Chandler Mountain
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Chandler Mountain clear sky chart from 2005-11-06 to 2024-02-15.

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%
23654
23%
79450
17%
23553
57%
23553
26%
48132

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
26%
753
22%
4009
10%
737
41%
737
13%
2433
January11th to 20thNight
30%
758
27%
3915
12%
740
43%
740
13%
2257
January21st to endNight
26%
831
20%
4112
13%
814
42%
814
14%
2662
February1st to 10thNight
30%
760
25%
2280
13%
760
42%
760
24%
1473
February11th to 20thNight
27%
722
21%
2153
10%
718
37%
718
22%
1413
February21st to endNight
24%
592
22%
1776
10%
592
34%
592
21%
1201
March1st to 10thNight
33%
720
24%
2160
13%
720
41%
720
26%
1344
March11th to 20thNight
32%
720
19%
2037
10%
720
40%
720
25%
1340
March21st to endNight
37%
744
24%
2130
13%
744
46%
744
27%
1359
April1st to 10thNight
42%
540
26%
1800
20%
540
52%
540
29%
1025
April11th to 20thNight
40%
533
28%
1775
18%
533
54%
533
29%
1025
April21st to endNight
50%
540
27%
1791
21%
540
60%
540
32%
993
May1st to 10thNight
56%
540
26%
1620
17%
540
64%
540
37%
920
May11th to 20thNight
57%
531
20%
1592
14%
531
61%
531
30%
976
May21st to endNight
70%
582
22%
1744
20%
582
72%
582
36%
1030
June1st to 10thNight
69%
540
18%
1620
17%
540
70%
540
30%
1006
June11th to 20thNight
76%
540
18%
1620
15%
540
79%
540
42%
884
June21st to endNight
75%
540
19%
1620
17%
540
76%
540
36%
947
July1st to 10thNight
74%
525
15%
1575
14%
525
75%
525
29%
1009
July11th to 20thNight
78%
522
17%
1566
16%
522
79%
522
34%
948
July21st to endNight
73%
591
17%
1672
17%
558
75%
558
29%
1090
August1st to 10thNight
80%
537
18%
1761
20%
534
80%
534
36%
972
August11th to 20thNight
73%
534
17%
1776
20%
534
74%
534
28%
1103
August21st to endNight
67%
594
21%
1980
25%
594
67%
594
25%
1275
September1st to 10thNight
70%
588
22%
1848
24%
588
71%
588
31%
1132
September11th to 20thNight
62%
720
23%
1980
19%
720
64%
720
31%
1282
September21st to endNight
65%
720
31%
1980
22%
720
70%
720
41%
1136
October1st to 10thNight
62%
720
34%
1980
25%
720
68%
720
44%
1109
October11th to 20thNight
54%
720
34%
1980
24%
720
63%
720
38%
1161
October21st to endNight
51%
792
30%
2492
26%
792
59%
792
31%
1445
November1st to 10thNight
54%
740
28%
2406
25%
740
62%
740
35%
1304
November11th to 20thNight
45%
760
30%
2470
21%
760
58%
760
33%
1352
November21st to endNight
43%
760
27%
2470
19%
760
55%
760
27%
1474
December1st to 10thNight
34%
760
23%
2470
14%
760
46%
760
20%
1613
December11th to 20thNight
34%
759
25%
2904
16%
758
44%
758
21%
1723
December21st to endNight
32%
826
15%
4386
15%
817
41%
817
12%
2716

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
13%6%35%5%35%5%6%7%41%
78811
Night
13%6%25%5%3445%7%45%
80275
TransparencyDay
41%5%10%20%19%4
78534
Night
38%5%10%21%21%6%
80071
SeeingDay
18%7%22%23%20%10%
13581
Night
16%7%20%30%23%5%
23681

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 10thDay
17%11%36%5%3445%5%36%
2836
11th to 20thDay
17%6%36%42333448%
2876
21st to endDay
25%9%23223235%41%
3476
February1st to 10thDay
20%8%35%42445%7%38%
1900
11th to 20thDay
22%8%35%423445%39%
1788
21st to endDay
21%8%36%5%33445%37%
1480
March1st to 10thDay
14%7%36%5%34446%44%
1800
11th to 20thDay
18%8%37%5%345%5%6%36%
1921
21st to endDay
14%7%36%6%45%5%5%8%38%
2240
April1st to 10thDay
12%5%35%435%5%5%8%46%
2160
11th to 20thDay
14%6%25%6%34445%47%
2134
21st to endDay
9%5%35%5%35%5%5%9%47%
2168
May1st to 10thDay
11%425%5%36%5%5%8%46%
2340
11th to 20thDay
10%5%36%6%45%6%6%9%42%
2301
21st to endDay
10%5%35%6%46%6%6%9%41%
2531
June1st to 10thDay
11%5%37%8%47%6%7%10%32%
2340
11th to 20thDay
5%425%5%5%6%6%9%10%43%
2340
21st to endDay
6%5%35%6%47%6%8%10%38%
2340
July1st to 10thDay
10%6%36%8%5%7%7%7%11%30%
2340
11th to 20thDay
8%5%36%7%49%8%9%11%30%
2340
21st to endDay
6%5%36%8%6%8%8%9%11%31%
2547
August1st to 10thDay
8%5%17%8%47%8%8%12%31%
2162
11th to 20thDay
10%6%37%7%5%7%6%7%10%31%
2125
21st to endDay
12%7%37%7%46%6%5%9%34%
2376
September1st to 10thDay
10%5%25%6%46%6%7%8%40%
2093
11th to 20thDay
14%5%16%6%36%46%8%42%
1980
21st to endDay
11%6%245%34345%51%
1980
October1st to 10thDay
11%5%235%2445%5%53%
1980
11th to 20thDay
10%5%245%2345%7%53%
1980
21st to endDay
14%5%2343435%5%53%
1858
November1st to 10thDay
13%5%25%424235%54%
1672
11th to 20thDay
12%5%25%5%23447%51%
1710
21st to endDay
16%6%25%4345%5%6%45%
1710
December1st to 10thDay
20%9%25%4335%5%6%39%
1710
11th to 20thDay
17%8%25%6%3444442%
2153
21st to endDay
19%8%46%6%3445%5%35%
3124
January1st to 10thNight
18%11%2443345%5%40%
4109
11th to 20thNight
17%8%45%42435%5%43%
4079
21st to endNight
22%12%3443333439%
4180
February1st to 10thNight
16%7%27%5%33446%42%
2280
11th to 20thNight
21%7%35%5%23335%43%
2153
21st to endNight
20%6%35%5%345%5%6%37%
1776
March1st to 10thNight
15%6%36%434437%45%
2160
11th to 20thNight
15%6%37%5%345%5%6%41%
2037
21st to endNight
14%6%36%6%2445%7%44%
2130
April1st to 10thNight
11%5%25%435%5%6%7%48%
1800
11th to 20thNight
14%6%25%323447%50%
1775
21st to endNight
9%425%5%235%5%8%51%
1791
May1st to 10thNight
9%3235%3445%8%53%
1620
11th to 20thNight
9%5%26%5%45%5%6%9%45%
1592
21st to endNight
7%5%25%435%7%7%10%46%
1744
June1st to 10thNight
6%425%6%5%6%6%8%11%40%
1620
11th to 20thNight
33236%36%47%11%52%
1620
21st to endNight
5%425%5%25%6%8%11%48%
1620
July1st to 10thNight
8%326%6%5%7%8%8%12%37%
1620
11th to 20thNight
6%4245%36%6%6%12%44%
1620
21st to endNight
5%5%26%6%48%6%8%11%39%
1771
August1st to 10thNight
4325%5%36%7%8%14%43%
1772
11th to 20thNight
8%5%35%5%46%6%7%9%42%
1776
21st to endNight
11%6%36%6%45%5%6%8%40%
1980
September1st to 10thNight
8%4246%46%6%6%8%45%
1848
11th to 20thNight
11%5%25%6%45%45%8%45%
1980
21st to endNight
7%5%245%3346%8%54%
1980
October1st to 10thNight
9%424323346%60%
1980
11th to 20thNight
11%5%2443445%6%53%
1980
21st to endNight
14%6%2442433454%
2492
November1st to 10thNight
12%324423445%57%
2406
11th to 20thNight
13%6%24333346%54%
2470
21st to endNight
14%6%25%434446%47%
2470
December1st to 10thNight
19%7%36%5%35%446%39%
2470
11th to 20thNight
17%7%35%433345%47%
3042
21st to endNight
18%7%36%6%345%6%7%33%
4532

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
50%35%17%22%4
2837
11th to 20thDay
40%45%24%24%3
2876
21st to endDay
47%26%19%21%5%
3476
February1st to 10thDay
47%26%22%19%4
1900
11th to 20thDay
48%2420%19%6%
1798
21st to endDay
49%36%13%23%6%
1480
March1st to 10thDay
42%48%16%22%10%
1800
11th to 20thDay
48%5%10%15%17%5%
1921
21st to endDay
44%49%21%19%2
2240
April1st to 10thDay
37%312%22%18%7%
2160
11th to 20thDay
39%46%20%24%7%
2134
21st to endDay
33%5%9%27%24%3
2168
May1st to 10thDay
36%6%10%23%21%4
2340
11th to 20thDay
39%6%15%24%16%1
2305
21st to endDay
37%6%12%25%17%2
2531
June1st to 10thDay
44%7%15%18%16%1
2340
11th to 20thDay
32%6%18%26%16%2
2340
21st to endDay
37%8%17%23%11%3
2340
July1st to 10thDay
43%9%18%19%10%1
2275
11th to 20thDay
42%9%20%19%8%1
2271
21st to endDay
40%10%19%21%9%
2405
August1st to 10thDay
40%9%19%25%7%1
2149
11th to 20thDay
44%8%16%19%11%2
2125
21st to endDay
45%7%14%20%11%4
2376
September1st to 10thDay
39%6%15%18%16%6%
2093
11th to 20thDay
40%5%12%19%20%4
1980
21st to endDay
36%410%21%22%8%
1980
October1st to 10thDay
33%47%21%27%8%
1980
11th to 20thDay
30%37%24%28%9%
1980
21st to endDay
34%3418%32%10%
1858
November1st to 10thDay
35%25%19%28%11%
1672
11th to 20thDay
34%37%20%26%10%
1710
21st to endDay
39%46%19%26%7%
1710
December1st to 10thDay
46%38%16%21%5%
1710
11th to 20thDay
46%25%19%21%6%
2150
21st to endDay
49%47%19%19%2
3124
January1st to 10thNight
47%36%18%24%3
4109
11th to 20thNight
43%35%22%19%7%
4079
21st to endNight
51%2317%23%5%
4180
February1st to 10thNight
44%25%20%21%7%
2280
11th to 20thNight
47%25%19%20%8%
2154
21st to endNight
46%5%7%14%20%8%
1776
March1st to 10thNight
41%37%17%22%11%
2160
11th to 20thNight
42%5%11%18%19%6%
2037
21st to endNight
40%48%25%19%4
2130
April1st to 10thNight
34%411%23%20%7%
1800
11th to 20thNight
36%35%22%22%12%
1775
21st to endNight
32%410%27%22%5%
1791
May1st to 10thNight
30%412%23%27%4
1620
11th to 20thNight
36%6%17%22%17%2
1593
21st to endNight
30%7%14%27%17%4
1745
June1st to 10thNight
36%7%16%22%17%2
1620
11th to 20thNight
24%7%22%25%19%3
1620
21st to endNight
29%8%19%23%17%4
1620
July1st to 10thNight
36%10%21%19%11%3
1575
11th to 20thNight
30%10%24%23%11%3
1566
21st to endNight
35%11%20%23%10%1
1672
August1st to 10thNight
28%7%24%30%9%1
1761
11th to 20thNight
36%9%21%18%14%3
1776
21st to endNight
41%7%14%21%12%4
1980
September1st to 10thNight
33%9%17%19%16%5%
1848
11th to 20thNight
38%7%10%19%21%5%
1980
21st to endNight
28%5%9%23%25%9%
1980
October1st to 10thNight
28%37%25%26%11%
1980
11th to 20thNight
32%37%21%26%11%
1980
21st to endNight
35%3416%31%11%
2492
November1st to 10thNight
31%37%19%26%14%
2406
11th to 20thNight
33%25%20%28%12%
2470
21st to endNight
38%36%21%24%8%
2470
December1st to 10thNight
46%47%18%20%4
2470
11th to 20thNight
41%27%17%28%5%
3044
21st to endNight
47%46%21%19%2
4532

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
30%17%34%16%3
270
11th to 20thDay
31%16%31%15%6%1
270
21st to endDay
28%18%39%11%41
297
February1st to 10thDay
30%17%32%17%5%
270
11th to 20thDay
38%17%34%10%1
252
21st to endDay
38%14%40%7%1
198
March1st to 10thDay
28%17%36%13%41
240
11th to 20thDay
24%16%34%17%7%1
361
21st to endDay
22%16%33%22%7%
462
April1st to 10thDay
22%12%29%23%12%2
420
11th to 20thDay
22%13%28%23%13%1
412
21st to endDay
15%10%31%25%16%2
420
May1st to 10thDay
15%8%29%24%19%5%
423
11th to 20thDay
13%423%31%18%11%
447
21st to endDay
14%318%26%26%14%
485
June1st to 10thDay
15%115%29%25%16%
450
11th to 20thDay
8%413%26%27%23%
450
21st to endDay
11%212%25%32%18%
450
July1st to 10thDay
11%7%25%33%24%
445
11th to 20thDay
9%16%21%33%30%
444
21st to endDay
8%27%20%39%25%
488
August1st to 10thDay
12%18%23%31%25%
446
11th to 20thDay
13%15%26%38%17%
439
21st to endDay
17%6%23%33%20%
495
September1st to 10thDay
10%28%27%39%14%
450
11th to 20thDay
16%312%25%30%15%
450
21st to endDay
12%314%31%31%8%
450
October1st to 10thDay
14%322%28%23%9%
450
11th to 20thDay
13%8%24%30%22%3
450
21st to endDay
21%9%23%33%13%2
350
November1st to 10thDay
20%6%31%26%15%3
270
11th to 20thDay
18%12%40%24%6%
270
21st to endDay
17%14%35%23%10%1
270
December1st to 10thDay
33%13%30%17%6%
270
11th to 20thDay
25%16%32%19%6%2
270
21st to endDay
31%14%29%21%5%
297
January1st to 10thNight
25%15%28%26%6%
760
11th to 20thNight
22%15%27%28%8%
760
21st to endNight
22%14%34%28%3
836
February1st to 10thNight
23%11%29%31%6%
760
11th to 20thNight
28%13%28%28%3
722
21st to endNight
25%13%34%26%3
592
March1st to 10thNight
19%13%30%32%6%
720
11th to 20thNight
19%11%31%27%10%1
720
21st to endNight
18%12%27%31%12%
744
April1st to 10thNight
15%10%28%31%15%1
540
11th to 20thNight
18%8%29%27%17%1
533
21st to endNight
12%7%23%39%17%2
540
May1st to 10thNight
10%5%23%34%25%3
540
11th to 20thNight
12%316%34%28%7%
531
21st to endNight
10%18%32%41%7%
584
June1st to 10thNight
9%9%37%39%6%
540
11th to 20thNight
5%18%29%39%17%
540
21st to endNight
9%6%30%45%10%
540
July1st to 10thNight
9%421%48%18%
525
11th to 20thNight
6%1320%50%20%
522
21st to endNight
7%16%24%46%17%
591
August1st to 10thNight
6%1327%49%15%
537
11th to 20thNight
11%425%47%12%
534
21st to endNight
15%1427%42%11%
594
September1st to 10thNight
11%16%27%45%11%
588
11th to 20thNight
13%111%26%42%6%
720
21st to endNight
11%213%29%42%3
720
October1st to 10thNight
11%318%32%29%7%
720
11th to 20thNight
13%6%20%33%25%2
720
21st to endNight
17%7%18%33%22%2
792
November1st to 10thNight
14%6%20%35%23%3
740
11th to 20thNight
16%7%28%36%12%1
760
21st to endNight
19%9%23%35%13%1
760
December1st to 10thNight
24%10%25%30%10%1
760
11th to 20thNight
23%10%27%29%10%1
760
21st to endNight
27%10%23%32%7%
836
Page generated at 2024-02-12 05:35:30. Version ac07

Copyright 2024 Attilla Danko


Chandler Mountain Clear Sky Chart |Charts Home