McKinney Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the McKinney Creek Observatory clear sky chart from 2005-11-05 to 2017-09-21.

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
71%
15301
29%
46913
27%
15266
74%
15266
43%
24727

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
65%
717
20%
2482
21%
716
67%
716
31%
1401
January16th to endNight
60%
768
25%
2496
25%
768
64%
768
29%
1501
February1st to 15thNight
60%
698
25%
2229
26%
697
63%
697
28%
1365
February16th to endNight
57%
632
24%
1895
24%
632
61%
632
29%
1179
March1st to 15thNight
56%
720
17%
2088
17%
720
58%
720
28%
1349
March16th to endNight
55%
768
20%
2037
15%
768
59%
768
31%
1321
April1st to 15thNight
59%
719
21%
1799
13%
719
61%
719
32%
1200
April16th to endNight
65%
720
25%
1800
14%
720
67%
720
44%
1067
May1st to 15thNight
69%
599
28%
1679
20%
599
71%
599
56%
814
May16th to endNight
77%
374
28%
1496
32%
374
79%
374
45%
642
June1st to 15thNight
81%
360
29%
1440
35%
360
85%
360
53%
561
June16th to endNight
90%
360
38%
1440
50%
360
91%
360
71%
458
July1st to 15thNight
96%
340
35%
1360
47%
340
96%
340
74%
419
July16th to endNight
89%
480
39%
1512
40%
450
90%
450
67%
581
August1st to 15thNight
89%
610
38%
1683
29%
607
90%
607
75%
722
August16th to endNight
93%
764
43%
1910
29%
764
93%
764
81%
864
September1st to 15thNight
92%
720
43%
1800
31%
720
93%
720
81%
804
September16th to endNight
87%
680
45%
1827
40%
680
89%
680
72%
825
October1st to 15thNight
76%
660
31%
1980
33%
660
78%
660
50%
980
October16th to endNight
78%
704
37%
2112
40%
704
81%
704
53%
1028
November1st to 15thNight
74%
700
30%
2267
33%
700
77%
700
43%
1148
November16th to endNight
64%
720
28%
2373
30%
720
67%
720
35%
1301
December1st to 15thNight
60%
720
22%
2520
22%
720
65%
720
26%
1508
December16th to endNight
51%
768
23%
2688
23%
768
56%
768
23%
1689

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
9%312212235%63%
47946
Night
11%312212235%61%
47104
TransparencyDay
24%37%18%24%21%
47627
Night
26%38%19%23%19%
46923
SeeingDay
12%9%29%31%11%4
5868
Night
12%27%32%34%9%
15312

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
18%412213335%52%
1453
16th to endDay
20%7%23313336%44%
1728
February1st to 15thDay
19%5%13313345%46%
1625
16th to endDay
22%8%24322345%39%
1579
March1st to 15thDay
18%7%25%32445%6%37%
1870
16th to endDay
17%6%24423447%42%
2187
April1st to 15thDay
16%7%24323446%45%
2149
16th to endDay
12%413213235%59%
2160
May1st to 15thDay
6%312212245%66%
2265
16th to endDay
8%414313345%60%
2615
June1st to 15thDay
4213313235%68%
2520
16th to endDay
1111112283%
2520
July1st to 15thDay
111122285%
2520
16th to endDay
1111212382%
2550
August1st to 15thDay
1111112285%
2268
16th to endDay
111122384%
2292
September1st to 15thDay
1111112383%
2160
16th to endDay
3111123478%
1923
October1st to 15thDay
6%212212346%65%
1650
16th to endDay
8%31231244464%
1760
November1st to 15thDay
9%313323346%56%
1592
16th to endDay
14%423323336%51%
1584
December1st to 15thDay
19%6%24423235%46%
1440
16th to endDay
22%6%24223345%42%
1536
January1st to 15thNight
16%41331335%6%49%
2482
16th to endNight
18%412423345%48%
2496
February1st to 15thNight
17%5%15%323347%45%
2227
16th to endNight
20%6%13313345%46%
1895
March1st to 15thNight
19%6%14323246%44%
2088
16th to endNight
19%5%13323346%46%
2037
April1st to 15thNight
15%424425%5%46%45%
1799
16th to endNight
10%412213445%59%
1800
May1st to 15thNight
6%21211225%6%68%
1679
16th to endNight
6%313212336%66%
1496
June1st to 15thNight
321212236%72%
1440
16th to endNight
11211111285%
1440
July1st to 15thNight
11122384%
1440
16th to endNight
21111112381%
1616
August1st to 15thNight
11112122282%
1692
16th to endNight
111122383%
1910
September1st to 15thNight
11112385%
1800
16th to endNight
11111212381%
1827
October1st to 15thNight
6%22322335%67%
1980
16th to endNight
7%11312336%67%
2112
November1st to 15thNight
10%312212346%61%
2267
16th to endNight
12%413323345%55%
2373
December1st to 15thNight
19%5%13413335%48%
2520
16th to endNight
23%6%13322345%43%
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
34%49%22%18%11%
1453
16th to endDay
42%39%14%18%12%
1728
February1st to 15thDay
39%48%21%20%6%
1625
16th to endDay
47%37%24%14%2
1579
March1st to 15thDay
43%5%11%16%17%5%
1870
16th to endDay
41%5%13%20%14%3
2187
April1st to 15thDay
39%5%11%23%15%4
2149
16th to endDay
28%411%26%23%6%
2160
May1st to 15thDay
19%38%28%33%8%
2265
16th to endDay
26%5%9%28%23%7%
2619
June1st to 15thDay
19%37%22%23%22%
2520
16th to endDay
8%1213%33%39%
2520
July1st to 15thDay
7%127%23%58%
2371
16th to endDay
9%229%22%53%
2392
August1st to 15thDay
7%118%29%50%
2252
16th to endDay
7%119%36%43%
2292
September1st to 15thDay
8%1312%34%40%
2160
16th to endDay
11%2322%35%23%
1923
October1st to 15thDay
18%37%22%27%19%
1650
16th to endDay
23%35%23%27%16%
1760
November1st to 15thDay
28%313%21%22%10%
1592
16th to endDay
33%48%19%27%6%
1584
December1st to 15thDay
42%29%20%19%5%
1440
16th to endDay
44%310%16%16%8%
1536
January1st to 15thNight
34%410%20%19%10%
2482
16th to endNight
38%39%14%17%15%
2496
February1st to 15thNight
38%47%20%19%8%
2238
16th to endNight
39%410%26%15%4
1895
March1st to 15thNight
41%411%16%19%6%
2088
16th to endNight
38%5%10%21%17%6%
2037
April1st to 15thNight
37%6%12%21%16%5%
1799
16th to endNight
27%5%12%26%20%8%
1800
May1st to 15thNight
16%311%25%30%12%
1680
16th to endNight
19%413%29%23%9%
1496
June1st to 15thNight
14%412%23%23%22%
1440
16th to endNight
8%315%31%40%
1440
July1st to 15thNight
6%136%22%59%
1360
16th to endNight
10%127%22%55%
1512
August1st to 15thNight
9%1211%27%48%
1683
16th to endNight
7%1210%31%47%
1910
September1st to 15thNight
6%1310%35%42%
1800
16th to endNight
11%1320%39%24%
1827
October1st to 15thNight
20%37%23%26%19%
1980
16th to endNight
18%36%23%28%18%
2112
November1st to 15thNight
24%311%23%22%14%
2267
16th to endNight
31%37%21%26%9%
2373
December1st to 15thNight
38%48%20%17%9%
2520
16th to endNight
44%39%15%16%9%
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
43%222%18%9%3
81
16th to endDay
26%7%19%26%14%5%
256
February1st to 15thDay
26%7%23%26%13%2
245
16th to endDay
25%14%25%22%11%
238
March1st to 15thDay
25%14%25%20%11%2
270
16th to endDay
23%13%33%17%10%1
288
April1st to 15thDay
23%19%31%18%5%1
269
16th to endDay
16%21%32%22%5%1
270
May1st to 15thDay
10%17%36%25%6%4
288
16th to endDay
11%16%21%33%10%6%
330
June1st to 15thDay
8%14%34%29%8%4
315
16th to endDay
16%33%38%10%8%
315
July1st to 15thDay
128%47%9%10%
305
16th to endDay
1131%44%11%8%
327
August1st to 15thDay
2135%42%10%6%
315
16th to endDay
1228%44%13%9%
332
September1st to 15thDay
15%34%40%14%4
315
16th to endDay
5%10%27%40%12%2
276
October1st to 15thDay
7%10%36%30%12%2
255
16th to endDay
13%11%25%29%18%1
272
November1st to 15thDay
12%39%28%38%8%
98
16th to endDay
19%14%16%29%17%2
84
December1st to 15thDay
31%8%28%20%11%
60
16th to endDay
21%6%20%21%17%12%
64
January1st to 15thNight
18%27%34%27%10%
720
16th to endNight
21%19%30%26%10%
768
February1st to 15thNight
18%38%34%27%7%
704
16th to endNight
24%48%33%22%6%
632
March1st to 15thNight
21%48%31%26%6%
720
16th to endNight
21%412%29%26%6%
768
April1st to 15thNight
18%411%36%26%3
719
16th to endNight
12%411%35%26%9%
720
May1st to 15thNight
7%217%35%30%6%
600
16th to endNight
6%28%31%45%5%
375
June1st to 15thNight
48%35%45%6%
360
16th to endNight
1436%51%6%
360
July1st to 15thNight
25%65%8%
340
16th to endNight
2320%54%18%
480
August1st to 15thNight
1329%51%13%
610
16th to endNight
1232%51%11%
764
September1st to 15thNight
1229%51%14%
720
16th to endNight
25%33%41%15%
680
October1st to 15thNight
8%18%35%33%13%
660
16th to endNight
8%17%32%33%16%
704
November1st to 15thNight
12%15%35%32%12%
700
16th to endNight
14%210%33%27%10%
720
December1st to 15thNight
22%37%37%20%9%
720
16th to endNight
26%311%31%21%5%
768
Page generated at 2017-09-22 04:35:39. Version ac04

Copyright 2017 A. Danko


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