The Rose Dorothea Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the The Rose Dorothea Observatory clear sky chart from 2005-11-06 to 2024-01-12.

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
34%
23012
17%
74531
10%
22964
43%
22964
19%
50513

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
17%
760
16%
2649
5%
757
31%
757
14%
1852
January11th to 20thNight
14%
727
12%
2541
2%
727
26%
727
9%
1933
January21st to endNight
18%
792
17%
2727
6%
792
32%
792
12%
1934
February1st to 10thNight
19%
720
13%
2282
3%
720
30%
720
13%
1667
February11th to 20thNight
13%
703
17%
2100
5%
700
27%
700
13%
1531
February21st to endNight
22%
592
22%
1776
9%
592
37%
592
17%
1220
March1st to 10thNight
23%
720
17%
2160
8%
720
35%
720
18%
1507
March11th to 20thNight
25%
720
18%
2013
8%
720
35%
720
19%
1421
March21st to endNight
26%
792
21%
2134
9%
792
36%
792
21%
1505
April1st to 10thNight
29%
720
19%
1800
6%
720
36%
720
22%
1301
April11th to 20thNight
33%
652
19%
1716
7%
652
39%
652
26%
1174
April21st to endNight
37%
540
19%
1620
10%
540
44%
540
21%
1118
May1st to 10thNight
35%
540
13%
1620
7%
540
38%
540
19%
1169
May11th to 20thNight
33%
532
16%
1594
8%
532
40%
532
22%
1112
May21st to endNight
47%
473
11%
1635
12%
472
50%
472
20%
1094
June1st to 10thNight
49%
360
12%
1440
15%
360
54%
360
16%
952
June11th to 20thNight
51%
360
15%
1440
21%
360
54%
360
19%
894
June21st to endNight
52%
360
12%
1440
16%
360
57%
360
20%
900
July1st to 10thNight
59%
350
12%
1400
17%
350
60%
350
20%
860
July11th to 20thNight
61%
348
16%
1392
20%
348
63%
348
23%
839
July21st to endNight
59%
434
18%
1524
21%
410
61%
410
23%
934
August1st to 10thNight
63%
538
16%
1600
14%
534
64%
534
32%
958
August11th to 20thNight
60%
532
17%
1596
11%
532
62%
532
26%
1042
August21st to endNight
63%
746
23%
1934
14%
746
65%
746
38%
1212
September1st to 10thNight
56%
720
20%
1854
12%
720
59%
720
33%
1219
September11th to 20thNight
54%
720
25%
1980
17%
720
59%
720
34%
1212
September21st to endNight
50%
720
23%
1980
16%
720
56%
720
29%
1303
October1st to 10thNight
41%
720
17%
1980
12%
720
45%
720
23%
1386
October11th to 20thNight
40%
720
21%
2167
12%
720
50%
720
27%
1362
October21st to endNight
27%
792
16%
2574
9%
792
37%
792
17%
1773
November1st to 10thNight
37%
740
19%
2407
13%
740
46%
740
22%
1537
November11th to 20thNight
26%
760
20%
2470
9%
760
40%
760
18%
1622
November21st to endNight
25%
760
19%
2470
7%
760
39%
760
17%
1612
December1st to 10thNight
18%
760
14%
2512
4%
760
30%
760
13%
1836
December11th to 20thNight
17%
760
15%
3196
4%
759
29%
759
10%
2153
December21st to endNight
17%
829
10%
4808
4%
817
32%
817
7%
3369

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
17%8%35%5%3445%7%40%
74824
Night
18%9%36%5%3445%7%36%
74875
TransparencyDay
44%412%23%14%2
74533
Night
49%411%21%13%2
74700
SeeingDay
21%7%24%30%15%3
14082
Night
23%9%25%28%12%2
23019

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
17%10%47%6%3445%6%35%
1517
11th to 20thDay
20%12%48%5%345%5%5%29%
1448
21st to endDay
16%10%47%7%43447%32%
1626
February1st to 10thDay
22%9%47%5%35%45%7%28%
1678
11th to 20thDay
15%9%5%7%6%35%5%5%6%34%
1748
21st to endDay
18%9%49%5%3445%7%31%
1480
March1st to 10thDay
17%9%37%5%345%5%8%35%
1797
11th to 20thDay
17%8%45%43445%7%39%
1944
21st to endDay
18%9%35%5%23445%41%
2218
April1st to 10thDay
20%8%35%423446%42%
2160
11th to 20thDay
17%7%25%42445%7%43%
2191
21st to endDay
19%7%16%5%3445%6%41%
2340
May1st to 10thDay
23%9%36%424447%35%
2340
11th to 20thDay
17%7%35%434348%44%
2301
21st to endDay
14%6%36%43445%8%44%
2655
June1st to 10thDay
19%7%35%425%5%7%9%35%
2520
11th to 20thDay
16%6%35%5%3445%9%41%
2520
21st to endDay
15%6%25%5%35%5%6%8%41%
2520
July1st to 10thDay
12%5%2442446%8%46%
2520
11th to 20thDay
11%6%35%5%45%5%6%10%42%
2520
21st to endDay
12%425%5%35%46%8%46%
2684
August1st to 10thDay
9%6%245%35%5%6%9%46%
2327
11th to 20thDay
12%7%35%4346%6%9%43%
2304
21st to endDay
13%5%2443445%9%49%
2418
September1st to 10thDay
13%6%244335%47%48%
2106
11th to 20thDay
14%6%23434445%52%
1980
21st to endDay
18%6%35%42335%7%44%
1980
October1st to 10thDay
21%6%24424346%44%
1980
11th to 20thDay
14%7%345%2445%7%46%
1788
21st to endDay
19%8%35%42346%7%39%
1782
November1st to 10thDay
20%6%34424447%43%
1671
11th to 20thDay
18%10%3442445%7%39%
1710
21st to endDay
18%7%36%425%45%8%38%
1710
December1st to 10thDay
19%12%47%5%3345%7%30%
1663
11th to 20thDay
20%11%6%7%434446%31%
1906
21st to endDay
23%14%5%7%5%3435%6%25%
2772
January1st to 10thNight
19%10%5%8%5%34445%33%
2649
11th to 20thNight
22%11%5%9%6%345%5%5%25%
2541
21st to endNight
16%12%47%8%35%5%5%6%30%
2727
February1st to 10thNight
18%11%48%6%35%5%5%5%29%
2282
11th to 20thNight
20%10%47%6%34446%31%
2098
21st to endNight
18%9%46%6%3445%7%34%
1776
March1st to 10thNight
18%9%47%5%35%5%5%6%34%
2150
11th to 20thNight
17%9%46%6%45%45%6%34%
2013
21st to endNight
19%10%36%5%24345%38%
2134
April1st to 10thNight
19%9%36%5%3445%5%36%
1800
11th to 20thNight
19%8%36%43445%7%38%
1716
21st to endNight
19%8%36%5%45%45%6%35%
1620
May1st to 10thNight
23%9%36%5%345%46%30%
1620
11th to 20thNight
18%8%36%5%445%5%8%33%
1593
21st to endNight
19%8%35%5%35%5%48%34%
1634
June1st to 10thNight
19%7%35%5%36%5%6%7%34%
1440
11th to 20thNight
18%8%35%435%46%7%37%
1440
21st to endNight
17%7%35%5%35%45%11%36%
1440
July1st to 10thNight
13%5%37%5%45%5%7%9%37%
1440
11th to 20thNight
12%9%35%5%35%5%6%10%38%
1440
21st to endNight
13%6%25%6%45%5%6%8%39%
1614
August1st to 10thNight
8%5%35%5%36%6%8%9%43%
1612
11th to 20thNight
10%7%26%5%36%7%8%8%38%
1596
21st to endNight
12%6%2443445%8%48%
1934
September1st to 10thNight
12%6%25%6%345%47%45%
1854
11th to 20thNight
13%6%25%42345%6%50%
1980
21st to endNight
16%6%25%5%345%6%5%43%
1980
October1st to 10thNight
22%7%345%3445%5%39%
1980
11th to 20thNight
17%5%35%4345%5%6%43%
2167
21st to endNight
22%9%36%5%2345%7%33%
2574
November1st to 10thNight
17%6%35%6%24446%42%
2407
11th to 20thNight
17%9%35%43445%7%38%
2470
21st to endNight
17%8%36%5%34447%39%
2470
December1st to 10thNight
22%11%5%7%5%3445%6%29%
2512
11th to 20thNight
19%11%5%6%42445%7%32%
3288
21st to endNight
20%14%5%8%5%34346%29%
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
51%410%23%11%1
1518
11th to 20thDay
56%6%11%19%7%1
1448
21st to endDay
53%49%22%11%1
1626
February1st to 10thDay
56%412%16%11%1
1678
11th to 20thDay
51%5%12%21%10%1
1757
21st to endDay
53%410%18%13%2
1480
March1st to 10thDay
49%412%21%12%2
1800
11th to 20thDay
45%311%23%15%3
1944
21st to endDay
47%310%20%17%3
2218
April1st to 10thDay
44%49%20%20%4
2160
11th to 20thDay
42%311%25%17%3
2191
21st to endDay
44%49%23%17%3
2340
May1st to 10thDay
52%38%21%14%2
2340
11th to 20thDay
42%311%21%19%3
2305
21st to endDay
40%5%15%25%14%1
2655
June1st to 10thDay
46%5%13%23%12%
2520
11th to 20thDay
42%413%24%16%1
2520
21st to endDay
40%6%16%24%12%1
2520
July1st to 10thDay
36%6%14%27%16%2
2450
11th to 20thDay
38%5%15%28%13%2
2445
21st to endDay
34%6%15%28%14%3
2534
August1st to 10thDay
35%5%17%30%13%1
2314
11th to 20thDay
38%5%16%25%14%1
2304
21st to endDay
34%414%26%19%2
2418
September1st to 10thDay
37%410%27%20%1
2106
11th to 20thDay
35%39%29%21%2
1980
21st to endDay
41%48%25%20%2
1980
October1st to 10thDay
43%310%25%16%3
1980
11th to 20thDay
40%311%31%14%1
1788
21st to endDay
45%313%22%14%3
1782
November1st to 10thDay
44%413%23%15%2
1671
11th to 20thDay
45%411%22%17%1
1710
21st to endDay
45%6%14%25%10%1
1710
December1st to 10thDay
54%413%15%13%1
1663
11th to 20thDay
56%413%15%10%2
1906
21st to endDay
60%5%12%15%7%1
2772
January1st to 10thNight
54%311%20%10%1
2649
11th to 20thNight
61%5%10%17%6%1
2541
21st to endNight
55%49%18%12%1
2727
February1st to 10thNight
57%412%18%9%1
2282
11th to 20thNight
56%38%21%11%1
2100
21st to endNight
50%39%23%12%3
1776
March1st to 10thNight
51%39%21%12%2
2160
11th to 20thNight
51%310%17%16%3
2014
21st to endNight
51%27%19%18%4
2134
April1st to 10thNight
51%38%19%16%4
1800
11th to 20thNight
46%37%23%18%3
1716
21st to endNight
50%38%20%16%3
1620
May1st to 10thNight
55%38%18%13%3
1620
11th to 20thNight
49%410%19%13%4
1594
21st to endNight
49%415%18%14%1
1635
June1st to 10thNight
50%5%13%20%11%1
1440
11th to 20thNight
47%310%23%16%1
1440
21st to endNight
44%5%14%23%13%1
1440
July1st to 10thNight
42%6%13%22%16%
1400
11th to 20thNight
42%413%31%9%1
1392
21st to endNight
42%5%12%29%11%2
1524
August1st to 10thNight
35%5%17%27%15%1
1600
11th to 20thNight
40%7%17%23%12%1
1596
21st to endNight
35%412%28%20%2
1934
September1st to 10thNight
39%410%26%19%2
1854
11th to 20thNight
35%49%25%24%2
1980
21st to endNight
42%5%7%23%21%2
1980
October1st to 10thNight
49%49%21%14%2
1980
11th to 20thNight
42%313%28%14%1
2167
21st to endNight
52%311%20%13%1
2574
November1st to 10thNight
45%312%22%15%3
2407
11th to 20thNight
47%310%21%16%3
2470
21st to endNight
46%413%26%10%2
2470
December1st to 10thNight
58%411%17%10%
2512
11th to 20thNight
52%412%17%14%1
3288
21st to endNight
58%411%18%9%
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
29%14%30%21%6%
180
11th to 20thDay
27%15%28%24%6%
162
21st to endDay
21%14%38%22%5%1
218
February1st to 10thDay
29%15%33%19%4
366
11th to 20thDay
24%16%39%19%2
416
21st to endDay
22%14%36%23%4
346
March1st to 10thDay
22%13%36%23%5%
420
11th to 20thDay
20%13%35%25%6%
420
21st to endDay
24%10%34%21%9%3
462
April1st to 10thDay
26%10%30%25%7%2
420
11th to 20thDay
22%6%31%31%8%1
412
21st to endDay
25%5%26%32%10%2
420
May1st to 10thDay
30%328%28%8%2
423
11th to 20thDay
19%329%34%14%2
447
21st to endDay
18%220%35%21%4
485
June1st to 10thDay
20%218%34%22%4
450
11th to 20thDay
17%220%40%18%3
450
21st to endDay
15%218%39%22%4
450
July1st to 10thDay
17%211%36%28%7%
445
11th to 20thDay
14%111%37%32%5%
444
21st to endDay
14%111%43%27%5%
488
August1st to 10thDay
13%110%43%27%6%
446
11th to 20thDay
16%111%32%32%7%
439
21st to endDay
14%213%36%24%10%
495
September1st to 10thDay
20%213%32%25%8%
450
11th to 20thDay
19%221%28%22%7%
450
21st to endDay
22%423%28%17%6%
450
October1st to 10thDay
26%319%30%18%5%
450
11th to 20thDay
17%7%28%27%18%2
376
21st to endDay
27%7%29%23%12%3
396
November1st to 10thDay
19%9%26%30%12%3
365
11th to 20thDay
26%14%27%24%8%1
370
21st to endDay
20%15%28%27%8%1
370
December1st to 10thDay
24%12%38%19%7%
323
11th to 20thDay
27%20%33%15%6%
180
21st to endDay
30%11%34%17%6%2
198
January1st to 10thNight
26%17%34%19%4
760
11th to 20thNight
29%16%32%19%4
727
21st to endNight
24%18%34%20%41
792
February1st to 10thNight
26%16%32%24%3
720
11th to 20thNight
27%16%37%16%3
703
21st to endNight
23%17%34%23%4
592
March1st to 10thNight
23%14%32%24%6%
720
11th to 20thNight
23%13%33%22%7%1
720
21st to endNight
24%10%30%26%10%1
792
April1st to 10thNight
25%9%31%27%7%1
720
11th to 20thNight
22%7%31%31%8%
652
21st to endNight
24%7%23%32%13%1
540
May1st to 10thNight
30%224%33%9%2
540
11th to 20thNight
23%429%32%11%2
532
21st to endNight
24%314%40%16%1
473
June1st to 10thNight
25%416%37%16%2
360
11th to 20thNight
22%313%43%16%3
360
21st to endNight
21%213%44%19%1
360
July1st to 10thNight
14%211%43%28%2
350
11th to 20thNight
16%210%44%26%1
348
21st to endNight
16%111%43%27%2
434
August1st to 10thNight
11%213%43%28%2
538
11th to 20thNight
14%212%44%27%2
532
21st to endNight
15%210%37%30%5%
746
September1st to 10thNight
15%216%37%27%4
720
11th to 20thNight
17%317%32%25%7%
720
21st to endNight
20%318%32%23%4
720
October1st to 10thNight
26%5%20%27%19%3
720
11th to 20thNight
20%6%27%29%15%2
720
21st to endNight
28%9%27%25%10%1
792
November1st to 10thNight
22%7%27%30%12%2
740
11th to 20thNight
24%16%28%23%9%1
760
21st to endNight
21%21%27%23%7%1
760
December1st to 10thNight
29%14%31%20%6%
760
11th to 20thNight
27%20%30%19%3
760
21st to endNight
26%16%34%19%4
836
Page generated at 2024-01-09 07:14:43. Version ac07

Copyright 2024 Attilla Danko


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