Pioneer Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pioneer Observatory clear sky chart from 2005-11-05 to 2017-10-06.

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
33%
16021
17%
47042
10%
15980
41%
15980
20%
31700

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
18%
900
13%
2506
4%
895
25%
895
14%
1852
January16th to endNight
18%
960
12%
2667
4%
960
24%
960
14%
2027
February1st to 15thNight
19%
770
14%
2181
3%
770
27%
770
16%
1577
February16th to endNight
23%
631
18%
1893
7%
631
33%
631
15%
1353
March1st to 15thNight
21%
720
13%
2160
7%
720
26%
720
15%
1552
March16th to endNight
27%
645
15%
2019
8%
645
35%
645
16%
1420
April1st to 15thNight
27%
539
15%
1797
10%
539
36%
539
17%
1196
April16th to endNight
29%
540
18%
1724
7%
540
41%
540
17%
1160
May1st to 15thNight
33%
540
16%
1620
9%
540
39%
540
19%
1119
May16th to endNight
42%
561
17%
1506
8%
561
49%
561
26%
989
June1st to 15thNight
44%
540
17%
1440
8%
540
51%
540
29%
910
June16th to endNight
44%
540
17%
1440
8%
540
50%
540
27%
951
July1st to 15thNight
59%
510
17%
1360
12%
510
62%
510
34%
828
July16th to endNight
60%
564
22%
1417
17%
531
67%
531
38%
832
August1st to 15thNight
68%
539
22%
1584
20%
536
71%
536
36%
897
August16th to endNight
62%
573
21%
1910
19%
573
69%
573
32%
1077
September1st to 15thNight
56%
558
28%
1818
26%
558
62%
558
32%
1012
September16th to endNight
57%
717
28%
1980
20%
717
63%
717
34%
1181
October1st to 15thNight
46%
684
26%
1941
19%
684
53%
684
30%
1193
October16th to endNight
26%
704
17%
2249
9%
704
36%
704
19%
1480
November1st to 15thNight
28%
700
24%
2276
15%
700
40%
700
21%
1419
November16th to endNight
20%
726
18%
2346
8%
726
32%
726
16%
1581
December1st to 15thNight
17%
900
13%
2520
4%
900
25%
900
13%
1887
December16th to endNight
12%
960
10%
2688
1%
960
19%
960
9%
2207

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
13%8%36%5%35%5%5%7%36%
48164
Night
14%7%36%5%24446%39%
47210
Cloud CoverDay
13%7%36%5%35%45%7%36%
48173
Night
14%7%36%5%24446%39%
47215
TransparencyDay
46%6%11%21%12%1
47850
Night
45%5%11%22%13%2
47042
SeeingDay
13%12%23%27%16%5%
6032
Night
15%21%23%25%12%1
16026

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
16%15%47%5%35%5%5%6%23%
1432
16th to endDay
13%16%8%9%5%34435%25%
1557
February1st to 15thDay
14%14%6%7%5%35%35%5%27%
1681
16th to endDay
15%10%5%9%6%44436%30%
1580
March1st to 15thDay
16%12%5%6%6%2445%6%28%
1790
16th to endDay
18%9%46%5%3445%7%30%
2214
April1st to 15thDay
18%10%36%6%24436%32%
2151
16th to endDay
19%7%245%345%5%6%34%
2235
May1st to 15thDay
18%9%36%5%3445%7%30%
2331
16th to endDay
12%5%36%6%35%45%7%40%
2606
June1st to 15thDay
10%425%4345%5%8%44%
2520
16th to endDay
9%435%5%36%6%6%9%37%
2520
July1st to 15thDay
7%425%5%36%5%5%10%43%
2520
16th to endDay
5%425%6%36%6%7%9%41%
2655
August1st to 15thDay
6%415%5%36%5%7%8%44%
2364
16th to endDay
8%426%6%35%5%6%8%42%
2292
September1st to 15thDay
13%3135%2445%8%46%
2130
16th to endDay
8%5%245%245%6%9%44%
1980
October1st to 15thDay
13%7%25%434447%42%
1814
16th to endDay
18%8%35%5%235%5%6%34%
1623
November1st to 15thDay
14%7%24423446%43%
1582
16th to endDay
17%8%46%424346%35%
1611
December1st to 15thDay
18%12%5%8%5%35%436%26%
1440
16th to endDay
21%15%6%8%5%2344422%
1536
January1st to 15thNight
18%11%47%5%24436%31%
2506
16th to endNight
14%11%7%8%6%34445%28%
2667
February1st to 15thNight
16%11%47%5%24345%34%
2179
16th to endNight
17%10%5%7%5%33446%33%
1893
March1st to 15thNight
16%12%46%5%3434434%
2147
16th to endNight
15%8%37%5%35%5%6%6%33%
2019
April1st to 15thNight
16%7%36%5%2435%6%37%
1797
16th to endNight
18%7%25%5%34345%38%
1724
May1st to 15thNight
18%7%245%2446%8%35%
1620
16th to endNight
10%5%345%245%7%7%43%
1504
June1st to 15thNight
10%426%423447%49%
1440
16th to endNight
8%5%347%25%47%8%42%
1440
July1st to 15thNight
6%223435%46%8%50%
1440
16th to endNight
5%31443437%10%49%
1513
August1st to 15thNight
3313445%46%10%52%
1593
16th to endNight
9%323325%448%51%
1910
September1st to 15thNight
11%41432345%6%53%
1818
16th to endNight
7%4145%2445%7%50%
1980
October1st to 15thNight
12%414424337%50%
1941
16th to endNight
20%8%35%423345%40%
2249
November1st to 15thNight
13%6%35%424347%44%
2276
16th to endNight
18%8%35%5%23446%37%
2346
December1st to 15thNight
20%10%47%5%23445%31%
2520
16th to endNight
22%15%5%8%6%3433421%
2688

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
15%15%48%5%46%5%5%6%23%
1432
16th to endDay
13%16%8%8%6%24435%25%
1557
February1st to 15thDay
14%14%6%7%5%3435%6%27%
1681
16th to endDay
14%11%49%5%44346%30%
1580
March1st to 15thDay
17%12%5%6%6%3445%6%28%
1800
16th to endDay
18%9%45%5%3445%7%30%
2213
April1st to 15thDay
18%10%36%5%24336%32%
2151
16th to endDay
19%7%245%3445%6%34%
2235
May1st to 15thDay
18%8%37%5%345%5%7%30%
2331
16th to endDay
12%5%36%6%35%45%7%40%
2606
June1st to 15thDay
10%425%5%34448%44%
2520
16th to endDay
9%435%5%37%6%7%9%37%
2520
July1st to 15thDay
7%5%245%36%5%5%9%43%
2520
16th to endDay
5%425%6%36%6%7%9%41%
2655
August1st to 15thDay
6%425%6%35%5%7%8%44%
2364
16th to endDay
8%425%6%35%5%5%8%42%
2292
September1st to 15thDay
13%31342445%8%46%
2130
16th to endDay
8%5%25%5%3447%8%44%
1980
October1st to 15thDay
13%6%24434447%42%
1814
16th to endDay
18%8%36%5%2345%6%33%
1623
November1st to 15thDay
15%7%24423446%43%
1582
16th to endDay
17%8%46%5%24346%35%
1611
December1st to 15thDay
18%12%5%8%5%35%5%36%25%
1440
16th to endDay
21%15%6%8%5%235%4422%
1536
January1st to 15thNight
18%11%47%5%24436%31%
2506
16th to endNight
14%11%7%8%6%34445%27%
2667
February1st to 15thNight
15%11%47%5%24345%34%
2172
16th to endNight
17%10%47%5%33346%32%
1893
March1st to 15thNight
16%11%46%5%3434434%
2160
16th to endNight
15%8%37%5%25%5%6%6%33%
2019
April1st to 15thNight
16%7%36%5%2436%6%37%
1797
16th to endNight
18%7%25%5%34345%38%
1724
May1st to 15thNight
18%7%2442445%7%35%
1619
16th to endNight
10%435%5%245%6%8%43%
1504
June1st to 15thNight
10%425%423448%49%
1440
16th to endNight
8%5%246%35%46%8%42%
1440
July1st to 15thNight
6%323435%46%8%50%
1440
16th to endNight
42245%25%47%10%49%
1513
August1st to 15thNight
33144345%6%9%52%
1593
16th to endNight
9%313325%45%8%51%
1910
September1st to 15thNight
11%41432245%6%53%
1818
16th to endNight
7%4245%3445%7%50%
1980
October1st to 15thNight
12%424424337%49%
1941
16th to endNight
20%8%25%423345%40%
2249
November1st to 15thNight
13%6%36%423347%43%
2276
16th to endNight
18%8%36%5%23446%37%
2346
December1st to 15thNight
20%10%48%5%23445%31%
2520
16th to endNight
21%15%5%8%6%34335%21%
2688

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
59%6%12%13%8%
1433
16th to endDay
61%5%10%15%6%
1557
February1st to 15thDay
58%5%10%17%8%1
1683
16th to endDay
55%5%10%21%5%1
1580
March1st to 15thDay
56%6%11%18%7%
1800
16th to endDay
54%5%12%21%5%
2214
April1st to 15thDay
51%5%8%21%12%
2151
16th to endDay
49%6%12%16%10%3
2235
May1st to 15thDay
52%6%11%21%6%
2331
16th to endDay
42%7%10%21%15%2
2610
June1st to 15thDay
36%7%10%24%18%1
2520
16th to endDay
38%9%13%20%15%2
2520
July1st to 15thDay
36%7%11%25%16%2
2371
16th to endDay
35%8%16%23%14%2
2488
August1st to 15thDay
33%8%13%25%16%1
2349
16th to endDay
37%7%11%23%16%3
2292
September1st to 15thDay
35%6%11%24%19%3
2130
16th to endDay
35%5%10%27%19%1
1980
October1st to 15thDay
40%7%9%26%14%1
1814
16th to endDay
49%5%13%21%9%1
1623
November1st to 15thDay
41%412%23%15%2
1582
16th to endDay
50%413%22%8%
1611
December1st to 15thDay
59%5%11%18%6%
1440
16th to endDay
65%5%10%12%6%
1536
January1st to 15thNight
54%412%17%9%
2506
16th to endNight
57%413%16%7%
2667
February1st to 15thNight
52%411%20%9%1
2181
16th to endNight
53%411%20%9%1
1893
March1st to 15thNight
53%5%10%19%9%1
2160
16th to endNight
48%7%13%20%8%1
2019
April1st to 15thNight
46%5%10%20%15%1
1797
16th to endNight
47%5%9%20%13%4
1724
May1st to 15thNight
47%5%11%23%11%
1620
16th to endNight
37%7%13%19%17%3
1506
June1st to 15thNight
34%6%10%25%19%3
1440
16th to endNight
38%6%12%22%18%1
1440
July1st to 15thNight
30%7%13%26%19%3
1360
16th to endNight
26%6%16%27%18%4
1417
August1st to 15thNight
26%7%16%27%20%2
1584
16th to endNight
30%6%12%26%19%5%
1910
September1st to 15thNight
30%5%10%25%24%4
1818
16th to endNight
31%5%9%28%21%3
1980
October1st to 15thNight
35%49%27%21%1
1941
16th to endNight
46%311%23%12%1
2249
November1st to 15thNight
41%48%24%17%3
2276
16th to endNight
48%413%23%10%
2346
December1st to 15thNight
56%410%19%8%
2520
16th to endNight
67%48%13%4
2688

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
24%8%36%24%5%
90
16th to endDay
11%11%33%35%7%1
96
February1st to 15thDay
18%12%48%18%1
90
16th to endDay
11%13%37%22%12%3
81
March1st to 15thDay
30%13%31%18%6%
90
16th to endDay
24%17%26%22%8%
257
April1st to 15thDay
21%20%24%23%9%1
270
16th to endDay
19%18%27%19%10%4
270
May1st to 15thDay
20%18%27%20%9%3
288
16th to endDay
13%16%26%28%11%2
506
June1st to 15thDay
10%15%22%31%17%3
495
16th to endDay
11%16%28%29%11%3
495
July1st to 15thDay
8%11%21%30%20%8%
475
16th to endDay
7%13%17%32%21%7%
515
August1st to 15thDay
7%7%11%34%24%14%
376
16th to endDay
8%7%14%27%28%14%
332
September1st to 15thDay
13%6%12%30%28%9%
315
16th to endDay
9%7%15%27%28%11%
314
October1st to 15thDay
19%6%21%28%18%5%
215
16th to endDay
21%6%36%30%5%
96
November1st to 15thDay
6%10%20%36%20%6%
90
16th to endDay
24%13%38%17%5%
90
December1st to 15thDay
15%15%41%23%31
90
16th to endDay
29%14%48%43
96
January1st to 15thNight
18%28%30%18%3
900
16th to endNight
16%26%29%23%3
960
February1st to 15thNight
19%23%31%20%4
773
16th to endNight
18%24%26%25%4
631
March1st to 15thNight
17%25%30%19%6%
720
16th to endNight
15%23%27%24%7%1
645
April1st to 15thNight
18%23%27%23%6%
539
16th to endNight
19%21%25%24%9%1
540
May1st to 15thNight
19%20%23%24%12%
540
16th to endNight
11%19%20%31%15%1
563
June1st to 15thNight
9%18%18%37%14%
540
16th to endNight
9%17%22%32%17%1
540
July1st to 15thNight
6%12%14%38%25%2
510
16th to endNight
5%17%10%37%24%4
564
August1st to 15thNight
5%9%9%39%29%6%
539
16th to endNight
9%10%11%30%32%5%
573
September1st to 15thNight
12%12%12%30%27%4
558
16th to endNight
8%12%15%29%29%5%
717
October1st to 15thNight
14%14%20%32%16%2
684
16th to endNight
21%19%29%20%7%
704
November1st to 15thNight
16%23%28%20%9%1
700
16th to endNight
18%28%28%17%6%
726
December1st to 15thNight
24%27%26%17%3
900
16th to endNight
24%27%29%16%2
960
Page generated at 2017-10-07 13:07:45. Version ac04

Copyright 2017 A. Danko


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