Fossil Falls
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fossil Falls clear sky chart from 2005-11-05 to 2017-12-04.

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
66%
15888
38%
47773
28%
15848
77%
15848
61%
20484

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
60%
718
30%
2506
23%
716
72%
716
49%
1071
January16th to endNight
54%
768
36%
2454
26%
768
69%
768
45%
1150
February1st to 15thNight
59%
700
37%
2103
28%
697
72%
697
53%
974
February16th to endNight
55%
632
37%
1895
28%
632
69%
632
53%
875
March1st to 15thNight
51%
720
31%
2160
21%
720
68%
720
52%
994
March16th to endNight
53%
768
38%
2011
20%
768
67%
768
56%
989
April1st to 15thNight
47%
719
36%
1799
13%
719
61%
719
58%
889
April16th to endNight
54%
720
41%
1800
15%
720
66%
720
68%
833
May1st to 15thNight
55%
566
37%
1646
21%
566
63%
566
69%
671
May16th to endNight
58%
561
36%
1685
22%
561
68%
561
66%
672
June1st to 15thNight
70%
381
36%
1461
34%
381
81%
381
68%
485
June16th to endNight
78%
360
42%
1440
44%
360
88%
360
80%
420
July1st to 15thNight
87%
340
35%
1360
40%
340
91%
340
65%
455
July16th to endNight
88%
486
39%
1517
38%
455
89%
455
64%
611
August1st to 15thNight
85%
717
37%
1790
24%
713
86%
713
82%
796
August16th to endNight
88%
764
45%
1910
29%
764
89%
764
83%
851
September1st to 15thNight
86%
720
42%
1830
29%
720
91%
720
77%
828
September16th to endNight
81%
716
49%
1980
40%
716
89%
716
83%
785
October1st to 15thNight
71%
720
40%
2004
32%
720
81%
720
67%
886
October16th to endNight
74%
768
46%
2367
41%
768
84%
768
66%
956
November1st to 15thNight
72%
760
37%
2470
33%
760
84%
760
64%
981
November16th to endNight
69%
780
40%
2535
37%
780
78%
780
60%
1030
December1st to 15thNight
62%
736
35%
2392
24%
736
76%
736
50%
1053
December16th to endNight
53%
768
33%
2658
25%
768
67%
768
40%
1229

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
111112236%76%
48715
Night
111112235%78%
47965
TransparencyDay
11%36%16%28%33%
48397
Night
10%36%19%30%28%
47783
SeeingDay
417%37%29%8%2
6079
Night
26%22%33%27%8%
15897

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
31112248%72%
1432
16th to endDay
5%32222335%66%
1769
February1st to 15thDay
111113249%71%
1751
16th to endDay
411121235%9%66%
1579
March1st to 15thDay
111111235%8%71%
1800
16th to endDay
211112349%70%
2211
April1st to 15thDay
112212435%73%
2149
16th to endDay
111236%78%
2160
May1st to 15thDay
1112235%80%
2302
16th to endDay
11211235%6%73%
2429
June1st to 15thDay
111235%81%
2496
16th to endDay
1111387%
2520
July1st to 15thDay
211212336%75%
2520
16th to endDay
1112213336%71%
2541
August1st to 15thDay
111222383%
2160
16th to endDay
1122385%
2292
September1st to 15thDay
11111235%80%
2130
16th to endDay
1112288%
1980
October1st to 15thDay
2112225%79%
1953
16th to endDay
1121122479%
1855
November1st to 15thDay
11111135%79%
1719
16th to endDay
21112236%76%
1755
December1st to 15thDay
1113112349%69%
1649
16th to endDay
1312212346%69%
1563
January1st to 15thNight
112213336%72%
2506
16th to endNight
4412212235%69%
2454
February1st to 15thNight
1211335%7%71%
2101
16th to endNight
421112347%70%
1895
March1st to 15thNight
11221135%7%72%
2160
16th to endNight
11121235%7%72%
2011
April1st to 15thNight
2111112236%76%
1799
16th to endNight
111123483%
1800
May1st to 15thNight
111237%81%
1646
16th to endNight
11125%83%
1684
June1st to 15thNight
123483%
1461
16th to endNight
11290%
1440
July1st to 15thNight
11111132480%
1440
16th to endNight
1212235%78%
1622
August1st to 15thNight
1112384%
1800
16th to endNight
1112386%
1910
September1st to 15thNight
11123383%
1830
16th to endNight
12388%
1980
October1st to 15thNight
1111123381%
2004
16th to endNight
11111235%81%
2367
November1st to 15thNight
111111235%80%
2470
16th to endNight
11112237%76%
2535
December1st to 15thNight
1112212346%71%
2392
16th to endNight
1212312347%68%
2658

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
12%6%10%25%30%13%
1432
16th to endDay
21%5%7%22%26%17%
1769
February1st to 15thDay
13%5%9%26%29%16%
1751
16th to endDay
15%6%10%24%30%11%
1579
March1st to 15thDay
11%411%27%26%18%
1800
16th to endDay
13%5%11%26%26%16%
2211
April1st to 15thDay
14%48%23%31%17%
2149
16th to endDay
8%37%22%37%19%
2160
May1st to 15thDay
8%35%19%34%28%
2302
16th to endDay
12%45%15%40%21%
2432
June1st to 15thDay
7%2411%26%48%
2496
16th to endDay
5%12416%70%
2520
July1st to 15thDay
11%337%14%58%
2371
16th to endDay
14%35%9%18%47%
2383
August1st to 15thDay
7%226%18%62%
2146
16th to endDay
5%227%24%56%
2292
September1st to 15thDay
8%339%21%53%
2130
16th to endDay
5%118%39%43%
1980
October1st to 15thDay
10%3314%34%34%
1953
16th to endDay
11%3312%34%34%
1855
November1st to 15thDay
10%36%20%38%20%
1719
16th to endDay
11%37%21%35%20%
1755
December1st to 15thDay
14%5%11%27%27%13%
1649
16th to endDay
18%7%12%26%21%14%
1563
January1st to 15thNight
14%5%9%25%30%14%
2506
16th to endNight
19%39%19%29%17%
2454
February1st to 15thNight
14%48%26%27%17%
2112
16th to endNight
15%38%25%36%10%
1895
March1st to 15thNight
12%5%8%25%26%20%
2160
16th to endNight
11%6%8%31%30%11%
2011
April1st to 15thNight
12%37%26%34%14%
1799
16th to endNight
7%35%28%38%18%
1800
May1st to 15thNight
6%36%21%39%22%
1647
16th to endNight
7%26%22%39%21%
1685
June1st to 15thNight
6%2315%31%40%
1461
16th to endNight
4116%20%65%
1440
July1st to 15thNight
8%337%16%61%
1360
16th to endNight
10%348%22%50%
1517
August1st to 15thNight
6%138%20%59%
1790
16th to endNight
5%126%30%53%
1910
September1st to 15thNight
6%337%22%55%
1830
16th to endNight
31210%36%45%
1980
October1st to 15thNight
9%3313%35%34%
2004
16th to endNight
8%2412%37%33%
2367
November1st to 15thNight
9%37%20%37%21%
2470
16th to endNight
10%37%22%32%23%
2535
December1st to 15thNight
14%5%11%26%29%12%
2392
16th to endNight
16%7%11%25%23%13%
2658

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
10%28%35%20%5%1
60
16th to endDay
12%20%32%25%7%1
236
February1st to 15thDay
323%33%29%9%1
266
16th to endDay
9%26%39%18%5%
238
March1st to 15thDay
5%26%37%19%8%2
270
16th to endDay
6%27%42%19%3
288
April1st to 15thDay
12%31%34%15%5%1
269
16th to endDay
7%34%39%15%21
270
May1st to 15thDay
225%44%20%42
288
16th to endDay
5%23%36%24%7%2
330
June1st to 15thDay
412%46%27%6%2
315
16th to endDay
114%33%34%10%4
315
July1st to 15thDay
25%34%39%13%4
305
16th to endDay
16%32%41%11%5%
327
August1st to 15thDay
27%42%32%8%6%
315
16th to endDay
5%34%39%11%8%
332
September1st to 15thDay
17%38%41%9%
315
16th to endDay
29%39%36%10%1
315
October1st to 15thDay
415%42%29%6%
315
16th to endDay
314%30%35%14%2
271
November1st to 15thDay
213%24%33%20%6%
135
16th to endDay
15%31%30%20%1
135
December1st to 15thDay
213%39%37%9%
100
16th to endDay
220%37%23%13%2
69
January1st to 15thNight
26%27%29%23%9%
720
16th to endNight
6%9%25%31%20%6%
768
February1st to 15thNight
26%29%30%23%8%
704
16th to endNight
6%8%28%30%19%5%
632
March1st to 15thNight
210%32%30%16%7%
720
16th to endNight
211%31%31%18%4
768
April1st to 15thNight
314%32%27%17%4
719
16th to endNight
12%31%29%20%5%
720
May1st to 15thNight
19%33%34%18%3
567
16th to endNight
110%27%36%21%1
563
June1st to 15thNight
423%43%24%3
381
16th to endNight
119%50%25%3
360
July1st to 15thNight
27%44%39%5%
340
16th to endNight
6%40%46%4
486
August1st to 15thNight
19%40%39%8%
717
16th to endNight
8%29%46%13%
764
September1st to 15thNight
19%30%46%12%
720
16th to endNight
214%30%36%14%
716
October1st to 15thNight
15%19%37%24%11%
720
16th to endNight
26%14%28%32%15%
768
November1st to 15thNight
15%19%32%29%11%
760
16th to endNight
26%20%33%27%9%
780
December1st to 15thNight
36%24%34%22%7%
736
16th to endNight
311%27%30%20%6%
768
Page generated at 2017-12-05 07:19:05. Version ac04

Copyright 2017 A. Danko


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