Blue Moon Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Blue Moon Observatory clear sky chart from 2005-11-06 to 2024-04-25.

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
44%
24412
22%
84708
16%
24262
52%
24262
25%
51526

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
23%
942
21%
4322
9%
926
34%
926
15%
2645
January11th to 20thNight
21%
950
21%
4125
7%
930
30%
930
12%
2659
January21st to endNight
22%
981
16%
4359
8%
963
34%
963
16%
2822
February1st to 10thNight
21%
760
18%
2280
8%
760
30%
760
19%
1606
February11th to 20thNight
20%
743
18%
2219
8%
740
27%
740
18%
1525
February21st to endNight
18%
628
19%
1884
7%
628
28%
628
19%
1292
March1st to 10thNight
29%
757
20%
3706
10%
745
38%
745
14%
2442
March11th to 20thNight
26%
703
22%
3642
10%
689
34%
689
16%
1936
March21st to endNight
32%
623
14%
3340
11%
605
42%
605
14%
1937
April1st to 10thNight
34%
570
26%
1900
14%
570
49%
570
28%
1102
April11th to 20thNight
37%
563
26%
1875
18%
563
51%
563
27%
1124
April21st to endNight
38%
555
21%
1850
15%
555
49%
555
26%
1138
May1st to 10thNight
41%
540
21%
1702
14%
540
49%
540
30%
1037
May11th to 20thNight
52%
531
18%
1592
14%
531
56%
531
28%
1007
May21st to endNight
62%
584
20%
1722
14%
582
66%
582
34%
1026
June1st to 10thNight
62%
540
22%
1440
17%
540
64%
540
33%
931
June11th to 20thNight
75%
540
29%
1440
22%
540
77%
540
51%
778
June21st to endNight
74%
540
25%
1440
19%
540
77%
540
45%
809
July1st to 10thNight
72%
525
17%
1400
15%
525
73%
525
34%
889
July11th to 20thNight
71%
522
22%
1392
20%
522
72%
522
40%
838
July21st to endNight
76%
591
24%
1642
23%
558
78%
558
40%
932
August1st to 10thNight
77%
537
21%
1778
24%
534
78%
534
35%
966
August11th to 20thNight
75%
534
23%
1776
27%
534
76%
534
34%
987
August21st to endNight
72%
594
24%
1980
29%
594
73%
594
34%
1112
September1st to 10thNight
71%
540
27%
1800
29%
540
73%
540
35%
1000
September11th to 20thNight
68%
648
29%
1908
25%
648
70%
648
36%
1109
September21st to endNight
63%
720
32%
1980
24%
720
68%
720
41%
1136
October1st to 10thNight
63%
720
33%
1980
26%
720
67%
720
43%
1096
October11th to 20thNight
50%
720
30%
2146
21%
720
59%
720
35%
1239
October21st to endNight
42%
792
27%
2453
20%
792
51%
792
29%
1500
November1st to 10thNight
48%
740
30%
2406
25%
740
57%
740
35%
1308
November11th to 20thNight
38%
760
30%
2470
20%
760
53%
760
33%
1374
November21st to endNight
37%
760
25%
2470
19%
760
47%
760
27%
1507
December1st to 10thNight
29%
760
21%
2470
13%
760
40%
760
19%
1656
December11th to 20thNight
32%
862
25%
3047
14%
862
43%
862
22%
1856
December21st to endNight
25%
1037
12%
4772
9%
1026
35%
1026
12%
3205

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
13%7%35%5%345%5%7%43%
83471
Night
14%7%25%43445%7%45%
85690
TransparencyDay
40%5%10%23%18%3
83184
Night
39%5%9%23%19%5%
85498
SeeingDay
16%10%23%25%18%8%
14520
Night
17%9%25%29%18%3
24447

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%14%47%6%23346%37%
2527
11th to 20thDay
21%8%36%42333444%
2694
21st to endDay
23%10%35%323446%37%
3228
February1st to 10thDay
19%10%45%5%33446%37%
1900
11th to 20thDay
20%8%47%423445%39%
1848
21st to endDay
22%9%36%434445%35%
1570
March1st to 10thDay
20%13%36%5%34435%33%
3120
11th to 20thDay
14%7%25%434346%47%
3300
21st to endDay
13%6%36%5%345%5%6%42%
4165
April1st to 10thDay
13%6%36%5%3445%7%46%
2280
11th to 20thDay
16%6%36%5%24445%44%
2254
21st to endDay
15%6%26%435%5%5%8%42%
2209
May1st to 10thDay
15%6%35%5%345%5%7%42%
2258
11th to 20thDay
13%6%36%6%35%5%5%7%40%
2301
21st to endDay
8%5%37%7%45%7%7%10%36%
2549
June1st to 10thDay
9%6%25%6%35%5%6%10%43%
2520
11th to 20thDay
43245%46%6%7%10%49%
2520
21st to endDay
6%4245%46%6%7%10%47%
2520
July1st to 10thDay
7%5%26%7%47%6%7%11%37%
2520
11th to 20thDay
8%6%35%5%47%7%8%11%38%
2520
21st to endDay
7%325%6%46%6%8%11%42%
2573
August1st to 10thDay
5%425%6%36%8%7%13%39%
2148
11th to 20thDay
9%5%36%446%6%7%10%40%
2125
21st to endDay
9%6%246%346%6%10%43%
2376
September1st to 10thDay
11%5%25%436%5%6%8%45%
2160
11th to 20thDay
12%5%26%5%3445%7%48%
2034
21st to endDay
10%7%2343445%6%51%
1980
October1st to 10thDay
10%42443345%6%56%
1980
11th to 20thDay
13%5%2342345%6%52%
1810
21st to endDay
19%7%3432324449%
1900
November1st to 10thDay
12%5%25%322345%57%
1672
11th to 20thDay
14%5%35%424445%51%
1710
21st to endDay
17%7%3442435%6%45%
1710
December1st to 10thDay
21%8%35%43445%5%38%
1710
11th to 20thDay
17%8%36%5%34446%41%
1997
21st to endDay
15%12%46%6%35%45%6%34%
2783
January1st to 10thNight
19%10%35%423446%40%
4428
11th to 20thNight
17%9%47%5%3433440%
4274
21st to endNight
26%9%24423345%39%
4433
February1st to 10thNight
21%10%36%6%34345%35%
2280
11th to 20thNight
20%7%46%6%3443440%
2218
21st to endNight
21%8%36%5%3445%5%39%
1884
March1st to 10thNight
23%9%36%5%24445%36%
3733
11th to 20thNight
15%7%25%433345%49%
3688
21st to endNight
14%7%36%5%345%5%8%40%
3466
April1st to 10thNight
12%5%3443445%7%49%
1900
11th to 20thNight
16%6%25%433346%47%
1875
21st to endNight
13%6%345%345%6%7%44%
1850
May1st to 10thNight
14%7%245%2335%7%48%
1702
11th to 20thNight
10%6%35%6%35%5%6%8%44%
1592
21st to endNight
6%425%6%35%6%7%11%45%
1722
June1st to 10thNight
8%5%26%5%35%47%9%44%
1440
11th to 20thNight
4313425%5%6%8%59%
1440
21st to endNight
3214436%5%6%13%53%
1440
July1st to 10thNight
7%425%5%45%6%8%11%43%
1440
11th to 20thNight
6%425%5%35%6%5%10%50%
1440
21st to endNight
5%324435%5%7%9%52%
1739
August1st to 10thNight
4424435%6%9%10%49%
1790
11th to 20thNight
6%3245%346%7%9%51%
1776
21st to endNight
8%425%5%245%5%10%50%
1980
September1st to 10thNight
10%3345%235%48%53%
1800
11th to 20thNight
9%5%34434448%53%
1908
21st to endNight
10%414434346%57%
1980
October1st to 10thNight
9%413323346%60%
1980
11th to 20thNight
13%5%24334345%54%
2146
21st to endNight
17%7%24323445%48%
2453
November1st to 10thNight
12%6%24422346%57%
2406
11th to 20thNight
12%425%42445%7%52%
2470
21st to endNight
17%7%25%424445%48%
2470
December1st to 10thNight
21%8%36%5%24346%39%
2470
11th to 20thNight
16%8%35%423445%46%
3193
21st to endNight
17%10%47%6%35%5%5%7%32%
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
48%46%22%18%2
2528
11th to 20thDay
45%38%23%20%1
2694
21st to endDay
49%38%23%15%2
3228
February1st to 10thDay
50%39%20%16%2
1900
11th to 20thDay
49%47%20%16%4
1858
21st to endDay
52%38%17%15%6%
1570
March1st to 10thDay
55%45%14%14%8%
3120
11th to 20thDay
39%5%7%26%17%6%
3300
21st to endDay
42%411%23%19%1
4165
April1st to 10thDay
39%5%9%23%21%3
2280
11th to 20thDay
43%48%20%21%5%
2254
21st to endDay
41%5%10%25%17%2
2209
May1st to 10thDay
41%5%12%25%15%1
2258
11th to 20thDay
43%6%12%22%16%1
2305
21st to endDay
40%9%16%23%11%2
2549
June1st to 10thDay
36%7%13%22%20%2
2520
11th to 20thDay
29%7%16%28%17%3
2520
21st to endDay
30%9%14%26%18%4
2520
July1st to 10thDay
37%10%16%21%12%4
2451
11th to 20thDay
36%9%17%21%13%4
2445
21st to endDay
33%8%17%28%12%1
2430
August1st to 10thDay
33%8%17%27%13%1
2136
11th to 20thDay
38%7%12%25%16%2
2125
21st to endDay
35%7%14%24%17%3
2376
September1st to 10thDay
36%7%11%26%16%4
2160
11th to 20thDay
37%5%9%22%23%4
2034
21st to endDay
33%5%7%24%24%6%
1980
October1st to 10thDay
29%5%10%23%26%6%
1980
11th to 20thDay
33%37%23%25%8%
1810
21st to endDay
40%36%22%23%6%
1900
November1st to 10thDay
31%48%24%28%5%
1672
11th to 20thDay
37%47%21%24%7%
1710
21st to endDay
41%37%24%20%5%
1710
December1st to 10thDay
48%5%6%22%16%3
1710
11th to 20thDay
45%48%23%17%3
1994
21st to endDay
51%410%22%12%1
2783
January1st to 10thNight
45%46%26%17%2
4428
11th to 20thNight
50%36%21%16%4
4274
21st to endNight
49%37%23%16%2
4433
February1st to 10thNight
53%39%16%17%2
2280
11th to 20thNight
49%47%19%17%5%
2219
21st to endNight
49%48%17%17%5%
1884
March1st to 10thNight
51%47%12%17%9%
3733
11th to 20thNight
39%49%22%16%10%
3688
21st to endNight
42%5%9%21%21%1
3466
April1st to 10thNight
36%5%10%25%19%5%
1900
11th to 20thNight
38%47%22%22%8%
1875
21st to endNight
39%5%9%24%19%3
1850
May1st to 10thNight
37%5%10%25%18%4
1702
11th to 20thNight
37%8%14%22%17%2
1593
21st to endNight
30%8%17%27%14%3
1723
June1st to 10thNight
37%6%12%21%23%1
1440
11th to 20thNight
21%5%17%33%20%5%
1440
21st to endNight
23%7%18%28%17%7%
1440
July1st to 10thNight
32%10%17%24%15%3
1400
11th to 20thNight
30%6%17%27%14%6%
1392
21st to endNight
26%8%19%31%15%1
1642
August1st to 10thNight
27%8%17%29%18%1
1778
11th to 20thNight
27%10%16%27%18%4
1776
21st to endNight
30%7%13%28%15%6%
1980
September1st to 10thNight
30%6%11%28%20%6%
1800
11th to 20thNight
31%6%10%22%27%4
1908
21st to endNight
28%5%7%28%25%7%
1980
October1st to 10thNight
26%5%8%25%27%9%
1980
11th to 20thNight
32%47%23%25%8%
2146
21st to endNight
39%36%20%25%7%
2453
November1st to 10thNight
31%36%24%28%8%
2406
11th to 20thNight
33%37%23%25%9%
2470
21st to endNight
40%36%23%23%5%
2470
December1st to 10thNight
48%48%19%18%3
2470
11th to 20thNight
42%27%24%21%4
3195
21st to endNight
51%5%8%19%13%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
26%22%35%13%4
270
11th to 20thDay
30%22%31%13%31
270
21st to endDay
24%24%37%11%3
297
February1st to 10thDay
27%20%30%18%41
270
11th to 20thDay
34%23%33%8%2
270
21st to endDay
37%24%26%9%3
225
March1st to 10thDay
27%19%37%12%4
270
11th to 20thDay
27%23%34%13%3
279
21st to endDay
27%16%32%18%7%
506
April1st to 10thDay
23%16%30%23%7%1
460
11th to 20thDay
21%17%30%23%9%1
452
21st to endDay
20%16%28%24%9%3
437
May1st to 10thDay
21%12%27%26%10%4
423
11th to 20thDay
14%8%26%27%16%8%
447
21st to endDay
10%5%19%31%19%15%
503
June1st to 10thDay
11%5%19%28%24%14%
630
11th to 20thDay
5%117%36%28%13%
630
21st to endDay
7%318%35%23%14%
630
July1st to 10thDay
8%113%27%29%21%
621
11th to 20thDay
9%212%26%34%17%
618
21st to endDay
7%212%29%30%20%
608
August1st to 10thDay
7%311%29%31%18%
446
11th to 20thDay
12%312%32%32%10%
439
21st to endDay
12%37%23%38%18%
495
September1st to 10thDay
9%412%29%35%13%
450
11th to 20thDay
11%113%25%35%14%
450
21st to endDay
14%5%16%31%22%12%
450
October1st to 10thDay
10%5%19%34%24%8%
450
11th to 20thDay
13%13%35%28%9%1
280
21st to endDay
27%16%29%19%8%1
297
November1st to 10thDay
15%10%35%27%12%1
270
11th to 20thDay
11%19%37%26%6%1
270
21st to endDay
24%16%30%18%10%2
270
December1st to 10thDay
29%19%27%17%6%1
270
11th to 20thDay
23%19%31%20%6%
270
21st to endDay
27%21%35%15%2
297
January1st to 10thNight
23%17%33%24%4
950
11th to 20thNight
26%18%31%21%4
950
21st to endNight
22%13%40%24%1
985
February1st to 10thNight
25%14%35%22%3
760
11th to 20thNight
25%16%35%21%2
743
21st to endNight
27%19%34%18%2
628
March1st to 10thNight
21%15%33%28%3
760
11th to 20thNight
24%13%33%24%6%1
709
21st to endNight
18%11%33%29%8%
627
April1st to 10thNight
15%11%36%29%8%1
570
11th to 20thNight
19%11%28%30%12%1
563
21st to endNight
15%8%35%30%10%2
555
May1st to 10thNight
15%7%33%30%14%2
540
11th to 20thNight
12%6%22%36%21%2
531
21st to endNight
8%319%34%30%6%
584
June1st to 10thNight
11%215%36%31%6%
540
11th to 20thNight
5%211%41%38%4
540
21st to endNight
4114%36%38%6%
540
July1st to 10thNight
7%28%30%42%10%
525
11th to 20thNight
7%29%27%45%10%
522
21st to endNight
6%110%30%44%9%
591
August1st to 10thNight
5%18%31%46%9%
537
11th to 20thNight
6%18%39%40%6%
534
21st to endNight
9%18%30%42%9%
594
September1st to 10thNight
11%18%30%44%6%
540
11th to 20thNight
10%312%31%38%7%
648
21st to endNight
11%217%34%32%4
720
October1st to 10thNight
11%317%34%31%4
720
11th to 20thNight
15%7%24%34%19%1
720
21st to endNight
21%7%27%30%13%2
792
November1st to 10thNight
15%7%26%34%17%1
740
11th to 20thNight
14%11%33%31%11%
760
21st to endNight
20%10%30%28%11%1
760
December1st to 10thNight
26%11%30%26%7%
760
11th to 20thNight
24%11%29%29%7%
864
21st to endNight
26%14%30%26%4
1045
Page generated at 2024-04-22 08:25:43. Version ac07

Copyright © 2024 Attilla Danko.


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