Treynor
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Treynor clear sky chart from 2005-11-06 to 2024-03-18.

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
38%
24895
20%
80540
12%
24796
47%
24796
26%
50461

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
30%
941
12%
4091
8%
926
39%
926
14%
3121
January11th to 20thNight
27%
947
19%
4027
8%
930
35%
930
15%
2652
January21st to endNight
25%
1034
12%
4511
7%
1023
34%
1023
13%
3304
February1st to 10thNight
25%
950
14%
2470
5%
950
30%
950
23%
1757
February11th to 20thNight
28%
929
18%
2404
6%
925
35%
925
28%
1599
February21st to endNight
26%
647
23%
1903
6%
647
40%
647
28%
1188
March1st to 10thNight
29%
575
23%
2095
13%
575
42%
575
25%
1220
March11th to 20thNight
28%
564
22%
2068
14%
564
40%
564
22%
1255
March21st to endNight
24%
594
12%
2178
6%
594
32%
594
15%
1506
April1st to 10thNight
25%
540
19%
1904
12%
540
37%
540
24%
1142
April11th to 20thNight
27%
533
23%
1706
12%
533
43%
533
24%
1057
April21st to endNight
30%
540
19%
1620
11%
540
43%
540
25%
1055
May1st to 10thNight
37%
540
15%
1620
10%
540
44%
540
24%
1067
May11th to 20thNight
37%
531
18%
1594
12%
531
45%
531
26%
1027
May21st to endNight
43%
584
13%
1609
7%
582
48%
582
27%
1080
June1st to 10thNight
60%
540
23%
1440
12%
540
64%
540
43%
834
June11th to 20thNight
53%
540
21%
1440
9%
540
57%
540
42%
838
June21st to endNight
53%
540
21%
1440
8%
540
58%
540
44%
816
July1st to 10thNight
70%
525
18%
1468
12%
525
71%
525
46%
798
July11th to 20thNight
71%
522
22%
1566
15%
522
75%
522
51%
782
July21st to endNight
72%
591
25%
1673
22%
558
75%
558
48%
853
August1st to 10thNight
65%
537
20%
1601
22%
534
68%
534
37%
920
August11th to 20thNight
68%
534
27%
1600
29%
534
73%
534
43%
865
August21st to endNight
62%
594
27%
1845
26%
594
69%
594
42%
974
September1st to 10thNight
54%
540
25%
1825
22%
540
63%
540
37%
956
September11th to 20thNight
53%
540
28%
1980
26%
540
63%
540
37%
1001
September21st to endNight
47%
540
30%
1980
23%
540
60%
540
37%
988
October1st to 10thNight
41%
682
25%
2122
17%
682
48%
682
33%
1229
October11th to 20thNight
33%
720
26%
2160
12%
720
44%
720
32%
1263
October21st to endNight
35%
792
24%
2376
12%
792
45%
792
30%
1420
November1st to 10thNight
39%
871
27%
2351
12%
871
50%
871
38%
1348
November11th to 20thNight
30%
950
26%
2582
9%
950
43%
950
33%
1563
November21st to endNight
33%
950
22%
2660
11%
950
42%
950
30%
1651
December1st to 10thNight
30%
950
18%
2660
7%
950
39%
950
26%
1740
December11th to 20thNight
29%
949
21%
3133
7%
948
38%
948
22%
1939
December21st to endNight
24%
1039
12%
4838
7%
1026
36%
1026
11%
3653

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%7%37%5%3445%7%42%
78773
Night
11%8%36%5%3445%7%45%
81062
TransparencyDay
41%6%14%24%13%2
78495
Night
39%6%13%25%15%2
80861
SeeingDay
15%8%30%29%15%3
14828
Night
14%8%33%33%11%1
24925

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
9%12%5%13%10%45%5%5%6%26%
2847
11th to 20thDay
9%11%5%9%7%39%45%8%29%
2850
21st to endDay
10%13%6%16%10%45%445%24%
3135
February1st to 10thDay
10%11%5%10%7%5%5%45%6%31%
1710
11th to 20thDay
10%9%5%8%5%345%5%8%39%
1664
21st to endDay
12%7%48%5%445%6%6%40%
1565
March1st to 10thDay
12%10%47%5%34445%42%
2084
11th to 20thDay
14%10%46%43445%7%39%
2057
21st to endDay
19%13%46%5%34347%30%
2178
April1st to 10thDay
16%7%36%424436%43%
2056
11th to 20thDay
16%8%36%6%3445%6%38%
2201
21st to endDay
19%7%25%5%345%5%7%37%
2340
May1st to 10thDay
16%7%36%6%35%5%5%7%37%
2340
11th to 20thDay
15%8%37%5%345%6%8%37%
2302
21st to endDay
16%7%36%6%35%5%6%8%33%
2663
June1st to 10thDay
9%5%245%445%7%10%46%
2520
11th to 20thDay
7%5%245%4446%9%48%
2520
21st to endDay
8%5%25%5%35%46%8%49%
2520
July1st to 10thDay
9%313435%46%9%53%
2444
11th to 20thDay
6%4245%346%6%7%54%
2340
21st to endDay
5%3245%35%5%6%10%51%
2546
August1st to 10thDay
8%5%25%6%46%7%7%8%41%
2328
11th to 20thDay
10%424435%6%6%8%49%
2301
21st to endDay
9%5%25%5%3445%8%51%
2510
September1st to 10thDay
13%41433435%6%54%
2132
11th to 20thDay
10%5%2433445%7%53%
1980
21st to endDay
11%5%2343445%6%55%
1980
October1st to 10thDay
15%5%2432345%7%50%
1818
11th to 20thDay
14%5%25%423245%54%
1800
21st to endDay
13%8%35%5%335%45%46%
1980
November1st to 10thDay
10%5%34413447%55%
1725
11th to 20thDay
10%7%28%6%345%46%44%
1596
21st to endDay
13%8%45%42435%7%43%
1520
December1st to 10thDay
9%9%37%6%45%35%7%42%
1520
11th to 20thDay
9%10%48%7%35%5%6%8%35%
1918
21st to endDay
17%10%6%14%8%445%5%5%22%
2783
January1st to 10thNight
9%10%5%16%12%4445%5%26%
4108
11th to 20thNight
9%11%47%6%38%6%9%6%32%
4120
21st to endNight
12%13%5%11%7%35%45%5%29%
4532
February1st to 10thNight
11%10%5%9%6%3445%7%36%
2470
11th to 20thNight
10%8%37%435%45%7%43%
2403
21st to endNight
9%7%37%5%34346%48%
1903
March1st to 10thNight
11%9%45%334347%48%
2095
11th to 20thNight
15%9%45%423346%46%
2068
21st to endNight
17%11%5%6%5%25%5%5%7%31%
2178
April1st to 10thNight
12%8%35%43445%7%46%
1904
11th to 20thNight
12%9%35%5%3345%7%45%
1706
21st to endNight
16%7%36%334347%43%
1620
May1st to 10thNight
15%7%36%5%2446%9%40%
1620
11th to 20thNight
13%6%35%5%335%5%7%45%
1593
21st to endNight
13%8%35%6%3445%8%41%
1608
June1st to 10thNight
7%32443447%9%55%
1440
11th to 20thNight
6%4244345%8%10%51%
1440
21st to endNight
4315%43446%8%56%
1440
July1st to 10thNight
5%323425%4410%57%
1511
11th to 20thNight
321241446%9%64%
1620
21st to endNight
42233245%7%9%58%
1772
August1st to 10thNight
5%325%435%6%7%9%51%
1611
11th to 20thNight
7%32442335%8%58%
1600
21st to endNight
7%4234235%5%7%59%
1845
September1st to 10thNight
10%42433335%7%58%
1825
11th to 20thNight
10%413323447%57%
1980
21st to endNight
10%424324346%60%
1980
October1st to 10thNight
13%5%2432335%7%51%
2122
11th to 20thNight
14%7%24423345%53%
2160
21st to endNight
14%6%25%324346%51%
2376
November1st to 10thNight
9%424423447%57%
2351
11th to 20thNight
10%6%35%423447%51%
2582
21st to endNight
12%8%45%423346%50%
2660
December1st to 10thNight
9%8%37%6%35%45%7%42%
2660
11th to 20thNight
9%9%46%6%34447%45%
3279
21st to endNight
18%14%6%12%5%2344429%
4880

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
57%7%14%15%7%1
2848
11th to 20thDay
54%5%12%22%7%
2850
21st to endDay
63%6%12%13%6%
3135
February1st to 10thDay
53%6%13%17%10%1
1710
11th to 20thDay
45%313%24%12%2
1673
21st to endDay
44%6%13%22%13%3
1565
March1st to 10thDay
45%5%13%24%12%2
2084
11th to 20thDay
45%7%11%23%12%2
2057
21st to endDay
56%5%14%16%8%1
2178
April1st to 10thDay
44%5%12%26%11%2
2056
11th to 20thDay
46%5%13%23%12%2
2201
21st to endDay
46%6%12%23%12%1
2340
May1st to 10thDay
46%8%14%20%12%1
2340
11th to 20thDay
44%7%14%23%11%
2306
21st to endDay
47%8%16%18%10%2
2663
June1st to 10thDay
33%8%18%27%13%3
2520
11th to 20thDay
32%7%15%29%16%1
2520
21st to endDay
32%8%16%27%14%3
2520
July1st to 10thDay
27%6%16%33%14%3
2379
11th to 20thDay
28%8%13%28%19%4
2271
21st to endDay
26%8%18%31%16%1
2405
August1st to 10thDay
36%10%18%23%11%1
2314
11th to 20thDay
32%7%14%31%16%1
2301
21st to endDay
32%7%12%27%18%5%
2510
September1st to 10thDay
31%414%28%18%5%
2132
11th to 20thDay
31%6%11%34%18%1
1980
21st to endDay
30%411%32%22%1
1980
October1st to 10thDay
34%412%28%20%1
1818
11th to 20thDay
34%49%26%23%4
1800
21st to endDay
40%5%11%21%19%4
1980
November1st to 10thDay
30%5%15%28%20%3
1725
11th to 20thDay
41%5%13%24%16%1
1596
21st to endDay
41%412%29%13%1
1520
December1st to 10thDay
42%6%16%24%12%1
1520
11th to 20thDay
47%6%16%25%5%
1915
21st to endDay
62%6%9%16%5%1
2783
January1st to 10thNight
57%6%11%15%10%1
4108
11th to 20thNight
48%6%14%22%10%1
4120
21st to endNight
56%6%14%15%8%1
4532
February1st to 10thNight
47%6%13%20%12%2
2470
11th to 20thNight
41%5%13%24%16%2
2404
21st to endNight
38%49%24%20%4
1903
March1st to 10thNight
38%412%27%16%3
2095
11th to 20thNight
41%49%26%16%3
2068
21st to endNight
51%7%13%19%8%2
2178
April1st to 10thNight
37%6%11%27%17%3
1904
11th to 20thNight
39%6%11%26%16%2
1706
21st to endNight
42%5%13%23%15%1
1620
May1st to 10thNight
42%7%15%21%13%2
1620
11th to 20thNight
38%8%13%24%16%1
1594
21st to endNight
41%7%18%19%11%3
1609
June1st to 10thNight
25%7%16%34%15%3
1440
11th to 20thNight
26%7%17%26%20%4
1440
21st to endNight
25%5%17%31%18%3
1440
July1st to 10thNight
24%5%17%31%19%4
1468
11th to 20thNight
18%7%20%31%20%5%
1566
21st to endNight
20%7%15%36%20%2
1673
August1st to 10thNight
27%9%18%31%15%1
1601
11th to 20thNight
25%5%15%33%19%3
1600
21st to endNight
24%6%13%26%21%9%
1845
September1st to 10thNight
27%5%13%26%22%6%
1825
11th to 20thNight
27%412%35%19%3
1980
21st to endNight
27%49%31%26%3
1980
October1st to 10thNight
33%5%11%27%22%2
2122
11th to 20thNight
34%48%24%25%5%
2160
21st to endNight
35%413%22%23%2
2376
November1st to 10thNight
27%5%16%24%23%4
2351
11th to 20thNight
34%413%30%17%2
2582
21st to endNight
37%412%28%17%2
2660
December1st to 10thNight
41%5%12%29%11%1
2660
11th to 20thNight
39%5%15%32%8%
3281
21st to endNight
59%6%9%19%6%1
4880

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
22%11%34%24%7%2
270
11th to 20thDay
20%14%36%22%6%1
270
21st to endDay
16%10%42%25%6%1
297
February1st to 10thDay
20%15%42%20%3
270
11th to 20thDay
19%15%37%22%6%1
270
21st to endDay
16%14%44%20%5%
225
March1st to 10thDay
20%11%45%18%41
270
11th to 20thDay
27%9%37%20%6%1
261
21st to endDay
35%12%36%13%31
264
April1st to 10thDay
23%13%38%21%41
316
11th to 20thDay
21%13%35%23%7%
479
21st to endDay
23%12%35%20%9%1
600
May1st to 10thDay
22%10%33%26%9%1
603
11th to 20thDay
20%8%30%26%12%3
625
21st to endDay
20%6%26%29%16%2
679
June1st to 10thDay
7%421%35%25%7%
630
11th to 20thDay
7%430%37%18%4
630
21st to endDay
9%6%31%34%17%3
630
July1st to 10thDay
11%116%31%30%10%
621
11th to 20thDay
6%125%36%24%7%
618
21st to endDay
6%117%44%28%4
684
August1st to 10thDay
8%219%41%24%6%
626
11th to 20thDay
11%218%38%28%4
615
21st to endDay
10%317%42%22%6%
629
September1st to 10thDay
14%227%35%19%4
422
11th to 20thDay
9%333%31%18%6%
270
21st to endDay
15%7%34%27%16%1
270
October1st to 10thDay
20%6%29%24%15%5%
270
11th to 20thDay
14%16%41%21%7%1
270
21st to endDay
21%13%37%17%10%2
297
November1st to 10thDay
16%11%39%26%5%2
270
11th to 20thDay
15%16%42%21%6%1
270
21st to endDay
22%11%37%22%7%1
270
December1st to 10thDay
10%13%38%30%8%1
270
11th to 20thDay
16%13%37%25%9%1
270
21st to endDay
22%13%44%18%3
297
January1st to 10thNight
13%12%36%30%8%1
950
11th to 20thNight
15%12%37%29%6%
950
21st to endNight
18%9%37%30%6%
1045
February1st to 10thNight
17%11%38%29%4
950
11th to 20thNight
14%11%40%30%5%
929
21st to endNight
15%13%42%24%5%1
647
March1st to 10thNight
17%13%36%27%6%1
575
11th to 20thNight
20%7%37%28%7%
564
21st to endNight
23%10%38%23%6%1
594
April1st to 10thNight
17%13%42%24%5%
540
11th to 20thNight
17%12%39%27%5%
533
21st to endNight
20%8%38%25%8%1
540
May1st to 10thNight
18%8%31%35%8%
540
11th to 20thNight
18%7%31%31%12%1
531
21st to endNight
17%5%28%35%14%1
584
June1st to 10thNight
8%323%46%19%1
540
11th to 20thNight
8%330%44%14%1
540
21st to endNight
6%331%44%16%
540
July1st to 10thNight
7%116%46%29%1
525
11th to 20thNight
3120%50%24%2
522
21st to endNight
5%115%53%25%1
591
August1st to 10thNight
6%120%48%23%3
537
11th to 20thNight
8%214%48%26%1
534
21st to endNight
9%222%42%23%3
594
September1st to 10thNight
12%225%38%20%2
540
11th to 20thNight
11%228%39%18%2
540
21st to endNight
13%432%36%14%1
540
October1st to 10thNight
16%5%33%32%11%2
682
11th to 20thNight
18%9%36%29%9%
720
21st to endNight
20%9%32%30%9%
792
November1st to 10thNight
13%10%34%34%9%
871
11th to 20thNight
14%11%41%28%6%
950
21st to endNight
17%10%36%28%8%
950
December1st to 10thNight
15%10%37%32%6%
950
11th to 20thNight
16%8%37%31%7%
950
21st to endNight
21%13%35%27%4
1045
Page generated at 2024-03-15 13:01:44. Version ac07

Copyright © 2024 Attilla Danko.


Treynor Clear Sky Chart |Charts Home