Skyview Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Skyview Observatory clear sky chart from 2005-11-06 to 2024-02-20.

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%
24235
32%
79271
20%
24136
64%
24136
43%
38873

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
45%
942
37%
4002
15%
926
59%
926
35%
1803
January11th to 20thNight
44%
876
38%
3860
18%
859
57%
859
42%
1432
January21st to endNight
44%
828
27%
3957
21%
814
62%
814
29%
1945
February1st to 10thNight
38%
760
35%
2280
15%
760
57%
760
43%
1176
February11th to 20thNight
35%
741
31%
2212
14%
738
51%
738
40%
1161
February21st to endNight
33%
592
37%
1776
12%
592
55%
592
41%
903
March1st to 10thNight
36%
720
30%
2160
12%
720
50%
720
36%
1191
March11th to 20thNight
35%
632
29%
2072
14%
632
49%
632
35%
1069
March21st to endNight
32%
594
36%
2066
16%
594
57%
594
42%
950
April1st to 10thNight
32%
540
35%
1800
16%
540
56%
540
45%
824
April11th to 20thNight
28%
533
32%
1777
15%
533
53%
533
42%
856
April21st to endNight
33%
540
34%
1800
16%
540
59%
540
47%
828
May1st to 10thNight
39%
540
31%
1663
18%
540
58%
540
47%
817
May11th to 20thNight
48%
531
27%
1593
19%
531
61%
531
42%
840
May21st to endNight
45%
584
26%
1745
17%
582
59%
582
39%
972
June1st to 10thNight
58%
540
24%
1620
19%
540
67%
540
46%
834
June11th to 20thNight
55%
540
29%
1620
20%
540
66%
540
57%
760
June21st to endNight
67%
540
28%
1620
25%
540
73%
540
55%
762
July1st to 10thNight
78%
525
24%
1575
24%
525
80%
525
45%
828
July11th to 20thNight
82%
522
29%
1566
31%
522
83%
522
51%
775
July21st to endNight
88%
591
31%
1731
35%
558
90%
558
57%
787
August1st to 10thNight
83%
537
30%
1779
35%
534
85%
534
50%
834
August11th to 20thNight
77%
534
26%
1778
32%
534
79%
534
35%
982
August21st to endNight
83%
594
28%
1980
32%
594
85%
594
45%
972
September1st to 10thNight
74%
540
28%
1814
31%
540
76%
540
38%
966
September11th to 20thNight
70%
540
29%
1980
32%
540
73%
540
33%
1055
September21st to endNight
67%
540
35%
1980
33%
540
73%
540
44%
893
October1st to 10thNight
60%
540
34%
1980
28%
540
69%
540
42%
945
October11th to 20thNight
55%
540
42%
1980
27%
540
72%
540
49%
850
October21st to endNight
56%
899
38%
2483
19%
899
67%
899
53%
1249
November1st to 10thNight
59%
925
37%
2405
17%
925
68%
925
61%
1196
November11th to 20thNight
54%
950
37%
2470
16%
950
65%
950
60%
1214
November21st to endNight
49%
950
37%
2470
16%
950
60%
950
48%
1349
December1st to 10thNight
47%
950
38%
2470
16%
950
60%
950
49%
1347
December11th to 20thNight
40%
948
36%
2887
14%
948
55%
948
40%
1569
December21st to endNight
40%
1037
24%
4320
16%
1026
54%
1026
35%
1939

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%42342445%7%60%
78930
Night
5%41332345%7%62%
80323
TransparencyDay
24%48%21%27%15%
78662
Night
22%49%21%28%16%
80114
SeeingDay
7%5%23%32%25%8%
14122
Night
7%6%31%40%16%1
24265

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
9%6%24423346%58%
2847
11th to 20thDay
3223223345%70%
2987
21st to endDay
6%6%25%5%34347%54%
3487
February1st to 10thDay
5%6%24323346%63%
1900
11th to 20thDay
7%3235%2435%6%60%
1839
21st to endDay
6%7%34423345%61%
1480
March1st to 10thDay
7%5%2343345%6%58%
1800
11th to 20thDay
10%42332236%6%59%
1886
21st to endDay
5%432323446%64%
2286
April1st to 10thDay
5%324323346%67%
2160
11th to 20thDay
8%424423446%61%
2131
21st to endDay
431332335%6%66%
2160
May1st to 10thDay
7%414424446%61%
2294
11th to 20thDay
10%42342446%7%54%
2302
21st to endDay
7%424335%45%7%56%
2531
June1st to 10thDay
43233245%5%10%59%
2340
11th to 20thDay
3323324448%64%
2340
21st to endDay
4212325%5%5%7%62%
2340
July1st to 10thDay
6%4245%36%5%6%10%49%
2340
11th to 20thDay
431442445%9%60%
2340
21st to endDay
3213436%5%7%10%56%
2481
August1st to 10thDay
22134345%7%11%58%
2149
11th to 20thDay
7%424435%6%6%10%50%
2123
21st to endDay
5%4244346%6%8%54%
2376
September1st to 10thDay
8%4245%4345%8%53%
2144
11th to 20thDay
10%5%145%36%5%49%47%
1980
21st to endDay
9%313323345%64%
1980
October1st to 10thDay
7%5%23423345%63%
1980
11th to 20thDay
8%31322322469%
1977
21st to endDay
7%42332233468%
1851
November1st to 10thDay
5%313222345%69%
1673
11th to 20thDay
231332335%5%69%
1710
21st to endDay
9%5%23213345%62%
1710
December1st to 10thDay
7%5%2432435%7%59%
1710
11th to 20thDay
6%4245%3335%6%59%
2161
21st to endDay
7%5%23323235%66%
3135
January1st to 10thNight
46%2343335%6%61%
4108
11th to 20thNight
3223313347%68%
4010
21st to endNight
5%7%3432445%7%56%
4180
February1st to 10thNight
6%5%33323335%63%
2280
11th to 20thNight
6%425%42335%7%60%
2212
21st to endNight
6%313324446%63%
1776
March1st to 10thNight
5%6%24424446%57%
2160
11th to 20thNight
8%5%235%2445%7%57%
2072
21st to endNight
5%31342345%7%63%
2066
April1st to 10thNight
431332445%7%66%
1800
11th to 20thNight
6%31442345%7%62%
1777
21st to endNight
4313324347%66%
1800
May1st to 10thNight
5%31342335%7%63%
1663
11th to 20thNight
7%41242445%7%60%
1593
21st to endNight
7%3144245%5%8%55%
1745
June1st to 10thNight
43143245%6%11%58%
1620
11th to 20thNight
22123235%6%11%63%
1620
21st to endNight
211332246%10%65%
1620
July1st to 10thNight
43134346%7%11%54%
1620
11th to 20thNight
42134245%7%11%58%
1620
21st to endNight
211222448%12%61%
1833
August1st to 10thNight
21243245%8%12%56%
1790
11th to 20thNight
4325%6%36%6%6%10%48%
1778
21st to endNight
42135%345%6%11%57%
1980
September1st to 10thNight
7%3144245%5%8%56%
1814
11th to 20thNight
10%42443445%8%52%
1980
21st to endNight
7%313323346%65%
1980
October1st to 10thNight
6%41441335%6%64%
1980
11th to 20thNight
8%312212235%72%
1980
21st to endNight
7%412222335%70%
2483
November1st to 10thNight
5%312212346%71%
2405
11th to 20thNight
231332325%7%70%
2470
21st to endNight
8%422323347%62%
2470
December1st to 10thNight
7%41332345%6%62%
2470
11th to 20thNight
6%424324447%59%
3036
21st to endNight
4424423445%63%
4532

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
29%3420%29%14%
2848
11th to 20thDay
18%36%23%36%14%
2987
21st to endDay
31%36%18%32%10%
3487
February1st to 10thDay
24%36%20%29%19%
1900
11th to 20thDay
26%35%21%26%19%
1849
21st to endDay
27%3311%34%23%
1480
March1st to 10thDay
27%35%16%31%19%
1800
11th to 20thDay
26%35%23%27%16%
1886
21st to endDay
22%36%22%28%18%
2286
April1st to 10thDay
20%35%17%30%25%
2160
11th to 20thDay
26%46%15%26%23%
2134
21st to endDay
19%47%21%31%18%
2160
May1st to 10thDay
25%46%14%25%24%
2294
11th to 20thDay
28%6%9%20%23%14%
2306
21st to endDay
28%6%10%21%16%19%
2531
June1st to 10thDay
21%5%16%28%19%10%
2340
11th to 20thDay
20%410%21%26%19%
2340
21st to endDay
20%6%10%25%26%13%
2340
July1st to 10thDay
29%7%14%26%19%4
2276
11th to 20thDay
20%5%13%27%29%6%
2271
21st to endDay
19%7%18%31%22%2
2343
August1st to 10thDay
18%6%14%32%23%7%
2136
11th to 20thDay
27%7%15%28%17%6%
2123
21st to endDay
27%6%13%26%20%9%
2376
September1st to 10thDay
30%5%11%20%22%12%
2144
11th to 20thDay
34%5%9%22%23%6%
1980
21st to endDay
24%37%20%34%12%
1980
October1st to 10thDay
25%410%22%24%15%
1980
11th to 20thDay
21%3415%31%26%
1977
21st to endDay
22%3420%31%19%
1851
November1st to 10thDay
19%36%18%32%22%
1673
11th to 20thDay
18%35%21%36%18%
1710
21st to endDay
25%35%16%31%21%
1710
December1st to 10thDay
26%26%24%28%13%
1710
11th to 20thDay
26%37%20%26%17%
2159
21st to endDay
23%26%19%33%17%
3135
January1st to 10thNight
23%46%25%30%12%
4108
11th to 20thNight
16%312%21%35%12%
4010
21st to endNight
27%5%7%20%29%12%
4180
February1st to 10thNight
25%36%16%29%22%
2280
11th to 20thNight
26%36%19%25%22%
2212
21st to endNight
23%4414%26%29%
1776
March1st to 10thNight
29%45%15%25%22%
2160
11th to 20thNight
27%47%20%23%20%
2072
21st to endNight
21%37%24%26%19%
2066
April1st to 10thNight
19%48%17%28%25%
1800
11th to 20thNight
22%39%18%26%22%
1777
21st to endNight
18%410%21%27%19%
1800
May1st to 10thNight
21%411%15%22%27%
1663
11th to 20thNight
23%7%13%19%20%18%
1594
21st to endNight
26%7%11%20%16%19%
1746
June1st to 10thNight
20%7%16%29%17%10%
1620
11th to 20thNight
15%5%13%23%26%18%
1620
21st to endNight
15%6%14%28%22%16%
1620
July1st to 10thNight
22%7%15%33%18%5%
1575
11th to 20thNight
19%5%10%25%31%9%
1566
21st to endNight
14%5%17%32%27%4
1731
August1st to 10thNight
18%5%12%31%26%8%
1779
11th to 20thNight
28%7%13%26%21%4
1778
21st to endNight
20%6%16%27%22%9%
1980
September1st to 10thNight
26%7%11%20%26%11%
1814
11th to 20thNight
30%5%14%18%26%7%
1980
21st to endNight
22%37%21%30%16%
1980
October1st to 10thNight
22%5%11%21%22%18%
1980
11th to 20thNight
19%35%16%31%26%
1980
21st to endNight
20%35%18%33%22%
2483
November1st to 10thNight
16%26%21%33%21%
2405
11th to 20thNight
15%26%20%37%20%
2470
21st to endNight
23%35%16%34%20%
2470
December1st to 10thNight
24%26%22%28%18%
2470
11th to 20thNight
26%35%19%30%17%
3037
21st to endNight
23%3419%33%17%
4532

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
12%10%30%31%14%2
270
11th to 20thDay
7%13%34%33%12%2
270
21st to endDay
7%8%35%32%17%1
297
February1st to 10thDay
9%8%38%34%10%1
270
11th to 20thDay
8%11%39%31%11%1
267
21st to endDay
9%14%44%26%6%1
198
March1st to 10thDay
8%7%40%33%11%
240
11th to 20thDay
14%8%31%32%13%2
240
21st to endDay
6%13%42%29%8%2
372
April1st to 10thDay
7%11%45%27%9%
420
11th to 20thDay
11%10%44%28%5%1
412
21st to endDay
7%11%39%30%10%1
420
May1st to 10thDay
6%8%38%35%12%2
557
11th to 20thDay
12%6%29%31%17%4
625
21st to endDay
9%6%30%34%19%3
679
June1st to 10thDay
5%316%43%28%4
630
11th to 20thDay
4222%42%25%5%
630
21st to endDay
3113%39%35%8%
630
July1st to 10thDay
6%25%31%39%18%
621
11th to 20thDay
41330%46%17%
618
21st to endDay
2326%49%20%
619
August1st to 10thDay
215%32%42%18%
447
11th to 20thDay
6%25%28%38%22%
437
21st to endDay
6%1425%41%23%
495
September1st to 10thDay
8%15%32%36%19%
434
11th to 20thDay
12432%44%17%
270
21st to endDay
12%211%23%39%14%
270
October1st to 10thDay
11%214%37%29%7%
270
11th to 20thDay
7%322%38%24%6%
270
21st to endDay
14%425%27%24%6%
297
November1st to 10thDay
13%424%33%23%3
270
11th to 20thDay
5%9%23%36%21%6%
270
21st to endDay
16%10%34%25%13%3
270
December1st to 10thDay
10%5%35%31%18%1
270
11th to 20thDay
7%9%30%41%13%1
270
21st to endDay
10%8%44%27%9%1
297
January1st to 10thNight
7%8%35%40%9%1
950
11th to 20thNight
6%7%37%38%10%1
879
21st to endNight
6%7%38%39%9%
836
February1st to 10thNight
9%7%43%32%8%1
760
11th to 20thNight
8%9%44%33%6%1
742
21st to endNight
8%11%46%33%3
592
March1st to 10thNight
8%11%41%35%5%
720
11th to 20thNight
10%11%40%32%6%
632
21st to endNight
5%12%48%30%5%
594
April1st to 10thNight
5%10%49%33%3
540
11th to 20thNight
6%9%53%28%3
533
21st to endNight
6%8%51%30%4
540
May1st to 10thNight
6%5%48%38%4
540
11th to 20thNight
8%5%36%38%13%1
531
21st to endNight
9%339%39%10%
584
June1st to 10thNight
4230%51%12%
540
11th to 20thNight
2238%47%11%
540
21st to endNight
3124%50%21%
540
July1st to 10thNight
5%19%47%35%3
525
11th to 20thNight
417%49%39%1
522
21st to endNight
21443%49%2
591
August1st to 10thNight
217%46%43%2
537
11th to 20thNight
5%15%46%40%2
534
21st to endNight
5%15%43%44%3
594
September1st to 10thNight
8%18%46%35%2
540
11th to 20thNight
11%110%47%29%1
540
21st to endNight
8%217%41%30%2
540
October1st to 10thNight
6%226%46%19%1
540
11th to 20thNight
10%429%44%12%1
540
21st to endNight
10%5%27%37%20%2
899
November1st to 10thNight
7%427%45%16%1
925
11th to 20thNight
46%31%42%15%2
950
21st to endNight
10%7%30%38%14%1
950
December1st to 10thNight
9%7%33%41%10%1
950
11th to 20thNight
10%7%39%35%9%
950
21st to endNight
10%8%37%36%9%1
1045
Page generated at 2024-02-17 05:28:41. Version ac07

Copyright 2024 Attilla Danko


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