Stephenville
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stephenville clear sky chart from 2005-11-05 to 2017-11-30.

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
19%
15458
6%
47788
3%
15413
22%
15413
8%
39763

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
5%
748
3%
2506
0%
746
7%
746
1%
2339
January16th to endNight
8%
800
3%
2688
2%
800
9%
800
2%
2496
February1st to 15thNight
7%
717
2%
2373
0%
716
9%
716
2%
2214
February16th to endNight
14%
631
3%
1925
1%
631
16%
631
7%
1653
March1st to 15thNight
17%
720
8%
2148
3%
716
21%
716
8%
1797
March16th to endNight
19%
633
8%
2001
4%
633
24%
633
8%
1627
April1st to 15thNight
18%
539
6%
1796
5%
539
21%
539
7%
1460
April16th to endNight
22%
540
10%
1624
5%
540
28%
540
11%
1223
May1st to 15thNight
32%
540
10%
1440
5%
540
35%
540
18%
1037
May16th to endNight
28%
561
6%
1496
3%
560
30%
560
14%
1166
June1st to 15thNight
26%
540
3%
1283
1%
540
27%
540
14%
1035
June16th to endNight
30%
540
4%
1266
2%
540
32%
540
15%
1014
July1st to 15thNight
33%
510
3%
1360
3%
510
33%
510
16%
1041
July16th to endNight
33%
565
8%
1419
3%
532
38%
532
17%
1086
August1st to 15thNight
41%
539
6%
1429
3%
535
43%
535
17%
1094
August16th to endNight
35%
573
8%
1816
5%
573
39%
573
15%
1326
September1st to 15thNight
29%
540
7%
1800
6%
540
33%
540
13%
1341
September16th to endNight
24%
538
10%
1968
8%
538
29%
538
12%
1426
October1st to 15thNight
22%
690
9%
2130
4%
690
27%
690
11%
1667
October16th to endNight
15%
815
7%
2493
2%
815
18%
815
8%
2051
November1st to 15thNight
13%
805
7%
2532
3%
805
17%
805
7%
2150
November16th to endNight
11%
824
4%
2781
2%
824
13%
824
4%
2464
December1st to 15thNight
7%
750
2%
2700
0%
750
9%
750
2%
2487
December16th to endNight
9%
800
3%
2814
2%
800
11%
800
3%
2569

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
24%12%5%8%6%33345%21%
48604
Night
24%14%6%10%7%3333417%
47972
TransparencyDay
66%311%13%4
48293
Night
71%310%11%3
47801
SeeingDay
28%20%20%18%9%2
8208
Night
27%24%19%19%7%1
15462

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
19%21%10%18%12%432123
1432
16th to endDay
15%22%9%19%15%421114
1536
February1st to 15thDay
16%13%8%19%16%5%33326%
1485
16th to endDay
17%17%9%16%10%3322313%
1548
March1st to 15thDay
19%14%7%10%10%45%34414%
1790
16th to endDay
17%15%7%12%8%4344316%
2221
April1st to 15thDay
26%16%6%8%413335%19%
2153
16th to endDay
24%10%45%42433431%
2334
May1st to 15thDay
23%10%45%322345%33%
2512
16th to endDay
29%8%35%5%24346%25%
2618
June1st to 15thDay
27%7%36%5%3445%7%25%
2676
16th to endDay
27%9%35%424446%27%
2690
July1st to 15thDay
23%6%3342445%7%33%
2520
16th to endDay
28%8%35%423346%28%
2653
August1st to 15thDay
24%7%36%5%2445%7%28%
2520
16th to endDay
25%7%25%5%345%5%7%27%
2383
September1st to 15thDay
27%7%25%6%2445%5%26%
2160
16th to endDay
27%10%37%5%245%5%5%23%
1992
October1st to 15thDay
29%10%35%423346%24%
1828
16th to endDay
33%17%47%43333413%
1731
November1st to 15thDay
30%21%46%5%2423413%
1653
16th to endDay
23%24%9%10%5%243339%
1502
December1st to 15thDay
23%22%10%16%7%222125%
1260
16th to endDay
20%23%10%13%11%222226%
1407
January1st to 15thNight
19%22%11%14%12%332114
2506
16th to endNight
15%18%9%19%14%6%32225%
2688
February1st to 15thNight
16%14%8%20%17%6%32125%
2373
16th to endNight
16%16%8%16%10%2433314%
1925
March1st to 15thNight
19%14%6%11%10%4433317%
2147
16th to endNight
17%16%6%10%8%45%5%3417%
2001
April1st to 15thNight
23%17%7%10%423335%17%
1796
16th to endNight
18%11%5%8%5%34446%27%
1624
May1st to 15thNight
26%8%24323336%34%
1440
16th to endNight
32%7%35%424447%24%
1494
June1st to 15thNight
28%10%36%41445%6%24%
1283
16th to endNight
26%8%46%5%3345%6%26%
1266
July1st to 15thNight
26%7%35%5%2445%7%26%
1440
16th to endNight
28%7%36%324448%26%
1515
August1st to 15thNight
22%8%35%6%25%5%5%6%27%
1440
16th to endNight
25%7%35%424346%30%
1816
September1st to 15thNight
31%7%2443435%6%26%
1800
16th to endNight
26%10%36%5%24347%26%
1968
October1st to 15thNight
26%9%47%434446%23%
2130
16th to endNight
32%16%47%423236%15%
2493
November1st to 15thNight
28%18%5%8%5%2334414%
2532
16th to endNight
27%22%8%10%6%332338%
2781
December1st to 15thNight
25%23%9%14%7%322225%
2700
16th to endNight
22%23%11%14%8%222235%
2814

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
89%15%3
1433
16th to endDay
89%1341
1536
February1st to 15thDay
83%25%6%
1488
16th to endDay
78%27%8%3
1548
March1st to 15thDay
72%38%11%4
1800
16th to endDay
70%37%12%4
2221
April1st to 15thDay
68%29%13%5%
2153
16th to endDay
57%312%15%9%
2334
May1st to 15thDay
55%312%19%9%
2512
16th to endDay
60%413%16%5%
2622
June1st to 15thDay
58%5%14%15%5%
2676
16th to endDay
59%413%15%6%
2690
July1st to 15thDay
48%6%16%22%5%
2372
16th to endDay
58%315%19%3
2486
August1st to 15thDay
56%417%17%3
2506
16th to endDay
57%419%15%3
2383
September1st to 15thDay
59%314%17%4
2160
16th to endDay
62%412%15%4
1992
October1st to 15thDay
61%312%15%5%
1828
16th to endDay
75%29%9%3
1731
November1st to 15thDay
76%36%10%2
1653
16th to endDay
79%46%7%1
1502
December1st to 15thDay
87%25%5%
1260
16th to endDay
84%25%5%1
1407
January1st to 15thNight
87%244
2506
16th to endNight
87%2341
2688
February1st to 15thNight
88%144
2374
16th to endNight
76%28%9%3
1925
March1st to 15thNight
70%38%12%4
2160
16th to endNight
69%39%11%5%
2001
April1st to 15thNight
70%29%11%4
1796
16th to endNight
58%312%15%8%
1624
May1st to 15thNight
52%213%23%6%1
1440
16th to endNight
60%412%17%5%
1496
June1st to 15thNight
62%412%15%4
1283
16th to endNight
59%5%11%17%5%
1266
July1st to 15thNight
57%416%17%4
1360
16th to endNight
57%412%20%5%
1419
August1st to 15thNight
56%5%17%15%3
1429
16th to endNight
54%5%18%17%4
1816
September1st to 15thNight
58%415%16%5%
1800
16th to endNight
57%417%15%5%
1968
October1st to 15thNight
60%6%11%13%6%
2130
16th to endNight
71%211%11%2
2493
November1st to 15thNight
72%49%11%2
2532
16th to endNight
80%37%6%2
2781
December1st to 15thNight
86%25%41
2700
16th to endNight
85%25%41
2814

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
21%39%25%11%11
240
16th to endDay
22%28%26%16%41
256
February1st to 15thDay
19%33%28%9%7%1
236
16th to endDay
26%28%21%12%5%4
212
March1st to 15thDay
22%28%23%14%9%2
240
16th to endDay
23%30%21%13%7%2
284
April1st to 15thDay
35%24%20%12%5%1
270
16th to endDay
25%23%21%18%9%2
408
May1st to 15thDay
27%19%16%21%8%5%
468
16th to endDay
33%15%17%18%10%3
519
June1st to 15thDay
30%17%14%23%11%2
495
16th to endDay
30%17%20%17%9%3
495
July1st to 15thDay
26%11%21%24%13%2
475
16th to endDay
28%15%16%21%15%1
514
August1st to 15thDay
25%11%19%26%13%3
493
16th to endDay
27%9%21%24%13%3
397
September1st to 15thDay
30%14%29%19%6%
315
16th to endDay
30%15%25%19%6%1
272
October1st to 15thDay
32%16%22%16%8%2
270
16th to endDay
40%20%15%15%42
288
November1st to 15thDay
34%22%18%14%8%1
280
16th to endDay
33%22%20%14%8%
285
December1st to 15thDay
29%30%26%8%4
240
16th to endDay
28%33%18%12%5%1
256
January1st to 15thNight
26%36%23%10%2
750
16th to endNight
18%34%27%15%4
800
February1st to 15thNight
20%34%24%14%5%
719
16th to endNight
24%26%24%14%8%2
631
March1st to 15thNight
20%30%22%19%6%
720
16th to endNight
21%29%21%19%7%1
633
April1st to 15thNight
29%24%20%16%8%
539
16th to endNight
21%25%19%24%6%1
540
May1st to 15thNight
25%20%14%24%12%2
540
16th to endNight
30%19%15%25%8%1
561
June1st to 15thNight
29%18%15%24%10%
540
16th to endNight
25%18%13%27%12%2
540
July1st to 15thNight
27%15%14%26%14%1
510
16th to endNight
25%18%11%26%16%
565
August1st to 15thNight
23%12%11%32%17%1
539
16th to endNight
27%11%16%27%14%2
573
September1st to 15thNight
32%14%18%24%8%
540
16th to endNight
27%15%26%24%6%
538
October1st to 15thNight
31%18%20%20%8%1
690
16th to endNight
37%20%20%17%4
815
November1st to 15thNight
32%23%22%13%6%
805
16th to endNight
34%26%18%15%4
824
December1st to 15thNight
28%35%19%13%3
750
16th to endNight
28%31%21%12%41
800
Page generated at 2017-12-01 13:43:36. Version ac04

Copyright 2017 A. Danko


Stephenville Clear Sky Chart |Charts Home