Bateson Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bateson Observatory clear sky chart from 2005-11-05 to 2019-06-10.

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
60%
17313
25%
53902
22%
17285
65%
17285
36%
29553

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
52%
836
17%
2926
16%
836
57%
836
23%
1824
January16th to endNight
54%
896
19%
2951
21%
896
56%
896
25%
1841
February1st to 15thNight
52%
816
20%
2665
19%
816
57%
816
26%
1616
February16th to endNight
49%
736
20%
2207
17%
736
54%
736
27%
1359
March1st to 15thNight
47%
840
15%
2440
12%
840
51%
840
24%
1589
March16th to endNight
44%
896
16%
2378
11%
896
48%
896
28%
1539
April1st to 15thNight
43%
839
17%
2099
7%
839
47%
839
27%
1407
April16th to endNight
55%
832
22%
2080
10%
832
59%
832
42%
1217
May1st to 15thNight
53%
571
28%
1831
19%
571
60%
571
41%
909
May16th to endNight
55%
438
15%
1752
17%
438
59%
438
24%
984
June1st to 15thNight
66%
408
25%
1632
31%
408
72%
408
38%
733
June16th to endNight
77%
390
30%
1560
42%
390
82%
390
54%
589
July1st to 15thNight
87%
370
33%
1480
45%
370
90%
370
64%
497
July16th to endNight
89%
452
39%
1585
46%
427
90%
427
68%
553
August1st to 15thNight
85%
601
37%
1746
30%
598
86%
598
66%
763
August16th to endNight
82%
828
42%
2070
27%
828
83%
828
77%
958
September1st to 15thNight
82%
780
42%
1950
28%
780
84%
780
72%
925
September16th to endNight
74%
776
41%
2099
32%
776
79%
776
65%
968
October1st to 15thNight
64%
780
30%
2340
28%
780
73%
780
48%
1153
October16th to endNight
70%
832
32%
2517
33%
832
75%
832
49%
1233
November1st to 15thNight
62%
820
24%
2665
24%
820
66%
820
32%
1514
November16th to endNight
56%
840
20%
2853
19%
840
61%
840
31%
1575
December1st to 15thNight
53%
840
19%
2940
18%
840
58%
840
24%
1806
December16th to endNight
45%
896
19%
3136
16%
896
52%
896
20%
2001

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
242442445%7%57%
54620
Night
232442445%8%56%
54078
TransparencyDay
26%6%11%20%20%15%
54295
Night
25%8%13%22%19%11%
53903
SeeingDay
11%17%27%25%14%3
7917
Night
6%9%17%35%26%4
17327

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
26%27%8%46%7%8%8%37%
1672
16th to endDay
37%46%6%5%5%6%8%9%36%
1977
February1st to 15thDay
3436%5%35%6%9%9%41%
1859
16th to endDay
36%48%6%46%6%6%8%39%
1839
March1st to 15thDay
47%37%7%47%6%6%9%37%
2176
16th to endDay
27%37%7%35%5%6%8%41%
2549
April1st to 15thDay
48%46%5%35%6%6%7%40%
2509
16th to endDay
45%24424347%53%
2485
May1st to 15thDay
3314423447%61%
2772
16th to endDay
6%6%37%6%34446%44%
3063
June1st to 15thDay
232443345%6%59%
2857
16th to endDay
111221232476%
2730
July1st to 15thDay
1121223478%
2730
16th to endDay
11111222479%
2835
August1st to 15thDay
111112235%78%
2455
16th to endDay
11122286%
2484
September1st to 15thDay
11212235%77%
2340
16th to endDay
1212212237%73%
2188
October1st to 15thDay
3214324345%64%
1950
16th to endDay
231442345%8%59%
2057
November1st to 15thDay
3315%5%35%5%6%9%49%
1854
16th to endDay
1425%436%7%6%9%46%
1767
December1st to 15thDay
46%25%6%36%6%8%10%39%
1680
16th to endDay
26%37%8%48%6%6%10%34%
1792
January1st to 15thNight
35%36%7%46%6%7%9%40%
2926
16th to endNight
37%25%5%46%6%6%9%41%
2951
February1st to 15thNight
35%25%436%6%7%10%44%
2653
16th to endNight
35%245%36%6%7%9%46%
2207
March1st to 15thNight
25%25%5%37%6%7%11%41%
2440
16th to endNight
25%25%5%35%6%7%8%46%
2378
April1st to 15thNight
25%35%6%46%6%6%11%40%
2099
16th to endNight
33133245%5%7%59%
2080
May1st to 15thNight
3314423348%60%
1831
16th to endNight
5%5%26%5%25%5%5%7%49%
1752
June1st to 15thNight
3324323347%63%
1632
16th to endNight
11232322377%
1560
July1st to 15thNight
1111223479%
1560
16th to endNight
111121482%
1684
August1st to 15thNight
111221233476%
1755
16th to endNight
1111122383%
2070
September1st to 15thNight
11111135%79%
1950
16th to endNight
2212111235%76%
2099
October1st to 15thNight
4312322335%67%
2340
16th to endNight
221222345%7%65%
2517
November1st to 15thNight
43143345%7%10%51%
2665
16th to endNight
1313435%6%7%11%50%
2853
December1st to 15thNight
35%26%425%5%7%11%44%
2940
16th to endNight
36%36%6%45%6%8%11%37%
3136

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
40%11%17%21%8%
1672
16th to endDay
40%10%15%18%12%2
1977
February1st to 15thDay
33%11%17%24%12%
1859
16th to endDay
40%8%15%25%8%1
1839
March1st to 15thDay
41%9%13%21%11%1
2176
16th to endDay
38%8%19%20%9%2
2549
April1st to 15thDay
39%8%14%22%13%
2509
16th to endDay
30%5%14%27%19%2
2485
May1st to 15thDay
22%411%28%27%5%
2772
16th to endDay
39%5%11%21%18%3
3067
June1st to 15thDay
24%410%20%28%11%
2857
16th to endDay
12%25%16%37%26%
2730
July1st to 15thDay
9%25%10%24%48%
2581
16th to endDay
10%2310%23%50%
2671
August1st to 15thDay
9%15%12%25%45%
2439
16th to endDay
6%1312%32%44%
2484
September1st to 15thDay
10%1412%31%39%
2340
16th to endDay
13%27%25%30%20%
2188
October1st to 15thDay
22%48%26%28%10%
1950
16th to endDay
22%5%13%23%24%9%
2057
November1st to 15thDay
29%7%16%25%16%4
1854
16th to endDay
31%10%17%22%16%1
1767
December1st to 15thDay
36%11%16%23%12%
1680
16th to endDay
43%10%14%20%10%
1792
January1st to 15thNight
37%8%18%24%10%
2926
16th to endNight
36%9%14%21%12%5%
2951
February1st to 15thNight
31%11%15%25%13%2
2665
16th to endNight
31%10%17%28%10%2
2207
March1st to 15thNight
33%13%17%20%11%2
2440
16th to endNight
31%12%20%22%11%2
2378
April1st to 15thNight
33%12%19%22%11%1
2099
16th to endNight
22%8%17%30%17%3
2080
May1st to 15thNight
22%413%29%24%5%
1832
16th to endNight
33%8%15%22%15%4
1752
June1st to 15thNight
22%413%23%26%9%
1632
16th to endNight
13%25%18%36%23%
1560
July1st to 15thNight
9%2411%27%45%
1480
16th to endNight
8%2210%27%47%
1585
August1st to 15thNight
11%2414%24%41%
1746
16th to endNight
8%1213%32%41%
2070
September1st to 15thNight
10%2311%30%41%
1950
16th to endNight
12%26%23%30%23%
2099
October1st to 15thNight
19%38%26%27%14%
2340
16th to endNight
17%6%12%26%27%9%
2517
November1st to 15thNight
26%11%16%24%16%5%
2665
16th to endNight
24%11%18%26%15%3
2853
December1st to 15thNight
32%13%13%23%16%
2940
16th to endNight
37%10%15%20%14%1
3136

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
21%12%30%25%7%1
120
16th to endDay
15%17%24%28%12%
313
February1st to 15thDay
16%21%25%27%6%
330
16th to endDay
19%21%26%25%6%
342
March1st to 15thDay
22%24%27%16%8%1
390
16th to endDay
19%27%26%19%7%
416
April1st to 15thDay
21%26%26%18%5%
389
16th to endDay
15%24%26%19%11%2
378
May1st to 15thDay
12%21%30%23%10%1
408
16th to endDay
14%19%27%17%16%4
458
June1st to 15thDay
11%20%28%21%15%2
412
16th to endDay
418%31%25%15%5%
375
July1st to 15thDay
26%32%33%20%4
365
16th to endDay
18%29%32%19%7%
391
August1st to 15thDay
211%30%29%18%6%
359
16th to endDay
110%29%30%21%7%
396
September1st to 15thDay
210%29%35%19%3
375
16th to endDay
5%14%28%29%19%2
375
October1st to 15thDay
9%20%28%25%14%1
375
16th to endDay
10%14%20%30%20%3
377
November1st to 15thDay
7%14%24%26%23%3
180
16th to endDay
10%21%24%24%16%3
145
December1st to 15thDay
18%18%22%20%16%4
120
16th to endDay
9%17%27%22%21%1
128
January1st to 15thNight
8%10%18%37%20%4
840
16th to endNight
9%9%19%34%22%4
896
February1st to 15thNight
9%12%19%35%21%2
824
16th to endNight
12%14%17%36%16%2
736
March1st to 15thNight
8%16%22%29%19%4
840
16th to endNight
9%19%22%29%16%1
896
April1st to 15thNight
8%17%24%31%16%1
839
16th to endNight
6%14%20%28%23%5%
832
May1st to 15thNight
5%12%25%31%21%3
572
16th to endNight
7%7%21%32%27%2
439
June1st to 15thNight
46%18%36%30%2
408
16th to endNight
2412%46%33%1
390
July1st to 15thNight
15%46%43%1
370
16th to endNight
5%44%45%2
452
August1st to 15thNight
27%41%43%4
601
16th to endNight
1112%42%38%3
828
September1st to 15thNight
3210%33%44%7%
780
16th to endNight
35%13%32%34%9%
776
October1st to 15thNight
6%7%17%34%27%6%
780
16th to endNight
6%6%12%31%31%11%
832
November1st to 15thNight
7%7%17%39%22%5%
820
16th to endNight
5%13%19%32%22%5%
840
December1st to 15thNight
10%10%16%37%20%4
840
16th to endNight
10%15%21%35%16%1
896
Page generated at 2019-06-10 16:29:49. Version ac04

Copyright 2019 A. Danko


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