MIRA Chews Ridge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the MIRA Chews Ridge Observatory clear sky chart from 2005-11-06 to 2024-03-28.

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
68%
24200
31%
80441
28%
24110
73%
24110
42%
41298

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
53%
750
26%
4102
21%
736
59%
736
20%
2031
January11th to 20thNight
59%
753
22%
4028
23%
740
65%
740
18%
2456
January21st to endNight
56%
829
17%
4360
26%
814
61%
814
17%
2757
February1st to 10thNight
56%
760
25%
2470
25%
760
61%
760
30%
1433
February11th to 20thNight
55%
740
29%
2250
25%
740
62%
740
35%
1261
February21st to endNight
53%
628
23%
1884
21%
628
58%
628
33%
1113
March1st to 10thNight
48%
760
18%
2152
15%
760
52%
760
25%
1433
March11th to 20thNight
54%
760
25%
2090
21%
760
59%
760
33%
1293
March21st to endNight
54%
820
22%
2201
13%
820
60%
820
36%
1312
April1st to 10thNight
53%
720
27%
1800
14%
720
59%
720
40%
1108
April11th to 20thNight
55%
711
32%
1779
15%
711
61%
711
47%
1007
April21st to endNight
58%
720
31%
1800
14%
720
65%
720
56%
936
May1st to 10thNight
64%
720
30%
1800
16%
720
68%
720
58%
929
May11th to 20thNight
72%
536
35%
1599
25%
536
77%
536
61%
706
May21st to endNight
71%
388
32%
1552
30%
388
80%
388
52%
583
June1st to 10thNight
71%
360
34%
1440
35%
360
80%
360
58%
508
June11th to 20thNight
79%
360
40%
1440
42%
360
88%
360
68%
464
June21st to endNight
89%
360
43%
1440
51%
360
94%
360
84%
407
July1st to 10thNight
92%
367
41%
1417
48%
367
95%
367
89%
397
July11th to 20thNight
95%
522
38%
1566
34%
522
95%
522
82%
593
July21st to endNight
95%
591
44%
1674
39%
558
96%
558
79%
650
August1st to 10thNight
90%
541
42%
1606
34%
538
91%
538
79%
626
August11th to 20thNight
91%
712
43%
1780
26%
712
92%
712
85%
776
August21st to endNight
93%
792
46%
1980
30%
792
94%
792
88%
852
September1st to 10thNight
91%
720
47%
1800
34%
720
93%
720
87%
772
September11th to 20thNight
84%
720
48%
1800
37%
720
88%
720
79%
816
September21st to endNight
83%
720
45%
2019
42%
720
88%
720
75%
836
October1st to 10thNight
79%
720
34%
2160
35%
720
84%
720
59%
966
October11th to 20thNight
76%
720
39%
2160
40%
720
81%
720
57%
1000
October21st to endNight
78%
792
41%
2376
42%
792
82%
792
59%
1073
November1st to 10thNight
70%
740
35%
2247
35%
740
75%
740
49%
1117
November11th to 20thNight
68%
760
31%
2470
30%
760
74%
760
43%
1229
November21st to endNight
67%
760
31%
2508
31%
760
72%
760
39%
1296
December1st to 10thNight
60%
760
26%
2660
26%
760
66%
760
32%
1461
December11th to 20thNight
52%
760
20%
3243
23%
759
57%
759
17%
2195
December21st to endNight
47%
828
15%
4788
22%
817
55%
817
14%
2906

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
5%424423346%63%
78957
Night
5%42443445%7%59%
81076
TransparencyDay
23%47%18%26%23%
78680
Night
25%48%17%23%23%
80875
SeeingDay
8%9%24%33%20%5%
14657
Night
7%5%15%32%32%9%
24237

By Month

Percentage Cloud Cover SW (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
8%7%37%8%46%45%7%43%
2763
11th to 20thDay
8%6%36%8%5%7%6%6%8%38%
2860
21st to endDay
10%9%47%8%45%5%6%8%34%
3146
February1st to 10thDay
10%7%35%5%35%5%5%6%45%
1710
11th to 20thDay
9%6%26%5%35%5%5%8%47%
1817
21st to endDay
10%11%35%434446%45%
1570
March1st to 10thDay
8%10%47%6%36%6%6%8%36%
2023
11th to 20thDay
9%7%37%5%36%5%6%9%40%
2090
21st to endDay
7%8%36%5%3445%7%47%
2309
April1st to 10thDay
8%7%445%345%6%7%47%
2160
11th to 20thDay
6%5%244245%48%57%
2129
21st to endDay
5%313324448%63%
2160
May1st to 10thDay
3313423348%65%
2160
11th to 20thDay
2212213348%71%
2288
21st to endDay
4212223447%69%
2723
June1st to 10thDay
2212323447%70%
2520
11th to 20thDay
11211112486%
2520
21st to endDay
111111112388%
2520
July1st to 10thDay
111112389%
2496
11th to 20thDay
111111223484%
2340
21st to endDay
111111223484%
2546
August1st to 10thDay
11111122386%
2324
11th to 20thDay
111123388%
2122
21st to endDay
111221289%
2376
September1st to 10thDay
11111112289%
2160
11th to 20thDay
1111212236%82%
2160
21st to endDay
1112212235%79%
1934
October1st to 10thDay
222232335%7%70%
1800
11th to 20thDay
3213323336%70%
1800
21st to endDay
331332335%6%68%
1980
November1st to 10thDay
5%4344345%47%57%
1831
11th to 20thDay
442443446%7%58%
1710
21st to endDay
7%6%25%4345%6%5%55%
1668
December1st to 10thDay
6%5%36%7%46%5%6%8%45%
1520
11th to 20thDay
16%11%47%7%3446%6%31%
1928
21st to endDay
10%9%38%6%45%5%6%6%37%
2794
January1st to 10thNight
6%8%26%7%4445%6%46%
4186
11th to 20thNight
7%9%38%7%5%6%6%6%8%36%
4110
21st to endNight
9%10%48%7%46%6%6%7%34%
4521
February1st to 10thNight
9%5%36%5%35%45%6%48%
2470
11th to 20thNight
6%6%25%5%35%5%6%9%47%
2249
21st to endNight
7%9%245%3445%7%48%
1884
March1st to 10thNight
7%8%38%7%5%6%6%5%6%39%
2152
11th to 20thNight
6%6%35%7%45%6%5%9%45%
2090
21st to endNight
6%5%25%5%346%6%8%49%
2201
April1st to 10thNight
5%5%35%5%45%5%5%8%51%
1800
11th to 20thNight
45%34435%447%59%
1779
21st to endNight
221332346%10%63%
1800
May1st to 10thNight
1213423348%68%
1800
11th to 20thNight
221231336%8%71%
1598
21st to endNight
1112323447%73%
1552
June1st to 10thNight
2112224337%73%
1440
11th to 20thNight
11221133484%
1440
21st to endNight
11112490%
1440
July1st to 10thNight
1112491%
1458
11th to 20thNight
11111122388%
1620
21st to endNight
111121235%84%
1773
August1st to 10thNight
1211222484%
1615
11th to 20thNight
1111121389%
1780
21st to endNight
111111390%
1980
September1st to 10thNight
111122388%
1800
11th to 20thNight
111222123483%
1800
21st to endNight
1111212125%84%
2019
October1st to 10thNight
3212323336%73%
2160
11th to 20thNight
231332445%6%68%
2160
21st to endNight
3212323247%72%
2376
November1st to 10thNight
331342445%9%60%
2247
11th to 20thNight
5%414425%45%9%56%
2470
21st to endNight
4425%4346%5%7%56%
2508
December1st to 10thNight
7%6%25%5%345%5%7%50%
2660
11th to 20thNight
13%10%48%6%45%46%6%33%
3276
21st to endNight
8%8%37%8%5%6%6%6%7%36%
4862

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
37%6%10%28%15%3
2763
11th to 20thDay
42%7%11%18%13%9%
2860
21st to endDay
46%6%7%19%14%7%
3146
February1st to 10thDay
38%48%15%22%14%
1710
11th to 20thDay
36%5%8%18%23%11%
1827
21st to endDay
40%5%8%20%19%8%
1570
March1st to 10thDay
43%6%9%17%18%7%
2023
11th to 20thDay
40%5%9%19%19%8%
2090
21st to endDay
36%5%11%23%19%6%
2309
April1st to 10thDay
35%411%21%20%9%
2160
11th to 20thDay
24%5%12%26%24%9%
2132
21st to endDay
20%5%10%30%29%6%
2160
May1st to 10thDay
18%49%25%33%11%
2160
11th to 20thDay
14%38%26%36%13%
2291
21st to endDay
16%5%12%30%29%8%
2724
June1st to 10thDay
13%5%10%21%34%17%
2520
11th to 20thDay
6%18%18%36%31%
2520
21st to endDay
6%1311%30%48%
2520
July1st to 10thDay
4138%25%59%
2428
11th to 20thDay
7%15%9%28%50%
2271
21st to endDay
6%2311%29%48%
2405
August1st to 10thDay
7%1310%26%53%
2308
11th to 20thDay
5%1310%33%48%
2122
21st to endDay
5%1211%33%47%
2376
September1st to 10thDay
5%138%28%55%
2160
11th to 20thDay
7%3416%38%32%
2160
21st to endDay
10%1416%42%26%
1934
October1st to 10thDay
14%47%18%27%31%
1800
11th to 20thDay
17%26%22%26%27%
1800
21st to endDay
18%27%18%28%27%
1980
November1st to 10thDay
25%47%18%27%18%
1831
11th to 20thDay
24%311%19%26%17%
1710
21st to endDay
29%46%17%26%17%
1668
December1st to 10thDay
35%5%9%17%19%15%
1520
11th to 20thDay
52%48%14%14%8%
1928
21st to endDay
45%6%10%20%15%5%
2794
January1st to 10thNight
32%6%13%26%18%5%
4186
11th to 20thNight
42%6%10%20%12%9%
4110
21st to endNight
43%7%10%14%16%9%
4521
February1st to 10thNight
37%39%15%20%16%
2470
11th to 20thNight
31%410%18%26%10%
2250
21st to endNight
34%49%22%21%9%
1884
March1st to 10thNight
43%5%12%16%17%7%
2152
11th to 20thNight
34%6%9%16%23%12%
2090
21st to endNight
32%413%21%22%8%
2201
April1st to 10thNight
31%5%11%21%21%11%
1800
11th to 20thNight
25%311%25%24%12%
1779
21st to endNight
16%413%26%30%10%
1800
May1st to 10thNight
16%49%18%36%17%
1800
11th to 20thNight
14%28%20%38%17%
1599
21st to endNight
13%412%26%31%14%
1552
June1st to 10thNight
10%312%16%33%26%
1440
11th to 20thNight
8%26%16%29%39%
1440
21st to endNight
3129%27%57%
1440
July1st to 10thNight
227%21%66%
1417
11th to 20thNight
5%129%23%59%
1566
21st to endNight
6%238%23%58%
1674
August1st to 10thNight
7%127%22%61%
1606
11th to 20thNight
5%127%25%61%
1780
21st to endNight
4128%30%55%
1980
September1st to 10thNight
4137%21%65%
1800
11th to 20thNight
8%2413%30%45%
1800
21st to endNight
8%1316%39%33%
2019
October1st to 10thNight
15%36%18%24%35%
2160
11th to 20thNight
16%36%16%30%28%
2160
21st to endNight
15%26%15%31%30%
2376
November1st to 10thNight
21%47%19%26%23%
2247
11th to 20thNight
23%411%18%25%19%
2470
21st to endNight
28%38%16%26%20%
2508
December1st to 10thNight
33%48%17%21%17%
2660
11th to 20thNight
51%48%14%15%8%
3276
21st to endNight
43%8%10%16%17%7%
4862

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%15%25%22%12%2
313
11th to 20thDay
11%14%27%28%19%2
370
21st to endDay
14%12%28%24%18%3
407
February1st to 10thDay
15%18%26%18%17%6%
370
11th to 20thDay
17%14%28%27%13%1
440
21st to endDay
15%15%30%25%14%1
382
March1st to 10thDay
18%16%31%26%8%1
460
11th to 20thDay
17%16%29%22%14%2
460
21st to endDay
14%18%35%24%8%1
491
April1st to 10thDay
13%16%31%25%13%1
420
11th to 20thDay
11%17%34%26%10%1
412
21st to endDay
7%15%32%29%11%5%
420
May1st to 10thDay
9%12%34%28%14%4
423
11th to 20thDay
7%13%32%30%14%4
448
21st to endDay
7%11%25%34%17%5%
485
June1st to 10thDay
5%6%30%32%20%7%
450
11th to 20thDay
39%25%41%16%6%
450
21st to endDay
2324%41%22%8%
450
July1st to 10thDay
120%47%24%8%
446
11th to 20thDay
111%47%29%11%
444
21st to endDay
111%47%28%13%
487
August1st to 10thDay
2219%47%22%7%
447
11th to 20thDay
116%45%27%11%
437
21st to endDay
113%46%29%10%
495
September1st to 10thDay
1416%44%28%7%
450
11th to 20thDay
2425%39%25%5%
450
21st to endDay
46%16%39%29%6%
450
October1st to 10thDay
37%26%35%25%5%
450
11th to 20thDay
38%21%32%29%7%
450
21st to endDay
6%7%24%32%26%6%
495
November1st to 10thDay
7%10%19%30%29%5%
427
11th to 20thDay
5%7%23%32%25%8%
270
21st to endDay
10%8%24%33%22%4
250
December1st to 10thDay
11%14%25%29%18%2
180
11th to 20thDay
11%14%25%26%17%7%
180
21st to endDay
15%21%21%25%14%5%
198
January1st to 10thNight
13%6%20%30%23%9%
760
11th to 20thNight
10%8%16%31%28%7%
760
21st to endNight
14%5%17%35%24%5%
836
February1st to 10thNight
13%7%18%33%23%6%
760
11th to 20thNight
12%9%18%31%24%6%
744
21st to endNight
13%7%21%36%19%3
628
March1st to 10thNight
15%8%21%33%19%4
760
11th to 20thNight
10%7%21%33%23%6%
760
21st to endNight
10%7%24%34%22%3
820
April1st to 10thNight
9%5%25%35%23%3
720
11th to 20thNight
7%10%23%31%22%6%
711
21st to endNight
37%29%28%24%9%
720
May1st to 10thNight
26%24%34%27%7%
720
11th to 20thNight
3318%38%30%8%
536
21st to endNight
4418%32%34%8%
389
June1st to 10thNight
3419%34%33%8%
360
11th to 20thNight
1314%36%39%7%
360
21st to endNight
28%34%46%9%
360
July1st to 10thNight
15%28%53%13%
367
11th to 20thNight
1120%54%23%
522
21st to endNight
120%57%22%
591
August1st to 10thNight
15%33%47%15%
541
11th to 20thNight
116%31%46%15%
712
21st to endNight
1424%56%16%
792
September1st to 10thNight
15%29%50%15%
720
11th to 20thNight
1111%34%43%10%
720
21st to endNight
229%27%45%15%
720
October1st to 10thNight
4310%36%36%11%
720
11th to 20thNight
4312%33%34%14%
720
21st to endNight
5%112%32%33%16%
792
November1st to 10thNight
7%413%34%31%11%
740
11th to 20thNight
7%414%35%33%8%
760
21st to endNight
7%316%39%27%8%
760
December1st to 10thNight
11%6%18%35%24%7%
760
11th to 20thNight
16%6%20%32%23%4
760
21st to endNight
14%11%20%32%19%4
836
Page generated at 2024-03-24 20:37:04. Version ac07

Copyright © 2024 Attilla Danko.


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