Anadromada Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Anadromada Observatory clear sky chart from 2005-11-05 to 2017-09-10.

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
63%
15189
34%
46772
25%
15149
73%
15149
47%
22887

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
63%
717
33%
2327
29%
716
71%
716
46%
1126
January16th to endNight
59%
768
37%
2496
30%
768
71%
768
43%
1195
February1st to 15thNight
63%
700
36%
2228
28%
697
75%
697
52%
995
February16th to endNight
50%
632
42%
1819
25%
632
68%
632
51%
867
March1st to 15thNight
53%
720
39%
1980
21%
720
68%
720
52%
971
March16th to endNight
56%
768
39%
2112
20%
768
71%
768
55%
1016
April1st to 15thNight
44%
563
37%
1822
17%
563
66%
563
46%
813
April16th to endNight
43%
540
42%
1800
23%
540
69%
540
55%
707
May1st to 15thNight
50%
539
33%
1799
23%
539
65%
539
56%
739
May16th to endNight
49%
561
35%
1707
21%
561
64%
561
51%
787
June1st to 15thNight
65%
540
31%
1620
24%
540
71%
540
58%
736
June16th to endNight
70%
540
23%
1620
18%
540
74%
540
46%
826
July1st to 15thNight
77%
510
19%
1530
16%
510
78%
510
36%
892
July16th to endNight
69%
564
19%
1593
17%
531
70%
531
29%
996
August1st to 15thNight
72%
539
16%
1701
17%
536
72%
536
26%
1090
August16th to endNight
75%
573
25%
1910
27%
573
77%
573
31%
1105
September1st to 15thNight
75%
525
25%
1750
28%
525
76%
525
30%
1027
September16th to endNight
78%
618
36%
1821
28%
618
83%
618
53%
891
October1st to 15thNight
72%
660
36%
1980
27%
660
77%
660
55%
924
October16th to endNight
77%
704
41%
2112
30%
704
84%
704
64%
914
November1st to 15thNight
73%
700
43%
2100
31%
700
82%
700
62%
920
November16th to endNight
67%
720
42%
2160
32%
720
76%
720
52%
1038
December1st to 15thNight
64%
720
39%
2289
32%
720
73%
720
48%
1090
December16th to endNight
59%
768
36%
2496
29%
768
69%
768
42%
1222

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
321332345%7%64%
47840
Night
321332345%7%63%
46978
TransparencyDay
19%36%14%26%27%
47536
Night
20%37%15%26%26%
46783
SeeingDay
6%11%21%30%22%8%
5110
Night
46%19%39%26%3
15199

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
3313323345%65%
1611
16th to endDay
7%213323345%61%
1728
February1st to 15thDay
2212313345%69%
1624
16th to endDay
2213213335%70%
1652
March1st to 15thDay
3213323345%67%
1980
16th to endDay
211112235%73%
2112
April1st to 15thDay
2212212336%72%
2126
16th to endDay
1111112482%
2160
May1st to 15thDay
111212336%74%
2151
16th to endDay
1121323477%
2402
June1st to 15thDay
111212345%73%
2340
16th to endDay
211232445%8%62%
2340
July1st to 15thDay
5%2145%36%6%8%12%44%
2340
16th to endDay
6%435%6%47%7%9%11%34%
2467
August1st to 15thDay
4315%5%46%6%8%11%42%
2248
16th to endDay
5%2145%35%5%8%10%46%
2292
September1st to 15thDay
7%414435%5%8%8%46%
2097
16th to endDay
5%22212346%68%
1805
October1st to 15thDay
221331235%5%68%
1650
16th to endDay
31111232476%
1760
November1st to 15thDay
122213236%72%
1759
16th to endDay
5%322212236%69%
1800
December1st to 15thDay
4212212345%67%
1668
16th to endDay
3423322347%63%
1728
January1st to 15thNight
4423323336%64%
2327
16th to endNight
6%312312345%63%
2496
February1st to 15thNight
2212212346%68%
2227
16th to endNight
3311212336%69%
1819
March1st to 15thNight
322222336%68%
1980
16th to endNight
321221323474%
2112
April1st to 15thNight
3211212345%70%
1822
16th to endNight
11111223478%
1800
May1st to 15thNight
212213335%74%
1799
16th to endNight
221221224471%
1707
June1st to 15thNight
211231336%6%67%
1620
16th to endNight
12135%245%8%9%55%
1620
July1st to 15thNight
3124437%9%10%14%38%
1620
16th to endNight
5%5%35%6%36%6%8%13%34%
1701
August1st to 15thNight
5%425%6%48%8%8%12%33%
1710
16th to endNight
5%3245%45%6%9%10%42%
1910
September1st to 15thNight
6%4245%35%6%7%9%45%
1750
16th to endNight
321322245%7%64%
1821
October1st to 15thNight
2212312346%69%
1980
16th to endNight
111212335%76%
2112
November1st to 15thNight
1112212235%75%
2100
16th to endNight
5%213212235%69%
2160
December1st to 15thNight
4214212346%65%
2289
16th to endNight
4323323335%64%
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
20%35%19%32%18%
1612
16th to endDay
25%35%13%35%18%
1728
February1st to 15thDay
17%25%14%27%32%
1625
16th to endDay
17%2212%36%28%
1652
March1st to 15thDay
18%2310%31%33%
1980
16th to endDay
13%139%31%39%
2112
April1st to 15thDay
14%138%35%36%
2126
16th to endDay
8%126%25%55%
2160
May1st to 15thDay
11%248%27%45%
2151
16th to endDay
10%248%23%49%
2405
June1st to 15thDay
12%237%22%51%
2340
16th to endDay
18%47%11%20%38%
2340
July1st to 15thDay
26%7%14%19%18%13%
2201
16th to endDay
36%10%16%23%12%1
2312
August1st to 15thDay
31%8%16%21%15%5%
2233
16th to endDay
30%8%12%18%19%10%
2292
September1st to 15thDay
31%6%11%20%18%11%
2097
16th to endDay
17%26%16%33%23%
1805
October1st to 15thDay
17%37%13%26%32%
1650
16th to endDay
14%1316%30%33%
1760
November1st to 15thDay
14%2417%31%28%
1759
16th to endDay
18%1316%33%26%
1800
December1st to 15thDay
18%26%22%32%16%
1668
16th to endDay
21%27%24%31%11%
1728
January1st to 15thNight
22%26%15%33%19%
2327
16th to endNight
22%2319%33%18%
2496
February1st to 15thNight
16%3415%30%29%
2237
16th to endNight
16%2413%35%27%
1819
March1st to 15thNight
17%25%13%29%32%
1980
16th to endNight
16%139%32%36%
2112
April1st to 15thNight
16%248%32%35%
1822
16th to endNight
11%138%25%49%
1800
May1st to 15thNight
13%1310%23%47%
1800
16th to endNight
17%348%23%42%
1708
June1st to 15thNight
15%35%9%17%48%
1620
16th to endNight
21%5%9%14%15%34%
1620
July1st to 15thNight
26%10%17%20%13%12%
1530
16th to endNight
35%8%21%22%10%1
1593
August1st to 15thNight
38%8%17%18%12%4
1701
16th to endNight
31%8%13%20%15%10%
1910
September1st to 15thNight
32%8%12%19%14%12%
1750
16th to endNight
19%37%18%30%21%
1821
October1st to 15thNight
16%38%14%24%32%
1980
16th to endNight
12%2416%27%37%
2112
November1st to 15thNight
13%2315%33%31%
2100
16th to endNight
19%2312%30%31%
2160
December1st to 15thNight
20%36%21%31%18%
2289
16th to endNight
22%35%23%33%11%
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
13%10%30%30%15%1
90
16th to endDay
7%14%25%29%14%9%
96
February1st to 15thDay
5%8%11%35%30%8%
90
16th to endDay
5%32%22%24%10%4
153
March1st to 15thDay
6%18%34%24%12%3
270
16th to endDay
8%22%28%25%9%4
288
April1st to 15thDay
6%24%31%23%11%1
269
16th to endDay
5%28%35%22%6%1
270
May1st to 15thDay
5%24%34%23%11%
288
16th to endDay
215%34%35%10%
330
June1st to 15thDay
38%27%33%21%4
315
16th to endDay
3217%41%26%8%
315
July1st to 15thDay
5%17%40%34%10%
305
16th to endDay
7%17%26%33%22%
327
August1st to 15thDay
46%32%36%19%
315
16th to endDay
46%30%40%18%
332
September1st to 15thDay
10%210%35%32%8%
294
16th to endDay
8%418%32%28%7%
211
October1st to 15thDay
4321%28%22%20%
90
16th to endDay
6%20%26%29%17%
96
November1st to 15thDay
5%15%24%23%23%7%
90
16th to endDay
18%16%20%26%16%1
90
December1st to 15thDay
6%12%14%25%34%6%
90
16th to endDay
10%16%25%34%13%
96
January1st to 15thNight
6%320%43%22%2
720
16th to endNight
8%7%18%42%20%2
768
February1st to 15thNight
38%21%42%21%2
704
16th to endNight
412%29%40%11%
632
March1st to 15thNight
5%11%25%38%16%1
720
16th to endNight
312%25%42%14%1
768
April1st to 15thNight
5%16%31%34%10%1
563
16th to endNight
215%36%33%10%1
540
May1st to 15thNight
311%32%41%10%
540
16th to endNight
37%35%39%13%
563
June1st to 15thNight
3225%48%19%
540
16th to endNight
2118%47%29%
540
July1st to 15thNight
37%38%44%4
510
16th to endNight
6%16%29%47%7%
564
August1st to 15thNight
6%1327%51%8%
539
16th to endNight
7%5%23%54%8%
573
September1st to 15thNight
9%436%46%2
525
16th to endNight
419%43%37%4
618
October1st to 15thNight
3115%47%28%2
660
16th to endNight
2214%39%35%5%
704
November1st to 15thNight
1317%39%32%5%
700
16th to endNight
7%416%38%29%4
720
December1st to 15thNight
6%5%17%41%25%3
720
16th to endNight
5%8%20%45%17%3
768
Page generated at 2017-09-11 17:35:25. Version ac04

Copyright 2017 A. Danko


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