Zion Gateway to the Stars
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Zion Gateway to the Stars clear sky chart from 2005-11-06 to 2024-01-16.

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
66%
24047
32%
74413
26%
23999
73%
23999
48%
36526

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 10thNight
61%
757
31%
2457
27%
756
69%
756
42%
1248
January11th to 20thNight
63%
744
34%
2418
31%
744
72%
744
46%
1163
January21st to endNight
58%
792
34%
2574
29%
792
68%
792
39%
1369
February1st to 10thNight
59%
720
29%
2318
26%
720
68%
720
43%
1165
February11th to 20thNight
58%
700
31%
2099
25%
700
67%
700
42%
1110
February21st to endNight
51%
592
31%
1776
25%
592
61%
592
38%
988
March1st to 10thNight
55%
720
28%
2044
21%
720
63%
720
41%
1139
March11th to 20thNight
59%
720
31%
1980
24%
720
66%
720
45%
1083
March21st to endNight
54%
792
30%
2178
18%
792
65%
792
44%
1186
April1st to 10thNight
53%
720
28%
1980
15%
720
62%
720
48%
1035
April11th to 20thNight
52%
597
35%
1706
17%
597
66%
597
51%
818
April21st to endNight
53%
540
36%
1620
21%
540
64%
540
47%
776
May1st to 10thNight
57%
540
34%
1620
23%
540
65%
540
50%
774
May11th to 20thNight
67%
531
35%
1595
27%
531
72%
531
57%
717
May21st to endNight
59%
583
29%
1746
19%
582
68%
582
49%
845
June1st to 10thNight
73%
540
33%
1620
28%
540
77%
540
68%
675
June11th to 20thNight
69%
540
33%
1620
30%
540
72%
540
65%
681
June21st to endNight
76%
540
31%
1620
28%
540
79%
540
67%
676
July1st to 10thNight
83%
525
27%
1575
25%
525
84%
525
56%
737
July11th to 20thNight
78%
522
23%
1566
21%
522
78%
522
41%
847
July21st to endNight
79%
591
22%
1674
20%
558
79%
558
34%
968
August1st to 10thNight
78%
537
30%
1602
24%
534
79%
534
49%
784
August11th to 20thNight
84%
534
36%
1602
31%
534
84%
534
54%
765
August21st to endNight
83%
673
36%
1883
30%
673
84%
673
55%
939
September1st to 10thNight
80%
720
33%
1980
28%
720
82%
720
54%
1003
September11th to 20thNight
81%
720
39%
1980
31%
720
85%
720
60%
955
September21st to endNight
77%
720
41%
1980
30%
720
84%
720
65%
907
October1st to 10thNight
68%
720
33%
2003
24%
720
75%
720
52%
1022
October11th to 20thNight
72%
720
41%
2160
33%
720
81%
720
63%
952
October21st to endNight
68%
792
42%
2376
31%
792
80%
792
60%
1046
November1st to 10thNight
73%
740
36%
2364
33%
740
80%
740
56%
1041
November11th to 20thNight
73%
760
39%
2470
36%
760
81%
760
58%
1041
November21st to endNight
66%
760
36%
2470
34%
760
74%
760
49%
1158
December1st to 10thNight
62%
760
33%
2470
30%
760
69%
760
44%
1218
December11th to 20thNight
62%
758
31%
2915
28%
758
69%
758
34%
1540
December21st to endNight
51%
827
18%
4372
22%
817
61%
817
22%
2155

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
442342445%7%61%
74959
Night
441332345%7%64%
74893
TransparencyDay
21%5%8%18%27%20%
74686
Night
20%5%8%19%28%20%
74688
SeeingDay
7%12%27%32%16%5%
13815
Night
6%417%40%27%5%
24066

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 10thDay
5%7%33423246%59%
1708
11th to 20thDay
36%2331235%6%65%
1669
21st to endDay
7%7%2432335%6%59%
1782
February1st to 10thDay
36%2332345%7%61%
1638
11th to 20thDay
6%7%23334447%57%
1750
21st to endDay
5%9%24424446%55%
1480
March1st to 10thDay
5%6%334345%5%5%56%
1914
11th to 20thDay
47%35%4245%5%7%55%
1980
21st to endDay
7%6%3342447%8%52%
2178
April1st to 10thDay
45%2342446%8%58%
1980
11th to 20thDay
342442345%7%63%
2196
21st to endDay
4413434446%63%
2340
May1st to 10thDay
43245%3446%8%58%
2340
11th to 20thDay
34134245%6%8%61%
2301
21st to endDay
44234345%5%7%61%
2530
June1st to 10thDay
111232335%6%73%
2340
11th to 20thDay
2212222335%75%
2340
21st to endDay
1112223446%72%
2340
July1st to 10thDay
4223425%5%5%6%62%
2340
11th to 20thDay
43145%35%5%7%9%53%
2340
21st to endDay
5%427%7%5%8%7%7%10%39%
2545
August1st to 10thDay
3415%6%35%5%5%7%56%
2328
11th to 20thDay
32144446%6%7%59%
2299
21st to endDay
43245%35%45%8%58%
2470
September1st to 10thDay
43145%345%5%7%61%
1980
11th to 20thDay
4213323435%70%
1980
21st to endDay
3213323335%70%
1980
October1st to 10thDay
7%31432244465%
1955
11th to 20thDay
421231323476%
1800
21st to endDay
3212323235%75%
1980
November1st to 10thDay
4322323345%71%
1711
11th to 20thDay
231221335%5%73%
1710
21st to endDay
5%5%1322335%7%63%
1710
December1st to 10thDay
5%7%14424336%61%
1710
11th to 20thDay
8%8%25%43446%7%50%
2169
21st to endDay
5%7%234335%7%9%53%
3146
January1st to 10thNight
7%7%13323446%61%
2457
11th to 20thNight
5%5%1232345%6%64%
2418
21st to endNight
6%6%24424446%58%
2574
February1st to 10thNight
46%22423447%62%
2318
11th to 20thNight
5%7%24323446%59%
2098
21st to endNight
410%35%423446%55%
1776
March1st to 10thNight
6%7%243245%5%8%54%
2044
11th to 20thNight
5%7%22325%45%8%57%
1980
21st to endNight
44233245%6%7%60%
2178
April1st to 10thNight
432342445%6%64%
1980
11th to 20thNight
231332345%7%66%
1706
21st to endNight
431332445%9%63%
1620
May1st to 10thNight
3313323447%66%
1620
11th to 20thNight
221232335%6%71%
1594
21st to endNight
3323423446%66%
1746
June1st to 10thNight
2112212348%74%
1620
11th to 20thNight
1112222346%77%
1620
21st to endNight
1113213345%75%
1620
July1st to 10thNight
21123245%6%8%66%
1620
11th to 20thNight
33145%45%6%6%8%55%
1620
21st to endNight
34245%46%8%8%10%45%
1773
August1st to 10thNight
22145%3445%7%64%
1611
11th to 20thNight
22133335%5%9%64%
1602
21st to endNight
321342335%7%66%
1883
September1st to 10thNight
5%31332345%7%65%
1980
11th to 20thNight
4212223335%73%
1980
21st to endNight
321221223477%
1980
October1st to 10thNight
5%313323345%67%
2003
11th to 20thNight
321211333477%
2160
21st to endNight
321222325%5%74%
2376
November1st to 10thNight
2313223447%70%
2364
11th to 20thNight
3212212447%72%
2470
21st to endNight
45%13323236%68%
2470
December1st to 10thNight
6%6%13313447%62%
2470
11th to 20thNight
7%6%2432446%10%52%
3041
21st to endNight
5%7%25%5%3445%7%53%
4521

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 10thDay
27%411%28%26%3
1709
11th to 20thDay
20%410%31%26%8%
1669
21st to endDay
27%5%11%28%23%7%
1782
February1st to 10thDay
22%5%14%23%27%9%
1638
11th to 20thDay
27%48%23%25%13%
1760
21st to endDay
30%5%9%17%30%10%
1480
March1st to 10thDay
27%5%7%21%32%8%
1914
11th to 20thDay
26%5%8%25%26%9%
1980
21st to endDay
28%6%9%25%24%8%
2178
April1st to 10thDay
23%5%8%23%26%16%
1980
11th to 20thDay
20%46%21%30%18%
2199
21st to endDay
20%47%21%35%13%
2340
May1st to 10thDay
23%47%18%33%15%
2340
11th to 20thDay
18%6%11%18%32%16%
2304
21st to endDay
21%5%9%15%32%19%
2530
June1st to 10thDay
11%36%12%34%34%
2340
11th to 20thDay
12%35%7%23%49%
2340
21st to endDay
10%45%8%22%51%
2340
July1st to 10thDay
21%5%7%10%16%41%
2276
11th to 20thDay
24%9%11%15%19%22%
2271
21st to endDay
34%10%13%18%13%14%
2404
August1st to 10thDay
23%8%10%13%16%30%
2313
11th to 20thDay
20%7%9%13%20%30%
2299
21st to endDay
22%6%8%16%26%22%
2470
September1st to 10thDay
21%5%10%11%18%35%
1980
11th to 20thDay
16%5%6%16%22%35%
1980
21st to endDay
15%47%12%32%30%
1980
October1st to 10thDay
21%47%18%24%26%
1955
11th to 20thDay
13%35%14%35%30%
1800
21st to endDay
13%46%19%39%20%
1980
November1st to 10thDay
17%35%22%35%17%
1711
11th to 20thDay
14%47%22%35%17%
1710
21st to endDay
21%38%20%35%13%
1710
December1st to 10thDay
25%411%22%27%10%
1710
11th to 20thDay
32%7%11%22%20%7%
2168
21st to endDay
27%6%12%21%26%8%
3146
January1st to 10thNight
25%412%28%26%5%
2457
11th to 20thNight
21%410%29%26%9%
2418
21st to endNight
28%48%28%24%8%
2574
February1st to 10thNight
23%410%25%26%11%
2318
11th to 20thNight
25%48%18%28%17%
2099
21st to endNight
30%49%17%30%10%
1776
March1st to 10thNight
26%6%8%23%30%8%
2044
11th to 20thNight
23%5%8%27%27%10%
1980
21st to endNight
22%6%10%27%25%10%
2178
April1st to 10thNight
21%48%23%28%16%
1980
11th to 20thNight
16%48%23%32%17%
1706
21st to endNight
18%5%7%20%39%12%
1620
May1st to 10thNight
18%48%17%37%15%
1620
11th to 20thNight
14%47%21%35%19%
1595
21st to endNight
19%47%15%35%20%
1746
June1st to 10thNight
10%36%11%35%35%
1620
11th to 20thNight
9%45%10%22%50%
1620
21st to endNight
11%247%21%55%
1620
July1st to 10thNight
15%5%9%11%16%45%
1575
11th to 20thNight
24%8%10%16%18%25%
1566
21st to endNight
28%10%14%22%13%14%
1674
August1st to 10thNight
20%411%15%19%31%
1602
11th to 20thNight
17%5%10%14%20%35%
1602
21st to endNight
18%47%15%27%29%
1883
September1st to 10thNight
18%48%14%20%35%
1980
11th to 20thNight
14%5%6%14%23%38%
1980
21st to endNight
12%35%13%33%34%
1980
October1st to 10thNight
19%47%16%27%27%
2003
11th to 20thNight
13%3414%35%31%
2160
21st to endNight
13%47%17%40%21%
2376
November1st to 10thNight
15%48%23%34%16%
2364
11th to 20thNight
13%48%20%39%17%
2470
21st to endNight
20%36%18%36%18%
2470
December1st to 10thNight
23%410%26%24%12%
2470
11th to 20thNight
28%5%12%23%25%8%
3041
21st to endNight
29%7%12%15%24%13%
4521

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 10thDay
14%5%31%38%11%1
270
11th to 20thDay
12%12%28%32%13%2
257
21st to endDay
8%6%27%38%17%4
264
February1st to 10thDay
9%13%27%29%18%4
258
11th to 20thDay
13%16%35%26%8%1
415
21st to endDay
10%23%34%25%7%1
346
March1st to 10thDay
11%20%34%24%10%1
420
11th to 20thDay
9%16%38%23%11%3
420
21st to endDay
12%24%34%24%5%1
462
April1st to 10thDay
9%21%35%22%10%3
420
11th to 20thDay
11%25%33%21%8%2
412
21st to endDay
9%23%26%28%12%2
420
May1st to 10thDay
10%19%37%23%10%2
423
11th to 20thDay
7%15%31%28%14%5%
448
21st to endDay
11%17%27%26%13%5%
485
June1st to 10thDay
311%32%36%14%5%
450
11th to 20thDay
414%27%36%14%6%
450
21st to endDay
27%27%41%18%5%
450
July1st to 10thDay
3324%40%21%9%
446
11th to 20thDay
3317%40%24%13%
444
21st to endDay
5%311%41%29%11%
487
August1st to 10thDay
4421%41%21%9%
447
11th to 20thDay
5%324%37%21%10%
437
21st to endDay
3322%37%25%11%
495
September1st to 10thDay
4423%35%24%10%
450
11th to 20thDay
411%26%34%20%5%
450
21st to endDay
5%12%22%35%21%6%
450
October1st to 10thDay
7%13%24%34%16%6%
425
11th to 20thDay
5%11%22%34%21%7%
270
21st to endDay
5%11%25%35%22%3
297
November1st to 10thDay
6%14%24%31%22%4
270
11th to 20thDay
39%29%35%16%8%
270
21st to endDay
10%9%27%30%20%4
270
December1st to 10thDay
9%8%28%29%24%2
270
11th to 20thDay
49%31%36%18%2
270
21st to endDay
16%13%27%31%12%1
297
January1st to 10thNight
11%319%40%19%7%
760
11th to 20thNight
8%321%41%21%5%
744
21st to endNight
9%421%40%19%7%
792
February1st to 10thNight
8%422%43%19%4
720
11th to 20thNight
8%6%22%43%17%4
704
21st to endNight
10%5%27%40%16%2
592
March1st to 10thNight
12%8%21%41%16%3
720
11th to 20thNight
7%7%21%37%24%3
720
21st to endNight
6%9%26%39%17%2
792
April1st to 10thNight
5%9%28%39%16%3
720
11th to 20thNight
410%29%38%16%3
597
21st to endNight
6%13%24%37%17%4
540
May1st to 10thNight
6%6%26%45%15%2
540
11th to 20thNight
36%21%39%28%4
531
21st to endNight
48%23%39%23%3
584
June1st to 10thNight
2418%44%31%2
540
11th to 20thNight
25%20%46%25%2
540
21st to endNight
2215%42%36%3
540
July1st to 10thNight
217%42%43%5%
525
11th to 20thNight
326%37%44%7%
522
21st to endNight
42329%53%9%
591
August1st to 10thNight
315%34%51%6%
537
11th to 20thNight
215%38%47%6%
534
21st to endNight
41437%44%10%
673
September1st to 10thNight
416%33%46%9%
720
11th to 20thNight
328%42%36%9%
720
21st to endNight
4212%35%36%10%
720
October1st to 10thNight
6%417%46%24%4
720
11th to 20thNight
4318%42%25%9%
720
21st to endNight
4419%39%26%8%
792
November1st to 10thNight
4215%48%24%8%
740
11th to 20thNight
4415%46%26%6%
760
21st to endNight
6%6%17%41%24%6%
760
December1st to 10thNight
10%319%42%21%5%
760
11th to 20thNight
11%219%43%20%4
760
21st to endNight
12%6%22%40%17%3
836
Page generated at 2024-01-13 17:28:28. Version ac07

Copyright 2024 Attilla Danko


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