WeBeWebbiers Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the WeBeWebbiers Observatory 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
79%
16258
33%
47046
30%
16216
80%
16216
51%
23844

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
72%
716
30%
2327
31%
716
75%
716
43%
1179
January16th to endNight
65%
768
33%
2304
29%
768
71%
768
39%
1278
February1st to 15thNight
74%
697
33%
2107
35%
697
77%
697
46%
1089
February16th to endNight
65%
632
28%
1895
31%
632
66%
632
32%
1143
March1st to 15thNight
75%
720
30%
2160
34%
720
77%
720
44%
1146
March16th to endNight
76%
768
28%
2032
26%
768
77%
768
48%
1127
April1st to 15thNight
69%
719
26%
1799
18%
719
70%
719
44%
1073
April16th to endNight
74%
720
31%
1800
20%
720
75%
720
52%
1008
May1st to 15thNight
76%
581
29%
1661
22%
581
78%
581
47%
898
May16th to endNight
76%
561
27%
1685
23%
561
77%
561
46%
891
June1st to 15thNight
85%
540
30%
1620
27%
540
86%
540
57%
769
June16th to endNight
94%
540
37%
1620
34%
540
94%
540
79%
632
July1st to 15thNight
93%
510
29%
1530
25%
510
93%
510
66%
665
July16th to endNight
89%
625
32%
1649
25%
587
89%
587
60%
790
August1st to 15thNight
92%
717
35%
1790
23%
713
92%
713
71%
861
August16th to endNight
93%
764
42%
1910
29%
764
93%
764
74%
902
September1st to 15thNight
89%
720
38%
1865
32%
720
89%
720
67%
899
September16th to endNight
88%
688
45%
1903
44%
688
89%
688
72%
832
October1st to 15thNight
81%
660
37%
1815
35%
660
83%
660
58%
899
October16th to endNight
78%
704
38%
2123
39%
704
81%
704
53%
1019
November1st to 15thNight
85%
700
35%
2275
40%
700
86%
700
53%
1030
November16th to endNight
77%
720
34%
2340
37%
720
79%
720
46%
1145
December1st to 15thNight
72%
720
33%
2340
35%
720
74%
720
39%
1227
December16th to endNight
65%
768
32%
2496
32%
768
69%
768
38%
1342

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
3312212336%67%
47847
Night
4313313346%65%
47252
TransparencyDay
19%26%16%27%28%
47548
Night
21%26%16%25%27%
47052
SeeingDay
46%21%38%21%7%
5937
Night
5%17%32%40%11%
16272

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
6%323323345%60%
1611
16th to endDay
9%413223436%58%
1917
February1st to 15thDay
6%313223446%61%
1751
16th to endDay
9%425%423346%52%
1579
March1st to 15thDay
42122235%5%8%61%
1800
16th to endDay
331232345%8%61%
2187
April1st to 15thDay
5%32432435%6%58%
2149
16th to endDay
2312112236%69%
2160
May1st to 15thDay
2412222337%66%
2289
16th to endDay
2413213337%65%
2429
June1st to 15thDay
3411212235%71%
2340
16th to endDay
1111112385%
2340
July1st to 15thDay
122222335%71%
2340
16th to endDay
122213349%67%
2403
August1st to 15thDay
1111223480%
2160
16th to endDay
1121223478%
2292
September1st to 15thDay
11121223477%
2094
16th to endDay
11221122479%
1893
October1st to 15thDay
3213322246%67%
1815
16th to endDay
3312213235%69%
1746
November1st to 15thDay
312223245%70%
1584
16th to endDay
5%313212347%64%
1620
December1st to 15thDay
5%21332345%9%57%
1620
16th to endDay
9%423312336%57%
1728
January1st to 15thNight
5%313323346%61%
2327
16th to endNight
7%424423436%56%
2304
February1st to 15thNight
5%423223445%62%
2101
16th to endNight
10%5%24424435%51%
1895
March1st to 15thNight
432332335%7%60%
2160
16th to endNight
4422313349%58%
2032
April1st to 15thNight
6%5%24323448%55%
1799
16th to endNight
4313313235%65%
1800
May1st to 15thNight
2423323339%62%
1661
16th to endNight
25%2432345%7%60%
1684
June1st to 15thNight
1213213335%69%
1620
16th to endNight
111112385%
1620
July1st to 15thNight
112112347%72%
1620
16th to endNight
211131345%7%68%
1762
August1st to 15thNight
21112247%74%
1800
16th to endNight
11111223479%
1910
September1st to 15thNight
1312212136%73%
1865
16th to endNight
12211112380%
1903
October1st to 15thNight
2213313335%69%
1815
16th to endNight
331321334467%
2123
November1st to 15thNight
2212213335%71%
2275
16th to endNight
4323323337%62%
2340
December1st to 15thNight
6%414323347%57%
2340
16th to endNight
9%413313246%58%
2496

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
26%25%13%25%26%
1612
16th to endDay
27%47%13%18%28%
1917
February1st to 15thDay
25%36%13%24%26%
1751
16th to endDay
34%37%16%24%12%
1579
March1st to 15thDay
21%47%21%23%21%
1800
16th to endDay
22%411%24%22%15%
2187
April1st to 15thDay
26%38%24%25%12%
2149
16th to endDay
18%28%22%30%17%
2160
May1st to 15thDay
20%37%22%27%19%
2289
16th to endDay
19%36%24%32%12%
2432
June1st to 15thDay
18%2417%32%25%
2340
16th to endDay
7%126%25%56%
2340
July1st to 15thDay
14%25%11%25%41%
2201
16th to endDay
14%38%21%28%23%
2253
August1st to 15thDay
8%1312%34%38%
2146
16th to endDay
11%2410%33%38%
2292
September1st to 15thDay
11%239%33%39%
2094
16th to endDay
11%1111%34%39%
1893
October1st to 15thDay
19%1418%27%27%
1815
16th to endDay
18%35%10%21%40%
1746
November1st to 15thDay
17%27%15%23%34%
1584
16th to endDay
21%35%13%21%34%
1620
December1st to 15thDay
25%310%17%17%26%
1620
16th to endDay
30%38%15%23%18%
1728
January1st to 15thNight
24%36%12%22%29%
2327
16th to endNight
30%28%11%16%30%
2304
February1st to 15thNight
24%27%15%21%27%
2112
16th to endNight
37%35%14%24%15%
1895
March1st to 15thNight
25%47%20%20%21%
2160
16th to endNight
24%411%22%21%16%
2032
April1st to 15thNight
29%39%23%20%13%
1799
16th to endNight
23%27%23%23%19%
1800
May1st to 15thNight
23%48%20%23%19%
1662
16th to endNight
24%39%24%24%12%
1685
June1st to 15thNight
17%27%18%33%21%
1620
16th to endNight
6%137%30%49%
1620
July1st to 15thNight
12%15%11%29%39%
1530
16th to endNight
14%48%24%30%17%
1649
August1st to 15thNight
11%1317%38%26%
1790
16th to endNight
9%2312%33%38%
1910
September1st to 15thNight
13%1410%32%36%
1865
16th to endNight
11%212%33%39%
1903
October1st to 15thNight
18%26%18%31%23%
1815
16th to endNight
20%2412%20%39%
2123
November1st to 15thNight
17%35%15%22%36%
2275
16th to endNight
23%26%14%18%34%
2340
December1st to 15thNight
27%37%16%19%25%
2340
16th to endNight
29%39%13%23%20%
2496

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
27%11%35%24%1
90
16th to endDay
12%9%23%36%16%2
285
February1st to 15thDay
7%6%27%33%22%3
266
16th to endDay
12%14%28%31%11%1
238
March1st to 15thDay
7%10%24%31%19%7%
270
16th to endDay
411%34%27%14%6%
288
April1st to 15thDay
6%13%33%27%13%4
269
16th to endDay
115%35%34%8%4
270
May1st to 15thDay
411%30%34%13%4
288
16th to endDay
48%28%36%16%4
330
June1st to 15thDay
3324%37%23%7%
315
16th to endDay
115%38%29%14%
315
July1st to 15thDay
118%44%29%14%
305
16th to endDay
35%43%33%13%
327
August1st to 15thDay
211%50%26%8%
315
16th to endDay
216%49%26%14%
332
September1st to 15thDay
2119%50%20%5%
315
16th to endDay
2324%42%19%7%
284
October1st to 15thDay
310%27%37%19%1
255
16th to endDay
4223%40%21%7%
214
November1st to 15thDay
412%28%34%20%
90
16th to endDay
5%5%15%38%27%6%
90
December1st to 15thDay
3213%38%35%6%
90
16th to endDay
15%219%35%26%1
96
January1st to 15thNight
7%110%41%28%10%
720
16th to endNight
10%213%37%28%7%
768
February1st to 15thNight
7%19%41%30%8%
704
16th to endNight
13%210%40%25%6%
632
March1st to 15thNight
8%19%42%31%6%
720
16th to endNight
5%27%39%35%9%
768
April1st to 15thNight
9%211%41%29%5%
719
16th to endNight
5%311%37%34%8%
720
May1st to 15thNight
429%36%39%8%
582
16th to endNight
4310%36%39%5%
563
June1st to 15thNight
216%36%46%6%
540
16th to endNight
1230%59%6%
540
July1st to 15thNight
19%65%13%
510
16th to endNight
2112%63%18%
625
August1st to 15thNight
114%65%16%
717
16th to endNight
110%63%24%
764
September1st to 15thNight
3118%57%19%
720
16th to endNight
3328%48%16%
688
October1st to 15thNight
316%37%38%11%
660
16th to endNight
6%16%29%35%19%
704
November1st to 15thNight
415%38%36%14%
700
16th to endNight
5%27%36%34%13%
720
December1st to 15thNight
9%19%39%29%10%
720
16th to endNight
11%212%41%23%8%
768
Page generated at 2017-09-24 06:15:55. Version ac04

Copyright 2017 A. Danko


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