Pegasus Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pegasus 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
46%
24023
18%
74484
13%
23973
52%
23973
22%
48965

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
26%
760
17%
2459
9%
757
37%
757
16%
1676
January11th to 20thNight
28%
732
18%
2378
10%
732
39%
732
16%
1621
January21st to endNight
27%
792
22%
2574
11%
792
41%
792
18%
1661
February1st to 10thNight
29%
720
20%
2259
11%
720
39%
720
22%
1462
February11th to 20thNight
21%
701
17%
2099
7%
700
31%
700
16%
1447
February21st to endNight
23%
592
21%
1776
9%
592
34%
592
18%
1237
March1st to 10thNight
30%
720
22%
2029
13%
720
38%
720
22%
1356
March11th to 20thNight
28%
720
16%
1980
8%
720
35%
720
20%
1384
March21st to endNight
30%
792
15%
2178
7%
792
36%
792
20%
1508
April1st to 10thNight
35%
720
20%
1980
11%
720
43%
720
27%
1258
April11th to 20thNight
40%
616
22%
1766
13%
616
47%
616
27%
1106
April21st to endNight
50%
540
23%
1620
16%
540
57%
540
28%
1012
May1st to 10thNight
50%
540
16%
1620
8%
540
54%
540
25%
1046
May11th to 20thNight
50%
531
12%
1593
8%
531
53%
531
21%
1107
May21st to endNight
65%
582
14%
1745
11%
582
66%
582
26%
1151
June1st to 10thNight
65%
540
12%
1620
10%
540
66%
540
25%
1083
June11th to 20thNight
68%
540
11%
1620
9%
540
71%
540
31%
1018
June21st to endNight
72%
540
15%
1620
13%
540
73%
540
29%
1031
July1st to 10thNight
68%
525
11%
1575
10%
525
69%
525
23%
1105
July11th to 20thNight
70%
522
10%
1566
9%
522
70%
522
22%
1096
July21st to endNight
71%
591
12%
1672
11%
558
72%
558
23%
1153
August1st to 10thNight
70%
537
10%
1600
9%
534
70%
534
22%
1127
August11th to 20thNight
65%
534
15%
1598
14%
534
65%
534
21%
1146
August21st to endNight
66%
638
14%
1941
13%
638
66%
638
21%
1341
September1st to 10thNight
62%
720
18%
1980
16%
720
63%
720
24%
1366
September11th to 20thNight
58%
720
18%
1980
15%
720
59%
720
22%
1401
September21st to endNight
58%
720
23%
1980
19%
720
60%
720
28%
1292
October1st to 10thNight
53%
720
23%
2008
19%
720
58%
720
29%
1283
October11th to 20thNight
48%
720
24%
2160
20%
720
55%
720
28%
1332
October21st to endNight
48%
792
30%
2376
22%
792
59%
792
30%
1401
November1st to 10thNight
54%
740
25%
2311
21%
740
61%
740
29%
1387
November11th to 20thNight
45%
760
26%
2470
20%
760
56%
760
27%
1483
November21st to endNight
42%
760
24%
2470
17%
760
52%
760
24%
1490
December1st to 10thNight
32%
760
18%
2470
11%
760
41%
760
16%
1719
December11th to 20thNight
35%
759
21%
2987
16%
759
45%
759
18%
1884
December21st to endNight
30%
827
12%
4424
11%
817
39%
817
10%
2795

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
10%7%37%6%46%6%6%8%37%
74902
Night
10%7%36%6%45%5%6%8%39%
74853
TransparencyDay
42%9%13%18%15%3
74625
Night
40%9%13%20%15%3
74649
SeeingDay
18%13%21%22%17%9%
13910
Night
16%11%19%30%20%4
24037

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
10%7%37%6%45%6%6%8%37%
1706
11th to 20thDay
12%7%47%6%47%5%5%6%37%
1644
21st to endDay
10%8%47%5%3445%7%43%
1782
February1st to 10thDay
12%7%46%6%36%6%6%6%38%
1696
11th to 20thDay
12%10%48%6%345%5%7%37%
1748
21st to endDay
12%8%37%6%45%5%5%6%39%
1480
March1st to 10thDay
11%6%35%5%35%5%7%7%44%
1930
11th to 20thDay
14%8%47%5%46%5%5%7%34%
1980
21st to endDay
12%9%47%6%35%5%6%8%36%
2178
April1st to 10thDay
9%5%35%6%36%6%6%9%43%
1980
11th to 20thDay
13%6%45%5%3446%9%42%
2155
21st to endDay
10%6%36%5%35%5%6%7%43%
2340
May1st to 10thDay
8%6%37%7%46%6%6%9%39%
2340
11th to 20thDay
11%6%37%7%5%6%7%6%8%32%
2301
21st to endDay
9%6%27%6%46%7%7%10%34%
2531
June1st to 10thDay
9%6%36%8%5%8%6%8%9%32%
2340
11th to 20thDay
6%6%37%8%5%7%8%7%10%33%
2340
21st to endDay
7%5%36%8%48%8%8%10%33%
2340
July1st to 10thDay
8%7%37%9%5%9%7%7%11%26%
2340
11th to 20thDay
9%7%37%9%6%7%8%8%9%26%
2340
21st to endDay
7%7%38%9%5%8%8%9%11%27%
2547
August1st to 10thDay
10%7%37%8%5%8%8%9%10%25%
2327
11th to 20thDay
10%7%38%7%5%8%8%8%9%27%
2303
21st to endDay
9%6%37%7%5%8%7%8%10%30%
2394
September1st to 10thDay
9%7%46%6%46%6%7%8%37%
1980
11th to 20thDay
13%7%36%6%5%6%6%6%9%34%
1980
21st to endDay
11%7%35%6%5%6%5%5%8%39%
1980
October1st to 10thDay
11%7%26%5%35%45%6%47%
1949
11th to 20thDay
8%5%35%5%34446%52%
1800
21st to endDay
10%7%34433446%51%
1980
November1st to 10thDay
8%5%25%423446%55%
1764
11th to 20thDay
8%7%25%43445%6%50%
1710
21st to endDay
10%7%36%43436%7%46%
1710
December1st to 10thDay
13%8%48%6%45%6%5%6%35%
1710
11th to 20thDay
11%7%37%5%345%7%8%40%
2153
21st to endDay
10%9%48%7%46%5%5%7%35%
3124
January1st to 10thNight
11%7%47%7%5%7%5%5%6%35%
2459
11th to 20thNight
11%9%48%6%46%6%6%7%34%
2378
21st to endNight
11%7%48%6%445%5%6%41%
2574
February1st to 10thNight
11%8%47%5%25%6%6%7%39%
2259
11th to 20thNight
14%8%47%6%36%46%6%37%
2098
21st to endNight
12%8%47%6%5%6%45%7%36%
1776
March1st to 10thNight
10%7%46%435%6%7%6%42%
2029
11th to 20thNight
11%9%47%6%45%6%6%8%34%
1980
21st to endNight
10%8%37%6%45%5%5%10%37%
2178
April1st to 10thNight
10%6%35%5%345%6%8%46%
1980
11th to 20thNight
8%7%36%5%35%5%5%8%46%
1766
21st to endNight
9%6%36%6%345%6%8%46%
1620
May1st to 10thNight
9%5%45%5%35%6%7%9%42%
1620
11th to 20thNight
9%6%37%7%46%6%8%8%37%
1592
21st to endNight
6%5%27%7%45%6%8%10%39%
1744
June1st to 10thNight
6%5%26%5%47%6%9%15%34%
1620
11th to 20thNight
45%45%5%35%6%9%12%41%
1620
21st to endNight
6%435%5%45%5%8%12%42%
1620
July1st to 10thNight
7%6%26%6%5%8%6%7%11%35%
1620
11th to 20thNight
7%5%36%7%46%8%10%12%33%
1620
21st to endNight
6%437%7%5%8%8%8%11%33%
1771
August1st to 10thNight
7%436%7%37%8%8%12%35%
1611
11th to 20thNight
9%6%37%7%46%7%7%10%34%
1598
21st to endNight
7%8%36%7%46%8%8%9%35%
1941
September1st to 10thNight
8%5%37%6%45%6%6%9%40%
1980
11th to 20thNight
11%8%36%7%46%45%9%37%
1980
21st to endNight
8%7%35%6%35%5%6%6%46%
1980
October1st to 10thNight
13%6%25%43445%6%47%
2008
11th to 20thNight
9%7%26%6%345%6%7%47%
2160
21st to endNight
9%7%25%5%245%5%5%52%
2376
November1st to 10thNight
10%6%35%4345%6%6%50%
2311
11th to 20thNight
10%7%35%5%3345%6%48%
2470
21st to endNight
10%7%26%5%345%6%6%45%
2470
December1st to 10thNight
13%9%47%7%45%5%6%7%33%
2470
11th to 20thNight
12%10%47%5%345%5%6%38%
3042
21st to endNight
11%9%48%8%46%6%7%8%30%
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
40%9%12%20%15%4
1707
11th to 20thDay
44%8%10%17%17%4
1644
21st to endDay
39%6%10%21%20%4
1782
February1st to 10thDay
44%7%11%18%16%3
1696
11th to 20thDay
46%8%10%17%16%3
1758
21st to endDay
46%6%10%16%16%6%
1480
March1st to 10thDay
37%7%9%20%20%6%
1930
11th to 20thDay
48%7%12%15%15%4
1980
21st to endDay
46%8%12%19%12%2
2178
April1st to 10thDay
36%7%13%23%18%4
1980
11th to 20thDay
39%6%10%19%21%6%
2155
21st to endDay
38%7%14%24%15%2
2340
May1st to 10thDay
40%10%15%20%14%2
2340
11th to 20thDay
47%11%15%16%10%1
2305
21st to endDay
42%11%15%22%10%1
2531
June1st to 10thDay
44%12%19%17%8%1
2340
11th to 20thDay
43%11%18%15%12%1
2340
21st to endDay
43%10%16%18%11%2
2340
July1st to 10thDay
49%12%16%14%8%1
2275
11th to 20thDay
48%12%19%11%9%2
2271
21st to endDay
44%14%19%16%7%1
2405
August1st to 10thDay
49%14%17%16%4
2314
11th to 20thDay
48%13%16%15%7%1
2303
21st to endDay
44%13%15%17%7%3
2394
September1st to 10thDay
42%10%15%16%13%3
1980
11th to 20thDay
44%9%12%18%14%2
1980
21st to endDay
42%7%13%18%16%5%
1980
October1st to 10thDay
35%8%12%18%22%5%
1949
11th to 20thDay
32%7%10%23%21%8%
1800
21st to endDay
34%5%7%23%24%7%
1980
November1st to 10thDay
30%5%9%21%27%9%
1764
11th to 20thDay
34%6%8%21%26%6%
1710
21st to endDay
36%6%9%22%22%5%
1710
December1st to 10thDay
48%7%8%18%15%4
1710
11th to 20thDay
36%6%14%17%23%5%
2150
21st to endDay
41%8%12%21%15%2
3124
January1st to 10thNight
44%10%11%16%16%3
2459
11th to 20thNight
46%8%11%15%17%3
2378
21st to endNight
43%6%9%20%20%3
2574
February1st to 10thNight
42%6%14%20%16%3
2259
11th to 20thNight
46%7%9%18%15%4
2099
21st to endNight
47%7%10%16%16%4
1776
March1st to 10thNight
41%7%9%16%21%6%
2029
11th to 20thNight
44%8%13%19%13%3
1980
21st to endNight
44%8%13%21%13%2
2178
April1st to 10thNight
35%7%14%23%18%2
1980
11th to 20thNight
35%7%12%22%19%5%
1766
21st to endNight
35%8%14%26%16%1
1620
May1st to 10thNight
37%10%16%25%10%2
1620
11th to 20thNight
41%13%15%21%9%1
1593
21st to endNight
37%12%18%24%8%1
1745
June1st to 10thNight
37%13%22%20%7%1
1620
11th to 20thNight
32%11%27%20%10%
1620
21st to endNight
33%11%21%20%11%2
1620
July1st to 10thNight
40%14%18%18%9%1
1575
11th to 20thNight
38%16%23%15%6%2
1566
21st to endNight
38%15%21%19%7%1
1672
August1st to 10thNight
36%19%22%16%6%
1600
11th to 20thNight
40%16%18%15%10%1
1598
21st to endNight
40%14%19%19%7%1
1941
September1st to 10thNight
39%13%14%20%12%3
1980
11th to 20thNight
44%10%13%17%15%1
1980
21st to endNight
36%9%11%23%17%3
1980
October1st to 10thNight
37%7%12%19%23%3
2008
11th to 20thNight
35%8%11%22%19%5%
2160
21st to endNight
32%7%7%22%25%7%
2376
November1st to 10thNight
33%7%10%21%22%7%
2311
11th to 20thNight
36%6%7%20%24%8%
2470
21st to endNight
37%5%9%24%20%4
2470
December1st to 10thNight
46%10%11%16%13%4
2470
11th to 20thNight
40%8%11%17%20%3
3044
21st to endNight
44%10%12%20%13%1
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
29%27%30%11%21
270
11th to 20thDay
32%23%22%19%4
248
21st to endDay
26%31%27%13%3
264
February1st to 10thDay
29%28%28%11%4
240
11th to 20thDay
40%28%23%9%
240
21st to endDay
38%28%23%8%21
198
March1st to 10thDay
25%21%27%20%6%1
370
11th to 20thDay
29%21%24%20%6%1
420
21st to endDay
27%21%26%19%6%
462
April1st to 10thDay
23%19%24%21%11%2
420
11th to 20thDay
20%18%25%20%13%4
412
21st to endDay
20%15%25%20%15%5%
420
May1st to 10thDay
16%20%23%22%14%6%
423
11th to 20thDay
17%10%19%27%16%10%
447
21st to endDay
11%7%20%27%20%15%
485
June1st to 10thDay
12%6%22%27%21%13%
450
11th to 20thDay
9%6%20%22%25%17%
450
21st to endDay
10%6%27%23%19%15%
450
July1st to 10thDay
9%313%22%31%21%
445
11th to 20thDay
8%410%26%27%25%
444
21st to endDay
7%313%23%31%23%
488
August1st to 10thDay
16%415%23%20%23%
446
11th to 20thDay
9%5%11%29%27%20%
439
21st to endDay
12%313%25%27%20%
495
September1st to 10thDay
10%313%26%32%16%
450
11th to 20thDay
15%6%13%22%30%15%
450
21st to endDay
14%6%18%29%26%8%
450
October1st to 10thDay
16%9%19%25%23%8%
450
11th to 20thDay
13%14%22%26%20%5%
450
21st to endDay
19%15%21%26%17%3
495
November1st to 10thDay
17%10%27%26%15%4
362
11th to 20thDay
19%21%33%17%9%1
270
21st to endDay
17%22%32%18%10%1
270
December1st to 10thDay
28%26%27%14%4
270
11th to 20thDay
23%20%30%19%8%1
270
21st to endDay
23%22%31%15%6%2
297
January1st to 10thNight
25%18%28%24%6%
760
11th to 20thNight
21%17%27%29%6%
732
21st to endNight
21%20%28%29%3
792
February1st to 10thNight
20%16%30%28%5%
720
11th to 20thNight
25%22%28%23%1
703
21st to endNight
23%22%29%22%3
592
March1st to 10thNight
18%19%30%30%3
720
11th to 20thNight
22%15%29%24%9%1
720
21st to endNight
17%18%30%26%8%
792
April1st to 10thNight
19%17%24%30%9%
720
11th to 20thNight
17%13%24%32%13%1
616
21st to endNight
14%11%19%40%15%1
540
May1st to 10thNight
14%9%22%37%17%1
540
11th to 20thNight
13%5%18%36%24%3
531
21st to endNight
8%312%34%37%6%
584
June1st to 10thNight
8%214%35%34%7%
540
11th to 20thNight
6%211%33%36%12%
540
21st to endNight
6%29%36%40%7%
540
July1st to 10thNight
9%36%27%47%9%
525
11th to 20thNight
9%3424%46%14%
522
21st to endNight
7%2324%49%14%
591
August1st to 10thNight
8%17%29%43%11%
537
11th to 20thNight
10%46%28%43%9%
534
21st to endNight
10%2428%44%11%
638
September1st to 10thNight
9%410%30%41%7%
720
11th to 20thNight
14%410%29%37%7%
720
21st to endNight
13%5%15%32%31%4
720
October1st to 10thNight
15%9%17%26%26%6%
720
11th to 20thNight
14%9%21%35%18%2
720
21st to endNight
15%12%19%35%16%2
792
November1st to 10thNight
16%8%17%39%18%3
740
11th to 20thNight
18%12%20%36%13%1
760
21st to endNight
18%14%22%33%13%1
760
December1st to 10thNight
22%17%23%31%7%
760
11th to 20thNight
18%14%27%32%8%1
760
21st to endNight
22%17%24%31%5%
836
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Copyright 2024 Attilla Danko


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