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 2024-11-05.

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
Transparency	Day	32% 13% 24% 22% 8% 1	104671
	Night	32% 12% 24% 22% 9% 1	102469
Seeing	Day	6% 2 9% 27% 41% 15%	17283
	Night	7% 2 9% 26% 41% 16%	27648

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	25% 11% 21% 30% 12% 1	3156
	11th to 20th	Day	29% 13% 23% 28% 5% 1	3160
	21st to end	Day	32% 12% 17% 26% 12% 1	3476
February	1st to 10th	Day	29% 8% 15% 27% 20% 2	1900
	11th to 20th	Day	26% 7% 14% 24% 26% 3	1857
	21st to end	Day	21% 6% 15% 28% 26% 5%	1615
March	1st to 10th	Day	29% 12% 25% 22% 11% 1	3435
	11th to 20th	Day	21% 9% 16% 38% 14% 1	3480
	21st to end	Day	22% 6% 15% 29% 25% 4	3935
April	1st to 10th	Day	20% 8% 18% 42% 11% 2	2280
	11th to 20th	Day	27% 9% 24% 27% 12% 1	2254
	21st to end	Day	32% 11% 18% 26% 12% 1	2280
May	1st to 10th	Day	24% 11% 18% 32% 14% 2	3800
	11th to 20th	Day	33% 9% 23% 32% 3	3768
	21st to end	Day	36% 15% 23% 21% 5%	4140
June	1st to 10th	Day	59% 13% 17% 10% 1	2280
	11th to 20th	Day	46% 16% 23% 15% 1	2280
	21st to end	Day	40% 20% 32% 8%	2280
July	1st to 10th	Day	24% 17% 46% 13%	3740
	11th to 20th	Day	28% 19% 40% 12%	3736
	21st to end	Day	25% 20% 38% 16% 1	3988
August	1st to 10th	Day	30% 19% 39% 12% 1	3774
	11th to 20th	Day	22% 15% 33% 28% 2	3766
	21st to end	Day	38% 18% 31% 12%	4180
September	1st to 10th	Day	37% 17% 33% 14%	2280
	11th to 20th	Day	34% 19% 30% 15% 1	2218
	21st to end	Day	39% 21% 24% 15%	2090
October	1st to 10th	Day	39% 14% 26% 14% 6%	3480
	11th to 20th	Day	47% 20% 21% 9% 4	3154
	21st to end	Day	38% 10% 16% 25% 8% 2	3428
November	1st to 10th	Day	43% 9% 15% 19% 12% 1	1898
	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	29% 10% 19% 28% 14%	3790
	11th to 20th	Night	29% 13% 25% 26% 6% 1	3800
	21st to end	Night	32% 12% 17% 24% 14% 1	4180
February	1st to 10th	Night	30% 9% 16% 26% 17% 2	2280
	11th to 20th	Night	23% 7% 15% 26% 27% 2	2220
	21st to end	Night	20% 5% 13% 29% 26% 7%	1832
March	1st to 10th	Night	29% 11% 24% 21% 14% 1	3418
	11th to 20th	Night	22% 8% 18% 38% 13% 1	3480
	21st to end	Night	25% 6% 13% 29% 22% 5%	3695
April	1st to 10th	Night	19% 8% 20% 36% 15% 2	1900
	11th to 20th	Night	29% 8% 19% 30% 12% 1	1875
	21st to end	Night	29% 9% 20% 27% 15% 1	1900
May	1st to 10th	Night	26% 13% 19% 27% 14% 1	3160
	11th to 20th	Night	32% 8% 21% 30% 8%	3131
	21st to end	Night	33% 10% 24% 28% 5%	3435
June	1st to 10th	Night	56% 14% 19% 10% 1	1900
	11th to 20th	Night	39% 19% 27% 14% 1	1900
	21st to end	Night	34% 18% 36% 12%	1900
July	1st to 10th	Night	26% 19% 39% 15%	3111
	11th to 20th	Night	29% 16% 40% 15%	3100
	21st to end	Night	23% 18% 40% 18% 1	3326
August	1st to 10th	Night	29% 16% 39% 14% 1	3131
	11th to 20th	Night	19% 13% 36% 30% 2	3127
	21st to end	Night	31% 17% 37% 15%	3476
September	1st to 10th	Night	30% 15% 34% 19% 1	1900
	11th to 20th	Night	30% 20% 31% 17% 2	1961
	21st to end	Night	35% 20% 25% 18% 2	2090
October	1st to 10th	Night	35% 14% 29% 16% 6%	3480
	11th to 20th	Night	48% 18% 22% 9% 3	3744
	21st to end	Night	43% 10% 16% 21% 8% 2	4120
November	1st to 10th	Night	45% 11% 13% 20% 10% 1	2280
	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	8% 4 18% 37% 30% 3	460
	21st to end	Day	6% 5% 17% 42% 28% 3	506
February	1st to 10th	Day	3 6% 16% 38% 35% 2	460
	11th to 20th	Day	5% 3 16% 36% 36% 5%	456
	21st to end	Day	4 3 13% 34% 40% 6%	382
March	1st to 10th	Day	4 3 22% 42% 28% 2	460
	11th to 20th	Day	4 2 13% 44% 36% 1	460
	21st to end	Day	5% 2 13% 42% 34% 3	506
April	1st to 10th	Day	4 1 7% 44% 40% 3	460
	11th to 20th	Day	4 3 13% 43% 35% 2	452
	21st to end	Day	7% 1 9% 47% 35% 2	460
May	1st to 10th	Day	6% 3 5% 34% 42% 9%	463
	11th to 20th	Day	14% 3 9% 29% 39% 5%	487
	21st to end	Day	10% 1 7% 20% 44% 17%	529
June	1st to 10th	Day	14% 5% 6% 19% 42% 13%	490
	11th to 20th	Day	9% 3 10% 44% 33%	490
	21st to end	Day	4 1 2 10% 53% 30%	490
July	1st to 10th	Day	1 1 10% 55% 33%	485
	11th to 20th	Day	1 2 13% 56% 27%	484
	21st to end	Day	5% 1 12% 53% 30%	532
August	1st to 10th	Day	3 2 11% 57% 27%	486
	11th to 20th	Day	2 1 8% 55% 34%	479
	21st to end	Day	6% 1 3 13% 52% 26%	539
September	1st to 10th	Day	6% 2 2 10% 38% 41%	490
	11th to 20th	Day	5% 1 8% 41% 44%	490
	21st to end	Day	7% 3 13% 40% 38%	490
October	1st to 10th	Day	11% 1 4 17% 45% 22%	490
	11th to 20th	Day	12% 3 4 19% 41% 21%	490
	21st to end	Day	9% 2 8% 29% 42% 9%	539
November	1st to 10th	Day	10% 3 14% 31% 36% 8%	472
	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	8% 4 14% 39% 33% 3	760
	21st to end	Night	6% 3 15% 44% 31% 2	836
February	1st to 10th	Night	5% 4 17% 36% 37% 1	760
	11th to 20th	Night	6% 3 14% 40% 33% 4	743
	21st to end	Night	4 2 11% 35% 41% 5%	628
March	1st to 10th	Night	7% 3 19% 36% 32% 3	760
	11th to 20th	Night	4 1 15% 41% 37% 2	760
	21st to end	Night	5% 2 14% 41% 34% 4	836
April	1st to 10th	Night	3 1 7% 45% 43% 2	760
	11th to 20th	Night	5% 2 10% 41% 38% 5%	751
	21st to end	Night	5% 1 10% 44% 39% 1	760
May	1st to 10th	Night	7% 1 8% 33% 44% 7%	760
	11th to 20th	Night	15% 3 7% 33% 38% 4	749
	21st to end	Night	10% 3 8% 23% 43% 13%	822
June	1st to 10th	Night	15% 4 6% 19% 41% 15%	760
	11th to 20th	Night	7% 1 4 11% 46% 31%	760
	21st to end	Night	6% 1 2 10% 50% 31%	760
July	1st to 10th	Night	3 2 10% 48% 36%	741
	11th to 20th	Night	6% 3 11% 50% 30%	736
	21st to end	Night	3 2 10% 50% 34%	831
August	1st to 10th	Night	4 3 14% 51% 28%	757
	11th to 20th	Night	3 1 10% 44% 42%	750
	21st to end	Night	5% 1 3 10% 51% 30%	836
September	1st to 10th	Night	6% 1 3 9% 35% 46%	760
	11th to 20th	Night	5% 1 1 8% 35% 50%	760
	21st to end	Night	5% 3 13% 41% 38%	760
October	1st to 10th	Night	10% 1 5% 16% 44% 23%	760
	11th to 20th	Night	9% 2 6% 17% 42% 25%	760
	21st to end	Night	15% 2 9% 25% 36% 12%	836
November	1st to 10th	Night	10% 2 15% 30% 37% 6%	760
	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 2024-11-03 02:11:16. Version ac07

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