Renaissance Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Renaissance Observatory clear sky chart from 2005-11-05 to 2017-10-31.

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
48%
15867
22%
47323
16%
15823
53%
15823
27%
30132

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
28%
900
18%
2506
9%
895
36%
895
21%
1785
January16th to endNight
26%
898
18%
2537
8%
898
34%
898
21%
1778
February1st to 15thNight
26%
704
17%
2112
7%
701
34%
701
19%
1486
February16th to endNight
25%
631
18%
1893
8%
631
34%
631
22%
1279
March1st to 15thNight
30%
720
17%
2160
9%
720
36%
720
20%
1482
March16th to endNight
38%
674
16%
2030
10%
674
43%
674
21%
1401
April1st to 15thNight
42%
539
24%
1797
16%
539
55%
539
29%
1076
April16th to endNight
45%
540
21%
1762
17%
540
53%
540
25%
1109
May1st to 15thNight
46%
539
18%
1619
12%
539
51%
539
25%
1080
May16th to endNight
65%
561
20%
1677
16%
561
67%
561
29%
1048
June1st to 15thNight
69%
540
22%
1440
18%
540
71%
540
40%
848
June16th to endNight
75%
540
23%
1440
18%
540
77%
540
42%
842
July1st to 15thNight
71%
510
20%
1360
17%
510
71%
510
37%
843
July16th to endNight
77%
564
24%
1478
21%
531
79%
531
42%
850
August1st to 15thNight
79%
539
24%
1714
26%
536
79%
536
38%
943
August16th to endNight
77%
573
26%
1910
30%
573
78%
573
38%
1016
September1st to 15thNight
67%
587
26%
1847
27%
587
69%
587
33%
1081
September16th to endNight
64%
717
29%
1980
23%
717
66%
717
37%
1179
October1st to 15thNight
60%
720
32%
1983
24%
720
64%
720
36%
1190
October16th to endNight
44%
768
27%
2431
22%
768
52%
768
29%
1479
November1st to 15thNight
49%
700
30%
2276
25%
700
57%
700
33%
1280
November16th to endNight
40%
720
23%
2340
19%
720
48%
720
25%
1437
December1st to 15thNight
32%
723
15%
2343
12%
723
36%
723
18%
1638
December16th to endNight
27%
960
16%
2688
7%
960
35%
960
19%
1982

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
13%6%25%5%3445%7%41%
48429
Night
14%6%24424446%44%
47504
TransparencyDay
41%6%11%22%15%2
48113
Night
40%5%10%23%17%3
47324
SeeingDay
14%418%24%24%13%
5891
Night
17%5%22%31%20%2
15870

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
21%7%38%433435%32%
1432
16th to endDay
15%10%46%433345%38%
1683
February1st to 15thDay
16%10%46%5%23336%35%
1750
16th to endDay
15%8%47%5%36%5%5%6%32%
1580
March1st to 15thDay
21%8%25%5%24435%37%
1800
16th to endDay
18%7%35%5%3445%6%34%
2203
April1st to 15thDay
14%5%25%5%35%447%41%
2151
16th to endDay
16%6%2442335%5%42%
2196
May1st to 15thDay
18%6%25%4345%6%8%34%
2331
16th to endDay
11%425%6%445%7%8%37%
2436
June1st to 15thDay
8%3245%25%5%5%8%47%
2520
16th to endDay
6%4245%36%6%7%9%43%
2520
July1st to 15thDay
10%5%24436%5%7%8%39%
2520
16th to endDay
5%3145%46%6%8%11%41%
2586
August1st to 15thDay
6%4346%35%5%7%9%43%
2232
16th to endDay
7%4244345%6%9%45%
2292
September1st to 15thDay
10%5%35%5%35%45%9%42%
2100
16th to endDay
11%425%424445%49%
1980
October1st to 15thDay
13%4235%23336%50%
1974
16th to endDay
15%6%2441233450%
1791
November1st to 15thDay
12%424423346%51%
1582
16th to endDay
20%6%2431334443%
1620
December1st to 15thDay
23%8%36%423335%34%
1614
16th to endDay
19%11%46%422246%34%
1536
January1st to 15thNight
18%9%36%5%24335%36%
2506
16th to endNight
17%9%45%42435%5%36%
2537
February1st to 15thNight
19%10%46%423345%35%
2103
16th to endNight
17%8%36%424445%37%
1893
March1st to 15thNight
17%9%25%5%2443439%
2160
16th to endNight
16%7%35%5%3445%5%37%
2030
April1st to 15thNight
13%5%24324347%47%
1797
16th to endNight
16%5%35%5%23446%42%
1762
May1st to 15thNight
17%4346%2435%8%38%
1619
16th to endNight
5%325%6%45%5%7%10%42%
1675
June1st to 15thNight
6%3243335%5%9%51%
1440
16th to endNight
5%312325%6%7%11%49%
1440
July1st to 15thNight
7%42443346%9%48%
1440
16th to endNight
6%3234345%6%9%52%
1579
August1st to 15thNight
5%3134245%5%9%52%
1725
16th to endNight
432442445%10%52%
1910
September1st to 15thNight
11%42332445%7%49%
1847
16th to endNight
10%5%13423347%52%
1980
October1st to 15thNight
10%414323345%53%
1983
16th to endNight
16%6%2442333450%
2431
November1st to 15thNight
13%423323335%54%
2276
16th to endNight
18%5%24324245%45%
2340
December1st to 15thNight
22%8%35%423345%33%
2343
16th to endNight
22%9%35%5%23335%33%
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
54%310%19%11%
1433
16th to endDay
48%48%29%7%1
1683
February1st to 15thDay
49%49%25%9%1
1752
16th to endDay
51%5%12%18%10%
1580
March1st to 15thDay
50%49%21%12%1
1800
16th to endDay
50%5%11%24%6%
2204
April1st to 15thDay
42%5%9%22%18%1
2151
16th to endDay
42%5%11%26%12%2
2196
May1st to 15thDay
46%7%12%21%10%
2331
16th to endDay
41%8%13%19%13%2
2440
June1st to 15thDay
32%7%12%25%19%2
2520
16th to endDay
33%9%13%19%20%3
2520
July1st to 15thDay
39%7%13%20%14%4
2371
16th to endDay
31%10%18%23%13%2
2424
August1st to 15thDay
34%8%12%23%18%1
2219
16th to endDay
32%7%12%22%18%4
2292
September1st to 15thDay
39%6%9%22%17%4
2100
16th to endDay
35%47%23%23%4
1980
October1st to 15thDay
35%48%23%23%3
1974
16th to endDay
37%37%26%20%4
1791
November1st to 15thDay
35%48%23%20%7%
1582
16th to endDay
43%38%25%16%2
1620
December1st to 15thDay
52%411%19%9%1
1614
16th to endDay
51%312%21%9%
1536
January1st to 15thNight
50%48%20%15%1
2506
16th to endNight
49%410%22%11%1
2537
February1st to 15thNight
51%49%23%9%1
2112
16th to endNight
47%412%23%11%
1893
March1st to 15thNight
48%49%19%13%4
2160
16th to endNight
47%6%12%21%9%1
2030
April1st to 15thNight
37%49%24%19%4
1797
16th to endNight
41%48%23%17%4
1762
May1st to 15thNight
44%411%23%14%
1620
16th to endNight
34%9%13%21%16%4
1677
June1st to 15thNight
27%7%13%25%21%3
1440
16th to endNight
25%8%16%21%22%6%
1440
July1st to 15thNight
33%5%11%26%17%5%
1360
16th to endNight
26%6%17%29%17%3
1478
August1st to 15thNight
26%7%14%24%23%3
1714
16th to endNight
26%5%13%27%20%4
1910
September1st to 15thNight
33%5%8%25%20%6%
1847
16th to endNight
32%48%21%25%7%
1980
October1st to 15thNight
32%48%20%28%5%
1983
16th to endNight
39%36%26%18%5%
2431
November1st to 15thNight
33%27%23%24%8%
2276
16th to endNight
41%39%24%18%3
2340
December1st to 15thNight
52%411%18%11%2
2343
16th to endNight
54%410%19%10%1
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
32%8%38%12%43
90
16th to endDay
14%15%48%17%3
96
February1st to 15thDay
22%18%41%12%5%
90
16th to endDay
20%12%38%23%4
81
March1st to 15thDay
28%6%45%13%5%
90
16th to endDay
22%10%28%25%13%
276
April1st to 15thDay
19%9%27%27%15%2
270
16th to endDay
19%7%22%27%16%6%
270
May1st to 15thDay
20%7%22%26%14%8%
288
16th to endDay
14%5%17%28%19%14%
336
June1st to 15thDay
9%214%24%33%15%
495
16th to endDay
4320%31%26%13%
495
July1st to 15thDay
14%112%27%28%15%
475
16th to endDay
6%5%21%36%30%
446
August1st to 15thDay
14%1418%30%31%
313
16th to endDay
11%26%21%39%18%
332
September1st to 15thDay
13%26%20%33%23%
315
16th to endDay
15%11%19%35%17%
314
October1st to 15thDay
13%417%25%26%12%
309
16th to endDay
15%7%29%26%17%4
144
November1st to 15thDay
8%423%30%21%12%
90
16th to endDay
27%8%28%23%10%1
90
December1st to 15thDay
17%10%35%23%7%5%
90
16th to endDay
21%17%40%14%5%
96
January1st to 15thNight
24%10%30%28%5%
900
16th to endNight
23%9%35%27%4
898
February1st to 15thNight
24%9%32%29%3
704
16th to endNight
22%9%37%27%2
631
March1st to 15thNight
22%8%32%30%5%
720
16th to endNight
20%6%28%32%11%1
674
April1st to 15thNight
15%6%31%32%12%1
539
16th to endNight
20%425%32%15%1
540
May1st to 15thNight
17%5%21%35%18%2
540
16th to endNight
6%118%37%31%5%
563
June1st to 15thNight
9%112%40%33%3
540
16th to endNight
6%19%39%40%2
540
July1st to 15thNight
9%110%29%45%4
510
16th to endNight
7%16%30%42%11%
564
August1st to 15thNight
7%429%49%8%
539
16th to endNight
5%6%31%48%7%
573
September1st to 15thNight
13%19%27%39%8%
587
16th to endNight
13%212%27%35%8%
717
October1st to 15thNight
13%314%32%30%5%
720
16th to endNight
18%5%26%30%17%1
768
November1st to 15thNight
14%6%24%33%18%1
700
16th to endNight
22%7%26%30%12%
720
December1st to 15thNight
27%7%27%27%8%1
723
16th to endNight
26%9%30%28%4
960
Page generated at 2017-11-01 16:23:32. Version ac04

Copyright 2017 A. Danko


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