Mount Fritz Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mount Fritz Observatory 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
28%
24656
27%
74497
9%
24593
47%
24593
28%
38560

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
14%
950
30%
2647
5%
946
37%
946
21%
1336
January11th to 20thNight
11%
915
30%
2580
4%
915
35%
915
18%
1282
January21st to endNight
8%
792
31%
2574
3%
792
42%
792
15%
1278
February1st to 10thNight
9%
720
27%
2340
3%
720
36%
720
13%
1163
February11th to 20thNight
12%
704
26%
2162
3%
700
37%
700
19%
1087
February21st to endNight
8%
592
34%
1776
2%
592
41%
592
17%
930
March1st to 10thNight
14%
720
28%
2160
5%
720
36%
720
21%
1115
March11th to 20thNight
24%
720
28%
1985
8%
720
39%
720
27%
1087
March21st to endNight
19%
671
25%
2057
6%
671
39%
671
23%
1109
April1st to 10thNight
17%
540
25%
1800
4%
540
43%
540
21%
940
April11th to 20thNight
18%
533
23%
1777
7%
533
39%
533
21%
960
April21st to endNight
28%
540
23%
1800
11%
540
47%
540
24%
1008
May1st to 10thNight
29%
540
19%
1617
7%
540
42%
540
24%
996
May11th to 20thNight
38%
531
19%
1418
11%
531
46%
531
31%
875
May21st to endNight
44%
584
19%
1552
9%
582
54%
582
37%
897
June1st to 10thNight
54%
540
21%
1440
13%
540
60%
540
47%
758
June11th to 20thNight
44%
540
25%
1440
11%
540
54%
540
45%
766
June21st to endNight
59%
540
27%
1440
18%
540
65%
540
51%
750
July1st to 10thNight
65%
525
21%
1400
15%
525
70%
525
43%
791
July11th to 20thNight
67%
522
27%
1392
19%
522
73%
522
53%
720
July21st to endNight
71%
591
25%
1509
19%
558
74%
558
44%
829
August1st to 10thNight
62%
537
20%
1602
14%
534
67%
534
40%
856
August11th to 20thNight
63%
534
29%
1731
23%
534
73%
534
46%
840
August21st to endNight
64%
594
31%
1980
30%
594
72%
594
42%
981
September1st to 10thNight
57%
540
30%
1800
23%
540
71%
540
44%
872
September11th to 20thNight
52%
540
36%
1802
26%
540
67%
540
44%
842
September21st to endNight
48%
553
34%
1993
23%
553
64%
553
39%
905
October1st to 10thNight
33%
720
29%
2160
11%
720
48%
720
35%
1124
October11th to 20thNight
27%
720
34%
2160
8%
720
48%
720
32%
1030
October21st to endNight
17%
841
31%
2425
5%
841
38%
841
26%
1302
November1st to 10thNight
20%
925
32%
2405
6%
925
38%
925
33%
1242
November11th to 20thNight
12%
950
35%
2470
4%
950
36%
950
24%
1281
November21st to endNight
13%
950
30%
2636
3%
950
36%
950
22%
1405
December1st to 10thNight
10%
950
27%
2660
2%
950
32%
950
19%
1356
December11th to 20thNight
11%
950
28%
3115
2%
949
34%
949
15%
1604
December21st to endNight
11%
1042
18%
4692
2%
1026
34%
1026
10%
2243

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
45%25%5%35%5%6%8%51%
74790
Night
35%2442445%8%59%
75018
TransparencyDay
29%7%12%25%20%7%
74495
Night
23%5%14%28%23%8%
74835
SeeingDay
11%26%32%21%8%2
14495
Night
9%31%28%23%9%1
24659

By Month

Percentage Cloud Cover SW (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
435%42335%8%61%
1518
11th to 20thDay
425%5%3445%9%58%
1503
21st to endDay
435%5%2446%9%56%
1782
February1st to 10thDay
5%36%5%3445%8%57%
1620
11th to 20thDay
435%435%5%6%9%56%
1684
21st to endDay
17%36%5%2336%10%55%
1480
March1st to 10thDay
25%46%5%25%46%9%53%
1800
11th to 20thDay
48%34435%46%7%52%
1970
21st to endDay
38%35%5%36%6%7%9%46%
2298
April1st to 10thDay
46%34435%5%6%8%52%
2160
11th to 20thDay
8%8%47%4345%7%8%43%
2131
21st to endDay
7%8%36%6%36%6%7%9%39%
2160
May1st to 10thDay
10%9%26%5%36%5%6%9%37%
2339
11th to 20thDay
12%11%35%5%35%6%6%8%37%
2478
21st to endDay
8%6%25%5%37%6%9%10%37%
2724
June1st to 10thDay
4424446%8%9%10%46%
2520
11th to 20thDay
6%4244346%6%10%51%
2520
21st to endDay
33145%46%6%7%9%52%
2520
July1st to 10thDay
6%4245%46%6%8%9%43%
2520
11th to 20thDay
23146%46%7%7%10%49%
2520
21st to endDay
5%425%7%47%7%8%10%41%
2716
August1st to 10thDay
5%425%7%5%6%8%9%8%40%
2328
11th to 20thDay
4425%5%36%6%7%8%50%
2170
21st to endDay
4425%7%36%6%6%9%49%
2376
September1st to 10thDay
45%244345%5%8%57%
2160
11th to 20thDay
5%314435%5%7%7%54%
2157
21st to endDay
6%5%25%323345%62%
1962
October1st to 10thDay
5%8%244245%5%6%56%
1800
11th to 20thDay
3323424446%65%
1800
21st to endDay
45%2432445%7%60%
1910
November1st to 10thDay
232332345%7%67%
1673
11th to 20thDay
142332336%10%64%
1710
21st to endDay
1424435%45%8%60%
1541
December1st to 10thDay
13243345%6%9%59%
1520
11th to 20thDay
35%2443346%9%58%
1926
21st to endDay
16%47%6%345%5%7%54%
2794
January1st to 10thNight
1433424447%65%
2647
11th to 20thNight
132442345%7%66%
2580
21st to endNight
15%245%34448%60%
2574
February1st to 10thNight
5%25%435%448%61%
2340
11th to 20thNight
435%435%5%5%6%60%
2161
21st to endNight
17%36%423447%59%
1776
March1st to 10thNight
25%35%42345%9%57%
2160
11th to 20thNight
36%3432346%7%58%
1985
21st to endNight
46%35%32446%8%55%
2057
April1st to 10thNight
37%35%3345%5%7%56%
1800
11th to 20thNight
6%7%35%5%2335%8%53%
1777
21st to endNight
9%9%2433345%8%49%
1800
May1st to 10thNight
11%6%25%435%6%5%8%45%
1617
11th to 20thNight
14%8%24423447%47%
1417
21st to endNight
5%5%35%435%46%9%51%
1552
June1st to 10thNight
431322348%10%59%
1440
11th to 20thNight
5%2133245%5%9%61%
1440
21st to endNight
431231346%9%63%
1440
July1st to 10thNight
6%3234245%8%9%55%
1440
11th to 20thNight
23233235%6%10%61%
1440
21st to endNight
3225%435%5%8%9%54%
1598
August1st to 10thNight
43245%25%5%7%11%52%
1611
11th to 20thNight
432332346%10%59%
1731
21st to endNight
33134346%6%9%58%
1980
September1st to 10thNight
6%31442345%7%61%
1800
11th to 20thNight
6%323323347%64%
1802
21st to endNight
5%31333245%6%65%
1993
October1st to 10thNight
6%6%1442345%6%61%
2160
11th to 20thNight
4413322346%69%
2160
21st to endNight
47%34423447%60%
2425
November1st to 10thNight
241322345%7%68%
2405
11th to 20thNight
141332335%7%66%
2470
21st to endNight
1425%32446%7%62%
2636
December1st to 10thNight
1325%42336%8%63%
2660
11th to 20thNight
25%2442445%10%58%
3271
21st to endNight
25%35%5%3445%8%55%
4873

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
22%419%32%20%4
1519
11th to 20thDay
23%5%19%27%22%5%
1503
21st to endDay
25%5%16%31%17%5%
1782
February1st to 10thDay
27%5%18%28%18%5%
1620
11th to 20thDay
24%5%14%31%22%5%
1693
21st to endDay
27%413%28%22%6%
1480
March1st to 10thDay
28%5%12%32%20%2
1800
11th to 20thDay
31%5%14%27%18%5%
1970
21st to endDay
32%7%14%28%16%3
2298
April1st to 10thDay
29%7%13%26%17%9%
2160
11th to 20thDay
37%6%12%22%18%5%
2134
21st to endDay
40%8%10%26%16%1
2160
May1st to 10thDay
42%7%12%23%14%2
2339
11th to 20thDay
45%5%15%23%11%1
2482
21st to endDay
37%10%15%20%15%4
2724
June1st to 10thDay
29%10%18%22%15%6%
2520
11th to 20thDay
28%6%11%19%23%13%
2520
21st to endDay
25%8%11%20%24%12%
2520
July1st to 10thDay
32%9%13%17%21%9%
2451
11th to 20thDay
28%9%10%22%19%13%
2445
21st to endDay
35%10%13%21%15%7%
2565
August1st to 10thDay
37%11%12%19%14%8%
2313
11th to 20thDay
30%9%9%19%22%11%
2170
21st to endDay
31%8%9%19%24%8%
2376
September1st to 10thDay
25%7%7%20%27%15%
2160
11th to 20thDay
25%8%8%22%25%12%
2157
21st to endDay
26%47%21%35%8%
1962
October1st to 10thDay
29%6%8%25%25%8%
1800
11th to 20thDay
20%5%9%29%29%9%
1800
21st to endDay
24%5%10%28%26%8%
1910
November1st to 10thDay
19%412%29%28%8%
1673
11th to 20thDay
19%413%31%26%7%
1710
21st to endDay
23%5%11%29%22%9%
1541
December1st to 10thDay
21%6%17%31%18%6%
1520
11th to 20thDay
22%6%13%32%23%3
1924
21st to endDay
29%5%10%26%20%9%
2794
January1st to 10thNight
20%416%31%22%7%
2647
11th to 20thNight
17%5%20%28%23%7%
2580
21st to endNight
23%413%33%21%6%
2574
February1st to 10thNight
22%5%18%31%19%5%
2340
11th to 20thNight
22%315%31%24%4
2162
21st to endNight
25%211%28%25%8%
1776
March1st to 10thNight
24%313%31%25%4
2160
11th to 20thNight
24%412%29%25%6%
1985
21st to endNight
27%5%16%32%18%3
2057
April1st to 10thNight
26%5%13%29%19%8%
1800
11th to 20thNight
30%414%29%17%5%
1777
21st to endNight
33%411%30%21%1
1800
May1st to 10thNight
36%7%15%24%16%3
1617
11th to 20thNight
36%417%30%13%
1418
21st to endNight
28%5%18%27%18%4
1552
June1st to 10thNight
20%5%24%29%15%6%
1440
11th to 20thNight
20%6%14%21%22%17%
1440
21st to endNight
17%6%11%25%27%14%
1440
July1st to 10thNight
25%7%13%26%22%8%
1400
11th to 20thNight
19%5%14%28%20%14%
1392
21st to endNight
24%6%18%30%15%7%
1509
August1st to 10thNight
24%8%19%26%17%7%
1602
11th to 20thNight
22%413%25%26%11%
1731
21st to endNight
22%6%11%24%27%9%
1980
September1st to 10thNight
22%411%20%26%17%
1800
11th to 20thNight
20%410%27%26%14%
1802
21st to endNight
20%48%28%32%9%
1993
October1st to 10thNight
24%411%26%26%9%
2160
11th to 20thNight
18%311%29%27%13%
2160
21st to endNight
25%411%25%26%8%
2425
November1st to 10thNight
16%5%14%28%28%9%
2405
11th to 20thNight
17%413%32%26%7%
2470
21st to endNight
22%6%10%29%26%8%
2636
December1st to 10thNight
20%419%29%22%7%
2660
11th to 20thNight
20%8%14%30%24%4
3272
21st to endNight
26%5%14%24%22%10%
4873

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
17%36%26%14%5%2
270
11th to 20thDay
12%51%22%12%2
254
21st to endDay
11%55%28%5%2
264
February1st to 10thDay
14%61%19%5%1
240
11th to 20thDay
13%53%26%6%3
240
21st to endDay
14%52%26%8%1
198
March1st to 10thDay
14%41%33%10%2
240
11th to 20thDay
15%33%36%12%3
410
21st to endDay
15%40%32%10%3
462
April1st to 10thDay
17%40%29%13%2
420
11th to 20thDay
26%35%27%9%21
412
21st to endDay
20%33%30%12%41
420
May1st to 10thDay
19%26%33%14%6%1
544
11th to 20thDay
19%17%33%20%9%2
625
21st to endDay
11%18%32%27%10%2
679
June1st to 10thDay
7%15%32%27%16%3
630
11th to 20thDay
8%18%39%26%7%2
630
21st to endDay
5%13%38%27%14%3
630
July1st to 10thDay
8%5%29%36%19%4
621
11th to 20thDay
26%38%31%17%6%
618
21st to endDay
5%7%31%34%18%5%
658
August1st to 10thDay
7%9%38%34%10%2
447
11th to 20thDay
6%8%38%33%13%3
437
21st to endDay
7%14%31%36%9%3
495
September1st to 10thDay
8%15%36%30%9%2
450
11th to 20thDay
6%16%42%25%10%1
447
21st to endDay
9%19%34%23%12%3
270
October1st to 10thDay
10%19%30%29%9%3
270
11th to 20thDay
11%37%31%14%6%1
270
21st to endDay
9%41%31%13%5%1
297
November1st to 10thDay
10%41%27%14%6%3
270
11th to 20thDay
12%44%29%11%31
270
21st to endDay
11%46%31%10%11
270
December1st to 10thDay
17%43%28%8%3
270
11th to 20thDay
15%53%26%6%1
270
21st to endDay
18%49%21%9%21
297
January1st to 10thNight
9%47%26%14%31
950
11th to 20thNight
12%52%21%10%41
915
21st to endNight
8%53%26%10%3
792
February1st to 10thNight
8%55%24%10%3
720
11th to 20thNight
9%44%30%15%1
704
21st to endNight
8%50%30%11%1
592
March1st to 10thNight
8%42%33%13%4
720
11th to 20thNight
8%35%30%21%5%
720
21st to endNight
10%34%34%18%31
671
April1st to 10thNight
13%31%37%17%2
540
11th to 20thNight
13%30%33%17%6%1
533
21st to endNight
16%24%29%24%6%1
540
May1st to 10thNight
14%16%38%23%9%2
540
11th to 20thNight
18%8%30%28%14%2
531
21st to endNight
7%12%30%32%17%1
584
June1st to 10thNight
5%8%29%38%18%2
540
11th to 20thNight
7%10%36%36%11%
540
21st to endNight
47%25%41%21%1
540
July1st to 10thNight
8%316%43%27%3
525
11th to 20thNight
2322%45%25%3
522
21st to endNight
4314%45%30%4
591
August1st to 10thNight
5%321%47%22%2
537
11th to 20thNight
4422%44%23%3
534
21st to endNight
45%20%42%25%4
594
September1st to 10thNight
7%6%25%40%18%4
540
11th to 20thNight
7%9%27%39%15%3
540
21st to endNight
6%15%27%36%13%3
553
October1st to 10thNight
9%20%34%26%10%1
720
11th to 20thNight
7%36%28%22%7%1
720
21st to endNight
10%34%36%14%5%1
841
November1st to 10thNight
7%38%33%16%5%1
925
11th to 20thNight
10%47%29%12%21
950
21st to endNight
8%43%32%14%3
950
December1st to 10thNight
10%50%27%11%2
950
11th to 20thNight
9%50%26%11%3
950
21st to endNight
12%50%23%11%4
1045
Page generated at 2024-01-12 14:17:42. Version ac07

Copyright 2024 Attilla Danko


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