Monitor Pass
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Monitor Pass 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
56%
23428
21%
74554
15%
23388
63%
23388
22%
48344

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
43%
756
16%
2646
10%
756
53%
756
16%
1791
January11th to 20thNight
51%
728
18%
2503
13%
728
59%
728
18%
1668
January21st to endNight
46%
792
19%
2574
13%
792
56%
792
17%
1788
February1st to 10thNight
50%
720
18%
2308
14%
720
57%
720
20%
1539
February11th to 20thNight
47%
700
18%
2099
12%
700
55%
700
20%
1424
February21st to endNight
44%
592
19%
1776
13%
592
54%
592
19%
1189
March1st to 10thNight
38%
720
15%
2160
8%
720
48%
720
18%
1489
March11th to 20thNight
45%
720
19%
2026
13%
720
53%
720
19%
1377
March21st to endNight
41%
792
17%
2026
6%
792
49%
792
21%
1413
April1st to 10thNight
44%
720
18%
1800
6%
720
51%
720
22%
1275
April11th to 20thNight
45%
711
19%
1779
8%
711
50%
711
22%
1245
April21st to endNight
48%
720
19%
1800
7%
720
54%
720
25%
1241
May1st to 10thNight
50%
612
22%
1692
10%
612
56%
612
24%
1111
May11th to 20thNight
56%
436
26%
1498
20%
436
64%
436
24%
910
May21st to endNight
60%
388
20%
1552
19%
388
67%
388
18%
973
June1st to 10thNight
61%
360
20%
1440
19%
360
69%
360
19%
894
June11th to 20thNight
65%
360
26%
1440
24%
360
77%
360
25%
803
June21st to endNight
70%
360
26%
1440
28%
360
79%
360
24%
806
July1st to 10thNight
75%
350
25%
1400
28%
350
82%
350
28%
744
July11th to 20thNight
71%
348
27%
1392
26%
348
79%
348
24%
795
July21st to endNight
76%
451
26%
1542
26%
426
79%
426
23%
956
August1st to 10thNight
74%
589
23%
1654
14%
586
77%
586
32%
1042
August11th to 20thNight
72%
712
26%
1780
14%
712
75%
712
33%
1163
August21st to endNight
72%
792
28%
1980
15%
792
74%
792
37%
1258
September1st to 10thNight
75%
720
29%
1800
17%
720
79%
720
38%
1127
September11th to 20thNight
71%
720
32%
1840
22%
720
76%
720
33%
1184
September21st to endNight
67%
720
28%
1980
22%
720
74%
720
33%
1240
October1st to 10thNight
63%
720
22%
2102
16%
720
71%
720
26%
1371
October11th to 20thNight
68%
720
28%
2160
26%
720
74%
720
28%
1341
October21st to endNight
66%
792
26%
2425
24%
792
72%
792
27%
1498
November1st to 10thNight
60%
740
18%
2405
14%
740
67%
740
18%
1630
November11th to 20thNight
54%
760
22%
2470
16%
760
64%
760
20%
1621
November21st to endNight
53%
760
23%
2484
18%
760
62%
760
22%
1583
December1st to 10thNight
47%
760
16%
2660
11%
760
54%
760
18%
1766
December11th to 20thNight
46%
760
16%
3168
13%
758
52%
758
12%
2179
December21st to endNight
39%
827
10%
4753
8%
817
48%
817
8%
2910

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
232332445%7%64%
74782
Night
232332345%7%64%
74958
TransparencyDay
13%36%6%14%17%13%
74490
Night
12%36%8%17%17%10%
74771
SeeingDay
9%19%30%26%13%4
13941
Night
5%9%26%34%20%5%
23446

By Month

Percentage Cloud Cover SW (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
2323336%7%7%11%52%
1519
11th to 20thDay
13335%35%5%7%9%56%
1496
21st to endDay
36%24435%5%8%11%47%
1782
February1st to 10thDay
232443347%8%59%
1651
11th to 20thDay
1435%4345%6%11%52%
1750
21st to endDay
1425%4245%6%9%58%
1480
March1st to 10thDay
2436%5%35%6%9%10%48%
1800
11th to 20thDay
16%34425%5%7%11%51%
1930
21st to endDay
14234345%7%10%55%
2329
April1st to 10thDay
3425%5%35%46%9%54%
2160
11th to 20thDay
34235%2346%7%61%
2129
21st to endDay
35%2332445%8%63%
2160
May1st to 10thDay
44245%24448%60%
2268
11th to 20thDay
5%42442445%6%60%
2392
21st to endDay
7%5%25%435%45%7%53%
2723
June1st to 10thDay
332333445%7%63%
2520
11th to 20thDay
2112222235%77%
2520
21st to endDay
321232333473%
2520
July1st to 10thDay
111222334476%
2520
11th to 20thDay
3112323335%73%
2520
21st to endDay
332342344469%
2681
August1st to 10thDay
221332334471%
2275
11th to 20thDay
2212323345%74%
2122
21st to endDay
111221223382%
2376
September1st to 10thDay
211111334479%
2160
11th to 20thDay
2213323345%74%
2120
21st to endDay
221221323477%
1980
October1st to 10thDay
431331344469%
1854
11th to 20thDay
2212322335%75%
1800
21st to endDay
131222345%7%72%
1928
November1st to 10thDay
242333346%7%64%
1674
11th to 20thDay
131232446%9%65%
1710
21st to endDay
13143245%5%10%62%
1691
December1st to 10thDay
35%143245%6%10%57%
1520
11th to 20thDay
36%47%6%46%7%7%9%42%
1928
21st to endDay
1436%5%35%6%7%13%44%
2794
January1st to 10thNight
2426%5%345%7%11%51%
2646
11th to 20thNight
14245%346%7%10%54%
2503
21st to endNight
26%35%5%35%5%6%10%51%
2574
February1st to 10thNight
1435%4345%6%7%59%
2308
11th to 20thNight
15%3443447%11%55%
2098
21st to endNight
15%244345%6%9%59%
1776
March1st to 10thNight
15%34435%5%6%10%54%
2160
11th to 20thNight
1423435%6%7%11%56%
2026
21st to endNight
15%3332445%9%61%
2026
April1st to 10thNight
34143245%7%9%58%
1800
11th to 20thNight
232332445%7%64%
1779
21st to endNight
4313313347%67%
1800
May1st to 10thNight
4413324448%64%
1692
11th to 20thNight
2414313347%66%
1498
21st to endNight
6%313334446%62%
1552
June1st to 10thNight
5%313322346%70%
1440
11th to 20thNight
1111212235%81%
1440
21st to endNight
311221232380%
1440
July1st to 10thNight
111111222484%
1440
11th to 20thNight
1212322335%77%
1440
21st to endNight
3212323435%72%
1633
August1st to 10thNight
321332334473%
1663
11th to 20thNight
222222235%79%
1780
21st to endNight
121121112385%
1980
September1st to 10thNight
111111222485%
1800
11th to 20thNight
211222224479%
1840
21st to endNight
221221234477%
1980
October1st to 10thNight
342332233472%
2102
11th to 20thNight
2312112235%77%
2160
21st to endNight
1212222346%76%
2425
November1st to 10thNight
231322346%8%66%
2405
11th to 20thNight
131232345%9%67%
2470
21st to endNight
231332346%7%65%
2484
December1st to 10thNight
25%243245%5%9%58%
2660
11th to 20thNight
35%345%35%5%7%11%48%
3276
21st to endNight
16%47%5%45%7%8%10%43%
4862

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
12%41%14%21%12%1
1519
11th to 20thDay
11%42%8%20%14%5%
1496
21st to endDay
20%39%8%17%12%5%
1782
February1st to 10thDay
15%35%7%20%17%6%
1651
11th to 20thDay
16%36%10%19%14%5%
1760
21st to endDay
14%36%12%20%13%4
1480
March1st to 10thDay
16%37%11%21%14%1
1800
11th to 20thDay
18%38%12%16%13%3
1930
21st to endDay
14%38%15%20%11%2
2329
April1st to 10thDay
16%37%10%18%13%6%
2160
11th to 20thDay
14%37%9%19%15%6%
2132
21st to endDay
14%36%9%20%17%4
2160
May1st to 10thDay
12%36%419%23%6%
2268
11th to 20thDay
13%36%5%18%21%7%
2395
21st to endDay
18%36%6%19%18%3
2724
June1st to 10thDay
15%36%7%15%20%6%
2520
11th to 20thDay
8%35%411%24%18%
2520
21st to endDay
11%36%27%23%21%
2520
July1st to 10thDay
6%37%1412%41%
2451
11th to 20thDay
10%36%1414%35%
2445
21st to endDay
11%37%26%14%30%
2532
August1st to 10thDay
10%36%26%13%34%
2259
11th to 20thDay
10%35%15%17%33%
2122
21st to endDay
6%35%319%37%
2376
September1st to 10thDay
8%35%16%19%31%
2160
11th to 20thDay
9%36%211%24%19%
2120
21st to endDay
7%35%212%24%20%
1980
October1st to 10thDay
13%35%5%12%19%15%
1854
11th to 20thDay
9%34%418%22%13%
1800
21st to endDay
7%37%5%18%23%10%
1928
November1st to 10thDay
13%41%8%17%14%8%
1674
11th to 20thDay
9%39%11%17%20%4
1710
21st to endDay
9%41%7%17%21%7%
1691
December1st to 10thDay
12%40%8%19%16%5%
1520
11th to 20thDay
28%33%9%17%9%4
1928
21st to endDay
22%28%15%19%14%2
2794
January1st to 10thNight
15%40%11%21%12%2
2646
11th to 20thNight
11%42%10%20%12%5%
2503
21st to endNight
19%37%10%17%13%4
2574
February1st to 10thNight
15%37%8%20%14%6%
2308
11th to 20thNight
16%36%10%23%13%3
2099
21st to endNight
13%38%13%20%13%3
1776
March1st to 10thNight
17%37%12%20%14%1
2160
11th to 20thNight
13%37%13%22%12%3
2026
21st to endNight
14%37%15%21%10%3
2026
April1st to 10thNight
15%37%11%20%11%6%
1800
11th to 20thNight
13%36%12%19%13%6%
1779
21st to endNight
13%35%9%23%17%3
1800
May1st to 10thNight
10%36%6%17%25%5%
1692
11th to 20thNight
9%36%7%20%22%6%
1498
21st to endNight
15%36%8%22%17%2
1552
June1st to 10thNight
12%37%8%19%18%6%
1440
11th to 20thNight
6%35%5%14%24%16%
1440
21st to endNight
7%34%312%24%20%
1440
July1st to 10thNight
235%15%20%37%
1400
11th to 20thNight
8%36%15%20%31%
1392
21st to endNight
10%37%16%16%29%
1542
August1st to 10thNight
8%35%111%15%30%
1654
11th to 20thNight
8%35%17%19%29%
1780
21st to endNight
5%35%15%22%33%
1980
September1st to 10thNight
335%18%23%31%
1800
11th to 20thNight
6%36%411%22%21%
1840
21st to endNight
6%35%312%26%18%
1980
October1st to 10thNight
12%35%5%15%21%12%
2102
11th to 20thNight
9%34%419%23%11%
2160
21st to endNight
8%36%420%22%11%
2425
November1st to 10thNight
11%42%7%19%14%8%
2405
11th to 20thNight
9%41%9%20%18%3
2470
21st to endNight
8%39%6%21%19%6%
2484
December1st to 10thNight
12%41%9%15%18%5%
2660
11th to 20thNight
22%35%12%18%11%3
3276
21st to endNight
26%27%14%19%11%3
4862

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
17%21%31%20%9%2
180
11th to 20thDay
14%21%26%22%14%4
204
21st to endDay
8%20%29%28%12%3
374
February1st to 10thDay
15%18%30%23%11%3
354
11th to 20thDay
11%23%33%24%9%
415
21st to endDay
10%25%33%24%7%1
346
March1st to 10thDay
14%26%32%20%6%2
420
11th to 20thDay
13%27%29%20%9%2
420
21st to endDay
14%26%31%21%8%
462
April1st to 10thDay
13%27%33%18%8%2
420
11th to 20thDay
20%26%28%17%7%2
412
21st to endDay
13%26%28%21%10%3
420
May1st to 10thDay
14%24%30%20%8%3
423
11th to 20thDay
13%25%28%22%10%3
448
21st to endDay
15%18%24%24%13%6%
485
June1st to 10thDay
10%22%28%23%12%5%
450
11th to 20thDay
9%21%34%22%10%4
450
21st to endDay
414%34%30%14%6%
450
July1st to 10thDay
314%31%31%17%3
446
11th to 20thDay
412%29%33%17%5%
444
21st to endDay
410%32%27%20%6%
487
August1st to 10thDay
314%30%28%19%6%
447
11th to 20thDay
313%32%27%18%8%
437
21st to endDay
213%33%32%16%4
495
September1st to 10thDay
411%30%33%17%4
450
11th to 20thDay
7%18%27%30%14%4
450
21st to endDay
7%13%31%36%10%3
450
October1st to 10thDay
6%16%30%27%18%3
450
11th to 20thDay
6%15%26%32%17%5%
450
21st to endDay
6%16%29%25%20%4
443
November1st to 10thDay
11%16%23%20%22%9%
270
11th to 20thDay
6%13%24%33%16%7%
270
21st to endDay
413%30%29%18%6%
261
December1st to 10thDay
12%18%24%22%16%8%
180
11th to 20thDay
7%23%31%19%14%6%
180
21st to endDay
17%13%29%24%12%5%
198
January1st to 10thNight
6%13%32%24%16%9%
760
11th to 20thNight
414%27%33%15%7%
728
21st to endNight
5%8%34%29%17%7%
792
February1st to 10thNight
5%10%30%34%17%4
720
11th to 20thNight
412%33%30%16%6%
704
21st to endNight
5%18%29%33%12%3
592
March1st to 10thNight
5%15%38%26%13%3
720
11th to 20thNight
5%18%29%25%20%3
720
21st to endNight
5%19%31%31%12%2
792
April1st to 10thNight
7%12%33%32%15%2
720
11th to 20thNight
7%16%28%28%16%4
711
21st to endNight
7%13%29%31%16%4
720
May1st to 10thNight
6%12%28%33%17%3
612
11th to 20thNight
5%9%25%41%19%2
436
21st to endNight
8%5%22%37%26%3
389
June1st to 10thNight
6%6%23%41%22%2
360
11th to 20thNight
25%26%40%26%1
360
21st to endNight
3421%44%24%3
360
July1st to 10thNight
1218%49%28%1
350
11th to 20thNight
2121%48%27%1
348
21st to endNight
4213%41%36%6%
451
August1st to 10thNight
3118%41%34%4
589
11th to 20thNight
3419%43%27%5%
712
21st to endNight
2321%45%26%4
792
September1st to 10thNight
1319%40%31%6%
720
11th to 20thNight
35%19%37%30%6%
720
21st to endNight
26%22%34%28%8%
720
October1st to 10thNight
6%423%38%21%8%
720
11th to 20thNight
5%8%16%40%24%7%
720
21st to endNight
37%23%31%24%12%
792
November1st to 10thNight
410%24%30%24%9%
740
11th to 20thNight
5%9%30%33%16%7%
760
21st to endNight
7%10%25%31%21%6%
760
December1st to 10thNight
6%11%32%31%15%6%
760
11th to 20thNight
6%12%30%32%13%6%
760
21st to endNight
8%13%33%32%11%3
836
Page generated at 2024-01-09 22:25:05. Version ac07

Copyright 2024 Attilla Danko


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