North Frontenac Dark Sky Preserve
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the North Frontenac Dark Sky Preserve clear sky chart from 2005-11-06 to 2024-03-18.

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
26%
22872
13%
80963
8%
22788
35%
22788
15%
57374

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%
752
7%
4414
2%
737
20%
737
4%
3400
January11th to 20thNight
14%
757
7%
4416
3%
740
22%
740
5%
3308
January21st to endNight
18%
828
7%
4624
6%
814
26%
814
6%
3702
February1st to 10thNight
14%
760
11%
2470
3%
760
24%
760
11%
1855
February11th to 20thNight
14%
741
14%
2405
4%
740
27%
740
13%
1740
February21st to endNight
18%
628
14%
1922
5%
628
29%
628
14%
1409
March1st to 10thNight
17%
760
16%
2211
7%
760
26%
760
15%
1597
March11th to 20thNight
21%
752
16%
2067
6%
752
30%
752
17%
1483
March21st to endNight
23%
792
21%
2106
7%
792
34%
792
21%
1463
April1st to 10thNight
19%
720
17%
1800
5%
720
26%
720
20%
1314
April11th to 20thNight
23%
711
18%
1775
6%
711
29%
711
21%
1265
April21st to endNight
30%
606
16%
1686
7%
606
36%
606
18%
1221
May1st to 10thNight
34%
378
18%
1458
14%
378
44%
378
18%
924
May11th to 20thNight
33%
354
22%
1416
15%
354
51%
354
20%
842
May21st to endNight
36%
388
15%
1551
11%
388
50%
388
24%
883
June1st to 10thNight
33%
360
11%
1440
8%
360
43%
360
16%
932
June11th to 20thNight
37%
360
13%
1440
15%
360
47%
360
22%
850
June21st to endNight
40%
360
11%
1440
13%
360
47%
360
18%
905
July1st to 10thNight
46%
350
15%
1400
18%
350
54%
350
27%
774
July11th to 20thNight
48%
348
16%
1392
20%
348
56%
348
25%
798
July21st to endNight
48%
394
16%
1486
14%
372
56%
372
27%
833
August1st to 10thNight
50%
478
16%
1542
13%
476
54%
476
29%
927
August11th to 20thNight
51%
534
18%
1598
11%
534
56%
534
30%
999
August21st to endNight
43%
760
18%
1948
7%
760
48%
760
32%
1270
September1st to 10thNight
41%
720
19%
1800
7%
720
47%
720
33%
1167
September11th to 20thNight
50%
720
23%
1800
12%
720
55%
720
37%
1148
September21st to endNight
41%
720
21%
2056
15%
720
47%
720
26%
1347
October1st to 10thNight
32%
720
17%
2160
11%
720
39%
720
20%
1472
October11th to 20thNight
23%
720
12%
2160
6%
720
31%
720
16%
1585
October21st to endNight
20%
792
13%
2459
5%
792
30%
792
13%
1841
November1st to 10thNight
24%
740
18%
2445
10%
740
36%
740
18%
1653
November11th to 20thNight
20%
760
16%
2660
10%
760
31%
760
13%
1882
November21st to endNight
18%
760
10%
2660
6%
760
25%
760
10%
2028
December1st to 10thNight
14%
760
7%
2660
2%
760
21%
760
7%
2145
December11th to 20thNight
13%
760
10%
3248
4%
759
22%
759
8%
2435
December21st to endNight
10%
829
5%
4848
1%
817
17%
817
4%
3977

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%10%48%6%45%45%6%31%
78532
Night
17%11%47%6%3445%6%32%
81254
TransparencyDay
52%6%11%18%10%1
78237
Night
52%6%12%19%10%1
81083
SeeingDay
23%17%31%18%8%2
13546
Night
22%14%32%23%8%1
22901

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
15%17%6%12%7%44445%21%
2517
11th to 20thDay
13%17%8%13%7%5%5%5%4420%
2520
21st to endDay
19%19%7%13%7%4423417%
3027
February1st to 10thDay
14%16%6%10%8%36%5%5%5%21%
1710
11th to 20thDay
13%15%6%9%7%34445%29%
1663
21st to endDay
19%14%48%7%35%446%25%
1531
March1st to 10thDay
15%12%5%9%8%4445%429%
1963
11th to 20thDay
14%14%47%6%46%5%5%5%30%
2058
21st to endDay
20%10%5%6%42344439%
2250
April1st to 10thDay
20%12%46%5%34346%31%
2160
11th to 20thDay
20%10%36%43435%5%38%
2134
21st to endDay
22%9%47%6%34445%32%
2290
May1st to 10thDay
19%8%37%5%346%5%6%34%
2502
11th to 20thDay
16%7%37%6%435%47%38%
2478
21st to endDay
14%5%36%6%45%5%6%7%38%
2725
June1st to 10thDay
20%8%37%6%35%5%6%6%30%
2520
11th to 20thDay
16%5%35%5%35%5%7%9%37%
2520
21st to endDay
17%6%37%6%36%5%5%8%33%
2520
July1st to 10thDay
11%6%35%7%46%5%6%9%39%
2520
11th to 20thDay
12%6%36%6%45%6%7%9%37%
2520
21st to endDay
12%6%35%6%46%7%7%9%36%
2744
August1st to 10thDay
12%5%37%6%46%6%6%8%37%
2382
11th to 20thDay
13%7%27%6%5%5%6%6%8%37%
2303
21st to endDay
15%6%27%6%446%6%7%37%
2390
September1st to 10thDay
14%6%25%6%445%5%7%40%
2160
11th to 20thDay
13%5%36%5%3445%7%46%
2160
21st to endDay
19%6%35%6%345%47%38%
1899
October1st to 10thDay
21%9%37%6%3335%6%35%
1800
11th to 20thDay
23%10%37%6%5%5%45%7%26%
1800
21st to endDay
27%11%46%6%35%346%24%
1895
November1st to 10thDay
15%8%48%5%46%6%5%7%34%
1633
11th to 20thDay
18%13%6%8%6%45%445%28%
1520
21st to endDay
21%15%5%9%7%44446%20%
1520
December1st to 10thDay
22%18%6%10%8%35%44417%
1520
11th to 20thDay
20%13%6%9%6%345%45%25%
1906
21st to endDay
27%19%5%11%6%3323319%
2772
January1st to 10thNight
17%14%9%12%7%4445%5%19%
4429
11th to 20thNight
12%14%6%11%9%5%6%5%5%6%20%
4440
21st to endNight
18%17%7%11%7%5%433420%
4628
February1st to 10thNight
13%15%6%9%7%45%5%6%7%23%
2470
11th to 20thNight
14%12%6%9%6%35%5%5%5%30%
2403
21st to endNight
13%13%5%6%7%35%5%5%7%29%
1922
March1st to 10thNight
15%12%47%7%45%45%6%32%
2201
11th to 20thNight
16%14%46%5%35%346%34%
2067
21st to endNight
15%9%46%6%3445%440%
2106
April1st to 10thNight
20%10%5%6%5%24447%34%
1800
11th to 20thNight
18%9%35%6%44346%38%
1775
21st to endNight
19%9%37%5%345%5%6%33%
1686
May1st to 10thNight
20%6%35%43445%7%38%
1458
11th to 20thNight
15%6%45%43346%8%43%
1415
21st to endNight
11%5%245%345%5%9%46%
1550
June1st to 10thNight
15%6%37%6%45%46%9%35%
1440
11th to 20thNight
12%6%35%5%345%6%7%43%
1440
21st to endNight
15%7%36%5%35%5%6%8%37%
1440
July1st to 10thNight
8%436%6%45%5%5%7%48%
1440
11th to 20thNight
11%435%44447%9%43%
1440
21st to endNight
10%4244346%7%9%47%
1574
August1st to 10thNight
10%6%35%5%3347%7%47%
1552
11th to 20thNight
9%7%25%6%35%5%6%8%44%
1598
21st to endNight
11%6%27%5%245%5%7%47%
1948
September1st to 10thNight
11%5%246%245%5%7%47%
1800
11th to 20thNight
14%42343445%5%50%
1800
21st to endNight
18%5%25%5%3345%6%44%
2056
October1st to 10thNight
18%8%36%5%3445%7%38%
2160
11th to 20thNight
21%11%36%6%35%45%6%31%
2160
21st to endNight
23%12%36%7%3345%6%28%
2459
November1st to 10thNight
17%10%36%435%5%5%7%36%
2445
11th to 20thNight
18%11%47%6%35%5%5%7%30%
2660
21st to endNight
21%13%5%7%6%45%45%6%24%
2660
December1st to 10thNight
20%17%5%10%6%35%5%47%18%
2660
11th to 20thNight
20%16%5%8%6%3444427%
3288
21st to endNight
28%17%5%10%7%3433416%
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
64%6%13%10%6%1
2518
11th to 20thDay
66%6%10%11%6%1
2520
21st to endDay
73%48%10%5%1
3027
February1st to 10thDay
63%6%9%16%5%1
1710
11th to 20thDay
58%411%16%10%1
1672
21st to endDay
61%5%11%11%11%1
1531
March1st to 10thDay
58%5%11%15%10%2
1966
11th to 20thDay
56%5%10%15%11%2
2058
21st to endDay
50%48%19%14%6%
2250
April1st to 10thDay
55%5%7%18%13%3
2160
11th to 20thDay
48%5%8%22%16%2
2134
21st to endDay
54%5%8%15%14%4
2290
May1st to 10thDay
48%7%10%17%14%4
2502
11th to 20thDay
46%6%9%21%16%2
2482
21st to endDay
43%7%14%20%14%3
2725
June1st to 10thDay
52%7%9%18%12%1
2520
11th to 20thDay
42%7%13%23%13%2
2520
21st to endDay
48%7%13%19%12%1
2520
July1st to 10thDay
40%7%11%27%14%1
2450
11th to 20thDay
40%8%16%25%11%
2445
21st to endDay
43%8%14%24%11%
2591
August1st to 10thDay
42%9%15%24%10%
2368
11th to 20thDay
44%7%16%23%9%1
2303
21st to endDay
43%7%13%25%11%1
2390
September1st to 10thDay
41%6%13%27%13%1
2160
11th to 20thDay
37%6%13%29%14%
2160
21st to endDay
45%6%12%28%9%
1899
October1st to 10thDay
50%6%11%21%12%1
1800
11th to 20thDay
57%7%13%16%6%1
1800
21st to endDay
62%5%9%16%7%
1895
November1st to 10thDay
48%6%18%20%8%1
1633
11th to 20thDay
57%6%12%15%8%2
1520
21st to endDay
65%6%11%10%7%1
1520
December1st to 10thDay
70%5%10%9%4
1520
11th to 20thDay
61%5%15%12%6%
1906
21st to endDay
72%37%13%5%
2772
January1st to 10thNight
66%6%13%12%3
4429
11th to 20thNight
64%6%15%11%41
4440
21st to endNight
69%410%9%6%1
4628
February1st to 10thNight
58%6%13%17%6%1
2470
11th to 20thNight
55%5%11%20%8%1
2405
21st to endNight
54%6%11%18%10%1
1922
March1st to 10thNight
53%5%11%17%12%2
2211
11th to 20thNight
51%5%12%20%11%2
2068
21st to endNight
47%48%21%16%3
2106
April1st to 10thNight
51%48%21%14%2
1800
11th to 20thNight
48%5%8%21%17%1
1775
21st to endNight
50%7%8%17%16%3
1686
May1st to 10thNight
46%49%20%17%4
1458
11th to 20thNight
41%5%9%26%16%3
1416
21st to endNight
35%7%15%20%19%3
1551
June1st to 10thNight
46%7%13%21%12%1
1440
11th to 20thNight
38%7%13%24%17%2
1440
21st to endNight
44%7%16%21%12%1
1440
July1st to 10thNight
33%7%13%26%19%3
1400
11th to 20thNight
35%7%13%31%13%
1392
21st to endNight
33%8%18%28%12%1
1486
August1st to 10thNight
35%7%19%27%12%1
1542
11th to 20thNight
36%7%17%28%11%1
1598
21st to endNight
36%7%15%29%12%1
1948
September1st to 10thNight
35%8%15%27%14%1
1800
11th to 20thNight
34%6%15%34%11%1
1800
21st to endNight
40%6%12%31%9%1
2056
October1st to 10thNight
47%6%12%21%14%
2160
11th to 20thNight
53%7%14%18%7%
2160
21st to endNight
57%5%12%15%9%
2459
November1st to 10thNight
47%6%15%21%10%1
2445
11th to 20thNight
53%6%12%18%9%2
2660
21st to endNight
59%7%13%15%5%
2660
December1st to 10thNight
66%7%11%12%4
2660
11th to 20thNight
61%5%11%15%7%1
3288
21st to endNight
73%48%12%3
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
24%23%33%17%4
180
11th to 20thDay
33%17%33%12%5%
180
21st to endDay
27%20%36%12%31
270
February1st to 10thDay
33%26%29%11%1
270
11th to 20thDay
28%28%39%5%
270
21st to endDay
36%19%33%11%1
343
March1st to 10thDay
25%24%33%15%3
460
11th to 20thDay
25%22%34%15%31
449
21st to endDay
34%20%27%13%5%1
462
April1st to 10thDay
30%23%28%14%5%
420
11th to 20thDay
30%23%22%16%7%2
412
21st to endDay
30%20%31%11%7%1
420
May1st to 10thDay
26%17%31%17%5%3
423
11th to 20thDay
17%19%36%18%8%2
447
21st to endDay
18%15%35%19%10%3
485
June1st to 10thDay
24%14%35%19%7%1
450
11th to 20thDay
15%18%32%23%11%2
450
21st to endDay
19%13%36%20%10%3
450
July1st to 10thDay
13%9%30%32%14%3
445
11th to 20thDay
14%10%32%26%15%3
444
21st to endDay
14%10%36%26%10%3
488
August1st to 10thDay
14%8%30%30%13%4
446
11th to 20thDay
14%7%28%30%16%5%
439
21st to endDay
14%10%34%23%12%6%
495
September1st to 10thDay
16%11%31%22%13%6%
450
11th to 20thDay
14%12%25%24%14%10%
450
21st to endDay
18%14%31%20%12%5%
450
October1st to 10thDay
25%19%24%15%13%3
450
11th to 20thDay
26%22%30%16%41
450
21st to endDay
32%20%27%18%4
453
November1st to 10thDay
25%18%32%18%7%
327
11th to 20thDay
30%20%33%11%42
180
21st to endDay
28%24%32%11%41
180
December1st to 10thDay
30%22%35%11%21
180
11th to 20thDay
33%25%30%10%11
180
21st to endDay
33%24%30%9%31
198
January1st to 10thNight
28%19%32%18%4
760
11th to 20thNight
29%16%33%16%5%1
760
21st to endNight
21%17%35%22%5%
836
February1st to 10thNight
22%21%37%18%2
760
11th to 20thNight
21%21%41%14%3
743
21st to endNight
22%22%35%18%3
628
March1st to 10thNight
22%19%36%21%3
760
11th to 20thNight
24%20%30%20%41
752
21st to endNight
21%16%35%20%7%1
792
April1st to 10thNight
25%16%34%22%3
720
11th to 20thNight
23%21%30%19%6%1
711
21st to endNight
22%15%29%24%9%
606
May1st to 10thNight
24%9%27%29%9%2
378
11th to 20thNight
17%11%35%30%7%
354
21st to endNight
13%8%39%27%12%1
389
June1st to 10thNight
17%9%35%31%8%
360
11th to 20thNight
13%14%31%31%11%1
360
21st to endNight
18%6%29%36%11%
360
July1st to 10thNight
7%6%32%39%16%1
350
11th to 20thNight
11%5%31%38%15%1
348
21st to endNight
10%432%42%11%1
394
August1st to 10thNight
13%327%35%21%1
478
11th to 20thNight
12%323%37%23%2
534
21st to endNight
13%6%31%29%18%3
760
September1st to 10thNight
13%7%33%27%18%2
720
11th to 20thNight
15%7%24%29%21%3
720
21st to endNight
20%11%23%25%18%3
720
October1st to 10thNight
23%12%29%21%13%2
720
11th to 20thNight
26%16%30%20%8%1
720
21st to endNight
29%15%30%20%5%
792
November1st to 10thNight
24%16%31%22%7%
740
11th to 20thNight
25%17%33%17%8%1
760
21st to endNight
30%18%27%19%5%
760
December1st to 10thNight
29%19%32%17%3
760
11th to 20thNight
26%20%34%18%11
760
21st to endNight
34%16%32%15%3
836
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