Emerald Lane Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Emerald Lane Observatory clear sky chart from 2005-11-06 to 2024-01-13.

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
46%
23430
23%
74114
16%
23377
54%
23377
28%
45210

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%
760
22%
2459
9%
757
37%
757
20%
1561
January11th to 20thNight
25%
729
21%
2317
10%
729
36%
729
17%
1601
January21st to endNight
25%
792
29%
2376
12%
792
42%
792
23%
1536
February1st to 10thNight
25%
720
22%
2160
10%
720
36%
720
23%
1430
February11th to 20thNight
23%
703
19%
2098
8%
699
33%
699
21%
1414
February21st to endNight
20%
592
21%
1776
8%
592
31%
592
18%
1248
March1st to 10thNight
30%
720
22%
2160
11%
720
39%
720
24%
1357
March11th to 20thNight
28%
720
18%
2074
10%
720
35%
720
24%
1372
March21st to endNight
31%
680
23%
2066
13%
680
41%
680
26%
1299
April1st to 10thNight
35%
540
27%
1800
17%
540
49%
540
29%
1033
April11th to 20thNight
38%
533
28%
1775
17%
533
54%
533
30%
998
April21st to endNight
42%
540
26%
1800
18%
540
53%
540
31%
999
May1st to 10thNight
50%
540
24%
1638
15%
540
58%
540
36%
941
May11th to 20thNight
53%
531
19%
1592
14%
531
57%
531
31%
963
May21st to endNight
64%
582
21%
1744
17%
582
67%
582
34%
1030
June1st to 10thNight
64%
540
20%
1620
16%
540
66%
540
31%
992
June11th to 20thNight
75%
540
22%
1613
18%
540
78%
540
45%
859
June21st to endNight
69%
540
21%
1440
15%
540
72%
540
42%
857
July1st to 10thNight
69%
525
15%
1421
12%
525
71%
525
32%
923
July11th to 20thNight
76%
522
18%
1566
16%
522
77%
522
35%
932
July21st to endNight
71%
591
17%
1689
16%
558
73%
558
31%
1043
August1st to 10thNight
82%
537
19%
1778
22%
534
83%
534
36%
999
August11th to 20thNight
72%
534
16%
1776
18%
534
73%
534
28%
1065
August21st to endNight
68%
594
21%
1980
25%
594
69%
594
27%
1210
September1st to 10thNight
72%
548
24%
1808
26%
548
72%
548
34%
1012
September11th to 20thNight
62%
720
23%
1980
18%
720
64%
720
33%
1233
September21st to endNight
64%
720
31%
1980
23%
720
70%
720
41%
1139
October1st to 10thNight
59%
720
34%
1980
27%
720
64%
720
43%
1106
October11th to 20thNight
47%
720
32%
1993
21%
720
57%
720
35%
1209
October21st to endNight
47%
792
30%
2520
26%
792
56%
792
31%
1444
November1st to 10thNight
52%
740
28%
2406
25%
740
60%
740
33%
1323
November11th to 20thNight
39%
760
29%
2470
20%
760
54%
760
32%
1396
November21st to endNight
38%
760
26%
2470
18%
760
49%
760
26%
1479
December1st to 10thNight
30%
760
24%
2470
14%
760
42%
760
20%
1599
December11th to 20thNight
32%
759
25%
2898
14%
758
44%
758
20%
1723
December21st to endNight
25%
826
14%
4421
12%
817
36%
817
11%
2885

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
12%6%35%6%35%5%6%8%41%
75140
Night
12%6%35%5%345%5%7%45%
74576
TransparencyDay
41%5%11%22%18%4
74862
Night
38%411%22%20%5%
74374
SeeingDay
15%10%22%24%19%10%
13697
Night
15%9%23%29%21%4
23443

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
17%9%35%5%3345%6%41%
1706
11th to 20thDay
20%10%46%5%2434438%
1683
21st to endDay
15%7%35%5%33446%45%
1980
February1st to 10thDay
17%11%35%5%3445%6%39%
1800
11th to 20thDay
19%8%47%7%34335%38%
1748
21st to endDay
20%9%36%6%34445%37%
1480
March1st to 10thDay
13%9%35%5%35%5%46%42%
1800
11th to 20thDay
16%8%37%5%35%5%5%6%36%
1885
21st to endDay
13%8%35%6%46%5%6%8%37%
2304
April1st to 10thDay
13%5%35%4345%5%8%46%
2160
11th to 20thDay
12%6%35%5%345%47%45%
2134
21st to endDay
10%6%25%5%35%47%9%44%
2160
May1st to 10thDay
12%5%26%435%45%8%46%
2320
11th to 20thDay
11%6%36%7%35%5%6%8%40%
2301
21st to endDay
8%5%36%5%36%6%6%9%42%
2531
June1st to 10thDay
9%6%36%6%47%7%6%9%37%
2340
11th to 20thDay
43245%47%7%8%11%45%
2340
21st to endDay
6%435%7%47%7%7%10%41%
2516
July1st to 10thDay
8%6%37%7%5%7%7%8%11%30%
2489
11th to 20thDay
7%426%6%6%7%8%8%12%33%
2340
21st to endDay
6%426%7%5%9%8%9%12%33%
2525
August1st to 10thDay
5%5%36%7%5%7%8%9%11%34%
2148
11th to 20thDay
8%5%25%7%5%7%8%9%9%35%
2125
21st to endDay
11%6%36%7%46%6%7%8%34%
2376
September1st to 10thDay
10%435%6%36%6%7%9%41%
2132
11th to 20thDay
10%5%26%6%35%5%6%8%43%
1980
21st to endDay
11%4243345%5%8%52%
1980
October1st to 10thDay
9%425%43445%5%55%
1980
11th to 20thDay
10%4145%3445%7%53%
1962
21st to endDay
14%5%25%423436%51%
1836
November1st to 10thDay
12%5%23424446%55%
1672
11th to 20thDay
11%7%24434446%51%
1710
21st to endDay
14%7%25%5%2445%6%44%
1710
December1st to 10thDay
19%7%37%6%346%5%5%36%
1710
11th to 20thDay
15%8%36%5%45%5%35%40%
2153
21st to endDay
14%10%5%7%6%45%46%7%33%
3124
January1st to 10thNight
17%7%36%434445%43%
2459
11th to 20thNight
17%9%46%6%34445%36%
2317
21st to endNight
15%9%36%434436%44%
2376
February1st to 10thNight
18%9%36%42445%6%40%
2160
11th to 20thNight
20%8%36%5%2434441%
2098
21st to endNight
21%7%36%6%345%45%36%
1776
March1st to 10thNight
15%7%2443445%7%43%
2160
11th to 20thNight
15%8%35%5%345%6%8%38%
2074
21st to endNight
13%7%35%5%345%6%6%44%
2066
April1st to 10thNight
11%5%146%345%6%8%47%
1800
11th to 20thNight
13%5%2442435%7%49%
1775
21st to endNight
11%5%24425%447%51%
1800
May1st to 10thNight
9%42443445%8%52%
1638
11th to 20thNight
9%5%35%5%35%46%10%44%
1592
21st to endNight
5%425%6%35%6%7%10%46%
1744
June1st to 10thNight
5%5%27%8%35%5%6%11%44%
1620
11th to 20thNight
32145%35%6%7%12%53%
1613
21st to endNight
5%4245%346%8%11%47%
1440
July1st to 10thNight
7%436%6%36%7%8%10%38%
1462
11th to 20thNight
5%425%446%7%7%13%42%
1620
21st to endNight
5%426%6%5%7%6%8%12%39%
1789
August1st to 10thNight
4215%5%46%8%9%12%44%
1790
11th to 20thNight
7%425%6%36%7%8%11%41%
1776
21st to endNight
9%5%35%6%47%46%9%42%
1980
September1st to 10thNight
8%4245%4446%9%50%
1808
11th to 20thNight
8%6%36%5%45%46%9%44%
1980
21st to endNight
7%42443445%8%55%
1980
October1st to 10thNight
11%413423346%59%
1980
11th to 20thNight
13%5%35%424445%52%
1993
21st to endNight
14%6%24323445%53%
2520
November1st to 10thNight
12%5%24324445%55%
2406
11th to 20thNight
12%5%24433345%53%
2470
21st to endNight
15%6%35%434446%47%
2470
December1st to 10thNight
17%9%35%5%3445%7%38%
2470
11th to 20thNight
15%7%35%424346%47%
3042
21st to endNight
15%9%48%6%45%6%5%7%31%
4532

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
45%38%21%19%4
1707
11th to 20thDay
51%27%19%18%3
1683
21st to endDay
41%36%24%22%4
1980
February1st to 10thDay
48%37%20%19%3
1800
11th to 20thDay
52%25%20%16%4
1758
21st to endDay
50%37%14%19%6%
1480
March1st to 10thDay
43%5%7%17%20%8%
1800
11th to 20thDay
49%5%11%15%17%4
1885
21st to endDay
45%411%23%15%2
2304
April1st to 10thDay
37%311%26%16%6%
2160
11th to 20thDay
39%47%21%23%6%
2134
21st to endDay
36%49%29%20%2
2160
May1st to 10thDay
38%411%25%17%4
2320
11th to 20thDay
42%5%13%24%15%1
2305
21st to endDay
37%6%15%25%16%2
2531
June1st to 10thDay
42%6%14%21%17%1
2340
11th to 20thDay
30%7%16%28%17%2
2340
21st to endDay
36%7%16%21%15%4
2516
July1st to 10thDay
44%7%17%20%10%2
2421
11th to 20thDay
37%9%22%19%9%3
2271
21st to endDay
41%7%19%23%9%1
2384
August1st to 10thDay
38%7%20%24%9%1
2136
11th to 20thDay
41%6%17%21%13%1
2125
21st to endDay
45%6%13%22%10%3
2376
September1st to 10thDay
38%6%16%18%17%4
2132
11th to 20thDay
38%5%13%18%22%4
1980
21st to endDay
32%49%26%21%8%
1980
October1st to 10thDay
32%46%24%27%7%
1980
11th to 20thDay
32%38%23%26%8%
1962
21st to endDay
36%3419%29%9%
1836
November1st to 10thDay
32%37%21%29%9%
1672
11th to 20thDay
36%35%21%27%8%
1710
21st to endDay
41%35%20%24%6%
1710
December1st to 10thDay
51%37%17%18%5%
1710
11th to 20thDay
48%35%21%19%4
2150
21st to endDay
51%28%22%13%3
3124
January1st to 10thNight
45%28%21%20%4
2459
11th to 20thNight
51%47%19%16%3
2317
21st to endNight
44%25%22%22%5%
2376
February1st to 10thNight
46%37%20%20%4
2160
11th to 20thNight
47%37%19%18%6%
2099
21st to endNight
52%35%16%17%6%
1776
March1st to 10thNight
41%38%17%21%10%
2160
11th to 20thNight
44%412%19%17%4
2074
21st to endNight
41%39%26%18%3
2066
April1st to 10thNight
35%411%25%20%5%
1800
11th to 20thNight
35%38%22%23%11%
1775
21st to endNight
33%410%29%21%4
1800
May1st to 10thNight
31%5%12%24%25%4
1638
11th to 20thNight
36%5%19%21%17%2
1593
21st to endNight
32%6%15%27%16%3
1745
June1st to 10thNight
36%6%15%23%18%3
1620
11th to 20thNight
24%5%19%29%20%3
1613
21st to endNight
28%6%18%26%18%4
1440
July1st to 10thNight
37%7%22%21%10%3
1421
11th to 20thNight
30%9%23%23%12%3
1566
21st to endNight
35%7%22%23%11%1
1689
August1st to 10thNight
28%8%21%30%12%1
1778
11th to 20thNight
34%9%21%21%12%3
1776
21st to endNight
38%6%17%23%11%4
1980
September1st to 10thNight
31%6%18%22%19%4
1808
11th to 20thNight
35%6%15%17%23%4
1980
21st to endNight
29%49%24%25%9%
1980
October1st to 10thNight
27%36%24%29%10%
1980
11th to 20thNight
36%36%22%22%11%
1993
21st to endNight
35%2420%29%10%
2520
November1st to 10thNight
32%37%21%24%12%
2406
11th to 20thNight
34%27%18%28%11%
2470
21st to endNight
39%35%22%24%6%
2470
December1st to 10thNight
46%38%20%19%3
2470
11th to 20thNight
41%36%20%26%5%
3044
21st to endNight
52%37%19%16%2
4532

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%27%34%12%4
270
11th to 20thDay
30%19%33%11%6%2
246
21st to endDay
21%27%35%14%4
264
February1st to 10thDay
24%25%33%16%1
240
11th to 20thDay
36%18%34%11%
240
21st to endDay
34%19%35%10%2
198
March1st to 10thDay
24%23%33%15%31
240
11th to 20thDay
22%20%33%18%5%1
325
21st to endDay
22%19%34%18%7%
462
April1st to 10thDay
17%16%31%23%10%2
420
11th to 20thDay
17%16%30%24%12%1
412
21st to endDay
15%14%29%29%10%2
420
May1st to 10thDay
16%8%31%26%13%6%
423
11th to 20thDay
12%6%23%28%21%10%
447
21st to endDay
11%5%19%29%22%14%
485
June1st to 10thDay
14%314%29%25%15%
450
11th to 20thDay
4315%29%26%23%
450
21st to endDay
8%317%28%28%15%
626
July1st to 10thDay
10%28%28%32%20%
591
11th to 20thDay
7%26%24%30%31%
444
21st to endDay
7%18%24%35%26%
488
August1st to 10thDay
9%110%24%33%24%
446
11th to 20thDay
10%18%30%36%16%
439
21st to endDay
16%28%20%33%21%
495
September1st to 10thDay
9%28%28%36%16%
450
11th to 20thDay
11%311%27%30%18%
450
21st to endDay
14%314%29%32%9%
450
October1st to 10thDay
12%320%30%26%8%
450
11th to 20thDay
13%9%29%35%12%3
432
21st to endDay
23%13%22%29%10%2
297
November1st to 10thDay
19%11%27%28%13%3
270
11th to 20thDay
13%17%39%24%6%
270
21st to endDay
17%19%32%22%8%2
270
December1st to 10thDay
29%18%27%20%6%
270
11th to 20thDay
20%23%32%14%11%
270
21st to endDay
21%20%41%13%5%1
297
January1st to 10thNight
22%19%34%21%5%
760
11th to 20thNight
22%18%30%22%7%
729
21st to endNight
20%18%35%25%2
792
February1st to 10thNight
22%15%34%24%5%
720
11th to 20thNight
27%15%32%24%3
703
21st to endNight
26%17%33%22%2
592
March1st to 10thNight
19%18%30%28%5%
720
11th to 20thNight
19%13%35%23%8%1
720
21st to endNight
17%14%33%25%11%
680
April1st to 10thNight
14%11%35%27%13%
540
11th to 20thNight
15%9%33%28%13%1
533
21st to endNight
14%9%31%29%16%1
540
May1st to 10thNight
10%6%29%31%20%3
540
11th to 20thNight
11%422%34%24%5%
531
21st to endNight
6%216%36%34%7%
584
June1st to 10thNight
6%215%35%36%6%
540
11th to 20thNight
4210%33%40%9%
540
21st to endNight
7%111%30%43%8%
540
July1st to 10thNight
8%27%28%43%12%
525
11th to 20thNight
7%15%29%42%17%
522
21st to endNight
7%27%29%42%13%
591
August1st to 10thNight
41228%53%11%
537
11th to 20thNight
9%15%33%42%10%
534
21st to endNight
11%26%29%42%10%
594
September1st to 10thNight
9%18%30%44%8%
548
11th to 20thNight
9%314%29%37%8%
720
21st to endNight
9%314%34%37%3
720
October1st to 10thNight
12%419%29%28%7%
720
11th to 20thNight
15%6%25%34%18%2
720
21st to endNight
18%8%22%31%20%2
792
November1st to 10thNight
15%8%20%34%20%3
740
11th to 20thNight
16%10%31%31%11%2
760
21st to endNight
19%11%28%30%11%1
760
December1st to 10thNight
23%15%26%29%7%
760
11th to 20thNight
22%13%30%26%9%
760
21st to endNight
23%15%30%26%6%
836
Page generated at 2024-01-10 00:25:05. Version ac07

Copyright 2024 Attilla Danko


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