Annbar Canyon
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Annbar Canyon clear sky chart from 2005-11-05 to 2017-09-10.

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%
15607
33%
46841
26%
15566
73%
15566
51%
22735

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
57%
720
31%
2327
27%
716
67%
716
44%
1149
January16th to endNight
57%
768
34%
2496
29%
768
68%
768
41%
1277
February1st to 15thNight
62%
700
32%
2202
29%
700
69%
700
49%
1065
February16th to endNight
50%
632
35%
1895
28%
632
62%
632
44%
994
March1st to 15thNight
57%
720
36%
2000
25%
720
68%
720
53%
1003
March16th to endNight
59%
768
34%
2112
23%
768
69%
768
52%
1074
April1st to 15thNight
49%
704
29%
1963
14%
704
60%
704
50%
1013
April16th to endNight
57%
540
42%
1632
26%
540
71%
540
60%
699
May1st to 15thNight
60%
540
35%
1619
24%
539
68%
539
57%
726
May16th to endNight
60%
561
34%
1684
22%
561
69%
561
57%
753
June1st to 15thNight
67%
540
31%
1620
25%
540
72%
540
67%
679
June16th to endNight
82%
540
34%
1620
30%
540
84%
540
75%
639
July1st to 15thNight
83%
510
22%
1530
20%
510
83%
510
47%
774
July16th to endNight
81%
564
20%
1593
18%
531
81%
531
35%
932
August1st to 15thNight
80%
539
30%
1611
26%
536
81%
536
49%
802
August16th to endNight
84%
633
35%
1821
29%
633
85%
633
50%
945
September1st to 15thNight
80%
700
29%
1925
24%
700
81%
700
47%
1065
September16th to endNight
77%
656
43%
1815
31%
656
84%
656
69%
802
October1st to 15thNight
68%
660
37%
1886
26%
660
76%
660
60%
878
October16th to endNight
73%
704
41%
2112
33%
704
80%
704
61%
941
November1st to 15thNight
66%
700
36%
2202
28%
700
76%
700
57%
983
November16th to endNight
65%
720
38%
2340
34%
720
74%
720
55%
1022
December1st to 15thNight
62%
720
33%
2340
28%
720
72%
720
45%
1159
December16th to endNight
56%
768
30%
2496
26%
768
62%
768
35%
1361

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
3313323346%62%
47784
Night
3312223346%67%
47037
TransparencyDay
22%47%17%27%19%
47479
Night
18%48%19%29%20%
46843
SeeingDay
6%9%23%30%20%8%
5414
Night
4420%35%29%5%
15613

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
35%13322245%66%
1611
16th to endDay
5%5%12313337%62%
1728
February1st to 15thDay
28%12312337%62%
1658
16th to endDay
47%24313436%56%
1579
March1st to 15thDay
3411214346%65%
1959
16th to endDay
332221335%6%65%
2112
April1st to 15thDay
2413424445%63%
1984
16th to endDay
2312213326%70%
2325
May1st to 15thDay
2212422336%68%
2331
16th to endDay
331231343467%
2429
June1st to 15thDay
1121223479%
2340
16th to endDay
11221223476%
2340
July1st to 15thDay
4315%5%37%46%7%49%
2340
16th to endDay
6%436%6%47%8%7%9%34%
2467
August1st to 15thDay
5%415%6%46%5%5%7%45%
2340
16th to endDay
44146%46%6%5%6%49%
2378
September1st to 15thDay
43145%35%446%54%
1922
16th to endDay
222213245%72%
1815
October1st to 15thDay
221232333471%
1742
16th to endDay
321221222473%
1760
November1st to 15thDay
1212112235%73%
1656
16th to endDay
441221112473%
1620
December1st to 15thDay
45%13322346%61%
1620
16th to endDay
5%7%23223447%54%
1728
January1st to 15thNight
3423322335%65%
2327
16th to endNight
6%5%23222335%62%
2496
February1st to 15thNight
2413312235%67%
2191
16th to endNight
45%13213445%62%
1895
March1st to 15thNight
231221346%6%65%
2000
16th to endNight
231221345%6%66%
2112
April1st to 15thNight
3313323236%67%
1963
16th to endNight
111112336%75%
1632
May1st to 15thNight
221212335%74%
1619
16th to endNight
1112213335%72%
1684
June1st to 15thNight
1122335%77%
1620
16th to endNight
11111223480%
1620
July1st to 15thNight
22123345%5%7%60%
1620
16th to endNight
23145%45%7%9%11%44%
1701
August1st to 15thNight
221332345%8%61%
1620
16th to endNight
21343345%7%63%
1821
September1st to 15thNight
32134245%5%6%61%
1925
16th to endNight
21111113380%
1815
October1st to 15thNight
2112112336%72%
1886
16th to endNight
1112212345%73%
2112
November1st to 15thNight
2212212236%71%
2202
16th to endNight
331212335%71%
2340
December1st to 15thNight
35%12213447%63%
2340
16th to endNight
6%7%12323337%56%
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
22%37%22%34%9%
1612
16th to endDay
24%39%19%32%10%
1728
February1st to 15thDay
23%37%25%21%17%
1658
16th to endDay
29%38%18%28%11%
1579
March1st to 15thDay
20%36%23%34%12%
1959
16th to endDay
20%37%23%30%14%
2112
April1st to 15thDay
21%46%19%31%15%
1984
16th to endDay
17%25%19%34%20%
2325
May1st to 15thDay
18%27%18%34%17%
2331
16th to endDay
20%45%14%35%19%
2432
June1st to 15thDay
10%248%27%46%
2340
16th to endDay
12%236%22%52%
2340
July1st to 15thDay
32%7%9%11%14%24%
2201
16th to endDay
40%12%14%12%13%6%
2312
August1st to 15thDay
35%7%10%12%17%15%
2325
16th to endDay
32%7%8%15%23%12%
2378
September1st to 15thDay
29%5%11%15%17%21%
1922
16th to endDay
15%36%16%29%28%
1815
October1st to 15thDay
17%35%16%29%26%
1742
16th to endDay
15%26%16%36%22%
1760
November1st to 15thDay
14%26%24%31%20%
1656
16th to endDay
18%17%19%32%20%
1620
December1st to 15thDay
24%412%25%24%8%
1620
16th to endDay
30%410%22%24%7%
1728
January1st to 15thNight
22%46%24%32%9%
2327
16th to endNight
25%37%21%29%12%
2496
February1st to 15thNight
19%49%24%25%16%
2202
16th to endNight
23%45%22%30%12%
1895
March1st to 15thNight
18%36%22%38%10%
2000
16th to endNight
18%48%22%32%13%
2112
April1st to 15thNight
19%36%17%36%15%
1963
16th to endNight
11%25%21%37%20%
1632
May1st to 15thNight
13%3419%36%21%
1620
16th to endNight
14%26%17%38%20%
1685
June1st to 15thNight
11%147%29%45%
1620
16th to endNight
8%146%22%57%
1620
July1st to 15thNight
19%7%14%15%15%29%
1530
16th to endNight
27%10%18%18%15%9%
1593
August1st to 15thNight
20%5%11%22%20%19%
1611
16th to endNight
19%5%10%21%25%16%
1821
September1st to 15thNight
20%7%11%18%20%21%
1925
16th to endNight
10%2415%32%35%
1815
October1st to 15thNight
14%37%18%29%26%
1886
16th to endNight
13%36%14%35%26%
2112
November1st to 15thNight
16%27%21%32%20%
2202
16th to endNight
15%27%21%30%22%
2340
December1st to 15thNight
21%49%27%25%10%
2340
16th to endNight
29%5%11%21%24%7%
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
24%20%22%24%7%1
90
16th to endDay
9%9%18%31%19%11%
96
February1st to 15thDay
6%8%34%26%19%4
173
16th to endDay
11%21%32%19%13%1
238
March1st to 15thDay
5%15%27%29%18%3
270
16th to endDay
6%17%29%27%16%3
288
April1st to 15thDay
7%20%29%23%12%6%
269
16th to endDay
5%25%31%23%10%4
270
May1st to 15thDay
414%34%29%12%3
288
16th to endDay
7%13%27%26%20%4
330
June1st to 15thDay
38%31%31%14%10%
315
16th to endDay
4315%40%25%10%
315
July1st to 15thDay
4218%40%26%8%
305
16th to endDay
9%9%34%34%12%
327
August1st to 15thDay
7%10%37%28%14%
315
16th to endDay
6%10%31%31%18%
332
September1st to 15thDay
5%218%33%30%8%
294
16th to endDay
7%6%19%31%24%11%
255
October1st to 15thDay
210%35%25%15%9%
182
16th to endDay
9%7%20%30%28%4
96
November1st to 15thDay
26%15%34%30%11%
90
16th to endDay
11%7%34%32%11%3
90
December1st to 15thDay
46%26%36%17%7%
90
16th to endDay
14%10%26%38%7%3
96
January1st to 15thNight
6%7%23%34%20%7%
720
16th to endNight
7%6%23%35%21%4
768
February1st to 15thNight
5%323%41%21%3
704
16th to endNight
6%8%33%33%17%2
632
March1st to 15thNight
46%29%33%22%3
720
16th to endNight
45%27%36%22%4
768
April1st to 15thNight
39%32%32%18%2
704
16th to endNight
38%29%38%16%4
540
May1st to 15thNight
35%29%40%19%2
540
16th to endNight
36%25%36%26%2
563
June1st to 15thNight
1224%44%25%2
540
16th to endNight
2111%42%39%2
540
July1st to 15thNight
4335%49%6%
510
16th to endNight
4426%55%9%
564
August1st to 15thNight
4429%53%7%
539
16th to endNight
3426%51%13%
633
September1st to 15thNight
316%28%49%10%
700
16th to endNight
2314%29%37%12%
656
October1st to 15thNight
3321%38%25%6%
660
16th to endNight
2318%36%29%10%
704
November1st to 15thNight
3223%37%26%6%
700
16th to endNight
45%22%37%22%7%
720
December1st to 15thNight
7%5%21%36%24%3
720
16th to endNight
11%7%22%36%19%4
768
Page generated at 2017-09-11 16:35:18. Version ac04

Copyright 2017 A. Danko


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