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 2005-11-06 to 2024-02-20.

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
34%
23357
14%
80268
10%
23258
40%
23258
16%
57633

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
11%
904
6%
4461
3%
886
17%
886
5%
3619
January11th to 20thNight
13%
754
5%
4114
3%
740
17%
740
4%
3508
January21st to endNight
17%
834
6%
4526
5%
814
24%
814
5%
3787
February1st to 10thNight
16%
760
9%
2470
3%
760
23%
760
9%
1968
February11th to 20thNight
21%
739
10%
2393
5%
738
28%
738
11%
1845
February21st to endNight
17%
592
11%
1776
3%
592
24%
592
12%
1380
March1st to 10thNight
25%
720
17%
2035
9%
720
31%
720
17%
1497
March11th to 20thNight
27%
720
19%
1980
9%
720
35%
720
20%
1401
March21st to endNight
31%
792
17%
2178
10%
792
37%
792
19%
1583
April1st to 10thNight
26%
720
15%
1918
7%
720
32%
720
21%
1379
April11th to 20thNight
32%
557
20%
1621
9%
557
41%
557
23%
1096
April21st to endNight
32%
540
18%
1620
7%
540
41%
540
21%
1101
May1st to 10thNight
37%
540
17%
1620
10%
540
43%
540
24%
1083
May11th to 20thNight
43%
531
18%
1593
11%
531
50%
531
25%
1019
May21st to endNight
52%
389
19%
1552
18%
389
61%
389
30%
827
June1st to 10thNight
48%
360
15%
1436
16%
360
57%
360
26%
791
June11th to 20thNight
54%
360
19%
1260
19%
360
62%
360
29%
736
June21st to endNight
56%
360
20%
1260
21%
360
63%
360
30%
717
July1st to 10thNight
67%
350
21%
1225
26%
350
72%
350
38%
636
July11th to 20thNight
62%
513
19%
1493
17%
513
66%
513
36%
870
July21st to endNight
63%
591
17%
1672
14%
558
67%
558
36%
970
August1st to 10thNight
68%
537
19%
1600
17%
534
69%
534
35%
939
August11th to 20thNight
67%
534
23%
1598
18%
534
70%
534
36%
921
August21st to endNight
60%
601
24%
1789
16%
601
64%
601
35%
1041
September1st to 10thNight
55%
720
19%
1852
11%
720
59%
720
35%
1177
September11th to 20thNight
61%
720
27%
1980
20%
720
65%
720
38%
1174
September21st to endNight
46%
720
20%
1980
15%
720
50%
720
28%
1316
October1st to 10thNight
43%
720
19%
2119
15%
720
49%
720
25%
1403
October11th to 20thNight
31%
720
16%
2160
10%
720
39%
720
19%
1521
October21st to endNight
23%
792
16%
2413
11%
792
31%
792
14%
1828
November1st to 10thNight
37%
740
20%
2406
16%
740
44%
740
21%
1585
November11th to 20thNight
22%
760
13%
2617
7%
760
30%
760
13%
1879
November21st to endNight
24%
760
8%
2660
6%
760
28%
760
10%
2066
December1st to 10thNight
16%
760
6%
2660
3%
760
20%
760
8%
2159
December11th to 20thNight
14%
760
7%
3261
3%
759
21%
759
7%
2553
December21st to endNight
12%
887
3%
4970
1%
878
17%
878
3%
4258

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
16%11%5%8%6%35%5%5%7%30%
78624
Night
16%11%5%8%6%35%45%6%29%
80520
TransparencyDay
54%411%20%10%1
78338
Night
56%311%19%10%1
80341
SeeingDay
20%9%28%24%14%5%
14007
Night
21%9%28%30%12%1
23386

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 10thDay
17%20%8%11%8%3433418%
2450
11th to 20thDay
14%20%11%16%9%5%6%4349%
2840
21st to endDay
24%21%10%11%7%4442311%
3124
February1st to 10thDay
16%16%6%11%10%5%6%5%4417%
1710
11th to 20thDay
14%13%9%13%11%5%5%35%5%18%
1654
21st to endDay
17%15%7%12%6%345%45%22%
1480
March1st to 10thDay
14%13%6%10%7%35%45%6%26%
1920
11th to 20thDay
14%13%6%8%6%34446%30%
1980
21st to endDay
20%10%5%8%6%34445%29%
2178
April1st to 10thDay
17%13%5%7%5%345%5%8%28%
2042
11th to 20thDay
19%10%35%5%34448%34%
2302
21st to endDay
21%10%46%6%2445%6%33%
2340
May1st to 10thDay
18%8%36%5%35%5%5%8%33%
2340
11th to 20thDay
18%8%35%5%3445%7%37%
2301
21st to endDay
13%5%35%5%346%6%8%41%
2721
June1st to 10thDay
14%5%36%6%45%5%6%8%40%
2520
11th to 20thDay
12%6%35%5%46%5%6%8%41%
2699
21st to endDay
13%5%25%5%35%6%5%8%42%
2700
July1st to 10thDay
10%425%5%35%5%6%9%47%
2700
11th to 20thDay
12%5%25%6%35%5%7%11%39%
2410
21st to endDay
10%5%35%6%46%5%7%9%40%
2547
August1st to 10thDay
10%5%25%6%46%7%7%10%39%
2327
11th to 20thDay
10%6%37%7%45%6%7%10%36%
2303
21st to endDay
12%6%35%6%35%5%6%8%42%
2548
September1st to 10thDay
12%6%37%5%47%5%6%8%39%
2106
11th to 20thDay
13%5%26%43446%9%43%
1980
21st to endDay
18%5%26%5%35%5%6%9%36%
1980
October1st to 10thDay
18%8%36%5%35%45%8%35%
1841
11th to 20thDay
21%10%37%6%45%47%6%26%
1800
21st to endDay
26%13%38%6%35%5%5%5%21%
1940
November1st to 10thDay
16%12%37%6%45%45%7%30%
1672
11th to 20thDay
16%16%47%5%35%5%6%7%25%
1562
21st to endDay
21%18%7%7%7%46%45%5%16%
1520
December1st to 10thDay
16%19%8%11%6%46%5%46%15%
1520
11th to 20thDay
19%17%9%13%7%445%4414%
1906
21st to endDay
29%19%9%10%6%34445%8%
2661
January1st to 10thNight
17%17%10%14%7%44435%15%
4479
11th to 20thNight
15%18%8%13%10%6%6%6%4411%
4120
21st to endNight
23%17%8%14%7%3444413%
4532
February1st to 10thNight
17%14%6%10%9%46%45%5%19%
2470
11th to 20thNight
15%13%7%9%7%5%6%6%6%6%21%
2393
21st to endNight
17%12%6%12%8%45%5%45%23%
1776
March1st to 10thNight
14%10%6%9%8%345%47%29%
2025
11th to 20thNight
14%11%47%7%3445%6%34%
1979
21st to endNight
19%11%5%8%5%3445%5%34%
2178
April1st to 10thNight
18%10%5%7%5%3446%6%33%
1918
11th to 20thNight
17%9%36%5%245%5%6%38%
1621
21st to endNight
15%9%47%6%35%5%6%7%34%
1620
May1st to 10thNight
17%8%36%5%2447%7%37%
1620
11th to 20thNight
13%6%45%6%35%5%6%7%40%
1592
21st to endNight
10%4243345%7%7%51%
1551
June1st to 10thNight
12%6%25%4345%6%8%45%
1436
11th to 20thNight
9%6%245%45%5%7%10%42%
1260
21st to endNight
10%425%5%45%45%8%47%
1260
July1st to 10thNight
6%325%5%3345%10%55%
1260
11th to 20thNight
9%6%24425%5%6%9%50%
1542
21st to endNight
8%4345%345%8%8%48%
1771
August1st to 10thNight
9%4145%346%8%8%46%
1611
11th to 20thNight
8%5%25%4345%7%9%48%
1598
21st to endNight
9%5%25%5%245%5%7%50%
1789
September1st to 10thNight
10%6%36%5%35%36%8%46%
1852
11th to 20thNight
11%5%2343445%8%50%
1980
21st to endNight
16%7%35%6%3345%6%42%
1980
October1st to 10thNight
16%7%37%5%35%35%8%39%
2119
11th to 20thNight
21%9%36%6%2445%7%32%
2160
21st to endNight
24%11%48%6%345%46%26%
2413
November1st to 10thNight
15%9%36%5%35%5%6%7%36%
2406
11th to 20thNight
17%13%5%7%6%36%6%6%8%24%
2617
21st to endNight
21%14%6%8%6%35%45%6%20%
2660
December1st to 10thNight
20%17%8%10%6%35%5%6%6%15%
2660
11th to 20thNight
15%20%8%11%6%35%5%46%18%
3288
21st to endNight
27%20%8%10%7%3443311%
4984

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
73%210%11%4
2451
11th to 20thDay
82%27%6%2
2840
21st to endDay
80%27%6%3
3124
February1st to 10thDay
70%39%13%41
1710
11th to 20thDay
68%37%14%7%
1663
21st to endDay
66%310%14%6%1
1480
March1st to 10thDay
60%311%17%7%1
1923
11th to 20thDay
57%310%18%10%2
1980
21st to endDay
58%38%19%10%1
2178
April1st to 10thDay
55%410%21%10%1
2042
11th to 20thDay
50%212%20%14%1
2302
21st to endDay
53%311%19%12%2
2340
May1st to 10thDay
50%310%24%12%1
2340
11th to 20thDay
47%411%22%14%2
2305
21st to endDay
40%5%13%26%15%2
2721
June1st to 10thDay
42%412%26%14%2
2520
11th to 20thDay
41%412%24%17%2
2699
21st to endDay
40%5%12%27%17%1
2700
July1st to 10thDay
34%410%30%19%3
2626
11th to 20thDay
39%413%29%14%1
2336
21st to endDay
40%5%12%26%16%2
2405
August1st to 10thDay
38%5%15%29%11%1
2314
11th to 20thDay
43%5%15%25%12%1
2303
21st to endDay
41%413%27%14%1
2548
September1st to 10thDay
42%5%14%25%13%1
2106
11th to 20thDay
38%313%32%14%
1980
21st to endDay
46%313%26%10%1
1980
October1st to 10thDay
48%411%22%13%1
1841
11th to 20thDay
58%413%17%8%1
1800
21st to endDay
64%411%15%6%
1940
November1st to 10thDay
53%5%10%22%8%2
1672
11th to 20thDay
58%415%14%8%1
1562
21st to endDay
70%411%13%3
1520
December1st to 10thDay
69%412%12%2
1520
11th to 20thDay
75%39%11%2
1906
21st to endDay
81%210%6%
2661
January1st to 10thNight
73%210%11%3
4479
11th to 20thNight
78%38%8%3
4120
21st to endNight
77%28%10%31
4532
February1st to 10thNight
67%49%15%6%
2470
11th to 20thNight
62%5%10%16%7%
2395
21st to endNight
64%39%17%7%
1776
March1st to 10thNight
56%39%21%10%1
2035
11th to 20thNight
51%310%22%11%2
1980
21st to endNight
54%37%21%12%2
2178
April1st to 10thNight
51%49%22%13%2
1918
11th to 20thNight
47%39%21%18%2
1621
21st to endNight
49%48%21%15%3
1620
May1st to 10thNight
46%49%24%14%3
1620
11th to 20thNight
42%5%10%24%15%4
1593
21st to endNight
32%5%14%28%18%3
1552
June1st to 10thNight
36%411%29%17%3
1436
11th to 20thNight
35%5%13%25%19%2
1260
21st to endNight
36%314%27%20%1
1260
July1st to 10thNight
29%39%31%23%5%
1225
11th to 20thNight
32%5%12%31%17%3
1493
21st to endNight
32%5%17%26%18%3
1672
August1st to 10thNight
33%5%15%33%14%1
1600
11th to 20thNight
32%415%32%14%2
1598
21st to endNight
33%5%13%31%17%2
1789
September1st to 10thNight
37%315%26%16%2
1852
11th to 20thNight
33%312%33%18%1
1980
21st to endNight
44%412%26%14%1
1980
October1st to 10thNight
46%310%23%17%1
2119
11th to 20thNight
52%312%22%10%1
2160
21st to endNight
60%48%18%10%1
2413
November1st to 10thNight
45%5%11%26%11%1
2406
11th to 20thNight
57%412%19%7%1
2617
21st to endNight
65%415%13%3
2660
December1st to 10thNight
69%411%12%4
2660
11th to 20thNight
68%311%14%4
3288
21st to endNight
80%210%7%2
4984

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
22%21%28%21%6%1
238
11th to 20thDay
20%14%47%14%41
270
21st to endDay
30%11%35%20%4
297
February1st to 10thDay
26%18%38%14%4
270
11th to 20thDay
26%20%36%16%1
267
21st to endDay
28%27%34%9%2
198
March1st to 10thDay
25%13%39%16%7%
363
11th to 20thDay
23%12%34%25%5%2
420
21st to endDay
29%13%30%21%6%1
462
April1st to 10thDay
20%15%32%23%8%1
420
11th to 20thDay
26%12%28%20%10%4
412
21st to endDay
24%11%31%22%8%3
420
May1st to 10thDay
23%9%28%27%9%4
423
11th to 20thDay
19%8%28%21%18%6%
447
21st to endDay
14%6%25%28%18%9%
485
June1st to 10thDay
15%432%30%15%4
450
11th to 20thDay
13%9%25%32%17%4
629
21st to endDay
14%6%26%33%16%4
630
July1st to 10thDay
10%5%19%31%24%10%
621
11th to 20thDay
16%423%30%20%8%
504
21st to endDay
11%420%32%24%9%
488
August1st to 10thDay
11%217%30%25%15%
446
11th to 20thDay
15%316%27%26%15%
439
21st to endDay
12%5%19%28%25%11%
495
September1st to 10thDay
12%6%20%28%22%11%
450
11th to 20thDay
11%221%24%28%14%
450
21st to endDay
19%8%22%26%16%9%
450
October1st to 10thDay
22%7%24%24%17%6%
450
11th to 20thDay
25%13%33%21%7%1
450
21st to endDay
30%12%34%19%41
455
November1st to 10thDay
21%15%32%19%9%3
270
11th to 20thDay
29%14%33%16%7%3
200
21st to endDay
30%12%37%17%3
180
December1st to 10thDay
27%17%32%17%6%1
180
11th to 20thDay
27%18%32%17%5%
180
21st to endDay
32%19%31%15%21
198
January1st to 10thNight
25%15%37%17%5%1
910
11th to 20thNight
29%13%31%23%4
760
21st to endNight
23%9%35%25%7%
836
February1st to 10thNight
25%14%35%24%3
760
11th to 20thNight
24%14%30%26%6%
742
21st to endNight
25%15%36%21%3
592
March1st to 10thNight
20%10%36%27%7%
720
11th to 20thNight
21%12%35%25%8%1
720
21st to endNight
25%9%28%28%9%1
792
April1st to 10thNight
23%13%30%29%5%
720
11th to 20thNight
22%10%32%26%10%1
557
21st to endNight
21%6%34%31%8%1
540
May1st to 10thNight
21%430%31%13%1
540
11th to 20thNight
16%427%40%11%2
531
21st to endNight
13%228%40%16%1
391
June1st to 10thNight
14%427%39%14%1
360
11th to 20thNight
14%323%45%15%
360
21st to endNight
11%5%19%49%16%1
360
July1st to 10thNight
6%117%50%24%2
350
11th to 20thNight
11%218%40%26%3
513
21st to endNight
9%315%48%23%2
591
August1st to 10thNight
9%110%46%31%3
537
11th to 20thNight
10%112%39%33%5%
534
21st to endNight
13%216%38%28%3
601
September1st to 10thNight
11%420%37%23%6%
720
11th to 20thNight
12%316%37%27%4
720
21st to endNight
18%7%19%33%17%5%
720
October1st to 10thNight
18%5%26%31%18%2
720
11th to 20thNight
25%10%27%28%10%1
720
21st to endNight
30%9%30%26%5%
792
November1st to 10thNight
20%11%26%32%10%1
740
11th to 20thNight
24%11%36%21%6%2
760
21st to endNight
29%11%30%25%6%
760
December1st to 10thNight
30%14%32%19%5%
760
11th to 20thNight
25%16%37%18%4
760
21st to endNight
29%12%35%21%3
897
Page generated at 2024-02-17 06:28:41. Version ac07

Copyright 2024 Attilla Danko


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