Melinda Heights Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Melinda Heights Observatory clear sky chart from 2005-11-05 to 2017-09-22.

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
77%
16035
31%
46765
28%
15991
79%
15991
47%
24465

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
70%
716
29%
2306
29%
716
74%
716
41%
1203
January16th to endNight
65%
768
32%
2304
30%
768
70%
768
39%
1277
February1st to 15thNight
73%
697
33%
2104
34%
697
76%
697
44%
1112
February16th to endNight
62%
632
27%
1895
29%
632
64%
632
32%
1141
March1st to 15thNight
71%
720
29%
2160
31%
720
74%
720
43%
1157
March16th to endNight
74%
768
27%
2019
24%
768
76%
768
46%
1158
April1st to 15thNight
69%
719
25%
1799
18%
719
71%
719
42%
1104
April16th to endNight
76%
720
29%
1800
19%
720
77%
720
50%
1012
May1st to 15thNight
74%
602
26%
1682
19%
602
75%
602
42%
971
May16th to endNight
77%
561
24%
1685
21%
561
78%
561
39%
970
June1st to 15thNight
80%
540
21%
1620
19%
540
80%
540
42%
907
June16th to endNight
92%
395
31%
1475
34%
395
92%
395
57%
575
July1st to 15thNight
88%
387
26%
1407
28%
387
88%
387
52%
592
July16th to endNight
87%
654
27%
1676
21%
614
87%
614
53%
884
August1st to 15thNight
91%
717
31%
1790
20%
713
91%
713
63%
911
August16th to endNight
93%
764
39%
1910
26%
764
93%
764
70%
930
September1st to 15thNight
88%
720
34%
1848
28%
720
88%
720
62%
926
September16th to endNight
87%
683
40%
1890
40%
683
88%
683
63%
888
October1st to 15thNight
81%
660
35%
1815
34%
660
82%
660
56%
907
October16th to endNight
78%
704
36%
2129
39%
704
80%
704
49%
1053
November1st to 15thNight
82%
700
34%
2275
38%
700
83%
700
52%
1034
November16th to endNight
75%
720
34%
2340
38%
720
78%
720
44%
1166
December1st to 15thNight
69%
720
32%
2340
33%
720
73%
720
37%
1253
December16th to endNight
60%
768
32%
2496
30%
768
67%
768
37%
1334

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
5%312212346%65%
48092
Night
5%313322346%62%
46970
TransparencyDay
20%37%17%25%25%
47789
Night
23%48%15%22%25%
46774
SeeingDay
6%419%39%23%6%
5974
Night
6%17%30%41%12%
16049

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
9%5%13323245%59%
1629
16th to endDay
11%413313345%55%
1920
February1st to 15thDay
9%413313246%59%
1751
16th to endDay
13%5%2431335%6%49%
1579
March1st to 15thDay
7%31222445%9%56%
1800
16th to endDay
5%31342345%8%56%
2202
April1st to 15thDay
7%424324336%57%
2149
16th to endDay
6%212212246%66%
2160
May1st to 15thDay
5%413323347%61%
2265
16th to endDay
45%1321225%9%61%
2429
June1st to 15thDay
5%413212247%65%
2340
16th to endDay
11111112482%
2478
July1st to 15thDay
132212346%70%
2463
16th to endDay
2212212346%69%
2373
August1st to 15thDay
111112336%78%
2160
16th to endDay
1121233477%
2292
September1st to 15thDay
11211123478%
2112
16th to endDay
12112224476%
1882
October1st to 15thDay
6%31321235%6%63%
1815
16th to endDay
5%31222223468%
1741
November1st to 15thDay
4212322235%68%
1584
16th to endDay
6%31321245%7%61%
1620
December1st to 15thDay
8%41431435%8%53%
1620
16th to endDay
12%423214335%55%
1728
January1st to 15thNight
8%414323346%58%
2306
16th to endNight
11%5%23322235%57%
2304
February1st to 15thNight
8%313213236%60%
2101
16th to endNight
14%6%24323435%50%
1895
March1st to 15thNight
7%5%1231345%7%56%
2160
16th to endNight
5%423333447%57%
2019
April1st to 15thNight
8%5%23322346%56%
1799
16th to endNight
5%313322336%64%
1800
May1st to 15thNight
35%1331235%9%57%
1682
16th to endNight
26%12324349%58%
1684
June1st to 15thNight
241232426%9%60%
1620
16th to endNight
11111239%75%
1475
July1st to 15thNight
121221335%8%65%
1491
16th to endNight
221232236%9%62%
1791
August1st to 15thNight
211122247%72%
1800
16th to endNight
11112236%76%
1910
September1st to 15thNight
1212122225%74%
1848
16th to endNight
22112122477%
1890
October1st to 15thNight
4212212236%68%
1815
16th to endNight
5%313322335%65%
2129
November1st to 15thNight
3312222236%68%
2275
16th to endNight
6%313313346%61%
2340
December1st to 15thNight
8%4235%23246%56%
2340
16th to endNight
12%5%23322235%57%
2496

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
26%36%14%22%25%
1630
16th to endDay
29%37%14%16%28%
1920
February1st to 15thDay
25%36%14%25%24%
1751
16th to endDay
34%37%18%26%9%
1579
March1st to 15thDay
23%310%21%20%21%
1800
16th to endDay
22%5%12%25%21%13%
2202
April1st to 15thDay
27%38%26%23%10%
2149
16th to endDay
18%310%23%25%17%
2160
May1st to 15thDay
23%39%20%26%16%
2265
16th to endDay
21%5%9%26%27%9%
2432
June1st to 15thDay
21%47%17%30%18%
2340
16th to endDay
9%25%9%27%46%
2478
July1st to 15thDay
14%38%10%25%37%
2318
16th to endDay
15%49%22%28%20%
2225
August1st to 15thDay
8%25%14%35%33%
2146
16th to endDay
10%2414%35%33%
2292
September1st to 15thDay
10%26%10%34%34%
2112
16th to endDay
11%25%13%32%34%
1882
October1st to 15thDay
21%3420%25%24%
1815
16th to endDay
20%35%12%21%37%
1741
November1st to 15thDay
19%28%17%20%32%
1584
16th to endDay
22%46%14%21%31%
1620
December1st to 15thDay
26%49%17%17%23%
1620
16th to endDay
31%47%16%19%19%
1728
January1st to 15thNight
26%37%11%20%30%
2306
16th to endNight
30%27%13%13%31%
2304
February1st to 15thNight
25%36%15%21%27%
2112
16th to endNight
36%47%13%21%16%
1895
March1st to 15thNight
26%47%20%19%21%
2160
16th to endNight
25%412%18%21%15%
2019
April1st to 15thNight
30%48%22%21%13%
1799
16th to endNight
22%5%10%21%21%19%
1800
May1st to 15thNight
26%6%10%17%20%17%
1683
16th to endNight
27%7%10%21%21%11%
1685
June1st to 15thNight
22%9%15%12%23%16%
1620
16th to endNight
11%413%10%21%38%
1475
July1st to 15thNight
15%411%13%22%31%
1407
16th to endNight
18%6%12%19%25%17%
1676
August1st to 15thNight
13%49%13%32%25%
1790
16th to endNight
11%37%12%30%35%
1910
September1st to 15thNight
15%38%9%31%32%
1848
16th to endNight
14%2410%31%36%
1890
October1st to 15thNight
18%37%16%31%22%
1815
16th to endNight
22%2411%22%37%
2129
November1st to 15thNight
19%16%14%19%37%
2275
16th to endNight
23%35%16%17%32%
2340
December1st to 15thNight
28%49%13%19%24%
2340
16th to endNight
30%29%14%22%20%
2496

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
25%316%40%12%
108
16th to endDay
15%7%27%34%13%1
288
February1st to 15thDay
10%5%25%33%22%2
266
16th to endDay
14%12%25%32%13%2
238
March1st to 15thDay
8%10%27%30%18%5%
270
16th to endDay
6%9%27%38%12%4
288
April1st to 15thDay
8%11%31%34%11%3
269
16th to endDay
211%39%33%8%3
270
May1st to 15thDay
7%6%28%38%13%3
288
16th to endDay
6%6%26%39%15%4
330
June1st to 15thDay
5%321%41%22%5%
315
16th to endDay
19%42%34%11%
315
July1st to 15thDay
27%35%40%12%
305
16th to endDay
2340%41%12%
327
August1st to 15thDay
7%45%37%8%
315
16th to endDay
440%40%13%
332
September1st to 15thDay
210%53%25%7%
315
16th to endDay
2215%48%22%8%
280
October1st to 15thDay
46%25%41%18%4
255
16th to endDay
5%318%38%26%7%
234
November1st to 15thDay
147%33%31%22%
90
16th to endDay
37%17%36%28%5%
90
December1st to 15thDay
8%213%30%41%4
90
16th to endDay
14%219%39%20%3
96
January1st to 15thNight
9%19%38%27%12%
720
16th to endNight
12%110%34%30%9%
768
February1st to 15thNight
9%17%36%32%11%
704
16th to endNight
15%110%37%25%8%
632
March1st to 15thNight
7%210%39%32%8%
720
16th to endNight
5%28%35%39%8%
768
April1st to 15thNight
8%210%38%33%5%
719
16th to endNight
5%28%38%35%9%
720
May1st to 15thNight
6%111%32%41%7%
603
16th to endNight
3111%34%42%6%
563
June1st to 15thNight
219%37%43%5%
540
16th to endNight
1320%66%8%
395
July1st to 15thNight
1213%64%17%
387
16th to endNight
2111%60%22%
654
August1st to 15thNight
1113%62%20%
717
16th to endNight
1111%60%25%
764
September1st to 15thNight
2316%55%21%
720
16th to endNight
3323%51%17%
683
October1st to 15thNight
45%36%41%11%
660
16th to endNight
6%15%27%40%18%
704
November1st to 15thNight
45%33%37%17%
700
16th to endNight
6%18%31%36%15%
720
December1st to 15thNight
10%28%36%32%10%
720
16th to endNight
13%214%33%26%8%
768
Page generated at 2017-09-23 03:43:34. Version ac04

Copyright 2017 A. Danko


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