Jackson
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Jackson clear sky chart from 2005-11-05 to 2017-12-02.

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
48%
15912
24%
47774
18%
15867
55%
15867
30%
29047

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
26%
900
23%
2473
10%
895
37%
895
24%
1644
January16th to endNight
24%
937
23%
2473
8%
937
35%
937
25%
1670
February1st to 15thNight
23%
704
18%
2112
7%
701
33%
701
21%
1421
February16th to endNight
25%
631
23%
1893
10%
631
35%
631
23%
1219
March1st to 15thNight
30%
720
18%
2160
10%
720
36%
720
23%
1429
March16th to endNight
39%
582
20%
1992
15%
582
46%
582
24%
1229
April1st to 15thNight
38%
539
24%
1797
15%
539
51%
539
30%
1044
April16th to endNight
43%
540
24%
1800
19%
540
54%
540
31%
1028
May1st to 15thNight
50%
540
21%
1700
17%
540
55%
540
28%
1047
May16th to endNight
62%
562
21%
1655
18%
561
64%
561
32%
1002
June1st to 15thNight
70%
540
24%
1440
19%
540
73%
540
40%
859
June16th to endNight
80%
540
25%
1440
22%
540
81%
540
45%
828
July1st to 15thNight
74%
510
18%
1360
16%
510
75%
510
36%
863
July16th to endNight
82%
564
23%
1541
23%
531
83%
531
44%
848
August1st to 15thNight
78%
539
22%
1788
27%
536
79%
536
37%
965
August16th to endNight
76%
573
25%
1910
31%
573
76%
573
34%
1073
September1st to 15thNight
67%
540
25%
1800
28%
540
70%
540
31%
1041
September16th to endNight
66%
717
32%
1980
26%
717
69%
717
40%
1141
October1st to 15thNight
61%
720
32%
2049
27%
720
65%
720
39%
1165
October16th to endNight
52%
768
34%
2334
25%
768
61%
768
38%
1301
November1st to 15thNight
48%
760
30%
2471
24%
760
58%
760
34%
1368
November16th to endNight
41%
780
27%
2535
21%
780
52%
780
28%
1499
December1st to 15thNight
32%
746
22%
2383
13%
746
43%
746
22%
1530
December16th to endNight
29%
960
20%
2688
10%
960
37%
960
22%
1833

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
12%5%25%5%3445%7%42%
48670
Night
12%5%2442345%7%47%
47963
TransparencyDay
39%6%10%22%17%3
48362
Night
35%5%10%23%19%5%
47776
SeeingDay
12%5%19%25%24%12%
5913
Night
14%7%23%30%20%3
15913

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%8%24423335%42%
1462
16th to endDay
15%6%36%433336%43%
1749
February1st to 15thDay
17%8%36%423335%40%
1750
16th to endDay
16%8%36%6%2435%5%36%
1580
March1st to 15thDay
19%9%35%434336%36%
1804
16th to endDay
15%7%35%5%35%45%7%36%
2235
April1st to 15thDay
13%5%25%5%23446%46%
2151
16th to endDay
12%5%26%5%3445%6%42%
2160
May1st to 15thDay
14%6%35%5%25%45%7%39%
2250
16th to endDay
8%6%36%5%36%5%6%9%39%
2455
June1st to 15thDay
6%425%5%35%5%7%9%44%
2520
16th to endDay
4324436%6%7%11%45%
2520
July1st to 15thDay
7%5%25%7%36%6%8%10%36%
2520
16th to endDay
6%3146%45%6%7%11%41%
2517
August1st to 15thDay
5%3246%46%6%8%10%41%
2160
16th to endDay
8%5%25%5%35%5%8%9%39%
2292
September1st to 15thDay
10%425%5%35%5%6%8%41%
2148
16th to endDay
11%424425%447%49%
1980
October1st to 15thDay
11%325%32335%6%51%
1908
16th to endDay
14%313312335%58%
1890
November1st to 15thDay
12%6%24311335%53%
1717
16th to endDay
16%5%23314346%48%
1755
December1st to 15thDay
19%7%3433435%5%39%
1611
16th to endDay
18%9%25%323346%39%
1536
January1st to 15thNight
17%7%25%423335%44%
2473
16th to endNight
17%6%35%423335%43%
2473
February1st to 15thNight
16%9%35%5%2433441%
2103
16th to endNight
15%7%245%34445%43%
1893
March1st to 15thNight
17%6%25%42345%6%41%
2160
16th to endNight
13%6%25%43345%7%43%
1992
April1st to 15thNight
11%5%2442345%7%48%
1797
16th to endNight
11%43441445%8%47%
1800
May1st to 15thNight
12%5%25%333347%46%
1699
16th to endNight
6%425%5%345%6%10%46%
1655
June1st to 15thNight
5%41442447%10%49%
1440
16th to endNight
2213335%47%12%52%
1440
July1st to 15thNight
5%415%436%6%7%10%44%
1440
16th to endNight
42123245%6%12%53%
1648
August1st to 15thNight
33145%245%7%10%51%
1800
16th to endNight
5%4245%336%6%9%48%
1910
September1st to 15thNight
9%5%145%2346%6%50%
1800
16th to endNight
7%424423346%55%
1980
October1st to 15thNight
9%32432345%6%54%
2049
16th to endNight
14%5%13222235%57%
2334
November1st to 15thNight
12%414323347%52%
2471
16th to endNight
13%6%24323345%50%
2535
December1st to 15thNight
18%7%24423336%41%
2383
16th to endNight
19%7%35%423345%39%
2688

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
44%38%21%18%2
1463
16th to endDay
44%39%23%16%2
1749
February1st to 15thDay
47%38%21%17%2
1752
16th to endDay
48%48%20%15%3
1580
March1st to 15thDay
50%47%17%14%4
1804
16th to endDay
47%5%11%22%13%
2237
April1st to 15thDay
38%48%22%20%4
2151
16th to endDay
41%5%9%22%18%2
2160
May1st to 15thDay
43%7%11%19%16%1
2250
16th to endDay
38%10%13%23%12%2
2459
June1st to 15thDay
33%8%14%23%18%1
2520
16th to endDay
29%9%14%24%19%3
2520
July1st to 15thDay
38%10%15%19%11%3
2371
16th to endDay
33%9%15%27%12%1
2361
August1st to 15thDay
33%9%15%23%15%2
2148
16th to endDay
37%7%13%22%15%2
2292
September1st to 15thDay
38%8%10%23%14%4
2148
16th to endDay
34%5%10%20%23%5%
1980
October1st to 15thDay
32%5%10%23%23%5%
1908
16th to endDay
30%35%22%31%7%
1890
November1st to 15thDay
34%36%19%27%8%
1717
16th to endDay
38%37%23%23%4
1755
December1st to 15thDay
45%48%22%14%4
1611
16th to endDay
47%310%20%14%2
1536
January1st to 15thNight
44%36%20%21%3
2473
16th to endNight
45%37%21%18%4
2473
February1st to 15thNight
46%310%19%16%3
2112
16th to endNight
42%49%22%17%3
1893
March1st to 15thNight
43%5%8%18%17%6%
2160
16th to endNight
40%5%12%22%17%1
1992
April1st to 15thNight
34%410%23%20%6%
1797
16th to endNight
33%5%10%25%21%4
1800
May1st to 15thNight
37%5%10%23%19%3
1700
16th to endNight
32%8%14%26%14%3
1657
June1st to 15thNight
27%7%13%26%21%2
1440
16th to endNight
23%7%16%26%20%4
1440
July1st to 15thNight
30%10%15%26%12%5%
1360
16th to endNight
22%8%21%31%15%1
1541
August1st to 15thNight
25%8%16%26%19%3
1788
16th to endNight
28%7%14%28%15%5%
1910
September1st to 15thNight
32%7%11%23%18%6%
1800
16th to endNight
29%49%25%24%7%
1980
October1st to 15thNight
28%5%9%23%23%9%
2049
16th to endNight
31%25%20%30%9%
2334
November1st to 15thNight
31%37%22%25%9%
2471
16th to endNight
37%36%20%25%6%
2535
December1st to 15thNight
44%38%20%17%5%
2383
16th to endNight
47%39%19%16%3
2688

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
30%11%43%10%41
90
16th to endDay
19%17%46%9%5%1
96
February1st to 15thDay
17%30%35%11%5%
90
16th to endDay
24%16%41%12%4
81
March1st to 15thDay
33%15%37%8%4
90
16th to endDay
19%10%33%24%10%
221
April1st to 15thDay
15%11%30%27%12%1
270
16th to endDay
17%7%24%32%15%4
270
May1st to 15thDay
19%9%24%26%13%6%
288
16th to endDay
14%422%28%20%10%
355
June1st to 15thDay
6%214%29%28%19%
495
16th to endDay
6%114%28%34%13%
495
July1st to 15thDay
8%114%30%29%16%
475
16th to endDay
5%17%19%35%30%
476
August1st to 15thDay
7%16%25%37%22%
313
16th to endDay
13%9%20%36%19%
332
September1st to 15thDay
11%19%21%37%18%
315
16th to endDay
13%312%22%30%18%
314
October1st to 15thDay
9%419%34%25%6%
243
16th to endDay
12%10%27%28%17%3
144
November1st to 15thDay
16%5%28%34%13%2
135
16th to endDay
20%7%30%22%14%4
135
December1st to 15thDay
24%11%34%20%8%1
94
16th to endDay
18%15%50%12%3
96
January1st to 15thNight
21%16%32%23%5%
900
16th to endNight
21%12%39%25%1
937
February1st to 15thNight
22%15%35%23%3
704
16th to endNight
18%17%36%24%2
631
March1st to 15thNight
19%13%34%28%4
720
16th to endNight
15%9%31%31%11%
582
April1st to 15thNight
13%10%35%29%10%
539
16th to endNight
12%6%32%32%13%1
540
May1st to 15thNight
14%5%23%38%15%2
540
16th to endNight
7%219%36%29%4
563
June1st to 15thNight
8%110%39%34%5%
540
16th to endNight
418%35%43%7%
540
July1st to 15thNight
6%18%33%41%9%
510
16th to endNight
5%5%24%47%16%
564
August1st to 15thNight
5%6%29%50%8%
539
16th to endNight
8%5%33%44%7%
573
September1st to 15thNight
10%19%31%39%7%
540
16th to endNight
9%213%32%35%6%
717
October1st to 15thNight
10%418%34%28%4
720
16th to endNight
16%5%23%33%19%1
768
November1st to 15thNight
14%7%26%30%18%2
760
16th to endNight
17%9%27%29%14%1
780
December1st to 15thNight
24%10%28%28%8%
746
16th to endNight
22%13%30%27%5%
960
Page generated at 2017-12-03 10:16:43. Version ac04

Copyright 2017 A. Danko


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