Widefield
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Widefield clear sky chart from 2005-11-05 to 2017-09-23.

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
62%
15909
29%
46933
22%
15868
69%
15868
45%
24564

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
62%
898
32%
2506
24%
895
69%
895
51%
1275
January16th to endNight
60%
795
36%
2523
30%
795
70%
795
49%
1197
February1st to 15thNight
55%
699
28%
2214
21%
698
64%
698
42%
1144
February16th to endNight
51%
632
36%
1894
21%
632
66%
632
48%
947
March1st to 15thNight
57%
720
30%
2127
19%
720
66%
720
49%
1081
March16th to endNight
53%
669
30%
2013
19%
669
63%
669
45%
1039
April1st to 15thNight
45%
539
26%
1798
17%
539
61%
539
40%
908
April16th to endNight
51%
540
24%
1800
23%
540
61%
540
33%
997
May1st to 15thNight
54%
540
22%
1662
21%
540
59%
540
34%
962
May16th to endNight
58%
562
20%
1498
15%
561
63%
561
41%
875
June1st to 15thNight
68%
540
24%
1440
18%
540
72%
540
52%
753
June16th to endNight
74%
540
24%
1440
19%
540
77%
540
48%
784
July1st to 15thNight
72%
510
18%
1360
16%
510
73%
510
36%
832
July16th to endNight
80%
564
23%
1455
21%
531
80%
531
40%
860
August1st to 15thNight
72%
539
16%
1704
18%
536
72%
536
31%
1001
August16th to endNight
78%
573
25%
1910
29%
573
79%
573
37%
1018
September1st to 15thNight
73%
540
27%
1800
30%
540
76%
540
38%
955
September16th to endNight
74%
516
38%
1868
38%
516
80%
516
49%
814
October1st to 15thNight
60%
627
32%
1947
23%
627
67%
627
46%
980
October16th to endNight
69%
731
37%
2139
25%
731
75%
731
55%
1038
November1st to 15thNight
68%
875
37%
2275
22%
875
73%
875
61%
1138
November16th to endNight
65%
900
39%
2352
25%
900
71%
900
58%
1190
December1st to 15thNight
58%
900
29%
2520
19%
900
64%
900
49%
1326
December16th to endNight
54%
960
31%
2688
19%
960
62%
960
45%
1450

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
43133245%6%9%54%
47987
Night
431332345%7%59%
47109
Cloud CoverDay
5%31332446%8%55%
47985
Night
431332345%7%59%
47109
TransparencyDay
25%411%25%23%10%
47665
Night
23%311%26%23%9%
46933
SeeingDay
8%7%26%30%19%7%
5831
Night
6%321%43%21%3
15917

By Month

Percentage Cloud Cover SW (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
231321235%8%65%
1432
16th to endDay
1313423338%64%
1710
February1st to 15thDay
1435%424348%57%
1648
16th to endDay
1424423348%60%
1580
March1st to 15thDay
341432335%8%58%
1830
16th to endDay
45%2331445%8%54%
2211
April1st to 15thDay
442333446%8%54%
2150
16th to endDay
8%6%25%32445%7%47%
2160
May1st to 15thDay
8%6%35%335%6%6%8%41%
2286
16th to endDay
7%413425%6%7%9%46%
2616
June1st to 15thDay
43133245%8%10%51%
2520
16th to endDay
2212325%6%7%9%54%
2520
July1st to 15thDay
5%2245%37%6%7%9%45%
2520
16th to endDay
32145%37%7%9%11%43%
2611
August1st to 15thDay
43145%36%6%9%11%42%
2247
16th to endDay
4313425%5%8%10%49%
2292
September1st to 15thDay
5%3134236%8%9%50%
2160
16th to endDay
322224347%66%
1926
October1st to 15thDay
5%212313447%62%
1680
16th to endDay
4212212336%68%
1721
November1st to 15thDay
1213223349%65%
1583
16th to endDay
1313211237%70%
1608
December1st to 15thDay
2315%5%23248%61%
1440
16th to endDay
343441335%9%57%
1536
January1st to 15thNight
1324323336%66%
2506
16th to endNight
1323323335%66%
2523
February1st to 15thNight
2425%31345%7%57%
2204
16th to endNight
1324423245%63%
1894
March1st to 15thNight
241322445%7%61%
2127
16th to endNight
45%23213447%61%
2013
April1st to 15thNight
5%3132235%47%59%
1798
16th to endNight
10%5%24323347%52%
1800
May1st to 15thNight
10%32433446%9%47%
1661
16th to endNight
8%4133245%5%9%52%
1497
June1st to 15thNight
4222145%6%9%60%
1440
16th to endNight
2212325%5%7%9%57%
1440
July1st to 15thNight
5%3245%45%6%7%10%44%
1440
16th to endNight
4213435%7%7%12%46%
1554
August1st to 15thNight
5%425%6%25%6%7%7%46%
1713
16th to endNight
5%2134345%7%11%49%
1910
September1st to 15thNight
6%31342447%9%51%
1800
16th to endNight
3213212346%67%
1868
October1st to 15thNight
6%5%13122345%62%
1947
16th to endNight
4312123336%67%
2139
November1st to 15thNight
1213222247%68%
2275
16th to endNight
1313212335%70%
2352
December1st to 15thNight
132442336%8%58%
2520
16th to endNight
25%24323447%59%
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
2323212347%66%
1432
16th to endDay
2313412237%65%
1710
February1st to 15thDay
2433424338%57%
1648
16th to endDay
1424324247%60%
1580
March1st to 15thDay
3424313447%59%
1830
16th to endDay
5%6%132235%5%7%55%
2209
April1st to 15thDay
45%1242445%7%56%
2150
16th to endDay
9%6%2442445%6%49%
2160
May1st to 15thDay
9%7%24325%6%6%8%42%
2286
16th to endDay
8%313426%5%7%9%47%
2616
June1st to 15thDay
6%2134245%7%10%51%
2520
16th to endDay
3223346%8%9%54%
2520
July1st to 15thDay
5%3145%36%6%6%9%47%
2520
16th to endDay
42135%36%6%9%11%44%
2611
August1st to 15thDay
6%314436%6%8%9%44%
2247
16th to endDay
5%313325%5%7%10%50%
2292
September1st to 15thDay
7%3133236%7%7%53%
2160
16th to endDay
3112223346%67%
1926
October1st to 15thDay
6%212323346%64%
1680
16th to endDay
5%213112235%69%
1721
November1st to 15thDay
121222235%8%66%
1583
16th to endDay
413211236%70%
1608
December1st to 15thDay
2325%423347%60%
1440
16th to endDay
35%3432235%7%58%
1536
January1st to 15thNight
1324322336%66%
2506
16th to endNight
2323323335%67%
2523
February1st to 15thNight
25%2432345%6%58%
2204
16th to endNight
141442334464%
1894
March1st to 15thNight
242331345%7%61%
2127
16th to endNight
4413213347%62%
2013
April1st to 15thNight
6%3132135%47%59%
1798
16th to endNight
11%5%14313346%53%
1800
May1st to 15thNight
11%4133335%5%8%48%
1661
16th to endNight
9%31331446%8%53%
1497
June1st to 15thNight
421121346%9%60%
1440
16th to endNight
33122145%6%8%59%
1440
July1st to 15thNight
6%323446%6%6%9%46%
1440
16th to endNight
5%213436%7%6%12%47%
1554
August1st to 15thNight
6%415%5%35%5%7%8%46%
1713
16th to endNight
6%21443447%10%50%
1910
September1st to 15thNight
7%41442346%9%52%
1800
16th to endNight
4212212436%68%
1868
October1st to 15thNight
7%412212345%63%
1947
16th to endNight
4312222336%67%
2139
November1st to 15thNight
1213212347%68%
2275
16th to endNight
2313212335%70%
2352
December1st to 15thNight
13145%23448%59%
2520
16th to endNight
35%24423346%59%
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
17%39%33%27%7%
1433
16th to endDay
20%27%31%27%11%
1710
February1st to 15thDay
25%310%33%19%6%
1649
16th to endDay
23%37%27%28%10%
1580
March1st to 15thDay
24%28%28%26%10%
1830
16th to endDay
27%410%25%24%7%
2211
April1st to 15thDay
26%311%26%22%9%
2150
16th to endDay
34%410%24%19%7%
2160
May1st to 15thDay
36%5%12%22%19%4
2286
16th to endDay
28%7%15%24%15%8%
2620
June1st to 15thDay
24%414%22%19%14%
2520
16th to endDay
21%5%9%22%25%15%
2520
July1st to 15thDay
30%6%12%21%17%12%
2371
16th to endDay
27%8%15%25%18%4
2447
August1st to 15thDay
29%8%14%23%14%9%
2232
16th to endDay
25%5%12%25%23%7%
2292
September1st to 15thDay
25%5%12%23%20%12%
2160
16th to endDay
17%36%23%34%13%
1926
October1st to 15thDay
21%310%19%33%10%
1680
16th to endDay
18%26%26%31%14%
1721
November1st to 15thDay
17%28%26%29%15%
1583
16th to endDay
16%15%26%34%15%
1608
December1st to 15thDay
24%212%30%24%5%
1440
16th to endDay
25%413%29%20%7%
1536
January1st to 15thNight
20%29%32%25%8%
2506
16th to endNight
21%28%28%28%10%
2523
February1st to 15thNight
25%310%32%21%5%
2214
16th to endNight
23%15%30%28%10%
1894
March1st to 15thNight
22%29%28%29%7%
2127
16th to endNight
23%412%23%29%7%
2013
April1st to 15thNight
24%411%25%22%10%
1798
16th to endNight
32%312%25%18%7%
1800
May1st to 15thNight
33%415%23%17%5%
1662
16th to endNight
27%6%18%24%14%9%
1498
June1st to 15thNight
19%5%18%25%15%16%
1440
16th to endNight
21%6%13%22%21%15%
1440
July1st to 15thNight
32%6%15%22%15%7%
1360
16th to endNight
28%7%17%26%17%3
1455
August1st to 15thNight
32%7%16%22%12%8%
1704
16th to endNight
26%6%13%28%18%5%
1910
September1st to 15thNight
27%5%13%25%18%10%
1800
16th to endNight
18%38%27%30%12%
1868
October1st to 15thNight
22%310%20%31%10%
1947
16th to endNight
18%27%26%30%14%
2139
November1st to 15thNight
16%28%27%28%16%
2275
16th to endNight
18%26%27%32%14%
2352
December1st to 15thNight
23%312%32%22%5%
2520
16th to endNight
25%313%26%24%6%
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
12%10%16%32%23%5%
90
16th to endDay
7%5%22%39%22%2
96
February1st to 15thDay
6%443%32%12%1
90
16th to endDay
8%43%34%11%2
81
March1st to 15thDay
10%33%42%11%
120
16th to endDay
11%20%40%19%5%1
288
April1st to 15thDay
8%18%44%17%8%2
269
16th to endDay
18%21%33%21%4
270
May1st to 15thDay
12%11%27%33%10%4
417
16th to endDay
12%6%29%28%16%6%
517
June1st to 15thDay
6%6%25%29%24%7%
495
16th to endDay
5%6%20%28%31%9%
495
July1st to 15thDay
9%117%25%33%12%
475
16th to endDay
5%211%30%33%17%
470
August1st to 15thDay
10%220%39%18%9%
315
16th to endDay
7%319%41%18%10%
332
September1st to 15thDay
6%432%32%14%8%
315
16th to endDay
4331%27%23%9%
144
October1st to 15thDay
5%423%34%18%13%
90
16th to endDay
6%427%29%25%8%
96
November1st to 15thDay
224%34%31%7%
90
16th to endDay
6%8%33%37%11%2
90
December1st to 15thDay
45%38%43%6%1
90
16th to endDay
6%6%17%55%14%
96
January1st to 15thNight
3423%46%16%5%
900
16th to endNight
3326%47%15%3
795
February1st to 15thNight
3330%49%10%1
704
16th to endNight
3435%43%11%1
632
March1st to 15thNight
4330%42%15%1
720
16th to endNight
7%430%43%12%1
669
April1st to 15thNight
9%6%34%37%11%
539
16th to endNight
15%7%23%43%10%1
540
May1st to 15thNight
12%6%21%40%17%1
540
16th to endNight
10%321%40%22%1
563
June1st to 15thNight
3318%47%23%2
540
16th to endNight
4312%46%31%1
540
July1st to 15thNight
6%18%35%41%5%
510
16th to endNight
5%1233%50%6%
564
August1st to 15thNight
7%15%34%44%5%
539
16th to endNight
6%1338%42%6%
573
September1st to 15thNight
8%19%40%33%7%
540
16th to endNight
5%213%40%31%5%
516
October1st to 15thNight
10%321%36%21%6%
627
16th to endNight
6%317%40%26%6%
731
November1st to 15thNight
2221%46%22%4
875
16th to endNight
5%420%48%17%4
900
December1st to 15thNight
3328%50%11%3
900
16th to endNight
7%5%26%46%12%2
960
Page generated at 2017-09-24 07:15:57. Version ac04

Copyright 2017 A. Danko


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