HiRes 2
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the HiRes 2 clear sky chart from 2005-11-06 to 2024-02-15.

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
60%
23714
24%
79380
22%
23630
64%
23630
33%
44799

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 10thNight
51%
749
17%
4029
14%
736
56%
736
15%
2440
January11th to 20thNight
52%
756
13%
4091
18%
740
56%
740
15%
2698
January21st to endNight
51%
827
12%
4436
18%
814
55%
814
15%
2571
February1st to 10thNight
51%
760
18%
2470
17%
760
57%
760
27%
1536
February11th to 20thNight
54%
718
21%
2187
19%
718
58%
718
29%
1350
February21st to endNight
53%
592
26%
1776
23%
592
60%
592
31%
1099
March1st to 10thNight
51%
720
21%
2084
18%
720
55%
720
27%
1349
March11th to 20thNight
55%
720
25%
1980
19%
720
60%
720
36%
1201
March21st to endNight
47%
792
23%
2178
13%
792
54%
792
30%
1386
April1st to 10thNight
49%
720
24%
1944
14%
720
55%
720
35%
1186
April11th to 20thNight
47%
574
27%
1642
17%
574
53%
574
34%
986
April21st to endNight
51%
540
28%
1620
19%
540
57%
540
36%
904
May1st to 10thNight
52%
540
26%
1620
18%
540
56%
540
33%
944
May11th to 20thNight
59%
531
25%
1595
20%
531
63%
531
37%
884
May21st to endNight
54%
582
18%
1746
14%
582
58%
582
31%
1038
June1st to 10thNight
63%
540
24%
1620
21%
540
68%
540
41%
854
June11th to 20thNight
59%
495
28%
1575
25%
495
67%
495
46%
753
June21st to endNight
71%
360
31%
1440
35%
360
81%
360
48%
580
July1st to 10thNight
71%
388
25%
1438
28%
388
77%
388
42%
655
July11th to 20thNight
67%
522
23%
1566
21%
522
70%
522
39%
854
July21st to endNight
73%
591
25%
1674
22%
558
74%
558
42%
917
August1st to 10thNight
66%
537
29%
1602
20%
534
72%
534
46%
823
August11th to 20thNight
73%
534
35%
1602
26%
534
76%
534
49%
791
August21st to endNight
72%
633
37%
1821
29%
633
75%
633
50%
925
September1st to 10thNight
76%
720
34%
1952
25%
720
81%
720
59%
961
September11th to 20thNight
73%
720
36%
1980
28%
720
79%
720
57%
988
September21st to endNight
72%
720
38%
1980
29%
720
78%
720
59%
968
October1st to 10thNight
68%
720
33%
2011
23%
720
74%
720
50%
1062
October11th to 20thNight
71%
720
36%
2160
30%
720
76%
720
49%
1070
October21st to endNight
67%
792
36%
2435
31%
792
73%
792
49%
1189
November1st to 10thNight
65%
740
30%
2405
28%
740
70%
740
39%
1269
November11th to 20thNight
65%
760
30%
2470
30%
760
70%
760
40%
1298
November21st to endNight
60%
760
28%
2470
27%
760
64%
760
35%
1373
December1st to 10thNight
59%
760
23%
2470
22%
760
62%
760
31%
1438
December11th to 20thNight
55%
758
21%
2910
18%
758
58%
758
21%
1792
December21st to endNight
42%
823
11%
4401
15%
817
46%
817
12%
2667

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%6%25%5%345%5%7%53%
79131
Night
6%7%35%5%35%5%5%7%49%
80005
TransparencyDay
31%39%20%21%15%
78855
Night
34%310%22%20%11%
79803
SeeingDay
7%8%22%31%23%9%
13844
Night
8%5%19%40%24%4
23759

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 10thDay
5%16%5%9%8%45%5%5%6%32%
2858
11th to 20thDay
6%15%5%11%8%45%5%5%6%30%
2860
21st to endDay
7%9%410%8%5%6%5%5%8%34%
3146
February1st to 10thDay
5%10%47%7%345%7%9%39%
1710
11th to 20thDay
6%8%37%5%35%5%5%8%44%
1753
21st to endDay
49%47%5%5%446%8%44%
1480
March1st to 10thDay
5%9%35%435%5%5%7%46%
1876
11th to 20thDay
5%8%45%6%36%6%6%9%43%
1980
21st to endDay
9%8%35%5%45%6%6%7%42%
2178
April1st to 10thDay
6%8%35%6%35%45%7%48%
2011
11th to 20thDay
6%7%46%5%35%445%52%
2265
21st to endDay
7%6%2443445%7%56%
2340
May1st to 10thDay
5%3145%45%5%6%8%54%
2340
11th to 20thDay
6%324435%5%6%9%53%
2301
21st to endDay
5%5%245%35%6%7%8%49%
2530
June1st to 10thDay
32234345%6%8%61%
2340
11th to 20thDay
4323323346%67%
2376
21st to endDay
2212323346%73%
2520
July1st to 10thDay
321332346%7%66%
2471
11th to 20thDay
33234245%6%7%63%
2340
21st to endDay
22134245%7%9%59%
2545
August1st to 10thDay
3213425%5%6%7%62%
2328
11th to 20thDay
221332345%6%68%
2299
21st to endDay
2313334446%66%
2532
September1st to 10thDay
2212213346%74%
2008
11th to 20thDay
2223332345%72%
1980
21st to endDay
321322233474%
1980
October1st to 10thDay
6%31332445%6%62%
1947
11th to 20thDay
442332335%7%66%
1800
21st to endDay
442432345%7%62%
1918
November1st to 10thDay
6%5%235%345%6%8%53%
1674
11th to 20thDay
6%6%35%4235%5%7%53%
1710
21st to endDay
7%7%36%5%335%5%7%49%
1710
December1st to 10thDay
6%10%47%43445%9%44%
1710
11th to 20thDay
7%10%5%8%7%46%7%6%9%32%
2169
21st to endDay
6%10%49%8%5%6%6%6%7%35%
3146
January1st to 10thNight
7%14%5%8%7%4445%8%35%
4097
11th to 20thNight
9%13%6%9%7%35%5%5%6%32%
4110
21st to endNight
7%10%48%10%5%6%5%6%8%30%
4521
February1st to 10thNight
7%9%47%6%35%5%6%9%40%
2470
11th to 20thNight
7%10%47%5%36%446%45%
2186
21st to endNight
5%8%46%6%46%5%6%7%45%
1776
March1st to 10thNight
6%11%47%6%45%446%42%
2084
11th to 20thNight
5%6%26%6%46%5%7%8%46%
1980
21st to endNight
8%9%36%435%46%8%45%
2178
April1st to 10thNight
9%7%25%435%347%50%
1944
11th to 20thNight
6%7%35%5%445%5%6%51%
1642
21st to endNight
8%5%35%42445%8%53%
1620
May1st to 10thNight
7%5%25%6%26%6%6%8%47%
1620
11th to 20thNight
6%5%25%5%35%5%6%9%51%
1594
21st to endNight
7%6%35%6%36%5%7%8%46%
1746
June1st to 10thNight
5%3335%25%5%5%8%56%
1620
11th to 20thNight
4324323436%65%
1575
21st to endNight
221342446%7%65%
1440
July1st to 10thNight
2224335%5%6%7%61%
1480
11th to 20thNight
4425%5%35%7%5%7%52%
1620
21st to endNight
33245%35%5%8%10%51%
1773
August1st to 10thNight
3325%435%6%6%9%54%
1611
11th to 20thNight
231432446%7%63%
1602
21st to endNight
33134345%6%6%63%
1821
September1st to 10thNight
3213323347%69%
1952
11th to 20thNight
3223323347%69%
1980
21st to endNight
5%31321234472%
1980
October1st to 10thNight
5%424224447%62%
2011
11th to 20thNight
5%32332335%7%65%
2160
21st to endNight
5%31332345%6%64%
2435
November1st to 10thNight
7%6%2342445%8%55%
2405
11th to 20thNight
5%5%245%2445%7%56%
2470
21st to endNight
6%7%36%433347%53%
2470
December1st to 10thNight
8%7%36%5%3445%7%48%
2470
11th to 20thNight
8%10%36%5%45%5%6%8%39%
3041
21st to endNight
7%10%5%9%7%45%5%5%7%34%
4521

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 10thDay
53%318%20%6%
2859
11th to 20thDay
56%318%18%4
2860
21st to endDay
46%223%20%8%1
3146
February1st to 10thDay
41%5%17%24%11%2
1710
11th to 20thDay
39%414%27%15%1
1763
21st to endDay
38%313%29%16%2
1480
March1st to 10thDay
37%412%26%19%2
1876
11th to 20thDay
37%39%31%16%4
1980
21st to endDay
43%5%10%24%15%4
2178
April1st to 10thDay
36%48%25%18%9%
2011
11th to 20thDay
36%37%20%26%8%
2268
21st to endDay
29%37%24%30%7%
2340
May1st to 10thDay
28%47%21%29%11%
2340
11th to 20thDay
28%5%6%22%28%11%
2304
21st to endDay
31%5%7%22%25%10%
2530
June1st to 10thDay
21%25%18%34%19%
2340
11th to 20thDay
20%2414%29%30%
2376
21st to endDay
14%218%26%48%
2520
July1st to 10thDay
18%3310%19%46%
2404
11th to 20thDay
19%4311%23%39%
2271
21st to endDay
22%46%14%23%31%
2404
August1st to 10thDay
21%4414%22%34%
2313
11th to 20thDay
18%339%28%39%
2299
21st to endDay
20%3213%28%33%
2532
September1st to 10thDay
13%2313%29%39%
2008
11th to 20thDay
17%3418%27%31%
1980
21st to endDay
16%3417%33%28%
1980
October1st to 10thDay
23%46%18%35%13%
1947
11th to 20thDay
20%36%26%36%9%
1800
21st to endDay
23%310%31%29%5%
1918
November1st to 10thDay
29%312%26%25%4
1674
11th to 20thDay
32%210%35%19%2
1710
21st to endDay
35%312%31%18%2
1710
December1st to 10thDay
39%317%27%11%2
1710
11th to 20thDay
47%316%24%9%
2168
21st to endDay
47%316%18%15%1
3146
January1st to 10thNight
47%315%27%8%
4097
11th to 20thNight
53%218%18%8%1
4110
21st to endNight
45%222%20%9%1
4521
February1st to 10thNight
41%415%29%10%1
2470
11th to 20thNight
40%310%24%20%2
2187
21st to endNight
37%5%9%30%17%2
1776
March1st to 10thNight
44%29%25%18%2
2084
11th to 20thNight
35%310%29%19%4
1980
21st to endNight
39%49%26%17%5%
2178
April1st to 10thNight
35%38%25%20%9%
1944
11th to 20thNight
34%37%23%26%6%
1642
21st to endNight
31%38%25%27%5%
1620
May1st to 10thNight
33%46%21%27%8%
1620
11th to 20thNight
30%45%23%26%12%
1595
21st to endNight
35%410%21%22%7%
1746
June1st to 10thNight
27%35%19%28%19%
1620
11th to 20thNight
22%25%14%30%28%
1575
21st to endNight
18%3110%28%40%
1440
July1st to 10thNight
21%5%411%16%43%
1438
11th to 20thNight
29%45%10%17%35%
1566
21st to endNight
27%5%7%13%19%29%
1674
August1st to 10thNight
24%36%14%21%31%
1602
11th to 20thNight
21%4311%24%37%
1602
21st to endNight
21%4412%26%33%
1821
September1st to 10thNight
17%3412%25%40%
1952
11th to 20thNight
18%3416%26%33%
1980
21st to endNight
18%2314%30%33%
1980
October1st to 10thNight
24%26%17%34%16%
2011
11th to 20thNight
21%3419%40%11%
2160
21st to endNight
22%36%32%30%8%
2435
November1st to 10thNight
29%38%27%25%8%
2405
11th to 20thNight
28%39%34%22%4
2470
21st to endNight
33%38%32%22%2
2470
December1st to 10thNight
37%314%28%16%3
2470
11th to 20thNight
42%413%30%11%
3041
21st to endNight
49%214%19%15%1
4521

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 10thDay
13%10%22%28%21%6%
270
11th to 20thDay
7%6%27%37%16%7%
270
21st to endDay
9%5%18%37%21%10%
297
February1st to 10thDay
11%10%30%26%15%8%
270
11th to 20thDay
10%9%24%36%16%6%
394
21st to endDay
5%13%34%36%10%3
346
March1st to 10thDay
10%12%24%33%18%3
420
11th to 20thDay
10%10%30%29%15%6%
420
21st to endDay
14%14%34%26%11%2
462
April1st to 10thDay
11%14%27%27%17%5%
420
11th to 20thDay
12%20%27%25%14%2
412
21st to endDay
12%18%29%22%14%6%
420
May1st to 10thDay
414%32%31%13%5%
423
11th to 20thDay
7%11%23%29%23%7%
448
21st to endDay
5%12%19%32%24%8%
485
June1st to 10thDay
410%20%31%24%11%
450
11th to 20thDay
413%25%27%25%7%
450
21st to endDay
35%23%35%27%8%
450
July1st to 10thDay
2217%37%32%10%
446
11th to 20thDay
3415%39%29%10%
444
21st to endDay
2110%36%37%14%
487
August1st to 10thDay
3316%37%29%12%
447
11th to 20thDay
4313%31%34%15%
437
21st to endDay
3315%29%35%14%
495
September1st to 10thDay
3414%31%30%18%
450
11th to 20thDay
36%17%30%30%13%
450
21st to endDay
48%18%27%32%11%
450
October1st to 10thDay
6%8%23%26%23%14%
417
11th to 20thDay
49%16%29%24%18%
270
21st to endDay
7%7%19%35%27%6%
297
November1st to 10thDay
11%8%21%29%19%13%
270
11th to 20thDay
6%424%34%20%11%
270
21st to endDay
10%8%18%26%26%12%
270
December1st to 10thDay
8%7%20%32%21%11%
270
11th to 20thDay
11%6%20%36%24%4
270
21st to endDay
12%8%23%36%16%4
297
January1st to 10thNight
10%7%17%37%23%6%
760
11th to 20thNight
11%5%17%39%24%5%
760
21st to endNight
10%5%16%40%23%5%
836
February1st to 10thNight
11%5%21%41%17%4
760
11th to 20thNight
10%420%43%20%2
722
21st to endNight
7%6%25%46%15%1
592
March1st to 10thNight
9%9%22%41%16%2
720
11th to 20thNight
8%6%23%40%21%3
720
21st to endNight
11%8%28%38%14%2
792
April1st to 10thNight
13%8%24%38%15%2
720
11th to 20thNight
8%11%28%37%15%2
574
21st to endNight
10%8%25%37%17%2
540
May1st to 10thNight
8%8%25%41%16%2
540
11th to 20thNight
9%422%38%24%4
531
21st to endNight
9%9%19%34%26%3
584
June1st to 10thNight
6%9%15%42%26%1
540
11th to 20thNight
6%8%21%40%24%1
495
21st to endNight
2319%43%32%1
360
July1st to 10thNight
2215%42%37%3
388
11th to 20thNight
5%317%46%27%2
522
21st to endNight
5%112%43%37%2
591
August1st to 10thNight
3220%45%29%1
537
11th to 20thNight
3118%45%32%2
534
21st to endNight
4315%41%34%4
633
September1st to 10thNight
3313%39%37%6%
720
11th to 20thNight
3316%39%32%8%
720
21st to endNight
6%415%34%33%9%
720
October1st to 10thNight
7%318%40%28%4
720
11th to 20thNight
6%315%38%31%7%
720
21st to endNight
6%320%37%29%5%
792
November1st to 10thNight
9%5%14%39%27%6%
740
11th to 20thNight
6%418%45%22%6%
760
21st to endNight
8%419%38%24%6%
760
December1st to 10thNight
11%416%44%21%4
760
11th to 20thNight
13%5%16%41%23%2
760
21st to endNight
17%422%39%15%3
836
Page generated at 2024-02-12 04:35:36. Version ac07

Copyright 2024 Attilla Danko


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