Raven Run Nature Conservancy
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Raven Run Nature Conservancy clear sky chart from 2005-11-05 to 2017-09-17.

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
44%
15415
19%
46797
14%
15371
50%
15371
24%
30707

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
20%
720
14%
2327
7%
716
29%
716
13%
1746
January16th to endNight
23%
768
17%
2496
10%
768
31%
768
16%
1755
February1st to 15thNight
21%
704
14%
2142
6%
701
29%
701
17%
1539
February16th to endNight
17%
631
15%
1893
6%
631
25%
631
15%
1393
March1st to 15thNight
28%
720
17%
2085
10%
720
33%
720
18%
1479
March16th to endNight
35%
768
14%
2112
8%
768
39%
768
21%
1485
April1st to 15thNight
36%
587
21%
1845
14%
587
46%
587
27%
1137
April16th to endNight
40%
540
20%
1659
12%
540
48%
540
24%
1105
May1st to 15thNight
40%
540
14%
1620
9%
540
45%
540
19%
1162
May16th to endNight
61%
562
19%
1684
15%
561
63%
561
27%
1079
June1st to 15thNight
70%
540
18%
1620
16%
540
72%
540
38%
915
June16th to endNight
69%
540
18%
1530
15%
540
71%
540
35%
930
July1st to 15thNight
63%
510
14%
1482
12%
510
64%
510
28%
970
July16th to endNight
75%
564
21%
1595
18%
531
78%
531
36%
936
August1st to 15thNight
75%
539
23%
1609
21%
536
77%
536
36%
942
August16th to endNight
75%
573
23%
1860
26%
573
76%
573
35%
1035
September1st to 15thNight
65%
672
24%
1932
21%
672
67%
672
31%
1208
September16th to endNight
60%
665
26%
1837
21%
665
63%
665
33%
1138
October1st to 15thNight
57%
660
32%
1845
26%
660
62%
660
38%
1086
October16th to endNight
42%
704
25%
2172
20%
704
51%
704
28%
1347
November1st to 15thNight
47%
700
28%
2276
24%
700
56%
700
32%
1287
November16th to endNight
35%
720
21%
2340
16%
720
43%
720
23%
1511
December1st to 15thNight
30%
720
14%
2340
9%
720
35%
720
15%
1681
December16th to endNight
25%
768
16%
2496
8%
768
34%
768
14%
1841

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
14%7%35%5%3445%7%37%
47947
Night
14%6%35%5%2445%7%40%
46990
Cloud CoverDay
14%7%35%5%3445%7%37%
47957
Night
13%7%35%5%2445%7%40%
46994
TransparencyDay
45%6%11%20%13%2
47658
Night
42%6%11%21%15%3
46797
SeeingDay
16%6%21%23%20%12%
5398
Night
17%7%24%29%19%2
15416

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
21%9%49%6%24436%28%
1611
16th to endDay
17%11%5%7%5%33335%32%
1728
February1st to 15thDay
16%11%5%9%5%24445%30%
1717
16th to endDay
16%11%47%6%3445%6%29%
1580
March1st to 15thDay
23%8%35%5%2334433%
1864
16th to endDay
19%8%35%5%3445%6%32%
2112
April1st to 15thDay
15%6%35%5%3445%6%40%
2112
16th to endDay
16%6%35%43445%8%38%
2301
May1st to 15thDay
21%6%35%5%3445%6%32%
2331
16th to endDay
9%6%26%6%45%5%5%8%39%
2431
June1st to 15thDay
8%425%5%45%6%6%8%41%
2340
16th to endDay
7%5%245%46%6%6%9%40%
2418
July1st to 15thDay
13%6%26%435%6%6%9%35%
2379
16th to endDay
9%5%25%6%47%6%7%10%34%
2465
August1st to 15thDay
9%5%246%35%5%7%9%39%
2340
16th to endDay
8%6%245%46%5%7%9%38%
2339
September1st to 15thDay
14%5%25%435%6%5%8%39%
2016
16th to endDay
14%5%25%423346%45%
1829
October1st to 15thDay
11%414433346%50%
1785
16th to endDay
18%7%24313325%47%
1699
November1st to 15thDay
13%5%24414336%49%
1582
16th to endDay
17%9%35%332335%41%
1620
December1st to 15thDay
23%10%45%42433431%
1620
16th to endDay
19%13%36%423446%30%
1728
January1st to 15thNight
18%10%5%9%6%3444428%
2327
16th to endNight
18%10%5%7%5%2444433%
2496
February1st to 15thNight
19%9%48%32335%6%32%
2140
16th to endNight
18%12%48%5%34346%29%
1893
March1st to 15thNight
17%10%46%5%23445%35%
2073
16th to endNight
15%8%46%5%34346%36%
2112
April1st to 15thNight
13%5%2442345%7%44%
1845
16th to endNight
13%6%35%5%35%45%6%40%
1659
May1st to 15thNight
16%7%36%6%345%7%7%31%
1620
16th to endNight
8%3146%36%6%7%9%40%
1682
June1st to 15thNight
5%4224245%8%11%48%
1620
16th to endNight
5%224435%5%8%13%44%
1530
July1st to 15thNight
9%425%5%35%5%5%8%43%
1572
16th to endNight
5%313435%5%8%11%46%
1703
August1st to 15thNight
5%2145%3447%8%51%
1620
16th to endNight
5%3135%3446%10%49%
1860
September1st to 15thNight
12%3234335%5%8%46%
1932
16th to endNight
9%5%25%5%24346%50%
1837
October1st to 15thNight
9%5%14423348%52%
1845
16th to endNight
16%5%245%13346%46%
2172
November1st to 15thNight
13%424312246%51%
2276
16th to endNight
18%7%25%413346%40%
2340
December1st to 15thNight
22%10%46%42435%5%31%
2340
16th to endNight
21%11%46%5%24345%29%
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
21%8%5%9%6%24436%27%
1611
16th to endDay
17%11%6%7%5%33335%32%
1728
February1st to 15thDay
17%11%5%9%5%24445%30%
1717
16th to endDay
15%12%47%6%4445%6%29%
1580
March1st to 15thDay
23%9%26%424345%33%
1875
16th to endDay
19%8%35%5%3445%7%32%
2111
April1st to 15thDay
15%6%35%5%3445%6%39%
2112
16th to endDay
16%6%25%43445%7%38%
2301
May1st to 15thDay
20%6%36%5%25%447%32%
2331
16th to endDay
9%6%26%6%35%5%6%8%39%
2431
June1st to 15thDay
9%425%6%45%6%6%8%40%
2340
16th to endDay
7%4245%46%6%7%9%41%
2418
July1st to 15thDay
12%6%26%5%35%5%7%8%35%
2379
16th to endDay
10%425%6%46%7%7%10%34%
2465
August1st to 15thDay
9%5%25%6%45%6%7%8%39%
2340
16th to endDay
9%5%25%5%46%5%7%10%37%
2339
September1st to 15thDay
14%5%25%5%35%5%5%8%39%
2016
16th to endDay
14%5%25%432346%45%
1829
October1st to 15thDay
11%414423346%51%
1785
16th to endDay
18%6%24313325%46%
1699
November1st to 15thDay
13%5%24414336%49%
1582
16th to endDay
17%9%35%423335%41%
1620
December1st to 15thDay
22%11%46%42434431%
1620
16th to endDay
19%13%46%5%23446%30%
1728
January1st to 15thNight
18%9%5%9%6%3444428%
2327
16th to endNight
18%9%5%7%5%2344433%
2496
February1st to 15thNight
19%9%47%42335%7%32%
2133
16th to endNight
18%12%38%5%34246%29%
1893
March1st to 15thNight
17%10%46%5%24445%35%
2085
16th to endNight
15%8%36%5%34346%36%
2112
April1st to 15thNight
12%6%25%42345%7%44%
1845
16th to endNight
12%6%35%6%35%45%6%40%
1659
May1st to 15thNight
16%7%37%6%245%6%7%32%
1619
16th to endNight
8%4146%45%5%7%9%40%
1682
June1st to 15thNight
5%4133145%8%12%47%
1620
16th to endNight
5%324435%5%8%13%43%
1530
July1st to 15thNight
9%425%5%35%5%5%9%43%
1572
16th to endNight
5%213436%6%7%11%46%
1703
August1st to 15thNight
5%2145%3446%9%51%
1620
16th to endNight
5%3244345%6%10%49%
1860
September1st to 15thNight
12%3244336%5%8%45%
1932
16th to endNight
9%5%25%433437%49%
1837
October1st to 15thNight
9%5%15%323348%51%
1845
16th to endNight
16%5%145%23346%46%
2172
November1st to 15thNight
13%5%24322246%51%
2276
16th to endNight
18%7%35%423347%40%
2340
December1st to 15thNight
22%10%36%433445%31%
2340
16th to endNight
21%12%46%5%34345%29%
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
58%5%7%17%10%
1612
16th to endDay
54%410%22%7%1
1728
February1st to 15thDay
56%5%7%21%7%1
1719
16th to endDay
54%5%10%19%8%
1580
March1st to 15thDay
53%311%17%11%1
1875
16th to endDay
51%5%11%21%8%
2112
April1st to 15thDay
44%5%9%23%14%2
2112
16th to endDay
44%6%10%21%13%4
2301
May1st to 15thDay
51%6%11%19%10%1
2331
16th to endDay
40%8%14%22%12%1
2435
June1st to 15thDay
37%8%14%23%14%1
2340
16th to endDay
36%10%12%18%18%3
2418
July1st to 15thDay
43%9%13%16%14%3
2240
16th to endDay
40%10%14%21%11%2
2310
August1st to 15thDay
39%8%13%21%14%1
2327
16th to endDay
39%7%12%21%15%3
2339
September1st to 15thDay
41%7%13%16%16%4
2016
16th to endDay
39%5%8%20%23%2
1829
October1st to 15thDay
34%48%24%23%3
1785
16th to endDay
40%49%25%17%2
1699
November1st to 15thDay
36%37%24%20%6%
1582
16th to endDay
45%37%22%19%1
1620
December1st to 15thDay
56%49%17%9%1
1620
16th to endDay
55%5%11%20%7%
1728
January1st to 15thNight
58%5%7%13%12%1
2327
16th to endNight
53%39%21%9%1
2496
February1st to 15thNight
52%411%20%9%1
2142
16th to endNight
56%410%18%10%
1893
March1st to 15thNight
50%48%20%12%2
2085
16th to endNight
47%6%12%21%10%
2112
April1st to 15thNight
37%5%10%21%20%4
1845
16th to endNight
43%6%9%20%14%6%
1659
May1st to 15thNight
48%8%10%20%9%2
1620
16th to endNight
35%10%13%21%15%3
1684
June1st to 15thNight
25%8%17%27%16%3
1620
16th to endNight
29%10%17%22%15%4
1530
July1st to 15thNight
37%9%12%19%16%4
1482
16th to endNight
26%10%16%26%17%3
1595
August1st to 15thNight
28%8%15%23%20%3
1609
16th to endNight
28%7%14%25%21%3
1860
September1st to 15thNight
34%8%11%20%18%6%
1932
16th to endNight
35%5%8%20%27%3
1837
October1st to 15thNight
30%5%8%26%22%5%
1845
16th to endNight
39%47%23%20%3
2172
November1st to 15thNight
34%27%23%24%6%
2276
16th to endNight
44%38%22%17%1
2340
December1st to 15thNight
54%410%17%10%1
2340
16th to endNight
57%49%17%8%1
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
34%12%38%7%42
90
16th to endDay
25%19%42%10%2
96
February1st to 15thDay
20%21%37%16%4
90
16th to endDay
28%11%34%19%6%
81
March1st to 15thDay
29%15%33%18%3
165
16th to endDay
20%12%30%23%11%1
288
April1st to 15thDay
18%12%23%27%14%2
270
16th to endDay
19%6%25%25%14%8%
270
May1st to 15thDay
23%9%25%19%15%6%
288
16th to endDay
15%220%26%17%16%
331
June1st to 15thDay
10%114%23%33%16%
315
16th to endDay
8%423%25%24%13%
393
July1st to 15thDay
18%216%25%19%17%
344
16th to endDay
11%7%22%27%30%
326
August1st to 15thDay
11%18%22%29%26%
313
16th to endDay
11%10%24%29%22%
332
September1st to 15thDay
16%112%17%30%22%
315
16th to endDay
16%311%20%31%15%
259
October1st to 15thDay
12%5%21%25%21%12%
255
16th to endDay
18%425%31%18%1
211
November1st to 15thDay
13%6%23%23%24%8%
90
16th to endDay
28%11%26%27%5%
90
December1st to 15thDay
22%14%32%25%32
90
16th to endDay
23%20%42%8%4
96
January1st to 15thNight
24%15%33%20%5%
720
16th to endNight
25%14%32%25%2
768
February1st to 15thNight
26%11%34%26%1
704
16th to endNight
22%13%40%20%2
631
March1st to 15thNight
22%13%29%27%6%
720
16th to endNight
18%10%30%27%12%
768
April1st to 15thNight
15%10%34%28%10%
587
16th to endNight
14%5%33%30%14%1
540
May1st to 15thNight
20%426%29%17%2
540
16th to endNight
10%216%36%29%5%
563
June1st to 15thNight
6%114%42%31%3
540
16th to endNight
6%113%39%34%4
540
July1st to 15thNight
9%113%35%35%4
510
16th to endNight
7%27%32%41%9%
564
August1st to 15thNight
7%8%31%45%7%
539
16th to endNight
5%9%33%43%6%
573
September1st to 15thNight
14%111%26%38%6%
672
16th to endNight
11%314%30%34%5%
665
October1st to 15thNight
12%5%20%31%26%5%
660
16th to endNight
18%5%28%29%15%1
704
November1st to 15thNight
16%7%24%28%19%3
700
16th to endNight
22%10%27%28%9%
720
December1st to 15thNight
27%10%26%26%8%
720
16th to endNight
27%11%30%25%4
768
Page generated at 2017-09-18 08:38:25. Version ac04

Copyright 2017 A. Danko


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