Cherry Hill Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Cherry Hill Observatory clear sky chart from 2005-11-05 to 2017-09-19.

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
44%
15660
25%
46892
16%
15613
53%
15613
31%
27898

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
28%
899
27%
2327
9%
895
41%
895
28%
1457
January16th to endNight
27%
960
29%
2496
9%
960
39%
960
30%
1551
February1st to 15thNight
25%
880
20%
2285
6%
875
34%
875
26%
1501
February16th to endNight
23%
567
26%
1829
10%
567
38%
567
25%
1080
March1st to 15thNight
28%
540
21%
1980
13%
540
39%
540
20%
1238
March16th to endNight
31%
576
19%
2112
15%
576
39%
576
22%
1308
April1st to 15thNight
29%
539
24%
1854
13%
539
44%
539
25%
1058
April16th to endNight
33%
540
23%
1800
16%
540
47%
540
28%
1045
May1st to 15thNight
40%
540
20%
1669
14%
540
50%
540
25%
1072
May16th to endNight
47%
563
21%
1685
17%
561
55%
561
31%
1037
June1st to 15thNight
66%
540
22%
1620
20%
540
72%
540
40%
889
June16th to endNight
70%
540
24%
1620
24%
540
74%
540
43%
863
July1st to 15thNight
74%
510
18%
1530
18%
510
77%
510
39%
876
July16th to endNight
81%
564
25%
1594
29%
531
83%
531
43%
850
August1st to 15thNight
78%
539
25%
1610
28%
536
80%
536
44%
861
August16th to endNight
72%
573
22%
1898
27%
573
72%
573
32%
1103
September1st to 15thNight
66%
540
25%
1836
26%
540
70%
540
33%
1038
September16th to endNight
67%
510
32%
1863
30%
510
73%
510
36%
964
October1st to 15thNight
52%
660
29%
1980
21%
660
57%
660
35%
1150
October16th to endNight
46%
704
34%
2112
21%
704
57%
704
40%
1126
November1st to 15thNight
44%
700
30%
2100
17%
700
55%
700
34%
1173
November16th to endNight
34%
816
29%
2256
15%
816
46%
816
27%
1431
December1st to 15thNight
32%
900
23%
2340
10%
900
41%
900
27%
1549
December16th to endNight
29%
960
24%
2496
10%
960
38%
960
25%
1678

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
12%6%25%5%3445%7%42%
47917
Night
10%5%2442345%7%50%
47090
TransparencyDay
40%6%10%20%17%4
47617
Night
33%5%10%22%21%6%
46895
SeeingDay
12%8%23%27%21%6%
5703
Night
13%11%25%27%19%2
15661

By Month

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%7%26%41323449%
1611
16th to endDay
16%6%25%32333449%
1728
February1st to 15thDay
17%6%24423435%45%
1575
16th to endDay
16%9%46%423335%41%
1652
March1st to 15thDay
17%7%35%423335%43%
1980
16th to endDay
17%8%45%5%24445%37%
2110
April1st to 15thDay
15%5%26%323446%44%
2094
16th to endDay
16%6%36%5%34446%38%
2160
May1st to 15thDay
17%6%36%6%35%345%37%
2279
16th to endDay
11%6%37%6%45%5%5%8%35%
2430
June1st to 15thDay
8%5%25%6%36%5%7%7%39%
2340
16th to endDay
5%5%35%5%36%6%5%9%41%
2340
July1st to 15thDay
8%5%36%6%46%7%8%10%32%
2340
16th to endDay
6%3246%48%7%7%10%37%
2466
August1st to 15thDay
7%315%5%45%7%8%10%40%
2340
16th to endDay
9%5%26%6%46%7%7%8%35%
2304
September1st to 15thDay
15%4145%345%5%7%41%
2121
16th to endDay
10%31342435%7%52%
1829
October1st to 15thDay
13%6%14433435%48%
1650
16th to endDay
13%312312245%57%
1760
November1st to 15thDay
10%424423347%53%
1758
16th to endDay
15%6%2442323450%
1702
December1st to 15thDay
14%8%24412445%45%
1620
16th to endDay
16%9%35%42233443%
1728
January1st to 15thNight
12%7%24313345%52%
2327
16th to endNight
13%5%2332334453%
2496
February1st to 15thNight
14%7%3431334447%
2278
16th to endNight
11%5%34423346%50%
1829
March1st to 15thNight
16%6%24433345%42%
1980
16th to endNight
12%7%35%5%245%46%43%
2112
April1st to 15thNight
10%42442425%7%50%
1854
16th to endNight
10%5%24423347%51%
1800
May1st to 15thNight
12%5%24434448%45%
1668
16th to endNight
6%5%35%4245%6%9%46%
1683
June1st to 15thNight
3325%42335%8%58%
1620
16th to endNight
431332345%8%59%
1620
July1st to 15thNight
5%2134247%9%13%45%
1620
16th to endNight
31134245%6%11%54%
1702
August1st to 15thNight
3312425%47%11%53%
1620
16th to endNight
5%425%5%245%7%11%44%
1898
September1st to 15thNight
10%41342445%7%52%
1836
16th to endNight
7%313424347%56%
1863
October1st to 15thNight
10%5%24322345%55%
1980
16th to endNight
10%322311235%62%
2112
November1st to 15thNight
9%5%2432325%5%57%
2100
16th to endNight
14%6%24323335%49%
2256
December1st to 15thNight
14%7%24423445%45%
2340
16th to endNight
15%7%35%424335%44%
2496

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
39%36%23%20%6%
1612
16th to endDay
40%35%22%23%4
1728
February1st to 15thDay
42%39%20%18%4
1576
16th to endDay
46%37%17%18%5%
1652
March1st to 15thDay
44%38%17%17%6%
1980
16th to endDay
49%5%8%19%14%2
2112
April1st to 15thDay
41%49%20%17%5%
2094
16th to endDay
46%6%8%17%17%3
2160
May1st to 15thDay
48%6%8%16%16%3
2279
16th to endDay
46%7%12%20%12%
2434
June1st to 15thDay
39%9%12%22%14%1
2340
16th to endDay
38%8%13%21%16%1
2340
July1st to 15thDay
40%10%15%22%9%
2201
16th to endDay
37%10%16%22%12%
2311
August1st to 15thDay
33%10%15%24%15%1
2326
16th to endDay
42%9%13%20%11%2
2304
September1st to 15thDay
41%6%10%18%14%8%
2121
16th to endDay
30%6%11%21%22%8%
1829
October1st to 15thDay
38%46%17%22%9%
1650
16th to endDay
30%37%19%27%12%
1760
November1st to 15thDay
32%49%24%22%7%
1758
16th to endDay
39%3419%24%7%
1702
December1st to 15thDay
41%49%20%17%5%
1620
16th to endDay
44%47%20%19%4
1728
January1st to 15thNight
35%47%19%28%5%
2327
16th to endNight
35%37%21%25%6%
2496
February1st to 15thNight
39%48%22%18%6%
2288
16th to endNight
36%38%24%18%7%
1829
March1st to 15thNight
43%48%15%18%8%
1980
16th to endNight
41%5%10%19%19%3
2112
April1st to 15thNight
33%5%11%20%19%9%
1854
16th to endNight
34%5%10%21%23%4
1800
May1st to 15thNight
38%7%10%19%17%6%
1669
16th to endNight
33%8%17%25%13%1
1685
June1st to 15thNight
25%6%12%31%21%2
1620
16th to endNight
22%7%13%27%25%3
1620
July1st to 15thNight
23%11%21%26%15%1
1530
16th to endNight
22%7%17%33%18%
1594
August1st to 15thNight
21%8%18%29%19%3
1610
16th to endNight
31%7%16%24%16%2
1898
September1st to 15thNight
30%7%10%21%21%8%
1836
16th to endNight
27%49%23%24%9%
1863
October1st to 15thNight
31%5%9%18%21%13%
1980
16th to endNight
27%36%19%29%14%
2112
November1st to 15thNight
30%38%22%23%10%
2100
16th to endNight
38%4417%27%7%
2256
December1st to 15thNight
40%49%17%19%7%
2340
16th to endNight
42%47%20%18%7%
2496

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
13%26%36%17%5%
90
16th to endDay
26%26%31%11%5%
96
February1st to 15thDay
22%15%51%6%31
90
16th to endDay
28%27%33%8%2
81
March1st to 15thDay
31%21%36%11%
90
16th to endDay
12%27%34%25%1
96
April1st to 15thDay
20%20%32%16%8%1
213
16th to endDay
20%16%29%20%10%1
270
May1st to 15thDay
14%16%36%21%9%1
416
16th to endDay
11%9%35%25%12%4
517
June1st to 15thDay
11%418%33%25%6%
495
16th to endDay
5%424%33%24%7%
495
July1st to 15thDay
6%222%35%26%6%
475
16th to endDay
4434%38%17%
515
August1st to 15thDay
10%9%35%34%10%
493
16th to endDay
13%18%30%35%11%
344
September1st to 15thDay
7%110%30%39%9%
276
16th to endDay
5%217%36%32%7%
99
October1st to 15thDay
6%7%35%36%7%5%
90
16th to endDay
20%331%35%7%2
96
November1st to 15thDay
17%13%24%28%14%1
90
16th to endDay
32%17%28%15%41
90
December1st to 15thDay
16%17%41%16%5%2
90
16th to endDay
18%32%34%9%5%
96
January1st to 15thNight
19%19%30%24%5%
900
16th to endNight
17%18%34%24%4
960
February1st to 15thNight
20%18%33%23%4
880
16th to endNight
17%18%39%19%4
567
March1st to 15thNight
20%14%33%26%5%
540
16th to endNight
14%15%33%26%8%
576
April1st to 15thNight
11%20%35%22%10%
539
16th to endNight
13%12%37%22%12%
540
May1st to 15thNight
14%9%31%30%13%
540
16th to endNight
9%5%31%31%19%2
563
June1st to 15thNight
5%117%37%35%2
540
16th to endNight
5%116%34%36%5%
540
July1st to 15thNight
410%35%42%4
510
16th to endNight
4430%50%10%
564
August1st to 15thNight
48%30%47%8%
539
16th to endNight
8%8%31%45%6%
573
September1st to 15thNight
11%111%28%41%4
540
16th to endNight
8%114%31%37%5%
510
October1st to 15thNight
14%6%23%28%23%3
660
16th to endNight
12%9%27%28%19%1
704
November1st to 15thNight
12%13%26%31%15%
700
16th to endNight
18%17%26%25%11%
816
December1st to 15thNight
21%14%29%28%7%
900
16th to endNight
22%14%30%25%6%
960
Page generated at 2017-09-20 03:49:47. Version ac04

Copyright 2017 A. Danko


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