Teeter's Telescopes Workshop
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Teeter's Telescopes Workshop clear sky chart from 2005-11-06 to 2024-01-15.

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
29%
23103
19%
74659
9%
23062
41%
23062
20%
48006

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
16%
760
22%
2649
6%
757
37%
757
17%
1600
January11th to 20thNight
20%
737
18%
2577
6%
737
36%
737
15%
1702
January21st to endNight
15%
792
23%
2614
5%
792
37%
792
18%
1603
February1st to 10thNight
15%
720
17%
2340
5%
720
31%
720
16%
1543
February11th to 20thNight
12%
703
20%
2118
3%
700
33%
700
16%
1405
February21st to endNight
16%
592
25%
1776
9%
592
35%
592
17%
1174
March1st to 10thNight
17%
720
20%
2160
6%
720
35%
720
20%
1366
March11th to 20thNight
20%
720
21%
2035
7%
720
34%
720
20%
1360
March21st to endNight
18%
792
22%
2016
5%
792
31%
792
23%
1372
April1st to 10thNight
17%
720
18%
1800
3%
720
26%
720
20%
1267
April11th to 20thNight
23%
711
18%
1775
4%
711
30%
711
23%
1239
April21st to endNight
25%
716
18%
1796
4%
716
33%
716
23%
1247
May1st to 10thNight
20%
537
14%
1617
6%
537
28%
537
17%
1149
May11th to 20thNight
26%
354
19%
1416
10%
354
40%
354
16%
907
May21st to endNight
42%
388
15%
1551
13%
388
50%
388
20%
961
June1st to 10thNight
40%
360
17%
1440
15%
360
53%
360
21%
875
June11th to 20thNight
39%
360
14%
1440
12%
360
50%
360
19%
890
June21st to endNight
51%
360
15%
1440
13%
360
60%
360
24%
830
July1st to 10thNight
50%
350
13%
1400
15%
350
55%
350
20%
871
July11th to 20thNight
52%
348
15%
1392
17%
348
56%
348
21%
854
July21st to endNight
53%
394
17%
1486
17%
372
59%
372
25%
853
August1st to 10thNight
54%
473
16%
1537
11%
471
58%
471
25%
968
August11th to 20thNight
51%
705
14%
1769
8%
705
52%
705
25%
1272
August21st to endNight
52%
792
18%
1980
8%
792
55%
792
28%
1354
September1st to 10thNight
45%
720
20%
1800
9%
720
49%
720
29%
1229
September11th to 20thNight
48%
720
26%
1858
16%
720
53%
720
35%
1165
September21st to endNight
42%
720
25%
1980
15%
720
51%
720
30%
1280
October1st to 10thNight
35%
720
16%
2106
11%
720
41%
720
23%
1407
October11th to 20thNight
35%
720
23%
2160
13%
720
49%
720
26%
1344
October21st to endNight
24%
792
21%
2501
9%
792
39%
792
21%
1617
November1st to 10thNight
32%
740
24%
2407
11%
740
50%
740
26%
1406
November11th to 20thNight
26%
760
25%
2470
12%
760
43%
760
22%
1504
November21st to endNight
24%
760
22%
2579
9%
760
42%
760
21%
1552
December1st to 10thNight
21%
760
19%
2660
6%
760
36%
760
16%
1724
December11th to 20thNight
20%
760
18%
3197
6%
759
35%
759
14%
1971
December21st to endNight
18%
827
13%
4817
5%
817
35%
817
9%
3145

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%6%35%5%35%5%5%7%39%
74774
Night
17%7%35%5%3445%7%42%
74988
TransparencyDay
43%7%12%21%15%2
74479
Night
41%7%12%22%16%2
74817
SeeingDay
23%16%30%20%9%2
13822
Night
21%14%32%25%8%1
23113

By Month

Percentage Cloud Cover NE (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%6%35%6%45%46%6%42%
1517
11th to 20thDay
16%9%36%6%45%5%46%36%
1472
21st to endDay
12%8%35%6%346%5%7%40%
1737
February1st to 10thDay
18%8%46%5%35%5%5%6%36%
1620
11th to 20thDay
14%8%36%5%35%446%41%
1729
21st to endDay
20%9%26%5%34445%38%
1480
March1st to 10thDay
15%7%35%5%3445%7%42%
1797
11th to 20thDay
15%7%35%5%45%5%6%8%37%
1921
21st to endDay
20%9%35%5%24446%39%
2340
April1st to 10thDay
17%9%35%5%24446%39%
2160
11th to 20thDay
17%5%36%6%345%47%40%
2134
21st to endDay
20%6%25%6%345%5%6%38%
2164
May1st to 10thDay
24%8%35%435%446%34%
2358
11th to 20thDay
20%5%35%6%35%5%5%7%35%
2478
21st to endDay
15%6%35%5%35%45%9%40%
2725
June1st to 10thDay
17%5%35%5%45%6%7%8%35%
2520
11th to 20thDay
17%6%26%5%46%6%6%9%33%
2520
21st to endDay
13%6%25%6%35%6%6%8%39%
2520
July1st to 10thDay
12%6%36%6%46%5%6%10%37%
2520
11th to 20thDay
11%435%5%46%7%7%9%39%
2520
21st to endDay
12%6%35%7%36%6%7%8%37%
2744
August1st to 10thDay
12%5%35%6%46%7%7%9%36%
2376
11th to 20thDay
12%6%36%6%45%6%7%8%36%
2126
21st to endDay
15%5%35%5%35%5%6%8%41%
2376
September1st to 10thDay
16%5%25%5%35%6%5%7%41%
2160
11th to 20thDay
15%5%24433447%50%
2101
21st to endDay
18%5%26%5%345%46%41%
1980
October1st to 10thDay
21%7%2443445%5%41%
1850
11th to 20thDay
16%6%25%43445%7%45%
1800
21st to endDay
21%5%35%4245%5%6%39%
1854
November1st to 10thDay
15%6%24323336%51%
1671
11th to 20thDay
19%6%2443445%6%45%
1710
21st to endDay
16%6%335%345%5%7%43%
1596
December1st to 10thDay
20%8%35%6%33446%38%
1520
11th to 20thDay
22%5%2443445%6%42%
1906
21st to endDay
18%9%37%7%45%5%5%8%28%
2772
January1st to 10thNight
15%7%34435%45%6%45%
2649
11th to 20thNight
18%7%36%5%3445%7%37%
2577
21st to endNight
14%8%35%5%25%35%8%43%
2614
February1st to 10thNight
18%9%35%5%34447%40%
2340
11th to 20thNight
16%7%36%5%345%5%6%40%
2116
21st to endNight
19%7%35%5%25%446%40%
1776
March1st to 10thNight
16%6%35%5%33446%45%
2150
11th to 20thNight
17%7%34425%45%6%43%
2034
21st to endNight
18%7%344245%5%8%41%
2016
April1st to 10thNight
18%8%25%5%35%5%6%7%38%
1800
11th to 20thNight
18%7%25%5%3445%7%40%
1775
21st to endNight
21%6%35%5%2445%6%41%
1796
May1st to 10thNight
22%8%36%5%35%446%34%
1617
11th to 20thNight
19%8%25%43436%7%39%
1415
21st to endNight
17%5%26%5%245%5%8%42%
1550
June1st to 10thNight
17%5%24435%45%8%43%
1440
11th to 20thNight
14%6%35%5%345%6%9%40%
1440
21st to endNight
12%4245%35%5%7%8%46%
1440
July1st to 10thNight
11%5%26%5%35%6%6%8%42%
1440
11th to 20thNight
12%425%5%36%6%6%10%39%
1440
21st to endNight
11%415%425%6%7%11%43%
1574
August1st to 10thNight
10%5%347%35%6%6%9%42%
1547
11th to 20thNight
13%6%37%6%45%6%6%9%36%
1769
21st to endNight
14%5%35%5%3445%8%44%
1980
September1st to 10thNight
16%6%26%5%345%47%43%
1800
11th to 20thNight
14%5%3442335%5%52%
1858
21st to endNight
18%6%25%424347%45%
1980
October1st to 10thNight
21%6%35%423446%42%
2106
11th to 20thNight
17%6%25%313446%48%
2160
21st to endNight
21%8%24423445%44%
2501
November1st to 10thNight
13%6%243245%5%6%51%
2407
11th to 20thNight
19%6%24423346%47%
2470
21st to endNight
15%435%4345%6%7%45%
2579
December1st to 10thNight
18%7%35%5%35%45%6%38%
2660
11th to 20thNight
18%7%245%2445%7%40%
3288
21st to endNight
19%9%36%5%34446%35%
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
41%5%13%25%12%4
1518
11th to 20thDay
48%7%12%19%11%3
1472
21st to endDay
42%5%12%24%15%3
1737
February1st to 10thDay
47%6%12%22%11%2
1620
11th to 20thDay
43%6%11%22%16%3
1738
21st to endDay
48%5%10%21%13%3
1480
March1st to 10thDay
42%5%12%23%15%3
1800
11th to 20thDay
43%6%12%22%14%2
1921
21st to endDay
47%49%18%17%5%
2340
April1st to 10thDay
45%6%10%20%15%5%
2160
11th to 20thDay
42%6%11%21%17%3
2134
21st to endDay
45%6%10%20%16%4
2164
May1st to 10thDay
50%6%9%17%15%2
2358
11th to 20thDay
46%7%11%19%14%3
2482
21st to endDay
42%8%14%21%14%2
2725
June1st to 10thDay
43%9%14%19%14%1
2520
11th to 20thDay
46%9%12%21%11%2
2520
21st to endDay
41%8%13%23%15%1
2520
July1st to 10thDay
42%9%12%21%15%1
2450
11th to 20thDay
36%10%16%23%14%2
2445
21st to endDay
42%9%12%18%17%3
2591
August1st to 10thDay
41%10%13%21%13%1
2362
11th to 20thDay
42%8%14%23%12%1
2126
21st to endDay
40%8%10%21%18%3
2376
September1st to 10thDay
41%8%11%20%17%3
2160
11th to 20thDay
35%6%10%21%25%3
2101
21st to endDay
44%6%10%18%19%3
1980
October1st to 10thDay
44%7%10%22%15%2
1850
11th to 20thDay
38%6%11%24%19%1
1800
21st to endDay
44%6%11%22%15%2
1854
November1st to 10thDay
36%5%12%25%20%3
1671
11th to 20thDay
39%5%11%22%19%3
1710
21st to endDay
40%5%14%28%11%2
1596
December1st to 10thDay
46%6%15%19%13%1
1520
11th to 20thDay
42%5%16%23%11%2
1906
21st to endDay
52%7%12%21%8%
2772
January1st to 10thNight
40%5%12%24%15%4
2649
11th to 20thNight
45%7%14%22%10%1
2577
21st to endNight
40%5%10%24%19%3
2614
February1st to 10thNight
45%6%12%23%12%2
2340
11th to 20thNight
44%5%12%18%16%5%
2118
21st to endNight
45%48%24%16%3
1776
March1st to 10thNight
40%5%13%24%14%4
2160
11th to 20thNight
43%6%11%20%17%3
2035
21st to endNight
41%6%11%17%19%5%
2016
April1st to 10thNight
45%6%12%20%15%3
1800
11th to 20thNight
43%7%9%20%19%2
1775
21st to endNight
44%6%10%20%17%4
1796
May1st to 10thNight
51%5%11%16%15%2
1617
11th to 20thNight
45%7%10%17%18%3
1416
21st to endNight
40%9%16%21%12%3
1551
June1st to 10thNight
41%6%11%21%19%1
1440
11th to 20thNight
39%10%14%24%12%1
1440
21st to endNight
33%10%15%26%15%1
1440
July1st to 10thNight
39%10%13%20%15%3
1400
11th to 20thNight
39%9%13%25%12%2
1392
21st to endNight
31%11%18%21%16%3
1486
August1st to 10thNight
36%11%14%23%15%2
1537
11th to 20thNight
43%10%14%22%10%1
1769
21st to endNight
40%8%11%19%20%2
1980
September1st to 10thNight
41%6%10%24%17%1
1800
11th to 20thNight
34%6%10%22%25%3
1858
21st to endNight
40%49%22%23%2
1980
October1st to 10thNight
44%6%10%23%15%2
2106
11th to 20thNight
37%7%12%27%15%2
2160
21st to endNight
43%6%11%24%15%1
2501
November1st to 10thNight
34%6%12%23%21%4
2407
11th to 20thNight
40%310%24%18%4
2470
21st to endNight
37%6%13%29%13%1
2579
December1st to 10thNight
44%6%13%22%12%1
2660
11th to 20thNight
43%6%13%19%15%3
3288
21st to endNight
48%8%12%21%11%
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
28%27%29%14%2
180
11th to 20thDay
33%26%31%8%2
168
21st to endDay
23%30%32%11%31
244
February1st to 10thDay
32%30%30%8%1
240
11th to 20thDay
29%24%38%9%1
397
21st to endDay
33%23%31%11%2
346
March1st to 10thDay
26%24%33%15%2
420
11th to 20thDay
25%24%34%13%31
420
21st to endDay
30%24%27%14%41
462
April1st to 10thDay
28%24%29%14%5%
420
11th to 20thDay
24%21%34%14%7%1
412
21st to endDay
32%21%29%13%32
420
May1st to 10thDay
35%18%27%13%5%2
423
11th to 20thDay
23%17%34%17%7%1
447
21st to endDay
21%10%28%27%12%2
485
June1st to 10thDay
19%13%32%23%11%2
450
11th to 20thDay
20%15%30%23%11%1
450
21st to endDay
14%13%34%26%12%2
450
July1st to 10thDay
17%6%26%30%17%5%
445
11th to 20thDay
12%5%27%35%18%2
444
21st to endDay
14%9%32%28%14%2
488
August1st to 10thDay
14%7%26%30%16%7%
446
11th to 20thDay
15%5%25%32%18%5%
439
21st to endDay
14%9%29%27%15%6%
495
September1st to 10thDay
19%12%25%24%14%7%
450
11th to 20thDay
17%8%30%21%14%10%
450
21st to endDay
20%14%30%20%11%4
450
October1st to 10thDay
27%9%29%19%12%4
450
11th to 20thDay
18%19%30%22%10%1
450
21st to endDay
27%17%30%17%7%1
432
November1st to 10thDay
21%15%30%23%9%2
365
11th to 20thDay
27%20%30%19%41
370
21st to endDay
23%21%34%17%5%
256
December1st to 10thDay
27%27%27%12%7%
180
11th to 20thDay
36%22%29%11%3
180
21st to endDay
29%20%34%12%5%
198
January1st to 10thNight
20%22%38%16%3
760
11th to 20thNight
26%18%32%21%3
737
21st to endNight
20%21%39%18%2
792
February1st to 10thNight
23%19%37%20%2
720
11th to 20thNight
24%22%39%14%1
703
21st to endNight
27%20%33%17%3
592
March1st to 10thNight
24%20%35%18%3
720
11th to 20thNight
23%22%33%18%31
720
21st to endNight
22%19%37%16%5%1
792
April1st to 10thNight
24%20%37%16%4
720
11th to 20thNight
22%17%35%21%5%
711
21st to endNight
24%15%33%24%4
716
May1st to 10thNight
27%13%36%18%6%
537
11th to 20thNight
21%12%37%24%6%
354
21st to endNight
19%7%24%36%13%1
389
June1st to 10thNight
19%6%29%33%13%1
360
11th to 20thNight
15%7%31%35%12%
360
21st to endNight
12%5%25%46%11%
360
July1st to 10thNight
11%6%27%35%20%1
350
11th to 20thNight
13%323%42%17%1
348
21st to endNight
14%424%44%14%2
394
August1st to 10thNight
11%222%42%20%2
473
11th to 20thNight
14%322%36%23%2
705
21st to endNight
16%420%39%19%2
792
September1st to 10thNight
18%424%35%17%2
720
11th to 20thNight
17%6%23%32%18%4
720
21st to endNight
20%6%26%33%13%2
720
October1st to 10thNight
23%8%28%24%14%2
720
11th to 20thNight
20%14%28%30%8%
720
21st to endNight
25%13%35%20%7%
792
November1st to 10thNight
18%13%32%26%10%1
740
11th to 20thNight
24%15%30%23%7%1
760
21st to endNight
17%19%36%22%6%1
760
December1st to 10thNight
25%17%33%21%41
760
11th to 20thNight
22%16%36%22%3
760
21st to endNight
24%17%36%20%3
836
Page generated at 2024-01-11 22:33:50. Version ac07

Copyright 2024 Attilla Danko


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