This page made possible by the sponsorship of: Fraser Valley Astronomers Society.

McDonald Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the McDonald Park clear sky chart from 2005-11-05 to 2017-09-10.

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
35%
14440
9%
46628
7%
14412
38%
14412
13%
34555

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
24%
750
10%
2686
9%
746
28%
746
9%
2149
January16th to endNight
28%
771
9%
2708
7%
771
31%
771
10%
2086
February1st to 15thNight
21%
700
5%
2294
3%
700
24%
700
7%
1872
February16th to endNight
28%
632
13%
2022
7%
632
36%
632
11%
1525
March1st to 15thNight
21%
720
4%
2085
3%
720
23%
720
9%
1716
March16th to endNight
23%
768
6%
2055
2%
768
25%
768
10%
1716
April1st to 15thNight
29%
719
5%
1799
3%
719
29%
719
12%
1479
April16th to endNight
30%
510
7%
1590
5%
510
33%
510
10%
1258
May1st to 15thNight
42%
359
11%
1440
16%
359
45%
359
14%
961
May16th to endNight
45%
374
5%
1496
8%
374
47%
374
12%
1046
June1st to 15thNight
46%
360
2%
1269
1%
360
46%
360
14%
913
June16th to endNight
47%
360
5%
1260
2%
360
48%
360
16%
859
July1st to 15thNight
64%
340
9%
1190
8%
340
65%
340
31%
641
July16th to endNight
66%
376
15%
1363
20%
354
74%
354
34%
646
August1st to 15thNight
71%
405
16%
1477
21%
403
72%
403
36%
707
August16th to endNight
65%
633
18%
1779
14%
633
67%
633
35%
1030
September1st to 15thNight
63%
700
19%
1750
11%
700
64%
700
38%
1068
September16th to endNight
46%
656
16%
1803
11%
656
49%
656
20%
1291
October1st to 15thNight
38%
660
11%
1980
10%
660
41%
660
18%
1390
October16th to endNight
31%
704
6%
2200
5%
704
34%
704
11%
1719
November1st to 15thNight
18%
700
5%
2444
3%
700
22%
700
6%
2062
November16th to endNight
20%
720
6%
2520
4%
720
24%
720
7%
2009
December1st to 15thNight
23%
723
8%
2538
4%
723
28%
723
9%
2003
December16th to endNight
15%
800
5%
2880
3%
800
18%
800
6%
2409

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
26%9%36%5%24345%28%
48021
Night
28%8%35%423345%29%
46784
Cloud CoverDay
25%9%36%5%24445%29%
48021
Night
27%9%35%5%24345%29%
46787
TransparencyDay
57%313%16%6%1
47681
Night
58%414%15%6%1
46628
SeeingDay
24%16%22%24%10%2
5993
Night
27%17%11%22%17%3
14446

By Month

Percentage Cloud Cover NW (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
40%9%35%42323419%
1253
16th to endDay
37%11%34323335%21%
1515
February1st to 15thDay
35%10%46%5%3433416%
1567
16th to endDay
28%12%45%5%35%33423%
1451
March1st to 15thDay
37%12%47%6%3433313%
1875
16th to endDay
31%14%48%6%35%34314%
2168
April1st to 15thDay
31%11%49%6%35%44414%
2149
16th to endDay
27%11%48%6%45%45%5%16%
2368
May1st to 15thDay
24%8%36%5%24445%29%
2511
16th to endDay
27%10%36%6%3445%5%22%
2615
June1st to 15thDay
30%9%46%5%33345%23%
2688
16th to endDay
23%9%36%5%35%435%27%
2700
July1st to 15thDay
13%6%23413345%51%
2700
16th to endDay
12%5%24423335%53%
2708
August1st to 15thDay
12%41342345%7%50%
2473
16th to endDay
13%5%24434347%46%
2423
September1st to 15thDay
13%6%25%42333451%
2097
16th to endDay
25%6%36%43443433%
1824
October1st to 15thDay
26%8%35%43435%430%
1650
16th to endDay
37%6%25%5%34246%20%
1672
November1st to 15thDay
46%9%25%5%3423412%
1411
16th to endDay
38%10%35%42433320%
1440
December1st to 15thDay
31%14%47%41333222%
1419
16th to endDay
40%13%48%42332214%
1344
January1st to 15thNight
42%9%2432222421%
2686
16th to endNight
35%12%3432333422%
2708
February1st to 15thNight
34%10%36%6%3433418%
2282
16th to endNight
28%10%36%5%3333427%
2022
March1st to 15thNight
36%10%46%424335%18%
2085
16th to endNight
33%11%47%5%3433317%
2051
April1st to 15thNight
26%12%36%6%35%45%5%19%
1799
16th to endNight
31%10%37%5%34435%21%
1590
May1st to 15thNight
19%5%37%5%345%45%34%
1439
16th to endNight
18%8%26%6%35%46%6%30%
1496
June1st to 15thNight
21%7%47%7%24445%31%
1269
16th to endNight
18%7%25%6%35%5%6%6%33%
1260
July1st to 15thNight
8%5%13323435%56%
1260
16th to endNight
9%212322336%62%
1458
August1st to 15thNight
9%21221235%6%60%
1485
16th to endNight
7%315%4345%5%8%51%
1779
September1st to 15thNight
10%34323346%55%
1750
16th to endNight
22%6%25%5%23445%36%
1803
October1st to 15thNight
24%6%25%424445%35%
1980
16th to endNight
34%9%27%5%23336%22%
2200
November1st to 15thNight
44%8%35%42334314%
2444
16th to endNight
39%9%35%42332421%
2520
December1st to 15thNight
35%11%3442333422%
2538
16th to endNight
41%13%36%42223216%
2880

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
38%10%46%32333320%
1253
16th to endDay
34%12%34323335%22%
1515
February1st to 15thDay
31%12%47%6%24335%17%
1567
16th to endDay
26%14%35%5%35%34423%
1451
March1st to 15thDay
32%14%39%6%3444313%
1875
16th to endDay
29%13%48%7%45%43314%
2168
April1st to 15thDay
28%15%47%6%35%44415%
2149
16th to endDay
25%12%48%6%45%45%417%
2368
May1st to 15thDay
23%8%35%6%25%445%29%
2511
16th to endDay
26%8%47%6%3445%5%23%
2615
June1st to 15thDay
30%8%47%5%23445%23%
2688
16th to endDay
22%9%47%6%345%45%27%
2700
July1st to 15thDay
13%6%2331335%5%51%
2700
16th to endDay
12%424323336%53%
2708
August1st to 15thDay
13%41342345%8%49%
2473
16th to endDay
12%5%25%42435%6%47%
2423
September1st to 15thDay
12%6%1442243452%
2097
16th to endDay
24%7%26%5%2343434%
1824
October1st to 15thDay
25%8%25%5%33445%30%
1650
16th to endDay
34%6%25%5%23446%22%
1672
November1st to 15thDay
44%9%26%433335%12%
1411
16th to endDay
35%11%46%32333220%
1440
December1st to 15thDay
28%14%48%5%2333323%
1419
16th to endDay
36%15%38%7%2332215%
1344
January1st to 15thNight
40%10%35%41222421%
2685
16th to endNight
33%12%35%423335%22%
2708
February1st to 15thNight
31%11%47%6%3433418%
2282
16th to endNight
26%11%345%34335%27%
2022
March1st to 15thNight
32%12%46%5%2434418%
2085
16th to endNight
30%14%46%6%3343417%
2055
April1st to 15thNight
24%12%48%6%34446%19%
1799
16th to endNight
28%9%48%5%35%44422%
1590
May1st to 15thNight
18%6%37%5%245%5%5%34%
1439
16th to endNight
20%7%26%6%3446%6%30%
1496
June1st to 15thNight
20%8%37%7%44445%29%
1269
16th to endNight
17%6%36%6%35%45%6%33%
1260
July1st to 15thNight
8%5%13324345%57%
1260
16th to endNight
10%213223335%61%
1458
August1st to 15thNight
8%31331225%7%60%
1485
16th to endNight
7%3146%2445%8%51%
1779
September1st to 15thNight
10%414323436%56%
1750
16th to endNight
20%6%25%5%34436%36%
1803
October1st to 15thNight
23%6%25%43445%434%
1980
16th to endNight
32%9%36%5%34345%22%
2200
November1st to 15thNight
42%9%35%42334414%
2444
16th to endNight
37%10%26%5%22335%21%
2520
December1st to 15thNight
31%11%35%42434422%
2538
16th to endNight
38%15%46%42222317%
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
69%39%10%6%
1253
16th to endDay
65%211%13%42
1515
February1st to 15thDay
70%5%9%7%6%1
1567
16th to endDay
63%311%15%5%
1451
March1st to 15thDay
74%39%9%1
1875
16th to endDay
74%310%10%
2168
April1st to 15thDay
72%410%10%1
2149
16th to endDay
67%412%10%4
2368
May1st to 15thDay
56%414%16%7%
2511
16th to endDay
61%5%17%13%1
2619
June1st to 15thDay
62%315%13%41
2688
16th to endDay
59%316%16%4
2700
July1st to 15thDay
35%415%28%12%2
2541
16th to endDay
32%317%31%12%2
2540
August1st to 15thDay
33%5%19%31%9%2
2456
16th to endDay
36%321%27%9%1
2423
September1st to 15thDay
35%317%21%19%3
2097
16th to endDay
53%313%16%10%1
1824
October1st to 15thDay
54%316%15%8%1
1650
16th to endDay
62%316%12%4
1672
November1st to 15thDay
76%38%8%11
1411
16th to endDay
69%29%10%7%1
1440
December1st to 15thDay
67%48%9%8%
1419
16th to endDay
76%26%9%31
1344
January1st to 15thNight
68%37%14%5%
2686
16th to endNight
64%212%12%42
2708
February1st to 15thNight
69%410%9%31
2294
16th to endNight
60%312%16%6%1
2022
March1st to 15thNight
68%314%10%2
2085
16th to endNight
70%314%11%1
2055
April1st to 15thNight
65%5%15%11%2
1799
16th to endNight
64%412%14%3
1590
May1st to 15thNight
50%417%18%7%1
1440
16th to endNight
52%7%22%13%4
1496
June1st to 15thNight
56%420%12%41
1269
16th to endNight
49%5%20%19%31
1260
July1st to 15thNight
30%417%28%16%1
1190
16th to endNight
25%318%32%16%3
1363
August1st to 15thNight
24%424%32%10%3
1477
16th to endNight
31%422%28%10%3
1779
September1st to 15thNight
30%417%22%20%3
1750
16th to endNight
50%413%19%8%3
1803
October1st to 15thNight
51%315%19%9%
1980
16th to endNight
64%315%12%4
2200
November1st to 15thNight
73%49%7%21
2444
16th to endNight
68%310%8%8%
2520
December1st to 15thNight
64%6%11%12%5%
2538
16th to endNight
73%39%7%5%1
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
6%10%28%26%21%6%
60
16th to endDay
45%117%14%17%4
64
February1st to 15thDay
39%18%18%14%7%1
227
16th to endDay
27%17%22%20%9%1
217
March1st to 15thDay
41%21%22%13%1
270
16th to endDay
33%21%23%17%4
288
April1st to 15thDay
34%21%21%12%8%1
269
16th to endDay
26%23%21%21%6%1
270
May1st to 15thDay
24%19%24%24%5%1
288
16th to endDay
27%17%14%23%12%4
330
June1st to 15thDay
22%20%20%25%9%2
483
16th to endDay
18%21%23%26%7%1
495
July1st to 15thDay
13%14%24%33%13%1
475
16th to endDay
9%16%25%32%11%4
377
August1st to 15thDay
12%9%19%32%18%7%
315
16th to endDay
11%12%25%30%12%6%
332
September1st to 15thDay
17%12%23%24%17%4
294
16th to endDay
22%12%22%27%12%2
255
October1st to 15thDay
31%10%22%24%8%1
255
16th to endDay
32%8%21%28%8%1
184
November1st to 15thDay
54%6%22%11%4
61
16th to endDay
33%5%21%21%11%6%
60
December1st to 15thDay
41%8%23%16%6%3
60
16th to endDay
37%323%21%10%3
64
January1st to 15thNight
35%20%13%14%13%1
750
16th to endNight
30%20%12%22%12%1
771
February1st to 15thNight
32%22%14%21%9%
704
16th to endNight
27%22%14%21%12%1
632
March1st to 15thNight
34%21%13%19%9%
720
16th to endNight
32%20%13%21%8%2
768
April1st to 15thNight
27%19%12%23%13%3
719
16th to endNight
30%19%8%28%11%2
510
May1st to 15thNight
19%19%8%27%21%4
360
16th to endNight
19%20%420%29%5%
375
June1st to 15thNight
18%18%6%24%26%5%
360
16th to endNight
15%20%5%26%28%3
360
July1st to 15thNight
9%13%6%22%40%7%
340
16th to endNight
9%17%220%38%12%
376
August1st to 15thNight
9%9%119%42%16%
405
16th to endNight
10%9%5%26%40%8%
633
September1st to 15thNight
11%10%7%28%32%10%
700
16th to endNight
24%11%7%26%25%4
656
October1st to 15thNight
26%12%14%24%18%3
660
16th to endNight
33%13%12%25%12%2
704
November1st to 15thNight
40%17%17%19%4
700
16th to endNight
37%22%11%15%9%2
720
December1st to 15thNight
33%21%16%23%5%
723
16th to endNight
39%21%16%18%4
800
Page generated at 2017-09-11 16:35:28. Version ac04

Copyright 2017 A. Danko


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