Rainwater Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rainwater Observatory clear sky chart from 2005-11-05 to

2017-09-12
.

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
49%
15412
25%
46818
17%
15368
56%
15368
31%
28111

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
29%
900
25%
2362
9%
895
41%
895
27%
1538
January16th to endNight
21%
893
24%
2429
7%
893
34%
893
24%
1637
February1st to 15thNight
26%
704
24%
2112
9%
701
39%
701
25%
1342
February16th to endNight
25%
631
25%
1893
10%
631
37%
631
24%
1208
March1st to 15thNight
30%
684
20%
2124
11%
684
39%
684
23%
1373
March16th to endNight
36%
576
24%
2008
15%
576
48%
576
26%
1169
April1st to 15thNight
39%
539
25%
1797
16%
539
52%
539
30%
1024
April16th to endNight
45%
540
27%
1800
20%
540
58%
540
33%
980
May1st to 15thNight
50%
540
21%
1800
14%
540
60%
540
30%
1050
May16th to endNight
64%
561
24%
1683
21%
561
68%
561
36%
987
June1st to 15thNight
73%
540
20%
1482
19%
540
75%
540
40%
892
June16th to endNight
75%
540
25%
1440
21%
540
76%
540
44%
822
July1st to 15thNight
79%
510
19%
1406
18%
510
79%
510
40%
830
July16th to endNight
79%
564
17%
1671
20%
531
80%
531
34%
980
August1st to 15thNight
80%
539
18%
1788
22%
536
81%
536
34%
1022
August16th to endNight
74%
573
23%
1910
28%
573
74%
573
27%
1177
September1st to 15thNight
66%
530
24%
1767
25%
530
69%
530
31%
1027
September16th to endNight
70%
644
30%
1802
25%
644
71%
644
39%
1045
October1st to 15thNight
63%
660
34%
1889
27%
660
68%
660
43%
1037
October16th to endNight
53%
704
34%
2112
27%
704
60%
704
37%
1174
November1st to 15thNight
48%
700
31%
2235
24%
700
59%
700
37%
1208
November16th to endNight
41%
720
28%
2340
20%
720
54%
720
31%
1335
December1st to 15thNight
34%
720
24%
2340
15%
720
45%
720
25%
1459
December16th to endNight
27%
900
19%
2628
10%
900
36%
900
21%
1795

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
11%5%25%5%35%5%5%7%41%
47813
Night
11%5%2442445%7%47%
47019
TransparencyDay
40%5%10%19%18%5%
47517
Night
35%410%20%20%7%
46820
SeeingDay
12%5%19%25%24%12%
5489
Night
13%7%23%28%21%4
15414

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
18%6%245%13446%41%
1573
16th to endDay
16%6%24423335%45%
1792
February1st to 15thDay
14%7%25%5%23446%42%
1750
16th to endDay
17%7%26%324335%41%
1580
March1st to 15thDay
15%7%36%6%24437%37%
1845
16th to endDay
12%7%25%5%35%5%5%5%41%
2212
April1st to 15thDay
12%5%245%3445%7%45%
2151
16th to endDay
10%5%25%5%34347%48%
2160
May1st to 15thDay
14%5%35%6%35%446%39%
2151
16th to endDay
8%425%7%47%6%6%7%38%
2429
June1st to 15thDay
5%426%7%47%6%6%10%37%
2474
16th to endDay
6%325%7%46%7%6%8%41%
2520
July1st to 15thDay
9%5%35%6%49%7%8%8%31%
2466
16th to endDay
9%426%7%48%8%8%9%29%
2379
August1st to 15thDay
7%5%25%7%5%7%7%7%8%35%
2160
16th to endDay
11%5%26%6%46%6%6%9%33%
2292
September1st to 15thDay
9%427%6%36%5%6%7%40%
2112
16th to endDay
13%4145%23346%48%
1815
October1st to 15thDay
8%41342445%6%53%
1738
16th to endDay
11%313313325%58%
1760
November1st to 15thDay
10%313313335%57%
1621
16th to endDay
15%6%33322235%49%
1620
December1st to 15thDay
17%8%45%423346%38%
1620
16th to endDay
18%8%35%433336%39%
1593
January1st to 15thNight
15%6%24323345%47%
2362
16th to endNight
18%7%35%42333442%
2429
February1st to 15thNight
15%7%24423345%45%
2103
16th to endNight
16%6%25%422335%46%
1893
March1st to 15thNight
16%6%1442445%7%40%
2124
16th to endNight
12%433424446%47%
2008
April1st to 15thNight
11%42342435%6%51%
1797
16th to endNight
8%314425%35%8%52%
1800
May1st to 15thNight
10%4134345%5%8%47%
1799
16th to endNight
6%3244245%7%10%47%
1683
June1st to 15thNight
33245%36%5%6%10%48%
1482
16th to endNight
32235%2447%13%50%
1440
July1st to 15thNight
33245%35%5%8%11%46%
1490
16th to endNight
4314336%6%8%12%44%
1786
August1st to 15thNight
5%213445%6%8%11%45%
1800
16th to endNight
7%315%5%35%6%7%10%42%
1910
September1st to 15thNight
8%41443445%6%50%
1767
16th to endNight
7%4234235%5%8%51%
1802
October1st to 15thNight
8%31331345%8%56%
1889
16th to endNight
14%313312225%58%
2112
November1st to 15thNight
11%413223346%56%
2235
16th to endNight
14%5%13313335%52%
2340
December1st to 15thNight
14%7%35%323446%44%
2340
16th to endNight
17%8%37%5%2334439%
2628

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
43%36%17%22%5%
1574
16th to endDay
42%3420%22%6%
1792
February1st to 15thDay
41%38%21%18%6%
1752
16th to endDay
45%35%16%21%7%
1580
March1st to 15thDay
48%37%18%16%6%
1845
16th to endDay
42%48%21%20%2
2214
April1st to 15thDay
37%49%20%21%6%
2151
16th to endDay
36%49%22%24%2
2160
May1st to 15thDay
44%5%9%17%18%4
2151
16th to endDay
41%6%14%21%13%1
2433
June1st to 15thDay
39%7%15%21%15%
2474
16th to endDay
36%7%15%19%17%3
2520
July1st to 15thDay
42%9%16%20%6%3
2321
16th to endDay
44%10%17%18%8%
2231
August1st to 15thDay
40%9%16%19%10%3
2148
16th to endDay
43%9%14%19%9%3
2292
September1st to 15thDay
40%8%12%19%13%5%
2112
16th to endDay
36%39%20%20%9%
1815
October1st to 15thDay
30%38%19%25%12%
1738
16th to endDay
30%2318%33%11%
1760
November1st to 15thDay
29%35%20%30%9%
1621
16th to endDay
37%26%18%25%9%
1620
December1st to 15thDay
46%38%19%14%7%
1620
16th to endDay
47%39%19%16%4
1593
January1st to 15thNight
40%35%17%27%6%
2362
16th to endNight
45%3417%21%7%
2429
February1st to 15thNight
41%35%20%21%8%
2112
16th to endNight
41%3419%20%8%
1893
March1st to 15thNight
42%49%17%18%7%
2124
16th to endNight
36%48%22%23%4
2008
April1st to 15thNight
34%39%22%21%8%
1797
16th to endNight
30%410%23%25%6%
1800
May1st to 15thNight
34%5%11%22%20%5%
1800
16th to endNight
29%7%15%25%18%3
1685
June1st to 15thNight
30%5%17%25%19%1
1482
16th to endNight
25%6%18%25%20%4
1440
July1st to 15thNight
26%8%22%26%11%4
1406
16th to endNight
27%11%22%27%10%1
1671
August1st to 15thNight
28%8%22%23%12%3
1788
16th to endNight
34%9%16%23%12%3
1910
September1st to 15thNight
33%6%13%24%16%7%
1767
16th to endNight
30%410%19%25%9%
1802
October1st to 15thNight
26%49%19%25%15%
1889
16th to endNight
31%2314%31%16%
2112
November1st to 15thNight
29%36%19%27%13%
2235
16th to endNight
34%35%19%24%13%
2340
December1st to 15thNight
41%38%20%19%6%
2340
16th to endNight
48%28%15%18%5%
2628

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%16%40%18%42
90
16th to endDay
25%25%40%5%22
96
February1st to 15thDay
16%24%41%12%5%
90
16th to endDay
23%11%48%14%2
81
March1st to 15thDay
28%23%34%12%1
90
16th to endDay
17%10%35%25%11%
198
April1st to 15thDay
19%11%27%25%12%2
270
16th to endDay
14%7%28%30%15%2
270
May1st to 15thDay
17%7%22%34%12%5%
288
16th to endDay
11%226%25%19%13%
331
June1st to 15thDay
8%114%28%32%14%
449
16th to endDay
6%213%31%31%15%
495
July1st to 15thDay
7%19%32%33%16%
475
16th to endDay
9%1420%37%26%
428
August1st to 15thDay
9%17%21%32%26%
313
16th to endDay
16%5%25%27%25%
332
September1st to 15thDay
7%411%21%39%16%
299
16th to endDay
12%19%31%33%11%
254
October1st to 15thDay
10%5%20%28%26%8%
178
16th to endDay
15%427%25%20%7%
96
November1st to 15thDay
16%5%33%26%15%2
90
16th to endDay
12%14%41%15%13%3
90
December1st to 15thDay
27%15%34%15%5%1
90
16th to endDay
23%14%39%16%5%
96
January1st to 15thNight
21%15%31%23%7%
900
16th to endNight
21%12%40%22%2
893
February1st to 15thNight
19%13%36%24%6%
704
16th to endNight
19%16%34%26%3
631
March1st to 15thNight
20%12%33%27%6%
684
16th to endNight
14%11%31%27%13%1
576
April1st to 15thNight
12%11%34%26%13%1
539
16th to endNight
10%9%31%34%12%2
540
May1st to 15thNight
12%426%37%16%2
540
16th to endNight
6%119%37%30%4
563
June1st to 15thNight
48%40%36%9%
540
16th to endNight
3110%26%44%13%
540
July1st to 15thNight
36%32%40%16%
510
16th to endNight
4425%46%18%
564
August1st to 15thNight
6%224%46%19%
539
16th to endNight
8%327%46%13%
573
September1st to 15thNight
10%211%28%39%8%
530
16th to endNight
9%29%35%37%5%
644
October1st to 15thNight
11%316%33%30%4
660
16th to endNight
16%7%19%29%24%2
704
November1st to 15thNight
12%6%28%28%20%4
700
16th to endNight
17%9%29%27%14%1
720
December1st to 15thNight
20%10%30%28%9%
720
16th to endNight
23%13%31%24%7%
900
Page generated at 2017-09-13 06:39:05. Version ac04

Copyright 2017 A. Danko


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