Hidden Lake Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hidden Lake Observatory clear sky chart from 2005-11-05 to 2017-10-06.

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
23%
14988
17%
47046
6%
14957
35%
14957
16%
30911

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
13%
720
18%
2506
7%
716
28%
716
11%
1633
January16th to endNight
11%
768
17%
2658
4%
768
29%
768
10%
1743
February1st to 15thNight
10%
704
14%
2213
2%
701
24%
701
10%
1514
February16th to endNight
12%
631
20%
1893
5%
631
31%
631
12%
1272
March1st to 15thNight
12%
720
15%
2160
4%
720
26%
720
11%
1472
March16th to endNight
16%
768
22%
2001
5%
768
30%
768
15%
1322
April1st to 15thNight
13%
718
15%
1796
2%
718
21%
718
14%
1323
April16th to endNight
20%
654
17%
1734
2%
654
30%
654
17%
1196
May1st to 15thNight
17%
507
17%
1587
5%
507
30%
507
14%
1092
May16th to endNight
25%
374
12%
1497
8%
374
35%
374
13%
978
June1st to 15thNight
25%
360
12%
1440
7%
360
38%
360
14%
945
June16th to endNight
39%
360
12%
1440
11%
360
49%
360
19%
851
July1st to 15thNight
41%
340
13%
1360
13%
340
49%
340
21%
804
July16th to endNight
41%
376
15%
1418
14%
354
51%
354
20%
846
August1st to 15thNight
44%
491
16%
1562
9%
489
51%
489
25%
931
August16th to endNight
48%
764
19%
1910
9%
764
52%
764
31%
1248
September1st to 15thNight
36%
720
20%
1812
8%
720
42%
720
29%
1184
September16th to endNight
45%
717
26%
1980
16%
717
53%
717
31%
1196
October1st to 15thNight
29%
684
21%
1968
11%
684
39%
684
21%
1283
October16th to endNight
20%
704
14%
2238
4%
704
33%
704
15%
1494
November1st to 15thNight
22%
700
20%
2277
8%
700
37%
700
16%
1462
November16th to endNight
19%
720
18%
2388
6%
720
34%
720
13%
1594
December1st to 15thNight
15%
720
14%
2520
3%
720
28%
720
10%
1687
December16th to endNight
10%
768
16%
2688
3%
768
26%
768
8%
1841

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
16%7%35%5%345%5%7%35%
48155
Night
16%7%35%43445%6%38%
47216
Cloud CoverDay
16%7%35%5%35%5%5%7%36%
48165
Night
16%6%35%5%3445%6%38%
47221
TransparencyDay
46%6%12%21%12%1
47843
Night
43%5%13%22%12%1
47046
SeeingDay
20%23%25%17%9%3
5857
Night
19%28%24%19%6%
14989

By Month

Percentage Cloud Cover NE (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
14%7%36%5%36%6%6%6%32%
1432
16th to endDay
14%7%45%6%346%5%7%33%
1563
February1st to 15thDay
14%8%46%8%5%6%5%5%6%28%
1646
16th to endDay
14%10%36%7%3345%7%32%
1580
March1st to 15thDay
17%8%36%6%345%5%7%32%
1790
16th to endDay
16%8%45%434446%37%
2220
April1st to 15thDay
17%9%45%5%34436%36%
2152
16th to endDay
15%6%26%6%3335%6%39%
2225
May1st to 15thDay
23%8%35%5%2435%5%31%
2373
16th to endDay
17%6%25%5%35%5%5%7%35%
2618
June1st to 15thDay
22%7%24445%5%5%8%29%
2520
16th to endDay
16%6%25%5%36%46%9%31%
2520
July1st to 15thDay
11%6%36%5%36%5%6%8%34%
2520
16th to endDay
12%6%35%6%45%5%6%8%36%
2654
August1st to 15thDay
14%6%25%6%36%6%7%8%33%
2373
16th to endDay
12%5%25%5%35%5%6%7%40%
2292
September1st to 15thDay
12%6%25%5%445%5%7%39%
2147
16th to endDay
14%5%2442435%6%46%
1980
October1st to 15thDay
19%9%25%33235%5%39%
1790
16th to endDay
17%7%35%6%3445%6%34%
1634
November1st to 15thDay
16%8%35%424447%39%
1581
16th to endDay
18%6%44434446%38%
1569
December1st to 15thDay
18%7%26%6%335%45%34%
1440
16th to endDay
18%10%46%5%35%5%5%7%26%
1536
January1st to 15thNight
16%8%345%345%6%6%34%
2506
16th to endNight
14%9%36%5%35%5%47%34%
2658
February1st to 15thNight
14%8%45%436%6%6%7%31%
2212
16th to endNight
15%9%35%6%3446%6%35%
1893
March1st to 15thNight
17%8%246%3446%7%34%
2147
16th to endNight
15%7%36%413445%41%
2001
April1st to 15thNight
16%8%37%5%34345%34%
1796
16th to endNight
18%7%35%5%23347%39%
1734
May1st to 15thNight
18%9%46%5%23446%35%
1587
16th to endNight
16%7%24435%5%6%7%35%
1495
June1st to 15thNight
20%7%35%42445%7%35%
1440
16th to endNight
14%425%4245%5%9%42%
1440
July1st to 15thNight
13%325%435%45%7%43%
1440
16th to endNight
11%5%25%436%46%7%42%
1514
August1st to 15thNight
11%42442445%8%46%
1572
16th to endNight
12%42443436%7%46%
1910
September1st to 15thNight
14%5%15%41345%7%46%
1812
16th to endNight
12%5%24323345%52%
1980
October1st to 15thNight
17%7%25%323335%44%
1968
16th to endNight
19%7%25%43346%6%36%
2238
November1st to 15thNight
16%7%35%324445%41%
2277
16th to endNight
17%7%35%5%2445%6%35%
2388
December1st to 15thNight
20%7%35%5%35%46%7%31%
2520
16th to endNight
19%7%346%45%5%5%8%28%
2688

Percentage Cloud Cover SE (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
14%6%36%5%36%5%7%6%34%
1432
16th to endDay
13%8%35%5%36%6%5%6%35%
1563
February1st to 15thDay
14%8%45%8%5%6%45%6%30%
1646
16th to endDay
15%8%37%6%36%346%34%
1580
March1st to 15thDay
16%7%37%6%3445%7%32%
1800
16th to endDay
16%9%35%42445%5%37%
2220
April1st to 15thDay
17%8%45%434435%37%
2152
16th to endDay
15%6%36%5%33447%39%
2225
May1st to 15thDay
23%8%25%5%25%445%32%
2373
16th to endDay
17%6%25%5%345%6%7%36%
2618
June1st to 15thDay
23%5%245%26%5%5%7%30%
2520
16th to endDay
15%6%35%5%45%5%6%9%31%
2520
July1st to 15thDay
11%6%26%5%46%5%6%7%35%
2520
16th to endDay
11%6%26%6%35%6%6%7%37%
2654
August1st to 15thDay
13%5%25%5%46%6%6%8%33%
2373
16th to endDay
11%6%26%5%35%5%5%7%40%
2292
September1st to 15thDay
12%6%26%5%35%45%6%40%
2147
16th to endDay
14%42432335%6%47%
1980
October1st to 15thDay
19%8%24423345%39%
1790
16th to endDay
17%7%26%6%35%45%6%35%
1634
November1st to 15thDay
16%7%25%32336%8%39%
1581
16th to endDay
18%6%25%434445%39%
1569
December1st to 15thDay
17%6%45%5%345%5%6%34%
1440
16th to endDay
18%10%45%5%346%6%6%27%
1536
January1st to 15thNight
16%7%35%5%3445%7%35%
2506
16th to endNight
14%8%45%5%245%5%7%36%
2658
February1st to 15thNight
13%7%46%5%26%6%5%6%34%
2205
16th to endNight
15%8%25%5%35%45%6%36%
1893
March1st to 15thNight
17%7%346%2445%7%34%
2160
16th to endNight
16%6%26%42345%6%41%
2000
April1st to 15thNight
16%8%36%5%45%345%35%
1796
16th to endNight
18%7%24424346%40%
1734
May1st to 15thNight
19%7%36%5%24345%35%
1587
16th to endNight
16%7%35%5%3446%7%36%
1495
June1st to 15thNight
21%5%24424447%35%
1440
16th to endNight
14%425%42445%9%42%
1440
July1st to 15thNight
12%4245%25%5%6%7%43%
1440
16th to endNight
10%5%26%425%5%5%8%41%
1514
August1st to 15thNight
11%4144345%5%8%46%
1572
16th to endNight
12%5%13435%36%7%45%
1910
September1st to 15thNight
13%5%25%32345%6%46%
1812
16th to endNight
12%5%23323345%52%
1980
October1st to 15thNight
17%7%24423246%44%
1968
16th to endNight
19%6%245%2346%6%36%
2238
November1st to 15thNight
16%7%35%424345%41%
2277
16th to endNight
17%7%35%5%35%45%5%36%
2388
December1st to 15thNight
20%6%245%445%6%6%32%
2520
16th to endNight
19%7%35%5%35%5%6%7%30%
2688

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
44%6%15%22%8%1
1433
16th to endDay
45%5%17%20%9%1
1563
February1st to 15thDay
52%5%13%18%9%
1649
16th to endDay
48%411%20%12%1
1580
March1st to 15thDay
49%5%13%20%9%1
1800
16th to endDay
45%5%9%20%15%4
2220
April1st to 15thDay
49%410%20%13%2
2152
16th to endDay
44%48%22%16%3
2225
May1st to 15thDay
53%48%19%11%2
2373
16th to endDay
45%7%13%19%12%1
2622
June1st to 15thDay
50%8%12%19%8%
2520
16th to endDay
46%7%14%19%11%
2520
July1st to 15thDay
44%7%11%21%13%1
2371
16th to endDay
42%8%15%20%11%1
2487
August1st to 15thDay
44%7%13%22%11%
2359
16th to endDay
40%6%11%25%15%
2292
September1st to 15thDay
42%6%11%21%15%1
2147
16th to endDay
36%49%24%23%1
1980
October1st to 15thDay
46%49%23%13%2
1790
16th to endDay
47%5%13%19%11%1
1634
November1st to 15thDay
42%5%15%21%13%1
1581
16th to endDay
45%412%22%12%2
1569
December1st to 15thDay
47%5%16%19%9%
1440
16th to endDay
51%6%16%18%7%
1536
January1st to 15thNight
46%415%20%11%2
2506
16th to endNight
45%5%13%21%11%1
2658
February1st to 15thNight
46%6%15%19%9%1
2213
16th to endNight
45%412%23%11%2
1893
March1st to 15thNight
46%6%14%20%10%1
2160
16th to endNight
41%411%21%15%5%
2001
April1st to 15thNight
50%5%10%19%13%1
1796
16th to endNight
45%49%21%16%3
1734
May1st to 15thNight
49%49%19%14%2
1587
16th to endNight
44%9%16%17%10%1
1497
June1st to 15thNight
47%6%13%21%9%
1440
16th to endNight
38%6%16%25%12%
1440
July1st to 15thNight
37%7%14%27%12%
1360
16th to endNight
37%8%16%24%12%1
1418
August1st to 15thNight
33%8%17%27%12%1
1562
16th to endNight
35%7%12%27%16%
1910
September1st to 15thNight
37%5%13%23%17%1
1812
16th to endNight
33%49%26%24%1
1980
October1st to 15thNight
43%311%22%16%2
1968
16th to endNight
45%5%16%22%9%
2238
November1st to 15thNight
43%412%20%15%3
2277
16th to endNight
46%5%13%21%10%1
2388
December1st to 15thNight
47%6%16%21%8%
2520
16th to endNight
49%6%14%20%8%
2688

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
25%33%30%8%3
60
16th to endDay
27%27%34%10%
69
February1st to 15thDay
24%38%26%8%1
162
16th to endDay
21%37%25%12%3
239
March1st to 15thDay
32%30%24%11%2
270
16th to endDay
28%32%21%10%32
288
April1st to 15thDay
25%30%25%12%5%
270
16th to endDay
18%28%25%16%7%3
270
May1st to 15thDay
32%27%18%14%43
288
16th to endDay
19%24%28%17%8%1
331
June1st to 15thDay
20%23%26%19%8%1
315
16th to endDay
17%23%28%19%9%1
315
July1st to 15thDay
14%14%34%23%11%1
305
16th to endDay
13%16%30%23%12%3
326
August1st to 15thDay
17%14%23%25%12%7%
313
16th to endDay
11%11%23%25%17%9%
332
September1st to 15thDay
13%18%24%20%14%8%
315
16th to endDay
14%14%24%17%18%11%
314
October1st to 15thDay
20%16%23%20%14%4
278
16th to endDay
20%28%24%21%5%
249
November1st to 15thDay
21%27%20%20%7%2
235
16th to endDay
23%33%22%11%6%2
189
December1st to 15thDay
25%31%31%8%3
60
16th to endDay
34%32%26%6%
64
January1st to 15thNight
20%37%25%14%2
720
16th to endNight
21%38%24%14%1
768
February1st to 15thNight
20%36%27%14%1
704
16th to endNight
22%38%22%13%2
631
March1st to 15thNight
25%35%23%12%2
720
16th to endNight
20%37%22%14%4
768
April1st to 15thNight
20%33%29%12%3
718
16th to endNight
22%31%23%15%6%
654
May1st to 15thNight
22%29%26%15%5%
507
16th to endNight
18%25%25%22%7%
375
June1st to 15thNight
20%23%25%23%6%
360
16th to endNight
14%21%22%33%8%
360
July1st to 15thNight
12%14%26%31%15%
340
16th to endNight
9%21%21%33%14%
376
August1st to 15thNight
15%13%22%34%13%1
491
16th to endNight
12%11%21%31%19%3
764
September1st to 15thNight
14%16%27%26%13%1
720
16th to endNight
15%15%20%25%17%5%
717
October1st to 15thNight
22%20%24%23%8%1
684
16th to endNight
22%26%26%21%3
704
November1st to 15thNight
19%31%23%18%6%1
700
16th to endNight
20%31%24%16%5%1
720
December1st to 15thNight
25%34%22%13%4
720
16th to endNight
25%40%21%10%1
768
Page generated at 2017-10-07 14:07:54. Version ac04

Copyright 2017 A. Danko


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