Pointed Rock Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pointed Rock Observatory clear sky chart from 2005-11-05 to 2018-01-20.

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
76%
16088
36%
48455
33%
16049
80%
16049
54%
23050

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
72%
779
32%
2522
33%
776
76%
776
48%
1196
January16th to endNight
68%
788
35%
2561
35%
788
75%
788
42%
1311
February1st to 15thNight
73%
700
36%
2202
36%
700
79%
700
52%
1036
February16th to endNight
65%
632
37%
1841
34%
632
72%
632
48%
946
March1st to 15thNight
69%
720
39%
1980
32%
720
75%
720
56%
978
March16th to endNight
74%
768
39%
2112
30%
768
81%
768
62%
996
April1st to 15thNight
70%
689
34%
1948
25%
689
77%
689
56%
941
April16th to endNight
72%
540
46%
1773
40%
540
82%
540
72%
656
May1st to 15thNight
73%
539
40%
1619
31%
539
81%
539
73%
644
May16th to endNight
76%
561
42%
1684
35%
561
81%
561
73%
668
June1st to 15thNight
83%
540
35%
1620
30%
540
84%
540
70%
669
June16th to endNight
86%
540
32%
1620
28%
540
87%
540
65%
703
July1st to 15thNight
83%
510
22%
1530
19%
510
83%
510
41%
829
July16th to endNight
81%
564
19%
1593
17%
531
81%
531
32%
963
August1st to 15thNight
84%
539
26%
1611
24%
536
84%
536
44%
847
August16th to endNight
85%
603
32%
1873
32%
603
85%
603
41%
1009
September1st to 15thNight
78%
720
30%
1980
26%
720
79%
720
44%
1120
September16th to endNight
83%
716
44%
1980
35%
716
87%
716
67%
906
October1st to 15thNight
81%
720
40%
2087
34%
720
85%
720
66%
920
October16th to endNight
87%
768
46%
2304
41%
768
90%
768
69%
972
November1st to 15thNight
81%
760
41%
2280
37%
760
84%
760
64%
998
November16th to endNight
75%
780
41%
2496
41%
780
79%
780
53%
1143
December1st to 15thNight
70%
780
37%
2535
38%
780
75%
780
48%
1212
December16th to endNight
68%
832
35%
2704
36%
832
72%
832
41%
1387

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
4212323345%66%
49068
Night
4212213346%67%
48651
TransparencyDay
19%35%11%24%35%
48763
Night
18%35%12%25%34%
48457
SeeingDay
6%7%21%34%22%6%
5810
Night
4110%37%37%7%
16096

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
5%213214445%63%
1746
16th to endDay
7%413322335%62%
1766
February1st to 15thDay
6%312212235%67%
1659
16th to endDay
8%312313346%61%
1631
March1st to 15thDay
5%213213335%66%
1980
16th to endDay
32221223473%
2112
April1st to 15thDay
3211212345%71%
2000
16th to endDay
2111212481%
2184
May1st to 15thDay
11111233479%
2331
16th to endDay
1111112382%
2429
June1st to 15thDay
3111112479%
2340
16th to endDay
111212345%74%
2340
July1st to 15thDay
3314445%8%7%8%47%
2340
16th to endDay
7%426%7%47%7%9%11%32%
2467
August1st to 15thDay
5%4235%46%6%6%8%45%
2340
16th to endDay
33135%36%6%6%8%51%
2323
September1st to 15thDay
5%214435%5%6%7%54%
1980
16th to endDay
32221223473%
1980
October1st to 15thDay
211212235%75%
1872
16th to endDay
11221223478%
1920
November1st to 15thDay
121212336%73%
1909
16th to endDay
422212235%70%
1792
December1st to 15thDay
8%312313236%62%
1755
16th to endDay
7%313313445%61%
1872
January1st to 15thNight
6%312223336%64%
2522
16th to endNight
8%313324435%59%
2561
February1st to 15thNight
5%322113245%66%
2191
16th to endNight
6%313214446%60%
1841
March1st to 15thNight
6%211112345%68%
1980
16th to endNight
211231223473%
2112
April1st to 15thNight
3212223335%69%
1948
16th to endNight
2111111385%
1773
May1st to 15thNight
11212235%78%
1619
16th to endNight
211111384%
1684
June1st to 15thNight
1111221480%
1620
16th to endNight
11221232476%
1620
July1st to 15thNight
2213427%6%8%10%49%
1620
16th to endNight
32246%36%8%9%15%37%
1701
August1st to 15thNight
2223425%5%8%10%54%
1620
16th to endNight
22145%35%5%7%10%52%
1873
September1st to 15thNight
33145%245%5%7%56%
1980
16th to endNight
211121323476%
1980
October1st to 15thNight
11221223476%
2087
16th to endNight
11111212379%
2304
November1st to 15thNight
222212236%73%
2280
16th to endNight
5%212212335%68%
2496
December1st to 15thNight
8%312212346%63%
2535
16th to endNight
8%414323345%59%
2704

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
21%3412%27%29%
1747
16th to endDay
24%2414%24%28%
1766
February1st to 15thDay
20%15%12%27%33%
1659
16th to endDay
24%2411%30%26%
1631
March1st to 15thDay
19%236%31%37%
1980
16th to endDay
15%237%31%39%
2112
April1st to 15thDay
14%126%37%37%
2000
16th to endDay
9%127%24%54%
2184
May1st to 15thDay
10%136%22%56%
2331
16th to endDay
9%127%24%55%
2432
June1st to 15thDay
10%2319%63%
2340
16th to endDay
12%245%17%58%
2340
July1st to 15thDay
28%8%13%14%15%20%
2201
16th to endDay
39%10%16%19%10%2
2312
August1st to 15thDay
32%6%11%14%19%15%
2325
16th to endDay
28%8%9%18%18%16%
2323
September1st to 15thDay
28%5%7%19%17%21%
1980
16th to endDay
15%238%32%38%
1980
October1st to 15thDay
12%2410%25%44%
1872
16th to endDay
11%139%24%49%
1920
November1st to 15thDay
12%1212%33%37%
1909
16th to endDay
17%229%28%40%
1792
December1st to 15thDay
23%1416%29%24%
1755
16th to endDay
24%35%17%30%18%
1872
January1st to 15thNight
21%25%11%29%28%
2522
16th to endNight
26%3413%27%24%
2561
February1st to 15thNight
19%2414%25%32%
2202
16th to endNight
22%25%12%30%25%
1841
March1st to 15thNight
18%139%26%39%
1980
16th to endNight
15%1310%32%36%
2112
April1st to 15thNight
18%127%35%34%
1948
16th to endNight
8%16%27%55%
1773
May1st to 15thNight
7%239%26%50%
1620
16th to endNight
8%116%24%58%
1685
June1st to 15thNight
10%12319%62%
1620
16th to endNight
13%13415%60%
1620
July1st to 15thNight
23%8%14%17%16%20%
1530
16th to endNight
29%11%21%22%11%3
1593
August1st to 15thNight
20%8%15%21%16%17%
1611
16th to endNight
24%7%12%19%18%17%
1873
September1st to 15thNight
25%6%8%22%19%17%
1980
16th to endNight
12%239%32%39%
1980
October1st to 15thNight
12%1413%24%43%
2087
16th to endNight
11%1211%23%49%
2304
November1st to 15thNight
13%1413%31%35%
2280
16th to endNight
19%1410%24%40%
2496
December1st to 15thNight
22%2415%28%26%
2535
16th to endNight
26%36%15%28%20%
2704

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
12%5%14%43%20%3
135
16th to endDay
11%22%33%24%8%
109
February1st to 15thDay
8%8%21%35%24%2
174
16th to endDay
12%15%36%23%10%2
238
March1st to 15thDay
7%16%25%30%13%5%
270
16th to endDay
418%32%24%15%3
288
April1st to 15thDay
8%19%30%26%11%4
269
16th to endDay
6%21%32%27%9%2
270
May1st to 15thDay
5%15%37%27%10%3
288
16th to endDay
29%35%38%12%2
330
June1st to 15thDay
6%6%28%37%17%4
315
16th to endDay
414%47%25%7%
315
July1st to 15thDay
5%11%44%29%7%
305
16th to endDay
7%19%32%29%18%
327
August1st to 15thDay
6%7%36%36%12%
315
16th to endDay
48%34%38%13%
332
September1st to 15thDay
9%119%35%25%8%
315
16th to endDay
5%5%26%35%21%5%
315
October1st to 15thDay
19%20%37%23%7%
207
16th to endDay
417%31%45%9%
144
November1st to 15thDay
5%6%14%36%31%5%
135
16th to endDay
7%5%14%39%25%6%
135
December1st to 15thDay
7%322%32%29%4
135
16th to endDay
13%6%17%29%25%8%
144
January1st to 15thNight
8%112%42%29%6%
780
16th to endNight
9%213%40%27%5%
788
February1st to 15thNight
7%112%44%28%5%
704
16th to endNight
8%318%46%21%2
632
March1st to 15thNight
6%217%39%27%5%
720
16th to endNight
3214%42%30%6%
768
April1st to 15thNight
4416%49%22%2
689
16th to endNight
2419%42%27%3
540
May1st to 15thNight
319%42%29%4
540
16th to endNight
2315%41%34%3
563
June1st to 15thNight
1110%44%37%3
540
16th to endNight
16%35%51%4
540
July1st to 15thNight
2419%63%9%
510
16th to endNight
4114%62%16%
564
August1st to 15thNight
3214%63%17%
539
16th to endNight
3117%62%15%
603
September1st to 15thNight
5%5%23%51%13%
720
16th to endNight
38%34%41%11%
716
October1st to 15thNight
211%40%37%6%
720
16th to endNight
215%38%41%11%
768
November1st to 15thNight
319%42%37%6%
760
16th to endNight
6%110%40%33%6%
780
December1st to 15thNight
9%112%40%30%5%
780
16th to endNight
9%212%42%25%7%
832
Page generated at 2018-01-21 10:19:30. Version ac04

Copyright 2018 A. Danko


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