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 2017-04-01.

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%
15085
29%
45332
20%
15041
60%
15041
39%
24726

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
36%
749
28%
2154
12%
744
47%
744
35%
1240
February16th to endNight
27%
627
31%
1889
11%
627
42%
627
35%
1033
March1st to 15thNight
35%
540
28%
1980
18%
540
49%
540
28%
1109
March16th to endNight
37%
576
25%
2112
17%
576
50%
576
30%
1138
April1st to 15thNight
32%
497
26%
1823
14%
497
50%
497
31%
956
April16th to endNight
35%
495
26%
1557
17%
495
50%
495
36%
862
May1st to 15thNight
38%
495
23%
1485
14%
495
52%
495
30%
910
May16th to endNight
52%
514
24%
1540
20%
513
62%
513
38%
873
June1st to 15thNight
72%
495
26%
1485
25%
495
78%
495
52%
730
June16th to endNight
74%
495
24%
1485
26%
495
77%
495
44%
787
July1st to 15thNight
78%
465
26%
1395
28%
465
81%
465
44%
736
July16th to endNight
88%
522
30%
1468
36%
489
89%
489
55%
695
August1st to 15thNight
91%
494
40%
1475
47%
491
92%
491
62%
652
August16th to endNight
80%
525
30%
1735
35%
525
81%
525
41%
894
September1st to 15thNight
73%
495
23%
1815
28%
495
74%
495
32%
982
September16th to endNight
74%
492
33%
1815
35%
492
78%
492
40%
880
October1st to 15thNight
61%
558
36%
1878
29%
558
68%
558
43%
939
October16th to endNight
53%
704
37%
2112
21%
704
63%
704
48%
1044
November1st to 15thNight
53%
730
31%
2130
18%
730
62%
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
50%
900
37%
1435
December16th to endNight
38%
960
28%
2496
12%
960
48%
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%3133223420%45%
45765
Night
7%3122123320%50%
45531
Cloud CoverDay
10%423324446%52%
45763
Night
9%313323346%57%
45531
TransparencyDay
31%5%10%22%22%7%
45463
Night
27%49%22%24%11%
45336
SeeingDay
10%420%29%27%7%
4833
Night
10%6%28%35%17%1
15089

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%4233222323%43%
1810
16th to endDay
10%5%123122322%42%
2068
May1st to 15thDay
10%5%144223423%37%
2136
16th to endDay
7%425%4343425%33%
2222
June1st to 15thDay
32342345%25%43%
2145
16th to endDay
21332245%24%48%
2145
July1st to 15thDay
321242335%18%50%
2145
16th to endDay
32123245%6%26%43%
2284
August1st to 15thDay
2112234418%56%
2145
16th to endDay
6%2134235%8%18%40%
2113
September1st to 15thDay
10%2144245%415%43%
1815
16th to endDay
7%21332345%16%49%
1815
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%3133122325%46%
1823
16th to endNight
9%2132123323%46%
1557
May1st to 15thNight
7%4134132325%41%
1484
16th to endNight
421231235%27%44%
1539
June1st to 15thNight
2112133425%52%
1485
16th to endNight
11132223325%52%
1485
July1st to 15thNight
3123123419%56%
1485
16th to endNight
21121123426%52%
1576
August1st to 15thNight
1111123418%65%
1485
16th to endNight
431332346%19%47%
1735
September1st to 15thNight
9%3132234415%48%
1815
16th to endNight
5%31322345%15%51%
1815
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%434324447%51%
1810
16th to endDay
12%5%2332445%6%50%
2068
May1st to 15thDay
13%435%42445%7%43%
2136
16th to endDay
11%5%25%5%26%5%5%7%41%
2222
June1st to 15thDay
4313325%46%8%55%
2145
16th to endDay
6%2144345%5%7%53%
2145
July1st to 15thDay
5%324425%46%9%49%
2145
16th to endDay
3213436%6%6%10%50%
2284
August1st to 15thDay
21232446%7%63%
2145
16th to endDay
7%2144346%7%11%45%
2113
September1st to 15thDay
11%3145%345%6%6%47%
1815
16th to endDay
9%31332346%8%55%
1815
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%
1823
16th to endNight
12%314314347%54%
1557
May1st to 15thNight
11%4245%2345%8%47%
1484
16th to endNight
7%32332346%9%53%
1539
June1st to 15thNight
221231346%8%64%
1485
16th to endNight
321431445%10%58%
1485
July1st to 15thNight
431242445%11%56%
1485
16th to endNight
211221345%10%62%
1576
August1st to 15thNight
11121235%7%70%
1485
16th to endNight
5%31242337%11%52%
1735
September1st to 15thNight
11%41432445%7%52%
1815
16th to endNight
6%31432345%7%58%
1815
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
34%310%21%17%12%
1810
16th to endDay
34%49%19%24%7%
2068
May1st to 15thDay
40%6%9%18%16%7%
2136
16th to endDay
40%7%12%20%17%2
2226
June1st to 15thDay
25%7%14%27%21%3
2145
16th to endDay
28%6%12%27%19%5%
2145
July1st to 15thDay
28%7%15%29%16%2
2006
16th to endDay
23%8%19%29%17%1
2129
August1st to 15thDay
16%6%13%32%27%3
2131
16th to endDay
28%9%17%27%14%2
2113
September1st to 15thDay
34%7%11%22%16%7%
1815
16th to endDay
26%5%8%23%25%10%
1815
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%19%18%16%
1823
16th to endNight
29%5%10%18%25%11%
1557
May1st to 15thNight
34%7%12%18%18%9%
1485
16th to endNight
26%7%16%23%21%3
1541
June1st to 15thNight
17%5%13%33%22%7%
1485
16th to endNight
22%6%11%27%23%7%
1485
July1st to 15thNight
22%6%11%34%19%5%
1395
16th to endNight
14%6%17%34%23%3
1468
August1st to 15thNight
11%411%32%32%6%
1475
16th to endNight
23%7%12%31%21%4
1735
September1st to 15thNight
30%5%12%21%19%9%
1815
16th to endNight
23%5%8%22%27%13%
1815
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
15%15%30%26%13%
46
16th to endDay
16%7%39%23%11%1
298
May1st to 15thDay
17%10%34%28%7%1
393
16th to endDay
14%7%30%27%15%3
437
June1st to 15thDay
7%16%39%27%8%
420
16th to endDay
5%214%35%32%11%
420
July1st to 15thDay
6%18%44%32%6%
400
16th to endDay
35%22%50%17%
445
August1st to 15thDay
2428%51%11%
418
16th to endDay
11%6%33%37%10%
281
September1st to 15thDay
3120%43%32%
90
16th to endDay
7%214%48%26%
90
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%46%28%4
497
16th to endNight
11%8%42%29%7%
495
May1st to 15thNight
12%5%38%34%6%2
495
16th to endNight
7%333%36%17%1
515
June1st to 15thNight
3120%48%24%1
495
16th to endNight
2114%45%31%3
495
July1st to 15thNight
411%47%32%3
465
16th to endNight
3443%45%3
522
August1st to 15thNight
1344%45%4
494
16th to endNight
7%5%40%38%7%
525
September1st to 15thNight
13%16%38%36%4
495
16th to endNight
8%11%35%38%5%
492
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 2017-04-02 06:39:08. Version ac04

Copyright 2017 A. Danko


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