Frog Hollow Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Frog Hollow 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
47%
24040
26%
74212
18%
23984
56%
23984
32%
43130

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
30%
948
27%
2458
10%
946
42%
946
31%
1560
January11th to 20thNight
27%
921
27%
2393
9%
921
39%
921
27%
1578
January21st to endNight
29%
990
29%
2574
10%
990
41%
990
30%
1634
February1st to 10thNight
26%
900
22%
2340
7%
900
35%
900
26%
1534
February11th to 20thNight
23%
804
20%
2199
6%
800
32%
800
25%
1461
February21st to endNight
24%
455
27%
1639
12%
455
41%
455
19%
1003
March1st to 10thNight
30%
540
26%
1980
16%
540
43%
540
24%
1177
March11th to 20thNight
29%
540
21%
1980
13%
540
41%
540
22%
1193
March21st to endNight
29%
594
23%
2178
13%
594
44%
594
24%
1283
April1st to 10thNight
31%
540
27%
1866
16%
540
47%
540
28%
1059
April11th to 20thNight
35%
533
27%
1775
18%
533
49%
533
28%
1026
April21st to endNight
35%
540
26%
1800
17%
540
50%
540
31%
995
May1st to 10thNight
44%
540
23%
1773
18%
540
55%
540
32%
1018
May11th to 20thNight
45%
531
22%
1594
19%
531
52%
531
32%
960
May21st to endNight
55%
584
23%
1746
19%
582
62%
582
33%
1043
June1st to 10thNight
73%
540
22%
1620
22%
540
77%
540
40%
902
June11th to 20thNight
76%
540
25%
1620
27%
540
78%
540
46%
839
June21st to endNight
76%
540
27%
1620
27%
540
79%
540
47%
830
July1st to 10thNight
74%
525
20%
1575
21%
525
76%
525
38%
893
July11th to 20thNight
81%
522
26%
1566
30%
522
82%
522
51%
772
July21st to endNight
80%
591
26%
1673
30%
558
81%
558
44%
896
August1st to 10thNight
81%
537
26%
1601
30%
534
82%
534
52%
784
August11th to 20thNight
76%
534
28%
1720
34%
534
77%
534
40%
909
August21st to endNight
77%
594
22%
1980
27%
594
77%
594
33%
1115
September1st to 10thNight
75%
540
27%
1800
30%
540
77%
540
38%
964
September11th to 20thNight
68%
540
29%
1901
30%
540
72%
540
34%
1025
September21st to endNight
70%
573
33%
2013
32%
573
75%
573
41%
999
October1st to 10thNight
69%
720
32%
2160
26%
720
73%
720
46%
1116
October11th to 20thNight
53%
720
35%
2160
21%
720
64%
720
40%
1179
October21st to endNight
44%
792
31%
2376
20%
792
54%
792
34%
1388
November1st to 10thNight
50%
740
31%
2220
21%
740
59%
740
37%
1257
November11th to 20thNight
44%
760
31%
2280
19%
760
55%
760
35%
1278
November21st to endNight
37%
836
30%
2356
17%
836
48%
836
30%
1469
December1st to 10thNight
35%
950
27%
2470
12%
950
46%
950
30%
1599
December11th to 20thNight
33%
948
28%
2872
12%
948
42%
948
25%
1815
December21st to endNight
30%
1038
16%
4334
10%
1026
40%
1026
19%
2577

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
13%6%25%5%345%5%7%44%
75018
Night
13%5%2442445%7%51%
74779
TransparencyDay
39%410%23%19%5%
74742
Night
34%39%22%23%8%
74575
SeeingDay
15%9%23%26%21%6%
14118
Night
15%8%25%31%18%2
24051

By Month

Percentage Cloud Cover SE (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
19%9%34423335%46%
1707
11th to 20thDay
19%7%3442425%5%44%
1656
21st to endDay
19%7%25%323335%49%
1782
February1st to 10thDay
23%7%35%42434439%
1620
11th to 20thDay
20%8%35%424435%40%
1650
21st to endDay
26%7%36%5%2233438%
1628
March1st to 10thDay
19%7%34424347%43%
1980
11th to 20thDay
20%7%36%5%34446%40%
1980
21st to endDay
15%8%36%5%34446%41%
2178
April1st to 10thDay
14%6%35%7%245%46%44%
2092
11th to 20thDay
16%6%35%5%35%446%45%
2134
21st to endDay
12%7%36%6%3445%6%43%
2160
May1st to 10thDay
16%7%36%5%33447%42%
2183
11th to 20thDay
12%7%25%6%35%5%6%8%39%
2302
21st to endDay
9%6%36%6%46%6%6%10%38%
2531
June1st to 10thDay
7%5%35%6%45%6%7%9%42%
2340
11th to 20thDay
7%425%7%5%6%6%7%8%44%
2340
21st to endDay
4335%5%36%6%6%10%50%
2340
July1st to 10thDay
7%437%7%5%7%7%8%11%35%
2340
11th to 20thDay
6%4246%45%6%7%12%45%
2340
21st to endDay
7%425%6%46%7%8%11%41%
2546
August1st to 10thDay
4315%6%47%6%9%10%45%
2328
11th to 20thDay
9%5%25%5%46%6%7%8%45%
2180
21st to endDay
7%5%25%6%46%7%8%9%43%
2376
September1st to 10thDay
9%5%25%5%35%5%6%7%48%
2160
11th to 20thDay
13%5%25%5%35%5%5%7%45%
2054
21st to endDay
9%424434447%54%
1927
October1st to 10thDay
9%415%42436%6%57%
1800
11th to 20thDay
13%7%14322345%56%
1800
21st to endDay
17%6%2442334452%
1980
November1st to 10thDay
14%5%3422335%6%53%
1858
11th to 20thDay
11%6%34423446%53%
1900
21st to endDay
21%7%2432333446%
1820
December1st to 10thDay
18%7%35%423345%47%
1710
11th to 20thDay
14%7%37%5%4443443%
2161
21st to endDay
17%8%37%5%345%46%39%
3135
January1st to 10thNight
18%7%23423246%50%
2458
11th to 20thNight
19%6%25%423235%48%
2393
21st to endNight
18%5%33323445%51%
2574
February1st to 10thNight
19%8%24323345%46%
2340
11th to 20thNight
20%7%35%423345%43%
2198
21st to endNight
21%6%25%422345%45%
1639
March1st to 10thNight
17%7%24434347%44%
1980
11th to 20thNight
18%7%35%423347%43%
1980
21st to endNight
16%6%35%423446%47%
2178
April1st to 10thNight
12%5%25%5%23347%51%
1866
11th to 20thNight
13%4345%34447%50%
1775
21st to endNight
12%5%3442435%6%52%
1800
May1st to 10thNight
11%5%25%43445%8%50%
1773
11th to 20thNight
13%5%25%5%34448%47%
1593
21st to endNight
9%5%35%5%35%45%10%47%
1745
June1st to 10thNight
44245%346%6%11%52%
1620
11th to 20thNight
431443446%7%60%
1620
21st to endNight
431332445%9%60%
1620
July1st to 10thNight
6%325%5%347%7%13%46%
1620
11th to 20thNight
421342347%13%58%
1620
21st to endNight
32245%35%6%6%11%53%
1772
August1st to 10thNight
2313325%47%12%57%
1611
11th to 20thNight
7%314425%5%6%12%52%
1720
21st to endNight
7%424435%6%7%9%48%
1980
September1st to 10thNight
6%42443445%7%57%
1800
11th to 20thNight
9%5%23435%5%6%8%51%
1901
21st to endNight
7%414423347%61%
2013
October1st to 10thNight
7%41342345%6%62%
2160
11th to 20thNight
12%42332335%5%59%
2160
21st to endNight
16%5%2342333455%
2376
November1st to 10thNight
11%414434345%57%
2220
11th to 20thNight
11%434424435%56%
2280
21st to endNight
17%5%3443333450%
2356
December1st to 10thNight
17%6%25%333445%47%
2470
11th to 20thNight
17%5%2443444448%
3036
21st to endNight
17%7%36%42233448%
4532

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
44%27%21%19%8%
1708
11th to 20thDay
44%2424%22%4
1656
21st to endDay
41%1321%28%5%
1782
February1st to 10thDay
49%26%19%18%6%
1620
11th to 20thDay
48%25%20%19%6%
1659
21st to endDay
51%25%12%21%8%
1628
March1st to 10thDay
43%36%18%20%10%
1980
11th to 20thDay
48%38%19%18%4
1980
21st to endDay
46%37%22%19%3
2178
April1st to 10thDay
41%38%23%19%6%
2092
11th to 20thDay
42%37%21%19%6%
2134
21st to endDay
41%310%22%21%3
2160
May1st to 10thDay
44%39%23%17%4
2183
11th to 20thDay
42%412%25%15%2
2306
21st to endDay
41%6%15%24%14%1
2531
June1st to 10thDay
37%5%13%27%14%2
2340
11th to 20thDay
35%6%12%28%16%2
2340
21st to endDay
30%5%11%31%20%2
2340
July1st to 10thDay
39%7%17%26%10%1
2276
11th to 20thDay
30%6%18%26%18%2
2271
21st to endDay
33%6%19%30%11%1
2405
August1st to 10thDay
30%7%18%31%15%1
2314
11th to 20thDay
35%6%14%26%16%2
2180
21st to endDay
35%7%15%26%13%3
2376
September1st to 10thDay
35%6%12%20%20%8%
2160
11th to 20thDay
38%5%9%20%21%6%
2054
21st to endDay
31%310%22%25%10%
1927
October1st to 10thDay
29%310%22%25%11%
1800
11th to 20thDay
33%25%18%28%14%
1800
21st to endDay
37%26%18%25%11%
1980
November1st to 10thDay
33%27%23%26%9%
1858
11th to 20thDay
34%26%19%29%11%
1900
21st to endDay
44%25%17%25%7%
1820
December1st to 10thDay
42%29%21%19%7%
1710
11th to 20thDay
46%2416%24%8%
2159
21st to endDay
48%25%19%21%6%
3135
January1st to 10thNight
39%26%19%27%7%
2458
11th to 20thNight
42%37%19%23%7%
2393
21st to endNight
39%2417%30%8%
2574
February1st to 10thNight
43%26%20%21%8%
2340
11th to 20thNight
45%36%20%20%7%
2199
21st to endNight
44%26%15%22%11%
1639
March1st to 10thNight
41%26%17%21%12%
1980
11th to 20thNight
43%39%17%21%8%
1980
21st to endNight
40%38%22%23%5%
2178
April1st to 10thNight
36%310%23%18%11%
1866
11th to 20thNight
36%47%22%22%10%
1775
21st to endNight
34%210%25%25%4
1800
May1st to 10thNight
34%410%26%19%7%
1773
11th to 20thNight
37%312%26%18%3
1594
21st to endNight
34%6%15%28%16%2
1746
June1st to 10thNight
27%6%14%32%18%3
1620
11th to 20thNight
23%411%34%24%4
1620
21st to endNight
22%5%13%29%26%5%
1620
July1st to 10thNight
28%7%21%27%16%1
1575
11th to 20thNight
19%5%20%32%20%4
1566
21st to endNight
25%5%18%34%17%1
1673
August1st to 10thNight
20%321%34%20%1
1601
11th to 20thNight
27%5%15%30%20%4
1720
21st to endNight
31%7%15%24%20%3
1980
September1st to 10thNight
27%6%12%22%24%9%
1800
11th to 20thNight
31%410%22%23%9%
1901
21st to endNight
25%48%23%27%13%
2013
October1st to 10thNight
25%39%24%25%15%
2160
11th to 20thNight
29%35%16%29%18%
2160
21st to endNight
35%25%19%25%14%
2376
November1st to 10thNight
31%37%20%27%12%
2220
11th to 20thNight
32%27%19%28%12%
2280
21st to endNight
39%25%19%27%8%
2356
December1st to 10thNight
40%38%20%21%8%
2470
11th to 20thNight
41%25%17%24%10%
3037
21st to endNight
42%26%21%25%5%
4532

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
30%13%34%19%4
270
11th to 20thDay
23%18%38%17%31
252
21st to endDay
23%27%33%13%5%
264
February1st to 10thDay
28%18%35%14%5%
240
11th to 20thDay
35%20%32%12%1
240
21st to endDay
39%24%28%7%3
198
March1st to 10thDay
29%19%33%16%3
240
11th to 20thDay
28%23%31%14%4
240
21st to endDay
24%20%36%17%2
264
April1st to 10thDay
21%16%36%18%9%1
352
11th to 20thDay
25%14%31%21%8%1
412
21st to endDay
17%16%34%22%9%2
420
May1st to 10thDay
18%13%31%27%9%1
446
11th to 20thDay
14%8%31%28%15%3
625
21st to endDay
11%5%25%35%19%5%
679
June1st to 10thDay
10%416%31%30%10%
630
11th to 20thDay
6%217%38%28%7%
630
21st to endDay
4220%35%29%10%
630
July1st to 10thDay
6%213%34%36%10%
621
11th to 20thDay
5%29%31%40%12%
618
21st to endDay
6%7%32%40%14%
684
August1st to 10thDay
5%111%30%41%11%
626
11th to 20thDay
12%26%33%36%11%
494
21st to endDay
11%15%21%42%19%
495
September1st to 10thDay
8%26%28%41%15%
450
11th to 20thDay
10%313%27%34%13%
344
21st to endDay
14%413%36%24%9%
270
October1st to 10thDay
7%228%37%23%3
270
11th to 20thDay
12%10%36%26%12%3
270
21st to endDay
26%10%30%24%9%1
297
November1st to 10thDay
18%12%30%25%13%3
270
11th to 20thDay
16%12%39%25%8%
270
21st to endDay
26%14%29%19%10%2
270
December1st to 10thDay
22%19%34%17%6%2
270
11th to 20thDay
25%15%35%17%6%1
270
21st to endDay
23%20%40%12%31
297
January1st to 10thNight
23%13%31%27%5%
950
11th to 20thNight
24%14%31%24%6%
921
21st to endNight
21%12%35%28%4
990
February1st to 10thNight
24%14%32%24%5%
900
11th to 20thNight
25%15%35%22%3
804
21st to endNight
24%17%33%22%4
455
March1st to 10thNight
21%12%34%27%5%
540
11th to 20thNight
20%14%34%27%5%1
540
21st to endNight
19%12%37%26%6%
594
April1st to 10thNight
16%13%36%27%7%
540
11th to 20thNight
13%14%35%27%11%1
533
21st to endNight
12%12%36%28%11%
540
May1st to 10thNight
13%7%33%36%11%1
540
11th to 20thNight
14%5%31%30%18%2
531
21st to endNight
10%324%37%23%3
584
June1st to 10thNight
5%212%40%37%3
540
11th to 20thNight
4112%47%34%2
540
21st to endNight
4211%40%36%7%
540
July1st to 10thNight
5%110%33%44%7%
525
11th to 20thNight
5%15%33%46%10%
522
21st to endNight
316%38%42%9%
591
August1st to 10thNight
317%36%45%8%
537
11th to 20thNight
7%10%38%37%8%
534
21st to endNight
8%16%32%46%8%
594
September1st to 10thNight
7%19%34%43%6%
540
11th to 20thNight
11%112%31%39%5%
540
21st to endNight
9%212%36%36%4
573
October1st to 10thNight
9%313%38%33%4
720
11th to 20thNight
14%5%25%36%19%1
720
21st to endNight
18%8%26%28%17%2
792
November1st to 10thNight
12%6%28%37%16%1
740
11th to 20thNight
12%10%29%37%12%
760
21st to endNight
20%12%28%28%11%
836
December1st to 10thNight
22%9%31%30%8%
950
11th to 20thNight
24%11%28%30%7%
950
21st to endNight
22%13%31%27%6%
1045
Page generated at 2024-01-11 21:33:47. Version ac07

Copyright 2024 Attilla Danko


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