EyeScope Star Shack
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the EyeScope Star Shack clear sky chart from 2005-11-05 to 2017-10-16.

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
29%
15890
11%
47203
7%
15847
33%
15847
14%
35562

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
10%
900
3%
2506
1%
895
11%
895
4%
2287
January16th to endNight
13%
960
6%
2688
3%
960
15%
960
5%
2374
February1st to 15thNight
16%
759
5%
2301
2%
758
18%
758
6%
1970
February16th to endNight
23%
631
8%
1893
5%
631
26%
631
8%
1561
March1st to 15thNight
28%
720
15%
2133
8%
720
34%
720
17%
1531
March16th to endNight
32%
731
19%
2075
11%
731
39%
731
20%
1422
April1st to 15thNight
26%
539
14%
1785
8%
539
34%
539
15%
1270
April16th to endNight
28%
540
18%
1620
7%
540
39%
540
18%
1092
May1st to 15thNight
33%
540
12%
1620
7%
540
39%
540
18%
1120
May16th to endNight
40%
562
15%
1498
7%
561
48%
561
26%
966
June1st to 15thNight
37%
378
13%
1278
8%
378
45%
378
18%
816
June16th to endNight
46%
382
12%
1282
9%
382
50%
382
22%
783
July1st to 15thNight
54%
510
14%
1360
9%
510
57%
510
33%
831
July16th to endNight
49%
564
15%
1417
10%
531
56%
531
32%
860
August1st to 15thNight
59%
539
18%
1551
14%
536
63%
536
34%
884
August16th to endNight
53%
573
16%
1774
11%
573
57%
573
26%
1084
September1st to 15thNight
48%
606
16%
1866
12%
606
53%
606
27%
1171
September16th to endNight
49%
717
19%
1980
14%
717
52%
717
27%
1311
October1st to 15thNight
33%
720
15%
2046
10%
720
38%
720
19%
1477
October16th to endNight
21%
708
9%
2300
5%
708
26%
708
9%
1858
November1st to 15thNight
22%
700
13%
2276
11%
700
27%
700
12%
1730
November16th to endNight
14%
751
6%
2449
4%
751
16%
751
5%
2129
December1st to 15thNight
8%
900
2%
2700
1%
900
9%
900
3%
2478
December16th to endNight
10%
960
3%
2805
1%
960
12%
960
4%
2557

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%9%47%5%34446%33%
48213
Night
16%12%5%9%6%34345%28%
47371
Cloud CoverDay
15%10%47%6%34446%33%
48222
Night
16%12%5%9%7%34345%28%
47376
TransparencyDay
52%412%20%9%
47899
Night
59%310%17%8%
47203
SeeingDay
17%14%23%26%14%4
6123
Night
19%20%22%25%10%1
15893

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 15thDay
17%19%11%13%11%45%2336%
1432
16th to endDay
13%17%10%16%12%442339%
1536
February1st to 15thDay
13%15%8%13%12%45%33413%
1558
16th to endDay
14%15%7%10%8%45%43421%
1580
March1st to 15thDay
11%10%5%8%7%445%47%30%
1817
16th to endDay
15%8%5%6%5%24347%36%
2160
April1st to 15thDay
20%11%25%333345%34%
2162
16th to endDay
18%9%35%324445%36%
2340
May1st to 15thDay
16%6%345%4445%6%37%
2331
16th to endDay
12%5%2443345%7%45%
2616
June1st to 15thDay
13%5%145%2446%9%41%
2679
16th to endDay
14%5%1443446%8%41%
2673
July1st to 15thDay
10%31342446%8%50%
2520
16th to endDay
10%41332445%8%49%
2655
August1st to 15thDay
9%41343446%9%47%
2398
16th to endDay
15%5%2442345%6%45%
2426
September1st to 15thDay
17%425%423347%43%
2082
16th to endDay
15%5%24435%45%8%40%
1980
October1st to 15thDay
23%9%36%434346%30%
1910
16th to endDay
28%15%37%6%44345%15%
1593
November1st to 15thDay
18%17%5%8%434345%24%
1582
16th to endDay
21%24%8%11%6%2332311%
1508
December1st to 15thDay
18%20%15%19%8%321127%
1260
16th to endDay
20%24%11%13%8%322227%
1415
January1st to 15thNight
17%18%10%16%12%322229%
2506
16th to endNight
15%17%8%15%11%4333311%
2688
February1st to 15thNight
12%16%9%14%12%35%33414%
2299
16th to endNight
14%15%6%13%9%45%43417%
1893
March1st to 15thNight
14%9%5%9%6%3334434%
2120
16th to endNight
14%8%46%5%2445%6%36%
2075
April1st to 15thNight
22%9%36%5%2434432%
1785
16th to endNight
17%9%25%6%24335%39%
1620
May1st to 15thNight
14%8%26%6%36%5%5%7%32%
1620
16th to endNight
12%6%34425%35%7%43%
1496
June1st to 15thNight
14%6%25%6%35%445%40%
1278
16th to endNight
12%4245%35%45%9%40%
1282
July1st to 15thNight
10%424425%45%7%48%
1440
16th to endNight
7%5%2442446%8%49%
1513
August1st to 15thNight
7%4145%3445%8%50%
1560
16th to endNight
13%5%14433447%46%
1774
September1st to 15thNight
15%6%25%5%23345%44%
1866
16th to endNight
18%425%43345%7%40%
1980
October1st to 15thNight
23%9%35%323346%33%
2046
16th to endNight
27%13%38%7%3433419%
2300
November1st to 15thNight
20%17%5%6%5%23345%25%
2276
16th to endNight
21%24%8%10%5%2332412%
2449
December1st to 15thNight
19%24%12%16%7%232128%
2700
16th to endNight
19%22%12%13%7%333328%
2805

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 15thDay
17%19%11%13%11%45%2436%
1432
16th to endDay
13%18%10%16%11%5%43239%
1536
February1st to 15thDay
13%15%8%13%12%45%33413%
1558
16th to endDay
13%15%7%11%8%35%43420%
1580
March1st to 15thDay
11%10%5%8%7%4445%7%30%
1827
16th to endDay
15%8%5%6%5%24347%35%
2159
April1st to 15thDay
20%11%25%334346%33%
2162
16th to endDay
18%9%35%424445%36%
2340
May1st to 15thDay
16%7%345%3445%6%37%
2331
16th to endDay
12%5%2443345%7%45%
2616
June1st to 15thDay
13%5%25%5%2446%8%40%
2679
16th to endDay
14%5%145%3446%8%41%
2673
July1st to 15thDay
11%31342446%8%49%
2520
16th to endDay
10%41432446%8%49%
2655
August1st to 15thDay
9%32442446%9%47%
2398
16th to endDay
15%5%24423446%44%
2426
September1st to 15thDay
16%425%5%33347%43%
2082
16th to endDay
15%424435%5%5%8%40%
1980
October1st to 15thDay
22%10%36%434346%30%
1910
16th to endDay
28%14%47%7%34445%15%
1593
November1st to 15thDay
18%17%5%8%424345%24%
1582
16th to endDay
20%24%8%11%7%2233212%
1508
December1st to 15thDay
18%20%15%18%8%321127%
1260
16th to endDay
20%24%10%13%9%322228%
1415
January1st to 15thNight
17%18%9%16%12%4322210%
2506
16th to endNight
15%17%8%15%12%4433411%
2688
February1st to 15thNight
12%16%8%14%12%35%33414%
2292
16th to endNight
14%15%5%13%9%46%43417%
1893
March1st to 15thNight
14%9%5%9%6%3434434%
2133
16th to endNight
14%8%46%5%2445%5%36%
2075
April1st to 15thNight
22%9%36%5%24345%31%
1785
16th to endNight
16%9%25%6%24335%39%
1620
May1st to 15thNight
14%8%36%6%36%5%5%7%32%
1619
16th to endNight
12%5%34425%46%7%43%
1496
June1st to 15thNight
14%6%25%5%345%46%40%
1278
16th to endNight
12%5%246%25%5%5%9%41%
1282
July1st to 15thNight
10%5%15%425%45%7%48%
1440
16th to endNight
7%5%2442446%8%49%
1513
August1st to 15thNight
6%4145%245%5%9%50%
1560
16th to endNight
13%5%24423447%46%
1774
September1st to 15thNight
15%5%25%5%23345%44%
1866
16th to endNight
18%5%25%42435%7%40%
1980
October1st to 15thNight
23%9%45%423346%33%
2046
16th to endNight
26%14%37%7%3433419%
2300
November1st to 15thNight
19%17%5%6%6%23336%25%
2276
16th to endNight
21%23%8%10%6%2432412%
2449
December1st to 15thNight
19%24%12%16%7%232127%
2700
16th to endNight
18%22%11%14%7%333338%
2805

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
83%45%5%
1433
16th to endDay
81%25%7%2
1536
February1st to 15thDay
75%48%9%2
1560
16th to endDay
68%310%12%5%
1580
March1st to 15thDay
55%413%18%6%1
1827
16th to endDay
49%412%23%7%1
2160
April1st to 15thDay
52%311%21%11%
2162
16th to endDay
50%311%16%16%2
2340
May1st to 15thDay
46%411%22%11%3
2331
16th to endDay
38%413%27%14%1
2620
June1st to 15thDay
40%414%26%12%
2679
16th to endDay
41%416%24%12%1
2673
July1st to 15thDay
32%414%32%15%1
2371
16th to endDay
34%415%27%16%
2488
August1st to 15thDay
34%418%30%12%
2383
16th to endDay
40%414%27%12%1
2426
September1st to 15thDay
42%313%27%12%
2082
16th to endDay
41%5%15%26%10%
1980
October1st to 15thDay
55%310%22%7%
1910
16th to endDay
71%412%8%3
1593
November1st to 15thDay
61%312%16%6%
1582
16th to endDay
79%38%6%1
1508
December1st to 15thDay
86%245%
1260
16th to endDay
84%26%41
1415
January1st to 15thNight
83%36%5%1
2506
16th to endNight
78%37%8%2
2688
February1st to 15thNight
75%37%10%1
2301
16th to endNight
70%39%11%4
1893
March1st to 15thNight
53%311%20%9%
2133
16th to endNight
47%312%22%12%1
2075
April1st to 15thNight
54%38%20%11%1
1785
16th to endNight
47%310%20%16%2
1620
May1st to 15thNight
49%411%20%10%3
1620
16th to endNight
40%312%27%13%2
1498
June1st to 15thNight
44%411%22%15%
1278
16th to endNight
38%5%16%24%14%
1282
July1st to 15thNight
34%313%28%18%1
1360
16th to endNight
33%416%26%17%1
1417
August1st to 15thNight
30%419%32%12%
1551
16th to endNight
36%6%16%24%14%1
1774
September1st to 15thNight
40%414%24%14%1
1866
16th to endNight
42%415%27%10%
1980
October1st to 15thNight
53%310%22%9%
2046
16th to endNight
67%49%13%4
2300
November1st to 15thNight
61%411%15%6%
2276
16th to endNight
77%39%6%1
2449
December1st to 15thNight
86%16%5%
2700
16th to endNight
82%37%5%1
2805

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
17%13%41%23%4
90
16th to endDay
36%7%22%22%8%2
96
February1st to 15thDay
23%21%31%18%5%
90
16th to endDay
23%9%40%23%2
81
March1st to 15thDay
16%20%26%24%11%
117
16th to endDay
23%15%22%25%11%2
288
April1st to 15thDay
22%16%24%23%10%1
270
16th to endDay
20%19%25%19%12%2
270
May1st to 15thDay
18%19%23%22%11%4
288
16th to endDay
15%18%24%25%12%3
516
June1st to 15thDay
15%16%26%26%12%2
495
16th to endDay
17%14%22%25%14%4
495
July1st to 15thDay
11%12%23%26%18%6%
475
16th to endDay
11%16%18%32%16%5%
515
August1st to 15thDay
9%7%14%34%22%10%
371
16th to endDay
19%7%14%29%19%8%
332
September1st to 15thDay
13%8%18%24%20%14%
315
16th to endDay
10%10%18%30%25%4
314
October1st to 15thDay
25%10%26%25%10%1
303
16th to endDay
32%7%34%21%41
99
November1st to 15thDay
17%8%31%32%8%1
90
16th to endDay
27%18%24%23%6%
77
December1st to 15thDay
31%23%28%13%11
60
16th to endDay
39%30%27%11
76
January1st to 15thNight
20%28%24%20%5%
900
16th to endNight
19%26%25%21%5%
960
February1st to 15thNight
18%26%26%22%5%
761
16th to endNight
18%22%22%28%7%
631
March1st to 15thNight
15%22%26%23%10%
720
16th to endNight
16%21%22%29%9%
731
April1st to 15thNight
21%21%25%24%5%1
539
16th to endNight
18%21%25%23%9%1
540
May1st to 15thNight
14%20%24%29%10%
540
16th to endNight
12%19%20%32%12%
563
June1st to 15thNight
15%20%18%34%10%
378
16th to endNight
10%18%16%33%18%2
382
July1st to 15thNight
12%13%12%36%21%3
510
16th to endNight
9%17%16%31%22%2
564
August1st to 15thNight
8%11%13%36%28%2
539
16th to endNight
15%11%13%32%24%2
573
September1st to 15thNight
16%10%18%28%19%5%
606
16th to endNight
18%10%15%31%19%4
717
October1st to 15thNight
25%13%20%26%12%1
720
16th to endNight
30%16%24%21%6%1
708
November1st to 15thNight
26%22%23%19%7%
700
16th to endNight
27%26%23%17%4
751
December1st to 15thNight
25%31%26%14%2
900
16th to endNight
23%26%25%19%31
960
Page generated at 2017-10-17 16:35:27. Version ac04

Copyright 2017 A. Danko


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