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Apple Orchard Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Apple Orchard Observatory clear sky chart from 2005-11-05 to 2018-02-13.

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
29%
15251
13%
48813
8%
15221
36%
15221
16%
34899

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%
780
6%
2716
3%
776
20%
776
7%
2191
January16th to endNight
19%
832
11%
2837
5%
832
26%
832
10%
2148
February1st to 15thNight
16%
751
9%
2444
3%
750
24%
750
10%
1872
February16th to endNight
22%
631
13%
1967
5%
631
32%
631
12%
1458
March1st to 15thNight
19%
720
12%
2076
6%
720
26%
720
14%
1563
March16th to endNight
30%
768
20%
2049
9%
768
38%
768
22%
1413
April1st to 15thNight
22%
718
15%
1796
5%
718
27%
718
19%
1323
April16th to endNight
28%
642
17%
1722
7%
642
35%
642
22%
1215
May1st to 15thNight
33%
360
17%
1440
15%
360
42%
360
16%
951
May16th to endNight
34%
375
14%
1497
10%
374
46%
374
19%
942
June1st to 15thNight
33%
360
9%
1440
8%
360
42%
360
15%
963
June16th to endNight
44%
360
8%
1440
11%
360
48%
360
18%
920
July1st to 15thNight
51%
340
14%
1360
20%
340
58%
340
27%
756
July16th to endNight
56%
376
14%
1418
15%
354
61%
354
27%
810
August1st to 15thNight
52%
468
15%
1539
12%
466
56%
466
24%
971
August16th to endNight
53%
693
21%
1839
11%
693
58%
693
36%
1137
September1st to 15thNight
44%
720
15%
1800
7%
720
47%
720
29%
1246
September16th to endNight
48%
717
22%
1966
15%
717
53%
717
31%
1256
October1st to 15thNight
33%
720
16%
2160
11%
720
41%
720
20%
1485
October16th to endNight
23%
768
11%
2382
5%
768
31%
768
13%
1790
November1st to 15thNight
27%
760
16%
2553
12%
760
34%
760
15%
1820
November16th to endNight
19%
780
10%
2730
6%
780
25%
780
9%
2111
December1st to 15thNight
16%
780
6%
2730
3%
780
21%
780
7%
2218
December16th to endNight
13%
832
9%
2912
3%
832
21%
832
8%
2340

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
17%9%36%6%34446%32%
49235
Night
17%9%46%6%34445%32%
48983
Cloud CoverDay
27%7%35%423345%31%
49245
Night
25%8%35%42333432%
48988
TransparencyDay
51%6%11%18%9%1
48923
Night
52%6%11%19%9%
48813
SeeingDay
22%13%29%20%10%3
5850
Night
22%12%29%24%9%
15253

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
19%14%5%8%8%3444321%
1552
16th to endDay
14%14%5%10%9%35%445%22%
1737
February1st to 15thDay
12%14%6%13%8%35%42423%
1683
16th to endDay
17%13%5%7%7%45%34426%
1506
March1st to 15thDay
17%11%48%7%45%33426%
1870
16th to endDay
14%9%45%434445%40%
2175
April1st to 15thDay
22%11%36%423435%33%
2152
16th to endDay
20%8%26%424345%36%
2247
May1st to 15thDay
20%8%36%5%24346%33%
2511
16th to endDay
17%6%35%5%345%46%35%
2618
June1st to 15thDay
21%7%35%5%3445%6%31%
2520
16th to endDay
17%6%25%6%35%5%6%7%33%
2520
July1st to 15thDay
12%6%25%436%5%7%8%37%
2520
16th to endDay
11%425%6%35%6%7%10%35%
2654
August1st to 15thDay
12%6%27%6%36%5%6%7%37%
2409
16th to endDay
12%5%25%5%35%5%6%7%40%
2351
September1st to 15thDay
17%5%245%24447%40%
2160
16th to endDay
14%425%33345%6%45%
1991
October1st to 15thDay
21%8%36%5%34446%33%
1800
16th to endDay
25%9%37%6%4443426%
1842
November1st to 15thDay
16%10%36%4345%46%33%
1633
16th to endDay
20%12%5%8%6%45%445%23%
1560
December1st to 15thDay
19%16%6%9%7%45%44416%
1560
16th to endDay
21%16%5%8%6%23435%21%
1664
January1st to 15thNight
16%14%7%10%8%35%5%4418%
2716
16th to endNight
13%14%5%8%8%25%435%25%
2837
February1st to 15thNight
12%15%6%10%7%35%446%23%
2442
16th to endNight
15%10%5%7%7%3445%6%28%
1967
March1st to 15thNight
17%12%6%8%6%33335%30%
2064
16th to endNight
14%7%45%6%33445%40%
2049
April1st to 15thNight
23%7%36%433345%34%
1796
16th to endNight
18%9%25%6%23445%37%
1722
May1st to 15thNight
21%8%3442334438%
1440
16th to endNight
15%5%245%35%5%5%7%39%
1495
June1st to 15thNight
17%6%36%435%5%46%36%
1440
16th to endNight
15%5%25%5%35%5%6%7%38%
1440
July1st to 15thNight
9%434425%5%48%47%
1440
16th to endNight
9%41443447%8%46%
1514
August1st to 15thNight
9%425%5%345%6%8%43%
1549
16th to endNight
9%4244245%47%50%
1839
September1st to 15thNight
16%6%25%5%33446%42%
1800
16th to endNight
15%5%24422245%49%
1966
October1st to 15thNight
19%6%25%5%3335%6%36%
2160
16th to endNight
22%10%36%5%25%445%28%
2382
November1st to 15thNight
20%9%35%6%24345%32%
2553
16th to endNight
21%13%5%9%6%2434424%
2730
December1st to 15thNight
20%17%5%8%6%35%44420%
2730
16th to endNight
22%15%6%8%7%3434420%
2912

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%14%6%8%7%3334422%
1552
16th to endDay
16%13%5%9%8%45%44422%
1737
February1st to 15thDay
19%13%6%12%7%3443322%
1683
16th to endDay
23%12%46%7%35%33324%
1506
March1st to 15thDay
34%7%25%42322329%
1881
16th to endDay
33%5%2321222338%
2174
April1st to 15thDay
31%8%2431323333%
2152
16th to endDay
29%6%24322335%35%
2247
May1st to 15thDay
40%6%25%41232328%
2511
16th to endDay
36%5%1432233431%
2618
June1st to 15thDay
33%5%24433335%29%
2520
16th to endDay
30%42442445%5%32%
2520
July1st to 15thDay
12%434435%6%6%9%38%
2520
16th to endDay
11%5%245%45%6%7%10%35%
2654
August1st to 15thDay
35%41443334429%
2409
16th to endDay
35%313223335%34%
2351
September1st to 15thDay
20%5%14433347%40%
2160
16th to endDay
18%424423446%44%
1991
October1st to 15thDay
24%7%25%5%24345%33%
1800
16th to endDay
27%8%36%5%3433428%
1842
November1st to 15thDay
26%8%24324335%34%
1633
16th to endDay
28%9%5%5%5%34235%26%
1560
December1st to 15thDay
25%15%5%8%6%35%435%17%
1560
16th to endDay
26%14%5%7%5%2344421%
1664
January1st to 15thNight
20%12%6%9%7%35%43420%
2716
16th to endNight
17%14%5%8%6%3444426%
2837
February1st to 15thNight
21%14%5%8%6%24345%22%
2435
16th to endNight
25%10%37%6%24345%25%
1967
March1st to 15thNight
36%7%35%31222330%
2076
16th to endNight
33%41332222339%
2049
April1st to 15thNight
29%6%25%422235%36%
1796
16th to endNight
23%8%34423345%37%
1722
May1st to 15thNight
36%6%2431222335%
1440
16th to endNight
30%413312345%36%
1495
June1st to 15thNight
22%5%35%5%2434439%
1440
16th to endNight
21%4145%24446%40%
1440
July1st to 15thNight
10%325%4245%5%8%47%
1440
16th to endNight
9%3134445%7%7%47%
1514
August1st to 15thNight
28%313323336%39%
1549
16th to endNight
30%3221223444%
1839
September1st to 15thNight
19%424423445%43%
1800
16th to endNight
19%414322235%50%
1966
October1st to 15thNight
22%6%35%424345%37%
2160
16th to endNight
26%9%36%5%23445%29%
2382
November1st to 15thNight
33%8%2342232331%
2553
16th to endNight
35%10%36%42223324%
2730
December1st to 15thNight
28%14%46%5%2434320%
2730
16th to endNight
29%13%47%6%2333320%
2912

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
65%5%10%11%5%1
1553
16th to endDay
64%5%10%12%6%
1737
February1st to 15thDay
64%410%14%4
1685
16th to endDay
61%5%9%13%9%1
1506
March1st to 15thDay
60%5%11%15%6%
1881
16th to endDay
45%5%8%19%15%5%
2175
April1st to 15thDay
54%47%18%13%2
2152
16th to endDay
48%48%18%16%3
2247
May1st to 15thDay
51%5%8%17%14%2
2511
16th to endDay
47%7%12%19%12%1
2622
June1st to 15thDay
52%7%10%20%9%
2520
16th to endDay
47%8%12%19%11%1
2520
July1st to 15thDay
37%8%15%25%12%
2371
16th to endDay
41%9%16%22%9%
2487
August1st to 15thDay
43%9%15%21%10%
2395
16th to endDay
39%8%16%25%9%
2351
September1st to 15thDay
42%6%12%26%11%
2160
16th to endDay
37%7%12%31%10%
1991
October1st to 15thDay
51%6%11%20%9%
1800
16th to endDay
61%6%12%14%4
1842
November1st to 15thDay
49%7%15%19%7%
1633
16th to endDay
62%6%10%12%6%1
1560
December1st to 15thDay
69%6%11%9%3
1560
16th to endDay
65%6%10%11%5%
1664
January1st to 15thNight
67%5%10%10%4
2716
16th to endNight
60%5%9%16%7%
2837
February1st to 15thNight
61%5%12%15%4
2444
16th to endNight
55%6%10%17%8%
1967
March1st to 15thNight
57%411%18%7%
2076
16th to endNight
45%49%20%15%3
2049
April1st to 15thNight
52%48%18%14%1
1796
16th to endNight
48%48%18%16%3
1722
May1st to 15thNight
48%5%8%18%14%3
1440
16th to endNight
42%7%13%19%14%2
1497
June1st to 15thNight
48%7%12%20%10%1
1440
16th to endNight
43%8%14%19%14%
1440
July1st to 15thNight
32%7%13%29%15%1
1360
16th to endNight
33%8%17%25%15%
1418
August1st to 15thNight
35%10%16%23%12%
1539
16th to endNight
31%6%16%32%11%
1839
September1st to 15thNight
41%6%12%27%10%1
1800
16th to endNight
37%5%12%34%9%
1966
October1st to 15thNight
47%5%11%22%12%
2160
16th to endNight
56%6%14%16%5%
2382
November1st to 15thNight
52%6%13%17%9%
2553
16th to endNight
62%6%11%15%3
2730
December1st to 15thNight
67%6%12%10%3
2730
16th to endNight
67%5%9%11%5%
2912

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
25%27%25%16%4
90
16th to endDay
30%15%41%11%
113
February1st to 15thDay
32%23%36%7%
126
16th to endDay
32%23%25%13%4
165
March1st to 15thDay
26%18%32%17%4
270
16th to endDay
23%18%29%17%9%1
288
April1st to 15thDay
27%22%27%14%7%
270
16th to endDay
24%19%25%16%10%3
270
May1st to 15thDay
30%12%27%16%8%3
288
16th to endDay
23%12%34%18%8%1
331
June1st to 15thDay
26%9%32%19%9%1
315
16th to endDay
17%11%33%24%12%1
315
July1st to 15thDay
15%430%29%13%5%
305
16th to endDay
11%6%30%31%15%4
326
August1st to 15thDay
13%6%24%34%12%7%
313
16th to endDay
14%5%26%27%15%10%
332
September1st to 15thDay
17%7%26%18%18%12%
315
16th to endDay
13%9%26%20%19%10%
314
October1st to 15thDay
23%11%27%24%9%2
315
16th to endDay
29%19%27%17%5%
316
November1st to 15thDay
26%12%29%22%7%1
197
16th to endDay
31%23%35%6%3
90
December1st to 15thDay
24%23%34%16%1
90
16th to endDay
38%26%28%6%1
96
January1st to 15thNight
24%18%34%17%4
780
16th to endNight
21%16%35%21%4
832
February1st to 15thNight
20%15%38%20%3
753
16th to endNight
21%19%32%21%5%
631
March1st to 15thNight
26%15%32%22%3
720
16th to endNight
19%16%29%24%9%
768
April1st to 15thNight
26%16%29%21%5%
718
16th to endNight
25%14%28%22%8%
642
May1st to 15thNight
27%7%26%27%9%1
360
16th to endNight
17%7%36%25%12%
375
June1st to 15thNight
20%8%30%30%9%
360
16th to endNight
17%6%27%36%12%
360
July1st to 15thNight
8%427%41%16%1
340
16th to endNight
9%126%45%14%1
376
August1st to 15thNight
11%423%38%19%1
468
16th to endNight
11%424%35%20%2
693
September1st to 15thNight
18%5%25%28%19%2
720
16th to endNight
16%9%22%25%23%3
717
October1st to 15thNight
23%9%28%23%12%1
720
16th to endNight
29%14%27%22%6%
768
November1st to 15thNight
25%11%30%21%10%
760
16th to endNight
31%17%24%18%6%
780
December1st to 15thNight
29%17%32%17%3
780
16th to endNight
32%14%32%16%3
832
Page generated at 2018-02-13 20:45:57. Version ac04

Copyright 2018 A. Danko


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