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 2017-05-01.

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
57%
14628
22%
45688
20%
14598
60%
14598
31%
27031

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
52%
416
24%
1412
17%
416
59%
416
35%
758
May16th to endNight
52%
342
13%
1368
13%
342
57%
342
22%
810
June1st to 15thNight
61%
330
20%
1320
27%
330
66%
330
29%
681
June16th to endNight
71%
330
27%
1320
36%
330
77%
330
46%
536
July1st to 15thNight
85%
310
29%
1240
41%
310
88%
310
57%
449
July16th to endNight
89%
374
36%
1328
44%
350
91%
350
66%
465
August1st to 15thNight
87%
496
36%
1479
31%
493
88%
493
62%
660
August16th to endNight
81%
700
41%
1750
25%
700
83%
700
77%
810
September1st to 15thNight
84%
660
42%
1650
27%
660
86%
660
75%
771
September16th to endNight
74%
656
38%
1782
32%
656
77%
656
59%
869
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%53%
46089
Night
9%8%24323346%51%
45863
TransparencyDay
32%49%19%20%13%
45763
Night
34%5%11%20%18%10%
45689
SeeingDay
14%15%29%24%12%3
5181
Night
12%6%17%35%24%4
14639

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%
2216
16th to endDay
12%7%36%424346%43%
2391
June1st to 15thDay
8%5%33324345%54%
2310
16th to endDay
42221223472%
2310
July1st to 15thDay
111212335%74%
2310
16th to endDay
1121222381%
2434
August1st to 15thDay
21111223378%
2142
16th to endDay
11111112382%
2100
September1st to 15thDay
112112235%77%
1980
16th to endDay
4312211236%70%
1845
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
9%313324336%57%
1412
16th to endNight
11%6%345%2445%7%43%
1368
June1st to 15thNight
10%413324446%54%
1320
16th to endNight
42221332472%
1320
July1st to 15thNight
111221333475%
1320
16th to endNight
11111322381%
1426
August1st to 15thNight
111221222476%
1488
16th to endNight
11111212382%
1750
September1st to 15thNight
111222482%
1650
16th to endNight
411221224471%
1782
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
28%5%10%27%20%6%
2216
16th to endDay
40%6%11%24%14%3
2395
June1st to 15thDay
30%5%9%17%24%11%
2310
16th to endDay
16%26%19%40%14%
2310
July1st to 15thDay
12%26%15%31%31%
2161
16th to endDay
9%2312%26%46%
2269
August1st to 15thDay
11%25%15%26%38%
2126
16th to endDay
9%1414%35%34%
2100
September1st to 15thDay
11%25%12%34%34%
1980
16th to endDay
17%28%24%28%19%
1845
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
28%5%12%24%22%6%
1413
16th to endNight
39%6%14%26%10%3
1368
June1st to 15thNight
29%6%13%21%22%6%
1320
16th to endNight
16%46%23%38%10%
1320
July1st to 15thNight
12%37%17%31%28%
1240
16th to endNight
9%2414%26%43%
1328
August1st to 15thNight
13%3417%26%34%
1479
16th to endNight
8%1416%34%33%
1750
September1st to 15thNight
8%25%12%34%36%
1650
16th to endNight
15%37%24%26%22%
1782
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
12%20%40%15%8%2
229
16th to endDay
21%10%28%20%12%7%
266
June1st to 15thDay
11%18%29%23%12%4
255
16th to endDay
5%14%33%26%14%5%
255
July1st to 15thDay
39%27%38%14%6%
245
16th to endDay
6%36%35%14%5%
271
August1st to 15thDay
5%8%35%29%14%6%
255
16th to endDay
111%32%27%17%7%
268
September1st to 15thDay
35%31%32%21%5%
255
16th to endDay
6%11%27%27%23%3
255
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%5%26%33%20%2
417
16th to endNight
14%6%18%34%23%2
343
June1st to 15thNight
9%319%42%23%
330
16th to endNight
6%215%44%29%1
330
July1st to 15thNight
26%47%41%1
310
16th to endNight
16%47%40%3
374
August1st to 15thNight
26%42%44%5%
496
16th to endNight
1112%43%36%4
700
September1st to 15thNight
1110%34%42%9%
660
16th to endNight
4314%31%36%10%
656
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 2017-05-02 05:43:35. Version ac04

Copyright 2017 A. Danko


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