Starry Zvezdachyot Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Starry Zvezdachyot Observatory 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
76%
15603
36%
46962
33%
15565
81%
15565
55%
22073

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
72%
718
33%
2327
34%
716
77%
716
50%
1082
January16th to endNight
68%
768
35%
2496
35%
768
75%
768
42%
1272
February1st to 15thNight
74%
699
36%
2202
37%
699
79%
699
53%
1019
February16th to endNight
65%
632
38%
1840
35%
632
71%
632
51%
931
March1st to 15thNight
69%
720
39%
1980
32%
720
76%
720
58%
961
March16th to endNight
75%
768
39%
2112
29%
768
82%
768
63%
995
April1st to 15thNight
71%
687
35%
1946
27%
687
77%
687
58%
922
April16th to endNight
73%
540
46%
1776
41%
540
83%
540
72%
654
May1st to 15thNight
75%
539
41%
1619
32%
539
83%
539
73%
641
May16th to endNight
77%
561
42%
1684
35%
561
81%
561
74%
659
June1st to 15thNight
83%
540
35%
1620
30%
540
84%
540
71%
666
June16th to endNight
86%
540
33%
1620
29%
540
86%
540
65%
697
July1st to 15thNight
84%
510
22%
1530
19%
510
84%
510
43%
810
July16th to endNight
81%
564
19%
1593
16%
531
81%
531
35%
937
August1st to 15thNight
86%
539
26%
1611
24%
536
86%
536
46%
831
August16th to endNight
85%
603
32%
1875
32%
603
85%
603
44%
983
September1st to 15thNight
79%
720
31%
1980
27%
720
80%
720
46%
1112
September16th to endNight
82%
683
44%
1890
34%
683
86%
683
67%
861
October1st to 15thNight
79%
660
41%
1914
35%
660
84%
660
66%
853
October16th to endNight
86%
704
44%
2112
40%
704
89%
704
69%
893
November1st to 15thNight
81%
700
43%
2100
39%
700
85%
700
68%
889
November16th to endNight
75%
720
39%
2299
38%
720
79%
720
53%
1056
December1st to 15thNight
73%
720
38%
2340
40%
720
77%
720
51%
1073
December16th to endNight
67%
768
35%
2496
35%
768
72%
768
42%
1276

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
4212323346%65%
47917
Night
4212213346%67%
47158
TransparencyDay
19%25%11%24%36%
47612
Night
18%25%13%25%35%
46964
SeeingDay
6%7%21%34%22%7%
5434
Night
4111%39%36%6%
15613

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
5%213312336%65%
1611
16th to endDay
8%323313346%61%
1728
February1st to 15thDay
6%312222235%67%
1658
16th to endDay
8%213323237%60%
1633
March1st to 15thDay
5%23213336%66%
1980
16th to endDay
311221233473%
2112
April1st to 15thDay
3211212346%71%
2000
16th to endDay
21111122481%
2181
May1st to 15thDay
11121222478%
2331
16th to endDay
1111212382%
2429
June1st to 15thDay
22111123479%
2340
16th to endDay
111312346%73%
2340
July1st to 15thDay
32236%37%7%8%9%45%
2340
16th to endDay
6%436%7%47%7%10%11%30%
2467
August1st to 15thDay
4325%6%37%6%7%8%44%
2340
16th to endDay
32145%45%6%7%8%49%
2323
September1st to 15thDay
5%223436%5%6%8%51%
1980
16th to endDay
32221333472%
1882
October1st to 15thDay
211212335%73%
1716
16th to endDay
111212225%77%
1760
November1st to 15thDay
121112245%75%
1759
16th to endDay
423212335%69%
1659
December1st to 15thDay
8%212322346%62%
1620
16th to endDay
7%313313346%61%
1728
January1st to 15thNight
6%312313335%66%
2327
16th to endNight
8%214324445%58%
2496
February1st to 15thNight
5%313213335%66%
2191
16th to endNight
7%312213446%60%
1840
March1st to 15thNight
6%211213345%68%
1980
16th to endNight
2212312235%73%
2112
April1st to 15thNight
3112213335%68%
1946
16th to endNight
211112385%
1776
May1st to 15thNight
1212245%78%
1619
16th to endNight
1111111384%
1684
June1st to 15thNight
11111221479%
1620
16th to endNight
111221223476%
1620
July1st to 15thNight
2213445%6%8%11%49%
1620
16th to endNight
32246%37%7%9%15%36%
1701
August1st to 15thNight
1213335%6%7%10%54%
1620
16th to endNight
22134346%7%10%51%
1875
September1st to 15thNight
331443345%8%55%
1980
16th to endNight
22121233475%
1890
October1st to 15thNight
11221323475%
1914
16th to endNight
11121222379%
2112
November1st to 15thNight
1212112325%75%
2100
16th to endNight
6%212222335%67%
2299
December1st to 15thNight
8%212212346%64%
2340
16th to endNight
8%414423335%58%
2496

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
20%2413%27%31%
1612
16th to endDay
25%2315%24%29%
1728
February1st to 15thDay
19%1312%27%33%
1658
16th to endDay
23%1313%30%27%
1633
March1st to 15thDay
18%127%31%38%
1980
16th to endDay
15%138%30%41%
2112
April1st to 15thDay
13%116%37%39%
2000
16th to endDay
9%27%24%56%
2181
May1st to 15thDay
10%126%22%57%
2331
16th to endDay
8%27%23%57%
2432
June1st to 15thDay
10%1319%65%
2340
16th to endDay
12%235%16%59%
2340
July1st to 15thDay
27%7%12%15%16%20%
2201
16th to endDay
40%8%16%20%11%2
2312
August1st to 15thDay
32%6%10%15%19%15%
2325
16th to endDay
28%6%10%18%19%17%
2323
September1st to 15thDay
28%5%6%19%18%21%
1980
16th to endDay
15%228%33%38%
1882
October1st to 15thDay
13%1411%24%43%
1716
16th to endDay
11%38%26%48%
1760
November1st to 15thDay
10%211%33%40%
1759
16th to endDay
17%139%28%39%
1659
December1st to 15thDay
21%1416%31%24%
1620
16th to endDay
23%15%20%31%17%
1728
January1st to 15thNight
20%2413%27%30%
2327
16th to endNight
26%2315%27%24%
2496
February1st to 15thNight
19%1415%25%33%
2202
16th to endNight
22%1413%31%26%
1840
March1st to 15thNight
18%1310%26%41%
1980
16th to endNight
15%1210%31%38%
2112
April1st to 15thNight
17%128%34%36%
1946
16th to endNight
8%16%26%56%
1776
May1st to 15thNight
8%138%26%52%
1620
16th to endNight
8%16%23%59%
1685
June1st to 15thNight
10%11420%62%
1620
16th to endNight
12%13416%61%
1620
July1st to 15thNight
22%7%15%17%16%20%
1530
16th to endNight
28%9%23%23%11%3
1593
August1st to 15thNight
20%6%15%22%17%17%
1611
16th to endNight
23%5%13%20%18%17%
1875
September1st to 15thNight
24%5%8%22%20%18%
1980
16th to endNight
12%2211%33%38%
1890
October1st to 15thNight
13%1314%25%41%
1914
16th to endNight
11%1211%23%49%
2112
November1st to 15thNight
12%1212%32%38%
2100
16th to endNight
19%1311%23%40%
2299
December1st to 15thNight
20%1416%30%25%
2340
16th to endNight
27%16%16%28%19%
2496

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
16%217%45%14%3
90
16th to endDay
9%115%37%28%8%
96
February1st to 15thDay
7%9%19%38%23%2
173
16th to endDay
13%14%36%23%10%2
238
March1st to 15thDay
8%14%25%30%13%7%
270
16th to endDay
417%33%22%16%4
288
April1st to 15thDay
8%17%29%26%13%4
269
16th to endDay
5%20%32%27%11%2
270
May1st to 15thDay
415%36%26%11%4
288
16th to endDay
18%35%36%13%2
330
June1st to 15thDay
5%5%28%39%15%5%
315
16th to endDay
3114%47%24%8%
315
July1st to 15thDay
419%43%31%8%
305
16th to endDay
7%19%31%30%20%
327
August1st to 15thDay
7%6%36%34%13%
315
16th to endDay
226%34%39%15%
332
September1st to 15thDay
8%117%37%25%8%
315
16th to endDay
7%423%34%23%5%
280
October1st to 15thDay
19%20%39%20%8%
156
16th to endDay
316%28%51%10%
96
November1st to 15thDay
310%18%35%25%6%
90
16th to endDay
5%6%25%38%22%1
90
December1st to 15thDay
6%15%30%42%5%
90
16th to endDay
19%6%20%33%18%1
96
January1st to 15thNight
8%13%45%27%4
720
16th to endNight
8%213%44%26%4
768
February1st to 15thNight
6%111%46%28%5%
704
16th to endNight
7%218%48%19%2
632
March1st to 15thNight
6%218%41%25%5%
720
16th to endNight
3313%44%31%4
768
April1st to 15thNight
4415%50%22%2
687
16th to endNight
2418%47%24%2
540
May1st to 15thNight
417%44%29%2
540
16th to endNight
2216%43%33%1
563
June1st to 15thNight
2110%46%36%2
540
16th to endNight
16%37%50%3
540
July1st to 15thNight
21322%62%7%
510
16th to endNight
4116%61%15%
564
August1st to 15thNight
315%65%13%
539
16th to endNight
2119%62%12%
603
September1st to 15thNight
45%25%50%12%
720
16th to endNight
39%33%44%9%
683
October1st to 15thNight
2112%42%35%6%
660
16th to endNight
27%41%38%9%
704
November1st to 15thNight
211%42%37%6%
700
16th to endNight
7%111%42%31%5%
720
December1st to 15thNight
8%112%41%30%5%
720
16th to endNight
9%212%47%20%6%
768
Page generated at 2017-09-23 03:43:46. Version ac04

Copyright 2017 A. Danko


Starry Zvezdachyot Observatory Clear Sky Chart | Charts Home