Lanphier Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lanphier Observatory clear sky chart from 2005-11-05 to 2017-12-02.

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
31%
16398
11%
47966
7%
16355
34%
16355
15%
36587

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
10%
900
2%
2506
1%
895
11%
895
4%
2299
January16th to endNight
10%
960
3%
2688
1%
960
12%
960
4%
2467
February1st to 15thNight
13%
778
3%
2291
1%
776
15%
776
5%
2020
February16th to endNight
19%
631
6%
1893
3%
631
22%
631
8%
1586
March1st to 15thNight
27%
720
12%
2151
7%
720
32%
720
15%
1613
March16th to endNight
34%
705
17%
2049
12%
705
39%
705
20%
1454
April1st to 15thNight
28%
539
13%
1797
8%
539
34%
539
16%
1266
April16th to endNight
36%
540
19%
1632
12%
540
43%
540
23%
1100
May1st to 15thNight
37%
540
13%
1600
8%
540
42%
540
19%
1133
May16th to endNight
47%
561
15%
1498
8%
561
53%
561
31%
974
June1st to 15thNight
48%
540
11%
1440
7%
540
51%
540
28%
963
June16th to endNight
53%
540
13%
1440
8%
540
56%
540
29%
956
July1st to 15thNight
63%
510
15%
1360
10%
510
65%
510
39%
808
July16th to endNight
59%
564
16%
1417
11%
531
62%
531
39%
862
August1st to 15thNight
61%
539
20%
1535
14%
536
66%
536
35%
905
August16th to endNight
57%
573
17%
1808
14%
573
61%
573
29%
1105
September1st to 15thNight
51%
591
16%
1851
14%
591
55%
591
27%
1148
September16th to endNight
51%
717
18%
1980
14%
717
53%
717
29%
1290
October1st to 15thNight
33%
720
15%
2049
10%
720
38%
720
19%
1503
October16th to endNight
24%
768
9%
2496
6%
768
29%
768
10%
1976
November1st to 15thNight
23%
760
12%
2471
9%
760
28%
760
11%
1914
November16th to endNight
14%
832
5%
2587
3%
832
17%
832
6%
2246
December1st to 15thNight
7%
910
1%
2715
1%
910
7%
910
3%
2513
December16th to endNight
7%
960
3%
2712
0%
960
10%
960
3%
2486

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%10%47%6%3445%6%32%
48486
Night
15%12%5%9%7%34345%28%
48134
Cloud CoverDay
14%10%47%6%34446%33%
48495
Night
15%12%5%9%6%34345%28%
48139
TransparencyDay
52%6%11%19%9%
48172
Night
58%5%11%16%7%
47966
SeeingDay
18%8%27%29%13%3
6288
Night
21%11%27%27%10%1
16401

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
15%20%10%15%11%5%43226%
1432
16th to endDay
11%17%11%17%13%7%6%3325%
1536
February1st to 15thDay
12%15%9%14%16%5%5%32310%
1570
16th to endDay
12%17%8%13%10%45%34415%
1580
March1st to 15thDay
11%11%412%10%35%445%28%
1799
16th to endDay
14%9%48%6%24446%32%
2184
April1st to 15thDay
18%12%35%5%3335%5%32%
2151
16th to endDay
16%9%36%424346%35%
2328
May1st to 15thDay
14%6%35%6%2446%5%39%
2349
16th to endDay
10%5%24435%5%5%7%45%
2617
June1st to 15thDay
12%5%245%3446%8%42%
2520
16th to endDay
10%5%245%345%6%8%43%
2520
July1st to 15thDay
9%32332446%7%50%
2520
16th to endDay
8%31342446%9%50%
2655
August1st to 15thDay
8%42442446%10%48%
2415
16th to endDay
14%5%25%323346%47%
2393
September1st to 15thDay
14%5%245%3445%6%42%
2097
16th to endDay
13%6%245%25%5%6%8%40%
1980
October1st to 15thDay
19%9%36%6%34447%30%
1910
16th to endDay
25%16%48%5%24345%18%
1728
November1st to 15thDay
19%18%46%5%24345%23%
1717
16th to endDay
19%25%8%11%5%3323413%
1700
December1st to 15thDay
17%21%15%18%8%232117%
1279
16th to endDay
20%25%11%11%8%242336%
1506
January1st to 15thNight
17%18%9%15%11%442229%
2506
16th to endNight
12%16%11%16%13%6%5%3339%
2688
February1st to 15thNight
12%15%8%15%14%5%5%33213%
2289
16th to endNight
14%15%7%15%9%45%235%16%
1893
March1st to 15thNight
12%11%5%9%7%35%435%31%
2138
16th to endNight
13%11%47%6%3445%6%33%
2049
April1st to 15thNight
21%10%35%5%2345%6%31%
1797
16th to endNight
16%9%25%5%24336%39%
1632
May1st to 15thNight
15%8%35%7%46%5%5%6%32%
1600
16th to endNight
10%6%25%4245%8%8%41%
1496
June1st to 15thNight
13%5%345%35%45%6%40%
1440
16th to endNight
9%5%345%25%45%9%42%
1440
July1st to 15thNight
9%423325%35%8%50%
1440
16th to endNight
7%5%1442445%7%51%
1513
August1st to 15thNight
5%4245%345%6%7%50%
1544
16th to endNight
13%5%245%2245%7%46%
1808
September1st to 15thNight
12%7%16%433346%46%
1851
16th to endNight
16%5%25%42335%8%42%
1980
October1st to 15thNight
21%10%36%5%32346%32%
2049
16th to endNight
23%12%5%8%6%34335%22%
2496
November1st to 15thNight
18%17%48%6%33345%25%
2471
16th to endNight
19%22%7%12%6%3343414%
2587
December1st to 15thNight
17%22%13%16%9%232128%
2715
16th to endNight
18%23%11%14%8%332238%
2712

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%21%11%15%10%5%43226%
1432
16th to endDay
12%17%10%19%11%7%5%3335%
1536
February1st to 15thDay
13%15%9%14%16%5%5%22311%
1570
16th to endDay
13%17%8%13%11%35%33414%
1580
March1st to 15thDay
12%11%411%9%35%445%27%
1809
16th to endDay
15%9%5%8%6%34346%32%
2183
April1st to 15thDay
19%12%36%42345%6%32%
2151
16th to endDay
17%10%35%5%25%436%35%
2328
May1st to 15thDay
15%6%35%5%2445%6%39%
2349
16th to endDay
10%5%244345%5%8%45%
2617
June1st to 15thDay
12%5%2444446%8%42%
2520
16th to endDay
10%5%25%425%46%8%44%
2520
July1st to 15thDay
9%31333446%7%50%
2520
16th to endDay
8%31342446%9%50%
2655
August1st to 15thDay
8%42442446%10%48%
2415
16th to endDay
15%5%24323346%47%
2393
September1st to 15thDay
15%5%2443445%6%42%
2097
16th to endDay
14%5%2443446%7%40%
1980
October1st to 15thDay
20%9%36%5%34447%30%
1910
16th to endDay
26%16%47%6%24345%18%
1728
November1st to 15thDay
18%19%46%423346%23%
1717
16th to endDay
19%26%8%10%42333413%
1700
December1st to 15thDay
18%21%15%17%7%231127%
1279
16th to endDay
20%25%11%11%7%342337%
1506
January1st to 15thNight
18%17%10%16%10%4432210%
2506
16th to endNight
12%16%10%16%13%5%43339%
2688
February1st to 15thNight
12%15%8%14%13%5%5%33313%
2282
16th to endNight
14%16%7%15%8%34345%16%
1893
March1st to 15thNight
13%10%6%9%6%34445%31%
2151
16th to endNight
14%11%47%5%3445%6%33%
2049
April1st to 15thNight
21%10%35%5%2435%6%32%
1797
16th to endNight
16%8%35%424336%40%
1632
May1st to 15thNight
16%6%35%7%46%5%5%6%32%
1599
16th to endNight
10%5%25%4245%8%9%41%
1496
June1st to 15thNight
14%5%245%3445%7%40%
1440
16th to endNight
9%6%245%3445%9%42%
1440
July1st to 15thNight
10%42332445%8%51%
1440
16th to endNight
7%42442345%7%51%
1513
August1st to 15thNight
5%4235%345%5%8%50%
1544
16th to endNight
13%5%145%2335%7%47%
1808
September1st to 15thNight
13%6%25%423336%47%
1851
16th to endNight
15%6%25%42335%8%42%
1980
October1st to 15thNight
22%9%36%5%22335%33%
2049
16th to endNight
23%13%48%6%24335%23%
2496
November1st to 15thNight
18%17%5%7%5%24345%25%
2471
16th to endNight
19%22%7%11%5%2433414%
2587
December1st to 15thNight
17%22%14%16%8%322128%
2715
16th to endNight
18%23%10%14%8%332338%
2712

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
87%344
1433
16th to endDay
85%5%43
1536
February1st to 15thDay
80%46%7%
1572
16th to endDay
72%6%9%7%3
1580
March1st to 15thDay
58%6%12%16%5%
1809
16th to endDay
52%6%12%21%41
2184
April1st to 15thDay
51%5%10%20%10%
2151
16th to endDay
49%410%17%15%2
2328
May1st to 15thDay
44%6%11%24%10%2
2349
16th to endDay
35%7%12%27%14%2
2621
June1st to 15thDay
38%6%13%27%12%
2520
16th to endDay
36%7%17%23%13%1
2520
July1st to 15thDay
30%6%12%32%16%1
2371
16th to endDay
30%7%15%27%17%1
2488
August1st to 15thDay
30%6%16%33%12%
2400
16th to endDay
37%5%13%27%14%1
2393
September1st to 15thDay
39%7%14%26%11%
2097
16th to endDay
41%6%16%26%9%
1980
October1st to 15thDay
52%5%11%21%7%
1910
16th to endDay
68%5%11%11%2
1728
November1st to 15thDay
62%5%10%14%6%
1717
16th to endDay
76%5%11%6%1
1700
December1st to 15thDay
87%244
1279
16th to endDay
84%46%3
1506
January1st to 15thNight
83%36%5%
2506
16th to endNight
82%46%5%
2688
February1st to 15thNight
77%47%8%1
2291
16th to endNight
70%411%9%3
1893
March1st to 15thNight
55%6%12%17%7%
2151
16th to endNight
51%412%21%9%
2049
April1st to 15thNight
52%5%9%20%10%1
1797
16th to endNight
45%5%10%20%15%3
1632
May1st to 15thNight
50%5%10%20%10%2
1600
16th to endNight
36%7%13%25%14%2
1498
June1st to 15thNight
42%5%13%23%14%1
1440
16th to endNight
37%8%13%23%14%1
1440
July1st to 15thNight
30%5%13%29%18%2
1360
16th to endNight
31%5%15%27%18%1
1417
August1st to 15thNight
31%6%16%32%11%
1535
16th to endNight
36%6%16%24%15%1
1808
September1st to 15thNight
40%413%24%16%
1851
16th to endNight
40%5%16%27%9%
1980
October1st to 15thNight
54%49%21%10%
2049
16th to endNight
64%5%11%13%4
2496
November1st to 15thNight
62%5%11%14%6%
2471
16th to endNight
75%410%6%1
2587
December1st to 15thNight
85%35%41
2715
16th to endNight
83%37%31
2712

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
23%21%34%18%2
90
16th to endDay
30%5%36%22%5%
96
February1st to 15thDay
15%25%42%14%2
90
16th to endDay
19%18%35%18%7%
81
March1st to 15thDay
17%23%27%22%10%
99
16th to endDay
27%6%27%26%10%1
288
April1st to 15thDay
26%9%29%23%8%2
270
16th to endDay
22%10%33%20%10%2
270
May1st to 15thDay
18%10%32%28%8%2
306
16th to endDay
15%7%30%30%12%3
517
June1st to 15thDay
17%5%30%29%12%3
495
16th to endDay
10%6%30%36%10%4
495
July1st to 15thDay
10%423%38%18%4
475
16th to endDay
8%227%39%16%4
515
August1st to 15thDay
11%117%39%22%6%
388
16th to endDay
20%418%30%20%5%
332
September1st to 15thDay
19%122%23%22%10%
315
16th to endDay
14%8%19%33%19%5%
314
October1st to 15thDay
24%10%27%23%10%1
282
16th to endDay
34%6%42%13%2
144
November1st to 15thDay
27%15%27%21%8%
135
16th to endDay
24%25%28%17%2
135
December1st to 15thDay
32%27%29%7%3
65
16th to endDay
32%32%30%21
91
January1st to 15thNight
24%21%28%20%4
900
16th to endNight
21%18%36%19%4
960
February1st to 15thNight
20%18%32%22%5%
779
16th to endNight
23%16%27%26%5%
631
March1st to 15thNight
18%13%32%26%8%1
720
16th to endNight
19%11%28%31%8%1
705
April1st to 15thNight
24%9%31%25%7%1
539
16th to endNight
19%7%30%30%10%1
540
May1st to 15thNight
19%6%28%33%10%
540
16th to endNight
13%428%34%16%2
563
June1st to 15thNight
16%422%39%15%1
540
16th to endNight
13%223%40%19%1
540
July1st to 15thNight
11%316%39%26%2
510
16th to endNight
8%223%37%25%2
564
August1st to 15thNight
6%122%39%27%3
539
16th to endNight
16%216%39%21%2
573
September1st to 15thNight
18%418%30%20%7%
591
16th to endNight
20%5%18%29%21%4
717
October1st to 15thNight
30%7%23%25%12%
720
16th to endNight
32%12%24%24%5%
768
November1st to 15thNight
30%13%27%22%5%
760
16th to endNight
32%19%26%18%3
832
December1st to 15thNight
31%22%30%13%2
910
16th to endNight
28%17%34%15%21
960
Page generated at 2017-12-03 11:16:44. Version ac04

Copyright 2017 A. Danko


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