Og's Bog
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Og's Bog 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
29%
14800
15%
46633
8%
14763
37%
14763
18%
32258

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
10%
719
9%
2470
3%
716
18%
716
7%
1955
January16th to endNight
16%
768
11%
2496
4%
768
25%
768
9%
1950
February1st to 15thNight
12%
701
11%
2287
2%
701
23%
701
9%
1750
February16th to endNight
17%
631
13%
2016
4%
631
28%
631
13%
1476
March1st to 15thNight
19%
720
14%
1980
6%
720
26%
720
14%
1479
March16th to endNight
26%
768
21%
2112
9%
768
36%
768
23%
1413
April1st to 15thNight
21%
718
15%
1826
4%
718
27%
718
21%
1319
April16th to endNight
31%
549
20%
1629
8%
549
40%
549
25%
1062
May1st to 15thNight
40%
495
17%
1575
11%
495
46%
495
25%
1016
May16th to endNight
40%
374
18%
1497
13%
374
54%
374
27%
816
June1st to 15thNight
38%
360
13%
1440
11%
360
50%
360
20%
855
June16th to endNight
46%
360
15%
1275
14%
360
54%
360
28%
724
July1st to 15thNight
57%
340
17%
1278
20%
340
64%
340
34%
657
July16th to endNight
50%
493
16%
1526
13%
462
56%
462
32%
869
August1st to 15thNight
57%
539
17%
1609
11%
536
61%
536
37%
905
August16th to endNight
55%
615
24%
1761
13%
615
61%
615
36%
1030
September1st to 15thNight
48%
720
21%
1820
9%
720
54%
720
37%
1135
September16th to endNight
48%
658
21%
1834
14%
658
53%
658
33%
1141
October1st to 15thNight
33%
660
17%
1980
13%
660
41%
660
21%
1342
October16th to endNight
18%
704
11%
2112
4%
704
27%
704
13%
1600
November1st to 15thNight
27%
700
18%
2382
14%
700
35%
700
17%
1609
November16th to endNight
22%
720
11%
2520
6%
720
29%
720
11%
1893
December1st to 15thNight
13%
720
6%
2520
3%
720
18%
720
8%
2014
December16th to endNight
11%
768
6%
2688
1%
768
16%
768
6%
2248

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
15%9%47%6%35%5%5%7%30%
48099
Night
14%9%47%6%3445%6%33%
46811
Cloud CoverDay
15%9%47%6%35%45%7%30%
48109
Night
14%8%46%6%35%45%6%34%
46815
TransparencyDay
51%5%11%20%10%
47796
Night
49%412%21%10%1
46633
SeeingDay
17%14%29%21%11%5%
5557
Night
19%13%31%24%10%1
14805

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%15%5%10%9%45%445%18%
1465
16th to endDay
12%17%7%13%9%45%5%5%5%15%
1728
February1st to 15thDay
13%16%7%11%8%5%6%45%415%
1575
16th to endDay
17%15%5%9%6%345%35%23%
1453
March1st to 15thDay
14%12%6%9%8%3445%427%
1969
16th to endDay
14%12%47%5%34335%34%
2112
April1st to 15thDay
18%13%45%42445%6%29%
2124
16th to endDay
18%8%35%423445%38%
2340
May1st to 15thDay
16%6%36%5%25%45%6%35%
2374
16th to endDay
12%5%25%5%35%5%6%7%39%
2618
June1st to 15thDay
16%7%244245%7%8%35%
2520
16th to endDay
13%425%5%35%5%6%9%37%
2679
July1st to 15thDay
8%426%5%46%6%5%9%39%
2601
16th to endDay
11%5%37%6%35%6%7%9%33%
2535
August1st to 15thDay
8%6%36%6%35%6%7%8%36%
2340
16th to endDay
12%6%25%6%46%5%6%9%35%
2429
September1st to 15thDay
15%7%25%6%3445%8%35%
2139
16th to endDay
15%6%36%6%34447%36%
1799
October1st to 15thDay
19%8%39%6%34435%32%
1650
16th to endDay
26%14%37%6%34445%19%
1760
November1st to 15thDay
13%11%46%6%35%35%7%28%
1473
16th to endDay
16%15%7%10%7%35%5%46%19%
1440
December1st to 15thDay
17%16%9%11%7%25%35%414%
1440
16th to endDay
20%15%7%10%7%35%46%5%13%
1536
January1st to 15thNight
17%15%6%8%8%45%45%418%
2470
16th to endNight
11%13%7%10%9%47%5%5%5%19%
2496
February1st to 15thNight
13%13%6%9%8%45%446%23%
2285
16th to endNight
12%12%5%10%7%45%45%6%25%
2016
March1st to 15thNight
16%10%5%10%6%34435%30%
1968
16th to endNight
13%9%36%5%24345%42%
2112
April1st to 15thNight
18%8%46%434446%34%
1826
16th to endNight
12%9%45%424445%41%
1629
May1st to 15thNight
14%6%25%5%345%5%7%40%
1575
16th to endNight
11%425%314347%50%
1495
June1st to 15thNight
12%325%5%45%5%5%9%40%
1440
16th to endNight
9%425%4245%6%8%46%
1275
July1st to 15thNight
5%3244345%36%56%
1356
16th to endNight
7%414435%5%6%8%48%
1631
August1st to 15thNight
5%5%144345%5%9%50%
1620
16th to endNight
8%5%2343445%7%51%
1761
September1st to 15thNight
12%4243235%6%7%48%
1820
16th to endNight
12%5%25%5%23348%47%
1834
October1st to 15thNight
18%6%36%5%34346%38%
1980
16th to endNight
22%9%47%6%35%5%5%6%24%
2112
November1st to 15thNight
16%9%36%5%3445%6%34%
2382
16th to endNight
17%12%47%6%445%5%7%23%
2520
December1st to 15thNight
18%14%6%8%7%35%5%5%6%17%
2520
16th to endNight
19%14%8%12%8%45%445%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%15%410%7%45%45%5%19%
1465
16th to endDay
12%17%6%12%8%5%5%445%15%
1728
February1st to 15thDay
14%16%6%10%9%46%5%45%16%
1575
16th to endDay
18%13%5%9%6%25%445%23%
1453
March1st to 15thDay
15%10%5%9%7%45%34427%
1980
16th to endDay
14%11%47%6%3434435%
2111
April1st to 15thDay
19%12%45%5%2445%6%29%
2124
16th to endDay
19%7%35%423445%39%
2340
May1st to 15thDay
17%6%36%5%35%45%6%35%
2374
16th to endDay
12%5%25%6%35%5%6%8%39%
2618
June1st to 15thDay
15%7%25%4335%6%9%35%
2520
16th to endDay
13%425%5%35%5%6%10%36%
2679
July1st to 15thDay
9%425%6%46%5%5%9%39%
2601
16th to endDay
11%5%45%6%46%5%7%9%34%
2535
August1st to 15thDay
8%6%26%6%45%6%6%8%37%
2340
16th to endDay
12%5%25%5%45%5%7%9%35%
2429
September1st to 15thDay
15%6%25%6%35%45%7%37%
2139
16th to endDay
15%6%37%6%34447%36%
1799
October1st to 15thDay
20%7%37%6%33435%32%
1650
16th to endDay
27%12%47%5%34445%20%
1760
November1st to 15thDay
15%10%46%5%445%5%8%29%
1473
16th to endDay
18%14%6%8%7%35%447%18%
1440
December1st to 15thDay
18%16%7%12%7%4444415%
1440
16th to endDay
20%14%7%10%6%35%5%5%6%13%
1536
January1st to 15thNight
19%14%5%9%6%35%445%19%
2470
16th to endNight
13%13%7%9%8%37%45%5%21%
2496
February1st to 15thNight
13%13%5%8%8%35%5%46%24%
2278
16th to endNight
12%12%5%10%6%45%45%6%25%
2016
March1st to 15thNight
17%9%48%6%3433431%
1980
16th to endNight
13%8%36%5%23345%42%
2112
April1st to 15thNight
18%8%36%425%35%5%34%
1826
16th to endNight
12%8%45%5%23346%42%
1629
May1st to 15thNight
15%4345%3445%7%40%
1574
16th to endNight
11%425%32435%7%50%
1495
June1st to 15thNight
12%5%25%5%35%5%49%40%
1440
16th to endNight
9%425%4345%6%8%46%
1275
July1st to 15thNight
6%324424446%56%
1356
16th to endNight
7%3235%35%5%5%8%48%
1631
August1st to 15thNight
6%4235%345%5%8%50%
1620
16th to endNight
8%42443435%6%51%
1761
September1st to 15thNight
12%3243245%5%6%48%
1820
16th to endNight
12%5%2442335%7%47%
1834
October1st to 15thNight
18%6%36%5%24347%37%
1980
16th to endNight
21%10%46%6%345%5%6%25%
2112
November1st to 15thNight
16%8%36%5%3445%6%34%
2382
16th to endNight
19%11%5%8%6%36%45%7%24%
2520
December1st to 15thNight
20%14%6%7%7%35%5%5%5%18%
2520
16th to endNight
21%13%7%11%7%45%5%4413%
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
66%410%12%5%
1466
16th to endDay
70%48%10%4
1728
February1st to 15thDay
69%5%6%14%3
1577
16th to endDay
62%48%15%7%1
1453
March1st to 15thDay
59%411%16%7%
1980
16th to endDay
51%49%19%13%1
2112
April1st to 15thDay
54%48%21%10%
2124
16th to endDay
47%310%22%14%1
2340
May1st to 15thDay
48%49%22%13%
2374
16th to endDay
41%414%22%14%1
2622
June1st to 15thDay
43%5%14%23%12%
2520
16th to endDay
41%6%15%24%12%
2679
July1st to 15thDay
39%5%12%25%16%1
2450
16th to endDay
44%5%13%23%10%1
2378
August1st to 15thDay
40%6%16%21%13%1
2327
16th to endDay
41%6%14%26%9%1
2429
September1st to 15thDay
44%5%12%25%10%1
2139
16th to endDay
45%412%26%9%
1799
October1st to 15thDay
53%49%20%9%
1650
16th to endDay
65%413%11%3
1760
November1st to 15thDay
53%413%18%8%
1473
16th to endDay
65%413%11%4
1440
December1st to 15thDay
71%5%11%10%1
1440
16th to endDay
68%6%10%11%2
1536
January1st to 15thNight
66%5%9%11%6%
2470
16th to endNight
63%5%10%15%4
2496
February1st to 15thNight
60%6%9%17%5%
2287
16th to endNight
57%312%18%7%
2016
March1st to 15thNight
56%411%20%7%
1980
16th to endNight
45%310%22%16%2
2112
April1st to 15thNight
50%410%19%14%
1826
16th to endNight
42%411%21%17%2
1629
May1st to 15thNight
42%411%23%15%2
1575
16th to endNight
34%414%28%15%3
1497
June1st to 15thNight
40%5%11%25%16%1
1440
16th to endNight
34%5%13%28%16%
1275
July1st to 15thNight
28%411%29%23%2
1278
16th to endNight
31%6%14%28%15%2
1526
August1st to 15thNight
29%5%19%29%14%1
1609
16th to endNight
31%5%11%33%16%1
1761
September1st to 15thNight
33%416%29%14%1
1820
16th to endNight
35%413%32%12%
1834
October1st to 15thNight
47%410%23%12%
1980
16th to endNight
57%5%13%16%7%
2112
November1st to 15thNight
49%412%21%10%1
2382
16th to endNight
59%5%14%16%3
2520
December1st to 15thNight
65%5%12%12%3
2520
16th to endNight
72%5%10%9%2
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
20%30%32%12%31
65
16th to endDay
34%25%28%11%1
96
February1st to 15thDay
18%38%33%7%1
90
16th to endDay
24%37%30%7%
82
March1st to 15thDay
20%22%31%19%5%
270
16th to endDay
22%17%32%17%7%1
288
April1st to 15thDay
22%20%31%14%8%1
270
16th to endDay
20%21%28%15%10%3
270
May1st to 15thDay
21%13%28%18%12%6%
288
16th to endDay
15%14%31%23%12%3
331
June1st to 15thDay
21%11%27%26%10%1
315
16th to endDay
14%12%36%24%10%2
474
July1st to 15thDay
8%8%30%30%13%7%
384
16th to endDay
10%7%30%30%14%7%
326
August1st to 15thDay
8%7%26%26%17%13%
313
16th to endDay
15%7%20%25%18%13%
332
September1st to 15thDay
13%6%25%23%16%14%
315
16th to endDay
16%426%22%19%10%
254
October1st to 15thDay
18%11%30%20%12%5%
255
16th to endDay
33%18%24%18%5%
272
November1st to 15thDay
14%15%38%22%6%2
83
16th to endDay
28%21%33%15%1
60
December1st to 15thDay
20%36%26%11%5%
60
16th to endDay
29%35%32%1
64
January1st to 15thNight
26%21%35%11%4
720
16th to endNight
18%16%36%20%6%
768
February1st to 15thNight
19%23%35%17%3
704
16th to endNight
18%19%37%19%4
631
March1st to 15thNight
22%22%31%21%2
720
16th to endNight
19%15%34%20%9%
768
April1st to 15thNight
22%15%36%20%4
718
16th to endNight
16%13%34%25%8%1
549
May1st to 15thNight
16%8%27%33%12%2
495
16th to endNight
12%6%35%30%14%
375
June1st to 15thNight
14%8%31%32%13%
360
16th to endNight
10%431%36%16%
360
July1st to 15thNight
7%325%42%20%1
340
16th to endNight
10%428%35%18%2
493
August1st to 15thNight
8%223%39%23%2
539
16th to endNight
10%324%33%25%2
615
September1st to 15thNight
14%6%25%27%19%6%
720
16th to endNight
15%6%24%29%20%3
658
October1st to 15thNight
22%8%29%23%13%1
660
16th to endNight
27%16%31%19%5%
704
November1st to 15thNight
21%14%31%22%9%1
700
16th to endNight
24%19%27%22%5%
720
December1st to 15thNight
28%19%34%14%3
720
16th to endNight
27%17%34%16%3
768
Page generated at 2017-09-16 17:07:01. Version ac04

Copyright 2017 A. Danko


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