PSU-Greenbush Astrophysical Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the PSU-Greenbush Astrophysical Observatory clear sky chart from 2005-11-06 to 2024-01-12.

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%
24362
24%
74762
15%
24300
51%
24300
31%
44451

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
30%
950
25%
2458
9%
946
42%
946
34%
1548
January11th to 20thNight
26%
908
26%
2360
9%
908
38%
908
33%
1487
January21st to endNight
28%
990
27%
2574
10%
990
39%
990
33%
1604
February1st to 10thNight
23%
900
19%
2340
6%
900
31%
900
26%
1590
February11th to 20thNight
24%
861
19%
2256
6%
857
32%
857
28%
1472
February21st to endNight
25%
520
26%
1704
11%
520
40%
520
24%
1036
March1st to 10thNight
31%
540
24%
1980
14%
540
45%
540
25%
1142
March11th to 20thNight
29%
540
20%
1980
11%
540
40%
540
22%
1206
March21st to endNight
23%
594
17%
2178
7%
594
37%
594
19%
1421
April1st to 10thNight
31%
540
22%
1908
12%
540
45%
540
28%
1070
April11th to 20thNight
33%
533
24%
1775
17%
533
46%
533
25%
1068
April21st to endNight
30%
540
21%
1689
13%
540
43%
540
26%
1058
May1st to 10thNight
37%
540
18%
1620
14%
540
44%
540
26%
1065
May11th to 20thNight
46%
531
20%
1594
18%
531
52%
531
31%
979
May21st to endNight
49%
584
18%
1746
13%
582
56%
582
28%
1104
June1st to 10thNight
68%
540
19%
1620
16%
540
72%
540
39%
900
June11th to 20thNight
62%
540
21%
1620
16%
540
66%
540
41%
879
June21st to endNight
63%
540
23%
1620
19%
540
68%
540
47%
834
July1st to 10thNight
72%
525
18%
1575
18%
525
73%
525
40%
876
July11th to 20thNight
77%
522
22%
1566
24%
522
79%
522
48%
800
July21st to endNight
70%
591
24%
1673
27%
558
72%
558
38%
951
August1st to 10thNight
71%
537
24%
1601
27%
534
74%
534
40%
879
August11th to 20thNight
75%
534
30%
1600
34%
534
76%
534
42%
867
August21st to endNight
76%
594
28%
1934
34%
594
77%
594
43%
974
September1st to 10thNight
66%
540
27%
1822
29%
540
68%
540
36%
978
September11th to 20thNight
64%
540
28%
1980
28%
540
70%
540
31%
1077
September21st to endNight
65%
540
32%
1980
32%
540
71%
540
39%
960
October1st to 10thNight
57%
692
29%
2132
21%
692
62%
692
41%
1137
October11th to 20thNight
36%
720
30%
2160
14%
720
48%
720
37%
1211
October21st to endNight
36%
792
27%
2376
14%
792
47%
792
32%
1412
November1st to 10thNight
40%
740
33%
2220
16%
740
54%
740
42%
1190
November11th to 20thNight
35%
914
28%
2434
12%
914
47%
914
36%
1459
November21st to endNight
32%
950
26%
2557
11%
950
43%
950
33%
1581
December1st to 10thNight
32%
950
23%
2660
9%
950
44%
950
31%
1643
December11th to 20thNight
29%
948
24%
3017
9%
948
39%
948
25%
1898
December21st to endNight
26%
1042
16%
4453
9%
1026
38%
1026
15%
3095

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%35%5%3445%7%46%
74536
Night
11%6%35%42445%7%50%
75182
TransparencyDay
38%6%12%25%16%3
74260
Night
34%5%11%25%20%4
74978
SeeingDay
13%8%27%28%18%5%
14399
Night
14%8%31%33%13%1
24367

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 10thDay
12%8%35%5%34346%49%
1707
11th to 20thDay
14%10%35%423347%45%
1629
21st to endDay
12%8%46%5%3345%6%44%
1782
February1st to 10thDay
16%9%46%5%33435%42%
1620
11th to 20thDay
13%7%38%5%24336%45%
1606
21st to endDay
15%9%36%5%346%45%41%
1550
March1st to 10thDay
13%9%46%5%34346%45%
1980
11th to 20thDay
21%8%26%44345%5%38%
1980
21st to endDay
20%9%46%5%3445%6%33%
2178
April1st to 10thDay
12%7%26%5%345%5%7%45%
2052
11th to 20thDay
15%7%35%5%45%5%5%6%41%
2134
21st to endDay
20%8%45%5%3435%6%38%
2268
May1st to 10thDay
20%6%36%6%3445%5%38%
2340
11th to 20thDay
15%7%35%5%345%6%7%39%
2302
21st to endDay
14%6%36%6%46%6%6%10%33%
2531
June1st to 10thDay
7%425%5%345%7%9%50%
2340
11th to 20thDay
8%5%245%35%6%6%7%48%
2340
21st to endDay
5%313335%47%9%57%
2340
July1st to 10thDay
9%5%25%446%6%7%11%41%
2340
11th to 20thDay
4314435%5%6%10%56%
2340
21st to endDay
8%425%5%46%6%6%10%44%
2546
August1st to 10thDay
7%325%5%46%6%6%11%46%
2328
11th to 20thDay
8%5%245%35%5%5%9%48%
2301
21st to endDay
6%4244345%5%7%54%
2420
September1st to 10thDay
11%5%24434446%52%
2134
11th to 20thDay
10%4245%36%5%5%7%48%
1980
21st to endDay
9%42443445%6%56%
1980
October1st to 10thDay
11%5%25%33435%6%52%
1809
11th to 20thDay
12%5%23323346%56%
1800
21st to endDay
19%7%3432333450%
1980
November1st to 10thDay
10%5%24322446%59%
1858
11th to 20thDay
14%6%24323325%55%
1744
21st to endDay
16%6%33423246%52%
1615
December1st to 10thDay
11%9%35%5%34445%48%
1520
11th to 20thDay
13%10%45%6%43335%43%
2027
21st to endDay
18%15%6%6%5%34446%29%
3135
January1st to 10thNight
11%7%24443446%51%
2458
11th to 20thNight
13%6%35%423446%50%
2360
21st to endNight
10%7%46%423446%51%
2574
February1st to 10thNight
14%10%35%5%34445%43%
2340
11th to 20thNight
14%7%36%423445%47%
2255
21st to endNight
16%7%35%5%2335%6%46%
1704
March1st to 10thNight
12%6%35%5%34446%48%
1980
11th to 20thNight
18%7%25%324347%44%
1980
21st to endNight
19%6%36%5%25%45%5%39%
2178
April1st to 10thNight
10%6%245%34447%51%
1908
11th to 20thNight
14%6%245%24345%49%
1775
21st to endNight
16%6%26%5%2345%8%44%
1689
May1st to 10thNight
15%6%26%5%36%448%42%
1620
11th to 20thNight
13%5%35%43336%7%48%
1593
21st to endNight
12%5%35%436%5%6%9%42%
1745
June1st to 10thNight
5%325%4245%6%9%54%
1620
11th to 20thNight
43234345%7%10%54%
1620
21st to endNight
5%21343445%8%61%
1620
July1st to 10thNight
7%425%4345%6%9%51%
1620
11th to 20thNight
32134345%5%10%60%
1620
21st to endNight
6%424435%5%8%11%48%
1772
August1st to 10thNight
5%315%435%47%10%53%
1611
11th to 20thNight
5%4244245%6%8%56%
1600
21st to endNight
5%32432446%8%60%
1934
September1st to 10thNight
9%434433446%57%
1822
11th to 20thNight
8%5%235%3445%7%51%
1980
21st to endNight
7%424433346%61%
1980
October1st to 10thNight
9%32332445%6%59%
2132
11th to 20thNight
13%5%25%322346%56%
2160
21st to endNight
15%6%24433235%53%
2376
November1st to 10thNight
10%423223335%63%
2220
11th to 20thNight
10%6%24424346%55%
2434
21st to endNight
16%6%24312345%53%
2557
December1st to 10thNight
13%6%35%423447%48%
2660
11th to 20thNight
13%8%45%424446%46%
3153
21st to endNight
17%12%5%7%5%34346%34%
4532

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
38%412%25%19%2
1708
11th to 20thDay
41%313%27%15%1
1629
21st to endDay
41%415%25%14%1
1782
February1st to 10thDay
47%5%10%24%12%2
1620
11th to 20thDay
44%412%23%15%3
1615
21st to endDay
44%5%8%21%15%6%
1550
March1st to 10thDay
42%410%21%18%5%
1980
11th to 20thDay
49%5%10%21%13%3
1980
21st to endDay
52%6%12%19%9%1
2178
April1st to 10thDay
38%8%13%23%16%2
2052
11th to 20thDay
43%7%13%22%13%3
2134
21st to endDay
48%5%11%24%11%
2268
May1st to 10thDay
48%6%12%20%12%1
2340
11th to 20thDay
43%7%13%26%11%1
2306
21st to endDay
45%10%15%21%9%
2531
June1st to 10thDay
29%8%18%26%17%2
2340
11th to 20thDay
32%8%14%30%15%2
2340
21st to endDay
22%7%16%32%19%4
2340
July1st to 10thDay
33%11%15%24%15%2
2276
11th to 20thDay
23%8%16%30%19%4
2271
21st to endDay
32%8%16%31%13%1
2405
August1st to 10thDay
30%9%18%25%17%2
2314
11th to 20thDay
33%7%13%27%19%1
2301
21st to endDay
27%9%13%24%20%7%
2420
September1st to 10thDay
33%6%11%27%17%7%
2134
11th to 20thDay
34%6%11%24%23%2
1980
21st to endDay
28%6%11%26%24%5%
1980
October1st to 10thDay
32%6%13%24%21%4
1809
11th to 20thDay
29%48%28%24%6%
1800
21st to endDay
40%49%23%18%6%
1980
November1st to 10thDay
28%410%31%22%5%
1858
11th to 20thDay
34%38%25%25%5%
1744
21st to endDay
36%310%26%23%1
1615
December1st to 10thDay
39%49%32%15%1
1520
11th to 20thDay
45%38%22%19%3
2025
21st to endDay
56%5%10%18%9%1
3135
January1st to 10thNight
35%412%27%18%4
2458
11th to 20thNight
37%311%29%18%2
2360
21st to endNight
35%413%29%15%4
2574
February1st to 10thNight
44%411%25%13%3
2340
11th to 20thNight
39%5%11%25%18%2
2256
21st to endNight
41%49%21%18%7%
1704
March1st to 10thNight
38%49%21%20%8%
1980
11th to 20thNight
41%5%11%20%19%3
1980
21st to endNight
47%5%10%22%13%2
2178
April1st to 10thNight
33%5%12%23%22%5%
1908
11th to 20thNight
38%5%10%24%19%5%
1775
21st to endNight
40%5%11%24%17%2
1689
May1st to 10thNight
42%6%13%21%15%2
1620
11th to 20thNight
37%5%16%24%17%1
1594
21st to endNight
36%9%18%24%12%1
1746
June1st to 10thNight
25%9%17%29%18%3
1620
11th to 20thNight
24%8%17%30%19%2
1620
21st to endNight
22%5%15%32%21%5%
1620
July1st to 10thNight
26%7%16%30%17%4
1575
11th to 20thNight
19%7%14%31%25%4
1566
21st to endNight
27%8%15%30%19%1
1673
August1st to 10thNight
26%7%15%36%14%3
1601
11th to 20thNight
24%7%10%29%26%3
1600
21st to endNight
22%7%14%28%22%8%
1934
September1st to 10thNight
29%411%26%21%8%
1822
11th to 20thNight
31%6%9%23%26%5%
1980
21st to endNight
25%49%27%30%5%
1980
October1st to 10thNight
25%6%10%24%27%7%
2132
11th to 20thNight
31%38%24%26%7%
2160
21st to endNight
35%48%21%26%6%
2376
November1st to 10thNight
26%410%28%25%7%
2220
11th to 20thNight
32%38%24%28%4
2434
21st to endNight
36%48%24%24%4
2557
December1st to 10thNight
36%5%13%27%19%1
2660
11th to 20thNight
40%49%24%21%2
3154
21st to endNight
52%5%9%21%11%2
4532

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
19%14%35%25%7%
270
11th to 20thDay
23%17%39%20%2
243
21st to endDay
13%12%48%21%5%
264
February1st to 10thDay
22%18%35%21%4
240
11th to 20thDay
18%19%41%18%41
240
21st to endDay
23%22%37%15%4
198
March1st to 10thDay
20%18%38%20%4
240
11th to 20thDay
27%17%30%22%4
240
21st to endDay
25%17%38%15%31
264
April1st to 10thDay
15%15%40%22%6%1
312
11th to 20thDay
18%13%39%24%6%
412
21st to endDay
23%13%34%22%8%1
528
May1st to 10thDay
17%12%34%28%8%1
603
11th to 20thDay
17%10%30%26%13%4
625
21st to endDay
15%8%29%23%18%8%
679
June1st to 10thDay
6%318%34%30%10%
630
11th to 20thDay
8%323%39%21%6%
630
21st to endDay
5%5%26%40%21%4
630
July1st to 10thDay
9%312%31%32%13%
621
11th to 20thDay
4214%36%35%8%
618
21st to endDay
7%210%35%34%12%
684
August1st to 10thDay
9%113%39%33%6%
626
11th to 20thDay
8%216%33%33%9%
615
21st to endDay
8%110%30%41%10%
539
September1st to 10thDay
11%213%33%32%9%
424
11th to 20thDay
5%115%37%30%12%
270
21st to endDay
10%420%35%23%7%
270
October1st to 10thDay
13%7%29%23%16%11%
270
11th to 20thDay
11%12%44%24%7%1
270
21st to endDay
28%11%30%23%7%1
297
November1st to 10thDay
15%10%35%25%13%2
270
11th to 20thDay
16%16%33%23%10%2
270
21st to endDay
19%14%34%24%7%2
270
December1st to 10thDay
13%11%45%19%8%3
270
11th to 20thDay
18%14%35%24%7%1
270
21st to endDay
18%24%40%16%2
297
January1st to 10thNight
15%13%39%27%5%
950
11th to 20thNight
17%12%40%25%5%
908
21st to endNight
14%13%41%28%5%
990
February1st to 10thNight
19%12%41%23%4
900
11th to 20thNight
19%14%39%26%3
861
21st to endNight
22%13%37%25%3
520
March1st to 10thNight
14%12%39%31%4
540
11th to 20thNight
21%11%36%26%6%
540
21st to endNight
22%13%39%21%5%
594
April1st to 10thNight
13%12%40%28%6%
540
11th to 20thNight
18%12%33%30%6%
533
21st to endNight
18%10%39%26%7%
540
May1st to 10thNight
16%6%35%34%8%1
540
11th to 20thNight
14%6%29%34%16%1
531
21st to endNight
14%427%33%21%1
584
June1st to 10thNight
6%315%44%29%2
540
11th to 20thNight
6%125%48%20%1
540
21st to endNight
6%224%49%19%1
540
July1st to 10thNight
9%112%40%36%3
525
11th to 20thNight
4111%45%37%3
522
21st to endNight
8%113%40%36%3
591
August1st to 10thNight
5%214%44%34%1
537
11th to 20thNight
8%19%53%27%2
534
21st to endNight
5%112%37%42%3
594
September1st to 10thNight
10%215%44%26%3
540
11th to 20thNight
11%215%42%26%4
540
21st to endNight
7%320%44%24%2
540
October1st to 10thNight
10%327%35%23%2
692
11th to 20thNight
14%7%40%31%8%1
720
21st to endNight
16%11%33%29%10%1
792
November1st to 10thNight
11%8%39%31%10%1
740
11th to 20thNight
13%12%36%30%9%
914
21st to endNight
18%12%34%28%7%
950
December1st to 10thNight
16%10%39%29%6%
950
11th to 20thNight
19%10%38%29%4
950
21st to endNight
17%14%38%27%3
1045
Page generated at 2024-01-09 06:14:45. Version ac07

Copyright 2024 Attilla Danko


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