LaBelle Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the LaBelle Observatory clear sky chart from 2005-11-05 to 2017-09-22.

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
64%
16199
39%
47031
28%
16158
74%
16158
61%
20667

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%
716
33%
2327
29%
716
74%
716
48%
1076
January16th to endNight
58%
768
38%
2328
28%
768
70%
768
46%
1125
February1st to 15thNight
61%
700
38%
2112
29%
700
74%
700
51%
981
February16th to endNight
49%
632
35%
1895
27%
632
63%
632
42%
950
March1st to 15thNight
53%
720
36%
2141
28%
720
67%
720
54%
955
March16th to endNight
52%
768
36%
2073
22%
768
65%
768
57%
975
April1st to 15thNight
41%
719
37%
1799
13%
719
56%
719
54%
884
April16th to endNight
46%
720
41%
1800
14%
720
62%
720
66%
815
May1st to 15thNight
50%
555
41%
1634
21%
554
63%
554
68%
641
May16th to endNight
47%
562
41%
1685
20%
561
62%
561
69%
634
June1st to 15thNight
53%
540
38%
1620
23%
540
63%
540
78%
599
June16th to endNight
65%
540
39%
1620
27%
540
72%
540
82%
603
July1st to 15thNight
83%
510
31%
1530
26%
510
86%
510
70%
629
July16th to endNight
81%
593
35%
1620
26%
558
83%
558
62%
734
August1st to 15thNight
87%
717
38%
1790
24%
713
88%
713
77%
821
August16th to endNight
89%
764
45%
1910
30%
764
90%
764
75%
891
September1st to 15thNight
85%
720
40%
1893
29%
720
90%
720
74%
850
September16th to endNight
77%
683
49%
1890
39%
683
87%
683
82%
750
October1st to 15thNight
63%
660
44%
1815
30%
660
77%
660
67%
786
October16th to endNight
74%
704
46%
2098
39%
704
84%
704
73%
833
November1st to 15thNight
74%
700
38%
2275
36%
700
82%
700
63%
902
November16th to endNight
69%
720
41%
2340
37%
720
79%
720
59%
959
December1st to 15thNight
63%
720
36%
2340
33%
720
72%
720
47%
1080
December16th to endNight
56%
768
34%
2496
29%
768
67%
768
43%
1194

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
111212346%73%
47847
Night
111212236%75%
47229
TransparencyDay
13%25%14%25%37%
47545
Night
11%26%15%25%38%
47032
SeeingDay
5%13%31%32%14%3
5887
Night
37%21%33%26%7%
16208

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
2213223247%65%
1611
16th to endDay
33232346%8%60%
1894
February1st to 15thDay
2212223438%65%
1751
16th to endDay
211342345%11%57%
1579
March1st to 15thDay
211221235%8%69%
1818
16th to endDay
11122445%7%68%
2148
April1st to 15thDay
1111423347%69%
2149
16th to endDay
111247%79%
2160
May1st to 15thDay
1212235%79%
2314
16th to endDay
2225%84%
2429
June1st to 15thDay
11112484%
2340
16th to endDay
1111288%
2340
July1st to 15thDay
2112213345%71%
2340
16th to endDay
22231345%7%65%
2436
August1st to 15thDay
11121233475%
2160
16th to endDay
211213345%72%
2292
September1st to 15thDay
211213335%74%
2067
16th to endDay
11111111284%
1882
October1st to 15thDay
111212346%75%
1815
16th to endDay
11111233479%
1770
November1st to 15thDay
111113335%75%
1584
16th to endDay
112222447%70%
1620
December1st to 15thDay
421132445%7%61%
1620
16th to endDay
22231445%9%62%
1728
January1st to 15thNight
1212323347%65%
2327
16th to endNight
4212323338%65%
2328
February1st to 15thNight
212313249%68%
2101
16th to endNight
11243445%9%60%
1895
March1st to 15thNight
11112133410%67%
2141
16th to endNight
1221335%9%68%
2073
April1st to 15thNight
1112212228%73%
1799
16th to endNight
111135%82%
1800
May1st to 15thNight
11226%81%
1634
16th to endNight
1112387%
1684
June1st to 15thNight
111388%
1620
16th to endNight
111290%
1620
July1st to 15thNight
1111234477%
1620
16th to endNight
1211212237%72%
1730
August1st to 15thNight
1111225%82%
1800
16th to endNight
111113481%
1910
September1st to 15thNight
111223381%
1893
16th to endNight
111290%
1890
October1st to 15thNight
1112235%79%
1815
16th to endNight
1112246%79%
2098
November1st to 15thNight
1123335%76%
2275
16th to endNight
1211112336%73%
2340
December1st to 15thNight
221222345%7%64%
2340
16th to endNight
32232335%8%63%
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
19%37%15%27%26%
1612
16th to endDay
21%48%16%24%24%
1894
February1st to 15thDay
17%28%16%26%28%
1751
16th to endDay
21%410%21%22%19%
1579
March1st to 15thDay
13%26%17%29%29%
1818
16th to endDay
14%39%17%31%23%
2148
April1st to 15thDay
14%36%18%35%21%
2149
16th to endDay
7%16%21%31%32%
2160
May1st to 15thDay
9%1316%29%39%
2314
16th to endDay
5%2415%33%38%
2432
June1st to 15thDay
6%138%23%56%
2340
16th to endDay
5%1411%75%
2340
July1st to 15thDay
15%339%19%48%
2201
16th to endDay
17%48%18%24%27%
2283
August1st to 15thDay
12%3310%24%45%
2146
16th to endDay
13%25%9%23%45%
2292
September1st to 15thDay
13%2410%21%46%
2067
16th to endDay
9%126%26%55%
1882
October1st to 15thDay
10%3415%28%38%
1815
16th to endDay
10%25%10%21%49%
1770
November1st to 15thDay
11%16%15%29%35%
1584
16th to endDay
14%36%15%23%36%
1620
December1st to 15thDay
22%28%20%20%25%
1620
16th to endDay
19%5%11%21%25%17%
1728
January1st to 15thNight
17%37%17%24%28%
2327
16th to endNight
20%39%16%20%30%
2328
February1st to 15thNight
16%38%17%24%30%
2112
16th to endNight
20%49%19%23%22%
1895
March1st to 15thNight
13%39%18%27%28%
2141
16th to endNight
11%49%19%29%25%
2073
April1st to 15thNight
12%28%18%35%21%
1799
16th to endNight
6%15%20%30%34%
1800
May1st to 15thNight
6%15%17%28%40%
1635
16th to endNight
5%1418%32%37%
1685
June1st to 15thNight
41110%23%57%
1620
16th to endNight
5%310%78%
1620
July1st to 15thNight
9%247%20%54%
1530
16th to endNight
13%27%14%27%32%
1620
August1st to 15thNight
7%2212%24%49%
1790
16th to endNight
9%128%23%52%
1910
September1st to 15thNight
8%239%25%50%
1893
16th to endNight
418%27%58%
1890
October1st to 15thNight
8%25%16%29%38%
1815
16th to endNight
7%16%14%22%48%
2098
November1st to 15thNight
10%26%13%30%37%
2275
16th to endNight
12%26%17%27%34%
2340
December1st to 15thNight
18%39%19%24%24%
2340
16th to endNight
19%412%19%22%20%
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
18%17%18%34%10%
90
16th to endDay
12%17%31%28%8%
262
February1st to 15thDay
6%17%32%34%8%
266
16th to endDay
11%28%27%23%7%
238
March1st to 15thDay
9%20%34%23%10%2
270
16th to endDay
10%20%33%23%10%1
288
April1st to 15thDay
10%26%32%18%9%2
269
16th to endDay
8%24%34%22%7%1
270
May1st to 15thDay
422%36%26%7%2
288
16th to endDay
318%41%25%8%1
330
June1st to 15thDay
117%35%26%15%2
315
16th to endDay
2340%28%20%5%
315
July1st to 15thDay
329%40%20%4
305
16th to endDay
2219%40%25%9%
327
August1st to 15thDay
1225%42%20%7%
315
16th to endDay
2120%46%21%7%
332
September1st to 15thDay
3433%42%13%2
315
16th to endDay
412%30%38%12%2
280
October1st to 15thDay
5%14%38%32%9%
255
16th to endDay
212%31%32%18%2
191
November1st to 15thDay
8%12%16%28%27%5%
90
16th to endDay
11%16%26%27%17%
90
December1st to 15thDay
6%7%14%45%24%1
90
16th to endDay
15%15%21%33%13%
96
January1st to 15thNight
38%17%33%27%10%
720
16th to endNight
10%5%20%30%26%6%
768
February1st to 15thNight
47%20%31%26%8%
704
16th to endNight
6%13%27%26%18%6%
632
March1st to 15thNight
5%11%27%29%21%4
720
16th to endNight
5%12%28%27%20%5%
768
April1st to 15thNight
5%18%33%22%16%4
719
16th to endNight
416%32%24%16%6%
720
May1st to 15thNight
311%33%34%16%1
555
16th to endNight
216%33%29%16%1
563
June1st to 15thNight
7%38%36%16%1
540
16th to endNight
1230%45%18%2
540
July1st to 15thNight
1110%51%31%3
510
16th to endNight
210%48%34%3
593
August1st to 15thNight
18%42%38%8%
717
16th to endNight
2434%47%10%
764
September1st to 15thNight
119%35%42%9%
720
16th to endNight
1315%33%34%10%
683
October1st to 15thNight
29%22%29%26%8%
660
16th to endNight
417%30%28%17%
704
November1st to 15thNight
25%15%35%30%11%
700
16th to endNight
36%16%27%29%15%
720
December1st to 15thNight
5%6%17%32%26%9%
720
16th to endNight
9%8%22%29%23%7%
768
Page generated at 2017-09-23 03:43:34. Version ac04

Copyright 2017 A. Danko


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