Presbyterian Point
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Presbyterian Point clear sky chart from 2005-11-05 to 2019-06-10.

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
42%
17993
21%
54028
13%
17957
51%
17957
25%
34173

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
26%
836
24%
2717
10%
836
42%
836
19%
1687
January16th to endNight
23%
896
25%
2912
11%
896
41%
896
22%
1773
February1st to 15thNight
22%
821
21%
2677
8%
821
39%
821
21%
1642
February16th to endNight
21%
735
25%
2183
10%
735
39%
735
24%
1349
March1st to 15thNight
26%
840
24%
2310
11%
840
40%
840
25%
1492
March16th to endNight
29%
896
21%
2464
10%
896
38%
896
26%
1603
April1st to 15thNight
31%
838
23%
2124
7%
838
42%
838
31%
1371
April16th to endNight
39%
831
20%
2077
7%
831
44%
831
31%
1369
May1st to 15thNight
41%
674
18%
1934
9%
674
46%
674
25%
1263
May16th to endNight
58%
651
16%
1965
11%
651
61%
651
29%
1255
June1st to 15thNight
61%
408
18%
1632
22%
408
64%
408
23%
979
June16th to endNight
69%
447
17%
1617
18%
447
71%
447
26%
980
July1st to 15thNight
69%
555
15%
1665
13%
555
70%
555
30%
1048
July16th to endNight
66%
612
15%
1739
12%
579
68%
579
28%
1125
August1st to 15thNight
65%
575
17%
1715
15%
572
65%
572
25%
1155
August16th to endNight
66%
813
16%
2055
10%
813
67%
813
30%
1420
September1st to 15thNight
61%
780
23%
1950
16%
780
63%
780
32%
1318
September16th to endNight
48%
777
17%
2174
14%
777
51%
777
22%
1540
October1st to 15thNight
49%
780
25%
2340
22%
780
56%
780
27%
1478
October16th to endNight
43%
832
32%
2496
20%
832
59%
832
34%
1408
November1st to 15thNight
42%
820
25%
2461
16%
820
53%
820
29%
1510
November16th to endNight
42%
840
25%
2843
18%
840
55%
840
26%
1622
December1st to 15thNight
30%
840
20%
2940
11%
840
44%
840
19%
1869
December16th to endNight
28%
896
22%
3038
11%
896
42%
896
19%
1917

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
13%5%2443445%8%42%
54453
Night
13%5%2442445%7%44%
54222
Cloud CoverDay
13%5%2443445%7%43%
54463
Night
14%5%2442445%7%44%
54226
TransparencyDay
38%7%12%21%16%3
54164
Night
38%6%10%20%18%4
54029
SeeingDay
18%9%24%23%17%6%
7968
Night
17%9%26%30%16%1
18002

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%6%34423446%44%
1881
16th to endDay
16%5%23323346%48%
2016
February1st to 15thDay
15%5%24423446%43%
1845
16th to endDay
18%5%23424437%43%
1857
March1st to 15thDay
15%6%2442345%7%45%
2299
16th to endDay
16%5%24424346%42%
2464
April1st to 15thDay
11%42332335%7%51%
2484
16th to endDay
12%5%245%3445%7%45%
2488
May1st to 15thDay
13%5%25%5%25%45%9%39%
2687
16th to endDay
10%425%5%45%5%6%9%40%
2850
June1st to 15thDay
9%4245%35%5%7%9%42%
2856
16th to endDay
6%325%5%45%6%6%11%42%
2667
July1st to 15thDay
7%425%6%37%7%8%9%36%
2535
16th to endDay
6%427%6%47%7%8%10%33%
2673
August1st to 15thDay
9%5%36%6%35%5%6%10%35%
2487
16th to endDay
9%416%6%46%6%7%10%35%
2486
September1st to 15thDay
10%4245%35%5%6%7%42%
2340
16th to endDay
21%5%25%4335%46%37%
2112
October1st to 15thDay
17%5%24422335%48%
1950
16th to endDay
11%423412335%56%
2080
November1st to 15thDay
16%5%23412436%49%
2057
16th to endDay
12%414413345%52%
1772
December1st to 15thDay
16%5%25%414347%43%
1680
16th to endDay
18%7%25%314346%41%
1887
January1st to 15thNight
16%6%24333446%44%
2717
16th to endNight
16%5%24423345%47%
2912
February1st to 15thNight
17%6%23323347%44%
2675
16th to endNight
14%6%24413446%46%
2183
March1st to 15thNight
15%41443345%6%46%
2298
16th to endNight
16%5%25%423446%44%
2464
April1st to 15thNight
12%5%2442445%9%46%
2124
16th to endNight
14%413425%5%6%6%45%
2077
May1st to 15thNight
14%6%2442445%9%40%
1934
16th to endNight
11%425%435%35%9%44%
1964
June1st to 15thNight
9%4245%35%46%9%43%
1632
16th to endNight
7%324435%6%6%10%43%
1617
July1st to 15thNight
8%3145%36%5%7%10%42%
1755
16th to endNight
6%426%5%46%7%7%11%38%
1847
August1st to 15thNight
9%435%6%36%5%6%9%38%
1726
16th to endNight
8%426%5%35%6%7%10%37%
2055
September1st to 15thNight
12%5%25%5%2436%8%44%
1950
16th to endNight
17%7%26%5%3445%5%36%
2174
October1st to 15thNight
15%5%24423336%47%
2340
16th to endNight
11%413223345%55%
2496
November1st to 15thNight
15%5%24422345%49%
2461
16th to endNight
13%423324446%51%
2843
December1st to 15thNight
17%6%24424345%42%
2940
16th to endNight
18%7%25%423347%41%
3038

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%6%25%324345%44%
1881
16th to endDay
15%5%23423436%47%
2016
February1st to 15thDay
15%6%2443345%6%44%
1845
16th to endDay
18%5%14423346%43%
1857
March1st to 15thDay
15%6%2432345%6%45%
2310
16th to endDay
16%6%34433346%43%
2463
April1st to 15thDay
11%42333435%7%51%
2484
16th to endDay
12%5%25%4345%47%45%
2488
May1st to 15thDay
13%5%25%6%2445%9%39%
2687
16th to endDay
10%4245%45%5%6%9%40%
2850
June1st to 15thDay
9%4245%35%5%6%9%42%
2856
16th to endDay
6%3245%36%5%6%10%42%
2667
July1st to 15thDay
8%426%6%46%7%7%10%35%
2535
16th to endDay
7%426%7%5%7%6%9%9%33%
2673
August1st to 15thDay
10%5%35%6%45%46%10%35%
2487
16th to endDay
9%5%25%6%46%6%7%11%34%
2486
September1st to 15thDay
11%4145%445%6%8%42%
2340
16th to endDay
21%426%32345%7%36%
2112
October1st to 15thDay
17%5%24413245%49%
1950
16th to endDay
11%32442233457%
2080
November1st to 15thDay
18%423313345%48%
2057
16th to endDay
12%424323346%52%
1772
December1st to 15thDay
16%5%25%424347%43%
1680
16th to endDay
19%7%25%323347%41%
1887
January1st to 15thNight
15%6%2442335%6%45%
2717
16th to endNight
16%5%3432334448%
2912
February1st to 15thNight
16%6%23323346%45%
2668
16th to endNight
15%6%24413446%46%
2183
March1st to 15thNight
15%5%23424346%46%
2310
16th to endNight
16%4245%23345%45%
2464
April1st to 15thNight
12%42432345%8%46%
2124
16th to endNight
14%324435%5%5%6%45%
2077
May1st to 15thNight
14%6%2432435%8%41%
1933
16th to endNight
11%425%43345%9%44%
1964
June1st to 15thNight
10%325%6%345%5%10%42%
1632
16th to endNight
6%3245%35%6%6%10%43%
1617
July1st to 15thNight
7%325%5%35%5%7%10%42%
1755
16th to endNight
6%5%246%46%6%7%10%38%
1847
August1st to 15thNight
8%426%7%35%6%5%10%38%
1726
16th to endNight
8%5%25%6%45%6%7%10%37%
2055
September1st to 15thNight
13%425%5%2335%9%44%
1950
16th to endNight
18%7%25%5%3445%5%36%
2174
October1st to 15thNight
16%5%25%5%23345%47%
2340
16th to endNight
11%313323445%55%
2496
November1st to 15thNight
16%5%24413345%49%
2461
16th to endNight
13%423424445%51%
2843
December1st to 15thNight
17%6%25%5%24345%42%
2940
16th to endNight
18%6%34423336%41%
3038

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
41%5%7%20%19%4
1882
16th to endDay
37%5%9%22%19%6%
2016
February1st to 15thDay
39%5%8%23%18%3
1847
16th to endDay
41%412%19%17%4
1857
March1st to 15thDay
39%5%9%20%19%5%
2310
16th to endDay
42%5%9%21%16%4
2464
April1st to 15thDay
31%5%11%25%17%7%
2484
16th to endDay
38%6%11%19%17%7%
2488
May1st to 15thDay
41%7%14%21%12%2
2687
16th to endDay
37%9%14%26%10%1
2854
June1st to 15thDay
35%9%15%23%14%1
2856
16th to endDay
34%10%15%19%16%2
2667
July1st to 15thDay
38%11%15%17%12%3
2396
16th to endDay
40%11%17%18%11%
2518
August1st to 15thDay
42%9%16%20%10%1
2474
16th to endDay
39%11%16%20%11%1
2486
September1st to 15thDay
38%9%13%15%19%3
2340
16th to endDay
46%6%10%18%17%1
2112
October1st to 15thDay
38%49%23%18%4
1950
16th to endDay
30%36%27%24%7%
2080
November1st to 15thDay
36%49%19%22%6%
2057
16th to endDay
32%49%22%25%5%
1772
December1st to 15thDay
41%49%24%16%4
1680
16th to endDay
44%311%21%15%3
1887
January1st to 15thNight
39%5%8%18%20%6%
2717
16th to endNight
39%47%23%20%5%
2912
February1st to 15thNight
40%49%20%20%4
2677
16th to endNight
38%49%22%19%5%
2183
March1st to 15thNight
38%5%8%21%20%5%
2310
16th to endNight
40%5%9%21%19%3
2464
April1st to 15thNight
35%5%10%22%19%5%
2124
16th to endNight
37%6%10%20%18%7%
2077
May1st to 15thNight
39%7%12%21%15%2
1934
16th to endNight
36%8%14%26%12%1
1966
June1st to 15thNight
36%9%15%22%14%1
1632
16th to endNight
33%10%15%19%17%3
1617
July1st to 15thNight
33%10%16%23%12%4
1665
16th to endNight
35%10%17%21%12%1
1739
August1st to 15thNight
39%10%17%17%14%1
1715
16th to endNight
37%10%17%21%10%2
2055
September1st to 15thNight
37%8%14%18%17%4
1950
16th to endNight
46%7%10%13%18%2
2174
October1st to 15thNight
39%5%8%20%21%4
2340
16th to endNight
30%47%24%26%7%
2496
November1st to 15thNight
37%48%17%23%8%
2461
16th to endNight
34%47%18%26%7%
2843
December1st to 15thNight
43%5%8%20%18%3
2940
16th to endNight
44%310%21%15%3
3038

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
25%22%39%10%2
180
16th to endDay
21%26%35%14%1
192
February1st to 15thDay
25%25%35%11%2
180
16th to endDay
29%18%32%17%2
298
March1st to 15thDay
26%18%34%14%5%
390
16th to endDay
18%16%38%18%6%1
416
April1st to 15thDay
19%16%33%20%8%1
390
16th to endDay
19%7%30%28%10%3
379
May1st to 15thDay
17%12%30%25%12%2
408
16th to endDay
17%320%29%23%5%
459
June1st to 15thDay
11%423%26%25%9%
411
16th to endDay
9%321%30%26%8%
375
July1st to 15thDay
9%114%32%31%9%
365
16th to endDay
11%112%30%32%11%
390
August1st to 15thDay
15%115%27%25%13%
358
16th to endDay
8%11%29%30%18%
396
September1st to 15thDay
17%313%22%23%20%
375
16th to endDay
28%214%24%20%10%
374
October1st to 15thDay
21%423%21%22%6%
375
16th to endDay
12%13%27%25%16%3
400
November1st to 15thDay
24%9%27%22%13%2
385
16th to endDay
16%13%24%32%10%2
197
December1st to 15thDay
26%15%33%16%5%1
120
16th to endDay
28%21%32%14%3
155
January1st to 15thNight
20%18%30%24%5%
840
16th to endNight
20%17%34%24%3
896
February1st to 15thNight
23%16%34%22%3
824
16th to endNight
17%17%40%21%2
735
March1st to 15thNight
19%14%37%24%4
840
16th to endNight
19%12%36%24%7%
896
April1st to 15thNight
15%14%36%26%7%
838
16th to endNight
15%9%32%32%9%
831
May1st to 15thNight
17%6%29%32%13%
674
16th to endNight
14%117%39%25%
653
June1st to 15thNight
12%117%42%23%1
408
16th to endNight
6%114%47%26%2
447
July1st to 15thNight
8%12%38%35%3
555
16th to endNight
7%12%34%38%4
612
August1st to 15thNight
11%111%40%31%3
575
16th to endNight
10%110%36%34%7%
813
September1st to 15thNight
14%114%31%31%5%
780
16th to endNight
21%217%30%25%2
777
October1st to 15thNight
18%5%19%29%23%4
780
16th to endNight
14%9%29%25%18%2
832
November1st to 15thNight
20%7%25%30%14%1
820
16th to endNight
16%13%24%29%14%1
840
December1st to 15thNight
22%12%30%25%9%
840
16th to endNight
23%13%29%28%4
896
Page generated at 2019-06-10 19:29:50. Version ac04

Copyright 2019 A. Danko


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