Red Top
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Red Top 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
37%
24910
15%
74226
9%
24850
43%
24850
22%
51040

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
29%
950
14%
2712
6%
946
36%
946
20%
1928
January11th to 20thNight
27%
906
10%
2535
5%
906
32%
906
17%
1905
January21st to endNight
25%
990
13%
2601
4%
990
31%
990
16%
2027
February1st to 10thNight
28%
900
15%
2340
3%
900
36%
900
24%
1659
February11th to 20thNight
30%
878
18%
2273
6%
874
37%
874
24%
1586
February21st to endNight
30%
705
17%
1889
5%
705
38%
705
22%
1357
March1st to 10thNight
33%
608
15%
2048
11%
608
38%
608
19%
1408
March11th to 20thNight
31%
540
19%
1980
12%
540
42%
540
21%
1262
March21st to endNight
37%
594
16%
2155
13%
594
44%
594
17%
1476
April1st to 10thNight
29%
540
15%
1800
10%
540
38%
540
20%
1217
April11th to 20thNight
35%
533
17%
1730
14%
533
43%
533
19%
1207
April21st to endNight
35%
540
15%
1620
10%
540
42%
540
19%
1145
May1st to 10thNight
37%
540
15%
1490
7%
540
42%
540
24%
1032
May11th to 20thNight
42%
531
17%
1417
9%
531
46%
531
29%
941
May21st to endNight
48%
583
13%
1552
6%
582
51%
582
29%
1025
June1st to 10thNight
54%
540
11%
1440
5%
540
56%
540
33%
932
June11th to 20thNight
48%
540
15%
1260
6%
540
52%
540
36%
851
June21st to endNight
57%
540
15%
1260
7%
540
59%
540
36%
837
July1st to 10thNight
70%
525
18%
1225
9%
525
72%
525
49%
726
July11th to 20thNight
59%
522
19%
1357
9%
522
61%
522
41%
817
July21st to endNight
67%
591
22%
1487
11%
558
69%
558
50%
809
August1st to 10thNight
68%
537
20%
1581
16%
534
71%
534
40%
893
August11th to 20thNight
57%
534
22%
1600
20%
534
63%
534
36%
941
August21st to endNight
58%
594
23%
1867
23%
594
64%
594
34%
1078
September1st to 10thNight
58%
540
21%
1800
20%
540
64%
540
33%
991
September11th to 20thNight
52%
540
22%
1826
20%
540
60%
540
32%
1047
September21st to endNight
40%
605
20%
2045
13%
605
50%
605
26%
1250
October1st to 10thNight
39%
720
19%
2160
12%
720
45%
720
27%
1381
October11th to 20thNight
30%
720
18%
2160
8%
720
38%
720
20%
1476
October21st to endNight
28%
792
15%
2420
8%
792
35%
792
17%
1751
November1st to 10thNight
32%
893
17%
2559
10%
893
38%
893
20%
1804
November11th to 20thNight
26%
950
13%
2660
5%
950
32%
950
15%
2011
November21st to endNight
26%
950
13%
2660
6%
950
32%
950
17%
1941
December1st to 10thNight
26%
950
8%
2660
4%
950
30%
950
14%
2062
December11th to 20thNight
21%
949
11%
3200
2%
948
28%
948
11%
2446
December21st to endNight
20%
1040
7%
4857
4%
1026
27%
1026
7%
3821

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%9%47%6%35%5%5%7%36%
75124
Night
12%9%47%6%35%45%7%37%
74549
TransparencyDay
46%7%13%23%10%1
74817
Night
46%6%13%22%11%1
74377
SeeingDay
15%7%27%30%17%4
14888
Night
16%7%31%32%12%1
24918

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
7%12%7%9%9%5%6%5%48%28%
1434
11th to 20thDay
10%13%7%13%8%45%6%6%8%19%
1448
21st to endDay
9%14%7%13%8%5%6%6%7%7%21%
1753
February1st to 10thDay
8%12%5%8%7%46%5%6%7%31%
1620
11th to 20thDay
8%11%5%8%7%45%5%5%7%36%
1574
21st to endDay
10%12%5%9%7%46%5%47%31%
1365
March1st to 10thDay
12%10%5%8%6%5%5%5%47%33%
1926
11th to 20thDay
14%9%47%6%345%5%8%35%
1980
21st to endDay
17%11%48%5%445%5%8%29%
2200
April1st to 10thDay
15%11%37%6%445%5%6%33%
2160
11th to 20thDay
18%11%5%7%6%3445%6%30%
2176
21st to endDay
21%9%46%5%45%446%32%
2340
May1st to 10thDay
16%9%46%6%4445%6%35%
2467
11th to 20thDay
16%7%36%6%345%5%8%37%
2479
21st to endDay
15%6%26%6%35%5%5%8%38%
2725
June1st to 10thDay
10%5%35%5%35%5%6%9%45%
2520
11th to 20thDay
13%6%36%5%35%5%6%8%41%
2695
21st to endDay
8%5%26%6%36%6%8%10%39%
2700
July1st to 10thDay
6%424435%5%6%10%52%
2700
11th to 20thDay
8%6%24445%5%7%8%48%
2556
21st to endDay
7%3245%35%5%6%10%50%
2743
August1st to 10thDay
9%435%5%45%6%6%8%45%
2346
11th to 20thDay
12%6%25%4345%5%8%45%
2301
21st to endDay
11%6%2442445%8%49%
2489
September1st to 10thDay
9%6%35%5%345%6%10%45%
2160
11th to 20thDay
12%5%36%5%35%5%5%7%45%
2130
21st to endDay
15%8%25%4445%5%8%41%
1896
October1st to 10thDay
17%10%37%5%245%5%7%36%
1800
11th to 20thDay
15%13%47%5%45%346%34%
1800
21st to endDay
19%11%48%5%345%45%32%
1936
November1st to 10thDay
13%12%6%7%7%35%445%33%
1519
11th to 20thDay
12%14%8%12%9%345%45%24%
1520
21st to endDay
14%11%5%8%6%5%5%5%5%7%29%
1520
December1st to 10thDay
10%14%6%10%10%5%6%6%5%5%23%
1520
11th to 20thDay
10%14%6%12%9%46%5%45%24%
1918
21st to endDay
22%18%7%12%8%33345%16%
2708
January1st to 10thNight
9%8%410%9%45%5%6%7%31%
2712
11th to 20thNight
9%13%7%10%7%45%46%8%26%
2535
21st to endNight
11%13%5%12%7%46%6%6%7%23%
2601
February1st to 10thNight
6%9%6%9%8%46%5%5%7%36%
2340
11th to 20thNight
7%10%48%7%46%46%7%38%
2273
21st to endNight
12%11%48%8%45%45%8%32%
1889
March1st to 10thNight
11%11%5%8%7%445%45%37%
2048
11th to 20thNight
12%10%47%6%35%446%41%
1980
21st to endNight
17%9%37%6%4445%6%35%
2155
April1st to 10thNight
17%10%36%5%25%45%7%36%
1800
11th to 20thNight
20%11%46%433345%36%
1730
21st to endNight
19%8%47%5%35%447%33%
1620
May1st to 10thNight
13%10%36%6%35%447%38%
1490
11th to 20thNight
14%6%36%4246%6%7%41%
1416
21st to endNight
14%5%26%5%35%5%7%8%41%
1551
June1st to 10thNight
11%425%5%35%5%7%8%44%
1440
11th to 20thNight
10%6%25%6%345%5%8%46%
1260
21st to endNight
9%6%25%5%35%5%6%6%49%
1260
July1st to 10thNight
3423435%5%6%8%58%
1260
11th to 20thNight
8%423435%45%7%55%
1402
21st to endNight
422443346%9%60%
1575
August1st to 10thNight
6%4244345%7%9%52%
1590
11th to 20thNight
13%42442335%7%53%
1600
21st to endNight
10%5%2443345%7%53%
1867
September1st to 10thNight
8%425%4345%5%8%53%
1800
11th to 20thNight
8%425%43445%8%51%
1826
21st to endNight
15%5%25%42445%7%47%
2045
October1st to 10thNight
15%7%35%5%2445%7%43%
2160
11th to 20thNight
16%10%47%44345%6%37%
2160
21st to endNight
18%10%49%5%3445%6%33%
2420
November1st to 10thNight
14%10%38%6%35%5%5%6%36%
2559
11th to 20thNight
15%10%5%9%6%5%6%5%5%6%29%
2660
21st to endNight
12%8%47%7%46%5%6%7%34%
2660
December1st to 10thNight
9%12%6%12%8%45%5%6%7%24%
2660
11th to 20thNight
9%15%5%11%8%46%6%5%7%23%
3279
21st to endNight
23%18%5%8%7%34345%20%
4926

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
55%5%11%21%7%1
1435
11th to 20thDay
60%8%9%15%8%
1448
21st to endDay
60%7%10%14%9%1
1753
February1st to 10thDay
50%411%22%11%2
1620
11th to 20thDay
47%6%13%23%9%1
1583
21st to endDay
52%5%9%20%13%1
1365
March1st to 10thDay
50%6%14%20%8%1
1926
11th to 20thDay
46%6%14%24%9%1
1980
21st to endDay
53%6%9%23%7%1
2200
April1st to 10thDay
50%5%12%18%13%2
2160
11th to 20thDay
53%5%11%18%12%1
2176
21st to endDay
53%6%11%19%11%
2340
May1st to 10thDay
48%7%11%23%9%2
2467
11th to 20thDay
44%8%14%23%10%2
2483
21st to endDay
44%8%12%25%11%1
2725
June1st to 10thDay
34%8%17%31%9%1
2520
11th to 20thDay
40%8%15%23%14%1
2695
21st to endDay
36%10%16%27%10%1
2700
July1st to 10thDay
26%8%16%33%16%1
2626
11th to 20thDay
32%9%14%28%15%2
2479
21st to endDay
27%9%18%29%16%1
2591
August1st to 10thDay
34%9%14%31%10%3
2331
11th to 20thDay
36%8%16%29%11%1
2301
21st to endDay
32%7%15%30%15%1
2489
September1st to 10thDay
34%7%15%34%9%
2160
11th to 20thDay
37%8%18%29%8%
2130
21st to endDay
42%7%14%30%7%
1896
October1st to 10thDay
47%7%13%24%8%1
1800
11th to 20thDay
52%6%11%20%10%1
1800
21st to endDay
53%5%12%21%8%
1936
November1st to 10thDay
54%5%11%19%10%1
1519
11th to 20thDay
62%6%14%12%5%1
1520
21st to endDay
54%8%17%15%42
1520
December1st to 10thDay
63%8%12%13%4
1520
11th to 20thDay
61%6%13%16%5%
1915
21st to endDay
71%49%9%6%
2708
January1st to 10thNight
50%6%12%20%10%1
2712
11th to 20thNight
54%7%15%15%8%1
2535
21st to endNight
58%6%10%16%8%1
2601
February1st to 10thNight
47%5%12%23%11%1
2340
11th to 20thNight
46%5%14%23%11%2
2274
21st to endNight
50%5%11%20%12%1
1889
March1st to 10thNight
49%6%14%21%10%1
2048
11th to 20thNight
45%5%13%22%15%
1980
21st to endNight
50%6%12%21%10%2
2155
April1st to 10thNight
48%5%10%19%16%2
1800
11th to 20thNight
53%38%20%15%2
1730
21st to endNight
51%6%9%20%13%2
1620
May1st to 10thNight
46%6%13%22%13%1
1490
11th to 20thNight
40%6%14%24%14%3
1417
21st to endNight
38%8%14%24%14%2
1552
June1st to 10thNight
35%8%18%27%10%3
1440
11th to 20thNight
36%7%15%24%17%2
1260
21st to endNight
33%8%16%28%13%2
1260
July1st to 10thNight
23%7%18%34%18%1
1225
11th to 20thNight
28%7%14%29%18%4
1357
21st to endNight
21%6%19%33%19%3
1487
August1st to 10thNight
26%8%16%34%12%4
1581
11th to 20thNight
31%6%16%31%15%1
1600
21st to endNight
31%6%12%31%18%2
1867
September1st to 10thNight
29%7%16%34%13%1
1800
11th to 20thNight
31%7%16%33%12%
1826
21st to endNight
38%6%13%33%10%
2045
October1st to 10thNight
40%6%13%28%12%1
2160
11th to 20thNight
46%6%13%23%11%1
2160
21st to endNight
53%6%12%20%9%1
2420
November1st to 10thNight
49%6%13%22%9%2
2559
11th to 20thNight
56%7%14%14%9%
2660
21st to endNight
50%9%17%18%5%1
2660
December1st to 10thNight
58%7%15%14%5%1
2660
11th to 20thNight
59%6%12%15%6%2
3281
21st to endNight
66%5%9%14%6%
4926

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%31%30%13%3
270
11th to 20thDay
14%9%32%38%7%
243
21st to endDay
16%7%36%24%17%1
264
February1st to 10thDay
14%12%40%29%5%
240
11th to 20thDay
16%14%36%26%7%2
240
21st to endDay
17%10%38%29%6%
198
March1st to 10thDay
17%10%33%29%8%3
240
11th to 20thDay
18%6%32%27%15%2
240
21st to endDay
21%12%25%26%14%3
286
April1st to 10thDay
19%13%30%30%8%1
420
11th to 20thDay
26%7%24%27%14%1
454
21st to endDay
23%6%31%24%12%4
600
May1st to 10thDay
18%6%30%31%12%2
603
11th to 20thDay
17%8%26%30%15%4
625
21st to endDay
17%5%24%27%22%4
679
June1st to 10thDay
10%325%30%27%4
630
11th to 20thDay
13%429%35%17%1
630
21st to endDay
11%5%24%33%19%8%
630
July1st to 10thDay
9%218%33%28%11%
621
11th to 20thDay
9%421%35%22%9%
618
21st to endDay
8%322%35%23%9%
684
August1st to 10thDay
10%319%34%27%6%
626
11th to 20thDay
13%419%31%27%7%
615
21st to endDay
12%7%22%31%23%5%
608
September1st to 10thDay
11%5%28%31%20%4
450
11th to 20thDay
11%5%24%34%22%3
420
21st to endDay
21%10%27%24%12%6%
270
October1st to 10thDay
21%429%25%14%7%
270
11th to 20thDay
16%17%31%27%8%
270
21st to endDay
25%9%39%19%7%
297
November1st to 10thDay
20%11%29%31%9%1
270
11th to 20thDay
17%14%40%23%5%
270
21st to endDay
20%14%38%24%4
270
December1st to 10thDay
14%11%39%25%11%
270
11th to 20thDay
17%15%36%25%7%
270
21st to endDay
28%10%32%25%31
297
January1st to 10thNight
13%8%37%32%10%1
950
11th to 20thNight
16%6%37%32%9%1
906
21st to endNight
16%8%37%30%9%1
990
February1st to 10thNight
10%7%41%32%9%1
900
11th to 20thNight
12%9%41%28%10%1
879
21st to endNight
16%9%34%29%11%1
705
March1st to 10thNight
16%9%35%30%10%1
608
11th to 20thNight
16%8%39%28%9%
540
21st to endNight
20%7%28%31%10%4
594
April1st to 10thNight
21%7%36%29%6%1
540
11th to 20thNight
26%8%26%32%8%1
533
21st to endNight
23%6%27%31%11%1
540
May1st to 10thNight
16%8%33%31%10%1
540
11th to 20thNight
17%6%29%35%11%2
531
21st to endNight
15%5%25%37%18%1
584
June1st to 10thNight
12%323%42%18%1
540
11th to 20thNight
11%330%42%13%
540
21st to endNight
11%5%20%40%23%1
540
July1st to 10thNight
5%217%44%29%3
525
11th to 20thNight
9%223%39%23%3
522
21st to endNight
5%219%46%24%3
591
August1st to 10thNight
7%216%51%21%4
537
11th to 20thNight
14%320%34%25%4
534
21st to endNight
10%421%38%25%2
594
September1st to 10thNight
10%5%22%39%21%3
540
11th to 20thNight
11%427%35%21%1
540
21st to endNight
17%8%32%29%13%2
605
October1st to 10thNight
19%8%29%29%13%1
720
11th to 20thNight
21%11%33%28%7%1
720
21st to endNight
25%11%30%28%6%
792
November1st to 10thNight
19%11%29%31%10%
893
11th to 20thNight
19%12%34%26%8%1
950
21st to endNight
16%13%38%25%8%
950
December1st to 10thNight
15%11%34%30%9%1
950
11th to 20thNight
20%8%36%27%8%1
950
21st to endNight
25%8%33%26%6%1
1045
Page generated at 2024-01-08 21:31:23. Version ac07

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