Picketwire Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Picketwire Observatory clear sky chart from 2005-11-05 to 2017-09-17.

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
42%
15824
31%
46874
14%
15780
58%
15780
38%
24026

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
38%
873
34%
2479
14%
868
57%
868
44%
1181
January16th to endNight
32%
768
38%
2496
17%
768
56%
768
40%
1112
February1st to 15thNight
28%
701
30%
2195
11%
700
49%
700
34%
1095
February16th to endNight
23%
632
40%
1894
8%
632
53%
632
36%
896
March1st to 15thNight
30%
720
31%
2109
9%
720
49%
720
35%
1079
March16th to endNight
30%
678
34%
2022
11%
678
52%
678
37%
979
April1st to 15thNight
21%
539
31%
1798
9%
539
48%
539
32%
837
April16th to endNight
31%
540
28%
1800
12%
540
55%
540
27%
947
May1st to 15thNight
35%
540
23%
1716
12%
540
50%
540
29%
981
May16th to endNight
39%
563
26%
1522
10%
561
54%
561
38%
844
June1st to 15thNight
45%
540
25%
1440
11%
540
56%
540
45%
773
June16th to endNight
55%
540
23%
1440
14%
540
63%
540
42%
816
July1st to 15thNight
61%
510
17%
1360
11%
510
67%
510
32%
878
July16th to endNight
74%
564
16%
1514
16%
531
75%
531
32%
932
August1st to 15thNight
69%
539
14%
1725
12%
536
71%
536
28%
1029
August16th to endNight
65%
573
23%
1910
22%
573
69%
573
33%
1076
September1st to 15thNight
58%
540
26%
1800
20%
540
69%
540
35%
973
September16th to endNight
58%
498
36%
1799
30%
498
70%
498
46%
778
October1st to 15thNight
45%
630
35%
1950
19%
630
58%
630
45%
943
October16th to endNight
48%
704
38%
2112
17%
704
63%
704
48%
1000
November1st to 15thNight
44%
872
39%
2272
15%
872
58%
872
53%
1091
November16th to endNight
42%
900
40%
2340
15%
900
58%
900
50%
1163
December1st to 15thNight
31%
900
34%
2493
9%
900
52%
900
41%
1227
December16th to endNight
32%
960
32%
2688
11%
960
50%
960
36%
1396

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
44133245%6%8%54%
47908
Night
231332345%7%62%
47056
Cloud CoverDay
44233245%6%8%53%
47906
Night
231332345%7%61%
47056
TransparencyDay
24%7%11%22%23%10%
47592
Night
20%6%11%25%26%10%
46874
SeeingDay
9%18%29%25%13%4
5726
Night
5%17%30%28%14%2
15827

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
413212237%68%
1468
16th to endDay
132321235%6%68%
1728
February1st to 15thDay
1325%413448%60%
1666
16th to endDay
42322335%7%64%
1580
March1st to 15thDay
16%2332345%7%59%
1848
16th to endDay
25%2331345%10%55%
2202
April1st to 15thDay
45%133245%5%8%55%
2150
16th to endDay
6%7%1442446%8%48%
2160
May1st to 15thDay
7%6%23425%5%6%8%47%
2235
16th to endDay
5%324325%47%8%52%
2589
June1st to 15thDay
3213435%5%7%9%53%
2520
16th to endDay
213426%7%9%9%52%
2520
July1st to 15thDay
7%425%436%7%8%10%39%
2520
16th to endDay
6%325%6%38%8%8%11%35%
2546
August1st to 15thDay
9%425%5%46%7%6%9%37%
2225
16th to endDay
8%425%446%6%7%8%41%
2292
September1st to 15thDay
7%3245%36%5%6%8%45%
2160
16th to endDay
3212423345%66%
1866
October1st to 15thDay
5%313223347%62%
1678
16th to endDay
4211212245%71%
1752
November1st to 15thDay
2121345%8%69%
1583
16th to endDay
31221435%7%66%
1620
December1st to 15thDay
223211347%68%
1464
16th to endDay
133322435%9%60%
1536
January1st to 15thNight
212212346%70%
2479
16th to endNight
412322236%69%
2496
February1st to 15thNight
1425%324337%62%
2185
16th to endNight
323312235%70%
1894
March1st to 15thNight
15%23213437%63%
2109
16th to endNight
3312212447%66%
2022
April1st to 15thNight
2412312347%65%
1798
16th to endNight
45%1332445%6%58%
1800
May1st to 15thNight
5%5%23325%5%5%7%53%
1715
16th to endNight
5%31232445%7%59%
1521
June1st to 15thNight
221232445%9%61%
1440
16th to endNight
3112335%7%7%12%52%
1440
July1st to 15thNight
5%2245%37%7%9%11%40%
1440
16th to endNight
4314427%6%8%11%44%
1619
August1st to 15thNight
32125%5%7%7%8%9%45%
1734
16th to endNight
6%324325%5%8%10%47%
1910
September1st to 15thNight
6%313315%5%6%12%49%
1800
16th to endNight
3212213246%69%
1799
October1st to 15thNight
4312212245%68%
1950
16th to endNight
2212213346%68%
2112
November1st to 15thNight
22212346%73%
2272
16th to endNight
131221235%5%70%
2340
December1st to 15thNight
21321335%8%66%
2493
16th to endNight
132322345%7%63%
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
1413312237%67%
1468
16th to endDay
132411335%6%67%
1728
February1st to 15thDay
1335%323449%58%
1666
16th to endDay
42321335%8%63%
1580
March1st to 15thDay
16%2432445%8%58%
1848
16th to endDay
35%2332346%10%53%
2200
April1st to 15thDay
36%133245%5%8%54%
2150
16th to endDay
6%8%2443446%9%46%
2160
May1st to 15thDay
6%6%34426%47%7%46%
2235
16th to endDay
5%5%13425%46%9%51%
2589
June1st to 15thDay
3213435%6%7%9%53%
2520
16th to endDay
2113435%7%9%9%51%
2520
July1st to 15thDay
6%425%437%7%8%10%38%
2520
16th to endDay
5%5%25%7%38%8%9%10%33%
2546
August1st to 15thDay
9%5%25%5%46%6%7%9%36%
2225
16th to endDay
8%5%25%5%46%6%6%8%41%
2292
September1st to 15thDay
7%5%15%436%6%6%8%45%
2160
16th to endDay
3213423345%65%
1866
October1st to 15thDay
5%32232335%7%62%
1678
16th to endDay
3311112335%69%
1752
November1st to 15thDay
121211345%7%68%
1583
16th to endDay
312223348%65%
1620
December1st to 15thDay
224211348%67%
1464
16th to endDay
133332336%9%59%
1536
January1st to 15thNight
212223347%69%
2479
16th to endNight
312312345%69%
2496
February1st to 15thNight
425%323347%62%
2185
16th to endNight
323312346%69%
1894
March1st to 15thNight
15%23323347%62%
2109
16th to endNight
3312113347%65%
2022
April1st to 15thNight
2423312347%64%
1798
16th to endNight
45%1331445%6%57%
1800
May1st to 15thNight
5%5%24325%5%5%6%52%
1715
16th to endNight
5%31231446%8%57%
1521
June1st to 15thNight
221242335%10%60%
1440
16th to endNight
3112325%6%8%11%51%
1440
July1st to 15thNight
5%425%5%46%7%9%11%39%
1440
16th to endNight
4324427%7%8%11%43%
1619
August1st to 15thNight
32135%47%7%9%9%45%
1734
16th to endNight
6%413435%6%7%10%46%
1910
September1st to 15thNight
6%3134245%7%11%48%
1800
16th to endNight
332212346%68%
1799
October1st to 15thNight
4412312246%67%
1950
16th to endNight
2313213246%68%
2112
November1st to 15thNight
123211346%72%
2272
16th to endNight
131221235%6%69%
2340
December1st to 15thNight
21321235%8%66%
2493
16th to endNight
1323314347%63%
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
17%39%29%33%7%
1469
16th to endDay
16%39%26%32%11%
1728
February1st to 15thDay
23%410%27%26%7%
1667
16th to endDay
18%46%25%31%12%
1580
March1st to 15thDay
21%5%8%23%28%11%
1848
16th to endDay
24%5%9%25%28%6%
2202
April1st to 15thDay
24%6%7%26%24%10%
2150
16th to endDay
30%6%10%21%21%9%
2160
May1st to 15thDay
30%9%12%19%21%6%
2235
16th to endDay
26%8%12%18%22%12%
2593
June1st to 15thDay
23%8%12%17%18%19%
2520
16th to endDay
21%8%12%19%20%16%
2520
July1st to 15thDay
34%11%14%16%13%9%
2371
16th to endDay
35%13%17%22%8%2
2388
August1st to 15thDay
38%12%17%14%10%6%
2210
16th to endDay
35%10%12%19%18%4
2292
September1st to 15thDay
32%8%13%22%15%7%
2160
16th to endDay
17%6%9%22%32%11%
1866
October1st to 15thDay
21%48%22%31%11%
1678
16th to endDay
15%46%24%36%13%
1752
November1st to 15thDay
12%48%24%33%16%
1583
16th to endDay
16%3421%35%17%
1620
December1st to 15thDay
16%313%29%26%9%
1464
16th to endDay
21%314%28%24%8%
1536
January1st to 15thNight
15%39%30%31%9%
2479
16th to endNight
16%39%26%32%11%
2496
February1st to 15thNight
22%49%31%25%7%
2195
16th to endNight
17%36%26%34%11%
1894
March1st to 15thNight
20%48%25%31%8%
2109
16th to endNight
18%49%27%31%9%
2022
April1st to 15thNight
19%48%32%25%9%
1798
16th to endNight
26%6%11%24%23%8%
1800
May1st to 15thNight
28%8%10%21%22%7%
1716
16th to endNight
22%7%15%21%20%13%
1522
June1st to 15thNight
18%7%13%19%21%20%
1440
16th to endNight
20%10%12%18%20%17%
1440
July1st to 15thNight
32%11%15%18%12%9%
1360
16th to endNight
27%14%22%24%9%2
1514
August1st to 15thNight
27%14%23%16%11%6%
1725
16th to endNight
26%10%16%25%15%4
1910
September1st to 15thNight
24%9%18%25%14%6%
1800
16th to endNight
16%5%10%24%30%12%
1799
October1st to 15thNight
18%411%20%33%12%
1950
16th to endNight
15%46%22%35%14%
2112
November1st to 15thNight
13%27%25%32%18%
2272
16th to endNight
15%25%25%33%16%
2340
December1st to 15thNight
16%310%33%28%7%
2493
16th to endNight
19%414%26%24%10%
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
20%22%17%22%16%1
90
16th to endDay
430%28%19%16%1
96
February1st to 15thDay
5%37%35%15%5%
90
16th to endDay
13%28%32%19%32
81
March1st to 15thDay
10%31%38%16%2
138
16th to endDay
17%40%29%9%2
288
April1st to 15thDay
13%40%28%11%31
269
16th to endDay
18%38%30%11%1
270
May1st to 15thDay
13%24%36%17%6%1
372
16th to endDay
9%20%31%24%10%2
517
June1st to 15thDay
6%14%30%27%15%5%
495
16th to endDay
37%30%30%21%6%
495
July1st to 15thDay
9%322%30%25%8%
475
16th to endDay
8%217%36%24%10%
405
August1st to 15thDay
11%420%37%17%7%
315
16th to endDay
9%332%35%15%2
332
September1st to 15thDay
5%10%37%27%14%4
315
16th to endDay
6%13%29%32%12%4
131
October1st to 15thDay
320%30%26%12%7%
90
16th to endDay
8%21%25%27%14%3
96
November1st to 15thDay
314%26%30%21%4
90
16th to endDay
12%28%36%14%7%
90
December1st to 15thDay
5%43%31%16%21
90
16th to endDay
12%36%31%17%2
96
January1st to 15thNight
422%31%25%11%3
873
16th to endNight
5%25%35%23%10%1
768
February1st to 15thNight
423%40%25%5%
704
16th to endNight
5%29%40%21%3
632
March1st to 15thNight
6%25%34%24%7%1
720
16th to endNight
7%25%35%26%4
678
April1st to 15thNight
7%28%39%19%4
539
16th to endNight
9%25%31%25%8%
540
May1st to 15thNight
8%16%35%30%7%1
540
16th to endNight
7%14%35%26%13%2
563
June1st to 15thNight
410%34%31%15%2
540
16th to endNight
2432%34%23%2
540
July1st to 15thNight
6%318%35%31%4
510
16th to endNight
5%110%32%42%8%
564
August1st to 15thNight
4214%32%39%6%
539
16th to endNight
7%115%32%36%6%
573
September1st to 15thNight
8%223%32%27%5%
540
16th to endNight
5%8%24%34%22%4
498
October1st to 15thNight
6%14%30%28%15%4
630
16th to endNight
415%29%30%15%4
704
November1st to 15thNight
319%31%30%13%1
872
16th to endNight
419%31%29%12%2
900
December1st to 15thNight
425%37%24%6%1
900
16th to endNight
5%27%32%26%7%1
960
Page generated at 2017-09-18 06:38:28. Version ac04

Copyright 2017 A. Danko


Picketwire Observatory Clear Sky Chart | Charts Home