Reid Lake Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Reid Lake Observatory clear sky chart from 2005-11-05 to 2017-12-01.

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
41%
15111
9%
47711
7%
15083
45%
15083
17%
34345

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
28%
805
6%
2742
4%
802
31%
802
8%
2265
January16th to endNight
33%
800
10%
2880
8%
800
37%
800
11%
2229
February1st to 15thNight
35%
704
7%
2401
6%
704
38%
704
12%
1821
February16th to endNight
44%
632
12%
2053
10%
632
48%
632
18%
1427
March1st to 15thNight
32%
720
11%
2112
7%
720
36%
720
15%
1605
March16th to endNight
45%
768
12%
2057
7%
767
47%
767
19%
1521
April1st to 15thNight
43%
656
11%
1736
6%
656
45%
656
19%
1284
April16th to endNight
39%
433
10%
1513
10%
433
44%
433
15%
1075
May1st to 15thNight
44%
359
6%
1413
4%
359
46%
359
15%
959
May16th to endNight
46%
374
0%
1228
0%
374
46%
374
19%
836
June1st to 15thNight
46%
360
0%
1080
0%
360
46%
360
22%
738
June16th to endNight
51%
360
0%
1080
0%
360
51%
360
23%
738
July1st to 15thNight
51%
340
0%
1070
0%
340
51%
340
22%
706
July16th to endNight
63%
376
3%
1239
1%
354
66%
354
35%
667
August1st to 15thNight
71%
360
11%
1382
15%
358
73%
358
33%
694
August16th to endNight
56%
545
13%
1691
13%
545
58%
545
25%
1097
September1st to 15thNight
61%
711
17%
1791
11%
711
63%
711
37%
1124
September16th to endNight
48%
716
16%
1977
9%
716
51%
716
23%
1372
October1st to 15thNight
44%
720
11%
2160
8%
720
48%
720
21%
1491
October16th to endNight
34%
768
10%
2538
5%
768
41%
768
14%
1867
November1st to 15thNight
33%
760
9%
2660
7%
760
37%
760
13%
1938
November16th to endNight
33%
917
10%
2941
6%
917
37%
917
13%
2236
December1st to 15thNight
37%
935
9%
2895
6%
935
40%
935
13%
2226
December16th to endNight
31%
992
9%
3072
5%
992
35%
992
11%
2429

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
11%10%48%7%46%6%6%7%27%
48761
Night
11%11%5%8%7%46%5%5%6%27%
47853
TransparencyDay
52%316%20%5%
48403
Night
54%315%19%5%
47715
SeeingDay
14%6%23%29%19%5%
7073
Night
17%5%18%33%21%3
15120

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
11%16%6%10%10%5%7%6%5%415%
1206
16th to endDay
10%13%6%10%8%5%7%45%6%22%
1344
February1st to 15thDay
15%13%48%6%45%5%6%6%23%
1462
16th to endDay
7%12%5%8%8%46%5%48%29%
1421
March1st to 15thDay
9%14%7%9%7%47%45%6%22%
1848
16th to endDay
8%11%6%8%7%5%7%6%7%8%23%
2162
April1st to 15thDay
9%13%6%10%9%5%7%6%6%5%19%
2211
16th to endDay
13%13%6%9%9%46%45%5%20%
2446
May1st to 15thDay
11%10%6%9%7%5%5%5%5%6%26%
2535
16th to endDay
12%8%49%9%47%6%6%7%24%
2885
June1st to 15thDay
13%8%38%7%5%6%5%5%7%27%
2880
16th to endDay
12%7%47%8%46%7%7%7%24%
2880
July1st to 15thDay
13%6%37%6%46%6%7%7%30%
2823
16th to endDay
8%5%26%6%46%5%7%8%36%
2846
August1st to 15thDay
5%427%6%46%6%5%9%40%
2571
16th to endDay
11%7%47%7%36%5%6%7%31%
2509
September1st to 15thDay
7%6%35%6%36%6%6%6%41%
2169
16th to endDay
14%7%38%6%45%6%6%7%28%
1982
October1st to 15thDay
14%11%27%6%45%7%5%7%26%
1800
16th to endDay
16%11%47%6%45%5%5%6%23%
1686
November1st to 15thDay
14%13%5%8%6%35%45%5%25%
1528
16th to endDay
10%15%411%9%5%8%6%5%6%17%
1335
December1st to 15thDay
13%11%5%11%7%46%5%5%6%24%
1080
16th to endDay
7%16%411%9%47%6%7%6%19%
1152
January1st to 15thNight
11%15%7%10%10%46%5%46%16%
2742
16th to endNight
12%13%5%8%8%45%5%47%22%
2880
February1st to 15thNight
13%15%5%8%7%45%45%5%23%
2389
16th to endNight
7%10%5%10%7%36%5%5%7%29%
2053
March1st to 15thNight
10%13%6%11%8%36%5%45%24%
2112
16th to endNight
7%10%49%7%5%8%8%6%6%25%
2057
April1st to 15thNight
10%13%5%8%7%47%5%5%5%26%
1736
16th to endNight
10%10%5%8%8%5%6%5%46%28%
1513
May1st to 15thNight
12%8%48%8%46%5%5%8%26%
1412
16th to endNight
12%7%47%7%47%7%6%8%25%
1228
June1st to 15thNight
15%5%37%6%5%5%6%7%10%27%
1080
16th to endNight
9%7%37%8%47%5%7%10%28%
1080
July1st to 15thNight
12%6%26%6%46%5%6%8%32%
1134
16th to endNight
8%6%234245%7%8%45%
1323
August1st to 15thNight
6%4133345%6%8%50%
1389
16th to endNight
10%7%26%6%45%6%6%7%35%
1691
September1st to 15thNight
7%6%26%5%345%5%8%45%
1791
16th to endNight
13%8%36%6%45%6%5%7%31%
1977
October1st to 15thNight
12%9%37%6%45%5%6%5%33%
2160
16th to endNight
16%12%47%6%36%6%5%6%23%
2538
November1st to 15thNight
14%10%47%8%46%6%5%7%23%
2660
16th to endNight
10%14%6%8%7%45%45%6%24%
2941
December1st to 15thNight
14%12%5%8%7%4445%5%26%
2895
16th to endNight
7%14%7%11%9%5%6%45%6%20%
3072

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
69%5%14%8%1
1206
16th to endDay
63%413%12%41
1344
February1st to 15thDay
60%316%13%5%
1462
16th to endDay
52%215%19%8%
1421
March1st to 15thDay
59%211%19%6%
1848
16th to endDay
53%217%19%5%
2162
April1st to 15thDay
59%311%19%5%
2211
16th to endDay
62%310%18%5%
2446
May1st to 15thDay
54%212%21%8%
2535
16th to endDay
53%316%21%4
2889
June1st to 15thDay
51%314%23%7%
2880
16th to endDay
51%316%22%5%
2880
July1st to 15thDay
46%316%23%8%1
2658
16th to endDay
37%424%27%5%
2667
August1st to 15thDay
35%325%29%5%
2553
16th to endDay
46%420%23%4
2509
September1st to 15thDay
36%326%26%6%
2169
16th to endDay
50%417%23%3
1982
October1st to 15thDay
52%420%18%3
1800
16th to endDay
57%320%15%2
1686
November1st to 15thDay
59%214%17%6%
1528
16th to endDay
67%49%16%2
1335
December1st to 15thDay
61%5%15%15%2
1080
16th to endDay
63%5%13%15%2
1152
January1st to 15thNight
69%5%13%10%1
2742
16th to endNight
62%5%13%11%5%1
2880
February1st to 15thNight
62%315%12%6%
2401
16th to endNight
53%216%19%7%
2053
March1st to 15thNight
58%410%18%6%1
2112
16th to endNight
52%5%14%19%6%
2061
April1st to 15thNight
55%39%23%8%
1736
16th to endNight
56%211%20%7%
1513
May1st to 15thNight
54%210%20%11%
1413
16th to endNight
50%314%25%5%
1228
June1st to 15thNight
50%213%24%7%
1080
16th to endNight
48%316%25%5%
1080
July1st to 15thNight
47%314%21%11%1
1070
16th to endNight
32%226%32%6%
1239
August1st to 15thNight
30%320%36%9%
1382
16th to endNight
44%320%25%4
1691
September1st to 15thNight
35%219%32%8%
1791
16th to endNight
47%414%24%7%
1977
October1st to 15thNight
49%319%21%5%
2160
16th to endNight
58%318%17%2
2538
November1st to 15thNight
57%416%15%5%
2660
16th to endNight
59%413%16%4
2941
December1st to 15thNight
61%414%17%2
2895
16th to endNight
64%412%15%3
3072

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
6%313%20%41%15%
60
16th to endDay
20%410%31%18%14%
64
February1st to 15thDay
18%8%25%26%16%4
152
16th to endDay
13%6%22%33%15%8%
211
March1st to 15thDay
17%10%39%23%7%1
266
16th to endDay
15%12%28%27%14%1
288
April1st to 15thDay
18%11%29%24%11%3
269
16th to endDay
17%13%32%22%11%3
270
May1st to 15thDay
16%11%26%26%15%3
312
16th to endDay
13%7%22%27%23%6%
599
June1st to 15thDay
16%6%19%28%23%4
675
16th to endDay
13%423%30%21%5%
675
July1st to 15thDay
15%5%18%29%23%6%
592
16th to endDay
11%5%18%33%26%4
515
August1st to 15thDay
4320%31%30%9%
366
16th to endDay
13%6%27%34%15%2
332
September1st to 15thDay
13%327%33%18%5%
315
16th to endDay
16%5%34%25%15%2
315
October1st to 15thDay
19%8%24%26%16%4
315
16th to endDay
20%7%21%26%18%3
178
November1st to 15thDay
21%326%26%11%11%
90
16th to endDay
12%316%40%16%11%
90
December1st to 15thDay
13%113%23%35%13%
60
16th to endDay
14%17%34%29%12%
64
January1st to 15thNight
21%8%19%30%17%3
807
16th to endNight
21%7%21%33%13%2
800
February1st to 15thNight
22%7%16%31%18%3
709
16th to endNight
14%416%37%23%3
632
March1st to 15thNight
17%9%23%34%13%2
720
16th to endNight
13%7%17%33%26%3
768
April1st to 15thNight
19%6%14%33%22%4
656
16th to endNight
18%5%21%33%18%3
433
May1st to 15thNight
15%6%17%36%21%3
360
16th to endNight
16%5%14%30%29%3
375
June1st to 15thNight
18%321%28%26%1
360
16th to endNight
11%117%35%30%3
360
July1st to 15thNight
15%17%34%29%3
340
16th to endNight
9%115%38%30%4
376
August1st to 15thNight
6%28%32%39%10%
360
16th to endNight
15%211%36%30%3
545
September1st to 15thNight
11%213%32%34%4
711
16th to endNight
18%415%35%20%5%
716
October1st to 15thNight
20%419%32%19%5%
720
16th to endNight
22%6%21%31%15%2
768
November1st to 15thNight
22%7%21%33%13%1
760
16th to endNight
21%7%22%33%12%2
917
December1st to 15thNight
21%5%17%35%18%1
935
16th to endNight
16%6%20%34%17%3
992
Page generated at 2017-12-02 06:14:17. Version ac04

Copyright 2017 A. Danko


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