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 2026-06-16.

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%	137198
	Night	16% 13% 5% 10% 5% 4 4 3 5% 6% 29%	134810
Transparency	Day	54% 4 10% 19% 11% 1	140830
	Night	56% 4 10% 18% 11% 1	139237
Seeing	Day	26% 15% 29% 19% 9% 3	16623
	Night	24% 14% 27% 23% 10% 1	26466

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% 21% 8% 27% 5% 3 3 2 3 3 9%	5258
	11th to 20th	Day	10% 21% 9% 21% 11% 7% 4 2 3 3 9%	5280
	21st to end	Day	18% 17% 9% 15% 10% 8% 4 2 3 3 12%	5780
February	1st to 10th	Day	16% 21% 6% 12% 8% 5% 3 3 4 4 19%	1890
	11th to 20th	Day	15% 16% 7% 16% 9% 5% 4 3 4 4 18%	1890
	21st to end	Day	16% 16% 5% 14% 5% 5% 5% 3 5% 4 21%	1730
March	1st to 10th	Day	18% 12% 7% 12% 5% 4 3 3 5% 6% 26%	4945
	11th to 20th	Day	12% 13% 6% 11% 5% 5% 4 3 4 5% 34%	5090
	21st to end	Day	21% 14% 5% 10% 4 4 4 3 4 5% 26%	5586
April	1st to 10th	Day	18% 14% 5% 8% 4 4 4 2 6% 6% 29%	2360
	11th to 20th	Day	19% 13% 3 6% 5% 3 5% 4 4 6% 32%	2660
	21st to end	Day	20% 13% 3 8% 3 4 3 4 4 5% 34%	2730
May	1st to 10th	Day	21% 10% 3 8% 5% 5% 4 4 5% 5% 29%	7616
	11th to 20th	Day	18% 10% 3 7% 5% 4 4 4 5% 8% 33%	7626
	21st to end	Day	18% 8% 2 7% 4 4 5% 4 5% 6% 37%	8588
June	1st to 10th	Day	15% 6% 2 6% 5% 5% 5% 4 5% 8% 37%	2940
	11th to 20th	Day	14% 7% 2 7% 5% 4 5% 4 6% 8% 37%	2870
	21st to end	Day	12% 6% 2 5% 5% 4 5% 4 7% 10% 40%	2800
July	1st to 10th	Day	10% 6% 3 7% 4 4 6% 4 7% 9% 42%	5949
	11th to 20th	Day	11% 6% 2 7% 5% 5% 6% 4 7% 10% 38%	5900
	21st to end	Day	12% 6% 3 7% 4 5% 5% 4 6% 9% 41%	6424
August	1st to 10th	Day	13% 8% 3 7% 5% 5% 5% 5% 7% 9% 34%	4234
	11th to 20th	Day	13% 6% 3 7% 5% 5% 6% 5% 7% 9% 34%	4174
	21st to end	Day	10% 5% 2 6% 5% 5% 6% 4 7% 10% 39%	4586
September	1st to 10th	Day	15% 6% 2 6% 4 4 4 4 6% 7% 42%	2307
	11th to 20th	Day	10% 6% 2 7% 5% 4 4 3 6% 9% 44%	2200
	21st to end	Day	20% 8% 3 6% 4 4 4 3 5% 6% 36%	2200
October	1st to 10th	Day	16% 7% 2 6% 4 4 5% 3 5% 8% 40%	2059
	11th to 20th	Day	21% 10% 3 7% 3 5% 4 3 5% 6% 33%	2000
	21st to end	Day	24% 12% 3 7% 5% 4 4 3 5% 5% 27%	2200
November	1st to 10th	Day	14% 12% 4 8% 5% 3 4 4 5% 7% 35%	1852
	11th to 20th	Day	19% 19% 4 8% 4 3 4 4 4 6% 25%	1837
	21st to end	Day	19% 21% 7% 9% 5% 4 4 3 5% 6% 16%	1680
December	1st to 10th	Day	17% 19% 10% 16% 6% 3 4 3 4 4 14%	2680
	11th to 20th	Day	23% 22% 8% 11% 5% 3 3 3 4 5% 12%	3070
	21st to end	Day	25% 26% 7% 13% 5% 4 4 3 3 3 8%	4207
January	1st to 10th	Night	15% 21% 9% 27% 5% 3 3 2 3 3 9%	7635
	11th to 20th	Night	11% 19% 10% 20% 9% 6% 5% 3 3 3 10%	7680
	21st to end	Night	17% 18% 7% 13% 7% 5% 5% 3 4 4 16%	8401
February	1st to 10th	Night	19% 17% 5% 14% 7% 4 4 3 4 5% 19%	2730
	11th to 20th	Night	16% 15% 6% 14% 7% 6% 4 3 4 4 19%	2614
	21st to end	Night	19% 15% 5% 13% 6% 4 4 3 4 4 23%	2076
March	1st to 10th	Night	21% 15% 5% 9% 4 3 3 3 4 4 31%	5127
	11th to 20th	Night	13% 11% 6% 8% 4 4 4 3 5% 6% 36%	5090
	21st to end	Night	19% 13% 5% 9% 5% 4 4 3 4 5% 31%	5588
April	1st to 10th	Night	19% 15% 4 7% 5% 4 5% 3 5% 6% 28%	2259
	11th to 20th	Night	15% 11% 3 7% 5% 5% 5% 4 6% 6% 32%	1926
	21st to end	Night	14% 12% 3 6% 5% 4 5% 4 5% 6% 36%	1890
May	1st to 10th	Night	25% 10% 3 7% 4 5% 5% 3 5% 5% 28%	5237
	11th to 20th	Night	17% 10% 3 6% 4 4 4 3 6% 7% 37%	5234
	21st to end	Night	21% 7% 2 5% 3 4 4 3 5% 8% 37%	5546
June	1st to 10th	Night	10% 7% 3 6% 4 5% 6% 5% 6% 6% 42%	1680
	11th to 20th	Night	10% 5% 2 7% 5% 5% 5% 4 6% 9% 40%	1640
	21st to end	Night	11% 5% 2 7% 4 5% 4 4 8% 11% 40%	1600
July	1st to 10th	Night	9% 6% 2 6% 5% 4 4 4 6% 9% 45%	4003
	11th to 20th	Night	11% 6% 2 6% 4 4 4 4 6% 8% 43%	4057
	21st to end	Night	9% 6% 2 6% 5% 4 4 3 5% 8% 48%	4427
August	1st to 10th	Night	10% 8% 3 7% 5% 5% 5% 4 6% 8% 40%	2915
	11th to 20th	Night	16% 8% 2 6% 4 4 3 3 4 7% 43%	2875
	21st to end	Night	8% 5% 3 8% 5% 5% 6% 4 6% 8% 43%	3279
September	1st to 10th	Night	12% 6% 1 5% 4 5% 4 4 5% 7% 46%	2090
	11th to 20th	Night	9% 5% 1 5% 4 4 4 3 5% 7% 53%	2200
	21st to end	Night	17% 9% 2 8% 5% 5% 4 4 5% 6% 38%	2200
October	1st to 10th	Night	14% 6% 2 6% 4 4 3 4 5% 7% 45%	2340
	11th to 20th	Night	20% 8% 2 8% 4 5% 4 3 5% 6% 34%	2400
	21st to end	Night	25% 10% 3 6% 4 4 4 3 5% 6% 30%	2640
November	1st to 10th	Night	15% 11% 3 7% 5% 4 4 3 6% 6% 37%	2661
	11th to 20th	Night	17% 18% 5% 8% 5% 5% 3 3 5% 6% 25%	2780
	21st to end	Night	21% 19% 5% 8% 5% 5% 3 3 4 5% 20%	2940
December	1st to 10th	Night	15% 19% 9% 14% 6% 5% 4 3 5% 4 15%	4720
	11th to 20th	Night	20% 22% 10% 11% 5% 3 3 3 3 4 16%	5345
	21st to end	Night	23% 23% 7% 12% 5% 4 4 3 3 4 11%	6985

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% 2 8% 5% 2	5259
	11th to 20th	Day	82% 3 6% 6% 3	5280
	21st to end	Day	80% 2 5% 10% 3	5780
February	1st to 10th	Day	70% 3 7% 14% 6%	1890
	11th to 20th	Day	70% 4 7% 13% 5%	1899
	21st to end	Day	65% 4 11% 13% 6% 1	1730
March	1st to 10th	Day	60% 3 12% 19% 6%	4945
	11th to 20th	Day	53% 4 14% 21% 6% 1	5090
	21st to end	Day	61% 4 7% 17% 11% 1	5586
April	1st to 10th	Day	56% 3 11% 17% 12% 1	2360
	11th to 20th	Day	53% 4 10% 18% 12% 2	2660
	21st to end	Day	53% 4 10% 21% 10% 2	2730
May	1st to 10th	Day	55% 5% 9% 20% 9% 3	7651
	11th to 20th	Day	49% 5% 11% 22% 12% 1	7630
	21st to end	Day	47% 4 10% 18% 17% 4	8603
June	1st to 10th	Day	44% 5% 10% 26% 14% 1	2940
	11th to 20th	Day	44% 5% 15% 21% 15% 1	2870
	21st to end	Day	39% 5% 14% 24% 16% 2	2800
July	1st to 10th	Day	38% 4 12% 28% 16% 2	5884
	11th to 20th	Day	40% 6% 13% 25% 15% 1	5831
	21st to end	Day	39% 6% 11% 22% 21% 1	6240
August	1st to 10th	Day	44% 5% 15% 24% 12%	4221
	11th to 20th	Day	43% 6% 11% 29% 10% 1	4213
	21st to end	Day	38% 6% 14% 30% 11% 1	4586
September	1st to 10th	Day	40% 5% 13% 23% 16% 3	2307
	11th to 20th	Day	37% 4 15% 27% 17% 2	2200
	21st to end	Day	48% 4 9% 23% 14% 1	2200
October	1st to 10th	Day	34% 5% 13% 28% 19% 1	3345
	11th to 20th	Day	47% 5% 11% 19% 16% 3	3240
	21st to end	Day	45% 4 12% 23% 15% 1	3538
November	1st to 10th	Day	49% 5% 10% 22% 13% 1	1852
	11th to 20th	Day	61% 4 9% 17% 8% 2	1837
	21st to end	Day	70% 4 8% 12% 6%	1680
December	1st to 10th	Day	75% 4 10% 9% 2	2680
	11th to 20th	Day	76% 3 8% 11% 2	3066
	21st to end	Day	83% 3 7% 7% 1	4207
January	1st to 10th	Night	82% 3 5% 7% 3	7636
	11th to 20th	Night	82% 2 6% 7% 3	7680
	21st to end	Night	72% 2 8% 12% 5%	8401
February	1st to 10th	Night	69% 4 8% 14% 6%	2730
	11th to 20th	Night	68% 4 7% 15% 5%	2616
	21st to end	Night	65% 4 8% 14% 8% 1	2076
March	1st to 10th	Night	58% 3 12% 18% 9%	5127
	11th to 20th	Night	47% 6% 14% 22% 10% 1	5090
	21st to end	Night	55% 6% 8% 18% 13% 1	5588
April	1st to 10th	Night	56% 4 10% 16% 12% 2	2259
	11th to 20th	Night	52% 4 11% 17% 14% 2	1926
	21st to end	Night	48% 4 10% 20% 15% 2	1890
May	1st to 10th	Night	57% 4 9% 16% 10% 4	5264
	11th to 20th	Night	45% 5% 11% 24% 14% 1	5235
	21st to end	Night	46% 4 12% 21% 16% 2	5555
June	1st to 10th	Night	41% 5% 9% 24% 17% 4	1680
	11th to 20th	Night	40% 4 15% 20% 18% 2	1640
	21st to end	Night	37% 7% 12% 25% 17% 1	1600
July	1st to 10th	Night	35% 5% 13% 25% 18% 3	3960
	11th to 20th	Night	37% 5% 13% 27% 15% 2	4006
	21st to end	Night	35% 5% 12% 20% 27% 2	4297
August	1st to 10th	Night	41% 6% 12% 25% 14% 2	2904
	11th to 20th	Night	42% 5% 10% 30% 12% 1	2902
	21st to end	Night	37% 6% 12% 29% 15% 2	3279
September	1st to 10th	Night	37% 5% 11% 28% 17% 3	2090
	11th to 20th	Night	31% 5% 13% 29% 21% 2	2200
	21st to end	Night	47% 4 10% 20% 18% 1	2200
October	1st to 10th	Night	33% 4 10% 29% 23% 1	3821
	11th to 20th	Night	45% 5% 10% 20% 18% 2	3899
	21st to end	Night	43% 4 12% 25% 15% 1	4252
November	1st to 10th	Night	47% 4 11% 23% 13% 2	2661
	11th to 20th	Night	61% 3 10% 16% 8% 3	2780
	21st to end	Night	67% 4 9% 15% 5%	2940
December	1st to 10th	Night	72% 4 11% 10% 4	4720
	11th to 20th	Night	73% 3 8% 13% 2	5348
	21st to end	Night	77% 4 9% 9% 1	6985

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	35% 26% 28% 9% 2	330
	11th to 20th	Day	39% 28% 26% 5% 1 1	330
	21st to end	Day	35% 29% 27% 6% 2	363
February	1st to 10th	Day	35% 23% 34% 7% 1 1	330
	11th to 20th	Day	38% 28% 29% 5% 1	330
	21st to end	Day	40% 28% 28% 4	273
March	1st to 10th	Day	32% 23% 31% 11% 3	488
	11th to 20th	Day	35% 20% 31% 11% 3 1	540
	21st to end	Day	36% 22% 27% 12% 3	594
April	1st to 10th	Day	31% 21% 29% 14% 4	540
	11th to 20th	Day	34% 19% 26% 14% 7% 1	532
	21st to end	Day	32% 15% 33% 15% 4 1	540
May	1st to 10th	Day	30% 17% 31% 16% 4 2	543
	11th to 20th	Day	27% 10% 33% 22% 6% 3	567
	21st to end	Day	21% 9% 31% 24% 11% 3	617
June	1st to 10th	Day	19% 10% 38% 21% 10% 3	570
	11th to 20th	Day	19% 11% 29% 27% 11% 2	550
	21st to end	Day	17% 11% 32% 25% 12% 4	530
July	1st to 10th	Day	14% 7% 24% 31% 17% 7%	525
	11th to 20th	Day	15% 6% 27% 28% 17% 6%	524
	21st to end	Day	12% 8% 28% 29% 16% 7%	576
August	1st to 10th	Day	13% 5% 25% 31% 19% 6%	526
	11th to 20th	Day	16% 6% 25% 29% 15% 8%	519
	21st to end	Day	13% 6% 28% 27% 18% 8%	583
September	1st to 10th	Day	18% 8% 23% 25% 18% 7%	530
	11th to 20th	Day	11% 4 22% 32% 22% 10%	530
	21st to end	Day	24% 9% 27% 23% 11% 5%	530
October	1st to 10th	Day	17% 11% 28% 23% 18% 4	530
	11th to 20th	Day	26% 18% 33% 16% 6% 2	530
	21st to end	Day	35% 17% 30% 15% 3	583
November	1st to 10th	Day	27% 20% 32% 14% 6% 1	330
	11th to 20th	Day	39% 18% 26% 11% 4 1	302
	21st to end	Day	38% 20% 36% 6%	220
December	1st to 10th	Day	34% 21% 30% 11% 2 1	220
	11th to 20th	Day	37% 26% 26% 9% 2	220
	21st to end	Day	40% 24% 27% 9%	278
January	1st to 10th	Night	31% 23% 30% 13% 3	840
	11th to 20th	Night	34% 25% 28% 12% 2	840
	21st to end	Night	30% 23% 30% 15% 2	924
February	1st to 10th	Night	31% 22% 29% 16% 2	840
	11th to 20th	Night	29% 24% 29% 17% 1	823
	21st to end	Night	30% 23% 32% 13% 1	692
March	1st to 10th	Night	26% 22% 30% 18% 4	840
	11th to 20th	Night	28% 18% 30% 18% 5% 1	840
	21st to end	Night	27% 17% 32% 19% 5% 1	924
April	1st to 10th	Night	29% 16% 30% 20% 5%	840
	11th to 20th	Night	23% 16% 34% 18% 8% 1	682
	21st to end	Night	22% 13% 33% 25% 7%	630
May	1st to 10th	Night	25% 10% 30% 27% 8% 1	630
	11th to 20th	Night	20% 8% 29% 32% 9% 2	621
	21st to end	Night	16% 3 28% 35% 16% 1	610
June	1st to 10th	Night	12% 6% 31% 39% 12%	420
	11th to 20th	Night	13% 6% 30% 37% 13% 1	410
	21st to end	Night	12% 6% 28% 37% 17% 1	400
July	1st to 10th	Night	10% 2 17% 41% 27% 4	556
	11th to 20th	Night	10% 3 22% 37% 24% 5%	582
	21st to end	Night	12% 2 18% 42% 24% 2	657
August	1st to 10th	Night	10% 4 16% 43% 24% 3	597
	11th to 20th	Night	15% 3 14% 36% 29% 3	594
	21st to end	Night	11% 3 20% 34% 27% 4	690
September	1st to 10th	Night	16% 6% 17% 34% 24% 3	800
	11th to 20th	Night	13% 2 18% 35% 28% 5%	800
	21st to end	Night	20% 8% 25% 28% 16% 3	800
October	1st to 10th	Night	18% 9% 27% 27% 17% 2	800
	11th to 20th	Night	27% 12% 29% 24% 7% 1	800
	21st to end	Night	33% 13% 31% 19% 4	880
November	1st to 10th	Night	23% 15% 29% 24% 8% 1	820
	11th to 20th	Night	30% 20% 28% 15% 6% 1	840
	21st to end	Night	36% 18% 30% 13% 4	840
December	1st to 10th	Night	34% 21% 29% 13% 4	840
	11th to 20th	Night	30% 25% 29% 13% 3	840
	21st to end	Night	35% 19% 31% 13% 1	924

Page generated at 2026-06-13 02:31:43. Version ac07

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