Builderbug Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Builderbug Observatory clear sky chart from 2005-11-06 to 2024-01-13.

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
57%
24307
22%
74851
19%
24265
61%
24265
32%
44506

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
49%
756
13%
2457
12%
756
51%
756
18%
1720
January11th to 20thNight
49%
732
14%
2379
13%
732
52%
732
19%
1660
January21st to endNight
52%
792
14%
2574
15%
792
54%
792
20%
1803
February1st to 10thNight
47%
720
12%
2340
13%
720
50%
720
21%
1583
February11th to 20thNight
46%
700
16%
2206
16%
700
50%
700
24%
1427
February21st to endNight
44%
592
19%
1776
16%
592
50%
592
25%
1170
March1st to 10thNight
47%
720
16%
2030
14%
720
51%
720
24%
1397
March11th to 20thNight
53%
720
22%
1980
18%
720
57%
720
35%
1214
March21st to endNight
46%
792
17%
2178
12%
792
49%
792
27%
1442
April1st to 10thNight
47%
702
19%
1962
15%
702
49%
702
29%
1242
April11th to 20thNight
49%
533
23%
1642
17%
533
55%
533
33%
969
April21st to endNight
52%
540
23%
1620
17%
540
57%
540
33%
960
May1st to 10thNight
53%
540
22%
1620
17%
540
55%
540
32%
967
May11th to 20thNight
61%
531
23%
1595
19%
531
63%
531
38%
879
May21st to endNight
56%
582
18%
1746
15%
582
59%
582
34%
1017
June1st to 10thNight
62%
540
23%
1599
21%
540
66%
540
41%
835
June11th to 20thNight
63%
540
28%
1476
22%
540
69%
540
54%
744
June21st to endNight
70%
540
27%
1620
27%
540
74%
540
58%
739
July1st to 10thNight
68%
525
21%
1575
19%
525
72%
525
45%
812
July11th to 20thNight
72%
522
22%
1566
21%
522
73%
522
42%
843
July21st to endNight
75%
591
25%
1674
22%
558
75%
558
41%
899
August1st to 10thNight
71%
537
27%
1602
21%
534
74%
534
45%
826
August11th to 20thNight
76%
534
32%
1602
26%
534
78%
534
48%
813
August21st to endNight
78%
594
36%
1804
34%
594
79%
594
49%
897
September1st to 10thNight
74%
664
32%
1924
27%
664
78%
664
53%
952
September11th to 20thNight
71%
720
34%
1980
27%
720
76%
720
53%
1020
September21st to endNight
70%
720
36%
1980
28%
720
75%
720
54%
1016
October1st to 10thNight
61%
720
28%
2067
20%
720
67%
720
43%
1132
October11th to 20thNight
65%
720
33%
2160
27%
720
70%
720
44%
1144
October21st to endNight
62%
792
32%
2376
25%
792
67%
792
43%
1257
November1st to 10thNight
58%
740
26%
2400
22%
740
64%
740
33%
1348
November11th to 20thNight
57%
760
25%
2470
22%
760
61%
760
34%
1384
November21st to endNight
53%
855
21%
2565
18%
855
57%
855
31%
1575
December1st to 10thNight
50%
950
15%
2660
12%
950
53%
950
30%
1739
December11th to 20thNight
47%
950
14%
3176
10%
949
49%
949
18%
2214
December21st to endNight
38%
841
7%
4470
10%
836
40%
836
10%
2867

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
8%8%35%5%345%5%7%47%
74491
Night
8%8%35%5%3445%7%48%
75234
TransparencyDay
34%5%12%19%19%11%
74216
Night
34%6%13%21%17%10%
75030
SeeingDay
11%7%23%34%21%4
13738
Night
12%419%38%24%3
24331

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 10thDay
14%14%35%6%35%5%5%7%34%
1708
11th to 20thDay
9%13%6%9%5%34446%37%
1642
21st to endDay
9%16%7%8%6%35%445%32%
1782
February1st to 10thDay
11%12%6%8%7%45%45%5%34%
1620
11th to 20thDay
10%14%5%8%6%35%45%5%34%
1641
21st to endDay
9%17%6%9%6%3445%6%30%
1480
March1st to 10thDay
9%12%47%6%36%6%6%7%34%
1928
11th to 20thDay
8%12%47%5%35%6%7%7%38%
1980
21st to endDay
11%15%48%6%36%46%7%30%
2178
April1st to 10thDay
10%12%47%5%35%45%7%38%
1997
11th to 20thDay
10%10%5%7%5%35%5%6%6%39%
2262
21st to endDay
9%10%36%5%24448%45%
2340
May1st to 10thDay
8%8%36%5%37%6%6%8%41%
2340
11th to 20thDay
7%6%35%5%35%48%9%44%
2301
21st to endDay
8%8%35%5%46%7%7%8%40%
2530
June1st to 10thDay
5%5%244345%6%9%54%
2341
11th to 20thDay
7%41442345%6%61%
2462
21st to endDay
3323333345%69%
2340
July1st to 10thDay
2313435%45%8%63%
2340
11th to 20thDay
4424425%6%6%7%57%
2340
21st to endDay
5%3145%35%6%8%7%53%
2545
August1st to 10thDay
4414445%6%7%7%55%
2328
11th to 20thDay
441342445%7%62%
2299
21st to endDay
5%4233335%6%7%60%
2552
September1st to 10thDay
331322345%7%68%
2033
11th to 20thDay
5%31333445%6%63%
1980
21st to endDay
6%323223335%67%
1980
October1st to 10thDay
10%6%24434445%53%
1891
11th to 20thDay
7%6%34322347%59%
1800
21st to endDay
7%7%34335%5%46%54%
1980
November1st to 10thDay
12%7%45%5%2445%5%48%
1675
11th to 20thDay
12%8%35%5%2435%7%45%
1710
21st to endDay
8%10%5%8%6%44445%42%
1592
December1st to 10thDay
12%11%47%5%245%47%39%
1520
11th to 20thDay
13%11%5%9%6%45%5%6%7%29%
1926
21st to endDay
8%12%5%8%7%45%5%6%6%34%
3128
January1st to 10thNight
13%10%36%5%345%6%8%36%
2457
11th to 20thNight
10%13%37%5%34347%40%
2379
21st to endNight
10%14%47%5%345%5%8%35%
2574
February1st to 10thNight
9%13%46%5%35%5%5%7%38%
2340
11th to 20thNight
8%12%48%6%35%346%42%
2205
21st to endNight
7%13%5%9%5%35%6%6%7%35%
1776
March1st to 10thNight
9%14%47%5%35%5%5%6%35%
2030
11th to 20thNight
8%9%35%5%25%5%7%8%43%
1980
21st to endNight
10%12%46%435%5%6%8%37%
2178
April1st to 10thNight
13%12%35%324446%44%
1962
11th to 20thNight
7%9%35%5%36%5%5%6%46%
1642
21st to endNight
10%7%45%5%3445%5%48%
1620
May1st to 10thNight
9%7%25%6%46%5%6%6%43%
1620
11th to 20thNight
8%6%25%5%3345%8%51%
1594
21st to endNight
10%6%26%5%245%6%8%46%
1746
June1st to 10thNight
7%4243345%5%7%55%
1599
11th to 20thNight
6%412423346%66%
1476
21st to endNight
432331245%7%67%
1620
July1st to 10thNight
4424435%5%5%7%56%
1620
11th to 20thNight
4425%6%36%6%6%7%52%
1620
21st to endNight
5%426%4345%7%8%52%
1773
August1st to 10thNight
4325%425%5%5%9%55%
1611
11th to 20thNight
3325%4346%5%8%58%
1602
21st to endNight
44134345%6%7%59%
1804
September1st to 10thNight
3313424345%67%
1924
11th to 20thNight
6%313323347%62%
1980
21st to endNight
7%414312235%69%
1980
October1st to 10thNight
9%42342435%6%57%
2067
11th to 20thNight
7%6%24423345%61%
2160
21st to endNight
7%6%23324446%59%
2376
November1st to 10thNight
11%8%2432346%6%51%
2400
11th to 20thNight
11%6%3442345%8%51%
2470
21st to endNight
9%9%36%42345%7%47%
2565
December1st to 10thNight
11%10%45%5%2345%7%45%
2660
11th to 20thNight
15%11%46%6%35%45%7%34%
3271
21st to endNight
9%11%5%9%7%45%5%5%6%33%
4553

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
47%13%18%18%41
1709
11th to 20thDay
49%8%18%15%8%2
1642
21st to endDay
52%11%16%14%6%1
1782
February1st to 10thDay
49%11%15%15%9%1
1620
11th to 20thDay
49%5%16%19%11%1
1650
21st to endDay
50%5%16%19%10%1
1480
March1st to 10thDay
43%8%16%22%10%2
1928
11th to 20thDay
39%6%16%23%13%2
1980
21st to endDay
49%5%18%17%8%3
2178
April1st to 10thDay
44%5%12%18%16%5%
1997
11th to 20thDay
41%414%22%16%3
2265
21st to endDay
36%412%25%20%3
2340
May1st to 10thDay
35%5%12%24%19%5%
2340
11th to 20thDay
31%410%25%23%7%
2304
21st to endDay
35%5%13%23%19%4
2530
June1st to 10thDay
24%49%21%30%12%
2341
11th to 20thDay
23%27%17%28%22%
2462
21st to endDay
16%2311%28%39%
2340
July1st to 10thDay
18%37%12%25%35%
2276
11th to 20thDay
22%47%13%24%30%
2271
21st to endDay
24%411%13%22%26%
2404
August1st to 10thDay
24%48%18%20%27%
2313
11th to 20thDay
21%36%12%28%29%
2299
21st to endDay
21%35%19%30%22%
2552
September1st to 10thDay
16%36%16%28%31%
2033
11th to 20thDay
19%39%19%25%23%
1980
21st to endDay
19%46%20%33%19%
1980
October1st to 10thDay
31%5%8%21%26%10%
1891
11th to 20thDay
26%49%29%26%6%
1800
21st to endDay
27%6%16%27%20%3
1980
November1st to 10thDay
37%5%14%22%18%4
1675
11th to 20thDay
38%5%14%26%15%1
1710
21st to endDay
42%8%15%21%12%2
1592
December1st to 10thDay
45%8%19%19%8%2
1520
11th to 20thDay
52%8%14%20%6%
1924
21st to endDay
45%10%19%15%10%
3128
January1st to 10thNight
46%11%18%20%5%1
2457
11th to 20thNight
46%11%17%18%8%1
2379
21st to endNight
46%10%19%17%7%1
2574
February1st to 10thNight
44%9%19%19%8%1
2340
11th to 20thNight
43%5%14%22%14%1
2206
21st to endNight
44%5%15%23%11%2
1776
March1st to 10thNight
46%6%13%23%11%
2030
11th to 20thNight
34%5%14%27%16%3
1980
21st to endNight
41%6%15%24%10%3
2178
April1st to 10thNight
40%412%21%17%7%
1962
11th to 20thNight
35%414%22%22%3
1642
21st to endNight
35%413%23%23%2
1620
May1st to 10thNight
35%5%12%23%21%4
1620
11th to 20thNight
30%410%27%22%8%
1595
21st to endNight
33%5%13%27%18%4
1746
June1st to 10thNight
25%48%21%28%12%
1599
11th to 20thNight
19%37%18%29%24%
1476
21st to endNight
17%25%10%27%39%
1620
July1st to 10thNight
24%46%13%18%35%
1575
11th to 20thNight
27%48%13%19%29%
1566
21st to endNight
27%410%15%19%25%
1674
August1st to 10thNight
24%410%17%19%25%
1602
11th to 20thNight
22%48%12%25%29%
1602
21st to endNight
21%47%16%28%25%
1804
September1st to 10thNight
19%45%14%25%32%
1924
11th to 20thNight
21%37%18%26%25%
1980
21st to endNight
20%35%16%33%23%
1980
October1st to 10thNight
27%39%22%28%10%
2067
11th to 20thNight
26%38%26%29%8%
2160
21st to endNight
26%412%29%24%5%
2376
November1st to 10thNight
31%5%11%26%21%5%
2400
11th to 20thNight
32%5%16%28%16%3
2470
21st to endNight
36%6%16%27%13%3
2565
December1st to 10thNight
39%7%19%24%10%2
2660
11th to 20thNight
47%8%17%21%8%
3272
21st to endNight
48%8%20%15%8%
4553

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
28%7%21%24%15%5%
270
11th to 20thDay
15%7%28%31%17%2
248
21st to endDay
17%328%34%14%3
264
February1st to 10thDay
20%7%32%29%10%3
240
11th to 20thDay
16%7%32%31%12%2
306
21st to endDay
16%10%34%28%11%2
346
March1st to 10thDay
17%11%28%28%13%2
420
11th to 20thDay
17%7%26%32%17%1
420
21st to endDay
19%12%31%26%11%
462
April1st to 10thDay
18%13%23%30%14%2
420
11th to 20thDay
15%17%31%24%10%2
412
21st to endDay
15%15%27%23%16%3
420
May1st to 10thDay
11%12%30%30%14%3
423
11th to 20thDay
12%6%25%34%18%5%
448
21st to endDay
9%9%23%31%22%6%
485
June1st to 10thDay
5%8%22%36%24%5%
451
11th to 20thDay
8%6%24%34%25%2
572
21st to endDay
45%25%42%21%4
450
July1st to 10thDay
2318%45%27%5%
446
11th to 20thDay
5%218%45%25%4
444
21st to endDay
3110%48%30%7%
487
August1st to 10thDay
7%118%43%28%4
447
11th to 20thDay
5%317%38%30%7%
437
21st to endDay
5%316%41%30%6%
495
September1st to 10thDay
4417%35%32%7%
450
11th to 20thDay
8%5%21%33%28%6%
450
21st to endDay
8%8%16%33%29%6%
450
October1st to 10thDay
12%8%22%28%25%5%
361
11th to 20thDay
9%10%18%29%26%9%
270
21st to endDay
10%6%29%35%17%2
297
November1st to 10thDay
20%7%21%27%20%4
270
11th to 20thDay
12%8%20%39%14%7%
270
21st to endDay
15%5%18%31%26%5%
270
December1st to 10thDay
16%7%20%32%20%5%
270
11th to 20thDay
15%7%23%38%14%3
270
21st to endDay
23%7%20%36%12%1
297
January1st to 10thNight
18%420%34%20%4
760
11th to 20thNight
16%420%35%21%4
732
21st to endNight
16%5%19%38%18%4
792
February1st to 10thNight
17%322%41%13%3
720
11th to 20thNight
14%5%26%37%17%2
704
21st to endNight
12%6%27%39%14%2
592
March1st to 10thNight
18%6%23%38%13%3
720
11th to 20thNight
12%421%40%20%3
720
21st to endNight
15%8%25%37%13%2
792
April1st to 10thNight
19%8%21%36%15%2
702
11th to 20thNight
10%7%28%40%14%1
533
21st to endNight
13%6%22%36%21%2
540
May1st to 10thNight
10%7%23%41%18%1
540
11th to 20thNight
10%417%36%31%3
531
21st to endNight
12%5%18%36%25%4
584
June1st to 10thNight
9%7%17%37%29%2
540
11th to 20thNight
7%422%43%22%2
540
21st to endNight
5%216%41%33%3
540
July1st to 10thNight
6%214%32%41%5%
525
11th to 20thNight
6%112%45%33%4
522
21st to endNight
6%17%32%52%2
591
August1st to 10thNight
5%112%44%36%2
537
11th to 20thNight
4110%44%38%3
534
21st to endNight
5%29%43%39%2
594
September1st to 10thNight
5%212%40%36%5%
664
11th to 20thNight
7%215%34%36%6%
720
21st to endNight
8%314%32%35%8%
720
October1st to 10thNight
12%319%35%27%4
720
11th to 20thNight
10%416%38%28%5%
720
21st to endNight
10%420%38%24%4
792
November1st to 10thNight
13%5%19%36%23%4
740
11th to 20thNight
14%420%41%18%4
760
21st to endNight
13%5%20%36%21%4
855
December1st to 10thNight
17%423%36%17%2
950
11th to 20thNight
20%6%19%40%13%2
950
21st to endNight
20%6%23%39%12%1
855
Page generated at 2024-01-10 17:35:26. Version ac07

Copyright 2024 Attilla Danko


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