River Ridge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the River Ridge Observatory 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
47%
24118
25%
74601
18%
24059
55%
24059
31%
43758

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
30%
949
27%
2458
9%
946
42%
946
31%
1550
January11th to 20thNight
26%
908
26%
2360
9%
908
37%
908
28%
1546
January21st to endNight
28%
990
30%
2574
9%
990
41%
990
33%
1592
February1st to 10thNight
26%
900
20%
2340
7%
900
33%
900
25%
1588
February11th to 20thNight
23%
767
20%
2163
7%
764
32%
764
26%
1414
February21st to endNight
22%
552
26%
1736
9%
552
36%
552
23%
1095
March1st to 10thNight
32%
540
25%
1980
15%
540
45%
540
25%
1153
March11th to 20thNight
30%
540
21%
1980
14%
540
40%
540
19%
1245
March21st to endNight
30%
594
20%
2178
11%
594
43%
594
22%
1344
April1st to 10thNight
35%
540
27%
1807
16%
540
50%
540
30%
1013
April11th to 20thNight
34%
533
27%
1775
17%
533
50%
533
30%
1000
April21st to endNight
35%
540
25%
1800
16%
540
51%
540
29%
1041
May1st to 10thNight
49%
540
21%
1800
17%
540
58%
540
29%
1056
May11th to 20thNight
48%
531
22%
1603
19%
531
55%
531
30%
982
May21st to endNight
58%
584
20%
1746
17%
582
63%
582
30%
1063
June1st to 10thNight
72%
540
24%
1499
22%
540
75%
540
44%
850
June11th to 20thNight
77%
540
28%
1440
25%
540
79%
540
50%
788
June21st to endNight
77%
540
27%
1609
26%
540
79%
540
47%
835
July1st to 10thNight
76%
525
20%
1575
22%
525
78%
525
38%
899
July11th to 20thNight
80%
522
23%
1566
25%
522
81%
522
42%
845
July21st to endNight
81%
591
26%
1673
29%
558
82%
558
41%
923
August1st to 10thNight
79%
537
21%
1601
24%
534
79%
534
40%
897
August11th to 20thNight
76%
534
26%
1751
32%
534
78%
534
37%
955
August21st to endNight
76%
594
23%
1980
28%
594
77%
594
36%
1079
September1st to 10thNight
76%
540
28%
1800
33%
540
77%
540
38%
972
September11th to 20thNight
68%
540
32%
1800
33%
540
70%
540
33%
1002
September21st to endNight
69%
624
31%
2062
29%
624
72%
624
42%
1036
October1st to 10thNight
65%
720
31%
2160
25%
720
69%
720
44%
1144
October11th to 20thNight
50%
720
34%
2160
21%
720
61%
720
40%
1169
October21st to endNight
43%
792
30%
2376
20%
792
53%
792
32%
1418
November1st to 10thNight
52%
740
33%
2220
23%
740
61%
740
38%
1218
November11th to 20thNight
44%
760
32%
2331
20%
760
57%
760
36%
1278
November21st to endNight
39%
812
27%
2522
18%
812
49%
812
30%
1500
December1st to 10thNight
33%
950
23%
2660
10%
950
45%
950
29%
1693
December11th to 20thNight
35%
948
26%
3104
12%
948
44%
948
23%
1923
December21st to endNight
29%
1041
16%
4412
9%
1026
40%
1026
18%
2652

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
12%5%25%5%35%5%5%7%45%
74548
Night
12%5%2443445%7%51%
75157
TransparencyDay
38%6%10%23%19%5%
74271
Night
34%5%10%23%22%6%
74954
SeeingDay
14%10%22%27%21%6%
14203
Night
14%8%26%32%18%2
24125

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
17%8%35%433345%46%
1707
11th to 20thDay
16%7%35%5%44436%44%
1629
21st to endDay
16%6%245%24345%51%
1782
February1st to 10thDay
20%7%25%42345%444%
1620
11th to 20thDay
17%7%45%5%3435%5%42%
1683
21st to endDay
22%8%35%5%33445%37%
1534
March1st to 10thDay
18%6%25%5%33345%45%
1980
11th to 20thDay
19%7%36%434435%42%
1980
21st to endDay
17%7%36%5%3435%6%40%
2178
April1st to 10thDay
12%5%345%345%5%7%45%
2151
11th to 20thDay
15%6%26%5%34446%46%
2134
21st to endDay
15%5%35%6%445%5%6%42%
2160
May1st to 10thDay
15%6%36%5%25%45%8%41%
2160
11th to 20thDay
12%5%246%36%5%7%8%43%
2288
21st to endDay
9%5%36%6%47%7%7%9%37%
2531
June1st to 10thDay
8%5%35%6%35%7%6%9%43%
2452
11th to 20thDay
4325%5%46%6%8%10%46%
2517
21st to endDay
43246%36%6%7%9%50%
2340
July1st to 10thDay
6%436%7%5%7%7%8%11%35%
2340
11th to 20thDay
5%325%6%47%6%8%9%45%
2340
21st to endDay
7%425%6%46%6%8%10%41%
2546
August1st to 10thDay
7%426%6%46%7%8%11%39%
2328
11th to 20thDay
11%5%15%6%346%7%10%42%
2148
21st to endDay
7%5%246%45%6%6%9%45%
2376
September1st to 10thDay
12%5%25%5%25%5%5%7%47%
2160
11th to 20thDay
14%5%244346%5%7%48%
2158
21st to endDay
10%424335%5%46%54%
1877
October1st to 10thDay
7%425%4245%5%6%57%
1800
11th to 20thDay
14%5%24423345%56%
1800
21st to endDay
18%424323345%52%
1980
November1st to 10thDay
12%5%23323346%57%
1858
11th to 20thDay
10%6%2433235%7%56%
1844
21st to endDay
17%7%245%24336%46%
1654
December1st to 10thDay
18%6%34423346%47%
1520
11th to 20thDay
13%8%36%5%35%44444%
1918
21st to endDay
12%7%37%6%45%5%5%6%39%
3075
January1st to 10thNight
18%5%24323345%50%
2458
11th to 20thNight
17%7%34433435%48%
2360
21st to endNight
17%5%23324345%53%
2574
February1st to 10thNight
19%7%36%423346%43%
2340
11th to 20thNight
17%8%45%424346%45%
2162
21st to endNight
19%8%2432444446%
1736
March1st to 10thNight
17%6%25%42345%5%47%
1980
11th to 20thNight
17%8%37%424235%45%
1980
21st to endNight
16%6%35%5%34447%44%
2178
April1st to 10thNight
11%5%24433447%51%
1807
11th to 20thNight
12%42443445%7%52%
1775
21st to endNight
13%5%25%5%245%5%6%49%
1800
May1st to 10thNight
13%42442435%9%49%
1800
11th to 20thNight
12%6%3442446%8%46%
1603
21st to endNight
8%5%35%6%35%47%10%45%
1745
June1st to 10thNight
442443446%10%55%
1499
11th to 20thNight
332343445%9%60%
1440
21st to endNight
33133235%5%9%61%
1609
July1st to 10thNight
34245%35%6%7%12%48%
1620
11th to 20thNight
4214435%5%7%12%53%
1620
21st to endNight
3214435%6%7%12%53%
1772
August1st to 10thNight
5%325%5%445%7%11%50%
1611
11th to 20thNight
6%424335%5%6%10%52%
1751
21st to endNight
5%3145%35%6%6%10%51%
1980
September1st to 10thNight
7%42433445%6%58%
1800
11th to 20thNight
10%4244245%5%7%53%
1800
21st to endNight
8%41333246%7%60%
2062
October1st to 10thNight
8%314423447%61%
2160
11th to 20thNight
10%423423335%60%
2160
21st to endNight
17%41443322455%
2376
November1st to 10thNight
11%32432325%5%59%
2220
11th to 20thNight
11%423424347%57%
2331
21st to endNight
14%5%34424446%51%
2522
December1st to 10thNight
17%5%25%5%3345%5%46%
2660
11th to 20thNight
15%5%35%43443449%
3279
21st to endNight
14%7%35%5%34446%45%
4587

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
43%36%24%18%6%
1708
11th to 20thDay
44%47%22%20%2
1629
21st to endDay
37%37%25%22%6%
1782
February1st to 10thDay
45%410%21%16%4
1620
11th to 20thDay
46%47%20%18%5%
1692
21st to endDay
51%46%15%16%8%
1534
March1st to 10thDay
43%48%17%19%10%
1980
11th to 20thDay
47%48%20%18%4
1980
21st to endDay
46%410%23%15%2
2178
April1st to 10thDay
37%6%9%23%20%4
2151
11th to 20thDay
40%5%8%23%17%7%
2134
21st to endDay
43%6%9%20%20%2
2160
May1st to 10thDay
43%6%11%18%19%3
2160
11th to 20thDay
38%8%13%24%16%2
2292
21st to endDay
40%9%13%24%13%1
2531
June1st to 10thDay
35%8%14%24%16%2
2452
11th to 20thDay
29%9%14%28%18%2
2517
21st to endDay
29%8%10%27%21%4
2340
July1st to 10thDay
35%13%15%23%13%1
2276
11th to 20thDay
33%9%12%27%17%3
2271
21st to endDay
33%10%16%28%12%1
2405
August1st to 10thDay
34%10%16%29%11%1
2314
11th to 20thDay
36%9%12%23%17%2
2148
21st to endDay
33%9%13%25%14%5%
2376
September1st to 10thDay
36%8%10%21%19%7%
2160
11th to 20thDay
36%6%11%17%24%5%
2158
21st to endDay
31%5%7%21%26%8%
1877
October1st to 10thDay
27%6%9%23%27%8%
1800
11th to 20thDay
32%35%20%29%10%
1800
21st to endDay
35%45%23%23%9%
1980
November1st to 10thDay
30%48%27%23%8%
1858
11th to 20thDay
29%49%21%28%9%
1844
21st to endDay
43%36%18%24%6%
1654
December1st to 10thDay
42%38%24%18%6%
1520
11th to 20thDay
44%36%20%22%5%
1915
21st to endDay
44%5%9%18%18%6%
3075
January1st to 10thNight
38%38%20%27%5%
2458
11th to 20thNight
41%38%21%21%5%
2360
21st to endNight
36%36%24%26%6%
2574
February1st to 10thNight
45%38%20%19%6%
2340
11th to 20thNight
43%36%22%20%6%
2163
21st to endNight
43%38%17%21%9%
1736
March1st to 10thNight
39%48%16%21%12%
1980
11th to 20thNight
45%47%20%17%6%
1980
21st to endNight
43%48%22%19%4
2178
April1st to 10thNight
33%411%23%20%8%
1807
11th to 20thNight
32%5%8%24%22%9%
1775
21st to endNight
36%411%25%22%3
1800
May1st to 10thNight
35%6%11%23%19%6%
1800
11th to 20thNight
36%5%13%26%17%2
1604
21st to endNight
34%8%16%26%16%1
1746
June1st to 10thNight
24%7%14%31%21%2
1499
11th to 20thNight
22%5%12%32%26%3
1440
21st to endNight
20%7%13%29%24%7%
1609
July1st to 10thNight
26%10%20%27%17%2
1575
11th to 20thNight
22%9%18%28%18%5%
1566
21st to endNight
22%10%15%34%18%1
1673
August1st to 10thNight
25%8%20%33%14%1
1601
11th to 20thNight
27%7%15%29%20%2
1751
21st to endNight
27%8%17%27%18%4
1980
September1st to 10thNight
27%7%11%26%22%8%
1800
11th to 20thNight
30%7%9%22%26%7%
1800
21st to endNight
24%5%10%22%30%9%
2062
October1st to 10thNight
25%411%24%24%11%
2160
11th to 20thNight
28%37%17%33%11%
2160
21st to endNight
36%36%19%26%10%
2376
November1st to 10thNight
29%37%24%26%11%
2220
11th to 20thNight
29%45%24%28%10%
2331
21st to endNight
36%47%20%28%6%
2522
December1st to 10thNight
40%39%20%21%7%
2660
11th to 20thNight
40%35%21%25%6%
3281
21st to endNight
41%5%8%23%20%4
4587

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
27%15%33%19%5%1
270
11th to 20thDay
25%19%35%18%2
243
21st to endDay
17%26%34%17%5%
264
February1st to 10thDay
25%20%33%17%4
240
11th to 20thDay
28%27%30%12%3
240
21st to endDay
35%21%31%10%31
198
March1st to 10thDay
24%21%32%18%5%
240
11th to 20thDay
28%25%32%14%1
240
21st to endDay
25%22%34%14%4
264
April1st to 10thDay
17%17%36%22%8%1
411
11th to 20thDay
21%18%30%23%8%
412
21st to endDay
20%14%34%22%10%1
420
May1st to 10thDay
17%14%29%29%10%1
423
11th to 20thDay
14%7%26%31%19%3
611
21st to endDay
8%6%24%34%22%6%
679
June1st to 10thDay
10%418%30%29%9%
630
11th to 20thDay
5%217%38%31%7%
630
21st to endDay
4318%38%27%10%
630
July1st to 10thDay
5%311%33%36%13%
621
11th to 20thDay
4212%32%33%17%
618
21st to endDay
6%28%32%35%17%
684
August1st to 10thDay
7%111%34%37%10%
626
11th to 20thDay
14%27%30%35%11%
462
21st to endDay
11%25%24%40%18%
495
September1st to 10thDay
11%28%26%39%14%
450
11th to 20thDay
10%113%25%38%13%
448
21st to endDay
12%5%17%36%21%8%
270
October1st to 10thDay
8%427%34%22%5%
270
11th to 20thDay
14%12%33%26%12%2
270
21st to endDay
27%14%29%20%9%1
297
November1st to 10thDay
16%12%32%23%16%2
270
11th to 20thDay
11%18%35%27%8%1
270
21st to endDay
24%18%26%23%9%1
270
December1st to 10thDay
22%20%31%17%9%1
270
11th to 20thDay
25%17%31%19%8%
270
21st to endDay
19%23%37%17%4
297
January1st to 10thNight
21%13%34%28%5%
950
11th to 20thNight
20%14%35%26%4
908
21st to endNight
20%12%38%26%4
990
February1st to 10thNight
22%14%34%26%4
900
11th to 20thNight
21%13%41%23%1
767
21st to endNight
24%15%37%21%3
552
March1st to 10thNight
19%10%36%32%4
540
11th to 20thNight
21%13%33%29%5%
540
21st to endNight
16%12%37%28%6%
594
April1st to 10thNight
14%11%37%31%7%
540
11th to 20thNight
14%11%38%27%10%1
533
21st to endNight
13%9%39%29%10%
540
May1st to 10thNight
15%5%27%43%9%
540
11th to 20thNight
15%6%27%31%18%2
531
21st to endNight
9%320%39%25%4
584
June1st to 10thNight
5%114%38%37%5%
540
11th to 20thNight
3110%48%35%3
540
21st to endNight
4111%40%38%6%
540
July1st to 10thNight
317%40%42%6%
525
11th to 20thNight
419%34%46%7%
522
21st to endNight
48%36%43%9%
591
August1st to 10thNight
415%39%44%6%
537
11th to 20thNight
8%18%36%40%7%
534
21st to endNight
6%18%31%48%6%
594
September1st to 10thNight
8%17%37%42%4
540
11th to 20thNight
11%110%34%39%3
540
21st to endNight
9%215%33%37%4
624
October1st to 10thNight
10%318%35%32%3
720
11th to 20thNight
12%6%28%37%17%1
720
21st to endNight
18%8%27%31%14%1
792
November1st to 10thNight
12%6%26%41%15%1
740
11th to 20thNight
13%11%30%36%11%
760
21st to endNight
15%13%30%30%11%
812
December1st to 10thNight
21%9%34%31%6%
950
11th to 20thNight
23%11%27%33%6%
950
21st to endNight
20%15%31%29%4
1045
Page generated at 2024-01-09 06:14:38. Version ac07

Copyright 2024 Attilla Danko


River Ridge Observatory Clear Sky Chart |Charts Home