Moonridge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Moonridge Observatory clear sky chart from 2005-11-06 to 2024-01-14.

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
36%
23446
20%
74714
11%
23401
47%
23401
24%
46802

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
17%
757
22%
2569
6%
757
37%
757
20%
1576
January11th to 20thNight
25%
736
22%
2391
9%
736
40%
736
18%
1561
January21st to endNight
18%
792
23%
2574
7%
792
38%
792
20%
1588
February1st to 10thNight
23%
720
18%
2340
7%
720
37%
720
19%
1502
February11th to 20thNight
14%
700
18%
2261
4%
700
32%
700
16%
1454
February21st to endNight
15%
592
23%
1772
6%
592
34%
592
18%
1178
March1st to 10thNight
22%
720
24%
1980
8%
720
38%
720
26%
1229
March11th to 20thNight
24%
720
21%
1980
9%
720
37%
720
21%
1306
March21st to endNight
20%
792
19%
2170
6%
792
32%
792
22%
1454
April1st to 10thNight
23%
720
17%
1800
3%
720
32%
720
23%
1237
April11th to 20thNight
32%
711
19%
1775
6%
711
38%
711
29%
1177
April21st to endNight
32%
720
19%
1800
6%
720
39%
720
28%
1204
May1st to 10thNight
39%
545
17%
1625
9%
545
46%
545
24%
1086
May11th to 20thNight
43%
456
16%
1517
10%
456
48%
456
21%
1002
May21st to endNight
49%
388
15%
1551
15%
388
55%
388
21%
932
June1st to 10thNight
53%
360
20%
1440
21%
360
60%
360
25%
827
June11th to 20thNight
56%
360
16%
1440
18%
360
62%
360
22%
864
June21st to endNight
56%
360
18%
1440
19%
360
63%
360
27%
798
July1st to 10thNight
59%
350
15%
1400
17%
350
63%
350
20%
862
July11th to 20thNight
69%
458
16%
1502
13%
458
71%
458
30%
895
July21st to endNight
67%
591
16%
1672
12%
558
72%
558
32%
1023
August1st to 10thNight
65%
537
16%
1600
13%
534
66%
534
27%
1048
August11th to 20thNight
60%
572
18%
1636
12%
572
62%
572
27%
1094
August21st to endNight
60%
792
19%
1980
12%
792
62%
792
32%
1335
September1st to 10thNight
54%
720
21%
1800
11%
720
58%
720
32%
1205
September11th to 20thNight
57%
720
30%
1805
21%
720
61%
720
38%
1127
September21st to endNight
45%
720
20%
2076
14%
720
52%
720
25%
1378
October1st to 10thNight
46%
720
20%
2160
17%
720
54%
720
28%
1374
October11th to 20thNight
40%
720
26%
2160
18%
720
53%
720
30%
1282
October21st to endNight
34%
792
27%
2376
15%
792
50%
792
30%
1422
November1st to 10thNight
38%
740
28%
2282
17%
740
52%
740
33%
1307
November11th to 20thNight
31%
760
25%
2536
13%
760
48%
760
25%
1457
November21st to endNight
31%
760
22%
2660
12%
760
46%
760
23%
1541
December1st to 10thNight
23%
760
20%
2660
7%
760
39%
760
17%
1681
December11th to 20thNight
24%
760
20%
3170
9%
759
40%
759
18%
1903
December21st to endNight
27%
825
14%
4814
10%
817
42%
817
12%
2893

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
14%6%25%5%35%5%6%8%41%
74671
Night
14%6%25%5%35%5%5%8%43%
75096
TransparencyDay
39%7%13%23%16%3
74383
Night
39%6%13%23%16%3
74903
SeeingDay
19%14%26%23%14%5%
13795
Night
18%11%29%29%12%1
23464

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 10thDay
14%7%25%5%36%45%7%42%
1595
11th to 20thDay
15%7%35%5%345%5%7%40%
1647
21st to endDay
15%8%36%5%35%45%6%40%
1782
February1st to 10thDay
13%9%36%5%46%5%6%6%37%
1620
11th to 20thDay
17%7%37%6%2345%7%39%
1587
21st to endDay
18%8%346%25%45%6%39%
1480
March1st to 10thDay
12%6%25%43435%7%47%
1980
11th to 20thDay
16%6%35%5%445%5%7%40%
1980
21st to endDay
18%6%37%5%35%5%5%7%37%
2185
April1st to 10thDay
12%6%35%6%35%5%5%9%40%
2160
11th to 20thDay
13%5%35%435%45%8%45%
2134
21st to endDay
18%6%35%5%345%5%6%40%
2170
May1st to 10thDay
16%7%25%5%35%5%6%8%37%
2340
11th to 20thDay
20%6%35%5%35%5%5%8%36%
2375
21st to endDay
15%6%25%5%345%6%8%41%
2725
June1st to 10thDay
12%4245%35%5%7%9%43%
2520
11th to 20thDay
11%5%26%5%36%6%7%9%39%
2520
21st to endDay
10%315%5%45%6%7%11%44%
2520
July1st to 10thDay
9%5%25%6%46%5%7%9%41%
2520
11th to 20thDay
6%325%6%47%7%7%10%43%
2404
21st to endDay
10%5%35%7%46%6%6%10%38%
2547
August1st to 10thDay
9%6%26%5%46%7%7%10%38%
2327
11th to 20thDay
12%6%26%7%35%5%6%9%40%
2245
21st to endDay
10%5%26%5%46%6%7%9%42%
2376
September1st to 10thDay
16%5%25%5%245%5%6%44%
2160
11th to 20thDay
13%5%25%43446%7%48%
2152
21st to endDay
19%5%35%5%35%45%7%39%
1883
October1st to 10thDay
16%5%35%434448%46%
1800
11th to 20thDay
17%4344335%5%5%47%
1800
21st to endDay
15%5%24434446%49%
1980
November1st to 10thDay
11%7%2442345%7%51%
1796
11th to 20thDay
16%5%2432445%6%48%
1639
21st to endDay
15%5%34336%5%47%45%
1520
December1st to 10thDay
16%8%35%5%35%5%5%7%37%
1520
11th to 20thDay
16%425%5%3446%7%42%
1910
21st to endDay
17%6%25%6%36%6%6%8%33%
2772
January1st to 10thNight
14%7%35%4345%5%7%43%
2569
11th to 20thNight
18%5%26%6%345%5%8%38%
2391
21st to endNight
15%7%35%425%45%7%43%
2574
February1st to 10thNight
14%7%36%5%35%46%8%39%
2340
11th to 20thNight
16%7%35%435%5%5%5%41%
2259
21st to endNight
18%8%25%5%345%5%6%39%
1772
March1st to 10thNight
13%5%25%5%25%447%47%
1980
11th to 20thNight
19%6%2442445%6%44%
1980
21st to endNight
16%6%45%6%3445%6%41%
2170
April1st to 10thNight
14%7%36%6%445%6%6%39%
1800
11th to 20thNight
13%436%5%3445%9%44%
1775
21st to endNight
17%5%24425%45%8%43%
1800
May1st to 10thNight
16%7%26%5%35%46%8%39%
1625
11th to 20thNight
18%6%35%435%5%6%8%37%
1517
21st to endNight
13%6%26%5%35%5%6%10%41%
1550
June1st to 10thNight
11%425%436%5%7%9%45%
1440
11th to 20thNight
12%5%25%5%346%7%10%40%
1440
21st to endNight
9%4245%36%47%12%43%
1440
July1st to 10thNight
9%5%26%5%5%6%7%7%10%38%
1440
11th to 20thNight
6%5%25%5%45%6%8%9%46%
1552
21st to endNight
7%5%23437%7%7%11%42%
1771
August1st to 10thNight
8%5%26%6%5%6%6%7%9%40%
1611
11th to 20thNight
9%7%36%6%45%5%6%8%41%
1636
21st to endNight
11%5%25%5%36%6%7%8%43%
1980
September1st to 10thNight
16%5%25%4345%6%8%43%
1800
11th to 20thNight
11%436%433436%53%
1805
21st to endNight
18%6%26%5%3435%6%42%
2076
October1st to 10thNight
19%424424446%46%
2160
11th to 20thNight
15%5%24433446%51%
2160
21st to endNight
16%5%2442335%6%50%
2376
November1st to 10thNight
11%5%25%323446%54%
2282
11th to 20thNight
14%6%344235%5%7%48%
2536
21st to endNight
14%425%5%345%5%8%46%
2660
December1st to 10thNight
16%7%36%5%345%5%6%40%
2660
11th to 20thNight
17%6%25%5%3446%7%41%
3285
21st to endNight
16%6%25%5%36%7%7%9%34%
4884

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
42%6%11%23%15%3
1596
11th to 20thDay
44%5%13%24%13%2
1647
21st to endDay
44%5%12%22%14%3
1782
February1st to 10thDay
45%6%14%22%11%2
1620
11th to 20thDay
45%5%10%24%14%2
1596
21st to endDay
46%5%11%19%14%4
1480
March1st to 10thDay
37%5%13%24%19%2
1980
11th to 20thDay
43%5%11%18%17%5%
1980
21st to endDay
46%6%11%18%16%3
2185
April1st to 10thDay
39%7%13%18%18%4
2160
11th to 20thDay
37%6%11%21%19%6%
2134
21st to endDay
43%7%9%22%16%4
2170
May1st to 10thDay
43%7%13%20%15%2
2340
11th to 20thDay
46%8%12%19%13%3
2379
21st to endDay
40%8%15%25%12%1
2725
June1st to 10thDay
35%9%15%25%16%1
2520
11th to 20thDay
38%10%16%21%14%2
2520
21st to endDay
32%9%16%26%15%1
2520
July1st to 10thDay
38%9%12%22%16%2
2450
11th to 20thDay
31%10%14%26%16%3
2331
21st to endDay
38%10%14%20%16%2
2405
August1st to 10thDay
39%10%16%23%11%1
2314
11th to 20thDay
39%9%14%22%15%2
2245
21st to endDay
36%9%16%24%13%3
2376
September1st to 10thDay
39%7%12%19%19%4
2160
11th to 20thDay
34%6%10%26%21%3
2152
21st to endDay
44%6%11%19%19%2
1883
October1st to 10thDay
38%6%11%25%17%3
1800
11th to 20thDay
38%5%11%24%20%3
1800
21st to endDay
36%410%27%20%3
1980
November1st to 10thDay
33%413%26%20%5%
1796
11th to 20thDay
36%412%23%21%4
1639
21st to endDay
38%5%12%28%15%2
1520
December1st to 10thDay
45%6%13%23%11%2
1520
11th to 20thDay
39%6%12%30%10%3
1906
21st to endDay
44%7%17%23%9%1
2772
January1st to 10thNight
39%5%10%24%17%4
2569
11th to 20thNight
44%5%13%23%13%1
2391
21st to endNight
41%411%27%15%2
2574
February1st to 10thNight
43%5%14%23%13%2
2340
11th to 20thNight
43%5%10%22%15%4
2261
21st to endNight
45%411%21%13%5%
1772
March1st to 10thNight
36%412%28%17%3
1980
11th to 20thNight
40%6%10%21%19%3
1980
21st to endNight
43%5%12%20%15%5%
2170
April1st to 10thNight
42%7%11%20%17%4
1800
11th to 20thNight
37%7%12%20%18%6%
1775
21st to endNight
39%6%13%25%13%4
1800
May1st to 10thNight
42%7%11%22%12%4
1625
11th to 20thNight
44%8%13%18%16%2
1518
21st to endNight
37%9%17%23%12%1
1551
June1st to 10thNight
34%9%12%26%18%2
1440
11th to 20thNight
37%9%15%22%14%2
1440
21st to endNight
33%7%16%24%18%2
1440
July1st to 10thNight
38%11%16%19%12%4
1400
11th to 20thNight
32%10%17%22%17%2
1502
21st to endNight
29%12%19%23%15%2
1672
August1st to 10thNight
37%10%16%21%14%1
1600
11th to 20thNight
39%9%15%21%15%2
1636
21st to endNight
37%9%14%23%15%3
1980
September1st to 10thNight
38%8%13%20%18%4
1800
11th to 20thNight
33%5%10%26%23%3
1805
21st to endNight
43%5%11%20%18%3
2076
October1st to 10thNight
40%5%11%24%18%3
2160
11th to 20thNight
35%410%27%22%2
2160
21st to endNight
35%5%10%25%22%2
2376
November1st to 10thNight
32%5%10%27%22%5%
2282
11th to 20thNight
35%5%9%25%22%5%
2536
21st to endNight
35%5%13%25%18%3
2660
December1st to 10thNight
44%5%12%25%13%1
2660
11th to 20thNight
41%5%11%24%17%3
3288
21st to endNight
41%9%18%19%12%1
4884

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
27%29%28%13%3
218
11th to 20thDay
27%27%31%12%3
249
21st to endDay
27%31%30%8%31
264
February1st to 10thDay
24%30%33%9%4
240
11th to 20thDay
33%29%31%6%1
254
21st to endDay
31%19%33%15%2
346
March1st to 10thDay
23%25%28%22%3
420
11th to 20thDay
25%22%30%17%42
420
21st to endDay
21%22%33%18%5%1
462
April1st to 10thDay
21%25%25%20%7%1
420
11th to 20thDay
17%16%29%20%14%3
412
21st to endDay
27%17%27%19%8%2
420
May1st to 10thDay
24%18%26%19%9%3
423
11th to 20thDay
20%15%26%22%15%3
447
21st to endDay
19%8%22%23%21%6%
485
June1st to 10thDay
14%8%27%26%18%6%
450
11th to 20thDay
14%9%29%27%16%5%
450
21st to endDay
10%6%28%32%18%6%
450
July1st to 10thDay
12%5%17%26%27%13%
445
11th to 20thDay
5%319%32%33%8%
444
21st to endDay
12%420%32%23%8%
488
August1st to 10thDay
12%420%25%25%13%
446
11th to 20thDay
13%419%29%23%12%
439
21st to endDay
9%420%31%21%15%
495
September1st to 10thDay
20%6%19%22%22%11%
450
11th to 20thDay
14%420%31%19%11%
450
21st to endDay
22%10%24%26%14%4
450
October1st to 10thDay
18%7%20%28%20%6%
450
11th to 20thDay
18%13%26%29%12%3
450
21st to endDay
17%14%34%24%9%3
495
November1st to 10thDay
18%12%30%26%11%4
426
11th to 20thDay
22%15%31%21%10%1
299
21st to endDay
22%21%30%21%6%1
180
December1st to 10thDay
21%24%36%15%31
180
11th to 20thDay
23%25%26%21%6%
180
21st to endDay
22%21%32%18%7%1
198
January1st to 10thNight
19%20%40%18%3
760
11th to 20thNight
24%15%31%26%4
736
21st to endNight
19%18%41%21%2
792
February1st to 10thNight
18%19%36%25%2
720
11th to 20thNight
23%22%36%17%2
703
21st to endNight
25%19%37%16%3
592
March1st to 10thNight
20%17%38%22%3
720
11th to 20thNight
24%19%30%21%5%1
720
21st to endNight
20%16%38%21%41
792
April1st to 10thNight
19%19%35%23%4
720
11th to 20thNight
16%12%35%29%8%
711
21st to endNight
20%12%32%29%7%
720
May1st to 10thNight
21%8%27%33%11%
545
11th to 20thNight
20%7%24%38%10%1
456
21st to endNight
15%422%40%17%1
389
June1st to 10thNight
11%325%38%23%1
360
11th to 20thNight
13%5%20%40%20%1
360
21st to endNight
8%423%46%19%1
360
July1st to 10thNight
11%317%39%27%3
350
11th to 20thNight
8%112%41%35%3
458
21st to endNight
8%217%42%28%3
591
August1st to 10thNight
9%212%45%28%4
537
11th to 20thNight
10%413%38%31%3
572
21st to endNight
14%316%38%26%4
792
September1st to 10thNight
17%219%33%26%3
720
11th to 20thNight
13%319%35%27%3
720
21st to endNight
20%5%21%31%22%1
720
October1st to 10thNight
21%6%21%29%20%3
720
11th to 20thNight
16%12%27%32%13%1
720
21st to endNight
19%10%33%28%10%
792
November1st to 10thNight
14%9%34%32%11%1
740
11th to 20thNight
18%15%32%27%7%1
760
21st to endNight
16%16%32%29%7%
760
December1st to 10thNight
22%16%34%22%7%
760
11th to 20thNight
19%11%40%25%4
760
21st to endNight
20%13%35%30%2
836
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