day	8% 6% 3 5% 5% 4 5% 5% 8% 9% 43%	1980
October	1st to 10th	Day	6% 4 2 5% 5% 3 6% 6% 7% 8% 48%	1980
	11th to 20th	Day	10% 5% 2 5% 5% 3 5% 5% 5% 8% 48%	1877
	21st to end	Day	9% 4 2 5% 2 3 4 4 4 6% 58%	1980
November	1st to 10th	Day	10% 4 2 6% 5% 3 6% 6% 6% 7% 45%	1858
	11th to 20th	Day	14% 7% 3 6% 4 3 4 4 5% 6% 44%	1900
	21st to end	Day	17% 6% 3 4 5% 3 5% 5% 4 7% 42%	1723
December	1st to 10th	Day	19% 6% 2 4 5% 2 3 4 4 7% 43%	1710
	11th to 20th	Day	16% 7% 2 5% 5% 3 5% 4 5% 7% 40%	2161
	21st to end	Day	16% 5% 2 5% 5% 3 4 4 4 7% 44%	3135
January	1st to 10th	Night	19% 5% 2 5% 4 2 3 4 4 5% 46%	4108
	11th to 20th	Night	15% 5% 2 4 3 2 3 3 4 7% 53%	4120
	21st to end	Night	23% 7% 3 6% 4 2 4 4 5% 6% 35%	4198
February	1st to 10th	Night	18% 7% 2 4 4 3 4 5% 5% 5% 43%	2280
	11th to 20th	Night	19% 6% 3 4 3 2 4 4 4 5% 45%	2218
	21st to end	Night	17% 6% 3 4 5% 2 3 3 4 6% 47%	1860
March	1st to 10th	Night	17% 6% 3 5% 3 3 3 4 5% 7% 43%	2090
	11th to 20th	Night	16% 9% 3 6% 6% 3 4 5% 4 7% 37%	2068
	21st to end	Night	13% 5% 3 4 4 2 3 3 5% 8% 51%	2178
April	1st to 10th	Night	13% 6% 2 5% 5% 3 5% 5% 7% 10% 39%	1980
	11th to 20th	Night	18% 6% 2 4 4 2 4 5% 5% 6% 43%	1953
	21st to end	Night	15% 6% 3 5% 5% 3 5% 5% 5% 7% 41%	1827
May	1st to 10th	Night	11% 5% 3 5% 5% 3 5% 4 7% 9% 43%	1620
	11th to 20th	Night	11% 5% 2 4 6% 4 5% 5% 7% 9% 43%	1593
	21st to end	Night	6% 4 3 5% 5% 3 4 5% 7% 13% 44%	1745
June	1st to 10th	Night	3 3 1 3 5% 3 4 4 6% 10% 59%	1620
	11th to 20th	Night	3 2 2 4 5% 2 4 4 7% 10% 56%	1620
	21st to end	Night	5% 4 2 4 3 4 4 5% 8% 11% 52%	1620
July	1st to 10th	Night	6% 4 2 4 5% 2 5% 5% 7% 13% 48%	1620
	11th to 20th	Night	2 1 1 2 3 2 4 4 7% 11% 63%	1620
	21st to end	Night	3 2 1 2 3 2 3 4 5% 11% 65%	1772
August	1st to 10th	Night	1 1 1 1 2 1 2 3 5% 8% 76%	1700
	11th to 20th	Night	3 2 1 2 3 1 3 3 5% 11% 66%	1778
	21st to end	Night	3 3 2 4 4 3 4 5% 6% 9% 58%	2137
September	1st to 10th	Night	6% 5% 2 5% 6% 3 4 5% 7% 10% 49%	1980
	11th to 20th	Night	9% 6% 2 5% 5% 3 5% 6% 5% 9% 47%	1980
	21st to end	Night	6% 4 2 4 3 3 4 4 5% 8% 56%	1980
October	1st to 10th	Night	4 3 1 3 3 2 4 4 5% 7% 64%	1980
	11th to 20th	Night	10% 5% 2 3 3 1 3 4 5% 7% 57%	2065
	21st to end	Night	10% 3 2 4 3 1 3 3 3 4 65%	2376
November	1st to 10th	Night	11% 4 2 3 4 2 4 4 4 6% 56%	2220
	11th to 20th	Night	14% 5% 2 6% 4 2 4 3 3 5% 53%	2280
	21st to end	Night	16% 7% 3 5% 4 2 4 4 5% 5% 47%	2454
December	1st to 10th	Night	17% 6% 3 4 4 2 3 3 3 7% 47%	2470
	11th to 20th	Night	18% 7% 3 5% 4 3 3 4 4 6% 42%	3036
	21st to end	Night	14% 8% 3 6% 4 2 4 4 5% 6% 44%	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% 7% 7% 14% 20% 14%	2848
	11th to 20th	Day	34% 5% 7% 23% 18% 13%	2859
	21st to end	Day	47% 5% 7% 15% 17% 9%	3487
February	1st to 10th	Day	47% 5% 8% 10% 17% 13%	1900
	11th to 20th	Day	41% 3 10% 18% 16% 11%	1859
	21st to end	Day	41% 5% 7% 18% 19% 9%	1594
March	1st to 10th	Day	44% 6% 13% 15% 13% 8%	2090
	11th to 20th	Day	46% 6% 11% 12% 15% 10%	2057
	21st to end	Day	35% 6% 13% 19% 17% 10%	2178
April	1st to 10th	Day	38% 6% 14% 18% 16% 8%	1980
	11th to 20th	Day	39% 8% 10% 18% 14% 10%	1956
	21st to end	Day	34% 8% 12% 21% 15% 10%	2128
May	1st to 10th	Day	35% 9% 14% 20% 14% 8%	2340
	11th to 20th	Day	38% 8% 12% 21% 18% 3	2306
	21st to end	Day	31% 10% 13% 26% 19% 1	2531
June	1st to 10th	Day	23% 8% 16% 32% 18% 3	2340
	11th to 20th	Day	25% 10% 13% 30% 18% 3	2340
	21st to end	Day	31% 13% 19% 27% 9% 1	2340
July	1st to 10th	Day	37% 13% 17% 25% 8%	2276
	11th to 20th	Day	25% 9% 25% 29% 12%	2271
	21st to end	Day	24% 11% 26% 33% 6%	2405
August	1st to 10th	Day	17% 9% 23% 39% 11%	2219
	11th to 20th	Day	21% 10% 25% 37% 6%	2123
	21st to end	Day	31% 12% 23% 24% 8% 2	2217
September	1st to 10th	Day	41% 12% 15% 16% 13% 2	1980
	11th to 20th	Day	41% 11% 14% 19% 12% 3	1980
	21st to end	Day	32% 10% 14% 22% 14% 7%	1980
October	1st to 10th	Day	30% 9% 12% 21% 24% 5%	1980
	11th to 20th	Day	33% 8% 10% 21% 17% 12%	1877
	21st to end	Day	26% 6% 7% 19% 26% 15%	1980
November	1st to 10th	Day	35% 7% 11% 20% 19% 8%	1858
	11th to 20th	Day	42% 5% 12% 16% 15% 11%	1900
	21st to end	Day	42% 6% 11% 15% 18% 10%	1723
December	1st to 10th	Day	41% 5% 10% 19% 18% 7%	1710
	11th to 20th	Day	42% 7% 8% 13% 17% 13%	2159
	21st to end	Day	40% 6% 7% 18% 20% 9%	3135
January	1st to 10th	Night	39% 5% 8% 12% 17% 19%	4108
	11th to 20th	Night	32% 4 7% 21% 19% 16%	4120
	21st to end	Night	49% 5% 7% 13% 18% 8%	4198
February	1st to 10th	Night	42% 6% 10% 13% 14% 15%	2280
	11th to 20th	Night	42% 6% 10% 15% 17% 11%	2218
	21st to end	Night	41% 5% 9% 20% 16% 9%	1860
March	1st to 10th	Night	40% 6% 14% 17% 15% 8%	2090
	11th to 20th	Night	47% 7% 10% 12% 15% 10%	2068
	21st to end	Night	33% 5% 15% 19% 16% 10%	2178
April	1st to 10th	Night	40% 7% 15% 18% 13% 7%	1980
	11th to 20th	Night	41% 6% 11% 17% 14% 11%	1953
	21st to end	Night	42% 7% 10% 17% 15% 9%	1827
May	1st to 10th	Night	37% 7% 15% 20% 11% 9%	1620
	11th to 20th	Night	36% 8% 14% 23% 16% 3	1594
	21st to end	Night	29% 9% 21% 27% 13% 1	1746
June	1st to 10th	Night	21% 6% 20% 33% 18% 2	1620
	11th to 20th	Night	22% 7% 14% 37% 17% 2	1620
	21st to end	Night	25% 9% 25% 31% 9% 1	1620
July	1st to 10th	Night	27% 11% 25% 29% 7% 1	1575
	11th to 20th	Night	14% 11% 31% 33% 11%	1566
	21st to end	Night	14% 9% 32% 37% 8%	1673
August	1st to 10th	Night	8% 8% 30% 43% 10%	1690
	11th to 20th	Night	15% 9% 31% 38% 6%	1778
	21st to end	Night	23% 11% 26% 31% 8% 1	2137
September	1st to 10th	Night	31% 10% 26% 19% 12% 3	1980
	11th to 20th	Night	34% 9% 18% 26% 10% 2	1980
	21st to end	Night	27% 8% 16% 27% 17% 5%	1980
October	1st to 10th	Night	20% 7% 16% 29% 21% 7%	1980
	11th to 20th	Night	26% 7% 12% 25% 18% 12%	2065
	21st to end	Night	24% 5% 7% 21% 26% 17%	2376
November	1st to 10th	Night	28% 8% 12% 21% 23% 8%	2220
	11th to 20th	Night	36% 5% 12% 19% 18% 10%	2280
	21st to end	Night	39% 5% 11% 21% 14% 10%	2454
December	1st to 10th	Night	39% 5% 11% 20% 16% 9%	2470
	11th to 20th	Night	42% 6% 7% 17% 13% 14%	3037
	21st to end	Night	40% 7% 10% 13% 17% 13%	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	21% 8% 31% 28% 9% 3	270
	11th to 20th	Day	17% 7% 35% 29% 10% 2	270
	21st to end	Day	23% 11% 33% 23% 10% 1	297
February	1st to 10th	Day	25% 10% 28% 23% 15%	270
	11th to 20th	Day	23% 9% 33% 27% 8%	270
	21st to end	Day	18% 12% 43% 21% 6%	225
March	1st to 10th	Day	20% 11% 34% 29% 6%	270
	11th to 20th	Day	21% 11% 42% 20% 5%	261
	21st to end	Day	14% 10% 39% 32% 4	264
April	1st to 10th	Day	18% 7% 37% 30% 8% 1	240
	11th to 20th	Day	13% 14% 35% 26% 9% 1	234
	21st to end	Day	12% 9% 40% 31% 8% 1	388
May	1st to 10th	Day	11% 8% 44% 27% 10%	603
	11th to 20th	Day	12% 5% 38% 32% 11% 2	625
	21st to end	Day	8% 3 35% 37% 16% 1	679
June	1st to 10th	Day	4 1 17% 42% 30% 5%	630
	11th to 20th	Day	5% 1 18% 46% 27% 4	630
	21st to end	Day	7% 2 13% 39% 30% 10%	630
July	1st to 10th	Day	6% 1 10% 41% 33% 9%	621
	11th to 20th	Day	3 1 6% 41% 39% 11%	618
	21st to end	Day	4 1 6% 41% 37% 11%	684
August	1st to 10th	Day	1 1 6% 45% 33% 14%	531
	11th to 20th	Day	3 1 7% 43% 32% 14%	437
	21st to end	Day	4 2 4 31% 32% 26%	336
September	1st to 10th	Day	11% 5% 25% 41% 18%	270
	11th to 20th	Day	6% 6% 19% 46% 23%	270
	21st to end	Day	7% 1 9% 20% 41% 21%	270
October	1st to 10th	Day	7% 1 5% 30% 40% 17%	270
	11th to 20th	Day	12% 13% 32% 28% 16%	270
	21st to end	Day	12% 5% 25% 31% 22% 6%	297
November	1st to 10th	Day	14% 3 16% 33% 29% 6%	270
	11th to 20th	Day	22% 4 18% 25% 25% 6%	270
	21st to end	Day	25% 6% 27% 26% 12% 4	270
December	1st to 10th	Day	22% 3 19% 32% 19% 6%	270
	11th to 20th	Day	18% 13% 26% 28% 14% 2	270
	21st to end	Day	19% 12% 25% 28% 12% 4	297
January	1st to 10th	Night	21% 6% 26% 35% 11%	950
	11th to 20th	Night	19% 7% 29% 36% 8% 1	950
	21st to end	Night	22% 8% 26% 35% 9%	841
February	1st to 10th	Night	22% 7% 33% 32% 6%	760
	11th to 20th	Night	23% 8% 31% 31% 6%	744
	21st to end	Night	22% 9% 39% 25% 5%	604
March	1st to 10th	Night	21% 9% 33% 29% 6% 1	570
	11th to 20th	Night	19% 9% 36% 31% 5%	564
	21st to end	Night	13% 7% 40% 34% 5%	594
April	1st to 10th	Night	13% 7% 41% 33% 6%	540
	11th to 20th	Night	20% 7% 34% 32% 7%	533
	21st to end	Night	17% 7% 41% 29% 6%	540
May	1st to 10th	Night	12% 6% 41% 34% 7%	540
	11th to 20th	Night	12% 4 33% 41% 10%	531
	21st to end	Night	8% 3 28% 46% 14%	584
June	1st to 10th	Night	3 1 17% 52% 25% 1	540
	11th to 20th	Night	4 1 17% 58% 19% 1	540
	21st to end	Night	5% 2 14% 44% 34% 2	540
July	1st to 10th	Night	6% 1 9% 47% 33% 4	525
	11th to 20th	Night	1 1 5% 46% 44% 3	522
	21st to end	Night	2 7% 47% 40% 4	591
August	1st to 10th	Night	4 46% 46% 4	537
	11th to 20th	Night	4 4 43% 45% 4	534
	21st to end	Night	5% 1 5% 30% 52% 8%	594
September	1st to 10th	Night	6% 1 5% 30% 51% 7%	540
	11th to 20th	Night	11% 1 5% 24% 50% 11%	540
	21st to end	Night	9% 1 8% 29% 47% 7%	540
October	1st to 10th	Night	4 1 5% 37% 48% 4	540
	11th to 20th	Night	12% 2 14% 42% 27% 4	625
	21st to end	Night	9% 3 23% 41% 22% 1	792
November	1st to 10th	Night	11% 3 18% 42% 24% 2	740
	11th to 20th	Night	17% 2 24% 37% 19% 2	760
	21st to end	Night	19% 6% 24% 34% 17% 1	934
December	1st to 10th	Night	18% 5% 23% 36% 16% 1	950
	11th to 20th	Night	24% 7% 25% 34% 10%	950
	21st to end	Night	19% 6% 29% 35% 11% 1	1045

Page generated at 2024-03-15 13:01:41. Version ac07

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