Pinhead Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pinhead Observatory clear sky chart from 2005-11-05 to 2017-03-31.

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
70%
15249
35%
45247
29%
15200
77%
15200
53%
21545

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
54%
720
29%
2479
25%
716
64%
716
38%
1215
January16th to endNight
50%
768
34%
2370
23%
768
63%
768
37%
1255
February1st to 15thNight
58%
700
33%
2107
27%
699
68%
699
43%
1104
February16th to endNight
57%
632
29%
1895
28%
632
64%
632
36%
1070
March1st to 15thNight
59%
720
29%
2160
24%
720
68%
720
46%
1095
March16th to endNight
65%
768
31%
2004
23%
768
71%
768
49%
1100
April1st to 15thNight
60%
659
32%
1649
17%
659
67%
659
48%
925
April16th to endNight
67%
660
32%
1650
17%
660
72%
660
62%
832
May1st to 15thNight
71%
563
34%
1553
23%
563
74%
563
60%
735
May16th to endNight
70%
513
33%
1541
25%
513
74%
513
66%
645
June1st to 15thNight
82%
405
37%
1395
35%
405
87%
405
71%
506
June16th to endNight
96%
330
40%
1320
48%
330
97%
330
80%
386
July1st to 15thNight
91%
310
38%
1240
46%
310
91%
310
66%
413
July16th to endNight
88%
556
34%
1494
28%
516
89%
516
64%
673
August1st to 15thNight
93%
657
40%
1640
27%
653
94%
653
80%
742
August16th to endNight
94%
700
43%
1750
29%
700
94%
700
80%
793
September1st to 15thNight
92%
660
44%
1672
35%
660
93%
660
79%
748
September16th to endNight
87%
656
45%
1815
41%
656
91%
656
80%
749
October1st to 15thNight
76%
660
38%
1835
34%
660
81%
660
58%
894
October16th to endNight
74%
704
42%
2137
39%
704
82%
704
57%
969
November1st to 15thNight
70%
700
36%
2275
34%
700
80%
700
55%
996
November16th to endNight
66%
720
37%
2340
34%
720
75%
720
49%
1096
December1st to 15thNight
57%
720
33%
2340
27%
720
68%
720
37%
1227
December16th to endNight
51%
768
31%
2586
25%
768
62%
768
33%
1377

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
2212312335%70%
45814
Night
2213323345%68%
45444
TransparencyDay
17%36%15%28%29%
45505
Night
18%26%15%27%29%
45253
SeeingDay
5%12%34%34%10%2
5243
Night
3416%34%32%8%
15256

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
4425%423346%60%
1456
16th to endDay
7%6%26%313336%55%
1851
February1st to 15thDay
332432435%6%59%
1751
16th to endDay
5%5%26%5%33435%54%
1579
March1st to 15thDay
23234235%5%9%56%
1800
16th to endDay
23235%245%6%7%56%
2211
April1st to 15thDay
4413322246%63%
1969
16th to endDay
2112213346%71%
1980
May1st to 15thDay
112313346%70%
2065
16th to endDay
1111212236%74%
2221
June1st to 15thDay
11222225%77%
2230
16th to endDay
1111287%
2310
July1st to 15thDay
11221212379%
2310
16th to endDay
2111212236%75%
2247
August1st to 15thDay
111112385%
1980
16th to endDay
11122483%
2100
September1st to 15thDay
111112385%
1956
16th to endDay
121222383%
1815
October1st to 15thDay
213323235%70%
1793
16th to endDay
111221333474%
1733
November1st to 15thDay
221232334469%
1584
16th to endDay
231342335%7%61%
1620
December1st to 15thDay
33244245%6%9%53%
1620
16th to endDay
7%5%24433346%54%
1633
January1st to 15thNight
45%23323447%57%
2479
16th to endNight
5%42442335%6%56%
2370
February1st to 15thNight
242341335%6%59%
2101
16th to endNight
4326%42445%5%53%
1895
March1st to 15thNight
232432446%7%59%
2160
16th to endNight
131343446%7%59%
2004
April1st to 15thNight
2423324235%65%
1649
16th to endNight
212213336%72%
1650
May1st to 15thNight
132335%7%70%
1553
16th to endNight
112211235%77%
1540
June1st to 15thNight
1112235%80%
1395
16th to endNight
1111289%
1320
July1st to 15thNight
11221212381%
1320
16th to endNight
212313235%73%
1608
August1st to 15thNight
11112484%
1650
16th to endNight
11112384%
1750
September1st to 15thNight
111212484%
1672
16th to endNight
11112385%
1815
October1st to 15thNight
111333333472%
1835
16th to endNight
111232323474%
2137
November1st to 15thNight
1212322345%71%
2275
16th to endNight
1212334447%64%
2340
December1st to 15thNight
3415%424347%57%
2340
16th to endNight
5%42443435%6%55%
2586

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
25%27%14%26%24%
1456
16th to endDay
30%36%16%19%23%
1851
February1st to 15thDay
24%35%16%26%22%
1751
16th to endDay
33%36%16%30%10%
1579
March1st to 15thDay
23%49%21%22%18%
1800
16th to endDay
26%410%23%21%14%
2211
April1st to 15thDay
24%49%24%25%11%
1969
16th to endDay
15%49%20%33%16%
1980
May1st to 15thDay
15%310%19%29%21%
2065
16th to endDay
13%39%22%38%12%
2224
June1st to 15thDay
12%25%13%31%33%
2230
16th to endDay
6%135%30%52%
2310
July1st to 15thDay
12%146%22%52%
2161
16th to endDay
12%3417%29%33%
2098
August1st to 15thDay
6%28%32%48%
1966
16th to endDay
7%129%35%43%
2100
September1st to 15thDay
6%149%28%48%
1956
16th to endDay
9%128%35%42%
1815
October1st to 15thDay
18%3415%29%29%
1793
16th to endDay
15%3411%26%37%
1733
November1st to 15thDay
19%3415%32%25%
1584
16th to endDay
23%26%14%25%28%
1620
December1st to 15thDay
24%410%18%22%18%
1620
16th to endDay
32%47%20%20%15%
1633
January1st to 15thNight
25%27%15%26%23%
2479
16th to endNight
27%28%13%20%25%
2370
February1st to 15thNight
24%46%14%25%24%
2112
16th to endNight
31%36%17%27%14%
1895
March1st to 15thNight
22%39%19%25%20%
2160
16th to endNight
22%39%23%25%15%
2004
April1st to 15thNight
23%37%28%20%15%
1649
16th to endNight
13%38%22%32%18%
1650
May1st to 15thNight
14%39%21%29%21%
1554
16th to endNight
10%29%24%39%13%
1541
June1st to 15thNight
8%18%16%30%34%
1395
16th to endNight
437%26%56%
1320
July1st to 15thNight
9%138%19%57%
1240
16th to endNight
14%1412%28%38%
1494
August1st to 15thNight
6%115%31%53%
1640
16th to endNight
8%28%32%47%
1750
September1st to 15thNight
7%148%26%51%
1672
16th to endNight
6%128%35%44%
1815
October1st to 15thNight
17%1413%32%29%
1835
16th to endNight
15%339%27%40%
2137
November1st to 15thNight
17%1414%30%30%
2275
16th to endNight
19%26%16%24%29%
2340
December1st to 15thNight
26%5%6%15%24%21%
2340
16th to endNight
29%38%15%24%17%
2586

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
14%25%34%21%4
84
16th to endDay
14%17%36%24%5%1
277
February1st to 15thDay
6%22%33%28%6%1
266
16th to endDay
12%24%30%26%6%
238
March1st to 15thDay
10%17%34%24%12%
270
16th to endDay
6%17%40%25%7%1
286
April1st to 15thDay
11%21%41%18%5%1
209
16th to endDay
6%29%35%22%32
210
May1st to 15thDay
321%39%27%5%2
228
16th to endDay
414%42%28%7%3
266
June1st to 15thDay
111%41%35%7%3
255
16th to endDay
2437%38%9%7%
255
July1st to 15thDay
1330%47%12%4
245
16th to endDay
224%50%14%6%
271
August1st to 15thDay
1134%46%9%6%
255
16th to endDay
127%52%11%7%
268
September1st to 15thDay
331%49%12%2
255
16th to endDay
17%32%41%15%
255
October1st to 15thDay
315%39%30%10%1
255
16th to endDay
28%33%37%17%
245
November1st to 15thDay
410%14%32%33%5%
90
16th to endDay
8%10%38%32%10%
90
December1st to 15thDay
5%8%23%42%16%3
90
16th to endDay
17%18%27%28%7%
80
January1st to 15thNight
8%7%24%38%17%4
720
16th to endNight
10%8%23%34%20%3
768
February1st to 15thNight
5%5%23%39%20%5%
704
16th to endNight
7%8%23%34%20%5%
632
March1st to 15thNight
36%25%35%22%5%
720
16th to endNight
25%20%37%28%4
768
April1st to 15thNight
5%7%21%38%24%3
659
16th to endNight
26%21%34%28%7%
660
May1st to 15thNight
15%19%38%30%5%
564
16th to endNight
5%19%35%34%4
515
June1st to 15thNight
212%39%41%3
405
16th to endNight
140%51%6%
330
July1st to 15thNight
1115%69%12%
310
16th to endNight
1322%56%15%
556
August1st to 15thNight
1225%53%17%
657
16th to endNight
1119%55%21%
700
September1st to 15thNight
223%51%21%
660
16th to endNight
8%30%45%14%
656
October1st to 15thNight
1312%41%33%8%
660
16th to endNight
2217%32%32%12%
704
November1st to 15thNight
3318%39%29%7%
700
16th to endNight
35%21%36%26%7%
720
December1st to 15thNight
6%6%20%39%24%2
720
16th to endNight
9%9%23%38%17%2
768
Page generated at 2017-04-01 05:23:15. Version ac04

Copyright 2017 A. Danko


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