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 2024-04-03.

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	14% 11% 5% 8% 6% 3 4 4 5% 7% 33%	78742
	Night	15% 14% 6% 9% 7% 4 4 4 4 5% 28%	81440
Transparency	Day	50% 7% 13% 19% 10% 1	78443
	Night	57% 7% 11% 16% 8% 1	81260
Seeing	Day	17% 7% 22% 30% 19% 5%	14976
	Night	20% 8% 24% 30% 15% 2	25045

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% 29% 13% 15% 8% 3 4 2 2 2 8%	2527
	11th to 20th	Day	14% 18% 11% 18% 16% 8% 5% 2 2 2 5%	2530
	21st to end	Day	18% 21% 11% 13% 9% 4 5% 3 3 3 9%	2783
February	1st to 10th	Day	12% 13% 8% 14% 15% 4 5% 3 4 5% 15%	1690
	11th to 20th	Day	13% 14% 8% 17% 12% 4 4 3 3 4 17%	1848
	21st to end	Day	13% 14% 8% 13% 8% 5% 5% 4 4 5% 21%	1570
March	1st to 10th	Day	13% 10% 6% 8% 8% 3 5% 4 5% 5% 32%	1900
	11th to 20th	Day	12% 9% 5% 9% 7% 3 4 4 5% 8% 34%	1990
	21st to end	Day	16% 11% 4 8% 6% 3 4 4 6% 7% 30%	2441
April	1st to 10th	Day	18% 12% 6% 6% 6% 3 3 4 4 7% 32%	2184
	11th to 20th	Day	19% 9% 4 5% 5% 3 4 4 5% 6% 35%	2160
	21st to end	Day	15% 9% 3 6% 6% 3 4 5% 5% 7% 37%	2340
May	1st to 10th	Day	13% 8% 4 6% 5% 3 5% 5% 6% 8% 38%	2340
	11th to 20th	Day	16% 6% 2 5% 5% 3 4 4 5% 8% 42%	2393
	21st to end	Day	10% 5% 3 5% 5% 3 5% 5% 6% 9% 45%	2725
June	1st to 10th	Day	11% 5% 2 6% 5% 3 4 4 5% 8% 48%	2520
	11th to 20th	Day	12% 5% 2 4 5% 2 4 4 5% 10% 46%	2520
	21st to end	Day	10% 5% 2 4 5% 3 5% 4 6% 10% 47%	2520
July	1st to 10th	Day	6% 3 1 3 4 2 3 5% 6% 10% 56%	2520
	11th to 20th	Day	8% 4 2 4 4 2 4 4 5% 8% 54%	2520
	21st to end	Day	7% 4 2 4 4 2 5% 4 7% 9% 52%	2743
August	1st to 10th	Day	8% 4 2 4 4 3 5% 5% 7% 10% 49%	2430
	11th to 20th	Day	9% 3 2 5% 4 2 4 4 6% 8% 51%	2297
	21st to end	Day	11% 5% 2 4 4 3 4 4 5% 7% 50%	2376
September	1st to 10th	Day	12% 6% 2 6% 6% 3 4 4 5% 6% 46%	2160
	11th to 20th	Day	12% 5% 2 5% 4 3 4 4 5% 7% 48%	1991
	21st to end	Day	14% 8% 3 6% 5% 3 5% 5% 5% 7% 40%	1980
October	1st to 10th	Day	16% 7% 3 5% 6% 3 4 3 5% 6% 41%	1980
	11th to 20th	Day	25% 12% 3 7% 6% 4 4 5% 6% 6% 21%	1719
	21st to end	Day	25% 13% 4 8% 5% 3 4 3 5% 6% 23%	1782
November	1st to 10th	Day	17% 13% 4 7% 6% 3 4 3 4 6% 33%	1672
	11th to 20th	Day	15% 23% 7% 10% 5% 3 5% 4 5% 6% 17%	1710
	21st to end	Day	21% 20% 8% 11% 6% 3 3 3 3 5% 17%	1660
December	1st to 10th	Day	15% 22% 15% 15% 7% 3 3 3 3 3 12%	1520
	11th to 20th	Day	15% 23% 11% 14% 8% 3 4 3 4 4 10%	1918
	21st to end	Day	19% 23% 11% 12% 8% 4 4 3 2 4 9%	2783
January	1st to 10th	Night	15% 26% 12% 14% 8% 3 3 2 2 3 12%	4428
	11th to 20th	Night	13% 19% 10% 19% 12% 9% 4 2 2 2 7%	4440
	21st to end	Night	17% 23% 11% 15% 10% 4 5% 2 2 3 8%	4884
February	1st to 10th	Night	12% 17% 8% 14% 13% 5% 4 4 3 4 17%	2485
	11th to 20th	Night	13% 13% 9% 15% 12% 5% 4 3 4 5% 18%	2218
	21st to end	Night	15% 14% 7% 12% 9% 3 4 4 5% 6% 22%	1884
March	1st to 10th	Night	14% 10% 5% 8% 7% 4 4 4 4 7% 33%	2280
	11th to 20th	Night	12% 9% 5% 8% 6% 3 4 4 5% 6% 38%	2190
	21st to end	Night	18% 9% 4 8% 6% 4 5% 4 6% 6% 32%	2171
April	1st to 10th	Night	17% 12% 5% 7% 5% 3 4 3 6% 7% 32%	1820
	11th to 20th	Night	20% 10% 3 5% 5% 3 5% 3 5% 6% 36%	1749
	21st to end	Night	18% 9% 3 6% 5% 3 4 4 5% 6% 37%	1620
May	1st to 10th	Night	14% 7% 3 7% 6% 4 5% 5% 5% 8% 35%	1620
	11th to 20th	Night	14% 7% 3 6% 6% 4 5% 5% 6% 7% 37%	1498
	21st to end	Night	12% 7% 3 6% 5% 3 3 4 6% 10% 42%	1551
June	1st to 10th	Night	12% 5% 3 5% 5% 4 4 5% 6% 7% 45%	1440
	11th to 20th	Night	12% 5% 3 6% 5% 3 4 4 5% 9% 45%	1440
	21st to end	Night	9% 5% 2 4 5% 3 5% 5% 6% 9% 46%	1440
July	1st to 10th	Night	7% 2 2 3 4 3 4 5% 6% 9% 53%	1440
	11th to 20th	Night	7% 4 2 6% 5% 2 4 6% 6% 8% 51%	1440
	21st to end	Night	6% 4 2 6% 6% 2 4 4 6% 8% 50%	1575
August	1st to 10th	Night	8% 4 2 5% 5% 3 5% 5% 7% 8% 49%	1507
	11th to 20th	Night	8% 4 2 4 4 3 4 4 6% 8% 52%	1602
	21st to end	Night	12% 5% 2 4 5% 2 4 4 5% 7% 49%	1980
September	1st to 10th	Night	12% 5% 2 4 6% 3 5% 4 4 7% 48%	1800
	11th to 20th	Night	12% 4 2 4 3 2 4 4 5% 6% 53%	1950
	21st to end	Night	16% 6% 2 5% 5% 4 5% 4 5% 6% 41%	1980
October	1st to 10th	Night	19% 6% 2 5% 4 2 4 3 4 7% 44%	1980
	11th to 20th	Night	24% 11% 4 7% 7% 3 4 3 4 5% 30%	2238
	21st to end	Night	27% 12% 4 7% 5% 3 4 4 5% 5% 25%	2574
November	1st to 10th	Night	15% 14% 5% 7% 6% 3 4 3 4 6% 33%	2406
	11th to 20th	Night	17% 22% 6% 10% 5% 3 4 4 4 4 19%	2470
	21st to end	Night	20% 21% 8% 8% 5% 3 3 3 4 5% 21%	2517
December	1st to 10th	Night	16% 25% 12% 12% 7% 3 4 3 3 4 12%	2660
	11th to 20th	Night	17% 22% 10% 14% 7% 3 4 4 4 4 12%	3279
	21st to end	Night	23% 23% 9% 10% 6% 3 3 4 3 4 11%	4884

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	82% 6% 6% 5% 1	2528
	11th to 20th	Day	88% 5% 3 3	2530
	21st to end	Day	80% 7% 8% 3 1	2783
February	1st to 10th	Day	71% 8% 8% 11% 2	1690
	11th to 20th	Day	70% 6% 9% 10% 4	1858
	21st to end	Day	65% 7% 12% 11% 4	1570
March	1st to 10th	Day	53% 8% 16% 16% 6% 1	1900
	11th to 20th	Day	47% 8% 13% 18% 11% 2	1990
	21st to end	Day	51% 7% 14% 20% 8% 1	2441
April	1st to 10th	Day	52% 6% 13% 20% 9%	2184
	11th to 20th	Day	47% 7% 10% 20% 14% 2	2160
	21st to end	Day	45% 7% 14% 18% 13% 2	2340
May	1st to 10th	Day	42% 8% 12% 25% 12% 1	2340
	11th to 20th	Day	41% 6% 14% 22% 16% 2	2397
	21st to end	Day	37% 8% 14% 26% 14% 1	2725
June	1st to 10th	Day	36% 6% 12% 26% 18% 2	2520
	11th to 20th	Day	34% 8% 14% 24% 19% 1	2520
	21st to end	Day	34% 9% 16% 23% 16% 1	2520
July	1st to 10th	Day	23% 8% 15% 32% 17% 3	2451
	11th to 20th	Day	28% 8% 15% 30% 17% 3	2445
	21st to end	Day	27% 8% 16% 28% 18% 3	2591
August	1st to 10th	Day	28% 8% 18% 30% 14% 1	2415
	11th to 20th	Day	29% 8% 19% 28% 14% 2	2297
	21st to end	Day	32% 7% 15% 27% 18% 2	2376
September	1st to 10th	Day	36% 8% 14% 25% 15% 2	2160
	11th to 20th	Day	34% 7% 15% 31% 11% 1	1991
	21st to end	Day	40% 8% 14% 27% 10%	1980
October	1st to 10th	Day	43% 7% 12% 25% 13%	1980
	11th to 20th	Day	60% 8% 14% 13% 5%	1719
	21st to end	Day	61% 7% 13% 13% 6%	1782
November	1st to 10th	Day	53% 7% 11% 19% 10% 1	1672
	11th to 20th	Day	68% 6% 12% 10% 4	1710
	21st to end	Day	71% 5% 13% 9% 3	1660
December	1st to 10th	Day	79% 6% 7% 6% 2	1520
	11th to 20th	Day	77% 5% 11% 5% 1	1915
	21st to end	Day	80% 7% 7% 5% 1	2783
January	1st to 10th	Night	78% 6% 8% 7% 1	4428
	11th to 20th	Night	86% 5% 4 3 1	4440
	21st to end	Night	82% 7% 8% 3	4884
February	1st to 10th	Night	72% 5% 7% 10% 5% 1	2485
	11th to 20th	Night	69% 6% 8% 12% 4	2219
	21st to end	Night	64% 6% 11% 13% 6%	1884
March	1st to 10th	Night	52% 7% 15% 19% 6% 1	2280
	11th to 20th	Night	46% 8% 12% 20% 12% 2	2190
	21st to end	Night	50% 7% 11% 22% 9% 1	2171
April	1st to 10th	Night	51% 7% 11% 18% 12% 1	1820
	11th to 20th	Night	49% 6% 7% 19% 15% 3	1749
	21st to end	Night	46% 6% 11% 21% 12% 4	1620
May	1st to 10th	Night	46% 7% 13% 21% 12% 1	1620
	11th to 20th	Night	44% 7% 11% 19% 16% 4	1499
	21st to end	Night	40% 6% 12% 25% 15% 3	1552
June	1st to 10th	Night	35% 7% 13% 27% 15% 3	1440
	11th to 20th	Night	34% 7% 13% 24% 19% 2	1440
	21st to end	Night	31% 10% 16% 25% 14% 4	1440
July	1st to 10th	Night	26% 8% 13% 28% 21% 4	1400
	11th to 20th	Night	29% 7% 15% 28% 18% 4	1392
	21st to end	Night	28% 10% 15% 25% 18% 3	1487
August	1st to 10th	Night	30% 8% 17% 28% 14% 2	1498
	11th to 20th	Night	29% 7% 15% 31% 16% 1	1602
	21st to end	Night	32% 8% 11% 26% 19% 2	1980
September	1st to 10th	Night	36% 8% 11% 24% 19% 2	1800
	11th to 20th	Night	31% 6% 12% 36% 11% 3	1950
	21st to end	Night	43% 7% 13% 26% 11% 1	1980
October	1st to 10th	Night	41% 6% 10% 26% 15% 1	1980
	11th to 20th	Night	57% 5% 13% 17% 7% 1	2238
	21st to end	Night	60% 7% 12% 14% 6%	2574
November	1st to 10th	Night	52% 6% 11% 20% 11% 1	2406
	11th to 20th	Night	68% 6% 10% 10% 5%	2470
	21st to end	Night	67% 5% 14% 11% 2 1	2517
December	1st to 10th	Night	78% 6% 7% 7% 3	2660
	11th to 20th	Night	75% 8% 9% 5% 2	3281
	21st to end	Night	76% 7% 10% 6% 2	4884

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	19% 12% 34% 27% 6% 2	270
	11th to 20th	Day	23% 12% 34% 25% 6%	270
	21st to end	Day	24% 10% 30% 28% 7%	297
February	1st to 10th	Day	19% 14% 37% 20% 8% 3	270
	11th to 20th	Day	15% 18% 39% 24% 4	270
	21st to end	Day	21% 13% 41% 23% 2	225
March	1st to 10th	Day	17% 13% 41% 23% 6%	270
	11th to 20th	Day	19% 13% 28% 26% 14% 1	360
	21st to end	Day	25% 11% 25% 29% 9% 1	506
April	1st to 10th	Day	21% 10% 30% 31% 8%	428
	11th to 20th	Day	23% 10% 29% 23% 11% 4	412
	21st to end	Day	18% 5% 27% 32% 15% 1	420
May	1st to 10th	Day	19% 6% 23% 35% 13% 3	423
	11th to 20th	Day	16% 4 22% 32% 23% 3	539
	21st to end	Day	13% 2 17% 33% 27% 7%	679
June	1st to 10th	Day	10% 3 18% 39% 25% 5%	630
	11th to 20th	Day	15% 2 16% 36% 27% 4	630
	21st to end	Day	12% 3 16% 39% 25% 4	630
July	1st to 10th	Day	6% 2 12% 33% 36% 10%	621
	11th to 20th	Day	8% 2 14% 40% 29% 7%	618
	21st to end	Day	7% 2 12% 42% 31% 6%	684
August	1st to 10th	Day	10% 2 11% 36% 29% 12%	549
	11th to 20th	Day	11% 3 10% 31% 32% 13%	439
	21st to end	Day	13% 3 16% 29% 31% 8%	495
September	1st to 10th	Day	14% 3 15% 36% 24% 8%	450
	11th to 20th	Day	10% 3 14% 30% 30% 11%	450
	21st to end	Day	15% 9% 22% 20% 25% 9%	450
October	1st to 10th	Day	18% 7% 22% 25% 21% 7%	450
	11th to 20th	Day	30% 10% 24% 28% 8%	297
	21st to end	Day	35% 6% 32% 21% 5% 1	297
November	1st to 10th	Day	21% 11% 27% 27% 11% 2	270
	11th to 20th	Day	23% 19% 32% 23% 4	270
	21st to end	Day	27% 13% 35% 21% 4	270
December	1st to 10th	Day	23% 19% 31% 20% 6% 1	270
	11th to 20th	Day	26% 19% 31% 17% 6% 1	270
	21st to end	Day	29% 16% 32% 16% 6%	297
January	1st to 10th	Night	23% 15% 32% 23% 6% 1	950
	11th to 20th	Night	27% 11% 33% 22% 6% 1	950
	21st to end	Night	21% 11% 34% 28% 7%	1045
February	1st to 10th	Night	20% 14% 33% 27% 6% 1	870
	11th to 20th	Night	18% 13% 35% 27% 6%	743
	21st to end	Night	24% 14% 32% 25% 4	628
March	1st to 10th	Night	19% 8% 31% 30% 10% 1	760
	11th to 20th	Night	17% 8% 31% 33% 10% 2	760
	21st to end	Night	20% 7% 25% 33% 13% 2	708
April	1st to 10th	Night	19% 10% 28% 33% 9% 1	546
	11th to 20th	Night	25% 5% 24% 32% 13% 2	533
	21st to end	Night	21% 4 23% 34% 16% 1	540
May	1st to 10th	Night	16% 5% 21% 42% 14% 2	540
	11th to 20th	Night	17% 4 16% 38% 23% 2	531
	21st to end	Night	14% 3 15% 36% 28% 5%	584
June	1st to 10th	Night	14% 2 13% 41% 27% 4	540
	11th to 20th	Night	13% 3 15% 38% 27% 5%	540
	21st to end	Night	10% 2 11% 41% 31% 4	540
July	1st to 10th	Night	8% 1 7% 36% 39% 8%	525
	11th to 20th	Night	7% 3 11% 37% 35% 6%	522
	21st to end	Night	9% 2 10% 41% 33% 5%	591
August	1st to 10th	Night	9% 2 10% 39% 33% 7%	537
	11th to 20th	Night	10% 2 10% 35% 34% 9%	534
	21st to end	Night	13% 3 14% 33% 34% 4	594
September	1st to 10th	Night	14% 3 14% 36% 25% 7%	540
	11th to 20th	Night	13% 4 13% 33% 29% 8%	690
	21st to end	Night	18% 6% 19% 26% 25% 7%	720
October	1st to 10th	Night	21% 5% 19% 29% 22% 4	720
	11th to 20th	Night	31% 10% 22% 26% 11% 1	720
	21st to end	Night	33% 10% 25% 23% 7% 1	792
November	1st to 10th	Night	23% 10% 26% 29% 11% 1	740
	11th to 20th	Night	27% 15% 28% 24% 6%	760
	21st to end	Night	29% 12% 31% 23% 6%	807
December	1st to 10th	Night	29% 15% 31% 21% 3	950
	11th to 20th	Night	28% 16% 32% 21% 3 1	950
	21st to end	Night	31% 15% 33% 20% 2	1045

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