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 2024-12-24.

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
38%
24387
18%
97618
12%
24138
48%
24138
19%
61120

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
20%
753
19%
4359
9%
737
38%
737
13%
2650
January11th to 20thNight
25%
759
22%
4046
9%
740
39%
740
12%
2429
January21st to endNight
22%
831
14%
4463
9%
814
40%
814
12%
2946
February1st to 10thNight
25%
760
18%
2470
11%
760
37%
760
20%
1618
February11th to 20thNight
17%
743
19%
2349
4%
740
36%
740
19%
1518
February21st to endNight
17%
628
20%
1884
6%
628
33%
628
19%
1279
March1st to 10thNight
25%
757
20%
3501
8%
745
40%
745
15%
2277
March11th to 20thNight
26%
755
24%
3414
9%
740
38%
740
17%
1823
March21st to endNight
24%
831
14%
3578
8%
814
35%
814
17%
2118
April1st to 10thNight
23%
760
18%
1900
5%
760
31%
760
23%
1346
April11th to 20thNight
34%
751
19%
1875
7%
751
40%
751
31%
1250
April21st to endNight
34%
760
18%
1900
5%
760
40%
760
28%
1296
May1st to 10thNight
38%
617
16%
2869
9%
611
44%
611
13%
2009
May11th to 20thNight
41%
370
10%
2482
14%
364
49%
364
9%
1732
May21st to endNight
53%
402
12%
2710
15%
399
58%
399
14%
1459
June1st to 10thNight
53%
380
20%
1520
22%
380
60%
380
24%
873
June11th to 20thNight
56%
380
15%
1520
16%
380
62%
380
23%
896
June21st to endNight
60%
380
17%
1520
20%
380
64%
380
25%
866
July1st to 10thNight
56%
362
15%
2362
16%
360
59%
360
13%
1317
July11th to 20thNight
71%
361
13%
2317
22%
358
75%
358
16%
1352
July21st to endNight
65%
596
12%
2815
14%
555
70%
555
18%
1743
August1st to 10thNight
67%
553
13%
2699
14%
544
70%
544
17%
1749
August11th to 20thNight
60%
623
17%
2640
12%
619
61%
619
19%
1714
August21st to endNight
62%
818
14%
3086
10%
814
64%
814
24%
1879
September1st to 10thNight
56%
760
24%
1900
12%
760
60%
760
34%
1243
September11th to 20thNight
62%
760
30%
1900
22%
760
65%
760
39%
1183
September21st to endNight
48%
760
20%
2166
16%
760
53%
760
25%
1454
October1st to 10thNight
47%
760
12%
3052
15%
740
53%
740
18%
2127
October11th to 20thNight
44%
760
19%
2599
16%
740
54%
740
26%
1562
October21st to endNight
39%
836
23%
2805
17%
814
52%
814
27%
1691
November1st to 10thNight
43%
780
28%
2495
18%
780
57%
780
32%
1422
November11th to 20thNight
34%
800
23%
2634
14%
800
47%
800
26%
1592
November21st to endNight
32%
800
22%
2800
12%
800
47%
800
24%
1658
December1st to 10thNight
25%
800
18%
2800
7%
800
40%
800
18%
1824
December11th to 20thNight
27%
800
18%
3340
8%
799
41%
799
18%
2069
December21st to endNight
29%
841
12%
4848
8%
832
41%
832
12%
3156

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%7%26%445%46%7%39%
101703
Night
14%7%36%44446%7%41%
98370
TransparencyDay
41%7%12%23%15%2
105340
Night
40%6%12%24%16%2
102872
SeeingDay
18%11%26%24%15%6%
15034
Night
17%8%29%32%13%1
24518

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
15%7%37%5%4435%6%42%
2517
11th to 20thDay
13%12%411%5%45%345%33%
2785
21st to endDay
16%12%49%6%5%435%5%32%
3124
February1st to 10thDay
14%10%26%5%5%45%7%6%37%
1710
11th to 20thDay
14%9%27%5%5%345%5%39%
1717
21st to endDay
18%10%37%5%4335%437%
1570
March1st to 10thDay
22%7%36%45%435%7%36%
3326
11th to 20thDay
10%6%27%5%6%5%36%7%43%
3480
21st to endDay
20%8%36%433345%41%
3909
April1st to 10thDay
14%9%36%5%5%5%45%6%38%
2280
11th to 20thDay
13%6%26%445%45%7%43%
2254
21st to endDay
17%7%27%34446%6%39%
2280
May1st to 10thDay
27%7%26%43446%7%30%
4034
11th to 20thDay
22%8%37%5%5%5%45%7%28%
4393
21st to endDay
10%5%26%445%47%9%43%
4823
June1st to 10thDay
12%6%26%45%5%5%6%10%39%
2660
11th to 20thDay
11%6%36%5%5%5%5%7%9%40%
2660
21st to endDay
9%416%5%5%5%48%9%44%
2660
July1st to 10thDay
6%426%5%6%6%5%8%11%41%
4440
11th to 20thDay
8%5%25%5%5%6%47%10%41%
4440
21st to endDay
10%7%38%5%5%5%5%7%8%36%
4477
August1st to 10thDay
16%5%36%5%6%5%5%6%9%34%
4104
11th to 20thDay
10%6%27%45%6%5%7%8%40%
3868
21st to endDay
12%5%25%44435%7%48%
4180
September1st to 10thDay
16%6%25%445%346%46%
2280
11th to 20thDay
12%6%25%33435%9%48%
2280
21st to endDay
19%8%36%434347%38%
2010
October1st to 10thDay
17%5%25%34445%7%44%
1900
11th to 20thDay
15%7%25%334346%47%
1900
21st to endDay
15%7%25%43436%5%45%
2090
November1st to 10thDay
12%6%3434335%7%51%
1801
11th to 20thDay
14%5%26%43445%6%46%
1765
21st to endDay
15%7%25%5%45%45%7%43%
1600
December1st to 10thDay
16%7%47%5%45%37%8%35%
1600
11th to 20thDay
16%9%38%5%5%435%7%36%
1990
21st to endDay
16%9%38%5%45%46%7%32%
2796
January1st to 10thNight
13%10%48%5%5%435%6%36%
4429
11th to 20thNight
17%9%37%44435%6%39%
4170
21st to endNight
19%11%37%5%43345%34%
4532
February1st to 10thNight
16%9%26%5%4435%6%39%
2470
11th to 20thNight
16%9%37%34435%6%39%
2347
21st to endNight
16%9%37%43445%6%38%
1884
March1st to 10thNight
20%9%26%44335%5%37%
3524
11th to 20thNight
11%6%36%5%4435%6%47%
3480
21st to endNight
13%9%37%433345%45%
3722
April1st to 10thNight
15%9%37%44446%7%36%
1900
11th to 20thNight
13%6%26%5%4436%8%43%
1875
21st to endNight
17%6%35%33447%7%41%
1900
May1st to 10thNight
24%8%37%444347%31%
2890
11th to 20thNight
22%8%27%6%4446%6%29%
2495
21st to endNight
10%6%26%5%45%47%10%40%
2732
June1st to 10thNight
13%5%25%44446%7%46%
1520
11th to 20thNight
9%6%26%5%45%6%6%11%40%
1520
21st to endNight
8%5%26%5%45%48%10%43%
1520
July1st to 10thNight
5%5%26%5%6%6%6%8%9%41%
2520
11th to 20thNight
6%5%37%6%6%5%6%8%10%39%
2520
21st to endNight
12%7%36%5%45%46%8%41%
3072
August1st to 10thNight
18%5%26%45%5%47%8%35%
2825
11th to 20thNight
9%7%38%5%5%446%8%40%
2926
21st to endNight
12%5%25%435%46%7%47%
3476
September1st to 10thNight
12%5%27%44436%7%46%
1900
11th to 20thNight
11%6%2433435%7%52%
1900
21st to endNight
19%6%26%44435%7%40%
2166
October1st to 10thNight
19%6%25%43335%5%45%
2280
11th to 20thNight
14%5%25%43435%6%49%
2280
21st to endNight
16%6%2433335%7%48%
2508
November1st to 10thNight
10%5%25%43335%6%53%
2495
11th to 20thNight
14%7%26%44435%6%45%
2634
21st to endNight
13%5%26%5%4446%7%44%
2800
December1st to 10thNight
16%8%27%445%45%7%37%
2800
11th to 20thNight
17%7%27%5%5%445%6%38%
3425
21st to endNight
16%9%38%5%5%5%5%6%8%32%
4933

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
40%7%13%25%11%4
2518
11th to 20thDay
50%7%10%17%12%3
2785
21st to endDay
52%6%10%23%7%2
3124
February1st to 10thDay
46%6%12%23%11%2
1710
11th to 20thDay
45%6%10%25%13%3
1726
21st to endDay
49%5%10%20%12%4
1570
March1st to 10thDay
47%6%10%24%11%2
3326
11th to 20thDay
35%7%11%26%16%4
3480
21st to endDay
45%5%9%22%16%3
3909
April1st to 10thDay
44%7%11%19%16%4
2280
11th to 20thDay
40%6%11%22%17%4
2254
21st to endDay
43%6%10%22%17%3
2280
May1st to 10thDay
52%7%9%20%10%1
4071
11th to 20thDay
52%9%12%17%8%1
4397
21st to endDay
33%9%14%25%17%2
4837
June1st to 10thDay
38%8%13%24%16%1
2660
11th to 20thDay
39%9%14%23%13%2
2660
21st to endDay
33%8%14%27%16%1
2660
July1st to 10thDay
35%9%16%23%14%4
4370
11th to 20thDay
36%7%16%26%13%2
4365
21st to endDay
42%8%11%19%18%2
4334
August1st to 10thDay
45%8%14%24%9%
4091
11th to 20thDay
37%7%12%28%15%1
3907
21st to endDay
34%6%11%27%19%2
4180
September1st to 10thDay
39%6%11%19%20%4
2280
11th to 20thDay
33%6%10%27%20%4
2280
21st to endDay
46%5%9%18%20%2
2010
October1st to 10thDay
37%47%21%26%5%
3160
11th to 20thDay
27%412%28%22%7%
3140
21st to endDay
26%410%29%28%2
3428
November1st to 10thDay
34%313%25%21%4
1801
11th to 20thDay
38%5%10%24%19%3
1765
21st to endDay
40%6%11%30%11%2
1600
December1st to 10thDay
47%5%15%21%10%1
1600
11th to 20thDay
45%8%11%27%8%1
1986
21st to endDay
48%9%15%18%10%1
2796
January1st to 10thNight
43%7%11%25%11%3
4429
11th to 20thNight
43%6%12%25%12%2
4170
21st to endNight
49%6%8%26%9%2
4532
February1st to 10thNight
45%5%13%24%12%1
2470
11th to 20thNight
45%310%21%18%3
2349
21st to endNight
45%6%10%19%14%5%
1884
March1st to 10thNight
47%6%10%25%11%1
3524
11th to 20thNight
34%8%10%32%14%2
3480
21st to endNight
41%5%7%21%21%4
3722
April1st to 10thNight
45%6%10%19%16%4
1900
11th to 20thNight
38%7%11%21%19%5%
1875
21st to endNight
40%6%10%22%17%4
1900
May1st to 10thNight
52%7%8%18%12%3
2918
11th to 20thNight
52%10%11%14%11%1
2496
21st to endNight
35%10%15%25%11%3
2739
June1st to 10thNight
35%8%11%26%18%2
1520
11th to 20thNight
35%10%14%22%16%2
1520
21st to endNight
34%8%14%25%17%2
1520
July1st to 10thNight
36%9%18%19%13%5%
2480
11th to 20thNight
36%9%16%23%14%1
2472
21st to endNight
39%8%13%19%18%1
2974
August1st to 10thNight
44%7%18%22%8%1
2814
11th to 20thNight
40%7%11%26%16%1
2953
21st to endNight
35%6%12%29%16%2
3476
September1st to 10thNight
37%6%11%20%21%4
1900
11th to 20thNight
32%6%9%25%25%3
1900
21st to endNight
43%6%10%19%19%3
2166
October1st to 10thNight
41%5%11%20%21%2
3800
11th to 20thNight
26%411%27%27%5%
3779
21st to endNight
25%411%33%24%3
4120
November1st to 10thNight
33%5%10%26%22%4
2495
11th to 20thNight
39%49%24%19%5%
2634
21st to endNight
37%6%12%27%16%2
2800
December1st to 10thNight
46%5%13%24%12%1
2800
11th to 20thNight
43%5%13%22%15%2
3428
21st to endNight
46%9%15%20%9%1
4933

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
26%23%32%15%4
256
21st to endDay
22%22%37%14%5%1
297
February1st to 10thDay
22%19%39%16%31
270
11th to 20thDay
26%22%40%11%1
324
21st to endDay
28%18%34%17%3
382
March1st to 10thDay
19%19%32%25%5%
460
11th to 20thDay
21%20%35%19%32
460
21st to endDay
25%16%30%20%7%2
506
April1st to 10thDay
21%17%35%18%8%2
460
11th to 20thDay
17%17%29%19%12%5%
452
21st to endDay
25%12%27%24%9%3
460
May1st to 10thDay
28%11%26%20%12%4
463
11th to 20thDay
21%9%27%25%14%5%
487
21st to endDay
16%5%19%28%24%9%
529
June1st to 10thDay
15%7%26%26%18%9%
490
11th to 20thDay
13%7%22%28%21%8%
490
21st to endDay
11%5%24%31%21%8%
490
July1st to 10thDay
11%5%16%29%26%14%
485
11th to 20thDay
5%417%30%31%13%
484
21st to endDay
12%417%33%25%8%
532
August1st to 10thDay
12%315%30%29%11%
486
11th to 20thDay
12%5%16%28%25%13%
479
21st to endDay
11%5%14%29%27%14%
539
September1st to 10thDay
17%5%17%22%22%16%
490
11th to 20thDay
13%414%30%25%15%
490
21st to endDay
26%8%21%25%14%6%
490
October1st to 10thDay
19%7%22%24%17%11%
490
11th to 20thDay
16%9%29%24%18%3
490
21st to endDay
16%9%36%25%11%4
539
November1st to 10thDay
15%11%29%29%14%2
415
11th to 20thDay
17%15%30%26%11%1
365
21st to endDay
18%21%35%19%9%
200
December1st to 10thDay
23%18%34%18%6%3
200
11th to 20thDay
26%16%33%18%7%1
200
21st to endDay
21%14%33%23%10%
204
January1st to 10thNight
17%13%43%23%3
760
11th to 20thNight
21%14%32%29%4
760
21st to endNight
17%13%43%25%2
836
February1st to 10thNight
21%14%34%29%3
760
11th to 20thNight
22%15%41%21%1
743
21st to endNight
21%16%41%19%3
628
March1st to 10thNight
17%13%40%25%5%
760
11th to 20thNight
21%13%36%25%5%
760
21st to endNight
21%10%38%25%5%1
836
April1st to 10thNight
21%13%38%24%5%
760
11th to 20thNight
17%9%34%31%9%
751
21st to endNight
20%9%32%29%9%
760
May1st to 10thNight
19%9%26%33%12%
622
11th to 20thNight
20%427%38%11%
374
21st to endNight
14%318%43%20%2
411
June1st to 10thNight
13%222%41%20%1
380
11th to 20thNight
11%323%44%18%1
380
21st to endNight
9%221%52%16%
380
July1st to 10thNight
8%317%41%28%3
370
11th to 20thNight
5%212%46%32%3
368
21st to endNight
11%212%45%28%2
609
August1st to 10thNight
11%28%48%29%2
567
11th to 20thNight
11%410%42%30%3
640
21st to endNight
12%213%38%31%3
836
September1st to 10thNight
14%316%36%28%3
760
11th to 20thNight
12%214%38%30%4
760
21st to endNight
22%319%33%21%2
760
October1st to 10thNight
21%5%21%29%21%4
760
11th to 20thNight
16%7%28%34%14%1
760
21st to endNight
19%5%34%31%11%
836
November1st to 10thNight
14%6%32%36%11%1
780
11th to 20thNight
17%11%33%30%8%1
800
21st to endNight
14%12%37%29%8%
800
December1st to 10thNight
21%11%37%24%6%
800
11th to 20thNight
18%9%39%30%5%
800
21st to endNight
19%10%36%33%2
851
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