Tombstone Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tombstone Observatory clear sky chart from 2005-11-05 to 2017-09-24.

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
74%
15511
35%
46960
30%
15471
79%
15471
52%
22554

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
72%
718
32%
2327
33%
716
77%
716
52%
1072
January16th to endNight
66%
768
35%
2496
34%
768
74%
768
43%
1253
February1st to 15thNight
71%
698
37%
2232
34%
696
81%
696
55%
1004
February16th to endNight
62%
632
41%
1789
33%
632
71%
632
54%
891
March1st to 15thNight
64%
720
41%
1980
31%
720
73%
720
60%
950
March16th to endNight
67%
768
39%
2112
25%
768
78%
768
63%
993
April1st to 15thNight
65%
653
37%
1912
26%
653
74%
653
59%
878
April16th to endNight
67%
540
44%
1800
37%
540
81%
540
68%
676
May1st to 15thNight
69%
539
38%
1679
29%
539
78%
539
70%
663
May16th to endNight
77%
561
42%
1684
36%
561
83%
561
74%
667
June1st to 15thNight
83%
540
35%
1620
31%
540
85%
540
67%
685
June16th to endNight
85%
540
29%
1620
26%
540
85%
540
54%
764
July1st to 15thNight
79%
510
15%
1530
14%
510
80%
510
34%
900
July16th to endNight
76%
564
13%
1593
11%
531
76%
531
25%
1055
August1st to 15thNight
79%
539
19%
1611
19%
536
79%
536
32%
968
August16th to endNight
81%
573
25%
1897
28%
573
81%
573
33%
1093
September1st to 15thNight
76%
684
24%
1944
22%
684
76%
684
36%
1166
September16th to endNight
84%
692
41%
1914
31%
692
88%
692
64%
905
October1st to 15thNight
81%
660
40%
1944
32%
660
86%
660
64%
868
October16th to endNight
86%
704
42%
2112
37%
704
90%
704
69%
891
November1st to 15thNight
80%
700
43%
2100
38%
700
85%
700
69%
880
November16th to endNight
70%
720
40%
2228
35%
720
76%
720
53%
1051
December1st to 15thNight
73%
720
38%
2340
38%
720
77%
720
52%
1063
December16th to endNight
67%
768
35%
2496
35%
768
72%
768
46%
1218

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
4213323346%63%
47954
Night
3212213346%66%
47165
TransparencyDay
21%46%12%26%28%
47649
Night
18%37%14%28%26%
46971
SeeingDay
6%7%18%28%25%12%
5371
Night
4113%40%34%4
15522

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
4312313346%64%
1611
16th to endDay
6%423214247%59%
1728
February1st to 15thDay
5%21222223470%
1619
16th to endDay
5%423213335%65%
1684
March1st to 15thDay
423213245%68%
1980
16th to endDay
221221223473%
2112
April1st to 15thDay
313212345%71%
2034
16th to endDay
21111111383%
2160
May1st to 15thDay
11121123479%
2268
16th to endDay
11111222479%
2429
June1st to 15thDay
21121322477%
2340
16th to endDay
2213425%446%62%
2340
July1st to 15thDay
6%4146%46%7%8%10%38%
2340
16th to endDay
9%426%7%5%8%7%8%11%27%
2467
August1st to 15thDay
9%425%6%47%6%6%9%37%
2340
16th to endDay
6%2136%36%6%8%8%45%
2304
September1st to 15thDay
8%325%6%25%5%6%7%45%
2013
16th to endDay
421231334468%
1904
October1st to 15thDay
311221233473%
1684
16th to endDay
211112235%76%
1760
November1st to 15thDay
2111111336%76%
1759
16th to endDay
5%21221323469%
1730
December1st to 15thDay
6%21212335%6%65%
1620
16th to endDay
6%31331235%6%62%
1728
January1st to 15thNight
5%312212336%66%
2327
16th to endNight
7%32331435%6%59%
2496
February1st to 15thNight
2312213336%69%
2230
16th to endNight
3314313345%66%
1789
March1st to 15thNight
3213212245%71%
1980
16th to endNight
211221233474%
2112
April1st to 15thNight
221222233471%
1912
16th to endNight
11111122382%
1800
May1st to 15thNight
1111235%79%
1679
16th to endNight
1111222483%
1684
June1st to 15thNight
311112235%77%
1620
16th to endNight
211233346%6%65%
1620
July1st to 15thNight
33145%36%5%9%14%42%
1620
16th to endNight
4326%7%48%7%9%16%30%
1701
August1st to 15thNight
3315%5%45%7%7%10%46%
1620
16th to endNight
6%314435%6%7%11%46%
1897
September1st to 15thNight
8%424325%5%6%8%49%
1944
16th to endNight
221212336%73%
1914
October1st to 15thNight
212212345%75%
1944
16th to endNight
11222225%78%
2112
November1st to 15thNight
111112236%77%
2100
16th to endNight
5%312312235%69%
2228
December1st to 15thNight
6%212112346%66%
2340
16th to endNight
6%41331234463%
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
20%37%13%33%22%
1612
16th to endDay
24%2416%29%22%
1728
February1st to 15thDay
18%1312%31%31%
1619
16th to endDay
22%2312%33%26%
1684
March1st to 15thDay
17%238%36%32%
1980
16th to endDay
15%138%35%36%
2112
April1st to 15thDay
14%227%38%35%
2034
16th to endDay
9%116%29%51%
2160
May1st to 15thDay
10%127%25%51%
2268
16th to endDay
10%136%27%50%
2432
June1st to 15thDay
12%225%21%56%
2340
16th to endDay
21%45%7%21%39%
2340
July1st to 15thDay
35%10%16%14%13%9%
2201
16th to endDay
46%14%18%13%5%1
2312
August1st to 15thDay
41%10%15%16%14%3
2325
16th to endDay
33%9%15%17%14%10%
2304
September1st to 15thDay
35%7%11%16%18%10%
2013
16th to endDay
18%26%15%33%22%
1904
October1st to 15thDay
15%27%14%27%33%
1684
16th to endDay
11%2312%30%38%
1760
November1st to 15thDay
11%1314%36%32%
1759
16th to endDay
19%1313%31%31%
1730
December1st to 15thDay
19%25%17%35%18%
1620
16th to endDay
21%27%20%32%14%
1728
January1st to 15thNight
18%37%12%32%25%
2327
16th to endNight
25%3416%31%19%
2496
February1st to 15thNight
16%2414%30%30%
2241
16th to endNight
19%2412%35%24%
1789
March1st to 15thNight
16%1312%32%33%
1980
16th to endNight
14%1410%36%31%
2112
April1st to 15thNight
16%1310%38%29%
1912
16th to endNight
9%129%29%47%
1800
May1st to 15thNight
9%147%31%45%
1680
16th to endNight
7%239%32%44%
1685
June1st to 15thNight
11%22425%52%
1620
16th to endNight
17%35%8%24%39%
1620
July1st to 15thNight
27%11%21%19%11%9%
1530
16th to endNight
34%14%29%15%31
1593
August1st to 15thNight
29%10%17%19%17%3
1611
16th to endNight
28%9%17%17%16%9%
1897
September1st to 15thNight
29%8%14%19%18%9%
1944
16th to endNight
14%27%17%38%20%
1914
October1st to 15thNight
12%37%18%26%30%
1944
16th to endNight
10%1414%27%40%
2112
November1st to 15thNight
10%1417%35%30%
2100
16th to endNight
19%2313%29%31%
2228
December1st to 15thNight
18%35%20%33%19%
2340
16th to endNight
23%27%19%32%14%
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
8%7%18%36%27%
90
16th to endDay
7%5%16%39%22%8%
96
February1st to 15thDay
210%16%27%38%5%
134
16th to endDay
6%24%29%20%15%3
238
March1st to 15thDay
5%14%28%22%18%8%
270
16th to endDay
419%27%22%15%9%
288
April1st to 15thDay
6%15%30%26%17%4
269
16th to endDay
320%31%26%12%5%
270
May1st to 15thDay
214%34%27%13%7%
288
16th to endDay
38%26%39%16%6%
330
June1st to 15thDay
4322%37%19%12%
315
16th to endDay
2112%35%32%14%
315
July1st to 15thDay
8%18%31%33%15%
305
16th to endDay
8%18%25%29%25%
327
August1st to 15thDay
10%5%24%33%26%
315
16th to endDay
6%421%43%24%
332
September1st to 15thDay
11%28%31%32%14%
315
16th to endDay
5%319%27%32%10%
288
October1st to 15thDay
2216%27%30%20%
124
16th to endDay
5%9%18%39%27%
96
November1st to 15thDay
210%15%32%27%12%
90
16th to endDay
6%7%26%31%25%2
90
December1st to 15thDay
5%316%25%33%15%
90
16th to endDay
16%7%16%33%25%1
96
January1st to 15thNight
5%114%48%26%2
720
16th to endNight
7%217%46%23%1
768
February1st to 15thNight
2218%46%26%4
704
16th to endNight
3225%49%17%
632
March1st to 15thNight
3324%42%24%2
720
16th to endNight
2222%42%26%2
768
April1st to 15thNight
2323%50%18%1
653
16th to endNight
2323%51%17%1
540
May1st to 15thNight
1223%46%25%
540
16th to endNight
1116%47%30%1
563
June1st to 15thNight
318%52%32%1
540
16th to endNight
25%40%49%1
540
July1st to 15thNight
4325%59%6%
510
16th to endNight
3319%60%13%
564
August1st to 15thNight
3115%63%15%
539
16th to endNight
5%216%60%13%
573
September1st to 15thNight
7%5%20%57%8%
684
16th to endNight
37%35%46%5%
692
October1st to 15thNight
112%46%33%5%
660
16th to endNight
118%42%40%7%
704
November1st to 15thNight
212%42%35%6%
700
16th to endNight
7%114%40%30%5%
720
December1st to 15thNight
6%214%44%27%4
720
16th to endNight
7%315%46%22%4
768
Page generated at 2017-09-25 06:02:23. Version ac04

Copyright 2017 A. Danko


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