Allendale
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Allendale 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
37%
15965
14%
46745
10%
15923
41%
15923
19%
33528

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
16%
900
6%
2506
3%
895
19%
895
8%
2153
January16th to endNight
19%
960
5%
2688
3%
960
20%
960
8%
2329
February1st to 15thNight
19%
731
8%
2211
4%
731
23%
731
9%
1810
February16th to endNight
24%
631
11%
1893
6%
631
30%
631
13%
1483
March1st to 15thNight
33%
720
15%
2145
10%
720
37%
720
19%
1521
March16th to endNight
35%
714
18%
2058
12%
714
42%
714
23%
1398
April1st to 15thNight
33%
539
13%
1797
9%
539
40%
539
18%
1249
April16th to endNight
39%
540
21%
1652
12%
540
48%
540
25%
1074
May1st to 15thNight
39%
540
15%
1620
9%
540
43%
540
22%
1101
May16th to endNight
46%
562
16%
1537
11%
561
50%
561
29%
1017
June1st to 15thNight
53%
540
15%
1440
10%
540
57%
540
34%
912
June16th to endNight
55%
540
14%
1440
10%
540
58%
540
33%
918
July1st to 15thNight
67%
510
16%
1360
12%
510
69%
510
43%
789
July16th to endNight
69%
564
20%
1417
16%
531
70%
531
40%
842
August1st to 15thNight
68%
539
23%
1581
17%
536
71%
536
39%
891
August16th to endNight
64%
573
22%
1840
21%
573
68%
573
33%
1058
September1st to 15thNight
63%
579
25%
1804
23%
579
67%
579
36%
1021
September16th to endNight
58%
657
22%
1815
17%
657
61%
657
35%
1115
October1st to 15thNight
47%
660
23%
1847
17%
660
51%
660
28%
1211
October16th to endNight
29%
704
13%
2288
9%
704
36%
704
16%
1649
November1st to 15thNight
35%
700
18%
2276
16%
700
41%
700
19%
1572
November16th to endNight
25%
720
10%
2340
7%
720
29%
720
10%
1856
December1st to 15thNight
14%
882
4%
2502
2%
882
16%
882
6%
2209
December16th to endNight
14%
960
6%
2688
2%
960
17%
960
7%
2350

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%8%46%5%3445%7%34%
47894
Night
15%10%47%5%34446%33%
46913
Cloud CoverDay
14%8%46%5%3445%7%34%
47903
Night
15%10%47%5%34446%33%
46918
TransparencyDay
49%412%21%11%1
47580
Night
52%410%19%10%1
46745
SeeingDay
16%7%26%26%15%6%
5961
Night
20%6%25%31%13%1
15969

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%14%8%12%10%6%6%44411%
1432
16th to endDay
14%18%12%13%10%5%442211%
1536
February1st to 15thDay
12%14%9%12%11%45%44416%
1647
16th to endDay
14%13%7%10%7%5%5%446%20%
1580
March1st to 15thDay
15%12%37%6%345%6%7%27%
1804
16th to endDay
17%8%36%6%24446%35%
2178
April1st to 15thDay
21%9%46%42325%5%32%
2151
16th to endDay
16%6%25%425%45%8%38%
2307
May1st to 15thDay
19%6%25%43445%7%36%
2331
16th to endDay
9%5%245%24448%45%
2575
June1st to 15thDay
11%425%435%46%8%42%
2520
16th to endDay
9%4245%25%45%9%45%
2520
July1st to 15thDay
6%323335%46%8%50%
2520
16th to endDay
8%3234245%7%9%46%
2655
August1st to 15thDay
9%425%5%2446%9%44%
2370
16th to endDay
11%425%42445%9%44%
2360
September1st to 15thDay
12%42443345%8%44%
2031
16th to endDay
11%5%345%25%45%8%41%
1815
October1st to 15thDay
17%7%27%5%34335%39%
1782
16th to endDay
24%8%36%6%34446%26%
1584
November1st to 15thDay
15%11%26%425%446%35%
1582
16th to endDay
22%18%47%6%34346%18%
1620
December1st to 15thDay
17%21%12%11%8%2322412%
1458
16th to endDay
20%21%10%11%6%2434412%
1536
January1st to 15thNight
20%15%8%12%8%35%34315%
2506
16th to endNight
13%14%11%11%10%44445%13%
2688
February1st to 15thNight
13%17%7%10%9%4444420%
2209
16th to endNight
16%13%5%10%6%35%5%45%23%
1893
March1st to 15thNight
16%9%36%5%34447%34%
2132
16th to endNight
15%7%36%5%3445%7%36%
2058
April1st to 15thNight
19%8%345%3445%6%33%
1797
16th to endNight
18%6%25%3245%45%41%
1652
May1st to 15thNight
18%5%246%4445%7%36%
1620
16th to endNight
12%6%25%5%2445%7%41%
1535
June1st to 15thNight
10%5%2443445%9%45%
1440
16th to endNight
8%4246%25%5%7%8%42%
1440
July1st to 15thNight
6%3243145%6%8%53%
1440
16th to endNight
6%3144245%6%7%53%
1513
August1st to 15thNight
6%42333446%7%52%
1590
16th to endNight
10%42442335%6%50%
1840
September1st to 15thNight
11%313324347%53%
1804
16th to endNight
10%5%25%424347%49%
1815
October1st to 15thNight
20%6%24412446%42%
1847
16th to endNight
24%8%36%424345%32%
2288
November1st to 15thNight
17%11%35%434345%35%
2276
16th to endNight
21%15%5%8%5%34346%20%
2340
December1st to 15thNight
21%19%10%11%6%3432311%
2502
16th to endNight
21%19%10%10%7%33345%12%
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%13%8%12%10%6%6%34411%
1432
16th to endDay
14%18%11%14%9%5%442311%
1536
February1st to 15thDay
12%15%8%12%11%45%345%16%
1647
16th to endDay
13%14%7%11%7%45%45%6%19%
1580
March1st to 15thDay
15%11%37%5%45%5%6%7%27%
1814
16th to endDay
17%8%36%6%2445%6%35%
2177
April1st to 15thDay
20%10%45%42325%6%31%
2151
16th to endDay
17%6%35%425%45%8%37%
2307
May1st to 15thDay
19%5%25%42445%7%37%
2331
16th to endDay
9%5%25%5%34448%44%
2575
June1st to 15thDay
11%4245%35%46%8%42%
2520
16th to endDay
9%424435%46%9%45%
2520
July1st to 15thDay
6%414335%5%5%9%50%
2520
16th to endDay
8%323425%6%6%9%46%
2655
August1st to 15thDay
9%425%5%2447%10%44%
2370
16th to endDay
12%425%42445%9%43%
2360
September1st to 15thDay
12%42443436%8%45%
2031
16th to endDay
11%6%345%35%45%9%40%
1815
October1st to 15thDay
17%7%26%5%3433439%
1782
16th to endDay
24%8%36%6%34446%26%
1584
November1st to 15thDay
15%11%35%435%436%35%
1582
16th to endDay
21%18%5%6%6%34345%19%
1620
December1st to 15thDay
17%21%11%12%7%3322412%
1458
16th to endDay
20%21%9%11%6%2434412%
1536
January1st to 15thNight
20%15%7%12%8%35%34315%
2506
16th to endNight
13%15%11%12%10%45%43413%
2688
February1st to 15thNight
13%17%7%11%8%45%34420%
2202
16th to endNight
16%13%5%10%6%345%45%23%
1893
March1st to 15thNight
17%9%36%5%34447%34%
2145
16th to endNight
15%7%35%5%3445%7%36%
2058
April1st to 15thNight
19%9%35%5%35%45%6%33%
1797
16th to endNight
18%6%25%424445%41%
1652
May1st to 15thNight
18%5%346%44447%36%
1619
16th to endNight
12%6%25%6%2445%8%41%
1535
June1st to 15thNight
10%5%2443445%9%45%
1440
16th to endNight
9%4246%35%5%7%8%42%
1440
July1st to 15thNight
6%3143245%6%8%53%
1440
16th to endNight
6%3144245%5%7%53%
1513
August1st to 15thNight
7%42332446%7%52%
1590
16th to endNight
10%5%2442325%7%50%
1840
September1st to 15thNight
10%313324346%54%
1804
16th to endNight
9%5%25%5%24347%49%
1815
October1st to 15thNight
19%6%2441235%6%42%
1847
16th to endNight
23%9%36%424345%31%
2288
November1st to 15thNight
17%11%35%5%34446%35%
2276
16th to endNight
21%15%5%9%434336%20%
2340
December1st to 15thNight
21%20%10%11%6%3432411%
2502
16th to endNight
21%19%9%10%6%23335%12%
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
76%5%9%7%1
1433
16th to endDay
80%27%6%2
1536
February1st to 15thDay
71%47%13%2
1649
16th to endDay
65%410%14%5%
1580
March1st to 15thDay
54%414%18%7%
1814
16th to endDay
49%414%24%6%1
2178
April1st to 15thDay
53%39%21%11%
2151
16th to endDay
45%313%18%14%2
2307
May1st to 15thDay
46%412%25%10%1
2331
16th to endDay
38%5%13%27%13%1
2579
June1st to 15thDay
38%412%26%16%
2520
16th to endDay
35%416%23%18%1
2520
July1st to 15thDay
30%5%11%29%19%2
2371
16th to endDay
32%5%14%25%18%2
2488
August1st to 15thDay
34%5%13%31%13%1
2355
16th to endDay
37%412%25%16%2
2360
September1st to 15thDay
37%410%29%14%2
2031
16th to endDay
39%412%26%16%
1815
October1st to 15thDay
48%39%24%13%
1782
16th to endDay
59%414%15%5%
1584
November1st to 15thDay
50%411%20%11%
1582
16th to endDay
67%410%14%3
1620
December1st to 15thDay
78%37%8%2
1458
16th to endDay
76%49%7%1
1536
January1st to 15thNight
74%37%10%3
2506
16th to endNight
74%410%7%2
2688
February1st to 15thNight
68%48%14%4
2211
16th to endNight
63%311%15%5%
1893
March1st to 15thNight
51%412%20%9%1
2145
16th to endNight
47%312%24%10%2
2058
April1st to 15thNight
51%38%19%15%1
1797
16th to endNight
44%310%20%16%5%
1652
May1st to 15thNight
48%310%22%11%2
1620
16th to endNight
41%411%23%15%2
1537
June1st to 15thNight
36%411%28%17%1
1440
16th to endNight
37%5%15%23%16%1
1440
July1st to 15thNight
28%413%28%22%2
1360
16th to endNight
29%5%14%26%21%2
1417
August1st to 15thNight
29%412%33%18%2
1581
16th to endNight
34%39%28%19%3
1840
September1st to 15thNight
31%411%30%18%2
1804
16th to endNight
35%312%30%16%
1815
October1st to 15thNight
42%49%27%15%1
1847
16th to endNight
55%412%18%8%
2288
November1st to 15thNight
51%310%20%12%1
2276
16th to endNight
65%5%10%15%2
2340
December1st to 15thNight
78%37%6%3
2502
16th to endNight
75%49%8%1
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
22%12%33%30%2
90
16th to endDay
29%6%33%23%7%
96
February1st to 15thDay
18%23%37%15%22
90
16th to endDay
23%11%29%25%8%1
81
March1st to 15thDay
31%12%27%18%9%
104
16th to endDay
27%7%25%26%10%2
288
April1st to 15thDay
30%6%29%25%7%1
270
16th to endDay
20%8%30%21%12%5%
270
May1st to 15thDay
22%7%25%27%11%5%
288
16th to endDay
12%9%29%27%15%5%
475
June1st to 15thDay
13%431%31%13%5%
495
16th to endDay
12%6%32%29%12%6%
495
July1st to 15thDay
7%328%30%19%10%
475
16th to endDay
9%226%31%19%10%
515
August1st to 15thDay
11%216%25%26%18%
343
16th to endDay
16%312%27%26%13%
332
September1st to 15thDay
13%215%33%24%10%
294
16th to endDay
13%5%16%26%27%10%
254
October1st to 15thDay
16%12%19%26%21%3
244
16th to endDay
23%9%40%23%2
96
November1st to 15thDay
11%13%32%22%16%4
90
16th to endDay
34%10%35%10%10%
90
December1st to 15thDay
28%23%33%6%7%
90
16th to endDay
31%26%34%7%1
96
January1st to 15thNight
27%12%30%21%7%
900
16th to endNight
21%8%30%33%4
960
February1st to 15thNight
20%10%34%27%6%
734
16th to endNight
23%10%31%27%7%
631
March1st to 15thNight
22%9%28%29%9%
720
16th to endNight
17%7%31%30%11%1
714
April1st to 15thNight
23%5%30%32%7%
539
16th to endNight
21%5%30%32%9%1
540
May1st to 15thNight
20%428%36%10%
540
16th to endNight
15%326%36%18%
563
June1st to 15thNight
11%225%41%18%
540
16th to endNight
10%224%43%18%1
540
July1st to 15thNight
7%17%44%27%2
510
16th to endNight
7%114%44%30%1
564
August1st to 15thNight
8%13%47%26%3
539
16th to endNight
12%112%37%30%5%
573
September1st to 15thNight
13%314%38%24%5%
579
16th to endNight
15%416%32%26%4
657
October1st to 15thNight
23%5%18%31%19%1
660
16th to endNight
29%8%27%23%9%
704
November1st to 15thNight
23%8%26%29%12%
700
16th to endNight
29%11%25%25%7%
720
December1st to 15thNight
31%11%28%23%5%
882
16th to endNight
30%8%34%22%3
960
Page generated at 2017-09-11 19:35:32. Version ac04

Copyright 2017 A. Danko


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