Barton Warnock Visitor Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Barton Warnock Visitor Center clear sky chart from 2005-11-05 to 2017-09-20.

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
71%
15296
32%
47149
27%
15256
77%
15256
46%
23765

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
72%
716
35%
2148
30%
716
76%
716
46%
1113
January16th to endNight
68%
768
36%
2304
31%
768
74%
768
45%
1194
February1st to 15thNight
66%
700
36%
2106
26%
696
76%
696
52%
1008
February16th to endNight
68%
632
36%
1894
28%
632
75%
632
56%
875
March1st to 15thNight
63%
720
35%
2148
24%
720
71%
720
50%
1076
March16th to endNight
62%
642
37%
1986
25%
642
73%
642
50%
955
April1st to 15thNight
55%
539
37%
1798
25%
539
72%
539
47%
821
April16th to endNight
57%
540
36%
1800
29%
540
72%
540
53%
781
May1st to 15thNight
56%
539
28%
1799
23%
539
69%
539
45%
857
May16th to endNight
65%
561
26%
1823
27%
561
72%
561
40%
959
June1st to 15thNight
74%
540
25%
1620
25%
540
78%
540
51%
799
June16th to endNight
77%
540
25%
1692
25%
540
80%
540
44%
864
July1st to 15thNight
77%
510
19%
1700
23%
510
79%
510
37%
921
July16th to endNight
81%
564
23%
1771
27%
531
82%
531
36%
976
August1st to 15thNight
83%
539
26%
1789
31%
536
84%
536
39%
926
August16th to endNight
80%
573
23%
1910
27%
573
80%
573
30%
1107
September1st to 15thNight
77%
540
21%
1821
22%
540
79%
540
32%
1045
September16th to endNight
72%
507
24%
1870
28%
507
73%
507
28%
1064
October1st to 15thNight
79%
495
35%
1815
38%
495
81%
495
46%
814
October16th to endNight
79%
692
39%
2100
31%
692
81%
692
58%
954
November1st to 15thNight
81%
757
38%
2157
27%
757
85%
757
63%
981
November16th to endNight
75%
900
39%
2340
24%
900
80%
900
61%
1166
December1st to 15thNight
75%
900
37%
2340
27%
900
78%
900
52%
1271
December16th to endNight
69%
882
38%
2418
27%
882
75%
882
53%
1238

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
321232345%7%62%
47644
Night
321332445%7%60%
47375
Cloud CoverDay
421232345%7%62%
47642
Night
421332345%7%60%
47375
TransparencyDay
19%5%9%19%24%21%
47364
Night
20%5%9%18%23%22%
47157
SeeingDay
45%17%32%30%10%
5081
Night
4215%46%28%1
15307

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%314413346%57%
1790
16th to endDay
5%422323345%63%
1920
February1st to 15thDay
233223345%68%
1750
16th to endDay
2211212245%72%
1580
March1st to 15thDay
2313322447%64%
1809
16th to endDay
4212212346%67%
2236
April1st to 15thDay
121222435%5%68%
2150
16th to endDay
111221234473%
2160
May1st to 15thDay
1112223346%70%
2151
16th to endDay
21122346%7%66%
2285
June1st to 15thDay
111345%7%71%
2340
16th to endDay
2133245%6%11%58%
2262
July1st to 15thDay
4214435%6%6%10%51%
2160
16th to endDay
4313435%7%7%11%46%
2277
August1st to 15thDay
31134245%7%11%53%
2160
16th to endDay
5%3145%25%6%8%11%47%
2292
September1st to 15thDay
5%425%5%245%7%10%44%
2138
16th to endDay
7%41342445%8%52%
1859
October1st to 15thDay
31221345%8%66%
1815
16th to endDay
422213245%71%
1768
November1st to 15thDay
5%212212245%70%
1687
16th to endDay
4212212235%70%
1620
December1st to 15thDay
45%23422246%61%
1620
16th to endDay
341331345%6%62%
1815
January1st to 15thNight
6%31222345%5%61%
2148
16th to endNight
6%31332335%6%59%
2304
February1st to 15thNight
231331334469%
2102
16th to endNight
2211314347%67%
1894
March1st to 15thNight
3323213445%64%
2148
16th to endNight
331321225%5%66%
1986
April1st to 15thNight
3212224346%66%
1798
16th to endNight
22222333471%
1800
May1st to 15thNight
4213323447%63%
1799
16th to endNight
3214425%46%8%56%
1822
June1st to 15thNight
113315%5%8%11%57%
1620
16th to endNight
21133245%8%12%53%
1692
July1st to 15thNight
2224436%7%9%11%47%
1800
16th to endNight
3213335%7%8%11%46%
1891
August1st to 15thNight
32133347%8%14%47%
1800
16th to endNight
23235%47%7%9%13%39%
1910
September1st to 15thNight
3215%5%46%5%6%11%46%
1821
16th to endNight
6%325%5%35%6%6%9%45%
1870
October1st to 15thNight
31123235%5%8%62%
1815
16th to endNight
3212212135%72%
2100
November1st to 15thNight
41122235%75%
2157
16th to endNight
4112112235%72%
2340
December1st to 15thNight
4312222447%63%
2340
16th to endNight
3313213445%65%
2418

Percentage Cloud Cover SE (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%323423345%58%
1790
16th to endDay
5%422313335%64%
1920
February1st to 15thDay
231332323469%
1750
16th to endDay
2211212245%72%
1580
March1st to 15thDay
333313447%64%
1809
16th to endDay
4213212336%68%
2234
April1st to 15thDay
221231335%5%68%
2150
16th to endDay
222213335%74%
2160
May1st to 15thDay
2212212346%70%
2151
16th to endDay
31221446%6%67%
2285
June1st to 15thDay
1121345%7%71%
2340
16th to endDay
211332447%10%58%
2262
July1st to 15thDay
5%214425%46%9%52%
2160
16th to endDay
4314435%7%7%12%46%
2277
August1st to 15thDay
41134245%6%11%53%
2160
16th to endDay
5%2235%346%7%12%46%
2292
September1st to 15thDay
7%425%425%47%10%45%
2138
16th to endDay
8%31442445%6%53%
1859
October1st to 15thDay
312212447%67%
1815
16th to endDay
421121223473%
1768
November1st to 15thDay
5%32211225%71%
1687
16th to endDay
5%22212235%70%
1620
December1st to 15thDay
45%13323236%62%
1620
16th to endDay
331231445%6%63%
1815
January1st to 15thNight
6%31222345%5%61%
2148
16th to endNight
6%31332335%6%60%
2304
February1st to 15thNight
231321333469%
2102
16th to endNight
2212213347%67%
1894
March1st to 15thNight
5%313223436%63%
2148
16th to endNight
3413212445%66%
1986
April1st to 15thNight
3212323346%67%
1798
16th to endNight
221221334471%
1800
May1st to 15thNight
423323446%64%
1799
16th to endNight
42134245%6%7%57%
1822
June1st to 15thNight
1133246%7%11%57%
1620
16th to endNight
22123245%7%12%54%
1692
July1st to 15thNight
3314436%6%8%11%47%
1800
16th to endNight
4313335%7%8%11%46%
1891
August1st to 15thNight
3113435%6%9%13%47%
1800
16th to endNight
33145%37%8%8%13%39%
1910
September1st to 15thNight
3216%5%35%6%8%10%46%
1821
16th to endNight
6%424445%5%6%9%44%
1870
October1st to 15thNight
4223135%5%7%62%
1815
16th to endNight
3212212235%72%
2100
November1st to 15thNight
321211245%74%
2157
16th to endNight
5%12112235%72%
2340
December1st to 15thNight
4312223446%63%
2340
16th to endNight
341322344465%
2418

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
27%37%19%29%13%
1791
16th to endDay
22%26%17%34%15%
1920
February1st to 15thDay
19%45%13%25%32%
1751
16th to endDay
14%35%13%33%29%
1580
March1st to 15thDay
18%35%18%23%30%
1809
16th to endDay
18%35%11%25%36%
2236
April1st to 15thDay
15%36%11%24%38%
2150
16th to endDay
12%35%9%22%46%
2160
May1st to 15thDay
15%36%15%23%36%
2151
16th to endDay
15%48%17%23%29%
2288
June1st to 15thDay
10%48%20%30%25%
2340
16th to endDay
18%6%13%22%22%15%
2262
July1st to 15thDay
25%7%15%23%20%7%
2031
16th to endDay
24%10%16%29%15%3
2134
August1st to 15thDay
21%8%15%28%20%4
2147
16th to endDay
26%9%18%23%15%7%
2292
September1st to 15thDay
31%9%16%20%15%6%
2138
16th to endDay
28%7%12%18%21%11%
1859
October1st to 15thDay
15%5%12%23%24%18%
1815
16th to endDay
16%25%16%29%30%
1768
November1st to 15thDay
16%36%20%30%22%
1687
16th to endDay
16%38%16%25%28%
1620
December1st to 15thDay
23%37%18%30%15%
1620
16th to endDay
20%36%23%33%12%
1815
January1st to 15thNight
23%46%16%31%17%
2148
16th to endNight
24%35%15%32%19%
2304
February1st to 15thNight
18%35%12%24%36%
2112
16th to endNight
16%25%13%31%30%
1894
March1st to 15thNight
20%3415%22%32%
2148
16th to endNight
18%45%13%21%35%
1986
April1st to 15thNight
18%36%11%20%38%
1798
16th to endNight
15%46%14%18%41%
1800
May1st to 15thNight
20%5%7%15%20%31%
1800
16th to endNight
23%7%9%18%16%24%
1824
June1st to 15thNight
16%7%11%24%25%14%
1620
16th to endNight
21%7%14%21%21%13%
1692
July1st to 15thNight
24%9%18%25%16%5%
1700
16th to endNight
25%10%17%30%13%3
1771
August1st to 15thNight
21%9%17%27%20%3
1789
16th to endNight
29%10%17%22%14%4
1910
September1st to 15thNight
28%9%20%21%12%7%
1821
16th to endNight
33%7%13%18%16%11%
1870
October1st to 15thNight
18%5%13%23%20%19%
1815
16th to endNight
16%2416%27%32%
2100
November1st to 15thNight
12%37%17%31%26%
2157
16th to endNight
15%28%12%24%35%
2340
December1st to 15thNight
20%5%6%20%26%21%
2340
16th to endNight
20%25%18%31%20%
2418

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
13%318%37%23%3
90
16th to endDay
411%21%38%21%2
96
February1st to 15thDay
36%13%32%32%12%
90
16th to endDay
7%8%17%35%25%4
81
March1st to 15thDay
5%318%38%27%8%
99
16th to endDay
212%31%32%14%5%
288
April1st to 15thDay
416%37%29%11%1
269
16th to endDay
214%34%34%10%4
270
May1st to 15thDay
114%39%32%10%1
288
16th to endDay
46%29%39%18%2
372
June1st to 15thDay
1112%33%43%7%
495
16th to endDay
29%35%41%10%
417
July1st to 15thDay
5%8%29%37%17%
305
16th to endDay
315%36%33%19%
327
August1st to 15thDay
31326%43%21%
315
16th to endDay
5%7%31%34%20%
332
September1st to 15thDay
5%8%32%33%19%
293
16th to endDay
13%5%15%45%18%
102
October1st to 15thDay
10%10%22%40%17%
90
16th to endDay
38%30%32%26%
96
November1st to 15thDay
11%313%31%34%6%
90
16th to endDay
14%8%12%28%30%5%
90
December1st to 15thDay
8%5%8%20%46%10%
90
16th to endDay
7%418%42%26%1
96
January1st to 15thNight
7%13%55%21%1
720
16th to endNight
7%413%51%22%
768
February1st to 15thNight
4320%47%22%1
704
16th to endNight
2320%60%12%
632
March1st to 15thNight
5%322%50%16%1
720
16th to endNight
5%423%47%18%1
642
April1st to 15thNight
27%30%48%10%
539
16th to endNight
25%31%51%9%
540
May1st to 15thNight
4430%52%8%
540
16th to endNight
3221%57%14%
563
June1st to 15thNight
118%53%25%
540
16th to endNight
213%45%38%
540
July1st to 15thNight
39%40%43%2
510
16th to endNight
5%5%37%46%3
564
August1st to 15thNight
2326%61%5%
539
16th to endNight
4430%55%5%
573
September1st to 15thNight
317%31%54%2
540
16th to endNight
9%6%40%41%1
507
October1st to 15thNight
49%48%34%1
495
16th to endNight
5%19%40%38%4
692
November1st to 15thNight
418%47%34%4
757
16th to endNight
5%212%45%31%2
900
December1st to 15thNight
6%111%50%28%1
900
16th to endNight
4315%53%19%2
882
Page generated at 2017-09-21 06:18:17. Version ac04

Copyright 2017 A. Danko


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