Sheridan Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sheridan Lake clear sky chart from 2005-11-05 to 2017-09-24.

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
38%
14824
8%
46779
6%
14797
40%
14797
14%
35017

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
26%
757
5%
2695
4%
755
28%
755
7%
2267
January16th to endNight
35%
781
7%
2765
6%
781
38%
781
10%
2144
February1st to 15thNight
32%
697
6%
2377
6%
696
34%
696
10%
1881
February16th to endNight
44%
632
11%
2014
11%
632
47%
632
19%
1400
March1st to 15thNight
27%
720
9%
2130
5%
720
31%
720
13%
1633
March16th to endNight
34%
768
9%
2025
4%
768
37%
768
16%
1586
April1st to 15thNight
39%
719
8%
1799
4%
719
41%
719
17%
1401
April16th to endNight
36%
446
10%
1526
8%
446
39%
446
13%
1136
May1st to 15thNight
38%
359
8%
1440
10%
359
41%
359
13%
1022
May16th to endNight
42%
374
3%
1398
2%
374
42%
374
12%
1057
June1st to 15thNight
39%
360
0%
1080
0%
360
39%
360
14%
848
June16th to endNight
40%
360
0%
1080
0%
360
40%
360
15%
812
July1st to 15thNight
54%
340
1%
1120
0%
340
54%
340
25%
708
July16th to endNight
57%
376
7%
1318
8%
354
60%
354
22%
802
August1st to 15thNight
68%
360
14%
1432
22%
358
69%
358
26%
793
August16th to endNight
59%
592
17%
1738
16%
592
60%
592
29%
1096
September1st to 15thNight
58%
720
16%
1800
9%
720
59%
720
33%
1187
September16th to endNight
46%
692
17%
1886
11%
692
50%
692
24%
1287
October1st to 15thNight
44%
660
12%
1980
11%
660
46%
660
20%
1370
October16th to endNight
32%
704
8%
2257
6%
704
37%
704
14%
1692
November1st to 15thNight
28%
700
8%
2450
5%
700
31%
700
9%
1905
November16th to endNight
29%
798
6%
2598
4%
798
32%
798
9%
2124
December1st to 15thNight
30%
917
5%
2799
4%
917
32%
917
10%
2292
December16th to endNight
24%
992
5%
3072
3%
992
26%
992
8%
2574

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
12%10%47%7%45%5%5%6%29%
48175
Night
10%12%48%6%45%5%5%7%28%
46930
TransparencyDay
53%8%14%15%6%
47830
Night
54%8%15%15%5%
46779
SeeingDay
17%13%25%24%15%3
6497
Night
16%11%23%29%16%2
14835

By Month

Percentage Cloud Cover NW (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
11%14%6%12%8%26%6%5%7%17%
1253
16th to endDay
9%15%5%10%9%5%5%5%5%5%22%
1458
February1st to 15thDay
10%16%8%10%6%345%45%23%
1486
16th to endDay
7%13%7%9%7%46%5%6%6%26%
1460
March1st to 15thDay
6%16%6%9%8%46%6%6%7%20%
1828
16th to endDay
7%11%6%11%8%5%6%5%5%7%22%
2199
April1st to 15thDay
10%15%6%9%8%46%5%6%7%20%
2149
16th to endDay
11%14%5%9%8%5%6%5%6%6%20%
2430
May1st to 15thDay
13%11%5%7%7%35%5%47%28%
2511
16th to endDay
17%10%38%7%46%5%5%6%24%
2708
June1st to 15thDay
20%9%48%6%35%5%46%24%
2880
16th to endDay
15%7%47%8%45%6%6%7%26%
2880
July1st to 15thDay
9%5%35%5%35%46%7%42%
2769
16th to endDay
9%425%5%345%5%6%47%
2759
August1st to 15thDay
7%4245%445%6%8%45%
2520
16th to endDay
10%5%25%6%35%46%7%42%
2462
September1st to 15thDay
10%5%25%42335%6%48%
2160
16th to endDay
18%7%26%6%2445%7%34%
1930
October1st to 15thDay
12%10%36%5%35%35%7%35%
1650
16th to endDay
17%14%36%5%2445%6%28%
1615
November1st to 15thDay
15%17%6%9%5%3446%6%21%
1408
16th to endDay
11%15%6%9%8%45%5%5%6%20%
1350
December1st to 15thDay
11%15%7%10%8%5%6%6%5%5%18%
1158
16th to endDay
9%15%7%10%8%46%5%5%5%20%
1152
January1st to 15thNight
12%17%8%11%8%445%5%5%16%
2695
16th to endNight
9%13%5%9%7%45%6%6%7%22%
2765
February1st to 15thNight
10%17%7%9%7%3445%6%22%
2365
16th to endNight
7%10%5%8%7%345%5%7%33%
2014
March1st to 15thNight
6%15%6%9%6%46%6%5%6%26%
2130
16th to endNight
411%411%7%47%7%8%6%25%
2021
April1st to 15thNight
5%14%5%9%7%37%5%6%6%26%
1799
16th to endNight
9%12%5%7%8%5%6%5%6%7%27%
1526
May1st to 15thNight
12%11%49%7%3446%7%28%
1439
16th to endNight
16%8%47%6%46%8%6%6%23%
1398
June1st to 15thNight
18%7%410%6%45%5%47%24%
1080
16th to endNight
15%8%37%6%46%5%6%7%28%
1080
July1st to 15thNight
11%4245%36%5%6%10%41%
1189
16th to endNight
9%425%5%47%5%6%9%39%
1409
August1st to 15thNight
8%425%435%46%7%48%
1440
16th to endNight
8%5%15%5%45%5%7%9%40%
1738
September1st to 15thNight
10%5%25%6%2445%6%47%
1800
16th to endNight
13%8%25%6%3445%7%39%
1886
October1st to 15thNight
11%9%37%5%345%5%6%36%
1980
16th to endNight
15%12%46%7%345%5%6%27%
2257
November1st to 15thNight
14%14%47%6%35%5%5%6%24%
2450
16th to endNight
11%16%6%9%7%46%5%45%21%
2598
December1st to 15thNight
11%15%6%10%7%5%5%45%7%20%
2799
16th to endNight
7%19%8%11%8%45%5%5%6%18%
3072

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
65%12%13%6%2
1253
16th to endDay
61%9%15%10%2
1458
February1st to 15thDay
62%8%14%9%4
1486
16th to endDay
56%7%16%12%6%
1460
March1st to 15thDay
60%9%14%10%4
1828
16th to endDay
58%8%15%13%2
2199
April1st to 15thDay
61%8%12%12%4
2149
16th to endDay
62%8%12%11%4
2430
May1st to 15thDay
55%6%13%13%10%
2511
16th to endDay
58%10%13%13%3
2712
June1st to 15thDay
59%7%12%12%7%
2880
16th to endDay
54%10%15%12%6%
2880
July1st to 15thDay
40%7%15%20%14%1
2609
16th to endDay
35%9%15%28%9%1
2587
August1st to 15thDay
34%9%18%26%10%
2503
16th to endDay
39%8%18%23%8%1
2462
September1st to 15thDay
35%7%17%26%11%1
2160
16th to endDay
50%7%13%18%7%1
1930
October1st to 15thDay
48%7%20%18%4
1650
16th to endDay
56%8%18%14%1
1615
November1st to 15thDay
63%9%10%11%4
1408
16th to endDay
62%10%11%11%3
1350
December1st to 15thDay
64%11%11%9%2
1158
16th to endDay
63%10%14%8%2
1152
January1st to 15thNight
69%8%11%7%3
2695
16th to endNight
58%10%15%11%21
2765
February1st to 15thNight
62%8%12%11%4
2377
16th to endNight
48%7%19%17%6%
2014
March1st to 15thNight
55%9%15%14%5%
2130
16th to endNight
52%11%17%14%2
2025
April1st to 15thNight
55%8%14%16%5%
1799
16th to endNight
55%8%14%15%5%
1526
May1st to 15thNight
53%7%12%16%9%
1440
16th to endNight
56%10%16%12%4
1398
June1st to 15thNight
59%7%10%16%5%
1080
16th to endNight
53%9%16%13%6%
1080
July1st to 15thNight
38%9%17%17%15%3
1120
16th to endNight
37%9%16%24%11%
1318
August1st to 15thNight
32%8%16%29%12%1
1432
16th to endNight
36%8%19%25%8%2
1738
September1st to 15thNight
35%7%14%26%12%2
1800
16th to endNight
43%6%15%20%10%3
1886
October1st to 15thNight
46%7%17%22%5%
1980
16th to endNight
55%7%17%17%1
2257
November1st to 15thNight
58%10%14%11%4
2450
16th to endNight
63%9%11%10%4
2598
December1st to 15thNight
63%9%15%10%2
2799
16th to endNight
65%10%12%8%2
3072

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
15%5%16%30%23%10%
60
16th to endDay
20%26%26%15%9%1
64
February1st to 15thDay
17%17%28%26%10%
146
16th to endDay
14%15%28%26%12%3
218
March1st to 15thDay
18%29%29%16%41
270
16th to endDay
20%24%33%16%4
288
April1st to 15thDay
18%20%27%21%8%3
269
16th to endDay
19%20%32%19%6%2
270
May1st to 15thDay
15%18%28%21%13%3
288
16th to endDay
21%8%19%25%20%4
423
June1st to 15thDay
21%10%24%23%17%1
675
16th to endDay
16%9%23%28%18%3
675
July1st to 15thDay
12%6%26%29%22%3
543
16th to endDay
11%7%22%31%21%5%
428
August1st to 15thDay
7%6%16%31%27%9%
315
16th to endDay
10%10%26%29%16%6%
332
September1st to 15thDay
18%10%24%24%13%7%
315
16th to endDay
20%12%24%23%14%4
288
October1st to 15thDay
18%16%27%20%14%2
255
16th to endDay
19%13%28%23%11%3
131
November1st to 15thDay
33%23%26%10%6%
60
16th to endDay
16%15%20%15%21%11%
60
December1st to 15thDay
18%13%21%13%20%13%
60
16th to endDay
18%12%28%18%17%4
64
January1st to 15thNight
23%11%24%27%12%1
759
16th to endNight
17%9%27%31%12%1
781
February1st to 15thNight
19%9%22%32%12%2
704
16th to endNight
13%9%21%34%17%2
632
March1st to 15thNight
16%18%30%23%9%2
720
16th to endNight
9%19%26%26%15%1
768
April1st to 15thNight
12%11%24%29%18%3
719
16th to endNight
14%11%30%29%12%2
446
May1st to 15thNight
16%9%27%30%14%1
360
16th to endNight
18%420%29%22%3
375
June1st to 15thNight
20%7%21%33%15%2
360
16th to endNight
16%6%25%30%18%2
360
July1st to 15thNight
13%320%33%26%2
340
16th to endNight
10%319%32%30%3
376
August1st to 15thNight
7%39%32%38%8%
360
16th to endNight
11%5%16%32%30%3
592
September1st to 15thNight
12%416%30%29%6%
720
16th to endNight
18%10%19%27%20%4
692
October1st to 15thNight
17%12%20%30%17%2
660
16th to endNight
22%13%23%26%12%1
704
November1st to 15thNight
22%20%23%24%7%1
700
16th to endNight
23%13%24%25%10%3
798
December1st to 15thNight
17%12%24%31%12%1
917
16th to endNight
17%15%30%28%8%
992
Page generated at 2017-09-25 06:02:24. Version ac04

Copyright 2017 A. Danko


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