Codorus Creek Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Codorus Creek Observatory clear sky chart from 2005-11-06 to 2024-01-16.

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
39%
23310
20%
74720
12%
23261
48%
23261
24%
47526

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
21%
758
21%
2649
9%
757
38%
757
21%
1671
January11th to 20thNight
26%
744
20%
2441
10%
744
40%
744
19%
1612
January21st to endNight
23%
792
23%
2574
9%
792
40%
792
23%
1613
February1st to 10thNight
24%
720
17%
2340
9%
720
35%
720
19%
1551
February11th to 20thNight
17%
703
19%
2222
4%
700
36%
700
19%
1442
February21st to endNight
16%
592
22%
1776
6%
592
33%
592
18%
1213
March1st to 10thNight
25%
720
22%
2048
8%
720
41%
720
27%
1279
March11th to 20thNight
27%
720
21%
1980
9%
720
38%
720
23%
1341
March21st to endNight
25%
792
21%
2124
8%
792
35%
792
25%
1435
April1st to 10thNight
24%
720
17%
1800
5%
720
32%
720
24%
1275
April11th to 20thNight
35%
711
20%
1775
7%
711
40%
711
31%
1175
April21st to endNight
34%
720
19%
1800
6%
720
40%
720
28%
1232
May1st to 10thNight
39%
590
17%
1670
9%
590
44%
590
24%
1137
May11th to 20thNight
42%
354
18%
1416
15%
354
49%
354
18%
892
May21st to endNight
55%
388
16%
1551
16%
388
59%
388
21%
940
June1st to 10thNight
53%
360
19%
1440
21%
360
59%
360
24%
830
June11th to 20thNight
55%
360
15%
1440
16%
360
61%
360
22%
866
June21st to endNight
62%
360
18%
1440
21%
360
66%
360
26%
815
July1st to 10thNight
57%
350
13%
1400
16%
350
59%
350
20%
883
July11th to 20thNight
72%
348
18%
1392
22%
348
75%
348
28%
757
July21st to endNight
67%
576
17%
1658
14%
544
71%
544
32%
1001
August1st to 10thNight
68%
537
17%
1600
13%
534
70%
534
30%
981
August11th to 20thNight
61%
605
18%
1669
12%
605
62%
605
28%
1133
August21st to endNight
62%
792
19%
1980
10%
792
64%
792
33%
1314
September1st to 10thNight
55%
720
22%
1800
11%
720
59%
720
33%
1189
September11th to 20thNight
62%
720
31%
1800
22%
720
65%
720
39%
1118
September21st to endNight
50%
720
22%
2051
17%
720
56%
720
27%
1345
October1st to 10thNight
48%
720
17%
2160
15%
720
53%
720
27%
1387
October11th to 20thNight
43%
720
23%
2160
16%
720
54%
720
30%
1313
October21st to endNight
36%
792
26%
2376
15%
792
51%
792
30%
1479
November1st to 10thNight
42%
740
26%
2367
17%
740
56%
740
31%
1363
November11th to 20thNight
34%
760
24%
2502
14%
760
47%
760
26%
1512
November21st to endNight
33%
760
22%
2660
13%
760
48%
760
24%
1573
December1st to 10thNight
25%
760
17%
2660
7%
760
39%
760
18%
1752
December11th to 20thNight
28%
760
18%
3200
8%
759
43%
759
18%
1970
December21st to endNight
28%
826
12%
4799
8%
817
40%
817
11%
3137

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%35%5%35%5%6%8%40%
74727
Night
14%6%35%5%345%6%7%42%
75083
TransparencyDay
41%7%12%22%15%3
74436
Night
40%6%12%23%16%3
74893
SeeingDay
18%10%26%24%15%6%
13783
Night
17%8%29%32%13%1
23323

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
13%8%36%5%35%45%7%40%
1517
11th to 20thDay
14%9%48%5%35%5%5%7%36%
1642
21st to endDay
12%10%47%7%445%6%6%37%
1782
February1st to 10thDay
15%9%35%6%45%5%7%6%35%
1620
11th to 20thDay
15%8%36%6%445%5%6%39%
1624
21st to endDay
19%9%46%5%3445%5%37%
1480
March1st to 10thDay
13%6%35%5%34447%46%
1909
11th to 20thDay
16%7%35%5%45%45%8%38%
1980
21st to endDay
19%7%46%6%335%5%6%37%
2231
April1st to 10thDay
13%8%36%5%46%5%5%6%39%
2160
11th to 20thDay
14%5%25%5%35%5%48%43%
2134
21st to endDay
18%6%36%435%5%6%6%39%
2160
May1st to 10thDay
17%7%26%5%35%5%6%8%35%
2305
11th to 20thDay
19%7%35%5%36%5%5%7%35%
2473
21st to endDay
13%6%36%5%35%5%6%9%40%
2725
June1st to 10thDay
13%5%25%446%6%6%10%39%
2520
11th to 20thDay
11%6%36%5%45%6%7%8%39%
2520
21st to endDay
10%3245%45%5%8%10%44%
2520
July1st to 10thDay
9%5%25%5%5%6%5%6%10%42%
2520
11th to 20thDay
6%425%5%47%6%8%9%43%
2520
21st to endDay
9%6%36%7%46%7%8%9%36%
2558
August1st to 10thDay
8%436%6%46%7%7%9%39%
2327
11th to 20thDay
11%6%25%6%35%6%7%9%38%
2211
21st to endDay
13%5%25%5%45%5%6%9%42%
2376
September1st to 10thDay
16%5%25%5%35%446%45%
2160
11th to 20thDay
13%5%2442345%9%49%
2160
21st to endDay
17%7%35%424448%40%
1905
October1st to 10thDay
17%5%25%4345%5%7%44%
1800
11th to 20thDay
16%7%34434446%45%
1800
21st to endDay
16%7%245%2446%5%44%
1980
November1st to 10thDay
12%6%3443345%7%50%
1709
11th to 20thDay
15%5%25%5%245%5%6%46%
1677
21st to endDay
16%6%35%5%345%5%7%43%
1520
December1st to 10thDay
17%7%46%6%3446%8%34%
1520
11th to 20thDay
16%9%37%5%45%45%6%37%
1910
21st to endDay
16%9%47%6%35%5%6%7%32%
2772
January1st to 10thNight
13%8%46%5%35%5%5%7%40%
2649
11th to 20thNight
17%7%36%5%35%45%7%38%
2441
21st to endNight
13%8%35%5%35%45%7%42%
2574
February1st to 10thNight
16%9%36%5%3445%7%38%
2340
11th to 20thNight
16%8%37%435%45%7%39%
2220
21st to endNight
16%8%37%5%25%446%38%
1776
March1st to 10thNight
13%5%25%5%3446%6%46%
2048
11th to 20thNight
16%7%35%6%35%45%5%42%
1980
21st to endNight
16%8%36%5%33447%40%
2124
April1st to 10thNight
15%8%37%5%35%5%5%7%37%
1800
11th to 20thNight
13%5%25%6%35%36%9%44%
1775
21st to endNight
17%6%3442447%7%41%
1800
May1st to 10thNight
16%8%26%5%445%48%39%
1670
11th to 20thNight
17%6%25%6%345%6%7%38%
1415
21st to endNight
11%6%26%5%35%5%7%8%41%
1550
June1st to 10thNight
13%434435%5%5%7%47%
1440
11th to 20thNight
10%6%25%6%35%7%6%11%39%
1440
21st to endNight
9%435%5%35%5%7%10%44%
1440
July1st to 10thNight
8%6%36%7%46%7%7%9%39%
1440
11th to 20thNight
5%3245%35%7%8%10%48%
1440
21st to endNight
9%5%245%35%6%6%10%46%
1756
August1st to 10thNight
9%4245%46%7%9%8%43%
1611
11th to 20thNight
9%6%37%6%45%5%6%7%41%
1669
21st to endNight
12%425%5%35%6%6%8%44%
1980
September1st to 10thNight
13%426%5%3446%7%46%
1800
11th to 20thNight
11%5%24434447%53%
1800
21st to endNight
17%6%25%5%35%45%7%42%
2051
October1st to 10thNight
19%6%2442345%5%45%
2160
11th to 20thNight
15%5%25%43445%6%48%
2160
21st to endNight
17%6%2432345%7%47%
2376
November1st to 10thNight
11%5%25%5%3445%6%52%
2367
11th to 20thNight
14%6%35%43435%6%46%
2502
21st to endNight
13%435%5%345%6%7%45%
2660
December1st to 10thNight
16%8%36%5%36%45%7%37%
2660
11th to 20thNight
16%6%26%6%45%5%6%6%39%
3285
21st to endNight
16%8%36%6%45%6%6%8%31%
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%12%22%14%3
1518
11th to 20thDay
47%7%13%20%11%2
1642
21st to endDay
47%5%11%23%12%3
1782
February1st to 10thDay
47%6%12%22%10%2
1620
11th to 20thDay
45%6%10%25%12%2
1633
21st to endDay
49%410%20%12%4
1480
March1st to 10thDay
39%413%25%16%2
1909
11th to 20thDay
44%5%11%18%16%5%
1980
21st to endDay
47%5%9%19%16%3
2231
April1st to 10thDay
43%6%11%19%16%4
2160
11th to 20thDay
40%6%11%22%17%4
2134
21st to endDay
43%6%10%22%16%3
2160
May1st to 10thDay
44%7%11%21%14%2
2305
11th to 20thDay
48%7%11%19%13%3
2477
21st to endDay
40%8%15%23%12%2
2725
June1st to 10thDay
39%8%13%23%15%1
2520
11th to 20thDay
40%9%14%22%13%2
2520
21st to endDay
33%9%14%27%15%1
2520
July1st to 10thDay
37%9%12%21%17%3
2450
11th to 20thDay
33%8%15%26%16%3
2445
21st to endDay
39%10%12%20%15%2
2415
August1st to 10thDay
38%11%14%23%14%
2314
11th to 20thDay
39%8%13%22%15%2
2211
21st to endDay
38%8%13%24%15%4
2376
September1st to 10thDay
41%6%12%19%18%4
2160
11th to 20thDay
33%6%10%27%20%4
2160
21st to endDay
44%5%9%19%21%2
1905
October1st to 10thDay
40%6%11%24%17%2
1800
11th to 20thDay
39%5%12%23%19%2
1800
21st to endDay
41%6%9%25%18%2
1980
November1st to 10thDay
34%413%25%20%4
1709
11th to 20thDay
38%5%11%23%19%3
1677
21st to endDay
40%6%11%30%10%2
1520
December1st to 10thDay
47%5%15%21%10%1
1520
11th to 20thDay
45%8%11%28%8%1
1906
21st to endDay
48%9%15%18%9%1
2772
January1st to 10thNight
43%5%10%24%14%4
2649
11th to 20thNight
46%5%13%23%11%1
2441
21st to endNight
41%5%10%27%15%3
2574
February1st to 10thNight
46%5%13%23%11%2
2340
11th to 20thNight
45%311%21%17%3
2222
21st to endNight
46%6%9%19%15%4
1776
March1st to 10thNight
37%6%11%26%18%2
2048
11th to 20thNight
43%6%9%22%16%3
1980
21st to endNight
44%5%10%20%17%5%
2124
April1st to 10thNight
45%6%10%19%16%4
1800
11th to 20thNight
38%6%11%21%19%5%
1775
21st to endNight
41%6%10%22%17%4
1800
May1st to 10thNight
44%7%10%21%14%4
1670
11th to 20thNight
44%7%11%17%18%2
1416
21st to endNight
38%9%15%22%12%3
1551
June1st to 10thNight
35%8%11%25%18%2
1440
11th to 20thNight
37%10%15%21%16%2
1440
21st to endNight
33%8%14%26%17%2
1440
July1st to 10thNight
39%11%15%20%13%3
1400
11th to 20thNight
29%10%16%26%17%3
1392
21st to endNight
31%10%17%22%17%3
1658
August1st to 10thNight
34%9%18%25%13%1
1600
11th to 20thNight
40%9%13%20%17%1
1669
21st to endNight
36%8%14%22%17%3
1980
September1st to 10thNight
37%7%12%21%20%4
1800
11th to 20thNight
32%6%10%25%25%3
1800
21st to endNight
41%6%10%20%20%3
2051
October1st to 10thNight
40%6%13%23%16%2
2160
11th to 20thNight
37%5%11%28%18%2
2160
21st to endNight
37%5%10%27%18%2
2376
November1st to 10thNight
33%5%10%26%21%5%
2367
11th to 20thNight
39%49%24%19%5%
2502
21st to endNight
37%5%12%27%16%2
2660
December1st to 10thNight
47%5%12%23%12%1
2660
11th to 20thNight
43%5%13%22%15%2
3288
21st to endNight
47%9%15%21%8%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
24%20%34%16%5%1
180
11th to 20thDay
24%23%33%15%4
243
21st to endDay
22%22%36%14%5%1
264
February1st to 10thDay
25%19%39%13%31
240
11th to 20thDay
26%21%42%10%1
291
21st to endDay
29%17%35%16%2
346
March1st to 10thDay
17%20%32%26%5%
420
11th to 20thDay
22%17%36%19%32
420
21st to endDay
25%17%29%20%7%2
462
April1st to 10thDay
20%17%36%18%8%2
420
11th to 20thDay
17%16%29%19%13%5%
412
21st to endDay
26%11%28%24%8%3
420
May1st to 10thDay
26%11%28%19%12%4
423
11th to 20thDay
21%9%28%25%14%4
447
21st to endDay
17%418%28%24%9%
485
June1st to 10thDay
15%6%26%26%18%9%
450
11th to 20thDay
15%7%22%28%20%8%
450
21st to endDay
11%423%32%22%8%
450
July1st to 10thDay
11%5%15%28%25%15%
445
11th to 20thDay
5%416%30%32%14%
444
21st to endDay
12%318%32%25%9%
488
August1st to 10thDay
11%215%31%30%11%
446
11th to 20thDay
12%6%13%28%27%14%
439
21st to endDay
11%5%14%29%26%15%
495
September1st to 10thDay
18%5%16%22%22%17%
450
11th to 20thDay
13%415%30%23%15%
450
21st to endDay
22%8%22%26%15%6%
450
October1st to 10thDay
20%7%21%24%18%10%
450
11th to 20thDay
17%9%29%24%18%3
450
21st to endDay
17%10%36%25%9%3
495
November1st to 10thDay
16%11%27%29%14%3
383
11th to 20thDay
18%15%30%24%11%1
337
21st to endDay
18%18%35%20%9%
180
December1st to 10thDay
23%18%32%17%7%3
180
11th to 20thDay
24%16%33%18%7%1
180
21st to endDay
21%14%33%23%9%1
198
January1st to 10thNight
17%13%43%23%3
760
11th to 20thNight
22%14%32%29%4
744
21st to endNight
17%13%43%26%2
792
February1st to 10thNight
21%14%34%28%2
720
11th to 20thNight
21%15%42%21%1
703
21st to endNight
21%17%42%18%3
592
March1st to 10thNight
16%13%41%25%5%
720
11th to 20thNight
21%12%36%25%5%
720
21st to endNight
21%10%38%25%5%1
792
April1st to 10thNight
20%14%37%23%5%
720
11th to 20thNight
17%9%34%30%9%
711
21st to endNight
21%9%32%29%9%
720
May1st to 10thNight
18%9%27%33%12%1
590
11th to 20thNight
19%5%27%39%10%
354
21st to endNight
14%417%43%21%2
389
June1st to 10thNight
14%222%41%21%1
360
11th to 20thNight
11%324%42%19%1
360
21st to endNight
9%119%54%16%
360
July1st to 10thNight
9%316%40%28%3
350
11th to 20thNight
5%212%46%32%3
348
21st to endNight
10%213%45%28%2
576
August1st to 10thNight
10%29%49%28%2
537
11th to 20thNight
11%410%40%31%3
605
21st to endNight
12%213%37%32%4
792
September1st to 10thNight
15%316%34%29%3
720
11th to 20thNight
12%214%38%30%4
720
21st to endNight
20%320%34%22%2
720
October1st to 10thNight
22%421%29%21%4
720
11th to 20thNight
17%7%29%34%13%1
720
21st to endNight
20%5%36%28%10%1
792
November1st to 10thNight
14%6%32%36%11%1
740
11th to 20thNight
16%11%34%30%8%1
760
21st to endNight
14%11%36%30%8%
760
December1st to 10thNight
21%11%37%24%6%
760
11th to 20thNight
18%8%40%30%5%
760
21st to endNight
19%10%36%33%2
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