Grand Canyon Star Party (South Rim)
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Grand Canyon Star Party (South Rim) clear sky chart from 2005-11-05 to 2017-04-01.

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
58%
15075
33%
45349
24%
15033
68%
15033
45%
22594

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
55%
720
30%
2327
25%
716
66%
716
41%
1169
January16th to endNight
52%
768
34%
2496
26%
768
65%
768
38%
1304
February1st to 15thNight
56%
700
31%
2219
27%
700
65%
700
44%
1107
February16th to endNight
45%
632
34%
1895
25%
632
59%
632
39%
1004
March1st to 15thNight
50%
720
36%
1998
24%
720
63%
720
45%
1019
March16th to endNight
50%
768
34%
2112
19%
768
63%
768
47%
1082
April1st to 15thNight
40%
641
29%
1802
13%
641
53%
641
37%
958
April16th to endNight
47%
495
38%
1499
19%
495
64%
495
49%
675
May1st to 15thNight
47%
495
36%
1484
22%
494
58%
494
49%
686
May16th to endNight
49%
514
31%
1540
18%
513
60%
513
45%
733
June1st to 15thNight
53%
495
33%
1485
24%
495
61%
495
58%
654
June16th to endNight
64%
495
31%
1485
25%
495
70%
495
63%
632
July1st to 15thNight
70%
465
22%
1395
17%
465
73%
465
40%
754
July16th to endNight
72%
522
22%
1467
20%
489
72%
489
36%
846
August1st to 15thNight
76%
494
30%
1476
25%
491
79%
491
44%
772
August16th to endNight
76%
563
34%
1653
27%
563
80%
563
48%
845
September1st to 15thNight
73%
660
29%
1815
23%
660
76%
660
45%
1011
September16th to endNight
73%
656
43%
1815
29%
656
81%
656
64%
828
October1st to 15thNight
61%
660
37%
1895
23%
660
72%
660
54%
909
October16th to endNight
65%
704
41%
2112
31%
704
75%
704
53%
975
November1st to 15thNight
59%
700
36%
2203
26%
700
72%
700
51%
1016
November16th to endNight
59%
720
38%
2340
32%
720
70%
720
48%
1074
December1st to 15thNight
57%
720
32%
2340
25%
720
69%
720
42%
1159
December16th to endNight
50%
768
29%
2496
25%
768
58%
768
33%
1382

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
3313424446%59%
45756
Night
3313323346%64%
45545
TransparencyDay
26%35%19%28%17%
45451
Night
21%36%21%29%18%
45351
SeeingDay
10%17%34%26%8%1
4751
Night
6%8%22%32%24%5%
15080

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
3314313336%64%
1611
16th to endDay
6%5%1431335%6%58%
1728
February1st to 15thDay
25%24413348%59%
1643
16th to endDay
6%6%2432445%5%54%
1579
March1st to 15thDay
332232345%6%62%
1962
16th to endDay
3323323348%61%
2112
April1st to 15thDay
3424423346%60%
1831
16th to endDay
2313323336%65%
2128
May1st to 15thDay
2223325%447%59%
2136
16th to endDay
3313333446%63%
2221
June1st to 15thDay
112212345%75%
2145
16th to endDay
11221223476%
2145
July1st to 15thDay
3326%6%46%6%7%6%45%
2145
16th to endDay
45%48%7%48%8%6%9%32%
2285
August1st to 15thDay
3325%7%5%6%7%6%8%40%
2145
16th to endDay
3325%6%45%6%5%7%49%
2193
September1st to 15thDay
4314436%5%5%6%53%
1815
16th to endDay
221222334469%
1815
October1st to 15thDay
231231334468%
1735
16th to endDay
212323345%70%
1760
November1st to 15thDay
1211212237%71%
1654
16th to endDay
431221332471%
1620
December1st to 15thDay
441332435%7%58%
1620
16th to endDay
8%7%22324446%53%
1728
January1st to 15thNight
4423313345%63%
2327
16th to endNight
7%5%13323436%59%
2496
February1st to 15thNight
2413323346%64%
2208
16th to endNight
441332245%6%59%
1895
March1st to 15thNight
231322336%7%63%
1998
16th to endNight
221231245%7%64%
2112
April1st to 15thNight
2223324445%63%
1802
16th to endNight
2112213346%71%
1499
May1st to 15thNight
1112224347%67%
1484
16th to endNight
112323446%69%
1540
June1st to 15thNight
112212246%74%
1485
16th to endNight
112111245%78%
1485
July1st to 15thNight
2313425%5%6%9%54%
1485
16th to endNight
3326%5%35%6%8%11%44%
1575
August1st to 15thNight
323435%5%5%8%57%
1485
16th to endNight
1243245%7%10%57%
1653
September1st to 15thNight
232442445%7%57%
1815
16th to endNight
1121233477%
1815
October1st to 15thNight
212212335%71%
1895
16th to endNight
2212212236%72%
2112
November1st to 15thNight
1212224347%68%
2203
16th to endNight
3311213246%70%
2340
December1st to 15thNight
441321345%7%61%
2340
16th to endNight
7%5%23423447%53%
2496

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
24%26%28%30%7%
1612
16th to endDay
28%37%24%27%7%
1728
February1st to 15thDay
25%27%27%21%14%
1643
16th to endDay
32%16%20%30%8%
1579
March1st to 15thDay
21%3326%37%8%
1962
16th to endDay
24%35%25%29%11%
2112
April1st to 15thDay
26%2321%30%15%
1831
16th to endDay
21%3322%33%15%
2128
May1st to 15thDay
24%3416%37%14%
2136
16th to endDay
24%3316%33%18%
2224
June1st to 15thDay
13%119%28%44%
2145
16th to endDay
13%26%25%51%
2145
July1st to 15thDay
37%46%9%14%25%
2006
16th to endDay
45%6%11%14%14%7%
2130
August1st to 15thDay
40%47%12%18%16%
2130
16th to endDay
35%45%17%24%12%
2193
September1st to 15thDay
30%47%15%18%23%
1815
16th to endDay
18%3214%33%27%
1815
October1st to 15thDay
21%2318%32%21%
1735
16th to endDay
18%3417%38%17%
1760
November1st to 15thDay
15%16%28%31%16%
1654
16th to endDay
19%25%22%35%14%
1620
December1st to 15thDay
26%310%28%26%3
1620
16th to endDay
32%210%25%21%6%
1728
January1st to 15thNight
25%27%25%32%7%
2327
16th to endNight
29%16%21%30%10%
2496
February1st to 15thNight
23%36%26%25%14%
2219
16th to endNight
26%35%23%30%10%
1895
March1st to 15thNight
20%2426%36%8%
1998
16th to endNight
19%35%26%31%12%
2112
April1st to 15thNight
25%2419%34%14%
1802
16th to endNight
16%1224%36%17%
1499
May1st to 15thNight
17%2321%36%17%
1485
16th to endNight
18%2319%37%18%
1541
June1st to 15thNight
13%217%28%45%
1485
16th to endNight
11%215%24%55%
1485
July1st to 15thNight
26%410%15%14%27%
1395
16th to endNight
31%5%14%20%16%11%
1467
August1st to 15thNight
25%39%20%22%18%
1476
16th to endNight
20%5%8%23%25%16%
1653
September1st to 15thNight
26%37%19%19%24%
1815
16th to endNight
11%2216%32%33%
1815
October1st to 15thNight
17%26%19%30%24%
1895
16th to endNight
16%2415%37%22%
2112
November1st to 15thNight
18%26%22%32%17%
2203
16th to endNight
18%2321%34%18%
2340
December1st to 15thNight
22%48%28%27%8%
2340
16th to endNight
32%210%26%20%6%
2496

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
23%22%27%17%8%
90
16th to endDay
13%16%28%26%15%
96
February1st to 15thDay
7%18%34%25%12%1
158
16th to endDay
20%31%31%14%1
238
March1st to 15thDay
12%22%34%22%5%2
270
16th to endDay
13%27%33%19%32
288
April1st to 15thDay
16%31%30%15%41
211
16th to endDay
18%28%31%14%6%
210
May1st to 15thDay
11%22%48%16%1
228
16th to endDay
14%23%37%19%31
266
June1st to 15thDay
5%18%45%20%9%1
255
16th to endDay
38%45%32%10%
255
July1st to 15thDay
7%8%42%32%7%
245
16th to endDay
7%5%26%42%14%2
271
August1st to 15thDay
5%7%29%38%16%2
255
16th to endDay
8%7%27%38%14%3
268
September1st to 15thDay
7%8%38%36%5%4
255
16th to endDay
11%12%29%27%13%4
255
October1st to 15thDay
9%23%30%23%8%4
175
16th to endDay
10%16%28%33%11%
96
November1st to 15thDay
6%13%25%27%24%2
90
16th to endDay
13%20%36%22%7%
90
December1st to 15thDay
315%34%32%13%1
90
16th to endDay
16%26%20%28%7%1
96
January1st to 15thNight
9%9%23%33%19%5%
720
16th to endNight
12%8%23%30%20%5%
768
February1st to 15thNight
7%8%24%35%20%3
704
16th to endNight
10%12%30%31%14%2
632
March1st to 15thNight
7%15%25%29%18%4
720
16th to endNight
6%12%27%33%17%2
768
April1st to 15thNight
8%20%28%25%14%2
641
16th to endNight
6%16%27%29%15%4
495
May1st to 15thNight
5%11%32%32%14%2
495
16th to endNight
314%29%27%20%3
515
June1st to 15thNight
38%32%36%15%2
495
16th to endNight
26%25%38%23%3
495
July1st to 15thNight
6%113%39%31%6%
465
16th to endNight
6%8%37%38%8%
522
August1st to 15thNight
5%37%35%39%9%
494
16th to endNight
4110%30%41%11%
563
September1st to 15thNight
5%310%30%41%9%
660
16th to endNight
35%16%28%35%10%
656
October1st to 15thNight
5%7%21%35%21%7%
660
16th to endNight
47%18%30%29%9%
704
November1st to 15thNight
37%25%30%26%6%
700
16th to endNight
6%10%20%33%22%5%
720
December1st to 15thNight
9%8%21%35%21%2
720
16th to endNight
13%9%22%30%21%2
768
Page generated at 2017-04-02 04:39:05. Version ac04

Copyright 2017 A. Danko


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