Thedford
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Thedford clear sky chart from 2005-11-06 to 2024-03-01.

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%
24901
22%
80067
12%
24803
49%
24803
31%
46712

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
30%
940
21%
4363
8%
926
42%
926
18%
2664
January11th to 20thNight
30%
947
23%
4317
9%
930
43%
930
20%
2343
January21st to endNight
29%
1035
16%
4592
7%
1023
40%
1023
21%
2499
February1st to 10thNight
27%
879
17%
2399
6%
879
36%
879
26%
1609
February11th to 20thNight
25%
744
21%
2218
7%
740
37%
740
28%
1375
February21st to endNight
31%
628
22%
1884
7%
628
43%
628
33%
1104
March1st to 10thNight
33%
722
23%
2166
9%
722
43%
722
32%
1268
March11th to 20thNight
34%
590
23%
2030
15%
590
46%
590
29%
1158
March21st to endNight
33%
594
16%
2124
10%
594
42%
594
22%
1338
April1st to 10thNight
30%
540
19%
1800
11%
540
42%
540
26%
1087
April11th to 20thNight
26%
533
19%
1735
9%
533
41%
533
24%
1079
April21st to endNight
38%
540
20%
1620
16%
540
47%
540
27%
1031
May1st to 10thNight
41%
540
16%
1620
12%
540
48%
540
27%
1033
May11th to 20thNight
37%
531
15%
1593
10%
531
43%
531
26%
1033
May21st to endNight
39%
583
14%
1608
7%
582
43%
582
26%
1096
June1st to 10thNight
54%
540
17%
1440
9%
540
56%
540
39%
864
June11th to 20thNight
45%
540
17%
1440
6%
540
48%
540
36%
894
June21st to endNight
58%
540
18%
1440
10%
540
61%
540
41%
845
July1st to 10thNight
56%
525
15%
1400
7%
525
58%
525
42%
825
July11th to 20thNight
60%
522
23%
1392
13%
522
64%
522
44%
811
July21st to endNight
62%
591
23%
1505
16%
558
65%
558
40%
898
August1st to 10thNight
62%
537
18%
1601
17%
534
65%
534
33%
958
August11th to 20thNight
60%
534
25%
1600
23%
534
67%
534
40%
888
August21st to endNight
57%
594
27%
1966
25%
594
67%
594
42%
995
September1st to 10thNight
55%
540
27%
1822
24%
540
66%
540
40%
929
September11th to 20thNight
54%
540
29%
1980
26%
540
66%
540
38%
975
September21st to endNight
47%
540
29%
1980
21%
540
60%
540
36%
974
October1st to 10thNight
44%
540
30%
1980
23%
540
55%
540
30%
1075
October11th to 20thNight
43%
719
31%
2159
15%
719
55%
719
40%
1150
October21st to endNight
37%
990
28%
2574
12%
990
45%
990
38%
1539
November1st to 10thNight
43%
925
29%
2405
11%
925
52%
925
43%
1365
November11th to 20thNight
36%
950
31%
2470
12%
950
49%
950
41%
1438
November21st to endNight
39%
950
28%
2470
13%
950
49%
950
40%
1466
December1st to 10thNight
30%
950
23%
2541
8%
950
43%
950
37%
1500
December11th to 20thNight
32%
949
26%
3073
11%
948
43%
948
33%
1639
December21st to endNight
28%
1039
16%
4760
8%
1026
41%
1026
17%
2967

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
9%6%25%43445%7%51%
78478
Night
8%6%25%5%3445%7%51%
80979
TransparencyDay
32%7%14%27%17%4
78185
Night
32%6%14%27%17%3
80795
SeeingDay
11%8%31%32%15%3
14787
Night
10%8%37%36%8%
24932

By Month

Percentage Cloud Cover SW (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
410%49%5%23335%50%
2538
11th to 20thDay
5%8%36%5%46%6%6%9%42%
2540
21st to endDay
46%36%5%345%5%7%54%
2825
February1st to 10thDay
7%9%6%7%6%35%5%5%7%41%
1795
11th to 20thDay
8%7%47%5%33446%49%
1849
21st to endDay
8%7%35%424345%55%
1570
March1st to 10thDay
8%5%15%5%2335%7%56%
1800
11th to 20thDay
9%8%334245%5%8%48%
1930
21st to endDay
12%9%46%6%345%5%7%39%
2227
April1st to 10thDay
13%6%2433435%8%49%
2160
11th to 20thDay
15%7%35%5%35%346%42%
2171
21st to endDay
15%6%25%324446%47%
2340
May1st to 10thDay
13%5%344345%5%7%47%
2340
11th to 20thDay
16%5%245%35%45%8%44%
2302
21st to endDay
15%6%345%345%5%8%42%
2665
June1st to 10thDay
7%3234345%6%10%54%
2520
11th to 20thDay
11%42442446%8%52%
2520
21st to endDay
42134345%6%8%60%
2520
July1st to 10thDay
7%4245%35%5%6%9%51%
2520
11th to 20thDay
6%2134245%5%8%59%
2520
21st to endDay
6%3245%35%5%7%9%52%
2721
August1st to 10thDay
7%425%5%45%7%8%9%45%
2328
11th to 20thDay
6%3245%345%5%8%55%
2301
21st to endDay
7%324425%346%60%
2388
September1st to 10thDay
9%42432336%5%59%
2138
11th to 20thDay
7%31431345%7%61%
1980
21st to endDay
10%423323345%62%
1980
October1st to 10thDay
13%5%23322345%58%
1980
11th to 20thDay
9%5%2332345%6%59%
1781
21st to endDay
12%6%25%423336%54%
1782
November1st to 10thDay
6%42443446%8%56%
1673
11th to 20thDay
5%6%245%24446%58%
1710
21st to endDay
7%7%34324446%56%
1710
December1st to 10thDay
6%8%35%43445%8%50%
1634
11th to 20thDay
5%5%345%2346%8%55%
1926
21st to endDay
13%13%36%7%23446%38%
2794
January1st to 10thNight
5%10%39%7%345%5%7%41%
4417
11th to 20thNight
48%48%5%3445%8%48%
4430
21st to endNight
36%37%6%35%5%5%7%50%
4840
February1st to 10thNight
9%9%47%6%45%45%6%43%
2399
11th to 20thNight
6%7%36%6%45%5%5%7%45%
2218
21st to endNight
5%8%34445%45%6%53%
1884
March1st to 10thNight
7%8%25%5%3445%6%52%
2166
11th to 20thNight
10%8%25%42345%7%51%
2030
21st to endNight
12%8%35%5%345%6%8%41%
2124
April1st to 10thNight
12%6%35%43446%7%45%
1800
11th to 20thNight
15%7%3433446%6%46%
1735
21st to endNight
13%5%345%35%36%7%46%
1620
May1st to 10thNight
12%6%25%435%46%9%45%
1620
11th to 20thNight
16%6%25%4345%5%7%44%
1593
21st to endNight
17%6%24435%6%6%10%39%
1607
June1st to 10thNight
9%3244235%410%54%
1440
11th to 20thNight
11%424435%5%6%9%49%
1440
21st to endNight
5%2145%36%5%8%10%51%
1440
July1st to 10thNight
6%3235%25%5%6%10%53%
1440
11th to 20thNight
4413435%5%6%8%57%
1440
21st to endNight
4325%5%45%5%7%9%52%
1594
August1st to 10thNight
5%4247%35%5%6%9%49%
1611
11th to 20thNight
7%31343436%8%56%
1600
21st to endNight
5%32342446%9%59%
1966
September1st to 10thNight
8%314424446%60%
1822
11th to 20thNight
7%4144235%46%60%
1980
21st to endNight
11%413223335%62%
1980
October1st to 10thNight
15%323423347%55%
1980
11th to 20thNight
9%5%14323346%61%
2159
21st to endNight
11%6%24323335%58%
2574
November1st to 10thNight
6%5%243245%5%7%58%
2405
11th to 20thNight
5%5%245%3446%7%56%
2470
21st to endNight
6%6%3443445%8%55%
2470
December1st to 10thNight
6%6%35%5%33448%54%
2541
11th to 20thNight
5%7%3442346%8%55%
3271
21st to endNight
14%12%35%5%23346%42%
4873

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
38%5%11%29%15%1
2539
11th to 20thDay
35%11%17%21%13%2
2540
21st to endDay
30%6%20%27%15%3
2825
February1st to 10thDay
43%6%14%22%13%3
1795
11th to 20thDay
37%414%23%17%5%
1859
21st to endDay
32%5%14%28%16%5%
1570
March1st to 10thDay
29%5%15%27%21%3
1800
11th to 20thDay
33%6%16%26%18%2
1930
21st to endDay
43%9%16%21%9%1
2227
April1st to 10thDay
34%6%18%26%13%3
2160
11th to 20thDay
42%7%12%23%14%3
2174
21st to endDay
37%6%14%27%14%1
2340
May1st to 10thDay
36%7%16%27%14%
2340
11th to 20thDay
39%8%18%25%9%1
2306
21st to endDay
39%8%18%21%12%2
2665
June1st to 10thDay
26%8%20%32%12%2
2520
11th to 20thDay
29%8%16%27%17%4
2520
21st to endDay
21%7%16%31%21%3
2520
July1st to 10thDay
28%8%16%27%18%3
2451
11th to 20thDay
22%7%13%26%24%7%
2445
21st to endDay
26%8%14%29%19%4
2570
August1st to 10thDay
31%11%17%24%13%4
2314
11th to 20thDay
26%7%12%32%20%3
2301
21st to endDay
25%6%10%27%24%8%
2388
September1st to 10thDay
25%6%12%25%23%10%
2138
11th to 20thDay
22%6%12%29%25%6%
1980
21st to endDay
26%49%31%26%4
1980
October1st to 10thDay
29%5%10%26%26%4
1980
11th to 20thDay
25%5%13%29%21%7%
1781
21st to endDay
33%410%28%19%6%
1782
November1st to 10thDay
26%6%17%26%20%5%
1673
11th to 20thDay
27%5%11%29%22%5%
1710
21st to endDay
30%413%28%20%5%
1710
December1st to 10thDay
32%6%13%28%17%3
1634
11th to 20thDay
27%6%15%35%15%1
1924
21st to endDay
46%6%10%25%11%2
2794
January1st to 10thNight
40%7%12%25%13%1
4417
11th to 20thNight
35%5%16%28%14%1
4430
21st to endNight
32%8%16%27%16%1
4840
February1st to 10thNight
42%5%14%22%14%3
2399
11th to 20thNight
37%7%13%26%13%4
2218
21st to endNight
32%5%15%25%18%5%
1884
March1st to 10thNight
34%5%13%26%19%4
2166
11th to 20thNight
34%6%11%25%22%2
2030
21st to endNight
40%8%16%23%12%1
2124
April1st to 10thNight
37%7%16%21%15%4
1800
11th to 20thNight
39%6%14%24%14%3
1735
21st to endNight
38%7%12%28%13%2
1620
May1st to 10thNight
35%10%17%24%13%1
1620
11th to 20thNight
38%9%16%25%10%1
1594
21st to endNight
40%9%18%21%9%2
1608
June1st to 10thNight
26%9%20%30%12%2
1440
11th to 20thNight
31%8%17%26%12%6%
1440
21st to endNight
25%9%17%31%16%2
1440
July1st to 10thNight
26%8%17%31%15%3
1400
11th to 20thNight
23%9%13%28%21%6%
1392
21st to endNight
27%9%16%24%21%4
1505
August1st to 10thNight
30%10%19%25%13%3
1601
11th to 20thNight
26%7%14%32%17%4
1600
21st to endNight
21%8%12%27%24%8%
1966
September1st to 10thNight
25%5%10%26%27%7%
1822
11th to 20thNight
23%7%12%29%23%6%
1980
21st to endNight
27%410%28%28%4
1980
October1st to 10thNight
31%6%10%26%24%4
1980
11th to 20thNight
26%410%29%24%7%
2159
21st to endNight
31%410%25%23%7%
2574
November1st to 10thNight
25%6%14%25%24%6%
2405
11th to 20thNight
27%5%13%26%23%6%
2470
21st to endNight
29%5%13%27%23%4
2470
December1st to 10thNight
30%5%16%27%18%4
2541
11th to 20thNight
28%5%13%37%16%1
3272
21st to endNight
43%6%11%27%11%2
4873

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
7%10%39%28%14%2
270
11th to 20thDay
10%14%36%30%9%1
270
21st to endDay
11%11%43%23%8%3
297
February1st to 10thDay
12%12%46%24%5%
270
11th to 20thDay
14%12%41%23%9%1
270
21st to endDay
12%15%45%24%4
225
March1st to 10thDay
11%12%38%24%13%2
240
11th to 20thDay
13%9%35%30%11%1
240
21st to endDay
18%14%35%24%7%3
313
April1st to 10thDay
14%15%36%28%6%
420
11th to 20thDay
20%13%35%25%6%
452
21st to endDay
18%12%30%27%11%2
600
May1st to 10thDay
14%8%34%30%12%2
603
11th to 20thDay
19%8%31%26%13%3
625
21st to endDay
17%8%30%29%14%3
679
June1st to 10thDay
5%427%33%22%8%
630
11th to 20thDay
11%5%31%33%16%3
630
21st to endDay
5%5%28%39%20%3
630
July1st to 10thDay
6%5%21%39%24%5%
621
11th to 20thDay
5%123%43%24%5%
618
21st to endDay
6%420%44%25%3
684
August1st to 10thDay
7%318%45%23%4
626
11th to 20thDay
7%325%40%22%3
615
21st to endDay
5%425%38%23%5%
507
September1st to 10thDay
8%429%34%20%6%
428
11th to 20thDay
4425%33%26%9%
270
21st to endDay
14%8%29%31%16%2
270
October1st to 10thDay
18%6%23%32%15%6%
270
11th to 20thDay
9%10%38%30%10%3
270
21st to endDay
13%12%29%32%11%2
297
November1st to 10thDay
10%14%35%24%14%3
270
11th to 20thDay
10%9%40%31%9%1
270
21st to endDay
16%8%39%24%9%4
270
December1st to 10thDay
10%10%47%24%8%1
270
11th to 20thDay
13%10%41%25%11%
270
21st to endDay
17%12%42%23%41
297
January1st to 10thNight
8%11%44%29%7%1
950
11th to 20thNight
8%15%41%29%5%1
950
21st to endNight
9%10%45%28%8%
1045
February1st to 10thNight
13%10%44%28%4
879
11th to 20thNight
10%9%51%24%5%
744
21st to endNight
9%10%46%31%4
628
March1st to 10thNight
12%10%42%32%5%
722
11th to 20thNight
12%9%42%33%5%
590
21st to endNight
17%7%38%31%7%
594
April1st to 10thNight
15%10%41%31%2
540
11th to 20thNight
17%11%43%25%3
533
21st to endNight
15%11%31%33%9%
540
May1st to 10thNight
14%8%31%38%8%1
540
11th to 20thNight
18%6%34%31%10%1
531
21st to endNight
17%7%32%35%8%1
584
June1st to 10thNight
10%428%42%14%1
540
11th to 20thNight
11%6%35%38%10%
540
21st to endNight
5%428%51%12%
540
July1st to 10thNight
5%430%44%16%
525
11th to 20thNight
5%228%54%11%
522
21st to endNight
5%224%56%13%
591
August1st to 10thNight
6%320%55%15%
537
11th to 20thNight
7%325%52%13%
534
21st to endNight
5%231%47%15%
594
September1st to 10thNight
8%430%45%13%1
540
11th to 20thNight
7%430%45%14%1
540
21st to endNight
13%6%31%39%10%1
540
October1st to 10thNight
17%6%30%35%13%
540
11th to 20thNight
11%10%32%36%10%
719
21st to endNight
14%11%34%31%9%1
990
November1st to 10thNight
7%7%39%39%7%1
925
11th to 20thNight
8%10%41%34%7%
950
21st to endNight
9%7%41%34%8%1
950
December1st to 10thNight
9%13%44%28%6%
950
11th to 20thNight
10%10%42%31%6%
950
21st to endNight
13%12%40%30%5%
1045
Page generated at 2024-02-27 05:30:16. Version ac07

Copyright © 2024 Attilla Danko.


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