Lost Valley Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lost Valley Observatory clear sky chart from 2005-11-06 to 2024-01-16.

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
65%
23720
31%
74667
26%
23675
72%
23675
44%
38126

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
48%
756
23%
2646
17%
756
58%
756
28%
1485
January11th to 20thNight
53%
744
28%
2509
23%
744
64%
744
35%
1358
January21st to endNight
51%
792
30%
2574
22%
792
63%
792
31%
1481
February1st to 10thNight
53%
720
29%
2232
23%
720
62%
720
34%
1277
February11th to 20thNight
53%
700
31%
2098
25%
700
63%
700
37%
1179
February21st to endNight
51%
592
24%
1776
21%
592
58%
592
30%
1089
March1st to 10thNight
50%
720
20%
2160
18%
720
56%
720
27%
1364
March11th to 20thNight
55%
720
21%
2044
17%
720
60%
720
31%
1256
March21st to endNight
54%
792
21%
2012
13%
792
60%
792
37%
1244
April1st to 10thNight
59%
720
25%
1800
13%
720
65%
720
41%
1083
April11th to 20thNight
56%
711
28%
1779
13%
711
61%
711
42%
1057
April21st to endNight
61%
720
27%
1800
12%
720
66%
720
50%
999
May1st to 10thNight
65%
644
29%
1724
16%
644
69%
644
49%
910
May11th to 20thNight
68%
531
33%
1595
24%
531
73%
531
55%
742
May21st to endNight
68%
401
29%
1565
26%
401
77%
401
48%
641
June1st to 10thNight
76%
360
32%
1440
37%
360
80%
360
51%
574
June11th to 20thNight
80%
360
38%
1440
44%
360
87%
360
66%
473
June21st to endNight
82%
360
39%
1440
45%
360
90%
360
72%
447
July1st to 10thNight
86%
350
40%
1400
48%
350
91%
350
76%
423
July11th to 20thNight
82%
348
38%
1392
43%
348
88%
348
61%
490
July21st to endNight
82%
506
39%
1594
36%
478
86%
478
58%
682
August1st to 10thNight
82%
667
37%
1732
24%
664
85%
664
75%
780
August11th to 20thNight
88%
712
40%
1780
24%
712
90%
712
77%
821
August21st to endNight
87%
792
45%
1980
28%
792
89%
792
80%
900
September1st to 10thNight
88%
720
47%
1800
32%
720
90%
720
83%
791
September11th to 20thNight
84%
720
46%
1861
37%
720
87%
720
75%
840
September21st to endNight
81%
720
44%
1980
37%
720
88%
720
72%
870
October1st to 10thNight
76%
720
35%
2059
33%
720
82%
720
58%
987
October11th to 20thNight
73%
720
39%
2160
37%
720
80%
720
60%
973
October21st to endNight
71%
792
44%
2407
40%
792
82%
792
61%
1048
November1st to 10thNight
68%
740
32%
2405
33%
740
74%
740
43%
1203
November11th to 20thNight
64%
760
35%
2470
30%
760
74%
760
46%
1186
November21st to endNight
58%
760
32%
2470
28%
760
68%
760
38%
1303
December1st to 10thNight
55%
760
26%
2555
22%
760
64%
760
33%
1416
December11th to 20thNight
48%
760
22%
3227
20%
759
58%
759
19%
2105
December21st to endNight
44%
830
17%
4761
18%
817
56%
817
16%
2649

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
8%5%23323345%62%
74817
Night
8%5%23323346%63%
75007
TransparencyDay
25%47%21%27%17%
74528
Night
24%48%22%27%16%
74818
SeeingDay
12%10%30%32%12%5%
14109
Night
10%416%33%28%10%
23735

By Month

Percentage Cloud Cover SW (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
16%9%13323448%45%
1519
11th to 20thDay
13%5%24333346%52%
1574
21st to endDay
14%10%24434447%44%
1782
February1st to 10thDay
14%10%23223447%50%
1727
11th to 20thDay
10%12%24424445%48%
1750
21st to endDay
16%12%46%424345%41%
1480
March1st to 10thDay
15%13%46%4245%46%36%
1800
11th to 20thDay
14%13%34434447%41%
1913
21st to endDay
14%11%343245%46%43%
2342
April1st to 10thDay
11%9%35%323447%48%
2160
11th to 20thDay
12%8%25%433445%51%
2129
21st to endDay
10%7%2432335%7%53%
2160
May1st to 10thDay
9%6%23323346%60%
2236
11th to 20thDay
8%5%1332345%6%62%
2301
21st to endDay
10%5%14423347%58%
2706
June1st to 10thDay
431332345%7%64%
2520
11th to 20thDay
12121223481%
2520
21st to endDay
221221222383%
2520
July1st to 10thDay
111221222484%
2520
11th to 20thDay
221221233480%
2520
21st to endDay
2212213346%74%
2626
August1st to 10thDay
221121122383%
2195
11th to 20thDay
11121123483%
2122
21st to endDay
11121122385%
2376
September1st to 10thDay
21121122384%
2160
11th to 20thDay
211221232480%
2098
21st to endDay
421121233477%
1980
October1st to 10thDay
5%42232234469%
1898
11th to 20thDay
4212323345%70%
1800
21st to endDay
7%212212435%70%
1947
November1st to 10thDay
8%7%24423447%55%
1674
11th to 20thDay
8%41332345%6%62%
1710
21st to endDay
8%6%33423346%58%
1710
December1st to 10thDay
13%424423447%53%
1620
11th to 20thDay
22%9%36%6%34335%36%
1928
21st to endDay
10%11%46%5%345%5%8%41%
2794
January1st to 10thNight
15%6%2332345%7%48%
2646
11th to 20thNight
11%5%233245%6%7%53%
2509
21st to endNight
13%8%23323448%51%
2574
February1st to 10thNight
13%8%23223347%52%
2232
11th to 20thNight
10%8%23323348%54%
2098
21st to endNight
14%9%34333345%50%
1776
March1st to 10thNight
14%10%3432445%6%45%
2160
11th to 20thNight
10%10%2433435%8%46%
2044
21st to endNight
12%9%23323336%54%
2012
April1st to 10thNight
11%7%1322345%7%55%
1800
11th to 20thNight
8%6%13423445%60%
1779
21st to endNight
7%413322446%63%
1800
May1st to 10thNight
5%413324346%65%
1724
11th to 20thNight
6%312213346%71%
1594
21st to endNight
6%313212335%71%
1565
June1st to 10thNight
4322313236%71%
1440
11th to 20thNight
11211223384%
1440
21st to endNight
11111222288%
1440
July1st to 10thNight
111123487%
1440
11th to 20thNight
221221123380%
1440
21st to endNight
2213313435%74%
1688
August1st to 10thNight
23111122483%
1741
11th to 20thNight
11121222385%
1780
21st to endNight
211121122287%
1980
September1st to 10thNight
11111112390%
1800
11th to 20thNight
221111123383%
1861
21st to endNight
21111223382%
1980
October1st to 10thNight
431222333473%
2059
11th to 20thNight
5%112213335%74%
2160
21st to endNight
5%2221223478%
2407
November1st to 10thNight
8%5%13322347%62%
2405
11th to 20thNight
7%32331335%7%63%
2470
21st to endNight
8%6%23324446%58%
2470
December1st to 10thNight
13%6%24333247%54%
2555
11th to 20thNight
23%8%24324446%39%
3276
21st to endNight
11%8%36%6%35%5%6%8%40%
4862

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
37%5%9%25%19%5%
1519
11th to 20thDay
33%6%8%20%19%14%
1574
21st to endDay
41%48%19%19%9%
1782
February1st to 10thDay
35%46%25%19%10%
1727
11th to 20thDay
37%5%6%22%22%8%
1760
21st to endDay
47%47%23%17%2
1480
March1st to 10thDay
48%6%9%17%15%5%
1800
11th to 20thDay
42%5%10%22%17%5%
1913
21st to endDay
42%6%14%23%13%3
2342
April1st to 10thDay
36%6%13%25%18%3
2160
11th to 20thDay
36%5%10%24%22%3
2132
21st to endDay
31%5%12%33%18%2
2160
May1st to 10thDay
25%5%9%32%25%3
2236
11th to 20thDay
23%5%9%32%26%4
2304
21st to endDay
27%5%10%36%20%2
2707
June1st to 10thDay
19%5%11%25%30%9%
2520
11th to 20thDay
9%37%23%40%18%
2520
21st to endDay
10%2214%42%31%
2520
July1st to 10thDay
8%3111%31%46%
2451
11th to 20thDay
10%3314%31%38%
2445
21st to endDay
12%5%417%28%35%
2480
August1st to 10thDay
9%2312%32%41%
2179
11th to 20thDay
6%3214%39%36%
2122
21st to endDay
7%3111%42%36%
2376
September1st to 10thDay
8%329%36%42%
2160
11th to 20thDay
10%3323%37%24%
2098
21st to endDay
12%3320%39%22%
1980
October1st to 10thDay
19%45%19%30%23%
1898
11th to 20thDay
17%5%421%30%24%
1800
21st to endDay
17%4420%34%21%
1947
November1st to 10thDay
29%5%7%19%23%16%
1674
11th to 20thDay
23%47%22%32%12%
1710
21st to endDay
29%46%17%28%15%
1710
December1st to 10thDay
31%5%8%21%23%12%
1620
11th to 20thDay
52%5%7%13%15%9%
1928
21st to endDay
43%38%25%15%6%
2794
January1st to 10thNight
36%39%25%21%6%
2646
11th to 20thNight
29%5%9%24%22%11%
2509
21st to endNight
33%5%8%19%24%10%
2574
February1st to 10thNight
33%37%26%20%11%
2232
11th to 20thNight
29%5%8%24%25%9%
2099
21st to endNight
38%410%25%17%6%
1776
March1st to 10thNight
39%5%10%22%19%5%
2160
11th to 20thNight
36%5%11%24%18%6%
2044
21st to endNight
33%5%17%28%14%4
2012
April1st to 10thNight
29%5%16%28%16%6%
1800
11th to 20thNight
27%6%12%28%21%6%
1779
21st to endNight
21%5%14%39%19%2
1800
May1st to 10thNight
21%5%11%35%24%4
1724
11th to 20thNight
17%39%38%28%4
1595
21st to endNight
16%413%37%26%3
1565
June1st to 10thNight
16%312%27%34%8%
1440
11th to 20thNight
8%37%25%40%17%
1440
21st to endNight
6%2314%42%33%
1440
July1st to 10thNight
5%2111%34%46%
1400
11th to 20thNight
11%3412%35%35%
1392
21st to endNight
14%4315%31%33%
1594
August1st to 10thNight
9%2316%29%41%
1732
11th to 20thNight
7%3115%39%34%
1780
21st to endNight
8%1113%41%36%
1980
September1st to 10thNight
5%1113%33%47%
1800
11th to 20thNight
8%3420%44%21%
1861
21st to endNight
9%3324%39%22%
1980
October1st to 10thNight
16%46%19%32%22%
2059
11th to 20thNight
14%35%22%31%24%
2160
21st to endNight
13%3324%35%22%
2407
November1st to 10thNight
24%47%22%25%18%
2405
11th to 20thNight
21%48%21%32%14%
2470
21st to endNight
28%47%19%30%13%
2470
December1st to 10thNight
33%48%20%22%14%
2555
11th to 20thNight
46%5%8%17%17%8%
3276
21st to endNight
41%49%22%17%6%
4862

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
33%9%24%20%11%2
180
11th to 20thDay
19%10%27%25%13%5%
262
21st to endDay
20%8%25%27%14%5%
374
February1st to 10thDay
21%11%23%26%15%4
388
11th to 20thDay
18%16%33%22%9%2
415
21st to endDay
19%17%36%19%8%1
346
March1st to 10thDay
25%14%34%19%7%1
420
11th to 20thDay
24%15%27%22%9%3
420
21st to endDay
25%15%33%22%6%
462
April1st to 10thDay
18%13%34%26%8%2
420
11th to 20thDay
21%19%28%24%6%2
412
21st to endDay
15%10%34%26%11%4
420
May1st to 10thDay
17%15%32%25%8%4
423
11th to 20thDay
16%13%28%27%12%5%
448
21st to endDay
17%9%26%31%10%7%
485
June1st to 10thDay
5%13%27%33%15%8%
450
11th to 20thDay
5%10%28%37%13%7%
450
21st to endDay
28%32%35%14%8%
450
July1st to 10thDay
2227%45%14%10%
446
11th to 20thDay
2123%44%16%13%
444
21st to endDay
2323%49%12%11%
487
August1st to 10thDay
26%36%35%13%8%
447
11th to 20thDay
2430%43%12%10%
437
21st to endDay
2428%45%16%5%
495
September1st to 10thDay
46%33%40%13%4
450
11th to 20thDay
5%9%36%37%11%2
450
21st to endDay
7%9%32%39%12%1
450
October1st to 10thDay
6%13%32%36%12%1
450
11th to 20thDay
411%31%40%12%2
450
21st to endDay
7%10%32%33%16%2
462
November1st to 10thDay
11%11%30%29%17%3
270
11th to 20thDay
7%10%31%30%17%4
270
21st to endDay
10%13%29%29%15%4
270
December1st to 10thDay
18%7%29%28%17%2
228
11th to 20thDay
17%8%27%29%14%4
180
21st to endDay
22%10%30%21%11%6%
198
January1st to 10thNight
19%6%19%27%18%11%
760
11th to 20thNight
13%5%25%32%18%9%
744
21st to endNight
19%5%20%31%17%7%
792
February1st to 10thNight
19%419%34%18%8%
720
11th to 20thNight
13%6%21%30%21%9%
704
21st to endNight
19%5%18%39%14%5%
592
March1st to 10thNight
19%8%15%36%17%6%
720
11th to 20thNight
15%5%16%28%26%10%
720
21st to endNight
17%5%17%36%21%5%
792
April1st to 10thNight
15%5%16%39%20%6%
720
11th to 20thNight
12%5%21%31%24%7%
711
21st to endNight
8%6%20%35%23%9%
720
May1st to 10thNight
8%418%36%27%7%
644
11th to 20thNight
8%216%34%33%6%
531
21st to endNight
7%218%29%33%11%
402
June1st to 10thNight
6%111%36%38%8%
360
11th to 20thNight
1312%37%38%9%
360
21st to endNight
1211%34%43%9%
360
July1st to 10thNight
1110%25%55%9%
350
11th to 20thNight
319%28%47%12%
348
21st to endNight
218%22%47%20%
506
August1st to 10thNight
3110%28%46%12%
667
11th to 20thNight
26%27%52%13%
712
21st to endNight
217%27%49%14%
792
September1st to 10thNight
217%29%46%15%
720
11th to 20thNight
318%34%38%15%
720
21st to endNight
3113%33%35%14%
720
October1st to 10thNight
6%212%44%26%11%
720
11th to 20thNight
6%215%34%29%13%
720
21st to endNight
5%415%30%28%18%
792
November1st to 10thNight
11%313%33%26%14%
740
11th to 20thNight
9%319%38%22%9%
760
21st to endNight
11%420%34%21%9%
760
December1st to 10thNight
16%418%37%17%7%
760
11th to 20thNight
21%5%21%32%16%5%
760
21st to endNight
20%7%22%30%17%4
836
Page generated at 2024-01-13 16:28:28. Version ac07

Copyright 2024 Attilla Danko


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