Taylor Dark Sky Site
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Taylor Dark Sky Site clear sky chart from 2005-11-05 to 2017-04-02.

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
42%
15318
20%
45342
14%
15272
48%
15272
26%
29460

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
24%
900
17%
2506
7%
895
33%
895
21%
1775
January16th to endNight
24%
960
17%
2598
7%
960
32%
960
20%
1863
February1st to 15thNight
22%
731
13%
2139
5%
728
29%
728
16%
1548
February16th to endNight
25%
631
17%
1893
8%
631
34%
631
20%
1282
March1st to 15thNight
25%
720
15%
2160
9%
720
31%
720
19%
1517
March16th to endNight
31%
630
14%
2013
10%
630
37%
630
20%
1379
April1st to 15thNight
38%
500
22%
1667
14%
500
51%
500
25%
1028
April16th to endNight
42%
495
19%
1625
15%
495
49%
495
24%
1043
May1st to 15thNight
39%
495
16%
1485
10%
495
45%
495
21%
1036
May16th to endNight
56%
515
17%
1434
13%
513
59%
513
29%
944
June1st to 15thNight
61%
495
21%
1320
17%
495
64%
495
37%
806
June16th to endNight
65%
495
20%
1320
15%
495
67%
495
37%
814
July1st to 15thNight
67%
465
18%
1240
15%
465
67%
465
36%
777
July16th to endNight
75%
522
24%
1305
19%
489
76%
489
44%
748
August1st to 15thNight
79%
494
23%
1563
25%
491
81%
491
40%
855
August16th to endNight
74%
525
23%
1750
26%
525
76%
525
37%
952
September1st to 15thNight
67%
510
29%
1665
30%
510
70%
510
35%
931
September16th to endNight
61%
657
28%
1815
21%
657
65%
657
36%
1087
October1st to 15thNight
55%
660
30%
1870
23%
660
61%
660
38%
1095
October16th to endNight
36%
704
23%
2216
16%
704
46%
704
27%
1373
November1st to 15thNight
44%
700
27%
2276
21%
700
54%
700
31%
1283
November16th to endNight
33%
720
20%
2340
14%
720
41%
720
22%
1513
December1st to 15thNight
26%
834
13%
2454
7%
834
33%
834
18%
1778
December16th to endNight
21%
960
14%
2688
5%
960
29%
960
16%
2033

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%6%35%5%3445%7%40%
45786
Night
14%6%35%424446%42%
45511
Cloud CoverDay
14%6%35%5%3445%7%40%
45795
Night
14%6%35%424446%42%
45516
TransparencyDay
42%6%12%22%13%2
45472
Night
41%5%11%22%15%2
45343
SeeingDay
15%5%21%25%21%10%
5111
Night
17%7%26%30%15%1
15318

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
19%8%5%7%5%34445%31%
1432
16th to endDay
14%12%46%5%34346%35%
1626
February1st to 15thDay
14%10%5%8%434447%32%
1720
16th to endDay
12%11%5%7%6%45%5%5%6%31%
1580
March1st to 15thDay
19%9%36%43433435%
1790
16th to endDay
17%9%36%5%3345%6%32%
2220
April1st to 15thDay
17%6%24433345%42%
1983
16th to endDay
18%6%25%434446%38%
2005
May1st to 15thDay
21%7%26%5%245%5%7%32%
2136
16th to endDay
11%5%25%5%46%5%5%7%39%
2326
June1st to 15thDay
10%4235%3446%9%45%
2310
16th to endDay
9%425%5%35%6%5%8%42%
2310
July1st to 15thDay
11%424435%6%6%8%42%
2310
16th to endDay
5%3135%36%6%8%11%43%
2459
August1st to 15thDay
8%3146%35%5%5%10%45%
2055
16th to endDay
7%4245%345%7%10%45%
2100
September1st to 15thDay
12%425%5%345%5%7%42%
1953
16th to endDay
10%5%25%42435%7%48%
1815
October1st to 15thDay
14%414423247%49%
1759
16th to endDay
16%5%23323345%48%
1656
November1st to 15thDay
13%424423346%50%
1582
16th to endDay
19%8%35%422235%41%
1620
December1st to 15thDay
22%9%5%5%5%24345%31%
1503
16th to endDay
21%12%35%424446%30%
1536
January1st to 15thNight
17%7%47%424335%37%
2506
16th to endNight
15%9%46%6%34345%35%
2598
February1st to 15thNight
16%8%48%5%24446%33%
2137
16th to endNight
16%9%35%5%33345%38%
1893
March1st to 15thNight
18%8%46%424345%36%
2147
16th to endNight
17%8%25%6%33446%36%
2013
April1st to 15thNight
15%5%35%324335%46%
1667
16th to endNight
17%6%3442445%7%40%
1625
May1st to 15thNight
18%5%26%5%25%5%47%35%
1485
16th to endNight
10%425%435%5%6%9%42%
1433
June1st to 15thNight
9%32443445%7%49%
1320
16th to endNight
7%423426%5%6%9%47%
1320
July1st to 15thNight
8%334425%5%6%8%48%
1320
16th to endNight
421442446%9%54%
1401
August1st to 15thNight
6%2133245%5%10%53%
1572
16th to endNight
5%3145%2446%9%52%
1750
September1st to 15thNight
11%324323448%52%
1665
16th to endNight
10%325%423446%51%
1815
October1st to 15thNight
11%413424446%53%
1870
16th to endNight
17%5%2442234447%
2216
November1st to 15thNight
10%5%24423345%52%
2276
16th to endNight
18%8%3442323442%
2340
December1st to 15thNight
21%9%45%5%23446%31%
2454
16th to endNight
25%9%35%5%24345%30%
2688

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
19%8%48%6%34445%31%
1432
16th to endDay
14%11%45%5%34346%35%
1626
February1st to 15thDay
14%9%5%8%434447%32%
1720
16th to endDay
12%11%5%7%6%45%5%5%5%31%
1580
March1st to 15thDay
20%8%36%43433435%
1800
16th to endDay
18%8%36%5%3445%6%32%
2219
April1st to 15thDay
17%6%33424346%42%
1983
16th to endDay
18%6%25%434446%38%
2005
May1st to 15thDay
21%7%25%5%25%5%47%32%
2136
16th to endDay
11%5%25%5%45%5%5%8%39%
2326
June1st to 15thDay
9%4235%345%6%9%44%
2310
16th to endDay
8%5%25%5%35%6%6%8%42%
2310
July1st to 15thDay
11%425%425%6%6%8%42%
2310
16th to endDay
5%3145%36%6%8%11%42%
2459
August1st to 15thDay
8%3146%3446%10%44%
2055
16th to endDay
7%424435%5%6%10%44%
2100
September1st to 15thDay
12%5%25%5%3445%7%42%
1953
16th to endDay
10%5%34423347%48%
1815
October1st to 15thDay
15%414324347%48%
1759
16th to endDay
16%5%24323345%48%
1656
November1st to 15thDay
13%5%24423346%50%
1582
16th to endDay
19%8%45%412235%41%
1620
December1st to 15thDay
22%9%46%5%25%345%30%
1503
16th to endDay
22%12%45%424445%30%
1536
January1st to 15thNight
17%7%47%5%24335%37%
2506
16th to endNight
15%9%47%5%34445%35%
2598
February1st to 15thNight
16%8%48%5%345%45%33%
2130
16th to endNight
16%8%35%5%33435%38%
1893
March1st to 15thNight
18%8%46%424346%36%
2160
16th to endNight
17%8%35%6%34446%36%
2013
April1st to 15thNight
15%5%35%333335%46%
1667
16th to endNight
16%6%3442445%8%39%
1625
May1st to 15thNight
17%5%26%6%35%447%35%
1484
16th to endNight
10%425%335%47%8%42%
1433
June1st to 15thNight
9%32443446%7%49%
1320
16th to endNight
7%323325%5%6%10%47%
1320
July1st to 15thNight
7%3244245%5%9%48%
1320
16th to endNight
422433446%8%54%
1401
August1st to 15thNight
6%1132345%6%10%53%
1572
16th to endNight
5%3145%3346%10%52%
1750
September1st to 15thNight
10%324323347%52%
1665
16th to endNight
10%425%32345%6%51%
1815
October1st to 15thNight
11%313433436%53%
1870
16th to endNight
17%5%23423245%47%
2216
November1st to 15thNight
10%5%24323445%51%
2276
16th to endNight
18%8%2443233442%
2340
December1st to 15thNight
21%9%36%5%14447%31%
2454
16th to endNight
25%9%35%434345%30%
2688

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
54%411%18%10%
1433
16th to endDay
50%413%24%7%
1626
February1st to 15thDay
51%5%13%21%7%1
1722
16th to endDay
52%6%12%21%7%
1580
March1st to 15thDay
52%5%11%20%9%1
1800
16th to endDay
51%5%13%22%6%
2220
April1st to 15thDay
42%5%11%25%14%
1983
16th to endDay
45%412%23%11%2
2005
May1st to 15thDay
51%8%11%18%10%
2136
16th to endDay
41%8%14%16%15%2
2330
June1st to 15thDay
34%8%14%24%15%2
2310
16th to endDay
37%8%14%21%14%3
2310
July1st to 15thDay
37%8%13%21%16%3
2161
16th to endDay
31%10%16%27%12%1
2292
August1st to 15thDay
33%7%13%26%16%2
2040
16th to endDay
32%9%12%22%16%6%
2100
September1st to 15thDay
40%5%9%19%19%5%
1953
16th to endDay
35%39%25%21%3
1815
October1st to 15thDay
35%410%26%18%3
1759
16th to endDay
38%311%26%19%
1656
November1st to 15thDay
36%411%23%18%6%
1582
16th to endDay
46%49%23%13%2
1620
December1st to 15thDay
55%5%12%16%9%
1503
16th to endDay
55%5%11%20%5%1
1536
January1st to 15thNight
50%49%23%12%
2506
16th to endNight
50%412%22%9%
2598
February1st to 15thNight
52%6%12%18%10%
2139
16th to endNight
47%414%22%10%
1893
March1st to 15thNight
49%5%10%21%10%2
2160
16th to endNight
48%414%21%9%1
2013
April1st to 15thNight
40%48%25%17%3
1667
16th to endNight
41%6%9%23%13%4
1625
May1st to 15thNight
47%7%12%20%12%
1485
16th to endNight
36%9%15%16%17%4
1435
June1st to 15thNight
32%5%12%26%20%1
1320
16th to endNight
30%8%13%21%20%6%
1320
July1st to 15thNight
32%7%13%22%19%4
1240
16th to endNight
24%6%14%31%19%2
1305
August1st to 15thNight
24%7%16%25%22%3
1563
16th to endNight
27%6%12%25%21%6%
1750
September1st to 15thNight
31%5%9%25%21%7%
1665
16th to endNight
32%48%22%25%5%
1815
October1st to 15thNight
31%410%26%21%5%
1870
16th to endNight
39%49%26%17%3
2216
November1st to 15thNight
33%310%22%22%6%
2276
16th to endNight
45%310%22%17%
2340
December1st to 15thNight
52%5%11%18%10%
2454
16th to endNight
57%410%17%8%1
2688

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
35%7%36%13%6%
90
16th to endDay
17%16%46%15%3
96
February1st to 15thDay
14%22%40%18%4
90
16th to endDay
16%12%33%30%7%
81
March1st to 15thDay
28%10%37%20%3
90
16th to endDay
21%12%34%22%8%
249
April1st to 15thDay
18%14%23%28%15%
214
16th to endDay
20%326%26%14%7%
210
May1st to 15thDay
23%8%25%24%13%4
228
16th to endDay
14%226%27%17%11%
370
June1st to 15thDay
12%320%30%23%9%
420
16th to endDay
10%225%30%21%9%
420
July1st to 15thDay
14%215%28%21%17%
400
16th to endDay
6%18%31%34%17%
445
August1st to 15thDay
13%1317%36%27%
270
16th to endDay
9%110%19%39%19%
268
September1st to 15thDay
10%212%25%32%16%
255
16th to endDay
14%212%25%27%16%
254
October1st to 15thDay
10%224%25%29%8%
199
16th to endDay
16%5%34%33%9%1
96
November1st to 15thDay
8%10%18%27%22%12%
90
16th to endDay
30%14%24%22%8%
90
December1st to 15thDay
17%10%38%22%6%4
90
16th to endDay
29%9%45%13%2
96
January1st to 15thNight
21%12%36%25%3
900
16th to endNight
20%12%36%26%3
960
February1st to 15thNight
22%11%35%27%3
731
16th to endNight
19%12%38%28%1
631
March1st to 15thNight
21%10%36%25%5%
720
16th to endNight
21%8%33%27%8%
630
April1st to 15thNight
18%11%29%31%9%
500
16th to endNight
21%5%24%35%11%1
495
May1st to 15thNight
18%329%36%10%1
495
16th to endNight
11%321%34%26%2
515
June1st to 15thNight
10%318%43%22%1
495
16th to endNight
8%117%43%28%1
495
July1st to 15thNight
9%114%37%34%3
465
16th to endNight
5%10%35%39%8%
522
August1st to 15thNight
7%6%38%40%6%
494
16th to endNight
7%8%32%43%7%
525
September1st to 15thNight
12%112%33%34%5%
510
16th to endNight
12%215%30%32%5%
657
October1st to 15thNight
12%5%21%33%22%5%
660
16th to endNight
22%8%30%27%10%
704
November1st to 15thNight
12%8%31%31%15%1
700
16th to endNight
22%9%30%27%10%
720
December1st to 15thNight
26%8%32%23%8%
834
16th to endNight
30%9%31%23%4
960
Page generated at 2017-04-03 00:35:05. Version ac04

Copyright 2017 A. Danko


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