Monitor Pass
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Monitor Pass clear sky chart from 2005-11-05 to 2017-09-18.

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
63%
15226
30%
46874
24%
15198
70%
15198
48%
22510

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 15thNight
61%
716
24%
2506
22%
716
68%
716
36%
1259
January16th to endNight
59%
768
27%
2526
24%
768
65%
768
38%
1309
February1st to 15thNight
56%
697
24%
2210
23%
697
61%
697
39%
1131
February16th to endNight
53%
632
27%
1895
23%
632
62%
632
41%
972
March1st to 15thNight
54%
720
23%
2130
18%
720
61%
720
44%
1067
March16th to endNight
50%
768
23%
2010
14%
768
57%
768
46%
1076
April1st to 15thNight
52%
719
23%
1799
11%
719
57%
719
41%
1024
April16th to endNight
55%
720
24%
1800
12%
720
59%
720
44%
1009
May1st to 15thNight
61%
580
29%
1660
20%
580
65%
580
51%
811
May16th to endNight
65%
374
27%
1496
29%
374
70%
374
39%
673
June1st to 15thNight
68%
360
28%
1440
31%
360
75%
360
49%
581
June16th to endNight
76%
360
35%
1440
42%
360
84%
360
69%
462
July1st to 15thNight
86%
340
33%
1360
42%
340
89%
340
66%
458
July16th to endNight
80%
415
38%
1452
41%
390
83%
390
58%
559
August1st to 15thNight
78%
634
35%
1707
24%
631
80%
631
69%
785
August16th to endNight
77%
764
42%
1910
25%
764
79%
764
77%
868
September1st to 15thNight
82%
720
41%
1800
27%
720
86%
720
77%
823
September16th to endNight
74%
667
43%
1814
34%
667
80%
667
67%
824
October1st to 15thNight
67%
660
33%
1945
28%
660
76%
660
55%
919
October16th to endNight
71%
704
37%
2142
35%
704
80%
704
57%
952
November1st to 15thNight
68%
700
32%
2275
31%
700
75%
700
48%
1076
November16th to endNight
57%
720
32%
2349
27%
720
68%
720
46%
1077
December1st to 15thNight
54%
720
21%
2520
18%
720
61%
720
34%
1317
December16th to endNight
49%
768
24%
2688
20%
768
58%
768
29%
1478

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
231332345%7%63%
47930
Night
131221335%7%65%
47052
TransparencyDay
20%410%21%24%17%
47605
Night
18%413%26%24%13%
46876
SeeingDay
10%18%28%24%12%4
5770
Night
5%6%20%36%24%7%
15239

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 15thDay
1223325%6%8%8%54%
1432
16th to endDay
3423425%5%8%10%48%
1695
February1st to 15thDay
141432347%10%54%
1651
16th to endDay
132442446%10%54%
1579
March1st to 15thDay
3343245%8%11%51%
1827
16th to endDay
5%233245%7%11%54%
2214
April1st to 15thDay
24245%35%46%9%50%
2149
16th to endDay
341331335%7%63%
2160
May1st to 15thDay
4413413437%61%
2287
16th to endDay
6%5%1442445%6%53%
2615
June1st to 15thDay
4213323446%63%
2520
16th to endDay
11121232477%
2520
July1st to 15thDay
111232334471%
2520
16th to endDay
221231243372%
2616
August1st to 15thDay
22222233472%
2244
16th to endDay
11221223378%
2292
September1st to 15thDay
111121223476%
2160
16th to endDay
211121223476%
1870
October1st to 15thDay
332313445%66%
1683
16th to endDay
2312222446%68%
1728
November1st to 15thDay
23122235%6%7%61%
1584
16th to endDay
1312225%45%9%61%
1608
December1st to 15thDay
1424325%6%5%9%53%
1440
16th to endDay
425%435%6%7%12%45%
1536
January1st to 15thNight
1325%42447%9%54%
2506
16th to endNight
15%2442446%10%53%
2526
February1st to 15thNight
14233235%7%10%54%
2200
16th to endNight
142342446%10%55%
1895
March1st to 15thNight
32232446%10%58%
2130
16th to endNight
142231345%10%60%
2010
April1st to 15thNight
2324225%5%7%9%55%
1799
16th to endNight
4212213447%65%
1800
May1st to 15thNight
232223338%67%
1660
16th to endNight
4413323346%63%
1496
June1st to 15thNight
4212212235%71%
1440
16th to endNight
111221383%
1440
July1st to 15thNight
11111222479%
1440
16th to endNight
211131222476%
1551
August1st to 15thNight
21221223476%
1716
16th to endNight
1111113382%
1910
September1st to 15thNight
1111122482%
1800
16th to endNight
21211133377%
1814
October1st to 15thNight
3312223345%69%
1945
16th to endNight
231212346%71%
2142
November1st to 15thNight
13211336%8%65%
2275
16th to endNight
13332336%8%64%
2349
December1st to 15thNight
13234245%7%10%53%
2520
16th to endNight
435%4245%7%11%50%
2688

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 15thDay
24%6%18%30%17%3
1432
16th to endDay
28%7%13%24%18%8%
1695
February1st to 15thDay
24%417%28%19%4
1651
16th to endDay
25%317%31%18%3
1579
March1st to 15thDay
23%6%20%25%20%4
1827
16th to endDay
22%7%23%26%16%3
2214
April1st to 15thDay
27%6%14%26%19%5%
2149
16th to endDay
22%416%29%22%5%
2160
May1st to 15thDay
23%38%30%27%6%
2287
16th to endDay
30%210%25%24%6%
2619
June1st to 15thDay
20%310%20%28%15%
2520
16th to endDay
12%1312%34%35%
2520
July1st to 15thDay
16%237%20%49%
2371
16th to endDay
17%249%19%46%
2452
August1st to 15thDay
16%339%20%46%
2228
16th to endDay
13%127%33%41%
2292
September1st to 15thDay
15%1310%31%37%
2160
16th to endDay
13%1422%36%22%
1870
October1st to 15thDay
18%27%25%32%13%
1683
16th to endDay
17%210%28%30%10%
1728
November1st to 15thDay
20%414%30%21%8%
1584
16th to endDay
18%5%16%27%27%4
1608
December1st to 15thDay
25%7%17%29%18%1
1440
16th to endDay
29%9%17%20%19%2
1536
January1st to 15thNight
25%5%16%30%20%2
2506
16th to endNight
25%5%16%26%19%7%
2526
February1st to 15thNight
23%418%31%14%6%
2211
16th to endNight
22%419%32%16%3
1895
March1st to 15thNight
19%5%21%28%19%5%
2130
16th to endNight
19%5%24%29%16%3
2010
April1st to 15thNight
23%5%19%30%18%2
1799
16th to endNight
21%6%16%29%21%4
1800
May1st to 15thNight
17%411%30%28%7%
1661
16th to endNight
22%311%30%25%6%
1496
June1st to 15thNight
16%310%23%29%16%
1440
16th to endNight
8%417%34%33%
1440
July1st to 15thNight
9%139%28%46%
1360
16th to endNight
13%139%24%46%
1452
August1st to 15thNight
12%1315%24%42%
1707
16th to endNight
8%1213%37%36%
1910
September1st to 15thNight
8%15%14%35%35%
1800
16th to endNight
11%25%21%35%23%
1814
October1st to 15thNight
17%28%32%30%9%
1945
16th to endNight
14%210%30%33%8%
2142
November1st to 15thNight
16%6%12%33%22%8%
2275
16th to endNight
17%413%32%26%4
2349
December1st to 15thNight
24%8%19%27%16%2
2520
16th to endNight
27%9%17%25%16%3
2688

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 15thDay
23%10%33%20%8%5%
60
16th to endDay
13%13%21%27%19%3
223
February1st to 15thDay
15%13%22%26%18%2
249
16th to endDay
12%20%29%24%12%1
238
March1st to 15thDay
15%23%22%23%11%4
270
16th to endDay
15%29%25%20%8%
288
April1st to 15thDay
17%25%26%20%5%3
269
16th to endDay
14%30%26%22%41
270
May1st to 15thDay
15%26%25%20%7%3
288
16th to endDay
14%21%22%23%12%5%
330
June1st to 15thDay
11%23%31%20%10%2
315
16th to endDay
5%15%38%25%10%6%
315
July1st to 15thDay
415%26%28%17%5%
305
16th to endDay
413%35%26%13%5%
327
August1st to 15thDay
6%17%33%21%13%7%
315
16th to endDay
313%33%23%16%9%
332
September1st to 15thDay
6%11%33%29%12%6%
315
16th to endDay
8%15%25%35%10%4
264
October1st to 15thDay
9%16%32%23%12%4
255
16th to endDay
10%17%30%28%10%1
240
November1st to 15thDay
6%6%20%20%27%18%
90
16th to endDay
10%17%25%30%10%6%
88
December1st to 15thDay
16%16%36%18%10%1
60
16th to endDay
15%7%15%31%25%4
64
January1st to 15thNight
5%7%17%34%22%11%
720
16th to endNight
6%324%38%18%9%
768
February1st to 15thNight
6%5%24%33%23%6%
704
16th to endNight
5%10%25%34%17%7%
632
March1st to 15thNight
410%26%33%19%5%
720
16th to endNight
413%27%32%19%2
768
April1st to 15thNight
7%10%25%34%19%2
719
16th to endNight
8%12%21%30%19%7%
720
May1st to 15thNight
5%9%21%38%20%4
581
16th to endNight
8%317%37%29%3
375
June1st to 15thNight
5%221%45%22%3
360
16th to endNight
118%45%28%4
360
July1st to 15thNight
27%51%35%2
340
16th to endNight
310%40%38%5%
415
August1st to 15thNight
3113%40%35%5%
634
16th to endNight
2115%39%33%6%
764
September1st to 15thNight
1111%37%39%9%
720
16th to endNight
3316%29%35%11%
667
October1st to 15thNight
5%5%16%35%24%11%
660
16th to endNight
5%414%34%26%13%
704
November1st to 15thNight
4418%37%24%9%
700
16th to endNight
6%8%23%30%21%9%
720
December1st to 15thNight
6%6%26%35%16%8%
720
16th to endNight
6%8%28%36%15%5%
768
Page generated at 2017-09-19 04:32:33. Version ac04

Copyright 2017 A. Danko


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