Cat Island (South)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cat Island (South) clear sky chart from 2005-11-06 to 2024-01-12.

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
Transparency	Day	36% 13% 22% 20% 8% 1	75016
	Night	36% 12% 21% 21% 9% 1	74229
Seeing	Day	7% 2 8% 26% 41% 16%	16090
	Night	7% 2 9% 26% 41% 16%	26455

By Month

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	33% 9% 17% 28% 12% 1	1896
	11th to 20th	Day	40% 11% 18% 20% 9% 2	1810
	21st to end	Day	33% 8% 16% 28% 14% 1	1980
February	1st to 10th	Day	30% 8% 15% 27% 20% 2	1800
	11th to 20th	Day	26% 7% 14% 24% 27% 2	1757
	21st to end	Day	23% 6% 15% 28% 25% 4	1522
March	1st to 10th	Day	31% 8% 16% 25% 18% 2	1980
	11th to 20th	Day	27% 9% 17% 29% 16% 2	1980
	21st to end	Day	29% 7% 17% 31% 14% 2	2243
April	1st to 10th	Day	21% 8% 18% 41% 10% 1	2160
	11th to 20th	Day	28% 9% 24% 26% 11% 1	2134
	21st to end	Day	33% 11% 18% 26% 12% 1	2160
May	1st to 10th	Day	29% 11% 18% 28% 11% 3	2160
	11th to 20th	Day	52% 11% 18% 15% 5%	2128
	21st to end	Day	49% 12% 19% 15% 5%	2336
June	1st to 10th	Day	59% 14% 17% 10% 1	2160
	11th to 20th	Day	45% 16% 24% 14% 1	2160
	21st to end	Day	40% 19% 33% 8%	2160
July	1st to 10th	Day	29% 17% 36% 17% 1	2100
	11th to 20th	Day	34% 19% 32% 15%	2096
	21st to end	Day	31% 20% 33% 16% 1	2220
August	1st to 10th	Day	29% 16% 33% 21% 1	2136
	11th to 20th	Day	26% 19% 36% 18% 1	2126
	21st to end	Day	37% 18% 29% 16%	2376
September	1st to 10th	Day	38% 17% 31% 13%	2160
	11th to 20th	Day	34% 18% 30% 16% 1	2102
	21st to end	Day	40% 22% 25% 13%	1980
October	1st to 10th	Day	44% 15% 22% 14% 5%	1980
	11th to 20th	Day	46% 17% 21% 10% 7%	1814
	21st to end	Day	45% 11% 15% 18% 9% 3	1980
November	1st to 10th	Day	43% 10% 15% 20% 12% 1	1857
	11th to 20th	Day	45% 11% 14% 18% 12% 1	1900
	21st to end	Day	35% 10% 17% 23% 13% 2	1900
December	1st to 10th	Day	27% 9% 19% 28% 16% 1	1900
	11th to 20th	Day	37% 9% 14% 23% 13% 5%	2387
	21st to end	Day	40% 12% 20% 17% 10% 1	3476
January	1st to 10th	Night	34% 8% 16% 28% 14% 1	2270
	11th to 20th	Night	39% 10% 19% 20% 10% 2	2179
	21st to end	Night	31% 9% 17% 27% 15% 1	2376
February	1st to 10th	Night	31% 9% 16% 26% 17% 2	2160
	11th to 20th	Night	24% 7% 15% 26% 27% 2	2100
	21st to end	Night	21% 5% 13% 30% 25% 6%	1727
March	1st to 10th	Night	30% 8% 14% 25% 21% 1	1980
	11th to 20th	Night	28% 7% 17% 31% 16% 2	1980
	21st to end	Night	27% 7% 18% 28% 18% 3	2111
April	1st to 10th	Night	20% 9% 21% 35% 14% 2	1800
	11th to 20th	Night	31% 9% 19% 30% 11% 1	1775
	21st to end	Night	29% 9% 20% 27% 14% 1	1800
May	1st to 10th	Night	29% 9% 18% 27% 14% 3	1800
	11th to 20th	Night	50% 10% 18% 16% 6%	1771
	21st to end	Night	49% 9% 18% 16% 7%	1939
June	1st to 10th	Night	56% 14% 18% 11% 1	1800
	11th to 20th	Night	38% 19% 28% 14% 1	1800
	21st to end	Night	34% 18% 35% 12%	1800
July	1st to 10th	Night	29% 16% 36% 18% 1	1751
	11th to 20th	Night	36% 16% 30% 18%	1740
	21st to end	Night	27% 17% 36% 19% 1	1858
August	1st to 10th	Night	30% 12% 32% 23% 2	1778
	11th to 20th	Night	27% 16% 36% 20% 1	1774
	21st to end	Night	32% 14% 33% 20% 1	1980
September	1st to 10th	Night	31% 16% 33% 19% 1	1800
	11th to 20th	Night	30% 19% 32% 18% 2	1857
	21st to end	Night	36% 21% 26% 16% 1	1980
October	1st to 10th	Night	44% 14% 23% 15% 3	1980
	11th to 20th	Night	47% 16% 20% 12% 5%	2139
	21st to end	Night	46% 11% 16% 16% 9% 2	2376
November	1st to 10th	Night	46% 11% 13% 21% 9% 1	2221
	11th to 20th	Night	45% 11% 16% 17% 10% 1	2280
	21st to end	Night	37% 7% 19% 24% 12% 2	2280
December	1st to 10th	Night	32% 9% 19% 27% 12%	2280
	11th to 20th	Night	38% 9% 16% 22% 11% 4	2807
	21st to end	Night	48% 10% 16% 17% 8% 1	4180

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	7% 3 13% 36% 36% 5%	460
	11th to 20th	Day	9% 4 19% 39% 27% 3	424
	21st to end	Day	6% 5% 17% 40% 29% 3	462
February	1st to 10th	Day	3 4 15% 39% 37% 2	420
	11th to 20th	Day	5% 2 13% 36% 38% 5%	416
	21st to end	Day	4 3 12% 32% 42% 6%	346
March	1st to 10th	Day	4 3 21% 41% 28% 2	420
	11th to 20th	Day	4 1 13% 43% 37% 1	420
	21st to end	Day	5% 3 12% 43% 34% 3	462
April	1st to 10th	Day	5% 1 7% 43% 40% 4	420
	11th to 20th	Day	4 3 12% 42% 36% 2	412
	21st to end	Day	7% 1 9% 45% 36% 2	420
May	1st to 10th	Day	6% 3 6% 34% 41% 10%	423
	11th to 20th	Day	15% 3 10% 27% 39% 6%	447
	21st to end	Day	11% 1 7% 21% 44% 16%	485
June	1st to 10th	Day	15% 5% 6% 19% 41% 14%	450
	11th to 20th	Day	8% 3 10% 45% 34%	450
	21st to end	Day	3 1 2 10% 53% 31%	450
July	1st to 10th	Day	1 1 10% 55% 32%	445
	11th to 20th	Day	2 2 14% 54% 27%	444
	21st to end	Day	5% 1 12% 51% 30%	488
August	1st to 10th	Day	3 2 10% 57% 27%	446
	11th to 20th	Day	2 1 8% 56% 33%	439
	21st to end	Day	6% 1 3 14% 49% 27%	495
September	1st to 10th	Day	7% 2 2 11% 35% 44%	450
	11th to 20th	Day	5% 1 8% 41% 44%	450
	21st to end	Day	6% 3 12% 38% 40%	450
October	1st to 10th	Day	11% 1 4 17% 46% 21%	450
	11th to 20th	Day	13% 3 4 19% 41% 21%	450
	21st to end	Day	10% 2 8% 27% 43% 10%	495
November	1st to 10th	Day	9% 2 14% 30% 36% 8%	455
	11th to 20th	Day	7% 3 13% 30% 39% 7%	460
	21st to end	Day	7% 1 11% 38% 34% 9%	460
December	1st to 10th	Day	4 11% 34% 41% 9%	460
	11th to 20th	Day	7% 3 10% 35% 40% 5%	460
	21st to end	Day	7% 3 18% 30% 36% 6%	506
January	1st to 10th	Night	6% 3 13% 33% 41% 5%	760
	11th to 20th	Night	9% 4 14% 38% 32% 2	727
	21st to end	Night	6% 2 15% 43% 32% 2	792
February	1st to 10th	Night	5% 3 17% 36% 39% 1	720
	11th to 20th	Night	6% 3 14% 39% 34% 4	703
	21st to end	Night	5% 2 10% 35% 43% 6%	592
March	1st to 10th	Night	8% 3 19% 36% 32% 3	720
	11th to 20th	Night	4 1 15% 40% 37% 3	720
	21st to end	Night	5% 2 13% 42% 35% 4	792
April	1st to 10th	Night	3 1 7% 44% 44% 2	720
	11th to 20th	Night	5% 2 10% 39% 38% 5%	711
	21st to end	Night	5% 1 10% 43% 39% 1	720
May	1st to 10th	Night	7% 1 7% 34% 44% 7%	720
	11th to 20th	Night	16% 3 7% 31% 38% 5%	709
	21st to end	Night	11% 3 9% 24% 41% 13%	778
June	1st to 10th	Night	15% 3 6% 18% 41% 15%	720
	11th to 20th	Night	7% 1 4 11% 45% 32%	720
	21st to end	Night	6% 1 2 10% 50% 31%	720
July	1st to 10th	Night	3 3 10% 48% 36%	701
	11th to 20th	Night	6% 3 11% 49% 31%	696
	21st to end	Night	3 2 10% 49% 36%	787
August	1st to 10th	Night	4 3 14% 51% 28%	717
	11th to 20th	Night	3 1 10% 45% 41%	710
	21st to end	Night	5% 1 3 11% 50% 30%	792
September	1st to 10th	Night	7% 1 3 9% 32% 47%	720
	11th to 20th	Night	5% 1 1 8% 35% 49%	720
	21st to end	Night	5% 3 13% 39% 39%	720
October	1st to 10th	Night	11% 2 5% 17% 43% 23%	720
	11th to 20th	Night	10% 2 6% 16% 42% 25%	720
	21st to end	Night	16% 2 9% 24% 37% 13%	792
November	1st to 10th	Night	11% 2 15% 29% 37% 6%	740
	11th to 20th	Night	9% 3 12% 26% 43% 7%	760
	21st to end	Night	9% 3 12% 35% 36% 6%	760
December	1st to 10th	Night	6% 2 12% 31% 42% 8%	760
	11th to 20th	Night	8% 3 11% 32% 41% 5%	760
	21st to end	Night	10% 3 14% 28% 38% 6%	836

Page generated at 2024-01-09 07:14:43. Version ac07

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