"Way The Held Out" Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the "Way The Held Out" Observatory clear sky chart from 2005-11-06 to 2024-01-27.

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
28%
23225
12%
75092
8%
23171
33%
23171
14%
56088

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
8%
758
6%
2516
2%
757
12%
757
4%
2182
January11th to 20thNight
10%
760
4%
2470
2%
760
12%
760
5%
2134
January21st to endNight
9%
820
6%
2664
2%
820
14%
820
5%
2323
February1st to 10thNight
11%
720
5%
2340
2%
720
14%
720
6%
1982
February11th to 20thNight
10%
703
6%
2275
3%
700
14%
700
7%
1880
February21st to endNight
11%
592
9%
1802
2%
592
20%
592
8%
1458
March1st to 10thNight
17%
720
13%
1980
6%
720
23%
720
13%
1554
March11th to 20thNight
21%
720
16%
1980
8%
720
28%
720
15%
1484
March21st to endNight
20%
792
15%
2178
8%
792
26%
792
15%
1675
April1st to 10thNight
22%
720
12%
1886
4%
720
26%
720
17%
1428
April11th to 20thNight
24%
649
14%
1713
6%
649
30%
649
20%
1253
April21st to endNight
28%
540
16%
1620
7%
540
35%
540
19%
1148
May1st to 10thNight
34%
540
13%
1620
7%
540
39%
540
18%
1137
May11th to 20thNight
35%
528
15%
1589
10%
528
40%
528
20%
1107
May21st to endNight
46%
388
17%
1551
15%
388
55%
388
25%
882
June1st to 10thNight
43%
360
15%
1440
14%
360
53%
360
21%
861
June11th to 20thNight
47%
360
16%
1440
18%
360
54%
360
21%
871
June21st to endNight
47%
360
16%
1440
18%
360
54%
360
21%
873
July1st to 10thNight
58%
350
16%
1400
21%
350
62%
350
25%
791
July11th to 20thNight
55%
519
16%
1563
15%
519
58%
519
31%
954
July21st to endNight
59%
591
16%
1672
14%
558
61%
558
29%
1063
August1st to 10thNight
62%
537
19%
1600
16%
534
64%
534
33%
973
August11th to 20thNight
60%
534
18%
1598
13%
534
62%
534
27%
1032
August21st to endNight
53%
662
20%
1850
13%
662
56%
662
30%
1171
September1st to 10thNight
51%
720
19%
1800
12%
720
54%
720
31%
1205
September11th to 20thNight
54%
720
23%
1979
17%
720
57%
720
33%
1233
September21st to endNight
40%
720
18%
1980
14%
720
45%
720
24%
1369
October1st to 10thNight
40%
720
17%
2154
15%
720
44%
720
24%
1440
October11th to 20thNight
26%
720
12%
2160
7%
720
34%
720
16%
1581
October21st to endNight
17%
792
14%
2376
7%
792
26%
792
12%
1834
November1st to 10thNight
29%
740
15%
2350
12%
740
35%
740
17%
1639
November11th to 20thNight
15%
760
12%
2631
6%
760
23%
760
9%
2030
November21st to endNight
14%
760
9%
2660
5%
760
20%
760
9%
2154
December1st to 10thNight
10%
760
4%
2660
3%
760
12%
760
5%
2300
December11th to 20thNight
9%
760
4%
3276
2%
759
13%
759
4%
2742
December21st to endNight
8%
830
3%
4879
1%
817
14%
817
2%
4345

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
17%12%5%8%6%3445%7%29%
74744
Night
17%13%5%8%6%34446%28%
75306
TransparencyDay
55%6%11%17%9%1
74460
Night
57%6%11%16%9%1
75110
SeeingDay
24%16%29%19%9%3
13485
Night
25%15%27%22%9%1
23234

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
18%19%9%14%9%45%43412%
1645
11th to 20thDay
19%22%8%12%9%4433412%
1710
21st to endDay
17%19%10%16%11%3333410%
1836
February1st to 10thDay
18%19%8%14%11%4422415%
1620
11th to 20thDay
17%16%9%14%9%4444416%
1573
21st to endDay
19%18%5%13%6%3344421%
1448
March1st to 10thDay
18%14%7%10%6%3345%8%23%
1980
11th to 20thDay
17%16%6%9%5%34445%28%
1980
21st to endDay
21%15%5%8%6%2433428%
2178
April1st to 10thDay
17%13%46%5%3445%6%31%
2074
11th to 20thDay
21%12%345%345%46%32%
2212
21st to endDay
22%12%36%6%23346%33%
2340
May1st to 10thDay
19%10%47%5%35%5%5%7%31%
2340
11th to 20thDay
20%9%46%5%35%46%7%32%
2301
21st to endDay
13%6%35%6%45%5%7%8%38%
2725
June1st to 10thDay
17%7%36%5%35%6%5%8%36%
2520
11th to 20thDay
15%7%36%5%45%5%6%8%37%
2520
21st to endDay
15%6%25%6%35%5%6%9%39%
2520
July1st to 10thDay
11%6%35%5%35%5%5%10%43%
2520
11th to 20thDay
14%5%35%5%45%5%7%10%38%
2340
21st to endDay
12%6%26%6%36%7%6%9%37%
2547
August1st to 10thDay
11%6%26%6%45%6%6%10%39%
2327
11th to 20thDay
12%7%37%7%47%6%8%9%31%
2303
21st to endDay
13%6%36%6%36%5%6%9%38%
2486
September1st to 10thDay
18%6%26%6%35%46%8%37%
2159
11th to 20thDay
13%5%37%6%35%45%8%41%
1980
21st to endDay
19%8%26%6%44447%35%
1980
October1st to 10thDay
18%7%35%5%46%5%5%8%34%
1805
11th to 20thDay
24%9%37%7%44447%27%
1800
21st to endDay
28%14%37%5%345%45%22%
1980
November1st to 10thDay
14%14%47%6%345%5%6%33%
1726
11th to 20thDay
20%18%48%6%34346%23%
1547
21st to endDay
21%23%6%8%5%3445%6%16%
1520
December1st to 10thDay
19%26%12%9%5%3343412%
1520
11th to 20thDay
18%22%10%14%434445%13%
1910
21st to endDay
26%25%9%10%5%2323310%
2772
January1st to 10thNight
20%19%10%14%7%3433413%
2516
11th to 20thNight
21%19%9%14%7%3333414%
2470
21st to endNight
16%22%9%13%9%4434313%
2664
February1st to 10thNight
20%19%6%12%9%35%33415%
2340
11th to 20thNight
17%16%8%14%8%45%435%17%
2273
21st to endNight
20%13%6%15%7%4343421%
1802
March1st to 10thNight
16%13%7%10%7%3445%5%25%
1980
11th to 20thNight
18%14%6%8%5%2435%5%31%
1980
21st to endNight
18%15%5%8%6%35%44429%
2178
April1st to 10thNight
17%14%5%6%5%45%45%5%30%
1886
11th to 20thNight
19%9%35%6%45%5%5%7%32%
1713
21st to endNight
15%10%46%6%35%5%6%7%33%
1620
May1st to 10thNight
20%8%36%7%3445%7%33%
1620
11th to 20thNight
15%9%46%6%25%448%35%
1589
21st to endNight
13%5%234435%5%11%45%
1550
June1st to 10thNight
9%6%27%6%35%5%6%10%40%
1440
11th to 20thNight
11%5%38%5%35%5%5%7%43%
1440
21st to endNight
13%5%35%5%35%5%6%9%42%
1440
July1st to 10thNight
8%5%25%6%345%6%8%48%
1440
11th to 20thNight
10%6%25%435%5%5%10%45%
1616
21st to endNight
10%425%5%45%6%7%8%43%
1771
August1st to 10thNight
9%5%145%45%46%8%48%
1611
11th to 20thNight
10%5%35%5%45%6%6%9%41%
1598
21st to endNight
12%5%245%346%6%8%44%
1850
September1st to 10thNight
14%6%245%336%5%8%45%
1800
11th to 20thNight
13%5%35%42436%7%48%
1979
21st to endNight
17%7%26%6%3446%7%38%
1980
October1st to 10thNight
19%7%25%5%235%47%41%
2154
11th to 20thNight
21%9%37%6%45%45%6%30%
2160
21st to endNight
28%11%47%5%34445%26%
2376
November1st to 10thNight
17%11%47%5%3445%7%33%
2350
11th to 20thNight
19%18%5%7%7%34445%24%
2631
21st to endNight
20%21%6%8%6%34446%19%
2660
December1st to 10thNight
22%23%10%9%6%3333414%
2660
11th to 20thNight
17%24%9%12%7%2433415%
3285
21st to endNight
25%24%8%10%7%343449%
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
77%5%9%7%2
1646
11th to 20thDay
78%49%7%2
1710
21st to endDay
80%46%7%2
1836
February1st to 10thDay
77%38%8%3
1620
11th to 20thDay
73%5%8%9%5%
1582
21st to endDay
67%5%10%12%5%2
1448
March1st to 10thDay
61%5%12%17%5%
1980
11th to 20thDay
59%5%10%15%8%2
1980
21st to endDay
61%47%17%9%1
2178
April1st to 10thDay
53%6%13%16%12%1
2074
11th to 20thDay
52%5%11%19%12%2
2212
21st to endDay
54%410%18%10%3
2340
May1st to 10thDay
52%7%10%19%10%2
2340
11th to 20thDay
50%7%11%18%12%3
2305
21st to endDay
41%9%14%22%12%1
2725
June1st to 10thDay
44%7%13%23%12%1
2520
11th to 20thDay
44%7%13%21%13%1
2520
21st to endDay
41%6%12%25%14%1
2520
July1st to 10thDay
37%7%12%25%16%2
2450
11th to 20thDay
40%7%14%24%14%1
2271
21st to endDay
40%9%15%21%14%2
2405
August1st to 10thDay
39%8%16%26%11%
2314
11th to 20thDay
45%10%14%21%8%2
2303
21st to endDay
41%8%14%21%14%2
2486
September1st to 10thDay
45%7%14%20%12%2
2159
11th to 20thDay
40%7%14%23%14%1
1980
21st to endDay
48%7%12%22%11%1
1980
October1st to 10thDay
47%7%15%18%12%1
1805
11th to 20thDay
57%6%14%16%7%1
1800
21st to endDay
65%5%11%12%6%1
1980
November1st to 10thDay
52%6%11%18%11%2
1726
11th to 20thDay
63%5%10%13%6%2
1547
21st to endDay
70%6%9%10%5%
1520
December1st to 10thDay
77%5%7%9%1
1520
11th to 20thDay
75%6%7%10%2
1906
21st to endDay
82%47%7%1
2772
January1st to 10thNight
78%47%8%3
2516
11th to 20thNight
77%49%8%2
2470
21st to endNight
77%47%9%21
2664
February1st to 10thNight
73%410%10%3
2340
11th to 20thNight
71%5%9%11%4
2275
21st to endNight
68%49%12%7%1
1802
March1st to 10thNight
60%6%9%18%7%
1980
11th to 20thNight
56%5%10%18%10%1
1980
21st to endNight
60%46%15%13%2
2178
April1st to 10thNight
56%5%10%17%11%1
1886
11th to 20thNight
51%6%11%17%13%2
1713
21st to endNight
50%6%12%19%10%4
1620
May1st to 10thNight
51%5%11%18%12%3
1620
11th to 20thNight
48%7%10%18%14%3
1590
21st to endNight
35%7%16%26%14%2
1551
June1st to 10thNight
38%8%13%24%15%2
1440
11th to 20thNight
39%8%12%23%16%2
1440
21st to endNight
38%9%13%23%16%1
1440
July1st to 10thNight
35%7%10%25%20%3
1400
11th to 20thNight
35%7%11%25%19%3
1563
21st to endNight
35%11%14%23%17%2
1672
August1st to 10thNight
34%7%12%31%15%2
1600
11th to 20thNight
38%9%16%26%11%1
1598
21st to endNight
36%8%14%24%15%3
1850
September1st to 10thNight
37%8%14%24%14%3
1800
11th to 20thNight
35%7%14%24%19%1
1979
21st to endNight
45%6%13%21%15%1
1980
October1st to 10thNight
43%7%12%21%17%1
2154
11th to 20thNight
53%7%13%17%10%1
2160
21st to endNight
60%5%11%14%7%2
2376
November1st to 10thNight
50%6%14%19%9%3
2350
11th to 20thNight
63%5%9%14%6%3
2631
21st to endNight
68%5%10%13%31
2660
December1st to 10thNight
76%5%8%8%2
2660
11th to 20thNight
75%410%9%2
3288
21st to endNight
80%6%8%6%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
36%25%27%10%2
240
11th to 20thDay
34%30%27%6%3
270
21st to endDay
30%37%26%6%2
282
February1st to 10thDay
36%24%36%4
240
11th to 20thDay
38%30%28%5%
240
21st to endDay
40%29%26%6%
198
March1st to 10thDay
33%23%32%9%3
420
11th to 20thDay
30%21%32%12%21
420
21st to endDay
36%21%25%15%2
462
April1st to 10thDay
26%27%27%14%41
420
11th to 20thDay
31%21%25%14%8%2
412
21st to endDay
31%19%31%14%41
420
May1st to 10thDay
29%18%29%17%5%2
423
11th to 20thDay
23%15%31%21%8%2
447
21st to endDay
16%11%30%26%12%5%
485
June1st to 10thDay
19%14%33%24%9%3
450
11th to 20thDay
20%10%29%26%14%2
450
21st to endDay
15%11%37%24%11%2
450
July1st to 10thDay
11%7%26%29%20%7%
445
11th to 20thDay
16%7%28%28%16%5%
444
21st to endDay
11%9%35%27%14%5%
488
August1st to 10thDay
11%9%27%28%18%7%
446
11th to 20thDay
17%7%24%30%13%10%
439
21st to endDay
14%9%28%27%17%6%
495
September1st to 10thDay
17%8%26%26%17%6%
450
11th to 20thDay
13%6%26%29%20%7%
450
21st to endDay
21%14%28%21%12%4
450
October1st to 10thDay
20%12%30%20%15%3
450
11th to 20thDay
28%20%32%14%5%1
450
21st to endDay
39%18%28%13%2
495
November1st to 10thDay
29%19%29%15%7%1
324
11th to 20thDay
41%23%23%10%3
192
21st to endDay
33%22%37%8%
180
December1st to 10thDay
39%28%25%431
180
11th to 20thDay
34%27%29%8%1
180
21st to endDay
35%26%30%8%1
198
January1st to 10thNight
34%24%30%10%2
760
11th to 20thNight
37%21%27%13%2
760
21st to endNight
30%23%31%15%2
820
February1st to 10thNight
35%20%29%14%1
720
11th to 20thNight
29%23%33%14%2
703
21st to endNight
32%22%30%15%1
592
March1st to 10thNight
26%20%34%17%3
720
11th to 20thNight
27%20%29%19%41
720
21st to endNight
26%17%31%20%5%1
792
April1st to 10thNight
26%17%32%21%4
720
11th to 20thNight
26%14%32%20%7%1
649
21st to endNight
20%14%33%28%5%1
540
May1st to 10thNight
25%9%25%31%9%1
540
11th to 20thNight
20%8%30%32%9%1
528
21st to endNight
13%6%31%28%20%2
389
June1st to 10thNight
11%5%35%34%14%
360
11th to 20thNight
14%8%23%42%13%
360
21st to endNight
12%7%28%36%17%
360
July1st to 10thNight
10%319%43%20%5%
350
11th to 20thNight
12%422%34%24%4
519
21st to endNight
12%419%40%24%2
591
August1st to 10thNight
11%417%40%24%4
537
11th to 20thNight
12%416%35%28%4
534
21st to endNight
14%6%22%29%25%3
662
September1st to 10thNight
17%7%20%30%22%4
720
11th to 20thNight
14%6%19%32%24%5%
720
21st to endNight
19%11%23%26%17%4
720
October1st to 10thNight
21%9%26%24%17%2
720
11th to 20thNight
28%15%28%23%6%1
720
21st to endNight
35%16%30%17%2
792
November1st to 10thNight
23%16%28%24%8%1
740
11th to 20thNight
32%20%29%13%5%1
760
21st to endNight
34%19%31%13%4
760
December1st to 10thNight
38%20%28%11%4
760
11th to 20thNight
30%29%26%13%2
760
21st to endNight
34%22%30%12%1
836
Page generated at 2024-01-24 09:37:30. Version ac07

Copyright 2024 Attilla Danko


"Way The Held Out" Observatory Clear Sky Chart |Charts Home