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 2017-10-06.

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%
13419
6%
46699
5%
13388
40%
13388
11%
36299

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
48%
591
12%
2014
13%
591
49%
591
14%
1493
April1st to 15thNight
41%
539
7%
1680
5%
539
42%
539
14%
1259
April16th to endNight
44%
540
2%
1440
1%
540
44%
540
15%
1125
May1st to 15thNight
51%
389
0%
1164
0%
389
51%
389
16%
860
May16th to endNight
51%
375
0%
1114
0%
374
51%
374
18%
817
June1st to 15thNight
45%
240
0%
780
0%
240
45%
240
12%
602
June16th to endNight
57%
180
0%
720
0%
180
57%
180
11%
541
July1st to 15thNight
51%
334
0%
844
0%
334
51%
334
15%
675
July16th to endNight
50%
376
0%
1039
0%
354
50%
354
16%
776
August1st to 15thNight
36%
391
0%
1258
0%
389
37%
389
8%
1028
August16th to endNight
42%
573
4%
1561
3%
573
43%
573
16%
1219
September1st to 15thNight
35%
540
3%
1770
3%
540
36%
540
9%
1458
September16th to endNight
39%
557
7%
1970
6%
557
41%
557
10%
1551
October1st to 15thNight
36%
574
8%
2077
10%
574
36%
574
10%
1633
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%
48564
Night
20%12%47%6%34345%26%
46812
TransparencyDay
59%9%14%11%4
48178
Night
59%9%12%12%5%
46704
SeeingDay
25%5%16%23%22%6%
8896
Night
22%6%16%25%20%7%
13424

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
11%15%5%7%7%2444430%
2205
April1st to 15thDay
15%15%49%6%45%34426%
2268
16th to endDay
16%14%5%8%8%35%445%23%
2520
May1st to 15thDay
19%13%5%7%5%3434427%
2787
16th to endDay
18%9%45%5%35%45%6%30%
2999
June1st to 15thDay
25%10%5%7%5%34435%25%
3177
16th to endDay
22%9%46%5%35%5%6%7%21%
3240
July1st to 15thDay
21%9%47%6%36%45%7%24%
3064
16th to endDay
29%6%24424346%29%
3059
August1st to 15thDay
33%8%35%5%34445%21%
2694
16th to endDay
30%8%36%5%34445%23%
2641
September1st to 15thDay
35%10%46%5%3445%6%14%
2190
16th to endDay
27%9%37%6%3445%5%23%
1989
October1st to 15thDay
29%12%35%5%23235%25%
1680
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
11%14%47%6%35%45%5%30%
2014
April1st to 15thNight
16%16%5%6%5%23435%29%
1680
16th to endNight
14%13%5%7%6%36%45%5%27%
1440
May1st to 15thNight
18%11%36%5%34446%31%
1163
16th to endNight
16%11%5%7%42336%5%32%
1113
June1st to 15thNight
23%9%47%5%35%445%26%
780
16th to endNight
20%8%35%5%6%6%6%5%6%25%
720
July1st to 15thNight
21%9%36%6%5%5%347%26%
894
16th to endNight
28%5%26%32335%8%31%
1110
August1st to 15thNight
32%8%37%6%43435%20%
1264
16th to endNight
29%8%25%43325%6%28%
1561
September1st to 15thNight
35%9%37%433335%21%
1770
16th to endNight
29%9%46%42333326%
1970
October1st to 15thNight
30%12%45%5%2233425%
2077
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
55%9%10%11%11%2
2205
April1st to 15thDay
61%9%12%11%5%
2268
16th to endDay
59%10%14%12%3
2520
May1st to 15thDay
58%7%14%14%5%
2787
16th to endDay
51%9%17%17%3
3003
June1st to 15thDay
59%10%15%12%1
3177
16th to endDay
59%12%18%8%1
3240
July1st to 15thDay
58%12%20%8%
2885
16th to endDay
54%11%20%12%
2867
August1st to 15thDay
62%11%17%7%
2675
16th to endDay
63%8%13%10%3
2641
September1st to 15thDay
68%10%12%6%1
2190
16th to endDay
62%8%13%12%2
1989
October1st to 15thDay
61%8%11%14%3
1680
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
55%7%9%13%11%1
2019
April1st to 15thNight
55%7%14%15%6%
1680
16th to endNight
56%9%14%14%5%
1440
May1st to 15thNight
53%7%12%19%6%
1164
16th to endNight
51%8%15%19%4
1114
June1st to 15thNight
56%10%18%12%1
780
16th to endNight
54%11%23%8%1
720
July1st to 15thNight
54%13%21%10%
844
16th to endNight
52%9%26%10%
1039
August1st to 15thNight
63%11%16%8%
1258
16th to endNight
57%8%19%12%2
1561
September1st to 15thNight
66%7%15%7%2
1770
16th to endNight
61%8%13%14%2
1970
October1st to 15thNight
63%6%12%12%4
2077
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
16%5%16%29%22%9%
448
April1st to 15thDay
22%8%17%25%19%5%
425
16th to endDay
20%7%18%22%25%4
450
May1st to 15thDay
25%7%14%26%21%5%
468
16th to endDay
22%218%26%26%4
526
June1st to 15thDay
26%314%23%24%8%
675
16th to endDay
22%28%22%35%7%
675
July1st to 15thDay
24%110%22%32%9%
645
16th to endDay
27%312%23%24%9%
538
August1st to 15thDay
34%215%22%19%6%
494
16th to endDay
33%318%25%15%3
515
September1st to 15thDay
38%315%19%17%5%
450
16th to endDay
32%5%11%21%21%7%
360
October1st to 15thDay
31%5%14%21%19%7%
242
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%412%26%25%14%
592
April1st to 15thNight
20%5%17%21%21%14%
539
16th to endNight
15%6%15%23%28%10%
540
May1st to 15thNight
19%48%22%32%13%
390
16th to endNight
20%38%24%33%10%
375
June1st to 15thNight
24%47%21%30%12%
240
16th to endNight
17%35%21%35%16%
180
July1st to 15thNight
24%2217%34%17%
334
16th to endNight
25%48%19%25%16%
376
August1st to 15thNight
32%29%24%20%9%
391
16th to endNight
31%210%23%22%8%
573
September1st to 15thNight
35%412%19%18%9%
540
16th to endNight
29%6%11%21%20%11%
557
October1st to 15thNight
32%412%22%22%5%
574
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 2017-10-07 10:07:48. Version ac04

Copyright 2017 A. Danko


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