Dine Sky Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Dine Sky Observatory clear sky chart from 2005-11-05 to 2017-09-24.

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
67%
15462
31%
47042
26%
15423
72%
15423
45%
23998

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
67%
717
29%
2327
31%
716
70%
716
42%
1174
January16th to endNight
64%
768
33%
2496
32%
768
70%
768
41%
1288
February1st to 15thNight
63%
699
28%
2288
28%
699
68%
699
42%
1154
February16th to endNight
55%
632
35%
1869
29%
632
64%
632
44%
982
March1st to 15thNight
63%
720
35%
1980
28%
720
69%
720
50%
1027
March16th to endNight
61%
768
33%
2112
22%
768
69%
768
52%
1073
April1st to 15thNight
49%
605
30%
1864
17%
605
63%
605
43%
934
April16th to endNight
52%
540
33%
1770
23%
540
67%
540
45%
832
May1st to 15thNight
62%
540
30%
1619
22%
539
70%
539
49%
788
May16th to endNight
57%
562
29%
1684
18%
561
66%
561
49%
812
June1st to 15thNight
66%
540
30%
1620
23%
540
72%
540
62%
710
June16th to endNight
75%
540
29%
1620
26%
540
78%
540
60%
720
July1st to 15thNight
75%
510
19%
1530
16%
510
77%
510
36%
875
July16th to endNight
74%
564
16%
1593
14%
531
74%
531
25%
1062
August1st to 15thNight
81%
539
20%
1611
18%
536
81%
536
31%
972
August16th to endNight
78%
573
26%
1850
26%
573
79%
573
35%
1037
September1st to 15thNight
79%
603
29%
1863
28%
603
81%
603
38%
1031
September16th to endNight
76%
692
42%
1914
29%
692
83%
692
64%
886
October1st to 15thNight
70%
660
34%
1972
26%
660
75%
660
52%
951
October16th to endNight
74%
704
40%
2112
31%
704
81%
704
60%
957
November1st to 15thNight
74%
700
36%
2100
31%
700
78%
700
55%
988
November16th to endNight
69%
720
37%
2334
34%
720
75%
720
52%
1053
December1st to 15thNight
65%
798
29%
2418
25%
798
70%
798
44%
1256
December16th to endNight
56%
768
25%
2496
24%
768
62%
768
32%
1436

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
331342445%6%60%
47862
Night
3313323446%62%
47238
TransparencyDay
24%5%10%18%24%17%
47557
Night
21%5%9%20%26%16%
47044
SeeingDay
7%9%21%29%24%8%
5252
Night
5%418%36%29%5%
15471

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
3413324345%62%
1611
16th to endDay
4414423247%59%
1728
February1st to 15thDay
25%24423336%61%
1575
16th to endDay
341443445%7%54%
1602
March1st to 15thDay
4313313446%63%
1980
16th to endDay
3222224447%62%
2112
April1st to 15thDay
3313324347%61%
2084
16th to endDay
2313323446%63%
2188
May1st to 15thDay
2213424346%63%
2331
16th to endDay
3213413347%63%
2429
June1st to 15thDay
21121323474%
2340
16th to endDay
11213235%76%
2340
July1st to 15thDay
32146%35%6%7%8%48%
2340
16th to endDay
5%316%6%48%8%9%11%32%
2467
August1st to 15thDay
6%326%7%46%6%8%8%40%
2340
16th to endDay
43245%46%6%6%8%46%
2351
September1st to 15thDay
4213435%5%6%8%53%
2094
16th to endDay
31231234471%
1904
October1st to 15thDay
411222234469%
1658
16th to endDay
331221223472%
1760
November1st to 15thDay
2212212235%72%
1759
16th to endDay
321321223471%
1626
December1st to 15thDay
5%5%24224445%58%
1515
16th to endDay
5%6%2443445%7%52%
1728
January1st to 15thNight
36%13223335%64%
2327
16th to endNight
5%423312246%62%
2496
February1st to 15thNight
35%13312335%65%
2277
16th to endNight
3313313346%64%
1869
March1st to 15thNight
2312323346%65%
1980
16th to endNight
321221346%8%63%
2112
April1st to 15thNight
341331345%7%61%
1864
16th to endNight
3213114336%67%
1770
May1st to 15thNight
1113223346%66%
1619
16th to endNight
3212313336%67%
1684
June1st to 15thNight
311212335%73%
1620
16th to endNight
112213346%71%
1620
July1st to 15thNight
32245%446%6%10%49%
1620
16th to endNight
3336%6%47%8%9%10%35%
1701
August1st to 15thNight
21145%47%6%8%10%46%
1620
16th to endNight
4214426%7%7%10%48%
1850
September1st to 15thNight
4213425%6%7%7%54%
1863
16th to endNight
211121223476%
1914
October1st to 15thNight
222223446%68%
1972
16th to endNight
111212345%74%
2112
November1st to 15thNight
3211212346%68%
2100
16th to endNight
32221233472%
2334
December1st to 15thNight
3313323447%62%
2418
16th to endNight
5%6%25%324446%52%
2496

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
25%411%34%21%2
1612
16th to endDay
26%5%10%31%22%4
1728
February1st to 15thDay
26%5%13%23%23%7%
1575
16th to endDay
29%48%20%30%6%
1602
March1st to 15thDay
22%47%23%33%9%
1980
16th to endDay
21%310%22%30%11%
2112
April1st to 15thDay
23%47%18%31%15%
2084
16th to endDay
21%47%18%29%17%
2188
May1st to 15thDay
22%48%16%31%16%
2331
16th to endDay
21%48%13%30%22%
2432
June1st to 15thDay
13%247%26%45%
2340
16th to endDay
11%247%20%53%
2340
July1st to 15thDay
29%9%13%13%12%22%
2201
16th to endDay
36%14%17%14%10%6%
2312
August1st to 15thDay
37%9%13%12%13%13%
2325
16th to endDay
32%8%12%15%17%13%
2351
September1st to 15thDay
26%8%12%13%19%18%
2094
16th to endDay
16%47%13%28%30%
1904
October1st to 15thDay
18%47%16%33%20%
1658
16th to endDay
17%36%17%36%18%
1760
November1st to 15thDay
16%28%24%34%13%
1759
16th to endDay
18%37%24%34%11%
1626
December1st to 15thDay
28%5%13%31%18%2
1515
16th to endDay
32%6%18%28%12%1
1728
January1st to 15thNight
23%410%31%27%3
2327
16th to endNight
25%49%26%27%6%
2496
February1st to 15thNight
24%311%27%22%10%
2288
16th to endNight
22%5%8%22%33%8%
1869
March1st to 15thNight
20%36%26%33%9%
1980
16th to endNight
18%48%23%34%11%
2112
April1st to 15thNight
22%37%20%29%16%
1864
16th to endNight
19%37%17%32%19%
1770
May1st to 15thNight
18%48%17%33%16%
1620
16th to endNight
19%48%13%31%23%
1685
June1st to 15thNight
13%248%24%46%
1620
16th to endNight
13%35%7%17%52%
1620
July1st to 15thNight
27%9%12%16%10%23%
1530
16th to endNight
37%12%16%15%9%8%
1593
August1st to 15thNight
29%11%16%12%14%15%
1611
16th to endNight
27%8%15%18%16%13%
1850
September1st to 15thNight
23%9%10%17%18%19%
1863
16th to endNight
14%26%15%28%32%
1914
October1st to 15thNight
17%46%19%27%24%
1972
16th to endNight
13%37%16%38%19%
2112
November1st to 15thNight
17%38%21%35%14%
2100
16th to endNight
17%36%23%34%15%
2334
December1st to 15thNight
23%5%12%31%24%3
2418
16th to endNight
32%5%15%27%16%1
2496

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%8%26%20%20%5%
90
16th to endDay
10%7%11%36%23%10%
96
February1st to 15thDay
6%323%26%31%8%
90
16th to endDay
10%22%31%20%12%3
189
March1st to 15thDay
6%16%30%28%17%1
270
16th to endDay
7%21%31%25%13%2
288
April1st to 15thDay
8%19%28%24%11%7%
269
16th to endDay
11%23%29%22%12%
270
May1st to 15thDay
412%38%26%14%3
288
16th to endDay
5%12%28%30%16%6%
330
June1st to 15thDay
6%8%23%33%19%8%
315
16th to endDay
3313%39%27%12%
315
July1st to 15thDay
6%11%36%35%10%
305
16th to endDay
7%6%28%39%17%
327
August1st to 15thDay
7%10%28%35%16%
315
16th to endDay
6%10%30%35%16%
332
September1st to 15thDay
4118%39%29%7%
315
16th to endDay
5%7%22%27%28%8%
288
October1st to 15thDay
45%20%27%34%8%
98
16th to endDay
9%225%29%25%9%
96
November1st to 15thDay
2422%25%34%11%
90
16th to endDay
6%15%25%32%16%3
90
December1st to 15thDay
8%7%24%35%16%6%
90
16th to endDay
11%15%13%28%26%5%
96
January1st to 15thNight
7%415%38%27%6%
720
16th to endNight
8%5%17%38%22%7%
768
February1st to 15thNight
6%421%39%25%3
704
16th to endNight
5%9%27%39%15%1
632
March1st to 15thNight
48%20%38%24%2
720
16th to endNight
37%25%37%24%2
768
April1st to 15thNight
6%11%28%36%14%2
605
16th to endNight
5%9%29%32%19%2
540
May1st to 15thNight
4325%42%21%2
540
16th to endNight
6%5%26%35%23%2
563
June1st to 15thNight
3224%40%26%2
540
16th to endNight
216%36%41%2
540
July1st to 15thNight
6%7%37%42%5%
510
16th to endNight
6%227%54%8%
564
August1st to 15thNight
3427%53%10%
539
16th to endNight
5%8%31%45%9%
573
September1st to 15thNight
47%36%44%5%
603
16th to endNight
3114%33%36%10%
692
October1st to 15thNight
3319%43%25%4
660
16th to endNight
1218%34%33%9%
704
November1st to 15thNight
4316%36%32%6%
700
16th to endNight
6%417%33%29%8%
720
December1st to 15thNight
6%6%18%42%21%3
798
16th to endNight
10%6%21%35%23%3
768
Page generated at 2017-09-25 07:02:24. Version ac04

Copyright 2017 A. Danko


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