StarPines Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the StarPines Observatory clear sky chart from 2005-11-05 to 2018-01-20.

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
69%
16179
36%
48471
29%
16140
76%
16140
51%
23387

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
63%
779
33%
2522
29%
776
72%
776
42%
1259
January16th to endNight
58%
788
36%
2561
33%
788
68%
788
39%
1335
February1st to 15thNight
64%
698
36%
2172
29%
698
76%
698
48%
1040
February16th to endNight
57%
632
35%
1895
32%
632
65%
632
43%
994
March1st to 15thNight
59%
720
37%
1998
27%
720
70%
720
50%
1015
March16th to endNight
63%
768
36%
2112
25%
768
72%
768
53%
1051
April1st to 15thNight
54%
719
30%
1978
16%
719
64%
719
49%
1022
April16th to endNight
57%
543
44%
1647
26%
543
72%
543
63%
672
May1st to 15thNight
66%
539
37%
1619
27%
539
73%
539
56%
722
May16th to endNight
67%
561
39%
1684
28%
561
74%
561
66%
696
June1st to 15thNight
72%
540
33%
1620
27%
540
75%
540
66%
681
June16th to endNight
83%
540
34%
1620
31%
540
84%
540
71%
665
July1st to 15thNight
82%
510
24%
1530
20%
510
83%
510
49%
770
July16th to endNight
79%
564
24%
1593
21%
531
82%
531
40%
884
August1st to 15thNight
86%
539
30%
1611
26%
536
87%
536
50%
797
August16th to endNight
83%
663
34%
1857
29%
663
83%
663
46%
1000
September1st to 15thNight
80%
720
30%
1980
26%
720
83%
720
50%
1049
September16th to endNight
80%
716
46%
1980
35%
716
86%
716
71%
874
October1st to 15thNight
73%
720
39%
2046
31%
720
79%
720
61%
942
October16th to endNight
77%
768
44%
2304
38%
768
84%
768
62%
1014
November1st to 15thNight
72%
760
37%
2368
32%
760
80%
760
53%
1098
November16th to endNight
68%
780
41%
2535
38%
780
77%
780
52%
1134
December1st to 15thNight
67%
780
35%
2535
32%
780
75%
780
44%
1236
December16th to endNight
61%
832
35%
2704
31%
832
69%
832
37%
1437

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
4313323346%62%
49051
Night
3313323345%65%
48667
TransparencyDay
22%2415%28%26%
48746
Night
19%2415%28%28%
48473
SeeingDay
6%12%26%31%17%5%
5878
Night
5%414%32%34%9%
16189

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
6%414313235%61%
1746
16th to endDay
7%413324445%57%
1766
February1st to 15thDay
46%23323345%59%
1688
16th to endDay
6%6%2442336%7%53%
1579
March1st to 15thDay
3423413446%61%
1962
16th to endDay
4324314345%63%
2112
April1st to 15thDay
331432335%6%63%
1970
16th to endDay
2212212336%69%
2310
May1st to 15thDay
3214213335%68%
2331
16th to endDay
3212212335%70%
2429
June1st to 15thDay
111212235%77%
2340
16th to endDay
11121222480%
2340
July1st to 15thDay
2224436%5%6%7%53%
2340
16th to endDay
7%426%7%47%8%8%8%34%
2467
August1st to 15thDay
5%4145%35%5%7%8%47%
2340
16th to endDay
5%5%244345%6%7%50%
2340
September1st to 15thDay
5%2145%35%45%7%53%
1980
16th to endDay
2111312235%73%
1980
October1st to 15thDay
221231323472%
1911
16th to endDay
2212212245%72%
1920
November1st to 15thDay
1213323436%66%
1818
16th to endDay
5%313212336%67%
1755
December1st to 15thDay
5%7%225%13346%57%
1755
16th to endDay
7%6%2442335%5%54%
1872
January1st to 15thNight
4424323346%60%
2522
16th to endNight
7%5%2432233460%
2561
February1st to 15thNight
35%13312345%65%
2161
16th to endNight
44134225%5%6%57%
1895
March1st to 15thNight
341331245%5%63%
1998
16th to endNight
3212313345%67%
2112
April1st to 15thNight
332331334464%
1978
16th to endNight
1111211235%77%
1647
May1st to 15thNight
22221233473%
1619
16th to endNight
22121122379%
1684
June1st to 15thNight
11221223378%
1620
16th to endNight
221112381%
1620
July1st to 15thNight
2213425%5%6%7%58%
1620
16th to endNight
23245%46%7%7%12%43%
1701
August1st to 15thNight
21123345%7%10%56%
1620
16th to endNight
21145%35%5%6%8%55%
1857
September1st to 15thNight
231342446%8%58%
1980
16th to endNight
211111225%79%
1980
October1st to 15thNight
311221233473%
2046
16th to endNight
121221223474%
2304
November1st to 15thNight
2312314235%68%
2368
16th to endNight
4312212325%70%
2535
December1st to 15thNight
4412423445%61%
2535
16th to endNight
7%414434445%55%
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
25%2316%33%19%
1747
16th to endDay
27%2418%29%17%
1766
February1st to 15thDay
26%1318%26%22%
1688
16th to endDay
29%2319%29%16%
1579
March1st to 15thDay
22%2214%35%22%
1962
16th to endDay
23%2317%35%18%
2112
April1st to 15thDay
21%1217%34%21%
1970
16th to endDay
16%1114%35%30%
2310
May1st to 15thDay
18%2115%32%30%
2331
16th to endDay
16%2211%34%33%
2432
June1st to 15thDay
11%17%26%52%
2340
16th to endDay
9%25%19%62%
2340
July1st to 15thDay
25%5%8%15%16%28%
2201
16th to endDay
36%7%15%17%15%6%
2312
August1st to 15thDay
28%47%18%20%19%
2325
16th to endDay
28%48%18%25%14%
2340
September1st to 15thDay
27%46%18%23%19%
1980
16th to endDay
14%1111%34%36%
1980
October1st to 15thDay
16%2214%27%36%
1911
16th to endDay
14%1312%34%33%
1920
November1st to 15thDay
18%1318%31%26%
1818
16th to endDay
19%1217%29%30%
1755
December1st to 15thDay
26%36%19%24%18%
1755
16th to endDay
30%25%20%27%12%
1872
January1st to 15thNight
25%2415%32%20%
2522
16th to endNight
28%1316%28%20%
2561
February1st to 15thNight
21%15%18%27%24%
2172
16th to endNight
25%2418%29%19%
1895
March1st to 15thNight
20%2312%35%24%
1998
16th to endNight
18%25%17%33%21%
2112
April1st to 15thNight
21%2313%33%24%
1978
16th to endNight
10%1214%34%36%
1647
May1st to 15thNight
15%2114%30%35%
1620
16th to endNight
11%1111%38%35%
1685
June1st to 15thNight
12%15%23%56%
1620
16th to endNight
9%1415%67%
1620
July1st to 15thNight
20%5%11%14%19%28%
1530
16th to endNight
25%7%16%22%20%7%
1593
August1st to 15thNight
19%411%20%20%23%
1611
16th to endNight
24%47%22%23%17%
1857
September1st to 15thNight
21%49%19%21%23%
1980
16th to endNight
10%1110%36%39%
1980
October1st to 15thNight
15%1315%27%36%
2046
16th to endNight
13%2411%26%42%
2304
November1st to 15thNight
19%1216%35%24%
2368
16th to endNight
18%1215%29%33%
2535
December1st to 15thNight
23%2419%25%23%
2535
16th to endNight
29%25%19%28%14%
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
22%415%34%17%4
135
16th to endDay
8%12%23%22%24%8%
109
February1st to 15thDay
6%17%33%28%11%3
203
16th to endDay
13%26%31%18%9%
238
March1st to 15thDay
7%21%33%22%12%2
270
16th to endDay
7%24%32%22%10%2
288
April1st to 15thDay
8%24%34%18%8%4
269
16th to endDay
5%32%34%19%6%1
270
May1st to 15thDay
6%20%38%23%7%2
288
16th to endDay
418%31%32%10%2
330
June1st to 15thDay
313%42%23%13%3
315
16th to endDay
1330%40%16%7%
315
July1st to 15thDay
2225%44%19%5%
305
16th to endDay
7%211%38%27%12%
327
August1st to 15thDay
4113%44%28%8%
315
16th to endDay
7%11%42%27%9%
332
September1st to 15thDay
5%323%42%17%6%
315
16th to endDay
6%9%25%41%13%4
315
October1st to 15thDay
415%34%24%17%3
246
16th to endDay
4417%34%28%9%
144
November1st to 15thDay
48%17%42%22%5%
135
16th to endDay
7%11%26%26%22%5%
135
December1st to 15thDay
313%19%29%32%1
135
16th to endDay
10%9%15%31%26%6%
144
January1st to 15thNight
7%316%37%23%10%
780
16th to endNight
11%6%16%34%24%7%
788
February1st to 15thNight
6%6%16%39%26%5%
704
16th to endNight
8%5%21%40%19%4
632
March1st to 15thNight
7%7%20%33%27%4
720
16th to endNight
47%19%34%28%4
768
April1st to 15thNight
49%23%35%23%3
719
16th to endNight
111%26%33%22%4
543
May1st to 15thNight
36%19%39%26%5%
540
16th to endNight
2420%34%32%4
563
June1st to 15thNight
2218%39%32%4
540
16th to endNight
9%37%44%7%
540
July1st to 15thNight
25%25%53%11%
510
16th to endNight
31216%56%20%
564
August1st to 15thNight
3215%60%18%
539
16th to endNight
31316%52%23%
663
September1st to 15thNight
315%22%50%16%
720
16th to endNight
3111%29%42%11%
716
October1st to 15thNight
3314%37%35%5%
720
16th to endNight
2311%29%38%14%
768
November1st to 15thNight
3215%37%31%8%
760
16th to endNight
6%415%31%32%10%
780
December1st to 15thNight
8%412%37%31%5%
780
16th to endNight
10%6%13%39%23%6%
832
Page generated at 2018-01-21 10:19:21. Version ac04

Copyright 2018 A. Danko


StarPines Observatory Clear Sky Chart |Charts Home