Purple Crow Lidar Facility
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Purple Crow Lidar Facility clear sky chart from 2005-11-05 to 2017-08-12.

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%
14945
14%
46306
10%
14906
40%
14906
19%
32556

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
12%
813
8%
2462
3%
810
17%
810
8%
2034
January16th to endNight
16%
768
9%
2496
3%
768
22%
768
8%
2048
February1st to 15thNight
17%
701
7%
2287
2%
701
23%
701
8%
1817
February16th to endNight
23%
631
11%
1949
5%
631
30%
631
13%
1495
March1st to 15thNight
25%
720
15%
2017
8%
720
31%
720
16%
1526
March16th to endNight
34%
768
19%
2112
11%
768
40%
768
21%
1481
April1st to 15thNight
28%
674
16%
1830
7%
674
34%
674
21%
1308
April16th to endNight
36%
540
20%
1620
10%
540
45%
540
25%
1044
May1st to 15thNight
41%
540
17%
1620
11%
540
47%
540
24%
1065
May16th to endNight
47%
431
17%
1554
14%
431
55%
431
27%
892
June1st to 15thNight
51%
360
14%
1377
15%
360
58%
360
25%
792
June16th to endNight
58%
360
17%
1260
18%
360
65%
360
31%
709
July1st to 15thNight
68%
390
20%
1254
23%
390
70%
390
38%
668
July16th to endNight
66%
564
16%
1595
15%
531
69%
531
37%
916
August1st to 15thNight
69%
527
18%
1575
15%
524
71%
524
35%
914
August16th to endNight
64%
530
23%
1580
16%
530
68%
530
37%
900
September1st to 15thNight
56%
660
23%
1737
15%
660
59%
660
34%
1097
September16th to endNight
56%
657
21%
1815
16%
657
59%
657
33%
1131
October1st to 15thNight
44%
660
18%
1955
15%
660
49%
660
25%
1291
October16th to endNight
23%
704
13%
2135
7%
704
30%
704
15%
1601
November1st to 15thNight
35%
700
19%
2309
17%
700
41%
700
20%
1545
November16th to endNight
23%
720
10%
2520
7%
720
28%
720
11%
1907
December1st to 15thNight
14%
720
5%
2520
2%
720
18%
720
8%
2048
December16th to endNight
12%
807
6%
2727
2%
807
16%
807
6%
2327

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
15%9%47%6%35%45%7%30%
47642
Night
15%9%47%6%3445%6%31%
46484
Cloud CoverDay
15%9%47%6%35%45%7%30%
47652
Night
15%9%47%6%3445%6%31%
46488
TransparencyDay
52%412%20%10%
47338
Night
51%411%20%10%1
46306
SeeingDay
18%7%26%24%15%7%
5527
Night
20%8%27%29%12%1
14951

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
20%15%7%12%8%45%33414%
1468
16th to endDay
14%17%8%13%8%5%5%43413%
1728
February1st to 15thDay
16%16%7%9%9%5%5%34416%
1575
16th to endDay
15%14%8%12%7%45%445%17%
1521
March1st to 15thDay
16%13%6%10%6%34345%23%
1930
16th to endDay
17%9%5%8%5%34445%28%
2112
April1st to 15thDay
20%12%35%5%2445%7%28%
2127
16th to endDay
17%9%36%5%23347%36%
2340
May1st to 15thDay
18%7%35%5%2445%8%33%
2331
16th to endDay
13%5%345%345%6%7%39%
2559
June1st to 15thDay
14%5%25%5%3446%7%39%
2580
16th to endDay
13%425%5%36%6%6%8%38%
2700
July1st to 15thDay
10%415%5%35%5%6%9%41%
2625
16th to endDay
10%5%25%6%35%5%7%10%37%
2465
August1st to 15thDay
9%5%26%6%36%7%6%8%36%
2288
16th to endDay
10%5%35%6%345%5%9%38%
2259
September1st to 15thDay
15%6%27%435%45%7%36%
1892
16th to endDay
16%5%25%5%2445%9%38%
1815
October1st to 15thDay
18%7%36%5%3446%6%32%
1675
16th to endDay
28%11%37%6%24345%21%
1735
November1st to 15thDay
16%10%36%6%35%45%7%31%
1549
16th to endDay
20%16%5%8%7%35%5%5%5%17%
1440
December1st to 15thDay
18%18%9%11%5%34445%14%
1440
16th to endDay
21%19%9%11%8%334449%
1488
January1st to 15thNight
21%14%7%10%7%4444416%
2462
16th to endNight
15%16%8%10%9%45%5%35%14%
2496
February1st to 15thNight
15%14%6%10%8%5%6%45%418%
2285
16th to endNight
16%11%6%10%7%45%45%5%22%
1949
March1st to 15thNight
16%11%5%9%7%335%45%27%
2005
16th to endNight
15%9%46%5%2335%5%36%
2112
April1st to 15thNight
19%10%35%424346%34%
1830
16th to endNight
11%7%36%5%245%5%7%39%
1620
May1st to 15thNight
15%6%35%5%2437%7%36%
1620
16th to endNight
10%4344335%6%7%46%
1552
June1st to 15thNight
10%6%25%435%5%6%9%42%
1377
16th to endNight
9%4245%345%6%10%44%
1260
July1st to 15thNight
5%325%323348%55%
1329
16th to endNight
7%4235%245%7%9%46%
1703
August1st to 15thNight
6%414435%6%8%9%46%
1586
16th to endNight
10%5%23423346%52%
1580
September1st to 15thNight
12%5%2443436%7%43%
1737
16th to endNight
12%5%245%3435%7%45%
1815
October1st to 15thNight
17%6%36%434348%37%
1955
16th to endNight
25%10%37%5%24446%26%
2135
November1st to 15thNight
15%8%36%5%245%5%7%33%
2309
16th to endNight
21%14%5%7%5%2445%7%20%
2520
December1st to 15thNight
20%16%8%9%5%2445%5%15%
2520
16th to endNight
20%15%8%13%8%35%43311%
2727

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
20%15%7%12%8%45%33414%
1468
16th to endDay
13%18%9%12%8%5%5%43414%
1728
February1st to 15thDay
16%15%8%10%9%5%6%345%15%
1575
16th to endDay
15%13%8%11%7%46%44417%
1521
March1st to 15thDay
17%13%6%10%6%34345%24%
1941
16th to endDay
18%9%48%6%34446%29%
2111
April1st to 15thDay
19%12%46%42445%7%28%
2127
16th to endDay
17%9%35%423247%36%
2340
May1st to 15thDay
18%6%35%5%25%45%7%34%
2331
16th to endDay
13%5%35%4345%6%7%39%
2559
June1st to 15thDay
14%425%5%25%45%8%39%
2580
16th to endDay
13%425%5%36%5%6%8%38%
2700
July1st to 15thDay
10%4246%35%6%5%10%41%
2625
16th to endDay
10%5%26%6%35%5%7%9%38%
2465
August1st to 15thDay
10%5%35%6%36%7%6%8%36%
2288
16th to endDay
11%5%35%5%345%6%9%38%
2259
September1st to 15thDay
14%6%26%5%3445%7%36%
1892
16th to endDay
16%5%244245%5%9%38%
1815
October1st to 15thDay
18%7%27%5%3435%7%33%
1675
16th to endDay
28%11%37%5%23445%21%
1735
November1st to 15thDay
16%9%35%5%445%47%32%
1549
16th to endDay
20%15%6%8%6%35%45%5%17%
1440
December1st to 15thDay
18%18%8%10%7%235%45%15%
1440
16th to endDay
21%19%9%11%7%344449%
1488
January1st to 15thNight
20%13%7%10%8%3443417%
2462
16th to endNight
15%15%8%10%8%37%5%4415%
2496
February1st to 15thNight
14%15%6%10%8%45%5%5%419%
2278
16th to endNight
16%10%6%10%6%45%45%6%22%
1949
March1st to 15thNight
17%10%5%8%8%24445%27%
2017
16th to endNight
16%9%36%5%24346%36%
2112
April1st to 15thNight
19%9%45%43445%6%33%
1830
16th to endNight
12%7%35%6%245%48%39%
1620
May1st to 15thNight
15%6%35%425%46%8%36%
1619
16th to endNight
10%5%345%3346%6%46%
1552
June1st to 15thNight
11%5%24436%46%9%41%
1377
16th to endNight
9%424435%5%6%9%44%
1260
July1st to 15thNight
5%325%32335%8%55%
1329
16th to endNight
7%424435%5%7%9%47%
1703
August1st to 15thNight
6%313435%5%7%10%46%
1586
16th to endNight
9%5%14323346%53%
1580
September1st to 15thNight
12%5%2443446%7%44%
1737
16th to endNight
12%5%1443346%7%44%
1815
October1st to 15thNight
17%6%35%5%24448%38%
1955
16th to endNight
24%9%36%6%2445%6%26%
2135
November1st to 15thNight
15%8%35%6%245%5%8%34%
2309
16th to endNight
21%13%5%7%5%2445%7%20%
2520
December1st to 15thNight
20%15%8%9%5%3445%5%16%
2520
16th to endNight
21%14%8%14%8%35%44412%
2727

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
73%38%10%3
1469
16th to endDay
72%48%11%3
1728
February1st to 15thDay
69%39%13%4
1577
16th to endDay
68%39%13%4
1521
March1st to 15thDay
62%310%14%7%
1941
16th to endDay
55%311%19%8%1
2112
April1st to 15thDay
54%311%20%9%
2127
16th to endDay
47%312%20%14%1
2340
May1st to 15thDay
48%411%23%11%1
2331
16th to endDay
42%412%25%13%1
2563
June1st to 15thDay
41%413%25%13%1
2580
16th to endDay
41%6%13%24%14%
2700
July1st to 15thDay
36%49%29%17%2
2471
16th to endDay
39%5%14%25%13%2
2310
August1st to 15thDay
41%5%14%23%12%1
2275
16th to endDay
40%414%25%13%1
2259
September1st to 15thDay
45%413%24%11%
1892
16th to endDay
42%313%29%10%
1815
October1st to 15thDay
49%412%18%13%
1675
16th to endDay
63%313%13%5%
1735
November1st to 15thDay
50%413%19%9%1
1549
16th to endDay
66%5%12%12%2
1440
December1st to 15thDay
70%413%10%1
1440
16th to endDay
77%37%9%1
1488
January1st to 15thNight
70%48%11%5%
2462
16th to endNight
70%38%14%2
2496
February1st to 15thNight
66%49%13%4
2287
16th to endNight
62%311%17%5%
1949
March1st to 15thNight
58%39%20%6%
2017
16th to endNight
50%39%22%12%2
2112
April1st to 15thNight
50%38%22%12%1
1830
16th to endNight
42%48%22%18%3
1620
May1st to 15thNight
44%410%24%13%2
1620
16th to endNight
35%5%12%27%14%3
1554
June1st to 15thNight
37%5%12%27%16%1
1377
16th to endNight
34%415%26%18%1
1260
July1st to 15thNight
28%48%33%22%3
1254
16th to endNight
30%5%17%25%18%2
1595
August1st to 15thNight
30%6%15%31%14%2
1575
16th to endNight
31%411%32%18%2
1580
September1st to 15thNight
37%314%27%15%1
1737
16th to endNight
37%313%30%14%
1815
October1st to 15thNight
45%310%22%16%1
1955
16th to endNight
58%311%17%7%
2135
November1st to 15thNight
47%411%23%11%1
2309
16th to endNight
62%313%16%3
2520
December1st to 15thNight
69%412%10%2
2520
16th to endNight
75%38%9%2
2727

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
20%20%39%13%41
83
16th to endDay
35%12%35%16%
96
February1st to 15thDay
21%18%45%14%
90
16th to endDay
19%18%48%11%2
81
March1st to 15thDay
26%11%32%21%7%
231
16th to endDay
25%6%34%22%7%3
288
April1st to 15thDay
24%11%27%22%12%1
270
16th to endDay
21%6%34%19%10%7%
270
May1st to 15thDay
22%6%27%25%11%6%
288
16th to endDay
14%6%30%24%16%7%
331
June1st to 15thDay
16%427%30%17%4
375
16th to endDay
13%6%27%31%15%4
495
July1st to 15thDay
13%422%31%19%8%
458
16th to endDay
11%5%16%29%26%11%
326
August1st to 15thDay
11%315%27%24%17%
297
16th to endDay
11%313%23%26%20%
268
September1st to 15thDay
14%315%19%30%16%
255
16th to endDay
16%416%27%21%12%
254
October1st to 15thDay
21%6%23%26%17%4
255
16th to endDay
34%10%29%21%4
247
November1st to 15thDay
15%16%29%24%10%3
85
16th to endDay
28%16%36%10%8%
60
December1st to 15thDay
35%25%23%11%5%
60
16th to endDay
26%23%39%10%
64
January1st to 15thNight
28%14%35%16%5%
815
16th to endNight
23%10%34%24%6%
768
February1st to 15thNight
23%15%32%23%4
704
16th to endNight
23%11%31%26%6%
631
March1st to 15thNight
23%10%32%25%8%
720
16th to endNight
21%8%28%29%10%1
768
April1st to 15thNight
25%10%29%26%6%
674
16th to endNight
16%7%33%32%9%1
540
May1st to 15thNight
18%427%34%14%
540
16th to endNight
13%328%37%14%2
432
June1st to 15thNight
14%323%43%14%
360
16th to endNight
11%219%48%16%1
360
July1st to 15thNight
7%115%50%22%2
390
16th to endNight
9%114%46%26%1
564
August1st to 15thNight
8%11%45%29%3
527
16th to endNight
13%113%35%31%4
530
September1st to 15thNight
13%5%18%34%23%5%
660
16th to endNight
15%5%15%35%23%5%
657
October1st to 15thNight
19%5%23%31%17%2
660
16th to endNight
29%9%30%24%5%
704
November1st to 15thNight
19%9%29%29%9%2
700
16th to endNight
30%11%27%22%7%
720
December1st to 15thNight
30%14%33%16%4
720
16th to endNight
27%12%37%17%4
807
Page generated at 2017-08-13 14:16:26. Version ac04

Copyright 2017 A. Danko


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