Achray Campground
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Achray Campground clear sky chart from 2005-11-05 to 2018-02-22.

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%
15261
13%
48763
8%
15232
34%
15232
16%
35086

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
16%
780
6%
2716
2%
776
20%
776
6%
2222
January16th to endNight
21%
832
11%
2804
6%
832
28%
832
11%
2156
February1st to 15thNight
16%
762
10%
2482
3%
761
24%
761
11%
1931
February16th to endNight
19%
659
12%
2099
5%
659
28%
659
12%
1582
March1st to 15thNight
17%
720
13%
2034
6%
720
24%
720
13%
1564
March16th to endNight
28%
768
19%
2082
9%
768
37%
768
22%
1434
April1st to 15thNight
22%
718
16%
1796
5%
718
28%
718
20%
1324
April16th to endNight
31%
597
17%
1677
9%
597
36%
597
21%
1188
May1st to 15thNight
32%
379
17%
1459
15%
379
42%
379
17%
970
May16th to endNight
32%
374
13%
1497
10%
374
43%
374
18%
953
June1st to 15thNight
32%
360
8%
1440
7%
360
40%
360
18%
925
June16th to endNight
42%
360
10%
1299
10%
360
47%
360
20%
835
July1st to 15thNight
46%
340
15%
1306
17%
340
54%
340
28%
720
July16th to endNight
47%
376
14%
1418
15%
354
54%
354
25%
811
August1st to 15thNight
50%
508
14%
1579
11%
506
54%
506
27%
985
August16th to endNight
48%
651
20%
1797
10%
651
55%
651
35%
1083
September1st to 15thNight
43%
720
16%
1800
7%
720
45%
720
30%
1215
September16th to endNight
48%
717
21%
1985
14%
717
52%
717
31%
1272
October1st to 15thNight
30%
720
16%
2160
11%
720
39%
720
20%
1499
October16th to endNight
23%
768
12%
2349
7%
768
30%
768
12%
1817
November1st to 15thNight
27%
760
14%
2612
11%
760
35%
760
14%
1870
November16th to endNight
19%
780
9%
2730
6%
780
24%
780
9%
2140
December1st to 15thNight
13%
780
8%
2730
2%
780
19%
780
7%
2225
December16th to endNight
14%
832
9%
2912
4%
832
20%
832
7%
2365

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
18%10%47%6%34446%30%
49489
Night
16%11%47%6%34446%31%
48933
TransparencyDay
54%410%19%9%1
49177
Night
54%411%19%9%
48763
SeeingDay
24%12%29%20%9%3
5978
Night
23%11%29%25%9%
15264

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
19%13%7%9%7%35%33419%
1552
16th to endDay
14%14%7%9%8%46%43421%
1771
February1st to 15thDay
10%15%7%13%9%46%5%45%18%
1710
16th to endDay
17%16%5%9%5%4444422%
1521
March1st to 15thDay
16%14%5%9%6%44345%26%
1913
16th to endDay
13%9%48%6%24345%37%
2142
April1st to 15thDay
23%11%46%5%2324431%
2152
16th to endDay
22%8%25%5%2333437%
2294
May1st to 15thDay
20%10%45%5%2435%5%31%
2490
16th to endDay
17%7%36%5%35%446%35%
2618
June1st to 15thDay
22%6%36%5%25%45%7%29%
2520
16th to endDay
16%6%35%5%45%5%5%8%33%
2656
July1st to 15thDay
15%5%345%35%5%6%7%36%
2568
16th to endDay
13%5%35%6%36%6%6%10%32%
2654
August1st to 15thDay
14%6%36%6%45%5%5%7%33%
2370
16th to endDay
13%5%26%6%35%6%6%8%34%
2393
September1st to 15thDay
19%6%25%5%24447%37%
2160
16th to endDay
18%7%25%423446%41%
1972
October1st to 15thDay
21%9%26%5%34436%32%
1800
16th to endDay
27%15%36%5%2334421%
1875
November1st to 15thDay
17%13%5%7%43435%6%29%
1574
16th to endDay
23%14%7%9%6%3333419%
1560
December1st to 15thDay
18%18%6%10%9%45%34413%
1560
16th to endDay
21%17%7%8%6%33445%18%
1664
January1st to 15thNight
16%14%7%12%8%36%445%15%
2716
16th to endNight
13%15%6%10%8%34445%23%
2804
February1st to 15thNight
11%14%6%11%8%46%446%21%
2480
16th to endNight
15%14%49%8%35%44425%
2099
March1st to 15thNight
17%13%5%9%7%34335%27%
2022
16th to endNight
13%9%47%6%23335%39%
2082
April1st to 15thNight
21%10%35%5%2343434%
1796
16th to endNight
19%8%25%433446%35%
1677
May1st to 15thNight
21%8%25%424346%35%
1459
16th to endNight
14%7%346%3345%7%37%
1495
June1st to 15thNight
18%6%36%4335%5%7%36%
1440
16th to endNight
16%4145%35%5%6%8%37%
1299
July1st to 15thNight
10%4144245%47%49%
1386
16th to endNight
9%5%24435%5%7%9%43%
1514
August1st to 15thNight
11%415%6%2446%7%43%
1589
16th to endNight
9%3344245%5%8%47%
1797
September1st to 15thNight
14%6%35%42335%6%43%
1800
16th to endNight
15%6%24422346%46%
1985
October1st to 15thNight
21%8%35%423245%37%
2160
16th to endNight
25%12%36%5%2345%5%24%
2349
November1st to 15thNight
18%10%46%6%3445%5%30%
2612
16th to endNight
22%14%5%9%6%3433422%
2730
December1st to 15thNight
19%19%6%9%6%35%34418%
2730
16th to endNight
20%18%6%10%6%33335%17%
2912

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
67%48%11%6%
1553
16th to endDay
65%38%14%6%1
1771
February1st to 15thDay
67%49%13%5%
1712
16th to endDay
64%29%13%9%
1521
March1st to 15thDay
60%310%16%7%1
1924
16th to endDay
47%48%20%14%4
2142
April1st to 15thDay
57%28%18%10%2
2152
16th to endDay
51%26%21%15%2
2294
May1st to 15thDay
53%39%17%12%2
2490
16th to endDay
50%48%22%11%2
2622
June1st to 15thDay
54%411%19%10%
2520
16th to endDay
47%5%11%22%11%1
2656
July1st to 15thDay
42%5%12%25%12%1
2419
16th to endDay
45%6%13%24%9%
2487
August1st to 15thDay
49%6%13%19%10%
2356
16th to endDay
44%7%14%25%7%
2393
September1st to 15thDay
46%413%24%10%
2160
16th to endDay
44%412%30%7%
1972
October1st to 15thDay
53%5%11%18%10%
1800
16th to endDay
65%5%10%13%4
1875
November1st to 15thDay
55%5%13%17%7%
1574
16th to endDay
69%39%12%31
1560
December1st to 15thDay
73%48%10%3
1560
16th to endDay
68%310%12%4
1664
January1st to 15thNight
69%5%9%10%4
2716
16th to endNight
62%49%15%7%
2804
February1st to 15thNight
63%311%15%5%
2482
16th to endNight
60%310%18%7%
2099
March1st to 15thNight
60%39%18%7%
2034
16th to endNight
47%39%19%16%2
2082
April1st to 15thNight
53%27%20%13%2
1796
16th to endNight
49%37%20%14%3
1677
May1st to 15thNight
50%37%19%15%2
1459
16th to endNight
44%6%11%22%12%2
1497
June1st to 15thNight
46%5%13%22%12%
1440
16th to endNight
43%7%13%23%12%
1299
July1st to 15thNight
33%5%12%28%18%1
1306
16th to endNight
35%6%15%30%11%
1418
August1st to 15thNight
37%7%16%25%12%
1579
16th to endNight
32%5%19%32%9%
1797
September1st to 15thNight
40%5%14%27%11%
1800
16th to endNight
39%414%32%8%
1985
October1st to 15thNight
49%410%23%11%
2160
16th to endNight
60%5%11%17%4
2349
November1st to 15thNight
54%413%17%8%
2612
16th to endNight
65%311%14%2
2730
December1st to 15thNight
70%49%11%4
2730
16th to endNight
70%38%10%6%
2912

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
28%15%34%17%3
90
16th to endDay
29%14%37%15%2
121
February1st to 15thDay
25%25%40%8%
135
16th to endDay
39%19%27%11%2
142
March1st to 15thDay
31%17%29%17%4
270
16th to endDay
21%20%26%21%9%1
288
April1st to 15thDay
28%17%30%16%6%1
270
16th to endDay
28%14%28%12%11%4
270
May1st to 15thDay
34%10%21%18%9%4
288
16th to endDay
21%15%33%16%9%2
331
June1st to 15thDay
28%10%27%23%8%
315
16th to endDay
19%12%32%21%11%1
451
July1st to 15thDay
16%6%35%29%9%2
353
16th to endDay
13%433%29%15%3
326
August1st to 15thDay
15%429%29%15%6%
313
16th to endDay
15%7%27%25%14%9%
332
September1st to 15thDay
20%7%24%19%17%10%
315
16th to endDay
20%7%23%24%17%7%
314
October1st to 15thDay
25%12%29%19%10%2
315
16th to endDay
36%14%26%17%4
325
November1st to 15thDay
23%15%32%21%6%
138
16th to endDay
36%16%33%12%1
90
December1st to 15thDay
27%21%31%14%5%
90
16th to endDay
29%28%31%10%1
96
January1st to 15thNight
25%14%32%21%5%
780
16th to endNight
21%14%31%25%5%
832
February1st to 15thNight
19%14%39%21%4
764
16th to endNight
23%17%32%21%3
659
March1st to 15thNight
26%17%30%20%3
720
16th to endNight
19%15%29%23%9%1
768
April1st to 15thNight
28%15%29%22%5%
718
16th to endNight
26%9%28%23%10%
597
May1st to 15thNight
24%7%27%27%11%
379
16th to endNight
18%8%33%27%12%
375
June1st to 15thNight
21%6%34%28%8%1
360
16th to endNight
19%5%26%37%9%
360
July1st to 15thNight
11%332%35%15%1
340
16th to endNight
10%330%35%18%
376
August1st to 15thNight
13%322%35%21%2
508
16th to endNight
12%327%36%17%1
651
September1st to 15thNight
19%5%27%27%17%3
720
16th to endNight
19%5%21%29%20%2
717
October1st to 15thNight
25%9%28%25%9%1
720
16th to endNight
32%12%25%22%6%
768
November1st to 15thNight
23%13%28%22%9%1
760
16th to endNight
31%15%26%20%6%
780
December1st to 15thNight
29%16%32%17%3
780
16th to endNight
33%13%28%18%31
832
Page generated at 2018-02-23 11:21:27. Version ac04

Copyright 2018 A. Danko


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