Eustis Ridge Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Eustis Ridge Observatory 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
28%
14599
13%
46539
7%
14567
36%
14567
14%
33193

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
19%
720
13%
2506
4%
716
29%
716
10%
1809
January16th to endNight
15%
768
12%
2688
3%
768
27%
768
9%
1933
February1st to 15thNight
16%
704
11%
2297
3%
701
25%
701
10%
1717
February16th to endNight
14%
631
14%
1893
2%
631
28%
631
11%
1392
March1st to 15thNight
18%
720
14%
2139
5%
720
28%
720
12%
1583
March16th to endNight
27%
768
18%
2055
6%
768
36%
768
17%
1446
April1st to 15thNight
23%
715
14%
1793
4%
715
29%
715
17%
1344
April16th to endNight
28%
540
15%
1620
6%
540
35%
540
17%
1133
May1st to 15thNight
30%
531
13%
1611
8%
531
37%
531
16%
1172
May16th to endNight
34%
375
10%
1497
10%
374
42%
374
13%
1072
June1st to 15thNight
31%
360
8%
1308
6%
360
37%
360
12%
962
June16th to endNight
45%
360
9%
1314
9%
360
50%
360
20%
861
July1st to 15thNight
48%
340
10%
1360
14%
340
51%
340
19%
853
July16th to endNight
50%
376
11%
1418
12%
354
55%
354
19%
898
August1st to 15thNight
47%
462
11%
1511
9%
460
50%
460
21%
990
August16th to endNight
47%
585
18%
1635
10%
585
51%
585
30%
1017
September1st to 15thNight
45%
660
15%
1716
8%
660
49%
660
30%
1128
September16th to endNight
47%
657
21%
1815
14%
657
52%
657
29%
1161
October1st to 15thNight
34%
660
16%
1878
7%
660
43%
660
18%
1337
October16th to endNight
23%
704
10%
2288
5%
704
31%
704
11%
1719
November1st to 15thNight
27%
700
15%
2277
10%
700
34%
700
13%
1676
November16th to endNight
27%
729
16%
2436
9%
729
36%
729
12%
1758
December1st to 15thNight
17%
750
9%
2700
3%
750
25%
750
8%
2072
December16th to endNight
13%
784
11%
2784
3%
784
23%
784
6%
2160

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
15%10%47%6%35%5%5%7%28%
47433
Night
13%8%47%6%35%5%5%7%31%
46709
TransparencyDay
54%6%11%17%8%1
47121
Night
51%6%12%19%9%1
46539
SeeingDay
24%15%27%20%10%3
5893
Night
22%15%26%24%9%
14599

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
11%8%310%10%5%7%7%6%7%21%
1432
16th to endDay
9%10%5%8%8%46%5%6%8%27%
1536
February1st to 15thDay
9%13%5%10%10%5%5%5%5%5%22%
1560
16th to endDay
8%14%49%8%37%7%5%6%22%
1580
March1st to 15thDay
14%11%6%9%6%3435%6%27%
1811
16th to endDay
13%11%49%7%34345%32%
2167
April1st to 15thDay
15%12%5%8%6%34346%30%
2155
16th to endDay
17%12%37%5%34345%32%
2340
May1st to 15thDay
22%11%36%5%34346%26%
2349
16th to endDay
19%9%38%6%46%5%5%7%24%
2618
June1st to 15thDay
26%7%36%5%45%5%5%6%22%
2649
16th to endDay
19%7%37%6%35%46%7%27%
2642
July1st to 15thDay
13%7%36%7%45%6%6%9%28%
2520
16th to endDay
14%7%37%7%46%6%7%10%23%
2654
August1st to 15thDay
15%8%36%6%46%6%7%7%26%
2342
16th to endDay
11%6%36%5%35%47%8%36%
2215
September1st to 15thDay
14%6%36%5%24446%41%
1914
16th to endDay
13%7%26%43445%7%40%
1815
October1st to 15thDay
16%10%47%5%2445%6%31%
1752
16th to endDay
15%14%5%8%6%36%5%5%6%22%
1584
November1st to 15thDay
15%10%5%7%6%36%446%28%
1581
16th to endDay
13%11%48%5%435%6%6%30%
1522
December1st to 15thDay
12%16%7%9%8%46%446%21%
1260
16th to endDay
16%13%6%10%7%44445%20%
1435
January1st to 15thNight
8%10%5%8%8%45%6%8%9%24%
2506
16th to endNight
8%9%49%8%5%7%5%6%9%25%
2688
February1st to 15thNight
7%9%5%10%8%48%6%6%9%23%
2296
16th to endNight
10%11%48%6%45%5%7%7%28%
1893
March1st to 15thNight
13%11%5%7%5%35%5%5%5%30%
2126
16th to endNight
11%8%46%6%35%5%6%6%36%
2055
April1st to 15thNight
15%8%47%6%35%5%6%5%29%
1793
16th to endNight
18%8%26%6%34247%35%
1620
May1st to 15thNight
17%8%38%5%245%47%31%
1611
16th to endNight
18%6%47%6%35%5%5%7%29%
1495
June1st to 15thNight
22%8%36%7%44347%27%
1308
16th to endNight
18%5%244246%6%9%34%
1314
July1st to 15thNight
12%5%35%6%35%5%6%9%36%
1440
16th to endNight
13%425%445%6%6%8%39%
1514
August1st to 15thNight
12%6%36%43446%7%40%
1521
16th to endNight
12%42442345%8%46%
1635
September1st to 15thNight
13%5%25%5%2435%6%44%
1716
16th to endNight
13%5%24424447%46%
1815
October1st to 15thNight
15%9%36%6%43447%34%
1878
16th to endNight
18%9%48%5%35%47%7%25%
2288
November1st to 15thNight
13%8%5%8%7%35%6%5%7%28%
2277
16th to endNight
13%8%46%7%35%5%5%7%31%
2436
December1st to 15thNight
15%12%5%8%7%36%45%6%23%
2700
16th to endNight
16%13%5%9%7%35%5%5%6%20%
2784

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
57%7%10%14%8%1
1433
16th to endDay
54%5%11%18%9%
1536
February1st to 15thDay
62%5%9%12%8%
1563
16th to endDay
60%49%13%9%2
1580
March1st to 15thDay
58%49%14%10%2
1821
16th to endDay
53%48%17%13%2
2167
April1st to 15thDay
55%47%16%11%3
2155
16th to endDay
54%49%16%11%3
2340
May1st to 15thDay
58%48%18%9%
2349
16th to endDay
57%7%11%15%7%
2622
June1st to 15thDay
61%6%11%14%5%
2649
16th to endDay
55%6%10%19%6%
2642
July1st to 15thDay
48%8%14%21%6%
2371
16th to endDay
53%9%12%19%5%
2487
August1st to 15thDay
53%7%15%18%4
2328
16th to endDay
43%6%15%22%11%
2215
September1st to 15thDay
43%5%13%26%10%
1914
16th to endDay
41%5%12%26%13%
1815
October1st to 15thDay
51%5%10%21%10%
1752
16th to endDay
59%6%11%15%7%
1584
November1st to 15thDay
56%6%10%14%10%1
1581
16th to endDay
54%5%12%17%7%1
1522
December1st to 15thDay
63%6%7%15%6%
1260
16th to endDay
64%5%7%12%9%
1435
January1st to 15thNight
52%8%12%17%7%1
2506
16th to endNight
53%6%10%17%9%1
2688
February1st to 15thNight
56%7%11%17%7%1
2297
16th to endNight
54%5%10%15%11%1
1893
March1st to 15thNight
55%5%9%17%10%2
2139
16th to endNight
47%5%11%18%14%2
2055
April1st to 15thNight
52%6%9%17%13%
1793
16th to endNight
50%411%17%12%2
1620
May1st to 15thNight
53%6%8%20%10%1
1611
16th to endNight
53%7%13%18%6%
1497
June1st to 15thNight
58%5%12%16%7%
1308
16th to endNight
45%6%16%22%9%
1314
July1st to 15thNight
41%8%16%23%8%
1360
16th to endNight
41%8%16%23%8%
1418
August1st to 15thNight
42%8%18%24%6%
1511
16th to endNight
35%6%18%26%12%
1635
September1st to 15thNight
37%6%15%30%10%
1716
16th to endNight
37%5%12%29%13%
1815
October1st to 15thNight
49%6%11%21%11%
1878
16th to endNight
57%5%10%18%7%
2288
November1st to 15thNight
55%6%12%16%8%1
2277
16th to endNight
54%5%10%19%9%1
2436
December1st to 15thNight
61%5%9%16%5%
2700
16th to endNight
63%5%9%12%8%
2784

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
18%26%36%15%3
60
16th to endDay
21%21%31%21%3
64
February1st to 15thDay
25%19%29%22%2
181
16th to endDay
21%29%21%23%4
239
March1st to 15thDay
27%18%30%19%4
270
16th to endDay
23%22%23%17%8%3
288
April1st to 15thDay
27%20%28%15%43
270
16th to endDay
31%20%23%12%7%4
270
May1st to 15thDay
35%14%26%11%9%3
288
16th to endDay
23%15%36%16%6%
331
June1st to 15thDay
30%12%25%20%10%
444
16th to endDay
20%10%28%25%12%2
437
July1st to 15thDay
17%11%37%16%14%3
305
16th to endDay
16%7%33%29%11%1
326
August1st to 15thDay
18%7%30%22%14%6%
297
16th to endDay
18%7%23%24%16%8%
268
September1st to 15thDay
17%6%24%23%19%7%
255
16th to endDay
20%9%21%20%14%12%
254
October1st to 15thDay
27%15%19%16%16%4
246
16th to endDay
27%18%25%21%6%
240
November1st to 15thDay
25%17%20%23%10%2
235
16th to endDay
26%19%21%19%8%2
201
December1st to 15thDay
21%26%35%15%1
60
16th to endDay
39%17%34%7%1
64
January1st to 15thNight
20%22%32%20%4
720
16th to endNight
20%21%34%19%3
768
February1st to 15thNight
19%21%33%22%3
704
16th to endNight
22%22%33%16%4
631
March1st to 15thNight
28%18%28%22%2
720
16th to endNight
20%21%24%24%8%
768
April1st to 15thNight
24%18%28%22%5%
715
16th to endNight
25%15%26%24%8%
540
May1st to 15thNight
23%12%28%25%9%1
531
16th to endNight
21%8%26%31%10%
375
June1st to 15thNight
30%6%23%31%8%
360
16th to endNight
20%6%21%35%15%
360
July1st to 15thNight
14%424%39%16%1
340
16th to endNight
16%222%35%22%
376
August1st to 15thNight
17%321%34%21%
462
16th to endNight
16%5%23%32%20%1
585
September1st to 15thNight
17%8%22%31%18%2
660
16th to endNight
19%8%20%30%19%1
657
October1st to 15thNight
24%13%21%24%13%2
660
16th to endNight
28%17%25%21%6%
704
November1st to 15thNight
22%18%23%24%9%1
700
16th to endNight
24%17%24%22%8%2
729
December1st to 15thNight
28%19%29%18%4
750
16th to endNight
29%22%26%17%3
784
Page generated at 2017-08-13 14:16:43. Version ac04

Copyright 2017 A. Danko


Eustis Ridge Observatory Clear Sky Chart | Charts Home