Saranac Lake Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Saranac Lake Observatory clear sky chart from 2005-11-06 to 2024-01-31.

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
23%
22749
11%
74976
7%
22710
29%
22710
12%
56573

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
9%
760
6%
2649
3%
757
13%
757
4%
2297
January11th to 20thNight
10%
760
7%
2660
3%
760
15%
760
5%
2260
January21st to endNight
14%
835
8%
2897
5%
835
19%
835
7%
2352
February1st to 10thNight
8%
720
6%
2340
1%
720
13%
720
5%
1986
February11th to 20thNight
10%
703
8%
2174
3%
700
17%
700
7%
1809
February21st to endNight
12%
592
12%
1776
3%
592
22%
592
7%
1441
March1st to 10thNight
15%
720
11%
2160
7%
720
23%
720
9%
1714
March11th to 20thNight
16%
720
12%
2069
5%
720
24%
720
12%
1606
March21st to endNight
22%
792
18%
1998
6%
792
30%
792
15%
1514
April1st to 10thNight
16%
720
14%
1800
3%
720
22%
720
13%
1401
April11th to 20thNight
22%
711
12%
1775
4%
711
26%
711
15%
1378
April21st to endNight
22%
618
14%
1698
6%
618
27%
618
15%
1252
May1st to 10thNight
24%
431
13%
1511
9%
431
31%
431
12%
1089
May11th to 20thNight
31%
354
18%
1416
14%
354
43%
354
15%
919
May21st to endNight
38%
388
12%
1551
11%
388
46%
388
17%
995
June1st to 10thNight
30%
360
11%
1440
8%
360
40%
360
14%
992
June11th to 20thNight
39%
360
11%
1440
13%
360
46%
360
18%
910
June21st to endNight
33%
360
10%
1440
10%
360
42%
360
16%
964
July1st to 10thNight
45%
350
13%
1400
16%
350
52%
350
23%
818
July11th to 20thNight
46%
348
15%
1392
16%
348
54%
348
22%
817
July21st to endNight
41%
394
14%
1486
13%
372
48%
372
21%
906
August1st to 10thNight
47%
358
17%
1422
17%
356
53%
356
23%
837
August11th to 20thNight
46%
606
14%
1670
8%
606
49%
606
26%
1128
August21st to endNight
40%
792
16%
1980
8%
792
42%
792
28%
1365
September1st to 10thNight
42%
720
13%
1800
6%
720
44%
720
27%
1243
September11th to 20thNight
44%
720
21%
1862
13%
720
48%
720
31%
1216
September21st to endNight
37%
720
20%
1980
14%
720
41%
720
25%
1333
October1st to 10thNight
29%
720
14%
2112
10%
720
35%
720
17%
1522
October11th to 20thNight
27%
720
13%
2162
8%
720
34%
720
14%
1602
October21st to endNight
18%
792
9%
2574
5%
792
24%
792
9%
2030
November1st to 10thNight
19%
740
12%
2407
6%
740
26%
740
11%
1820
November11th to 20thNight
18%
760
15%
2517
10%
760
25%
760
10%
1947
November21st to endNight
15%
760
9%
2660
6%
760
20%
760
6%
2153
December1st to 10thNight
8%
760
6%
2660
2%
760
12%
760
4%
2300
December11th to 20thNight
12%
760
8%
3256
4%
759
18%
759
4%
2686
December21st to endNight
8%
825
4%
4842
1%
817
12%
817
2%
3971

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
17%12%5%9%7%35%5%5%6%27%
74905
Night
16%14%6%10%7%35%445%26%
75221
TransparencyDay
58%410%18%9%1
74610
Night
60%410%16%8%1
75050
SeeingDay
28%18%28%16%7%2
13575
Night
26%19%25%21%8%1
22761

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
10%20%10%16%10%46%33414%
1517
11th to 20thDay
11%18%9%14%11%4444418%
1520
21st to endDay
9%15%10%14%11%6%6%5%45%16%
1682
February1st to 10thDay
11%17%9%15%13%5%6%33314%
1620
11th to 20thDay
10%15%9%16%10%5%5%45%417%
1672
21st to endDay
12%18%7%16%8%6%5%34417%
1480
March1st to 10thDay
12%15%9%13%10%35%33422%
1797
11th to 20thDay
14%16%7%10%8%4445%424%
1890
21st to endDay
16%15%6%9%6%33335%30%
2358
April1st to 10thDay
18%16%7%7%5%2444428%
2160
11th to 20thDay
17%15%46%6%34445%32%
2134
21st to endDay
23%14%48%5%24346%26%
2261
May1st to 10thDay
21%12%47%5%34446%30%
2465
11th to 20thDay
18%11%36%5%35%445%35%
2478
21st to endDay
18%8%36%6%45%5%5%8%32%
2725
June1st to 10thDay
26%8%46%6%35%5%5%7%26%
2520
11th to 20thDay
20%8%36%5%35%5%6%8%31%
2520
21st to endDay
22%8%36%7%45%5%6%7%27%
2520
July1st to 10thDay
15%7%37%5%45%5%6%8%34%
2520
11th to 20thDay
16%7%37%6%46%6%6%8%31%
2520
21st to endDay
16%6%37%7%36%7%7%8%29%
2744
August1st to 10thDay
16%7%37%7%46%6%6%8%31%
2506
11th to 20thDay
14%8%37%6%46%6%6%9%31%
2208
21st to endDay
16%7%26%7%45%6%6%8%32%
2376
September1st to 10thDay
17%7%35%6%35%5%5%8%37%
2160
11th to 20thDay
18%8%244235%47%42%
2097
21st to endDay
17%9%35%5%346%5%7%36%
1980
October1st to 10thDay
24%10%37%6%345%46%27%
1846
11th to 20thDay
19%15%47%6%3445%6%28%
1796
21st to endDay
25%19%5%7%5%33335%22%
1782
November1st to 10thDay
15%16%6%8%7%45%446%26%
1671
11th to 20thDay
15%18%7%10%6%44445%23%
1662
21st to endDay
14%19%7%12%8%45%44419%
1520
December1st to 10thDay
15%22%12%13%9%3334312%
1520
11th to 20thDay
16%17%7%17%7%35%445%15%
1906
21st to endDay
19%19%8%11%9%35%44415%
2772
January1st to 10thNight
13%20%9%17%9%5%5%44410%
2649
11th to 20thNight
11%18%9%15%11%47%43414%
2660
21st to endNight
9%15%9%15%11%47%5%45%17%
2897
February1st to 10thNight
11%16%9%18%13%45%33414%
2340
11th to 20thNight
10%13%10%16%11%5%7%45%316%
2172
21st to endNight
11%16%7%17%9%5%5%5%3319%
1776
March1st to 10thNight
13%17%8%10%8%45%44423%
2150
11th to 20thNight
12%18%8%10%7%3434426%
2068
21st to endNight
16%15%6%9%5%34345%32%
1998
April1st to 10thNight
18%17%7%8%6%23345%27%
1800
11th to 20thNight
20%15%5%7%5%345%45%28%
1775
21st to endNight
20%13%47%6%33436%31%
1698
May1st to 10thNight
23%12%46%5%34446%30%
1511
11th to 20thNight
16%10%35%5%36%5%6%6%36%
1415
21st to endNight
15%7%36%5%35%5%5%9%35%
1550
June1st to 10thNight
24%7%35%5%26%5%6%7%31%
1440
11th to 20thNight
19%6%36%4345%5%7%38%
1440
21st to endNight
20%7%36%6%35%46%7%33%
1440
July1st to 10thNight
13%5%26%6%45%35%9%42%
1440
11th to 20thNight
12%5%25%6%35%6%7%9%39%
1440
21st to endNight
15%6%36%5%245%6%8%39%
1574
August1st to 10thNight
14%5%26%4346%5%9%41%
1432
11th to 20thNight
16%7%25%6%26%5%6%8%37%
1670
21st to endNight
15%7%35%5%45%5%6%8%38%
1980
September1st to 10thNight
17%8%35%5%3445%7%40%
1800
11th to 20thNight
16%8%25%333446%46%
1862
21st to endNight
19%8%2442446%7%39%
1980
October1st to 10thNight
22%11%36%5%2446%7%30%
2112
11th to 20thNight
18%15%47%5%35%5%46%28%
2162
21st to endNight
24%19%46%6%34445%20%
2574
November1st to 10thNight
16%17%6%8%6%3345%5%26%
2407
11th to 20thNight
16%16%8%10%7%34345%24%
2517
21st to endNight
15%19%9%13%7%34345%18%
2660
December1st to 10thNight
16%25%11%15%7%3333311%
2660
11th to 20thNight
15%20%8%14%8%25%44416%
3288
21st to endNight
20%18%7%16%8%3444313%
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
72%5%5%13%4
1518
11th to 20thDay
70%4411%8%2
1520
21st to endDay
68%5%7%10%7%2
1682
February1st to 10thDay
75%4412%42
1620
11th to 20thDay
68%5%7%11%8%1
1681
21st to endDay
69%5%7%9%8%2
1480
March1st to 10thDay
66%5%8%12%8%2
1800
11th to 20thDay
62%5%10%10%11%3
1890
21st to endDay
60%25%15%14%4
2358
April1st to 10thDay
60%37%18%10%2
2160
11th to 20thDay
55%47%19%13%1
2134
21st to endDay
61%29%14%11%3
2261
May1st to 10thDay
56%38%20%11%2
2465
11th to 20thDay
51%5%7%23%12%2
2482
21st to endDay
51%5%14%19%10%1
2725
June1st to 10thDay
59%410%17%9%
2520
11th to 20thDay
52%410%23%9%2
2520
21st to endDay
58%5%11%18%8%1
2520
July1st to 10thDay
47%413%25%11%
2450
11th to 20thDay
49%5%13%26%6%
2445
21st to endDay
50%6%13%21%9%
2591
August1st to 10thDay
52%5%14%22%8%
2492
11th to 20thDay
48%6%16%23%8%
2208
21st to endDay
47%6%13%24%10%1
2376
September1st to 10thDay
45%411%27%12%1
2160
11th to 20thDay
42%310%29%15%1
2097
21st to endDay
46%6%13%23%10%2
1980
October1st to 10thDay
59%48%18%11%
1846
11th to 20thDay
57%5%13%18%8%1
1796
21st to endDay
66%39%14%7%1
1782
November1st to 10thDay
59%411%17%9%
1671
11th to 20thDay
63%49%13%7%3
1662
21st to endDay
66%6%11%13%5%
1520
December1st to 10thDay
77%37%9%3
1520
11th to 20thDay
70%5%8%10%5%
1906
21st to endDay
73%36%10%8%
2772
January1st to 10thNight
77%5%5%7%5%
2649
11th to 20thNight
73%6%5%10%5%1
2660
21st to endNight
68%6%6%11%8%2
2897
February1st to 10thNight
75%47%7%6%1
2340
11th to 20thNight
70%5%6%11%7%
2174
21st to endNight
68%5%6%13%8%1
1776
March1st to 10thNight
65%49%12%9%1
2160
11th to 20thNight
62%48%16%9%2
2069
21st to endNight
56%47%17%13%3
1998
April1st to 10thNight
61%37%17%11%2
1800
11th to 20thNight
59%49%18%10%
1775
21st to endNight
57%310%17%11%3
1698
May1st to 10thNight
56%5%8%16%14%2
1511
11th to 20thNight
49%5%9%22%14%2
1416
21st to endNight
46%6%15%19%13%1
1551
June1st to 10thNight
53%6%12%21%7%1
1440
11th to 20thNight
46%5%15%21%13%1
1440
21st to endNight
50%6%13%24%7%
1440
July1st to 10thNight
40%416%27%12%1
1400
11th to 20thNight
40%5%16%31%9%
1392
21st to endNight
41%7%16%25%10%1
1486
August1st to 10thNight
40%420%28%8%
1422
11th to 20thNight
43%5%16%25%10%1
1670
21st to endNight
43%5%15%27%9%
1980
September1st to 10thNight
44%5%14%27%10%1
1800
11th to 20thNight
41%213%31%12%1
1862
21st to endNight
44%5%13%25%12%2
1980
October1st to 10thNight
54%412%19%10%1
2112
11th to 20thNight
56%5%13%17%8%1
2162
21st to endNight
67%311%12%6%2
2574
November1st to 10thNight
61%312%13%9%2
2407
11th to 20thNight
62%5%9%14%8%3
2517
21st to endNight
69%5%9%12%5%1
2660
December1st to 10thNight
78%36%9%3
2660
11th to 20thNight
71%5%6%11%7%
3288
21st to endNight
75%36%11%5%
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
27%21%33%13%6%1
180
11th to 20thDay
24%27%36%10%12
180
21st to endDay
23%27%36%11%3
204
February1st to 10thDay
43%33%19%5%
240
11th to 20thDay
37%25%29%7%1
340
21st to endDay
34%27%24%12%3
346
March1st to 10thDay
29%24%29%15%3
420
11th to 20thDay
33%22%29%12%31
420
21st to endDay
32%26%24%11%7%1
462
April1st to 10thDay
34%17%29%12%7%1
420
11th to 20thDay
36%17%24%14%7%2
412
21st to endDay
38%16%26%12%6%2
420
May1st to 10thDay
35%17%28%10%5%4
423
11th to 20thDay
27%19%29%17%7%1
447
21st to endDay
25%18%28%21%7%1
485
June1st to 10thDay
34%16%27%15%6%2
450
11th to 20thDay
26%13%31%21%6%3
450
21st to endDay
30%14%31%17%6%2
450
July1st to 10thDay
18%10%35%24%11%2
445
11th to 20thDay
17%13%36%24%8%2
444
21st to endDay
18%11%42%21%6%2
488
August1st to 10thDay
18%14%29%23%12%4
446
11th to 20thDay
19%10%30%23%13%5%
439
21st to endDay
19%14%27%23%12%5%
495
September1st to 10thDay
19%15%30%17%13%7%
450
11th to 20thDay
20%16%22%19%14%10%
450
21st to endDay
19%14%30%20%11%6%
450
October1st to 10thDay
30%16%21%16%12%6%
450
11th to 20thDay
29%22%25%15%10%1
448
21st to endDay
36%18%25%16%4
396
November1st to 10thDay
32%17%27%16%8%
365
11th to 20thDay
34%24%21%13%7%1
322
21st to endDay
33%22%33%11%2
180
December1st to 10thDay
34%21%29%12%31
180
11th to 20thDay
36%26%28%7%2
180
21st to endDay
34%28%24%11%31
198
January1st to 10thNight
27%28%29%13%3
760
11th to 20thNight
25%29%29%15%31
760
21st to endNight
18%29%31%18%4
835
February1st to 10thNight
25%31%30%13%2
720
11th to 20thNight
25%28%30%14%2
703
21st to endNight
25%27%31%15%2
592
March1st to 10thNight
28%23%28%18%3
720
11th to 20thNight
29%24%26%16%41
720
21st to endNight
28%21%24%20%6%1
792
April1st to 10thNight
30%21%28%17%4
720
11th to 20thNight
29%23%21%20%6%
711
21st to endNight
32%17%23%20%7%
618
May1st to 10thNight
33%12%24%22%9%
431
11th to 20thNight
20%15%28%30%7%1
354
21st to endNight
18%11%29%29%12%1
389
June1st to 10thNight
26%9%28%25%12%
360
11th to 20thNight
20%7%25%36%11%
360
21st to endNight
19%9%31%29%12%
360
July1st to 10thNight
15%7%27%35%15%1
350
11th to 20thNight
12%10%24%33%19%2
348
21st to endNight
15%6%32%35%12%1
394
August1st to 10thNight
17%7%22%38%15%1
358
11th to 20thNight
19%5%21%33%18%3
606
21st to endNight
19%9%25%27%18%2
792
September1st to 10thNight
20%11%21%31%15%3
720
11th to 20thNight
19%8%22%28%19%4
720
21st to endNight
22%13%23%21%19%2
720
October1st to 10thNight
29%15%21%20%13%2
720
11th to 20thNight
28%16%23%22%9%1
720
21st to endNight
35%20%21%19%5%
792
November1st to 10thNight
29%20%25%19%7%
740
11th to 20thNight
30%24%22%15%8%2
760
21st to endNight
29%28%21%15%6%1
760
December1st to 10thNight
33%30%21%12%4
760
11th to 20thNight
30%25%26%15%41
760
21st to endNight
30%26%27%14%3
836
Page generated at 2024-01-28 05:26:34. Version ac07

Copyright 2024 Attilla Danko


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