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 2018-11-30.

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
52%
17184
29%
51737
20%
17140
60%
17140
39%
28241

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
42%
972
30%
2522
14%
970
52%
970
42%
1455
January16th to endNight
39%
1040
34%
2704
14%
1040
51%
1040
42%
1551
February1st to 15thNight
36%
813
27%
2338
12%
808
46%
808
35%
1345
February16th to endNight
27%
679
29%
2045
10%
679
41%
679
33%
1161
March1st to 15thNight
35%
585
28%
2145
18%
585
49%
585
28%
1195
March16th to endNight
37%
624
25%
2288
17%
624
51%
624
30%
1226
April1st to 15thNight
33%
584
25%
2142
13%
584
51%
584
32%
1113
April16th to endNight
37%
579
27%
1818
18%
579
52%
579
37%
990
May1st to 15thNight
40%
585
24%
1755
15%
585
54%
585
33%
1040
May16th to endNight
53%
610
25%
1828
22%
609
63%
609
40%
1020
June1st to 15thNight
72%
585
25%
1755
25%
585
77%
585
52%
864
June16th to endNight
75%
585
25%
1755
28%
585
78%
585
46%
912
July1st to 15thNight
80%
555
24%
1665
27%
555
82%
555
45%
869
July16th to endNight
88%
612
32%
1738
38%
579
89%
579
56%
812
August1st to 15thNight
89%
575
38%
1717
45%
572
90%
572
58%
790
August16th to endNight
81%
621
30%
2051
35%
621
82%
621
42%
1046
September1st to 15thNight
73%
585
22%
2145
27%
585
74%
585
32%
1166
September16th to endNight
71%
582
32%
2145
34%
582
75%
582
37%
1084
October1st to 15thNight
62%
660
34%
2220
28%
660
68%
660
41%
1131
October16th to endNight
52%
832
36%
2496
21%
832
62%
832
45%
1279
November1st to 15thNight
51%
856
30%
2496
18%
856
59%
856
41%
1372
November16th to endNight
43%
1050
34%
2730
16%
1050
55%
1050
42%
1566
December1st to 15thNight
40%
975
31%
2535
14%
975
50%
975
37%
1553
December16th to endNight
37%
1040
28%
2704
12%
1040
46%
1040
34%
1701

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%3133233418%46%
52559
Night
7%3132123318%50%
51936
Cloud CoverDay
10%423324446%52%
52557
Night
9%313323346%57%
51936
TransparencyDay
31%5%10%23%22%7%
52257
Night
27%49%22%24%11%
51741
SeeingDay
10%419%28%26%9%
7126
Night
11%5%27%36%17%1
17188

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%221112319%48%
1746
16th to endDay
8%3122122319%51%
1872
February1st to 15thDay
10%4233213219%44%
1861
16th to endDay
14%5%132111219%45%
1713
March1st to 15thDay
15%3124222319%40%
2145
16th to endDay
9%3133232320%45%
2288
April1st to 15thDay
8%4243232321%44%
2136
16th to endDay
9%4133123420%44%
2411
May1st to 15thDay
10%4144223420%41%
2526
16th to endDay
6%415%4343422%38%
2638
June1st to 15thDay
32342345%23%46%
2535
16th to endDay
21342335%22%49%
2535
July1st to 15thDay
321343335%17%51%
2535
16th to endDay
2122245%6%23%45%
2674
August1st to 15thDay
21123344417%54%
2486
16th to endDay
6%3144235%7%16%43%
2500
September1st to 15thDay
11%3145%244413%44%
2145
16th to endDay
10%3133244414%47%
2145
October1st to 15thDay
9%2134232412%52%
2057
16th to endDay
10%2122112211%60%
2080
November1st to 15thDay
10%3133233316%47%
2019
16th to endDay
9%3122212219%52%
1885
December1st to 15thDay
16%5%133212319%40%
1755
16th to endDay
14%6%133222320%40%
1872
January1st to 15thNight
8%3132122219%50%
2522
16th to endNight
8%2121121219%55%
2704
February1st to 15thNight
10%5%122122219%47%
2331
16th to endNight
11%3123112219%48%
2045
March1st to 15thNight
13%4132122320%43%
2145
16th to endNight
6%3122122320%51%
2288
April1st to 15thNight
8%2132122322%47%
2142
16th to endNight
8%3122123321%48%
1818
May1st to 15thNight
7%4134132321%46%
1754
16th to endNight
421232235%25%46%
1827
June1st to 15thNight
21231335%23%53%
1755
16th to endNight
1132223423%54%
1755
July1st to 15thNight
211221235%18%57%
1755
16th to endNight
2121123423%55%
1846
August1st to 15thNight
1112123416%64%
1727
16th to endNight
431332345%17%49%
2051
September1st to 15thNight
9%3133234414%49%
2145
16th to endNight
7%3133233413%51%
2145
October1st to 15thNight
8%3133223314%54%
2220
16th to endNight
9%2122112211%60%
2496
November1st to 15thNight
7%4132133315%52%
2496
16th to endNight
9%3132213318%50%
2730
December1st to 15thNight
11%6%133122319%44%
2535
16th to endNight
12%5%133122420%41%
2704

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%23212335%56%
1746
16th to endDay
12%312212345%58%
1872
February1st to 15thDay
13%434322335%53%
1861
16th to endDay
18%5%2421223452%
1713
March1st to 15thDay
16%423423445%48%
2145
16th to endDay
13%5%25%423345%50%
2286
April1st to 15thDay
10%434323446%51%
2136
16th to endDay
12%42332445%6%51%
2411
May1st to 15thDay
12%435%424447%46%
2526
16th to endDay
10%5%25%5%25%5%5%7%44%
2638
June1st to 15thDay
4313325%46%8%55%
2535
16th to endDay
5%21443445%8%54%
2535
July1st to 15thDay
5%324425%46%9%50%
2535
16th to endDay
3213336%6%6%10%52%
2674
August1st to 15thDay
322335%46%8%59%
2486
16th to endDay
6%2144345%7%10%47%
2500
September1st to 15thDay
11%4145%3445%6%47%
2145
16th to endDay
10%31332345%7%52%
2145
October1st to 15thDay
10%313423345%56%
2057
16th to endDay
10%31221222366%
2080
November1st to 15thDay
11%323323345%55%
2019
16th to endDay
11%312222225%62%
1885
December1st to 15thDay
16%5%2332224452%
1755
16th to endDay
17%6%13422345%47%
1872
January1st to 15thNight
10%423212325%60%
2522
16th to endNight
12%312212235%60%
2704
February1st to 15thNight
12%423312235%56%
2331
16th to endNight
15%412312235%55%
2045
March1st to 15thNight
14%423313345%51%
2145
16th to endNight
10%423323336%56%
2288
April1st to 15thNight
10%323313349%54%
2142
16th to endNight
10%314313347%56%
1818
May1st to 15thNight
10%323423447%51%
1754
16th to endNight
6%32332446%10%53%
1827
June1st to 15thNight
221231346%8%63%
1755
16th to endNight
221431445%10%59%
1755
July1st to 15thNight
331241445%11%57%
1755
16th to endNight
21221345%10%63%
1846
August1st to 15thNight
111121246%7%68%
1727
16th to endNight
431342436%10%54%
2051
September1st to 15thNight
10%41332445%7%52%
2145
16th to endNight
8%324323347%56%
2145
October1st to 15thNight
8%323322346%59%
2220
16th to endNight
10%21221223465%
2496
November1st to 15thNight
8%41422234460%
2496
16th to endNight
10%31332333460%
2730
December1st to 15thNight
12%6%22323335%54%
2535
16th to endNight
15%5%23322245%50%
2704

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
31%37%21%27%8%
1747
16th to endDay
29%27%19%30%10%
1872
February1st to 15thDay
35%47%21%22%8%
1862
16th to endDay
36%26%19%22%11%
1713
March1st to 15thDay
38%47%18%21%9%
2145
16th to endDay
36%5%10%19%20%7%
2288
April1st to 15thDay
33%411%21%17%11%
2136
16th to endDay
32%5%9%19%25%7%
2411
May1st to 15thDay
37%6%9%18%19%7%
2526
16th to endDay
36%7%11%22%18%2
2642
June1st to 15thDay
25%7%14%27%21%3
2535
16th to endDay
27%6%12%27%21%5%
2535
July1st to 15thDay
28%7%15%30%15%2
2396
16th to endDay
21%8%19%30%18%1
2519
August1st to 15thDay
20%7%13%31%25%3
2472
16th to endDay
27%9%16%27%15%3
2500
September1st to 15thDay
35%7%10%22%17%6%
2145
16th to endDay
29%5%9%23%23%9%
2145
October1st to 15thDay
29%411%21%19%13%
2057
16th to endDay
23%26%20%28%17%
2080
November1st to 15thDay
31%48%22%23%9%
2019
16th to endDay
26%26%20%31%12%
1885
December1st to 15thDay
35%37%20%25%7%
1755
16th to endDay
39%36%20%22%7%
1872
January1st to 15thNight
28%27%18%29%13%
2522
16th to endNight
27%25%18%29%16%
2704
February1st to 15thNight
31%38%18%23%14%
2341
16th to endNight
33%28%19%22%13%
2045
March1st to 15thNight
34%47%17%22%13%
2145
16th to endNight
30%5%11%21%24%6%
2288
April1st to 15thNight
28%5%11%20%19%14%
2142
16th to endNight
27%5%10%19%26%11%
1818
May1st to 15thNight
32%6%11%19%20%9%
1755
16th to endNight
25%7%15%26%21%3
1829
June1st to 15thNight
17%5%12%33%23%6%
1755
16th to endNight
21%6%11%27%25%7%
1755
July1st to 15thNight
21%7%12%34%19%4
1665
16th to endNight
13%6%16%34%24%3
1738
August1st to 15thNight
13%5%11%31%30%6%
1717
16th to endNight
22%6%12%30%22%4
2051
September1st to 15thNight
30%5%11%21%20%9%
2145
16th to endNight
26%48%22%26%11%
2145
October1st to 15thNight
26%310%24%19%16%
2220
16th to endNight
24%2417%29%21%
2496
November1st to 15thNight
27%38%23%23%13%
2496
16th to endNight
27%35%16%31%14%
2730
December1st to 15thNight
32%38%20%23%11%
2535
16th to endNight
36%37%20%21%9%
2704

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
20%8%32%28%11%
135
16th to endDay
10%9%39%24%13%2
144
February1st to 15thDay
10%8%42%29%8%
135
16th to endDay
28%12%34%20%5%
120
March1st to 15thDay
18%13%37%22%7%
135
16th to endDay
11%9%41%27%10%
144
April1st to 15thDay
14%17%28%26%12%
135
16th to endDay
13%9%38%24%12%1
423
May1st to 15thDay
15%9%31%32%8%2
543
16th to endDay
11%6%29%29%17%4
597
June1st to 15thDay
6%14%43%27%7%
570
16th to endDay
4113%34%35%9%
570
July1st to 15thDay
6%17%35%33%16%
550
16th to endDay
25%21%49%20%
595
August1st to 15thDay
4427%49%13%
549
16th to endDay
8%5%31%38%16%
412
September1st to 15thDay
8%1315%36%35%
180
16th to endDay
18%419%38%18%
180
October1st to 15thDay
6%217%25%37%11%
180
16th to endDay
17%419%27%25%6%
192
November1st to 15thDay
20%7%27%23%17%3
180
16th to endDay
15%10%32%23%15%2
178
December1st to 15thDay
25%325%27%11%5%
135
16th to endDay
22%13%34%23%6%
144
January1st to 15thNight
12%8%31%36%10%
975
16th to endNight
13%9%35%34%7%
1040
February1st to 15thNight
14%10%36%32%5%
813
16th to endNight
17%11%42%25%3
679
March1st to 15thNight
16%8%36%31%6%
585
16th to endNight
10%10%40%32%6%
624
April1st to 15thNight
9%10%45%28%5%
584
16th to endNight
11%8%40%30%8%
579
May1st to 15thNight
11%5%38%35%7%1
585
16th to endNight
7%333%36%18%1
611
June1st to 15thNight
3120%50%23%1
585
16th to endNight
2115%48%28%3
585
July1st to 15thNight
39%44%36%4
555
16th to endNight
2443%44%4
612
August1st to 15thNight
2345%44%4
575
16th to endNight
6%440%40%6%
621
September1st to 15thNight
12%15%37%37%5%
585
16th to endNight
10%10%37%34%6%
582
October1st to 15thNight
10%120%37%26%3
660
16th to endNight
12%6%27%33%19%1
832
November1st to 15thNight
10%5%29%36%17%1
856
16th to endNight
12%8%33%32%12%
1050
December1st to 15thNight
16%8%32%35%7%
975
16th to endNight
18%7%34%32%6%
1040
Page generated at 2018-12-01 10:35:31. Version ac04

Copyright 2018 A. Danko


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