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 2018-02-22.

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
24%
15326
11%
48952
6%
15294
29%
15294
12%
37226

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
10%
780
8%
2716
4%
776
15%
776
5%
2266
January16th to endNight
14%
832
10%
2912
2%
832
23%
832
7%
2306
February1st to 15thNight
13%
764
8%
2547
2%
761
21%
761
6%
2088
February16th to endNight
13%
659
12%
1976
3%
659
23%
659
9%
1561
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
44%
441
10%
1512
9%
439
47%
439
18%
1047
August16th to endNight
42%
620
16%
1766
10%
620
46%
620
25%
1182
September1st to 15thNight
36%
720
11%
1866
5%
720
38%
720
23%
1320
September16th to endNight
41%
717
18%
1980
11%
717
45%
717
27%
1296
October1st to 15thNight
27%
720
15%
2072
7%
720
35%
720
18%
1485
October16th to endNight
17%
768
8%
2496
4%
768
22%
768
9%
1981
November1st to 15thNight
24%
760
14%
2472
10%
760
30%
760
11%
1878
November16th to endNight
19%
812
11%
2762
7%
812
25%
812
9%
2164
December1st to 15thNight
10%
825
4%
2925
1%
825
14%
825
4%
2482
December16th to endNight
11%
877
9%
3107
3%
877
18%
877
5%
2579

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
22%12%47%6%34445%24%
49297
Night
20%12%48%6%3444426%
49122
TransparencyDay
61%5%10%16%6%
48985
Night
59%5%10%16%7%
48952
SeeingDay
29%15%26%17%8%1
6603
Night
26%16%26%21%8%
15326

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
18%16%7%11%9%35%43316%
1552
16th to endDay
10%16%8%11%9%445%5%420%
1664
February1st to 15thDay
11%17%8%11%11%5%5%43415%
1641
16th to endDay
15%16%8%12%7%25%34319%
1644
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%
2424
16th to endDay
20%7%26%5%345%47%33%
2435
September1st to 15thDay
27%6%24423345%34%
2094
16th to endDay
21%7%24423446%39%
1980
October1st to 15thDay
26%13%35%32333429%
1885
16th to endDay
29%18%26%42333419%
1728
November1st to 15thDay
23%17%5%6%43333324%
1716
16th to endDay
24%18%6%8%42233421%
1526
December1st to 15thDay
22%22%6%10%7%3333214%
1365
16th to endDay
22%18%9%10%5%3442315%
1466
January1st to 15thNight
19%16%7%12%9%2433316%
2716
16th to endNight
10%15%7%10%8%45%6%5%418%
2912
February1st to 15thNight
10%15%7%11%11%6%6%43318%
2546
16th to endNight
14%19%6%11%7%2423323%
1976
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%31%
1522
16th to endNight
19%5%2443445%8%38%
1766
September1st to 15thNight
25%5%25%414445%37%
1866
16th to endNight
21%413323346%44%
1980
October1st to 15thNight
24%9%25%42435%433%
2072
16th to endNight
29%15%26%5%2433322%
2496
November1st to 15thNight
20%14%46%6%34435%26%
2472
16th to endNight
21%16%6%9%5%2333324%
2762
December1st to 15thNight
22%18%9%11%6%3322315%
2925
16th to endNight
20%18%7%10%6%4432317%
3107

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%
1553
16th to endDay
64%6%6%15%7%
1664
February1st to 15thDay
71%47%10%4
1644
16th to endDay
69%35%13%6%1
1644
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
2410
16th to endDay
49%5%15%23%6%
2435
September1st to 15thDay
51%413%19%10%
2094
16th to endDay
46%413%25%9%
1980
October1st to 15thDay
58%311%20%5%
1885
16th to endDay
69%38%14%3
1728
November1st to 15thDay
64%410%14%6%
1716
16th to endDay
67%47%13%5%
1526
December1st to 15thDay
75%37%10%2
1365
16th to endDay
74%448%6%
1466
January1st to 15thNight
71%5%6%11%4
2716
16th to endNight
63%7%7%14%6%
2912
February1st to 15thNight
68%5%7%12%5%
2547
16th to endNight
65%37%13%9%
1976
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
48%8%18%22%2
1512
16th to endNight
41%7%17%27%5%
1766
September1st to 15thNight
48%5%14%23%8%1
1866
16th to endNight
40%5%17%25%10%
1980
October1st to 15thNight
52%412%22%8%
2072
16th to endNight
65%410%14%4
2496
November1st to 15thNight
59%6%12%14%6%
2472
16th to endNight
64%49%15%5%
2762
December1st to 15thNight
75%37%10%2
2925
16th to endNight
71%5%6%9%6%
3107

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
25%24%43%6%
90
16th to endDay
19%34%37%6%11
96
February1st to 15thDay
30%20%28%14%5%
188
16th to endDay
25%22%30%16%4
265
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%29%19%11%2
313
16th to endDay
26%10%22%23%10%5%
332
September1st to 15thDay
26%12%24%20%12%4
315
16th to endDay
21%14%26%16%16%5%
314
October1st to 15thDay
32%16%20%19%8%3
300
16th to endDay
39%18%20%13%6%
288
November1st to 15thDay
29%23%16%21%7%1
280
16th to endDay
32%20%23%16%6%1
193
December1st to 15thDay
38%24%22%10%31
90
16th to endDay
39%23%23%11%1
96
January1st to 15thNight
26%24%30%15%2
780
16th to endNight
22%20%34%19%3
832
February1st to 15thNight
17%25%35%16%4
764
16th to endNight
27%19%31%16%5%
659
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%21%30%21%
441
16th to endNight
20%6%24%32%14%2
620
September1st to 15thNight
25%7%25%28%11%2
720
16th to endNight
23%10%23%28%12%1
717
October1st to 15thNight
25%14%25%23%9%1
720
16th to endNight
37%18%21%15%7%
768
November1st to 15thNight
27%19%23%20%8%
760
16th to endNight
29%21%24%16%5%1
812
December1st to 15thNight
31%23%26%13%4
825
16th to endNight
31%23%23%15%4
877
Page generated at 2018-02-23 11:21:27. Version ac04

Copyright 2018 A. Danko


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