MAC-Hunter Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the MAC-Hunter Observatory clear sky chart from 2005-11-05 to 2017-04-30.

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
50%
15423
22%
45595
15%
15384
57%
15384
29%
28544

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
34%
718
22%
2327
12%
716
48%
716
26%
1405
January16th to endNight
32%
768
25%
2496
14%
768
46%
768
26%
1526
February1st to 15thNight
35%
702
22%
2260
11%
701
49%
701
26%
1373
February16th to endNight
32%
631
27%
1830
13%
631
46%
631
30%
1120
March1st to 15thNight
37%
720
25%
1980
14%
720
47%
720
31%
1242
March16th to endNight
42%
768
21%
2112
11%
768
50%
768
32%
1323
April1st to 15thNight
41%
718
24%
1902
12%
718
49%
718
36%
1176
April16th to endNight
47%
690
24%
1765
12%
690
53%
690
37%
1106
May1st to 15thNight
50%
495
20%
1485
11%
495
56%
495
27%
927
May16th to endNight
63%
513
18%
1538
14%
513
65%
513
28%
973
June1st to 15thNight
64%
495
16%
1485
15%
495
65%
495
26%
1002
June16th to endNight
73%
495
15%
1485
14%
495
73%
495
29%
960
July1st to 15thNight
69%
465
11%
1395
10%
465
69%
465
23%
964
July16th to endNight
73%
522
12%
1469
10%
489
74%
489
27%
966
August1st to 15thNight
72%
494
17%
1474
15%
491
73%
491
26%
985
August16th to endNight
66%
640
15%
1690
12%
640
66%
640
26%
1190
September1st to 15thNight
70%
660
21%
1768
18%
660
71%
660
30%
1158
September16th to endNight
50%
657
15%
1815
12%
657
53%
657
21%
1297
October1st to 15thNight
53%
660
29%
1954
26%
660
60%
660
33%
1167
October16th to endNight
54%
704
33%
2112
26%
704
65%
704
37%
1170
November1st to 15thNight
53%
700
31%
2101
23%
700
64%
700
38%
1165
November16th to endNight
47%
720
27%
2316
21%
720
58%
720
31%
1340
December1st to 15thNight
43%
720
24%
2340
16%
720
53%
720
26%
1422
December16th to endNight
39%
768
24%
2496
18%
768
47%
768
24%
1587

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
12%5%2442445%7%43%
46121
Night
12%5%2442445%7%45%
45796
TransparencyDay
37%6%12%19%18%4
45822
Night
37%6%11%19%19%6%
45599
SeeingDay
14%419%23%24%14%
5152
Night
14%422%33%21%2
15429

By Month

Percentage Cloud Cover SE (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
15%6%36%42344444%
1611
16th to endDay
14%6%23423345%47%
1728
February1st to 15thDay
17%6%14323345%46%
1599
16th to endDay
16%5%15%313335%48%
1642
March1st to 15thDay
14%424313345%50%
1980
16th to endDay
14%5%25%5%2445%6%44%
2111
April1st to 15thDay
10%323314449%50%
2044
16th to endDay
11%5%24424447%47%
2183
May1st to 15thDay
10%5%25%6%35%45%7%41%
2136
16th to endDay
9%5%25%5%35%5%7%8%40%
2223
June1st to 15thDay
10%425%5%35%5%8%11%38%
2145
16th to endDay
6%325%5%35%6%8%12%41%
2145
July1st to 15thDay
8%427%7%36%7%8%10%33%
2145
16th to endDay
6%425%6%48%7%9%11%34%
2283
August1st to 15thDay
12%4246%36%6%9%9%33%
2145
16th to endDay
12%5%25%5%35%6%7%11%32%
2146
September1st to 15thDay
8%4245%35%6%6%9%42%
1859
16th to endDay
18%6%25%5%2435%6%37%
1815
October1st to 15thDay
16%5%13423335%50%
1675
16th to endDay
11%41332223459%
1760
November1st to 15thDay
13%413322235%56%
1757
16th to endDay
13%5%1432335%6%50%
1641
December1st to 15thDay
15%7%25%5%23345%42%
1620
16th to endDay
20%6%24324435%42%
1728
January1st to 15thNight
14%434423445%48%
2327
16th to endNight
17%5%24423345%46%
2496
February1st to 15thNight
17%31332445%5%47%
2253
16th to endNight
13%4245%24346%49%
1830
March1st to 15thNight
12%423425%446%48%
1980
16th to endNight
14%325%42435%7%46%
2112
April1st to 15thNight
10%5%23423445%51%
1902
16th to endNight
11%41432445%7%50%
1765
May1st to 15thNight
9%5%345%35%5%7%7%43%
1484
16th to endNight
9%424445%5%5%9%43%
1538
June1st to 15thNight
11%4345%37%7%6%8%36%
1485
16th to endNight
5%325%5%36%7%8%12%40%
1485
July1st to 15thNight
7%5%25%7%47%7%7%11%32%
1485
16th to endNight
6%325%6%38%6%9%12%35%
1577
August1st to 15thNight
10%4245%35%5%9%11%36%
1485
16th to endNight
10%6%26%6%35%5%7%11%32%
1690
September1st to 15thNight
8%5%25%5%35%6%6%9%41%
1768
16th to endNight
16%7%36%6%34435%37%
1815
October1st to 15thNight
16%5%23222236%51%
1954
16th to endNight
10%5%2322233458%
2112
November1st to 15thNight
11%423213235%58%
2101
16th to endNight
13%42431345%5%51%
2316
December1st to 15thNight
16%5%24423346%46%
2340
16th to endNight
18%7%24423446%41%
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
42%5%8%15%22%6%
1612
16th to endDay
38%46%17%23%9%
1728
February1st to 15thDay
40%27%19%24%4
1601
16th to endDay
38%37%21%22%6%
1642
March1st to 15thDay
36%48%21%22%7%
1980
16th to endDay
40%5%9%21%18%4
2112
April1st to 15thDay
30%5%11%22%23%6%
2044
16th to endDay
35%5%10%19%21%7%
2183
May1st to 15thDay
39%7%15%19%15%1
2136
16th to endDay
37%9%13%23%14%1
2227
June1st to 15thDay
35%10%18%25%9%1
2145
16th to endDay
31%10%19%23%13%2
2145
July1st to 15thDay
39%12%17%18%9%3
2006
16th to endDay
35%13%22%18%8%1
2128
August1st to 15thDay
41%10%17%17%12%
2132
16th to endDay
41%11%16%18%10%1
2146
September1st to 15thDay
36%8%14%19%16%3
1859
16th to endDay
46%6%8%16%16%4
1815
October1st to 15thDay
35%48%20%24%5%
1675
16th to endDay
30%36%20%28%11%
1760
November1st to 15thDay
31%36%18%28%11%
1757
16th to endDay
35%47%17%24%9%
1641
December1st to 15thDay
43%48%18%18%5%
1620
16th to endDay
44%39%18%17%6%
1728
January1st to 15thNight
38%410%14%24%7%
2327
16th to endNight
40%36%18%21%9%
2496
February1st to 15thNight
38%47%17%23%8%
2262
16th to endNight
36%49%21%21%7%
1830
March1st to 15thNight
36%5%9%18%21%8%
1980
16th to endNight
36%5%12%20%20%5%
2112
April1st to 15thNight
33%48%22%23%7%
1902
16th to endNight
32%6%11%20%20%8%
1765
May1st to 15thNight
37%7%14%20%18%2
1485
16th to endNight
36%8%13%26%12%2
1540
June1st to 15thNight
39%9%15%23%9%1
1485
16th to endNight
32%13%18%22%11%2
1485
July1st to 15thNight
41%12%17%16%9%3
1395
16th to endNight
34%12%23%16%11%1
1469
August1st to 15thNight
37%11%18%22%8%2
1474
16th to endNight
41%10%20%18%8%
1690
September1st to 15thNight
36%9%16%18%13%6%
1768
16th to endNight
49%6%10%14%15%3
1815
October1st to 15thNight
35%310%18%24%7%
1954
16th to endNight
29%36%19%26%13%
2112
November1st to 15thNight
30%26%16%29%14%
2101
16th to endNight
34%46%17%25%11%
2316
December1st to 15thNight
38%49%19%18%7%
2340
16th to endNight
43%49%17%17%7%
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
20%13%27%30%8%
90
16th to endDay
17%14%43%14%9%
96
February1st to 15thDay
20%12%44%21%2
90
16th to endDay
16%11%38%25%6%
143
March1st to 15thDay
12%8%35%33%9%
270
16th to endDay
14%8%31%27%15%1
288
April1st to 15thDay
12%10%29%20%21%5%
270
16th to endDay
13%319%28%24%10%
266
May1st to 15thDay
12%328%27%18%10%
228
16th to endDay
14%110%17%28%27%
267
June1st to 15thDay
13%10%25%25%24%
255
16th to endDay
8%9%21%30%29%
255
July1st to 15thDay
7%7%29%30%23%
245
16th to endDay
7%315%43%29%
270
August1st to 15thDay
15%5%17%35%24%
253
16th to endDay
13%17%14%30%33%
268
September1st to 15thDay
10%6%22%32%27%
255
16th to endDay
25%214%22%21%13%
254
October1st to 15thDay
23%215%27%23%7%
255
16th to endDay
10%420%24%28%11%
272
November1st to 15thDay
18%322%27%20%6%
265
16th to endDay
9%5%22%30%27%4
111
December1st to 15thDay
21%6%37%20%12%2
90
16th to endDay
28%8%34%14%14%
96
January1st to 15thNight
17%8%33%30%10%
720
16th to endNight
20%7%35%32%3
768
February1st to 15thNight
19%9%33%32%4
704
16th to endNight
14%8%38%31%5%
631
March1st to 15thNight
15%7%35%32%8%
720
16th to endNight
16%5%30%36%10%
768
April1st to 15thNight
12%8%34%31%12%
718
16th to endNight
12%5%28%35%17%
690
May1st to 15thNight
12%5%23%40%16%1
495
16th to endNight
11%113%33%36%3
515
June1st to 15thNight
11%210%39%31%5%
495
16th to endNight
5%19%37%34%10%
495
July1st to 15thNight
10%16%35%40%5%
465
16th to endNight
6%6%31%47%7%
522
August1st to 15thNight
13%425%49%7%
494
16th to endNight
13%15%28%45%6%
640
September1st to 15thNight
9%16%30%45%7%
660
16th to endNight
21%114%29%29%2
657
October1st to 15thNight
20%218%28%27%2
660
16th to endNight
12%6%22%32%25%2
704
November1st to 15thNight
14%423%36%18%3
700
16th to endNight
15%6%26%31%17%1
720
December1st to 15thNight
18%5%26%35%12%1
720
16th to endNight
21%6%27%34%8%
768
Page generated at 2017-04-30 20:40:05. Version ac04

Copyright 2017 A. Danko


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