Camp Crosley/WAS Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Camp Crosley/WAS Observatory clear sky chart from 2005-11-06 to 2024-02-05.

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
35%
24567
15%
80404
10%
24460
41%
24460
18%
56808

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
16%
942
9%
4399
4%
926
23%
926
7%
3439
January11th to 20thNight
15%
948
7%
4419
3%
930
20%
930
6%
3702
January21st to endNight
16%
1004
5%
4792
3%
983
22%
983
6%
3956
February1st to 10thNight
18%
739
9%
2287
4%
739
23%
739
12%
1755
February11th to 20thNight
20%
700
13%
2099
6%
700
27%
700
14%
1583
February21st to endNight
16%
592
13%
1776
4%
592
24%
592
14%
1329
March1st to 10thNight
25%
720
13%
2160
7%
720
30%
720
17%
1538
March11th to 20thNight
27%
720
20%
2034
8%
720
37%
720
22%
1372
March21st to endNight
29%
734
16%
2120
9%
734
37%
734
19%
1531
April1st to 10thNight
29%
540
15%
1800
9%
540
37%
540
19%
1184
April11th to 20thNight
30%
533
20%
1752
12%
533
39%
533
20%
1167
April21st to endNight
31%
540
17%
1620
9%
540
39%
540
22%
1105
May1st to 10thNight
32%
540
13%
1620
7%
540
37%
540
19%
1177
May11th to 20thNight
39%
531
16%
1592
11%
531
45%
531
22%
1090
May21st to endNight
49%
583
15%
1635
10%
582
53%
582
30%
1041
June1st to 10thNight
54%
540
17%
1440
11%
540
60%
540
37%
878
June11th to 20thNight
51%
540
19%
1440
13%
540
56%
540
33%
930
June21st to endNight
55%
540
17%
1440
12%
540
59%
540
34%
924
July1st to 10thNight
66%
525
17%
1400
14%
525
68%
525
36%
860
July11th to 20thNight
66%
522
21%
1392
17%
522
68%
522
40%
829
July21st to endNight
66%
591
22%
1521
17%
558
69%
558
40%
904
August1st to 10thNight
70%
537
21%
1600
20%
534
72%
534
38%
908
August11th to 20thNight
67%
534
23%
1611
19%
534
71%
534
34%
947
August21st to endNight
63%
594
22%
1980
22%
594
67%
594
33%
1101
September1st to 10thNight
61%
558
23%
1818
21%
558
64%
558
31%
1058
September11th to 20thNight
63%
720
32%
1980
26%
720
66%
720
40%
1140
September21st to endNight
49%
720
26%
1980
18%
720
55%
720
32%
1249
October1st to 10thNight
49%
720
25%
1980
19%
720
54%
720
32%
1240
October11th to 20thNight
32%
720
19%
2156
10%
720
42%
720
22%
1443
October21st to endNight
27%
792
18%
2574
12%
792
37%
792
19%
1750
November1st to 10thNight
34%
740
21%
2406
16%
740
43%
740
24%
1502
November11th to 20thNight
23%
760
19%
2470
9%
760
35%
760
17%
1707
November21st to endNight
24%
760
14%
2470
10%
760
30%
760
15%
1831
December1st to 10thNight
18%
798
8%
2508
4%
798
23%
798
11%
1918
December11th to 20thNight
20%
950
8%
3266
4%
949
25%
949
11%
2604
December21st to endNight
12%
1040
5%
4867
2%
1026
18%
1026
5%
4116

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
15%10%47%6%345%5%7%34%
78201
Night
16%11%5%7%6%3445%6%33%
80697
TransparencyDay
50%6%12%20%12%1
77906
Night
51%5%11%19%12%2
80513
SeeingDay
19%11%28%23%15%6%
14590
Night
19%10%29%28%12%1
24587

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
15%14%12%12%6%4445%5%19%
2527
11th to 20thDay
14%17%9%11%9%5%5%8%7%5%11%
2530
21st to endDay
27%22%9%11%42322414%
2845
February1st to 10thDay
16%16%7%9%8%4445%5%22%
1764
11th to 20thDay
16%11%7%12%9%36%446%23%
1748
21st to endDay
17%14%8%10%6%34448%23%
1480
March1st to 10thDay
17%11%5%8%7%45%448%27%
1800
11th to 20thDay
16%9%5%6%6%45%5%6%7%30%
1926
21st to endDay
22%14%47%6%34346%26%
2250
April1st to 10thDay
18%11%5%6%6%3445%6%32%
2160
11th to 20thDay
19%9%35%5%345%5%6%35%
2156
21st to endDay
19%9%36%6%345%5%6%34%
2340
May1st to 10thDay
19%7%47%5%345%6%7%33%
2340
11th to 20thDay
20%8%36%6%35%45%6%35%
2301
21st to endDay
11%5%36%6%35%5%7%8%40%
2637
June1st to 10thDay
11%6%25%6%445%6%7%43%
2520
11th to 20thDay
9%6%25%5%346%7%8%44%
2520
21st to endDay
12%425%6%36%6%6%9%40%
2520
July1st to 10thDay
9%5%246%35%5%6%9%47%
2520
11th to 20thDay
9%425%445%5%7%9%46%
2520
21st to endDay
7%5%35%5%46%6%6%10%43%
2703
August1st to 10thDay
7%426%5%35%5%7%9%46%
2327
11th to 20thDay
10%426%6%45%6%7%10%42%
2286
21st to endDay
9%425%5%35%5%6%9%48%
2376
September1st to 10thDay
11%6%25%5%35%5%6%7%44%
2123
11th to 20thDay
10%424435%5%6%9%48%
1980
21st to endDay
12%6%25%435%5%5%8%45%
1980
October1st to 10thDay
14%6%25%5%3446%8%43%
1980
11th to 20thDay
18%7%36%5%345%6%7%35%
1799
21st to endDay
21%10%47%6%445%5%7%28%
1782
November1st to 10thDay
12%9%35%5%3445%6%44%
1672
11th to 20thDay
17%14%5%7%6%23347%30%
1710
21st to endDay
21%14%5%9%5%34445%27%
1710
December1st to 10thDay
16%17%6%11%6%34446%22%
1668
11th to 20thDay
13%16%9%10%7%435%46%23%
1918
21st to endDay
24%22%7%12%7%3443410%
2783
January1st to 10thNight
18%16%8%9%7%3445%5%20%
4428
11th to 20thNight
15%20%8%14%7%447%5%414%
4440
21st to endNight
26%17%9%10%5%2433416%
4818
February1st to 10thNight
19%13%6%8%8%3445%5%25%
2287
11th to 20thNight
15%13%6%9%8%35%446%28%
2098
21st to endNight
21%12%6%8%6%34445%28%
1776
March1st to 10thNight
16%9%5%7%7%45%45%6%33%
2160
11th to 20thNight
14%9%36%6%35%5%6%7%38%
2034
21st to endNight
21%9%47%43445%6%33%
2120
April1st to 10thNight
15%8%35%6%445%5%7%38%
1800
11th to 20thNight
19%8%36%5%34446%37%
1752
21st to endNight
17%9%36%5%25%46%6%36%
1620
May1st to 10thNight
19%9%36%6%35%6%5%6%32%
1620
11th to 20thNight
20%6%35%5%3445%8%37%
1592
21st to endNight
10%6%25%5%446%6%8%44%
1634
June1st to 10thNight
9%425%435%47%9%48%
1440
11th to 20thNight
7%6%35%5%35%5%5%7%48%
1440
21st to endNight
10%5%25%5%345%6%10%43%
1440
July1st to 10thNight
6%425%5%3446%8%51%
1440
11th to 20thNight
9%4234345%5%10%51%
1440
21st to endNight
5%5%15%5%346%6%10%51%
1611
August1st to 10thNight
8%4244245%8%9%50%
1611
11th to 20thNight
7%5%245%35%5%6%8%50%
1611
21st to endNight
9%4245%3445%7%52%
1980
September1st to 10thNight
12%5%25%434348%50%
1818
11th to 20thNight
10%424324448%54%
1980
21st to endNight
13%6%35%4345%46%49%
1980
October1st to 10thNight
13%6%245%2445%7%48%
1980
11th to 20thNight
19%7%35%6%33447%39%
2156
21st to endNight
23%8%26%5%34446%36%
2574
November1st to 10thNight
14%8%36%5%3345%7%43%
2406
11th to 20thNight
17%12%46%5%3446%7%32%
2470
21st to endNight
20%14%48%6%3445%6%27%
2470
December1st to 10thNight
17%15%7%9%6%35%45%6%24%
2508
11th to 20thNight
17%15%7%11%7%34445%22%
3279
21st to endNight
26%18%8%10%6%34445%13%
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
67%411%14%5%
2528
11th to 20thDay
72%5%8%10%5%
2530
21st to endDay
79%27%9%3
2845
February1st to 10thDay
65%5%10%13%8%1
1764
11th to 20thDay
63%5%9%15%8%1
1758
21st to endDay
61%5%11%16%7%1
1480
March1st to 10thDay
58%5%10%18%8%
1800
11th to 20thDay
52%6%12%18%10%1
1926
21st to endDay
61%410%19%5%1
2250
April1st to 10thDay
54%6%10%19%11%
2160
11th to 20thDay
49%6%10%21%12%3
2156
21st to endDay
50%6%12%18%12%3
2340
May1st to 10thDay
51%7%11%21%9%
2340
11th to 20thDay
50%6%10%19%13%1
2305
21st to endDay
40%8%12%24%14%2
2637
June1st to 10thDay
39%6%11%26%17%2
2520
11th to 20thDay
36%6%12%25%18%3
2520
21st to endDay
40%8%15%19%16%2
2520
July1st to 10thDay
33%8%12%24%18%4
2451
11th to 20thDay
33%7%15%27%17%2
2445
21st to endDay
34%7%14%25%17%3
2553
August1st to 10thDay
33%8%15%28%14%2
2314
11th to 20thDay
35%8%16%25%14%2
2286
21st to endDay
33%6%13%24%19%5%
2376
September1st to 10thDay
38%8%15%19%17%3
2123
11th to 20thDay
33%6%12%27%20%1
1980
21st to endDay
37%6%10%25%19%1
1980
October1st to 10thDay
40%6%12%24%17%2
1980
11th to 20thDay
47%5%11%21%16%
1799
21st to endDay
57%412%17%9%1
1782
November1st to 10thDay
41%6%12%25%16%1
1672
11th to 20thDay
56%411%18%10%1
1710
21st to endDay
61%412%17%6%1
1710
December1st to 10thDay
63%5%11%14%6%
1668
11th to 20thDay
63%5%11%17%4
1915
21st to endDay
79%46%7%4
2783
January1st to 10thNight
65%6%10%13%6%
4428
11th to 20thNight
74%39%11%3
4440
21st to endNight
73%39%11%3
4818
February1st to 10thNight
62%412%13%8%1
2287
11th to 20thNight
58%5%10%18%9%1
2099
21st to endNight
59%311%16%9%2
1776
March1st to 10thNight
52%5%13%19%10%1
2160
11th to 20thNight
46%5%12%22%12%3
2034
21st to endNight
52%5%9%22%10%1
2120
April1st to 10thNight
45%7%13%21%14%1
1800
11th to 20thNight
48%49%20%16%3
1752
21st to endNight
48%5%11%20%13%3
1620
May1st to 10thNight
52%6%10%20%10%2
1620
11th to 20thNight
46%6%10%21%15%2
1593
21st to endNight
37%7%16%22%15%3
1635
June1st to 10thNight
32%6%12%28%19%3
1440
11th to 20thNight
35%8%11%24%19%3
1440
21st to endNight
36%7%18%21%16%3
1440
July1st to 10thNight
31%8%13%25%19%5%
1400
11th to 20thNight
29%6%15%26%20%3
1392
21st to endNight
28%7%16%24%20%5%
1521
August1st to 10thNight
27%8%14%30%19%1
1600
11th to 20thNight
31%8%14%25%20%2
1611
21st to endNight
30%6%11%25%22%5%
1980
September1st to 10thNight
34%5%13%23%18%5%
1818
11th to 20thNight
29%5%9%32%24%2
1980
21st to endNight
37%5%9%28%19%2
1980
October1st to 10thNight
36%5%9%28%20%1
1980
11th to 20thNight
46%49%23%16%1
2156
21st to endNight
50%411%21%13%1
2574
November1st to 10thNight
41%411%25%17%2
2406
11th to 20thNight
51%5%13%20%11%1
2470
21st to endNight
58%412%19%6%
2470
December1st to 10thNight
61%5%12%15%7%
2508
11th to 20thNight
64%5%11%13%6%1
3281
21st to endNight
74%5%10%8%3
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
21%22%35%16%5%
270
11th to 20thDay
26%16%42%13%4
270
21st to endDay
33%15%30%18%3
297
February1st to 10thDay
27%19%36%15%2
252
11th to 20thDay
27%21%38%11%3
240
21st to endDay
27%28%34%8%3
198
March1st to 10thDay
22%23%38%13%3
240
11th to 20thDay
27%11%33%22%7%1
366
21st to endDay
34%15%27%18%5%2
462
April1st to 10thDay
23%14%33%21%8%1
420
11th to 20thDay
23%17%30%17%10%3
412
21st to endDay
25%14%30%18%10%2
420
May1st to 10thDay
26%14%30%19%8%4
423
11th to 20thDay
22%11%27%23%13%4
447
21st to endDay
14%5%29%26%17%8%
591
June1st to 10thDay
13%7%28%29%17%5%
630
11th to 20thDay
13%7%29%27%18%6%
630
21st to endDay
13%7%27%31%17%6%
630
July1st to 10thDay
11%318%30%24%14%
621
11th to 20thDay
9%425%29%23%11%
618
21st to endDay
10%5%20%29%26%11%
644
August1st to 10thDay
10%213%29%29%17%
446
11th to 20thDay
11%320%28%28%10%
439
21st to endDay
11%416%27%29%13%
495
September1st to 10thDay
15%420%26%26%9%
450
11th to 20thDay
10%5%16%24%33%13%
450
21st to endDay
17%10%19%26%22%6%
450
October1st to 10thDay
14%6%28%28%16%8%
450
11th to 20thDay
20%18%30%23%10%
385
21st to endDay
32%14%35%16%2
297
November1st to 10thDay
15%14%35%22%11%3
270
11th to 20thDay
26%16%33%16%8%
270
21st to endDay
31%14%37%14%3
270
December1st to 10thDay
24%20%35%14%7%
270
11th to 20thDay
20%21%37%16%4
270
21st to endDay
27%22%38%12%1
297
January1st to 10thNight
24%16%35%21%4
950
11th to 20thNight
25%16%35%20%41
950
21st to endNight
23%14%36%24%3
1005
February1st to 10thNight
27%12%35%23%4
739
11th to 20thNight
22%15%37%24%2
703
21st to endNight
29%15%35%18%3
592
March1st to 10thNight
20%14%35%25%6%1
720
11th to 20thNight
18%12%37%27%5%1
720
21st to endNight
26%11%30%28%5%
734
April1st to 10thNight
19%13%35%26%6%1
540
11th to 20thNight
22%11%33%26%7%1
533
21st to endNight
21%9%34%27%8%1
540
May1st to 10thNight
21%7%34%30%8%
540
11th to 20thNight
22%5%27%30%15%1
531
21st to endNight
14%326%37%18%1
584
June1st to 10thNight
11%326%42%17%
540
11th to 20thNight
9%327%43%17%1
540
21st to endNight
10%324%36%25%2
540
July1st to 10thNight
9%114%42%30%4
525
11th to 20thNight
10%315%40%29%3
522
21st to endNight
7%216%40%32%2
591
August1st to 10thNight
9%112%43%30%5%
537
11th to 20thNight
9%215%40%30%4
534
21st to endNight
11%216%33%34%4
594
September1st to 10thNight
13%416%36%27%4
558
11th to 20thNight
12%316%34%32%3
720
21st to endNight
16%6%25%30%20%3
720
October1st to 10thNight
16%6%24%33%18%3
720
11th to 20thNight
22%12%29%28%8%1
720
21st to endNight
28%10%31%25%6%
792
November1st to 10thNight
16%14%31%27%11%1
740
11th to 20thNight
23%15%34%22%6%1
760
21st to endNight
27%11%31%25%5%
760
December1st to 10thNight
24%17%34%19%5%
798
11th to 20thNight
24%15%34%22%5%
950
21st to endNight
31%15%33%18%3
1045
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