Sam's Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sam's Point clear sky chart from 2005-11-06 to 2024-01-14.

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	16% 6% 3 5% 5% 3 5% 5% 6% 7% 38%	74764
	Night	17% 7% 3 5% 5% 3 4 4 5% 7% 40%	74985
Transparency	Day	44% 8% 12% 21% 14% 2	74469
	Night	42% 7% 13% 22% 14% 2	74814
Seeing	Day	23% 16% 28% 21% 9% 3	13763
	Night	21% 14% 28% 27% 9% 1	23022

By Month

Percentage Cloud Cover NE (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	12% 7% 3 5% 5% 4 5% 6% 6% 7% 40%	1517
	11th to 20th	Day	15% 10% 3 6% 6% 4 6% 6% 7% 6% 31%	1464
	21st to end	Day	12% 7% 4 6% 5% 4 5% 6% 5% 7% 39%	1706
February	1st to 10th	Day	16% 10% 4 6% 7% 4 5% 5% 5% 7% 31%	1620
	11th to 20th	Day	14% 8% 3 6% 6% 4 5% 4 5% 6% 39%	1718
	21st to end	Day	20% 9% 3 6% 5% 3 4 3 4 4 37%	1480
March	1st to 10th	Day	14% 7% 3 7% 6% 4 4 5% 5% 7% 39%	1797
	11th to 20th	Day	15% 9% 4 6% 7% 3 5% 5% 5% 7% 35%	1912
	21st to end	Day	20% 8% 3 5% 5% 3 4 4 4 5% 38%	2344
April	1st to 10th	Day	18% 7% 3 6% 6% 3 5% 5% 5% 6% 37%	2160
	11th to 20th	Day	17% 6% 3 6% 6% 3 5% 4 5% 6% 40%	2134
	21st to end	Day	20% 6% 3 6% 5% 3 5% 5% 5% 6% 36%	2186
May	1st to 10th	Day	23% 8% 2 6% 5% 3 5% 5% 5% 6% 33%	2376
	11th to 20th	Day	19% 5% 2 5% 6% 3 5% 5% 5% 7% 37%	2478
	21st to end	Day	15% 6% 2 5% 5% 3 5% 5% 7% 8% 40%	2725
June	1st to 10th	Day	18% 4 2 6% 5% 3 5% 6% 6% 9% 34%	2520
	11th to 20th	Day	16% 6% 3 6% 5% 4 6% 5% 7% 9% 34%	2520
	21st to end	Day	14% 5% 3 6% 5% 4 6% 5% 6% 9% 37%	2520
July	1st to 10th	Day	12% 5% 2 5% 5% 5% 5% 7% 7% 9% 37%	2520
	11th to 20th	Day	12% 4 2 5% 6% 4 5% 5% 8% 10% 39%	2520
	21st to end	Day	13% 5% 3 5% 6% 4 6% 6% 6% 9% 38%	2744
August	1st to 10th	Day	12% 5% 2 5% 6% 4 6% 6% 7% 9% 37%	2422
	11th to 20th	Day	13% 5% 2 5% 5% 3 6% 6% 8% 9% 37%	2126
	21st to end	Day	14% 5% 2 5% 5% 3 4 5% 6% 9% 41%	2376
September	1st to 10th	Day	15% 6% 3 6% 5% 3 5% 4 6% 6% 41%	2160
	11th to 20th	Day	16% 4 1 4 4 3 4 4 5% 7% 49%	2098
	21st to end	Day	17% 5% 2 5% 5% 3 5% 5% 5% 7% 42%	1980
October	1st to 10th	Day	21% 6% 2 5% 4 3 4 4 4 6% 41%	1853
	11th to 20th	Day	17% 5% 2 4 6% 3 5% 5% 6% 7% 41%	1800
	21st to end	Day	24% 8% 2 4 6% 3 4 5% 5% 7% 33%	1836
November	1st to 10th	Day	15% 6% 2 4 4 2 3 3 4 6% 49%	1671
	11th to 20th	Day	19% 5% 3 5% 4 3 5% 5% 6% 6% 41%	1710
	21st to end	Day	17% 8% 3 5% 5% 3 5% 5% 5% 8% 38%	1573
December	1st to 10th	Day	18% 7% 4 7% 6% 3 4 5% 5% 7% 32%	1520
	11th to 20th	Day	22% 5% 2 4 5% 3 4 4 5% 7% 39%	1906
	21st to end	Day	19% 9% 4 9% 7% 4 5% 6% 6% 6% 26%	2772
January	1st to 10th	Night	15% 6% 2 6% 5% 3 5% 5% 5% 7% 42%	2649
	11th to 20th	Night	18% 7% 3 7% 5% 3 5% 5% 5% 7% 35%	2569
	21st to end	Night	12% 7% 3 5% 5% 3 5% 5% 7% 8% 40%	2646
February	1st to 10th	Night	16% 9% 3 6% 5% 3 4 4 6% 7% 37%	2340
	11th to 20th	Night	14% 8% 3 6% 6% 3 4 5% 6% 7% 38%	2126
	21st to end	Night	18% 8% 3 6% 5% 3 4 4 4 5% 40%	1776
March	1st to 10th	Night	16% 7% 2 5% 4 3 4 4 5% 7% 43%	2150
	11th to 20th	Night	15% 8% 3 7% 4 4 4 4 5% 7% 40%	2045
	21st to end	Night	16% 7% 3 5% 5% 3 5% 4 6% 7% 39%	2011
April	1st to 10th	Night	18% 7% 3 6% 6% 3 5% 5% 6% 6% 36%	1800
	11th to 20th	Night	18% 6% 3 5% 5% 3 4 4 5% 8% 38%	1775
	21st to end	Night	21% 6% 3 5% 5% 3 3 3 5% 6% 40%	1774
May	1st to 10th	Night	23% 8% 3 6% 4 2 4 4 6% 6% 35%	1598
	11th to 20th	Night	19% 8% 3 4 5% 3 4 4 6% 7% 39%	1415
	21st to end	Night	14% 5% 2 5% 5% 3 5% 4 5% 8% 43%	1550
June	1st to 10th	Night	17% 5% 2 5% 4 3 5% 5% 4 8% 41%	1440
	11th to 20th	Night	15% 6% 2 3 5% 3 5% 4 6% 8% 41%	1440
	21st to end	Night	12% 4 2 4 4 3 3 5% 7% 12% 45%	1440
July	1st to 10th	Night	15% 4 3 5% 4 3 4 4 6% 10% 43%	1440
	11th to 20th	Night	13% 5% 2 4 5% 4 5% 5% 5% 11% 42%	1440
	21st to end	Night	12% 5% 2 5% 5% 3 6% 6% 6% 8% 43%	1574
August	1st to 10th	Night	11% 5% 2 4 5% 3 4 5% 7% 8% 45%	1511
	11th to 20th	Night	13% 5% 3 5% 5% 3 5% 6% 6% 7% 40%	1757
	21st to end	Night	16% 5% 2 4 5% 3 4 5% 5% 6% 45%	1980
September	1st to 10th	Night	16% 5% 3 4 4 2 5% 4 5% 7% 46%	1800
	11th to 20th	Night	15% 4 2 3 4 3 3 4 5% 6% 52%	1862
	21st to end	Night	17% 6% 2 4 3 2 3 4 6% 6% 46%	1980
October	1st to 10th	Night	23% 6% 2 5% 5% 3 4 3 4 5% 41%	2105
	11th to 20th	Night	19% 5% 2 4 4 3 3 4 6% 7% 45%	2160
	21st to end	Night	24% 7% 2 5% 4 2 4 4 4 7% 37%	2520
November	1st to 10th	Night	14% 5% 3 5% 4 2 4 5% 4 5% 47%	2407
	11th to 20th	Night	20% 6% 2 4 4 2 5% 5% 4 6% 43%	2470
	21st to end	Night	16% 6% 2 5% 5% 3 3 5% 6% 7% 42%	2603
December	1st to 10th	Night	20% 7% 3 6% 5% 3 4 4 6% 7% 36%	2660
	11th to 20th	Night	21% 8% 2 5% 5% 2 5% 5% 6% 7% 36%	3288
	21st to end	Night	21% 10% 3 6% 5% 3 4 4 4 6% 34%	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	41% 7% 12% 26% 12% 3	1518
	11th to 20th	Day	48% 9% 13% 17% 10% 3	1464
	21st to end	Day	43% 6% 12% 24% 13% 2	1706
February	1st to 10th	Day	51% 7% 11% 17% 13% 1	1620
	11th to 20th	Day	45% 6% 10% 20% 15% 3	1727
	21st to end	Day	50% 5% 10% 21% 12% 2	1480
March	1st to 10th	Day	43% 6% 13% 22% 13% 3	1800
	11th to 20th	Day	47% 6% 11% 22% 13% 2	1912
	21st to end	Day	49% 6% 8% 17% 16% 5%	2344
April	1st to 10th	Day	46% 6% 9% 21% 13% 4	2160
	11th to 20th	Day	44% 6% 11% 22% 15% 3	2134
	21st to end	Day	47% 6% 10% 20% 13% 4	2186
May	1st to 10th	Day	50% 7% 10% 17% 13% 3	2376
	11th to 20th	Day	45% 7% 11% 20% 15% 2	2482
	21st to end	Day	40% 10% 15% 21% 12% 2	2725
June	1st to 10th	Day	43% 9% 15% 19% 13% 1	2520
	11th to 20th	Day	44% 10% 13% 22% 11% 1	2520
	21st to end	Day	41% 10% 11% 25% 12% 1	2520
July	1st to 10th	Day	41% 10% 13% 19% 15% 2	2450
	11th to 20th	Day	37% 10% 15% 23% 14% 1	2445
	21st to end	Day	41% 9% 13% 19% 15% 3	2591
August	1st to 10th	Day	39% 10% 14% 23% 13% 1	2408
	11th to 20th	Day	40% 10% 16% 23% 11%	2126
	21st to end	Day	38% 7% 14% 23% 16% 2	2376
September	1st to 10th	Day	42% 7% 12% 22% 16% 2	2160
	11th to 20th	Day	35% 6% 10% 23% 24% 2	2098
	21st to end	Day	40% 7% 11% 21% 18% 3	1980
October	1st to 10th	Day	45% 7% 9% 22% 14% 3	1853
	11th to 20th	Day	40% 7% 13% 25% 14% 1	1800
	21st to end	Day	50% 6% 11% 18% 12% 2	1836
November	1st to 10th	Day	37% 5% 13% 25% 17% 3	1671
	11th to 20th	Day	42% 6% 12% 22% 16% 3	1710
	21st to end	Day	44% 6% 13% 25% 9% 2	1573
December	1st to 10th	Day	50% 8% 13% 16% 12% 1	1520
	11th to 20th	Day	44% 8% 15% 22% 10% 2	1906
	21st to end	Day	55% 9% 10% 18% 7%	2772
January	1st to 10th	Night	41% 6% 12% 22% 15% 3	2649
	11th to 20th	Night	48% 7% 14% 21% 8% 2	2569
	21st to end	Night	39% 7% 13% 22% 16% 2	2646
February	1st to 10th	Night	46% 6% 15% 20% 12% 1	2340
	11th to 20th	Night	45% 7% 11% 18% 16% 3	2128
	21st to end	Night	46% 5% 8% 24% 14% 3	1776
March	1st to 10th	Night	40% 6% 14% 23% 14% 3	2160
	11th to 20th	Night	43% 5% 12% 22% 15% 3	2046
	21st to end	Night	44% 6% 11% 19% 17% 4	2011
April	1st to 10th	Night	47% 6% 10% 20% 14% 2	1800
	11th to 20th	Night	44% 7% 11% 19% 18% 1	1775
	21st to end	Night	45% 6% 10% 21% 15% 4	1774
May	1st to 10th	Night	50% 6% 10% 18% 15% 2	1598
	11th to 20th	Night	44% 7% 10% 19% 18% 2	1416
	21st to end	Night	39% 9% 16% 23% 11% 2	1551
June	1st to 10th	Night	42% 7% 10% 23% 17% 1	1440
	11th to 20th	Night	38% 10% 15% 26% 10%	1440
	21st to end	Night	31% 9% 17% 28% 15% 1	1440
July	1st to 10th	Night	36% 9% 15% 23% 14% 3	1400
	11th to 20th	Night	36% 9% 15% 28% 11% 1	1392
	21st to end	Night	34% 10% 16% 21% 17% 3	1486
August	1st to 10th	Night	35% 8% 16% 25% 14% 1	1501
	11th to 20th	Night	41% 9% 16% 22% 11%	1757
	21st to end	Night	38% 8% 12% 23% 18% 1	1980
September	1st to 10th	Night	39% 7% 12% 26% 15% 1	1800
	11th to 20th	Night	33% 6% 11% 25% 25% 2	1862
	21st to end	Night	37% 7% 9% 24% 22% 1	1980
October	1st to 10th	Night	46% 7% 10% 21% 15% 2	2105
	11th to 20th	Night	38% 7% 13% 28% 13% 1	2160
	21st to end	Night	47% 6% 12% 22% 12% 1	2520
November	1st to 10th	Night	38% 6% 11% 22% 20% 3	2407
	11th to 20th	Night	42% 5% 12% 22% 16% 4	2470
	21st to end	Night	39% 6% 15% 28% 10% 1	2603
December	1st to 10th	Night	46% 7% 13% 22% 11% 1	2660
	11th to 20th	Night	45% 7% 15% 18% 13% 2	3288
	21st to end	Night	51% 6% 13% 21% 9%	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	28% 22% 29% 16% 6%	180
	11th to 20th	Day	34% 27% 25% 11% 2 1	166
	21st to end	Day	21% 30% 32% 12% 5%	230
February	1st to 10th	Day	39% 27% 25% 8% 2	240
	11th to 20th	Day	27% 29% 32% 11% 1	386
	21st to end	Day	34% 23% 28% 14% 1	346
March	1st to 10th	Day	25% 23% 33% 16% 4	420
	11th to 20th	Day	28% 25% 27% 17% 3 1	420
	21st to end	Day	31% 20% 28% 14% 5% 2	462
April	1st to 10th	Day	30% 21% 26% 15% 7% 1	420
	11th to 20th	Day	27% 23% 27% 13% 8% 2	412
	21st to end	Day	31% 21% 27% 14% 6% 2	420
May	1st to 10th	Day	34% 19% 27% 11% 6% 2	423
	11th to 20th	Day	21% 16% 34% 21% 6% 2	447
	21st to end	Day	19% 9% 30% 24% 15% 3	485
June	1st to 10th	Day	20% 14% 30% 20% 14% 1	450
	11th to 20th	Day	19% 14% 27% 26% 12% 1	450
	21st to end	Day	15% 13% 30% 28% 12% 3	450
July	1st to 10th	Day	15% 9% 27% 28% 16% 5%	445
	11th to 20th	Day	13% 7% 27% 32% 17% 4	444
	21st to end	Day	14% 8% 35% 30% 11% 3	488
August	1st to 10th	Day	12% 8% 27% 32% 15% 7%	446
	11th to 20th	Day	17% 6% 25% 30% 16% 6%	439
	21st to end	Day	13% 11% 27% 28% 14% 7%	495
September	1st to 10th	Day	21% 10% 24% 24% 15% 7%	450
	11th to 20th	Day	16% 11% 26% 22% 14% 11%	450
	21st to end	Day	19% 13% 26% 25% 12% 5%	450
October	1st to 10th	Day	29% 13% 21% 21% 12% 5%	450
	11th to 20th	Day	19% 17% 28% 23% 12% 2	450
	21st to end	Day	27% 14% 33% 18% 7% 1	423
November	1st to 10th	Day	21% 17% 25% 26% 9% 2	365
	11th to 20th	Day	25% 23% 25% 21% 5% 1	370
	21st to end	Day	24% 22% 30% 19% 4 1	233
December	1st to 10th	Day	26% 30% 28% 11% 6%	180
	11th to 20th	Day	38% 16% 29% 14% 3	180
	21st to end	Day	27% 26% 28% 16% 3	198
January	1st to 10th	Night	20% 20% 37% 20% 3	760
	11th to 20th	Night	23% 18% 30% 25% 3	735
	21st to end	Night	18% 20% 35% 23% 3	792
February	1st to 10th	Night	23% 20% 33% 22% 2	720
	11th to 20th	Night	22% 22% 37% 17% 1	703
	21st to end	Night	27% 18% 35% 16% 4	592
March	1st to 10th	Night	24% 19% 32% 21% 4	720
	11th to 20th	Night	23% 22% 29% 22% 4	720
	21st to end	Night	21% 19% 33% 21% 5%	792
April	1st to 10th	Night	24% 18% 32% 21% 4	720
	11th to 20th	Night	23% 16% 31% 25% 6%	711
	21st to end	Night	26% 16% 27% 24% 6% 1	694
May	1st to 10th	Night	26% 13% 26% 25% 9%	518
	11th to 20th	Night	21% 11% 31% 31% 6%	354
	21st to end	Night	17% 8% 20% 39% 15% 1	389
June	1st to 10th	Night	17% 5% 26% 36% 14% 1	360
	11th to 20th	Night	16% 6% 24% 37% 16% 1	360
	21st to end	Night	11% 4 23% 48% 14%	360
July	1st to 10th	Night	15% 4 18% 40% 21% 1	350
	11th to 20th	Night	12% 4 18% 45% 19% 1	348
	21st to end	Night	12% 5% 21% 44% 18% 1	394
August	1st to 10th	Night	11% 1 22% 43% 21% 2	437
	11th to 20th	Night	14% 4 18% 39% 23% 3	693
	21st to end	Night	17% 6% 15% 36% 25% 2	792
September	1st to 10th	Night	17% 6% 21% 35% 19% 3	720
	11th to 20th	Night	17% 7% 21% 30% 20% 5%	720
	21st to end	Night	19% 7% 22% 33% 17% 3	720
October	1st to 10th	Night	25% 11% 22% 25% 16% 2	720
	11th to 20th	Night	21% 13% 25% 32% 9% 1	720
	21st to end	Night	28% 14% 30% 22% 7%	792
November	1st to 10th	Night	17% 13% 30% 30% 10%	740
	11th to 20th	Night	24% 20% 25% 23% 7% 1	760
	21st to end	Night	20% 17% 30% 26% 7% 1	760
December	1st to 10th	Night	26% 17% 30% 22% 5%	760
	11th to 20th	Night	24% 21% 26% 25% 4	760
	21st to end	Night	27% 16% 34% 22% 2	836

Page generated at 2024-01-11 04:22:40. Version ac07

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