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 2017-04-25.

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%
15550
14%
45572
10%
15508
40%
15508
19%
33009

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
38%
525
21%
1604
12%
525
47%
525
26%
1039
May1st to 15thNight
38%
495
15%
1485
9%
495
44%
495
20%
1031
May16th to endNight
48%
514
14%
1413
10%
513
52%
513
28%
943
June1st to 15thNight
51%
495
15%
1320
11%
495
55%
495
31%
866
June16th to endNight
57%
495
13%
1320
9%
495
59%
495
31%
849
July1st to 15thNight
65%
465
17%
1240
13%
465
66%
465
42%
725
July16th to endNight
68%
522
18%
1305
15%
489
69%
489
38%
787
August1st to 15thNight
66%
494
24%
1454
18%
491
70%
491
38%
820
August16th to endNight
66%
525
20%
1682
19%
525
69%
525
33%
977
September1st to 15thNight
62%
553
25%
1708
23%
553
66%
553
34%
986
September16th to endNight
57%
657
21%
1815
16%
657
60%
657
34%
1126
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%47%6%3445%7%33%
46074
Night
15%10%5%7%6%34446%32%
45740
Cloud CoverDay
14%9%47%5%3445%7%33%
46083
Night
15%10%47%5%34446%32%
45745
TransparencyDay
49%6%12%20%10%1
45760
Night
52%5%11%18%10%1
45572
SeeingDay
17%7%26%25%15%6%
5340
Night
19%7%27%31%12%1
15554

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%38%
2243
May1st to 15thDay
20%5%36%43336%7%35%
2136
16th to endDay
10%5%25%5%35%45%8%43%
2347
June1st to 15thDay
12%5%25%436%5%47%40%
2310
16th to endDay
9%425%5%35%45%9%43%
2310
July1st to 15thDay
6%415%4245%7%9%48%
2310
16th to endDay
9%4145%245%7%10%44%
2459
August1st to 15thDay
9%415%5%3446%10%42%
2167
16th to endDay
12%5%245%3445%9%43%
2167
September1st to 15thDay
12%5%245%2446%7%43%
1911
16th to endDay
12%5%345%25%5%5%8%40%
1815
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
16%6%25%3235%5%5%42%
1604
May1st to 15thNight
18%6%25%6%345%5%6%35%
1485
16th to endNight
11%6%25%5%34448%41%
1411
June1st to 15thNight
10%5%25%6%235%5%9%42%
1320
16th to endNight
8%4346%35%5%7%9%42%
1320
July1st to 15thNight
6%31442445%8%53%
1320
16th to endNight
6%32443436%8%52%
1401
August1st to 15thNight
6%42332446%7%53%
1463
16th to endNight
10%415%423347%50%
1682
September1st to 15thNight
11%323423346%53%
1708
16th to endNight
10%5%245%23346%50%
1815
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%2445%6%38%
2243
May1st to 15thDay
19%6%26%5%24448%34%
2136
16th to endDay
10%6%245%35%45%8%43%
2347
June1st to 15thDay
11%6%35%5%36%5%47%40%
2310
16th to endDay
9%425%5%35%5%5%10%42%
2310
July1st to 15thDay
6%4244246%6%9%47%
2310
16th to endDay
9%4144246%7%10%44%
2459
August1st to 15thDay
8%425%5%3446%10%42%
2167
16th to endDay
12%415%43446%9%42%
2167
September1st to 15thDay
12%5%25%43446%7%43%
1911
16th to endDay
11%6%25%5%25%46%9%40%
1815
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%6%344235%46%41%
1604
May1st to 15thNight
18%6%26%5%345%5%6%35%
1484
16th to endNight
11%5%36%5%3445%7%42%
1411
June1st to 15thNight
11%425%6%245%5%8%43%
1320
16th to endNight
7%4345%35%5%7%9%42%
1320
July1st to 15thNight
6%225%42346%8%53%
1320
16th to endNight
6%41442435%9%52%
1401
August1st to 15thNight
6%42432446%7%52%
1463
16th to endNight
10%425%423447%50%
1682
September1st to 15thNight
11%4143225%46%53%
1708
16th to endNight
10%6%245%23346%49%
1815
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%13%18%14%3
2243
May1st to 15thDay
47%5%13%23%8%1
2136
16th to endDay
37%6%12%27%13%1
2351
June1st to 15thDay
40%6%12%23%15%
2310
16th to endDay
35%7%16%21%18%1
2310
July1st to 15thDay
30%6%13%26%18%3
2161
16th to endDay
32%8%15%24%16%2
2292
August1st to 15thDay
35%6%13%29%13%2
2152
16th to endDay
36%6%13%24%15%2
2167
September1st to 15thDay
37%5%13%27%14%1
1911
16th to endDay
38%5%13%25%15%
1815
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
42%410%20%16%4
1604
May1st to 15thNight
48%6%12%21%10%1
1485
16th to endNight
40%6%11%22%16%2
1413
June1st to 15thNight
38%6%11%27%14%1
1320
16th to endNight
35%8%16%20%16%1
1320
July1st to 15thNight
27%5%13%27%21%3
1240
16th to endNight
29%7%14%25%19%2
1305
August1st to 15thNight
28%5%12%31%18%2
1454
16th to endNight
33%410%27%19%3
1682
September1st to 15thNight
31%6%12%29%18%2
1708
16th to endNight
35%412%29%16%
1815
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
19%8%30%22%13%6%
250
May1st to 15thDay
24%6%31%22%9%6%
228
16th to endDay
12%8%27%28%16%6%
391
June1st to 15thDay
14%7%31%28%13%5%
420
16th to endDay
11%6%29%30%14%6%
420
July1st to 15thDay
9%326%30%20%10%
400
16th to endDay
9%326%31%19%9%
445
August1st to 15thDay
10%216%25%25%20%
275
16th to endDay
18%312%28%23%13%
268
September1st to 15thDay
13%216%30%25%11%
255
16th to endDay
14%316%27%28%10%
254
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%31%9%1
525
May1st to 15thNight
19%5%28%35%9%
495
16th to endNight
13%225%37%19%
515
June1st to 15thNight
12%326%40%17%
495
16th to endNight
9%224%43%18%1
495
July1st to 15thNight
8%116%45%25%2
465
16th to endNight
7%116%43%29%1
522
August1st to 15thNight
7%114%47%26%2
494
16th to endNight
10%213%38%30%4
525
September1st to 15thNight
13%315%38%23%5%
553
16th to endNight
13%419%32%26%5%
657
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 2017-04-26 17:21:34. Version ac04

Copyright 2017 A. Danko


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