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 2026-01-17.

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	17% 7% 2 6% 4 4 5% 4 6% 7% 37%	127459
	Night	17% 7% 2 6% 4 4 4 3 5% 7% 40%	124194
Transparency	Day	43% 7% 12% 22% 14% 2	130960
	Night	42% 6% 12% 22% 15% 2	128767
Seeing	Day	23% 17% 28% 21% 9% 3	16344
	Night	21% 14% 28% 27% 9% 1	25570

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% 8% 3 9% 5% 4 4 4 6% 6% 39%	3677
	11th to 20th	Day	13% 10% 4 9% 6% 4 5% 4 6% 6% 33%	3618
	21st to end	Day	16% 10% 4 7% 4 4 4 4 4 5% 37%	4264
February	1st to 10th	Day	14% 10% 3 8% 6% 6% 5% 4 6% 6% 33%	1800
	11th to 20th	Day	13% 9% 2 7% 6% 5% 5% 3 5% 6% 39%	1915
	21st to end	Day	19% 10% 3 7% 5% 4 4 3 4 5% 38%	1650
March	1st to 10th	Day	21% 7% 2 6% 4 4 4 3 5% 5% 38%	4476
	11th to 20th	Day	13% 7% 3 7% 5% 4 4 4 5% 7% 41%	4814
	21st to end	Day	20% 8% 2 6% 4 4 4 4 5% 6% 37%	5896
April	1st to 10th	Day	19% 8% 2 7% 5% 4 4 4 4 6% 36%	2400
	11th to 20th	Day	17% 7% 2 7% 5% 3 5% 3 5% 6% 39%	2374
	21st to end	Day	18% 6% 3 7% 5% 4 4 4 5% 6% 37%	2430
May	1st to 10th	Day	31% 7% 2 6% 4 4 4 4 5% 7% 27%	5978
	11th to 20th	Day	22% 7% 3 6% 5% 4 4 4 6% 6% 33%	6318
	21st to end	Day	21% 6% 2 5% 4 4 6% 5% 8% 9% 31%	6949
June	1st to 10th	Day	17% 5% 2 7% 4 5% 5% 5% 7% 9% 34%	2800
	11th to 20th	Day	16% 6% 2 7% 4 4 5% 5% 7% 9% 34%	2800
	21st to end	Day	14% 6% 2 7% 4 5% 6% 4 7% 9% 37%	2800
July	1st to 10th	Day	12% 7% 3 7% 5% 5% 5% 4 7% 9% 36%	6360
	11th to 20th	Day	11% 6% 2 7% 5% 5% 6% 5% 9% 11% 34%	6360
	21st to end	Day	15% 6% 2 6% 4 4 4 4 5% 8% 41%	6926
August	1st to 10th	Day	21% 6% 2 6% 5% 5% 5% 4 6% 7% 33%	4391
	11th to 20th	Day	14% 5% 2 6% 4 4 5% 4 8% 8% 38%	3850
	21st to end	Day	14% 5% 2 5% 3 4 4 4 6% 10% 44%	4312
September	1st to 10th	Day	14% 6% 2 6% 5% 4 4 3 6% 6% 43%	2400
	11th to 20th	Day	14% 4 1 5% 3 3 4 3 5% 7% 50%	2330
	21st to end	Day	18% 5% 2 5% 4 4 5% 4 6% 6% 40%	2200
October	1st to 10th	Day	19% 6% 2 5% 4 4 4 3 4 5% 43%	2058
	11th to 20th	Day	16% 6% 3 5% 4 4 5% 4 6% 7% 41%	2000
	21st to end	Day	22% 7% 2 5% 5% 4 3 4 5% 7% 35%	2040
November	1st to 10th	Day	14% 7% 2 6% 3 3 3 3 4 6% 50%	1851
	11th to 20th	Day	17% 6% 2 6% 3 4 4 4 6% 6% 42%	1890
	21st to end	Day	17% 9% 2 6% 4 4 4 4 5% 7% 36%	1738
December	1st to 10th	Day	16% 6% 3 8% 5% 4 5% 4 6% 6% 36%	2680
	11th to 20th	Day	23% 6% 2 5% 4 3 4 3 5% 6% 40%	3066
	21st to end	Day	18% 8% 3 8% 5% 5% 5% 4 6% 7% 31%	4048
January	1st to 10th	Night	13% 6% 2 7% 5% 5% 5% 4 6% 7% 39%	6489
	11th to 20th	Night	12% 9% 3 9% 5% 4 4 4 5% 8% 37%	6400
	21st to end	Night	16% 9% 3 5% 4 4 5% 4 5% 7% 38%	6674
February	1st to 10th	Night	15% 9% 3 7% 5% 4 4 3 6% 7% 38%	2600
	11th to 20th	Night	14% 8% 3 7% 5% 4 4 5% 6% 7% 37%	2369
	21st to end	Night	17% 8% 3 6% 5% 4 4 3 4 5% 39%	1980
March	1st to 10th	Night	20% 8% 2 5% 3 3 3 3 5% 6% 41%	5364
	11th to 20th	Night	14% 8% 3 6% 4 4 4 3 6% 6% 41%	5129
	21st to end	Night	18% 10% 3 7% 4 4 4 3 5% 6% 38%	5021
April	1st to 10th	Night	19% 7% 2 7% 5% 5% 5% 4 6% 6% 34%	2000
	11th to 20th	Night	19% 8% 3 6% 4 4 4 3 5% 8% 37%	1975
	21st to end	Night	20% 7% 2 6% 4 3 3 3 4 7% 41%	1970
May	1st to 10th	Night	33% 7% 2 5% 3 2 3 3 6% 6% 29%	3990
	11th to 20th	Night	22% 8% 3 6% 4 4 4 3 5% 7% 34%	3575
	21st to end	Night	21% 7% 2 7% 4 5% 4 3 5% 8% 34%	3926
June	1st to 10th	Night	17% 6% 2 6% 4 4 4 4 5% 9% 40%	1600
	11th to 20th	Night	15% 7% 2 4 4 4 4 4 6% 9% 41%	1600
	21st to end	Night	12% 5% 2 4 4 4 3 4 7% 11% 44%	1600
July	1st to 10th	Night	14% 6% 3 6% 4 4 4 4 6% 8% 40%	3600
	11th to 20th	Night	15% 7% 2 6% 5% 4 5% 4 6% 9% 37%	3600
	21st to end	Night	14% 5% 2 5% 3 4 4 4 5% 7% 47%	3926
August	1st to 10th	Night	21% 6% 2 6% 4 4 4 4 5% 7% 35%	2740
	11th to 20th	Night	15% 6% 3 6% 4 4 4 4 5% 6% 43%	3179
	21st to end	Night	13% 5% 2 4 4 3 4 3 5% 6% 53%	3586
September	1st to 10th	Night	15% 6% 2 5% 3 3 4 3 5% 7% 47%	2000
	11th to 20th	Night	14% 4 2 5% 3 3 3 3 5% 6% 53%	2070
	21st to end	Night	18% 7% 2 5% 3 4 3 3 6% 6% 44%	2200
October	1st to 10th	Night	21% 6% 2 6% 4 3 3 3 4 5% 43%	2339
	11th to 20th	Night	19% 5% 1 4 3 3 3 3 6% 6% 46%	2400
	21st to end	Night	22% 7% 2 5% 4 3 4 3 5% 7% 38%	2800
November	1st to 10th	Night	13% 5% 3 6% 4 4 4 3 5% 6% 47%	2667
	11th to 20th	Night	19% 7% 2 5% 3 4 4 4 5% 6% 43%	2730
	21st to end	Night	16% 7% 2 6% 4 4 4 4 6% 7% 41%	2877
December	1st to 10th	Night	14% 9% 3 6% 3 4 4 3 5% 7% 41%	4720
	11th to 20th	Night	25% 8% 2 4 3 3 3 3 5% 5% 38%	5348
	21st to end	Night	20% 9% 3 7% 4 5% 4 3 4 6% 35%	7150

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% 6% 10% 27% 13% 3	3678
	11th to 20th	Day	47% 7% 9% 19% 13% 5%	3648
	21st to end	Day	47% 6% 9% 24% 13% 1	4264
February	1st to 10th	Day	50% 7% 11% 18% 14% 1	1800
	11th to 20th	Day	45% 6% 10% 21% 15% 3	1924
	21st to end	Day	48% 5% 11% 22% 12% 2	1650
March	1st to 10th	Day	47% 4 12% 17% 13% 8%	4479
	11th to 20th	Day	40% 7% 13% 28% 8% 4	4814
	21st to end	Day	46% 6% 9% 13% 22% 5%	5896
April	1st to 10th	Day	48% 6% 9% 20% 13% 4	2400
	11th to 20th	Day	45% 6% 11% 20% 15% 3	2374
	21st to end	Day	46% 6% 10% 20% 14% 4	2430
May	1st to 10th	Day	54% 8% 12% 14% 10% 1	5989
	11th to 20th	Day	49% 7% 12% 19% 12% 1	6322
	21st to end	Day	45% 9% 13% 22% 11% 1	6949
June	1st to 10th	Day	43% 9% 14% 20% 13% 1	2800
	11th to 20th	Day	43% 9% 13% 22% 11% 1	2800
	21st to end	Day	41% 10% 11% 25% 13% 1	2800
July	1st to 10th	Day	43% 9% 13% 20% 14% 1	6290
	11th to 20th	Day	39% 9% 15% 25% 11%	6285
	21st to end	Day	40% 6% 12% 23% 18% 1	6728
August	1st to 10th	Day	48% 8% 13% 20% 10% 1	4377
	11th to 20th	Day	39% 8% 16% 27% 10%	3886
	21st to end	Day	34% 6% 13% 31% 14% 1	4312
September	1st to 10th	Day	40% 7% 11% 23% 17% 2	2400
	11th to 20th	Day	33% 6% 10% 25% 24% 2	2330
	21st to end	Day	43% 7% 11% 20% 17% 2	2200
October	1st to 10th	Day	40% 5% 7% 20% 24% 3	3344
	11th to 20th	Day	33% 5% 9% 27% 23% 3	3240
	21st to end	Day	32% 5% 16% 26% 18% 4	3278
November	1st to 10th	Day	36% 5% 13% 25% 18% 3	1851
	11th to 20th	Day	41% 5% 11% 22% 17% 3	1890
	21st to end	Day	46% 6% 13% 25% 8% 1	1738
December	1st to 10th	Day	45% 7% 14% 24% 9% 1	2680
	11th to 20th	Day	44% 6% 14% 21% 13% 2	3066
	21st to end	Day	49% 7% 10% 18% 14% 2	4048
January	1st to 10th	Night	42% 5% 10% 23% 17% 2	6489
	11th to 20th	Night	44% 5% 15% 18% 13% 5%	6445
	21st to end	Night	45% 6% 12% 17% 17% 4	6674
February	1st to 10th	Night	46% 6% 15% 21% 12% 1	2600
	11th to 20th	Night	44% 7% 11% 18% 17% 3	2371
	21st to end	Night	45% 5% 9% 23% 14% 4	1980
March	1st to 10th	Night	43% 4 14% 18% 15% 6%	5374
	11th to 20th	Night	41% 6% 17% 23% 10% 3	5130
	21st to end	Night	47% 5% 8% 14% 22% 3	5021
April	1st to 10th	Night	49% 6% 10% 19% 13% 3	2000
	11th to 20th	Night	45% 7% 11% 19% 18% 1	1975
	21st to end	Night	43% 6% 10% 21% 17% 4	1970
May	1st to 10th	Night	55% 6% 13% 15% 10% 1	3996
	11th to 20th	Night	48% 8% 12% 16% 15% 1	3576
	21st to end	Night	46% 8% 13% 22% 10% 1	3927
June	1st to 10th	Night	41% 7% 10% 23% 17% 1	1600
	11th to 20th	Night	38% 9% 16% 26% 10%	1600
	21st to end	Night	32% 8% 16% 27% 15% 1	1600
July	1st to 10th	Night	40% 8% 15% 19% 15% 3	3560
	11th to 20th	Night	42% 8% 15% 22% 11% 1	3552
	21st to end	Night	35% 6% 14% 26% 18% 1	3809
August	1st to 10th	Night	48% 7% 16% 19% 9% 1	2730
	11th to 20th	Night	41% 6% 14% 28% 10%	3209
	21st to end	Night	31% 6% 12% 35% 15% 1	3586
September	1st to 10th	Night	37% 7% 12% 26% 17% 1	2000
	11th to 20th	Night	32% 6% 10% 26% 25% 1	2070
	21st to end	Night	39% 7% 10% 23% 21% 2	2200
October	1st to 10th	Night	41% 5% 9% 22% 20% 2	3820
	11th to 20th	Night	28% 4 10% 29% 24% 4	3899
	21st to end	Night	34% 5% 14% 29% 17% 1	4512
November	1st to 10th	Night	37% 6% 11% 23% 20% 3	2667
	11th to 20th	Night	42% 5% 11% 21% 18% 3	2730
	21st to end	Night	40% 6% 15% 28% 10% 1	2877
December	1st to 10th	Night	42% 5% 13% 30% 9% 1	4720
	11th to 20th	Night	47% 4 14% 18% 15% 2	5348
	21st to end	Night	50% 5% 11% 18% 13% 3	7150

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% 26% 26% 15% 5%	220
	11th to 20th	Day	34% 29% 23% 12% 2	212
	21st to end	Day	23% 29% 31% 13% 4	287
February	1st to 10th	Day	34% 27% 27% 9% 2	300
	11th to 20th	Day	31% 28% 29% 11% 1	463
	21st to end	Day	32% 23% 30% 13% 2	414
March	1st to 10th	Day	28% 23% 30% 15% 4	500
	11th to 20th	Day	28% 24% 28% 16% 3 1	500
	21st to end	Day	31% 21% 29% 13% 4 2	550
April	1st to 10th	Day	33% 23% 25% 13% 6% 1	500
	11th to 20th	Day	30% 24% 26% 12% 7% 2	492
	21st to end	Day	29% 21% 29% 15% 6% 2	500
May	1st to 10th	Day	36% 18% 26% 13% 6% 2	503
	11th to 20th	Day	21% 17% 33% 20% 7% 2	527
	21st to end	Day	21% 10% 31% 23% 13% 2	573
June	1st to 10th	Day	21% 14% 31% 21% 13% 1	530
	11th to 20th	Day	19% 14% 27% 27% 11% 2	530
	21st to end	Day	15% 13% 31% 28% 11% 2	530
July	1st to 10th	Day	14% 10% 29% 28% 16% 4	525
	11th to 20th	Day	13% 7% 27% 32% 17% 4	524
	21st to end	Day	15% 8% 34% 30% 11% 3	576
August	1st to 10th	Day	13% 8% 26% 31% 15% 7%	526
	11th to 20th	Day	16% 7% 24% 31% 16% 7%	519
	21st to end	Day	12% 10% 28% 28% 14% 7%	583
September	1st to 10th	Day	20% 10% 24% 25% 15% 7%	530
	11th to 20th	Day	14% 10% 24% 23% 17% 12%	530
	21st to end	Day	21% 12% 25% 26% 12% 5%	530
October	1st to 10th	Day	25% 13% 22% 21% 13% 6%	530
	11th to 20th	Day	19% 18% 28% 22% 11% 2	530
	21st to end	Day	24% 14% 34% 19% 8% 1	495
November	1st to 10th	Day	20% 18% 27% 25% 8% 2	425
	11th to 20th	Day	24% 24% 24% 22% 5% 1	430
	21st to end	Day	27% 23% 29% 17% 4 1	278
December	1st to 10th	Day	25% 29% 29% 11% 5%	220
	11th to 20th	Day	38% 18% 27% 14% 3	220
	21st to end	Day	28% 24% 28% 17% 4	242
January	1st to 10th	Night	21% 21% 36% 20% 3	840
	11th to 20th	Night	24% 19% 30% 24% 3	825
	21st to end	Night	19% 20% 36% 22% 3	880
February	1st to 10th	Night	22% 19% 34% 24% 1	800
	11th to 20th	Night	24% 22% 36% 16% 1	783
	21st to end	Night	26% 18% 36% 16% 4	660
March	1st to 10th	Night	25% 20% 32% 20% 4	800
	11th to 20th	Night	23% 22% 29% 22% 4	800
	21st to end	Night	22% 20% 33% 20% 5%	880
April	1st to 10th	Night	26% 18% 32% 21% 4	800
	11th to 20th	Night	24% 16% 31% 24% 5%	791
	21st to end	Night	24% 16% 28% 24% 6% 1	770
May	1st to 10th	Night	27% 12% 27% 25% 8%	575
	11th to 20th	Night	22% 12% 29% 31% 7%	394
	21st to end	Night	17% 8% 22% 38% 14% 1	433
June	1st to 10th	Night	17% 7% 27% 36% 14% 1	400
	11th to 20th	Night	17% 6% 23% 38% 16% 1	400
	21st to end	Night	13% 4 23% 45% 15% 1	400
July	1st to 10th	Night	15% 4 18% 42% 21% 1	390
	11th to 20th	Night	11% 5% 19% 45% 19% 1	388
	21st to end	Night	12% 5% 20% 45% 17% 1	438
August	1st to 10th	Night	12% 2 20% 43% 22% 1	487
	11th to 20th	Night	14% 4 18% 38% 24% 2	772
	21st to end	Night	16% 6% 16% 36% 24% 1	880
September	1st to 10th	Night	17% 6% 21% 34% 20% 2	800
	11th to 20th	Night	16% 6% 20% 31% 23% 5%	800
	21st to end	Night	20% 7% 21% 33% 17% 2	800
October	1st to 10th	Night	23% 11% 22% 25% 17% 2	800
	11th to 20th	Night	21% 13% 25% 32% 10% 1	800
	21st to end	Night	26% 13% 30% 24% 7%	880
November	1st to 10th	Night	18% 13% 31% 29% 9%	820
	11th to 20th	Night	23% 20% 26% 23% 7% 1	840
	21st to end	Night	21% 18% 29% 25% 7%	840
December	1st to 10th	Night	25% 16% 31% 22% 5%	840
	11th to 20th	Night	25% 20% 26% 24% 4	840
	21st to end	Night	27% 16% 33% 22% 2	924

Page generated at 2026-01-14 01:14:30. Version ac07

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