Good Hope Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Good Hope Observatory clear sky chart from 2005-11-05 to 2018-11-30.

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
38%
17048
15%
51884
11%
17010
43%
17010
19%
36735

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
18%
777
10%
2522
5%
776
25%
776
8%
2040
January16th to endNight
16%
832
11%
2704
5%
832
24%
832
10%
2105
February1st to 15thNight
20%
762
9%
2482
4%
761
25%
761
12%
1899
February16th to endNight
15%
683
11%
2073
4%
683
22%
683
11%
1638
March1st to 15thNight
23%
780
15%
2145
9%
780
29%
780
16%
1615
March16th to endNight
24%
832
16%
2288
9%
832
31%
832
19%
1671
April1st to 15thNight
28%
778
14%
2028
6%
778
33%
778
20%
1483
April16th to endNight
37%
634
19%
1790
9%
634
43%
634
26%
1202
May1st to 15thNight
41%
585
14%
1755
8%
585
45%
585
19%
1256
May16th to endNight
51%
609
14%
1828
10%
609
54%
609
24%
1236
June1st to 15thNight
57%
426
16%
1596
17%
426
62%
426
23%
990
June16th to endNight
55%
471
16%
1641
16%
471
59%
471
25%
1029
July1st to 15thNight
58%
555
13%
1665
12%
555
60%
555
24%
1125
July16th to endNight
66%
612
15%
1739
13%
579
69%
579
31%
1074
August1st to 15thNight
64%
575
18%
1715
14%
572
65%
572
28%
1102
August16th to endNight
68%
696
23%
1938
17%
696
69%
696
34%
1182
September1st to 15thNight
58%
780
22%
2042
15%
780
60%
780
32%
1350
September16th to endNight
56%
777
24%
2145
20%
777
59%
777
30%
1389
October1st to 15thNight
51%
780
22%
2324
22%
780
55%
780
28%
1496
October16th to endNight
36%
832
21%
2496
15%
832
45%
832
21%
1693
November1st to 15thNight
41%
820
21%
2570
18%
820
47%
820
22%
1711
November16th to endNight
27%
840
15%
2863
11%
840
34%
840
14%
2060
December1st to 15thNight
21%
780
7%
2730
5%
780
24%
780
8%
2186
December16th to endNight
19%
832
11%
2805
6%
832
27%
832
10%
2203

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%7%32%
52394
Night
17%9%36%5%3445%6%34%
52077
Cloud CoverDay
17%9%36%5%3445%7%32%
52404
Night
17%9%36%5%24446%34%
52081
TransparencyDay
51%6%11%18%11%1
52105
Night
49%6%11%18%11%1
51884
SeeingDay
23%10%21%21%14%7%
7031
Night
22%10%23%27%14%1
17055

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
20%14%7%10%8%3334420%
1746
16th to endDay
20%16%7%8%6%3323422%
1872
February1st to 15thDay
22%14%5%8%7%33345%20%
1710
16th to endDay
20%15%410%5%2334424%
1683
March1st to 15thDay
19%15%5%5%413335%31%
2134
16th to endDay
21%11%36%5%34446%28%
2288
April1st to 15thDay
19%9%35%424446%34%
2248
16th to endDay
19%6%25%5%35%35%6%35%
2457
May1st to 15thDay
19%6%36%6%4445%7%29%
2526
16th to endDay
16%6%27%7%35%447%34%
2639
June1st to 15thDay
14%425%5%36%46%8%37%
2691
16th to endDay
15%6%25%6%45%5%6%9%32%
2642
July1st to 15thDay
14%5%36%5%45%5%6%7%34%
2535
16th to endDay
13%6%36%6%46%5%6%9%31%
2673
August1st to 15thDay
13%6%36%6%35%7%7%9%29%
2487
16th to endDay
11%6%25%5%345%7%9%39%
2603
September1st to 15thDay
16%5%25%42345%8%41%
2246
16th to endDay
17%6%25%5%24445%40%
2145
October1st to 15thDay
19%6%25%433346%39%
1966
16th to endDay
22%7%1442334440%
2080
November1st to 15thDay
17%8%25%5%24446%38%
1945
16th to endDay
19%12%46%42345%5%30%
1750
December1st to 15thDay
24%13%7%8%5%3433422%
1560
16th to endDay
23%16%6%8%423346%20%
1768
January1st to 15thNight
22%14%6%8%6%3443420%
2522
16th to endNight
19%16%5%8%6%3333425%
2704
February1st to 15thNight
19%14%48%6%34445%25%
2480
16th to endNight
18%15%5%9%6%3444423%
2073
March1st to 15thNight
20%11%36%435%345%30%
2133
16th to endNight
22%9%34423445%33%
2288
April1st to 15thNight
20%8%35%43435%7%33%
2028
16th to endNight
15%5%26%5%2345%7%40%
1790
May1st to 15thNight
18%6%36%5%25%5%5%7%33%
1755
16th to endNight
13%5%26%5%345%5%7%39%
1826
June1st to 15thNight
9%425%5%346%6%9%41%
1596
16th to endNight
10%5%24435%46%8%43%
1641
July1st to 15thNight
11%5%35%6%345%7%8%38%
1755
16th to endNight
8%425%435%5%7%9%42%
1847
August1st to 15thNight
9%5%245%36%6%7%9%40%
1726
16th to endNight
9%4245%2445%8%47%
1938
September1st to 15thNight
12%5%35%43435%6%45%
2042
16th to endNight
14%5%24425%446%45%
2145
October1st to 15thNight
15%425%5%2345%7%42%
2324
16th to endNight
22%5%14425%445%39%
2496
November1st to 15thNight
18%8%25%32445%5%40%
2570
16th to endNight
19%11%47%6%34335%31%
2863
December1st to 15thNight
23%13%6%9%5%2433421%
2730
16th to endNight
21%15%6%7%435%345%23%
2805

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
20%13%7%10%8%3334420%
1746
16th to endDay
20%16%6%9%6%2323422%
1872
February1st to 15thDay
22%13%6%8%7%33345%21%
1710
16th to endDay
20%15%5%9%5%24335%24%
1683
March1st to 15thDay
19%15%5%6%423335%31%
2145
16th to endDay
21%12%36%6%24445%28%
2287
April1st to 15thDay
19%9%45%424446%34%
2248
16th to endDay
19%6%25%5%3445%7%35%
2457
May1st to 15thDay
19%7%36%7%45%45%7%28%
2526
16th to endDay
16%6%26%6%35%45%7%34%
2639
June1st to 15thDay
14%4246%35%5%6%8%37%
2691
16th to endDay
15%6%25%6%36%5%6%9%32%
2642
July1st to 15thDay
14%6%36%5%46%5%6%7%34%
2535
16th to endDay
13%5%36%6%46%5%6%8%32%
2673
August1st to 15thDay
13%7%26%6%35%6%7%10%29%
2487
16th to endDay
11%5%25%4345%7%10%38%
2603
September1st to 15thDay
16%5%25%4235%5%7%41%
2246
16th to endDay
17%7%26%4335%4440%
2145
October1st to 15thDay
19%6%25%5%33446%39%
1966
16th to endDay
21%8%24413335%40%
2080
November1st to 15thDay
17%8%25%424446%38%
1945
16th to endDay
19%13%45%5%2445%5%30%
1750
December1st to 15thDay
24%13%6%7%5%3434422%
1560
16th to endDay
23%17%5%7%5%23346%20%
1768
January1st to 15thNight
22%14%6%8%6%35%43420%
2522
16th to endNight
19%16%5%7%6%3333425%
2704
February1st to 15thNight
19%14%48%6%2443425%
2473
16th to endNight
18%14%5%8%6%34435%23%
2073
March1st to 15thNight
20%11%46%5%25%445%30%
2145
16th to endNight
22%9%35%424345%33%
2288
April1st to 15thNight
20%9%34424447%33%
2028
16th to endNight
15%5%26%5%2445%7%40%
1790
May1st to 15thNight
18%5%36%5%35%5%47%33%
1754
16th to endNight
13%5%26%5%35%5%5%7%39%
1826
June1st to 15thNight
9%5%345%35%6%5%10%40%
1596
16th to endNight
10%4244345%7%8%42%
1641
July1st to 15thNight
11%5%35%6%35%5%6%8%38%
1755
16th to endNight
8%424435%5%7%9%42%
1847
August1st to 15thNight
9%5%146%37%5%7%9%39%
1726
16th to endNight
9%5%1443445%9%47%
1938
September1st to 15thNight
12%5%3443435%6%45%
2042
16th to endNight
15%5%24324446%45%
2145
October1st to 15thNight
15%415%5%2345%7%43%
2324
16th to endNight
22%5%14424345%39%
2496
November1st to 15thNight
19%7%24414445%40%
2570
16th to endNight
19%11%37%6%34435%31%
2863
December1st to 15thNight
23%14%6%9%6%2433421%
2730
16th to endNight
21%15%6%7%5%24345%23%
2805

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
67%48%12%5%
1747
16th to endDay
66%38%15%4
1872
February1st to 15thDay
66%410%13%4
1712
16th to endDay
63%49%15%6%
1683
March1st to 15thDay
55%49%20%8%1
2145
16th to endDay
57%47%18%10%
2288
April1st to 15thDay
49%5%10%17%14%1
2248
16th to endDay
48%5%10%16%14%3
2457
May1st to 15thDay
54%7%12%16%8%1
2526
16th to endDay
47%8%13%19%9%1
2643
June1st to 15thDay
41%9%13%20%12%
2691
16th to endDay
47%7%13%19%11%
2642
July1st to 15thDay
46%8%10%18%12%3
2396
16th to endDay
46%7%12%20%11%1
2518
August1st to 15thDay
46%8%13%21%9%
2474
16th to endDay
38%8%14%25%11%2
2603
September1st to 15thDay
40%6%11%20%18%2
2246
16th to endDay
44%5%9%20%18%
2145
October1st to 15thDay
46%5%11%21%14%1
1966
16th to endDay
46%49%25%13%
2080
November1st to 15thDay
46%49%19%15%4
1945
16th to endDay
54%5%10%17%11%
1750
December1st to 15thDay
66%49%13%5%1
1560
16th to endDay
66%311%12%5%
1768
January1st to 15thNight
68%48%10%6%1
2522
16th to endNight
63%411%15%4
2704
February1st to 15thNight
61%312%14%7%
2482
16th to endNight
62%5%9%14%6%
2073
March1st to 15thNight
55%49%21%6%1
2145
16th to endNight
52%410%18%11%1
2288
April1st to 15thNight
50%5%9%19%13%2
2028
16th to endNight
42%6%12%16%16%5%
1790
May1st to 15thNight
49%7%12%17%10%2
1755
16th to endNight
42%8%15%20%11%1
1828
June1st to 15thNight
37%10%13%23%14%
1596
16th to endNight
36%10%13%21%16%1
1641
July1st to 15thNight
41%9%13%17%15%2
1665
16th to endNight
33%8%15%23%16%1
1739
August1st to 15thNight
36%9%18%20%13%1
1715
16th to endNight
32%6%11%28%16%3
1938
September1st to 15thNight
38%6%13%19%19%3
2042
16th to endNight
39%5%10%23%20%1
2145
October1st to 15thNight
39%6%12%22%16%2
2324
16th to endNight
46%47%24%15%1
2496
November1st to 15thNight
45%5%10%18%15%5%
2570
16th to endNight
55%49%16%12%1
2863
December1st to 15thNight
67%48%11%5%1
2730
16th to endNight
64%410%15%4
2805

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
27%28%25%13%41
135
16th to endDay
38%19%32%7%1
144
February1st to 15thDay
42%25%25%5%
135
16th to endDay
35%23%29%10%
137
March1st to 15thDay
32%15%29%17%5%
330
16th to endDay
30%17%25%17%7%1
352
April1st to 15thDay
28%16%26%19%8%1
330
16th to endDay
24%11%25%20%11%6%
319
May1st to 15thDay
25%16%23%16%10%6%
348
16th to endDay
22%7%21%23%15%9%
395
June1st to 15thDay
15%421%30%20%7%
375
16th to endDay
17%9%27%23%13%8%
375
July1st to 15thDay
19%320%26%16%12%
365
16th to endDay
16%118%25%24%13%
390
August1st to 15thDay
20%211%26%22%17%
358
16th to endDay
14%214%27%24%16%
396
September1st to 15thDay
18%5%13%23%22%16%
375
16th to endDay
20%5%16%22%21%11%
374
October1st to 15thDay
20%6%22%23%22%5%
375
16th to endDay
24%16%25%20%11%2
400
November1st to 15thDay
30%8%20%26%11%4
273
16th to endDay
32%20%24%15%6%2
140
December1st to 15thDay
31%27%20%12%5%3
90
16th to endDay
41%26%20%8%2
120
January1st to 15thNight
32%18%25%19%3
780
16th to endNight
31%18%30%18%1
832
February1st to 15thNight
29%16%30%22%1
764
16th to endNight
29%16%34%18%1
683
March1st to 15thNight
30%14%27%22%5%
780
16th to endNight
27%11%32%20%6%1
832
April1st to 15thNight
25%14%28%24%6%
778
16th to endNight
17%9%29%29%12%
634
May1st to 15thNight
21%8%24%32%12%
585
16th to endNight
15%419%31%23%4
611
June1st to 15thNight
10%222%38%24%1
426
16th to endNight
13%122%37%23%1
471
July1st to 15thNight
14%115%38%25%3
555
16th to endNight
9%112%33%35%5%
612
August1st to 15thNight
12%110%40%31%4
575
16th to endNight
12%19%34%36%5%
696
September1st to 15thNight
16%214%31%29%5%
780
16th to endNight
17%415%28%29%4
777
October1st to 15thNight
18%5%18%30%22%3
780
16th to endNight
26%10%22%25%13%1
832
November1st to 15thNight
24%8%23%28%14%1
820
16th to endNight
26%15%24%22%9%1
840
December1st to 15thNight
31%18%23%21%6%
780
16th to endNight
29%16%28%24%1
832
Page generated at 2018-12-01 11:35:31. Version ac04

Copyright 2018 A. Danko


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