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Sky Retreat at Westwater
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sky Retreat at Westwater clear sky chart from 2005-11-05 to 2020-06-03.

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
68%
19530
26%
57915
22%
19494
71%
19494
40%
32213

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
70%
896
19%
2912
19%
896
71%
896
33%
1691
January16th to endNight
67%
960
22%
3120
24%
960
69%
960
30%
1892
February1st to 15thNight
65%
878
15%
2873
16%
878
67%
878
28%
1770
February16th to endNight
59%
792
26%
2426
22%
792
65%
792
33%
1449
March1st to 15thNight
63%
900
24%
2475
21%
900
66%
900
40%
1438
March16th to endNight
61%
960
24%
2640
18%
960
65%
960
37%
1580
April1st to 15thNight
53%
719
23%
2293
19%
719
60%
719
33%
1303
April16th to endNight
53%
669
25%
2150
19%
669
62%
669
36%
1184
May1st to 15thNight
63%
675
24%
2025
20%
675
67%
675
38%
1139
May16th to endNight
65%
705
27%
2005
22%
705
69%
705
43%
1096
June1st to 15thNight
69%
637
30%
1699
23%
637
72%
637
57%
861
June16th to endNight
77%
630
31%
1680
27%
630
80%
630
62%
817
July1st to 15thNight
79%
600
22%
1736
20%
600
80%
600
47%
918
July16th to endNight
84%
660
23%
1881
21%
627
85%
627
46%
978
August1st to 15thNight
81%
620
26%
1854
24%
617
81%
617
43%
995
August16th to endNight
81%
669
32%
2139
33%
669
83%
669
47%
1066
September1st to 15thNight
78%
650
33%
2120
35%
650
81%
650
48%
1013
September16th to endNight
76%
836
38%
2324
30%
836
81%
836
58%
1128
October1st to 15thNight
68%
840
32%
2520
25%
840
73%
840
50%
1253
October16th to endNight
72%
896
36%
2688
29%
896
78%
896
51%
1333
November1st to 15thNight
73%
891
35%
2698
30%
891
77%
891
52%
1296
November16th to endNight
68%
1125
28%
3150
23%
1125
70%
1125
46%
1719
December1st to 15thNight
64%
1125
17%
3150
14%
1125
65%
1125
34%
1956
December16th to endNight
58%
1197
14%
3357
12%
1197
60%
1197
24%
2338

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
331442446%9%56%
58488
Night
442442445%8%54%
58109
TransparencyDay
23%5%13%22%20%14%
58183
Night
26%6%13%22%19%11%
57915
SeeingDay
5%6%21%34%25%6%
9227
Night
6%216%42%29%3
19542

By Month

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
3425%6%36%7%8%13%37%
2016
16th to endDay
5%5%245%35%5%6%12%43%
2160
February1st to 15thDay
35%36%5%25%5%8%13%40%
1980
16th to endDay
5%6%36%5%246%5%8%46%
1924
March1st to 15thDay
45%2442445%10%50%
2475
16th to endDay
3424425%6%6%10%50%
2640
April1st to 15thDay
45%1442345%8%53%
2645
16th to endDay
231442445%8%55%
2741
May1st to 15thDay
3413435%5%6%8%52%
2916
16th to endDay
221333346%8%58%
3163
June1st to 15thDay
121221235%7%68%
2970
16th to endDay
112212236%75%
2940
July1st to 15thDay
22133345%7%10%56%
2790
16th to endDay
22134346%7%11%50%
2883
August1st to 15thDay
2215%4346%7%9%52%
2680
16th to endDay
22332435%8%62%
2767
September1st to 15thDay
3212223447%64%
2496
16th to endDay
2212212235%72%
2295
October1st to 15thDay
5%212213345%66%
2100
16th to endDay
221321236%6%67%
2240
November1st to 15thDay
2313322336%67%
2132
16th to endDay
431442345%6%59%
1800
December1st to 15thDay
5%6%36%5%2445%10%44%
1800
16th to endDay
5%8%36%6%36%6%6%12%34%
1935
January1st to 15thNight
4424436%6%7%10%47%
2912
16th to endNight
5%6%245%35%5%7%10%43%
3120
February1st to 15thNight
35%245%35%7%6%10%44%
2862
16th to endNight
46%34435%46%7%47%
2426
March1st to 15thNight
45%244245%47%53%
2475
16th to endNight
4425%4345%5%8%50%
2640
April1st to 15thNight
5%5%25%425%46%6%50%
2293
16th to endNight
5%5%245%3445%8%50%
2150
May1st to 15thNight
44244345%5%7%53%
2024
16th to endNight
4212435%46%8%56%
2004
June1st to 15thNight
321231245%6%66%
1699
16th to endNight
212312435%71%
1680
July1st to 15thNight
22134245%7%10%52%
1826
16th to endNight
1113435%7%9%13%48%
1989
August1st to 15thNight
23143345%6%10%53%
1863
16th to endNight
22133335%6%9%56%
2139
September1st to 15thNight
321332346%8%61%
2120
16th to endNight
3112312335%71%
2324
October1st to 15thNight
5%313212246%65%
2520
16th to endNight
3313223347%65%
2688
November1st to 15thNight
2313223346%66%
2698
16th to endNight
4412323447%60%
3150
December1st to 15thNight
6%6%25%5%1445%7%50%
3150
16th to endNight
5%10%36%5%36%6%7%8%36%
3357

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
32%12%24%25%4
2017
16th to endDay
32%11%22%24%8%
2160
February1st to 15thDay
31%8%25%21%10%1
1980
16th to endDay
34%6%13%29%14%2
1924
March1st to 15thDay
28%5%16%28%17%3
2475
16th to endDay
27%7%14%28%16%5%
2640
April1st to 15thDay
26%5%13%24%21%8%
2645
16th to endDay
24%5%12%25%23%8%
2741
May1st to 15thDay
26%5%11%19%26%10%
2916
16th to endDay
21%5%10%20%26%15%
3166
June1st to 15thDay
14%36%15%28%32%
2970
16th to endDay
11%248%23%50%
2940
July1st to 15thDay
20%5%11%15%17%29%
2651
16th to endDay
22%5%13%20%18%19%
2728
August1st to 15thDay
24%6%13%18%14%22%
2665
16th to endDay
18%38%20%26%22%
2767
September1st to 15thDay
18%48%16%25%26%
2496
16th to endDay
14%28%18%34%20%
2295
October1st to 15thDay
19%410%22%28%14%
2100
16th to endDay
17%411%30%30%5%
2240
November1st to 15thDay
19%411%29%29%6%
2132
16th to endDay
25%317%34%17%1
1800
December1st to 15thDay
34%10%23%24%7%
1800
16th to endDay
40%12%21%19%4
1935
January1st to 15thNight
28%10%23%28%8%
2912
16th to endNight
34%8%21%27%7%1
3120
February1st to 15thNight
31%12%21%22%10%2
2873
16th to endNight
32%6%13%26%17%2
2426
March1st to 15thNight
27%6%14%27%20%4
2475
16th to endNight
31%5%11%23%22%4
2640
April1st to 15thNight
31%5%10%21%20%10%
2293
16th to endNight
30%411%21%22%9%
2150
May1st to 15thNight
28%6%11%17%27%9%
2025
16th to endNight
24%6%9%20%27%12%
2005
June1st to 15thNight
17%37%12%25%33%
1699
16th to endNight
15%35%8%18%48%
1680
July1st to 15thNight
22%5%10%14%17%29%
1736
16th to endNight
20%7%14%20%18%18%
1881
August1st to 15thNight
23%6%11%18%19%20%
1854
16th to endNight
20%5%9%18%20%25%
2139
September1st to 15thNight
20%410%15%18%31%
2120
16th to endNight
17%26%17%29%26%
2324
October1st to 15thNight
20%47%19%28%18%
2520
16th to endNight
19%48%24%32%10%
2688
November1st to 15thNight
18%39%26%32%8%
2698
16th to endNight
23%5%11%31%24%4
3150
December1st to 15thNight
32%8%18%25%13%1
3150
16th to endNight
40%11%19%21%4
3357

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
12%116%39%21%8%
225
16th to endDay
10%19%40%29%7%
240
February1st to 15thDay
9%316%47%16%6%
225
16th to endDay
7%422%44%17%3
265
March1st to 15thDay
10%8%23%34%21%2
450
16th to endDay
6%12%32%33%13%1
480
April1st to 15thDay
8%15%25%31%14%4
449
16th to endDay
6%15%28%29%18%1
438
May1st to 15thDay
410%30%30%17%5%
468
16th to endDay
5%9%23%30%25%6%
632
June1st to 15thDay
37%20%33%29%5%
656
16th to endDay
2420%34%32%4
645
July1st to 15thDay
2214%29%39%12%
485
16th to endDay
3111%38%37%7%
455
August1st to 15thDay
3216%39%28%8%
419
16th to endDay
3115%36%35%6%
460
September1st to 15thDay
2223%32%28%10%
435
16th to endDay
49%23%28%26%7%
420
October1st to 15thDay
8%9%20%30%22%8%
225
16th to endDay
46%19%32%32%5%
240
November1st to 15thDay
2418%36%30%7%
225
16th to endDay
8%422%39%19%5%
225
December1st to 15thDay
8%123%44%17%4
225
16th to endDay
9%311%46%25%4
240
January1st to 15thNight
5%213%45%28%4
900
16th to endNight
8%214%44%24%4
960
February1st to 15thNight
6%118%48%22%3
884
16th to endNight
7%321%50%15%1
792
March1st to 15thNight
6%318%47%22%1
900
16th to endNight
5%321%47%20%1
960
April1st to 15thNight
7%5%26%44%14%
719
16th to endNight
8%5%25%34%22%2
669
May1st to 15thNight
6%221%43%22%2
675
16th to endNight
5%418%38%29%3
707
June1st to 15thNight
3219%39%32%2
637
16th to endNight
2113%45%34%2
630
July1st to 15thNight
218%34%48%5%
600
16th to endNight
2430%56%5%
660
August1st to 15thNight
5%438%47%3
620
16th to endNight
38%33%47%6%
669
September1st to 15thNight
49%40%39%5%
650
16th to endNight
4112%32%39%8%
836
October1st to 15thNight
5%119%44%24%4
840
16th to endNight
5%215%38%33%4
896
November1st to 15thNight
3115%46%28%4
891
16th to endNight
6%317%43%25%4
1125
December1st to 15thNight
9%216%50%19%1
1125
16th to endNight
10%217%44%22%2
1197
Page generated at 2020-06-04 01:18:56. Version ac04

Copyright 2020 A. Danko


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