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 2017-12-20.

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%
15590
14%
48051
9%
15559
48%
15559
22%
32245

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
33%
899
12%
2685
7%
895
38%
895
16%
1960
January16th to endNight
36%
814
18%
2734
12%
814
46%
814
20%
1804
February1st to 15thNight
42%
700
13%
2419
11%
697
48%
697
19%
1600
February16th to endNight
39%
632
13%
1974
11%
632
44%
632
19%
1393
March1st to 15thNight
35%
720
14%
2121
8%
720
42%
720
20%
1493
March16th to endNight
32%
768
12%
2085
4%
768
38%
768
19%
1535
April1st to 15thNight
34%
629
11%
1709
5%
629
37%
629
18%
1272
April16th to endNight
37%
540
12%
1620
9%
540
39%
540
18%
1164
May1st to 15thNight
43%
416
11%
1417
10%
416
48%
416
21%
927
May16th to endNight
43%
374
5%
1309
3%
374
45%
374
15%
933
June1st to 15thNight
43%
360
0%
1260
0%
360
44%
360
15%
911
June16th to endNight
54%
360
1%
1260
0%
360
54%
360
24%
796
July1st to 15thNight
64%
340
2%
1190
0%
340
65%
340
28%
694
July16th to endNight
62%
376
10%
1284
11%
354
65%
354
31%
714
August1st to 15thNight
65%
396
12%
1468
15%
394
67%
394
26%
855
August16th to endNight
65%
573
21%
1719
18%
573
68%
573
42%
923
September1st to 15thNight
58%
667
17%
1813
12%
667
59%
667
36%
1116
September16th to endNight
56%
716
21%
1980
15%
716
61%
716
36%
1200
October1st to 15thNight
44%
720
16%
2122
10%
720
50%
720
23%
1444
October16th to endNight
44%
768
20%
2496
14%
768
53%
768
25%
1583
November1st to 15thNight
37%
888
17%
2598
10%
888
45%
888
23%
1746
November16th to endNight
34%
975
15%
2912
7%
975
42%
975
21%
1976
December1st to 15thNight
40%
975
14%
2925
10%
975
43%
975
19%
2100
December16th to endNight
38%
984
15%
2951
9%
984
44%
984
18%
2106

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%5%35%5%6%8%34%
48825
Night
8%8%36%6%35%5%6%8%37%
48202
Cloud CoverDay
10%8%36%6%35%5%6%8%34%
48826
Night
8%9%47%6%35%5%6%8%36%
48205
TransparencyDay
45%8%15%20%8%1
48480
Night
42%8%15%22%9%1
48051
SeeingDay
16%7%26%29%15%4
6278
Night
12%5%29%35%15%2
15597

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%10%5%7%5%25%46%8%36%
1253
16th to endDay
5%11%48%5%45%46%9%34%
1500
February1st to 15thDay
49%48%5%46%6%7%8%32%
1443
16th to endDay
410%6%9%7%5%6%5%7%7%28%
1500
March1st to 15thDay
49%48%8%46%5%6%8%32%
1839
16th to endDay
7%14%6%9%7%37%5%7%7%24%
2138
April1st to 15thDay
12%16%6%6%6%35%46%7%25%
2238
16th to endDay
13%12%47%6%45%5%6%7%28%
2340
May1st to 15thDay
12%9%36%6%35%5%6%7%32%
2531
16th to endDay
22%8%37%5%35%5%6%8%23%
2802
June1st to 15thDay
21%8%36%6%45%5%6%7%25%
2700
16th to endDay
14%5%35%6%35%5%6%9%33%
2700
July1st to 15thDay
11%424435%6%7%9%40%
2700
16th to endDay
6%3145%25%6%7%9%46%
2795
August1st to 15thDay
12%5%245%25%5%7%8%40%
2484
16th to endDay
9%3144245%6%9%48%
2483
September1st to 15thDay
13%6%24423346%49%
2145
16th to endDay
9%6%35%5%2445%8%44%
1980
October1st to 15thDay
14%10%37%5%4445%7%32%
1837
16th to endDay
7%9%36%5%346%6%8%37%
1728
November1st to 15thDay
7%11%47%7%3447%7%34%
1577
16th to endDay
6%11%38%5%2446%7%40%
1375
December1st to 15thDay
38%412%7%5%7%6%5%7%31%
1365
16th to endDay
311%48%5%45%6%8%10%31%
1372
January1st to 15thNight
6%10%5%8%8%46%6%6%8%28%
2685
16th to endNight
5%10%5%7%5%35%5%7%8%35%
2734
February1st to 15thNight
5%9%47%5%46%46%8%36%
2408
16th to endNight
410%5%10%7%35%6%5%7%32%
1974
March1st to 15thNight
38%5%8%8%45%5%7%9%32%
2121
16th to endNight
6%13%6%8%6%35%6%6%8%28%
2082
April1st to 15thNight
12%12%48%5%35%45%7%29%
1709
16th to endNight
13%11%47%5%245%5%7%31%
1620
May1st to 15thNight
12%7%36%5%345%6%7%36%
1416
16th to endNight
21%5%25%6%35%5%5%7%31%
1309
June1st to 15thNight
17%7%37%5%35%45%6%30%
1260
16th to endNight
12%5%25%435%6%6%9%38%
1260
July1st to 15thNight
7%324436%5%5%10%46%
1260
16th to endNight
6%5%143245%6%7%51%
1372
August1st to 15thNight
10%3244235%6%10%45%
1476
16th to endNight
7%41221345%8%56%
1719
September1st to 15thNight
12%6%1232335%7%50%
1813
16th to endNight
10%41342445%8%49%
1980
October1st to 15thNight
12%8%35%5%345%6%7%37%
2122
16th to endNight
7%9%25%5%345%6%8%40%
2496
November1st to 15thNight
5%11%35%5%35%5%6%7%40%
2598
16th to endNight
5%10%48%6%45%45%7%37%
2912
December1st to 15thNight
410%5%9%8%46%6%6%7%32%
2925
16th to endNight
39%410%8%45%6%6%7%30%
2951

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%11%5%7%5%35%5%6%8%34%
1253
16th to endDay
6%11%47%6%36%5%7%9%32%
1500
February1st to 15thDay
5%9%5%8%7%47%5%7%8%31%
1443
16th to endDay
5%10%7%9%7%46%6%6%7%28%
1500
March1st to 15thDay
410%5%9%8%36%6%5%8%31%
1839
16th to endDay
8%13%6%8%8%35%5%6%8%24%
2139
April1st to 15thDay
11%16%6%8%5%245%6%7%24%
2238
16th to endDay
14%12%36%6%35%5%6%7%28%
2340
May1st to 15thDay
11%8%36%7%35%5%6%7%33%
2531
16th to endDay
22%8%25%7%35%5%6%8%24%
2802
June1st to 15thDay
20%7%36%6%36%5%5%7%25%
2700
16th to endDay
13%6%26%5%35%6%7%8%33%
2700
July1st to 15thDay
10%415%5%346%7%9%40%
2700
16th to endDay
6%314425%6%7%9%46%
2795
August1st to 15thDay
12%5%24425%5%7%8%40%
2484
16th to endDay
9%31442346%8%49%
2483
September1st to 15thDay
13%6%24423346%48%
2145
16th to endDay
9%7%36%5%23449%43%
1980
October1st to 15thDay
14%10%37%5%3446%7%32%
1837
16th to endDay
6%9%46%5%35%6%6%8%37%
1728
November1st to 15thDay
7%11%5%8%6%345%6%7%33%
1577
16th to endDay
6%12%47%6%3336%7%38%
1375
December1st to 15thDay
49%5%10%8%47%5%6%6%30%
1365
16th to endDay
312%49%6%35%6%7%10%30%
1372
January1st to 15thNight
6%10%5%9%9%45%6%6%8%27%
2685
16th to endNight
5%11%47%435%5%7%9%34%
2734
February1st to 15thNight
6%9%47%5%46%5%6%8%35%
2408
16th to endNight
410%6%9%8%5%5%6%5%7%30%
1974
March1st to 15thNight
310%48%7%45%6%7%9%30%
2121
16th to endNight
7%13%6%8%6%347%6%8%28%
2085
April1st to 15thNight
12%12%48%6%36%448%28%
1709
16th to endNight
12%11%5%6%5%345%6%8%30%
1620
May1st to 15thNight
10%9%46%5%3445%7%37%
1416
16th to endNight
19%6%25%5%37%35%9%30%
1309
June1st to 15thNight
17%9%37%435%5%5%8%29%
1260
16th to endNight
11%5%25%5%45%5%7%8%37%
1260
July1st to 15thNight
7%315%4445%6%8%46%
1260
16th to endNight
6%43342446%7%52%
1372
August1st to 15thNight
10%3144336%6%9%44%
1476
16th to endNight
7%41231345%8%56%
1719
September1st to 15thNight
12%5%1332346%7%49%
1813
16th to endNight
10%41432445%8%49%
1980
October1st to 15thNight
11%9%36%5%3446%8%36%
2122
16th to endNight
7%8%35%5%246%6%8%40%
2496
November1st to 15thNight
6%10%36%5%346%5%7%39%
2598
16th to endNight
5%11%5%7%6%45%5%5%8%35%
2912
December1st to 15thNight
410%5%9%8%5%5%6%6%7%31%
2925
16th to endNight
39%410%9%46%6%6%7%29%
2951

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
44%7%15%24%6%2
1253
16th to endDay
45%7%15%17%10%3
1500
February1st to 15thDay
45%9%16%19%7%2
1443
16th to endDay
50%10%12%17%8%
1500
March1st to 15thDay
47%9%18%17%6%
1839
16th to endDay
56%8%14%15%5%
2139
April1st to 15thDay
56%7%14%14%6%
2238
16th to endDay
52%8%12%17%7%1
2340
May1st to 15thDay
46%8%14%19%9%
2531
16th to endDay
56%8%13%15%4
2807
June1st to 15thDay
55%9%13%14%5%1
2700
16th to endDay
44%8%17%20%6%1
2700
July1st to 15thDay
37%11%19%22%7%1
2541
16th to endDay
31%11%18%27%10%
2620
August1st to 15thDay
38%10%21%22%6%
2467
16th to endDay
30%9%17%29%10%1
2483
September1st to 15thDay
36%5%15%23%16%3
2145
16th to endDay
37%7%13%27%11%2
1980
October1st to 15thDay
49%7%13%19%9%
1837
16th to endDay
41%8%16%24%8%
1728
November1st to 15thDay
46%9%13%21%8%1
1577
16th to endDay
41%6%17%23%8%2
1375
December1st to 15thDay
50%9%13%17%8%1
1365
16th to endDay
44%8%15%19%9%1
1372
January1st to 15thNight
50%8%13%17%6%2
2685
16th to endNight
41%9%13%20%11%3
2734
February1st to 15thNight
44%8%14%21%9%1
2419
16th to endNight
48%8%11%19%11%
1974
March1st to 15thNight
44%10%17%21%5%
2121
16th to endNight
51%7%14%17%8%
2085
April1st to 15thNight
54%6%13%16%8%
1709
16th to endNight
49%8%13%21%6%1
1620
May1st to 15thNight
44%6%13%24%10%
1417
16th to endNight
50%8%15%18%41
1309
June1st to 15thNight
51%9%13%16%8%
1260
16th to endNight
39%8%20%24%7%
1260
July1st to 15thNight
32%9%21%27%8%
1190
16th to endNight
28%9%17%30%11%1
1284
August1st to 15thNight
32%10%19%28%8%
1468
16th to endNight
23%6%19%31%14%2
1719
September1st to 15thNight
32%6%16%22%17%3
1813
16th to endNight
30%7%16%27%13%4
1980
October1st to 15thNight
44%7%14%22%10%1
2122
16th to endNight
37%8%17%25%10%
2496
November1st to 15thNight
41%8%14%21%12%
2598
16th to endNight
44%7%17%18%9%3
2912
December1st to 15thNight
49%8%13%20%6%1
2925
16th to endNight
48%8%13%20%7%
2951

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
15%5%11%30%18%20%
60
16th to endDay
6%6%15%39%23%9%
64
February1st to 15thDay
10%10%20%41%13%4
68
16th to endDay
10%5%27%38%16%
159
March1st to 15thDay
7%14%46%24%6%
270
16th to endDay
13%20%34%22%7%1
288
April1st to 15thDay
23%12%34%22%5%1
269
16th to endDay
23%14%26%26%7%2
270
May1st to 15thDay
16%7%31%23%16%3
366
16th to endDay
24%5%20%24%20%4
517
June1st to 15thDay
22%8%23%28%13%3
495
16th to endDay
16%428%30%16%4
495
July1st to 15thDay
13%420%30%25%5%
475
16th to endDay
8%428%34%18%4
464
August1st to 15thDay
17%222%31%19%5%
315
16th to endDay
10%6%25%34%15%7%
332
September1st to 15thDay
18%6%25%29%14%5%
315
16th to endDay
14%10%22%33%13%4
315
October1st to 15thDay
23%7%20%32%12%3
208
16th to endDay
14%8%26%29%15%5%
144
November1st to 15thDay
20%325%37%7%5%
135
16th to endDay
6%7%32%27%15%10%
92
December1st to 15thDay
2230%38%17%8%
90
16th to endDay
15%5%25%26%19%8%
72
January1st to 15thNight
10%9%33%35%9%2
900
16th to endNight
10%9%32%35%10%1
814
February1st to 15thNight
9%8%28%33%15%4
704
16th to endNight
9%333%33%17%3
632
March1st to 15thNight
7%5%40%34%10%2
720
16th to endNight
13%5%33%35%10%1
768
April1st to 15thNight
17%6%30%31%14%1
629
16th to endNight
20%429%31%14%
540
May1st to 15thNight
14%5%29%32%17%
417
16th to endNight
23%222%31%18%
375
June1st to 15thNight
21%324%33%16%1
360
16th to endNight
13%320%38%23%1
360
July1st to 15thNight
9%117%41%27%3
340
16th to endNight
9%118%44%22%2
376
August1st to 15thNight
12%114%34%32%4
396
16th to endNight
7%319%41%27%
573
September1st to 15thNight
16%218%32%25%4
667
16th to endNight
12%322%36%20%4
716
October1st to 15thNight
18%326%31%16%3
720
16th to endNight
12%429%38%13%1
768
November1st to 15thNight
12%7%34%34%8%2
888
16th to endNight
9%6%39%33%8%1
975
December1st to 15thNight
9%6%31%36%13%2
975
16th to endNight
7%5%32%39%12%2
984
Page generated at 2017-12-21 05:04:44. Version ac04

Copyright 2017 A. Danko


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