Many Worlds Cross Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Many Worlds Cross Observatory clear sky chart from 2005-11-05 to 2017-09-24.

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
53%
14777
17%
46940
16%
14752
55%
14752
26%
29640

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
38%
716
10%
2506
10%
716
40%
716
15%
1795
January16th to endNight
46%
768
16%
2601
15%
768
50%
768
20%
1727
February1st to 15thNight
39%
698
8%
2288
8%
697
41%
697
14%
1648
February16th to endNight
40%
632
14%
1951
13%
632
44%
632
18%
1393
March1st to 15thNight
37%
720
9%
2085
7%
720
40%
720
17%
1524
March16th to endNight
36%
768
9%
2049
6%
768
38%
768
18%
1523
April1st to 15thNight
39%
719
10%
1799
5%
719
40%
719
20%
1355
April16th to endNight
50%
684
14%
1764
9%
684
52%
684
28%
1193
May1st to 15thNight
58%
365
17%
1445
17%
365
64%
365
27%
792
May16th to endNight
58%
374
12%
1496
17%
374
61%
374
18%
960
June1st to 15thNight
60%
360
13%
1440
19%
360
64%
360
23%
837
June16th to endNight
72%
360
21%
1440
34%
360
76%
360
40%
656
July1st to 15thNight
87%
340
23%
1360
37%
340
89%
340
59%
490
July16th to endNight
83%
376
34%
1416
47%
354
87%
354
60%
510
August1st to 15thNight
88%
499
33%
1573
31%
497
90%
497
64%
650
August16th to endNight
81%
714
39%
1860
27%
714
83%
714
70%
864
September1st to 15thNight
80%
720
37%
1800
23%
720
82%
720
71%
869
September16th to endNight
67%
692
29%
1883
25%
692
69%
692
43%
1072
October1st to 15thNight
57%
660
20%
1980
18%
660
61%
660
33%
1180
October16th to endNight
52%
704
17%
2159
17%
704
54%
704
24%
1429
November1st to 15thNight
40%
700
13%
2317
12%
700
43%
700
16%
1657
November16th to endNight
41%
720
10%
2520
9%
720
44%
720
17%
1731
December1st to 15thNight
43%
720
12%
2520
11%
720
45%
720
16%
1784
December16th to endNight
33%
768
11%
2688
9%
768
37%
768
13%
2001

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
35%35%5%35%5%6%8%46%
48012
Night
25%25%5%35%6%7%9%46%
47108
Cloud CoverDay
46%25%5%35%5%6%7%48%
48012
Night
35%245%35%5%6%8%48%
47112
TransparencyDay
34%10%12%20%16%6%
47683
Night
33%12%14%20%14%4
46941
SeeingDay
9%18%28%25%13%4
5648
Night
7%11%22%34%20%2
14789

By Month

Percentage Cloud Cover NW (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
4435%6%48%7%10%9%32%
1432
16th to endDay
47%36%6%37%6%7%10%37%
1622
February1st to 15thDay
28%5%7%6%5%7%7%9%13%27%
1576
16th to endDay
28%48%8%47%7%8%10%28%
1523
March1st to 15thDay
26%47%8%49%8%9%10%28%
1875
16th to endDay
26%5%7%8%5%8%8%8%10%27%
2175
April1st to 15thDay
49%5%9%8%46%6%6%7%28%
2149
16th to endDay
37%46%6%35%5%6%9%40%
2195
May1st to 15thDay
5%6%35%5%35%5%6%8%43%
2505
16th to endDay
8%8%48%7%46%447%35%
2615
June1st to 15thDay
6%6%37%6%3446%8%41%
2520
16th to endDay
4414434447%56%
2520
July1st to 15thDay
112323345%70%
2520
16th to endDay
2112213335%73%
2657
August1st to 15thDay
1112323347%68%
2376
16th to endDay
11221233475%
2342
September1st to 15thDay
1212212336%72%
2160
16th to endDay
5%424425%5%5%6%53%
1933
October1st to 15thDay
5%8%35%7%36%5%46%43%
1650
16th to endDay
4435%6%37%6%7%7%43%
1712
November1st to 15thDay
36%37%7%46%8%8%9%33%
1539
16th to endDay
1426%5%49%8%11%12%32%
1440
December1st to 15thDay
36%48%6%47%6%8%11%33%
1440
16th to endDay
27%48%7%5%8%7%9%9%29%
1536
January1st to 15thNight
35%27%6%37%8%10%11%32%
2506
16th to endNight
16%36%5%36%7%9%10%37%
2601
February1st to 15thNight
18%47%6%47%6%8%11%32%
2276
16th to endNight
27%46%5%48%6%7%9%36%
1951
March1st to 15thNight
3425%6%48%8%10%12%32%
2085
16th to endNight
2435%7%5%8%10%9%12%30%
2045
April1st to 15thNight
48%37%7%36%7%8%9%33%
1799
16th to endNight
36%26%5%35%6%5%9%45%
1764
May1st to 15thNight
35%245%235%6%10%49%
1445
16th to endNight
5%6%45%6%36%5%6%7%42%
1496
June1st to 15thNight
5%7%3442445%7%49%
1440
16th to endNight
3313314345%64%
1440
July1st to 15thNight
1112346%75%
1440
16th to endNight
21121112479%
1512
August1st to 15thNight
112212236%75%
1581
16th to endNight
11111223479%
1860
September1st to 15thNight
1221224479%
1800
16th to endNight
321342445%8%60%
1883
October1st to 15thNight
35%245%3345%8%51%
1980
16th to endNight
45%25%6%46%5%6%7%44%
2159
November1st to 15thNight
25%26%7%5%8%9%9%10%32%
2317
16th to endNight
1325%7%47%7%9%11%38%
2520
December1st to 15thNight
26%47%6%46%7%8%11%35%
2520
16th to endNight
15%27%8%5%9%8%10%10%29%
2688

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
5%5%36%6%37%6%8%10%35%
1432
16th to endDay
5%8%36%5%446%6%9%39%
1622
February1st to 15thDay
39%36%6%37%6%8%11%32%
1576
16th to endDay
29%48%7%46%7%7%9%33%
1523
March1st to 15thDay
27%47%6%5%6%8%9%10%29%
1875
16th to endDay
37%46%8%48%8%8%10%30%
2175
April1st to 15thDay
6%12%48%7%35%5%7%7%31%
2149
16th to endDay
5%7%35%5%35%5%6%8%43%
2195
May1st to 15thDay
6%7%25%426%46%7%46%
2505
16th to endDay
11%8%36%6%36%446%37%
2615
June1st to 15thDay
8%6%35%6%3445%8%43%
2520
16th to endDay
4424324446%57%
2520
July1st to 15thDay
11221344471%
2520
16th to endDay
21121333474%
2657
August1st to 15thDay
111232335%5%69%
2376
16th to endDay
11121233476%
2342
September1st to 15thDay
1112212336%74%
2160
16th to endDay
5%423414447%56%
1933
October1st to 15thDay
6%8%25%6%35%447%44%
1650
16th to endDay
5%6%25%5%36%6%6%6%46%
1712
November1st to 15thDay
48%26%7%46%6%7%7%36%
1539
16th to endDay
2435%5%46%9%10%11%35%
1440
December1st to 15thDay
39%46%6%35%5%9%8%36%
1440
16th to endDay
210%46%8%46%6%7%10%31%
1536
January1st to 15thNight
36%36%6%46%7%8%10%35%
2506
16th to endNight
37%35%6%36%6%7%9%39%
2601
February1st to 15thNight
29%47%7%35%6%7%9%35%
2276
16th to endNight
38%36%5%46%5%7%9%39%
1951
March1st to 15thNight
35%25%6%36%7%8%11%36%
2085
16th to endNight
25%36%6%5%6%8%9%11%32%
2049
April1st to 15thNight
6%10%35%5%37%7%6%7%35%
1799
16th to endNight
5%6%34435%5%6%8%45%
1764
May1st to 15thNight
45%13435%5%5%8%51%
1445
16th to endNight
7%7%245%36%6%48%41%
1496
June1st to 15thNight
8%5%25%4245%46%50%
1440
16th to endNight
4312312436%65%
1440
July1st to 15thNight
11212345%76%
1440
16th to endNight
11121212480%
1512
August1st to 15thNight
111211246%75%
1581
16th to endNight
1111122481%
1860
September1st to 15thNight
1111223479%
1800
16th to endNight
431331335%7%61%
1883
October1st to 15thNight
5%6%1443345%6%54%
1980
16th to endNight
5%5%26%6%35%6%5%7%45%
2159
November1st to 15thNight
5%7%26%6%46%7%7%9%35%
2317
16th to endNight
25%35%5%36%7%8%10%40%
2520
December1st to 15thNight
48%46%5%35%6%7%8%39%
2520
16th to endNight
28%46%8%37%7%8%9%32%
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
42%16%17%13%9%1
1432
16th to endDay
40%12%15%17%9%4
1622
February1st to 15thDay
42%17%15%16%7%
1576
16th to endDay
45%16%14%17%5%
1523
March1st to 15thDay
45%17%14%14%6%
1875
16th to endDay
45%17%16%15%4
2175
April1st to 15thDay
50%10%14%19%5%
2149
16th to endDay
38%9%17%21%11%1
2195
May1st to 15thDay
35%9%13%25%14%1
2505
16th to endDay
47%7%13%20%9%
2619
June1st to 15thDay
39%8%11%25%12%2
2520
16th to endDay
26%5%12%30%19%4
2520
July1st to 15thDay
15%410%20%30%18%
2371
16th to endDay
14%36%13%34%28%
2490
August1st to 15thDay
15%39%25%27%17%
2359
16th to endDay
12%36%23%38%15%
2342
September1st to 15thDay
13%36%24%35%16%
2160
16th to endDay
27%7%11%26%19%7%
1933
October1st to 15thDay
39%8%12%16%16%6%
1650
16th to endDay
36%12%14%18%17%1
1712
November1st to 15thDay
44%12%15%17%10%
1539
16th to endDay
37%19%17%14%10%
1440
December1st to 15thDay
41%17%15%18%7%
1440
16th to endDay
48%14%14%15%6%1
1536
January1st to 15thNight
42%17%16%12%9%1
2506
16th to endNight
38%13%15%17%9%6%
2601
February1st to 15thNight
43%16%18%13%8%
2288
16th to endNight
42%15%15%20%6%1
1951
March1st to 15thNight
39%19%17%14%8%
2085
16th to endNight
40%18%21%16%3
2049
April1st to 15thNight
45%13%17%15%7%
1799
16th to endNight
35%12%19%21%10%1
1764
May1st to 15thNight
30%8%18%27%12%2
1446
16th to endNight
40%12%15%24%7%
1496
June1st to 15thNight
34%9%13%27%12%2
1440
16th to endNight
21%5%13%35%18%4
1440
July1st to 15thNight
10%411%29%27%16%
1360
16th to endNight
11%2417%37%25%
1416
August1st to 15thNight
11%38%30%33%13%
1573
16th to endNight
8%47%26%37%13%
1860
September1st to 15thNight
10%36%27%38%14%
1800
16th to endNight
22%9%11%23%23%10%
1883
October1st to 15thNight
29%9%14%21%18%6%
1980
16th to endNight
36%12%15%16%17%1
2159
November1st to 15thNight
43%15%14%16%8%1
2317
16th to endNight
36%19%15%14%12%1
2520
December1st to 15thNight
41%17%13%19%7%
2520
16th to endNight
44%18%14%14%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
16%5%31%28%15%3
60
16th to endDay
12%20%27%28%10%1
150
February1st to 15thDay
16%25%25%25%7%
236
16th to endDay
10%34%26%22%6%
229
March1st to 15thDay
12%39%23%20%3
270
16th to endDay
11%36%31%13%6%
288
April1st to 15thDay
14%25%30%16%9%4
269
16th to endDay
13%28%31%17%6%3
270
May1st to 15thDay
13%23%30%19%11%1
288
16th to endDay
16%14%23%24%16%5%
330
June1st to 15thDay
11%18%27%24%15%4
315
16th to endDay
8%9%34%25%18%3
315
July1st to 15thDay
36%32%33%16%8%
305
16th to endDay
27%33%33%16%6%
327
August1st to 15thDay
26%28%34%17%10%
315
16th to endDay
39%23%27%23%12%
332
September1st to 15thDay
36%27%32%23%6%
315
16th to endDay
5%15%24%34%18%1
288
October1st to 15thDay
12%20%24%25%15%1
255
16th to endDay
15%19%26%22%13%2
224
November1st to 15thDay
8%13%33%37%42
83
16th to endDay
6%30%28%20%13%1
60
December1st to 15thDay
15%25%43%16%
60
16th to endDay
12%15%31%31%7%1
64
January1st to 15thNight
7%18%29%25%15%2
720
16th to endNight
9%13%23%31%19%3
768
February1st to 15thNight
8%17%24%32%15%
704
16th to endNight
7%15%31%34%11%1
632
March1st to 15thNight
7%22%27%28%12%2
720
16th to endNight
6%19%32%27%13%
768
April1st to 15thNight
11%14%28%28%15%1
719
16th to endNight
10%9%26%30%19%3
684
May1st to 15thNight
9%5%23%38%21%1
366
16th to endNight
10%6%18%36%25%2
375
June1st to 15thNight
9%5%19%42%21%1
360
16th to endNight
6%115%53%22%
360
July1st to 15thNight
17%57%32%
340
16th to endNight
211%55%30%1
376
August1st to 15thNight
35%43%42%5%
499
16th to endNight
1211%40%39%4
714
September1st to 15thNight
1113%39%37%6%
720
16th to endNight
5%417%38%28%5%
692
October1st to 15thNight
8%6%21%35%22%4
660
16th to endNight
9%11%22%31%19%6%
704
November1st to 15thNight
9%14%31%31%11%1
700
16th to endNight
7%23%23%26%15%3
720
December1st to 15thNight
10%14%25%31%16%1
720
16th to endNight
6%24%29%24%13%
768
Page generated at 2017-09-25 06:02:19. Version ac04

Copyright 2017 A. Danko


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