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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 2018-02-22.

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
36%
15787
20%
48922
10%
15746
47%
15746
24%
31079

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%
779
20%
2677
8%
776
37%
776
19%
1682
January16th to endNight
18%
832
23%
2704
7%
832
38%
832
21%
1704
February1st to 15thNight
16%
764
17%
2482
4%
761
32%
761
17%
1603
February16th to endNight
16%
659
24%
1988
6%
659
37%
659
19%
1279
March1st to 15thNight
23%
720
20%
2037
7%
720
37%
720
22%
1343
March16th to endNight
23%
768
20%
2067
7%
768
34%
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
50%
375
16%
1497
14%
374
56%
374
20%
910
June1st to 15thNight
53%
360
17%
1440
17%
360
61%
360
24%
839
June16th to endNight
58%
360
16%
1440
18%
360
62%
360
25%
833
July1st to 15thNight
53%
340
11%
1360
14%
340
55%
340
17%
888
July16th to endNight
68%
486
15%
1519
14%
455
72%
455
31%
872
August1st to 15thNight
66%
542
18%
1612
14%
539
67%
539
31%
1008
August16th to endNight
64%
764
19%
1910
11%
764
65%
764
35%
1248
September1st to 15thNight
54%
720
25%
1800
13%
720
58%
720
34%
1176
September16th to endNight
55%
717
25%
1962
20%
717
59%
717
32%
1244
October1st to 15thNight
44%
720
21%
2160
18%
720
52%
720
25%
1394
October16th to endNight
35%
768
28%
2304
15%
768
50%
768
30%
1359
November1st to 15thNight
36%
760
22%
2456
13%
760
50%
760
25%
1513
November16th to endNight
31%
780
23%
2666
12%
780
46%
780
21%
1609
December1st to 15thNight
24%
780
16%
2730
6%
780
37%
780
15%
1813
December16th to endNight
20%
832
19%
2912
5%
832
36%
832
18%
1853

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%
49326
Night
14%5%25%42445%7%43%
49102
Cloud CoverDay
14%6%25%5%245%5%7%40%
49336
Night
14%5%25%42445%7%43%
49107
TransparencyDay
41%6%12%22%15%2
49024
Night
39%6%12%22%16%2
48922
SeeingDay
18%9%25%24%16%6%
6155
Night
17%10%30%28%12%1
15788

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
14%7%35%425%5%5%6%38%
1588
16th to endDay
13%8%35%5%3445%5%40%
1872
February1st to 15thDay
14%8%35%4345%5%7%37%
1710
16th to endDay
14%8%36%5%24447%38%
1632
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
15%6%25%5%35%46%9%37%
2618
June1st to 15thDay
13%4245%25%5%7%9%38%
2520
16th to endDay
11%326%5%35%45%10%41%
2520
July1st to 15thDay
9%426%5%35%6%7%9%38%
2520
16th to endDay
7%425%6%36%6%8%10%37%
2542
August1st to 15thDay
11%5%25%5%36%6%6%8%37%
2324
16th to endDay
12%5%244345%6%8%41%
2292
September1st to 15thDay
15%5%25%424347%45%
2160
16th to endDay
13%6%25%5%2445%8%42%
1995
October1st to 15thDay
18%6%1342435%6%44%
1800
16th to endDay
16%5%2442445%5%45%
1920
November1st to 15thDay
15%6%24324447%44%
1731
16th to endDay
17%6%24324435%45%
1622
December1st to 15thDay
15%6%35%5%3445%7%37%
1560
16th to endDay
15%6%346%345%46%37%
1664
January1st to 15thNight
16%6%35%42345%7%40%
2677
16th to endNight
15%7%25%423346%43%
2704
February1st to 15thNight
13%8%26%5%3335%6%40%
2480
16th to endNight
15%5%26%5%2445%5%42%
1988
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
13%6%2442445%8%42%
1495
June1st to 15thNight
12%415%32446%8%45%
1440
16th to endNight
9%423435%5%6%10%43%
1440
July1st to 15thNight
7%5%26%7%46%6%6%9%37%
1440
16th to endNight
6%324425%5%6%10%48%
1624
August1st to 15thNight
9%4245%4447%8%44%
1623
16th to endNight
11%3244345%5%6%47%
1910
September1st to 15thNight
12%5%25%42335%7%48%
1800
16th to endNight
13%5%24424446%47%
1962
October1st to 15thNight
19%6%24313445%44%
2160
16th to endNight
15%413323346%51%
2304
November1st to 15thNight
13%6%245%2433448%
2456
16th to endNight
15%5%2442445%7%43%
2666
December1st to 15thNight
16%6%26%6%35%45%6%35%
2730
16th to endNight
16%6%345%3446%7%38%
2912

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%34335%5%5%6%38%
1588
16th to endDay
13%8%35%434446%40%
1872
February1st to 15thDay
14%8%25%5%245%5%7%37%
1710
16th to endDay
13%8%26%6%23447%39%
1632
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
15%5%25%5%345%6%9%36%
2618
June1st to 15thDay
12%5%25%435%6%7%10%36%
2520
16th to endDay
11%425%5%25%5%6%8%41%
2520
July1st to 15thDay
8%6%25%5%35%6%8%9%37%
2520
16th to endDay
6%5%26%5%47%7%7%11%36%
2542
August1st to 15thDay
10%6%25%5%36%6%6%8%37%
2324
16th to endDay
12%5%25%425%5%7%8%40%
2292
September1st to 15thDay
14%5%2442435%7%44%
2160
16th to endDay
14%6%245%25%448%41%
1995
October1st to 15thDay
18%6%1442335%6%43%
1800
16th to endDay
15%6%243135%45%46%
1920
November1st to 15thDay
15%5%2332445%6%44%
1731
16th to endDay
17%6%24423346%45%
1622
December1st to 15thDay
16%6%26%42445%6%39%
1560
16th to endDay
15%6%36%5%25%5%5%6%37%
1664
January1st to 15thNight
16%5%35%42335%7%40%
2677
16th to endNight
16%7%25%423346%44%
2704
February1st to 15thNight
14%8%36%5%3435%6%41%
2473
16th to endNight
15%5%25%5%2445%5%42%
1988
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
13%6%2442445%7%43%
1495
June1st to 15thNight
12%42442445%9%44%
1440
16th to endNight
9%4245%345%6%9%43%
1440
July1st to 15thNight
8%427%8%37%6%6%9%36%
1440
16th to endNight
5%325%435%5%7%10%47%
1624
August1st to 15thNight
9%5%245%345%5%9%43%
1623
16th to endNight
11%423425%45%8%46%
1910
September1st to 15thNight
12%5%25%423447%48%
1800
16th to endNight
13%6%24434446%46%
1962
October1st to 15thNight
18%5%24323445%44%
2160
16th to endNight
15%413232346%51%
2304
November1st to 15thNight
13%6%3442334447%
2456
16th to endNight
14%5%2442445%7%44%
2666
December1st to 15thNight
17%6%36%5%35%446%36%
2730
16th to endNight
16%6%25%42446%7%38%
2912

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
44%5%13%20%12%4
1589
16th to endDay
44%413%22%12%2
1872
February1st to 15thDay
44%6%11%23%10%2
1712
16th to endDay
44%412%25%11%1
1632
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
42%8%14%20%12%1
2622
June1st to 15thDay
39%9%12%23%13%
2520
16th to endDay
37%8%15%22%15%1
2520
July1st to 15thDay
39%9%12%20%14%3
2371
16th to endDay
36%9%14%23%12%1
2384
August1st to 15thDay
41%7%14%18%16%
2311
16th to endDay
36%7%12%24%15%2
2292
September1st to 15thDay
38%6%11%20%19%3
2160
16th to endDay
41%5%8%21%21%2
1995
October1st to 15thDay
40%6%11%22%17%2
1800
16th to endDay
38%5%10%26%18%
1920
November1st to 15thDay
39%5%12%20%16%4
1731
16th to endDay
41%311%27%14%2
1622
December1st to 15thDay
44%6%14%22%10%1
1560
16th to endDay
45%5%13%21%11%
1664
January1st to 15thNight
42%5%12%20%15%3
2677
16th to endNight
42%410%27%14%1
2704
February1st to 15thNight
43%5%12%22%13%1
2482
16th to endNight
41%49%24%17%1
1988
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
38%9%15%18%15%3
1497
June1st to 15thNight
35%7%13%25%16%
1440
16th to endNight
33%9%13%25%15%2
1440
July1st to 15thNight
43%10%12%17%11%3
1360
16th to endNight
29%9%19%21%18%1
1519
August1st to 15thNight
35%7%13%23%17%1
1612
16th to endNight
35%6%11%24%18%3
1910
September1st to 15thNight
36%5%10%20%22%3
1800
16th to endNight
37%5%9%21%22%3
1962
October1st to 15thNight
41%5%10%22%18%2
2160
16th to endNight
33%410%29%19%2
2304
November1st to 15thNight
39%49%23%16%6%
2456
16th to endNight
38%5%9%25%17%2
2666
December1st to 15thNight
47%6%11%22%11%1
2730
16th to endNight
43%5%16%21%11%1
2912

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
29%26%23%16%31
98
16th to endDay
20%24%38%12%3
144
February1st to 15thDay
24%27%39%8%
135
16th to endDay
19%17%45%15%1
253
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
20%420%26%20%7%
331
June1st to 15thDay
16%7%26%24%18%6%
315
16th to endDay
16%425%33%15%4
315
July1st to 15thDay
15%23%27%25%6%
305
16th to endDay
7%215%35%29%10%
326
August1st to 15thDay
14%114%31%26%10%
313
16th to endDay
11%19%32%27%17%
332
September1st to 15thDay
17%5%19%20%23%13%
315
16th to endDay
18%415%25%23%13%
314
October1st to 15thDay
24%319%26%18%7%
315
16th to endDay
15%13%30%25%13%2
336
November1st to 15thDay
17%9%27%28%15%1
284
16th to endDay
18%16%38%17%9%
152
December1st to 15thDay
20%25%27%14%8%3
90
16th to endDay
19%21%40%12%5%
96
January1st to 15thNight
20%15%37%22%4
780
16th to endNight
19%16%42%20%1
832
February1st to 15thNight
19%17%40%20%1
764
16th to endNight
17%22%38%18%1
659
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
16%223%38%17%1
375
June1st to 15thNight
12%225%38%20%1
360
16th to endNight
10%121%48%16%
360
July1st to 15thNight
11%120%39%26%
340
16th to endNight
9%14%43%28%3
486
August1st to 15thNight
12%13%45%26%2
542
16th to endNight
13%112%40%28%3
764
September1st to 15thNight
13%321%32%25%3
720
16th to endNight
15%217%30%28%5%
717
October1st to 15thNight
23%6%21%26%18%3
720
16th to endNight
17%11%32%25%12%
768
November1st to 15thNight
16%10%31%28%11%1
760
16th to endNight
17%16%31%25%8%
780
December1st to 15thNight
20%14%35%21%7%
780
16th to endNight
18%16%40%22%2
832
Page generated at 2018-02-23 11:21:30. Version ac04

Copyright 2018 A. Danko


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