LaBelle Astronomical Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the LaBelle Astronomical Observatory clear sky chart from 2005-11-05 to 2017-09-21.

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%
16084
20%
47005
17%
16045
67%
16045
29%
29995

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
54%
717
18%
2327
16%
716
60%
716
26%
1441
January16th to endNight
52%
768
25%
2424
20%
768
60%
768
31%
1424
February1st to 15thNight
51%
701
25%
2107
18%
699
58%
699
33%
1251
February16th to endNight
56%
631
30%
1794
19%
631
66%
631
40%
1004
March1st to 15thNight
58%
720
31%
1980
20%
720
68%
720
45%
1074
March16th to endNight
60%
768
28%
2112
23%
768
64%
768
41%
1200
April1st to 15thNight
68%
718
24%
1976
21%
718
72%
718
44%
1094
April16th to endNight
63%
720
27%
1848
18%
720
66%
720
43%
1090
May1st to 15thNight
75%
652
25%
1732
18%
652
78%
652
46%
994
May16th to endNight
78%
561
19%
1683
16%
561
79%
561
33%
1053
June1st to 15thNight
67%
540
8%
1620
7%
540
67%
540
17%
1224
June16th to endNight
74%
540
8%
1620
6%
540
74%
540
20%
1211
July1st to 15thNight
72%
510
6%
1530
6%
510
72%
510
18%
1164
July16th to endNight
78%
564
6%
1595
6%
531
78%
531
23%
1157
August1st to 15thNight
77%
539
7%
1615
8%
536
77%
536
22%
1174
August16th to endNight
64%
762
6%
2099
5%
762
64%
762
16%
1614
September1st to 15thNight
62%
720
5%
1980
5%
720
62%
720
15%
1524
September16th to endNight
57%
681
7%
1881
7%
681
57%
681
15%
1454
October1st to 15thNight
69%
660
22%
1879
22%
660
71%
660
30%
1195
October16th to endNight
61%
704
22%
2112
22%
704
64%
704
29%
1345
November1st to 15thNight
66%
700
29%
2101
27%
700
71%
700
36%
1216
November16th to endNight
61%
720
29%
2160
25%
720
67%
720
35%
1270
December1st to 15thNight
61%
720
25%
2334
25%
720
66%
720
30%
1396
December16th to endNight
63%
768
23%
2496
23%
768
67%
768
33%
1426

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
8%5%37%7%46%6%6%8%34%
47837
Night
6%425%5%35%5%6%9%43%
47209
TransparencyDay
44%9%14%15%12%4
47538
Night
34%9%16%19%14%4
47012
SeeingDay
8%110%21%25%31%
5918
Night
8%115%33%29%11%
16093

By Month

Percentage Cloud Cover SE (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
8%5%35%5%36%5%6%8%39%
1611
16th to endDay
8%426%435%6%5%7%45%
1798
February1st to 15thDay
11%5%24425%45%8%45%
1750
16th to endDay
5%4244445%6%9%48%
1677
March1st to 15thDay
4215%5%35%46%9%50%
1980
16th to endDay
6%415%5%35%45%9%47%
2111
April1st to 15thDay
5%3146%46%5%7%9%43%
1972
16th to endDay
6%425%6%35%5%6%9%42%
2109
May1st to 15thDay
5%314436%7%7%8%46%
2226
16th to endDay
8%5%37%8%5%7%6%7%7%31%
2431
June1st to 15thDay
13%9%49%8%47%6%8%7%20%
2340
16th to endDay
9%7%38%10%6%7%7%7%9%21%
2340
July1st to 15thDay
9%7%48%9%7%9%8%8%7%19%
2340
16th to endDay
8%7%39%10%6%9%8%7%8%20%
2465
August1st to 15thDay
8%6%28%10%5%9%7%8%9%22%
2317
16th to endDay
10%6%39%11%5%8%7%7%8%20%
2101
September1st to 15thDay
8%6%410%10%6%8%7%7%9%20%
1980
16th to endDay
11%11%410%10%46%6%6%9%19%
1872
October1st to 15thDay
7%6%27%7%5%6%6%6%8%33%
1749
16th to endDay
10%6%16%6%36%5%5%8%38%
1760
November1st to 15thDay
5%416%6%25%5%7%7%47%
1757
16th to endDay
8%436%5%45%447%46%
1800
December1st to 15thDay
9%5%27%5%35%5%6%7%40%
1623
16th to endDay
6%425%6%36%6%6%10%42%
1728
January1st to 15thNight
7%6%35%5%36%5%7%9%40%
2327
16th to endNight
8%4244345%7%8%45%
2424
February1st to 15thNight
9%5%3332345%8%48%
2103
16th to endNight
43234245%6%9%52%
1794
March1st to 15thNight
4213325%46%9%56%
1980
16th to endNight
322442445%9%55%
2112
April1st to 15thNight
321332446%9%55%
1976
16th to endNight
5%314425%36%10%52%
1848
May1st to 15thNight
3213435%449%57%
1732
16th to endNight
5%2245%36%6%6%10%44%
1682
June1st to 15thNight
10%5%36%7%5%7%7%8%11%25%
1620
16th to endNight
5%5%37%7%46%8%6%12%31%
1620
July1st to 15thNight
7%5%47%7%47%6%8%10%29%
1620
16th to endNight
3446%6%5%8%6%8%13%32%
1703
August1st to 15thNight
5%5%26%6%47%7%8%11%34%
1626
16th to endNight
9%5%36%7%48%6%7%12%28%
2099
September1st to 15thNight
7%7%38%8%48%7%8%9%27%
1980
16th to endNight
9%9%38%8%46%6%7%10%25%
1881
October1st to 15thNight
7%5%25%5%35%47%7%45%
1879
16th to endNight
11%5%2443446%7%44%
2112
November1st to 15thNight
6%42442446%7%51%
2101
16th to endNight
8%325%42435%8%50%
2160
December1st to 15thNight
6%435%5%35%45%8%47%
2334
16th to endNight
5%4245%35%5%6%9%47%
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
40%7%10%19%18%4
1612
16th to endDay
36%6%7%21%20%6%
1798
February1st to 15thDay
35%5%8%18%19%12%
1752
16th to endDay
30%6%12%20%19%10%
1677
March1st to 15thDay
29%6%12%23%20%7%
1980
16th to endDay
33%6%11%19%19%9%
2112
April1st to 15thDay
33%8%14%21%17%5%
1972
16th to endDay
35%6%13%16%22%5%
2109
May1st to 15thDay
31%8%13%20%18%7%
2226
16th to endDay
46%9%13%16%12%
2435
June1st to 15thDay
58%11%14%10%3
2340
16th to endDay
55%12%18%11%1
2340
July1st to 15thDay
58%17%17%5%
2201
16th to endDay
55%15%20%8%
2310
August1st to 15thDay
52%14%24%8%
2304
16th to endDay
59%14%18%7%
2101
September1st to 15thDay
57%14%18%7%1
1980
16th to endDay
60%12%13%9%3
1872
October1st to 15thDay
45%9%12%14%14%4
1749
16th to endDay
42%6%10%13%18%9%
1760
November1st to 15thDay
32%6%9%20%21%9%
1757
16th to endDay
37%5%9%17%18%11%
1800
December1st to 15thDay
41%6%12%17%16%5%
1623
16th to endDay
33%8%13%20%17%6%
1728
January1st to 15thNight
37%7%13%21%15%4
2327
16th to endNight
33%6%11%22%18%7%
2424
February1st to 15thNight
33%5%8%20%21%11%
2112
16th to endNight
25%7%14%22%22%7%
1794
March1st to 15thNight
22%6%12%30%20%6%
1980
16th to endNight
25%7%13%25%20%7%
2112
April1st to 15thNight
23%7%16%30%16%6%
1976
16th to endNight
26%6%14%23%23%5%
1848
May1st to 15thNight
23%7%16%25%19%6%
1733
16th to endNight
31%10%18%24%15%
1684
June1st to 15thNight
47%14%19%13%4
1620
16th to endNight
42%17%22%14%3
1620
July1st to 15thNight
46%15%27%9%1
1530
16th to endNight
39%15%31%12%
1595
August1st to 15thNight
38%17%30%13%
1615
16th to endNight
46%18%24%10%
2099
September1st to 15thNight
47%17%22%10%1
1980
16th to endNight
49%15%19%12%3
1881
October1st to 15thNight
34%9%16%16%19%4
1879
16th to endNight
37%7%11%14%21%7%
2112
November1st to 15thNight
30%6%9%21%22%8%
2101
16th to endNight
31%6%9%21%20%10%
2160
December1st to 15thNight
34%6%12%22%17%5%
2334
16th to endNight
30%7%14%21%19%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
16%8%28%27%15%2
90
16th to endDay
15%12%29%23%14%4
96
February1st to 15thDay
8%5%23%31%20%11%
90
16th to endDay
7%324%40%22%
178
March1st to 15thDay
4221%39%28%3
270
16th to endDay
6%6%17%32%30%6%
288
April1st to 15thDay
3318%30%34%8%
270
16th to endDay
8%19%30%34%15%
270
May1st to 15thDay
7%16%23%33%27%
288
16th to endDay
7%6%20%26%38%
331
June1st to 15thDay
16%17%11%23%39%
315
16th to endDay
6%29%20%60%
315
July1st to 15thDay
5%419%68%
305
16th to endDay
10%29%16%61%
326
August1st to 15thDay
8%7%16%67%
313
16th to endDay
12%310%18%53%
332
September1st to 15thDay
8%2210%21%54%
315
16th to endDay
9%210%26%50%
275
October1st to 15thDay
7%18%26%36%19%
255
16th to endDay
11%20%28%24%14%
272
November1st to 15thDay
10%10%30%32%15%
265
16th to endDay
8%118%39%27%5%
270
December1st to 15thDay
21%123%36%15%2
93
16th to endDay
2316%33%38%6%
96
January1st to 15thNight
10%421%40%21%1
720
16th to endNight
9%427%43%14%
768
February1st to 15thNight
12%325%42%14%
704
16th to endNight
7%228%47%14%
631
March1st to 15thNight
5%328%45%17%
720
16th to endNight
6%224%47%18%
768
April1st to 15thNight
5%119%49%22%
718
16th to endNight
7%120%47%22%
720
May1st to 15thNight
413%46%32%2
653
16th to endNight
5%6%37%42%8%
563
June1st to 15thNight
11%5%18%46%16%
540
16th to endNight
4214%45%32%
540
July1st to 15thNight
6%26%44%39%
510
16th to endNight
315%43%44%
564
August1st to 15thNight
7%16%43%40%
539
16th to endNight
11%5%13%37%32%
762
September1st to 15thNight
10%5%13%39%29%
720
16th to endNight
13%6%17%42%18%
681
October1st to 15thNight
11%7%38%35%7%
660
16th to endNight
14%116%32%29%5%
704
November1st to 15thNight
6%118%42%28%2
700
16th to endNight
9%220%42%23%2
720
December1st to 15thNight
8%220%41%25%1
720
16th to endNight
6%220%39%27%2
768
Page generated at 2017-09-22 07:35:34. Version ac04

Copyright 2017 A. Danko


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