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 2017-04-07.

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%
14742
11%
45367
8%
14702
34%
14702
14%
34692

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
10%
898
3%
2589
1%
895
12%
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
20%
631
8%
1963
4%
631
25%
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
26%
633
14%
1734
5%
633
33%
633
19%
1270
April16th to endNight
41%
495
17%
1485
10%
495
45%
495
22%
1007
May1st to 15thNight
42%
495
16%
1485
13%
495
47%
495
24%
989
May16th to endNight
48%
358
16%
1385
14%
358
57%
358
24%
810
June1st to 15thNight
44%
330
13%
1194
13%
330
51%
330
22%
739
June16th to endNight
52%
330
14%
1155
16%
330
56%
330
25%
713
July1st to 15thNight
63%
310
19%
1085
23%
310
67%
310
35%
581
July16th to endNight
59%
522
12%
1426
10%
489
60%
489
31%
883
August1st to 15thNight
60%
494
17%
1474
13%
491
63%
491
29%
935
August16th to endNight
59%
525
19%
1575
14%
525
61%
525
29%
974
September1st to 15thNight
52%
654
18%
1724
11%
654
55%
654
30%
1143
September16th to endNight
51%
657
18%
1815
12%
657
54%
657
27%
1203
October1st to 15thNight
36%
660
14%
1958
12%
660
40%
660
18%
1419
October16th to endNight
21%
704
7%
2153
4%
704
25%
704
9%
1775
November1st to 15thNight
27%
700
14%
2339
12%
700
32%
700
13%
1779
November16th to endNight
20%
720
7%
2520
6%
720
22%
720
6%
2138
December1st to 15thNight
10%
720
2%
2520
1%
720
11%
720
2%
2328
December16th to endNight
8%
927
2%
2847
0%
927
11%
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%30%
45861
Night
16%12%5%9%6%34445%27%
45539
Cloud CoverDay
16%10%47%6%34446%30%
45871
Night
16%11%5%9%6%34445%27%
45543
TransparencyDay
54%5%11%18%9%
45551
Night
59%5%9%15%8%
45367
SeeingDay
21%7%26%24%13%6%
5083
Night
22%10%27%26%11%1
14747

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
19%13%46%42344431%
2038
16th to endDay
17%9%24423347%38%
2145
May1st to 15thDay
17%6%25%43345%7%38%
2136
16th to endDay
13%5%2443445%7%45%
2377
June1st to 15thDay
14%7%25%5%3445%8%38%
2434
16th to endDay
14%425%425%45%8%41%
2475
July1st to 15thDay
10%414425%46%9%45%
2472
16th to endDay
10%424425%5%7%9%43%
2327
August1st to 15thDay
12%5%25%5%345%5%9%40%
2145
16th to endDay
13%6%245%25%5%6%7%42%
2269
September1st to 15thDay
17%7%26%42445%8%36%
1899
16th to endDay
18%6%25%423448%39%
1815
October1st to 15thDay
23%8%47%5%33445%29%
1672
16th to endDay
33%13%47%6%23335%15%
1716
November1st to 15thDay
17%16%5%7%7%35%445%24%
1517
16th to endDay
19%20%7%12%7%35%335%12%
1440
December1st to 15thDay
18%24%13%15%6%233235%
1440
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%12%34424446%32%
1734
16th to endNight
17%8%36%434345%37%
1485
May1st to 15thNight
15%7%26%42445%8%37%
1485
16th to endNight
11%425%5%3445%7%44%
1383
June1st to 15thNight
14%6%36%425%35%9%39%
1194
16th to endNight
13%5%245%25%45%7%43%
1155
July1st to 15thNight
7%21443435%9%52%
1155
16th to endNight
9%4144246%6%10%44%
1533
August1st to 15thNight
10%425%6%345%48%45%
1485
16th to endNight
11%5%25%5%24437%48%
1575
September1st to 15thNight
14%425%42446%6%43%
1724
16th to endNight
14%5%25%434346%43%
1815
October1st to 15thNight
20%8%27%5%3345%6%32%
1958
16th to endNight
28%12%39%5%24435%19%
2153
November1st to 15thNight
19%12%47%5%4445%6%25%
2339
16th to endNight
22%20%7%10%5%2433415%
2520
December1st to 15thNight
20%23%10%14%6%342228%
2520
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%14%46%42335%5%30%
2038
16th to endDay
18%9%35%323347%37%
2145
May1st to 15thDay
18%6%25%43435%6%38%
2136
16th to endDay
13%5%24424348%44%
2377
June1st to 15thDay
14%7%25%5%2445%9%37%
2434
16th to endDay
14%424435%45%9%40%
2475
July1st to 15thDay
10%5%14425%5%6%9%44%
2472
16th to endDay
10%4245%245%7%9%42%
2327
August1st to 15thDay
12%5%25%5%35%46%10%38%
2145
16th to endDay
12%6%245%346%5%8%40%
2269
September1st to 15thDay
16%8%26%42446%8%35%
1899
16th to endDay
17%6%2442445%7%39%
1815
October1st to 15thDay
22%8%37%6%33446%29%
1672
16th to endDay
32%14%37%6%33335%15%
1716
November1st to 15thDay
17%15%48%6%35%44424%
1517
16th to endDay
19%20%7%10%7%35%43313%
1440
December1st to 15thDay
18%24%12%14%7%333335%
1440
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%23447%32%
1734
16th to endNight
17%7%25%5%35%346%37%
1485
May1st to 15thNight
15%7%345%2445%7%38%
1484
16th to endNight
10%5%25%435%45%7%45%
1383
June1st to 15thNight
14%6%35%425%35%9%38%
1194
16th to endNight
12%434435%35%8%42%
1155
July1st to 15thNight
7%22443335%9%52%
1155
16th to endNight
8%3244346%6%10%44%
1533
August1st to 15thNight
9%425%5%345%48%45%
1485
16th to endNight
10%6%35%433446%48%
1575
September1st to 15thNight
14%425%43445%6%42%
1724
16th to endNight
14%6%25%5%3435%6%44%
1815
October1st to 15thNight
19%7%46%5%335%5%6%31%
1958
16th to endNight
28%11%48%5%24445%19%
2153
November1st to 15thNight
19%11%47%6%35%45%7%25%
2339
16th to endNight
21%19%8%8%6%2433415%
2520
December1st to 15thNight
19%22%10%13%7%343228%
2520
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
54%5%8%19%10%
2038
16th to endDay
45%5%10%21%14%2
2145
May1st to 15thDay
45%5%9%25%13%
2136
16th to endDay
38%5%13%24%15%2
2381
June1st to 15thDay
42%6%12%24%13%
2434
16th to endDay
40%6%12%26%12%
2475
July1st to 15thDay
33%6%14%26%16%2
2313
16th to endDay
35%7%16%25%13%1
2171
August1st to 15thDay
39%6%14%24%13%1
2132
16th to endDay
39%7%15%25%11%1
2269
September1st to 15thDay
45%7%12%24%9%
1899
16th to endDay
43%5%15%26%9%
1815
October1st to 15thDay
55%5%10%17%10%1
1672
16th to endDay
72%5%9%9%3
1716
November1st to 15thDay
61%6%10%13%7%
1517
16th to endDay
76%5%7%7%2
1440
December1st to 15thDay
85%45%3
1440
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
52%5%9%18%12%
1734
16th to endNight
47%48%18%18%2
1485
May1st to 15thNight
44%5%10%23%14%2
1485
16th to endNight
38%5%11%26%15%2
1385
June1st to 15thNight
41%5%11%24%15%1
1194
16th to endNight
39%6%11%24%16%1
1155
July1st to 15thNight
28%6%11%28%23%2
1085
16th to endNight
34%7%15%23%16%1
1426
August1st to 15thNight
36%7%13%26%13%2
1474
16th to endNight
37%6%11%29%14%1
1575
September1st to 15thNight
39%6%13%28%10%1
1724
16th to endNight
41%5%13%26%11%
1815
October1st to 15thNight
51%7%10%18%12%
1958
16th to endNight
67%6%10%10%4
2153
November1st to 15thNight
58%6%11%16%5%1
2339
16th to endNight
74%49%9%1
2520
December1st to 15thNight
84%5%6%31
2520
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
28%8%25%24%8%3
235
16th to endDay
26%7%23%20%12%9%
210
May1st to 15thDay
21%431%20%14%7%
228
16th to endDay
18%425%22%19%8%
267
June1st to 15thDay
18%9%26%25%16%2
379
16th to endDay
16%5%28%30%15%4
420
July1st to 15thDay
12%5%28%31%15%7%
400
16th to endDay
11%327%28%19%9%
313
August1st to 15thDay
15%124%24%18%16%
253
16th to endDay
16%415%27%21%15%
268
September1st to 15thDay
14%418%27%20%14%
255
16th to endDay
21%418%24%20%11%
254
October1st to 15thDay
23%6%23%28%12%4
255
16th to endDay
38%10%27%18%5%
228
November1st to 15thDay
17%15%29%21%15%1
79
16th to endDay
30%16%33%15%13
60
December1st to 15thDay
38%23%30%6%1
60
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
27%9%31%23%7%
633
16th to endNight
23%8%22%30%12%1
495
May1st to 15thNight
22%326%31%14%1
495
16th to endNight
13%326%38%15%1
359
June1st to 15thNight
18%5%24%36%13%1
330
16th to endNight
16%223%40%15%1
330
July1st to 15thNight
8%120%49%18%2
310
16th to endNight
10%221%39%25%1
522
August1st to 15thNight
11%216%40%26%2
494
16th to endNight
13%116%34%29%3
525
September1st to 15thNight
16%321%32%19%6%
654
16th to endNight
17%6%19%33%19%4
657
October1st to 15thNight
24%6%25%27%14%1
660
16th to endNight
35%11%25%23%3
704
November1st to 15thNight
27%12%28%20%10%1
700
16th to endNight
33%16%23%20%5%
720
December1st to 15thNight
34%15%31%15%2
720
16th to endNight
31%13%33%17%4
927
Page generated at 2017-04-08 05:35:19. Version ac04

Copyright 2017 A. Danko


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