Sola Virtus Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sola Virtus Observatory clear sky chart from 2005-11-06 to 2024-01-16.

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	14% 6% 3 5% 5% 3 5% 5% 6% 8% 40%	74732
	Night	15% 6% 3 5% 5% 3 4 5% 5% 7% 43%	75069
Transparency	Day	27% 38% 8% 15% 10% 2	74440
	Night	27% 38% 8% 15% 11% 2	74880
Seeing	Day	19% 13% 27% 23% 13% 4	13818
	Night	18% 11% 30% 28% 11% 1	23342

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% 7% 3 6% 4 3 5% 4 6% 6% 42%	1517
	11th to 20th	Day	16% 8% 4 6% 5% 3 5% 5% 5% 7% 38%	1622
	21st to end	Day	13% 9% 3 6% 5% 4 6% 5% 4 6% 37%	1782
February	1st to 10th	Day	14% 9% 4 6% 5% 3 5% 5% 6% 8% 36%	1620
	11th to 20th	Day	15% 8% 3 5% 6% 3 4 5% 5% 7% 38%	1645
	21st to end	Day	19% 10% 2 7% 6% 3 3 3 4 6% 38%	1480
March	1st to 10th	Day	13% 6% 2 5% 6% 3 4 4 4 5% 47%	1890
	11th to 20th	Day	15% 7% 3 5% 6% 2 4 5% 5% 8% 40%	1980
	21st to end	Day	18% 8% 3 6% 6% 3 4 4 5% 5% 38%	2244
April	1st to 10th	Day	14% 7% 3 6% 5% 3 5% 6% 5% 8% 39%	2160
	11th to 20th	Day	14% 5% 3 5% 5% 2 5% 4 5% 7% 45%	2134
	21st to end	Day	18% 6% 2 5% 5% 3 4 5% 6% 7% 40%	2160
May	1st to 10th	Day	17% 7% 3 5% 5% 3 5% 5% 6% 7% 36%	2289
	11th to 20th	Day	20% 6% 3 5% 5% 3 5% 5% 5% 8% 35%	2478
	21st to end	Day	14% 5% 3 5% 5% 3 4 5% 6% 10% 39%	2725
June	1st to 10th	Day	12% 5% 2 6% 4 3 5% 6% 7% 11% 37%	2520
	11th to 20th	Day	13% 5% 3 6% 5% 4 5% 5% 8% 8% 38%	2520
	21st to end	Day	10% 3 2 5% 6% 3 5% 6% 7% 10% 42%	2520
July	1st to 10th	Day	9% 6% 2 5% 6% 4 6% 5% 9% 10% 40%	2520
	11th to 20th	Day	6% 4 2 5% 5% 4 6% 7% 8% 11% 42%	2520
	21st to end	Day	9% 7% 2 7% 5% 5% 7% 6% 8% 10% 36%	2576
August	1st to 10th	Day	9% 6% 2 6% 6% 4 7% 7% 6% 9% 37%	2327
	11th to 20th	Day	10% 6% 3 6% 6% 4 7% 5% 8% 9% 38%	2191
	21st to end	Day	12% 5% 2 5% 6% 3 5% 6% 7% 9% 40%	2376
September	1st to 10th	Day	15% 6% 2 5% 5% 3 5% 4 5% 7% 43%	2160
	11th to 20th	Day	13% 5% 2 4 5% 3 5% 4 5% 8% 48%	2160
	21st to end	Day	18% 8% 3 5% 4 3 4 5% 4 8% 38%	1914
October	1st to 10th	Day	18% 6% 2 5% 4 3 4 3 5% 7% 43%	1800
	11th to 20th	Day	17% 6% 2 4 4 2 3 4 6% 5% 46%	1800
	21st to end	Day	16% 6% 3 6% 4 2 4 5% 4 5% 44%	1980
November	1st to 10th	Day	13% 5% 2 4 3 2 3 4 5% 6% 51%	1694
	11th to 20th	Day	16% 5% 2 4 3 2 4 5% 5% 6% 48%	1706
	21st to end	Day	15% 6% 2 5% 5% 3 5% 4 4 7% 45%	1520
December	1st to 10th	Day	17% 8% 3 6% 5% 3 5% 4 5% 7% 38%	1520
	11th to 20th	Day	18% 7% 2 6% 4 3 5% 4 5% 7% 40%	1910
	21st to end	Day	15% 8% 3 7% 6% 3 5% 5% 6% 6% 36%	2772
January	1st to 10th	Night	14% 7% 3 5% 5% 3 4 4 5% 7% 43%	2649
	11th to 20th	Night	18% 7% 3 6% 5% 3 3 4 5% 7% 39%	2444
	21st to end	Night	14% 6% 3 5% 5% 3 4 4 5% 6% 46%	2574
February	1st to 10th	Night	16% 9% 3 6% 5% 3 3 4 5% 7% 39%	2340
	11th to 20th	Night	17% 7% 3 6% 4 3 4 4 5% 5% 41%	2200
	21st to end	Night	16% 8% 3 6% 5% 3 4 4 4 5% 41%	1776
March	1st to 10th	Night	14% 3 3 4 4 3 4 5% 5% 7% 48%	2066
	11th to 20th	Night	16% 8% 2 4 5% 3 4 5% 4 6% 43%	1980
	21st to end	Night	16% 8% 3 6% 5% 2 4 3 5% 7% 42%	2111
April	1st to 10th	Night	15% 7% 3 6% 6% 4 4 4 5% 8% 39%	1800
	11th to 20th	Night	14% 5% 2 5% 5% 3 4 5% 5% 8% 44%	1775
	21st to end	Night	20% 6% 2 4 4 2 3 5% 4 6% 43%	1800
May	1st to 10th	Night	17% 7% 3 6% 5% 3 5% 4 4 7% 39%	1687
	11th to 20th	Night	18% 7% 3 6% 5% 2 5% 4 5% 7% 38%	1415
	21st to end	Night	14% 6% 2 4 4 3 5% 5% 6% 9% 41%	1550
June	1st to 10th	Night	12% 5% 3 5% 5% 3 4 5% 5% 8% 46%	1440
	11th to 20th	Night	11% 6% 2 5% 6% 4 5% 5% 7% 10% 39%	1440
	21st to end	Night	11% 3 2 4 4 4 5% 7% 6% 10% 44%	1440
July	1st to 10th	Night	9% 6% 3 6% 8% 3 6% 5% 7% 9% 38%	1440
	11th to 20th	Night	6% 3 2 5% 6% 3 6% 6% 8% 10% 46%	1440
	21st to end	Night	8% 4 2 5% 5% 3 6% 6% 6% 10% 45%	1739
August	1st to 10th	Night	9% 5% 2 4 6% 4 5% 6% 6% 11% 42%	1611
	11th to 20th	Night	11% 6% 3 7% 5% 3 5% 5% 5% 9% 39%	1691
	21st to end	Night	13% 4 3 4 5% 2 5% 5% 6% 9% 43%	1980
September	1st to 10th	Night	14% 6% 2 5% 5% 2 3 4 5% 7% 45%	1800
	11th to 20th	Night	11% 6% 2 4 4 2 4 3 4 7% 54%	1800
	21st to end	Night	17% 7% 2 5% 4 3 4 4 5% 6% 43%	2042
October	1st to 10th	Night	20% 6% 3 4 4 2 3 4 5% 5% 44%	2160
	11th to 20th	Night	16% 5% 2 4 3 2 3 4 5% 6% 49%	2160
	21st to end	Night	17% 6% 1 4 3 3 4 4 4 7% 47%	2376
November	1st to 10th	Night	11% 5% 2 4 4 3 4 4 4 5% 53%	2382
	11th to 20th	Night	15% 7% 3 5% 4 2 4 4 4 6% 47%	2472
	21st to end	Night	13% 5% 2 4 5% 3 5% 4 6% 7% 47%	2660
December	1st to 10th	Night	17% 7% 3 5% 5% 3 4 4 5% 7% 38%	2660
	11th to 20th	Night	17% 6% 2 5% 5% 3 5% 4 4 7% 42%	3285
	21st to end	Night	16% 7% 3 6% 6% 3 5% 6% 7% 7% 34%	4884

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	26% 41% 8% 17% 8%	1518
	11th to 20th	Day	29% 41% 9% 12% 8% 1	1622
	21st to end	Day	31% 37% 8% 15% 8% 1	1782
February	1st to 10th	Day	28% 37% 8% 19% 8% 1	1620
	11th to 20th	Day	30% 37% 7% 17% 8% 1	1654
	21st to end	Day	33% 35% 7% 13% 9% 3	1480
March	1st to 10th	Day	24% 36% 8% 21% 9% 1	1890
	11th to 20th	Day	27% 38% 8% 11% 12% 4	1980
	21st to end	Day	32% 36% 6% 14% 10% 1	2244
April	1st to 10th	Day	26% 38% 9% 13% 10% 3	2160
	11th to 20th	Day	26% 37% 7% 13% 12% 4	2134
	21st to end	Day	27% 38% 8% 13% 12% 3	2160
May	1st to 10th	Day	29% 37% 7% 13% 11% 2	2289
	11th to 20th	Day	31% 39% 7% 11% 10% 2	2482
	21st to end	Day	25% 39% 9% 15% 9% 2	2725
June	1st to 10th	Day	25% 40% 10% 14% 10% 1	2520
	11th to 20th	Day	27% 39% 10% 14% 7% 2	2520
	21st to end	Day	23% 40% 10% 17% 9% 1	2520
July	1st to 10th	Day	25% 41% 9% 14% 10% 2	2450
	11th to 20th	Day	21% 40% 10% 18% 9% 2	2445
	21st to end	Day	27% 42% 8% 12% 10% 1	2432
August	1st to 10th	Day	27% 40% 10% 14% 8%	2314
	11th to 20th	Day	27% 38% 9% 13% 13% 2	2191
	21st to end	Day	29% 39% 7% 14% 7% 3	2376
September	1st to 10th	Day	27% 37% 6% 12% 14% 3	2160
	11th to 20th	Day	21% 37% 8% 16% 15% 3	2160
	21st to end	Day	30% 37% 6% 12% 13% 2	1914
October	1st to 10th	Day	26% 38% 7% 17% 12% 1	1800
	11th to 20th	Day	26% 37% 9% 14% 12% 1	1800
	21st to end	Day	28% 38% 7% 14% 12% 1	1980
November	1st to 10th	Day	19% 40% 8% 18% 14% 1	1694
	11th to 20th	Day	25% 40% 7% 13% 11% 2	1706
	21st to end	Day	27% 40% 7% 17% 8% 1	1520
December	1st to 10th	Day	27% 41% 10% 15% 6%	1520
	11th to 20th	Day	30% 33% 8% 22% 7%	1906
	21st to end	Day	36% 28% 13% 15% 8%	2772
January	1st to 10th	Night	25% 41% 7% 18% 8%	2649
	11th to 20th	Night	27% 41% 8% 15% 8% 1	2444
	21st to end	Night	26% 38% 6% 19% 10% 1	2574
February	1st to 10th	Night	30% 37% 8% 15% 10% 1	2340
	11th to 20th	Night	29% 37% 8% 14% 10% 2	2202
	21st to end	Night	32% 36% 6% 14% 10% 3	1776
March	1st to 10th	Night	21% 37% 9% 20% 12% 1	2066
	11th to 20th	Night	30% 38% 7% 13% 10% 2	1980
	21st to end	Night	29% 37% 7% 14% 10% 3	2111
April	1st to 10th	Night	29% 36% 8% 11% 12% 3	1800
	11th to 20th	Night	26% 36% 7% 13% 14% 4	1775
	21st to end	Night	26% 37% 7% 14% 11% 4	1800
May	1st to 10th	Night	28% 37% 9% 11% 12% 3	1687
	11th to 20th	Night	29% 39% 8% 8% 14% 1	1416
	21st to end	Night	22% 41% 11% 14% 9% 2	1551
June	1st to 10th	Night	22% 39% 10% 16% 11% 2	1440
	11th to 20th	Night	25% 40% 10% 14% 9% 1	1440
	21st to end	Night	23% 39% 9% 17% 11% 1	1440
July	1st to 10th	Night	29% 41% 10% 12% 6% 2	1400
	11th to 20th	Night	20% 41% 12% 15% 10% 2	1392
	21st to end	Night	21% 41% 12% 13% 12% 1	1642
August	1st to 10th	Night	24% 38% 12% 17% 8% 1	1600
	11th to 20th	Night	29% 38% 9% 12% 11% 1	1691
	21st to end	Night	29% 39% 8% 13% 8% 3	1980
September	1st to 10th	Night	26% 37% 6% 12% 15% 4	1800
	11th to 20th	Night	20% 36% 7% 17% 17% 2	1800
	21st to end	Night	29% 37% 6% 12% 13% 3	2042
October	1st to 10th	Night	27% 37% 6% 16% 13% 1	2160
	11th to 20th	Night	25% 37% 8% 17% 11% 1	2160
	21st to end	Night	25% 38% 7% 16% 13% 1	2376
November	1st to 10th	Night	19% 41% 6% 17% 15% 3	2382
	11th to 20th	Night	26% 40% 6% 15% 10% 3	2472
	21st to end	Night	25% 41% 7% 15% 12% 1	2660
December	1st to 10th	Night	27% 40% 7% 16% 9% 1	2660
	11th to 20th	Night	28% 33% 8% 15% 13% 2	3288
	21st to end	Night	35% 30% 12% 15% 8%	4884

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	26% 27% 29% 14% 3 1	180
	11th to 20th	Day	30% 25% 29% 15% 1	234
	21st to end	Day	20% 33% 32% 9% 5%	264
February	1st to 10th	Day	27% 25% 34% 11% 4	240
	11th to 20th	Day	28% 26% 40% 5% 1	312
	21st to end	Day	32% 18% 34% 15% 1	346
March	1st to 10th	Day	21% 26% 31% 20% 3	420
	11th to 20th	Day	22% 23% 34% 16% 4 2	420
	21st to end	Day	25% 19% 32% 16% 5% 1	462
April	1st to 10th	Day	21% 21% 35% 16% 6% 1	420
	11th to 20th	Day	18% 20% 29% 20% 9% 4	412
	21st to end	Day	26% 15% 34% 18% 6% 2	420
May	1st to 10th	Day	23% 19% 26% 19% 11% 1	423
	11th to 20th	Day	21% 14% 28% 23% 11% 2	447
	21st to end	Day	19% 5% 23% 27% 20% 6%	485
June	1st to 10th	Day	14% 9% 31% 24% 16% 5%	450
	11th to 20th	Day	18% 7% 26% 29% 15% 5%	450
	21st to end	Day	14% 6% 25% 34% 16% 6%	450
July	1st to 10th	Day	13% 3 19% 28% 26% 12%	445
	11th to 20th	Day	5% 3 19% 36% 29% 8%	444
	21st to end	Day	12% 5% 23% 33% 22% 6%	488
August	1st to 10th	Day	11% 3 21% 32% 25% 9%	446
	11th to 20th	Day	12% 3 17% 34% 23% 11%	439
	21st to end	Day	11% 5% 21% 31% 21% 12%	495
September	1st to 10th	Day	20% 6% 19% 21% 22% 12%	450
	11th to 20th	Day	15% 4 21% 28% 22% 10%	450
	21st to end	Day	23% 10% 22% 26% 14% 4	450
October	1st to 10th	Day	23% 6% 23% 25% 16% 6%	450
	11th to 20th	Day	19% 13% 27% 25% 14% 2	450
	21st to end	Day	18% 13% 38% 22% 7% 2	495
November	1st to 10th	Day	16% 12% 30% 27% 12% 2	377
	11th to 20th	Day	19% 17% 33% 20% 10%	366
	21st to end	Day	23% 19% 33% 18% 6% 1	180
December	1st to 10th	Day	25% 22% 35% 13% 3 2	180
	11th to 20th	Day	29% 22% 30% 13% 6%	180
	21st to end	Day	23% 20% 32% 17% 8%	198
January	1st to 10th	Night	18% 17% 43% 19% 3	760
	11th to 20th	Night	23% 16% 33% 25% 3	741
	21st to end	Night	18% 18% 44% 20% 1	792
February	1st to 10th	Night	21% 18% 38% 21% 2	720
	11th to 20th	Night	22% 22% 39% 16% 1	703
	21st to end	Night	22% 23% 37% 16% 2	592
March	1st to 10th	Night	18% 19% 39% 21% 4	720
	11th to 20th	Night	21% 18% 35% 19% 5% 1	720
	21st to end	Night	20% 14% 41% 20% 5% 1	792
April	1st to 10th	Night	21% 19% 38% 19% 4	720
	11th to 20th	Night	17% 13% 34% 28% 7%	711
	21st to end	Night	23% 11% 33% 25% 7%	720
May	1st to 10th	Night	21% 10% 29% 31% 9% 1	607
	11th to 20th	Night	20% 7% 32% 32% 9%	354
	21st to end	Night	17% 4 20% 41% 17% 1	389
June	1st to 10th	Night	13% 3 26% 39% 19% 1	360
	11th to 20th	Night	12% 4 24% 43% 16% 1	360
	21st to end	Night	11% 2 22% 48% 17%	360
July	1st to 10th	Night	11% 1 18% 39% 28% 3	350
	11th to 20th	Night	6% 2 15% 45% 28% 3	348
	21st to end	Night	10% 2 17% 45% 25% 2	559
August	1st to 10th	Night	11% 2 13% 45% 26% 2	537
	11th to 20th	Night	13% 2 17% 37% 30% 2	627
	21st to end	Night	14% 2 16% 39% 26% 3	792
September	1st to 10th	Night	16% 3 20% 33% 24% 4	720
	11th to 20th	Night	13% 3 17% 36% 26% 5%	720
	21st to end	Night	20% 4 22% 32% 20% 2	720
October	1st to 10th	Night	22% 6% 22% 27% 18% 4	720
	11th to 20th	Night	19% 9% 28% 31% 12% 1	720
	21st to end	Night	20% 11% 33% 23% 12%	792
November	1st to 10th	Night	14% 9% 34% 32% 10% 1	740
	11th to 20th	Night	19% 15% 31% 27% 7% 1	760
	21st to end	Night	15% 16% 35% 26% 7%	760
December	1st to 10th	Night	22% 16% 36% 20% 6%	760
	11th to 20th	Night	18% 15% 40% 22% 5%	760
	21st to end	Night	19% 16% 36% 27% 2	836

Page generated at 2024-01-13 01:38:08. Version ac07

Copyright 2024 Attilla Danko