Quail Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Quail Creek Observatory clear sky chart from 2005-11-05 to 2017-09-19.

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
51%
15592
29%
46937
20%
15548
60%
15548
39%
25521

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
41%
897
30%
2327
14%
895
50%
895
41%
1350
January16th to endNight
39%
960
34%
2496
14%
960
51%
960
41%
1440
February1st to 15thNight
35%
749
28%
2154
12%
744
46%
744
35%
1240
February16th to endNight
27%
627
31%
1889
11%
627
42%
627
35%
1033
March1st to 15thNight
34%
540
28%
1980
18%
540
48%
540
28%
1109
March16th to endNight
36%
576
25%
2112
17%
576
49%
576
30%
1138
April1st to 15thNight
32%
539
24%
1977
14%
539
50%
539
31%
1032
April16th to endNight
35%
540
27%
1698
17%
540
51%
540
36%
937
May1st to 15thNight
39%
540
23%
1620
14%
540
52%
540
32%
967
May16th to endNight
50%
562
26%
1684
21%
561
62%
561
39%
953
June1st to 15thNight
70%
540
24%
1620
23%
540
76%
540
51%
804
June16th to endNight
74%
540
26%
1620
28%
540
76%
540
45%
852
July1st to 15thNight
77%
510
24%
1530
27%
510
80%
510
45%
801
July16th to endNight
87%
564
32%
1594
38%
531
89%
531
56%
746
August1st to 15thNight
90%
539
37%
1610
44%
536
90%
536
59%
737
August16th to endNight
79%
573
30%
1893
35%
573
80%
573
39%
992
September1st to 15thNight
73%
540
23%
1980
28%
540
74%
540
35%
1038
September16th to endNight
74%
504
33%
1857
35%
504
78%
504
41%
893
October1st to 15thNight
60%
558
36%
1878
29%
558
67%
558
43%
939
October16th to endNight
53%
704
37%
2112
21%
704
63%
704
48%
1044
November1st to 15thNight
52%
730
31%
2130
18%
730
61%
730
44%
1126
November16th to endNight
42%
900
33%
2340
16%
900
52%
900
40%
1373
December1st to 15thNight
39%
900
31%
2340
14%
900
49%
900
37%
1435
December16th to endNight
37%
960
28%
2496
12%
960
47%
960
35%
1542

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%3133233420%46%
47870
Night
7%3122123320%50%
47136
Cloud CoverDay
10%423324446%52%
47868
Night
9%313323347%57%
47136
TransparencyDay
31%5%10%23%22%7%
47568
Night
27%49%22%24%11%
46941
SeeingDay
10%419%29%27%8%
5589
Night
10%6%27%36%17%1
15596

By Month

Percentage Cloud Cover SW (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
10%5%221112321%47%
1611
16th to endDay
9%3122222321%48%
1728
February1st to 15thDay
10%4233213220%45%
1714
16th to endDay
12%4131111220%48%
1583
March1st to 15thDay
16%4134122320%39%
1980
16th to endDay
9%4133222321%45%
2112
April1st to 15thDay
7%4243232222%44%
1971
16th to endDay
9%4133123421%43%
2256
May1st to 15thDay
10%4144223421%40%
2331
16th to endDay
7%425%4344424%35%
2430
June1st to 15thDay
33342345%24%44%
2340
16th to endDay
21332345%23%48%
2340
July1st to 15thDay
321243335%17%51%
2340
16th to endDay
2123245%6%25%44%
2466
August1st to 15thDay
211233445%17%54%
2340
16th to endDay
6%3144335%8%17%41%
2306
September1st to 15thDay
9%2134244414%47%
1980
16th to endDay
7%21332345%16%49%
1848
October1st to 15thDay
9%2133222413%52%
1741
16th to endDay
7%3132112213%61%
1760
November1st to 15thDay
8%3133232318%49%
1725
16th to endDay
10%3122211221%49%
1620
December1st to 15thDay
16%5%133212320%39%
1620
16th to endDay
13%5%133122321%41%
1728
January1st to 15thNight
9%4132122220%49%
2327
16th to endNight
8%3122122320%53%
2496
February1st to 15thNight
11%5%122122220%47%
2147
16th to endNight
9%3123212220%51%
1889
March1st to 15thNight
14%4122122321%42%
1980
16th to endNight
6%3122122321%50%
2112
April1st to 15thNight
7%3132122324%46%
1977
16th to endNight
9%3122222322%47%
1698
May1st to 15thNight
7%4134132323%45%
1619
16th to endNight
421231235%26%44%
1683
June1st to 15thNight
2123133423%53%
1620
16th to endNight
132223424%52%
1620
July1st to 15thNight
21123123419%56%
1620
16th to endNight
2121133425%54%
1702
August1st to 15thNight
1112123416%63%
1620
16th to endNight
431332346%18%46%
1893
September1st to 15thNight
8%3132234414%51%
1980
16th to endNight
5%31322345%15%52%
1857
October1st to 15thNight
8%3133212314%56%
1878
16th to endNight
7%2122112213%61%
2112
November1st to 15thNight
5%3132122318%54%
2130
16th to endNight
10%3132113220%47%
2340
December1st to 15thNight
11%6%133122320%42%
2340
16th to endNight
11%5%133222321%42%
2496

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
13%5%22212325%56%
1611
16th to endDay
13%312322445%56%
1728
February1st to 15thDay
13%424222335%53%
1714
16th to endDay
15%5%2321223455%
1583
March1st to 15thDay
17%423423345%47%
1980
16th to endDay
13%5%25%423335%50%
2110
April1st to 15thDay
10%434323447%52%
1971
16th to endDay
12%42332445%6%50%
2256
May1st to 15thDay
12%435%424446%46%
2331
16th to endDay
10%5%25%5%25%5%5%7%42%
2430
June1st to 15thDay
5%313335%46%8%54%
2340
16th to endDay
6%2144345%5%8%53%
2340
July1st to 15thDay
5%324425%46%9%50%
2340
16th to endDay
3213436%6%6%11%51%
2466
August1st to 15thDay
313425%46%8%59%
2340
16th to endDay
7%3144345%7%10%45%
2306
September1st to 15thDay
10%3135%3445%6%50%
1980
16th to endDay
8%21332346%8%55%
1848
October1st to 15thDay
10%213413345%57%
1741
16th to endDay
8%31221122469%
1760
November1st to 15thDay
9%32332333458%
1725
16th to endDay
12%312222125%60%
1620
December1st to 15thDay
16%5%2332224451%
1620
16th to endDay
16%5%13422345%49%
1728
January1st to 15thNight
11%42321222460%
2327
16th to endNight
12%312222335%59%
2496
February1st to 15thNight
13%5%2331223456%
2147
16th to endNight
13%412322245%58%
1889
March1st to 15thNight
15%423313345%51%
1980
16th to endNight
10%424323336%55%
2112
April1st to 15thNight
9%323313349%53%
1977
16th to endNight
11%314313347%55%
1698
May1st to 15thNight
10%32342345%8%50%
1619
16th to endNight
7%32332346%10%52%
1683
June1st to 15thNight
321231346%8%64%
1620
16th to endNight
221431445%10%58%
1620
July1st to 15thNight
431242445%11%56%
1620
16th to endNight
21221345%10%63%
1702
August1st to 15thNight
11121245%7%69%
1620
16th to endNight
5%31342437%10%52%
1893
September1st to 15thNight
10%31332445%6%54%
1980
16th to endNight
6%31432345%7%58%
1857
October1st to 15thNight
8%312322236%61%
1878
16th to endNight
8%212212235%67%
2112
November1st to 15thNight
7%31421233463%
2130
16th to endNight
12%31332333459%
2340
December1st to 15thNight
13%5%22323345%54%
2340
16th to endNight
14%5%23323345%52%
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
32%37%20%27%9%
1612
16th to endDay
30%37%18%29%9%
1728
February1st to 15thDay
34%36%21%24%9%
1715
16th to endDay
33%26%20%23%12%
1583
March1st to 15thDay
39%46%17%21%9%
1980
16th to endDay
36%5%9%19%21%7%
2112
April1st to 15thDay
33%410%22%17%11%
1971
16th to endDay
33%5%9%19%23%7%
2256
May1st to 15thDay
38%6%9%17%20%7%
2331
16th to endDay
38%7%12%20%17%2
2434
June1st to 15thDay
26%7%13%26%21%3
2340
16th to endDay
28%6%12%27%20%5%
2340
July1st to 15thDay
28%7%15%30%15%2
2201
16th to endDay
22%8%20%29%17%1
2311
August1st to 15thDay
19%7%13%31%24%3
2326
16th to endDay
29%9%17%26%14%3
2306
September1st to 15thDay
31%6%10%24%19%7%
1980
16th to endDay
25%5%9%23%25%10%
1848
October1st to 15thDay
28%410%21%21%14%
1741
16th to endDay
21%26%21%30%17%
1760
November1st to 15thDay
30%37%23%25%10%
1725
16th to endDay
28%26%18%30%13%
1620
December1st to 15thDay
36%37%21%25%5%
1620
16th to endDay
37%37%21%23%8%
1728
January1st to 15thNight
29%26%16%30%13%
2327
16th to endNight
28%26%19%28%15%
2496
February1st to 15thNight
31%37%17%24%15%
2157
16th to endNight
30%28%20%23%14%
1889
March1st to 15thNight
34%48%18%21%13%
1980
16th to endNight
30%5%11%20%25%6%
2112
April1st to 15thNight
28%5%10%20%19%14%
1977
16th to endNight
28%5%10%20%24%11%
1698
May1st to 15thNight
32%6%11%18%20%10%
1620
16th to endNight
26%7%16%24%21%3
1685
June1st to 15thNight
18%5%12%33%23%7%
1620
16th to endNight
21%6%11%27%25%7%
1620
July1st to 15thNight
22%6%11%34%20%4
1530
16th to endNight
13%6%17%35%23%3
1594
August1st to 15thNight
12%5%11%32%30%6%
1610
16th to endNight
24%6%12%30%20%4
1893
September1st to 15thNight
28%5%12%22%21%10%
1980
16th to endNight
23%49%22%26%13%
1857
October1st to 15thNight
25%29%23%21%17%
1878
16th to endNight
21%2417%30%22%
2112
November1st to 15thNight
25%27%24%25%14%
2130
16th to endNight
29%36%14%30%15%
2340
December1st to 15thNight
33%37%20%24%9%
2340
16th to endNight
34%47%21%22%10%
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
21%10%31%27%10%
90
16th to endDay
14%7%40%22%13%1
96
February1st to 15thDay
6%8%43%35%5%
90
16th to endDay
17%8%44%22%7%
81
March1st to 15thDay
23%14%33%18%8%1
90
16th to endDay
9%11%37%26%14%1
96
April1st to 15thDay
12%16%25%26%18%
90
16th to endDay
15%10%39%24%10%
366
May1st to 15thDay
14%10%34%29%7%2
468
16th to endDay
13%7%32%28%14%3
517
June1st to 15thDay
7%114%41%27%8%
495
16th to endDay
5%213%33%35%10%
495
July1st to 15thDay
6%18%39%33%10%
475
16th to endDay
35%21%50%18%
515
August1st to 15thDay
3427%49%13%
493
16th to endDay
10%5%34%36%12%
346
September1st to 15thDay
2119%44%31%
135
16th to endDay
7%216%49%25%
99
October1st to 15thDay
215%30%44%7%
90
16th to endDay
12%417%32%27%6%
96
November1st to 15thDay
18%7%23%27%20%2
90
16th to endDay
27%12%31%20%5%3
90
December1st to 15thDay
32%320%24%13%6%
90
16th to endDay
12%14%41%22%8%
96
January1st to 15thNight
13%8%32%35%9%
900
16th to endNight
13%9%35%34%7%
960
February1st to 15thNight
15%10%35%32%5%
749
16th to endNight
14%12%43%25%3
627
March1st to 15thNight
17%8%35%31%6%
540
16th to endNight
11%10%39%31%6%
576
April1st to 15thNight
8%11%44%29%5%
539
16th to endNight
11%8%41%29%7%
540
May1st to 15thNight
11%5%38%35%7%2
540
16th to endNight
7%334%35%17%1
563
June1st to 15thNight
3120%48%24%2
540
16th to endNight
2114%47%30%3
540
July1st to 15thNight
410%46%35%3
510
16th to endNight
3442%45%4
564
August1st to 15thNight
2344%45%4
539
16th to endNight
7%5%40%39%6%
573
September1st to 15thNight
12%6%38%37%4
540
16th to endNight
7%11%36%37%5%
504
October1st to 15thNight
10%122%37%25%3
558
16th to endNight
10%6%28%33%20%
704
November1st to 15thNight
9%5%29%36%18%1
730
16th to endNight
13%8%33%32%11%
900
December1st to 15thNight
16%8%33%35%7%
900
16th to endNight
16%7%35%33%7%
960
Page generated at 2017-09-20 03:49:54. Version ac04

Copyright 2017 A. Danko


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