LOAM
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the LOAM clear sky chart from 2005-11-05 to 2017-09-20.

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
30%
14640
14%
46873
8%
14608
37%
14608
16%
33210

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
17%
720
7%
2506
2%
716
23%
716
7%
2002
January16th to endNight
20%
768
11%
2664
5%
768
28%
768
12%
1986
February1st to 15thNight
19%
704
12%
2287
4%
701
29%
701
11%
1738
February16th to endNight
23%
631
15%
1937
7%
631
33%
631
13%
1458
March1st to 15thNight
20%
720
14%
2119
7%
720
29%
720
14%
1600
March16th to endNight
30%
768
21%
2020
9%
768
38%
768
21%
1403
April1st to 15thNight
24%
718
16%
1796
5%
718
30%
718
20%
1311
April16th to endNight
28%
638
18%
1718
7%
638
36%
638
22%
1200
May1st to 15thNight
32%
360
17%
1440
14%
360
42%
360
16%
956
May16th to endNight
36%
375
14%
1497
10%
374
48%
374
18%
951
June1st to 15thNight
35%
360
9%
1440
8%
360
43%
360
15%
966
June16th to endNight
45%
360
9%
1440
12%
360
49%
360
19%
915
July1st to 15thNight
54%
340
13%
1360
19%
340
59%
340
25%
765
July16th to endNight
54%
376
13%
1418
17%
354
58%
354
25%
809
August1st to 15thNight
57%
413
14%
1484
14%
411
61%
411
24%
900
August16th to endNight
53%
720
20%
1866
10%
720
57%
720
36%
1147
September1st to 15thNight
45%
720
15%
1800
6%
720
49%
720
29%
1234
September16th to endNight
47%
677
21%
1838
13%
677
52%
677
31%
1176
October1st to 15thNight
33%
660
18%
1980
11%
660
42%
660
19%
1362
October16th to endNight
25%
704
11%
2216
6%
704
32%
704
14%
1661
November1st to 15thNight
26%
700
18%
2319
11%
700
37%
700
16%
1629
November16th to endNight
20%
720
11%
2520
6%
720
28%
720
9%
1927
December1st to 15thNight
17%
720
8%
2520
3%
720
23%
720
9%
1978
December16th to endNight
13%
768
11%
2688
3%
768
22%
768
8%
2136

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%36%5%3445%6%32%
47970
Night
18%9%36%5%34445%33%
47042
Cloud CoverDay
19%8%36%5%3445%6%32%
47979
Night
18%9%36%5%34445%33%
47048
TransparencyDay
52%411%20%9%1
47657
Night
52%411%20%10%
46873
SeeingDay
24%10%28%22%10%3
5502
Night
23%10%27%26%10%1
14640

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
23%15%5%8%6%3433420%
1432
16th to endDay
15%14%6%8%6%35%35%425%
1557
February1st to 15thDay
12%14%5%12%7%345%4424%
1575
16th to endDay
18%13%5%8%7%4334426%
1536
March1st to 15thDay
18%10%5%7%7%45%44427%
1829
16th to endDay
17%7%35%5%25%445%39%
2203
April1st to 15thDay
23%9%45%42334433%
2152
16th to endDay
21%7%35%5%34335%35%
2252
May1st to 15thDay
21%8%36%5%33446%31%
2511
16th to endDay
20%6%26%5%34447%33%
2618
June1st to 15thDay
22%6%35%5%35%45%6%30%
2520
16th to endDay
19%5%25%435%6%6%8%30%
2520
July1st to 15thDay
14%5%25%6%36%5%6%8%36%
2520
16th to endDay
13%5%26%5%36%5%7%8%33%
2654
August1st to 15thDay
12%5%26%7%45%5%6%8%34%
2463
16th to endDay
11%4145%35%5%6%8%42%
2322
September1st to 15thDay
17%5%15%43445%7%40%
2160
16th to endDay
18%42442325%6%46%
1889
October1st to 15thDay
22%7%35%434336%35%
1650
16th to endDay
28%9%27%6%3444424%
1655
November1st to 15thDay
16%9%45%5%4445%7%32%
1536
16th to endDay
27%10%36%5%23336%24%
1440
December1st to 15thDay
23%14%6%8%6%35%34418%
1440
16th to endDay
23%16%6%8%6%2433320%
1536
January1st to 15thNight
19%17%5%8%6%4444419%
2506
16th to endNight
13%15%5%8%6%35%445%26%
2664
February1st to 15thNight
12%13%6%10%8%45%445%24%
2285
16th to endNight
17%12%5%7%6%34345%28%
1937
March1st to 15thNight
19%10%5%9%7%3334428%
2106
16th to endNight
15%8%26%5%2434441%
2020
April1st to 15thNight
25%7%23424435%35%
1796
16th to endNight
19%8%26%414437%37%
1718
May1st to 15thNight
22%7%36%423345%35%
1440
16th to endNight
17%6%35%43445%7%37%
1495
June1st to 15thNight
20%6%35%5%35%5%6%6%33%
1440
16th to endNight
16%5%25%435%47%7%37%
1440
July1st to 15thNight
11%4243345%6%7%46%
1440
16th to endNight
8%5%35%435%5%6%8%44%
1514
August1st to 15thNight
11%5%25%4346%6%9%40%
1494
16th to endNight
10%41442445%7%50%
1866
September1st to 15thNight
15%5%245%445%5%6%40%
1800
16th to endNight
17%424423335%48%
1838
October1st to 15thNight
20%7%25%5%2345%6%36%
1980
16th to endNight
25%8%36%5%33345%28%
2216
November1st to 15thNight
20%7%36%5%35%346%32%
2319
16th to endNight
22%11%47%7%34435%25%
2520
December1st to 15thNight
23%14%6%6%5%3443422%
2520
16th to endNight
24%15%5%8%6%2333421%
2688

Percentage Cloud Cover SE (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
23%15%6%8%5%2443421%
1432
16th to endDay
15%14%6%9%6%35%345%25%
1557
February1st to 15thDay
12%15%5%11%8%3444425%
1575
16th to endDay
18%13%6%8%6%2434426%
1536
March1st to 15thDay
17%10%47%6%35%44430%
1839
16th to endDay
16%7%34434445%41%
2202
April1st to 15thDay
23%9%36%423335%33%
2152
16th to endDay
20%7%35%5%34435%35%
2252
May1st to 15thDay
20%7%36%433445%36%
2511
16th to endDay
19%5%25%5%24446%38%
2618
June1st to 15thDay
21%7%35%6%25%5%5%7%29%
2520
16th to endDay
19%5%35%5%36%6%6%8%30%
2520
July1st to 15thDay
14%5%25%5%35%5%6%8%36%
2520
16th to endDay
12%6%35%6%35%6%7%7%35%
2654
August1st to 15thDay
16%5%36%5%45%5%5%7%33%
2463
16th to endDay
15%425%5%3445%8%40%
2322
September1st to 15thDay
17%5%245%3445%7%40%
2160
16th to endDay
17%42441325%7%45%
1889
October1st to 15thDay
22%8%34434346%35%
1650
16th to endDay
27%9%36%6%35%34424%
1655
November1st to 15thDay
16%9%445%3445%8%32%
1536
16th to endDay
26%10%37%5%3334425%
1440
December1st to 15thDay
23%15%5%8%6%34345%18%
1440
16th to endDay
24%17%5%8%6%3333419%
1536
January1st to 15thNight
19%16%6%8%6%45%44419%
2506
16th to endNight
13%15%5%9%6%35%445%26%
2664
February1st to 15thNight
12%13%6%11%8%35%445%24%
2278
16th to endNight
16%12%5%8%6%34445%28%
1937
March1st to 15thNight
19%9%47%6%34345%31%
2119
16th to endNight
15%8%35%5%2433444%
2020
April1st to 15thNight
25%7%24424345%35%
1796
16th to endNight
19%7%35%424346%37%
1718
May1st to 15thNight
21%7%36%424345%37%
1440
16th to endNight
17%5%345%24447%39%
1495
June1st to 15thNight
19%7%25%445%45%7%32%
1440
16th to endNight
16%5%34425%5%6%8%37%
1440
July1st to 15thNight
11%3245%245%6%8%45%
1440
16th to endNight
8%5%345%35%5%6%8%44%
1514
August1st to 15thNight
12%5%244346%7%8%39%
1494
16th to endNight
12%42442435%7%48%
1866
September1st to 15thNight
15%5%25%6%34447%41%
1800
16th to endNight
17%423424236%48%
1838
October1st to 15thNight
20%6%35%42345%5%36%
1980
16th to endNight
25%8%35%6%34445%28%
2216
November1st to 15thNight
20%8%25%6%34445%33%
2319
16th to endNight
22%11%48%6%34445%25%
2520
December1st to 15thNight
23%14%6%6%5%24335%22%
2520
16th to endNight
24%16%47%6%2333421%
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
68%37%14%5%
1433
16th to endDay
61%49%15%8%
1557
February1st to 15thDay
62%310%18%4
1577
16th to endDay
61%38%15%9%1
1536
March1st to 15thDay
60%311%15%8%1
1839
16th to endDay
46%39%18%16%5%
2203
April1st to 15thDay
53%37%19%13%2
2152
16th to endDay
52%35%20%14%4
2252
May1st to 15thDay
53%36%19%14%1
2511
16th to endDay
50%410%20%11%1
2622
June1st to 15thDay
53%5%10%20%8%
2520
16th to endDay
48%6%13%20%9%1
2520
July1st to 15thDay
42%6%14%26%11%
2371
16th to endDay
45%6%15%21%9%
2487
August1st to 15thDay
46%7%15%21%9%
2449
16th to endDay
38%6%17%28%9%
2322
September1st to 15thDay
43%5%12%26%11%
2160
16th to endDay
40%413%31%9%
1889
October1st to 15thDay
50%413%19%11%
1650
16th to endDay
62%5%11%14%5%
1655
November1st to 15thDay
50%415%19%8%
1536
16th to endDay
62%5%10%15%5%
1440
December1st to 15thDay
68%411%12%2
1440
16th to endDay
69%48%11%6%
1536
January1st to 15thNight
68%410%12%4
2506
16th to endNight
59%49%17%7%
2664
February1st to 15thNight
62%39%18%6%
2287
16th to endNight
58%47%18%10%
1937
March1st to 15thNight
58%38%18%9%1
2119
16th to endNight
46%48%20%16%3
2020
April1st to 15thNight
52%27%19%16%1
1796
16th to endNight
47%48%19%17%2
1718
May1st to 15thNight
50%46%18%15%4
1440
16th to endNight
45%5%10%21%14%1
1497
June1st to 15thNight
50%5%11%22%9%
1440
16th to endNight
43%6%12%21%15%
1440
July1st to 15thNight
33%7%13%29%14%1
1360
16th to endNight
35%6%16%25%14%
1418
August1st to 15thNight
37%8%19%24%10%
1484
16th to endNight
32%5%16%34%11%
1866
September1st to 15thNight
42%5%13%25%11%1
1800
16th to endNight
38%411%35%9%
1838
October1st to 15thNight
48%5%10%23%11%
1980
16th to endNight
57%5%13%18%5%
2216
November1st to 15thNight
53%413%18%10%
2319
16th to endNight
61%410%17%4
2520
December1st to 15thNight
64%412%14%3
2520
16th to endNight
67%49%13%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
38%13%21%18%8%
60
16th to endDay
32%10%35%13%7%
67
February1st to 15thDay
36%18%33%10%1
90
16th to endDay
34%13%28%21%2
195
March1st to 15thDay
28%14%30%19%6%
270
16th to endDay
23%16%30%15%10%2
288
April1st to 15thDay
28%17%29%16%6%1
270
16th to endDay
27%14%29%16%10%2
270
May1st to 15thDay
31%10%29%17%8%2
288
16th to endDay
27%10%32%16%9%2
331
June1st to 15thDay
26%8%33%22%7%1
315
16th to endDay
21%9%30%24%12%1
315
July1st to 15thDay
15%6%34%23%15%4
305
16th to endDay
12%432%30%16%3
326
August1st to 15thDay
11%6%21%40%14%5%
313
16th to endDay
15%422%30%16%10%
332
September1st to 15thDay
20%6%21%23%17%10%
315
16th to endDay
21%8%21%22%15%10%
270
October1st to 15thDay
29%9%22%19%15%3
255
16th to endDay
35%11%25%22%5%
253
November1st to 15thDay
22%10%34%21%11%1
190
16th to endDay
43%6%31%16%1
60
December1st to 15thDay
28%15%33%23%
60
16th to endDay
45%18%31%4
64
January1st to 15thNight
29%12%31%21%5%
720
16th to endNight
22%12%32%24%7%1
768
February1st to 15thNight
19%14%35%24%5%
704
16th to endNight
23%15%28%26%5%
631
March1st to 15thNight
27%12%33%22%4
720
16th to endNight
20%15%28%25%9%
768
April1st to 15thNight
28%13%28%23%4
718
16th to endNight
26%12%28%23%7%
638
May1st to 15thNight
26%5%28%28%8%2
360
16th to endNight
20%8%28%30%11%1
375
June1st to 15thNight
21%6%26%35%9%
360
16th to endNight
20%421%38%13%1
360
July1st to 15thNight
10%323%40%20%1
340
16th to endNight
11%221%41%21%1
376
August1st to 15thNight
14%215%38%25%2
413
16th to endNight
12%420%36%23%2
720
September1st to 15thNight
20%424%30%19%1
720
16th to endNight
20%5%22%28%19%3
677
October1st to 15thNight
25%10%25%27%11%
660
16th to endNight
30%10%26%23%8%
704
November1st to 15thNight
26%10%29%20%12%1
700
16th to endNight
29%16%24%20%7%
720
December1st to 15thNight
32%14%28%19%4
720
16th to endNight
35%10%31%16%41
768
Page generated at 2017-09-21 07:18:20. Version ac04

Copyright 2017 A. Danko


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