Crow's Nest Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Crow's Nest Observatory clear sky chart from 2005-11-06 to 2024-03-08.

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
33%
23151
11%
80932
6%
23068
39%
23068
10%
61995

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
18%
750
16%
4340
2%
737
27%
737
6%
2867
January11th to 20thNight
15%
757
15%
4326
2%
740
22%
740
4%
2977
January21st to endNight
17%
829
8%
4842
4%
814
28%
814
5%
3617
February1st to 10thNight
20%
760
10%
2478
4%
760
27%
760
9%
1966
February11th to 20thNight
16%
741
13%
2225
3%
740
27%
740
9%
1765
February21st to endNight
23%
628
14%
1884
5%
628
34%
628
12%
1458
March1st to 10thNight
19%
751
12%
2251
4%
751
30%
751
10%
1791
March11th to 20thNight
26%
720
10%
2008
5%
720
31%
720
11%
1619
March21st to endNight
27%
792
14%
2141
5%
792
34%
792
14%
1658
April1st to 10thNight
26%
720
12%
1800
4%
720
31%
720
14%
1455
April11th to 20thNight
35%
610
13%
1674
6%
610
39%
610
16%
1299
April21st to endNight
32%
540
11%
1620
5%
540
37%
540
12%
1276
May1st to 10thNight
36%
540
9%
1620
7%
540
39%
540
12%
1302
May11th to 20thNight
36%
532
10%
1594
5%
532
41%
532
10%
1291
May21st to endNight
40%
398
9%
1560
13%
397
42%
397
9%
1210
June1st to 10thNight
41%
360
8%
1440
9%
360
45%
360
8%
1160
June11th to 20thNight
50%
360
8%
1440
13%
360
51%
360
9%
1116
June21st to endNight
51%
360
7%
1440
10%
360
53%
360
8%
1141
July1st to 10thNight
57%
350
5%
1400
9%
350
57%
350
8%
1109
July11th to 20thNight
55%
348
8%
1392
13%
348
56%
348
11%
1049
July21st to endNight
59%
394
10%
1486
12%
372
61%
372
12%
1104
August1st to 10thNight
58%
524
8%
1587
6%
521
59%
521
13%
1235
August11th to 20thNight
56%
532
12%
1596
9%
532
58%
532
14%
1247
August21st to endNight
59%
682
12%
1870
7%
682
61%
682
16%
1440
September1st to 10thNight
54%
720
12%
1854
6%
720
58%
720
19%
1427
September11th to 20thNight
47%
720
17%
1980
10%
720
53%
720
19%
1466
September21st to endNight
49%
720
14%
1980
9%
720
52%
720
18%
1494
October1st to 10thNight
42%
720
12%
1980
7%
720
46%
720
14%
1553
October11th to 20thNight
36%
720
12%
2213
5%
720
43%
720
12%
1721
October21st to endNight
28%
792
12%
2574
6%
792
35%
792
11%
2012
November1st to 10thNight
33%
740
12%
2407
8%
740
39%
740
12%
1863
November11th to 20thNight
26%
760
15%
2470
8%
760
37%
760
11%
1907
November21st to endNight
24%
769
11%
2489
5%
769
32%
769
10%
1952
December1st to 10thNight
18%
850
8%
2790
2%
850
26%
850
8%
2283
December11th to 20thNight
18%
835
11%
3369
2%
834
27%
834
8%
2527
December21st to endNight
17%
827
7%
4812
2%
817
24%
817
4%
3638

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
18%7%35%5%3445%7%40%
78012
Night
18%8%35%5%3445%6%39%
81537
TransparencyDay
29%36%9%15%9%1
77718
Night
32%35%8%15%9%1
81366
SeeingDay
20%9%30%28%12%2
14072
Night
22%10%29%27%11%1
23182

By Month

Percentage Cloud Cover NE (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
16%7%35%6%3445%6%42%
2517
11th to 20thDay
18%6%245%34446%43%
2520
21st to endDay
18%11%35%424446%38%
2772
February1st to 10thDay
19%9%25%5%36%5%5%6%37%
1700
11th to 20thDay
13%8%36%6%45%5%6%7%38%
1839
21st to endDay
16%10%46%5%35%45%5%37%
1570
March1st to 10thDay
17%8%26%5%44447%38%
1867
11th to 20thDay
18%6%26%43345%6%44%
1951
21st to endDay
17%8%35%5%24445%43%
2214
April1st to 10thDay
20%7%35%5%245%5%6%37%
2160
11th to 20thDay
18%5%26%5%3345%8%41%
2234
21st to endDay
23%7%25%6%3445%6%35%
2340
May1st to 10thDay
24%6%35%6%3445%5%34%
2340
11th to 20thDay
19%7%36%5%2345%7%38%
2305
21st to endDay
18%6%35%5%445%5%7%38%
2725
June1st to 10thDay
23%6%36%5%3445%7%35%
2520
11th to 20thDay
18%6%245%345%5%7%42%
2520
21st to endDay
22%6%36%5%35%46%7%34%
2520
July1st to 10thDay
15%6%25%5%35%5%5%9%38%
2520
11th to 20thDay
13%6%35%5%35%5%7%9%38%
2520
21st to endDay
13%5%245%45%5%6%9%41%
2738
August1st to 10thDay
12%5%25%435%6%6%10%43%
2327
11th to 20thDay
13%5%26%5%35%5%6%9%41%
2304
21st to endDay
11%4235%35%5%6%8%47%
2484
September1st to 10thDay
13%5%234245%5%8%48%
2106
11th to 20thDay
12%6%33423446%54%
1980
21st to endDay
17%7%2442445%7%46%
1980
October1st to 10thDay
18%7%36%433346%42%
1980
11th to 20thDay
18%6%25%6%34345%43%
1742
21st to endDay
23%8%24424445%40%
1782
November1st to 10thDay
17%7%24423446%48%
1671
11th to 20thDay
21%42432345%5%46%
1710
21st to endDay
22%7%35%423435%44%
1687
December1st to 10thDay
22%8%35%5%35%345%38%
1387
11th to 20thDay
23%7%24323446%41%
1708
21st to endDay
25%9%36%5%345%5%6%30%
2772
January1st to 10thNight
16%9%35%42445%6%43%
4429
11th to 20thNight
14%8%38%7%345%5%6%38%
4440
21st to endNight
20%10%46%5%34446%34%
4884
February1st to 10thNight
17%9%36%6%45%5%5%6%36%
2478
11th to 20thNight
14%9%45%5%45%5%45%39%
2223
21st to endNight
15%9%35%5%25%35%5%41%
1884
March1st to 10thNight
16%10%36%5%4445%6%38%
2241
11th to 20thNight
18%6%37%5%345%5%8%37%
2007
21st to endNight
19%8%35%423346%43%
2141
April1st to 10thNight
22%8%35%5%35%446%37%
1800
11th to 20thNight
19%5%245%35%5%6%7%39%
1674
21st to endNight
25%6%25%6%4445%6%34%
1620
May1st to 10thNight
21%9%35%436%5%6%7%31%
1620
11th to 20thNight
20%8%25%6%35%6%6%8%32%
1593
21st to endNight
21%10%46%334446%34%
1559
June1st to 10thNight
22%8%35%5%45%45%6%32%
1440
11th to 20thNight
17%8%35%4245%5%7%38%
1440
21st to endNight
24%7%24435%5%5%8%32%
1440
July1st to 10thNight
17%6%35%6%25%5%6%8%37%
1440
11th to 20thNight
17%8%26%5%345%6%10%35%
1440
21st to endNight
14%5%35%5%45%5%7%8%38%
1574
August1st to 10thNight
13%6%36%435%5%7%9%40%
1598
11th to 20thNight
15%6%46%6%25%6%6%8%37%
1596
21st to endNight
15%6%24435%45%6%47%
1870
September1st to 10thNight
13%6%244345%5%6%48%
1854
11th to 20thNight
16%7%24423346%50%
1980
21st to endNight
15%6%244245%46%48%
1980
October1st to 10thNight
20%6%25%43446%7%39%
1980
11th to 20thNight
17%6%26%5%3446%6%41%
2213
21st to endNight
25%7%25%43345%5%37%
2574
November1st to 10thNight
17%6%25%5%245%45%45%
2407
11th to 20thNight
19%5%24435%5%5%5%44%
2470
21st to endNight
16%7%25%5%2445%7%42%
2489
December1st to 10thNight
22%9%445%34446%35%
2790
11th to 20thNight
23%6%2442345%6%41%
3485
21st to endNight
24%9%36%5%34336%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
34%27%11%22%6%
2518
11th to 20thDay
33%27%11%20%8%1
2520
21st to endDay
39%25%10%18%7%
2772
February1st to 10thDay
31%36%8%14%9%2
1700
11th to 20thDay
28%37%10%14%9%2
1848
21st to endDay
33%35%8%15%7%2
1570
March1st to 10thDay
32%36%9%13%7%3
1870
11th to 20thDay
29%36%8%17%8%2
1951
21st to endDay
26%36%6%14%14%4
2214
April1st to 10thDay
29%37%8%13%12%2
2160
11th to 20thDay
27%37%7%17%10%2
2234
21st to endDay
30%37%6%13%10%3
2340
May1st to 10thDay
33%36%5%13%11%1
2340
11th to 20thDay
29%37%7%12%12%3
2309
21st to endDay
29%38%8%14%9%2
2725
June1st to 10thDay
35%37%8%15%5%
2520
11th to 20thDay
28%39%8%15%9%2
2520
21st to endDay
35%39%8%12%5%1
2520
July1st to 10thDay
29%40%10%15%6%
2450
11th to 20thDay
26%40%11%17%7%
2445
21st to endDay
23%40%10%17%8%1
2585
August1st to 10thDay
24%39%13%17%6%
2314
11th to 20thDay
26%37%10%17%9%1
2304
21st to endDay
23%39%9%16%11%1
2484
September1st to 10thDay
24%37%9%17%13%1
2106
11th to 20thDay
19%37%8%18%16%2
1980
21st to endDay
28%37%7%16%11%1
1980
October1st to 10thDay
27%38%8%16%11%1
1980
11th to 20thDay
30%37%8%18%6%1
1742
21st to endDay
29%37%7%15%10%2
1782
November1st to 10thDay
24%41%8%15%12%1
1671
11th to 20thDay
23%41%8%15%12%1
1710
21st to endDay
28%40%11%15%5%
1687
December1st to 10thDay
33%40%8%11%7%1
1387
11th to 20thDay
32%34%6%14%10%3
1708
21st to endDay
44%27%9%13%42
2772
January1st to 10thNight
33%27%11%22%6%1
4429
11th to 20thNight
36%27%10%16%8%2
4440
21st to endNight
43%25%7%16%7%1
4884
February1st to 10thNight
34%36%8%13%8%1
2478
11th to 20thNight
32%36%6%15%8%2
2225
21st to endNight
31%35%8%16%7%3
1884
March1st to 10thNight
34%35%5%14%9%1
2251
11th to 20thNight
32%38%10%12%7%1
2008
21st to endNight
28%36%6%14%12%3
2141
April1st to 10thNight
32%37%6%12%11%3
1800
11th to 20thNight
28%36%8%15%12%1
1674
21st to endNight
33%36%8%13%10%2
1620
May1st to 10thNight
33%37%7%12%9%2
1620
11th to 20thNight
33%39%7%11%7%4
1594
21st to endNight
31%39%8%12%9%1
1560
June1st to 10thNight
34%39%7%12%6%1
1440
11th to 20thNight
31%39%9%11%9%1
1440
21st to endNight
34%38%10%11%7%
1440
July1st to 10thNight
33%40%11%12%41
1400
11th to 20thNight
27%39%10%16%7%
1392
21st to endNight
25%40%11%16%7%1
1486
August1st to 10thNight
29%38%9%18%5%
1587
11th to 20thNight
28%39%10%14%10%
1596
21st to endNight
26%39%7%18%10%1
1870
September1st to 10thNight
26%36%8%17%12%1
1854
11th to 20thNight
23%36%7%20%14%1
1980
21st to endNight
25%37%8%17%12%2
1980
October1st to 10thNight
29%38%8%15%11%
1980
11th to 20thNight
29%38%8%16%8%1
2213
21st to endNight
31%37%7%14%10%1
2574
November1st to 10thNight
26%42%7%15%10%1
2407
11th to 20thNight
26%41%7%15%9%2
2470
21st to endNight
28%40%9%14%8%1
2489
December1st to 10thNight
33%41%8%12%5%1
2790
11th to 20thNight
31%35%9%14%11%
3486
21st to endNight
44%26%9%12%8%
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
24%20%27%23%6%
180
11th to 20thDay
26%17%28%23%5%1
180
21st to endDay
18%12%38%24%8%1
198
February1st to 10thDay
24%13%38%21%4
360
11th to 20thDay
18%17%44%19%2
452
21st to endDay
20%15%37%22%6%
382
March1st to 10thDay
22%13%36%25%4
448
11th to 20thDay
18%14%42%21%5%
420
21st to endDay
22%14%34%19%8%3
462
April1st to 10thDay
24%15%32%20%7%2
420
11th to 20thDay
23%10%35%23%9%
412
21st to endDay
28%7%33%25%6%1
420
May1st to 10thDay
26%6%33%25%8%2
423
11th to 20thDay
20%439%26%10%2
447
21st to endDay
20%5%31%32%10%2
485
June1st to 10thDay
22%5%26%35%10%2
450
11th to 20thDay
17%5%31%33%10%3
450
21st to endDay
21%426%31%15%3
450
July1st to 10thDay
19%319%38%18%3
445
11th to 20thDay
16%218%40%20%3
444
21st to endDay
13%217%43%21%4
488
August1st to 10thDay
14%221%37%22%3
446
11th to 20thDay
17%219%36%20%6%
439
21st to endDay
13%319%38%22%4
495
September1st to 10thDay
14%422%32%23%4
450
11th to 20thDay
14%7%28%30%16%6%
450
21st to endDay
18%5%27%29%17%4
450
October1st to 10thDay
21%8%22%30%16%4
450
11th to 20thDay
22%7%30%26%13%3
360
21st to endDay
29%9%28%24%9%1
396
November1st to 10thDay
18%14%29%26%10%2
365
11th to 20thDay
24%12%34%21%8%1
370
21st to endDay
24%15%32%21%8%1
370
December1st to 10thDay
26%11%39%15%8%
237
11th to 20thDay
25%18%34%18%41
180
21st to endDay
25%21%29%18%7%1
198
January1st to 10thNight
21%18%37%20%4
760
11th to 20thNight
23%20%35%18%4
760
21st to endNight
20%17%38%20%4
836
February1st to 10thNight
22%18%35%21%4
760
11th to 20thNight
20%18%40%20%2
743
21st to endNight
19%15%37%23%6%
628
March1st to 10thNight
23%15%38%21%3
751
11th to 20thNight
23%11%34%22%9%1
720
21st to endNight
23%12%31%26%7%1
792
April1st to 10thNight
28%10%33%24%6%
720
11th to 20thNight
21%7%33%30%9%1
610
21st to endNight
28%5%28%27%11%1
540
May1st to 10thNight
24%327%31%12%2
540
11th to 20thNight
24%5%27%32%10%2
532
21st to endNight
27%420%31%16%2
398
June1st to 10thNight
26%418%34%15%3
360
11th to 20thNight
19%418%40%17%2
360
21st to endNight
24%315%41%16%1
360
July1st to 10thNight
21%211%43%21%2
350
11th to 20thNight
20%213%39%24%2
348
21st to endNight
17%213%40%25%3
394
August1st to 10thNight
15%314%43%24%2
524
11th to 20thNight
15%214%42%23%4
532
21st to endNight
16%315%36%27%4
682
September1st to 10thNight
16%218%37%25%2
720
11th to 20thNight
19%323%28%22%4
720
21st to endNight
18%323%33%19%3
720
October1st to 10thNight
23%7%21%29%19%2
720
11th to 20thNight
20%8%29%30%11%3
720
21st to endNight
29%9%29%26%7%1
792
November1st to 10thNight
20%8%34%28%9%2
740
11th to 20thNight
20%15%34%22%8%1
760
21st to endNight
19%17%35%22%7%
769
December1st to 10thNight
27%12%38%16%7%
850
11th to 20thNight
24%18%36%19%3
835
21st to endNight
28%14%34%19%4
836
Page generated at 2024-03-05 07:23:59. Version ac07

Copyright © 2024 Attilla Danko.


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