The Backyard Country Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the The Backyard Country Observatory clear sky chart from 2005-11-06 to 2024-02-20.

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
39%
24706
21%
80197
13%
24605
48%
24605
27%
49567

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 10thNight
28%
938
17%
4074
9%
926
39%
926
16%
2875
January11th to 20thNight
24%
950
21%
4018
7%
930
35%
930
16%
2622
January21st to endNight
25%
1036
12%
4507
6%
1023
35%
1023
14%
3230
February1st to 10thNight
24%
950
17%
2470
6%
950
31%
950
23%
1728
February11th to 20thNight
28%
926
18%
2398
7%
922
36%
922
27%
1594
February21st to endNight
22%
588
24%
1772
6%
588
37%
588
26%
1108
March1st to 10thNight
28%
540
24%
1980
11%
540
44%
540
26%
1135
March11th to 20thNight
30%
540
19%
1980
12%
540
41%
540
20%
1239
March21st to endNight
19%
594
12%
2178
6%
594
28%
594
14%
1524
April1st to 10thNight
27%
540
21%
1868
11%
540
42%
540
29%
1045
April11th to 20thNight
28%
533
21%
1775
13%
533
42%
533
25%
1084
April21st to endNight
29%
540
22%
1652
12%
540
43%
540
23%
1076
May1st to 10thNight
34%
540
16%
1620
11%
540
42%
540
23%
1072
May11th to 20thNight
41%
531
19%
1594
15%
531
47%
531
28%
1005
May21st to endNight
45%
584
18%
1600
10%
582
52%
582
31%
1016
June1st to 10thNight
62%
540
22%
1440
12%
540
67%
540
45%
817
June11th to 20thNight
58%
540
23%
1440
12%
540
62%
540
43%
828
June21st to endNight
57%
540
24%
1440
12%
540
63%
540
52%
763
July1st to 10thNight
70%
525
18%
1469
14%
525
72%
525
44%
816
July11th to 20thNight
72%
522
23%
1566
19%
522
75%
522
50%
782
July21st to endNight
69%
591
25%
1673
23%
558
73%
558
43%
877
August1st to 10thNight
70%
537
22%
1601
23%
534
73%
534
43%
857
August11th to 20thNight
70%
534
29%
1600
29%
534
75%
534
43%
852
August21st to endNight
70%
594
28%
1916
30%
594
74%
594
42%
983
September1st to 10thNight
62%
540
27%
1800
26%
540
68%
540
37%
961
September11th to 20thNight
62%
540
30%
1944
29%
540
70%
540
36%
1025
September21st to endNight
56%
540
30%
1980
26%
540
65%
540
38%
984
October1st to 10thNight
46%
720
25%
2160
17%
720
51%
720
36%
1237
October11th to 20thNight
34%
720
27%
2160
13%
720
46%
720
34%
1245
October21st to endNight
31%
792
25%
2376
12%
792
42%
792
29%
1434
November1st to 10thNight
41%
763
31%
2243
16%
763
54%
763
41%
1175
November11th to 20thNight
31%
950
26%
2603
9%
950
45%
950
35%
1556
November21st to endNight
32%
950
23%
2660
9%
950
43%
950
30%
1651
December1st to 10thNight
31%
950
20%
2660
7%
950
41%
950
27%
1705
December11th to 20thNight
27%
948
22%
3143
8%
948
37%
948
23%
1931
December21st to endNight
24%
1040
13%
4837
7%
1026
37%
1026
11%
3735

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
12%7%36%5%3445%7%42%
78497
Night
12%7%36%43445%6%46%
80741
TransparencyDay
41%5%13%25%14%2
78219
Night
39%5%12%26%16%3
80539
SeeingDay
15%8%28%29%16%4
14670
Night
14%8%32%33%12%1
24735

By Month

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 10thDay
14%10%49%7%2446%8%33%
2847
11th to 20thDay
11%12%49%7%48%435%35%
2850
21st to endDay
14%13%7%13%7%34446%25%
3135
February1st to 10thDay
14%10%47%6%45%45%6%34%
1710
11th to 20thDay
12%9%5%6%5%345%47%41%
1655
21st to endDay
12%10%46%5%34447%41%
1498
March1st to 10thDay
12%9%48%5%3445%5%41%
1980
11th to 20thDay
18%11%46%423446%36%
1980
21st to endDay
21%13%47%5%3435%6%28%
2178
April1st to 10thDay
15%7%35%5%25%45%6%44%
2091
11th to 20thDay
16%9%26%5%34447%40%
2134
21st to endDay
22%7%25%6%34347%36%
2304
May1st to 10thDay
16%8%36%6%35%5%6%7%35%
2340
11th to 20thDay
16%6%35%7%35%45%7%40%
2302
21st to endDay
15%6%36%6%45%5%6%6%38%
2673
June1st to 10thDay
7%425%6%35%46%9%48%
2520
11th to 20thDay
8%5%245%35%5%6%9%49%
2520
21st to endDay
8%325%5%36%5%6%9%48%
2520
July1st to 10thDay
9%425%435%6%6%10%47%
2442
11th to 20thDay
7%415%5%345%6%9%51%
2340
21st to endDay
7%425%5%35%5%7%9%49%
2546
August1st to 10thDay
7%5%35%6%35%6%7%10%43%
2328
11th to 20thDay
10%5%25%5%3446%9%49%
2301
21st to endDay
8%5%2443446%7%53%
2440
September1st to 10thDay
13%31443345%7%52%
2160
11th to 20thDay
10%5%25%5%4445%8%50%
2013
21st to endDay
10%414333446%56%
1960
October1st to 10thDay
15%5%25%5%2435%6%49%
1800
11th to 20thDay
14%5%25%323345%54%
1800
21st to endDay
15%6%35%32445%6%46%
1980
November1st to 10thDay
9%6%24434447%54%
1833
11th to 20thDay
13%6%25%42335%7%49%
1576
21st to endDay
16%8%35%414447%44%
1520
December1st to 10thDay
9%8%37%5%36%46%8%42%
1520
11th to 20thDay
12%9%47%6%35%5%47%40%
1918
21st to endDay
17%14%8%13%5%24445%24%
2783
January1st to 10thNight
9%8%414%8%35%5%46%33%
4108
11th to 20thNight
11%9%5%8%5%37%5%6%5%37%
4120
21st to endNight
15%12%5%12%5%34445%32%
4532
February1st to 10thNight
12%11%47%5%34446%38%
2470
11th to 20thNight
11%8%46%5%35%35%7%43%
2397
21st to endNight
12%9%36%43445%6%46%
1772
March1st to 10thNight
11%6%46%434346%49%
1980
11th to 20thNight
17%8%35%435%35%6%41%
1980
21st to endNight
22%10%47%5%3445%6%31%
2178
April1st to 10thNight
11%6%25%33346%7%50%
1868
11th to 20thNight
14%8%36%5%24346%46%
1775
21st to endNight
16%7%35%5%34446%43%
1652
May1st to 10thNight
15%5%35%6%445%6%7%40%
1620
11th to 20thNight
14%6%145%2445%8%46%
1593
21st to endNight
11%5%25%5%35%45%7%48%
1599
June1st to 10thNight
5%3135%35%46%9%56%
1440
11th to 20thNight
5%3245%345%7%11%52%
1440
21st to endNight
5%22432345%10%60%
1440
July1st to 10thNight
8%42332447%10%54%
1513
11th to 20thNight
421432445%8%63%
1620
21st to endNight
6%32443445%12%52%
1772
August1st to 10thNight
5%3234345%7%10%55%
1611
11th to 20thNight
7%42433435%8%58%
1600
21st to endNight
7%314324446%61%
1916
September1st to 10thNight
10%324324446%57%
1800
11th to 20thNight
10%4133346%47%55%
1944
21st to endNight
8%423434447%59%
1980
October1st to 10thNight
13%5%24423337%54%
2160
11th to 20thNight
14%5%24333345%54%
2160
21st to endNight
16%6%3442333451%
2376
November1st to 10thNight
8%413323447%61%
2243
11th to 20thNight
11%5%34434446%53%
2603
21st to endNight
14%8%34423346%49%
2660
December1st to 10thNight
10%8%35%435%5%5%7%44%
2660
11th to 20thNight
12%9%36%5%23346%46%
3279
21st to endNight
20%16%7%10%5%2333428%
4880

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 10thDay
50%5%14%21%10%1
2848
11th to 20thDay
54%413%19%10%
2850
21st to endDay
60%5%10%16%9%1
3135
February1st to 10thDay
51%5%11%21%10%3
1710
11th to 20thDay
43%5%13%24%13%2
1664
21st to endDay
44%411%25%14%2
1498
March1st to 10thDay
46%312%23%14%2
1980
11th to 20thDay
51%48%22%14%2
1980
21st to endDay
58%5%11%18%7%1
2178
April1st to 10thDay
42%5%13%24%15%2
2091
11th to 20thDay
45%412%23%14%1
2134
21st to endDay
49%5%11%24%11%1
2304
May1st to 10thDay
48%7%12%20%12%1
2340
11th to 20thDay
44%6%14%23%13%
2306
21st to endDay
46%6%15%20%12%2
2673
June1st to 10thDay
32%8%15%30%14%2
2520
11th to 20thDay
31%7%14%27%19%1
2520
21st to endDay
31%6%16%28%15%3
2520
July1st to 10thDay
30%7%17%29%13%4
2377
11th to 20thDay
31%6%12%28%19%4
2271
21st to endDay
30%6%14%34%15%1
2405
August1st to 10thDay
34%8%18%26%12%2
2314
11th to 20thDay
32%7%10%31%18%1
2301
21st to endDay
30%6%13%27%19%6%
2440
September1st to 10thDay
31%6%12%26%19%5%
2160
11th to 20thDay
34%5%11%26%21%2
2013
21st to endDay
29%49%32%23%3
1960
October1st to 10thDay
36%412%27%19%2
1800
11th to 20thDay
34%37%27%23%5%
1800
21st to endDay
39%410%25%17%5%
1980
November1st to 10thDay
31%412%29%20%4
1833
11th to 20thDay
36%311%29%19%2
1576
21st to endDay
41%412%25%18%
1520
December1st to 10thDay
41%6%15%25%14%1
1520
11th to 20thDay
45%415%27%7%1
1915
21st to endDay
64%411%15%7%1
2783
January1st to 10thNight
50%7%10%21%11%1
4108
11th to 20thNight
48%412%23%12%1
4120
21st to endNight
56%414%16%9%1
4532
February1st to 10thNight
47%5%12%20%13%3
2470
11th to 20thNight
42%413%22%17%3
2398
21st to endNight
40%410%23%16%6%
1772
March1st to 10thNight
37%412%28%17%3
1980
11th to 20thNight
44%5%10%23%15%3
1980
21st to endNight
55%412%18%9%2
2178
April1st to 10thNight
33%413%27%19%4
1868
11th to 20thNight
40%411%28%14%3
1775
21st to endNight
42%6%9%24%17%1
1652
May1st to 10thNight
42%7%13%22%14%2
1620
11th to 20thNight
38%6%12%26%17%1
1594
21st to endNight
36%7%15%26%13%3
1600
June1st to 10thNight
23%7%18%31%17%3
1440
11th to 20thNight
24%8%15%30%20%3
1440
21st to endNight
20%5%18%34%20%4
1440
July1st to 10thNight
25%6%16%31%18%4
1469
11th to 20thNight
19%6%17%32%23%4
1566
21st to endNight
24%5%13%36%19%2
1673
August1st to 10thNight
23%7%20%31%17%1
1601
11th to 20thNight
26%413%34%21%2
1600
21st to endNight
24%6%12%27%24%8%
1916
September1st to 10thNight
29%410%27%21%8%
1800
11th to 20thNight
28%5%9%30%24%4
1944
21st to endNight
26%48%31%27%4
1980
October1st to 10thNight
32%410%27%23%5%
2160
11th to 20thNight
33%37%26%23%8%
2160
21st to endNight
38%39%23%24%3
2376
November1st to 10thNight
24%415%28%23%6%
2243
11th to 20thNight
33%39%31%21%4
2603
21st to endNight
38%311%28%18%2
2660
December1st to 10thNight
39%5%12%29%14%1
2660
11th to 20thNight
40%412%33%11%1
3281
21st to endNight
63%46%18%8%1
4880

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 10thDay
24%11%33%25%6%
270
11th to 20thDay
26%12%40%19%3
270
21st to endDay
16%12%39%28%4
297
February1st to 10thDay
19%16%43%19%21
270
11th to 20thDay
18%15%43%17%6%1
267
21st to endDay
18%17%45%16%41
198
March1st to 10thDay
20%14%45%19%3
240
11th to 20thDay
31%8%36%20%5%1
240
21st to endDay
37%13%31%15%31
264
April1st to 10thDay
21%12%36%22%8%1
351
11th to 20thDay
19%13%38%22%7%1
412
21st to endDay
25%12%34%19%9%1
564
May1st to 10thDay
20%10%33%27%8%1
603
11th to 20thDay
21%6%32%25%13%3
625
21st to endDay
17%8%27%29%16%4
679
June1st to 10thDay
7%419%35%27%8%
630
11th to 20thDay
7%327%38%20%5%
630
21st to endDay
9%5%33%36%15%3
630
July1st to 10thDay
12%212%31%31%11%
621
11th to 20thDay
9%317%38%26%8%
618
21st to endDay
8%114%43%29%6%
684
August1st to 10thDay
8%217%39%27%7%
626
11th to 20thDay
9%314%39%28%7%
615
21st to endDay
10%116%31%32%10%
559
September1st to 10thDay
15%318%31%28%5%
450
11th to 20thDay
9%219%40%23%8%
303
21st to endDay
13%6%29%30%18%4
270
October1st to 10thDay
19%6%25%28%14%9%
270
11th to 20thDay
13%20%40%19%7%1
270
21st to endDay
18%13%37%23%7%2
297
November1st to 10thDay
16%7%41%26%9%2
270
11th to 20thDay
17%17%35%24%7%1
270
21st to endDay
23%9%35%24%7%1
270
December1st to 10thDay
8%16%40%27%7%2
270
11th to 20thDay
21%11%34%27%6%1
270
21st to endDay
21%19%39%18%2
297
January1st to 10thNight
12%13%39%29%7%
950
11th to 20thNight
15%12%41%25%6%1
950
21st to endNight
16%9%41%30%4
1045
February1st to 10thNight
18%11%41%26%4
950
11th to 20thNight
16%13%37%28%5%
927
21st to endNight
16%15%45%17%6%1
588
March1st to 10thNight
14%13%41%27%5%
540
11th to 20thNight
21%9%34%31%41
540
21st to endNight
28%9%37%22%4
594
April1st to 10thNight
14%11%43%27%4
540
11th to 20thNight
19%9%36%30%5%
533
21st to endNight
19%10%37%26%7%1
540
May1st to 10thNight
18%7%34%33%7%1
540
11th to 20thNight
18%6%30%35%10%1
531
21st to endNight
13%6%29%36%15%1
584
June1st to 10thNight
6%322%46%20%2
540
11th to 20thNight
7%325%43%21%1
540
21st to endNight
6%228%48%15%
540
July1st to 10thNight
9%211%42%33%3
525
11th to 20thNight
6%116%47%30%1
522
21st to endNight
7%113%48%30%1
591
August1st to 10thNight
6%117%46%29%1
537
11th to 20thNight
7%213%45%30%4
534
21st to endNight
9%113%42%32%4
594
September1st to 10thNight
12%218%41%24%3
540
11th to 20thNight
11%220%41%24%2
540
21st to endNight
10%325%42%18%1
540
October1st to 10thNight
14%5%29%33%16%2
720
11th to 20thNight
17%7%38%30%8%
720
21st to endNight
20%9%36%28%8%
792
November1st to 10thNight
9%10%36%34%11%1
763
11th to 20thNight
14%13%37%28%7%
950
21st to endNight
19%9%35%30%7%
950
December1st to 10thNight
15%11%37%29%6%1
950
11th to 20thNight
19%8%38%29%6%
950
21st to endNight
21%13%35%27%4
1045
Page generated at 2024-02-17 05:28:37. Version ac07

Copyright 2024 Attilla Danko


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