Hammond
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hammond clear sky chart from 2005-11-05 to 2017-12-04.

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
35%
14959
13%
47837
9%
14927
40%
14927
17%
34295

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
21%
720
6%
2506
5%
716
24%
716
8%
2026
January16th to endNight
26%
768
10%
2661
7%
768
31%
768
12%
1998
February1st to 15thNight
23%
704
10%
2287
6%
701
28%
701
11%
1782
February16th to endNight
28%
631
14%
1934
8%
631
37%
631
15%
1461
March1st to 15thNight
26%
720
13%
2121
9%
720
32%
720
15%
1600
March16th to endNight
36%
768
20%
2019
11%
768
43%
768
24%
1411
April1st to 15thNight
30%
718
15%
1796
7%
718
34%
718
22%
1333
April16th to endNight
33%
648
17%
1728
8%
648
38%
648
24%
1219
May1st to 15thNight
35%
360
16%
1440
15%
360
44%
360
16%
964
May16th to endNight
40%
375
13%
1497
12%
374
48%
374
18%
964
June1st to 15thNight
41%
360
9%
1440
9%
360
48%
360
15%
996
June16th to endNight
46%
360
9%
1440
13%
360
50%
360
19%
916
July1st to 15thNight
60%
340
13%
1360
21%
340
64%
340
26%
773
July16th to endNight
59%
376
13%
1418
18%
354
61%
354
25%
826
August1st to 15thNight
55%
416
13%
1487
13%
414
58%
414
23%
931
August16th to endNight
57%
726
19%
1872
10%
726
60%
726
35%
1179
September1st to 15thNight
52%
720
15%
1800
8%
720
54%
720
29%
1250
September16th to endNight
53%
717
23%
1950
15%
717
57%
717
31%
1244
October1st to 15thNight
39%
720
17%
2160
12%
720
46%
720
23%
1485
October16th to endNight
29%
768
11%
2418
8%
768
35%
768
14%
1822
November1st to 15thNight
32%
760
16%
2511
12%
760
39%
760
17%
1786
November16th to endNight
24%
780
10%
2730
7%
780
28%
780
11%
2086
December1st to 15thNight
22%
736
7%
2574
4%
736
26%
736
9%
2074
December16th to endNight
18%
768
9%
2688
5%
768
24%
768
8%
2169

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
18%8%36%5%3445%6%33%
48667
Night
18%9%36%5%24445%33%
48006
Cloud CoverDay
18%8%36%5%3445%6%32%
48676
Night
18%9%36%5%34445%32%
48012
TransparencyDay
50%6%12%19%9%1
48354
Night
52%6%11%19%9%1
47837
SeeingDay
21%7%24%26%14%5%
5749
Night
22%6%27%30%11%
14959

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
23%14%6%8%6%33335%20%
1432
16th to endDay
14%16%5%8%7%34445%24%
1560
February1st to 15thDay
14%14%5%10%8%35%345%24%
1575
16th to endDay
20%12%5%8%6%35%345%25%
1539
March1st to 15thDay
18%10%49%6%35%34427%
1828
16th to endDay
17%7%35%424346%39%
2205
April1st to 15thDay
23%10%35%422335%33%
2152
16th to endDay
21%7%26%5%24345%35%
2243
May1st to 15thDay
21%7%36%6%34346%33%
2511
16th to endDay
18%6%35%5%345%5%6%34%
2618
June1st to 15thDay
22%6%35%5%45%45%7%30%
2520
16th to endDay
19%5%25%435%6%6%8%31%
2520
July1st to 15thDay
13%5%245%35%47%8%37%
2520
16th to endDay
12%5%25%5%36%6%7%8%36%
2654
August1st to 15thDay
12%6%25%6%45%5%5%7%38%
2460
16th to endDay
10%425%435%46%9%44%
2318
September1st to 15thDay
16%42442445%7%42%
2160
16th to endDay
15%5%23324347%47%
2008
October1st to 15thDay
21%7%36%423446%34%
1800
16th to endDay
26%9%36%7%33345%26%
1806
November1st to 15thDay
17%7%45%6%345%46%32%
1674
16th to endDay
22%12%48%5%2334426%
1560
December1st to 15thDay
24%14%5%7%5%45%5%45%19%
1468
16th to endDay
24%15%6%8%6%3333420%
1536
January1st to 15thNight
20%15%6%10%6%35%33420%
2506
16th to endNight
15%15%5%7%6%35%445%26%
2661
February1st to 15thNight
13%12%7%11%8%46%44422%
2285
16th to endNight
17%11%47%6%35%345%28%
1934
March1st to 15thNight
19%11%47%7%2434429%
2108
16th to endNight
16%8%36%5%2433441%
2019
April1st to 15thNight
25%8%24424345%35%
1796
16th to endNight
19%8%26%423336%38%
1728
May1st to 15thNight
23%7%35%324345%36%
1440
16th to endNight
18%6%244245%5%6%38%
1495
June1st to 15thNight
20%7%25%5%35%46%7%32%
1440
16th to endNight
18%425%3245%6%8%36%
1440
July1st to 15thNight
10%424435%5%6%8%46%
1440
16th to endNight
9%4245%246%5%8%44%
1514
August1st to 15thNight
10%6%25%6%245%6%9%40%
1497
16th to endNight
10%42442445%7%49%
1872
September1st to 15thNight
15%5%25%6%25%446%41%
1800
16th to endNight
16%423423336%49%
1950
October1st to 15thNight
19%7%25%434446%38%
2160
16th to endNight
24%8%27%6%24445%28%
2418
November1st to 15thNight
22%8%26%5%23345%33%
2511
16th to endNight
22%11%48%5%34445%25%
2730
December1st to 15thNight
23%14%5%6%6%35%44421%
2574
16th to endNight
25%15%5%7%6%2444420%
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
23%14%6%9%5%2434420%
1432
16th to endDay
13%16%5%9%6%45%446%24%
1560
February1st to 15thDay
14%13%6%10%7%34445%24%
1575
16th to endDay
19%11%5%8%6%35%445%25%
1539
March1st to 15thDay
18%10%5%9%7%35%445%26%
1838
16th to endDay
17%7%35%5%24335%39%
2204
April1st to 15thDay
23%10%35%423335%33%
2152
16th to endDay
20%7%36%5%23345%35%
2243
May1st to 15thDay
20%7%26%6%3445%5%34%
2511
16th to endDay
18%6%345%3445%7%34%
2618
June1st to 15thDay
22%5%35%6%3445%7%30%
2520
16th to endDay
18%5%25%5%35%6%6%8%30%
2520
July1st to 15thDay
13%425%5%35%5%6%8%37%
2520
16th to endDay
10%6%26%6%35%5%8%8%35%
2654
August1st to 15thDay
11%6%36%5%36%5%6%7%37%
2460
16th to endDay
9%425%435%46%8%44%
2318
September1st to 15thDay
17%42433445%7%42%
2160
16th to endDay
15%5%23323346%48%
2008
October1st to 15thDay
20%8%35%424447%34%
1800
16th to endDay
25%8%46%6%44345%25%
1806
November1st to 15thDay
16%7%46%6%445%5%7%31%
1674
16th to endDay
21%11%47%6%33345%27%
1560
December1st to 15thDay
24%13%47%6%35%5%45%18%
1468
16th to endDay
24%15%5%8%6%2433420%
1536
January1st to 15thNight
20%15%6%10%6%35%33420%
2506
16th to endNight
15%15%5%8%6%35%345%26%
2661
February1st to 15thNight
13%12%6%12%7%36%5%4422%
2278
16th to endNight
17%12%5%7%5%35%45%428%
1934
March1st to 15thNight
20%10%5%7%6%2433429%
2121
16th to endNight
15%9%36%5%2433442%
2019
April1st to 15thNight
26%7%24423345%34%
1796
16th to endNight
18%8%26%6%23336%38%
1728
May1st to 15thNight
23%7%145%235%4435%
1440
16th to endNight
17%7%244335%5%6%38%
1495
June1st to 15thNight
20%6%35%5%25%46%8%30%
1440
16th to endNight
17%5%244246%6%9%36%
1440
July1st to 15thNight
10%4244345%5%8%45%
1440
16th to endNight
9%4346%345%6%7%44%
1514
August1st to 15thNight
10%6%25%5%345%6%10%39%
1497
16th to endNight
10%42442446%6%48%
1872
September1st to 15thNight
14%5%25%5%345%46%41%
1800
16th to endNight
15%414423345%49%
1950
October1st to 15thNight
18%7%35%424446%37%
2160
16th to endNight
23%9%27%6%33446%28%
2418
November1st to 15thNight
21%9%26%5%23345%33%
2511
16th to endNight
21%11%48%5%3444426%
2730
December1st to 15thNight
22%15%5%7%6%3444421%
2574
16th to endNight
25%14%5%7%6%2443420%
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
67%48%13%5%
1433
16th to endDay
60%5%11%13%7%
1560
February1st to 15thDay
61%5%11%17%3
1577
16th to endDay
60%410%13%9%1
1539
March1st to 15thDay
59%5%11%13%7%1
1838
16th to endDay
46%5%9%18%15%5%
2205
April1st to 15thDay
53%38%19%12%2
2152
16th to endDay
50%48%18%14%4
2243
May1st to 15thDay
51%5%8%19%13%2
2511
16th to endDay
47%7%13%18%11%1
2622
June1st to 15thDay
53%6%11%19%8%
2520
16th to endDay
47%8%14%18%9%
2520
July1st to 15thDay
40%7%16%24%11%
2371
16th to endDay
41%11%16%21%9%
2487
August1st to 15thDay
43%10%16%21%9%
2446
16th to endDay
34%8%18%27%10%
2318
September1st to 15thDay
39%7%13%26%11%
2160
16th to endDay
37%6%12%32%10%
2008
October1st to 15thDay
50%5%12%21%9%
1800
16th to endDay
60%6%13%14%5%
1806
November1st to 15thDay
50%7%15%17%8%1
1674
16th to endDay
59%7%11%15%6%
1560
December1st to 15thDay
66%8%12%10%2
1468
16th to endDay
68%5%9%11%5%
1536
January1st to 15thNight
68%5%10%10%4
2506
16th to endNight
59%5%11%15%6%
2661
February1st to 15thNight
63%5%10%16%4
2287
16th to endNight
58%5%8%18%9%
1934
March1st to 15thNight
57%5%10%17%8%1
2121
16th to endNight
47%49%19%15%4
2019
April1st to 15thNight
51%5%7%18%14%1
1796
16th to endNight
48%48%18%16%3
1728
May1st to 15thNight
49%6%7%16%14%5%
1440
16th to endNight
44%7%12%19%13%2
1497
June1st to 15thNight
50%8%12%19%9%
1440
16th to endNight
42%8%14%19%15%
1440
July1st to 15thNight
33%8%14%28%14%
1360
16th to endNight
35%7%16%24%15%
1418
August1st to 15thNight
38%9%18%21%10%
1487
16th to endNight
32%7%17%31%11%
1872
September1st to 15thNight
42%6%12%25%11%
1800
16th to endNight
36%6%12%32%11%
1950
October1st to 15thNight
46%5%11%24%10%
2160
16th to endNight
56%6%13%17%5%
2418
November1st to 15thNight
52%5%13%17%9%1
2511
16th to endNight
60%6%12%15%4
2730
December1st to 15thNight
65%6%12%12%2
2574
16th to endNight
67%5%9%11%5%
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
30%11%21%26%6%3
60
16th to endDay
35%127%29%41
68
February1st to 15thDay
31%8%43%15%1
90
16th to endDay
34%6%29%25%5%
198
March1st to 15thDay
24%11%29%26%8%
270
16th to endDay
22%9%25%27%10%4
288
April1st to 15thDay
28%10%29%19%10%1
270
16th to endDay
20%11%26%22%14%4
270
May1st to 15thDay
27%6%26%22%10%5%
288
16th to endDay
19%10%30%22%14%2
331
June1st to 15thDay
22%6%28%27%10%3
315
16th to endDay
19%6%22%30%18%2
315
July1st to 15thDay
15%222%33%19%7%
305
16th to endDay
14%219%33%23%6%
326
August1st to 15thDay
14%317%33%23%7%
313
16th to endDay
11%417%32%19%14%
332
September1st to 15thDay
18%419%18%22%17%
315
16th to endDay
16%5%19%20%22%14%
314
October1st to 15thDay
23%6%25%23%17%3
315
16th to endDay
29%10%24%26%10%
307
November1st to 15thDay
22%10%23%28%13%1
238
16th to endDay
26%20%23%21%8%
90
December1st to 15thDay
22%5%34%26%10%
67
16th to endDay
42%10%34%12%
64
January1st to 15thNight
26%9%30%28%5%
720
16th to endNight
22%8%31%29%7%
768
February1st to 15thNight
19%7%38%28%6%
704
16th to endNight
25%6%33%28%6%
631
March1st to 15thNight
26%9%30%28%5%
720
16th to endNight
19%7%30%31%10%
768
April1st to 15thNight
27%7%29%30%4
718
16th to endNight
24%9%28%28%8%
648
May1st to 15thNight
26%426%30%9%1
360
16th to endNight
18%6%29%31%13%1
375
June1st to 15thNight
20%326%39%10%
360
16th to endNight
18%226%36%15%1
360
July1st to 15thNight
8%223%44%20%
340
16th to endNight
11%117%45%22%1
376
August1st to 15thNight
14%217%38%24%2
416
16th to endNight
11%319%37%25%1
726
September1st to 15thNight
17%320%36%20%1
720
16th to endNight
18%420%28%25%2
717
October1st to 15thNight
22%429%28%14%
720
16th to endNight
28%8%27%27%8%
768
November1st to 15thNight
26%7%26%27%11%
760
16th to endNight
26%12%28%22%10%
780
December1st to 15thNight
32%8%30%22%5%
736
16th to endNight
32%9%29%22%41
768
Page generated at 2017-12-05 10:18:59. Version ac04

Copyright 2017 A. Danko


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