Halliday Parkwood Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Halliday Parkwood Observatory clear sky chart from 2005-11-05 to 2017-09-22.

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
61%
15908
21%
46996
17%
15869
65%
15869
30%
29523

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
46%
718
21%
2327
16%
716
55%
716
26%
1451
January16th to endNight
44%
768
23%
2443
18%
768
52%
768
28%
1480
February1st to 15thNight
47%
701
24%
2106
17%
700
55%
700
32%
1269
February16th to endNight
45%
631
24%
1850
14%
631
54%
631
30%
1148
March1st to 15thNight
53%
720
29%
1980
18%
720
62%
720
40%
1138
March16th to endNight
57%
768
26%
2112
20%
768
61%
768
40%
1213
April1st to 15thNight
59%
718
25%
1976
18%
718
64%
718
42%
1116
April16th to endNight
62%
715
27%
1844
18%
715
66%
715
44%
1074
May1st to 15thNight
74%
539
25%
1619
20%
539
78%
539
42%
882
May16th to endNight
77%
561
24%
1682
20%
561
78%
561
36%
1001
June1st to 15thNight
71%
540
13%
1620
11%
540
71%
540
24%
1122
June16th to endNight
72%
540
9%
1620
8%
540
73%
540
22%
1162
July1st to 15thNight
74%
510
8%
1530
7%
510
74%
510
20%
1111
July16th to endNight
76%
564
6%
1595
6%
531
77%
531
21%
1153
August1st to 15thNight
76%
539
6%
1609
6%
536
76%
536
22%
1143
August16th to endNight
69%
699
10%
2034
10%
699
69%
699
20%
1458
September1st to 15thNight
66%
720
9%
1980
8%
720
66%
720
20%
1437
September16th to endNight
62%
685
14%
1892
14%
685
62%
685
19%
1388
October1st to 15thNight
69%
660
25%
1869
26%
660
70%
660
33%
1138
October16th to endNight
63%
704
28%
2112
27%
704
67%
704
34%
1249
November1st to 15thNight
63%
700
29%
2101
25%
700
69%
700
38%
1182
November16th to endNight
54%
720
27%
2259
22%
720
62%
720
32%
1313
December1st to 15thNight
54%
720
28%
2340
26%
720
60%
720
29%
1394
December16th to endNight
55%
768
24%
2496
22%
768
61%
768
29%
1501

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
8%5%26%6%46%6%6%8%37%
47871
Night
8%425%5%35%5%6%9%44%
47202
TransparencyDay
41%9%13%16%13%6%
47572
Night
34%9%15%19%14%6%
47005
SeeingDay
9%211%19%26%30%
5763
Night
9%216%32%28%8%
15916

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 15thDay
11%6%35%4345%5%6%42%
1611
16th to endDay
10%425%425%5%6%6%45%
1779
February1st to 15thDay
13%425%5%2445%5%45%
1750
16th to endDay
10%5%2443445%6%48%
1622
March1st to 15thDay
7%3245%3346%8%50%
1980
16th to endDay
7%5%25%4245%5%6%49%
2111
April1st to 15thDay
6%424435%46%8%49%
1972
16th to endDay
6%413435%5%5%9%50%
2122
May1st to 15thDay
5%314436%5%6%8%50%
2331
16th to endDay
7%3247%46%5%8%9%38%
2431
June1st to 15thDay
9%5%27%8%5%9%7%7%10%26%
2340
16th to endDay
8%6%38%8%5%8%8%8%9%24%
2340
July1st to 15thDay
9%6%37%9%5%8%7%8%9%22%
2340
16th to endDay
8%7%49%8%6%8%7%9%9%19%
2465
August1st to 15thDay
6%6%38%9%6%8%8%8%11%20%
2340
16th to endDay
10%6%47%9%5%9%7%8%9%22%
2151
September1st to 15thDay
9%6%38%9%5%7%7%8%9%23%
1980
16th to endDay
11%7%38%7%5%7%6%6%8%25%
1881
October1st to 15thDay
8%6%36%7%35%5%5%9%38%
1760
16th to endDay
9%4236%25%5%5%6%47%
1760
November1st to 15thDay
6%41443445%8%51%
1757
16th to endDay
8%5%35%5%35%347%47%
1700
December1st to 15thDay
10%6%35%5%145%5%9%41%
1620
16th to endDay
7%5%25%5%36%5%6%7%44%
1728
January1st to 15thNight
11%6%35%5%3446%9%40%
2327
16th to endNight
14%4234235%5%7%45%
2443
February1st to 15thNight
10%5%24423445%50%
2103
16th to endNight
8%5%25%42445%6%47%
1850
March1st to 15thNight
6%3135%245%5%7%55%
1980
16th to endNight
7%41442335%7%55%
2112
April1st to 15thNight
6%313323449%55%
1976
16th to endNight
6%32342346%7%56%
1844
May1st to 15thNight
43233335%5%9%56%
1619
16th to endNight
5%3244345%5%8%51%
1682
June1st to 15thNight
9%425%6%47%6%7%10%35%
1620
16th to endNight
7%5%36%6%36%7%8%12%32%
1620
July1st to 15thNight
6%4247%48%7%7%14%32%
1620
16th to endNight
4326%6%5%8%8%9%11%31%
1703
August1st to 15thNight
4426%7%5%7%7%9%15%30%
1620
16th to endNight
9%5%35%6%46%6%7%11%33%
2034
September1st to 15thNight
8%5%36%6%36%6%7%10%33%
1980
16th to endNight
8%7%36%7%5%6%6%7%9%29%
1892
October1st to 15thNight
7%6%2443445%8%49%
1869
16th to endNight
9%5%25%32435%6%51%
2112
November1st to 15thNight
5%42432345%8%53%
2101
16th to endNight
6%435%5%3446%7%48%
2259
December1st to 15thNight
10%425%4345%5%7%46%
2340
16th to endNight
8%5%24435%46%8%44%
2496

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
40%6%7%19%17%8%
1612
16th to endDay
36%5%7%16%22%10%
1779
February1st to 15thDay
39%5%6%13%20%14%
1752
16th to endDay
36%5%9%16%20%11%
1622
March1st to 15thDay
30%5%10%23%20%8%
1980
16th to endDay
34%5%11%19%18%9%
2112
April1st to 15thDay
29%7%11%19%22%8%
1972
16th to endDay
29%6%12%21%21%8%
2122
May1st to 15thDay
29%7%13%22%18%9%
2331
16th to endDay
37%8%16%19%14%3
2435
June1st to 15thDay
49%11%16%18%4
2340
16th to endDay
51%12%18%13%3
2340
July1st to 15thDay
52%14%21%10%1
2201
16th to endDay
52%16%18%10%1
2310
August1st to 15thDay
50%16%22%9%1
2327
16th to endDay
53%14%16%13%1
2151
September1st to 15thDay
52%14%18%9%4
1980
16th to endDay
52%11%13%13%7%2
1881
October1st to 15thDay
41%7%8%15%14%11%
1760
16th to endDay
36%5%8%14%23%12%
1760
November1st to 15thDay
30%5%9%21%21%11%
1757
16th to endDay
36%6%8%17%19%12%
1700
December1st to 15thDay
39%6%12%18%17%5%
1620
16th to endDay
35%6%12%20%15%8%
1728
January1st to 15thNight
39%5%10%19%15%8%
2327
16th to endNight
37%5%9%15%22%9%
2443
February1st to 15thNight
34%5%8%16%19%16%
2112
16th to endNight
35%6%10%15%22%8%
1850
March1st to 15thNight
26%6%11%25%21%8%
1980
16th to endNight
28%5%12%23%19%10%
2112
April1st to 15thNight
25%6%13%24%21%7%
1976
16th to endNight
26%5%13%24%21%7%
1844
May1st to 15thNight
23%7%18%25%17%7%
1620
16th to endNight
29%8%16%24%18%2
1684
June1st to 15thNight
40%12%20%22%5%
1620
16th to endNight
41%14%22%17%3
1620
July1st to 15thNight
40%17%26%13%2
1530
16th to endNight
39%17%28%11%2
1595
August1st to 15thNight
35%19%32%11%
1609
16th to endNight
41%15%23%17%2
2034
September1st to 15thNight
41%16%22%14%5%
1980
16th to endNight
45%12%15%17%6%2
1892
October1st to 15thNight
32%8%12%19%18%8%
1869
16th to endNight
33%5%9%13%27%10%
2112
November1st to 15thNight
28%5%10%23%21%9%
2101
16th to endNight
32%6%10%19%17%13%
2259
December1st to 15thNight
35%5%10%26%15%6%
2340
16th to endNight
34%7%12%22%14%8%
2496

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
17%5%26%27%14%7%
90
16th to endDay
11%14%33%19%16%4
96
February1st to 15thDay
6%15%22%26%21%7%
90
16th to endDay
13%8%26%28%21%1
123
March1st to 15thDay
7%428%33%24%2
270
16th to endDay
11%122%29%28%7%
288
April1st to 15thDay
8%418%30%30%8%
270
16th to endDay
6%15%20%37%18%
270
May1st to 15thDay
4211%23%34%23%
288
16th to endDay
5%15%16%32%38%
331
June1st to 15thDay
13%1314%23%42%
315
16th to endDay
6%38%20%60%
315
July1st to 15thDay
7%320%66%
305
16th to endDay
8%410%19%56%
326
August1st to 15thDay
9%5%9%18%56%
313
16th to endDay
12%37%20%54%
332
September1st to 15thDay
12%5%10%29%41%
315
16th to endDay
13%48%34%37%
278
October1st to 15thDay
9%110%25%37%15%
255
16th to endDay
8%18%29%31%11%
272
November1st to 15thDay
9%114%33%30%10%
265
16th to endDay
10%120%35%27%5%
170
December1st to 15thDay
6%5%36%33%14%3
90
16th to endDay
8%212%40%28%8%
96
January1st to 15thNight
14%6%26%34%17%
720
16th to endNight
16%6%28%36%11%
768
February1st to 15thNight
14%429%38%13%
704
16th to endNight
10%5%30%42%9%
631
March1st to 15thNight
9%5%27%42%14%
720
16th to endNight
8%424%42%18%1
768
April1st to 15thNight
7%224%44%19%1
718
16th to endNight
7%221%43%23%
715
May1st to 15thNight
5%110%48%30%3
540
16th to endNight
5%7%34%43%7%
563
June1st to 15thNight
11%6%25%40%15%
540
16th to endNight
9%216%43%27%
540
July1st to 15thNight
8%12%41%36%
510
16th to endNight
5%210%50%29%
564
August1st to 15thNight
5%18%50%33%
539
16th to endNight
10%413%40%30%
699
September1st to 15thNight
11%6%20%41%20%
720
16th to endNight
11%8%25%44%10%
685
October1st to 15thNight
8%110%35%38%5%
660
16th to endNight
11%215%35%32%3
704
November1st to 15thNight
7%319%39%27%3
700
16th to endNight
8%225%41%19%1
720
December1st to 15thNight
12%423%36%22%1
720
16th to endNight
10%422%38%22%1
768
Page generated at 2017-09-23 06:43:42. Version ac04

Copyright 2017 A. Danko


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