Chandler Mountain
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chandler Mountain clear sky chart from 2005-11-05 to 2017-04-24.

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
50%
14852
24%
45608
18%
14809
58%
14809
29%
27626

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
29%
720
24%
2327
11%
716
44%
716
21%
1462
January16th to endNight
28%
768
26%
2346
12%
768
43%
768
23%
1517
February1st to 15thNight
31%
704
26%
2112
11%
701
44%
701
27%
1289
February16th to endNight
30%
631
25%
1893
13%
631
41%
631
25%
1195
March1st to 15thNight
33%
720
21%
2138
12%
720
40%
720
25%
1355
March16th to endNight
41%
735
23%
2079
15%
735
48%
735
30%
1286
April1st to 15thNight
44%
539
25%
1797
19%
539
55%
539
32%
994
April16th to endNight
49%
522
26%
1734
20%
522
59%
522
31%
981
May1st to 15thNight
55%
495
24%
1485
16%
495
62%
495
31%
909
May16th to endNight
68%
513
22%
1538
18%
513
71%
513
37%
884
June1st to 15thNight
75%
495
20%
1485
17%
495
76%
495
36%
867
June16th to endNight
83%
495
20%
1485
18%
495
83%
495
41%
831
July1st to 15thNight
74%
465
16%
1395
15%
465
75%
465
30%
878
July16th to endNight
74%
522
15%
1469
15%
489
76%
489
30%
947
August1st to 15thNight
80%
494
22%
1628
24%
491
81%
491
36%
909
August16th to endNight
69%
525
20%
1750
24%
525
69%
525
24%
1129
September1st to 15thNight
66%
580
21%
1735
21%
580
67%
580
28%
1127
September16th to endNight
63%
657
27%
1815
21%
657
66%
657
36%
1096
October1st to 15thNight
59%
660
34%
1815
26%
660
65%
660
40%
1053
October16th to endNight
52%
704
34%
2130
28%
704
61%
704
36%
1201
November1st to 15thNight
51%
700
30%
2276
25%
700
61%
700
35%
1219
November16th to endNight
43%
720
28%
2340
19%
720
55%
720
28%
1353
December1st to 15thNight
37%
720
23%
2340
15%
720
48%
720
23%
1474
December16th to endNight
32%
768
21%
2496
16%
768
41%
768
18%
1670

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
12%5%25%5%35%5%5%7%40%
45993
Night
11%5%2442445%7%46%
45807
TransparencyDay
41%410%20%18%4
45694
Night
37%410%21%20%6%
45610
SeeingDay
15%5%17%22%24%14%
4622
Night
15%7%19%29%23%4
14854

By Month

Percentage Cloud Cover SE (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
20%6%25%42434442%
1611
16th to endDay
17%6%24334335%45%
1875
February1st to 15thDay
16%7%35%424346%41%
1750
16th to endDay
17%7%35%43245%5%41%
1580
March1st to 15thDay
16%8%26%5%24446%38%
1821
16th to endDay
13%6%35%43445%7%40%
2153
April1st to 15thDay
12%5%25%5%25%45%6%44%
2151
16th to endDay
10%5%35%5%245%5%8%44%
2084
May1st to 15thDay
12%435%5%45%5%6%8%38%
2136
16th to endDay
10%426%5%35%5%7%7%41%
2223
June1st to 15thDay
8%5%26%7%47%6%7%11%33%
2145
16th to endDay
33245%47%6%8%11%43%
2145
July1st to 15thDay
10%436%7%48%8%7%10%27%
2145
16th to endDay
6%5%36%7%5%9%7%9%11%28%
2283
August1st to 15thDay
6%416%7%46%7%8%11%33%
1988
16th to endDay
10%7%37%7%5%6%6%6%8%29%
2100
September1st to 15thDay
11%5%25%6%5%7%6%6%6%34%
1884
16th to endDay
13%5%246%2435%6%44%
1815
October1st to 15thDay
12%4135%2445%5%49%
1815
16th to endDay
12%42331323457%
1739
November1st to 15thDay
13%424313245%53%
1582
16th to endDay
15%5%23423446%47%
1620
December1st to 15thDay
17%8%25%4335%45%39%
1620
16th to endDay
23%8%345%2334435%
1728
January1st to 15thNight
16%6%25%423345%43%
2327
16th to endNight
15%7%345%24445%40%
2346
February1st to 15thNight
15%5%15%423336%46%
2103
16th to endNight
16%5%25%5%33345%45%
1893
March1st to 15thNight
16%5%25%5%23437%42%
2138
16th to endNight
11%5%3442335%7%46%
2079
April1st to 15thNight
12%41432445%7%49%
1797
16th to endNight
9%425%423446%51%
1734
May1st to 15thNight
9%4245%35%45%8%45%
1484
16th to endNight
4414335%6%6%10%48%
1538
June1st to 15thNight
34235%46%5%7%11%44%
1485
16th to endNight
2213427%5%8%12%50%
1485
July1st to 15thNight
8%4245%37%8%6%9%39%
1485
16th to endNight
4425%6%37%6%8%11%38%
1577
August1st to 15thNight
4314435%6%7%13%44%
1639
16th to endNight
9%5%25%6%36%5%6%9%38%
1750
September1st to 15thNight
7%4246%46%6%6%9%39%
1735
16th to endNight
8%425%5%3435%7%49%
1815
October1st to 15thNight
9%424314346%54%
1815
16th to endNight
10%5%2441323357%
2130
November1st to 15thNight
11%423323335%56%
2276
16th to endNight
13%6%25%333335%50%
2340
December1st to 15thNight
15%6%36%434345%42%
2340
16th to endNight
21%7%36%5%33345%37%
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
45%26%18%23%4
1612
16th to endDay
42%25%22%21%6%
1875
February1st to 15thDay
44%15%25%18%3
1752
16th to endDay
45%26%17%23%4
1580
March1st to 15thDay
46%39%15%19%5%
1821
16th to endDay
43%311%21%18%2
2154
April1st to 15thDay
39%310%20%19%6%
2151
16th to endDay
37%49%22%22%3
2084
May1st to 15thDay
41%5%12%21%16%3
2136
16th to endDay
38%5%14%24%14%2
2227
June1st to 15thDay
41%6%16%21%13%
2145
16th to endDay
31%6%16%23%17%3
2145
July1st to 15thDay
45%7%16%20%8%1
2006
16th to endDay
43%9%19%19%8%
2128
August1st to 15thDay
39%7%16%21%12%2
1975
16th to endDay
49%6%13%18%9%2
2100
September1st to 15thDay
45%6%13%18%11%5%
1884
16th to endDay
40%310%18%20%5%
1815
October1st to 15thDay
34%37%18%25%9%
1815
16th to endDay
31%1417%33%10%
1739
November1st to 15thDay
33%2419%30%10%
1582
16th to endDay
37%35%17%27%7%
1620
December1st to 15thDay
45%38%18%18%5%
1620
16th to endDay
53%27%19%13%3
1728
January1st to 15thNight
43%27%17%24%4
2327
16th to endNight
44%2420%20%7%
2346
February1st to 15thNight
40%15%23%21%8%
2112
16th to endNight
41%35%19%25%5%
1893
March1st to 15thNight
41%29%19%18%7%
2138
16th to endNight
37%39%24%21%3
2079
April1st to 15thNight
33%210%24%19%9%
1797
16th to endNight
33%48%23%23%7%
1734
May1st to 15thNight
36%412%19%22%3
1485
16th to endNight
29%6%16%27%15%4
1540
June1st to 15thNight
31%5%18%25%16%1
1485
16th to endNight
24%8%19%23%21%3
1485
July1st to 15thNight
35%8%20%21%10%3
1395
16th to endNight
35%9%21%21%10%1
1469
August1st to 15thNight
28%7%19%25%15%3
1628
16th to endNight
41%7%14%20%12%3
1750
September1st to 15thNight
38%8%17%16%13%5%
1735
16th to endNight
33%48%22%22%7%
1815
October1st to 15thNight
31%27%21%24%12%
1815
16th to endNight
31%2313%33%14%
2130
November1st to 15thNight
30%15%19%27%14%
2276
16th to endNight
36%25%18%26%10%
2340
December1st to 15thNight
43%28%19%20%5%
2340
16th to endNight
49%26%19%15%5%
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
25%12%33%20%7%1
90
16th to endDay
21%21%46%35%1
96
February1st to 15thDay
22%18%42%15%1
90
16th to endDay
33%8%44%12%1
81
March1st to 15thDay
23%18%36%15%5%
111
16th to endDay
19%9%30%25%13%1
288
April1st to 15thDay
21%8%25%22%18%2
270
16th to endDay
14%5%21%29%24%4
243
May1st to 15thDay
13%5%23%25%21%10%
228
16th to endDay
13%210%25%27%19%
267
June1st to 15thDay
10%7%25%27%27%
255
16th to endDay
39%23%28%33%
255
July1st to 15thDay
8%18%21%32%26%
245
16th to endDay
8%1216%35%34%
270
August1st to 15thDay
12%5%19%33%27%
253
16th to endDay
15%1217%42%19%
268
September1st to 15thDay
9%37%17%40%22%
255
16th to endDay
17%48%30%31%8%
254
October1st to 15thDay
16%316%27%26%8%
255
16th to endDay
18%415%31%24%4
182
November1st to 15thDay
24%13%22%20%18%1
90
16th to endDay
18%10%37%16%15%1
90
December1st to 15thDay
23%15%34%17%8%
90
16th to endDay
33%13%26%22%31
96
January1st to 15thNight
23%15%26%26%8%
720
16th to endNight
20%13%32%29%4
768
February1st to 15thNight
21%12%29%31%4
704
16th to endNight
21%12%32%30%3
631
March1st to 15thNight
20%12%28%30%7%
720
16th to endNight
15%10%26%30%16%
735
April1st to 15thNight
15%8%28%28%18%1
539
16th to endNight
12%6%23%37%18%1
522
May1st to 15thNight
10%419%34%25%5%
495
16th to endNight
7%112%30%41%6%
515
June1st to 15thNight
5%7%35%40%11%
495
16th to endNight
35%24%51%14%
495
July1st to 15thNight
8%422%49%14%
465
16th to endNight
6%5%21%46%19%
522
August1st to 15thNight
6%1323%50%14%
494
16th to endNight
13%1423%46%10%
525
September1st to 15thNight
10%18%25%42%11%
580
16th to endNight
10%112%32%40%3
657
October1st to 15thNight
12%318%31%29%4
660
16th to endNight
13%6%19%31%25%3
704
November1st to 15thNight
15%5%22%31%21%3
700
16th to endNight
17%11%22%34%13%1
720
December1st to 15thNight
20%10%24%31%11%1
720
16th to endNight
26%11%23%29%8%
768
Page generated at 2017-04-25 06:48:22. Version ac04

Copyright 2017 A. Danko


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