Stella Nova Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stella Nova Observatory clear sky chart from 2005-11-06 to 2024-01-13.

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
38%
23274
20%
74673
11%
23229
48%
23229
23%
47443

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
21%
758
22%
2649
9%
757
39%
757
21%
1622
January11th to 20thNight
28%
732
20%
2439
9%
732
42%
732
19%
1592
January21st to endNight
22%
792
23%
2574
8%
792
40%
792
24%
1585
February1st to 10thNight
21%
720
17%
2340
7%
720
34%
720
18%
1543
February11th to 20thNight
17%
703
19%
2195
4%
700
36%
700
18%
1421
February21st to endNight
17%
592
22%
1776
7%
592
35%
592
18%
1208
March1st to 10thNight
25%
720
23%
2084
8%
720
42%
720
27%
1278
March11th to 20thNight
24%
720
20%
1980
9%
720
36%
720
23%
1325
March21st to endNight
25%
792
21%
2102
8%
792
36%
792
25%
1438
April1st to 10thNight
23%
720
18%
1800
4%
720
32%
720
24%
1245
April11th to 20thNight
36%
711
20%
1775
8%
711
41%
711
30%
1185
April21st to endNight
33%
720
19%
1800
6%
720
40%
720
28%
1239
May1st to 10thNight
38%
589
16%
1669
9%
589
44%
589
24%
1147
May11th to 20thNight
39%
354
17%
1416
14%
354
46%
354
16%
913
May21st to endNight
56%
388
15%
1551
16%
388
60%
388
20%
950
June1st to 10thNight
54%
360
18%
1440
19%
360
62%
360
23%
847
June11th to 20thNight
55%
360
14%
1440
17%
360
60%
360
21%
893
June21st to endNight
62%
360
17%
1440
21%
360
65%
360
26%
812
July1st to 10thNight
55%
350
13%
1400
16%
350
58%
350
18%
894
July11th to 20thNight
71%
348
17%
1392
21%
348
73%
348
26%
778
July21st to endNight
66%
528
16%
1613
14%
499
69%
499
28%
987
August1st to 10thNight
65%
537
17%
1600
14%
534
67%
534
28%
1009
August11th to 20thNight
61%
631
16%
1695
11%
631
61%
631
27%
1147
August21st to endNight
61%
792
17%
1980
9%
792
62%
792
32%
1327
September1st to 10thNight
55%
720
22%
1800
11%
720
59%
720
32%
1217
September11th to 20thNight
63%
720
30%
1800
21%
720
66%
720
40%
1115
September21st to endNight
51%
720
22%
2037
17%
720
56%
720
27%
1354
October1st to 10thNight
46%
720
17%
2160
15%
720
52%
720
25%
1423
October11th to 20thNight
43%
720
23%
2160
18%
720
53%
720
29%
1328
October21st to endNight
36%
792
25%
2376
15%
792
49%
792
29%
1467
November1st to 10thNight
44%
740
25%
2402
16%
740
58%
740
32%
1352
November11th to 20thNight
34%
760
24%
2470
14%
760
48%
760
25%
1501
November21st to endNight
34%
760
22%
2660
13%
760
48%
760
23%
1563
December1st to 10thNight
26%
760
18%
2660
7%
760
41%
760
18%
1748
December11th to 20thNight
25%
760
19%
3192
7%
759
40%
759
17%
1954
December21st to endNight
27%
825
13%
4806
9%
817
40%
817
12%
3036

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%6%25%5%35%5%6%8%41%
74714
Night
15%6%35%5%345%5%7%43%
75034
TransparencyDay
41%7%12%22%15%3
74420
Night
40%7%12%22%16%3
74847
SeeingDay
19%10%27%24%15%6%
13799
Night
18%8%29%31%12%1
23288

By Month

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 10thDay
13%8%36%5%3445%6%42%
1517
11th to 20thDay
15%8%36%5%35%45%8%38%
1573
21st to endDay
13%9%38%6%45%5%5%6%37%
1782
February1st to 10thDay
15%9%35%5%345%5%8%36%
1620
11th to 20thDay
17%7%246%3446%7%40%
1651
21st to endDay
20%10%36%5%3434438%
1480
March1st to 10thDay
13%6%25%5%35%446%47%
1875
11th to 20thDay
17%6%35%5%445%5%7%40%
1980
21st to endDay
20%7%35%5%3445%5%39%
2254
April1st to 10thDay
14%7%35%6%35%5%5%7%40%
2160
11th to 20thDay
14%6%246%245%5%7%44%
2134
21st to endDay
18%6%25%5%345%6%7%40%
2160
May1st to 10thDay
17%7%26%6%345%5%7%38%
2306
11th to 20thDay
20%6%36%5%45%46%7%36%
2478
21st to endDay
14%6%25%5%35%46%10%40%
2725
June1st to 10thDay
13%5%25%5%46%5%7%10%39%
2520
11th to 20thDay
13%5%26%6%36%6%6%9%38%
2520
21st to endDay
11%425%5%36%6%6%11%42%
2520
July1st to 10thDay
10%5%26%6%36%6%6%10%40%
2520
11th to 20thDay
7%325%5%36%7%8%11%43%
2520
21st to endDay
9%6%36%6%5%6%6%8%8%37%
2605
August1st to 10thDay
9%6%26%6%5%6%6%6%9%38%
2327
11th to 20thDay
11%5%37%5%45%5%7%9%40%
2186
21st to endDay
12%5%245%35%6%6%8%43%
2376
September1st to 10thDay
16%6%35%5%34447%43%
2160
11th to 20thDay
14%5%23434348%50%
2160
21st to endDay
18%7%25%4345%5%8%39%
1919
October1st to 10thDay
18%6%244235%5%7%43%
1800
11th to 20thDay
18%5%34444446%45%
1800
21st to endDay
17%6%2442446%6%44%
1980
November1st to 10thDay
13%6%24423348%51%
1676
11th to 20thDay
16%5%244245%46%48%
1708
21st to endDay
16%5%35%435%5%5%6%44%
1520
December1st to 10thDay
17%8%36%435%45%7%38%
1520
11th to 20thDay
19%7%2443446%7%40%
1910
21st to endDay
16%8%37%6%46%5%6%6%35%
2772
January1st to 10thNight
14%6%35%5%345%5%7%43%
2649
11th to 20thNight
19%7%345%3445%7%38%
2439
21st to endNight
13%7%35%5%2445%6%45%
2574
February1st to 10thNight
17%8%36%5%3445%6%39%
2340
11th to 20thNight
17%7%36%435%45%6%41%
2193
21st to endNight
17%9%35%435%445%40%
1776
March1st to 10thNight
14%5%245%245%5%7%48%
2084
11th to 20thNight
17%8%35%434445%43%
1980
21st to endNight
17%7%36%5%24445%42%
2102
April1st to 10thNight
17%7%35%5%3446%7%39%
1800
11th to 20thNight
14%5%35%44446%7%44%
1775
21st to endNight
20%7%24423447%43%
1800
May1st to 10thNight
18%6%26%5%345%5%8%38%
1669
11th to 20thNight
18%7%36%5%3445%8%37%
1415
21st to endNight
13%7%25%5%345%6%9%42%
1550
June1st to 10thNight
13%4344346%6%8%45%
1440
11th to 20thNight
13%426%5%45%5%6%11%38%
1440
21st to endNight
10%4245%35%6%7%10%44%
1440
July1st to 10thNight
9%6%37%7%36%5%7%8%38%
1440
11th to 20thNight
6%3245%46%6%7%10%47%
1440
21st to endNight
9%5%25%5%37%6%6%10%44%
1708
August1st to 10thNight
9%5%35%6%45%6%7%9%43%
1611
11th to 20thNight
10%7%25%6%36%6%6%8%40%
1695
21st to endNight
13%5%246%35%46%8%45%
1980
September1st to 10thNight
14%6%36%5%3345%7%46%
1800
11th to 20thNight
12%5%2442235%7%53%
1800
21st to endNight
18%6%245%345%47%42%
2037
October1st to 10thNight
20%6%35%333446%43%
2160
11th to 20thNight
16%5%25%424346%49%
2160
21st to endNight
19%5%2332345%6%47%
2376
November1st to 10thNight
11%425%5%24446%53%
2402
11th to 20thNight
15%7%345%24345%48%
2470
21st to endNight
13%425%5%35%5%5%7%46%
2660
December1st to 10thNight
18%7%25%6%35%45%7%38%
2660
11th to 20thNight
18%5%25%5%35%45%7%41%
3285
21st to endNight
17%7%35%5%45%6%6%8%34%
4884

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
42%5%13%21%15%4
1518
11th to 20thDay
46%6%13%20%13%2
1573
21st to endDay
47%5%10%22%13%2
1782
February1st to 10thDay
45%6%13%24%10%2
1620
11th to 20thDay
43%5%11%26%13%3
1660
21st to endDay
50%49%20%13%4
1480
March1st to 10thDay
39%5%12%27%14%2
1875
11th to 20thDay
43%5%12%18%17%5%
1980
21st to endDay
48%5%9%19%17%3
2254
April1st to 10thDay
42%7%11%19%16%5%
2160
11th to 20thDay
38%7%11%22%16%5%
2134
21st to endDay
42%6%11%20%17%4
2160
May1st to 10thDay
44%7%10%21%15%3
2306
11th to 20thDay
46%8%12%20%12%2
2482
21st to endDay
39%9%15%23%12%2
2725
June1st to 10thDay
39%8%14%23%15%1
2520
11th to 20thDay
40%9%13%23%12%3
2520
21st to endDay
34%10%15%25%15%1
2520
July1st to 10thDay
38%10%13%21%15%3
2450
11th to 20thDay
30%10%15%27%15%2
2445
21st to endDay
40%10%12%21%15%2
2459
August1st to 10thDay
39%10%13%23%14%1
2314
11th to 20thDay
39%9%13%21%16%1
2186
21st to endDay
37%9%13%23%14%4
2376
September1st to 10thDay
41%6%11%19%18%4
2160
11th to 20thDay
34%5%11%26%21%4
2160
21st to endDay
43%7%8%19%20%3
1919
October1st to 10thDay
39%7%13%23%17%2
1800
11th to 20thDay
40%6%11%22%20%2
1800
21st to endDay
40%5%10%26%17%1
1980
November1st to 10thDay
34%5%14%24%20%4
1676
11th to 20thDay
37%6%11%24%20%3
1708
21st to endDay
40%6%11%29%11%2
1520
December1st to 10thDay
46%6%16%20%11%1
1520
11th to 20thDay
42%5%12%30%9%1
1906
21st to endDay
47%8%15%20%10%1
2772
January1st to 10thNight
40%6%11%25%15%4
2649
11th to 20thNight
45%6%15%22%12%1
2439
21st to endNight
39%5%11%26%16%3
2574
February1st to 10thNight
46%5%13%23%12%2
2340
11th to 20thNight
44%410%21%17%3
2195
21st to endNight
46%6%9%20%15%4
1776
March1st to 10thNight
36%5%12%26%19%2
2084
11th to 20thNight
43%6%10%21%16%4
1980
21st to endNight
43%6%9%20%17%5%
2102
April1st to 10thNight
43%6%11%19%17%4
1800
11th to 20thNight
38%7%11%21%20%4
1775
21st to endNight
41%7%10%20%17%5%
1800
May1st to 10thNight
44%7%11%19%15%4
1669
11th to 20thNight
46%8%11%15%18%2
1416
21st to endNight
38%10%15%21%14%3
1551
June1st to 10thNight
36%9%12%24%18%2
1440
11th to 20thNight
38%10%14%20%16%1
1440
21st to endNight
34%8%14%26%16%2
1440
July1st to 10thNight
42%11%14%18%13%3
1400
11th to 20thNight
31%10%16%24%16%2
1392
21st to endNight
32%11%17%20%18%1
1613
August1st to 10thNight
36%9%16%24%14%1
1600
11th to 20thNight
39%10%15%19%15%2
1695
21st to endNight
36%9%14%21%17%3
1980
September1st to 10thNight
38%8%10%21%19%4
1800
11th to 20thNight
32%5%11%24%25%4
1800
21st to endNight
42%6%10%19%20%3
2037
October1st to 10thNight
42%6%11%22%17%2
2160
11th to 20thNight
37%6%10%27%18%2
2160
21st to endNight
37%5%11%26%18%2
2376
November1st to 10thNight
32%5%12%26%20%5%
2402
11th to 20thNight
39%410%23%19%5%
2470
21st to endNight
36%6%12%27%16%2
2660
December1st to 10thNight
46%6%12%23%13%1
2660
11th to 20thNight
41%7%13%22%15%3
3288
21st to endNight
43%10%15%21%10%1
4884

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
26%20%35%16%31
180
11th to 20thDay
25%24%33%17%2
216
21st to endDay
21%22%36%14%6%1
264
February1st to 10thDay
29%19%36%13%3
240
11th to 20thDay
25%22%42%10%1
318
21st to endDay
30%14%35%18%2
346
March1st to 10thDay
19%21%31%24%5%
420
11th to 20thDay
21%18%36%18%5%1
420
21st to endDay
24%16%32%21%6%2
462
April1st to 10thDay
21%14%36%20%7%2
420
11th to 20thDay
17%17%28%21%13%5%
412
21st to endDay
26%12%31%21%8%2
420
May1st to 10thDay
25%14%25%20%12%3
423
11th to 20thDay
21%10%30%21%13%4
447
21st to endDay
19%421%24%22%11%
485
June1st to 10thDay
15%429%25%18%8%
450
11th to 20thDay
17%6%25%27%19%6%
450
21st to endDay
14%225%31%19%9%
450
July1st to 10thDay
13%313%27%28%16%
445
11th to 20thDay
5%313%35%32%13%
444
21st to endDay
14%220%32%25%7%
488
August1st to 10thDay
11%219%28%28%12%
446
11th to 20thDay
11%416%27%28%14%
439
21st to endDay
12%417%29%24%15%
495
September1st to 10thDay
20%417%21%23%14%
450
11th to 20thDay
16%320%24%24%13%
450
21st to endDay
22%8%21%26%16%7%
450
October1st to 10thDay
23%5%21%25%18%8%
450
11th to 20thDay
18%10%26%27%16%3
450
21st to endDay
19%8%35%26%9%2
495
November1st to 10thDay
16%9%31%27%14%3
368
11th to 20thDay
17%16%31%24%11%1
368
21st to endDay
18%18%36%19%8%1
180
December1st to 10thDay
24%16%34%18%42
180
11th to 20thDay
25%19%33%14%8%1
180
21st to endDay
21%17%31%22%8%
198
January1st to 10thNight
18%13%42%23%4
760
11th to 20thNight
24%12%32%28%4
732
21st to endNight
18%13%42%25%2
792
February1st to 10thNight
20%16%37%26%2
720
11th to 20thNight
22%18%39%20%2
703
21st to endNight
22%18%39%19%2
592
March1st to 10thNight
17%15%38%25%4
720
11th to 20thNight
20%15%36%23%6%1
720
21st to endNight
21%10%39%24%6%1
792
April1st to 10thNight
21%14%37%24%5%
720
11th to 20thNight
17%10%33%31%9%
711
21st to endNight
23%8%31%30%8%
720
May1st to 10thNight
21%7%28%33%10%1
589
11th to 20thNight
20%5%29%36%10%
354
21st to endNight
15%319%41%21%2
389
June1st to 10thNight
13%322%40%21%1
360
11th to 20thNight
14%321%43%18%1
360
21st to endNight
12%315%53%17%
360
July1st to 10thNight
11%215%40%28%3
350
11th to 20thNight
8%112%45%32%3
348
21st to endNight
10%116%45%26%2
528
August1st to 10thNight
10%29%46%31%2
537
11th to 20thNight
13%212%38%32%3
631
21st to endNight
13%314%39%28%4
792
September1st to 10thNight
16%317%35%25%4
720
11th to 20thNight
13%315%36%29%4
720
21st to endNight
20%319%35%21%2
720
October1st to 10thNight
23%421%29%20%4
720
11th to 20thNight
18%7%27%34%14%1
720
21st to endNight
20%7%33%27%12%
792
November1st to 10thNight
13%6%32%36%13%1
740
11th to 20thNight
19%11%31%31%8%1
760
21st to endNight
16%12%34%30%8%
760
December1st to 10thNight
23%13%33%25%6%1
760
11th to 20thNight
18%10%40%26%5%
760
21st to endNight
20%11%38%29%2
836
Page generated at 2024-01-10 10:16:10. Version ac07

Copyright 2024 Attilla Danko


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