Star Hoppers Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Star Hoppers Observatory clear sky chart from 2005-11-05 to 2017-12-02.

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
36%
16034
15%
47851
10%
15992
42%
15992
20%
33568

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
17%
900
8%
2506
3%
895
22%
895
11%
2022
January16th to endNight
21%
870
8%
2598
4%
870
26%
870
11%
2070
February1st to 15thNight
18%
701
9%
2261
3%
701
24%
701
11%
1760
February16th to endNight
23%
631
13%
1893
6%
631
30%
631
14%
1431
March1st to 15thNight
27%
720
15%
2081
9%
720
32%
720
18%
1513
March16th to endNight
33%
768
18%
2112
10%
768
39%
768
21%
1497
April1st to 15thNight
28%
582
13%
1804
8%
582
35%
582
18%
1266
April16th to endNight
35%
540
20%
1620
9%
540
44%
540
25%
1064
May1st to 15thNight
38%
540
13%
1620
7%
540
44%
540
22%
1118
May16th to endNight
49%
562
15%
1663
12%
561
54%
561
29%
1055
June1st to 15thNight
56%
441
15%
1341
14%
441
60%
441
31%
818
June16th to endNight
57%
464
17%
1364
15%
464
61%
464
32%
835
July1st to 15thNight
65%
510
16%
1360
14%
510
67%
510
40%
808
July16th to endNight
68%
564
18%
1491
15%
531
70%
531
38%
887
August1st to 15thNight
65%
539
19%
1609
16%
536
68%
536
34%
976
August16th to endNight
61%
573
22%
1738
17%
573
66%
573
34%
1020
September1st to 15thNight
59%
663
23%
1923
19%
663
62%
663
35%
1130
September16th to endNight
58%
717
24%
1980
18%
717
62%
717
33%
1227
October1st to 15thNight
44%
720
18%
2068
15%
720
49%
720
25%
1405
October16th to endNight
26%
768
15%
2412
8%
768
34%
768
15%
1738
November1st to 15thNight
35%
760
18%
2471
14%
760
40%
760
20%
1654
November16th to endNight
24%
780
14%
2597
8%
780
31%
780
14%
1882
December1st to 15thNight
16%
761
7%
2579
3%
761
21%
761
9%
2043
December16th to endNight
14%
960
6%
2760
2%
960
19%
960
8%
2349

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
14%8%47%6%35%45%7%32%
48568
Night
15%9%46%5%34446%35%
48028
Cloud CoverDay
14%9%47%6%35%45%7%32%
48578
Night
15%9%46%5%34446%35%
48032
TransparencyDay
50%6%12%19%10%1
48263
Night
49%5%11%20%11%1
47851
SeeingDay
17%7%27%24%15%7%
6104
Night
19%8%28%29%12%1
16038

By Month

Percentage Cloud Cover NE (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
16%16%7%11%7%44445%16%
1432
16th to endDay
15%18%9%11%8%5%433414%
1624
February1st to 15thDay
14%16%6%11%7%46%5%46%17%
1599
16th to endDay
12%14%8%12%8%33445%21%
1580
March1st to 15thDay
16%12%48%7%34446%27%
1867
16th to endDay
17%11%5%8%6%34345%29%
2112
April1st to 15thDay
20%10%45%5%25%446%30%
2154
16th to endDay
16%7%36%5%24446%37%
2340
May1st to 15thDay
20%7%35%5%3445%5%33%
2331
16th to endDay
14%5%25%5%3446%8%38%
2449
June1st to 15thDay
10%6%26%6%35%5%6%8%39%
2610
16th to endDay
10%426%6%45%6%6%9%35%
2588
July1st to 15thDay
8%425%5%35%5%7%8%43%
2520
16th to endDay
9%325%6%37%6%7%9%37%
2574
August1st to 15thDay
10%5%25%6%46%6%6%7%37%
2340
16th to endDay
12%5%245%35%5%6%8%39%
2462
September1st to 15thDay
11%5%35%5%345%5%9%40%
2024
16th to endDay
13%425%425%5%5%9%40%
1980
October1st to 15thDay
16%7%35%5%24446%38%
1890
16th to endDay
21%9%36%5%34346%31%
1809
November1st to 15thDay
15%9%36%5%2345%6%36%
1717
16th to endDay
16%13%5%8%6%34346%26%
1690
December1st to 15thDay
15%15%8%12%6%33345%21%
1415
16th to endDay
19%17%9%11%6%2343417%
1461
January1st to 15thNight
21%13%6%8%6%3434422%
2506
16th to endNight
13%12%8%12%7%45%5%46%20%
2598
February1st to 15thNight
15%15%6%8%7%35%33426%
2259
16th to endNight
15%13%49%8%34345%26%
1893
March1st to 15thNight
16%11%46%5%34445%33%
2069
16th to endNight
15%8%35%5%25%446%35%
2112
April1st to 15thNight
19%9%345%3445%6%33%
1804
16th to endNight
15%7%25%42445%6%40%
1620
May1st to 15thNight
18%6%25%6%245%5%7%35%
1620
16th to endNight
12%4245%245%48%44%
1661
June1st to 15thNight
10%5%244235%5%9%45%
1341
16th to endNight
9%5%3443446%9%45%
1364
July1st to 15thNight
8%31442335%9%52%
1440
16th to endNight
6%413425%5%6%9%50%
1593
August1st to 15thNight
6%3145%35%5%7%8%47%
1620
16th to endNight
9%4245%23247%52%
1738
September1st to 15thNight
12%41442335%7%50%
1923
16th to endNight
10%6%25%4245%5%6%47%
1980
October1st to 15thNight
17%6%36%42345%6%39%
2068
16th to endNight
22%8%26%6%34445%32%
2412
November1st to 15thNight
15%9%25%4345%5%5%37%
2471
16th to endNight
20%12%46%5%34446%28%
2597
December1st to 15thNight
19%14%8%9%5%24335%22%
2579
16th to endNight
20%16%8%10%6%25%34415%
2760

Percentage Cloud Cover SE (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
16%15%8%11%6%5%4445%16%
1432
16th to endDay
15%18%10%11%9%4433414%
1624
February1st to 15thDay
13%16%6%11%9%46%5%45%17%
1599
16th to endDay
12%15%7%11%8%3434421%
1580
March1st to 15thDay
16%11%48%7%35%346%26%
1878
16th to endDay
17%11%5%8%7%34335%29%
2111
April1st to 15thDay
19%11%45%5%24446%30%
2154
16th to endDay
16%8%26%5%3335%6%37%
2340
May1st to 15thDay
19%7%46%5%35%45%6%33%
2331
16th to endDay
14%6%345%3445%8%38%
2449
June1st to 15thDay
10%6%26%6%26%5%5%8%38%
2610
16th to endDay
10%5%26%6%46%6%7%9%34%
2588
July1st to 15thDay
7%425%6%35%5%7%8%42%
2520
16th to endDay
8%425%6%36%7%6%9%36%
2574
August1st to 15thDay
10%5%25%6%46%6%6%9%36%
2340
16th to endDay
11%5%35%5%45%5%6%8%39%
2462
September1st to 15thDay
11%435%5%35%46%8%40%
2024
16th to endDay
13%5%25%425%5%6%8%39%
1980
October1st to 15thDay
15%7%36%5%24447%37%
1890
16th to endDay
20%11%36%5%33446%30%
1809
November1st to 15thDay
15%9%46%5%3345%7%34%
1717
16th to endDay
15%15%48%6%35%436%26%
1690
December1st to 15thDay
15%13%9%12%8%33335%21%
1415
16th to endDay
19%17%9%10%6%3343417%
1461
January1st to 15thNight
21%14%6%8%6%4433422%
2506
16th to endNight
13%12%8%11%7%35%5%45%21%
2598
February1st to 15thNight
15%14%6%9%6%3443426%
2252
16th to endNight
15%13%5%8%8%34345%26%
1893
March1st to 15thNight
16%11%47%5%23445%32%
2081
16th to endNight
15%7%46%5%35%45%6%35%
2112
April1st to 15thNight
19%9%445%3445%6%33%
1804
16th to endNight
14%7%35%42445%6%40%
1620
May1st to 15thNight
17%6%35%6%245%5%7%35%
1619
16th to endNight
12%4244336%47%44%
1661
June1st to 15thNight
9%5%243245%5%9%45%
1341
16th to endNight
9%435%43446%9%45%
1364
July1st to 15thNight
7%41442345%8%53%
1440
16th to endNight
5%3144335%6%9%50%
1593
August1st to 15thNight
6%314435%5%6%8%47%
1620
16th to endNight
8%5%24423348%51%
1738
September1st to 15thNight
11%42432435%6%51%
1923
16th to endNight
10%5%25%42445%6%47%
1980
October1st to 15thNight
16%6%36%42345%5%40%
2068
16th to endNight
21%8%26%6%34445%32%
2412
November1st to 15thNight
15%8%35%5%25%45%6%37%
2471
16th to endNight
20%11%46%5%24446%28%
2597
December1st to 15thNight
19%14%6%9%6%34335%22%
2579
16th to endNight
21%16%8%11%6%2433416%
2760

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
69%5%9%10%3
1433
16th to endDay
73%5%7%8%4
1624
February1st to 15thDay
66%7%8%12%4
1601
16th to endDay
64%410%12%6%1
1580
March1st to 15thDay
56%6%12%16%6%
1878
16th to endDay
57%5%10%18%7%1
2112
April1st to 15thDay
54%5%10%19%10%
2154
16th to endDay
46%5%14%16%14%2
2340
May1st to 15thDay
50%7%10%20%9%2
2331
16th to endDay
42%6%13%23%12%1
2453
June1st to 15thDay
40%7%13%22%14%1
2610
16th to endDay
42%8%13%19%15%
2588
July1st to 15thDay
36%6%11%24%17%2
2371
16th to endDay
38%9%14%20%14%2
2413
August1st to 15thDay
41%8%13%23%11%1
2327
16th to endDay
40%8%11%23%14%1
2462
September1st to 15thDay
39%8%14%24%12%
2024
16th to endDay
38%7%12%29%12%
1980
October1st to 15thDay
46%5%11%22%11%1
1890
16th to endDay
53%6%14%17%7%
1809
November1st to 15thDay
48%5%12%21%9%1
1717
16th to endDay
58%5%13%16%5%
1690
December1st to 15thDay
66%412%13%3
1415
16th to endDay
72%411%8%3
1461
January1st to 15thNight
65%410%12%6%
2506
16th to endNight
63%6%12%13%3
2598
February1st to 15thNight
61%5%10%14%6%
2261
16th to endNight
58%411%17%6%
1893
March1st to 15thNight
53%5%10%19%10%1
2081
16th to endNight
48%6%11%22%9%1
2112
April1st to 15thNight
50%5%10%19%13%
1804
16th to endNight
42%5%11%19%17%3
1620
May1st to 15thNight
46%6%12%20%11%2
1620
16th to endNight
38%6%13%23%14%3
1663
June1st to 15thNight
33%7%13%28%15%1
1341
16th to endNight
34%6%14%25%18%1
1364
July1st to 15thNight
29%5%10%28%22%2
1360
16th to endNight
27%8%16%23%21%2
1491
August1st to 15thNight
31%8%12%30%14%2
1609
16th to endNight
32%5%12%29%17%2
1738
September1st to 15thNight
32%5%12%29%18%1
1923
16th to endNight
34%5%12%29%16%
1980
October1st to 15thNight
44%6%10%21%16%1
2068
16th to endNight
53%5%12%20%7%
2412
November1st to 15thNight
45%7%12%22%11%1
2471
16th to endNight
55%5%13%19%6%
2597
December1st to 15thNight
65%5%11%12%5%
2579
16th to endNight
71%5%9%9%3
2760

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
18%15%43%20%2
90
16th to endDay
35%7%38%15%3
96
February1st to 15thDay
27%17%44%10%
90
16th to endDay
19%19%35%19%4
81
March1st to 15thDay
26%14%30%23%5%
168
16th to endDay
24%7%32%23%10%1
288
April1st to 15thDay
22%11%30%25%7%2
270
16th to endDay
21%8%32%18%11%7%
270
May1st to 15thDay
27%7%27%19%13%4
288
16th to endDay
20%7%25%22%16%8%
349
June1st to 15thDay
13%5%32%28%15%4
495
16th to endDay
12%7%32%24%17%5%
495
July1st to 15thDay
11%422%31%19%10%
475
16th to endDay
8%323%31%21%10%
434
August1st to 15thDay
13%114%27%21%21%
313
16th to endDay
14%318%21%21%19%
332
September1st to 15thDay
10%5%20%21%25%17%
315
16th to endDay
15%315%22%28%14%
314
October1st to 15thDay
20%6%22%26%19%5%
315
16th to endDay
25%10%32%25%5%
225
November1st to 15thDay
21%13%26%25%11%2
135
16th to endDay
24%20%34%16%4
120
December1st to 15thDay
19%22%38%15%4
63
16th to endDay
21%31%37%9%
83
January1st to 15thNight
26%13%35%17%5%
900
16th to endNight
18%11%37%26%6%
870
February1st to 15thNight
23%13%37%22%3
704
16th to endNight
21%12%32%28%3
631
March1st to 15thNight
22%11%31%26%6%
720
16th to endNight
17%9%33%28%9%1
768
April1st to 15thNight
21%13%31%26%41
582
16th to endNight
18%7%35%27%8%1
540
May1st to 15thNight
21%429%34%8%1
540
16th to endNight
14%326%38%16%1
563
June1st to 15thNight
10%324%48%13%
441
16th to endNight
10%323%45%16%1
464
July1st to 15thNight
10%18%40%26%3
510
16th to endNight
6%117%49%21%3
564
August1st to 15thNight
9%16%42%27%3
539
16th to endNight
11%217%31%30%5%
573
September1st to 15thNight
13%318%31%26%5%
663
16th to endNight
12%5%16%32%27%5%
717
October1st to 15thNight
20%5%23%32%15%2
720
16th to endNight
26%11%32%23%5%
768
November1st to 15thNight
20%9%30%25%12%1
760
16th to endNight
26%13%30%21%7%
780
December1st to 15thNight
25%14%36%19%4
761
16th to endNight
28%11%38%19%2
960
Page generated at 2017-12-03 11:16:38. Version ac04

Copyright 2017 A. Danko


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