"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 2018-04-23.

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
47%
16723
28%
49556
16%
16677
59%
16677
40%
25783

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%
858
30%
2599
18%
853
58%
853
48%
1215
January16th to endNight
43%
832
34%
2704
23%
832
60%
832
45%
1260
February1st to 15thNight
36%
758
26%
2483
13%
756
52%
756
40%
1226
February16th to endNight
30%
684
35%
2050
13%
684
53%
684
41%
1034
March1st to 15thNight
40%
780
30%
2183
14%
780
54%
780
43%
1105
March16th to endNight
37%
803
29%
2259
13%
803
50%
803
42%
1154
April1st to 15thNight
28%
584
25%
1948
10%
584
47%
584
30%
979
April16th to endNight
34%
558
29%
1859
14%
558
54%
558
32%
940
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
62%
618
36%
1959
25%
618
74%
618
46%
961
October1st to 15thNight
48%
720
29%
2160
15%
720
59%
720
44%
1095
October16th to endNight
54%
768
40%
2304
22%
768
68%
768
49%
1097
November1st to 15thNight
48%
861
33%
2381
17%
861
58%
861
50%
1174
November16th to endNight
45%
975
37%
2629
18%
975
59%
975
52%
1285
December1st to 15thNight
34%
975
25%
2730
8%
975
48%
975
45%
1375
December16th to endNight
34%
1040
28%
2912
15%
1040
46%
1040
38%
1624

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%3445%6%47%
49960
Night
132332445%7%59%
49744
TransparencyDay
34%411%23%20%5%
49648
Night
22%414%28%23%6%
49558
SeeingDay
17%21%22%21%13%2
6384
Night
6%11%29%31%18%2
16729

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
215%5%335%7%9%56%
1681
16th to endDay
435%5%23346%61%
1872
February1st to 15thDay
428%42445%7%54%
1710
16th to endDay
437%6%2445%11%47%
1710
March1st to 15thDay
16%45%5%24447%53%
2106
16th to endDay
27%46%425%45%7%48%
2317
April1st to 15thDay
29%26%5%36%45%7%46%
2330
16th to endDay
310%46%7%3445%7%44%
2215
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%3443451%
1998
October1st to 15thDay
7%8%24423335%56%
1800
16th to endDay
341432344464%
1920
November1st to 15thDay
1413222445%66%
1792
16th to endDay
213313236%69%
1657
December1st to 15thDay
5%3442345%7%58%
1560
16th to endDay
436%5%2445%8%53%
1664
January1st to 15thNight
123322347%67%
2599
16th to endNight
224223346%67%
2704
February1st to 15thNight
3244235%47%61%
2472
16th to endNight
32443435%7%60%
2050
March1st to 15thNight
32431345%7%63%
2183
16th to endNight
142322335%7%63%
2259
April1st to 15thNight
15%1332446%7%57%
1948
16th to endNight
16%23325%45%7%58%
1859
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
431332235%6%64%
1959
October1st to 15thNight
4313323446%62%
2160
16th to endNight
1313312336%68%
2304
November1st to 15thNight
222213447%66%
2381
16th to endNight
322312347%68%
2629
December1st to 15thNight
324323447%64%
2730
16th to endNight
325%42445%8%58%
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
23%317%33%19%3
1682
16th to endDay
24%311%31%22%6%
1872
February1st to 15thDay
28%415%30%15%5%
1710
16th to endDay
31%48%26%23%5%
1710
March1st to 15thDay
29%311%29%21%4
2106
16th to endDay
32%312%29%19%2
2317
April1st to 15thDay
34%410%26%18%5%
2330
16th to endDay
37%39%27%19%2
2215
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
34%26%23%27%5%
1998
October1st to 15thDay
31%25%24%26%9%
1800
16th to endDay
22%27%27%32%6%
1920
November1st to 15thDay
18%39%26%32%9%
1792
16th to endDay
15%210%34%28%8%
1657
December1st to 15thDay
25%417%28%18%6%
1560
16th to endDay
27%8%15%25%18%4
1664
January1st to 15thNight
16%317%32%24%5%
2599
16th to endNight
18%410%35%25%5%
2704
February1st to 15thNight
22%416%31%19%5%
2483
16th to endNight
22%29%32%28%5%
2050
March1st to 15thNight
19%314%32%25%4
2183
16th to endNight
20%314%34%22%3
2259
April1st to 15thNight
23%5%15%28%22%3
1948
16th to endNight
25%312%34%19%4
1859
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
20%39%30%31%4
1959
October1st to 15thNight
22%310%25%28%9%
2160
16th to endNight
18%36%30%35%5%
2304
November1st to 15thNight
15%5%12%29%29%7%
2381
16th to endNight
16%310%34%28%8%
2629
December1st to 15thNight
19%320%28%22%5%
2730
16th to endNight
22%8%14%28%21%3
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
12%19%25%28%13%
135
16th to endDay
8%18%31%28%11%1
144
February1st to 15thDay
20%23%25%24%5%
135
16th to endDay
17%33%20%22%41
120
March1st to 15thDay
21%29%27%16%5%
291
16th to endDay
27%37%24%8%1
352
April1st to 15thDay
31%31%24%8%2
329
16th to endDay
32%37%17%10%2
288
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
20%22%24%16%15%
237
October1st to 15thDay
17%20%22%17%18%3
135
16th to endDay
11%17%25%20%20%4
144
November1st to 15thDay
14%17%24%25%17%2
135
16th to endDay
19%28%23%20%8%
135
December1st to 15thDay
11%26%32%21%5%1
135
16th to endDay
13%22%30%22%10%
144
January1st to 15thNight
414%33%35%10%2
858
16th to endNight
411%36%34%11%2
832
February1st to 15thNight
312%42%33%7%
764
16th to endNight
8%13%44%27%5%
684
March1st to 15thNight
6%18%31%32%10%
780
16th to endNight
7%15%35%32%8%
803
April1st to 15thNight
11%19%36%26%5%
584
16th to endNight
8%19%33%25%11%
558
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
7%6%18%33%27%5%
618
October1st to 15thNight
7%9%29%33%17%3
720
16th to endNight
5%8%25%35%20%4
768
November1st to 15thNight
7%12%29%33%15%2
861
16th to endNight
7%11%33%31%13%2
975
December1st to 15thNight
6%15%40%28%8%1
975
16th to endNight
8%13%38%27%9%1
1040
Page generated at 2018-04-24 08:03:03. Version ac04

Copyright 2018 A. Danko


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