Round Top
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Round Top clear sky chart from 2005-11-06 to 2024-04-10.

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% 3 5% 5% 3 5% 5% 6% 7% 43%	83607
	Night	13% 6% 2 5% 4 3 4 4 5% 7% 48%	85227
Transparency	Day	39% 6% 11% 19% 18% 8%	83332
	Night	36% 6% 11% 20% 18% 10%	85022
Seeing	Day	12% 7% 20% 27% 25% 9%	13980
	Night	14% 8% 25% 35% 17% 2	24058

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	14% 10% 2 4 4 2 4 4 5% 6% 45%	2847
	11th to 20th	Day	16% 5% 2 4 4 2 2 3 4 6% 52%	2850
	21st to end	Day	23% 9% 3 6% 4 2 2 3 4 7% 38%	3144
February	1st to 10th	Day	22% 8% 4 5% 5% 2 3 3 3 5% 41%	1900
	11th to 20th	Day	21% 7% 2 5% 5% 3 3 4 4 4 42%	1849
	21st to end	Day	18% 7% 3 6% 4 2 3 3 5% 6% 43%	1645
March	1st to 10th	Day	14% 8% 3 8% 6% 3 5% 4 6% 7% 35%	3436
	11th to 20th	Day	19% 8% 3 8% 7% 4 5% 5% 5% 6% 30%	3480
	21st to end	Day	16% 7% 3 5% 5% 3 4 4 5% 6% 43%	3814
April	1st to 10th	Day	14% 8% 3 7% 5% 3 5% 5% 4 7% 39%	2079
	11th to 20th	Day	15% 8% 3 7% 5% 3 5% 4 4 5% 41%	2012
	21st to end	Day	13% 6% 3 5% 5% 3 5% 4 4 6% 46%	2171
May	1st to 10th	Day	12% 6% 3 5% 6% 3 6% 5% 6% 8% 40%	2340
	11th to 20th	Day	11% 6% 3 7% 5% 3 5% 5% 5% 8% 42%	2302
	21st to end	Day	11% 7% 3 7% 6% 4 7% 6% 6% 10% 34%	2531
June	1st to 10th	Day	5% 4 2 5% 6% 4 6% 6% 7% 9% 46%	2340
	11th to 20th	Day	5% 4 2 4 6% 3 6% 7% 9% 10% 45%	2340
	21st to end	Day	6% 6% 3 6% 7% 5% 7% 7% 8% 10% 34%	2340
July	1st to 10th	Day	10% 5% 3 6% 7% 4 6% 6% 7% 9% 36%	2340
	11th to 20th	Day	4 4 3 5% 6% 4 6% 7% 9% 11% 42%	2340
	21st to end	Day	4 2 2 4 6% 5% 6% 6% 9% 13% 43%	2546
August	1st to 10th	Day	2 2 1 4 6% 4 5% 6% 6% 11% 53%	2328
	11th to 20th	Day	5% 4 2 5% 6% 4 6% 6% 7% 10% 46%	2297
	21st to end	Day	6% 3 2 5% 6% 4 6% 8% 8% 10% 41%	2183
September	1st to 10th	Day	6% 5% 2 6% 6% 4 7% 6% 6% 8% 43%	1980
	11th to 20th	Day	11% 6% 3 6% 7% 4 5% 6% 6% 8% 39%	1980
	21st to end	Day	6% 6% 2 5% 6% 4 5% 6% 6% 7% 48%	1980
October	1st to 10th	Day	6% 3 1 4 5% 3 5% 5% 5% 8% 54%	1949
	11th to 20th	Day	12% 5% 2 5% 4 3 4 4 4 6% 51%	1800
	21st to end	Day	13% 4 2 4 3 2 4 3 4 5% 56%	1980
November	1st to 10th	Day	11% 6% 2 5% 4 3 5% 4 5% 8% 46%	1858
	11th to 20th	Day	12% 5% 2 5% 4 2 4 5% 4 6% 52%	1900
	21st to end	Day	17% 7% 3 6% 4 3 4 4 4 6% 42%	1720
December	1st to 10th	Day	16% 7% 3 5% 5% 3 4 3 4 6% 43%	1710
	11th to 20th	Day	16% 8% 2 6% 5% 3 4 3 4 6% 43%	2161
	21st to end	Day	16% 7% 3 5% 4 3 3 3 4 4 48%	3135
January	1st to 10th	Night	17% 8% 2 4 3 2 3 3 4 6% 47%	4108
	11th to 20th	Night	15% 6% 2 3 3 2 2 2 3 4 58%	4120
	21st to end	Night	22% 8% 3 5% 4 2 2 3 4 6% 41%	4532
February	1st to 10th	Night	19% 8% 3 6% 4 2 3 2 4 5% 43%	2285
	11th to 20th	Night	20% 8% 3 5% 4 2 2 2 3 6% 45%	2218
	21st to end	Night	22% 6% 3 3 5% 3 3 4 4 5% 42%	1808
March	1st to 10th	Night	19% 11% 3 6% 4 3 3 5% 5% 6% 33%	3419
	11th to 20th	Night	23% 9% 3 7% 6% 3 4 4 5% 6% 31%	3480
	21st to end	Night	14% 7% 3 6% 5% 3 4 4 4 5% 44%	3817
April	1st to 10th	Night	12% 6% 3 5% 4 2 5% 4 6% 8% 45%	2090
	11th to 20th	Night	14% 7% 4 5% 5% 2 3 4 4 7% 45%	1897
	21st to end	Night	13% 7% 2 5% 5% 2 4 3 4 6% 48%	1783
May	1st to 10th	Night	12% 7% 2 5% 5% 3 5% 4 6% 9% 43%	1620
	11th to 20th	Night	9% 6% 3 5% 4 3 4 4 5% 9% 48%	1593
	21st to end	Night	7% 4 3 4 5% 3 5% 5% 7% 10% 47%	1745
June	1st to 10th	Night	4 3 2 5% 4 2 4 4 5% 11% 56%	1620
	11th to 20th	Night	3 3 1 3 4 3 4 4 7% 11% 57%	1620
	21st to end	Night	4 3 2 5% 5% 3 6% 5% 9% 10% 46%	1620
July	1st to 10th	Night	6% 4 2 5% 4 3 5% 5% 6% 11% 49%	1620
	11th to 20th	Night	2 2 1 3 4 2 4 5% 6% 10% 60%	1620
	21st to end	Night	2 2 1 3 4 3 5% 5% 6% 14% 55%	1772
August	1st to 10th	Night	1 1 1 2 3 2 3 4 5% 12% 67%	1611
	11th to 20th	Night	4 4 1 3 3 3 5% 5% 6% 13% 53%	1600
	21st to end	Night	4 2 1 5% 5% 3 6% 6% 8% 12% 47%	2168
September	1st to 10th	Night	5% 4 2 4 5% 3 5% 5% 6% 9% 52%	1980
	11th to 20th	Night	9% 6% 3 6% 5% 3 4 5% 6% 9% 46%	1980
	21st to end	Night	8% 4 2 4 4 3 4 4 6% 9% 53%	1980
October	1st to 10th	Night	4 3 2 4 4 2 3 4 5% 7% 63%	1992
	11th to 20th	Night	11% 4 2 4 3 2 3 3 5% 6% 57%	2160
	21st to end	Night	12% 5% 2 3 3 2 3 3 3 4 60%	2376
November	1st to 10th	Night	10% 6% 2 4 4 2 4 4 4 6% 53%	2220
	11th to 20th	Night	11% 6% 2 4 4 3 3 4 5% 6% 51%	2280
	21st to end	Night	15% 6% 3 5% 4 2 3 3 5% 7% 45%	2455
December	1st to 10th	Night	17% 8% 2 4 4 3 3 4 4 7% 45%	2470
	11th to 20th	Night	16% 7% 4 6% 4 3 4 4 5% 5% 44%	3036
	21st to end	Night	16% 7% 2 4 3 3 3 3 3 5% 50%	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	40% 5% 5% 17% 21% 11%	2848
	11th to 20th	Day	35% 4 5% 21% 25% 10%	2850
	21st to end	Day	48% 3 4 11% 22% 11%	3144
February	1st to 10th	Day	48% 4 5% 13% 19% 12%	1900
	11th to 20th	Day	46% 5% 6% 15% 18% 10%	1859
	21st to end	Day	43% 4 9% 16% 16% 13%	1645
March	1st to 10th	Day	47% 5% 10% 15% 18% 6%	3436
	11th to 20th	Day	54% 5% 9% 10% 15% 7%	3480
	21st to end	Day	42% 4 8% 17% 22% 6%	3814
April	1st to 10th	Day	45% 5% 7% 17% 15% 11%	2079
	11th to 20th	Day	45% 5% 7% 14% 19% 10%	2012
	21st to end	Day	40% 5% 6% 20% 21% 8%	2171
May	1st to 10th	Day	40% 8% 10% 18% 16% 9%	2340
	11th to 20th	Day	40% 6% 12% 21% 18% 3	2306
	21st to end	Day	43% 8% 13% 21% 13% 2	2531
June	1st to 10th	Day	33% 6% 14% 27% 17% 2	2340
	11th to 20th	Day	29% 9% 15% 26% 18% 3	2340
	21st to end	Day	41% 11% 14% 23% 10% 1	2340
July	1st to 10th	Day	40% 9% 18% 24% 9% 1	2276
	11th to 20th	Day	31% 10% 20% 23% 15% 1	2271
	21st to end	Day	27% 10% 25% 30% 8% 1	2405
August	1st to 10th	Day	24% 10% 18% 33% 14% 1	2314
	11th to 20th	Day	31% 10% 20% 25% 11% 3	2297
	21st to end	Day	34% 10% 18% 24% 11% 3	2183
September	1st to 10th	Day	36% 9% 14% 21% 15% 6%	1980
	11th to 20th	Day	43% 8% 11% 17% 17% 4	1980
	21st to end	Day	34% 7% 9% 20% 17% 12%	1980
October	1st to 10th	Day	27% 5% 12% 22% 22% 13%	1949
	11th to 20th	Day	35% 5% 7% 17% 21% 16%	1800
	21st to end	Day	32% 4 6% 16% 23% 19%	1980
November	1st to 10th	Day	36% 6% 9% 18% 20% 10%	1858
	11th to 20th	Day	34% 5% 11% 16% 21% 13%	1900
	21st to end	Day	44% 4 7% 15% 17% 12%	1720
December	1st to 10th	Day	43% 4 9% 18% 19% 7%	1710
	11th to 20th	Day	43% 4 7% 11% 23% 11%	2159
	21st to end	Day	40% 4 5% 15% 25% 12%	3135
January	1st to 10th	Night	39% 4 6% 16% 19% 15%	4108
	11th to 20th	Night	33% 4 5% 18% 28% 13%	4120
	21st to end	Night	46% 3 4 14% 22% 11%	4532
February	1st to 10th	Night	46% 4 6% 11% 18% 15%	2285
	11th to 20th	Night	43% 4 6% 16% 18% 13%	2218
	21st to end	Night	46% 4 6% 14% 15% 14%	1808
March	1st to 10th	Night	50% 6% 10% 13% 15% 6%	3419
	11th to 20th	Night	54% 6% 8% 14% 11% 6%	3480
	21st to end	Night	42% 5% 9% 14% 21% 9%	3817
April	1st to 10th	Night	37% 7% 9% 19% 17% 11%	2090
	11th to 20th	Night	40% 4 10% 15% 16% 14%	1897
	21st to end	Night	38% 5% 9% 21% 19% 8%	1783
May	1st to 10th	Night	40% 7% 10% 19% 16% 9%	1620
	11th to 20th	Night	35% 6% 13% 26% 18% 4	1594
	21st to end	Night	32% 7% 15% 30% 13% 1	1746
June	1st to 10th	Night	24% 5% 17% 32% 20% 2	1620
	11th to 20th	Night	21% 7% 17% 32% 18% 4	1620
	21st to end	Night	30% 9% 18% 29% 13% 1	1620
July	1st to 10th	Night	29% 9% 23% 30% 9%	1575
	11th to 20th	Night	18% 10% 26% 33% 13%	1566
	21st to end	Night	17% 9% 32% 32% 9%	1673
August	1st to 10th	Night	12% 6% 27% 38% 16% 1	1601
	11th to 20th	Night	22% 10% 25% 33% 10% 1	1600
	21st to end	Night	27% 11% 23% 27% 9% 2	2168
September	1st to 10th	Night	27% 9% 19% 24% 14% 6%	1980
	11th to 20th	Night	36% 7% 16% 22% 14% 6%	1980
	21st to end	Night	29% 6% 16% 19% 18% 12%	1980
October	1st to 10th	Night	21% 5% 13% 26% 21% 13%	1992
	11th to 20th	Night	29% 5% 7% 20% 21% 18%	2160
	21st to end	Night	29% 3 7% 17% 21% 22%	2376
November	1st to 10th	Night	32% 6% 10% 20% 20% 12%	2220
	11th to 20th	Night	34% 4 10% 19% 20% 13%	2280
	21st to end	Night	39% 4 9% 17% 18% 13%	2455
December	1st to 10th	Night	40% 4 7% 21% 17% 10%	2470
	11th to 20th	Night	43% 5% 6% 11% 19% 16%	3037
	21st to end	Night	39% 4 5% 15% 28% 11%	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	23% 9% 35% 26% 6% 1	270
	11th to 20th	Day	23% 14% 27% 29% 6% 2	270
	21st to end	Day	23% 15% 34% 21% 6% 1	297
February	1st to 10th	Day	31% 14% 29% 17% 9%	270
	11th to 20th	Day	27% 19% 30% 17% 7%	270
	21st to end	Day	27% 15% 40% 15% 3	225
March	1st to 10th	Day	17% 18% 38% 20% 8%	270
	11th to 20th	Day	18% 17% 39% 20% 6%	270
	21st to end	Day	19% 14% 36% 23% 7% 1	297
April	1st to 10th	Day	18% 18% 37% 21% 6% 1	267
	11th to 20th	Day	19% 18% 27% 26% 9% 1	290
	21st to end	Day	15% 11% 36% 25% 11% 1	431
May	1st to 10th	Day	13% 10% 37% 28% 12%	603
	11th to 20th	Day	14% 6% 27% 34% 16% 3	625
	21st to end	Day	11% 5% 25% 35% 21% 3	679
June	1st to 10th	Day	6% 1 14% 37% 34% 8%	630
	11th to 20th	Day	5% 1 13% 40% 32% 8%	630
	21st to end	Day	8% 1 12% 30% 37% 13%	630
July	1st to 10th	Day	7% 2 7% 32% 34% 17%	621
	11th to 20th	Day	2 1 3 29% 47% 17%	618
	21st to end	Day	3 1 4 27% 48% 18%	684
August	1st to 10th	Day	3 3 26% 48% 21%	626
	11th to 20th	Day	6% 3 22% 49% 20%	611
	21st to end	Day	6% 2 4 18% 27% 43%	302
September	1st to 10th	Day	6% 1 3 23% 37% 30%	270
	11th to 20th	Day	6% 1 9% 18% 43% 23%	270
	21st to end	Day	9% 2 7% 19% 40% 23%	270
October	1st to 10th	Day	5% 2 10% 30% 39% 14%	270
	11th to 20th	Day	11% 4 15% 35% 25% 10%	270
	21st to end	Day	20% 10% 22% 24% 19% 5%	297
November	1st to 10th	Day	15% 6% 19% 34% 20% 6%	270
	11th to 20th	Day	18% 7% 22% 32% 17% 4	270
	21st to end	Day	22% 16% 31% 19% 10% 3	270
December	1st to 10th	Day	19% 8% 29% 27% 14% 4	270
	11th to 20th	Day	21% 16% 31% 23% 7% 2	270
	21st to end	Day	20% 9% 39% 24% 6% 2	297
January	1st to 10th	Night	20% 10% 32% 30% 8%	950
	11th to 20th	Night	21% 12% 29% 30% 8%	950
	21st to end	Night	20% 12% 31% 31% 6%	1045
February	1st to 10th	Night	24% 13% 32% 26% 4	765
	11th to 20th	Night	25% 11% 34% 26% 4	744
	21st to end	Night	27% 13% 39% 18% 3	552
March	1st to 10th	Night	21% 13% 37% 25% 3	570
	11th to 20th	Night	18% 11% 38% 27% 5%	570
	21st to end	Night	16% 10% 43% 26% 4	627
April	1st to 10th	Night	12% 13% 42% 30% 2	570
	11th to 20th	Night	17% 11% 39% 26% 6%	533
	21st to end	Night	14% 12% 39% 28% 7% 1	540
May	1st to 10th	Night	14% 11% 41% 29% 4	540
	11th to 20th	Night	11% 7% 31% 38% 13% 1	531
	21st to end	Night	8% 2 30% 42% 16%	584
June	1st to 10th	Night	4 3 15% 52% 25% 1	540
	11th to 20th	Night	4 1 24% 51% 20% 1	540
	21st to end	Night	5% 1 11% 48% 32% 3	540
July	1st to 10th	Night	7% 2 8% 47% 32% 5%	525
	11th to 20th	Night	2 1 7% 48% 40% 2	522
	21st to end	Night	2 1 6% 51% 36% 4	591
August	1st to 10th	Night	1 5% 54% 37% 2	537
	11th to 20th	Night	5% 4 49% 36% 5%	534
	21st to end	Night	5% 4 36% 49% 6%	594
September	1st to 10th	Night	6% 1 7% 33% 47% 6%	540
	11th to 20th	Night	10% 1 8% 35% 42% 3	540
	21st to end	Night	9% 1 13% 32% 40% 5%	540
October	1st to 10th	Night	4 3 11% 44% 33% 5%	552
	11th to 20th	Night	11% 4 21% 42% 20% 2	720
	21st to end	Night	13% 8% 25% 32% 19% 2	792
November	1st to 10th	Night	11% 5% 23% 40% 20% 1	740
	11th to 20th	Night	13% 8% 24% 39% 14% 1	760
	21st to end	Night	17% 10% 30% 29% 14% 1	935
December	1st to 10th	Night	20% 9% 26% 31% 13% 1	950
	11th to 20th	Night	22% 15% 26% 30% 7% 1	950
	21st to end	Night	20% 10% 30% 31% 8% 1	1045

Page generated at 2024-04-07 08:28:11. Version ac07

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