The Observatory at Tangleroot Farm
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the The Observatory at Tangleroot Farm clear sky chart from 2005-11-06 to 2024-01-22.

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%
22720
13%
74856
8%
22681
35%
22681
15%
52912

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
16%
760
9%
2649
3%
757
23%
757
8%
2041
January11th to 20thNight
15%
760
8%
2660
2%
760
22%
760
8%
2084
January21st to endNight
20%
800
13%
2798
6%
800
30%
800
12%
1986
February1st to 10thNight
15%
720
8%
2354
3%
720
22%
720
10%
1793
February11th to 20thNight
15%
703
12%
2140
3%
700
27%
700
12%
1582
February21st to endNight
19%
592
15%
1776
5%
592
30%
592
13%
1316
March1st to 10thNight
21%
720
14%
2160
7%
720
30%
720
13%
1634
March11th to 20thNight
19%
720
14%
2102
5%
720
29%
720
14%
1527
March21st to endNight
22%
792
20%
1980
6%
792
32%
792
19%
1440
April1st to 10thNight
21%
720
16%
1800
4%
720
27%
720
18%
1333
April11th to 20thNight
24%
711
13%
1775
4%
711
28%
711
18%
1325
April21st to endNight
24%
586
15%
1666
5%
586
31%
586
17%
1185
May1st to 10thNight
26%
478
15%
1558
10%
478
33%
478
15%
1094
May11th to 20thNight
28%
354
19%
1416
14%
354
43%
354
17%
894
May21st to endNight
38%
388
13%
1551
14%
388
46%
388
19%
952
June1st to 10thNight
34%
360
11%
1440
10%
360
44%
360
15%
956
June11th to 20thNight
40%
360
12%
1440
13%
360
48%
360
19%
886
June21st to endNight
40%
360
9%
1440
11%
360
46%
360
19%
932
July1st to 10thNight
50%
350
13%
1400
16%
350
57%
350
24%
797
July11th to 20thNight
53%
348
15%
1392
19%
348
59%
348
24%
799
July21st to endNight
54%
394
16%
1486
18%
372
59%
372
25%
844
August1st to 10thNight
58%
358
18%
1422
20%
356
63%
356
26%
810
August11th to 20thNight
55%
597
17%
1661
11%
597
57%
597
30%
1088
August21st to endNight
50%
792
18%
1980
9%
792
53%
792
31%
1315
September1st to 10thNight
48%
720
15%
1800
6%
720
50%
720
34%
1182
September11th to 20thNight
46%
720
21%
1891
12%
720
51%
720
33%
1185
September21st to endNight
40%
720
21%
1980
15%
720
45%
720
29%
1294
October1st to 10thNight
34%
720
15%
2069
9%
720
40%
720
19%
1460
October11th to 20thNight
34%
720
15%
2194
10%
720
41%
720
19%
1543
October21st to endNight
23%
792
12%
2574
6%
792
31%
792
13%
1901
November1st to 10thNight
23%
740
15%
2407
8%
740
33%
740
15%
1677
November11th to 20thNight
23%
760
17%
2471
10%
760
32%
760
15%
1740
November21st to endNight
20%
760
11%
2660
6%
760
27%
760
10%
1957
December1st to 10thNight
14%
760
7%
2660
2%
760
19%
760
7%
2137
December11th to 20thNight
17%
759
10%
3249
3%
759
24%
759
7%
2465
December21st to endNight
13%
826
5%
4855
2%
817
20%
817
4%
3758

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
14%9%47%6%45%5%6%7%33%
74835
Night
15%9%48%6%45%5%5%7%33%
75095
TransparencyDay
49%8%13%19%10%1
74540
Night
50%7%13%19%10%1
74924
SeeingDay
21%20%30%19%8%2
13604
Night
20%16%29%25%8%1
22732

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
11%14%5%9%10%46%6%6%7%22%
1517
11th to 20thDay
13%12%6%12%8%45%346%26%
1520
21st to endDay
8%10%5%11%9%5%8%6%5%7%27%
1592
February1st to 10thDay
12%12%5%10%9%5%6%46%7%22%
1602
11th to 20thDay
9%11%6%10%9%46%5%5%6%29%
1707
21st to endDay
14%12%6%10%7%45%446%28%
1480
March1st to 10thDay
12%10%5%10%8%5%6%5%5%6%29%
1797
11th to 20thDay
13%14%5%9%7%35%5%45%30%
1855
21st to endDay
14%10%5%8%8%34435%35%
2376
April1st to 10thDay
17%11%47%6%3445%5%33%
2160
11th to 20thDay
16%8%47%6%3445%6%37%
2134
21st to endDay
20%8%37%6%35%5%46%32%
2294
May1st to 10thDay
17%8%47%5%45%5%5%6%33%
2417
11th to 20thDay
15%7%46%6%45%5%6%7%36%
2478
21st to endDay
13%6%25%7%45%6%6%9%37%
2725
June1st to 10thDay
19%7%36%5%45%5%6%9%29%
2520
11th to 20thDay
13%6%26%6%45%5%6%8%38%
2520
21st to endDay
16%7%38%6%46%6%6%9%30%
2520
July1st to 10thDay
11%6%25%7%5%6%6%6%9%38%
2520
11th to 20thDay
9%6%36%6%47%6%8%10%35%
2520
21st to endDay
11%5%26%6%47%6%7%9%36%
2744
August1st to 10thDay
9%5%26%7%47%7%8%9%38%
2506
11th to 20thDay
9%5%27%6%46%6%7%10%38%
2217
21st to endDay
10%5%36%6%45%6%6%8%40%
2376
September1st to 10thDay
11%6%24425%5%6%8%46%
2160
11th to 20thDay
11%6%245%335%5%7%49%
2067
21st to endDay
12%5%26%6%35%5%7%8%40%
1980
October1st to 10thDay
19%10%37%6%35%5%6%6%32%
1889
11th to 20thDay
14%8%37%7%45%7%6%7%33%
1765
21st to endDay
20%9%39%6%45%45%5%29%
1782
November1st to 10thDay
12%11%47%6%46%5%47%34%
1671
11th to 20thDay
16%9%48%6%5%6%5%5%6%31%
1706
21st to endDay
14%12%47%6%46%5%6%6%30%
1520
December1st to 10thDay
17%18%5%10%7%45%445%20%
1520
11th to 20thDay
19%13%5%6%6%45%5%6%7%24%
1906
21st to endDay
23%13%5%10%7%45%45%6%20%
2772
January1st to 10thNight
14%13%6%10%8%5%6%5%6%7%22%
2649
11th to 20thNight
14%13%6%12%8%5%5%5%5%5%22%
2660
21st to endNight
8%10%6%9%8%46%5%5%7%31%
2798
February1st to 10thNight
10%11%6%13%9%5%7%5%5%6%23%
2354
11th to 20thNight
9%11%6%11%8%45%5%5%6%29%
2138
21st to endNight
13%10%6%10%7%45%5%5%5%30%
1776
March1st to 10thNight
13%13%5%10%7%45%5%5%5%30%
2150
11th to 20thNight
15%12%5%9%6%35%45%5%32%
2101
21st to endNight
15%10%47%6%34445%38%
1980
April1st to 10thNight
16%9%48%7%45%46%7%31%
1800
11th to 20thNight
19%7%37%7%345%46%34%
1775
21st to endNight
19%8%37%5%45%446%35%
1666
May1st to 10thNight
20%8%36%6%445%5%7%32%
1558
11th to 20thNight
16%7%37%6%3445%6%40%
1415
21st to endNight
10%6%36%435%5%7%9%41%
1550
June1st to 10thNight
19%6%36%6%445%5%8%35%
1440
11th to 20thNight
16%6%25%445%5%5%9%40%
1440
21st to endNight
15%6%27%6%35%6%5%8%38%
1440
July1st to 10thNight
11%5%245%345%7%9%44%
1440
11th to 20thNight
10%5%344346%7%11%43%
1440
21st to endNight
10%435%435%5%7%9%45%
1574
August1st to 10thNight
9%3246%45%5%6%10%46%
1432
11th to 20thNight
8%5%27%6%45%6%5%9%43%
1661
21st to endNight
9%5%45%5%346%5%9%44%
1980
September1st to 10thNight
10%5%246%345%6%7%48%
1800
11th to 20thNight
12%6%25%5%3335%7%50%
1891
21st to endNight
13%5%245%35%45%7%45%
1980
October1st to 10thNight
18%7%26%6%35%6%5%6%35%
2069
11th to 20thNight
16%8%37%6%35%5%6%7%34%
2194
21st to endNight
21%10%37%7%3445%7%29%
2574
November1st to 10thNight
16%10%47%6%35%5%5%6%35%
2407
11th to 20thNight
17%8%37%6%35%5%5%7%34%
2471
21st to endNight
15%12%5%7%6%45%5%5%7%28%
2660
December1st to 10thNight
17%15%5%10%8%5%6%5%5%6%20%
2660
11th to 20thNight
19%12%5%9%7%45%45%5%25%
3288
21st to endNight
22%13%6%10%8%44445%20%
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
59%8%13%16%5%
1518
11th to 20thDay
59%6%11%14%8%1
1520
21st to endDay
56%7%14%13%9%1
1592
February1st to 10thDay
61%8%8%15%5%2
1602
11th to 20thDay
56%8%11%16%8%1
1716
21st to endDay
58%6%11%13%10%2
1480
March1st to 10thDay
55%8%11%15%8%2
1800
11th to 20thDay
56%6%11%13%12%3
1855
21st to endDay
52%6%8%18%13%4
2376
April1st to 10thDay
52%7%9%19%10%3
2160
11th to 20thDay
48%7%10%19%15%2
2134
21st to endDay
54%5%11%17%11%3
2294
May1st to 10thDay
50%7%9%18%14%2
2417
11th to 20thDay
46%7%8%19%17%3
2482
21st to endDay
43%10%14%20%11%2
2725
June1st to 10thDay
51%8%13%17%10%1
2520
11th to 20thDay
44%8%12%21%13%2
2520
21st to endDay
50%8%13%18%9%1
2520
July1st to 10thDay
41%9%13%24%12%1
2450
11th to 20thDay
41%11%14%26%8%
2445
21st to endDay
41%11%16%22%10%1
2591
August1st to 10thDay
39%12%17%22%10%
2492
11th to 20thDay
38%11%18%24%9%
2217
21st to endDay
40%9%13%26%12%1
2376
September1st to 10thDay
35%9%13%29%13%1
2160
11th to 20thDay
34%6%13%31%15%1
2067
21st to endDay
39%9%16%23%10%2
1980
October1st to 10thDay
50%7%12%19%11%
1889
11th to 20thDay
47%10%15%21%7%
1765
21st to endDay
56%7%13%15%7%1
1782
November1st to 10thDay
50%7%15%18%10%1
1671
11th to 20thDay
52%7%13%15%10%2
1706
21st to endDay
53%8%15%18%5%1
1520
December1st to 10thDay
67%7%11%11%4
1520
11th to 20thDay
58%8%14%15%5%
1906
21st to endDay
63%7%12%14%3
2772
January1st to 10thNight
60%8%13%13%6%
2649
11th to 20thNight
62%8%11%13%6%
2660
21st to endNight
51%8%11%17%11%1
2798
February1st to 10thNight
59%7%14%11%8%1
2354
11th to 20thNight
55%7%12%17%9%1
2140
21st to endNight
55%6%13%16%9%2
1776
March1st to 10thNight
58%6%10%16%9%1
2160
11th to 20thNight
53%5%10%19%10%2
2102
21st to endNight
47%7%10%19%13%4
1980
April1st to 10thNight
52%6%10%19%12%2
1800
11th to 20thNight
51%6%11%18%13%1
1775
21st to endNight
50%6%11%18%12%4
1666
May1st to 10thNight
52%5%7%17%16%3
1558
11th to 20thNight
44%6%9%20%17%3
1416
21st to endNight
38%10%15%21%13%2
1551
June1st to 10thNight
47%8%13%19%10%2
1440
11th to 20thNight
42%7%14%22%13%2
1440
21st to endNight
43%9%16%22%10%1
1440
July1st to 10thNight
35%7%17%24%16%1
1400
11th to 20thNight
34%9%16%28%12%1
1392
21st to endNight
33%10%18%27%11%1
1486
August1st to 10thNight
33%9%20%27%11%
1422
11th to 20thNight
36%9%15%27%12%
1661
21st to endNight
36%8%16%26%12%
1980
September1st to 10thNight
34%8%17%28%12%1
1800
11th to 20thNight
34%7%15%30%14%
1891
21st to endNight
39%7%14%26%13%2
1980
October1st to 10thNight
47%8%13%21%11%1
2069
11th to 20thNight
47%8%15%23%7%
2194
21st to endNight
55%7%14%15%8%1
2574
November1st to 10thNight
48%8%14%19%10%2
2407
11th to 20thNight
50%7%13%19%8%3
2471
21st to endNight
55%8%15%17%5%
2660
December1st to 10thNight
65%8%13%12%2
2660
11th to 20thNight
60%7%11%14%7%1
3288
21st to endNight
66%6%12%14%3
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
20%26%29%18%7%1
180
11th to 20thDay
26%28%33%11%11
180
21st to endDay
20%26%36%14%31
178
February1st to 10thDay
33%35%25%5%1
232
11th to 20thDay
25%31%32%10%2
375
21st to endDay
29%25%32%12%2
346
March1st to 10thDay
27%24%30%16%2
420
11th to 20thDay
26%28%26%15%31
420
21st to endDay
27%28%25%13%6%2
462
April1st to 10thDay
30%21%27%16%5%1
420
11th to 20thDay
27%27%24%14%5%3
412
21st to endDay
30%27%23%13%5%2
420
May1st to 10thDay
26%22%31%11%8%1
423
11th to 20thDay
21%20%33%19%5%2
447
21st to endDay
16%19%33%23%8%1
485
June1st to 10thDay
26%16%34%17%6%1
450
11th to 20thDay
17%18%34%22%8%1
450
21st to endDay
19%18%32%21%8%2
450
July1st to 10thDay
16%12%31%29%12%1
445
11th to 20thDay
11%9%39%27%11%2
444
21st to endDay
14%10%35%30%10%2
488
August1st to 10thDay
9%9%34%29%15%3
446
11th to 20thDay
12%9%32%27%14%5%
439
21st to endDay
12%16%27%28%11%5%
495
September1st to 10thDay
15%12%29%24%13%7%
450
11th to 20thDay
16%13%25%21%15%8%
450
21st to endDay
14%14%33%23%12%5%
450
October1st to 10thDay
22%19%24%18%14%2
450
11th to 20thDay
21%22%30%19%7%1
432
21st to endDay
28%21%27%20%4
396
November1st to 10thDay
25%19%28%20%7%1
365
11th to 20thDay
30%21%29%14%5%2
366
21st to endDay
28%26%28%15%2
180
December1st to 10thDay
26%28%28%13%41
180
11th to 20thDay
27%29%34%9%1
180
21st to endDay
30%24%31%12%3
198
January1st to 10thNight
21%21%36%18%4
760
11th to 20thNight
25%22%31%19%3
760
21st to endNight
13%21%39%22%5%
800
February1st to 10thNight
18%21%38%20%3
720
11th to 20thNight
19%23%36%19%2
703
21st to endNight
21%22%34%20%3
592
March1st to 10thNight
25%19%31%23%2
720
11th to 20thNight
24%23%28%19%5%1
720
21st to endNight
24%21%28%21%6%1
792
April1st to 10thNight
22%22%28%23%4
720
11th to 20thNight
25%21%27%19%8%
711
21st to endNight
23%19%30%22%6%
586
May1st to 10thNight
25%15%28%25%7%
478
11th to 20thNight
15%17%35%27%6%1
354
21st to endNight
13%14%31%29%12%1
389
June1st to 10thNight
23%8%28%29%12%1
360
11th to 20thNight
19%8%25%37%11%1
360
21st to endNight
16%7%31%34%11%1
360
July1st to 10thNight
14%5%27%37%16%1
350
11th to 20thNight
11%324%43%16%2
348
21st to endNight
12%5%24%44%15%1
394
August1st to 10thNight
11%422%44%18%1
358
11th to 20thNight
11%5%21%38%22%3
597
21st to endNight
12%8%22%36%20%2
792
September1st to 10thNight
13%7%27%35%16%3
720
11th to 20thNight
16%9%24%29%19%3
720
21st to endNight
15%10%31%27%16%2
720
October1st to 10thNight
23%14%23%25%14%1
720
11th to 20thNight
21%15%26%28%9%1
720
21st to endNight
28%15%29%24%5%
792
November1st to 10thNight
23%16%32%21%8%1
740
11th to 20thNight
21%20%32%18%8%1
760
21st to endNight
24%22%28%20%6%1
760
December1st to 10thNight
26%23%29%18%4
760
11th to 20thNight
24%20%32%20%4
760
21st to endNight
28%20%32%17%2
836
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Copyright 2024 Attilla Danko


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