Antelope Hills Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Antelope Hills Observatory clear sky chart from 2005-11-05 to 2018-03-11.

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
53%
16707
26%
49104
18%
16665
61%
16665
40%
27397

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
52%
974
29%
2716
20%
970
60%
970
45%
1488
January16th to endNight
50%
904
33%
2776
23%
904
62%
904
42%
1470
February1st to 15thNight
45%
759
23%
2407
16%
758
55%
758
34%
1388
February16th to endNight
42%
684
31%
2050
15%
684
57%
684
38%
1138
March1st to 15thNight
47%
764
27%
2277
15%
764
57%
764
42%
1235
March16th to endNight
42%
658
25%
2002
14%
658
54%
658
36%
1148
April1st to 15thNight
34%
539
22%
1798
13%
539
48%
539
31%
1031
April16th to endNight
41%
540
20%
1800
14%
540
51%
540
27%
1099
May1st to 15thNight
44%
540
18%
1617
14%
540
50%
540
27%
1024
May16th to endNight
48%
562
18%
1498
11%
561
54%
561
35%
925
June1st to 15thNight
57%
540
19%
1440
12%
540
62%
540
44%
821
June16th to endNight
66%
540
25%
1440
18%
540
70%
540
50%
771
July1st to 15thNight
65%
510
16%
1360
12%
510
68%
510
35%
848
July16th to endNight
70%
564
23%
1416
18%
531
72%
531
39%
844
August1st to 15thNight
64%
539
16%
1692
15%
536
66%
536
32%
977
August16th to endNight
68%
573
26%
1910
29%
573
72%
573
39%
1007
September1st to 15thNight
64%
540
27%
1800
27%
540
71%
540
39%
948
September16th to endNight
65%
537
33%
1953
32%
537
73%
537
43%
908
October1st to 15thNight
50%
675
29%
2115
19%
675
59%
675
38%
1147
October16th to endNight
62%
825
36%
2361
22%
825
69%
825
48%
1229
November1st to 15thNight
56%
950
32%
2470
17%
950
63%
950
54%
1320
November16th to endNight
57%
975
35%
2564
21%
975
64%
975
49%
1402
December1st to 15thNight
49%
975
25%
2730
14%
975
57%
975
42%
1505
December16th to endNight
45%
1040
27%
2912
17%
1040
54%
1040
37%
1724

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
5%41332445%8%54%
49538
Night
5%5%2432345%7%55%
49276
Cloud CoverDay
5%42332445%8%54%
49536
Night
5%5%2432445%7%55%
49276
TransparencyDay
26%5%11%24%22%8%
49212
Night
27%5%12%24%21%8%
49104
SeeingDay
8%6%25%31%20%7%
6396
Night
7%329%42%15%1
16714

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
36%24323336%59%
1552
16th to endDay
25%23423346%60%
1810
February1st to 15thDay
26%35%424447%53%
1783
16th to endDay
26%24423446%57%
1710
March1st to 15thDay
35%2442435%7%56%
1916
16th to endDay
7%6%233245%5%8%50%
2221
April1st to 15thDay
8%6%2332335%7%52%
2150
16th to endDay
11%5%244245%5%8%45%
2160
May1st to 15thDay
11%5%24425%5%5%8%43%
2332
16th to endDay
8%413435%5%6%9%47%
2616
June1st to 15thDay
7%2133245%7%8%51%
2520
16th to endDay
32123246%7%9%59%
2520
July1st to 15thDay
6%3134246%6%9%50%
2520
16th to endDay
42145%346%7%9%50%
2656
August1st to 15thDay
4214425%5%7%11%49%
2256
16th to endDay
42133345%6%9%55%
2292
September1st to 15thDay
6%31232335%8%58%
2160
16th to endDay
5%32323346%64%
2007
October1st to 15thDay
6%413323337%60%
1842
16th to endDay
6%412222335%65%
1851
November1st to 15thDay
24134235%47%59%
1718
16th to endDay
3323223348%63%
1722
December1st to 15thDay
27%23325%45%5%56%
1560
16th to endDay
46%35%5%2335%7%52%
1664
January1st to 15thNight
25%24423347%58%
2716
16th to endNight
36%24423235%59%
2776
February1st to 15thNight
37%35%42445%7%51%
2397
16th to endNight
38%35%423346%55%
2050
March1st to 15thNight
35%24324446%57%
2277
16th to endNight
7%5%23333446%53%
2002
April1st to 15thNight
8%5%245%3335%7%50%
1798
16th to endNight
15%6%24423346%46%
1800
May1st to 15thNight
13%5%15%32445%8%44%
1616
16th to endNight
9%4243245%5%9%49%
1497
June1st to 15thNight
43134235%5%9%56%
1440
16th to endNight
32123135%6%10%58%
1440
July1st to 15thNight
5%224436%6%8%8%45%
1440
16th to endNight
4323435%6%7%11%47%
1512
August1st to 15thNight
5%325%5%36%5%6%9%47%
1700
16th to endNight
5%3133345%5%9%53%
1910
September1st to 15thNight
7%3133245%6%7%55%
1800
16th to endNight
5%313312446%63%
1953
October1st to 15thNight
8%423322345%58%
2115
16th to endNight
5%413223346%62%
2361
November1st to 15thNight
3213313448%62%
2470
16th to endNight
35%13324346%61%
2564
December1st to 15thNight
35%24323447%57%
2730
16th to endNight
38%45%42345%6%51%
2912

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
36%24423336%59%
1552
16th to endDay
25%23423346%59%
1810
February1st to 15thDay
26%35%325%347%53%
1783
16th to endDay
25%34423446%57%
1710
March1st to 15thDay
35%2442435%7%56%
1916
16th to endDay
7%6%2432445%8%50%
2219
April1st to 15thDay
8%6%2332345%7%52%
2150
16th to endDay
11%5%244245%5%8%45%
2160
May1st to 15thDay
11%6%14425%5%5%8%43%
2332
16th to endDay
8%423335%5%6%9%47%
2616
June1st to 15thDay
6%3233345%7%8%51%
2520
16th to endDay
22122246%6%9%58%
2520
July1st to 15thDay
6%3134246%7%10%50%
2520
16th to endDay
42144346%7%9%50%
2656
August1st to 15thDay
5%223435%5%7%10%49%
2256
16th to endDay
42133345%6%10%55%
2292
September1st to 15thDay
6%31232335%8%59%
2160
16th to endDay
5%32323346%64%
2007
October1st to 15thDay
6%312313337%61%
1842
16th to endDay
6%411222335%66%
1851
November1st to 15thDay
2413423447%59%
1718
16th to endDay
3323223348%63%
1722
December1st to 15thDay
27%24425%35%6%56%
1560
16th to endDay
45%346%2345%7%51%
1664
January1st to 15thNight
25%25%423347%58%
2716
16th to endNight
36%24422335%59%
2776
February1st to 15thNight
36%35%425%45%6%51%
2397
16th to endNight
38%25%41335%6%55%
2050
March1st to 15thNight
45%23324346%57%
2277
16th to endNight
7%5%23424346%53%
2002
April1st to 15thNight
8%5%245%3335%6%49%
1798
16th to endNight
15%6%24424346%45%
1800
May1st to 15thNight
13%5%2442445%7%44%
1616
16th to endNight
8%4234245%49%49%
1497
June1st to 15thNight
43134235%5%10%55%
1440
16th to endNight
21132235%6%10%59%
1440
July1st to 15thNight
5%215%436%7%8%8%46%
1440
16th to endNight
3324435%5%8%10%48%
1512
August1st to 15thNight
4325%5%35%5%7%9%47%
1700
16th to endNight
5%32342446%8%53%
1910
September1st to 15thNight
7%3133245%6%7%55%
1800
16th to endNight
5%213313346%62%
1953
October1st to 15thNight
9%423313345%58%
2115
16th to endNight
5%412223346%62%
2361
November1st to 15thNight
3313323447%62%
2470
16th to endNight
4423324346%61%
2564
December1st to 15thNight
36%24323447%57%
2730
16th to endNight
38%35%423447%51%
2912

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
24%312%30%22%5%
1553
16th to endDay
24%39%31%23%7%
1810
February1st to 15thDay
30%412%33%13%4
1784
16th to endDay
25%48%29%25%7%
1710
March1st to 15thDay
26%311%23%24%10%
1916
16th to endDay
30%6%14%22%20%6%
2221
April1st to 15thDay
30%5%12%24%20%7%
2150
16th to endDay
34%7%12%22%18%4
2160
May1st to 15thDay
36%8%12%23%16%3
2332
16th to endDay
31%8%17%24%13%5%
2620
June1st to 15thDay
26%7%15%20%19%10%
2520
16th to endDay
19%5%10%23%29%11%
2520
July1st to 15thDay
28%6%12%22%17%12%
2371
16th to endDay
27%6%13%26%17%7%
2489
August1st to 15thDay
27%7%15%22%16%10%
2240
16th to endDay
23%6%12%22%26%9%
2292
September1st to 15thDay
23%410%21%23%15%
2160
16th to endDay
20%38%21%35%10%
2007
October1st to 15thDay
23%410%22%27%11%
1842
16th to endDay
20%37%27%26%13%
1851
November1st to 15thDay
22%49%25%25%12%
1718
16th to endDay
21%27%23%32%11%
1722
December1st to 15thDay
26%5%10%31%20%5%
1560
16th to endDay
30%414%25%19%6%
1664
January1st to 15thNight
24%411%28%24%5%
2716
16th to endNight
27%38%26%26%8%
2776
February1st to 15thNight
30%6%13%28%16%3
2407
16th to endNight
28%48%26%22%9%
2050
March1st to 15thNight
26%411%24%25%8%
2277
16th to endNight
29%5%12%21%24%5%
2002
April1st to 15thNight
33%5%11%24%17%7%
1798
16th to endNight
37%6%12%23%15%5%
1800
May1st to 15thNight
37%7%14%23%12%4
1617
16th to endNight
30%8%20%21%12%6%
1498
June1st to 15thNight
23%8%19%24%13%10%
1440
16th to endNight
18%7%13%26%24%9%
1440
July1st to 15thNight
30%9%16%20%14%8%
1360
16th to endNight
28%7%17%23%19%4
1416
August1st to 15thNight
29%9%18%21%14%6%
1692
16th to endNight
24%7%12%25%22%7%
1910
September1st to 15thNight
27%413%21%20%12%
1800
16th to endNight
21%410%26%28%8%
1953
October1st to 15thNight
27%5%11%20%24%11%
2115
16th to endNight
22%48%24%28%12%
2361
November1st to 15thNight
20%39%24%27%14%
2470
16th to endNight
23%38%24%29%10%
2564
December1st to 15thNight
26%413%28%19%7%
2730
16th to endNight
31%413%25%21%3
2912

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
7%5%16%48%20%2
135
16th to endDay
6%232%38%15%4
144
February1st to 15thDay
48%45%32%8%
135
16th to endDay
15%46%30%13%1
120
March1st to 15thDay
310%29%42%13%
133
16th to endDay
14%19%32%22%9%1
288
April1st to 15thDay
12%15%34%26%8%3
269
16th to endDay
22%19%31%17%8%1
270
May1st to 15thDay
14%9%26%28%16%3
450
16th to endDay
12%8%26%30%17%5%
517
June1st to 15thDay
7%6%21%32%22%8%
495
16th to endDay
4323%32%27%8%
495
July1st to 15thDay
9%217%28%31%11%
475
16th to endDay
4113%30%35%13%
515
August1st to 15thDay
7%225%30%23%11%
318
16th to endDay
5%320%37%23%9%
332
September1st to 15thDay
9%426%26%20%13%
315
16th to endDay
9%423%27%21%13%
162
October1st to 15thDay
9%221%25%25%14%
135
16th to endDay
7%325%31%24%7%
144
November1st to 15thDay
1322%39%24%8%
135
16th to endDay
8%5%31%41%11%
135
December1st to 15thDay
7%11%34%34%11%
135
16th to endDay
2333%46%12%1
144
January1st to 15thNight
4332%43%13%2
975
16th to endNight
6%334%43%10%1
904
February1st to 15thNight
6%337%44%7%
764
16th to endNight
6%7%39%39%6%
684
March1st to 15thNight
5%437%40%10%
764
16th to endNight
9%7%35%38%8%
658
April1st to 15thNight
10%8%43%31%5%
539
16th to endNight
16%6%31%36%8%
540
May1st to 15thNight
15%430%37%11%
540
16th to endNight
9%233%36%16%
563
June1st to 15thNight
6%227%43%18%1
540
16th to endNight
3123%50%20%
540
July1st to 15thNight
6%117%43%29%2
510
16th to endNight
5%14%46%29%2
564
August1st to 15thNight
5%117%48%25%1
539
16th to endNight
6%17%50%22%2
573
September1st to 15thNight
8%19%49%18%4
540
16th to endNight
6%221%45%22%1
537
October1st to 15thNight
12%329%36%16%2
675
16th to endNight
7%322%42%20%2
825
November1st to 15thNight
4330%44%14%2
950
16th to endNight
6%428%44%13%1
975
December1st to 15thNight
5%435%42%11%
975
16th to endNight
7%5%34%40%11%1
1040
Page generated at 2018-03-12 11:28:02. Version ac04

Copyright 2018 A. Danko


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