Red n Blue Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Red n Blue Observatory clear sky chart from 2005-11-05 to 2017-09-23.

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
45%
15774
20%
46883
15%
15729
50%
15729
26%
30239

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
24%
900
16%
2506
7%
895
32%
895
19%
1813
January16th to endNight
24%
922
16%
2581
7%
922
32%
922
20%
1840
February1st to 15thNight
25%
704
15%
2112
6%
701
32%
701
18%
1497
February16th to endNight
24%
631
16%
1893
6%
631
32%
631
20%
1313
March1st to 15thNight
24%
720
15%
2160
8%
720
30%
720
19%
1517
March16th to endNight
36%
674
15%
2030
9%
674
42%
674
21%
1392
April1st to 15thNight
39%
539
22%
1797
15%
539
51%
539
27%
1099
April16th to endNight
44%
540
20%
1749
16%
540
51%
540
25%
1109
May1st to 15thNight
44%
540
16%
1619
10%
539
49%
539
23%
1104
May16th to endNight
57%
561
18%
1644
15%
561
60%
561
27%
1067
June1st to 15thNight
64%
540
20%
1440
15%
540
67%
540
38%
876
June16th to endNight
69%
540
22%
1440
17%
540
72%
540
41%
857
July1st to 15thNight
70%
510
20%
1360
17%
510
71%
510
38%
828
July16th to endNight
76%
564
25%
1457
22%
531
79%
531
42%
826
August1st to 15thNight
75%
539
23%
1693
24%
536
76%
536
39%
934
August16th to endNight
78%
573
26%
1910
30%
573
80%
573
38%
1012
September1st to 15thNight
66%
585
26%
1845
26%
585
68%
585
33%
1059
September16th to endNight
61%
689
28%
1903
21%
689
65%
689
35%
1159
October1st to 15thNight
58%
660
32%
1824
25%
660
63%
660
38%
1072
October16th to endNight
42%
704
24%
2237
20%
704
50%
704
27%
1373
November1st to 15thNight
45%
700
28%
2276
23%
700
55%
700
31%
1316
November16th to endNight
35%
720
23%
2340
17%
720
44%
720
24%
1476
December1st to 15thNight
29%
759
14%
2379
9%
759
34%
759
17%
1688
December16th to endNight
23%
960
14%
2688
6%
960
31%
960
17%
2012

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%40%
48031
Night
14%6%35%424447%42%
47063
TransparencyDay
42%5%11%22%14%2
47713
Night
41%5%11%22%15%3
46885
SeeingDay
15%5%20%24%22%11%
5802
Night
17%6%24%30%18%2
15776

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
20%9%48%5%23335%31%
1432
16th to endDay
14%10%47%6%2335%6%36%
1641
February1st to 15thDay
15%10%47%5%24446%34%
1750
16th to endDay
12%10%37%6%36%45%6%31%
1580
March1st to 15thDay
22%8%36%42434436%
1800
16th to endDay
17%9%35%6%25%447%32%
2204
April1st to 15thDay
15%6%35%424447%41%
2151
16th to endDay
17%5%25%5%2335%6%39%
2209
May1st to 15thDay
19%6%35%6%34447%35%
2331
16th to endDay
10%6%25%6%45%5%6%8%37%
2467
June1st to 15thDay
8%425%5%3446%8%47%
2520
16th to endDay
7%4245%35%6%7%9%43%
2520
July1st to 15thDay
11%425%6%46%5%6%10%36%
2520
16th to endDay
6%4145%35%6%8%11%42%
2610
August1st to 15thDay
7%415%5%445%6%8%45%
2253
16th to endDay
7%4246%35%5%6%8%46%
2292
September1st to 15thDay
10%5%25%6%2445%6%44%
2103
16th to endDay
12%5%24323347%48%
1894
October1st to 15thDay
12%424423446%50%
1804
16th to endDay
17%5%14323345%46%
1634
November1st to 15thDay
11%42441445%7%49%
1582
16th to endDay
20%8%35%423335%40%
1620
December1st to 15thDay
23%10%35%5%2333432%
1578
16th to endDay
21%9%46%5%23336%32%
1536
January1st to 15thNight
18%9%48%5%3343434%
2506
16th to endNight
16%9%46%5%24446%33%
2581
February1st to 15thNight
18%7%47%5%35%335%33%
2103
16th to endNight
16%10%36%43346%6%34%
1893
March1st to 15thNight
17%9%46%5%33435%36%
2160
16th to endNight
17%6%35%425%45%7%36%
2030
April1st to 15thNight
14%7%24423447%44%
1797
16th to endNight
16%4244245%5%7%41%
1749
May1st to 15thNight
16%6%25%4345%47%39%
1619
16th to endNight
8%425%5%26%6%6%10%39%
1643
June1st to 15thNight
7%4245%15%46%9%48%
1440
16th to endNight
6%323425%46%10%50%
1440
July1st to 15thNight
7%4235%2436%9%50%
1440
16th to endNight
5%21443446%10%52%
1556
August1st to 15thNight
6%31342445%9%53%
1704
16th to endNight
332443446%9%53%
1910
September1st to 15thNight
10%41342446%7%49%
1845
16th to endNight
10%5%25%414346%50%
1903
October1st to 15thNight
9%5%14324345%54%
1824
16th to endNight
17%6%24423235%48%
2237
November1st to 15thNight
12%5%24414345%50%
2276
16th to endNight
18%7%24422346%42%
2340
December1st to 15thNight
23%9%36%424346%31%
2379
16th to endNight
23%10%36%5%23445%30%
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%312%17%11%
1433
16th to endDay
48%413%26%7%
1641
February1st to 15thDay
50%410%23%8%1
1752
16th to endDay
51%5%13%20%8%
1580
March1st to 15thDay
51%49%21%11%1
1800
16th to endDay
50%5%13%23%6%1
2205
April1st to 15thDay
42%6%11%21%17%
2151
16th to endDay
43%411%23%12%3
2209
May1st to 15thDay
49%5%12%20%11%
2331
16th to endDay
42%8%13%20%13%2
2471
June1st to 15thDay
34%5%12%27%17%3
2520
16th to endDay
33%9%13%22%18%3
2520
July1st to 15thDay
41%6%13%18%14%4
2371
16th to endDay
31%9%16%24%15%2
2446
August1st to 15thDay
34%8%12%24%17%2
2240
16th to endDay
33%6%13%22%18%5%
2292
September1st to 15thDay
39%5%9%21%19%5%
2103
16th to endDay
35%5%7%24%22%4
1894
October1st to 15thDay
33%5%8%26%23%3
1804
16th to endDay
39%39%27%17%2
1634
November1st to 15thDay
34%310%24%18%7%
1582
16th to endDay
46%39%22%16%2
1620
December1st to 15thDay
55%411%18%9%
1578
16th to endDay
54%313%21%6%1
1536
January1st to 15thNight
53%39%19%12%
2506
16th to endNight
50%412%22%8%1
2581
February1st to 15thNight
52%311%22%8%1
2112
16th to endNight
49%413%21%10%
1893
March1st to 15thNight
50%48%21%11%3
2160
16th to endNight
46%6%15%21%9%1
2030
April1st to 15thNight
39%410%23%18%3
1797
16th to endNight
41%5%10%24%14%4
1749
May1st to 15thNight
44%6%11%22%13%
1620
16th to endNight
36%10%13%17%17%4
1645
June1st to 15thNight
30%6%13%24%20%3
1440
16th to endNight
27%7%15%21%20%7%
1440
July1st to 15thNight
31%6%12%26%19%4
1360
16th to endNight
26%6%13%30%19%4
1457
August1st to 15thNight
27%6%15%24%21%4
1693
16th to endNight
25%7%13%27%20%5%
1910
September1st to 15thNight
32%5%9%23%21%7%
1845
16th to endNight
34%46%22%24%7%
1903
October1st to 15thNight
31%38%24%25%6%
1824
16th to endNight
40%36%27%17%4
2237
November1st to 15thNight
35%39%21%22%7%
2276
16th to endNight
43%310%23%17%2
2340
December1st to 15thNight
53%411%19%9%1
2379
16th to endNight
56%411%17%8%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
38%7%31%15%5%1
90
16th to endDay
16%18%47%13%3
96
February1st to 15thDay
21%23%34%15%5%
90
16th to endDay
22%13%37%19%7%
81
March1st to 15thDay
33%10%37%15%3
90
16th to endDay
21%10%33%23%8%2
276
April1st to 15thDay
16%10%29%26%14%2
270
16th to endDay
19%6%27%26%14%6%
270
May1st to 15thDay
24%8%25%23%11%6%
288
16th to endDay
15%325%24%17%13%
367
June1st to 15thDay
11%316%27%29%12%
495
16th to endDay
8%323%29%23%10%
495
July1st to 15thDay
14%215%28%25%13%
475
16th to endDay
7%18%25%36%21%
470
August1st to 15thDay
15%7%20%28%27%
313
16th to endDay
10%28%21%39%17%
332
September1st to 15thDay
10%312%22%29%21%
315
16th to endDay
16%212%18%29%21%
283
October1st to 15thDay
11%420%27%27%9%
244
16th to endDay
18%427%35%14%
96
November1st to 15thDay
5%10%20%33%17%13%
90
16th to endDay
34%7%25%20%12%
90
December1st to 15thDay
17%13%32%26%6%3
90
16th to endDay
30%13%39%14%2
96
January1st to 15thNight
23%11%34%26%3
900
16th to endNight
20%10%38%26%2
922
February1st to 15thNight
22%11%35%26%3
704
16th to endNight
22%10%37%27%2
631
March1st to 15thNight
22%10%36%25%4
720
16th to endNight
21%7%29%32%8%1
674
April1st to 15thNight
17%9%29%31%11%
539
16th to endNight
20%426%34%13%
540
May1st to 15thNight
17%424%34%17%1
540
16th to endNight
11%318%33%29%4
563
June1st to 15thNight
9%16%42%28%1
540
16th to endNight
7%113%43%30%2
540
July1st to 15thNight
10%8%39%37%2
510
16th to endNight
6%17%30%44%9%
564
August1st to 15thNight
7%6%33%42%8%
539
16th to endNight
5%7%33%46%7%
573
September1st to 15thNight
12%211%29%36%7%
585
16th to endNight
12%314%28%34%6%
689
October1st to 15thNight
13%318%33%24%6%
660
16th to endNight
20%5%28%30%13%
704
November1st to 15thNight
14%8%28%32%16%
700
16th to endNight
22%11%27%27%10%
720
December1st to 15thNight
28%7%29%25%7%1
759
16th to endNight
28%8%34%25%3
960
Page generated at 2017-09-24 09:15:45. Version ac04

Copyright 2017 A. Danko


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