SkyStar Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the SkyStar Observatory clear sky chart from 2005-11-06 to 2024-03-06.

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
68%
25135
32%
79638
28%
25039
73%
25039
43%
41330

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 10thNight
55%
753
35%
3992
25%
736
64%
736
27%
1695
January11th to 20thNight
56%
749
34%
3868
29%
740
65%
740
24%
1933
January21st to endNight
51%
829
23%
3968
24%
814
65%
814
20%
2296
February1st to 10thNight
54%
760
33%
2280
26%
760
64%
760
38%
1271
February11th to 20thNight
55%
740
30%
2219
27%
740
62%
740
33%
1303
February21st to endNight
49%
628
27%
1884
25%
628
55%
628
30%
1141
March1st to 10thNight
46%
742
22%
2225
21%
742
52%
742
28%
1391
March11th to 20thNight
60%
720
26%
2062
25%
720
64%
720
36%
1218
March21st to endNight
59%
792
25%
2084
20%
792
62%
792
37%
1277
April1st to 10thNight
58%
720
28%
1800
19%
720
61%
720
40%
1107
April11th to 20thNight
60%
711
31%
1779
19%
711
63%
711
47%
1021
April21st to endNight
65%
720
30%
1800
18%
720
68%
720
47%
1050
May1st to 10thNight
62%
594
30%
1674
20%
594
66%
594
44%
928
May11th to 20thNight
68%
531
29%
1595
22%
531
69%
531
45%
844
May21st to endNight
63%
582
28%
1746
21%
582
65%
582
44%
925
June1st to 10thNight
77%
540
33%
1620
28%
540
79%
540
58%
758
June11th to 20thNight
83%
540
36%
1620
31%
540
84%
540
67%
692
June21st to endNight
87%
540
36%
1620
32%
540
87%
540
70%
675
July1st to 10thNight
92%
525
36%
1575
31%
525
92%
525
77%
617
July11th to 20thNight
94%
522
34%
1566
29%
522
94%
522
67%
661
July21st to endNight
89%
675
33%
1754
25%
638
89%
638
57%
867
August1st to 10thNight
92%
716
36%
1780
23%
712
92%
712
77%
828
August11th to 20thNight
94%
712
41%
1780
27%
712
94%
712
78%
820
August21st to endNight
92%
792
43%
1980
31%
792
92%
792
75%
932
September1st to 10thNight
88%
720
40%
1829
32%
720
89%
720
69%
883
September11th to 20thNight
85%
720
42%
1980
39%
720
86%
720
70%
883
September21st to endNight
82%
720
43%
1980
39%
720
85%
720
69%
881
October1st to 10thNight
75%
720
36%
1980
33%
720
78%
720
52%
1022
October11th to 20thNight
74%
720
41%
1980
36%
720
78%
720
57%
974
October21st to endNight
71%
792
38%
2449
36%
792
77%
792
54%
1126
November1st to 10thNight
70%
740
35%
2405
36%
740
76%
740
49%
1134
November11th to 20thNight
68%
760
36%
2470
33%
760
77%
760
49%
1163
November21st to endNight
58%
760
31%
2470
30%
760
65%
760
35%
1332
December1st to 10thNight
57%
760
30%
2470
27%
760
63%
760
34%
1366
December11th to 20thNight
50%
760
28%
2958
25%
759
60%
759
24%
1786
December21st to endNight
52%
830
19%
4396
27%
817
61%
817
19%
2530

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
6%413323346%65%
79129
Night
7%6%23323346%61%
80477
TransparencyDay
21%46%16%26%28%
78862
Night
24%5%6%15%23%28%
80267
SeeingDay
8%11%29%33%13%5%
14750
Night
8%414%32%33%9%
25172

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 10thDay
10%5%13312335%63%
2858
11th to 20thDay
9%5%2432445%8%55%
2998
21st to endDay
16%7%1342445%7%47%
3498
February1st to 10thDay
12%5%14324345%58%
1900
11th to 20thDay
11%6%2432345%7%54%
1850
21st to endDay
14%8%44425%446%46%
1570
March1st to 10thDay
12%6%244245%5%10%47%
1851
11th to 20thDay
10%5%1433445%6%55%
1898
21st to endDay
7%5%2442445%7%57%
2268
April1st to 10thDay
9%5%2432435%7%55%
2160
11th to 20thDay
5%323323445%64%
2129
21st to endDay
8%412212348%65%
2160
May1st to 10thDay
8%6%13322337%61%
2286
11th to 20thDay
3413313337%69%
2301
21st to endDay
5%423323346%65%
2530
June1st to 10thDay
3212222246%73%
2340
11th to 20thDay
2211212235%80%
2340
21st to endDay
121121124382%
2340
July1st to 10thDay
212212347%76%
2340
11th to 20thDay
111222345%8%72%
2340
21st to endDay
21123235%7%8%65%
2456
August1st to 10thDay
112112345%79%
2149
11th to 20thDay
1112212235%81%
2122
21st to endDay
1111223345%77%
2376
September1st to 10thDay
221222234476%
2129
11th to 20thDay
22111112385%
1980
21st to endDay
221221223478%
1980
October1st to 10thDay
5%313323345%68%
1980
11th to 20thDay
5%41222233472%
1980
21st to endDay
431322223474%
1901
November1st to 10thDay
6%422313346%68%
1674
11th to 20thDay
4423322346%67%
1710
21st to endDay
8%5%3232445%7%58%
1710
December1st to 10thDay
9%5%2432435%7%56%
1710
11th to 20thDay
13%7%245%345%6%7%44%
2169
21st to endDay
12%8%25%7%45%5%5%5%42%
3146
January1st to 10thNight
7%7%23323335%62%
4097
11th to 20thNight
8%7%2443435%8%51%
3972
21st to endNight
18%7%23323445%48%
4180
February1st to 10thNight
10%7%24313345%58%
2280
11th to 20thNight
10%8%335%3433455%
2218
21st to endNight
12%10%24324446%48%
1884
March1st to 10thNight
12%11%26%433448%45%
2225
11th to 20thNight
12%7%2332345%7%51%
2062
21st to endNight
8%8%3343445%7%50%
2084
April1st to 10thNight
9%8%2442345%7%52%
1800
11th to 20thNight
6%8%34423236%59%
1779
21st to endNight
9%7%23323437%58%
1800
May1st to 10thNight
5%8%25%423247%57%
1674
11th to 20thNight
47%35%324347%57%
1594
21st to endNight
6%9%25%423346%57%
1746
June1st to 10thNight
25%23323347%66%
1620
11th to 20thNight
1411322226%75%
1620
21st to endNight
221221223480%
1620
July1st to 10thNight
1112112236%80%
1620
11th to 20thNight
11111335%7%76%
1620
21st to endNight
211232345%8%68%
1857
August1st to 10thNight
1111111337%79%
1790
11th to 20thNight
1211112345%81%
1780
21st to endNight
121221223480%
1980
September1st to 10thNight
1213223345%75%
1829
11th to 20thNight
231221122381%
1980
21st to endNight
331221223379%
1980
October1st to 10thNight
6%423323345%67%
1980
11th to 20thNight
6%413223235%70%
1980
21st to endNight
5%413322335%70%
2449
November1st to 10thNight
7%5%13213235%69%
2405
11th to 20thNight
4423323346%67%
2470
21st to endNight
8%5%24424447%56%
2470
December1st to 10thNight
10%6%2442345%6%54%
2470
11th to 20thNight
13%8%3443447%6%44%
3041
21st to endNight
11%8%36%5%345%5%6%44%
4521

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 10thDay
23%5%5%16%30%21%
2859
11th to 20thDay
27%6%8%23%22%15%
2998
21st to endDay
34%7%7%12%23%17%
3498
February1st to 10thDay
29%45%13%21%29%
1900
11th to 20thDay
30%46%13%25%22%
1860
21st to endDay
38%5%5%12%20%19%
1570
March1st to 10thDay
32%5%6%16%19%21%
1851
11th to 20thDay
29%5%6%14%27%19%
1898
21st to endDay
27%5%8%21%24%15%
2268
April1st to 10thDay
29%48%22%25%12%
2160
11th to 20thDay
20%47%19%28%22%
2132
21st to endDay
20%47%21%33%16%
2160
May1st to 10thDay
24%47%18%27%20%
2286
11th to 20thDay
16%37%23%33%19%
2304
21st to endDay
18%27%25%35%12%
2530
June1st to 10thDay
13%35%21%33%26%
2340
11th to 20thDay
9%2414%24%48%
2340
21st to endDay
9%227%22%57%
2340
July1st to 10thDay
10%3410%22%50%
2276
11th to 20thDay
11%7%8%20%27%27%
2271
21st to endDay
14%9%12%21%28%16%
2320
August1st to 10thDay
8%36%13%29%39%
2135
11th to 20thDay
9%3417%31%37%
2122
21st to endDay
11%3413%33%36%
2376
September1st to 10thDay
13%45%11%29%39%
2129
11th to 20thDay
7%129%34%47%
1980
21st to endDay
12%3410%30%41%
1980
October1st to 10thDay
19%36%15%24%33%
1980
11th to 20thDay
17%2311%25%41%
1980
21st to endDay
15%3411%21%47%
1901
November1st to 10thDay
20%3414%23%37%
1674
11th to 20thDay
19%36%10%24%39%
1710
21st to endDay
26%45%11%23%32%
1710
December1st to 10thDay
28%46%14%18%29%
1710
11th to 20thDay
36%7%9%12%18%18%
2168
21st to endDay
39%7%6%17%18%13%
3146
January1st to 10thNight
24%5%5%14%27%24%
4097
11th to 20thNight
30%6%8%20%20%16%
3972
21st to endNight
36%6%6%9%24%18%
4180
February1st to 10thNight
29%45%12%21%29%
2280
11th to 20thNight
33%5%410%22%26%
2219
21st to endNight
37%45%13%20%22%
1884
March1st to 10thNight
39%5%6%13%15%21%
2225
11th to 20thNight
30%7%6%13%24%20%
2062
21st to endNight
32%6%8%16%21%16%
2084
April1st to 10thNight
31%5%8%19%22%16%
1800
11th to 20thNight
26%38%17%22%23%
1779
21st to endNight
27%37%20%24%20%
1800
May1st to 10thNight
26%5%8%18%21%23%
1674
11th to 20thNight
24%49%22%22%19%
1595
21st to endNight
25%48%21%27%15%
1746
June1st to 10thNight
15%48%18%26%28%
1620
11th to 20thNight
11%2316%20%47%
1620
21st to endNight
10%239%22%55%
1620
July1st to 10thNight
7%2314%24%50%
1575
11th to 20thNight
9%5%8%21%28%28%
1566
21st to endNight
15%6%9%25%28%17%
1754
August1st to 10thNight
7%46%15%29%39%
1780
11th to 20thNight
7%3323%29%36%
1780
21st to endNight
9%3316%28%41%
1980
September1st to 10thNight
11%45%16%25%40%
1829
11th to 20thNight
11%2310%27%47%
1980
21st to endNight
11%3411%31%40%
1980
October1st to 10thNight
21%35%16%22%32%
1980
11th to 20thNight
18%3414%23%39%
1980
21st to endNight
17%35%10%18%46%
2449
November1st to 10thNight
21%3411%24%37%
2405
11th to 20thNight
20%3412%20%40%
2470
21st to endNight
29%5%5%12%18%31%
2470
December1st to 10thNight
30%5%6%11%19%28%
2470
11th to 20thNight
37%7%7%12%18%19%
3041
21st to endNight
37%8%6%18%18%14%
4521

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 10thDay
21%11%25%31%11%1
270
11th to 20thDay
14%12%26%38%9%1
356
21st to endDay
15%19%33%25%7%2
506
February1st to 10thDay
16%16%34%23%8%3
460
11th to 20thDay
15%19%33%25%8%
455
21st to endDay
19%24%31%20%7%
382
March1st to 10thDay
17%21%37%18%5%1
441
11th to 20thDay
16%18%32%24%8%3
420
21st to endDay
13%22%36%21%7%
462
April1st to 10thDay
11%17%34%25%10%3
420
11th to 20thDay
8%23%39%19%9%2
412
21st to endDay
9%16%32%26%11%5%
420
May1st to 10thDay
13%16%35%22%11%3
423
11th to 20thDay
7%13%36%30%10%3
448
21st to endDay
9%15%32%28%12%4
485
June1st to 10thDay
38%31%36%17%6%
450
11th to 20thDay
27%31%35%18%7%
450
21st to endDay
25%29%35%20%8%
450
July1st to 10thDay
2219%48%18%11%
446
11th to 20thDay
218%45%19%16%
444
21st to endDay
2110%52%19%15%
487
August1st to 10thDay
2124%42%18%13%
447
11th to 20thDay
2117%47%18%15%
437
21st to endDay
1217%52%16%13%
495
September1st to 10thDay
3228%46%14%7%
450
11th to 20thDay
4435%37%15%5%
450
21st to endDay
311%28%35%17%6%
450
October1st to 10thDay
6%11%32%34%15%2
450
11th to 20thDay
5%11%34%34%13%2
450
21st to endDay
6%10%28%36%17%3
387
November1st to 10thDay
9%11%24%39%15%3
270
11th to 20thDay
7%10%30%36%16%1
270
21st to endDay
13%14%33%26%12%3
270
December1st to 10thDay
9%14%31%31%16%
270
11th to 20thDay
7%11%31%33%14%2
270
21st to endDay
21%18%24%26%9%2
297
January1st to 10thNight
10%7%21%32%21%8%
760
11th to 20thNight
9%6%22%35%21%6%
760
21st to endNight
15%8%19%35%20%3
836
February1st to 10thNight
13%7%21%30%22%6%
760
11th to 20thNight
13%8%18%34%21%6%
744
21st to endNight
16%9%20%34%18%3
628
March1st to 10thNight
16%9%23%32%18%2
742
11th to 20thNight
13%6%16%34%23%7%
720
21st to endNight
11%7%17%37%23%5%
792
April1st to 10thNight
12%5%18%36%23%5%
720
11th to 20thNight
11%7%17%35%24%6%
711
21st to endNight
10%417%32%29%8%
720
May1st to 10thNight
7%7%18%34%30%4
594
11th to 20thNight
5%5%16%34%32%9%
531
21st to endNight
7%6%18%34%30%4
584
June1st to 10thNight
3215%39%35%7%
540
11th to 20thNight
329%40%41%5%
540
21st to endNight
217%33%50%7%
540
July1st to 10thNight
1324%61%12%
525
11th to 20thNight
1223%62%12%
522
21st to endNight
21317%61%18%
675
August1st to 10thNight
1324%53%19%
716
11th to 20thNight
2214%58%24%
712
21st to endNight
2215%57%25%
792
September1st to 10thNight
115%22%56%15%
720
11th to 20thNight
227%31%49%11%
720
21st to endNight
419%34%38%14%
720
October1st to 10thNight
7%39%40%35%6%
720
11th to 20thNight
7%313%37%30%10%
720
21st to endNight
6%216%34%27%14%
792
November1st to 10thNight
8%314%39%28%9%
740
11th to 20thNight
6%317%37%27%11%
760
21st to endNight
11%6%18%34%24%8%
760
December1st to 10thNight
12%5%21%33%22%7%
760
11th to 20thNight
16%6%21%34%18%5%
760
21st to endNight
14%7%21%32%19%6%
836
Page generated at 2024-03-03 03:28:59. Version ac07

Copyright © 2024 Attilla Danko.


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