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 2018-02-22.

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%
16080
35%
48843
28%
16038
74%
16038
49%
23924

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%
778
31%
2522
31%
776
71%
776
44%
1246
January16th to endNight
61%
832
35%
2704
33%
832
70%
832
42%
1362
February1st to 15thNight
64%
761
35%
2454
31%
757
75%
757
50%
1128
February16th to endNight
53%
660
39%
1875
29%
660
64%
660
48%
975
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
77%
539
22%
1611
21%
536
77%
536
34%
948
August16th to endNight
77%
573
28%
1890
30%
573
78%
573
35%
1051
September1st to 15thNight
70%
658
26%
1918
25%
658
71%
658
33%
1172
September16th to endNight
76%
716
40%
1980
30%
716
81%
716
57%
983
October1st to 15thNight
76%
720
37%
2130
29%
720
81%
720
60%
981
October16th to endNight
76%
768
44%
2304
35%
768
83%
768
66%
990
November1st to 15thNight
71%
760
40%
2280
32%
760
79%
760
61%
1009
November16th to endNight
65%
780
41%
2434
35%
780
73%
780
52%
1133
December1st to 15thNight
64%
780
36%
2535
33%
780
70%
780
46%
1221
December16th to endNight
59%
832
35%
2704
32%
832
66%
832
41%
1370

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%
49396
Night
3313323446%62%
49045
TransparencyDay
22%36%13%28%25%
49091
Night
20%35%14%28%26%
48851
SeeingDay
6%9%25%35%19%4
5807
Night
4317%37%30%5%
16088

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%324336%58%
1746
16th to endDay
7%5%23222335%60%
1872
February1st to 15thDay
4423312246%63%
1730
16th to endDay
45%25%424335%56%
1744
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%5%36%6%35%7%8%9%36%
2340
16th to endDay
7%5%245%46%6%7%9%42%
2311
September1st to 15thDay
8%6%246%35%5%5%8%43%
2038
16th to endDay
4212213445%65%
1980
October1st to 15thDay
2213323235%68%
1827
16th to endDay
2211312345%72%
1920
November1st to 15thDay
133213245%70%
1909
16th to endDay
241331233468%
1852
December1st to 15thDay
45%24323346%59%
1755
16th to endDay
5%5%2432335%6%56%
1872
January1st to 15thNight
5%424323445%59%
2522
16th to endNight
6%424423345%58%
2704
February1st to 15thNight
3323423435%64%
2449
16th to endNight
45%2442345%5%57%
1875
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
44245%46%7%8%10%40%
1620
16th to endNight
4424435%6%8%9%45%
1890
September1st to 15thNight
8%5%25%435%5%6%7%45%
1918
16th to endNight
3212312235%69%
1980
October1st to 15thNight
221321322471%
2130
16th to endNight
13122112377%
2304
November1st to 15thNight
222322336%69%
2280
16th to endNight
432332233466%
2434
December1st to 15thNight
6%424323346%58%
2535
16th to endNight
45%25%423445%56%
2704

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
26%15%14%33%18%
1747
16th to endDay
25%2415%31%21%
1872
February1st to 15thDay
21%1414%30%27%
1730
16th to endDay
26%25%13%31%21%
1744
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%
2325
16th to endDay
32%7%13%17%18%10%
2311
September1st to 15thDay
34%5%8%17%21%13%
2038
16th to endDay
17%2316%35%24%
1980
October1st to 15thDay
17%1413%30%31%
1827
16th to endDay
12%2314%35%31%
1920
November1st to 15thDay
14%2316%38%25%
1909
16th to endDay
18%1313%35%27%
1852
December1st to 15thDay
24%2421%30%16%
1755
16th to endDay
24%27%21%32%10%
1872
January1st to 15thNight
24%2414%32%20%
2522
16th to endNight
25%2315%32%20%
2704
February1st to 15thNight
19%2416%28%28%
2460
16th to endNight
22%2315%33%21%
1875
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
30%8%16%18%16%9%
1611
16th to endNight
28%7%15%18%18%11%
1890
September1st to 15thNight
33%6%9%19%17%12%
1918
16th to endNight
17%2214%35%27%
1980
October1st to 15thNight
16%15%14%28%33%
2130
16th to endNight
12%1315%29%38%
2304
November1st to 15thNight
14%2417%35%26%
2280
16th to endNight
19%1313%29%31%
2434
December1st to 15thNight
23%1418%34%17%
2535
16th to endNight
26%27%18%31%13%
2704

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
10%10%25%40%12%
135
16th to endDay
6%7%32%27%20%4
144
February1st to 15thDay
6%8%24%30%24%5%
155
16th to endDay
8%25%34%25%6%
264
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
7%6%38%38%8%
315
16th to endDay
5%110%36%38%7%
332
September1st to 15thDay
12%113%45%23%3
315
16th to endDay
6%6%28%35%18%4
315
October1st to 15thDay
3327%34%20%11%
162
16th to endDay
4214%40%29%7%
144
November1st to 15thDay
47%35%32%17%2
135
16th to endDay
15%28%32%20%2
135
December1st to 15thDay
27%27%42%19%
135
16th to endDay
15%8%23%33%16%2
144
January1st to 15thNight
6%317%46%22%2
780
16th to endNight
7%5%18%41%24%3
832
February1st to 15thNight
35%19%38%28%4
764
16th to endNight
5%7%28%40%18%
660
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%52%17%
539
16th to endNight
6%322%53%13%
573
September1st to 15thNight
8%16%28%44%9%
658
16th to endNight
6%10%36%37%7%
716
October1st to 15thNight
2114%41%33%6%
720
16th to endNight
2113%38%34%8%
768
November1st to 15thNight
2217%38%31%6%
760
16th to endNight
6%219%38%28%5%
780
December1st to 15thNight
6%318%42%26%2
780
16th to endNight
5%5%21%41%20%5%
832
Page generated at 2018-02-23 09:21:31. Version ac04

Copyright 2018 A. Danko


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