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 2017-03-14.

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%
14826
19%
45046
14%
14782
50%
14782
24%
29646

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%
716
17%
2074
10%
716
33%
716
18%
1474
March16th to endNight
34%
704
14%
1936
8%
704
38%
704
21%
1365
April1st to 15thNight
35%
538
22%
1691
15%
538
47%
538
27%
1045
April16th to endNight
41%
495
20%
1521
12%
495
48%
495
24%
1013
May1st to 15thNight
41%
495
15%
1485
10%
495
46%
495
19%
1071
May16th to endNight
63%
514
18%
1540
16%
513
64%
513
28%
985
June1st to 15thNight
68%
495
19%
1485
17%
495
71%
495
37%
850
June16th to endNight
70%
495
17%
1403
14%
495
71%
495
35%
854
July1st to 15thNight
63%
465
15%
1351
13%
465
63%
465
27%
892
July16th to endNight
75%
522
18%
1469
16%
489
77%
489
35%
872
August1st to 15thNight
76%
494
25%
1474
22%
491
78%
491
38%
847
August16th to endNight
75%
525
22%
1704
24%
525
75%
525
34%
957
September1st to 15thNight
66%
616
25%
1771
23%
616
68%
616
31%
1106
September16th to endNight
60%
657
26%
1815
21%
657
63%
657
33%
1129
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
15%7%35%5%3445%7%37%
45632
Night
14%7%35%5%2445%7%40%
45239
Cloud CoverDay
14%7%36%5%3445%7%37%
45642
Night
14%7%35%5%2445%7%40%
45243
TransparencyDay
45%6%11%20%13%2
45343
Night
42%6%10%21%15%3
45046
SeeingDay
17%6%20%22%20%13%
4649
Night
17%7%24%29%18%2
14827

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
24%8%35%5%2334433%
1847
16th to endDay
20%8%35%5%3445%6%32%
1936
April1st to 15thDay
15%6%35%5%3445%6%40%
1935
16th to endDay
16%6%34434447%39%
2109
May1st to 15thDay
21%7%36%5%35%45%7%30%
2136
16th to endDay
9%6%26%6%45%6%5%8%39%
2223
June1st to 15thDay
9%425%6%45%6%6%8%39%
2145
16th to endDay
7%5%245%46%6%6%9%39%
2216
July1st to 15thDay
14%6%25%435%6%6%9%33%
2181
16th to endDay
10%5%25%6%5%7%6%8%10%32%
2283
August1st to 15thDay
9%4246%35%6%7%9%39%
2145
16th to endDay
9%6%35%5%46%5%7%9%38%
2143
September1st to 15thDay
13%425%436%6%5%8%39%
1848
16th to endDay
14%5%26%423346%45%
1815
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%
2062
16th to endNight
15%8%46%5%34446%36%
1936
April1st to 15thNight
14%5%2442445%7%45%
1691
16th to endNight
13%6%35%5%25%45%6%40%
1521
May1st to 15thNight
17%7%35%6%345%7%6%31%
1485
16th to endNight
8%4146%36%6%7%9%41%
1538
June1st to 15thNight
5%4234245%8%12%46%
1485
16th to endNight
5%224335%5%8%13%44%
1403
July1st to 15thNight
9%5%26%5%35%5%5%8%42%
1441
16th to endNight
6%313436%6%8%11%45%
1577
August1st to 15thNight
5%21443437%8%53%
1485
16th to endNight
5%3135%3446%10%49%
1704
September1st to 15thNight
10%3244345%5%8%45%
1771
16th to endNight
9%5%25%5%34336%49%
1815
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%
1858
16th to endDay
19%8%35%5%2445%6%32%
1935
April1st to 15thDay
15%6%35%5%2435%6%40%
1935
16th to endDay
15%6%35%43445%7%39%
2109
May1st to 15thDay
20%7%36%5%35%45%7%30%
2136
16th to endDay
9%6%26%6%35%5%6%8%39%
2223
June1st to 15thDay
9%425%6%45%6%7%8%39%
2145
16th to endDay
7%435%5%46%6%7%9%40%
2216
July1st to 15thDay
13%6%26%5%35%6%7%8%34%
2181
16th to endDay
10%425%6%46%7%7%10%32%
2283
August1st to 15thDay
8%425%6%45%6%7%9%39%
2145
16th to endDay
9%5%25%5%45%5%7%9%37%
2143
September1st to 15thDay
13%5%25%5%35%6%5%8%39%
1848
16th to endDay
14%5%25%422346%45%
1815
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%45%5%24445%35%
2074
16th to endNight
15%8%36%5%34346%36%
1936
April1st to 15thNight
13%6%2442445%7%45%
1691
16th to endNight
12%6%35%6%245%5%6%40%
1521
May1st to 15thNight
16%7%37%6%245%6%6%32%
1484
16th to endNight
8%4146%45%5%7%9%41%
1538
June1st to 15thNight
5%4234146%8%12%46%
1485
16th to endNight
5%324435%5%8%13%43%
1403
July1st to 15thNight
9%5%35%5%45%5%5%9%42%
1441
16th to endNight
6%213436%6%7%11%45%
1577
August1st to 15thNight
5%21443446%9%53%
1485
16th to endNight
5%3244345%6%10%50%
1704
September1st to 15thNight
10%4244346%5%8%45%
1771
16th to endNight
9%5%25%433437%49%
1815
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
1858
16th to endDay
51%5%10%22%8%
1936
April1st to 15thDay
44%5%10%22%13%3
1935
16th to endDay
43%5%9%21%14%4
2109
May1st to 15thDay
52%6%11%18%9%
2136
16th to endDay
40%8%14%21%12%1
2227
June1st to 15thDay
39%8%14%23%12%1
2145
16th to endDay
37%11%13%17%16%2
2216
July1st to 15thDay
44%9%13%15%14%2
2042
16th to endDay
41%10%15%20%9%2
2128
August1st to 15thDay
38%9%14%22%15%1
2132
16th to endDay
39%8%12%21%14%3
2143
September1st to 15thDay
40%7%13%15%17%5%
1848
16th to endDay
39%5%8%20%23%2
1815
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
51%48%20%12%2
2074
16th to endNight
48%5%11%22%10%
1936
April1st to 15thNight
38%5%10%21%20%4
1691
16th to endNight
42%6%9%19%14%6%
1521
May1st to 15thNight
48%9%10%20%9%2
1485
16th to endNight
36%9%14%20%15%3
1540
June1st to 15thNight
26%9%17%28%15%2
1485
16th to endNight
28%10%18%22%14%5%
1403
July1st to 15thNight
38%9%12%18%16%4
1351
16th to endNight
27%11%17%26%14%2
1469
August1st to 15thNight
27%8%15%24%20%3
1474
16th to endNight
28%8%13%23%21%3
1704
September1st to 15thNight
33%8%12%18%19%6%
1771
16th to endNight
35%5%7%20%26%3
1815
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
30%13%33%19%3
159
16th to endDay
22%9%31%21%12%2
224
April1st to 15thDay
20%14%20%28%14%2
210
16th to endDay
20%6%23%22%17%9%
210
May1st to 15thDay
23%8%23%19%17%7%
228
16th to endDay
14%217%25%19%19%
267
June1st to 15thDay
11%214%24%32%14%
255
16th to endDay
8%420%25%26%14%
326
July1st to 15thDay
20%216%24%17%18%
281
16th to endDay
12%16%21%25%32%
270
August1st to 15thDay
11%6%22%28%30%
253
16th to endDay
12%10%21%29%26%
268
September1st to 15thDay
14%9%16%33%25%
255
16th to endDay
17%312%21%31%14%
254
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%
716
16th to endNight
19%11%29%26%12%
704
April1st to 15thNight
16%10%34%29%8%
538
16th to endNight
13%5%33%30%14%1
495
May1st to 15thNight
20%325%30%17%2
495
16th to endNight
10%214%36%30%5%
515
June1st to 15thNight
6%115%44%28%3
495
16th to endNight
6%113%37%35%4
495
July1st to 15thNight
10%213%35%34%4
465
16th to endNight
7%27%32%40%9%
522
August1st to 15thNight
7%8%30%45%7%
494
16th to endNight
5%9%32%43%7%
525
September1st to 15thNight
12%110%27%39%7%
616
16th to endNight
11%315%30%34%4
657
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 2017-03-15 11:32:39. Version ac04

Copyright 2017 A. Danko


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