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Hideaway Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hideaway Observatory clear sky chart from 2005-11-05 to 2018-02-22.

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
72%
15983
35%
48828
30%
15944
78%
15944
50%
23780

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
70%
778
32%
2522
34%
776
75%
776
47%
1228
January16th to endNight
67%
832
37%
2704
36%
832
75%
832
45%
1331
February1st to 15thNight
72%
758
35%
2479
34%
757
79%
757
52%
1127
February16th to endNight
61%
660
41%
1857
31%
660
71%
660
52%
953
March1st to 15thNight
62%
720
40%
1980
28%
720
72%
720
58%
975
March16th to endNight
69%
768
39%
2112
26%
768
79%
768
63%
991
April1st to 15thNight
61%
608
36%
1867
25%
608
72%
608
53%
849
April16th to endNight
61%
540
44%
1800
33%
540
80%
540
66%
685
May1st to 15thNight
64%
539
35%
1715
28%
539
75%
539
62%
714
May16th to endNight
73%
561
37%
1684
32%
561
78%
561
66%
708
June1st to 15thNight
77%
540
33%
1620
28%
540
80%
540
62%
712
June16th to endNight
78%
540
24%
1620
22%
540
79%
540
52%
774
July1st to 15thNight
74%
510
18%
1530
15%
510
75%
510
32%
920
July16th to endNight
78%
564
15%
1593
14%
531
79%
531
27%
1019
August1st to 15thNight
78%
539
21%
1626
20%
536
78%
536
31%
978
August16th to endNight
78%
573
24%
1910
26%
573
79%
573
31%
1092
September1st to 15thNight
76%
597
25%
1857
25%
597
78%
597
32%
1119
September16th to endNight
80%
716
41%
1980
31%
716
85%
716
61%
946
October1st to 15thNight
78%
720
37%
2160
32%
720
82%
720
61%
983
October16th to endNight
83%
768
44%
2304
36%
768
88%
768
70%
960
November1st to 15thNight
80%
760
42%
2280
35%
760
84%
760
67%
979
November16th to endNight
72%
780
42%
2389
36%
780
79%
780
55%
1116
December1st to 15thNight
71%
780
36%
2535
35%
780
76%
780
47%
1225
December16th to endNight
67%
832
34%
2704
33%
832
73%
832
41%
1396

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
4212323346%65%
49416
Night
4212323346%64%
49028
TransparencyDay
18%47%14%27%27%
49111
Night
19%47%14%27%26%
48834
SeeingDay
5%7%20%33%24%8%
5734
Night
4215%43%31%3
15994

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
4314323345%63%
1746
16th to endDay
7%312212236%64%
1872
February1st to 15thDay
5%213312236%68%
1710
16th to endDay
5%31332335%6%62%
1760
March1st to 15thDay
3213223345%67%
1980
16th to endDay
311212336%74%
2112
April1st to 15thDay
222312337%70%
2079
16th to endDay
1111112482%
2160
May1st to 15thDay
11223345%73%
2232
16th to endDay
211112235%76%
2429
June1st to 15thDay
211112236%76%
2340
16th to endDay
2112213446%67%
2340
July1st to 15thDay
4214436%7%8%11%45%
2340
16th to endDay
6%2245%48%6%9%12%37%
2467
August1st to 15thDay
5%314436%6%7%10%45%
2325
16th to endDay
6%214435%5%6%10%49%
2292
September1st to 15thDay
7%4145%3446%8%50%
2100
16th to endDay
421112335%73%
1978
October1st to 15thDay
3112212236%73%
1800
16th to endDay
21111223478%
1920
November1st to 15thDay
211212346%73%
1909
16th to endDay
42221223472%
1898
December1st to 15thDay
5%212223346%64%
1755
16th to endDay
6%323423336%62%
1872
January1st to 15thNight
6%213323246%63%
2522
16th to endNight
8%312213336%63%
2704
February1st to 15thNight
5%212213446%67%
2472
16th to endNight
5%21222335%6%63%
1857
March1st to 15thNight
422213346%68%
1980
16th to endNight
3212112235%74%
2112
April1st to 15thNight
3112213445%69%
1867
16th to endNight
11111232381%
1800
May1st to 15thNight
111211224475%
1715
16th to endNight
3112336%75%
1684
June1st to 15thNight
212212235%75%
1620
16th to endNight
11134135%5%7%63%
1620
July1st to 15thNight
33246%46%7%8%11%42%
1620
16th to endNight
32146%47%8%11%14%33%
1701
August1st to 15thNight
3215%5%45%7%9%10%43%
1635
16th to endNight
3225%5%36%6%8%10%44%
1910
September1st to 15thNight
5%4145%36%6%6%9%45%
1857
16th to endNight
212212235%72%
1980
October1st to 15thNight
21232323474%
2160
16th to endNight
1111222480%
2304
November1st to 15thNight
111213336%73%
2280
16th to endNight
5%212212245%69%
2389
December1st to 15thNight
7%32313245%63%
2535
16th to endNight
8%313323446%59%
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%15%34%18%
1747
16th to endDay
22%25%14%33%21%
1872
February1st to 15thDay
19%25%15%29%28%
1710
16th to endDay
22%45%14%31%21%
1760
March1st to 15thDay
19%239%34%30%
1980
16th to endDay
13%2311%38%30%
2112
April1st to 15thDay
15%2310%36%32%
2079
16th to endDay
8%129%30%47%
2160
May1st to 15thDay
11%35%10%27%42%
2232
16th to endDay
11%25%8%25%46%
2432
June1st to 15thDay
10%135%23%54%
2340
16th to endDay
15%45%10%19%44%
2340
July1st to 15thDay
26%9%14%18%14%15%
2201
16th to endDay
33%13%18%21%10%1
2312
August1st to 15thDay
29%10%13%19%19%7%
2310
16th to endDay
28%8%14%17%18%11%
2292
September1st to 15thDay
29%6%11%18%20%14%
2100
16th to endDay
14%2416%34%26%
1978
October1st to 15thDay
14%36%13%29%32%
1800
16th to endDay
10%15%15%33%33%
1920
November1st to 15thDay
12%25%15%36%27%
1909
16th to endDay
17%3313%35%27%
1898
December1st to 15thDay
21%36%23%29%16%
1755
16th to endDay
24%38%20%32%10%
1872
January1st to 15thNight
22%25%15%32%19%
2522
16th to endNight
24%2416%32%19%
2704
February1st to 15thNight
18%35%16%27%28%
2483
16th to endNight
20%35%16%31%22%
1857
March1st to 15thNight
17%2413%30%31%
1980
16th to endNight
14%2311%36%31%
2112
April1st to 15thNight
16%2312%35%29%
1867
16th to endNight
9%129%29%46%
1800
May1st to 15thNight
12%249%27%44%
1716
16th to endNight
11%26%9%25%44%
1685
June1st to 15thNight
13%235%22%52%
1620
16th to endNight
17%5%8%10%16%42%
1620
July1st to 15thNight
31%9%14%19%11%14%
1530
16th to endNight
31%14%25%20%6%2
1593
August1st to 15thNight
30%10%17%18%15%7%
1626
16th to endNight
29%9%16%16%17%10%
1910
September1st to 15thNight
31%8%11%19%15%12%
1857
16th to endNight
15%2415%33%27%
1980
October1st to 15thNight
14%26%14%27%33%
2160
16th to endNight
10%1415%29%39%
2304
November1st to 15thNight
11%2417%35%28%
2280
16th to endNight
18%25%11%31%31%
2389
December1st to 15thNight
22%25%19%32%16%
2535
16th to endNight
25%47%19%31%11%
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
14%317%36%23%5%
135
16th to endDay
1418%37%25%13%
144
February1st to 15thDay
8%210%27%38%11%
135
16th to endDay
10%16%31%28%9%3
240
March1st to 15thDay
6%17%26%25%15%7%
270
16th to endDay
419%29%26%13%6%
288
April1st to 15thDay
219%32%30%12%2
269
16th to endDay
5%21%32%27%10%1
270
May1st to 15thDay
315%37%27%14%1
288
16th to endDay
29%33%37%15%1
330
June1st to 15thDay
45%25%38%20%6%
315
16th to endDay
4116%41%26%9%
315
July1st to 15thDay
6%11%43%27%10%
305
16th to endDay
410%33%32%18%
327
August1st to 15thDay
7%7%33%36%14%
315
16th to endDay
6%7%31%38%16%
332
September1st to 15thDay
11%111%35%31%9%
315
16th to endDay
6%323%33%27%6%
313
October1st to 15thDay
1114%33%26%22%
135
16th to endDay
2112%25%35%22%
144
November1st to 15thDay
6%216%35%29%8%
135
16th to endDay
6%6%21%28%27%9%
135
December1st to 15thDay
5%211%38%34%7%
135
16th to endDay
11%8%13%38%20%6%
144
January1st to 15thNight
6%215%47%24%3
780
16th to endNight
9%314%46%24%1
832
February1st to 15thNight
5%217%46%26%2
764
16th to endNight
5%325%48%16%
660
March1st to 15thNight
4426%42%20%1
720
16th to endNight
2420%48%22%1
768
April1st to 15thNight
37%24%46%18%
608
16th to endNight
25%29%45%16%1
540
May1st to 15thNight
2326%47%18%1
540
16th to endNight
2319%49%25%
563
June1st to 15thNight
2114%53%27%
540
16th to endNight
1110%49%36%
540
July1st to 15thNight
38%36%48%3
510
16th to endNight
4427%54%8%
564
August1st to 15thNight
45%23%56%10%
539
16th to endNight
45%24%57%7%
573
September1st to 15thNight
416%33%49%5%
597
16th to endNight
3110%40%40%3
716
October1st to 15thNight
212%46%35%2
720
16th to endNight
2111%43%37%4
768
November1st to 15thNight
213%45%32%4
760
16th to endNight
6%114%42%30%4
780
December1st to 15thNight
7%114%46%27%2
780
16th to endNight
9%215%48%19%3
832
Page generated at 2018-02-23 09:21:30. Version ac04

Copyright 2018 A. Danko


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