This page made possible by the sponsorship of: Kenneth Magar.

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 2017-09-10.

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
44%
15745
19%
46723
14%
15703
49%
15703
25%
30664

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
23%
900
15%
2506
7%
895
31%
895
17%
1888
January16th to endNight
25%
892
14%
2615
7%
892
30%
892
17%
1934
February1st to 15thNight
24%
702
13%
2112
5%
701
31%
701
18%
1498
February16th to endNight
28%
631
16%
1893
9%
631
34%
631
18%
1346
March1st to 15thNight
30%
720
15%
2142
10%
720
34%
720
20%
1496
March16th to endNight
34%
723
16%
2067
9%
723
41%
723
22%
1440
April1st to 15thNight
35%
539
19%
1797
12%
539
46%
539
25%
1130
April16th to endNight
40%
540
21%
1698
13%
540
49%
540
27%
1062
May1st to 15thNight
40%
540
15%
1620
10%
540
44%
540
21%
1123
May16th to endNight
57%
561
18%
1667
14%
561
60%
561
30%
1046
June1st to 15thNight
63%
540
19%
1440
15%
540
65%
540
38%
870
June16th to endNight
66%
540
20%
1440
15%
540
69%
540
39%
865
July1st to 15thNight
71%
510
18%
1360
14%
510
71%
510
38%
822
July16th to endNight
75%
564
24%
1479
21%
531
78%
531
44%
834
August1st to 15thNight
71%
539
23%
1613
22%
536
73%
536
38%
933
August16th to endNight
76%
573
24%
1910
26%
573
78%
573
41%
979
September1st to 15thNight
70%
592
27%
1817
25%
592
73%
592
37%
1024
September16th to endNight
62%
657
27%
1815
22%
657
65%
657
35%
1106
October1st to 15thNight
57%
660
31%
1815
23%
660
64%
660
38%
1077
October16th to endNight
39%
704
22%
2255
17%
704
47%
704
25%
1417
November1st to 15thNight
45%
700
26%
2276
21%
700
54%
700
29%
1336
November16th to endNight
34%
720
19%
2340
13%
720
42%
720
20%
1581
December1st to 15thNight
26%
738
13%
2358
8%
738
31%
738
15%
1757
December16th to endNight
22%
960
12%
2688
5%
960
29%
960
14%
2100

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
13%7%35%5%3445%7%37%
47904
Night
14%7%36%5%2445%6%39%
46898
Cloud CoverDay
13%7%35%5%3445%7%37%
47913
Night
14%7%36%5%2445%6%39%
46903
TransparencyDay
45%311%23%13%2
47597
Night
44%311%22%15%2
46723
SeeingDay
15%420%25%21%11%
5769
Night
17%5%23%33%17%2
15749

By Month

Percentage Cloud Cover NE (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
19%11%49%6%34345%26%
1432
16th to endDay
11%14%6%8%6%35%347%28%
1605
February1st to 15thDay
14%11%6%8%6%44436%29%
1750
16th to endDay
14%11%5%9%6%34446%30%
1580
March1st to 15thDay
21%7%36%6%34446%30%
1808
16th to endDay
15%10%47%6%3445%7%30%
2168
April1st to 15thDay
16%7%345%2345%7%37%
2151
16th to endDay
18%6%35%5%23447%37%
2262
May1st to 15thDay
20%7%35%6%3445%7%32%
2331
16th to endDay
11%5%25%5%45%5%7%7%37%
2445
June1st to 15thDay
10%5%235%26%5%5%9%43%
2520
16th to endDay
8%5%25%435%46%10%42%
2520
July1st to 15thDay
11%426%435%6%6%9%40%
2520
16th to endDay
7%324436%5%7%10%44%
2586
August1st to 15thDay
8%425%5%35%6%6%9%43%
2334
16th to endDay
6%4245%35%5%7%9%43%
2292
September1st to 15thDay
12%5%235%345%5%7%42%
2019
16th to endDay
13%424434348%46%
1815
October1st to 15thDay
13%5%25%43445%6%45%
1815
16th to endDay
16%6%35%43445%6%39%
1614
November1st to 15thDay
11%424424446%49%
1582
16th to endDay
18%11%36%5%2335%5%35%
1620
December1st to 15thDay
22%11%5%7%434345%27%
1599
16th to endDay
20%13%5%7%5%23435%25%
1536
January1st to 15thNight
19%10%5%8%6%34445%28%
2506
16th to endNight
16%12%5%8%6%34345%29%
2615
February1st to 15thNight
17%10%5%7%5%3435%5%31%
2110
16th to endNight
16%10%38%6%34445%31%
1893
March1st to 15thNight
16%9%36%5%3445%5%34%
2129
16th to endNight
16%8%36%4345%37%34%
2067
April1st to 15thNight
14%7%35%42445%5%41%
1797
16th to endNight
15%435%42435%8%41%
1698
May1st to 15thNight
18%6%36%5%25%45%6%34%
1620
16th to endNight
10%425%5%25%6%5%9%41%
1665
June1st to 15thNight
8%325%5%3445%9%48%
1440
16th to endNight
7%223425%5%6%9%48%
1440
July1st to 15thNight
8%5%243245%6%8%48%
1440
16th to endNight
5%3135%3436%7%55%
1580
August1st to 15thNight
5%3145%35%6%47%51%
1624
16th to endNight
5%31342446%9%53%
1910
September1st to 15thNight
10%31342445%7%51%
1817
16th to endNight
12%414424347%49%
1815
October1st to 15thNight
10%315%33335%7%51%
1815
16th to endNight
17%7%25%324336%43%
2255
November1st to 15thNight
11%5%3432435%6%47%
2276
16th to endNight
19%9%44423446%35%
2340
December1st to 15thNight
22%10%49%5%2434427%
2358
16th to endNight
24%11%46%6%3433425%
2688

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
20%10%6%8%6%24445%26%
1432
16th to endDay
10%14%5%8%7%34447%28%
1605
February1st to 15thDay
14%11%6%8%6%34446%29%
1750
16th to endDay
14%11%5%9%6%34446%30%
1580
March1st to 15thDay
22%7%46%6%345%46%30%
1818
16th to endDay
14%10%47%6%3445%6%31%
2167
April1st to 15thDay
16%8%345%335%5%6%37%
2151
16th to endDay
17%7%35%6%23447%37%
2262
May1st to 15thDay
20%7%35%6%2445%7%31%
2331
16th to endDay
11%5%26%5%35%5%7%7%37%
2445
June1st to 15thDay
10%4235%36%45%8%44%
2520
16th to endDay
8%5%34435%46%10%42%
2520
July1st to 15thDay
11%425%5%35%5%6%9%39%
2520
16th to endDay
7%324436%6%6%11%43%
2586
August1st to 15thDay
8%425%5%35%6%6%8%43%
2334
16th to endDay
7%4245%35%5%7%9%43%
2292
September1st to 15thDay
12%5%145%35%5%5%8%42%
2019
16th to endDay
12%5%24434347%46%
1815
October1st to 15thDay
13%5%25%5%34446%44%
1815
16th to endDay
16%6%26%43446%6%39%
1614
November1st to 15thDay
11%5%24424446%49%
1582
16th to endDay
18%10%45%5%23345%35%
1620
December1st to 15thDay
22%10%5%7%435%345%27%
1599
16th to endDay
20%14%48%5%23345%26%
1536
January1st to 15thNight
19%9%5%8%6%34445%28%
2506
16th to endNight
16%12%5%8%6%35%345%29%
2615
February1st to 15thNight
17%10%5%8%5%3345%5%31%
2103
16th to endNight
16%11%48%6%3445%5%31%
1893
March1st to 15thNight
17%9%37%5%2445%5%33%
2142
16th to endNight
16%8%37%4345%47%35%
2067
April1st to 15thNight
14%7%35%4245%5%5%41%
1797
16th to endNight
14%5%36%42445%8%41%
1698
May1st to 15thNight
18%6%36%5%25%45%7%34%
1619
16th to endNight
10%5%35%435%5%6%9%41%
1665
June1st to 15thNight
8%325%5%3445%9%47%
1440
16th to endNight
7%224425%5%6%9%48%
1440
July1st to 15thNight
8%5%244335%5%8%48%
1440
16th to endNight
6%31342436%8%54%
1580
August1st to 15thNight
5%315%5%25%5%5%7%51%
1624
16th to endNight
5%31342446%9%52%
1910
September1st to 15thNight
10%41342345%7%51%
1817
16th to endNight
11%424433347%50%
1815
October1st to 15thNight
9%41443335%6%52%
1815
16th to endNight
17%6%25%324336%43%
2255
November1st to 15thNight
11%5%3442435%6%46%
2276
16th to endNight
19%10%35%424446%35%
2340
December1st to 15thNight
22%10%49%5%2434427%
2358
16th to endNight
23%11%47%6%2434425%
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
60%28%16%11%
1433
16th to endDay
56%212%21%5%
1605
February1st to 15thDay
55%311%18%10%
1752
16th to endDay
55%311%22%7%
1580
March1st to 15thDay
55%311%20%8%
1818
16th to endDay
52%315%21%6%
2168
April1st to 15thDay
46%310%24%13%1
2151
16th to endDay
45%311%21%12%4
2262
May1st to 15thDay
51%412%21%10%
2331
16th to endDay
42%5%12%21%15%2
2449
June1st to 15thDay
36%412%27%17%2
2520
16th to endDay
36%414%24%16%3
2520
July1st to 15thDay
39%412%22%17%2
2371
16th to endDay
32%5%18%28%13%2
2424
August1st to 15thDay
35%5%12%24%19%2
2321
16th to endDay
33%5%11%26%16%6%
2292
September1st to 15thDay
39%39%24%17%5%
2019
16th to endDay
37%37%24%25%1
1815
October1st to 15thDay
39%38%25%20%2
1815
16th to endDay
44%211%25%14%1
1614
November1st to 15thDay
36%311%24%19%5%
1582
16th to endDay
51%19%23%12%
1620
December1st to 15thDay
60%210%17%9%
1599
16th to endDay
60%310%19%41
1536
January1st to 15thNight
57%36%20%10%
2506
16th to endNight
57%211%19%7%
2615
February1st to 15thNight
54%213%20%8%
2112
16th to endNight
54%212%20%9%
1893
March1st to 15thNight
51%211%21%10%2
2142
16th to endNight
49%312%24%8%1
2067
April1st to 15thNight
43%210%24%16%2
1797
16th to endNight
41%39%22%15%6%
1698
May1st to 15thNight
48%5%11%22%11%1
1620
16th to endNight
38%5%14%20%15%4
1667
June1st to 15thNight
32%411%27%21%2
1440
16th to endNight
30%6%15%24%20%4
1440
July1st to 15thNight
32%414%23%19%6%
1360
16th to endNight
27%313%33%18%3
1479
August1st to 15thNight
30%414%25%21%3
1613
16th to endNight
26%314%28%20%6%
1910
September1st to 15thNight
31%311%23%23%6%
1817
16th to endNight
35%37%23%25%4
1815
October1st to 15thNight
32%38%27%23%4
1815
16th to endNight
43%29%27%14%2
2255
November1st to 15thNight
37%38%23%22%5%
2276
16th to endNight
50%39%22%14%
2340
December1st to 15thNight
60%29%17%8%
2358
16th to endNight
62%38%15%8%
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
33%11%23%23%7%1
90
16th to endDay
11%18%46%18%4
96
February1st to 15thDay
12%14%45%23%4
90
16th to endDay
13%8%38%30%7%1
81
March1st to 15thDay
31%8%33%21%4
108
16th to endDay
20%9%34%25%9%1
288
April1st to 15thDay
18%10%26%28%11%3
270
16th to endDay
22%425%24%15%7%
270
May1st to 15thDay
24%9%21%25%11%6%
288
16th to endDay
19%222%23%17%15%
345
June1st to 15thDay
12%215%30%26%11%
495
16th to endDay
11%224%30%21%10%
495
July1st to 15thDay
16%113%30%23%14%
475
16th to endDay
6%17%25%35%23%
446
August1st to 15thDay
12%17%18%30%29%
313
16th to endDay
8%27%23%36%21%
332
September1st to 15thDay
10%210%26%31%18%
294
16th to endDay
14%312%21%30%17%
254
October1st to 15thDay
10%319%31%26%8%
255
16th to endDay
16%8%36%29%7%1
118
November1st to 15thDay
10%10%21%20%28%10%
90
16th to endDay
30%436%18%8%1
90
December1st to 15thDay
20%10%32%27%5%4
90
16th to endDay
21%17%43%14%2
96
January1st to 15thNight
24%9%33%28%3
900
16th to endNight
21%10%33%30%5%
892
February1st to 15thNight
22%8%36%29%2
704
16th to endNight
22%8%33%31%4
631
March1st to 15thNight
21%9%31%30%6%
720
16th to endNight
20%5%31%33%8%1
723
April1st to 15thNight
16%7%34%30%10%
539
16th to endNight
17%430%33%12%
540
May1st to 15thNight
20%5%23%35%13%1
540
16th to endNight
11%318%37%26%3
563
June1st to 15thNight
9%15%45%26%1
540
16th to endNight
9%13%44%29%1
540
July1st to 15thNight
10%16%42%34%4
510
16th to endNight
7%17%38%39%6%
564
August1st to 15thNight
7%18%37%38%6%
539
16th to endNight
5%16%32%47%5%
573
September1st to 15thNight
12%19%36%33%6%
592
16th to endNight
14%210%31%34%5%
657
October1st to 15thNight
12%420%34%23%5%
660
16th to endNight
21%5%30%30%12%1
704
November1st to 15thNight
14%8%26%32%16%2
700
16th to endNight
23%9%26%31%8%1
720
December1st to 15thNight
27%7%29%25%8%1
738
16th to endNight
28%8%30%26%4
960
Page generated at 2017-09-11 19:35:22. Version ac04

Copyright 2017 A. Danko


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