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 2017-10-06.

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%
15879
35%
47022
29%
15830
77%
15830
54%
22252

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
61%
719
31%
1799
17%
719
67%
719
50%
995
April16th to endNight
67%
720
34%
1800
18%
720
72%
720
62%
899
May1st to 15thNight
72%
614
32%
1694
22%
614
75%
614
62%
790
May16th to endNight
70%
561
35%
1685
26%
561
74%
561
66%
708
June1st to 15thNight
83%
442
35%
1522
34%
442
87%
442
72%
545
June16th to endNight
96%
360
42%
1440
51%
360
97%
360
81%
418
July1st to 15thNight
92%
340
36%
1360
44%
340
92%
340
66%
451
July16th to endNight
89%
602
36%
1624
30%
562
90%
562
66%
722
August1st to 15thNight
93%
717
38%
1790
25%
713
93%
713
80%
810
August16th to endNight
94%
764
45%
1910
31%
764
94%
764
81%
859
September1st to 15thNight
92%
720
42%
1824
34%
720
93%
720
79%
820
September16th to endNight
88%
716
48%
1980
43%
716
91%
716
80%
813
October1st to 15thNight
77%
684
37%
1901
34%
684
82%
684
59%
918
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
2212212335%70%
48154
Night
2212323345%69%
47219
TransparencyDay
17%26%15%28%29%
47845
Night
17%26%15%27%30%
47028
SeeingDay
412%33%34%11%3
5992
Night
3416%33%33%8%
15886

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%5%7%56%
2217
April1st to 15thDay
3413322246%64%
2149
16th to endDay
12213347%71%
2160
May1st to 15thDay
112313346%70%
2254
16th to endDay
1111212236%74%
2429
June1st to 15thDay
11222235%78%
2433
16th to endDay
1111288%
2520
July1st to 15thDay
11221222379%
2520
16th to endDay
2111212236%75%
2425
August1st to 15thDay
111112385%
2160
16th to endDay
11122483%
2292
September1st to 15thDay
111122384%
2134
16th to endDay
121122383%
1980
October1st to 15thDay
212323235%71%
1854
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
2423323235%66%
1799
16th to endNight
112213346%72%
1800
May1st to 15thNight
132335%7%71%
1694
16th to endNight
112211225%77%
1684
June1st to 15thNight
112236%80%
1522
16th to endNight
1111290%
1440
July1st to 15thNight
11221212381%
1440
16th to endNight
212313235%74%
1738
August1st to 15thNight
11112385%
1800
16th to endNight
11112385%
1910
September1st to 15thNight
111212483%
1824
16th to endNight
111112385%
1980
October1st to 15thNight
1322333473%
1901
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%
2217
April1st to 15thDay
23%48%25%27%11%
2149
16th to endDay
14%410%20%32%16%
2160
May1st to 15thDay
15%39%19%30%20%
2254
16th to endDay
13%39%21%39%12%
2432
June1st to 15thDay
11%25%14%31%33%
2433
16th to endDay
6%135%27%56%
2520
July1st to 15thDay
11%146%22%53%
2371
16th to endDay
12%35%16%28%34%
2276
August1st to 15thDay
7%27%31%50%
2146
16th to endDay
7%128%35%44%
2292
September1st to 15thDay
7%25%10%29%45%
2134
16th to endDay
8%129%36%41%
1980
October1st to 15thDay
17%3415%29%29%
1854
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
22%37%28%24%14%
1799
16th to endNight
13%39%23%31%18%
1800
May1st to 15thNight
13%39%22%31%20%
1695
16th to endNight
10%29%23%38%15%
1685
June1st to 15thNight
7%17%18%29%34%
1522
16th to endNight
437%24%59%
1440
July1st to 15thNight
9%137%19%58%
1360
16th to endNight
13%1413%27%39%
1624
August1st to 15thNight
6%115%29%54%
1790
16th to endNight
7%28%32%48%
1910
September1st to 15thNight
7%148%27%49%
1824
16th to endNight
6%138%37%43%
1980
October1st to 15thNight
17%1313%33%30%
1901
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
288
April1st to 15thDay
9%20%39%21%7%1
269
16th to endDay
5%28%37%21%5%2
270
May1st to 15thDay
319%37%29%6%3
288
16th to endDay
413%41%28%9%3
330
June1st to 15thDay
11%36%35%10%4
315
16th to endDay
2433%38%12%9%
315
July1st to 15thDay
1225%46%16%7%
305
16th to endDay
221%49%17%8%
327
August1st to 15thDay
231%47%10%7%
315
16th to endDay
24%50%15%9%
332
September1st to 15thDay
333%47%13%2
315
16th to endDay
7%32%41%16%1
315
October1st to 15thDay
215%38%32%9%1
278
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
47%21%37%25%3
719
16th to endNight
27%20%35%27%6%
720
May1st to 15thNight
15%19%38%30%5%
615
16th to endNight
5%19%36%33%4
563
June1st to 15thNight
211%38%43%4
442
16th to endNight
137%54%6%
360
July1st to 15thNight
1115%69%12%
340
16th to endNight
1222%56%15%
602
August1st to 15thNight
1225%54%15%
717
16th to endNight
1119%54%22%
764
September1st to 15thNight
225%50%19%
720
16th to endNight
8%31%44%14%
716
October1st to 15thNight
1312%41%33%7%
684
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 2017-10-07 11:07:51. Version ac04

Copyright 2017 A. Danko


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