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 2017-09-18.

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
44%
15848
29%
46888
14%
15806
58%
15806
39%
24555

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
36%
879
31%
2485
14%
874
53%
874
45%
1199
January16th to endNight
31%
768
35%
2496
16%
768
54%
768
44%
1111
February1st to 15thNight
26%
699
28%
2215
9%
699
46%
699
37%
1126
February16th to endNight
22%
632
37%
1894
9%
632
51%
632
41%
912
March1st to 15thNight
33%
720
29%
2103
11%
720
49%
720
38%
1085
March16th to endNight
33%
684
33%
2028
12%
684
54%
684
40%
1025
April1st to 15thNight
28%
539
28%
1798
11%
539
51%
539
36%
852
April16th to endNight
34%
540
25%
1800
12%
540
53%
540
28%
970
May1st to 15thNight
37%
539
22%
1710
12%
539
51%
539
28%
1015
May16th to endNight
41%
562
23%
1498
9%
561
53%
561
36%
865
June1st to 15thNight
54%
540
24%
1440
14%
540
62%
540
44%
769
June16th to endNight
64%
540
22%
1440
15%
540
70%
540
42%
822
July1st to 15thNight
64%
510
16%
1360
12%
510
67%
510
29%
905
July16th to endNight
76%
564
15%
1509
15%
531
77%
531
29%
964
August1st to 15thNight
72%
539
13%
1704
14%
536
73%
536
26%
1060
August16th to endNight
69%
573
21%
1910
23%
573
72%
573
29%
1110
September1st to 15thNight
66%
540
24%
1800
22%
540
72%
540
33%
1010
September16th to endNight
63%
501
34%
1802
29%
501
75%
501
47%
795
October1st to 15thNight
52%
643
32%
1963
19%
643
63%
643
44%
975
October16th to endNight
50%
704
36%
2112
17%
704
64%
704
46%
1040
November1st to 15thNight
46%
872
36%
2272
15%
872
58%
872
54%
1116
November16th to endNight
39%
900
38%
2341
15%
900
55%
900
52%
1174
December1st to 15thNight
27%
900
30%
2520
6%
900
47%
900
44%
1259
December16th to endNight
28%
960
30%
2688
10%
960
46%
960
39%
1396

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
23244245%6%8%55%
47912
Night
231332345%7%60%
47069
Cloud CoverDay
34244245%6%8%54%
47910
Night
232332445%7%59%
47069
TransparencyDay
23%8%13%23%22%8%
47595
Night
21%6%13%26%24%8%
46888
SeeingDay
6%16%31%26%14%3
5752
Night
5%12%33%30%16%2
15855

By Month

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
1313223348%66%
1462
16th to endDay
323312246%69%
1728
February1st to 15thDay
435%412348%60%
1645
16th to endDay
31422336%8%62%
1580
March1st to 15thDay
142442445%7%58%
1856
16th to endDay
15%333245%6%9%54%
2196
April1st to 15thDay
25%1342445%9%55%
2150
16th to endDay
46%25%435%6%5%7%47%
2160
May1st to 15thDay
6%6%25%5%35%5%6%9%44%
2238
16th to endDay
43134245%6%9%52%
2616
June1st to 15thDay
2213425%5%6%9%55%
2520
16th to endDay
1124346%8%9%57%
2520
July1st to 15thDay
43345%36%7%9%10%40%
2520
16th to endDay
3315%6%37%7%9%11%38%
2552
August1st to 15thDay
5%325%5%47%7%9%10%39%
2244
16th to endDay
4325%5%45%5%6%8%46%
2292
September1st to 15thDay
5%314425%5%7%10%49%
2160
16th to endDay
2212313446%67%
1881
October1st to 15thDay
431232445%5%62%
1664
16th to endDay
2312212336%70%
1752
November1st to 15thDay
31321235%8%68%
1583
16th to endDay
32321245%6%67%
1617
December1st to 15thDay
324223239%65%
1440
16th to endDay
132431345%9%59%
1536
January1st to 15thNight
1213312337%68%
2485
16th to endNight
1313213336%68%
2496
February1st to 15thNight
1436%413336%62%
2205
16th to endNight
324312346%67%
1894
March1st to 15thNight
25%1321346%7%61%
2103
16th to endNight
232321235%7%65%
2028
April1st to 15thNight
2423212447%63%
1798
16th to endNight
47%24324247%55%
1800
May1st to 15thNight
5%7%24335%5%6%6%50%
1709
16th to endNight
6%41332436%7%55%
1497
June1st to 15thNight
2223245%6%8%60%
1440
16th to endNight
122336%5%6%10%55%
1440
July1st to 15thNight
6%415%5%46%7%6%9%40%
1440
16th to endNight
3314437%8%9%11%41%
1613
August1st to 15thNight
2215%6%46%6%8%9%46%
1713
16th to endNight
6%3235%35%5%7%11%45%
1910
September1st to 15thNight
5%3134346%6%9%49%
1800
16th to endNight
321121245%6%67%
1802
October1st to 15thNight
3313313346%65%
1963
16th to endNight
2313222336%67%
2112
November1st to 15thNight
212312346%71%
2272
16th to endNight
1312212347%70%
2341
December1st to 15thNight
131332235%8%64%
2520
16th to endNight
132432335%6%63%
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
131332335%8%64%
1462
16th to endDay
323212346%67%
1728
February1st to 15thDay
435%422348%59%
1645
16th to endDay
315%32345%9%60%
1580
March1st to 15thDay
141442445%7%57%
1856
16th to endDay
2433425%5%6%9%53%
2194
April1st to 15thDay
25%1432446%9%54%
2150
16th to endDay
47%25%5%35%5%5%8%46%
2160
May1st to 15thDay
6%6%25%5%35%46%8%43%
2238
16th to endDay
4413425%6%6%9%51%
2616
June1st to 15thDay
2213425%6%6%9%53%
2520
16th to endDay
113335%6%8%9%56%
2520
July1st to 15thDay
4425%5%37%7%9%9%40%
2520
16th to endDay
3416%6%37%8%9%11%37%
2552
August1st to 15thDay
5%415%5%46%7%8%10%38%
2244
16th to endDay
45%25%5%35%5%6%8%45%
2292
September1st to 15thDay
5%314435%5%6%9%48%
2160
16th to endDay
221332335%6%66%
1881
October1st to 15thDay
4312424346%61%
1664
16th to endDay
2312212335%69%
1752
November1st to 15thDay
1312213347%67%
1583
16th to endDay
1323212447%67%
1617
December1st to 15thDay
324322348%64%
1440
16th to endDay
1424313449%58%
1536
January1st to 15thNight
1312313347%67%
2485
16th to endNight
1313213436%67%
2496
February1st to 15thNight
1426%413335%61%
2205
16th to endNight
32421235%6%66%
1894
March1st to 15thNight
15%2331345%7%60%
2103
16th to endNight
232321235%7%64%
2028
April1st to 15thNight
2423312447%63%
1798
16th to endNight
48%24324348%54%
1800
May1st to 15thNight
6%6%34325%5%5%7%48%
1709
16th to endNight
6%42342435%8%54%
1497
June1st to 15thNight
2212225%5%6%9%60%
1440
16th to endNight
212326%5%7%9%55%
1440
July1st to 15thNight
6%425%6%46%6%6%9%40%
1440
16th to endNight
33145%37%7%9%12%40%
1613
August1st to 15thNight
22246%46%6%7%9%45%
1713
16th to endNight
6%4235%35%6%7%10%44%
1910
September1st to 15thNight
6%323425%6%7%9%48%
1800
16th to endNight
321221345%6%66%
1802
October1st to 15thNight
3313213347%64%
1963
16th to endNight
3313213436%66%
2112
November1st to 15thNight
121221325%6%70%
2272
16th to endNight
1312112246%69%
2341
December1st to 15thNight
1213323349%63%
2520
16th to endNight
132342335%6%62%
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
16%5%14%34%24%5%
1463
16th to endDay
16%412%31%26%8%
1728
February1st to 15thDay
22%413%30%22%5%
1646
16th to endDay
18%410%28%31%6%
1580
March1st to 15thDay
23%5%9%25%27%8%
1856
16th to endDay
25%7%11%25%25%4
2196
April1st to 15thDay
23%6%11%29%19%9%
2150
16th to endDay
31%8%10%23%20%5%
2160
May1st to 15thDay
33%9%13%18%19%4
2238
16th to endDay
26%9%13%21%18%10%
2620
June1st to 15thDay
22%8%13%17%21%16%
2520
16th to endDay
18%7%12%21%25%14%
2520
July1st to 15thDay
32%12%14%18%14%7%
2371
16th to endDay
30%16%19%23%7%2
2393
August1st to 15thDay
34%14%16%15%12%6%
2229
16th to endDay
30%11%15%20%19%3
2292
September1st to 15thDay
27%10%15%23%16%7%
2160
16th to endDay
17%5%10%22%35%9%
1881
October1st to 15thDay
20%6%9%20%33%9%
1664
16th to endDay
16%48%25%35%8%
1752
November1st to 15thDay
14%411%24%31%12%
1583
16th to endDay
15%48%26%33%11%
1617
December1st to 15thDay
17%417%31%23%5%
1440
16th to endDay
21%5%19%28%18%6%
1536
January1st to 15thNight
15%414%30%28%5%
2485
16th to endNight
15%411%32%28%7%
2496
February1st to 15thNight
24%312%33%20%4
2215
16th to endNight
17%310%29%30%7%
1894
March1st to 15thNight
20%5%11%28%29%5%
2103
16th to endNight
19%5%10%28%30%5%
2028
April1st to 15thNight
19%413%30%24%8%
1798
16th to endNight
28%6%12%25%22%5%
1800
May1st to 15thNight
31%8%10%22%20%6%
1710
16th to endNight
26%7%15%22%17%10%
1498
June1st to 15thNight
19%7%14%20%19%19%
1440
16th to endNight
21%10%12%18%21%15%
1440
July1st to 15thNight
34%12%13%18%11%9%
1360
16th to endNight
28%16%21%21%9%2
1509
August1st to 15thNight
30%15%20%14%13%6%
1704
16th to endNight
29%11%16%22%15%4
1910
September1st to 15thNight
26%10%18%23%13%7%
1800
16th to endNight
15%6%12%25%30%10%
1802
October1st to 15thNight
19%5%12%21%32%9%
1963
16th to endNight
17%6%7%24%34%10%
2112
November1st to 15thNight
13%310%28%29%14%
2272
16th to endNight
15%38%28%33%10%
2341
December1st to 15thNight
16%5%15%33%22%5%
2520
16th to endNight
19%5%17%28%22%5%
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
12%20%28%25%12%1
90
16th to endDay
220%41%22%12%
96
February1st to 15thDay
430%42%18%4
90
16th to endDay
432%30%27%4
81
March1st to 15thDay
432%38%20%4
146
16th to endDay
9%39%36%11%2
288
April1st to 15thDay
8%39%33%13%31
269
16th to endDay
14%37%35%9%1
270
May1st to 15thDay
10%19%41%18%8%1
375
16th to endDay
8%15%34%24%13%2
517
June1st to 15thDay
313%31%27%19%4
495
16th to endDay
36%29%31%22%5%
495
July1st to 15thDay
7%423%33%24%7%
475
16th to endDay
5%116%39%28%8%
411
August1st to 15thDay
7%426%33%21%6%
315
16th to endDay
9%327%42%15%2
332
September1st to 15thDay
5%11%38%25%15%3
315
16th to endDay
210%37%30%14%5%
140
October1st to 15thDay
118%26%32%14%6%
90
16th to endDay
9%17%27%25%16%4
96
November1st to 15thDay
315%27%28%21%3
90
16th to endDay
6%36%34%16%5%
90
December1st to 15thDay
5%36%41%15%1
90
16th to endDay
6%32%40%18%2
96
January1st to 15thNight
219%38%27%9%2
879
16th to endNight
417%44%24%8%1
768
February1st to 15thNight
313%50%25%5%
704
16th to endNight
222%48%21%4
632
March1st to 15thNight
5%19%39%26%8%
720
16th to endNight
419%39%29%6%
684
April1st to 15thNight
6%21%39%26%5%
539
16th to endNight
10%17%34%27%8%
540
May1st to 15thNight
9%10%35%31%11%1
540
16th to endNight
9%11%31%27%17%2
563
June1st to 15thNight
410%27%37%18%2
540
16th to endNight
4322%37%28%2
540
July1st to 15thNight
8%112%37%34%5%
510
16th to endNight
415%33%46%8%
564
August1st to 15thNight
419%35%43%5%
539
16th to endNight
7%110%34%37%7%
573
September1st to 15thNight
7%216%40%27%5%
540
16th to endNight
47%20%35%24%6%
501
October1st to 15thNight
5%10%28%36%14%4
643
16th to endNight
49%32%31%18%3
704
November1st to 15thNight
115%33%33%13%1
872
16th to endNight
415%39%28%11%1
900
December1st to 15thNight
218%49%22%7%
900
16th to endNight
319%44%24%7%
960
Page generated at 2017-09-19 05:32:25. Version ac04

Copyright 2017 A. Danko


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