Foxtrotter Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Foxtrotter Observatory clear sky chart from 2005-11-05 to 2017-09-21.

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
60%
15856
21%
46988
17%
15817
65%
15817
31%
29165

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
44%
717
20%
2327
15%
716
52%
716
26%
1452
January16th to endNight
41%
768
24%
2439
17%
768
51%
768
27%
1501
February1st to 15thNight
45%
701
25%
2106
17%
699
54%
699
33%
1265
February16th to endNight
44%
631
24%
1866
14%
631
53%
631
29%
1171
March1st to 15thNight
50%
720
28%
1980
18%
720
59%
720
40%
1147
March16th to endNight
54%
768
27%
2112
19%
768
60%
768
41%
1202
April1st to 15thNight
55%
718
24%
1976
16%
718
61%
718
39%
1157
April16th to endNight
62%
684
28%
1821
19%
684
67%
684
44%
1031
May1st to 15thNight
72%
539
27%
1619
21%
539
76%
539
43%
857
May16th to endNight
76%
561
24%
1682
20%
561
77%
561
38%
961
June1st to 15thNight
70%
540
13%
1620
12%
540
71%
540
26%
1107
June16th to endNight
75%
540
10%
1620
8%
540
76%
540
26%
1098
July1st to 15thNight
75%
510
9%
1530
8%
510
75%
510
22%
1076
July16th to endNight
78%
564
7%
1595
7%
531
79%
531
24%
1108
August1st to 15thNight
76%
539
7%
1618
7%
536
76%
536
22%
1143
August16th to endNight
67%
683
11%
2020
12%
683
67%
683
21%
1426
September1st to 15thNight
67%
720
9%
1980
8%
720
67%
720
21%
1406
September16th to endNight
60%
681
16%
1881
15%
681
61%
681
22%
1346
October1st to 15thNight
69%
660
27%
1862
27%
660
70%
660
36%
1118
October16th to endNight
63%
704
30%
2112
29%
704
68%
704
36%
1219
November1st to 15thNight
62%
700
30%
2101
27%
700
69%
700
40%
1163
November16th to endNight
52%
720
28%
2285
22%
720
62%
720
33%
1305
December1st to 15thNight
52%
720
27%
2340
24%
720
59%
720
30%
1393
December16th to endNight
54%
768
24%
2496
22%
768
60%
768
28%
1513

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
9%5%26%6%36%6%6%8%38%
47863
Night
8%5%245%35%5%6%9%45%
47194
TransparencyDay
40%8%13%17%13%6%
47564
Night
34%8%15%19%15%7%
46997
SeeingDay
10%212%21%26%27%
5718
Night
10%317%33%27%7%
15865

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
11%6%35%435%45%7%42%
1611
16th to endDay
12%5%24425%347%46%
1782
February1st to 15thDay
15%424423346%47%
1750
16th to endDay
11%5%25%42445%5%48%
1607
March1st to 15thDay
9%41442335%8%52%
1980
16th to endDay
8%425%42445%6%49%
2111
April1st to 15thDay
7%4245%35%5%6%8%48%
1972
16th to endDay
6%214435%6%6%8%49%
2148
May1st to 15thDay
6%324435%46%9%49%
2331
16th to endDay
7%425%6%37%6%6%9%40%
2431
June1st to 15thDay
10%5%37%7%5%7%7%7%9%28%
2340
16th to endDay
8%5%36%8%5%9%9%7%10%25%
2340
July1st to 15thDay
9%5%37%8%5%8%9%8%10%23%
2340
16th to endDay
7%6%48%9%6%9%7%8%10%20%
2465
August1st to 15thDay
10%5%38%9%5%8%9%9%11%17%
2328
16th to endDay
12%6%37%9%5%8%7%8%9%21%
2169
September1st to 15thDay
10%6%27%8%5%8%9%8%9%23%
1980
16th to endDay
11%6%39%9%46%6%7%8%25%
1872
October1st to 15thDay
9%5%37%6%35%5%6%7%40%
1768
16th to endDay
9%416%5%25%45%6%49%
1760
November1st to 15thDay
6%424434348%52%
1757
16th to endDay
9%5%245%24447%49%
1673
December1st to 15thDay
11%5%25%435%45%6%43%
1620
16th to endDay
9%5%245%346%5%9%42%
1728
January1st to 15thNight
10%6%36%5%25%45%8%41%
2327
16th to endNight
15%5%2442445%7%44%
2439
February1st to 15thNight
11%425%423345%51%
2103
16th to endNight
9%6%25%5%33447%46%
1866
March1st to 15thNight
7%3235%2445%7%53%
1980
16th to endNight
7%42442335%7%56%
2112
April1st to 15thNight
7%42442345%8%53%
1976
16th to endNight
6%21342435%9%55%
1821
May1st to 15thNight
5%21232446%8%57%
1619
16th to endNight
5%313426%5%5%9%52%
1682
June1st to 15thNight
10%5%245%36%6%7%13%34%
1620
16th to endNight
7%4245%36%6%9%13%35%
1620
July1st to 15thNight
45%25%6%46%7%10%14%32%
1620
16th to endNight
2427%7%47%7%10%13%32%
1703
August1st to 15thNight
5%425%6%46%9%9%13%32%
1629
16th to endNight
9%5%26%6%36%6%6%10%34%
2020
September1st to 15thNight
9%6%25%6%45%8%8%10%31%
1980
16th to endNight
11%7%35%6%46%5%7%10%31%
1881
October1st to 15thNight
6%5%245%2445%8%50%
1862
16th to endNight
7%5%25%42445%7%52%
2112
November1st to 15thNight
7%32422435%7%55%
2101
16th to endNight
8%41443445%7%50%
2285
December1st to 15thNight
9%5%25%43435%8%46%
2340
16th to endNight
9%6%25%435%45%8%44%
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
40%5%7%18%18%9%
1612
16th to endDay
38%37%18%21%10%
1782
February1st to 15thDay
39%46%14%20%15%
1752
16th to endDay
36%5%10%13%22%12%
1607
March1st to 15thDay
30%310%23%21%10%
1980
16th to endDay
33%411%22%17%10%
2112
April1st to 15thDay
32%6%10%18%23%8%
1972
16th to endDay
30%6%10%22%21%9%
2148
May1st to 15thDay
31%5%12%21%19%9%
2331
16th to endDay
36%6%15%21%15%4
2435
June1st to 15thDay
47%10%15%19%5%
2340
16th to endDay
48%12%19%15%3
2340
July1st to 15thDay
50%13%22%12%1
2201
16th to endDay
51%13%21%10%2
2310
August1st to 15thDay
52%15%21%9%1
2315
16th to endDay
53%14%17%12%1
2169
September1st to 15thDay
50%14%18%10%5%
1980
16th to endDay
52%10%11%15%8%3
1872
October1st to 15thDay
41%7%7%15%16%11%
1768
16th to endDay
34%5%7%13%23%14%
1760
November1st to 15thDay
31%39%22%20%11%
1757
16th to endDay
34%48%19%21%12%
1673
December1st to 15thDay
39%5%10%21%17%5%
1620
16th to endDay
37%6%11%21%14%9%
1728
January1st to 15thNight
40%5%9%18%17%8%
2327
16th to endNight
39%48%14%23%9%
2439
February1st to 15thNight
34%47%16%20%16%
2112
16th to endNight
36%6%8%15%21%10%
1866
March1st to 15thNight
28%413%23%20%9%
1980
16th to endNight
27%412%23%19%10%
2112
April1st to 15thNight
28%6%11%21%23%8%
1976
16th to endNight
26%5%12%27%20%8%
1821
May1st to 15thNight
23%5%15%26%19%8%
1620
16th to endNight
28%6%16%26%19%2
1684
June1st to 15thNight
39%10%21%22%5%
1620
16th to endNight
35%13%24%19%5%
1620
July1st to 15thNight
37%16%28%14%2
1530
16th to endNight
36%16%31%12%3
1595
August1st to 15thNight
36%18%31%12%1
1618
16th to endNight
41%14%23%18%2
2020
September1st to 15thNight
41%14%25%13%5%
1980
16th to endNight
45%9%16%16%8%2
1881
October1st to 15thNight
30%7%13%17%20%10%
1862
16th to endNight
31%48%17%24%12%
2112
November1st to 15thNight
27%5%10%23%23%10%
2101
16th to endNight
32%49%19%17%15%
2285
December1st to 15thNight
35%5%10%26%15%6%
2340
16th to endNight
37%5%11%21%14%9%
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
14%11%30%22%11%11%
90
16th to endDay
12%17%34%18%15%1
96
February1st to 15thDay
10%17%25%22%21%3
90
16th to endDay
8%8%28%36%16%1
108
March1st to 15thDay
9%5%26%37%18%2
270
16th to endDay
10%422%27%29%4
288
April1st to 15thDay
8%7%20%28%29%6%
270
16th to endDay
5%115%29%30%17%
270
May1st to 15thDay
7%313%22%30%22%
288
16th to endDay
7%16%17%31%35%
331
June1st to 15thDay
16%414%26%37%
315
16th to endDay
6%29%27%53%
315
July1st to 15thDay
6%115%24%60%
305
16th to endDay
9%15%7%18%57%
326
August1st to 15thDay
15%48%17%53%
313
16th to endDay
11%149%22%50%
332
September1st to 15thDay
16%1312%30%36%
315
16th to endDay
12%1216%37%29%
275
October1st to 15thDay
11%18%33%31%13%
255
16th to endDay
8%116%36%30%6%
272
November1st to 15thDay
8%215%35%29%8%
265
16th to endDay
5%124%38%23%6%
143
December1st to 15thDay
5%140%35%15%2
90
16th to endDay
11%415%37%25%6%
96
January1st to 15thNight
13%6%28%34%16%
720
16th to endNight
17%7%25%38%10%
768
February1st to 15thNight
13%5%31%37%11%1
704
16th to endNight
12%7%30%40%8%
631
March1st to 15thNight
8%5%30%41%12%
720
16th to endNight
8%427%40%18%
768
April1st to 15thNight
8%5%26%40%18%
718
16th to endNight
7%221%45%21%1
684
May1st to 15thNight
5%214%47%25%4
540
16th to endNight
6%7%35%40%8%
563
June1st to 15thNight
13%1427%40%13%
540
16th to endNight
8%1215%45%25%
540
July1st to 15thNight
6%311%42%35%
510
16th to endNight
4210%57%24%
564
August1st to 15thNight
6%1210%50%28%
539
16th to endNight
12%1316%45%20%
683
September1st to 15thNight
11%15%25%41%15%
720
16th to endNight
14%16%29%39%7%
681
October1st to 15thNight
8%110%38%36%4
660
16th to endNight
9%215%41%28%2
704
November1st to 15thNight
8%320%39%26%2
700
16th to endNight
10%327%38%18%1
720
December1st to 15thNight
11%424%38%20%
720
16th to endNight
12%420%40%20%1
768
Page generated at 2017-09-22 07:35:34. Version ac04

Copyright 2017 A. Danko


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