Tombstone Sky Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tombstone Sky Observatory clear sky chart from 2005-11-06 to 2024-01-16.

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
71%
23844
34%
74321
29%
23797
77%
23797
50%
35854

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
68%
758
33%
2457
32%
756
75%
756
49%
1167
January11th to 20thNight
69%
744
37%
2417
36%
744
77%
744
54%
1091
January21st to endNight
61%
792
37%
2574
33%
792
71%
792
43%
1283
February1st to 10thNight
69%
720
36%
2340
34%
720
78%
720
53%
1065
February11th to 20thNight
58%
700
34%
2100
26%
700
69%
700
48%
1050
February21st to endNight
53%
592
41%
1628
29%
592
65%
592
53%
832
March1st to 10thNight
55%
720
39%
1980
25%
720
68%
720
55%
996
March11th to 20thNight
63%
720
38%
1980
25%
720
73%
720
60%
949
March21st to endNight
61%
792
38%
2178
23%
792
73%
792
58%
1072
April1st to 10thNight
67%
714
39%
1974
25%
714
77%
714
66%
899
April11th to 20thNight
59%
533
42%
1777
32%
533
75%
533
62%
699
April21st to endNight
66%
540
45%
1800
38%
540
79%
540
68%
678
May1st to 10thNight
66%
540
39%
1710
30%
540
78%
540
65%
692
May11th to 20thNight
75%
531
41%
1594
35%
531
80%
531
68%
660
May21st to endNight
76%
582
44%
1746
37%
582
82%
582
77%
677
June1st to 10thNight
82%
540
36%
1620
32%
540
83%
540
65%
695
June11th to 20thNight
82%
540
37%
1620
32%
540
84%
540
71%
662
June21st to endNight
81%
540
26%
1620
24%
540
81%
540
48%
814
July1st to 10thNight
79%
525
19%
1575
16%
525
79%
525
37%
887
July11th to 20thNight
76%
522
12%
1566
10%
522
76%
522
24%
1043
July21st to endNight
70%
591
10%
1674
9%
558
69%
558
21%
1164
August1st to 10thNight
78%
537
15%
1602
14%
534
78%
534
30%
989
August11th to 20thNight
78%
534
20%
1670
21%
534
78%
534
31%
1002
August21st to endNight
78%
594
23%
1980
24%
594
78%
594
28%
1207
September1st to 10thNight
73%
667
23%
1927
22%
667
73%
667
33%
1172
September11th to 20thNight
84%
720
38%
1980
32%
720
86%
720
57%
1005
September21st to endNight
81%
720
35%
1980
26%
720
86%
720
59%
979
October1st to 10thNight
81%
720
37%
2101
30%
720
84%
720
60%
976
October11th to 20thNight
80%
720
41%
2160
33%
720
85%
720
66%
932
October21st to endNight
81%
792
44%
2376
36%
792
87%
792
72%
977
November1st to 10thNight
80%
740
45%
2220
38%
740
85%
740
69%
933
November11th to 20thNight
78%
760
43%
2280
36%
760
84%
760
62%
1013
November21st to endNight
61%
760
39%
2389
32%
760
70%
760
48%
1146
December1st to 10thNight
68%
760
37%
2470
36%
760
73%
760
48%
1169
December11th to 20thNight
63%
759
33%
2931
31%
758
73%
758
38%
1473
December21st to endNight
64%
825
23%
4325
34%
817
70%
817
33%
1806

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
431342445%6%63%
75010
Night
431332345%7%65%
74834
TransparencyDay
20%5%7%12%26%30%
74737
Night
19%5%7%14%27%28%
74629
SeeingDay
5%7%18%29%27%14%
13683
Night
4216%43%31%4
23864

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 10thDay
5%423324447%62%
1708
11th to 20thDay
6%313324346%64%
1665
21st to endDay
6%423323347%64%
1782
February1st to 10thDay
5%32332334468%
1620
11th to 20thDay
7%42342334464%
1744
21st to endDay
6%5%2321233469%
1628
March1st to 10thDay
6%31432345%7%62%
1980
11th to 20thDay
4323323246%70%
1980
21st to endDay
3212323345%71%
2178
April1st to 10thDay
223223446%71%
1984
11th to 20thDay
321221223380%
2131
21st to endDay
21112222482%
2160
May1st to 10thDay
221222222479%
2245
11th to 20thDay
2112222245%76%
2301
21st to endDay
211121122483%
2530
June1st to 10thDay
2212213346%73%
2340
11th to 20thDay
1112223335%77%
2340
21st to endDay
43245%35%6%5%8%56%
2340
July1st to 10thDay
6%4146%46%7%8%9%44%
2340
11th to 20thDay
6%426%8%5%8%8%9%11%33%
2340
21st to endDay
9%6%36%7%5%8%7%9%12%29%
2545
August1st to 10thDay
7%426%6%47%6%8%10%39%
2328
11th to 20thDay
6%425%7%46%7%7%10%41%
2229
21st to endDay
6%3146%46%8%8%9%44%
2376
September1st to 10thDay
8%425%7%35%6%6%7%46%
2028
11th to 20thDay
4224425%45%6%62%
1980
21st to endDay
321342345%5%68%
1980
October1st to 10thDay
211331335%5%72%
1858
11th to 20thDay
321122233477%
1800
21st to endDay
212213345%76%
1980
November1st to 10thDay
1112223347%74%
1859
11th to 20thDay
3212223445%71%
1900
21st to endDay
6%42442445%6%62%
1786
December1st to 10thDay
7%31232435%7%62%
1710
11th to 20thDay
6%6%35%43346%7%54%
2169
21st to endDay
6%41343345%6%62%
3146
January1st to 10thNight
6%414323447%63%
2457
11th to 20thNight
6%322312346%67%
2417
21st to endNight
7%42332445%5%61%
2574
February1st to 10thNight
4413223445%69%
2340
11th to 20thNight
6%5%24323436%63%
2100
21st to endNight
45%1432334466%
1628
March1st to 10thNight
432432345%7%65%
1980
11th to 20thNight
4312223335%71%
1980
21st to endNight
3223424445%68%
2178
April1st to 10thNight
2212223235%75%
1974
11th to 20thNight
221221234477%
1777
21st to endNight
2212212225%81%
1800
May1st to 10thNight
2112212235%78%
1710
11th to 20thNight
1112212345%79%
1594
21st to endNight
21111211386%
1746
June1st to 10thNight
4211113347%73%
1620
11th to 20thNight
311221124479%
1620
21st to endNight
2213445%5%6%7%60%
1620
July1st to 10thNight
3325%5%36%6%8%11%49%
1620
11th to 20thNight
3427%8%6%9%7%10%15%30%
1620
21st to endNight
45%38%9%47%7%10%15%26%
1773
August1st to 10thNight
4425%6%46%7%9%11%43%
1611
11th to 20thNight
6%325%6%45%7%8%11%44%
1670
21st to endNight
6%325%5%47%7%8%11%42%
1980
September1st to 10thNight
8%5%25%5%36%5%7%9%46%
1927
11th to 20thNight
321332345%7%68%
1980
21st to endNight
3213213446%69%
1980
October1st to 10thNight
221321335%6%72%
2101
11th to 20thNight
2112312335%76%
2160
21st to endNight
1212212225%80%
2376
November1st to 10thNight
2211222236%78%
2220
11th to 20thNight
33222345%6%72%
2280
21st to endNight
6%323412346%65%
2389
December1st to 10thNight
7%413223447%64%
2470
11th to 20thNight
5%425%5%34446%58%
3041
21st to endNight
7%5%243235%5%460%
4521

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
21%47%14%35%20%
1709
11th to 20thDay
21%36%12%33%25%
1665
21st to endDay
21%3416%30%26%
1782
February1st to 10thDay
20%2413%26%35%
1620
11th to 20thDay
23%3413%29%28%
1754
21st to endDay
20%239%29%37%
1628
March1st to 10thDay
21%249%33%30%
1980
11th to 20thDay
17%2410%30%37%
1980
21st to endDay
15%349%36%33%
2178
April1st to 10thDay
14%237%37%37%
1984
11th to 20thDay
11%126%28%51%
2134
21st to endDay
9%227%33%47%
2160
May1st to 10thDay
11%227%22%55%
2245
11th to 20thDay
11%25%8%26%47%
2304
21st to endDay
8%125%26%57%
2530
June1st to 10thDay
13%348%25%48%
2340
11th to 20thDay
11%335%17%61%
2340
21st to endDay
24%6%7%10%21%32%
2340
July1st to 10thDay
31%9%12%16%15%16%
2276
11th to 20thDay
37%15%19%17%9%3
2271
21st to endDay
42%16%18%14%8%2
2404
August1st to 10thDay
36%12%17%16%14%5%
2313
11th to 20thDay
35%11%17%17%14%6%
2229
21st to endDay
31%11%13%19%15%9%
2376
September1st to 10thDay
33%8%11%14%18%15%
2028
11th to 20thDay
21%5%9%16%25%24%
1980
21st to endDay
17%5%7%16%32%23%
1980
October1st to 10thDay
14%39%16%26%32%
1858
11th to 20thDay
12%25%11%31%39%
1800
21st to endDay
11%3412%31%40%
1980
November1st to 10thDay
12%2315%36%31%
1859
11th to 20thDay
16%2414%32%32%
1900
21st to endDay
22%3415%28%28%
1786
December1st to 10thDay
21%45%17%31%22%
1710
11th to 20thDay
27%47%17%27%18%
2168
21st to endDay
20%5%5%13%39%17%
3146
January1st to 10thNight
20%47%14%33%21%
2457
11th to 20thNight
18%35%15%32%27%
2417
21st to endNight
25%35%14%31%22%
2574
February1st to 10thNight
17%45%13%25%37%
2340
11th to 20thNight
23%35%14%29%27%
2101
21st to endNight
20%349%29%35%
1628
March1st to 10thNight
19%3413%30%31%
1980
11th to 20thNight
16%25%11%29%37%
1980
21st to endNight
16%35%11%37%28%
2178
April1st to 10thNight
13%1311%37%34%
1974
11th to 20thNight
12%2310%30%44%
1777
21st to endNight
10%239%33%44%
1800
May1st to 10thNight
11%247%26%50%
1710
11th to 20thNight
9%449%30%44%
1595
21st to endNight
7%126%31%53%
1746
June1st to 10thNight
12%346%31%44%
1620
11th to 20thNight
9%235%22%58%
1620
21st to endNight
20%6%7%10%21%35%
1620
July1st to 10thNight
26%9%16%19%13%16%
1575
11th to 20thNight
36%15%23%17%7%2
1566
21st to endNight
39%16%26%13%42
1674
August1st to 10thNight
29%14%17%20%15%5%
1602
11th to 20thNight
31%11%20%16%17%6%
1670
21st to endNight
31%13%16%17%15%7%
1980
September1st to 10thNight
31%9%14%16%17%13%
1927
11th to 20thNight
17%5%9%21%27%22%
1980
21st to endNight
15%5%9%17%33%22%
1980
October1st to 10thNight
13%5%9%15%26%31%
2101
11th to 20thNight
12%25%16%25%40%
2160
21st to endNight
9%2414%31%40%
2376
November1st to 10thNight
10%2415%37%31%
2220
11th to 20thNight
14%3416%32%31%
2280
21st to endNight
21%3415%31%25%
2389
December1st to 10thNight
21%36%19%29%22%
2470
11th to 20thNight
24%5%7%17%29%17%
3041
21st to endNight
21%6%6%14%33%20%
4521

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
7%8%22%36%25%3
270
11th to 20thDay
11%5%16%40%23%5%
255
21st to endDay
5%8%20%39%22%6%
264
February1st to 10thDay
46%20%33%30%8%
240
11th to 20thDay
10%18%28%27%16%1
400
21st to endDay
9%24%30%25%10%3
346
March1st to 10thDay
8%17%31%29%12%4
420
11th to 20thDay
6%17%26%24%18%9%
420
21st to endDay
6%20%28%27%14%5%
462
April1st to 10thDay
312%30%28%21%6%
420
11th to 20thDay
5%14%31%28%16%6%
412
21st to endDay
215%27%30%18%7%
420
May1st to 10thDay
313%29%28%16%11%
423
11th to 20thDay
28%25%33%23%10%
448
21st to endDay
27%25%38%21%7%
485
June1st to 10thDay
4421%37%22%13%
450
11th to 20thDay
2418%34%31%12%
450
21st to endDay
3212%34%35%15%
450
July1st to 10thDay
6%28%26%36%23%
446
11th to 20thDay
6%26%22%37%28%
444
21st to endDay
8%27%20%32%31%
487
August1st to 10thDay
7%1418%34%36%
447
11th to 20thDay
6%25%22%37%28%
437
21st to endDay
5%5%17%39%34%
495
September1st to 10thDay
8%39%28%32%21%
450
11th to 20thDay
5%9%29%36%20%
450
21st to endDay
4316%28%34%16%
450
October1st to 10thDay
2316%28%34%17%
328
11th to 20thDay
3314%25%36%19%
270
21st to endDay
3413%29%33%19%
297
November1st to 10thDay
27%14%36%31%10%
270
11th to 20thDay
3313%34%37%10%
270
21st to endDay
6%8%25%33%24%5%
270
December1st to 10thDay
7%5%20%31%28%8%
270
11th to 20thDay
7%420%39%24%4
270
21st to endDay
12%10%19%33%22%4
297
January1st to 10thNight
6%316%50%23%2
760
11th to 20thNight
5%317%49%24%2
744
21st to endNight
8%322%46%19%1
792
February1st to 10thNight
4221%47%24%3
720
11th to 20thNight
7%425%48%15%2
704
21st to endNight
5%5%32%44%14%
592
March1st to 10thNight
45%31%45%14%1
720
11th to 20thNight
45%24%40%24%3
720
21st to endNight
3426%45%20%2
792
April1st to 10thNight
2324%51%19%1
714
11th to 20thNight
25%31%45%16%1
533
21st to endNight
2325%54%14%1
540
May1st to 10thNight
3225%50%19%1
540
11th to 20thNight
2118%52%26%1
531
21st to endNight
2218%54%23%
584
June1st to 10thNight
4110%54%30%1
540
11th to 20thNight
3111%53%33%1
540
21st to endNight
318%43%44%1
540
July1st to 10thNight
416%31%54%4
525
11th to 20thNight
4323%61%8%
522
21st to endNight
415%23%56%11%
591
August1st to 10thNight
41318%61%13%
537
11th to 20thNight
32419%61%10%
534
21st to endNight
5%2320%60%10%
594
September1st to 10thNight
8%15%25%54%7%
667
11th to 20thNight
315%31%56%5%
720
21st to endNight
3110%42%40%5%
720
October1st to 10thNight
2112%49%32%4
720
11th to 20thNight
2113%48%32%4
720
21st to endNight
1213%44%35%6%
792
November1st to 10thNight
2114%45%32%6%
740
11th to 20thNight
4212%47%32%3
760
21st to endNight
7%321%45%21%3
760
December1st to 10thNight
7%217%49%22%3
760
11th to 20thNight
5%420%49%20%2
760
21st to endNight
8%319%48%19%4
836
Page generated at 2024-01-13 07:37:56. Version ac07

Copyright 2024 Attilla Danko


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