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 2018-03-21.

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%
16313
35%
49166
31%
16275
78%
16275
52%
23794

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%
778
31%
2522
31%
776
73%
776
47%
1215
January16th to endNight
66%
832
34%
2704
34%
832
74%
832
42%
1373
February1st to 15thNight
70%
760
35%
2396
34%
760
77%
760
50%
1147
February16th to endNight
61%
684
36%
1989
33%
684
67%
684
45%
1050
March1st to 15thNight
65%
780
38%
2145
30%
780
72%
780
54%
1079
March16th to endNight
70%
792
39%
2178
28%
792
78%
792
60%
1041
April1st to 15thNight
64%
683
34%
1942
24%
683
73%
683
54%
947
April16th to endNight
70%
540
45%
1779
38%
540
81%
540
70%
664
May1st to 15thNight
70%
539
40%
1619
30%
539
79%
539
71%
652
May16th to endNight
74%
561
41%
1684
33%
561
79%
561
72%
667
June1st to 15thNight
81%
540
35%
1620
30%
540
83%
540
68%
681
June16th to endNight
84%
540
31%
1620
27%
540
85%
540
62%
718
July1st to 15thNight
80%
510
20%
1530
18%
510
81%
510
40%
845
July16th to endNight
77%
564
17%
1593
15%
531
77%
531
30%
995
August1st to 15thNight
84%
539
25%
1611
24%
536
84%
536
41%
885
August16th to endNight
84%
595
31%
1870
31%
595
84%
595
39%
1013
September1st to 15thNight
76%
720
29%
1980
25%
720
77%
720
43%
1144
September16th to endNight
81%
716
44%
1980
34%
716
85%
716
65%
923
October1st to 15thNight
77%
720
39%
2091
31%
720
82%
720
64%
938
October16th to endNight
84%
768
45%
2304
40%
768
88%
768
67%
986
November1st to 15thNight
78%
760
40%
2280
36%
760
82%
760
62%
1020
November16th to endNight
72%
780
39%
2490
38%
780
76%
780
51%
1169
December1st to 15thNight
67%
780
36%
2535
35%
780
72%
780
46%
1226
December16th to endNight
64%
832
34%
2704
35%
832
69%
832
39%
1416

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
4313323345%63%
49684
Night
4313323345%65%
49362
TransparencyDay
20%35%11%24%33%
49379
Night
19%35%12%25%32%
49168
SeeingDay
7%8%23%34%19%4
6024
Night
5%212%36%35%7%
16322

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%314313445%62%
1746
16th to endDay
8%423212335%61%
1872
February1st to 15thDay
7%312213235%65%
1796
16th to endDay
9%424313235%58%
1771
March1st to 15thDay
5%313313336%63%
2145
16th to endDay
4212113235%71%
2173
April1st to 15thDay
321221334469%
2005
16th to endDay
2211112479%
2178
May1st to 15thDay
22121322477%
2331
16th to endDay
111121122380%
2429
June1st to 15thDay
32111222378%
2340
16th to endDay
113212345%71%
2340
July1st to 15thDay
43246%36%7%7%8%44%
2340
16th to endDay
9%5%36%7%46%7%8%10%30%
2467
August1st to 15thDay
7%3245%46%6%6%8%42%
2340
16th to endDay
43146%36%6%6%7%48%
2328
September1st to 15thDay
6%415%435%5%7%6%49%
1980
16th to endDay
31231323373%
1980
October1st to 15thDay
211221223474%
1869
16th to endDay
22221223476%
1920
November1st to 15thDay
122212345%71%
1909
16th to endDay
5%312312235%68%
1798
December1st to 15thDay
9%313313336%59%
1755
16th to endDay
7%414323345%58%
1872
January1st to 15thNight
6%313323336%62%
2522
16th to endNight
8%41332434459%
2704
February1st to 15thNight
6%312213236%65%
2385
16th to endNight
7%5%1322433459%
1989
March1st to 15thNight
6%312213335%66%
2145
16th to endNight
4212312236%70%
2178
April1st to 15thNight
4313322335%67%
1942
16th to endNight
2111112284%
1779
May1st to 15thNight
11112346%76%
1619
16th to endNight
2111121482%
1684
June1st to 15thNight
212212125%78%
1620
16th to endNight
111221323474%
1620
July1st to 15thNight
32145%45%7%7%11%46%
1620
16th to endNight
4426%6%46%7%8%14%34%
1701
August1st to 15thNight
32134346%7%11%50%
1620
16th to endNight
3214445%5%7%9%50%
1870
September1st to 15thNight
5%42342445%6%55%
1980
16th to endNight
21221333375%
1980
October1st to 15thNight
221221223475%
2091
16th to endNight
21121222378%
2304
November1st to 15thNight
2212212345%71%
2280
16th to endNight
5%31321333466%
2490
December1st to 15thNight
8%312213346%60%
2535
16th to endNight
8%425%222335%58%
2704

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
23%25%12%27%28%
1747
16th to endDay
25%25%12%25%28%
1872
February1st to 15thDay
21%15%12%26%32%
1796
16th to endDay
27%1311%28%26%
1771
March1st to 15thDay
21%237%31%33%
2145
16th to endDay
16%239%32%35%
2173
April1st to 15thDay
15%127%37%35%
2005
16th to endDay
11%127%24%52%
2178
May1st to 15thDay
11%137%23%52%
2331
16th to endDay
10%127%25%52%
2432
June1st to 15thDay
10%1420%60%
2340
16th to endDay
13%247%16%55%
2340
July1st to 15thDay
30%9%13%14%14%18%
2201
16th to endDay
41%11%16%18%9%2
2312
August1st to 15thDay
34%8%11%13%19%13%
2325
16th to endDay
30%7%11%16%18%14%
2328
September1st to 15thDay
30%5%9%18%16%19%
1980
16th to endDay
16%248%32%35%
1980
October1st to 15thDay
13%2410%26%41%
1869
16th to endDay
12%148%25%46%
1920
November1st to 15thDay
13%2312%33%34%
1909
16th to endDay
18%139%27%39%
1798
December1st to 15thDay
24%25%15%29%22%
1755
16th to endDay
26%26%18%30%16%
1872
January1st to 15thNight
22%25%12%28%27%
2522
16th to endNight
26%2413%27%24%
2704
February1st to 15thNight
20%2414%25%32%
2396
16th to endNight
26%2412%29%24%
1989
March1st to 15thNight
20%1410%26%36%
2145
16th to endNight
16%1311%32%33%
2178
April1st to 15thNight
19%138%35%31%
1942
16th to endNight
8%118%27%52%
1779
May1st to 15thNight
8%2410%27%47%
1620
16th to endNight
8%127%24%55%
1685
June1st to 15thNight
11%12419%60%
1620
16th to endNight
14%235%16%58%
1620
July1st to 15thNight
24%8%15%16%15%18%
1530
16th to endNight
31%11%22%20%10%3
1593
August1st to 15thNight
22%9%14%20%17%15%
1611
16th to endNight
25%7%13%19%19%15%
1870
September1st to 15thNight
26%6%9%22%18%16%
1980
16th to endNight
13%2311%34%34%
1980
October1st to 15thNight
13%2412%25%41%
2091
16th to endNight
12%1311%23%47%
2304
November1st to 15thNight
14%1313%32%33%
2280
16th to endNight
20%1310%23%39%
2490
December1st to 15thNight
23%25%15%28%25%
2535
16th to endNight
28%26%15%26%20%
2704

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
17%317%39%20%1
135
16th to endDay
11%123%35%22%6%
144
February1st to 15thDay
9%8%22%33%19%5%
221
16th to endDay
12%17%35%25%7%1
290
March1st to 15thDay
9%15%30%29%13%2
330
16th to endDay
5%21%31%24%15%2
311
April1st to 15thDay
8%21%31%23%11%3
269
16th to endDay
7%25%32%24%7%2
270
May1st to 15thDay
6%17%38%23%11%3
288
16th to endDay
210%39%35%10%1
330
June1st to 15thDay
5%6%34%36%13%2
315
16th to endDay
4219%46%22%4
315
July1st to 15thDay
6%12%49%26%4
305
16th to endDay
10%9%35%29%14%
327
August1st to 15thDay
6%8%41%34%8%
315
16th to endDay
5%9%38%36%9%
332
September1st to 15thDay
10%118%41%20%7%
315
16th to endDay
6%6%27%40%16%3
315
October1st to 15thDay
29%24%36%21%4
204
16th to endDay
5%110%37%38%6%
144
November1st to 15thDay
5%8%15%42%23%3
135
16th to endDay
8%6%22%31%28%2
135
December1st to 15thDay
10%223%37%22%2
135
16th to endDay
18%419%27%23%6%
144
January1st to 15thNight
8%114%42%26%5%
780
16th to endNight
11%214%41%25%5%
832
February1st to 15thNight
7%113%40%29%6%
764
16th to endNight
9%319%44%20%2
684
March1st to 15thNight
8%318%39%25%4
780
16th to endNight
3316%40%30%5%
792
April1st to 15thNight
45%18%45%22%2
683
16th to endNight
25%19%42%26%3
540
May1st to 15thNight
1421%41%28%3
540
16th to endNight
2317%40%32%3
563
June1st to 15thNight
1111%43%37%3
540
16th to endNight
117%35%49%5%
540
July1st to 15thNight
2424%58%9%
510
16th to endNight
4216%61%14%
564
August1st to 15thNight
4115%61%17%
539
16th to endNight
4119%57%17%
595
September1st to 15thNight
6%5%24%49%13%
720
16th to endNight
310%34%40%10%
716
October1st to 15thNight
3112%39%35%7%
720
16th to endNight
216%37%39%11%
768
November1st to 15thNight
3112%41%34%6%
760
16th to endNight
7%112%38%32%6%
780
December1st to 15thNight
10%214%38%29%4
780
16th to endNight
11%213%41%25%6%
832
Page generated at 2018-03-22 08:34:19. Version ac04

Copyright 2018 A. Danko


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