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 2018-01-20.

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
37%
16462
20%
48581
12%
16415
45%
16415
32%
29259

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
29%
975
20%
2522
8%
970
38%
970
33%
1589
January16th to endNight
25%
985
21%
2561
8%
985
34%
985
33%
1617
February1st to 15thNight
22%
880
14%
2288
5%
876
27%
876
22%
1641
February16th to endNight
24%
671
19%
1933
6%
671
34%
671
29%
1215
March1st to 15thNight
30%
540
19%
1980
11%
540
40%
540
24%
1156
March16th to endNight
23%
576
14%
2112
9%
576
31%
576
18%
1392
April1st to 15thNight
28%
539
18%
1860
12%
539
40%
539
27%
1085
April16th to endNight
25%
540
16%
1688
9%
540
35%
540
23%
1102
May1st to 15thNight
33%
539
17%
1620
13%
539
41%
539
25%
1067
May16th to endNight
38%
563
15%
1655
11%
561
42%
561
33%
1004
June1st to 15thNight
50%
540
17%
1440
10%
540
53%
540
40%
855
June16th to endNight
51%
540
20%
1450
10%
540
55%
540
53%
767
July1st to 15thNight
62%
510
16%
1530
13%
510
64%
510
41%
838
July16th to endNight
61%
564
20%
1594
20%
531
66%
531
43%
843
August1st to 15thNight
71%
539
23%
1610
25%
536
74%
536
45%
842
August16th to endNight
65%
573
25%
1799
27%
573
69%
573
40%
969
September1st to 15thNight
57%
540
24%
1864
25%
540
62%
540
32%
1050
September16th to endNight
56%
537
26%
1980
22%
537
65%
537
36%
1002
October1st to 15thNight
41%
705
26%
2145
19%
705
46%
705
33%
1271
October16th to endNight
38%
768
28%
2304
14%
768
48%
768
38%
1266
November1st to 15thNight
37%
848
26%
2368
13%
848
46%
848
38%
1337
November16th to endNight
28%
975
22%
2701
8%
975
39%
975
34%
1607
December1st to 15thNight
26%
975
17%
2730
7%
975
34%
975
26%
1789
December16th to endNight
23%
1040
19%
2847
7%
1040
34%
1040
24%
1955

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%39%
48933
Night
8%5%1317%23345%44%
48776
Cloud CoverDay
11%6%25%42445%7%44%
48931
Night
10%5%2442345%6%50%
48776
TransparencyDay
38%6%13%24%14%2
48631
Night
34%5%12%26%17%2
48581
SeeingDay
13%7%27%30%17%4
6300
Night
13%8%31%33%12%
16463

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
8%5%15%20%23336%37%
1746
16th to endDay
10%7%35%20%1333435%
1767
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%23335%46%
2094
16th to endDay
6%31411%34446%49%
1980
October1st to 15thDay
13%41312%22335%45%
1802
16th to endDay
9%41312%12245%51%
1920
November1st to 15thDay
7%41316%23325%49%
1817
16th to endDay
12%42317%12235%42%
1586
December1st to 15thDay
12%7%25%19%2334335%
1560
16th to endDay
10%7%37%20%2333433%
1726
January1st to 15thNight
6%5%2319%2334442%
2522
16th to endNight
7%7%2419%1324441%
2561
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%31211%2345%6%52%
1980
October1st to 15thNight
14%41310%2323350%
2145
16th to endNight
7%32311%1223456%
2304
November1st to 15thNight
7%31215%2223452%
2368
16th to endNight
9%5%1317%1222447%
2701
December1st to 15thNight
10%7%1420%2333439%
2730
16th to endNight
11%9%26%19%1323436%
2847

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%5%34437%45%
1746
16th to endDay
12%8%46%5%24345%42%
1767
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%23446%49%
2094
16th to endDay
6%414335%45%6%52%
1980
October1st to 15thDay
14%5%24313336%49%
1802
16th to endDay
12%42431235%5%53%
1920
November1st to 15thDay
9%5%13424336%55%
1817
16th to endDay
14%5%34313346%48%
1586
December1st to 15thDay
13%8%25%4345%45%41%
1560
16th to endDay
13%8%38%5%34446%36%
1726
January1st to 15thNight
8%6%2442345%6%49%
2522
16th to endNight
8%7%35%324346%50%
2561
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%31233445%7%56%
1980
October1st to 15thNight
15%42332324453%
2145
16th to endNight
10%423323235%59%
2304
November1st to 15thNight
9%423223336%58%
2368
16th to endNight
11%6%23313336%54%
2701
December1st to 15thNight
12%8%245%24335%45%
2730
16th to endNight
14%9%37%423345%40%
2847

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%13%24%14%1
1747
16th to endDay
43%5%14%23%10%1
1767
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%
2094
16th to endDay
31%6%9%31%19%1
1980
October1st to 15thDay
36%410%25%19%3
1802
16th to endDay
31%411%26%20%4
1920
November1st to 15thDay
31%411%26%20%4
1817
16th to endDay
36%410%27%19%
1586
December1st to 15thDay
44%6%14%22%11%
1560
16th to endDay
48%5%13%20%11%1
1726
January1st to 15thNight
34%5%16%26%17%
2522
16th to endNight
35%415%27%15%2
2561
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%12%29%23%3
1980
October1st to 15thNight
34%47%23%23%6%
2145
16th to endNight
28%39%27%26%4
2304
November1st to 15thNight
28%413%24%22%6%
2368
16th to endNight
32%410%31%18%2
2701
December1st to 15thNight
41%5%13%26%13%
2730
16th to endNight
45%5%12%21%12%2
2847

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
21%12%39%21%4
135
16th to endDay
14%13%42%23%5%
109
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%24%8%
249
16th to endDay
8%223%44%14%5%
135
October1st to 15thDay
16%5%29%32%9%5%
135
16th to endDay
11%12%38%27%8%
144
November1st to 15thDay
17%5%28%32%11%5%
135
16th to endDay
24%12%37%15%10%
135
December1st to 15thDay
10%23%41%16%43
135
16th to endDay
18%20%39%20%1
144
January1st to 15thNight
10%13%38%28%7%
975
16th to endNight
12%11%41%30%4
985
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%324%38%23%2
537
October1st to 15thNight
16%6%29%28%17%1
705
16th to endNight
13%8%36%31%9%
768
November1st to 15thNight
11%11%31%33%11%
848
16th to endNight
15%11%39%25%7%
975
December1st to 15thNight
17%12%34%28%6%
975
16th to endNight
19%10%37%28%4
1040
Page generated at 2018-01-21 11:19:24. Version ac04

Copyright 2018 A. Danko


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