The Farm
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the The Farm clear sky chart from 2005-11-05 to 2017-09-15.

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
42%
15897
22%
46961
14%
15850
51%
15850
31%
28315

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
32%
900
23%
2327
9%
895
42%
895
33%
1460
January16th to endNight
29%
960
25%
2496
9%
960
39%
960
32%
1590
February1st to 15thNight
25%
880
15%
2288
5%
876
31%
876
22%
1641
February16th to endNight
29%
671
24%
1933
8%
671
41%
671
29%
1215
March1st to 15thNight
35%
540
21%
1980
12%
540
46%
540
24%
1156
March16th to endNight
26%
576
15%
2112
9%
576
35%
576
18%
1392
April1st to 15thNight
33%
539
20%
1860
13%
539
46%
539
27%
1085
April16th to endNight
32%
540
21%
1688
13%
540
45%
540
23%
1102
May1st to 15thNight
40%
539
19%
1620
15%
539
47%
539
25%
1067
May16th to endNight
46%
563
18%
1655
14%
561
51%
561
33%
1004
June1st to 15thNight
60%
540
19%
1440
11%
540
64%
540
40%
855
June16th to endNight
61%
540
25%
1450
14%
540
66%
540
53%
767
July1st to 15thNight
71%
510
18%
1530
14%
510
73%
510
41%
838
July16th to endNight
73%
564
24%
1594
23%
531
77%
531
43%
843
August1st to 15thNight
77%
539
24%
1610
26%
536
80%
536
45%
842
August16th to endNight
70%
573
27%
1799
29%
573
73%
573
40%
969
September1st to 15thNight
63%
540
25%
1864
26%
540
68%
540
32%
1050
September16th to endNight
60%
492
28%
1815
25%
492
69%
492
35%
920
October1st to 15thNight
45%
646
29%
1966
21%
646
50%
646
34%
1151
October16th to endNight
39%
704
28%
2112
14%
704
50%
704
37%
1176
November1st to 15thNight
43%
781
29%
2181
14%
781
53%
781
39%
1212
November16th to endNight
32%
900
24%
2493
9%
900
43%
900
33%
1499
December1st to 15thNight
29%
900
18%
2520
7%
900
38%
900
24%
1692
December16th to endNight
29%
960
21%
2628
8%
960
40%
960
24%
1789

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%2418%23346%38%
47755
Night
8%5%1318%23345%43%
47156
Cloud CoverDay
11%6%25%42445%7%44%
47753
Night
10%5%2432345%6%50%
47156
TransparencyDay
38%6%13%24%14%2
47453
Night
34%5%13%26%17%3
46961
SeeingDay
13%6%26%30%18%4
5918
Night
13%7%31%33%12%1
15898

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
7%5%15%21%23336%37%
1611
16th to endDay
10%7%35%21%1333435%
1728
February1st to 15thDay
10%7%35%20%23335%33%
1575
16th to endDay
9%8%2420%23335%35%
1549
March1st to 15thDay
9%8%3421%23426%31%
1980
16th to endDay
15%8%25%20%23225%31%
2112
April1st to 15thDay
13%6%15%21%2323434%
2088
16th to endDay
17%6%25%21%2335%5%26%
2270
May1st to 15thDay
12%6%25%20%24336%32%
2331
16th to endDay
12%5%2421%2445%6%30%
2457
June1st to 15thDay
7%31421%24446%38%
2520
16th to endDay
22320%2445%8%44%
2505
July1st to 15thDay
7%31320%245%5%7%37%
2340
16th to endDay
5%31321%2345%8%42%
2466
August1st to 15thDay
6%41412%235%5%8%44%
2340
16th to endDay
7%5%1312%2345%6%47%
2402
September1st to 15thDay
10%41412%2333446%
2083
16th to endDay
6%31412%24446%49%
1815
October1st to 15thDay
12%41312%22335%46%
1652
16th to endDay
9%41412%12345%49%
1760
November1st to 15thDay
6%31217%23325%50%
1674
16th to endDay
13%42319%22235%41%
1464
December1st to 15thDay
13%8%25%20%2334331%
1440
16th to endDay
10%7%37%21%2333433%
1593
January1st to 15thNight
6%5%2320%2334442%
2327
16th to endNight
7%7%2419%1334440%
2496
February1st to 15thNight
8%9%26%21%2333433%
2278
16th to endNight
8%5%15%20%23345%39%
1933
March1st to 15thNight
9%5%2420%23335%39%
1980
16th to endNight
15%6%1419%22345%32%
2112
April1st to 15thNight
8%5%1320%23235%41%
1860
16th to endNight
15%6%2419%23435%31%
1688
May1st to 15thNight
11%415%19%24345%38%
1619
16th to endNight
9%42320%23246%40%
1653
June1st to 15thNight
5%21219%135%5%6%45%
1440
16th to endNight
21119%13339%52%
1450
July1st to 15thNight
5%2219%1245%8%45%
1620
16th to endNight
421220%1345%8%45%
1702
August1st to 15thNight
211313%2336%9%53%
1620
16th to endNight
5%31312%12246%55%
1799
September1st to 15thNight
8%31411%33445%48%
1864
16th to endNight
5%31212%23446%52%
1815
October1st to 15thNight
13%41311%2223350%
1966
16th to endNight
7%42312%1223455%
2112
November1st to 15thNight
6%31316%2223453%
2181
16th to endNight
10%5%1319%1222447%
2493
December1st to 15thNight
11%7%2421%2333435%
2520
16th to endNight
11%8%25%20%1223436%
2628

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
10%6%25%6%33437%45%
1611
16th to endDay
12%9%46%5%24345%42%
1728
February1st to 15thDay
11%9%47%5%34447%38%
1575
16th to endDay
10%9%35%434447%41%
1549
March1st to 15thDay
12%10%445%345%47%37%
1980
16th to endDay
19%9%46%5%24336%34%
2110
April1st to 15thDay
15%7%25%5%24345%42%
2088
16th to endDay
20%7%25%5%2346%5%34%
2270
May1st to 15thDay
16%8%36%5%34446%36%
2331
16th to endDay
14%5%25%5%25%46%8%38%
2457
June1st to 15thDay
8%425%5%36%5%5%8%44%
2520
16th to endDay
5%214335%6%7%9%50%
2505
July1st to 15thDay
8%424435%6%7%8%44%
2340
16th to endDay
6%3135%245%6%9%49%
2466
August1st to 15thDay
7%4143345%6%10%47%
2340
16th to endDay
10%5%2432445%6%49%
2402
September1st to 15thDay
12%4245%23445%49%
2083
16th to endDay
6%414335%45%6%52%
1815
October1st to 15thDay
13%5%23313437%50%
1652
16th to endDay
12%42432235%5%52%
1760
November1st to 15thDay
8%413424336%56%
1674
16th to endDay
15%5%34323346%47%
1464
December1st to 15thDay
14%9%25%5%345%45%38%
1440
16th to endDay
13%8%48%5%24446%37%
1593
January1st to 15thNight
8%6%2443345%6%50%
2327
16th to endNight
9%7%35%324346%49%
2496
February1st to 15thNight
10%11%37%6%24446%38%
2278
16th to endNight
9%6%245%3445%6%47%
1933
March1st to 15thNight
10%5%2442445%6%47%
1980
16th to endNight
20%7%25%33335%6%37%
2112
April1st to 15thNight
11%5%25%423346%49%
1860
16th to endNight
18%6%24323446%41%
1688
May1st to 15thNight
12%5%25%435%45%5%43%
1619
16th to endNight
10%4243235%48%49%
1653
June1st to 15thNight
6%313325%5%7%8%52%
1440
16th to endNight
411132345%10%61%
1450
July1st to 15thNight
6%3123245%6%9%53%
1620
16th to endNight
5%2134245%7%10%52%
1702
August1st to 15thNight
31134245%6%10%56%
1620
16th to endNight
6%42342325%7%57%
1799
September1st to 15thNight
9%42432445%5%52%
1864
16th to endNight
6%32233445%7%56%
1815
October1st to 15thNight
14%42322324454%
1966
16th to endNight
10%423322235%58%
2112
November1st to 15thNight
8%423222336%60%
2181
16th to endNight
12%6%23312335%53%
2493
December1st to 15thNight
13%8%25%5%34445%43%
2520
16th to endNight
14%9%37%313345%41%
2628

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%14%24%15%1
1612
16th to endDay
43%5%14%23%10%1
1728
February1st to 15thDay
46%5%16%22%8%1
1576
16th to endDay
42%5%14%22%13%2
1549
March1st to 15thDay
45%5%12%22%11%1
1980
16th to endDay
52%5%12%19%8%1
2112
April1st to 15thDay
44%412%22%15%
2088
16th to endDay
49%6%12%20%10%
2270
May1st to 15thDay
48%6%11%22%11%
2331
16th to endDay
42%8%15%20%11%1
2461
June1st to 15thDay
35%8%13%25%14%1
2520
16th to endDay
26%7%17%29%16%1
2505
July1st to 15thDay
34%8%16%25%13%2
2201
16th to endDay
27%7%16%31%16%2
2311
August1st to 15thDay
29%9%15%26%17%1
2326
16th to endDay
33%6%12%24%17%5%
2402
September1st to 15thDay
36%6%11%22%16%5%
2083
16th to endDay
30%6%9%29%20%1
1815
October1st to 15thDay
34%410%26%20%3
1652
16th to endDay
32%412%25%19%4
1760
November1st to 15thDay
29%411%27%21%5%
1674
16th to endDay
37%411%27%17%
1464
December1st to 15thDay
46%6%14%21%9%
1440
16th to endDay
47%5%13%21%10%1
1593
January1st to 15thNight
33%5%15%26%17%
2327
16th to endNight
36%415%26%15%2
2496
February1st to 15thNight
47%6%11%21%10%2
2288
16th to endNight
36%5%12%22%19%3
1933
March1st to 15thNight
36%6%12%24%16%3
1980
16th to endNight
46%5%13%22%9%1
2112
April1st to 15thNight
35%5%11%25%20%2
1860
16th to endNight
42%5%10%23%15%1
1688
May1st to 15thNight
40%7%11%22%16%1
1620
16th to endNight
34%5%18%25%14%1
1655
June1st to 15thNight
25%8%16%30%15%3
1440
16th to endNight
18%6%15%34%22%3
1450
July1st to 15thNight
24%7%14%32%16%3
1530
16th to endNight
22%6%14%34%20%1
1594
August1st to 15thNight
21%7%17%32%18%2
1610
16th to endNight
26%5%10%27%23%7%
1799
September1st to 15thNight
31%6%11%23%20%6%
1864
16th to endNight
26%5%11%27%24%3
1815
October1st to 15thNight
33%47%24%23%5%
1966
16th to endNight
29%310%27%23%4
2112
November1st to 15thNight
26%413%24%23%6%
2181
16th to endNight
33%311%30%17%2
2493
December1st to 15thNight
43%5%13%25%11%
2520
16th to endNight
44%5%12%22%12%2
2628

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
23%12%42%15%5%1
90
16th to endDay
16%15%40%22%4
96
February1st to 15thDay
13%22%40%20%4
90
16th to endDay
13%20%38%14%11%1
81
March1st to 15thDay
17%16%46%15%21
90
16th to endDay
23%13%43%15%3
96
April1st to 15thDay
20%10%33%25%9%
207
16th to endDay
26%10%34%19%7%1
380
May1st to 15thDay
18%12%31%24%10%2
468
16th to endDay
18%6%35%23%12%2
517
June1st to 15thDay
7%427%35%20%4
495
16th to endDay
35%31%38%15%4
495
July1st to 15thDay
11%119%38%23%5%
475
16th to endDay
6%112%37%35%6%
515
August1st to 15thDay
7%111%39%33%6%
493
16th to endDay
11%215%33%27%7%
442
September1st to 15thDay
10%218%36%25%8%
246
16th to endDay
6%228%35%17%8%
90
October1st to 15thDay
8%5%22%44%11%7%
90
16th to endDay
11%8%37%32%10%
96
November1st to 15thDay
8%422%43%13%7%
90
16th to endDay
33%10%36%15%4
90
December1st to 15thDay
13%21%42%13%5%4
90
16th to endDay
21%21%33%20%2
96
January1st to 15thNight
10%14%38%28%8%
900
16th to endNight
13%11%41%30%4
960
February1st to 15thNight
16%10%40%28%3
880
16th to endNight
13%11%42%26%5%
671
March1st to 15thNight
13%10%36%31%6%
540
16th to endNight
23%9%37%25%4
576
April1st to 15thNight
14%11%37%30%6%
539
16th to endNight
24%7%32%26%8%
540
May1st to 15thNight
14%6%33%34%10%
540
16th to endNight
10%433%36%12%1
563
June1st to 15thNight
7%322%44%19%1
540
16th to endNight
4228%46%16%1
540
July1st to 15thNight
7%115%46%27%1
510
16th to endNight
6%12%48%31%1
564
August1st to 15thNight
2111%47%36%1
539
16th to endNight
8%114%37%33%4
573
September1st to 15thNight
11%217%39%25%3
540
16th to endNight
7%323%37%24%3
492
October1st to 15thNight
16%5%29%29%17%1
646
16th to endNight
14%8%35%30%10%
704
November1st to 15thNight
10%11%31%33%12%
781
16th to endNight
16%11%37%25%7%
900
December1st to 15thNight
18%12%34%28%5%
900
16th to endNight
19%9%36%29%5%
960
Page generated at 2017-09-15 23:58:31. Version ac04

Copyright 2017 A. Danko


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