Farfel Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Farfel Observatory clear sky chart from 2005-11-06 to 2024-03-06.

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
48%
22957
13%
80697
14%
22865
50%
22865
17%
57487

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 10thNight
28%
752
4%
4406
7%
736
30%
736
4%
3840
January11th to 20thNight
30%
757
5%
4348
9%
740
32%
740
5%
3746
January21st to endNight
37%
835
7%
4484
13%
814
39%
814
7%
3720
February1st to 10thNight
36%
760
7%
2470
8%
760
36%
760
10%
2025
February11th to 20thNight
39%
740
10%
2404
9%
740
41%
740
12%
1858
February21st to endNight
36%
628
11%
1962
9%
628
38%
628
12%
1532
March1st to 10thNight
36%
742
9%
2096
7%
742
38%
742
14%
1660
March11th to 20thNight
42%
720
11%
1980
9%
720
44%
720
16%
1548
March21st to endNight
34%
792
5%
2156
4%
792
34%
792
11%
1811
April1st to 10thNight
35%
720
9%
1800
6%
720
35%
720
13%
1467
April11th to 20thNight
42%
711
11%
1779
6%
711
43%
711
19%
1372
April21st to endNight
45%
557
11%
1637
8%
557
47%
557
16%
1222
May1st to 10thNight
48%
468
13%
1548
12%
468
50%
468
22%
1009
May11th to 20thNight
55%
354
13%
1416
18%
354
56%
354
16%
957
May21st to endNight
51%
389
10%
1552
12%
388
55%
388
16%
1039
June1st to 10thNight
55%
360
10%
1440
15%
360
58%
360
18%
930
June11th to 20thNight
53%
360
13%
1440
17%
360
58%
360
24%
833
June21st to endNight
71%
360
19%
1440
29%
360
75%
360
39%
653
July1st to 10thNight
74%
350
22%
1400
31%
350
81%
350
48%
571
July11th to 20thNight
68%
348
29%
1392
33%
348
81%
348
48%
566
July21st to endNight
76%
461
36%
1552
37%
436
87%
436
71%
543
August1st to 10thNight
81%
537
29%
1602
25%
534
84%
534
58%
727
August11th to 20thNight
83%
534
35%
1602
28%
534
85%
534
61%
710
August21st to endNight
73%
725
35%
1913
22%
725
77%
725
59%
957
September1st to 10thNight
72%
720
34%
1800
20%
720
74%
720
60%
937
September11th to 20thNight
70%
720
29%
1822
20%
720
72%
720
43%
1083
September21st to endNight
65%
720
24%
2052
23%
720
66%
720
35%
1235
October1st to 10thNight
60%
720
17%
2160
16%
720
62%
720
31%
1345
October11th to 20thNight
59%
720
19%
2160
21%
720
60%
720
26%
1422
October21st to endNight
46%
792
17%
2376
16%
792
49%
792
19%
1683
November1st to 10thNight
38%
740
11%
2465
11%
740
40%
740
13%
1872
November11th to 20thNight
36%
760
9%
2660
10%
760
37%
760
10%
2083
November21st to endNight
44%
760
9%
2660
9%
760
45%
760
15%
1932
December1st to 10thNight
42%
760
11%
2660
11%
760
44%
760
14%
1976
December11th to 20thNight
33%
759
6%
3241
8%
759
33%
759
7%
2665
December21st to endNight
25%
826
4%
4822
6%
817
26%
817
4%
3958

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
20%8%36%5%34446%36%
78545
Night
21%9%37%5%34445%33%
81005
TransparencyDay
50%5%12%18%12%3
78252
Night
53%5%11%17%10%3
80819
SeeingDay
22%10%22%27%15%4
13828
Night
24%6%12%32%23%3
22984

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 10thDay
32%15%47%7%46%5%6%5%10%
2539
11th to 20thDay
38%13%5%9%7%2423413%
2601
21st to endDay
27%11%49%8%46%5%6%7%15%
3146
February1st to 10thDay
27%11%48%7%45%5%6%6%17%
1710
11th to 20thDay
26%13%5%7%7%4445%6%20%
1665
21st to endDay
28%13%48%7%35%445%18%
1490
March1st to 10thDay
25%11%49%7%45%45%6%19%
1979
11th to 20thDay
26%12%37%6%45%45%6%23%
1980
21st to endDay
29%11%5%8%7%45%5%46%16%
2200
April1st to 10thDay
27%13%5%9%7%45%44419%
2160
11th to 20thDay
26%11%47%7%35%445%25%
2129
21st to endDay
22%8%47%6%345%5%7%29%
2321
May1st to 10thDay
17%9%36%6%3445%6%38%
2410
11th to 20thDay
20%8%36%5%35%5%6%8%30%
2477
21st to endDay
24%8%46%6%24447%31%
2723
June1st to 10thDay
21%8%35%5%25%446%34%
2520
11th to 20thDay
18%7%36%5%35%45%8%36%
2520
21st to endDay
10%5%23423346%59%
2520
July1st to 10thDay
6%313322345%68%
2520
11th to 20thDay
7%312222336%69%
2520
21st to endDay
321221322476%
2670
August1st to 10thDay
4313213346%70%
2328
11th to 20thDay
4213222346%71%
2298
21st to endDay
5%313323346%66%
2442
September1st to 10thDay
6%313222335%70%
2160
11th to 20thDay
11%5%35%424447%50%
2136
21st to endDay
14%5%26%5%345%46%47%
1908
October1st to 10thDay
16%8%25%435%45%5%42%
1800
11th to 20thDay
19%7%36%6%35%5%5%7%35%
1800
21st to endDay
21%9%47%6%345%5%7%30%
1980
November1st to 10thDay
29%8%49%6%35%446%20%
1611
11th to 20thDay
28%9%47%6%4445%8%20%
1520
21st to endDay
27%9%48%6%4446%7%21%
1520
December1st to 10thDay
24%10%36%7%346%5%8%24%
1520
11th to 20thDay
24%12%411%9%5%6%5%6%6%12%
1928
21st to endDay
31%13%5%10%8%4445%6%9%
2794
January1st to 10thNight
29%17%6%10%7%4444310%
4406
11th to 20thNight
36%16%5%9%6%3433312%
4358
21st to endNight
34%12%5%8%7%34345%15%
4521
February1st to 10thNight
25%14%5%9%6%45%45%6%18%
2470
11th to 20thNight
26%11%37%6%44445%24%
2402
21st to endNight
26%12%47%5%345%5%7%22%
1962
March1st to 10thNight
25%11%38%6%3445%7%22%
2096
11th to 20thNight
22%8%47%8%446%5%6%26%
1980
21st to endNight
28%12%47%6%45%445%20%
2156
April1st to 10thNight
27%12%47%7%35%43424%
1800
11th to 20thNight
21%11%47%5%2445%7%30%
1779
21st to endNight
23%7%35%5%45%5%5%7%30%
1637
May1st to 10thNight
16%9%35%6%24446%41%
1548
11th to 20thNight
16%8%36%6%46%45%7%35%
1416
21st to endNight
18%6%37%6%345%5%8%37%
1552
June1st to 10thNight
18%7%35%4345%5%6%40%
1440
11th to 20thNight
15%7%3432345%9%46%
1440
21st to endNight
9%312213436%65%
1440
July1st to 10thNight
6%22221233473%
1440
11th to 20thNight
5%21332333473%
1440
21st to endNight
211211122483%
1643
August1st to 10thNight
3212213436%72%
1611
11th to 20thNight
321222224477%
1602
21st to endNight
5%212222335%73%
1913
September1st to 10thNight
7%212212245%72%
1800
11th to 20thNight
9%42443435%6%57%
1822
21st to endNight
12%42443445%7%52%
2052
October1st to 10thNight
15%6%25%5%23346%49%
2160
11th to 20thNight
17%6%35%5%345%46%43%
2160
21st to endNight
21%10%25%5%34446%35%
2376
November1st to 10thNight
27%8%37%6%45%5%5%6%23%
2465
11th to 20thNight
28%10%48%6%345%5%6%21%
2660
21st to endNight
23%9%37%7%35%45%6%27%
2660
December1st to 10thNight
25%8%47%6%445%6%6%26%
2660
11th to 20thNight
26%12%5%9%8%5%5%5%45%16%
3276
21st to endNight
27%12%6%13%7%45%45%5%11%
4862

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 10thDay
75%412%6%21
2539
11th to 20thDay
77%46%6%5%3
2601
21st to endDay
68%5%11%9%5%1
3146
February1st to 10thDay
65%6%12%10%6%
1710
11th to 20thDay
66%5%12%10%42
1674
21st to endDay
69%410%10%5%2
1490
March1st to 10thDay
67%5%11%12%4
1979
11th to 20thDay
63%5%11%16%5%1
1980
21st to endDay
70%7%10%11%2
2200
April1st to 10thDay
70%411%11%4
2160
11th to 20thDay
62%5%12%12%6%3
2132
21st to endDay
56%6%15%14%8%1
2321
May1st to 10thDay
48%6%17%20%8%1
2410
11th to 20thDay
52%7%15%20%6%1
2480
21st to endDay
55%6%17%19%3
2724
June1st to 10thDay
52%5%15%22%5%
2520
11th to 20thDay
47%6%20%21%6%
2520
21st to endDay
28%416%32%16%4
2520
July1st to 10thDay
20%413%28%26%8%
2451
11th to 20thDay
20%48%23%33%12%
2445
21st to endDay
13%25%28%41%10%
2521
August1st to 10thDay
17%414%35%23%7%
2312
11th to 20thDay
17%311%34%28%7%
2298
21st to endDay
20%412%31%29%5%
2442
September1st to 10thDay
19%38%32%25%13%
2160
11th to 20thDay
34%5%12%25%17%7%
2136
21st to endDay
38%5%12%22%18%6%
1908
October1st to 10thDay
42%7%10%18%18%6%
1800
11th to 20thDay
48%6%13%17%14%3
1800
21st to endDay
53%6%11%14%13%3
1980
November1st to 10thDay
65%5%11%13%6%
1611
11th to 20thDay
62%6%12%10%7%3
1520
21st to endDay
61%5%11%7%13%3
1520
December1st to 10thDay
59%5%11%13%11%1
1520
11th to 20thDay
69%5%12%11%3
1928
21st to endDay
76%410%7%21
2794
January1st to 10thNight
79%5%7%5%31
4406
11th to 20thNight
76%5%6%7%42
4358
21st to endNight
73%37%10%5%1
4521
February1st to 10thNight
68%6%10%12%41
2470
11th to 20thNight
61%6%13%12%5%2
2404
21st to endNight
62%5%12%12%6%2
1962
March1st to 10thNight
62%6%13%13%6%1
2096
11th to 20thNight
58%7%13%16%5%1
1980
21st to endNight
68%6%12%12%3
2156
April1st to 10thNight
65%5%11%14%5%
1800
11th to 20thNight
54%7%16%14%5%3
1779
21st to endNight
54%8%14%16%5%2
1637
May1st to 10thNight
44%7%17%22%9%1
1548
11th to 20thNight
49%8%15%20%6%3
1416
21st to endNight
46%10%18%22%4
1552
June1st to 10thNight
43%9%15%28%4
1440
11th to 20thNight
37%7%22%27%8%1
1440
21st to endNight
22%5%18%36%15%4
1440
July1st to 10thNight
17%414%30%25%11%
1400
11th to 20thNight
18%39%24%35%12%
1392
21st to endNight
8%26%32%42%11%
1552
August1st to 10thNight
14%412%40%23%6%
1602
11th to 20thNight
14%311%36%29%7%
1602
21st to endNight
16%410%35%27%7%
1913
September1st to 10thNight
17%310%30%27%13%
1800
11th to 20thNight
28%5%13%30%16%9%
1822
21st to endNight
33%5%13%22%18%8%
2052
October1st to 10thNight
37%6%11%22%18%6%
2160
11th to 20thNight
42%6%14%19%16%3
2160
21st to endNight
50%6%10%14%15%4
2376
November1st to 10thNight
59%6%11%14%8%1
2465
11th to 20thNight
64%6%10%11%7%2
2660
21st to endNight
57%5%11%12%11%5%
2660
December1st to 10thNight
59%411%15%10%1
2660
11th to 20thNight
70%411%10%5%
3276
21st to endNight
72%6%11%8%21
4862

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 10thDay
46%9%19%14%9%2
180
11th to 20thDay
40%9%13%21%14%3
215
21st to endDay
29%11%20%22%15%3
407
February1st to 10thDay
36%6%21%24%10%3
370
11th to 20thDay
36%12%22%19%8%2
365
21st to endDay
37%16%18%20%7%2
344
March1st to 10thDay
34%13%26%18%7%1
441
11th to 20thDay
31%11%24%23%9%2
420
21st to endDay
34%15%23%19%8%1
462
April1st to 10thDay
32%16%20%20%10%2
420
11th to 20thDay
34%14%24%16%8%4
412
21st to endDay
30%12%23%23%10%3
420
May1st to 10thDay
22%12%28%24%11%4
423
11th to 20thDay
27%12%18%26%14%2
448
21st to endDay
20%12%22%27%14%4
485
June1st to 10thDay
21%11%22%27%16%3
450
11th to 20thDay
18%14%30%26%9%2
450
21st to endDay
8%6%26%39%18%4
450
July1st to 10thDay
8%5%24%41%19%3
446
11th to 20thDay
48%27%39%17%5%
444
21st to endDay
2324%43%23%5%
487
August1st to 10thDay
3321%44%23%5%
447
11th to 20thDay
3319%42%27%6%
437
21st to endDay
7%5%25%38%20%4
495
September1st to 10thDay
7%5%26%34%22%5%
450
11th to 20thDay
16%7%20%33%19%5%
450
21st to endDay
17%8%25%30%16%5%
450
October1st to 10thDay
20%9%25%21%19%7%
450
11th to 20thDay
22%10%16%26%19%7%
450
21st to endDay
28%10%21%21%16%4
495
November1st to 10thDay
29%13%21%19%14%4
247
11th to 20thDay
31%7%21%18%17%7%
180
21st to endDay
33%9%14%22%17%5%
180
December1st to 10thDay
32%11%17%18%12%9%
180
11th to 20thDay
36%9%18%21%13%3
180
21st to endDay
38%9%17%20%15%1
198
January1st to 10thNight
38%9%14%23%12%3
760
11th to 20thNight
34%7%13%24%17%4
760
21st to endNight
31%6%11%30%19%3
836
February1st to 10thNight
33%7%12%29%19%1
760
11th to 20thNight
30%8%13%30%18%1
744
21st to endNight
31%12%14%28%15%1
628
March1st to 10thNight
31%11%12%32%13%1
742
11th to 20thNight
24%9%14%33%18%1
720
21st to endNight
33%9%14%27%16%1
792
April1st to 10thNight
34%8%13%25%18%1
720
11th to 20thNight
25%8%16%31%18%2
711
21st to endNight
26%6%13%30%22%2
557
May1st to 10thNight
18%7%16%32%24%2
468
11th to 20thNight
19%411%35%28%3
354
21st to endNight
20%314%35%25%2
389
June1st to 10thNight
19%412%39%24%2
360
11th to 20thNight
15%6%19%36%21%3
360
21st to endNight
11%211%46%29%1
360
July1st to 10thNight
6%311%47%32%1
350
11th to 20thNight
5%320%48%24%1
348
21st to endNight
3217%40%37%1
461
August1st to 10thNight
4210%39%40%6%
537
11th to 20thNight
416%40%43%6%
534
21st to endNight
5%315%42%31%4
725
September1st to 10thNight
8%313%38%36%2
720
11th to 20thNight
10%49%30%41%6%
720
21st to endNight
14%5%9%36%32%4
720
October1st to 10thNight
16%412%34%30%5%
720
11th to 20thNight
20%48%32%29%6%
720
21st to endNight
27%8%11%29%21%5%
792
November1st to 10thNight
30%6%13%31%18%2
740
11th to 20thNight
34%8%11%27%18%2
760
21st to endNight
26%9%10%33%19%4
760
December1st to 10thNight
29%8%10%29%21%4
760
11th to 20thNight
37%8%9%27%18%1
760
21st to endNight
42%8%13%27%9%1
836
Page generated at 2024-03-03 03:29:00. Version ac07

Copyright © 2024 Attilla Danko.


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