Loowit Imaging Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Loowit Imaging Observatory clear sky chart from 2005-11-05 to 2018-10-08.

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
42%
15893
10%
50836
9%
15864
44%
15864
16%
37052

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
30%
815
8%
2869
6%
811
33%
811
8%
2359
January16th to endNight
34%
832
7%
2844
7%
832
36%
832
10%
2276
February1st to 15thNight
29%
757
5%
2483
3%
757
32%
757
8%
2060
February16th to endNight
29%
684
9%
2196
6%
684
33%
684
11%
1719
March1st to 15thNight
27%
780
6%
2215
5%
780
30%
780
10%
1854
March16th to endNight
28%
832
6%
2256
4%
832
30%
832
9%
1900
April1st to 15thNight
32%
779
7%
1949
3%
779
34%
779
14%
1573
April16th to endNight
41%
604
10%
1762
6%
604
44%
604
20%
1263
May1st to 15thNight
48%
389
12%
1559
17%
389
50%
389
17%
1029
May16th to endNight
54%
407
7%
1624
9%
406
58%
406
15%
1096
June1st to 15thNight
45%
390
5%
1437
6%
390
47%
390
19%
956
June16th to endNight
49%
390
8%
1365
8%
390
51%
390
22%
873
July1st to 15thNight
71%
370
14%
1295
17%
370
73%
370
37%
678
July16th to endNight
78%
408
18%
1535
27%
386
83%
386
46%
641
August1st to 15thNight
79%
512
19%
1658
20%
510
81%
510
45%
805
August16th to endNight
69%
682
22%
1924
17%
682
71%
682
43%
1050
September1st to 15thNight
70%
780
23%
1950
13%
780
72%
780
47%
1119
September16th to endNight
52%
776
18%
2142
14%
776
54%
776
25%
1453
October1st to 15thNight
48%
752
13%
2256
12%
752
50%
752
21%
1556
October16th to endNight
36%
768
10%
2351
8%
768
40%
768
14%
1802
November1st to 15thNight
27%
760
6%
2648
4%
760
30%
760
8%
2177
November16th to endNight
30%
780
6%
2730
4%
780
33%
780
9%
2151
December1st to 15thNight
36%
780
8%
2730
7%
780
38%
780
11%
2130
December16th to endNight
22%
866
6%
3058
4%
866
25%
866
7%
2532

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
18%8%37%6%35%45%6%30%
52320
Night
19%7%36%5%3445%7%32%
50993
Cloud CoverDay
19%7%36%6%35%45%6%30%
52320
Night
20%7%35%5%3445%6%33%
50996
TransparencyDay
53%10%13%14%6%
51980
Night
50%9%14%16%7%1
50837
SeeingDay
22%12%23%23%14%3
7381
Night
23%7%19%27%19%2
15901

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
33%9%5%7%6%3443416%
1397
16th to endDay
28%10%5%9%6%35%45%315%
1732
February1st to 15thDay
26%10%5%10%7%3445%5%15%
1711
16th to endDay
24%10%5%7%6%3444422%
1564
March1st to 15thDay
32%10%49%7%3443415%
2073
16th to endDay
26%11%49%8%45%5%5%314%
2320
April1st to 15thDay
25%9%47%6%45%5%5%5%18%
2329
16th to endDay
18%8%49%8%35%45%6%24%
2471
May1st to 15thDay
15%7%36%6%36%5%5%7%31%
2721
16th to endDay
15%9%47%7%46%6%6%7%25%
2839
June1st to 15thDay
14%7%47%7%45%7%6%7%26%
2850
16th to endDay
10%7%37%7%5%5%6%6%9%30%
2925
July1st to 15thDay
6%5%25%5%3445%6%51%
2925
16th to endDay
6%31443435%7%54%
2889
August1st to 15thDay
5%414425%46%7%51%
2544
16th to endDay
7%415%5%3445%6%50%
2629
September1st to 15thDay
8%5%25%5%24347%50%
2340
16th to endDay
15%7%27%6%35%446%35%
2145
October1st to 15thDay
21%8%45%5%4445%6%29%
1873
16th to endDay
27%9%37%6%45%35%6%20%
1872
November1st to 15thDay
32%11%47%7%36%435%14%
1537
16th to endDay
33%10%26%5%35%345%18%
1560
December1st to 15thDay
26%9%48%6%35%445%19%
1560
16th to endDay
30%13%47%6%35%33418%
1514
January1st to 15thNight
33%8%46%5%33445%20%
2869
16th to endNight
25%9%46%6%35%45%7%20%
2844
February1st to 15thNight
24%11%47%6%35%45%6%19%
2471
16th to endNight
20%10%47%6%45%446%26%
2196
March1st to 15thNight
30%8%47%5%35%5%45%19%
2215
16th to endNight
26%9%37%5%35%6%46%19%
2252
April1st to 15thNight
20%7%38%7%446%5%7%25%
1949
16th to endNight
16%6%25%6%35%46%9%32%
1762
May1st to 15thNight
12%6%35%5%35%5%5%8%38%
1559
16th to endNight
9%436%5%46%6%7%8%37%
1624
June1st to 15thNight
9%6%45%5%35%5%8%10%35%
1437
16th to endNight
8%5%25%5%36%5%5%7%44%
1365
July1st to 15thNight
32134245%5%7%59%
1365
16th to endNight
3111112348%69%
1630
August1st to 15thNight
31221345%10%64%
1666
16th to endNight
6%312323438%59%
1924
September1st to 15thNight
4313312348%62%
1950
16th to endNight
13%5%25%5%3445%6%42%
2142
October1st to 15thNight
19%7%25%423446%38%
2256
16th to endNight
26%7%26%5%34446%26%
2351
November1st to 15thNight
32%8%36%5%245%5%6%19%
2648
16th to endNight
27%7%37%6%35%45%6%22%
2730
December1st to 15thNight
22%8%37%6%45%5%46%24%
2730
16th to endNight
31%11%37%5%2344420%
3058

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
34%9%36%6%45%235%17%
1397
16th to endDay
29%10%5%8%6%34446%15%
1732
February1st to 15thDay
27%11%48%6%35%45%5%16%
1711
16th to endDay
26%9%46%6%35%445%23%
1564
March1st to 15thDay
33%9%5%8%6%3443416%
2073
16th to endDay
27%9%5%8%8%35%5%5%415%
2320
April1st to 15thDay
26%8%47%7%345%7%5%19%
2329
16th to endDay
18%8%48%8%35%5%5%6%25%
2471
May1st to 15thDay
16%6%26%6%45%6%5%7%32%
2721
16th to endDay
16%7%47%6%46%5%6%8%26%
2839
June1st to 15thDay
14%8%38%6%46%6%6%8%26%
2850
16th to endDay
11%7%37%7%46%5%7%7%32%
2925
July1st to 15thDay
6%425%434446%51%
2925
16th to endDay
7%31342445%7%55%
2889
August1st to 15thDay
6%42443445%7%52%
2544
16th to endDay
8%4245%34446%51%
2629
September1st to 15thDay
8%6%25%5%24347%51%
2340
16th to endDay
16%7%26%6%345%5%6%36%
2145
October1st to 15thDay
22%8%346%35%45%6%30%
1873
16th to endDay
28%8%36%5%25%46%6%21%
1872
November1st to 15thDay
33%9%46%5%345%4416%
1537
16th to endDay
32%9%36%5%35%445%19%
1560
December1st to 15thDay
27%8%37%7%5%5%445%19%
1560
16th to endDay
31%12%47%6%35%33417%
1514
January1st to 15thNight
34%9%345%23445%21%
2868
16th to endNight
26%9%47%5%35%45%6%21%
2844
February1st to 15thNight
25%11%37%6%4445%6%20%
2471
16th to endNight
21%9%46%7%35%45%6%26%
2196
March1st to 15thNight
31%7%46%6%245%46%19%
2215
16th to endNight
27%9%47%5%445%5%6%20%
2256
April1st to 15thNight
20%6%36%8%46%6%46%25%
1949
16th to endNight
17%6%346%25%45%9%32%
1762
May1st to 15thNight
12%6%36%4445%5%8%38%
1559
16th to endNight
9%436%5%46%6%6%9%37%
1624
June1st to 15thNight
9%6%45%6%35%5%6%9%37%
1437
16th to endNight
8%5%25%6%26%6%47%44%
1365
July1st to 15thNight
321442345%7%61%
1365
16th to endNight
3111212337%70%
1630
August1st to 15thNight
321312448%66%
1666
16th to endNight
6%314223437%60%
1924
September1st to 15thNight
431321345%6%63%
1950
16th to endNight
13%5%25%5%245%47%42%
2142
October1st to 15thNight
20%6%25%433346%39%
2256
16th to endNight
26%7%25%6%345%46%28%
2351
November1st to 15thNight
32%8%46%43445%5%20%
2648
16th to endNight
27%7%36%6%35%5%5%6%22%
2730
December1st to 15thNight
24%7%46%6%35%45%6%25%
2730
16th to endNight
32%11%37%5%2334420%
3058

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%7%6%8%5%
1397
16th to endDay
71%8%9%7%21
1732
February1st to 15thDay
68%10%9%7%3
1711
16th to endDay
64%9%9%10%5%
1564
March1st to 15thDay
72%7%8%9%1
2073
16th to endDay
72%10%6%9%
2320
April1st to 15thDay
65%11%12%8%1
2329
16th to endDay
59%10%12%13%4
2471
May1st to 15thDay
49%10%17%15%5%
2721
16th to endDay
54%14%16%11%2
2843
June1st to 15thDay
53%14%18%10%3
2850
16th to endDay
48%13%17%15%3
2925
July1st to 15thDay
32%10%15%24%15%1
2766
16th to endDay
26%10%16%28%15%2
2721
August1st to 15thDay
29%9%20%26%12%2
2527
16th to endDay
33%8%16%27%10%1
2629
September1st to 15thDay
34%8%14%20%17%4
2340
16th to endDay
48%10%14%17%7%1
2145
October1st to 15thDay
53%9%14%15%6%
1873
16th to endDay
63%9%11%11%4
1872
November1st to 15thDay
71%8%9%6%21
1537
16th to endDay
68%7%8%9%4
1560
December1st to 15thDay
67%8%7%11%5%
1560
16th to endDay
71%6%8%8%4
1514
January1st to 15thNight
66%8%9%10%41
2869
16th to endNight
62%8%10%10%5%1
2844
February1st to 15thNight
64%10%11%8%5%
2483
16th to endNight
59%9%11%13%5%
2196
March1st to 15thNight
65%8%9%13%2
2215
16th to endNight
63%11%12%10%2
2256
April1st to 15thNight
56%10%13%15%3
1949
16th to endNight
46%9%18%17%6%
1762
May1st to 15thNight
42%10%16%19%7%1
1560
16th to endNight
42%14%22%17%3
1624
June1st to 15thNight
42%10%26%16%4
1437
16th to endNight
36%12%24%20%31
1365
July1st to 15thNight
21%10%20%31%12%3
1295
16th to endNight
13%8%20%35%17%4
1535
August1st to 15thNight
16%10%24%30%15%4
1658
16th to endNight
24%6%22%31%12%2
1924
September1st to 15thNight
20%9%19%24%20%6%
1950
16th to endNight
40%9%14%21%11%2
2142
October1st to 15thNight
46%7%13%21%9%
2256
16th to endNight
56%8%12%14%8%
2351
November1st to 15thNight
64%9%11%9%21
2648
16th to endNight
61%8%13%9%6%
2730
December1st to 15thNight
60%8%11%12%5%
2730
16th to endNight
67%8%9%9%4
3058

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
35%315%16%23%5%
90
16th to endDay
45%16%15%14%5%1
164
February1st to 15thDay
35%19%17%20%6%
281
16th to endDay
38%18%23%14%31
256
March1st to 15thDay
42%15%23%12%5%
330
16th to endDay
35%18%25%12%6%1
352
April1st to 15thDay
33%17%26%15%6%1
329
16th to endDay
27%16%26%19%7%3
318
May1st to 15thDay
24%13%22%23%11%3
348
16th to endDay
18%10%22%27%14%6%
394
June1st to 15thDay
18%13%31%20%14%2
495
16th to endDay
11%16%31%27%11%1
570
July1st to 15thDay
7%7%25%34%22%2
550
16th to endDay
7%320%31%31%6%
398
August1st to 15thDay
6%6%16%31%29%9%
359
16th to endDay
11%7%19%29%25%6%
396
September1st to 15thDay
13%6%21%31%20%6%
375
16th to endDay
18%11%20%29%17%2
375
October1st to 15thDay
29%10%25%18%13%2
345
16th to endDay
37%13%16%19%10%3
288
November1st to 15thDay
40%19%22%11%5%
92
16th to endDay
41%8%22%13%8%5%
90
December1st to 15thDay
35%15%17%13%15%2
90
16th to endDay
38%11%21%19%7%1
96
January1st to 15thNight
38%11%13%20%15%1
815
16th to endNight
29%11%16%23%17%1
832
February1st to 15thNight
31%12%18%23%12%1
764
16th to endNight
26%14%24%21%11%1
684
March1st to 15thNight
33%11%21%19%12%2
780
16th to endNight
30%12%22%23%9%1
832
April1st to 15thNight
23%12%25%23%14%1
779
16th to endNight
18%6%25%33%15%1
604
May1st to 15thNight
14%6%23%33%19%1
390
16th to endNight
10%421%37%23%1
407
June1st to 15thNight
10%5%29%33%20%
390
16th to endNight
10%5%28%33%21%
390
July1st to 15thNight
6%115%42%32%1
370
16th to endNight
3212%46%32%3
408
August1st to 15thNight
410%30%47%6%
512
16th to endNight
9%214%32%35%5%
682
September1st to 15thNight
7%116%31%36%6%
780
16th to endNight
16%419%32%23%3
776
October1st to 15thNight
23%5%16%29%21%3
752
16th to endNight
32%5%17%23%18%2
768
November1st to 15thNight
35%10%21%24%7%
760
16th to endNight
30%9%23%20%14%2
780
December1st to 15thNight
30%6%19%26%15%2
780
16th to endNight
38%10%21%19%10%
866
Page generated at 2018-10-09 07:39:17. Version ac04

Copyright 2018 A. Danko


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