J.S.M. Blue Lake Township Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the J.S.M. Blue Lake Township Observatory 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
30%
24272
11%
74972
7%
24216
34%
24216
15%
56963

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
13%
950
4%
2648
2%
946
14%
946
6%
2350
January11th to 20thNight
14%
915
4%
2561
2%
915
16%
915
6%
2295
January21st to endNight
15%
990
3%
2772
2%
990
17%
990
6%
2472
February1st to 10thNight
15%
770
6%
2390
3%
770
18%
770
6%
2079
February11th to 20thNight
17%
700
9%
2125
3%
699
22%
699
9%
1737
February21st to endNight
17%
592
9%
1776
2%
592
24%
592
9%
1443
March1st to 10thNight
27%
720
16%
2160
9%
720
32%
720
18%
1527
March11th to 20thNight
24%
720
17%
2013
7%
720
31%
720
19%
1466
March21st to endNight
31%
761
16%
2147
10%
761
37%
761
20%
1541
April1st to 10thNight
24%
540
12%
1800
7%
540
30%
540
14%
1320
April11th to 20thNight
30%
533
18%
1661
10%
533
37%
533
19%
1176
April21st to endNight
33%
540
15%
1620
7%
540
40%
540
20%
1129
May1st to 10thNight
33%
540
14%
1620
8%
540
40%
540
21%
1136
May11th to 20thNight
35%
531
15%
1545
11%
531
41%
531
21%
1090
May21st to endNight
47%
583
14%
1552
7%
582
53%
582
31%
1007
June1st to 10thNight
41%
388
15%
1288
11%
388
47%
388
24%
803
June11th to 20thNight
50%
360
15%
1260
13%
360
54%
360
26%
754
June21st to endNight
48%
395
15%
1295
12%
395
53%
395
27%
801
July1st to 10thNight
63%
525
16%
1400
11%
525
66%
525
41%
819
July11th to 20thNight
58%
522
16%
1392
12%
522
61%
522
35%
861
July21st to endNight
53%
591
16%
1487
11%
558
56%
558
34%
932
August1st to 10thNight
60%
537
17%
1547
14%
534
64%
534
33%
938
August11th to 20thNight
61%
534
18%
1598
14%
534
66%
534
33%
951
August21st to endNight
52%
594
16%
1851
15%
594
54%
594
26%
1172
September1st to 10thNight
53%
566
18%
1826
15%
566
57%
566
29%
1090
September11th to 20thNight
52%
720
22%
1980
17%
720
55%
720
32%
1264
September21st to endNight
42%
720
16%
1980
11%
720
45%
720
23%
1404
October1st to 10thNight
39%
720
17%
1987
11%
720
44%
720
24%
1379
October11th to 20thNight
24%
720
10%
2236
6%
720
30%
720
14%
1710
October21st to endNight
21%
792
10%
2574
7%
792
27%
792
11%
2056
November1st to 10thNight
25%
740
14%
2406
10%
740
32%
740
14%
1800
November11th to 20thNight
16%
760
9%
2470
6%
760
21%
760
9%
1994
November21st to endNight
16%
764
6%
2602
3%
764
19%
764
7%
2198
December1st to 10thNight
12%
950
2%
2850
1%
950
13%
950
4%
2563
December11th to 20thNight
12%
950
3%
3522
2%
949
14%
949
5%
3115
December21st to endNight
9%
1039
2%
5031
0%
1026
11%
1026
2%
4591

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%11%5%9%7%35%45%7%30%
74576
Night
14%13%6%10%7%45%446%28%
75158
TransparencyDay
53%7%11%18%10%1
74282
Night
56%8%11%16%8%1
74987
SeeingDay
19%14%30%23%10%4
14466
Night
18%12%32%28%9%1
24282

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
12%18%9%16%11%5%7%34312%
1517
11th to 20thDay
15%19%10%15%12%5%44449%
1461
21st to endDay
11%17%11%17%11%5%6%42310%
1584
February1st to 10thDay
10%16%9%14%17%5%7%445%10%
1570
11th to 20thDay
11%16%7%14%13%5%45%4417%
1718
21st to endDay
12%17%9%14%10%44345%17%
1480
March1st to 10thDay
13%12%5%11%10%45%45%5%27%
1798
11th to 20thDay
11%11%6%10%7%35%45%7%30%
1946
21st to endDay
17%12%5%7%7%3445%6%29%
2225
April1st to 10thDay
18%14%6%9%6%345%46%26%
2160
11th to 20thDay
20%14%46%5%34346%32%
2247
21st to endDay
15%12%5%9%5%345%6%7%30%
2340
May1st to 10thDay
17%10%36%5%35%5%5%6%35%
2340
11th to 20thDay
15%9%46%5%34446%40%
2345
21st to endDay
12%7%25%6%36%5%5%8%42%
2725
June1st to 10thDay
14%6%25%5%35%46%8%41%
2668
11th to 20thDay
13%6%25%5%46%5%7%9%39%
2700
21st to endDay
14%6%36%5%35%5%7%8%39%
2659
July1st to 10thDay
10%4244246%7%10%47%
2520
11th to 20thDay
12%7%25%5%35%5%6%8%42%
2520
21st to endDay
10%5%36%435%5%7%8%44%
2743
August1st to 10thDay
10%6%36%6%45%6%7%9%38%
2381
11th to 20thDay
12%6%25%6%45%6%6%8%41%
2303
21st to endDay
15%7%35%5%3445%7%42%
2502
September1st to 10thDay
15%6%36%5%3446%8%41%
2116
11th to 20thDay
14%6%25%5%2446%8%44%
1980
21st to endDay
16%8%36%5%345%6%9%34%
1980
October1st to 10thDay
19%11%47%5%3445%6%34%
1972
11th to 20thDay
25%17%5%8%6%3445%419%
1720
21st to endDay
22%17%5%9%8%45%45%7%16%
1782
November1st to 10thDay
16%17%6%7%5%4445%6%25%
1672
11th to 20thDay
13%20%9%12%7%36%45%5%16%
1710
21st to endDay
16%21%11%13%6%3334415%
1568
December1st to 10thDay
14%18%12%17%8%45%34410%
1330
11th to 20thDay
14%20%10%16%10%3444411%
1671
21st to endDay
19%21%11%20%8%332237%
2623
January1st to 10thNight
13%15%9%19%10%6%6%43312%
2648
11th to 20thNight
15%18%8%15%12%5%5%43312%
2561
21st to endNight
11%15%9%15%14%6%7%43411%
2772
February1st to 10thNight
10%16%8%13%15%7%7%44413%
2390
11th to 20thNight
11%13%8%15%9%5%6%445%19%
2125
21st to endNight
14%15%7%14%9%4443421%
1776
March1st to 10thNight
10%12%6%8%7%5%45%46%35%
2149
11th to 20thNight
11%13%5%9%7%34445%34%
2013
21st to endNight
15%11%47%7%35%45%5%35%
2147
April1st to 10thNight
18%13%49%6%35%5%6%5%28%
1800
11th to 20thNight
20%11%45%4345%47%33%
1661
21st to endNight
16%10%47%5%2346%6%35%
1620
May1st to 10thNight
15%8%46%7%35%6%5%8%33%
1620
11th to 20thNight
13%11%46%6%346%5%7%34%
1545
21st to endNight
12%6%35%4345%6%8%44%
1551
June1st to 10thNight
12%6%35%6%35%45%7%43%
1288
11th to 20thNight
9%5%26%5%35%6%7%9%43%
1260
21st to endNight
10%8%3443446%8%46%
1295
July1st to 10thNight
8%425%33446%10%51%
1440
11th to 20thNight
7%5%35%435%5%6%7%49%
1440
21st to endNight
8%5%35%5%345%6%7%49%
1575
August1st to 10thNight
8%6%245%3446%10%47%
1556
11th to 20thNight
10%4245%345%5%6%52%
1598
21st to endNight
13%7%25%6%345%5%7%44%
1851
September1st to 10thNight
12%6%25%42345%7%49%
1826
11th to 20thNight
15%5%245%24348%48%
1980
21st to endNight
18%8%26%5%35%5%6%6%36%
1980
October1st to 10thNight
18%8%36%42445%6%39%
1987
11th to 20thNight
22%13%46%6%345%46%25%
2236
21st to endNight
24%15%48%6%345%35%23%
2574
November1st to 10thNight
13%17%5%8%6%45%448%27%
2406
11th to 20thNight
15%17%8%11%7%45%5%45%19%
2470
21st to endNight
17%19%10%11%6%44445%16%
2602
December1st to 10thNight
12%18%12%19%9%4443410%
2850
11th to 20thNight
12%18%9%17%11%45%44412%
3526
21st to endNight
20%23%10%15%7%343438%
5040

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
76%7%7%7%3
1518
11th to 20thDay
78%7%8%42
1461
21st to endDay
79%6%5%6%3
1584
February1st to 10thDay
77%5%8%8%2
1570
11th to 20thDay
69%7%8%10%6%1
1728
21st to endDay
68%6%10%13%31
1480
March1st to 10thDay
59%6%11%15%8%1
1800
11th to 20thDay
54%6%12%18%7%3
1946
21st to endDay
54%7%11%19%9%1
2225
April1st to 10thDay
59%6%10%16%8%
2160
11th to 20thDay
53%5%10%18%13%1
2247
21st to endDay
52%8%12%13%13%3
2340
May1st to 10thDay
47%7%11%21%11%2
2340
11th to 20thDay
45%7%10%21%14%3
2349
21st to endDay
39%8%14%23%14%1
2725
June1st to 10thDay
38%8%13%25%14%2
2668
11th to 20thDay
39%9%13%21%16%1
2700
21st to endDay
41%7%15%23%13%1
2659
July1st to 10thDay
30%9%14%26%19%2
2451
11th to 20thDay
37%8%13%26%15%1
2445
21st to endDay
35%8%15%24%17%1
2591
August1st to 10thDay
39%10%16%23%10%1
2366
11th to 20thDay
38%9%13%26%12%1
2303
21st to endDay
41%7%14%23%13%2
2502
September1st to 10thDay
41%7%12%23%15%1
2116
11th to 20thDay
36%8%16%28%11%1
1980
21st to endDay
46%7%16%23%8%
1980
October1st to 10thDay
51%7%9%23%9%1
1972
11th to 20thDay
65%8%8%15%3
1720
21st to endDay
69%7%11%9%4
1782
November1st to 10thDay
57%8%11%17%7%
1672
11th to 20thDay
68%9%11%8%4
1710
21st to endDay
73%6%11%9%2
1568
December1st to 10thDay
79%7%6%7%11
1330
11th to 20thDay
77%7%8%6%1
1671
21st to endDay
83%6%5%32
2623
January1st to 10thNight
76%7%8%6%3
2648
11th to 20thNight
76%7%7%6%3
2561
21st to endNight
76%7%8%7%2
2772
February1st to 10thNight
74%7%7%9%31
2390
11th to 20thNight
66%7%9%14%4
2126
21st to endNight
66%6%10%13%5%
1776
March1st to 10thNight
49%7%13%21%10%1
2160
11th to 20thNight
51%6%10%19%11%2
2014
21st to endNight
50%6%11%19%13%1
2147
April1st to 10thNight
54%8%10%17%11%1
1800
11th to 20thNight
51%6%9%19%13%2
1661
21st to endNight
48%7%12%18%13%3
1620
May1st to 10thNight
47%7%12%19%10%4
1620
11th to 20thNight
48%7%9%20%14%2
1546
21st to endNight
36%7%15%24%14%3
1552
June1st to 10thNight
39%7%12%24%17%1
1288
11th to 20thNight
35%9%14%26%14%2
1260
21st to endNight
36%9%13%25%16%2
1295
July1st to 10thNight
26%8%16%29%19%2
1400
11th to 20thNight
31%9%15%26%18%1
1392
21st to endNight
33%8%16%27%16%1
1487
August1st to 10thNight
32%8%19%28%12%1
1547
11th to 20thNight
30%9%18%27%16%1
1598
21st to endNight
38%8%16%22%15%1
1851
September1st to 10thNight
34%8%13%26%17%2
1826
11th to 20thNight
36%7%17%29%11%1
1980
21st to endNight
46%8%16%22%8%
1980
October1st to 10thNight
44%7%12%24%12%1
1987
11th to 20thNight
57%8%13%16%5%
2236
21st to endNight
63%8%10%14%5%
2574
November1st to 10thNight
54%9%13%17%6%1
2406
11th to 20thNight
64%8%12%10%5%1
2470
21st to endNight
70%8%12%8%1
2602
December1st to 10thNight
76%9%7%7%2
2850
11th to 20thNight
74%9%9%6%2
3525
21st to endNight
78%10%6%32
5040

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%19%39%16%6%
270
11th to 20thDay
26%20%34%17%2
248
21st to endDay
21%16%37%19%6%
264
February1st to 10thDay
19%31%38%10%2
240
11th to 20thDay
22%29%34%13%2
240
21st to endDay
27%28%37%6%2
198
March1st to 10thDay
24%27%34%14%2
240
11th to 20thDay
22%14%38%18%7%1
386
21st to endDay
26%14%29%23%8%1
462
April1st to 10thDay
25%16%33%18%6%1
420
11th to 20thDay
31%16%28%13%9%2
412
21st to endDay
23%15%31%20%10%2
420
May1st to 10thDay
22%22%28%17%9%4
423
11th to 20thDay
19%13%30%26%8%4
491
21st to endDay
14%13%29%29%11%4
679
June1st to 10thDay
15%14%33%24%11%3
630
11th to 20thDay
16%13%30%28%10%4
630
21st to endDay
17%8%30%31%12%3
630
July1st to 10thDay
10%8%27%32%16%8%
621
11th to 20thDay
12%9%29%28%16%6%
618
21st to endDay
10%7%32%30%16%5%
684
August1st to 10thDay
10%6%25%27%20%11%
500
11th to 20thDay
14%6%20%29%19%12%
439
21st to endDay
18%9%22%29%15%7%
495
September1st to 10thDay
18%8%26%24%15%8%
450
11th to 20thDay
13%9%22%30%17%9%
450
21st to endDay
20%11%22%27%15%6%
450
October1st to 10thDay
23%16%26%21%12%2
450
11th to 20thDay
31%16%33%17%2
370
21st to endDay
32%22%30%11%41
297
November1st to 10thDay
24%19%33%18%5%1
270
11th to 20thDay
19%27%36%17%2
270
21st to endDay
21%28%35%14%2
207
December1st to 10thDay
27%17%38%11%42
180
11th to 20thDay
27%20%40%12%11
180
21st to endDay
26%28%35%10%11
252
January1st to 10thNight
18%17%36%21%6%1
950
11th to 20thNight
22%16%35%21%6%
915
21st to endNight
17%13%38%26%5%1
990
February1st to 10thNight
16%18%39%24%41
770
11th to 20thNight
18%21%33%23%5%
703
21st to endNight
23%17%34%23%3
592
March1st to 10thNight
14%14%38%24%9%1
720
11th to 20thNight
18%16%37%24%6%
720
21st to endNight
20%12%31%30%7%1
761
April1st to 10thNight
22%13%34%24%5%1
540
11th to 20thNight
23%11%32%25%8%
533
21st to endNight
18%11%31%31%8%1
540
May1st to 10thNight
17%10%34%31%8%
540
11th to 20thNight
17%10%31%32%9%1
531
21st to endNight
13%7%28%37%14%1
584
June1st to 10thNight
14%7%31%39%9%1
388
11th to 20thNight
8%6%29%46%12%
360
21st to endNight
11%7%28%39%14%1
395
July1st to 10thNight
9%221%46%21%1
525
11th to 20thNight
8%424%37%25%2
522
21st to endNight
10%425%37%22%1
591
August1st to 10thNight
11%318%44%23%1
537
11th to 20thNight
11%5%17%36%28%4
534
21st to endNight
14%6%21%38%20%1
594
September1st to 10thNight
15%323%35%20%4
566
11th to 20thNight
17%6%21%33%19%4
720
21st to endNight
20%9%23%30%15%3
720
October1st to 10thNight
21%8%26%31%12%1
720
11th to 20thNight
29%13%29%23%6%
720
21st to endNight
32%13%30%20%5%1
792
November1st to 10thNight
22%14%33%25%6%1
740
11th to 20thNight
21%17%38%20%4
760
21st to endNight
24%14%38%21%3
764
December1st to 10thNight
20%17%39%20%3
950
11th to 20thNight
20%18%40%18%31
950
21st to endNight
25%17%38%18%2
1045
Page generated at 2024-01-10 19:35:23. Version ac07

Copyright 2024 Attilla Danko


J.S.M. Blue Lake Township Observatory Clear Sky Chart |Charts Home