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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 2005-11-05 to 2017-05-24.

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 TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(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

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
35%
14837
20%
45877
10%
14796
46%
14796
24%
29198

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
21%
719
20%
2470
8%
716
37%
716
18%
1567
January16th to endNight
17%
768
23%
2496
6%
768
37%
768
21%
1576
February1st to 15thNight
17%
704
18%
2287
4%
701
33%
701
18%
1456
February16th to endNight
17%
631
23%
1904
6%
631
38%
631
19%
1216
March1st to 15thNight
24%
720
20%
2037
7%
720
38%
720
22%
1343
March16th to endNight
22%
768
20%
2067
7%
768
33%
768
25%
1384
April1st to 15thNight
23%
718
18%
1796
4%
718
31%
718
26%
1209
April16th to endNight
35%
720
17%
1800
6%
720
41%
720
29%
1227
May1st to 15thNight
37%
523
16%
1603
9%
523
44%
523
21%
1089
May16th to endNight
51%
361
16%
1441
14%
360
58%
360
21%
866
June1st to 15thNight
50%
330
18%
1320
17%
330
59%
330
23%
781
June16th to endNight
59%
330
16%
1320
19%
330
63%
330
26%
763
July1st to 15thNight
52%
310
12%
1240
15%
310
54%
310
18%
797
July16th to endNight
68%
449
14%
1398
12%
418
73%
418
31%
804
August1st to 15thNight
66%
497
19%
1477
15%
494
67%
494
32%
913
August16th to endNight
63%
700
18%
1750
10%
700
64%
700
34%
1152
September1st to 15thNight
54%
660
26%
1650
14%
660
59%
660
34%
1082
September16th to endNight
54%
657
24%
1798
19%
657
58%
657
31%
1160
October1st to 15thNight
43%
660
22%
1980
18%
660
51%
660
26%
1270
October16th to endNight
34%
704
25%
2112
13%
704
50%
704
29%
1256
November1st to 15thNight
35%
700
23%
2262
13%
700
50%
700
25%
1385
November16th to endNight
30%
720
21%
2461
11%
720
44%
720
19%
1518
December1st to 15thNight
24%
720
17%
2520
6%
720
37%
720
15%
1664
December16th to endNight
19%
768
19%
2688
5%
768
36%
768
17%
1720

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 ForecastData
Points
Cloud CoverDay
14%6%25%5%3445%7%40%
46393
Night
14%5%25%42445%7%43%
46057
Cloud CoverDay
14%6%25%5%245%5%7%40%
46403
Night
14%5%25%42445%7%43%
46062
TransparencyDay
41%6%12%21%15%2
46091
Night
40%6%12%22%16%2
45877
SeeingDay
18%9%25%24%16%6%
5228
Night
17%10%30%27%12%1
14838

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
15%7%35%435%5%5%6%38%
1465
16th to endDay
13%8%45%5%25%45%5%40%
1728
February1st to 15thDay
13%8%35%4345%6%7%37%
1575
16th to endDay
13%8%35%5%245%47%38%
1569
March1st to 15thDay
14%7%245%35%446%40%
1909
16th to endDay
16%7%35%5%33446%39%
2157
April1st to 15thDay
15%6%25%42445%7%41%
2152
16th to endDay
16%5%25%423346%44%
2160
May1st to 15thDay
17%6%245%35%46%7%35%
2358
16th to endDay
14%5%25%5%35%46%9%38%
2517
June1st to 15thDay
14%4245%26%5%7%9%37%
2310
16th to endDay
11%426%5%3445%9%41%
2310
July1st to 15thDay
9%5%26%5%35%6%7%9%38%
2310
16th to endDay
7%425%6%36%6%8%10%36%
2355
August1st to 15thDay
10%5%25%5%36%6%6%8%38%
2131
16th to endDay
12%5%24435%5%6%8%41%
2100
September1st to 15thDay
14%424424347%45%
1980
16th to endDay
15%6%245%24448%41%
1829
October1st to 15thDay
17%5%1342445%6%44%
1650
16th to endDay
17%5%2332445%5%44%
1760
November1st to 15thDay
15%5%2432445%7%45%
1595
16th to endDay
18%6%24324445%43%
1497
December1st to 15thDay
16%6%35%5%3445%7%37%
1440
16th to endDay
16%6%346%345%46%38%
1536
January1st to 15thNight
16%6%35%42345%7%38%
2470
16th to endNight
15%7%25%423346%43%
2496
February1st to 15thNight
13%8%26%433346%41%
2285
16th to endNight
15%5%26%5%2445%5%43%
1904
March1st to 15thNight
15%5%245%24446%43%
2025
16th to endNight
15%6%35%423346%42%
2067
April1st to 15thNight
14%6%25%5%2446%8%39%
1796
16th to endNight
17%5%25%323346%43%
1800
May1st to 15thNight
16%7%35%424447%38%
1603
16th to endNight
12%6%2442445%8%43%
1439
June1st to 15thNight
13%415%32446%8%44%
1320
16th to endNight
10%4235%35%5%6%9%44%
1320
July1st to 15thNight
7%5%36%7%46%6%5%9%38%
1320
16th to endNight
6%324425%6%6%9%47%
1503
August1st to 15thNight
8%4245%445%6%9%45%
1488
16th to endNight
12%3244345%5%6%47%
1750
September1st to 15thNight
12%5%2442335%7%48%
1650
16th to endNight
14%6%24424446%46%
1798
October1st to 15thNight
19%5%23313446%45%
1980
16th to endNight
15%414323346%50%
2112
November1st to 15thNight
13%6%245%2433448%
2262
16th to endNight
16%5%2442445%7%42%
2461
December1st to 15thNight
16%6%26%6%35%45%6%36%
2520
16th to endNight
16%6%245%3446%7%37%
2688

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
15%7%35%435%5%5%6%38%
1465
16th to endDay
14%8%35%434446%40%
1728
February1st to 15thDay
13%8%25%5%245%5%7%38%
1575
16th to endDay
13%8%26%6%24447%39%
1569
March1st to 15thDay
14%7%35%6%25%446%41%
1920
16th to endDay
16%7%35%5%24445%39%
2156
April1st to 15thDay
15%6%25%4235%5%7%41%
2152
16th to endDay
16%5%25%42345%6%44%
2160
May1st to 15thDay
17%6%345%345%5%7%35%
2358
16th to endDay
14%5%25%5%345%6%9%38%
2517
June1st to 15thDay
12%5%25%335%6%7%10%36%
2310
16th to endDay
11%425%6%25%5%6%8%41%
2310
July1st to 15thDay
8%6%35%5%35%6%8%9%37%
2310
16th to endDay
6%5%26%5%47%7%7%11%36%
2355
August1st to 15thDay
10%6%25%5%36%6%6%8%38%
2131
16th to endDay
12%5%24425%5%7%8%39%
2100
September1st to 15thDay
14%424424348%44%
1980
16th to endDay
15%6%245%24448%41%
1829
October1st to 15thDay
17%5%1342335%7%44%
1650
16th to endDay
16%6%233135%45%45%
1760
November1st to 15thDay
15%5%2432445%6%45%
1595
16th to endDay
18%6%24423446%42%
1497
December1st to 15thDay
16%6%26%425%45%6%38%
1440
16th to endDay
16%6%36%5%25%45%6%38%
1536
January1st to 15thNight
17%5%35%42345%8%39%
2470
16th to endNight
16%6%25%423346%43%
2496
February1st to 15thNight
14%7%36%5%3335%5%42%
2278
16th to endNight
14%5%25%5%2445%5%43%
1904
March1st to 15thNight
16%4244245%46%43%
2037
16th to endNight
14%7%35%5%24346%42%
2067
April1st to 15thNight
14%6%25%5%3445%8%40%
1796
16th to endNight
18%5%25%323447%43%
1800
May1st to 15thNight
18%7%25%425%347%38%
1603
16th to endNight
12%6%2442446%7%44%
1439
June1st to 15thNight
13%4245%2445%9%43%
1320
16th to endNight
9%4245%35%5%6%9%44%
1320
July1st to 15thNight
7%436%7%37%5%6%9%37%
1320
16th to endNight
5%325%435%5%7%10%47%
1503
August1st to 15thNight
8%4245%345%5%9%44%
1488
16th to endNight
12%423425%45%8%46%
1750
September1st to 15thNight
12%5%25%42345%7%47%
1650
16th to endNight
14%6%24423446%45%
1798
October1st to 15thNight
18%5%2432345%5%44%
1980
16th to endNight
15%413232446%50%
2112
November1st to 15thNight
13%6%3442334449%
2262
16th to endNight
15%5%2442445%7%42%
2461
December1st to 15thNight
17%6%35%5%35%446%36%
2520
16th to endNight
16%6%25%42446%7%38%
2688

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
45%5%13%20%11%3
1466
16th to endDay
44%413%22%12%3
1728
February1st to 15thDay
43%6%11%24%11%2
1577
16th to endDay
44%413%24%11%2
1569
March1st to 15thDay
43%411%24%13%1
1920
16th to endDay
45%5%10%19%16%2
2157
April1st to 15thDay
41%6%10%20%16%3
2152
16th to endDay
39%5%9%18%20%5%
2160
May1st to 15thDay
46%6%10%20%14%1
2358
16th to endDay
41%8%14%20%12%1
2521
June1st to 15thDay
40%9%13%23%12%
2310
16th to endDay
38%8%15%22%14%1
2310
July1st to 15thDay
39%9%12%20%14%3
2161
16th to endDay
36%10%14%23%13%1
2197
August1st to 15thDay
40%7%14%19%16%1
2118
16th to endDay
37%7%11%24%15%2
2100
September1st to 15thDay
37%6%11%19%20%3
1980
16th to endDay
41%5%8%19%21%2
1829
October1st to 15thDay
38%6%12%23%16%2
1650
16th to endDay
39%5%11%25%17%
1760
November1st to 15thDay
38%5%12%20%17%4
1595
16th to endDay
43%411%26%13%2
1497
December1st to 15thDay
44%6%14%22%10%1
1440
16th to endDay
45%5%13%22%11%
1536
January1st to 15thNight
42%5%12%20%14%3
2470
16th to endNight
42%411%26%14%1
2496
February1st to 15thNight
43%412%23%14%1
2287
16th to endNight
41%410%23%17%1
1904
March1st to 15thNight
40%6%11%25%14%1
2037
16th to endNight
42%5%12%20%16%2
2067
April1st to 15thNight
41%412%20%17%3
1796
16th to endNight
40%6%9%19%19%5%
1800
May1st to 15thNight
45%6%11%18%16%2
1603
16th to endNight
37%9%15%18%15%3
1441
June1st to 15thNight
37%7%13%24%16%
1320
16th to endNight
33%8%12%26%16%1
1320
July1st to 15thNight
43%9%12%18%12%3
1240
16th to endNight
29%9%19%20%18%2
1398
August1st to 15thNight
35%6%14%24%17%1
1477
16th to endNight
36%6%10%24%18%3
1750
September1st to 15thNight
36%6%11%20%22%3
1650
16th to endNight
38%5%9%20%23%3
1798
October1st to 15thNight
40%5%10%22%17%2
1980
16th to endNight
34%5%10%27%19%1
2112
November1st to 15thNight
39%48%23%17%6%
2262
16th to endNight
40%5%10%24%16%2
2461
December1st to 15thNight
46%6%11%22%11%1
2520
16th to endNight
44%5%16%21%11%1
2688

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
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
35%26%23%13%1
65
16th to endDay
22%25%34%14%3
96
February1st to 15thDay
22%30%35%11%1
90
16th to endDay
18%19%43%16%1
228
March1st to 15thDay
16%20%34%22%5%
270
16th to endDay
21%14%37%19%43
288
April1st to 15thDay
19%15%31%22%8%2
270
16th to endDay
21%8%28%21%13%6%
270
May1st to 15thDay
26%14%25%18%13%2
288
16th to endDay
18%418%26%22%8%
302
June1st to 15thDay
17%7%25%25%18%5%
255
16th to endDay
17%323%32%17%5%
255
July1st to 15thDay
16%121%25%27%8%
245
16th to endDay
5%215%36%30%9%
270
August1st to 15thDay
13%112%33%28%9%
253
16th to endDay
11%17%32%26%19%
268
September1st to 15thDay
15%418%18%26%16%
255
16th to endDay
21%217%24%20%12%
254
October1st to 15thDay
21%420%28%18%5%
255
16th to endDay
15%12%30%27%11%1
272
November1st to 15thDay
17%9%28%26%17%1
238
16th to endDay
22%13%35%18%10%
117
December1st to 15thDay
21%26%26%11%8%5%
60
16th to endDay
23%17%40%12%6%
64
January1st to 15thNight
20%16%36%22%4
720
16th to endNight
19%16%42%19%1
768
February1st to 15thNight
19%17%40%21%1
704
16th to endNight
17%23%37%19%1
631
March1st to 15thNight
18%18%35%22%4
720
16th to endNight
18%13%40%19%6%1
768
April1st to 15thNight
19%15%39%21%4
718
16th to endNight
20%9%30%29%10%
720
May1st to 15thNight
22%7%28%31%8%
523
16th to endNight
14%324%38%17%1
361
June1st to 15thNight
13%226%36%19%
330
16th to endNight
10%219%49%17%
330
July1st to 15thNight
11%121%38%26%
310
16th to endNight
8%14%43%28%3
449
August1st to 15thNight
12%12%47%25%1
497
16th to endNight
13%113%39%28%3
700
September1st to 15thNight
13%420%31%26%3
660
16th to endNight
17%218%30%27%3
657
October1st to 15thNight
22%6%22%26%18%2
660
16th to endNight
17%11%31%26%11%
704
November1st to 15thNight
16%10%32%28%11%1
700
16th to endNight
18%17%30%24%8%
720
December1st to 15thNight
20%14%35%21%7%
720
16th to endNight
19%16%39%21%2
768
Page generated at 2017-05-25 13:27:40. Version ac04

Copyright 2017 A. Danko


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