Gardner
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gardner clear sky chart from 2005-11-05 to 2017-09-17.

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
42%
15879
23%
47004
14%
15832
50%
15832
32%
28208

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
31%
900
22%
2327
9%
895
42%
895
33%
1461
January16th to endNight
28%
960
25%
2496
9%
960
38%
960
34%
1579
February1st to 15thNight
25%
880
16%
2288
6%
876
31%
876
24%
1602
February16th to endNight
26%
660
25%
1922
8%
660
39%
660
30%
1182
March1st to 15thNight
31%
540
22%
1980
11%
540
45%
540
25%
1149
March16th to endNight
25%
576
15%
2112
9%
576
34%
576
19%
1385
April1st to 15thNight
33%
539
21%
1860
13%
539
47%
539
27%
1070
April16th to endNight
31%
540
21%
1704
13%
540
44%
540
24%
1099
May1st to 15thNight
39%
540
20%
1620
16%
540
47%
540
27%
1046
May16th to endNight
47%
563
18%
1682
15%
561
52%
561
33%
1005
June1st to 15thNight
61%
540
20%
1440
12%
540
65%
540
42%
848
June16th to endNight
62%
540
26%
1482
16%
540
67%
540
53%
790
July1st to 15thNight
70%
510
18%
1530
15%
510
72%
510
41%
845
July16th to endNight
72%
564
25%
1594
25%
531
75%
531
43%
835
August1st to 15thNight
78%
539
25%
1610
30%
536
79%
536
43%
864
August16th to endNight
71%
573
28%
1809
31%
573
74%
573
40%
971
September1st to 15thNight
60%
540
26%
1861
27%
540
65%
540
32%
1040
September16th to endNight
61%
498
29%
1837
26%
498
69%
498
34%
964
October1st to 15thNight
47%
649
29%
1969
21%
649
52%
649
35%
1135
October16th to endNight
39%
704
28%
2112
14%
704
50%
704
36%
1164
November1st to 15thNight
40%
764
29%
2164
14%
764
52%
764
39%
1208
November16th to endNight
33%
900
25%
2478
10%
900
44%
900
33%
1502
December1st to 15thNight
28%
900
19%
2520
7%
900
38%
900
25%
1676
December16th to endNight
27%
960
22%
2607
8%
960
38%
960
24%
1788

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
12%6%25%42445%7%44%
47752
Night
10%5%24423446%49%
47199
TransparencyDay
38%5%13%25%14%2
47452
Night
34%412%26%17%3
47004
SeeingDay
13%6%24%30%19%4
5901
Night
13%7%31%32%13%1
15879

By Month

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
10%6%26%5%2343448%
1611
16th to endDay
11%8%46%424246%43%
1728
February1st to 15thDay
11%9%6%6%433345%41%
1575
16th to endDay
12%9%25%5%23447%41%
1558
March1st to 15thDay
11%9%46%5%345%5%7%37%
1980
16th to endDay
20%10%46%423345%34%
2110
April1st to 15thDay
15%8%35%5%14346%42%
2088
16th to endDay
19%7%36%5%3444435%
2253
May1st to 15thDay
17%8%45%5%34445%36%
2331
16th to endDay
14%5%25%5%25%5%5%8%37%
2430
June1st to 15thDay
8%5%245%25%5%7%9%43%
2517
16th to endDay
5%2134345%6%9%51%
2472
July1st to 15thDay
8%4235%245%6%9%46%
2340
16th to endDay
7%2245%35%5%6%10%47%
2466
August1st to 15thDay
6%414335%5%6%9%47%
2340
16th to endDay
9%41443445%8%49%
2393
September1st to 15thDay
12%5%25%423347%48%
2097
16th to endDay
8%325%3235%6%7%51%
1828
October1st to 15thDay
13%6%24323246%50%
1650
16th to endDay
12%424423336%52%
1760
November1st to 15thDay
9%413323347%55%
1692
16th to endDay
15%6%33423336%49%
1479
December1st to 15thDay
14%9%34433346%40%
1440
16th to endDay
14%8%47%314446%39%
1614
January1st to 15thNight
9%6%24334446%50%
2327
16th to endNight
8%6%36%423345%49%
2496
February1st to 15thNight
10%10%46%5%34445%40%
2278
16th to endNight
10%6%35%423346%47%
1922
March1st to 15thNight
10%7%25%413346%47%
1980
16th to endNight
19%7%35%423446%38%
2112
April1st to 15thNight
11%5%25%42335%6%50%
1860
16th to endNight
17%6%25%5%23335%43%
1704
May1st to 15thNight
14%5%34335%35%8%43%
1619
16th to endNight
11%424323449%48%
1680
June1st to 15thNight
5%213425%5%6%9%52%
1440
16th to endNight
411232245%10%60%
1482
July1st to 15thNight
6%3123245%7%9%51%
1620
16th to endNight
5%213425%47%9%54%
1702
August1st to 15thNight
42134245%7%10%54%
1620
16th to endNight
7%214423446%57%
1809
September1st to 15thNight
9%424423446%51%
1861
16th to endNight
7%31342445%6%54%
1837
October1st to 15thNight
13%41331234455%
1969
16th to endNight
10%5%1331333458%
2112
November1st to 15thNight
8%414323246%58%
2164
16th to endNight
13%6%24322236%52%
2478
December1st to 15thNight
13%8%36%423445%42%
2520
16th to endNight
14%8%5%7%423235%40%
2607

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%313%25%16%1
1612
16th to endDay
42%315%25%11%1
1728
February1st to 15thDay
45%415%24%9%1
1576
16th to endDay
42%414%23%12%2
1558
March1st to 15thDay
45%5%12%23%11%1
1980
16th to endDay
52%412%20%8%1
2112
April1st to 15thDay
43%411%23%15%
2088
16th to endDay
50%5%11%20%11%
2253
May1st to 15thDay
49%5%10%22%11%
2331
16th to endDay
44%6%16%20%11%1
2434
June1st to 15thDay
33%7%15%26%14%1
2517
16th to endDay
26%6%17%28%18%2
2472
July1st to 15thDay
31%7%17%27%12%2
2201
16th to endDay
27%8%14%32%15%1
2311
August1st to 15thDay
31%8%14%27%16%1
2326
16th to endDay
33%7%10%26%15%6%
2393
September1st to 15thDay
35%412%24%17%5%
2097
16th to endDay
30%5%12%28%21%1
1828
October1st to 15thDay
35%310%26%20%4
1650
16th to endDay
33%411%26%19%4
1760
November1st to 15thDay
29%411%27%20%5%
1692
16th to endDay
37%210%29%18%
1479
December1st to 15thDay
45%414%25%9%
1440
16th to endDay
45%412%22%11%2
1614
January1st to 15thNight
34%415%25%18%1
2327
16th to endNight
36%314%27%16%2
2496
February1st to 15thNight
45%5%11%23%12%1
2288
16th to endNight
38%211%25%18%2
1922
March1st to 15thNight
37%412%24%16%4
1980
16th to endNight
46%5%12%22%10%2
2112
April1st to 15thNight
35%49%26%20%2
1860
16th to endNight
43%311%24%16%1
1704
May1st to 15thNight
40%5%12%23%16%1
1620
16th to endNight
33%6%18%25%13%2
1682
June1st to 15thNight
25%7%15%32%15%2
1440
16th to endNight
18%6%14%33%22%3
1482
July1st to 15thNight
25%6%14%32%16%4
1530
16th to endNight
23%6%12%33%21%2
1594
August1st to 15thNight
22%7%14%33%17%3
1610
16th to endNight
27%49%27%24%7%
1809
September1st to 15thNight
32%5%10%25%19%7%
1861
16th to endNight
28%5%10%27%24%3
1837
October1st to 15thNight
32%38%25%23%6%
1969
16th to endNight
29%39%29%22%4
2112
November1st to 15thNight
28%312%24%23%8%
2164
16th to endNight
34%39%30%19%2
2478
December1st to 15thNight
43%413%25%12%
2520
16th to endNight
45%411%21%12%3
2607

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%17%38%18%4
90
16th to endDay
17%10%47%18%41
96
February1st to 15thDay
8%20%42%24%4
90
16th to endDay
16%20%37%17%8%
81
March1st to 15thDay
15%22%44%15%11
90
16th to endDay
26%14%35%20%3
96
April1st to 15thDay
16%13%35%25%8%
207
16th to endDay
23%12%32%20%8%1
363
May1st to 15thDay
19%8%33%23%13%1
468
16th to endDay
18%5%33%26%12%3
517
June1st to 15thDay
9%423%35%21%5%
495
16th to endDay
6%5%27%35%21%3
495
July1st to 15thDay
10%216%38%26%6%
475
16th to endDay
6%11%37%37%5%
515
August1st to 15thDay
8%8%39%36%6%
493
16th to endDay
11%212%33%30%9%
433
September1st to 15thDay
8%114%38%27%8%
252
16th to endDay
6%323%35%20%10%
93
October1st to 15thDay
6%6%27%35%14%8%
90
16th to endDay
9%7%39%30%12%1
96
November1st to 15thDay
8%7%21%37%16%7%
90
16th to endDay
33%13%31%17%31
90
December1st to 15thDay
20%13%42%15%5%3
90
16th to endDay
21%19%33%21%3
96
January1st to 15thNight
12%12%39%28%6%1
900
16th to endNight
12%10%43%29%4
960
February1st to 15thNight
16%11%39%29%3
880
16th to endNight
15%13%41%25%4
660
March1st to 15thNight
15%11%37%28%7%
540
16th to endNight
22%9%39%23%4
576
April1st to 15thNight
15%11%35%31%5%
539
16th to endNight
19%9%35%27%8%
540
May1st to 15thNight
17%434%30%12%
540
16th to endNight
12%432%33%14%2
563
June1st to 15thNight
5%224%46%19%1
540
16th to endNight
4127%47%17%1
540
July1st to 15thNight
9%114%47%26%2
510
16th to endNight
5%112%43%34%1
564
August1st to 15thNight
48%46%37%2
539
16th to endNight
9%12%39%33%4
573
September1st to 15thNight
11%217%40%24%3
540
16th to endNight
8%320%39%23%4
498
October1st to 15thNight
15%428%31%17%2
649
16th to endNight
13%8%36%28%12%
704
November1st to 15thNight
10%9%35%30%12%1
764
16th to endNight
17%12%35%27%6%
900
December1st to 15thNight
19%10%37%26%5%
900
16th to endNight
18%10%36%28%4
960
Page generated at 2017-09-18 07:38:30. Version ac04

Copyright 2017 A. Danko


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