Ore Lake Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Ore Lake Observatory clear sky chart from 2005-11-05 to 2019-06-24.

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
37%
18300
15%
54153
10%
18258
43%
18258
21%
37487

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
19%
1050
11%
2926
4%
1045
25%
1045
13%
2265
January16th to endNight
20%
1013
8%
3029
3%
1013
25%
1013
12%
2368
February1st to 15thNight
18%
821
9%
2633
3%
821
24%
821
11%
2047
February16th to endNight
23%
735
14%
2205
6%
735
31%
735
15%
1616
March1st to 15thNight
27%
840
16%
2433
9%
840
33%
840
18%
1742
March16th to endNight
33%
896
19%
2464
11%
896
40%
896
23%
1696
April1st to 15thNight
28%
674
14%
2111
7%
674
35%
674
18%
1468
April16th to endNight
35%
624
19%
1870
8%
624
45%
624
24%
1249
May1st to 15thNight
38%
630
14%
1890
9%
630
43%
630
21%
1314
May16th to endNight
50%
658
14%
1952
10%
657
55%
657
29%
1242
June1st to 15thNight
55%
630
15%
1680
11%
630
59%
630
33%
1067
June16th to endNight
57%
609
15%
1624
12%
609
61%
609
36%
1018
July1st to 15thNight
67%
555
18%
1480
16%
555
70%
555
41%
864
July16th to endNight
69%
612
20%
1627
16%
579
72%
579
41%
933
August1st to 15thNight
68%
575
21%
1715
17%
572
71%
572
36%
1007
August16th to endNight
63%
621
21%
1899
17%
621
67%
621
33%
1126
September1st to 15thNight
60%
715
26%
2080
20%
715
64%
715
34%
1231
September16th to endNight
59%
777
25%
2145
19%
777
63%
777
35%
1307
October1st to 15thNight
45%
780
19%
2233
15%
780
49%
780
26%
1486
October16th to endNight
26%
832
17%
2616
10%
832
36%
832
19%
1794
November1st to 15thNight
33%
820
18%
2666
15%
820
40%
820
21%
1775
November16th to endNight
24%
840
14%
2741
9%
840
31%
840
14%
1988
December1st to 15thNight
20%
873
9%
2973
5%
873
26%
873
11%
2257
December16th to endNight
16%
1120
8%
3161
2%
1120
21%
1120
9%
2627

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
14%9%37%6%35%45%7%32%
54652
Night
15%8%36%5%3445%6%35%
54330
Cloud CoverDay
14%8%47%6%35%45%7%32%
54662
Night
15%8%36%5%3445%6%35%
54334
TransparencyDay
49%5%11%20%11%1
54348
Night
48%411%21%11%1
54153
SeeingDay
19%7%26%23%15%6%
8170
Night
19%7%27%30%12%1
18304

By Month

Percentage Cloud Cover NE (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
16%16%5%11%7%445%45%16%
1672
16th to endDay
17%16%7%9%7%45%5%45%17%
1897
February1st to 15thDay
16%14%7%10%10%35%445%19%
1887
16th to endDay
16%14%6%11%8%24446%21%
1840
March1st to 15thDay
16%12%48%6%3445%6%27%
2176
16th to endDay
17%10%47%5%34436%31%
2464
April1st to 15thDay
19%11%45%6%34446%29%
2509
16th to endDay
17%8%36%5%23346%37%
2695
May1st to 15thDay
19%8%36%6%35%35%6%30%
2721
16th to endDay
12%7%26%5%35%45%9%37%
2864
June1st to 15thDay
11%5%25%5%345%6%8%40%
2940
16th to endDay
11%425%6%36%5%7%10%34%
2843
July1st to 15thDay
6%5%15%5%35%5%6%9%46%
2730
16th to endDay
8%5%35%5%45%5%7%10%38%
2788
August1st to 15thDay
8%5%26%6%47%5%5%9%38%
2487
16th to endDay
11%5%26%5%35%5%6%8%38%
2653
September1st to 15thDay
12%5%25%5%45%45%8%40%
2197
16th to endDay
11%5%25%5%345%6%8%40%
2145
October1st to 15thDay
14%7%36%7%34446%37%
2057
16th to endDay
20%9%45%6%34346%32%
1957
November1st to 15thDay
16%9%36%6%3435%6%34%
1852
16th to endDay
17%13%47%6%25%446%27%
1873
December1st to 15thDay
15%14%6%11%7%24445%22%
1644
16th to endDay
21%15%9%10%6%43345%16%
1761
January1st to 15thNight
20%12%5%7%6%34445%24%
2926
16th to endNight
13%12%7%12%7%45%5%45%20%
3029
February1st to 15thNight
17%15%5%8%6%35%44424%
2631
16th to endNight
17%10%49%7%3435%6%27%
2205
March1st to 15thNight
16%9%46%6%33447%32%
2421
16th to endNight
15%7%46%5%345%46%36%
2464
April1st to 15thNight
18%9%35%5%3445%6%32%
2111
16th to endNight
17%7%245%2445%6%38%
1870
May1st to 15thNight
18%6%36%5%35%45%7%34%
1890
16th to endNight
12%425%5%35%448%43%
1950
June1st to 15thNight
10%425%43446%8%45%
1680
16th to endNight
9%5%344245%6%10%42%
1624
July1st to 15thNight
7%31443445%9%52%
1560
16th to endNight
44145%3446%9%52%
1729
August1st to 15thNight
5%4235%45%5%5%8%49%
1726
16th to endNight
8%5%25%42345%6%51%
1899
September1st to 15thNight
11%5%1432345%6%50%
2080
16th to endNight
10%5%25%43335%7%48%
2145
October1st to 15thNight
15%6%26%5%2445%6%39%
2233
16th to endNight
19%9%36%434445%35%
2616
November1st to 15thNight
16%8%35%5%3445%6%36%
2666
16th to endNight
20%12%46%5%33346%28%
2741
December1st to 15thNight
19%12%5%9%6%35%445%23%
2973
16th to endNight
21%16%6%10%6%44445%16%
3161

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 15thDay
17%16%5%10%8%45%5%4417%
1672
16th to endDay
18%16%7%8%8%44435%17%
1897
February1st to 15thDay
16%14%6%11%9%35%35%419%
1887
16th to endDay
16%14%5%11%7%2435%6%21%
1840
March1st to 15thDay
17%11%47%6%35%45%6%27%
2187
16th to endDay
17%10%5%7%5%24436%31%
2463
April1st to 15thDay
20%10%45%5%24446%29%
2509
16th to endDay
17%7%36%5%23446%37%
2695
May1st to 15thDay
19%7%36%6%35%446%31%
2721
16th to endDay
13%6%26%5%35%45%9%37%
2864
June1st to 15thDay
11%5%25%5%35%5%5%8%40%
2940
16th to endDay
11%5%35%6%36%5%7%10%34%
2843
July1st to 15thDay
6%5%245%345%6%9%46%
2730
16th to endDay
8%5%26%6%35%5%7%10%38%
2788
August1st to 15thDay
8%436%6%46%6%6%9%38%
2487
16th to endDay
11%5%26%6%35%5%7%8%38%
2653
September1st to 15thDay
12%5%245%45%5%5%8%40%
2197
16th to endDay
11%5%35%5%35%5%6%8%40%
2145
October1st to 15thDay
15%7%36%6%34446%37%
2057
16th to endDay
20%9%36%5%24346%32%
1957
November1st to 15thDay
16%9%36%5%3445%6%34%
1852
16th to endDay
17%12%48%6%34445%28%
1873
December1st to 15thDay
15%14%7%10%7%24446%22%
1644
16th to endDay
21%16%8%10%7%3434416%
1761
January1st to 15thNight
20%13%48%6%34345%24%
2926
16th to endNight
13%12%7%11%8%345%45%20%
3029
February1st to 15thNight
16%16%5%8%6%35%44425%
2624
16th to endNight
17%10%48%7%34446%27%
2205
March1st to 15thNight
16%9%46%6%33446%32%
2433
16th to endNight
15%8%35%5%345%5%7%36%
2464
April1st to 15thNight
18%8%35%5%345%47%32%
2111
16th to endNight
17%7%2442445%6%38%
1870
May1st to 15thNight
18%6%36%5%35%447%34%
1889
16th to endNight
13%425%5%35%45%8%42%
1950
June1st to 15thNight
10%415%44446%8%44%
1680
16th to endNight
9%435%4236%7%9%42%
1624
July1st to 15thNight
6%31432446%8%52%
1560
16th to endNight
44145%25%45%10%51%
1729
August1st to 15thNight
5%4245%35%46%8%49%
1726
16th to endNight
9%425%424447%50%
1899
September1st to 15thNight
11%42442445%6%50%
2080
16th to endNight
10%5%2442436%7%48%
2145
October1st to 15thNight
15%6%35%5%2445%6%39%
2233
16th to endNight
20%8%35%5%24445%35%
2616
November1st to 15thNight
16%8%35%5%34446%37%
2666
16th to endNight
20%11%5%5%5%34346%28%
2741
December1st to 15thNight
19%12%5%8%6%345%45%23%
2973
16th to endNight
21%16%6%9%6%34445%16%
3161

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
67%410%13%4
1673
16th to endDay
68%410%11%4
1897
February1st to 15thDay
66%48%14%5%
1889
16th to endDay
63%310%15%5%
1840
March1st to 15thDay
57%411%17%7%1
2187
16th to endDay
53%310%21%9%1
2464
April1st to 15thDay
55%410%18%11%
2509
16th to endDay
47%412%17%15%2
2695
May1st to 15thDay
52%5%11%19%9%1
2721
16th to endDay
44%413%23%12%1
2868
June1st to 15thDay
39%5%12%25%14%1
2940
16th to endDay
42%7%12%21%15%1
2843
July1st to 15thDay
34%6%10%24%20%4
2581
16th to endDay
39%7%12%21%16%2
2628
August1st to 15thDay
40%6%12%25%13%1
2474
16th to endDay
40%7%10%24%15%1
2653
September1st to 15thDay
41%6%11%25%13%1
2197
16th to endDay
39%5%10%30%14%
2145
October1st to 15thDay
46%5%11%22%12%1
2057
16th to endDay
52%414%19%8%
1957
November1st to 15thDay
49%410%21%11%1
1852
16th to endDay
57%412%19%5%
1873
December1st to 15thDay
62%312%15%4
1644
16th to endDay
71%410%9%3
1761
January1st to 15thNight
61%311%16%7%
2926
16th to endNight
62%413%13%4
3029
February1st to 15thNight
62%5%10%14%6%
2633
16th to endNight
56%311%19%7%
2205
March1st to 15thNight
52%410%19%11%1
2433
16th to endNight
47%411%24%11%1
2464
April1st to 15thNight
50%411%19%13%
2111
16th to endNight
45%411%18%17%3
1870
May1st to 15thNight
49%5%10%22%10%2
1890
16th to endNight
39%5%13%24%14%2
1952
June1st to 15thNight
36%5%12%27%15%1
1680
16th to endNight
34%5%16%25%16%1
1624
July1st to 15thNight
29%5%10%29%21%3
1480
16th to endNight
27%5%16%26%20%3
1627
August1st to 15thNight
30%6%13%32%15%2
1715
16th to endNight
33%6%11%27%18%3
1899
September1st to 15thNight
33%5%10%28%20%2
2080
16th to endNight
34%410%31%17%1
2145
October1st to 15thNight
43%411%22%16%
2233
16th to endNight
49%312%23%10%
2616
November1st to 15thNight
47%412%22%12%1
2666
16th to endNight
56%312%19%6%
2741
December1st to 15thNight
61%5%12%14%6%
2973
16th to endNight
68%5%10%11%3
3161

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
20%12%38%20%5%2
180
16th to endDay
30%13%41%11%2
192
February1st to 15thDay
31%16%37%13%1
180
16th to endDay
28%16%33%19%1
159
March1st to 15thDay
28%10%31%24%5%
267
16th to endDay
23%7%30%27%9%1
416
April1st to 15thDay
24%13%31%21%7%1
390
16th to endDay
26%7%29%16%14%5%
379
May1st to 15thDay
26%5%28%20%13%4
408
16th to endDay
17%9%23%24%17%8%
476
June1st to 15thDay
13%5%29%31%16%3
645
16th to endDay
15%5%28%27%17%5%
611
July1st to 15thDay
9%5%22%26%23%12%
550
16th to endDay
11%419%27%25%11%
504
August1st to 15thDay
9%115%29%24%18%
358
16th to endDay
15%415%22%27%15%
396
September1st to 15thDay
14%215%21%25%20%
375
16th to endDay
14%5%16%22%28%13%
374
October1st to 15thDay
21%5%24%26%16%6%
375
16th to endDay
25%10%28%29%5%
277
November1st to 15thDay
21%12%28%23%11%1
180
16th to endDay
26%17%33%18%4
175
December1st to 15thDay
22%18%33%13%12%
120
16th to endDay
26%23%32%14%2
183
January1st to 15thNight
26%12%33%21%5%
1050
16th to endNight
20%11%35%26%5%
1013
February1st to 15thNight
26%12%33%23%3
824
16th to endNight
24%11%31%28%3
735
March1st to 15thNight
21%11%32%27%6%
840
16th to endNight
18%10%30%29%9%1
896
April1st to 15thNight
21%10%33%27%5%
674
16th to endNight
21%6%32%28%10%1
624
May1st to 15thNight
22%5%27%32%10%1
630
16th to endNight
15%324%34%18%2
659
June1st to 15thNight
12%222%48%14%
630
16th to endNight
11%120%43%21%1
609
July1st to 15thNight
9%114%41%29%3
555
16th to endNight
5%214%46%27%3
612
August1st to 15thNight
7%114%45%27%4
575
16th to endNight
11%113%35%33%4
621
September1st to 15thNight
13%316%31%27%6%
715
16th to endNight
12%415%33%28%6%
777
October1st to 15thNight
19%5%23%31%17%2
780
16th to endNight
24%10%33%24%5%
832
November1st to 15thNight
20%9%28%28%11%1
820
16th to endNight
27%12%30%21%7%
840
December1st to 15thNight
25%11%34%23%5%
873
16th to endNight
30%10%33%21%3
1120
Page generated at 2019-06-24 20:41:30. Version ac04

Copyright 2019 A. Danko


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