Fifth Meridian
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fifth Meridian clear sky chart from 2005-11-05 to 2017-09-21.

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
36%
15208
15%
46845
8%
15175
44%
15175
24%
29999

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
27%
900
14%
2685
6%
895
34%
895
18%
1855
January16th to endNight
28%
801
19%
2721
11%
801
40%
801
21%
1698
February1st to 15thNight
32%
701
15%
2405
9%
697
43%
697
19%
1539
February16th to endNight
33%
632
15%
1971
9%
632
42%
632
19%
1365
March1st to 15thNight
24%
720
16%
2115
6%
720
36%
720
20%
1424
March16th to endNight
28%
768
12%
2092
2%
768
36%
768
20%
1515
April1st to 15thNight
31%
631
13%
1711
5%
631
36%
631
19%
1221
April16th to endNight
33%
540
13%
1620
9%
540
38%
540
21%
1107
May1st to 15thNight
40%
437
12%
1449
11%
437
45%
437
23%
894
May16th to endNight
40%
374
6%
1309
4%
374
44%
374
17%
916
June1st to 15thNight
38%
360
2%
1260
0%
360
38%
360
19%
828
June16th to endNight
49%
360
3%
1260
0%
360
50%
360
26%
746
July1st to 15thNight
57%
340
4%
1190
1%
340
58%
340
32%
645
July16th to endNight
60%
376
13%
1296
14%
354
67%
354
37%
648
August1st to 15thNight
64%
412
15%
1484
18%
410
68%
410
31%
805
August16th to endNight
56%
573
24%
1719
18%
573
61%
573
44%
898
September1st to 15thNight
53%
668
20%
1820
12%
668
57%
668
39%
1066
September16th to endNight
47%
680
23%
1881
13%
680
55%
680
39%
1087
October1st to 15thNight
40%
660
18%
1936
10%
660
48%
660
24%
1292
October16th to endNight
38%
704
23%
2288
11%
704
52%
704
27%
1367
November1st to 15thNight
25%
811
20%
2386
8%
811
37%
811
24%
1504
November16th to endNight
26%
900
15%
2667
5%
900
35%
900
23%
1731
December1st to 15thNight
31%
900
15%
2700
8%
900
38%
900
19%
1861
December16th to endNight
28%
960
17%
2880
7%
960
38%
960
19%
1987

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
10%8%36%5%35%5%6%8%37%
48055
Night
7%8%36%5%35%46%8%40%
46997
Cloud CoverDay
10%8%36%5%35%5%6%8%37%
48056
Night
7%8%36%5%35%5%5%8%40%
47000
TransparencyDay
42%6%16%22%9%1
47711
Night
40%6%16%24%11%1
46845
SeeingDay
15%14%31%24%10%2
6012
Night
11%10%33%30%12%1
15213

By Month

Percentage Cloud Cover NW (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
39%5%6%6%35%45%9%39%
1253
16th to endDay
39%5%8%7%35%6%6%8%36%
1514
February1st to 15thDay
49%48%5%25%6%7%8%35%
1458
16th to endDay
312%5%9%8%36%6%7%9%28%
1503
March1st to 15thDay
29%5%8%6%36%6%6%9%36%
1845
16th to endDay
7%12%5%9%7%45%5%5%7%27%
2129
April1st to 15thDay
12%13%5%7%5%3446%7%27%
2236
16th to endDay
14%12%35%5%25%5%6%7%31%
2340
May1st to 15thDay
13%8%36%435%5%6%7%35%
2502
16th to endDay
23%6%35%6%35%5%5%8%26%
2802
June1st to 15thDay
21%7%36%436%5%6%7%28%
2700
16th to endDay
14%5%25%6%35%5%6%8%36%
2700
July1st to 15thDay
10%4145%26%6%6%8%43%
2700
16th to endDay
6%314335%5%5%8%51%
2781
August1st to 15thDay
11%5%134246%6%8%43%
2467
16th to endDay
9%41332346%7%52%
2483
September1st to 15thDay
14%413433335%51%
2139
16th to endDay
9%5%13433448%50%
1871
October1st to 15thDay
12%9%46%5%2345%7%36%
1693
16th to endDay
6%8%45%5%35%5%6%10%37%
1584
November1st to 15thDay
7%9%36%5%46%5%5%7%39%
1461
16th to endDay
411%5%7%42346%9%40%
1290
December1st to 15thDay
310%5%9%7%5%7%6%5%7%30%
1260
16th to endDay
310%5%8%435%5%8%8%36%
1344
January1st to 15thNight
49%5%9%7%35%5%6%9%33%
2685
16th to endNight
39%47%6%345%6%9%38%
2721
February1st to 15thNight
410%5%6%5%35%46%8%38%
2394
16th to endNight
5%9%6%8%6%46%5%5%6%35%
1971
March1st to 15thNight
39%5%8%6%36%5%6%10%35%
2115
16th to endNight
6%11%5%8%6%25%5%7%8%31%
2089
April1st to 15thNight
11%12%46%4245%6%7%34%
1711
16th to endNight
11%10%46%5%25%45%5%37%
1620
May1st to 15thNight
11%8%345%3445%9%39%
1448
16th to endNight
21%7%244445%5%8%31%
1309
June1st to 15thNight
17%7%346%3435%7%36%
1260
16th to endNight
11%324435%5%5%8%44%
1260
July1st to 15thNight
7%31443445%9%50%
1260
16th to endNight
6%22332437%7%56%
1385
August1st to 15thNight
8%3235%2436%8%49%
1492
16th to endNight
9%3222235%7%59%
1719
September1st to 15thNight
13%413322346%55%
1820
16th to endNight
10%41322235%9%53%
1881
October1st to 15thNight
12%7%35%5%25%46%7%38%
1936
16th to endNight
8%8%2442446%9%44%
2288
November1st to 15thNight
6%7%345%35%47%9%43%
2386
16th to endNight
310%5%7%5%35%45%9%38%
2667
December1st to 15thNight
39%5%8%6%37%6%6%8%34%
2700
16th to endNight
312%48%7%36%5%6%7%33%
2880

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
410%38%6%35%45%9%39%
1253
16th to endDay
39%5%7%7%45%5%6%9%35%
1514
February1st to 15thDay
5%9%5%7%6%35%5%6%9%34%
1458
16th to endDay
311%6%9%7%45%5%7%8%29%
1503
March1st to 15thDay
38%5%8%6%46%6%5%10%34%
1845
16th to endDay
7%13%5%9%7%45%6%5%7%27%
2130
April1st to 15thDay
12%12%47%6%45%5%5%8%27%
2236
16th to endDay
13%11%36%435%5%5%8%31%
2340
May1st to 15thDay
13%8%25%5%35%5%6%7%35%
2502
16th to endDay
23%7%25%6%35%46%8%26%
2802
June1st to 15thDay
20%7%26%5%36%5%6%8%27%
2700
16th to endDay
14%5%245%36%6%6%8%35%
2700
July1st to 15thDay
10%414435%6%6%8%43%
2700
16th to endDay
6%3134345%6%8%52%
2781
August1st to 15thDay
11%4234245%7%8%44%
2467
16th to endDay
9%31332446%8%52%
2483
September1st to 15thDay
14%5%14423335%51%
2139
16th to endDay
10%5%1432445%8%49%
1871
October1st to 15thDay
12%9%37%6%2346%7%36%
1693
16th to endDay
7%8%35%6%35%5%7%9%38%
1584
November1st to 15thDay
7%8%36%5%46%6%5%7%38%
1461
16th to endDay
412%47%5%2245%10%39%
1290
December1st to 15thDay
411%5%10%7%48%6%5%6%30%
1260
16th to endDay
310%47%7%25%5%6%9%34%
1344
January1st to 15thNight
49%5%10%7%35%5%6%10%31%
2685
16th to endNight
410%47%6%25%6%5%8%38%
2721
February1st to 15thNight
410%5%7%5%35%5%5%8%38%
2394
16th to endNight
6%9%6%8%7%46%5%5%6%33%
1971
March1st to 15thNight
39%5%7%6%36%6%6%9%34%
2115
16th to endNight
6%12%5%9%5%35%5%6%9%31%
2092
April1st to 15thNight
11%12%36%4345%5%7%33%
1711
16th to endNight
11%10%27%6%25%5%5%6%36%
1620
May1st to 15thNight
11%8%36%43445%9%38%
1448
16th to endNight
21%6%245%35%45%8%31%
1309
June1st to 15thNight
17%5%26%6%33447%37%
1260
16th to endNight
11%324325%5%5%9%44%
1260
July1st to 15thNight
7%41442346%8%52%
1260
16th to endNight
6%21433337%8%55%
1385
August1st to 15thNight
8%32442445%9%48%
1492
16th to endNight
9%31231235%8%59%
1719
September1st to 15thNight
12%412322346%55%
1820
16th to endNight
11%31422345%8%52%
1881
October1st to 15thNight
12%6%36%5%25%5%6%7%38%
1936
16th to endNight
8%7%145%2446%8%44%
2288
November1st to 15thNight
5%8%35%435%5%6%9%42%
2386
16th to endNight
411%5%7%5%25%45%9%38%
2667
December1st to 15thNight
39%49%6%37%6%6%8%33%
2700
16th to endNight
312%49%7%45%5%6%6%33%
2880

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
41%6%16%25%7%2
1253
16th to endDay
42%7%14%20%10%3
1514
February1st to 15thDay
42%7%17%22%7%2
1458
16th to endDay
49%5%16%20%7%
1503
March1st to 15thDay
42%8%19%22%6%
1845
16th to endDay
54%6%14%17%6%
2130
April1st to 15thDay
53%5%15%17%7%1
2236
16th to endDay
50%416%19%8%
2340
May1st to 15thDay
46%415%24%9%
2502
16th to endDay
54%5%17%16%5%
2807
June1st to 15thDay
52%7%15%16%7%1
2700
16th to endDay
42%7%18%21%8%1
2700
July1st to 15thDay
35%6%20%25%10%1
2541
16th to endDay
28%6%17%27%15%3
2607
August1st to 15thDay
33%7%23%25%7%1
2450
16th to endDay
28%5%17%32%13%2
2483
September1st to 15thDay
35%313%24%18%4
2139
16th to endDay
33%5%11%31%13%3
1871
October1st to 15thDay
45%6%16%20%10%1
1693
16th to endDay
39%7%16%26%8%1
1584
November1st to 15thDay
43%7%16%22%10%
1461
16th to endDay
40%5%19%23%9%2
1290
December1st to 15thDay
51%7%13%19%8%
1260
16th to endDay
42%6%16%21%10%1
1344
January1st to 15thNight
46%6%18%18%7%2
2685
16th to endNight
40%6%15%21%12%3
2721
February1st to 15thNight
42%6%15%23%10%1
2405
16th to endNight
48%6%11%22%10%
1971
March1st to 15thNight
42%7%18%23%7%
2115
16th to endNight
47%7%15%19%8%
2092
April1st to 15thNight
48%6%13%21%9%
1711
16th to endNight
46%5%14%24%7%1
1620
May1st to 15thNight
41%416%26%10%
1449
16th to endNight
51%5%15%19%5%1
1309
June1st to 15thNight
46%5%15%22%9%1
1260
16th to endNight
35%6%17%25%12%1
1260
July1st to 15thNight
30%5%21%29%12%1
1190
16th to endNight
25%5%18%32%14%4
1296
August1st to 15thNight
30%6%18%29%12%1
1484
16th to endNight
23%414%33%20%2
1719
September1st to 15thNight
30%313%27%19%4
1820
16th to endNight
29%417%29%14%4
1881
October1st to 15thNight
42%6%14%23%11%1
1936
16th to endNight
35%6%16%28%12%
2288
November1st to 15thNight
36%6%17%23%14%
2386
16th to endNight
41%5%20%17%10%3
2667
December1st to 15thNight
45%7%17%20%8%
2700
16th to endNight
47%6%13%23%8%
2880

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
8%5%33%13%23%16%
60
16th to endDay
10%14%32%23%7%10%
64
February1st to 15thDay
8%22%39%21%5%2
71
16th to endDay
10%13%39%27%8%
162
March1st to 15thDay
8%31%45%11%2
270
16th to endDay
13%27%36%15%5%
288
April1st to 15thDay
21%26%32%14%4
269
16th to endDay
26%15%31%18%6%1
270
May1st to 15thDay
19%14%27%24%12%2
357
16th to endDay
24%9%20%27%14%3
517
June1st to 15thDay
21%11%28%24%12%2
495
16th to endDay
14%10%32%26%11%3
495
July1st to 15thDay
11%9%29%30%16%2
475
16th to endDay
7%15%35%26%12%2
450
August1st to 15thDay
13%11%29%31%11%3
315
16th to endDay
9%12%39%24%9%3
332
September1st to 15thDay
20%13%26%26%9%2
315
16th to endDay
15%19%30%24%7%2
276
October1st to 15thDay
21%14%31%23%8%
156
16th to endDay
11%6%31%33%11%6%
96
November1st to 15thDay
18%20%26%26%5%2
90
16th to endDay
10%12%26%24%13%12%
65
December1st to 15thDay
313%35%35%11%1
60
16th to endDay
10%12%29%23%15%7%
64
January1st to 15thNight
10%16%37%25%8%
900
16th to endNight
8%14%40%27%7%
801
February1st to 15thNight
8%15%33%27%11%3
704
16th to endNight
10%9%35%29%12%2
632
March1st to 15thNight
9%14%43%23%8%1
720
16th to endNight
11%12%37%29%7%1
768
April1st to 15thNight
16%12%30%29%9%1
631
16th to endNight
16%10%28%32%11%
540
May1st to 15thNight
15%8%28%30%16%
438
16th to endNight
22%6%21%31%17%
375
June1st to 15thNight
20%8%25%29%15%1
360
16th to endNight
12%6%25%34%19%1
360
July1st to 15thNight
9%222%41%22%1
340
16th to endNight
7%322%42%21%1
376
August1st to 15thNight
10%214%41%27%2
412
16th to endNight
10%5%24%39%19%1
573
September1st to 15thNight
14%422%31%22%4
668
16th to endNight
13%6%29%31%14%4
680
October1st to 15thNight
17%7%28%30%13%3
660
16th to endNight
12%8%33%33%8%1
704
November1st to 15thNight
9%17%42%23%5%1
811
16th to endNight
10%14%42%24%6%2
900
December1st to 15thNight
8%14%37%27%10%2
900
16th to endNight
10%11%38%28%9%1
960
Page generated at 2017-09-22 05:35:33. Version ac04

Copyright 2017 A. Danko


Fifth Meridian Clear Sky Chart | Charts Home