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 2005-11-05 to 2018-02-22.

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
71%
16179
31%
48935
28%
16143
75%
16143
46%
24892

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 15thNight
61%
776
22%
2558
22%
776
65%
776
31%
1487
January16th to endNight
62%
832
24%
2704
26%
832
65%
832
30%
1601
February1st to 15thNight
62%
760
27%
2443
28%
760
66%
760
32%
1410
February16th to endNight
56%
660
24%
1979
23%
660
60%
660
31%
1210
March1st to 15thNight
59%
720
20%
2019
19%
720
61%
720
31%
1273
March16th to endNight
59%
768
23%
2076
17%
768
63%
768
36%
1252
April1st to 15thNight
52%
719
25%
1799
14%
719
56%
719
37%
1128
April16th to endNight
63%
720
29%
1800
14%
720
68%
720
53%
967
May1st to 15thNight
70%
683
30%
1763
18%
683
73%
683
61%
886
May16th to endNight
73%
410
34%
1533
30%
410
81%
410
55%
590
June1st to 15thNight
75%
360
33%
1440
34%
360
84%
360
57%
519
June16th to endNight
91%
360
42%
1440
49%
360
96%
360
82%
413
July1st to 15thNight
93%
406
35%
1426
37%
406
94%
406
84%
456
July16th to endNight
94%
564
40%
1593
36%
531
94%
531
78%
619
August1st to 15thNight
92%
601
41%
1674
31%
598
92%
598
84%
667
August16th to endNight
93%
764
46%
1910
30%
764
94%
764
88%
824
September1st to 15thNight
92%
720
44%
1800
33%
720
93%
720
81%
806
September16th to endNight
84%
716
48%
1947
43%
716
88%
716
78%
822
October1st to 15thNight
77%
720
32%
2160
34%
720
81%
720
53%
1027
October16th to endNight
79%
768
39%
2304
43%
768
81%
768
54%
1103
November1st to 15thNight
73%
760
32%
2364
32%
760
76%
760
47%
1182
November16th to endNight
70%
780
28%
2561
29%
780
73%
780
38%
1342
December1st to 15thNight
64%
780
26%
2730
26%
780
69%
780
29%
1559
December16th to endNight
53%
832
24%
2912
24%
832
58%
832
24%
1749

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%413313345%63%
49309
Night
4313323346%61%
49126
TransparencyDay
22%37%17%26%23%
48999
Night
23%37%16%24%24%
48936
SeeingDay
8%7%23%33%20%5%
6564
Night
7%212%29%34%12%
16189

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 15thDay
9%6%25%5%35%45%8%42%
1707
16th to endDay
11%7%35%42445%6%45%
1872
February1st to 15thDay
10%7%26%425%446%46%
1749
16th to endDay
14%9%35%434447%38%
1641
March1st to 15thDay
8%7%36%5%25%5%5%9%38%
1938
16th to endDay
9%8%36%425%45%8%43%
2148
April1st to 15thDay
10%8%34423446%45%
2149
16th to endDay
5%313314438%59%
2160
May1st to 15thDay
2212213348%67%
2184
16th to endDay
3212212446%66%
2578
June1st to 15thDay
222212346%70%
2520
16th to endDay
111387%
2520
July1st to 15thDay
1112387%
2444
16th to endDay
111112384%
2468
August1st to 15thDay
112387%
2276
16th to endDay
1111289%
2292
September1st to 15thDay
111112385%
2160
16th to endDay
111112235%78%
2009
October1st to 15thDay
3213323347%65%
1800
16th to endDay
3313323345%65%
1920
November1st to 15thDay
6%434423336%56%
1824
16th to endDay
6%6%2443445%7%50%
1726
December1st to 15thDay
9%7%35%5%35%46%6%42%
1560
16th to endDay
10%10%35%425%35%6%41%
1664
January1st to 15thNight
7%6%26%6%2446%7%44%
2558
16th to endNight
10%5%35%43445%7%44%
2704
February1st to 15thNight
8%5%26%5%35%5%5%8%44%
2432
16th to endNight
9%8%245%3445%6%44%
1979
March1st to 15thNight
7%6%35%5%36%5%47%43%
2019
16th to endNight
6%5%244346%6%8%46%
2076
April1st to 15thNight
6%6%34435%5%5%6%48%
1799
16th to endNight
221332345%8%61%
1800
May1st to 15thNight
212312347%69%
1763
16th to endNight
112213347%71%
1532
June1st to 15thNight
12213437%72%
1440
16th to endNight
111390%
1440
July1st to 15thNight
1112487%
1512
16th to endNight
1112385%
1701
August1st to 15thNight
1111387%
1683
16th to endNight
1111389%
1910
September1st to 15thNight
111122384%
1800
16th to endNight
1111111482%
1947
October1st to 15thNight
3212323346%66%
2160
16th to endNight
322323346%65%
2304
November1st to 15thNight
4313323448%59%
2364
16th to endNight
44144245%5%9%52%
2561
December1st to 15thNight
6%6%35%5%345%5%6%47%
2730
16th to endNight
9%8%35%5%3345%7%42%
2912

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 15thDay
39%38%19%18%10%
1707
16th to endDay
37%5%8%14%19%14%
1872
February1st to 15thDay
36%46%17%24%10%
1749
16th to endDay
45%5%8%19%15%5%
1641
March1st to 15thDay
39%5%10%19%15%9%
1938
16th to endDay
39%411%20%18%5%
2148
April1st to 15thDay
37%310%23%19%4
2149
16th to endDay
22%5%11%26%26%7%
2160
May1st to 15thDay
15%28%26%35%11%
2184
16th to endDay
16%411%25%30%10%
2582
June1st to 15thDay
14%39%20%28%23%
2520
16th to endDay
5%1213%33%44%
2520
July1st to 15thDay
5%126%24%59%
2301
16th to endDay
7%2410%26%50%
2313
August1st to 15thDay
6%310%30%49%
2260
16th to endDay
4211%36%44%
2292
September1st to 15thDay
7%1412%30%44%
2160
16th to endDay
9%1418%38%26%
2009
October1st to 15thDay
18%36%19%25%25%
1800
16th to endDay
21%26%22%25%21%
1920
November1st to 15thDay
28%39%19%27%11%
1824
16th to endDay
31%47%19%27%10%
1726
December1st to 15thDay
39%47%15%18%14%
1560
16th to endDay
41%311%15%17%9%
1664
January1st to 15thNight
36%38%20%21%9%
2558
16th to endNight
35%410%11%18%17%
2704
February1st to 15thNight
35%38%17%23%12%
2443
16th to endNight
37%311%21%18%7%
1979
March1st to 15thNight
36%6%11%16%17%11%
2019
16th to endNight
32%414%18%19%10%
2076
April1st to 15thNight
34%311%23%20%6%
1799
16th to endNight
18%413%25%27%10%
1800
May1st to 15thNight
15%36%21%35%17%
1764
16th to endNight
12%310%24%33%15%
1533
June1st to 15thNight
11%210%17%26%31%
1440
16th to endNight
31210%26%56%
1440
July1st to 15thNight
425%19%67%
1426
16th to endNight
6%238%21%57%
1593
August1st to 15thNight
5%17%25%58%
1674
16th to endNight
417%31%53%
1910
September1st to 15thNight
6%1210%21%56%
1800
16th to endNight
8%217%36%34%
1947
October1st to 15thNight
19%26%19%26%26%
2160
16th to endNight
18%26%17%30%24%
2304
November1st to 15thNight
22%310%20%28%14%
2364
16th to endNight
28%39%18%26%13%
2561
December1st to 15thNight
35%36%15%20%16%
2730
16th to endNight
40%310%16%17%11%
2912

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 15thDay
22%9%21%24%19%3
246
16th to endDay
15%10%25%23%19%5%
304
February1st to 15thDay
13%11%24%22%21%6%
291
16th to endDay
19%13%25%26%12%1
264
March1st to 15thDay
16%12%27%24%17%1
270
16th to endDay
14%10%38%25%10%1
288
April1st to 15thDay
19%18%30%19%11%1
269
16th to endDay
10%18%37%25%7%1
270
May1st to 15thDay
9%9%35%29%13%2
288
16th to endDay
6%11%22%37%16%5%
330
June1st to 15thDay
5%7%32%35%13%5%
315
16th to endDay
323%42%21%7%
315
July1st to 15thDay
117%44%28%6%
305
16th to endDay
1112%44%30%9%
327
August1st to 15thDay
2117%45%25%6%
315
16th to endDay
112%48%26%10%
332
September1st to 15thDay
1213%46%29%5%
315
16th to endDay
45%14%43%26%4
315
October1st to 15thDay
37%25%40%20%2
315
16th to endDay
7%5%27%27%24%7%
336
November1st to 15thDay
8%6%18%27%32%5%
240
16th to endDay
8%9%25%31%20%5%
128
December1st to 15thDay
13%10%25%24%18%7%
90
16th to endDay
13%10%13%28%26%8%
96
January1st to 15thNight
14%212%28%30%11%
780
16th to endNight
14%312%30%30%9%
832
February1st to 15thNight
13%314%30%28%9%
764
16th to endNight
15%5%16%30%26%6%
660
March1st to 15thNight
13%415%31%26%8%
720
16th to endNight
11%420%30%28%5%
768
April1st to 15thNight
12%5%21%32%22%4
719
16th to endNight
5%7%20%30%26%10%
720
May1st to 15thNight
2218%36%28%11%
684
16th to endNight
3314%32%35%10%
411
June1st to 15thNight
1216%34%36%7%
360
16th to endNight
6%32%48%10%
360
July1st to 15thNight
1320%51%22%
406
16th to endNight
1114%51%31%
564
August1st to 15thNight
323%49%21%
601
16th to endNight
420%56%17%
764
September1st to 15thNight
325%50%19%
720
16th to endNight
118%23%46%18%
716
October1st to 15thNight
5%210%34%33%15%
720
16th to endNight
6%19%26%36%19%
768
November1st to 15thNight
6%111%35%30%13%
760
16th to endNight
7%312%33%31%11%
780
December1st to 15thNight
11%312%34%29%8%
780
16th to endNight
17%5%16%31%22%6%
832
Page generated at 2018-02-23 08:21:34. Version ac04

Copyright 2018 A. Danko


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