Hugo
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hugo clear sky chart from 2005-11-05 to 2017-09-24.

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
51%
15940
27%
46930
17%
15895
59%
15895
39%
26004

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
51%
900
30%
2506
20%
895
58%
895
47%
1326
January16th to endNight
47%
861
34%
2589
20%
861
60%
861
45%
1306
February1st to 15thNight
41%
704
23%
2166
12%
700
53%
700
35%
1228
February16th to endNight
41%
632
33%
1894
17%
632
55%
632
42%
999
March1st to 15thNight
45%
720
27%
2160
15%
720
55%
720
41%
1173
March16th to endNight
40%
630
25%
2004
14%
630
52%
630
37%
1082
April1st to 15thNight
31%
539
21%
1798
11%
539
46%
539
32%
984
April16th to endNight
36%
540
20%
1791
14%
540
48%
540
26%
1083
May1st to 15thNight
46%
540
22%
1620
16%
540
55%
540
31%
985
May16th to endNight
41%
561
17%
1541
10%
561
49%
561
31%
974
June1st to 15thNight
48%
540
19%
1440
9%
540
55%
540
41%
826
June16th to endNight
57%
540
22%
1440
13%
540
63%
540
41%
842
July1st to 15thNight
66%
510
17%
1360
13%
510
68%
510
33%
869
July16th to endNight
72%
564
21%
1416
18%
531
73%
531
34%
899
August1st to 15thNight
63%
539
15%
1711
15%
536
66%
536
26%
1082
August16th to endNight
70%
573
23%
1910
28%
573
73%
573
38%
1024
September1st to 15thNight
60%
540
26%
1802
23%
540
67%
540
35%
993
September16th to endNight
62%
519
36%
1914
32%
519
73%
519
45%
852
October1st to 15thNight
47%
572
29%
1892
21%
572
56%
572
33%
1024
October16th to endNight
60%
781
35%
2189
20%
781
68%
781
53%
1092
November1st to 15thNight
59%
875
35%
2275
19%
875
66%
875
54%
1187
November16th to endNight
54%
900
36%
2340
20%
900
62%
900
53%
1227
December1st to 15thNight
47%
900
25%
2484
15%
900
54%
900
41%
1411
December16th to endNight
43%
960
29%
2688
15%
960
54%
960
37%
1536

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
5%41332445%8%56%
48022
Night
5%42432445%7%56%
47102
Cloud CoverDay
5%41332445%7%56%
48020
Night
5%42442445%7%56%
47102
TransparencyDay
25%5%12%25%22%8%
47696
Night
26%5%12%25%22%7%
46930
SeeingDay
9%7%26%29%20%6%
5877
Night
7%6%30%38%16%2
15942

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
3423312445%62%
1432
16th to endDay
3423322237%63%
1647
February1st to 15thDay
25%26%423437%56%
1696
16th to endDay
35%25%423346%58%
1580
March1st to 15thDay
341332445%7%59%
1800
16th to endDay
6%6%1431346%8%53%
2219
April1st to 15thDay
7%42342345%8%53%
2150
16th to endDay
10%5%245%2445%8%45%
2168
May1st to 15thDay
9%5%25%4245%6%8%46%
2331
16th to endDay
8%4133245%6%9%50%
2571
June1st to 15thDay
6%3123345%6%10%52%
2520
16th to endDay
221231346%9%62%
2520
July1st to 15thDay
4314435%5%6%9%50%
2520
16th to endDay
5%214435%6%7%10%49%
2656
August1st to 15thDay
5%424425%6%7%10%47%
2238
16th to endDay
5%31332438%9%54%
2292
September1st to 15thDay
7%21332346%7%56%
2157
16th to endDay
423223236%68%
1904
October1st to 15thDay
7%5%12212236%63%
1735
16th to endDay
5%312212236%66%
1672
November1st to 15thDay
321332245%6%63%
1583
16th to endDay
2412313236%67%
1620
December1st to 15thDay
46%23323447%56%
1475
16th to endDay
46%3441335%7%55%
1536
January1st to 15thNight
242332445%6%60%
2506
16th to endNight
2424312345%64%
2589
February1st to 15thNight
35%244245%5%8%52%
2156
16th to endNight
343431335%7%59%
1894
March1st to 15thNight
45%24323446%59%
2160
16th to endNight
6%5%23323447%55%
2004
April1st to 15thNight
6%5%2442446%7%50%
1798
16th to endNight
11%6%25%32346%7%45%
1791
May1st to 15thNight
9%6%243245%47%49%
1619
16th to endNight
10%5%1343446%8%46%
1540
June1st to 15thNight
4313335%46%10%53%
1440
16th to endNight
33135%35%6%6%8%53%
1440
July1st to 15thNight
6%2146%45%5%7%10%43%
1440
16th to endNight
5%315%5%46%47%9%47%
1512
August1st to 15thNight
5%6%35%436%6%8%8%41%
1719
16th to endNight
6%4123145%6%10%53%
1910
September1st to 15thNight
8%4143236%5%7%52%
1802
16th to endNight
4212313337%66%
1914
October1st to 15thNight
8%5%23323335%57%
1892
16th to endNight
4312212345%68%
2189
November1st to 15thNight
221231435%7%65%
2275
16th to endNight
2424312346%66%
2340
December1st to 15thNight
35%25%5%2435%6%55%
2484
16th to endNight
46%244245%46%55%
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
35%23322436%62%
1432
16th to endDay
3423323236%64%
1647
February1st to 15thDay
25%26%423347%56%
1696
16th to endDay
35%25%413446%58%
1580
March1st to 15thDay
341332445%6%60%
1800
16th to endDay
6%6%2431345%8%52%
2217
April1st to 15thDay
7%42342445%7%53%
2150
16th to endDay
11%5%144345%5%7%45%
2168
May1st to 15thDay
9%5%2443446%7%46%
2331
16th to endDay
8%5%233245%5%8%50%
2571
June1st to 15thDay
7%3342446%10%52%
2520
16th to endDay
311221346%8%63%
2520
July1st to 15thDay
4314426%5%6%9%50%
2520
16th to endDay
5%213435%5%8%9%49%
2656
August1st to 15thDay
5%314425%5%7%10%48%
2238
16th to endDay
6%31332447%8%55%
2292
September1st to 15thDay
7%21342345%7%56%
2157
16th to endDay
422322245%68%
1904
October1st to 15thDay
7%412212336%63%
1735
16th to endDay
5%312212335%67%
1672
November1st to 15thDay
3213322446%63%
1583
16th to endDay
2422222336%67%
1620
December1st to 15thDay
46%23323446%57%
1475
16th to endDay
46%3432445%8%54%
1536
January1st to 15thNight
242341345%7%60%
2506
16th to endNight
2424312345%64%
2589
February1st to 15thNight
45%244245%5%8%52%
2156
16th to endNight
25%3431335%6%59%
1894
March1st to 15thNight
45%23314446%59%
2160
16th to endNight
6%42332345%7%55%
2004
April1st to 15thNight
7%5%2433445%7%51%
1798
16th to endNight
12%7%2442435%7%45%
1791
May1st to 15thNight
9%5%233245%47%48%
1619
16th to endNight
10%5%2342445%8%46%
1540
June1st to 15thNight
42135%245%6%9%53%
1440
16th to endNight
3214425%7%5%8%54%
1440
July1st to 15thNight
6%2146%45%6%6%10%43%
1440
16th to endNight
5%3245%36%5%7%8%46%
1512
August1st to 15thNight
5%6%35%5%35%7%8%8%40%
1719
16th to endNight
6%31231446%11%52%
1910
September1st to 15thNight
8%3144135%6%6%53%
1802
16th to endNight
4213213337%65%
1914
October1st to 15thNight
8%6%13323335%57%
1892
16th to endNight
4312213336%68%
2189
November1st to 15thNight
221231335%7%65%
2275
16th to endNight
2424213246%66%
2340
December1st to 15thNight
35%25%434346%56%
2484
16th to endNight
46%2442445%6%54%
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
24%311%30%24%5%
1433
16th to endDay
22%210%30%25%8%
1647
February1st to 15thDay
28%412%32%16%5%
1697
16th to endDay
26%48%27%25%7%
1580
March1st to 15thDay
22%5%11%27%24%9%
1800
16th to endDay
28%414%24%21%5%
2219
April1st to 15thDay
29%5%11%26%20%6%
2150
16th to endDay
35%6%12%22%16%5%
2168
May1st to 15thDay
34%6%12%26%17%3
2331
16th to endDay
29%7%16%23%15%7%
2575
June1st to 15thDay
24%6%15%23%17%11%
2520
16th to endDay
16%6%11%26%24%14%
2520
July1st to 15thDay
27%7%12%23%20%9%
2371
16th to endDay
26%7%14%26%20%4
2489
August1st to 15thDay
28%7%14%24%15%9%
2222
16th to endDay
24%5%9%27%24%7%
2292
September1st to 15thDay
26%5%11%21%24%11%
2157
16th to endDay
18%37%23%36%9%
1904
October1st to 15thDay
23%39%23%31%8%
1735
16th to endDay
19%28%27%30%11%
1672
November1st to 15thDay
21%310%25%25%13%
1583
16th to endDay
19%28%24%32%13%
1620
December1st to 15thDay
27%411%31%21%3
1475
16th to endDay
27%414%28%18%6%
1536
January1st to 15thNight
22%411%28%26%6%
2506
16th to endNight
22%39%30%26%7%
2589
February1st to 15thNight
30%5%13%29%16%4
2166
16th to endNight
25%310%27%25%8%
1894
March1st to 15thNight
26%410%22%28%7%
2160
16th to endNight
27%5%14%22%23%7%
2004
April1st to 15thNight
30%5%11%25%21%6%
1798
16th to endNight
37%5%11%23%16%4
1791
May1st to 15thNight
33%7%12%26%15%3
1620
16th to endNight
34%8%18%19%12%7%
1541
June1st to 15thNight
24%8%20%22%15%8%
1440
16th to endNight
24%8%12%24%18%10%
1440
July1st to 15thNight
32%9%13%24%13%6%
1360
16th to endNight
32%9%14%21%18%4
1416
August1st to 15thNight
36%10%15%20%10%6%
1711
16th to endNight
26%6%13%27%19%6%
1910
September1st to 15thNight
29%5%13%21%20%9%
1802
16th to endNight
19%49%26%31%8%
1914
October1st to 15thNight
28%6%9%18%28%8%
1892
16th to endNight
18%39%25%28%14%
2189
November1st to 15thNight
17%49%24%27%15%
2275
16th to endNight
20%28%26%28%13%
2340
December1st to 15thNight
28%313%29%20%4
2484
16th to endNight
29%412%27%21%3
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
14%423%36%14%6%
90
16th to endDay
9%10%29%34%14%2
96
February1st to 15thDay
7%10%46%25%8%1
90
16th to endDay
1359%16%14%4
81
March1st to 15thDay
312%34%28%20%1
90
16th to endDay
15%15%33%22%8%2
257
April1st to 15thDay
10%20%40%17%9%2
269
16th to endDay
19%17%35%20%6%
278
May1st to 15thDay
12%13%29%25%15%2
468
16th to endDay
12%8%30%25%18%3
517
June1st to 15thDay
8%5%27%27%22%9%
495
16th to endDay
4324%35%24%6%
495
July1st to 15thDay
6%117%33%30%9%
475
16th to endDay
8%10%33%35%11%
515
August1st to 15thDay
7%121%37%26%5%
351
16th to endDay
3122%43%22%5%
332
September1st to 15thDay
5%326%34%18%10%
312
16th to endDay
7%423%21%29%13%
114
October1st to 15thDay
5%225%28%23%14%
90
16th to endDay
6%7%26%23%22%13%
96
November1st to 15thDay
6%5%23%26%34%3
90
16th to endDay
16%16%27%21%17%
90
December1st to 15thDay
11%7%36%38%41
90
16th to endDay
11%10%26%38%10%3
96
January1st to 15thNight
45%33%38%15%2
900
16th to endNight
38%35%39%11%1
861
February1st to 15thNight
7%442%38%6%
704
16th to endNight
5%7%40%37%9%
632
March1st to 15thNight
7%6%35%34%13%1
720
16th to endNight
7%10%38%34%9%
630
April1st to 15thNight
10%12%43%27%6%
539
16th to endNight
14%12%32%29%9%
540
May1st to 15thNight
10%7%31%35%12%1
540
16th to endNight
11%7%32%33%13%
563
June1st to 15thNight
5%5%34%38%14%
540
16th to endNight
3328%46%16%
540
July1st to 15thNight
6%114%48%27%1
510
16th to endNight
6%110%42%34%3
564
August1st to 15thNight
7%116%43%28%2
539
16th to endNight
7%114%45%27%3
573
September1st to 15thNight
9%222%39%23%3
540
16th to endNight
5%225%40%21%3
519
October1st to 15thNight
12%6%29%31%16%3
572
16th to endNight
5%6%24%36%21%5%
781
November1st to 15thNight
4428%39%20%3
875
16th to endNight
5%7%28%39%15%3
900
December1st to 15thNight
6%7%32%39%11%2
900
16th to endNight
7%9%32%36%12%1
960
Page generated at 2017-09-25 07:02:26. Version ac04

Copyright 2017 A. Danko


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