TBM Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the TBM Observatory clear sky chart from 2005-11-05 to

2017-09-12
.

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
40%
15194
20%
46828
12%
15157
50%
15157
25%
29557

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 15thNight
26%
718
22%
2472
9%
716
42%
716
20%
1536
January16th to endNight
24%
768
22%
2496
9%
768
41%
768
22%
1569
February1st to 15thNight
23%
703
19%
2272
7%
701
39%
701
22%
1419
February16th to endNight
21%
631
25%
1893
8%
631
42%
631
23%
1186
March1st to 15thNight
29%
720
21%
2055
10%
720
41%
720
27%
1306
March16th to endNight
29%
768
21%
2054
9%
768
38%
768
27%
1371
April1st to 15thNight
27%
718
20%
1796
5%
718
36%
718
31%
1178
April16th to endNight
41%
720
20%
1800
7%
720
46%
720
31%
1181
May1st to 15thNight
39%
560
17%
1640
10%
560
44%
560
24%
1117
May16th to endNight
56%
374
16%
1497
16%
374
61%
374
22%
912
June1st to 15thNight
56%
360
18%
1440
20%
360
62%
360
25%
843
June16th to endNight
59%
360
15%
1440
16%
360
63%
360
23%
843
July1st to 15thNight
59%
340
13%
1360
16%
340
61%
340
20%
861
July16th to endNight
71%
482
17%
1516
16%
452
74%
452
30%
887
August1st to 15thNight
67%
572
18%
1642
14%
569
68%
569
31%
1031
August16th to endNight
65%
764
19%
1910
10%
764
66%
764
34%
1268
September1st to 15thNight
61%
707
24%
1768
15%
707
64%
707
34%
1174
September16th to endNight
55%
657
21%
1787
18%
657
58%
657
29%
1191
October1st to 15thNight
47%
660
23%
1980
21%
660
54%
660
27%
1259
October16th to endNight
39%
704
27%
2112
17%
704
53%
704
31%
1253
November1st to 15thNight
38%
700
24%
2269
15%
700
51%
700
27%
1366
November16th to endNight
34%
720
21%
2421
12%
720
47%
720
21%
1507
December1st to 15thNight
28%
720
18%
2520
8%
720
41%
720
19%
1608
December16th to endNight
25%
768
21%
2688
9%
768
42%
768
20%
1691

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
13%5%2442445%8%44%
47827
Night
14%5%2442445%7%43%
47007
Cloud CoverDay
13%5%2442445%8%44%
47837
Night
14%5%2442445%7%43%
47012
TransparencyDay
37%6%12%24%16%2
47525
Night
39%5%11%23%17%3
46828
SeeingDay
16%6%23%25%18%8%
5724
Night
16%7%28%30%14%1
15198

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 15thDay
16%6%2443335%7%42%
1465
16th to endDay
16%6%24424446%43%
1728
February1st to 15thDay
15%7%145%2445%7%42%
1589
16th to endDay
12%7%35%5%245%45%42%
1580
March1st to 15thDay
14%5%2432345%6%45%
1891
16th to endDay
16%5%25%434335%43%
2169
April1st to 15thDay
14%5%2432445%7%45%
2152
16th to endDay
15%5%23323347%46%
2160
May1st to 15thDay
15%5%243245%5%8%40%
2322
16th to endDay
13%423425%5%6%9%41%
2618
June1st to 15thDay
11%3234345%7%10%41%
2520
16th to endDay
9%3234245%7%10%46%
2520
July1st to 15thDay
8%424435%5%7%10%43%
2520
16th to endDay
5%314437%6%8%12%42%
2545
August1st to 15thDay
11%4244345%6%10%41%
2295
16th to endDay
9%415%5%345%6%10%44%
2292
September1st to 15thDay
12%32442445%7%47%
2112
16th to endDay
14%6%25%5%345%46%41%
1840
October1st to 15thDay
17%424313347%46%
1650
16th to endDay
14%5%24322345%50%
1760
November1st to 15thDay
14%5%2332435%6%47%
1587
16th to endDay
15%5%244245%46%44%
1536
December1st to 15thDay
15%5%345%24447%43%
1440
16th to endDay
17%6%25%5%23346%41%
1536
January1st to 15thNight
16%6%3442445%7%41%
2472
16th to endNight
17%6%34424346%43%
2496
February1st to 15thNight
14%6%25%424446%42%
2270
16th to endNight
15%6%13423336%46%
1893
March1st to 15thNight
16%5%14314347%45%
2043
16th to endNight
16%6%35%423447%42%
2054
April1st to 15thNight
13%5%2442445%8%44%
1796
16th to endNight
17%41432445%6%46%
1800
May1st to 15thNight
16%6%24435%45%6%39%
1640
16th to endNight
12%6%25%435%5%5%8%41%
1495
June1st to 15thNight
11%434425%46%8%44%
1440
16th to endNight
8%425%5%45%6%7%9%41%
1440
July1st to 15thNight
7%436%5%47%6%6%9%37%
1440
16th to endNight
6%2145%37%6%6%12%42%
1620
August1st to 15thNight
7%5%245%35%5%6%9%43%
1653
16th to endNight
9%5%25%425%46%8%43%
1910
September1st to 15thNight
13%415%42445%6%47%
1768
16th to endNight
14%6%25%5%3435%6%43%
1787
October1st to 15thNight
16%6%25%422346%44%
1980
16th to endNight
15%414422336%50%
2112
November1st to 15thNight
14%5%25%41334449%
2269
16th to endNight
14%6%2443445%6%42%
2421
December1st to 15thNight
17%5%25%4245%5%7%38%
2520
16th to endNight
17%5%25%42445%6%41%
2688

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 15thDay
15%6%245%2335%6%43%
1465
16th to endDay
16%5%24424445%44%
1728
February1st to 15thDay
15%7%145%2345%6%43%
1589
16th to endDay
13%6%35%5%2445%6%42%
1580
March1st to 15thDay
14%5%24425%446%45%
1902
16th to endDay
16%6%25%5%24335%43%
2168
April1st to 15thDay
14%5%14434447%46%
2152
16th to endDay
15%5%34323247%46%
2160
May1st to 15thDay
15%5%2442446%8%41%
2322
16th to endDay
13%4244345%6%9%41%
2618
June1st to 15thDay
11%324425%5%6%11%42%
2520
16th to endDay
9%3234245%7%10%47%
2520
July1st to 15thDay
8%4245%25%5%7%9%43%
2520
16th to endDay
5%3145%36%5%8%12%42%
2545
August1st to 15thDay
10%5%244345%7%10%42%
2295
16th to endDay
9%4145%345%6%9%44%
2292
September1st to 15thDay
12%4235%2445%7%47%
2112
16th to endDay
15%7%25%5%245%46%41%
1840
October1st to 15thDay
17%5%14323446%46%
1650
16th to endDay
15%5%24323345%50%
1760
November1st to 15thDay
16%414324347%47%
1587
16th to endDay
15%5%234245%45%44%
1536
December1st to 15thDay
15%5%3342445%6%43%
1440
16th to endDay
17%7%25%5%23346%41%
1536
January1st to 15thNight
15%6%34424447%41%
2472
16th to endNight
17%6%3342435%5%44%
2496
February1st to 15thNight
14%6%35%424346%43%
2263
16th to endNight
15%6%14424336%46%
1893
March1st to 15thNight
16%5%24324447%45%
2055
16th to endNight
16%6%25%5%24347%42%
2054
April1st to 15thNight
13%5%24324448%44%
1796
16th to endNight
17%42332345%7%45%
1800
May1st to 15thNight
15%7%25%5%3445%6%39%
1640
16th to endNight
11%6%34435%5%49%41%
1495
June1st to 15thNight
10%425%435%46%8%44%
1440
16th to endNight
8%425%5%35%5%7%9%40%
1440
July1st to 15thNight
7%5%26%6%46%6%6%9%37%
1440
16th to endNight
6%3145%46%6%6%12%41%
1620
August1st to 15thNight
7%426%5%35%5%6%9%43%
1653
16th to endNight
9%5%25%4245%7%8%43%
1910
September1st to 15thNight
12%42443345%6%47%
1768
16th to endNight
14%5%245%3345%7%42%
1787
October1st to 15thNight
16%6%35%423345%45%
1980
16th to endNight
15%414413346%50%
2112
November1st to 15thNight
14%5%25%42334449%
2269
16th to endNight
14%6%2443445%6%42%
2421
December1st to 15thNight
17%6%25%4245%5%7%38%
2520
16th to endNight
17%5%2442445%6%41%
2688

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 15thDay
41%414%22%13%4
1466
16th to endDay
41%410%25%14%3
1728
February1st to 15thDay
40%412%25%14%2
1591
16th to endDay
41%311%26%14%1
1580
March1st to 15thDay
38%5%12%25%15%2
1902
16th to endDay
43%49%21%18%2
2169
April1st to 15thDay
37%5%10%24%17%4
2152
16th to endDay
37%411%18%22%6%
2160
May1st to 15thDay
38%8%13%21%16%2
2322
16th to endDay
36%8%14%26%12%1
2622
June1st to 15thDay
34%8%14%27%13%1
2520
16th to endDay
30%9%15%23%19%1
2520
July1st to 15thDay
35%8%13%24%14%3
2371
16th to endDay
29%10%16%25%15%1
2387
August1st to 15thDay
35%7%14%24%15%1
2282
16th to endDay
33%7%14%22%17%4
2292
September1st to 15thDay
35%5%13%22%19%2
2112
16th to endDay
43%5%8%18%22%1
1840
October1st to 15thDay
38%5%8%27%16%2
1650
16th to endDay
36%38%29%19%2
1760
November1st to 15thDay
36%5%12%23%19%3
1587
16th to endDay
38%5%10%26%16%2
1536
December1st to 15thDay
40%5%14%24%11%3
1440
16th to endDay
44%311%23%14%1
1536
January1st to 15thNight
42%411%22%16%3
2472
16th to endNight
41%410%26%15%1
2496
February1st to 15thNight
41%411%24%16%2
2272
16th to endNight
39%39%24%19%2
1893
March1st to 15thNight
39%411%25%15%2
2055
16th to endNight
42%411%20%17%3
2054
April1st to 15thNight
38%411%21%20%4
1796
16th to endNight
37%6%9%20%19%6%
1800
May1st to 15thNight
43%6%10%21%15%2
1640
16th to endNight
38%8%16%19%14%2
1497
June1st to 15thNight
37%6%13%24%17%
1440
16th to endNight
35%8%13%22%17%2
1440
July1st to 15thNight
40%9%14%18%13%3
1360
16th to endNight
32%8%16%27%14%1
1516
August1st to 15thNight
35%7%15%22%18%1
1642
16th to endNight
35%7%12%21%19%2
1910
September1st to 15thNight
36%7%10%22%18%4
1768
16th to endNight
40%6%7%19%21%4
1787
October1st to 15thNight
41%49%24%17%3
1980
16th to endNight
35%39%28%20%2
2112
November1st to 15thNight
37%48%23%17%7%
2269
16th to endNight
40%5%10%21%17%3
2421
December1st to 15thNight
43%5%11%23%13%2
2520
16th to endNight
43%413%22%13%2
2688

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 15thDay
18%21%36%16%41
65
16th to endDay
27%16%40%10%5%
96
February1st to 15thDay
26%15%41%11%4
105
16th to endDay
16%15%39%25%1
239
March1st to 15thDay
19%12%31%28%8%
270
16th to endDay
17%12%37%20%8%3
288
April1st to 15thDay
19%8%30%26%12%2
270
16th to endDay
20%5%25%24%19%5%
270
May1st to 15thDay
25%12%27%17%10%5%
288
16th to endDay
19%221%22%21%12%
331
June1st to 15thDay
14%222%23%22%13%
315
16th to endDay
11%221%33%22%8%
315
July1st to 15thDay
10%116%34%25%12%
305
16th to endDay
6%18%29%38%15%
326
August1st to 15thDay
13%114%24%31%14%
313
16th to endDay
6%10%31%31%19%
332
September1st to 15thDay
13%320%21%22%19%
299
16th to endDay
25%113%27%16%15%
254
October1st to 15thDay
21%221%24%18%10%
255
16th to endDay
16%6%29%26%18%1
272
November1st to 15thDay
17%9%24%27%18%3
236
16th to endDay
19%11%32%21%12%3
156
December1st to 15thDay
18%21%26%16%13%3
60
16th to endDay
39%10%32%10%6%
64
January1st to 15thNight
19%14%35%26%4
720
16th to endNight
19%12%39%25%2
768
February1st to 15thNight
18%12%39%26%1
704
16th to endNight
18%17%37%23%2
631
March1st to 15thNight
19%12%35%27%5%
720
16th to endNight
18%8%38%26%7%1
768
April1st to 15thNight
16%10%41%25%5%
718
16th to endNight
19%6%29%31%12%
720
May1st to 15thNight
18%7%29%30%13%
560
16th to endNight
12%420%41%21%1
375
June1st to 15thNight
12%121%41%22%
360
16th to endNight
7%219%49%20%1
360
July1st to 15thNight
11%17%40%29%
340
16th to endNight
6%110%43%34%4
482
August1st to 15thNight
10%12%42%32%2
572
16th to endNight
11%112%34%35%4
764
September1st to 15thNight
14%15%35%29%3
707
16th to endNight
17%216%33%27%3
657
October1st to 15thNight
19%6%18%33%18%2
660
16th to endNight
17%8%30%28%13%
704
November1st to 15thNight
16%7%30%27%15%2
700
16th to endNight
16%14%30%28%9%1
720
December1st to 15thNight
20%11%33%22%10%1
720
16th to endNight
20%11%36%26%4
768
Page generated at 2017-09-13 07:39:10. Version ac04

Copyright 2017 A. Danko


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