Hancock Field Station
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hancock Field Station clear sky chart from 2005-11-05 to

2017-09-12
.

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
57%
14652
18%
46799
17%
14628
60%
14628
27%
28898

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
40%
716
10%
2506
10%
716
43%
716
12%
1892
January16th to endNight
49%
768
14%
2654
14%
768
53%
768
17%
1832
February1st to 15thNight
49%
697
9%
2288
10%
697
51%
697
17%
1626
February16th to endNight
45%
632
16%
1933
15%
632
48%
632
21%
1302
March1st to 15thNight
47%
720
11%
2122
9%
720
49%
720
19%
1523
March16th to endNight
44%
768
12%
2022
7%
768
46%
768
22%
1442
April1st to 15thNight
47%
719
14%
1799
8%
719
49%
719
25%
1292
April16th to endNight
53%
662
18%
1742
11%
662
56%
662
32%
1135
May1st to 15thNight
62%
359
21%
1439
25%
359
66%
359
31%
727
May16th to endNight
61%
374
14%
1496
20%
374
65%
374
26%
839
June1st to 15thNight
61%
360
14%
1440
20%
360
65%
360
27%
782
June16th to endNight
67%
360
19%
1440
31%
360
71%
360
40%
643
July1st to 15thNight
85%
340
22%
1360
36%
340
88%
340
60%
478
July16th to endNight
88%
376
34%
1416
48%
354
91%
354
65%
477
August1st to 15thNight
87%
438
33%
1511
36%
436
88%
436
62%
585
August16th to endNight
82%
729
38%
1875
27%
729
83%
729
71%
870
September1st to 15thNight
83%
706
36%
1765
22%
706
84%
706
72%
832
September16th to endNight
74%
656
31%
1780
26%
656
76%
656
48%
962
October1st to 15thNight
62%
660
22%
1980
22%
660
65%
660
35%
1149
October16th to endNight
57%
704
18%
2196
20%
704
60%
704
27%
1391
November1st to 15thNight
51%
700
16%
2307
17%
700
52%
700
19%
1595
November16th to endNight
47%
720
10%
2520
11%
720
50%
720
17%
1744
December1st to 15thNight
45%
720
11%
2520
11%
720
47%
720
16%
1803
December16th to endNight
40%
768
10%
2688
9%
768
42%
768
14%
1977

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
7%6%35%5%35%45%6%45%
47881
Night
7%7%36%5%35%45%7%43%
46967
Cloud CoverDay
8%7%25%5%2445%6%45%
47881
Night
9%8%35%5%3445%7%42%
46971
TransparencyDay
37%311%23%16%6%
47552
Night
39%414%23%13%4
46800
SeeingDay
12%11%24%27%17%6%
5514
Night
12%412%41%24%3
14665

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
10%9%410%9%5%9%8%6%6%18%
1432
16th to endDay
10%10%7%8%6%35%6%6%7%27%
1569
February1st to 15thDay
8%11%410%6%5%6%5%6%7%27%
1576
16th to endDay
8%9%5%7%6%46%6%7%8%30%
1541
March1st to 15thDay
9%11%49%9%47%6%6%7%23%
1836
16th to endDay
9%11%48%9%46%5%5%8%24%
2200
April1st to 15thDay
9%10%48%7%45%6%6%6%29%
2149
16th to endDay
8%7%26%6%35%5%5%7%42%
2217
May1st to 15thDay
7%6%245%3446%6%48%
2511
16th to endDay
12%6%36%6%25%5%5%7%38%
2615
June1st to 15thDay
9%5%45%5%35%5%46%45%
2520
16th to endDay
6%313434345%59%
2520
July1st to 15thDay
112213335%73%
2520
16th to endDay
21121213477%
2657
August1st to 15thDay
1112212245%73%
2439
16th to endDay
221212235%75%
2327
September1st to 15thDay
21221122476%
2114
16th to endDay
7%313424446%55%
1846
October1st to 15thDay
10%7%26%6%3445%6%43%
1650
16th to endDay
10%8%26%6%35%45%6%40%
1675
November1st to 15thDay
11%9%37%7%36%6%7%8%28%
1551
16th to endDay
8%9%5%9%7%5%6%7%7%9%23%
1440
December1st to 15thDay
9%10%48%7%5%7%5%6%8%27%
1440
16th to endDay
13%12%5%10%7%46%5%7%7%19%
1536
January1st to 15thNight
8%10%5%9%11%5%7%5%6%6%21%
2506
16th to endNight
11%8%5%9%7%45%5%6%8%28%
2654
February1st to 15thNight
8%11%48%7%46%5%6%7%28%
2276
16th to endNight
9%9%37%7%35%5%6%7%34%
1933
March1st to 15thNight
9%9%48%7%47%5%6%9%28%
2122
16th to endNight
6%8%48%7%47%7%6%9%29%
2018
April1st to 15thNight
10%9%37%6%35%5%5%7%34%
1799
16th to endNight
6%8%25%5%35%45%6%46%
1742
May1st to 15thNight
6%426%44335%6%52%
1439
16th to endNight
8%5%35%4345%5%9%44%
1496
June1st to 15thNight
9%41442445%8%50%
1440
16th to endNight
5%313322346%62%
1440
July1st to 15thNight
11213445%73%
1440
16th to endNight
11332479%
1512
August1st to 15thNight
11221234474%
1519
16th to endNight
11211224477%
1875
September1st to 15thNight
1111132478%
1765
16th to endNight
5%213323446%60%
1780
October1st to 15thNight
7%6%36%42345%6%50%
1980
16th to endNight
9%7%27%6%345%6%6%41%
2196
November1st to 15thNight
9%10%37%6%46%5%6%8%29%
2307
16th to endNight
10%9%38%7%46%6%5%7%30%
2520
December1st to 15thNight
10%13%5%8%6%35%45%7%28%
2520
16th to endNight
9%12%5%10%9%45%5%6%7%21%
2688

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
12%11%5%8%8%48%6%7%9%17%
1432
16th to endDay
13%10%46%6%35%5%6%7%29%
1569
February1st to 15thDay
11%12%6%8%7%45%5%5%7%26%
1576
16th to endDay
11%10%5%7%5%45%6%6%7%29%
1541
March1st to 15thDay
10%13%5%9%7%46%5%5%7%23%
1836
16th to endDay
11%13%5%7%8%46%5%6%7%24%
2200
April1st to 15thDay
10%12%37%7%46%5%5%6%29%
2149
16th to endDay
10%8%25%5%35%45%6%42%
2217
May1st to 15thDay
8%6%25%425%35%6%48%
2511
16th to endDay
12%8%35%6%25%45%7%38%
2615
June1st to 15thDay
10%5%35%5%35%5%46%44%
2520
16th to endDay
7%313423346%58%
2520
July1st to 15thDay
212213235%74%
2520
16th to endDay
21111123477%
2657
August1st to 15thDay
112212335%74%
2439
16th to endDay
22111223476%
2327
September1st to 15thDay
21211222477%
2114
16th to endDay
8%413424446%54%
1846
October1st to 15thDay
10%6%25%7%24446%43%
1650
16th to endDay
12%7%36%5%3445%6%40%
1675
November1st to 15thDay
14%10%36%5%36%5%6%7%29%
1551
16th to endDay
11%11%49%6%35%5%7%9%22%
1440
December1st to 15thDay
11%13%37%6%37%5%6%7%27%
1440
16th to endDay
15%13%410%8%35%5%6%6%19%
1536
January1st to 15thNight
10%12%6%9%8%46%46%7%21%
2506
16th to endNight
13%9%47%7%35%46%7%28%
2654
February1st to 15thNight
11%12%38%7%45%5%6%7%28%
2276
16th to endNight
10%12%5%6%5%35%5%5%7%33%
1933
March1st to 15thNight
10%10%48%7%46%5%6%8%28%
2122
16th to endNight
8%10%47%6%45%6%7%9%28%
2022
April1st to 15thNight
12%9%46%5%3446%7%33%
1799
16th to endNight
8%9%24435%446%45%
1742
May1st to 15thNight
6%5%25%434346%53%
1439
16th to endNight
9%5%344245%5%9%43%
1496
June1st to 15thNight
9%424415%347%50%
1440
16th to endNight
6%412313346%62%
1440
July1st to 15thNight
21212446%72%
1440
16th to endNight
111124479%
1512
August1st to 15thNight
111212445%73%
1519
16th to endNight
11211213477%
1875
September1st to 15thNight
1111123478%
1765
16th to endNight
5%5%12323346%60%
1780
October1st to 15thNight
9%7%2442335%7%49%
1980
16th to endNight
12%7%35%5%3445%5%41%
2196
November1st to 15thNight
13%10%46%6%45%5%6%8%28%
2307
16th to endNight
12%11%37%6%35%5%6%7%29%
2520
December1st to 15thNight
12%14%47%5%35%5%47%28%
2520
16th to endNight
12%14%5%9%6%35%5%5%7%22%
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
58%7%13%16%4
1432
16th to endDay
51%417%17%6%1
1569
February1st to 15thDay
54%5%17%17%4
1576
16th to endDay
48%418%21%5%
1541
March1st to 15thDay
57%315%16%6%
1836
16th to endDay
56%414%20%4
2200
April1st to 15thDay
52%315%20%7%
2149
16th to endDay
40%416%27%10%1
2217
May1st to 15thDay
36%211%30%17%1
2511
16th to endDay
44%312%26%11%
2619
June1st to 15thDay
39%310%25%17%3
2520
16th to endDay
26%29%33%21%6%
2520
July1st to 15thDay
14%16%21%33%21%
2371
16th to endDay
12%1414%34%31%
2490
August1st to 15thDay
13%1426%33%20%
2422
16th to endDay
12%1430%36%15%
2327
September1st to 15thDay
13%1428%35%16%
2114
16th to endDay
29%310%28%21%6%
1846
October1st to 15thDay
40%213%24%16%2
1650
16th to endDay
42%316%24%12%
1675
November1st to 15thDay
49%6%14%22%6%
1551
16th to endDay
53%6%17%18%4
1440
December1st to 15thDay
52%8%14%19%5%
1440
16th to endDay
61%416%14%2
1536
January1st to 15thNight
58%6%15%15%3
2506
16th to endNight
51%416%18%7%1
2654
February1st to 15thNight
51%6%19%17%4
2288
16th to endNight
48%415%25%6%
1933
March1st to 15thNight
51%5%16%19%6%1
2122
16th to endNight
47%6%18%24%3
2022
April1st to 15thNight
47%416%23%7%
1799
16th to endNight
38%417%27%10%1
1742
May1st to 15thNight
31%215%31%17%1
1440
16th to endNight
36%420%27%10%
1496
June1st to 15thNight
33%5%14%29%14%2
1440
16th to endNight
23%212%37%17%5%
1440
July1st to 15thNight
11%210%27%28%19%
1360
16th to endNight
8%25%18%34%30%
1416
August1st to 15thNight
12%17%25%33%18%
1511
16th to endNight
10%17%30%36%13%
1875
September1st to 15thNight
10%18%30%33%15%
1765
16th to endNight
25%210%28%24%9%
1780
October1st to 15thNight
34%212%28%19%2
1980
16th to endNight
42%315%22%15%1
2196
November1st to 15thNight
50%5%14%22%7%
2307
16th to endNight
51%5%16%21%5%
2520
December1st to 15thNight
53%6%16%19%4
2520
16th to endNight
58%417%15%4
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
23%5%33%20%18%
60
16th to endDay
17%5%11%30%24%10%
97
February1st to 15thDay
17%5%15%31%21%7%
236
16th to endDay
18%12%25%25%16%1
231
March1st to 15thDay
23%17%27%22%7%1
270
16th to endDay
23%19%24%22%9%
288
April1st to 15thDay
18%14%26%23%11%6%
269
16th to endDay
17%19%27%22%9%4
270
May1st to 15thDay
19%12%27%25%12%3
288
16th to endDay
17%10%20%24%16%10%
330
June1st to 15thDay
12%14%26%24%13%7%
315
16th to endDay
9%15%24%26%18%6%
315
July1st to 15thDay
48%29%26%20%10%
305
16th to endDay
310%33%25%17%9%
327
August1st to 15thDay
5%8%27%28%19%10%
315
16th to endDay
48%21%27%25%12%
332
September1st to 15thDay
38%23%31%22%11%
300
16th to endDay
6%10%21%33%24%3
255
October1st to 15thDay
17%11%21%26%18%4
255
16th to endDay
15%6%20%31%18%6%
187
November1st to 15thDay
10%5%10%51%18%2
85
16th to endDay
13%11%21%30%20%3
60
December1st to 15thDay
20%10%18%31%20%
60
16th to endDay
14%110%43%26%3
64
January1st to 15thNight
17%5%15%36%21%2
720
16th to endNight
17%410%37%26%3
768
February1st to 15thNight
16%313%42%22%2
704
16th to endNight
16%6%16%40%18%1
632
March1st to 15thNight
14%8%13%44%16%1
720
16th to endNight
14%7%20%41%15%1
768
April1st to 15thNight
17%7%15%38%19%1
719
16th to endNight
13%7%18%35%20%3
662
May1st to 15thNight
9%316%45%23%1
360
16th to endNight
10%311%38%32%2
375
June1st to 15thNight
11%313%47%23%1
360
16th to endNight
7%313%48%25%1
360
July1st to 15thNight
29%45%39%2
340
16th to endNight
115%57%33%1
376
August1st to 15thNight
2342%43%7%
438
16th to endNight
119%41%36%7%
729
September1st to 15thNight
218%38%40%8%
706
16th to endNight
7%27%42%32%7%
656
October1st to 15thNight
11%210%44%25%4
660
16th to endNight
14%211%41%24%5%
704
November1st to 15thNight
16%5%9%49%18%1
700
16th to endNight
15%8%15%37%17%4
720
December1st to 15thNight
18%413%43%16%3
720
16th to endNight
18%5%17%41%16%1
768
Page generated at 2017-09-13 04:39:16. Version ac04

Copyright 2017 A. Danko


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