Hay House Farm Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hay House Farm Observatory clear sky chart from 2005-11-05 to 2018-02-13.

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
41%
15987
22%
48831
13%
15951
51%
15951
27%
30436

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
25%
776
24%
2522
9%
776
43%
776
22%
1549
January16th to endNight
24%
832
25%
2704
11%
832
43%
832
25%
1637
February1st to 15thNight
24%
750
21%
2444
9%
750
41%
750
23%
1489
February16th to endNight
22%
631
27%
1910
10%
631
42%
631
24%
1182
March1st to 15thNight
27%
720
24%
1980
10%
720
40%
720
27%
1274
March16th to endNight
29%
768
21%
2112
10%
768
39%
768
26%
1391
April1st to 15thNight
27%
718
21%
1805
5%
718
38%
718
32%
1151
April16th to endNight
39%
720
21%
1800
9%
720
44%
720
34%
1164
May1st to 15thNight
41%
554
16%
1634
8%
554
47%
554
24%
1104
May16th to endNight
56%
447
17%
1569
14%
447
60%
447
25%
965
June1st to 15thNight
63%
360
20%
1440
21%
360
68%
360
26%
802
June16th to endNight
61%
360
18%
1440
19%
360
67%
360
26%
825
July1st to 15thNight
60%
436
13%
1456
14%
436
62%
436
26%
923
July16th to endNight
71%
564
17%
1595
13%
531
74%
531
35%
943
August1st to 15thNight
67%
539
18%
1609
15%
536
68%
536
30%
1038
August16th to endNight
61%
735
18%
1881
11%
735
62%
735
29%
1290
September1st to 15thNight
61%
720
24%
1800
17%
720
63%
720
33%
1188
September16th to endNight
51%
717
22%
2000
18%
717
53%
717
26%
1330
October1st to 15thNight
48%
720
24%
2160
22%
720
55%
720
27%
1366
October16th to endNight
42%
768
32%
2304
21%
768
58%
768
33%
1331
November1st to 15thNight
41%
760
26%
2331
17%
760
53%
760
29%
1415
November16th to endNight
38%
780
25%
2693
16%
780
52%
780
27%
1525
December1st to 15thNight
30%
780
20%
2730
10%
780
44%
780
20%
1729
December16th to endNight
32%
832
23%
2912
13%
832
47%
832
21%
1825

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
14%5%245%3445%7%42%
49185
Night
14%5%2442445%7%44%
49023
Cloud CoverDay
14%5%245%3445%7%42%
49195
Night
14%5%2442445%7%44%
49027
TransparencyDay
40%5%11%23%16%3
48895
Night
39%410%23%18%4
48832
SeeingDay
18%7%24%26%16%7%
6122
Night
16%8%26%31%15%1
15996

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
15%5%34423447%43%
1743
16th to endDay
16%5%244245%45%44%
1872
February1st to 15thDay
15%6%25%5%2435%6%41%
1683
16th to endDay
14%6%25%5%3435%7%41%
1558
March1st to 15thDay
15%425%5%24336%45%
1969
16th to endDay
17%5%35%5%33447%39%
2112
April1st to 15thDay
12%424414346%50%
2142
16th to endDay
17%5%2443345%6%42%
2160
May1st to 15thDay
17%6%244245%5%7%37%
2327
16th to endDay
15%324435%5%5%7%41%
2542
June1st to 15thDay
11%424436%5%6%9%42%
2520
16th to endDay
8%315%5%36%5%7%10%41%
2520
July1st to 15thDay
12%425%5%36%5%7%9%36%
2412
16th to endDay
7%315%7%47%6%8%11%36%
2465
August1st to 15thDay
12%5%15%7%5%6%5%6%8%34%
2340
16th to endDay
11%5%25%6%36%6%7%7%37%
2307
September1st to 15thDay
11%425%5%345%5%6%45%
2160
16th to endDay
18%6%244345%5%7%37%
1958
October1st to 15thDay
18%5%24323235%47%
1800
16th to endDay
13%41443323453%
1920
November1st to 15thDay
14%413423445%49%
1855
16th to endDay
15%423313446%50%
1596
December1st to 15thDay
16%6%24323437%44%
1560
16th to endDay
18%6%36%422445%41%
1664
January1st to 15thNight
17%434423346%45%
2522
16th to endNight
16%6%24424446%45%
2704
February1st to 15thNight
14%6%2442435%6%44%
2442
16th to endNight
13%6%34424336%46%
1910
March1st to 15thNight
17%41432345%7%44%
1968
16th to endNight
17%5%34423346%43%
2112
April1st to 15thNight
12%42442435%8%46%
1805
16th to endNight
14%42442345%7%46%
1800
May1st to 15thNight
17%6%24435%5%5%7%37%
1634
16th to endNight
12%5%23435%5%6%9%40%
1568
June1st to 15thNight
8%4245%246%7%10%44%
1440
16th to endNight
7%4245%26%47%9%44%
1440
July1st to 15thNight
9%6%25%425%5%6%8%42%
1544
16th to endNight
6%3145%45%6%8%10%43%
1703
August1st to 15thNight
9%425%5%36%5%5%9%41%
1620
16th to endNight
11%5%26%6%45%46%9%36%
1881
September1st to 15thNight
12%4244445%5%7%45%
1800
16th to endNight
18%5%25%424446%41%
2000
October1st to 15thNight
19%414433336%44%
2160
16th to endNight
14%323323435%53%
2304
November1st to 15thNight
14%5%2442333450%
2331
16th to endNight
15%313324445%50%
2693
December1st to 15thNight
16%7%35%5%34445%41%
2730
16th to endNight
17%5%2442345%6%41%
2912

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
15%5%34424346%43%
1743
16th to endDay
16%5%243245%45%44%
1872
February1st to 15thDay
15%6%245%3435%7%41%
1683
16th to endDay
14%5%35%5%3435%6%41%
1558
March1st to 15thDay
15%425%5%33336%45%
1980
16th to endDay
17%5%36%5%34346%39%
2111
April1st to 15thDay
12%424424346%50%
2142
16th to endDay
17%5%3443335%6%42%
2160
May1st to 15thDay
17%6%34425%46%6%37%
2327
16th to endDay
15%324435%5%5%7%41%
2542
June1st to 15thDay
11%324436%5%6%9%42%
2520
16th to endDay
8%325%6%35%6%7%10%41%
2520
July1st to 15thDay
11%425%5%46%6%7%9%36%
2412
16th to endDay
7%415%7%47%6%8%11%36%
2465
August1st to 15thDay
12%5%25%6%46%5%6%9%34%
2340
16th to endDay
11%5%25%5%46%5%7%7%36%
2307
September1st to 15thDay
11%426%5%345%5%7%44%
2160
16th to endDay
17%7%245%25%5%5%7%37%
1958
October1st to 15thDay
18%6%24423245%47%
1800
16th to endDay
13%414423235%52%
1920
November1st to 15thDay
14%5%23424345%49%
1855
16th to endDay
15%423223446%51%
1596
December1st to 15thDay
16%6%243235%36%44%
1560
16th to endDay
18%7%35%42335%5%40%
1664
January1st to 15thNight
16%435%423346%45%
2522
16th to endNight
16%6%24324346%45%
2704
February1st to 15thNight
14%6%25%424446%44%
2435
16th to endNight
13%7%34424346%46%
1910
March1st to 15thNight
16%4243245%5%7%44%
1980
16th to endNight
17%5%34413446%43%
2112
April1st to 15thNight
12%425%42445%7%46%
1805
16th to endNight
14%42442445%8%45%
1800
May1st to 15thNight
17%6%24435%5%5%7%37%
1633
16th to endNight
12%423335%5%6%9%40%
1568
June1st to 15thNight
8%324425%6%7%10%43%
1440
16th to endNight
7%425%436%5%7%9%44%
1440
July1st to 15thNight
8%7%25%5%246%6%8%42%
1544
16th to endNight
6%314446%6%7%11%42%
1703
August1st to 15thNight
9%416%5%36%5%5%9%41%
1620
16th to endNight
10%5%36%7%45%46%10%35%
1881
September1st to 15thNight
11%5%25%435%45%7%45%
1800
16th to endNight
17%5%35%424446%41%
2000
October1st to 15thNight
19%414423345%45%
2160
16th to endNight
13%413323345%53%
2304
November1st to 15thNight
14%424423335%50%
2331
16th to endNight
14%3133245%45%50%
2693
December1st to 15thNight
16%7%35%433445%41%
2730
16th to endNight
16%6%345%2445%6%41%
2912

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
41%310%20%18%5%
1744
16th to endDay
41%39%23%17%4
1872
February1st to 15thDay
43%37%24%17%3
1685
16th to endDay
42%210%22%18%2
1558
March1st to 15thDay
39%49%23%16%5%
1980
16th to endDay
45%48%21%16%4
2112
April1st to 15thDay
34%310%26%18%6%
2142
16th to endDay
41%310%18%19%6%
2160
May1st to 15thDay
45%5%13%19%14%1
2327
16th to endDay
40%5%14%26%12%
2546
June1st to 15thDay
36%6%16%25%13%1
2520
16th to endDay
34%7%17%22%16%2
2520
July1st to 15thDay
40%7%13%20%13%4
2272
16th to endDay
36%7%14%25%14%1
2310
August1st to 15thDay
44%7%11%22%12%1
2327
16th to endDay
42%7%13%23%11%1
2307
September1st to 15thDay
37%6%10%20%21%4
2160
16th to endDay
45%47%20%19%1
1958
October1st to 15thDay
39%37%26%18%4
1800
16th to endDay
35%25%29%22%4
1920
November1st to 15thDay
37%38%22%22%6%
1855
16th to endDay
34%48%24%23%4
1596
December1st to 15thDay
40%410%23%16%4
1560
16th to endDay
45%39%24%15%1
1664
January1st to 15thNight
40%39%18%19%7%
2522
16th to endNight
40%29%25%18%3
2704
February1st to 15thNight
40%38%25%18%4
2444
16th to endNight
39%37%24%20%4
1910
March1st to 15thNight
38%5%9%27%16%3
1980
16th to endNight
41%49%22%17%3
2112
April1st to 15thNight
36%310%21%21%6%
1805
16th to endNight
36%411%20%19%7%
1800
May1st to 15thNight
44%5%12%19%14%2
1634
16th to endNight
37%7%14%25%11%2
1570
June1st to 15thNight
33%7%15%27%14%2
1440
16th to endNight
33%7%15%21%18%2
1440
July1st to 15thNight
38%8%15%19%13%4
1456
16th to endNight
30%8%19%25%15%1
1595
August1st to 15thNight
37%7%14%23%15%1
1609
16th to endNight
43%5%13%23%12%1
1881
September1st to 15thNight
36%6%11%21%17%4
1800
16th to endNight
43%48%20%19%3
2000
October1st to 15thNight
41%37%24%18%4
2160
16th to endNight
33%36%27%23%5%
2304
November1st to 15thNight
37%36%20%23%7%
2331
16th to endNight
36%38%24%23%5%
2693
December1st to 15thNight
44%49%21%16%3
2730
16th to endNight
42%410%22%15%3
2912

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
17%25%36%16%3
134
16th to endDay
28%20%34%13%3
144
February1st to 15thDay
27%22%38%9%1
126
16th to endDay
21%16%29%31%2
190
March1st to 15thDay
18%12%35%26%7%
270
16th to endDay
19%13%35%21%9%1
288
April1st to 15thDay
17%13%30%20%17%1
270
16th to endDay
21%5%27%26%12%5%
270
May1st to 15thDay
27%11%28%16%11%4
288
16th to endDay
20%126%25%20%5%
331
June1st to 15thDay
14%221%28%22%10%
315
16th to endDay
8%6%26%32%20%6%
315
July1st to 15thDay
17%119%34%20%7%
305
16th to endDay
7%111%35%27%16%
326
August1st to 15thDay
14%114%27%29%12%
313
16th to endDay
12%112%29%24%18%
332
September1st to 15thDay
13%417%22%22%19%
315
16th to endDay
26%115%28%14%14%
314
October1st to 15thDay
23%318%26%20%8%
315
16th to endDay
12%11%26%27%17%4
336
November1st to 15thDay
20%6%22%29%16%4
313
16th to endDay
18%11%30%26%10%2
126
December1st to 15thDay
23%11%33%18%12%1
90
16th to endDay
31%19%28%17%3
96
January1st to 15thNight
20%13%34%26%5%
780
16th to endNight
19%13%38%25%2
832
February1st to 15thNight
19%11%39%27%1
753
16th to endNight
18%17%37%24%1
631
March1st to 15thNight
20%12%36%26%4
720
16th to endNight
20%11%32%27%7%
768
April1st to 15thNight
14%13%38%24%7%
718
16th to endNight
16%9%29%31%13%
720
May1st to 15thNight
21%426%32%13%1
554
16th to endNight
14%119%38%23%2
449
June1st to 15thNight
7%117%43%28%1
360
16th to endNight
7%319%45%23%1
360
July1st to 15thNight
11%116%38%31%1
436
16th to endNight
7%10%40%35%5%
564
August1st to 15thNight
12%17%43%31%3
539
16th to endNight
14%28%36%33%4
735
September1st to 15thNight
13%214%32%32%4
720
16th to endNight
19%215%32%26%3
717
October1st to 15thNight
21%5%17%29%22%3
720
16th to endNight
15%8%30%30%14%1
768
November1st to 15thNight
16%8%26%32%14%1
760
16th to endNight
16%9%30%30%11%1
780
December1st to 15thNight
20%8%34%26%8%
780
16th to endNight
20%10%32%33%3
832
Page generated at 2018-02-13 20:46:05. Version ac04

Copyright 2018 A. Danko


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