Sisk Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sisk Observatory clear sky chart from 2005-11-06 to 2024-01-12.

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
42%
24360
16%
74907
10%
24297
48%
24297
16%
54742

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
29%
950
15%
2458
5%
946
37%
946
17%
1872
January11th to 20thNight
26%
906
17%
2354
6%
906
34%
906
17%
1792
January21st to endNight
28%
990
16%
2574
6%
990
34%
990
16%
1988
February1st to 10thNight
22%
900
13%
2340
4%
900
28%
900
14%
1857
February11th to 20thNight
23%
879
13%
2274
3%
875
29%
875
15%
1761
February21st to endNight
24%
507
19%
1691
6%
507
35%
507
12%
1236
March1st to 10thNight
28%
540
16%
1980
8%
540
39%
540
13%
1392
March11th to 20thNight
27%
540
13%
1980
9%
540
34%
540
11%
1495
March21st to endNight
25%
594
11%
2178
4%
594
33%
594
10%
1673
April1st to 10thNight
34%
540
14%
1893
9%
540
43%
540
15%
1334
April11th to 20thNight
32%
533
18%
1775
12%
533
42%
533
14%
1290
April21st to endNight
30%
540
15%
1715
8%
540
40%
540
14%
1300
May1st to 10thNight
40%
540
11%
1620
7%
540
46%
540
13%
1259
May11th to 20thNight
46%
531
14%
1594
13%
531
50%
531
17%
1191
May21st to endNight
49%
584
12%
1746
9%
582
54%
582
15%
1344
June1st to 10thNight
68%
540
13%
1620
11%
540
70%
540
19%
1148
June11th to 20thNight
65%
540
16%
1620
12%
540
68%
540
22%
1107
June21st to endNight
66%
540
17%
1620
14%
540
68%
540
23%
1105
July1st to 10thNight
72%
525
14%
1575
14%
525
73%
525
21%
1112
July11th to 20thNight
78%
522
15%
1566
16%
522
80%
522
22%
1084
July21st to endNight
72%
591
15%
1673
17%
558
73%
558
19%
1209
August1st to 10thNight
70%
537
16%
1601
17%
534
73%
534
21%
1114
August11th to 20thNight
77%
534
22%
1600
26%
534
77%
534
22%
1112
August21st to endNight
77%
594
20%
1952
23%
594
79%
594
23%
1275
September1st to 10thNight
68%
540
18%
1800
19%
540
71%
540
18%
1268
September11th to 20thNight
64%
540
18%
1975
20%
540
66%
540
15%
1388
September21st to endNight
63%
540
22%
1980
21%
540
68%
540
21%
1263
October1st to 10thNight
55%
707
22%
2147
17%
707
58%
707
25%
1416
October11th to 20thNight
37%
720
20%
2160
9%
720
46%
720
19%
1537
October21st to endNight
37%
792
17%
2376
8%
792
44%
792
16%
1750
November1st to 10thNight
38%
740
21%
2220
9%
740
49%
740
20%
1537
November11th to 20thNight
35%
893
19%
2413
8%
893
42%
893
17%
1813
November21st to endNight
32%
950
16%
2615
7%
950
38%
950
17%
1950
December1st to 10thNight
30%
950
14%
2660
4%
950
38%
950
15%
2032
December11th to 20thNight
28%
948
16%
3108
5%
948
35%
948
11%
2316
December21st to endNight
26%
1043
10%
4454
5%
1026
34%
1026
8%
3422

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
12%6%35%5%3445%7%45%
74382
Night
11%6%35%42445%7%50%
75329
TransparencyDay
26%37%7%17%11%2
74105
Night
23%37%7%17%13%3
75126
SeeingDay
14%9%26%28%18%5%
14396
Night
14%8%31%33%13%1
24364

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
12%8%445%24446%47%
1707
11th to 20thDay
13%9%47%423447%43%
1629
21st to endDay
12%8%37%43445%6%43%
1782
February1st to 10thDay
16%9%47%5%3435%441%
1620
11th to 20thDay
13%8%47%5%34345%45%
1584
21st to endDay
14%10%35%5%345%5%6%40%
1567
March1st to 10thDay
13%9%5%5%424337%44%
1980
11th to 20thDay
21%9%35%5%345%45%37%
1980
21st to endDay
20%10%46%5%3446%5%32%
2178
April1st to 10thDay
11%7%35%5%35%45%7%44%
2065
11th to 20thDay
15%6%37%5%3445%6%41%
2134
21st to endDay
21%7%46%43445%6%37%
2241
May1st to 10thDay
19%7%35%5%35%45%6%37%
2340
11th to 20thDay
15%6%35%5%4446%8%39%
2302
21st to endDay
13%7%46%6%45%5%7%10%34%
2531
June1st to 10thDay
7%3245%345%6%10%49%
2340
11th to 20thDay
7%425%6%35%6%7%8%48%
2340
21st to endDay
5%2234245%7%10%57%
2340
July1st to 10thDay
9%425%5%46%8%7%10%40%
2340
11th to 20thDay
5%2145%35%5%7%11%53%
2340
21st to endDay
8%425%5%36%6%6%10%45%
2546
August1st to 10thDay
7%4245%46%5%6%10%47%
2328
11th to 20thDay
7%425%6%45%5%6%8%47%
2301
21st to endDay
6%424435%5%6%8%53%
2404
September1st to 10thDay
12%5%2442345%6%53%
2160
11th to 20thDay
11%425%5%35%45%8%48%
1981
21st to endDay
9%42343445%7%55%
1973
October1st to 10thDay
12%424434446%53%
1800
11th to 20thDay
13%6%2332335%6%55%
1800
21st to endDay
19%8%25%32333449%
1980
November1st to 10thDay
9%5%35%323346%59%
1858
11th to 20thDay
13%6%24423335%54%
1765
21st to endDay
15%7%25%422245%51%
1559
December1st to 10thDay
12%9%35%42435%7%45%
1520
11th to 20thDay
13%8%47%5%33335%44%
1932
21st to endDay
16%16%7%6%5%3435%6%28%
3135
January1st to 10thNight
11%8%25%5%34446%50%
2458
11th to 20thNight
13%6%36%423445%49%
2354
21st to endNight
10%7%36%43335%6%50%
2574
February1st to 10thNight
14%9%46%433445%43%
2340
11th to 20thNight
14%8%35%334446%46%
2273
21st to endNight
15%8%35%334436%45%
1691
March1st to 10thNight
13%6%36%5%24446%48%
1980
11th to 20thNight
17%8%35%433447%43%
1980
21st to endNight
18%8%36%5%3435%6%39%
2178
April1st to 10thNight
10%6%2442345%7%51%
1893
11th to 20thNight
14%6%35%424445%49%
1775
21st to endNight
16%6%35%43435%6%44%
1715
May1st to 10thNight
14%6%45%435%5%46%43%
1620
11th to 20thNight
13%5%25%43446%7%47%
1593
21st to endNight
11%5%35%435%5%7%9%42%
1745
June1st to 10thNight
5%424435%45%10%54%
1620
11th to 20thNight
4324435%5%6%11%53%
1620
21st to endNight
422342445%9%60%
1620
July1st to 10thNight
7%4134246%8%9%50%
1620
11th to 20thNight
42134345%6%9%60%
1620
21st to endNight
7%4234245%8%10%51%
1772
August1st to 10thNight
5%3344246%5%9%54%
1611
11th to 20thNight
5%415%3245%6%9%56%
1600
21st to endNight
432442446%8%59%
1952
September1st to 10thNight
9%5%2442445%7%55%
1800
11th to 20thNight
10%425%5%23448%52%
1975
21st to endNight
7%5%235%24346%60%
1980
October1st to 10thNight
8%42432335%6%60%
2147
11th to 20thNight
14%5%14323345%56%
2160
21st to endNight
15%6%24323245%52%
2376
November1st to 10thNight
11%5%1332333463%
2220
11th to 20thNight
10%6%35%423346%54%
2413
21st to endNight
16%6%34422335%53%
2615
December1st to 10thNight
13%7%35%42445%7%47%
2660
11th to 20thNight
13%7%35%5%2445%6%45%
3247
21st to endNight
16%14%5%6%5%33445%34%
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
22%39%8%19%11%1
1708
11th to 20thDay
25%41%8%15%10%1
1629
21st to endDay
30%37%8%17%7%1
1782
February1st to 10thDay
32%36%6%15%10%1
1620
11th to 20thDay
30%37%6%15%10%3
1593
21st to endDay
30%35%5%16%8%4
1567
March1st to 10thDay
27%36%6%15%13%2
1980
11th to 20thDay
36%36%7%13%7%1
1980
21st to endDay
37%37%8%13%41
2178
April1st to 10thDay
25%37%8%17%12%2
2065
11th to 20thDay
28%36%8%15%11%2
2134
21st to endDay
33%36%7%16%8%
2241
May1st to 10thDay
35%37%8%12%7%1
2340
11th to 20thDay
29%38%8%17%8%
2306
21st to endDay
30%39%11%15%6%
2531
June1st to 10thDay
20%38%12%19%10%1
2340
11th to 20thDay
20%39%9%21%10%1
2340
21st to endDay
15%38%9%20%14%4
2340
July1st to 10thDay
21%40%9%17%11%2
2276
11th to 20thDay
17%40%9%18%14%3
2271
21st to endDay
22%40%10%19%8%1
2405
August1st to 10thDay
20%38%10%17%13%1
2314
11th to 20thDay
23%37%7%18%14%1
2301
21st to endDay
17%37%7%18%15%7%
2404
September1st to 10thDay
24%36%417%11%7%
2160
11th to 20thDay
25%37%5%14%17%2
1981
21st to endDay
17%37%6%17%20%4
1973
October1st to 10thDay
18%36%7%19%18%3
1800
11th to 20thDay
22%36%5%19%16%3
1800
21st to endDay
27%36%5%17%11%3
1980
November1st to 10thDay
15%40%6%21%13%4
1858
11th to 20thDay
21%39%6%15%16%2
1765
21st to endDay
23%39%6%15%15%1
1559
December1st to 10thDay
25%40%6%21%9%1
1520
11th to 20thDay
31%32%7%15%15%
1929
21st to endDay
47%25%7%14%6%1
3135
January1st to 10thNight
22%39%8%19%11%1
2458
11th to 20thNight
21%41%6%19%12%1
2354
21st to endNight
26%37%8%19%8%2
2574
February1st to 10thNight
31%36%6%16%10%1
2340
11th to 20thNight
26%37%7%16%12%2
2274
21st to endNight
26%35%7%15%12%4
1691
March1st to 10thNight
25%35%7%15%14%5%
1980
11th to 20thNight
29%37%7%14%11%2
1980
21st to endNight
31%36%9%14%9%1
2178
April1st to 10thNight
23%36%6%16%14%5%
1893
11th to 20thNight
26%35%5%14%16%4
1775
21st to endNight
28%37%7%16%11%2
1715
May1st to 10thNight
29%38%8%13%10%2
1620
11th to 20thNight
23%39%9%16%12%1
1594
21st to endNight
25%40%10%18%7%1
1746
June1st to 10thNight
18%38%10%21%10%2
1620
11th to 20thNight
14%39%11%21%13%2
1620
21st to endNight
15%37%10%19%15%4
1620
July1st to 10thNight
17%39%9%20%12%3
1575
11th to 20thNight
16%38%8%18%16%4
1566
21st to endNight
19%40%10%19%12%1
1673
August1st to 10thNight
17%38%9%23%11%2
1601
11th to 20thNight
17%37%6%20%18%2
1600
21st to endNight
13%37%8%19%16%7%
1952
September1st to 10thNight
21%37%5%15%14%8%
1800
11th to 20thNight
22%37%5%14%18%4
1975
21st to endNight
15%35%418%22%5%
1980
October1st to 10thNight
13%37%6%16%23%5%
2147
11th to 20thNight
21%35%417%17%4
2160
21st to endNight
24%36%5%14%17%3
2376
November1st to 10thNight
14%40%7%20%16%4
2220
11th to 20thNight
21%39%5%16%17%2
2413
21st to endNight
21%39%6%15%15%4
2615
December1st to 10thNight
24%40%8%17%11%1
2660
11th to 20thNight
29%33%6%17%14%1
3249
21st to endNight
43%25%7%17%6%2
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
22%13%34%26%5%
270
11th to 20thDay
23%17%38%20%1
243
21st to endDay
14%14%47%19%5%
264
February1st to 10thDay
24%17%38%19%3
240
11th to 20thDay
20%21%39%16%4
240
21st to endDay
24%22%38%12%4
198
March1st to 10thDay
20%19%36%21%3
240
11th to 20thDay
27%16%31%23%3
240
21st to endDay
31%15%38%12%31
264
April1st to 10thDay
16%14%42%22%5%1
325
11th to 20thDay
18%16%37%22%7%
412
21st to endDay
23%14%30%23%9%1
501
May1st to 10thDay
18%13%34%25%9%1
603
11th to 20thDay
16%9%32%25%15%3
625
21st to endDay
15%6%29%24%18%7%
679
June1st to 10thDay
7%218%33%30%10%
630
11th to 20thDay
7%321%41%21%6%
630
21st to endDay
4428%38%21%5%
630
July1st to 10thDay
10%314%31%30%13%
621
11th to 20thDay
4215%38%32%9%
618
21st to endDay
7%311%34%33%12%
684
August1st to 10thDay
9%212%40%31%5%
626
11th to 20thDay
9%215%34%33%7%
615
21st to endDay
9%19%30%40%11%
523
September1st to 10thDay
10%212%32%35%10%
450
11th to 20thDay
5%214%37%31%12%
271
21st to endDay
13%418%35%23%7%
270
October1st to 10thDay
11%10%25%26%19%9%
270
11th to 20thDay
14%12%40%26%7%1
270
21st to endDay
30%12%29%23%5%1
297
November1st to 10thDay
16%11%36%23%11%2
270
11th to 20thDay
15%17%35%22%9%3
270
21st to endDay
23%16%31%23%7%1
270
December1st to 10thDay
16%12%43%19%8%3
270
11th to 20thDay
18%16%37%22%6%1
270
21st to endDay
21%18%42%16%2
297
January1st to 10thNight
16%13%39%25%6%
950
11th to 20thNight
18%13%40%24%5%
906
21st to endNight
14%14%40%28%4
990
February1st to 10thNight
20%12%41%23%3
900
11th to 20thNight
18%14%41%24%3
879
21st to endNight
21%16%35%25%2
507
March1st to 10thNight
16%12%40%26%5%
540
11th to 20thNight
21%11%38%25%5%
540
21st to endNight
23%11%38%22%5%
594
April1st to 10thNight
13%13%36%31%6%
540
11th to 20thNight
19%11%34%29%7%
533
21st to endNight
18%9%40%25%8%
540
May1st to 10thNight
16%5%32%38%8%1
540
11th to 20thNight
16%5%28%34%16%1
531
21st to endNight
13%425%37%18%2
584
June1st to 10thNight
6%315%44%31%1
540
11th to 20thNight
6%124%46%22%1
540
21st to endNight
2322%52%19%1
540
July1st to 10thNight
9%111%41%35%3
525
11th to 20thNight
4112%46%34%3
522
21st to endNight
7%112%42%36%3
591
August1st to 10thNight
5%215%43%34%1
537
11th to 20thNight
6%29%54%27%3
534
21st to endNight
5%110%38%42%4
594
September1st to 10thNight
10%213%44%30%1
540
11th to 20thNight
11%315%42%26%4
540
21st to endNight
9%221%41%24%3
540
October1st to 10thNight
8%329%35%22%3
707
11th to 20thNight
16%7%37%31%9%1
720
21st to endNight
19%10%32%28%11%1
792
November1st to 10thNight
13%7%38%32%10%
740
11th to 20thNight
14%13%34%30%8%
893
21st to endNight
19%11%36%27%7%
950
December1st to 10thNight
17%11%39%28%6%
950
11th to 20thNight
19%11%36%29%4
950
21st to endNight
18%15%38%26%3
1045
Page generated at 2024-01-08 21:31:25. Version ac07

Copyright 2024 Attilla Danko


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