Rannie Road
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rannie Road clear sky chart from 2005-11-05 to 2018-04-23.

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
31%
15366
8%
49484
6%
15338
34%
15338
13%
38126

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
22%
825
10%
2911
7%
821
27%
821
9%
2364
January16th to endNight
20%
846
8%
2972
6%
846
23%
846
8%
2417
February1st to 15thNight
19%
760
6%
2483
3%
760
23%
760
8%
2068
February16th to endNight
21%
684
12%
2203
5%
684
30%
684
11%
1717
March1st to 15thNight
19%
780
4%
2243
3%
780
21%
780
9%
1921
March16th to endNight
20%
832
6%
2239
2%
832
22%
832
9%
1931
April1st to 15thNight
23%
779
6%
1949
3%
779
25%
779
11%
1656
April16th to endNight
26%
517
6%
1633
5%
517
29%
517
11%
1319
May1st to 15thNight
42%
359
11%
1439
15%
359
45%
359
15%
992
May16th to endNight
48%
374
5%
1469
7%
374
49%
374
13%
1063
June1st to 15thNight
43%
360
2%
1260
1%
360
44%
360
14%
930
June16th to endNight
47%
360
4%
1260
2%
360
47%
360
14%
920
July1st to 15thNight
68%
340
9%
1190
8%
340
69%
340
31%
672
July16th to endNight
73%
376
14%
1337
20%
354
76%
354
34%
681
August1st to 15thNight
76%
417
15%
1489
20%
415
76%
415
38%
744
August16th to endNight
66%
618
17%
1764
15%
618
66%
618
33%
1076
September1st to 15thNight
64%
720
19%
1800
10%
720
66%
720
40%
1105
September16th to endNight
42%
716
15%
1974
12%
716
44%
716
19%
1464
October1st to 15thNight
35%
720
10%
2160
9%
720
37%
720
17%
1585
October16th to endNight
26%
768
7%
2404
5%
768
29%
768
10%
1969
November1st to 15thNight
12%
760
4%
2660
2%
760
16%
760
5%
2332
November16th to endNight
15%
780
5%
2730
2%
780
19%
780
7%
2266
December1st to 15thNight
21%
795
9%
2795
4%
795
27%
795
9%
2244
December16th to endNight
8%
880
6%
3120
1%
880
14%
880
5%
2690

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
33%9%35%42333426%
50057
Night
34%9%2442333427%
49638
Cloud CoverDay
35%9%2442333426%
50057
Night
35%9%2442323427%
49641
TransparencyDay
62%5%10%14%5%1
49715
Night
61%5%11%13%6%1
49485
SeeingDay
35%8%21%23%9%2
6740
Night
38%5%19%22%13%1
15372

By Month

Percentage Cloud Cover NW (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
48%10%3322222317%
1358
16th to endDay
44%11%2332332318%
1600
February1st to 15thDay
42%12%35%42323416%
1711
16th to endDay
31%16%45%33323421%
1557
March1st to 15thDay
46%14%3442322312%
2044
16th to endDay
41%15%37%5%2331312%
2337
April1st to 15thDay
37%13%47%6%3333311%
2329
16th to endDay
35%12%46%6%2443414%
2435
May1st to 15thDay
29%9%36%424345%26%
2511
16th to endDay
31%8%46%6%33445%21%
2639
June1st to 15thDay
36%8%35%423335%22%
2700
16th to endDay
32%8%36%5%34335%23%
2700
July1st to 15thDay
17%425%413245%47%
2700
16th to endDay
17%5%23323335%48%
2739
August1st to 15thDay
17%5%23313346%48%
2461
16th to endDay
18%5%25%423346%42%
2438
September1st to 15thDay
18%6%23422235%47%
2160
16th to endDay
34%6%25%5%1333329%
1984
October1st to 15thDay
34%8%2432344428%
1800
16th to endDay
45%9%1431233419%
1818
November1st to 15thDay
55%9%35%32211211%
1528
16th to endDay
47%11%2432222416%
1560
December1st to 15thDay
37%13%3431232223%
1492
16th to endDay
46%17%25%41221214%
1456
January1st to 15thNight
45%10%2431223420%
2911
16th to endNight
41%12%3431223419%
2972
February1st to 15thNight
41%11%2442333418%
2471
16th to endNight
32%12%26%41323326%
2203
March1st to 15thNight
43%11%4442332316%
2243
16th to endNight
40%12%35%42333316%
2235
April1st to 15thNight
33%10%46%5%33445%17%
1949
16th to endNight
32%10%26%5%34345%21%
1633
May1st to 15thNight
22%6%27%5%2435%6%34%
1439
16th to endNight
23%7%35%435%45%6%30%
1469
June1st to 15thNight
25%7%26%5%33246%30%
1260
16th to endNight
22%8%36%3445%45%31%
1260
July1st to 15thNight
10%324423346%55%
1260
16th to endNight
10%313314345%58%
1429
August1st to 15thNight
10%312322345%59%
1497
16th to endNight
11%42432346%7%48%
1764
September1st to 15thNight
11%313323335%58%
1800
16th to endNight
29%7%26%323235%32%
1974
October1st to 15thNight
29%6%2442333433%
2160
16th to endNight
42%6%245%33235%20%
2404
November1st to 15thNight
52%8%25%42222313%
2660
16th to endNight
44%9%3442222319%
2730
December1st to 15thNight
38%11%3432323422%
2795
16th to endNight
46%14%2431122216%
3120

Percentage Cloud Cover SW (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
48%10%2331322218%
1358
16th to endDay
44%13%2331132419%
1600
February1st to 15thDay
44%11%25%41322317%
1711
16th to endDay
31%20%3442332421%
1557
March1st to 15thDay
48%13%4432322213%
2044
16th to endDay
42%16%36%42232212%
2337
April1st to 15thDay
40%13%46%5%2433312%
2329
16th to endDay
37%11%46%5%2433415%
2435
May1st to 15thDay
31%8%35%424435%26%
2511
16th to endDay
35%8%36%424335%21%
2639
June1st to 15thDay
40%8%35%32233421%
2700
16th to endDay
34%8%35%42334423%
2700
July1st to 15thDay
19%424323345%47%
2700
16th to endDay
20%42431324448%
2739
August1st to 15thDay
18%424323236%47%
2461
16th to endDay
20%6%24422446%42%
2438
September1st to 15thDay
19%6%14322235%47%
2160
16th to endDay
34%7%25%42322429%
1984
October1st to 15thDay
34%7%2432334429%
1800
16th to endDay
47%8%24312235%19%
1818
November1st to 15thDay
57%9%2431212212%
1528
16th to endDay
49%10%1431222317%
1560
December1st to 15thDay
38%13%3421223323%
1492
16th to endDay
48%16%25%32111114%
1456
January1st to 15thNight
46%9%2331223321%
2910
16th to endNight
42%12%2421323419%
2972
February1st to 15thNight
42%11%25%312335%17%
2471
16th to endNight
33%12%25%42223326%
2203
March1st to 15thNight
44%11%3431322316%
2243
16th to endNight
41%12%45%41323316%
2239
April1st to 15thNight
34%11%36%5%34335%17%
1949
16th to endNight
35%9%26%5%2433421%
1633
May1st to 15thNight
24%5%36%423447%32%
1439
16th to endNight
26%6%3443445%6%29%
1469
June1st to 15thNight
28%7%35%5%33345%28%
1260
16th to endNight
25%7%35%5%25%45%430%
1260
July1st to 15thNight
11%42442325%5%54%
1260
16th to endNight
11%213323345%58%
1429
August1st to 15thNight
11%212222446%58%
1497
16th to endNight
11%5%1342346%7%48%
1764
September1st to 15thNight
12%313323236%56%
1800
16th to endNight
30%6%25%413236%32%
1974
October1st to 15thNight
30%6%2442423433%
2160
16th to endNight
42%7%24432335%20%
2404
November1st to 15thNight
54%8%2431222312%
2660
16th to endNight
45%10%2442322319%
2730
December1st to 15thNight
39%11%2332323422%
2795
16th to endNight
48%14%2432212216%
3120

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
73%5%5%9%5%1
1358
16th to endDay
72%37%11%31
1600
February1st to 15thDay
74%47%7%42
1711
16th to endDay
68%47%13%5%
1557
March1st to 15thDay
79%45%8%2
2044
16th to endDay
79%46%8%1
2337
April1st to 15thDay
77%5%7%8%1
2329
16th to endDay
72%6%8%8%3
2435
May1st to 15thDay
60%6%11%15%5%
2511
16th to endDay
65%6%13%12%2
2643
June1st to 15thDay
65%5%14%9%31
2700
16th to endDay
63%6%12%13%4
2700
July1st to 15thDay
40%5%14%24%12%2
2541
16th to endDay
37%5%16%27%10%1
2569
August1st to 15thDay
37%7%15%27%9%1
2444
16th to endDay
41%7%17%24%6%1
2438
September1st to 15thDay
41%5%12%22%15%3
2160
16th to endDay
59%5%9%15%7%2
1984
October1st to 15thDay
58%5%11%14%8%
1800
16th to endDay
68%5%10%10%4
1818
November1st to 15thDay
81%346%21
1528
16th to endDay
73%35%8%7%
1560
December1st to 15thDay
67%5%6%9%8%1
1492
16th to endDay
80%348%21
1456
January1st to 15thNight
69%35%14%5%1
2911
16th to endNight
69%47%11%42
2972
February1st to 15thNight
70%49%8%32
2483
16th to endNight
63%38%15%7%1
2203
March1st to 15thNight
73%49%10%2
2243
16th to endNight
73%410%8%2
2239
April1st to 15thNight
69%6%10%11%2
1949
16th to endNight
65%6%12%11%3
1633
May1st to 15thNight
50%7%15%17%7%1
1440
16th to endNight
53%9%18%14%3
1469
June1st to 15thNight
56%6%18%11%41
1260
16th to endNight
53%8%14%16%41
1260
July1st to 15thNight
32%5%15%27%15%2
1190
16th to endNight
25%7%17%33%12%3
1337
August1st to 15thNight
25%5%24%28%12%3
1489
16th to endNight
32%7%20%24%9%3
1764
September1st to 15thNight
30%6%16%22%20%4
1800
16th to endNight
55%411%18%7%2
1974
October1st to 15thNight
55%411%17%10%
2160
16th to endNight
67%5%9%11%5%
2404
November1st to 15thNight
78%46%5%21
2660
16th to endNight
71%47%7%7%
2730
December1st to 15thNight
67%47%11%6%1
2795
16th to endNight
76%35%6%5%1
3120

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
34%416%20%17%6%
90
16th to endDay
71%113%10%4
97
February1st to 15thDay
53%6%14%18%5%
281
16th to endDay
44%7%22%16%8%
255
March1st to 15thDay
55%10%15%13%4
330
16th to endDay
53%10%17%12%5%
352
April1st to 15thDay
46%10%20%16%5%1
329
16th to endDay
36%13%23%18%7%
288
May1st to 15thDay
33%9%27%21%6%1
288
16th to endDay
30%11%17%24%11%4
354
June1st to 15thDay
30%11%23%23%9%1
495
16th to endDay
28%11%26%24%8%1
495
July1st to 15thDay
18%6%25%36%10%2
475
16th to endDay
16%6%25%37%10%4
408
August1st to 15thDay
17%5%22%35%13%5%
315
16th to endDay
17%7%24%33%14%2
332
September1st to 15thDay
23%7%21%33%13%1
315
16th to endDay
29%7%20%26%11%3
315
October1st to 15thDay
37%6%24%21%7%1
315
16th to endDay
46%6%17%19%8%1
245
November1st to 15thDay
64%8%14%11%1
90
16th to endDay
63%5%11%36%10%
90
December1st to 15thDay
54%110%12%16%5%
90
16th to endDay
57%220%13%5%1
96
January1st to 15thNight
49%5%19%19%5%
825
16th to endNight
47%7%20%20%3
846
February1st to 15thNight
47%5%21%20%4
764
16th to endNight
38%8%27%17%8%
684
March1st to 15thNight
48%8%19%17%6%
780
16th to endNight
47%6%18%18%7%
832
April1st to 15thNight
39%6%22%22%9%
779
16th to endNight
39%5%20%24%8%
517
May1st to 15thNight
23%320%31%18%1
360
16th to endNight
25%214%32%24%
375
June1st to 15thNight
25%5%16%26%22%2
360
16th to endNight
24%5%16%30%21%1
360
July1st to 15thNight
11%39%33%37%4
340
16th to endNight
11%28%27%46%4
376
August1st to 15thNight
11%5%26%47%6%
417
16th to endNight
15%110%32%36%3
618
September1st to 15thNight
12%115%34%32%2
720
16th to endNight
32%313%29%18%1
716
October1st to 15thNight
34%222%26%12%1
720
16th to endNight
45%418%23%7%
768
November1st to 15thNight
54%7%22%13%2
760
16th to endNight
50%7%20%13%6%
780
December1st to 15thNight
45%6%22%21%4
795
16th to endNight
53%8%25%11%1
880
Page generated at 2018-04-24 07:03:03. Version ac04

Copyright 2018 A. Danko


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