Millers Ferry
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Millers Ferry clear sky chart from 2005-11-05 to 2017-09-23.

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
52%
15222
24%
47055
18%
15179
59%
15179
30%
28391

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
32%
720
26%
2261
13%
716
47%
716
25%
1365
January16th to endNight
29%
768
26%
2304
12%
768
41%
768
24%
1489
February1st to 15thNight
34%
704
26%
2112
13%
701
46%
701
28%
1282
February16th to endNight
32%
631
25%
1893
12%
631
42%
631
26%
1192
March1st to 15thNight
32%
720
22%
2160
12%
720
40%
720
27%
1321
March16th to endNight
43%
670
26%
2029
16%
670
52%
670
31%
1182
April1st to 15thNight
44%
539
24%
1797
18%
539
54%
539
32%
1003
April16th to endNight
53%
540
28%
1800
22%
540
64%
540
36%
973
May1st to 15thNight
53%
539
22%
1710
15%
539
61%
539
34%
993
May16th to endNight
68%
561
23%
1682
19%
561
72%
561
33%
1017
June1st to 15thNight
72%
540
13%
1620
13%
540
73%
540
29%
1058
June16th to endNight
75%
540
17%
1620
16%
540
75%
540
32%
1001
July1st to 15thNight
79%
510
11%
1530
12%
510
79%
510
28%
989
July16th to endNight
75%
564
14%
1716
15%
531
77%
531
28%
1071
August1st to 15thNight
78%
539
14%
1788
17%
536
78%
536
25%
1136
August16th to endNight
70%
573
19%
1910
24%
573
70%
573
21%
1293
September1st to 15thNight
64%
603
20%
1863
20%
603
65%
603
27%
1200
September16th to endNight
66%
689
27%
1903
21%
689
68%
689
34%
1171
October1st to 15thNight
63%
660
34%
1815
25%
660
69%
660
45%
1003
October16th to endNight
56%
704
35%
2090
29%
704
64%
704
40%
1124
November1st to 15thNight
53%
700
31%
2276
26%
700
63%
700
37%
1194
November16th to endNight
46%
720
30%
2340
23%
720
57%
720
32%
1308
December1st to 15thNight
42%
720
25%
2340
20%
720
51%
720
29%
1380
December16th to endNight
33%
768
20%
2496
14%
768
42%
768
20%
1646

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
10%5%25%5%35%5%5%7%41%
47834
Night
10%42442445%8%46%
47266
TransparencyDay
39%6%11%18%18%5%
47547
Night
34%6%11%18%20%8%
47057
SeeingDay
12%6%16%23%25%16%
5155
Night
12%6%20%29%24%5%
15225

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
16%7%24323345%45%
1675
16th to endDay
16%6%3431345%5%46%
1920
February1st to 15thDay
14%5%345%23446%45%
1750
16th to endDay
17%7%25%43433443%
1580
March1st to 15thDay
14%6%245%3445%6%43%
1800
16th to endDay
11%5%25%5%3445%6%44%
2203
April1st to 15thDay
11%5%245%245%48%44%
2151
16th to endDay
8%315%5%35%447%49%
2160
May1st to 15thDay
10%5%25%5%45%45%7%42%
2241
16th to endDay
6%425%6%46%6%5%8%43%
2431
June1st to 15thDay
6%427%6%5%6%6%7%11%34%
2340
16th to endDay
5%425%5%47%7%9%11%36%
2340
July1st to 15thDay
8%5%26%8%48%9%8%10%27%
2340
16th to endDay
7%426%7%5%8%9%8%10%29%
2330
August1st to 15thDay
6%415%7%5%8%8%9%10%31%
2160
16th to endDay
11%6%36%7%47%6%6%7%31%
2292
September1st to 15thDay
11%5%26%6%45%5%6%8%37%
2085
16th to endDay
10%5%245%3436%6%47%
1894
October1st to 15thDay
8%5%24423447%52%
1815
16th to endDay
8%424324337%55%
1777
November1st to 15thDay
10%424214336%55%
1582
16th to endDay
12%42332335%6%52%
1620
December1st to 15thDay
13%7%35%333445%44%
1620
16th to endDay
17%9%26%5%245%3436%
1728
January1st to 15thNight
15%5%24423345%48%
2261
16th to endNight
19%6%34422336%44%
2304
February1st to 15thNight
13%6%24423346%48%
2103
16th to endNight
15%6%25%42334448%
1893
March1st to 15thNight
13%5%245%24347%45%
2160
16th to endNight
12%413324445%51%
2029
April1st to 15thNight
10%42332446%8%48%
1797
16th to endNight
7%322325%36%7%54%
1800
May1st to 15thNight
9%4144245%5%9%48%
1709
16th to endNight
5%314436%6%6%10%45%
1682
June1st to 15thNight
5%3246%47%7%9%13%35%
1620
16th to endNight
5%325%6%35%6%9%13%39%
1620
July1st to 15thNight
5%325%6%35%7%8%14%36%
1620
16th to endNight
4325%6%46%7%9%11%37%
1835
August1st to 15thNight
6%3146%46%8%9%14%36%
1800
16th to endNight
8%5%35%6%46%5%7%10%36%
1910
September1st to 15thNight
10%5%25%5%35%6%6%8%41%
1863
16th to endNight
7%426%5%2445%9%47%
1903
October1st to 15thNight
7%31332336%8%55%
1815
16th to endNight
10%31322223462%
2090
November1st to 15thNight
10%313323346%57%
2276
16th to endNight
10%5%24324345%53%
2340
December1st to 15thNight
13%5%24424336%49%
2340
16th to endNight
17%7%35%5%33445%38%
2496

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%45%15%24%8%
1676
16th to endDay
40%35%16%24%8%
1920
February1st to 15thDay
39%35%18%24%7%
1752
16th to endDay
45%3416%21%8%
1580
March1st to 15thDay
41%39%18%21%5%
1800
16th to endDay
39%5%9%18%21%5%
2204
April1st to 15thDay
37%48%21%20%7%
2151
16th to endDay
33%6%10%21%23%5%
2160
May1st to 15thDay
39%6%10%17%21%6%
2241
16th to endDay
35%8%13%22%16%2
2435
June1st to 15thDay
41%9%13%23%10%1
2340
16th to endDay
37%9%16%20%13%2
2340
July1st to 15thDay
44%12%19%15%7%1
2201
16th to endDay
43%12%19%18%5%
2186
August1st to 15thDay
40%11%19%17%9%1
2148
16th to endDay
47%9%14%15%9%2
2292
September1st to 15thDay
42%8%12%17%13%5%
2085
16th to endDay
36%6%10%20%20%6%
1894
October1st to 15thDay
30%410%15%27%12%
1815
16th to endDay
29%35%15%29%16%
1777
November1st to 15thDay
30%35%18%29%11%
1582
16th to endDay
33%37%17%25%12%
1620
December1st to 15thDay
41%37%21%19%5%
1620
16th to endDay
50%38%18%14%5%
1728
January1st to 15thNight
38%36%17%26%8%
2261
16th to endNight
43%3414%24%10%
2304
February1st to 15thNight
37%36%19%20%12%
2112
16th to endNight
40%3416%23%11%
1893
March1st to 15thNight
38%39%18%21%8%
2160
16th to endNight
32%5%8%20%24%8%
2029
April1st to 15thNight
31%411%17%22%11%
1797
16th to endNight
28%5%9%24%23%9%
1800
May1st to 15thNight
32%5%13%17%21%8%
1710
16th to endNight
30%8%14%22%17%5%
1684
June1st to 15thNight
34%11%19%18%13%1
1620
16th to endNight
33%8%20%21%13%3
1620
July1st to 15thNight
32%13%27%15%7%2
1530
16th to endNight
32%11%26%22%5%
1716
August1st to 15thNight
32%14%20%20%8%3
1788
16th to endNight
40%13%14%15%14%2
1910
September1st to 15thNight
37%9%12%20%13%7%
1863
16th to endNight
33%6%11%19%20%8%
1903
October1st to 15thNight
25%49%18%24%17%
1815
16th to endNight
27%3413%29%21%
2090
November1st to 15thNight
28%25%18%27%16%
2276
16th to endNight
33%25%17%23%17%
2340
December1st to 15thNight
36%310%20%22%5%
2340
16th to endNight
46%47%16%19%5%
2496

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
22%13%30%21%8%4
90
16th to endDay
14%28%33%15%7%1
96
February1st to 15thDay
14%24%35%24%1
90
16th to endDay
16%18%41%20%2
81
March1st to 15thDay
17%27%40%12%2
90
16th to endDay
15%12%27%27%18%
273
April1st to 15thDay
16%14%22%25%19%2
270
16th to endDay
7%9%22%32%22%6%
270
May1st to 15thDay
10%7%21%28%23%7%
288
16th to endDay
10%314%29%26%15%
331
June1st to 15thDay
12%11%25%30%20%
315
16th to endDay
7%15%22%34%28%
315
July1st to 15thDay
7%417%38%32%
305
16th to endDay
6%419%37%32%
326
August1st to 15thDay
9%9%17%31%31%
313
16th to endDay
13%26%16%31%29%
332
September1st to 15thDay
13%29%20%31%23%
315
16th to endDay
12%16%31%31%18%
283
October1st to 15thDay
12%415%30%29%8%
255
16th to endDay
11%7%16%31%22%11%
151
November1st to 15thDay
23%336%18%14%3
90
16th to endDay
5%18%32%32%8%2
90
December1st to 15thDay
25%16%34%15%5%2
90
16th to endDay
21%17%27%22%10%
96
January1st to 15thNight
19%14%28%30%6%
720
16th to endNight
21%13%31%27%5%
768
February1st to 15thNight
16%11%31%33%6%
704
16th to endNight
16%16%31%28%6%
631
March1st to 15thNight
15%12%35%27%8%
720
16th to endNight
13%9%29%30%15%
670
April1st to 15thNight
11%8%30%29%19%
539
16th to endNight
10%7%27%37%16%1
540
May1st to 15thNight
10%423%34%23%3
540
16th to endNight
7%14%35%36%5%
563
June1st to 15thNight
6%17%31%43%9%
540
16th to endNight
6%5%24%46%15%
540
July1st to 15thNight
6%126%44%19%
510
16th to endNight
6%1421%47%17%
564
August1st to 15thNight
7%121%50%17%
539
16th to endNight
10%15%22%41%17%
573
September1st to 15thNight
13%28%22%39%13%
603
16th to endNight
9%111%35%37%4
689
October1st to 15thNight
10%119%33%31%3
660
16th to endNight
12%6%19%28%28%4
704
November1st to 15thNight
11%6%23%33%21%4
700
16th to endNight
13%9%25%36%13%1
720
December1st to 15thNight
16%8%27%32%12%
720
16th to endNight
21%10%29%27%10%
768
Page generated at 2017-09-24 08:15:49. Version ac04

Copyright 2017 A. Danko


Millers Ferry Clear Sky Chart | Charts Home