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LÓr Na Cruinne Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the LÓr Na Cruinne Observatory clear sky chart from 2005-11-05 to 2020-06-03.

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%
18757
14%
57830
10%
18726
48%
18726
22%
38840

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
37%
1124
12%
3360
8%
1120
41%
1120
17%
2434
January16th to endNight
36%
1018
20%
3418
12%
1018
47%
1018
20%
2243
February1st to 15thNight
40%
880
14%
3037
12%
877
46%
877
18%
2041
February16th to endNight
38%
792
15%
2474
12%
792
45%
792
19%
1732
March1st to 15thNight
39%
900
16%
2651
11%
900
45%
900
22%
1827
March16th to endNight
35%
960
12%
2606
4%
960
40%
960
19%
1909
April1st to 15thNight
32%
787
10%
2137
4%
787
35%
787
17%
1617
April16th to endNight
35%
669
13%
2007
9%
669
39%
669
19%
1411
May1st to 15thNight
42%
520
11%
1771
11%
520
46%
520
20%
1175
May16th to endNight
43%
470
6%
1645
4%
470
45%
470
16%
1160
June1st to 15thNight
44%
424
1%
1486
0%
424
44%
424
17%
1035
June16th to endNight
55%
420
1%
1470
0%
420
55%
420
25%
926
July1st to 15thNight
61%
400
3%
1400
0%
400
62%
400
27%
824
July16th to endNight
64%
440
11%
1516
12%
418
67%
418
32%
824
August1st to 15thNight
66%
456
13%
1690
18%
454
68%
454
26%
977
August16th to endNight
64%
669
20%
2007
17%
669
67%
669
39%
1102
September1st to 15thNight
55%
778
18%
2114
12%
778
57%
778
33%
1333
September16th to endNight
52%
836
19%
2310
13%
836
56%
836
32%
1474
October1st to 15thNight
44%
840
17%
2476
11%
840
50%
840
22%
1701
October16th to endNight
44%
896
20%
2912
14%
896
54%
896
26%
1822
November1st to 15thNight
36%
1028
17%
3008
10%
1028
44%
1028
21%
2060
November16th to endNight
36%
1125
15%
3360
8%
1125
43%
1125
22%
2260
December1st to 15thNight
39%
1125
16%
3375
11%
1125
44%
1125
19%
2404
December16th to endNight
38%
1200
16%
3600
9%
1200
44%
1200
19%
2549

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
10%8%36%6%35%5%6%8%35%
58620
Night
7%8%47%6%35%5%6%8%37%
57981
Cloud CoverDay
10%8%36%6%35%5%6%8%34%
58621
Night
7%9%47%6%35%5%6%8%36%
57984
TransparencyDay
45%8%15%20%8%1
58275
Night
43%8%14%21%10%1
57830
SeeingDay
16%7%26%29%16%4
9448
Night
12%5%29%35%15%2
18764

By Month

Percentage Cloud Cover NW (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
6%9%5%8%6%25%46%8%36%
1568
16th to endDay
410%48%6%45%5%7%9%34%
1875
February1st to 15thDay
410%5%9%7%46%6%6%8%29%
1815
16th to endDay
39%6%9%8%46%5%6%8%30%
1879
March1st to 15thDay
410%48%8%45%5%6%8%33%
2299
16th to endDay
7%14%6%9%6%36%5%6%7%27%
2673
April1st to 15thDay
11%15%6%7%6%35%5%6%6%24%
2800
16th to endDay
12%11%37%6%345%5%7%30%
2888
May1st to 15thDay
12%9%37%6%36%5%5%7%31%
3167
16th to endDay
22%7%36%5%35%46%8%25%
3522
June1st to 15thDay
19%7%36%6%45%5%6%7%26%
3183
16th to endDay
14%5%35%6%35%5%6%9%33%
3150
July1st to 15thDay
11%4245%35%6%7%9%39%
3150
16th to endDay
7%3135%25%6%6%8%48%
3267
August1st to 15thDay
12%5%245%25%5%7%8%41%
2845
16th to endDay
9%3144245%6%9%48%
2899
September1st to 15thDay
14%6%24423335%47%
2504
16th to endDay
11%8%35%5%24448%40%
2310
October1st to 15thDay
13%10%36%5%445%5%6%33%
2143
16th to endDay
7%8%35%6%346%6%8%39%
2016
November1st to 15thDay
7%12%47%7%345%6%7%32%
1825
16th to endDay
6%10%38%42346%7%39%
1587
December1st to 15thDay
38%411%7%5%7%6%5%7%32%
1575
16th to endDay
211%49%6%45%6%7%9%31%
1680
January1st to 15thNight
5%10%5%8%9%46%6%6%8%28%
3360
16th to endNight
49%5%7%5%35%5%7%8%36%
3418
February1st to 15thNight
5%9%5%8%6%46%5%5%7%35%
3026
16th to endNight
39%6%11%7%45%6%6%7%33%
2474
March1st to 15thNight
38%5%9%8%45%5%6%8%34%
2651
16th to endNight
6%13%6%8%6%35%5%6%8%29%
2603
April1st to 15thNight
12%13%410%6%35%45%7%28%
2137
16th to endNight
12%11%48%5%245%5%8%33%
2007
May1st to 15thNight
11%8%36%6%3446%7%35%
1770
16th to endNight
20%5%26%5%35%45%7%32%
1645
June1st to 15thNight
16%7%36%5%35%45%8%33%
1486
16th to endNight
12%425%435%6%7%9%38%
1470
July1st to 15thNight
8%324435%45%10%45%
1470
16th to endNight
6%4133245%6%8%52%
1604
August1st to 15thNight
11%3144235%7%9%45%
1698
16th to endNight
7%3133135%5%8%54%
2007
September1st to 15thNight
12%8%2332335%7%47%
2114
16th to endNight
12%6%2442435%8%45%
2310
October1st to 15thNight
11%9%36%5%346%5%7%36%
2476
16th to endNight
6%8%35%5%345%6%9%40%
2912
November1st to 15thNight
5%11%46%5%35%5%6%7%38%
3008
16th to endNight
5%10%48%5%45%45%7%37%
3360
December1st to 15thNight
410%5%9%7%46%5%6%7%32%
3375
16th to endNight
39%410%8%45%6%7%7%31%
3600

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
6%10%5%7%5%35%5%6%8%35%
1568
16th to endDay
5%10%48%7%36%5%7%9%32%
1875
February1st to 15thDay
5%9%5%9%8%47%5%6%7%28%
1815
16th to endDay
49%7%9%7%46%6%6%8%29%
1879
March1st to 15thDay
410%5%9%7%36%6%5%8%32%
2299
16th to endDay
8%13%6%8%7%35%5%6%7%27%
2674
April1st to 15thDay
11%15%6%8%6%35%5%6%7%23%
2800
16th to endDay
13%11%36%6%35%5%6%7%30%
2888
May1st to 15thDay
11%10%36%7%35%5%6%7%31%
3167
16th to endDay
21%7%25%6%345%6%7%26%
3522
June1st to 15thDay
19%7%36%6%36%5%6%8%26%
3183
16th to endDay
13%5%25%5%35%6%7%8%34%
3150
July1st to 15thDay
10%415%5%35%6%7%8%40%
3150
16th to endDay
6%314425%6%7%9%48%
3267
August1st to 15thDay
12%6%24425%5%6%8%41%
2845
16th to endDay
9%4145%235%7%7%49%
2899
September1st to 15thDay
14%7%24423336%47%
2504
16th to endDay
11%8%36%5%23448%40%
2310
October1st to 15thDay
13%10%37%5%3445%7%33%
2143
16th to endDay
6%9%36%5%36%6%6%8%38%
2016
November1st to 15thDay
8%12%5%8%6%345%5%8%31%
1825
16th to endDay
6%11%47%5%3346%7%38%
1587
December1st to 15thDay
49%5%10%7%5%7%5%6%6%31%
1575
16th to endDay
311%49%7%35%6%7%9%30%
1680
January1st to 15thNight
5%9%5%9%9%46%6%6%8%27%
3360
16th to endNight
410%47%5%45%5%7%9%35%
3418
February1st to 15thNight
5%9%5%9%7%45%5%6%7%34%
3026
16th to endNight
49%6%10%7%5%5%5%5%7%31%
2474
March1st to 15thNight
39%5%8%7%45%5%7%8%33%
2651
16th to endNight
6%13%6%8%6%35%6%6%8%29%
2606
April1st to 15thNight
12%13%49%7%35%447%26%
2137
16th to endNight
11%11%46%6%3445%8%32%
2007
May1st to 15thNight
11%9%36%6%3445%7%36%
1770
16th to endNight
19%6%25%5%36%35%8%31%
1645
June1st to 15thNight
16%8%27%435%46%8%32%
1486
16th to endNight
11%425%5%45%5%6%9%38%
1470
July1st to 15thNight
7%425%5%445%6%8%45%
1470
16th to endNight
6%42332446%8%53%
1604
August1st to 15thNight
10%4144345%6%10%44%
1698
16th to endNight
7%4133235%5%8%54%
2007
September1st to 15thNight
13%7%1332345%7%47%
2114
16th to endNight
12%6%15%32445%8%45%
2310
October1st to 15thNight
10%9%36%6%345%6%7%35%
2476
16th to endNight
6%8%35%5%25%6%6%9%40%
2912
November1st to 15thNight
6%11%46%5%346%5%7%36%
3008
16th to endNight
5%11%48%6%45%5%5%8%36%
3360
December1st to 15thNight
410%5%9%8%5%5%5%6%7%31%
3375
16th to endNight
39%410%9%46%6%6%7%30%
3600

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
43%7%15%23%7%2
1568
16th to endDay
45%7%14%18%10%3
1875
February1st to 15thDay
49%8%14%17%7%2
1815
16th to endDay
49%10%11%17%9%1
1879
March1st to 15thDay
45%9%16%18%7%1
2299
16th to endDay
54%8%13%15%6%
2674
April1st to 15thDay
57%7%13%14%6%
2800
16th to endDay
50%8%12%19%8%
2888
May1st to 15thDay
48%8%14%19%7%
3167
16th to endDay
54%8%14%16%5%
3527
June1st to 15thDay
53%9%14%15%6%1
3183
16th to endDay
44%8%17%21%6%1
3150
July1st to 15thDay
38%11%18%22%7%1
2991
16th to endDay
30%10%17%27%12%1
3092
August1st to 15thDay
37%9%21%23%6%
2828
16th to endDay
30%9%18%30%10%1
2899
September1st to 15thDay
38%5%15%22%14%2
2504
16th to endDay
41%7%13%25%10%2
2310
October1st to 15thDay
48%7%13%20%8%
2143
16th to endDay
40%7%15%24%10%
2016
November1st to 15thDay
49%9%13%19%7%1
1825
16th to endDay
41%6%17%23%9%2
1587
December1st to 15thDay
48%8%13%17%9%1
1575
16th to endDay
45%8%15%18%9%2
1680
January1st to 15thNight
50%8%13%17%7%2
3360
16th to endNight
41%9%13%19%12%3
3418
February1st to 15thNight
46%7%12%20%10%2
3037
16th to endNight
48%7%11%19%11%1
2474
March1st to 15thNight
42%9%15%23%6%1
2651
16th to endNight
50%7%14%17%8%1
2606
April1st to 15thNight
55%6%12%15%8%
2137
16th to endNight
47%8%13%21%7%2
2007
May1st to 15thNight
45%6%13%23%9%
1771
16th to endNight
49%9%14%19%5%1
1645
June1st to 15thNight
48%8%14%18%9%
1486
16th to endNight
38%8%20%23%8%
1470
July1st to 15thNight
33%9%20%26%9%
1400
16th to endNight
27%8%16%31%13%1
1516
August1st to 15thNight
32%10%19%29%8%
1690
16th to endNight
25%7%19%30%13%2
2007
September1st to 15thNight
34%6%16%23%15%3
2114
16th to endNight
35%7%15%25%12%3
2310
October1st to 15thNight
44%7%13%22%10%1
2476
16th to endNight
37%8%16%25%11%
2912
November1st to 15thNight
43%9%14%21%11%
3008
16th to endNight
44%7%16%19%9%2
3360
December1st to 15thNight
48%7%13%20%7%1
3375
16th to endNight
48%7%12%20%9%
3600

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
10%7%13%37%20%10%
150
16th to endDay
8%323%45%16%4
160
February1st to 15thDay
10%8%27%36%11%5%
170
16th to endDay
7%6%28%38%17%1
298
March1st to 15thDay
9%14%36%25%11%3
450
16th to endDay
14%16%31%22%10%4
480
April1st to 15thDay
22%10%36%22%7%1
449
16th to endDay
21%15%26%25%9%2
438
May1st to 15thDay
18%7%28%23%18%3
566
16th to endDay
25%420%24%20%4
757
June1st to 15thDay
21%8%24%27%14%3
656
16th to endDay
16%427%28%18%4
645
July1st to 15thDay
14%422%30%23%4
625
16th to endDay
9%427%31%20%6%
616
August1st to 15thDay
17%221%31%21%5%
419
16th to endDay
11%5%25%33%18%7%
460
September1st to 15thDay
21%5%27%27%13%4
435
16th to endDay
21%11%21%29%11%3
435
October1st to 15thDay
24%7%18%32%13%3
310
16th to endDay
11%12%25%27%17%5%
240
November1st to 15thDay
20%5%27%36%7%4
225
16th to endDay
8%7%27%29%17%10%
154
December1st to 15thDay
4228%39%16%8%
150
16th to endDay
9%5%26%36%16%6%
160
January1st to 15thNight
9%8%32%38%10%1
1125
16th to endNight
9%8%34%36%9%1
1018
February1st to 15thNight
8%8%29%35%14%3
884
16th to endNight
8%333%33%18%2
792
March1st to 15thNight
7%6%35%34%12%3
900
16th to endNight
13%432%35%11%2
960
April1st to 15thNight
17%5%31%31%13%
787
16th to endNight
18%5%31%30%14%
669
May1st to 15thNight
16%5%28%33%15%
521
16th to endNight
22%223%30%19%
471
June1st to 15thNight
20%325%33%16%1
424
16th to endNight
14%319%37%24%
420
July1st to 15thNight
11%118%41%24%2
400
16th to endNight
9%117%43%23%2
440
August1st to 15thNight
12%113%36%32%4
456
16th to endNight
8%319%42%25%
669
September1st to 15thNight
18%218%33%23%3
778
16th to endNight
17%322%34%17%3
836
October1st to 15thNight
17%325%32%17%2
840
16th to endNight
11%430%37%13%1
896
November1st to 15thNight
13%7%35%34%8%1
1028
16th to endNight
9%6%37%33%10%1
1125
December1st to 15thNight
9%6%32%36%13%2
1125
16th to endNight
7%5%33%39%11%2
1200
Page generated at 2020-06-04 01:18:55. Version ac04

Copyright 2020 A. Danko


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