Elizabeth Ridge
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Elizabeth Ridge clear sky chart from 2005-11-05 to 2017-09-22.

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
40%
15929
21%
47010
13%
15890
47%
15890
28%
28638

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
38%
717
19%
2327
15%
716
45%
716
21%
1534
January16th to endNight
36%
768
20%
2496
15%
768
43%
768
21%
1612
February1st to 15thNight
35%
697
17%
2288
12%
697
42%
697
19%
1499
February16th to endNight
24%
632
18%
1959
10%
632
35%
632
19%
1300
March1st to 15thNight
29%
720
19%
1983
7%
720
40%
720
25%
1275
March16th to endNight
28%
768
15%
2112
7%
768
35%
768
23%
1382
April1st to 15thNight
26%
611
15%
1870
8%
611
32%
611
19%
1214
April16th to endNight
32%
540
17%
1632
10%
540
38%
540
21%
1070
May1st to 15thNight
39%
539
18%
1619
12%
539
44%
539
29%
964
May16th to endNight
40%
563
16%
1610
12%
561
45%
561
29%
981
June1st to 15thNight
42%
540
19%
1440
11%
540
49%
540
39%
798
June16th to endNight
55%
540
29%
1440
20%
540
65%
540
56%
701
July1st to 15thNight
60%
510
18%
1481
15%
510
66%
510
38%
822
July16th to endNight
62%
564
21%
1593
18%
531
64%
531
39%
871
August1st to 15thNight
56%
539
23%
1611
15%
536
62%
536
39%
860
August16th to endNight
65%
573
36%
1764
27%
573
73%
573
47%
862
September1st to 15thNight
61%
623
30%
1883
20%
623
72%
623
44%
939
September16th to endNight
54%
683
34%
1890
21%
683
62%
683
46%
988
October1st to 15thNight
44%
660
24%
1955
14%
660
52%
660
30%
1152
October16th to endNight
41%
704
27%
2112
14%
704
52%
704
31%
1220
November1st to 15thNight
39%
700
23%
2239
17%
700
47%
700
25%
1331
November16th to endNight
31%
885
22%
2505
12%
885
40%
885
26%
1533
December1st to 15thNight
26%
900
14%
2520
6%
900
33%
900
20%
1745
December16th to endNight
26%
953
15%
2681
8%
953
31%
953
16%
1985

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
49%5%8%6%3445%6%40%
47863
Night
26%47%6%3445%7%47%
47205
TransparencyDay
43%410%20%15%5%
47558
Night
36%413%23%17%5%
47011
SeeingDay
13%30%28%17%7%2
5720
Night
8%19%26%25%16%3
15940

By Month

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
8%9%12%6%35%345%39%
1611
16th to endDay
10%5%10%8%33345%43%
1728
February1st to 15thDay
112%7%14%9%44345%31%
1575
16th to endDay
8%10%15%10%3446%6%29%
1512
March1st to 15thDay
9%5%11%8%34449%37%
1977
16th to endDay
111%9%12%8%35%5%5%7%29%
2112
April1st to 15thDay
213%6%11%6%3435%6%36%
2078
16th to endDay
416%7%10%6%2445%6%31%
2325
May1st to 15thDay
6%13%47%6%345%5%7%35%
2331
16th to endDay
7%14%49%7%35%5%5%7%30%
2501
June1st to 15thDay
6%7%36%5%35%45%7%44%
2520
16th to endDay
431442435%6%60%
2520
July1st to 15thDay
7%6%37%6%46%5%5%6%41%
2385
16th to endDay
9%6%36%6%445%5%6%39%
2467
August1st to 15thDay
6%5%37%7%46%6%6%6%39%
2340
16th to endDay
6%5%26%6%35%5%5%6%44%
2438
September1st to 15thDay
6%5%25%43445%6%51%
2075
16th to endDay
7%6%25%322435%56%
1882
October1st to 15thDay
412%35%5%22345%49%
1675
16th to endDay
310%27%5%23347%49%
1760
November1st to 15thDay
28%5%8%31445%6%48%
1617
16th to endDay
17%5%8%7%346%6%6%42%
1441
December1st to 15thDay
19%7%12%7%5%5%45%9%31%
1440
16th to endDay
18%8%14%11%5%445%5%31%
1553
January1st to 15thNight
7%6%10%9%45%346%40%
2327
16th to endNight
16%6%10%7%5%5%446%41%
2496
February1st to 15thNight
8%6%10%7%35%45%7%39%
2277
16th to endNight
6%411%11%3446%8%37%
1959
March1st to 15thNight
6%48%8%345%6%8%42%
1983
16th to endNight
8%6%10%5%245%6%7%42%
2112
April1st to 15thNight
111%5%8%5%245%46%42%
1870
16th to endNight
211%6%9%6%3445%7%39%
1632
May1st to 15thNight
47%44436%46%7%45%
1619
16th to endNight
5%6%245%35%5%7%10%42%
1609
June1st to 15thNight
33134245%5%10%54%
1440
16th to endNight
212212345%72%
1440
July1st to 15thNight
32145%36%5%7%7%53%
1571
16th to endNight
33146%36%5%6%7%50%
1701
August1st to 15thNight
33135%345%6%8%53%
1620
16th to endNight
221232446%7%61%
1764
September1st to 15thNight
22133245%6%7%60%
1883
16th to endNight
45%12312345%66%
1890
October1st to 15thNight
37%35%5%3435%5%53%
1955
16th to endNight
28%35%32346%7%51%
2112
November1st to 15thNight
28%45%5%2447%7%47%
2239
16th to endNight
16%48%5%25%45%6%48%
2505
December1st to 15thNight
10%410%9%3446%7%38%
2520
16th to endNight
19%5%13%12%445%5%7%30%
2681

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
48%5%17%16%10%1
1612
16th to endDay
45%412%19%13%5%
1728
February1st to 15thDay
55%5%8%16%11%2
1575
16th to endDay
54%5%11%19%7%1
1512
March1st to 15thDay
45%417%20%9%2
1977
16th to endDay
54%5%15%15%6%2
2112
April1st to 15thDay
48%414%21%9%1
2078
16th to endDay
52%412%22%6%
2325
May1st to 15thDay
47%311%25%10%
2331
16th to endDay
52%413%21%8%
2504
June1st to 15thDay
38%49%24%19%3
2520
16th to endDay
24%3417%33%16%
2520
July1st to 15thDay
41%46%14%18%14%
2246
16th to endDay
42%46%14%19%12%
2312
August1st to 15thDay
41%47%16%16%13%
2325
16th to endDay
38%5%5%23%20%7%
2438
September1st to 15thDay
33%46%20%23%11%
2075
16th to endDay
31%38%27%23%4
1882
October1st to 15thDay
38%310%29%15%2
1675
16th to endDay
35%411%29%17%2
1760
November1st to 15thDay
36%5%10%25%17%5%
1617
16th to endDay
40%7%12%23%14%2
1441
December1st to 15thDay
49%7%18%16%6%1
1440
16th to endDay
55%410%18%8%1
1553
January1st to 15thNight
46%415%18%12%3
2327
16th to endNight
45%410%20%12%6%
2496
February1st to 15thNight
44%5%11%20%14%3
2288
16th to endNight
45%411%22%13%2
1959
March1st to 15thNight
39%416%23%12%3
1983
16th to endNight
40%5%19%23%8%2
2112
April1st to 15thNight
42%5%13%23%11%2
1870
16th to endNight
43%416%25%9%
1632
May1st to 15thNight
34%415%29%14%
1620
16th to endNight
36%417%31%9%
1610
June1st to 15thNight
24%414%29%22%4
1440
16th to endNight
14%25%17%44%14%
1440
July1st to 15thNight
28%48%17%25%15%
1481
16th to endNight
27%5%12%19%20%15%
1593
August1st to 15thNight
25%5%11%21%20%14%
1611
16th to endNight
20%49%29%28%8%
1764
September1st to 15thNight
21%411%23%26%12%
1883
16th to endNight
21%310%31%29%4
1890
October1st to 15thNight
33%313%26%20%2
1955
16th to endNight
30%6%11%31%17%2
2112
November1st to 15thNight
35%5%11%21%18%6%
2239
16th to endNight
35%414%24%16%4
2505
December1st to 15thNight
44%6%15%21%9%1
2520
16th to endNight
53%6%11%18%8%2
2681

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
11%28%27%22%10%
90
16th to endDay
7%26%33%20%11%1
96
February1st to 15thDay
13%35%27%12%11%
90
16th to endDay
18%47%22%7%4
171
March1st to 15thDay
14%47%26%10%
270
16th to endDay
17%47%26%7%
288
April1st to 15thDay
19%42%20%10%41
269
16th to endDay
22%44%21%9%2
270
May1st to 15thDay
19%31%30%13%31
288
16th to endDay
21%25%23%16%9%2
402
June1st to 15thDay
11%24%29%22%10%2
495
16th to endDay
422%32%21%12%5%
495
July1st to 15thDay
8%21%27%24%14%3
350
16th to endDay
10%21%40%19%7%1
327
August1st to 15thDay
9%22%36%25%5%1
315
16th to endDay
9%21%29%26%10%2
332
September1st to 15thDay
13%27%27%20%7%3
315
16th to endDay
13%26%27%18%9%3
280
October1st to 15thDay
11%26%27%17%14%1
115
16th to endDay
16%33%20%19%7%2
96
November1st to 15thDay
428%24%18%16%6%
90
16th to endDay
10%40%36%7%41
90
December1st to 15thDay
15%45%21%15%11
90
16th to endDay
6%39%27%15%8%3
96
January1st to 15thNight
10%20%23%26%15%3
720
16th to endNight
8%22%27%25%13%2
768
February1st to 15thNight
10%20%27%26%12%2
704
16th to endNight
8%29%32%22%6%1
632
March1st to 15thNight
7%25%33%21%9%2
720
16th to endNight
7%29%30%22%9%
768
April1st to 15thNight
12%29%28%18%9%
611
16th to endNight
12%25%24%24%10%2
540
May1st to 15thNight
10%15%30%27%12%2
540
16th to endNight
11%14%27%25%16%4
563
June1st to 15thNight
6%15%32%29%15%1
540
16th to endNight
311%26%32%21%3
540
July1st to 15thNight
47%18%31%33%3
510
16th to endNight
4416%37%32%3
564
August1st to 15thNight
5%5%25%36%25%2
539
16th to endNight
45%21%30%34%4
573
September1st to 15thNight
310%19%31%27%7%
623
16th to endNight
7%14%20%22%25%9%
683
October1st to 15thNight
8%22%22%24%16%5%
660
16th to endNight
10%21%23%25%13%6%
704
November1st to 15thNight
10%21%25%23%18%2
700
16th to endNight
8%28%28%19%11%3
885
December1st to 15thNight
11%27%28%21%8%1
900
16th to endNight
10%27%29%22%7%2
953
Page generated at 2017-09-23 04:43:34. Version ac04

Copyright 2017 A. Danko


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