Hawk's Hollow Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hawk's Hollow Observatory clear sky chart from 2005-11-05 to 2017-09-23.

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
37%
16010
14%
46886
10%
15968
41%
15968
19%
33784

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
16%
900
6%
2506
3%
895
19%
895
8%
2160
January16th to endNight
20%
960
5%
2688
3%
960
21%
960
7%
2344
February1st to 15thNight
20%
725
8%
2208
4%
725
23%
725
9%
1809
February16th to endNight
24%
631
11%
1893
5%
631
30%
631
12%
1491
March1st to 15thNight
32%
720
15%
2142
10%
720
36%
720
19%
1528
March16th to endNight
35%
718
18%
2062
12%
718
41%
718
23%
1407
April1st to 15thNight
32%
539
12%
1797
9%
539
38%
539
18%
1258
April16th to endNight
37%
540
20%
1649
11%
540
46%
540
25%
1079
May1st to 15thNight
38%
540
14%
1620
9%
540
43%
540
21%
1113
May16th to endNight
46%
562
15%
1545
10%
561
50%
561
27%
1034
June1st to 15thNight
52%
540
15%
1440
10%
540
55%
540
33%
922
June16th to endNight
56%
540
14%
1440
10%
540
59%
540
31%
921
July1st to 15thNight
65%
510
16%
1360
12%
510
67%
510
42%
798
July16th to endNight
68%
564
20%
1417
16%
531
70%
531
39%
847
August1st to 15thNight
67%
539
22%
1587
17%
536
70%
536
38%
897
August16th to endNight
65%
573
21%
1836
20%
573
68%
573
32%
1071
September1st to 15thNight
63%
603
25%
1863
22%
603
66%
603
35%
1067
September16th to endNight
58%
689
22%
1903
17%
689
61%
689
34%
1175
October1st to 15thNight
47%
660
22%
1845
17%
660
51%
660
28%
1209
October16th to endNight
29%
704
13%
2288
9%
704
35%
704
15%
1647
November1st to 15thNight
35%
700
18%
2276
16%
700
40%
700
19%
1579
November16th to endNight
25%
720
9%
2340
7%
720
29%
720
10%
1855
December1st to 15thNight
15%
873
4%
2493
1%
873
16%
873
6%
2215
December16th to endNight
13%
960
6%
2688
1%
960
17%
960
7%
2358

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
14%9%46%6%3445%7%34%
48030
Night
15%10%47%6%34446%33%
47054
Cloud CoverDay
14%9%47%5%3445%7%33%
48039
Night
15%10%47%5%34446%33%
47059
TransparencyDay
48%6%12%20%10%1
47716
Night
51%5%11%19%10%1
46886
SeeingDay
16%7%26%26%15%6%
6006
Night
19%7%26%31%13%1
16014

By Month

Percentage Cloud Cover NE (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
17%14%7%12%11%5%6%435%12%
1432
16th to endDay
14%18%12%13%10%45%32310%
1536
February1st to 15thDay
12%15%8%12%11%45%43416%
1650
16th to endDay
14%13%7%11%8%35%5%5%420%
1580
March1st to 15thDay
15%10%48%6%35%5%5%7%27%
1808
16th to endDay
17%8%36%6%24447%34%
2172
April1st to 15thDay
20%12%45%423246%31%
2151
16th to endDay
16%7%25%5%3345%7%37%
2310
May1st to 15thDay
19%6%35%43336%7%36%
2331
16th to endDay
10%5%35%5%35%45%8%43%
2567
June1st to 15thDay
11%5%25%435%5%5%7%42%
2520
16th to endDay
9%425%5%35%5%5%9%43%
2520
July1st to 15thDay
6%415%425%5%7%9%48%
2520
16th to endDay
9%4145%245%7%9%45%
2655
August1st to 15thDay
9%415%5%345%7%10%41%
2364
16th to endDay
12%5%245%3445%9%43%
2365
September1st to 15thDay
12%5%245%2445%7%45%
2085
16th to endDay
11%5%35%425%5%5%8%41%
1894
October1st to 15thDay
17%7%26%5%34335%39%
1784
16th to endDay
25%8%35%6%45%44426%
1584
November1st to 15thDay
15%11%35%5%25%35%7%35%
1582
16th to endDay
21%17%48%5%35%346%19%
1620
December1st to 15thDay
16%20%9%13%6%34235%12%
1464
16th to endDay
20%21%9%11%6%2443412%
1536
January1st to 15thNight
20%15%8%11%8%3433415%
2506
16th to endNight
14%14%11%11%10%445%4414%
2688
February1st to 15thNight
13%17%8%10%9%44435%20%
2206
16th to endNight
15%14%5%9%7%35%445%23%
1893
March1st to 15thNight
15%10%36%5%24347%34%
2129
16th to endNight
15%6%45%5%24447%36%
2062
April1st to 15thNight
19%9%44435%35%6%33%
1797
16th to endNight
17%6%35%4235%5%5%41%
1649
May1st to 15thNight
18%6%25%6%345%5%6%36%
1620
16th to endNight
11%6%25%5%34448%41%
1543
June1st to 15thNight
9%425%5%235%5%9%45%
1440
16th to endNight
8%4245%35%5%7%9%42%
1440
July1st to 15thNight
6%32442445%8%53%
1440
16th to endNight
6%32443436%8%53%
1513
August1st to 15thNight
6%42332446%7%52%
1596
16th to endNight
10%425%423447%50%
1836
September1st to 15thNight
10%32342335%6%53%
1863
16th to endNight
9%5%245%24346%50%
1903
October1st to 15thNight
19%5%24322446%43%
1845
16th to endNight
23%8%36%5%2345%5%32%
2288
November1st to 15thNight
16%11%35%43445%6%35%
2276
16th to endNight
20%16%5%8%5%23446%20%
2340
December1st to 15thNight
20%20%9%11%7%3333412%
2493
16th to endNight
21%18%9%9%7%2333413%
2688

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
16%14%7%11%10%5%6%445%12%
1432
16th to endDay
14%18%11%13%11%4442410%
1536
February1st to 15thDay
12%15%9%13%10%4443416%
1650
16th to endDay
15%12%7%11%6%45%5%5%5%19%
1580
March1st to 15thDay
15%11%37%6%35%5%48%27%
1818
16th to endDay
17%9%36%6%24446%34%
2171
April1st to 15thDay
21%12%45%42325%6%31%
2151
16th to endDay
16%7%25%5%3445%6%37%
2310
May1st to 15thDay
19%6%25%5%24448%35%
2331
16th to endDay
10%6%25%5%35%45%8%43%
2567
June1st to 15thDay
10%5%35%435%5%48%42%
2520
16th to endDay
9%4245%35%5%5%10%42%
2520
July1st to 15thDay
6%4244246%7%9%47%
2520
16th to endDay
8%4144246%7%9%44%
2655
August1st to 15thDay
8%426%5%345%6%10%41%
2364
16th to endDay
12%415%5%3446%8%42%
2365
September1st to 15thDay
12%5%2443446%7%44%
2085
16th to endDay
11%5%25%5%25%46%9%41%
1894
October1st to 15thDay
17%7%26%5%34345%38%
1784
16th to endDay
24%8%37%5%35%445%26%
1584
November1st to 15thDay
15%11%26%5%34446%35%
1582
16th to endDay
20%17%5%8%5%34446%19%
1620
December1st to 15thDay
16%20%9%13%7%44235%12%
1464
16th to endDay
21%21%8%12%5%2433412%
1536
January1st to 15thNight
19%15%8%11%8%35%33415%
2506
16th to endNight
14%14%10%11%10%45%435%13%
2688
February1st to 15thNight
13%17%8%10%8%45%335%20%
2199
16th to endNight
15%14%5%10%6%35%5%45%23%
1893
March1st to 15thNight
16%10%46%5%34447%33%
2142
16th to endNight
15%6%45%6%24447%36%
2062
April1st to 15thNight
19%9%35%435%446%33%
1797
16th to endNight
16%7%344235%46%40%
1649
May1st to 15thNight
18%6%26%5%345%5%6%36%
1619
16th to endNight
11%6%36%5%3445%6%41%
1543
June1st to 15thNight
10%325%5%2445%8%45%
1440
16th to endNight
8%4345%35%5%7%9%42%
1440
July1st to 15thNight
6%225%42346%8%53%
1440
16th to endNight
5%41442435%9%53%
1513
August1st to 15thNight
6%4243245%6%7%52%
1596
16th to endNight
10%425%423446%50%
1836
September1st to 15thNight
10%414332446%54%
1863
16th to endNight
9%5%245%23346%50%
1903
October1st to 15thNight
18%6%24323346%43%
1845
16th to endNight
23%8%35%433445%32%
2288
November1st to 15thNight
16%11%36%42445%6%35%
2276
16th to endNight
20%15%5%7%5%34446%21%
2340
December1st to 15thNight
20%20%9%12%6%3423412%
2493
16th to endNight
22%18%9%10%6%3333413%
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
73%6%10%7%1
1433
16th to endDay
79%47%6%2
1536
February1st to 15thDay
71%5%7%13%2
1652
16th to endDay
64%6%11%12%4
1580
March1st to 15thDay
53%6%14%17%7%
1818
16th to endDay
49%5%13%23%6%1
2172
April1st to 15thDay
54%49%20%11%
2151
16th to endDay
44%5%14%17%14%3
2310
May1st to 15thDay
46%5%13%24%9%1
2331
16th to endDay
38%6%13%26%13%1
2571
June1st to 15thDay
38%6%12%25%16%
2520
16th to endDay
35%7%16%21%18%1
2520
July1st to 15thDay
30%6%13%27%17%2
2371
16th to endDay
32%7%14%25%17%2
2488
August1st to 15thDay
35%6%13%29%12%1
2349
16th to endDay
36%6%13%25%15%2
2365
September1st to 15thDay
36%5%12%27%15%1
2085
16th to endDay
38%5%13%26%15%
1894
October1st to 15thDay
48%49%23%12%1
1784
16th to endDay
58%5%14%15%5%
1584
November1st to 15thDay
49%6%11%20%11%1
1582
16th to endDay
66%5%10%13%3
1620
December1st to 15thDay
76%5%7%7%2
1464
16th to endDay
75%6%9%7%1
1536
January1st to 15thNight
73%48%9%3
2506
16th to endNight
73%6%10%6%2
2688
February1st to 15thNight
67%5%8%14%3
2208
16th to endNight
62%5%11%15%4
1893
March1st to 15thNight
50%5%13%19%9%1
2142
16th to endNight
46%413%24%9%2
2062
April1st to 15thNight
51%49%18%14%1
1797
16th to endNight
43%410%19%16%4
1649
May1st to 15thNight
47%5%11%20%11%2
1620
16th to endNight
41%6%11%22%15%2
1545
June1st to 15thNight
36%6%11%27%17%1
1440
16th to endNight
35%8%16%22%16%1
1440
July1st to 15thNight
27%6%13%28%20%3
1360
16th to endNight
29%6%14%25%20%2
1417
August1st to 15thNight
28%5%13%31%18%2
1587
16th to endNight
33%5%10%27%19%3
1836
September1st to 15thNight
30%6%11%29%19%2
1863
16th to endNight
34%412%30%16%
1903
October1st to 15thNight
41%5%10%25%15%1
1845
16th to endNight
54%5%13%18%8%
2288
November1st to 15thNight
49%5%11%19%12%1
2276
16th to endNight
64%6%11%14%2
2340
December1st to 15thNight
77%5%6%6%3
2493
16th to endNight
75%5%9%7%1
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
22%15%37%23%1
90
16th to endDay
29%7%34%22%5%1
96
February1st to 15thDay
18%30%34%13%3
90
16th to endDay
24%14%25%25%7%1
81
March1st to 15thDay
32%12%25%19%11%
108
16th to endDay
28%8%26%23%11%2
288
April1st to 15thDay
31%6%28%24%7%1
270
16th to endDay
21%8%31%20%12%5%
270
May1st to 15thDay
21%9%28%24%10%5%
288
16th to endDay
13%10%29%26%14%5%
467
June1st to 15thDay
12%6%31%30%13%5%
495
16th to endDay
11%7%33%29%12%5%
495
July1st to 15thDay
8%327%30%19%9%
475
16th to endDay
9%325%31%20%9%
515
August1st to 15thDay
9%217%24%27%18%
337
16th to endDay
17%313%29%22%13%
332
September1st to 15thDay
12%216%30%24%13%
315
16th to endDay
13%215%27%28%12%
283
October1st to 15thDay
15%11%22%26%20%3
249
16th to endDay
26%9%43%19%1
96
November1st to 15thDay
13%12%30%24%17%2
90
16th to endDay
32%12%36%10%8%
90
December1st to 15thDay
31%23%31%7%6%
90
16th to endDay
32%30%29%7%1
96
January1st to 15thNight
27%12%31%20%7%
900
16th to endNight
20%10%30%34%4
960
February1st to 15thNight
20%11%35%26%5%
728
16th to endNight
22%11%32%26%6%
631
March1st to 15thNight
22%9%30%28%8%
720
16th to endNight
17%9%31%30%9%1
718
April1st to 15thNight
22%7%32%30%6%
539
16th to endNight
20%6%32%30%8%1
540
May1st to 15thNight
19%5%29%35%9%
540
16th to endNight
14%327%36%18%1
563
June1st to 15thNight
11%326%40%17%
540
16th to endNight
10%224%43%17%1
540
July1st to 15thNight
7%117%45%25%2
510
16th to endNight
7%115%43%30%1
564
August1st to 15thNight
8%114%47%26%2
539
16th to endNight
11%213%37%30%4
573
September1st to 15thNight
12%315%37%24%5%
603
16th to endNight
12%418%32%26%5%
689
October1st to 15thNight
21%6%20%32%18%1
660
16th to endNight
28%10%28%23%9%
704
November1st to 15thNight
21%9%28%29%11%
700
16th to endNight
27%11%27%25%6%
720
December1st to 15thNight
30%11%30%23%4
873
16th to endNight
30%8%36%20%3
960
Page generated at 2017-09-24 09:15:47. Version ac04

Copyright 2017 A. Danko


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