Powders Mill
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Powders Mill clear sky chart from 2005-11-06 to 2024-01-31.

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
40%
24386
22%
74902
14%
24323
49%
24323
27%
46123

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 10thNight
20%
950
21%
2582
6%
946
33%
946
23%
1686
January11th to 20thNight
19%
950
23%
2470
6%
950
31%
950
23%
1658
January21st to endNight
20%
1043
22%
2711
5%
1043
31%
1043
25%
1813
February1st to 10thNight
19%
900
19%
2340
4%
900
29%
900
23%
1604
February11th to 20thNight
16%
729
19%
2125
5%
726
27%
726
22%
1353
February21st to endNight
18%
592
23%
1776
6%
592
32%
592
19%
1171
March1st to 10thNight
25%
643
22%
2083
9%
643
36%
643
22%
1310
March11th to 20thNight
27%
540
17%
1980
11%
540
36%
540
17%
1308
March21st to endNight
24%
594
13%
2102
8%
594
32%
594
16%
1442
April1st to 10thNight
29%
540
24%
1800
11%
540
45%
540
28%
1010
April11th to 20thNight
32%
533
23%
1775
16%
533
45%
533
24%
1074
April21st to endNight
27%
540
19%
1800
9%
540
41%
540
22%
1154
May1st to 10thNight
38%
540
18%
1800
11%
540
49%
540
28%
1078
May11th to 20thNight
41%
531
21%
1514
15%
531
47%
531
29%
988
May21st to endNight
48%
584
17%
1552
11%
582
53%
582
27%
1064
June1st to 10thNight
62%
540
19%
1440
14%
540
66%
540
36%
878
June11th to 20thNight
69%
540
30%
1440
24%
540
72%
540
54%
752
June21st to endNight
68%
540
26%
1440
18%
540
72%
540
49%
773
July1st to 10thNight
73%
525
19%
1400
17%
525
74%
525
38%
850
July11th to 20thNight
75%
522
22%
1481
21%
522
77%
522
45%
796
July21st to endNight
71%
591
24%
1673
23%
558
74%
558
37%
969
August1st to 10thNight
73%
537
21%
1605
23%
534
75%
534
35%
926
August11th to 20thNight
72%
534
24%
1776
27%
534
75%
534
35%
982
August21st to endNight
72%
594
24%
1980
27%
594
75%
594
36%
1065
September1st to 10thNight
67%
540
26%
1800
27%
540
71%
540
35%
986
September11th to 20thNight
67%
540
31%
1800
29%
540
73%
540
34%
1004
September21st to endNight
57%
692
29%
2005
20%
692
64%
692
40%
1117
October1st to 10thNight
57%
720
30%
2160
22%
720
64%
720
44%
1129
October11th to 20thNight
39%
720
32%
2160
17%
720
53%
720
33%
1231
October21st to endNight
34%
792
26%
2376
15%
792
45%
792
27%
1492
November1st to 10thNight
40%
740
30%
2330
19%
740
53%
740
35%
1266
November11th to 20thNight
34%
760
29%
2470
16%
760
50%
760
29%
1410
November21st to endNight
29%
808
24%
2518
14%
808
40%
808
25%
1574
December1st to 10thNight
28%
950
21%
2660
8%
950
40%
950
24%
1742
December11th to 20thNight
28%
949
21%
3148
10%
948
37%
948
20%
2044
December21st to endNight
20%
1043
12%
4830
6%
1026
33%
1026
11%
3424

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%6%35%5%35%5%5%7%44%
74867
Night
14%6%25%43445%7%47%
75283
TransparencyDay
39%7%12%23%16%3
74581
Night
37%6%12%24%18%4
75090
SeeingDay
17%12%26%25%16%5%
14420
Night
17%11%28%28%14%2
24389

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 10thDay
18%6%25%424345%45%
1579
11th to 20thDay
17%8%36%5%34447%40%
1710
21st to endDay
15%8%36%423436%46%
1872
February1st to 10thDay
18%8%37%5%34345%40%
1620
11th to 20thDay
16%7%37%4245%6%6%40%
1721
21st to endDay
17%10%35%6%35%446%37%
1480
March1st to 10thDay
17%7%35%423346%46%
1893
11th to 20thDay
21%9%36%5%34445%38%
1980
21st to endDay
20%9%36%5%35%45%7%32%
2252
April1st to 10thDay
13%6%36%42346%6%47%
2160
11th to 20thDay
17%8%36%5%34446%40%
2134
21st to endDay
18%6%35%6%3445%6%38%
2160
May1st to 10thDay
16%6%35%7%35%5%5%7%37%
2160
11th to 20thDay
15%5%35%5%35%5%6%8%41%
2375
21st to endDay
10%5%37%7%37%6%7%9%36%
2725
June1st to 10thDay
8%435%6%47%5%5%9%44%
2520
11th to 20thDay
5%4245%46%6%7%9%49%
2520
21st to endDay
5%324435%6%9%10%49%
2520
July1st to 10thDay
9%5%25%6%36%5%6%9%42%
2520
11th to 20thDay
5%315%5%47%6%7%10%48%
2426
21st to endDay
7%5%35%6%47%6%7%10%42%
2546
August1st to 10thDay
8%425%6%36%7%8%11%41%
2324
11th to 20thDay
10%5%25%6%36%6%7%8%43%
2125
21st to endDay
8%5%25%5%45%7%6%8%46%
2376
September1st to 10thDay
10%5%24435%5%5%8%48%
2160
11th to 20thDay
9%7%35%5%2445%8%48%
2160
21st to endDay
9%5%24323447%56%
1934
October1st to 10thDay
10%5%244335%5%6%55%
1800
11th to 20thDay
13%7%24433335%54%
1800
21st to endDay
19%7%34423345%46%
1980
November1st to 10thDay
11%5%244235%45%55%
1746
11th to 20thDay
13%6%25%424445%51%
1710
21st to endDay
20%7%35%42333446%
1658
December1st to 10thDay
16%8%35%5%3345%7%41%
1520
11th to 20thDay
17%8%46%5%34346%40%
1918
21st to endDay
17%15%36%4345%45%33%
2783
January1st to 10thNight
17%7%35%434445%45%
2582
11th to 20thNight
17%7%36%423446%44%
2470
21st to endNight
15%8%35%43445%6%43%
2711
February1st to 10thNight
17%9%36%424345%42%
2340
11th to 20thNight
16%6%45%5%24346%45%
2124
21st to endNight
20%7%35%424445%42%
1776
March1st to 10thNight
17%8%3443335%5%45%
2083
11th to 20thNight
20%6%36%425%446%39%
1980
21st to endNight
21%8%37%5%25%446%35%
2102
April1st to 10thNight
10%5%2443445%7%52%
1800
11th to 20thNight
14%6%25%5%335%6%6%44%
1775
21st to endNight
19%6%25%5%2445%7%42%
1800
May1st to 10thNight
14%5%2442445%8%47%
1800
11th to 20thNight
16%6%24334447%47%
1514
21st to endNight
9%7%35%6%46%6%6%9%39%
1551
June1st to 10thNight
7%5%25%44447%9%49%
1440
11th to 20thNight
5%32322346%11%60%
1440
21st to endNight
4223325%5%6%10%59%
1440
July1st to 10thNight
8%3234446%7%9%50%
1440
11th to 20thNight
4224425%48%10%56%
1530
21st to endNight
5%3245%35%6%7%9%51%
1772
August1st to 10thNight
5%425%5%25%6%8%11%48%
1615
11th to 20thNight
6%4244345%6%8%53%
1776
21st to endNight
7%4243345%6%8%54%
1980
September1st to 10thNight
9%425%42336%7%54%
1800
11th to 20thNight
9%5%24435%5%5%7%54%
1800
21st to endNight
8%425%42445%7%56%
2005
October1st to 10thNight
7%42442335%6%61%
2160
11th to 20thNight
14%5%13323346%56%
2160
21st to endNight
19%6%2432333450%
2376
November1st to 10thNight
12%5%23323445%58%
2330
11th to 20thNight
14%6%24323348%51%
2470
21st to endNight
19%7%24423346%46%
2518
December1st to 10thNight
18%7%35%43435%6%42%
2660
11th to 20thNight
18%7%35%5%34346%42%
3279
21st to endNight
19%13%47%6%345%5%6%30%
4884

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 10thDay
42%48%26%16%4
1580
11th to 20thDay
45%5%11%24%14%1
1710
21st to endDay
41%412%25%15%4
1872
February1st to 10thDay
48%410%23%14%1
1620
11th to 20thDay
44%5%11%21%15%4
1731
21st to endDay
48%6%7%21%12%6%
1480
March1st to 10thDay
41%49%23%19%5%
1893
11th to 20thDay
49%6%9%18%14%4
1980
21st to endDay
52%6%11%19%10%2
2252
April1st to 10thDay
37%5%11%25%19%2
2160
11th to 20thDay
46%5%10%19%17%4
2134
21st to endDay
47%7%10%21%15%1
2160
May1st to 10thDay
45%8%13%21%12%1
2160
11th to 20thDay
40%7%14%22%14%2
2379
21st to endDay
42%11%14%20%11%2
2725
June1st to 10thDay
36%8%14%24%17%1
2520
11th to 20thDay
28%9%14%28%18%4
2520
21st to endDay
26%9%19%26%15%5%
2520
July1st to 10thDay
36%8%16%23%13%4
2451
11th to 20thDay
28%10%17%24%18%4
2352
21st to endDay
35%11%13%28%12%1
2405
August1st to 10thDay
33%10%17%25%14%1
2310
11th to 20thDay
37%7%14%28%13%1
2125
21st to endDay
33%8%16%22%16%6%
2376
September1st to 10thDay
33%7%12%27%15%5%
2160
11th to 20thDay
35%6%8%23%26%2
2160
21st to endDay
29%6%9%26%27%3
1934
October1st to 10thDay
30%7%9%25%24%5%
1800
11th to 20thDay
34%38%24%24%7%
1800
21st to endDay
41%48%25%17%5%
1980
November1st to 10thDay
33%410%24%22%6%
1746
11th to 20thDay
35%5%6%24%23%7%
1710
21st to endDay
43%48%24%19%2
1658
December1st to 10thDay
42%6%10%26%14%3
1520
11th to 20thDay
46%5%7%21%20%1
1915
21st to endDay
52%5%10%16%13%3
2783
January1st to 10thNight
41%410%23%19%3
2582
11th to 20thNight
42%5%10%24%17%2
2470
21st to endNight
42%411%25%16%2
2711
February1st to 10thNight
45%411%23%16%2
2340
11th to 20thNight
41%412%21%18%3
2125
21st to endNight
44%5%8%22%16%5%
1776
March1st to 10thNight
42%48%20%18%7%
2083
11th to 20thNight
47%6%10%19%14%3
1980
21st to endNight
51%5%11%20%12%1
2102
April1st to 10thNight
31%6%14%24%22%4
1800
11th to 20thNight
38%5%11%23%17%6%
1775
21st to endNight
42%6%10%25%16%2
1800
May1st to 10thNight
36%6%15%24%18%2
1800
11th to 20thNight
37%8%13%22%18%2
1515
21st to endNight
40%9%15%19%14%2
1552
June1st to 10thNight
30%8%16%23%21%2
1440
11th to 20thNight
19%5%15%36%20%5%
1440
21st to endNight
20%7%18%29%19%8%
1440
July1st to 10thNight
28%9%18%24%18%4
1400
11th to 20thNight
22%7%18%29%20%4
1481
21st to endNight
27%9%15%33%15%1
1673
August1st to 10thNight
27%10%17%31%14%2
1605
11th to 20thNight
28%8%15%29%18%2
1776
21st to endNight
27%7%17%25%19%5%
1980
September1st to 10thNight
29%6%11%30%18%5%
1800
11th to 20thNight
30%7%11%24%26%3
1800
21st to endNight
28%5%11%23%29%4
2005
October1st to 10thNight
24%412%28%27%6%
2160
11th to 20thNight
32%38%25%25%6%
2160
21st to endNight
39%48%22%20%6%
2376
November1st to 10thNight
29%410%28%23%6%
2330
11th to 20thNight
34%48%24%23%7%
2470
21st to endNight
41%48%23%22%2
2518
December1st to 10thNight
42%411%23%18%2
2660
11th to 20thNight
44%49%24%17%2
3281
21st to endNight
52%7%11%17%10%2
4884

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 10thDay
30%18%33%16%2
270
11th to 20thDay
33%26%29%12%1
270
21st to endDay
22%30%36%9%3
294
February1st to 10thDay
28%24%34%11%3
240
11th to 20thDay
33%26%28%11%2
240
21st to endDay
37%20%31%10%11
198
March1st to 10thDay
27%24%35%13%2
240
11th to 20thDay
35%21%33%8%3
240
21st to endDay
32%20%34%11%3
338
April1st to 10thDay
22%18%34%19%6%
420
11th to 20thDay
25%19%30%17%7%1
412
21st to endDay
20%20%33%20%5%1
420
May1st to 10thDay
19%21%33%20%7%1
423
11th to 20thDay
18%12%32%21%13%4
589
21st to endDay
10%9%33%28%15%5%
679
June1st to 10thDay
10%424%30%26%7%
630
11th to 20thDay
6%422%41%22%5%
630
21st to endDay
5%6%28%37%20%5%
630
July1st to 10thDay
11%314%29%33%11%
621
11th to 20thDay
4319%34%31%9%
618
21st to endDay
8%314%35%31%10%
684
August1st to 10thDay
8%314%38%27%9%
622
11th to 20thDay
15%415%28%31%7%
439
21st to endDay
12%114%27%31%14%
495
September1st to 10thDay
9%416%33%29%8%
450
11th to 20thDay
8%417%29%29%13%
450
21st to endDay
14%8%21%30%19%8%
394
October1st to 10thDay
14%9%29%32%13%3
270
11th to 20thDay
20%16%37%21%6%
270
21st to endDay
27%20%29%19%5%
297
November1st to 10thDay
16%13%37%23%8%1
270
11th to 20thDay
23%16%35%18%9%
270
21st to endDay
32%14%29%17%6%1
270
December1st to 10thDay
20%23%32%17%6%2
270
11th to 20thDay
26%19%32%16%7%
270
21st to endDay
30%24%31%12%3
297
January1st to 10thNight
23%19%35%19%4
950
11th to 20thNight
24%20%34%18%3
950
21st to endNight
21%18%38%21%2
1043
February1st to 10thNight
24%16%39%19%1
900
11th to 20thNight
23%19%38%18%2
729
21st to endNight
25%22%33%19%2
592
March1st to 10thNight
25%15%33%26%2
643
11th to 20thNight
24%14%32%26%4
540
21st to endNight
25%12%34%23%5%
594
April1st to 10thNight
13%16%39%27%5%
540
11th to 20thNight
18%16%30%27%9%
533
21st to endNight
20%11%39%22%7%1
540
May1st to 10thNight
14%10%37%30%10%
540
11th to 20thNight
19%6%32%26%15%2
531
21st to endNight
13%5%26%35%17%4
584
June1st to 10thNight
6%5%18%36%32%3
540
11th to 20thNight
6%119%46%25%2
540
21st to endNight
4221%41%30%3
540
July1st to 10thNight
10%111%32%37%9%
525
11th to 20thNight
5%211%40%36%6%
522
21st to endNight
5%113%37%38%5%
591
August1st to 10thNight
5%210%39%40%4
537
11th to 20thNight
7%113%37%38%4
534
21st to endNight
9%110%34%39%7%
594
September1st to 10thNight
10%213%35%36%4
540
11th to 20thNight
12%114%29%37%7%
540
21st to endNight
10%6%22%29%29%4
692
October1st to 10thNight
10%425%34%24%3
720
11th to 20thNight
16%11%31%29%12%1
720
21st to endNight
23%12%28%28%8%
792
November1st to 10thNight
15%9%34%30%11%1
740
11th to 20thNight
18%12%33%28%9%1
760
21st to endNight
23%13%31%24%8%
808
December1st to 10thNight
23%13%32%26%5%
950
11th to 20thNight
26%12%30%26%5%
950
21st to endNight
28%15%33%21%3
1045
Page generated at 2024-01-28 04:26:34. Version ac07

Copyright 2024 Attilla Danko


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