G-2 Farms Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the G-2 Farms Observatory clear sky chart from 2005-11-05 to 2017-10-16.

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
35%
15291
13%
47053
9%
15252
39%
15252
17%
34118

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
12%
862
6%
2503
3%
859
16%
859
7%
2142
January16th to endNight
15%
768
6%
2496
3%
768
19%
768
7%
2115
February1st to 15thNight
15%
701
6%
2287
2%
701
19%
701
7%
1873
February16th to endNight
22%
631
9%
1942
4%
631
28%
631
11%
1534
March1st to 15thNight
24%
720
13%
2025
7%
720
29%
720
15%
1564
March16th to endNight
34%
768
18%
2112
11%
768
39%
768
21%
1500
April1st to 15thNight
29%
664
15%
1826
7%
664
35%
664
21%
1308
April16th to endNight
37%
540
19%
1620
10%
540
44%
540
24%
1074
May1st to 15thNight
41%
540
17%
1620
10%
540
47%
540
23%
1087
May16th to endNight
48%
442
16%
1565
15%
442
55%
442
26%
926
June1st to 15thNight
51%
360
14%
1350
14%
360
57%
360
23%
816
June16th to endNight
56%
360
17%
1260
18%
360
63%
360
29%
731
July1st to 15thNight
67%
399
19%
1249
21%
399
69%
399
38%
679
July16th to endNight
65%
564
15%
1587
13%
531
68%
531
33%
955
August1st to 15thNight
68%
539
17%
1609
14%
536
69%
536
30%
987
August16th to endNight
62%
573
23%
1719
17%
573
65%
573
34%
1008
September1st to 15thNight
55%
717
20%
1902
14%
717
58%
717
31%
1236
September16th to endNight
55%
717
22%
1980
17%
717
58%
717
31%
1269
October1st to 15thNight
42%
720
16%
2127
13%
720
46%
720
22%
1448
October16th to endNight
22%
708
10%
2156
6%
708
28%
708
12%
1662
November1st to 15thNight
33%
700
18%
2300
16%
700
38%
700
17%
1609
November16th to endNight
22%
720
8%
2520
7%
720
25%
720
9%
1999
December1st to 15thNight
12%
720
3%
2520
2%
720
14%
720
6%
2142
December16th to endNight
11%
858
4%
2778
1%
858
15%
858
5%
2454

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
15%9%47%6%3445%7%31%
48360
Night
16%10%5%7%6%34446%30%
47230
Cloud CoverDay
15%9%47%5%3445%7%31%
48370
Night
16%10%5%7%6%34446%30%
47234
TransparencyDay
51%6%11%18%9%
48055
Night
53%6%11%18%9%1
47053
SeeingDay
19%7%25%24%15%7%
5825
Night
21%8%27%28%12%1
15298

By Month

Percentage Cloud Cover NE (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
20%17%8%11%8%5%432413%
1431
16th to endDay
14%18%10%12%9%35%33412%
1728
February1st to 15thDay
16%15%7%11%9%5%443416%
1575
16th to endDay
15%15%7%12%7%45%436%17%
1530
March1st to 15thDay
16%12%7%11%6%34435%23%
1924
16th to endDay
16%9%5%7%6%3445%5%29%
2112
April1st to 15thDay
20%11%35%42446%7%29%
2133
16th to endDay
17%8%35%42345%7%37%
2340
May1st to 15thDay
18%6%25%42445%7%35%
2331
16th to endDay
13%6%24425%5%5%7%40%
2550
June1st to 15thDay
12%6%24435%46%8%40%
2606
16th to endDay
12%425%5%45%5%6%8%40%
2700
July1st to 15thDay
9%425%435%5%6%9%44%
2634
16th to endDay
9%425%6%35%6%6%10%39%
2471
August1st to 15thDay
9%5%245%46%6%7%8%36%
2340
16th to endDay
12%6%25%5%35%46%8%39%
2474
September1st to 15thDay
12%6%36%5%345%6%7%37%
2053
16th to endDay
15%5%25%4345%5%8%40%
1980
October1st to 15thDay
18%7%36%5%345%6%6%31%
1833
16th to endDay
29%12%36%6%2335%420%
1734
November1st to 15thDay
16%10%37%6%25%5%5%6%30%
1558
16th to endDay
20%17%7%8%8%35%445%15%
1440
December1st to 15thDay
19%19%9%12%7%3444211%
1440
16th to endDay
21%20%10%12%7%233349%
1443
January1st to 15thNight
21%14%7%12%8%44335%13%
2503
16th to endNight
16%15%10%11%9%45%34413%
2496
February1st to 15thNight
16%14%7%11%10%5%5%44417%
2285
16th to endNight
16%12%6%9%7%45%45%6%21%
1942
March1st to 15thNight
17%10%6%8%7%34346%26%
2013
16th to endNight
15%9%5%7%5%24345%35%
2112
April1st to 15thNight
20%9%35%424347%34%
1826
16th to endNight
13%8%26%6%24447%39%
1620
May1st to 15thNight
15%6%35%6%235%5%8%36%
1620
16th to endNight
11%5%344245%5%7%46%
1563
June1st to 15thNight
10%6%26%5%3446%8%41%
1350
16th to endNight
9%5%245%245%5%8%47%
1260
July1st to 15thNight
6%32443245%8%54%
1324
16th to endNight
7%3345%346%6%8%46%
1694
August1st to 15thNight
6%425%5%35%6%7%8%45%
1620
16th to endNight
10%5%24334347%50%
1719
September1st to 15thNight
12%5%35%424447%44%
1902
16th to endNight
11%6%25%435%45%6%45%
1980
October1st to 15thNight
18%7%36%434446%37%
2127
16th to endNight
27%11%36%5%33446%24%
2156
November1st to 15thNight
16%10%46%5%3346%6%31%
2300
16th to endNight
22%17%6%7%6%24445%18%
2520
December1st to 15thNight
20%19%9%10%6%3443413%
2520
16th to endNight
21%16%10%11%8%4432410%
2778

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
20%16%8%11%8%5%332413%
1431
16th to endDay
14%17%10%13%9%45%33412%
1728
February1st to 15thDay
16%15%7%12%9%5%433317%
1575
16th to endDay
15%16%7%12%7%44445%17%
1530
March1st to 15thDay
17%12%7%10%6%34436%23%
1935
16th to endDay
17%9%5%7%6%3445%5%30%
2111
April1st to 15thDay
20%11%45%32446%7%29%
2133
16th to endDay
17%8%35%42245%6%37%
2340
May1st to 15thDay
19%6%36%43445%8%35%
2331
16th to endDay
13%6%345%25%5%5%7%41%
2550
June1st to 15thDay
12%6%24435%46%8%40%
2606
16th to endDay
12%425%5%35%5%6%8%40%
2700
July1st to 15thDay
9%415%5%35%5%6%9%44%
2634
16th to endDay
9%425%5%36%5%6%10%39%
2471
August1st to 15thDay
9%5%25%6%46%6%7%8%37%
2340
16th to endDay
12%5%35%5%35%5%6%8%39%
2474
September1st to 15thDay
13%7%35%5%345%5%7%37%
2053
16th to endDay
15%5%25%4345%5%8%40%
1980
October1st to 15thDay
18%8%36%5%2446%6%32%
1833
16th to endDay
29%12%36%6%2434421%
1734
November1st to 15thDay
16%11%37%5%35%45%6%30%
1558
16th to endDay
20%17%6%7%8%35%5%45%15%
1440
December1st to 15thDay
20%18%9%11%8%345%3212%
1440
16th to endDay
21%20%10%12%7%2333410%
1443
January1st to 15thNight
21%14%7%11%8%4433413%
2503
16th to endNight
16%15%9%11%9%45%34413%
2496
February1st to 15thNight
16%14%7%11%10%45%445%17%
2278
16th to endNight
16%11%6%10%7%45%5%46%21%
1942
March1st to 15thNight
17%10%6%8%7%34346%26%
2025
16th to endNight
15%9%47%5%24345%35%
2112
April1st to 15thNight
21%8%35%42435%7%34%
1826
16th to endNight
13%8%26%5%24447%39%
1620
May1st to 15thNight
16%6%35%5%345%5%8%36%
1619
16th to endNight
11%5%3442445%7%46%
1563
June1st to 15thNight
10%6%25%5%3446%9%41%
1350
16th to endNight
9%4245%25%5%5%7%47%
1260
July1st to 15thNight
6%32442345%8%54%
1324
16th to endNight
7%4245%245%7%8%47%
1694
August1st to 15thNight
7%415%6%35%6%7%8%45%
1620
16th to endNight
10%5%24324347%51%
1719
September1st to 15thNight
12%5%344245%47%44%
1902
16th to endNight
11%6%25%43445%5%46%
1980
October1st to 15thNight
18%7%26%5%23446%37%
2127
16th to endNight
27%10%36%433345%24%
2156
November1st to 15thNight
16%10%47%5%3445%6%32%
2300
16th to endNight
22%17%5%7%6%3345%5%18%
2520
December1st to 15thNight
20%19%9%10%6%3443413%
2520
16th to endNight
21%17%10%12%8%3432410%
2778

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
75%5%8%8%3
1432
16th to endDay
74%5%9%7%2
1728
February1st to 15thDay
70%5%8%11%3
1577
16th to endDay
67%6%9%10%4
1530
March1st to 15thDay
63%5%10%13%6%
1935
16th to endDay
55%5%11%18%8%1
2112
April1st to 15thDay
53%6%12%18%9%
2133
16th to endDay
46%5%12%19%14%2
2340
May1st to 15thDay
47%6%10%22%12%1
2331
16th to endDay
41%7%12%23%14%1
2554
June1st to 15thDay
40%7%12%25%12%1
2606
16th to endDay
41%7%13%22%14%
2700
July1st to 15thDay
35%7%10%26%17%2
2480
16th to endDay
38%8%13%23%13%2
2315
August1st to 15thDay
41%8%13%21%12%1
2327
16th to endDay
40%6%14%23%13%1
2474
September1st to 15thDay
43%7%13%22%12%
2053
16th to endDay
40%7%12%28%11%
1980
October1st to 15thDay
50%6%12%17%11%
1833
16th to endDay
64%5%12%11%4
1734
November1st to 15thDay
52%7%12%18%8%
1558
16th to endDay
69%7%10%10%1
1440
December1st to 15thDay
74%7%10%7%
1440
16th to endDay
79%5%7%6%1
1443
January1st to 15thNight
72%5%8%9%4
2503
16th to endNight
72%5%9%10%1
2496
February1st to 15thNight
68%6%9%12%3
2287
16th to endNight
61%7%11%14%4
1942
March1st to 15thNight
58%6%10%18%6%
2025
16th to endNight
50%410%22%11%1
2112
April1st to 15thNight
50%49%20%12%
1826
16th to endNight
44%5%9%19%17%3
1620
May1st to 15thNight
44%6%9%24%12%3
1620
16th to endNight
36%6%12%25%15%3
1565
June1st to 15thNight
37%8%12%24%16%
1350
16th to endNight
34%6%13%26%17%2
1260
July1st to 15thNight
29%410%31%21%3
1249
16th to endNight
31%7%15%23%18%2
1587
August1st to 15thNight
33%9%12%29%14%1
1609
16th to endNight
33%412%30%16%2
1719
September1st to 15thNight
37%6%13%25%15%2
1902
16th to endNight
37%6%11%28%15%
1980
October1st to 15thNight
46%5%11%20%15%1
2127
16th to endNight
60%5%12%14%6%
2156
November1st to 15thNight
50%6%11%19%10%1
2300
16th to endNight
64%6%12%12%3
2520
December1st to 15thNight
72%6%10%7%2
2520
16th to endNight
78%48%6%2
2778

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
24%23%30%15%41
85
16th to endDay
35%10%42%11%
96
February1st to 15thDay
23%18%45%12%
90
16th to endDay
20%20%40%14%2
81
March1st to 15thDay
29%14%31%19%5%
225
16th to endDay
24%7%31%25%8%2
288
April1st to 15thDay
26%11%25%23%12%
270
16th to endDay
22%8%30%21%9%7%
270
May1st to 15thDay
21%6%27%26%13%5%
288
16th to endDay
15%6%29%25%16%7%
331
June1st to 15thDay
14%426%31%16%4
401
16th to endDay
14%6%29%28%15%5%
495
July1st to 15thDay
13%5%24%28%20%8%
475
16th to endDay
9%319%30%25%10%
331
August1st to 15thDay
13%315%26%24%17%
313
16th to endDay
16%315%23%22%18%
332
September1st to 15thDay
11%219%20%29%15%
315
16th to endDay
15%416%23%23%15%
314
October1st to 15thDay
21%6%25%24%17%4
315
16th to endDay
37%9%27%21%4
240
November1st to 15thDay
18%13%26%24%12%3
86
16th to endDay
30%16%38%6%6%1
60
December1st to 15thDay
33%28%21%11%5%
60
16th to endDay
26%29%35%7%
64
January1st to 15thNight
29%14%34%15%4
864
16th to endNight
25%10%33%24%6%
768
February1st to 15thNight
23%14%34%23%3
704
16th to endNight
25%11%31%25%6%
631
March1st to 15thNight
21%12%32%26%7%
720
16th to endNight
20%8%29%29%10%1
768
April1st to 15thNight
26%10%29%26%7%
664
16th to endNight
17%7%31%32%9%1
540
May1st to 15thNight
19%5%27%34%12%
540
16th to endNight
13%426%38%15%2
444
June1st to 15thNight
14%225%43%14%
360
16th to endNight
10%221%47%18%
360
July1st to 15thNight
7%18%47%22%4
399
16th to endNight
8%116%45%25%1
564
August1st to 15thNight
9%111%42%32%2
539
16th to endNight
13%116%33%31%3
573
September1st to 15thNight
14%418%32%24%5%
717
16th to endNight
14%418%30%25%6%
717
October1st to 15thNight
21%5%23%28%18%1
720
16th to endNight
33%9%30%22%3
708
November1st to 15thNight
20%10%29%27%9%1
700
16th to endNight
30%11%27%22%6%
720
December1st to 15thNight
32%15%32%16%3
720
16th to endNight
29%13%35%17%3
858
Page generated at 2017-10-17 16:35:23. Version ac04

Copyright 2017 A. Danko


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