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 2005-11-05 to 2019-06-02.

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
27%
16929
13%
53814
7%
16898
34%
16898
14%
38108

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
14%
840
10%
2926
3%
836
22%
836
8%
2255
January16th to endNight
16%
896
11%
3136
4%
896
25%
896
9%
2292
February1st to 15thNight
13%
824
9%
2653
3%
821
21%
821
9%
2055
February16th to endNight
18%
735
12%
2205
5%
735
28%
735
12%
1611
March1st to 15thNight
19%
840
13%
2520
7%
840
27%
840
11%
1897
March16th to endNight
21%
896
19%
2335
6%
896
31%
896
17%
1663
April1st to 15thNight
19%
838
15%
2096
4%
838
26%
838
15%
1571
April16th to endNight
23%
727
15%
1973
4%
727
30%
727
16%
1401
May1st to 15thNight
25%
512
16%
1772
10%
512
35%
512
13%
1224
May16th to endNight
31%
438
13%
1753
11%
438
41%
438
16%
1112
June1st to 15thNight
29%
392
11%
1569
8%
392
41%
392
13%
1051
June16th to endNight
39%
390
10%
1560
11%
390
46%
390
18%
965
July1st to 15thNight
46%
370
14%
1480
17%
370
53%
370
23%
818
July16th to endNight
48%
408
14%
1546
16%
386
58%
386
23%
880
August1st to 15thNight
49%
430
16%
1571
14%
428
54%
428
21%
960
August16th to endNight
54%
828
19%
2070
10%
828
56%
828
34%
1318
September1st to 15thNight
46%
780
16%
1952
8%
780
48%
780
30%
1314
September16th to endNight
44%
777
22%
2145
15%
777
49%
777
30%
1343
October1st to 15thNight
33%
780
16%
2275
10%
780
39%
780
19%
1575
October16th to endNight
24%
832
11%
2664
6%
832
32%
832
13%
1990
November1st to 15thNight
23%
820
15%
2667
9%
820
31%
820
13%
1921
November16th to endNight
19%
840
13%
2870
7%
840
29%
840
10%
2093
December1st to 15thNight
17%
840
8%
2940
3%
840
22%
840
7%
2301
December16th to endNight
13%
896
8%
3136
3%
896
20%
896
6%
2498

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
13%8%36%6%35%5%5%7%32%
54530
Night
14%8%47%6%3445%6%33%
53984
Cloud CoverDay
15%8%36%6%35%5%5%7%32%
54540
Night
15%9%47%6%3445%6%32%
53989
TransparencyDay
50%7%12%18%9%1
54218
Night
50%7%12%18%9%1
53814
SeeingDay
20%22%27%17%8%2
7739
Night
18%24%24%22%8%
16930

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
12%12%5%9%8%45%5%6%6%21%
1672
16th to endDay
9%10%410%8%5%7%447%27%
1792
February1st to 15thDay
10%11%6%9%9%5%6%45%6%23%
1864
16th to endDay
12%11%6%10%7%3435%6%28%
1840
March1st to 15thDay
14%13%5%8%6%5%6%5%45%24%
2090
16th to endDay
12%9%5%8%6%3443437%
2591
April1st to 15thDay
17%9%37%6%3435%6%32%
2512
16th to endDay
17%8%36%5%34436%36%
2592
May1st to 15thDay
18%8%37%5%3445%5%33%
2851
16th to endDay
14%6%25%6%35%5%6%7%34%
3066
June1st to 15thDay
19%7%35%5%35%46%7%30%
2744
16th to endDay
14%5%26%6%46%5%6%9%32%
2730
July1st to 15thDay
8%6%25%6%46%6%6%9%36%
2730
16th to endDay
10%426%6%46%6%7%9%34%
2878
August1st to 15thDay
9%5%36%6%46%7%7%9%32%
2617
16th to endDay
7%425%6%35%5%6%8%42%
2484
September1st to 15thDay
12%7%145%3445%7%44%
2337
16th to endDay
9%425%42446%7%47%
2145
October1st to 15thDay
18%8%36%6%335%5%6%32%
2014
16th to endDay
17%10%47%6%45%5%45%30%
1911
November1st to 15thDay
15%10%36%5%45%446%32%
1851
16th to endDay
15%10%37%6%45%45%5%29%
1747
December1st to 15thDay
15%17%5%8%6%35%5%5%5%21%
1680
16th to endDay
20%16%7%7%5%34446%19%
1792
January1st to 15thNight
13%11%5%11%8%46%45%5%23%
2926
16th to endNight
9%11%5%10%7%45%5%5%6%28%
3136
February1st to 15thNight
10%11%6%12%9%46%5%5%5%22%
2652
16th to endNight
12%10%5%10%6%35%445%30%
2205
March1st to 15thNight
16%12%5%8%7%3433429%
2507
16th to endNight
13%9%47%5%2435%5%37%
2335
April1st to 15thNight
17%8%47%6%44446%31%
2096
16th to endNight
20%7%26%5%34345%37%
1973
May1st to 15thNight
18%8%26%6%3345%6%33%
1772
16th to endNight
13%6%35%5%345%5%9%38%
1751
June1st to 15thNight
20%7%25%5%33447%33%
1569
16th to endNight
13%425%4345%6%9%39%
1560
July1st to 15thNight
9%4245%245%6%10%43%
1560
16th to endNight
9%4244345%6%9%44%
1642
August1st to 15thNight
9%415%6%45%5%5%9%42%
1581
16th to endNight
8%4244345%6%8%47%
2070
September1st to 15thNight
13%5%245%34447%45%
1952
16th to endNight
12%41443335%7%48%
2145
October1st to 15thNight
16%7%27%4345%5%5%37%
2275
16th to endNight
20%9%36%6%345%45%29%
2664
November1st to 15thNight
17%9%47%5%345%45%32%
2667
16th to endNight
16%9%48%6%35%45%5%29%
2870
December1st to 15thNight
17%13%5%8%7%46%5%5%5%21%
2940
16th to endNight
17%14%5%9%7%45%44421%
3136

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
14%13%6%9%7%36%6%5%5%20%
1672
16th to endDay
11%11%5%9%7%36%5%47%26%
1792
February1st to 15thDay
11%12%5%9%8%36%5%46%24%
1864
16th to endDay
13%12%6%9%7%3345%6%27%
1840
March1st to 15thDay
15%14%5%8%6%35%5%5%5%24%
2100
16th to endDay
13%10%5%7%6%3334437%
2591
April1st to 15thDay
18%9%36%5%34447%32%
2512
16th to endDay
18%8%35%434436%36%
2592
May1st to 15thDay
19%9%27%5%2445%6%33%
2851
16th to endDay
15%5%25%5%35%5%6%8%35%
3066
June1st to 15thDay
21%7%25%6%35%5%5%7%30%
2744
16th to endDay
15%5%35%5%36%6%6%8%32%
2730
July1st to 15thDay
9%6%25%5%46%5%6%9%38%
2730
16th to endDay
12%425%6%46%7%7%8%35%
2878
August1st to 15thDay
10%5%36%7%36%6%7%9%34%
2617
16th to endDay
8%425%5%345%7%8%42%
2484
September1st to 15thDay
13%6%2442345%6%44%
2337
16th to endDay
10%42442436%8%47%
2145
October1st to 15thDay
19%7%36%6%34347%32%
2014
16th to endDay
19%11%36%5%3345%5%29%
1911
November1st to 15thDay
18%11%35%5%35%446%32%
1851
16th to endDay
18%9%38%5%345%5%6%28%
1747
December1st to 15thDay
16%16%5%9%6%45%5%46%20%
1680
16th to endDay
22%17%5%6%6%35%35%5%18%
1792
January1st to 15thNight
14%13%5%11%7%4445%6%21%
2926
16th to endNight
11%12%6%10%7%35%45%6%26%
3136
February1st to 15thNight
11%12%6%13%9%4445%421%
2645
16th to endNight
13%13%5%8%7%35%445%28%
2205
March1st to 15thNight
17%13%5%7%6%3433428%
2520
16th to endNight
14%9%5%8%6%23236%36%
2334
April1st to 15thNight
19%9%47%5%2435%6%30%
2096
16th to endNight
21%8%25%5%2344437%
1973
May1st to 15thNight
19%8%35%434446%33%
1772
16th to endNight
14%6%35%5%4445%8%37%
1751
June1st to 15thNight
21%7%26%42445%7%33%
1569
16th to endNight
14%425%5%35%5%5%8%38%
1560
July1st to 15thNight
9%325%425%48%9%43%
1560
16th to endNight
10%425%435%46%9%43%
1642
August1st to 15thNight
10%425%5%446%6%8%41%
1581
16th to endNight
8%5%2442447%8%45%
2070
September1st to 15thNight
15%5%15%5%23447%44%
1952
16th to endNight
12%4234235%5%7%48%
2145
October1st to 15thNight
19%7%26%434446%35%
2275
16th to endNight
22%10%36%5%35%445%27%
2664
November1st to 15thNight
19%10%36%5%23445%31%
2667
16th to endNight
17%12%47%5%34446%28%
2870
December1st to 15thNight
18%15%5%9%6%45%445%20%
2940
16th to endNight
18%16%6%9%6%34345%20%
3136

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
59%7%11%14%6%
1673
16th to endDay
56%5%15%13%8%
1792
February1st to 15thDay
60%8%8%15%5%
1867
16th to endDay
57%6%11%12%10%1
1840
March1st to 15thDay
61%7%10%13%6%1
2100
16th to endDay
51%48%17%15%3
2591
April1st to 15thDay
51%7%9%18%11%2
2512
16th to endDay
49%5%10%18%13%3
2592
May1st to 15thDay
52%6%8%18%13%1
2851
16th to endDay
46%9%12%18%11%1
3070
June1st to 15thDay
52%7%12%17%9%1
2744
16th to endDay
47%8%13%18%10%1
2730
July1st to 15thDay
40%9%13%24%11%
2581
16th to endDay
42%10%15%20%9%
2711
August1st to 15thDay
43%11%16%20%7%
2603
16th to endDay
36%8%15%26%12%
2484
September1st to 15thDay
38%7%13%27%12%1
2337
16th to endDay
34%7%16%27%13%1
2145
October1st to 15thDay
50%7%12%20%9%
2014
16th to endDay
55%7%13%17%5%
1911
November1st to 15thDay
52%6%13%16%8%1
1851
16th to endDay
53%7%12%16%8%1
1747
December1st to 15thDay
63%7%12%12%4
1680
16th to endDay
65%7%9%10%7%
1792
January1st to 15thNight
59%8%12%13%6%
2926
16th to endNight
54%7%11%16%9%
3136
February1st to 15thNight
60%6%13%12%6%
2653
16th to endNight
53%6%13%16%9%
2205
March1st to 15thNight
58%410%18%7%
2520
16th to endNight
47%6%10%17%14%3
2335
April1st to 15thNight
53%49%17%13%
2096
16th to endNight
48%5%9%18%13%2
1973
May1st to 15thNight
50%6%7%16%16%2
1772
16th to endNight
41%8%13%21%12%1
1753
June1st to 15thNight
49%7%13%18%10%
1569
16th to endNight
39%8%14%23%11%1
1560
July1st to 15thNight
32%8%17%26%14%1
1480
16th to endNight
33%9%17%24%14%1
1546
August1st to 15thNight
37%8%18%24%10%
1571
16th to endNight
32%7%16%30%13%
2070
September1st to 15thNight
38%7%14%26%11%1
1952
16th to endNight
34%6%13%30%13%1
2145
October1st to 15thNight
46%6%14%21%10%
2275
16th to endNight
55%7%13%16%6%
2664
November1st to 15thNight
52%7%12%16%9%2
2667
16th to endNight
54%6%13%17%6%1
2870
December1st to 15thNight
61%7%13%13%3
2940
16th to endNight
64%6%10%12%5%
3136

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
18%28%30%14%7%1
120
16th to endDay
23%35%28%9%3
128
February1st to 15thDay
27%35%27%8%1
211
16th to endDay
22%34%27%12%2
343
March1st to 15thDay
26%26%25%18%2
390
16th to endDay
19%34%22%15%6%1
416
April1st to 15thDay
25%30%26%12%41
390
16th to endDay
26%30%20%13%6%2
379
May1st to 15thDay
28%23%28%12%5%1
408
16th to endDay
18%25%31%18%41
459
June1st to 15thDay
23%21%31%16%5%
379
16th to endDay
15%21%34%20%6%1
375
July1st to 15thDay
12%14%30%23%15%2
365
16th to endDay
12%13%32%28%11%2
390
August1st to 15thDay
12%12%32%23%15%4
358
16th to endDay
10%14%22%27%16%8%
396
September1st to 15thDay
14%11%23%24%16%8%
375
16th to endDay
12%14%28%17%16%11%
374
October1st to 15thDay
22%18%26%17%12%2
375
16th to endDay
25%25%25%19%5%
348
November1st to 15thDay
26%20%26%17%8%1
325
16th to endDay
31%26%24%12%41
187
December1st to 15thDay
15%29%37%11%5%
120
16th to endDay
35%22%32%8%1
128
January1st to 15thNight
16%31%30%17%3
840
16th to endNight
15%31%31%17%3
896
February1st to 15thNight
16%28%33%19%2
824
16th to endNight
17%32%26%19%3
735
March1st to 15thNight
24%29%22%20%2
840
16th to endNight
18%31%22%19%6%
896
April1st to 15thNight
21%30%25%19%2
838
16th to endNight
21%29%22%18%7%
727
May1st to 15thNight
19%24%24%22%7%
512
16th to endNight
12%24%29%23%8%
439
June1st to 15thNight
21%20%22%25%9%
392
16th to endNight
12%18%22%33%10%1
390
July1st to 15thNight
9%13%24%31%19%1
370
16th to endNight
10%17%18%35%17%
408
August1st to 15thNight
12%10%19%35%20%1
430
16th to endNight
10%12%17%32%23%2
828
September1st to 15thNight
15%11%22%30%17%2
780
16th to endNight
13%14%24%22%20%4
777
October1st to 15thNight
20%18%22%25%12%
780
16th to endNight
24%21%24%21%6%
832
November1st to 15thNight
20%24%26%19%8%1
820
16th to endNight
21%31%23%15%8%
840
December1st to 15thNight
23%30%23%17%4
840
16th to endNight
25%28%27%15%3
896
Page generated at 2019-06-02 19:43:10. Version ac04

Copyright 2019 A. Danko


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