Hidden Hill Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hidden Hill Observatory clear sky chart from 2005-11-05 to 2017-03-22.

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
68%
14848
30%
45284
26%
14812
73%
14812
45%
22786

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
60%
716
20%
2407
19%
716
64%
716
32%
1342
January16th to endNight
58%
768
25%
2496
24%
768
63%
768
30%
1457
February1st to 15thNight
57%
699
25%
2264
24%
699
63%
699
31%
1303
February16th to endNight
53%
632
26%
1895
21%
632
61%
632
33%
1107
March1st to 15thNight
54%
720
20%
2034
18%
720
58%
720
32%
1256
March16th to endNight
52%
732
21%
1975
14%
732
57%
732
33%
1186
April1st to 15thNight
50%
659
25%
1649
12%
659
55%
659
34%
1020
April16th to endNight
56%
660
27%
1650
10%
660
63%
660
50%
883
May1st to 15thNight
66%
596
31%
1586
18%
596
72%
596
61%
770
May16th to endNight
69%
342
29%
1368
28%
342
78%
342
59%
478
June1st to 15thNight
73%
330
32%
1320
34%
330
83%
330
54%
495
June16th to endNight
87%
330
37%
1320
45%
330
91%
330
77%
397
July1st to 15thNight
93%
320
38%
1250
47%
320
95%
320
78%
382
July16th to endNight
92%
522
36%
1467
32%
489
92%
489
74%
587
August1st to 15thNight
92%
534
43%
1517
33%
531
92%
531
82%
601
August16th to endNight
93%
700
44%
1750
28%
700
94%
700
86%
754
September1st to 15thNight
92%
660
46%
1650
33%
660
93%
660
83%
734
September16th to endNight
84%
656
45%
1784
40%
656
87%
656
74%
776
October1st to 15thNight
74%
660
32%
1980
32%
660
80%
660
52%
946
October16th to endNight
74%
704
38%
2112
38%
704
80%
704
54%
992
November1st to 15thNight
69%
700
31%
2208
30%
700
75%
700
49%
1046
November16th to endNight
65%
720
27%
2394
26%
720
70%
720
37%
1223
December1st to 15thNight
57%
720
22%
2520
20%
720
64%
720
27%
1469
December16th to endNight
49%
768
23%
2688
20%
768
57%
768
24%
1582

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
6%313323345%62%
45600
Night
6%313323346%60%
45471
TransparencyDay
22%38%19%26%20%
45285
Night
22%39%18%24%20%
45285
SeeingDay
8%10%21%33%21%4
5271
Night
7%5%12%30%33%11%
14859

By Month

Percentage Cloud Cover SW (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
10%5%25%5%2435%6%46%
1529
16th to endDay
14%5%345%34436%44%
1728
February1st to 15thDay
12%7%35%425%345%44%
1598
16th to endDay
16%6%35%5%34445%38%
1579
March1st to 15thDay
10%7%36%6%45%5%5%8%36%
1924
16th to endDay
9%6%26%6%345%5%7%40%
2045
April1st to 15thDay
12%6%36%434446%44%
1969
16th to endDay
6%322213347%61%
1980
May1st to 15thDay
2313222247%66%
2033
16th to endDay
431231345%7%61%
2391
June1st to 15thDay
3312213337%67%
2310
16th to endDay
111112483%
2310
July1st to 15thDay
11112387%
2296
16th to endDay
1212384%
2286
August1st to 15thDay
11112387%
2101
16th to endDay
11112387%
2100
September1st to 15thDay
11121386%
1980
16th to endDay
311112335%76%
1843
October1st to 15thDay
3213312347%65%
1650
16th to endDay
4313323335%63%
1760
November1st to 15thDay
6%425%33446%7%53%
1649
16th to endDay
8%4245%3335%6%51%
1563
December1st to 15thDay
10%7%37%6%34446%40%
1440
16th to endDay
12%9%35%5%3445%7%40%
1536
January1st to 15thNight
9%425%43446%8%46%
2407
16th to endNight
12%425%42445%6%46%
2496
February1st to 15thNight
11%5%34425%5%6%8%42%
2253
16th to endNight
11%5%2344345%7%45%
1895
March1st to 15thNight
10%6%35%425%5%47%43%
2034
16th to endNight
8%425%5%2435%8%46%
1975
April1st to 15thNight
7%425%6%245%7%6%46%
1649
16th to endNight
4213224347%61%
1650
May1st to 15thNight
222212349%67%
1586
16th to endNight
2121235%7%70%
1368
June1st to 15thNight
1112213345%71%
1320
16th to endNight
1122386%
1320
July1st to 15thNight
212484%
1331
16th to endNight
1111122382%
1575
August1st to 15thNight
11111387%
1526
16th to endNight
1111289%
1750
September1st to 15thNight
11111486%
1650
16th to endNight
11111112480%
1784
October1st to 15thNight
4113323348%64%
1980
16th to endNight
4212222447%65%
2112
November1st to 15thNight
5%21231336%9%58%
2208
16th to endNight
6%3145%35%45%7%52%
2394
December1st to 15thNight
10%6%35%5%3445%7%44%
2520
16th to endNight
12%5%25%5%3445%6%44%
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
35%411%21%17%9%
1529
16th to endDay
40%48%15%19%12%
1728
February1st to 15thDay
39%410%19%19%6%
1598
16th to endDay
43%411%22%15%3
1579
March1st to 15thDay
40%5%12%18%17%5%
1924
16th to endDay
38%5%13%19%16%4
2045
April1st to 15thDay
37%411%21%20%4
1969
16th to endDay
21%312%27%26%8%
1980
May1st to 15thDay
15%28%27%33%11%
2033
16th to endDay
18%313%25%27%10%
2395
June1st to 15thDay
15%410%21%26%21%
2310
16th to endDay
6%1215%34%38%
2310
July1st to 15thDay
5%118%25%57%
2148
16th to endDay
7%148%28%50%
2131
August1st to 15thDay
6%113%30%48%
2085
16th to endDay
4112%38%42%
2100
September1st to 15thDay
5%1213%34%43%
1980
16th to endDay
10%2423%36%23%
1843
October1st to 15thDay
17%37%25%25%20%
1650
16th to endDay
22%28%21%26%17%
1760
November1st to 15thDay
26%312%24%23%9%
1649
16th to endDay
31%410%21%28%4
1563
December1st to 15thDay
41%311%16%20%5%
1440
16th to endDay
41%312%16%19%6%
1536
January1st to 15thNight
31%413%21%19%8%
2407
16th to endNight
34%5%12%13%18%16%
2496
February1st to 15thNight
34%311%21%19%8%
2264
16th to endNight
33%313%26%17%5%
1895
March1st to 15thNight
34%6%14%19%16%8%
2034
16th to endNight
31%5%14%18%19%9%
1975
April1st to 15thNight
31%413%24%19%5%
1649
16th to endNight
20%213%26%26%11%
1650
May1st to 15thNight
13%49%20%33%18%
1587
16th to endNight
11%113%26%33%12%
1368
June1st to 15thNight
13%310%17%25%30%
1320
16th to endNight
5%1411%30%46%
1320
July1st to 15thNight
5%126%21%63%
1250
16th to endNight
8%139%22%53%
1467
August1st to 15thNight
5%1113%29%49%
1517
16th to endNight
4111%35%46%
1750
September1st to 15thNight
5%138%27%53%
1650
16th to endNight
9%1319%33%33%
1784
October1st to 15thNight
17%39%22%24%22%
1980
16th to endNight
17%28%22%28%20%
2112
November1st to 15thNight
19%314%23%27%11%
2208
16th to endNight
26%410%22%25%10%
2394
December1st to 15thNight
35%5%11%17%21%8%
2520
16th to endNight
37%412%17%19%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
15%14%29%28%8%2
157
16th to endDay
14%13%26%25%16%2
256
February1st to 15thDay
16%13%25%25%18%
241
16th to endDay
18%18%25%21%13%2
238
March1st to 15thDay
16%18%24%22%15%2
270
16th to endDay
12%16%32%26%10%1
250
April1st to 15thDay
16%26%25%20%11%
209
16th to endDay
10%21%27%31%7%1
210
May1st to 15thDay
8%14%30%32%11%2
228
16th to endDay
7%13%22%30%21%3
266
June1st to 15thDay
6%12%29%35%13%3
255
16th to endDay
1425%39%22%6%
255
July1st to 15thDay
111%42%37%6%
245
16th to endDay
8%45%35%8%
271
August1st to 15thDay
1215%36%33%10%
255
16th to endDay
117%44%34%11%
268
September1st to 15thDay
212%40%37%7%
255
16th to endDay
5%416%39%28%6%
255
October1st to 15thDay
6%10%23%34%20%4
255
16th to endDay
8%9%25%37%18%
272
November1st to 15thDay
10%9%12%24%35%7%
155
16th to endDay
9%14%24%38%8%3
81
December1st to 15thDay
11%28%16%28%13%1
60
16th to endDay
15%14%12%32%18%6%
64
January1st to 15thNight
12%413%28%28%13%
720
16th to endNight
13%5%13%29%25%13%
768
February1st to 15thNight
15%413%29%25%11%
704
16th to endNight
13%8%17%30%21%7%
632
March1st to 15thNight
13%8%14%27%29%6%
720
16th to endNight
11%9%17%32%23%5%
732
April1st to 15thNight
9%12%18%32%23%3
659
16th to endNight
5%12%20%26%26%9%
660
May1st to 15thNight
2420%32%30%8%
597
16th to endNight
3419%30%35%6%
343
June1st to 15thNight
2215%41%31%5%
330
16th to endNight
8%39%42%8%
330
July1st to 15thNight
1333%49%11%
320
16th to endNight
1224%54%16%
522
August1st to 15thNight
332%48%14%
534
16th to endNight
228%56%12%
700
September1st to 15thNight
325%53%15%
660
16th to endNight
217%28%41%17%
656
October1st to 15thNight
6%48%32%32%16%
660
16th to endNight
6%410%27%32%19%
704
November1st to 15thNight
5%415%28%32%14%
700
16th to endNight
6%5%12%33%29%12%
720
December1st to 15thNight
12%8%11%33%24%9%
720
16th to endNight
14%11%15%29%23%5%
768
Page generated at 2017-03-23 04:36:16. Version ac04

Copyright 2017 A. Danko


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