Hidden Loft Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hidden Loft Observatory clear sky chart from 2005-11-05 to 2017-04-24.

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
73%
15122
35%
45562
31%
15084
77%
15084
52%
22051

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%
718
32%
2327
31%
716
73%
716
49%
1104
January16th to endNight
65%
768
34%
2496
33%
768
72%
768
40%
1295
February1st to 15thNight
70%
700
35%
2208
34%
700
77%
700
50%
1059
February16th to endNight
61%
632
37%
1838
33%
632
67%
632
46%
953
March1st to 15thNight
64%
720
38%
1980
31%
720
71%
720
54%
995
March16th to endNight
70%
768
38%
2112
28%
768
78%
768
60%
1009
April1st to 15thNight
64%
683
34%
1942
24%
683
73%
683
54%
947
April16th to endNight
71%
522
44%
1721
39%
522
81%
522
71%
642
May1st to 15thNight
70%
494
42%
1484
31%
494
80%
494
71%
595
May16th to endNight
73%
513
39%
1540
32%
513
78%
513
71%
619
June1st to 15thNight
80%
495
37%
1485
31%
495
82%
495
67%
628
June16th to endNight
84%
495
29%
1485
25%
495
84%
495
62%
661
July1st to 15thNight
80%
465
21%
1395
18%
465
80%
465
40%
767
July16th to endNight
78%
522
18%
1467
16%
489
78%
489
31%
895
August1st to 15thNight
83%
494
27%
1476
26%
491
83%
491
41%
812
August16th to endNight
83%
545
28%
1713
29%
545
83%
545
38%
941
September1st to 15thNight
76%
660
30%
1815
26%
660
77%
660
43%
1049
September16th to endNight
80%
656
41%
1815
31%
656
84%
656
63%
857
October1st to 15thNight
76%
660
39%
1917
32%
660
81%
660
62%
875
October16th to endNight
84%
704
43%
2112
38%
704
88%
704
66%
911
November1st to 15thNight
78%
700
42%
2100
37%
700
82%
700
65%
912
November16th to endNight
71%
720
37%
2298
36%
720
75%
720
50%
1087
December1st to 15thNight
69%
720
36%
2340
37%
720
74%
720
48%
1113
December16th to endNight
63%
768
33%
2496
34%
768
67%
768
38%
1325

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%313323345%63%
46046
Night
4313323345%65%
45758
TransparencyDay
20%35%11%24%33%
45741
Night
19%35%13%25%32%
45564
SeeingDay
8%9%25%35%17%3
4831
Night
5%212%37%35%7%
15131

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
6%413312345%63%
1611
16th to endDay
8%423212336%59%
1728
February1st to 15thDay
7%412212235%66%
1654
16th to endDay
8%424313335%59%
1636
March1st to 15thDay
5%313313326%64%
1980
16th to endDay
321211323471%
2112
April1st to 15thDay
321221334469%
2005
16th to endDay
2211112379%
2095
May1st to 15thDay
21111322477%
2136
16th to endDay
211111122380%
2221
June1st to 15thDay
32111222378%
2145
16th to endDay
113212345%72%
2145
July1st to 15thDay
5%3247%36%7%7%8%43%
2145
16th to endDay
9%5%36%6%46%7%8%10%31%
2285
August1st to 15thDay
8%4245%46%6%7%8%40%
2145
16th to endDay
43146%36%6%6%8%46%
2133
September1st to 15thDay
6%424435%5%7%6%48%
1815
16th to endDay
41231324371%
1815
October1st to 15thDay
311232223472%
1713
16th to endDay
21221223476%
1760
November1st to 15thDay
121212245%73%
1759
16th to endDay
5%312312335%68%
1660
December1st to 15thDay
9%312312336%61%
1620
16th to endDay
8%314222346%58%
1728
January1st to 15thNight
7%313322335%64%
2327
16th to endNight
8%41332434458%
2496
February1st to 15thNight
6%312213236%65%
2197
16th to endNight
6%5%13224435%60%
1838
March1st to 15thNight
6%31221233467%
1980
16th to endNight
4212312236%70%
2112
April1st to 15thNight
4313322335%67%
1942
16th to endNight
2111112284%
1721
May1st to 15thNight
11112346%76%
1484
16th to endNight
2111121482%
1540
June1st to 15thNight
21221212478%
1485
16th to endNight
111221323475%
1485
July1st to 15thNight
32145%35%7%7%11%47%
1485
16th to endNight
4426%5%46%8%8%13%35%
1575
August1st to 15thNight
32134247%7%10%51%
1485
16th to endNight
3224446%6%7%10%48%
1713
September1st to 15thNight
5%42342445%6%55%
1815
16th to endNight
22221333374%
1815
October1st to 15thNight
221221223473%
1917
16th to endNight
22121222378%
2112
November1st to 15thNight
221221224473%
2100
16th to endNight
6%31321333467%
2298
December1st to 15thNight
8%312213346%62%
2340
16th to endNight
9%5%25%22233457%
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
22%25%12%27%29%
1612
16th to endDay
26%25%13%24%27%
1728
February1st to 15thDay
21%15%12%26%32%
1654
16th to endDay
26%1412%29%25%
1636
March1st to 15thDay
20%236%31%34%
1980
16th to endDay
16%239%32%36%
2112
April1st to 15thDay
15%127%37%35%
2005
16th to endDay
11%127%25%52%
2095
May1st to 15thDay
11%127%23%53%
2136
16th to endDay
10%136%26%51%
2224
June1st to 15thDay
11%1419%62%
2145
16th to endDay
13%247%16%55%
2145
July1st to 15thDay
31%9%13%14%13%18%
2006
16th to endDay
41%9%16%19%9%2
2130
August1st to 15thDay
34%8%11%13%17%13%
2130
16th to endDay
31%7%12%17%18%11%
2133
September1st to 15thDay
31%5%9%18%15%18%
1815
16th to endDay
17%249%31%34%
1815
October1st to 15thDay
14%35%11%25%40%
1713
16th to endDay
12%148%26%46%
1760
November1st to 15thDay
11%1311%34%37%
1759
16th to endDay
18%149%27%38%
1660
December1st to 15thDay
23%25%15%30%22%
1620
16th to endDay
25%26%19%30%16%
1728
January1st to 15thNight
21%25%12%28%29%
2327
16th to endNight
27%3414%26%23%
2496
February1st to 15thNight
20%2414%25%31%
2208
16th to endNight
24%2413%30%24%
1838
March1st to 15thNight
20%149%26%37%
1980
16th to endNight
16%1311%32%34%
2112
April1st to 15thNight
19%138%35%31%
1942
16th to endNight
8%117%27%53%
1721
May1st to 15thNight
8%249%26%48%
1485
16th to endNight
9%126%25%54%
1541
June1st to 15thNight
11%12417%62%
1485
16th to endNight
14%23417%57%
1485
July1st to 15thNight
25%7%16%17%15%18%
1395
16th to endNight
30%10%22%21%10%3
1467
August1st to 15thNight
22%9%14%20%16%16%
1476
16th to endNight
26%7%14%19%18%13%
1713
September1st to 15thNight
26%6%8%22%19%16%
1815
16th to endNight
14%2311%32%35%
1815
October1st to 15thNight
14%2413%25%39%
1917
16th to endNight
12%1311%22%47%
2112
November1st to 15thNight
13%1312%32%36%
2100
16th to endNight
21%1411%22%39%
2298
December1st to 15thNight
22%25%15%29%24%
2340
16th to endNight
29%26%16%26%18%
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
23%323%38%10%1
90
16th to endDay
12%126%31%22%6%
96
February1st to 15thDay
9%8%24%38%17%1
169
16th to endDay
11%18%37%22%8%1
238
March1st to 15thDay
9%17%29%27%13%3
270
16th to endDay
5%22%31%23%14%2
288
April1st to 15thDay
8%21%31%23%11%3
269
16th to endDay
7%23%33%24%8%3
243
May1st to 15thDay
6%17%42%25%6%1
228
16th to endDay
211%38%37%7%1
266
June1st to 15thDay
6%7%35%37%11%1
255
16th to endDay
5%222%47%19%3
255
July1st to 15thDay
7%14%51%23%2
245
16th to endDay
11%10%39%28%9%
271
August1st to 15thDay
7%18%45%29%7%
255
16th to endDay
5%10%41%34%7%
268
September1st to 15thDay
12%118%41%18%6%
255
16th to endDay
8%5%25%39%16%4
255
October1st to 15thDay
311%24%36%18%4
153
16th to endDay
5%19%44%35%4
96
November1st to 15thDay
5%11%18%38%21%4
90
16th to endDay
8%10%28%28%22%1
90
December1st to 15thDay
6%120%35%33%3
90
16th to endDay
22%6%25%30%14%1
96
January1st to 15thNight
8%115%42%26%5%
720
16th to endNight
11%214%41%24%5%
768
February1st to 15thNight
8%114%41%28%5%
704
16th to endNight
8%419%43%21%2
632
March1st to 15thNight
8%320%37%25%5%
720
16th to endNight
3316%40%30%5%
768
April1st to 15thNight
45%18%45%22%2
683
16th to endNight
25%18%41%27%3
522
May1st to 15thNight
422%42%27%2
495
16th to endNight
2317%41%31%3
515
June1st to 15thNight
2211%44%36%3
495
16th to endNight
117%34%49%5%
495
July1st to 15thNight
2425%57%9%
465
16th to endNight
4117%63%12%
522
August1st to 15thNight
4115%61%16%
494
16th to endNight
4120%57%17%
545
September1st to 15thNight
6%5%23%49%13%
660
16th to endNight
310%33%40%11%
656
October1st to 15thNight
3113%39%33%8%
660
16th to endNight
217%38%38%11%
704
November1st to 15thNight
2113%40%34%7%
700
16th to endNight
8%113%39%31%5%
720
December1st to 15thNight
10%213%38%30%5%
720
16th to endNight
11%313%42%22%6%
768
Page generated at 2017-04-25 04:48:19. Version ac04

Copyright 2017 A. Danko


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