Reuben H. Fleet Science Center
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Reuben H. Fleet Science Center clear sky chart from 2005-11-05 to 2017-08-12.

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
71%
16137
27%
46607
26%
16092
72%
16092
39%
26928

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
74%
717
28%
2303
30%
716
76%
716
41%
1194
January16th to endNight
69%
768
32%
2304
31%
768
73%
768
38%
1317
February1st to 15thNight
72%
698
31%
2108
32%
698
74%
698
39%
1169
February16th to endNight
61%
632
25%
1895
29%
632
63%
632
28%
1203
March1st to 15thNight
69%
720
25%
2160
28%
720
70%
720
37%
1219
March16th to endNight
68%
768
23%
2033
21%
768
69%
768
35%
1277
April1st to 15thNight
65%
719
24%
1799
17%
719
66%
719
38%
1136
April16th to endNight
67%
720
25%
1800
17%
720
68%
720
40%
1119
May1st to 15thNight
62%
599
21%
1680
16%
599
62%
599
30%
1119
May16th to endNight
58%
561
18%
1685
14%
561
58%
561
26%
1147
June1st to 15thNight
62%
540
15%
1620
14%
540
62%
540
26%
1116
June16th to endNight
76%
540
23%
1620
20%
540
76%
540
43%
903
July1st to 15thNight
75%
510
19%
1530
16%
510
75%
510
37%
915
July16th to endNight
74%
656
22%
1678
16%
616
74%
616
36%
1045
August1st to 15thNight
74%
701
23%
1750
16%
697
75%
697
44%
1057
August16th to endNight
82%
700
31%
1750
23%
700
82%
700
54%
967
September1st to 15thNight
79%
660
31%
1713
27%
660
79%
660
49%
961
September16th to endNight
80%
656
36%
1815
36%
656
81%
656
53%
928
October1st to 15thNight
77%
660
32%
1815
31%
660
78%
660
46%
987
October16th to endNight
75%
704
33%
2098
35%
704
76%
704
43%
1107
November1st to 15thNight
79%
700
31%
2275
37%
700
80%
700
47%
1097
November16th to endNight
75%
720
32%
2340
37%
720
76%
720
40%
1231
December1st to 15thNight
68%
720
30%
2340
32%
720
69%
720
34%
1311
December16th to endNight
66%
768
30%
2496
31%
768
70%
768
35%
1403

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
5%423313348%59%
47354
Night
7%7%24323347%53%
46813
TransparencyDay
24%49%17%23%21%
47058
Night
30%48%14%19%21%
46611
SeeingDay
7%319%41%24%4
5804
Night
10%17%28%39%13%
16149

By Month

Percentage Cloud Cover SW (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
7%423323336%58%
1632
16th to endDay
10%5%14312348%54%
1920
February1st to 15thDay
7%413314347%57%
1751
16th to endDay
10%5%26%4235%5%7%45%
1579
March1st to 15thDay
6%4233233410%56%
1800
16th to endDay
5%324324448%56%
2188
April1st to 15thDay
7%5%2332335%7%54%
2149
16th to endDay
5%312212249%63%
2160
May1st to 15thDay
7%5%23313337%57%
2270
16th to endDay
5%6%23212248%59%
2429
June1st to 15thDay
6%8%33212338%56%
2340
16th to endDay
15%24212236%67%
2340
July1st to 15thDay
46%244233410%55%
2340
16th to endDay
342322345%9%58%
2372
August1st to 15thDay
2412212247%66%
2114
16th to endDay
1213323249%65%
2100
September1st to 15thDay
1323313338%64%
1917
16th to endDay
2313212247%69%
1815
October1st to 15thDay
5%32422335%7%59%
1815
16th to endDay
5%412212237%65%
1771
November1st to 15thDay
5%223213247%63%
1584
16th to endDay
6%413313346%62%
1620
December1st to 15thDay
7%424423447%53%
1620
16th to endDay
12%31432325%7%53%
1728
January1st to 15thNight
7%413313347%58%
2303
16th to endNight
10%5%13312346%56%
2304
February1st to 15thNight
8%423423346%56%
2101
16th to endNight
11%7%45%423435%46%
1895
March1st to 15thNight
7%5%24324448%51%
2160
16th to endNight
7%8%343235%5%8%48%
2033
April1st to 15thNight
11%7%24222338%51%
1799
16th to endNight
9%8%34312237%53%
1800
May1st to 15thNight
7%12%36%5%2325%9%41%
1679
16th to endNight
11%13%46%322247%40%
1684
June1st to 15thNight
8%15%46%42335%10%35%
1620
16th to endNight
211%35%31236%9%50%
1620
July1st to 15thNight
5%11%3432335%10%45%
1620
16th to endNight
5%9%45%32345%9%46%
1793
August1st to 15thNight
39%343233411%49%
1760
16th to endNight
16%13323349%60%
1750
September1st to 15thNight
25%25%322338%60%
1713
16th to endNight
4423311346%64%
1815
October1st to 15thNight
4414322347%59%
1815
16th to endNight
7%5%23213337%60%
2098
November1st to 15thNight
5%422312346%64%
2275
16th to endNight
5%5%24323447%57%
2340
December1st to 15thNight
9%5%24413347%52%
2340
16th to endNight
12%323323345%55%
2496

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
27%47%13%20%27%
1633
16th to endDay
30%39%14%14%27%
1920
February1st to 15thDay
27%38%14%20%25%
1751
16th to endDay
37%5%7%15%23%10%
1579
March1st to 15thDay
24%5%9%18%20%20%
1800
16th to endDay
26%5%11%23%19%13%
2188
April1st to 15thDay
28%49%23%24%8%
2149
16th to endDay
19%5%12%23%20%18%
2160
May1st to 15thDay
27%5%8%22%20%15%
2270
16th to endDay
24%411%22%28%8%
2432
June1st to 15thDay
27%5%10%17%22%17%
2340
16th to endDay
18%29%10%22%36%
2340
July1st to 15thDay
25%39%14%24%22%
2201
16th to endDay
22%5%15%21%24%10%
2225
August1st to 15thDay
19%38%14%31%21%
2100
16th to endDay
16%49%15%31%23%
2100
September1st to 15thDay
19%37%13%29%25%
1917
16th to endDay
15%38%14%30%27%
1815
October1st to 15thDay
24%37%16%25%22%
1815
16th to endDay
20%36%13%21%33%
1771
November1st to 15thDay
21%48%14%16%33%
1584
16th to endDay
22%38%15%18%31%
1620
December1st to 15thDay
30%411%12%17%23%
1620
16th to endDay
30%5%10%15%20%18%
1728
January1st to 15thNight
26%38%13%20%27%
2303
16th to endNight
30%48%11%14%31%
2304
February1st to 15thNight
28%47%14%18%26%
2112
16th to endNight
40%45%12%21%15%
1895
March1st to 15thNight
30%49%16%17%21%
2160
16th to endNight
33%6%10%17%18%13%
2033
April1st to 15thNight
34%48%22%21%10%
1799
16th to endNight
32%49%16%19%17%
1800
May1st to 15thNight
41%5%10%13%14%15%
1680
16th to endNight
44%5%9%14%15%10%
1685
June1st to 15thNight
45%5%11%11%15%10%
1620
16th to endNight
29%29%12%16%29%
1620
July1st to 15thNight
33%39%11%21%20%
1530
16th to endNight
34%5%12%20%20%6%
1678
August1st to 15thNight
30%310%16%25%13%
1750
16th to endNight
22%38%14%27%24%
1750
September1st to 15thNight
24%36%10%28%25%
1713
16th to endNight
21%2411%33%27%
1815
October1st to 15thNight
24%47%17%23%22%
1815
16th to endNight
26%35%12%19%33%
2098
November1st to 15thNight
22%37%16%16%34%
2275
16th to endNight
26%47%14%16%30%
2340
December1st to 15thNight
32%47%15%17%22%
2340
16th to endNight
31%49%15%17%21%
2496

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
21%18%41%17%
111
16th to endDay
13%6%27%38%12%1
288
February1st to 15thDay
9%424%40%18%1
266
16th to endDay
9%8%34%31%13%2
238
March1st to 15thDay
7%428%39%15%4
270
16th to endDay
5%6%27%41%15%3
288
April1st to 15thDay
10%433%35%12%4
269
16th to endDay
5%6%35%37%10%4
270
May1st to 15thDay
11%429%36%14%2
288
16th to endDay
11%5%25%38%17%1
330
June1st to 15thDay
6%23%43%23%2
315
16th to endDay
38%47%34%5%
315
July1st to 15thDay
7%7%40%37%6%
305
16th to endDay
5%234%47%10%
327
August1st to 15thDay
36%46%37%6%
300
16th to endDay
3241%45%6%
268
September1st to 15thDay
5%11%54%27%1
255
16th to endDay
314%55%21%4
255
October1st to 15thDay
5%229%45%16%1
255
16th to endDay
10%19%39%24%4
225
November1st to 15thDay
17%13%27%34%15%
90
16th to endDay
12%6%17%28%27%6%
90
December1st to 15thDay
5%311%43%30%6%
90
16th to endDay
15%6%14%39%21%2
96
January1st to 15thNight
7%110%37%32%10%
720
16th to endNight
12%110%33%34%8%
768
February1st to 15thNight
9%28%32%36%10%
704
16th to endNight
13%211%40%26%6%
632
March1st to 15thNight
9%210%37%33%7%
720
16th to endNight
10%28%32%37%8%
768
April1st to 15thNight
12%310%34%33%5%
719
16th to endNight
12%210%33%31%9%
720
May1st to 15thNight
12%111%30%35%8%
600
16th to endNight
15%113%26%33%8%
563
June1st to 15thNight
14%9%33%35%6%
540
16th to endNight
5%422%56%10%
540
July1st to 15thNight
10%213%53%19%
510
16th to endNight
9%211%48%28%
656
August1st to 15thNight
8%114%50%24%
701
16th to endNight
5%17%47%38%
700
September1st to 15thNight
6%213%54%23%
660
16th to endNight
6%421%50%17%
656
October1st to 15thNight
7%15%31%44%9%
660
16th to endNight
11%15%26%36%18%
704
November1st to 15thNight
7%15%31%40%14%
700
16th to endNight
6%15%31%37%16%
720
December1st to 15thNight
13%17%35%32%10%
720
16th to endNight
13%210%33%30%9%
768
Page generated at 2017-08-13 11:16:37. Version ac04

Copyright 2017 A. Danko


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