Newcastle Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Newcastle Observatory 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
39%
14967
14%
47404
10%
14934
44%
14934
19%
33222

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
14%
719
7%
2506
3%
716
19%
716
7%
2075
January16th to endNight
21%
768
10%
2505
4%
768
27%
768
8%
2047
February1st to 15thNight
17%
701
9%
2287
4%
701
24%
701
10%
1799
February16th to endNight
25%
631
12%
2015
5%
631
33%
631
14%
1491
March1st to 15thNight
26%
720
14%
1989
6%
720
33%
720
17%
1498
March16th to endNight
39%
768
21%
2109
11%
768
47%
768
27%
1396
April1st to 15thNight
38%
718
16%
1796
7%
718
42%
718
25%
1304
April16th to endNight
47%
597
20%
1677
10%
597
53%
597
30%
1094
May1st to 15thNight
53%
450
15%
1530
15%
450
56%
450
23%
992
May16th to endNight
60%
374
17%
1497
20%
374
65%
374
26%
830
June1st to 15thNight
55%
360
12%
1440
14%
360
62%
360
21%
877
June16th to endNight
60%
360
11%
1440
18%
360
62%
360
23%
840
July1st to 15thNight
71%
340
16%
1360
26%
340
73%
340
33%
681
July16th to endNight
70%
441
16%
1478
20%
414
73%
414
31%
833
August1st to 15thNight
69%
539
16%
1609
14%
536
71%
536
34%
957
August16th to endNight
65%
648
22%
1794
14%
648
68%
648
35%
1085
September1st to 15thNight
59%
720
20%
1800
11%
720
62%
720
35%
1178
September16th to endNight
58%
717
23%
1998
18%
717
61%
717
31%
1267
October1st to 15thNight
40%
720
16%
2160
14%
720
45%
720
21%
1498
October16th to endNight
30%
768
13%
2303
9%
768
36%
768
16%
1700
November1st to 15thNight
38%
700
18%
2383
16%
700
45%
700
20%
1603
November16th to endNight
27%
720
10%
2520
7%
720
32%
720
11%
1920
December1st to 15thNight
16%
720
6%
2520
2%
720
20%
720
8%
2050
December16th to endNight
16%
768
6%
2688
2%
768
21%
768
8%
2207

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
14%7%36%5%35%5%5%7%34%
48350
Night
16%8%36%5%3445%6%35%
47580
Cloud CoverDay
14%7%36%5%35%5%5%7%35%
48360
Night
16%8%36%5%3445%6%35%
47585
TransparencyDay
46%6%14%21%10%1
48044
Night
49%6%11%19%11%1
47404
SeeingDay
17%419%30%21%6%
5564
Night
20%7%24%29%15%2
14972

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
18%14%6%7%6%34446%24%
1432
16th to endDay
13%14%6%10%8%5%7%445%19%
1719
February1st to 15thDay
14%12%5%12%8%46%445%21%
1575
16th to endDay
17%12%6%8%5%25%44428%
1458
March1st to 15thDay
16%9%48%6%36%45%6%29%
1957
16th to endDay
16%8%45%5%24345%38%
2114
April1st to 15thDay
19%7%37%6%2445%6%30%
2152
16th to endDay
17%7%25%5%24446%39%
2294
May1st to 15thDay
14%6%35%6%36%45%7%36%
2420
16th to endDay
11%5%25%435%5%6%8%41%
2618
June1st to 15thDay
16%5%25%4346%5%8%35%
2520
16th to endDay
12%4244345%6%10%40%
2520
July1st to 15thDay
8%423436%5%6%10%45%
2520
16th to endDay
8%425%5%46%6%7%9%40%
2588
August1st to 15thDay
7%5%25%6%35%6%6%8%42%
2340
16th to endDay
9%5%244245%6%9%44%
2396
September1st to 15thDay
14%4144445%47%43%
2160
16th to endDay
12%425%42445%6%45%
1959
October1st to 15thDay
19%7%345%35%45%5%34%
1800
16th to endDay
21%9%36%6%3445%5%28%
1920
November1st to 15thDay
15%8%47%5%35%45%8%31%
1472
16th to endDay
19%12%46%6%35%5%47%24%
1440
December1st to 15thDay
18%12%6%9%6%445%5%6%19%
1440
16th to endDay
20%13%6%8%7%35%446%18%
1536
January1st to 15thNight
21%12%6%7%6%34435%22%
2506
16th to endNight
15%12%6%9%6%36%5%46%23%
2505
February1st to 15thNight
14%14%6%8%6%36%445%25%
2285
16th to endNight
16%10%47%6%345%5%6%29%
2015
March1st to 15thNight
19%9%47%6%3443432%
1977
16th to endNight
15%6%35%433335%44%
2109
April1st to 15thNight
19%7%35%425%446%36%
1796
16th to endNight
13%7%24425%446%44%
1677
May1st to 15thNight
15%4246%35%46%7%38%
1530
16th to endNight
12%3244235%5%7%47%
1495
June1st to 15thNight
12%5%25%5%25%6%5%8%40%
1440
16th to endNight
11%5%25%43445%9%42%
1440
July1st to 15thNight
5%314424448%55%
1440
16th to endNight
9%3143345%5%9%48%
1579
August1st to 15thNight
8%3144245%6%9%48%
1620
16th to endNight
7%424434446%52%
1794
September1st to 15thNight
13%5%1332445%5%48%
1800
16th to endNight
13%5%24423446%48%
1998
October1st to 15thNight
18%6%26%5%33446%37%
2160
16th to endNight
20%8%36%5%345%5%6%30%
2303
November1st to 15thNight
16%7%35%435%45%6%36%
2383
16th to endNight
22%10%45%435%5%5%7%25%
2520
December1st to 15thNight
21%13%48%5%35%447%21%
2520
16th to endNight
22%11%5%7%6%46%45%6%18%
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
17%14%6%7%5%35%5%47%22%
1432
16th to endDay
14%14%5%10%9%5%6%5%46%18%
1719
February1st to 15thDay
14%11%6%10%9%45%5%6%6%20%
1575
16th to endDay
17%11%6%8%5%34436%27%
1458
March1st to 15thDay
16%8%49%6%35%5%5%5%29%
1968
16th to endDay
16%8%345%34346%39%
2113
April1st to 15thDay
20%6%36%5%3446%7%31%
2152
16th to endDay
17%6%35%424446%40%
2294
May1st to 15thDay
14%5%35%6%36%46%7%37%
2420
16th to endDay
11%5%25%435%5%5%8%42%
2618
June1st to 15thDay
16%5%25%425%5%5%9%37%
2520
16th to endDay
12%5%145%2447%10%41%
2520
July1st to 15thDay
7%323425%5%6%10%47%
2520
16th to endDay
8%424436%5%6%10%42%
2588
August1st to 15thDay
6%5%35%4446%6%8%43%
2340
16th to endDay
9%5%2431447%9%46%
2396
September1st to 15thDay
14%424335%5%5%7%44%
2160
16th to endDay
12%42442445%7%46%
1959
October1st to 15thDay
20%6%35%5%34446%34%
1800
16th to endDay
22%7%37%6%3345%6%28%
1920
November1st to 15thDay
14%7%36%6%45%45%8%32%
1472
16th to endDay
20%10%47%6%25%5%5%6%25%
1440
December1st to 15thDay
19%13%5%9%6%45%45%7%19%
1440
16th to endDay
20%14%5%8%7%245%46%19%
1536
January1st to 15thNight
22%12%6%8%7%35%345%20%
2506
16th to endNight
15%13%6%8%6%46%5%46%22%
2505
February1st to 15thNight
14%13%6%9%7%35%445%24%
2278
16th to endNight
16%10%47%6%45%45%6%28%
2015
March1st to 15thNight
20%9%46%5%34345%32%
1989
16th to endNight
15%6%34434325%44%
2109
April1st to 15thNight
20%7%35%424446%36%
1796
16th to endNight
14%6%25%323446%44%
1677
May1st to 15thNight
15%5%146%35%5%5%8%37%
1530
16th to endNight
12%43342445%7%47%
1495
June1st to 15thNight
13%425%5%347%6%7%39%
1440
16th to endNight
12%4246%25%5%5%9%42%
1440
July1st to 15thNight
5%32432435%8%55%
1440
16th to endNight
8%423325%5%5%9%48%
1579
August1st to 15thNight
8%4244245%6%9%48%
1620
16th to endNight
7%5%25%4345%46%52%
1794
September1st to 15thNight
14%5%1332445%5%48%
1800
16th to endNight
13%5%24423347%48%
1998
October1st to 15thNight
18%6%25%5%3435%5%37%
2160
16th to endNight
21%7%36%5%3446%6%30%
2303
November1st to 15thNight
16%7%35%4345%5%7%36%
2383
16th to endNight
22%9%45%5%25%5%5%8%24%
2520
December1st to 15thNight
21%14%47%6%3445%6%21%
2520
16th to endNight
22%12%5%7%6%45%5%5%6%18%
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
62%8%12%11%4
1433
16th to endDay
68%7%7%10%5%
1719
February1st to 15thDay
65%6%10%13%3
1577
16th to endDay
59%5%12%15%7%
1458
March1st to 15thDay
54%5%14%17%7%
1968
16th to endDay
46%310%20%16%2
2114
April1st to 15thDay
48%6%12%18%12%1
2152
16th to endDay
43%411%22%15%2
2294
May1st to 15thDay
42%5%13%22%13%1
2420
16th to endDay
37%6%15%25%12%2
2622
June1st to 15thDay
41%6%15%23%11%
2520
16th to endDay
35%7%18%24%13%
2520
July1st to 15thDay
28%7%15%29%16%1
2371
16th to endDay
34%8%17%26%11%1
2426
August1st to 15thDay
34%6%19%24%14%1
2327
16th to endDay
31%6%17%31%12%1
2396
September1st to 15thDay
36%7%16%27%11%1
2160
16th to endDay
36%6%15%30%11%
1959
October1st to 15thDay
50%5%12%21%9%1
1800
16th to endDay
55%6%17%14%5%1
1920
November1st to 15thDay
48%7%15%18%8%1
1472
16th to endDay
59%5%14%14%4
1440
December1st to 15thDay
66%7%13%10%1
1440
16th to endDay
68%7%10%10%2
1536
January1st to 15thNight
67%8%8%10%3
2506
16th to endNight
65%8%7%12%5%
2505
February1st to 15thNight
63%6%10%15%4
2287
16th to endNight
57%412%18%6%
2015
March1st to 15thNight
57%411%19%7%
1989
16th to endNight
43%39%23%17%2
2109
April1st to 15thNight
48%5%10%19%15%1
1796
16th to endNight
40%410%21%18%3
1677
May1st to 15thNight
43%5%12%20%15%2
1530
16th to endNight
34%6%13%25%17%2
1497
June1st to 15thNight
41%6%11%23%16%1
1440
16th to endNight
37%6%13%23%16%1
1440
July1st to 15thNight
26%6%13%26%24%1
1360
16th to endNight
32%6%13%26%18%2
1478
August1st to 15thNight
31%7%17%27%13%1
1609
16th to endNight
32%5%12%31%15%1
1794
September1st to 15thNight
36%5%14%26%15%1
1800
16th to endNight
37%410%30%15%
1998
October1st to 15thNight
48%5%10%22%13%
2160
16th to endNight
53%6%14%16%7%
2303
November1st to 15thNight
46%6%13%19%12%1
2383
16th to endNight
59%7%13%13%5%
2520
December1st to 15thNight
65%8%12%10%2
2520
16th to endNight
68%6%11%10%3
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
20%21%31%18%5%3
60
16th to endDay
30%10%33%20%5%
95
February1st to 15thDay
20%18%42%17%1
90
16th to endDay
23%10%35%25%4
117
March1st to 15thDay
24%8%30%27%10%
270
16th to endDay
23%429%31%10%1
288
April1st to 15thDay
20%5%30%31%10%1
270
16th to endDay
20%227%29%15%4
270
May1st to 15thDay
21%15%34%21%6%
288
16th to endDay
12%112%38%27%6%
331
June1st to 15thDay
21%113%36%26%1
315
16th to endDay
15%13%37%27%5%
315
July1st to 15thDay
9%10%30%38%9%
305
16th to endDay
9%11%41%28%8%
326
August1st to 15thDay
8%28%31%36%11%
313
16th to endDay
12%12%25%34%14%
332
September1st to 15thDay
12%313%23%34%12%
315
16th to endDay
15%413%28%21%17%
314
October1st to 15thDay
21%5%22%26%18%6%
315
16th to endDay
25%11%27%24%11%
336
November1st to 15thDay
14%426%39%12%2
115
16th to endDay
25%5%26%30%11%1
60
December1st to 15thDay
13%16%38%23%8%
60
16th to endDay
31%23%31%14%
64
January1st to 15thNight
28%16%32%16%5%
720
16th to endNight
22%12%32%25%6%
768
February1st to 15thNight
22%12%39%21%4
704
16th to endNight
22%10%32%28%5%
631
March1st to 15thNight
25%10%30%27%5%
720
16th to endNight
19%5%29%29%14%2
768
April1st to 15thNight
21%6%28%33%10%
718
16th to endNight
17%324%36%16%2
597
May1st to 15thNight
18%18%36%22%3
450
16th to endNight
12%16%41%24%4
375
June1st to 15thNight
14%118%38%23%3
360
16th to endNight
12%111%43%26%3
360
July1st to 15thNight
6%11%44%30%5%
340
16th to endNight
9%210%40%31%4
441
August1st to 15thNight
9%110%38%31%7%
539
16th to endNight
10%112%33%34%6%
648
September1st to 15thNight
17%412%29%30%6%
720
16th to endNight
15%315%26%27%10%
717
October1st to 15thNight
22%5%22%26%18%3
720
16th to endNight
24%9%28%28%9%
768
November1st to 15thNight
21%6%27%29%13%2
700
16th to endNight
26%11%26%24%9%1
720
December1st to 15thNight
30%12%32%18%4
720
16th to endNight
28%11%34%20%3
768
Page generated at 2017-11-01 17:23:37. Version ac04

Copyright 2017 A. Danko


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