Golden State Star Party
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Golden State Star Party clear sky chart from 2005-11-05 to 2017-09-24.

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
58%
15019
22%
46946
20%
14989
61%
14989
32%
27588

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
52%
717
15%
2506
16%
716
54%
716
22%
1593
January16th to endNight
50%
768
21%
2541
22%
768
52%
768
24%
1621
February1st to 15thNight
48%
698
14%
2288
13%
696
52%
696
21%
1533
February16th to endNight
47%
632
18%
1903
17%
632
51%
632
23%
1263
March1st to 15thNight
42%
720
12%
2084
11%
720
44%
720
19%
1502
March16th to endNight
41%
768
15%
2045
10%
768
44%
768
24%
1408
April1st to 15thNight
39%
719
14%
1799
7%
719
42%
719
21%
1341
April16th to endNight
49%
720
19%
1800
10%
720
52%
720
36%
1134
May1st to 15thNight
53%
449
22%
1529
16%
449
59%
449
35%
820
May16th to endNight
54%
374
16%
1496
17%
374
59%
374
24%
861
June1st to 15thNight
61%
360
19%
1440
25%
360
66%
360
29%
754
June16th to endNight
73%
360
29%
1440
39%
360
79%
360
48%
570
July1st to 15thNight
86%
340
28%
1360
39%
340
89%
340
59%
483
July16th to endNight
89%
405
38%
1443
47%
381
91%
381
68%
499
August1st to 15thNight
87%
541
34%
1614
29%
538
88%
538
61%
726
August16th to endNight
82%
764
43%
1910
27%
764
84%
764
77%
880
September1st to 15thNight
84%
720
40%
1800
26%
720
86%
720
73%
853
September16th to endNight
73%
692
38%
1875
32%
692
77%
692
59%
920
October1st to 15thNight
65%
660
27%
1980
25%
660
71%
660
43%
1041
October16th to endNight
63%
704
25%
2132
26%
704
67%
704
36%
1210
November1st to 15thNight
56%
700
20%
2275
20%
700
59%
700
24%
1461
November16th to endNight
48%
720
15%
2478
15%
720
52%
720
23%
1559
December1st to 15thNight
47%
720
15%
2520
14%
720
51%
720
20%
1652
December16th to endNight
39%
768
17%
2688
16%
768
42%
768
16%
1904

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
8%7%24323345%54%
47998
Night
9%8%24323346%51%
47121
TransparencyDay
31%49%19%20%13%
47672
Night
33%5%11%20%18%10%
46947
SeeingDay
13%14%28%25%14%4
5757
Night
12%6%17%35%24%4
15030

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
10%9%36%43445%6%40%
1432
16th to endDay
14%13%25%423345%38%
1683
February1st to 15thDay
12%11%35%5%24445%38%
1576
16th to endDay
9%14%5%7%424346%37%
1571
March1st to 15thDay
13%14%5%6%5%34446%30%
1875
16th to endDay
14%14%35%423347%33%
2178
April1st to 15thDay
11%13%5%7%6%24346%32%
2149
16th to endDay
9%9%35%422336%47%
2160
May1st to 15thDay
7%424334347%54%
2416
16th to endDay
12%7%26%424346%45%
2615
June1st to 15thDay
8%5%34424345%53%
2520
16th to endDay
32221223473%
2520
July1st to 15thDay
111212325%76%
2520
16th to endDay
1121222380%
2627
August1st to 15thDay
21111224376%
2337
16th to endDay
11111122382%
2292
September1st to 15thDay
112212235%76%
2160
16th to endDay
4312312246%68%
1940
October1st to 15thDay
7%413212345%60%
1650
16th to endDay
10%6%15%5%22336%51%
1738
November1st to 15thDay
12%9%3442335%7%42%
1584
16th to endDay
12%12%45%314347%38%
1479
December1st to 15thDay
15%10%35%5%245%5%5%36%
1440
16th to endDay
17%15%46%424445%30%
1536
January1st to 15thNight
10%11%36%42335%7%40%
2506
16th to endNight
11%13%3443333443%
2541
February1st to 15thNight
11%11%35%5%35%446%37%
2276
16th to endNight
10%13%35%42435%5%40%
1903
March1st to 15thNight
12%16%45%43335%7%32%
2084
16th to endNight
12%13%34424349%37%
2045
April1st to 15thNight
10%12%47%5%35%45%7%33%
1799
16th to endNight
10%9%23313335%52%
1800
May1st to 15thNight
8%313324336%57%
1529
16th to endNight
11%6%34424447%46%
1496
June1st to 15thNight
10%41332445%6%53%
1440
16th to endNight
322213325%72%
1440
July1st to 15thNight
111221323476%
1440
16th to endNight
11111222382%
1541
August1st to 15thNight
121221222475%
1623
16th to endNight
11111212382%
1910
September1st to 15thNight
1121222480%
1800
16th to endNight
421221224471%
1875
October1st to 15thNight
5%5%2432324462%
1980
16th to endNight
8%5%2331345%6%54%
2132
November1st to 15thNight
13%8%24425%45%6%42%
2275
16th to endNight
10%10%345%24448%40%
2478
December1st to 15thNight
15%11%24424347%38%
2520
16th to endNight
17%16%45%423335%33%
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
42%8%13%22%10%1
1432
16th to endDay
47%48%20%10%8%
1683
February1st to 15thDay
44%5%13%21%11%2
1576
16th to endDay
46%5%15%22%8%2
1571
March1st to 15thDay
53%7%8%17%12%1
1875
16th to endDay
48%7%16%15%8%3
2178
April1st to 15thDay
51%6%11%19%11%
2149
16th to endDay
37%414%25%15%3
2160
May1st to 15thDay
27%5%11%28%20%5%
2416
16th to endDay
38%6%10%24%16%4
2619
June1st to 15thDay
31%5%10%18%23%10%
2520
16th to endDay
15%27%18%38%17%
2520
July1st to 15thDay
11%25%14%31%34%
2371
16th to endDay
9%2311%25%47%
2462
August1st to 15thDay
11%35%15%26%36%
2321
16th to endDay
9%1414%35%34%
2292
September1st to 15thDay
11%25%13%33%33%
2160
16th to endDay
17%28%24%27%18%
1940
October1st to 15thDay
25%410%26%23%9%
1650
16th to endDay
33%411%21%19%8%
1738
November1st to 15thDay
40%5%14%20%13%4
1584
16th to endDay
43%6%12%21%12%4
1479
December1st to 15thDay
46%7%11%21%12%
1440
16th to endDay
54%6%6%19%10%1
1536
January1st to 15thNight
41%7%15%20%12%3
2506
16th to endNight
43%410%17%14%9%
2541
February1st to 15thNight
44%6%13%17%12%3
2288
16th to endNight
43%5%15%22%10%2
1903
March1st to 15thNight
49%7%13%15%12%2
2084
16th to endNight
43%7%17%18%10%2
2045
April1st to 15thNight
48%8%12%20%8%1
1799
16th to endNight
34%416%27%13%3
1800
May1st to 15thNight
27%6%12%25%22%6%
1530
16th to endNight
37%5%13%26%11%4
1496
June1st to 15thNight
30%5%13%21%21%6%
1440
16th to endNight
15%46%21%37%13%
1440
July1st to 15thNight
11%26%15%30%32%
1360
16th to endNight
8%2413%26%44%
1443
August1st to 15thNight
13%3420%25%32%
1614
16th to endNight
8%1415%35%34%
1910
September1st to 15thNight
9%25%13%33%35%
1800
16th to endNight
16%37%24%26%21%
1875
October1st to 15thNight
24%310%25%24%10%
1980
16th to endNight
28%6%12%24%19%7%
2132
November1st to 15thNight
40%7%13%22%11%4
2275
16th to endNight
40%6%14%17%15%4
2478
December1st to 15thNight
44%6%12%20%15%
2520
16th to endNight
52%5%8%16%14%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
26%18%35%20%
60
16th to endDay
25%13%20%21%16%1
211
February1st to 15thDay
24%16%23%28%7%
236
16th to endDay
24%17%29%23%4
237
March1st to 15thDay
24%27%23%14%10%
270
16th to endDay
25%25%25%16%7%
288
April1st to 15thDay
23%22%28%18%5%1
269
16th to endDay
17%25%26%18%10%1
270
May1st to 15thDay
11%20%37%19%8%2
288
16th to endDay
19%10%26%21%16%6%
330
June1st to 15thDay
13%17%28%21%15%3
315
16th to endDay
412%31%27%19%5%
315
July1st to 15thDay
27%25%39%18%6%
305
16th to endDay
6%33%35%16%7%
327
August1st to 15thDay
47%29%29%19%9%
315
16th to endDay
19%29%28%21%9%
332
September1st to 15thDay
2429%31%23%8%
315
16th to endDay
8%11%28%26%21%2
288
October1st to 15thDay
10%14%28%25%14%4
255
16th to endDay
19%14%26%24%11%3
250
November1st to 15thDay
13%6%17%32%30%
90
16th to endDay
17%13%40%17%10%
67
December1st to 15thDay
33%18%21%23%3
60
16th to endDay
20%10%21%29%17%
64
January1st to 15thNight
14%419%37%20%3
720
16th to endNight
16%7%19%31%21%4
768
February1st to 15thNight
15%8%18%38%17%1
704
16th to endNight
15%10%20%37%14%2
632
March1st to 15thNight
21%9%18%29%17%4
720
16th to endNight
18%11%22%30%15%1
768
April1st to 15thNight
14%11%27%29%15%2
719
16th to endNight
14%10%22%27%20%4
720
May1st to 15thNight
10%6%26%33%21%2
450
16th to endNight
13%6%18%33%24%3
375
June1st to 15thNight
11%318%41%24%
360
16th to endNight
5%115%44%31%1
360
July1st to 15thNight
26%46%42%1
340
16th to endNight
16%47%40%3
405
August1st to 15thNight
25%39%46%5%
541
16th to endNight
1111%41%39%4
764
September1st to 15thNight
1110%34%43%8%
720
16th to endNight
4314%32%34%10%
692
October1st to 15thNight
10%415%35%28%6%
660
16th to endNight
10%414%33%26%8%
704
November1st to 15thNight
15%5%16%37%20%4
700
16th to endNight
15%6%20%34%20%3
720
December1st to 15thNight
17%8%19%32%19%2
720
16th to endNight
23%10%19%32%13%1
768
Page generated at 2017-09-25 06:02:26. Version ac04

Copyright 2017 A. Danko


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