Rogers' Astrophysics Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rogers' Astrophysics Observatory clear sky chart from 2005-11-06 to 2024-01-11.

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
47%
24024
15%
74345
10%
23966
53%
23966
14%
55803

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
28%
760
16%
2459
6%
757
40%
757
13%
1834
January11th to 20thNight
31%
724
15%
2352
7%
724
40%
724
10%
1818
January21st to endNight
24%
792
16%
2574
6%
792
36%
792
12%
1939
February1st to 10thNight
35%
720
16%
2200
8%
720
43%
720
13%
1651
February11th to 20thNight
24%
703
16%
2098
5%
699
36%
699
14%
1590
February21st to endNight
27%
592
15%
1776
6%
592
37%
592
14%
1340
March1st to 10thNight
35%
720
19%
2033
11%
720
42%
720
18%
1493
March11th to 20thNight
32%
720
14%
1980
6%
720
39%
720
15%
1525
March21st to endNight
35%
792
14%
2178
6%
792
41%
792
15%
1685
April1st to 10thNight
40%
720
18%
1980
10%
720
45%
720
18%
1437
April11th to 20thNight
43%
619
21%
1805
11%
619
52%
619
20%
1263
April21st to endNight
50%
540
20%
1620
13%
540
56%
540
18%
1172
May1st to 10thNight
50%
540
13%
1620
7%
540
55%
540
15%
1204
May11th to 20thNight
50%
531
10%
1593
6%
531
53%
531
12%
1255
May21st to endNight
60%
582
12%
1744
9%
582
61%
582
15%
1313
June1st to 10thNight
65%
540
11%
1620
9%
540
65%
540
15%
1255
June11th to 20thNight
65%
540
12%
1620
10%
540
67%
540
17%
1216
June21st to endNight
70%
540
11%
1620
9%
540
71%
540
15%
1242
July1st to 10thNight
63%
525
6%
1575
6%
525
63%
525
10%
1317
July11th to 20thNight
69%
522
7%
1566
6%
522
70%
522
12%
1259
July21st to endNight
67%
591
8%
1672
6%
558
68%
558
12%
1348
August1st to 10thNight
64%
537
10%
1600
9%
534
64%
534
13%
1267
August11th to 20thNight
64%
534
13%
1598
12%
534
65%
534
13%
1283
August21st to endNight
60%
638
8%
2005
7%
638
60%
638
9%
1674
September1st to 10thNight
68%
720
12%
1980
10%
720
68%
720
15%
1553
September11th to 20thNight
58%
720
13%
1980
10%
720
60%
720
15%
1552
September21st to endNight
57%
720
15%
1980
11%
720
62%
720
17%
1493
October1st to 10thNight
57%
720
19%
1982
16%
720
60%
720
20%
1442
October11th to 20thNight
53%
720
19%
2160
16%
720
59%
720
17%
1582
October21st to endNight
53%
792
20%
2376
15%
792
60%
792
19%
1688
November1st to 10thNight
53%
740
20%
2291
18%
740
58%
740
20%
1595
November11th to 20thNight
41%
760
18%
2470
12%
760
50%
760
15%
1816
November21st to endNight
45%
760
16%
2470
12%
760
52%
760
14%
1857
December1st to 10thNight
35%
760
17%
2470
10%
760
44%
760
12%
1871
December11th to 20thNight
38%
759
21%
2898
13%
758
45%
758
12%
2004
December21st to endNight
30%
831
11%
4400
8%
817
39%
817
7%
2970

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
13%5%25%5%35%5%6%8%44%
74873
Night
14%5%25%5%345%5%7%44%
74829
TransparencyDay
25%38%7%13%13%4
74596
Night
25%38%7%13%14%4
74625
SeeingDay
16%8%21%25%20%11%
13918
Night
16%7%23%31%20%4
24032

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
17%5%345%24447%45%
1706
11th to 20thDay
17%7%35%434445%44%
1620
21st to endDay
18%5%24424336%48%
1782
February1st to 10thDay
16%5%26%6%345%5%5%42%
1755
11th to 20thDay
21%5%25%324346%44%
1748
21st to endDay
20%7%245%24446%41%
1480
March1st to 10thDay
16%5%2442435%6%52%
1926
11th to 20thDay
18%5%25%5%25%5%5%6%41%
1980
21st to endDay
17%5%25%5%345%5%7%41%
2178
April1st to 10thDay
11%4245%345%6%8%48%
1980
11th to 20thDay
11%5%25%5%345%5%7%48%
2116
21st to endDay
10%5%2433446%8%53%
2340
May1st to 10thDay
9%425%435%5%6%9%49%
2340
11th to 20thDay
12%5%25%5%35%6%6%9%42%
2301
21st to endDay
11%5%24435%6%6%11%42%
2531
June1st to 10thDay
8%5%26%6%46%6%8%11%36%
2340
11th to 20thDay
5%4246%46%6%8%11%43%
2340
21st to endDay
6%315%6%47%8%8%13%39%
2340
July1st to 10thDay
8%7%36%7%5%7%7%8%12%31%
2340
11th to 20thDay
8%5%25%7%46%8%9%12%35%
2340
21st to endDay
6%426%6%5%7%7%9%11%36%
2547
August1st to 10thDay
9%6%26%7%5%7%8%8%11%31%
2327
11th to 20thDay
11%5%27%6%46%7%7%11%34%
2303
21st to endDay
12%6%37%6%47%6%7%9%34%
2326
September1st to 10thDay
9%425%6%47%7%7%8%42%
1980
11th to 20thDay
14%5%25%5%245%6%8%43%
1980
21st to endDay
16%42433446%6%47%
1980
October1st to 10thDay
15%5%13322346%56%
1976
11th to 20thDay
14%424323345%57%
1800
21st to endDay
11%424423345%57%
1980
November1st to 10thDay
13%5%23322336%57%
1784
11th to 20thDay
14%42442445%7%51%
1710
21st to endDay
15%5%24424446%50%
1710
December1st to 10thDay
22%6%25%42445%6%39%
1710
11th to 20thDay
18%5%2442345%6%48%
2153
21st to endDay
23%5%24423347%42%
3124
January1st to 10thNight
19%5%25%424435%47%
2459
11th to 20thNight
16%7%35%5%3445%6%44%
2352
21st to endNight
17%6%34423345%49%
2574
February1st to 10thNight
17%6%245%34346%47%
2200
11th to 20thNight
21%6%25%424345%45%
2098
21st to endNight
19%5%25%42445%6%43%
1776
March1st to 10thNight
14%5%245%33446%50%
2033
11th to 20thNight
17%5%24435%5%5%6%43%
1980
21st to endNight
15%5%36%5%345%6%6%44%
2178
April1st to 10thNight
13%32443445%6%51%
1980
11th to 20thNight
11%5%25%5%23447%52%
1805
21st to endNight
10%5%25%434447%53%
1620
May1st to 10thNight
10%5%25%5%345%5%8%48%
1620
11th to 20thNight
12%6%35%6%36%6%7%9%38%
1592
21st to endNight
11%5%26%6%35%6%6%10%39%
1744
June1st to 10thNight
11%425%7%47%6%9%11%34%
1620
11th to 20thNight
7%5%346%45%6%6%12%42%
1620
21st to endNight
8%425%5%36%6%10%13%37%
1620
July1st to 10thNight
9%6%37%7%49%7%9%11%28%
1620
11th to 20thNight
8%435%6%47%7%10%14%31%
1620
21st to endNight
6%5%37%8%5%7%7%9%11%32%
1771
August1st to 10thNight
10%7%37%6%46%8%8%12%29%
1611
11th to 20thNight
11%6%45%7%46%7%7%11%33%
1598
21st to endNight
11%6%48%7%5%5%7%7%10%31%
2005
September1st to 10thNight
9%5%25%6%5%47%7%8%41%
1980
11th to 20thNight
16%6%35%5%345%7%8%39%
1980
21st to endNight
13%5%245%335%5%6%48%
1980
October1st to 10thNight
13%42442345%6%52%
1982
11th to 20thNight
13%5%24423445%53%
2160
21st to endNight
13%323324346%58%
2376
November1st to 10thNight
13%5%24323335%57%
2291
11th to 20thNight
16%5%23423345%53%
2470
21st to endNight
16%4244345%5%7%47%
2470
December1st to 10thNight
19%6%35%5%3445%5%42%
2470
11th to 20thNight
18%424322345%53%
3042
21st to endNight
20%6%26%5%45%45%7%36%
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
24%40%5%14%15%3
1707
11th to 20thDay
27%41%410%15%3
1620
21st to endDay
29%36%313%15%4
1782
February1st to 10thDay
28%36%6%12%13%5%
1755
11th to 20thDay
28%37%412%15%5%
1758
21st to endDay
28%36%6%11%14%5%
1480
March1st to 10thDay
21%36%5%15%17%7%
1926
11th to 20thDay
29%37%8%10%11%5%
1980
21st to endDay
29%37%7%16%11%1
2178
April1st to 10thDay
22%37%7%14%16%4
1980
11th to 20thDay
22%35%414%17%8%
2116
21st to endDay
19%37%7%20%14%3
2340
May1st to 10thDay
25%37%10%13%11%4
2340
11th to 20thDay
26%39%11%13%10%1
2305
21st to endDay
21%39%9%18%12%1
2531
June1st to 10thDay
24%41%12%15%7%1
2340
11th to 20thDay
22%40%12%16%8%1
2340
21st to endDay
21%41%10%13%10%4
2340
July1st to 10thDay
30%41%10%10%7%2
2275
11th to 20thDay
25%44%11%11%6%3
2271
21st to endDay
25%43%14%12%6%
2405
August1st to 10thDay
25%41%12%16%6%
2314
11th to 20thDay
30%39%11%13%6%1
2303
21st to endDay
33%41%9%11%6%1
2326
September1st to 10thDay
27%40%9%11%11%3
1980
11th to 20thDay
27%37%6%12%15%2
1980
21st to endDay
24%38%7%13%14%6%
1980
October1st to 10thDay
19%35%5%13%22%6%
1976
11th to 20thDay
22%36%5%15%16%6%
1800
21st to endDay
20%37%312%21%7%
1980
November1st to 10thDay
15%39%6%11%21%9%
1784
11th to 20thDay
21%40%414%16%6%
1710
21st to endDay
24%39%413%16%5%
1710
December1st to 10thDay
27%40%5%11%13%4
1710
11th to 20thDay
28%32%5%14%14%8%
2150
21st to endDay
30%25%417%21%2
3124
January1st to 10thNight
24%39%5%13%16%3
2459
11th to 20thNight
26%41%413%14%3
2352
21st to endNight
28%37%311%16%5%
2574
February1st to 10thNight
28%35%413%15%5%
2200
11th to 20thNight
27%36%312%16%6%
2099
21st to endNight
27%36%6%12%14%6%
1776
March1st to 10thNight
23%36%5%12%18%7%
2033
11th to 20thNight
26%37%8%10%15%4
1980
21st to endNight
26%38%6%13%14%2
2178
April1st to 10thNight
21%36%7%14%18%4
1980
11th to 20thNight
20%35%315%20%7%
1805
21st to endNight
21%38%6%17%14%4
1620
May1st to 10thNight
25%37%10%13%14%2
1620
11th to 20thNight
29%39%10%12%9%1
1593
21st to endNight
25%39%10%16%9%2
1745
June1st to 10thNight
26%40%11%14%8%1
1620
11th to 20thNight
23%39%11%17%9%1
1620
21st to endNight
23%42%11%10%10%4
1620
July1st to 10thNight
32%43%11%6%7%2
1575
11th to 20thNight
25%45%13%9%6%2
1566
21st to endNight
26%45%15%11%4
1672
August1st to 10thNight
26%43%12%16%4
1600
11th to 20thNight
29%40%9%13%7%1
1598
21st to endNight
35%41%9%9%5%1
2005
September1st to 10thNight
27%40%10%12%9%3
1980
11th to 20thNight
28%38%8%12%13%1
1980
21st to endNight
24%37%6%12%15%6%
1980
October1st to 10thNight
22%35%5%10%22%5%
1982
11th to 20thNight
23%37%5%13%17%6%
2160
21st to endNight
20%37%413%19%8%
2376
November1st to 10thNight
15%40%411%20%9%
2291
11th to 20thNight
23%39%311%17%7%
2470
21st to endNight
25%39%312%16%5%
2470
December1st to 10thNight
25%40%413%13%5%
2470
11th to 20thNight
25%32%5%11%22%4
3044
21st to endNight
34%26%418%15%3
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
21%16%37%21%4
270
11th to 20thDay
23%18%25%26%7%
240
21st to endDay
20%23%35%16%41
264
February1st to 10thDay
20%18%36%23%4
240
11th to 20thDay
37%11%35%15%2
240
21st to endDay
28%24%30%15%3
198
March1st to 10thDay
18%13%31%30%8%
366
11th to 20thDay
19%14%38%21%8%1
420
21st to endDay
20%15%33%21%9%1
462
April1st to 10thDay
17%15%25%27%14%1
420
11th to 20thDay
13%12%32%24%16%3
412
21st to endDay
16%9%24%27%17%8%
420
May1st to 10thDay
11%11%31%24%15%7%
423
11th to 20thDay
15%7%15%29%21%13%
447
21st to endDay
14%6%16%23%24%17%
485
June1st to 10thDay
12%414%30%25%16%
450
11th to 20thDay
8%5%14%27%26%22%
450
21st to endDay
10%212%29%27%19%
450
July1st to 10thDay
10%28%21%30%28%
445
11th to 20thDay
7%37%23%36%23%
444
21st to endDay
6%17%26%39%22%
488
August1st to 10thDay
14%411%24%26%21%
446
11th to 20thDay
12%27%23%35%21%
439
21st to endDay
13%29%24%30%21%
495
September1st to 10thDay
9%211%27%31%20%
450
11th to 20thDay
16%212%20%34%15%
450
21st to endDay
17%415%26%28%11%
450
October1st to 10thDay
19%5%16%29%20%12%
450
11th to 20thDay
13%422%32%24%5%
450
21st to endDay
16%7%23%30%21%4
495
November1st to 10thDay
19%8%25%25%18%6%
382
11th to 20thDay
17%13%33%27%8%2
270
21st to endDay
13%11%31%29%14%3
270
December1st to 10thDay
30%12%29%23%7%
270
11th to 20thDay
23%12%31%26%6%2
270
21st to endDay
32%16%27%15%8%2
297
January1st to 10thNight
22%14%31%27%6%
760
11th to 20thNight
22%11%30%30%7%
724
21st to endNight
20%13%39%26%3
792
February1st to 10thNight
19%10%31%35%5%
720
11th to 20thNight
25%11%36%25%3
703
21st to endNight
20%13%36%28%3
592
March1st to 10thNight
18%10%34%34%5%
720
11th to 20thNight
17%10%35%28%10%1
720
21st to endNight
17%11%31%29%11%1
792
April1st to 10thNight
14%13%30%32%11%
720
11th to 20thNight
12%10%28%33%15%1
619
21st to endNight
13%6%25%34%21%1
540
May1st to 10thNight
11%6%25%38%19%1
540
11th to 20thNight
14%420%36%24%3
531
21st to endNight
14%213%30%36%5%
584
June1st to 10thNight
12%213%35%31%7%
540
11th to 20thNight
9%216%27%34%13%
540
21st to endNight
8%111%38%34%8%
540
July1st to 10thNight
10%28%28%40%11%
525
11th to 20thNight
9%17%24%46%12%
522
21st to endNight
7%19%29%45%9%
591
August1st to 10thNight
12%29%25%41%10%
537
11th to 20thNight
15%26%28%39%9%
534
21st to endNight
12%310%26%40%10%
638
September1st to 10thNight
11%29%28%39%10%
720
11th to 20thNight
18%112%27%35%6%
720
21st to endNight
16%314%33%31%3
720
October1st to 10thNight
14%5%18%30%27%7%
720
11th to 20thNight
14%5%23%33%22%3
720
21st to endNight
15%6%22%34%22%2
792
November1st to 10thNight
15%6%22%34%21%3
740
11th to 20thNight
18%8%29%31%13%1
760
21st to endNight
17%8%25%36%13%1
760
December1st to 10thNight
21%12%25%34%8%
760
11th to 20thNight
20%8%29%32%11%1
760
21st to endNight
25%11%28%29%7%
836
Page generated at 2024-01-08 11:14:18. Version ac07

Copyright 2024 Attilla Danko


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