Hawkeye Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hawkeye 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
38%
16030
17%
46915
10%
15987
44%
15987
24%
31352

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
23%
900
13%
2506
5%
895
30%
895
18%
1831
January16th to endNight
23%
960
12%
2625
5%
960
29%
960
17%
1985
February1st to 15thNight
23%
850
14%
2262
4%
850
30%
850
20%
1614
February16th to endNight
27%
631
18%
1893
8%
631
36%
631
18%
1319
March1st to 15thNight
30%
717
14%
2157
7%
717
36%
717
20%
1470
March16th to endNight
31%
576
15%
1998
11%
576
38%
576
17%
1392
April1st to 15thNight
28%
539
16%
1797
10%
539
38%
539
20%
1211
April16th to endNight
35%
540
18%
1767
12%
540
45%
540
22%
1184
May1st to 15thNight
36%
540
15%
1525
8%
540
42%
540
21%
1088
May16th to endNight
45%
563
17%
1497
9%
561
51%
561
30%
982
June1st to 15thNight
53%
540
16%
1440
10%
540
56%
540
35%
911
June16th to endNight
50%
540
16%
1440
8%
540
54%
540
32%
936
July1st to 15thNight
66%
510
18%
1360
12%
510
68%
510
43%
794
July16th to endNight
69%
564
21%
1417
16%
531
72%
531
44%
823
August1st to 15thNight
73%
539
23%
1560
22%
536
74%
536
41%
871
August16th to endNight
65%
573
20%
1910
22%
573
68%
573
33%
1084
September1st to 15thNight
63%
540
27%
1800
27%
540
68%
540
37%
963
September16th to endNight
55%
659
25%
1873
18%
659
61%
659
34%
1119
October1st to 15thNight
43%
660
25%
1950
17%
660
50%
660
30%
1204
October16th to endNight
33%
704
18%
2209
10%
704
42%
704
22%
1443
November1st to 15thNight
34%
700
24%
2276
17%
700
44%
700
26%
1372
November16th to endNight
26%
825
16%
2445
8%
825
34%
825
20%
1697
December1st to 15thNight
20%
900
12%
2520
4%
900
27%
900
16%
1909
December16th to endNight
19%
960
11%
2688
3%
960
26%
960
13%
2150

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%8%36%5%3445%7%36%
47999
Night
14%7%35%424446%40%
47084
Cloud CoverDay
14%7%36%5%3445%7%37%
48007
Night
14%7%35%424446%40%
47089
TransparencyDay
46%6%12%22%11%1
47685
Night
43%5%11%22%14%1
46916
SeeingDay
16%7%27%26%16%6%
6041
Night
17%7%30%30%12%1
16033

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
13%11%6%7%5%35%5%6%6%28%
1432
16th to endDay
13%14%6%11%7%24346%25%
1599
February1st to 15thDay
12%14%6%7%5%35%445%30%
1600
16th to endDay
13%11%47%6%34336%34%
1580
March1st to 15thDay
15%10%36%5%24348%34%
1802
16th to endDay
18%9%37%5%34345%32%
2226
April1st to 15thDay
18%9%47%4335%5%5%30%
2151
16th to endDay
20%9%25%43435%6%33%
2193
May1st to 15thDay
19%8%37%6%3446%6%27%
2424
16th to endDay
13%6%36%6%345%6%6%37%
2617
June1st to 15thDay
13%5%25%5%45%5%5%7%38%
2520
16th to endDay
9%5%25%5%35%6%7%10%37%
2520
July1st to 15thDay
6%4145%35%5%7%9%44%
2520
16th to endDay
7%5%25%5%36%6%6%10%40%
2655
August1st to 15thDay
6%4246%35%6%7%8%41%
2387
16th to endDay
11%5%245%25%5%6%6%44%
2292
September1st to 15thDay
12%423434446%50%
2160
16th to endDay
9%5%35%425%45%8%44%
1912
October1st to 15thDay
16%6%24423347%44%
1678
16th to endDay
18%7%35%434447%37%
1661
November1st to 15thDay
11%7%46%5%3445%6%40%
1582
16th to endDay
17%11%36%323336%37%
1512
December1st to 15thDay
17%13%5%7%435%336%28%
1440
16th to endDay
21%14%5%8%6%24445%22%
1536
January1st to 15thNight
15%10%5%8%5%34345%34%
2506
16th to endNight
12%11%5%9%6%45%446%28%
2625
February1st to 15thNight
12%13%46%434345%36%
2260
16th to endNight
15%10%37%423446%35%
1893
March1st to 15thNight
16%9%35%5%33446%38%
2144
16th to endNight
18%7%45%5%345%46%33%
1998
April1st to 15thNight
18%8%35%424446%37%
1797
16th to endNight
19%6%35%42445%6%38%
1767
May1st to 15thNight
18%6%26%435%45%9%33%
1525
16th to endNight
9%5%25%5%245%5%10%42%
1496
June1st to 15thNight
10%42442446%9%46%
1440
16th to endNight
8%425%5%35%5%6%9%42%
1440
July1st to 15thNight
5%31441446%9%54%
1440
16th to endNight
6%3233245%7%10%49%
1513
August1st to 15thNight
431442336%9%55%
1569
16th to endNight
9%42443345%6%51%
1910
September1st to 15thNight
8%423323345%58%
1800
16th to endNight
8%425%32445%6%50%
1873
October1st to 15thNight
12%5%25%424346%48%
1950
16th to endNight
18%6%24423346%41%
2209
November1st to 15thNight
12%7%25%32335%5%48%
2276
16th to endNight
18%8%35%5%24436%37%
2445
December1st to 15thNight
19%11%37%6%34435%29%
2520
16th to endNight
22%12%49%6%2444423%
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
13%12%5%7%5%35%6%5%6%28%
1432
16th to endDay
14%13%6%12%6%2435%5%25%
1599
February1st to 15thDay
12%14%6%7%5%35%435%31%
1600
16th to endDay
15%11%37%6%34336%34%
1580
March1st to 15thDay
16%9%46%433248%34%
1812
16th to endDay
18%9%36%6%34445%32%
2224
April1st to 15thDay
18%9%46%5%3445%6%30%
2151
16th to endDay
21%9%25%5%34446%33%
2193
May1st to 15thDay
20%7%36%6%345%5%7%28%
2424
16th to endDay
14%6%25%6%35%5%6%8%37%
2617
June1st to 15thDay
14%425%6%35%5%5%7%39%
2520
16th to endDay
10%425%6%25%6%7%10%38%
2520
July1st to 15thDay
7%324436%6%7%9%44%
2520
16th to endDay
8%5%35%435%6%6%9%41%
2655
August1st to 15thDay
6%425%5%35%5%7%8%42%
2387
16th to endDay
13%5%245%2435%7%44%
2292
September1st to 15thDay
13%323434347%50%
2160
16th to endDay
10%435%435%45%8%44%
1912
October1st to 15thDay
16%7%23423336%45%
1678
16th to endDay
19%7%345%33347%37%
1661
November1st to 15thDay
12%7%45%5%3445%5%40%
1582
16th to endDay
18%11%26%423335%38%
1512
December1st to 15thDay
18%13%47%5%34335%29%
1440
16th to endDay
21%14%5%7%6%34345%22%
1536
January1st to 15thNight
15%11%5%7%5%34335%34%
2506
16th to endNight
13%11%6%9%6%35%446%29%
2625
February1st to 15thNight
13%13%5%5%5%33345%37%
2253
16th to endNight
16%10%46%5%24445%36%
1893
March1st to 15thNight
16%9%35%5%34436%38%
2157
16th to endNight
18%7%45%5%35%447%33%
1998
April1st to 15thNight
19%8%35%42445%5%37%
1797
16th to endNight
19%7%26%42345%5%38%
1767
May1st to 15thNight
18%6%35%4345%6%8%33%
1524
16th to endNight
10%425%425%46%9%43%
1496
June1st to 15thNight
11%32442445%9%46%
1440
16th to endNight
9%425%5%246%6%9%42%
1440
July1st to 15thNight
5%41431345%9%55%
1440
16th to endNight
6%3133245%7%10%50%
1513
August1st to 15thNight
5%21443345%9%55%
1569
16th to endNight
9%325%434447%50%
1910
September1st to 15thNight
8%413314345%59%
1800
16th to endNight
8%425%43445%6%50%
1873
October1st to 15thNight
12%5%25%424335%49%
1950
16th to endNight
19%5%24423346%41%
2209
November1st to 15thNight
13%7%24413345%48%
2276
16th to endNight
18%8%36%424446%36%
2445
December1st to 15thNight
20%11%47%5%34435%29%
2520
16th to endNight
22%12%5%8%5%2434424%
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
54%6%14%15%8%
1433
16th to endDay
60%5%11%15%6%
1599
February1st to 15thDay
55%411%19%7%1
1602
16th to endDay
52%6%9%22%8%1
1580
March1st to 15thDay
49%5%14%20%8%1
1812
16th to endDay
53%6%12%20%6%
2226
April1st to 15thDay
53%6%10%20%8%
2151
16th to endDay
51%5%10%18%11%2
2193
May1st to 15thDay
55%6%12%19%6%
2424
16th to endDay
44%7%11%20%13%1
2621
June1st to 15thDay
42%8%12%22%14%
2520
16th to endDay
38%7%14%23%14%1
2520
July1st to 15thDay
34%8%15%24%15%1
2371
16th to endDay
37%7%17%21%13%2
2488
August1st to 15thDay
34%9%13%28%13%1
2372
16th to endDay
37%7%10%26%15%2
2292
September1st to 15thDay
34%5%9%29%20%1
2160
16th to endDay
36%6%12%28%15%1
1912
October1st to 15thDay
41%410%28%14%
1678
16th to endDay
46%5%12%23%10%1
1661
November1st to 15thDay
44%412%24%12%1
1582
16th to endDay
50%416%22%5%
1512
December1st to 15thDay
58%414%15%6%
1440
16th to endDay
64%411%10%7%
1536
January1st to 15thNight
52%5%10%19%11%
2506
16th to endNight
55%5%13%15%9%
2625
February1st to 15thNight
50%411%20%11%1
2262
16th to endNight
49%5%12%21%8%2
1893
March1st to 15thNight
47%5%14%18%12%1
2157
16th to endNight
50%6%11%21%8%1
1998
April1st to 15thNight
47%49%21%14%1
1797
16th to endNight
46%5%10%21%12%3
1767
May1st to 15thNight
46%8%13%20%11%
1525
16th to endNight
35%9%13%21%17%2
1498
June1st to 15thNight
33%7%12%26%20%1
1440
16th to endNight
35%8%12%21%19%3
1440
July1st to 15thNight
25%7%13%30%20%2
1360
16th to endNight
24%7%17%28%18%4
1417
August1st to 15thNight
26%5%12%31%20%2
1560
16th to endNight
32%5%13%27%17%3
1910
September1st to 15thNight
28%5%10%26%27%2
1800
16th to endNight
32%5%10%32%17%1
1873
October1st to 15thNight
37%49%24%21%2
1950
16th to endNight
44%5%11%25%12%1
2209
November1st to 15thNight
37%5%10%24%18%3
2276
16th to endNight
48%5%13%21%10%
2445
December1st to 15thNight
57%410%20%7%
2520
16th to endNight
63%411%12%6%
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%10%34%28%3
90
16th to endDay
21%6%33%25%12%1
96
February1st to 15thDay
21%17%37%16%6%
90
16th to endDay
25%16%27%23%6%1
81
March1st to 15thDay
30%13%40%14%11
90
16th to endDay
30%8%27%19%11%2
210
April1st to 15thDay
24%10%32%21%10%
270
16th to endDay
22%11%25%25%9%4
270
May1st to 15thDay
24%9%29%23%8%3
381
16th to endDay
17%9%29%24%13%5%
517
June1st to 15thDay
13%5%29%30%17%5%
495
16th to endDay
12%5%32%28%13%6%
495
July1st to 15thDay
9%223%32%21%10%
475
16th to endDay
9%322%30%23%10%
515
August1st to 15thDay
7%220%30%27%10%
456
16th to endDay
15%414%25%27%12%
332
September1st to 15thDay
10%318%27%30%9%
315
16th to endDay
10%6%22%27%24%9%
283
October1st to 15thDay
10%8%29%28%18%4
118
16th to endDay
23%10%29%29%7%
96
November1st to 15thDay
412%32%24%18%7%
90
16th to endDay
42%12%30%8%6%
90
December1st to 15thDay
22%12%37%24%12
90
16th to endDay
30%15%44%8%1
96
January1st to 15thNight
20%11%37%23%6%
900
16th to endNight
18%10%37%28%3
960
February1st to 15thNight
19%11%37%25%6%
853
16th to endNight
22%10%33%26%6%
631
March1st to 15thNight
20%10%33%27%7%
717
16th to endNight
19%8%34%25%9%1
576
April1st to 15thNight
22%10%33%28%5%
539
16th to endNight
22%6%31%29%8%
540
May1st to 15thNight
21%431%30%11%
540
16th to endNight
12%332%36%14%
563
June1st to 15thNight
12%325%42%15%
540
16th to endNight
8%430%38%17%
540
July1st to 15thNight
8%118%42%27%2
510
16th to endNight
8%115%46%26%2
564
August1st to 15thNight
5%112%45%31%4
539
16th to endNight
10%213%38%30%4
573
September1st to 15thNight
9%220%34%28%4
540
16th to endNight
11%422%31%27%2
659
October1st to 15thNight
15%5%30%29%17%1
660
16th to endNight
21%9%32%27%9%
704
November1st to 15thNight
16%8%37%26%11%
700
16th to endNight
23%10%33%24%7%
825
December1st to 15thNight
26%9%36%22%5%
900
16th to endNight
27%9%32%25%3
960
Page generated at 2017-09-24 08:15:52. Version ac04

Copyright 2017 A. Danko


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