Baker Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Baker 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
38%
18161
23%
53966
13%
18114
48%
18114
29%
33093

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
21%
1050
22%
2717
6%
1045
32%
1045
25%
1819
January16th to endNight
20%
1120
24%
2912
7%
1120
32%
1120
28%
1904
February1st to 15thNight
17%
1030
19%
2678
4%
1026
27%
1026
25%
1800
February16th to endNight
16%
754
21%
2224
4%
754
29%
754
22%
1458
March1st to 15thNight
22%
630
22%
2310
10%
630
36%
630
19%
1454
March16th to endNight
26%
672
15%
2464
10%
672
33%
672
17%
1645
April1st to 15thNight
31%
629
23%
2108
12%
629
47%
629
28%
1210
April16th to endNight
29%
624
20%
2078
11%
624
44%
624
24%
1301
May1st to 15thNight
39%
630
20%
1929
15%
630
47%
630
26%
1225
May16th to endNight
46%
659
18%
1865
14%
657
53%
657
30%
1196
June1st to 15thNight
64%
612
23%
1632
17%
612
67%
612
44%
932
June16th to endNight
65%
585
26%
1560
17%
585
70%
585
50%
844
July1st to 15thNight
70%
555
19%
1615
18%
555
72%
555
40%
929
July16th to endNight
78%
612
24%
1738
25%
579
82%
579
45%
918
August1st to 15thNight
75%
575
24%
1717
28%
572
76%
572
39%
980
August16th to endNight
72%
621
26%
2054
30%
621
76%
621
39%
1083
September1st to 15thNight
65%
585
29%
1950
30%
585
69%
585
33%
1096
September16th to endNight
60%
629
30%
2152
25%
629
67%
629
34%
1165
October1st to 15thNight
46%
780
28%
2340
18%
780
53%
780
35%
1362
October16th to endNight
38%
832
29%
2496
15%
832
51%
832
36%
1402
November1st to 15thNight
33%
820
29%
2499
14%
820
47%
820
32%
1470
November16th to endNight
27%
987
25%
2877
10%
987
40%
987
29%
1760
December1st to 15thNight
23%
1050
20%
2940
6%
1050
34%
1050
24%
1974
December16th to endNight
20%
1120
20%
3111
6%
1120
31%
1120
21%
2166

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
12%6%25%5%2445%7%42%
54527
Night
11%6%24423347%48%
54161
TransparencyDay
41%5%11%23%15%2
54227
Night
36%411%25%18%3
53966
SeeingDay
15%9%25%27%17%4
8083
Night
15%9%32%28%12%1
18161

By Month

Percentage Cloud Cover SE (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%7%35%5%23435%45%
1881
16th to endDay
10%7%46%413447%43%
2016
February1st to 15thDay
12%10%36%6%3445%6%36%
1845
16th to endDay
13%11%45%5%245%5%5%36%
1830
March1st to 15thDay
13%10%45%424336%39%
2310
16th to endDay
20%9%36%5%24445%32%
2462
April1st to 15thDay
13%8%26%5%24346%42%
2500
16th to endDay
17%9%35%5%245%45%36%
2487
May1st to 15thDay
18%6%25%425%45%6%37%
2680
16th to endDay
11%5%25%6%35%5%6%7%39%
2950
June1st to 15thDay
8%425%425%47%10%45%
2857
16th to endDay
5%313435%5%6%10%48%
2730
July1st to 15thDay
9%4245%35%5%6%10%41%
2581
16th to endDay
7%4245%36%6%8%9%41%
2674
August1st to 15thDay
8%425%5%36%5%6%9%42%
2486
16th to endDay
7%425%5%36%5%6%8%43%
2499
September1st to 15thDay
13%5%2433345%7%44%
2340
16th to endDay
9%6%25%6%345%46%46%
2121
October1st to 15thDay
14%6%2442343449%
1950
16th to endDay
11%5%25%422346%52%
2080
November1st to 15thDay
13%7%24413326%50%
2016
16th to endDay
14%7%34323236%48%
1739
December1st to 15thDay
14%8%35%413447%40%
1680
16th to endDay
12%11%5%7%5%23346%37%
1813
January1st to 15thNight
13%8%35%42335%5%43%
2717
16th to endNight
9%8%35%423445%46%
2912
February1st to 15thNight
13%8%35%423447%43%
2668
16th to endNight
15%7%26%424346%42%
2224
March1st to 15thNight
14%9%36%42434443%
2310
16th to endNight
17%8%35%5%24446%37%
2464
April1st to 15thNight
10%6%2323445%8%49%
2108
16th to endNight
15%7%24424447%42%
2078
May1st to 15thNight
13%425%423446%46%
1928
16th to endNight
11%4245%25%36%8%45%
1863
June1st to 15thNight
6%32332445%10%53%
1632
16th to endNight
411233335%9%61%
1560
July1st to 15thNight
6%3133345%7%9%51%
1705
16th to endNight
33133235%7%11%54%
1846
August1st to 15thNight
6%31443446%7%54%
1727
16th to endNight
5%31442345%8%56%
2054
September1st to 15thNight
11%414423346%53%
1950
16th to endNight
9%31433435%7%54%
2152
October1st to 15thNight
12%413323346%53%
2340
16th to endNight
12%5%13312346%54%
2496
November1st to 15thNight
12%6%24322346%52%
2499
16th to endNight
12%7%24323346%49%
2877
December1st to 15thNight
16%7%36%422348%40%
2940
16th to endNight
14%10%36%434346%38%
3111

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
41%310%24%18%1
1882
16th to endDay
41%5%12%25%13%2
2016
February1st to 15thDay
48%412%21%11%
1846
16th to endDay
49%49%20%12%3
1830
March1st to 15thDay
47%48%19%14%4
2310
16th to endDay
53%5%10%18%10%
2464
April1st to 15thDay
44%313%21%15%1
2500
16th to endDay
50%5%10%20%11%2
2487
May1st to 15thDay
47%5%13%21%11%
2680
16th to endDay
42%7%14%22%12%
2954
June1st to 15thDay
34%6%14%27%15%1
2857
16th to endDay
28%7%16%30%14%2
2730
July1st to 15thDay
37%7%14%26%11%2
2442
16th to endDay
34%7%15%27%13%1
2519
August1st to 15thDay
37%7%13%23%17%
2472
16th to endDay
37%6%12%21%15%5%
2499
September1st to 15thDay
38%6%10%22%17%5%
2340
16th to endDay
38%48%27%18%3
2121
October1st to 15thDay
38%48%23%19%5%
1950
16th to endDay
33%38%28%20%6%
2080
November1st to 15thDay
37%28%25%18%6%
2016
16th to endDay
39%38%23%23%1
1739
December1st to 15thDay
44%410%25%14%1
1680
16th to endDay
49%311%19%13%2
1813
January1st to 15thNight
42%39%24%17%1
2717
16th to endNight
39%311%25%16%2
2912
February1st to 15thNight
42%412%25%13%1
2678
16th to endNight
44%310%22%16%2
2224
March1st to 15thNight
45%38%20%17%4
2310
16th to endNight
48%6%9%22%12%1
2464
April1st to 15thNight
33%413%25%18%3
2108
16th to endNight
41%411%25%14%1
2078
May1st to 15thNight
39%5%11%25%16%1
1929
16th to endNight
37%7%16%24%12%2
1865
June1st to 15thNight
26%5%15%30%20%1
1632
16th to endNight
20%5%15%33%20%3
1560
July1st to 15thNight
27%6%15%29%17%4
1615
16th to endNight
21%7%15%37%18%
1738
August1st to 15thNight
28%6%12%32%18%1
1717
16th to endNight
25%6%14%27%20%5%
2054
September1st to 15thNight
32%49%26%20%6%
1950
16th to endNight
30%49%27%25%2
2152
October1st to 15thNight
32%49%24%22%6%
2340
16th to endNight
31%38%27%22%6%
2496
November1st to 15thNight
34%48%25%20%6%
2499
16th to endNight
37%47%26%22%2
2877
December1st to 15thNight
44%410%22%16%1
2940
16th to endNight
48%411%19%12%3
3111

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
25%17%38%15%2
180
16th to endDay
14%30%36%16%2
192
February1st to 15thDay
20%21%43%12%2
180
16th to endDay
28%26%30%11%2
159
March1st to 15thDay
25%22%36%14%1
180
16th to endDay
21%19%40%15%3
192
April1st to 15thDay
17%19%35%22%4
379
16th to endDay
23%12%34%18%8%
379
May1st to 15thDay
20%9%33%24%10%1
577
16th to endDay
16%8%31%24%13%4
677
June1st to 15thDay
9%319%36%25%6%
616
16th to endDay
8%226%39%18%4
570
July1st to 15thDay
12%212%34%28%8%
550
16th to endDay
9%110%32%35%11%
595
August1st to 15thDay
10%10%36%33%8%
549
16th to endDay
10%212%37%30%6%
411
September1st to 15thDay
14%110%30%33%10%
375
16th to endDay
13%22%29%22%10%
218
October1st to 15thDay
20%8%30%28%8%3
180
16th to endDay
11%12%33%33%7%1
192
November1st to 15thDay
22%11%30%24%10%1
180
16th to endDay
20%20%31%18%7%1
180
December1st to 15thDay
19%22%34%15%5%3
180
16th to endDay
15%27%39%13%4
192
January1st to 15thNight
19%18%37%18%5%
1050
16th to endNight
16%18%42%19%3
1120
February1st to 15thNight
18%16%44%18%1
1030
16th to endNight
20%17%42%17%1
754
March1st to 15thNight
21%13%39%21%3
630
16th to endNight
21%11%36%23%6%
672
April1st to 15thNight
14%13%38%27%5%
629
16th to endNight
19%9%39%24%6%
624
May1st to 15thNight
15%6%33%33%10%
630
16th to endNight
13%430%32%17%1
659
June1st to 15thNight
7%220%44%24%1
612
16th to endNight
5%123%45%23%1
585
July1st to 15thNight
7%16%44%27%4
555
16th to endNight
39%43%38%4
612
August1st to 15thNight
8%8%41%36%3
575
16th to endNight
8%13%43%29%5%
621
September1st to 15thNight
12%112%35%33%3
585
16th to endNight
12%218%39%22%4
629
October1st to 15thNight
14%5%31%28%16%3
780
16th to endNight
16%8%32%31%9%
832
November1st to 15thNight
16%10%37%26%9%
820
16th to endNight
17%13%38%20%8%
987
December1st to 15thNight
22%14%37%21%4
1050
16th to endNight
22%13%40%20%2
1120
Page generated at 2019-06-10 18:29:45. Version ac04

Copyright 2019 A. Danko


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