Gayle H. Riggsbee Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gayle H. Riggsbee Observatory clear sky chart from 2005-11-06 to 2024-01-15.

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
45%
24363
21%
74382
14%
24313
53%
24313
26%
46894

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%
758
23%
2459
9%
757
44%
757
24%
1489
January11th to 20thNight
32%
737
24%
2393
11%
737
47%
737
23%
1482
January21st to endNight
28%
792
27%
2574
14%
792
44%
792
26%
1570
February1st to 10thNight
31%
720
20%
2340
11%
720
44%
720
24%
1456
February11th to 20thNight
21%
701
21%
2138
8%
699
36%
699
22%
1406
February21st to endNight
26%
592
26%
1698
10%
592
41%
592
26%
1081
March1st to 10thNight
32%
720
26%
1980
14%
720
43%
720
31%
1242
March11th to 20thNight
30%
720
20%
1980
10%
720
39%
720
25%
1289
March21st to endNight
32%
792
20%
2178
8%
792
42%
792
26%
1437
April1st to 10thNight
35%
720
24%
1967
11%
720
46%
720
32%
1210
April11th to 20thNight
39%
711
25%
1775
10%
711
47%
711
35%
1121
April21st to endNight
46%
653
26%
1733
14%
653
51%
653
34%
1066
May1st to 10thNight
44%
540
20%
1620
10%
540
50%
540
31%
958
May11th to 20thNight
49%
531
15%
1593
9%
531
54%
531
24%
1075
May21st to endNight
61%
582
19%
1744
14%
582
64%
582
27%
1114
June1st to 10thNight
58%
540
15%
1620
12%
540
60%
540
23%
1115
June11th to 20thNight
57%
540
13%
1620
9%
540
60%
540
23%
1103
June21st to endNight
64%
540
14%
1620
12%
540
66%
540
25%
1089
July1st to 10thNight
63%
525
11%
1575
10%
525
64%
525
23%
1102
July11th to 20thNight
68%
522
11%
1566
10%
522
68%
522
25%
1060
July21st to endNight
67%
591
15%
1672
12%
558
68%
558
23%
1153
August1st to 10thNight
63%
537
13%
1600
13%
534
64%
534
22%
1109
August11th to 20thNight
63%
534
15%
1598
14%
534
64%
534
21%
1126
August21st to endNight
62%
767
14%
1955
11%
767
63%
767
24%
1420
September1st to 10thNight
65%
720
20%
1916
15%
720
66%
720
32%
1244
September11th to 20thNight
58%
720
21%
1980
17%
720
61%
720
28%
1321
September21st to endNight
54%
720
19%
1980
16%
720
58%
720
25%
1357
October1st to 10thNight
55%
720
25%
2110
23%
720
60%
720
34%
1262
October11th to 20thNight
50%
720
31%
2160
26%
720
60%
720
34%
1238
October21st to endNight
51%
792
32%
2376
24%
792
62%
792
36%
1337
November1st to 10thNight
49%
740
28%
2221
22%
740
58%
740
33%
1297
November11th to 20thNight
42%
760
28%
2365
19%
760
54%
760
31%
1368
November21st to endNight
43%
760
27%
2470
19%
760
55%
760
30%
1437
December1st to 10thNight
35%
760
23%
2470
14%
760
47%
760
22%
1601
December11th to 20thNight
41%
759
27%
2928
21%
758
52%
758
24%
1684
December21st to endNight
33%
827
16%
4408
14%
817
44%
817
14%
2475

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%5%25%5%35%5%6%8%42%
74952
Night
13%6%25%5%3445%7%44%
74828
TransparencyDay
39%7%11%19%18%5%
74675
Night
38%7%11%19%19%6%
74624
SeeingDay
16%9%24%24%19%8%
14233
Night
16%7%25%31%19%2
24379

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
16%6%25%433445%46%
1706
11th to 20thDay
16%6%345%345%36%45%
1656
21st to endDay
16%5%25%42345%5%47%
1782
February1st to 10thDay
16%7%35%5%33447%43%
1620
11th to 20thDay
20%6%2432345%6%46%
1705
21st to endDay
20%6%36%5%2345%5%41%
1556
March1st to 10thDay
15%5%24423245%53%
1980
11th to 20thDay
15%7%35%5%35%5%5%7%40%
1980
21st to endDay
15%7%35%5%35%5%5%7%41%
2178
April1st to 10thDay
11%3245%345%5%8%51%
1992
11th to 20thDay
11%6%35%425%45%8%46%
2134
21st to endDay
11%5%25%5%245%5%7%50%
2240
May1st to 10thDay
8%5%26%6%46%5%6%8%45%
2340
11th to 20thDay
12%6%26%5%36%6%6%8%39%
2301
21st to endDay
12%5%36%7%45%6%7%8%37%
2531
June1st to 10thDay
10%5%37%7%45%6%7%10%36%
2340
11th to 20thDay
8%4247%47%7%8%10%38%
2340
21st to endDay
7%436%7%47%7%8%11%37%
2340
July1st to 10thDay
9%427%8%5%7%7%7%11%32%
2340
11th to 20thDay
8%6%36%7%5%8%8%9%12%30%
2340
21st to endDay
7%5%36%7%5%9%6%10%11%32%
2547
August1st to 10thDay
11%6%36%7%5%6%8%8%11%29%
2327
11th to 20thDay
12%7%36%8%46%9%7%10%28%
2303
21st to endDay
11%5%26%7%45%7%7%10%34%
2381
September1st to 10thDay
8%5%26%7%46%5%7%9%41%
2039
11th to 20thDay
12%6%26%6%35%5%6%7%41%
1980
21st to endDay
19%6%35%5%245%5%7%41%
1980
October1st to 10thDay
16%5%23435%446%49%
1850
11th to 20thDay
12%424433446%55%
1800
21st to endDay
13%325%333335%56%
1980
November1st to 10thDay
13%424323345%57%
1857
11th to 20thDay
14%42432345%5%54%
1810
21st to endDay
14%425%42445%6%50%
1710
December1st to 10thDay
17%8%25%6%3445%6%39%
1710
11th to 20thDay
16%424323347%52%
2153
21st to endDay
18%7%35%42345%6%44%
3124
January1st to 10thNight
17%6%35%423445%48%
2459
11th to 20thNight
15%6%25%5%34446%46%
2393
21st to endNight
16%6%25%424345%48%
2574
February1st to 10thNight
17%6%245%2445%5%45%
2340
11th to 20thNight
19%7%35%5%33445%44%
2138
21st to endNight
17%6%34424446%46%
1698
March1st to 10thNight
14%6%35%424345%50%
1980
11th to 20thNight
16%5%26%5%345%6%7%42%
1980
21st to endNight
15%5%25%5%3445%7%43%
2178
April1st to 10thNight
12%5%235%3445%7%50%
1967
11th to 20thNight
11%4345%2445%7%52%
1775
21st to endNight
12%3246%3445%7%50%
1733
May1st to 10thNight
10%4344345%6%9%48%
1620
11th to 20thNight
11%6%25%7%36%7%6%9%37%
1592
21st to endNight
11%425%5%35%47%9%43%
1744
June1st to 10thNight
11%6%46%6%5%6%5%7%9%35%
1620
11th to 20thNight
10%6%36%5%46%6%8%10%35%
1620
21st to endNight
8%5%26%7%46%6%8%12%36%
1620
July1st to 10thNight
7%6%38%7%5%6%7%8%11%32%
1620
11th to 20thNight
8%5%27%6%35%7%9%12%35%
1620
21st to endNight
6%5%37%8%47%7%8%12%34%
1771
August1st to 10thNight
10%5%26%7%5%6%6%9%11%33%
1611
11th to 20thNight
11%6%37%7%47%6%8%10%33%
1598
21st to endNight
10%7%36%7%5%6%6%8%13%30%
1955
September1st to 10thNight
9%5%25%6%345%6%10%44%
1916
11th to 20thNight
12%7%26%5%345%6%7%43%
1980
21st to endNight
17%7%245%45%5%5%6%41%
1980
October1st to 10thNight
14%5%24423436%52%
2110
11th to 20thNight
13%435%323346%54%
2160
21st to endNight
11%5%24423345%56%
2376
November1st to 10thNight
13%6%34333335%55%
2221
11th to 20thNight
12%6%24423346%53%
2365
21st to endNight
15%42433436%7%48%
2470
December1st to 10thNight
18%7%35%434446%42%
2470
11th to 20thNight
17%5%24423335%52%
3042
21st to endNight
19%6%2443445%6%43%
4532

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
40%6%8%18%23%6%
1707
11th to 20thDay
41%6%7%17%23%6%
1656
21st to endDay
39%35%21%24%7%
1782
February1st to 10thDay
42%5%8%22%18%6%
1620
11th to 20thDay
41%46%19%24%5%
1715
21st to endDay
45%5%8%16%19%8%
1556
March1st to 10thDay
35%47%22%24%8%
1980
11th to 20thDay
43%6%9%17%18%7%
1980
21st to endDay
43%6%10%18%19%4
2178
April1st to 10thDay
32%5%10%21%27%6%
1992
11th to 20thDay
36%5%8%21%20%10%
2134
21st to endDay
33%7%10%23%22%5%
2240
May1st to 10thDay
35%8%13%20%21%4
2340
11th to 20thDay
42%8%14%18%16%1
2305
21st to endDay
41%10%13%20%15%1
2531
June1st to 10thDay
40%9%15%23%10%2
2340
11th to 20thDay
37%11%17%21%13%2
2340
21st to endDay
36%12%16%21%13%2
2340
July1st to 10thDay
41%12%18%16%10%3
2275
11th to 20thDay
40%13%22%17%7%1
2271
21st to endDay
39%13%19%20%8%1
2405
August1st to 10thDay
45%12%16%18%8%1
2314
11th to 20thDay
46%13%16%15%9%
2303
21st to endDay
41%12%16%19%9%3
2381
September1st to 10thDay
37%9%14%18%18%3
2039
11th to 20thDay
40%8%11%16%21%4
1980
21st to endDay
43%6%8%20%17%6%
1980
October1st to 10thDay
36%5%8%19%25%5%
1850
11th to 20thDay
31%48%24%24%8%
1800
21st to endDay
32%46%20%28%11%
1980
November1st to 10thDay
31%47%17%31%11%
1857
11th to 20thDay
31%5%9%19%26%10%
1810
21st to endDay
36%49%19%23%9%
1710
December1st to 10thDay
46%5%8%19%18%5%
1710
11th to 20thDay
34%36%21%26%10%
2150
21st to endDay
41%48%21%23%3
3124
January1st to 10thNight
40%49%17%24%6%
2459
11th to 20thNight
41%49%17%22%6%
2393
21st to endNight
40%35%19%25%8%
2574
February1st to 10thNight
41%49%18%21%7%
2340
11th to 20thNight
44%5%6%16%22%7%
2139
21st to endNight
40%411%18%19%8%
1698
March1st to 10thNight
37%47%18%23%11%
1980
11th to 20thNight
41%5%12%16%20%7%
1980
21st to endNight
40%7%11%18%19%5%
2178
April1st to 10thNight
33%6%9%20%24%8%
1967
11th to 20thNight
33%5%9%21%22%10%
1775
21st to endNight
33%6%11%24%21%5%
1733
May1st to 10thNight
32%8%14%24%19%4
1620
11th to 20thNight
41%10%14%19%16%1
1593
21st to endNight
36%10%14%25%13%3
1745
June1st to 10thNight
43%9%14%21%10%1
1620
11th to 20thNight
41%11%17%19%11%1
1620
21st to endNight
37%13%17%18%11%3
1620
July1st to 10thNight
41%13%20%15%8%3
1575
11th to 20thNight
37%13%24%17%7%2
1566
21st to endNight
38%15%19%19%9%1
1672
August1st to 10thNight
41%12%19%20%6%1
1600
11th to 20thNight
43%12%18%16%9%2
1598
21st to endNight
42%13%17%19%7%2
1955
September1st to 10thNight
35%10%15%19%15%6%
1916
11th to 20thNight
40%8%13%16%21%3
1980
21st to endNight
43%8%11%17%17%5%
1980
October1st to 10thNight
34%5%10%20%26%6%
2110
11th to 20thNight
32%47%23%24%10%
2160
21st to endNight
31%47%20%27%12%
2376
November1st to 10thNight
34%47%16%27%13%
2221
11th to 20thNight
34%46%17%26%13%
2365
21st to endNight
35%47%20%26%8%
2470
December1st to 10thNight
43%6%9%16%20%6%
2470
11th to 20thNight
37%47%18%25%10%
3044
21st to endNight
41%48%20%23%3
4532

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
20%20%43%15%2
270
11th to 20thDay
22%20%33%19%6%
252
21st to endDay
21%25%33%17%3
264
February1st to 10thDay
20%23%36%16%5%
240
11th to 20thDay
36%13%43%7%2
240
21st to endDay
24%19%35%18%3
274
March1st to 10thDay
18%17%35%23%6%
420
11th to 20thDay
20%18%38%18%42
420
21st to endDay
20%16%34%22%7%1
462
April1st to 10thDay
19%15%31%23%10%1
420
11th to 20thDay
12%18%30%22%14%4
412
21st to endDay
15%11%29%25%17%4
420
May1st to 10thDay
10%14%36%23%14%4
423
11th to 20thDay
16%5%22%26%23%8%
447
21st to endDay
15%417%24%27%13%
485
June1st to 10thDay
13%218%31%28%9%
450
11th to 20thDay
10%417%26%30%14%
450
21st to endDay
9%216%33%31%10%
450
July1st to 10thDay
9%29%21%36%22%
445
11th to 20thDay
9%28%27%36%18%
444
21st to endDay
8%19%31%35%15%
488
August1st to 10thDay
16%213%26%25%18%
446
11th to 20thDay
12%210%28%29%20%
439
21st to endDay
13%212%28%27%18%
495
September1st to 10thDay
8%210%33%31%16%
450
11th to 20thDay
14%412%25%34%12%
450
21st to endDay
19%5%17%28%24%6%
450
October1st to 10thDay
18%5%19%28%22%8%
450
11th to 20thDay
12%8%24%28%22%7%
450
21st to endDay
14%9%27%26%18%5%
495
November1st to 10thDay
17%7%26%29%16%4
455
11th to 20thDay
19%12%35%24%9%2
370
21st to endDay
11%14%36%24%11%3
270
December1st to 10thDay
24%14%38%18%5%
270
11th to 20thDay
20%13%35%21%9%2
270
21st to endDay
27%11%37%15%8%1
297
January1st to 10thNight
19%13%35%26%7%
760
11th to 20thNight
19%12%33%29%6%
737
21st to endNight
20%9%39%28%4
792
February1st to 10thNight
20%10%35%30%5%
720
11th to 20thNight
22%12%41%23%2
703
21st to endNight
20%13%37%27%4
592
March1st to 10thNight
18%10%37%31%5%
720
11th to 20thNight
18%12%36%26%9%1
720
21st to endNight
18%10%35%29%7%
792
April1st to 10thNight
15%15%32%29%9%
720
11th to 20thNight
14%12%31%30%13%
711
21st to endNight
13%8%27%40%12%
653
May1st to 10thNight
12%8%31%36%12%
540
11th to 20thNight
14%426%37%18%1
531
21st to endNight
13%215%34%35%2
584
June1st to 10thNight
12%317%40%26%3
540
11th to 20thNight
12%415%32%29%8%
540
21st to endNight
11%212%37%32%5%
540
July1st to 10thNight
9%111%34%37%8%
525
11th to 20thNight
10%18%30%45%6%
522
21st to endNight
8%111%36%40%5%
591
August1st to 10thNight
12%211%27%42%7%
537
11th to 20thNight
15%17%32%38%7%
534
21st to endNight
13%211%28%40%6%
767
September1st to 10thNight
11%29%32%39%6%
720
11th to 20thNight
15%215%28%36%5%
720
21st to endNight
20%415%31%27%3
720
October1st to 10thNight
16%5%19%27%28%6%
720
11th to 20thNight
15%6%23%31%22%2
720
21st to endNight
14%7%24%32%21%2
792
November1st to 10thNight
17%6%23%34%17%3
740
11th to 20thNight
15%10%30%32%12%1
760
21st to endNight
16%9%28%32%14%2
760
December1st to 10thNight
19%10%30%33%7%1
760
11th to 20thNight
20%8%27%35%11%
760
21st to endNight
24%13%25%29%9%
836
Page generated at 2024-01-11 22:33:48. Version ac07

Copyright 2024 Attilla Danko


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