A Shooting Star Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the A Shooting Star Observatory clear sky chart from 2005-11-05 to 2018-02-22.

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%
16220
33%
48883
21%
16179
64%
16179
41%
24714

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
49%
780
30%
2522
22%
776
62%
776
37%
1295
January16th to endNight
46%
832
33%
2704
25%
832
59%
832
34%
1419
February1st to 15thNight
47%
760
31%
2412
22%
760
62%
760
40%
1204
February16th to endNight
36%
660
36%
1979
22%
660
55%
660
33%
1034
March1st to 15thNight
43%
720
35%
1980
19%
720
59%
720
39%
1047
March16th to endNight
42%
768
34%
2112
16%
768
58%
768
40%
1097
April1st to 15thNight
33%
687
28%
1946
10%
687
48%
687
32%
1015
April16th to endNight
39%
540
40%
1667
18%
540
61%
540
42%
747
May1st to 15thNight
40%
540
34%
1619
17%
539
54%
539
44%
754
May16th to endNight
40%
561
33%
1684
17%
561
53%
561
42%
784
June1st to 15thNight
46%
540
31%
1620
19%
540
56%
540
52%
721
June16th to endNight
63%
540
33%
1620
26%
540
70%
540
60%
697
July1st to 15thNight
65%
510
20%
1530
14%
510
69%
510
40%
835
July16th to endNight
65%
564
16%
1593
12%
531
67%
531
28%
1010
August1st to 15thNight
73%
539
25%
1611
21%
536
74%
536
38%
897
August16th to endNight
74%
603
33%
1812
28%
603
78%
603
43%
953
September1st to 15thNight
71%
720
27%
1980
19%
720
76%
720
43%
1111
September16th to endNight
66%
716
44%
1980
26%
716
79%
716
60%
899
October1st to 15thNight
53%
720
35%
2076
19%
720
67%
720
49%
985
October16th to endNight
60%
768
43%
2304
30%
768
73%
768
51%
1072
November1st to 15thNight
53%
760
35%
2358
25%
760
65%
760
43%
1147
November16th to endNight
53%
780
38%
2535
29%
780
67%
780
44%
1175
December1st to 15thNight
49%
780
32%
2535
22%
780
64%
780
38%
1271
December16th to endNight
43%
832
31%
2704
22%
832
55%
832
29%
1545

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
342442445%6%56%
49368
Night
131332445%6%62%
49079
TransparencyDay
28%46%18%27%15%
49063
Night
22%37%20%29%17%
48885
SeeingDay
12%20%27%24%12%3
5911
Night
6%14%21%27%22%7%
16226

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
14245%23347%59%
1746
16th to endDay
25%24423445%58%
1872
February1st to 15thDay
17%245%23447%56%
1778
16th to endDay
5%245%3445%9%53%
1641
March1st to 15thDay
14233235%5%8%59%
1980
16th to endDay
243332335%7%59%
2112
April1st to 15thDay
1414424447%59%
2000
16th to endDay
1424413436%62%
2291
May1st to 15thDay
3414423446%59%
2331
16th to endDay
3324324445%61%
2429
June1st to 15thDay
211221424473%
2340
16th to endDay
221232333470%
2340
July1st to 15thDay
6%5%27%6%46%7%7%6%38%
2340
16th to endDay
10%7%37%9%5%7%7%8%8%23%
2467
August1st to 15thDay
10%7%36%8%5%6%6%5%5%34%
2340
16th to endDay
6%6%26%8%46%5%5%7%39%
2388
September1st to 15thDay
6%5%25%6%48%5%6%6%43%
1980
16th to endDay
221332334466%
1980
October1st to 15thDay
322331332469%
1883
16th to endDay
3312312246%68%
1920
November1st to 15thDay
212323346%68%
1828
16th to endDay
131232324469%
1755
December1st to 15thDay
24133235%46%60%
1755
16th to endDay
1425%6%26%6%6%7%49%
1872
January1st to 15thNight
325%4245%46%59%
2522
16th to endNight
25%135%2445%5%58%
2704
February1st to 15thNight
4133235%5%6%62%
2401
16th to endNight
1313425%5%5%8%59%
1979
March1st to 15thNight
1212425%45%7%61%
1980
16th to endNight
131231445%6%64%
2112
April1st to 15thNight
1323324445%63%
1946
16th to endNight
12213336%71%
1667
May1st to 15thNight
1212322346%68%
1619
16th to endNight
2212313235%71%
1684
June1st to 15thNight
1112313235%73%
1620
16th to endNight
11122223477%
1620
July1st to 15thNight
33234245%7%8%52%
1620
16th to endNight
4435%6%37%7%10%11%35%
1701
August1st to 15thNight
32135%35%5%6%9%52%
1620
16th to endNight
32144245%7%9%54%
1812
September1st to 15thNight
33234346%6%6%56%
1980
16th to endNight
111212235%77%
1980
October1st to 15thNight
1112223345%71%
2076
16th to endNight
2312211345%71%
2304
November1st to 15thNight
1213325%45%6%64%
2358
16th to endNight
121332335%468%
2535
December1st to 15thNight
14123245%5%8%60%
2535
16th to endNight
1425%5%35%5%6%7%51%
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%35%23%32%8%
1747
16th to endDay
28%27%20%30%10%
1872
February1st to 15thDay
28%27%25%20%15%
1778
16th to endDay
28%38%22%28%9%
1641
March1st to 15thDay
23%36%23%32%11%
1980
16th to endDay
24%36%26%27%10%
2112
April1st to 15thDay
25%36%22%31%12%
2000
16th to endDay
24%2420%33%13%
2291
May1st to 15thDay
25%3419%34%12%
2331
16th to endDay
25%4416%35%13%
2432
June1st to 15thDay
15%2211%31%36%
2340
16th to endDay
18%317%28%40%
2340
July1st to 15thDay
41%8%9%10%11%19%
2201
16th to endDay
52%10%12%11%9%2
2312
August1st to 15thDay
48%6%9%11%15%9%
2325
16th to endDay
42%7%8%16%18%6%
2388
September1st to 15thDay
39%6%8%13%17%14%
1980
16th to endDay
20%4416%34%20%
1980
October1st to 15thDay
22%2317%30%23%
1883
16th to endDay
18%2417%40%16%
1920
November1st to 15thDay
18%25%26%30%16%
1828
16th to endDay
19%3418%36%17%
1755
December1st to 15thDay
25%410%25%23%11%
1755
16th to endDay
34%38%22%22%8%
1872
January1st to 15thNight
26%37%22%30%10%
2522
16th to endNight
28%36%19%30%12%
2704
February1st to 15thNight
22%47%24%25%16%
2412
16th to endNight
24%46%21%30%12%
1979
March1st to 15thNight
21%45%24%33%10%
1980
16th to endNight
20%47%26%30%11%
2112
April1st to 15thNight
22%35%21%34%12%
1946
16th to endNight
15%2323%37%16%
1667
May1st to 15thNight
17%35%25%32%16%
1620
16th to endNight
17%2419%41%14%
1685
June1st to 15thNight
14%2210%31%38%
1620
16th to endNight
12%126%26%49%
1620
July1st to 15thNight
26%6%14%14%15%22%
1530
16th to endNight
36%8%19%17%13%4
1593
August1st to 15thNight
26%8%13%17%23%11%
1611
16th to endNight
23%5%12%25%23%9%
1812
September1st to 15thNight
25%5%11%20%22%15%
1980
16th to endNight
11%2317%35%28%
1980
October1st to 15thNight
16%35%19%30%24%
2076
16th to endNight
16%2316%38%21%
2304
November1st to 15thNight
20%35%23%29%17%
2358
16th to endNight
19%25%18%33%20%
2535
December1st to 15thNight
24%37%24%24%15%
2535
16th to endNight
33%47%21%23%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
15%19%29%20%11%3
135
16th to endDay
13%19%28%18%16%3
144
February1st to 15thDay
13%23%23%21%15%3
203
16th to endDay
20%33%25%15%4
264
March1st to 15thDay
14%25%31%19%6%2
270
16th to endDay
15%29%32%16%5%1
288
April1st to 15thDay
17%31%30%10%7%2
269
16th to endDay
19%32%31%11%4
270
May1st to 15thDay
12%31%34%14%5%
288
16th to endDay
12%26%30%22%6%
330
June1st to 15thDay
6%26%33%22%8%3
315
16th to endDay
5%8%37%31%13%2
315
July1st to 15thDay
8%9%31%34%12%3
305
16th to endDay
15%5%16%34%22%4
327
August1st to 15thDay
13%5%21%35%17%6%
315
16th to endDay
11%419%37%21%5%
332
September1st to 15thDay
10%12%26%31%14%5%
315
16th to endDay
9%18%26%27%13%4
315
October1st to 15thDay
10%32%27%17%10%3
218
16th to endDay
10%13%25%27%15%7%
144
November1st to 15thDay
7%22%25%26%10%6%
135
16th to endDay
11%25%21%20%17%4
135
December1st to 15thDay
9%20%30%19%18%1
135
16th to endDay
13%17%23%30%13%1
144
January1st to 15thNight
8%11%24%28%16%10%
780
16th to endNight
9%15%22%27%19%6%
832
February1st to 15thNight
5%15%26%26%19%5%
764
16th to endNight
8%23%29%22%12%3
660
March1st to 15thNight
7%21%23%24%17%5%
720
16th to endNight
6%21%26%27%14%3
768
April1st to 15thNight
8%30%23%22%12%2
687
16th to endNight
425%28%24%12%4
540
May1st to 15thNight
422%30%28%12%2
540
16th to endNight
5%22%25%24%19%3
563
June1st to 15thNight
214%32%31%15%3
540
16th to endNight
27%22%38%25%3
540
July1st to 15thNight
5%215%34%34%7%
510
16th to endNight
6%110%29%40%9%
564
August1st to 15thNight
5%29%27%45%10%
539
16th to endNight
428%30%37%16%
603
September1st to 15thNight
5%5%9%26%41%11%
720
16th to endNight
411%13%25%32%12%
716
October1st to 15thNight
415%23%29%19%7%
720
16th to endNight
5%11%17%26%24%13%
768
November1st to 15thNight
315%22%28%22%7%
760
16th to endNight
5%15%22%27%20%9%
780
December1st to 15thNight
7%14%23%26%22%4
780
16th to endNight
10%15%25%26%17%4
832
Page generated at 2018-02-23 09:21:40. Version ac04

Copyright 2018 A. Danko


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