Deep Sky West Remote Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Deep Sky West Remote Observatory clear sky chart from 2005-11-05 to 2017-08-12.

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
50%
15593
31%
46546
17%
15550
63%
15550
43%
23964

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
42%
764
33%
2372
18%
761
59%
761
49%
1100
January16th to endNight
37%
768
36%
2496
18%
768
60%
768
45%
1168
February1st to 15thNight
39%
702
29%
2193
14%
700
56%
700
40%
1105
February16th to endNight
31%
632
39%
1894
14%
632
57%
632
46%
929
March1st to 15thNight
43%
720
34%
2058
16%
720
58%
720
45%
1051
March16th to endNight
41%
707
35%
2051
16%
707
57%
707
49%
1001
April1st to 15thNight
33%
539
33%
1798
14%
539
57%
539
39%
839
April16th to endNight
37%
540
35%
1800
18%
540
64%
540
42%
821
May1st to 15thNight
44%
539
26%
1799
18%
539
59%
539
40%
889
May16th to endNight
50%
563
30%
1559
14%
561
66%
561
47%
823
June1st to 15thNight
59%
540
24%
1440
15%
540
66%
540
47%
793
June16th to endNight
69%
540
24%
1440
19%
540
71%
540
47%
793
July1st to 15thNight
72%
510
18%
1412
15%
510
72%
510
31%
900
July16th to endNight
79%
564
17%
1593
17%
531
79%
531
33%
949
August1st to 15thNight
74%
527
16%
1695
18%
524
74%
524
30%
1020
August16th to endNight
75%
525
22%
1750
26%
525
77%
525
32%
1012
September1st to 15thNight
68%
495
25%
1650
25%
495
71%
495
29%
992
September16th to endNight
65%
495
34%
1761
29%
495
75%
495
42%
844
October1st to 15thNight
57%
660
36%
1980
22%
660
67%
660
49%
977
October16th to endNight
56%
704
38%
2112
20%
704
68%
704
53%
983
November1st to 15thNight
52%
799
39%
2199
18%
799
65%
799
60%
1008
November16th to endNight
50%
900
38%
2340
20%
900
60%
900
53%
1209
December1st to 15thNight
37%
900
34%
2466
11%
900
54%
900
44%
1297
December16th to endNight
33%
960
31%
2688
13%
960
49%
960
40%
1461

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
431332445%7%59%
47423
Night
331332445%7%61%
46736
Cloud CoverDay
331332445%7%58%
47421
Night
331332445%7%60%
46736
TransparencyDay
22%5%9%21%26%15%
47114
Night
21%410%21%26%14%
46547
SeeingDay
7%11%27%31%19%3
5417
Night
49%30%34%18%2
15597

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
2312212337%68%
1576
16th to endDay
3312323245%66%
1728
February1st to 15thDay
25%13422347%63%
1669
16th to endDay
241222325%7%63%
1580
March1st to 15thDay
241342345%7%61%
1900
16th to endDay
2313313246%65%
2172
April1st to 15thDay
331331336%8%60%
2150
16th to endDay
3312312345%67%
2160
May1st to 15thDay
4213325%35%6%59%
2151
16th to endDay
421231345%6%65%
2550
June1st to 15thDay
21123245%5%7%64%
2520
16th to endDay
21241446%8%62%
2520
July1st to 15thDay
5%425%6%36%6%7%11%41%
2460
16th to endDay
5%3245%46%8%8%10%38%
2467
August1st to 15thDay
5%314446%7%6%10%45%
2169
16th to endDay
6%3145%35%6%7%9%45%
2100
September1st to 15thDay
9%4246%345%5%7%45%
1980
16th to endDay
3213224445%65%
1865
October1st to 15thDay
6%22322235%66%
1650
16th to endDay
32221233473%
1760
November1st to 15thDay
122212347%71%
1648
16th to endDay
4312212335%68%
1620
December1st to 15thDay
3412213346%64%
1492
16th to endDay
45%1332435%7%57%
1536
January1st to 15thNight
223322345%69%
2372
16th to endNight
3322213347%65%
2496
February1st to 15thNight
25%14322246%63%
2183
16th to endNight
3412313346%65%
1894
March1st to 15thNight
231432335%7%62%
2058
16th to endNight
4212313246%67%
2051
April1st to 15thNight
331232335%7%62%
1798
16th to endNight
3313312335%68%
1800
May1st to 15thNight
321333445%7%61%
1799
16th to endNight
421221445%6%63%
1558
June1st to 15thNight
21124245%6%9%59%
1440
16th to endNight
2214335%45%9%58%
1440
July1st to 15thNight
6%3146%26%6%8%9%43%
1496
16th to endNight
4313437%7%8%11%43%
1701
August1st to 15thNight
43246%47%7%7%9%42%
1704
16th to endNight
42245%36%6%7%11%44%
1750
September1st to 15thNight
6%425%436%6%8%9%42%
1650
16th to endNight
5%313223345%64%
1761
October1st to 15thNight
5%212213246%66%
1980
16th to endNight
312312345%70%
2112
November1st to 15thNight
111212246%73%
2199
16th to endNight
331221333468%
2340
December1st to 15thNight
4413323336%64%
2466
16th to endNight
3423423348%58%
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
2213212247%68%
1576
16th to endDay
3322313345%65%
1728
February1st to 15thDay
142332225%7%62%
1669
16th to endDay
25%1222245%7%63%
1580
March1st to 15thDay
241332345%8%60%
1900
16th to endDay
2323323346%65%
2170
April1st to 15thDay
331332346%8%59%
2150
16th to endDay
3313313346%65%
2160
May1st to 15thDay
3213425%45%6%58%
2151
16th to endDay
321331445%6%64%
2550
June1st to 15thDay
11123245%6%7%63%
2520
16th to endDay
111232446%7%62%
2520
July1st to 15thDay
4425%5%47%6%7%10%40%
2460
16th to endDay
4325%6%5%7%8%8%9%38%
2467
August1st to 15thDay
4314446%7%7%11%43%
2169
16th to endDay
44245%35%7%9%9%44%
2100
September1st to 15thDay
8%5%245%35%46%9%43%
1980
16th to endDay
321332345%6%64%
1865
October1st to 15thDay
5%312322345%66%
1650
16th to endDay
311231232472%
1760
November1st to 15thDay
121213347%70%
1648
16th to endDay
4312312346%67%
1620
December1st to 15thDay
3413213346%64%
1492
16th to endDay
35%2432335%8%56%
1536
January1st to 15thNight
2313312336%68%
2372
16th to endNight
3312323446%64%
2496
February1st to 15thNight
25%23323247%62%
2183
16th to endNight
2412213446%64%
1894
March1st to 15thNight
131333335%7%62%
2058
16th to endNight
3312222336%67%
2051
April1st to 15thNight
3313314347%61%
1798
16th to endNight
3313422245%67%
1800
May1st to 15thNight
3213414447%60%
1799
16th to endNight
411232445%6%62%
1558
June1st to 15thNight
11134245%7%9%58%
1440
16th to endNight
1114325%5%5%10%57%
1440
July1st to 15thNight
44236%35%7%9%11%42%
1496
16th to endNight
3314437%8%9%11%42%
1701
August1st to 15thNight
43237%46%7%8%10%41%
1704
16th to endNight
32146%36%7%7%10%44%
1750
September1st to 15thNight
5%326%5%35%7%8%10%40%
1650
16th to endNight
4312224346%63%
1761
October1st to 15thNight
5%312222336%66%
1980
16th to endNight
312312345%70%
2112
November1st to 15thNight
121213246%72%
2199
16th to endNight
3312322335%67%
2340
December1st to 15thNight
4413223346%63%
2466
16th to endNight
342342335%7%58%
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
16%49%27%36%6%
1577
16th to endDay
20%27%23%34%11%
1728
February1st to 15thDay
21%38%25%26%14%
1670
16th to endDay
18%35%24%33%14%
1580
March1st to 15thDay
22%36%19%32%15%
1900
16th to endDay
20%36%18%35%15%
2172
April1st to 15thDay
21%46%22%30%15%
2150
16th to endDay
19%37%17%34%18%
2160
May1st to 15thDay
22%6%9%16%27%17%
2151
16th to endDay
19%48%19%23%24%
2553
June1st to 15thDay
16%5%10%16%20%29%
2520
16th to endDay
17%411%16%20%28%
2520
July1st to 15thDay
33%8%14%16%14%12%
2316
16th to endDay
33%10%17%25%11%1
2312
August1st to 15thDay
30%9%16%21%13%7%
2154
16th to endDay
32%7%14%21%18%5%
2100
September1st to 15thDay
36%5%14%20%14%8%
1980
16th to endDay
21%37%20%28%18%
1865
October1st to 15thDay
21%36%18%29%20%
1650
16th to endDay
15%35%20%34%20%
1760
November1st to 15thDay
12%37%22%37%15%
1648
16th to endDay
18%25%20%37%16%
1620
December1st to 15thDay
19%410%33%24%7%
1492
16th to endDay
24%413%28%23%5%
1536
January1st to 15thNight
17%310%27%32%9%
2372
16th to endNight
18%38%23%34%11%
2496
February1st to 15thNight
22%48%25%25%13%
2193
16th to endNight
19%3422%35%15%
1894
March1st to 15thNight
20%47%23%30%13%
2058
16th to endNight
18%26%19%35%17%
2051
April1st to 15thNight
20%27%21%28%18%
1798
16th to endNight
18%35%18%32%20%
1800
May1st to 15thNight
21%5%10%18%25%18%
1800
16th to endNight
19%5%11%16%23%23%
1559
June1st to 15thNight
20%7%12%13%17%28%
1440
16th to endNight
22%5%11%17%15%27%
1440
July1st to 15thNight
33%9%13%17%13%11%
1412
16th to endNight
30%9%25%24%9%1
1593
August1st to 15thNight
32%9%19%18%13%6%
1695
16th to endNight
30%8%16%25%12%7%
1750
September1st to 15thNight
33%8%17%18%14%8%
1650
16th to endNight
22%48%17%27%19%
1761
October1st to 15thNight
20%37%17%27%23%
1980
16th to endNight
15%45%16%36%21%
2112
November1st to 15thNight
13%26%22%40%15%
2199
16th to endNight
19%25%20%34%18%
2340
December1st to 15thNight
21%38%30%28%7%
2466
16th to endNight
23%412%27%26%5%
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
6%15%42%21%10%4
90
16th to endDay
219%44%19%13%
96
February1st to 15thDay
416%25%36%16%
90
16th to endDay
8%25%34%23%7%
81
March1st to 15thDay
9%22%33%26%7%
190
16th to endDay
11%25%36%18%6%1
288
April1st to 15thDay
9%29%33%20%5%1
269
16th to endDay
10%29%39%17%2
270
May1st to 15thDay
422%43%21%6%1
288
16th to endDay
6%10%35%32%15%1
498
June1st to 15thDay
36%25%34%24%4
495
16th to endDay
3120%35%33%5%
495
July1st to 15thDay
7%12%39%32%7%
420
16th to endDay
8%18%27%37%16%
327
August1st to 15thDay
5%12%43%32%6%
300
16th to endDay
6%20%38%29%4
268
September1st to 15thDay
11%124%45%16%
255
16th to endDay
6%426%47%13%1
145
October1st to 15thDay
11%7%27%31%18%3
90
16th to endDay
10%6%23%28%23%7%
96
November1st to 15thDay
5%12%34%28%16%2
90
16th to endDay
14%26%27%26%4
90
December1st to 15thDay
6%21%44%21%6%
90
16th to endDay
13%20%39%23%2
96
January1st to 15thNight
410%38%31%13%1
765
16th to endNight
5%13%42%27%11%
768
February1st to 15thNight
5%14%37%33%8%
704
16th to endNight
5%14%47%27%4
632
March1st to 15thNight
313%36%35%9%
720
16th to endNight
413%38%33%10%
707
April1st to 15thNight
420%39%28%6%
539
16th to endNight
416%37%33%7%
540
May1st to 15thNight
29%38%39%9%
540
16th to endNight
46%34%37%15%1
563
June1st to 15thNight
2329%44%20%
540
16th to endNight
2319%45%27%2
540
July1st to 15thNight
8%9%40%39%3
510
16th to endNight
35%31%50%7%
564
August1st to 15thNight
417%32%45%7%
527
16th to endNight
48%39%40%6%
525
September1st to 15thNight
6%214%42%31%3
495
16th to endNight
6%320%40%26%3
495
October1st to 15thNight
6%5%27%39%18%3
660
16th to endNight
36%28%35%22%2
704
November1st to 15thNight
29%33%35%17%2
799
16th to endNight
5%10%30%36%14%2
900
December1st to 15thNight
7%14%39%30%7%
900
16th to endNight
6%16%40%29%6%
960
Page generated at 2017-08-13 12:16:37. Version ac04

Copyright 2017 A. Danko


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