FLSR Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the FLSR Observatory 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
72%
15985
35%
46809
29%
15944
76%
15944
52%
23035

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
59%
716
29%
2327
26%
716
66%
716
40%
1188
January16th to endNight
57%
768
32%
2325
26%
768
66%
768
38%
1280
February1st to 15thNight
60%
698
33%
2108
30%
697
68%
697
41%
1131
February16th to endNight
55%
632
29%
1895
28%
632
60%
632
33%
1128
March1st to 15thNight
60%
720
29%
2160
27%
720
68%
720
41%
1170
March16th to endNight
66%
768
31%
2031
24%
768
71%
768
48%
1123
April1st to 15thNight
60%
719
29%
1799
17%
719
65%
719
46%
1040
April16th to endNight
65%
720
33%
1800
18%
720
70%
720
54%
979
May1st to 15thNight
71%
564
34%
1644
23%
564
75%
564
58%
771
May16th to endNight
69%
561
32%
1685
25%
561
72%
561
57%
776
June1st to 15thNight
82%
540
33%
1620
30%
540
83%
540
69%
673
June16th to endNight
92%
412
41%
1492
44%
412
94%
412
80%
482
July1st to 15thNight
92%
406
34%
1426
36%
406
92%
406
68%
521
July16th to endNight
84%
600
32%
1626
26%
564
85%
564
62%
746
August1st to 15thNight
93%
717
38%
1790
25%
713
93%
713
79%
806
August16th to endNight
93%
764
43%
1910
30%
764
93%
764
78%
872
September1st to 15thNight
91%
720
39%
1863
32%
720
91%
720
73%
854
September16th to endNight
88%
688
47%
1903
43%
688
91%
688
79%
790
October1st to 15thNight
75%
660
39%
1815
35%
660
79%
660
56%
908
October16th to endNight
76%
704
40%
2139
40%
704
80%
704
55%
994
November1st to 15thNight
72%
700
35%
2275
35%
700
79%
700
54%
1024
November16th to endNight
69%
720
36%
2340
38%
720
74%
720
45%
1149
December1st to 15thNight
60%
720
31%
2340
28%
720
68%
720
37%
1251
December16th to endNight
50%
768
32%
2496
27%
768
60%
768
33%
1379

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
3313213346%66%
48074
Night
3313313335%66%
47008
TransparencyDay
19%25%15%27%29%
47769
Night
20%25%15%26%29%
46814
SeeingDay
7%9%33%34%10%4
5905
Night
6%312%32%33%11%
15998

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
5%5%1332235%7%58%
1611
16th to endDay
6%6%25%32335%5%54%
1896
February1st to 15thDay
36%24314346%58%
1751
16th to endDay
7%9%36%423246%49%
1579
March1st to 15thDay
5%5%133235%5%7%57%
1800
16th to endDay
332422435%8%57%
2188
April1st to 15thDay
6%423323346%59%
2149
16th to endDay
3213222247%67%
2160
May1st to 15thDay
221232335%6%67%
2304
16th to endDay
2212222237%71%
2429
June1st to 15thDay
11213245%75%
2340
16th to endDay
111111286%
2460
July1st to 15thDay
212222345%72%
2442
16th to endDay
221222345%8%64%
2428
August1st to 15thDay
11212335%78%
2160
16th to endDay
111122335%75%
2292
September1st to 15thDay
112212346%74%
2097
16th to endDay
11121233379%
1893
October1st to 15thDay
222431223469%
1815
16th to endDay
121222234471%
1728
November1st to 15thDay
3313312335%67%
1584
16th to endDay
35%23324336%60%
1620
December1st to 15thDay
45%144245%7%9%50%
1620
16th to endDay
7%8%24323446%52%
1728
January1st to 15thNight
5%6%14423347%57%
2327
16th to endNight
7%6%25%323345%55%
2325
February1st to 15thNight
47%25%313336%57%
2101
16th to endNight
6%6%46%424446%48%
1895
March1st to 15thNight
36%23424347%56%
2160
16th to endNight
2425%323448%57%
2031
April1st to 15thNight
35%24323347%57%
1799
16th to endNight
2223323435%67%
1800
May1st to 15thNight
1212212347%68%
1644
16th to endNight
1113313345%70%
1684
June1st to 15thNight
11212235%78%
1620
16th to endNight
1112288%
1492
July1st to 15thNight
11122222477%
1512
16th to endNight
1222312245%69%
1737
August1st to 15thNight
111222482%
1800
16th to endNight
11111111384%
1910
September1st to 15thNight
111112235%78%
1863
16th to endNight
11212384%
1903
October1st to 15thNight
231421223469%
1815
16th to endNight
121331333372%
2139
November1st to 15thNight
141321233469%
2275
16th to endNight
2424323336%61%
2340
December1st to 15thNight
6%6%24324447%53%
2340
16th to endNight
7%7%34413345%53%
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
25%26%15%28%22%
1612
16th to endDay
31%16%15%21%23%
1896
February1st to 15thDay
27%1417%26%22%
1751
16th to endDay
36%16%15%27%12%
1579
March1st to 15thDay
24%36%20%24%20%
1800
16th to endDay
24%39%21%26%13%
2188
April1st to 15thDay
27%3422%29%11%
2149
16th to endDay
19%37%20%29%19%
2160
May1st to 15thDay
18%27%18%30%21%
2304
16th to endDay
15%47%21%35%15%
2432
June1st to 15thDay
13%25%12%31%34%
2340
16th to endDay
7%12421%61%
2460
July1st to 15thDay
12%249%22%48%
2299
16th to endDay
18%26%17%23%30%
2276
August1st to 15thDay
9%1311%27%47%
2146
16th to endDay
11%249%33%38%
2292
September1st to 15thDay
10%16%9%30%40%
2097
16th to endDay
10%210%33%41%
1893
October1st to 15thDay
20%2314%29%29%
1815
16th to endDay
17%2310%27%38%
1728
November1st to 15thDay
19%16%14%29%27%
1584
16th to endDay
24%2414%24%29%
1620
December1st to 15thDay
27%48%18%20%20%
1620
16th to endDay
32%27%19%21%16%
1728
January1st to 15thNight
27%25%14%24%25%
2327
16th to endNight
30%27%13%20%25%
2325
February1st to 15thNight
28%2415%23%24%
2112
16th to endNight
36%2416%24%15%
1895
March1st to 15thNight
27%35%18%23%21%
2160
16th to endNight
24%28%23%26%14%
2031
April1st to 15thNight
26%36%23%25%14%
1799
16th to endNight
19%4422%31%18%
1800
May1st to 15thNight
15%37%21%32%19%
1645
16th to endNight
15%39%20%34%16%
1685
June1st to 15thNight
10%2414%31%36%
1620
16th to endNight
5%26%22%61%
1492
July1st to 15thNight
10%310%20%53%
1426
16th to endNight
14%27%17%26%30%
1626
August1st to 15thNight
7%1212%30%45%
1790
16th to endNight
8%1210%34%42%
1910
September1st to 15thNight
8%349%31%41%
1863
16th to endNight
7%1312%33%42%
1903
October1st to 15thNight
19%2314%32%27%
1815
16th to endNight
17%229%26%41%
2139
November1st to 15thNight
18%1414%28%32%
2275
16th to endNight
24%2415%23%30%
2340
December1st to 15thNight
29%36%15%22%22%
2340
16th to endNight
31%37%15%24%17%
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
31%422%32%7%2
90
16th to endDay
15%12%32%28%9%2
264
February1st to 15thDay
9%14%31%30%11%2
266
16th to endDay
22%15%29%25%7%
238
March1st to 15thDay
13%13%32%27%10%2
270
16th to endDay
10%15%39%24%8%1
288
April1st to 15thDay
14%18%39%15%8%2
269
16th to endDay
8%26%35%23%42
270
May1st to 15thDay
8%15%39%26%5%4
288
16th to endDay
5%13%42%26%6%4
330
June1st to 15thDay
29%41%32%8%5%
315
16th to endDay
2232%42%11%8%
315
July1st to 15thDay
1125%50%12%8%
305
16th to endDay
4117%52%14%9%
327
August1st to 15thDay
2234%42%9%8%
315
16th to endDay
2126%47%13%9%
332
September1st to 15thDay
3240%38%13%2
315
16th to endDay
36%34%41%11%2
284
October1st to 15thDay
6%11%40%31%8%
255
16th to endDay
5%11%33%28%19%1
203
November1st to 15thDay
47%16%33%25%12%
90
16th to endDay
8%12%27%35%15%
90
December1st to 15thDay
10%6%28%35%16%2
90
16th to endDay
15%7%28%34%13%1
96
January1st to 15thNight
10%418%35%22%9%
720
16th to endNight
12%5%17%32%24%7%
768
February1st to 15thNight
9%6%17%36%23%7%
704
16th to endNight
13%7%18%32%21%6%
632
March1st to 15thNight
7%6%19%36%22%7%
720
16th to endNight
5%6%16%37%26%7%
768
April1st to 15thNight
7%8%18%38%20%6%
719
16th to endNight
47%19%34%25%8%
720
May1st to 15thNight
4217%37%30%6%
565
16th to endNight
2420%34%29%8%
563
June1st to 15thNight
1112%40%39%4
540
16th to endNight
437%48%8%
412
July1st to 15thNight
1124%58%12%
406
16th to endNight
21322%57%13%
600
August1st to 15thNight
1123%53%19%
717
16th to endNight
1116%54%25%
764
September1st to 15thNight
2224%47%22%
720
16th to endNight
16%31%41%18%
688
October1st to 15thNight
6%310%35%33%11%
660
16th to endNight
3312%30%32%17%
704
November1st to 15thNight
5%115%33%32%11%
700
16th to endNight
6%313%33%29%12%
720
December1st to 15thNight
12%415%35%24%8%
720
16th to endNight
14%7%19%32%19%5%
768
Page generated at 2017-09-24 06:15:52. Version ac04

Copyright 2017 A. Danko


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