ForestGate Farm Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the ForestGate Farm Observatory clear sky chart from 2005-11-05 to

2017-09-12
.

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
27%
16144
13%
46785
6%
16097
33%
16097
18%
33523

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
14%
900
10%
2506
2%
895
22%
895
11%
2009
January16th to endNight
10%
960
8%
2688
1%
960
16%
960
10%
2187
February1st to 15thNight
16%
880
11%
2325
2%
875
22%
875
13%
1818
February16th to endNight
19%
636
11%
1898
5%
636
24%
636
12%
1466
March1st to 15thNight
24%
720
15%
2160
8%
720
31%
720
17%
1529
March16th to endNight
31%
606
18%
2010
12%
606
39%
606
18%
1351
April1st to 15thNight
23%
539
13%
1797
6%
539
33%
539
17%
1257
April16th to endNight
28%
540
15%
1692
8%
540
36%
540
18%
1190
May1st to 15thNight
27%
540
12%
1458
5%
540
33%
540
20%
1077
May16th to endNight
34%
562
13%
1498
6%
561
39%
561
28%
999
June1st to 15thNight
41%
540
9%
1440
3%
540
45%
540
27%
957
June16th to endNight
39%
540
9%
1440
4%
540
42%
540
29%
943
July1st to 15thNight
47%
510
12%
1360
5%
510
51%
510
37%
822
July16th to endNight
51%
564
16%
1417
8%
531
55%
531
42%
831
August1st to 15thNight
53%
539
22%
1431
14%
536
59%
536
39%
870
August16th to endNight
45%
573
18%
1884
15%
573
51%
573
29%
1100
September1st to 15thNight
51%
530
21%
1767
16%
530
60%
530
31%
995
September16th to endNight
39%
638
14%
1796
9%
638
43%
638
25%
1206
October1st to 15thNight
30%
660
18%
1947
9%
660
38%
660
21%
1322
October16th to endNight
26%
704
8%
2264
4%
704
31%
704
13%
1692
November1st to 15thNight
19%
703
14%
2279
7%
703
29%
703
14%
1649
November16th to endNight
19%
900
10%
2520
5%
900
24%
900
12%
2013
December1st to 15thNight
13%
900
8%
2520
2%
900
19%
900
10%
1994
December16th to endNight
12%
960
9%
2688
2%
960
19%
960
8%
2246

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%11%48%6%35%45%6%28%
47884
Night
14%10%47%6%35%45%6%30%
46954
Cloud CoverDay
15%11%48%6%35%446%28%
47894
Night
14%10%47%6%35%45%6%30%
46959
Cloud CoverDay
15%11%48%6%35%45%6%28%
47893
Night
14%10%47%6%35%45%6%30%
46959
TransparencyDay
56%210%20%8%
47569
Night
54%212%21%8%
46787
SeeingDay
23%12%31%19%9%3
6128
Night
21%11%31%24%9%
16145

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
12%12%8%12%10%47%5%35%16%
1432
16th to endDay
11%15%8%13%9%45%45%5%15%
1536
February1st to 15thDay
8%14%5%11%10%48%5%6%5%18%
1533
16th to endDay
13%13%6%12%8%5%6%445%17%
1575
March1st to 15thDay
13%13%5%7%7%45%446%26%
1790
16th to endDay
17%15%6%8%6%23345%26%
2226
April1st to 15thDay
17%13%5%7%6%2434429%
2151
16th to endDay
19%13%46%5%245%5%5%27%
2268
May1st to 15thDay
21%11%46%5%34336%29%
2490
16th to endDay
13%9%36%6%35%5%6%7%31%
2617
June1st to 15thDay
18%7%36%5%35%45%7%33%
2520
16th to endDay
16%6%26%6%36%5%6%7%31%
2520
July1st to 15thDay
11%6%25%5%35%5%5%8%38%
2520
16th to endDay
10%436%436%5%5%8%40%
2655
August1st to 15thDay
10%6%36%6%35%45%8%39%
2520
16th to endDay
16%6%246%3345%8%37%
2315
September1st to 15thDay
14%7%36%5%34446%39%
2112
16th to endDay
19%9%36%6%24336%31%
1823
October1st to 15thDay
21%12%25%5%33346%30%
1683
16th to endDay
23%19%5%7%5%24325%18%
1606
November1st to 15thDay
17%17%5%6%424245%27%
1576
16th to endDay
17%15%7%14%9%34345%14%
1440
December1st to 15thDay
12%16%7%15%9%35%335%16%
1440
16th to endDay
17%18%7%17%7%45%3349%
1536
January1st to 15thNight
16%11%6%10%8%45%6%5%5%18%
2506
16th to endNight
10%14%7%11%11%6%6%5%5%5%15%
2688
February1st to 15thNight
9%11%7%10%7%5%7%6%5%6%21%
2324
16th to endNight
12%14%6%8%10%46%46%6%19%
1898
March1st to 15thNight
14%9%47%6%35%345%34%
2147
16th to endNight
13%10%46%5%25%45%6%34%
2010
April1st to 15thNight
18%9%47%6%33446%31%
1797
16th to endNight
19%9%46%5%23346%33%
1692
May1st to 15thNight
20%8%47%5%24446%30%
1458
16th to endNight
12%6%35%435%5%6%7%39%
1496
June1st to 15thNight
14%7%245%3445%8%40%
1440
16th to endNight
13%5%15%435%5%6%8%40%
1440
July1st to 15thNight
9%42443446%9%47%
1440
16th to endNight
7%32442446%8%51%
1513
August1st to 15thNight
9%5%1342446%7%50%
1440
16th to endNight
15%5%15%323346%49%
1884
September1st to 15thNight
10%5%2442345%6%48%
1767
16th to endNight
16%6%15%5%3445%7%38%
1796
October1st to 15thNight
19%8%25%433446%36%
1947
16th to endNight
19%14%37%5%35%5%5%6%23%
2264
November1st to 15thNight
16%14%46%435%446%27%
2279
16th to endNight
17%14%6%11%7%4445%6%18%
2520
December1st to 15thNight
14%14%7%12%8%34446%19%
2520
16th to endNight
16%16%7%13%8%45%33416%
2688

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
11%12%8%12%11%47%5%35%16%
1432
16th to endDay
11%15%8%14%9%45%445%14%
1536
February1st to 15thDay
8%14%5%11%9%47%5%6%6%18%
1533
16th to endDay
13%13%6%13%9%5%5%5%35%17%
1575
March1st to 15thDay
13%13%5%8%6%46%445%26%
1800
16th to endDay
16%15%6%8%6%23345%25%
2226
April1st to 15thDay
18%13%48%5%34345%29%
2151
16th to endDay
19%13%46%5%25%5%5%5%27%
2268
May1st to 15thDay
20%11%36%5%25%435%29%
2490
16th to endDay
14%8%36%6%35%46%6%32%
2617
June1st to 15thDay
17%7%36%5%35%45%7%33%
2520
16th to endDay
15%6%27%6%36%5%6%8%31%
2520
July1st to 15thDay
11%6%25%5%35%6%6%9%37%
2520
16th to endDay
10%5%36%5%26%5%6%8%40%
2655
August1st to 15thDay
10%6%27%6%45%5%5%8%39%
2520
16th to endDay
15%6%25%5%335%48%38%
2315
September1st to 15thDay
14%7%27%5%34347%38%
2112
16th to endDay
19%9%47%5%34346%32%
1823
October1st to 15thDay
21%11%36%424346%30%
1683
16th to endDay
23%19%5%8%5%34335%18%
1606
November1st to 15thDay
17%17%5%7%5%34345%26%
1576
16th to endDay
17%15%7%14%9%34345%13%
1440
December1st to 15thDay
12%16%7%15%10%35%335%16%
1440
16th to endDay
17%18%8%16%8%45%3449%
1536
January1st to 15thNight
15%12%6%10%8%45%6%5%5%18%
2506
16th to endNight
10%13%7%10%11%6%6%6%5%6%15%
2688
February1st to 15thNight
9%12%6%10%7%5%7%6%5%6%20%
2317
16th to endNight
12%14%6%8%10%5%6%45%6%19%
1898
March1st to 15thNight
14%9%5%7%6%35%335%34%
2160
16th to endNight
13%10%46%6%34447%34%
2010
April1st to 15thNight
17%9%47%6%25%346%31%
1797
16th to endNight
19%9%36%434346%32%
1692
May1st to 15thNight
19%9%47%5%3435%6%30%
1457
16th to endNight
12%5%35%5%35%5%5%8%39%
1496
June1st to 15thNight
14%7%345%3436%7%40%
1440
16th to endNight
12%5%25%4345%6%8%39%
1440
July1st to 15thNight
9%5%1443445%9%47%
1440
16th to endNight
6%32443346%9%50%
1513
August1st to 15thNight
8%423425%46%7%50%
1440
16th to endNight
15%5%24313346%49%
1884
September1st to 15thNight
10%5%2442445%6%48%
1767
16th to endNight
16%6%15%5%345%48%38%
1796
October1st to 15thNight
18%9%245%23446%36%
1947
16th to endNight
19%13%46%5%35%45%6%23%
2264
November1st to 15thNight
16%14%46%5%35%446%28%
2279
16th to endNight
17%13%6%11%7%45%45%6%18%
2520
December1st to 15thNight
14%14%6%12%8%34446%19%
2520
16th to endNight
15%17%7%13%8%35%44316%
2688

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
12%12%8%12%11%5%7%435%16%
1432
16th to endDay
11%15%8%14%10%45%45%5%14%
1536
February1st to 15thDay
8%14%5%11%10%48%6%6%5%17%
1533
16th to endDay
12%14%6%14%8%5%6%5%45%17%
1575
March1st to 15thDay
13%13%5%8%7%46%436%26%
1800
16th to endDay
16%15%6%9%6%23345%25%
2225
April1st to 15thDay
18%12%5%8%5%24435%29%
2151
16th to endDay
19%13%46%5%245%5%5%27%
2268
May1st to 15thDay
20%12%46%5%24445%29%
2490
16th to endDay
14%8%46%6%36%5%5%6%32%
2617
June1st to 15thDay
17%8%36%5%35%45%7%32%
2520
16th to endDay
15%6%27%6%36%5%6%8%31%
2520
July1st to 15thDay
11%6%25%6%35%5%6%8%37%
2520
16th to endDay
10%5%35%5%36%5%6%8%40%
2655
August1st to 15thDay
10%5%27%5%45%46%7%39%
2520
16th to endDay
15%7%25%5%3445%7%38%
2315
September1st to 15thDay
14%7%36%43445%6%39%
2112
16th to endDay
20%9%37%5%33436%31%
1823
October1st to 15thDay
21%11%36%424346%30%
1683
16th to endDay
23%19%5%8%5%34335%17%
1606
November1st to 15thDay
17%18%6%7%5%2425%5%25%
1576
16th to endDay
17%15%8%13%9%44345%13%
1440
December1st to 15thDay
11%16%6%16%11%4434415%
1440
16th to endDay
17%18%8%16%8%45%3348%
1536
January1st to 15thNight
15%12%6%11%8%46%5%5%5%18%
2506
16th to endNight
10%13%7%11%11%6%6%6%5%5%14%
2688
February1st to 15thNight
9%12%7%11%7%5%8%6%5%6%19%
2317
16th to endNight
12%14%6%8%10%5%6%5%46%19%
1898
March1st to 15thNight
13%10%48%6%35%335%34%
2160
16th to endNight
13%10%47%6%34447%34%
2010
April1st to 15thNight
18%9%47%6%34446%31%
1797
16th to endNight
19%10%36%433346%32%
1692
May1st to 15thNight
19%9%36%6%2445%6%30%
1457
16th to endNight
12%6%35%5%35%5%5%8%39%
1496
June1st to 15thNight
14%6%3443445%7%40%
1440
16th to endNight
12%6%15%435%5%6%8%39%
1440
July1st to 15thNight
9%41443436%9%47%
1440
16th to endNight
6%3234245%6%9%50%
1513
August1st to 15thNight
8%42343446%7%50%
1440
16th to endNight
14%5%15%313346%49%
1884
September1st to 15thNight
10%6%2442445%6%48%
1767
16th to endNight
16%6%25%5%35%447%38%
1796
October1st to 15thNight
17%9%2443445%6%36%
1947
16th to endNight
19%14%37%5%35%45%6%23%
2264
November1st to 15thNight
15%15%46%5%35%445%27%
2279
16th to endNight
17%13%6%10%8%3445%6%18%
2520
December1st to 15thNight
14%14%7%12%8%35%5%45%18%
2520
16th to endNight
15%17%7%13%8%45%43415%
2688

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
71%17%15%4
1433
16th to endDay
71%111%11%3
1536
February1st to 15thDay
64%112%17%3
1534
16th to endDay
68%19%14%5%
1575
March1st to 15thDay
60%112%15%8%1
1800
16th to endDay
61%111%17%5%1
2226
April1st to 15thDay
58%19%20%9%
2151
16th to endDay
57%27%20%9%1
2268
May1st to 15thDay
57%38%19%10%
2490
16th to endDay
50%310%21%12%1
2621
June1st to 15thDay
49%111%23%11%
2520
16th to endDay
49%413%21%10%
2520
July1st to 15thDay
42%49%28%12%1
2371
16th to endDay
40%413%22%16%1
2488
August1st to 15thDay
43%311%30%9%1
2505
16th to endDay
45%314%24%12%
2315
September1st to 15thDay
45%212%29%9%
2112
16th to endDay
54%114%22%6%
1823
October1st to 15thDay
55%110%22%9%
1683
16th to endDay
70%28%13%4
1606
November1st to 15thDay
60%110%18%7%
1576
16th to endDay
73%29%10%3
1440
December1st to 15thDay
72%8%14%4
1440
16th to endDay
80%7%9%1
1536
January1st to 15thNight
65%29%18%3
2506
16th to endNight
68%29%15%3
2688
February1st to 15thNight
61%310%17%6%
2327
16th to endNight
64%111%17%4
1898
March1st to 15thNight
53%29%22%10%
2160
16th to endNight
50%212%22%10%1
2010
April1st to 15thNight
54%28%22%10%1
1797
16th to endNight
53%28%20%14%
1692
May1st to 15thNight
54%310%20%10%1
1458
16th to endNight
42%314%24%13%
1498
June1st to 15thNight
42%414%25%13%
1440
16th to endNight
41%319%24%9%1
1440
July1st to 15thNight
32%414%32%14%
1360
16th to endNight
29%319%29%15%2
1417
August1st to 15thNight
32%313%33%14%1
1431
16th to endNight
37%215%25%16%2
1884
September1st to 15thNight
35%214%34%13%
1767
16th to endNight
44%415%28%6%
1796
October1st to 15thNight
48%212%26%8%
1947
16th to endNight
60%214%16%5%
2264
November1st to 15thNight
58%211%18%9%
2279
16th to endNight
66%212%13%41
2520
December1st to 15thNight
66%112%16%3
2520
16th to endNight
72%17%14%3
2688

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%16%40%20%2
90
16th to endDay
33%10%41%7%6%1
96
February1st to 15thDay
31%22%42%4
90
16th to endDay
30%27%25%16%
81
March1st to 15thDay
26%20%32%15%32
90
16th to endDay
34%12%25%15%7%3
228
April1st to 15thDay
31%7%30%23%5%1
270
16th to endDay
31%16%24%15%9%2
270
May1st to 15thDay
31%17%27%14%6%2
447
16th to endDay
26%13%33%16%6%3
517
June1st to 15thDay
23%10%36%18%7%3
495
16th to endDay
22%11%32%19%10%3
495
July1st to 15thDay
16%10%31%24%11%5%
475
16th to endDay
11%11%35%23%12%5%
515
August1st to 15thDay
15%8%27%26%15%6%
493
16th to endDay
23%6%24%22%17%4
338
September1st to 15thDay
15%10%23%26%17%5%
299
16th to endDay
23%7%33%21%12%1
254
October1st to 15thDay
26%9%31%17%13%2
123
16th to endDay
36%17%32%10%3
96
November1st to 15thDay
24%18%36%12%5%2
90
16th to endDay
35%16%25%15%42
90
December1st to 15thDay
25%12%48%11%2
90
16th to endDay
38%26%30%5%
96
January1st to 15thNight
25%15%36%17%5%
900
16th to endNight
19%15%43%15%4
960
February1st to 15thNight
20%14%39%19%6%
880
16th to endNight
22%16%33%21%5%
636
March1st to 15thNight
23%15%30%23%7%
720
16th to endNight
20%11%30%27%8%1
606
April1st to 15thNight
23%12%33%23%5%
539
16th to endNight
25%10%30%24%7%
540
May1st to 15thNight
26%8%32%23%7%1
540
16th to endNight
17%6%34%29%11%
563
June1st to 15thNight
20%8%23%35%12%
540
16th to endNight
17%7%31%31%11%
540
July1st to 15thNight
12%430%34%16%
510
16th to endNight
8%429%35%18%2
564
August1st to 15thNight
11%225%33%22%3
539
16th to endNight
18%427%29%18%2
573
September1st to 15thNight
13%5%23%33%19%4
530
16th to endNight
22%6%25%31%13%
638
October1st to 15thNight
25%11%28%23%11%
660
16th to endNight
29%10%26%22%9%
704
November1st to 15thNight
27%13%33%18%6%
703
16th to endNight
27%14%31%21%5%
900
December1st to 15thNight
24%19%33%18%4
900
16th to endNight
27%15%31%18%5%
960
Page generated at 2017-09-13 07:39:18. Version ac04

Copyright 2017 A. Danko


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