Irving Nature Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Irving Nature Park clear sky chart from 2005-11-05 to 2017-09-21.

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
26%
14904
14%
46794
6%
14861
35%
14861
16%
33155

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
17%
742
14%
2637
2%
738
32%
738
13%
1813
January16th to endNight
14%
768
16%
2555
2%
768
31%
768
13%
1783
February1st to 15thNight
16%
704
13%
2286
3%
701
28%
701
14%
1608
February16th to endNight
20%
631
13%
1984
3%
631
31%
631
14%
1431
March1st to 15thNight
19%
720
15%
2025
4%
720
31%
720
17%
1467
March16th to endNight
24%
768
17%
2112
6%
768
33%
768
19%
1496
April1st to 15thNight
23%
598
15%
1784
6%
598
32%
598
16%
1324
April16th to endNight
25%
540
15%
1620
6%
540
33%
540
19%
1154
May1st to 15thNight
29%
540
11%
1596
6%
540
34%
540
15%
1204
May16th to endNight
29%
561
10%
1496
5%
560
35%
560
16%
1163
June1st to 15thNight
29%
363
8%
1263
6%
363
33%
363
12%
959
June16th to endNight
36%
360
8%
1260
7%
360
39%
360
12%
938
July1st to 15thNight
42%
340
8%
1190
9%
340
44%
340
15%
836
July16th to endNight
36%
486
8%
1466
7%
455
38%
455
14%
1107
August1st to 15thNight
45%
539
10%
1608
9%
535
46%
535
18%
1181
August16th to endNight
43%
573
18%
1725
11%
573
47%
573
23%
1152
September1st to 15thNight
37%
609
15%
1869
10%
609
42%
609
24%
1229
September16th to endNight
39%
681
24%
1880
14%
681
47%
681
30%
1198
October1st to 15thNight
33%
660
20%
1966
9%
660
43%
660
23%
1291
October16th to endNight
23%
704
16%
2161
5%
704
35%
704
18%
1490
November1st to 15thNight
28%
717
15%
2376
8%
717
37%
717
19%
1603
November16th to endNight
24%
750
15%
2520
6%
750
35%
750
14%
1756
December1st to 15thNight
12%
750
14%
2535
2%
750
25%
750
11%
1851
December16th to endNight
11%
800
13%
2880
3%
800
24%
800
10%
2121

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
21%7%35%424446%33%
48072
Night
22%8%35%424446%32%
46965
TransparencyDay
51%411%21%10%1
47761
Night
52%410%20%10%
46794
SeeingDay
28%10%27%23%9%1
6949
Night
27%11%28%23%8%
14904

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
15%12%36%325%45%7%33%
1300
16th to endDay
17%11%35%42345%8%32%
1668
February1st to 15thDay
14%11%26%7%35%5%6%7%30%
1575
16th to endDay
13%11%47%5%345%47%32%
1488
March1st to 15thDay
19%9%46%5%34446%30%
1924
16th to endDay
16%9%35%5%34446%36%
2112
April1st to 15thDay
22%9%36%5%33335%33%
2162
16th to endDay
24%5%25%5%23447%34%
2340
May1st to 15thDay
25%8%35%5%24446%28%
2353
16th to endDay
27%6%35%42445%7%27%
2624
June1st to 15thDay
27%8%37%5%35%345%26%
2700
16th to endDay
28%6%35%42345%7%29%
2700
July1st to 15thDay
21%6%25%435%45%7%33%
2700
16th to endDay
21%7%35%5%245%5%7%30%
2583
August1st to 15thDay
19%7%35%43445%7%33%
2340
16th to endDay
16%5%245%25%45%7%39%
2477
September1st to 15thDay
20%5%1432345%6%42%
2090
16th to endDay
19%413433346%47%
1873
October1st to 15thDay
20%5%14424345%41%
1664
16th to endDay
21%7%36%5%24445%34%
1711
November1st to 15thDay
23%6%25%5%1335%6%35%
1482
16th to endDay
21%7%26%5%34448%31%
1440
December1st to 15thDay
28%8%2432345%7%29%
1422
16th to endDay
25%9%36%5%23337%28%
1344
January1st to 15thNight
18%9%35%435%45%8%33%
2637
16th to endNight
16%10%36%4345%5%8%31%
2555
February1st to 15thNight
17%9%35%435%6%6%8%30%
2285
16th to endNight
16%12%47%5%25%5%45%30%
1984
March1st to 15thNight
19%9%36%425%45%5%32%
2013
16th to endNight
18%9%35%434446%35%
2112
April1st to 15thNight
25%8%25%5%34445%30%
1784
16th to endNight
24%8%25%423446%32%
1620
May1st to 15thNight
26%8%35%5%34446%26%
1596
16th to endNight
26%7%35%5%44438%26%
1494
June1st to 15thNight
33%9%245%2335%7%21%
1263
16th to endNight
29%8%35%5%23426%26%
1260
July1st to 15thNight
24%8%36%5%2435%7%28%
1260
16th to endNight
25%9%45%5%25%5%47%24%
1570
August1st to 15thNight
23%8%35%4245%5%7%29%
1620
16th to endNight
18%8%245%1445%7%38%
1725
September1st to 15thNight
22%6%24422447%37%
1869
16th to endNight
18%5%14323345%46%
1880
October1st to 15thNight
22%5%24424335%40%
1966
16th to endNight
23%7%245%23335%36%
2161
November1st to 15thNight
22%5%25%5%23446%36%
2376
16th to endNight
22%7%35%4335%45%35%
2520
December1st to 15thNight
28%10%25%323345%29%
2535
16th to endNight
25%11%34423347%28%
2880

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
50%5%15%19%8%1
1301
16th to endDay
50%310%22%11%
1668
February1st to 15thDay
53%412%19%8%1
1578
16th to endDay
51%314%20%8%1
1488
March1st to 15thDay
54%310%20%10%1
1935
16th to endDay
48%29%21%14%2
2112
April1st to 15thDay
53%27%19%13%2
2162
16th to endDay
49%310%19%14%2
2340
May1st to 15thDay
57%38%19%10%
2353
16th to endDay
55%5%12%20%5%
2628
June1st to 15thDay
60%310%16%7%1
2700
16th to endDay
56%410%18%8%
2700
July1st to 15thDay
48%6%15%19%10%
2541
16th to endDay
52%7%12%20%6%
2425
August1st to 15thDay
49%6%11%23%9%
2327
16th to endDay
41%6%14%25%11%
2477
September1st to 15thDay
42%412%24%13%1
2090
16th to endDay
40%38%29%16%1
1873
October1st to 15thDay
43%39%31%11%
1664
16th to endDay
50%410%23%10%
1711
November1st to 15thDay
50%413%17%13%
1482
16th to endDay
53%412%17%11%
1440
December1st to 15thDay
55%411%21%7%
1422
16th to endDay
58%49%16%10%
1344
January1st to 15thNight
51%413%19%9%1
2637
16th to endNight
51%410%23%9%
2555
February1st to 15thNight
51%5%12%19%9%
2286
16th to endNight
55%211%17%10%1
1984
March1st to 15thNight
53%310%18%12%1
2025
16th to endNight
50%39%19%15%1
2112
April1st to 15thNight
56%38%14%13%3
1784
16th to endNight
52%39%18%13%1
1620
May1st to 15thNight
59%49%16%8%1
1596
16th to endNight
58%5%10%16%7%1
1496
June1st to 15thNight
62%410%17%41
1263
16th to endNight
61%38%17%8%
1260
July1st to 15thNight
54%412%18%9%
1190
16th to endNight
57%6%11%16%6%
1466
August1st to 15thNight
53%6%11%20%8%
1608
16th to endNight
46%411%26%10%
1725
September1st to 15thNight
46%210%24%13%
1869
16th to endNight
40%29%29%16%
1880
October1st to 15thNight
46%210%26%12%1
1966
16th to endNight
50%310%23%12%
2161
November1st to 15thNight
49%414%19%11%
2376
16th to endNight
51%5%11%19%11%
2520
December1st to 15thNight
57%48%21%7%
2535
16th to endNight
58%49%18%8%
2880

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
23%26%21%28%
60
16th to endDay
20%18%40%17%2
196
February1st to 15thDay
21%20%35%18%4
236
16th to endDay
20%16%33%22%6%
224
March1st to 15thDay
24%18%34%18%3
270
16th to endDay
26%14%30%18%8%1
288
April1st to 15thDay
32%12%30%17%6%
270
16th to endDay
29%7%31%21%7%2
270
May1st to 15thDay
34%8%28%18%8%1
309
16th to endDay
34%9%25%20%9%2
519
June1st to 15thDay
31%7%27%23%10%
495
16th to endDay
32%6%23%23%10%2
495
July1st to 15thDay
29%420%28%13%2
475
16th to endDay
30%6%21%26%11%2
378
August1st to 15thDay
26%420%32%14%1
313
16th to endDay
21%5%22%31%15%2
332
September1st to 15thDay
26%424%31%11%1
315
16th to endDay
22%429%28%12%3
275
October1st to 15thDay
25%10%25%22%12%3
228
16th to endDay
25%16%32%19%41
240
November1st to 15thDay
25%12%28%22%7%2
235
16th to endDay
27%20%29%15%6%
240
December1st to 15thDay
32%13%34%14%4
222
16th to endDay
35%20%34%7%1
64
January1st to 15thNight
24%18%33%19%4
742
16th to endNight
23%18%37%16%4
768
February1st to 15thNight
24%15%39%17%2
704
16th to endNight
25%15%31%22%4
631
March1st to 15thNight
25%12%34%23%3
720
16th to endNight
23%13%31%23%7%
768
April1st to 15thNight
30%8%31%23%6%
598
16th to endNight
28%6%33%24%5%
540
May1st to 15thNight
32%5%24%26%9%1
540
16th to endNight
30%8%24%27%8%
561
June1st to 15thNight
38%6%17%26%10%
363
16th to endNight
35%314%32%13%1
360
July1st to 15thNight
31%413%33%16%1
340
16th to endNight
29%6%16%29%17%
486
August1st to 15thNight
26%315%33%18%1
539
16th to endNight
23%321%33%15%1
573
September1st to 15thNight
27%424%28%13%1
609
16th to endNight
22%6%26%28%14%1
681
October1st to 15thNight
24%8%28%25%10%2
660
16th to endNight
28%13%31%21%5%
704
November1st to 15thNight
24%10%29%25%9%1
717
16th to endNight
26%16%28%20%7%
750
December1st to 15thNight
34%16%31%14%3
750
16th to endNight
34%17%32%13%2
800
Page generated at 2017-09-22 08:35:37. Version ac04

Copyright 2017 A. Danko


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