Mahoning Valley Cortese Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mahoning Valley Cortese Observatory clear sky chart from 2005-11-06 to 2024-01-31.

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
32%
23392
14%
75123
9%
23338
38%
23338
17%
53560

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
10%
758
10%
2459
2%
757
18%
757
8%
1987
January11th to 20thNight
13%
760
7%
2470
4%
760
17%
760
7%
2031
January21st to endNight
14%
835
8%
2711
4%
835
20%
835
8%
2246
February1st to 10thNight
13%
720
8%
2340
3%
720
19%
720
8%
1890
February11th to 20thNight
13%
702
9%
2256
4%
700
20%
700
9%
1796
February21st to endNight
13%
592
12%
1776
2%
592
23%
592
10%
1388
March1st to 10thNight
20%
720
16%
2003
7%
720
28%
720
16%
1479
March11th to 20thNight
25%
720
18%
1980
9%
720
33%
720
18%
1426
March21st to endNight
24%
792
16%
2178
9%
792
31%
792
18%
1610
April1st to 10thNight
24%
720
13%
1920
5%
720
29%
720
18%
1414
April11th to 20thNight
26%
616
17%
1680
7%
616
34%
616
22%
1173
April21st to endNight
29%
540
18%
1620
7%
540
37%
540
22%
1094
May1st to 10thNight
34%
540
12%
1620
7%
540
39%
540
18%
1151
May11th to 20thNight
40%
531
17%
1593
11%
531
46%
531
23%
1069
May21st to endNight
53%
484
16%
1647
13%
484
60%
484
29%
970
June1st to 10thNight
43%
360
15%
1440
15%
360
53%
360
22%
863
June11th to 20thNight
51%
360
18%
1440
19%
360
61%
360
22%
836
June21st to endNight
48%
360
18%
1440
18%
360
56%
360
24%
820
July1st to 10thNight
64%
457
16%
1507
17%
457
66%
457
30%
898
July11th to 20thNight
59%
522
18%
1566
16%
522
63%
522
34%
930
July21st to endNight
60%
591
17%
1672
14%
558
62%
558
30%
1047
August1st to 10thNight
64%
537
19%
1600
15%
534
66%
534
33%
951
August11th to 20thNight
61%
534
20%
1598
15%
534
64%
534
30%
989
August21st to endNight
58%
639
22%
1827
15%
639
61%
639
34%
1114
September1st to 10thNight
53%
720
22%
1851
13%
720
57%
720
33%
1194
September11th to 20thNight
62%
720
26%
1980
19%
720
66%
720
37%
1176
September21st to endNight
44%
720
21%
1980
16%
720
49%
720
27%
1312
October1st to 10thNight
43%
720
19%
2124
16%
720
47%
720
27%
1346
October11th to 20thNight
30%
720
16%
2160
10%
720
39%
720
19%
1497
October21st to endNight
25%
792
18%
2376
11%
792
34%
792
17%
1710
November1st to 10thNight
35%
740
20%
2374
15%
740
44%
740
22%
1520
November11th to 20thNight
20%
760
15%
2548
9%
760
29%
760
13%
1853
November21st to endNight
19%
760
12%
2660
7%
760
26%
760
11%
2012
December1st to 10thNight
15%
760
7%
2660
4%
760
20%
760
8%
2123
December11th to 20thNight
15%
759
8%
3261
3%
758
23%
758
6%
2548
December21st to endNight
13%
831
4%
4806
2%
817
20%
817
4%
4097

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
16%10%47%6%45%5%5%7%30%
74758
Night
16%11%47%6%35%45%7%32%
75368
TransparencyDay
53%5%11%19%10%1
74479
Night
52%5%11%19%11%1
75166
SeeingDay
22%15%28%20%11%4
13536
Night
21%12%28%25%12%1
23403

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
18%17%8%11%8%35%445%17%
1706
11th to 20thDay
19%19%8%12%7%44445%15%
1710
21st to endDay
19%19%8%13%8%4445%413%
1872
February1st to 10thDay
18%17%7%12%9%3433420%
1620
11th to 20thDay
16%14%8%12%9%35%45%5%19%
1591
21st to endDay
18%16%411%5%445%45%23%
1480
March1st to 10thDay
18%11%7%7%6%33447%29%
1956
11th to 20thDay
17%13%5%8%5%34447%29%
1980
21st to endDay
22%12%5%8%6%3345%5%28%
2178
April1st to 10thDay
16%12%5%6%6%345%5%7%32%
2039
11th to 20thDay
19%10%46%6%35%45%6%32%
2244
21st to endDay
21%10%46%6%34346%34%
2340
May1st to 10thDay
16%9%47%7%46%5%5%7%29%
2340
11th to 20thDay
19%8%36%6%35%5%5%6%32%
2301
21st to endDay
11%6%26%6%46%6%6%9%38%
2629
June1st to 10thDay
14%6%36%6%5%6%6%6%7%36%
2520
11th to 20thDay
13%7%37%7%4445%9%38%
2520
21st to endDay
12%5%25%5%45%7%6%9%40%
2520
July1st to 10thDay
9%6%36%5%45%5%6%9%41%
2404
11th to 20thDay
11%5%25%7%46%6%7%10%38%
2340
21st to endDay
10%6%35%6%46%6%7%9%37%
2547
August1st to 10thDay
8%6%36%7%46%6%6%10%38%
2327
11th to 20thDay
10%7%36%7%47%6%7%11%32%
2303
21st to endDay
10%6%36%7%46%6%7%10%37%
2509
September1st to 10thDay
15%6%36%5%3445%8%41%
2106
11th to 20thDay
11%5%35%6%35%47%9%42%
1980
21st to endDay
18%8%36%5%345%46%38%
1980
October1st to 10thDay
16%6%37%6%35%5%6%7%36%
1836
11th to 20thDay
22%10%37%6%3445%6%31%
1800
21st to endDay
23%10%47%6%35%46%6%26%
1980
November1st to 10thDay
12%9%37%7%35%45%7%38%
1704
11th to 20thDay
19%15%5%6%7%3445%6%28%
1630
21st to endDay
18%16%6%8%7%35%5%6%5%21%
1520
December1st to 10thDay
19%19%8%9%7%35%5%4415%
1520
11th to 20thDay
19%17%9%12%6%345%5%5%16%
1910
21st to endDay
27%22%7%11%6%3333311%
2816
January1st to 10thNight
18%16%8%12%7%34445%19%
2459
11th to 20thNight
19%18%7%11%7%35%445%17%
2470
21st to endNight
18%17%8%13%7%44445%17%
2711
February1st to 10thNight
21%15%6%10%8%3435%5%19%
2340
11th to 20thNight
18%13%7%11%8%5%5%5%45%21%
2254
21st to endNight
22%13%5%10%6%34445%24%
1776
March1st to 10thNight
17%11%6%7%6%445%5%5%30%
2003
11th to 20thNight
19%10%47%5%3446%7%32%
1980
21st to endNight
19%11%47%6%35%445%32%
2178
April1st to 10thNight
16%11%48%5%35%46%6%32%
1920
11th to 20thNight
16%9%47%5%35%5%5%7%35%
1680
21st to endNight
15%8%36%5%35%5%6%8%35%
1620
May1st to 10thNight
18%7%46%7%45%5%5%6%33%
1620
11th to 20thNight
14%9%46%5%245%5%9%36%
1592
21st to endNight
9%435%5%346%6%12%43%
1646
June1st to 10thNight
9%5%36%7%46%6%7%7%41%
1440
11th to 20thNight
10%5%26%6%345%6%9%43%
1440
21st to endNight
10%6%25%445%6%7%9%43%
1440
July1st to 10thNight
7%5%36%5%35%5%7%8%47%
1552
11th to 20thNight
8%425%6%35%46%10%47%
1620
21st to endNight
9%5%25%445%6%7%8%43%
1771
August1st to 10thNight
6%6%35%5%3446%9%48%
1611
11th to 20thNight
9%6%35%5%45%5%6%8%45%
1598
21st to endNight
10%425%5%35%6%6%7%48%
1827
September1st to 10thNight
12%6%245%245%5%8%46%
1851
11th to 20thNight
11%4244345%5%8%51%
1980
21st to endNight
14%6%36%6%4445%7%41%
1980
October1st to 10thNight
15%5%25%5%346%5%8%43%
2124
11th to 20thNight
19%7%37%6%345%5%7%35%
2160
21st to endNight
23%9%36%5%3445%6%31%
2376
November1st to 10thNight
14%8%35%5%35%5%5%8%39%
2374
11th to 20thNight
18%14%5%7%6%35%446%29%
2548
21st to endNight
19%17%47%5%3445%5%25%
2660
December1st to 10thNight
21%17%7%8%6%35%445%19%
2660
11th to 20thNight
17%19%7%10%6%34345%21%
3285
21st to endNight
27%19%7%9%7%35%445%11%
4822

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
70%411%11%4
1707
11th to 20thDay
73%311%10%2
1710
21st to endDay
75%47%10%31
1872
February1st to 10thDay
70%38%12%5%
1620
11th to 20thDay
68%47%13%7%
1600
21st to endDay
63%410%15%6%2
1480
March1st to 10thDay
57%412%21%6%
1956
11th to 20thDay
57%5%9%18%10%1
1980
21st to endDay
59%48%18%10%2
2178
April1st to 10thDay
52%412%18%13%1
2039
11th to 20thDay
53%5%11%17%13%2
2244
21st to endDay
52%5%10%21%10%2
2340
May1st to 10thDay
54%6%11%19%9%2
2340
11th to 20thDay
51%6%11%17%13%2
2305
21st to endDay
41%7%14%24%12%2
2629
June1st to 10thDay
45%6%12%24%12%1
2520
11th to 20thDay
44%5%14%21%14%2
2520
21st to endDay
39%7%13%25%15%2
2520
July1st to 10thDay
40%7%11%24%15%3
2339
11th to 20thDay
40%6%13%25%15%1
2271
21st to endDay
39%8%13%23%15%1
2405
August1st to 10thDay
39%7%15%27%12%1
2314
11th to 20thDay
43%7%15%23%10%2
2303
21st to endDay
40%8%14%22%13%3
2509
September1st to 10thDay
41%5%13%22%14%3
2106
11th to 20thDay
38%6%14%25%15%1
1980
21st to endDay
46%5%11%25%13%1
1980
October1st to 10thDay
45%6%12%22%14%1
1836
11th to 20thDay
54%5%10%22%9%1
1800
21st to endDay
58%5%12%14%9%1
1980
November1st to 10thDay
46%6%12%21%14%1
1704
11th to 20thDay
56%6%10%18%7%3
1630
21st to endDay
63%7%9%14%7%
1520
December1st to 10thDay
72%6%7%12%3
1520
11th to 20thDay
70%5%8%14%3
1906
21st to endDay
81%38%6%2
2816
January1st to 10thNight
68%49%13%6%
2459
11th to 20thNight
70%5%10%13%3
2470
21st to endNight
71%48%13%41
2711
February1st to 10thNight
67%5%10%13%5%
2340
11th to 20thNight
66%5%8%15%6%
2256
21st to endNight
63%48%15%8%1
1776
March1st to 10thNight
55%49%22%9%1
2003
11th to 20thNight
50%6%11%19%12%2
1980
21st to endNight
55%47%19%12%2
2178
April1st to 10thNight
51%7%10%18%13%2
1920
11th to 20thNight
48%5%13%18%15%2
1680
21st to endNight
45%6%12%20%14%3
1620
May1st to 10thNight
52%5%10%18%12%3
1620
11th to 20thNight
45%6%11%20%14%4
1593
21st to endNight
34%7%17%25%15%2
1647
June1st to 10thNight
39%7%11%25%15%3
1440
11th to 20thNight
37%7%13%23%17%2
1440
21st to endNight
36%7%14%24%18%1
1440
July1st to 10thNight
35%6%11%24%20%4
1507
11th to 20thNight
31%8%14%26%20%2
1566
21st to endNight
36%7%15%23%15%3
1672
August1st to 10thNight
33%6%14%29%18%1
1600
11th to 20thNight
36%7%16%26%13%2
1598
21st to endNight
33%7%13%25%18%4
1827
September1st to 10thNight
37%5%12%26%17%4
1851
11th to 20thNight
31%6%14%27%21%2
1980
21st to endNight
42%5%12%22%18%1
1980
October1st to 10thNight
39%6%13%23%18%1
2124
11th to 20thNight
49%5%11%23%11%1
2160
21st to endNight
53%5%11%20%10%1
2376
November1st to 10thNight
42%6%11%24%14%3
2374
11th to 20thNight
57%49%19%8%3
2548
21st to endNight
61%5%11%18%5%1
2660
December1st to 10thNight
67%411%12%5%
2660
11th to 20thNight
66%412%15%3
3288
21st to endNight
76%5%10%8%1
4822

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
33%26%28%9%4
270
11th to 20thDay
32%27%30%9%2
270
21st to endDay
30%31%28%8%2
294
February1st to 10thDay
33%25%35%7%
240
11th to 20thDay
32%34%29%41
240
21st to endDay
33%31%30%5%
198
March1st to 10thDay
24%25%34%12%5%
396
11th to 20thDay
27%21%34%11%6%1
420
21st to endDay
34%20%27%15%4
462
April1st to 10thDay
24%24%29%15%8%1
420
11th to 20thDay
28%17%28%16%9%3
412
21st to endDay
27%19%29%17%5%2
420
May1st to 10thDay
30%17%27%17%6%3
423
11th to 20thDay
25%12%31%20%8%4
447
21st to endDay
15%9%29%23%17%6%
485
June1st to 10thDay
16%10%35%24%11%3
450
11th to 20thDay
19%11%25%26%14%5%
450
21st to endDay
16%8%32%25%15%4
450
July1st to 10thDay
13%422%28%23%10%
445
11th to 20thDay
15%427%29%17%9%
444
21st to endDay
11%6%28%29%17%8%
488
August1st to 10thDay
13%6%20%30%20%11%
446
11th to 20thDay
16%6%25%24%20%10%
439
21st to endDay
11%6%23%29%22%9%
495
September1st to 10thDay
14%9%21%27%20%9%
450
11th to 20thDay
13%419%31%21%12%
450
21st to endDay
22%10%26%21%15%6%
450
October1st to 10thDay
15%10%29%22%20%4
450
11th to 20thDay
26%17%32%17%7%1
450
21st to endDay
30%18%29%18%5%
495
November1st to 10thDay
20%23%27%17%11%3
302
11th to 20thDay
32%19%27%16%5%
232
21st to endDay
27%19%42%11%1
180
December1st to 10thDay
31%25%28%12%32
180
11th to 20thDay
27%28%35%9%1
180
21st to endDay
34%24%31%9%2
213
January1st to 10thNight
27%22%36%12%4
760
11th to 20thNight
30%21%31%15%3
760
21st to endNight
25%22%31%19%3
835
February1st to 10thNight
31%19%30%20%1
720
11th to 20thNight
27%19%37%16%2
703
21st to endNight
30%17%34%15%3
592
March1st to 10thNight
24%17%34%21%4
720
11th to 20thNight
24%17%30%22%7%1
720
21st to endNight
24%14%32%23%6%1
792
April1st to 10thNight
23%15%33%23%6%
720
11th to 20thNight
22%13%35%22%8%1
616
21st to endNight
18%9%38%27%7%
540
May1st to 10thNight
21%8%27%33%9%1
540
11th to 20thNight
18%7%28%33%13%2
531
21st to endNight
12%426%33%22%3
486
June1st to 10thNight
10%335%39%12%1
360
11th to 20thNight
13%5%23%43%16%1
360
21st to endNight
12%5%27%35%20%1
360
July1st to 10thNight
8%216%40%29%5%
457
11th to 20thNight
9%221%36%27%3
522
21st to endNight
10%317%40%27%2
591
August1st to 10thNight
9%316%41%28%4
537
11th to 20thNight
12%314%37%29%4
534
21st to endNight
12%220%33%29%4
639
September1st to 10thNight
15%5%18%31%26%4
720
11th to 20thNight
12%415%37%28%5%
720
21st to endNight
17%8%23%28%20%4
720
October1st to 10thNight
19%8%24%26%20%3
720
11th to 20thNight
23%12%31%24%9%1
720
21st to endNight
30%12%28%23%6%
792
November1st to 10thNight
19%13%27%28%11%1
740
11th to 20thNight
25%18%31%18%7%1
760
21st to endNight
28%18%32%17%5%
760
December1st to 10thNight
31%18%30%16%5%
760
11th to 20thNight
26%23%29%18%4
760
21st to endNight
31%18%31%19%2
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