Treynor
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Treynor clear sky chart from 2005-11-05 to 2018-02-14.

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
40%
16678
21%
48880
12%
16632
48%
16632
30%
29888

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
33%
975
19%
2522
8%
970
41%
970
29%
1656
January16th to endNight
29%
1040
23%
2704
9%
1040
39%
1040
28%
1788
February1st to 15thNight
26%
950
12%
2470
6%
946
30%
946
22%
1774
February16th to endNight
29%
702
24%
1964
7%
702
42%
702
32%
1220
March1st to 15thNight
36%
543
22%
1983
16%
543
46%
543
26%
1142
March16th to endNight
27%
576
15%
2112
9%
576
36%
576
18%
1376
April1st to 15thNight
30%
539
20%
1865
12%
539
43%
539
24%
1131
April16th to endNight
31%
540
20%
1632
13%
540
43%
540
24%
1072
May1st to 15thNight
40%
540
18%
1620
12%
540
48%
540
26%
1044
May16th to endNight
43%
562
16%
1592
8%
561
49%
561
28%
1035
June1st to 15thNight
53%
540
18%
1440
7%
540
57%
540
38%
870
June16th to endNight
58%
540
22%
1440
9%
540
63%
540
50%
772
July1st to 15thNight
69%
510
17%
1459
11%
510
70%
510
46%
779
July16th to endNight
76%
564
24%
1594
21%
531
78%
531
51%
788
August1st to 15thNight
70%
539
21%
1610
23%
536
72%
536
40%
895
August16th to endNight
62%
573
25%
1761
24%
573
67%
573
38%
986
September1st to 15thNight
55%
540
24%
1878
22%
540
63%
540
34%
1006
September16th to endNight
50%
537
29%
1980
23%
537
62%
537
36%
1004
October1st to 15thNight
37%
696
26%
2136
16%
696
46%
696
31%
1268
October16th to endNight
39%
768
26%
2304
14%
768
49%
768
34%
1322
November1st to 15thNight
37%
914
26%
2445
11%
914
47%
914
37%
1442
November16th to endNight
33%
975
24%
2730
10%
975
43%
975
33%
1647
December1st to 15thNight
27%
975
16%
2730
6%
975
35%
975
24%
1830
December16th to endNight
29%
1040
19%
2909
8%
1040
39%
1040
21%
2041

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
11%6%25%5%3445%7%43%
49178
Night
10%6%2442335%7%48%
49070
Cloud CoverDay
12%6%25%5%2445%7%43%
49189
Night
10%6%2442335%7%48%
49074
Cloud CoverDay
11%6%35%5%3445%7%43%
49187
Night
10%6%2442335%7%48%
49074
TransparencyDay
40%5%14%24%13%1
48886
Night
35%5%13%26%16%2
48880
SeeingDay
13%7%29%30%16%2
6450
Night
13%8%32%33%11%
16679

By Month

Percentage Cloud Cover NE (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
9%7%36%7%35%5%5%7%39%
1746
16th to endDay
10%10%48%6%24447%36%
1872
February1st to 15thDay
10%9%5%9%6%4445%7%32%
1694
16th to endDay
12%7%48%5%2345%6%38%
1518
March1st to 15thDay
11%8%5%6%425%446%40%
1965
16th to endDay
18%10%35%434347%34%
2112
April1st to 15thDay
16%8%26%5%24435%40%
2082
16th to endDay
22%7%25%433446%34%
2327
May1st to 15thDay
15%6%25%5%35%5%47%38%
2331
16th to endDay
15%5%36%5%3446%8%36%
2521
June1st to 15thDay
10%5%345%3446%8%42%
2520
16th to endDay
6%3145%25%46%8%51%
2520
July1st to 15thDay
8%3135%345%5%8%50%
2409
16th to endDay
42133345%5%9%54%
2466
August1st to 15thDay
7%3145%35%6%7%9%43%
2340
16th to endDay
9%424435%5%5%7%46%
2439
September1st to 15thDay
11%42433345%5%51%
2081
16th to endDay
10%42332345%6%54%
1980
October1st to 15thDay
16%5%13312346%49%
1812
16th to endDay
13%6%245%2334448%
1920
November1st to 15thDay
9%5%24423446%54%
1739
16th to endDay
12%7%35%424447%42%
1560
December1st to 15thDay
11%10%47%6%3335%5%37%
1560
16th to endDay
13%10%49%8%25%445%30%
1664
January1st to 15thNight
8%6%35%7%3446%7%42%
2522
16th to endNight
10%8%45%5%24346%44%
2704
February1st to 15thNight
12%10%48%5%34346%35%
2467
16th to endNight
9%5%36%42335%6%48%
1964
March1st to 15thNight
10%7%34223347%49%
1971
16th to endNight
16%8%4442445%7%36%
2112
April1st to 15thNight
13%7%24423446%46%
1865
16th to endNight
16%7%26%323346%41%
1632
May1st to 15thNight
14%5%3442435%7%43%
1620
16th to endNight
12%6%245%33448%44%
1590
June1st to 15thNight
8%42441347%8%50%
1440
16th to endNight
311322447%9%58%
1440
July1st to 15thNight
422241445%10%58%
1548
16th to endNight
311231346%10%60%
1702
August1st to 15thNight
42144245%5%9%53%
1620
16th to endNight
9%323323345%56%
1761
September1st to 15thNight
10%423323347%54%
1878
16th to endNight
9%5%13312446%57%
1980
October1st to 15thNight
14%5%24313336%50%
2136
16th to endNight
12%423323345%54%
2304
November1st to 15thNight
9%5%23323346%54%
2445
16th to endNight
11%5%24423346%52%
2730
December1st to 15thNight
11%9%36%5%2425%6%41%
2730
16th to endNight
13%9%47%5%2345%6%37%
2909

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 15thDay
9%7%35%7%35%5%5%7%39%
1746
16th to endDay
10%10%48%6%24447%36%
1872
February1st to 15thDay
10%10%5%8%6%4445%6%32%
1694
16th to endDay
12%8%47%5%2345%6%38%
1518
March1st to 15thDay
11%8%5%7%425%446%40%
1976
16th to endDay
18%10%35%424347%34%
2112
April1st to 15thDay
16%8%26%5%24335%40%
2082
16th to endDay
22%7%25%433446%34%
2327
May1st to 15thDay
15%6%25%5%35%45%7%38%
2331
16th to endDay
15%5%36%5%3446%8%36%
2521
June1st to 15thDay
10%5%345%3446%8%42%
2520
16th to endDay
6%3145%25%46%8%50%
2520
July1st to 15thDay
8%3135%345%6%8%49%
2409
16th to endDay
43134345%5%9%54%
2466
August1st to 15thDay
7%3145%45%6%7%9%43%
2340
16th to endDay
9%424435%5%5%7%46%
2439
September1st to 15thDay
11%5%1432335%5%51%
2081
16th to endDay
10%413323346%54%
1980
October1st to 15thDay
16%5%23312346%49%
1812
16th to endDay
13%6%245%2334448%
1920
November1st to 15thDay
9%5%23423446%54%
1739
16th to endDay
12%7%25%424447%42%
1560
December1st to 15thDay
12%10%47%6%3335%6%37%
1560
16th to endDay
12%10%49%7%3445%5%31%
1664
January1st to 15thNight
8%6%35%6%3446%7%42%
2522
16th to endNight
10%8%45%5%24346%44%
2704
February1st to 15thNight
12%10%48%5%34346%36%
2460
16th to endNight
9%5%36%42335%6%48%
1964
March1st to 15thNight
11%7%34223337%49%
1983
16th to endNight
16%8%3442445%7%36%
2112
April1st to 15thNight
13%7%34423446%46%
1865
16th to endNight
16%7%26%333346%41%
1632
May1st to 15thNight
14%5%2442435%7%44%
1619
16th to endNight
12%6%245%33448%44%
1590
June1st to 15thNight
8%42442347%8%50%
1440
16th to endNight
311322447%9%58%
1440
July1st to 15thNight
421241445%10%58%
1548
16th to endNight
311231346%9%60%
1702
August1st to 15thNight
42144345%6%9%53%
1620
16th to endNight
9%324313345%56%
1761
September1st to 15thNight
10%423323346%55%
1878
16th to endNight
9%423312446%57%
1980
October1st to 15thNight
14%5%23313346%50%
2136
16th to endNight
12%423323345%54%
2304
November1st to 15thNight
9%5%24323346%54%
2445
16th to endNight
11%5%24323346%51%
2730
December1st to 15thNight
11%9%36%43435%6%41%
2730
16th to endNight
13%9%47%5%2345%6%37%
2909

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
9%7%26%7%35%5%5%7%39%
1746
16th to endDay
10%10%49%5%245%37%36%
1872
February1st to 15thDay
10%10%5%9%6%4435%7%32%
1694
16th to endDay
12%7%47%5%2445%6%38%
1518
March1st to 15thDay
11%8%47%42445%6%39%
1976
16th to endDay
18%10%45%424347%34%
2110
April1st to 15thDay
16%8%26%5%24336%40%
2082
16th to endDay
22%7%35%423446%34%
2327
May1st to 15thDay
15%6%35%5%35%447%38%
2331
16th to endDay
15%5%36%5%3446%8%36%
2521
June1st to 15thDay
11%5%345%3446%8%42%
2520
16th to endDay
6%3145%2446%8%50%
2520
July1st to 15thDay
8%3235%345%5%8%49%
2409
16th to endDay
42133345%5%9%54%
2466
August1st to 15thDay
7%3145%45%6%7%9%43%
2340
16th to endDay
10%425%425%5%5%7%46%
2439
September1st to 15thDay
11%5%1433335%5%51%
2081
16th to endDay
10%323323446%54%
1980
October1st to 15thDay
16%5%1331235%6%49%
1812
16th to endDay
13%6%245%3344448%
1920
November1st to 15thDay
9%5%24423446%53%
1739
16th to endDay
12%7%36%424347%42%
1560
December1st to 15thDay
11%10%47%5%33346%36%
1560
16th to endDay
13%10%49%7%35%45%6%30%
1664
January1st to 15thNight
8%6%35%6%3446%8%42%
2522
16th to endNight
10%8%35%5%23346%44%
2704
February1st to 15thNight
12%10%48%5%34346%36%
2460
16th to endNight
9%6%26%43335%7%47%
1964
March1st to 15thNight
11%8%34223337%49%
1983
16th to endNight
16%8%4442445%7%36%
2112
April1st to 15thNight
13%7%34423346%46%
1865
16th to endNight
16%7%26%333346%42%
1632
May1st to 15thNight
14%6%35%42445%7%44%
1619
16th to endNight
11%7%245%23447%44%
1590
June1st to 15thNight
8%42342347%8%49%
1440
16th to endNight
321332447%9%58%
1440
July1st to 15thNight
4212415%45%10%58%
1548
16th to endNight
311231346%9%60%
1702
August1st to 15thNight
42144345%6%9%53%
1620
16th to endNight
9%424313346%56%
1761
September1st to 15thNight
10%423323346%55%
1878
16th to endNight
9%423312346%58%
1980
October1st to 15thNight
14%5%24323246%50%
2136
16th to endNight
12%424323345%54%
2304
November1st to 15thNight
9%5%24323347%54%
2445
16th to endNight
11%5%24423346%52%
2730
December1st to 15thNight
11%9%46%5%3435%6%41%
2730
16th to endNight
13%9%47%5%2345%6%36%
2909

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
43%5%18%21%10%
1747
16th to endDay
49%416%19%9%
1872
February1st to 15thDay
51%415%19%7%
1695
16th to endDay
45%5%14%21%11%1
1518
March1st to 15thDay
44%6%14%22%11%1
1976
16th to endDay
50%5%15%19%6%1
2112
April1st to 15thDay
46%410%26%9%1
2082
16th to endDay
50%5%12%20%9%
2327
May1st to 15thDay
45%6%13%22%11%
2331
16th to endDay
44%7%15%21%9%
2525
June1st to 15thDay
38%7%15%23%13%2
2520
16th to endDay
29%7%17%29%13%2
2520
July1st to 15thDay
31%7%15%27%13%3
2269
16th to endDay
24%7%17%30%17%1
2311
August1st to 15thDay
33%8%17%24%14%
2326
16th to endDay
35%6%11%25%16%4
2439
September1st to 15thDay
33%413%27%18%2
2081
16th to endDay
30%412%33%18%
1980
October1st to 15thDay
35%311%27%19%1
1812
16th to endDay
38%411%23%18%3
1920
November1st to 15thDay
31%414%27%20%1
1739
16th to endDay
41%413%28%11%
1560
December1st to 15thDay
48%5%16%20%8%1
1560
16th to endDay
53%5%13%18%8%
1664
January1st to 15thNight
38%5%16%24%14%
2522
16th to endNight
40%5%15%26%11%
2704
February1st to 15thNight
49%5%14%21%9%1
2470
16th to endNight
36%313%25%18%2
1964
March1st to 15thNight
36%412%27%15%2
1983
16th to endNight
45%6%13%24%8%1
2112
April1st to 15thNight
38%5%9%28%16%1
1865
16th to endNight
43%413%22%13%1
1632
May1st to 15thNight
40%6%12%23%15%1
1620
16th to endNight
38%7%16%22%13%2
1592
June1st to 15thNight
30%6%15%29%15%2
1440
16th to endNight
21%5%17%30%21%3
1440
July1st to 15thNight
21%6%19%30%16%4
1459
16th to endNight
18%5%16%37%19%2
1594
August1st to 15thNight
24%8%17%31%16%2
1610
16th to endNight
29%412%26%19%8%
1761
September1st to 15thNight
29%412%26%20%5%
1878
16th to endNight
28%310%34%20%2
1980
October1st to 15thNight
35%49%24%23%3
2136
16th to endNight
31%412%25%23%2
2304
November1st to 15thNight
30%414%24%22%3
2445
16th to endNight
34%313%30%15%1
2730
December1st to 15thNight
44%415%25%9%
2730
16th to endNight
46%6%13%21%10%1
2909

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
20%7%40%27%5%
135
16th to endDay
20%5%41%26%6%
144
February1st to 15thDay
17%15%40%23%2
130
16th to endDay
19%12%32%28%42
81
March1st to 15thDay
22%13%45%16%2
90
16th to endDay
26%13%37%18%4
96
April1st to 15thDay
19%9%36%25%7%
201
16th to endDay
26%13%30%20%8%
437
May1st to 15thDay
18%10%30%27%11%1
468
16th to endDay
18%6%31%28%13%1
517
June1st to 15thDay
9%429%32%20%3
495
16th to endDay
5%5%31%34%19%3
495
July1st to 15thDay
9%222%32%27%6%
475
16th to endDay
319%43%28%4
515
August1st to 15thDay
6%219%40%26%4
493
16th to endDay
11%318%34%25%6%
479
September1st to 15thDay
7%327%33%21%6%
236
16th to endDay
7%440%29%16%1
135
October1st to 15thDay
19%8%29%27%8%6%
135
16th to endDay
12%12%38%24%11%
144
November1st to 15thDay
10%8%41%28%8%2
135
16th to endDay
30%13%36%17%2
135
December1st to 15thDay
12%21%41%18%5%
135
16th to endDay
18%18%41%16%4
144
January1st to 15thNight
11%13%35%32%6%
975
16th to endNight
14%10%38%30%6%
1040
February1st to 15thNight
16%12%36%29%4
950
16th to endNight
11%10%44%25%6%
702
March1st to 15thNight
15%11%32%31%8%
543
16th to endNight
19%10%40%22%6%
576
April1st to 15thNight
16%12%37%28%5%
539
16th to endNight
18%8%36%25%9%
540
May1st to 15thNight
15%9%30%32%12%
540
16th to endNight
14%5%30%36%12%
563
June1st to 15thNight
9%326%44%14%
540
16th to endNight
4230%45%16%
540
July1st to 15thNight
5%19%45%27%
510
16th to endNight
4113%53%26%1
564
August1st to 15thNight
416%49%25%2
539
16th to endNight
10%218%40%24%3
573
September1st to 15thNight
12%422%33%23%3
540
16th to endNight
12%430%34%17%1
537
October1st to 15thNight
16%7%33%29%10%2
696
16th to endNight
15%8%32%33%9%
768
November1st to 15thNight
12%10%35%31%9%
914
16th to endNight
14%11%38%26%8%
975
December1st to 15thNight
17%12%36%27%4
975
16th to endNight
17%10%32%32%6%
1040
Page generated at 2018-02-15 09:58:48. Version ac04

Copyright 2018 A. Danko


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