Boundary Road
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Boundary Road clear sky chart from 2005-11-06 to 2024-01-17.

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%
22578
13%
74798
9%
22540
39%
22540
16%
53542

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
19%
760
8%
2649
5%
757
25%
757
8%
2141
January11th to 20thNight
20%
748
9%
2616
6%
748
24%
748
9%
2072
January21st to endNight
28%
792
12%
2718
8%
792
35%
792
14%
1985
February1st to 10thNight
21%
720
9%
2340
5%
720
27%
720
11%
1838
February11th to 20thNight
24%
701
13%
2253
7%
700
33%
700
14%
1654
February21st to endNight
26%
592
15%
1776
9%
592
36%
592
15%
1318
March1st to 10thNight
25%
720
14%
2160
9%
720
32%
720
14%
1640
March11th to 20thNight
26%
720
16%
2001
8%
720
34%
720
18%
1462
March21st to endNight
33%
792
21%
2048
9%
792
39%
792
23%
1452
April1st to 10thNight
27%
720
15%
1800
6%
720
32%
720
21%
1340
April11th to 20thNight
28%
711
16%
1775
6%
711
33%
711
22%
1289
April21st to endNight
31%
614
16%
1694
7%
614
37%
614
20%
1224
May1st to 10thNight
34%
360
16%
1440
13%
360
42%
360
16%
939
May11th to 20thNight
36%
354
20%
1416
17%
354
50%
354
19%
879
May21st to endNight
40%
389
13%
1551
12%
388
50%
388
22%
934
June1st to 10thNight
42%
360
10%
1440
10%
360
49%
360
16%
967
June11th to 20thNight
44%
360
12%
1440
15%
360
51%
360
20%
885
June21st to endNight
43%
360
11%
1440
16%
360
48%
360
17%
935
July1st to 10thNight
54%
350
14%
1400
21%
350
61%
350
24%
805
July11th to 20thNight
54%
348
15%
1392
23%
348
57%
348
24%
805
July21st to endNight
57%
394
15%
1486
18%
372
60%
372
22%
898
August1st to 10thNight
54%
367
16%
1431
16%
365
59%
365
23%
862
August11th to 20thNight
59%
557
17%
1621
12%
557
63%
557
30%
1035
August21st to endNight
51%
792
17%
1980
8%
792
54%
792
32%
1313
September1st to 10thNight
52%
720
16%
1800
8%
720
54%
720
31%
1225
September11th to 20thNight
54%
720
22%
1813
14%
720
57%
720
34%
1169
September21st to endNight
46%
720
21%
2015
15%
720
51%
720
27%
1328
October1st to 10thNight
40%
720
16%
2160
11%
720
47%
720
21%
1504
October11th to 20thNight
31%
720
15%
2160
10%
720
39%
720
17%
1564
October21st to endNight
28%
792
12%
2538
9%
792
35%
792
14%
1900
November1st to 10thNight
31%
740
15%
2407
11%
740
38%
740
18%
1667
November11th to 20thNight
25%
760
16%
2627
10%
760
34%
760
14%
1886
November21st to endNight
22%
760
10%
2660
5%
760
28%
760
11%
2031
December1st to 10thNight
21%
760
8%
2660
5%
760
25%
760
8%
2188
December11th to 20thNight
19%
759
12%
3246
7%
759
27%
759
8%
2460
December21st to endNight
18%
826
5%
4845
3%
817
23%
817
5%
3948

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
18%9%46%6%35%5%5%7%33%
74771
Night
18%10%47%6%35%45%6%32%
75050
TransparencyDay
50%7%12%20%10%1
74476
Night
52%6%11%19%10%1
74879
SeeingDay
21%11%28%24%13%4
13390
Night
22%8%29%30%11%1
22591

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
19%16%7%10%7%3444421%
1517
11th to 20thDay
18%15%6%9%8%44436%23%
1488
21st to endDay
13%14%5%10%7%5%6%6%5%5%25%
1634
February1st to 10thDay
14%16%6%9%8%5%445%6%23%
1620
11th to 20thDay
14%16%5%10%5%345%5%7%27%
1595
21st to endDay
19%14%47%7%46%5%5%5%24%
1480
March1st to 10thDay
16%11%5%9%8%46%445%29%
1797
11th to 20thDay
18%11%47%6%45%5%46%31%
1957
21st to endDay
20%9%35%5%34446%36%
2308
April1st to 10thDay
21%11%45%5%34436%33%
2160
11th to 20thDay
22%7%36%6%24346%36%
2134
21st to endDay
23%10%36%6%34445%32%
2278
May1st to 10thDay
20%8%36%6%35%447%34%
2520
11th to 20thDay
16%7%36%6%3445%6%39%
2478
21st to endDay
15%6%25%7%45%6%5%7%37%
2725
June1st to 10thDay
22%9%35%7%345%5%7%29%
2520
11th to 20thDay
14%6%35%5%45%5%6%8%39%
2520
21st to endDay
19%6%36%5%46%6%7%7%31%
2520
July1st to 10thDay
11%6%26%6%36%5%6%9%40%
2520
11th to 20thDay
12%6%35%5%36%6%7%9%38%
2520
21st to endDay
12%5%26%5%35%6%7%10%38%
2744
August1st to 10thDay
12%6%36%6%45%5%6%8%40%
2494
11th to 20thDay
12%6%345%46%6%6%9%40%
2260
21st to endDay
13%6%36%5%35%46%10%41%
2376
September1st to 10thDay
13%5%35%5%35%5%5%8%42%
2160
11th to 20thDay
13%5%2443445%8%47%
2147
21st to endDay
17%6%35%5%35%45%8%39%
1943
October1st to 10thDay
20%9%36%6%245%6%6%34%
1800
11th to 20thDay
22%8%47%6%45%6%5%7%28%
1800
21st to endDay
27%9%36%6%44446%27%
1818
November1st to 10thDay
16%8%46%6%46%5%7%7%32%
1671
11th to 20thDay
19%11%48%6%35%45%6%28%
1549
21st to endDay
21%15%48%6%46%5%5%5%22%
1520
December1st to 10thDay
22%15%5%9%6%446%5%6%17%
1520
11th to 20thDay
22%15%5%7%6%35%45%5%23%
1906
21st to endDay
28%17%6%10%5%3432320%
2772
January1st to 10thNight
18%17%6%10%7%45%44419%
2649
11th to 20thNight
19%16%5%11%7%4443423%
2616
21st to endNight
13%14%6%9%6%35%446%29%
2718
February1st to 10thNight
15%14%6%10%7%5%6%5%5%6%22%
2340
11th to 20thNight
14%11%6%9%8%45%5%5%5%28%
2251
21st to endNight
17%13%5%7%7%25%445%30%
1776
March1st to 10thNight
16%14%5%7%7%45%445%28%
2150
11th to 20thNight
17%12%47%8%43445%33%
2000
21st to endNight
18%9%47%6%3334439%
2048
April1st to 10thNight
23%9%36%5%35%445%33%
1800
11th to 20thNight
19%8%36%6%345%46%36%
1775
21st to endNight
21%8%36%6%3445%6%33%
1694
May1st to 10thNight
22%7%25%5%34447%36%
1440
11th to 20thNight
19%7%35%434447%40%
1415
21st to endNight
13%5%25%5%346%5%7%43%
1550
June1st to 10thNight
17%6%35%6%5%5%7%6%8%31%
1440
11th to 20thNight
15%6%35%5%346%6%7%41%
1440
21st to endNight
17%7%36%5%35%5%6%9%35%
1440
July1st to 10thNight
11%5%35%6%45%5%6%8%44%
1440
11th to 20thNight
11%6%26%6%25%5%6%9%42%
1440
21st to endNight
9%6%35%5%36%5%8%8%43%
1574
August1st to 10thNight
10%6%36%5%345%7%10%41%
1441
11th to 20thNight
11%6%25%5%35%5%5%8%44%
1621
21st to endNight
12%5%26%5%3446%8%44%
1980
September1st to 10thNight
11%6%37%5%35%45%6%45%
1800
11th to 20thNight
14%5%25%42346%7%49%
1813
21st to endNight
16%6%35%5%34446%44%
2015
October1st to 10thNight
19%7%26%5%4445%6%37%
2160
11th to 20thNight
20%10%46%6%35%5%5%6%32%
2160
21st to endNight
23%10%47%6%45%446%28%
2538
November1st to 10thNight
20%10%36%5%34446%35%
2407
11th to 20thNight
19%10%38%6%45%5%46%31%
2627
21st to endNight
21%12%5%9%7%3445%6%25%
2660
December1st to 10thNight
21%15%5%9%8%45%5%5%5%18%
2660
11th to 20thNight
24%13%5%7%7%3434427%
3288
21st to endNight
31%16%49%5%2433418%
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
66%5%10%14%5%
1518
11th to 20thDay
64%5%8%12%9%1
1488
21st to endDay
59%6%13%13%8%1
1634
February1st to 10thDay
62%5%10%18%42
1620
11th to 20thDay
57%5%13%16%8%1
1604
21st to endDay
61%5%10%14%9%1
1480
March1st to 10thDay
58%5%10%17%10%1
1800
11th to 20thDay
53%5%12%16%11%3
1957
21st to endDay
49%5%9%18%14%5%
2308
April1st to 10thDay
53%48%19%13%3
2160
11th to 20thDay
49%48%22%15%2
2134
21st to endDay
55%5%9%14%14%3
2278
May1st to 10thDay
50%6%7%20%14%4
2520
11th to 20thDay
45%6%10%21%16%2
2482
21st to endDay
44%8%13%20%13%2
2725
June1st to 10thDay
53%6%11%18%11%1
2520
11th to 20thDay
42%8%12%23%12%2
2520
21st to endDay
48%9%13%20%9%1
2520
July1st to 10thDay
38%8%12%26%15%1
2450
11th to 20thDay
38%9%16%27%10%
2445
21st to endDay
39%10%15%25%10%
2591
August1st to 10thDay
41%9%16%25%10%
2480
11th to 20thDay
38%10%16%26%9%1
2260
21st to endDay
38%8%14%27%12%1
2376
September1st to 10thDay
38%7%15%27%12%
2160
11th to 20thDay
36%7%13%32%13%1
2147
21st to endDay
42%7%15%27%8%
1943
October1st to 10thDay
50%5%12%22%11%
1800
11th to 20thDay
55%8%14%15%6%1
1800
21st to endDay
59%6%11%16%8%1
1818
November1st to 10thDay
48%9%14%21%7%1
1671
11th to 20thDay
56%6%13%16%9%1
1549
21st to endDay
62%7%13%11%6%
1520
December1st to 10thDay
67%7%12%10%2
1520
11th to 20thDay
63%7%13%13%4
1906
21st to endDay
72%47%14%3
2772
January1st to 10thNight
67%6%10%11%5%
2649
11th to 20thNight
66%6%10%10%8%1
2616
21st to endNight
57%5%10%16%10%1
2718
February1st to 10thNight
63%6%10%14%6%1
2340
11th to 20thNight
57%5%11%19%8%
2253
21st to endNight
57%49%18%11%1
1776
March1st to 10thNight
58%6%9%15%10%2
2160
11th to 20thNight
54%410%17%11%3
2001
21st to endNight
49%48%19%15%5%
2048
April1st to 10thNight
53%5%10%17%14%2
1800
11th to 20thNight
50%5%8%20%16%1
1775
21st to endNight
51%6%9%16%15%4
1694
May1st to 10thNight
48%6%8%18%15%5%
1440
11th to 20thNight
44%6%8%21%19%3
1416
21st to endNight
39%8%14%20%17%2
1551
June1st to 10thNight
46%9%13%20%10%1
1440
11th to 20thNight
41%8%11%21%17%2
1440
21st to endNight
44%9%14%18%14%1
1440
July1st to 10thNight
35%8%13%26%16%2
1400
11th to 20thNight
35%8%14%30%12%
1392
21st to endNight
36%10%15%25%14%
1486
August1st to 10thNight
37%9%19%22%12%1
1431
11th to 20thNight
37%8%15%29%11%1
1621
21st to endNight
36%8%16%27%11%1
1980
September1st to 10thNight
38%8%11%27%15%1
1800
11th to 20thNight
34%7%13%34%11%1
1813
21st to endNight
41%7%12%30%10%
2015
October1st to 10thNight
47%7%11%22%13%1
2160
11th to 20thNight
52%7%12%20%8%
2160
21st to endNight
57%6%13%16%8%1
2538
November1st to 10thNight
51%5%15%20%9%1
2407
11th to 20thNight
54%6%12%17%10%1
2627
21st to endNight
60%6%13%15%5%
2660
December1st to 10thNight
68%7%9%13%3
2660
11th to 20thNight
62%5%10%16%7%1
3288
21st to endNight
71%5%8%12%4
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
21%16%28%27%7%1
180
11th to 20thDay
26%12%33%20%6%2
172
21st to endDay
20%11%35%26%7%1
198
February1st to 10thDay
32%16%37%14%1
240
11th to 20thDay
24%16%40%18%2
262
21st to endDay
29%11%34%23%4
346
March1st to 10thDay
23%11%33%25%8%
420
11th to 20thDay
23%15%32%24%6%1
420
21st to endDay
29%11%27%21%9%2
462
April1st to 10thDay
25%14%35%18%8%1
420
11th to 20thDay
27%16%24%19%13%2
412
21st to endDay
28%12%30%18%10%2
420
May1st to 10thDay
25%11%28%22%11%3
423
11th to 20thDay
15%14%31%25%10%4
447
21st to endDay
17%11%31%25%14%3
485
June1st to 10thDay
25%8%25%27%10%4
450
11th to 20thDay
16%11%26%27%15%5%
450
21st to endDay
21%9%24%26%14%5%
450
July1st to 10thDay
14%422%35%18%7%
445
11th to 20thDay
11%7%27%31%19%5%
444
21st to endDay
14%5%26%32%18%4
488
August1st to 10thDay
13%6%22%32%21%6%
446
11th to 20thDay
14%422%24%26%10%
439
21st to endDay
13%8%25%23%20%10%
495
September1st to 10thDay
14%8%26%22%17%13%
450
11th to 20thDay
13%6%22%23%23%13%
450
21st to endDay
18%10%24%23%17%7%
450
October1st to 10thDay
23%10%25%20%16%6%
450
11th to 20thDay
24%12%32%20%10%2
450
21st to endDay
32%12%23%25%8%
414
November1st to 10thDay
23%17%26%22%11%1
365
11th to 20thDay
28%11%34%17%6%3
209
21st to endDay
26%18%31%16%8%2
180
December1st to 10thDay
29%11%31%22%6%1
180
11th to 20thDay
29%19%31%18%31
180
21st to endDay
31%15%33%15%5%1
198
January1st to 10thNight
24%11%33%26%6%
760
11th to 20thNight
26%12%30%26%5%1
748
21st to endNight
19%8%33%31%8%1
792
February1st to 10thNight
22%9%36%28%4
720
11th to 20thNight
21%10%36%27%5%
703
21st to endNight
24%10%31%31%4
592
March1st to 10thNight
23%11%33%28%5%
720
11th to 20thNight
23%12%31%27%6%
720
21st to endNight
22%11%28%30%9%1
792
April1st to 10thNight
27%9%30%28%6%
720
11th to 20thNight
23%12%32%24%9%1
711
21st to endNight
25%10%27%28%9%1
614
May1st to 10thNight
25%7%27%29%10%2
360
11th to 20thNight
21%8%29%32%9%1
354
21st to endNight
14%6%34%32%14%
389
June1st to 10thNight
18%429%40%9%1
360
11th to 20thNight
16%5%28%38%13%1
360
21st to endNight
17%5%27%34%17%1
360
July1st to 10thNight
9%5%26%42%18%
350
11th to 20thNight
11%420%45%18%1
348
21st to endNight
11%322%46%16%1
394
August1st to 10thNight
13%224%40%21%1
367
11th to 20thNight
14%315%38%29%2
557
21st to endNight
14%423%35%21%2
792
September1st to 10thNight
14%424%37%20%1
720
11th to 20thNight
17%5%19%33%23%3
720
21st to endNight
18%6%24%27%23%2
720
October1st to 10thNight
24%5%26%28%15%2
720
11th to 20thNight
23%8%30%28%9%1
720
21st to endNight
27%10%27%28%7%
792
November1st to 10thNight
26%10%26%28%10%1
740
11th to 20thNight
25%12%33%20%10%
760
21st to endNight
26%11%30%25%8%
760
December1st to 10thNight
29%11%30%25%5%1
760
11th to 20thNight
28%11%32%22%6%1
760
21st to endNight
33%10%30%23%4
836
Page generated at 2024-01-14 09:55:00. Version ac07

Copyright 2024 Attilla Danko


Boundary Road Clear Sky Chart |Charts Home