Sid's Scoop
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sid's Scoop clear sky chart from 2005-11-05 to 2017-09-19.

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
40%
14534
10%
46741
8%
14506
43%
14506
15%
33708

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
27%
749
8%
2686
6%
746
31%
746
7%
2202
January16th to endNight
29%
779
8%
2703
7%
779
32%
779
8%
2138
February1st to 15thNight
27%
700
6%
2288
4%
700
31%
700
7%
1852
February16th to endNight
32%
632
10%
2050
8%
632
37%
632
11%
1552
March1st to 15thNight
25%
720
6%
2040
4%
720
28%
720
9%
1697
March16th to endNight
28%
768
7%
2088
4%
768
31%
768
10%
1695
April1st to 15thNight
37%
710
9%
1790
5%
710
39%
710
17%
1365
April16th to endNight
40%
531
11%
1611
7%
531
44%
531
15%
1173
May1st to 15thNight
47%
359
13%
1439
16%
359
53%
359
17%
889
May16th to endNight
49%
375
8%
1470
10%
374
52%
374
15%
943
June1st to 15thNight
47%
360
5%
1260
4%
360
49%
360
19%
811
June16th to endNight
49%
360
8%
1260
4%
360
51%
360
20%
772
July1st to 15thNight
66%
340
12%
1190
11%
340
70%
340
37%
582
July16th to endNight
71%
376
17%
1333
21%
354
80%
354
44%
576
August1st to 15thNight
73%
465
17%
1539
20%
463
75%
463
38%
750
August16th to endNight
68%
606
22%
1752
17%
606
71%
606
39%
945
September1st to 15thNight
71%
720
23%
1800
14%
720
73%
720
48%
1001
September16th to endNight
51%
671
19%
1854
12%
671
54%
671
23%
1246
October1st to 15thNight
44%
660
11%
1980
10%
660
47%
660
19%
1364
October16th to endNight
35%
704
8%
2181
5%
704
40%
704
12%
1683
November1st to 15thNight
26%
700
7%
2450
5%
700
30%
700
7%
2014
November16th to endNight
28%
720
7%
2520
4%
720
32%
720
8%
2006
December1st to 15thNight
27%
729
5%
2577
4%
729
31%
729
7%
2075
December16th to endNight
18%
800
6%
2880
3%
800
23%
800
6%
2377

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%8%37%6%35%5%5%7%30%
48104
Night
18%8%36%5%35%45%7%32%
46895
Cloud CoverDay
17%8%36%5%3445%6%32%
48104
Night
18%8%35%5%3445%6%34%
46898
TransparencyDay
51%11%14%16%5%
47761
Night
50%9%15%17%6%1
46742
SeeingDay
16%13%18%24%20%5%
6181
Night
19%19%13%21%19%5%
14540

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
27%11%6%9%7%4443317%
1253
16th to endDay
24%12%6%8%7%45%45%7%12%
1516
February1st to 15thDay
28%14%48%7%3344414%
1576
16th to endDay
18%12%48%7%45%46%6%19%
1424
March1st to 15thDay
25%12%5%8%7%45%45%5%14%
1920
16th to endDay
22%13%5%10%8%46%44414%
2136
April1st to 15thDay
18%10%5%8%8%5%7%6%6%6%17%
2157
16th to endDay
17%9%37%8%47%5%6%8%21%
2349
May1st to 15thDay
12%7%37%6%36%6%6%7%30%
2511
16th to endDay
14%8%38%7%46%5%6%7%27%
2639
June1st to 15thDay
11%6%37%6%35%6%7%8%33%
2700
16th to endDay
12%5%25%6%46%6%6%7%35%
2700
July1st to 15thDay
6%31432345%7%55%
2700
16th to endDay
5%21331345%8%59%
2742
August1st to 15thDay
7%315%42335%6%55%
2412
16th to endDay
7%3144245%6%9%48%
2450
September1st to 15thDay
8%42441345%8%52%
2160
16th to endDay
17%6%26%6%445%48%33%
1849
October1st to 15thDay
20%9%37%6%46%446%26%
1650
16th to endDay
23%10%5%8%6%35%6%5%6%18%
1688
November1st to 15thDay
34%9%47%5%35%335%15%
1408
16th to endDay
27%11%6%10%5%35%445%15%
1440
December1st to 15thDay
24%13%48%6%34445%20%
1380
16th to endDay
27%13%48%7%25%345%15%
1344
January1st to 15thNight
28%9%47%6%35%445%20%
2686
16th to endNight
24%10%37%6%45%5%5%7%20%
2703
February1st to 15thNight
24%10%47%7%45%446%20%
2276
16th to endNight
19%9%47%6%35%5%5%6%26%
2050
March1st to 15thNight
25%10%46%6%46%5%5%6%18%
2040
16th to endNight
21%10%47%6%36%5%5%6%20%
2084
April1st to 15thNight
18%7%36%6%35%6%6%8%27%
1790
16th to endNight
18%7%35%5%35%5%5%9%30%
1611
May1st to 15thNight
11%5%35%5%45%5%5%6%41%
1439
16th to endNight
9%6%26%6%345%7%9%37%
1470
June1st to 15thNight
11%6%35%5%3345%8%41%
1260
16th to endNight
9%425%425%46%11%42%
1260
July1st to 15thNight
5%222323348%61%
1260
16th to endNight
322212247%70%
1425
August1st to 15thNight
2312313447%64%
1547
16th to endNight
6%21231345%9%58%
1752
September1st to 15thNight
5%213213346%64%
1800
16th to endNight
14%7%245%34449%39%
1854
October1st to 15thNight
17%7%25%5%34445%38%
1980
16th to endNight
26%8%26%6%345%46%24%
2181
November1st to 15thNight
30%9%36%6%46%445%19%
2450
16th to endNight
22%10%5%7%7%45%445%22%
2520
December1st to 15thNight
23%11%47%5%45%45%5%21%
2577
16th to endNight
25%12%48%6%35%346%18%
2880

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
28%13%5%7%6%35%33417%
1253
16th to endDay
25%14%5%9%7%34445%14%
1516
February1st to 15thDay
27%14%48%6%34345%15%
1576
16th to endDay
18%12%49%7%35%45%6%20%
1424
March1st to 15thDay
24%12%6%8%6%4445%6%15%
1920
16th to endDay
22%14%49%7%45%44416%
2136
April1st to 15thDay
18%10%47%7%5%7%5%6%7%19%
2157
16th to endDay
18%9%47%6%36%5%7%7%23%
2349
May1st to 15thDay
13%6%37%6%45%5%5%7%33%
2511
16th to endDay
15%9%47%5%35%5%5%7%30%
2639
June1st to 15thDay
12%6%46%5%25%5%6%7%36%
2700
16th to endDay
12%6%25%6%36%5%6%7%37%
2700
July1st to 15thDay
6%324324446%57%
2700
16th to endDay
6%213223346%62%
2742
August1st to 15thDay
7%313314347%56%
2412
16th to endDay
7%215%434448%51%
2450
September1st to 15thDay
8%41342345%8%53%
2160
16th to endDay
18%6%35%6%24447%36%
1849
October1st to 15thDay
21%9%36%5%35%5%5%5%27%
1650
16th to endDay
25%12%48%5%2345%7%19%
1688
November1st to 15thDay
32%11%47%5%3344418%
1408
16th to endDay
26%12%5%9%5%44346%17%
1440
December1st to 15thDay
24%13%5%6%5%25%445%21%
1380
16th to endDay
28%12%47%6%35%5%5%5%16%
1344
January1st to 15thNight
29%10%36%5%35%44422%
2685
16th to endNight
24%11%37%6%3445%6%22%
2703
February1st to 15thNight
24%11%47%6%45%436%23%
2276
16th to endNight
19%9%37%6%45%446%28%
2050
March1st to 15thNight
24%10%36%7%35%5%5%5%21%
2040
16th to endNight
21%10%47%5%35%5%5%6%23%
2088
April1st to 15thNight
18%7%35%5%35%6%5%7%31%
1790
16th to endNight
19%7%36%4345%5%8%32%
1611
May1st to 15thNight
12%5%345%25%5%5%5%44%
1439
16th to endNight
10%6%346%25%5%6%8%38%
1470
June1st to 15thNight
11%6%35%5%245%46%42%
1260
16th to endNight
10%3244345%6%9%44%
1260
July1st to 15thNight
5%213313335%65%
1260
16th to endNight
411212235%72%
1425
August1st to 15thNight
321331335%5%66%
1547
16th to endNight
6%313313447%61%
1752
September1st to 15thNight
6%21321234467%
1800
16th to endNight
15%4245%345%48%41%
1854
October1st to 15thNight
18%6%25%5%3344440%
1980
16th to endNight
25%8%25%6%4435%5%27%
2181
November1st to 15thNight
30%8%35%7%35%5%45%20%
2450
16th to endNight
21%9%5%8%6%35%5%45%24%
2520
December1st to 15thNight
22%12%47%5%35%45%5%23%
2577
16th to endNight
26%13%47%5%35%44421%
2880

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
72%7%7%8%4
1253
16th to endDay
73%8%8%7%1
1516
February1st to 15thDay
70%9%7%8%3
1576
16th to endDay
63%9%12%11%3
1424
March1st to 15thDay
69%11%9%7%1
1920
16th to endDay
69%9%10%9%1
2136
April1st to 15thDay
61%13%10%12%2
2157
16th to endDay
56%13%14%11%3
2349
May1st to 15thDay
49%12%13%17%6%
2511
16th to endDay
52%13%16%15%2
2643
June1st to 15thDay
45%15%20%13%4
2700
16th to endDay
44%13%18%18%4
2700
July1st to 15thDay
28%11%17%28%12%2
2541
16th to endDay
22%10%20%33%11%1
2571
August1st to 15thDay
28%11%17%30%9%2
2395
16th to endDay
30%11%20%28%8%1
2450
September1st to 15thDay
28%10%17%24%16%1
2160
16th to endDay
47%11%15%16%7%
1849
October1st to 15thDay
56%11%12%14%5%
1650
16th to endDay
62%10%14%9%3
1688
November1st to 15thDay
69%8%9%8%21
1408
16th to endDay
67%8%10%9%2
1440
December1st to 15thDay
66%9%10%9%4
1380
16th to endDay
69%8%10%8%2
1344
January1st to 15thNight
65%8%10%10%4
2686
16th to endNight
61%8%10%13%41
2703
February1st to 15thNight
63%9%12%10%4
2288
16th to endNight
56%8%13%16%4
2050
March1st to 15thNight
63%10%10%13%2
2040
16th to endNight
59%10%12%14%2
2088
April1st to 15thNight
50%10%16%17%4
1790
16th to endNight
49%10%14%19%5%
1611
May1st to 15thNight
39%9%16%23%10%1
1440
16th to endNight
40%11%22%20%4
1470
June1st to 15thNight
40%9%22%21%41
1260
16th to endNight
34%11%23%23%5%2
1260
July1st to 15thNight
22%6%19%33%14%4
1190
16th to endNight
14%7%22%34%17%2
1333
August1st to 15thNight
18%8%21%32%14%4
1539
16th to endNight
21%8%22%32%11%3
1752
September1st to 15thNight
20%6%19%26%21%6%
1800
16th to endNight
40%9%15%22%11%2
1854
October1st to 15thNight
45%8%17%18%9%
1980
16th to endNight
56%8%15%12%5%
2181
November1st to 15thNight
65%8%10%9%21
2450
16th to endNight
61%9%10%10%6%
2520
December1st to 15thNight
63%9%12%9%4
2577
16th to endNight
66%8%11%8%4
2880

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
16%10%21%18%33%
60
16th to endDay
41%12%21%17%6%
109
February1st to 15thDay
30%24%20%18%6%
236
16th to endDay
22%22%23%19%10%1
212
March1st to 15thDay
34%22%22%14%5%
270
16th to endDay
25%21%23%19%6%2
288
April1st to 15thDay
20%19%18%23%13%3
269
16th to endDay
18%15%23%25%14%2
270
May1st to 15thDay
15%14%17%30%19%2
288
16th to endDay
14%12%18%20%26%7%
354
June1st to 15thDay
10%16%18%29%22%3
495
16th to endDay
10%15%20%29%20%3
495
July1st to 15thDay
7%10%12%27%33%9%
475
16th to endDay
311%11%27%34%11%
411
August1st to 15thDay
7%6%8%25%33%18%
315
16th to endDay
6%7%12%29%34%9%
332
September1st to 15thDay
11%6%14%30%28%9%
315
16th to endDay
19%10%20%23%22%4
268
October1st to 15thDay
25%13%19%25%15%1
255
16th to endDay
30%12%22%18%12%3
220
November1st to 15thDay
38%5%30%21%5%
60
16th to endDay
28%8%18%18%13%13%
60
December1st to 15thDay
41%6%28%15%8%
60
16th to endDay
26%20%23%21%6%1
64
January1st to 15thNight
27%24%12%17%14%2
750
16th to endNight
25%20%14%18%17%2
779
February1st to 15thNight
24%25%14%17%14%3
704
16th to endNight
21%23%14%21%15%3
632
March1st to 15thNight
26%25%18%16%10%4
720
16th to endNight
21%23%17%22%11%3
768
April1st to 15thNight
18%21%16%20%18%4
710
16th to endNight
20%19%13%30%13%2
531
May1st to 15thNight
13%19%12%26%20%8%
360
16th to endNight
9%19%11%26%26%6%
375
June1st to 15thNight
12%17%16%21%27%4
360
16th to endNight
11%19%12%27%22%6%
360
July1st to 15thNight
6%12%8%27%36%8%
340
16th to endNight
416%425%38%10%
376
August1st to 15thNight
410%421%41%17%
465
16th to endNight
8%9%9%25%35%10%
606
September1st to 15thNight
7%9%7%25%32%18%
720
16th to endNight
17%10%12%23%27%9%
671
October1st to 15thNight
21%12%14%24%20%7%
660
16th to endNight
29%13%11%21%16%6%
704
November1st to 15thNight
29%20%16%23%9%1
700
16th to endNight
21%26%16%18%13%3
720
December1st to 15thNight
25%24%14%22%11%1
729
16th to endNight
27%25%22%15%8%
800
Page generated at 2017-09-20 01:49:57. Version ac04

Copyright 2017 A. Danko


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