Evans Above Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Evans Above Observatory 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
42%
22721
12%
80568
11%
22636
46%
22636
16%
58059

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
27%
752
4%
4400
7%
736
30%
736
4%
3787
January11th to 20thNight
33%
754
9%
4397
9%
740
36%
740
5%
3566
January21st to endNight
33%
834
6%
4620
11%
814
36%
814
6%
3885
February1st to 10thNight
33%
760
7%
2470
6%
760
34%
760
9%
2039
February11th to 20thNight
31%
740
8%
2404
7%
740
34%
740
12%
1908
February21st to endNight
31%
628
10%
1965
9%
628
35%
628
11%
1580
March1st to 10thNight
35%
722
10%
2085
8%
722
37%
722
13%
1663
March11th to 20thNight
35%
720
11%
1980
8%
720
38%
720
15%
1561
March21st to endNight
31%
792
5%
2129
3%
792
32%
792
12%
1777
April1st to 10thNight
32%
720
7%
1800
3%
720
33%
720
15%
1465
April11th to 20thNight
37%
711
11%
1779
5%
711
39%
711
19%
1376
April21st to endNight
36%
541
10%
1621
6%
541
39%
541
16%
1199
May1st to 10thNight
38%
389
14%
1469
13%
389
44%
389
20%
918
May11th to 20thNight
48%
354
13%
1416
13%
354
54%
354
20%
895
May21st to endNight
43%
389
9%
1552
9%
388
50%
388
16%
1016
June1st to 10thNight
41%
360
9%
1440
10%
360
47%
360
17%
929
June11th to 20thNight
38%
360
9%
1440
9%
360
44%
360
19%
894
June21st to endNight
51%
360
18%
1307
19%
360
61%
360
36%
661
July1st to 10thNight
62%
350
17%
1400
20%
350
71%
350
40%
616
July11th to 20thNight
52%
348
24%
1392
22%
348
70%
348
46%
583
July21st to endNight
64%
394
31%
1488
32%
372
81%
372
67%
497
August1st to 10thNight
70%
494
25%
1560
19%
492
79%
492
57%
677
August11th to 20thNight
76%
534
30%
1602
22%
534
81%
534
58%
736
August21st to endNight
61%
717
31%
1905
16%
717
69%
717
51%
1016
September1st to 10thNight
61%
720
28%
1800
13%
720
66%
720
53%
998
September11th to 20thNight
59%
720
22%
1800
13%
720
62%
720
34%
1181
September21st to endNight
58%
720
21%
2060
17%
720
61%
720
34%
1238
October1st to 10thNight
52%
720
16%
2160
14%
720
55%
720
28%
1391
October11th to 20thNight
49%
720
19%
2160
19%
720
53%
720
24%
1446
October21st to endNight
40%
792
16%
2426
14%
792
45%
792
20%
1715
November1st to 10thNight
36%
740
11%
2508
11%
740
39%
740
12%
1996
November11th to 20thNight
32%
760
8%
2660
6%
760
35%
760
10%
2120
November21st to endNight
40%
760
7%
2660
6%
760
42%
760
12%
2019
December1st to 10thNight
36%
760
10%
2660
9%
760
38%
760
11%
2043
December11th to 20thNight
27%
759
7%
3211
6%
759
28%
759
6%
2611
December21st to endNight
24%
827
3%
4842
5%
817
26%
817
4%
4057

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
23%9%37%6%34446%32%
78507
Night
25%9%36%5%34445%32%
80876
TransparencyDay
54%5%12%17%10%2
78210
Night
55%5%12%17%9%2
80694
SeeingDay
23%5%20%27%18%6%
13714
Night
27%318%35%16%1
22751

By Month

Percentage Cloud Cover SW (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
43%14%38%7%445%337%
2539
11th to 20thDay
39%13%47%6%3333317%
2540
21st to endDay
38%13%5%8%6%3443413%
3027
February1st to 10thDay
34%11%47%6%3445%5%16%
1710
11th to 20thDay
33%12%5%8%7%4433417%
1665
21st to endDay
34%13%5%6%6%3334419%
1488
March1st to 10thDay
30%12%49%7%345%5%6%16%
1879
11th to 20thDay
33%11%49%6%34446%18%
1980
21st to endDay
31%12%49%8%45%45%5%13%
2227
April1st to 10thDay
29%12%5%9%7%35%35%6%16%
2160
11th to 20thDay
26%11%47%6%46%345%24%
2129
21st to endDay
22%9%48%7%46%6%5%7%24%
2335
May1st to 10thDay
16%8%47%7%35%5%46%35%
2489
11th to 20thDay
19%8%48%6%45%46%7%30%
2477
21st to endDay
24%8%37%5%46%5%6%7%26%
2723
June1st to 10thDay
23%7%37%6%45%45%6%30%
2520
11th to 20thDay
20%8%36%6%46%6%6%7%26%
2520
21st to endDay
9%5%36%5%35%447%50%
2608
July1st to 10thDay
7%5%24435%447%56%
2520
11th to 20thDay
7%424323446%60%
2520
21st to endDay
5%222322235%70%
2741
August1st to 10thDay
5%5%2442335%6%61%
2368
11th to 20thDay
6%31332235%6%65%
2298
21st to endDay
8%5%25%5%345%47%53%
2450
September1st to 10thDay
7%425%324446%60%
2160
11th to 20thDay
13%7%36%5%34447%43%
2160
21st to endDay
17%6%26%6%35%45%5%43%
1896
October1st to 10thDay
23%8%26%5%3445%5%34%
1800
11th to 20thDay
23%7%37%6%4445%6%31%
1800
21st to endDay
31%9%47%5%3433429%
1929
November1st to 10thDay
32%12%5%8%7%35%445%15%
1567
11th to 20thDay
35%11%37%5%34435%20%
1520
21st to endDay
31%11%5%7%6%3434422%
1520
December1st to 10thDay
30%12%46%6%3334423%
1520
11th to 20thDay
33%13%5%6%6%35%45%5%14%
1928
21st to endDay
33%13%5%10%8%45%44410%
2794
January1st to 10thNight
39%13%48%7%35%44410%
4406
11th to 20thNight
38%14%37%5%3433417%
4420
21st to endNight
38%13%48%5%3333415%
4632
February1st to 10thNight
31%11%47%7%44445%19%
2470
11th to 20thNight
31%11%46%6%34335%23%
2402
21st to endNight
30%12%47%6%345%45%19%
1965
March1st to 10thNight
29%11%5%6%5%36%5%35%23%
2085
11th to 20thNight
28%9%36%7%346%5%6%23%
1980
21st to endNight
29%12%48%7%35%446%19%
2129
April1st to 10thNight
27%12%48%7%35%445%21%
1800
11th to 20thNight
22%9%47%6%35%45%7%29%
1779
21st to endNight
26%9%37%5%34347%30%
1621
May1st to 10thNight
14%8%37%6%2445%6%40%
1469
11th to 20thNight
17%7%35%6%346%6%8%36%
1416
21st to endNight
15%8%37%5%446%6%7%36%
1552
June1st to 10thNight
19%6%37%7%45%436%38%
1440
11th to 20thNight
17%7%37%6%33446%40%
1440
21st to endNight
6%5%26%423335%61%
1307
July1st to 10thNight
5%313323345%66%
1440
11th to 20thNight
5%22321433470%
1440
21st to endNight
311121122481%
1576
August1st to 10thNight
3212222347%71%
1568
11th to 20thNight
4213323236%72%
1602
21st to endNight
6%323423446%64%
1905
September1st to 10thNight
7%313323345%67%
1800
11th to 20thNight
12%5%25%6%3445%5%48%
1800
21st to endNight
12%435%4345%47%50%
2060
October1st to 10thNight
18%6%35%433345%45%
2160
11th to 20thNight
20%6%36%5%24447%38%
2160
21st to endNight
26%8%35%423346%35%
2426
November1st to 10thNight
32%9%46%6%345%46%21%
2508
11th to 20thNight
36%9%36%6%34435%22%
2660
21st to endNight
30%7%37%6%45%5%3427%
2660
December1st to 10thNight
31%9%45%5%3445%5%24%
2660
11th to 20thNight
32%11%47%6%34446%19%
3276
21st to endNight
32%13%5%9%7%45%5%4414%
4862

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
82%5%7%42
2539
11th to 20thDay
74%36%11%42
2540
21st to endDay
76%6%7%7%4
3027
February1st to 10thDay
70%5%9%11%4
1710
11th to 20thDay
73%5%7%10%41
1674
21st to endDay
69%5%10%10%5%1
1488
March1st to 10thDay
69%5%10%11%5%
1879
11th to 20thDay
68%5%8%14%5%1
1980
21st to endDay
73%5%12%9%1
2227
April1st to 10thDay
69%5%11%12%2
2160
11th to 20thDay
63%5%10%14%7%2
2132
21st to endDay
60%6%12%12%8%1
2335
May1st to 10thDay
50%416%20%9%1
2489
11th to 20thDay
53%5%17%17%6%1
2480
21st to endDay
57%7%16%17%3
2724
June1st to 10thDay
54%5%17%17%6%
2520
11th to 20thDay
55%7%19%14%5%
2520
21st to endDay
34%5%19%27%10%4
2608
July1st to 10thDay
29%6%15%26%19%5%
2451
11th to 20thDay
25%411%29%26%6%
2445
21st to endDay
16%312%32%31%6%
2589
August1st to 10thDay
24%5%15%33%19%5%
2351
11th to 20thDay
21%415%32%20%7%
2298
21st to endDay
30%6%12%29%19%4
2450
September1st to 10thDay
26%413%26%20%11%
2160
11th to 20thDay
41%6%13%17%15%7%
2160
21st to endDay
43%5%13%19%15%5%
1896
October1st to 10thDay
51%5%8%20%13%3
1800
11th to 20thDay
54%5%13%16%11%2
1800
21st to endDay
62%28%14%13%1
1929
November1st to 10thDay
72%5%8%12%4
1567
11th to 20thDay
67%5%11%9%6%2
1520
21st to endDay
67%5%6%10%11%1
1520
December1st to 10thDay
66%49%12%8%1
1520
11th to 20thDay
70%6%10%12%2
1928
21st to endDay
79%48%6%2
2794
January1st to 10thNight
77%49%6%31
4406
11th to 20thNight
72%37%12%41
4420
21st to endNight
75%48%9%5%1
4632
February1st to 10thNight
68%6%10%12%4
2470
11th to 20thNight
66%411%12%6%2
2404
21st to endNight
66%5%11%11%6%1
1965
March1st to 10thNight
63%5%11%16%5%
2085
11th to 20thNight
61%6%12%14%6%1
1980
21st to endNight
67%6%14%12%1
2129
April1st to 10thNight
64%414%13%4
1800
11th to 20thNight
56%6%14%15%7%3
1779
21st to endNight
56%6%14%16%5%3
1621
May1st to 10thNight
44%5%17%23%9%2
1469
11th to 20thNight
44%6%20%21%6%3
1416
21st to endNight
45%9%21%19%6%
1552
June1st to 10thNight
49%415%25%6%1
1440
11th to 20thNight
45%423%22%5%
1440
21st to endNight
27%420%33%11%5%
1307
July1st to 10thNight
22%415%31%21%7%
1400
11th to 20thNight
20%314%29%29%6%
1392
21st to endNight
9%211%39%29%10%
1488
August1st to 10thNight
14%418%37%21%5%
1560
11th to 20thNight
15%418%36%18%9%
1602
21st to endNight
21%5%14%36%19%5%
1905
September1st to 10thNight
21%414%31%20%10%
1800
11th to 20thNight
38%5%13%23%12%9%
1800
21st to endNight
34%5%17%20%18%6%
2060
October1st to 10thNight
41%410%25%16%3
2160
11th to 20thNight
45%5%12%20%15%2
2160
21st to endNight
52%410%16%15%2
2426
November1st to 10thNight
64%6%8%16%6%
2508
11th to 20thNight
66%5%10%10%7%2
2660
21st to endNight
61%5%9%11%12%1
2660
December1st to 10thNight
62%6%10%13%9%1
2660
11th to 20thNight
68%7%10%11%4
3276
21st to endNight
73%7%9%8%2
4862

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
49%316%13%15%4
180
11th to 20thDay
44%413%21%9%7%
180
21st to endDay
37%6%14%21%14%7%
340
February1st to 10thDay
43%5%16%18%14%4
370
11th to 20thDay
41%5%21%22%10%2
365
21st to endDay
41%9%19%19%10%3
343
March1st to 10thDay
34%9%23%22%11%2
421
11th to 20thDay
30%7%24%22%14%3
420
21st to endDay
34%8%20%22%13%3
462
April1st to 10thDay
31%9%20%23%12%5%
420
11th to 20thDay
30%10%25%20%11%5%
412
21st to endDay
24%6%28%23%14%4
420
May1st to 10thDay
19%11%23%25%18%4
423
11th to 20thDay
27%8%18%22%18%7%
448
21st to endDay
20%7%19%26%21%7%
485
June1st to 10thDay
23%5%21%27%20%4
450
11th to 20thDay
18%7%25%32%14%3
450
21st to endDay
7%6%26%35%22%6%
538
July1st to 10thDay
10%418%35%25%8%
446
11th to 20thDay
7%5%21%36%24%7%
444
21st to endDay
5%216%39%31%6%
487
August1st to 10thDay
8%216%35%29%11%
447
11th to 20thDay
5%115%34%33%13%
437
21st to endDay
9%421%34%22%10%
495
September1st to 10thDay
8%421%38%21%8%
450
11th to 20thDay
15%316%31%25%10%
450
21st to endDay
18%420%32%21%5%
450
October1st to 10thDay
23%5%16%29%21%7%
450
11th to 20thDay
26%417%26%19%8%
450
21st to endDay
32%6%19%23%13%7%
444
November1st to 10thDay
32%5%23%23%14%4
219
11th to 20thDay
36%423%16%14%7%
180
21st to endDay
37%318%19%16%6%
180
December1st to 10thDay
40%219%16%17%6%
180
11th to 20thDay
44%6%19%19%9%3
180
21st to endDay
38%6%16%25%13%3
198
January1st to 10thNight
43%6%13%23%13%2
760
11th to 20thNight
40%412%28%15%1
760
21st to endNight
35%313%31%17%2
836
February1st to 10thNight
35%416%30%14%1
760
11th to 20thNight
37%417%27%15%1
744
21st to endNight
36%416%32%11%
628
March1st to 10thNight
33%5%15%31%14%1
722
11th to 20thNight
30%418%34%13%
720
21st to endNight
33%6%17%29%15%
792
April1st to 10thNight
32%6%17%29%16%1
720
11th to 20thNight
27%421%34%12%2
711
21st to endNight
30%220%33%15%1
541
May1st to 10thNight
17%5%28%35%14%1
389
11th to 20thNight
18%319%46%14%1
354
21st to endNight
19%422%37%18%
389
June1st to 10thNight
21%224%40%13%
360
11th to 20thNight
18%327%43%8%1
360
21st to endNight
8%232%49%10%
360
July1st to 10thNight
6%125%54%13%1
350
11th to 20thNight
6%334%44%13%
348
21st to endNight
2130%55%11%1
394
August1st to 10thNight
5%218%48%26%2
494
11th to 20thNight
4112%51%29%3
534
21st to endNight
8%224%44%21%1
717
September1st to 10thNight
9%322%46%19%2
720
11th to 20thNight
14%313%36%31%4
720
21st to endNight
14%218%43%22%2
720
October1st to 10thNight
21%317%35%21%3
720
11th to 20thNight
23%215%33%23%3
720
21st to endNight
30%218%33%16%2
792
November1st to 10thNight
35%314%35%12%1
740
11th to 20thNight
40%415%26%14%1
760
21st to endNight
31%315%34%16%1
760
December1st to 10thNight
35%414%31%14%2
760
11th to 20thNight
42%416%26%11%1
760
21st to endNight
42%5%18%25%10%1
836
Page generated at 2024-02-27 03:30:19. Version ac07

Copyright © 2024 Attilla Danko.


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