Black Mesa Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Black Mesa Observatory clear sky chart from 2005-11-05 to 2017-09-19.

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
61%
15418
33%
46906
24%
15378
71%
15378
47%
23080

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
64%
720
31%
2327
28%
716
73%
716
43%
1135
January16th to endNight
57%
768
35%
2496
29%
768
69%
768
43%
1225
February1st to 15thNight
58%
700
31%
2288
27%
700
67%
700
48%
1069
February16th to endNight
43%
632
40%
1819
22%
632
64%
632
50%
869
March1st to 15thNight
53%
720
37%
1980
23%
720
66%
720
51%
992
March16th to endNight
55%
768
36%
2112
21%
768
67%
768
57%
1027
April1st to 15thNight
43%
626
34%
1885
16%
626
61%
626
48%
885
April16th to endNight
47%
540
38%
1800
23%
540
67%
540
53%
750
May1st to 15thNight
54%
539
35%
1620
22%
539
66%
539
56%
729
May16th to endNight
57%
561
34%
1684
22%
561
68%
561
59%
742
June1st to 15thNight
65%
540
32%
1620
25%
540
71%
540
63%
711
June16th to endNight
75%
540
30%
1620
26%
540
77%
540
57%
737
July1st to 15thNight
70%
510
17%
1530
15%
510
71%
510
32%
910
July16th to endNight
68%
564
13%
1593
12%
531
67%
531
23%
1050
August1st to 15thNight
75%
539
19%
1611
18%
536
75%
536
29%
990
August16th to endNight
75%
573
23%
1866
23%
573
76%
573
30%
1114
September1st to 15thNight
75%
635
27%
1895
23%
635
78%
635
37%
1091
September16th to endNight
75%
671
39%
1856
28%
671
81%
671
61%
871
October1st to 15thNight
65%
660
40%
1961
25%
660
76%
660
62%
853
October16th to endNight
72%
704
40%
2112
30%
704
80%
704
60%
946
November1st to 15thNight
67%
700
39%
2100
29%
700
75%
700
60%
928
November16th to endNight
61%
720
39%
2295
30%
720
71%
720
52%
1031
December1st to 15thNight
57%
720
35%
2340
28%
720
69%
720
46%
1105
December16th to endNight
48%
768
31%
2496
24%
768
59%
768
37%
1320

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
3313424446%61%
47909
Night
3213323446%64%
47102
TransparencyDay
23%47%16%28%19%
47604
Night
20%48%19%29%18%
46908
SeeingDay
6%10%22%29%21%8%
5282
Night
46%23%35%25%5%
15425

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
131332445%6%62%
1611
16th to endDay
25%12322446%63%
1728
February1st to 15thDay
27%22222236%66%
1575
16th to endDay
2423424437%61%
1652
March1st to 15thDay
14321345%6%63%
1980
16th to endDay
2312213346%68%
2112
April1st to 15thDay
1311313446%68%
2063
16th to endDay
421221223472%
2160
May1st to 15thDay
2113423336%67%
2327
16th to endDay
3112323345%68%
2429
June1st to 15thDay
111213335%76%
2340
16th to endDay
112223345%70%
2340
July1st to 15thDay
5%315%6%46%7%7%8%42%
2340
16th to endDay
6%326%9%6%10%7%9%10%26%
2467
August1st to 15thDay
8%425%6%47%7%8%8%35%
2340
16th to endDay
6%3246%47%7%6%8%42%
2333
September1st to 15thDay
6%3146%36%5%5%7%49%
2062
16th to endDay
312213236%70%
1849
October1st to 15thDay
41221333473%
1669
16th to endDay
321221323473%
1760
November1st to 15thDay
121212235%74%
1759
16th to endDay
231332222471%
1665
December1st to 15thDay
2413312446%64%
1620
16th to endDay
35%24323447%58%
1728
January1st to 15thNight
2312323445%65%
2327
16th to endNight
3412423445%64%
2496
February1st to 15thNight
2412212345%67%
2277
16th to endNight
22123225%6%7%64%
1819
March1st to 15thNight
241221235%5%68%
1980
16th to endNight
2112212246%70%
2112
April1st to 15thNight
2312322246%68%
1885
16th to endNight
222212335%73%
1800
May1st to 15thNight
2211312237%70%
1620
16th to endNight
1112312225%75%
1684
June1st to 15thNight
211112246%74%
1620
16th to endNight
212214345%71%
1620
July1st to 15thNight
44245%26%6%7%9%45%
1620
16th to endNight
7%325%6%49%9%8%12%31%
1701
August1st to 15thNight
3325%6%46%6%7%10%44%
1620
16th to endNight
4225%5%47%7%8%9%43%
1866
September1st to 15thNight
4325%4346%6%7%52%
1895
16th to endNight
312212236%73%
1856
October1st to 15thNight
212212235%75%
1961
16th to endNight
21221223475%
2112
November1st to 15thNight
112213335%73%
2100
16th to endNight
2312212236%71%
2295
December1st to 15thNight
3312323246%66%
2340
16th to endNight
441432446%6%57%
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
22%47%24%32%8%
1612
16th to endDay
21%48%19%34%11%
1728
February1st to 15thDay
22%26%26%24%17%
1575
16th to endDay
24%35%21%32%13%
1652
March1st to 15thDay
20%25%15%39%15%
1980
16th to endDay
18%25%17%38%16%
2112
April1st to 15thDay
16%36%17%37%19%
2063
16th to endDay
17%2413%36%25%
2160
May1st to 15thDay
19%25%15%31%26%
2327
16th to endDay
20%3411%33%26%
2432
June1st to 15thDay
11%227%27%47%
2340
16th to endDay
16%348%22%43%
2340
July1st to 15thDay
35%9%11%14%10%17%
2201
16th to endDay
46%12%17%15%7%
2312
August1st to 15thDay
41%11%10%13%14%8%
2325
16th to endDay
36%9%11%15%19%7%
2333
September1st to 15thDay
34%7%9%14%21%11%
2062
16th to endDay
17%4315%32%26%
1849
October1st to 15thDay
16%25%17%33%24%
1669
16th to endDay
15%35%13%41%21%
1760
November1st to 15thDay
14%2424%34%19%
1759
16th to endDay
18%3319%32%22%
1665
December1st to 15thDay
20%410%27%27%9%
1620
16th to endDay
26%313%25%26%4
1728
January1st to 15thNight
20%5%7%24%33%9%
2327
16th to endNight
22%38%22%34%8%
2496
February1st to 15thNight
19%39%24%24%18%
2288
16th to endNight
16%38%25%32%13%
1819
March1st to 15thNight
18%35%16%41%15%
1980
16th to endNight
16%26%18%40%15%
2112
April1st to 15thNight
18%15%20%35%17%
1885
16th to endNight
14%26%17%38%22%
1800
May1st to 15thNight
15%27%19%31%23%
1621
16th to endNight
14%26%14%37%25%
1685
June1st to 15thNight
13%228%24%48%
1620
16th to endNight
15%338%22%45%
1620
July1st to 15thNight
31%8%14%16%11%17%
1530
16th to endNight
38%11%22%18%6%1
1593
August1st to 15thNight
31%11%15%14%15%11%
1611
16th to endNight
32%9%16%18%16%7%
1866
September1st to 15thNight
27%7%14%17%20%11%
1895
16th to endNight
13%3420%31%26%
1856
October1st to 15thNight
13%16%22%30%25%
1961
16th to endNight
14%26%15%35%26%
2112
November1st to 15thNight
14%25%23%36%18%
2100
16th to endNight
16%35%18%31%24%
2295
December1st to 15thNight
20%39%25%29%12%
2340
16th to endNight
25%5%12%24%25%5%
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%22%24%27%13%3
90
16th to endDay
7%14%21%28%17%10%
96
February1st to 15thDay
35%24%33%27%5%
90
16th to endDay
8%31%24%19%13%2
228
March1st to 15thDay
7%19%28%25%14%4
270
16th to endDay
6%20%34%23%13%2
288
April1st to 15thDay
8%18%33%22%11%5%
269
16th to endDay
11%22%34%18%9%2
270
May1st to 15thDay
317%34%28%12%3
288
16th to endDay
6%14%29%31%14%3
330
June1st to 15thDay
28%31%32%19%6%
315
16th to endDay
2217%40%26%11%
315
July1st to 15thDay
5%212%37%28%12%
305
16th to endDay
9%10%26%31%21%
327
August1st to 15thDay
10%8%27%34%17%
315
16th to endDay
7%110%28%34%16%
332
September1st to 15thDay
9%120%31%28%8%
315
16th to endDay
5%5%23%33%22%8%
268
October1st to 15thDay
3419%32%26%13%
109
16th to endDay
7%219%26%35%9%
96
November1st to 15thDay
10%418%26%27%12%
90
16th to endDay
320%22%38%14%1
90
December1st to 15thDay
8%8%22%31%18%10%
90
16th to endDay
9%19%22%36%8%3
96
January1st to 15thNight
48%19%39%21%6%
720
16th to endNight
5%8%24%36%19%5%
768
February1st to 15thNight
46%27%38%18%4
704
16th to endNight
314%36%31%12%1
632
March1st to 15thNight
411%28%34%17%3
720
16th to endNight
37%31%37%16%2
768
April1st to 15thNight
312%36%33%11%1
626
16th to endNight
410%35%31%15%2
540
May1st to 15thNight
46%30%42%13%1
540
16th to endNight
2431%39%19%2
563
June1st to 15thNight
1227%48%19%
540
16th to endNight
2116%46%31%1
540
July1st to 15thNight
7%8%38%39%4
510
16th to endNight
9%7%22%49%10%
564
August1st to 15thNight
5%6%21%53%12%
539
16th to endNight
5%8%30%45%10%
573
September1st to 15thNight
5%10%31%44%7%
635
16th to endNight
3213%37%34%8%
671
October1st to 15thNight
2324%38%23%7%
660
16th to endNight
2318%37%31%7%
704
November1st to 15thNight
2424%35%27%7%
700
16th to endNight
47%23%33%23%7%
720
December1st to 15thNight
6%8%23%34%24%2
720
16th to endNight
7%9%30%31%16%5%
768
Page generated at 2017-09-20 01:49:54. Version ac04

Copyright 2017 A. Danko


Black Mesa Observatory Clear Sky Chart | Charts Home