Telescope Array Black Rock Mesa FD
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Telescope Array Black Rock Mesa FD clear sky chart from 2005-11-05 to 2018-03-11.

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
64%
16279
25%
49103
22%
16243
67%
16243
38%
27606

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
62%
776
17%
2522
18%
776
64%
776
27%
1573
January16th to endNight
60%
832
20%
2704
21%
832
62%
832
25%
1745
February1st to 15thNight
58%
760
16%
2440
17%
760
61%
760
26%
1538
February16th to endNight
55%
684
23%
2051
22%
684
60%
684
31%
1259
March1st to 15thNight
61%
764
28%
2162
24%
764
66%
764
41%
1229
March16th to endNight
56%
768
24%
2112
17%
768
61%
768
38%
1268
April1st to 15thNight
50%
686
20%
1886
13%
686
53%
686
33%
1168
April16th to endNight
52%
540
28%
1620
18%
540
58%
540
36%
918
May1st to 15thNight
57%
539
24%
1620
19%
539
59%
539
37%
907
May16th to endNight
61%
561
23%
1685
20%
561
65%
561
38%
922
June1st to 15thNight
61%
540
25%
1620
21%
540
67%
540
50%
789
June16th to endNight
68%
540
29%
1620
25%
540
75%
540
64%
694
July1st to 15thNight
70%
510
20%
1530
16%
510
73%
510
41%
832
July16th to endNight
72%
564
22%
1593
19%
531
74%
531
38%
881
August1st to 15thNight
68%
539
30%
1611
23%
536
73%
536
45%
820
August16th to endNight
76%
600
35%
1746
28%
600
78%
600
50%
873
September1st to 15thNight
79%
720
32%
1977
24%
720
83%
720
58%
965
September16th to endNight
75%
716
39%
1980
31%
716
79%
716
59%
963
October1st to 15thNight
69%
720
31%
2064
25%
720
74%
720
48%
1090
October16th to endNight
72%
768
36%
2316
32%
768
77%
768
50%
1149
November1st to 15thNight
67%
760
29%
2470
29%
760
71%
760
40%
1287
November16th to endNight
67%
780
30%
2535
31%
780
69%
780
41%
1320
December1st to 15thNight
64%
780
21%
2535
21%
780
66%
780
31%
1483
December16th to endNight
50%
832
15%
2704
15%
832
52%
832
18%
1933

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
442442445%7%55%
49528
Night
5%5%2442445%7%52%
49297
TransparencyDay
27%410%19%20%16%
49223
Night
29%410%21%20%13%
49103
SeeingDay
7%5%16%28%27%14%
5966
Night
8%316%40%27%3
16290

By Month

Percentage Cloud Cover SW (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
5%9%48%8%5%6%5%5%7%32%
1746
16th to endDay
7%7%48%8%46%46%7%33%
1872
February1st to 15thDay
5%8%35%6%35%5%5%10%39%
1752
16th to endDay
5%8%345%3345%7%47%
1709
March1st to 15thDay
45%34425%46%7%51%
2033
16th to endDay
7%6%25%4245%6%8%47%
2112
April1st to 15thDay
5%5%15%4235%5%6%53%
2059
16th to endDay
5%424424346%56%
2340
May1st to 15thDay
43134245%6%7%57%
2331
16th to endDay
441332345%8%57%
2429
June1st to 15thDay
331221335%7%66%
2340
16th to endDay
11111123480%
2340
July1st to 15thDay
22232446%8%60%
2340
16th to endDay
22135%345%6%8%55%
2467
August1st to 15thDay
221333445%7%61%
2340
16th to endDay
22322345%6%66%
2453
September1st to 15thDay
223222345%69%
1983
16th to endDay
22221133474%
1980
October1st to 15thDay
5%313214437%61%
1896
16th to endDay
341322235%5%64%
1905
November1st to 15thDay
7%315%5%2445%7%52%
1719
16th to endDay
6%5%25%425%45%7%49%
1755
December1st to 15thDay
6%7%47%7%45%6%5%7%37%
1755
16th to endDay
10%10%5%8%7%46%45%7%28%
1872
January1st to 15thNight
6%8%26%6%45%45%9%40%
2522
16th to endNight
7%8%36%5%35%46%9%38%
2704
February1st to 15thNight
6%8%36%6%445%5%7%42%
2429
16th to endNight
5%8%345%3445%7%45%
2051
March1st to 15thNight
6%5%2442445%8%52%
2162
16th to endNight
6%6%25%43446%8%47%
2112
April1st to 15thNight
7%6%25%5%24447%48%
1886
16th to endNight
7%5%244235%5%7%51%
1620
May1st to 15thNight
6%5%14424447%53%
1619
16th to endNight
5%424425%46%7%52%
1684
June1st to 15thNight
331332335%5%64%
1620
16th to endNight
21221223475%
1620
July1st to 15thNight
23146%35%5%6%7%53%
1620
16th to endNight
2215%5%36%6%7%9%48%
1701
August1st to 15thNight
24145%345%6%7%55%
1620
16th to endNight
23133335%5%7%59%
1746
September1st to 15thNight
211332335%7%66%
1977
16th to endNight
4212212235%70%
1980
October1st to 15thNight
5%323312346%62%
2064
16th to endNight
331232335%6%64%
2316
November1st to 15thNight
5%5%24324246%58%
2470
16th to endNight
5%5%23423347%57%
2535
December1st to 15thNight
7%7%25%42345%7%49%
2535
16th to endNight
9%12%47%7%45%5%48%30%
2704

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
45%8%20%19%5%
1747
16th to endDay
47%8%18%20%5%
1872
February1st to 15thDay
37%10%20%19%10%1
1752
16th to endDay
35%5%13%30%15%1
1709
March1st to 15thDay
30%5%12%31%17%3
2033
16th to endDay
33%5%11%27%15%6%
2112
April1st to 15thDay
29%410%25%21%7%
2059
16th to endDay
28%39%22%26%10%
2340
May1st to 15thDay
24%6%8%17%29%13%
2331
16th to endDay
23%5%8%18%29%14%
2432
June1st to 15thDay
16%36%11%31%30%
2340
16th to endDay
10%137%21%57%
2340
July1st to 15thDay
20%37%13%16%38%
2201
16th to endDay
23%48%16%19%27%
2312
August1st to 15thDay
19%37%13%21%34%
2325
16th to endDay
16%35%12%26%33%
2453
September1st to 15thDay
16%46%12%25%33%
1983
16th to endDay
15%26%18%31%26%
1980
October1st to 15thDay
21%48%22%33%9%
1896
16th to endDay
20%310%28%32%4
1905
November1st to 15thDay
30%412%28%18%4
1719
16th to endDay
30%5%15%29%16%2
1755
December1st to 15thDay
40%7%17%25%8%
1755
16th to endDay
51%6%17%18%5%
1872
January1st to 15thNight
37%7%19%26%8%
2522
16th to endNight
40%7%16%25%10%
2704
February1st to 15thNight
39%6%16%23%12%1
2440
16th to endNight
36%5%12%25%20%
2051
March1st to 15thNight
27%5%9%31%22%3
2162
16th to endNight
32%411%24%20%6%
2112
April1st to 15thNight
35%48%21%18%10%
1886
16th to endNight
30%49%22%25%7%
1620
May1st to 15thNight
29%46%17%27%13%
1620
16th to endNight
27%48%18%25%14%
1685
June1st to 15thNight
19%37%11%27%31%
1620
16th to endNight
13%136%17%57%
1620
July1st to 15thNight
25%6%7%9%13%37%
1530
16th to endNight
27%6%10%13%16%25%
1593
August1st to 15thNight
22%47%19%16%29%
1611
16th to endNight
20%47%12%21%33%
1746
September1st to 15thNight
16%37%13%20%38%
1977
16th to endNight
16%25%16%28%30%
1980
October1st to 15thNight
23%37%17%34%13%
2064
16th to endNight
20%37%21%39%6%
2316
November1st to 15thNight
27%38%26%25%8%
2470
16th to endNight
26%310%33%22%3
2535
December1st to 15thNight
34%5%15%31%12%1
2535
16th to endNight
51%6%16%19%5%
2704

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
23%310%25%24%11%
135
16th to endDay
12%39%28%30%15%
144
February1st to 15thDay
9%414%32%25%13%
177
16th to endDay
8%10%19%31%23%6%
290
March1st to 15thDay
7%7%18%29%28%8%
312
16th to endDay
13%11%22%28%17%6%
288
April1st to 15thDay
10%14%23%23%18%9%
269
16th to endDay
11%14%26%20%21%6%
270
May1st to 15thDay
37%26%33%20%8%
288
16th to endDay
7%6%16%26%27%15%
330
June1st to 15thDay
6%7%20%29%25%12%
315
16th to endDay
1318%24%33%18%
315
July1st to 15thDay
3115%31%26%21%
305
16th to endDay
419%31%39%13%
327
August1st to 15thDay
3114%35%28%15%
315
16th to endDay
3113%22%34%23%
332
September1st to 15thDay
4216%29%30%17%
315
16th to endDay
5%417%19%32%21%
315
October1st to 15thDay
35%18%33%23%15%
231
16th to endDay
6%39%29%30%20%
144
November1st to 15thDay
5%6%11%27%25%22%
135
16th to endDay
11%5%12%28%30%11%
135
December1st to 15thDay
15%28%35%25%11%
135
16th to endDay
9%6%11%35%27%10%
144
January1st to 15thNight
9%411%40%27%7%
780
16th to endNight
11%212%39%27%5%
832
February1st to 15thNight
11%215%45%21%4
764
16th to endNight
10%420%43%19%1
684
March1st to 15thNight
8%419%44%22%1
764
16th to endNight
9%5%23%41%19%1
768
April1st to 15thNight
10%7%24%36%18%1
686
16th to endNight
10%7%25%34%20%1
540
May1st to 15thNight
10%5%20%40%20%2
540
16th to endNight
7%6%19%38%26%2
563
June1st to 15thNight
5%423%42%23%1
540
16th to endNight
2122%44%27%1
540
July1st to 15thNight
313%39%38%4
510
16th to endNight
411%43%37%2
564
August1st to 15thNight
4116%49%27%
539
16th to endNight
4111%37%41%4
600
September1st to 15thNight
212%36%40%6%
720
16th to endNight
5%114%30%42%6%
716
October1st to 15thNight
6%216%42%27%4
720
16th to endNight
6%313%34%36%5%
768
November1st to 15thNight
6%216%40%30%3
760
16th to endNight
8%313%43%25%6%
780
December1st to 15thNight
10%314%45%23%2
780
16th to endNight
15%415%40%22%2
832
Page generated at 2018-03-12 11:28:05. Version ac04

Copyright 2018 A. Danko


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