Pleasant Grove Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Pleasant Grove Observatory clear sky chart from 2005-11-05 to 2019-07-16.

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
47%
18029
22%
54236
15%
17986
56%
17986
27%
34043

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
29%
840
24%
2717
11%
836
45%
836
19%
1697
January16th to endNight
28%
896
26%
2912
12%
896
45%
896
22%
1763
February1st to 15thNight
31%
824
26%
2488
11%
821
47%
821
24%
1531
February16th to endNight
27%
735
24%
2205
10%
735
41%
735
24%
1396
March1st to 15thNight
31%
840
25%
2360
11%
840
42%
840
27%
1484
March16th to endNight
38%
896
21%
2464
11%
896
46%
896
28%
1563
April1st to 15thNight
42%
824
25%
2292
14%
824
50%
824
32%
1380
April16th to endNight
46%
624
24%
1906
14%
624
56%
624
31%
1127
May1st to 15thNight
51%
630
20%
1890
12%
630
57%
630
30%
1177
May16th to endNight
60%
657
19%
1971
14%
657
63%
657
27%
1258
June1st to 15thNight
65%
630
16%
1890
13%
630
66%
630
29%
1208
June16th to endNight
71%
630
14%
1890
13%
630
72%
630
31%
1188
July1st to 15thNight
65%
600
10%
1800
8%
600
65%
600
21%
1271
July16th to endNight
72%
615
14%
1748
11%
582
74%
582
25%
1173
August1st to 15thNight
68%
575
15%
1715
15%
572
68%
572
22%
1194
August16th to endNight
65%
648
14%
2039
14%
648
66%
648
21%
1405
September1st to 15thNight
64%
780
16%
2145
14%
780
65%
780
25%
1481
September16th to endNight
58%
777
22%
2145
17%
777
62%
777
29%
1404
October1st to 15thNight
54%
780
29%
2203
23%
780
61%
780
34%
1334
October16th to endNight
53%
832
34%
2496
25%
832
66%
832
38%
1365
November1st to 15thNight
51%
820
30%
2588
24%
820
61%
820
34%
1464
November16th to endNight
43%
840
27%
2730
20%
840
56%
840
30%
1537
December1st to 15thNight
36%
840
24%
2730
14%
840
49%
840
22%
1716
December16th to endNight
31%
896
21%
2912
14%
896
42%
896
19%
1927

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
13%5%245%3445%7%42%
55074
Night
13%42442445%7%45%
54434
TransparencyDay
39%7%11%19%17%4
54775
Night
37%6%11%19%19%6%
54237
SeeingDay
18%6%20%23%19%11%
7875
Night
16%7%21%29%21%3
18031

By Month

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
18%5%2442334445%
1881
16th to endDay
17%5%24313345%48%
2016
February1st to 15thDay
17%5%244235%45%43%
2033
16th to endDay
20%5%35%423346%42%
1840
March1st to 15thDay
16%4245%23346%46%
2260
16th to endDay
15%5%245%3445%6%44%
2463
April1st to 15thDay
13%425%325%45%7%45%
2326
16th to endDay
11%314424447%49%
2657
May1st to 15thDay
10%4245%35%46%7%44%
2721
16th to endDay
12%4245%35%5%6%9%41%
2847
June1st to 15thDay
10%425%5%46%6%7%11%34%
2730
16th to endDay
42147%37%7%8%11%39%
2730
July1st to 15thDay
10%5%36%6%36%7%7%11%31%
2730
16th to endDay
7%5%25%7%46%7%8%12%32%
2676
August1st to 15thDay
11%5%16%6%47%7%7%9%31%
2487
16th to endDay
13%6%36%7%36%5%7%9%29%
2496
September1st to 15thDay
12%5%25%6%45%6%6%8%36%
2145
16th to endDay
17%5%2342345%7%43%
2145
October1st to 15thDay
15%414212335%54%
2087
16th to endDay
11%31332223460%
2080
November1st to 15thDay
15%323323345%52%
1928
16th to endDay
14%5%14313346%51%
1890
December1st to 15thDay
20%7%25%333345%41%
1890
16th to endDay
25%7%2442233438%
2016
January1st to 15thNight
17%5%25%32433446%
2717
16th to endNight
17%6%23423345%47%
2912
February1st to 15thNight
16%5%23423345%48%
2479
16th to endNight
19%423423345%45%
2205
March1st to 15thNight
14%42442445%5%48%
2360
16th to endNight
13%42442436%7%46%
2464
April1st to 15thNight
13%313423347%50%
2292
16th to endNight
11%314423446%50%
1906
May1st to 15thNight
10%5%2443445%8%45%
1889
16th to endNight
9%5%15%445%5%6%8%43%
1970
June1st to 15thNight
7%5%245%35%6%7%13%37%
1890
16th to endNight
5%3245%25%6%10%12%40%
1890
July1st to 15thNight
9%5%37%5%45%7%6%11%32%
1890
16th to endNight
5%425%6%37%7%9%15%32%
1856
August1st to 15thNight
11%5%145%46%7%10%9%31%
1726
16th to endNight
10%5%25%6%46%7%7%11%33%
2039
September1st to 15thNight
10%415%5%46%7%7%9%36%
2145
16th to endNight
14%5%244335%5%7%43%
2145
October1st to 15thNight
14%323323346%52%
2203
16th to endNight
10%313323335%59%
2496
November1st to 15thNight
14%323413235%55%
2588
16th to endNight
14%323413346%52%
2730
December1st to 15thNight
18%5%25%423345%44%
2730
16th to endNight
21%6%25%423336%39%
2912

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
42%48%16%23%4
1882
16th to endDay
38%36%19%23%8%
2016
February1st to 15thDay
41%48%19%21%4
2035
16th to endDay
43%46%19%18%6%
1840
March1st to 15thDay
39%48%18%19%9%
2260
16th to endDay
40%5%10%21%17%4
2464
April1st to 15thDay
37%5%10%20%21%5%
2326
16th to endDay
34%6%9%21%21%6%
2657
May1st to 15thDay
35%8%13%20%18%3
2721
16th to endDay
38%9%13%21%15%2
2851
June1st to 15thDay
40%10%18%19%9%1
2730
16th to endDay
33%12%18%20%12%2
2730
July1st to 15thDay
41%13%17%17%7%2
2591
16th to endDay
39%13%19%18%7%1
2521
August1st to 15thDay
44%11%14%18%8%1
2474
16th to endDay
48%11%15%14%9%1
2496
September1st to 15thDay
43%8%13%16%15%2
2145
16th to endDay
39%6%11%20%17%4
2145
October1st to 15thDay
32%411%20%23%6%
2087
16th to endDay
29%35%19%29%12%
2080
November1st to 15thDay
34%47%17%25%10%
1928
16th to endDay
34%48%20%26%7%
1890
December1st to 15thDay
45%46%18%17%7%
1890
16th to endDay
49%47%18%13%6%
2016
January1st to 15thNight
41%36%15%25%6%
2717
16th to endNight
39%35%19%22%9%
2912
February1st to 15thNight
38%37%19%23%7%
2488
16th to endNight
40%48%20%20%6%
2205
March1st to 15thNight
37%5%10%15%22%9%
2360
16th to endNight
37%5%11%18%21%6%
2464
April1st to 15thNight
33%49%23%21%7%
2292
16th to endNight
33%6%10%21%19%9%
1906
May1st to 15thNight
36%6%14%20%19%2
1890
16th to endNight
35%9%12%24%13%3
1972
June1st to 15thNight
35%9%19%22%11%1
1890
16th to endNight
30%13%20%21%12%2
1890
July1st to 15thNight
41%13%19%16%6%1
1800
16th to endNight
35%14%22%18%7%2
1748
August1st to 15thNight
41%12%17%18%9%
1715
16th to endNight
39%14%18%15%10%1
2039
September1st to 15thNight
38%13%15%16%12%3
2145
16th to endNight
38%7%13%19%16%5%
2145
October1st to 15thNight
33%5%10%20%23%7%
2203
16th to endNight
28%45%18%30%12%
2496
November1st to 15thNight
32%36%17%27%11%
2588
16th to endNight
32%47%18%27%10%
2730
December1st to 15thNight
42%47%19%18%7%
2730
16th to endNight
47%38%16%18%5%
2912

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
30%10%31%25%3
180
16th to endDay
24%19%33%17%31
192
February1st to 15thDay
27%17%37%15%2
180
16th to endDay
35%11%36%15%
159
March1st to 15thDay
21%17%30%24%6%
340
16th to endDay
18%12%35%19%11%1
416
April1st to 15thDay
21%10%26%23%15%2
390
16th to endDay
15%5%27%26%18%6%
379
May1st to 15thDay
10%8%26%21%21%10%
408
16th to endDay
18%414%22%24%15%
459
June1st to 15thDay
14%312%25%25%18%
435
16th to endDay
7%115%26%24%23%
435
July1st to 15thDay
12%18%22%28%26%
425
16th to endDay
10%16%27%31%22%
391
August1st to 15thDay
19%18%22%28%20%
358
16th to endDay
15%110%25%27%19%
396
September1st to 15thDay
14%29%20%32%20%
375
16th to endDay
21%110%25%28%12%
374
October1st to 15thDay
21%317%26%19%11%
375
16th to endDay
13%8%21%26%25%5%
400
November1st to 15thDay
28%7%23%23%15%1
256
16th to endDay
15%8%31%28%12%3
180
December1st to 15thDay
35%12%30%15%5%
180
16th to endDay
34%16%29%17%2
192
January1st to 15thNight
22%16%25%26%8%
840
16th to endNight
21%16%30%27%3
896
February1st to 15thNight
19%14%30%31%4
824
16th to endNight
20%15%33%26%3
735
March1st to 15thNight
18%12%34%28%5%
840
16th to endNight
16%11%28%28%13%
896
April1st to 15thNight
14%11%28%31%13%
824
16th to endNight
12%8%25%30%21%
624
May1st to 15thNight
11%424%33%22%2
630
16th to endNight
14%214%31%31%5%
659
June1st to 15thNight
10%113%31%32%9%
630
16th to endNight
7%11%30%37%11%
630
July1st to 15thNight
12%16%28%38%12%
600
16th to endNight
6%7%30%44%10%
615
August1st to 15thNight
13%6%27%41%10%
575
16th to endNight
13%8%27%38%11%
648
September1st to 15thNight
12%111%23%40%10%
780
16th to endNight
17%114%29%32%4
777
October1st to 15thNight
16%420%26%25%6%
780
16th to endNight
11%7%22%32%24%2
832
November1st to 15thNight
15%5%22%32%21%1
820
16th to endNight
15%10%25%30%16%1
840
December1st to 15thNight
21%11%24%30%11%
840
16th to endNight
25%10%26%29%7%
896
Page generated at 2019-07-17 08:53:06. Version ac04

Copyright 2019 A. Danko


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