Martz Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Martz 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
25%
14953
11%
46849
7%
14914
30%
14914
12%
35485

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
8%
717
6%
2434
2%
716
11%
716
4%
2131
January16th to endNight
8%
768
5%
2496
2%
768
12%
768
4%
2193
February1st to 15thNight
9%
703
5%
2287
2%
701
12%
701
5%
1981
February16th to endNight
11%
631
8%
1986
2%
631
17%
631
6%
1672
March1st to 15thNight
13%
720
11%
1980
5%
720
18%
720
8%
1636
March16th to endNight
18%
768
14%
2112
6%
768
26%
768
12%
1616
April1st to 15thNight
18%
718
11%
1815
4%
718
23%
718
15%
1402
April16th to endNight
26%
608
17%
1688
4%
608
35%
608
20%
1161
May1st to 15thNight
27%
522
14%
1602
7%
522
35%
522
14%
1150
May16th to endNight
35%
374
17%
1497
15%
374
43%
374
16%
928
June1st to 15thNight
32%
360
12%
1440
9%
360
42%
360
16%
924
June16th to endNight
34%
360
13%
1440
11%
360
45%
360
16%
903
July1st to 15thNight
50%
340
14%
1360
18%
340
54%
340
21%
801
July16th to endNight
46%
535
14%
1566
9%
502
55%
502
25%
959
August1st to 15thNight
55%
539
16%
1609
12%
536
58%
536
27%
1020
August16th to endNight
55%
654
19%
1800
12%
654
58%
654
31%
1137
September1st to 15thNight
43%
707
20%
1768
12%
707
46%
707
27%
1219
September16th to endNight
43%
657
18%
1843
13%
657
45%
657
23%
1266
October1st to 15thNight
34%
660
15%
1980
13%
660
39%
660
19%
1386
October16th to endNight
17%
704
10%
2112
5%
704
24%
704
11%
1656
November1st to 15thNight
27%
700
16%
2306
13%
700
33%
700
14%
1647
November16th to endNight
14%
720
9%
2520
5%
720
21%
720
7%
2045
December1st to 15thNight
10%
720
4%
2520
3%
720
12%
720
3%
2219
December16th to endNight
6%
768
2%
2688
0%
768
8%
768
3%
2433

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%11%5%7%6%34446%27%
47804
Night
17%12%5%8%6%34445%27%
47031
Cloud CoverDay
18%11%5%7%6%34446%26%
47814
Night
17%12%5%8%6%34445%27%
47035
TransparencyDay
57%5%10%15%8%
47504
Night
58%5%10%15%8%1
46849
SeeingDay
23%20%23%18%9%4
5410
Night
21%26%22%19%9%1
14958

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
17%18%9%14%9%2333313%
1504
16th to endDay
13%17%11%17%10%5%43339%
1728
February1st to 15thDay
17%19%10%13%9%4332312%
1575
16th to endDay
15%17%6%12%10%2433419%
1485
March1st to 15thDay
18%17%7%10%5%24435%22%
1969
16th to endDay
18%13%7%7%5%23346%27%
2112
April1st to 15thDay
20%15%5%5%423445%28%
2131
16th to endDay
20%9%24433336%37%
2283
May1st to 15thDay
19%10%47%6%24446%30%
2346
16th to endDay
17%5%35%435%5%5%7%36%
2618
June1st to 15thDay
19%6%36%5%245%5%6%32%
2520
16th to endDay
18%6%25%435%5%6%9%32%
2520
July1st to 15thDay
12%5%36%7%46%5%6%7%34%
2520
16th to endDay
14%6%35%6%36%6%7%10%30%
2493
August1st to 15thDay
14%7%26%6%446%7%8%31%
2340
16th to endDay
15%6%25%6%35%5%7%9%32%
2389
September1st to 15thDay
22%7%36%5%2345%6%33%
2111
16th to endDay
18%6%35%5%35%45%7%33%
1785
October1st to 15thDay
22%8%36%6%24446%29%
1650
16th to endDay
28%13%47%5%3433420%
1760
November1st to 15thDay
14%16%46%5%2336%7%29%
1549
16th to endDay
22%20%6%8%5%23345%17%
1440
December1st to 15thDay
19%23%12%11%5%2333312%
1440
16th to endDay
20%22%12%15%5%333228%
1536
January1st to 15thNight
19%19%8%15%8%2332311%
2434
16th to endNight
14%18%10%14%10%5%5%33212%
2496
February1st to 15thNight
15%18%8%13%10%45%23314%
2285
16th to endNight
14%13%7%16%10%3433317%
1986
March1st to 15thNight
18%14%7%11%6%34435%20%
1968
16th to endNight
15%12%7%8%5%34345%28%
2112
April1st to 15thNight
22%13%44424345%30%
1815
16th to endNight
14%11%245%34347%38%
1688
May1st to 15thNight
18%7%26%6%245%46%34%
1602
16th to endNight
12%6%25%435%447%42%
1495
June1st to 15thNight
14%7%25%5%245%5%7%38%
1440
16th to endNight
14%6%25%425%5%6%8%38%
1440
July1st to 15thNight
9%5%246%3346%7%46%
1440
16th to endNight
11%4245%245%6%9%43%
1673
August1st to 15thNight
9%4245%346%7%9%42%
1620
16th to endNight
11%5%235%2446%8%45%
1800
September1st to 15thNight
17%6%24424446%42%
1768
16th to endNight
18%7%24424447%38%
1843
October1st to 15thNight
20%8%25%434346%36%
1980
16th to endNight
30%10%35%43435%5%23%
2112
November1st to 15thNight
18%13%45%424445%32%
2306
16th to endNight
18%21%6%7%5%3443419%
2520
December1st to 15thNight
21%21%11%10%5%3342311%
2520
16th to endNight
18%20%9%16%6%343338%
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
18%17%9%13%9%2334413%
1504
16th to endDay
14%17%10%17%10%443439%
1728
February1st to 15thDay
17%20%9%12%9%4422213%
1575
16th to endDay
16%15%6%12%9%2433419%
1485
March1st to 15thDay
19%15%8%11%5%2334421%
1980
16th to endDay
17%14%7%6%5%23345%27%
2111
April1st to 15thDay
21%13%6%4424445%27%
2131
16th to endDay
20%9%24423445%37%
2283
May1st to 15thDay
20%10%37%5%23447%29%
2346
16th to endDay
17%6%25%5%35%45%7%36%
2618
June1st to 15thDay
19%7%36%5%35%5%5%7%31%
2520
16th to endDay
18%6%15%435%5%6%9%31%
2520
July1st to 15thDay
12%6%27%6%36%6%5%8%34%
2520
16th to endDay
13%6%45%6%46%6%6%8%31%
2493
August1st to 15thDay
14%7%27%6%46%5%6%8%30%
2340
16th to endDay
15%6%16%5%45%6%7%9%31%
2389
September1st to 15thDay
21%8%345%33446%33%
2111
16th to endDay
18%7%36%5%34447%33%
1785
October1st to 15thDay
23%7%36%5%34446%29%
1650
16th to endDay
28%15%37%5%24335%20%
1760
November1st to 15thDay
15%16%35%43435%8%29%
1549
16th to endDay
23%21%6%7%413445%17%
1440
December1st to 15thDay
18%24%12%10%5%1233312%
1440
16th to endDay
20%21%12%16%5%233237%
1536
January1st to 15thNight
19%19%8%15%8%2423312%
2434
16th to endNight
14%18%10%14%10%5%433312%
2496
February1st to 15thNight
15%17%8%12%11%45%33314%
2278
16th to endNight
15%13%7%15%10%35%33318%
1986
March1st to 15thNight
19%14%7%10%6%33335%20%
1980
16th to endNight
15%12%6%8%6%34345%28%
2112
April1st to 15thNight
22%13%44424446%29%
1815
16th to endNight
13%11%145%34448%37%
1688
May1st to 15thNight
19%6%35%5%3445%6%34%
1601
16th to endNight
13%7%3343445%7%42%
1495
June1st to 15thNight
15%5%35%5%245%5%7%37%
1440
16th to endNight
15%6%25%4345%5%8%38%
1440
July1st to 15thNight
9%5%25%5%345%5%8%45%
1440
16th to endNight
11%3244345%6%8%43%
1673
August1st to 15thNight
9%424435%6%6%10%41%
1620
16th to endNight
11%5%2343346%9%45%
1800
September1st to 15thNight
16%6%25%42445%5%41%
1768
16th to endNight
18%6%35%5%2445%6%38%
1843
October1st to 15thNight
19%8%35%334246%36%
1980
16th to endNight
29%11%35%424345%24%
2112
November1st to 15thNight
18%14%34423446%32%
2306
16th to endNight
19%20%6%8%5%2433419%
2520
December1st to 15thNight
21%20%11%10%6%2343212%
2520
16th to endNight
19%19%10%16%7%343239%
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
76%47%7%3
1505
16th to endDay
80%47%6%1
1728
February1st to 15thDay
79%46%6%3
1577
16th to endDay
69%310%12%3
1485
March1st to 15thDay
65%410%13%5%
1980
16th to endDay
57%48%18%8%1
2112
April1st to 15thDay
57%411%17%9%
2131
16th to endDay
49%5%9%18%15%2
2283
May1st to 15thDay
55%5%10%19%8%
2346
16th to endDay
46%6%14%18%11%1
2622
June1st to 15thDay
50%7%11%19%9%1
2520
16th to endDay
47%6%15%18%11%
2520
July1st to 15thDay
47%7%9%20%14%
2371
16th to endDay
47%8%15%17%10%
2337
August1st to 15thDay
48%8%13%18%10%
2327
16th to endDay
45%7%13%20%11%1
2389
September1st to 15thDay
52%6%10%19%11%
2111
16th to endDay
49%6%9%20%13%
1785
October1st to 15thDay
55%6%9%14%11%1
1650
16th to endDay
67%5%11%11%3
1760
November1st to 15thDay
53%5%12%14%11%2
1549
16th to endDay
70%5%8%10%41
1440
December1st to 15thDay
77%39%7%1
1440
16th to endDay
82%5%6%41
1536
January1st to 15thNight
77%46%5%4
2434
16th to endNight
78%47%7%2
2496
February1st to 15thNight
77%38%8%2
2287
16th to endNight
72%38%11%4
1986
March1st to 15thNight
67%5%7%14%5%
1980
16th to endNight
57%5%9%14%11%1
2112
April1st to 15thNight
56%5%10%17%10%
1815
16th to endNight
45%5%10%20%13%4
1688
May1st to 15thNight
49%8%10%20%10%1
1602
16th to endNight
40%8%12%22%13%2
1497
June1st to 15thNight
43%7%13%22%12%
1440
16th to endNight
41%8%12%24%11%1
1440
July1st to 15thNight
36%8%12%23%17%1
1360
16th to endNight
36%7%15%22%15%2
1566
August1st to 15thNight
35%8%16%28%10%1
1609
16th to endNight
34%7%15%26%13%1
1800
September1st to 15thNight
42%6%12%22%14%1
1768
16th to endNight
46%411%20%14%1
1843
October1st to 15thNight
48%5%11%17%15%
1980
16th to endNight
62%5%13%14%4
2112
November1st to 15thNight
53%5%11%16%9%4
2306
16th to endNight
68%48%13%4
2520
December1st to 15thNight
78%47%6%2
2520
16th to endNight
82%48%4
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
34%38%16%45%
72
16th to endDay
28%40%23%5%11
96
February1st to 15thDay
31%41%25%2
90
16th to endDay
25%27%40%5%
118
March1st to 15thDay
31%29%20%13%5%
270
16th to endDay
29%30%21%13%41
288
April1st to 15thDay
29%28%19%14%6%1
270
16th to endDay
23%22%24%15%8%3
270
May1st to 15thDay
32%23%17%16%7%1
288
16th to endDay
18%21%25%19%9%4
331
June1st to 15thDay
20%20%26%21%8%2
315
16th to endDay
23%20%26%20%7%2
315
July1st to 15thDay
15%15%24%25%12%7%
305
16th to endDay
12%14%26%26%12%7%
326
August1st to 15thDay
15%11%22%23%15%10%
313
16th to endDay
17%10%20%22%14%14%
332
September1st to 15thDay
18%11%19%19%21%9%
299
16th to endDay
16%13%21%19%19%9%
254
October1st to 15thDay
22%13%22%24%11%5%
255
16th to endDay
34%20%27%13%3
272
November1st to 15thDay
23%13%26%27%6%2
147
16th to endDay
36%18%30%11%3
60
December1st to 15thDay
41%26%15%10%5%1
60
16th to endDay
48%25%26%
64
January1st to 15thNight
23%38%25%8%3
720
16th to endNight
23%40%23%11%1
768
February1st to 15thNight
24%36%26%11%1
704
16th to endNight
21%33%29%12%2
631
March1st to 15thNight
26%32%22%14%3
720
16th to endNight
21%32%23%17%4
768
April1st to 15thNight
26%29%23%16%4
718
16th to endNight
17%26%25%22%6%1
608
May1st to 15thNight
19%25%18%27%8%
522
16th to endNight
12%21%26%26%12%
375
June1st to 15thNight
15%20%26%26%10%
360
16th to endNight
13%21%24%29%10%
360
July1st to 15thNight
11%14%16%36%19%1
340
16th to endNight
12%18%15%28%22%1
535
August1st to 15thNight
10%12%16%32%25%1
539
16th to endNight
11%10%16%28%28%3
654
September1st to 15thNight
17%13%18%24%23%2
707
16th to endNight
17%15%17%22%21%5%
657
October1st to 15thNight
22%17%21%23%13%1
660
16th to endNight
33%19%25%17%3
704
November1st to 15thNight
21%25%22%22%6%1
700
16th to endNight
28%33%20%11%5%
720
December1st to 15thNight
31%36%18%10%2
720
16th to endNight
27%37%23%9%1
768
Page generated at 2017-09-13 07:39:04. Version ac04

Copyright 2017 A. Danko


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