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 2005-11-05 to 2017-10-06.

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
69%
15517
27%
47130
25%
15481
72%
15481
38%
26237

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
66%
716
21%
2383
23%
716
69%
716
34%
1322
January16th to endNight
61%
768
26%
2496
27%
768
64%
768
30%
1472
February1st to 15thNight
61%
697
26%
2270
26%
697
66%
697
29%
1340
February16th to endNight
56%
632
23%
1895
20%
632
61%
632
31%
1170
March1st to 15thNight
59%
720
19%
2020
17%
720
63%
720
31%
1284
March16th to endNight
56%
768
21%
2079
16%
768
60%
768
33%
1317
April1st to 15thNight
57%
719
24%
1799
14%
719
60%
719
36%
1133
April16th to endNight
61%
720
26%
1800
13%
720
65%
720
46%
1031
May1st to 15thNight
69%
651
24%
1731
16%
651
71%
651
43%
985
May16th to endNight
69%
387
25%
1510
26%
387
73%
387
33%
756
June1st to 15thNight
74%
360
25%
1440
28%
360
79%
360
35%
697
June16th to endNight
86%
360
32%
1440
42%
360
87%
360
44%
609
July1st to 15thNight
88%
379
27%
1399
33%
379
88%
379
43%
637
July16th to endNight
79%
564
29%
1593
27%
531
80%
531
38%
868
August1st to 15thNight
74%
580
27%
1653
21%
577
74%
577
37%
951
August16th to endNight
82%
764
33%
1910
22%
764
82%
764
50%
1098
September1st to 15thNight
85%
720
37%
1800
27%
720
86%
720
59%
958
September16th to endNight
81%
716
41%
1953
38%
716
83%
716
56%
987
October1st to 15thNight
75%
684
30%
2052
33%
684
79%
684
47%
1050
October16th to endNight
74%
704
34%
2112
36%
704
76%
704
44%
1115
November1st to 15thNight
72%
700
31%
2190
32%
700
76%
700
44%
1124
November16th to endNight
70%
720
27%
2397
28%
720
74%
720
38%
1260
December1st to 15thNight
59%
720
23%
2520
23%
720
64%
720
28%
1487
December16th to endNight
55%
768
21%
2688
21%
768
61%
768
26%
1586

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%423323346%59%
48068
Night
8%424424347%54%
47318
TransparencyDay
27%28%20%25%16%
47755
Night
30%38%19%22%15%
47131
SeeingDay
8%7%20%33%21%7%
6095
Night
10%39%32%34%10%
15530

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 15thDay
13%325%422446%49%
1552
16th to endDay
16%6%34323346%45%
1728
February1st to 15thDay
15%7%24423335%45%
1594
16th to endDay
17%6%36%5%24435%39%
1579
March1st to 15thDay
13%5%345%36%5%6%9%37%
1938
16th to endDay
11%6%26%5%25%5%47%42%
2145
April1st to 15thDay
13%6%35%424347%44%
2149
16th to endDay
7%323323347%57%
2160
May1st to 15thDay
3413312347%64%
2217
16th to endDay
5%5%24423346%57%
2599
June1st to 15thDay
3424223347%61%
2520
16th to endDay
112212226%75%
2520
July1st to 15thDay
212212235%75%
2475
16th to endDay
1112112236%75%
2468
August1st to 15thDay
1213322335%70%
2297
16th to endDay
112212236%74%
2292
September1st to 15thDay
1211112235%75%
2160
16th to endDay
322212335%71%
2004
October1st to 15thDay
4213222347%63%
1705
16th to endDay
6%313323447%59%
1760
November1st to 15thDay
8%312434445%56%
1668
16th to endDay
11%423324445%53%
1562
December1st to 15thDay
15%6%25%5%2444444%
1440
16th to endDay
16%6%35%423346%41%
1536
January1st to 15thNight
11%424325%45%7%48%
2383
16th to endNight
15%5%23413346%48%
2496
February1st to 15thNight
13%5%2342445%7%45%
2259
16th to endNight
15%6%25%424347%44%
1895
March1st to 15thNight
13%6%3442445%7%42%
2020
16th to endNight
12%5%25%424348%45%
2079
April1st to 15thNight
11%5%2342445%6%47%
1799
16th to endNight
6%423224348%58%
1800
May1st to 15thNight
2325%426%348%56%
1731
16th to endNight
35%24423447%56%
1509
June1st to 15thNight
132442445%8%58%
1440
16th to endNight
213323336%68%
1440
July1st to 15thNight
113225%46%7%63%
1482
16th to endNight
325%435%5%5%8%54%
1701
August1st to 15thNight
5%36%5%3445%9%52%
1662
16th to endNight
21443445%8%59%
1910
September1st to 15thNight
1312313347%67%
1800
16th to endNight
2313222247%68%
1953
October1st to 15thNight
5%412322247%61%
2052
16th to endNight
5%314423336%60%
2112
November1st to 15thNight
7%41321435%6%59%
2190
16th to endNight
7%423424447%55%
2397
December1st to 15thNight
14%5%24413346%47%
2520
16th to endNight
18%424324446%46%
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
35%311%21%17%9%
1552
16th to endDay
40%38%14%19%13%
1728
February1st to 15thDay
40%27%22%19%7%
1594
16th to endDay
46%29%23%14%3
1579
March1st to 15thDay
41%411%20%15%5%
1938
16th to endDay
40%315%19%17%3
2145
April1st to 15thDay
39%311%22%19%2
2149
16th to endDay
27%312%25%21%8%
2160
May1st to 15thDay
21%210%30%28%7%
2217
16th to endDay
29%211%27%22%6%
2603
June1st to 15thDay
24%310%23%24%13%
2520
16th to endDay
13%1417%36%25%
2520
July1st to 15thDay
14%228%25%46%
2329
16th to endDay
12%2310%31%38%
2313
August1st to 15thDay
19%1111%32%33%
2281
16th to endDay
14%2113%37%31%
2292
September1st to 15thDay
13%2115%34%32%
2160
16th to endDay
16%1226%33%18%
2004
October1st to 15thDay
20%27%22%25%20%
1705
16th to endDay
24%28%24%23%16%
1760
November1st to 15thDay
28%310%24%25%7%
1668
16th to endDay
32%210%20%28%5%
1562
December1st to 15thDay
41%211%17%20%6%
1440
16th to endDay
42%212%17%17%6%
1536
January1st to 15thNight
33%212%23%18%9%
2383
16th to endNight
36%310%15%17%16%
2496
February1st to 15thNight
39%19%23%18%7%
2270
16th to endNight
39%212%26%14%3
1895
March1st to 15thNight
40%213%20%15%7%
2020
16th to endNight
38%312%21%17%7%
2079
April1st to 15thNight
35%313%25%18%3
1799
16th to endNight
24%412%28%20%9%
1800
May1st to 15thNight
28%39%21%26%10%
1732
16th to endNight
28%411%26%23%5%
1510
June1st to 15thNight
25%5%9%19%22%16%
1440
16th to endNight
21%2213%32%28%
1440
July1st to 15thNight
21%416%23%42%
1399
16th to endNight
29%339%20%33%
1593
August1st to 15thNight
32%319%23%29%
1653
16th to endNight
25%319%31%29%
1910
September1st to 15thNight
18%3210%31%34%
1800
16th to endNight
19%2219%36%19%
1953
October1st to 15thNight
24%16%23%21%21%
2052
16th to endNight
27%16%23%23%17%
2112
November1st to 15thNight
25%311%25%25%9%
2190
16th to endNight
28%310%23%25%9%
2397
December1st to 15thNight
39%29%19%20%8%
2520
16th to endNight
39%214%17%18%7%
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
18%10%19%32%15%4
180
16th to endDay
18%7%20%26%19%7%
256
February1st to 15thDay
14%12%21%26%20%4
239
16th to endDay
17%12%26%26%15%2
238
March1st to 15thDay
15%13%23%25%16%5%
270
16th to endDay
12%12%33%27%11%1
288
April1st to 15thDay
17%15%31%23%10%2
269
16th to endDay
11%16%32%25%11%3
270
May1st to 15thDay
8%13%30%31%12%3
288
16th to endDay
8%10%22%32%20%5%
330
June1st to 15thDay
6%6%31%35%13%6%
315
16th to endDay
1217%41%26%10%
315
July1st to 15thDay
12%43%30%11%
305
16th to endDay
18%44%31%14%
327
August1st to 15thDay
413%39%31%10%
315
16th to endDay
110%40%31%15%
332
September1st to 15thDay
2114%40%28%12%
315
16th to endDay
4416%34%29%10%
315
October1st to 15thDay
6%8%24%35%20%5%
278
16th to endDay
9%421%34%25%4
272
November1st to 15thDay
7%5%13%27%27%18%
174
16th to endDay
8%10%21%32%26%1
80
December1st to 15thDay
21%11%18%33%13%1
60
16th to endDay
14%9%7%31%28%9%
64
January1st to 15thNight
13%19%35%30%9%
720
16th to endNight
18%27%32%26%11%
768
February1st to 15thNight
16%310%32%28%8%
704
16th to endNight
18%414%37%20%5%
632
March1st to 15thNight
15%411%32%29%6%
720
16th to endNight
14%6%13%35%25%4
768
April1st to 15thNight
13%7%14%37%23%3
719
16th to endNight
8%6%17%34%25%8%
720
May1st to 15thNight
4113%39%32%7%
652
16th to endNight
5%49%34%38%7%
388
June1st to 15thNight
3310%39%38%4
360
16th to endNight
21337%49%6%
360
July1st to 15thNight
2318%59%15%
379
16th to endNight
23317%51%21%
564
August1st to 15thNight
445%24%49%13%
580
16th to endNight
215%23%52%14%
764
September1st to 15thNight
2427%48%15%
720
16th to endNight
416%29%43%13%
716
October1st to 15thNight
8%36%34%31%15%
684
16th to endNight
8%28%30%31%19%
704
November1st to 15thNight
9%19%35%31%12%
700
16th to endNight
8%28%37%30%11%
720
December1st to 15thNight
18%29%35%26%8%
720
16th to endNight
20%412%35%22%4
768
Page generated at 2017-10-07 11:07:45. Version ac04

Copyright 2017 A. Danko


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