Homer
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Homer clear sky chart from 2005-11-05 to 2017-03-19.

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%
12930
6%
45221
5%
12899
40%
12899
11%
35124

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
36%
775
8%
3015
6%
771
39%
771
9%
2370
January16th to endNight
34%
800
9%
3011
6%
800
37%
800
8%
2429
February1st to 15thNight
34%
731
7%
2579
4%
729
37%
729
11%
1988
February16th to endNight
29%
533
10%
2086
5%
533
36%
533
10%
1593
March1st to 15thNight
35%
570
14%
2179
11%
570
43%
570
14%
1489
March16th to endNight
46%
551
9%
1890
10%
551
47%
551
12%
1437
April1st to 15thNight
41%
494
7%
1541
6%
494
42%
494
14%
1153
April16th to endNight
45%
495
2%
1320
1%
495
45%
495
15%
1031
May1st to 15thNight
51%
357
0%
1068
0%
357
51%
357
16%
785
May16th to endNight
52%
343
0%
1019
0%
342
52%
342
18%
745
June1st to 15thNight
45%
220
0%
715
0%
220
45%
220
12%
550
June16th to endNight
57%
165
0%
660
0%
165
57%
165
10%
499
July1st to 15thNight
51%
304
0%
769
0%
304
51%
304
15%
617
July16th to endNight
50%
348
0%
957
0%
326
50%
326
16%
712
August1st to 15thNight
35%
358
0%
1152
0%
356
35%
356
9%
933
August16th to endNight
44%
525
4%
1430
3%
525
45%
525
17%
1097
September1st to 15thNight
35%
495
3%
1622
3%
495
36%
495
9%
1325
September16th to endNight
39%
505
7%
1805
6%
505
41%
505
10%
1409
October1st to 15thNight
36%
550
8%
2005
10%
550
37%
550
10%
1569
October16th to endNight
38%
736
7%
2425
6%
736
39%
736
11%
1908
November1st to 15thNight
31%
730
5%
2633
3%
730
32%
730
7%
2136
November16th to endNight
36%
750
11%
2880
6%
750
41%
750
11%
2136
December1st to 15thNight
31%
763
6%
3064
5%
763
34%
763
8%
2469
December16th to endNight
28%
832
5%
3396
3%
832
30%
832
6%
2744

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
22%11%47%6%34445%25%
45663
Night
20%12%47%6%34345%26%
45334
TransparencyDay
59%10%14%11%4
45277
Night
59%9%12%12%5%
45226
SeeingDay
24%5%17%24%22%6%
7929
Night
21%7%17%25%20%7%
12935

By Month

Percentage Cloud Cover NW (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
18%13%5%8%7%2435%5%25%
922
16th to endDay
17%14%5%8%5%46%5%46%21%
1212
February1st to 15thDay
18%14%5%9%6%3443326%
1285
16th to endDay
15%14%38%7%3445%6%25%
1385
March1st to 15thDay
14%13%46%5%24335%36%
1781
16th to endDay
12%15%5%8%8%34445%28%
2059
April1st to 15thDay
15%15%5%9%6%45%34425%
2077
16th to endDay
15%14%5%8%8%45%445%23%
2310
May1st to 15thDay
19%13%5%7%5%3434427%
2553
16th to endDay
17%9%45%5%35%45%6%31%
2742
June1st to 15thDay
25%10%5%7%424435%25%
2912
16th to endDay
21%10%47%5%35%5%6%7%21%
2970
July1st to 15thDay
21%9%47%6%36%45%7%24%
2809
16th to endDay
30%6%24424346%30%
2833
August1st to 15thDay
34%7%25%5%34445%22%
2470
16th to endDay
28%8%36%5%34445%24%
2420
September1st to 15thDay
34%9%36%5%2445%6%15%
2008
16th to endDay
26%8%37%6%3446%424%
1824
October1st to 15thDay
29%12%35%5%23235%26%
1625
16th to endDay
19%14%38%7%345%3425%
1446
November1st to 15thDay
19%13%5%8%6%35%45%5%20%
1224
16th to endDay
16%12%47%6%4443429%
1080
December1st to 15thDay
21%13%5%7%6%45%44422%
891
16th to endDay
17%15%7%9%10%4342321%
825
January1st to 15thNight
16%13%48%7%45%34426%
3015
16th to endNight
18%16%5%8%7%44445%20%
3011
February1st to 15thNight
16%15%5%8%7%3433427%
2567
16th to endNight
15%14%49%7%33435%26%
2086
March1st to 15thNight
12%13%36%6%3433437%
2179
16th to endNight
12%15%48%7%35%45%5%27%
1890
April1st to 15thNight
16%15%5%6%5%24445%29%
1541
16th to endNight
14%13%5%7%5%36%45%5%28%
1320
May1st to 15thNight
19%11%35%424446%31%
1067
16th to endNight
16%10%5%7%42436%5%33%
1018
June1st to 15thNight
24%9%46%5%35%44426%
715
16th to endNight
19%8%346%7%6%7%5%6%24%
660
July1st to 15thNight
21%8%36%6%5%5%347%25%
819
16th to endNight
27%5%26%423448%31%
1028
August1st to 15thNight
32%8%36%6%33435%20%
1158
16th to endNight
27%8%25%43325%6%30%
1430
September1st to 15thNight
35%9%37%423235%22%
1622
16th to endNight
29%9%37%42433427%
1805
October1st to 15thNight
29%12%45%5%2233425%
2005
16th to endNight
20%13%47%6%4433427%
2425
November1st to 15thNight
18%13%49%7%35%35%5%21%
2633
16th to endNight
16%11%48%5%2436%5%30%
2880
December1st to 15thNight
22%13%5%8%5%3335%5%23%
3064
16th to endNight
17%16%6%8%8%34345%21%
3396

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
62%7%9%12%7%1
922
16th to endDay
63%9%10%8%6%1
1212
February1st to 15thDay
60%8%8%12%8%1
1285
16th to endDay
56%10%12%12%7%
1385
March1st to 15thDay
51%7%7%14%13%6%
1781
16th to endDay
57%10%10%11%8%1
2059
April1st to 15thDay
62%9%12%11%3
2077
16th to endDay
58%10%14%12%4
2310
May1st to 15thDay
59%7%14%14%4
2553
16th to endDay
50%9%18%17%4
2746
June1st to 15thDay
59%10%15%12%1
2912
16th to endDay
59%12%18%7%1
2970
July1st to 15thDay
58%12%19%9%
2630
16th to endDay
54%11%21%12%
2641
August1st to 15thDay
61%11%17%8%
2451
16th to endDay
62%8%14%11%3
2420
September1st to 15thDay
67%10%13%6%1
2008
16th to endDay
61%9%12%13%2
1824
October1st to 15thDay
61%8%11%15%3
1625
16th to endDay
60%10%11%10%6%
1446
November1st to 15thDay
64%11%10%8%4
1224
16th to endDay
57%9%10%14%6%1
1080
December1st to 15thDay
62%13%8%9%6%
891
16th to endDay
67%7%8%11%3
825
January1st to 15thNight
62%8%8%9%9%2
3015
16th to endNight
64%8%9%9%7%
3011
February1st to 15thNight
57%10%8%11%8%3
2579
16th to endNight
60%7%11%12%7%
2086
March1st to 15thNight
51%6%6%16%13%6%
2179
16th to endNight
58%7%9%14%8%1
1895
April1st to 15thNight
55%7%14%16%4
1541
16th to endNight
55%9%14%14%5%
1320
May1st to 15thNight
52%7%13%19%6%
1068
16th to endNight
50%8%16%18%4
1019
June1st to 15thNight
56%10%18%12%1
715
16th to endNight
54%12%23%7%1
660
July1st to 15thNight
54%14%20%10%
769
16th to endNight
52%9%26%10%
957
August1st to 15thNight
63%10%17%8%
1152
16th to endNight
54%8%20%13%3
1430
September1st to 15thNight
65%8%15%8%2
1622
16th to endNight
61%8%13%14%2
1805
October1st to 15thNight
62%7%12%12%5%
2005
16th to endNight
59%9%12%9%6%
2425
November1st to 15thNight
64%9%12%9%3
2633
16th to endNight
53%10%12%15%7%
2880
December1st to 15thNight
62%11%11%8%6%
3064
16th to endNight
64%10%9%11%4
3396

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
16%9%21%26%17%7%
210
16th to endDay
18%8%23%28%15%5%
224
February1st to 15thDay
19%6%25%25%11%11%
217
16th to endDay
19%12%26%23%14%4
211
March1st to 15thDay
15%7%31%20%19%5%
258
16th to endDay
17%6%16%30%21%7%
398
April1st to 15thDay
21%9%18%24%21%4
362
16th to endDay
17%8%21%25%24%2
375
May1st to 15thDay
25%7%15%25%21%4
393
16th to endDay
20%318%26%26%4
445
June1st to 15thDay
25%315%24%24%6%
585
16th to endDay
20%39%24%35%6%
585
July1st to 15thDay
22%111%21%32%9%
555
16th to endDay
26%313%25%22%8%
466
August1st to 15thDay
33%216%21%18%6%
419
16th to endDay
30%320%27%14%3
438
September1st to 15thDay
36%415%20%18%4
390
16th to endDay
30%5%12%20%23%8%
308
October1st to 15thDay
32%5%13%20%20%8%
225
16th to endDay
26%6%15%28%16%6%
240
November1st to 15thDay
24%10%21%21%14%7%
227
16th to endDay
21%10%20%22%20%4
210
December1st to 15thDay
22%6%24%23%16%8%
99
16th to endDay
21%13%20%24%13%6%
89
January1st to 15thNight
18%9%20%29%18%3
775
16th to endNight
18%8%20%31%18%3
800
February1st to 15thNight
18%8%24%25%16%6%
734
16th to endNight
19%8%24%25%16%4
533
March1st to 15thNight
14%8%27%28%15%5%
570
16th to endNight
16%5%13%25%25%13%
552
April1st to 15thNight
20%5%17%20%22%13%
494
16th to endNight
13%6%16%25%27%10%
495
May1st to 15thNight
19%38%22%31%13%
358
16th to endNight
19%37%23%34%11%
343
June1st to 15thNight
24%47%23%30%10%
220
16th to endNight
15%36%22%35%16%
165
July1st to 15thNight
23%3217%35%17%
304
16th to endNight
23%5%9%20%25%14%
348
August1st to 15thNight
34%29%23%20%9%
358
16th to endNight
28%311%23%23%9%
525
September1st to 15thNight
34%413%19%18%9%
495
16th to endNight
28%6%12%20%20%12%
505
October1st to 15thNight
31%412%22%22%5%
550
16th to endNight
24%6%15%25%19%8%
736
November1st to 15thNight
21%9%22%25%16%4
730
16th to endNight
19%10%22%27%16%3
750
December1st to 15thNight
20%9%20%26%15%6%
763
16th to endNight
21%10%23%26%15%2
832
Page generated at 2017-03-20 04:18:29. Version ac04

Copyright 2017 A. Danko


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