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 2018-10-27.

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%
17184
38%
51319
34%
17145
82%
17145
57%
23793

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%
778
33%
2522
34%
776
78%
776
46%
1235
January16th to endNight
71%
832
38%
2704
38%
832
78%
832
46%
1323
February1st to 15thNight
77%
759
38%
2335
38%
758
83%
758
55%
1073
February16th to endNight
69%
684
36%
2051
37%
684
74%
684
46%
1060
March1st to 15thNight
71%
780
40%
2155
34%
780
78%
780
58%
1048
March16th to endNight
74%
832
40%
2288
31%
832
81%
832
63%
1059
April1st to 15thNight
69%
779
35%
2143
23%
779
77%
779
58%
1030
April16th to endNight
68%
592
45%
1795
34%
592
78%
592
70%
716
May1st to 15thNight
73%
584
41%
1754
32%
584
79%
584
66%
733
May16th to endNight
76%
609
40%
1828
31%
609
81%
609
73%
729
June1st to 15thNight
84%
585
37%
1755
32%
585
85%
585
75%
698
June16th to endNight
88%
585
35%
1755
30%
585
89%
585
76%
696
July1st to 15thNight
81%
555
26%
1665
21%
555
82%
555
51%
851
July16th to endNight
83%
612
28%
1737
23%
579
85%
579
43%
941
August1st to 15thNight
86%
575
33%
1719
30%
572
86%
572
49%
862
August16th to endNight
86%
739
33%
2046
28%
739
86%
739
52%
1071
September1st to 15thNight
81%
780
36%
2145
31%
780
83%
780
55%
1080
September16th to endNight
86%
776
43%
2145
36%
776
89%
776
71%
945
October1st to 15thNight
81%
780
42%
2213
36%
780
84%
780
66%
1001
October16th to endNight
85%
816
46%
2448
41%
816
89%
816
71%
1002
November1st to 15thNight
85%
760
41%
2342
40%
760
87%
760
63%
1018
November16th to endNight
79%
780
42%
2535
44%
780
83%
780
56%
1101
December1st to 15thNight
77%
780
37%
2535
38%
780
80%
780
49%
1188
December16th to endNight
74%
832
39%
2704
40%
832
77%
832
45%
1333

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%
52230
Night
3112212345%70%
51517
TransparencyDay
15%2311%25%41%
51925
Night
16%2310%22%43%
51323
SeeingDay
35%16%31%31%10%
6964
Night
3210%40%38%4
17194

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
4213323245%67%
1746
16th to endDay
6%213212236%66%
1872
February1st to 15thDay
3313212245%68%
1854
16th to endDay
5%313222336%64%
1709
March1st to 15thDay
3212213335%69%
2133
16th to endDay
2112312345%71%
2288
April1st to 15thDay
111212348%71%
2135
16th to endDay
11111225%81%
2436
May1st to 15thDay
1111225%82%
2526
16th to endDay
211112383%
2637
June1st to 15thDay
1111112483%
2535
16th to endDay
111112385%
2535
July1st to 15thDay
21242346%7%64%
2535
16th to endDay
32145%25%5%7%10%48%
2675
August1st to 15thDay
311332346%8%61%
2485
16th to endDay
31232345%8%63%
2504
September1st to 15thDay
422323346%66%
2145
16th to endDay
21111122281%
2145
October1st to 15thDay
31211222477%
2077
16th to endDay
11121133479%
2032
November1st to 15thDay
12112235%76%
1844
16th to endDay
4112211225%73%
1755
December1st to 15thDay
433323446%63%
1755
16th to endDay
5%31421335%7%60%
1872
January1st to 15thNight
4213323336%63%
2522
16th to endNight
7%213223235%65%
2704
February1st to 15thNight
3212212245%70%
2326
16th to endNight
5%213423336%63%
2051
March1st to 15thNight
4212212335%70%
2155
16th to endNight
312212236%74%
2288
April1st to 15thNight
2112213345%71%
2143
16th to endNight
1111122482%
1795
May1st to 15thNight
1121223478%
1754
16th to endNight
111111286%
1828
June1st to 15thNight
1222482%
1755
16th to endNight
111121384%
1755
July1st to 15thNight
12332346%10%59%
1755
16th to endNight
2213435%6%9%11%49%
1845
August1st to 15thNight
11124345%7%8%59%
1728
16th to endNight
12123235%6%8%60%
2046
September1st to 15thNight
321221345%6%66%
2145
16th to endNight
1121222381%
2145
October1st to 15thNight
311211223477%
2213
16th to endNight
111111135%79%
2448
November1st to 15thNight
1212111345%74%
2342
16th to endNight
3212212225%73%
2535
December1st to 15thNight
5%213222446%65%
2535
16th to endNight
5%313323335%63%
2704

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
21%2414%30%25%
1747
16th to endDay
21%2314%28%30%
1872
February1st to 15thDay
19%2416%28%30%
1854
16th to endDay
22%1315%30%26%
1709
March1st to 15thDay
18%129%29%37%
2133
16th to endDay
16%139%32%36%
2288
April1st to 15thDay
12%228%34%39%
2135
16th to endDay
9%126%23%56%
2436
May1st to 15thDay
8%117%23%57%
2526
16th to endDay
8%115%20%62%
2640
June1st to 15thDay
8%1314%71%
2535
16th to endDay
7%139%77%
2535
July1st to 15thDay
18%47%13%19%36%
2396
16th to endDay
26%6%11%23%20%11%
2520
August1st to 15thDay
19%5%7%17%19%30%
2470
16th to endDay
18%5%7%15%28%24%
2504
September1st to 15thDay
19%3411%25%35%
2145
16th to endDay
10%11426%54%
2145
October1st to 15thDay
13%2210%24%47%
2077
16th to endDay
10%238%28%47%
2032
November1st to 15thDay
13%1114%30%38%
1844
16th to endDay
16%1210%28%41%
1755
December1st to 15thDay
23%3414%27%26%
1755
16th to endDay
23%35%20%29%17%
1872
January1st to 15thNight
22%3411%24%33%
2522
16th to endNight
23%2212%25%33%
2704
February1st to 15thNight
17%2414%24%37%
2337
16th to endNight
24%2310%25%33%
2051
March1st to 15thNight
16%228%23%46%
2155
16th to endNight
14%128%29%43%
2288
April1st to 15thNight
16%127%27%44%
2143
16th to endNight
8%115%21%61%
1795
May1st to 15thNight
10%125%23%55%
1755
16th to endNight
8%15%16%67%
1829
June1st to 15thNight
8%11313%71%
1755
16th to endNight
8%1136%79%
1755
July1st to 15thNight
19%5%9%13%16%36%
1665
16th to endNight
21%8%10%21%21%15%
1737
August1st to 15thNight
20%5%5%19%19%30%
1719
16th to endNight
20%49%13%24%27%
2046
September1st to 15thNight
17%46%15%21%34%
2145
16th to endNight
10%115%20%60%
2145
October1st to 15thNight
13%129%22%50%
2213
16th to endNight
9%129%19%57%
2448
November1st to 15thNight
13%219%28%44%
2342
16th to endNight
16%128%23%46%
2535
December1st to 15thNight
20%2413%25%33%
2535
16th to endNight
24%1415%29%23%
2704

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%215%40%24%3
135
16th to endDay
6%413%32%31%11%
144
February1st to 15thDay
5%6%18%26%31%11%
279
16th to endDay
8%10%26%34%19%1
290
March1st to 15thDay
411%20%30%24%9%
330
16th to endDay
210%25%30%24%6%
352
April1st to 15thDay
314%21%30%22%7%
329
16th to endDay
415%29%27%15%6%
318
May1st to 15thDay
211%26%33%20%4
348
16th to endDay
26%23%37%25%4
394
June1st to 15thDay
2322%33%30%7%
375
16th to endDay
110%38%34%13%
375
July1st to 15thDay
117%36%38%14%
365
16th to endDay
2430%37%24%
391
August1st to 15thDay
2329%47%17%
359
16th to endDay
115%25%46%20%
396
September1st to 15thDay
5%9%31%38%13%
375
16th to endDay
4216%29%33%14%
375
October1st to 15thDay
7%316%33%31%7%
307
16th to endDay
228%29%39%17%
178
November1st to 15thDay
214%34%40%8%
135
16th to endDay
6%317%33%30%8%
135
December1st to 15thDay
5%211%37%38%5%
135
16th to endDay
6%419%28%32%8%
144
January1st to 15thNight
5%111%45%32%3
780
16th to endNight
8%211%45%28%3
832
February1st to 15thNight
5%210%47%30%4
764
16th to endNight
5%314%50%24%2
684
March1st to 15thNight
4316%40%31%3
780
16th to endNight
3314%41%32%4
832
April1st to 15thNight
36%15%42%29%2
779
16th to endNight
26%20%42%24%4
592
May1st to 15thNight
1418%42%30%2
585
16th to endNight
2216%42%35%1
611
June1st to 15thNight
1111%50%32%1
585
16th to endNight
17%39%48%2
585
July1st to 15thNight
28%30%53%5%
555
16th to endNight
2425%58%8%
612
August1st to 15thNight
21325%56%10%
575
16th to endNight
1422%59%11%
739
September1st to 15thNight
316%28%52%7%
780
16th to endNight
116%37%44%7%
776
October1st to 15thNight
310%43%39%1
780
16th to endNight
28%37%45%6%
816
November1st to 15thNight
18%45%40%3
760
16th to endNight
318%41%39%5%
780
December1st to 15thNight
6%29%45%34%2
780
16th to endNight
7%29%45%30%4
832
Page generated at 2018-10-28 05:41:06. Version ac04

Copyright 2018 A. Danko


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