Leslie C. Peltier Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Leslie C. Peltier Observatory clear sky chart from 2005-11-05 to

2017-09-12
.

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
27%
14929
19%
46785
8%
14897
39%
14897
21%
29910

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
16%
720
22%
2506
7%
716
34%
716
18%
1549
January16th to endNight
16%
768
22%
2655
5%
768
37%
768
17%
1657
February1st to 15thNight
15%
704
17%
2201
4%
701
31%
701
16%
1444
February16th to endNight
16%
631
24%
1893
7%
631
38%
631
19%
1226
March1st to 15thNight
16%
720
18%
2160
6%
720
31%
720
17%
1438
March16th to endNight
19%
768
25%
2002
7%
768
34%
768
23%
1311
April1st to 15thNight
18%
718
17%
1796
3%
718
26%
718
22%
1271
April16th to endNight
21%
657
18%
1737
3%
657
31%
657
23%
1179
May1st to 15thNight
21%
525
17%
1605
6%
525
32%
525
18%
1089
May16th to endNight
30%
375
13%
1497
10%
374
38%
374
17%
929
June1st to 15thNight
30%
360
14%
1440
9%
360
44%
360
17%
936
June16th to endNight
41%
360
14%
1440
13%
360
51%
360
25%
817
July1st to 15thNight
42%
340
13%
1360
14%
340
47%
340
23%
799
July16th to endNight
48%
376
15%
1418
17%
354
54%
354
23%
832
August1st to 15thNight
45%
507
18%
1578
9%
505
52%
505
30%
931
August16th to endNight
52%
764
20%
1910
9%
764
55%
764
34%
1242
September1st to 15thNight
38%
707
22%
1784
9%
707
45%
707
32%
1155
September16th to endNight
45%
657
26%
1815
17%
657
51%
657
32%
1115
October1st to 15thNight
33%
660
22%
1895
11%
660
44%
660
26%
1213
October16th to endNight
23%
704
18%
2238
6%
704
37%
704
21%
1440
November1st to 15thNight
27%
700
22%
2277
9%
700
44%
700
21%
1435
November16th to endNight
23%
720
21%
2370
8%
720
38%
720
18%
1530
December1st to 15thNight
21%
720
17%
2520
5%
720
35%
720
17%
1625
December16th to endNight
16%
768
19%
2688
4%
768
34%
768
15%
1747

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
16%6%25%5%3445%7%39%
47882
Night
16%6%25%42445%6%41%
46955
Cloud CoverDay
16%6%25%43445%7%39%
47892
Night
17%6%2442445%6%41%
46960
TransparencyDay
44%411%22%15%2
47570
Night
43%312%23%15%2
46785
SeeingDay
21%14%30%20%9%3
5789
Night
21%13%32%23%7%
14929

By Month

Percentage Cloud Cover NE (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
15%6%25%435%6%5%5%39%
1432
16th to endDay
14%6%25%425%45%8%39%
1569
February1st to 15thDay
15%6%26%5%35%5%5%6%35%
1659
16th to endDay
15%7%35%435%5%46%39%
1580
March1st to 15thDay
16%7%25%5%3445%7%35%
1790
16th to endDay
17%7%34423446%40%
2218
April1st to 15thDay
18%7%24425%45%6%38%
2152
16th to endDay
17%5%25%323447%43%
2223
May1st to 15thDay
23%7%2443345%6%34%
2355
16th to endDay
17%5%25%5%335%5%7%38%
2618
June1st to 15thDay
22%6%24435%5%5%7%32%
2520
16th to endDay
13%5%25%5%36%5%6%8%36%
2520
July1st to 15thDay
12%6%25%7%35%5%6%7%37%
2520
16th to endDay
12%5%25%5%45%5%6%7%37%
2654
August1st to 15thDay
13%5%25%6%35%6%7%7%36%
2357
16th to endDay
11%425%435%45%9%42%
2292
September1st to 15thDay
13%5%25%5%345%45%44%
2096
16th to endDay
14%5%14333346%48%
1815
October1st to 15thDay
18%8%25%324345%41%
1734
16th to endDay
17%4246%34446%41%
1634
November1st to 15thDay
18%5%23423347%43%
1581
16th to endDay
17%6%23333447%42%
1587
December1st to 15thDay
17%6%26%4345%46%39%
1440
16th to endDay
18%9%25%4245%6%6%33%
1536
January1st to 15thNight
16%6%25%5%2335%6%41%
2506
16th to endNight
14%8%35%42345%6%41%
2655
February1st to 15thNight
14%8%35%435%45%6%39%
2200
16th to endNight
16%6%245%24445%42%
1893
March1st to 15thNight
17%7%35%4245%46%39%
2147
16th to endNight
16%6%25%413446%44%
2002
April1st to 15thNight
17%7%24444446%38%
1796
16th to endNight
19%5%25%423345%42%
1737
May1st to 15thNight
20%7%35%433347%36%
1605
16th to endNight
19%7%2332436%7%38%
1495
June1st to 15thNight
22%5%34324346%38%
1440
16th to endNight
14%425%42335%8%44%
1440
July1st to 15thNight
13%5%245%345%7%9%39%
1440
16th to endNight
10%426%5%35%47%9%39%
1514
August1st to 15thNight
11%5%2443345%9%46%
1588
16th to endNight
13%3235%345%5%6%45%
1910
September1st to 15thNight
15%425%423447%45%
1784
16th to endNight
13%6%1432334451%
1815
October1st to 15thNight
17%6%25%422346%43%
1895
16th to endNight
19%5%25%424445%41%
2238
November1st to 15thNight
17%6%34423346%43%
2277
16th to endNight
18%7%3443435%5%39%
2370
December1st to 15thNight
19%6%25%5%345%5%5%38%
2520
16th to endNight
20%7%244235%46%37%
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
15%6%24426%5%6%6%39%
1432
16th to endDay
14%6%25%4245%5%8%39%
1569
February1st to 15thDay
15%6%26%5%36%5%5%6%35%
1659
16th to endDay
16%7%245%35%445%39%
1580
March1st to 15thDay
17%7%25%5%3446%7%35%
1800
16th to endDay
17%7%34423445%41%
2218
April1st to 15thDay
19%6%24424445%39%
2152
16th to endDay
17%5%25%324446%44%
2223
May1st to 15thDay
23%6%2442345%6%34%
2355
16th to endDay
18%5%245%2445%7%38%
2618
June1st to 15thDay
22%6%25%4345%48%32%
2520
16th to endDay
13%5%25%5%45%5%6%9%36%
2520
July1st to 15thDay
13%5%35%6%35%6%6%7%36%
2520
16th to endDay
12%5%26%6%36%5%6%8%38%
2654
August1st to 15thDay
13%5%25%6%36%5%6%8%35%
2357
16th to endDay
11%5%25%43446%8%42%
2292
September1st to 15thDay
13%5%25%5%335%45%44%
2096
16th to endDay
14%5%2433345%6%47%
1815
October1st to 15thDay
18%7%35%323245%42%
1734
16th to endDay
17%5%15%5%35%446%41%
1634
November1st to 15thDay
19%5%24422346%43%
1581
16th to endDay
18%5%23323346%42%
1587
December1st to 15thDay
17%6%25%434446%39%
1440
16th to endDay
19%9%245%25%5%5%6%34%
1536
January1st to 15thNight
16%7%25%42335%6%41%
2506
16th to endNight
15%8%34423446%42%
2655
February1st to 15thNight
14%8%344345%46%39%
2193
16th to endNight
16%7%2443335%5%42%
1893
March1st to 15thNight
17%7%35%424446%39%
2160
16th to endNight
16%6%24413446%44%
2001
April1st to 15thNight
17%8%244345%46%38%
1796
16th to endNight
19%5%35%424345%42%
1737
May1st to 15thNight
21%6%25%43345%6%36%
1605
16th to endNight
19%7%2332445%8%38%
1495
June1st to 15thNight
22%5%25%424346%38%
1440
16th to endNight
14%325%32446%7%44%
1440
July1st to 15thNight
13%4245%245%8%9%38%
1440
16th to endNight
10%435%6%36%46%9%39%
1514
August1st to 15thNight
12%41443445%8%46%
1588
16th to endNight
13%323435%45%7%45%
1910
September1st to 15thNight
15%5%14424447%45%
1784
16th to endNight
14%42441334450%
1815
October1st to 15thNight
16%6%24433346%44%
1895
16th to endNight
19%5%25%423445%41%
2238
November1st to 15thNight
17%6%25%313345%44%
2277
16th to endNight
19%6%24434345%40%
2370
December1st to 15thNight
19%5%35%42445%6%37%
2520
16th to endNight
21%7%2442345%6%36%
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
43%413%25%11%2
1433
16th to endDay
42%311%27%13%1
1569
February1st to 15thDay
47%412%21%13%1
1662
16th to endDay
45%39%24%14%2
1580
March1st to 15thDay
47%313%23%10%2
1800
16th to endDay
44%38%21%17%4
2218
April1st to 15thDay
45%39%22%15%3
2152
16th to endDay
40%39%22%19%3
2223
May1st to 15thDay
50%47%21%13%2
2355
16th to endDay
44%5%13%21%13%2
2622
June1st to 15thDay
49%5%12%21%10%1
2520
16th to endDay
42%6%13%24%13%
2520
July1st to 15thDay
45%5%10%21%16%1
2371
16th to endDay
41%415%21%14%2
2487
August1st to 15thDay
43%413%22%14%
2343
16th to endDay
38%410%26%18%1
2292
September1st to 15thDay
40%410%22%20%1
2096
16th to endDay
36%37%25%24%2
1815
October1st to 15thDay
44%39%25%15%2
1734
16th to endDay
43%311%24%13%2
1634
November1st to 15thDay
42%312%21%17%2
1581
16th to endDay
42%211%26%14%2
1587
December1st to 15thDay
44%316%19%13%1
1440
16th to endDay
49%5%14%18%11%
1536
January1st to 15thNight
43%212%24%13%2
2506
16th to endNight
42%310%24%15%2
2655
February1st to 15thNight
45%413%21%12%2
2201
16th to endNight
43%29%24%16%2
1893
March1st to 15thNight
45%312%22%12%2
2160
16th to endNight
40%38%23%19%4
2002
April1st to 15thNight
46%49%22%15%2
1796
16th to endNight
44%38%22%18%3
1737
May1st to 15thNight
49%210%19%15%3
1605
16th to endNight
44%5%17%19%12%1
1497
June1st to 15thNight
47%413%20%12%1
1440
16th to endNight
37%415%27%14%
1440
July1st to 15thNight
38%6%13%25%14%1
1360
16th to endNight
39%416%23%12%2
1418
August1st to 15thNight
35%5%14%27%15%1
1578
16th to endNight
36%5%11%26%18%
1910
September1st to 15thNight
38%411%25%19%1
1784
16th to endNight
36%46%24%26%1
1815
October1st to 15thNight
42%311%22%17%2
1895
16th to endNight
44%213%24%14%
2238
November1st to 15thNight
42%310%20%18%3
2277
16th to endNight
46%211%24%12%2
2370
December1st to 15thNight
46%315%21%13%
2520
16th to endNight
47%313%21%12%
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
23%30%30%13%3
60
16th to endDay
24%24%42%8%
69
February1st to 15thDay
24%23%35%16%1
175
16th to endDay
23%20%34%16%4
239
March1st to 15thDay
26%20%31%17%4
270
16th to endDay
20%22%37%12%5%1
288
April1st to 15thDay
26%18%32%14%7%1
270
16th to endDay
23%14%33%17%7%3
270
May1st to 15thDay
37%12%24%14%8%2
288
16th to endDay
23%11%31%22%9%1
331
June1st to 15thDay
25%13%25%21%12%1
315
16th to endDay
17%12%37%24%8%
315
July1st to 15thDay
18%9%28%28%14%
305
16th to endDay
11%10%30%28%16%3
326
August1st to 15thDay
15%6%29%28%14%6%
313
16th to endDay
12%5%30%25%18%8%
332
September1st to 15thDay
16%12%27%21%13%8%
299
16th to endDay
18%8%27%20%12%12%
254
October1st to 15thDay
21%9%26%24%12%5%
255
16th to endDay
19%22%28%22%6%
249
November1st to 15thDay
25%12%28%22%10%1
235
16th to endDay
24%18%28%18%7%2
207
December1st to 15thDay
23%28%33%10%5%
60
16th to endDay
39%18%26%15%
64
January1st to 15thNight
24%16%38%17%3
720
16th to endNight
23%19%36%18%1
768
February1st to 15thNight
22%18%36%20%1
704
16th to endNight
24%20%34%17%2
631
March1st to 15thNight
24%21%33%17%2
720
16th to endNight
21%21%32%18%4
768
April1st to 15thNight
23%19%37%16%3
718
16th to endNight
23%17%33%19%5%
657
May1st to 15thNight
26%15%34%19%3
525
16th to endNight
23%9%31%28%6%1
375
June1st to 15thNight
25%8%30%26%10%
360
16th to endNight
16%332%38%8%
360
July1st to 15thNight
14%331%32%17%
340
16th to endNight
12%326%38%17%1
376
August1st to 15thNight
13%329%37%14%
507
16th to endNight
15%321%37%19%2
764
September1st to 15thNight
18%5%31%30%12%1
707
16th to endNight
16%7%24%26%20%3
657
October1st to 15thNight
21%9%30%26%10%1
660
16th to endNight
24%13%35%20%6%
704
November1st to 15thNight
23%14%30%22%7%2
700
16th to endNight
25%13%32%20%7%
720
December1st to 15thNight
24%16%34%19%5%
720
16th to endNight
27%18%33%17%2
768
Page generated at 2017-09-13 07:39:10. Version ac04

Copyright 2017 A. Danko


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