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 2017-09-23.

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
38%
15916
16%
47059
10%
15874
43%
15874
21%
32443

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
16%
900
10%
2506
4%
895
22%
895
12%
1962
January16th to endNight
20%
869
8%
2597
3%
869
25%
869
12%
2048
February1st to 15thNight
18%
701
9%
2250
3%
701
24%
701
11%
1723
February16th to endNight
25%
631
15%
1893
6%
631
33%
631
16%
1375
March1st to 15thNight
27%
720
15%
2085
8%
720
32%
720
18%
1507
March16th to endNight
33%
768
18%
2112
10%
768
40%
768
22%
1467
April1st to 15thNight
30%
578
14%
1809
7%
578
37%
578
18%
1241
April16th to endNight
35%
540
20%
1620
9%
540
45%
540
25%
1075
May1st to 15thNight
37%
540
14%
1620
8%
540
43%
540
22%
1118
May16th to endNight
50%
562
15%
1666
11%
561
55%
561
29%
1054
June1st to 15thNight
57%
540
14%
1440
11%
540
61%
540
33%
908
June16th to endNight
57%
540
17%
1440
12%
540
62%
540
36%
896
July1st to 15thNight
66%
510
16%
1360
15%
510
68%
510
40%
805
July16th to endNight
68%
564
20%
1492
16%
531
72%
531
41%
855
August1st to 15thNight
67%
539
20%
1609
16%
536
70%
536
36%
946
August16th to endNight
65%
573
23%
1752
19%
573
68%
573
34%
1036
September1st to 15thNight
60%
660
26%
1920
20%
660
64%
660
36%
1119
September16th to endNight
60%
689
25%
1903
19%
689
64%
689
34%
1167
October1st to 15thNight
47%
660
20%
1889
16%
660
51%
660
28%
1219
October16th to endNight
26%
704
15%
2214
9%
704
35%
704
18%
1549
November1st to 15thNight
36%
700
20%
2276
17%
700
43%
700
23%
1462
November16th to endNight
25%
720
14%
2349
10%
720
31%
720
14%
1699
December1st to 15thNight
18%
748
8%
2548
4%
748
24%
748
10%
1952
December16th to endNight
16%
960
8%
2709
2%
960
22%
960
9%
2260

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%8%37%6%35%45%7%32%
47835
Night
15%8%36%5%3445%6%35%
47236
Cloud CoverDay
14%8%47%6%35%45%7%32%
47845
Night
15%8%46%5%34446%35%
47240
TransparencyDay
49%5%11%20%11%1
47531
Night
48%412%21%11%1
47059
SeeingDay
17%7%26%24%17%7%
5874
Night
19%7%27%30%13%1
15920

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
17%16%5%12%7%445%45%16%
1432
16th to endDay
17%17%7%9%7%44445%15%
1626
February1st to 15thDay
14%14%7%11%10%35%45%5%18%
1610
16th to endDay
14%14%6%11%8%3445%5%21%
1580
March1st to 15thDay
16%11%48%6%3445%6%27%
1864
16th to endDay
17%10%5%7%6%34435%30%
2112
April1st to 15thDay
19%11%35%5%25%446%30%
2150
16th to endDay
16%7%37%5%23346%38%
2340
May1st to 15thDay
19%7%36%6%35%35%6%31%
2331
16th to endDay
12%7%25%435%45%9%38%
2446
June1st to 15thDay
10%5%26%5%35%5%6%8%39%
2520
16th to endDay
10%425%6%36%5%7%10%34%
2520
July1st to 15thDay
7%5%25%5%35%5%6%9%44%
2520
16th to endDay
8%425%5%45%5%7%10%38%
2571
August1st to 15thDay
8%5%26%6%47%5%5%9%38%
2340
16th to endDay
10%6%26%5%35%47%8%39%
2448
September1st to 15thDay
11%5%25%5%45%45%8%41%
2028
16th to endDay
11%5%25%5%345%6%8%39%
1894
October1st to 15thDay
14%7%36%6%34446%38%
1741
16th to endDay
20%10%45%6%34346%31%
1656
November1st to 15thDay
15%7%26%6%3445%6%37%
1582
16th to endDay
17%12%47%7%35%446%26%
1605
December1st to 15thDay
16%13%6%11%7%25%445%21%
1410
16th to endDay
21%15%9%11%6%4324415%
1509
January1st to 15thNight
21%13%5%7%6%34445%23%
2506
16th to endNight
14%12%7%12%7%445%45%20%
2597
February1st to 15thNight
16%14%5%8%6%35%44426%
2248
16th to endNight
16%9%49%7%3435%6%28%
1893
March1st to 15thNight
17%9%46%6%33447%32%
2073
16th to endNight
15%7%46%5%345%46%36%
2112
April1st to 15thNight
18%8%345%345%5%6%33%
1809
16th to endNight
15%7%345%2446%6%39%
1620
May1st to 15thNight
18%6%36%5%35%45%8%34%
1620
16th to endNight
12%4245%35%438%44%
1664
June1st to 15thNight
9%4245%3446%7%46%
1440
16th to endNight
8%4344345%7%10%43%
1440
July1st to 15thNight
7%31443445%9%51%
1440
16th to endNight
441443346%9%52%
1594
August1st to 15thNight
44245%45%6%5%8%48%
1620
16th to endNight
9%425%423446%51%
1752
September1st to 15thNight
11%41432345%6%52%
1920
16th to endNight
10%5%25%5%3435%7%47%
1903
October1st to 15thNight
14%6%26%42445%7%41%
1889
16th to endNight
20%9%26%5%34445%33%
2214
November1st to 15thNight
14%7%25%5%35%45%6%39%
2276
16th to endNight
21%12%46%434346%28%
2349
December1st to 15thNight
21%11%5%9%5%35%44422%
2548
16th to endNight
22%15%6%10%6%445%45%15%
2709

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%6%11%7%445%45%17%
1432
16th to endDay
17%17%7%9%8%44445%15%
1626
February1st to 15thDay
14%14%6%12%8%35%45%5%19%
1610
16th to endDay
15%14%6%11%8%35%35%5%21%
1580
March1st to 15thDay
17%11%5%8%6%25%45%6%27%
1875
16th to endDay
17%9%5%7%6%34436%30%
2111
April1st to 15thDay
20%10%45%5%24446%30%
2150
16th to endDay
17%7%46%5%23446%38%
2340
May1st to 15thDay
19%7%36%6%35%45%6%31%
2331
16th to endDay
13%6%25%435%45%9%38%
2446
June1st to 15thDay
10%5%26%5%35%5%5%8%39%
2520
16th to endDay
10%435%6%46%5%7%11%34%
2520
July1st to 15thDay
6%5%245%35%5%6%9%44%
2520
16th to endDay
8%426%5%35%5%7%10%38%
2571
August1st to 15thDay
8%436%6%46%6%6%9%38%
2340
16th to endDay
10%5%36%6%35%5%7%8%39%
2448
September1st to 15thDay
12%4245%45%5%5%9%40%
2028
16th to endDay
12%5%35%5%345%6%8%39%
1894
October1st to 15thDay
14%6%36%6%24446%38%
1741
16th to endDay
21%9%36%5%34346%31%
1656
November1st to 15thDay
15%8%26%5%3445%6%37%
1582
16th to endDay
18%11%47%6%35%446%26%
1605
December1st to 15thDay
16%13%8%10%7%24446%21%
1410
16th to endDay
21%16%8%11%6%3324415%
1509
January1st to 15thNight
21%14%5%7%5%3434423%
2506
16th to endNight
14%12%7%11%8%445%45%20%
2597
February1st to 15thNight
15%15%5%9%6%35%44426%
2241
16th to endNight
16%10%5%8%7%34447%28%
1893
March1st to 15thNight
18%9%46%6%33446%32%
2085
16th to endNight
15%7%35%5%35%45%6%35%
2112
April1st to 15thNight
19%7%345%345%46%33%
1809
16th to endNight
15%7%245%2445%6%39%
1620
May1st to 15thNight
17%5%36%5%45%448%34%
1619
16th to endNight
13%4245%35%448%43%
1664
June1st to 15thNight
10%425%5%4446%8%45%
1440
16th to endNight
8%435%4236%7%9%43%
1440
July1st to 15thNight
7%315%325%45%8%51%
1440
16th to endNight
5%42442445%10%52%
1594
August1st to 15thNight
5%4245%35%5%6%8%49%
1620
16th to endNight
9%425%424437%51%
1752
September1st to 15thNight
11%424324446%52%
1920
16th to endNight
10%5%245%3435%7%47%
1903
October1st to 15thNight
14%5%35%42445%6%42%
1889
16th to endNight
20%8%35%5%24445%34%
2214
November1st to 15thNight
14%8%345%34446%40%
2276
16th to endNight
20%11%5%5%5%24346%28%
2349
December1st to 15thNight
21%11%5%8%6%345%45%22%
2548
16th to endNight
22%15%6%9%6%44445%15%
2709

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
68%411%12%3
1433
16th to endDay
70%410%10%4
1626
February1st to 15thDay
66%5%8%13%6%
1612
16th to endDay
63%410%15%5%
1580
March1st to 15thDay
57%411%17%7%1
1875
16th to endDay
55%411%20%7%1
2112
April1st to 15thDay
54%310%19%11%
2150
16th to endDay
46%413%17%15%2
2340
May1st to 15thDay
52%411%19%9%2
2331
16th to endDay
43%413%24%12%1
2450
June1st to 15thDay
40%5%13%24%14%1
2520
16th to endDay
41%7%13%21%15%1
2520
July1st to 15thDay
35%6%10%25%19%2
2371
16th to endDay
38%7%12%22%16%2
2411
August1st to 15thDay
40%6%12%25%13%1
2327
16th to endDay
39%7%10%23%16%2
2448
September1st to 15thDay
40%6%11%26%14%1
2028
16th to endDay
39%5%10%31%13%
1894
October1st to 15thDay
44%5%12%23%13%1
1741
16th to endDay
53%414%19%7%
1656
November1st to 15thDay
46%5%11%22%12%1
1582
16th to endDay
57%412%19%5%
1605
December1st to 15thDay
63%313%14%3
1410
16th to endDay
72%311%9%3
1509
January1st to 15thNight
62%311%15%6%
2506
16th to endNight
63%413%12%4
2597
February1st to 15thNight
60%5%11%15%6%1
2250
16th to endNight
55%312%19%7%
1893
March1st to 15thNight
52%410%19%10%1
2085
16th to endNight
48%412%23%10%1
2112
April1st to 15thNight
49%411%19%14%
1809
16th to endNight
44%411%18%17%2
1620
May1st to 15thNight
49%410%21%11%2
1620
16th to endNight
39%413%23%15%3
1666
June1st to 15thNight
35%5%13%27%15%1
1440
16th to endNight
33%5%16%25%17%1
1440
July1st to 15thNight
30%410%30%21%2
1360
16th to endNight
27%5%16%26%20%3
1492
August1st to 15thNight
31%6%12%31%15%2
1609
16th to endNight
33%5%11%27%19%3
1752
September1st to 15thNight
32%410%30%21%1
1920
16th to endNight
35%410%31%17%
1903
October1st to 15thNight
40%412%23%17%1
1889
16th to endNight
51%313%22%8%
2214
November1st to 15thNight
43%412%23%13%1
2276
16th to endNight
56%312%20%6%
2349
December1st to 15thNight
62%5%12%14%5%
2548
16th to endNight
69%5%10%10%3
2709

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
18%16%37%20%5%1
90
16th to endDay
33%8%39%15%3
96
February1st to 15thDay
22%22%41%13%1
90
16th to endDay
22%12%39%23%2
81
March1st to 15thDay
29%10%30%23%6%
165
16th to endDay
25%7%28%27%10%2
288
April1st to 15thDay
23%10%31%24%9%1
270
16th to endDay
22%7%32%16%14%7%
270
May1st to 15thDay
25%5%27%21%13%5%
288
16th to endDay
16%9%24%24%16%8%
346
June1st to 15thDay
11%430%30%17%4
495
16th to endDay
12%5%32%26%16%6%
495
July1st to 15thDay
10%5%24%26%22%10%
475
16th to endDay
9%420%27%25%11%
431
August1st to 15thDay
10%116%27%23%19%
313
16th to endDay
13%415%20%28%17%
332
September1st to 15thDay
11%318%21%25%19%
315
16th to endDay
15%313%21%31%13%
283
October1st to 15thDay
20%321%28%19%7%
255
16th to endDay
28%7%29%28%6%
168
November1st to 15thDay
10%13%26%31%16%2
90
16th to endDay
24%16%35%18%5%
87
December1st to 15thDay
18%25%33%18%5%
60
16th to endDay
24%29%35%10%
91
January1st to 15thNight
27%12%34%18%5%
900
16th to endNight
20%11%34%27%6%
869
February1st to 15thNight
25%12%34%24%3
704
16th to endNight
22%11%32%29%4
631
March1st to 15thNight
22%11%31%27%6%
720
16th to endNight
18%10%30%29%9%1
768
April1st to 15thNight
21%10%32%29%6%
578
16th to endNight
19%7%33%29%9%1
540
May1st to 15thNight
21%5%27%33%9%1
540
16th to endNight
14%324%35%19%2
563
June1st to 15thNight
11%221%48%15%
540
16th to endNight
9%122%43%21%1
540
July1st to 15thNight
9%115%42%28%3
510
16th to endNight
5%215%47%25%3
564
August1st to 15thNight
7%115%44%27%4
539
16th to endNight
11%112%35%33%4
573
September1st to 15thNight
13%317%31%27%5%
660
16th to endNight
12%414%33%28%6%
689
October1st to 15thNight
17%5%23%32%18%2
660
16th to endNight
25%10%33%24%5%
704
November1st to 15thNight
18%9%29%27%13%2
700
16th to endNight
28%12%28%22%8%
720
December1st to 15thNight
26%12%34%22%4
748
16th to endNight
30%10%33%21%3
960
Page generated at 2017-09-24 09:15:49. Version ac04

Copyright 2017 A. Danko


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