Zion Camp
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Zion Camp clear sky chart from 2005-11-05 to 2017-04-30.

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
25%
14287
13%
45682
7%
14256
33%
14256
14%
32826

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
14%
720
6%
2506
3%
716
19%
716
5%
2071
January16th to endNight
17%
768
11%
2616
4%
768
25%
768
10%
1974
February1st to 15thNight
15%
703
9%
2287
4%
701
22%
701
9%
1779
February16th to endNight
17%
631
13%
1980
4%
631
28%
631
10%
1498
March1st to 15thNight
17%
720
13%
2067
6%
720
24%
720
12%
1584
March16th to endNight
25%
768
20%
2058
8%
768
34%
768
19%
1404
April1st to 15thNight
20%
718
15%
1796
5%
718
25%
718
18%
1327
April16th to endNight
22%
625
18%
1700
5%
625
32%
625
17%
1189
May1st to 15thNight
31%
330
19%
1320
17%
330
42%
330
14%
848
May16th to endNight
27%
343
14%
1369
7%
342
44%
342
16%
860
June1st to 15thNight
28%
330
10%
1320
8%
330
39%
330
13%
871
June16th to endNight
38%
330
9%
1320
10%
330
45%
330
16%
821
July1st to 15thNight
45%
310
15%
1240
19%
310
53%
310
24%
690
July16th to endNight
44%
348
13%
1306
11%
326
57%
326
24%
731
August1st to 15thNight
50%
433
16%
1414
14%
431
54%
431
24%
877
August16th to endNight
48%
621
19%
1671
9%
621
54%
621
33%
1021
September1st to 15thNight
38%
660
14%
1650
6%
660
41%
660
25%
1156
September16th to endNight
43%
657
19%
1806
13%
657
47%
657
30%
1159
October1st to 15thNight
28%
660
18%
1980
12%
660
37%
660
18%
1391
October16th to endNight
23%
704
10%
2178
6%
704
29%
704
12%
1693
November1st to 15thNight
25%
700
16%
2370
12%
700
33%
700
14%
1684
November16th to endNight
17%
720
9%
2520
5%
720
22%
720
8%
1971
December1st to 15thNight
13%
720
7%
2520
3%
720
18%
720
6%
2052
December16th to endNight
12%
768
9%
2688
4%
768
18%
768
6%
2175

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
18%9%36%5%3445%6%31%
46051
Night
18%10%47%5%34446%31%
45852
TransparencyDay
52%411%19%9%1
45739
Night
54%410%19%9%
45682
SeeingDay
22%18%25%19%9%3
4859
Night
21%23%23%22%8%
14288

By Month

Percentage Cloud Cover NE (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
21%15%6%9%7%2433321%
1432
16th to endDay
15%16%5%9%8%4433422%
1606
February1st to 15thDay
12%14%7%12%8%34445%21%
1575
16th to endDay
17%14%5%7%6%43446%25%
1492
March1st to 15thDay
16%13%47%6%36%43427%
1880
16th to endDay
14%7%5%5%6%24346%40%
2166
April1st to 15thDay
23%11%34422345%33%
2152
16th to endDay
22%7%36%423345%37%
2247
May1st to 15thDay
18%8%35%5%24347%34%
2301
16th to endDay
16%7%35%6%35%45%7%35%
2394
June1st to 15thDay
21%7%37%5%345%5%6%29%
2310
16th to endDay
16%5%25%5%36%6%6%8%34%
2310
July1st to 15thDay
13%5%25%5%26%5%7%8%36%
2310
16th to endDay
10%6%25%5%35%5%7%10%36%
2458
August1st to 15thDay
13%6%26%5%35%5%5%7%37%
2204
16th to endDay
12%5%25%5%346%6%9%37%
2168
September1st to 15thDay
18%5%35%5%24348%38%
1980
16th to endDay
17%6%2442445%5%42%
1821
October1st to 15thDay
22%8%36%6%34336%32%
1650
16th to endDay
29%10%37%5%3344424%
1694
November1st to 15thDay
17%9%37%6%33446%33%
1485
16th to endDay
25%14%5%6%6%34445%20%
1440
December1st to 15thDay
20%18%6%10%8%3434415%
1440
16th to endDay
23%19%6%8%5%23235%19%
1536
January1st to 15thNight
19%16%6%11%7%45%34416%
2506
16th to endNight
14%14%6%8%6%3435%426%
2616
February1st to 15thNight
12%15%6%12%8%35%445%21%
2285
16th to endNight
15%12%6%10%6%35%34427%
1980
March1st to 15thNight
19%13%46%7%34335%27%
2055
16th to endNight
15%8%45%5%23345%39%
2058
April1st to 15thNight
21%10%36%423345%32%
1796
16th to endNight
19%8%36%424346%36%
1700
May1st to 15thNight
21%7%35%423247%37%
1320
16th to endNight
15%6%3443445%8%38%
1367
June1st to 15thNight
19%6%35%6%25%45%6%35%
1320
16th to endNight
16%425%5%3445%7%38%
1320
July1st to 15thNight
11%3245%25%5%48%45%
1320
16th to endNight
10%4234246%7%10%42%
1402
August1st to 15thNight
10%425%5%346%6%7%42%
1424
16th to endNight
9%32443445%7%48%
1671
September1st to 15thNight
16%6%35%434446%39%
1650
16th to endNight
17%5%25%312236%48%
1806
October1st to 15thNight
22%7%25%5%23335%37%
1980
16th to endNight
25%12%35%5%35%445%24%
2178
November1st to 15thNight
20%9%45%5%34446%31%
2370
16th to endNight
24%13%48%6%3334423%
2520
December1st to 15thNight
21%18%6%8%6%3433418%
2520
16th to endNight
24%16%7%8%6%2433418%
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
68%38%12%5%
1433
16th to endDay
64%49%14%6%
1606
February1st to 15thDay
64%311%15%4
1577
16th to endDay
61%210%14%9%1
1492
March1st to 15thDay
60%211%17%7%
1891
16th to endDay
45%310%20%14%5%
2166
April1st to 15thDay
54%27%19%13%2
2152
16th to endDay
50%26%21%15%3
2247
May1st to 15thDay
50%29%19%15%2
2301
16th to endDay
48%410%20%13%1
2398
June1st to 15thDay
54%411%20%9%
2310
16th to endDay
45%5%14%21%11%1
2310
July1st to 15thDay
40%5%13%26%12%
2161
16th to endDay
43%5%17%22%9%
2291
August1st to 15thDay
46%5%15%21%10%
2190
16th to endDay
39%6%16%26%10%
2168
September1st to 15thDay
44%414%26%9%
1980
16th to endDay
42%413%30%8%
1821
October1st to 15thDay
52%412%19%9%
1650
16th to endDay
63%412%15%4
1694
November1st to 15thDay
52%415%19%8%
1485
16th to endDay
67%411%11%41
1440
December1st to 15thDay
72%49%10%2
1440
16th to endDay
70%310%11%4
1536
January1st to 15thNight
71%48%10%4
2506
16th to endNight
61%48%17%7%
2616
February1st to 15thNight
64%310%16%4
2287
16th to endNight
61%29%17%8%
1980
March1st to 15thNight
60%38%18%7%
2067
16th to endNight
46%310%19%17%3
2058
April1st to 15thNight
53%37%18%14%2
1796
16th to endNight
49%27%19%16%3
1700
May1st to 15thNight
47%45%20%17%4
1320
16th to endNight
44%5%10%23%14%2
1369
June1st to 15thNight
48%5%13%23%8%1
1320
16th to endNight
43%5%13%21%15%
1320
July1st to 15thNight
34%5%14%27%16%1
1240
16th to endNight
35%414%30%13%
1306
August1st to 15thNight
37%7%15%26%12%
1414
16th to endNight
33%418%32%10%
1671
September1st to 15thNight
44%5%11%26%10%
1650
16th to endNight
40%313%34%7%
1806
October1st to 15thNight
49%5%9%23%11%
1980
16th to endNight
60%5%12%15%5%
2178
November1st to 15thNight
53%5%13%18%9%
2370
16th to endNight
65%411%14%3
2520
December1st to 15thNight
70%410%12%3
2520
16th to endNight
69%39%11%5%
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
35%16%25%20%3
60
16th to endDay
39%17%23%15%3
76
February1st to 15thDay
36%14%36%11%1
90
16th to endDay
34%27%24%11%1
151
March1st to 15thDay
23%25%27%17%5%
270
16th to endDay
19%25%28%17%7%1
288
April1st to 15thDay
28%28%22%10%7%1
270
16th to endDay
23%27%22%15%7%3
266
May1st to 15thDay
26%19%22%18%7%4
228
16th to endDay
17%24%28%20%6%2
267
June1st to 15thDay
27%20%24%19%7%
255
16th to endDay
13%16%30%24%12%1
255
July1st to 15thDay
13%13%26%28%13%5%
245
16th to endDay
12%15%29%27%11%4
270
August1st to 15thDay
16%11%17%30%15%8%
253
16th to endDay
14%11%22%29%13%8%
268
September1st to 15thDay
19%10%21%21%14%12%
255
16th to endDay
19%13%24%20%15%6%
254
October1st to 15thDay
22%18%24%21%11%1
255
16th to endDay
33%20%23%14%8%
260
November1st to 15thDay
20%14%34%16%13%
139
16th to endDay
43%11%30%8%6%
60
December1st to 15thDay
25%15%46%10%3
60
16th to endDay
42%23%29%4
64
January1st to 15thNight
24%27%24%18%5%
720
16th to endNight
20%26%26%20%5%
768
February1st to 15thNight
17%28%28%20%3
704
16th to endNight
21%29%25%18%4
631
March1st to 15thNight
24%27%22%20%4
720
16th to endNight
19%27%24%19%9%
768
April1st to 15thNight
22%27%25%18%5%
718
16th to endNight
20%28%24%20%5%
625
May1st to 15thNight
19%24%18%27%8%1
330
16th to endNight
15%21%31%23%7%
343
June1st to 15thNight
18%24%23%28%5%
330
16th to endNight
16%21%17%30%12%
330
July1st to 15thNight
9%15%23%34%16%
310
16th to endNight
10%19%20%34%14%
348
August1st to 15thNight
12%12%14%36%20%3
433
16th to endNight
11%12%21%32%20%1
621
September1st to 15thNight
18%13%23%25%17%2
660
16th to endNight
17%14%19%28%18%1
657
October1st to 15thNight
25%17%23%21%11%
660
16th to endNight
29%18%23%20%6%
704
November1st to 15thNight
20%23%25%19%10%1
700
16th to endNight
26%29%20%16%6%
720
December1st to 15thNight
28%29%21%16%3
720
16th to endNight
30%26%21%16%4
768
Page generated at 2017-04-30 20:40:13. Version ac04

Copyright 2017 A. Danko


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