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 2005-11-05 to 2017-09-17.

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
43%
15816
24%
47133
15%
15769
52%
15769
33%
27821

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%
900
25%
2327
9%
895
40%
895
34%
1453
January16th to endNight
32%
960
29%
2496
11%
960
43%
960
36%
1496
February1st to 15thNight
27%
880
20%
2288
7%
876
34%
876
29%
1493
February16th to endNight
28%
630
25%
1892
9%
630
40%
630
29%
1146
March1st to 15thNight
33%
540
22%
1980
13%
540
45%
540
24%
1183
March16th to endNight
28%
576
16%
2112
10%
576
37%
576
21%
1333
April1st to 15thNight
33%
539
22%
1869
14%
539
46%
539
28%
1068
April16th to endNight
34%
540
21%
1725
15%
540
44%
540
25%
1076
May1st to 15thNight
40%
540
20%
1620
16%
540
48%
540
27%
1042
May16th to endNight
48%
563
19%
1685
15%
561
55%
561
30%
1060
June1st to 15thNight
62%
540
18%
1620
13%
540
66%
540
38%
910
June16th to endNight
62%
540
21%
1620
15%
540
67%
540
46%
844
July1st to 15thNight
69%
510
18%
1530
18%
510
70%
510
41%
847
July16th to endNight
76%
564
26%
1594
28%
531
78%
531
42%
866
August1st to 15thNight
77%
539
26%
1610
31%
536
78%
536
42%
862
August16th to endNight
75%
573
27%
1821
32%
573
76%
573
41%
960
September1st to 15thNight
64%
540
25%
1875
28%
540
67%
540
32%
1049
September16th to endNight
62%
498
29%
1837
26%
498
69%
498
32%
958
October1st to 15thNight
49%
643
29%
1963
21%
643
55%
643
36%
1101
October16th to endNight
42%
704
30%
2112
15%
704
53%
704
40%
1126
November1st to 15thNight
40%
737
31%
2137
15%
737
54%
737
39%
1188
November16th to endNight
31%
900
26%
2394
10%
900
43%
900
33%
1480
December1st to 15thNight
31%
900
21%
2520
8%
900
41%
900
30%
1595
December16th to endNight
30%
960
25%
2506
10%
960
41%
960
27%
1685

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%2443445%6%45%
47627
Night
10%5%24423346%51%
47328
TransparencyDay
38%6%12%25%15%2
47327
Night
33%5%12%26%19%3
47133
SeeingDay
12%5%24%30%22%5%
5842
Night
13%7%30%32%14%1
15816

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
11%7%145%2323452%
1611
16th to endDay
13%5%34423346%47%
1728
February1st to 15thDay
12%8%45%423445%44%
1575
16th to endDay
12%7%35%425%445%44%
1588
March1st to 15thDay
14%8%35%434445%39%
1980
16th to endDay
21%8%46%423346%35%
2110
April1st to 15thDay
14%7%25%42445%6%43%
2079
16th to endDay
19%8%36%5%34345%35%
2232
May1st to 15thDay
18%6%35%6%33445%36%
2331
16th to endDay
14%5%35%5%35%5%6%8%36%
2430
June1st to 15thDay
8%5%25%5%345%6%7%46%
2340
16th to endDay
6%212335%47%9%51%
2340
July1st to 15thDay
8%424436%5%6%9%43%
2340
16th to endDay
6%314435%6%6%10%46%
2466
August1st to 15thDay
7%324445%5%5%10%47%
2340
16th to endDay
6%424435%6%5%8%48%
2379
September1st to 15thDay
12%5%24434446%47%
2082
16th to endDay
9%4145%24446%51%
1828
October1st to 15thDay
13%6%23312346%51%
1656
16th to endDay
11%6%2332324454%
1760
November1st to 15thDay
10%5%23223346%56%
1719
16th to endDay
16%6%12312236%53%
1560
December1st to 15thDay
14%8%25%433336%44%
1440
16th to endDay
16%8%46%423336%41%
1713
January1st to 15thNight
12%5%23333335%53%
2327
16th to endNight
8%425%423346%54%
2496
February1st to 15thNight
11%9%3442433448%
2278
16th to endNight
12%5%25%41345%6%48%
1892
March1st to 15thNight
12%6%25%424347%45%
1980
16th to endNight
17%6%25%425%445%41%
2112
April1st to 15thNight
11%5%24423346%51%
1869
16th to endNight
14%6%25%5%23346%44%
1725
May1st to 15thNight
13%5%16%5%24346%44%
1619
16th to endNight
11%5%2433445%9%43%
1683
June1st to 15thNight
5%324424448%55%
1620
16th to endNight
32133335%6%9%56%
1620
July1st to 15thNight
6%32332346%9%52%
1620
16th to endNight
43233245%6%11%53%
1702
August1st to 15thNight
5%21432447%9%55%
1620
16th to endNight
5%31432446%8%56%
1821
September1st to 15thNight
10%424423446%53%
1875
16th to endNight
5%424434447%54%
1837
October1st to 15thNight
12%323313345%55%
1963
16th to endNight
8%314222236%60%
2112
November1st to 15thNight
8%5%14323335%59%
2137
16th to endNight
13%6%2431233454%
2394
December1st to 15thNight
16%6%35%313347%45%
2520
16th to endNight
14%8%36%423245%43%
2506

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
36%312%28%17%1
1612
16th to endDay
38%314%26%14%1
1728
February1st to 15thDay
42%5%14%26%10%1
1576
16th to endDay
42%5%10%24%14%3
1588
March1st to 15thDay
46%5%8%22%13%3
1980
16th to endDay
51%5%12%19%9%1
2112
April1st to 15thDay
40%6%14%22%14%1
2079
16th to endDay
51%5%10%21%10%1
2232
May1st to 15thDay
48%5%11%22%11%
2331
16th to endDay
44%8%14%21%10%
2434
June1st to 15thDay
34%7%13%25%16%1
2340
16th to endDay
25%7%16%29%18%2
2340
July1st to 15thDay
33%8%16%27%13%1
2201
16th to endDay
29%8%16%31%13%1
2311
August1st to 15thDay
31%7%16%23%20%1
2326
16th to endDay
31%8%13%24%15%6%
2379
September1st to 15thDay
37%6%10%22%16%6%
2082
16th to endDay
32%5%10%28%18%4
1828
October1st to 15thDay
33%412%24%20%4
1656
16th to endDay
32%39%29%19%5%
1760
November1st to 15thDay
29%49%28%21%5%
1719
16th to endDay
35%210%26%23%1
1560
December1st to 15thDay
41%311%29%13%
1440
16th to endDay
45%410%23%12%3
1713
January1st to 15thNight
34%311%27%20%3
2327
16th to endNight
31%313%30%17%3
2496
February1st to 15thNight
39%412%26%14%2
2288
16th to endNight
36%412%25%18%2
1892
March1st to 15thNight
39%410%21%18%5%
1980
16th to endNight
43%5%12%21%14%1
2112
April1st to 15thNight
34%411%25%20%3
1869
16th to endNight
40%411%23%17%2
1725
May1st to 15thNight
41%5%12%21%17%1
1620
16th to endNight
35%8%18%23%13%1
1685
June1st to 15thNight
27%6%15%29%18%2
1620
16th to endNight
21%6%17%30%20%3
1620
July1st to 15thNight
26%6%14%30%18%3
1530
16th to endNight
23%7%12%31%22%2
1594
August1st to 15thNight
24%6%13%32%19%4
1610
16th to endNight
23%6%12%28%21%7%
1821
September1st to 15thNight
32%411%23%20%7%
1875
16th to endNight
29%49%26%25%3
1837
October1st to 15thNight
30%410%21%24%7%
1963
16th to endNight
26%39%28%26%5%
2112
November1st to 15thNight
28%39%26%23%8%
2137
16th to endNight
34%37%26%22%4
2394
December1st to 15thNight
38%413%26%16%
2520
16th to endNight
42%410%23%14%4
2506

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
24%17%28%23%5%
90
16th to endDay
16%14%37%25%5%1
96
February1st to 15thDay
7%24%42%17%7%
90
16th to endDay
7%20%41%23%6%
81
March1st to 15thDay
23%22%42%10%2
90
16th to endDay
22%13%32%21%9%
96
April1st to 15thDay
14%10%38%27%8%1
198
16th to endDay
24%9%35%19%9%
342
May1st to 15thDay
17%9%32%27%10%2
468
16th to endDay
17%5%32%25%13%4
517
June1st to 15thDay
8%223%35%25%4
495
16th to endDay
7%225%38%21%5%
495
July1st to 15thDay
10%215%38%28%5%
475
16th to endDay
6%5%32%43%11%
515
August1st to 15thDay
8%11%32%40%7%
493
16th to endDay
9%11%34%36%6%
419
September1st to 15thDay
8%113%31%33%11%
237
16th to endDay
4220%34%25%12%
93
October1st to 15thDay
8%428%33%10%14%
90
16th to endDay
14%137%35%8%3
96
November1st to 15thDay
16%224%27%23%5%
90
16th to endDay
28%20%27%17%23
90
December1st to 15thDay
14%10%50%14%7%3
90
16th to endDay
20%16%35%22%4
96
January1st to 15thNight
15%13%40%24%5%
900
16th to endNight
11%11%40%30%6%
960
February1st to 15thNight
16%12%39%28%3
880
16th to endNight
16%11%40%28%3
630
March1st to 15thNight
15%10%35%31%5%
540
16th to endNight
20%9%39%24%6%
576
April1st to 15thNight
15%9%37%30%6%
539
16th to endNight
18%8%35%28%9%
540
May1st to 15thNight
15%5%33%31%12%1
540
16th to endNight
15%227%32%20%1
563
June1st to 15thNight
6%220%44%23%1
540
16th to endNight
4126%45%20%
540
July1st to 15thNight
9%15%42%29%1
510
16th to endNight
6%9%36%43%3
564
August1st to 15thNight
5%18%45%37%2
539
16th to endNight
7%10%40%38%2
573
September1st to 15thNight
12%213%38%29%3
540
16th to endNight
7%220%37%28%4
498
October1st to 15thNight
14%327%29%21%2
643
16th to endNight
11%7%36%30%13%
704
November1st to 15thNight
10%10%35%29%13%1
737
16th to endNight
17%11%36%26%8%
900
December1st to 15thNight
19%10%36%28%5%
900
16th to endNight
18%10%36%29%4
960
Page generated at 2017-09-18 07:38:18. Version ac04

Copyright 2017 A. Danko


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