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 2005-11-05 to 2017-12-02.

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
36%
16278
25%
47813
10%
16232
50%
16232
33%
26305

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
21%
900
26%
2506
6%
895
39%
895
27%
1352
January16th to endNight
16%
801
30%
2529
7%
801
42%
801
27%
1283
February1st to 15thNight
13%
701
21%
2264
3%
698
34%
698
22%
1220
February16th to endNight
13%
632
27%
1894
2%
632
38%
632
27%
1042
March1st to 15thNight
25%
720
25%
2100
7%
720
42%
720
30%
1168
March16th to endNight
25%
688
24%
2032
7%
688
42%
688
30%
1143
April1st to 15thNight
27%
539
21%
1798
9%
539
42%
539
27%
979
April16th to endNight
28%
540
20%
1800
10%
540
43%
540
24%
1036
May1st to 15thNight
37%
540
17%
1593
9%
540
46%
540
24%
1042
May16th to endNight
50%
563
16%
1498
9%
561
56%
561
33%
921
June1st to 15thNight
55%
540
21%
1440
13%
540
61%
540
46%
776
June16th to endNight
70%
540
27%
1440
21%
540
75%
540
56%
728
July1st to 15thNight
71%
510
17%
1360
13%
510
74%
510
36%
839
July16th to endNight
78%
564
22%
1452
20%
531
79%
531
39%
848
August1st to 15thNight
74%
539
19%
1651
19%
536
76%
536
38%
890
August16th to endNight
71%
573
26%
1910
28%
573
74%
573
36%
1022
September1st to 15thNight
61%
540
27%
1800
23%
540
70%
540
36%
975
September16th to endNight
60%
543
33%
1929
27%
543
71%
543
41%
926
October1st to 15thNight
41%
720
27%
2160
12%
720
53%
720
38%
1174
October16th to endNight
31%
790
31%
2326
10%
790
48%
790
35%
1250
November1st to 15thNight
27%
950
30%
2470
8%
950
42%
950
40%
1334
November16th to endNight
21%
975
31%
2625
6%
975
42%
975
38%
1378
December1st to 15thNight
16%
910
21%
2548
2%
910
33%
910
27%
1416
December16th to endNight
16%
960
22%
2688
4%
960
32%
960
25%
1563

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
5%5%24435%5%6%8%49%
48647
Night
342332445%8%57%
47989
TransparencyDay
31%9%15%22%16%5%
48325
Night
23%7%16%26%19%5%
47813
SeeingDay
10%14%37%22%11%3
6093
Night
8%16%34%24%13%2
16281

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 15thDay
43433445%8%57%
1432
16th to endDay
425%42235%8%60%
1705
February1st to 15thDay
5%26%43445%10%52%
1598
16th to endDay
5%35%32435%8%56%
1580
March1st to 15thDay
2425%5%35%5%5%8%50%
1857
16th to endDay
48%24335%47%10%44%
2190
April1st to 15thDay
5%6%24435%5%6%8%47%
2150
16th to endDay
9%10%35%5%35%5%6%7%38%
2160
May1st to 15thDay
10%9%26%5%35%5%5%8%36%
2356
16th to endDay
10%6%24446%6%7%9%36%
2616
June1st to 15thDay
5%323436%6%7%9%46%
2520
16th to endDay
3213435%5%8%9%51%
2520
July1st to 15thDay
8%4135%46%6%7%8%41%
2520
16th to endDay
5%425%6%36%6%8%10%40%
2614
August1st to 15thDay
7%5%25%6%36%6%6%10%40%
2298
16th to endDay
5%4145%36%6%7%9%44%
2292
September1st to 15thDay
7%4134245%6%7%52%
2160
16th to endDay
6%423424346%59%
2028
October1st to 15thDay
5%413335%46%5%56%
1800
16th to endDay
45%23323346%60%
1884
November1st to 15thDay
131332335%10%61%
1718
16th to endDay
1325%31335%10%59%
1664
December1st to 15thDay
15%25%5%4445%7%54%
1449
16th to endDay
2416%42336%9%55%
1536
January1st to 15thNight
22332445%8%61%
2506
16th to endNight
42431335%6%62%
2529
February1st to 15thNight
434324448%59%
2254
16th to endNight
6%2442345%7%59%
1894
March1st to 15thNight
14143245%7%9%56%
2100
16th to endNight
36%2331345%7%57%
2032
April1st to 15thNight
36%233145%5%7%55%
1798
16th to endNight
9%8%3332235%7%49%
1800
May1st to 15thNight
11%7%243245%6%8%43%
1592
16th to endNight
7%5%1332446%7%51%
1497
June1st to 15thNight
32231347%8%60%
1440
16th to endNight
111222336%9%65%
1440
July1st to 15thNight
5%213425%6%7%10%49%
1440
16th to endNight
42134346%6%8%53%
1551
August1st to 15thNight
331432446%10%55%
1660
16th to endNight
4313435%5%6%7%54%
1910
September1st to 15thNight
7%31342335%7%56%
1800
16th to endNight
5%312323346%64%
1929
October1st to 15thNight
5%413314446%60%
2160
16th to endNight
45%24323246%60%
2326
November1st to 15thNight
131331335%7%64%
2470
16th to endNight
121321435%8%64%
2625
December1st to 15thNight
142342435%8%59%
2548
16th to endNight
1335%3245%6%8%54%
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
23%9%24%24%14%3
1433
16th to endDay
23%6%18%29%17%4
1705
February1st to 15thDay
28%9%23%25%9%3
1599
16th to endDay
26%6%18%28%16%2
1580
March1st to 15thDay
28%8%15%27%16%2
1857
16th to endDay
33%8%17%25%12%3
2190
April1st to 15thDay
33%9%14%23%14%4
2150
16th to endDay
42%10%13%20%11%1
2160
May1st to 15thDay
45%10%13%19%10%
2356
16th to endDay
42%12%14%18%9%3
2620
June1st to 15thDay
30%11%15%16%18%7%
2520
16th to endDay
25%9%12%20%24%8%
2520
July1st to 15thDay
38%10%13%15%13%9%
2371
16th to endDay
34%12%16%20%10%5%
2450
August1st to 15thDay
37%12%13%15%13%6%
2283
16th to endDay
33%9%14%19%18%4
2292
September1st to 15thDay
28%8%13%20%19%9%
2160
16th to endDay
26%5%11%24%28%3
2028
October1st to 15thDay
28%9%11%20%26%4
1800
16th to endDay
24%6%12%26%24%5%
1884
November1st to 15thDay
20%8%16%24%22%6%
1718
16th to endDay
20%417%28%22%6%
1664
December1st to 15thDay
29%8%20%28%11%1
1449
16th to endDay
26%9%19%26%14%3
1536
January1st to 15thNight
19%9%22%27%18%3
2506
16th to endNight
21%6%17%29%19%5%
2529
February1st to 15thNight
24%8%21%28%14%2
2264
16th to endNight
23%8%15%27%19%5%
1894
March1st to 15thNight
21%9%15%28%20%3
2100
16th to endNight
26%6%15%30%17%2
2032
April1st to 15thNight
26%8%15%26%17%5%
1798
16th to endNight
32%6%15%26%16%2
1800
May1st to 15thNight
36%11%14%22%13%1
1593
16th to endNight
28%10%19%23%13%3
1498
June1st to 15thNight
19%8%18%24%18%10%
1440
16th to endNight
14%7%12%24%28%13%
1440
July1st to 15thNight
28%10%15%20%14%10%
1360
16th to endNight
25%10%16%25%13%8%
1452
August1st to 15thNight
24%8%19%21%17%7%
1651
16th to endNight
26%7%13%22%23%6%
1910
September1st to 15thNight
26%7%13%21%18%12%
1800
16th to endNight
21%5%12%26%28%5%
1929
October1st to 15thNight
24%6%13%21%26%7%
2160
16th to endNight
25%414%24%25%6%
2326
November1st to 15thNight
18%6%14%26%24%9%
2470
16th to endNight
18%5%14%30%24%5%
2625
December1st to 15thNight
22%9%21%28%14%3
2548
16th to endNight
26%9%22%26%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
11%13%41%17%13%3
90
16th to endDay
5%28%40%22%3
96
February1st to 15thDay
13%41%36%8%
90
16th to endDay
8%29%35%22%3
81
March1st to 15thDay
12%31%40%13%2
147
16th to endDay
15%31%42%9%1
288
April1st to 15thDay
15%28%40%11%3
269
16th to endDay
22%27%35%10%3
270
May1st to 15thDay
14%16%40%19%7%1
414
16th to endDay
16%12%33%22%12%3
517
June1st to 15thDay
6%7%35%28%17%4
495
16th to endDay
4440%24%19%5%
495
July1st to 15thDay
12%326%30%18%8%
475
16th to endDay
5%330%29%22%9%
473
August1st to 15thDay
9%7%37%34%8%1
315
16th to endDay
9%6%32%37%11%2
332
September1st to 15thDay
9%11%41%24%9%3
315
16th to endDay
8%9%43%22%12%2
192
October1st to 15thDay
7%14%43%21%10%2
135
16th to endDay
11%15%45%20%43
144
November1st to 15thDay
311%48%19%14%2
135
16th to endDay
10%28%51%9%
135
December1st to 15thDay
12%28%47%10%
94
16th to endDay
334%45%12%4
96
January1st to 15thNight
12%27%36%15%5%1
900
16th to endNight
10%28%41%14%5%
801
February1st to 15thNight
9%27%43%14%4
704
16th to endNight
8%25%48%14%3
632
March1st to 15thNight
6%23%41%19%8%
720
16th to endNight
8%21%41%23%4
688
April1st to 15thNight
9%16%43%23%6%
539
16th to endNight
13%18%34%24%9%
540
May1st to 15thNight
15%6%36%26%12%1
540
16th to endNight
11%6%27%33%17%3
563
June1st to 15thNight
6%231%36%18%3
540
16th to endNight
2122%40%30%2
540
July1st to 15thNight
6%13%36%36%7%
510
16th to endNight
47%33%45%7%
564
August1st to 15thNight
5%10%43%36%4
539
16th to endNight
7%112%36%34%8%
573
September1st to 15thNight
7%222%33%25%7%
540
16th to endNight
7%5%23%37%21%5%
543
October1st to 15thNight
9%12%35%28%12%2
720
16th to endNight
8%17%39%20%10%3
790
November1st to 15thNight
6%20%43%20%7%1
950
16th to endNight
6%23%46%19%3
975
December1st to 15thNight
12%24%44%15%2
910
16th to endNight
8%26%44%15%5%
960
Page generated at 2017-12-03 09:16:40. Version ac04

Copyright 2017 A. Danko


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