UFOWorks Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the UFOWorks Observatory clear sky chart from 2005-11-05 to

2017-09-12
.

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
24%
14898
18%
46777
7%
14866
37%
14866
19%
30548

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
11%
720
19%
2506
5%
716
30%
716
15%
1597
January16th to endNight
12%
768
19%
2688
4%
768
33%
768
13%
1720
February1st to 15thNight
10%
704
16%
2183
4%
701
26%
701
15%
1467
February16th to endNight
12%
631
22%
1893
5%
631
32%
631
15%
1252
March1st to 15thNight
13%
720
17%
2160
5%
720
27%
720
15%
1480
March16th to endNight
18%
768
23%
2016
6%
768
31%
768
20%
1348
April1st to 15thNight
17%
718
16%
1796
3%
718
26%
718
18%
1303
April16th to endNight
20%
624
18%
1704
3%
624
30%
624
20%
1174
May1st to 15thNight
19%
540
16%
1620
6%
540
29%
540
17%
1126
May16th to endNight
28%
386
11%
1508
9%
385
35%
385
16%
980
June1st to 15thNight
29%
360
12%
1440
7%
360
42%
360
15%
943
June16th to endNight
38%
360
13%
1440
12%
360
47%
360
21%
875
July1st to 15thNight
45%
340
12%
1360
12%
340
52%
340
21%
829
July16th to endNight
45%
376
14%
1418
14%
354
51%
354
21%
863
August1st to 15thNight
43%
483
16%
1554
10%
481
49%
481
28%
949
August16th to endNight
49%
764
20%
1910
10%
764
53%
764
34%
1240
September1st to 15thNight
35%
707
20%
1804
8%
707
42%
707
29%
1195
September16th to endNight
44%
657
25%
1815
16%
657
51%
657
33%
1104
October1st to 15thNight
30%
660
22%
1864
11%
660
43%
660
25%
1225
October16th to endNight
21%
704
16%
2266
5%
704
34%
704
18%
1491
November1st to 15thNight
24%
700
21%
2277
7%
700
42%
700
20%
1443
November16th to endNight
21%
720
19%
2347
7%
720
36%
720
17%
1529
December1st to 15thNight
17%
720
17%
2520
5%
720
32%
720
15%
1634
December16th to endNight
13%
768
18%
2688
4%
768
30%
768
13%
1781

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%25%5%3445%7%38%
47894
Night
16%7%35%5%24446%39%
46947
Cloud CoverDay
17%6%25%43445%6%38%
47904
Night
16%7%35%424446%39%
46952
TransparencyDay
44%5%11%22%14%2
47582
Night
44%5%12%22%14%2
46777
SeeingDay
20%15%31%20%8%3
5827
Night
20%16%33%21%6%
14898

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%15%435%5%6%6%38%
1432
16th to endDay
14%6%35%5%2446%6%39%
1536
February1st to 15thDay
16%6%36%6%35%6%5%7%32%
1675
16th to endDay
15%8%46%5%34345%37%
1580
March1st to 15thDay
19%8%35%434446%35%
1790
16th to endDay
18%6%35%434345%41%
2208
April1st to 15thDay
18%8%35%5%34246%37%
2152
16th to endDay
17%6%24434437%41%
2256
May1st to 15thDay
25%7%35%5%25%346%31%
2332
16th to endDay
17%6%25%5%34447%38%
2617
June1st to 15thDay
22%6%35%42435%7%32%
2520
16th to endDay
15%435%5%35%5%6%9%33%
2520
July1st to 15thDay
12%6%246%45%5%6%8%36%
2520
16th to endDay
13%6%25%436%5%6%8%37%
2654
August1st to 15thDay
13%5%36%5%35%6%6%8%36%
2382
16th to endDay
11%426%5%35%5%47%43%
2292
September1st to 15thDay
13%6%25%5%24445%45%
2076
16th to endDay
15%414313345%51%
1815
October1st to 15thDay
18%6%25%323346%41%
1763
16th to endDay
15%7%26%424445%41%
1606
November1st to 15thDay
17%8%24423345%43%
1581
16th to endDay
17%6%25%324446%42%
1611
December1st to 15thDay
18%6%25%42445%5%38%
1440
16th to endDay
20%9%34425%45%6%33%
1536
January1st to 15thNight
16%7%35%5%24347%39%
2506
16th to endNight
14%8%45%5%25%35%5%38%
2688
February1st to 15thNight
14%8%36%5%35%446%36%
2182
16th to endNight
15%8%25%5%34445%38%
1893
March1st to 15thNight
18%8%246%35%45%6%35%
2147
16th to endNight
16%7%36%423346%41%
2016
April1st to 15thNight
17%8%36%6%3445%5%34%
1796
16th to endNight
21%6%25%423235%39%
1704
May1st to 15thNight
18%8%36%434445%35%
1620
16th to endNight
17%6%35%5%2436%8%35%
1506
June1st to 15thNight
22%5%4442445%7%36%
1440
16th to endNight
15%425%4235%6%8%41%
1440
July1st to 15thNight
12%5%25%5%35%5%6%7%39%
1440
16th to endNight
10%5%26%5%35%6%6%8%39%
1514
August1st to 15thNight
9%4245%35%5%5%8%45%
1564
16th to endNight
11%424425%45%8%45%
1910
September1st to 15thNight
13%6%25%4245%45%45%
1804
16th to endNight
14%5%33322445%51%
1815
October1st to 15thNight
17%5%25%433335%44%
1864
16th to endNight
17%7%35%424446%38%
2266
November1st to 15thNight
16%6%245%2335%5%44%
2277
16th to endNight
17%7%35%424445%39%
2347
December1st to 15thNight
18%8%25%424445%37%
2520
16th to endNight
19%7%35%5%2445%6%34%
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%235%35%5%5%6%39%
1432
16th to endDay
14%7%35%5%2445%7%39%
1536
February1st to 15thDay
15%7%36%7%45%5%5%7%32%
1675
16th to endDay
16%8%36%5%24345%37%
1580
March1st to 15thDay
20%7%35%433447%35%
1800
16th to endDay
18%7%24424345%41%
2208
April1st to 15thDay
19%7%36%5%34335%38%
2152
16th to endDay
18%5%15%434347%41%
2256
May1st to 15thDay
26%6%35%42335%6%31%
2332
16th to endDay
18%6%25%42435%7%38%
2617
June1st to 15thDay
23%6%25%43445%8%32%
2520
16th to endDay
15%5%35%5%36%6%6%9%33%
2520
July1st to 15thDay
12%5%26%6%35%5%6%8%36%
2520
16th to endDay
13%5%25%5%35%5%6%7%38%
2654
August1st to 15thDay
13%5%17%6%35%5%6%7%36%
2382
16th to endDay
11%5%25%5%35%45%7%43%
2292
September1st to 15thDay
13%6%245%25%445%45%
2076
16th to endDay
15%5%24322346%50%
1815
October1st to 15thDay
19%5%25%323446%41%
1763
16th to endDay
16%6%26%5%24445%41%
1606
November1st to 15thDay
18%7%24323336%43%
1581
16th to endDay
16%7%24424447%41%
1611
December1st to 15thDay
18%6%35%5%145%46%38%
1440
16th to endDay
20%8%35%434446%33%
1536
January1st to 15thNight
16%8%26%424346%39%
2506
16th to endNight
15%9%45%5%2435%5%39%
2688
February1st to 15thNight
14%8%36%5%445%5%5%37%
2175
16th to endNight
16%8%35%5%34445%38%
1893
March1st to 15thNight
18%7%25%5%35%45%6%35%
2160
16th to endNight
16%6%35%423346%41%
2015
April1st to 15thNight
17%8%36%5%3446%5%34%
1796
16th to endNight
21%6%35%423335%39%
1704
May1st to 15thNight
18%8%36%435%445%35%
1620
16th to endNight
17%7%25%43445%8%35%
1506
June1st to 15thNight
22%5%245%2345%6%37%
1440
16th to endNight
15%5%2432445%8%41%
1440
July1st to 15thNight
13%5%25%5%345%7%7%39%
1440
16th to endNight
12%425%5%35%5%6%8%39%
1514
August1st to 15thNight
9%5%15%5%35%46%8%44%
1564
16th to endNight
12%415%43445%8%45%
1910
September1st to 15thNight
12%6%35%424446%45%
1804
16th to endNight
15%42432234451%
1815
October1st to 15thNight
17%5%25%424335%43%
1864
16th to endNight
17%7%26%4245%36%38%
2266
November1st to 15thNight
17%6%24423445%44%
2277
16th to endNight
17%7%35%42445%5%39%
2347
December1st to 15thNight
18%8%35%42345%5%38%
2520
16th to endNight
19%7%36%5%245%46%34%
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%5%13%23%10%2
1433
16th to endDay
42%5%13%25%12%1
1536
February1st to 15thDay
48%6%12%20%11%
1678
16th to endDay
47%310%22%13%2
1580
March1st to 15thDay
48%412%22%9%2
1800
16th to endDay
44%310%20%15%4
2208
April1st to 15thDay
48%310%19%15%2
2152
16th to endDay
42%49%20%18%3
2256
May1st to 15thDay
53%46%20%12%1
2332
16th to endDay
44%5%13%21%12%1
2621
June1st to 15thDay
50%6%11%21%10%
2520
16th to endDay
43%8%13%20%12%
2520
July1st to 15thDay
44%7%10%22%13%1
2371
16th to endDay
41%6%15%20%13%2
2487
August1st to 15thDay
44%6%13%22%12%
2368
16th to endDay
38%5%8%27%17%1
2292
September1st to 15thDay
40%5%11%22%19%1
2076
16th to endDay
35%37%25%25%2
1815
October1st to 15thDay
43%411%23%13%3
1763
16th to endDay
43%314%23%13%2
1606
November1st to 15thDay
43%413%21%15%2
1581
16th to endDay
42%411%24%15%2
1611
December1st to 15thDay
44%5%17%19%13%
1440
16th to endDay
49%5%14%18%10%
1536
January1st to 15thNight
45%313%22%12%2
2506
16th to endNight
45%411%23%13%2
2688
February1st to 15thNight
46%413%20%12%1
2183
16th to endNight
45%310%22%15%2
1893
March1st to 15thNight
48%411%19%13%2
2160
16th to endNight
43%39%20%17%5%
2016
April1st to 15thNight
49%5%9%18%15%2
1796
16th to endNight
47%38%19%16%4
1704
May1st to 15thNight
49%410%18%13%2
1620
16th to endNight
46%6%17%19%9%1
1508
June1st to 15thNight
47%6%13%20%11%
1440
16th to endNight
40%7%12%24%14%
1440
July1st to 15thNight
39%8%13%25%13%
1360
16th to endNight
40%6%14%24%11%2
1418
August1st to 15thNight
35%7%15%24%13%2
1554
16th to endNight
35%6%11%28%17%
1910
September1st to 15thNight
39%5%10%24%18%
1804
16th to endNight
35%38%23%26%2
1815
October1st to 15thNight
42%411%22%15%3
1864
16th to endNight
45%413%23%12%
2266
November1st to 15thNight
41%5%11%20%18%3
2277
16th to endNight
45%413%21%13%1
2347
December1st to 15thNight
46%414%22%11%
2520
16th to endNight
47%5%12%22%10%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
15%36%30%13%5%
60
16th to endDay
21%26%35%15%
64
February1st to 15thDay
22%29%32%14%1
199
16th to endDay
18%30%32%14%3
239
March1st to 15thDay
28%22%32%13%3
270
16th to endDay
21%29%29%12%5%1
288
April1st to 15thDay
25%18%37%12%5%
270
16th to endDay
22%17%30%21%5%3
270
May1st to 15thDay
35%15%25%14%7%1
288
16th to endDay
19%11%36%22%8%1
331
June1st to 15thDay
25%14%26%23%8%1
315
16th to endDay
16%11%37%23%7%2
315
July1st to 15thDay
20%9%30%25%12%1
305
16th to endDay
14%6%30%31%12%3
326
August1st to 15thDay
14%6%30%30%14%5%
313
16th to endDay
13%7%28%25%15%9%
332
September1st to 15thDay
17%10%29%23%12%7%
299
16th to endDay
18%7%26%23%11%13%
254
October1st to 15thDay
23%10%25%22%12%5%
255
16th to endDay
13%24%33%22%5%
244
November1st to 15thDay
23%11%34%17%11%1
235
16th to endDay
22%19%30%17%7%1
231
December1st to 15thDay
16%33%36%8%5%
60
16th to endDay
32%32%25%7%1
64
January1st to 15thNight
20%25%37%13%2
720
16th to endNight
23%23%34%16%1
768
February1st to 15thNight
20%23%40%14%1
704
16th to endNight
22%26%35%14%1
631
March1st to 15thNight
23%25%34%14%1
720
16th to endNight
22%23%32%18%3
768
April1st to 15thNight
21%21%36%16%3
718
16th to endNight
24%18%32%17%5%
624
May1st to 15thNight
24%18%35%18%3
540
16th to endNight
20%9%37%25%6%
386
June1st to 15thNight
23%8%34%26%6%
360
16th to endNight
15%337%35%6%
360
July1st to 15thNight
14%6%27%40%10%
340
16th to endNight
13%231%38%14%
376
August1st to 15thNight
10%334%36%13%
483
16th to endNight
14%424%37%17%2
764
September1st to 15thNight
15%9%33%29%11%
707
16th to endNight
17%5%27%30%16%3
657
October1st to 15thNight
22%12%31%22%10%1
660
16th to endNight
23%19%32%19%5%
704
November1st to 15thNight
19%18%32%20%7%1
700
16th to endNight
21%19%32%17%7%
720
December1st to 15thNight
25%19%34%16%4
720
16th to endNight
22%24%36%14%1
768
Page generated at 2017-09-13 07:39:26. Version ac04

Copyright 2017 A. Danko


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