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 2017-03-14.

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%
15157
14%
45236
9%
15115
41%
15115
20%
31890

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
17%
701
9%
2261
3%
701
24%
701
11%
1760
February16th to endNight
23%
631
13%
1893
6%
631
31%
631
14%
1431
March1st to 15thNight
27%
716
15%
2070
9%
716
32%
716
17%
1509
March16th to endNight
34%
704
18%
1936
10%
704
40%
704
22%
1358
April1st to 15thNight
28%
534
14%
1654
8%
534
35%
534
19%
1155
April16th to endNight
35%
495
20%
1485
8%
495
45%
495
25%
977
May1st to 15thNight
38%
495
14%
1485
8%
495
45%
495
22%
1027
May16th to endNight
52%
514
15%
1521
12%
513
56%
513
30%
947
June1st to 15thNight
54%
404
16%
1229
14%
404
59%
404
29%
766
June16th to endNight
58%
425
15%
1250
13%
425
61%
425
31%
773
July1st to 15thNight
65%
465
17%
1240
15%
465
67%
465
40%
734
July16th to endNight
67%
522
16%
1372
13%
489
69%
489
37%
826
August1st to 15thNight
65%
494
21%
1474
17%
491
68%
491
34%
894
August16th to endNight
62%
525
21%
1592
16%
525
66%
525
34%
935
September1st to 15thNight
58%
608
24%
1763
20%
608
62%
608
34%
1045
September16th to endNight
57%
657
21%
1815
16%
657
60%
657
32%
1139
October1st to 15thNight
45%
660
19%
1895
15%
660
50%
660
26%
1269
October16th to endNight
24%
704
13%
2211
7%
704
32%
704
15%
1609
November1st to 15thNight
35%
700
19%
2276
15%
700
41%
700
21%
1504
November16th to endNight
25%
720
13%
2397
9%
720
31%
720
14%
1764
December1st to 15thNight
16%
753
7%
2553
3%
753
21%
753
9%
2027
December16th to endNight
14%
960
7%
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%9%47%6%35%45%7%32%
45445
Night
15%9%46%5%34446%34%
45413
Cloud CoverDay
14%9%47%6%35%45%7%31%
45455
Night
15%9%46%5%34446%34%
45417
TransparencyDay
50%6%12%18%10%1
45140
Night
49%5%11%20%11%1
45236
SeeingDay
17%7%26%24%15%8%
5053
Night
19%8%29%29%11%1
15161

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%6%34446%27%
1850
16th to endDay
16%11%6%8%6%34345%30%
1936
April1st to 15thDay
19%11%46%5%25%445%30%
1974
16th to endDay
16%7%36%5%23446%38%
2145
May1st to 15thDay
20%7%45%5%3446%5%32%
2136
16th to endDay
14%5%25%5%3445%7%40%
2239
June1st to 15thDay
11%6%26%6%35%45%8%37%
2392
16th to endDay
10%426%6%45%6%6%9%35%
2373
July1st to 15thDay
8%425%5%35%5%7%8%43%
2310
16th to endDay
9%325%6%47%6%8%9%36%
2385
August1st to 15thDay
10%5%25%6%46%6%6%7%37%
2145
16th to endDay
12%4245%35%5%6%8%39%
2256
September1st to 15thDay
12%5%35%5%345%5%9%39%
1856
16th to endDay
14%5%25%425%5%5%9%38%
1815
October1st to 15thDay
15%8%35%5%34446%38%
1733
16th to endDay
22%9%37%5%34345%30%
1658
November1st to 15thDay
14%9%36%5%235%5%6%36%
1582
16th to endDay
16%13%5%9%6%34346%24%
1560
December1st to 15thDay
15%15%8%12%6%33335%20%
1404
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%32%
2058
16th to endNight
14%8%35%5%35%447%36%
1936
April1st to 15thNight
19%9%345%3445%6%34%
1654
16th to endNight
15%7%25%42445%6%41%
1485
May1st to 15thNight
17%6%25%6%245%5%7%34%
1485
16th to endNight
12%4244245%48%46%
1519
June1st to 15thNight
11%5%344335%5%9%44%
1229
16th to endNight
9%4344345%6%9%44%
1250
July1st to 15thNight
9%314423349%52%
1320
16th to endNight
6%414425%5%6%10%49%
1474
August1st to 15thNight
7%3145%25%5%7%8%48%
1485
16th to endNight
10%4245%23247%52%
1592
September1st to 15thNight
13%414423347%50%
1763
16th to endNight
10%6%25%4245%5%6%46%
1815
October1st to 15thNight
16%6%35%42345%6%40%
1895
16th to endNight
22%8%36%6%34435%31%
2211
November1st to 15thNight
15%9%25%4345%5%6%38%
2276
16th to endNight
21%12%46%5%34445%27%
2397
December1st to 15thNight
19%14%8%9%5%24335%22%
2553
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%6%35%346%26%
1861
16th to endDay
16%11%5%8%7%34335%30%
1935
April1st to 15thDay
19%12%45%5%25%445%29%
1974
16th to endDay
16%8%26%5%33446%37%
2145
May1st to 15thDay
19%7%46%5%35%45%6%31%
2136
16th to endDay
14%5%35%5%3445%8%39%
2239
June1st to 15thDay
10%6%26%6%36%45%8%37%
2392
16th to endDay
10%5%26%6%47%5%7%9%34%
2373
July1st to 15thDay
7%4246%35%5%7%9%42%
2310
16th to endDay
8%425%6%37%7%7%9%36%
2385
August1st to 15thDay
10%5%26%6%46%6%6%8%36%
2145
16th to endDay
11%5%245%35%5%6%8%39%
2256
September1st to 15thDay
12%5%35%5%35%46%8%39%
1856
16th to endDay
13%5%25%425%5%6%9%37%
1815
October1st to 15thDay
14%8%36%6%24447%37%
1733
16th to endDay
21%10%36%5%23445%30%
1658
November1st to 15thDay
15%8%36%5%3445%7%35%
1582
16th to endDay
16%14%5%8%6%35%446%25%
1560
December1st to 15thDay
15%14%9%12%7%33335%21%
1404
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%
2070
16th to endNight
14%7%46%5%35%45%6%35%
1936
April1st to 15thNight
18%9%4443445%6%33%
1654
16th to endNight
14%8%35%42445%6%40%
1485
May1st to 15thNight
17%5%35%6%245%5%8%34%
1484
16th to endNight
12%4334235%48%46%
1519
June1st to 15thNight
10%6%35%4245%5%9%44%
1229
16th to endNight
9%5%35%43446%9%44%
1250
July1st to 15thNight
8%41442445%8%53%
1320
16th to endNight
6%3144335%6%10%50%
1474
August1st to 15thNight
7%314435%5%6%9%48%
1485
16th to endNight
9%5%24423348%51%
1592
September1st to 15thNight
12%5%24323346%50%
1763
16th to endNight
10%6%25%42445%6%46%
1815
October1st to 15thNight
15%6%26%5%2345%6%41%
1895
16th to endNight
21%8%26%6%44445%31%
2211
November1st to 15thNight
14%8%35%5%25%5%5%6%38%
2276
16th to endNight
21%11%46%5%24446%27%
2397
December1st to 15thNight
19%14%6%9%6%34335%22%
2553
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
57%6%12%16%6%
1861
16th to endDay
56%5%10%19%7%1
1936
April1st to 15thDay
55%49%19%10%
1974
16th to endDay
46%5%14%16%13%2
2145
May1st to 15thDay
52%7%11%19%8%1
2136
16th to endDay
42%6%13%23%13%1
2243
June1st to 15thDay
42%7%12%21%14%1
2392
16th to endDay
42%8%13%18%16%
2373
July1st to 15thDay
36%6%12%24%17%2
2161
16th to endDay
38%9%14%20%13%2
2224
August1st to 15thDay
41%9%12%22%12%2
2132
16th to endDay
39%8%12%23%14%1
2256
September1st to 15thDay
39%8%14%23%12%
1856
16th to endDay
40%7%12%28%11%
1815
October1st to 15thDay
46%5%12%22%12%1
1733
16th to endDay
54%6%15%17%6%
1658
November1st to 15thDay
47%5%12%21%10%1
1582
16th to endDay
59%5%12%16%5%
1560
December1st to 15thDay
66%412%13%3
1404
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%9%1
2070
16th to endNight
47%6%12%23%10%1
1936
April1st to 15thNight
49%5%10%19%14%
1654
16th to endNight
43%5%10%19%17%3
1485
May1st to 15thNight
46%6%12%20%11%1
1485
16th to endNight
36%6%14%23%14%4
1521
June1st to 15thNight
36%7%12%25%16%
1229
16th to endNight
35%6%15%24%17%1
1250
July1st to 15thNight
29%5%10%28%22%2
1240
16th to endNight
29%8%16%23%19%2
1372
August1st to 15thNight
31%8%12%30%14%2
1474
16th to endNight
32%5%13%28%17%2
1592
September1st to 15thNight
33%412%28%18%1
1763
16th to endNight
36%5%12%28%16%
1815
October1st to 15thNight
42%6%10%22%16%1
1895
16th to endNight
54%5%12%19%7%
2211
November1st to 15thNight
44%7%12%22%11%1
2276
16th to endNight
57%5%12%18%5%
2397
December1st to 15thNight
65%5%11%12%5%
2553
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
27%14%29%22%6%
162
16th to endDay
20%7%33%25%12%1
224
April1st to 15thDay
21%12%27%26%8%3
210
16th to endDay
23%5%30%19%12%9%
210
May1st to 15thDay
28%6%26%19%14%4
228
16th to endDay
17%5%23%25%18%9%
283
June1st to 15thDay
15%6%30%28%15%4
420
16th to endDay
12%6%28%25%20%6%
420
July1st to 15thDay
12%421%30%19%11%
400
16th to endDay
8%324%32%20%10%
371
August1st to 15thDay
12%114%28%20%22%
253
16th to endDay
14%218%20%21%22%
268
September1st to 15thDay
12%5%18%21%25%17%
255
16th to endDay
17%315%22%28%11%
254
October1st to 15thDay
19%6%20%27%20%5%
255
16th to endDay
25%12%33%21%5%
170
November1st to 15thDay
13%15%26%27%14%2
90
16th to endDay
23%21%32%17%5%
80
December1st to 15thDay
20%23%38%16%1
60
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%
716
16th to endNight
16%9%34%28%9%1
704
April1st to 15thNight
20%14%32%26%5%1
534
16th to endNight
19%8%33%27%9%1
495
May1st to 15thNight
20%428%35%8%1
495
16th to endNight
14%323%38%17%1
515
June1st to 15thNight
11%325%46%13%
404
16th to endNight
10%322%45%17%1
425
July1st to 15thNight
11%17%40%26%3
465
16th to endNight
7%117%49%20%3
522
August1st to 15thNight
9%116%42%26%4
494
16th to endNight
12%216%31%30%5%
525
September1st to 15thNight
14%318%31%26%4
608
16th to endNight
13%5%16%33%26%4
657
October1st to 15thNight
19%5%23%33%15%2
660
16th to endNight
26%11%32%22%5%
704
November1st to 15thNight
19%10%30%25%13%1
700
16th to endNight
27%12%29%22%7%
720
December1st to 15thNight
25%14%36%19%3
753
16th to endNight
28%11%38%19%2
960
Page generated at 2017-03-15 11:32:41. Version ac04

Copyright 2017 A. Danko


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