Humarock Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Humarock Observatory clear sky chart from 2005-11-05 to 2017-09-18.

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
31%
14935
16%
46823
8%
14901
40%
14901
19%
31323

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
15%
720
16%
2506
6%
716
27%
716
14%
1699
January16th to endNight
13%
768
16%
2686
3%
768
29%
768
12%
1825
February1st to 15thNight
15%
704
13%
2174
3%
701
27%
701
15%
1525
February16th to endNight
18%
631
21%
1893
7%
631
36%
631
19%
1277
March1st to 15thNight
20%
720
16%
2138
8%
720
30%
720
16%
1490
March16th to endNight
23%
768
21%
2059
8%
768
34%
768
21%
1425
April1st to 15thNight
27%
718
17%
1796
5%
718
34%
718
21%
1271
April16th to endNight
33%
573
17%
1653
5%
573
41%
573
20%
1138
May1st to 15thNight
31%
540
14%
1620
7%
540
38%
540
16%
1156
May16th to endNight
35%
456
11%
1578
8%
455
40%
455
15%
1078
June1st to 15thNight
40%
360
11%
1440
13%
360
44%
360
14%
978
June16th to endNight
50%
360
11%
1440
13%
360
55%
360
19%
873
July1st to 15thNight
55%
340
12%
1360
17%
340
57%
340
20%
807
July16th to endNight
53%
379
14%
1421
18%
357
60%
357
20%
887
August1st to 15thNight
56%
539
16%
1608
12%
535
59%
535
24%
1037
August16th to endNight
61%
698
21%
1844
13%
698
64%
698
33%
1171
September1st to 15thNight
54%
720
19%
1881
11%
720
57%
720
32%
1206
September16th to endNight
51%
669
26%
1847
17%
669
58%
669
32%
1131
October1st to 15thNight
35%
660
22%
1837
12%
660
44%
660
24%
1212
October16th to endNight
26%
704
15%
2280
7%
704
37%
704
19%
1504
November1st to 15thNight
29%
700
15%
2277
10%
700
37%
700
17%
1533
November16th to endNight
23%
720
17%
2340
7%
720
34%
720
17%
1531
December1st to 15thNight
19%
720
16%
2457
5%
720
32%
720
14%
1686
December16th to endNight
13%
768
15%
2688
4%
768
27%
768
11%
1883

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%6%2442445%7%40%
47976
Night
16%6%25%42445%7%38%
46995
Cloud CoverDay
16%6%2442445%7%40%
47986
Night
16%6%25%424447%39%
47000
TransparencyDay
41%6%13%21%14%1
47666
Night
45%6%12%20%13%1
46823
SeeingDay
18%12%22%27%15%3
5968
Night
17%19%25%25%10%1
14935

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
16%10%2432445%7%38%
1432
16th to endDay
16%7%35%42435%6%40%
1536
February1st to 15thDay
19%7%33426%45%7%34%
1685
16th to endDay
13%7%3343446%8%38%
1580
March1st to 15thDay
20%6%2443445%7%34%
1811
16th to endDay
16%7%34323347%42%
2163
April1st to 15thDay
16%6%3442445%6%40%
2152
16th to endDay
17%414423447%44%
2305
May1st to 15thDay
23%7%25%423346%34%
2332
16th to endDay
16%5%24424448%42%
2546
June1st to 15thDay
24%5%234235%5%9%33%
2520
16th to endDay
13%4245%35%5%7%10%38%
2520
July1st to 15thDay
10%4245%25%5%6%9%41%
2520
16th to endDay
11%424435%6%6%9%40%
2639
August1st to 15thDay
10%425%4345%7%8%42%
2340
16th to endDay
10%41333446%8%47%
2357
September1st to 15thDay
12%42342345%6%49%
2079
16th to endDay
14%423423446%51%
1838
October1st to 15thDay
20%424323346%43%
1793
16th to endDay
16%6%2432445%6%43%
1591
November1st to 15thDay
22%7%23313445%39%
1581
16th to endDay
18%5%25%435%447%39%
1620
December1st to 15thDay
16%8%36%6%34347%36%
1500
16th to endDay
23%10%35%424345%31%
1536
January1st to 15thNight
17%8%36%434446%36%
2506
16th to endNight
18%10%345%2345%8%33%
2686
February1st to 15thNight
16%8%45%5%25%5%5%7%34%
2173
16th to endNight
16%8%345%3335%6%39%
1893
March1st to 15thNight
18%8%15%5%34447%36%
2125
16th to endNight
16%8%35%425%34442%
2059
April1st to 15thNight
17%8%246%25%35%6%36%
1796
16th to endNight
19%6%25%5%35%445%39%
1653
May1st to 15thNight
20%7%36%434447%33%
1620
16th to endNight
20%5%26%43435%9%34%
1576
June1st to 15thNight
21%7%35%42445%6%33%
1440
16th to endNight
15%5%2432445%9%40%
1440
July1st to 15thNight
10%5%25%5%2447%9%41%
1440
16th to endNight
13%436%5%35%5%6%9%37%
1517
August1st to 15thNight
7%5%25%5%35%6%7%8%41%
1620
16th to endNight
11%4234235%6%9%46%
1844
September1st to 15thNight
11%41442445%7%47%
1881
16th to endNight
14%41331345%7%50%
1847
October1st to 15thNight
21%424422345%44%
1837
16th to endNight
18%6%2442435%5%40%
2280
November1st to 15thNight
18%6%26%423446%39%
2277
16th to endNight
17%6%25%424348%38%
2340
December1st to 15thNight
18%7%35%5%3335%7%36%
2457
16th to endNight
19%9%245%2435%7%33%
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
17%9%3432345%6%40%
1432
16th to endDay
16%6%35%423346%40%
1536
February1st to 15thDay
18%7%25%335%45%6%36%
1685
16th to endDay
14%7%14435%447%40%
1580
March1st to 15thDay
20%7%25%42445%6%35%
1821
16th to endDay
16%7%2442335%7%41%
2163
April1st to 15thDay
17%7%345%24447%38%
2152
16th to endDay
17%424424447%44%
2305
May1st to 15thDay
24%7%35%424346%33%
2332
16th to endDay
15%5%2443435%7%42%
2546
June1st to 15thDay
25%42342445%8%33%
2520
16th to endDay
12%4245%346%7%10%37%
2520
July1st to 15thDay
11%5%25%425%5%7%9%40%
2520
16th to endDay
11%4245%36%5%6%9%39%
2639
August1st to 15thDay
11%4245%345%7%9%41%
2340
16th to endDay
11%4144245%5%7%46%
2357
September1st to 15thDay
12%414424447%48%
2079
16th to endDay
14%5%23223347%49%
1838
October1st to 15thDay
20%6%24322347%43%
1793
16th to endDay
16%6%15%423447%43%
1591
November1st to 15thDay
23%7%2332334440%
1581
16th to endDay
17%5%245%245%47%39%
1620
December1st to 15thDay
16%8%35%5%25%345%38%
1500
16th to endDay
22%10%25%42434433%
1536
January1st to 15thNight
17%8%26%423346%39%
2506
16th to endNight
17%10%35%423346%37%
2686
February1st to 15thNight
15%9%35%5%3445%6%36%
2166
16th to endNight
16%7%345%34336%41%
1893
March1st to 15thNight
19%7%245%34446%37%
2138
16th to endNight
16%7%35%434335%42%
2058
April1st to 15thNight
16%8%26%43445%6%36%
1796
16th to endNight
19%6%35%435%345%39%
1653
May1st to 15thNight
21%7%35%434347%33%
1620
16th to endNight
19%6%26%435%45%9%33%
1576
June1st to 15thNight
23%5%35%42445%7%33%
1440
16th to endNight
15%5%25%325%449%41%
1440
July1st to 15thNight
11%5%25%425%5%6%9%41%
1440
16th to endNight
13%425%6%25%6%7%8%36%
1517
August1st to 15thNight
8%425%6%35%5%7%9%40%
1620
16th to endNight
12%31442446%8%47%
1844
September1st to 15thNight
12%3145%245%47%47%
1881
16th to endNight
13%5%23423446%50%
1847
October1st to 15thNight
21%42442234444%
1837
16th to endNight
17%6%25%424346%40%
2280
November1st to 15thNight
18%7%25%434336%39%
2277
16th to endNight
16%7%25%5%2435%7%39%
2340
December1st to 15thNight
19%6%26%424436%38%
2457
16th to endNight
19%9%35%42445%7%34%
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
45%5%13%23%9%3
1433
16th to endDay
45%5%14%24%9%
1536
February1st to 15thDay
48%6%14%19%10%1
1688
16th to endDay
41%7%15%21%11%1
1580
March1st to 15thDay
48%5%14%19%9%1
1821
16th to endDay
41%5%12%21%14%4
2163
April1st to 15thDay
43%5%11%20%16%2
2152
16th to endDay
39%5%10%24%16%3
2305
May1st to 15thDay
50%5%9%17%14%2
2332
16th to endDay
40%7%15%21%12%1
2550
June1st to 15thDay
47%7%14%19%10%
2520
16th to endDay
37%8%16%21%14%1
2520
July1st to 15thDay
35%8%16%23%14%2
2371
16th to endDay
35%10%16%23%11%3
2473
August1st to 15thDay
34%9%16%24%14%
2327
16th to endDay
31%8%13%26%19%1
2357
September1st to 15thDay
33%6%13%20%23%1
2079
16th to endDay
33%410%26%22%2
1838
October1st to 15thDay
40%5%11%23%16%2
1793
16th to endDay
40%5%12%24%13%2
1591
November1st to 15thDay
46%5%12%21%12%1
1581
16th to endDay
45%5%13%22%11%1
1620
December1st to 15thDay
48%6%14%16%13%
1500
16th to endDay
56%5%14%15%8%
1536
January1st to 15thNight
49%5%13%19%11%
2506
16th to endNight
49%5%13%18%11%1
2686
February1st to 15thNight
49%5%14%19%9%1
2174
16th to endNight
45%5%12%21%13%2
1893
March1st to 15thNight
48%5%11%19%11%2
2138
16th to endNight
45%48%17%18%4
2059
April1st to 15thNight
47%49%18%17%2
1796
16th to endNight
47%5%9%19%15%3
1653
May1st to 15thNight
50%6%9%15%14%2
1620
16th to endNight
47%8%13%19%8%2
1578
June1st to 15thNight
50%7%12%17%11%
1440
16th to endNight
39%7%13%22%15%1
1440
July1st to 15thNight
38%7%13%25%13%
1360
16th to endNight
41%7%13%26%8%2
1421
August1st to 15thNight
37%9%12%23%15%1
1608
16th to endNight
33%7%12%27%18%
1844
September1st to 15thNight
34%6%13%25%18%1
1881
16th to endNight
33%5%7%26%25%2
1847
October1st to 15thNight
42%411%21%16%2
1837
16th to endNight
44%6%12%21%13%
2280
November1st to 15thNight
46%5%12%19%13%2
2277
16th to endNight
45%414%20%11%2
2340
December1st to 15thNight
48%6%14%20%9%
2457
16th to endNight
51%6%13%17%9%
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
21%13%30%30%5%
60
16th to endDay
25%9%29%35%
64
February1st to 15thDay
23%19%36%17%2
255
16th to endDay
11%20%37%23%7%
239
March1st to 15thDay
21%21%32%19%4
270
16th to endDay
17%22%31%20%7%
288
April1st to 15thDay
18%17%27%24%10%
270
16th to endDay
18%14%22%29%11%2
270
May1st to 15thDay
28%13%24%18%11%4
288
16th to endDay
17%10%17%35%17%1
331
June1st to 15thDay
20%10%19%32%15%1
315
16th to endDay
12%10%17%38%18%2
315
July1st to 15thDay
14%7%11%35%25%5%
305
16th to endDay
13%9%9%34%27%4
326
August1st to 15thDay
14%6%11%34%26%6%
313
16th to endDay
12%5%10%31%28%11%
332
September1st to 15thDay
15%6%18%28%23%8%
315
16th to endDay
19%8%14%27%14%14%
262
October1st to 15thDay
25%7%19%22%18%5%
251
16th to endDay
14%12%33%28%10%
240
November1st to 15thDay
24%14%22%23%12%2
235
16th to endDay
18%23%26%20%9%1
240
December1st to 15thDay
20%15%36%17%10%
120
16th to endDay
26%14%40%15%3
64
January1st to 15thNight
17%26%36%16%2
720
16th to endNight
20%27%34%14%2
768
February1st to 15thNight
19%26%34%18%1
704
16th to endNight
19%24%33%18%3
631
March1st to 15thNight
21%23%29%21%3
720
16th to endNight
17%22%31%20%8%
768
April1st to 15thNight
17%21%28%26%5%
718
16th to endNight
16%19%24%29%9%
573
May1st to 15thNight
20%18%23%25%10%1
540
16th to endNight
20%18%19%30%10%
456
June1st to 15thNight
20%17%14%33%12%1
360
16th to endNight
13%17%12%40%15%
360
July1st to 15thNight
9%12%12%45%19%1
340
16th to endNight
11%17%10%40%19%1
379
August1st to 15thNight
10%10%12%45%21%
539
16th to endNight
12%9%9%37%27%3
698
September1st to 15thNight
11%9%17%39%20%2
720
16th to endNight
15%10%15%28%22%6%
669
October1st to 15thNight
22%12%22%27%12%2
660
16th to endNight
20%16%33%21%8%
704
November1st to 15thNight
19%22%23%22%11%1
700
16th to endNight
17%27%27%19%7%
720
December1st to 15thNight
21%25%30%17%5%
720
16th to endNight
22%28%32%15%1
768
Page generated at 2017-09-19 07:32:22. Version ac04

Copyright 2017 A. Danko


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