Solon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Solon clear sky chart from 2005-11-06 to 2025-02-21.

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% 12% 4 10% 5% 4 4 3 5% 6% 29%	108622
	Night	16% 14% 5% 10% 5% 4 4 3 5% 6% 28%	109964
Transparency	Day	54% 4 11% 19% 10% 1	112298
	Night	56% 4 10% 18% 10% 1	114414
Seeing	Day	25% 14% 29% 19% 9% 3	14876
	Night	24% 14% 27% 24% 10% 1	24801

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	13% 21% 9% 28% 4 3 2 2 3 3 11%	4056
	11th to 20th	Day	12% 23% 8% 21% 9% 7% 4 2 3 3 10%	4060
	21st to end	Day	21% 19% 10% 15% 7% 5% 3 2 3 3 11%	4466
February	1st to 10th	Day	16% 22% 6% 12% 8% 4 3 2 4 4 18%	1800
	11th to 20th	Day	15% 16% 6% 15% 9% 5% 4 3 4 4 18%	1798
	21st to end	Day	17% 17% 4 14% 5% 5% 4 3 5% 4 21%	1570
March	1st to 10th	Day	22% 12% 7% 9% 4 3 4 3 5% 6% 25%	3365
	11th to 20th	Day	13% 15% 6% 10% 6% 4 3 3 4 5% 31%	3480
	21st to end	Day	22% 13% 5% 10% 4 4 4 3 4 5% 27%	3815
April	1st to 10th	Day	16% 14% 4 7% 4 4 4 3 6% 6% 30%	2135
	11th to 20th	Day	19% 13% 3 6% 5% 3 5% 4 4 6% 32%	2404
	21st to end	Day	20% 13% 3 8% 3 4 3 4 4 5% 33%	2470
May	1st to 10th	Day	21% 9% 3 8% 5% 5% 4 4 5% 6% 30%	4082
	11th to 20th	Day	20% 9% 2 7% 5% 4 4 4 5% 8% 33%	4081
	21st to end	Day	13% 6% 2 7% 5% 4 5% 4 6% 8% 39%	4589
June	1st to 10th	Day	16% 7% 2 6% 5% 5% 5% 5% 6% 8% 36%	2660
	11th to 20th	Day	14% 7% 2 7% 5% 4 5% 4 7% 8% 38%	2660
	21st to end	Day	13% 6% 2 6% 5% 4 5% 4 7% 9% 39%	2660
July	1st to 10th	Day	10% 6% 3 7% 5% 5% 6% 4 7% 10% 38%	4155
	11th to 20th	Day	10% 5% 2 6% 4 4 5% 4 7% 10% 42%	4120
	21st to end	Day	10% 6% 3 7% 5% 6% 6% 4 6% 8% 38%	4466
August	1st to 10th	Day	13% 8% 3 7% 5% 5% 5% 5% 7% 9% 34%	4104
	11th to 20th	Day	13% 6% 3 7% 5% 5% 6% 5% 7% 8% 34%	4044
	21st to end	Day	10% 5% 2 6% 5% 5% 6% 4 7% 10% 39%	4446
September	1st to 10th	Day	15% 6% 2 6% 4 4 4 4 6% 8% 41%	2192
	11th to 20th	Day	11% 6% 2 7% 5% 4 4 3 6% 9% 42%	2090
	21st to end	Day	21% 8% 3 6% 4 4 4 3 5% 6% 36%	2090
October	1st to 10th	Day	16% 7% 2 7% 5% 4 5% 3 5% 8% 38%	1956
	11th to 20th	Day	22% 11% 3 8% 3 5% 4 3 5% 6% 32%	1900
	21st to end	Day	24% 12% 3 7% 5% 4 4 3 5% 5% 27%	2090
November	1st to 10th	Day	14% 12% 4 8% 5% 3 4 4 5% 7% 35%	1762
	11th to 20th	Day	19% 19% 4 8% 4 3 4 4 4 6% 25%	1750
	21st to end	Day	19% 21% 6% 10% 5% 4 4 3 5% 5% 17%	1600
December	1st to 10th	Day	17% 19% 10% 16% 6% 3 4 3 4 4 14%	2600
	11th to 20th	Day	24% 22% 8% 11% 5% 3 3 3 4 5% 12%	2990
	21st to end	Day	25% 26% 7% 13% 5% 4 4 3 3 3 8%	4116
January	1st to 10th	Night	14% 21% 10% 27% 5% 3 3 2 3 4 10%	5889
	11th to 20th	Night	12% 21% 11% 20% 9% 5% 5% 3 3 3 9%	5900
	21st to end	Night	21% 20% 8% 15% 6% 3 4 3 3 3 14%	6490
February	1st to 10th	Night	20% 18% 6% 14% 7% 4 3 3 4 4 18%	2600
	11th to 20th	Night	17% 16% 6% 14% 7% 6% 4 3 4 4 19%	2487
	21st to end	Night	20% 14% 5% 13% 7% 4 4 3 4 4 23%	1885
March	1st to 10th	Night	22% 15% 4 7% 4 3 3 3 3 4 32%	3487
	11th to 20th	Night	16% 13% 6% 8% 4 4 4 4 4 5% 32%	3480
	21st to end	Night	19% 13% 5% 9% 4 3 3 3 4 5% 32%	3817
April	1st to 10th	Night	17% 15% 4 7% 5% 4 5% 4 5% 6% 30%	2044
	11th to 20th	Night	16% 11% 2 7% 5% 5% 5% 3 6% 6% 33%	1740
	21st to end	Night	15% 12% 4 6% 5% 4 5% 4 6% 6% 35%	1710
May	1st to 10th	Night	25% 10% 3 6% 4 4 4 3 5% 6% 29%	2813
	11th to 20th	Night	17% 10% 3 6% 4 4 4 3 7% 8% 36%	2812
	21st to end	Night	13% 5% 1 4 3 4 4 4 7% 11% 44%	2962
June	1st to 10th	Night	11% 7% 2 6% 4 5% 6% 5% 6% 6% 41%	1520
	11th to 20th	Night	10% 5% 2 7% 5% 5% 5% 4 6% 9% 41%	1520
	21st to end	Night	11% 5% 2 6% 5% 4 4 4 8% 11% 39%	1520
July	1st to 10th	Night	10% 7% 2 6% 5% 4 3 3 5% 9% 46%	2799
	11th to 20th	Night	10% 5% 2 5% 4 3 4 4 6% 8% 48%	2840
	21st to end	Night	9% 6% 3 6% 5% 5% 5% 4 6% 8% 45%	3087
August	1st to 10th	Night	10% 8% 3 7% 5% 5% 5% 4 6% 8% 39%	2825
	11th to 20th	Night	17% 8% 2 6% 4 4 3 3 4 7% 42%	2785
	21st to end	Night	8% 5% 3 7% 5% 5% 6% 4 6% 8% 43%	3178
September	1st to 10th	Night	13% 6% 2 5% 4 5% 4 4 5% 7% 45%	1985
	11th to 20th	Night	10% 5% 2 5% 4 4 4 3 5% 7% 51%	2090
	21st to end	Night	16% 9% 2 8% 5% 5% 4 3 5% 6% 38%	2090
October	1st to 10th	Night	14% 7% 2 6% 4 4 4 4 5% 7% 43%	2223
	11th to 20th	Night	21% 8% 2 8% 4 4 4 3 5% 6% 33%	2280
	21st to end	Night	25% 10% 3 6% 4 4 4 3 5% 6% 29%	2508
November	1st to 10th	Night	15% 11% 3 7% 5% 4 4 3 6% 6% 37%	2531
	11th to 20th	Night	18% 19% 5% 8% 5% 5% 3 3 5% 6% 25%	2647
	21st to end	Night	21% 19% 5% 8% 5% 5% 3 4 5% 5% 20%	2800
December	1st to 10th	Night	16% 19% 9% 14% 6% 5% 4 3 5% 4 15%	4580
	11th to 20th	Night	20% 22% 10% 11% 5% 3 3 3 3 4 16%	5205
	21st to end	Night	23% 24% 7% 11% 5% 4 4 3 4 4 11%	6835

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	81% 2 8% 7% 3	4057
	11th to 20th	Day	81% 3 7% 6% 3	4060
	21st to end	Day	81% 2 5% 8% 3	4466
February	1st to 10th	Day	71% 3 7% 13% 6%	1800
	11th to 20th	Day	70% 3 7% 14% 5%	1807
	21st to end	Day	66% 4 10% 13% 7% 2	1570
March	1st to 10th	Day	61% 3 10% 21% 4	3365
	11th to 20th	Day	56% 5% 14% 19% 6% 1	3480
	21st to end	Day	60% 4 8% 17% 11% 1	3815
April	1st to 10th	Day	54% 4 11% 17% 13% 1	2135
	11th to 20th	Day	53% 4 10% 18% 13% 2	2404
	21st to end	Day	54% 3 10% 20% 10% 2	2470
May	1st to 10th	Day	54% 4 9% 23% 9% 1	4120
	11th to 20th	Day	50% 4 12% 23% 10% 1	4085
	21st to end	Day	42% 4 13% 20% 16% 5%	4603
June	1st to 10th	Day	45% 5% 10% 26% 13% 1	2660
	11th to 20th	Day	42% 5% 15% 22% 15% 1	2660
	21st to end	Day	40% 4 13% 25% 16% 2	2660
July	1st to 10th	Day	41% 4 12% 24% 16% 3	4090
	11th to 20th	Day	36% 5% 13% 27% 18% 1	4051
	21st to end	Day	41% 6% 13% 19% 19% 2	4324
August	1st to 10th	Day	44% 5% 14% 24% 11%	4091
	11th to 20th	Day	43% 6% 11% 29% 10% 1	4083
	21st to end	Day	38% 6% 14% 29% 11% 2	4446
September	1st to 10th	Day	41% 5% 13% 22% 16% 3	2192
	11th to 20th	Day	39% 4 14% 24% 17% 2	2090
	21st to end	Day	49% 4 9% 23% 14% 1	2090
October	1st to 10th	Day	35% 5% 13% 27% 19% 1	3242
	11th to 20th	Day	48% 5% 10% 19% 16% 3	3140
	21st to end	Day	45% 4 13% 24% 15% 1	3428
November	1st to 10th	Day	48% 5% 10% 22% 14% 1	1762
	11th to 20th	Day	60% 4 9% 17% 8% 3	1750
	21st to end	Day	70% 4 8% 12% 6%	1600
December	1st to 10th	Day	75% 4 11% 9% 2	2600
	11th to 20th	Day	76% 3 7% 11% 2	2986
	21st to end	Day	83% 3 7% 7% 1	4116
January	1st to 10th	Night	81% 3 5% 8% 3	5889
	11th to 20th	Night	83% 2 6% 6% 2	5900
	21st to end	Night	76% 2 8% 9% 4	6490
February	1st to 10th	Night	70% 3 8% 13% 6%	2600
	11th to 20th	Night	68% 4 7% 15% 5%	2489
	21st to end	Night	66% 4 8% 14% 7% 1	1885
March	1st to 10th	Night	56% 3 11% 21% 8%	3487
	11th to 20th	Night	52% 7% 16% 15% 9% 1	3480
	21st to end	Night	53% 7% 7% 21% 10% 1	3817
April	1st to 10th	Night	54% 4 10% 17% 12% 2	2044
	11th to 20th	Night	51% 4 12% 17% 15% 2	1740
	21st to end	Night	48% 5% 11% 20% 14% 3	1710
May	1st to 10th	Night	56% 3 10% 20% 10% 2	2840
	11th to 20th	Night	45% 5% 12% 23% 12% 2	2813
	21st to end	Night	33% 5% 16% 26% 18% 3	2969
June	1st to 10th	Night	42% 5% 10% 26% 15% 3	1520
	11th to 20th	Night	39% 4 15% 21% 19% 2	1520
	21st to end	Night	37% 7% 12% 26% 17% 2	1520
July	1st to 10th	Night	37% 4 11% 25% 18% 5%	2754
	11th to 20th	Night	33% 4 12% 29% 19% 2	2786
	21st to end	Night	37% 5% 13% 19% 24% 2	2988
August	1st to 10th	Night	42% 6% 12% 25% 13% 1	2814
	11th to 20th	Night	43% 5% 10% 29% 12% 1	2812
	21st to end	Night	37% 6% 11% 29% 15% 2	3178
September	1st to 10th	Night	38% 5% 11% 26% 17% 3	1985
	11th to 20th	Night	32% 5% 13% 28% 21% 2	2090
	21st to end	Night	47% 4 10% 21% 18% 1	2090
October	1st to 10th	Night	34% 4 10% 29% 22% 1	3704
	11th to 20th	Night	46% 5% 10% 20% 17% 2	3779
	21st to end	Night	43% 4 12% 25% 15% 1	4120
November	1st to 10th	Night	47% 4 11% 22% 13% 3	2531
	11th to 20th	Night	61% 3 9% 16% 8% 3	2647
	21st to end	Night	67% 4 10% 15% 5%	2800
December	1st to 10th	Night	72% 4 11% 10% 3	4580
	11th to 20th	Night	73% 3 8% 13% 2	5208
	21st to end	Night	77% 4 9% 9% 1	6835

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	34% 26% 28% 9% 2	300
	11th to 20th	Day	37% 28% 27% 6% 1 1	300
	21st to end	Day	34% 29% 28% 6% 2	330
February	1st to 10th	Day	37% 23% 33% 6% 1	300
	11th to 20th	Day	38% 28% 28% 6%	300
	21st to end	Day	43% 27% 25% 4	225
March	1st to 10th	Day	33% 20% 31% 13% 3	412
	11th to 20th	Day	33% 19% 33% 12% 3 1	460
	21st to end	Day	37% 20% 26% 13% 3	506
April	1st to 10th	Day	28% 22% 30% 15% 5%	460
	11th to 20th	Day	34% 17% 27% 13% 7% 2	452
	21st to end	Day	33% 15% 33% 14% 4 1	460
May	1st to 10th	Day	29% 16% 31% 18% 4 2	463
	11th to 20th	Day	26% 9% 32% 23% 7% 3	487
	21st to end	Day	17% 8% 32% 26% 13% 4	529
June	1st to 10th	Day	20% 10% 36% 22% 10% 3	490
	11th to 20th	Day	18% 10% 29% 28% 12% 3	490
	21st to end	Day	17% 11% 33% 23% 11% 4	490
July	1st to 10th	Day	14% 7% 25% 30% 18% 8%	485
	11th to 20th	Day	15% 6% 28% 28% 17% 6%	484
	21st to end	Day	12% 8% 28% 29% 16% 7%	532
August	1st to 10th	Day	14% 6% 26% 29% 19% 6%	486
	11th to 20th	Day	17% 7% 26% 28% 15% 8%	479
	21st to end	Day	13% 5% 27% 28% 18% 8%	539
September	1st to 10th	Day	19% 7% 24% 26% 18% 6%	490
	11th to 20th	Day	12% 4 22% 32% 22% 9%	490
	21st to end	Day	25% 10% 28% 22% 11% 4	490
October	1st to 10th	Day	17% 12% 29% 23% 17% 3	490
	11th to 20th	Day	27% 18% 31% 16% 7% 2	490
	21st to end	Day	35% 16% 30% 15% 3	539
November	1st to 10th	Day	25% 21% 32% 15% 6% 1	300
	11th to 20th	Day	38% 18% 27% 12% 4 1	275
	21st to end	Day	36% 20% 38% 6% 1	200
December	1st to 10th	Day	33% 22% 30% 12% 3 2	200
	11th to 20th	Day	35% 27% 29% 9% 2	200
	21st to end	Day	39% 24% 29% 8%	253
January	1st to 10th	Night	30% 24% 31% 12% 3	800
	11th to 20th	Night	34% 24% 28% 12% 2	800
	21st to end	Night	30% 22% 30% 15% 2	880
February	1st to 10th	Night	32% 23% 28% 16% 2	800
	11th to 20th	Night	29% 23% 29% 17% 1	783
	21st to end	Night	31% 23% 31% 14% 1	629
March	1st to 10th	Night	26% 22% 29% 19% 4	760
	11th to 20th	Night	26% 19% 30% 18% 6% 1	760
	21st to end	Night	28% 16% 31% 20% 6% 1	836
April	1st to 10th	Night	27% 16% 30% 21% 6%	760
	11th to 20th	Night	23% 16% 34% 18% 8% 1	616
	21st to end	Night	23% 12% 34% 25% 6%	570
May	1st to 10th	Night	24% 10% 29% 28% 8% 1	570
	11th to 20th	Night	21% 7% 28% 33% 9% 2	561
	21st to end	Night	13% 3 29% 36% 18% 1	551
June	1st to 10th	Night	12% 6% 31% 39% 12% 1	380
	11th to 20th	Night	13% 5% 29% 39% 14% 1	380
	21st to end	Night	12% 6% 28% 37% 16%	380
July	1st to 10th	Night	11% 2 17% 40% 27% 4	527
	11th to 20th	Night	11% 3 22% 37% 23% 5%	552
	21st to end	Night	12% 2 18% 42% 24% 2	624
August	1st to 10th	Night	10% 3 17% 42% 25% 3	567
	11th to 20th	Night	15% 3 14% 37% 27% 3	564
	21st to end	Night	11% 3 21% 33% 28% 4	655
September	1st to 10th	Night	17% 6% 17% 34% 24% 3	760
	11th to 20th	Night	13% 2 19% 34% 27% 4	760
	21st to end	Night	20% 8% 26% 28% 15% 4	760
October	1st to 10th	Night	18% 9% 28% 26% 16% 3	760
	11th to 20th	Night	27% 13% 28% 24% 8% 1	760
	21st to end	Night	33% 13% 31% 19% 5%	836
November	1st to 10th	Night	23% 15% 29% 24% 9% 1	780
	11th to 20th	Night	30% 20% 28% 15% 6% 1	800
	21st to end	Night	35% 18% 30% 13% 5%	800
December	1st to 10th	Night	34% 21% 29% 12% 4	800
	11th to 20th	Night	31% 25% 28% 14% 3	800
	21st to end	Night	35% 19% 31% 14% 1	880

Page generated at 2025-02-18 03:26:32. Version ac07

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