Golden
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Golden clear sky chart from 2005-11-05 to 2017-08-12.

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
53%
15827
27%
46504
17%
15785
63%
15785
40%
25156

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
38%
898
32%
2506
14%
895
55%
895
45%
1292
January16th to endNight
36%
803
33%
2531
17%
803
55%
803
38%
1296
February1st to 15thNight
33%
699
25%
2253
9%
698
52%
698
34%
1202
February16th to endNight
36%
632
31%
1894
13%
632
54%
632
39%
1018
March1st to 15thNight
42%
720
28%
2109
13%
720
56%
720
42%
1138
March16th to endNight
43%
682
27%
2026
14%
682
56%
682
38%
1109
April1st to 15thNight
43%
539
24%
1798
15%
539
56%
539
34%
943
April16th to endNight
42%
540
22%
1800
15%
540
53%
540
28%
1060
May1st to 15thNight
52%
540
19%
1606
16%
540
57%
540
28%
1029
May16th to endNight
60%
563
18%
1498
12%
561
65%
561
37%
893
June1st to 15thNight
72%
540
22%
1440
17%
540
75%
540
51%
761
June16th to endNight
80%
540
28%
1440
23%
540
82%
540
58%
713
July1st to 15thNight
76%
510
18%
1360
15%
510
78%
510
36%
824
July16th to endNight
81%
564
24%
1449
23%
531
82%
531
43%
812
August1st to 15thNight
78%
527
19%
1626
20%
524
79%
524
38%
885
August16th to endNight
78%
525
26%
1750
29%
525
79%
525
38%
919
September1st to 15thNight
73%
495
29%
1650
29%
495
77%
495
39%
879
September16th to endNight
71%
492
35%
1768
33%
492
79%
492
48%
790
October1st to 15thNight
57%
654
29%
1974
20%
654
64%
654
41%
1067
October16th to endNight
55%
729
33%
2137
17%
729
65%
729
46%
1117
November1st to 15thNight
52%
875
33%
2275
17%
875
61%
875
50%
1204
November16th to endNight
49%
900
34%
2406
16%
900
62%
900
51%
1259
December1st to 15thNight
38%
900
25%
2520
9%
900
52%
900
41%
1378
December16th to endNight
39%
960
26%
2688
10%
960
53%
960
35%
1568

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
5%4134245%6%8%52%
47484
Night
4423323347%59%
46680
TransparencyDay
28%8%12%23%20%7%
47162
Night
24%5%13%25%23%8%
46504
SeeingDay
9%8%29%30%17%4
5709
Night
6%6%28%39%16%2
15834

By Month

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
16%23322349%60%
1432
16th to endDay
15%33312347%63%
1704
February1st to 15thDay
16%35%324447%55%
1609
16th to endDay
16%24323447%58%
1580
March1st to 15thDay
442432345%7%56%
1848
16th to endDay
6%7%233235%7%8%50%
2197
April1st to 15thDay
7%7%1332335%8%53%
2150
16th to endDay
12%7%14425%45%7%44%
2160
May1st to 15thDay
12%7%245%346%6%7%40%
2343
16th to endDay
11%423435%6%7%9%42%
2616
June1st to 15thDay
5%213436%5%7%9%49%
2520
16th to endDay
3212425%6%7%11%52%
2520
July1st to 15thDay
8%3145%36%6%8%10%42%
2520
16th to endDay
6%314445%5%8%10%44%
2617
August1st to 15thDay
7%3145%46%7%7%9%41%
2239
16th to endDay
6%214436%5%7%8%48%
2100
September1st to 15thDay
7%4134235%47%54%
1980
16th to endDay
43231345%6%64%
1862
October1st to 15thDay
6%312314446%60%
1653
16th to endDay
6%412112246%65%
1724
November1st to 15thDay
241331335%8%62%
1583
16th to endDay
233321235%8%63%
1551
December1st to 15thDay
2425%323349%57%
1440
16th to endDay
35%25%323348%56%
1536
January1st to 15thNight
1324322337%65%
2506
16th to endNight
16%2431333462%
2531
February1st to 15thNight
17%34423336%58%
2243
16th to endNight
26%25%32325%6%59%
1894
March1st to 15thNight
242332346%8%57%
2109
16th to endNight
6%6%23223337%59%
2026
April1st to 15thNight
6%6%12213447%58%
1798
16th to endNight
13%7%14323336%50%
1800
May1st to 15thNight
14%5%14424347%46%
1605
16th to endNight
8%41332345%8%54%
1497
June1st to 15thNight
5%11222345%8%63%
1440
16th to endNight
21111346%9%66%
1440
July1st to 15thNight
5%213426%5%7%9%51%
1440
16th to endNight
4112226%6%7%9%54%
1548
August1st to 15thNight
422242447%9%55%
1635
16th to endNight
5%2143245%5%8%56%
1750
September1st to 15thNight
9%21232335%7%57%
1650
16th to endNight
422313335%68%
1768
October1st to 15thNight
6%5%12213345%62%
1974
16th to endNight
5%5%13212346%63%
2137
November1st to 15thNight
2313312335%68%
2275
16th to endNight
2423212337%66%
2406
December1st to 15thNight
25%35%323249%58%
2520
16th to endNight
26%34324348%55%
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
21%6%13%32%21%4
1433
16th to endDay
21%5%10%33%20%7%
1704
February1st to 15thDay
27%6%14%30%15%4
1610
16th to endDay
25%410%26%27%5%
1580
March1st to 15thDay
26%6%11%26%22%6%
1848
16th to endDay
30%7%13%23%20%5%
2197
April1st to 15thDay
29%7%13%23%18%7%
2150
16th to endDay
37%9%12%20%16%3
2160
May1st to 15thDay
41%10%13%18%13%2
2343
16th to endDay
35%11%14%20%11%5%
2620
June1st to 15thDay
27%10%15%19%17%10%
2520
16th to endDay
22%8%12%20%25%10%
2520
July1st to 15thDay
32%11%12%18%15%9%
2371
16th to endDay
30%11%15%22%13%6%
2453
August1st to 15thDay
35%11%13%17%14%8%
2224
16th to endDay
29%10%12%21%20%6%
2100
September1st to 15thDay
28%6%11%19%20%13%
1980
16th to endDay
19%6%8%23%33%8%
1862
October1st to 15thDay
24%6%13%19%26%8%
1653
16th to endDay
21%49%26%29%9%
1724
November1st to 15thDay
20%412%24%26%11%
1583
16th to endDay
19%310%25%31%9%
1551
December1st to 15thDay
25%5%14%31%20%3
1440
16th to endDay
26%6%14%26%19%6%
1536
January1st to 15thNight
19%413%30%25%5%
2506
16th to endNight
24%311%27%24%9%
2531
February1st to 15thNight
27%413%30%19%4
2253
16th to endNight
25%49%26%24%9%
1894
March1st to 15thNight
23%5%10%25%27%7%
2109
16th to endNight
27%412%25%24%5%
2026
April1st to 15thNight
25%6%13%24%21%8%
1798
16th to endNight
35%5%11%24%18%4
1800
May1st to 15thNight
37%8%14%20%15%4
1606
16th to endNight
29%7%20%22%13%5%
1498
June1st to 15thNight
18%7%17%27%15%12%
1440
16th to endNight
13%6%12%24%29%12%
1440
July1st to 15thNight
26%11%15%20%15%9%
1360
16th to endNight
22%9%16%29%16%6%
1449
August1st to 15thNight
25%8%16%24%17%8%
1626
16th to endNight
24%7%13%23%22%7%
1750
September1st to 15thNight
26%5%13%20%19%14%
1650
16th to endNight
19%39%26%33%7%
1768
October1st to 15thNight
24%6%12%20%26%10%
1974
16th to endNight
22%410%23%29%9%
2137
November1st to 15thNight
19%310%24%27%13%
2275
16th to endNight
20%49%24%31%10%
2406
December1st to 15thNight
24%415%29%20%5%
2520
16th to endNight
28%6%14%25%20%3
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
6%12%26%32%17%4
90
16th to endDay
9%440%34%10%1
96
February1st to 15thDay
5%20%44%27%2
90
16th to endDay
311%41%30%11%1
81
March1st to 15thDay
323%36%28%7%
138
16th to endDay
13%28%32%21%2
288
April1st to 15thDay
11%22%37%18%6%2
269
16th to endDay
21%20%37%16%5%
270
May1st to 15thDay
16%8%30%30%10%2
417
16th to endDay
13%7%27%29%16%5%
517
June1st to 15thDay
5%327%33%23%7%
495
16th to endDay
3227%35%22%8%
495
July1st to 15thDay
10%220%28%28%9%
475
16th to endDay
5%218%32%31%9%
476
August1st to 15thDay
8%6%28%33%19%4
300
16th to endDay
10%5%25%38%14%4
268
September1st to 15thDay
7%5%35%36%12%1
255
16th to endDay
4227%36%22%6%
137
October1st to 15thDay
3327%32%27%5%
90
16th to endDay
10%429%32%18%5%
96
November1st to 15thDay
3425%30%30%6%
90
16th to endDay
7%16%36%27%11%
90
December1st to 15thDay
7%20%38%27%5%
90
16th to endDay
45%41%42%5%1
96
January1st to 15thNight
312%41%30%10%2
900
16th to endNight
413%40%32%8%1
803
February1st to 15thNight
5%11%43%34%5%
704
16th to endNight
5%9%43%36%4
632
March1st to 15thNight
47%40%37%9%
720
16th to endNight
9%8%35%38%7%
682
April1st to 15thNight
11%10%32%38%7%
539
16th to endNight
16%6%31%33%11%
540
May1st to 15thNight
16%320%42%14%2
540
16th to endNight
9%222%41%21%2
563
June1st to 15thNight
5%116%51%21%3
540
16th to endNight
3112%47%33%1
540
July1st to 15thNight
5%19%35%42%5%
510
16th to endNight
46%35%46%6%
564
August1st to 15thNight
417%44%38%3
527
16th to endNight
5%17%42%35%6%
525
September1st to 15thNight
8%110%47%25%6%
495
16th to endNight
4116%42%27%7%
492
October1st to 15thNight
10%326%39%16%4
654
16th to endNight
7%5%26%41%15%3
729
November1st to 15thNight
48%29%41%14%2
875
16th to endNight
45%35%43%9%1
900
December1st to 15thNight
310%41%37%6%
900
16th to endNight
5%9%38%36%8%1
960
Page generated at 2017-08-13 12:16:51. Version ac04

Copyright 2017 A. Danko


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