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 2017-09-16.

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%
14462
8%
46707
6%
14434
35%
14434
13%
35842

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
21%
750
11%
2686
7%
746
26%
746
9%
2188
January16th to endNight
22%
777
9%
2743
6%
777
26%
777
9%
2190
February1st to 15thNight
19%
700
6%
2288
3%
700
23%
700
8%
1900
February16th to endNight
21%
632
12%
2035
5%
632
30%
632
12%
1582
March1st to 15thNight
17%
720
3%
2070
2%
720
19%
720
8%
1797
March16th to endNight
19%
768
5%
2067
2%
768
21%
768
8%
1787
April1st to 15thNight
26%
719
6%
1799
3%
719
27%
719
12%
1511
April16th to endNight
25%
498
6%
1578
5%
498
28%
498
10%
1274
May1st to 15thNight
43%
359
11%
1439
15%
359
46%
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
46%
360
4%
1260
2%
360
46%
360
14%
920
July1st to 15thNight
70%
340
9%
1190
8%
340
71%
340
31%
672
July16th to endNight
73%
376
14%
1337
20%
354
76%
354
34%
681
August1st to 15thNight
75%
417
15%
1489
20%
415
76%
415
38%
744
August16th to endNight
65%
618
17%
1764
15%
618
65%
618
33%
1076
September1st to 15thNight
63%
720
19%
1800
10%
720
65%
720
40%
1105
September16th to endNight
41%
660
15%
1819
12%
660
43%
660
19%
1349
October1st to 15thNight
34%
660
10%
1980
9%
660
36%
660
17%
1459
October16th to endNight
25%
704
5%
2204
4%
704
27%
704
9%
1833
November1st to 15thNight
11%
700
5%
2450
2%
700
16%
700
5%
2139
November16th to endNight
16%
720
5%
2520
2%
720
21%
720
7%
2056
December1st to 15thNight
17%
730
8%
2580
3%
730
24%
730
7%
2108
December16th to endNight
9%
800
6%
2880
1%
800
15%
800
5%
2486

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%
48076
Night
33%9%2442333427%
46861
Cloud CoverDay
35%9%25%42333426%
48076
Night
34%9%2432333427%
46864
TransparencyDay
62%5%10%14%5%1
47734
Night
60%5%11%14%6%1
46708
SeeingDay
33%8%21%24%9%2
6096
Night
37%5%19%22%13%1
14468

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
47%10%3322323317%
1253
16th to endDay
41%10%2442332320%
1477
February1st to 15thDay
41%12%35%42323415%
1576
16th to endDay
31%15%5%6%43323420%
1439
March1st to 15thDay
47%14%35%42322211%
1887
16th to endDay
41%14%47%5%2331312%
2157
April1st to 15thDay
36%13%47%6%3433312%
2149
16th to endDay
35%12%46%6%2443414%
2377
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
35%6%25%5%1323429%
1828
October1st to 15thDay
34%8%2432344427%
1650
16th to endDay
45%10%15%312335%17%
1666
November1st to 15thDay
56%9%35%32211211%
1408
16th to endDay
45%10%2432222418%
1440
December1st to 15thDay
38%14%4431232221%
1377
16th to endDay
46%17%25%41221213%
1344
January1st to 15thNight
45%10%2421223320%
2686
16th to endNight
39%12%3432233421%
2743
February1st to 15thNight
40%11%2442333418%
2276
16th to endNight
32%12%25%41323326%
2035
March1st to 15thNight
44%11%4442332315%
2070
16th to endNight
41%12%35%42333316%
2063
April1st to 15thNight
30%11%46%5%34445%19%
1799
16th to endNight
32%10%26%5%34345%21%
1578
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
31%6%25%323235%32%
1819
October1st to 15thNight
30%6%25%43433433%
1980
16th to endNight
43%6%25%5%3323418%
2204
November1st to 15thNight
52%8%2442222313%
2450
16th to endNight
41%9%35%42323420%
2520
December1st to 15thNight
40%11%3432323320%
2580
16th to endNight
47%14%2431222216%
2880

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%
1253
16th to endDay
41%12%2331232420%
1477
February1st to 15thDay
43%11%25%42322316%
1576
16th to endDay
31%19%3442332421%
1439
March1st to 15thDay
49%12%4432322211%
1887
16th to endDay
42%16%46%42232212%
2157
April1st to 15thDay
38%14%47%5%2423313%
2149
16th to endDay
37%11%46%5%2433414%
2377
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
35%7%25%32222429%
1828
October1st to 15thDay
35%7%2432334427%
1650
16th to endDay
47%8%24312235%18%
1666
November1st to 15thDay
58%9%2431212211%
1408
16th to endDay
46%10%1431322319%
1440
December1st to 15thDay
40%14%3421223321%
1377
16th to endDay
48%16%25%32121213%
1344
January1st to 15thNight
46%9%2321223321%
2685
16th to endNight
40%12%3431323421%
2743
February1st to 15thNight
40%11%25%312335%17%
2276
16th to endNight
34%11%35%32223326%
2035
March1st to 15thNight
46%11%3431322315%
2070
16th to endNight
41%12%45%41333316%
2067
April1st to 15thNight
32%11%36%5%34335%18%
1799
16th to endNight
34%9%26%5%2433421%
1578
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
31%6%25%313236%32%
1819
October1st to 15thNight
31%6%2442423433%
1980
16th to endNight
43%7%24432335%18%
2204
November1st to 15thNight
54%8%2431222313%
2450
16th to endNight
42%10%2442323321%
2520
December1st to 15thNight
40%12%3322323421%
2580
16th to endNight
48%14%2422212216%
2880

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
1253
16th to endDay
69%48%11%31
1477
February1st to 15thDay
74%47%6%42
1576
16th to endDay
68%47%13%5%
1439
March1st to 15thDay
81%45%7%1
1887
16th to endDay
78%47%8%1
2157
April1st to 15thDay
75%5%7%8%1
2149
16th to endDay
72%6%8%8%3
2377
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%16%7%2
1828
October1st to 15thDay
59%5%11%14%7%
1650
16th to endDay
69%5%11%9%3
1666
November1st to 15thDay
81%346%11
1408
16th to endDay
71%36%9%8%
1440
December1st to 15thDay
69%5%6%8%7%1
1377
16th to endDay
80%347%21
1344
January1st to 15thNight
70%3414%5%1
2686
16th to endNight
67%47%12%42
2743
February1st to 15thNight
70%5%9%8%32
2288
16th to endNight
63%48%15%7%1
2035
March1st to 15thNight
75%49%8%2
2070
16th to endNight
74%410%8%2
2067
April1st to 15thNight
67%6%11%12%2
1799
16th to endNight
65%6%12%11%3
1578
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
1819
October1st to 15thNight
56%412%16%9%
1980
16th to endNight
69%5%10%10%4
2204
November1st to 15thNight
78%46%6%22
2450
16th to endNight
69%48%8%8%
2520
December1st to 15thNight
69%47%11%5%1
2580
16th to endNight
77%35%7%5%1
2880

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
23%5%23%25%15%8%
60
16th to endDay
58%118%15%6%
65
February1st to 15thDay
52%7%13%18%6%
236
16th to endDay
43%8%19%19%9%
215
March1st to 15thDay
58%12%15%11%1
270
16th to endDay
52%11%19%12%4
288
April1st to 15thDay
43%10%20%18%7%1
269
16th to endDay
37%12%24%18%6%
270
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
258
October1st to 15thDay
40%5%23%21%7%1
255
16th to endDay
46%6%17%20%7%2
189
November1st to 15thDay
70%6%16%6%
60
16th to endDay
51%315%5%10%15%
60
December1st to 15thDay
70%113%10%5%
60
16th to endDay
56%320%10%7%1
64
January1st to 15thNight
49%6%20%19%4
750
16th to endNight
44%7%20%22%3
777
February1st to 15thNight
45%6%22%20%4
704
16th to endNight
38%8%27%17%8%
632
March1st to 15thNight
49%9%20%15%5%
720
16th to endNight
48%6%19%18%6%
768
April1st to 15thNight
36%6%22%23%9%
719
16th to endNight
38%5%21%24%9%
498
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
34%313%28%18%1
660
October1st to 15thNight
35%322%25%12%1
660
16th to endNight
46%418%22%7%
704
November1st to 15thNight
54%7%22%13%2
700
16th to endNight
47%8%21%15%7%
720
December1st to 15thNight
47%7%23%19%2
730
16th to endNight
53%9%24%11%1
800
Page generated at 2017-09-17 09:05:43. Version ac04

Copyright 2017 A. Danko


Rannie Road Clear Sky Chart | Charts Home