Little Point Sable
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Little Point Sable clear sky chart from 2005-11-06 to 2025-08-05.

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
Cloud Cover	Day	13% 11% 5% 9% 5% 4 4 3 5% 7% 35%	125695
	Night	14% 14% 5% 11% 5% 5% 4 3 4 5% 29%	122608
Transparency	Day	48% 6% 12% 21% 11% 1	129208
	Night	55% 6% 11% 17% 10% 1	127169
Seeing	Day	16% 8% 23% 30% 18% 4	16942
	Night	20% 9% 24% 30% 15% 2	26776

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	11% 26% 13% 25% 5% 3 3 1 2 2 8%	3617
	11th to 20th	Day	10% 18% 10% 23% 17% 8% 5% 2 1 2 3	3620
	21st to end	Day	13% 18% 10% 18% 8% 5% 7% 2 2 3 12%	3982
February	1st to 10th	Day	11% 16% 7% 16% 13% 6% 4 3 4 5% 15%	1780
	11th to 20th	Day	12% 17% 8% 19% 10% 5% 4 2 3 4 16%	1948
	21st to end	Day	13% 16% 7% 14% 7% 7% 4 3 4 5% 20%	1650
March	1st to 10th	Day	12% 10% 4 12% 6% 5% 4 4 5% 5% 33%	4480
	11th to 20th	Day	11% 9% 6% 10% 4 4 4 3 5% 8% 35%	4745
	21st to end	Day	20% 13% 6% 10% 5% 4 3 3 4 5% 27%	5819
April	1st to 10th	Day	17% 13% 4 7% 5% 4 4 3 4 7% 32%	2400
	11th to 20th	Day	18% 10% 3 6% 4 4 4 3 5% 5% 36%	2404
	21st to end	Day	15% 10% 2 7% 5% 4 5% 4 5% 7% 36%	2600
May	1st to 10th	Day	13% 7% 3 6% 4 4 4 4 6% 8% 42%	5862
	11th to 20th	Day	12% 7% 2 7% 4 4 4 3 5% 9% 41%	6107
	21st to end	Day	12% 7% 2 5% 4 4 4 3 5% 8% 46%	6935
June	1st to 10th	Day	11% 6% 2 6% 4 4 4 3 5% 8% 47%	2800
	11th to 20th	Day	12% 5% 2 5% 4 3 4 4 6% 9% 45%	2800
	21st to end	Day	10% 6% 2 5% 4 4 5% 3 7% 9% 46%	2800
July	1st to 10th	Day	12% 6% 2 6% 4 3 4 4 5% 9% 44%	6360
	11th to 20th	Day	8% 4 2 5% 4 3 4 3 5% 8% 54%	6360
	21st to end	Day	7% 5% 2 6% 4 4 4 4 7% 10% 48%	6924
August	1st to 10th	Day	9% 5% 2 6% 4 4 6% 4 7% 9% 44%	4333
	11th to 20th	Day	11% 4 2 5% 3 3 3 3 5% 7% 53%	4024
	21st to end	Day	9% 6% 2 6% 4 5% 5% 4 6% 7% 47%	4180
September	1st to 10th	Day	12% 6% 2 6% 5% 4 3 3 5% 6% 47%	2280
	11th to 20th	Day	12% 5% 2 6% 3 3 4 4 5% 7% 49%	2101
	21st to end	Day	14% 8% 3 6% 4 4 5% 4 5% 7% 41%	2090
October	1st to 10th	Day	15% 7% 3 6% 4 4 3 3 6% 6% 42%	2090
	11th to 20th	Day	24% 13% 3 8% 5% 5% 4 4 6% 7% 23%	1814
	21st to end	Day	24% 13% 4 8% 5% 4 4 3 5% 6% 24%	1881
November	1st to 10th	Day	17% 15% 3 8% 6% 4 4 2 4 5% 32%	1762
	11th to 20th	Day	14% 24% 6% 12% 5% 4 4 3 5% 6% 17%	1800
	21st to end	Day	20% 22% 8% 13% 5% 3 3 2 3 4 16%	1747
December	1st to 10th	Day	12% 26% 20% 16% 5% 3 2 2 2 2 10%	2610
	11th to 20th	Day	13% 25% 13% 15% 10% 4 4 2 3 4 8%	3008
	21st to end	Day	20% 23% 10% 14% 6% 5% 3 3 3 4 10%	3982
January	1st to 10th	Night	12% 24% 11% 26% 6% 4 3 2 2 2 9%	6348
	11th to 20th	Night	12% 20% 10% 25% 10% 11% 3 1 1 1 5%	6360
	21st to end	Night	12% 23% 10% 18% 7% 6% 6% 1 2 3 11%	6996
February	1st to 10th	Night	12% 19% 6% 17% 11% 5% 4 3 3 4 17%	2615
	11th to 20th	Night	13% 15% 8% 17% 10% 7% 3 2 4 4 17%	2338
	21st to end	Night	15% 16% 6% 13% 7% 4 4 3 5% 6% 22%	1980
March	1st to 10th	Night	15% 10% 4 12% 4 4 4 3 4 6% 35%	5373
	11th to 20th	Night	11% 10% 4 9% 5% 4 4 3 5% 7% 38%	5215
	21st to end	Night	17% 12% 4 10% 5% 5% 4 3 5% 5% 29%	5151
April	1st to 10th	Night	17% 13% 4 8% 4 4 3 3 6% 7% 33%	2000
	11th to 20th	Night	19% 10% 3 6% 4 4 4 3 5% 5% 35%	1945
	21st to end	Night	17% 9% 3 6% 5% 4 3 3 6% 5% 38%	1800
May	1st to 10th	Night	14% 7% 3 7% 4 4 4 4 6% 8% 38%	4033
	11th to 20th	Night	11% 7% 3 7% 5% 5% 4 5% 6% 7% 40%	3782
	21st to end	Night	19% 8% 2 5% 3 3 4 3 5% 6% 42%	3942
June	1st to 10th	Night	11% 7% 2 5% 4 5% 4 4 6% 7% 44%	1600
	11th to 20th	Night	11% 5% 2 6% 4 4 4 4 6% 10% 43%	1600
	21st to end	Night	10% 6% 2 5% 5% 4 5% 5% 6% 9% 44%	1600
July	1st to 10th	Night	10% 8% 3 7% 5% 4 5% 4 6% 8% 40%	3618
	11th to 20th	Night	7% 6% 2 5% 4 4 4 4 5% 7% 53%	3617
	21st to end	Night	6% 6% 2 7% 4 3 4 3 6% 8% 50%	3947
August	1st to 10th	Night	10% 5% 2 5% 4 4 5% 4 7% 8% 46%	2689
	11th to 20th	Night	10% 7% 2 5% 3 4 3 3 5% 7% 52%	2803
	21st to end	Night	9% 6% 2 6% 5% 4 5% 4 6% 8% 47%	3476
September	1st to 10th	Night	12% 5% 2 5% 5% 4 4 3 4 6% 49%	1900
	11th to 20th	Night	12% 5% 2 4 3 3 4 3 5% 7% 53%	2059
	21st to end	Night	15% 7% 2 5% 5% 5% 5% 3 5% 6% 42%	2090
October	1st to 10th	Night	18% 6% 2 5% 3 3 4 3 4 7% 44%	2090
	11th to 20th	Night	22% 11% 3 8% 5% 4 4 2 4 5% 31%	2363
	21st to end	Night	25% 13% 3 7% 4 4 4 3 5% 5% 26%	2717
November	1st to 10th	Night	16% 15% 4 8% 5% 4 3 3 4 5% 33%	2536
	11th to 20th	Night	16% 24% 6% 11% 5% 5% 4 3 4 4 19%	2600
	21st to end	Night	19% 23% 7% 9% 5% 4 3 2 4 4 20%	2650
December	1st to 10th	Night	13% 25% 11% 20% 5% 3 3 2 3 3 11%	4580
	11th to 20th	Night	16% 26% 11% 14% 9% 4 3 2 3 4 9%	5199
	21st to end	Night	22% 22% 8% 13% 5% 4 3 3 4 5% 11%	6996

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	83% 5% 5% 6% 1	3618
	11th to 20th	Day	91% 4 2 2	3620
	21st to end	Day	77% 6% 8% 8% 1	3982
February	1st to 10th	Day	71% 8% 8% 11% 2	1780
	11th to 20th	Day	71% 6% 9% 10% 4	1958
	21st to end	Day	65% 6% 12% 11% 5%	1650
March	1st to 10th	Day	50% 6% 17% 18% 8% 1	4480
	11th to 20th	Day	44% 8% 17% 20% 10% 1	4745
	21st to end	Day	58% 6% 11% 15% 10%	5821
April	1st to 10th	Day	51% 6% 13% 20% 10%	2400
	11th to 20th	Day	47% 7% 10% 21% 14% 2	2404
	21st to end	Day	45% 7% 14% 19% 13% 2	2600
May	1st to 10th	Day	38% 7% 13% 24% 14% 4	5897
	11th to 20th	Day	38% 9% 14% 22% 16% 2	6111
	21st to end	Day	36% 7% 12% 27% 18% 1	6949
June	1st to 10th	Day	37% 6% 11% 27% 17% 2	2800
	11th to 20th	Day	35% 8% 14% 24% 18% 1	2800
	21st to end	Day	35% 9% 16% 24% 16% 1	2800
July	1st to 10th	Day	36% 6% 13% 30% 13% 2	6291
	11th to 20th	Day	28% 7% 14% 32% 18% 1	6285
	21st to end	Day	30% 8% 17% 26% 18% 2	6728
August	1st to 10th	Day	34% 7% 15% 29% 15% 1	4318
	11th to 20th	Day	30% 6% 16% 32% 14% 1	4063
	21st to end	Day	34% 7% 16% 25% 18% 1	4179
September	1st to 10th	Day	35% 8% 15% 26% 15% 2	2280
	11th to 20th	Day	33% 7% 15% 31% 13% 1	2101
	21st to end	Day	40% 8% 14% 27% 12%	2090
October	1st to 10th	Day	27% 4 10% 38% 18% 2	3480
	11th to 20th	Day	47% 7% 12% 22% 12%	2991
	21st to end	Day	52% 5% 17% 17% 8%	3081
November	1st to 10th	Day	53% 7% 11% 19% 9% 1	1762
	11th to 20th	Day	68% 6% 11% 10% 4	1800
	21st to end	Day	72% 4 12% 8% 3	1747
December	1st to 10th	Day	82% 5% 6% 6% 1	2610
	11th to 20th	Day	82% 4 8% 5% 1	3005
	21st to end	Day	79% 6% 6% 8% 2	3982
January	1st to 10th	Night	82% 5% 6% 5% 1	6348
	11th to 20th	Night	89% 4 4 2 1	6360
	21st to end	Night	79% 5% 9% 6% 1	6996
February	1st to 10th	Night	72% 6% 8% 9% 5% 1	2615
	11th to 20th	Night	70% 6% 8% 12% 4	2339
	21st to end	Night	63% 6% 12% 12% 6%	1980
March	1st to 10th	Night	50% 6% 17% 21% 7%	5373
	11th to 20th	Night	44% 7% 16% 23% 10% 1	5215
	21st to end	Night	53% 7% 10% 18% 10% 1	5151
April	1st to 10th	Night	50% 7% 11% 19% 12% 1	2000
	11th to 20th	Night	49% 6% 8% 19% 15% 3	1945
	21st to end	Night	45% 6% 11% 21% 13% 3	1800
May	1st to 10th	Night	43% 6% 12% 19% 15% 4	4060
	11th to 20th	Night	39% 8% 13% 22% 15% 2	3783
	21st to end	Night	44% 5% 8% 22% 16% 5%	3950
June	1st to 10th	Night	36% 7% 13% 27% 16% 2	1600
	11th to 20th	Night	36% 7% 13% 23% 18% 2	1600
	21st to end	Night	34% 9% 16% 23% 15% 4	1600
July	1st to 10th	Night	39% 6% 12% 25% 14% 4	3580
	11th to 20th	Night	30% 5% 12% 31% 20% 3	3572
	21st to end	Night	32% 6% 14% 24% 22% 2	3832
August	1st to 10th	Night	33% 6% 14% 26% 19% 1	2680
	11th to 20th	Night	32% 5% 11% 32% 19% 1	2830
	21st to end	Night	34% 7% 11% 24% 22% 2	3476
September	1st to 10th	Night	36% 7% 11% 25% 19% 2	1900
	11th to 20th	Night	30% 6% 12% 35% 14% 2	2059
	21st to end	Night	43% 7% 12% 26% 12% 1	2090
October	1st to 10th	Night	34% 4 10% 32% 18% 1	3480
	11th to 20th	Night	44% 5% 12% 25% 14% 1	3925
	21st to end	Night	48% 5% 12% 23% 11%	4467
November	1st to 10th	Night	53% 6% 11% 19% 11% 1	2536
	11th to 20th	Night	68% 5% 10% 10% 6% 1	2600
	21st to end	Night	68% 5% 14% 11% 2 1	2650
December	1st to 10th	Night	79% 5% 8% 6% 2	4580
	11th to 20th	Night	81% 5% 7% 5% 2	5201
	21st to end	Night	76% 6% 9% 6% 3	6996

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	18% 12% 36% 26% 5% 2	300
	11th to 20th	Day	22% 14% 35% 23% 5%	300
	21st to end	Day	23% 13% 31% 26% 7%	330
February	1st to 10th	Day	19% 16% 35% 20% 7% 2	300
	11th to 20th	Day	17% 19% 38% 23% 3	300
	21st to end	Day	21% 15% 41% 22% 2	249
March	1st to 10th	Day	17% 12% 42% 23% 5%	300
	11th to 20th	Day	19% 14% 28% 25% 13% 1	395
	21st to end	Day	25% 12% 27% 27% 8% 1	550
April	1st to 10th	Day	21% 11% 31% 30% 7%	500
	11th to 20th	Day	21% 12% 30% 24% 10% 3	492
	21st to end	Day	17% 9% 26% 33% 14% 1	500
May	1st to 10th	Day	18% 7% 24% 36% 13% 2	503
	11th to 20th	Day	15% 4 22% 32% 23% 4	630
	21st to end	Day	13% 3 18% 35% 24% 6%	789
June	1st to 10th	Day	10% 3 20% 39% 23% 4	730
	11th to 20th	Day	15% 2 19% 36% 24% 4	730
	21st to end	Day	13% 4 17% 38% 24% 4	730
July	1st to 10th	Day	7% 2 13% 36% 32% 9%	721
	11th to 20th	Day	8% 3 14% 39% 28% 7%	718
	21st to end	Day	7% 2 12% 42% 30% 6%	794
August	1st to 10th	Day	9% 2 12% 35% 28% 13%	615
	11th to 20th	Day	11% 3 12% 32% 31% 11%	479
	21st to end	Day	13% 4 15% 29% 31% 8%	539
September	1st to 10th	Day	13% 4 16% 34% 25% 7%	490
	11th to 20th	Day	10% 3 14% 30% 32% 11%	490
	21st to end	Day	15% 8% 21% 23% 25% 8%	490
October	1st to 10th	Day	17% 7% 23% 26% 20% 6%	490
	11th to 20th	Day	28% 10% 24% 29% 9%	328
	21st to end	Day	33% 8% 32% 21% 5% 1	330
November	1st to 10th	Day	24% 11% 29% 25% 10% 2	300
	11th to 20th	Day	23% 20% 31% 22% 4	300
	21st to end	Day	27% 12% 34% 22% 4	300
December	1st to 10th	Day	24% 19% 29% 20% 7% 1	300
	11th to 20th	Day	25% 19% 32% 17% 6% 1	300
	21st to end	Day	30% 15% 32% 16% 6% 1	330
January	1st to 10th	Night	23% 16% 32% 22% 6% 1	1000
	11th to 20th	Night	27% 13% 33% 21% 5% 1	1000
	21st to end	Night	21% 12% 35% 27% 6%	1100
February	1st to 10th	Night	21% 14% 33% 26% 5% 1	915
	11th to 20th	Night	18% 14% 35% 26% 6%	783
	21st to end	Night	23% 14% 33% 25% 4	660
March	1st to 10th	Night	19% 9% 32% 30% 10% 1	800
	11th to 20th	Night	17% 8% 31% 33% 10% 2	800
	21st to end	Night	21% 7% 25% 33% 13% 1	745
April	1st to 10th	Night	20% 10% 28% 33% 9% 1	600
	11th to 20th	Night	24% 7% 24% 31% 13% 2	593
	21st to end	Night	21% 6% 23% 35% 15% 1	600
May	1st to 10th	Night	16% 5% 21% 42% 15% 2	600
	11th to 20th	Night	16% 4 18% 37% 23% 3	591
	21st to end	Night	15% 3 15% 36% 26% 4	650
June	1st to 10th	Night	13% 2 15% 42% 25% 3	600
	11th to 20th	Night	13% 3 16% 39% 26% 5%	600
	21st to end	Night	11% 2 13% 41% 29% 4	600
July	1st to 10th	Night	9% 1 9% 36% 38% 7%	585
	11th to 20th	Night	8% 3 11% 37% 34% 7%	582
	21st to end	Night	8% 2 11% 41% 33% 5%	657
August	1st to 10th	Night	8% 2 11% 38% 33% 7%	579
	11th to 20th	Night	10% 2 10% 35% 33% 9%	564
	21st to end	Night	13% 3 13% 33% 34% 4	627
September	1st to 10th	Night	14% 3 15% 35% 25% 7%	570
	11th to 20th	Night	13% 4 12% 33% 30% 8%	729
	21st to end	Night	18% 6% 19% 27% 24% 7%	760
October	1st to 10th	Night	21% 5% 20% 29% 21% 3	760
	11th to 20th	Night	29% 10% 22% 26% 11% 1	760
	21st to end	Night	31% 11% 25% 24% 7% 1	836
November	1st to 10th	Night	24% 11% 26% 28% 11% 1	780
	11th to 20th	Night	27% 15% 28% 24% 6%	800
	21st to end	Night	30% 12% 31% 22% 6%	850
December	1st to 10th	Night	29% 15% 30% 21% 3	1000
	11th to 20th	Night	29% 16% 31% 20% 3 1	1000
	21st to end	Night	31% 15% 32% 19% 3	1100

Page generated at 2025-08-02 01:32:28. Version ac07

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