Elentirmo Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Elentirmo Observatory clear sky chart from 2005-11-05 to 2017-12-20.

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
21%
15572
13%
47864
5%
15528
29%
15528
14%
34522

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
11%
750
11%
2506
2%
746
21%
746
8%
1881
January16th to endNight
10%
769
11%
2505
1%
769
22%
769
8%
1921
February1st to 15thNight
10%
703
9%
2286
1%
701
19%
701
8%
1742
February16th to endNight
14%
631
10%
2033
3%
631
22%
631
9%
1504
March1st to 15thNight
16%
720
14%
1980
4%
720
25%
720
14%
1475
March16th to endNight
17%
768
14%
2112
4%
768
26%
768
14%
1531
April1st to 15thNight
16%
548
15%
1805
5%
548
28%
548
12%
1297
April16th to endNight
20%
540
15%
1632
5%
540
29%
540
15%
1160
May1st to 15thNight
22%
540
11%
1534
5%
540
27%
540
13%
1155
May16th to endNight
25%
561
10%
1496
4%
560
30%
560
16%
1112
June1st to 15thNight
23%
540
7%
1440
4%
540
26%
540
13%
1132
June16th to endNight
28%
381
8%
1281
4%
381
33%
381
11%
952
July1st to 15thNight
37%
434
10%
1284
7%
434
40%
434
19%
880
July16th to endNight
33%
565
9%
1479
7%
532
37%
532
17%
1110
August1st to 15thNight
41%
539
13%
1608
10%
535
44%
535
20%
1098
August16th to endNight
42%
573
18%
1783
11%
573
48%
573
23%
1141
September1st to 15thNight
35%
540
18%
1800
14%
540
43%
540
23%
1128
September16th to endNight
33%
708
23%
2006
12%
708
42%
708
24%
1321
October1st to 15thNight
29%
720
20%
2160
9%
720
38%
720
22%
1384
October16th to endNight
19%
768
17%
2304
6%
768
29%
768
18%
1564
November1st to 15thNight
25%
800
14%
2615
8%
800
32%
800
15%
1836
November16th to endNight
16%
825
13%
2730
4%
825
25%
825
12%
1949
December1st to 15thNight
10%
825
10%
2730
1%
825
20%
825
8%
2111
December16th to endNight
8%
824
10%
2755
1%
824
18%
824
7%
2138

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
21%8%36%5%3445%6%29%
48970
Night
21%8%36%5%3445%7%29%
48040
TransparencyDay
53%311%19%9%
48664
Night
55%311%20%8%
47864
SeeingDay
24%22%27%16%6%1
7788
Night
23%25%25%18%6%
15573

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
15%12%5%8%6%46%5%5%7%21%
1432
16th to endDay
18%10%48%6%36%5%7%6%21%
1716
February1st to 15thDay
17%10%5%10%7%45%5%5%6%20%
1575
16th to endDay
13%11%5%10%8%36%36%6%25%
1438
March1st to 15thDay
20%10%5%8%7%3444427%
1969
16th to endDay
16%9%5%9%5%24346%31%
2112
April1st to 15thDay
22%11%5%7%6%3334427%
2144
16th to endDay
23%8%35%5%33347%32%
2325
May1st to 15thDay
25%8%47%5%3345%6%25%
2416
16th to endDay
24%9%35%42445%7%27%
2618
June1st to 15thDay
27%9%47%6%3434424%
2520
16th to endDay
25%7%36%6%345%47%26%
2686
July1st to 15thDay
19%6%25%435%5%5%8%33%
2582
16th to endDay
22%8%36%6%345%5%7%25%
2587
August1st to 15thDay
18%6%36%5%35%6%6%8%31%
2340
16th to endDay
15%5%235%35%46%8%40%
2417
September1st to 15thDay
18%5%25%42445%7%39%
2160
16th to endDay
17%5%15%5%23346%43%
1952
October1st to 15thDay
20%435%423447%39%
1800
16th to endDay
20%8%25%6%35%446%31%
1920
November1st to 15thDay
22%9%47%5%34347%27%
1573
16th to endDay
21%8%48%6%35%45%6%24%
1560
December1st to 15thDay
27%8%36%6%36%6%5%6%19%
1560
16th to endDay
25%12%47%6%35%5%5%6%18%
1568
January1st to 15thNight
17%10%48%7%35%6%6%7%23%
2506
16th to endNight
18%10%5%7%7%36%5%7%8%20%
2505
February1st to 15thNight
17%11%47%6%46%6%7%7%20%
2285
16th to endNight
14%10%48%7%36%6%5%7%24%
2033
March1st to 15thNight
20%9%46%6%34447%29%
1968
16th to endNight
18%9%46%5%25%45%6%31%
2112
April1st to 15thNight
25%8%26%43435%5%29%
1805
16th to endNight
23%7%36%434445%32%
1632
May1st to 15thNight
27%9%35%424346%27%
1534
16th to endNight
21%9%36%42345%7%29%
1494
June1st to 15thNight
31%9%36%324346%25%
1440
16th to endNight
28%6%36%5%25%347%27%
1281
July1st to 15thNight
16%7%35%4345%6%7%34%
1362
16th to endNight
21%9%245%3435%8%28%
1580
August1st to 15thNight
18%7%35%43445%6%37%
1620
16th to endNight
16%6%25%424347%42%
1783
September1st to 15thNight
17%5%33425%45%6%41%
1800
16th to endNight
18%6%23423447%42%
2006
October1st to 15thNight
19%5%15%42335%7%41%
2160
16th to endNight
23%5%24425%45%6%36%
2304
November1st to 15thNight
22%7%345%3445%7%31%
2615
16th to endNight
22%6%35%6%25%446%30%
2730
December1st to 15thNight
24%9%46%6%35%5%5%7%21%
2730
16th to endNight
24%9%48%6%345%5%7%20%
2755

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
61%413%16%4
1433
16th to endDay
61%38%18%8%
1716
February1st to 15thDay
62%411%14%6%
1578
16th to endDay
57%312%18%7%1
1438
March1st to 15thDay
58%210%16%9%1
1980
16th to endDay
52%29%21%12%1
2112
April1st to 15thDay
57%37%16%13%1
2144
16th to endDay
51%211%20%12%2
2325
May1st to 15thDay
59%39%17%9%
2416
16th to endDay
54%413%18%8%1
2622
June1st to 15thDay
60%5%10%14%7%1
2520
16th to endDay
56%411%17%9%
2686
July1st to 15thDay
47%416%21%9%1
2432
16th to endDay
55%5%12%19%6%
2425
August1st to 15thDay
47%5%14%21%10%
2327
16th to endDay
38%5%14%29%11%
2417
September1st to 15thDay
43%312%24%14%1
2160
16th to endDay
40%39%28%16%1
1952
October1st to 15thDay
43%311%27%14%
1800
16th to endDay
52%211%24%8%
1920
November1st to 15thDay
56%312%17%8%1
1573
16th to endDay
59%5%12%16%7%
1560
December1st to 15thDay
65%410%15%4
1560
16th to endDay
65%28%14%7%
1568
January1st to 15thNight
60%313%17%5%
2506
16th to endNight
62%310%18%4
2505
February1st to 15thNight
62%312%14%6%
2286
16th to endNight
59%214%17%5%
2033
March1st to 15thNight
56%212%18%9%
1980
16th to endNight
53%210%20%11%
2112
April1st to 15thNight
56%38%16%12%2
1805
16th to endNight
53%29%19%12%2
1632
May1st to 15thNight
58%310%19%7%
1534
16th to endNight
54%413%18%8%1
1496
June1st to 15thNight
63%38%17%6%
1440
16th to endNight
60%310%17%7%
1281
July1st to 15thNight
48%5%14%22%8%
1284
16th to endNight
56%412%18%7%
1479
August1st to 15thNight
48%412%24%9%
1608
16th to endNight
43%312%26%13%
1783
September1st to 15thNight
42%310%29%12%1
1800
16th to endNight
43%38%29%15%
2006
October1st to 15thNight
43%311%28%13%
2160
16th to endNight
48%313%23%11%
2304
November1st to 15thNight
52%414%19%9%
2615
16th to endNight
55%315%18%7%
2730
December1st to 15thNight
63%411%16%4
2730
16th to endNight
64%310%16%5%
2755

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
18%33%29%16%1
240
16th to endDay
20%30%36%9%2
256
February1st to 15thDay
20%33%26%17%1
236
16th to endDay
18%29%32%13%4
213
March1st to 15thDay
22%36%26%10%3
270
16th to endDay
25%31%27%8%5%1
288
April1st to 15thDay
28%28%30%8%4
270
16th to endDay
19%27%30%17%41
270
May1st to 15thDay
31%22%23%16%42
372
16th to endDay
29%22%25%17%41
519
June1st to 15thDay
28%21%26%16%6%
495
16th to endDay
28%18%25%18%6%2
495
July1st to 15thDay
27%12%22%24%12%2
475
16th to endDay
27%15%23%21%10%1
448
August1st to 15thDay
23%11%27%24%10%2
313
16th to endDay
20%11%25%24%13%3
332
September1st to 15thDay
19%14%32%20%10%2
315
16th to endDay
21%12%31%20%10%4
305
October1st to 15thDay
20%15%34%17%9%3
270
16th to endDay
21%28%26%15%6%1
288
November1st to 15thDay
20%23%27%17%8%1
280
16th to endDay
25%27%30%10%4
285
December1st to 15thDay
29%29%28%10%2
285
16th to endDay
30%30%25%10%2
268
January1st to 15thNight
19%34%30%14%1
750
16th to endNight
23%33%29%11%2
769
February1st to 15thNight
23%32%29%12%1
704
16th to endNight
19%34%27%14%4
631
March1st to 15thNight
22%31%25%15%4
720
16th to endNight
21%34%23%15%5%
768
April1st to 15thNight
23%27%28%16%4
548
16th to endNight
23%25%26%18%4
540
May1st to 15thNight
31%22%20%17%7%1
540
16th to endNight
23%21%21%24%7%1
561
June1st to 15thNight
28%20%21%25%4
540
16th to endNight
29%19%16%25%8%1
381
July1st to 15thNight
22%12%20%30%12%
434
16th to endNight
24%18%17%26%12%
565
August1st to 15thNight
23%11%15%28%19%1
539
16th to endNight
18%11%22%31%13%2
573
September1st to 15thNight
20%13%26%27%11%
540
16th to endNight
22%14%24%22%12%2
708
October1st to 15thNight
20%17%28%22%8%1
720
16th to endNight
23%23%30%16%5%
768
November1st to 15thNight
21%24%24%19%6%2
800
16th to endNight
23%30%25%13%6%
825
December1st to 15thNight
28%30%26%11%3
825
16th to endNight
28%32%27%10%1
824
Page generated at 2017-12-21 08:04:46. Version ac04

Copyright 2017 A. Danko


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