Mount Graham
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mount Graham clear sky chart from 2005-11-05 to 2017-08-12.

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%
15325
34%
46506
28%
15283
73%
15283
49%
22796

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
65%
718
31%
2327
31%
716
71%
716
45%
1146
January16th to endNight
59%
768
35%
2496
32%
768
69%
768
40%
1285
February1st to 15thNight
63%
701
35%
2261
31%
697
75%
697
50%
1042
February16th to endNight
54%
632
40%
1793
29%
632
66%
632
50%
912
March1st to 15thNight
55%
720
40%
1980
26%
720
67%
720
55%
980
March16th to endNight
62%
768
38%
2112
22%
768
74%
768
60%
1004
April1st to 15thNight
52%
641
35%
1900
19%
641
66%
641
52%
883
April16th to endNight
58%
540
44%
1800
32%
540
76%
540
64%
686
May1st to 15thNight
61%
539
36%
1663
24%
539
73%
539
61%
699
May16th to endNight
65%
561
39%
1684
30%
561
74%
561
66%
708
June1st to 15thNight
74%
540
34%
1620
28%
540
77%
540
64%
704
June16th to endNight
77%
540
28%
1620
24%
540
78%
540
55%
764
July1st to 15thNight
72%
510
19%
1530
16%
510
72%
510
32%
918
July16th to endNight
72%
564
15%
1593
14%
531
72%
531
27%
1009
August1st to 15thNight
76%
527
22%
1575
21%
524
76%
524
34%
933
August16th to endNight
77%
525
26%
1732
27%
525
78%
525
34%
973
September1st to 15thNight
69%
603
27%
1758
26%
603
70%
603
32%
1086
September16th to endNight
75%
656
38%
1815
28%
656
81%
656
58%
900
October1st to 15thNight
74%
660
38%
1952
29%
660
80%
660
58%
910
October16th to endNight
76%
704
42%
2112
34%
704
82%
704
67%
905
November1st to 15thNight
71%
700
41%
2100
32%
700
79%
700
63%
916
November16th to endNight
64%
720
39%
2247
32%
720
72%
720
51%
1056
December1st to 15thNight
65%
720
36%
2340
34%
720
71%
720
48%
1104
December16th to endNight
58%
768
34%
2496
30%
768
65%
768
40%
1273

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
4423323446%60%
47455
Night
3313323446%62%
46708
TransparencyDay
22%36%13%28%25%
47150
Night
20%36%14%28%27%
46514
SeeingDay
6%10%25%35%18%3
5164
Night
4317%38%30%5%
15333

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%25%314336%60%
1611
16th to endDay
8%5%23222335%58%
1728
February1st to 15thDay
4423312246%63%
1593
16th to endDay
36%25%423336%57%
1680
March1st to 15thDay
35%23333335%61%
1980
16th to endDay
2312312335%68%
2112
April1st to 15thDay
2312313345%66%
2048
16th to endDay
1212111135%76%
2160
May1st to 15thDay
221222334371%
2284
16th to endDay
211231332472%
2429
June1st to 15thDay
1212212335%71%
2340
16th to endDay
3213323347%64%
2340
July1st to 15thDay
6%4145%36%7%7%9%43%
2340
16th to endDay
7%5%25%6%48%7%8%10%31%
2467
August1st to 15thDay
6%6%36%6%35%7%7%9%36%
2290
16th to endDay
7%5%245%46%6%6%10%40%
2118
September1st to 15thDay
8%6%246%35%5%5%8%42%
1868
16th to endDay
5%212213445%65%
1815
October1st to 15thDay
3313323236%66%
1675
16th to endDay
221311345%72%
1760
November1st to 15thDay
133212245%72%
1759
16th to endDay
241331333467%
1710
December1st to 15thDay
45%23313346%61%
1620
16th to endDay
5%5%2422336%7%56%
1728
January1st to 15thNight
5%423323345%60%
2327
16th to endNight
7%424424345%56%
2496
February1st to 15thNight
3323423436%63%
2256
16th to endNight
342442345%5%59%
1793
March1st to 15thNight
2423213236%64%
1980
16th to endNight
232223335%69%
2112
April1st to 15thNight
232342334466%
1900
16th to endNight
111121122379%
1800
May1st to 15thNight
2211213335%72%
1663
16th to endNight
221111223476%
1684
June1st to 15thNight
3111212235%73%
1620
16th to endNight
121332345%5%65%
1620
July1st to 15thNight
5%4145%46%6%9%8%42%
1620
16th to endNight
4425%6%48%8%11%12%28%
1701
August1st to 15thNight
44346%46%7%8%10%40%
1584
16th to endNight
4424435%6%8%9%44%
1732
September1st to 15thNight
8%5%25%436%5%6%7%44%
1758
16th to endNight
4312312235%69%
1815
October1st to 15thNight
321321322470%
1952
16th to endNight
13122112377%
2112
November1st to 15thNight
222322335%71%
2100
16th to endNight
5%32332233366%
2247
December1st to 15thNight
5%324223446%59%
2340
16th to endNight
45%25%423445%55%
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
25%15%14%33%19%
1612
16th to endDay
26%2416%29%20%
1728
February1st to 15thDay
20%1415%30%26%
1593
16th to endDay
24%2414%32%21%
1680
March1st to 15thDay
22%239%36%25%
1980
16th to endDay
16%1311%41%26%
2112
April1st to 15thDay
16%139%40%28%
2048
16th to endDay
11%119%31%44%
2160
May1st to 15thDay
15%139%30%39%
2284
16th to endDay
13%239%28%42%
2432
June1st to 15thDay
13%22425%52%
2340
16th to endDay
18%249%20%44%
2340
July1st to 15thDay
29%8%13%16%15%15%
2201
16th to endDay
38%9%21%19%9%1
2312
August1st to 15thDay
36%8%12%18%17%6%
2275
16th to endDay
33%7%14%17%17%9%
2118
September1st to 15thDay
35%5%8%17%20%11%
1868
16th to endDay
18%2315%35%24%
1815
October1st to 15thDay
19%15%13%29%30%
1675
16th to endDay
12%2314%35%31%
1760
November1st to 15thDay
13%1214%40%26%
1759
16th to endDay
18%1414%33%26%
1710
December1st to 15thDay
22%2422%30%17%
1620
16th to endDay
24%27%22%32%10%
1728
January1st to 15thNight
24%2414%32%22%
2327
16th to endNight
26%2316%30%19%
2496
February1st to 15thNight
19%2417%28%27%
2267
16th to endNight
21%2315%34%22%
1793
March1st to 15thNight
18%2312%30%32%
1980
16th to endNight
15%1311%38%29%
2112
April1st to 15thNight
18%1310%39%26%
1900
16th to endNight
10%118%32%45%
1800
May1st to 15thNight
12%238%31%42%
1664
16th to endNight
12%211%26%45%
1685
June1st to 15thNight
13%12421%57%
1620
16th to endNight
17%35%8%18%46%
1620
July1st to 15thNight
32%7%11%19%12%15%
1530
16th to endNight
34%10%25%20%6%1
1593
August1st to 15thNight
31%7%15%17%17%10%
1575
16th to endNight
29%7%16%18%18%10%
1732
September1st to 15thNight
34%7%9%19%17%11%
1758
16th to endNight
17%2214%35%27%
1815
October1st to 15thNight
17%15%16%27%31%
1952
16th to endNight
12%1315%29%38%
2112
November1st to 15thNight
13%2315%36%28%
2100
16th to endNight
20%1313%28%31%
2247
December1st to 15thNight
22%1419%33%18%
2340
16th to endNight
26%28%19%31%11%
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
12%13%25%40%7%1
90
16th to endDay
10%7%28%31%17%5%
96
February1st to 15thDay
5%10%25%35%20%3
108
16th to endDay
6%26%34%25%6%
238
March1st to 15thDay
6%19%31%25%15%1
270
16th to endDay
425%30%26%9%3
288
April1st to 15thDay
7%21%34%26%5%4
269
16th to endDay
5%26%36%22%6%2
270
May1st to 15thDay
418%42%24%7%2
288
16th to endDay
39%39%35%11%
330
June1st to 15thDay
25%30%41%16%2
315
16th to endDay
5%118%44%25%3
315
July1st to 15thDay
7%11%51%26%3
305
16th to endDay
7%9%38%32%11%
327
August1st to 15thDay
8%6%38%38%9%
300
16th to endDay
4111%39%37%5%
268
September1st to 15thDay
13%113%45%22%3
255
16th to endDay
8%5%26%35%19%4
255
October1st to 15thDay
5%328%30%20%12%
115
16th to endDay
6%313%43%29%4
96
November1st to 15thDay
5%11%36%27%15%3
90
16th to endDay
23%33%31%11%1
90
December1st to 15thDay
17%23%43%24%
90
16th to endDay
17%11%31%33%5%1
96
January1st to 15thNight
6%318%47%21%2
720
16th to endNight
7%5%18%41%23%3
768
February1st to 15thNight
35%20%39%27%3
704
16th to endNight
37%28%40%18%
632
March1st to 15thNight
38%27%33%23%3
720
16th to endNight
36%23%35%27%2
768
April1st to 15thNight
39%27%39%18%1
641
16th to endNight
19%28%40%16%4
540
May1st to 15thNight
35%26%40%20%3
540
16th to endNight
3422%42%26%1
563
June1st to 15thNight
2216%48%27%2
540
16th to endNight
211%44%36%4
540
July1st to 15thNight
7%6%35%41%7%
510
16th to endNight
5%328%49%12%
564
August1st to 15thNight
4320%51%18%
527
16th to endNight
5%424%52%12%
525
September1st to 15thNight
8%16%28%43%10%
603
16th to endNight
6%110%35%38%8%
656
October1st to 15thNight
3115%40%32%6%
660
16th to endNight
3113%39%33%8%
704
November1st to 15thNight
2219%37%31%7%
700
16th to endNight
6%219%39%27%4
720
December1st to 15thNight
6%318%41%27%3
720
16th to endNight
45%22%42%19%5%
768
Page generated at 2017-08-13 11:16:53. Version ac04

Copyright 2017 A. Danko


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