Franklin
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Franklin clear sky chart from 2005-11-05 to 2017-08-12.

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%
15333
23%
46385
17%
15289
55%
15289
29%
28584

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
28%
900
21%
2506
10%
895
37%
895
23%
1692
January16th to endNight
27%
774
22%
2379
11%
774
38%
774
21%
1594
February1st to 15thNight
26%
704
18%
2112
9%
701
35%
701
22%
1434
February16th to endNight
26%
631
21%
1893
10%
631
36%
631
21%
1281
March1st to 15thNight
30%
720
19%
2160
10%
720
37%
720
22%
1450
March16th to endNight
38%
692
20%
2038
13%
692
44%
692
26%
1319
April1st to 15thNight
42%
539
26%
1797
18%
539
54%
539
32%
1009
April16th to endNight
45%
540
25%
1782
18%
540
56%
540
32%
1015
May1st to 15thNight
47%
539
21%
1620
13%
539
54%
539
29%
1028
May16th to endNight
63%
561
19%
1683
15%
561
66%
561
34%
1002
June1st to 15thNight
70%
540
21%
1557
16%
540
73%
540
39%
900
June16th to endNight
77%
540
25%
1440
18%
540
79%
540
46%
819
July1st to 15thNight
72%
510
17%
1360
15%
510
73%
510
38%
833
July16th to endNight
78%
564
22%
1569
21%
531
79%
531
39%
897
August1st to 15thNight
78%
527
22%
1715
23%
524
80%
524
37%
945
August16th to endNight
75%
525
21%
1750
26%
525
75%
525
33%
1010
September1st to 15thNight
66%
553
24%
1708
24%
553
68%
553
30%
1047
September16th to endNight
65%
657
30%
1815
24%
657
67%
657
38%
1077
October1st to 15thNight
56%
660
35%
1815
27%
660
62%
660
39%
1052
October16th to endNight
50%
704
31%
2189
25%
704
58%
704
33%
1263
November1st to 15thNight
49%
700
31%
2276
26%
700
58%
700
34%
1260
November16th to endNight
41%
720
27%
2340
21%
720
51%
720
29%
1380
December1st to 15thNight
33%
720
21%
2340
15%
720
42%
720
21%
1538
December16th to endNight
30%
813
20%
2541
12%
813
39%
813
20%
1739

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%6%25%5%35%5%5%7%40%
47580
Night
12%5%2442445%7%44%
46572
TransparencyDay
41%410%22%16%3
47270
Night
38%410%23%19%4
46386
SeeingDay
14%417%23%24%15%
5404
Night
15%6%22%30%21%3
15336

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%7%25%5%24445%37%
1432
16th to endDay
17%6%35%433335%41%
1840
February1st to 15thDay
16%9%37%5%33345%36%
1750
16th to endDay
15%8%37%5%35%45%6%35%
1580
March1st to 15thDay
18%8%37%5%33345%36%
1800
16th to endDay
14%7%37%5%36%5%5%6%34%
2194
April1st to 15thDay
11%5%245%345%46%45%
2151
16th to endDay
13%5%35%6%3445%7%40%
2176
May1st to 15thDay
17%5%25%43445%6%39%
2331
16th to endDay
9%6%27%5%35%5%5%8%38%
2431
June1st to 15thDay
7%425%6%35%6%7%8%42%
2399
16th to endDay
5%325%6%46%7%7%10%40%
2520
July1st to 15thDay
9%435%7%47%7%7%9%33%
2520
16th to endDay
6%325%6%47%8%8%10%34%
2489
August1st to 15thDay
5%335%7%47%6%8%11%36%
2145
16th to endDay
9%5%26%6%46%6%6%9%34%
2100
September1st to 15thDay
11%5%25%7%46%6%6%8%34%
1911
16th to endDay
11%5%145%24447%48%
1815
October1st to 15thDay
12%5%24323246%51%
1815
16th to endDay
15%423323435%53%
1682
November1st to 15thDay
14%5%12323246%53%
1582
16th to endDay
15%5%2421435%6%48%
1620
December1st to 15thDay
20%9%36%42335%5%35%
1620
16th to endDay
19%9%25%6%23335%37%
1677
January1st to 15thNight
16%9%35%5%23345%39%
2506
16th to endNight
16%8%35%424445%39%
2379
February1st to 15thNight
17%8%35%5%23335%38%
2103
16th to endNight
16%7%36%5%2445%5%37%
1893
March1st to 15thNight
16%6%36%5%34446%38%
2160
16th to endNight
13%7%35%425%447%40%
2038
April1st to 15thNight
11%423423448%49%
1797
16th to endNight
11%42443445%7%47%
1782
May1st to 15thNight
10%7%26%5%25%45%6%44%
1619
16th to endNight
6%425%5%345%6%9%46%
1682
June1st to 15thNight
5%4145%25%46%10%49%
1557
16th to endNight
2213435%48%12%50%
1440
July1st to 15thNight
8%325%335%5%6%12%43%
1440
16th to endNight
42135%26%6%8%12%46%
1676
August1st to 15thNight
4314435%5%6%12%48%
1726
16th to endNight
6%325%5%25%6%6%11%43%
1750
September1st to 15thNight
9%4246%35%6%5%7%44%
1708
16th to endNight
10%32442335%6%52%
1815
October1st to 15thNight
10%6%23323346%53%
1815
16th to endNight
14%5%24312345%52%
2189
November1st to 15thNight
11%5%24323346%53%
2276
16th to endNight
15%6%24322346%48%
2340
December1st to 15thNight
17%9%345%2435%5%38%
2340
16th to endNight
20%8%36%43433436%
2541

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
48%26%22%16%2
1433
16th to endDay
45%28%26%14%1
1840
February1st to 15thDay
49%28%21%14%3
1752
16th to endDay
48%39%22%13%2
1580
March1st to 15thDay
50%39%19%14%4
1800
16th to endDay
49%411%21%12%
2195
April1st to 15thDay
38%49%23%20%4
2151
16th to endDay
42%47%24%17%3
2176
May1st to 15thDay
44%410%22%15%2
2331
16th to endDay
42%5%13%24%12%2
2435
June1st to 15thDay
36%5%13%26%16%1
2399
16th to endDay
34%6%12%22%18%4
2520
July1st to 15thDay
42%6%17%19%11%3
2371
16th to endDay
37%7%18%23%10%1
2333
August1st to 15thDay
37%5%15%23%14%2
2132
16th to endDay
42%6%12%22%13%3
2100
September1st to 15thDay
44%6%11%19%14%4
1911
16th to endDay
34%310%23%24%3
1815
October1st to 15thDay
34%37%23%25%5%
1815
16th to endDay
34%35%22%28%6%
1682
November1st to 15thDay
33%25%22%27%7%
1582
16th to endDay
37%26%29%19%4
1620
December1st to 15thDay
50%27%21%14%3
1620
16th to endDay
49%311%20%12%2
1677
January1st to 15thNight
46%37%21%17%2
2506
16th to endNight
48%36%21%16%3
2379
February1st to 15thNight
49%29%21%15%2
2112
16th to endNight
48%38%21%15%2
1893
March1st to 15thNight
45%48%18%17%5%
2160
16th to endNight
42%412%25%14%1
2038
April1st to 15thNight
32%410%24%22%5%
1797
16th to endNight
34%310%26%21%4
1782
May1st to 15thNight
39%411%24%17%2
1620
16th to endNight
32%6%17%24%15%3
1684
June1st to 15thNight
28%6%16%29%17%2
1557
16th to endNight
23%6%16%31%16%4
1440
July1st to 15thNight
31%6%17%24%15%4
1360
16th to endNight
27%7%19%28%15%2
1569
August1st to 15thNight
26%7%17%28%17%2
1715
16th to endNight
32%6%15%24%17%3
1750
September1st to 15thNight
36%5%13%21%17%4
1708
16th to endNight
32%48%21%26%7%
1815
October1st to 15thNight
31%37%22%28%7%
1815
16th to endNight
34%3321%28%8%
2189
November1st to 15thNight
32%2421%27%10%
2276
16th to endNight
37%27%23%23%4
2340
December1st to 15thNight
47%38%20%16%4
2340
16th to endNight
51%28%19%16%2
2541

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
25%13%37%11%11%1
90
16th to endDay
19%9%47%18%4
96
February1st to 15thDay
22%12%43%15%5%1
90
16th to endDay
23%9%40%17%7%1
81
March1st to 15thDay
26%13%35%21%3
90
16th to endDay
16%8%30%29%13%1
285
April1st to 15thDay
13%10%25%29%17%2
270
16th to endDay
17%424%28%20%5%
270
May1st to 15thDay
19%7%23%23%18%8%
288
16th to endDay
15%215%28%24%14%
331
June1st to 15thDay
10%13%16%29%29%
374
16th to endDay
7%111%29%29%21%
495
July1st to 15thDay
10%111%28%30%17%
475
16th to endDay
7%1416%26%43%
349
August1st to 15thDay
7%1320%36%30%
297
16th to endDay
15%116%38%26%
268
September1st to 15thDay
13%17%18%33%25%
255
16th to endDay
17%27%25%34%12%
254
October1st to 15thDay
15%120%26%26%10%
255
16th to endDay
22%117%32%19%7%
125
November1st to 15thDay
13%5%22%30%23%5%
90
16th to endDay
18%12%33%18%15%1
90
December1st to 15thDay
21%11%38%20%6%2
90
16th to endDay
17%14%42%18%6%
96
January1st to 15thNight
23%12%30%26%5%
900
16th to endNight
22%9%36%28%3
774
February1st to 15thNight
20%11%35%27%4
704
16th to endNight
21%13%34%28%3
631
March1st to 15thNight
19%10%34%28%6%
720
16th to endNight
17%8%29%29%14%1
692
April1st to 15thNight
12%10%32%30%11%1
539
16th to endNight
12%5%29%38%11%1
540
May1st to 15thNight
13%327%33%18%2
540
16th to endNight
8%213%36%32%5%
563
June1st to 15thNight
7%110%37%35%7%
540
16th to endNight
39%33%45%8%
540
July1st to 15thNight
8%15%34%41%8%
510
16th to endNight
45%23%50%14%
564
August1st to 15thNight
4327%51%10%
527
16th to endNight
8%433%43%10%
525
September1st to 15thNight
10%29%28%43%6%
553
16th to endNight
12%211%29%40%3
657
October1st to 15thNight
13%318%30%26%7%
660
16th to endNight
16%5%22%32%20%2
704
November1st to 15thNight
13%6%25%30%19%4
700
16th to endNight
19%8%26%31%12%1
720
December1st to 15thNight
22%9%27%29%9%1
720
16th to endNight
24%8%31%28%6%
813
Page generated at 2017-08-13 13:16:18. Version ac04

Copyright 2017 A. Danko


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