Starfest
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Starfest clear sky chart from 2005-11-05 to 2018-03-21.

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
31%
15825
11%
49085
8%
15787
35%
15787
15%
36917

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
10%
931
5%
2784
2%
929
13%
929
6%
2429
January16th to endNight
15%
832
4%
2704
2%
832
17%
832
5%
2373
February1st to 15thNight
16%
761
5%
2482
2%
761
20%
761
6%
2139
February16th to endNight
19%
683
9%
2142
4%
683
25%
683
9%
1732
March1st to 15thNight
21%
780
11%
2178
6%
780
26%
780
14%
1705
March16th to endNight
33%
792
19%
2178
10%
792
40%
792
22%
1552
April1st to 15thNight
26%
682
14%
1817
6%
682
32%
682
19%
1358
April16th to endNight
37%
540
17%
1620
11%
540
41%
540
21%
1120
May1st to 15thNight
41%
540
15%
1620
11%
540
45%
540
22%
1107
May16th to endNight
46%
374
16%
1497
14%
374
57%
374
23%
903
June1st to 15thNight
43%
360
12%
1347
12%
360
51%
360
21%
844
June16th to endNight
50%
360
15%
1260
17%
360
56%
360
26%
762
July1st to 15thNight
65%
340
18%
1190
23%
340
68%
340
33%
653
July16th to endNight
56%
544
14%
1567
12%
511
58%
511
29%
968
August1st to 15thNight
62%
539
16%
1609
12%
536
65%
536
30%
988
August16th to endNight
58%
583
21%
1729
15%
583
61%
583
30%
1079
September1st to 15thNight
52%
720
17%
1866
10%
720
55%
720
30%
1231
September16th to endNight
53%
717
20%
1980
14%
717
55%
717
30%
1282
October1st to 15thNight
38%
720
13%
2149
10%
720
42%
720
19%
1539
October16th to endNight
24%
768
10%
2328
6%
768
29%
768
11%
1855
November1st to 15thNight
27%
760
13%
2559
12%
760
32%
760
12%
1927
November16th to endNight
21%
780
8%
2730
7%
780
24%
780
9%
2213
December1st to 15thNight
11%
780
2%
2730
1%
780
13%
780
4%
2433
December16th to endNight
8%
939
3%
3019
0%
939
11%
939
4%
2725

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
16%11%48%6%3445%6%28%
49750
Night
16%11%5%8%6%34446%28%
49256
Cloud CoverDay
17%11%47%6%34446%28%
49760
Night
16%11%5%8%6%34445%28%
49260
TransparencyDay
55%6%10%16%9%
49439
Night
57%5%10%16%8%1
49085
SeeingDay
21%8%26%22%13%5%
6269
Night
22%9%28%27%10%1
15832

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
17%15%10%15%11%4433311%
1475
16th to endDay
12%19%9%15%9%35%43411%
1872
February1st to 15thDay
14%18%9%17%10%45%32310%
1710
16th to endDay
16%18%7%12%8%35%34315%
1614
March1st to 15thDay
14%14%6%11%8%44335%23%
2101
16th to endDay
15%9%5%7%6%45%445%30%
2174
April1st to 15thDay
20%12%47%42445%5%28%
2141
16th to endDay
19%10%25%323247%37%
2340
May1st to 15thDay
19%7%36%42345%6%36%
2331
16th to endDay
14%6%34435%45%6%40%
2618
June1st to 15thDay
16%7%35%325%46%8%37%
2610
16th to endDay
16%5%24435%5%6%8%36%
2700
July1st to 15thDay
12%5%26%435%5%6%8%39%
2700
16th to endDay
11%6%36%5%35%46%10%35%
2490
August1st to 15thDay
12%6%26%6%45%5%7%9%33%
2340
16th to endDay
13%5%26%6%45%5%7%8%34%
2459
September1st to 15thDay
17%7%26%43336%7%35%
2093
16th to endDay
17%6%24424447%39%
1980
October1st to 15thDay
23%10%35%5%34345%30%
1810
16th to endDay
31%13%46%6%24245%17%
1893
November1st to 15thDay
18%15%47%5%24436%24%
1626
16th to endDay
20%20%7%9%6%34335%14%
1560
December1st to 15thDay
16%22%11%14%8%35%2247%
1560
16th to endDay
19%22%10%12%9%333337%
1553
January1st to 15thNight
20%16%7%14%9%4334311%
2784
16th to endNight
14%16%9%14%11%5%5%44410%
2704
February1st to 15thNight
13%17%8%13%10%45%33313%
2480
16th to endNight
16%13%9%12%7%34345%18%
2142
March1st to 15thNight
15%13%5%10%7%34435%25%
2166
16th to endNight
14%9%46%5%24335%37%
2178
April1st to 15thNight
20%12%45%423346%31%
1817
16th to endNight
14%10%25%5%445%46%37%
1620
May1st to 15thNight
16%7%36%5%3445%7%36%
1620
16th to endNight
10%6%245%26%46%7%43%
1495
June1st to 15thNight
14%5%35%425%449%38%
1347
16th to endNight
13%4245%346%5%8%43%
1260
July1st to 15thNight
8%42441346%7%51%
1260
16th to endNight
9%425%5%25%5%6%9%43%
1673
August1st to 15thNight
10%4145%35%6%5%8%44%
1620
16th to endNight
10%425%5%34336%48%
1729
September1st to 15thNight
14%4245%2445%7%44%
1866
16th to endNight
13%6%35%43435%6%44%
1980
October1st to 15thNight
20%8%35%43335%7%33%
2149
16th to endNight
27%11%36%6%34445%22%
2328
November1st to 15thNight
18%12%37%6%35%445%26%
2559
16th to endNight
21%17%6%8%6%24345%18%
2730
December1st to 15thNight
18%23%9%12%6%3443410%
2730
16th to endNight
20%18%10%14%8%443338%
3019

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
17%15%10%14%11%4433311%
1475
16th to endDay
12%19%9%16%9%4434411%
1872
February1st to 15thDay
14%18%9%16%11%4433310%
1710
16th to endDay
16%18%7%11%9%4434414%
1614
March1st to 15thDay
15%13%6%11%9%34325%23%
2112
16th to endDay
15%10%5%8%5%35%445%30%
2173
April1st to 15thDay
20%13%46%43345%5%28%
2141
16th to endDay
19%10%34423247%37%
2340
May1st to 15thDay
19%8%25%5%2345%6%35%
2331
16th to endDay
14%6%345%3445%7%40%
2618
June1st to 15thDay
16%6%25%435%45%8%36%
2610
16th to endDay
17%5%245%245%5%9%36%
2700
July1st to 15thDay
12%6%25%5%35%6%5%7%38%
2700
16th to endDay
11%6%35%5%35%5%6%10%35%
2490
August1st to 15thDay
13%6%26%6%45%6%6%9%32%
2340
16th to endDay
13%5%26%6%36%5%6%7%34%
2459
September1st to 15thDay
18%6%36%42345%7%35%
2093
16th to endDay
18%5%25%42345%7%39%
1980
October1st to 15thDay
24%9%35%5%24435%30%
1810
16th to endDay
31%13%46%5%24445%17%
1893
November1st to 15thDay
19%16%47%5%35%337%24%
1626
16th to endDay
21%19%8%9%6%34435%14%
1560
December1st to 15thDay
16%22%11%15%8%343338%
1560
16th to endDay
19%22%11%12%7%333347%
1553
January1st to 15thNight
20%16%7%13%9%4433411%
2784
16th to endNight
13%16%9%14%11%5%5%43410%
2704
February1st to 15thNight
13%17%9%13%10%45%43313%
2473
16th to endNight
15%13%8%12%8%3445%5%18%
2142
March1st to 15thNight
15%12%6%10%7%34445%25%
2178
16th to endNight
14%10%5%6%5%34435%37%
2178
April1st to 15thNight
20%12%45%423436%30%
1817
16th to endNight
14%10%25%5%345%46%36%
1620
May1st to 15thNight
15%8%26%5%3445%6%36%
1619
16th to endNight
11%5%25%436%45%7%43%
1495
June1st to 15thNight
14%6%34435%45%8%39%
1347
16th to endNight
13%4244245%5%8%43%
1260
July1st to 15thNight
7%42432345%8%51%
1260
16th to endNight
9%425%5%245%6%8%44%
1673
August1st to 15thNight
10%4144345%6%8%44%
1620
16th to endNight
11%5%25%433436%48%
1729
September1st to 15thNight
14%42443435%6%45%
1866
16th to endNight
13%7%25%42435%6%44%
1980
October1st to 15thNight
20%7%3443445%7%33%
2149
16th to endNight
26%12%35%6%34445%22%
2328
November1st to 15thNight
18%13%36%6%35%5%46%26%
2559
16th to endNight
22%17%6%8%6%24345%19%
2730
December1st to 15thNight
18%23%9%13%6%2433410%
2730
16th to endNight
20%18%11%14%8%433338%
3019

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
79%46%7%2
1476
16th to endDay
76%48%6%3
1872
February1st to 15thDay
80%448%2
1712
16th to endDay
72%48%8%5%
1614
March1st to 15thDay
65%310%12%8%
2112
16th to endDay
54%5%11%16%11%1
2174
April1st to 15thDay
56%5%8%19%9%
2141
16th to endDay
48%410%19%14%1
2340
May1st to 15thDay
47%6%9%21%13%
2331
16th to endDay
43%5%14%20%14%1
2622
June1st to 15thDay
44%6%12%23%12%
2610
16th to endDay
43%8%13%23%10%
2700
July1st to 15thDay
40%7%12%22%15%1
2541
16th to endDay
42%8%13%22%10%1
2333
August1st to 15thDay
44%7%14%19%11%1
2327
16th to endDay
45%9%13%21%9%1
2459
September1st to 15thDay
46%8%12%21%9%1
2093
16th to endDay
43%5%12%27%9%
1980
October1st to 15thDay
55%5%9%16%11%1
1810
16th to endDay
69%5%10%10%4
1893
November1st to 15thDay
61%5%11%13%6%
1626
16th to endDay
71%5%9%9%31
1560
December1st to 15thDay
82%5%6%4
1560
16th to endDay
82%45%6%1
1553
January1st to 15thNight
76%48%5%4
2784
16th to endNight
76%5%8%5%2
2704
February1st to 15thNight
75%47%9%2
2482
16th to endNight
67%49%10%7%
2142
March1st to 15thNight
61%5%8%16%7%
2178
16th to endNight
50%49%19%14%2
2178
April1st to 15thNight
55%48%18%12%
1817
16th to endNight
47%6%8%16%17%2
1620
May1st to 15thNight
47%5%8%23%12%2
1620
16th to endNight
39%7%11%26%12%3
1497
June1st to 15thNight
42%5%11%24%14%
1347
16th to endNight
36%7%12%26%15%1
1260
July1st to 15thNight
28%7%11%28%22%1
1190
16th to endNight
35%7%15%23%16%1
1567
August1st to 15thNight
34%8%16%25%13%1
1609
16th to endNight
36%6%11%29%15%1
1729
September1st to 15thNight
38%6%12%28%12%1
1866
16th to endNight
39%5%15%26%12%
1980
October1st to 15thNight
49%7%11%18%12%
2149
16th to endNight
62%6%12%12%5%
2328
November1st to 15thNight
58%6%11%15%6%1
2559
16th to endNight
67%5%11%11%2
2730
December1st to 15thNight
79%5%8%41
2730
16th to endNight
81%47%5%1
3019

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%16%43%14%2
109
16th to endDay
29%10%36%21%2
144
February1st to 15thDay
31%20%37%11%
135
16th to endDay
29%23%35%10%1
120
March1st to 15thDay
25%12%34%17%9%1
297
16th to endDay
22%6%36%21%10%2
311
April1st to 15thDay
24%10%30%22%10%1
270
16th to endDay
24%11%24%21%9%7%
270
May1st to 15thDay
25%6%26%22%14%4
288
16th to endDay
19%6%30%19%17%6%
331
June1st to 15thDay
19%9%23%28%16%2
405
16th to endDay
16%6%30%28%14%3
495
July1st to 15thDay
14%6%25%25%20%7%
475
16th to endDay
12%421%33%17%11%
331
August1st to 15thDay
14%317%28%20%15%
313
16th to endDay
16%317%22%23%15%
332
September1st to 15thDay
14%5%17%25%21%15%
315
16th to endDay
17%420%23%21%12%
314
October1st to 15thDay
25%6%26%23%13%4
315
16th to endDay
37%12%23%20%4
309
November1st to 15thDay
31%11%28%17%8%1
114
16th to endDay
33%16%34%10%41
90
December1st to 15thDay
30%30%24%14%1
90
16th to endDay
36%13%40%9%
96
January1st to 15thNight
25%16%36%16%4
934
16th to endNight
21%11%34%25%6%
832
February1st to 15thNight
22%14%37%22%3
764
16th to endNight
23%12%34%24%4
683
March1st to 15thNight
21%12%36%22%6%
780
16th to endNight
20%9%31%26%11%1
792
April1st to 15thNight
25%10%30%25%7%
682
16th to endNight
21%9%27%29%9%2
540
May1st to 15thNight
21%424%33%13%2
540
16th to endNight
13%330%34%17%
375
June1st to 15thNight
15%428%39%11%
360
16th to endNight
16%225%40%15%
360
July1st to 15thNight
9%118%50%20%
340
16th to endNight
12%219%40%22%2
544
August1st to 15thNight
11%116%39%29%2
539
16th to endNight
13%219%31%30%3
583
September1st to 15thNight
17%321%30%19%7%
720
16th to endNight
17%419%32%21%5%
717
October1st to 15thNight
24%6%26%27%13%2
720
16th to endNight
33%8%29%24%4
768
November1st to 15thNight
25%11%29%22%9%
760
16th to endNight
29%15%27%21%5%
780
December1st to 15thNight
30%16%31%18%3
780
16th to endNight
29%13%36%17%2
939
Page generated at 2018-03-22 11:34:21. Version ac04

Copyright 2018 A. Danko


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