Park Place Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Park Place Observatory clear sky chart from 2005-11-06 to 2024-01-14.

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
33%
23154
19%
74671
10%
23109
44%
23109
21%
47943

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 10thNight
17%
760
21%
2649
7%
757
36%
757
18%
1644
January11th to 20thNight
22%
735
17%
2533
6%
735
37%
735
15%
1692
January21st to endNight
20%
792
21%
2574
6%
792
38%
792
19%
1629
February1st to 10thNight
19%
720
17%
2340
6%
720
33%
720
17%
1541
February11th to 20thNight
13%
703
18%
2172
3%
700
33%
700
16%
1434
February21st to endNight
15%
592
24%
1776
7%
592
36%
592
18%
1175
March1st to 10thNight
23%
720
21%
2142
8%
720
38%
720
21%
1328
March11th to 20thNight
22%
720
22%
1980
8%
720
36%
720
21%
1311
March21st to endNight
22%
792
21%
2066
6%
792
33%
792
23%
1419
April1st to 10thNight
21%
720
17%
1800
3%
720
29%
720
22%
1255
April11th to 20thNight
26%
711
18%
1775
6%
711
31%
711
26%
1225
April21st to endNight
27%
720
19%
1800
5%
720
34%
720
26%
1220
May1st to 10thNight
30%
538
15%
1618
8%
538
36%
538
20%
1127
May11th to 20thNight
31%
354
18%
1416
12%
354
43%
354
17%
903
May21st to endNight
49%
388
14%
1551
13%
388
55%
388
19%
973
June1st to 10thNight
45%
360
18%
1440
17%
360
55%
360
21%
877
June11th to 20thNight
48%
360
14%
1440
14%
360
55%
360
21%
884
June21st to endNight
54%
360
16%
1440
17%
360
61%
360
25%
821
July1st to 10thNight
55%
350
14%
1400
17%
350
59%
350
20%
861
July11th to 20thNight
59%
348
17%
1392
20%
348
63%
348
23%
797
July21st to endNight
58%
427
16%
1518
16%
404
61%
404
26%
884
August1st to 10thNight
61%
537
16%
1600
12%
534
63%
534
27%
1031
August11th to 20thNight
53%
654
16%
1718
10%
654
54%
654
24%
1201
August21st to endNight
54%
792
18%
1980
9%
792
56%
792
31%
1339
September1st to 10thNight
47%
720
21%
1800
9%
720
52%
720
31%
1215
September11th to 20thNight
52%
720
28%
1813
18%
720
57%
720
35%
1144
September21st to endNight
45%
720
24%
2002
17%
720
53%
720
29%
1301
October1st to 10thNight
40%
720
17%
2160
13%
720
47%
720
25%
1422
October11th to 20thNight
39%
720
22%
2160
14%
720
51%
720
27%
1334
October21st to endNight
30%
792
22%
2434
12%
792
45%
792
24%
1545
November1st to 10thNight
34%
740
23%
2407
13%
740
49%
740
27%
1406
November11th to 20thNight
30%
760
24%
2470
13%
760
44%
760
22%
1531
November21st to endNight
28%
760
20%
2641
9%
760
44%
760
21%
1605
December1st to 10thNight
20%
760
17%
2660
7%
760
33%
760
14%
1788
December11th to 20thNight
23%
760
17%
3209
6%
759
38%
759
14%
2009
December21st to endNight
22%
829
11%
4795
6%
817
37%
817
10%
3072

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
16%6%35%5%35%5%6%8%38%
74737
Night
17%6%25%43445%7%42%
75012
TransparencyDay
43%7%13%21%14%2
74445
Night
42%6%12%22%15%2
74839
SeeingDay
21%16%28%21%11%3
13772
Night
20%12%30%27%10%1
23162

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 10thDay
13%7%45%6%45%5%6%6%39%
1517
11th to 20thDay
16%8%46%6%5%6%5%6%6%31%
1497
21st to endDay
14%8%47%5%36%5%5%8%36%
1782
February1st to 10thDay
17%6%36%7%45%5%6%8%33%
1620
11th to 20thDay
15%7%35%5%36%5%6%7%38%
1674
21st to endDay
21%7%35%6%45%45%6%34%
1480
March1st to 10thDay
14%7%25%5%35%46%7%41%
1815
11th to 20thDay
16%7%25%7%45%5%6%9%35%
1980
21st to endDay
21%7%35%43445%7%37%
2290
April1st to 10thDay
17%7%45%5%35%47%7%37%
2160
11th to 20thDay
17%6%35%5%3446%7%39%
2134
21st to endDay
17%6%245%346%6%8%38%
2160
May1st to 10thDay
20%6%35%5%35%5%6%6%35%
2355
11th to 20thDay
21%6%25%5%45%5%5%7%35%
2478
21st to endDay
17%6%245%345%7%8%38%
2725
June1st to 10thDay
15%5%35%5%46%5%6%10%37%
2520
11th to 20thDay
16%5%36%5%35%6%7%9%35%
2520
21st to endDay
13%6%246%35%5%6%10%41%
2520
July1st to 10thDay
11%5%26%6%36%6%8%9%37%
2520
11th to 20thDay
10%425%5%35%6%7%10%42%
2520
21st to endDay
11%6%36%6%46%6%6%8%37%
2708
August1st to 10thDay
12%6%26%5%36%7%7%9%36%
2327
11th to 20thDay
12%5%36%6%45%5%7%8%38%
2163
21st to endDay
15%6%245%35%47%9%39%
2376
September1st to 10thDay
18%4346%35%5%5%7%40%
2160
11th to 20thDay
14%42432445%7%50%
2147
21st to endDay
19%7%25%4345%5%5%41%
1954
October1st to 10thDay
20%5%24435%46%6%41%
1800
11th to 20thDay
18%5%24435%45%7%43%
1800
21st to endDay
21%6%344345%5%7%38%
1921
November1st to 10thDay
15%6%24323337%52%
1671
11th to 20thDay
18%6%244345%6%6%43%
1710
21st to endDay
18%5%344345%6%8%41%
1535
December1st to 10thDay
20%7%36%6%35%5%5%6%34%
1520
11th to 20thDay
21%6%244346%5%6%38%
1906
21st to endDay
20%8%47%7%45%6%6%6%28%
2772
January1st to 10thNight
15%6%25%5%35%45%8%42%
2649
11th to 20thNight
18%8%35%5%35%5%5%6%36%
2533
21st to endNight
13%9%35%5%345%6%7%41%
2574
February1st to 10thNight
18%7%45%4335%5%7%39%
2340
11th to 20thNight
17%6%45%5%35%5%6%5%39%
2170
21st to endNight
20%7%35%5%2445%6%41%
1776
March1st to 10thNight
15%6%243245%6%6%45%
2132
11th to 20thNight
18%7%35%424346%44%
1979
21st to endNight
18%7%25%43445%8%40%
2066
April1st to 10thNight
17%6%36%5%35%5%5%7%38%
1800
11th to 20thNight
16%6%26%5%35%46%7%41%
1775
21st to endNight
21%5%2432445%6%44%
1800
May1st to 10thNight
22%7%26%5%3445%6%36%
1618
11th to 20thNight
18%6%26%5%3445%7%40%
1415
21st to endNight
16%6%25%435%5%5%7%42%
1550
June1st to 10thNight
17%6%245%34448%43%
1440
11th to 20thNight
14%5%24435%6%6%8%42%
1440
21st to endNight
12%424435%6%6%10%45%
1440
July1st to 10thNight
12%426%5%36%6%5%10%42%
1440
11th to 20thNight
11%4245%25%6%5%9%45%
1440
21st to endNight
12%5%24445%6%7%10%43%
1607
August1st to 10thNight
12%6%25%5%35%5%7%9%41%
1611
11th to 20thNight
13%7%35%6%35%5%5%8%38%
1718
21st to endNight
15%6%25%4245%7%9%41%
1980
September1st to 10thNight
16%6%25%434346%46%
1800
11th to 20thNight
13%6%235%33436%52%
1813
21st to endNight
17%6%26%33345%6%46%
2002
October1st to 10thNight
23%5%24324346%44%
2160
11th to 20thNight
18%5%2333345%6%47%
2160
21st to endNight
22%5%2333345%6%44%
2434
November1st to 10thNight
13%5%243345%5%5%51%
2407
11th to 20thNight
17%7%25%433346%46%
2470
21st to endNight
16%5%25%5%3445%7%43%
2641
December1st to 10thNight
21%6%35%6%36%5%46%35%
2660
11th to 20thNight
19%6%25%435%5%6%7%38%
3288
21st to endNight
21%8%36%5%3445%6%36%
4884

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 10thDay
44%6%13%24%11%2
1518
11th to 20thDay
51%8%12%17%10%2
1497
21st to endDay
45%7%12%22%12%2
1782
February1st to 10thDay
47%7%14%19%11%1
1620
11th to 20thDay
45%7%12%22%13%2
1683
21st to endDay
49%6%10%21%11%3
1480
March1st to 10thDay
41%6%13%25%12%3
1818
11th to 20thDay
45%6%12%20%14%3
1980
21st to endDay
46%6%10%18%16%3
2290
April1st to 10thDay
45%6%11%20%14%5%
2160
11th to 20thDay
43%6%11%22%15%3
2134
21st to endDay
43%7%11%20%15%5%
2160
May1st to 10thDay
48%7%10%18%15%3
2355
11th to 20thDay
48%7%11%19%13%2
2482
21st to endDay
42%9%13%22%13%2
2725
June1st to 10thDay
41%9%15%21%13%2
2520
11th to 20thDay
43%10%14%21%11%2
2520
21st to endDay
38%10%13%25%13%1
2520
July1st to 10thDay
40%10%14%21%15%1
2450
11th to 20thDay
33%10%16%25%15%2
2445
21st to endDay
41%9%12%21%15%2
2557
August1st to 10thDay
39%11%15%21%14%
2314
11th to 20thDay
41%9%13%22%14%1
2163
21st to endDay
39%8%12%20%17%3
2376
September1st to 10thDay
42%6%12%20%17%2
2160
11th to 20thDay
33%6%11%23%24%3
2147
21st to endDay
44%6%9%18%20%2
1954
October1st to 10thDay
43%6%13%21%15%2
1800
11th to 20thDay
40%6%12%24%17%1
1800
21st to endDay
45%5%12%21%14%2
1921
November1st to 10thDay
35%415%24%20%3
1671
11th to 20thDay
40%6%10%24%18%2
1710
21st to endDay
40%5%15%29%9%2
1535
December1st to 10thDay
50%6%15%18%10%1
1520
11th to 20thDay
45%6%17%23%8%1
1906
21st to endDay
53%7%13%19%7%
2772
January1st to 10thNight
41%5%12%24%14%3
2649
11th to 20thNight
47%6%15%21%9%2
2533
21st to endNight
41%5%11%24%15%2
2574
February1st to 10thNight
45%5%14%23%11%2
2340
11th to 20thNight
45%5%12%20%15%3
2172
21st to endNight
45%49%23%16%3
1776
March1st to 10thNight
38%5%13%25%15%3
2142
11th to 20thNight
43%5%10%22%17%3
1980
21st to endNight
44%5%10%18%18%4
2066
April1st to 10thNight
44%6%11%22%14%3
1800
11th to 20thNight
41%7%10%20%20%1
1775
21st to endNight
41%6%11%20%17%5%
1800
May1st to 10thNight
48%6%11%18%15%3
1618
11th to 20thNight
44%8%12%17%17%2
1416
21st to endNight
41%9%16%18%13%3
1551
June1st to 10thNight
41%6%11%23%18%1
1440
11th to 20thNight
39%9%15%23%14%1
1440
21st to endNight
33%9%15%29%13%1
1440
July1st to 10thNight
40%9%13%22%14%2
1400
11th to 20thNight
35%9%16%26%14%2
1392
21st to endNight
33%9%18%22%15%2
1518
August1st to 10thNight
37%9%14%22%16%1
1600
11th to 20thNight
43%10%13%18%16%1
1718
21st to endNight
38%8%13%20%19%2
1980
September1st to 10thNight
39%6%10%23%19%3
1800
11th to 20thNight
35%5%9%23%25%3
1813
21st to endNight
40%5%10%22%22%1
2002
October1st to 10thNight
42%6%11%24%14%2
2160
11th to 20thNight
37%6%11%29%14%2
2160
21st to endNight
41%5%11%25%16%1
2434
November1st to 10thNight
34%6%14%23%19%4
2407
11th to 20thNight
41%410%24%17%3
2470
21st to endNight
40%5%13%27%13%2
2641
December1st to 10thNight
48%6%13%21%11%1
2660
11th to 20thNight
45%5%15%20%14%2
3288
21st to endNight
49%6%13%23%9%
4884

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 10thDay
27%27%28%16%3
180
11th to 20thDay
30%29%28%10%21
181
21st to endDay
20%32%31%11%5%1
264
February1st to 10thDay
24%35%30%8%2
240
11th to 20thDay
26%26%39%9%1
342
21st to endDay
32%22%30%16%1
346
March1st to 10thDay
24%25%30%18%3
420
11th to 20thDay
24%25%30%15%41
420
21st to endDay
29%22%29%13%6%1
462
April1st to 10thDay
22%28%28%16%5%1
420
11th to 20thDay
22%24%27%17%8%3
412
21st to endDay
28%20%32%14%5%2
420
May1st to 10thDay
29%22%25%14%7%3
423
11th to 20thDay
23%16%31%19%9%1
447
21st to endDay
20%9%28%21%18%4
485
June1st to 10thDay
16%16%28%25%13%2
450
11th to 20thDay
20%14%28%25%11%2
450
21st to endDay
14%11%32%25%14%2
450
July1st to 10thDay
13%6%26%27%22%7%
445
11th to 20thDay
10%425%32%23%5%
444
21st to endDay
14%7%31%31%13%5%
488
August1st to 10thDay
13%5%23%31%21%7%
446
11th to 20thDay
14%5%22%32%20%7%
439
21st to endDay
14%8%29%24%16%10%
495
September1st to 10thDay
20%9%21%24%18%8%
450
11th to 20thDay
16%429%26%15%11%
450
21st to endDay
24%14%22%21%14%5%
450
October1st to 10thDay
26%9%23%22%15%5%
450
11th to 20thDay
19%16%28%24%11%2
450
21st to endDay
25%14%34%17%8%1
465
November1st to 10thDay
19%16%28%24%10%3
365
11th to 20thDay
23%22%30%20%5%1
370
21st to endDay
23%23%36%14%4
195
December1st to 10thDay
24%31%28%12%5%1
180
11th to 20thDay
30%28%26%12%4
180
21st to endDay
27%22%34%12%42
198
January1st to 10thNight
19%19%41%18%3
760
11th to 20thNight
25%17%31%24%3
735
21st to endNight
17%19%39%24%1
792
February1st to 10thNight
22%18%36%22%2
720
11th to 20thNight
22%22%38%16%2
703
21st to endNight
24%21%36%18%2
592
March1st to 10thNight
21%19%33%24%3
720
11th to 20thNight
22%18%34%21%5%1
720
21st to endNight
22%14%39%20%5%1
792
April1st to 10thNight
22%19%35%20%5%
720
11th to 20thNight
20%13%37%23%7%
711
21st to endNight
24%11%34%24%7%
720
May1st to 10thNight
26%10%30%26%8%1
538
11th to 20thNight
19%8%34%31%8%
354
21st to endNight
18%421%42%14%1
389
June1st to 10thNight
18%6%25%33%18%
360
11th to 20thNight
14%8%26%40%11%1
360
21st to endNight
12%426%44%14%
360
July1st to 10thNight
12%419%42%23%2
350
11th to 20thNight
11%420%41%24%1
348
21st to endNight
12%322%40%22%1
427
August1st to 10thNight
13%315%44%23%2
537
11th to 20thNight
16%5%16%36%25%2
654
21st to endNight
16%419%35%25%2
792
September1st to 10thNight
17%424%33%20%1
720
11th to 20thNight
16%5%20%33%21%5%
720
21st to endNight
20%7%22%32%19%1
720
October1st to 10thNight
24%8%24%25%17%3
720
11th to 20thNight
20%10%26%33%10%
720
21st to endNight
26%11%31%25%8%
792
November1st to 10thNight
16%12%34%26%11%1
740
11th to 20thNight
20%17%29%26%7%1
760
21st to endNight
18%16%34%26%6%
760
December1st to 10thNight
25%16%32%22%5%1
760
11th to 20thNight
21%15%35%24%4
760
21st to endNight
23%16%34%25%3
836
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