"Flying F" Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the "Flying F" Observatory clear sky chart from 2005-11-05 to 2017-09-16.

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
47%
15825
28%
46895
15%
15779
58%
15779
40%
24598

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
43%
792
30%
2398
18%
787
57%
787
47%
1136
January16th to endNight
41%
768
33%
2496
21%
768
58%
768
43%
1186
February1st to 15thNight
36%
698
26%
2288
13%
696
52%
696
38%
1140
February16th to endNight
31%
632
35%
1894
13%
632
54%
632
43%
943
March1st to 15thNight
39%
720
30%
2015
13%
720
53%
720
43%
1022
March16th to endNight
37%
741
29%
2085
13%
741
49%
741
41%
1080
April1st to 15thNight
28%
539
24%
1798
10%
539
46%
539
30%
911
April16th to endNight
34%
540
29%
1800
14%
540
54%
540
33%
899
May1st to 15thNight
36%
540
23%
1698
12%
539
49%
539
32%
910
May16th to endNight
42%
563
25%
1502
11%
561
54%
561
38%
816
June1st to 15thNight
54%
540
29%
1440
17%
540
62%
540
54%
704
June16th to endNight
64%
540
28%
1440
22%
540
69%
540
50%
744
July1st to 15thNight
66%
510
14%
1383
12%
510
67%
510
27%
906
July16th to endNight
74%
564
12%
1593
12%
531
76%
531
27%
1020
August1st to 15thNight
71%
539
15%
1630
14%
536
72%
536
28%
1001
August16th to endNight
67%
573
21%
1910
20%
573
71%
573
29%
1128
September1st to 15thNight
69%
540
24%
1800
21%
540
76%
540
32%
1030
September16th to endNight
64%
569
35%
1805
25%
569
75%
569
47%
876
October1st to 15thNight
49%
660
30%
1980
16%
660
60%
660
42%
1029
October16th to endNight
53%
704
38%
2112
20%
704
67%
704
47%
1022
November1st to 15thNight
48%
793
33%
2193
17%
793
59%
793
50%
1088
November16th to endNight
44%
900
36%
2427
17%
900
58%
900
52%
1193
December1st to 15thNight
32%
900
24%
2520
7%
900
47%
900
43%
1284
December16th to endNight
33%
960
26%
2688
13%
960
45%
960
36%
1530

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
46%36%5%35%45%6%47%
47863
Night
232332445%8%59%
47083
TransparencyDay
35%411%23%20%5%
47551
Night
23%414%28%22%5%
46897
SeeingDay
17%21%22%22%13%3
5682
Night
6%11%28%31%19%2
15831

By Month

Percentage Cloud Cover SW (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
225%5%3346%9%56%
1551
16th to endDay
436%5%23347%59%
1728
February1st to 15thDay
429%42445%8%53%
1575
16th to endDay
446%6%2445%11%47%
1580
March1st to 15thDay
16%45%5%245%48%52%
1944
16th to endDay
27%46%435%45%7%48%
2139
April1st to 15thDay
210%26%5%36%45%7%45%
2150
16th to endDay
310%46%6%3445%7%44%
2160
May1st to 15thDay
5%10%47%5%36%5%46%39%
2250
16th to endDay
6%7%26%5%3435%6%46%
2608
June1st to 15thDay
4423425%5%5%7%53%
2520
16th to endDay
3325%5%36%5%5%5%53%
2520
July1st to 15thDay
9%8%38%8%48%5%6%6%30%
2492
16th to endDay
11%7%39%10%5%7%6%6%6%23%
2467
August1st to 15thDay
13%9%47%8%45%5%5%5%28%
2319
16th to endDay
10%8%37%8%45%6%5%6%32%
2292
September1st to 15thDay
9%7%38%7%45%46%6%36%
2160
16th to endDay
7%6%25%5%3444451%
1841
October1st to 15thDay
7%8%24423335%55%
1650
16th to endDay
35%15%32344463%
1760
November1st to 15thDay
15%233225%46%64%
1651
16th to endDay
214313236%69%
1530
December1st to 15thDay
5%35%42345%7%56%
1440
16th to endDay
436%5%2445%9%52%
1536
January1st to 15thNight
223322347%66%
2398
16th to endNight
22422335%7%65%
2496
February1st to 15thNight
3244235%5%7%61%
2277
16th to endNight
323425%35%7%61%
1894
March1st to 15thNight
325%31345%7%62%
2015
16th to endNight
142322335%8%62%
2085
April1st to 15thNight
15%14325%46%7%57%
1798
16th to endNight
16%23325%45%7%59%
1800
May1st to 15thNight
36%345%34447%53%
1698
16th to endNight
442331335%7%60%
1502
June1st to 15thNight
111223347%68%
1440
16th to endNight
122231445%7%64%
1440
July1st to 15thNight
46%15%5%47%7%7%11%38%
1465
16th to endNight
5%4245%35%7%9%11%40%
1701
August1st to 15thNight
4425%5%35%6%8%10%43%
1639
16th to endNight
5%4245%35%6%6%10%43%
1910
September1st to 15thNight
44245%35%5%7%9%46%
1800
16th to endNight
321332235%6%65%
1805
October1st to 15thNight
5%313324446%60%
1980
16th to endNight
1313312336%67%
2112
November1st to 15thNight
222214447%66%
2193
16th to endNight
322312346%68%
2427
December1st to 15thNight
32432345%8%63%
2520
16th to endNight
325%5%2445%9%56%
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
23%318%33%18%2
1552
16th to endDay
25%312%29%22%5%
1728
February1st to 15thDay
28%315%29%16%6%
1575
16th to endDay
31%49%28%22%4
1580
March1st to 15thDay
29%311%29%21%3
1944
16th to endDay
33%312%28%19%2
2139
April1st to 15thDay
35%311%26%17%5%
2150
16th to endDay
37%39%27%19%2
2160
May1st to 15thDay
43%310%24%16%1
2250
16th to endDay
35%49%23%20%5%
2612
June1st to 15thDay
26%39%22%25%12%
2520
16th to endDay
29%46%16%28%14%
2520
July1st to 15thDay
48%8%12%12%11%6%
2345
16th to endDay
56%7%16%11%6%1
2312
August1st to 15thDay
55%6%11%11%10%4
2304
16th to endDay
49%5%12%17%12%2
2292
September1st to 15thDay
46%5%11%15%16%4
2160
16th to endDay
33%26%23%27%4
1841
October1st to 15thDay
33%2425%25%7%
1650
16th to endDay
23%28%26%32%6%
1760
November1st to 15thDay
20%310%25%31%9%
1651
16th to endDay
16%29%34%27%8%
1530
December1st to 15thDay
26%417%29%17%3
1440
16th to endDay
28%8%16%25%16%4
1536
January1st to 15thNight
17%318%31%23%4
2398
16th to endNight
19%411%34%23%6%
2496
February1st to 15thNight
23%415%30%20%5%
2288
16th to endNight
21%29%33%27%5%
1894
March1st to 15thNight
20%215%33%24%3
2015
16th to endNight
22%314%33%22%4
2085
April1st to 15thNight
25%415%28%22%4
1798
16th to endNight
25%313%35%19%4
1800
May1st to 15thNight
30%313%31%19%2
1699
16th to endNight
23%416%30%20%5%
1503
June1st to 15thNight
15%210%24%30%15%
1440
16th to endNight
18%49%20%29%17%
1440
July1st to 15thNight
39%7%16%14%12%9%
1383
16th to endNight
34%12%25%17%6%3
1593
August1st to 15thNight
33%10%17%18%13%7%
1630
16th to endNight
34%6%18%22%14%2
1910
September1st to 15thNight
32%5%18%18%18%6%
1800
16th to endNight
19%39%30%31%4
1805
October1st to 15thNight
24%311%25%27%7%
1980
16th to endNight
19%36%30%35%5%
2112
November1st to 15thNight
15%5%13%28%29%7%
2193
16th to endNight
16%210%34%28%7%
2427
December1st to 15thNight
20%421%29%21%3
2520
16th to endNight
23%9%15%29%18%4
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
15%18%23%26%15%
90
16th to endDay
8%19%34%26%10%1
96
February1st to 15thDay
17%24%24%26%6%
90
16th to endDay
18%27%18%27%6%2
81
March1st to 15thDay
20%30%28%16%3
234
16th to endDay
29%36%23%7%11
288
April1st to 15thDay
32%29%25%8%31
269
16th to endDay
32%37%17%10%1
270
May1st to 15thDay
19%37%26%13%2
288
16th to endDay
18%23%22%20%11%2
509
June1st to 15thDay
9%23%24%21%17%4
495
16th to endDay
5%14%21%26%24%7%
495
July1st to 15thDay
12%10%15%30%23%8%
449
16th to endDay
15%8%16%34%21%2
327
August1st to 15thDay
21%9%17%33%13%4
315
16th to endDay
19%8%21%29%19%1
332
September1st to 15thDay
11%18%28%21%15%3
315
16th to endDay
14%22%25%18%18%1
187
October1st to 15thDay
10%17%25%21%20%5%
90
16th to endDay
15%16%27%16%18%5%
96
November1st to 15thDay
11%12%21%28%23%3
90
16th to endDay
21%33%21%17%6%
90
December1st to 15thDay
14%28%35%18%2
90
16th to endDay
13%19%32%27%7%
96
January1st to 15thNight
414%33%33%11%2
792
16th to endNight
411%37%33%10%2
768
February1st to 15thNight
312%42%33%8%
704
16th to endNight
8%13%43%28%6%
632
March1st to 15thNight
6%17%32%31%10%
720
16th to endNight
7%14%36%31%9%
741
April1st to 15thNight
10%18%37%26%6%
539
16th to endNight
8%19%34%25%11%
540
May1st to 15thNight
8%12%33%32%13%
540
16th to endNight
9%14%27%27%19%2
563
June1st to 15thNight
49%27%33%22%2
540
16th to endNight
37%19%33%33%2
540
July1st to 15thNight
7%48%33%41%5%
510
16th to endNight
7%1227%52%8%
564
August1st to 15thNight
7%25%29%49%6%
539
16th to endNight
6%210%30%40%8%
573
September1st to 15thNight
5%312%39%34%4
540
16th to endNight
5%6%18%33%29%6%
569
October1st to 15thNight
8%8%27%33%17%3
660
16th to endNight
5%8%25%35%19%4
704
November1st to 15thNight
7%11%29%31%16%2
793
16th to endNight
7%11%34%29%13%2
900
December1st to 15thNight
7%16%41%25%8%1
900
16th to endNight
8%14%38%27%9%1
960
Page generated at 2017-09-17 10:05:41. Version ac04

Copyright 2017 A. Danko


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