Stoneham
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stoneham clear sky chart from 2005-11-05 to 2017-10-06.

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
28%
14685
12%
47058
6%
14654
35%
14654
14%
34685

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
15%
720
10%
2506
3%
716
23%
716
8%
1981
January16th to endNight
22%
768
11%
2688
5%
768
31%
768
10%
2021
February1st to 15thNight
20%
703
11%
2363
3%
701
30%
701
12%
1780
February16th to endNight
19%
631
12%
1893
5%
631
28%
631
12%
1481
March1st to 15thNight
21%
720
14%
2160
7%
720
29%
720
14%
1590
March16th to endNight
29%
768
18%
2022
7%
768
37%
768
20%
1455
April1st to 15thNight
25%
718
15%
1796
5%
718
31%
718
18%
1383
April16th to endNight
25%
540
15%
1620
6%
540
33%
540
17%
1143
May1st to 15thNight
30%
447
12%
1527
10%
447
37%
447
15%
1093
May16th to endNight
30%
375
10%
1473
9%
374
38%
374
13%
1046
June1st to 15thNight
33%
360
6%
1260
5%
360
36%
360
13%
926
June16th to endNight
41%
360
7%
1260
7%
360
43%
360
16%
907
July1st to 15thNight
46%
340
7%
1327
10%
340
48%
340
17%
884
July16th to endNight
47%
376
9%
1418
12%
354
51%
354
16%
949
August1st to 15thNight
52%
408
11%
1479
11%
406
55%
406
18%
1011
August16th to endNight
43%
644
15%
1790
9%
644
46%
644
23%
1235
September1st to 15thNight
42%
720
10%
1844
6%
720
44%
720
24%
1320
September16th to endNight
40%
717
17%
1980
10%
717
45%
717
26%
1336
October1st to 15thNight
31%
684
16%
1978
8%
684
39%
684
20%
1412
October16th to endNight
23%
704
9%
2288
5%
704
29%
704
12%
1733
November1st to 15thNight
30%
700
16%
2277
10%
700
37%
700
14%
1647
November16th to endNight
27%
737
12%
2562
7%
737
34%
737
11%
1927
December1st to 15thNight
16%
750
6%
2700
2%
750
21%
750
7%
2184
December16th to endNight
16%
795
11%
2847
4%
795
24%
795
7%
2241

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
21%9%36%5%34445%28%
48137
Night
20%10%46%5%34445%30%
47228
TransparencyDay
56%7%11%15%7%1
47825
Night
55%6%11%17%8%1
47058
SeeingDay
28%11%26%21%9%2
6130
Night
25%10%27%26%8%
14686

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%15%6%8%6%33445%23%
1432
16th to endDay
11%14%8%8%7%245%45%26%
1536
February1st to 15thDay
8%15%7%11%7%45%44424%
1494
16th to endDay
15%13%5%10%7%3445%5%23%
1580
March1st to 15thDay
18%12%5%8%5%23435%28%
1790
16th to endDay
15%11%46%6%35%44434%
2202
April1st to 15thDay
24%12%345%2433430%
2152
16th to endDay
24%10%25%423345%34%
2339
May1st to 15thDay
26%7%35%43335%5%30%
2433
16th to endDay
25%6%36%6%35%45%5%26%
2641
June1st to 15thDay
24%6%36%5%345%6%6%27%
2700
16th to endDay
25%8%36%6%35%446%23%
2700
July1st to 15thDay
18%6%36%7%35%6%6%7%27%
2550
16th to endDay
21%6%26%6%45%7%6%7%25%
2654
August1st to 15thDay
22%7%25%7%45%5%5%9%23%
2457
16th to endDay
17%7%25%6%45%5%47%33%
2411
September1st to 15thDay
23%6%24424346%36%
2115
16th to endDay
22%5%245%24446%38%
1980
October1st to 15thDay
25%7%26%424345%31%
1780
16th to endDay
30%10%46%5%2443422%
1584
November1st to 15thDay
22%11%46%6%33435%26%
1581
16th to endDay
25%15%5%5%41323426%
1392
December1st to 15thDay
27%16%5%7%41332324%
1260
16th to endDay
22%17%6%9%42344321%
1374
January1st to 15thNight
18%16%6%8%8%34435%22%
2506
16th to endNight
10%14%6%8%6%46%5%5%5%25%
2688
February1st to 15thNight
9%12%5%11%8%46%5%45%26%
2362
16th to endNight
15%16%5%9%6%34345%25%
1893
March1st to 15thNight
18%10%36%5%35%445%31%
2147
16th to endNight
14%10%35%6%34445%36%
2022
April1st to 15thNight
25%11%45%424445%29%
1796
16th to endNight
22%7%26%324246%37%
1620
May1st to 15thNight
26%6%34425%435%33%
1527
16th to endNight
27%6%15%433345%32%
1471
June1st to 15thNight
23%7%35%5%35%45%6%28%
1260
16th to endNight
25%5%345%3335%6%31%
1260
July1st to 15thNight
19%5%24435%5%49%34%
1407
16th to endNight
18%5%25%5%3446%7%36%
1514
August1st to 15thNight
18%5%245%435%6%8%34%
1489
16th to endNight
17%425%436%45%6%39%
1790
September1st to 15thNight
23%6%24423446%39%
1844
16th to endNight
23%423312236%44%
1980
October1st to 15thNight
22%8%33433345%35%
1978
16th to endNight
28%9%35%32344428%
2288
November1st to 15thNight
21%10%35%43335%6%31%
2277
16th to endNight
24%13%36%424325%28%
2562
December1st to 15thNight
24%16%6%8%6%3333421%
2700
16th to endNight
22%17%6%8%5%2333423%
2847

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%6%10%13%7%
1433
16th to endDay
57%6%9%16%8%
1536
February1st to 15thDay
60%5%11%13%8%1
1497
16th to endDay
62%48%14%8%2
1580
March1st to 15thDay
57%5%9%14%11%1
1800
16th to endDay
53%5%8%16%12%3
2202
April1st to 15thDay
57%49%14%10%4
2152
16th to endDay
52%5%10%16%12%2
2339
May1st to 15thDay
54%5%11%16%10%1
2433
16th to endDay
58%8%10%15%7%
2645
June1st to 15thDay
54%9%12%14%7%1
2700
16th to endDay
59%7%11%13%7%
2700
July1st to 15thDay
52%10%15%16%5%
2401
16th to endDay
55%10%13%15%4
2487
August1st to 15thDay
55%11%17%12%3
2443
16th to endDay
47%8%17%20%5%
2411
September1st to 15thDay
49%6%15%20%8%
2115
16th to endDay
45%6%16%23%8%
1980
October1st to 15thDay
54%6%12%18%7%
1780
16th to endDay
65%6%9%15%3
1584
November1st to 15thDay
60%6%9%16%6%
1581
16th to endDay
62%410%15%5%
1392
December1st to 15thDay
66%5%9%13%5%
1260
16th to endDay
66%7%6%11%7%
1374
January1st to 15thNight
64%5%8%14%5%
2506
16th to endNight
59%6%8%16%8%
2688
February1st to 15thNight
58%6%9%16%8%1
2363
16th to endNight
62%48%12%10%1
1893
March1st to 15thNight
54%6%10%14%11%2
2160
16th to endNight
49%5%10%19%12%3
2022
April1st to 15thNight
56%47%15%12%2
1796
16th to endNight
48%7%8%18%14%3
1620
May1st to 15thNight
53%6%10%16%11%2
1527
16th to endNight
53%6%11%17%10%
1473
June1st to 15thNight
55%8%12%16%6%1
1260
16th to endNight
52%7%10%17%11%
1260
July1st to 15thNight
45%8%18%20%6%
1327
16th to endNight
47%8%16%19%8%
1418
August1st to 15thNight
45%10%20%20%3
1479
16th to endNight
43%9%16%25%5%
1790
September1st to 15thNight
45%7%14%22%8%
1844
16th to endNight
42%6%15%25%8%
1980
October1st to 15thNight
50%5%12%22%8%
1978
16th to endNight
58%6%12%16%5%
2288
November1st to 15thNight
53%6%13%17%8%
2277
16th to endNight
59%5%10%16%7%
2562
December1st to 15thNight
68%5%10%10%5%
2700
16th to endNight
65%5%8%11%8%
2847

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
28%15%36%18%1
60
16th to endDay
23%21%35%12%41
64
February1st to 15thDay
22%18%33%16%8%
118
16th to endDay
23%12%36%23%4
239
March1st to 15thDay
27%17%28%19%7%
270
16th to endDay
22%15%22%22%12%3
288
April1st to 15thDay
34%13%24%19%6%1
270
16th to endDay
33%12%28%15%7%2
270
May1st to 15thDay
36%9%28%16%7%1
288
16th to endDay
29%16%27%19%6%
354
June1st to 15thDay
27%9%25%26%9%
495
16th to endDay
30%9%27%22%8%1
495
July1st to 15thDay
24%8%30%22%12%
335
16th to endDay
25%7%26%30%9%1
326
August1st to 15thDay
25%5%27%24%13%3
313
16th to endDay
22%10%22%22%13%7%
332
September1st to 15thDay
27%9%22%21%14%4
315
16th to endDay
21%11%25%21%14%4
314
October1st to 15thDay
28%10%26%22%10%1
271
16th to endDay
40%10%22%18%7%
240
November1st to 15thDay
32%15%20%19%10%1
235
16th to endDay
35%16%21%18%6%2
114
December1st to 15thDay
43%10%31%10%5%
60
16th to endDay
37%29%23%9%
64
January1st to 15thNight
26%15%32%21%4
720
16th to endNight
18%13%32%26%6%
768
February1st to 15thNight
14%15%37%26%6%
704
16th to endNight
25%12%33%22%4
631
March1st to 15thNight
24%14%34%22%4
720
16th to endNight
18%15%31%25%7%1
768
April1st to 15thNight
30%12%26%23%6%
718
16th to endNight
27%13%30%21%7%
540
May1st to 15thNight
27%9%29%25%8%
447
16th to endNight
31%5%27%28%6%
375
June1st to 15thNight
27%5%25%32%8%
360
16th to endNight
24%323%36%12%
360
July1st to 15thNight
22%222%33%17%1
340
16th to endNight
19%320%42%14%
376
August1st to 15thNight
21%315%36%22%
408
16th to endNight
18%424%35%14%1
644
September1st to 15thNight
24%5%23%31%13%2
720
16th to endNight
24%7%22%27%16%1
717
October1st to 15thNight
25%8%28%25%10%
684
16th to endNight
33%11%26%20%6%
704
November1st to 15thNight
26%12%24%26%8%1
700
16th to endNight
31%14%20%23%8%1
737
December1st to 15thNight
33%14%24%22%5%
750
16th to endNight
31%16%26%20%41
795
Page generated at 2017-10-07 14:07:44. Version ac04

Copyright 2017 A. Danko


Stoneham Clear Sky Chart | Charts Home