C.O.A.M.N.D.
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the C.O.A.M.N.D. clear sky chart from 2005-11-05 to 2017-08-12.

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
23%
14522
11%
46480
6%
14490
29%
14490
12%
35381

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
9%
720
8%
2506
3%
716
15%
716
5%
2099
January16th to endNight
14%
768
9%
2688
3%
768
23%
768
7%
2136
February1st to 15thNight
14%
704
8%
2347
2%
701
21%
701
7%
1911
February16th to endNight
13%
631
11%
1893
3%
631
22%
631
10%
1495
March1st to 15thNight
17%
720
13%
2142
7%
720
25%
720
12%
1635
March16th to endNight
27%
768
17%
2047
7%
768
33%
768
16%
1515
April1st to 15thNight
21%
703
14%
1781
4%
703
27%
703
15%
1391
April16th to endNight
24%
540
14%
1620
6%
540
30%
540
16%
1165
May1st to 15thNight
27%
489
12%
1569
9%
489
34%
489
14%
1161
May16th to endNight
29%
375
10%
1446
8%
374
37%
374
12%
1038
June1st to 15thNight
28%
360
7%
1260
4%
360
33%
360
11%
955
June16th to endNight
38%
360
7%
1260
7%
360
41%
360
16%
898
July1st to 15thNight
40%
340
7%
1300
9%
340
42%
340
16%
878
July16th to endNight
43%
376
8%
1418
11%
354
45%
354
15%
955
August1st to 15thNight
45%
430
10%
1479
10%
428
48%
428
18%
1020
August16th to endNight
41%
568
14%
1618
9%
568
45%
568
25%
1085
September1st to 15thNight
35%
660
10%
1710
5%
660
38%
660
23%
1220
September16th to endNight
37%
657
17%
1815
10%
657
42%
657
26%
1195
October1st to 15thNight
26%
660
16%
1899
8%
660
34%
660
17%
1376
October16th to endNight
16%
704
7%
2288
4%
704
21%
704
8%
1830
November1st to 15thNight
24%
700
14%
2277
10%
700
30%
700
11%
1737
November16th to endNight
20%
741
11%
2549
7%
741
26%
741
9%
2001
December1st to 15thNight
10%
750
4%
2700
1%
750
13%
750
4%
2295
December16th to endNight
11%
798
8%
2868
3%
798
17%
798
5%
2390

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
23%12%47%6%34445%24%
47489
Night
20%12%5%8%6%3444426%
46650
TransparencyDay
61%5%10%15%6%
47177
Night
59%5%10%16%7%
46480
SeeingDay
29%15%26%18%8%1
6027
Night
26%16%26%21%7%
14522

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
17%17%7%10%9%35%43316%
1432
16th to endDay
10%16%8%11%9%445%5%419%
1536
February1st to 15thDay
11%16%8%11%11%5%5%44415%
1511
16th to endDay
14%17%8%12%7%35%33319%
1580
March1st to 15thDay
18%16%6%8%5%3343424%
1807
16th to endDay
17%13%5%8%6%25%33429%
2175
April1st to 15thDay
24%15%45%42332429%
2167
16th to endDay
22%11%36%423345%31%
2340
May1st to 15thDay
25%10%36%5%35%34427%
2391
16th to endDay
26%9%46%6%35%445%23%
2667
June1st to 15thDay
28%8%35%6%35%45%6%22%
2700
16th to endDay
26%9%36%6%35%5%45%22%
2700
July1st to 15thDay
22%7%36%6%45%5%5%7%25%
2576
16th to endDay
24%8%26%6%36%5%5%7%23%
2654
August1st to 15thDay
25%7%26%7%445%5%7%22%
2372
16th to endDay
20%7%26%5%34447%33%
2231
September1st to 15thDay
27%6%24423346%33%
1920
16th to endDay
23%7%24423435%38%
1815
October1st to 15thDay
26%14%35%32333428%
1728
16th to endDay
30%19%26%42343317%
1584
November1st to 15thDay
23%18%5%6%43333324%
1581
16th to endDay
24%18%6%8%41223423%
1409
December1st to 15thDay
24%23%6%10%7%2333214%
1260
16th to endDay
23%18%9%10%5%2432315%
1353
January1st to 15thNight
18%16%7%12%9%2433316%
2506
16th to endNight
10%15%8%10%8%45%6%6%418%
2688
February1st to 15thNight
10%14%7%12%11%6%6%43319%
2346
16th to endNight
14%19%6%11%7%2423323%
1893
March1st to 15thNight
19%13%5%7%6%2443428%
2129
16th to endNight
14%11%5%8%5%34445%32%
2047
April1st to 15thNight
23%14%46%43344426%
1781
16th to endNight
21%9%35%5%24345%34%
1620
May1st to 15thNight
24%9%35%5%25%44429%
1569
16th to endNight
25%8%37%5%24435%30%
1444
June1st to 15thNight
26%9%36%5%45%45%424%
1260
16th to endNight
20%8%26%5%35%5%46%30%
1260
July1st to 15thNight
19%6%36%5%35%45%6%33%
1380
16th to endNight
19%6%35%6%35%45%6%34%
1514
August1st to 15thNight
19%6%25%5%35%5%5%8%32%
1489
16th to endNight
20%5%2343445%8%37%
1618
September1st to 15thNight
25%5%24414345%36%
1710
16th to endNight
22%413323346%43%
1815
October1st to 15thNight
25%9%35%42435%431%
1899
16th to endNight
28%16%36%6%2433322%
2288
November1st to 15thNight
20%14%46%6%34435%25%
2277
16th to endNight
22%16%6%9%5%2433324%
2549
December1st to 15thNight
23%18%8%12%6%2422215%
2700
16th to endNight
21%19%6%10%6%3432317%
2868

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
71%46%11%5%
1433
16th to endDay
64%6%6%15%7%
1536
February1st to 15thDay
71%48%10%5%
1514
16th to endDay
69%35%12%6%1
1580
March1st to 15thDay
63%37%13%10%
1817
16th to endDay
57%48%16%10%1
2175
April1st to 15thDay
59%28%17%9%3
2167
16th to endDay
55%47%17%11%2
2340
May1st to 15thDay
60%39%17%8%
2391
16th to endDay
61%5%10%15%6%
2671
June1st to 15thDay
61%6%9%16%5%
2700
16th to endDay
62%5%11%14%5%
2700
July1st to 15thDay
55%6%15%17%5%
2427
16th to endDay
60%6%12%16%4
2487
August1st to 15thDay
59%8%15%12%3
2358
16th to endDay
48%5%16%22%6%
2231
September1st to 15thDay
51%5%14%18%10%
1920
16th to endDay
48%411%25%9%
1815
October1st to 15thDay
60%311%19%5%
1728
16th to endDay
70%38%13%3
1584
November1st to 15thDay
64%410%13%6%
1581
16th to endDay
66%48%14%5%
1409
December1st to 15thDay
76%37%10%2
1260
16th to endDay
75%349%6%
1353
January1st to 15thNight
72%5%6%11%4
2506
16th to endNight
63%7%7%14%6%
2688
February1st to 15thNight
68%5%7%13%5%
2347
16th to endNight
65%37%13%9%
1893
March1st to 15thNight
58%6%7%17%8%1
2142
16th to endNight
53%5%8%18%11%1
2047
April1st to 15thNight
59%45%17%11%2
1781
16th to endNight
52%5%9%16%13%2
1620
May1st to 15thNight
55%6%9%16%11%
1569
16th to endNight
56%5%12%16%8%
1446
June1st to 15thNight
60%5%9%16%6%
1260
16th to endNight
51%7%14%19%7%
1260
July1st to 15thNight
47%8%17%18%7%
1300
16th to endNight
49%6%16%19%8%
1418
August1st to 15thNight
47%8%18%22%2
1479
16th to endNight
42%7%18%26%5%
1618
September1st to 15thNight
48%5%15%21%7%1
1710
16th to endNight
41%5%15%27%9%
1815
October1st to 15thNight
53%411%21%8%
1899
16th to endNight
66%49%14%4
2288
November1st to 15thNight
59%6%12%14%7%
2277
16th to endNight
65%48%16%5%
2549
December1st to 15thNight
75%37%10%2
2700
16th to endNight
72%47%9%6%
2868

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
23%23%46%6%
60
16th to endDay
20%28%39%9%11
64
February1st to 15thDay
29%16%28%18%6%
148
16th to endDay
25%20%31%17%5%
239
March1st to 15thDay
27%25%27%15%4
270
16th to endDay
26%19%20%17%12%3
288
April1st to 15thDay
33%19%24%15%5%1
270
16th to endDay
28%18%28%16%5%2
270
May1st to 15thDay
35%11%32%13%5%1
288
16th to endDay
29%16%30%17%5%
380
June1st to 15thDay
34%12%23%20%8%
495
16th to endDay
30%9%29%20%9%
495
July1st to 15thDay
26%11%31%20%10%
361
16th to endDay
26%8%31%23%7%1
326
August1st to 15thDay
27%9%28%20%12%2
297
16th to endDay
24%8%25%25%11%5%
268
September1st to 15thDay
24%10%23%22%12%5%
255
16th to endDay
25%15%25%13%14%5%
254
October1st to 15thDay
33%14%20%18%7%4
245
16th to endDay
40%17%21%12%6%
240
November1st to 15thDay
27%25%17%20%8%1
235
16th to endDay
32%18%20%18%8%1
155
December1st to 15thDay
41%23%25%6%3
60
16th to endDay
45%26%21%6%
64
January1st to 15thNight
26%25%30%14%2
720
16th to endNight
21%20%34%19%3
768
February1st to 15thNight
16%25%34%17%4
704
16th to endNight
26%19%31%16%5%
631
March1st to 15thNight
25%19%32%18%3
720
16th to endNight
19%20%27%23%8%
768
April1st to 15thNight
30%17%25%19%6%
703
16th to endNight
29%12%27%21%7%
540
May1st to 15thNight
26%13%26%22%10%
489
16th to endNight
27%8%25%29%8%
375
June1st to 15thNight
30%8%25%25%10%
360
16th to endNight
22%8%26%31%11%
360
July1st to 15thNight
20%7%25%30%14%
340
16th to endNight
20%421%39%13%
376
August1st to 15thNight
20%5%20%30%22%
430
16th to endNight
20%6%24%32%14%1
568
September1st to 15thNight
25%7%25%28%10%2
660
16th to endNight
23%10%24%28%10%1
657
October1st to 15thNight
27%14%25%23%8%1
660
16th to endNight
37%18%21%15%6%
704
November1st to 15thNight
26%20%24%20%7%
700
16th to endNight
31%19%23%17%6%1
741
December1st to 15thNight
31%23%27%13%4
750
16th to endNight
33%23%22%14%5%
798
Page generated at 2017-08-13 14:16:35. Version ac04

Copyright 2017 A. Danko


C.O.A.M.N.D. Clear Sky Chart | Charts Home