San Marcos Baptist Academy
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the San Marcos Baptist Academy clear sky chart from 2005-11-06 to 2024-10-20.

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	13% 6% 2 5% 4 4 4 4 5% 7% 45%	100868
	Night	15% 6% 2 4 3 3 3 3 5% 7% 49%	97919
Transparency	Day	37% 7% 11% 20% 18% 8%	100679
	Night	35% 6% 12% 20% 18% 10%	97779
Seeing	Day	14% 7% 21% 29% 23% 6%	14762
	Night	16% 6% 24% 35% 17% 1	24643

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% 8% 2 5% 3 2 3 2 4 6% 50%	2847
	11th to 20th	Day	19% 4 2 3 2 2 2 2 4 5% 55%	2850
	21st to end	Day	20% 7% 2 5% 3 2 3 3 4 8% 42%	3341
February	1st to 10th	Day	22% 6% 2 6% 3 3 3 2 5% 4 44%	1900
	11th to 20th	Day	20% 8% 2 5% 3 3 3 3 4 5% 44%	1849
	21st to end	Day	19% 7% 2 5% 2 3 3 2 3 6% 47%	1570
March	1st to 10th	Day	17% 8% 2 7% 4 4 4 2 4 6% 42%	3420
	11th to 20th	Day	22% 9% 3 8% 5% 5% 4 3 3 4 32%	3480
	21st to end	Day	18% 7% 2 4 4 3 4 3 4 5% 46%	3814
April	1st to 10th	Day	16% 8% 2 6% 4 4 4 3 4 6% 42%	2090
	11th to 20th	Day	21% 5% 2 6% 4 4 4 3 4 5% 41%	2066
	21st to end	Day	16% 8% 2 6% 5% 4 4 3 4 7% 43%	2404
May	1st to 10th	Day	26% 9% 3 7% 5% 3 4 4 5% 5% 30%	4082
	11th to 20th	Day	16% 6% 2 6% 4 4 5% 3 5% 7% 42%	4082
	21st to end	Day	12% 6% 2 6% 5% 5% 6% 5% 8% 9% 37%	4477
June	1st to 10th	Day	7% 4 1 5% 4 5% 6% 4 7% 9% 47%	2470
	11th to 20th	Day	8% 5% 2 6% 6% 5% 5% 4 6% 9% 44%	2470
	21st to end	Day	8% 6% 2 7% 6% 6% 6% 6% 7% 10% 36%	2470
July	1st to 10th	Day	7% 5% 2 5% 5% 5% 6% 4 5% 8% 48%	4120
	11th to 20th	Day	5% 4 2 5% 4 5% 5% 6% 7% 11% 44%	4120
	21st to end	Day	10% 6% 2 6% 5% 6% 5% 5% 7% 10% 36%	4465
August	1st to 10th	Day	1 2 1 3 3 2 3 3 5% 8% 69%	4104
	11th to 20th	Day	3 3 1 3 3 3 5% 4 7% 11% 57%	3732
	21st to end	Day	5% 3 2 5% 4 6% 6% 5% 7% 11% 47%	3988
September	1st to 10th	Day	9% 6% 2 8% 6% 5% 5% 4 6% 6% 43%	2090
	11th to 20th	Day	12% 6% 2 7% 5% 5% 5% 4 6% 8% 41%	2090
	21st to end	Day	9% 4 2 4 4 5% 6% 5% 6% 8% 49%	2090
October	1st to 10th	Day	6% 4 2 5% 4 4 4 4 6% 7% 54%	2090
	11th to 20th	Day	12% 5% 2 4 4 4 4 3 4 7% 51%	1947
	21st to end	Day	12% 4 2 5% 3 3 3 2 4 5% 57%	1980
November	1st to 10th	Day	14% 8% 2 6% 4 3 3 4 5% 6% 45%	1858
	11th to 20th	Day	13% 5% 2 5% 4 3 4 3 5% 5% 50%	1796
	21st to end	Day	19% 7% 2 6% 4 4 3 2 4 4 44%	1710
December	1st to 10th	Day	16% 8% 2 4 4 3 3 4 5% 6% 45%	1710
	11th to 20th	Day	17% 8% 2 6% 4 4 4 3 4 4 43%	2161
	21st to end	Day	18% 6% 1 4 2 3 2 2 4 5% 53%	3135
January	1st to 10th	Night	21% 6% 1 3 2 2 2 2 3 6% 51%	4108
	11th to 20th	Night	15% 4 1 3 2 2 2 2 3 3 65%	4120
	21st to end	Night	23% 6% 2 6% 4 2 3 2 4 6% 42%	4340
February	1st to 10th	Night	20% 7% 2 5% 3 3 3 2 5% 6% 45%	2280
	11th to 20th	Night	22% 7% 2 3 3 3 2 2 2 6% 48%	2218
	21st to end	Night	23% 6% 2 4 3 2 3 3 4 5% 44%	1884
March	1st to 10th	Night	22% 8% 2 5% 4 4 3 3 4 6% 39%	3433
	11th to 20th	Night	24% 11% 3 7% 4 4 4 3 4 5% 32%	3480
	21st to end	Night	19% 7% 3 5% 3 3 4 3 4 6% 44%	3817
April	1st to 10th	Night	16% 7% 2 5% 5% 3 3 3 5% 7% 45%	2090
	11th to 20th	Night	21% 6% 2 5% 3 3 4 2 4 6% 43%	2063
	21st to end	Night	19% 8% 3 4 3 3 3 2 4 6% 46%	1769
May	1st to 10th	Night	29% 9% 3 4 3 3 3 3 4 5% 35%	2823
	11th to 20th	Night	15% 6% 1 5% 3 3 4 3 5% 7% 49%	2823
	21st to end	Night	15% 7% 2 4 3 3 4 4 6% 8% 43%	3090
June	1st to 10th	Night	7% 4 1 4 3 3 3 3 5% 8% 59%	1710
	11th to 20th	Night	5% 4 2 4 3 3 3 3 6% 10% 56%	1710
	21st to end	Night	8% 5% 2 4 4 4 4 4 7% 8% 49%	1710
July	1st to 10th	Night	6% 4 1 4 3 4 4 4 6% 10% 54%	2850
	11th to 20th	Night	5% 4 1 5% 4 4 5% 4 7% 11% 51%	2850
	21st to end	Night	12% 7% 2 6% 5% 4 5% 4 6% 9% 40%	3098
August	1st to 10th	Night	2 1 1 2 2 2 3 2 4 8% 74%	2836
	11th to 20th	Night	3 3 1 4 3 3 4 4 7% 10% 58%	3102
	21st to end	Night	5% 3 1 4 4 4 4 4 7% 10% 55%	3673
September	1st to 10th	Night	9% 5% 2 5% 4 4 4 3 6% 9% 49%	2090
	11th to 20th	Night	10% 6% 3 6% 4 4 5% 4 6% 8% 45%	2090
	21st to end	Night	9% 5% 2 5% 3 4 4 3 6% 8% 52%	2090
October	1st to 10th	Night	7% 3 1 4 3 3 4 2 4 7% 61%	2090
	11th to 20th	Night	14% 6% 2 5% 3 3 3 3 5% 5% 53%	2199
	21st to end	Night	16% 4 1 4 2 2 2 2 3 4 59%	2376
November	1st to 10th	Night	14% 7% 2 6% 3 2 3 2 4 6% 53%	2220
	11th to 20th	Night	12% 5% 2 4 4 3 4 3 4 6% 53%	2379
	21st to end	Night	20% 6% 2 4 3 3 4 3 4 6% 46%	2470
December	1st to 10th	Night	16% 7% 1 4 3 3 3 3 5% 5% 50%	2470
	11th to 20th	Night	19% 9% 3 5% 3 3 3 2 3 4 46%	3036
	21st to end	Night	21% 6% 2 3 2 2 2 2 3 5% 53%	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	36% 4 6% 14% 25% 14%	2848
	11th to 20th	Day	33% 3 7% 15% 26% 17%	2850
	21st to end	Day	41% 4 6% 11% 28% 10%	3341
February	1st to 10th	Day	44% 4 6% 12% 20% 15%	1900
	11th to 20th	Day	42% 4 8% 16% 18% 12%	1859
	21st to end	Day	40% 5% 8% 16% 17% 15%	1570
March	1st to 10th	Day	43% 6% 9% 14% 19% 9%	3420
	11th to 20th	Day	54% 8% 6% 8% 16% 8%	3480
	21st to end	Day	38% 6% 9% 15% 21% 10%	3814
April	1st to 10th	Day	43% 6% 8% 16% 16% 12%	2090
	11th to 20th	Day	44% 6% 8% 15% 17% 11%	2066
	21st to end	Day	42% 6% 6% 19% 18% 9%	2404
May	1st to 10th	Day	52% 8% 9% 13% 13% 5%	4120
	11th to 20th	Day	39% 9% 9% 17% 19% 6%	4086
	21st to end	Day	36% 11% 15% 26% 11% 1	4489
June	1st to 10th	Day	29% 10% 14% 26% 18% 3	2470
	11th to 20th	Day	35% 8% 12% 25% 17% 4	2470
	21st to end	Day	40% 10% 12% 24% 13% 3	2470
July	1st to 10th	Day	32% 7% 17% 37% 6% 1	4056
	11th to 20th	Day	31% 7% 19% 28% 14% 2	4051
	21st to end	Day	40% 7% 18% 27% 8%	4325
August	1st to 10th	Day	14% 5% 12% 42% 26% 1	4090
	11th to 20th	Day	20% 6% 24% 37% 11% 2	3768
	21st to end	Day	29% 9% 20% 24% 17% 2	3987
September	1st to 10th	Day	40% 8% 9% 19% 16% 8%	2090
	11th to 20th	Day	39% 8% 12% 18% 17% 5%	2090
	21st to end	Day	31% 8% 10% 20% 17% 13%	2090
October	1st to 10th	Day	27% 7% 11% 19% 23% 13%	2090
	11th to 20th	Day	33% 5% 11% 15% 19% 17%	1947
	21st to end	Day	29% 5% 7% 15% 24% 20%	1980
November	1st to 10th	Day	38% 7% 9% 17% 18% 10%	1858
	11th to 20th	Day	36% 5% 9% 17% 20% 13%	1796
	21st to end	Day	44% 4 6% 14% 18% 13%	1710
December	1st to 10th	Day	39% 5% 10% 17% 20% 8%	1710
	11th to 20th	Day	42% 7% 6% 10% 21% 14%	2159
	21st to end	Day	36% 3 6% 15% 26% 14%	3135
January	1st to 10th	Night	35% 4 6% 14% 21% 19%	4108
	11th to 20th	Night	27% 3 5% 16% 30% 19%	4120
	21st to end	Night	44% 5% 5% 11% 24% 11%	4340
February	1st to 10th	Night	41% 4 8% 12% 19% 17%	2280
	11th to 20th	Night	40% 4 6% 15% 19% 15%	2218
	21st to end	Night	42% 4 7% 15% 17% 15%	1884
March	1st to 10th	Night	45% 7% 8% 15% 16% 9%	3433
	11th to 20th	Night	52% 8% 8% 10% 12% 9%	3480
	21st to end	Night	41% 7% 10% 15% 19% 10%	3817
April	1st to 10th	Night	38% 6% 9% 17% 15% 14%	2090
	11th to 20th	Night	43% 5% 8% 13% 16% 14%	2063
	21st to end	Night	41% 5% 9% 20% 16% 10%	1769
May	1st to 10th	Night	50% 7% 8% 15% 13% 6%	2850
	11th to 20th	Night	34% 9% 11% 21% 18% 7%	2824
	21st to end	Night	35% 9% 15% 28% 11% 1	3099
June	1st to 10th	Night	23% 7% 17% 28% 23% 3	1710
	11th to 20th	Night	24% 6% 16% 30% 19% 5%	1710
	21st to end	Night	29% 9% 17% 27% 14% 3	1710
July	1st to 10th	Night	26% 8% 23% 37% 5% 1	2805
	11th to 20th	Night	26% 9% 21% 29% 14% 1	2796
	21st to end	Night	39% 7% 23% 25% 6%	2999
August	1st to 10th	Night	11% 5% 17% 46% 21% 1	2826
	11th to 20th	Night	19% 9% 31% 31% 9% 1	3132
	21st to end	Night	24% 11% 22% 26% 15% 2	3673
September	1st to 10th	Night	33% 7% 16% 21% 15% 7%	2090
	11th to 20th	Night	36% 8% 14% 22% 14% 6%	2090
	21st to end	Night	29% 8% 14% 20% 16% 13%	2090
October	1st to 10th	Night	23% 6% 13% 23% 21% 14%	2090
	11th to 20th	Night	32% 4 10% 16% 20% 18%	2199
	21st to end	Night	30% 4 7% 16% 22% 22%	2376
November	1st to 10th	Night	34% 6% 9% 18% 20% 13%	2220
	11th to 20th	Night	33% 6% 9% 17% 20% 15%	2379
	21st to end	Night	41% 4 8% 15% 18% 14%	2470
December	1st to 10th	Night	37% 5% 8% 19% 19% 11%	2470
	11th to 20th	Night	42% 5% 6% 10% 19% 19%	3037
	21st to end	Night	36% 4 4 14% 29% 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	22% 14% 34% 25% 4 1	270
	11th to 20th	Day	27% 14% 25% 25% 8% 2	270
	21st to end	Day	19% 13% 36% 25% 6%	297
February	1st to 10th	Day	34% 11% 28% 20% 8%	270
	11th to 20th	Day	25% 18% 32% 20% 4	270
	21st to end	Day	24% 18% 41% 16% 1	225
March	1st to 10th	Day	23% 16% 38% 19% 4	270
	11th to 20th	Day	19% 17% 41% 18% 4 1	270
	21st to end	Day	22% 13% 35% 23% 6%	297
April	1st to 10th	Day	21% 14% 37% 22% 4	270
	11th to 20th	Day	20% 18% 33% 19% 10%	264
	21st to end	Day	19% 13% 36% 26% 7%	584
May	1st to 10th	Day	18% 12% 34% 27% 9%	653
	11th to 20th	Day	18% 7% 27% 33% 13% 2	675
	21st to end	Day	16% 6% 24% 35% 17% 2	734
June	1st to 10th	Day	8% 2 13% 40% 30% 7%	680
	11th to 20th	Day	8% 2 14% 44% 29% 4	680
	21st to end	Day	10% 2 12% 36% 29% 11%	680
July	1st to 10th	Day	9% 2 9% 33% 35% 11%	671
	11th to 20th	Day	5% 1 6% 30% 48% 11%	668
	21st to end	Day	5% 1 5% 33% 43% 12%	739
August	1st to 10th	Day	3 1 5% 28% 50% 14%	676
	11th to 20th	Day	5% 1 5% 33% 44% 13%	483
	21st to end	Day	5% 1 5% 26% 38% 25%	425
September	1st to 10th	Day	10% 1 7% 27% 38% 17%	300
	11th to 20th	Day	7% 1 4 26% 46% 16%	300
	21st to end	Day	8% 1 9% 28% 38% 16%	300
October	1st to 10th	Day	5% 2 16% 33% 35% 10%	300
	11th to 20th	Day	11% 4 18% 38% 23% 6%	297
	21st to end	Day	21% 10% 25% 23% 15% 6%	297
November	1st to 10th	Day	19% 7% 27% 28% 16% 4	270
	11th to 20th	Day	20% 9% 26% 29% 15% 2	270
	21st to end	Day	22% 14% 35% 17% 11% 1	270
December	1st to 10th	Day	19% 7% 33% 29% 7% 6%	270
	11th to 20th	Day	23% 17% 26% 27% 8%	270
	21st to end	Day	22% 9% 36% 24% 8%	297
January	1st to 10th	Night	21% 9% 28% 32% 9% 1	950
	11th to 20th	Night	21% 9% 30% 31% 8%	950
	21st to end	Night	23% 9% 28% 32% 8%	931
February	1st to 10th	Night	26% 11% 30% 26% 6%	760
	11th to 20th	Night	26% 11% 33% 26% 4	744
	21st to end	Night	25% 14% 39% 21% 2	628
March	1st to 10th	Night	24% 10% 35% 27% 3	584
	11th to 20th	Night	24% 10% 33% 28% 5%	570
	21st to end	Night	20% 9% 39% 28% 3	627
April	1st to 10th	Night	18% 9% 41% 29% 4	570
	11th to 20th	Night	21% 12% 37% 25% 5%	563
	21st to end	Night	20% 10% 37% 25% 8%	570
May	1st to 10th	Night	19% 10% 38% 27% 6%	570
	11th to 20th	Night	17% 5% 30% 37% 11%	561
	21st to end	Night	15% 4 32% 36% 12%	617
June	1st to 10th	Night	7% 2 19% 48% 23% 1	570
	11th to 20th	Night	5% 2 28% 49% 14% 1	570
	21st to end	Night	6% 2 17% 43% 27% 4	570
July	1st to 10th	Night	9% 1 10% 46% 31% 3	555
	11th to 20th	Night	4 1 11% 48% 34% 2	552
	21st to end	Night	5% 1 9% 48% 34% 3	624
August	1st to 10th	Night	2 8% 48% 38% 4	567
	11th to 20th	Night	4 1 7% 50% 34% 3	564
	21st to end	Night	7% 1 6% 37% 45% 5%	627
September	1st to 10th	Night	8% 1 8% 39% 38% 5%	570
	11th to 20th	Night	12% 2 7% 36% 40% 3	570
	21st to end	Night	10% 1 12% 35% 38% 3	570
October	1st to 10th	Night	7% 1 11% 45% 32% 5%	570
	11th to 20th	Night	13% 4 21% 37% 23% 2	683
	21st to end	Night	16% 7% 22% 32% 20% 2	792
November	1st to 10th	Night	14% 6% 20% 37% 21% 1	740
	11th to 20th	Night	14% 6% 25% 38% 15% 2	859
	21st to end	Night	22% 10% 25% 30% 12% 1	950
December	1st to 10th	Night	20% 7% 28% 32% 11% 1	950
	11th to 20th	Night	24% 10% 26% 32% 8%	950
	21st to end	Night	23% 7% 28% 33% 8%	1045

Page generated at 2024-10-17 12:09:42. Version ac07

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