Quilchena Ranch
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Quilchena Ranch clear sky chart from 2005-11-05 to 2017-10-31.

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
42%
14891
10%
47226
8%
14866
45%
14866
18%
32946

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%
744
5%
2671
4%
743
28%
743
7%
2228
January16th to endNight
35%
768
6%
2688
5%
768
37%
768
10%
2126
February1st to 15thNight
38%
697
7%
2363
7%
697
40%
697
12%
1813
February16th to endNight
43%
632
12%
1991
10%
632
47%
632
18%
1404
March1st to 15thNight
30%
720
8%
2139
6%
720
34%
720
14%
1587
March16th to endNight
34%
768
10%
2016
4%
768
37%
768
18%
1486
April1st to 15thNight
41%
719
9%
1799
4%
719
43%
719
21%
1315
April16th to endNight
45%
488
13%
1568
9%
488
50%
488
20%
1050
May1st to 15thNight
47%
359
11%
1440
16%
359
52%
359
20%
891
May16th to endNight
50%
374
6%
1496
8%
374
51%
374
18%
969
June1st to 15thNight
46%
360
2%
1145
0%
360
47%
360
22%
758
June16th to endNight
45%
360
4%
1092
0%
360
45%
360
28%
674
July1st to 15thNight
62%
340
7%
1190
3%
340
63%
340
38%
600
July16th to endNight
67%
376
14%
1390
18%
354
73%
354
43%
595
August1st to 15thNight
77%
360
19%
1432
28%
358
79%
358
43%
622
August16th to endNight
63%
630
21%
1776
16%
630
66%
630
38%
1009
September1st to 15thNight
65%
720
20%
1800
11%
720
66%
720
44%
1045
September16th to endNight
55%
716
20%
1951
13%
716
58%
716
31%
1226
October1st to 15thNight
49%
720
12%
2160
11%
720
52%
720
24%
1426
October16th to endNight
40%
768
11%
2452
8%
768
45%
768
17%
1726
November1st to 15thNight
31%
700
9%
2420
8%
700
33%
700
11%
1846
November16th to endNight
31%
741
7%
2541
4%
741
35%
741
10%
2001
December1st to 15thNight
34%
900
8%
2700
6%
900
37%
900
12%
2141
December16th to endNight
27%
931
7%
3006
3%
931
31%
931
10%
2408

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
9%8%37%6%35%5%6%7%34%
48545
Night
8%9%47%6%35%5%6%7%34%
47382
Cloud CoverDay
9%8%37%6%36%5%6%7%34%
48545
Night
8%9%37%6%35%5%6%7%35%
47385
TransparencyDay
47%8%15%18%8%1
48205
Night
46%9%17%18%7%1
47226
SeeingDay
15%15%25%23%14%4
6345
Night
13%9%23%32%17%2
14903

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%11%49%7%49%7%6%8%18%
1267
16th to endDay
9%12%411%8%36%5%7%8%23%
1536
February1st to 15thDay
10%13%5%10%8%47%5%6%6%20%
1501
16th to endDay
5%12%5%10%8%46%7%6%8%25%
1482
March1st to 15thDay
7%15%5%9%7%47%5%47%22%
1821
16th to endDay
7%11%5%8%8%37%7%7%7%24%
2207
April1st to 15thDay
10%11%48%7%5%7%7%8%7%22%
2149
16th to endDay
9%10%48%7%36%6%6%9%26%
2391
May1st to 15thDay
8%8%37%6%46%6%6%7%34%
2511
16th to endDay
13%7%37%8%46%5%7%7%27%
2615
June1st to 15thDay
15%7%36%5%36%5%6%6%32%
2812
16th to endDay
10%6%35%6%46%5%5%7%38%
2865
July1st to 15thDay
431442445%7%56%
2700
16th to endDay
5%213325%446%58%
2684
August1st to 15thDay
5%3134245%6%8%54%
2520
16th to endDay
6%3145%345%6%8%49%
2425
September1st to 15thDay
8%425%433447%51%
2160
16th to endDay
13%5%36%5%35%5%6%8%37%
2005
October1st to 15thDay
10%9%48%6%445%5%7%34%
1800
16th to endDay
13%11%47%5%45%5%6%7%27%
1769
November1st to 15thDay
17%11%48%5%45%45%6%26%
1437
16th to endDay
9%14%5%8%7%47%5%5%9%21%
1404
December1st to 15thDay
7%11%7%9%10%47%6%6%7%21%
1260
16th to endDay
9%12%6%8%8%5%5%6%6%7%23%
1224
January1st to 15thNight
12%15%6%11%7%46%5%5%7%15%
2671
16th to endNight
9%15%49%9%36%6%5%7%20%
2688
February1st to 15thNight
10%15%5%8%8%45%5%6%7%23%
2351
16th to endNight
48%5%9%8%45%6%6%8%33%
1991
March1st to 15thNight
7%12%47%6%46%5%6%8%28%
2139
16th to endNight
5%10%37%6%46%6%7%8%32%
2012
April1st to 15thNight
6%8%37%6%46%6%6%7%35%
1799
16th to endNight
6%8%45%6%45%5%8%8%36%
1568
May1st to 15thNight
6%8%346%25%45%7%43%
1439
16th to endNight
10%7%46%5%35%5%6%8%36%
1496
June1st to 15thNight
11%6%245%45%6%8%10%34%
1145
16th to endNight
5%425%5%45%46%7%45%
1092
July1st to 15thNight
22133245%6%8%58%
1260
16th to endNight
421222345%7%64%
1485
August1st to 15thNight
321232435%7%64%
1440
16th to endNight
43134346%6%7%54%
1776
September1st to 15thNight
7%213333446%59%
1800
16th to endNight
8%6%244235%6%9%46%
1951
October1st to 15thNight
9%7%25%6%35%5%45%43%
2160
16th to endNight
11%9%36%6%36%5%6%7%32%
2452
November1st to 15thNight
13%13%48%6%46%45%6%26%
2420
16th to endNight
12%14%6%8%7%35%5%6%7%21%
2541
December1st to 15thNight
9%13%6%10%8%5%6%5%5%7%22%
2700
16th to endNight
10%12%6%10%8%46%6%6%7%21%
3006

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
11%11%5%8%7%48%6%8%8%19%
1267
16th to endDay
8%12%49%8%36%5%6%9%24%
1536
February1st to 15thDay
9%12%5%10%8%46%6%6%7%20%
1501
16th to endDay
6%10%410%8%37%8%6%7%25%
1482
March1st to 15thDay
7%13%6%10%8%46%6%6%7%22%
1821
16th to endDay
7%11%5%9%7%46%7%6%9%21%
2207
April1st to 15thDay
9%12%49%8%47%6%8%7%21%
2149
16th to endDay
9%11%48%6%46%7%6%9%25%
2391
May1st to 15thDay
8%8%47%7%46%6%6%7%33%
2511
16th to endDay
12%8%38%8%46%5%6%7%27%
2615
June1st to 15thDay
15%6%36%6%35%5%6%7%30%
2812
16th to endDay
11%6%26%6%36%5%5%8%36%
2865
July1st to 15thDay
432343445%7%55%
2700
16th to endDay
5%213325%45%6%58%
2684
August1st to 15thDay
43134345%6%8%54%
2520
16th to endDay
6%3145%35%5%6%8%49%
2425
September1st to 15thDay
8%415%5%33437%51%
2160
16th to endDay
12%6%26%5%35%5%7%7%38%
2005
October1st to 15thDay
9%9%37%7%45%5%5%6%34%
1800
16th to endDay
13%9%47%7%45%6%6%7%28%
1769
November1st to 15thDay
15%12%46%6%47%36%8%24%
1437
16th to endDay
8%15%5%7%8%37%6%6%9%22%
1404
December1st to 15thDay
6%11%49%10%5%8%7%8%6%21%
1260
16th to endDay
9%12%5%9%8%46%6%6%8%22%
1224
January1st to 15thNight
12%14%6%11%7%45%6%6%7%16%
2670
16th to endNight
8%15%5%9%7%5%6%5%6%7%22%
2688
February1st to 15thNight
8%14%5%10%7%35%5%5%7%24%
2351
16th to endNight
48%49%8%45%5%6%7%34%
1991
March1st to 15thNight
6%12%48%6%46%6%7%8%28%
2139
16th to endNight
5%8%48%7%46%5%8%9%31%
2016
April1st to 15thNight
5%8%47%7%46%5%6%8%34%
1799
16th to endNight
5%7%36%6%5%5%6%7%8%35%
1568
May1st to 15thNight
6%7%345%46%36%7%42%
1439
16th to endNight
9%7%38%5%35%46%8%37%
1496
June1st to 15thNight
12%5%24436%7%9%8%35%
1145
16th to endNight
5%5%26%5%36%5%6%7%45%
1092
July1st to 15thNight
221332348%8%58%
1260
16th to endNight
411221245%8%63%
1485
August1st to 15thNight
321232425%7%64%
1440
16th to endNight
4314425%5%6%6%55%
1776
September1st to 15thNight
6%213323447%58%
1800
16th to endNight
7%6%25%42445%8%46%
1951
October1st to 15thNight
8%7%35%6%35%45%5%44%
2160
16th to endNight
11%9%37%6%35%5%6%7%33%
2452
November1st to 15thNight
13%13%47%6%35%6%5%6%26%
2420
16th to endNight
11%13%5%9%8%445%6%6%24%
2541
December1st to 15thNight
9%13%5%10%8%5%6%5%5%6%23%
2700
16th to endNight
9%13%5%9%8%46%6%6%6%21%
3006

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
60%14%13%9%2
1267
16th to endDay
56%9%17%12%21
1536
February1st to 15thDay
60%11%14%10%2
1501
16th to endDay
52%11%16%12%6%
1482
March1st to 15thDay
59%8%14%13%2
1821
16th to endDay
56%9%18%12%3
2207
April1st to 15thDay
57%10%13%14%3
2149
16th to endDay
53%7%17%15%5%
2391
May1st to 15thDay
47%7%14%18%10%
2511
16th to endDay
53%8%17%16%4
2619
June1st to 15thDay
50%8%14%17%6%1
2812
16th to endDay
44%6%16%21%10%1
2865
July1st to 15thDay
27%6%15%25%19%4
2541
16th to endDay
25%6%15%28%20%3
2516
August1st to 15thDay
26%6%19%29%14%4
2503
16th to endDay
30%8%17%27%13%3
2425
September1st to 15thDay
32%6%14%26%17%2
2160
16th to endDay
42%9%16%20%8%2
2005
October1st to 15thDay
47%7%17%20%6%
1800
16th to endDay
53%9%16%17%3
1769
November1st to 15thDay
56%9%15%13%3
1437
16th to endDay
58%9%14%13%3
1404
December1st to 15thDay
59%10%13%13%3
1260
16th to endDay
58%13%12%13%2
1224
January1st to 15thNight
65%10%12%9%1
2671
16th to endNight
60%9%14%11%21
2688
February1st to 15thNight
57%9%16%13%3
2363
16th to endNight
46%10%18%18%7%
1991
March1st to 15thNight
50%10%19%15%3
2139
16th to endNight
47%10%20%18%2
2016
April1st to 15thNight
45%9%19%20%4
1799
16th to endNight
42%10%22%20%4
1568
May1st to 15thNight
38%9%18%19%12%1
1440
16th to endNight
43%9%21%19%6%
1496
June1st to 15thNight
39%10%20%20%7%1
1145
16th to endNight
35%7%23%21%11%
1092
July1st to 15thNight
21%8%17%29%18%4
1190
16th to endNight
17%5%18%32%20%5%
1390
August1st to 15thNight
18%6%21%32%17%4
1432
16th to endNight
25%8%18%28%15%3
1776
September1st to 15thNight
25%6%17%28%18%3
1800
16th to endNight
34%7%18%23%11%4
1951
October1st to 15thNight
40%8%18%22%9%
2160
16th to endNight
48%8%18%20%3
2452
November1st to 15thNight
56%9%14%12%4
2420
16th to endNight
60%9%13%12%4
2541
December1st to 15thNight
60%8%13%15%2
2700
16th to endNight
59%11%14%11%2
3006

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
6%10%36%28%18%
60
16th to endDay
21%118%35%18%3
64
February1st to 15thDay
19%15%20%29%13%1
161
16th to endDay
12%19%25%22%16%3
222
March1st to 15thDay
28%28%23%14%4
270
16th to endDay
20%29%29%14%6%
288
April1st to 15thDay
22%22%27%18%6%2
269
16th to endDay
22%20%31%15%7%2
270
May1st to 15thDay
18%17%27%21%10%4
288
16th to endDay
19%13%20%23%15%6%
330
June1st to 15thDay
16%14%26%23%15%2
607
16th to endDay
15%15%24%24%17%3
660
July1st to 15thDay
6%17%30%28%14%2
475
16th to endDay
9%11%28%30%14%5%
353
August1st to 15thDay
6%6%23%29%24%10%
315
16th to endDay
10%13%26%27%16%6%
332
September1st to 15thDay
12%13%22%25%20%6%
315
16th to endDay
15%12%26%21%16%6%
315
October1st to 15thDay
22%13%25%18%11%8%
315
16th to endDay
22%9%19%28%16%2
187
November1st to 15thDay
23%21%29%16%9%
65
16th to endDay
10%8%20%31%13%16%
60
December1st to 15thDay
11%6%25%28%20%8%
60
16th to endDay
10%9%28%28%18%4
64
January1st to 15thNight
23%10%23%26%14%2
747
16th to endNight
16%10%24%32%13%3
768
February1st to 15thNight
18%6%21%34%14%3
704
16th to endNight
7%9%25%36%19%1
632
March1st to 15thNight
16%16%27%26%11%1
720
16th to endNight
12%17%26%29%12%2
768
April1st to 15thNight
12%12%20%34%18%1
719
16th to endNight
9%13%26%36%13%1
488
May1st to 15thNight
10%11%24%34%16%2
360
16th to endNight
12%5%22%32%26%1
375
June1st to 15thNight
12%8%26%34%15%2
360
16th to endNight
8%10%29%36%14%1
360
July1st to 15thNight
46%22%42%23%
340
16th to endNight
4420%43%25%2
376
August1st to 15thNight
3111%37%40%5%
360
16th to endNight
7%5%18%35%30%3
630
September1st to 15thNight
9%414%33%28%9%
720
16th to endNight
11%8%19%30%26%4
716
October1st to 15thNight
13%7%18%36%21%2
720
16th to endNight
16%10%24%28%16%2
768
November1st to 15thNight
21%12%26%31%7%
700
16th to endNight
19%12%25%28%12%2
741
December1st to 15thNight
14%10%26%34%13%1
900
16th to endNight
16%11%30%30%9%1
931
Page generated at 2017-11-01 14:23:29. Version ac04

Copyright 2017 A. Danko


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