Red Door Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Red Door 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
49%
15789
23%
46958
15%
15750
57%
15750
29%
29136

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
33%
718
24%
2327
12%
716
48%
716
25%
1399
January16th to endNight
31%
768
26%
2496
13%
768
47%
768
27%
1495
February1st to 15thNight
32%
702
24%
2244
12%
701
47%
701
29%
1309
February16th to endNight
26%
631
29%
1866
12%
631
43%
631
30%
1119
March1st to 15thNight
36%
720
27%
1980
15%
720
47%
720
33%
1213
March16th to endNight
38%
768
21%
2112
11%
768
45%
768
27%
1376
April1st to 15thNight
40%
718
23%
1922
11%
718
49%
718
35%
1184
April16th to endNight
46%
630
24%
1710
13%
630
53%
630
33%
1065
May1st to 15thNight
47%
540
17%
1620
8%
540
54%
540
27%
1049
May16th to endNight
62%
561
18%
1684
14%
561
64%
561
29%
1055
June1st to 15thNight
66%
540
15%
1620
13%
540
67%
540
27%
1062
June16th to endNight
68%
540
17%
1620
14%
540
70%
540
28%
1039
July1st to 15thNight
69%
510
11%
1530
9%
510
69%
510
27%
1007
July16th to endNight
72%
564
14%
1595
11%
531
74%
531
28%
1041
August1st to 15thNight
66%
539
14%
1609
13%
536
67%
536
26%
1092
August16th to endNight
67%
663
19%
1809
16%
663
68%
663
29%
1231
September1st to 15thNight
67%
720
20%
1965
17%
720
68%
720
32%
1248
September16th to endNight
54%
685
19%
1892
16%
685
57%
685
25%
1300
October1st to 15thNight
53%
660
30%
1935
26%
660
60%
660
34%
1138
October16th to endNight
54%
704
34%
2112
26%
704
66%
704
38%
1153
November1st to 15thNight
51%
700
30%
2134
23%
700
61%
700
37%
1187
November16th to endNight
45%
720
28%
2340
21%
720
56%
720
30%
1337
December1st to 15thNight
41%
720
24%
2340
16%
720
52%
720
25%
1433
December16th to endNight
37%
768
24%
2496
17%
768
47%
768
22%
1604

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%5%2443445%8%43%
47920
Night
13%42442445%7%44%
47155
TransparencyDay
37%5%12%22%18%4
47621
Night
37%411%20%19%5%
46958
SeeingDay
15%417%24%24%14%
5631
Night
15%5%21%31%22%3
15795

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%5%24333435%43%
1611
16th to endDay
15%5%23324445%48%
1728
February1st to 15thDay
15%5%1333445%6%46%
1615
16th to endDay
14%5%23423346%48%
1606
March1st to 15thDay
15%413323347%48%
1980
16th to endDay
17%424323447%45%
2111
April1st to 15thDay
11%31322446%8%49%
2026
16th to endDay
16%424425%446%47%
2259
May1st to 15thDay
11%5%25%5%35%45%7%41%
2331
16th to endDay
11%5%15%425%45%9%43%
2431
June1st to 15thDay
9%5%25%5%35%5%7%9%40%
2340
16th to endDay
6%3245%36%6%6%12%42%
2340
July1st to 15thDay
8%6%36%6%46%5%7%11%34%
2340
16th to endDay
7%3246%46%7%8%11%34%
2465
August1st to 15thDay
12%5%25%6%46%7%7%9%32%
2340
16th to endDay
11%5%26%6%46%6%6%11%32%
2381
September1st to 15thDay
10%424336%6%5%9%43%
1992
16th to endDay
18%6%25%42335%6%40%
1881
October1st to 15thDay
15%413212335%55%
1694
16th to endDay
13%41331323359%
1760
November1st to 15thDay
11%423213336%57%
1721
16th to endDay
15%423413345%50%
1620
December1st to 15thDay
16%6%2332445%6%44%
1620
16th to endDay
20%7%24323345%42%
1728
January1st to 15thNight
16%5%13324345%48%
2327
16th to endNight
17%42442345%447%
2496
February1st to 15thNight
15%5%14423345%49%
2235
16th to endNight
14%5%2432335%7%47%
1866
March1st to 15thNight
13%41442435%6%49%
1980
16th to endNight
17%424425%346%43%
2112
April1st to 15thNight
12%413424346%50%
1922
16th to endNight
13%424433447%47%
1710
May1st to 15thNight
10%436%5%345%5%8%40%
1619
16th to endNight
10%425%5%45%5%5%9%42%
1682
June1st to 15thNight
10%425%5%37%6%6%11%35%
1620
16th to endNight
5%325%6%47%6%8%10%38%
1620
July1st to 15thNight
7%5%26%6%37%6%9%11%33%
1620
16th to endNight
5%5%25%6%37%8%8%12%33%
1703
August1st to 15thNight
10%5%35%6%347%6%10%34%
1620
16th to endNight
8%6%17%5%35%6%9%10%35%
1809
September1st to 15thNight
9%5%25%435%5%7%9%42%
1965
16th to endNight
18%5%25%435%45%5%38%
1892
October1st to 15thNight
15%5%14212345%52%
1935
16th to endNight
12%31431333458%
2112
November1st to 15thNight
12%313323335%56%
2134
16th to endNight
13%423424346%50%
2340
December1st to 15thNight
16%5%245%23445%45%
2340
16th to endNight
21%5%24323446%40%
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
43%27%20%20%4
1612
16th to endDay
37%36%23%20%8%
1728
February1st to 15thDay
36%38%22%22%5%
1617
16th to endDay
36%37%26%19%5%
1606
March1st to 15thDay
36%37%23%23%5%
1980
16th to endDay
39%411%22%17%3
2112
April1st to 15thDay
31%311%25%22%5%
2026
16th to endDay
38%49%20%19%7%
2259
May1st to 15thDay
40%5%14%22%15%1
2331
16th to endDay
37%5%16%25%13%2
2435
June1st to 15thDay
36%7%17%26%11%
2340
16th to endDay
32%8%18%24%14%2
2340
July1st to 15thDay
40%7%18%20%10%2
2201
16th to endDay
36%8%20%21%11%1
2310
August1st to 15thDay
44%7%15%21%9%1
2327
16th to endDay
42%8%16%20%10%1
2381
September1st to 15thDay
35%7%14%21%17%3
1992
16th to endDay
44%49%18%18%4
1881
October1st to 15thDay
32%38%23%26%5%
1694
16th to endDay
31%25%23%28%9%
1760
November1st to 15thDay
30%27%19%30%9%
1721
16th to endDay
36%27%22%24%6%
1620
December1st to 15thDay
39%310%21%19%5%
1620
16th to endDay
45%29%18%18%5%
1728
January1st to 15thNight
38%38%16%25%7%
2327
16th to endNight
39%25%21%24%6%
2496
February1st to 15thNight
36%27%22%23%6%
2244
16th to endNight
36%29%24%23%3
1866
March1st to 15thNight
35%39%21%22%7%
1980
16th to endNight
41%49%20%18%5%
2112
April1st to 15thNight
34%38%24%23%5%
1922
16th to endNight
36%410%18%21%8%
1710
May1st to 15thNight
40%6%13%21%15%2
1620
16th to endNight
38%5%14%26%13%1
1684
June1st to 15thNight
39%7%17%23%9%1
1620
16th to endNight
36%9%15%23%11%4
1620
July1st to 15thNight
38%9%19%21%8%2
1530
16th to endNight
36%9%21%20%9%2
1595
August1st to 15thNight
42%7%20%16%11%1
1609
16th to endNight
39%8%18%22%10%1
1809
September1st to 15thNight
36%6%15%19%17%4
1965
16th to endNight
45%411%13%19%3
1892
October1st to 15thNight
34%39%22%24%6%
1935
16th to endNight
29%26%20%28%11%
2112
November1st to 15thNight
31%27%18%27%13%
2134
16th to endNight
35%36%20%26%7%
2340
December1st to 15thNight
40%39%19%20%6%
2340
16th to endNight
45%39%18%18%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
23%12%26%32%5%
90
16th to endDay
17%19%41%11%9%
96
February1st to 15thDay
16%14%50%16%2
90
16th to endDay
15%11%33%28%11%
107
March1st to 15thDay
15%11%32%31%9%
270
16th to endDay
19%5%32%28%12%1
288
April1st to 15thDay
17%9%23%25%20%3
270
16th to endDay
20%422%23%20%9%
270
May1st to 15thDay
13%5%30%21%21%6%
288
16th to endDay
14%112%19%31%20%
331
June1st to 15thDay
12%28%24%31%21%
315
16th to endDay
10%9%26%27%25%
315
July1st to 15thDay
9%15%21%34%26%
305
16th to endDay
7%5%19%37%30%
326
August1st to 15thDay
15%1422%29%26%
313
16th to endDay
13%1423%26%30%
332
September1st to 15thDay
15%27%18%30%25%
315
16th to endDay
23%212%18%28%13%
278
October1st to 15thDay
19%218%30%21%7%
255
16th to endDay
14%5%13%30%25%8%
272
November1st to 15thDay
19%320%28%20%7%
229
16th to endDay
11%422%31%27%3
90
December1st to 15thDay
18%8%30%26%14%1
90
16th to endDay
28%13%31%17%9%
96
January1st to 15thNight
18%12%29%31%8%
720
16th to endNight
19%10%34%32%2
768
February1st to 15thNight
17%8%36%33%2
704
16th to endNight
16%11%40%26%3
631
March1st to 15thNight
15%9%33%33%7%
720
16th to endNight
20%8%27%33%10%
768
April1st to 15thNight
15%10%29%30%14%
718
16th to endNight
16%7%24%32%19%
630
May1st to 15thNight
14%423%36%19%1
540
16th to endNight
12%212%33%35%3
563
June1st to 15thNight
11%19%36%32%8%
540
16th to endNight
8%9%30%41%9%
540
July1st to 15thNight
10%15%30%44%7%
510
16th to endNight
6%16%27%48%10%
564
August1st to 15thNight
11%1231%44%8%
539
16th to endNight
11%2424%48%8%
663
September1st to 15thNight
10%18%29%41%8%
720
16th to endNight
21%211%26%32%4
685
October1st to 15thNight
18%320%29%24%4
660
16th to endNight
13%5%20%33%23%3
704
November1st to 15thNight
15%324%33%19%3
700
16th to endNight
15%7%26%33%16%1
720
December1st to 15thNight
20%6%23%38%10%
720
16th to endNight
24%7%24%33%8%
768
Page generated at 2017-09-23 06:43:45. Version ac04

Copyright 2017 A. Danko


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