Arden
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Arden 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
28%
14685
14%
46795
8%
14654
36%
14654
17%
32687

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%
720
8%
2506
2%
716
21%
716
6%
1992
January16th to endNight
18%
768
12%
2586
5%
768
27%
768
11%
1949
February1st to 15thNight
15%
704
11%
2287
3%
701
25%
701
11%
1716
February16th to endNight
19%
631
15%
1973
6%
631
31%
631
14%
1434
March1st to 15thNight
19%
720
14%
2055
6%
720
27%
720
16%
1516
March16th to endNight
29%
768
21%
2064
9%
768
38%
768
24%
1383
April1st to 15thNight
21%
718
17%
1796
4%
718
27%
718
20%
1296
April16th to endNight
28%
648
18%
1728
7%
648
35%
648
23%
1185
May1st to 15thNight
37%
375
18%
1455
16%
375
47%
375
18%
922
May16th to endNight
33%
374
15%
1497
10%
374
47%
374
22%
878
June1st to 15thNight
34%
360
10%
1440
8%
360
44%
360
16%
943
June16th to endNight
42%
360
10%
1440
11%
360
48%
360
18%
908
July1st to 15thNight
50%
340
16%
1360
21%
340
57%
340
28%
740
July16th to endNight
54%
376
15%
1418
15%
354
60%
354
29%
785
August1st to 15thNight
52%
507
16%
1578
11%
505
57%
505
29%
956
August16th to endNight
50%
687
22%
1833
11%
687
56%
687
38%
1097
September1st to 15thNight
44%
700
19%
1750
8%
700
49%
700
32%
1147
September16th to endNight
46%
657
21%
1806
13%
657
52%
657
31%
1157
October1st to 15thNight
32%
660
17%
1980
11%
660
40%
660
19%
1376
October16th to endNight
20%
704
10%
2160
4%
704
28%
704
11%
1675
November1st to 15thNight
27%
700
18%
2355
14%
700
35%
700
17%
1619
November16th to endNight
19%
720
12%
2520
7%
720
27%
720
10%
1897
December1st to 15thNight
15%
720
7%
2520
2%
720
20%
720
8%
1959
December16th to endNight
12%
768
9%
2688
3%
768
19%
768
8%
2157

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%5%3445%6%32%
47839
Night
17%9%36%5%3445%6%34%
46965
Cloud CoverDay
17%9%36%5%34446%32%
47849
Night
17%9%36%5%3445%6%34%
46970
TransparencyDay
51%5%11%19%10%1
47527
Night
50%5%11%20%10%1
46795
SeeingDay
22%13%29%20%10%4
5419
Night
22%12%30%23%9%
14686

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%15%5%7%6%2333424%
1432
16th to endDay
14%15%6%10%8%35%33423%
1638
February1st to 15thDay
13%15%5%11%8%25%445%22%
1575
16th to endDay
18%14%48%6%35%34426%
1499
March1st to 15thDay
16%13%47%8%4443427%
1891
16th to endDay
15%8%46%423345%40%
2160
April1st to 15thDay
22%11%35%424335%33%
2152
16th to endDay
20%8%25%433335%38%
2241
May1st to 15thDay
19%7%35%5%35%35%6%33%
2494
16th to endDay
15%5%26%6%35%5%5%7%37%
2618
June1st to 15thDay
22%6%25%435%5%5%7%29%
2520
16th to endDay
16%6%36%6%36%5%5%8%32%
2520
July1st to 15thDay
12%5%25%5%36%5%7%8%37%
2520
16th to endDay
11%6%36%6%37%5%6%8%34%
2654
August1st to 15thDay
11%6%36%6%36%6%5%8%36%
2370
16th to endDay
14%6%25%4345%6%8%38%
2357
September1st to 15thDay
15%6%245%2435%6%41%
2098
16th to endDay
17%5%24423347%42%
1820
October1st to 15thDay
21%8%35%5%2345%7%32%
1650
16th to endDay
28%10%27%6%3444424%
1711
November1st to 15thDay
15%8%37%6%3445%5%34%
1503
16th to endDay
24%12%5%6%434345%25%
1440
December1st to 15thDay
22%15%5%9%6%34446%19%
1440
16th to endDay
22%17%6%8%434335%20%
1536
January1st to 15thNight
21%13%5%8%7%4434420%
2506
16th to endNight
13%14%5%9%7%3445%5%25%
2586
February1st to 15thNight
14%14%5%8%6%345%5%6%24%
2285
16th to endNight
15%13%46%5%3345%6%29%
1973
March1st to 15thNight
18%12%47%5%24345%31%
2043
16th to endNight
16%7%45%423345%42%
2064
April1st to 15thNight
21%9%34423446%36%
1796
16th to endNight
17%6%25%42345%6%40%
1728
May1st to 15thNight
20%6%15%424446%38%
1455
16th to endNight
12%5%25%5%35%448%42%
1495
June1st to 15thNight
17%6%36%5%34348%35%
1440
16th to endNight
13%5%25%5%35%5%6%9%37%
1440
July1st to 15thNight
9%3245%35%45%8%47%
1440
16th to endNight
9%3143245%6%9%48%
1514
August1st to 15thNight
9%5%145%345%5%8%45%
1588
16th to endNight
9%42342345%8%51%
1833
September1st to 15thNight
14%5%24423448%44%
1750
16th to endNight
16%424323446%47%
1806
October1st to 15thNight
19%8%25%5%2445%5%35%
1980
16th to endNight
25%9%46%6%24445%26%
2160
November1st to 15thNight
17%9%25%5%35%5%5%5%35%
2355
16th to endNight
23%11%37%5%25%445%26%
2520
December1st to 15thNight
21%14%47%5%34445%22%
2520
16th to endNight
22%16%6%8%5%2433420%
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
21%15%5%7%5%2443425%
1432
16th to endDay
13%16%5%10%8%3443423%
1638
February1st to 15thDay
14%15%6%11%7%45%435%22%
1575
16th to endDay
19%15%47%7%3344425%
1499
March1st to 15thDay
17%13%48%8%5%343426%
1902
16th to endDay
16%8%36%5%23245%39%
2159
April1st to 15thDay
22%11%35%424335%33%
2152
16th to endDay
20%9%345%23246%37%
2241
May1st to 15thDay
19%7%36%5%24446%33%
2494
16th to endDay
14%6%36%5%35%45%6%38%
2618
June1st to 15thDay
23%5%25%435%45%7%30%
2520
16th to endDay
17%6%26%6%36%45%7%33%
2520
July1st to 15thDay
13%5%25%445%5%7%8%38%
2520
16th to endDay
11%5%26%6%46%5%7%8%34%
2654
August1st to 15thDay
11%6%26%6%45%5%6%7%36%
2370
16th to endDay
14%425%5%3445%8%40%
2357
September1st to 15thDay
16%6%24424436%42%
2098
16th to endDay
18%5%25%32435%7%42%
1820
October1st to 15thDay
20%7%35%424446%34%
1650
16th to endDay
29%9%36%6%33445%24%
1711
November1st to 15thDay
15%9%36%6%25%45%5%34%
1503
16th to endDay
24%11%45%434446%25%
1440
December1st to 15thDay
22%14%6%7%6%33446%20%
1440
16th to endDay
22%17%6%8%433435%19%
1536
January1st to 15thNight
21%13%5%9%7%35%43420%
2506
16th to endNight
13%14%5%9%7%3445%5%25%
2586
February1st to 15thNight
14%13%5%8%7%345%6%6%24%
2278
16th to endNight
16%13%46%5%3445%6%29%
1973
March1st to 15thNight
19%12%46%5%24446%30%
2055
16th to endNight
16%7%35%423335%42%
2064
April1st to 15thNight
21%8%34423345%36%
1796
16th to endNight
17%7%25%33345%6%39%
1728
May1st to 15thNight
20%6%3442345%6%38%
1455
16th to endNight
12%5%35%5%3445%8%43%
1495
June1st to 15thNight
18%5%36%435%5%5%7%35%
1440
16th to endNight
15%4245%35%5%7%8%37%
1440
July1st to 15thNight
9%325%435%45%7%48%
1440
16th to endNight
8%3243245%6%9%48%
1514
August1st to 15thNight
9%5%2443445%9%45%
1588
16th to endNight
8%42442346%8%51%
1833
September1st to 15thNight
15%42443335%8%45%
1750
16th to endNight
16%424324345%47%
1806
October1st to 15thNight
19%6%36%5%3445%5%36%
1980
16th to endNight
24%9%37%6%34445%25%
2160
November1st to 15thNight
17%9%35%5%345%5%6%34%
2355
16th to endNight
24%10%37%5%35%345%26%
2520
December1st to 15thNight
22%14%48%5%2435%5%22%
2520
16th to endNight
23%15%5%9%5%3434420%
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
63%49%15%5%1
1433
16th to endDay
64%48%11%9%1
1638
February1st to 15thDay
63%5%9%15%4
1577
16th to endDay
61%39%12%11%1
1499
March1st to 15thDay
60%411%15%6%1
1902
16th to endDay
47%37%20%15%5%
2160
April1st to 15thDay
54%36%18%13%2
2152
16th to endDay
48%38%20%16%3
2241
May1st to 15thDay
50%5%10%17%13%2
2494
16th to endDay
45%5%13%20%12%2
2622
June1st to 15thDay
51%6%11%19%10%
2520
16th to endDay
48%5%13%19%11%
2520
July1st to 15thDay
38%8%13%27%11%
2371
16th to endDay
45%7%15%22%9%
2487
August1st to 15thDay
43%7%15%22%10%
2356
16th to endDay
41%5%15%27%9%
2357
September1st to 15thDay
41%6%12%25%12%
2098
16th to endDay
42%411%30%10%
1820
October1st to 15thDay
50%5%11%21%10%
1650
16th to endDay
61%5%10%16%5%
1711
November1st to 15thDay
49%5%14%18%10%
1503
16th to endDay
59%7%11%12%7%1
1440
December1st to 15thDay
65%5%13%12%3
1440
16th to endDay
66%5%9%11%6%
1536
January1st to 15thNight
66%5%9%12%5%
2506
16th to endNight
59%5%10%15%8%
2586
February1st to 15thNight
58%6%12%17%5%
2287
16th to endNight
54%410%19%10%
1973
March1st to 15thNight
55%410%20%9%
2055
16th to endNight
44%310%21%17%2
2064
April1st to 15thNight
49%37%21%15%1
1796
16th to endNight
43%5%9%19%18%3
1728
May1st to 15thNight
45%49%20%14%4
1455
16th to endNight
39%5%14%22%15%2
1497
June1st to 15thNight
47%6%11%20%12%
1440
16th to endNight
41%8%13%21%13%
1440
July1st to 15thNight
32%5%12%29%18%1
1360
16th to endNight
31%7%16%28%15%
1418
August1st to 15thNight
34%7%16%27%12%1
1578
16th to endNight
30%5%15%33%14%
1833
September1st to 15thNight
37%5%14%29%11%
1750
16th to endNight
38%412%31%11%
1806
October1st to 15thNight
48%6%11%21%12%
1980
16th to endNight
59%6%11%14%7%
2160
November1st to 15thNight
48%6%12%18%11%1
2355
16th to endNight
59%5%10%17%5%
2520
December1st to 15thNight
62%5%13%13%3
2520
16th to endNight
67%410%10%6%
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
25%33%20%15%6%
60
16th to endDay
37%12%33%13%3
81
February1st to 15thDay
33%27%34%31
90
16th to endDay
34%20%30%11%3
158
March1st to 15thDay
29%13%31%20%5%
270
16th to endDay
25%15%35%13%8%2
288
April1st to 15thDay
27%21%26%15%7%1
270
16th to endDay
23%21%25%15%9%4
270
May1st to 15thDay
28%13%28%15%9%4
288
16th to endDay
16%16%36%16%9%3
331
June1st to 15thDay
25%10%30%22%9%1
315
16th to endDay
17%12%31%24%12%1
315
July1st to 15thDay
15%8%27%27%15%5%
305
16th to endDay
14%7%36%23%13%5%
326
August1st to 15thDay
10%429%31%16%7%
313
16th to endDay
16%5%25%26%15%11%
332
September1st to 15thDay
18%9%27%20%13%10%
294
16th to endDay
21%7%26%24%11%8%
254
October1st to 15thDay
25%9%32%17%11%3
255
16th to endDay
32%18%27%18%3
263
November1st to 15thDay
22%8%31%25%10%1
157
16th to endDay
26%18%25%20%8%1
60
December1st to 15thDay
25%25%30%16%3
60
16th to endDay
46%21%25%6%
64
January1st to 15thNight
29%19%28%17%5%
720
16th to endNight
21%15%35%22%4
768
February1st to 15thNight
22%19%37%17%3
704
16th to endNight
23%16%35%18%5%
631
March1st to 15thNight
26%16%33%21%1
720
16th to endNight
20%14%32%22%9%1
768
April1st to 15thNight
25%17%32%20%3
718
16th to endNight
22%15%30%20%10%
648
May1st to 15thNight
24%6%26%32%8%1
375
16th to endNight
13%7%39%26%12%
375
June1st to 15thNight
18%9%30%29%10%1
360
16th to endNight
18%428%35%12%
360
July1st to 15thNight
8%330%38%18%
340
16th to endNight
10%227%42%16%
376
August1st to 15thNight
13%322%36%21%2
507
16th to endNight
11%427%30%22%3
687
September1st to 15thNight
16%5%27%28%19%2
700
16th to endNight
18%8%22%27%20%2
657
October1st to 15thNight
24%11%26%23%12%1
660
16th to endNight
30%13%28%21%6%
704
November1st to 15thNight
22%12%31%22%10%
700
16th to endNight
32%16%25%17%8%
720
December1st to 15thNight
30%19%29%17%3
720
16th to endNight
32%14%32%16%2
768
Page generated at 2017-09-11 19:35:19. Version ac04

Copyright 2017 A. Danko


Arden Clear Sky Chart | Charts Home