This page made possible by the sponsorship of: Albany Area Amateur Astronomers.

George Landis Arboretum
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the George Landis Arboretum clear sky chart from 2005-11-05 to 2020-06-03.

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
28%
18322
15%
57808
8%
18291
36%
18291
16%
40512

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
13%
900
13%
3136
5%
896
24%
896
8%
2292
January16th to endNight
14%
960
12%
3293
3%
960
25%
960
9%
2431
February1st to 15thNight
9%
884
10%
2842
2%
881
19%
881
8%
2220
February16th to endNight
15%
791
13%
2373
5%
791
26%
791
10%
1787
March1st to 15thNight
15%
900
13%
2687
5%
900
24%
900
11%
2046
March16th to endNight
21%
960
19%
2496
7%
960
31%
960
17%
1801
April1st to 15thNight
19%
898
14%
2246
3%
898
25%
898
15%
1689
April16th to endNight
26%
841
17%
2177
5%
841
33%
841
20%
1570
May1st to 15thNight
27%
548
15%
1898
8%
548
35%
548
15%
1320
May16th to endNight
36%
470
13%
1881
10%
470
45%
470
17%
1205
June1st to 15thNight
36%
425
14%
1701
11%
425
48%
425
16%
1094
June16th to endNight
48%
420
13%
1680
14%
420
57%
420
25%
962
July1st to 15thNight
51%
400
15%
1600
18%
400
58%
400
24%
897
July16th to endNight
54%
440
16%
1674
18%
418
59%
418
24%
958
August1st to 15thNight
49%
540
17%
1771
13%
538
54%
538
26%
1097
August16th to endNight
53%
892
18%
2230
9%
892
56%
892
34%
1453
September1st to 15thNight
46%
840
19%
2100
9%
840
50%
840
30%
1398
September16th to endNight
52%
837
24%
2288
18%
837
57%
837
33%
1411
October1st to 15thNight
35%
840
16%
2481
11%
840
42%
840
20%
1712
October16th to endNight
23%
896
13%
2817
6%
896
33%
896
14%
2030
November1st to 15thNight
27%
880
17%
2862
9%
880
38%
880
15%
1975
November16th to endNight
25%
900
15%
3065
9%
900
33%
900
12%
2169
December1st to 15thNight
17%
900
10%
3150
4%
900
26%
900
8%
2380
December16th to endNight
14%
960
9%
3360
3%
960
22%
960
6%
2615

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
15%8%36%6%35%5%5%7%32%
58606
Night
15%8%36%5%35%45%7%33%
57978
Cloud CoverDay
15%8%37%6%35%5%5%7%32%
58615
Night
15%8%36%6%35%45%7%33%
57984
TransparencyDay
49%7%11%19%10%1
58294
Night
49%6%11%19%11%1
57808
SeeingDay
22%17%27%19%9%3
9063
Night
21%17%27%24%8%
18323

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
14%9%47%7%5%5%7%6%6%24%
1792
16th to endDay
13%11%49%7%46%5%6%5%25%
1983
February1st to 15thDay
14%11%5%9%9%5%7%5%5%5%20%
2007
16th to endDay
14%11%6%9%8%36%5%35%26%
1980
March1st to 15thDay
15%11%49%7%345%5%7%26%
2251
16th to endDay
16%9%46%6%24345%36%
2782
April1st to 15thDay
17%9%47%6%34445%31%
2692
16th to endDay
17%8%36%5%34445%35%
2717
May1st to 15thDay
20%8%27%6%25%446%31%
3055
16th to endDay
14%6%25%6%35%5%5%8%35%
3290
June1st to 15thDay
19%5%35%5%3446%9%31%
2968
16th to endDay
13%7%26%5%46%6%5%10%31%
2940
July1st to 15thDay
10%425%6%36%7%7%8%36%
2940
16th to endDay
11%5%25%6%46%6%6%8%35%
3102
August1st to 15thDay
11%5%26%6%46%6%5%9%34%
2743
16th to endDay
11%5%145%36%6%6%8%39%
2676
September1st to 15thDay
14%6%25%5%345%6%6%38%
2520
16th to endDay
12%5%24423447%48%
2332
October1st to 15thDay
18%8%26%5%34445%34%
2138
16th to endDay
20%9%36%6%345%6%7%27%
2109
November1st to 15thDay
17%8%25%5%34348%35%
1986
16th to endDay
15%9%38%6%2445%7%32%
1883
December1st to 15thDay
18%13%48%7%35%5%45%23%
1800
16th to endDay
17%11%6%8%7%35%5%5%6%21%
1920
January1st to 15thNight
15%11%47%6%36%5%6%8%24%
3136
16th to endNight
11%11%5%8%8%45%5%6%6%25%
3293
February1st to 15thNight
14%11%5%10%8%45%5%46%21%
2841
16th to endNight
14%11%48%6%45%5%47%26%
2373
March1st to 15thNight
16%11%48%6%36%445%27%
2674
16th to endNight
15%8%46%5%3445%5%36%
2496
April1st to 15thNight
17%9%37%6%35%437%31%
2246
16th to endNight
20%6%25%5%24436%37%
2177
May1st to 15thNight
21%8%36%335%345%33%
1898
16th to endNight
14%7%346%25%5%5%8%36%
1879
June1st to 15thNight
19%6%25%424447%37%
1701
16th to endNight
12%4145%2345%10%43%
1680
July1st to 15thNight
8%425%5%35%46%10%44%
1680
16th to endNight
11%425%42446%8%44%
1770
August1st to 15thNight
11%415%5%346%6%8%42%
1781
16th to endNight
10%5%144345%5%8%45%
2230
September1st to 15thNight
14%426%43335%7%45%
2100
16th to endNight
11%42432335%7%50%
2288
October1st to 15thNight
19%7%25%433446%37%
2481
16th to endNight
20%8%36%5%3445%7%29%
2817
November1st to 15thNight
16%8%37%5%3445%6%34%
2862
16th to endNight
16%9%37%6%45%45%6%31%
3065
December1st to 15thNight
18%10%5%6%6%36%5%5%7%24%
3150
16th to endNight
18%12%5%8%6%46%5%5%6%21%
3360

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
13%10%47%7%46%6%6%7%24%
1792
16th to endDay
12%11%5%9%7%45%6%6%6%24%
1983
February1st to 15thDay
14%10%6%9%8%6%7%5%45%20%
2007
16th to endDay
13%11%5%10%7%35%5%35%26%
1980
March1st to 15thDay
15%12%49%7%335%47%26%
2261
16th to endDay
16%9%46%5%34336%35%
2781
April1st to 15thDay
17%9%47%6%34445%32%
2692
16th to endDay
17%9%36%5%34445%35%
2717
May1st to 15thDay
19%8%37%5%24446%31%
3055
16th to endDay
14%5%26%5%45%5%6%7%35%
3290
June1st to 15thDay
19%6%36%5%35%5%6%9%31%
2968
16th to endDay
14%7%35%6%36%6%5%9%30%
2940
July1st to 15thDay
10%5%26%6%36%6%7%8%36%
2940
16th to endDay
12%425%6%46%6%7%8%34%
3102
August1st to 15thDay
11%6%26%7%46%6%6%8%34%
2743
16th to endDay
11%4145%35%6%6%9%38%
2676
September1st to 15thDay
15%5%25%5%345%5%7%38%
2520
16th to endDay
12%5%2342445%7%47%
2332
October1st to 15thDay
18%8%36%6%2445%5%34%
2138
16th to endDay
20%8%37%6%345%5%6%28%
2109
November1st to 15thDay
17%9%35%5%24446%35%
1986
16th to endDay
14%10%47%5%345%5%6%32%
1883
December1st to 15thDay
17%12%49%7%35%5%45%23%
1800
16th to endDay
16%12%5%9%7%46%5%5%6%21%
1920
January1st to 15thNight
14%11%48%6%35%5%6%7%25%
3136
16th to endNight
11%10%5%8%8%45%6%6%7%25%
3293
February1st to 15thNight
14%12%5%10%8%46%5%5%6%22%
2834
16th to endNight
14%10%49%7%35%5%5%7%25%
2373
March1st to 15thNight
16%11%38%7%45%345%27%
2687
16th to endNight
14%8%46%5%35%45%5%36%
2496
April1st to 15thNight
17%9%47%6%35%346%31%
2246
16th to endNight
20%7%345%24346%37%
2177
May1st to 15thNight
20%9%26%434446%33%
1898
16th to endNight
14%6%35%5%445%5%7%37%
1879
June1st to 15thNight
18%6%35%42445%7%37%
1701
16th to endNight
12%315%43445%11%43%
1680
July1st to 15thNight
8%4246%35%5%410%44%
1680
16th to endNight
11%5%244345%6%8%44%
1770
August1st to 15thNight
10%5%15%5%35%5%6%8%42%
1781
16th to endNight
11%5%2443445%8%45%
2230
September1st to 15thNight
14%5%25%42445%7%45%
2100
16th to endNight
11%414423447%50%
2288
October1st to 15thNight
19%6%25%5%24346%37%
2481
16th to endNight
20%8%36%5%3445%8%30%
2817
November1st to 15thNight
16%8%36%6%34447%34%
2862
16th to endNight
15%8%37%6%4445%6%31%
3065
December1st to 15thNight
17%11%47%6%35%5%5%7%24%
3150
16th to endNight
17%11%5%8%7%45%5%5%6%21%
3360

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
54%7%11%17%8%1
1793
16th to endDay
57%7%11%14%7%1
1983
February1st to 15thDay
63%7%9%12%6%
2010
16th to endDay
59%5%9%16%9%
1980
March1st to 15thDay
56%5%12%15%8%1
2261
16th to endDay
50%49%16%15%3
2782
April1st to 15thDay
53%48%20%10%1
2692
16th to endDay
50%5%7%20%13%2
2717
May1st to 15thDay
53%6%8%18%11%1
3055
16th to endDay
45%8%12%22%10%1
3294
June1st to 15thDay
49%7%13%18%9%
2968
16th to endDay
46%9%12%19%10%
2940
July1st to 15thDay
40%9%12%23%13%
2791
16th to endDay
43%9%13%21%12%
2935
August1st to 15thDay
44%9%14%20%9%1
2729
16th to endDay
39%8%12%26%13%
2676
September1st to 15thDay
43%7%11%22%13%1
2520
16th to endDay
35%6%10%28%17%1
2332
October1st to 15thDay
49%6%10%21%10%1
2138
16th to endDay
53%7%12%17%8%1
2109
November1st to 15thDay
48%6%12%20%11%1
1986
16th to endDay
50%6%14%17%10%
1883
December1st to 15thDay
61%7%11%14%5%
1800
16th to endDay
61%8%11%12%5%
1920
January1st to 15thNight
55%7%11%14%10%
3136
16th to endNight
54%7%11%16%8%1
3293
February1st to 15thNight
61%6%10%14%6%
2842
16th to endNight
56%6%11%15%8%1
2373
March1st to 15thNight
58%5%9%19%7%1
2687
16th to endNight
48%6%9%19%13%2
2496
April1st to 15thNight
52%5%10%19%9%1
2246
16th to endNight
48%5%9%18%15%1
2177
May1st to 15thNight
51%5%9%16%14%2
1898
16th to endNight
44%7%14%21%11%1
1881
June1st to 15thNight
46%5%12%22%10%1
1701
16th to endNight
35%6%16%27%13%
1680
July1st to 15thNight
34%7%13%27%15%1
1600
16th to endNight
35%7%15%27%12%1
1674
August1st to 15thNight
36%8%14%28%11%
1771
16th to endNight
35%6%14%29%13%
2230
September1st to 15thNight
38%6%13%25%15%1
2100
16th to endNight
33%5%11%27%19%1
2288
October1st to 15thNight
46%6%11%18%15%1
2481
16th to endNight
50%7%14%17%8%
2817
November1st to 15thNight
48%6%11%18%13%1
2862
16th to endNight
51%7%12%19%8%1
3065
December1st to 15thNight
56%8%12%15%6%
3150
16th to endNight
60%9%10%12%7%
3360

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
28%32%26%8%41
150
16th to endDay
28%24%33%7%4
181
February1st to 15thDay
29%36%26%6%1
254
16th to endDay
23%29%29%15%2
399
March1st to 15thDay
27%25%32%11%3
450
16th to endDay
26%27%24%14%6%1
480
April1st to 15thDay
27%28%22%13%7%
450
16th to endDay
28%19%28%12%6%3
439
May1st to 15thDay
30%21%23%15%5%3
468
16th to endDay
19%14%31%22%9%2
523
June1st to 15thDay
22%14%31%21%9%1
443
16th to endDay
19%15%29%24%10%
435
July1st to 15thDay
11%7%28%30%17%4
425
16th to endDay
14%432%29%13%5%
454
August1st to 15thDay
12%7%31%24%16%6%
418
16th to endDay
12%9%25%26%16%8%
460
September1st to 15thDay
17%9%24%21%17%8%
435
16th to endDay
14%7%26%22%16%13%
434
October1st to 15thDay
25%10%24%20%14%2
435
16th to endDay
29%20%26%17%6%
417
November1st to 15thDay
27%19%22%18%10%1
370
16th to endDay
25%25%23%18%5%1
233
December1st to 15thDay
24%28%30%10%6%
150
16th to endDay
27%33%26%11%
160
January1st to 15thNight
22%28%29%16%3
900
16th to endNight
19%27%32%18%2
960
February1st to 15thNight
22%25%33%15%1
884
16th to endNight
23%27%28%18%1
791
March1st to 15thNight
25%24%31%15%2
900
16th to endNight
21%24%27%20%5%
960
April1st to 15thNight
25%22%27%20%3
898
16th to endNight
23%20%26%20%8%
841
May1st to 15thNight
26%13%26%23%8%1
548
16th to endNight
18%9%28%30%11%1
471
June1st to 15thNight
22%10%23%30%11%
425
16th to endNight
14%426%38%14%
420
July1st to 15thNight
10%424%39%21%
400
16th to endNight
12%322%39%19%2
440
August1st to 15thNight
15%325%34%19%1
540
16th to endNight
14%420%34%22%3
892
September1st to 15thNight
16%6%24%31%19%2
840
16th to endNight
14%8%21%30%19%5%
837
October1st to 15thNight
22%11%23%28%12%1
840
16th to endNight
26%16%28%23%5%
896
November1st to 15thNight
21%18%25%25%7%1
880
16th to endNight
22%21%26%21%7%
900
December1st to 15thNight
25%23%28%17%4
900
16th to endNight
26%28%25%16%2
960
Page generated at 2020-06-04 03:18:53. Version ac04

Copyright 2020 A. Danko


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