Hawks Landing Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hawks Landing Observatory clear sky chart from 2005-11-05 to 2017-09-19.

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
75%
16257
31%
46997
29%
16213
76%
16213
47%
24967

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
68%
717
29%
2318
29%
716
73%
716
42%
1197
January16th to endNight
66%
768
34%
2304
31%
768
72%
768
38%
1287
February1st to 15thNight
70%
698
33%
2110
33%
698
74%
698
43%
1116
February16th to endNight
61%
632
28%
1895
31%
632
62%
632
31%
1152
March1st to 15thNight
68%
720
29%
2160
32%
720
71%
720
40%
1194
March16th to endNight
72%
768
28%
2035
25%
768
74%
768
43%
1189
April1st to 15thNight
66%
719
26%
1799
19%
719
67%
719
41%
1104
April16th to endNight
71%
720
29%
1800
19%
720
72%
720
47%
1055
May1st to 15thNight
69%
585
27%
1665
19%
585
70%
585
41%
961
May16th to endNight
67%
561
25%
1685
20%
561
67%
561
39%
980
June1st to 15thNight
75%
540
26%
1620
22%
540
75%
540
43%
901
June16th to endNight
89%
540
33%
1620
29%
540
89%
540
68%
695
July1st to 15thNight
88%
510
25%
1530
22%
510
88%
510
55%
745
July16th to endNight
85%
635
29%
1658
21%
596
84%
596
51%
871
August1st to 15thNight
85%
717
32%
1790
20%
713
86%
713
65%
894
August16th to endNight
88%
764
37%
1910
27%
764
88%
764
67%
961
September1st to 15thNight
87%
720
35%
1872
30%
720
87%
720
61%
947
September16th to endNight
85%
671
44%
1856
42%
671
86%
671
68%
838
October1st to 15thNight
77%
660
36%
1815
34%
660
79%
660
53%
939
October16th to endNight
74%
704
36%
2104
38%
704
75%
704
47%
1072
November1st to 15thNight
79%
700
33%
2275
38%
700
81%
700
50%
1062
November16th to endNight
76%
720
34%
2340
37%
720
79%
720
43%
1171
December1st to 15thNight
66%
720
32%
2340
34%
720
69%
720
38%
1257
December16th to endNight
63%
768
31%
2496
30%
768
69%
768
36%
1379

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
5%313313346%63%
47804
Night
6%5%23323346%58%
47201
TransparencyDay
21%25%16%26%27%
47506
Night
24%35%15%23%27%
47000
SeeingDay
7%6%26%39%15%4
5931
Night
7%26%32%39%12%
16269

By Month

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
8%414412345%58%
1617
16th to endDay
11%423313346%55%
1920
February1st to 15thDay
8%313414435%57%
1751
16th to endDay
13%5%25%4245%47%45%
1579
March1st to 15thDay
6%42332335%9%55%
1800
16th to endDay
5%323324447%57%
2184
April1st to 15thDay
7%425%323446%55%
2149
16th to endDay
6%312212346%66%
2160
May1st to 15thDay
6%5%13213346%61%
2283
16th to endDay
45%13312236%63%
2429
June1st to 15thDay
5%5%23322245%64%
2340
16th to endDay
1111223478%
2340
July1st to 15thDay
231332435%7%64%
2340
16th to endDay
221222346%8%63%
2392
August1st to 15thDay
1212212235%74%
2160
16th to endDay
112222336%73%
2292
September1st to 15thDay
122212336%72%
2088
16th to endDay
121212235%75%
1849
October1st to 15thDay
432432344462%
1815
16th to endDay
6%41221222468%
1764
November1st to 15thDay
5%21232335%6%64%
1584
16th to endDay
6%313213447%60%
1620
December1st to 15thDay
8%413424349%53%
1620
16th to endDay
12%412323336%54%
1728
January1st to 15thNight
6%41342425%6%58%
2318
16th to endNight
10%423313346%55%
2304
February1st to 15thNight
8%323323345%60%
2101
16th to endNight
13%6%24424345%47%
1895
March1st to 15thNight
8%5%33313348%54%
2160
16th to endNight
7%5%2332345%8%51%
2035
April1st to 15thNight
9%7%24222347%51%
1799
16th to endNight
7%7%13323326%58%
1800
May1st to 15thNight
6%9%24424338%50%
1665
16th to endNight
8%10%3341435%6%48%
1684
June1st to 15thNight
48%3442445%8%49%
1620
16th to endNight
121222325%7%67%
1620
July1st to 15thNight
15%1233447%6%58%
1620
16th to endNight
33223345%6%9%55%
1772
August1st to 15thNight
1412223448%63%
1800
16th to endNight
13231345%7%66%
1910
September1st to 15thNight
131222235%6%65%
1872
16th to endNight
3212212225%74%
1856
October1st to 15thNight
4313313346%62%
1815
16th to endNight
7%413323335%62%
2104
November1st to 15thNight
5%21231344466%
2275
16th to endNight
5%423323436%60%
2340
December1st to 15thNight
9%42432335%6%53%
2340
16th to endNight
12%423323345%55%
2496

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
28%25%12%24%27%
1618
16th to endDay
30%27%14%16%29%
1920
February1st to 15thDay
27%4413%22%27%
1751
16th to endDay
38%45%15%22%13%
1579
March1st to 15thDay
26%35%19%22%23%
1800
16th to endDay
25%38%25%21%16%
2184
April1st to 15thDay
29%26%23%26%10%
2149
16th to endDay
19%26%23%27%19%
2160
May1st to 15thDay
24%25%20%28%19%
2283
16th to endDay
22%15%23%34%12%
2432
June1st to 15thDay
20%2216%29%26%
2340
16th to endDay
8%127%21%57%
2340
July1st to 15thDay
16%3411%25%38%
2201
16th to endDay
16%49%23%29%16%
2243
August1st to 15thDay
12%2214%35%32%
2146
16th to endDay
12%2311%35%33%
2292
September1st to 15thDay
13%2310%34%36%
2088
16th to endDay
11%1210%34%39%
1849
October1st to 15thDay
24%2415%26%26%
1815
16th to endDay
20%2311%20%41%
1764
November1st to 15thDay
20%17%13%19%36%
1584
16th to endDay
22%3413%20%35%
1620
December1st to 15thDay
29%28%15%17%26%
1620
16th to endDay
32%36%16%22%18%
1728
January1st to 15thNight
26%36%12%20%30%
2318
16th to endNight
30%36%11%15%32%
2304
February1st to 15thNight
26%27%13%21%28%
2112
16th to endNight
38%3415%22%16%
1895
March1st to 15thNight
30%25%18%18%24%
2160
16th to endNight
28%48%19%21%16%
2035
April1st to 15thNight
32%36%23%21%12%
1799
16th to endNight
27%37%19%21%21%
1800
May1st to 15thNight
29%37%18%21%19%
1666
16th to endNight
31%36%21%22%13%
1685
June1st to 15thNight
27%3415%28%20%
1620
16th to endNight
9%329%21%53%
1620
July1st to 15thNight
18%3410%25%37%
1530
16th to endNight
19%5%9%20%30%14%
1658
August1st to 15thNight
13%3416%33%27%
1790
16th to endNight
13%25%11%31%35%
1910
September1st to 15thNight
16%2311%31%34%
1872
16th to endNight
12%1111%33%38%
1856
October1st to 15thNight
21%25%18%27%25%
1815
16th to endNight
24%2210%20%39%
2104
November1st to 15thNight
20%25%15%17%38%
2275
16th to endNight
24%3415%18%33%
2340
December1st to 15thNight
30%27%15%18%25%
2340
16th to endNight
31%39%13%19%22%
2496

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
26%417%36%15%
96
16th to endDay
15%10%33%33%5%2
288
February1st to 15thDay
9%9%33%34%11%1
266
16th to endDay
17%13%30%29%7%
238
March1st to 15thDay
8%14%27%32%13%5%
270
16th to endDay
7%11%33%32%11%4
288
April1st to 15thDay
9%16%33%27%10%2
269
16th to endDay
6%14%41%26%7%3
270
May1st to 15thDay
14%8%32%33%7%2
288
16th to endDay
9%9%32%33%13%1
330
June1st to 15thDay
4428%39%20%3
315
16th to endDay
118%46%23%8%
315
July1st to 15thDay
3112%48%27%6%
305
16th to endDay
46%53%24%10%
327
August1st to 15thDay
1114%52%21%7%
315
16th to endDay
39%56%21%7%
332
September1st to 15thDay
3125%51%14%3
315
16th to endDay
4430%42%13%4
268
October1st to 15thDay
49%42%31%10%1
255
16th to endDay
10%5%27%35%16%3
215
November1st to 15thDay
5%224%26%36%4
90
16th to endDay
12%225%44%14%1
90
December1st to 15thDay
4316%42%27%5%
90
16th to endDay
18%5%19%38%16%1
96
January1st to 15thNight
8%212%37%26%12%
720
16th to endNight
12%210%39%26%8%
768
February1st to 15thNight
11%27%36%31%10%
704
16th to endNight
14%39%41%24%7%
632
March1st to 15thNight
11%38%40%30%6%
720
16th to endNight
8%26%37%36%8%
768
April1st to 15thNight
11%47%42%27%6%
719
16th to endNight
9%37%36%33%9%
720
May1st to 15thNight
9%36%35%36%8%
586
16th to endNight
9%5%7%30%41%5%
563
June1st to 15thNight
5%16%38%40%6%
540
16th to endNight
2132%54%8%
540
July1st to 15thNight
216%67%12%
510
16th to endNight
2111%63%20%
635
August1st to 15thNight
1217%58%20%
717
16th to endNight
29%57%29%
764
September1st to 15thNight
3118%57%18%
720
16th to endNight
31228%46%16%
671
October1st to 15thNight
6%15%37%38%10%
660
16th to endNight
9%2429%35%19%
704
November1st to 15thNight
6%17%35%36%13%
700
16th to endNight
7%16%36%31%17%
720
December1st to 15thNight
11%210%38%26%11%
720
16th to endNight
15%310%37%23%9%
768
Page generated at 2017-09-20 01:49:56. Version ac04

Copyright 2017 A. Danko


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