Rosemere
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Rosemere clear sky chart from 2005-11-06 to 2024-01-16.

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
33%
22546
15%
74755
10%
22505
41%
22505
18%
52051

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
19%
760
10%
2649
5%
757
26%
757
10%
2053
January11th to 20thNight
21%
744
11%
2602
6%
744
28%
744
11%
1973
January21st to endNight
27%
792
14%
2772
9%
792
35%
792
15%
1957
February1st to 10thNight
20%
720
12%
2377
5%
720
29%
720
12%
1815
February11th to 20thNight
25%
703
15%
2186
7%
700
35%
700
16%
1561
February21st to endNight
26%
592
17%
1776
8%
592
38%
592
17%
1293
March1st to 10thNight
26%
720
16%
2160
11%
720
34%
720
16%
1567
March11th to 20thNight
28%
720
16%
2090
8%
720
37%
720
18%
1506
March21st to endNight
32%
792
21%
1985
9%
792
40%
792
24%
1433
April1st to 10thNight
28%
720
17%
1800
5%
720
34%
720
20%
1342
April11th to 20thNight
31%
711
17%
1775
5%
711
37%
711
23%
1282
April21st to endNight
28%
576
18%
1656
8%
576
37%
576
21%
1171
May1st to 10thNight
31%
406
17%
1486
11%
406
41%
406
18%
982
May11th to 20thNight
34%
354
20%
1416
18%
354
47%
354
19%
890
May21st to endNight
35%
389
13%
1551
12%
388
47%
388
20%
962
June1st to 10thNight
39%
360
11%
1440
12%
360
48%
360
17%
960
June11th to 20thNight
43%
360
12%
1440
14%
360
50%
360
21%
875
June21st to endNight
43%
360
10%
1440
14%
360
49%
360
17%
931
July1st to 10thNight
52%
350
14%
1400
18%
350
60%
350
26%
787
July11th to 20thNight
54%
348
14%
1392
22%
348
57%
348
25%
800
July21st to endNight
56%
394
14%
1486
18%
372
60%
372
23%
848
August1st to 10thNight
60%
358
17%
1422
21%
356
63%
356
24%
823
August11th to 20thNight
56%
527
18%
1591
14%
527
59%
527
30%
992
August21st to endNight
52%
792
19%
1980
10%
792
55%
792
33%
1314
September1st to 10thNight
53%
720
16%
1800
7%
720
56%
720
34%
1186
September11th to 20thNight
55%
720
21%
1872
13%
720
58%
720
35%
1181
September21st to endNight
46%
720
22%
1980
16%
720
52%
720
30%
1293
October1st to 10thNight
39%
720
21%
2103
14%
720
47%
720
24%
1412
October11th to 20thNight
34%
720
17%
2197
10%
720
42%
720
20%
1525
October21st to endNight
29%
792
13%
2574
8%
792
36%
792
16%
1849
November1st to 10thNight
31%
740
18%
2407
11%
740
41%
740
18%
1652
November11th to 20thNight
27%
760
19%
2550
13%
760
37%
760
18%
1770
November21st to endNight
24%
760
13%
2660
6%
760
33%
760
13%
1948
December1st to 10thNight
21%
760
10%
2660
5%
760
28%
760
10%
2051
December11th to 20thNight
18%
760
13%
3239
5%
759
29%
759
10%
2399
December21st to endNight
17%
826
7%
4841
4%
817
26%
817
6%
3668

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%9%37%6%35%5%5%7%34%
74785
Night
18%10%47%6%3445%6%33%
75019
TransparencyDay
51%312%22%11%1
74490
Night
53%311%21%11%1
74848
SeeingDay
22%8%27%26%13%4
13455
Night
23%6%27%31%11%1
22556

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
18%16%5%10%7%45%44424%
1517
11th to 20thDay
18%14%5%8%7%34446%28%
1480
21st to endDay
11%13%49%7%46%6%5%6%29%
1584
February1st to 10thDay
14%15%5%9%6%35%5%46%27%
1580
11th to 20thDay
14%12%5%9%6%46%5%5%6%28%
1662
21st to endDay
18%14%7%8%6%3445%428%
1480
March1st to 10thDay
16%11%49%7%45%45%6%29%
1797
11th to 20thDay
16%12%36%7%25%446%33%
1867
21st to endDay
19%9%47%6%34445%36%
2371
April1st to 10thDay
21%10%47%6%34445%32%
2160
11th to 20thDay
20%7%35%6%43445%37%
2134
21st to endDay
21%10%47%6%245%45%32%
2304
May1st to 10thDay
19%7%46%6%25%5%5%7%34%
2490
11th to 20thDay
19%6%25%6%4446%7%37%
2478
21st to endDay
17%6%36%6%36%5%6%8%35%
2725
June1st to 10thDay
20%8%36%5%45%5%5%8%30%
2520
11th to 20thDay
15%5%46%6%45%5%6%8%38%
2520
21st to endDay
19%7%37%6%45%5%6%8%30%
2520
July1st to 10thDay
11%6%25%6%37%6%6%8%40%
2520
11th to 20thDay
12%5%25%6%36%7%7%10%37%
2520
21st to endDay
11%5%36%5%35%7%8%10%37%
2744
August1st to 10thDay
11%6%36%7%36%6%7%9%36%
2506
11th to 20thDay
9%5%37%6%35%5%7%8%40%
2289
21st to endDay
12%6%245%346%6%8%43%
2376
September1st to 10thDay
12%5%25%5%35%6%6%9%41%
2160
11th to 20thDay
14%5%2443445%6%49%
2087
21st to endDay
15%6%35%5%34448%42%
1980
October1st to 10thDay
20%6%36%5%3445%7%36%
1854
11th to 20thDay
19%7%36%9%45%5%6%7%28%
1762
21st to endDay
25%9%47%5%3345%6%30%
1782
November1st to 10thDay
17%9%46%4445%5%8%35%
1671
11th to 20thDay
18%11%47%5%35%45%7%31%
1627
21st to endDay
22%10%37%5%46%5%5%7%27%
1520
December1st to 10thDay
24%12%6%10%6%3444422%
1520
11th to 20thDay
22%13%5%7%5%3445%5%28%
1906
21st to endDay
27%16%49%5%3333421%
2772
January1st to 10thNight
17%16%6%10%8%35%445%21%
2649
11th to 20thNight
17%15%6%8%7%35%44426%
2602
21st to endNight
12%12%5%9%8%3445%6%31%
2772
February1st to 10thNight
14%14%6%11%8%46%5%5%6%23%
2377
11th to 20thNight
15%10%49%7%45%5%5%6%31%
2184
21st to endNight
16%13%5%9%6%25%445%31%
1776
March1st to 10thNight
17%13%5%7%6%35%446%30%
2150
11th to 20thNight
17%13%47%5%3445%6%32%
2090
21st to endNight
17%10%46%6%3444438%
1985
April1st to 10thNight
24%9%37%5%345%46%31%
1800
11th to 20thNight
22%7%36%5%34446%37%
1775
21st to endNight
21%9%35%5%245%45%35%
1656
May1st to 10thNight
21%8%36%6%35%446%34%
1486
11th to 20thNight
19%6%36%5%345%5%6%38%
1415
21st to endNight
16%6%26%6%35%5%5%7%40%
1550
June1st to 10thNight
20%7%36%5%35%47%8%32%
1440
11th to 20thNight
17%6%36%5%345%6%7%39%
1440
21st to endNight
17%6%46%5%35%5%5%8%35%
1440
July1st to 10thNight
10%435%6%346%7%9%43%
1440
11th to 20thNight
11%5%346%36%6%7%9%40%
1440
21st to endNight
11%5%35%6%345%7%9%41%
1574
August1st to 10thNight
12%5%25%5%36%45%9%43%
1432
11th to 20thNight
12%5%36%5%345%6%8%43%
1591
21st to endNight
13%5%25%5%345%6%9%42%
1980
September1st to 10thNight
11%5%36%6%35%5%5%7%45%
1800
11th to 20thNight
15%435%423348%49%
1872
21st to endNight
16%5%26%43445%7%44%
1980
October1st to 10thNight
18%6%36%5%34446%40%
2103
11th to 20thNight
20%8%47%5%3435%6%35%
2197
21st to endNight
22%9%47%6%3445%5%31%
2574
November1st to 10thNight
19%9%36%6%35%5%5%7%33%
2407
11th to 20thNight
19%9%47%5%345%5%6%34%
2550
21st to endNight
22%12%47%7%34445%29%
2660
December1st to 10thNight
21%14%6%9%6%445%46%22%
2660
11th to 20thNight
23%13%5%8%5%34445%27%
3288
21st to endNight
28%15%5%9%5%2334422%
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
66%39%16%5%
1518
11th to 20thDay
61%310%14%11%1
1480
21st to endDay
55%411%19%10%1
1584
February1st to 10thDay
60%210%19%6%2
1580
11th to 20thDay
58%411%17%9%1
1671
21st to endDay
61%29%17%10%2
1480
March1st to 10thDay
57%39%18%10%2
1800
11th to 20thDay
53%312%16%14%3
1867
21st to endDay
51%39%19%14%3
2371
April1st to 10thDay
56%37%19%13%2
2160
11th to 20thDay
50%27%23%16%2
2134
21st to endDay
55%38%18%12%4
2304
May1st to 10thDay
50%37%22%16%2
2490
11th to 20thDay
47%49%21%16%3
2482
21st to endDay
46%5%13%20%14%2
2725
June1st to 10thDay
52%49%21%12%2
2520
11th to 20thDay
44%410%25%14%3
2520
21st to endDay
52%412%20%11%1
2520
July1st to 10thDay
39%5%13%28%13%1
2450
11th to 20thDay
40%416%30%10%
2445
21st to endDay
41%417%28%9%
2591
August1st to 10thDay
43%5%17%27%9%
2492
11th to 20thDay
40%418%28%11%
2289
21st to endDay
38%415%28%15%
2376
September1st to 10thDay
39%414%30%13%1
2160
11th to 20thDay
36%312%33%15%1
2087
21st to endDay
43%413%28%11%1
1980
October1st to 10thDay
49%312%24%12%
1854
11th to 20thDay
55%413%21%7%
1762
21st to endDay
56%212%20%8%1
1782
November1st to 10thDay
49%213%25%9%1
1671
11th to 20thDay
55%311%19%11%
1627
21st to endDay
59%414%17%6%1
1520
December1st to 10thDay
67%212%14%5%
1520
11th to 20thDay
60%311%19%7%
1906
21st to endDay
70%212%10%6%
2772
January1st to 10thNight
66%39%17%5%
2649
11th to 20thNight
63%410%14%8%1
2602
21st to endNight
56%39%19%12%1
2772
February1st to 10thNight
63%39%18%6%1
2377
11th to 20thNight
56%210%22%9%1
2186
21st to endNight
57%28%18%14%1
1776
March1st to 10thNight
57%29%18%12%2
2160
11th to 20thNight
55%39%17%14%3
2091
21st to endNight
51%27%21%15%4
1985
April1st to 10thNight
55%36%20%15%2
1800
11th to 20thNight
51%25%23%15%2
1775
21st to endNight
52%37%20%14%5%
1656
May1st to 10thNight
52%16%20%15%5%
1486
11th to 20thNight
48%37%20%18%4
1416
21st to endNight
44%5%12%20%17%2
1551
June1st to 10thNight
51%49%23%13%1
1440
11th to 20thNight
43%411%24%15%3
1440
21st to endNight
47%6%12%20%14%
1440
July1st to 10thNight
37%5%14%27%17%1
1400
11th to 20thNight
38%416%29%12%
1392
21st to endNight
39%5%18%26%12%
1486
August1st to 10thNight
39%418%26%12%
1422
11th to 20thNight
39%418%26%13%
1591
21st to endNight
40%415%28%13%1
1980
September1st to 10thNight
39%313%28%15%1
1800
11th to 20thNight
37%313%34%13%1
1872
21st to endNight
42%411%29%15%
1980
October1st to 10thNight
46%49%27%13%1
2103
11th to 20thNight
52%311%26%9%
2197
21st to endNight
56%312%19%9%1
2574
November1st to 10thNight
52%311%24%9%1
2407
11th to 20thNight
53%312%21%10%1
2550
21st to endNight
60%211%19%7%
2660
December1st to 10thNight
65%312%16%4
2660
11th to 20thNight
62%29%19%8%
3288
21st to endNight
68%210%16%5%
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
26%7%27%30%11%
180
11th to 20thDay
30%11%30%23%5%2
170
21st to endDay
19%11%31%28%8%2
176
February1st to 10thDay
34%16%31%17%2
222
11th to 20thDay
24%9%37%25%4
329
21st to endDay
29%9%31%26%5%
346
March1st to 10thDay
25%10%31%25%9%
420
11th to 20thDay
22%10%33%27%7%1
420
21st to endDay
28%8%31%21%9%3
462
April1st to 10thDay
28%12%26%22%10%3
420
11th to 20thDay
27%12%25%22%11%3
412
21st to endDay
28%10%28%21%9%3
420
May1st to 10thDay
23%9%31%25%9%3
423
11th to 20thDay
21%6%31%25%12%5%
447
21st to endDay
18%9%32%25%13%3
485
June1st to 10thDay
25%8%25%26%13%3
450
11th to 20thDay
18%8%22%31%16%4
450
21st to endDay
20%6%24%28%18%4
450
July1st to 10thDay
14%420%33%21%7%
445
11th to 20thDay
14%426%33%19%5%
444
21st to endDay
14%322%35%20%6%
488
August1st to 10thDay
15%320%32%21%8%
446
11th to 20thDay
12%418%33%21%13%
439
21st to endDay
15%6%24%25%21%10%
495
September1st to 10thDay
13%425%29%19%10%
450
11th to 20thDay
15%5%24%24%20%12%
450
21st to endDay
18%6%26%23%19%7%
450
October1st to 10thDay
21%9%26%23%15%6%
450
11th to 20thDay
22%9%32%22%12%3
430
21st to endDay
34%9%24%25%8%1
396
November1st to 10thDay
28%10%25%25%12%1
365
11th to 20thDay
25%10%34%20%8%1
287
21st to endDay
32%8%26%24%7%2
180
December1st to 10thDay
30%9%24%27%8%2
180
11th to 20thDay
26%12%37%19%41
180
21st to endDay
32%14%29%17%8%1
198
January1st to 10thNight
28%8%30%28%6%
760
11th to 20thNight
25%8%32%27%6%
744
21st to endNight
20%7%34%31%8%1
792
February1st to 10thNight
22%6%37%28%6%1
720
11th to 20thNight
23%8%34%29%6%1
703
21st to endNight
24%7%32%33%5%
592
March1st to 10thNight
25%8%30%31%6%
720
11th to 20thNight
27%8%31%27%8%
720
21st to endNight
23%6%29%33%8%
792
April1st to 10thNight
27%9%27%31%6%
720
11th to 20thNight
27%8%28%29%7%1
711
21st to endNight
28%7%29%27%9%
576
May1st to 10thNight
24%5%31%31%8%1
406
11th to 20thNight
23%430%34%8%1
354
21st to endNight
19%333%34%10%1
389
June1st to 10thNight
28%323%33%13%
360
11th to 20thNight
19%426%36%14%1
360
21st to endNight
20%323%37%16%1
360
July1st to 10thNight
12%326%42%17%1
350
11th to 20thNight
12%221%47%18%1
348
21st to endNight
12%317%47%20%1
394
August1st to 10thNight
16%312%43%25%1
358
11th to 20thNight
15%218%37%26%3
527
21st to endNight
17%221%36%23%2
792
September1st to 10thNight
15%221%43%18%1
720
11th to 20thNight
19%316%38%22%2
720
21st to endNight
18%326%33%18%2
720
October1st to 10thNight
21%5%27%34%13%1
720
11th to 20thNight
26%5%25%32%12%1
720
21st to endNight
28%7%28%30%7%
792
November1st to 10thNight
25%9%27%30%10%
740
11th to 20thNight
24%8%32%25%11%1
760
21st to endNight
30%9%27%24%9%1
760
December1st to 10thNight
31%8%28%26%7%
760
11th to 20thNight
28%9%32%23%6%1
760
21st to endNight
34%10%28%22%6%
836
Page generated at 2024-01-13 09:37:57. Version ac07

Copyright 2024 Attilla Danko


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