Little Piney Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Little Piney Observatory clear sky chart from 2005-11-05 to 2017-09-18.

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
50%
15699
24%
47213
18%
15655
57%
15655
32%
28092

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
35%
898
28%
2327
11%
895
45%
895
31%
1457
January16th to endNight
34%
960
29%
2496
11%
960
44%
960
34%
1543
February1st to 15thNight
32%
880
21%
2288
7%
876
40%
876
30%
1472
February16th to endNight
28%
598
27%
1860
10%
598
42%
598
29%
1091
March1st to 15thNight
37%
540
21%
1980
16%
540
46%
540
21%
1217
March16th to endNight
38%
576
19%
2112
18%
576
44%
576
22%
1333
April1st to 15thNight
38%
539
24%
1824
15%
539
51%
539
29%
1046
April16th to endNight
40%
540
22%
1800
17%
540
51%
540
26%
1098
May1st to 15thNight
47%
539
19%
1686
17%
539
53%
539
26%
1082
May16th to endNight
60%
562
19%
1685
18%
561
63%
561
30%
1053
June1st to 15thNight
75%
540
22%
1620
22%
540
77%
540
45%
848
June16th to endNight
78%
540
24%
1620
24%
540
79%
540
45%
857
July1st to 15thNight
74%
510
18%
1530
18%
510
75%
510
37%
896
July16th to endNight
85%
564
24%
1594
27%
531
85%
531
42%
867
August1st to 15thNight
79%
539
23%
1612
27%
536
80%
536
39%
911
August16th to endNight
78%
573
23%
1910
28%
573
79%
573
34%
1083
September1st to 15thNight
70%
540
26%
1800
28%
540
72%
540
34%
1006
September16th to endNight
70%
530
30%
1863
28%
530
74%
530
34%
1000
October1st to 15thNight
56%
660
30%
1980
23%
660
61%
660
36%
1132
October16th to endNight
53%
704
34%
2112
23%
704
62%
704
40%
1139
November1st to 15thNight
51%
700
31%
2100
21%
700
60%
700
37%
1165
November16th to endNight
39%
807
27%
2356
16%
807
48%
807
28%
1460
December1st to 15thNight
37%
900
20%
2520
11%
900
43%
900
27%
1626
December16th to endNight
35%
960
24%
2538
11%
960
43%
960
25%
1710

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
15%424424446%45%
47572
Night
14%423323346%50%
47408
TransparencyDay
38%6%11%22%17%3
47272
Night
33%5%11%23%20%5%
47213
SeeingDay
13%5%18%27%25%8%
5748
Night
15%7%21%32%20%2
15703

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
19%5%1331313451%
1611
16th to endDay
16%424322335%50%
1728
February1st to 15thDay
19%5%3432323349%
1575
16th to endDay
19%7%34422245%44%
1621
March1st to 15thDay
20%5%14323436%43%
1980
16th to endDay
22%6%34423335%39%
2110
April1st to 15thDay
20%5%14313345%44%
2123
16th to endDay
23%5%14424445%38%
2160
May1st to 15thDay
20%6%346%34346%37%
2263
16th to endDay
14%6%36%5%346%5%7%36%
2430
June1st to 15thDay
10%424435%5%7%9%41%
2340
16th to endDay
7%3145%35%6%7%9%44%
2340
July1st to 15thDay
9%5%246%46%6%7%9%37%
2340
16th to endDay
6%3146%36%6%6%9%45%
2466
August1st to 15thDay
8%4245%35%5%6%10%43%
2337
16th to endDay
9%4246%46%5%5%8%42%
2292
September1st to 15thDay
14%323325%45%6%48%
2160
16th to endDay
10%314424447%51%
1807
October1st to 15thDay
15%423323345%51%
1650
16th to endDay
15%31221343458%
1760
November1st to 15thDay
14%423313135%56%
1758
16th to endDay
20%42422233349%
1598
December1st to 15thDay
20%5%13322346%46%
1440
16th to endDay
24%5%23323235%44%
1683
January1st to 15thNight
18%41222224353%
2327
16th to endNight
15%5%2322233454%
2496
February1st to 15thNight
17%6%23223345%48%
2278
16th to endNight
16%423312346%51%
1860
March1st to 15thNight
21%413324345%43%
1980
16th to endNight
21%6%14323335%44%
2112
April1st to 15thNight
14%323323447%49%
1824
16th to endNight
16%42443345%6%44%
1800
May1st to 15thNight
16%424325%35%7%44%
1685
16th to endNight
10%5%2442445%10%45%
1683
June1st to 15thNight
6%21222345%10%57%
1620
16th to endNight
5%31231446%10%57%
1620
July1st to 15thNight
43245%3448%11%47%
1620
16th to endNight
413325%5%7%11%54%
1702
August1st to 15thNight
5%213435%46%9%52%
1622
16th to endNight
6%3234245%7%10%48%
1910
September1st to 15thNight
10%42332245%8%52%
1800
16th to endNight
7%32333436%6%53%
1863
October1st to 15thNight
13%313222346%54%
1980
16th to endNight
15%21221223462%
2112
November1st to 15thNight
11%423213346%56%
2100
16th to endNight
20%42221323451%
2356
December1st to 15thNight
21%5%2342232447%
2520
16th to endNight
20%6%25%313235%45%
2538

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
38%37%26%19%4
1612
16th to endDay
37%47%26%20%3
1728
February1st to 15thDay
41%310%24%16%3
1576
16th to endDay
43%310%20%17%4
1621
March1st to 15thDay
42%5%10%18%16%6%
1980
16th to endDay
48%49%22%12%2
2112
April1st to 15thDay
41%5%9%20%19%3
2123
16th to endDay
46%6%8%17%18%2
2160
May1st to 15thDay
48%6%9%16%16%1
2263
16th to endDay
43%9%12%21%11%1
2434
June1st to 15thDay
36%8%14%23%17%
2340
16th to endDay
32%9%15%24%15%2
2340
July1st to 15thDay
38%9%15%24%9%1
2201
16th to endDay
31%10%17%26%13%1
2311
August1st to 15thDay
34%9%16%22%15%2
2323
16th to endDay
36%9%16%19%13%4
2292
September1st to 15thDay
35%7%11%20%16%7%
2160
16th to endDay
31%6%10%21%25%4
1807
October1st to 15thDay
35%48%21%21%7%
1650
16th to endDay
30%47%23%25%8%
1760
November1st to 15thDay
31%49%27%19%8%
1758
16th to endDay
39%38%20%22%5%
1598
December1st to 15thDay
40%410%22%19%3
1440
16th to endDay
44%38%23%16%3
1683
January1st to 15thNight
35%37%23%25%4
2327
16th to endNight
34%38%25%22%5%
2496
February1st to 15thNight
38%39%26%17%4
2288
16th to endNight
35%310%27%17%6%
1860
March1st to 15thNight
42%5%11%16%19%6%
1980
16th to endNight
44%49%22%16%2
2112
April1st to 15thNight
34%410%22%20%6%
1824
16th to endNight
38%5%9%23%20%3
1800
May1st to 15thNight
39%7%11%18%18%4
1686
16th to endNight
35%8%18%22%14%1
1685
June1st to 15thNight
22%6%14%31%22%2
1620
16th to endNight
23%5%16%26%22%5%
1620
July1st to 15thNight
27%9%18%26%17%1
1530
16th to endNight
20%10%18%30%17%2
1594
August1st to 15thNight
26%7%16%28%17%2
1612
16th to endNight
28%9%18%22%18%3
1910
September1st to 15thNight
28%7%10%27%16%9%
1800
16th to endNight
28%6%10%21%25%7%
1863
October1st to 15thNight
30%5%10%20%21%10%
1980
16th to endNight
27%36%22%29%10%
2112
November1st to 15thNight
28%49%25%22%9%
2100
16th to endNight
38%36%21%25%5%
2356
December1st to 15thNight
41%310%20%18%5%
2520
16th to endNight
43%39%20%17%4
2538

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
25%13%31%22%7%
90
16th to endDay
14%28%30%18%8%
96
February1st to 15thDay
13%24%41%16%31
90
16th to endDay
18%22%34%17%6%1
81
March1st to 15thDay
26%20%38%12%2
90
16th to endDay
16%27%27%21%7%
96
April1st to 15thDay
19%13%30%23%12%
242
16th to endDay
29%8%26%19%13%2
270
May1st to 15thDay
20%9%27%27%13%2
400
16th to endDay
15%6%26%33%13%4
517
June1st to 15thDay
11%213%30%34%8%
495
16th to endDay
7%115%34%30%10%
495
July1st to 15thDay
9%112%33%32%10%
475
16th to endDay
4324%43%22%
515
August1st to 15thDay
10%9%26%40%13%
490
16th to endDay
14%5%23%40%15%
332
September1st to 15thDay
11%27%22%40%15%
315
16th to endDay
8%9%38%27%15%
107
October1st to 15thDay
5%5%22%38%22%5%
90
16th to endDay
18%5%16%37%17%4
96
November1st to 15thDay
11%5%25%34%22%1
90
16th to endDay
34%13%25%17%7%1
90
December1st to 15thDay
18%12%31%25%7%4
90
16th to endDay
27%13%31%25%3
96
January1st to 15thNight
21%13%26%31%7%
900
16th to endNight
19%10%32%32%5%
960
February1st to 15thNight
19%14%30%31%4
880
16th to endNight
19%13%35%28%3
598
March1st to 15thNight
22%9%27%37%4
540
16th to endNight
22%7%27%32%8%
576
April1st to 15thNight
14%9%34%31%9%
539
16th to endNight
17%6%30%32%11%
540
May1st to 15thNight
16%5%26%36%15%
540
16th to endNight
10%220%40%23%1
563
June1st to 15thNight
6%110%39%39%3
540
16th to endNight
410%34%45%5%
540
July1st to 15thNight
5%10%34%43%5%
510
16th to endNight
5%125%54%13%
564
August1st to 15thNight
7%429%48%9%
539
16th to endNight
7%5%30%47%7%
573
September1st to 15thNight
11%18%27%45%4
540
16th to endNight
9%113%35%34%5%
530
October1st to 15thNight
14%220%32%25%4
660
16th to endNight
15%6%21%34%19%2
704
November1st to 15thNight
12%9%22%36%17%1
700
16th to endNight
21%11%24%27%15%
807
December1st to 15thNight
24%9%26%33%7%
900
16th to endNight
23%12%24%33%5%
960
Page generated at 2017-09-19 06:32:25. Version ac04

Copyright 2017 A. Danko


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