Maycroft
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Maycroft clear sky chart from 2005-11-05 to 2017-09-22.

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
34%
15199
15%
46851
8%
15166
41%
15166
21%
29574

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
23%
900
12%
2685
5%
895
30%
895
15%
1866
January16th to endNight
26%
774
18%
2694
10%
774
38%
774
18%
1664
February1st to 15thNight
29%
701
13%
2399
8%
697
39%
697
16%
1550
February16th to endNight
30%
632
16%
1956
9%
632
40%
632
19%
1304
March1st to 15thNight
22%
720
14%
2118
4%
720
33%
720
18%
1369
March16th to endNight
28%
768
11%
2088
2%
768
34%
768
17%
1476
April1st to 15thNight
27%
641
11%
1721
3%
641
32%
641
17%
1219
April16th to endNight
30%
540
13%
1620
8%
540
34%
540
20%
1082
May1st to 15thNight
41%
446
11%
1482
11%
446
45%
446
22%
908
May16th to endNight
42%
374
8%
1309
8%
374
45%
374
16%
901
June1st to 15thNight
40%
360
4%
1260
1%
360
42%
360
20%
785
June16th to endNight
45%
360
5%
1260
0%
360
48%
360
23%
741
July1st to 15thNight
58%
340
7%
1190
3%
340
60%
340
36%
592
July16th to endNight
61%
376
15%
1325
16%
354
68%
354
38%
627
August1st to 15thNight
65%
417
18%
1489
20%
415
70%
415
35%
760
August16th to endNight
54%
573
27%
1719
21%
573
59%
573
41%
892
September1st to 15thNight
52%
681
20%
1830
12%
681
55%
681
38%
1058
September16th to endNight
43%
683
21%
1890
11%
683
51%
683
32%
1109
October1st to 15thNight
38%
660
16%
1928
8%
660
46%
660
21%
1263
October16th to endNight
34%
704
21%
2288
10%
704
48%
704
21%
1379
November1st to 15thNight
20%
789
17%
2364
7%
789
31%
789
16%
1477
November16th to endNight
20%
900
13%
2656
4%
900
29%
900
17%
1780
December1st to 15thNight
27%
900
14%
2700
7%
900
34%
900
16%
1829
December16th to endNight
23%
960
14%
2880
5%
960
31%
960
16%
1943

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
9%8%36%5%35%5%6%8%38%
48061
Night
5%7%36%5%345%6%9%42%
47005
Cloud CoverDay
8%8%36%5%35%5%6%8%38%
48062
Night
5%7%36%5%345%6%8%42%
47008
TransparencyDay
41%7%17%21%9%1
47720
Night
37%8%19%23%9%1
46851
SeeingDay
17%22%27%19%10%2
5986
Night
13%19%26%25%13%2
15204

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
16%37%8%35%48%12%37%
1258
16th to endDay
28%5%9%8%45%5%5%10%34%
1536
February1st to 15thDay
39%36%7%45%5%6%10%37%
1464
16th to endDay
210%6%9%6%36%6%6%9%32%
1518
March1st to 15thDay
27%6%8%5%35%6%6%10%38%
1842
16th to endDay
8%14%5%8%6%45%5%6%9%27%
2132
April1st to 15thDay
9%12%5%7%5%45%6%6%8%26%
2227
16th to endDay
9%14%5%7%6%35%45%6%31%
2340
May1st to 15thDay
11%10%46%5%35%46%7%33%
2468
16th to endDay
23%10%37%5%35%5%5%7%22%
2802
June1st to 15thDay
17%9%36%6%46%5%5%6%29%
2700
16th to endDay
13%6%25%5%36%5%6%8%37%
2700
July1st to 15thDay
8%414435%5%7%8%45%
2700
16th to endDay
5%3134245%6%6%54%
2751
August1st to 15thDay
9%5%134345%6%8%46%
2461
16th to endDay
8%3134345%6%7%52%
2483
September1st to 15thDay
14%6%23323446%48%
2126
16th to endDay
10%5%1332435%7%51%
1882
October1st to 15thDay
10%10%47%5%45%45%6%34%
1699
16th to endDay
5%9%344346%6%11%39%
1584
November1st to 15thDay
47%35%325%5%8%11%42%
1482
16th to endDay
410%5%7%41445%9%42%
1302
December1st to 15thDay
26%38%6%36%6%8%9%39%
1260
16th to endDay
17%5%8%7%25%5%7%10%39%
1344
January1st to 15thNight
17%47%8%36%5%6%11%36%
2685
16th to endNight
17%37%5%45%5%6%10%40%
2694
February1st to 15thNight
38%37%6%35%5%7%10%36%
2388
16th to endNight
28%5%9%6%35%5%6%8%37%
1956
March1st to 15thNight
16%5%7%5%345%6%11%41%
2118
16th to endNight
5%9%5%8%5%35%5%7%10%34%
2085
April1st to 15thNight
9%10%46%42447%8%35%
1721
16th to endNight
7%12%46%5%245%5%8%37%
1620
May1st to 15thNight
11%7%34415%46%8%41%
1481
16th to endNight
20%7%25%5%24448%32%
1309
June1st to 15thNight
14%5%25%425%5%5%8%39%
1260
16th to endNight
9%424427%6%5%7%44%
1260
July1st to 15thNight
5%41431345%9%55%
1260
16th to endNight
421342445%6%61%
1416
August1st to 15thNight
7%22432337%8%54%
1497
16th to endNight
7%413212348%59%
1719
September1st to 15thNight
11%5%13212346%57%
1830
16th to endNight
10%42232435%8%51%
1890
October1st to 15thNight
10%9%245%2345%8%41%
1928
16th to endNight
5%7%35%4245%7%10%43%
2288
November1st to 15thNight
37%25%435%5%6%8%47%
2364
16th to endNight
36%5%7%5%345%6%10%40%
2656
December1st to 15thNight
27%48%6%36%6%8%8%38%
2700
16th to endNight
17%5%8%7%35%6%6%8%38%
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
25%39%7%35%48%12%38%
1258
16th to endDay
29%48%8%5%6%5%5%10%35%
1536
February1st to 15thDay
39%37%6%35%5%6%10%37%
1464
16th to endDay
210%6%10%7%446%6%8%32%
1518
March1st to 15thDay
28%5%7%6%35%5%7%9%38%
1842
16th to endDay
8%13%5%8%6%35%5%6%9%26%
2133
April1st to 15thDay
9%12%5%7%6%46%5%5%8%27%
2227
16th to endDay
8%14%47%6%35%45%7%30%
2340
May1st to 15thDay
11%10%36%5%45%45%7%33%
2468
16th to endDay
22%9%36%6%35%5%5%7%22%
2802
June1st to 15thDay
17%8%36%5%46%5%5%6%29%
2700
16th to endDay
13%6%25%446%5%5%8%37%
2700
July1st to 15thDay
8%4145%35%5%7%8%45%
2700
16th to endDay
5%313335%5%5%7%54%
2751
August1st to 15thDay
9%5%244345%6%8%45%
2461
16th to endDay
8%3133345%6%7%52%
2483
September1st to 15thDay
13%6%24314446%48%
2126
16th to endDay
10%42332435%7%50%
1882
October1st to 15thDay
10%10%47%5%45%45%6%35%
1699
16th to endDay
5%9%35%435%5%6%10%39%
1584
November1st to 15thDay
5%7%443345%7%10%42%
1482
16th to endDay
411%5%6%5%1345%9%41%
1302
December1st to 15thDay
25%38%6%37%6%9%8%38%
1260
16th to endDay
17%49%6%3447%11%38%
1344
January1st to 15thNight
28%47%7%46%5%6%10%36%
2685
16th to endNight
27%47%6%36%5%6%10%40%
2694
February1st to 15thNight
39%37%7%45%5%7%10%36%
2388
16th to endNight
29%48%7%36%5%5%8%37%
1956
March1st to 15thNight
17%5%7%5%346%7%10%40%
2118
16th to endNight
5%9%5%7%5%35%5%7%10%34%
2088
April1st to 15thNight
9%10%5%6%43447%7%35%
1721
16th to endNight
7%12%46%5%345%5%7%37%
1620
May1st to 15thNight
9%8%26%425%46%8%41%
1481
16th to endNight
19%8%25%5%345%47%33%
1309
June1st to 15thNight
14%5%16%435%6%47%40%
1260
16th to endNight
9%424346%6%6%8%44%
1260
July1st to 15thNight
45%1431446%8%55%
1260
16th to endNight
421242445%6%60%
1416
August1st to 15thNight
7%22333346%7%54%
1497
16th to endNight
8%32321235%8%58%
1719
September1st to 15thNight
11%413312336%57%
1830
16th to endNight
10%5%1332345%8%51%
1890
October1st to 15thNight
10%9%245%2345%9%40%
1928
16th to endNight
5%7%35%4346%6%9%43%
2288
November1st to 15thNight
47%25%6%3446%8%47%
2364
16th to endNight
37%46%6%345%6%9%40%
2656
December1st to 15thNight
36%48%6%35%6%7%8%38%
2700
16th to endNight
17%5%9%7%36%5%6%8%37%
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
38%12%23%20%32
1258
16th to endDay
45%7%18%19%6%3
1536
February1st to 15thDay
40%7%22%20%7%1
1464
16th to endDay
47%8%16%22%4
1518
March1st to 15thDay
40%11%21%20%6%
1842
16th to endDay
52%9%16%17%4
2133
April1st to 15thDay
51%8%17%15%6%
2227
16th to endDay
52%5%16%18%5%
2340
May1st to 15thDay
48%5%16%19%8%
2468
16th to endDay
59%6%15%12%5%
2807
June1st to 15thDay
52%7%12%17%9%
2700
16th to endDay
43%6%14%23%10%1
2700
July1st to 15thDay
33%7%16%27%13%2
2541
16th to endDay
27%5%14%28%19%4
2580
August1st to 15thDay
33%6%18%27%11%2
2444
16th to endDay
27%5%15%30%17%2
2483
September1st to 15thDay
35%412%26%17%3
2126
16th to endDay
31%5%16%30%12%3
1882
October1st to 15thDay
48%6%17%18%8%
1699
16th to endDay
37%9%22%23%6%
1584
November1st to 15thDay
33%12%21%22%9%
1482
16th to endDay
39%9%21%20%6%2
1302
December1st to 15thDay
38%10%25%19%5%
1260
16th to endDay
38%8%22%20%9%
1344
January1st to 15thNight
41%12%21%17%5%1
2685
16th to endNight
37%8%18%23%9%2
2694
February1st to 15thNight
41%8%19%21%7%1
2399
16th to endNight
43%6%16%23%8%
1956
March1st to 15thNight
35%10%27%20%6%
2118
16th to endNight
43%10%20%19%6%
2088
April1st to 15thNight
45%8%16%21%8%
1721
16th to endNight
43%6%17%24%6%1
1620
May1st to 15thNight
38%6%19%25%10%
1482
16th to endNight
49%6%17%19%6%
1309
June1st to 15thNight
42%5%18%23%9%1
1260
16th to endNight
34%7%19%25%12%
1260
July1st to 15thNight
23%5%19%33%13%3
1190
16th to endNight
22%5%16%30%19%6%
1325
August1st to 15thNight
26%5%18%31%14%2
1489
16th to endNight
23%313%34%21%2
1719
September1st to 15thNight
28%313%30%17%4
1830
16th to endNight
29%5%18%27%14%3
1890
October1st to 15thNight
39%7%18%23%10%
1928
16th to endNight
34%8%18%28%9%
2288
November1st to 15thNight
33%9%21%24%9%
2364
16th to endNight
38%11%21%17%8%2
2656
December1st to 15thNight
40%11%21%19%6%1
2700
16th to endNight
42%7%20%20%7%
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
5%8%31%26%11%16%
60
16th to endDay
14%25%26%17%9%7%
64
February1st to 15thDay
19%18%43%12%5%
71
16th to endDay
11%28%31%19%7%
177
March1st to 15thDay
16%44%31%6%1
270
16th to endDay
23%37%26%11%1
288
April1st to 15thDay
21%33%28%12%2
269
16th to endDay
28%22%26%15%5%1
270
May1st to 15thDay
21%24%23%19%8%3
332
16th to endDay
26%13%18%20%16%4
517
June1st to 15thDay
20%20%22%21%12%3
495
16th to endDay
15%18%28%21%13%4
495
July1st to 15thDay
11%12%25%25%21%3
475
16th to endDay
7%20%34%21%13%2
420
August1st to 15thDay
11%13%31%29%10%3
315
16th to endDay
12%17%34%24%8%3
332
September1st to 15thDay
25%19%25%20%6%3
315
16th to endDay
13%27%32%17%7%
280
October1st to 15thDay
26%23%20%21%6%
164
16th to endDay
12%19%31%17%14%4
96
November1st to 15thDay
24%38%17%14%31
90
16th to endDay
13%16%34%14%10%10%
67
December1st to 15thDay
11%25%16%31%13%1
60
16th to endDay
18%20%23%15%17%4
64
January1st to 15thNight
17%23%30%22%6%1
900
16th to endNight
10%23%32%23%7%1
774
February1st to 15thNight
11%19%29%23%10%4
704
16th to endNight
10%15%33%27%12%
632
March1st to 15thNight
9%26%33%20%8%1
720
16th to endNight
13%22%25%27%9%1
768
April1st to 15thNight
15%24%25%22%10%1
641
16th to endNight
17%17%26%24%12%1
540
May1st to 15thNight
16%15%21%25%19%1
447
16th to endNight
24%10%15%25%23%
375
June1st to 15thNight
16%14%23%26%15%3
360
16th to endNight
12%11%23%29%21%1
360
July1st to 15thNight
8%7%20%35%25%2
340
16th to endNight
6%6%19%41%22%1
376
August1st to 15thNight
9%415%35%32%2
417
16th to endNight
9%11%20%34%21%2
573
September1st to 15thNight
15%8%18%25%22%8%
681
16th to endNight
14%15%22%24%18%3
683
October1st to 15thNight
17%18%19%27%14%2
660
16th to endNight
11%22%24%26%12%2
704
November1st to 15thNight
17%32%25%17%6%
789
16th to endNight
12%24%36%18%6%1
900
December1st to 15thNight
11%20%32%25%8%1
900
16th to endNight
11%25%30%23%8%1
960
Page generated at 2017-09-23 04:43:47. Version ac04

Copyright 2017 A. Danko


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