Wildflower Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Wildflower Observatory clear sky chart from 2005-11-05 to 2017-09-18.

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
78%
15710
38%
46934
34%
15671
82%
15671
57%
21839

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
73%
718
33%
2327
34%
716
78%
716
47%
1128
January16th to endNight
70%
768
37%
2496
37%
768
77%
768
44%
1244
February1st to 15thNight
76%
699
39%
2152
38%
698
82%
698
55%
983
February16th to endNight
69%
632
36%
1895
37%
632
73%
632
45%
987
March1st to 15thNight
70%
720
41%
1989
34%
720
78%
720
59%
967
March16th to endNight
74%
768
41%
2112
31%
768
81%
768
63%
977
April1st to 15thNight
68%
719
34%
1978
22%
719
76%
719
57%
960
April16th to endNight
68%
552
47%
1675
35%
552
78%
552
72%
656
May1st to 15thNight
73%
539
39%
1619
31%
539
79%
539
65%
681
May16th to endNight
75%
561
41%
1684
31%
561
81%
561
72%
678
June1st to 15thNight
83%
540
36%
1620
31%
540
85%
540
74%
649
June16th to endNight
88%
540
36%
1620
31%
540
89%
540
76%
644
July1st to 15thNight
82%
510
27%
1530
22%
510
83%
510
53%
765
July16th to endNight
82%
564
29%
1593
23%
531
84%
531
42%
869
August1st to 15thNight
85%
539
31%
1611
28%
536
85%
536
47%
824
August16th to endNight
85%
682
34%
1888
29%
682
85%
682
50%
1005
September1st to 15thNight
80%
720
34%
1980
28%
720
82%
720
53%
1017
September16th to endNight
86%
667
43%
1847
36%
667
89%
667
70%
821
October1st to 15thNight
81%
660
43%
1873
37%
660
85%
660
68%
833
October16th to endNight
86%
704
45%
2112
41%
704
90%
704
70%
873
November1st to 15thNight
86%
700
42%
2157
42%
700
88%
700
66%
907
November16th to endNight
79%
720
41%
2340
42%
720
82%
720
56%
1018
December1st to 15thNight
77%
720
37%
2340
39%
720
80%
720
49%
1097
December16th to endNight
73%
768
37%
2496
39%
768
76%
768
43%
1256

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
2112212335%71%
47856
Night
3112212345%70%
47132
TransparencyDay
15%2311%25%41%
47551
Night
16%2310%22%43%
46938
SeeingDay
36%17%32%30%9%
5508
Night
3210%40%38%4
15720

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
4213223245%68%
1611
16th to endDay
6%213212336%65%
1728
February1st to 15thDay
3313212245%68%
1707
16th to endDay
5%313222337%63%
1579
March1st to 15thDay
3212213335%70%
1969
16th to endDay
2112312245%72%
2112
April1st to 15thDay
211213348%71%
1970
16th to endDay
1111122482%
2281
May1st to 15thDay
1111225%82%
2331
16th to endDay
211112383%
2429
June1st to 15thDay
1111112384%
2340
16th to endDay
1111112385%
2340
July1st to 15thDay
211242346%6%64%
2340
16th to endDay
42145%26%5%7%10%48%
2467
August1st to 15thDay
321332446%8%60%
2340
16th to endDay
3123235%5%7%63%
2310
September1st to 15thDay
5%23323346%64%
1980
16th to endDay
21111222381%
1838
October1st to 15thDay
111112225%77%
1757
16th to endDay
11111123479%
1760
November1st to 15thDay
12112235%78%
1699
16th to endDay
4112211225%74%
1620
December1st to 15thDay
4312323446%63%
1620
16th to endDay
5%31421335%7%60%
1728
January1st to 15thNight
4213323335%65%
2327
16th to endNight
7%224323325%64%
2496
February1st to 15thNight
3212213245%70%
2143
16th to endNight
5%213423336%62%
1895
March1st to 15thNight
4212112335%70%
1989
16th to endNight
312112235%74%
2112
April1st to 15thNight
2112213245%70%
1978
16th to endNight
111112384%
1675
May1st to 15thNight
11122223478%
1619
16th to endNight
111111285%
1684
June1st to 15thNight
1222482%
1620
16th to endNight
111121384%
1620
July1st to 15thNight
12332346%10%60%
1620
16th to endNight
2213436%6%8%10%50%
1701
August1st to 15thNight
11124345%7%8%58%
1620
16th to endNight
22134245%6%7%59%
1888
September1st to 15thNight
321321345%7%64%
1980
16th to endNight
1121222380%
1847
October1st to 15thNight
211211223477%
1873
16th to endNight
111112235%79%
2112
November1st to 15thNight
1111111345%76%
2157
16th to endNight
3112212225%73%
2340
December1st to 15thNight
5%212212446%65%
2340
16th to endNight
6%313423335%62%
2496

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
20%2315%29%27%
1612
16th to endDay
21%2314%27%29%
1728
February1st to 15thDay
18%1417%27%29%
1707
16th to endDay
22%1316%30%25%
1579
March1st to 15thDay
18%118%30%39%
1969
16th to endDay
16%139%32%37%
2112
April1st to 15thDay
13%227%34%39%
1970
16th to endDay
8%127%23%56%
2281
May1st to 15thDay
8%117%23%56%
2331
16th to endDay
8%115%22%60%
2432
June1st to 15thDay
7%1314%71%
2340
16th to endDay
7%139%76%
2340
July1st to 15thDay
18%47%13%19%36%
2201
16th to endDay
27%6%11%22%20%11%
2312
August1st to 15thDay
20%6%7%16%19%30%
2325
16th to endDay
18%5%6%14%28%26%
2310
September1st to 15thDay
20%35%11%25%33%
1980
16th to endDay
10%21426%55%
1838
October1st to 15thDay
12%2210%25%47%
1757
16th to endDay
10%237%28%48%
1760
November1st to 15thDay
11%1112%31%41%
1699
16th to endDay
15%1210%28%41%
1620
December1st to 15thDay
23%3414%29%24%
1620
16th to endDay
24%35%20%29%15%
1728
January1st to 15thNight
22%3410%24%35%
2327
16th to endNight
25%2212%25%32%
2496
February1st to 15thNight
17%1414%23%36%
2154
16th to endNight
25%2310%25%33%
1895
March1st to 15thNight
15%318%23%48%
1989
16th to endNight
14%128%29%43%
2112
April1st to 15thNight
16%226%27%44%
1978
16th to endNight
7%116%21%62%
1675
May1st to 15thNight
11%125%24%55%
1620
16th to endNight
8%115%16%65%
1685
June1st to 15thNight
8%11314%71%
1620
16th to endNight
8%1137%78%
1620
July1st to 15thNight
17%5%9%13%16%36%
1530
16th to endNight
22%8%10%20%21%16%
1593
August1st to 15thNight
21%5%5%18%18%30%
1611
16th to endNight
21%48%12%24%28%
1888
September1st to 15thNight
19%46%15%21%32%
1980
16th to endNight
11%115%20%59%
1847
October1st to 15thNight
12%1210%22%50%
1873
16th to endNight
10%129%17%58%
2112
November1st to 15thNight
11%218%27%47%
2157
16th to endNight
16%129%22%46%
2340
December1st to 15thNight
20%2413%27%31%
2340
16th to endNight
25%2415%29%22%
2496

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
16%320%46%13%
90
16th to endDay
6%6%14%33%29%10%
96
February1st to 15thDay
47%21%27%34%5%
222
16th to endDay
9%10%25%31%21%1
238
March1st to 15thDay
413%21%27%22%10%
270
16th to endDay
212%25%29%23%6%
288
April1st to 15thDay
415%22%29%20%6%
269
16th to endDay
317%33%25%14%5%
270
May1st to 15thDay
212%27%33%20%3
288
16th to endDay
36%23%35%26%4
330
June1st to 15thDay
2324%34%26%7%
315
16th to endDay
111%41%32%11%
315
July1st to 15thDay
28%39%37%10%
305
16th to endDay
25%31%37%22%
327
August1st to 15thDay
2330%47%14%
315
16th to endDay
116%26%46%18%
332
September1st to 15thDay
6%10%34%37%10%
315
16th to endDay
4119%31%34%8%
264
October1st to 15thDay
45%17%33%29%9%
197
16th to endDay
31434%46%10%
96
November1st to 15thDay
416%33%35%10%
90
16th to endDay
5%5%17%44%23%3
90
December1st to 15thDay
4211%32%42%7%
90
16th to endDay
9%6%27%31%25%1
96
January1st to 15thNight
4112%45%32%3
720
16th to endNight
8%211%44%28%3
768
February1st to 15thNight
4210%48%29%3
704
16th to endNight
6%314%49%24%2
632
March1st to 15thNight
4416%39%31%4
720
16th to endNight
3314%41%32%4
768
April1st to 15thNight
36%15%43%27%2
719
16th to endNight
25%21%42%23%4
552
May1st to 15thNight
1418%42%29%2
540
16th to endNight
2217%39%36%1
563
June1st to 15thNight
1112%52%31%1
540
16th to endNight
17%40%48%2
540
July1st to 15thNight
29%31%52%4
510
16th to endNight
21424%59%8%
564
August1st to 15thNight
21325%55%11%
539
16th to endNight
1423%59%10%
682
September1st to 15thNight
317%28%50%7%
720
16th to endNight
126%38%43%7%
667
October1st to 15thNight
3110%42%40%2
660
16th to endNight
217%38%44%6%
704
November1st to 15thNight
118%44%40%4
700
16th to endNight
318%42%38%4
720
December1st to 15thNight
6%29%43%35%2
720
16th to endNight
8%29%47%28%3
768
Page generated at 2017-09-19 04:32:25. Version ac04

Copyright 2017 A. Danko


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