High Plains Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the High Plains 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
61%
15972
28%
46941
21%
15932
67%
15932
43%
25452

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
57%
897
31%
2506
22%
895
65%
895
48%
1316
January16th to endNight
54%
825
34%
2553
26%
825
64%
825
42%
1349
February1st to 15thNight
51%
699
26%
2247
19%
698
60%
698
37%
1238
February16th to endNight
46%
632
31%
1894
19%
632
59%
632
39%
1058
March1st to 15thNight
55%
720
29%
2124
16%
720
66%
720
45%
1143
March16th to endNight
54%
673
26%
2017
17%
673
64%
673
40%
1117
April1st to 15thNight
48%
539
24%
1798
18%
539
59%
539
34%
981
April16th to endNight
49%
540
23%
1800
21%
540
57%
540
28%
1057
May1st to 15thNight
54%
540
19%
1590
17%
540
57%
540
29%
993
May16th to endNight
62%
562
19%
1498
14%
561
65%
561
40%
875
June1st to 15thNight
69%
540
20%
1440
16%
540
71%
540
50%
786
June16th to endNight
75%
540
27%
1440
22%
540
77%
540
56%
736
July1st to 15thNight
72%
510
18%
1360
16%
510
73%
510
37%
825
July16th to endNight
78%
564
28%
1425
25%
531
78%
531
47%
783
August1st to 15thNight
78%
539
22%
1668
22%
536
79%
536
42%
861
August16th to endNight
79%
573
30%
1910
35%
573
81%
573
42%
974
September1st to 15thNight
73%
540
29%
1800
31%
540
77%
540
41%
925
September16th to endNight
74%
519
37%
1872
38%
519
81%
519
48%
845
October1st to 15thNight
63%
643
30%
1963
22%
643
69%
643
42%
1042
October16th to endNight
66%
742
35%
2150
24%
742
72%
742
47%
1126
November1st to 15thNight
64%
875
33%
2275
21%
875
69%
875
52%
1226
November16th to endNight
62%
900
35%
2403
23%
900
68%
900
53%
1276
December1st to 15thNight
51%
900
26%
2520
16%
900
60%
900
45%
1390
December16th to endNight
52%
960
29%
2688
17%
960
61%
960
40%
1530

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
5%42442446%8%52%
48000
Night
5%5%2432345%7%56%
47114
Cloud CoverDay
5%42442446%8%52%
47998
Night
5%5%2432345%7%56%
47114
TransparencyDay
28%310%26%22%8%
47676
Night
27%310%27%22%8%
46941
SeeingDay
9%6%19%31%24%8%
5898
Night
7%320%47%19%2
15981

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
17%23322248%60%
1432
16th to endDay
25%34323346%60%
1681
February1st to 15thDay
26%35%325%36%7%53%
1615
16th to endDay
25%2441345%6%58%
1580
March1st to 15thDay
342443435%9%53%
1833
16th to endDay
6%5%2432346%8%49%
2206
April1st to 15thDay
8%5%2441445%8%51%
2150
16th to endDay
11%7%2343445%7%43%
2160
May1st to 15thDay
11%6%245%25%5%6%8%41%
2356
16th to endDay
9%5%23426%5%6%10%42%
2616
June1st to 15thDay
5%313425%5%7%9%49%
2520
16th to endDay
22123246%8%10%55%
2520
July1st to 15thDay
6%413425%6%8%10%46%
2520
16th to endDay
3214435%6%8%10%49%
2644
August1st to 15thDay
4313436%8%6%11%43%
2283
16th to endDay
3313425%6%6%10%51%
2292
September1st to 15thDay
6%21332345%8%57%
2160
16th to endDay
4312323336%65%
1946
October1st to 15thDay
6%41432335%6%57%
1664
16th to endDay
5%413212246%64%
1709
November1st to 15thDay
1423324347%60%
1583
16th to endDay
242331336%7%60%
1554
December1st to 15thDay
36%26%32245%8%53%
1440
16th to endDay
45%3442445%7%52%
1536
January1st to 15thNight
1434323337%62%
2506
16th to endNight
36%34313346%59%
2553
February1st to 15thNight
28%35%323347%53%
2237
16th to endNight
29%35%423346%54%
1894
March1st to 15thNight
35%2342335%8%56%
2124
16th to endNight
6%6%24413348%54%
2017
April1st to 15thNight
6%5%2442445%7%52%
1798
16th to endNight
14%6%24423347%47%
1800
May1st to 15thNight
12%6%15%4245%6%6%44%
1589
16th to endNight
9%5%1342245%8%51%
1497
June1st to 15thNight
5%3232445%9%57%
1440
16th to endNight
121332346%9%62%
1440
July1st to 15thNight
6%415%335%6%6%9%49%
1440
16th to endNight
3223325%5%7%9%53%
1521
August1st to 15thNight
33134245%6%11%53%
1677
16th to endNight
431432446%9%55%
1910
September1st to 15thNight
7%21332346%8%55%
1800
16th to endNight
4212213346%65%
1872
October1st to 15thNight
7%41331335%5%58%
1963
16th to endNight
6%423213335%62%
2150
November1st to 15thNight
3314323336%63%
2275
16th to endNight
3423213347%63%
2403
December1st to 15thNight
37%25%32235%8%55%
2520
16th to endNight
36%345%1345%8%52%
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
17%23322249%59%
1432
16th to endDay
25%34323337%60%
1681
February1st to 15thDay
26%35%325%45%7%53%
1615
16th to endDay
35%2442336%6%58%
1580
March1st to 15thDay
3424435%35%8%53%
1833
16th to endDay
7%5%3432346%9%50%
2204
April1st to 15thDay
8%5%2442445%7%51%
2150
16th to endDay
11%7%24443448%43%
2160
May1st to 15thDay
12%6%145%35%5%6%8%40%
2356
16th to endDay
9%5%14336%5%6%9%43%
2616
June1st to 15thDay
5%313426%5%7%9%49%
2520
16th to endDay
22124245%7%10%55%
2520
July1st to 15thDay
6%313425%6%8%10%47%
2520
16th to endDay
42245%35%6%8%9%49%
2644
August1st to 15thDay
4414436%7%7%11%43%
2283
16th to endDay
3213425%6%6%10%51%
2292
September1st to 15thDay
7%21332345%8%57%
2160
16th to endDay
4413323335%65%
1946
October1st to 15thDay
6%41431335%6%57%
1664
16th to endDay
5%413212246%65%
1709
November1st to 15thDay
2414324448%60%
1583
16th to endDay
242332346%7%60%
1554
December1st to 15thDay
36%26%42336%8%53%
1440
16th to endDay
45%34424447%52%
1536
January1st to 15thNight
1434323347%62%
2506
16th to endNight
36%34313346%59%
2553
February1st to 15thNight
28%35%323347%53%
2237
16th to endNight
29%35%423346%54%
1894
March1st to 15thNight
35%2432335%7%56%
2124
16th to endNight
7%6%24423348%54%
2017
April1st to 15thNight
7%5%2442445%6%53%
1798
16th to endNight
14%6%24313346%47%
1800
May1st to 15thNight
13%5%244245%6%6%44%
1589
16th to endNight
8%5%1442345%9%51%
1497
June1st to 15thNight
5%3232446%8%58%
1440
16th to endNight
121332246%9%62%
1440
July1st to 15thNight
6%314435%5%6%9%49%
1440
16th to endNight
3213325%47%9%54%
1521
August1st to 15thNight
33133245%7%11%53%
1677
16th to endNight
421432445%9%56%
1910
September1st to 15thNight
7%2133335%6%7%55%
1800
16th to endNight
5%213313436%65%
1872
October1st to 15thNight
7%42332335%5%58%
1963
16th to endNight
6%413213335%62%
2150
November1st to 15thNight
3314313346%63%
2275
16th to endNight
3413212346%63%
2403
December1st to 15thNight
37%25%32235%8%55%
2520
16th to endNight
46%345%1335%8%53%
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
24%111%36%22%4
1433
16th to endDay
25%27%35%22%7%
1681
February1st to 15thDay
28%313%36%13%4
1616
16th to endDay
25%26%34%26%4
1580
March1st to 15thDay
28%28%28%24%7%
1833
16th to endDay
30%312%26%21%5%
2206
April1st to 15thDay
31%39%26%21%8%
2150
16th to endDay
38%39%24%18%4
2160
May1st to 15thDay
39%411%26%14%3
2356
16th to endDay
34%5%15%24%14%5%
2620
June1st to 15thDay
28%5%14%21%21%9%
2520
16th to endDay
20%49%23%29%12%
2520
July1st to 15thDay
29%6%9%22%17%14%
2371
16th to endDay
27%5%9%26%21%8%
2478
August1st to 15thDay
30%5%11%22%17%12%
2268
16th to endDay
24%48%25%25%10%
2292
September1st to 15thDay
24%28%24%21%17%
2160
16th to endDay
21%2425%36%9%
1946
October1st to 15thDay
26%39%23%26%10%
1664
16th to endDay
21%26%29%29%10%
1709
November1st to 15thDay
23%37%26%27%12%
1583
16th to endDay
21%26%27%32%9%
1554
December1st to 15thDay
28%211%35%18%2
1440
16th to endDay
29%313%27%18%5%
1536
January1st to 15thNight
23%211%31%26%4
2506
16th to endNight
27%27%29%25%7%
2553
February1st to 15thNight
31%310%33%18%3
2247
16th to endNight
30%25%28%24%8%
1894
March1st to 15thNight
27%27%27%27%7%
2124
16th to endNight
29%212%26%23%5%
2017
April1st to 15thNight
31%39%27%19%7%
1798
16th to endNight
37%39%26%18%5%
1800
May1st to 15thNight
37%6%14%22%15%4
1590
16th to endNight
30%421%24%12%6%
1498
June1st to 15thNight
22%419%27%15%10%
1440
16th to endNight
17%412%25%30%10%
1440
July1st to 15thNight
31%6%12%21%17%10%
1360
16th to endNight
24%412%30%20%8%
1425
August1st to 15thNight
24%5%17%25%18%8%
1668
16th to endNight
24%48%26%25%9%
1910
September1st to 15thNight
26%310%24%18%16%
1800
16th to endNight
19%36%26%33%10%
1872
October1st to 15thNight
26%311%20%27%10%
1963
16th to endNight
24%26%27%27%10%
2150
November1st to 15thNight
22%27%26%27%13%
2275
16th to endNight
22%26%28%30%9%
2403
December1st to 15thNight
26%213%33%19%4
2520
16th to endNight
29%412%31%19%3
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
8%6%16%38%16%12%
90
16th to endDay
5%120%45%21%5%
96
February1st to 15thDay
311%30%50%41
90
16th to endDay
7%229%39%14%6%
81
March1st to 15thDay
6%11%22%41%13%4
123
16th to endDay
14%15%31%29%8%1
288
April1st to 15thDay
15%14%30%24%11%3
269
16th to endDay
21%15%30%21%8%2
270
May1st to 15thDay
16%8%17%34%19%3
436
16th to endDay
17%6%16%31%20%7%
517
June1st to 15thDay
7%319%30%27%10%
495
16th to endDay
4419%31%31%9%
495
July1st to 15thDay
11%210%27%35%11%
475
16th to endDay
6%212%21%44%12%
503
August1st to 15thDay
6%5%22%32%23%9%
315
16th to endDay
6%417%29%29%12%
332
September1st to 15thDay
6%418%34%26%9%
315
16th to endDay
5%316%33%27%13%
156
October1st to 15thDay
6%113%33%27%17%
90
16th to endDay
6%414%32%30%12%
96
November1st to 15thDay
3110%36%22%26%
90
16th to endDay
10%6%22%40%20%1
90
December1st to 15thDay
6%338%40%6%4
90
16th to endDay
4129%46%16%2
96
January1st to 15thNight
3326%48%15%2
900
16th to endNight
5%129%49%12%1
825
February1st to 15thNight
7%228%51%9%
704
16th to endNight
7%431%47%9%
632
March1st to 15thNight
5%229%49%11%
720
16th to endNight
9%425%49%11%
673
April1st to 15thNight
10%6%29%45%8%
539
16th to endNight
17%6%21%40%13%
540
May1st to 15thNight
15%417%43%17%1
540
16th to endNight
10%316%44%23%1
563
June1st to 15thNight
7%215%49%22%2
540
16th to endNight
2213%50%30%
540
July1st to 15thNight
8%27%38%38%4
510
16th to endNight
416%36%46%3
564
August1st to 15thNight
5%25%41%42%2
539
16th to endNight
6%15%43%39%4
573
September1st to 15thNight
7%110%41%31%6%
540
16th to endNight
5%112%47%29%3
519
October1st to 15thNight
10%218%45%21%2
643
16th to endNight
8%116%50%19%3
742
November1st to 15thNight
5%419%52%16%1
875
16th to endNight
6%223%52%14%1
900
December1st to 15thNight
7%230%48%10%
900
16th to endNight
6%426%49%11%1
960
Page generated at 2017-09-25 07:02:23. Version ac04

Copyright 2017 A. Danko


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