Transit Dreams Observatory
Clear Sky Chart
History

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

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
46%
24307
21%
79744
14%
24205
54%
24205
24%
49701

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
27%
755
27%
3980
9%
737
44%
737
17%
1986
January11th to 20thNight
31%
758
28%
3938
13%
740
45%
740
16%
2055
January21st to endNight
28%
830
18%
4450
12%
814
48%
814
16%
2608
February1st to 10thNight
35%
760
23%
2399
14%
760
46%
760
26%
1462
February11th to 20thNight
22%
742
21%
2218
6%
739
38%
739
23%
1447
February21st to endNight
26%
628
22%
1884
10%
628
39%
628
24%
1231
March1st to 10thNight
36%
743
26%
2061
15%
743
45%
743
29%
1303
March11th to 20thNight
29%
720
20%
1980
10%
720
38%
720
26%
1300
March21st to endNight
33%
792
19%
2178
9%
792
41%
792
25%
1464
April1st to 10thNight
36%
720
23%
1980
11%
720
47%
720
31%
1230
April11th to 20thNight
41%
669
24%
1805
13%
669
48%
669
33%
1107
April21st to endNight
48%
540
28%
1620
18%
540
55%
540
32%
981
May1st to 10thNight
46%
540
18%
1620
9%
540
52%
540
29%
1010
May11th to 20thNight
49%
531
12%
1593
7%
531
52%
531
21%
1103
May21st to endNight
62%
582
16%
1745
12%
582
63%
582
24%
1164
June1st to 10thNight
61%
540
13%
1620
11%
540
63%
540
23%
1101
June11th to 20thNight
62%
540
13%
1620
11%
540
64%
540
25%
1087
June21st to endNight
67%
540
13%
1620
11%
540
67%
540
24%
1115
July1st to 10thNight
64%
525
8%
1575
7%
525
65%
525
18%
1158
July11th to 20thNight
71%
522
10%
1566
9%
522
71%
522
24%
1073
July21st to endNight
70%
591
12%
1672
11%
558
70%
558
22%
1185
August1st to 10thNight
63%
537
10%
1600
9%
534
63%
534
20%
1158
August11th to 20thNight
64%
534
14%
1598
12%
534
65%
534
20%
1154
August21st to endNight
62%
670
15%
1948
13%
670
63%
670
21%
1383
September1st to 10thNight
65%
720
19%
1980
16%
720
66%
720
29%
1319
September11th to 20thNight
56%
720
17%
1980
14%
720
58%
720
23%
1402
September21st to endNight
55%
720
21%
1980
16%
720
59%
720
28%
1312
October1st to 10thNight
54%
720
25%
2026
21%
720
60%
720
33%
1257
October11th to 20thNight
50%
720
28%
2160
22%
720
60%
720
33%
1265
October21st to endNight
53%
792
32%
2376
26%
792
64%
792
37%
1332
November1st to 10thNight
51%
740
28%
2257
22%
740
60%
740
33%
1322
November11th to 20thNight
43%
760
26%
2470
19%
760
55%
760
31%
1408
November21st to endNight
43%
760
27%
2470
18%
760
55%
760
28%
1452
December1st to 10thNight
36%
760
24%
2470
13%
760
50%
760
21%
1600
December11th to 20thNight
38%
759
28%
2904
16%
758
50%
758
25%
1612
December21st to endNight
34%
827
15%
4401
13%
817
45%
817
14%
2555

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
15%5%25%5%35%5%6%8%44%
78917
Night
16%5%245%3445%7%45%
80613
TransparencyDay
37%8%12%19%18%5%
78640
Night
38%7%11%18%20%6%
80409
SeeingDay
17%8%21%24%19%10%
14156
Night
17%7%23%30%20%3
24333

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
17%423323348%52%
2836
11th to 20thDay
15%6%2432433454%
2840
21st to endDay
26%5%23213335%46%
3124
February1st to 10thDay
16%5%244245%5%7%44%
1776
11th to 20thDay
20%5%24434336%45%
1848
21st to endDay
20%6%24435%445%42%
1570
March1st to 10thDay
16%423434346%52%
2014
11th to 20thDay
18%6%35%435%5%5%7%40%
1980
21st to endDay
19%424435%5%5%7%41%
2178
April1st to 10thDay
13%4244345%6%8%48%
1980
11th to 20thDay
15%4235%3445%7%47%
2118
21st to endDay
12%4245%35%46%7%49%
2340
May1st to 10thDay
10%5%26%5%35%5%6%7%46%
2340
11th to 20thDay
14%5%25%5%46%6%6%7%38%
2301
21st to endDay
12%5%25%5%35%6%8%11%38%
2531
June1st to 10thDay
11%5%35%6%5%6%7%8%11%33%
2340
11th to 20thDay
7%5%25%6%47%8%9%9%39%
2340
21st to endDay
8%5%247%47%7%8%11%37%
2340
July1st to 10thDay
9%5%37%8%46%7%8%10%33%
2340
11th to 20thDay
9%5%35%7%5%7%7%9%11%31%
2340
21st to endDay
8%426%6%5%8%8%8%11%34%
2547
August1st to 10thDay
12%6%26%7%5%8%6%8%10%30%
2327
11th to 20thDay
12%5%25%7%5%8%7%8%11%31%
2303
21st to endDay
12%5%36%6%45%6%7%9%37%
2386
September1st to 10thDay
9%426%5%47%6%6%8%44%
1980
11th to 20thDay
14%6%26%4345%5%8%42%
1980
21st to endDay
16%5%35%44445%6%44%
1980
October1st to 10thDay
17%413222346%55%
1932
11th to 20thDay
14%413323246%59%
1800
21st to endDay
14%324323335%58%
1980
November1st to 10thDay
13%414322346%57%
1819
11th to 20thDay
14%414424446%53%
1710
21st to endDay
17%414423445%52%
1710
December1st to 10thDay
21%6%35%5%2445%5%41%
1710
11th to 20thDay
17%5%2342235%6%51%
2153
21st to endDay
22%414323347%44%
3124
January1st to 10thNight
18%323323445%52%
4109
11th to 20thNight
13%5%24425%45%6%50%
4120
21st to endNight
26%5%24323235%44%
4532
February1st to 10thNight
15%6%24423446%49%
2399
11th to 20thNight
22%5%245%2344445%
2218
21st to endNight
17%6%35%5%245%5%6%43%
1884
March1st to 10thNight
15%5%25%434345%49%
2061
11th to 20thNight
18%6%25%42345%8%43%
1980
21st to endNight
16%5%36%5%3445%6%43%
2178
April1st to 10thNight
14%5%25%424447%50%
1980
11th to 20thNight
13%5%25%433346%51%
1805
21st to endNight
13%5%2443346%5%51%
1620
May1st to 10thNight
11%5%25%5%45%5%5%7%46%
1620
11th to 20thNight
14%435%8%46%6%6%8%37%
1592
21st to endNight
13%436%6%46%46%9%39%
1744
June1st to 10thNight
10%5%25%7%46%7%9%12%32%
1620
11th to 20thNight
12%5%15%5%36%6%8%9%40%
1620
21st to endNight
9%5%26%6%46%7%6%11%37%
1620
July1st to 10thNight
9%5%28%8%5%7%8%9%10%29%
1620
11th to 20thNight
8%6%25%6%5%6%7%9%12%34%
1620
21st to endNight
7%436%7%47%7%11%14%30%
1771
August1st to 10thNight
12%6%25%7%46%7%8%11%31%
1611
11th to 20thNight
13%5%46%7%45%5%8%10%34%
1598
21st to endNight
12%7%37%6%46%5%7%10%34%
1948
September1st to 10thNight
11%5%26%5%45%46%10%41%
1980
11th to 20thNight
16%7%35%6%35%5%5%7%37%
1980
21st to endNight
17%5%25%434446%45%
1980
October1st to 10thNight
17%424423445%51%
2026
11th to 20thNight
15%42432335%6%53%
2160
21st to endNight
15%323323235%58%
2376
November1st to 10thNight
15%423423345%55%
2257
11th to 20thNight
16%423323445%53%
2470
21st to endNight
16%5%2342445%6%49%
2470
December1st to 10thNight
21%7%25%5%23445%43%
2470
11th to 20thNight
17%5%23323345%53%
3042
21st to endNight
22%5%245%345%46%41%
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
32%5%7%26%23%7%
2837
11th to 20thDay
36%5%6%15%33%5%
2840
21st to endDay
41%37%18%25%6%
3124
February1st to 10thDay
39%411%19%20%6%
1776
11th to 20thDay
42%48%18%21%6%
1858
21st to endDay
45%6%7%16%19%7%
1570
March1st to 10thDay
36%48%21%22%8%
2014
11th to 20thDay
43%7%11%17%16%6%
1980
21st to endDay
41%7%12%19%18%3
2178
April1st to 10thDay
33%5%11%21%24%6%
1980
11th to 20thDay
36%6%9%18%21%9%
2118
21st to endDay
33%6%14%25%18%4
2340
May1st to 10thDay
35%8%15%20%18%3
2340
11th to 20thDay
41%10%15%18%13%2
2305
21st to endDay
37%11%16%23%13%1
2531
June1st to 10thDay
39%12%17%21%9%1
2340
11th to 20thDay
34%12%20%20%12%1
2340
21st to endDay
36%13%17%19%13%2
2340
July1st to 10thDay
41%14%17%15%9%3
2275
11th to 20thDay
40%15%20%14%8%2
2271
21st to endDay
37%14%20%19%9%1
2405
August1st to 10thDay
45%13%17%18%7%
2314
11th to 20thDay
44%14%18%16%8%1
2303
21st to endDay
40%12%17%19%9%3
2386
September1st to 10thDay
35%11%14%19%17%4
1980
11th to 20thDay
39%8%14%16%20%3
1980
21st to endDay
40%7%10%19%18%6%
1980
October1st to 10thDay
30%7%10%19%27%6%
1932
11th to 20thDay
28%5%10%24%24%9%
1800
21st to endDay
31%47%20%27%11%
1980
November1st to 10thDay
30%5%8%18%29%9%
1819
11th to 20thDay
33%5%7%21%25%9%
1710
21st to endDay
36%48%21%24%7%
1710
December1st to 10thDay
45%5%7%21%17%5%
1710
11th to 20thDay
34%49%19%22%11%
2150
21st to endDay
39%6%9%22%21%4
3124
January1st to 10thNight
34%48%19%28%7%
4109
11th to 20thNight
33%7%8%15%29%7%
4120
21st to endNight
42%47%15%24%7%
4532
February1st to 10thNight
38%5%9%20%22%6%
2399
11th to 20thNight
43%5%7%16%24%6%
2219
21st to endNight
41%6%9%16%21%7%
1884
March1st to 10thNight
38%5%8%16%23%10%
2061
11th to 20thNight
40%6%12%16%19%7%
1980
21st to endNight
42%6%9%20%19%4
2178
April1st to 10thNight
35%5%10%19%25%6%
1980
11th to 20thNight
34%5%9%22%22%9%
1805
21st to endNight
34%6%10%24%21%5%
1620
May1st to 10thNight
36%8%14%21%19%3
1620
11th to 20thNight
43%11%13%17%15%1
1593
21st to endNight
41%10%12%23%12%3
1745
June1st to 10thNight
39%12%18%19%10%1
1620
11th to 20thNight
37%13%18%21%10%1
1620
21st to endNight
38%15%17%14%12%4
1620
July1st to 10thNight
44%16%17%14%7%2
1575
11th to 20thNight
38%14%24%16%6%2
1566
21st to endNight
37%17%20%18%6%1
1672
August1st to 10thNight
43%15%20%15%7%
1600
11th to 20thNight
44%14%19%14%9%1
1598
21st to endNight
43%12%16%18%7%3
1948
September1st to 10thNight
37%10%16%19%14%4
1980
11th to 20thNight
43%11%13%15%16%2
1980
21st to endNight
40%7%10%19%19%5%
1980
October1st to 10thNight
35%6%11%18%25%5%
2026
11th to 20thNight
33%5%9%23%20%9%
2160
21st to endNight
30%46%20%28%12%
2376
November1st to 10thNight
33%5%7%18%26%11%
2257
11th to 20thNight
33%5%7%16%27%12%
2470
21st to endNight
36%5%6%20%26%7%
2470
December1st to 10thNight
44%5%8%17%20%6%
2470
11th to 20thNight
34%49%17%27%9%
3044
21st to endNight
42%6%9%20%19%3
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
20%19%37%20%4
270
11th to 20thDay
26%18%32%17%7%
270
21st to endDay
23%15%41%16%4
297
February1st to 10thDay
19%21%33%20%7%
270
11th to 20thDay
35%17%31%15%2
270
21st to endDay
29%24%30%13%4
225
March1st to 10thDay
21%14%32%23%9%1
419
11th to 20thDay
20%16%36%21%6%1
420
21st to endDay
21%15%33%23%8%
462
April1st to 10thDay
17%13%31%25%13%1
420
11th to 20thDay
15%13%29%26%14%3
412
21st to endDay
20%8%24%27%14%7%
420
May1st to 10thDay
13%10%32%22%16%5%
423
11th to 20thDay
17%5%16%27%24%11%
447
21st to endDay
16%414%26%25%15%
485
June1st to 10thDay
13%214%34%24%13%
450
11th to 20thDay
10%412%29%24%22%
450
21st to endDay
10%314%30%26%17%
450
July1st to 10thDay
10%27%22%31%28%
445
11th to 20thDay
8%26%27%32%25%
444
21st to endDay
6%26%28%34%23%
488
August1st to 10thDay
19%29%24%25%20%
446
11th to 20thDay
13%27%26%32%19%
439
21st to endDay
15%210%18%29%25%
495
September1st to 10thDay
10%212%21%34%21%
450
11th to 20thDay
18%212%18%31%19%
450
21st to endDay
20%317%25%27%7%
450
October1st to 10thDay
21%315%27%23%10%
450
11th to 20thDay
15%5%25%28%22%6%
450
21st to endDay
18%7%20%34%17%5%
495
November1st to 10thDay
21%6%22%29%17%5%
417
11th to 20thDay
18%13%33%27%8%2
270
21st to endDay
11%13%31%30%12%3
270
December1st to 10thDay
27%13%33%20%7%
270
11th to 20thDay
24%12%29%24%10%
270
21st to endDay
28%12%33%19%8%2
297
January1st to 10thNight
20%13%34%26%6%
760
11th to 20thNight
21%12%32%30%5%
760
21st to endNight
20%12%35%30%3
836
February1st to 10thNight
19%12%31%35%3
760
11th to 20thNight
23%12%39%24%2
743
21st to endNight
19%13%39%26%3
628
March1st to 10thNight
19%11%31%36%4
743
11th to 20thNight
21%12%33%26%8%1
720
21st to endNight
20%10%31%31%8%
792
April1st to 10thNight
16%12%32%30%11%
720
11th to 20thNight
15%11%28%31%15%1
669
21st to endNight
16%5%27%32%19%1
540
May1st to 10thNight
12%7%27%34%19%
540
11th to 20thNight
18%319%33%24%3
531
21st to endNight
16%210%29%38%6%
584
June1st to 10thNight
12%214%32%35%5%
540
11th to 20thNight
14%212%29%31%12%
540
21st to endNight
10%28%31%41%8%
540
July1st to 10thNight
11%17%25%45%10%
525
11th to 20thNight
11%17%23%47%11%
522
21st to endNight
8%27%30%45%9%
591
August1st to 10thNight
16%27%25%40%11%
537
11th to 20thNight
14%18%27%39%9%
534
21st to endNight
13%28%26%42%9%
670
September1st to 10thNight
12%310%27%41%8%
720
11th to 20thNight
18%213%25%36%7%
720
21st to endNight
18%316%31%29%3
720
October1st to 10thNight
17%318%28%28%6%
720
11th to 20thNight
17%5%22%31%23%2
720
21st to endNight
16%5%21%37%19%2
792
November1st to 10thNight
17%5%21%36%18%3
740
11th to 20thNight
17%8%28%34%12%1
760
21st to endNight
18%7%28%33%13%1
760
December1st to 10thNight
23%10%25%33%9%
760
11th to 20thNight
19%8%30%33%10%1
760
21st to endNight
27%7%26%32%8%
836
Page generated at 2024-03-03 06:28:56. Version ac07

Copyright © 2024 Attilla Danko.


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