Poker Flat Research Range
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Poker Flat Research Range clear sky chart from 2005-11-05 to 2017-12-20.

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
53%
13807
8%
47750
7%
13794
54%
13794
16%
34312

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%
892
8%
3414
7%
892
54%
892
14%
2431
January16th to endNight
58%
824
11%
3352
11%
824
60%
824
15%
2294
February1st to 15thNight
58%
726
16%
2761
15%
726
60%
726
21%
1731
February16th to endNight
52%
659
13%
2212
13%
659
53%
659
16%
1578
March1st to 15thNight
53%
585
17%
2196
19%
585
57%
585
21%
1400
March16th to endNight
62%
582
15%
2011
14%
581
64%
581
26%
1211
April1st to 15thNight
54%
539
3%
1577
2%
539
55%
539
18%
1176
April16th to endNight
63%
502
0%
1276
0%
502
63%
502
30%
865
May1st to 15thNight
58%
254
0%
969
0%
254
58%
254
16%
663
May16th to endNight
60%
187
0%
664
0%
187
60%
187
21%
420
June1st to 15thNight
55%
180
0%
378
0%
180
55%
180
22%
306
June16th to endNight
61%
180
0%
360
0%
180
61%
180
25%
287
July1st to 15thNight
61%
170
0%
371
0%
170
61%
170
22%
287
July16th to endNight
48%
188
0%
711
0%
177
47%
177
9%
552
August1st to 15thNight
46%
336
0%
1053
0%
335
46%
335
10%
861
August16th to endNight
46%
556
0%
1449
0%
556
46%
556
16%
1135
September1st to 15thNight
56%
540
3%
1672
3%
540
56%
540
17%
1235
September16th to endNight
42%
542
4%
1959
5%
542
43%
542
9%
1524
October1st to 15thNight
45%
711
6%
2286
6%
711
46%
711
12%
1816
October16th to endNight
52%
816
7%
2777
7%
816
53%
816
15%
2048
November1st to 15thNight
49%
805
6%
3099
7%
805
49%
805
13%
2266
November16th to endNight
52%
912
12%
3494
13%
912
53%
912
14%
2480
December1st to 15thNight
48%
1065
9%
3778
9%
1065
50%
1065
13%
2816
December16th to endNight
52%
1056
6%
3931
5%
1056
52%
1056
12%
2930

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
13%9%47%7%46%5%5%7%28%
49206
Night
8%11%5%8%7%45%5%5%6%30%
47812
TransparencyDay
53%9%16%15%4
48768
Night
52%7%15%16%6%1
47755
SeeingDay
17%315%24%26%11%
9166
Night
13%211%29%31%11%
13822

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
5%11%7%11%9%28%35%5%29%
536
16th to endDay
38%5%8%7%47%7%8%8%30%
870
February1st to 15thDay
39%5%11%8%35%8%5%5%32%
1101
16th to endDay
310%7%10%8%36%6%6%6%29%
1262
March1st to 15thDay
38%6%7%7%47%5%5%5%37%
1764
16th to endDay
36%5%7%6%36%45%7%43%
2206
April1st to 15thDay
7%11%5%8%8%46%5%6%7%26%
2368
16th to endDay
47%36%6%46%6%6%8%39%
2682
May1st to 15thDay
7%10%5%8%8%5%6%5%5%7%29%
2982
16th to endDay
10%7%37%6%46%6%7%7%32%
3449
June1st to 15thDay
16%8%48%7%5%6%6%6%7%22%
3580
16th to endDay
17%6%25%5%36%5%6%9%30%
3600
July1st to 15thDay
19%7%36%6%36%5%6%9%25%
3564
16th to endDay
26%9%37%6%46%6%5%6%18%
3410
August1st to 15thDay
26%9%46%6%35%45%6%19%
2901
16th to endDay
23%9%47%6%4445%7%23%
2751
September1st to 15thDay
18%8%37%6%35%46%6%28%
2286
16th to endDay
21%15%47%6%35%5%4420%
2001
October1st to 15thDay
11%17%5%8%8%35%5%46%24%
1674
16th to endDay
10%13%49%5%345%6%6%29%
1445
November1st to 15thDay
6%12%5%10%11%6%7%5%5%5%25%
1089
16th to endDay
10%9%410%7%445%45%32%
783
December1st to 15thDay
8%15%7%7%7%35%447%29%
510
16th to endDay
312%7%9%7%5%48%7%7%26%
392
January1st to 15thNight
5%12%7%9%8%45%5%45%31%
3414
16th to endNight
410%6%8%6%47%6%5%6%31%
3352
February1st to 15thNight
27%5%10%7%345%5%6%40%
2749
16th to endNight
411%6%10%8%46%5%5%7%29%
2212
March1st to 15thNight
39%5%8%7%36%446%39%
2196
16th to endNight
310%45%5%35%5%5%7%44%
2011
April1st to 15thNight
6%12%47%7%47%6%7%7%28%
1577
16th to endNight
46%35%7%35%6%7%7%42%
1276
May1st to 15thNight
7%9%37%7%5%7%5%5%9%31%
968
16th to endNight
9%6%27%6%246%6%9%37%
664
June1st to 15thNight
13%428%8%5%7%5%10%6%26%
378
16th to endNight
15%328%5%5%5%5%8%8%31%
360
July1st to 15thNight
11%6%246%47%5%9%10%30%
393
16th to endNight
22%10%38%6%4445%6%25%
759
August1st to 15thNight
21%12%38%7%36%45%7%19%
1058
16th to endNight
23%9%36%6%3345%429%
1449
September1st to 15thNight
16%9%25%6%35%6%6%7%29%
1672
16th to endNight
18%12%47%6%35%5%6%6%23%
1959
October1st to 15thNight
13%16%47%6%36%5%5%5%24%
2286
16th to endNight
10%14%5%7%7%3445%6%31%
2777
November1st to 15thNight
6%13%6%11%8%45%45%6%28%
3099
16th to endNight
8%12%49%7%3445%5%31%
3494
December1st to 15thNight
7%13%6%10%7%36%45%5%28%
3778
16th to endNight
411%6%10%8%5%7%7%6%6%25%
3931

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
56%5%11%16%7%2
536
16th to endDay
48%7%18%16%8%
870
February1st to 15thDay
50%6%8%19%12%2
1101
16th to endDay
50%7%12%17%10%1
1262
March1st to 15thDay
45%6%13%20%11%3
1764
16th to endDay
38%7%19%19%13%2
2206
April1st to 15thDay
54%7%15%20%2
2368
16th to endDay
39%8%18%26%5%
2682
May1st to 15thDay
51%8%13%23%3
2982
16th to endDay
46%9%16%20%7%
3453
June1st to 15thDay
59%9%14%14%2
3580
16th to endDay
49%11%19%17%2
3600
July1st to 15thDay
53%12%20%11%1
3357
16th to endDay
64%12%16%7%
3195
August1st to 15thDay
62%11%19%6%
2881
16th to endDay
59%10%18%10%
2751
September1st to 15thDay
54%9%23%11%1
2286
16th to endDay
64%10%12%11%1
2001
October1st to 15thDay
59%10%16%9%4
1674
16th to endDay
53%8%22%15%
1445
November1st to 15thDay
59%7%16%13%2
1089
16th to endDay
52%8%11%19%7%
783
December1st to 15thDay
54%9%15%13%6%1
510
16th to endDay
52%9%22%11%4
392
January1st to 15thNight
53%7%13%16%5%3
3414
16th to endNight
50%6%15%19%6%1
3352
February1st to 15thNight
43%5%10%23%14%3
2761
16th to endNight
53%5%12%16%10%1
2212
March1st to 15thNight
45%410%23%11%4
2196
16th to endNight
38%5%15%21%16%2
2016
April1st to 15thNight
52%8%14%22%2
1577
16th to endNight
38%8%22%21%8%
1276
May1st to 15thNight
49%7%15%24%2
969
16th to endNight
42%7%17%24%9%
664
June1st to 15thNight
53%8%16%18%2
378
16th to endNight
47%12%19%18%2
360
July1st to 15thNight
46%13%25%11%2
371
16th to endNight
59%11%20%9%
711
August1st to 15thNight
63%9%18%8%
1053
16th to endNight
56%8%21%12%
1449
September1st to 15thNight
50%10%22%15%1
1672
16th to endNight
60%9%14%13%1
1959
October1st to 15thNight
59%9%17%9%3
2286
16th to endNight
53%8%20%14%2
2777
November1st to 15thNight
56%6%17%17%1
3099
16th to endNight
53%6%12%19%7%
3494
December1st to 15thNight
56%7%14%14%6%1
3778
16th to endNight
56%8%18%11%4
3931

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
6%36%46%20%16%
30
16th to endDay
6%438%29%20%
86
February1st to 15thDay
6%29%25%28%28%
209
16th to endDay
7%318%34%27%9%
211
March1st to 15thDay
8%419%28%26%13%
240
16th to endDay
6%217%29%30%13%
386
April1st to 15thDay
12%5%19%28%25%8%
443
16th to endDay
4423%33%27%6%
450
May1st to 15thDay
11%5%18%25%29%9%
474
16th to endDay
12%6%18%29%24%8%
789
June1st to 15thDay
17%319%27%24%7%
855
16th to endDay
18%29%21%31%16%
855
July1st to 15thDay
19%110%23%31%13%
812
16th to endDay
25%316%20%21%12%
700
August1st to 15thDay
25%414%21%24%9%
494
16th to endDay
29%316%18%24%7%
523
September1st to 15thDay
22%5%13%21%24%12%
475
16th to endDay
30%8%17%20%16%7%
309
October1st to 15thDay
23%6%16%15%17%20%
270
16th to endDay
18%28%21%28%20%
288
November1st to 15thDay
17%17%31%26%14%
141
16th to endDay
8%6%26%37%20%
45
December1st to 15thDay
17%8%26%28%17%
45
16th to endDay
16%8%8%27%25%13%
36
January1st to 15thNight
9%211%32%31%12%
897
16th to endNight
8%311%38%30%9%
824
February1st to 15thNight
5%113%30%35%13%
734
16th to endNight
9%413%39%27%5%
659
March1st to 15thNight
8%416%35%29%5%
585
16th to endNight
8%113%30%33%12%
582
April1st to 15thNight
11%215%29%33%7%
539
16th to endNight
6%114%29%39%8%
502
May1st to 15thNight
12%39%27%38%9%
255
16th to endNight
13%48%31%34%7%
188
June1st to 15thNight
13%311%31%33%6%
180
16th to endNight
17%15%22%42%11%
180
July1st to 15thNight
12%111%21%41%11%
170
16th to endNight
24%27%26%29%9%
188
August1st to 15thNight
29%25%21%34%7%
336
16th to endNight
28%110%16%29%13%
556
September1st to 15thNight
20%29%22%29%14%
540
16th to endNight
26%412%21%30%4
542
October1st to 15thNight
22%410%24%28%9%
711
16th to endNight
15%18%28%31%14%
816
November1st to 15thNight
15%210%32%26%12%
805
16th to endNight
14%210%26%31%14%
912
December1st to 15thNight
12%410%31%27%12%
1065
16th to endNight
9%210%28%34%14%
1056
Page generated at 2017-12-21 03:04:53. Version ac04

Copyright 2017 A. Danko


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