Joyce Observatory 2
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Joyce Observatory 2 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
63%
24553
13%
74511
11%
24504
65%
24504
16%
56069

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
52%
757
14%
2459
11%
757
58%
757
16%
1794
January11th to 20thNight
54%
727
15%
2360
13%
727
58%
727
14%
1761
January21st to endNight
44%
792
15%
2410
10%
792
49%
792
16%
1809
February1st to 10thNight
49%
720
16%
2160
11%
720
53%
720
16%
1607
February11th to 20thNight
58%
700
15%
2099
10%
700
64%
700
17%
1546
February21st to endNight
61%
592
23%
1684
18%
592
66%
592
22%
1175
March1st to 10thNight
55%
720
22%
1980
13%
720
62%
720
27%
1325
March11th to 20thNight
59%
720
20%
1980
13%
720
64%
720
23%
1383
March21st to endNight
61%
792
22%
2178
17%
792
65%
792
25%
1511
April1st to 10thNight
63%
720
16%
1980
13%
720
66%
720
22%
1400
April11th to 20thNight
58%
711
15%
1953
11%
711
62%
711
21%
1406
April21st to endNight
62%
720
19%
1832
11%
720
66%
720
23%
1337
May1st to 10thNight
75%
617
22%
1697
17%
617
77%
617
27%
1136
May11th to 20thNight
72%
531
13%
1592
10%
531
74%
531
19%
1160
May21st to endNight
74%
582
13%
1745
11%
582
74%
582
18%
1296
June1st to 10thNight
69%
540
10%
1620
9%
540
70%
540
14%
1288
June11th to 20thNight
76%
540
7%
1620
6%
540
76%
540
15%
1233
June21st to endNight
76%
540
7%
1620
6%
540
76%
540
11%
1336
July1st to 10thNight
73%
525
4%
1575
4%
525
73%
525
11%
1317
July11th to 20thNight
75%
522
3%
1566
3%
522
75%
522
10%
1326
July21st to endNight
79%
591
5%
1672
5%
558
79%
558
12%
1387
August1st to 10thNight
73%
537
3%
1609
3%
534
74%
534
13%
1314
August11th to 20thNight
75%
565
3%
1807
4%
565
75%
565
12%
1459
August21st to endNight
61%
792
4%
2178
4%
792
61%
792
8%
1882
September1st to 10thNight
69%
720
3%
1980
3%
720
69%
720
11%
1625
September11th to 20thNight
65%
720
5%
1980
4%
720
65%
720
10%
1656
September21st to endNight
61%
720
6%
1980
6%
720
61%
720
11%
1656
October1st to 10thNight
65%
720
13%
1980
12%
720
66%
720
16%
1529
October11th to 20thNight
64%
720
15%
2129
14%
720
67%
720
14%
1653
October21st to endNight
61%
792
16%
2376
15%
792
64%
792
17%
1749
November1st to 10thNight
60%
740
18%
2221
15%
740
65%
740
16%
1663
November11th to 20thNight
57%
760
19%
2280
16%
760
62%
760
18%
1674
November21st to endNight
58%
760
16%
2344
14%
760
62%
760
17%
1711
December1st to 10thNight
60%
760
17%
2470
16%
760
64%
760
16%
1793
December11th to 20thNight
58%
759
16%
2932
13%
758
60%
758
12%
2077
December21st to endNight
56%
829
10%
4463
16%
817
61%
817
10%
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
6%425%6%46%6%7%10%42%
74817
Night
7%5%25%6%45%6%7%10%44%
74897
TransparencyDay
23%39%12%13%9%3
74540
Night
24%39%11%14%10%3
74693
SeeingDay
7%315%26%27%22%
14449
Night
8%315%34%29%10%
24569

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
8%5%35%5%445%6%9%47%
1706
11th to 20thDay
7%5%244346%6%10%50%
1629
21st to endDay
9%435%6%445%5%8%47%
1943
February1st to 10thDay
9%435%43447%8%49%
1800
11th to 20thDay
5%2234235%6%8%59%
1748
21st to endDay
6%3134245%6%10%55%
1570
March1st to 10thDay
321343345%8%63%
1980
11th to 20thDay
5%31443446%10%56%
1980
21st to endDay
441443446%8%58%
2178
April1st to 10thDay
5%21442447%10%56%
1980
11th to 20thDay
6%324435%5%8%12%48%
1956
21st to endDay
4313435%5%7%9%55%
2126
May1st to 10thDay
32123235%6%10%64%
2276
11th to 20thDay
7%425%5%45%6%8%11%42%
2301
21st to endDay
6%435%6%5%8%7%7%9%40%
2531
June1st to 10thDay
10%8%47%7%47%7%7%11%29%
2340
11th to 20thDay
6%435%7%5%7%9%9%13%32%
2340
21st to endDay
6%6%37%8%5%8%8%9%12%28%
2340
July1st to 10thDay
6%5%37%8%6%8%8%10%12%27%
2340
11th to 20thDay
5%427%7%6%10%10%9%12%26%
2340
21st to endDay
6%6%37%8%5%9%10%10%12%24%
2547
August1st to 10thDay
5%436%8%6%9%9%9%12%29%
2311
11th to 20thDay
5%5%29%8%5%9%9%9%13%27%
2074
21st to endDay
8%5%27%8%6%8%9%10%11%24%
2178
September1st to 10thDay
6%437%8%5%9%9%10%13%27%
1980
11th to 20thDay
9%6%26%8%5%8%8%9%10%27%
1980
21st to endDay
6%5%37%9%5%7%8%9%10%31%
1980
October1st to 10thDay
6%5%27%8%5%7%6%6%9%39%
1980
11th to 20thDay
6%5%246%46%5%6%10%46%
1828
21st to endDay
8%5%245%36%46%8%49%
1980
November1st to 10thDay
7%423425%5%6%8%54%
1857
11th to 20thDay
7%5%35%5%35%5%6%9%47%
1900
21st to endDay
6%5%245%35%5%6%9%49%
1831
December1st to 10thDay
5%425%5%35%6%7%9%51%
1710
11th to 20thDay
9%5%245%345%6%9%49%
2153
21st to endDay
10%6%36%8%5%6%7%7%8%34%
3124
January1st to 10thNight
7%4245%36%5%6%10%46%
2459
11th to 20thNight
8%5%25%436%5%6%9%46%
2360
21st to endNight
10%5%26%5%35%6%7%8%43%
2410
February1st to 10thNight
9%5%25%6%35%46%8%47%
2160
11th to 20thNight
7%42433445%8%54%
2098
21st to endNight
6%423445%46%9%53%
1684
March1st to 10thNight
331332335%10%62%
1980
11th to 20thNight
6%3245%345%6%9%54%
1980
21st to endNight
3215%4345%5%8%60%
2178
April1st to 10thNight
42244345%6%9%56%
1980
11th to 20thNight
5%4245%45%5%6%9%51%
1953
21st to endNight
5%3245%46%45%8%54%
1832
May1st to 10thNight
22133245%5%9%63%
1697
11th to 20thNight
6%426%5%35%6%7%9%46%
1592
21st to endNight
5%435%5%35%6%6%9%48%
1744
June1st to 10thNight
10%5%36%8%46%5%8%10%35%
1620
11th to 20thNight
5%5%26%7%5%6%7%7%12%38%
1620
21st to endNight
5%437%7%5%7%9%9%14%30%
1620
July1st to 10thNight
6%6%37%8%47%7%9%12%30%
1620
11th to 20thNight
5%6%37%7%5%7%8%10%15%27%
1620
21st to endNight
4436%7%5%10%9%10%14%29%
1771
August1st to 10thNight
6%6%36%7%46%8%9%14%31%
1620
11th to 20thNight
5%426%9%47%8%9%13%32%
1807
21st to endNight
9%7%38%8%6%7%7%8%10%27%
2178
September1st to 10thNight
5%5%37%8%5%8%7%10%13%29%
1980
11th to 20thNight
10%6%37%7%5%6%7%8%10%31%
1980
21st to endNight
9%7%38%8%6%7%6%8%9%29%
1980
October1st to 10thNight
7%6%27%5%35%7%8%9%41%
1980
11th to 20thNight
7%6%25%5%36%5%6%9%46%
2129
21st to endNight
9%4246%3447%9%47%
2376
November1st to 10thNight
7%5%245%35%5%6%8%50%
2221
11th to 20thNight
7%5%25%6%46%5%5%8%48%
2280
21st to endNight
7%5%25%5%345%7%10%48%
2344
December1st to 10thNight
6%425%6%35%5%6%9%49%
2470
11th to 20thNight
9%5%3443446%8%50%
3042
21st to endNight
10%7%36%7%46%6%7%10%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
21%40%7%16%12%4
1707
11th to 20thDay
19%41%7%16%11%5%
1629
21st to endDay
22%38%7%16%10%6%
1943
February1st to 10thDay
23%37%6%13%15%7%
1800
11th to 20thDay
15%39%10%17%12%6%
1758
21st to endDay
15%37%9%14%20%5%
1570
March1st to 10thDay
12%36%8%18%19%6%
1980
11th to 20thDay
15%37%8%20%14%5%
1980
21st to endDay
15%36%10%20%15%4
2178
April1st to 10thDay
15%37%14%20%10%4
1980
11th to 20thDay
18%37%12%19%12%3
1956
21st to endDay
15%38%11%16%16%4
2126
May1st to 10thDay
8%36%12%25%18%2
2276
11th to 20thDay
19%40%14%16%11%
2305
21st to endDay
25%40%12%16%7%1
2531
June1st to 10thDay
30%39%17%10%3
2340
11th to 20thDay
24%40%20%14%2
2340
21st to endDay
33%42%15%8%2
2340
July1st to 10thDay
33%44%16%6%1
2275
11th to 20thDay
31%44%19%5%
2271
21st to endDay
30%45%17%8%
2405
August1st to 10thDay
28%44%21%6%1
2298
11th to 20thDay
32%42%19%7%
2074
21st to endDay
34%44%15%5%2
2178
September1st to 10thDay
28%45%20%7%1
1980
11th to 20thDay
32%44%14%9%2
1980
21st to endDay
30%42%12%11%41
1980
October1st to 10thDay
24%39%11%12%9%5%
1980
11th to 20thDay
24%38%9%16%10%4
1828
21st to endDay
21%39%7%14%15%5%
1980
November1st to 10thDay
18%41%5%13%13%11%
1857
11th to 20thDay
19%39%8%17%13%5%
1900
21st to endDay
19%40%9%15%13%4
1831
December1st to 10thDay
18%41%10%16%11%4
1710
11th to 20thDay
24%33%8%15%12%8%
2150
21st to endDay
37%27%8%12%13%3
3124
January1st to 10thNight
19%42%8%16%11%4
2459
11th to 20thNight
21%42%7%15%10%4
2360
21st to endNight
23%39%9%14%10%5%
2410
February1st to 10thNight
25%36%7%11%14%7%
2160
11th to 20thNight
22%39%7%17%11%5%
2099
21st to endNight
16%37%7%17%18%6%
1684
March1st to 10thNight
12%36%7%23%17%5%
1980
11th to 20thNight
16%37%10%20%14%4
1980
21st to endNight
15%37%8%21%16%3
2178
April1st to 10thNight
17%37%12%19%11%4
1980
11th to 20thNight
20%36%11%17%13%3
1953
21st to endNight
19%37%8%18%16%3
1832
May1st to 10thNight
11%37%8%25%16%3
1697
11th to 20thNight
20%39%14%18%10%
1593
21st to endNight
21%39%12%18%10%
1745
June1st to 10thNight
29%40%12%15%4
1620
11th to 20thNight
24%40%20%13%3
1620
21st to endNight
30%43%14%9%4
1620
July1st to 10thNight
31%43%19%6%1
1575
11th to 20thNight
31%45%18%5%1
1566
21st to endNight
26%47%18%9%
1672
August1st to 10thNight
28%43%21%7%1
1609
11th to 20thNight
29%42%23%6%
1807
21st to endNight
35%44%13%7%1
2178
September1st to 10thNight
28%45%19%7%1
1980
11th to 20thNight
31%44%14%10%1
1980
21st to endNight
33%42%14%7%5%
1980
October1st to 10thNight
25%40%11%10%10%5%
1980
11th to 20thNight
26%39%9%12%10%3
2129
21st to endNight
22%39%7%14%14%4
2376
November1st to 10thNight
21%41%411%14%8%
2221
11th to 20thNight
20%40%7%16%13%5%
2280
21st to endNight
20%40%8%15%13%3
2344
December1st to 10thNight
20%40%8%16%12%4
2470
11th to 20thNight
25%35%6%16%11%8%
3044
21st to endNight
34%27%11%11%13%4
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
9%7%39%29%14%1
270
11th to 20thDay
7%8%32%35%13%5%
243
21st to endDay
14%8%44%28%6%1
264
February1st to 10thDay
6%8%32%32%19%5%
240
11th to 20thDay
45%28%40%18%5%
240
21st to endDay
5%425%39%24%3
288
March1st to 10thDay
35%35%36%19%2
420
11th to 20thDay
6%5%25%34%25%4
420
21st to endDay
45%26%36%25%5%
462
April1st to 10thDay
6%429%33%23%5%
420
11th to 20thDay
8%6%23%36%22%5%
412
21st to endDay
7%317%34%32%6%
420
May1st to 10thDay
4214%37%27%16%
423
11th to 20thDay
10%312%30%25%19%
447
21st to endDay
8%27%21%34%29%
485
June1st to 10thDay
13%47%18%30%29%
450
11th to 20thDay
7%2418%30%39%
450
21st to endDay
5%2212%29%50%
450
July1st to 10thDay
5%119%24%59%
445
11th to 20thDay
4218%32%52%
444
21st to endDay
9%2114%25%49%
488
August1st to 10thDay
7%1111%31%48%
446
11th to 20thDay
4219%32%53%
439
21st to endDay
9%2416%32%38%
495
September1st to 10thDay
7%2411%34%42%
450
11th to 20thDay
7%3416%32%37%
450
21st to endDay
7%1418%36%34%
450
October1st to 10thDay
9%38%34%34%12%
450
11th to 20thDay
7%212%33%34%12%
450
21st to endDay
10%313%34%29%12%
495
November1st to 10thDay
7%318%33%29%11%
455
11th to 20thDay
10%421%34%24%6%
460
21st to endDay
9%323%35%26%5%
391
December1st to 10thDay
7%6%29%32%17%9%
270
11th to 20thDay
10%429%30%20%6%
270
21st to endDay
9%425%36%23%4
297
January1st to 10thNight
9%6%24%41%18%1
760
11th to 20thNight
10%5%24%44%16%1
727
21st to endNight
13%6%28%38%14%
792
February1st to 10thNight
12%428%38%18%
720
11th to 20thNight
9%5%23%43%19%1
703
21st to endNight
8%419%49%20%
592
March1st to 10thNight
4432%44%15%
720
11th to 20thNight
7%323%47%19%1
720
21st to endNight
4325%48%19%1
792
April1st to 10thNight
6%322%47%21%1
720
11th to 20thNight
6%425%45%19%1
711
21st to endNight
6%223%45%23%1
720
May1st to 10thNight
3115%48%30%3
617
11th to 20thNight
7%19%45%33%4
531
21st to endNight
5%36%36%41%8%
584
June1st to 10thNight
12%1326%44%14%
540
11th to 20thNight
5%2412%52%25%
540
21st to endNight
5%1213%44%35%
540
July1st to 10thNight
7%225%43%41%
525
11th to 20thNight
5%316%44%42%
522
21st to endNight
4117%47%39%
591
August1st to 10thNight
7%215%50%34%
537
11th to 20thNight
7%217%41%43%
565
21st to endNight
12%3416%38%27%
792
September1st to 10thNight
7%2414%45%28%
720
11th to 20thNight
12%2318%42%23%
720
21st to endNight
12%35%24%38%18%
720
October1st to 10thNight
11%210%40%30%7%
720
11th to 20thNight
9%313%36%34%6%
720
21st to endNight
12%214%41%27%5%
792
November1st to 10thNight
9%321%41%25%2
740
11th to 20thNight
8%422%42%22%3
760
21st to endNight
9%319%43%24%1
760
December1st to 10thNight
6%421%41%26%2
760
11th to 20thNight
9%5%22%40%23%2
760
21st to endNight
9%422%40%24%1
836
Page generated at 2024-01-09 07:14:39. Version ac07

Copyright 2024 Attilla Danko


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