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 2005-11-05 to

2017-09-12
.

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
49%
15599
22%
46866
15%
15556
57%
15556
28%
29351

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
32%
720
24%
2327
11%
716
48%
716
23%
1432
January16th to endNight
27%
768
25%
2496
12%
768
44%
768
24%
1527
February1st to 15thNight
34%
704
27%
2137
13%
701
49%
701
27%
1294
February16th to endNight
29%
631
26%
1893
11%
631
44%
631
30%
1139
March1st to 15thNight
37%
720
24%
2016
14%
720
46%
720
30%
1265
March16th to endNight
39%
768
20%
2112
11%
768
46%
768
29%
1358
April1st to 15thNight
44%
715
25%
1973
15%
715
52%
715
35%
1170
April16th to endNight
49%
540
24%
1641
16%
540
56%
540
30%
1005
May1st to 15thNight
49%
540
19%
1620
11%
540
55%
540
27%
1028
May16th to endNight
61%
561
19%
1683
14%
561
64%
561
29%
1053
June1st to 15thNight
68%
540
15%
1620
13%
540
70%
540
29%
1054
June16th to endNight
73%
540
15%
1620
14%
540
73%
540
31%
1021
July1st to 15thNight
65%
510
9%
1530
8%
510
65%
510
23%
1077
July16th to endNight
72%
564
14%
1595
13%
531
74%
531
27%
1049
August1st to 15thNight
67%
539
15%
1609
14%
536
68%
536
23%
1114
August16th to endNight
65%
603
16%
1869
16%
603
65%
603
21%
1295
September1st to 15thNight
65%
707
17%
1944
14%
707
67%
707
27%
1301
September16th to endNight
55%
657
20%
1815
15%
657
59%
657
28%
1209
October1st to 15thNight
54%
660
31%
1873
26%
660
60%
660
35%
1128
October16th to endNight
57%
704
34%
2112
27%
704
68%
704
40%
1155
November1st to 15thNight
54%
700
31%
2205
26%
700
63%
700
38%
1199
November16th to endNight
43%
720
27%
2340
20%
720
55%
720
30%
1363
December1st to 15thNight
42%
720
24%
2340
17%
720
52%
720
25%
1459
December16th to endNight
34%
768
23%
2496
15%
768
45%
768
21%
1656

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%4244345%5%8%43%
47788
Night
13%42442445%7%44%
47066
TransparencyDay
37%6%12%20%17%4
47489
Night
37%6%10%19%19%6%
46869
SeeingDay
15%5%17%24%22%15%
5460
Night
15%5%22%31%21%3
15601

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
17%5%245%23435%45%
1611
16th to endDay
16%5%24323335%48%
1728
February1st to 15thDay
14%41442445%5%47%
1720
16th to endDay
16%6%24412346%47%
1580
March1st to 15thDay
16%413423346%48%
1944
16th to endDay
17%424424446%44%
2111
April1st to 15thDay
11%41343445%7%48%
1984
16th to endDay
10%4244245%5%7%49%
2319
May1st to 15thDay
10%425%435%45%8%44%
2331
16th to endDay
10%413435%6%6%10%42%
2431
June1st to 15thDay
8%3245%46%6%7%12%37%
2340
16th to endDay
42145%47%7%8%12%41%
2340
July1st to 15thDay
8%5%35%6%46%6%7%12%32%
2340
16th to endDay
6%325%5%47%7%9%11%36%
2465
August1st to 15thDay
8%5%26%6%46%7%8%10%33%
2340
16th to endDay
12%5%27%6%46%6%6%10%31%
2316
September1st to 15thDay
10%4146%36%6%6%8%40%
1936
16th to endDay
18%41432345%7%42%
1815
October1st to 15thDay
15%5%13212135%56%
1757
16th to endDay
10%41431223461%
1760
November1st to 15thDay
13%422222446%55%
1652
16th to endDay
15%414413346%49%
1620
December1st to 15thDay
18%5%25%413446%42%
1620
16th to endDay
24%6%2442224440%
1728
January1st to 15thNight
17%5%2432433447%
2327
16th to endNight
17%6%34413345%46%
2496
February1st to 15thNight
14%5%14424335%50%
2130
16th to endNight
15%414324346%49%
1893
March1st to 15thNight
14%5%24423445%48%
2016
16th to endNight
14%425%42345%6%46%
2112
April1st to 15thNight
13%313424346%52%
1973
16th to endNight
10%5%245%25%446%48%
1641
May1st to 15thNight
11%5%25%6%3446%8%41%
1619
16th to endNight
8%4235%35%7%6%9%42%
1682
June1st to 15thNight
9%4246%36%5%8%12%36%
1620
16th to endNight
6%3245%35%7%8%12%40%
1620
July1st to 15thNight
8%5%26%6%47%7%9%12%29%
1620
16th to endNight
6%325%6%46%7%9%12%34%
1703
August1st to 15thNight
9%5%35%6%35%7%8%12%30%
1620
16th to endNight
10%5%26%7%45%7%7%9%32%
1869
September1st to 15thNight
11%4145%447%7%9%37%
1944
16th to endNight
15%5%3442345%6%42%
1815
October1st to 15thNight
14%423313345%52%
1873
16th to endNight
10%312323335%59%
2112
November1st to 15thNight
11%423323235%58%
2205
16th to endNight
16%423322345%50%
2340
December1st to 15thNight
15%6%24423345%45%
2340
16th to endNight
20%6%25%434345%39%
2496

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
41%38%17%24%4
1612
16th to endDay
38%37%20%22%8%
1728
February1st to 15thDay
37%39%20%23%5%
1722
16th to endDay
39%36%22%20%6%
1580
March1st to 15thDay
36%47%21%20%8%
1944
16th to endDay
40%5%11%22%17%3
2112
April1st to 15thDay
34%5%10%20%22%5%
1984
16th to endDay
33%6%9%22%21%6%
2319
May1st to 15thDay
36%6%14%20%18%3
2331
16th to endDay
35%8%16%24%14%1
2435
June1st to 15thDay
36%9%21%22%8%1
2340
16th to endDay
31%10%18%22%13%3
2340
July1st to 15thDay
39%11%18%20%7%2
2201
16th to endDay
35%13%19%19%9%2
2310
August1st to 15thDay
42%11%15%19%9%1
2327
16th to endDay
45%12%15%14%10%1
2316
September1st to 15thDay
38%10%12%17%17%3
1936
16th to endDay
40%6%11%19%17%5%
1815
October1st to 15thDay
31%39%20%26%7%
1757
16th to endDay
28%35%20%31%11%
1760
November1st to 15thDay
30%37%17%29%11%
1652
16th to endDay
37%36%20%25%6%
1620
December1st to 15thDay
42%48%19%17%7%
1620
16th to endDay
48%36%19%15%6%
1728
January1st to 15thNight
40%37%15%25%7%
2327
16th to endNight
40%35%18%23%8%
2496
February1st to 15thNight
37%35%20%24%8%
2139
16th to endNight
36%37%22%22%7%
1893
March1st to 15thNight
36%49%17%22%8%
2016
16th to endNight
37%5%10%18%21%5%
2112
April1st to 15thNight
32%38%23%23%7%
1973
16th to endNight
35%6%8%21%19%8%
1641
May1st to 15thNight
38%6%12%20%18%2
1620
16th to endNight
35%8%14%26%12%2
1684
June1st to 15thNight
36%9%19%23%9%1
1620
16th to endNight
32%11%17%21%13%3
1620
July1st to 15thNight
40%13%20%16%6%1
1530
16th to endNight
34%13%22%18%8%2
1595
August1st to 15thNight
41%11%16%20%9%1
1609
16th to endNight
42%11%17%15%11%1
1869
September1st to 15thNight
37%11%16%18%13%3
1944
16th to endNight
40%6%12%17%16%6%
1815
October1st to 15thNight
34%49%18%25%8%
1873
16th to endNight
28%36%19%29%13%
2112
November1st to 15thNight
30%25%17%31%12%
2205
16th to endNight
35%36%17%27%10%
2340
December1st to 15thNight
40%47%19%19%8%
2340
16th to endNight
47%48%14%18%6%
2496

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%6%32%31%5%
90
16th to endDay
15%28%33%19%3
96
February1st to 15thDay
12%15%54%17%
90
16th to endDay
22%11%35%25%4
81
March1st to 15thDay
15%12%27%33%10%
234
16th to endDay
19%7%31%23%17%1
288
April1st to 15thDay
15%10%21%24%23%3
270
16th to endDay
12%222%30%20%10%
270
May1st to 15thDay
10%8%28%22%16%13%
288
16th to endDay
15%413%20%23%22%
331
June1st to 15thDay
11%28%24%26%26%
315
16th to endDay
9%10%24%24%30%
315
July1st to 15thDay
10%9%22%29%26%
305
16th to endDay
6%1420%38%27%
326
August1st to 15thDay
17%6%20%30%23%
313
16th to endDay
13%8%23%28%25%
332
September1st to 15thDay
14%19%20%30%24%
299
16th to endDay
24%112%25%24%12%
254
October1st to 15thDay
20%316%31%20%7%
255
16th to endDay
11%5%16%29%30%6%
272
November1st to 15thDay
24%6%20%23%18%8%
160
16th to endDay
12%6%17%40%20%3
90
December1st to 15thDay
25%7%27%30%7%1
90
16th to endDay
34%18%23%13%9%
96
January1st to 15thNight
20%10%30%29%8%
720
16th to endNight
20%11%35%29%2
768
February1st to 15thNight
16%11%32%35%3
704
16th to endNight
16%10%40%28%4
631
March1st to 15thNight
17%9%32%33%7%
720
16th to endNight
15%8%30%29%15%
768
April1st to 15thNight
13%10%28%32%15%
715
16th to endNight
13%425%33%21%1
540
May1st to 15thNight
13%323%37%19%2
540
16th to endNight
11%115%31%34%5%
563
June1st to 15thNight
11%11%30%34%10%
540
16th to endNight
7%10%30%37%12%
540
July1st to 15thNight
10%17%29%41%9%
510
16th to endNight
7%7%26%46%11%
564
August1st to 15thNight
12%15%27%43%9%
539
16th to endNight
14%7%26%42%8%
603
September1st to 15thNight
14%9%25%40%9%
707
16th to endNight
19%114%32%27%3
657
October1st to 15thNight
15%420%28%25%5%
660
16th to endNight
11%322%34%24%2
704
November1st to 15thNight
13%324%34%21%3
700
16th to endNight
17%7%26%31%15%1
720
December1st to 15thNight
19%7%23%36%12%
720
16th to endNight
23%7%29%31%8%
768
Page generated at 2017-09-13 07:39:14. Version ac04

Copyright 2017 A. Danko


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