Kitt Peak
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kitt Peak 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
74%
15527
36%
46537
31%
15489
79%
15489
54%
21982

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
74%
718
33%
2327
35%
716
78%
716
51%
1068
January16th to endNight
65%
768
34%
2496
32%
768
73%
768
41%
1280
February1st to 15thNight
73%
699
37%
2163
35%
699
80%
699
52%
1010
February16th to endNight
61%
632
37%
1860
32%
632
70%
632
47%
949
March1st to 15thNight
66%
720
41%
1980
32%
720
74%
720
57%
964
March16th to endNight
70%
768
39%
2112
28%
768
80%
768
61%
1001
April1st to 15thNight
63%
714
35%
1973
22%
714
72%
714
57%
946
April16th to endNight
68%
540
46%
1748
37%
540
81%
540
72%
647
May1st to 15thNight
69%
539
39%
1619
29%
539
78%
539
68%
659
May16th to endNight
70%
561
42%
1684
31%
561
78%
561
72%
670
June1st to 15thNight
78%
540
35%
1620
29%
540
81%
540
70%
670
June16th to endNight
84%
540
33%
1620
28%
540
85%
540
67%
690
July1st to 15thNight
80%
510
19%
1530
15%
510
80%
510
40%
845
July16th to endNight
82%
564
19%
1593
17%
531
82%
531
32%
970
August1st to 15thNight
86%
527
27%
1575
25%
524
86%
524
48%
804
August16th to endNight
83%
599
29%
1748
27%
599
83%
599
42%
965
September1st to 15thNight
77%
660
31%
1815
26%
660
79%
660
46%
1035
September16th to endNight
82%
656
43%
1815
35%
656
86%
656
68%
826
October1st to 15thNight
78%
660
42%
1892
33%
660
84%
660
65%
834
October16th to endNight
84%
704
44%
2112
39%
704
89%
704
70%
878
November1st to 15thNight
79%
700
42%
2100
37%
700
84%
700
66%
896
November16th to endNight
71%
720
38%
2319
37%
720
76%
720
51%
1063
December1st to 15thNight
71%
720
38%
2340
37%
720
76%
720
48%
1079
December16th to endNight
65%
768
35%
2496
35%
768
70%
768
43%
1233

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
3213323346%64%
47431
Night
2212323346%67%
46733
TransparencyDay
19%35%10%24%35%
47126
Night
17%36%12%25%34%
46539
SeeingDay
5%10%24%31%21%7%
5331
Night
3313%34%35%9%
15537

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
231342434464%
1611
16th to endDay
5%313423345%61%
1728
February1st to 15thDay
3423222337%66%
1697
16th to endDay
4423322336%62%
1612
March1st to 15thDay
2213322447%65%
1980
16th to endDay
221221233472%
2112
April1st to 15thDay
2111323346%70%
1973
16th to endDay
1122112481%
2209
May1st to 15thDay
1221222378%
2331
16th to endDay
1121112384%
2429
June1st to 15thDay
11111112480%
2340
16th to endDay
211221323475%
2340
July1st to 15thDay
4415%5%27%7%7%8%44%
2340
16th to endDay
6%5%37%8%48%6%8%11%27%
2467
August1st to 15thDay
5%4236%47%7%7%9%41%
2290
16th to endDay
4325%5%35%7%6%8%46%
2099
September1st to 15thDay
6%5%235%25%6%6%7%48%
1815
16th to endDay
32222433470%
1815
October1st to 15thDay
1112223235%75%
1738
16th to endDay
111121123477%
1760
November1st to 15thDay
11112336%74%
1759
16th to endDay
3212213345%68%
1638
December1st to 15thDay
6%21342235%5%62%
1620
16th to endDay
431342345%6%60%
1728
January1st to 15thNight
3213313445%66%
2327
16th to endNight
5%31343444458%
2496
February1st to 15thNight
221231335%5%67%
2152
16th to endNight
23235%24346%62%
1860
March1st to 15thNight
2212223345%70%
1980
16th to endNight
2112313335%72%
2112
April1st to 15thNight
2213222245%70%
1973
16th to endNight
1111112384%
1748
May1st to 15thNight
1112345%77%
1619
16th to endNight
111221383%
1684
June1st to 15thNight
1112222479%
1620
16th to endNight
111211222476%
1620
July1st to 15thNight
22235%36%7%7%11%47%
1620
16th to endNight
4214447%8%11%16%33%
1701
August1st to 15thNight
22133245%6%10%56%
1584
16th to endNight
3313435%6%5%10%52%
1748
September1st to 15thNight
5%324334446%58%
1815
16th to endNight
22221124475%
1815
October1st to 15thNight
11121323477%
1892
16th to endNight
1211222480%
2112
November1st to 15thNight
112212335%75%
2100
16th to endNight
331332235%467%
2319
December1st to 15thNight
4322213346%64%
2340
16th to endNight
4314423346%60%
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
21%3412%24%33%
1612
16th to endDay
23%3414%25%28%
1728
February1st to 15thDay
19%25%11%27%34%
1697
16th to endDay
22%3412%29%27%
1612
March1st to 15thDay
17%237%29%39%
1980
16th to endDay
15%237%31%39%
2112
April1st to 15thDay
14%135%36%37%
1973
16th to endDay
9%136%25%54%
2209
May1st to 15thDay
10%135%21%57%
2331
16th to endDay
7%125%25%56%
2432
June1st to 15thDay
9%11320%63%
2340
16th to endDay
14%13416%59%
2340
July1st to 15thDay
31%8%11%15%14%18%
2201
16th to endDay
43%13%14%19%6%2
2312
August1st to 15thDay
34%9%11%14%15%13%
2275
16th to endDay
32%7%12%19%16%11%
2099
September1st to 15thDay
30%5%9%16%18%18%
1815
16th to endDay
16%249%33%32%
1815
October1st to 15thDay
12%25%10%28%40%
1738
16th to endDay
11%148%26%49%
1760
November1st to 15thDay
11%129%34%39%
1759
16th to endDay
18%238%27%39%
1638
December1st to 15thDay
22%25%13%29%26%
1620
16th to endDay
21%47%16%30%19%
1728
January1st to 15thNight
18%36%12%27%32%
2327
16th to endNight
26%35%12%28%23%
2496
February1st to 15thNight
17%35%14%24%34%
2163
16th to endNight
21%3412%32%26%
1860
March1st to 15thNight
16%2210%27%40%
1980
16th to endNight
14%25%10%32%35%
2112
April1st to 15thNight
17%138%33%35%
1973
16th to endNight
8%18%26%54%
1748
May1st to 15thNight
8%237%26%51%
1620
16th to endNight
8%125%24%57%
1685
June1st to 15thNight
10%13319%62%
1620
16th to endNight
11%14318%59%
1620
July1st to 15thNight
24%8%16%14%16%20%
1530
16th to endNight
29%11%22%23%11%2
1593
August1st to 15thNight
20%6%15%23%18%16%
1575
16th to endNight
24%7%14%20%19%14%
1748
September1st to 15thNight
24%5%9%20%21%18%
1815
16th to endNight
11%2312%35%34%
1815
October1st to 15thNight
11%2414%27%39%
1892
16th to endNight
10%1311%24%48%
2112
November1st to 15thNight
11%2312%31%38%
2100
16th to endNight
18%249%24%39%
2319
December1st to 15thNight
19%3414%28%29%
2340
16th to endNight
23%36%17%28%20%
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
315%25%33%22%
90
16th to endDay
5%15%19%32%16%10%
96
February1st to 15thDay
312%26%37%17%1
212
16th to endDay
7%19%37%24%9%1
238
March1st to 15thDay
5%20%29%25%11%7%
270
16th to endDay
221%32%23%14%5%
288
April1st to 15thDay
419%34%22%13%6%
269
16th to endDay
224%34%22%10%5%
270
May1st to 15thDay
6%19%31%26%12%3
288
16th to endDay
112%36%30%16%2
330
June1st to 15thDay
45%36%38%13%2
315
16th to endDay
4118%43%25%6%
315
July1st to 15thDay
6%113%41%29%8%
305
16th to endDay
6%10%33%29%19%
327
August1st to 15thDay
6%9%32%35%16%
300
16th to endDay
6%8%33%39%10%
268
September1st to 15thDay
11%215%34%28%7%
255
16th to endDay
9%419%32%25%7%
255
October1st to 15thDay
213%21%33%22%6%
178
16th to endDay
3213%32%40%8%
96
November1st to 15thDay
111%23%27%30%6%
90
16th to endDay
312%26%30%26%1
90
December1st to 15thDay
47%15%28%33%10%
90
16th to endDay
7%10%32%27%20%2
96
January1st to 15thNight
5%311%42%30%7%
720
16th to endNight
7%316%37%27%6%
768
February1st to 15thNight
4412%40%30%6%
704
16th to endNight
38%21%40%21%3
632
March1st to 15thNight
27%19%36%26%6%
720
16th to endNight
2415%39%31%6%
768
April1st to 15thNight
35%22%40%25%2
714
16th to endNight
17%21%39%25%4
540
May1st to 15thNight
6%21%38%27%4
540
16th to endNight
1321%36%32%4
563
June1st to 15thNight
2113%44%32%5%
540
16th to endNight
38%34%47%6%
540
July1st to 15thNight
25%24%56%10%
510
16th to endNight
5%121%52%18%
564
August1st to 15thNight
2220%57%16%
527
16th to endNight
4420%52%18%
599
September1st to 15thNight
5%6%21%47%18%
660
16th to endNight
310%30%41%14%
656
October1st to 15thNight
1412%36%34%9%
660
16th to endNight
19%32%41%14%
704
November1st to 15thNight
2212%37%35%9%
700
16th to endNight
4413%35%30%11%
720
December1st to 15thNight
6%5%11%37%30%7%
720
16th to endNight
6%5%15%39%25%7%
768
Page generated at 2017-08-13 11:16:14. Version ac04

Copyright 2017 A. Danko


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