ICStars Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the ICStars Ranch clear sky chart from 2005-11-06 to 2024-01-12.

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%
24454
22%
74710
14%
24391
49%
24391
29%
46162

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
28%
950
21%
2458
7%
946
38%
946
28%
1625
January11th to 20thNight
23%
908
21%
2360
7%
908
32%
908
26%
1630
January21st to endNight
26%
990
21%
2574
6%
990
35%
990
26%
1743
February1st to 10thNight
21%
900
15%
2340
5%
900
27%
900
22%
1666
February11th to 20thNight
25%
879
18%
2274
6%
875
31%
875
25%
1541
February21st to endNight
21%
566
23%
1750
7%
566
34%
566
23%
1131
March1st to 10thNight
27%
540
24%
1980
11%
540
42%
540
24%
1161
March11th to 20thNight
32%
540
18%
1980
12%
540
40%
540
18%
1281
March21st to endNight
24%
594
12%
2178
7%
594
32%
594
14%
1538
April1st to 10thNight
33%
540
22%
1839
14%
540
46%
540
28%
1053
April11th to 20thNight
36%
533
22%
1775
18%
533
46%
533
25%
1086
April21st to endNight
33%
540
20%
1743
12%
540
47%
540
25%
1112
May1st to 10thNight
38%
540
18%
1620
13%
540
47%
540
25%
1061
May11th to 20thNight
47%
531
19%
1594
16%
531
52%
531
28%
1013
May21st to endNight
48%
584
20%
1586
12%
582
54%
582
30%
1029
June1st to 10thNight
71%
540
22%
1440
15%
540
74%
540
44%
818
June11th to 20thNight
62%
540
24%
1440
15%
540
65%
540
41%
849
June21st to endNight
65%
540
26%
1440
17%
540
69%
540
51%
766
July1st to 10thNight
72%
525
19%
1467
16%
525
72%
525
40%
861
July11th to 20thNight
74%
522
23%
1566
21%
522
76%
522
47%
806
July21st to endNight
71%
591
23%
1673
24%
558
74%
558
41%
911
August1st to 10thNight
74%
537
22%
1601
26%
534
75%
534
41%
880
August11th to 20thNight
71%
534
29%
1600
32%
534
74%
534
42%
874
August21st to endNight
75%
594
28%
1975
34%
594
78%
594
43%
1002
September1st to 10thNight
65%
540
27%
1800
30%
540
67%
540
36%
971
September11th to 20thNight
64%
540
30%
1886
29%
540
70%
540
36%
980
September21st to endNight
62%
575
30%
2015
26%
575
68%
575
37%
1034
October1st to 10thNight
54%
720
27%
2160
20%
720
59%
720
39%
1199
October11th to 20thNight
36%
720
28%
2160
16%
720
46%
720
34%
1246
October21st to endNight
34%
792
25%
2376
13%
792
44%
792
28%
1468
November1st to 10thNight
41%
740
30%
2220
17%
740
52%
740
36%
1234
November11th to 20thNight
35%
878
27%
2550
12%
878
47%
878
32%
1501
November21st to endNight
30%
950
23%
2660
9%
950
41%
950
28%
1701
December1st to 10thNight
28%
950
20%
2660
8%
950
39%
950
27%
1735
December11th to 20thNight
29%
949
21%
3138
9%
948
38%
948
23%
1986
December21st to endNight
23%
1042
12%
4832
7%
1026
34%
1026
11%
3670

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
13%7%35%5%3445%7%44%
74622
Night
12%7%35%43445%7%47%
75102
TransparencyDay
39%7%12%25%15%2
74344
Night
37%6%11%26%17%3
74901
SeeingDay
15%8%27%27%18%5%
14488
Night
15%8%31%32%13%1
24458

By Month

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 10thDay
12%7%47%6%345%5%6%42%
1707
11th to 20thDay
14%11%48%6%34345%39%
1629
21st to endDay
14%10%46%5%35%446%39%
1782
February1st to 10thDay
15%11%5%7%6%33446%36%
1620
11th to 20thDay
15%8%47%5%34347%39%
1574
21st to endDay
15%10%36%5%3345%7%39%
1520
March1st to 10thDay
12%10%46%6%3345%6%41%
1980
11th to 20thDay
21%9%5%6%5%23347%34%
1980
21st to endDay
22%10%47%5%35%446%30%
2178
April1st to 10thDay
15%7%36%5%3345%6%43%
2119
11th to 20thDay
17%8%35%5%335%46%41%
2134
21st to endDay
20%7%47%6%34447%35%
2214
May1st to 10thDay
18%7%46%7%35%45%6%37%
2340
11th to 20thDay
17%6%26%5%34448%40%
2302
21st to endDay
14%7%36%6%45%6%6%8%35%
2686
June1st to 10thDay
7%424435%6%6%10%48%
2520
11th to 20thDay
8%425%5%45%5%5%8%48%
2520
21st to endDay
6%315%4346%8%9%51%
2520
July1st to 10thDay
10%425%425%5%7%11%45%
2445
11th to 20thDay
4424425%5%7%10%52%
2340
21st to endDay
9%5%25%5%35%5%7%8%45%
2546
August1st to 10thDay
8%5%25%5%35%6%6%11%45%
2328
11th to 20thDay
8%425%5%35%5%6%8%47%
2301
21st to endDay
7%4144345%6%9%52%
2380
September1st to 10thDay
11%42443345%7%52%
2160
11th to 20thDay
10%4234245%6%8%52%
2070
21st to endDay
8%424434447%56%
1926
October1st to 10thDay
12%425%423346%54%
1800
11th to 20thDay
13%6%25%323336%53%
1800
21st to endDay
18%7%35%5%23335%46%
1980
November1st to 10thDay
11%7%2332335%7%54%
1858
11th to 20thDay
15%7%24323346%50%
1622
21st to endDay
17%8%36%323335%46%
1520
December1st to 10thDay
11%9%45%5%34447%45%
1520
11th to 20thDay
13%9%5%7%434346%41%
1918
21st to endDay
17%16%6%10%5%34435%27%
2783
January1st to 10thNight
10%10%36%434436%47%
2458
11th to 20thNight
13%8%48%5%3445%6%40%
2360
21st to endNight
12%8%47%5%3445%6%41%
2574
February1st to 10thNight
14%9%5%7%6%3445%6%37%
2340
11th to 20thNight
13%8%47%5%24447%42%
2273
21st to endNight
15%9%35%424445%44%
1750
March1st to 10thNight
12%7%35%424346%48%
1980
11th to 20thNight
19%7%46%43445%6%40%
1980
21st to endNight
23%9%36%43445%7%32%
2178
April1st to 10thNight
11%7%2432345%7%50%
1839
11th to 20thNight
14%8%25%423446%46%
1775
21st to endNight
16%6%36%5%2445%7%42%
1743
May1st to 10thNight
16%6%25%5%3445%8%42%
1620
11th to 20thNight
15%6%2442446%7%46%
1593
21st to endNight
11%5%35%6%35%47%8%43%
1585
June1st to 10thNight
6%3233246%6%10%56%
1440
11th to 20thNight
5%424445%5%7%13%49%
1440
21st to endNight
42134335%6%9%60%
1440
July1st to 10thNight
9%3234246%6%10%50%
1510
11th to 20thNight
431433446%10%58%
1620
21st to endNight
8%3244245%8%10%51%
1772
August1st to 10thNight
42244346%6%9%56%
1611
11th to 20thNight
7%42442445%8%58%
1600
21st to endNight
6%3133335%5%7%61%
1975
September1st to 10thNight
11%42442335%6%56%
1800
11th to 20thNight
10%32343335%8%55%
1886
21st to endNight
7%314443447%58%
2015
October1st to 10thNight
9%5%2332445%6%57%
2160
11th to 20thNight
14%5%24323345%55%
2160
21st to endNight
16%6%25%42334451%
2376
November1st to 10thNight
11%5%24324335%59%
2220
11th to 20thNight
11%6%3442345%6%52%
2550
21st to endNight
16%7%35%424335%49%
2660
December1st to 10thNight
13%8%35%5%33446%45%
2660
11th to 20thNight
14%9%36%433447%44%
3279
21st to endNight
19%16%5%9%5%3333428%
4880

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
42%6%12%24%16%1
1708
11th to 20thDay
48%411%24%11%1
1629
21st to endDay
46%5%15%22%11%1
1782
February1st to 10thDay
51%412%21%11%1
1620
11th to 20thDay
46%5%12%20%14%2
1583
21st to endDay
46%5%11%22%14%3
1520
March1st to 10thDay
45%5%11%22%13%3
1980
11th to 20thDay
52%6%9%21%10%3
1980
21st to endDay
57%6%12%17%7%1
2178
April1st to 10thDay
41%6%12%24%16%1
2119
11th to 20thDay
44%6%13%22%14%1
2134
21st to endDay
50%6%11%23%11%
2214
May1st to 10thDay
49%7%11%22%11%1
2340
11th to 20thDay
44%8%12%24%13%
2306
21st to endDay
45%9%13%21%11%1
2686
June1st to 10thDay
28%10%17%31%14%1
2520
11th to 20thDay
33%9%13%26%17%2
2520
21st to endDay
27%8%16%30%14%4
2520
July1st to 10thDay
31%9%16%25%15%3
2380
11th to 20thDay
24%11%16%28%18%3
2271
21st to endDay
32%9%14%31%14%1
2405
August1st to 10thDay
31%10%18%26%14%1
2314
11th to 20thDay
32%8%14%29%15%1
2301
21st to endDay
27%7%14%26%20%6%
2380
September1st to 10thDay
31%7%13%27%17%6%
2160
11th to 20thDay
30%6%11%26%26%3
2070
21st to endDay
28%6%11%30%22%4
1926
October1st to 10thDay
32%5%11%26%22%3
1800
11th to 20thDay
34%48%28%22%4
1800
21st to endDay
42%49%21%18%5%
1980
November1st to 10thDay
31%5%13%27%20%5%
1858
11th to 20thDay
36%5%10%24%21%3
1622
21st to endDay
43%48%27%17%1
1520
December1st to 10thDay
41%5%11%29%13%1
1520
11th to 20thDay
45%5%13%25%10%2
1915
21st to endDay
60%6%10%15%8%1
2783
January1st to 10thNight
41%412%25%17%2
2458
11th to 20thNight
45%5%12%25%12%1
2360
21st to endNight
44%5%14%23%13%2
2574
February1st to 10thNight
48%5%11%20%12%3
2340
11th to 20thNight
43%5%12%20%17%3
2274
21st to endNight
42%6%10%21%17%5%
1750
March1st to 10thNight
39%49%25%19%4
1980
11th to 20thNight
46%6%9%21%15%4
1980
21st to endNight
53%6%12%18%9%1
2178
April1st to 10thNight
34%5%11%26%20%4
1839
11th to 20thNight
39%5%9%26%17%4
1775
21st to endNight
42%5%10%26%16%1
1743
May1st to 10thNight
40%8%13%24%14%1
1620
11th to 20thNight
38%7%14%24%16%1
1594
21st to endNight
37%8%15%26%12%2
1586
June1st to 10thNight
22%9%16%32%17%3
1440
11th to 20thNight
27%8%14%28%20%4
1440
21st to endNight
19%6%16%34%19%5%
1440
July1st to 10thNight
27%8%15%31%16%3
1467
11th to 20thNight
20%7%14%33%22%4
1566
21st to endNight
25%7%15%35%16%1
1673
August1st to 10thNight
23%10%18%33%15%2
1601
11th to 20thNight
26%6%11%32%24%1
1600
21st to endNight
22%6%12%27%25%7%
1975
September1st to 10thNight
29%5%12%26%22%7%
1800
11th to 20thNight
27%6%11%27%24%5%
1886
21st to endNight
27%5%9%28%28%5%
2015
October1st to 10thNight
28%5%9%26%25%6%
2160
11th to 20thNight
32%47%27%21%8%
2160
21st to endNight
38%5%8%22%23%5%
2376
November1st to 10thNight
29%5%12%26%23%5%
2220
11th to 20thNight
33%48%26%24%4
2550
21st to endNight
40%48%27%17%3
2660
December1st to 10thNight
40%6%12%26%15%1
2660
11th to 20thNight
41%5%11%29%14%1
3281
21st to endNight
59%6%8%17%8%2
4880

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
19%16%35%23%6%
270
11th to 20thDay
30%12%41%16%2
243
21st to endDay
17%17%45%17%3
264
February1st to 10thDay
27%15%40%14%4
240
11th to 20thDay
23%22%37%13%5%1
240
21st to endDay
26%23%34%15%21
198
March1st to 10thDay
18%15%48%16%3
240
11th to 20thDay
30%12%32%22%4
240
21st to endDay
36%16%31%13%5%
264
April1st to 10thDay
18%15%35%23%8%
379
11th to 20thDay
21%13%35%23%8%1
412
21st to endDay
23%13%33%22%8%1
474
May1st to 10thDay
18%12%34%26%10%1
603
11th to 20thDay
19%9%29%26%15%2
625
21st to endDay
17%8%27%24%19%6%
679
June1st to 10thDay
6%318%34%29%9%
630
11th to 20thDay
10%223%36%24%6%
630
21st to endDay
6%5%30%36%18%5%
630
July1st to 10thDay
12%213%27%31%15%
621
11th to 20thDay
5%216%35%32%10%
618
21st to endDay
10%114%34%31%10%
684
August1st to 10thDay
8%214%39%31%6%
626
11th to 20thDay
8%217%34%31%8%
615
21st to endDay
10%110%30%37%12%
499
September1st to 10thDay
12%214%37%26%9%
450
11th to 20thDay
7%313%38%31%8%
360
21st to endDay
9%6%25%32%21%7%
270
October1st to 10thDay
14%7%31%27%14%7%
270
11th to 20thDay
14%14%44%22%6%
270
21st to endDay
27%14%32%21%5%
297
November1st to 10thDay
16%8%37%25%9%5%
270
11th to 20thDay
17%16%31%24%9%2
270
21st to endDay
25%11%32%25%7%
270
December1st to 10thDay
14%14%39%23%7%2
270
11th to 20thDay
21%14%36%22%6%1
270
21st to endDay
21%22%40%16%
297
January1st to 10thNight
16%11%40%26%7%
950
11th to 20thNight
17%12%41%24%5%1
908
21st to endNight
15%13%40%28%3
990
February1st to 10thNight
18%12%43%23%4
900
11th to 20thNight
17%15%37%28%3
879
21st to endNight
21%14%42%20%3
566
March1st to 10thNight
17%13%41%24%5%
540
11th to 20thNight
21%10%33%30%6%1
540
21st to endNight
27%10%34%24%4
594
April1st to 10thNight
16%10%36%32%5%
540
11th to 20thNight
20%10%30%31%9%
533
21st to endNight
18%8%36%29%8%
540
May1st to 10thNight
17%6%32%38%8%
540
11th to 20thNight
17%5%26%34%16%1
531
21st to endNight
13%427%32%21%3
584
June1st to 10thNight
7%215%44%29%2
540
11th to 20thNight
7%124%44%22%2
540
21st to endNight
3324%50%18%1
540
July1st to 10thNight
8%111%42%33%4
525
11th to 20thNight
5%114%44%34%2
522
21st to endNight
10%111%42%35%2
591
August1st to 10thNight
5%112%47%34%1
537
11th to 20thNight
6%213%44%31%3
534
21st to endNight
6%111%37%40%4
594
September1st to 10thNight
13%214%42%26%3
540
11th to 20thNight
10%217%38%26%6%
540
21st to endNight
7%422%41%22%4
575
October1st to 10thNight
11%5%26%36%20%3
720
11th to 20thNight
16%7%37%31%9%
720
21st to endNight
19%10%34%26%11%
792
November1st to 10thNight
13%7%35%35%11%
740
11th to 20thNight
15%12%36%29%9%
878
21st to endNight
19%10%37%28%6%
950
December1st to 10thNight
17%10%39%27%6%1
950
11th to 20thNight
20%10%36%30%4
950
21st to endNight
20%15%37%25%3
1045
Page generated at 2024-01-09 06:14:39. Version ac07

Copyright 2024 Attilla Danko


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