The Cowpasture
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the The Cowpasture 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
54%
15722
25%
47932
19%
15677
60%
15677
33%
28259

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
36%
900
24%
2327
11%
895
45%
895
32%
1498
January16th to endNight
31%
948
24%
2484
10%
948
40%
948
29%
1651
February1st to 15thNight
36%
704
25%
2112
13%
701
45%
701
28%
1317
February16th to endNight
30%
631
25%
1893
12%
631
39%
631
28%
1182
March1st to 15thNight
34%
603
23%
2043
15%
603
43%
603
26%
1246
March16th to endNight
42%
576
24%
2052
18%
576
50%
576
30%
1151
April1st to 15thNight
45%
539
25%
1797
18%
539
56%
539
31%
1022
April16th to endNight
49%
540
28%
1800
23%
540
60%
540
36%
979
May1st to 15thNight
58%
540
22%
1800
19%
540
66%
540
33%
1008
May16th to endNight
69%
562
22%
1835
22%
561
72%
561
38%
991
June1st to 15thNight
78%
540
19%
1440
18%
540
78%
540
39%
868
June16th to endNight
77%
540
22%
1502
21%
540
78%
540
39%
874
July1st to 15thNight
80%
510
18%
1530
20%
510
81%
510
37%
887
July16th to endNight
80%
564
18%
1630
21%
531
80%
531
36%
950
August1st to 15thNight
82%
539
17%
1788
21%
536
82%
536
34%
1006
August16th to endNight
73%
573
21%
1910
26%
573
74%
573
28%
1177
September1st to 15thNight
72%
540
24%
1800
27%
540
73%
540
31%
1060
September16th to endNight
75%
664
32%
1927
29%
664
76%
664
41%
1074
October1st to 15thNight
68%
720
33%
2132
26%
720
72%
720
45%
1128
October16th to endNight
59%
768
35%
2304
29%
768
65%
768
41%
1250
November1st to 15thNight
56%
760
31%
2314
25%
760
63%
760
37%
1294
November16th to endNight
50%
780
31%
2535
24%
780
60%
780
35%
1384
December1st to 15thNight
41%
736
23%
2391
17%
736
50%
736
26%
1473
December16th to endNight
36%
945
19%
2586
12%
945
40%
945
23%
1789

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
11%5%25%5%35%5%5%7%42%
48532
Night
10%42442445%7%49%
48135
TransparencyDay
39%5%11%19%18%5%
48238
Night
33%411%20%20%8%
47934
SeeingDay
11%415%24%27%17%
5746
Night
12%421%31%24%5%
15723

By Month

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
18%5%25%323246%44%
1611
16th to endDay
18%5%35%41333445%
1737
February1st to 15thDay
15%8%24423446%43%
1750
16th to endDay
16%6%36%42333443%
1580
March1st to 15thDay
17%6%26%424346%41%
1926
16th to endDay
10%7%37%5%3445%6%40%
2170
April1st to 15thDay
12%426%425%45%8%43%
2151
16th to endDay
10%425%5%35%5%6%7%44%
2160
May1st to 15thDay
10%5%36%6%35%5%5%9%38%
2151
16th to endDay
8%425%5%46%6%6%8%40%
2271
June1st to 15thDay
6%426%7%46%7%7%9%37%
2520
16th to endDay
5%425%7%47%7%8%9%37%
2453
July1st to 15thDay
7%436%7%48%8%7%10%29%
2340
16th to endDay
9%5%35%5%5%7%9%8%10%29%
2427
August1st to 15thDay
6%426%7%46%7%7%10%36%
2160
16th to endDay
12%5%25%5%46%6%6%9%34%
2292
September1st to 15thDay
10%426%6%35%6%6%8%38%
2160
16th to endDay
11%41442445%6%49%
2019
October1st to 15thDay
7%32432445%6%56%
1824
16th to endDay
11%21331233460%
1920
November1st to 15thDay
9%424424346%53%
1872
16th to endDay
14%423412345%53%
1755
December1st to 15thDay
17%8%25%5%33347%39%
1651
16th to endDay
17%8%35%424346%39%
1632
January1st to 15thNight
15%5%24422335%49%
2327
16th to endNight
19%5%33423345%44%
2484
February1st to 15thNight
14%6%34423445%46%
2103
16th to endNight
17%5%34423345%46%
1893
March1st to 15thNight
15%5%25%5%23346%44%
2043
16th to endNight
11%5%23424446%50%
2052
April1st to 15thNight
9%42443445%7%49%
1797
16th to endNight
7%32443346%7%52%
1800
May1st to 15thNight
7%4144245%6%9%49%
1799
16th to endNight
6%32432446%10%51%
1835
June1st to 15thNight
25%235%446%7%10%47%
1440
16th to endNight
2324425%6%8%10%48%
1502
July1st to 15thNight
5%3234245%8%11%47%
1620
16th to endNight
42245%35%46%12%47%
1741
August1st to 15thNight
3313436%6%9%12%45%
1800
16th to endNight
8%416%5%35%5%7%11%41%
1910
September1st to 15thNight
9%4245%3446%9%47%
1800
16th to endNight
7%3133245%6%7%54%
1927
October1st to 15thNight
7%313313446%59%
2132
16th to endNight
12%32331222462%
2304
November1st to 15thNight
11%413223436%55%
2314
16th to endNight
12%423323335%55%
2535
December1st to 15thNight
15%5%34334446%45%
2391
16th to endNight
17%9%35%42334439%
2586

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
41%25%18%23%7%
1612
16th to endDay
42%3317%24%8%
1737
February1st to 15thDay
42%36%19%19%7%
1752
16th to endDay
44%25%17%22%7%
1580
March1st to 15thDay
44%39%16%20%5%
1926
16th to endDay
43%48%18%21%3
2172
April1st to 15thDay
38%48%22%21%6%
2151
16th to endDay
37%49%22%22%2
2160
May1st to 15thDay
43%5%11%16%17%5%
2151
16th to endDay
37%6%15%24%14%1
2275
June1st to 15thDay
38%8%16%23%12%1
2520
16th to endDay
38%8%16%19%15%1
2453
July1st to 15thDay
42%11%18%19%6%2
2201
16th to endDay
43%10%18%18%7%
2275
August1st to 15thDay
39%8%19%21%8%2
2148
16th to endDay
44%8%15%18%9%3
2292
September1st to 15thDay
41%7%14%17%13%6%
2160
16th to endDay
33%412%21%20%8%
2019
October1st to 15thDay
28%39%18%25%14%
1824
16th to endDay
28%2315%36%14%
1920
November1st to 15thDay
32%27%17%30%9%
1872
16th to endDay
34%26%16%25%13%
1755
December1st to 15thDay
46%310%17%14%7%
1651
16th to endDay
45%38%21%16%4
1632
January1st to 15thNight
39%27%15%24%9%
2327
16th to endNight
41%35%17%22%8%
2484
February1st to 15thNight
40%26%19%21%9%
2112
16th to endNight
39%36%17%22%9%
1893
March1st to 15thNight
40%38%18%21%7%
2043
16th to endNight
34%410%22%22%5%
2052
April1st to 15thNight
33%410%22%20%9%
1797
16th to endNight
30%39%23%25%6%
1800
May1st to 15thNight
29%7%13%23%19%6%
1800
16th to endNight
27%5%17%28%17%3
1837
June1st to 15thNight
29%6%17%25%18%1
1440
16th to endNight
28%6%21%22%17%4
1502
July1st to 15thNight
27%8%24%27%8%3
1530
16th to endNight
27%9%26%25%9%1
1630
August1st to 15thNight
25%11%25%22%12%2
1788
16th to endNight
33%10%18%20%12%4
1910
September1st to 15thNight
33%6%15%22%15%6%
1800
16th to endNight
27%413%21%22%10%
1927
October1st to 15thNight
24%48%20%25%16%
2132
16th to endNight
28%2413%28%21%
2304
November1st to 15thNight
31%36%19%27%12%
2314
16th to endNight
31%26%17%24%16%
2535
December1st to 15thNight
41%311%18%19%6%
2391
16th to endNight
48%27%16%18%6%
2586

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
20%13%35%18%12%
90
16th to endDay
14%21%44%13%41
96
February1st to 15thDay
11%11%52%20%5%
90
16th to endDay
16%11%48%22%2
81
March1st to 15thDay
24%22%33%17%2
90
16th to endDay
16%13%21%37%10%
156
April1st to 15thDay
15%9%26%29%16%2
270
16th to endDay
14%5%21%34%21%2
270
May1st to 15thDay
11%5%22%34%18%6%
288
16th to endDay
11%216%29%24%14%
331
June1st to 15thDay
8%25%32%35%15%
495
16th to endDay
7%18%24%35%22%
495
July1st to 15thDay
5%326%38%26%
475
16th to endDay
8%1217%35%35%
476
August1st to 15thDay
11%1115%36%33%
313
16th to endDay
14%1312%35%32%
332
September1st to 15thDay
7%27%16%38%26%
315
16th to endDay
8%6%22%38%22%
314
October1st to 15thDay
6%20%32%28%11%
159
16th to endDay
13%6%25%30%17%6%
144
November1st to 15thDay
13%431%35%10%4
135
16th to endDay
10%11%32%22%17%5%
135
December1st to 15thDay
21%7%35%21%12%4
100
16th to endDay
20%14%37%20%5%1
96
January1st to 15thNight
17%8%33%31%9%
900
16th to endNight
22%8%33%31%4
948
February1st to 15thNight
18%9%32%33%6%
704
16th to endNight
20%11%34%29%4
631
March1st to 15thNight
16%7%36%32%7%
603
16th to endNight
14%5%32%34%11%1
576
April1st to 15thNight
9%8%33%34%12%1
539
16th to endNight
7%5%32%36%16%1
540
May1st to 15thNight
11%321%43%18%2
540
16th to endNight
6%114%39%33%4
563
June1st to 15thNight
5%5%35%47%6%
540
16th to endNight
316%26%45%16%
540
July1st to 15thNight
4228%49%14%
510
16th to endNight
41122%51%19%
564
August1st to 15thNight
5%120%48%22%
539
16th to endNight
8%221%49%16%
573
September1st to 15thNight
9%15%24%46%12%
540
16th to endNight
9%16%30%44%8%
664
October1st to 15thNight
9%115%33%33%6%
720
16th to endNight
14%418%32%26%4
768
November1st to 15thNight
12%421%35%21%3
760
16th to endNight
13%427%32%19%1
780
December1st to 15thNight
17%6%28%34%12%
736
16th to endNight
22%8%28%30%10%
945
Page generated at 2017-12-05 09:18:59. Version ac04

Copyright 2017 A. Danko


The Cowpasture Clear Sky Chart |Charts Home