Hiddenwell Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hiddenwell Observatory clear sky chart from 2005-11-05 to 2017-12-02.

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%
15489
11%
47692
8%
15449
35%
15449
14%
36295

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
9%
898
3%
2589
1%
895
11%
895
4%
2346
January16th to endNight
13%
789
4%
2517
2%
789
15%
789
4%
2267
February1st to 15thNight
15%
702
3%
2287
1%
701
18%
701
5%
2007
February16th to endNight
19%
631
8%
1963
3%
631
24%
631
9%
1610
March1st to 15thNight
22%
720
11%
2025
6%
720
26%
720
12%
1624
March16th to endNight
33%
768
17%
2112
11%
768
38%
768
21%
1514
April1st to 15thNight
27%
660
14%
1809
5%
660
33%
660
20%
1315
April16th to endNight
39%
540
17%
1620
10%
540
43%
540
22%
1102
May1st to 15thNight
42%
540
15%
1620
12%
540
46%
540
24%
1088
May16th to endNight
46%
391
16%
1514
14%
391
56%
391
22%
898
June1st to 15thNight
46%
360
12%
1302
12%
360
52%
360
22%
805
June16th to endNight
50%
360
14%
1260
17%
360
55%
360
25%
784
July1st to 15thNight
62%
340
18%
1190
22%
340
65%
340
34%
647
July16th to endNight
59%
564
14%
1548
12%
531
60%
531
32%
950
August1st to 15thNight
60%
539
16%
1609
12%
536
63%
536
29%
1019
August16th to endNight
58%
573
20%
1719
15%
573
60%
573
29%
1061
September1st to 15thNight
53%
714
18%
1881
11%
714
56%
714
31%
1226
September16th to endNight
53%
717
20%
1980
14%
717
56%
717
28%
1300
October1st to 15thNight
36%
720
14%
2136
12%
720
40%
720
18%
1545
October16th to endNight
21%
768
8%
2349
5%
768
26%
768
9%
1927
November1st to 15thNight
26%
760
13%
2539
12%
760
30%
760
12%
1960
November16th to endNight
19%
780
7%
2730
6%
780
21%
780
6%
2308
December1st to 15thNight
10%
728
2%
2546
1%
728
11%
728
2%
2354
December16th to endNight
8%
927
2%
2847
0%
927
10%
927
4%
2638

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%10%47%6%34446%31%
48747
Night
16%12%5%9%6%34445%27%
47864
Cloud CoverDay
16%10%47%6%34446%30%
48757
Night
16%11%5%9%6%34445%27%
47868
TransparencyDay
53%5%11%18%9%
48437
Night
58%5%9%15%8%
47692
SeeingDay
20%8%27%23%13%6%
6019
Night
22%10%27%27%11%1
15494

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%17%11%15%9%45%3338%
1346
16th to endDay
12%19%9%18%11%434337%
1704
February1st to 15thDay
14%17%9%16%10%3433212%
1575
16th to endDay
15%17%8%12%8%35%33416%
1509
March1st to 15thDay
14%11%7%12%8%34435%24%
1924
16th to endDay
15%9%5%7%6%24445%33%
2112
April1st to 15thDay
18%12%46%5%23445%31%
2148
16th to endDay
17%9%25%423347%38%
2340
May1st to 15thDay
18%6%25%43345%6%39%
2331
16th to endDay
13%5%25%43445%7%43%
2599
June1st to 15thDay
14%7%25%5%3445%8%39%
2655
16th to endDay
14%425%435%46%8%40%
2700
July1st to 15thDay
10%414426%46%9%44%
2697
16th to endDay
11%4244245%7%9%43%
2513
August1st to 15thDay
11%5%25%5%345%5%9%40%
2340
16th to endDay
13%6%245%25%5%6%7%41%
2476
September1st to 15thDay
16%7%26%425%45%7%37%
2071
16th to endDay
17%6%24423447%39%
1980
October1st to 15thDay
23%8%47%5%33445%30%
1824
16th to endDay
31%13%47%6%23335%16%
1872
November1st to 15thDay
17%16%5%7%7%35%435%23%
1646
16th to endDay
19%20%7%11%7%35%335%12%
1560
December1st to 15thDay
18%24%13%15%6%233235%
1451
16th to endDay
19%24%11%11%7%343246%
1374
January1st to 15thNight
20%17%8%13%10%434349%
2589
16th to endNight
14%16%9%16%11%45%4348%
2517
February1st to 15thNight
13%17%10%14%11%5%432313%
2285
16th to endNight
14%13%9%13%9%34445%18%
1963
March1st to 15thNight
14%14%6%12%7%3433424%
2013
16th to endNight
16%9%48%5%24345%36%
2112
April1st to 15thNight
20%11%34424446%33%
1809
16th to endNight
16%7%25%5%35%445%37%
1620
May1st to 15thNight
17%6%26%42445%7%37%
1620
16th to endNight
11%5%25%5%345%5%7%43%
1512
June1st to 15thNight
14%6%35%42435%9%38%
1302
16th to endNight
13%5%14426%45%7%42%
1260
July1st to 15thNight
8%31443435%9%51%
1260
16th to endNight
9%4144246%6%10%44%
1655
August1st to 15thNight
9%425%6%345%48%45%
1620
16th to endNight
10%5%25%5%24437%48%
1719
September1st to 15thNight
14%425%42436%6%44%
1881
16th to endNight
13%5%25%434346%44%
1980
October1st to 15thNight
20%8%27%5%3345%6%32%
2136
16th to endNight
28%12%39%5%34435%19%
2349
November1st to 15thNight
19%13%47%5%4445%5%24%
2539
16th to endNight
22%20%7%10%6%3433416%
2730
December1st to 15thNight
20%23%10%14%6%342228%
2546
16th to endNight
20%20%12%13%7%333337%
2847

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
16%16%11%16%8%45%3339%
1346
16th to endDay
12%19%9%18%11%443447%
1704
February1st to 15thDay
14%17%10%15%10%4433212%
1575
16th to endDay
16%17%8%12%8%45%43415%
1509
March1st to 15thDay
14%11%7%11%9%34435%23%
1935
16th to endDay
15%9%6%7%6%235%45%33%
2111
April1st to 15thDay
18%13%46%5%2345%5%31%
2148
16th to endDay
18%9%35%333348%37%
2340
May1st to 15thDay
18%6%25%43435%6%38%
2331
16th to endDay
13%5%25%43435%8%42%
2599
June1st to 15thDay
14%6%25%42445%9%38%
2655
16th to endDay
14%424435%45%9%39%
2700
July1st to 15thDay
10%5%14425%5%6%9%44%
2697
16th to endDay
10%4245%245%6%9%42%
2513
August1st to 15thDay
11%5%26%5%35%5%6%9%38%
2340
16th to endDay
12%6%245%346%5%8%39%
2476
September1st to 15thDay
15%7%26%42445%7%36%
2071
16th to endDay
17%6%2442445%6%40%
1980
October1st to 15thDay
22%8%37%6%33446%30%
1824
16th to endDay
30%14%38%6%33335%17%
1872
November1st to 15thDay
17%15%48%7%35%44423%
1646
16th to endDay
18%20%7%10%7%35%43313%
1560
December1st to 15thDay
18%24%11%14%7%333335%
1451
16th to endDay
19%23%10%12%8%334237%
1374
January1st to 15thNight
20%17%7%13%10%444349%
2589
16th to endNight
13%16%9%16%11%45%3449%
2517
February1st to 15thNight
13%17%9%14%10%5%5%33313%
2278
16th to endNight
15%13%8%13%9%44345%17%
1963
March1st to 15thNight
14%13%6%12%7%4444424%
2025
16th to endNight
16%10%47%5%2434436%
2112
April1st to 15thNight
20%11%445%24447%33%
1809
16th to endNight
17%7%25%5%35%446%36%
1620
May1st to 15thNight
16%6%25%5%2445%7%38%
1619
16th to endNight
10%6%25%5%35%5%5%6%44%
1512
June1st to 15thNight
14%6%25%435%36%9%38%
1302
16th to endNight
13%424435%45%8%42%
1260
July1st to 15thNight
8%32443335%9%51%
1260
16th to endNight
9%3244346%6%10%44%
1655
August1st to 15thNight
9%425%5%35%5%5%8%45%
1620
16th to endNight
10%6%245%33446%48%
1719
September1st to 15thNight
14%425%42445%6%44%
1881
16th to endNight
13%6%25%5%3435%6%45%
1980
October1st to 15thNight
19%7%46%5%335%5%6%32%
2136
16th to endNight
27%11%39%5%34445%20%
2349
November1st to 15thNight
20%12%47%6%35%45%6%24%
2539
16th to endNight
21%19%7%8%6%2433416%
2730
December1st to 15thNight
19%22%10%13%8%343228%
2546
16th to endNight
20%19%11%14%7%343337%
2847

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
81%5%5%6%1
1347
16th to endDay
81%46%42
1704
February1st to 15thDay
78%46%9%1
1577
16th to endDay
71%5%7%9%4
1509
March1st to 15thDay
63%6%8%14%6%
1935
16th to endDay
50%5%13%17%11%1
2112
April1st to 15thDay
53%5%9%20%10%
2148
16th to endDay
45%5%10%21%14%1
2340
May1st to 15thDay
45%5%9%24%13%
2331
16th to endDay
39%5%13%24%14%2
2603
June1st to 15thDay
41%6%12%24%13%
2655
16th to endDay
40%6%12%27%12%
2700
July1st to 15thDay
34%7%14%25%16%2
2538
16th to endDay
35%7%15%26%13%1
2357
August1st to 15thDay
39%7%14%24%12%1
2327
16th to endDay
40%6%15%24%11%
2476
September1st to 15thDay
45%7%12%24%9%1
2071
16th to endDay
42%5%14%27%9%
1980
October1st to 15thDay
55%49%18%9%1
1824
16th to endDay
70%5%10%9%4
1872
November1st to 15thDay
63%6%10%12%6%
1646
16th to endDay
76%5%8%7%2
1560
December1st to 15thDay
85%45%3
1451
16th to endDay
84%45%4
1374
January1st to 15thNight
79%5%6%42
2589
16th to endNight
78%6%7%41
2517
February1st to 15thNight
77%47%8%1
2287
16th to endNight
68%5%10%10%5%
1963
March1st to 15thNight
62%6%8%15%6%
2025
16th to endNight
51%39%19%13%1
2112
April1st to 15thNight
51%5%10%19%12%
1809
16th to endNight
47%5%9%17%17%2
1620
May1st to 15thNight
45%5%9%22%14%2
1620
16th to endNight
39%5%11%25%14%2
1514
June1st to 15thNight
41%5%11%24%15%1
1302
16th to endNight
40%6%11%24%15%1
1260
July1st to 15thNight
29%6%11%28%22%1
1190
16th to endNight
34%7%15%24%17%1
1548
August1st to 15thNight
36%8%13%26%13%1
1609
16th to endNight
36%6%11%29%14%1
1719
September1st to 15thNight
38%6%12%28%12%1
1881
16th to endNight
40%6%13%27%11%
1980
October1st to 15thNight
51%7%9%19%11%
2136
16th to endNight
67%6%11%10%4
2349
November1st to 15thNight
60%6%10%15%5%
2539
16th to endNight
73%49%9%1
2730
December1st to 15thNight
84%5%6%31
2546
16th to endNight
82%5%6%4
2847

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
16%25%45%8%5%
75
16th to endDay
33%11%27%26%2
96
February1st to 15thDay
30%24%34%11%
90
16th to endDay
23%24%33%14%3
81
March1st to 15thDay
23%15%32%20%7%
225
16th to endDay
26%5%31%22%10%2
288
April1st to 15thDay
26%9%27%24%8%2
270
16th to endDay
25%8%29%18%10%7%
270
May1st to 15thDay
24%5%30%19%13%6%
288
16th to endDay
19%6%29%21%16%7%
331
June1st to 15thDay
17%8%26%27%17%2
450
16th to endDay
15%7%31%28%13%3
495
July1st to 15thDay
13%5%27%31%16%6%
475
16th to endDay
12%325%28%20%9%
373
August1st to 15thDay
14%123%26%19%14%
313
16th to endDay
18%414%27%21%14%
332
September1st to 15thDay
13%419%26%21%14%
315
16th to endDay
19%417%23%23%12%
314
October1st to 15thDay
24%6%25%26%12%4
315
16th to endDay
35%12%28%18%4
288
November1st to 15thDay
22%16%29%18%11%
118
16th to endDay
27%21%33%13%22
90
December1st to 15thDay
36%23%30%7%1
63
16th to endDay
48%15%34%1
64
January1st to 15thNight
27%19%32%15%5%
900
16th to endNight
22%12%36%22%6%
789
February1st to 15thNight
22%16%34%22%4
704
16th to endNight
22%13%29%27%6%
631
March1st to 15thNight
20%16%33%24%5%
720
16th to endNight
20%10%29%27%11%1
768
April1st to 15thNight
26%9%32%23%6%
660
16th to endNight
22%9%24%30%12%1
540
May1st to 15thNight
22%326%31%14%1
540
16th to endNight
14%426%38%15%1
392
June1st to 15thNight
17%5%24%37%13%1
360
16th to endNight
16%224%40%14%1
360
July1st to 15thNight
9%220%47%19%2
340
16th to endNight
10%220%40%24%1
564
August1st to 15thNight
10%215%40%27%2
539
16th to endNight
13%117%34%28%3
573
September1st to 15thNight
15%320%31%21%7%
714
16th to endNight
15%5%19%33%21%4
717
October1st to 15thNight
24%6%25%27%14%1
720
16th to endNight
35%11%26%23%3
768
November1st to 15thNight
28%12%28%20%9%1
760
16th to endNight
32%17%24%20%5%
780
December1st to 15thNight
33%15%32%15%2
728
16th to endNight
31%13%33%17%4
927
Page generated at 2017-12-03 11:16:37. Version ac04

Copyright 2017 A. Danko


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