Royal Palm Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Royal Palm 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%
16283
17%
46993
15%
16243
67%
16243
28%
30539

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
55%
716
16%
2327
14%
716
60%
716
25%
1466
January16th to endNight
54%
768
24%
2472
19%
768
62%
768
30%
1451
February1st to 15thNight
52%
703
26%
2093
20%
699
60%
699
34%
1231
February16th to endNight
57%
631
29%
1735
20%
631
65%
631
38%
1008
March1st to 15thNight
58%
720
25%
1980
17%
720
65%
720
39%
1156
March16th to endNight
58%
768
24%
2112
20%
768
61%
768
40%
1236
April1st to 15thNight
68%
718
23%
1976
20%
718
72%
718
47%
1080
April16th to endNight
63%
720
24%
1803
15%
720
67%
720
40%
1103
May1st to 15thNight
73%
719
23%
1799
16%
719
75%
719
47%
1045
May16th to endNight
71%
611
14%
1733
12%
611
71%
611
26%
1181
June1st to 15thNight
65%
540
8%
1620
7%
540
65%
540
15%
1234
June16th to endNight
77%
540
7%
1620
7%
540
77%
540
22%
1143
July1st to 15thNight
73%
510
6%
1530
6%
510
73%
510
17%
1141
July16th to endNight
82%
564
9%
1595
9%
531
82%
531
27%
1061
August1st to 15thNight
77%
614
7%
1684
7%
611
77%
611
25%
1162
August16th to endNight
70%
764
6%
2018
5%
764
70%
764
19%
1514
September1st to 15thNight
68%
720
4%
1980
4%
720
68%
720
16%
1527
September16th to endNight
62%
685
6%
1892
7%
685
62%
685
14%
1494
October1st to 15thNight
66%
660
15%
1919
17%
660
67%
660
22%
1322
October16th to endNight
56%
704
17%
2112
17%
704
59%
704
23%
1431
November1st to 15thNight
62%
700
25%
2101
21%
700
68%
700
34%
1269
November16th to endNight
57%
720
23%
2160
20%
720
62%
720
28%
1384
December1st to 15thNight
59%
720
20%
2236
19%
720
64%
720
26%
1426
December16th to endNight
63%
768
23%
2496
22%
768
67%
768
29%
1474

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%6%38%8%5%8%7%7%9%26%
47864
Night
5%425%5%35%6%7%10%40%
47198
TransparencyDay
48%11%13%13%9%2
47565
Night
35%10%18%19%11%3
47001
SeeingDay
10%215%22%25%24%
6090
Night
8%215%31%29%13%
16291

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%6%37%7%37%7%8%8%31%
1611
16th to endDay
8%5%27%6%46%5%6%9%36%
1749
February1st to 15thDay
10%7%25%6%35%5%5%8%39%
1760
16th to endDay
6%5%246%36%5%6%9%41%
1738
March1st to 15thDay
5%436%7%47%6%7%9%38%
1980
16th to endDay
6%6%27%6%47%6%7%9%35%
2111
April1st to 15thDay
4425%7%5%7%6%7%13%35%
1972
16th to endDay
6%436%7%47%7%7%9%33%
2155
May1st to 15thDay
3325%6%48%7%7%9%40%
2152
16th to endDay
9%7%37%9%6%9%8%8%8%21%
2388
June1st to 15thDay
11%8%5%12%10%6%8%7%7%6%14%
2340
16th to endDay
7%7%410%10%6%10%9%8%9%14%
2340
July1st to 15thDay
7%7%5%10%10%6%10%8%8%9%15%
2340
16th to endDay
6%7%310%11%6%9%9%8%11%16%
2465
August1st to 15thDay
7%7%49%10%6%9%7%10%10%17%
2250
16th to endDay
9%6%48%10%6%8%9%10%10%14%
2179
September1st to 15thDay
7%7%5%12%12%7%8%9%7%8%13%
1980
16th to endDay
12%10%5%13%11%6%7%6%5%5%14%
1881
October1st to 15thDay
8%5%49%10%5%9%8%9%8%19%
1708
16th to endDay
13%7%38%6%47%7%5%8%26%
1760
November1st to 15thDay
6%5%27%7%5%7%6%6%8%36%
1757
16th to endDay
8%6%36%6%5%7%6%6%8%33%
1800
December1st to 15thDay
9%7%37%7%46%6%6%6%33%
1720
16th to endDay
7%5%35%7%36%5%8%10%35%
1728
January1st to 15thNight
7%5%26%6%35%5%7%10%39%
2327
16th to endNight
4425%425%6%6%10%46%
2472
February1st to 15thNight
7%5%245%335%6%7%48%
2090
16th to endNight
4313425%5%7%8%53%
1735
March1st to 15thNight
3213425%6%7%9%51%
1980
16th to endNight
5%3145%3446%10%50%
2112
April1st to 15thNight
221332447%10%57%
1976
16th to endNight
5%4244245%7%9%49%
1803
May1st to 15thNight
2212325%6%6%10%55%
1799
16th to endNight
7%435%5%36%6%10%14%32%
1732
June1st to 15thNight
9%7%37%7%47%8%8%11%24%
1620
16th to endNight
5%315%7%36%7%11%15%30%
1620
July1st to 15thNight
4438%7%47%6%8%11%31%
1620
16th to endNight
2426%5%35%7%8%14%39%
1703
August1st to 15thNight
3415%6%47%6%8%14%36%
1695
16th to endNight
6%425%7%37%8%9%12%31%
2018
September1st to 15thNight
5%437%8%5%8%8%9%13%24%
1980
16th to endNight
6%6%38%8%5%9%7%9%9%24%
1892
October1st to 15thNight
5%5%27%6%47%6%10%11%32%
1919
16th to endNight
11%6%36%6%345%6%9%35%
2112
November1st to 15thNight
5%325%5%45%46%9%48%
2101
16th to endNight
8%425%6%45%45%8%42%
2160
December1st to 15thNight
7%5%26%5%35%5%6%11%41%
2236
16th to endNight
5%3246%35%5%7%9%46%
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
46%8%12%14%12%4
1612
16th to endDay
41%7%12%18%15%5%
1749
February1st to 15thDay
42%6%8%18%17%6%
1762
16th to endDay
35%8%11%22%16%5%
1738
March1st to 15thDay
38%7%14%20%16%3
1980
16th to endDay
41%7%11%18%13%6%
2112
April1st to 15thDay
36%9%15%22%13%2
1972
16th to endDay
40%9%11%17%16%3
2155
May1st to 15thDay
34%9%14%22%13%6%
2152
16th to endDay
53%12%12%15%5%
2392
June1st to 15thDay
65%11%11%8%3
2340
16th to endDay
57%17%15%8%1
2340
July1st to 15thDay
58%16%17%6%
2201
16th to endDay
54%16%20%8%
2310
August1st to 15thDay
52%17%17%11%
2237
16th to endDay
55%17%18%7%
2179
September1st to 15thDay
60%17%14%6%
1980
16th to endDay
67%12%10%6%2
1881
October1st to 15thDay
54%12%13%11%6%
1708
16th to endDay
50%7%10%13%12%4
1760
November1st to 15thDay
42%8%11%15%17%5%
1757
16th to endDay
45%8%9%11%17%7%
1800
December1st to 15thDay
48%7%11%14%15%2
1720
16th to endDay
41%7%11%20%15%3
1728
January1st to 15thNight
38%7%18%20%11%2
2327
16th to endNight
32%7%13%24%15%5%
2472
February1st to 15thNight
31%5%11%25%18%6%
2099
16th to endNight
26%8%14%26%18%5%
1735
March1st to 15thNight
28%6%14%25%19%5%
1980
16th to endNight
28%6%17%25%17%4
2112
April1st to 15thNight
21%7%20%30%18%2
1976
16th to endNight
29%7%15%24%19%4
1803
May1st to 15thNight
22%7%16%31%16%4
1800
16th to endNight
38%11%19%24%6%
1734
June1st to 15thNight
50%13%20%12%3
1620
16th to endNight
36%18%31%12%1
1620
July1st to 15thNight
44%17%26%10%
1530
16th to endNight
32%15%34%15%1
1595
August1st to 15thNight
33%17%30%17%1
1684
16th to endNight
40%19%26%12%
2018
September1st to 15thNight
45%19%23%9%1
1980
16th to endNight
50%16%18%10%3
1892
October1st to 15thNight
41%12%18%16%9%1
1919
16th to endNight
44%7%14%18%11%4
2112
November1st to 15thNight
33%5%14%18%20%5%
2101
16th to endNight
38%6%13%15%16%8%
2160
December1st to 15thNight
37%9%16%17%16%2
2236
16th to endNight
32%8%12%24%18%3
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
17%10%42%18%11%
90
16th to endDay
17%13%28%30%7%3
96
February1st to 15thDay
12%7%29%32%14%1
101
16th to endDay
9%428%34%21%1
239
March1st to 15thDay
8%5%31%32%18%4
270
16th to endDay
9%425%30%25%4
288
April1st to 15thDay
5%5%26%28%24%10%
270
16th to endDay
8%221%26%29%11%
270
May1st to 15thDay
4117%26%30%19%
288
16th to endDay
7%9%25%30%25%
331
June1st to 15thDay
13%29%17%27%28%
315
16th to endDay
6%6%13%26%46%
315
July1st to 15thDay
7%211%27%50%
305
16th to endDay
6%411%22%53%
326
August1st to 15thDay
10%1410%23%49%
313
16th to endDay
15%7%9%26%39%
332
September1st to 15thDay
8%7%11%23%48%
315
16th to endDay
19%5%8%24%42%
278
October1st to 15thDay
10%18%27%33%18%
255
16th to endDay
15%422%23%21%13%
272
November1st to 15thDay
10%117%30%29%10%
265
16th to endDay
9%326%31%26%2
270
December1st to 15thDay
22%313%34%19%6%
190
16th to endDay
7%417%45%21%3
96
January1st to 15thNight
10%5%21%35%25%2
720
16th to endNight
7%426%41%18%1
768
February1st to 15thNight
9%427%40%17%
704
16th to endNight
6%425%45%16%
631
March1st to 15thNight
6%425%39%21%1
720
16th to endNight
7%323%44%20%1
768
April1st to 15thNight
3221%46%25%2
718
16th to endNight
9%119%43%24%1
720
May1st to 15thNight
4115%45%31%2
720
16th to endNight
8%19%34%36%8%
613
June1st to 15thNight
12%17%17%39%22%
540
16th to endNight
5%210%46%35%
540
July1st to 15thNight
7%211%40%39%
510
16th to endNight
418%38%46%
564
August1st to 15thNight
7%29%42%38%
614
16th to endNight
9%15%15%36%32%
764
September1st to 15thNight
9%6%13%35%35%
720
16th to endNight
12%415%36%30%
685
October1st to 15thNight
9%10%31%36%11%
660
16th to endNight
16%115%29%26%9%
704
November1st to 15thNight
8%121%36%28%5%
700
16th to endNight
10%321%37%22%4
720
December1st to 15thNight
9%420%37%26%2
720
16th to endNight
7%217%38%29%3
768
Page generated at 2017-09-23 06:43:35. Version ac04

Copyright 2017 A. Danko


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