Sassafras Ridge
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sassafras Ridge 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	12% 9% 3 9% 6% 5% 5% 4 6% 7% 33%	125493
	Night	12% 9% 4 8% 5% 4 5% 4 5% 7% 37%	122598
Transparency	Day	44% 8% 11% 18% 14% 5%	129243
	Night	42% 7% 12% 18% 15% 5%	126916
Seeing	Day	22% 14% 23% 20% 14% 7%	15834
	Night	20% 11% 19% 26% 20% 4	25854

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	15% 11% 5% 7% 3 3 5% 4 4 4 38%	4056
	11th to 20th	Day	10% 9% 5% 13% 4 3 3 3 3 4 43%	4060
	21st to end	Day	15% 14% 6% 7% 4 3 3 3 4 6% 35%	4489
February	1st to 10th	Day	17% 12% 4 8% 5% 4 5% 4 5% 5% 33%	2000
	11th to 20th	Day	19% 11% 4 10% 6% 4 3 3 4 5% 31%	1948
	21st to end	Day	19% 11% 2 9% 5% 4 3 3 5% 4 35%	1650
March	1st to 10th	Day	17% 9% 3 8% 5% 6% 4 3 5% 6% 34%	4632
	11th to 20th	Day	10% 9% 2 7% 5% 4 3 3 5% 6% 46%	4980
	21st to end	Day	14% 11% 3 7% 5% 4 4 3 4 5% 40%	5465
April	1st to 10th	Day	11% 10% 3 7% 5% 5% 5% 5% 7% 7% 37%	2260
	11th to 20th	Day	15% 8% 2 7% 4 4 4 4 5% 7% 41%	2379
	21st to end	Day	14% 9% 3 7% 5% 4 5% 3 6% 7% 38%	2600
May	1st to 10th	Day	16% 10% 3 9% 6% 6% 6% 4 7% 6% 27%	5862
	11th to 20th	Day	16% 11% 4 11% 8% 6% 6% 4 6% 6% 22%	5861
	21st to end	Day	12% 8% 4 9% 6% 6% 6% 5% 7% 9% 29%	6433
June	1st to 10th	Day	11% 8% 3 8% 6% 7% 6% 6% 8% 9% 30%	2600
	11th to 20th	Day	6% 6% 3 10% 7% 7% 7% 6% 8% 10% 31%	2600
	21st to end	Day	9% 8% 3 7% 7% 6% 6% 6% 8% 11% 30%	2600
July	1st to 10th	Day	6% 6% 3 9% 8% 7% 8% 6% 7% 10% 30%	5900
	11th to 20th	Day	8% 7% 3 11% 9% 9% 9% 7% 8% 8% 22%	5900
	21st to end	Day	11% 10% 5% 13% 10% 9% 8% 6% 8% 8% 14%	6424
August	1st to 10th	Day	8% 6% 3 9% 6% 7% 7% 6% 8% 11% 29%	4156
	11th to 20th	Day	8% 5% 3 8% 7% 6% 7% 6% 9% 11% 31%	3920
	21st to end	Day	8% 6% 3 8% 6% 7% 7% 5% 7% 7% 36%	4180
September	1st to 10th	Day	12% 8% 3 9% 6% 6% 6% 5% 7% 7% 32%	2100
	11th to 20th	Day	15% 8% 3 8% 5% 5% 6% 4 6% 8% 31%	2090
	21st to end	Day	15% 7% 2 7% 5% 4 5% 4 6% 6% 39%	2090
October	1st to 10th	Day	11% 6% 2 6% 4 5% 5% 4 5% 5% 47%	2090
	11th to 20th	Day	12% 7% 2 6% 3 3 4 2 5% 6% 50%	1952
	21st to end	Day	13% 7% 2 5% 4 4 4 3 4 6% 49%	2085
November	1st to 10th	Day	11% 7% 1 5% 4 3 4 4 4 6% 52%	1762
	11th to 20th	Day	12% 8% 3 6% 4 4 4 4 5% 6% 45%	1800
	21st to end	Day	12% 10% 3 7% 4 3 4 3 5% 6% 42%	1800
December	1st to 10th	Day	15% 8% 4 6% 3 5% 5% 3 4 4 43%	2930
	11th to 20th	Day	14% 11% 5% 12% 7% 5% 5% 3 4 4 31%	3373
	21st to end	Day	12% 10% 5% 9% 5% 4 5% 4 5% 7% 34%	4466
January	1st to 10th	Night	13% 14% 4 8% 5% 4 3 3 4 5% 38%	5889
	11th to 20th	Night	15% 11% 4 8% 4 4 4 3 4 5% 38%	5900
	21st to end	Night	14% 14% 4 8% 4 3 4 3 4 4 39%	6465
February	1st to 10th	Night	14% 11% 4 9% 6% 4 5% 3 4 5% 36%	2400
	11th to 20th	Night	18% 12% 5% 10% 5% 4 3 3 3 4 32%	2338
	21st to end	Night	18% 13% 3 9% 4 4 4 3 4 5% 32%	1980
March	1st to 10th	Night	16% 12% 4 8% 5% 6% 5% 3 4 5% 30%	5219
	11th to 20th	Night	11% 7% 3 6% 4 4 4 4 5% 7% 45%	4980
	21st to end	Night	11% 10% 4 9% 5% 4 4 3 4 5% 40%	5467
April	1st to 10th	Night	13% 10% 3 6% 5% 4 4 3 5% 6% 41%	2156
	11th to 20th	Night	12% 10% 3 6% 4 3 4 4 5% 6% 44%	1969
	21st to end	Night	13% 8% 3 6% 5% 3 4 4 5% 7% 42%	1800
May	1st to 10th	Night	12% 9% 4 10% 7% 6% 6% 5% 6% 7% 27%	4033
	11th to 20th	Night	18% 11% 4 10% 6% 5% 5% 4 5% 7% 25%	4032
	21st to end	Night	10% 10% 4 10% 6% 5% 5% 4 6% 9% 32%	4421
June	1st to 10th	Night	8% 7% 2 7% 6% 5% 6% 5% 8% 10% 35%	1800
	11th to 20th	Night	6% 5% 2 6% 5% 5% 6% 5% 9% 12% 40%	1800
	21st to end	Night	8% 6% 3 7% 5% 6% 6% 5% 6% 10% 39%	1800
July	1st to 10th	Night	7% 7% 3 9% 6% 5% 5% 5% 7% 10% 35%	4058
	11th to 20th	Night	7% 5% 3 8% 6% 5% 6% 5% 9% 11% 33%	4057
	21st to end	Night	9% 8% 3 11% 8% 7% 8% 6% 8% 11% 22%	4427
August	1st to 10th	Night	7% 6% 2 8% 6% 5% 6% 6% 8% 12% 36%	2861
	11th to 20th	Night	7% 6% 4 9% 6% 6% 5% 4 6% 8% 39%	2904
	21st to end	Night	6% 5% 2 6% 5% 4 5% 4 7% 9% 46%	3476
September	1st to 10th	Night	11% 7% 3 7% 6% 5% 5% 4 7% 7% 39%	2061
	11th to 20th	Night	11% 8% 3 8% 6% 5% 5% 4 6% 7% 38%	2090
	21st to end	Night	12% 7% 3 7% 4 5% 4 4 4 6% 45%	2090
October	1st to 10th	Night	11% 6% 2 5% 4 3 3 3 4 5% 53%	2090
	11th to 20th	Night	13% 8% 2 5% 4 3 3 3 4 5% 49%	2226
	21st to end	Night	11% 7% 3 6% 4 3 3 3 4 5% 50%	2511
November	1st to 10th	Night	10% 8% 2 6% 5% 4 4 3 5% 5% 48%	2536
	11th to 20th	Night	12% 10% 3 7% 4 3 4 3 5% 5% 46%	2600
	21st to end	Night	13% 10% 3 7% 4 4 4 4 4 6% 41%	2600
December	1st to 10th	Night	13% 11% 4 10% 5% 4 4 3 4 4 37%	4250
	11th to 20th	Night	14% 12% 5% 11% 6% 5% 4 3 4 5% 32%	4822
	21st to end	Night	12% 13% 6% 12% 5% 4 5% 4 5% 6% 30%	6490

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	45% 4 6% 14% 24% 7%	4057
	11th to 20th	Day	43% 4 6% 12% 25% 11%	4060
	21st to end	Day	49% 4 6% 16% 17% 9%	4489
February	1st to 10th	Day	51% 5% 7% 18% 16% 4	2000
	11th to 20th	Day	53% 6% 5% 15% 16% 5%	1958
	21st to end	Day	52% 4 6% 12% 19% 6%	1650
March	1st to 10th	Day	48% 6% 6% 13% 19% 8%	4632
	11th to 20th	Day	36% 4 7% 17% 20% 16%	4980
	21st to end	Day	45% 5% 7% 27% 11% 5%	5465
April	1st to 10th	Day	42% 7% 11% 21% 17% 2	2260
	11th to 20th	Day	41% 6% 9% 19% 21% 4	2379
	21st to end	Day	43% 7% 10% 25% 13% 2	2600
May	1st to 10th	Day	51% 10% 12% 19% 8% 1	5897
	11th to 20th	Day	57% 10% 11% 17% 5%	5865
	21st to end	Day	45% 9% 11% 20% 13% 2	6447
June	1st to 10th	Day	45% 11% 14% 21% 7% 1	2600
	11th to 20th	Day	42% 12% 16% 19% 10% 1	2600
	21st to end	Day	42% 12% 16% 17% 11% 2	2600
July	1st to 10th	Day	41% 15% 16% 19% 8%	5835
	11th to 20th	Day	48% 17% 19% 11% 4 1	5831
	21st to end	Day	58% 14% 14% 10% 3	6240
August	1st to 10th	Day	42% 11% 18% 23% 6%	4143
	11th to 20th	Day	38% 12% 22% 15% 11% 2	3959
	21st to end	Day	40% 11% 12% 27% 9% 1	4179
September	1st to 10th	Day	46% 9% 11% 15% 16% 3	2100
	11th to 20th	Day	48% 8% 9% 18% 17% 1	2090
	21st to end	Day	42% 7% 12% 17% 17% 5%	2090
October	1st to 10th	Day	27% 6% 8% 17% 29% 13%	3480
	11th to 20th	Day	24% 3 5% 19% 25% 24%	3218
	21st to end	Day	28% 5% 5% 26% 22% 13%	3411
November	1st to 10th	Day	34% 4 8% 18% 27% 10%	1762
	11th to 20th	Day	37% 5% 5% 20% 25% 9%	1800
	21st to end	Day	40% 5% 8% 18% 25% 5%	1800
December	1st to 10th	Day	42% 5% 5% 16% 25% 8%	2930
	11th to 20th	Day	53% 5% 7% 14% 17% 5%	3370
	21st to end	Day	47% 4 12% 23% 12% 2	4466
January	1st to 10th	Night	45% 4 9% 13% 22% 8%	5889
	11th to 20th	Night	47% 3 5% 12% 23% 10%	5900
	21st to end	Night	46% 3 6% 13% 21% 10%	6465
February	1st to 10th	Night	49% 4 9% 16% 19% 4	2400
	11th to 20th	Night	54% 5% 6% 16% 15% 4	2339
	21st to end	Night	53% 4 7% 14% 16% 5%	1980
March	1st to 10th	Night	50% 8% 7% 12% 17% 6%	5219
	11th to 20th	Night	33% 6% 8% 20% 17% 15%	4980
	21st to end	Night	44% 5% 10% 23% 14% 4	5467
April	1st to 10th	Night	39% 7% 13% 21% 18% 3	2156
	11th to 20th	Night	38% 5% 11% 21% 21% 4	1969
	21st to end	Night	39% 7% 12% 28% 13% 1	1800
May	1st to 10th	Night	48% 11% 14% 20% 7% 1	4060
	11th to 20th	Night	55% 10% 15% 15% 6%	4033
	21st to end	Night	42% 11% 16% 22% 9% 1	4429
June	1st to 10th	Night	41% 11% 17% 22% 9% 1	1800
	11th to 20th	Night	32% 11% 21% 26% 8% 1	1800
	21st to end	Night	37% 10% 18% 21% 10% 3	1800
July	1st to 10th	Night	39% 11% 22% 22% 5%	4015
	11th to 20th	Night	37% 15% 28% 16% 3 1	4006
	21st to end	Night	48% 15% 20% 13% 4	4297
August	1st to 10th	Night	35% 12% 22% 25% 6%	2850
	11th to 20th	Night	33% 11% 26% 19% 10% 1	2931
	21st to end	Night	29% 11% 19% 32% 7% 1	3476
September	1st to 10th	Night	40% 10% 15% 17% 15% 4	2061
	11th to 20th	Night	42% 10% 12% 19% 16%	2090
	21st to end	Night	39% 7% 11% 21% 19% 4	2090
October	1st to 10th	Night	21% 5% 12% 24% 25% 13%	3480
	11th to 20th	Night	24% 4 7% 19% 26% 20%	3699
	21st to end	Night	29% 5% 5% 24% 24% 13%	4135
November	1st to 10th	Night	36% 5% 7% 20% 24% 9%	2536
	11th to 20th	Night	38% 5% 5% 18% 24% 9%	2600
	21st to end	Night	42% 4 6% 21% 21% 6%	2600
December	1st to 10th	Night	45% 5% 5% 15% 20% 9%	4250
	11th to 20th	Night	51% 6% 7% 15% 17% 5%	4824
	21st to end	Night	51% 5% 12% 17% 13% 1	6490

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	37% 25% 28% 8% 2	300
	11th to 20th	Day	36% 29% 19% 12% 4	300
	21st to end	Day	32% 32% 27% 7% 2	330
February	1st to 10th	Day	33% 23% 33% 10% 1	300
	11th to 20th	Day	51% 19% 26% 4 1	300
	21st to end	Day	44% 26% 23% 6% 1	249
March	1st to 10th	Day	35% 19% 29% 12% 4	361
	11th to 20th	Day	28% 26% 24% 16% 5% 1	500
	21st to end	Day	31% 23% 27% 15% 4 1	550
April	1st to 10th	Day	28% 18% 26% 18% 8% 1	500
	11th to 20th	Day	23% 22% 26% 17% 10% 3	492
	21st to end	Day	24% 16% 27% 19% 11% 3	500
May	1st to 10th	Day	24% 18% 29% 16% 9% 5%	503
	11th to 20th	Day	19% 12% 28% 21% 13% 7%	527
	21st to end	Day	19% 11% 20% 26% 13% 10%	573
June	1st to 10th	Day	17% 9% 21% 26% 17% 9%	530
	11th to 20th	Day	10% 7% 21% 27% 21% 15%	530
	21st to end	Day	12% 6% 24% 28% 17% 13%	530
July	1st to 10th	Day	12% 5% 16% 27% 24% 16%	525
	11th to 20th	Day	12% 4 16% 25% 25% 18%	524
	21st to end	Day	12% 4 15% 23% 26% 20%	576
August	1st to 10th	Day	18% 6% 17% 20% 22% 18%	502
	11th to 20th	Day	16% 4 16% 28% 24% 12%	479
	21st to end	Day	17% 3 11% 22% 27% 20%	539
September	1st to 10th	Day	11% 5% 14% 28% 29% 13%	490
	11th to 20th	Day	18% 6% 14% 24% 26% 12%	490
	21st to end	Day	20% 8% 15% 27% 23% 7%	490
October	1st to 10th	Day	17% 7% 22% 28% 19% 8%	490
	11th to 20th	Day	19% 12% 25% 23% 19% 3	490
	21st to end	Day	21% 11% 26% 24% 14% 3	534
November	1st to 10th	Day	20% 16% 32% 24% 8% 1	300
	11th to 20th	Day	26% 18% 30% 21% 5%	300
	21st to end	Day	21% 27% 33% 12% 7% 1	300
December	1st to 10th	Day	34% 21% 29% 13% 3	300
	11th to 20th	Day	28% 19% 32% 17% 3 1	300
	21st to end	Day	34% 18% 34% 11% 3	330
January	1st to 10th	Night	29% 18% 26% 23% 5%	800
	11th to 20th	Night	30% 20% 25% 20% 5%	800
	21st to end	Night	23% 20% 31% 24% 2	880
February	1st to 10th	Night	23% 17% 28% 27% 5%	800
	11th to 20th	Night	31% 19% 29% 19% 2	783
	21st to end	Night	32% 20% 29% 16% 3	660
March	1st to 10th	Night	22% 20% 30% 24% 5%	800
	11th to 20th	Night	23% 18% 27% 22% 8% 1	800
	21st to end	Night	24% 17% 29% 23% 7%	880
April	1st to 10th	Night	21% 19% 26% 24% 9% 1	756
	11th to 20th	Night	21% 15% 23% 27% 12% 2	593
	21st to end	Night	16% 12% 24% 32% 15% 1	600
May	1st to 10th	Night	16% 11% 24% 29% 19% 2	600
	11th to 20th	Night	18% 8% 18% 31% 23% 3	591
	21st to end	Night	15% 6% 13% 31% 29% 7%	650
June	1st to 10th	Night	14% 3 13% 32% 33% 6%	600
	11th to 20th	Night	8% 4 10% 31% 36% 11%	600
	21st to end	Night	11% 3 9% 30% 39% 8%	600
July	1st to 10th	Night	13% 3 5% 24% 45% 11%	585
	11th to 20th	Night	10% 3 4 24% 44% 15%	582
	21st to end	Night	10% 3 5% 24% 45% 14%	657
August	1st to 10th	Night	12% 4 6% 24% 44% 11%	579
	11th to 20th	Night	13% 4 7% 29% 38% 10%	564
	21st to end	Night	14% 2 7% 19% 45% 13%	627
September	1st to 10th	Night	13% 3 10% 25% 38% 10%	731
	11th to 20th	Night	16% 4 9% 28% 36% 6%	760
	21st to end	Night	16% 5% 13% 27% 35% 4	760
October	1st to 10th	Night	15% 7% 15% 27% 29% 8%	760
	11th to 20th	Night	17% 9% 22% 28% 21% 3	760
	21st to end	Night	17% 12% 20% 33% 16% 3	836
November	1st to 10th	Night	18% 9% 19% 31% 20% 4	780
	11th to 20th	Night	20% 14% 22% 31% 12% 2	800
	21st to end	Night	22% 14% 22% 27% 13% 1	800
December	1st to 10th	Night	27% 16% 23% 26% 7%	800
	11th to 20th	Night	25% 14% 24% 29% 7% 1	800
	21st to end	Night	28% 13% 24% 29% 6%	880

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

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