Longway Planetarium
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Longway Planetarium clear sky chart from 2005-11-06 to 2024-01-13.

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
33%
24194
15%
74883
9%
24136
40%
24136
19%
52415

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
17%
950
11%
2648
4%
946
24%
946
12%
2109
January11th to 20thNight
17%
911
8%
2549
3%
911
21%
911
11%
2087
January21st to endNight
21%
875
9%
2657
4%
875
26%
875
12%
2094
February1st to 10thNight
16%
720
9%
2340
3%
720
22%
720
9%
1853
February11th to 20thNight
20%
700
14%
2144
5%
699
28%
699
13%
1630
February21st to endNight
19%
592
14%
1776
5%
592
29%
592
14%
1325
March1st to 10thNight
25%
720
17%
2135
10%
720
32%
720
18%
1494
March11th to 20thNight
29%
720
21%
1980
10%
720
38%
720
22%
1359
March21st to endNight
27%
792
18%
2178
9%
792
35%
792
20%
1571
April1st to 10thNight
25%
599
16%
1859
8%
599
34%
599
19%
1272
April11th to 20thNight
28%
533
20%
1633
9%
533
39%
533
22%
1097
April21st to endNight
32%
540
19%
1620
8%
540
41%
540
23%
1092
May1st to 10thNight
33%
540
15%
1620
8%
540
39%
540
22%
1103
May11th to 20thNight
37%
531
19%
1593
11%
531
45%
531
25%
1031
May21st to endNight
50%
583
15%
1691
10%
582
56%
582
31%
1041
June1st to 10thNight
49%
450
18%
1350
14%
450
56%
450
31%
807
June11th to 20thNight
50%
360
21%
1260
21%
360
57%
360
29%
720
June21st to endNight
54%
478
20%
1378
14%
478
62%
478
34%
828
July1st to 10thNight
65%
525
17%
1400
15%
525
67%
525
42%
826
July11th to 20thNight
57%
522
21%
1392
16%
522
62%
522
40%
831
July21st to endNight
62%
591
19%
1582
14%
558
67%
558
39%
929
August1st to 10thNight
66%
537
19%
1600
16%
534
70%
534
38%
934
August11th to 20thNight
62%
534
23%
1598
17%
534
67%
534
34%
943
August21st to endNight
57%
594
23%
1810
17%
594
62%
594
35%
1052
September1st to 10thNight
55%
630
20%
1890
15%
630
59%
630
30%
1167
September11th to 20thNight
57%
720
28%
1980
20%
720
62%
720
38%
1177
September21st to endNight
49%
720
22%
1980
16%
720
53%
720
29%
1280
October1st to 10thNight
44%
720
21%
2020
17%
720
49%
720
27%
1324
October11th to 20thNight
30%
720
15%
2160
8%
720
38%
720
17%
1551
October21st to endNight
23%
792
15%
2546
8%
792
33%
792
16%
1827
November1st to 10thNight
32%
740
22%
2406
15%
740
44%
740
22%
1521
November11th to 20thNight
24%
760
15%
2470
9%
760
32%
760
15%
1744
November21st to endNight
20%
760
13%
2576
6%
760
28%
760
15%
1887
December1st to 10thNight
17%
760
7%
2660
4%
760
21%
760
9%
2104
December11th to 20thNight
15%
935
9%
3469
2%
933
22%
933
9%
2657
December21st to endNight
12%
1040
5%
4933
1%
1026
18%
1026
5%
4148

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%45%5%5%7%33%
74572
Night
16%10%47%6%3445%6%34%
75126
TransparencyDay
50%411%22%12%1
74279
Night
51%411%21%12%1
74940
SeeingDay
20%12%28%22%14%5%
14315
Night
21%10%29%29%11%1
24203

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
16%15%6%11%7%46%5%5%6%20%
1517
11th to 20thDay
16%17%8%13%8%4445%5%15%
1456
21st to endDay
15%17%8%11%8%5%5%35%5%17%
1696
February1st to 10thDay
14%15%6%11%9%45%5%5%7%19%
1620
11th to 20thDay
13%13%7%12%9%45%45%6%22%
1699
21st to endDay
15%16%6%9%8%35%445%24%
1480
March1st to 10thDay
15%10%410%8%45%46%7%28%
1824
11th to 20thDay
13%13%5%7%8%345%6%7%31%
1980
21st to endDay
18%12%49%7%44446%28%
2178
April1st to 10thDay
17%12%46%7%36%45%6%30%
2115
11th to 20thDay
18%10%36%5%345%5%7%35%
2275
21st to endDay
17%9%36%6%45%45%7%34%
2340
May1st to 10thDay
18%8%36%5%46%5%5%7%34%
2340
11th to 20thDay
19%8%26%5%35%5%46%37%
2301
21st to endDay
13%7%25%6%35%5%6%9%40%
2580
June1st to 10thDay
11%6%35%5%45%5%6%8%41%
2600
11th to 20thDay
11%6%36%5%35%5%6%9%41%
2700
21st to endDay
10%6%25%446%6%7%10%39%
2572
July1st to 10thDay
7%435%435%6%6%10%47%
2520
11th to 20thDay
10%5%245%36%5%7%8%45%
2520
21st to endDay
9%5%246%46%5%7%10%42%
2640
August1st to 10thDay
10%5%25%6%45%6%8%9%40%
2327
11th to 20thDay
11%5%26%7%46%6%8%7%40%
2303
21st to endDay
11%5%26%6%445%5%8%44%
2543
September1st to 10thDay
11%6%36%7%46%6%6%7%38%
2052
11th to 20thDay
11%5%344345%5%9%46%
1980
21st to endDay
14%8%345%36%5%6%8%37%
1980
October1st to 10thDay
14%7%27%6%45%45%7%39%
1939
11th to 20thDay
19%10%37%6%346%5%6%30%
1800
21st to endDay
23%10%36%6%35%5%5%6%28%
1806
November1st to 10thDay
12%10%47%7%35%5%5%7%36%
1672
11th to 20thDay
14%12%5%8%6%45%448%28%
1710
21st to endDay
18%13%6%8%6%45%447%26%
1600
December1st to 10thDay
14%16%9%13%8%45%445%20%
1520
11th to 20thDay
15%19%5%8%6%35%5%6%6%22%
1687
21st to endDay
24%22%6%11%6%3434412%
2700
January1st to 10thNight
17%14%7%11%6%5%5%45%5%22%
2648
11th to 20thNight
18%18%7%11%6%4435%5%20%
2549
21st to endNight
14%14%9%10%8%445%45%22%
2657
February1st to 10thNight
16%15%6%11%8%46%44422%
2340
11th to 20thNight
15%14%5%10%7%45%5%5%5%26%
2144
21st to endNight
19%12%5%8%8%345%45%28%
1776
March1st to 10thNight
15%12%5%7%6%34345%35%
2135
11th to 20thNight
13%10%47%5%345%5%6%38%
1980
21st to endNight
20%9%47%6%35%446%33%
2178
April1st to 10thNight
18%10%46%5%3445%7%34%
1859
11th to 20thNight
18%8%36%6%345%46%38%
1633
21st to endNight
18%8%25%5%345%6%7%37%
1620
May1st to 10thNight
15%9%38%6%345%5%8%35%
1620
11th to 20thNight
19%6%35%434446%42%
1592
21st to endNight
11%4246%35%6%5%9%45%
1690
June1st to 10thNight
12%426%5%345%5%9%46%
1350
11th to 20thNight
11%5%24435%5%6%8%46%
1260
21st to endNight
10%5%35%5%2445%9%48%
1378
July1st to 10thNight
7%424435%46%9%52%
1440
11th to 20thNight
9%4145%345%5%10%50%
1440
21st to endNight
7%425%5%345%6%9%50%
1675
August1st to 10thNight
8%424445%5%7%9%48%
1611
11th to 20thNight
9%325%5%46%5%5%8%49%
1598
21st to endNight
9%5%25%42445%7%51%
1810
September1st to 10thNight
11%6%345%346%7%6%46%
1890
11th to 20thNight
12%42442445%7%52%
1980
21st to endNight
15%6%25%5%3446%7%43%
1980
October1st to 10thNight
16%6%26%5%3435%6%43%
2020
11th to 20thNight
21%10%36%5%35%45%5%32%
2160
21st to endNight
23%10%37%6%3445%6%30%
2546
November1st to 10thNight
15%8%25%43445%7%41%
2406
11th to 20thNight
15%13%47%6%35%6%5%7%29%
2470
21st to endNight
20%13%5%6%5%35%45%6%27%
2576
December1st to 10thNight
17%17%8%9%7%45%5%36%19%
2660
11th to 20thNight
15%14%7%11%7%45%445%24%
3507
21st to endNight
25%23%6%10%6%3333413%
4948

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
66%410%14%5%1
1518
11th to 20thDay
71%5%11%9%4
1456
21st to endDay
71%37%13%6%1
1696
February1st to 10thDay
65%5%10%14%6%
1620
11th to 20thDay
64%38%16%8%1
1709
21st to endDay
63%310%15%8%1
1480
March1st to 10thDay
56%412%19%8%1
1824
11th to 20thDay
52%310%20%12%2
1980
21st to endDay
59%39%20%8%1
2178
April1st to 10thDay
56%410%20%10%
2115
11th to 20thDay
50%311%19%14%2
2275
21st to endDay
51%411%18%14%1
2340
May1st to 10thDay
49%410%23%11%2
2340
11th to 20thDay
49%310%22%14%2
2305
21st to endDay
42%414%22%15%2
2580
June1st to 10thDay
40%5%12%26%15%2
2600
11th to 20thDay
41%411%25%17%2
2700
21st to endDay
39%5%12%26%16%2
2572
July1st to 10thDay
32%5%11%29%19%3
2451
11th to 20thDay
35%5%12%28%18%2
2445
21st to endDay
37%6%12%24%18%3
2493
August1st to 10thDay
38%5%14%27%14%2
2314
11th to 20thDay
40%414%26%14%2
2303
21st to endDay
39%5%10%29%16%2
2543
September1st to 10thDay
43%6%12%26%11%2
2052
11th to 20thDay
36%312%34%14%1
1980
21st to endDay
44%412%26%13%1
1980
October1st to 10thDay
45%310%27%13%2
1939
11th to 20thDay
54%413%20%8%
1800
21st to endDay
57%412%19%8%1
1806
November1st to 10thDay
48%5%11%24%11%1
1672
11th to 20thDay
56%313%19%9%
1710
21st to endDay
60%314%16%6%1
1600
December1st to 10thDay
67%312%15%3
1520
11th to 20thDay
63%314%16%4
1683
21st to endDay
78%29%7%3
2700
January1st to 10thNight
65%49%16%7%
2648
11th to 20thNight
68%311%12%6%
2549
21st to endNight
65%310%15%5%1
2657
February1st to 10thNight
67%48%15%6%1
2340
11th to 20thNight
60%48%18%9%1
2145
21st to endNight
59%311%18%9%1
1776
March1st to 10thNight
53%310%23%10%1
2135
11th to 20thNight
47%410%22%15%2
1980
21st to endNight
53%38%23%11%2
2178
April1st to 10thNight
50%49%22%14%1
1859
11th to 20thNight
48%310%19%18%2
1633
21st to endNight
47%49%22%15%3
1620
May1st to 10thNight
48%410%23%12%3
1620
11th to 20thNight
44%38%22%17%5%
1593
21st to endNight
37%5%13%26%15%4
1691
June1st to 10thNight
36%411%28%19%2
1350
11th to 20thNight
36%413%24%21%2
1260
21st to endNight
35%412%29%18%2
1378
July1st to 10thNight
29%5%10%30%22%4
1400
11th to 20thNight
31%413%28%20%2
1392
21st to endNight
30%6%16%25%21%2
1582
August1st to 10thNight
32%5%15%33%15%1
1600
11th to 20thNight
33%5%14%32%13%3
1598
21st to endNight
33%5%13%29%19%1
1810
September1st to 10thNight
36%6%11%28%16%2
1890
11th to 20thNight
33%412%32%18%1
1980
21st to endNight
41%411%30%14%1
1980
October1st to 10thNight
43%49%27%17%1
2020
11th to 20thNight
55%311%20%10%1
2160
21st to endNight
56%310%21%9%1
2546
November1st to 10thNight
43%412%27%14%1
2406
11th to 20thNight
55%413%20%8%1
2470
21st to endNight
58%315%18%6%
2576
December1st to 10thNight
68%310%14%5%
2660
11th to 20thNight
64%312%14%6%1
3510
21st to endNight
76%311%7%3
4948

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
24%16%38%15%6%1
270
11th to 20thDay
22%17%41%15%41
246
21st to endDay
28%16%34%16%5%1
264
February1st to 10thDay
28%21%38%13%
240
11th to 20thDay
25%20%37%17%1
240
21st to endDay
31%25%34%8%3
198
March1st to 10thDay
27%21%36%12%31
264
11th to 20thDay
22%13%34%21%9%
420
21st to endDay
28%13%30%20%7%1
462
April1st to 10thDay
24%14%34%19%8%1
420
11th to 20thDay
29%17%29%14%6%6%
412
21st to endDay
26%12%26%22%11%1
420
May1st to 10thDay
25%13%30%20%10%3
423
11th to 20thDay
23%9%28%21%13%6%
447
21st to endDay
16%7%23%28%19%7%
534
June1st to 10thDay
12%11%29%28%16%4
630
11th to 20thDay
17%9%28%25%16%5%
630
21st to endDay
13%8%28%30%17%5%
630
July1st to 10thDay
9%6%23%28%24%10%
621
11th to 20thDay
12%6%28%27%18%8%
618
21st to endDay
11%5%25%30%21%8%
581
August1st to 10thDay
11%421%24%24%15%
446
11th to 20thDay
14%420%26%24%11%
439
21st to endDay
15%5%22%24%23%11%
495
September1st to 10thDay
14%8%23%25%21%10%
450
11th to 20thDay
13%5%21%21%26%13%
450
21st to endDay
19%11%20%23%18%9%
450
October1st to 10thDay
18%11%28%19%18%6%
450
11th to 20thDay
24%17%26%24%7%1
450
21st to endDay
33%14%35%13%5%
321
November1st to 10thDay
19%17%39%17%6%2
270
11th to 20thDay
23%20%33%16%6%1
270
21st to endDay
29%17%36%14%3
218
December1st to 10thDay
26%21%31%16%6%1
180
11th to 20thDay
28%24%35%8%31
180
21st to endDay
32%22%32%13%1
276
January1st to 10thNight
23%15%33%22%5%1
950
11th to 20thNight
27%14%31%23%41
911
21st to endNight
21%11%34%28%6%
875
February1st to 10thNight
26%12%37%23%3
720
11th to 20thNight
23%15%32%24%6%
703
21st to endNight
27%15%33%22%2
592
March1st to 10thNight
22%14%32%24%7%
720
11th to 20thNight
19%12%34%28%6%1
720
21st to endNight
24%12%29%27%7%1
792
April1st to 10thNight
24%12%34%24%5%1
599
11th to 20thNight
23%9%37%23%9%1
533
21st to endNight
21%9%33%31%6%
540
May1st to 10thNight
20%5%32%33%8%1
540
11th to 20thNight
22%5%30%32%11%
531
21st to endNight
14%327%38%17%2
584
June1st to 10thNight
14%5%24%44%12%
450
11th to 20thNight
13%428%44%11%
360
21st to endNight
11%423%44%17%1
478
July1st to 10thNight
9%217%41%28%2
525
11th to 20thNight
11%322%41%20%2
522
21st to endNight
8%220%47%21%1
591
August1st to 10thNight
9%216%42%28%2
537
11th to 20thNight
9%316%39%29%4
534
21st to endNight
13%319%35%27%3
594
September1st to 10thNight
13%5%20%36%23%4
630
11th to 20thNight
14%419%32%26%4
720
21st to endNight
16%6%21%31%20%5%
720
October1st to 10thNight
21%7%23%32%17%1
720
11th to 20thNight
27%11%26%27%8%1
720
21st to endNight
28%10%32%25%4
792
November1st to 10thNight
20%13%29%27%10%1
740
11th to 20thNight
22%17%32%22%6%1
760
21st to endNight
27%12%36%20%5%
760
December1st to 10thNight
26%14%34%19%5%1
760
11th to 20thNight
23%15%36%21%4
935
21st to endNight
33%13%35%18%1
1045
Page generated at 2024-01-10 01:25:01. Version ac07

Copyright 2024 Attilla Danko


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