CARMA
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the CARMA clear sky chart from 2005-11-05 to 2017-09-16.

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
69%
15393
35%
46827
28%
15363
77%
15363
61%
20467

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
63%
716
29%
2506
23%
716
76%
716
56%
1022
January16th to endNight
57%
768
32%
2539
26%
768
70%
768
49%
1167
February1st to 15thNight
65%
700
34%
2105
29%
698
74%
698
57%
956
February16th to endNight
56%
632
33%
1895
26%
632
67%
632
54%
888
March1st to 15thNight
61%
720
32%
2160
25%
720
75%
720
60%
959
March16th to endNight
60%
768
35%
2006
19%
768
71%
768
60%
980
April1st to 15thNight
57%
719
33%
1799
16%
719
65%
719
57%
925
April16th to endNight
60%
720
35%
1800
16%
720
67%
720
64%
879
May1st to 15thNight
60%
551
33%
1631
22%
551
66%
551
58%
736
May16th to endNight
61%
507
30%
1630
22%
506
69%
506
50%
731
June1st to 15thNight
73%
360
33%
1440
34%
360
82%
360
57%
521
June16th to endNight
85%
360
38%
1440
46%
360
90%
360
77%
432
July1st to 15thNight
90%
340
31%
1360
39%
340
91%
340
55%
511
July16th to endNight
85%
400
35%
1438
41%
376
85%
376
53%
575
August1st to 15thNight
81%
716
36%
1790
24%
713
82%
713
73%
842
August16th to endNight
88%
764
43%
1910
28%
764
89%
764
77%
885
September1st to 15thNight
86%
720
43%
1818
30%
720
90%
720
77%
827
September16th to endNight
82%
660
44%
1826
37%
660
88%
660
75%
785
October1st to 15thNight
73%
660
39%
1862
34%
660
80%
660
64%
847
October16th to endNight
75%
704
42%
2178
40%
704
83%
704
69%
874
November1st to 15thNight
74%
700
39%
2275
35%
700
84%
700
72%
861
November16th to endNight
71%
720
38%
2340
34%
720
81%
720
65%
946
December1st to 15thNight
65%
720
31%
2391
23%
720
78%
720
51%
1086
December16th to endNight
55%
768
31%
2688
24%
768
69%
768
44%
1232

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
1212213346%69%
47937
Night
1212212346%70%
47009
TransparencyDay
14%27%19%28%26%
47612
Night
13%29%23%30%20%
46835
SeeingDay
6%12%31%29%15%4
5745
Night
2320%43%27%3
15403

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
21121335%9%68%
1432
16th to endDay
141331345%7%61%
1680
February1st to 15thDay
1113224349%66%
1751
16th to endDay
31331435%8%63%
1579
March1st to 15thDay
11231445%9%64%
1800
16th to endDay
11231445%10%64%
2214
April1st to 15thDay
2312313346%65%
2149
16th to endDay
1211212348%70%
2160
May1st to 15thDay
223313345%67%
2319
16th to endDay
2413423347%61%
2482
June1st to 15thDay
221232335%6%65%
2520
16th to endDay
11121222379%
2520
July1st to 15thDay
1212315%45%5%64%
2520
16th to endDay
2213324445%64%
2628
August1st to 15thDay
111222335%75%
2160
16th to endDay
111221224475%
2292
September1st to 15thDay
1112212335%74%
2142
16th to endDay
1111213381%
1823
October1st to 15thDay
2111212335%73%
1766
16th to endDay
121112346%74%
1694
November1st to 15thDay
111112335%75%
1584
16th to endDay
21122345%75%
1620
December1st to 15thDay
113323448%66%
1566
16th to endDay
22331335%9%63%
1536
January1st to 15thNight
12221335%8%68%
2506
16th to endNight
132332345%7%63%
2539
February1st to 15thNight
12221345%9%65%
2101
16th to endNight
131321235%8%65%
1895
March1st to 15thNight
21222345%6%68%
2160
16th to endNight
21121336%9%66%
2006
April1st to 15thNight
121222335%7%67%
1799
16th to endNight
112212336%73%
1800
May1st to 15thNight
2212213346%70%
1631
16th to endNight
231332325%6%66%
1629
June1st to 15thNight
112313235%72%
1440
16th to endNight
111125%83%
1440
July1st to 15thNight
1112223446%68%
1440
16th to endNight
223323245%69%
1536
August1st to 15thNight
1211233379%
1799
16th to endNight
111234477%
1910
September1st to 15thNight
111123480%
1818
16th to endNight
11111222480%
1826
October1st to 15thNight
1112212235%73%
1862
16th to endNight
1111224477%
2178
November1st to 15thNight
11112226%78%
2275
16th to endNight
111212248%72%
2340
December1st to 15thNight
21232335%8%64%
2391
16th to endNight
31331445%9%62%
2688

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
11%313%32%32%5%
1432
16th to endDay
19%313%26%25%11%
1680
February1st to 15thDay
14%212%30%28%11%
1751
16th to endDay
18%39%31%29%7%
1579
March1st to 15thDay
14%39%29%31%11%
1800
16th to endDay
14%213%30%28%10%
2214
April1st to 15thDay
16%29%26%29%15%
2149
16th to endDay
12%28%25%34%16%
2160
May1st to 15thDay
16%2421%39%15%
2319
16th to endDay
20%26%18%33%18%
2485
June1st to 15thDay
16%25%11%28%34%
2520
16th to endDay
10%125%21%58%
2520
July1st to 15thDay
18%35%7%12%51%
2371
16th to endDay
18%45%9%16%44%
2463
August1st to 15thDay
10%247%19%55%
2146
16th to endDay
11%226%24%52%
2292
September1st to 15thDay
12%3210%21%49%
2142
16th to endDay
8%1212%38%36%
1823
October1st to 15thDay
12%2417%39%23%
1766
16th to endDay
10%1420%40%22%
1694
November1st to 15thDay
10%19%31%33%13%
1584
16th to endDay
9%110%29%36%12%
1620
December1st to 15thDay
14%314%29%30%6%
1566
16th to endDay
16%6%16%27%24%8%
1536
January1st to 15thNight
13%315%31%29%6%
2506
16th to endNight
19%313%26%25%11%
2539
February1st to 15thNight
14%312%32%25%11%
2112
16th to endNight
16%312%30%30%5%
1895
March1st to 15thNight
13%210%32%28%11%
2160
16th to endNight
13%313%32%30%7%
2006
April1st to 15thNight
16%310%30%29%10%
1799
16th to endNight
11%29%30%33%12%
1800
May1st to 15thNight
14%25%26%37%12%
1632
16th to endNight
18%28%19%33%17%
1630
June1st to 15thNight
12%26%18%30%30%
1440
16th to endNight
5%38%28%52%
1440
July1st to 15thNight
14%25%11%16%49%
1360
16th to endNight
15%25%10%22%43%
1438
August1st to 15thNight
9%239%24%50%
1790
16th to endNight
9%1212%28%45%
1910
September1st to 15thNight
8%1312%29%44%
1818
16th to endNight
8%1314%34%37%
1826
October1st to 15thNight
14%1419%42%17%
1862
16th to endNight
9%15%20%44%18%
2178
November1st to 15thNight
8%112%28%35%13%
2275
16th to endNight
11%211%25%37%12%
2340
December1st to 15thNight
16%416%31%25%5%
2391
16th to endNight
17%6%15%28%22%8%
2688

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
111%35%40%5%6%
60
16th to endDay
5%9%25%33%18%7%
198
February1st to 15thDay
49%27%30%23%4
266
16th to endDay
5%11%36%31%12%2
238
March1st to 15thDay
417%34%24%10%8%
270
16th to endDay
6%19%35%27%11%1
288
April1st to 15thDay
14%21%28%21%11%2
269
16th to endDay
13%23%36%21%41
270
May1st to 15thDay
9%17%37%21%10%3
288
16th to endDay
12%15%27%25%13%5%
330
June1st to 15thDay
8%16%32%25%13%2
315
16th to endDay
214%29%27%19%5%
315
July1st to 15thDay
46%31%33%17%6%
305
16th to endDay
410%30%30%18%6%
327
August1st to 15thDay
213%39%23%15%5%
315
16th to endDay
3431%32%18%9%
332
September1st to 15thDay
5%9%30%31%17%5%
315
16th to endDay
310%31%34%16%5%
258
October1st to 15thDay
412%35%31%13%2
255
16th to endDay
5%7%33%34%17%1
206
November1st to 15thDay
1310%21%45%18%
90
16th to endDay
4322%50%17%2
90
December1st to 15thDay
429%46%18%
81
16th to endDay
6%326%31%31%1
64
January1st to 15thNight
2226%41%21%5%
720
16th to endNight
3329%40%18%4
768
February1st to 15thNight
2423%46%20%2
704
16th to endNight
36%30%40%17%1
632
March1st to 15thNight
2227%42%20%3
720
16th to endNight
16%26%43%20%1
768
April1st to 15thNight
45%27%42%18%1
719
16th to endNight
27%25%41%21%1
720
May1st to 15thNight
35%25%43%21%1
552
16th to endNight
45%21%41%25%
508
June1st to 15thNight
3314%48%29%
360
16th to endNight
11%58%28%
360
July1st to 15thNight
2246%45%3
340
16th to endNight
2346%45%2
400
August1st to 15thNight
112%46%36%1
716
16th to endNight
16%44%45%2
764
September1st to 15thNight
26%45%40%4
720
16th to endNight
1111%37%44%3
660
October1st to 15thNight
2217%41%31%4
660
16th to endNight
2315%40%31%6%
704
November1st to 15thNight
1120%42%26%7%
700
16th to endNight
1119%47%26%3
720
December1st to 15thNight
3324%49%17%2
720
16th to endNight
3230%42%18%1
768
Page generated at 2017-09-17 09:05:45. Version ac04

Copyright 2017 A. Danko


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