Arrow Heights Astroimaging Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Arrow Heights Astroimaging Observatory clear sky chart from 2005-11-05 to 2017-09-10.

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
42%
15823
21%
46806
14%
15777
49%
15777
27%
29646

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
25%
899
18%
2491
7%
895
34%
895
22%
1710
January16th to endNight
23%
960
19%
2496
6%
960
32%
960
24%
1737
February1st to 15thNight
25%
836
14%
2244
5%
833
31%
833
20%
1617
February16th to endNight
23%
631
20%
1893
6%
631
34%
631
23%
1224
March1st to 15thNight
24%
654
17%
2094
9%
654
33%
654
20%
1419
March16th to endNight
31%
576
14%
2034
9%
576
37%
576
17%
1394
April1st to 15thNight
31%
539
21%
1797
12%
539
45%
539
25%
1098
April16th to endNight
38%
540
22%
1800
16%
540
49%
540
26%
1118
May1st to 15thNight
40%
540
18%
1658
12%
539
48%
539
25%
1084
May16th to endNight
50%
563
20%
1497
13%
561
54%
561
30%
985
June1st to 15thNight
64%
540
21%
1440
14%
540
68%
540
42%
843
June16th to endNight
64%
540
22%
1440
15%
540
67%
540
42%
841
July1st to 15thNight
69%
510
19%
1360
16%
510
70%
510
40%
818
July16th to endNight
73%
564
23%
1493
21%
531
75%
531
42%
845
August1st to 15thNight
76%
539
23%
1673
26%
536
77%
536
38%
926
August16th to endNight
73%
573
24%
1910
27%
573
76%
573
37%
1028
September1st to 15thNight
64%
525
26%
1750
28%
525
67%
525
31%
1007
September16th to endNight
60%
605
31%
1764
23%
605
66%
605
35%
1031
October1st to 15thNight
51%
660
29%
1980
20%
660
58%
660
35%
1137
October16th to endNight
37%
704
26%
2123
17%
704
46%
704
32%
1252
November1st to 15thNight
40%
700
27%
2276
17%
700
53%
700
32%
1258
November16th to endNight
31%
765
22%
2385
13%
765
41%
765
26%
1482
December1st to 15thNight
28%
900
16%
2520
8%
900
35%
900
20%
1809
December16th to endNight
24%
960
16%
2688
7%
960
32%
960
18%
1983

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
12%6%25%5%3445%7%41%
47828
Night
13%6%25%424446%45%
46988
TransparencyDay
40%6%12%23%14%2
47514
Night
39%5%11%23%16%3
46808
SeeingDay
13%6%23%28%20%7%
5846
Night
15%7%28%30%14%1
15824

By Month

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
12%9%28%7%35%5%45%34%
1447
16th to endDay
13%9%37%7%33345%37%
1728
February1st to 15thDay
15%7%47%43445%7%34%
1616
16th to endDay
11%9%48%5%35%446%37%
1580
March1st to 15thDay
16%8%36%5%33435%38%
1875
16th to endDay
17%10%36%6%35%5%5%6%30%
2186
April1st to 15thDay
14%6%25%435%446%41%
2151
16th to endDay
17%6%35%6%34446%36%
2160
May1st to 15thDay
17%5%25%425%46%7%36%
2290
16th to endDay
11%5%246%36%5%7%7%39%
2617
June1st to 15thDay
8%424435%6%5%8%46%
2520
16th to endDay
6%323425%6%7%11%46%
2520
July1st to 15thDay
9%314445%6%6%9%44%
2520
16th to endDay
5%3135%25%6%7%10%47%
2570
August1st to 15thDay
7%4245%35%6%7%9%42%
2277
16th to endDay
8%5%25%5%35%5%5%9%44%
2292
September1st to 15thDay
13%42342446%7%45%
2097
16th to endDay
9%5%1442445%8%49%
1853
October1st to 15thDay
13%5%245%22345%51%
1650
16th to endDay
14%422422336%52%
1747
November1st to 15thDay
12%5%24322346%51%
1582
16th to endDay
18%7%24423336%41%
1574
December1st to 15thDay
17%11%35%5%24446%36%
1440
16th to endDay
17%12%45%42335%7%33%
1536
January1st to 15thNight
14%7%36%5%33445%39%
2491
16th to endNight
12%10%47%433446%38%
2496
February1st to 15thNight
14%10%47%5%25%346%35%
2235
16th to endNight
13%9%37%424235%43%
1893
March1st to 15thNight
19%8%35%42434439%
2094
16th to endNight
16%9%35%5%35%45%6%34%
2034
April1st to 15thNight
12%6%25%423436%46%
1797
16th to endNight
15%6%24423348%43%
1800
May1st to 15thNight
16%6%24323447%42%
1658
16th to endNight
9%5%35%5%2445%8%45%
1496
June1st to 15thNight
6%32443445%9%52%
1440
16th to endNight
6%3233235%5%10%52%
1440
July1st to 15thNight
9%32432435%8%52%
1440
16th to endNight
3325%4445%5%10%50%
1595
August1st to 15thNight
5%3134245%6%7%54%
1683
16th to endNight
4324425%46%8%53%
1910
September1st to 15thNight
11%42432445%7%49%
1750
16th to endNight
9%424424437%53%
1764
October1st to 15thNight
10%414323447%53%
1980
16th to endNight
16%5%1432224452%
2123
November1st to 15thNight
11%424313345%54%
2276
16th to endNight
16%7%24323346%45%
2385
December1st to 15thNight
20%9%36%42435%6%33%
2520
16th to endNight
19%10%46%5%3434433%
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
49%6%9%21%11%1
1448
16th to endDay
47%315%23%8%1
1728
February1st to 15thDay
47%5%13%22%9%
1618
16th to endDay
47%5%11%22%11%1
1580
March1st to 15thDay
48%411%21%12%1
1875
16th to endDay
53%6%13%16%8%
2188
April1st to 15thDay
42%5%11%22%16%1
2151
16th to endDay
46%6%11%21%11%1
2160
May1st to 15thDay
46%7%13%22%10%
2290
16th to endDay
41%8%14%18%14%2
2621
June1st to 15thDay
34%7%14%22%18%1
2520
16th to endDay
28%8%17%22%18%3
2520
July1st to 15thDay
33%8%13%25%14%4
2371
16th to endDay
29%8%16%27%16%1
2410
August1st to 15thDay
34%8%12%24%17%1
2263
16th to endDay
35%8%13%20%17%5%
2292
September1st to 15thDay
35%6%10%23%19%4
2097
16th to endDay
34%5%9%27%20%3
1853
October1st to 15thDay
35%310%24%20%4
1650
16th to endDay
33%410%30%18%3
1747
November1st to 15thDay
34%311%23%21%5%
1582
16th to endDay
44%411%25%12%1
1574
December1st to 15thDay
49%5%13%21%9%
1440
16th to endDay
51%313%20%9%1
1536
January1st to 15thNight
45%5%10%23%14%1
2491
16th to endNight
45%5%14%21%12%
2496
February1st to 15thNight
50%410%20%13%1
2244
16th to endNight
44%313%24%13%1
1893
March1st to 15thNight
48%49%22%12%2
2094
16th to endNight
49%6%12%21%9%
2034
April1st to 15thNight
39%49%24%18%3
1797
16th to endNight
40%5%8%27%16%2
1800
May1st to 15thNight
41%6%12%22%15%1
1659
16th to endNight
36%9%13%20%16%3
1498
June1st to 15thNight
27%5%14%28%20%2
1440
16th to endNight
25%8%15%24%21%5%
1440
July1st to 15thNight
30%5%12%30%15%5%
1360
16th to endNight
26%5%16%31%17%1
1493
August1st to 15thNight
26%7%14%27%21%2
1673
16th to endNight
27%5%12%23%24%5%
1910
September1st to 15thNight
33%5%8%21%22%7%
1750
16th to endNight
31%5%8%24%26%4
1764
October1st to 15thNight
30%5%10%24%23%6%
1980
16th to endNight
35%39%26%20%5%
2123
November1st to 15thNight
31%411%23%21%7%
2276
16th to endNight
40%310%26%17%1
2385
December1st to 15thNight
51%5%10%20%11%
2520
16th to endNight
54%410%18%9%2
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%43%12%21
90
16th to endDay
13%23%41%18%2
96
February1st to 15thDay
16%21%37%18%5%
90
16th to endDay
16%19%34%24%4
81
March1st to 15thDay
28%17%35%12%41
90
16th to endDay
23%13%33%25%4
172
April1st to 15thDay
16%11%32%23%15%
270
16th to endDay
23%7%30%22%14%1
270
May1st to 15thDay
16%11%29%26%13%2
331
16th to endDay
15%6%29%29%13%5%
517
June1st to 15thDay
9%322%31%21%10%
495
16th to endDay
7%325%37%19%6%
495
July1st to 15thDay
13%114%33%28%8%
475
16th to endDay
5%113%30%35%13%
515
August1st to 15thDay
11%9%31%30%16%
430
16th to endDay
9%112%28%36%12%
332
September1st to 15thDay
13%312%26%31%12%
294
16th to endDay
10%5%15%24%27%16%
251
October1st to 15thDay
10%12%15%41%16%4
90
16th to endDay
12%8%33%31%14%
96
November1st to 15thDay
6%425%25%27%10%
90
16th to endDay
40%14%26%11%6%1
90
December1st to 15thDay
14%14%41%20%5%4
90
16th to endDay
28%15%44%10%1
96
January1st to 15thNight
18%15%36%23%5%
900
16th to endNight
16%14%40%25%3
960
February1st to 15thNight
19%13%37%26%2
836
16th to endNight
18%12%40%26%1
631
March1st to 15thNight
23%10%37%23%4
654
16th to endNight
21%8%34%27%8%
576
April1st to 15thNight
14%13%36%26%8%
539
16th to endNight
17%6%34%31%8%
540
May1st to 15thNight
16%433%32%12%
540
16th to endNight
11%227%38%18%1
563
June1st to 15thNight
6%220%45%23%1
540
16th to endNight
8%21%44%22%2
540
July1st to 15thNight
10%11%45%28%3
510
16th to endNight
5%11%37%41%3
564
August1st to 15thNight
7%8%38%42%3
539
16th to endNight
5%11%40%36%5%
573
September1st to 15thNight
13%212%32%31%6%
525
16th to endNight
10%5%18%28%31%6%
605
October1st to 15thNight
13%5%25%29%23%3
660
16th to endNight
19%8%31%30%8%
704
November1st to 15thNight
13%9%32%29%13%
700
16th to endNight
19%10%35%26%6%
765
December1st to 15thNight
25%11%31%25%5%
900
16th to endNight
25%10%34%27%2
960
Page generated at 2017-09-11 18:35:19. Version ac04

Copyright 2017 A. Danko


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