Poinsettia Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Poinsettia Observatory clear sky chart from 2005-11-05 to 2017-09-21.

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
76%
16271
30%
47021
28%
16227
77%
16227
44%
25765

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
71%
717
29%
2315
30%
716
74%
716
42%
1203
January16th to endNight
69%
768
33%
2304
32%
768
72%
768
39%
1289
February1st to 15thNight
72%
698
32%
2106
34%
698
75%
698
43%
1125
February16th to endNight
62%
632
26%
1895
30%
632
63%
632
31%
1163
March1st to 15thNight
70%
720
28%
2160
31%
720
72%
720
40%
1194
March16th to endNight
73%
768
26%
2037
25%
768
74%
768
41%
1212
April1st to 15thNight
67%
719
25%
1799
18%
719
67%
719
41%
1106
April16th to endNight
72%
720
28%
1800
18%
720
73%
720
45%
1080
May1st to 15thNight
71%
587
25%
1667
19%
587
71%
587
38%
1009
May16th to endNight
67%
561
23%
1685
18%
561
68%
561
34%
1048
June1st to 15thNight
75%
540
21%
1620
19%
540
75%
540
37%
979
June16th to endNight
89%
540
31%
1620
27%
540
89%
540
57%
773
July1st to 15thNight
87%
510
23%
1530
20%
510
87%
510
46%
815
July16th to endNight
84%
638
27%
1661
20%
599
84%
599
44%
943
August1st to 15thNight
85%
717
30%
1790
20%
713
85%
713
55%
969
August16th to endNight
88%
764
36%
1910
26%
764
88%
764
60%
1010
September1st to 15thNight
85%
720
33%
1872
28%
720
85%
720
56%
982
September16th to endNight
86%
680
41%
1881
40%
680
87%
680
60%
902
October1st to 15thNight
79%
660
34%
1815
33%
660
80%
660
49%
964
October16th to endNight
74%
704
35%
2103
37%
704
75%
704
45%
1093
November1st to 15thNight
81%
700
33%
2275
39%
700
82%
700
49%
1076
November16th to endNight
78%
720
33%
2340
37%
720
80%
720
43%
1179
December1st to 15thNight
68%
720
31%
2340
35%
720
70%
720
36%
1274
December16th to endNight
65%
768
31%
2496
31%
768
69%
768
36%
1377

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%313313346%63%
47827
Night
6%5%23323347%58%
47229
TransparencyDay
22%26%17%25%24%
47529
Night
27%37%16%22%23%
47028
SeeingDay
7%5%23%41%18%4
5944
Night
8%16%30%40%12%
16283

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
9%414312345%58%
1620
16th to endDay
11%5%13313345%55%
1920
February1st to 15thDay
8%413324445%57%
1751
16th to endDay
13%6%245%24448%45%
1579
March1st to 15thDay
7%32332335%9%55%
1800
16th to endDay
6%323324447%57%
2184
April1st to 15thDay
7%5%23423346%55%
2149
16th to endDay
6%312212247%66%
2160
May1st to 15thDay
6%5%13212437%60%
2281
16th to endDay
5%423312236%63%
2429
June1st to 15thDay
5%5%23222245%63%
2340
16th to endDay
1111212225%78%
2340
July1st to 15thDay
2313323347%64%
2340
16th to endDay
221221345%8%63%
2390
August1st to 15thDay
1212212235%74%
2160
16th to endDay
112222336%73%
2292
September1st to 15thDay
1212211336%72%
2088
16th to endDay
1211211335%75%
1871
October1st to 15thDay
5%414322446%61%
1815
16th to endDay
7%412112225%68%
1766
November1st to 15thDay
5%212323346%64%
1584
16th to endDay
7%313213347%61%
1620
December1st to 15thDay
9%313423448%53%
1620
16th to endDay
13%413323346%53%
1728
January1st to 15thNight
7%413424346%58%
2315
16th to endNight
11%413323246%55%
2304
February1st to 15thNight
8%323313346%59%
2101
16th to endNight
13%6%24424345%47%
1895
March1st to 15thNight
8%5%24214448%53%
2160
16th to endNight
7%5%2332345%9%51%
2037
April1st to 15thNight
10%7%24312347%52%
1799
16th to endNight
8%6%23323336%58%
1800
May1st to 15thNight
6%9%34324338%50%
1667
16th to endNight
9%10%2432335%7%48%
1684
June1st to 15thNight
49%4332445%9%47%
1620
16th to endNight
121123236%7%66%
1620
July1st to 15thNight
26%1223446%7%57%
1620
16th to endNight
33133345%6%9%54%
1775
August1st to 15thNight
241232335%8%62%
1800
16th to endNight
1312312447%66%
1910
September1st to 15thNight
141332235%6%65%
1872
16th to endNight
3311212125%73%
1881
October1st to 15thNight
4412323346%62%
1815
16th to endNight
7%313322335%62%
2103
November1st to 15thNight
5%21231343466%
2275
16th to endNight
5%423323436%60%
2340
December1st to 15thNight
10%425%323347%53%
2340
16th to endNight
13%413313346%54%
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
28%26%12%23%27%
1621
16th to endDay
30%38%14%14%29%
1920
February1st to 15thDay
26%36%14%22%26%
1751
16th to endDay
36%48%14%23%12%
1579
March1st to 15thDay
26%27%19%21%21%
1800
16th to endDay
26%48%25%19%14%
2184
April1st to 15thDay
29%38%23%25%10%
2149
16th to endDay
20%38%24%24%19%
2160
May1st to 15thDay
25%27%21%25%16%
2281
16th to endDay
24%27%24%31%10%
2432
June1st to 15thDay
25%15%17%29%20%
2340
16th to endDay
13%137%29%45%
2340
July1st to 15thDay
20%35%13%26%31%
2201
16th to endDay
18%411%23%28%13%
2241
August1st to 15thDay
15%2318%34%26%
2146
16th to endDay
14%2415%35%28%
2292
September1st to 15thDay
15%3312%34%30%
2088
16th to endDay
13%2312%35%32%
1871
October1st to 15thDay
24%25%17%24%24%
1815
16th to endDay
20%1412%22%37%
1766
November1st to 15thDay
21%27%16%17%35%
1584
16th to endDay
23%26%15%18%33%
1620
December1st to 15thDay
28%310%15%16%25%
1620
16th to endDay
32%38%16%22%17%
1728
January1st to 15thNight
26%36%13%20%29%
2315
16th to endNight
30%38%11%14%31%
2304
February1st to 15thNight
26%37%15%20%27%
2112
16th to endNight
38%36%13%21%15%
1895
March1st to 15thNight
30%28%18%17%22%
2160
16th to endNight
29%5%10%19%20%14%
2037
April1st to 15thNight
33%28%24%20%11%
1799
16th to endNight
29%37%21%20%18%
1800
May1st to 15thNight
34%39%19%16%16%
1668
16th to endNight
36%38%22%16%11%
1685
June1st to 15thNight
34%29%15%23%13%
1620
16th to endNight
19%311%28%36%
1620
July1st to 15thNight
25%26%12%26%26%
1530
16th to endNight
25%5%9%23%25%9%
1661
August1st to 15thNight
22%25%21%31%17%
1790
16th to endNight
18%25%13%33%26%
1910
September1st to 15thNight
20%25%12%31%27%
1872
16th to endNight
17%1212%35%30%
1881
October1st to 15thNight
23%36%19%24%23%
1815
16th to endNight
26%2311%20%35%
2103
November1st to 15thNight
21%26%16%15%37%
2275
16th to endNight
25%36%16%16%32%
2340
December1st to 15thNight
31%37%15%18%24%
2340
16th to endNight
30%49%14%18%21%
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
24%219%37%17%
99
16th to endDay
13%9%29%36%7%2
288
February1st to 15thDay
8%6%31%38%14%1
266
16th to endDay
12%12%35%28%9%1
238
March1st to 15thDay
8%10%29%34%12%4
270
16th to endDay
410%30%38%11%4
288
April1st to 15thDay
8%10%37%29%9%3
269
16th to endDay
413%38%31%7%3
270
May1st to 15thDay
12%8%30%36%10%2
288
16th to endDay
9%7%30%36%15%1
330
June1st to 15thDay
5%224%46%18%2
315
16th to endDay
114%48%26%7%
315
July1st to 15thDay
5%9%46%31%6%
305
16th to endDay
5%347%33%10%
327
August1st to 15thDay
310%53%26%5%
315
16th to endDay
26%55%29%6%
332
September1st to 15thDay
3120%53%16%4
315
16th to endDay
4222%51%14%5%
276
October1st to 15thDay
46%40%34%12%1
255
16th to endDay
11%126%37%18%4
217
November1st to 15thDay
25%17%30%32%12%
90
16th to endDay
6%8%21%36%24%2
90
December1st to 15thDay
4314%38%32%6%
90
16th to endDay
17%317%37%21%2
96
January1st to 15thNight
7%110%38%29%12%
720
16th to endNight
12%29%37%29%8%
768
February1st to 15thNight
9%27%35%34%9%
704
16th to endNight
14%29%42%25%5%
632
March1st to 15thNight
10%37%40%31%6%
720
16th to endNight
9%27%35%36%7%
768
April1st to 15thNight
11%39%39%29%6%
719
16th to endNight
10%28%36%32%9%
720
May1st to 15thNight
9%18%34%37%7%
588
16th to endNight
11%29%32%40%4
563
June1st to 15thNight
8%8%39%38%4
540
16th to endNight
2228%59%6%
540
July1st to 15thNight
4214%65%12%
510
16th to endNight
4211%60%20%
638
August1st to 15thNight
4114%59%18%
717
16th to endNight
319%56%29%
764
September1st to 15thNight
4117%58%17%
720
16th to endNight
4327%48%15%
680
October1st to 15thNight
5%15%35%41%9%
660
16th to endNight
9%16%29%33%19%
704
November1st to 15thNight
6%15%34%37%14%
700
16th to endNight
6%6%33%35%17%
720
December1st to 15thNight
10%110%35%29%11%
720
16th to endNight
14%210%34%27%10%
768
Page generated at 2017-09-22 04:35:35. Version ac04

Copyright 2017 A. Danko


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