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 2018-01-12.

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
44%
16267
19%
48280
14%
16225
49%
16225
25%
31633

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
25%
956
15%
2662
7%
951
32%
951
17%
1984
January16th to endNight
24%
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
35%
631
18%
1346
March1st to 15thNight
30%
720
15%
2142
10%
720
35%
720
20%
1496
March16th to endNight
34%
723
16%
2067
9%
723
41%
723
22%
1440
April1st to 15thNight
36%
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
56%
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
65%
540
20%
1440
15%
540
68%
540
39%
865
July1st to 15thNight
70%
510
17%
1360
14%
510
71%
510
38%
822
July16th to endNight
75%
564
24%
1479
21%
531
77%
531
44%
834
August1st to 15thNight
71%
539
23%
1613
22%
536
73%
536
38%
933
August16th to endNight
75%
573
24%
1910
26%
573
77%
573
41%
979
September1st to 15thNight
68%
612
27%
1872
25%
612
72%
612
37%
1065
September16th to endNight
63%
717
29%
1980
24%
717
66%
717
37%
1190
October1st to 15thNight
55%
720
30%
1980
22%
720
62%
720
37%
1185
October16th to endNight
39%
768
23%
2460
18%
768
47%
768
25%
1540
November1st to 15thNight
45%
760
25%
2471
20%
760
53%
760
28%
1480
November16th to endNight
35%
780
21%
2535
14%
780
44%
780
21%
1680
December1st to 15thNight
27%
800
13%
2555
8%
800
33%
800
16%
1859
December16th to endNight
22%
1040
13%
2912
5%
1040
28%
1040
14%
2272

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%
49057
Night
14%7%36%5%2445%6%40%
48455
Cloud CoverDay
13%7%35%5%3445%7%37%
49066
Night
14%7%36%5%2445%6%40%
48460
TransparencyDay
45%311%23%13%2
48750
Night
44%310%23%15%2
48280
SeeingDay
15%5%20%25%20%11%
6176
Night
17%5%24%32%17%2
16271

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%5%9%6%34345%26%
1520
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
13%6%235%345%5%7%41%
2076
16th to endDay
12%424424348%48%
1980
October1st to 15thDay
14%5%25%43445%6%43%
1980
16th to endDay
16%6%36%43445%5%39%
1761
November1st to 15thDay
12%5%245%24446%47%
1717
16th to endDay
18%10%35%5%2335%6%36%
1755
December1st to 15thDay
20%11%47%5%34345%28%
1732
16th to endDay
21%13%5%7%5%33445%25%
1664
January1st to 15thNight
18%9%5%8%6%34445%29%
2662
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%31442445%6%51%
1872
16th to endNight
11%414424347%51%
1980
October1st to 15thNight
10%315%43335%7%51%
1980
16th to endNight
16%7%25%324336%43%
2460
November1st to 15thNight
12%5%35%42435%6%45%
2471
16th to endNight
18%9%44423446%37%
2535
December1st to 15thNight
20%10%49%5%2434430%
2555
16th to endNight
23%11%47%7%3433425%
2912

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
19%10%6%8%6%24445%26%
1520
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
13%5%145%345%5%7%41%
2076
16th to endDay
11%424434347%48%
1980
October1st to 15thDay
13%6%25%5%3445%6%43%
1980
16th to endDay
16%6%26%43445%5%39%
1761
November1st to 15thDay
12%5%245%24346%47%
1717
16th to endDay
18%10%35%5%13346%36%
1755
December1st to 15thDay
20%10%5%7%5%35%345%28%
1732
16th to endDay
20%14%47%5%33345%26%
1664
January1st to 15thNight
19%9%5%7%6%34445%29%
2662
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%
1872
16th to endNight
11%424433347%51%
1980
October1st to 15thNight
10%42443335%7%51%
1980
16th to endNight
17%6%25%324336%43%
2460
November1st to 15thNight
12%6%35%42435%7%45%
2471
16th to endNight
18%9%35%423346%37%
2535
December1st to 15thNight
20%10%49%5%2434430%
2555
16th to endNight
23%11%5%7%6%2433425%
2912

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%
1521
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
40%39%24%17%5%
2076
16th to endDay
35%37%26%25%1
1980
October1st to 15thDay
41%38%25%19%2
1980
16th to endDay
44%211%25%15%1
1761
November1st to 15thDay
38%310%24%17%5%
1717
16th to endDay
50%19%24%13%
1755
December1st to 15thDay
59%39%18%9%
1732
16th to endDay
60%310%19%41
1664
January1st to 15thNight
56%36%20%12%
2662
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
32%310%23%23%6%
1872
16th to endNight
33%37%25%25%3
1980
October1st to 15thNight
32%38%26%22%4
1980
16th to endNight
43%29%27%15%2
2460
November1st to 15thNight
39%38%23%20%4
2471
16th to endNight
48%29%23%15%
2535
December1st to 15thNight
58%19%18%10%
2555
16th to endNight
62%38%16%8%
2912

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
27%10%26%25%9%
123
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
13%210%25%29%18%
315
16th to endDay
13%313%19%31%20%
314
October1st to 15thDay
13%218%31%25%7%
315
16th to endDay
17%5%35%27%11%1
168
November1st to 15thDay
17%10%21%22%21%6%
135
16th to endDay
24%437%24%8%
135
December1st to 15thDay
14%16%36%22%5%4
135
16th to endDay
27%15%41%14%1
144
January1st to 15thNight
24%8%32%28%5%
956
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%35%33%7%
612
16th to endNight
13%211%29%36%5%
717
October1st to 15thNight
13%419%32%24%5%
720
16th to endNight
20%5%30%29%12%1
768
November1st to 15thNight
15%8%25%32%16%2
760
16th to endNight
22%8%26%32%8%1
780
December1st to 15thNight
26%7%29%26%8%1
800
16th to endNight
28%8%31%27%4
1040
Page generated at 2018-01-12 22:01:33. Version ac04

Copyright 2018 A. Danko


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