Colbeck Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Colbeck Observatory clear sky chart from 2005-11-05 to

2017-09-12
.

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
31%
14797
13%
46480
8%
14761
36%
14761
17%
33421

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
9%
716
6%
2446
2%
716
15%
716
6%
2059
January16th to endNight
16%
768
7%
2496
3%
768
20%
768
7%
2070
February1st to 15thNight
14%
701
7%
2287
2%
701
21%
701
9%
1845
February16th to endNight
17%
631
10%
1997
3%
631
24%
631
11%
1536
March1st to 15thNight
19%
720
13%
1995
6%
720
25%
720
15%
1513
March16th to endNight
29%
768
19%
2112
9%
768
38%
768
22%
1449
April1st to 15thNight
24%
702
14%
1825
5%
702
30%
702
20%
1348
April16th to endNight
35%
540
18%
1620
9%
540
42%
540
22%
1091
May1st to 15thNight
42%
522
16%
1602
11%
522
48%
522
23%
1079
May16th to endNight
44%
374
16%
1497
14%
374
55%
374
25%
855
June1st to 15thNight
43%
360
13%
1390
11%
360
53%
360
22%
822
June16th to endNight
47%
360
15%
1260
15%
360
54%
360
27%
740
July1st to 15thNight
59%
340
18%
1221
23%
340
64%
340
36%
646
July16th to endNight
56%
523
15%
1554
12%
490
60%
490
30%
936
August1st to 15thNight
61%
539
16%
1609
12%
536
63%
536
33%
949
August16th to endNight
56%
597
22%
1743
15%
597
60%
597
33%
1056
September1st to 15thNight
49%
707
18%
1809
10%
707
53%
707
33%
1170
September16th to endNight
50%
657
18%
1817
13%
657
53%
657
29%
1168
October1st to 15thNight
36%
660
15%
1980
12%
660
41%
660
20%
1397
October16th to endNight
20%
704
10%
2117
5%
704
26%
704
12%
1641
November1st to 15thNight
28%
700
15%
2375
13%
700
34%
700
15%
1669
November16th to endNight
20%
720
10%
2520
6%
720
25%
720
10%
1942
December1st to 15thNight
11%
720
4%
2520
2%
720
14%
720
5%
2142
December16th to endNight
9%
768
5%
2688
1%
768
14%
768
5%
2298

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%48%6%35%45%6%27%
48137
Night
14%10%5%8%6%35%45%6%30%
46654
Cloud CoverDay
14%10%48%6%35%45%7%27%
48147
Night
13%10%48%6%35%45%6%30%
46658
TransparencyDay
54%5%11%17%9%
47830
Night
53%5%12%18%9%1
46480
SeeingDay
18%10%28%23%13%5%
5636
Night
18%12%31%25%10%1
14805

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
15%16%9%15%10%45%33413%
1447
16th to endDay
10%17%9%15%10%5%5%44412%
1728
February1st to 15thDay
13%16%8%14%12%5%5%34411%
1575
16th to endDay
15%16%7%11%8%5%5%45%415%
1476
March1st to 15thDay
13%13%5%9%8%45%35%5%24%
1953
16th to endDay
13%10%5%8%6%35%445%30%
2112
April1st to 15thDay
18%11%46%5%34446%27%
2134
16th to endDay
17%10%34423347%36%
2340
May1st to 15thDay
17%8%27%5%34447%34%
2349
16th to endDay
13%6%25%5%3446%8%38%
2618
June1st to 15thDay
15%7%35%435%46%8%35%
2565
16th to endDay
14%5%245%35%5%7%9%34%
2700
July1st to 15thDay
10%5%26%5%35%6%7%8%36%
2664
16th to endDay
11%6%36%6%46%5%7%9%33%
2506
August1st to 15thDay
11%6%37%7%35%6%6%9%32%
2340
16th to endDay
11%7%37%7%36%6%7%8%31%
2447
September1st to 15thDay
16%7%36%5%4445%8%34%
2068
16th to endDay
15%7%36%5%3435%8%36%
1812
October1st to 15thDay
20%10%47%5%3434430%
1650
16th to endDay
26%15%47%6%33445%16%
1754
November1st to 15thDay
15%13%5%6%6%35%447%27%
1483
16th to endDay
17%15%7%11%7%3445%5%15%
1440
December1st to 15thDay
15%20%10%16%7%2443410%
1440
16th to endDay
16%19%12%15%8%342439%
1536
January1st to 15thNight
18%15%8%12%9%4443412%
2446
16th to endNight
12%13%7%14%11%5%7%5%45%12%
2496
February1st to 15thNight
12%13%8%11%10%46%5%5%6%15%
2285
16th to endNight
12%11%6%13%9%35%5%5%6%19%
1997
March1st to 15thNight
14%11%5%9%8%34446%26%
1983
16th to endNight
12%8%47%5%25%445%38%
2112
April1st to 15thNight
18%11%47%5%24345%32%
1825
16th to endNight
11%10%35%5%35%446%38%
1620
May1st to 15thNight
14%8%245%35%6%47%37%
1602
16th to endNight
10%4245%25%46%8%44%
1495
June1st to 15thNight
12%425%5%36%5%5%9%40%
1390
16th to endNight
11%5%25%42446%8%45%
1260
July1st to 15thNight
5%5%25%423347%54%
1293
16th to endNight
7%4245%345%6%7%46%
1661
August1st to 15thNight
7%5%143246%6%8%46%
1620
16th to endNight
7%5%25%5%24346%50%
1743
September1st to 15thNight
12%5%25%42435%7%46%
1809
16th to endNight
13%6%25%43435%6%43%
1817
October1st to 15thNight
18%8%36%5%34446%34%
1980
16th to endNight
20%11%48%6%35%45%7%22%
2117
November1st to 15thNight
15%10%27%7%45%5%5%8%28%
2375
16th to endNight
17%14%6%9%5%3446%7%19%
2520
December1st to 15thNight
17%18%8%13%9%35%33412%
2520
16th to endNight
18%16%10%14%7%3445%49%
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
14%16%8%14%9%5%5%33413%
1447
16th to endDay
10%16%9%15%10%5%5%45%412%
1728
February1st to 15thDay
12%16%9%13%12%6%5%34411%
1575
16th to endDay
15%15%6%11%9%45%5%5%5%15%
1476
March1st to 15thDay
14%13%5%9%7%45%45%5%23%
1964
16th to endDay
13%11%5%7%7%35%445%30%
2111
April1st to 15thDay
18%11%46%6%345%46%28%
2134
16th to endDay
17%10%3442335%7%36%
2340
May1st to 15thDay
17%8%37%5%24347%34%
2349
16th to endDay
12%7%25%5%3446%8%38%
2618
June1st to 15thDay
15%7%35%425%5%6%8%35%
2565
16th to endDay
14%5%25%435%5%7%9%34%
2700
July1st to 15thDay
10%5%36%5%35%6%7%10%36%
2664
16th to endDay
10%6%36%6%46%5%7%8%33%
2506
August1st to 15thDay
10%7%27%7%36%5%5%9%32%
2340
16th to endDay
10%7%36%7%46%6%7%8%31%
2447
September1st to 15thDay
16%6%36%5%3445%7%34%
2068
16th to endDay
15%6%36%6%3445%8%35%
1812
October1st to 15thDay
19%10%37%5%34445%30%
1650
16th to endDay
26%14%48%6%335%45%16%
1754
November1st to 15thDay
14%13%47%6%35%447%27%
1483
16th to endDay
16%15%8%10%7%35%5%5%5%16%
1440
December1st to 15thDay
15%20%11%15%7%2434410%
1440
16th to endDay
17%18%11%16%8%333439%
1536
January1st to 15thNight
18%15%8%12%8%45%44413%
2446
16th to endNight
12%12%7%13%11%5%7%5%46%12%
2496
February1st to 15thNight
12%12%8%11%10%46%5%5%6%17%
2278
16th to endNight
12%12%6%12%9%36%5%5%6%20%
1997
March1st to 15thNight
14%10%5%10%8%345%46%27%
1995
16th to endNight
12%8%47%5%3445%5%38%
2112
April1st to 15thNight
18%10%46%5%25%445%32%
1825
16th to endNight
11%9%35%5%35%446%38%
1620
May1st to 15thNight
14%7%25%6%346%5%6%37%
1601
16th to endNight
10%42443447%7%45%
1495
June1st to 15thNight
11%425%445%5%5%8%41%
1390
16th to endNight
11%425%42345%8%46%
1260
July1st to 15thNight
6%5%26%42335%7%53%
1293
16th to endNight
6%4245%346%6%8%46%
1661
August1st to 15thNight
6%4144346%7%8%47%
1620
16th to endNight
7%5%15%5%34347%49%
1743
September1st to 15thNight
12%5%25%42445%7%46%
1809
16th to endNight
13%6%25%42445%6%44%
1817
October1st to 15thNight
17%8%36%5%345%36%35%
1980
16th to endNight
20%10%48%5%36%45%6%23%
2117
November1st to 15thNight
14%10%26%7%45%45%8%29%
2375
16th to endNight
17%14%6%9%5%25%45%7%20%
2520
December1st to 15thNight
17%17%8%12%9%45%44413%
2520
16th to endNight
18%15%10%14%8%34445%9%
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
75%47%9%3
1448
16th to endDay
73%39%8%4
1728
February1st to 15thDay
75%36%11%1
1577
16th to endDay
69%48%10%5%
1476
March1st to 15thDay
61%5%10%14%7%
1964
16th to endDay
54%310%15%12%1
2112
April1st to 15thDay
56%5%7%18%10%
2134
16th to endDay
47%411%20%14%1
2340
May1st to 15thDay
49%410%21%12%
2349
16th to endDay
42%5%14%21%14%1
2622
June1st to 15thDay
45%6%12%23%12%
2565
16th to endDay
42%8%14%23%11%
2700
July1st to 15thDay
40%8%12%22%15%1
2508
16th to endDay
45%8%12%22%9%1
2350
August1st to 15thDay
46%8%12%18%12%1
2327
16th to endDay
46%8%13%20%8%1
2447
September1st to 15thDay
47%5%13%23%8%1
2068
16th to endDay
46%5%12%24%9%
1812
October1st to 15thDay
56%410%16%11%1
1650
16th to endDay
67%5%11%9%4
1754
November1st to 15thDay
56%6%13%15%7%
1483
16th to endDay
68%5%10%11%3
1440
December1st to 15thDay
76%5%9%6%1
1440
16th to endDay
80%36%8%1
1536
January1st to 15thNight
73%38%8%3
2446
16th to endNight
71%411%8%3
2496
February1st to 15thNight
66%5%11%13%3
2287
16th to endNight
62%313%12%7%
1997
March1st to 15thNight
57%411%18%7%
1995
16th to endNight
46%410%19%15%2
2112
April1st to 15thNight
54%38%19%13%
1825
16th to endNight
46%49%18%17%2
1620
May1st to 15thNight
45%6%9%23%14%1
1602
16th to endNight
35%6%14%26%13%2
1497
June1st to 15thNight
39%5%13%24%16%1
1390
16th to endNight
36%5%13%28%15%
1260
July1st to 15thNight
29%413%28%22%1
1221
16th to endNight
34%7%14%25%15%2
1554
August1st to 15thNight
30%8%18%27%13%1
1609
16th to endNight
35%412%28%16%1
1743
September1st to 15thNight
36%5%14%28%12%1
1809
16th to endNight
39%414%27%13%
1817
October1st to 15thNight
49%6%10%19%12%1
1980
16th to endNight
60%5%14%14%5%
2117
November1st to 15thNight
52%5%14%17%8%1
2375
16th to endNight
61%5%13%14%31
2520
December1st to 15thNight
74%5%11%6%2
2520
16th to endNight
75%410%8%1
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
20%24%39%14%1
69
16th to endDay
21%15%42%18%1
96
February1st to 15thDay
24%27%38%5%3
90
16th to endDay
19%27%39%12%1
81
March1st to 15thDay
20%16%38%16%7%
254
16th to endDay
23%8%32%22%10%2
288
April1st to 15thDay
23%12%34%17%11%
270
16th to endDay
25%11%26%21%9%5%
270
May1st to 15thDay
23%9%25%22%14%4
288
16th to endDay
15%8%32%24%13%5%
331
June1st to 15thDay
18%8%25%30%16%1
360
16th to endDay
14%8%32%28%13%2
495
July1st to 15thDay
14%6%24%29%17%6%
442
16th to endDay
12%323%32%18%8%
326
August1st to 15thDay
15%322%23%23%12%
313
16th to endDay
17%318%25%18%15%
332
September1st to 15thDay
14%6%20%24%20%13%
299
16th to endDay
16%6%20%26%18%10%
254
October1st to 15thDay
17%12%27%25%11%5%
255
16th to endDay
32%15%26%21%3
266
November1st to 15thDay
12%13%42%23%44
73
16th to endDay
25%23%30%13%8%
60
December1st to 15thDay
23%41%20%13%1
60
16th to endDay
25%39%34%1
64
January1st to 15thNight
26%20%32%15%4
720
16th to endNight
17%15%38%22%5%
768
February1st to 15thNight
20%18%38%19%3
704
16th to endNight
19%14%38%22%4
631
March1st to 15thNight
18%18%37%20%4
720
16th to endNight
17%12%35%23%10%1
768
April1st to 15thNight
23%13%33%23%5%
702
16th to endNight
19%9%31%27%10%1
540
May1st to 15thNight
18%6%26%32%13%2
522
16th to endNight
12%7%31%31%16%
375
June1st to 15thNight
13%6%28%38%13%
360
16th to endNight
12%331%37%15%
360
July1st to 15thNight
7%322%45%19%1
340
16th to endNight
9%224%40%20%2
523
August1st to 15thNight
8%121%37%27%3
539
16th to endNight
11%321%31%28%3
597
September1st to 15thNight
14%6%23%29%18%6%
707
16th to endNight
15%6%22%32%19%4
657
October1st to 15thNight
22%8%26%27%12%2
660
16th to endNight
25%15%33%21%3
704
November1st to 15thNight
19%14%32%22%9%1
700
16th to endNight
25%17%30%20%5%
720
December1st to 15thNight
26%20%33%17%2
720
16th to endNight
25%19%36%16%2
768
Page generated at 2017-09-13 07:39:19. Version ac04

Copyright 2017 A. Danko


Colbeck Observatory Clear Sky Chart | Charts Home