Southwind Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Southwind Observatory clear sky chart from 2005-11-05 to 2017-09-16.

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 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
27%
14963
19%
46832
8%
14931
40%
14931
21%
30087

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
16%
720
21%
2506
7%
716
35%
716
16%
1545
January16th to endNight
15%
768
21%
2646
5%
768
37%
768
16%
1645
February1st to 15thNight
14%
704
18%
2203
3%
701
31%
701
15%
1456
February16th to endNight
16%
631
24%
1893
7%
631
36%
631
18%
1213
March1st to 15thNight
16%
720
18%
2160
6%
720
31%
720
17%
1441
March16th to endNight
19%
768
24%
2001
7%
768
33%
768
21%
1309
April1st to 15thNight
18%
718
17%
1796
3%
718
26%
718
22%
1258
April16th to endNight
21%
663
17%
1743
3%
663
31%
663
22%
1190
May1st to 15thNight
22%
525
17%
1605
6%
525
33%
525
16%
1108
May16th to endNight
30%
375
14%
1497
10%
374
39%
374
17%
938
June1st to 15thNight
33%
360
14%
1440
9%
360
47%
360
17%
936
June16th to endNight
46%
360
14%
1440
14%
360
56%
360
25%
813
July1st to 15thNight
45%
340
12%
1360
13%
340
49%
340
21%
831
July16th to endNight
51%
376
16%
1418
16%
354
58%
354
22%
846
August1st to 15thNight
46%
518
17%
1589
9%
516
52%
516
28%
968
August16th to endNight
55%
764
19%
1910
10%
764
57%
764
33%
1261
September1st to 15thNight
40%
720
22%
1815
11%
720
45%
720
33%
1175
September16th to endNight
46%
661
26%
1825
18%
661
52%
661
31%
1137
October1st to 15thNight
34%
660
22%
1897
11%
660
45%
660
25%
1222
October16th to endNight
23%
704
18%
2233
6%
704
38%
704
20%
1445
November1st to 15thNight
27%
700
22%
2277
9%
700
43%
700
22%
1428
November16th to endNight
23%
720
21%
2370
9%
720
37%
720
18%
1531
December1st to 15thNight
22%
720
16%
2520
6%
720
36%
720
15%
1634
December16th to endNight
14%
768
19%
2688
4%
768
32%
768
14%
1757

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
16%6%2443445%7%39%
47935
Night
17%6%24424446%41%
47002
Cloud CoverDay
16%6%25%43445%7%39%
47945
Night
17%6%24424446%41%
47007
TransparencyDay
43%411%22%15%2
47623
Night
42%411%22%15%2
46832
SeeingDay
22%13%30%20%10%3
5809
Night
22%14%31%23%8%
14963

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
16%7%33425%446%41%
1432
16th to endDay
15%6%25%4245%5%6%40%
1577
February1st to 15thDay
16%6%26%435%45%6%36%
1657
16th to endDay
16%7%25%5%2435%5%40%
1580
March1st to 15thDay
18%7%25%4345%46%37%
1790
16th to endDay
18%6%34424345%41%
2220
April1st to 15thDay
20%7%235%24346%39%
2152
16th to endDay
17%5%25%424346%45%
2217
May1st to 15thDay
23%7%24433446%35%
2356
16th to endDay
17%6%244245%5%6%39%
2618
June1st to 15thDay
23%5%2443446%7%32%
2520
16th to endDay
13%5%25%5%35%5%6%10%36%
2520
July1st to 15thDay
13%5%246%45%6%5%8%37%
2520
16th to endDay
12%5%25%5%45%5%7%8%37%
2654
August1st to 15thDay
13%5%25%5%346%6%8%37%
2347
16th to endDay
12%5%25%43445%8%42%
2292
September1st to 15thDay
13%5%25%5%345%46%43%
2145
16th to endDay
14%4245%24446%47%
1825
October1st to 15thDay
18%7%25%41335%442%
1730
16th to endDay
17%5%145%345%46%41%
1639
November1st to 15thDay
18%5%23323347%43%
1581
16th to endDay
18%5%2442335%5%43%
1587
December1st to 15thDay
18%6%24434346%39%
1440
16th to endDay
20%9%245%2445%6%34%
1536
January1st to 15thNight
17%6%2442345%6%41%
2506
16th to endNight
15%8%34324346%42%
2646
February1st to 15thNight
15%7%35%43435%5%39%
2202
16th to endNight
16%7%34423345%43%
1893
March1st to 15thNight
18%6%25%4245%46%39%
2147
16th to endNight
17%6%24323348%43%
2001
April1st to 15thNight
18%6%34425%446%38%
1796
16th to endNight
19%434423445%42%
1743
May1st to 15thNight
20%6%25%5%23446%36%
1605
16th to endNight
18%6%24424447%39%
1495
June1st to 15thNight
21%5%43424446%38%
1440
16th to endNight
12%5%244145%5%9%44%
1440
July1st to 15thNight
13%5%245%35%5%6%8%40%
1440
16th to endNight
10%5%25%5%45%5%6%8%40%
1514
August1st to 15thNight
12%3245%25%45%8%45%
1599
16th to endNight
14%41443446%7%44%
1910
September1st to 15thNight
15%423424446%47%
1815
16th to endNight
14%5%24323435%50%
1825
October1st to 15thNight
16%6%24422346%44%
1897
16th to endNight
19%6%24424445%42%
2233
November1st to 15thNight
17%6%25%323345%45%
2277
16th to endNight
18%7%245%24345%40%
2370
December1st to 15thNight
21%6%2442445%6%37%
2520
16th to endNight
21%6%25%32445%6%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
16%6%244345%45%41%
1432
16th to endDay
15%6%25%425%45%7%40%
1577
February1st to 15thDay
16%6%26%435%5%5%6%36%
1657
16th to endDay
16%7%25%5%25%347%39%
1580
March1st to 15thDay
18%7%25%435%45%6%36%
1800
16th to endDay
19%6%25%423435%42%
2220
April1st to 15thDay
20%6%25%42335%6%39%
2152
16th to endDay
17%424424346%44%
2217
May1st to 15thDay
23%7%2442345%6%34%
2356
16th to endDay
18%5%25%4245%5%6%38%
2618
June1st to 15thDay
23%6%245%24447%33%
2520
16th to endDay
13%5%25%435%5%6%9%37%
2520
July1st to 15thDay
14%4246%35%5%6%8%37%
2520
16th to endDay
12%425%5%45%6%7%9%37%
2654
August1st to 15thDay
13%5%16%5%35%5%6%8%37%
2347
16th to endDay
11%5%26%43445%8%42%
2292
September1st to 15thDay
12%5%25%6%3345%6%44%
2145
16th to endDay
14%425%333446%46%
1825
October1st to 15thDay
18%7%25%422346%41%
1730
16th to endDay
18%5%15%435%446%41%
1639
November1st to 15thDay
18%5%24333346%43%
1581
16th to endDay
18%5%2442345%6%43%
1587
December1st to 15thDay
18%6%34433446%39%
1440
16th to endDay
20%8%2443435%6%35%
1536
January1st to 15thNight
18%6%2432345%5%42%
2506
16th to endNight
16%7%34323346%42%
2646
February1st to 15thNight
14%8%35%5%34446%40%
2195
16th to endNight
16%6%34433346%42%
1893
March1st to 15thNight
18%6%35%424446%39%
2160
16th to endNight
17%6%34314347%44%
2000
April1st to 15thNight
18%7%24434446%38%
1796
16th to endNight
19%5%35%423335%42%
1743
May1st to 15thNight
21%5%25%5%24346%35%
1605
16th to endNight
18%6%3442345%7%37%
1495
June1st to 15thNight
21%6%33425%346%38%
1440
16th to endNight
12%4234245%5%8%45%
1440
July1st to 15thNight
13%425%6%35%5%6%8%39%
1440
16th to endNight
10%5%25%5%445%7%9%39%
1514
August1st to 15thNight
12%5%145%35%5%6%7%44%
1599
16th to endNight
13%3234345%5%7%44%
1910
September1st to 15thNight
15%42442435%6%47%
1815
16th to endNight
14%5%24324335%50%
1825
October1st to 15thNight
17%6%24432346%44%
1897
16th to endNight
19%6%23423445%41%
2233
November1st to 15thNight
17%6%24423345%45%
2277
16th to endNight
18%6%25%5%24345%40%
2370
December1st to 15thNight
21%6%2442445%6%37%
2520
16th to endNight
21%6%2443445%6%36%
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
43%412%23%12%3
1433
16th to endDay
43%411%25%13%2
1577
February1st to 15thDay
46%412%20%14%1
1660
16th to endDay
44%310%24%14%2
1580
March1st to 15thDay
48%313%22%10%2
1800
16th to endDay
44%310%18%18%3
2220
April1st to 15thDay
45%39%22%15%3
2152
16th to endDay
40%48%23%19%3
2217
May1st to 15thDay
49%5%8%19%14%1
2356
16th to endDay
43%7%13%19%13%1
2622
June1st to 15thDay
50%5%11%20%10%1
2520
16th to endDay
41%6%14%24%12%
2520
July1st to 15thDay
44%6%9%22%15%1
2371
16th to endDay
41%6%14%21%14%2
2487
August1st to 15thDay
41%6%14%22%14%
2333
16th to endDay
39%5%9%25%18%1
2292
September1st to 15thDay
39%5%10%21%20%1
2145
16th to endDay
38%47%23%23%2
1825
October1st to 15thDay
44%49%23%16%2
1730
16th to endDay
43%410%24%14%2
1639
November1st to 15thDay
41%312%21%17%2
1581
16th to endDay
41%211%26%14%2
1587
December1st to 15thDay
45%317%18%14%1
1440
16th to endDay
49%414%18%11%
1536
January1st to 15thNight
42%313%23%13%3
2506
16th to endNight
42%310%24%16%2
2646
February1st to 15thNight
45%412%20%13%2
2203
16th to endNight
42%39%24%16%3
1893
March1st to 15thNight
45%412%21%13%3
2160
16th to endNight
40%39%22%19%4
2001
April1st to 15thNight
45%410%21%15%1
1796
16th to endNight
44%38%21%18%3
1743
May1st to 15thNight
49%49%18%15%2
1605
16th to endNight
45%5%16%18%12%1
1497
June1st to 15thNight
46%5%12%20%12%1
1440
16th to endNight
35%6%15%26%14%1
1440
July1st to 15thNight
39%7%13%23%13%1
1360
16th to endNight
39%6%15%23%11%3
1418
August1st to 15thNight
36%6%13%26%15%1
1589
16th to endNight
36%7%12%24%18%
1910
September1st to 15thNight
37%410%26%19%1
1815
16th to endNight
36%5%5%24%26%1
1825
October1st to 15thNight
41%410%23%17%3
1897
16th to endNight
44%313%22%15%
2233
November1st to 15thNight
41%311%20%18%3
2277
16th to endNight
46%310%24%12%2
2370
December1st to 15thNight
46%414%19%14%
2520
16th to endNight
47%312%21%13%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
25%30%28%11%5%
60
16th to endDay
28%19%39%12%
71
February1st to 15thDay
27%28%30%12%
173
16th to endDay
23%23%33%15%4
239
March1st to 15thDay
29%18%32%15%4
270
16th to endDay
24%22%34%11%5%1
288
April1st to 15thDay
29%16%31%13%7%1
270
16th to endDay
25%12%34%16%8%2
270
May1st to 15thDay
39%11%22%15%8%1
288
16th to endDay
21%10%33%24%8%1
331
June1st to 15thDay
26%12%26%20%12%1
315
16th to endDay
16%9%36%26%10%
315
July1st to 15thDay
17%7%30%29%13%1
305
16th to endDay
12%7%31%27%19%2
326
August1st to 15thDay
16%5%25%34%11%7%
313
16th to endDay
13%426%28%17%9%
332
September1st to 15thDay
13%11%29%22%14%8%
315
16th to endDay
17%7%28%19%13%14%
257
October1st to 15thDay
22%10%26%21%13%5%
255
16th to endDay
21%18%30%21%7%
250
November1st to 15thDay
21%17%25%23%10%1
235
16th to endDay
22%21%27%19%5%3
207
December1st to 15thDay
28%20%36%11%3
60
16th to endDay
39%21%26%12%
64
January1st to 15thNight
24%20%33%17%2
720
16th to endNight
25%20%33%17%2
768
February1st to 15thNight
22%19%37%18%1
704
16th to endNight
26%20%33%16%2
631
March1st to 15thNight
25%21%33%16%2
720
16th to endNight
23%22%31%18%4
768
April1st to 15thNight
24%19%36%16%3
718
16th to endNight
23%17%34%19%4
663
May1st to 15thNight
26%15%33%20%5%
525
16th to endNight
22%8%32%29%6%1
375
June1st to 15thNight
22%6%30%29%10%
360
16th to endNight
15%429%40%10%
360
July1st to 15thNight
15%230%34%16%
340
16th to endNight
11%5%23%37%19%2
376
August1st to 15thNight
16%227%35%16%1
518
16th to endNight
15%318%38%21%3
764
September1st to 15thNight
17%5%31%29%13%1
720
16th to endNight
16%7%23%27%20%3
661
October1st to 15thNight
20%9%30%26%11%1
660
16th to endNight
25%15%33%18%6%
704
November1st to 15thNight
23%13%32%20%8%1
700
16th to endNight
25%15%29%20%8%
720
December1st to 15thNight
27%16%29%20%5%
720
16th to endNight
29%20%33%15%2
768
Page generated at 2017-09-17 12:05:43. Version ac04

Copyright 2017 A. Danko


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