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 2017-12-20.

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%
16109
31%
48083
18%
16066
63%
16066
43%
24728

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
36%
768
37%
2496
18%
768
60%
768
45%
1168
February1st to 15thNight
38%
702
29%
2193
14%
700
55%
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
40%
707
36%
2051
16%
707
57%
707
49%
1001
April1st to 15thNight
32%
539
33%
1798
14%
539
57%
539
39%
839
April16th to endNight
38%
540
36%
1800
18%
540
65%
540
42%
821
May1st to 15thNight
45%
539
26%
1799
18%
539
60%
539
40%
889
May16th to endNight
50%
563
31%
1559
14%
561
66%
561
47%
823
June1st to 15thNight
59%
540
24%
1440
15%
540
66%
540
47%
793
June16th to endNight
68%
540
24%
1440
19%
540
70%
540
47%
793
July1st to 15thNight
71%
510
18%
1412
15%
510
71%
510
31%
900
July16th to endNight
79%
564
17%
1593
17%
531
79%
531
33%
949
August1st to 15thNight
75%
539
16%
1734
18%
536
75%
536
30%
1043
August16th to endNight
76%
573
23%
1910
27%
573
77%
573
32%
1106
September1st to 15thNight
70%
540
25%
1800
25%
540
73%
540
31%
1058
September16th to endNight
62%
540
35%
1921
30%
540
72%
540
40%
940
October1st to 15thNight
57%
720
35%
2160
22%
720
67%
720
49%
1067
October16th to endNight
56%
768
40%
2304
21%
768
69%
768
54%
1068
November1st to 15thNight
51%
867
38%
2387
18%
867
64%
867
60%
1097
November16th to endNight
51%
975
40%
2535
21%
975
61%
975
54%
1295
December1st to 15thNight
38%
975
34%
2672
12%
975
55%
975
45%
1401
December16th to endNight
33%
984
32%
2755
14%
984
49%
984
41%
1492

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%60%
48753
Night
331332345%7%61%
48273
Cloud CoverDay
331332445%7%59%
48751
Night
331332345%7%60%
48273
TransparencyDay
22%49%21%26%15%
48444
Night
21%410%21%26%14%
48084
SeeingDay
7%10%27%31%19%4
5846
Night
49%30%35%18%2
16113

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%214446%7%6%10%45%
2216
16th to endDay
6%314435%6%7%8%46%
2292
September1st to 15thDay
8%4235%345%5%7%47%
2160
16th to endDay
4213323445%64%
2034
October1st to 15thDay
6%212322235%67%
1800
16th to endDay
32221223473%
1920
November1st to 15thDay
122212347%70%
1789
16th to endDay
4312212335%69%
1755
December1st to 15thDay
3412213347%65%
1616
16th to endDay
45%1432435%7%58%
1568
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%8%9%42%
1743
16th to endNight
42245%36%6%7%10%44%
1910
September1st to 15thNight
6%424436%6%8%9%43%
1800
16th to endNight
5%413223345%62%
1921
October1st to 15thNight
5%212313245%67%
2160
16th to endNight
312312345%71%
2304
November1st to 15thNight
111212246%73%
2387
16th to endNight
3312213335%69%
2535
December1st to 15thNight
4313323336%64%
2672
16th to endNight
3423423348%59%
2755

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%
2216
16th to endDay
5%4245%35%7%8%8%44%
2292
September1st to 15thDay
7%4245%35%47%9%45%
2160
16th to endDay
421332345%6%63%
2034
October1st to 15thDay
5%312322335%67%
1800
16th to endDay
311231232473%
1920
November1st to 15thDay
121121335%8%69%
1789
16th to endDay
3312312346%67%
1755
December1st to 15thDay
3413213347%64%
1616
16th to endDay
35%2432335%8%57%
1568
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%
1743
16th to endNight
3215%5%36%7%7%10%44%
1910
September1st to 15thNight
5%325%5%35%7%8%11%41%
1800
16th to endNight
4413224446%60%
1921
October1st to 15thNight
5%312222236%66%
2160
16th to endNight
312312345%71%
2304
November1st to 15thNight
121213246%72%
2387
16th to endNight
3312322336%68%
2535
December1st to 15thNight
4313223346%63%
2672
16th to endNight
342342335%7%58%
2755

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%17%21%14%7%
2201
16th to endDay
31%7%14%21%19%5%
2292
September1st to 15thDay
34%5%13%21%16%8%
2160
16th to endDay
22%37%19%27%18%
2034
October1st to 15thDay
21%36%17%29%22%
1800
16th to endDay
14%36%20%35%19%
1920
November1st to 15thDay
12%37%23%37%14%
1789
16th to endDay
17%16%21%36%16%
1755
December1st to 15thDay
18%411%32%24%9%
1616
16th to endDay
24%413%28%24%5%
1568
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%20%18%13%6%
1734
16th to endNight
30%8%15%25%12%6%
1910
September1st to 15thNight
32%8%16%20%14%7%
1800
16th to endNight
23%48%17%26%18%
1921
October1st to 15thNight
20%37%16%27%24%
2160
16th to endNight
15%46%16%35%21%
2304
November1st to 15thNight
13%26%22%39%15%
2387
16th to endNight
18%26%20%34%18%
2535
December1st to 15thNight
20%38%29%27%9%
2672
16th to endNight
23%411%27%27%5%
2755

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%31%6%
315
16th to endDay
7%16%37%30%7%
332
September1st to 15thDay
9%120%45%18%4
315
16th to endDay
9%6%25%46%11%1
195
October1st to 15thDay
9%10%31%29%15%3
135
16th to endDay
6%428%29%24%5%
144
November1st to 15thDay
415%39%26%12%1
135
16th to endDay
10%21%33%25%9%
135
December1st to 15thDay
417%40%27%10%
135
16th to endDay
12%18%39%26%2
108
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%46%7%
539
16th to endNight
48%37%42%6%
573
September1st to 15thNight
6%212%42%32%3
540
16th to endNight
7%321%39%25%2
540
October1st to 15thNight
6%5%26%40%18%3
720
16th to endNight
36%29%35%22%3
768
November1st to 15thNight
28%34%35%16%1
867
16th to endNight
410%30%36%15%2
975
December1st to 15thNight
6%13%38%31%8%
975
16th to endNight
6%16%39%30%6%
984
Page generated at 2017-12-21 05:04:53. Version ac04

Copyright 2017 A. Danko


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