Eagle Ridge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Eagle Ridge Observatory clear sky chart from 2005-11-05 to

2017-09-12
.

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
65%
15795
34%
46791
26%
15744
73%
15744
45%
23037

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
48%
720
29%
2431
22%
716
61%
716
33%
1196
January16th to endNight
45%
768
34%
2428
21%
768
63%
768
32%
1265
February1st to 15thNight
54%
700
36%
2101
28%
696
66%
696
38%
1095
February16th to endNight
53%
632
28%
1895
25%
632
62%
632
29%
1101
March1st to 15thNight
59%
720
29%
2153
24%
720
69%
720
41%
1066
March16th to endNight
63%
768
30%
1992
22%
768
68%
768
43%
1103
April1st to 15thNight
61%
719
31%
1799
18%
719
66%
719
45%
994
April16th to endNight
65%
720
32%
1800
16%
720
70%
720
50%
944
May1st to 15thNight
67%
662
27%
1742
17%
662
69%
662
44%
947
May16th to endNight
68%
561
31%
1685
21%
561
74%
561
49%
785
June1st to 15thNight
74%
391
29%
1471
27%
391
79%
391
37%
675
June16th to endNight
78%
360
35%
1440
38%
360
85%
360
50%
534
July1st to 15thNight
80%
340
34%
1360
37%
340
84%
340
47%
513
July16th to endNight
75%
619
32%
1642
23%
580
83%
580
52%
797
August1st to 15thNight
82%
717
33%
1790
22%
713
83%
713
60%
905
August16th to endNight
84%
764
40%
1910
24%
764
86%
764
62%
942
September1st to 15thNight
82%
706
37%
1765
28%
706
83%
706
58%
918
September16th to endNight
84%
656
40%
1815
35%
656
89%
656
62%
822
October1st to 15thNight
75%
660
36%
1873
35%
660
79%
660
54%
899
October16th to endNight
70%
704
41%
2112
36%
704
80%
704
52%
968
November1st to 15thNight
64%
700
36%
2264
33%
700
74%
700
50%
973
November16th to endNight
56%
720
38%
2340
30%
720
70%
720
42%
1069
December1st to 15thNight
51%
720
36%
2340
27%
720
64%
720
34%
1179
December16th to endNight
46%
768
32%
2643
24%
768
61%
768
30%
1347

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
4312212346%66%
47849
Night
4312213346%66%
46993
TransparencyDay
19%37%18%28%23%
47540
Night
19%46%17%26%25%
46803
SeeingDay
5%14%22%34%18%5%
5961
Night
5%16%8%25%34%11%
15802

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
6%313422235%62%
1504
16th to endDay
11%423212235%59%
1794
February1st to 15thDay
8%422312347%60%
1751
16th to endDay
10%324424345%55%
1579
March1st to 15thDay
4323324447%60%
1806
16th to endDay
432232345%8%58%
2232
April1st to 15thDay
6%412213347%60%
2149
16th to endDay
4312212238%68%
2160
May1st to 15thDay
4412213348%63%
2205
16th to endDay
2312212349%67%
2429
June1st to 15thDay
45%13312348%59%
2484
16th to endDay
121112236%75%
2520
July1st to 15thDay
2211312346%69%
2520
16th to endDay
22221325%6%70%
2407
August1st to 15thDay
2211112235%74%
2160
16th to endDay
11112335%77%
2292
September1st to 15thDay
111112236%76%
2114
16th to endDay
121212235%76%
1815
October1st to 15thDay
5%32212335%69%
1755
16th to endDay
331321234470%
1760
November1st to 15thDay
3213222335%69%
1595
16th to endDay
4312313237%65%
1620
December1st to 15thDay
7%31332345%7%56%
1620
16th to endDay
10%313323337%57%
1578
January1st to 15thNight
6%5%12323346%59%
2431
16th to endNight
11%412312236%60%
2428
February1st to 15thNight
6%31431325%5%61%
2101
16th to endNight
12%314423335%54%
1895
March1st to 15thNight
4313213446%62%
2153
16th to endNight
4322324447%61%
1992
April1st to 15thNight
6%313212245%65%
1799
16th to endNight
3312123247%68%
1800
May1st to 15thNight
431221335%6%65%
1742
16th to endNight
121221325%6%71%
1684
June1st to 15thNight
122212345%8%64%
1471
16th to endNight
11112237%75%
1440
July1st to 15thNight
221212238%71%
1440
16th to endNight
221111245%8%66%
1755
August1st to 15thNight
12112225%9%70%
1800
16th to endNight
1112347%74%
1910
September1st to 15thNight
2112211247%71%
1765
16th to endNight
11112245%77%
1815
October1st to 15thNight
3212212345%70%
1873
16th to endNight
432112235%71%
2112
November1st to 15thNight
331111223473%
2264
16th to endNight
3213213246%66%
2340
December1st to 15thNight
7%413313345%60%
2340
16th to endNight
11%412213336%59%
2643

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
24%27%14%24%26%
1504
16th to endDay
27%26%18%18%26%
1794
February1st to 15thDay
24%3416%28%23%
1751
16th to endDay
30%47%19%27%10%
1579
March1st to 15thDay
23%49%20%22%20%
1806
16th to endDay
22%5%12%25%20%14%
2232
April1st to 15thDay
22%312%26%24%10%
2149
16th to endDay
17%310%23%28%16%
2160
May1st to 15thDay
20%39%22%25%17%
2205
16th to endDay
16%311%30%28%9%
2432
June1st to 15thDay
25%38%16%31%14%
2484
16th to endDay
11%4410%35%34%
2520
July1st to 15thDay
15%4412%28%35%
2371
16th to endDay
15%47%20%30%21%
2258
August1st to 15thDay
13%3213%37%29%
2146
16th to endDay
9%4211%43%29%
2292
September1st to 15thDay
10%35%13%29%37%
2114
16th to endDay
11%2215%34%33%
1815
October1st to 15thDay
18%27%22%24%25%
1755
16th to endDay
18%3414%23%35%
1760
November1st to 15thDay
17%3415%24%33%
1595
16th to endDay
20%27%16%21%31%
1620
December1st to 15thDay
24%48%17%23%21%
1620
16th to endDay
28%37%19%21%19%
1578
January1st to 15thNight
24%26%14%25%25%
2431
16th to endNight
27%26%14%16%32%
2428
February1st to 15thNight
24%3416%24%26%
2112
16th to endNight
33%35%16%25%15%
1895
March1st to 15thNight
20%39%21%26%18%
2153
16th to endNight
21%5%10%22%24%15%
1992
April1st to 15thNight
22%29%27%25%12%
1799
16th to endNight
16%48%24%27%19%
1800
May1st to 15thNight
20%5%9%21%26%15%
1743
16th to endNight
15%310%28%30%11%
1685
June1st to 15thNight
19%6%9%18%31%14%
1471
16th to endNight
9%6%412%34%33%
1440
July1st to 15thNight
11%4413%27%37%
1360
16th to endNight
14%5%8%21%26%22%
1642
August1st to 15thNight
11%6%5%11%34%30%
1790
16th to endNight
10%6%310%39%29%
1910
September1st to 15thNight
13%5%6%9%29%35%
1765
16th to endNight
9%6%212%33%36%
1815
October1st to 15thNight
16%35%19%27%27%
1873
16th to endNight
16%25%14%22%37%
2112
November1st to 15thNight
15%26%14%25%36%
2264
16th to endNight
18%2418%21%33%
2340
December1st to 15thNight
25%27%16%21%26%
2340
16th to endNight
27%37%17%23%20%
2643

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
12%15%45%21%3
132
16th to endDay
14%24%28%25%5%1
267
February1st to 15thDay
11%18%31%27%7%3
266
16th to endDay
15%20%25%27%10%
238
March1st to 15thDay
5%21%30%26%12%3
270
16th to endDay
5%17%28%34%11%2
288
April1st to 15thDay
6%20%31%25%10%5%
269
16th to endDay
322%34%28%7%2
270
May1st to 15thDay
6%19%25%30%13%3
288
16th to endDay
316%30%31%14%3
330
June1st to 15thDay
8%13%21%34%16%4
315
16th to endDay
19%10%40%26%11%
315
July1st to 15thDay
27%7%42%30%9%
305
16th to endDay
210%7%33%33%12%
327
August1st to 15thDay
35%7%49%26%7%
315
16th to endDay
5%8%40%34%10%
332
September1st to 15thDay
35%18%44%21%7%
300
16th to endDay
19%18%44%20%6%
255
October1st to 15thDay
313%27%36%16%1
255
16th to endDay
313%23%37%19%2
272
November1st to 15thDay
27%22%31%13%20%
101
16th to endDay
413%32%28%17%3
90
December1st to 15thDay
7%8%20%38%22%2
90
16th to endDay
8%15%36%26%11%1
71
January1st to 15thNight
8%19%16%32%17%5%
720
16th to endNight
11%21%15%29%19%2
768
February1st to 15thNight
6%19%13%33%21%6%
704
16th to endNight
12%18%8%33%23%3
632
March1st to 15thNight
5%19%9%34%25%5%
720
16th to endNight
5%18%8%30%31%5%
768
April1st to 15thNight
5%19%8%31%30%4
719
16th to endNight
419%7%28%32%8%
720
May1st to 15thNight
418%6%28%34%7%
663
16th to endNight
118%7%28%37%6%
563
June1st to 15thNight
117%223%44%10%
391
16th to endNight
116%15%55%10%
360
July1st to 15thNight
311%1454%25%
340
16th to endNight
216%1445%29%
619
August1st to 15thNight
19%19%54%22%
717
16th to endNight
18%18%48%31%
764
September1st to 15thNight
28%214%49%23%
706
16th to endNight
19%117%51%17%
656
October1st to 15thNight
39%6%27%42%9%
660
16th to endNight
5%9%8%26%36%12%
704
November1st to 15thNight
316%11%34%25%10%
700
16th to endNight
418%13%29%25%8%
720
December1st to 15thNight
7%20%13%31%22%5%
720
16th to endNight
13%21%13%29%18%2
768
Page generated at 2017-09-13 04:39:25. Version ac04

Copyright 2017 A. Danko


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