Stoney Hill Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stoney Hill Observatory clear sky chart from 2005-11-05 to 2018-11-30.

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
29%
16401
15%
51679
7%
16371
37%
16371
18%
35211

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
16%
780
14%
2716
5%
776
27%
776
13%
1891
January16th to endNight
15%
832
12%
2863
3%
832
26%
832
12%
2003
February1st to 15thNight
12%
763
11%
2440
2%
761
23%
761
11%
1830
February16th to endNight
18%
683
14%
2049
5%
683
29%
683
14%
1464
March1st to 15thNight
15%
780
13%
2340
4%
780
25%
780
12%
1731
March16th to endNight
20%
832
20%
2155
6%
832
31%
832
19%
1501
April1st to 15thNight
17%
778
14%
1946
3%
778
24%
778
18%
1434
April16th to endNight
26%
718
16%
1874
4%
718
34%
718
23%
1300
May1st to 15thNight
25%
497
17%
1667
7%
497
36%
497
17%
1125
May16th to endNight
36%
406
12%
1625
10%
406
45%
406
17%
1041
June1st to 15thNight
34%
390
13%
1560
10%
390
46%
390
16%
1021
June16th to endNight
45%
390
13%
1560
12%
390
53%
390
24%
898
July1st to 15thNight
54%
370
15%
1480
19%
370
59%
370
24%
842
July16th to endNight
56%
408
15%
1546
16%
386
61%
386
25%
900
August1st to 15thNight
53%
505
16%
1646
11%
503
57%
503
28%
1003
August16th to endNight
53%
828
18%
2070
9%
828
56%
828
33%
1357
September1st to 15thNight
45%
780
18%
1950
8%
780
48%
780
30%
1318
September16th to endNight
49%
777
24%
2135
17%
777
55%
777
35%
1309
October1st to 15thNight
35%
780
18%
2285
11%
780
44%
780
22%
1542
October16th to endNight
24%
832
14%
2626
7%
832
34%
832
18%
1825
November1st to 15thNight
27%
820
17%
2667
9%
820
39%
820
18%
1789
November16th to endNight
25%
840
15%
2837
9%
840
35%
840
15%
1940
December1st to 15thNight
19%
780
11%
2730
3%
780
29%
780
13%
1974
December16th to endNight
14%
832
11%
2912
2%
832
25%
832
9%
2173

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
14%7%36%6%35%5%5%7%34%
52622
Night
15%7%35%5%35%45%7%36%
51849
Cloud CoverDay
15%7%36%6%35%5%5%7%35%
52631
Night
15%7%35%5%3445%6%37%
51855
TransparencyDay
47%7%13%19%11%1
52310
Night
46%6%13%20%11%1
51679
SeeingDay
19%14%29%22%11%3
7208
Night
19%14%31%24%7%
16403

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
13%9%47%6%46%6%6%6%28%
1552
16th to endDay
12%8%48%7%45%6%6%7%28%
1710
February1st to 15thDay
14%10%5%8%8%46%7%45%24%
1750
16th to endDay
14%9%48%8%3445%5%30%
1710
March1st to 15thDay
17%9%5%7%5%345%5%7%28%
1940
16th to endDay
13%9%46%5%3435%6%37%
2416
April1st to 15thDay
17%8%47%6%34435%35%
2332
16th to endDay
15%7%25%5%24447%38%
2360
May1st to 15thDay
18%6%35%6%36%45%6%33%
2623
16th to endDay
14%5%35%5%35%6%6%7%35%
2842
June1st to 15thDay
16%5%36%7%36%46%7%32%
2730
16th to endDay
13%5%26%6%46%6%6%8%32%
2730
July1st to 15thDay
8%426%5%46%6%6%9%37%
2730
16th to endDay
11%426%7%37%6%7%9%34%
2878
August1st to 15thDay
10%6%25%7%45%6%7%8%35%
2541
16th to endDay
10%5%245%35%6%6%8%40%
2484
September1st to 15thDay
13%6%25%5%35%5%5%7%38%
2340
16th to endDay
13%31442345%7%48%
2154
October1st to 15thDay
17%7%36%5%34445%36%
2002
16th to endDay
18%8%26%5%35%45%7%31%
1948
November1st to 15thDay
16%7%35%4345%46%36%
1851
16th to endDay
15%6%37%5%246%5%7%35%
1775
December1st to 15thDay
16%11%5%7%5%45%5%47%26%
1560
16th to endDay
18%10%48%7%35%45%7%24%
1664
January1st to 15thNight
14%11%36%6%25%45%7%31%
2716
16th to endNight
12%10%47%5%35%5%5%6%31%
2863
February1st to 15thNight
12%10%49%8%46%5%6%6%26%
2439
16th to endNight
13%8%47%6%36%5%5%7%31%
2049
March1st to 15thNight
19%9%36%5%35%5%5%5%30%
2327
16th to endNight
14%6%345%35%5%5%6%38%
2155
April1st to 15thNight
17%7%46%6%26%446%33%
1946
16th to endNight
18%435%5%24446%39%
1874
May1st to 15thNight
17%7%36%5%33446%37%
1667
16th to endNight
12%5%345%45%46%7%38%
1623
June1st to 15thNight
17%5%35%4345%6%7%36%
1560
16th to endNight
10%4145%25%5%6%9%44%
1560
July1st to 15thNight
8%325%5%36%5%7%7%44%
1560
16th to endNight
10%424435%5%5%9%43%
1642
August1st to 15thNight
10%5%245%345%6%7%45%
1656
16th to endNight
12%4245%3446%7%46%
2070
September1st to 15thNight
15%6%25%324447%43%
1950
16th to endNight
11%413424447%51%
2135
October1st to 15thNight
16%7%26%42445%5%40%
2285
16th to endNight
17%6%25%6%3445%7%35%
2626
November1st to 15thNight
16%7%35%42445%6%37%
2667
16th to endNight
16%6%35%6%35%446%36%
2837
December1st to 15thNight
18%9%36%5%3446%7%29%
2730
16th to endNight
19%9%47%6%4445%6%26%
2912

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
13%9%46%6%47%5%6%7%28%
1552
16th to endDay
12%8%46%8%45%5%7%6%29%
1710
February1st to 15thDay
14%11%48%7%46%6%5%5%25%
1750
16th to endDay
14%10%37%8%4445%6%31%
1710
March1st to 15thDay
18%10%46%6%3445%7%29%
1950
16th to endDay
13%8%46%6%34445%38%
2415
April1st to 15thDay
18%6%47%6%34435%35%
2332
16th to endDay
16%7%25%5%2445%6%39%
2360
May1st to 15thDay
19%6%25%5%26%45%6%34%
2623
16th to endDay
15%6%25%435%5%6%8%36%
2842
June1st to 15thDay
17%5%27%6%445%5%8%32%
2730
16th to endDay
13%5%26%7%45%6%6%8%33%
2730
July1st to 15thDay
9%5%345%46%6%6%9%38%
2730
16th to endDay
11%425%7%45%6%7%8%35%
2878
August1st to 15thDay
10%6%26%6%45%6%5%8%36%
2541
16th to endDay
11%4235%45%5%6%8%41%
2484
September1st to 15thDay
14%6%25%435%46%7%39%
2340
16th to endDay
14%413324447%49%
2154
October1st to 15thDay
19%6%35%5%34445%37%
2002
16th to endDay
19%7%25%5%35%45%7%32%
1948
November1st to 15thDay
17%6%36%43445%6%37%
1851
16th to endDay
16%7%25%5%345%5%7%35%
1775
December1st to 15thDay
17%11%5%6%6%35%446%28%
1560
16th to endDay
18%10%48%6%445%46%25%
1664
January1st to 15thNight
14%11%46%5%25%5%5%7%31%
2716
16th to endNight
13%10%37%5%45%45%6%31%
2863
February1st to 15thNight
13%11%49%7%36%5%5%6%27%
2432
16th to endNight
14%9%37%7%36%5%5%6%31%
2049
March1st to 15thNight
19%8%36%6%35%5%5%5%31%
2340
16th to endNight
15%6%245%35%5%5%6%39%
2155
April1st to 15thNight
17%8%37%5%34446%34%
1946
16th to endNight
19%425%5%24446%39%
1874
May1st to 15thNight
18%7%25%5%34445%38%
1667
16th to endNight
13%425%5%25%5%6%8%38%
1623
June1st to 15thNight
17%6%244246%5%7%36%
1560
16th to endNight
11%423435%47%9%44%
1560
July1st to 15thNight
9%325%436%5%5%8%44%
1560
16th to endNight
11%325%435%46%9%43%
1642
August1st to 15thNight
11%3245%245%5%8%45%
1656
16th to endNight
12%4245%2345%6%46%
2070
September1st to 15thNight
16%6%245%2445%7%42%
1950
16th to endNight
11%423424348%50%
2135
October1st to 15thNight
17%6%36%423445%40%
2285
16th to endNight
18%7%35%5%3446%6%35%
2626
November1st to 15thNight
16%8%25%42445%7%38%
2667
16th to endNight
18%5%35%5%35%446%37%
2837
December1st to 15thNight
19%9%36%5%3445%6%30%
2730
16th to endNight
19%9%47%6%3445%6%26%
2912

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
52%7%13%17%8%
1553
16th to endDay
51%8%15%16%7%
1710
February1st to 15thDay
58%8%11%13%7%
1753
16th to endDay
53%6%12%16%10%
1710
March1st to 15thDay
54%5%13%16%7%1
1950
16th to endDay
47%5%9%17%15%3
2416
April1st to 15thDay
51%5%9%20%11%1
2332
16th to endDay
44%6%9%20%15%3
2360
May1st to 15thDay
48%7%10%18%12%1
2623
16th to endDay
44%9%13%20%11%1
2846
June1st to 15thDay
49%8%13%19%9%
2730
16th to endDay
45%9%14%18%11%
2730
July1st to 15thDay
38%10%13%22%14%1
2581
16th to endDay
41%9%16%19%12%
2711
August1st to 15thDay
43%9%15%21%9%1
2527
16th to endDay
38%8%13%25%13%
2484
September1st to 15thDay
41%8%12%21%13%1
2340
16th to endDay
34%6%10%28%17%1
2154
October1st to 15thDay
48%6%10%21%11%1
2002
16th to endDay
50%7%14%18%8%1
1948
November1st to 15thDay
47%6%13%19%11%1
1851
16th to endDay
46%6%15%18%11%
1775
December1st to 15thDay
57%6%14%15%6%
1560
16th to endDay
58%7%15%12%5%
1664
January1st to 15thNight
50%6%14%17%10%
2716
16th to endNight
51%6%14%17%8%1
2863
February1st to 15thNight
56%7%12%15%7%
2440
16th to endNight
51%5%15%17%8%1
2049
March1st to 15thNight
53%7%10%18%8%1
2340
16th to endNight
44%6%12%19%14%3
2155
April1st to 15thNight
50%6%11%19%11%1
1946
16th to endNight
44%5%11%19%16%2
1874
May1st to 15thNight
48%5%10%18%15%2
1667
16th to endNight
42%9%15%19%11%1
1625
June1st to 15thNight
45%7%14%21%9%
1560
16th to endNight
34%8%16%26%12%
1560
July1st to 15thNight
33%8%14%26%14%2
1480
16th to endNight
36%7%16%25%12%1
1546
August1st to 15thNight
34%8%17%26%11%1
1646
16th to endNight
36%6%13%29%13%
2070
September1st to 15thNight
40%6%13%22%16%
1950
16th to endNight
33%5%12%26%21%
2135
October1st to 15thNight
45%5%13%18%15%1
2285
16th to endNight
47%7%15%20%8%
2626
November1st to 15thNight
45%6%12%19%13%2
2667
16th to endNight
48%6%14%20%8%1
2837
December1st to 15thNight
53%7%15%16%6%
2730
16th to endNight
57%7%13%14%7%
2912

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
20%28%31%13%6%
90
16th to endDay
27%25%31%14%1
107
February1st to 15thDay
29%25%35%7%2
176
16th to endDay
21%24%35%15%2
291
March1st to 15thDay
26%21%32%16%2
330
16th to endDay
19%24%29%18%6%1
352
April1st to 15thDay
26%21%29%16%5%
330
16th to endDay
20%19%32%15%8%3
319
May1st to 15thDay
25%16%28%17%8%2
348
16th to endDay
17%10%31%26%11%2
395
June1st to 15thDay
17%14%28%25%12%1
375
16th to endDay
16%11%30%25%13%1
375
July1st to 15thDay
11%7%24%33%18%5%
365
16th to endDay
13%330%31%17%4
390
August1st to 15thDay
13%430%29%16%6%
358
16th to endDay
11%6%22%30%20%8%
396
September1st to 15thDay
17%6%24%21%20%8%
375
16th to endDay
15%8%22%22%16%13%
374
October1st to 15thDay
22%8%23%26%14%3
375
16th to endDay
22%18%33%20%5%
359
November1st to 15thDay
24%17%24%23%8%1
325
16th to endDay
20%21%30%20%5%1
217
December1st to 15thDay
15%25%37%12%7%1
90
16th to endDay
25%27%42%5%
96
January1st to 15thNight
21%18%38%18%2
780
16th to endNight
21%20%38%19%1
832
February1st to 15thNight
20%21%38%18%1
764
16th to endNight
20%22%34%19%2
683
March1st to 15thNight
26%22%33%16%1
780
16th to endNight
18%24%33%18%4
832
April1st to 15thNight
22%19%35%19%2
778
16th to endNight
20%19%31%21%6%
718
May1st to 15thNight
19%16%33%22%7%
497
16th to endNight
12%11%33%32%8%
407
June1st to 15thNight
21%8%30%28%10%
390
16th to endNight
12%333%39%10%
390
July1st to 15thNight
11%324%38%21%
370
16th to endNight
11%224%43%15%1
408
August1st to 15thNight
12%324%41%15%1
505
16th to endNight
14%420%34%22%3
828
September1st to 15thNight
19%424%33%15%1
780
16th to endNight
13%6%26%30%18%4
777
October1st to 15thNight
19%9%28%28%13%
780
16th to endNight
22%13%34%25%4
832
November1st to 15thNight
21%15%31%23%7%
820
16th to endNight
21%17%32%20%7%
840
December1st to 15thNight
26%15%34%19%3
780
16th to endNight
26%21%33%17%1
832
Page generated at 2018-12-01 11:35:37. Version ac04

Copyright 2018 A. Danko


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