Tatum
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tatum clear sky chart from 2005-11-06 to 2024-03-18.

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
54%
24278
33%
79191
21%
24185
66%
24185
45%
37942

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
47%
923
38%
4217
17%
908
61%
908
36%
1729
January11th to 20thNight
46%
756
43%
3739
22%
740
62%
740
43%
1249
January21st to endNight
47%
826
28%
3881
21%
814
66%
814
32%
1755
February1st to 10thNight
39%
760
38%
2280
16%
760
60%
760
49%
1109
February11th to 20thNight
36%
742
31%
2218
14%
740
51%
740
42%
1163
February21st to endNight
30%
628
36%
1884
12%
628
51%
628
43%
948
March1st to 10thNight
37%
760
34%
2280
16%
760
53%
760
42%
1195
March11th to 20thNight
41%
736
31%
2195
15%
736
54%
736
41%
1147
March21st to endNight
34%
594
40%
1980
18%
594
60%
594
46%
895
April1st to 10thNight
37%
540
37%
1800
19%
540
60%
540
48%
812
April11th to 20thNight
32%
533
34%
1777
17%
533
56%
533
43%
847
April21st to endNight
38%
540
38%
1800
21%
540
65%
540
53%
763
May1st to 10thNight
41%
540
30%
1792
20%
540
60%
540
48%
830
May11th to 20thNight
51%
531
30%
1593
22%
531
63%
531
48%
799
May21st to endNight
50%
583
29%
1745
20%
582
63%
582
47%
879
June1st to 10thNight
57%
540
25%
1620
19%
540
66%
540
50%
809
June11th to 20thNight
60%
540
34%
1491
24%
540
71%
540
62%
715
June21st to endNight
68%
540
29%
1440
22%
540
73%
540
56%
740
July1st to 10thNight
76%
525
24%
1400
21%
525
77%
525
46%
789
July11th to 20thNight
82%
522
28%
1507
27%
522
84%
522
51%
758
July21st to endNight
84%
591
26%
1859
31%
558
84%
558
48%
872
August1st to 10thNight
83%
537
28%
1779
34%
534
83%
534
45%
871
August11th to 20thNight
79%
534
26%
1778
30%
534
81%
534
38%
928
August21st to endNight
79%
594
25%
1980
29%
594
80%
594
40%
1028
September1st to 10thNight
75%
540
26%
1800
30%
540
76%
540
38%
953
September11th to 20thNight
70%
540
31%
1926
33%
540
73%
540
35%
1020
September21st to endNight
71%
540
35%
1980
36%
540
76%
540
43%
907
October1st to 10thNight
65%
540
36%
1980
32%
540
73%
540
42%
939
October11th to 20thNight
60%
650
40%
2090
25%
650
72%
650
53%
944
October21st to endNight
59%
793
41%
2377
22%
793
70%
793
54%
1111
November1st to 10thNight
63%
925
38%
2405
19%
925
71%
925
62%
1182
November11th to 20thNight
60%
950
36%
2470
18%
950
69%
950
58%
1247
November21st to endNight
51%
950
38%
2470
17%
950
63%
950
50%
1319
December1st to 10thNight
50%
950
39%
2470
18%
950
62%
950
50%
1338
December11th to 20thNight
43%
948
38%
2886
16%
948
58%
948
43%
1518
December21st to endNight
41%
1037
25%
4302
17%
1026
55%
1026
38%
1834

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
5%42332345%7%62%
79420
Night
5%31332345%7%63%
80374
TransparencyDay
23%47%19%28%19%
79149
Night
21%48%19%28%20%
80168
SeeingDay
6%6%22%32%26%9%
14102
Night
6%5%31%40%17%1
24314

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
5%7%25%423335%61%
2603
11th to 20thDay
3211112346%75%
3045
21st to endDay
6%6%2442445%7%55%
3487
February1st to 10thDay
4423323445%65%
1900
11th to 20thDay
6%5%24323436%62%
1849
21st to endDay
4423323346%65%
1570
March1st to 10thDay
45%2343345%8%58%
1900
11th to 20thDay
8%5%23322436%61%
1925
21st to endDay
44133235%5%7%63%
2376
April1st to 10thDay
4312223446%69%
2160
11th to 20thDay
5%423222346%66%
2131
21st to endDay
3312313346%71%
2160
May1st to 10thDay
5%413323245%67%
2168
11th to 20thDay
7%42432346%6%59%
2302
21st to endDay
5%21332345%7%64%
2531
June1st to 10thDay
3223424448%63%
2340
11th to 20thDay
3212324449%67%
2462
21st to endDay
42234345%6%8%59%
2520
July1st to 10thDay
5%4245%45%5%8%10%48%
2520
11th to 20thDay
42235%345%5%8%58%
2397
21st to endDay
42145%36%6%7%9%52%
2349
August1st to 10thDay
3313345%5%7%11%55%
2149
11th to 20thDay
5%325%5%46%7%7%9%45%
2123
21st to endDay
5%3146%45%5%7%9%50%
2376
September1st to 10thDay
9%4244346%5%8%52%
2160
11th to 20thDay
10%5%25%5%35%45%6%50%
2033
21st to endDay
8%313312346%65%
1980
October1st to 10thDay
7%32442235%6%62%
1980
11th to 20thDay
8%31332222471%
1867
21st to endDay
5%31231224472%
1958
November1st to 10thDay
5%312313336%70%
1673
11th to 20thDay
3324322246%70%
1710
21st to endDay
8%422222446%64%
1710
December1st to 10thDay
6%424223446%61%
1710
11th to 20thDay
34244345%6%7%58%
2161
21st to endDay
5%423212235%71%
3135
January1st to 10thNight
35%2332445%7%62%
4339
11th to 20thNight
321221335%7%70%
3912
21st to endNight
5%32442446%9%58%
4180
February1st to 10thNight
4423313446%65%
2280
11th to 20thNight
6%32442335%7%60%
2218
21st to endNight
44134245%5%5%64%
1884
March1st to 10thNight
5%5%3442335%6%61%
2280
11th to 20thNight
7%424323447%60%
2195
21st to endNight
3423323346%68%
1980
April1st to 10thNight
3323323445%69%
1800
11th to 20thNight
6%31332335%7%63%
1777
21st to endNight
3212322447%71%
1800
May1st to 10thNight
442232335%7%66%
1792
11th to 20thNight
6%313423347%64%
1593
21st to endNight
6%213325%46%8%61%
1745
June1st to 10thNight
32134246%7%11%58%
1620
11th to 20thNight
2123235%6%9%66%
1491
21st to endNight
33132245%7%10%62%
1440
July1st to 10thNight
5%314435%5%6%9%55%
1440
11th to 20thNight
32134345%6%11%58%
1555
21st to endNight
42134245%7%12%56%
1969
August1st to 10thNight
32244345%7%11%54%
1790
11th to 20thNight
4314435%5%7%11%50%
1778
21st to endNight
42145%35%6%8%10%52%
1980
September1st to 10thNight
7%4234345%6%8%55%
1800
11th to 20thNight
9%5%1442346%7%55%
1926
21st to endNight
8%312323345%65%
1980
October1st to 10thNight
7%314333435%65%
1980
11th to 20thNight
7%31221233374%
2090
21st to endNight
6%31222233472%
2377
November1st to 10thNight
5%312212335%73%
2405
11th to 20thNight
2213223447%70%
2470
21st to endNight
7%31332335%7%63%
2470
December1st to 10thNight
6%5%14223347%62%
2470
11th to 20thNight
442442445%7%61%
3036
21st to endNight
4413423335%68%
4532

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
26%3315%32%20%
2604
11th to 20thDay
12%27%22%40%17%
3045
21st to endDay
28%46%20%29%14%
3487
February1st to 10thDay
22%26%17%28%25%
1900
11th to 20thDay
25%3418%26%24%
1859
21st to endDay
22%4211%32%30%
1570
March1st to 10thDay
26%2314%33%22%
1900
11th to 20thDay
26%3415%30%22%
1925
21st to endDay
21%35%18%29%25%
2376
April1st to 10thDay
17%4414%31%30%
2160
11th to 20thDay
20%3416%24%32%
2134
21st to endDay
16%25%19%31%27%
2160
May1st to 10thDay
21%26%15%25%31%
2168
11th to 20thDay
25%5%7%16%25%22%
2306
21st to endDay
20%5%9%19%21%26%
2531
June1st to 10thDay
21%5%11%25%23%16%
2340
11th to 20thDay
16%38%18%25%30%
2462
21st to endDay
22%5%9%21%25%18%
2520
July1st to 10thDay
29%6%14%24%20%7%
2451
11th to 20thDay
22%5%14%25%26%8%
2322
21st to endDay
24%7%18%30%19%2
2219
August1st to 10thDay
21%6%15%30%23%5%
2136
11th to 20thDay
31%8%15%23%18%5%
2123
21st to endDay
28%7%13%24%21%7%
2376
September1st to 10thDay
29%7%12%18%21%13%
2160
11th to 20thDay
35%5%8%19%25%9%
2033
21st to endDay
22%45%20%33%16%
1980
October1st to 10thDay
23%48%22%24%19%
1980
11th to 20thDay
21%3413%31%29%
1867
21st to endDay
18%3220%34%24%
1958
November1st to 10thDay
18%25%17%33%26%
1673
11th to 20thDay
18%25%19%36%20%
1710
21st to endDay
22%35%16%30%23%
1710
December1st to 10thDay
26%35%21%31%15%
1710
11th to 20thDay
25%47%20%26%18%
2159
21st to endDay
19%2320%33%23%
3135
January1st to 10thNight
21%4417%40%15%
4339
11th to 20thNight
15%28%20%36%18%
3912
21st to endNight
24%46%22%31%14%
4180
February1st to 10thNight
21%35%17%26%28%
2280
11th to 20thNight
25%4416%27%25%
2218
21st to endNight
22%4411%25%35%
1884
March1st to 10thNight
25%3314%24%29%
2280
11th to 20thNight
25%35%15%29%23%
2195
21st to endNight
19%36%18%27%27%
1980
April1st to 10thNight
18%35%14%27%32%
1800
11th to 20thNight
21%46%16%23%31%
1777
21st to endNight
15%36%21%28%28%
1800
May1st to 10thNight
20%38%15%20%34%
1792
11th to 20thNight
21%5%10%18%23%24%
1594
21st to endNight
21%412%20%17%26%
1746
June1st to 10thNight
19%5%14%26%21%15%
1620
11th to 20thNight
13%5%9%19%26%28%
1491
21st to endNight
16%6%13%22%25%17%
1440
July1st to 10thNight
24%6%18%28%19%6%
1400
11th to 20thNight
20%5%15%25%28%7%
1507
21st to endNight
19%5%19%32%21%3
1859
August1st to 10thNight
21%6%15%31%21%7%
1779
11th to 20thNight
25%6%16%28%19%5%
1778
21st to endNight
23%7%15%27%20%7%
1980
September1st to 10thNight
27%6%13%18%25%12%
1800
11th to 20thNight
29%6%13%21%21%11%
1926
21st to endNight
22%37%18%31%18%
1980
October1st to 10thNight
23%48%21%23%21%
1980
11th to 20thNight
19%25%13%31%31%
2090
21st to endNight
18%2416%33%27%
2377
November1st to 10thNight
15%3419%33%26%
2405
11th to 20thNight
16%4416%36%24%
2470
21st to endNight
23%2417%32%23%
2470
December1st to 10thNight
23%2420%31%20%
2470
11th to 20thNight
23%35%18%32%19%
3037
21st to endNight
21%3315%38%20%
4532

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
10%7%41%29%13%1
270
11th to 20thDay
8%12%35%29%14%2
270
21st to endDay
411%33%33%16%2
297
February1st to 10thDay
8%10%35%34%11%1
270
11th to 20thDay
8%11%38%30%11%1
270
21st to endDay
7%17%41%31%4
225
March1st to 10thDay
7%9%37%37%9%1
270
11th to 20thDay
11%15%24%35%12%3
302
21st to endDay
5%15%37%32%9%2
462
April1st to 10thDay
7%10%35%35%12%1
420
11th to 20thDay
7%12%43%26%11%1
412
21st to endDay
5%11%36%34%12%2
420
May1st to 10thDay
310%35%39%11%2
431
11th to 20thDay
7%5%27%36%21%4
625
21st to endDay
6%428%41%19%2
679
June1st to 10thDay
4315%42%29%7%
630
11th to 20thDay
3116%47%27%6%
630
21st to endDay
4110%37%38%10%
630
July1st to 10thDay
5%5%29%42%18%
621
11th to 20thDay
31326%47%20%
575
21st to endDay
31220%46%29%
487
August1st to 10thDay
415%18%45%26%
447
11th to 20thDay
5%16%21%45%22%
437
21st to endDay
7%1421%41%27%
495
September1st to 10thDay
8%426%41%20%
450
11th to 20thDay
5%1424%49%18%
323
21st to endDay
12%17%23%41%16%
270
October1st to 10thDay
12%215%29%34%7%
270
11th to 20thDay
8%223%33%23%11%
270
21st to endDay
10%425%25%24%11%
297
November1st to 10thDay
10%6%24%31%25%4
270
11th to 20thDay
310%21%35%23%8%
270
21st to endDay
9%13%31%27%15%4
270
December1st to 10thDay
9%10%30%33%17%1
270
11th to 20thDay
5%10%34%39%12%1
270
21st to endDay
8%8%42%34%8%1
297
January1st to 10thNight
6%7%34%40%12%1
932
11th to 20thNight
7%6%38%35%12%2
760
21st to endNight
6%7%37%40%9%
836
February1st to 10thNight
7%6%45%32%9%1
760
11th to 20thNight
8%8%45%33%6%1
744
21st to endNight
6%9%52%29%3
628
March1st to 10thNight
7%9%43%36%5%
760
11th to 20thNight
10%9%37%36%7%1
736
21st to endNight
5%10%49%31%5%
594
April1st to 10thNight
47%47%36%5%
540
11th to 20thNight
7%9%50%32%2
533
21st to endNight
410%46%35%5%
540
May1st to 10thNight
6%6%45%39%4
540
11th to 20thNight
7%5%35%43%10%1
531
21st to endNight
6%338%43%10%
584
June1st to 10thNight
3235%51%9%
540
11th to 20thNight
2135%53%9%
540
21st to endNight
3125%48%23%
540
July1st to 10thNight
5%210%49%32%2
525
11th to 20thNight
45%48%42%2
522
21st to endNight
215%43%46%2
591
August1st to 10thNight
21440%50%2
537
11th to 20thNight
416%40%48%1
534
21st to endNight
6%7%39%47%2
594
September1st to 10thNight
7%18%45%35%3
540
11th to 20thNight
9%111%46%30%1
540
21st to endNight
9%115%45%28%1
540
October1st to 10thNight
7%321%48%21%
540
11th to 20thNight
9%326%44%17%2
650
21st to endNight
8%6%25%37%22%3
793
November1st to 10thNight
6%324%45%20%1
925
11th to 20thNight
25%28%45%18%1
950
21st to endNight
9%7%29%37%16%1
950
December1st to 10thNight
9%5%33%39%13%1
950
11th to 20thNight
8%6%39%38%9%
950
21st to endNight
8%9%38%34%9%1
1045
Page generated at 2024-03-15 12:01:42. Version ac07

Copyright © 2024 Attilla Danko.


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