Apple Ridge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Apple Ridge Observatory clear sky chart from 2005-11-05 to 2017-09-10.

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
32%
16010
13%
46790
8%
15968
37%
15968
18%
34151

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
15%
900
4%
2506
2%
895
17%
895
7%
2200
January16th to endNight
16%
960
5%
2688
1%
960
18%
960
8%
2339
February1st to 15thNight
18%
739
8%
2254
3%
739
22%
739
9%
1823
February16th to endNight
20%
631
10%
1893
4%
631
26%
631
11%
1529
March1st to 15thNight
26%
720
14%
2136
8%
720
32%
720
18%
1533
March16th to endNight
32%
726
17%
2070
11%
726
37%
726
21%
1456
April1st to 15thNight
27%
539
13%
1797
9%
539
34%
539
17%
1277
April16th to endNight
33%
540
19%
1627
10%
540
42%
540
23%
1089
May1st to 15thNight
34%
540
14%
1620
7%
540
41%
540
22%
1112
May16th to endNight
37%
562
16%
1522
7%
561
45%
561
32%
981
June1st to 15thNight
43%
540
12%
1440
8%
540
47%
540
29%
936
June16th to endNight
49%
540
13%
1440
7%
540
52%
540
32%
927
July1st to 15thNight
62%
510
17%
1360
12%
510
65%
510
42%
787
July16th to endNight
58%
564
16%
1417
10%
531
62%
531
38%
859
August1st to 15thNight
62%
539
22%
1572
16%
536
67%
536
39%
902
August16th to endNight
60%
573
21%
1803
19%
573
63%
573
32%
1073
September1st to 15thNight
57%
586
21%
1811
19%
586
60%
586
36%
1032
September16th to endNight
49%
657
20%
1815
14%
657
53%
657
32%
1159
October1st to 15thNight
41%
660
20%
1858
15%
660
46%
660
25%
1276
October16th to endNight
25%
704
11%
2288
7%
704
32%
704
14%
1687
November1st to 15thNight
28%
700
16%
2276
12%
700
35%
700
16%
1655
November16th to endNight
19%
720
7%
2340
4%
720
23%
720
9%
1921
December1st to 15thNight
13%
900
3%
2569
2%
900
14%
900
6%
2267
December16th to endNight
13%
960
5%
2688
2%
960
17%
960
7%
2331

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%10%47%6%3445%6%30%
47814
Night
15%10%5%7%6%3445%6%31%
46958
Cloud CoverDay
14%10%47%6%35%45%6%30%
47823
Night
13%10%5%7%6%3445%6%31%
46963
TransparencyDay
53%5%11%19%9%
47500
Night
53%5%12%18%9%
46790
SeeingDay
17%10%29%24%12%4
5987
Night
18%9%31%28%10%1
16014

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
16%16%9%15%10%46%32310%
1432
16th to endDay
13%18%11%14%12%5%6%3228%
1536
February1st to 15thDay
12%14%8%13%13%46%33414%
1606
16th to endDay
11%14%10%13%10%46%45%415%
1580
March1st to 15thDay
13%11%49%7%4446%6%26%
1814
16th to endDay
16%10%48%6%35%35%5%30%
2163
April1st to 15thDay
21%14%35%423345%30%
2151
16th to endDay
18%10%35%5%2445%6%33%
2331
May1st to 15thDay
18%8%36%5%2445%7%33%
2331
16th to endDay
13%6%244345%5%8%41%
2590
June1st to 15thDay
13%6%35%6%35%46%6%37%
2520
16th to endDay
13%5%25%6%35%5%6%7%38%
2520
July1st to 15thDay
9%425%4346%6%9%44%
2520
16th to endDay
11%5%25%5%35%5%5%10%40%
2655
August1st to 15thDay
8%5%26%6%36%5%6%8%39%
2379
16th to endDay
15%425%5%3445%7%41%
2396
September1st to 15thDay
17%424435%45%7%40%
2025
16th to endDay
14%6%25%5%35%46%7%37%
1815
October1st to 15thDay
21%8%25%5%35%345%34%
1770
16th to endDay
25%12%37%6%3435%7%20%
1584
November1st to 15thDay
16%12%47%43445%7%29%
1582
16th to endDay
20%19%8%9%5%24335%16%
1617
December1st to 15thDay
17%17%11%16%9%2432312%
1361
16th to endDay
21%19%9%12%8%34235%8%
1536
January1st to 15thNight
19%16%7%13%9%4433214%
2506
16th to endNight
11%15%9%14%10%5%6%445%12%
2688
February1st to 15thNight
11%13%8%11%10%36%445%19%
2252
16th to endNight
13%14%7%11%8%35%45%5%20%
1893
March1st to 15thNight
14%9%5%7%5%34447%32%
2123
16th to endNight
14%8%5%5%5%25%45%8%34%
2070
April1st to 15thNight
20%8%46%43445%6%31%
1797
16th to endNight
18%7%35%424346%39%
1627
May1st to 15thNight
16%5%25%6%45%5%6%7%33%
1620
16th to endNight
11%5%25%42436%9%42%
1520
June1st to 15thNight
13%5%25%43345%8%42%
1440
16th to endNight
10%426%5%2447%9%42%
1440
July1st to 15thNight
6%31333446%8%53%
1440
16th to endNight
6%425%5%2446%8%50%
1513
August1st to 15thNight
6%32443446%8%51%
1581
16th to endNight
11%5%2432345%6%50%
1803
September1st to 15thNight
13%41322335%6%52%
1811
16th to endNight
12%5%25%5%2445%8%43%
1815
October1st to 15thNight
18%8%24424345%39%
1858
16th to endNight
23%11%36%433445%28%
2288
November1st to 15thNight
14%14%46%5%34446%30%
2276
16th to endNight
20%18%6%7%5%3445%5%17%
2340
December1st to 15thNight
19%17%9%12%9%3433411%
2569
16th to endNight
19%18%9%11%7%2444412%
2688

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
16%15%9%15%10%5%6%32310%
1432
16th to endDay
11%18%11%14%12%5%6%3338%
1536
February1st to 15thDay
11%14%7%12%13%5%6%44414%
1606
16th to endDay
10%14%8%12%11%46%5%4416%
1580
March1st to 15thDay
13%10%38%7%45%46%7%26%
1824
16th to endDay
15%9%48%6%3445%5%30%
2162
April1st to 15thDay
20%13%45%424345%30%
2151
16th to endDay
16%11%36%5%2445%7%33%
2331
May1st to 15thDay
17%9%35%5%2445%7%33%
2331
16th to endDay
12%6%35%4245%5%8%41%
2590
June1st to 15thDay
12%7%36%6%35%45%6%38%
2520
16th to endDay
11%5%25%6%36%5%6%7%38%
2520
July1st to 15thDay
8%425%435%6%5%10%43%
2520
16th to endDay
9%5%25%5%35%5%5%9%40%
2655
August1st to 15thDay
8%5%26%6%36%6%5%9%38%
2379
16th to endDay
14%5%25%425%447%40%
2396
September1st to 15thDay
15%5%245%3445%6%40%
2025
16th to endDay
13%6%35%5%35%45%8%37%
1815
October1st to 15thDay
19%9%35%5%35%346%34%
1770
16th to endDay
21%13%47%7%3435%6%20%
1584
November1st to 15thDay
14%12%48%435%45%7%30%
1582
16th to endDay
19%20%9%8%6%24435%15%
1617
December1st to 15thDay
15%18%9%15%11%3332312%
1361
16th to endDay
20%19%8%12%8%45%3348%
1536
January1st to 15thNight
18%15%7%13%9%45%43314%
2506
16th to endNight
10%13%9%13%10%5%7%5%5%5%12%
2688
February1st to 15thNight
11%13%7%10%11%36%5%45%19%
2245
16th to endNight
13%12%6%11%9%5%5%5%45%20%
1893
March1st to 15thNight
13%9%5%7%6%3445%7%32%
2136
16th to endNight
14%7%46%5%45%45%7%34%
2070
April1st to 15thNight
19%9%47%5%24447%30%
1797
16th to endNight
17%7%25%5%23445%40%
1627
May1st to 15thNight
15%6%25%6%35%5%6%8%34%
1619
16th to endNight
11%5%25%5%2445%10%42%
1520
June1st to 15thNight
12%6%25%43446%8%41%
1440
16th to endNight
9%426%5%2447%9%42%
1440
July1st to 15thNight
6%3135%245%6%8%53%
1440
16th to endNight
5%4245%25%45%9%49%
1513
August1st to 15thNight
44244345%5%8%52%
1581
16th to endNight
9%5%2442436%6%49%
1803
September1st to 15thNight
12%42321345%6%52%
1811
16th to endNight
11%6%25%4245%5%7%43%
1815
October1st to 15thNight
16%8%35%424445%39%
1858
16th to endNight
21%11%47%5%2345%6%27%
2288
November1st to 15thNight
12%13%5%7%6%25%45%6%30%
2276
16th to endNight
17%18%6%8%6%35%5%5%5%17%
2340
December1st to 15thNight
18%15%8%12%8%4444412%
2569
16th to endNight
18%18%9%11%8%3444412%
2688

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
80%5%5%7%1
1433
16th to endDay
81%45%6%1
1536
February1st to 15thDay
72%5%8%12%1
1608
16th to endDay
69%5%9%10%4
1580
March1st to 15thDay
55%6%12%17%7%
1824
16th to endDay
54%5%11%20%6%1
2163
April1st to 15thDay
55%39%19%11%
2151
16th to endDay
50%412%14%15%2
2331
May1st to 15thDay
49%5%10%21%10%1
2331
16th to endDay
39%6%13%26%13%1
2594
June1st to 15thDay
44%5%11%23%14%
2520
16th to endDay
42%6%14%22%12%1
2520
July1st to 15thDay
34%6%12%28%17%1
2371
16th to endDay
38%7%12%23%15%2
2488
August1st to 15thDay
40%5%13%26%11%1
2364
16th to endDay
41%5%11%24%13%2
2396
September1st to 15thDay
42%5%11%27%11%1
2025
16th to endDay
44%5%15%23%11%
1815
October1st to 15thDay
51%5%10%23%9%
1770
16th to endDay
63%5%14%12%3
1584
November1st to 15thDay
53%5%13%19%7%
1582
16th to endDay
72%411%9%2
1617
December1st to 15thDay
79%36%7%1
1361
16th to endDay
80%47%5%1
1536
January1st to 15thNight
76%48%7%2
2506
16th to endNight
73%6%10%7%2
2688
February1st to 15thNight
66%5%8%15%3
2254
16th to endNight
65%410%12%5%
1893
March1st to 15thNight
51%6%12%18%10%1
2136
16th to endNight
48%5%12%22%9%
2070
April1st to 15thNight
52%5%9%18%13%
1797
16th to endNight
45%411%19%15%3
1627
May1st to 15thNight
46%5%12%21%11%2
1620
16th to endNight
37%5%13%26%14%2
1522
June1st to 15thNight
38%6%14%23%15%
1440
16th to endNight
36%7%15%23%16%
1440
July1st to 15thNight
26%6%12%31%20%2
1360
16th to endNight
30%6%17%28%15%1
1417
August1st to 15thNight
29%5%16%32%15%
1572
16th to endNight
34%5%13%26%18%1
1803
September1st to 15thNight
31%415%31%16%1
1811
16th to endNight
37%5%15%29%10%
1815
October1st to 15thNight
45%5%9%26%12%
1858
16th to endNight
56%5%15%17%5%
2288
November1st to 15thNight
54%5%11%17%9%1
2276
16th to endNight
68%5%13%9%2
2340
December1st to 15thNight
76%5%8%7%2
2569
16th to endNight
74%410%7%2
2688

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
14%12%51%22%
90
16th to endDay
27%443%21%21
96
February1st to 15thDay
16%30%38%12%2
90
16th to endDay
18%27%29%19%4
81
March1st to 15thDay
28%19%27%15%9%
114
16th to endDay
26%10%25%26%8%3
288
April1st to 15thDay
28%11%29%20%7%2
270
16th to endDay
21%12%30%21%8%5%
270
May1st to 15thDay
24%15%25%22%7%3
288
16th to endDay
15%14%32%25%8%3
490
June1st to 15thDay
15%10%36%25%9%2
495
16th to endDay
15%9%35%25%9%4
495
July1st to 15thDay
8%7%29%30%18%5%
475
16th to endDay
12%6%30%28%15%7%
515
August1st to 15thDay
9%322%28%25%11%
352
16th to endDay
21%318%27%18%10%
332
September1st to 15thDay
14%5%21%24%23%10%
294
16th to endDay
15%9%21%28%19%5%
254
October1st to 15thDay
22%8%28%26%10%2
249
16th to endDay
28%13%42%12%3
96
November1st to 15thDay
12%16%40%18%11%1
90
16th to endDay
25%21%35%12%5%
90
December1st to 15thDay
31%29%23%12%2
77
16th to endDay
28%34%29%8%
96
January1st to 15thNight
25%14%33%20%6%
900
16th to endNight
16%12%41%25%4
960
February1st to 15thNight
16%15%38%24%4
742
16th to endNight
20%14%34%25%4
631
March1st to 15thNight
19%11%36%22%8%
720
16th to endNight
17%10%34%27%8%1
726
April1st to 15thNight
21%12%34%26%41
539
16th to endNight
22%7%33%27%8%
540
May1st to 15thNight
18%8%35%29%8%
540
16th to endNight
12%7%36%29%11%1
563
June1st to 15thNight
14%6%30%34%13%
540
16th to endNight
11%328%40%14%1
540
July1st to 15thNight
9%121%43%22%2
510
16th to endNight
7%124%40%23%1
564
August1st to 15thNight
7%221%44%21%2
539
16th to endNight
10%417%40%24%2
573
September1st to 15thNight
15%320%36%20%4
586
16th to endNight
13%6%24%32%19%3
657
October1st to 15thNight
22%5%26%32%11%1
660
16th to endNight
28%10%29%23%7%
704
November1st to 15thNight
20%12%33%25%8%
700
16th to endNight
25%16%30%23%4
720
December1st to 15thNight
25%15%37%19%2
900
16th to endNight
25%13%36%20%3
960
Page generated at 2017-09-11 19:35:28. Version ac04

Copyright 2017 A. Danko


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