Space Hut Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Space Hut Observatory clear sky chart from 2005-11-05 to 2017-10-31.

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
41%
15377
10%
47273
7%
15349
44%
15349
19%
33367

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
34%
895
7%
2685
4%
895
36%
895
14%
2064
January16th to endNight
30%
914
14%
2834
8%
914
37%
914
18%
2021
February1st to 15thNight
40%
700
9%
2424
6%
697
44%
697
15%
1737
February16th to endNight
44%
632
12%
2031
12%
632
47%
632
19%
1412
March1st to 15thNight
38%
720
14%
2105
10%
720
43%
720
19%
1519
March16th to endNight
39%
768
10%
2101
7%
767
40%
767
17%
1627
April1st to 15thNight
41%
590
13%
1670
8%
590
44%
590
19%
1217
April16th to endNight
43%
540
12%
1620
11%
540
46%
540
19%
1134
May1st to 15thNight
45%
389
9%
1305
8%
389
47%
389
19%
875
May16th to endNight
41%
374
0%
1309
0%
374
41%
374
16%
936
June1st to 15thNight
42%
360
0%
1260
0%
360
42%
360
14%
907
June16th to endNight
51%
360
0%
1226
0%
360
51%
360
18%
834
July1st to 15thNight
57%
340
0%
1190
0%
340
57%
340
22%
757
July16th to endNight
58%
376
3%
1239
2%
354
59%
354
24%
756
August1st to 15thNight
64%
378
6%
1391
8%
376
65%
376
25%
828
August16th to endNight
56%
573
13%
1719
11%
573
57%
573
28%
1110
September1st to 15thNight
57%
614
15%
1770
11%
614
59%
614
33%
1078
September16th to endNight
51%
716
20%
1980
13%
716
57%
716
35%
1218
October1st to 15thNight
44%
720
15%
2149
10%
720
49%
720
22%
1471
October16th to endNight
38%
783
15%
2511
10%
783
44%
783
20%
1708
November1st to 15thNight
30%
875
14%
2474
9%
875
35%
875
17%
1852
November16th to endNight
29%
900
10%
2700
6%
900
33%
900
14%
2062
December1st to 15thNight
30%
900
9%
2700
5%
900
33%
900
13%
2121
December16th to endNight
37%
960
12%
2880
6%
960
42%
960
17%
2123

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
11%8%47%6%35%5%6%8%31%
48481
Night
9%9%48%7%45%5%6%7%31%
47429
TransparencyDay
48%7%18%19%5%
48131
Night
49%6%16%20%6%
47283
SeeingDay
15%5%22%30%20%6%
6263
Night
13%5%26%34%17%2
15388

By Month

Percentage Cloud Cover NW (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
5%12%6%10%9%5%7%5%5%6%24%
1253
16th to endDay
5%12%6%9%9%5%5%45%6%28%
1401
February1st to 15thDay
8%9%6%10%9%35%6%6%6%27%
1432
16th to endDay
5%11%8%12%9%36%6%5%5%24%
1443
March1st to 15thDay
7%12%5%9%9%36%5%6%9%23%
1855
16th to endDay
11%11%6%9%6%35%6%5%8%24%
2118
April1st to 15thDay
12%10%46%7%35%5%48%30%
2278
16th to endDay
14%11%36%6%35%46%8%29%
2340
May1st to 15thDay
9%8%36%6%45%5%5%7%35%
2644
16th to endDay
17%8%26%5%45%45%7%30%
2802
June1st to 15thDay
17%8%37%8%46%5%5%7%25%
2700
16th to endDay
15%6%26%7%45%47%9%30%
2700
July1st to 15thDay
11%5%25%5%35%5%6%9%37%
2700
16th to endDay
10%425%5%35%5%7%9%40%
2846
August1st to 15thDay
12%5%25%4346%7%11%36%
2560
16th to endDay
9%425%5%345%6%9%42%
2483
September1st to 15thDay
13%6%25%43445%8%40%
2189
16th to endDay
11%6%245%3445%8%44%
1980
October1st to 15thDay
14%9%47%6%3445%6%33%
1809
16th to endDay
10%10%46%5%35%5%6%9%31%
1700
November1st to 15thDay
9%11%5%8%7%45%5%5%8%28%
1384
16th to endDay
7%10%6%11%8%35%45%6%30%
1260
December1st to 15thDay
6%13%6%11%9%6%8%7%5%6%18%
1260
16th to endDay
6%11%49%10%47%7%6%7%24%
1344
January1st to 15thNight
6%11%6%10%9%5%7%6%5%6%24%
2685
16th to endNight
6%10%5%9%7%45%46%7%31%
2834
February1st to 15thNight
5%8%6%11%8%47%5%46%28%
2421
16th to endNight
6%12%5%9%6%45%5%6%8%30%
2031
March1st to 15thNight
8%9%49%7%46%5%6%8%28%
2105
16th to endNight
10%11%6%10%8%35%5%7%9%21%
2100
April1st to 15thNight
10%9%48%7%45%5%6%6%30%
1670
16th to endNight
14%10%36%5%445%5%7%32%
1620
May1st to 15thNight
11%7%47%7%46%6%6%5%32%
1304
16th to endNight
20%7%37%5%35%45%5%30%
1309
June1st to 15thNight
16%9%36%8%36%5%5%8%25%
1260
16th to endNight
11%6%26%7%37%6%6%11%30%
1226
July1st to 15thNight
11%5%247%35%6%7%10%37%
1260
16th to endNight
10%5%246%26%6%6%11%39%
1323
August1st to 15thNight
10%4245%35%47%8%42%
1398
16th to endNight
10%425%6%345%6%8%40%
1719
September1st to 15thNight
11%425%42335%7%48%
1770
16th to endNight
10%41442346%7%50%
1980
October1st to 15thNight
12%9%46%43446%7%35%
2149
16th to endNight
9%9%36%7%35%6%7%8%32%
2511
November1st to 15thNight
11%12%5%8%5%45%5%5%6%28%
2474
16th to endNight
7%12%6%10%8%46%5%5%5%27%
2700
December1st to 15thNight
9%13%6%11%9%5%5%45%7%21%
2700
16th to endNight
411%411%8%47%6%6%9%25%
2880

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
57%8%15%13%4
1253
16th to endDay
55%6%13%15%7%1
1401
February1st to 15thDay
54%6%18%14%5%
1432
16th to endDay
58%5%11%18%5%
1443
March1st to 15thDay
55%6%18%15%3
1855
16th to endDay
55%8%13%17%5%
2119
April1st to 15thDay
51%6%15%19%6%
2278
16th to endDay
51%5%16%17%7%1
2340
May1st to 15thDay
46%6%13%23%10%
2644
16th to endDay
52%6%12%18%9%
2807
June1st to 15thDay
55%6%15%18%3
2700
16th to endDay
47%8%21%17%4
2700
July1st to 15thDay
41%8%23%23%3
2541
16th to endDay
38%9%29%20%1
2667
August1st to 15thDay
39%10%30%17%2
2542
16th to endDay
36%7%25%24%5%
2483
September1st to 15thDay
40%6%20%24%6%1
2189
16th to endDay
36%7%19%28%6%1
1980
October1st to 15thDay
50%5%16%21%5%
1809
16th to endDay
46%8%16%24%4
1700
November1st to 15thDay
52%5%17%19%4
1384
16th to endDay
54%6%18%15%4
1260
December1st to 15thDay
63%8%10%14%2
1260
16th to endDay
56%6%14%15%6%
1344
January1st to 15thNight
58%6%17%13%31
2685
16th to endNight
51%5%15%18%6%1
2834
February1st to 15thNight
53%6%16%16%6%
2432
16th to endNight
49%5%15%18%8%1
2031
March1st to 15thNight
50%7%15%20%6%
2105
16th to endNight
57%6%12%18%6%
2103
April1st to 15thNight
51%6%13%18%7%1
1670
16th to endNight
49%6%11%19%10%1
1620
May1st to 15thNight
48%5%10%20%13%
1305
16th to endNight
54%5%9%19%8%2
1309
June1st to 15thNight
54%6%15%18%5%
1260
16th to endNight
46%8%21%18%4
1226
July1st to 15thNight
40%9%21%23%5%
1190
16th to endNight
37%8%24%25%3
1239
August1st to 15thNight
36%8%29%23%2
1391
16th to endNight
38%8%19%26%6%
1719
September1st to 15thNight
35%5%19%28%9%2
1770
16th to endNight
31%7%17%29%11%2
1980
October1st to 15thNight
45%6%14%25%7%
2149
16th to endNight
45%7%18%23%5%
2511
November1st to 15thNight
53%7%10%21%5%
2474
16th to endNight
57%7%15%14%5%
2700
December1st to 15thNight
62%5%14%13%4
2700
16th to endNight
53%6%17%17%5%
2880

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
11%5%21%36%18%6%
60
16th to endDay
4323%45%15%7%
64
February1st to 15thDay
12%328%30%19%6%
66
16th to endDay
13%320%29%23%8%
102
March1st to 15thDay
15%5%31%34%10%2
270
16th to endDay
14%326%31%21%2
288
April1st to 15thDay
18%9%20%31%17%2
269
16th to endDay
23%9%17%27%16%5%
270
May1st to 15thDay
10%8%22%33%17%6%
453
16th to endDay
20%417%29%19%7%
517
June1st to 15thDay
17%6%24%28%16%7%
495
16th to endDay
15%5%20%28%21%8%
495
July1st to 15thDay
10%414%33%29%8%
475
16th to endDay
11%420%30%26%6%
515
August1st to 15thDay
14%214%27%26%14%
374
16th to endDay
9%5%27%28%25%4
332
September1st to 15thDay
17%5%24%28%17%6%
315
16th to endDay
15%11%24%29%15%4
315
October1st to 15thDay
28%428%24%10%5%
174
16th to endDay
18%8%29%26%14%3
144
November1st to 15thDay
19%32%38%8%1
86
16th to endDay
11%5%28%26%15%13%
60
December1st to 15thDay
1135%35%21%5%
60
16th to endDay
7%123%34%23%9%
64
January1st to 15thNight
11%7%30%35%12%2
900
16th to endNight
11%8%34%31%12%2
914
February1st to 15thNight
9%6%24%36%19%2
704
16th to endNight
10%425%34%19%4
632
March1st to 15thNight
10%430%37%13%3
720
16th to endNight
14%425%35%17%2
768
April1st to 15thNight
13%6%26%32%17%2
590
16th to endNight
20%5%20%36%15%2
540
May1st to 15thNight
13%5%22%36%20%2
390
16th to endNight
20%5%21%29%21%2
375
June1st to 15thNight
20%6%20%34%15%3
360
16th to endNight
14%220%31%26%3
360
July1st to 15thNight
13%116%41%26%1
340
16th to endNight
12%217%38%25%3
376
August1st to 15thNight
12%213%32%32%6%
378
16th to endNight
10%219%37%27%2
573
September1st to 15thNight
13%218%37%26%2
614
16th to endNight
11%425%39%15%3
716
October1st to 15thNight
17%425%35%15%1
720
16th to endNight
14%5%31%35%11%1
783
November1st to 15thNight
17%7%33%28%9%2
875
16th to endNight
11%7%33%32%11%3
900
December1st to 15thNight
14%8%29%28%15%3
900
16th to endNight
10%429%33%17%4
960
Page generated at 2017-11-01 15:23:31. Version ac04

Copyright 2017 A. Danko


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