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 2017-09-21.

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%
15077
25%
46912
22%
15049
64%
15049
37%
25684

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%
716
17%
2506
16%
716
57%
716
25%
1538
January16th to endNight
53%
768
21%
2529
22%
768
56%
768
26%
1554
February1st to 15thNight
51%
696
18%
2277
17%
696
56%
696
25%
1397
February16th to endNight
49%
632
21%
1895
18%
632
54%
632
27%
1182
March1st to 15thNight
47%
720
14%
2091
12%
720
51%
720
25%
1349
March16th to endNight
43%
768
17%
2038
11%
768
47%
768
28%
1311
April1st to 15thNight
44%
719
17%
1799
7%
719
49%
719
29%
1186
April16th to endNight
53%
720
22%
1800
10%
720
57%
720
41%
1058
May1st to 15thNight
51%
488
26%
1568
18%
488
58%
488
40%
783
May16th to endNight
58%
374
18%
1496
19%
374
62%
374
27%
801
June1st to 15thNight
64%
360
22%
1440
27%
360
70%
360
35%
670
June16th to endNight
77%
360
31%
1440
43%
360
82%
360
52%
550
July1st to 15thNight
87%
340
32%
1360
44%
340
90%
340
65%
453
July16th to endNight
88%
417
40%
1454
46%
392
90%
392
68%
508
August1st to 15thNight
85%
563
36%
1636
29%
560
86%
560
65%
719
August16th to endNight
81%
764
43%
1910
28%
764
82%
764
76%
893
September1st to 15thNight
82%
720
40%
1800
27%
720
84%
720
71%
858
September16th to endNight
72%
680
41%
1836
32%
680
78%
680
64%
853
October1st to 15thNight
64%
660
29%
1980
26%
660
72%
660
47%
993
October16th to endNight
66%
704
30%
2129
30%
704
72%
704
45%
1086
November1st to 15thNight
62%
700
21%
2275
21%
700
66%
700
31%
1301
November16th to endNight
56%
720
20%
2445
19%
720
61%
720
33%
1315
December1st to 15thNight
51%
720
18%
2520
16%
720
57%
720
23%
1564
December16th to endNight
42%
768
19%
2688
16%
768
49%
768
19%
1762

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%6%57%
47963
Night
232442445%8%56%
47088
TransparencyDay
26%5%11%20%20%15%
47638
Night
25%7%13%22%19%12%
46913
SeeingDay
11%18%28%25%13%2
5769
Night
7%9%17%34%26%4
15091

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%26%7%36%7%8%8%39%
1432
16th to endDay
38%45%5%45%6%7%9%38%
1695
February1st to 15thDay
3436%5%35%6%9%9%41%
1587
16th to endDay
37%48%6%46%6%6%8%38%
1579
March1st to 15thDay
37%27%6%47%6%6%9%38%
1866
16th to endDay
27%37%7%35%5%6%7%41%
2185
April1st to 15thDay
48%47%5%35%6%6%7%40%
2149
16th to endDay
5%6%24434347%53%
2160
May1st to 15thDay
3214423446%61%
2376
16th to endDay
6%6%36%6%34446%47%
2615
June1st to 15thDay
332443445%6%57%
2520
16th to endDay
111221222476%
2520
July1st to 15thDay
121223478%
2520
16th to endDay
1111222480%
2615
August1st to 15thDay
111112235%78%
2313
16th to endDay
11122286%
2292
September1st to 15thDay
11212235%77%
2160
16th to endDay
222212237%72%
1913
October1st to 15thDay
3224324345%63%
1650
16th to endDay
33145%23448%57%
1741
November1st to 15thDay
4325%436%6%6%9%47%
1584
16th to endDay
2424436%7%6%8%48%
1515
December1st to 15thDay
36%35%6%26%6%9%9%39%
1440
16th to endDay
27%48%8%48%7%6%9%32%
1536
January1st to 15thNight
35%35%6%36%6%7%9%42%
2506
16th to endNight
47%25%5%46%5%6%8%43%
2529
February1st to 15thNight
35%25%346%6%7%11%43%
2265
16th to endNight
36%245%36%6%7%8%45%
1895
March1st to 15thNight
2425%5%37%6%7%11%42%
2091
16th to endNight
25%245%35%6%7%8%47%
2038
April1st to 15thNight
35%35%6%46%6%5%11%41%
1799
16th to endNight
342332445%8%58%
1800
May1st to 15thNight
3314323348%61%
1568
16th to endNight
5%425%5%25%5%5%6%52%
1496
June1st to 15thNight
3324323436%61%
1440
16th to endNight
11232322376%
1440
July1st to 15thNight
1111223479%
1440
16th to endNight
1111121482%
1553
August1st to 15thNight
211221234476%
1645
16th to endNight
1111222382%
1910
September1st to 15thNight
21112135%79%
1800
16th to endNight
2212111235%76%
1836
October1st to 15thNight
4313322335%65%
1980
16th to endNight
321322346%7%62%
2129
November1st to 15thNight
5%3144345%6%10%50%
2275
16th to endNight
1223435%5%7%11%52%
2445
December1st to 15thNight
35%25%426%6%7%11%44%
2520
16th to endNight
36%36%6%46%6%7%11%36%
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
37%11%17%24%9%
1432
16th to endDay
39%10%14%18%13%3
1695
February1st to 15thDay
33%11%17%23%12%
1587
16th to endDay
41%7%14%26%7%1
1579
March1st to 15thDay
40%9%14%21%12%2
1866
16th to endDay
39%8%19%19%10%3
2185
April1st to 15thDay
39%7%14%22%14%
2149
16th to endDay
31%5%13%27%18%3
2160
May1st to 15thDay
22%411%26%28%6%
2376
16th to endDay
37%410%23%20%4
2619
June1st to 15thDay
26%5%10%18%26%12%
2520
16th to endDay
12%25%16%37%26%
2520
July1st to 15thDay
9%2411%23%48%
2371
16th to endDay
9%2210%20%54%
2451
August1st to 15thDay
10%15%13%24%44%
2297
16th to endDay
6%1312%32%44%
2292
September1st to 15thDay
10%15%12%31%37%
2160
16th to endDay
14%27%26%30%19%
1913
October1st to 15thDay
23%48%27%28%8%
1650
16th to endDay
25%5%13%24%22%7%
1741
November1st to 15thDay
30%7%18%25%13%4
1584
16th to endDay
30%10%17%23%16%2
1515
December1st to 15thDay
36%11%17%23%11%
1440
16th to endDay
45%11%13%17%10%
1536
January1st to 15thNight
36%8%18%24%10%
2506
16th to endNight
36%8%14%21%13%6%
2529
February1st to 15thNight
31%12%15%23%13%2
2277
16th to endNight
33%9%16%27%9%2
1895
March1st to 15thNight
31%14%18%19%13%2
2091
16th to endNight
30%13%20%21%11%2
2038
April1st to 15thNight
33%10%19%23%11%1
1799
16th to endNight
23%8%17%28%17%4
1800
May1st to 15thNight
23%412%27%25%6%
1569
16th to endNight
30%7%15%24%18%4
1496
June1st to 15thNight
24%5%13%21%25%10%
1440
16th to endNight
14%35%17%36%22%
1440
July1st to 15thNight
9%2312%26%45%
1360
16th to endNight
8%229%24%51%
1454
August1st to 15thNight
12%3415%24%40%
1636
16th to endNight
9%1313%30%42%
1910
September1st to 15thNight
10%2411%31%39%
1800
16th to endNight
12%26%24%30%22%
1836
October1st to 15thNight
21%39%27%26%11%
1980
16th to endNight
19%6%13%28%24%7%
2129
November1st to 15thNight
27%10%17%24%14%5%
2275
16th to endNight
23%10%18%28%15%3
2445
December1st to 15thNight
32%13%14%24%14%
2520
16th to endNight
39%11%14%19%14%
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
26%15%36%20%1
60
16th to endDay
17%17%27%24%12%
223
February1st to 15thDay
15%20%26%30%7%
238
16th to endDay
21%18%26%25%7%
238
March1st to 15thDay
21%25%27%15%8%1
270
16th to endDay
20%29%26%17%5%
288
April1st to 15thDay
18%27%26%20%5%1
269
16th to endDay
19%26%28%16%8%
270
May1st to 15thDay
13%23%31%22%5%2
288
16th to endDay
13%20%27%18%16%3
330
June1st to 15thDay
13%21%29%20%12%2
315
16th to endDay
418%30%25%14%6%
315
July1st to 15thDay
26%33%34%19%4
305
16th to endDay
19%33%33%14%7%
327
August1st to 15thDay
212%32%30%15%6%
315
16th to endDay
111%29%30%19%8%
332
September1st to 15thDay
29%27%34%20%4
315
16th to endDay
6%18%26%27%18%2
276
October1st to 15thDay
10%19%25%25%16%2
255
16th to endDay
15%18%24%27%13%
253
November1st to 15thDay
8%8%18%25%33%4
90
16th to endDay
9%27%24%24%10%2
73
December1st to 15thDay
23%26%26%18%5%
60
16th to endDay
9%21%25%26%15%1
64
January1st to 15thNight
8%9%18%36%20%5%
720
16th to endNight
10%8%20%32%23%5%
768
February1st to 15thNight
9%12%19%34%21%2
704
16th to endNight
12%15%15%36%17%2
632
March1st to 15thNight
8%16%21%29%18%4
720
16th to endNight
10%20%22%28%17%1
768
April1st to 15thNight
8%17%23%32%16%1
719
16th to endNight
7%15%21%29%20%5%
720
May1st to 15thNight
5%12%26%31%19%3
489
16th to endNight
6%7%22%31%29%2
375
June1st to 15thNight
5%6%19%37%28%2
360
16th to endNight
1412%45%34%1
360
July1st to 15thNight
25%44%45%2
340
16th to endNight
6%45%43%2
417
August1st to 15thNight
27%42%41%4
563
16th to endNight
1112%43%37%3
764
September1st to 15thNight
3210%31%45%7%
720
16th to endNight
45%14%30%34%10%
680
October1st to 15thNight
7%6%17%32%28%7%
660
16th to endNight
7%6%14%30%28%10%
704
November1st to 15thNight
7%7%17%39%22%6%
700
16th to endNight
5%13%20%32%22%5%
720
December1st to 15thNight
11%11%18%35%19%4
720
16th to endNight
11%17%21%32%16%1
768
Page generated at 2017-09-22 04:35:31. Version ac04

Copyright 2017 A. Danko


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