Solis Lacus Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Solis Lacus Observatory 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	16% 10% 4 9% 5% 5% 5% 4 5% 7% 29%	126120
	Night	16% 11% 4 10% 6% 4 4 3 5% 6% 30%	121945
Transparency	Day	54% 4 11% 20% 10% 1	129650
	Night	55% 3 11% 19% 10% 1	126502
Seeing	Day	26% 14% 28% 19% 10% 3	15683
	Night	24% 12% 26% 26% 10% 1	24869

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	11% 15% 10% 24% 6% 3 4 3 3 4 16%	3597
	11th to 20th	Day	13% 15% 8% 19% 7% 6% 5% 3 4 5% 14%	3570
	21st to end	Day	14% 14% 8% 12% 7% 5% 4 4 5% 5% 23%	4465
February	1st to 10th	Day	15% 14% 5% 14% 7% 6% 5% 4 5% 5% 19%	1800
	11th to 20th	Day	12% 15% 6% 13% 9% 5% 5% 4 5% 5% 21%	1818
	21st to end	Day	19% 12% 3 12% 8% 5% 4 4 4 6% 24%	1650
March	1st to 10th	Day	20% 13% 6% 10% 6% 4 3 2 3 4 27%	4559
	11th to 20th	Day	11% 15% 4 9% 5% 4 4 3 4 6% 35%	4980
	21st to end	Day	14% 12% 4 11% 7% 5% 5% 4 5% 5% 29%	5733
April	1st to 10th	Day	18% 14% 4 8% 5% 4 4 3 5% 6% 29%	2400
	11th to 20th	Day	17% 10% 3 8% 5% 4 4 4 5% 6% 33%	2374
	21st to end	Day	18% 11% 3 8% 5% 4 3 3 3 7% 34%	2400
May	1st to 10th	Day	29% 10% 3 7% 4 4 4 3 5% 6% 25%	6195
	11th to 20th	Day	19% 10% 3 8% 5% 5% 5% 4 6% 7% 28%	6318
	21st to end	Day	20% 9% 3 7% 4 4 5% 4 7% 8% 29%	6949
June	1st to 10th	Day	18% 7% 3 6% 5% 5% 5% 4 6% 9% 32%	2800
	11th to 20th	Day	16% 7% 2 6% 5% 5% 5% 5% 7% 9% 33%	2800
	21st to end	Day	14% 8% 2 6% 5% 5% 6% 4 6% 9% 34%	2800
July	1st to 10th	Day	8% 6% 2 7% 5% 5% 6% 5% 8% 11% 36%	6360
	11th to 20th	Day	7% 6% 3 8% 6% 6% 7% 5% 8% 11% 32%	6360
	21st to end	Day	12% 6% 2 7% 5% 5% 5% 5% 7% 8% 38%	6926
August	1st to 10th	Day	18% 8% 3 8% 4 5% 5% 5% 7% 7% 31%	4157
	11th to 20th	Day	15% 8% 3 7% 4 6% 6% 5% 8% 10% 28%	3885
	21st to end	Day	14% 8% 3 6% 4 5% 5% 4 6% 8% 37%	4180
September	1st to 10th	Day	16% 8% 2 6% 4 4 4 4 6% 8% 38%	2280
	11th to 20th	Day	13% 7% 3 6% 4 4 4 4 5% 6% 44%	2280
	21st to end	Day	18% 8% 3 7% 4 5% 4 4 6% 7% 34%	2033
October	1st to 10th	Day	17% 8% 4 8% 5% 5% 4 3 6% 8% 33%	1900
	11th to 20th	Day	18% 8% 3 8% 5% 5% 4 3 5% 6% 33%	1900
	21st to end	Day	22% 13% 4 8% 5% 4 4 3 5% 7% 27%	2014
November	1st to 10th	Day	14% 11% 3 8% 5% 4 4 3 4 7% 37%	1761
	11th to 20th	Day	15% 15% 4 9% 5% 4 5% 4 5% 5% 30%	1730
	21st to end	Day	18% 15% 5% 10% 6% 5% 4 4 5% 7% 22%	1600
December	1st to 10th	Day	15% 15% 7% 15% 7% 6% 7% 3 4 6% 16%	2600
	11th to 20th	Day	18% 16% 9% 10% 5% 4 3 2 3 4 26%	2986
	21st to end	Day	18% 16% 6% 14% 7% 5% 4 3 4 5% 17%	3960
January	1st to 10th	Night	13% 13% 7% 25% 7% 4 4 3 4 5% 15%	6349
	11th to 20th	Night	10% 14% 8% 16% 8% 7% 5% 3 5% 6% 19%	6315
	21st to end	Night	16% 13% 5% 13% 8% 6% 5% 4 4 5% 20%	6490
February	1st to 10th	Night	16% 12% 5% 11% 8% 6% 6% 4 6% 5% 23%	2600
	11th to 20th	Night	14% 13% 5% 14% 8% 6% 6% 4 5% 5% 20%	2468
	21st to end	Night	18% 12% 4 14% 6% 4 4 3 5% 6% 24%	1980
March	1st to 10th	Night	17% 11% 6% 10% 7% 4 4 3 5% 5% 28%	5277
	11th to 20th	Night	15% 14% 5% 8% 5% 3 3 2 4 6% 35%	4979
	21st to end	Night	16% 13% 4 11% 5% 5% 4 4 5% 5% 27%	5197
April	1st to 10th	Night	21% 12% 3 9% 4 5% 4 4 4 7% 29%	2000
	11th to 20th	Night	20% 11% 3 7% 5% 2 3 4 4 7% 34%	1975
	21st to end	Night	17% 10% 3 6% 4 4 5% 2 5% 5% 37%	2000
May	1st to 10th	Night	31% 10% 3 7% 5% 4 3 3 4 5% 25%	3773
	11th to 20th	Night	18% 9% 3 7% 4 4 4 4 6% 7% 34%	3575
	21st to end	Night	20% 10% 3 8% 5% 4 4 4 5% 6% 30%	3926
June	1st to 10th	Night	17% 8% 2 6% 4 3 3 4 5% 8% 39%	1600
	11th to 20th	Night	16% 7% 2 5% 5% 4 5% 4 6% 8% 39%	1600
	21st to end	Night	11% 5% 2 6% 5% 4 5% 5% 5% 9% 44%	1600
July	1st to 10th	Night	8% 7% 3 8% 6% 5% 5% 3 6% 9% 39%	3600
	11th to 20th	Night	10% 7% 2 7% 4 5% 5% 5% 7% 10% 38%	3600
	21st to end	Night	11% 6% 2 6% 4 4 5% 4 6% 7% 45%	3926
August	1st to 10th	Night	18% 7% 3 8% 5% 4 4 4 6% 7% 35%	2856
	11th to 20th	Night	14% 8% 3 7% 5% 5% 4 3 5% 6% 40%	2911
	21st to end	Night	11% 8% 2 6% 4 4 5% 4 5% 8% 43%	3476
September	1st to 10th	Night	15% 5% 2 6% 4 4 4 4 6% 7% 43%	1900
	11th to 20th	Night	12% 6% 2 5% 3 4 4 3 5% 7% 49%	1900
	21st to end	Night	17% 7% 3 6% 5% 4 4 4 5% 7% 38%	2142
October	1st to 10th	Night	16% 8% 3 9% 5% 4 4 4 5% 7% 36%	2280
	11th to 20th	Night	19% 8% 3 7% 4 4 4 3 5% 6% 37%	2280
	21st to end	Night	22% 13% 3 8% 5% 4 3 2 5% 7% 28%	2584
November	1st to 10th	Night	12% 11% 3 8% 5% 4 5% 3 4 6% 39%	2537
	11th to 20th	Night	18% 11% 3 7% 5% 5% 5% 4 5% 6% 32%	2665
	21st to end	Night	14% 14% 5% 8% 5% 5% 5% 4 7% 7% 27%	2800
December	1st to 10th	Night	13% 16% 7% 12% 6% 5% 5% 4 5% 7% 20%	4580
	11th to 20th	Night	22% 15% 5% 9% 4 3 4 3 4 4 27%	5208
	21st to end	Night	20% 17% 6% 11% 7% 4 4 3 4 5% 19%	6996

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	75% 1 6% 14% 3	3598
	11th to 20th	Day	74% 3 7% 10% 5% 1	3600
	21st to end	Day	64% 2 10% 16% 7%	4465
February	1st to 10th	Day	68% 3 8% 14% 7% 1	1800
	11th to 20th	Day	65% 3 6% 19% 6%	1827
	21st to end	Day	63% 3 8% 17% 8% 1	1650
March	1st to 10th	Day	62% 2 9% 15% 10% 1	4562
	11th to 20th	Day	53% 2 15% 19% 8% 3	4980
	21st to end	Day	58% 3 7% 15% 15% 2	5733
April	1st to 10th	Day	57% 3 6% 23% 9% 2	2400
	11th to 20th	Day	53% 3 9% 19% 14% 2	2374
	21st to end	Day	53% 2 8% 21% 13% 3	2400
May	1st to 10th	Day	62% 3 9% 16% 9% 2	6206
	11th to 20th	Day	56% 3 9% 21% 10% 1	6322
	21st to end	Day	53% 3 11% 21% 11% 1	6949
June	1st to 10th	Day	49% 4 11% 22% 14% 1	2800
	11th to 20th	Day	47% 4 14% 24% 10% 1	2800
	21st to end	Day	45% 5% 13% 25% 11% 1	2800
July	1st to 10th	Day	41% 6% 16% 26% 11% 1	6290
	11th to 20th	Day	42% 7% 16% 25% 10%	6285
	21st to end	Day	42% 5% 12% 26% 14%	6728
August	1st to 10th	Day	51% 5% 13% 19% 11%	4143
	11th to 20th	Day	47% 6% 16% 24% 7%	3924
	21st to end	Day	45% 4 10% 32% 8% 1	4180
September	1st to 10th	Day	45% 4 10% 26% 14% 1	2280
	11th to 20th	Day	41% 3 11% 24% 20% 1	2280
	21st to end	Day	50% 3 11% 23% 12% 2	2033
October	1st to 10th	Day	47% 4 10% 24% 14% 1	3160
	11th to 20th	Day	46% 3 12% 23% 15% 1	3140
	21st to end	Day	42% 4 16% 27% 11% 1	3304
November	1st to 10th	Day	48% 3 12% 22% 13% 2	1761
	11th to 20th	Day	57% 2 10% 19% 10% 2	1730
	21st to end	Day	62% 3 13% 16% 5% 1	1600
December	1st to 10th	Day	71% 4 10% 12% 3	2600
	11th to 20th	Day	64% 3 11% 13% 8%	2986
	21st to end	Day	70% 3 10% 12% 6%	3960
January	1st to 10th	Night	75% 2 9% 10% 4	6349
	11th to 20th	Night	67% 3 11% 13% 5% 2	6360
	21st to end	Night	67% 2 8% 10% 11% 1	6490
February	1st to 10th	Night	62% 3 11% 15% 8%	2600
	11th to 20th	Night	66% 3 8% 14% 7% 1	2470
	21st to end	Night	62% 2 9% 17% 8% 1	1980
March	1st to 10th	Night	60% 2 11% 16% 10%	5287
	11th to 20th	Night	53% 2 17% 18% 6% 3	4980
	21st to end	Night	58% 3 6% 19% 13% 2	5197
April	1st to 10th	Night	58% 2 9% 19% 11% 2	2000
	11th to 20th	Night	51% 2 11% 19% 15%	1975
	21st to end	Night	50% 2 10% 21% 14% 3	2000
May	1st to 10th	Night	63% 3 7% 16% 9% 2	3779
	11th to 20th	Night	51% 4 13% 21% 11% 1	3576
	21st to end	Night	56% 3 10% 20% 11% 1	3927
June	1st to 10th	Night	44% 3 11% 25% 16%	1600
	11th to 20th	Night	43% 4 16% 25% 11% 2	1600
	21st to end	Night	38% 4 14% 29% 13% 1	1600
July	1st to 10th	Night	42% 6% 15% 22% 14% 1	3560
	11th to 20th	Night	41% 6% 15% 24% 14% 1	3552
	21st to end	Night	38% 4 12% 27% 18% 1	3809
August	1st to 10th	Night	49% 6% 15% 21% 8%	2846
	11th to 20th	Night	46% 4 14% 26% 9%	2938
	21st to end	Night	40% 4 12% 32% 11% 1	3476
September	1st to 10th	Night	41% 4 12% 26% 15% 1	1900
	11th to 20th	Night	36% 3 11% 31% 19% 1	1900
	21st to end	Night	47% 3 10% 24% 15% 1	2142
October	1st to 10th	Night	52% 4 10% 23% 10% 1	3800
	11th to 20th	Night	44% 3 14% 21% 15% 3	3779
	21st to end	Night	44% 3 15% 27% 10%	4244
November	1st to 10th	Night	47% 4 11% 22% 16% 2	2537
	11th to 20th	Night	53% 2 10% 21% 11% 2	2665
	21st to end	Night	56% 3 14% 21% 6%	2800
December	1st to 10th	Night	65% 4 11% 18% 3	4580
	11th to 20th	Night	62% 2 11% 15% 10%	5208
	21st to end	Night	69% 3 8% 13% 6% 1	6996

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	31% 21% 32% 14% 3 1	200
	11th to 20th	Day	42% 21% 25% 10% 3	200
	21st to end	Day	27% 28% 28% 13% 4 1	330
February	1st to 10th	Day	31% 27% 33% 8%	300
	11th to 20th	Day	40% 26% 26% 7% 1	365
	21st to end	Day	36% 22% 29% 11% 2	414
March	1st to 10th	Day	34% 18% 29% 13% 4 1	500
	11th to 20th	Day	35% 19% 27% 13% 5% 1	500
	21st to end	Day	34% 22% 27% 11% 3 2	550
April	1st to 10th	Day	39% 16% 27% 13% 4 1	500
	11th to 20th	Day	32% 23% 25% 11% 5% 3	492
	21st to end	Day	34% 16% 29% 12% 7% 1	500
May	1st to 10th	Day	34% 14% 28% 13% 8% 3	503
	11th to 20th	Day	25% 13% 30% 20% 8% 4	527
	21st to end	Day	21% 9% 30% 23% 13% 3	573
June	1st to 10th	Day	22% 10% 31% 22% 13% 2	530
	11th to 20th	Day	21% 10% 26% 28% 12% 2	530
	21st to end	Day	20% 9% 32% 26% 10% 2	530
July	1st to 10th	Day	15% 4 30% 29% 16% 6%	525
	11th to 20th	Day	12% 7% 27% 31% 18% 5%	524
	21st to end	Day	15% 6% 35% 27% 13% 3	576
August	1st to 10th	Day	15% 6% 24% 25% 22% 8%	502
	11th to 20th	Day	19% 5% 23% 29% 16% 9%	479
	21st to end	Day	13% 7% 27% 27% 15% 11%	539
September	1st to 10th	Day	20% 11% 22% 20% 18% 8%	490
	11th to 20th	Day	15% 5% 23% 25% 19% 12%	490
	21st to end	Day	24% 11% 27% 20% 13% 6%	490
October	1st to 10th	Day	26% 10% 23% 20% 14% 7%	490
	11th to 20th	Day	26% 15% 27% 20% 9% 2	490
	21st to end	Day	34% 12% 29% 18% 8%	499
November	1st to 10th	Day	27% 17% 23% 21% 11% 2	395
	11th to 20th	Day	33% 18% 24% 16% 8% 1	330
	21st to end	Day	39% 17% 33% 10% 3	200
December	1st to 10th	Day	33% 22% 31% 10% 3 2	200
	11th to 20th	Day	35% 19% 28% 16% 3	200
	21st to end	Day	35% 18% 32% 12% 2	220
January	1st to 10th	Night	27% 22% 31% 17% 2	800
	11th to 20th	Night	28% 18% 28% 22% 4	800
	21st to end	Night	21% 20% 36% 20% 3	880
February	1st to 10th	Night	29% 17% 31% 22% 2	800
	11th to 20th	Night	28% 20% 33% 17% 2	783
	21st to end	Night	34% 16% 30% 17% 3	660
March	1st to 10th	Night	28% 20% 28% 21% 4	800
	11th to 20th	Night	28% 18% 31% 18% 5%	800
	21st to end	Night	26% 19% 29% 20% 6% 1	880
April	1st to 10th	Night	30% 16% 29% 22% 3	800
	11th to 20th	Night	29% 15% 29% 20% 7% 1	791
	21st to end	Night	26% 14% 27% 26% 7%	800
May	1st to 10th	Night	31% 7% 22% 31% 10%	488
	11th to 20th	Night	19% 10% 29% 32% 9% 1	394
	21st to end	Night	15% 6% 27% 36% 15% 1	433
June	1st to 10th	Night	21% 7% 22% 38% 13% 1	400
	11th to 20th	Night	20% 5% 22% 38% 14% 1	400
	21st to end	Night	14% 4 28% 42% 13% 1	400
July	1st to 10th	Night	11% 3 19% 46% 18% 2	390
	11th to 20th	Night	12% 3 17% 46% 21% 1	388
	21st to end	Night	14% 2 18% 46% 18% 1	438
August	1st to 10th	Night	13% 1 21% 37% 26% 2	574
	11th to 20th	Night	16% 3 13% 35% 29% 5%	638
	21st to end	Night	15% 3 16% 37% 26% 2	836
September	1st to 10th	Night	19% 4 23% 33% 19% 3	760
	11th to 20th	Night	17% 4 16% 32% 26% 5%	760
	21st to end	Night	21% 8% 23% 28% 19% 2	760
October	1st to 10th	Night	23% 8% 22% 27% 18% 2	760
	11th to 20th	Night	24% 10% 25% 31% 9% 1	760
	21st to end	Night	32% 10% 28% 24% 6%	836
November	1st to 10th	Night	21% 12% 28% 29% 8% 1	780
	11th to 20th	Night	27% 14% 30% 21% 7% 1	800
	21st to end	Night	26% 16% 32% 20% 5% 1	800
December	1st to 10th	Night	30% 18% 29% 19% 5%	800
	11th to 20th	Night	28% 19% 28% 22% 3	800
	21st to end	Night	30% 17% 31% 19% 4	880

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

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