Warren Rupp Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Warren Rupp Observatory clear sky chart from 2005-11-05 to 2017-08-12.

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
34%
15394
16%
46542
10%
15354
41%
15354
20%
32206

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 15thNight
10%
719
11%
2327
3%
716
20%
716
8%
1853
January16th to endNight
14%
768
12%
2496
5%
768
22%
768
10%
1955
February1st to 15thNight
14%
702
10%
2270
4%
701
21%
701
11%
1741
February16th to endNight
16%
631
12%
1893
3%
631
24%
631
12%
1459
March1st to 15thNight
23%
720
14%
2037
7%
720
30%
720
16%
1511
March16th to endNight
25%
768
16%
2112
9%
768
31%
768
20%
1501
April1st to 15thNight
24%
656
14%
1861
5%
656
31%
656
21%
1315
April16th to endNight
32%
540
20%
1620
7%
540
43%
540
24%
1082
May1st to 15thNight
35%
540
14%
1620
8%
540
42%
540
20%
1140
May16th to endNight
47%
561
17%
1684
13%
561
51%
561
28%
1072
June1st to 15thNight
51%
540
14%
1620
10%
540
57%
540
33%
961
June16th to endNight
52%
540
15%
1489
10%
540
58%
540
33%
940
July1st to 15thNight
58%
510
16%
1459
14%
510
61%
510
33%
919
July16th to endNight
65%
564
19%
1595
15%
531
70%
531
38%
902
August1st to 15thNight
65%
527
21%
1575
18%
524
66%
524
34%
931
August16th to endNight
65%
525
23%
1575
18%
525
69%
525
38%
888
September1st to 15thNight
59%
654
28%
1801
19%
654
64%
654
37%
1066
September16th to endNight
54%
657
25%
1815
18%
657
58%
657
32%
1129
October1st to 15thNight
45%
660
23%
1917
19%
660
51%
660
29%
1204
October16th to endNight
23%
704
19%
2137
10%
704
34%
704
19%
1481
November1st to 15thNight
34%
700
22%
2276
16%
700
44%
700
24%
1417
November16th to endNight
22%
720
15%
2347
9%
720
30%
720
14%
1709
December1st to 15thNight
16%
720
9%
2520
5%
720
22%
720
9%
1989
December16th to endNight
13%
768
8%
2496
3%
768
20%
768
8%
2041

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
16%9%47%6%3445%7%31%
47400
Night
14%9%46%5%3445%6%34%
46734
Cloud CoverDay
15%9%47%6%3445%7%31%
47410
Night
14%9%46%5%3445%6%34%
46738
TransparencyDay
52%310%19%11%1
47110
Night
49%311%20%12%1
46542
SeeingDay
20%10%25%21%14%7%
5376
Night
19%11%28%25%12%1
15399

By Month

Percentage Cloud Cover NE (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 15thDay
20%14%7%10%8%33335%18%
1611
16th to endDay
14%18%8%12%8%5%333414%
1728
February1st to 15thDay
16%17%7%9%8%4433421%
1591
16th to endDay
14%15%6%10%6%24345%24%
1580
March1st to 15thDay
20%13%5%8%6%23345%24%
1912
16th to endDay
21%10%46%5%25%446%29%
2112
April1st to 15thDay
19%11%45%5%34346%30%
2095
16th to endDay
18%8%26%5%34437%35%
2340
May1st to 15thDay
21%7%36%6%35%5%45%29%
2331
16th to endDay
12%6%26%6%45%5%6%8%35%
2431
June1st to 15thDay
13%6%247%35%5%5%8%36%
2340
16th to endDay
12%5%25%6%45%6%6%9%34%
2464
July1st to 15thDay
12%7%37%5%36%45%8%35%
2406
16th to endDay
11%425%6%45%6%6%10%36%
2465
August1st to 15thDay
8%5%25%6%46%6%7%9%36%
2288
16th to endDay
10%6%25%5%25%5%6%9%39%
2270
September1st to 15thDay
14%435%43445%7%41%
1821
16th to endDay
18%7%35%5%23446%39%
1815
October1st to 15thDay
16%7%25%42346%7%37%
1713
16th to endDay
21%11%35%5%23346%32%
1735
November1st to 15thDay
12%10%35%5%2445%6%40%
1582
16th to endDay
20%13%5%7%6%2444426%
1608
December1st to 15thDay
20%16%8%11%5%24235%18%
1440
16th to endDay
20%18%8%9%6%3324417%
1722
January1st to 15thNight
19%16%7%9%8%2334320%
2327
16th to endNight
15%16%7%8%7%45%44421%
2496
February1st to 15thNight
17%13%6%10%7%2445%5%24%
2268
16th to endNight
15%14%6%9%7%34445%24%
1893
March1st to 15thNight
17%10%48%6%34445%29%
2025
16th to endNight
15%9%47%5%34446%33%
2112
April1st to 15thNight
16%8%46%5%35%45%7%32%
1861
16th to endNight
12%8%35%5%44447%38%
1620
May1st to 15thNight
17%7%36%6%35%46%7%32%
1620
16th to endNight
11%5%27%425%46%8%41%
1682
June1st to 15thNight
6%5%145%25%5%6%8%45%
1620
16th to endNight
10%424435%6%7%9%41%
1489
July1st to 15thNight
8%4245%35%47%8%45%
1548
16th to endNight
6%3235%25%5%7%10%48%
1703
August1st to 15thNight
7%4145%25%6%7%9%45%
1586
16th to endNight
8%4244245%5%7%51%
1575
September1st to 15thNight
12%323323446%52%
1801
16th to endNight
14%5%24423447%46%
1815
October1st to 15thNight
14%7%15%5%23446%45%
1917
16th to endNight
20%7%35%5%24346%34%
2137
November1st to 15thNight
13%8%25%42445%7%41%
2276
16th to endNight
21%11%46%6%24345%28%
2347
December1st to 15thNight
20%16%5%9%5%2444420%
2520
16th to endNight
20%16%8%9%6%35%345%17%
2496

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 15thDay
20%14%8%9%9%2433418%
1611
16th to endDay
15%17%8%12%8%4433414%
1728
February1st to 15thDay
16%17%7%10%7%4433421%
1591
16th to endDay
14%15%6%10%6%34345%25%
1580
March1st to 15thDay
21%12%5%8%6%24346%24%
1923
16th to endDay
20%10%46%5%24436%29%
2111
April1st to 15thDay
19%11%46%5%34446%30%
2095
16th to endDay
18%8%26%5%34437%35%
2340
May1st to 15thDay
20%7%36%7%345%46%29%
2331
16th to endDay
12%5%35%6%35%5%6%9%34%
2431
June1st to 15thDay
13%6%25%6%35%5%5%8%36%
2340
16th to endDay
12%5%25%6%36%6%6%9%33%
2464
July1st to 15thDay
11%7%37%6%35%45%8%35%
2406
16th to endDay
10%5%25%6%36%6%7%10%35%
2465
August1st to 15thDay
8%426%6%46%7%6%9%36%
2288
16th to endDay
10%5%35%5%35%5%6%9%39%
2270
September1st to 15thDay
13%5%25%43445%7%41%
1821
16th to endDay
18%7%35%5%23446%38%
1815
October1st to 15thDay
15%8%26%4335%6%7%37%
1713
16th to endDay
20%11%35%423346%33%
1735
November1st to 15thDay
12%9%45%424446%40%
1582
16th to endDay
20%13%5%7%6%3443426%
1608
December1st to 15thDay
21%16%8%11%6%24335%18%
1440
16th to endDay
21%17%8%9%6%23335%16%
1722
January1st to 15thNight
19%16%7%8%8%2334320%
2327
16th to endNight
15%16%7%8%8%35%445%21%
2496
February1st to 15thNight
16%13%5%10%7%24445%24%
2261
16th to endNight
15%14%6%9%6%35%445%24%
1893
March1st to 15thNight
17%10%48%6%34346%28%
2037
16th to endNight
16%8%37%6%345%46%33%
2112
April1st to 15thNight
16%9%36%5%35%45%7%32%
1861
16th to endNight
12%9%35%6%35%45%7%38%
1620
May1st to 15thNight
17%8%36%5%45%45%7%32%
1619
16th to endNight
11%437%425%5%6%9%40%
1682
June1st to 15thNight
5%5%245%35%5%7%9%45%
1620
16th to endNight
9%424435%5%7%9%41%
1489
July1st to 15thNight
7%4245%35%5%6%8%44%
1548
16th to endNight
5%3245%25%5%7%10%48%
1703
August1st to 15thNight
6%4246%35%6%7%9%45%
1586
16th to endNight
8%4244145%5%8%51%
1575
September1st to 15thNight
12%413323446%52%
1801
16th to endNight
13%5%2442345%7%46%
1815
October1st to 15thNight
13%7%25%5%23445%45%
1917
16th to endNight
20%8%36%5%34346%34%
2137
November1st to 15thNight
13%7%35%424447%41%
2276
16th to endNight
21%11%47%5%33345%28%
2347
December1st to 15thNight
21%15%6%9%6%24445%20%
2520
16th to endNight
20%15%8%9%6%34445%17%
2496

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 15thDay
70%38%12%5%
1612
16th to endDay
73%310%9%3
1728
February1st to 15thDay
67%37%14%6%
1593
16th to endDay
61%212%17%5%
1580
March1st to 15thDay
62%210%17%5%
1923
16th to endDay
56%210%23%7%
2112
April1st to 15thDay
55%212%16%11%
2095
16th to endDay
50%39%19%13%3
2340
May1st to 15thDay
55%311%18%9%1
2331
16th to endDay
45%6%11%22%12%1
2435
June1st to 15thDay
44%411%25%13%
2340
16th to endDay
45%5%13%19%14%1
2464
July1st to 15thDay
47%410%20%15%2
2266
16th to endDay
40%7%14%25%11%1
2310
August1st to 15thDay
41%6%11%24%15%1
2275
16th to endDay
39%412%24%14%4
2270
September1st to 15thDay
40%410%23%16%3
1821
16th to endDay
46%28%19%22%1
1815
October1st to 15thDay
44%410%23%16%
1713
16th to endDay
53%113%21%9%
1735
November1st to 15thDay
44%210%24%13%4
1582
16th to endDay
62%28%17%7%
1608
December1st to 15thDay
71%110%11%4
1440
16th to endDay
72%29%12%3
1722
January1st to 15thNight
68%27%14%6%
2327
16th to endNight
65%210%15%5%
2496
February1st to 15thNight
61%410%15%6%
2270
16th to endNight
62%38%18%6%
1893
March1st to 15thNight
56%311%19%7%1
2037
16th to endNight
51%311%22%9%1
2112
April1st to 15thNight
49%312%17%15%1
1861
16th to endNight
45%39%20%17%4
1620
May1st to 15thNight
51%410%21%11%1
1620
16th to endNight
39%5%13%23%15%2
1684
June1st to 15thNight
34%5%14%26%17%1
1620
16th to endNight
36%5%16%22%15%3
1489
July1st to 15thNight
36%5%11%23%19%3
1459
16th to endNight
29%5%16%30%15%3
1595
August1st to 15thNight
33%5%13%26%20%
1575
16th to endNight
30%414%27%19%3
1575
September1st to 15thNight
32%410%26%21%5%
1801
16th to endNight
37%37%24%25%1
1815
October1st to 15thNight
40%310%24%18%2
1917
16th to endNight
51%29%24%10%1
2137
November1st to 15thNight
42%311%22%15%4
2276
16th to endNight
58%210%19%8%
2347
December1st to 15thNight
67%210%13%5%
2520
16th to endNight
69%311%12%2
2496

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 15thDay
31%30%23%7%6%1
90
16th to endDay
30%33%27%7%2
96
February1st to 15thDay
23%38%28%8%
90
16th to endDay
20%24%44%8%1
81
March1st to 15thDay
28%18%32%15%4
213
16th to endDay
26%14%31%17%9%
288
April1st to 15thDay
26%14%30%18%9%1
270
16th to endDay
25%10%34%12%10%7%
270
May1st to 15thDay
26%9%31%16%10%5%
288
16th to endDay
19%8%28%22%11%9%
331
June1st to 15thDay
15%6%26%28%17%5%
315
16th to endDay
17%10%27%27%13%5%
439
July1st to 15thDay
19%422%25%18%9%
370
16th to endDay
10%215%31%26%14%
326
August1st to 15thDay
12%218%27%22%16%
297
16th to endDay
14%213%25%26%18%
268
September1st to 15thDay
12%414%23%26%19%
255
16th to endDay
23%412%19%25%14%
254
October1st to 15thDay
11%10%25%26%19%5%
255
16th to endDay
25%12%33%20%7%
247
November1st to 15thDay
14%13%21%24%24%2
90
16th to endDay
25%26%36%9%3
88
December1st to 15thDay
20%38%26%8%15%
60
16th to endDay
33%27%31%7%
95
January1st to 15thNight
29%22%32%12%2
720
16th to endNight
23%22%33%17%2
768
February1st to 15thNight
24%21%34%17%2
704
16th to endNight
23%18%35%19%3
631
March1st to 15thNight
24%16%31%23%4
720
16th to endNight
21%13%35%20%8%
768
April1st to 15thNight
22%14%34%21%6%
656
16th to endNight
16%9%37%24%10%2
540
May1st to 15thNight
22%7%27%30%11%1
540
16th to endNight
14%5%26%26%23%3
563
June1st to 15thNight
10%229%39%18%
540
16th to endNight
12%224%39%18%2
540
July1st to 15thNight
10%121%40%23%2
510
16th to endNight
7%117%39%29%4
564
August1st to 15thNight
9%113%42%26%6%
527
16th to endNight
10%213%34%32%6%
525
September1st to 15thNight
14%316%30%28%5%
654
16th to endNight
17%6%14%30%25%5%
657
October1st to 15thNight
18%6%24%30%18%2
660
16th to endNight
23%13%35%20%7%
704
November1st to 15thNight
18%13%29%23%12%2
700
16th to endNight
27%17%27%18%7%
720
December1st to 15thNight
30%15%31%17%3
720
16th to endNight
28%18%33%16%2
768
Page generated at 2017-08-13 14:16:55. Version ac04

Copyright 2017 A. Danko


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