OPT Parking Lot
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the OPT Parking Lot clear sky chart from 2005-11-05 to 2018-10-08.

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
72%
17728
28%
51151
27%
17683
73%
17683
39%
29352

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
75%
777
29%
2499
31%
776
76%
776
41%
1303
January16th to endNight
69%
832
33%
2496
33%
832
72%
832
39%
1389
February1st to 15thNight
74%
758
33%
2285
35%
758
77%
758
43%
1227
February16th to endNight
64%
684
28%
2051
31%
684
65%
684
31%
1264
March1st to 15thNight
69%
780
26%
2340
29%
780
71%
780
37%
1332
March16th to endNight
70%
832
23%
2194
22%
832
71%
832
37%
1358
April1st to 15thNight
64%
779
25%
1949
17%
779
65%
779
37%
1244
April16th to endNight
69%
772
26%
1930
17%
772
70%
772
41%
1195
May1st to 15thNight
65%
649
23%
1820
17%
649
65%
649
31%
1198
May16th to endNight
61%
609
19%
1829
16%
609
61%
609
28%
1221
June1st to 15thNight
60%
585
16%
1755
14%
585
60%
585
26%
1210
June16th to endNight
71%
585
19%
1755
17%
585
71%
585
34%
1084
July1st to 15thNight
74%
555
20%
1665
17%
555
74%
555
35%
1015
July16th to endNight
74%
710
21%
1828
16%
670
73%
670
36%
1131
August1st to 15thNight
72%
765
25%
1910
16%
761
72%
761
41%
1179
August16th to endNight
83%
828
31%
2070
23%
828
83%
828
52%
1163
September1st to 15thNight
79%
780
32%
2013
27%
780
79%
780
47%
1139
September16th to endNight
81%
776
37%
2145
37%
776
81%
776
52%
1090
October1st to 15thNight
79%
752
33%
2068
33%
752
79%
752
49%
1112
October16th to endNight
74%
768
36%
2305
38%
768
75%
768
45%
1190
November1st to 15thNight
81%
760
31%
2470
36%
760
82%
760
45%
1207
November16th to endNight
78%
780
34%
2535
38%
780
79%
780
42%
1298
December1st to 15thNight
70%
780
31%
2535
33%
780
72%
780
38%
1357
December16th to endNight
68%
832
33%
2704
34%
832
72%
832
38%
1446

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
441332345%8%58%
51968
Night
6%6%24423447%51%
51360
TransparencyDay
23%37%17%25%22%
51671
Night
31%37%15%21%21%
51158
SeeingDay
6%216%37%28%8%
7389
Night
9%15%28%41%13%
17740

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
7%42332336%6%56%
1768
16th to endDay
8%424323346%57%
2080
February1st to 15thDay
6%213323447%59%
1901
16th to endDay
8%5%24315%45%7%51%
1709
March1st to 15thDay
421342446%9%56%
1950
16th to endDay
442332347%8%56%
2379
April1st to 15thDay
5%423313449%55%
2329
16th to endDay
331322345%8%61%
2305
May1st to 15thDay
5%5%24324449%53%
2458
16th to endDay
5%5%2332335%8%56%
2637
June1st to 15thDay
5%7%2432345%9%52%
2535
16th to endDay
16%2331325%9%60%
2535
July1st to 15thDay
35%2342347%11%51%
2535
16th to endDay
241332436%12%55%
2574
August1st to 15thDay
231221235%8%65%
2293
16th to endDay
1232235%5%10%62%
2484
September1st to 15thDay
131332235%9%62%
2275
16th to endDay
2312312347%65%
2145
October1st to 15thDay
331442345%7%59%
2061
16th to endDay
4313213447%64%
1914
November1st to 15thDay
321332436%7%61%
1719
16th to endDay
4214213448%61%
1755
December1st to 15thDay
6%223423348%57%
1755
16th to endDay
9%323323446%56%
1872
January1st to 15thNight
6%324324447%56%
2499
16th to endNight
9%5%24323336%56%
2496
February1st to 15thNight
7%414323345%58%
2281
16th to endNight
10%6%36%5%3344447%
2051
March1st to 15thNight
7%6%24423448%50%
2340
16th to endNight
6%5%35%5%2346%7%48%
2194
April1st to 15thNight
9%8%3442325%7%48%
1949
16th to endNight
7%8%24323345%53%
1930
May1st to 15thNight
9%10%35%5%33349%41%
1819
16th to endNight
10%13%45%423447%38%
1828
June1st to 15thNight
8%15%5%7%424438%33%
1755
16th to endNight
311%46%5%35%45%10%39%
1755
July1st to 15thNight
5%11%35%5%345%5%9%41%
1755
16th to endNight
5%7%25%5%35%5%6%10%42%
1943
August1st to 15thNight
311%26%43435%8%47%
1920
16th to endNight
25%143245%6%11%53%
2070
September1st to 15thNight
36%2332345%7%56%
2013
16th to endNight
35%14212346%64%
2145
October1st to 15thNight
2415%42335%7%59%
2068
16th to endNight
5%5%23312346%60%
2305
November1st to 15thNight
3413223446%62%
2470
16th to endNight
442432445%7%56%
2535
December1st to 15thNight
7%32443335%7%54%
2535
16th to endNight
10%413323345%57%
2704

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
26%37%16%21%24%
1769
16th to endDay
27%37%16%14%29%
2080
February1st to 15thDay
24%46%14%24%25%
1901
16th to endDay
31%5%6%17%27%11%
1709
March1st to 15thDay
23%49%22%20%19%
1950
16th to endDay
24%412%23%22%12%
2379
April1st to 15thDay
26%49%25%22%11%
2329
16th to endDay
20%410%23%24%16%
2305
May1st to 15thDay
27%47%21%23%15%
2458
16th to endDay
24%47%27%28%7%
2640
June1st to 15thDay
28%35%17%30%14%
2535
16th to endDay
20%238%27%37%
2535
July1st to 15thDay
24%45%12%25%27%
2396
16th to endDay
20%5%12%23%25%13%
2426
August1st to 15thDay
17%2315%33%27%
2279
16th to endDay
17%35%15%33%23%
2484
September1st to 15thDay
19%2412%31%29%
2275
16th to endDay
18%2312%34%29%
2145
October1st to 15thDay
22%36%18%25%24%
2061
16th to endDay
19%35%13%21%36%
1914
November1st to 15thDay
21%37%18%17%30%
1719
16th to endDay
21%37%15%20%31%
1755
December1st to 15thDay
25%310%15%18%26%
1755
16th to endDay
28%48%16%21%20%
1872
January1st to 15thNight
27%37%14%20%26%
2499
16th to endNight
30%26%13%14%30%
2496
February1st to 15thNight
26%37%15%22%24%
2292
16th to endNight
38%3414%25%13%
2051
March1st to 15thNight
31%37%19%18%18%
2340
16th to endNight
32%5%10%18%19%12%
2194
April1st to 15thNight
35%37%22%18%11%
1949
16th to endNight
31%47%19%21%16%
1930
May1st to 15thNight
41%37%15%17%14%
1820
16th to endNight
43%47%19%16%8%
1829
June1st to 15thNight
47%37%10%21%9%
1755
16th to endNight
37%25%7%24%22%
1755
July1st to 15thNight
36%25%12%21%20%
1665
16th to endNight
35%311%20%21%7%
1828
August1st to 15thNight
32%35%16%25%15%
1910
16th to endNight
23%27%14%30%21%
2070
September1st to 15thNight
26%3410%31%23%
2013
16th to endNight
21%2412%31%27%
2145
October1st to 15thNight
23%36%20%26%20%
2068
16th to endNight
26%25%11%20%34%
2305
November1st to 15thNight
23%36%17%16%32%
2470
16th to endNight
25%37%15%17%30%
2535
December1st to 15thNight
29%38%14%18%25%
2535
16th to endNight
28%38%14%22%21%
2704

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
21%18%33%27%6%
157
16th to endDay
11%321%38%17%7%
352
February1st to 15thDay
7%322%34%24%8%
326
16th to endDay
9%7%28%33%17%3
290
March1st to 15thDay
6%226%35%21%6%
330
16th to endDay
5%425%39%18%6%
352
April1st to 15thDay
9%429%35%16%5%
329
16th to endDay
25%31%38%15%5%
318
May1st to 15thDay
9%5%22%36%21%4
348
16th to endDay
8%224%40%20%3
394
June1st to 15thDay
8%15%38%30%6%
375
16th to endDay
47%40%37%9%
375
July1st to 15thDay
6%431%44%13%
365
16th to endDay
5%132%44%15%
391
August1st to 15thDay
45%38%38%11%
359
16th to endDay
5%5%33%42%12%
396
September1st to 15thDay
5%19%48%30%5%
375
16th to endDay
5%14%44%26%8%
375
October1st to 15thDay
4222%42%23%4
345
16th to endDay
5%116%35%27%12%
288
November1st to 15thDay
5%49%28%37%14%
135
16th to endDay
4313%34%29%14%
135
December1st to 15thDay
214%34%33%14%
135
16th to endDay
9%116%26%32%13%
144
January1st to 15thNight
8%16%40%33%11%
780
16th to endNight
11%17%35%34%9%
832
February1st to 15thNight
8%16%33%37%11%
764
16th to endNight
11%37%41%29%6%
684
March1st to 15thNight
10%27%38%33%8%
780
16th to endNight
9%25%34%38%8%
832
April1st to 15thNight
13%210%33%33%6%
779
16th to endNight
9%28%33%36%9%
772
May1st to 15thNight
14%17%30%36%8%
650
16th to endNight
13%18%28%41%6%
611
June1st to 15thNight
14%15%32%39%6%
585
16th to endNight
7%422%55%9%
585
July1st to 15thNight
9%213%52%21%
555
16th to endNight
8%27%51%28%
710
August1st to 15thNight
9%1210%51%25%
765
16th to endNight
5%18%49%33%
828
September1st to 15thNight
7%213%56%19%
780
16th to endNight
5%1221%52%16%
776
October1st to 15thNight
45%34%44%10%
752
16th to endNight
9%15%24%41%17%
768
November1st to 15thNight
5%433%40%15%
760
16th to endNight
7%5%29%38%17%
780
December1st to 15thNight
10%27%35%35%9%
780
16th to endNight
13%19%34%30%9%
832
Page generated at 2018-10-09 07:39:13. Version ac04

Copyright 2018 A. Danko


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