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 2017-04-24.

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
68%
15013
27%
45623
25%
14977
71%
14977
37%
25495

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
62%
696
26%
1740
13%
696
65%
696
47%
992
May1st to 15thNight
70%
597
24%
1587
17%
597
72%
597
43%
903
May16th to endNight
68%
354
23%
1381
22%
354
73%
354
33%
686
June1st to 15thNight
74%
330
27%
1320
30%
330
79%
330
34%
645
June16th to endNight
85%
330
30%
1320
39%
330
86%
330
43%
567
July1st to 15thNight
87%
345
29%
1275
35%
345
88%
345
41%
595
July16th to endNight
78%
522
26%
1467
25%
489
80%
489
36%
816
August1st to 15thNight
74%
531
28%
1514
22%
528
74%
528
36%
877
August16th to endNight
82%
700
32%
1750
21%
700
82%
700
50%
1005
September1st to 15thNight
86%
660
39%
1650
28%
660
87%
660
61%
858
September16th to endNight
81%
656
39%
1790
37%
656
83%
656
54%
917
October1st to 15thNight
75%
660
31%
1980
33%
660
79%
660
46%
1024
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%58%
45985
Night
8%424424447%53%
45811
TransparencyDay
27%28%20%25%15%
45672
Night
31%28%19%22%14%
45624
SeeingDay
9%7%21%34%20%6%
5441
Night
10%39%32%33%10%
15026

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%
2079
May1st to 15thDay
3423313447%63%
2031
16th to endDay
5%5%24423347%56%
2376
June1st to 15thDay
3424223347%61%
2310
16th to endDay
112222226%75%
2310
July1st to 15thDay
213212235%73%
2269
16th to endDay
1112112337%74%
2286
August1st to 15thDay
213322225%72%
2106
16th to endDay
112212236%74%
2100
September1st to 15thDay
121112135%77%
1980
16th to endDay
322212335%72%
1837
October1st to 15thDay
4213323348%62%
1650
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%
1740
May1st to 15thNight
2325%426%348%55%
1587
16th to endNight
35%2342345%8%56%
1380
June1st to 15thNight
142442435%8%57%
1320
16th to endNight
1213323436%67%
1320
July1st to 15thNight
1113226%47%8%61%
1358
16th to endNight
325%436%5%5%9%52%
1575
August1st to 15thNight
5%36%5%3445%9%51%
1523
16th to endNight
31443445%8%59%
1750
September1st to 15thNight
121231235%7%69%
1650
16th to endNight
2313222247%67%
1790
October1st to 15thNight
6%412322247%60%
1980
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%26%21%8%
2079
May1st to 15thDay
21%210%29%27%8%
2031
16th to endDay
29%212%27%21%6%
2380
June1st to 15thDay
24%311%22%24%14%
2310
16th to endDay
14%1418%38%22%
2310
July1st to 15thDay
15%229%27%43%
2123
16th to endDay
13%2311%33%35%
2131
August1st to 15thDay
19%1111%32%34%
2090
16th to endDay
14%1112%38%30%
2100
September1st to 15thDay
12%2114%35%33%
1980
16th to endDay
16%1226%32%19%
1837
October1st to 15thDay
21%28%23%26%19%
1650
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
25%312%28%21%9%
1740
May1st to 15thNight
28%39%20%26%11%
1588
16th to endNight
27%412%26%22%6%
1381
June1st to 15thNight
26%5%10%19%21%17%
1320
16th to endNight
22%1214%33%26%
1320
July1st to 15thNight
22%417%25%38%
1275
16th to endNight
31%3310%21%28%
1467
August1st to 15thNight
33%319%23%29%
1514
16th to endNight
26%2110%32%27%
1750
September1st to 15thNight
16%329%32%35%
1650
16th to endNight
20%2118%36%20%
1790
October1st to 15thNight
25%26%24%22%19%
1980
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%31%25%11%3
243
May1st to 15thDay
8%13%31%32%11%2
228
16th to endDay
8%11%23%34%17%4
266
June1st to 15thDay
5%7%31%38%12%4
255
16th to endDay
1221%45%20%8%
255
July1st to 15thDay
114%49%26%8%
245
16th to endDay
18%47%31%10%
271
August1st to 15thDay
314%44%28%9%
255
16th to endDay
111%45%28%12%
268
September1st to 15thDay
1115%40%28%12%
255
16th to endDay
5%415%33%29%11%
255
October1st to 15thDay
6%8%23%34%21%5%
255
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%16%34%26%8%
696
May1st to 15thNight
3113%39%32%8%
598
16th to endNight
5%49%34%39%6%
355
June1st to 15thNight
3310%40%36%4
330
16th to endNight
21339%46%6%
330
July1st to 15thNight
2320%57%15%
345
16th to endNight
23316%52%21%
522
August1st to 15thNight
335%25%48%13%
531
16th to endNight
215%24%53%13%
700
September1st to 15thNight
2425%50%16%
660
16th to endNight
5%16%28%43%14%
656
October1st to 15thNight
8%36%32%32%15%
660
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 2017-04-25 04:48:17. Version ac04

Copyright 2017 A. Danko


BREIT IDEAS Observatory Clear Sky Chart | Charts Home