Skunk Ridge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Skunk Ridge Observatory clear sky chart from 2005-11-05 to 2017-10-31.

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
35%
15779
19%
47243
12%
15735
43%
15735
21%
31352

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
14%
897
13%
2503
5%
892
22%
892
12%
1959
January16th to endNight
17%
768
14%
2496
6%
768
27%
768
11%
1823
February1st to 15thNight
16%
703
13%
2136
4%
701
24%
701
12%
1553
February16th to endNight
14%
631
14%
1893
5%
631
22%
631
12%
1373
March1st to 15thNight
19%
720
15%
2107
7%
720
26%
720
16%
1491
March16th to endNight
24%
768
16%
2112
6%
768
32%
768
18%
1497
April1st to 15thNight
28%
548
18%
1806
11%
548
37%
548
20%
1149
April16th to endNight
29%
540
21%
1668
8%
540
42%
540
19%
1092
May1st to 15thNight
29%
540
15%
1620
6%
540
37%
540
18%
1150
May16th to endNight
42%
562
18%
1684
9%
561
50%
561
23%
1068
June1st to 15thNight
51%
540
19%
1539
13%
540
58%
540
31%
900
June16th to endNight
51%
540
19%
1440
10%
540
57%
540
33%
879
July1st to 15thNight
52%
510
17%
1360
13%
510
55%
510
30%
885
July16th to endNight
62%
564
21%
1571
14%
531
71%
531
33%
904
August1st to 15thNight
62%
539
23%
1609
19%
536
66%
536
33%
946
August16th to endNight
71%
573
24%
1873
22%
573
76%
573
37%
1004
September1st to 15thNight
59%
648
27%
1908
23%
648
63%
648
34%
1118
September16th to endNight
53%
717
29%
1980
21%
717
59%
717
33%
1190
October1st to 15thNight
50%
720
29%
2000
22%
720
57%
720
33%
1188
October16th to endNight
34%
768
24%
2411
17%
768
44%
768
23%
1530
November1st to 15thNight
37%
700
27%
2276
19%
700
49%
700
26%
1328
November16th to endNight
26%
720
19%
2340
11%
720
37%
720
15%
1580
December1st to 15thNight
19%
720
12%
2340
7%
720
25%
720
11%
1751
December16th to endNight
14%
843
13%
2571
5%
843
23%
843
10%
1994

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%38%
48490
Night
14%7%35%42445%7%40%
47424
Cloud CoverDay
15%7%35%5%3445%7%38%
48499
Night
14%7%35%42445%7%40%
47429
TransparencyDay
45%6%11%20%14%2
48189
Night
43%5%11%21%14%2
47243
SeeingDay
16%16%23%21%14%7%
5837
Night
16%22%21%22%14%2
15781

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%12%47%433445%28%
1432
16th to endDay
16%11%5%9%5%24345%31%
1726
February1st to 15thDay
17%12%5%7%423335%33%
1723
16th to endDay
16%12%5%7%5%25%346%30%
1580
March1st to 15thDay
23%8%25%5%2334434%
1841
16th to endDay
18%11%36%5%34445%32%
2112
April1st to 15thDay
18%7%24424447%39%
2151
16th to endDay
17%5%25%5%24448%38%
2290
May1st to 15thDay
23%6%25%5%34446%32%
2331
16th to endDay
12%6%25%7%36%5%6%9%35%
2431
June1st to 15thDay
10%425%5%45%5%6%8%42%
2418
16th to endDay
9%325%6%45%5%5%9%41%
2520
July1st to 15thDay
14%5%25%425%5%6%8%36%
2520
16th to endDay
8%425%6%46%6%7%8%39%
2489
August1st to 15thDay
7%425%6%36%6%6%9%42%
2340
16th to endDay
8%4245%35%5%7%9%43%
2326
September1st to 15thDay
12%425%5%2445%6%45%
2040
16th to endDay
13%424424345%48%
1980
October1st to 15thDay
12%435%5%24445%47%
1959
16th to endDay
18%7%24333346%42%
1809
November1st to 15thDay
10%7%34424336%50%
1582
16th to endDay
19%9%35%323336%39%
1620
December1st to 15thDay
26%10%5%6%6%2423428%
1620
16th to endDay
21%14%5%6%423345%28%
1650
January1st to 15thNight
19%11%5%9%7%2344427%
2503
16th to endNight
18%12%5%7%5%34335%30%
2496
February1st to 15thNight
20%11%5%7%423335%32%
2134
16th to endNight
18%12%5%6%5%24447%29%
1893
March1st to 15thNight
18%8%46%5%2435%5%34%
2094
16th to endNight
16%7%46%43435%7%35%
2112
April1st to 15thNight
15%6%35%42446%6%40%
1806
16th to endNight
15%5%25%6%34347%40%
1668
May1st to 15thNight
17%7%36%5%35%45%7%34%
1620
16th to endNight
9%425%435%6%6%11%41%
1682
June1st to 15thNight
5%42443345%10%51%
1539
16th to endNight
6%313335%5%7%11%48%
1440
July1st to 15thNight
9%5%25%5%2445%8%46%
1440
16th to endNight
7%2144446%6%8%49%
1678
August1st to 15thNight
6%3245%345%7%8%50%
1620
16th to endNight
5%2143246%5%10%53%
1873
September1st to 15thNight
12%31332345%8%50%
1908
16th to endNight
11%5%23413346%52%
1980
October1st to 15thNight
9%41342446%7%51%
2000
16th to endNight
16%6%25%423335%44%
2411
November1st to 15thNight
13%5%1332345%6%48%
2276
16th to endNight
19%9%35%424346%37%
2340
December1st to 15thNight
23%11%47%5%23345%28%
2340
16th to endNight
23%14%46%43343426%
2571

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%12%5%7%433435%28%
1432
16th to endDay
15%12%5%9%5%34345%31%
1726
February1st to 15thDay
17%12%5%7%5%23335%33%
1723
16th to endDay
16%12%5%7%434346%30%
1580
March1st to 15thDay
23%8%35%43334434%
1851
16th to endDay
18%10%36%5%34446%32%
2111
April1st to 15thDay
18%7%3442435%6%38%
2151
16th to endDay
17%6%245%24447%38%
2290
May1st to 15thDay
22%7%25%434446%32%
2331
16th to endDay
12%5%25%7%46%5%6%8%35%
2431
June1st to 15thDay
10%425%5%345%6%8%42%
2418
16th to endDay
8%4247%45%5%5%9%41%
2520
July1st to 15thDay
14%6%26%5%25%5%6%7%36%
2520
16th to endDay
8%425%6%36%6%7%8%39%
2489
August1st to 15thDay
7%326%5%35%6%6%9%42%
2340
16th to endDay
7%5%25%5%35%5%7%9%43%
2326
September1st to 15thDay
12%426%5%2446%5%45%
2040
16th to endDay
13%425%424346%47%
1980
October1st to 15thDay
11%5%35%5%24445%47%
1959
16th to endDay
18%7%24323346%42%
1809
November1st to 15thDay
10%7%34423336%49%
1582
16th to endDay
19%9%35%323336%39%
1620
December1st to 15thDay
26%10%5%6%5%2323428%
1620
16th to endDay
21%14%45%5%23345%28%
1650
January1st to 15thNight
19%11%5%9%6%24445%26%
2503
16th to endNight
18%12%5%7%5%2433430%
2496
February1st to 15thNight
20%11%5%7%423335%32%
2127
16th to endNight
18%12%5%6%5%24446%30%
1893
March1st to 15thNight
18%8%46%5%2335%6%34%
2107
16th to endNight
16%8%45%434448%35%
2112
April1st to 15thNight
15%6%35%42445%6%40%
1806
16th to endNight
15%5%35%6%24447%40%
1668
May1st to 15thNight
17%7%35%5%25%45%7%34%
1619
16th to endNight
9%425%4446%7%10%41%
1682
June1st to 15thNight
5%42343345%10%52%
1539
16th to endNight
6%313325%6%7%11%47%
1440
July1st to 15thNight
9%5%25%6%2445%8%45%
1440
16th to endNight
7%3144346%6%8%50%
1678
August1st to 15thNight
5%325%4345%6%8%50%
1620
16th to endNight
5%2143245%6%9%53%
1873
September1st to 15thNight
12%31332445%8%51%
1908
16th to endNight
11%42441335%6%51%
1980
October1st to 15thNight
9%3134245%5%7%51%
2000
16th to endNight
16%6%25%333345%44%
2411
November1st to 15thNight
13%5%1332345%6%48%
2276
16th to endNight
19%8%34424336%37%
2340
December1st to 15thNight
23%11%47%5%24345%28%
2340
16th to endNight
23%14%46%43443426%
2571

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%49%15%11%
1433
16th to endDay
55%410%22%6%
1726
February1st to 15thDay
54%39%21%9%
1725
16th to endDay
54%5%12%20%7%
1580
March1st to 15thDay
53%411%20%9%
1851
16th to endDay
53%410%21%9%
2112
April1st to 15thDay
45%49%22%15%1
2151
16th to endDay
44%410%22%13%4
2290
May1st to 15thDay
51%7%12%16%10%1
2331
16th to endDay
44%8%12%19%12%1
2435
June1st to 15thDay
38%7%13%22%17%2
2418
16th to endDay
39%8%12%19%16%3
2520
July1st to 15thDay
43%8%11%15%17%3
2371
16th to endDay
37%10%14%22%13%2
2333
August1st to 15thDay
35%8%12%23%17%2
2327
16th to endDay
34%8%12%23%16%5%
2326
September1st to 15thDay
38%5%10%19%19%5%
2040
16th to endDay
37%5%8%21%25%1
1980
October1st to 15thDay
37%49%25%18%3
1959
16th to endDay
42%49%26%15%1
1809
November1st to 15thDay
36%48%24%19%5%
1582
16th to endDay
47%38%22%15%1
1620
December1st to 15thDay
60%39%15%9%
1620
16th to endDay
60%410%16%8%
1650
January1st to 15thNight
60%5%6%17%9%
2503
16th to endNight
56%410%20%7%1
2496
February1st to 15thNight
55%311%20%6%1
2136
16th to endNight
54%413%19%8%
1893
March1st to 15thNight
50%410%20%11%2
2107
16th to endNight
48%6%13%22%8%1
2112
April1st to 15thNight
42%5%12%20%17%2
1806
16th to endNight
43%49%21%13%7%
1668
May1st to 15thNight
47%7%11%21%10%1
1620
16th to endNight
34%9%14%21%15%4
1684
June1st to 15thNight
28%6%13%28%18%4
1539
16th to endNight
28%9%17%20%19%4
1440
July1st to 15thNight
36%6%11%22%17%5%
1360
16th to endNight
27%8%14%28%18%2
1571
August1st to 15thNight
29%8%14%25%18%3
1609
16th to endNight
25%7%15%27%20%4
1873
September1st to 15thNight
30%6%11%22%21%7%
1908
16th to endNight
32%48%23%27%3
1980
October1st to 15thNight
30%6%10%26%22%4
2000
16th to endNight
42%38%25%17%2
2411
November1st to 15thNight
35%49%21%23%5%
2276
16th to endNight
49%39%20%15%1
2340
December1st to 15thNight
59%410%16%8%
2340
16th to endNight
61%49%15%7%
2571

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
37%21%30%6%22
90
16th to endDay
22%38%31%6%1
96
February1st to 15thDay
22%43%25%7%1
90
16th to endDay
22%20%46%7%2
81
March1st to 15thDay
24%28%29%16%1
141
16th to endDay
21%26%31%11%8%1
288
April1st to 15thDay
21%22%27%19%6%2
270
16th to endDay
18%22%26%16%11%4
270
May1st to 15thDay
21%23%28%12%7%5%
288
16th to endDay
19%18%22%21%8%9%
331
June1st to 15thDay
11%14%19%31%16%6%
393
16th to endDay
10%19%24%25%14%5%
495
July1st to 15thDay
18%13%21%22%16%8%
475
16th to endDay
9%10%12%28%20%17%
349
August1st to 15thDay
8%7%15%25%23%18%
313
16th to endDay
9%7%14%29%26%12%
332
September1st to 15thDay
11%9%16%25%22%15%
315
16th to endDay
14%8%15%20%24%15%
314
October1st to 15thDay
14%12%20%25%20%6%
315
16th to endDay
14%14%35%24%10%1
225
November1st to 15thDay
8%14%27%30%14%4
90
16th to endDay
28%17%30%17%41
90
December1st to 15thDay
27%18%34%12%42
90
16th to endDay
29%28%35%5%2
96
January1st to 15thNight
19%31%29%15%3
897
16th to endNight
21%31%26%18%2
768
February1st to 15thNight
22%30%26%19%
704
16th to endNight
21%29%29%17%1
631
March1st to 15thNight
18%29%28%19%4
720
16th to endNight
17%27%26%20%6%
768
April1st to 15thNight
15%25%29%21%7%
548
16th to endNight
15%25%25%22%10%
540
May1st to 15thNight
17%21%27%21%11%
540
16th to endNight
10%19%21%26%17%4
563
June1st to 15thNight
7%18%17%32%21%2
540
16th to endNight
6%17%19%30%23%1
540
July1st to 15thNight
10%13%14%31%26%3
510
16th to endNight
7%16%7%29%31%6%
564
August1st to 15thNight
7%10%10%31%33%6%
539
16th to endNight
5%9%8%32%37%6%
573
September1st to 15thNight
11%10%13%29%28%6%
648
16th to endNight
10%13%16%23%31%4
717
October1st to 15thNight
11%13%21%26%22%4
720
16th to endNight
17%17%27%23%11%1
768
November1st to 15thNight
13%23%24%19%17%1
700
16th to endNight
22%28%19%20%8%
720
December1st to 15thNight
26%28%20%15%7%1
720
16th to endNight
26%30%24%15%2
843
Page generated at 2017-11-01 17:23:39. Version ac04

Copyright 2017 A. Danko


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