Earwig Haven Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Earwig Haven Observatory clear sky chart from 2005-11-05 to 2017-09-23.

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%
14679
13%
46915
8%
14649
36%
14649
16%
33428

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
15%
720
7%
2506
3%
716
20%
716
7%
2027
January16th to endNight
21%
768
11%
2637
7%
768
27%
768
11%
1976
February1st to 15thNight
17%
702
10%
2287
4%
701
24%
701
11%
1757
February16th to endNight
22%
631
13%
1950
6%
631
31%
631
13%
1458
March1st to 15thNight
20%
720
13%
2097
7%
720
28%
720
15%
1563
March16th to endNight
30%
768
20%
2036
9%
768
38%
768
22%
1407
April1st to 15thNight
24%
718
16%
1796
6%
718
29%
718
20%
1313
April16th to endNight
30%
646
17%
1726
7%
646
36%
646
22%
1212
May1st to 15thNight
33%
360
17%
1440
14%
360
44%
360
16%
941
May16th to endNight
34%
375
13%
1497
10%
374
46%
374
19%
945
June1st to 15thNight
37%
360
9%
1440
8%
360
45%
360
15%
978
June16th to endNight
40%
360
9%
1440
12%
360
45%
360
18%
935
July1st to 15thNight
54%
340
15%
1360
21%
340
59%
340
27%
756
July16th to endNight
56%
376
14%
1418
17%
354
60%
354
27%
802
August1st to 15thNight
52%
446
15%
1517
13%
444
57%
444
25%
945
August16th to endNight
51%
708
21%
1854
10%
708
56%
708
37%
1147
September1st to 15thNight
45%
720
16%
1800
8%
720
48%
720
30%
1241
September16th to endNight
48%
689
23%
1877
15%
689
53%
689
32%
1197
October1st to 15thNight
33%
660
18%
1980
11%
660
43%
660
20%
1379
October16th to endNight
24%
704
11%
2197
6%
704
32%
704
12%
1675
November1st to 15thNight
26%
700
17%
2332
12%
700
35%
700
16%
1640
November16th to endNight
20%
720
10%
2520
6%
720
26%
720
9%
1932
December1st to 15thNight
17%
720
7%
2520
3%
720
22%
720
8%
2035
December16th to endNight
14%
768
9%
2688
4%
768
21%
768
7%
2167

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
17%8%36%5%35%45%6%33%
48002
Night
17%9%46%5%34446%33%
47084
Cloud CoverDay
18%8%36%5%3445%6%33%
48011
Night
18%9%36%5%34446%33%
47090
TransparencyDay
50%6%11%19%10%1
47689
Night
52%5%10%19%10%1
46915
SeeingDay
21%12%28%21%11%4
5498
Night
22%11%28%25%10%
14681

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
20%13%5%9%7%33435%22%
1432
16th to endDay
14%14%48%7%45%445%25%
1586
February1st to 15thDay
13%13%5%9%7%47%5%5%423%
1575
16th to endDay
17%13%37%6%35%5%46%27%
1521
March1st to 15thDay
17%9%5%6%8%35%5%4428%
1852
16th to endDay
15%8%35%42445%5%41%
2187
April1st to 15thDay
21%9%36%423346%33%
2152
16th to endDay
19%7%25%5%23445%37%
2244
May1st to 15thDay
19%7%36%6%25%446%33%
2511
16th to endDay
17%6%35%6%35%45%7%35%
2618
June1st to 15thDay
20%6%35%5%36%5%5%6%31%
2520
16th to endDay
16%6%26%5%36%6%6%8%32%
2520
July1st to 15thDay
13%5%245%35%5%6%7%39%
2520
16th to endDay
11%5%25%5%45%5%6%9%38%
2654
August1st to 15thDay
10%5%26%6%46%5%6%8%38%
2430
16th to endDay
10%5%25%5%45%5%6%9%41%
2336
September1st to 15thDay
15%425%5%23447%42%
2160
16th to endDay
14%4245%2435%7%45%
1919
October1st to 15thDay
20%6%35%6%345%5%6%33%
1650
16th to endDay
25%8%37%6%34435%26%
1675
November1st to 15thDay
15%8%35%5%45%45%6%33%
1524
16th to endDay
22%11%48%6%34445%24%
1440
December1st to 15thDay
21%14%48%8%45%5%46%17%
1440
16th to endDay
23%14%5%8%6%3433421%
1536
January1st to 15thNight
18%14%6%10%8%345%3419%
2506
16th to endNight
13%16%5%8%6%34346%26%
2637
February1st to 15thNight
13%12%6%11%7%45%445%24%
2285
16th to endNight
17%11%38%7%34346%28%
1950
March1st to 15thNight
18%11%5%7%6%23335%30%
2084
16th to endNight
15%7%35%5%3434442%
2036
April1st to 15thNight
22%8%35%5%24346%34%
1796
16th to endNight
18%7%25%43445%6%37%
1726
May1st to 15thNight
21%7%25%42445%5%35%
1440
16th to endNight
15%6%35%5%335%6%7%37%
1495
June1st to 15thNight
17%6%26%5%35%45%7%33%
1440
16th to endNight
16%5%25%5%25%46%8%37%
1440
July1st to 15thNight
10%3134445%5%9%46%
1440
16th to endNight
8%424426%5%6%7%46%
1514
August1st to 15thNight
9%5%26%4346%6%8%42%
1527
16th to endNight
9%415%43445%6%50%
1854
September1st to 15thNight
14%5%25%5%2445%6%43%
1800
16th to endNight
15%424423345%49%
1877
October1st to 15thNight
20%7%35%424446%36%
1980
16th to endNight
25%8%46%6%34346%26%
2197
November1st to 15thNight
19%9%36%5%24346%33%
2332
16th to endNight
22%10%5%8%6%24445%24%
2520
December1st to 15thNight
22%15%46%5%35%5%5%5%19%
2520
16th to endNight
24%15%5%8%7%24335%19%
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
21%13%6%10%7%2443421%
1432
16th to endDay
13%15%48%6%45%45%5%25%
1586
February1st to 15thDay
14%12%5%10%6%5%6%5%5%5%23%
1575
16th to endDay
18%12%47%6%35%345%26%
1521
March1st to 15thDay
20%8%46%6%3444430%
1862
16th to endDay
18%7%24423445%41%
2186
April1st to 15thDay
21%9%35%5%23346%33%
2152
16th to endDay
20%7%25%5%24446%37%
2244
May1st to 15thDay
22%7%45%5%34336%33%
2511
16th to endDay
21%5%245%3445%6%35%
2618
June1st to 15thDay
19%6%25%435%45%5%34%
2520
16th to endDay
15%6%26%5%35%5%6%6%36%
2520
July1st to 15thDay
13%5%245%35%6%6%8%39%
2520
16th to endDay
11%425%5%36%6%7%9%37%
2654
August1st to 15thDay
17%5%15%5%35%45%6%38%
2430
16th to endDay
15%415%4245%5%7%42%
2336
September1st to 15thDay
15%5%26%423347%42%
2160
16th to endDay
14%4235%24447%44%
1919
October1st to 15thDay
20%7%25%6%3446%5%33%
1650
16th to endDay
25%10%37%6%3444425%
1675
November1st to 15thDay
16%7%45%6%445%47%34%
1524
16th to endDay
22%12%37%6%34335%26%
1440
December1st to 15thDay
21%14%49%7%45%446%17%
1440
16th to endDay
23%15%5%7%6%3433421%
1536
January1st to 15thNight
18%14%7%11%6%35%43419%
2506
16th to endNight
13%16%5%8%6%34346%26%
2637
February1st to 15thNight
14%13%6%10%7%35%445%23%
2278
16th to endNight
17%12%48%6%34445%28%
1950
March1st to 15thNight
23%9%5%6%5%23325%32%
2097
16th to endNight
19%6%35%43333343%
2036
April1st to 15thNight
22%8%345%24336%35%
1796
16th to endNight
18%7%26%5%23446%38%
1726
May1st to 15thNight
23%6%25%424445%36%
1440
16th to endNight
18%6%35%42445%6%38%
1495
June1st to 15thNight
17%6%25%6%35%45%8%34%
1440
16th to endNight
15%6%25%435%45%7%38%
1440
July1st to 15thNight
10%314435%45%9%46%
1440
16th to endNight
9%424435%5%6%8%45%
1514
August1st to 15thNight
12%5%26%4235%5%9%41%
1527
16th to endNight
13%314423446%50%
1854
September1st to 15thNight
14%5%25%433446%44%
1800
16th to endNight
15%424423345%49%
1877
October1st to 15thNight
20%7%35%42445%5%36%
1980
16th to endNight
25%9%46%6%24346%26%
2197
November1st to 15thNight
19%9%35%5%24335%36%
2332
16th to endNight
21%10%47%5%24435%28%
2520
December1st to 15thNight
23%15%46%6%25%5%5%5%19%
2520
16th to endNight
25%15%5%8%6%2433419%
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
66%49%12%6%
1433
16th to endDay
61%5%12%11%8%
1586
February1st to 15thDay
62%5%11%16%3
1577
16th to endDay
59%410%14%9%1
1521
March1st to 15thDay
58%6%11%15%7%
1862
16th to endDay
44%5%9%19%15%6%
2187
April1st to 15thDay
53%37%19%13%2
2152
16th to endDay
48%47%19%16%3
2244
May1st to 15thDay
51%47%19%13%2
2511
16th to endDay
47%7%11%20%12%1
2622
June1st to 15thDay
52%6%10%20%9%
2520
16th to endDay
48%7%10%20%10%1
2520
July1st to 15thDay
38%7%14%26%11%
2371
16th to endDay
41%9%14%23%10%
2487
August1st to 15thDay
43%8%14%21%10%
2416
16th to endDay
37%7%15%28%11%
2336
September1st to 15thDay
41%6%12%27%11%
2160
16th to endDay
38%7%11%33%9%
1919
October1st to 15thDay
51%5%13%20%8%
1650
16th to endDay
62%5%11%13%6%
1675
November1st to 15thDay
50%7%14%19%8%
1524
16th to endDay
62%412%13%6%1
1440
December1st to 15thDay
68%6%10%11%2
1440
16th to endDay
67%5%10%11%5%
1536
January1st to 15thNight
67%5%8%11%5%
2506
16th to endNight
59%5%9%16%8%
2637
February1st to 15thNight
62%411%16%5%
2287
16th to endNight
58%49%17%9%
1950
March1st to 15thNight
57%49%19%8%
2097
16th to endNight
46%49%18%16%4
2036
April1st to 15thNight
52%37%20%15%
1796
16th to endNight
47%5%7%19%17%3
1726
May1st to 15thNight
49%47%19%14%4
1440
16th to endNight
44%5%12%21%14%2
1497
June1st to 15thNight
49%7%10%20%10%1
1440
16th to endNight
44%7%11%20%15%
1440
July1st to 15thNight
32%7%12%30%15%1
1360
16th to endNight
35%5%15%27%15%
1418
August1st to 15thNight
37%8%16%23%13%
1517
16th to endNight
32%5%15%32%12%
1854
September1st to 15thNight
42%5%10%29%11%1
1800
16th to endNight
37%411%34%11%
1877
October1st to 15thNight
48%5%10%22%12%
1980
16th to endNight
59%5%12%16%6%
2197
November1st to 15thNight
52%5%13%17%10%1
2332
16th to endNight
61%5%11%15%4
2520
December1st to 15thNight
65%7%11%12%3
2520
16th to endNight
68%49%11%5%
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
25%28%25%16%5%
60
16th to endDay
34%19%28%15%2
73
February1st to 15thDay
31%23%34%11%
90
16th to endDay
32%20%26%15%6%
180
March1st to 15thDay
25%14%32%21%5%
270
16th to endDay
21%16%29%19%10%2
288
April1st to 15thDay
27%20%27%17%6%1
270
16th to endDay
25%18%22%18%9%4
270
May1st to 15thDay
27%11%28%20%8%3
288
16th to endDay
16%14%35%19%11%1
331
June1st to 15thDay
24%11%29%23%8%2
315
16th to endDay
17%10%32%25%12%2
315
July1st to 15thDay
15%6%29%29%13%4
305
16th to endDay
13%5%26%30%17%5%
326
August1st to 15thDay
14%7%25%28%16%7%
313
16th to endDay
10%6%26%28%16%12%
332
September1st to 15thDay
19%7%22%18%20%11%
315
16th to endDay
14%7%26%19%20%11%
283
October1st to 15thDay
23%9%25%24%13%3
255
16th to endDay
31%16%24%19%7%
257
November1st to 15thDay
19%11%32%21%11%2
178
16th to endDay
35%13%30%20%1
60
December1st to 15thDay
23%20%38%15%11
60
16th to endDay
40%20%34%4
64
January1st to 15thNight
24%16%32%20%4
720
16th to endNight
22%13%33%24%5%
768
February1st to 15thNight
21%15%37%20%4
704
16th to endNight
25%15%30%22%6%
631
March1st to 15thNight
27%14%31%23%3
720
16th to endNight
20%16%26%26%9%
768
April1st to 15thNight
27%14%28%24%5%
718
16th to endNight
23%14%26%26%8%
646
May1st to 15thNight
25%8%27%28%10%1
360
16th to endNight
17%8%35%24%14%
375
June1st to 15thNight
21%8%26%33%9%
360
16th to endNight
20%329%33%12%
360
July1st to 15thNight
10%423%45%14%
340
16th to endNight
10%226%42%16%1
376
August1st to 15thNight
13%223%37%22%1
446
16th to endNight
11%425%33%23%2
708
September1st to 15thNight
18%6%25%28%19%2
720
16th to endNight
17%7%22%25%23%3
689
October1st to 15thNight
23%10%26%25%12%1
660
16th to endNight
30%12%24%23%7%
704
November1st to 15thNight
26%10%30%19%11%
700
16th to endNight
29%16%25%19%8%
720
December1st to 15thNight
31%14%29%19%4
720
16th to endNight
33%13%29%17%4
768
Page generated at 2017-09-24 09:15:45. Version ac04

Copyright 2017 A. Danko


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