Moore Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Moore Observatory clear sky chart from 2005-11-06 to 2024-11-08.

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
43%
24935
18%
95992
14%
24668
49%
24668
20%
61463

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%
944
12%
4385
6%
926
31%
926
10%
3147
January11th to 20thNight
20%
892
14%
4258
7%
874
27%
874
9%
3177
January21st to endNight
21%
832
11%
4469
8%
814
32%
814
9%
3268
February1st to 10thNight
23%
760
15%
2280
6%
760
31%
760
15%
1688
February11th to 20thNight
22%
743
17%
2219
8%
740
31%
740
20%
1552
February21st to endNight
17%
628
14%
1884
5%
628
25%
628
15%
1382
March1st to 10thNight
27%
757
17%
3705
11%
745
34%
745
12%
2556
March11th to 20thNight
27%
753
22%
3471
8%
740
35%
740
17%
1849
March21st to endNight
32%
811
10%
3625
9%
791
38%
791
14%
2235
April1st to 10thNight
35%
570
22%
1900
14%
570
46%
570
25%
1183
April11th to 20thNight
39%
563
22%
1875
16%
563
48%
563
25%
1186
April21st to endNight
35%
570
19%
1733
11%
570
43%
570
23%
1159
May1st to 10thNight
35%
566
13%
2795
8%
559
42%
559
12%
2026
May11th to 20thNight
50%
545
14%
2763
11%
541
54%
541
16%
1623
May21st to endNight
61%
603
16%
3038
14%
593
64%
593
20%
1651
June1st to 10thNight
63%
570
21%
1650
18%
570
67%
570
36%
981
June11th to 20thNight
68%
570
22%
1520
17%
570
70%
570
39%
895
June21st to endNight
69%
570
21%
1520
16%
570
71%
570
40%
894
July1st to 10thNight
64%
542
22%
2318
15%
535
66%
535
22%
1325
July11th to 20thNight
72%
537
21%
2204
19%
533
74%
533
29%
1152
July21st to endNight
68%
613
14%
2925
20%
569
72%
569
17%
1988
August1st to 10thNight
74%
551
28%
2512
22%
544
76%
544
27%
1259
August11th to 20thNight
70%
548
19%
2638
22%
543
73%
543
21%
1505
August21st to endNight
76%
607
23%
2919
27%
605
78%
605
34%
1237
September1st to 10thNight
67%
622
25%
1952
23%
622
70%
622
34%
1140
September11th to 20thNight
64%
760
29%
2090
23%
760
67%
760
40%
1215
September21st to endNight
57%
760
28%
2090
22%
760
62%
760
35%
1275
October1st to 10thNight
61%
760
28%
2207
25%
740
65%
740
37%
1322
October11th to 20thNight
45%
760
24%
2332
18%
740
53%
740
28%
1452
October21st to endNight
37%
836
20%
3070
18%
814
48%
814
21%
1983
November1st to 10thNight
45%
771
26%
2504
21%
771
54%
771
29%
1479
November11th to 20thNight
36%
760
26%
2470
18%
760
47%
760
25%
1542
November21st to endNight
38%
760
22%
2470
17%
760
45%
760
21%
1626
December1st to 10thNight
28%
760
15%
2470
8%
760
37%
760
17%
1730
December11th to 20thNight
27%
759
17%
2971
11%
759
35%
759
15%
2047
December21st to endNight
22%
982
9%
4760
8%
969
29%
969
9%
3734

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%8%36%44445%7%39%
101151
Night
15%9%37%44435%7%40%
97921
TransparencyDay
42%5%10%24%16%2
104848
Night
42%5%10%23%17%3
102363
SeeingDay
17%8%24%26%18%8%
15356
Night
19%6%24%31%17%2
25091

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%16%7%8%44435%6%30%
2527
11th to 20thDay
18%12%5%13%5%5%5%33428%
2604
21st to endDay
28%15%7%7%333246%23%
3133
February1st to 10thDay
18%12%49%43335%5%33%
1900
11th to 20thDay
18%9%48%5%3435%5%36%
1848
21st to endDay
19%13%47%445%35%6%31%
1570
March1st to 10thDay
26%14%36%433345%32%
3120
11th to 20thDay
14%7%26%45%436%7%43%
3416
21st to endDay
15%8%27%5%5%5%46%7%37%
3877
April1st to 10thDay
15%8%26%5%4445%7%38%
2280
11th to 20thDay
17%8%26%5%44346%40%
2254
21st to endDay
18%7%27%5%5%435%6%39%
2446
May1st to 10thDay
21%8%26%5%5%5%46%8%30%
4082
11th to 20thDay
21%7%26%44435%6%39%
4081
21st to endDay
12%6%27%5%6%5%5%7%9%37%
4476
June1st to 10thDay
11%5%27%6%4446%7%45%
2524
11th to 20thDay
7%5%25%45%6%5%7%8%46%
2660
21st to endDay
8%5%26%5%46%5%7%10%44%
2660
July1st to 10thDay
14%6%35%445%47%10%38%
4440
11th to 20thDay
7%5%15%445%46%10%48%
4384
21st to endDay
11%9%39%7%7%6%5%7%9%27%
4466
August1st to 10thDay
8%425%345%47%11%48%
4104
11th to 20thDay
8%5%27%45%5%6%8%10%40%
3864
21st to endDay
5%425%34445%8%57%
4180
September1st to 10thDay
13%6%26%44435%7%46%
2208
11th to 20thDay
10%5%25%34436%9%48%
2090
21st to endDay
14%5%35%444346%48%
2090
October1st to 10thDay
10%425%334346%55%
2090
11th to 20thDay
12%6%25%44435%7%47%
1998
21st to endDay
17%8%26%34335%6%42%
1889
November1st to 10thDay
11%6%25%334246%53%
1735
11th to 20thDay
15%11%35%43335%6%42%
1710
21st to endDay
19%9%35%43445%5%40%
1710
December1st to 10thDay
22%12%48%5%33345%32%
1710
11th to 20thDay
15%14%5%9%5%5%4345%32%
2153
21st to endDay
21%18%47%45%5%446%22%
2872
January1st to 10thNight
17%16%5%8%44435%6%27%
4428
11th to 20thNight
17%15%5%13%6%4333427%
4345
21st to endNight
26%15%5%6%433245%27%
4519
February1st to 10thNight
22%10%48%5%44445%29%
2280
11th to 20thNight
18%10%49%444445%36%
2218
21st to endNight
22%13%38%444345%30%
1884
March1st to 10thNight
24%13%36%43334433%
3733
11th to 20thNight
15%6%26%443345%48%
3529
21st to endNight
16%8%27%444446%40%
3769
April1st to 10thNight
13%8%36%44345%7%42%
1900
11th to 20thNight
17%8%36%444247%42%
1875
21st to endNight
18%7%26%45%445%7%39%
1733
May1st to 10thNight
19%10%38%6%45%35%7%28%
2813
11th to 20thNight
17%6%25%43445%7%43%
2812
21st to endNight
10%5%26%45%5%47%9%43%
3079
June1st to 10thNight
10%425%44446%9%48%
1650
11th to 20thNight
6%425%445%46%10%50%
1520
21st to endNight
6%325%445%48%11%49%
1520
July1st to 10thNight
10%5%26%44435%9%47%
2530
11th to 20thNight
7%42444446%9%54%
2582
21st to endNight
11%7%49%6%6%6%5%6%8%32%
3087
August1st to 10thNight
7%41434446%9%54%
2825
11th to 20thNight
7%5%26%45%5%47%9%46%
2961
21st to endNight
421433335%10%62%
3476
September1st to 10thNight
12%5%2434436%7%51%
1952
11th to 20thNight
10%5%25%34345%8%53%
2090
21st to endNight
13%5%26%343436%52%
2090
October1st to 10thNight
9%5%25%32325%6%59%
2090
11th to 20thNight
13%6%25%44335%6%49%
2180
21st to endNight
17%7%25%44335%6%45%
2707
November1st to 10thNight
13%6%25%43335%5%49%
2504
11th to 20thNight
15%7%27%5%34347%43%
2470
21st to endNight
19%10%35%443346%39%
2470
December1st to 10thNight
21%11%36%5%4335%5%33%
2470
11th to 20thNight
19%11%5%7%443345%33%
3042
21st to endNight
20%17%410%5%5%5%345%21%
4788

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
56%411%18%10%1
2528
11th to 20thDay
61%39%19%7%1
2604
21st to endDay
65%38%20%41
3133
February1st to 10thDay
53%38%23%11%2
1900
11th to 20thDay
51%49%22%12%2
1858
21st to endDay
55%49%20%10%3
1570
March1st to 10thDay
57%36%19%11%4
3120
11th to 20thDay
40%5%10%27%17%2
3416
21st to endDay
45%7%12%23%13%1
3877
April1st to 10thDay
43%5%11%24%15%2
2280
11th to 20thDay
46%48%23%16%3
2254
21st to endDay
45%5%10%26%12%2
2446
May1st to 10thDay
50%8%13%19%9%
4120
11th to 20thDay
46%6%10%24%13%1
4085
21st to endDay
41%7%13%18%19%1
4489
June1st to 10thDay
37%6%11%26%17%3
2524
11th to 20thDay
33%7%13%26%20%2
2660
21st to endDay
34%8%14%21%19%4
2660
July1st to 10thDay
41%6%12%22%18%2
4371
11th to 20thDay
29%6%12%35%16%2
4309
21st to endDay
52%7%12%18%10%1
4324
August1st to 10thDay
30%6%13%36%14%1
4091
11th to 20thDay
35%7%12%29%17%1
3903
21st to endDay
25%6%12%36%17%4
4179
September1st to 10thDay
38%5%9%23%19%6%
2208
11th to 20thDay
33%5%11%24%23%4
2090
21st to endDay
38%48%24%24%3
2090
October1st to 10thDay
20%25%29%39%3
3480
11th to 20thDay
26%39%27%31%2
3303
21st to endDay
33%38%28%22%6%
3089
November1st to 10thDay
33%39%30%21%4
1735
11th to 20thDay
43%46%24%18%5%
1710
21st to endDay
45%48%23%18%1
1710
December1st to 10thDay
56%310%21%10%1
1710
11th to 20thDay
56%47%20%12%1
2150
21st to endDay
61%6%9%16%7%1
2872
January1st to 10thNight
57%5%9%16%11%1
4428
11th to 20thNight
62%48%17%9%1
4345
21st to endNight
61%47%18%9%1
4519
February1st to 10thNight
57%49%20%8%1
2280
11th to 20thNight
51%48%23%13%1
2219
21st to endNight
56%410%15%12%3
1884
March1st to 10thNight
55%46%22%12%2
3733
11th to 20thNight
38%5%9%27%18%3
3529
21st to endNight
44%6%9%25%14%1
3769
April1st to 10thNight
41%5%10%24%17%3
1900
11th to 20thNight
44%38%19%20%6%
1875
21st to endNight
45%6%10%23%13%3
1733
May1st to 10thNight
53%9%10%19%8%2
2840
11th to 20thNight
41%7%14%27%10%1
2813
21st to endNight
34%9%13%25%16%3
3087
June1st to 10thNight
32%6%11%28%20%4
1650
11th to 20thNight
29%6%15%23%22%5%
1520
21st to endNight
28%7%18%22%19%7%
1520
July1st to 10thNight
34%7%11%26%18%4
2490
11th to 20thNight
26%6%12%36%18%2
2534
21st to endNight
48%7%13%20%11%1
2988
August1st to 10thNight
25%7%14%38%14%1
2814
11th to 20thNight
33%7%12%30%18%1
2988
21st to endNight
18%5%14%35%23%4
3476
September1st to 10thNight
33%6%11%24%21%6%
1952
11th to 20thNight
30%410%27%23%5%
2090
21st to endNight
35%5%7%25%24%4
2090
October1st to 10thNight
21%37%19%48%3
3480
11th to 20thNight
25%37%25%35%5%
3614
21st to endNight
32%37%22%30%7%
4457
November1st to 10thNight
37%48%24%23%4
2504
11th to 20thNight
42%47%21%22%5%
2470
21st to endNight
48%38%24%16%1
2470
December1st to 10thNight
53%410%21%12%1
2470
11th to 20thNight
53%48%21%12%2
3044
21st to endNight
65%5%9%13%7%1
4788

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
23%13%37%19%7%1
270
11th to 20thDay
26%19%36%14%5%
270
21st to endDay
29%13%36%19%3
297
February1st to 10thDay
26%15%39%16%5%
270
11th to 20thDay
27%19%37%11%6%
270
21st to endDay
34%12%35%15%4
225
March1st to 10thDay
25%16%40%15%5%
270
11th to 20thDay
23%14%37%18%6%2
422
21st to endDay
26%12%35%19%6%1
506
April1st to 10thDay
22%14%27%23%13%1
460
11th to 20thDay
23%11%25%26%12%3
452
21st to endDay
21%10%35%22%9%2
460
May1st to 10thDay
21%9%29%25%12%5%
463
11th to 20thDay
22%5%20%28%16%8%
487
21st to endDay
13%322%28%21%13%
529
June1st to 10thDay
14%418%28%25%12%
544
11th to 20thDay
8%5%14%36%25%11%
680
21st to endDay
10%420%32%22%12%
680
July1st to 10thDay
16%313%23%24%22%
671
11th to 20thDay
10%213%30%30%14%
638
21st to endDay
12%211%30%27%17%
532
August1st to 10thDay
10%212%29%29%19%
486
11th to 20thDay
13%316%28%29%12%
479
21st to endDay
9%18%30%34%18%
539
September1st to 10thDay
14%213%27%31%13%
490
11th to 20thDay
11%212%28%33%14%
490
21st to endDay
17%5%17%26%25%11%
490
October1st to 10thDay
11%418%36%24%7%
490
11th to 20thDay
12%11%31%27%15%4
490
21st to endDay
21%9%35%24%10%
338
November1st to 10thDay
14%9%32%32%10%4
291
11th to 20thDay
20%14%30%24%8%3
270
21st to endDay
24%9%33%25%9%1
270
December1st to 10thDay
23%16%30%23%7%1
270
11th to 20thDay
21%12%40%17%9%
270
21st to endDay
30%15%32%20%3
297
January1st to 10thNight
23%13%32%26%5%
950
11th to 20thNight
29%11%33%22%4
894
21st to endNight
25%11%37%25%2
836
February1st to 10thNight
28%9%32%28%3
760
11th to 20thNight
23%11%38%27%1
743
21st to endNight
28%11%37%22%2
628
March1st to 10thNight
25%11%32%26%6%
760
11th to 20thNight
23%8%35%25%8%1
760
21st to endNight
24%9%29%31%7%1
813
April1st to 10thNight
17%8%35%31%9%
570
11th to 20thNight
20%7%30%31%11%1
563
21st to endNight
19%5%35%32%8%2
570
May1st to 10thNight
21%5%32%28%14%1
570
11th to 20thNight
17%416%41%18%4
561
21st to endNight
10%216%39%28%5%
617
June1st to 10thNight
12%116%41%27%4
570
11th to 20thNight
8%211%44%31%4
570
21st to endNight
6%114%43%31%5%
570
July1st to 10thNight
13%28%28%37%11%
555
11th to 20thNight
10%16%35%42%6%
552
21st to endNight
12%28%37%34%8%
624
August1st to 10thNight
9%16%35%43%6%
567
11th to 20thNight
8%28%41%34%7%
564
21st to endNight
6%16%35%45%6%
627
September1st to 10thNight
14%18%36%36%5%
622
11th to 20thNight
12%213%30%39%4
760
21st to endNight
14%318%35%27%3
760
October1st to 10thNight
12%318%35%26%6%
760
11th to 20thNight
16%6%26%34%16%2
760
21st to endNight
20%6%32%29%13%
836
November1st to 10thNight
16%6%27%33%16%2
771
11th to 20thNight
18%9%31%29%12%
760
21st to endNight
23%9%25%31%11%1
760
December1st to 10thNight
26%7%32%29%5%1
760
11th to 20thNight
26%8%33%26%6%1
760
21st to endNight
31%10%30%25%4
988
Page generated at 2024-11-05 08:15:49. Version ac07

Copyright © 2024 Attilla Danko.


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