This page made possible by the sponsorship of: Richard Williams.

Astor
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Astor clear sky chart from 2005-11-06 to 2024-03-01.

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
55%
24698
19%
79927
15%
24593
60%
24593
25%
50783

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
38%
755
21%
4017
13%
737
51%
737
16%
2346
January11th to 20thNight
45%
756
20%
4055
19%
740
57%
740
15%
2640
January21st to endNight
31%
830
15%
4405
11%
814
46%
814
14%
2606
February1st to 10thNight
40%
760
22%
2280
13%
760
50%
760
27%
1434
February11th to 20thNight
41%
740
21%
2218
12%
739
51%
739
30%
1332
February21st to endNight
41%
628
26%
1780
15%
628
51%
628
35%
1059
March1st to 10thNight
46%
723
30%
1987
18%
723
56%
723
42%
1101
March11th to 20thNight
46%
720
25%
1980
16%
720
54%
720
34%
1197
March21st to endNight
45%
792
26%
2178
16%
792
54%
792
36%
1290
April1st to 10thNight
47%
720
23%
1980
15%
720
54%
720
37%
1164
April11th to 20thNight
45%
711
22%
1901
15%
711
51%
711
34%
1167
April21st to endNight
55%
720
28%
1800
16%
720
61%
720
44%
1073
May1st to 10thNight
64%
582
27%
1662
18%
582
70%
582
45%
898
May11th to 20thNight
69%
531
17%
1592
12%
531
71%
531
33%
966
May21st to endNight
74%
582
20%
1744
17%
582
74%
582
31%
1110
June1st to 10thNight
65%
540
13%
1620
9%
540
65%
540
23%
1127
June11th to 20thNight
71%
540
12%
1620
10%
540
72%
540
23%
1119
June21st to endNight
71%
540
9%
1620
7%
540
71%
540
22%
1150
July1st to 10thNight
69%
525
7%
1575
6%
525
69%
525
20%
1160
July11th to 20thNight
74%
522
7%
1566
6%
522
74%
522
19%
1150
July21st to endNight
73%
591
10%
1672
10%
558
75%
558
21%
1192
August1st to 10thNight
76%
537
7%
1600
7%
534
76%
534
22%
1134
August11th to 20thNight
75%
556
9%
1630
9%
556
75%
556
23%
1150
August21st to endNight
61%
792
10%
2178
9%
792
61%
792
18%
1640
September1st to 10thNight
65%
720
9%
1980
8%
720
66%
720
18%
1474
September11th to 20thNight
58%
720
7%
1980
7%
720
59%
720
17%
1497
September21st to endNight
62%
720
16%
1980
16%
720
63%
720
23%
1394
October1st to 10thNight
56%
720
20%
2011
18%
720
59%
720
25%
1355
October11th to 20thNight
66%
720
29%
2160
29%
720
71%
720
37%
1217
October21st to endNight
59%
792
26%
2376
24%
792
65%
792
32%
1403
November1st to 10thNight
53%
740
24%
2221
20%
740
60%
740
31%
1354
November11th to 20thNight
49%
760
25%
2280
20%
760
57%
760
29%
1411
November21st to endNight
46%
760
23%
2398
18%
760
55%
760
27%
1490
December1st to 10thNight
49%
760
27%
2470
20%
760
60%
760
30%
1438
December11th to 20thNight
46%
759
24%
2947
20%
758
54%
758
22%
1754
December21st to endNight
47%
834
14%
4464
19%
817
55%
817
15%
2791

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
10%6%36%7%46%6%6%8%37%
78872
Night
10%6%25%5%35%5%6%9%43%
80540
TransparencyDay
41%10%14%16%13%5%
78595
Night
36%10%15%19%14%6%
80336
SeeingDay
9%7%21%25%22%15%
14553
Night
10%5%21%32%25%6%
24721

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
13%7%25%6%3445%7%43%
2836
11th to 20thDay
22%9%37%5%34446%34%
2840
21st to endDay
12%5%26%5%35%5%5%7%45%
3164
February1st to 10thDay
13%7%35%6%35%6%6%7%41%
1900
11th to 20thDay
10%425%5%34346%53%
1848
21st to endDay
10%5%345%45%5%5%7%46%
1671
March1st to 10thDay
7%325%4345%49%54%
1980
11th to 20thDay
9%4245%45%6%6%7%48%
1980
21st to endDay
10%425%6%45%5%6%6%49%
2178
April1st to 10thDay
8%325%6%45%5%5%10%47%
1980
11th to 20thDay
9%5%36%7%5%6%7%6%8%39%
2007
21st to endDay
6%3246%345%7%9%51%
2160
May1st to 10thDay
6%424435%5%6%8%53%
2311
11th to 20thDay
8%5%26%7%46%6%7%9%40%
2301
21st to endDay
7%5%37%6%5%7%7%8%9%35%
2531
June1st to 10thDay
11%6%38%9%6%7%7%7%10%24%
2340
11th to 20thDay
6%5%37%10%7%9%9%9%9%28%
2340
21st to endDay
9%6%39%9%6%8%8%7%9%27%
2340
July1st to 10thDay
10%7%38%9%5%9%8%8%9%23%
2340
11th to 20thDay
7%7%410%10%6%9%8%9%9%22%
2340
21st to endDay
7%6%38%10%7%8%9%9%10%22%
2547
August1st to 10thDay
7%6%410%10%5%8%8%9%10%24%
2327
11th to 20thDay
7%6%38%9%7%7%9%9%12%23%
2245
21st to endDay
11%8%49%9%6%9%7%8%11%20%
2178
September1st to 10thDay
8%5%38%10%6%9%9%8%10%23%
1980
11th to 20thDay
10%8%310%9%6%7%8%8%10%22%
1980
21st to endDay
12%6%37%8%6%7%6%7%8%30%
1980
October1st to 10thDay
11%7%38%8%37%6%6%8%33%
1947
11th to 20thDay
7%5%25%7%36%5%6%9%46%
1800
21st to endDay
9%426%5%35%6%6%8%46%
1980
November1st to 10thDay
9%5%26%6%35%5%5%8%45%
1857
11th to 20thDay
11%6%36%6%46%5%5%7%41%
1900
21st to endDay
12%6%35%6%445%5%8%43%
1777
December1st to 10thDay
8%426%6%35%47%10%44%
1710
11th to 20thDay
14%7%26%6%36%5%5%6%40%
2153
21st to endDay
14%7%36%6%345%46%41%
3124
January1st to 10thNight
14%7%35%5%345%5%7%42%
4109
11th to 20thNight
18%10%45%5%3445%8%35%
4120
21st to endNight
14%6%26%5%35%5%6%7%41%
4489
February1st to 10thNight
13%6%25%5%3445%7%45%
2280
11th to 20thNight
10%5%25%5%3446%7%49%
2218
21st to endNight
8%6%245%3346%7%53%
1780
March1st to 10thNight
6%42442345%8%59%
1987
11th to 20thNight
9%4144445%6%9%50%
1980
21st to endNight
8%435%425%45%6%55%
2178
April1st to 10thNight
8%4134345%7%8%53%
1980
11th to 20thNight
9%435%5%3437%8%50%
1901
21st to endNight
7%3135%3446%9%55%
1800
May1st to 10thNight
5%2143245%5%9%61%
1662
11th to 20thNight
6%5%245%345%7%10%49%
1592
21st to endNight
6%4245%36%6%8%9%46%
1744
June1st to 10thNight
11%5%26%6%47%6%7%11%35%
1620
11th to 20thNight
5%5%36%7%47%8%9%12%34%
1620
21st to endNight
6%6%37%7%47%8%8%11%33%
1620
July1st to 10thNight
7%7%36%6%5%8%5%8%11%34%
1620
11th to 20thNight
5%5%37%8%5%8%8%8%9%33%
1620
21st to endNight
5%5%37%7%48%7%8%12%34%
1771
August1st to 10thNight
5%5%27%7%46%6%8%13%35%
1611
11th to 20thNight
6%5%36%6%47%7%8%12%35%
1630
21st to endNight
10%7%37%7%45%6%8%11%31%
2178
September1st to 10thNight
9%5%36%7%46%7%9%13%31%
1980
11th to 20thNight
11%6%37%8%5%6%7%8%11%28%
1980
21st to endNight
11%7%26%5%46%7%7%9%35%
1980
October1st to 10thNight
10%7%35%6%36%5%7%9%40%
2011
11th to 20thNight
5%4246%345%6%9%52%
2160
21st to endNight
10%5%25%43445%7%51%
2376
November1st to 10thNight
11%425%43445%8%49%
2221
11th to 20thNight
11%6%25%5%445%5%8%44%
2280
21st to endNight
11%6%35%5%45%5%7%8%43%
2398
December1st to 10thNight
8%436%6%3445%9%48%
2470
11th to 20thNight
14%6%25%5%34335%49%
3042
21st to endNight
16%8%36%5%35%5%5%7%38%
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
40%6%9%15%21%10%
2837
11th to 20thDay
51%5%6%14%15%9%
2840
21st to endDay
37%8%9%17%18%11%
3164
February1st to 10thDay
41%8%9%14%20%9%
1900
11th to 20thDay
33%5%10%19%22%12%
1858
21st to endDay
37%6%11%16%22%9%
1671
March1st to 10thDay
28%6%11%22%23%9%
1980
11th to 20thDay
34%8%13%21%15%9%
1980
21st to endDay
33%7%13%19%19%9%
2178
April1st to 10thDay
32%7%14%20%18%9%
1980
11th to 20thDay
39%10%10%18%17%5%
2007
21st to endDay
27%8%12%24%21%8%
2160
May1st to 10thDay
28%7%11%22%23%9%
2311
11th to 20thDay
37%10%18%19%13%3
2305
21st to endDay
40%12%14%18%14%2
2531
June1st to 10thDay
51%13%17%14%5%
2340
11th to 20thDay
46%16%18%17%2
2340
21st to endDay
48%14%21%13%4
2340
July1st to 10thDay
50%17%20%11%2
2275
11th to 20thDay
53%15%21%10%
2271
21st to endDay
49%17%21%13%1
2405
August1st to 10thDay
47%18%24%10%1
2314
11th to 20thDay
46%20%23%10%1
2245
21st to endDay
54%15%19%11%2
2178
September1st to 10thDay
50%20%16%10%41
1980
11th to 20thDay
52%15%18%11%3
1980
21st to endDay
47%12%14%14%10%3
1980
October1st to 10thDay
46%10%10%14%12%9%
1947
11th to 20thDay
34%7%10%22%21%6%
1800
21st to endDay
34%8%10%17%22%10%
1980
November1st to 10thDay
35%8%13%17%18%10%
1857
11th to 20thDay
41%7%9%16%20%7%
1900
21st to endDay
39%7%9%21%19%5%
1777
December1st to 10thDay
33%8%15%22%16%5%
1710
11th to 20thDay
41%8%10%14%18%10%
2150
21st to endDay
43%7%9%19%15%7%
3124
January1st to 10thNight
40%7%9%15%20%9%
4109
11th to 20thNight
47%7%8%19%15%5%
4120
21st to endNight
38%10%11%14%16%10%
4489
February1st to 10thNight
38%6%11%16%17%12%
2280
11th to 20thNight
32%7%13%18%19%11%
2219
21st to endNight
31%6%14%19%21%9%
1780
March1st to 10thNight
23%7%13%26%22%9%
1987
11th to 20thNight
31%8%15%24%15%8%
1980
21st to endNight
29%7%12%25%18%9%
2178
April1st to 10thNight
27%8%17%23%15%9%
1980
11th to 20thNight
32%7%12%25%19%6%
1901
21st to endNight
25%7%14%27%21%7%
1800
May1st to 10thNight
21%8%15%25%24%7%
1662
11th to 20thNight
28%12%22%23%13%2
1593
21st to endNight
32%12%16%21%18%2
1745
June1st to 10thNight
40%13%21%21%5%
1620
11th to 20thNight
37%16%23%21%3
1620
21st to endNight
40%15%23%15%6%1
1620
July1st to 10thNight
43%15%26%13%3
1575
11th to 20thNight
41%18%27%12%2
1566
21st to endNight
38%18%27%15%2
1672
August1st to 10thNight
37%18%33%12%1
1600
11th to 20thNight
35%19%30%14%2
1630
21st to endNight
44%17%21%15%2
2178
September1st to 10thNight
41%20%21%13%5%
1980
11th to 20thNight
45%17%20%13%5%
1980
21st to endNight
41%13%18%17%9%2
1980
October1st to 10thNight
38%12%14%17%11%8%
2011
11th to 20thNight
26%8%12%26%23%5%
2160
21st to endNight
31%8%12%17%22%11%
2376
November1st to 10thNight
34%7%13%18%18%10%
2221
11th to 20thNight
36%7%11%17%19%9%
2280
21st to endNight
36%8%12%20%18%6%
2398
December1st to 10thNight
32%7%16%27%13%6%
2470
11th to 20thNight
37%6%10%18%19%9%
3044
21st to endNight
43%8%13%17%14%5%
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
13%13%46%20%6%2
270
11th to 20thDay
9%14%42%22%9%4
270
21st to endDay
19%20%44%12%5%
297
February1st to 10thDay
16%16%36%20%10%2
270
11th to 20thDay
11%13%42%23%9%2
270
21st to endDay
8%15%34%26%16%1
326
March1st to 10thDay
6%14%36%30%13%1
420
11th to 20thDay
13%13%28%25%17%4
420
21st to endDay
10%11%29%30%18%3
462
April1st to 10thDay
10%13%30%30%15%3
420
11th to 20thDay
10%13%32%27%15%4
412
21st to endDay
8%7%29%28%17%11%
420
May1st to 10thDay
6%8%23%32%22%9%
423
11th to 20thDay
9%319%29%26%14%
447
21st to endDay
7%49%26%35%19%
485
June1st to 10thDay
12%413%25%28%19%
450
11th to 20thDay
6%311%23%30%26%
450
21st to endDay
6%36%20%33%31%
450
July1st to 10thDay
8%25%15%29%42%
445
11th to 20thDay
5%1416%32%42%
444
21st to endDay
8%26%21%30%33%
488
August1st to 10thDay
6%28%18%33%33%
446
11th to 20thDay
5%1416%34%41%
439
21st to endDay
11%16%19%31%32%
495
September1st to 10thDay
8%28%20%32%30%
450
11th to 20thDay
9%310%28%28%21%
450
21st to endDay
11%210%25%30%22%
450
October1st to 10thDay
13%7%24%30%19%7%
450
11th to 20thDay
6%7%17%33%29%8%
450
21st to endDay
9%5%25%34%23%4
495
November1st to 10thDay
11%8%24%30%23%4
455
11th to 20thDay
14%7%31%30%16%3
460
21st to endDay
13%8%33%32%10%2
337
December1st to 10thDay
7%13%37%24%16%2
270
11th to 20thDay
15%14%32%27%10%2
270
21st to endDay
10%10%32%36%10%2
297
January1st to 10thNight
13%12%33%30%11%
760
11th to 20thNight
12%10%29%34%15%1
760
21st to endNight
16%13%34%29%8%
836
February1st to 10thNight
15%8%33%31%12%1
760
11th to 20thNight
11%9%32%37%9%1
743
21st to endNight
11%8%35%38%8%
628
March1st to 10thNight
6%9%36%37%11%
723
11th to 20thNight
10%8%31%35%14%1
720
21st to endNight
9%8%33%38%12%1
792
April1st to 10thNight
9%8%33%36%15%
720
11th to 20thNight
10%8%33%31%16%1
711
21st to endNight
7%428%43%17%1
720
May1st to 10thNight
5%322%45%23%2
582
11th to 20thNight
8%213%42%31%3
531
21st to endNight
8%110%36%40%6%
584
June1st to 10thNight
12%38%33%38%7%
540
11th to 20thNight
6%37%24%41%19%
540
21st to endNight
6%35%24%45%18%
540
July1st to 10thNight
8%15%18%42%25%
525
11th to 20thNight
6%2215%48%27%
522
21st to endNight
5%15%20%48%21%
591
August1st to 10thNight
7%1221%49%20%
537
11th to 20thNight
6%1414%48%27%
556
21st to endNight
13%28%21%37%20%
792
September1st to 10thNight
9%37%24%39%18%
720
11th to 20thNight
13%29%29%36%11%
720
21st to endNight
13%28%28%38%11%
720
October1st to 10thNight
11%417%36%27%5%
720
11th to 20thNight
5%416%37%34%4
720
21st to endNight
12%5%16%37%27%3
792
November1st to 10thNight
13%423%36%23%2
740
11th to 20thNight
11%7%24%37%19%2
760
21st to endNight
11%6%30%37%16%1
760
December1st to 10thNight
9%7%26%34%22%1
760
11th to 20thNight
13%7%27%35%17%1
760
21st to endNight
14%8%25%36%17%
836
Page generated at 2024-02-27 06:30:16. Version ac07

Copyright © 2024 Attilla Danko.


Astor Clear Sky Chart |Charts Home