Leominster
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Leominster clear sky chart from 2005-11-06 to 2024-01-12.

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
25%
22912
18%
74574
7%
22866
38%
22866
19%
48283

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 10thNight
13%
760
21%
2649
5%
757
33%
757
17%
1632
January11th to 20thNight
13%
725
16%
2535
3%
725
29%
725
12%
1712
January21st to endNight
15%
792
20%
2772
5%
792
35%
792
17%
1732
February1st to 10thNight
13%
720
16%
2289
3%
720
28%
720
15%
1546
February11th to 20thNight
11%
703
19%
2100
3%
700
29%
700
15%
1392
February21st to endNight
13%
592
24%
1776
6%
592
36%
592
15%
1185
March1st to 10thNight
16%
720
21%
2160
7%
720
34%
720
18%
1415
March11th to 20thNight
15%
720
17%
2082
5%
720
28%
720
16%
1445
March21st to endNight
19%
792
22%
2030
5%
792
32%
792
20%
1405
April1st to 10thNight
19%
720
19%
1800
3%
720
29%
720
19%
1275
April11th to 20thNight
21%
711
16%
1775
3%
711
30%
711
22%
1237
April21st to endNight
18%
545
19%
1625
5%
545
29%
545
17%
1091
May1st to 10thNight
20%
540
13%
1620
5%
540
27%
540
15%
1166
May11th to 20thNight
20%
475
16%
1537
6%
475
30%
475
16%
1023
May21st to endNight
29%
389
13%
1551
9%
388
38%
388
17%
995
June1st to 10thNight
28%
360
14%
1440
9%
360
42%
360
17%
941
June11th to 20thNight
32%
360
13%
1440
11%
360
42%
360
16%
934
June21st to endNight
35%
360
13%
1440
10%
360
46%
360
22%
874
July1st to 10thNight
44%
350
13%
1400
15%
350
51%
350
21%
855
July11th to 20thNight
46%
348
13%
1392
13%
348
51%
348
20%
842
July21st to endNight
46%
394
18%
1486
18%
372
56%
372
24%
865
August1st to 10thNight
45%
460
17%
1524
11%
458
51%
458
27%
929
August11th to 20thNight
43%
581
16%
1645
8%
581
47%
581
24%
1099
August21st to endNight
47%
792
21%
1980
9%
792
51%
792
35%
1272
September1st to 10thNight
40%
720
20%
1800
7%
720
47%
720
33%
1179
September11th to 20thNight
42%
720
25%
1966
13%
720
51%
720
33%
1205
September21st to endNight
37%
720
25%
1980
15%
720
46%
720
29%
1272
October1st to 10thNight
31%
720
17%
1980
10%
720
39%
720
23%
1317
October11th to 20thNight
30%
720
21%
2208
8%
720
46%
720
25%
1380
October21st to endNight
21%
792
16%
2574
6%
792
34%
792
17%
1744
November1st to 10thNight
28%
740
22%
2407
11%
740
44%
740
23%
1480
November11th to 20thNight
22%
760
24%
2470
8%
760
40%
760
20%
1520
November21st to endNight
18%
760
22%
2470
6%
760
38%
760
18%
1539
December1st to 10thNight
16%
760
19%
2660
5%
760
32%
760
14%
1728
December11th to 20thNight
18%
760
17%
3201
4%
759
34%
759
13%
1971
December21st to endNight
14%
831
14%
4810
4%
817
33%
817
9%
3086

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%6%25%5%35%5%5%7%40%
74792
Night
16%7%35%5%3445%7%41%
74907
TransparencyDay
43%6%12%22%15%2
74497
Night
43%6%12%22%15%2
74736
SeeingDay
23%17%32%19%8%2
13875
Night
22%15%34%23%6%
22917

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 10thDay
12%8%36%6%3445%7%42%
1517
11th to 20thDay
17%7%35%5%36%5%6%7%36%
1448
21st to endDay
12%7%36%5%35%45%7%43%
1584
February1st to 10thDay
18%7%35%6%36%5%5%7%34%
1667
11th to 20thDay
12%7%36%5%37%46%8%39%
1748
21st to endDay
19%10%25%6%3446%5%36%
1480
March1st to 10thDay
15%8%25%5%45%5%6%7%39%
1797
11th to 20thDay
16%7%35%6%45%447%39%
1876
21st to endDay
18%7%35%5%34445%41%
2322
April1st to 10thDay
17%8%35%7%35%5%47%38%
2160
11th to 20thDay
16%6%25%5%26%5%5%7%40%
2134
21st to endDay
21%6%26%6%345%5%6%35%
2335
May1st to 10thDay
23%8%36%43445%6%32%
2340
11th to 20thDay
18%7%36%5%44446%40%
2372
21st to endDay
15%5%25%5%345%5%8%42%
2725
June1st to 10thDay
19%5%25%5%35%6%6%9%34%
2520
11th to 20thDay
17%5%35%5%35%6%6%9%37%
2520
21st to endDay
17%6%36%5%45%5%6%8%34%
2520
July1st to 10thDay
14%5%25%5%35%5%6%8%40%
2520
11th to 20thDay
13%5%25%6%36%6%7%9%39%
2520
21st to endDay
12%436%5%46%6%6%9%40%
2744
August1st to 10thDay
10%6%346%46%7%7%8%39%
2386
11th to 20thDay
13%5%26%6%46%5%6%9%39%
2251
21st to endDay
12%5%25%5%346%5%9%44%
2376
September1st to 10thDay
14%5%25%435%46%8%44%
2160
11th to 20thDay
16%5%2433335%6%50%
1994
21st to endDay
16%5%26%43445%7%45%
1980
October1st to 10thDay
24%6%245%34445%39%
1980
11th to 20thDay
14%6%345%3446%8%45%
1749
21st to endDay
22%6%35%5%24446%39%
1782
November1st to 10thDay
14%6%35%5%3344449%
1671
11th to 20thDay
19%7%23433345%47%
1710
21st to endDay
17%6%345%34446%43%
1706
December1st to 10thDay
17%7%36%5%35%5%6%5%38%
1520
11th to 20thDay
22%6%23423346%45%
1906
21st to endDay
20%11%36%5%3445%7%33%
2772
January1st to 10thNight
15%7%35%43445%6%44%
2649
11th to 20thNight
16%9%36%5%3445%7%36%
2535
21st to endNight
11%8%45%5%35%5%5%7%41%
2772
February1st to 10thNight
16%9%35%5%2446%7%38%
2289
11th to 20thNight
13%7%46%5%35%5%5%7%40%
2098
21st to endNight
16%9%35%5%2445%6%40%
1776
March1st to 10thNight
15%7%35%5%3445%6%43%
2150
11th to 20thNight
15%8%45%6%46%45%6%38%
2082
21st to endNight
16%8%26%5%3435%6%42%
2030
April1st to 10thNight
17%7%35%6%4446%8%37%
1800
11th to 20thNight
19%426%5%25%46%7%40%
1775
21st to endNight
21%7%26%5%34347%39%
1625
May1st to 10thNight
24%7%36%5%3445%7%32%
1620
11th to 20thNight
18%6%35%435%5%5%6%39%
1536
21st to endNight
17%6%26%5%45%45%7%40%
1550
June1st to 10thNight
19%6%36%5%3345%7%38%
1440
11th to 20thNight
20%6%35%6%2445%7%38%
1440
21st to endNight
15%5%245%3446%9%43%
1440
July1st to 10thNight
14%425%5%36%5%6%8%42%
1440
11th to 20thNight
13%6%25%5%445%6%10%40%
1440
21st to endNight
12%424446%6%5%8%46%
1574
August1st to 10thNight
10%5%25%5%25%5%7%10%44%
1534
11th to 20thNight
13%425%6%47%6%7%9%37%
1645
21st to endNight
16%41442345%7%49%
1980
September1st to 10thNight
14%5%135%3436%7%48%
1800
11th to 20thNight
13%6%2433435%6%53%
1966
21st to endNight
16%5%2443445%6%47%
1980
October1st to 10thNight
22%6%3432444443%
1980
11th to 20thNight
15%5%15%5%3445%7%46%
2208
21st to endNight
23%7%25%43445%7%38%
2574
November1st to 10thNight
15%6%15%434445%49%
2407
11th to 20thNight
17%7%24424346%46%
2470
21st to endNight
15%6%2443445%7%45%
2470
December1st to 10thNight
17%8%35%5%3445%7%39%
2660
11th to 20thNight
19%6%25%43446%7%41%
3288
21st to endNight
20%9%35%5%3445%6%36%
4884

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 10thDay
42%6%10%27%13%3
1518
11th to 20thDay
46%8%12%19%12%3
1448
21st to endDay
40%5%14%23%15%3
1584
February1st to 10thDay
48%7%13%18%12%3
1667
11th to 20thDay
45%6%11%20%14%3
1757
21st to endDay
50%5%8%19%15%3
1480
March1st to 10thDay
44%5%13%20%14%4
1800
11th to 20thDay
44%6%10%20%15%4
1876
21st to endDay
47%5%8%18%17%6%
2322
April1st to 10thDay
47%5%10%20%16%4
2160
11th to 20thDay
41%6%11%20%17%3
2134
21st to endDay
49%5%9%17%17%3
2335
May1st to 10thDay
52%6%9%19%12%2
2340
11th to 20thDay
44%5%11%20%18%3
2376
21st to endDay
40%7%14%23%14%2
2725
June1st to 10thDay
45%8%14%22%10%1
2520
11th to 20thDay
43%9%12%20%15%2
2520
21st to endDay
46%8%12%22%11%1
2520
July1st to 10thDay
41%8%11%23%15%2
2450
11th to 20thDay
39%9%14%25%12%1
2445
21st to endDay
38%7%15%22%14%3
2591
August1st to 10thDay
39%9%15%23%13%1
2372
11th to 20thDay
41%8%14%24%12%1
2251
21st to endDay
36%7%12%26%17%2
2376
September1st to 10thDay
38%7%12%24%18%2
2160
11th to 20thDay
36%5%9%25%23%3
1994
21st to endDay
39%410%23%21%2
1980
October1st to 10thDay
47%6%9%21%13%4
1980
11th to 20thDay
36%6%13%29%14%2
1749
21st to endDay
46%5%12%20%13%3
1782
November1st to 10thDay
39%5%13%25%16%2
1671
11th to 20thDay
39%5%10%22%20%2
1710
21st to endDay
42%6%15%23%12%2
1706
December1st to 10thDay
46%7%14%17%16%1
1520
11th to 20thDay
43%414%18%18%3
1906
21st to endDay
51%6%12%20%11%1
2772
January1st to 10thNight
41%5%12%22%16%3
2649
11th to 20thNight
48%7%14%20%8%3
2535
21st to endNight
42%5%11%20%19%3
2772
February1st to 10thNight
46%6%14%19%12%2
2289
11th to 20thNight
44%6%11%21%15%3
2100
21st to endNight
45%5%9%23%15%3
1776
March1st to 10thNight
43%5%10%24%14%4
2160
11th to 20thNight
46%7%10%17%17%4
2083
21st to endNight
45%5%9%17%19%5%
2030
April1st to 10thNight
46%6%10%19%16%3
1800
11th to 20thNight
43%6%10%20%19%2
1775
21st to endNight
46%6%10%19%14%5%
1625
May1st to 10thNight
51%6%9%18%12%3
1620
11th to 20thNight
43%9%12%18%15%3
1537
21st to endNight
45%7%13%21%13%1
1551
June1st to 10thNight
47%7%12%22%12%1
1440
11th to 20thNight
46%7%12%20%13%2
1440
21st to endNight
36%11%15%24%14%
1440
July1st to 10thNight
39%8%13%22%16%1
1400
11th to 20thNight
39%9%16%26%10%1
1392
21st to endNight
35%8%15%28%11%2
1486
August1st to 10thNight
34%10%15%25%15%1
1524
11th to 20thNight
40%10%17%22%12%
1645
21st to endNight
34%7%12%27%19%1
1980
September1st to 10thNight
37%6%13%25%18%1
1800
11th to 20thNight
33%6%10%24%26%2
1966
21st to endNight
38%6%9%26%19%3
1980
October1st to 10thNight
43%5%13%23%12%4
1980
11th to 20thNight
38%6%13%27%14%1
2208
21st to endNight
48%5%12%20%13%2
2574
November1st to 10thNight
38%6%11%21%20%4
2407
11th to 20thNight
41%412%21%19%3
2470
21st to endNight
40%6%14%26%14%1
2470
December1st to 10thNight
46%5%13%23%13%1
2660
11th to 20thNight
42%6%15%18%17%2
3288
21st to endNight
49%6%11%23%11%1
4884

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 10thDay
27%26%28%16%3
180
11th to 20thDay
30%25%31%10%4
162
21st to endDay
25%26%34%12%4
176
February1st to 10thDay
35%24%29%10%2
315
11th to 20thDay
28%28%33%10%1
416
21st to endDay
34%18%34%10%3
346
March1st to 10thDay
30%21%36%11%3
420
11th to 20thDay
28%28%29%12%31
420
21st to endDay
30%19%34%11%5%1
462
April1st to 10thDay
32%22%29%12%5%1
420
11th to 20thDay
27%21%33%11%7%
412
21st to endDay
30%19%32%15%32
420
May1st to 10thDay
32%22%27%14%41
423
11th to 20thDay
22%17%42%15%41
447
21st to endDay
18%14%36%22%9%1
485
June1st to 10thDay
18%13%37%20%8%2
450
11th to 20thDay
18%14%37%22%6%2
450
21st to endDay
19%12%37%22%7%3
450
July1st to 10thDay
18%10%27%29%13%3
445
11th to 20thDay
15%7%31%31%13%3
444
21st to endDay
12%8%37%31%10%2
488
August1st to 10thDay
10%10%33%31%14%2
446
11th to 20thDay
18%8%29%28%14%3
439
21st to endDay
12%10%32%27%14%4
495
September1st to 10thDay
18%11%28%24%14%6%
450
11th to 20thDay
19%10%30%21%13%7%
450
21st to endDay
18%14%31%23%9%6%
450
October1st to 10thDay
28%14%23%21%11%3
450
11th to 20thDay
18%18%30%24%8%2
409
21st to endDay
30%15%31%18%7%1
396
November1st to 10thDay
22%18%30%20%10%1
365
11th to 20thDay
30%21%26%18%41
370
21st to endDay
29%19%31%15%6%
366
December1st to 10thDay
23%30%28%14%4
180
11th to 20thDay
36%24%31%6%2
180
21st to endDay
31%22%34%9%41
198
January1st to 10thNight
23%19%40%16%1
760
11th to 20thNight
26%20%36%17%2
725
21st to endNight
20%21%39%18%3
792
February1st to 10thNight
25%20%38%16%2
720
11th to 20thNight
22%22%40%15%1
703
21st to endNight
27%22%34%15%2
592
March1st to 10thNight
24%21%36%17%2
720
11th to 20thNight
22%23%37%16%3
720
21st to endNight
24%20%33%18%4
792
April1st to 10thNight
25%20%32%20%3
720
11th to 20thNight
23%21%32%19%5%
711
21st to endNight
26%19%33%20%2
545
May1st to 10thNight
29%14%34%20%2
540
11th to 20thNight
20%19%38%20%4
475
21st to endNight
20%9%37%29%6%
389
June1st to 10thNight
21%7%37%27%8%
360
11th to 20thNight
21%9%34%31%5%1
360
21st to endNight
14%342%36%5%
360
July1st to 10thNight
15%5%32%37%10%1
350
11th to 20thNight
12%431%41%11%1
348
21st to endNight
12%433%41%9%
394
August1st to 10thNight
10%433%40%12%
460
11th to 20thNight
14%430%37%13%1
581
21st to endNight
17%425%38%15%1
792
September1st to 10thNight
17%6%32%33%12%1
720
11th to 20thNight
16%8%28%28%18%2
720
21st to endNight
19%9%30%28%12%2
720
October1st to 10thNight
25%12%27%24%10%2
720
11th to 20thNight
19%14%33%23%11%1
720
21st to endNight
28%15%32%19%5%
792
November1st to 10thNight
19%15%34%24%8%1
740
11th to 20thNight
24%19%32%18%6%1
760
21st to endNight
23%20%36%17%41
760
December1st to 10thNight
26%20%34%16%4
760
11th to 20thNight
25%20%34%18%2
760
21st to endNight
27%18%36%16%2
836
Page generated at 2024-01-08 22:31:28. Version ac07

Copyright 2024 Attilla Danko


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