Lanphier Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lanphier Observatory clear sky chart from 2005-11-06 to 2024-02-10.

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
30%
24894
10%
80960
7%
24796
33%
24796
13%
63020

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
8%
945
2%
4414
0%
926
10%
926
2%
4003
January11th to 20thNight
10%
948
2%
4440
1%
930
12%
930
2%
4171
January21st to endNight
11%
1033
1%
4882
1%
1023
12%
1023
2%
4471
February1st to 10thNight
13%
876
4%
2556
2%
876
15%
876
6%
2256
February11th to 20thNight
14%
702
8%
2099
2%
700
19%
700
6%
1780
February21st to endNight
16%
592
7%
1776
2%
592
21%
592
9%
1452
March1st to 10thNight
26%
720
13%
2160
7%
720
32%
720
16%
1598
March11th to 20thNight
27%
720
17%
2056
9%
720
34%
720
18%
1508
March21st to endNight
31%
698
16%
2084
11%
698
36%
698
18%
1488
April1st to 10thNight
27%
540
11%
1800
7%
540
32%
540
14%
1312
April11th to 20thNight
30%
533
17%
1705
11%
533
37%
533
19%
1194
April21st to endNight
36%
540
16%
1620
9%
540
43%
540
21%
1116
May1st to 10thNight
38%
540
14%
1620
10%
540
42%
540
21%
1119
May11th to 20thNight
39%
531
16%
1478
10%
531
45%
531
21%
1056
May21st to endNight
51%
582
14%
1552
8%
582
56%
582
32%
999
June1st to 10thNight
48%
540
13%
1440
7%
540
53%
540
29%
951
June11th to 20thNight
53%
540
14%
1440
10%
540
55%
540
29%
939
June21st to endNight
54%
540
15%
1440
9%
540
58%
540
32%
927
July1st to 10thNight
64%
525
16%
1400
10%
525
66%
525
42%
810
July11th to 20thNight
59%
522
16%
1392
11%
522
62%
522
37%
849
July21st to endNight
58%
591
18%
1487
14%
558
60%
558
36%
928
August1st to 10thNight
60%
537
19%
1487
14%
534
63%
534
32%
926
August11th to 20thNight
59%
534
20%
1598
14%
534
65%
534
33%
942
August21st to endNight
54%
594
16%
1914
14%
594
57%
594
27%
1182
September1st to 10thNight
52%
540
18%
1800
16%
540
56%
540
28%
1066
September11th to 20thNight
51%
705
20%
1965
15%
705
54%
705
30%
1265
September21st to endNight
44%
720
17%
1980
13%
720
46%
720
24%
1371
October1st to 10thNight
36%
720
17%
1980
11%
720
41%
720
21%
1420
October11th to 20thNight
25%
720
10%
2261
6%
720
30%
720
12%
1769
October21st to endNight
21%
792
9%
2574
7%
792
26%
792
9%
2092
November1st to 10thNight
24%
740
14%
2406
10%
740
30%
740
12%
1821
November11th to 20thNight
14%
760
9%
2470
5%
760
19%
760
7%
2068
November21st to endNight
14%
836
6%
2546
3%
836
17%
836
6%
2207
December1st to 10thNight
7%
950
2%
2831
1%
950
8%
950
3%
2586
December11th to 20thNight
8%
950
2%
3429
1%
949
10%
949
3%
3087
December21st to endNight
5%
1038
2%
4878
0%
1026
8%
1026
2%
4291

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
14%12%5%8%7%3445%6%32%
77831
Night
15%14%6%11%7%34445%26%
81162
TransparencyDay
54%6%11%19%9%1
77531
Night
62%5%10%15%7%1
80982
SeeingDay
18%12%29%26%12%3
14710
Night
22%13%27%26%11%1
24923

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
13%25%17%20%8%432225%
2527
11th to 20thDay
13%18%10%22%16%7%42223
2530
21st to endDay
18%22%13%14%9%443337%
2783
February1st to 10thDay
10%17%8%15%19%5%423412%
1604
11th to 20thDay
13%14%8%15%15%5%5%33415%
1748
21st to endDay
14%16%8%13%10%45%345%18%
1480
March1st to 10thDay
12%12%5%12%9%35%45%6%26%
1800
11th to 20thDay
12%10%5%10%7%45%445%34%
1903
21st to endDay
17%11%48%7%3445%6%30%
2286
April1st to 10thDay
18%14%48%6%3445%6%29%
2160
11th to 20thDay
20%13%45%423446%35%
2204
21st to endDay
16%9%48%5%35%45%7%35%
2340
May1st to 10thDay
14%8%36%5%245%5%7%41%
2340
11th to 20thDay
14%7%35%42446%7%43%
2415
21st to endDay
11%5%25%5%45%6%5%8%46%
2725
June1st to 10thDay
12%5%25%5%45%45%8%46%
2520
11th to 20thDay
11%425%5%45%5%6%10%45%
2520
21st to endDay
12%6%245%2446%9%45%
2520
July1st to 10thDay
8%3243345%7%8%53%
2520
11th to 20thDay
11%42443446%8%51%
2520
21st to endDay
8%4245%345%6%9%52%
2743
August1st to 10thDay
10%425%5%3446%10%47%
2440
11th to 20thDay
12%4345%3445%7%50%
2303
21st to endDay
14%6%35%42435%7%48%
2440
September1st to 10thDay
15%5%25%5%345%6%7%43%
2156
11th to 20thDay
14%5%24425%5%6%8%46%
1980
21st to endDay
16%7%36%5%345%7%7%36%
1980
October1st to 10thDay
18%10%36%5%34448%34%
1980
11th to 20thDay
24%16%48%7%34446%20%
1695
21st to endDay
26%17%49%6%35%445%17%
1782
November1st to 10thDay
18%19%46%434447%27%
1672
11th to 20thDay
15%25%9%10%7%3344416%
1710
21st to endDay
19%24%10%11%5%2333414%
1630
December1st to 10thDay
15%24%17%16%6%332239%
1344
11th to 20thDay
15%23%11%14%9%45%4448%
1748
21st to endDay
20%22%13%13%8%443338%
2783
January1st to 10thNight
13%26%11%21%8%3222210%
4428
11th to 20thNight
12%17%9%20%19%7%33226%
4440
21st to endNight
16%22%12%15%10%5%5%3338%
4884
February1st to 10thNight
11%15%9%16%16%6%443313%
2556
11th to 20thNight
13%14%7%17%12%5%5%33418%
2098
21st to endNight
16%17%7%14%8%34346%19%
1776
March1st to 10thNight
12%12%6%9%7%3445%6%32%
2160
11th to 20thNight
12%11%5%10%7%35%445%33%
2056
21st to endNight
17%10%48%6%3445%5%33%
2084
April1st to 10thNight
19%13%47%6%35%45%6%30%
1800
11th to 20thNight
20%9%5%5%5%3445%6%34%
1705
21st to endNight
17%9%36%5%35%45%6%36%
1620
May1st to 10thNight
17%7%36%6%46%46%7%34%
1620
11th to 20thNight
15%9%36%6%35%5%5%6%35%
1477
21st to endNight
11%5%25%4346%8%10%43%
1551
June1st to 10thNight
14%6%345%345%5%7%43%
1440
11th to 20thNight
13%6%25%5%35%5%6%9%42%
1440
21st to endNight
10%7%35%5%4445%9%46%
1440
July1st to 10thNight
9%4233245%6%10%52%
1440
11th to 20thNight
8%4346%35%5%5%8%49%
1440
21st to endNight
9%5%25%4345%6%7%50%
1575
August1st to 10thNight
7%5%35%5%36%5%5%9%47%
1496
11th to 20thNight
10%5%246%345%7%7%49%
1598
21st to endNight
13%6%25%6%3345%7%45%
1914
September1st to 10thNight
13%6%35%424347%48%
1800
11th to 20thNight
15%5%25%5%33447%47%
1965
21st to endNight
18%7%36%6%3446%8%37%
1980
October1st to 10thNight
19%10%37%6%33445%36%
1980
11th to 20thNight
25%13%47%6%34446%24%
2261
21st to endNight
25%17%5%9%7%3433421%
2574
November1st to 10thNight
16%18%5%7%6%35%35%6%27%
2406
11th to 20thNight
16%21%8%13%6%3443418%
2470
21st to endNight
17%22%10%11%6%3444415%
2546
December1st to 10thNight
14%24%15%16%6%3332310%
2831
11th to 20thNight
15%21%10%20%8%3433310%
3427
21st to endNight
24%22%11%11%7%3333311%
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
90%3421
2528
11th to 20thDay
92%332
2530
21st to endDay
85%48%21
2783
February1st to 10thDay
79%37%9%1
1604
11th to 20thDay
73%6%9%8%3
1758
21st to endDay
69%8%8%10%41
1480
March1st to 10thDay
57%7%12%16%7%1
1800
11th to 20thDay
52%6%11%21%7%2
1903
21st to endDay
54%7%12%19%7%1
2286
April1st to 10thDay
56%6%10%19%10%
2160
11th to 20thDay
50%6%9%19%15%2
2204
21st to endDay
48%6%11%17%15%2
2340
May1st to 10thDay
43%6%10%26%13%2
2340
11th to 20thDay
40%7%11%23%16%3
2419
21st to endDay
36%8%13%26%14%2
2725
June1st to 10thDay
37%7%12%27%15%2
2520
11th to 20thDay
34%8%13%24%19%1
2520
21st to endDay
36%7%17%24%15%1
2520
July1st to 10thDay
26%7%14%32%18%3
2451
11th to 20thDay
29%8%14%31%16%2
2445
21st to endDay
29%8%14%29%18%2
2591
August1st to 10thDay
32%7%17%32%11%1
2425
11th to 20thDay
33%7%14%31%13%2
2303
21st to endDay
37%6%15%26%15%1
2440
September1st to 10thDay
39%8%13%24%14%1
2156
11th to 20thDay
37%7%18%28%9%1
1980
21st to endDay
45%7%16%25%8%
1980
October1st to 10thDay
49%6%13%23%8%
1980
11th to 20thDay
67%5%11%14%3
1695
21st to endDay
70%5%11%10%3
1782
November1st to 10thDay
59%6%10%17%7%
1672
11th to 20thDay
73%5%10%9%3
1710
21st to endDay
75%5%12%7%1
1630
December1st to 10thDay
85%35%6%1
1344
11th to 20thDay
82%6%8%31
1744
21st to endDay
83%5%6%41
2783
January1st to 10thNight
84%37%5%1
4428
11th to 20thNight
88%35%3
4440
21st to endNight
84%6%8%31
4884
February1st to 10thNight
77%5%7%9%2
2556
11th to 20thNight
72%5%7%12%3
2099
21st to endNight
67%5%12%12%4
1776
March1st to 10thNight
54%7%13%20%7%
2160
11th to 20thNight
53%5%10%19%11%2
2056
21st to endNight
53%5%11%21%10%1
2084
April1st to 10thNight
55%6%9%19%10%1
1800
11th to 20thNight
50%6%9%19%13%3
1705
21st to endNight
48%5%11%20%13%3
1620
May1st to 10thNight
48%6%11%20%12%4
1620
11th to 20thNight
49%6%8%20%15%2
1478
21st to endNight
36%7%15%25%15%3
1552
June1st to 10thNight
40%6%11%28%13%2
1440
11th to 20thNight
39%6%13%23%16%3
1440
21st to endNight
35%8%13%26%16%2
1440
July1st to 10thNight
27%6%15%31%18%3
1400
11th to 20thNight
32%5%16%23%21%3
1392
21st to endNight
32%8%15%28%16%1
1487
August1st to 10thNight
34%8%15%29%12%2
1487
11th to 20thNight
31%7%16%29%16%1
1598
21st to endNight
38%6%15%23%16%1
1914
September1st to 10thNight
36%6%15%22%21%1
1800
11th to 20thNight
39%6%16%28%11%1
1965
21st to endNight
46%6%16%25%7%
1980
October1st to 10thNight
51%5%10%23%11%1
1980
11th to 20thNight
63%5%11%16%5%
2261
21st to endNight
68%5%10%13%4
2574
November1st to 10thNight
59%6%11%17%7%1
2406
11th to 20thNight
73%410%9%4
2470
21st to endNight
74%6%10%8%1
2546
December1st to 10thNight
83%45%7%1
2831
11th to 20thNight
81%6%8%42
3429
21st to endNight
80%5%10%31
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
20%23%36%14%6%1
270
11th to 20thDay
24%19%38%16%2
270
21st to endDay
23%15%36%22%3
297
February1st to 10thDay
17%29%35%14%5%1
267
11th to 20thDay
20%29%33%16%2
240
21st to endDay
23%27%40%8%2
198
March1st to 10thDay
19%24%40%15%3
240
11th to 20thDay
19%17%33%21%8%1
343
21st to endDay
29%14%26%24%7%1
462
April1st to 10thDay
24%16%31%22%5%1
420
11th to 20thDay
26%17%28%17%9%2
412
21st to endDay
18%17%30%24%9%2
420
May1st to 10thDay
19%14%32%24%9%2
423
11th to 20thDay
15%8%34%31%10%2
561
21st to endDay
13%8%28%33%16%3
679
June1st to 10thDay
13%7%31%30%16%3
630
11th to 20thDay
13%7%29%36%12%3
630
21st to endDay
13%6%26%37%14%3
630
July1st to 10thDay
9%323%40%21%5%
621
11th to 20thDay
11%6%24%36%18%5%
618
21st to endDay
8%427%40%18%4
684
August1st to 10thDay
10%321%35%25%6%
559
11th to 20thDay
13%5%19%34%21%9%
439
21st to endDay
17%6%23%31%20%3
495
September1st to 10thDay
22%6%25%24%18%6%
450
11th to 20thDay
12%7%25%32%20%4
450
21st to endDay
19%12%21%27%16%5%
450
October1st to 10thDay
22%14%28%20%13%2
450
11th to 20thDay
32%15%31%17%4
310
21st to endDay
37%15%31%12%5%
297
November1st to 10thDay
27%19%28%19%8%
270
11th to 20thDay
21%26%39%9%4
270
21st to endDay
24%27%33%14%2
270
December1st to 10thDay
31%22%31%11%5%
186
11th to 20thDay
26%28%33%9%3
202
21st to endDay
28%26%33%9%21
297
January1st to 10thNight
22%21%33%19%5%
950
11th to 20thNight
24%23%29%19%5%
950
21st to endNight
22%15%34%23%5%1
1045
February1st to 10thNight
19%20%32%21%6%1
876
11th to 20thNight
21%20%31%24%5%
703
21st to endNight
25%20%30%21%4
592
March1st to 10thNight
18%14%33%25%8%1
720
11th to 20thNight
18%16%34%25%7%1
720
21st to endNight
22%11%29%29%7%1
698
April1st to 10thNight
23%11%32%26%7%1
540
11th to 20thNight
24%10%31%26%9%1
533
21st to endNight
20%7%28%33%11%1
540
May1st to 10thNight
19%7%29%34%11%1
540
11th to 20thNight
18%7%27%34%12%2
531
21st to endNight
14%426%35%20%2
584
June1st to 10thNight
16%424%40%15%1
540
11th to 20thNight
14%6%19%41%18%2
540
21st to endNight
12%422%39%22%1
540
July1st to 10thNight
10%317%42%26%3
525
11th to 20thNight
10%220%35%28%3
522
21st to endNight
10%322%38%25%2
591
August1st to 10thNight
9%320%39%28%2
537
11th to 20thNight
10%419%34%28%6%
534
21st to endNight
15%420%41%19%2
594
September1st to 10thNight
16%421%32%21%4
540
11th to 20thNight
17%6%21%31%20%5%
705
21st to endNight
22%8%19%28%18%4
720
October1st to 10thNight
26%11%22%25%15%2
720
11th to 20thNight
32%14%23%25%6%
720
21st to endNight
35%13%23%22%6%1
792
November1st to 10thNight
27%15%28%24%5%1
740
11th to 20thNight
29%20%30%17%4
760
21st to endNight
29%19%29%19%3
836
December1st to 10thNight
29%23%29%16%3
950
11th to 20thNight
26%21%33%15%41
950
21st to endNight
31%19%33%15%1
1045
Page generated at 2024-02-07 06:11:57. Version ac07

Copyright 2024 Attilla Danko


Lanphier Observatory Clear Sky Chart |Charts Home