BREIT IDEAS Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the BREIT IDEAS Observatory clear sky chart from 2005-11-06 to 2024-01-16.

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
66%
23779
27%
74819
25%
23735
70%
23735
35%
42614

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
57%
756
20%
2547
20%
756
60%
756
27%
1551
January11th to 20thNight
62%
744
24%
2418
22%
744
67%
744
32%
1391
January21st to endNight
59%
792
26%
2574
27%
792
62%
792
30%
1523
February1st to 10thNight
59%
720
28%
2340
27%
720
65%
720
32%
1330
February11th to 20thNight
57%
700
26%
2156
24%
700
64%
700
33%
1249
February21st to endNight
55%
592
27%
1776
24%
592
61%
592
36%
1013
March1st to 10thNight
51%
720
18%
2040
15%
720
55%
720
26%
1361
March11th to 20thNight
55%
720
24%
1980
21%
720
59%
720
30%
1292
March21st to endNight
54%
792
20%
2128
14%
792
59%
792
34%
1327
April1st to 10thNight
58%
720
23%
1800
14%
720
61%
720
36%
1137
April11th to 20thNight
56%
711
27%
1779
14%
711
60%
711
38%
1088
April21st to endNight
61%
720
28%
1800
14%
720
65%
720
46%
1043
May1st to 10thNight
64%
709
24%
1789
15%
709
66%
709
42%
1072
May11th to 20thNight
69%
467
23%
1530
21%
467
71%
467
32%
846
May21st to endNight
61%
388
23%
1552
24%
388
66%
388
27%
850
June1st to 10thNight
71%
360
26%
1440
28%
360
77%
360
33%
713
June11th to 20thNight
74%
360
30%
1440
36%
360
79%
360
37%
663
June21st to endNight
79%
360
30%
1440
39%
360
81%
360
35%
691
July1st to 10thNight
80%
350
26%
1400
34%
350
81%
350
32%
689
July11th to 20thNight
83%
496
28%
1540
28%
496
83%
496
42%
792
July21st to endNight
76%
591
26%
1674
23%
558
77%
558
33%
969
August1st to 10thNight
70%
537
24%
1602
20%
534
70%
534
29%
958
August11th to 20thNight
80%
686
31%
1754
21%
686
81%
686
46%
1015
August21st to endNight
79%
792
31%
1980
20%
792
79%
792
46%
1183
September1st to 10thNight
85%
720
40%
1800
28%
720
85%
720
59%
956
September11th to 20thNight
77%
720
36%
1800
29%
720
78%
720
47%
1044
September21st to endNight
80%
720
39%
2028
38%
720
84%
720
57%
995
October1st to 10thNight
78%
720
31%
2160
32%
720
83%
720
50%
1069
October11th to 20thNight
73%
720
36%
2160
39%
720
76%
720
44%
1139
October21st to endNight
74%
792
37%
2376
38%
792
78%
792
48%
1205
November1st to 10thNight
70%
740
33%
2267
32%
740
74%
740
43%
1182
November11th to 20thNight
69%
760
30%
2470
30%
760
74%
760
41%
1271
November21st to endNight
69%
760
31%
2560
31%
760
74%
760
39%
1314
December1st to 10thNight
59%
760
25%
2660
25%
760
65%
760
31%
1497
December11th to 20thNight
54%
759
19%
3243
23%
759
59%
759
18%
2206
December21st to endNight
50%
825
14%
4816
20%
817
57%
817
14%
2990

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
7%424423447%59%
74728
Night
8%5%25%43445%7%53%
75096
TransparencyDay
28%37%20%25%17%
74448
Night
34%38%19%22%15%
74898
SeeingDay
8%7%20%31%24%10%
14300
Night
10%411%34%33%9%
23800

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
18%6%26%5%345%5%6%41%
1614
11th to 20thDay
11%4344345%5%7%52%
1669
21st to endDay
13%7%35%43346%7%44%
1782
February1st to 10thDay
15%7%23424346%49%
1620
11th to 20thDay
12%5%25%5%345%5%6%47%
1693
21st to endDay
14%5%36%5%34336%47%
1480
March1st to 10thDay
14%7%46%6%35%5%6%7%36%
1916
11th to 20thDay
15%7%25%5%46%5%6%9%38%
1980
21st to endDay
11%6%36%5%25%5%47%46%
2227
April1st to 10thDay
12%6%35%5%34448%47%
2160
11th to 20thDay
9%5%24434347%55%
2129
21st to endDay
6%42442345%8%58%
2160
May1st to 10thDay
46%24423447%61%
2168
11th to 20thDay
4424324446%64%
2361
21st to endDay
46%35%5%33347%57%
2723
June1st to 10thDay
3424323448%62%
2520
11th to 20thDay
1312222347%73%
2520
21st to endDay
1313322325%75%
2520
July1st to 10thDay
223313335%75%
2520
11th to 20thDay
1213213346%74%
2364
21st to endDay
1112213338%75%
2546
August1st to 10thDay
1324333346%69%
2328
11th to 20thDay
212312336%75%
2147
21st to endDay
224323236%73%
2376
September1st to 10thDay
221221212480%
2160
11th to 20thDay
231432345%7%67%
2160
21st to endDay
3212212235%77%
1927
October1st to 10thDay
3313322447%69%
1800
11th to 20thDay
4323323346%67%
1800
21st to endDay
5%5%23333446%63%
1980
November1st to 10thDay
7%4134345%5%7%57%
1809
11th to 20thDay
8%423435%447%55%
1710
21st to endDay
10%42322445%6%58%
1617
December1st to 10thDay
12%6%25%5%345%5%6%49%
1520
11th to 20thDay
27%8%35%5%3345%5%33%
1928
21st to endDay
14%9%46%6%3446%7%37%
2794
January1st to 10thNight
14%7%25%5%35%5%6%7%42%
2547
11th to 20thNight
11%5%25%435%5%5%7%48%
2418
21st to endNight
14%6%244245%5%7%47%
2574
February1st to 10thNight
14%6%24423446%52%
2340
11th to 20thNight
11%5%24425%5%6%8%48%
2155
21st to endNight
12%6%25%422347%52%
1776
March1st to 10thNight
14%9%46%5%3446%6%39%
2040
11th to 20thNight
15%6%35%5%35%46%8%41%
1980
21st to endNight
11%6%36%5%24338%49%
2128
April1st to 10thNight
11%6%245%25%5%6%7%48%
1800
11th to 20thNight
8%7%34424347%55%
1779
21st to endNight
5%5%3432445%10%55%
1800
May1st to 10thNight
36%36%435%35%8%54%
1789
11th to 20thNight
4425%5%36%35%9%53%
1529
21st to endNight
48%47%5%235%47%51%
1552
June1st to 10thNight
34345%24449%58%
1440
11th to 20thNight
15%245%44346%62%
1440
21st to endNight
15%25%5%33335%64%
1440
July1st to 10thNight
1226%5%35%447%59%
1440
11th to 20thNight
1225%4345%5%7%62%
1592
21st to endNight
1337%6%45%46%9%51%
1773
August1st to 10thNight
16%37%7%445%5%8%49%
1611
11th to 20thNight
1325%5%345%410%58%
1754
21st to endNight
1327%6%4435%7%60%
1980
September1st to 10thNight
1324312347%71%
1800
11th to 20thNight
3425%5%23347%61%
1800
21st to endNight
2413322246%72%
2028
October1st to 10thNight
4412422247%67%
2160
11th to 20thNight
5%5%2443235%8%61%
2160
21st to endNight
5%324423336%65%
2376
November1st to 10thNight
7%41432345%6%60%
2267
11th to 20thNight
8%42432345%9%54%
2470
21st to endNight
7%5%24425%446%59%
2560
December1st to 10thNight
14%6%24324446%50%
2660
11th to 20thNight
26%7%35%5%2345%6%34%
3276
21st to endNight
17%8%26%6%45%5%5%6%35%
4862

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
44%312%22%13%6%
1614
11th to 20thDay
33%412%20%18%13%
1669
21st to endDay
40%39%15%23%9%
1782
February1st to 10thDay
37%26%24%19%12%
1620
11th to 20thDay
38%38%20%23%9%
1703
21st to endDay
40%28%22%21%6%
1480
March1st to 10thDay
46%39%21%17%4
1916
11th to 20thDay
43%39%22%18%4
1980
21st to endDay
38%415%22%17%5%
2227
April1st to 10thDay
38%312%22%20%5%
2160
11th to 20thDay
32%312%25%20%7%
2132
21st to endDay
27%311%31%23%5%
2160
May1st to 10thDay
25%310%26%30%7%
2168
11th to 20thDay
23%28%32%26%9%
2364
21st to endDay
30%312%29%23%4
2724
June1st to 10thDay
24%211%27%26%9%
2520
11th to 20thDay
16%27%23%35%17%
2520
21st to endDay
17%2313%34%31%
2520
July1st to 10thDay
16%2210%25%46%
2451
11th to 20thDay
16%3411%25%42%
2293
21st to endDay
13%1210%35%39%
2405
August1st to 10thDay
22%2110%32%33%
2312
11th to 20thDay
14%2113%33%37%
2147
21st to endDay
18%2111%34%35%
2376
September1st to 10thDay
13%119%32%45%
2160
11th to 20thDay
19%3323%35%18%
2160
21st to endDay
14%1223%36%23%
1927
October1st to 10thDay
17%27%18%28%27%
1800
11th to 20thDay
20%27%21%24%26%
1800
21st to endDay
24%27%22%23%23%
1980
November1st to 10thDay
27%37%23%26%13%
1809
11th to 20thDay
29%310%23%26%9%
1710
21st to endDay
29%29%18%30%11%
1617
December1st to 10thDay
37%311%19%18%12%
1520
11th to 20thDay
54%38%16%15%5%
1928
21st to endDay
48%112%23%12%4
2794
January1st to 10thNight
41%312%24%15%6%
2547
11th to 20thNight
35%313%19%16%14%
2418
21st to endNight
37%413%16%19%11%
2574
February1st to 10thNight
37%16%22%21%13%
2340
11th to 20thNight
35%210%21%23%9%
2156
21st to endNight
34%210%29%19%7%
1776
March1st to 10thNight
45%313%18%15%6%
2040
11th to 20thNight
42%37%23%19%7%
1980
21st to endNight
37%312%23%17%7%
2128
April1st to 10thNight
35%414%21%20%6%
1800
11th to 20thNight
32%310%28%18%8%
1779
21st to endNight
26%411%31%22%6%
1800
May1st to 10thNight
31%39%22%24%11%
1789
11th to 20thNight
33%48%22%25%7%
1530
21st to endNight
36%411%23%24%4
1552
June1st to 10thNight
28%49%24%23%10%
1440
11th to 20thNight
25%36%15%32%19%
1440
21st to endNight
29%2112%26%29%
1440
July1st to 10thNight
29%416%21%40%
1400
11th to 20thNight
25%5%39%23%35%
1540
21st to endNight
35%429%22%28%
1674
August1st to 10thNight
38%419%21%27%
1602
11th to 20thNight
28%319%26%34%
1754
21st to endNight
29%318%29%30%
1980
September1st to 10thNight
18%417%27%44%
1800
11th to 20thNight
28%2217%31%19%
1800
21st to endNight
19%2217%38%22%
2028
October1st to 10thNight
22%27%17%24%28%
2160
11th to 20thNight
26%35%19%24%24%
2160
21st to endNight
25%15%21%24%24%
2376
November1st to 10thNight
27%37%24%23%17%
2267
11th to 20thNight
27%310%22%28%10%
2470
21st to endNight
28%39%20%25%15%
2560
December1st to 10thNight
36%38%21%19%13%
2660
11th to 20thNight
53%29%16%16%4
3276
21st to endNight
50%213%18%12%5%
4862

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
27%7%21%24%17%4
275
11th to 20thDay
17%8%19%29%21%7%
357
21st to endDay
14%7%18%29%24%8%
374
February1st to 10thDay
16%11%21%23%20%9%
340
11th to 20thDay
13%14%26%26%16%5%
389
21st to endDay
14%11%25%30%16%3
346
March1st to 10thDay
19%12%25%29%12%2
420
11th to 20thDay
20%10%23%27%15%5%
420
21st to endDay
15%13%30%26%14%3
462
April1st to 10thDay
15%10%30%26%15%4
420
11th to 20thDay
12%13%30%26%14%5%
412
21st to endDay
7%11%29%29%16%8%
420
May1st to 10thDay
7%11%30%30%17%5%
423
11th to 20thDay
8%8%29%32%15%7%
448
21st to endDay
7%11%25%31%19%7%
485
June1st to 10thDay
5%7%27%31%19%11%
450
11th to 20thDay
26%25%38%23%6%
450
21st to endDay
2420%37%28%10%
450
July1st to 10thDay
1115%39%33%12%
446
11th to 20thDay
19%39%36%16%
444
21st to endDay
19%37%35%17%
487
August1st to 10thDay
3117%37%31%11%
447
11th to 20thDay
1114%36%30%18%
437
21st to endDay
29%39%35%15%
495
September1st to 10thDay
339%36%32%17%
450
11th to 20thDay
2420%36%26%12%
450
21st to endDay
45%13%34%32%12%
450
October1st to 10thDay
5%6%20%29%28%13%
450
11th to 20thDay
5%6%19%28%30%13%
450
21st to endDay
8%418%28%29%12%
495
November1st to 10thDay
7%8%14%28%30%13%
405
11th to 20thDay
7%6%10%30%33%14%
270
21st to endDay
9%417%30%33%8%
225
December1st to 10thDay
12%8%18%26%24%12%
180
11th to 20thDay
16%9%16%23%27%10%
180
21st to endDay
19%9%15%29%23%6%
198
January1st to 10thNight
18%313%36%23%6%
760
11th to 20thNight
14%313%37%25%9%
744
21st to endNight
18%310%37%26%6%
792
February1st to 10thNight
18%412%34%26%6%
720
11th to 20thNight
13%418%34%23%7%
704
21st to endNight
17%416%40%20%3
592
March1st to 10thNight
17%6%13%36%23%4
720
11th to 20thNight
18%314%33%26%6%
720
21st to endNight
14%7%16%37%22%3
792
April1st to 10thNight
13%7%13%39%24%4
720
11th to 20thNight
11%7%18%36%23%6%
711
21st to endNight
8%5%18%36%25%8%
720
May1st to 10thNight
7%216%39%28%7%
709
11th to 20thNight
6%211%35%36%10%
467
21st to endNight
7%7%11%35%34%6%
389
June1st to 10thNight
45%10%36%38%6%
360
11th to 20thNight
25%9%43%37%4
360
21st to endNight
235%34%49%7%
360
July1st to 10thNight
21426%57%9%
350
11th to 20thNight
21217%58%20%
496
21st to endNight
24317%55%19%
591
August1st to 10thNight
45%425%48%13%
537
11th to 20thNight
23432%47%11%
686
21st to endNight
215%26%52%15%
792
September1st to 10thNight
215%28%48%15%
720
11th to 20thNight
426%33%43%11%
720
21st to endNight
438%29%42%13%
720
October1st to 10thNight
6%37%36%34%14%
720
11th to 20thNight
7%39%30%38%13%
720
21st to endNight
7%210%33%30%18%
792
November1st to 10thNight
9%212%34%32%11%
740
11th to 20thNight
10%29%38%33%8%
760
21st to endNight
9%311%42%28%8%
760
December1st to 10thNight
18%212%38%25%6%
760
11th to 20thNight
22%411%36%23%4
760
21st to endNight
20%417%36%20%4
836
Page generated at 2024-01-13 16:28:27. Version ac07

Copyright 2024 Attilla Danko


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