Fulcher Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fulcher Observatory clear sky chart from 2005-11-05 to 2018-01-20.

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
48%
16096
23%
48480
15%
16052
56%
16052
27%
30075

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
28%
780
23%
2522
10%
776
44%
776
20%
1556
January16th to endNight
25%
788
26%
2560
11%
788
43%
788
22%
1566
February1st to 15thNight
30%
704
26%
2114
10%
700
48%
700
26%
1275
February16th to endNight
26%
631
25%
1893
10%
631
42%
631
25%
1156
March1st to 15thNight
34%
720
24%
2025
12%
720
44%
720
27%
1278
March16th to endNight
39%
768
22%
2112
11%
768
48%
768
29%
1314
April1st to 15thNight
40%
700
25%
1958
15%
700
49%
700
34%
1149
April16th to endNight
48%
540
25%
1659
15%
540
57%
540
30%
990
May1st to 15thNight
48%
540
20%
1620
10%
540
55%
540
29%
1000
May16th to endNight
60%
561
20%
1683
14%
561
63%
561
30%
1045
June1st to 15thNight
65%
540
16%
1620
13%
540
67%
540
31%
1020
June16th to endNight
72%
540
16%
1620
14%
540
72%
540
31%
1019
July1st to 15thNight
67%
510
10%
1530
8%
510
68%
510
24%
1034
July16th to endNight
72%
564
14%
1595
12%
531
74%
531
27%
1067
August1st to 15thNight
66%
539
15%
1609
15%
536
66%
536
24%
1106
August16th to endNight
66%
594
15%
1890
15%
594
67%
594
20%
1302
September1st to 15thNight
65%
720
18%
1980
16%
720
66%
720
27%
1314
September16th to endNight
58%
717
24%
1980
18%
717
63%
717
30%
1273
October1st to 15thNight
52%
720
29%
2028
23%
720
59%
720
33%
1236
October16th to endNight
53%
768
36%
2304
27%
768
67%
768
39%
1258
November1st to 15thNight
53%
760
30%
2404
25%
760
64%
760
36%
1318
November16th to endNight
43%
780
28%
2535
19%
780
56%
780
29%
1444
December1st to 15thNight
39%
780
24%
2535
15%
780
52%
780
23%
1561
December16th to endNight
31%
832
22%
2704
14%
832
43%
832
19%
1794

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
13%4245%35%45%7%43%
49042
Night
12%42442445%7%46%
48679
TransparencyDay
38%7%11%19%17%5%
48743
Night
36%6%11%19%19%6%
48482
SeeingDay
17%6%19%23%21%11%
5887
Night
15%7%22%29%21%3
16098

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
16%6%2432345%445%
1746
16th to endDay
18%424323346%47%
1768
February1st to 15thDay
16%42442345%5%46%
1744
16th to endDay
17%6%23423346%45%
1580
March1st to 15thDay
16%31443435%5%47%
1934
16th to endDay
16%5%2342435%6%45%
2111
April1st to 15thDay
11%4245%3445%7%46%
1999
16th to endDay
10%424425%45%7%48%
2301
May1st to 15thDay
10%425%5%345%5%7%44%
2331
16th to endDay
9%4147%45%5%6%8%41%
2431
June1st to 15thDay
9%4245%48%6%7%10%35%
2340
16th to endDay
42135%37%8%8%11%41%
2340
July1st to 15thDay
9%5%247%47%7%8%10%31%
2340
16th to endDay
7%325%7%5%8%7%7%10%32%
2465
August1st to 15thDay
10%5%36%6%5%7%6%7%10%30%
2340
16th to endDay
14%6%36%7%47%6%6%8%28%
2295
September1st to 15thDay
13%5%246%35%5%5%7%39%
1980
16th to endDay
17%425%424447%43%
1980
October1st to 15thDay
15%414212245%55%
1932
16th to endDay
11%31342323360%
1920
November1st to 15thDay
12%313323346%54%
1783
16th to endDay
13%424423246%51%
1755
December1st to 15thDay
18%7%25%42343443%
1755
16th to endDay
23%7%25%323345%37%
1872
January1st to 15thNight
17%6%2442433447%
2522
16th to endNight
17%6%23423345%46%
2560
February1st to 15thNight
14%314424336%49%
2106
16th to endNight
15%424323345%48%
1893
March1st to 15thNight
13%4245%24445%48%
2025
16th to endNight
13%41433445%5%49%
2112
April1st to 15thNight
12%413314346%52%
1958
16th to endNight
11%4144245%47%49%
1659
May1st to 15thNight
10%5%235%3446%8%45%
1619
16th to endNight
7%4136%35%5%7%9%44%
1682
June1st to 15thNight
7%415%435%6%8%12%39%
1620
16th to endNight
6%2245%35%7%8%10%42%
1620
July1st to 15thNight
8%5%36%5%35%6%9%12%33%
1620
16th to endNight
4426%6%36%8%9%15%31%
1703
August1st to 15thNight
10%425%6%45%6%9%12%31%
1620
16th to endNight
11%5%146%36%6%8%10%33%
1890
September1st to 15thNight
10%5%25%445%5%7%10%39%
1980
16th to endNight
14%5%145%34347%45%
1980
October1st to 15thNight
14%424313335%52%
2028
16th to endNight
10%213313335%60%
2304
November1st to 15thNight
11%314313236%58%
2404
16th to endNight
14%423313345%52%
2535
December1st to 15thNight
16%5%25%324335%46%
2535
16th to endNight
19%7%25%423346%39%
2704

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
40%5%8%16%24%4
1747
16th to endDay
38%46%19%22%8%
1768
February1st to 15thDay
39%48%20%22%4
1746
16th to endDay
40%36%21%20%7%
1580
March1st to 15thDay
38%49%20%19%7%
1934
16th to endDay
39%5%11%21%17%4
2112
April1st to 15thDay
36%5%9%20%22%6%
1999
16th to endDay
34%6%9%20%22%6%
2301
May1st to 15thDay
37%6%13%20%18%3
2331
16th to endDay
38%8%14%22%14%2
2435
June1st to 15thDay
39%11%19%19%8%1
2340
16th to endDay
30%12%18%22%13%2
2340
July1st to 15thDay
41%12%17%18%7%2
2201
16th to endDay
40%12%18%18%7%2
2310
August1st to 15thDay
45%10%13%19%9%1
2327
16th to endDay
49%11%14%13%9%1
2295
September1st to 15thDay
42%8%11%18%16%2
1980
16th to endDay
39%6%11%20%17%4
1980
October1st to 15thDay
33%410%19%25%6%
1932
16th to endDay
28%35%19%30%12%
1920
November1st to 15thDay
32%39%15%28%10%
1783
16th to endDay
33%47%17%27%8%
1755
December1st to 15thDay
43%5%7%19%16%8%
1755
16th to endDay
50%47%18%13%6%
1872
January1st to 15thNight
41%37%16%24%6%
2522
16th to endNight
39%45%17%22%10%
2560
February1st to 15thNight
36%37%20%22%9%
2115
16th to endNight
37%36%21%23%7%
1893
March1st to 15thNight
37%5%9%16%22%9%
2025
16th to endNight
34%6%11%20%21%6%
2112
April1st to 15thNight
31%410%23%22%8%
1958
16th to endNight
33%6%9%21%19%9%
1659
May1st to 15thNight
36%6%13%20%19%3
1620
16th to endNight
32%10%15%24%13%3
1684
June1st to 15thNight
33%9%20%24%10%1
1620
16th to endNight
31%12%16%24%12%3
1620
July1st to 15thNight
37%12%21%18%7%2
1530
16th to endNight
34%14%24%16%7%2
1595
August1st to 15thNight
40%11%17%20%9%
1609
16th to endNight
40%13%17%15%10%
1890
September1st to 15thNight
37%10%15%17%15%3
1980
16th to endNight
37%7%13%19%16%5%
1980
October1st to 15thNight
34%48%19%24%8%
2028
16th to endNight
27%35%18%30%14%
2304
November1st to 15thNight
28%46%18%28%13%
2404
16th to endNight
33%37%17%26%11%
2535
December1st to 15thNight
39%48%19%18%8%
2535
16th to endNight
46%48%16%17%5%
2704

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
25%14%35%20%3
135
16th to endDay
22%25%33%15%2
109
February1st to 15thDay
22%15%47%14%
90
16th to endDay
25%11%44%16%2
81
March1st to 15thDay
19%14%28%27%9%
224
16th to endDay
17%11%29%25%14%1
288
April1st to 15thDay
20%9%24%21%20%3
270
16th to endDay
15%5%26%27%18%6%
270
May1st to 15thDay
13%10%30%18%14%12%
288
16th to endDay
16%417%23%22%15%
331
June1st to 15thDay
12%311%24%28%20%
315
16th to endDay
7%116%25%24%24%
315
July1st to 15thDay
10%110%24%29%23%
305
16th to endDay
9%7%24%35%23%
326
August1st to 15thDay
18%7%25%27%20%
313
16th to endDay
16%9%22%30%19%
332
September1st to 15thDay
15%111%22%33%14%
315
16th to endDay
20%213%27%25%11%
314
October1st to 15thDay
21%220%26%20%8%
315
16th to endDay
13%7%20%25%26%6%
336
November1st to 15thDay
24%6%20%30%14%2
201
16th to endDay
9%10%26%32%17%2
135
December1st to 15thDay
28%14%32%18%5%
135
16th to endDay
38%13%25%17%31
144
January1st to 15thNight
22%16%26%25%8%
780
16th to endNight
20%16%33%25%3
788
February1st to 15thNight
18%14%32%30%3
704
16th to endNight
18%16%34%27%3
631
March1st to 15thNight
16%14%32%30%6%
720
16th to endNight
16%10%29%31%12%
768
April1st to 15thNight
15%10%31%27%14%
700
16th to endNight
13%6%25%32%19%1
540
May1st to 15thNight
12%5%26%31%20%3
540
16th to endNight
11%216%32%32%5%
563
June1st to 15thNight
9%114%32%33%9%
540
16th to endNight
6%10%33%37%10%
540
July1st to 15thNight
12%6%29%40%11%
510
16th to endNight
6%7%32%43%9%
564
August1st to 15thNight
13%7%27%41%8%
539
16th to endNight
14%7%28%39%9%
594
September1st to 15thNight
13%111%24%41%8%
720
16th to endNight
17%115%30%32%3
717
October1st to 15thNight
16%321%28%25%5%
720
16th to endNight
11%7%22%30%25%2
768
November1st to 15thNight
13%5%21%34%22%1
760
16th to endNight
15%11%25%28%16%1
780
December1st to 15thNight
18%12%24%32%11%
780
16th to endNight
25%12%26%29%6%
832
Page generated at 2018-01-21 12:19:24. Version ac04

Copyright 2018 A. Danko


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