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 2017-04-28.

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
35%
15532
25%
45649
10%
15486
49%
15486
32%
25146

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%
534
20%
1780
10%
534
43%
534
25%
1020
May1st to 15thNight
34%
495
18%
1461
9%
495
45%
495
23%
971
May16th to endNight
51%
515
15%
1370
8%
513
56%
513
34%
835
June1st to 15thNight
54%
495
22%
1320
13%
495
60%
495
43%
726
June16th to endNight
70%
495
26%
1320
20%
495
75%
495
56%
661
July1st to 15thNight
70%
465
18%
1240
13%
465
73%
465
35%
776
July16th to endNight
78%
522
21%
1337
19%
489
79%
489
39%
774
August1st to 15thNight
74%
494
20%
1512
20%
491
76%
491
38%
816
August16th to endNight
69%
525
24%
1750
25%
525
73%
525
35%
944
September1st to 15thNight
59%
495
28%
1650
24%
495
68%
495
35%
901
September16th to endNight
62%
497
32%
1768
27%
497
73%
497
43%
830
October1st to 15thNight
41%
660
28%
1980
13%
660
53%
660
37%
1086
October16th to endNight
31%
724
30%
2132
10%
724
47%
724
35%
1149
November1st to 15thNight
28%
875
31%
2275
9%
875
43%
875
39%
1239
November16th to endNight
22%
900
31%
2423
7%
900
41%
900
38%
1262
December1st to 15thNight
16%
900
21%
2520
2%
900
34%
900
26%
1406
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%
46059
Night
342332445%8%57%
45825
TransparencyDay
31%9%15%22%16%5%
45737
Night
23%7%16%26%19%5%
45649
SeeingDay
11%15%37%22%10%2
5219
Night
8%16%34%24%13%2
15535

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%25%5%35%5%6%7%38%
2127
May1st to 15thDay
11%9%26%5%35%5%5%7%35%
2158
16th to endDay
10%5%24446%6%7%10%36%
2392
June1st to 15thDay
5%423436%6%7%9%45%
2310
16th to endDay
3213435%6%8%9%51%
2310
July1st to 15thDay
8%5%135%46%6%7%7%42%
2310
16th to endDay
5%425%6%36%6%8%9%40%
2422
August1st to 15thDay
7%5%25%6%46%6%6%10%40%
2107
16th to endDay
6%4145%36%6%7%9%44%
2100
September1st to 15thDay
7%4124245%6%7%51%
1980
16th to endDay
4423424346%61%
1859
October1st to 15thDay
5%41343445%6%56%
1650
16th to endDay
45%22323347%60%
1727
November1st to 15thDay
132332335%10%59%
1583
16th to endDay
1325%31335%10%59%
1536
December1st to 15thDay
15%25%5%4445%7%53%
1440
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%50%
1780
May1st to 15thNight
11%8%243245%6%8%41%
1460
16th to endNight
6%5%1332447%7%52%
1369
June1st to 15thNight
43231347%8%59%
1320
16th to endNight
11122346%9%65%
1320
July1st to 15thNight
5%2135%25%6%7%9%48%
1320
16th to endNight
42234346%6%8%54%
1436
August1st to 15thNight
331432446%9%55%
1521
16th to endNight
5%313435%5%6%7%53%
1750
September1st to 15thNight
8%31342335%7%55%
1650
16th to endNight
4212313346%65%
1768
October1st to 15thNight
6%413314446%59%
1980
16th to endNight
45%23323246%59%
2132
November1st to 15thNight
131332335%7%64%
2275
16th to endNight
121321435%7%64%
2423
December1st to 15thNight
142342445%9%58%
2520
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
41%11%13%20%10%1
2127
May1st to 15thDay
46%9%13%19%10%1
2158
16th to endDay
41%12%14%18%9%3
2396
June1st to 15thDay
31%11%14%16%17%8%
2310
16th to endDay
25%9%12%18%24%9%
2310
July1st to 15thDay
38%10%13%15%12%9%
2161
16th to endDay
34%11%15%20%10%5%
2258
August1st to 15thDay
37%13%13%14%14%6%
2092
16th to endDay
33%9%14%19%18%4
2100
September1st to 15thDay
29%8%13%19%18%10%
1980
16th to endDay
24%5%11%24%29%3
1859
October1st to 15thDay
28%9%12%21%25%3
1650
16th to endDay
24%6%12%26%24%4
1727
November1st to 15thDay
21%9%16%22%22%7%
1583
16th to endDay
21%417%29%21%6%
1536
December1st to 15thDay
29%8%20%27%11%1
1440
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
1780
May1st to 15thNight
37%12%13%21%12%2
1461
16th to endNight
27%10%20%23%12%4
1370
June1st to 15thNight
20%9%18%23%17%9%
1320
16th to endNight
13%7%12%24%27%14%
1320
July1st to 15thNight
29%11%15%20%12%11%
1240
16th to endNight
24%10%17%26%13%8%
1337
August1st to 15thNight
24%8%18%21%18%8%
1512
16th to endNight
27%7%14%23%21%6%
1750
September1st to 15thNight
27%7%12%20%18%13%
1650
16th to endNight
19%6%12%27%29%5%
1768
October1st to 15thNight
24%6%14%21%25%6%
1980
16th to endNight
25%414%24%25%5%
2132
November1st to 15thNight
19%6%14%25%24%9%
2275
16th to endNight
18%5%15%30%24%6%
2423
December1st to 15thNight
22%9%21%28%15%3
2520
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%26%35%11%3
259
May1st to 15thDay
15%16%42%16%6%1
343
16th to endDay
15%13%32%23%12%3
437
June1st to 15thDay
7%7%35%28%16%3
420
16th to endDay
45%39%24%21%6%
420
July1st to 15thDay
13%427%29%18%7%
400
16th to endDay
5%333%28%20%8%
407
August1st to 15thDay
9%8%35%35%9%1
255
16th to endDay
10%8%36%32%10%1
268
September1st to 15thDay
10%13%47%23%4
255
16th to endDay
27%44%24%16%3
142
October1st to 15thDay
5%12%41%24%12%4
90
16th to endDay
15%12%37%27%34
96
November1st to 15thDay
5%10%37%23%20%3
90
16th to endDay
14%28%45%11%
90
December1st to 15thDay
13%30%45%11%
90
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%23%9%
534
May1st to 15thNight
15%6%38%25%11%1
495
16th to endNight
11%7%26%35%16%3
515
June1st to 15thNight
7%331%38%16%2
495
16th to endNight
2122%39%31%2
495
July1st to 15thNight
7%13%36%35%5%
465
16th to endNight
47%35%43%7%
522
August1st to 15thNight
5%10%43%36%4
494
16th to endNight
8%113%36%33%8%
525
September1st to 15thNight
8%223%34%24%6%
495
16th to endNight
5%5%22%37%23%6%
497
October1st to 15thNight
9%13%34%26%13%3
660
16th to endNight
9%18%37%20%10%3
724
November1st to 15thNight
7%20%41%21%7%1
875
16th to endNight
6%23%45%20%3
900
December1st to 15thNight
12%24%43%15%2
900
16th to endNight
8%26%44%15%5%
960
Page generated at 2017-04-29 07:44:59. Version ac04

Copyright 2017 A. Danko


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