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 2005-11-06 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
75%
24630
30%
74182
28%
24578
77%
24578
44%
39363

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
64%
756
29%
2457
29%
756
68%
756
39%
1299
January11th to 20thNight
68%
732
35%
2257
32%
732
74%
732
43%
1176
January21st to endNight
62%
792
36%
2376
31%
792
70%
792
40%
1293
February1st to 10thNight
69%
720
35%
2160
34%
720
74%
720
45%
1129
February11th to 20thNight
65%
700
31%
2098
30%
700
70%
700
42%
1130
February21st to endNight
60%
592
28%
1776
29%
592
63%
592
34%
1040
March1st to 10thNight
62%
720
23%
2160
25%
720
66%
720
33%
1268
March11th to 20thNight
67%
720
25%
2106
27%
720
69%
720
40%
1198
March21st to endNight
68%
792
27%
2003
21%
792
71%
792
44%
1202
April1st to 10thNight
69%
720
26%
1800
20%
720
70%
720
39%
1130
April11th to 20thNight
68%
711
29%
1779
19%
711
70%
711
45%
1050
April21st to endNight
74%
720
27%
1800
17%
720
75%
720
46%
1057
May1st to 10thNight
70%
636
23%
1716
15%
636
71%
636
40%
1023
May11th to 20thNight
75%
531
24%
1595
19%
531
75%
531
35%
959
May21st to endNight
73%
582
24%
1746
20%
582
73%
582
38%
1018
June1st to 10thNight
74%
540
20%
1620
17%
540
75%
540
37%
954
June11th to 20thNight
84%
503
28%
1583
26%
503
84%
503
47%
791
June21st to endNight
90%
360
30%
1440
37%
360
90%
360
48%
593
July1st to 10thNight
89%
350
29%
1400
33%
350
89%
350
52%
541
July11th to 20thNight
91%
509
29%
1553
25%
509
91%
509
57%
721
July21st to endNight
88%
728
29%
1804
21%
688
88%
688
55%
961
August1st to 10thNight
90%
716
31%
1780
19%
712
90%
712
63%
903
August11th to 20thNight
94%
712
35%
1780
22%
712
94%
712
70%
870
August21st to endNight
92%
792
37%
1980
26%
792
92%
792
68%
973
September1st to 10thNight
86%
720
37%
1800
29%
720
86%
720
61%
934
September11th to 20thNight
89%
720
38%
1962
36%
720
89%
720
63%
929
September21st to endNight
86%
720
39%
1980
39%
720
87%
720
64%
933
October1st to 10thNight
81%
720
35%
1980
34%
720
82%
720
56%
981
October11th to 20thNight
80%
720
38%
2035
38%
720
81%
720
54%
1010
October21st to endNight
77%
792
38%
2438
39%
792
79%
792
52%
1153
November1st to 10thNight
79%
740
34%
2405
38%
740
82%
740
52%
1095
November11th to 20thNight
80%
760
36%
2470
40%
760
83%
760
51%
1151
November21st to endNight
70%
760
32%
2470
35%
760
73%
760
39%
1292
December1st to 10thNight
68%
760
31%
2470
30%
760
72%
760
39%
1292
December11th to 20thNight
61%
760
29%
2962
31%
759
67%
759
27%
1762
December21st to endNight
59%
824
19%
4441
29%
817
66%
817
20%
2552

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%413323346%64%
75220
Night
6%5%24323447%61%
74549
TransparencyDay
21%48%17%25%24%
74949
Night
24%5%9%15%21%25%
74342
SeeingDay
6%5%19%36%24%9%
14626
Night
6%29%32%39%11%
24652

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
10%5%2342425%7%55%
1708
11th to 20thDay
9%42242445%5%59%
1761
21st to endDay
11%6%24422345%58%
1980
February1st to 10thDay
10%424323245%61%
1800
11th to 20thDay
9%42431335%7%59%
1750
21st to endDay
11%7%2442335%6%54%
1480
March1st to 10thDay
10%6%335%35%5%6%8%48%
1800
11th to 20thDay
8%42442346%9%54%
1852
21st to endDay
5%4244335%5%7%57%
2349
April1st to 10thDay
7%5%2442445%8%56%
2160
11th to 20thDay
45%24323346%64%
2129
21st to endDay
6%31331335%7%65%
2160
May1st to 10thDay
7%5%2432335%8%58%
2240
11th to 20thDay
342332345%8%63%
2301
21st to endDay
6%6%1332335%9%57%
2530
June1st to 10thDay
442332235%8%64%
2340
11th to 20thDay
2313223346%72%
2367
21st to endDay
1222222235%77%
2520
July1st to 10thDay
1212213346%75%
2520
11th to 20thDay
1212212446%74%
2345
21st to endDay
221231345%7%69%
2404
August1st to 10thDay
1112112336%78%
2149
11th to 20thDay
1111112335%81%
2122
21st to endDay
121121234478%
2376
September1st to 10thDay
3112212345%78%
2160
11th to 20thDay
211211233480%
1998
21st to endDay
1212212345%77%
1980
October1st to 10thDay
5%32232245%467%
1980
11th to 20thDay
6%313222435%71%
1922
21st to endDay
4312223345%71%
1918
November1st to 10thDay
5%313322346%69%
1674
11th to 20thDay
4223323446%67%
1710
21st to endDay
6%42442345%8%58%
1710
December1st to 10thDay
8%5%2432345%7%56%
1710
11th to 20thDay
13%7%35%5%245%5%8%43%
2169
21st to endDay
11%7%36%6%45%45%6%42%
3146
January1st to 10thNight
10%42433345%7%54%
2457
11th to 20thNight
8%5%2432345%7%58%
2257
21st to endNight
11%5%23322346%59%
2376
February1st to 10thNight
8%424323336%62%
2160
11th to 20thNight
10%5%13323335%60%
2098
21st to endNight
12%7%24433445%52%
1776
March1st to 10thNight
9%7%25%4345%6%8%47%
2160
11th to 20thNight
9%7%2342345%7%53%
2106
21st to endNight
7%6%24434446%55%
2003
April1st to 10thNight
8%6%4432345%8%53%
1800
11th to 20thNight
5%6%245%33345%61%
1779
21st to endNight
5%5%244235%5%7%60%
1800
May1st to 10thNight
46%36%4235%5%8%55%
1716
11th to 20thNight
36%244345%5%10%53%
1594
21st to endNight
48%3432445%8%57%
1746
June1st to 10thNight
26%34435%36%8%56%
1620
11th to 20thNight
131332336%8%66%
1583
21st to endNight
221221245%9%70%
1440
July1st to 10thNight
121332346%7%69%
1440
11th to 20thNight
121222347%7%69%
1606
21st to endNight
321332346%8%65%
1910
August1st to 10thNight
3212123446%74%
1790
11th to 20thNight
1211212348%76%
1780
21st to endNight
112222346%76%
1980
September1st to 10thNight
2313222336%72%
1800
11th to 20thNight
231221242478%
1962
21st to endNight
231221123478%
1980
October1st to 10thNight
4313423346%68%
1980
11th to 20thNight
431331233471%
2035
21st to endNight
4413323345%69%
2438
November1st to 10thNight
4413322347%68%
2405
11th to 20thNight
4423323336%68%
2470
21st to endNight
7%425%42445%7%56%
2470
December1st to 10thNight
8%5%245%2335%8%56%
2470
11th to 20thNight
13%8%345%33447%45%
3041
21st to endNight
10%9%36%6%45%45%6%42%
4521

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
29%47%20%21%19%
1709
11th to 20thDay
26%46%14%24%26%
1761
21st to endDay
30%38%16%17%27%
1980
February1st to 10thDay
27%35%12%26%27%
1800
11th to 20thDay
24%27%17%27%22%
1760
21st to endDay
31%38%16%25%17%
1480
March1st to 10thDay
31%49%19%17%20%
1800
11th to 20thDay
25%411%20%24%15%
1852
21st to endDay
23%6%12%25%21%14%
2349
April1st to 10thDay
27%411%26%21%10%
2160
11th to 20thDay
22%48%21%27%19%
2132
21st to endDay
19%410%26%29%12%
2160
May1st to 10thDay
25%411%19%26%14%
2240
11th to 20thDay
21%7%8%23%29%12%
2304
21st to endDay
25%6%11%26%25%7%
2530
June1st to 10thDay
21%5%10%21%28%15%
2340
11th to 20thDay
16%36%13%31%30%
2367
21st to endDay
13%36%10%25%43%
2520
July1st to 10thDay
11%39%10%24%42%
2451
11th to 20thDay
12%410%19%29%26%
2275
21st to endDay
14%410%25%30%17%
2270
August1st to 10thDay
10%35%15%32%36%
2135
11th to 20thDay
8%36%17%32%35%
2122
21st to endDay
10%35%13%34%34%
2376
September1st to 10thDay
10%37%9%34%37%
2160
11th to 20thDay
10%36%10%35%37%
1998
21st to endDay
11%36%15%34%32%
1980
October1st to 10thDay
18%45%20%22%31%
1980
11th to 20thDay
17%46%15%26%33%
1922
21st to endDay
17%36%12%23%39%
1918
November1st to 10thDay
18%37%17%24%31%
1674
11th to 20thDay
18%47%16%18%36%
1710
21st to endDay
23%48%13%23%28%
1710
December1st to 10thDay
26%49%18%19%25%
1710
11th to 20thDay
39%5%9%14%19%15%
2168
21st to endDay
40%6%10%20%13%11%
3146
January1st to 10thNight
28%48%14%24%22%
2457
11th to 20thNight
26%38%13%21%29%
2257
21st to endNight
29%38%15%14%31%
2376
February1st to 10thNight
25%36%14%21%30%
2160
11th to 20thNight
28%37%14%21%27%
2099
21st to endNight
33%45%13%20%23%
1776
March1st to 10thNight
33%6%7%19%16%19%
2160
11th to 20thNight
30%410%17%21%18%
2106
21st to endNight
28%5%11%20%22%14%
2003
April1st to 10thNight
31%6%10%22%18%13%
1800
11th to 20thNight
25%7%8%18%23%19%
1779
21st to endNight
25%6%12%20%22%14%
1800
May1st to 10thNight
28%7%13%17%19%16%
1716
11th to 20thNight
30%9%10%19%21%12%
1595
21st to endNight
27%8%11%23%20%10%
1746
June1st to 10thNight
27%10%17%13%21%14%
1620
11th to 20thNight
19%8%12%13%24%25%
1583
21st to endNight
15%7%13%11%20%35%
1440
July1st to 10thNight
13%5%15%13%19%35%
1400
11th to 20thNight
13%7%12%20%24%24%
1553
21st to endNight
17%7%12%22%27%15%
1804
August1st to 10thNight
14%5%10%14%29%30%
1780
11th to 20thNight
10%411%13%29%32%
1780
21st to endNight
11%5%9%13%28%34%
1980
September1st to 10thNight
16%48%9%27%36%
1800
11th to 20thNight
13%47%9%28%39%
1962
21st to endNight
14%36%11%33%33%
1980
October1st to 10thNight
18%48%18%23%29%
1980
11th to 20thNight
19%37%13%26%32%
2035
21st to endNight
19%35%10%21%41%
2438
November1st to 10thNight
19%37%15%20%36%
2405
11th to 20thNight
20%36%14%18%40%
2470
21st to endNight
27%47%16%17%30%
2470
December1st to 10thNight
27%49%14%18%27%
2470
11th to 20thNight
37%5%8%13%20%16%
3041
21st to endNight
38%7%12%18%14%13%
4521

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
15%6%17%37%21%4
270
11th to 20thDay
12%7%22%38%17%4
367
21st to endDay
12%9%27%31%17%3
462
February1st to 10thDay
13%7%23%31%20%6%
420
11th to 20thDay
10%9%29%33%16%2
415
21st to endDay
13%13%28%33%12%1
346
March1st to 10thDay
14%12%32%29%10%3
420
11th to 20thDay
12%8%30%30%16%4
420
21st to endDay
8%13%31%35%11%2
462
April1st to 10thDay
8%8%31%29%20%5%
420
11th to 20thDay
5%11%33%34%12%4
412
21st to endDay
410%29%34%15%8%
420
May1st to 10thDay
10%7%30%33%14%6%
423
11th to 20thDay
6%5%25%38%20%5%
448
21st to endDay
7%8%25%38%17%5%
485
June1st to 10thDay
3418%38%28%8%
450
11th to 20thDay
3219%39%25%12%
450
21st to endDay
2113%40%31%12%
450
July1st to 10thDay
26%38%39%14%
446
11th to 20thDay
1434%39%21%
444
21st to endDay
1339%38%18%
487
August1st to 10thDay
117%41%37%13%
447
11th to 20thDay
115%42%33%18%
437
21st to endDay
115%39%38%17%
495
September1st to 10thDay
2210%47%26%13%
450
11th to 20thDay
2114%46%27%9%
450
21st to endDay
2318%38%27%12%
450
October1st to 10thDay
4420%38%27%7%
450
11th to 20thDay
45%20%39%25%8%
450
21st to endDay
4418%34%29%10%
433
November1st to 10thDay
5%416%35%32%8%
270
11th to 20thDay
4414%40%27%10%
270
21st to endDay
6%7%19%36%22%10%
270
December1st to 10thDay
12%415%33%31%4
270
11th to 20thDay
8%421%32%28%8%
270
21st to endDay
15%10%23%32%16%4
297
January1st to 10thNight
11%215%38%25%9%
760
11th to 20thNight
9%312%39%29%8%
732
21st to endNight
13%314%39%26%5%
792
February1st to 10thNight
10%112%38%30%9%
720
11th to 20thNight
10%314%38%26%8%
704
21st to endNight
15%313%40%23%6%
592
March1st to 10thNight
9%414%44%24%5%
720
11th to 20thNight
10%312%37%30%9%
720
21st to endNight
7%313%40%32%5%
792
April1st to 10thNight
10%29%42%32%5%
720
11th to 20thNight
6%414%38%32%6%
711
21st to endNight
6%39%38%35%8%
720
May1st to 10thNight
7%213%35%39%5%
636
11th to 20thNight
4211%33%41%8%
531
21st to endNight
5%214%36%37%5%
584
June1st to 10thNight
3212%39%38%6%
540
11th to 20thNight
217%33%52%6%
503
21st to endNight
31421%61%12%
360
July1st to 10thNight
15%13%63%18%
350
11th to 20thNight
1117%61%20%
509
21st to endNight
31212%61%22%
728
August1st to 10thNight
21318%58%19%
716
11th to 20thNight
1112%62%25%
712
21st to endNight
1114%63%21%
792
September1st to 10thNight
315%17%55%20%
720
11th to 20thNight
21322%56%15%
720
21st to endNight
315%28%48%16%
720
October1st to 10thNight
315%39%43%8%
720
11th to 20thNight
5%16%34%40%13%
720
21st to endNight
439%31%37%16%
792
November1st to 10thNight
428%35%36%14%
740
11th to 20thNight
5%17%39%35%13%
760
21st to endNight
6%311%39%32%9%
760
December1st to 10thNight
10%310%41%29%8%
760
11th to 20thNight
13%314%39%26%6%
760
21st to endNight
11%5%16%35%25%8%
836
Page generated at 2024-01-10 16:35:21. Version ac07

Copyright 2024 Attilla Danko


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