Ellsworth
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ellsworth clear sky chart from 2005-11-05 to 2018-02-13.

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
41%
16711
23%
48764
13%
16667
51%
16667
36%
28096

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
36%
975
23%
2716
11%
970
45%
970
35%
1585
January16th to endNight
34%
1040
26%
2912
12%
1040
46%
1040
37%
1681
February1st to 15thNight
29%
761
18%
2342
8%
760
39%
760
27%
1440
February16th to endNight
31%
632
22%
1894
8%
632
43%
632
32%
1125
March1st to 15thNight
36%
720
24%
2160
12%
720
46%
720
37%
1204
March16th to endNight
33%
597
21%
2025
13%
597
44%
597
28%
1205
April1st to 15thNight
29%
539
16%
1798
7%
539
42%
539
25%
1098
April16th to endNight
31%
540
16%
1704
10%
540
41%
540
24%
1076
May1st to 15thNight
39%
540
17%
1620
11%
540
47%
540
30%
992
May16th to endNight
40%
563
15%
1506
9%
561
44%
561
29%
1007
June1st to 15thNight
39%
540
13%
1440
4%
540
44%
540
33%
910
June16th to endNight
52%
540
18%
1440
9%
540
56%
540
45%
811
July1st to 15thNight
57%
510
17%
1360
9%
510
61%
510
43%
787
July16th to endNight
61%
564
27%
1416
18%
531
66%
531
53%
744
August1st to 15thNight
58%
539
20%
1560
15%
536
64%
536
39%
901
August16th to endNight
59%
573
26%
1910
24%
573
67%
573
45%
931
September1st to 15thNight
54%
540
27%
1827
23%
540
65%
540
39%
942
September16th to endNight
52%
537
31%
1980
26%
537
64%
537
40%
947
October1st to 15thNight
41%
597
27%
2037
19%
597
49%
597
29%
1154
October16th to endNight
48%
924
33%
2460
16%
924
56%
924
46%
1358
November1st to 15thNight
42%
950
29%
2470
13%
950
52%
950
44%
1414
November16th to endNight
46%
975
35%
2545
16%
975
57%
975
48%
1406
December1st to 15thNight
33%
975
21%
2730
8%
975
44%
975
34%
1626
December16th to endNight
35%
1040
24%
2912
10%
1040
47%
1040
32%
1752

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
7%5%2432445%7%51%
49301
Night
6%5%2442445%7%51%
48936
Cloud CoverDay
7%5%2432445%7%52%
49299
Night
7%5%2442445%7%51%
48936
TransparencyDay
30%314%28%17%4
48975
Night
31%315%27%17%4
48764
SeeingDay
10%5%29%33%17%3
6446
Night
9%6%36%36%10%
16718

By Month

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
36%25%4245%5%8%51%
1552
16th to endDay
5%5%14434347%54%
1664
February1st to 15thDay
6%8%36%5%345%5%7%42%
1796
16th to endDay
5%7%3442435%8%49%
1580
March1st to 15thDay
6%5%23324447%54%
1800
16th to endDay
9%6%36%4245%6%7%42%
2199
April1st to 15thDay
10%7%3442345%8%45%
2150
16th to endDay
15%8%35%32435%7%39%
2256
May1st to 15thDay
11%6%2442445%7%47%
2331
16th to endDay
12%5%24435%46%8%40%
2605
June1st to 15thDay
9%4143245%6%8%49%
2520
16th to endDay
221231445%8%64%
2520
July1st to 15thDay
6%3133345%6%9%52%
2520
16th to endDay
321333446%10%55%
2656
August1st to 15thDay
5%314446%6%7%9%47%
2390
16th to endDay
5%313323447%60%
2292
September1st to 15thDay
8%313423445%58%
2133
16th to endDay
7%312213346%63%
1980
October1st to 15thDay
12%6%23223246%53%
1921
16th to endDay
6%5%24212346%59%
1752
November1st to 15thDay
5%42332445%8%55%
1718
16th to endDay
432341345%6%59%
1742
December1st to 15thDay
5%6%35%42445%6%51%
1560
16th to endDay
5%7%26%42445%8%48%
1664
January1st to 15thNight
45%25%5%3445%8%50%
2716
16th to endNight
35%24435%35%8%52%
2912
February1st to 15thNight
5%8%35%5%35%5%5%6%45%
2332
16th to endNight
5%7%26%5%25%45%6%48%
1894
March1st to 15thNight
5%5%25%42335%7%53%
2160
16th to endNight
9%7%335%335%6%8%44%
2025
April1st to 15thNight
10%7%35%3345%5%6%43%
1798
16th to endNight
15%6%25%325%45%7%41%
1704
May1st to 15thNight
10%6%25%425%45%7%46%
1619
16th to endNight
13%6%25%4246%6%7%40%
1505
June1st to 15thNight
10%42432446%7%47%
1440
16th to endNight
5%213325%6%7%9%52%
1440
July1st to 15thNight
6%3134245%6%10%50%
1440
16th to endNight
321322446%9%58%
1512
August1st to 15thNight
43145%3448%10%47%
1568
16th to endNight
421332445%7%60%
1910
September1st to 15thNight
8%41332345%7%56%
1827
16th to endNight
7%413322346%61%
1980
October1st to 15thNight
12%5%24323245%52%
2037
16th to endNight
7%413312347%59%
2460
November1st to 15thNight
5%31442445%7%56%
2470
16th to endNight
441332345%7%58%
2545
December1st to 15thNight
5%5%36%5%24348%50%
2730
16th to endNight
6%7%35%424447%50%
2912

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
36%25%4245%5%7%51%
1552
16th to endDay
46%145%33347%54%
1664
February1st to 15thDay
6%8%45%6%3445%7%42%
1796
16th to endDay
6%7%25%42435%8%50%
1580
March1st to 15thDay
6%5%2432445%7%55%
1800
16th to endDay
9%6%36%425%46%7%42%
2197
April1st to 15thDay
11%7%3432335%8%45%
2150
16th to endDay
16%8%25%423448%39%
2256
May1st to 15thDay
12%5%2342445%7%47%
2331
16th to endDay
13%5%24435%46%9%39%
2605
June1st to 15thDay
9%42432447%7%49%
2520
16th to endDay
31122235%48%64%
2520
July1st to 15thDay
6%313325%5%6%9%52%
2520
16th to endDay
321333446%9%56%
2656
August1st to 15thDay
6%214435%6%7%9%48%
2390
16th to endDay
6%213213347%61%
2292
September1st to 15thDay
8%213323345%59%
2133
16th to endDay
7%312212247%63%
1980
October1st to 15thDay
12%6%23213245%54%
1921
16th to endDay
6%423313346%59%
1752
November1st to 15thDay
6%41432445%7%55%
1718
16th to endDay
432341335%7%59%
1742
December1st to 15thDay
5%6%35%424446%51%
1560
16th to endDay
5%7%26%324447%49%
1664
January1st to 15thNight
45%345%3445%7%50%
2716
16th to endNight
35%245%3445%8%52%
2912
February1st to 15thNight
6%8%35%5%35%446%45%
2332
16th to endNight
6%7%26%434446%49%
1894
March1st to 15thNight
6%5%25%41335%7%53%
2160
16th to endNight
9%6%245%2445%8%44%
2025
April1st to 15thNight
10%7%25%4345%5%6%43%
1798
16th to endNight
15%6%25%435%45%6%41%
1704
May1st to 15thNight
11%5%244245%5%5%46%
1619
16th to endNight
13%6%244345%6%6%41%
1505
June1st to 15thNight
10%5%2442445%8%46%
1440
16th to endNight
5%213325%6%6%9%52%
1440
July1st to 15thNight
7%313325%5%6%11%51%
1440
16th to endNight
3213225%46%9%58%
1512
August1st to 15thNight
5%3145%4448%9%48%
1568
16th to endNight
4212323448%61%
1910
September1st to 15thNight
8%413323447%56%
1827
16th to endNight
7%412323346%61%
1980
October1st to 15thNight
12%5%24423235%51%
2037
16th to endNight
7%313322346%60%
2460
November1st to 15thNight
5%224424447%56%
2470
16th to endNight
441332345%8%58%
2545
December1st to 15thNight
5%5%35%5%24447%51%
2730
16th to endNight
5%7%35%5%24346%50%
2912

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
30%419%30%12%2
1553
16th to endDay
30%319%31%13%2
1664
February1st to 15thDay
40%419%24%8%3
1797
16th to endDay
33%218%27%13%4
1580
March1st to 15thDay
29%216%28%19%3
1800
16th to endDay
39%5%16%22%15%1
2199
April1st to 15thDay
37%413%31%11%1
2150
16th to endDay
43%315%21%13%1
2256
May1st to 15thDay
36%316%30%11%1
2331
16th to endDay
40%418%24%9%2
2609
June1st to 15thDay
30%417%28%15%3
2520
16th to endDay
18%311%33%25%6%
2520
July1st to 15thDay
27%5%10%26%21%9%
2371
16th to endDay
23%410%29%23%8%
2489
August1st to 15thDay
29%5%15%25%16%6%
2374
16th to endDay
23%38%29%26%8%
2292
September1st to 15thDay
27%27%26%23%12%
2133
16th to endDay
21%28%33%28%4
1980
October1st to 15thDay
33%211%25%21%4
1921
16th to endDay
26%210%33%20%5%
1752
November1st to 15thDay
27%213%29%20%5%
1718
16th to endDay
24%214%33%22%2
1742
December1st to 15thDay
33%318%30%12%1
1560
16th to endDay
34%417%28%13%1
1664
January1st to 15thNight
31%318%29%14%1
2716
16th to endNight
29%316%30%16%2
2912
February1st to 15thNight
38%417%27%9%2
2342
16th to endNight
35%316%27%12%5%
1894
March1st to 15thNight
30%213%30%18%3
2160
16th to endNight
37%414%26%14%2
2025
April1st to 15thNight
38%416%23%13%2
1798
16th to endNight
41%414%25%12%1
1704
May1st to 15thNight
37%317%26%12%
1620
16th to endNight
39%6%20%21%8%2
1506
June1st to 15thNight
35%5%20%22%12%3
1440
16th to endNight
25%5%17%29%17%5%
1440
July1st to 15thNight
28%315%28%15%7%
1360
16th to endNight
20%313%32%23%6%
1416
August1st to 15thNight
29%5%19%26%13%6%
1560
16th to endNight
22%311%28%24%8%
1910
September1st to 15thNight
27%311%24%25%7%
1827
16th to endNight
25%29%31%24%6%
1980
October1st to 15thNight
35%310%23%23%4
2037
16th to endNight
25%212%28%23%7%
2460
November1st to 15thNight
27%312%27%22%6%
2470
16th to endNight
24%213%32%22%3
2545
December1st to 15thNight
33%316%30%12%2
2730
16th to endNight
34%418%27%13%2
2912

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
6%6%38%29%14%4
135
16th to endDay
11%434%38%9%2
144
February1st to 15thDay
15%7%55%16%3
126
16th to endDay
8%9%41%24%13%1
81
March1st to 15thDay
11%7%31%40%10%
90
16th to endDay
15%11%30%27%13%
204
April1st to 15thDay
10%14%37%28%8%1
269
16th to endDay
24%10%28%23%10%2
366
May1st to 15thDay
14%7%29%29%16%3
468
16th to endDay
17%7%28%29%13%3
517
June1st to 15thDay
9%428%31%18%6%
495
16th to endDay
4332%41%16%2
495
July1st to 15thDay
9%320%37%24%4
475
16th to endDay
5%23%41%24%4
515
August1st to 15thDay
8%122%41%22%3
483
16th to endDay
5%323%40%21%6%
332
September1st to 15thDay
6%424%34%21%9%
288
16th to endDay
11%419%40%20%4
135
October1st to 15thDay
14%5%35%25%14%4
135
16th to endDay
11%6%27%29%20%3
144
November1st to 15thDay
5%224%38%21%7%
135
16th to endDay
13%10%39%27%8%
135
December1st to 15thDay
8%11%46%22%9%1
135
16th to endDay
9%8%51%22%6%2
144
January1st to 15thNight
6%12%38%30%9%1
975
16th to endNight
6%9%42%33%6%
1040
February1st to 15thNight
9%7%45%31%6%
768
16th to endNight
10%8%43%30%6%
632
March1st to 15thNight
7%8%40%33%9%
720
16th to endNight
11%8%42%30%5%
597
April1st to 15thNight
13%8%42%32%3
539
16th to endNight
17%10%36%27%7%
540
May1st to 15thNight
13%7%34%31%11%1
540
16th to endNight
17%5%32%32%11%
563
June1st to 15thNight
12%437%32%11%1
540
16th to endNight
6%233%46%10%
540
July1st to 15thNight
7%125%48%15%
510
16th to endNight
4127%50%16%
564
August1st to 15thNight
6%125%48%16%
539
16th to endNight
4128%47%16%
573
September1st to 15thNight
10%127%42%14%1
540
16th to endNight
10%428%40%13%1
537
October1st to 15thNight
15%6%33%32%11%
597
16th to endNight
9%6%31%40%11%
924
November1st to 15thNight
7%7%38%35%10%1
950
16th to endNight
6%6%37%38%10%
975
December1st to 15thNight
7%10%42%32%6%
975
16th to endNight
10%9%37%34%7%
1040
Page generated at 2018-02-13 18:46:00. Version ac04

Copyright 2018 A. Danko


Ellsworth Clear Sky Chart |Charts Home