StonyHill Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the StonyHill 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
37%
23121
19%
74603
11%
23080
47%
23080
23%
48035

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
22%
760
22%
2649
9%
757
40%
757
21%
1594
January11th to 20thNight
25%
737
19%
2577
7%
737
41%
737
16%
1682
January21st to endNight
22%
792
22%
2682
10%
792
38%
792
22%
1627
February1st to 10thNight
22%
720
16%
2283
6%
720
35%
720
19%
1513
February11th to 20thNight
19%
703
19%
2100
6%
700
35%
700
22%
1400
February21st to endNight
23%
592
24%
1776
10%
592
42%
592
22%
1161
March1st to 10thNight
27%
720
21%
2160
9%
720
43%
720
26%
1370
March11th to 20thNight
30%
720
20%
2100
10%
720
41%
720
25%
1365
March21st to endNight
29%
792
22%
1980
7%
792
39%
792
27%
1371
April1st to 10thNight
31%
720
19%
1800
6%
720
38%
720
25%
1274
April11th to 20thNight
37%
711
17%
1775
6%
711
43%
711
27%
1236
April21st to endNight
37%
653
19%
1733
8%
653
43%
653
26%
1199
May1st to 10thNight
35%
540
14%
1620
7%
540
41%
540
18%
1163
May11th to 20thNight
34%
444
17%
1506
12%
444
41%
444
18%
1012
May21st to endNight
54%
388
13%
1551
15%
388
58%
388
18%
1002
June1st to 10thNight
48%
360
16%
1440
18%
360
55%
360
19%
905
June11th to 20thNight
59%
360
15%
1440
19%
360
62%
360
20%
890
June21st to endNight
64%
360
14%
1440
17%
360
68%
360
22%
866
July1st to 10thNight
62%
350
12%
1400
16%
350
64%
350
19%
877
July11th to 20thNight
65%
348
15%
1392
20%
348
66%
348
21%
850
July21st to endNight
62%
394
17%
1486
20%
372
67%
372
22%
890
August1st to 10thNight
66%
456
17%
1520
15%
454
68%
454
27%
903
August11th to 20thNight
59%
710
15%
1774
9%
710
60%
710
28%
1240
August21st to endNight
62%
792
18%
1980
9%
792
64%
792
33%
1327
September1st to 10thNight
52%
720
20%
1800
12%
720
55%
720
30%
1237
September11th to 20thNight
57%
720
25%
1910
18%
720
61%
720
35%
1198
September21st to endNight
47%
720
22%
1980
15%
720
54%
720
27%
1331
October1st to 10thNight
37%
720
16%
2023
11%
720
42%
720
23%
1391
October11th to 20thNight
44%
720
23%
2160
14%
720
54%
720
29%
1322
October21st to endNight
29%
792
18%
2560
10%
792
41%
792
20%
1699
November1st to 10thNight
39%
740
22%
2407
13%
740
52%
740
26%
1444
November11th to 20thNight
30%
760
24%
2470
13%
760
45%
760
24%
1524
November21st to endNight
31%
760
22%
2489
10%
760
47%
760
25%
1499
December1st to 10thNight
24%
760
18%
2660
7%
760
38%
760
18%
1722
December11th to 20thNight
24%
760
18%
3180
6%
759
37%
759
15%
1970
December21st to endNight
22%
827
13%
4800
8%
817
38%
817
11%
2981

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
15%6%25%5%3445%8%43%
74794
Night
17%6%35%5%3445%7%42%
74966
TransparencyDay
40%7%13%22%15%2
74499
Night
42%6%12%22%15%2
74795
SeeingDay
18%6%23%32%18%4
13930
Night
20%7%29%30%12%2
23131

By Month

Percentage Cloud Cover NE (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
15%5%35%5%3446%8%42%
1517
11th to 20thDay
16%8%46%5%345%6%7%37%
1472
21st to endDay
15%7%36%435%448%41%
1672
February1st to 10thDay
19%6%36%5%2445%7%39%
1675
11th to 20thDay
15%5%35%5%35%446%45%
1748
21st to endDay
19%8%35%5%34345%40%
1480
March1st to 10thDay
13%7%35%5%3445%7%44%
1797
11th to 20thDay
15%6%245%25%5%6%9%41%
1856
21st to endDay
19%8%25%5%23446%41%
2376
April1st to 10thDay
17%7%35%43445%6%42%
2160
11th to 20thDay
16%6%25%5%24446%45%
2134
21st to endDay
20%6%24325%45%7%43%
2224
May1st to 10thDay
22%7%2442445%8%38%
2340
11th to 20thDay
18%5%245%2446%8%41%
2402
21st to endDay
13%5%24435%5%6%9%44%
2725
June1st to 10thDay
17%5%25%5%245%5%9%41%
2520
11th to 20thDay
14%6%345%45%6%5%9%40%
2520
21st to endDay
10%5%35%6%345%5%9%45%
2520
July1st to 10thDay
10%5%25%5%35%5%7%9%44%
2520
11th to 20thDay
10%5%25%4345%7%10%45%
2520
21st to endDay
12%5%25%5%45%5%7%8%42%
2744
August1st to 10thDay
10%5%25%5%35%5%7%11%41%
2385
11th to 20thDay
12%5%25%44445%9%45%
2126
21st to endDay
12%425%5%335%6%8%46%
2376
September1st to 10thDay
13%5%245%35%5%5%7%46%
2160
11th to 20thDay
13%5%2432345%7%52%
2048
21st to endDay
17%7%25%5%35%45%6%43%
1980
October1st to 10thDay
23%5%24323447%44%
1935
11th to 20thDay
16%5%25%5%3445%7%46%
1800
21st to endDay
20%5%15%5%35%45%7%40%
1796
November1st to 10thDay
15%5%246%34436%49%
1671
11th to 20thDay
18%6%25%423437%48%
1710
21st to endDay
14%7%35%42445%7%45%
1687
December1st to 10thDay
17%6%36%5%35%47%8%36%
1520
11th to 20thDay
21%8%24313346%45%
1906
21st to endDay
18%10%48%5%3445%7%33%
2772
January1st to 10thNight
16%7%245%334410%43%
2649
11th to 20thNight
19%7%35%5%3445%6%39%
2577
21st to endNight
14%8%45%42345%8%43%
2682
February1st to 10thNight
17%9%35%5%2445%6%39%
2283
11th to 20thNight
19%7%35%5%245%5%6%39%
2098
21st to endNight
21%6%25%43435%6%42%
1776
March1st to 10thNight
17%6%2443445%7%45%
2150
11th to 20thNight
17%5%25%5%445%5%7%41%
2099
21st to endNight
17%9%36%43445%7%40%
1980
April1st to 10thNight
18%7%35%5%345%6%6%39%
1800
11th to 20thNight
19%6%35%5%24447%41%
1775
21st to endNight
19%7%45%5%23445%42%
1733
May1st to 10thNight
22%7%36%435%447%34%
1620
11th to 20thNight
19%9%35%5%25%46%6%36%
1505
21st to endNight
16%7%35%5%345%5%7%39%
1550
June1st to 10thNight
18%7%336%34448%40%
1440
11th to 20thNight
15%6%25%4245%6%10%40%
1440
21st to endNight
10%5%35%5%45%6%6%10%41%
1440
July1st to 10thNight
11%6%35%5%37%5%8%9%39%
1440
11th to 20thNight
11%5%36%436%6%6%10%39%
1440
21st to endNight
11%5%245%35%6%6%10%41%
1574
August1st to 10thNight
8%425%445%6%8%9%45%
1530
11th to 20thNight
12%6%36%6%45%5%7%9%37%
1774
21st to endNight
13%5%25%435%5%6%8%45%
1980
September1st to 10thNight
14%5%26%5%35%46%6%44%
1800
11th to 20thNight
15%425%424446%51%
1910
21st to endNight
18%5%25%5%34347%44%
1980
October1st to 10thNight
20%8%35%5%34346%40%
2023
11th to 20thNight
16%425%5%3335%7%47%
2160
21st to endNight
22%6%35%5%34446%40%
2560
November1st to 10thNight
13%6%25%5%3445%5%48%
2407
11th to 20thNight
19%6%33423445%47%
2470
21st to endNight
15%5%245%3446%7%47%
2489
December1st to 10thNight
21%7%35%434447%39%
2660
11th to 20thNight
20%6%25%43445%6%42%
3288
21st to endNight
20%9%36%5%3445%6%37%
4884

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
40%5%13%27%12%3
1518
11th to 20thDay
44%6%15%22%11%2
1472
21st to endDay
42%412%25%14%2
1672
February1st to 10thDay
45%5%14%22%12%1
1675
11th to 20thDay
41%5%11%25%16%2
1757
21st to endDay
47%5%10%21%14%3
1480
March1st to 10thDay
38%6%15%22%15%3
1800
11th to 20thDay
39%7%13%24%15%2
1856
21st to endDay
46%5%9%18%18%5%
2376
April1st to 10thDay
42%6%11%21%16%4
2160
11th to 20thDay
40%6%12%21%18%3
2134
21st to endDay
41%7%12%21%16%4
2224
May1st to 10thDay
46%8%11%20%14%2
2340
11th to 20thDay
41%7%12%20%16%3
2406
21st to endDay
37%10%18%20%13%2
2725
June1st to 10thDay
40%9%14%21%14%2
2520
11th to 20thDay
41%9%14%23%13%1
2520
21st to endDay
36%9%16%23%15%1
2520
July1st to 10thDay
36%10%15%22%16%1
2450
11th to 20thDay
34%8%16%25%14%2
2445
21st to endDay
37%9%14%21%16%2
2591
August1st to 10thDay
34%10%17%24%14%1
2371
11th to 20thDay
37%8%16%24%14%1
2126
21st to endDay
36%8%13%21%19%2
2376
September1st to 10thDay
38%7%15%20%18%2
2160
11th to 20thDay
33%6%12%24%24%2
2048
21st to endDay
43%6%10%19%20%3
1980
October1st to 10thDay
42%6%11%22%17%2
1935
11th to 20thDay
36%7%13%25%18%1
1800
21st to endDay
42%7%11%21%17%2
1796
November1st to 10thDay
37%6%13%23%20%2
1671
11th to 20thDay
39%5%11%23%20%3
1710
21st to endDay
38%6%14%27%11%2
1687
December1st to 10thDay
44%6%17%18%14%1
1520
11th to 20thDay
42%415%20%17%2
1906
21st to endDay
47%10%13%21%8%
2772
January1st to 10thNight
40%5%12%24%16%4
2649
11th to 20thNight
45%7%13%23%10%2
2577
21st to endNight
40%411%24%18%2
2682
February1st to 10thNight
45%6%13%22%12%2
2283
11th to 20thNight
44%5%11%19%15%4
2100
21st to endNight
44%49%23%16%4
1776
March1st to 10thNight
39%5%13%22%15%4
2160
11th to 20thNight
41%6%11%22%16%4
2100
21st to endNight
43%6%9%18%18%6%
1980
April1st to 10thNight
45%6%11%18%17%3
1800
11th to 20thNight
43%6%10%19%20%2
1775
21st to endNight
45%6%10%20%15%5%
1733
May1st to 10thNight
50%7%10%17%14%2
1620
11th to 20thNight
47%7%10%17%16%2
1506
21st to endNight
44%8%15%20%11%1
1551
June1st to 10thNight
44%6%11%20%17%2
1440
11th to 20thNight
40%9%14%25%12%1
1440
21st to endNight
37%9%15%25%13%1
1440
July1st to 10thNight
40%11%16%19%14%2
1400
11th to 20thNight
38%10%13%26%12%1
1392
21st to endNight
36%10%15%23%13%2
1486
August1st to 10thNight
32%11%18%24%13%1
1520
11th to 20thNight
40%10%15%24%11%1
1774
21st to endNight
36%9%14%22%18%2
1980
September1st to 10thNight
40%8%11%24%16%1
1800
11th to 20thNight
34%7%11%24%23%3
1910
21st to endNight
42%7%9%20%20%3
1980
October1st to 10thNight
46%6%11%21%14%3
2023
11th to 20thNight
37%5%14%28%15%1
2160
21st to endNight
45%6%12%21%16%1
2560
November1st to 10thNight
37%6%13%22%20%3
2407
11th to 20thNight
40%410%23%18%4
2470
21st to endNight
37%6%14%29%13%2
2489
December1st to 10thNight
46%5%14%21%13%1
2660
11th to 20thNight
43%5%12%19%18%2
3288
21st to endNight
46%7%13%23%11%1
4884

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
21%12%33%25%8%1
180
11th to 20thDay
16%16%38%24%5%1
168
21st to endDay
20%5%41%25%7%2
216
February1st to 10thDay
26%8%35%27%3
295
11th to 20thDay
20%9%40%29%3
416
21st to endDay
25%11%33%25%6%
346
March1st to 10thDay
14%10%39%31%7%
420
11th to 20thDay
17%7%39%30%5%1
420
21st to endDay
23%8%32%27%8%2
462
April1st to 10thDay
20%8%33%26%11%1
420
11th to 20thDay
18%7%25%36%15%1
412
21st to endDay
26%7%24%34%10%1
420
May1st to 10thDay
27%5%25%33%9%2
423
11th to 20thDay
20%321%37%18%1
447
21st to endDay
18%113%32%30%6%
485
June1st to 10thDay
19%312%35%26%4
450
11th to 20thDay
16%316%39%22%3
450
21st to endDay
12%214%37%30%6%
450
July1st to 10thDay
12%210%34%33%10%
445
11th to 20thDay
9%37%35%36%9%
444
21st to endDay
13%311%36%33%5%
488
August1st to 10thDay
11%19%41%29%9%
446
11th to 20thDay
15%37%35%32%8%
439
21st to endDay
11%312%37%26%11%
495
September1st to 10thDay
18%215%29%24%12%
450
11th to 20thDay
16%214%30%26%12%
450
21st to endDay
21%319%33%20%5%
450
October1st to 10thDay
26%317%27%19%8%
450
11th to 20thDay
15%6%26%34%17%3
450
21st to endDay
23%8%29%25%13%2
403
November1st to 10thDay
15%7%23%34%17%4
365
11th to 20thDay
19%14%31%27%8%1
370
21st to endDay
17%11%30%30%10%1
347
December1st to 10thDay
19%10%37%22%12%
180
11th to 20thDay
27%15%26%26%6%
180
21st to endDay
21%12%34%24%8%1
198
January1st to 10thNight
19%14%40%23%4
760
11th to 20thNight
25%11%34%28%3
737
21st to endNight
19%13%41%24%3
792
February1st to 10thNight
21%11%38%27%3
720
11th to 20thNight
23%10%44%21%2
703
21st to endNight
24%10%38%24%4
592
March1st to 10thNight
20%9%40%25%6%
720
11th to 20thNight
19%8%39%26%6%1
720
21st to endNight
21%6%38%27%6%1
792
April1st to 10thNight
22%7%36%29%6%1
720
11th to 20thNight
20%6%31%32%10%
711
21st to endNight
22%430%35%8%1
653
May1st to 10thNight
24%5%27%30%11%2
540
11th to 20thNight
21%430%33%10%
444
21st to endNight
21%313%37%25%2
389
June1st to 10thNight
21%220%36%19%2
360
11th to 20thNight
18%312%46%21%1
360
21st to endNight
10%216%50%21%2
360
July1st to 10thNight
13%312%41%28%2
350
11th to 20thNight
12%211%47%24%4
348
21st to endNight
14%213%48%22%1
394
August1st to 10thNight
8%114%47%28%2
456
11th to 20thNight
15%313%35%32%3
710
21st to endNight
14%312%37%29%5%
792
September1st to 10thNight
17%120%36%21%5%
720
11th to 20thNight
18%316%37%22%6%
720
21st to endNight
21%221%33%20%3
720
October1st to 10thNight
24%6%24%25%17%4
720
11th to 20thNight
18%7%26%34%13%1
720
21st to endNight
25%8%32%27%8%1
792
November1st to 10thNight
15%8%31%30%13%2
740
11th to 20thNight
21%10%34%25%9%1
760
21st to endNight
17%12%34%28%8%1
760
December1st to 10thNight
24%13%34%23%6%1
760
11th to 20thNight
22%11%38%24%4
760
21st to endNight
23%12%38%23%4
836
Page generated at 2024-01-11 22:33:45. Version ac07

Copyright 2024 Attilla Danko


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