Newmarket
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Newmarket clear sky chart from 2005-11-05 to 2017-12-20.

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
31%
15170
13%
47923
8%
15134
37%
15134
17%
33941

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
13%
719
8%
2485
3%
716
21%
716
7%
1988
January16th to endNight
17%
768
9%
2496
4%
768
23%
768
9%
2005
February1st to 15thNight
14%
701
9%
2287
2%
701
22%
701
9%
1809
February16th to endNight
18%
631
11%
2021
4%
631
26%
631
12%
1497
March1st to 15thNight
19%
720
13%
1980
5%
720
27%
720
15%
1492
March16th to endNight
27%
768
20%
2112
9%
768
36%
768
23%
1447
April1st to 15thNight
23%
718
14%
1817
5%
718
28%
718
21%
1340
April16th to endNight
32%
559
19%
1639
8%
559
41%
559
25%
1083
May1st to 15thNight
43%
481
16%
1561
12%
481
49%
481
22%
1025
May16th to endNight
42%
374
17%
1497
14%
374
53%
374
25%
825
June1st to 15thNight
39%
360
12%
1440
10%
360
48%
360
19%
865
June16th to endNight
47%
360
12%
1310
14%
360
52%
360
25%
783
July1st to 15thNight
57%
340
16%
1309
20%
340
63%
340
34%
682
July16th to endNight
55%
477
16%
1511
15%
447
59%
447
30%
886
August1st to 15thNight
60%
539
16%
1609
11%
536
64%
536
36%
944
August16th to endNight
56%
622
23%
1768
13%
622
61%
622
35%
1055
September1st to 15thNight
48%
720
19%
1806
9%
720
53%
720
34%
1169
September16th to endNight
53%
717
22%
2006
16%
717
56%
717
31%
1266
October1st to 15thNight
36%
720
15%
2160
12%
720
41%
720
21%
1510
October16th to endNight
21%
768
11%
2304
5%
768
30%
768
13%
1760
November1st to 15thNight
29%
760
16%
2590
13%
760
35%
760
17%
1808
November16th to endNight
22%
780
9%
2730
5%
780
27%
780
10%
2112
December1st to 15thNight
12%
780
5%
2730
2%
780
17%
780
7%
2249
December16th to endNight
9%
788
5%
2755
1%
788
14%
788
5%
2341

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
15%9%47%6%35%45%7%30%
48899
Night
15%9%46%6%3445%6%33%
48102
Cloud CoverDay
15%9%47%6%35%5%5%7%31%
48909
Night
15%9%46%6%3445%6%33%
48106
TransparencyDay
51%7%12%18%9%
48596
Night
49%7%12%19%10%1
47923
SeeingDay
18%11%29%23%12%5%
5786
Night
19%11%32%25%10%1
15175

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
17%12%7%9%7%35%5%46%19%
1451
16th to endDay
13%14%7%11%9%6%5%45%6%15%
1728
February1st to 15thDay
13%15%5%13%8%45%445%18%
1575
16th to endDay
16%14%6%9%6%24445%24%
1450
March1st to 15thDay
13%12%410%7%5%5%445%26%
1969
16th to endDay
14%11%46%6%34345%35%
2112
April1st to 15thDay
20%10%46%5%3346%5%29%
2131
16th to endDay
16%9%35%424446%37%
2331
May1st to 15thDay
15%7%35%6%345%5%7%35%
2388
16th to endDay
13%5%35%5%3446%6%39%
2618
June1st to 15thDay
17%6%345%2446%8%34%
2520
16th to endDay
14%5%245%45%5%5%9%36%
2643
July1st to 15thDay
9%435%5%45%5%7%9%39%
2565
16th to endDay
9%6%35%6%36%5%8%10%33%
2552
August1st to 15thDay
9%5%27%6%45%6%6%8%37%
2340
16th to endDay
12%6%246%345%7%9%37%
2421
September1st to 15thDay
15%6%26%5%35%5%6%7%36%
2151
16th to endDay
13%6%36%5%24446%40%
1953
October1st to 15thDay
20%8%37%6%34345%33%
1800
16th to endDay
25%13%37%5%34445%21%
1920
November1st to 15thDay
15%14%46%6%235%5%7%28%
1593
16th to endDay
17%14%6%10%7%35%436%19%
1560
December1st to 15thDay
16%16%7%11%8%36%5%3414%
1560
16th to endDay
19%13%7%10%8%35%45%6%14%
1568
January1st to 15thNight
17%15%6%8%7%45%45%6%18%
2485
16th to endNight
13%13%7%10%8%46%5%5%5%20%
2496
February1st to 15thNight
13%15%6%9%7%45%6%45%21%
2285
16th to endNight
13%11%410%7%45%45%6%25%
2021
March1st to 15thNight
16%11%5%7%7%35%345%30%
1968
16th to endNight
13%9%45%5%23445%40%
2112
April1st to 15thNight
18%9%35%5%35%345%35%
1817
16th to endNight
13%8%26%5%23445%42%
1639
May1st to 15thNight
15%5%245%35%5%5%7%38%
1561
16th to endNight
11%5%13424437%49%
1495
June1st to 15thNight
14%425%5%345%5%8%40%
1440
16th to endNight
10%5%25%5%245%5%8%44%
1310
July1st to 15thNight
6%32442445%6%55%
1389
16th to endNight
7%4235%345%6%8%47%
1615
August1st to 15thNight
7%41442446%9%49%
1620
16th to endNight
9%42443345%6%51%
1768
September1st to 15thNight
14%423425%446%46%
1806
16th to endNight
12%5%2442335%6%47%
2006
October1st to 15thNight
17%7%26%5%24446%37%
2160
16th to endNight
22%8%36%6%3445%7%26%
2304
November1st to 15thNight
19%9%345%25%45%6%32%
2590
16th to endNight
19%11%47%6%35%45%5%24%
2730
December1st to 15thNight
18%15%5%9%8%35%5%4417%
2730
16th to endNight
19%13%8%11%7%45%5%5%5%13%
2755

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%12%6%10%6%35%5%5%6%20%
1451
16th to endDay
13%15%7%10%9%5%6%45%5%16%
1728
February1st to 15thDay
13%15%7%12%8%35%445%18%
1575
16th to endDay
16%14%6%9%5%3444425%
1450
March1st to 15thDay
14%11%48%8%45%445%26%
1980
16th to endDay
15%10%46%6%3335%5%36%
2111
April1st to 15thDay
20%10%46%5%3445%5%29%
2131
16th to endDay
17%8%35%5%24346%37%
2331
May1st to 15thDay
15%7%36%6%345%5%7%35%
2388
16th to endDay
13%5%26%6%3446%6%39%
2618
June1st to 15thDay
17%5%35%435%5%6%8%34%
2520
16th to endDay
14%5%25%5%35%5%6%9%36%
2643
July1st to 15thDay
9%435%5%36%6%6%9%39%
2565
16th to endDay
9%6%36%6%35%6%7%10%33%
2552
August1st to 15thDay
9%5%27%6%35%5%7%8%37%
2340
16th to endDay
12%6%25%6%345%7%9%37%
2421
September1st to 15thDay
15%6%25%4345%5%8%36%
2151
16th to endDay
13%6%36%5%24447%40%
1953
October1st to 15thDay
20%8%37%6%34345%33%
1800
16th to endDay
24%13%47%5%3445%6%21%
1920
November1st to 15thDay
15%13%46%6%335%47%28%
1593
16th to endDay
18%14%6%8%8%35%5%46%19%
1560
December1st to 15thDay
16%16%7%10%8%45%5%45%15%
1560
16th to endDay
19%12%8%9%7%5%5%45%6%14%
1568
January1st to 15thNight
18%15%6%8%7%445%46%18%
2485
16th to endNight
13%12%7%10%7%46%5%5%5%20%
2496
February1st to 15thNight
13%14%6%8%7%35%5%5%6%21%
2278
16th to endNight
13%11%49%6%46%45%6%26%
2021
March1st to 15thNight
16%11%5%8%6%35%335%30%
1980
16th to endNight
13%9%46%424345%41%
2112
April1st to 15thNight
19%8%35%5%35%345%34%
1817
16th to endNight
12%9%27%423345%42%
1639
May1st to 15thNight
15%5%25%5%35%46%7%38%
1560
16th to endNight
11%414424446%50%
1495
June1st to 15thNight
13%5%25%5%245%5%8%40%
1440
16th to endNight
11%435%4245%5%8%43%
1310
July1st to 15thNight
6%325%32445%6%54%
1389
16th to endNight
7%4245%245%6%8%47%
1615
August1st to 15thNight
6%5%15%43446%10%48%
1620
16th to endNight
8%41433445%6%51%
1768
September1st to 15thNight
13%5%1442445%6%46%
1806
16th to endNight
12%5%24423446%47%
2006
October1st to 15thNight
17%7%36%5%2445%6%37%
2160
16th to endNight
22%8%36%7%3445%6%27%
2304
November1st to 15thNight
18%9%35%5%2445%6%32%
2590
16th to endNight
19%11%47%6%345%5%6%24%
2730
December1st to 15thNight
18%14%6%8%8%35%5%5%5%17%
2730
16th to endNight
19%14%8%11%7%346%45%13%
2755

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
63%8%11%12%4
1452
16th to endDay
66%8%9%10%4
1728
February1st to 15thDay
66%6%9%12%3
1577
16th to endDay
60%6%11%14%6%
1450
March1st to 15thDay
58%6%12%15%6%
1980
16th to endDay
49%5%10%17%15%1
2112
April1st to 15thDay
55%411%17%10%
2131
16th to endDay
46%6%10%20%14%1
2331
May1st to 15thDay
47%7%11%19%13%
2388
16th to endDay
42%7%13%21%13%1
2622
June1st to 15thDay
45%7%14%19%12%
2520
16th to endDay
43%7%14%20%12%
2643
July1st to 15thDay
37%8%14%22%14%1
2416
16th to endDay
42%9%15%20%10%1
2393
August1st to 15thDay
41%9%16%18%13%1
2327
16th to endDay
40%7%15%24%9%1
2421
September1st to 15thDay
43%8%14%22%10%
2151
16th to endDay
43%6%12%26%9%
1953
October1st to 15thDay
53%5%10%20%9%1
1800
16th to endDay
62%8%13%11%4
1920
November1st to 15thDay
54%8%12%15%7%
1593
16th to endDay
63%7%13%10%3
1560
December1st to 15thDay
68%8%11%9%1
1560
16th to endDay
68%8%10%9%2
1568
January1st to 15thNight
65%6%10%11%4
2485
16th to endNight
63%8%11%12%3
2496
February1st to 15thNight
61%8%9%15%4
2287
16th to endNight
55%6%14%16%6%
2021
March1st to 15thNight
56%5%12%18%6%
1980
16th to endNight
45%5%10%21%15%1
2112
April1st to 15thNight
51%410%19%13%
1817
16th to endNight
42%5%11%20%16%3
1639
May1st to 15thNight
43%7%11%20%15%2
1561
16th to endNight
33%6%14%26%15%2
1497
June1st to 15thNight
39%7%12%23%15%1
1440
16th to endNight
37%7%14%23%16%
1310
July1st to 15thNight
28%413%27%23%1
1309
16th to endNight
32%8%13%27%15%2
1511
August1st to 15thNight
29%8%19%27%13%1
1609
16th to endNight
31%6%13%31%15%1
1768
September1st to 15thNight
35%5%17%25%14%1
1806
16th to endNight
35%6%12%31%13%
2006
October1st to 15thNight
46%7%11%20%13%
2160
16th to endNight
55%8%14%14%6%
2304
November1st to 15thNight
50%6%13%18%9%1
2590
16th to endNight
58%9%14%13%3
2730
December1st to 15thNight
66%8%11%10%2
2730
16th to endNight
69%9%9%8%2
2755

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
19%26%31%17%4
63
16th to endDay
29%21%36%11%1
96
February1st to 15thDay
20%28%42%8%
90
16th to endDay
23%25%34%15%1
90
March1st to 15thDay
21%17%36%20%4
270
16th to endDay
22%14%34%19%6%2
288
April1st to 15thDay
24%16%33%16%7%1
270
16th to endDay
18%15%31%20%10%4
270
May1st to 15thDay
21%10%25%25%11%5%
288
16th to endDay
16%10%34%25%10%3
331
June1st to 15thDay
20%10%25%29%12%1
315
16th to endDay
17%7%31%29%12%1
438
July1st to 15thDay
11%428%32%16%6%
350
16th to endDay
7%7%26%34%14%8%
326
August1st to 15thDay
11%325%26%19%13%
313
16th to endDay
14%322%25%21%13%
332
September1st to 15thDay
10%5%23%25%20%14%
315
16th to endDay
13%5%22%23%23%12%
314
October1st to 15thDay
22%7%31%20%13%5%
315
16th to endDay
26%16%31%18%6%
336
November1st to 15thDay
20%15%29%24%8%2
124
16th to endDay
30%18%34%13%3
90
December1st to 15thDay
23%20%33%18%4
90
16th to endDay
27%23%41%6%
72
January1st to 15thNight
24%21%34%14%4
720
16th to endNight
18%14%38%22%5%
768
February1st to 15thNight
20%17%39%19%2
704
16th to endNight
19%16%36%22%4
631
March1st to 15thNight
22%18%34%20%3
720
16th to endNight
19%12%37%20%9%
768
April1st to 15thNight
23%13%35%22%4
718
16th to endNight
16%12%34%27%8%1
559
May1st to 15thNight
17%6%26%34%12%1
481
16th to endNight
12%433%31%16%1
375
June1st to 15thNight
15%7%31%31%13%
360
16th to endNight
12%428%40%13%
360
July1st to 15thNight
7%226%42%19%1
340
16th to endNight
7%327%40%19%1
477
August1st to 15thNight
8%319%40%25%2
539
16th to endNight
10%223%35%25%2
622
September1st to 15thNight
15%5%24%28%20%5%
720
16th to endNight
14%6%20%32%21%4
717
October1st to 15thNight
20%9%28%26%13%1
720
16th to endNight
26%12%32%22%5%
768
November1st to 15thNight
23%11%31%23%9%
760
16th to endNight
23%16%31%21%6%
780
December1st to 15thNight
26%17%37%15%2
780
16th to endNight
27%14%40%14%2
788
Page generated at 2017-12-21 07:04:42. Version ac04

Copyright 2017 A. Danko


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