TASS H (Droege) Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the TASS H (Droege) Observatory 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
38%
15972
18%
46855
11%
15931
45%
15931
25%
30850

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
20%
900
15%
2506
4%
895
30%
895
19%
1813
January16th to endNight
21%
960
14%
2647
5%
960
29%
960
17%
1974
February1st to 15thNight
21%
803
14%
2214
4%
803
29%
803
19%
1561
February16th to endNight
26%
631
18%
1893
8%
631
36%
631
19%
1304
March1st to 15thNight
28%
720
14%
2160
8%
720
33%
720
18%
1505
March16th to endNight
30%
615
16%
2010
11%
615
37%
615
19%
1366
April1st to 15thNight
28%
539
16%
1797
10%
539
38%
539
21%
1190
April16th to endNight
33%
540
19%
1743
11%
540
44%
540
23%
1144
May1st to 15thNight
38%
540
17%
1589
8%
540
46%
540
23%
1094
May16th to endNight
49%
561
18%
1498
10%
561
55%
561
33%
951
June1st to 15thNight
52%
540
17%
1440
10%
540
56%
540
37%
888
June16th to endNight
51%
540
17%
1440
9%
540
56%
540
32%
933
July1st to 15thNight
62%
510
18%
1360
12%
510
65%
510
42%
807
July16th to endNight
70%
564
24%
1417
17%
531
74%
531
45%
814
August1st to 15thNight
74%
539
22%
1576
21%
536
76%
536
43%
856
August16th to endNight
68%
573
22%
1910
22%
573
72%
573
36%
1038
September1st to 15thNight
63%
540
29%
1800
30%
540
69%
540
39%
939
September16th to endNight
57%
668
27%
1847
20%
668
61%
668
37%
1098
October1st to 15thNight
48%
660
27%
1906
20%
660
55%
660
34%
1127
October16th to endNight
31%
704
19%
2233
11%
704
41%
704
22%
1443
November1st to 15thNight
33%
700
24%
2276
16%
700
45%
700
25%
1386
November16th to endNight
27%
765
17%
2385
9%
765
36%
765
19%
1607
December1st to 15thNight
23%
900
13%
2520
5%
900
30%
900
18%
1854
December16th to endNight
17%
960
12%
2688
3%
960
25%
960
12%
2158

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
13%7%36%5%35%45%7%36%
47948
Night
14%7%35%42445%6%40%
47023
Cloud CoverDay
14%7%35%5%3445%7%36%
47957
Night
14%7%35%424446%40%
47028
TransparencyDay
46%412%22%12%1
47634
Night
44%311%23%14%2
46855
SeeingDay
15%9%26%26%15%6%
5980
Night
18%8%28%30%12%1
15977

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
15%12%47%7%3445%6%27%
1432
16th to endDay
14%14%5%11%6%24445%26%
1575
February1st to 15thDay
14%12%6%7%5%36%435%28%
1647
16th to endDay
16%10%47%5%24346%32%
1580
March1st to 15thDay
17%11%46%6%34446%30%
1790
16th to endDay
17%9%37%6%35%446%30%
2223
April1st to 15thDay
18%10%5%6%5%24445%31%
2151
16th to endDay
20%8%245%3445%7%34%
2217
May1st to 15thDay
18%8%36%6%45%5%5%7%29%
2361
16th to endDay
13%6%25%5%45%46%7%38%
2617
June1st to 15thDay
11%5%245%3445%7%43%
2520
16th to endDay
10%425%5%36%6%7%8%37%
2520
July1st to 15thDay
7%324436%6%6%8%45%
2520
16th to endDay
6%435%6%36%5%7%9%41%
2655
August1st to 15thDay
7%426%5%35%5%8%8%41%
2372
16th to endDay
10%4145%35%47%9%42%
2292
September1st to 15thDay
12%32342445%7%48%
2148
16th to endDay
8%6%25%5%335%5%8%44%
1837
October1st to 15thDay
13%7%245%2245%6%43%
1722
16th to endDay
18%7%36%42345%6%36%
1639
November1st to 15thDay
13%9%35%423445%41%
1582
16th to endDay
17%9%47%424346%35%
1572
December1st to 15thDay
17%11%5%9%5%35%425%29%
1440
16th to endDay
22%13%5%9%5%24345%23%
1536
January1st to 15thNight
16%11%48%5%23445%34%
2506
16th to endNight
13%11%7%9%6%24346%29%
2647
February1st to 15thNight
14%13%5%6%423345%35%
2212
16th to endNight
15%10%38%424446%34%
1893
March1st to 15thNight
16%9%45%5%34345%36%
2147
16th to endNight
16%8%45%6%245%5%7%33%
2010
April1st to 15thNight
17%7%36%5%3345%5%36%
1797
16th to endNight
18%7%36%324347%39%
1743
May1st to 15thNight
18%5%15%426%6%5%7%35%
1589
16th to endNight
10%425%43446%9%45%
1496
June1st to 15thNight
10%5%2442435%7%49%
1440
16th to endNight
8%5%24345%5%7%9%41%
1440
July1st to 15thNight
6%345%25%46%8%51%
1440
16th to endNight
5%3134246%7%10%50%
1513
August1st to 15thNight
331344446%9%53%
1585
16th to endNight
9%31432435%8%52%
1910
September1st to 15thNight
10%323313346%57%
1800
16th to endNight
8%4145%2345%8%49%
1847
October1st to 15thNight
12%423423436%50%
1906
16th to endNight
20%7%24423335%41%
2233
November1st to 15thNight
13%7%24424335%46%
2276
16th to endNight
18%8%36%423345%37%
2385
December1st to 15thNight
21%9%37%5%33346%31%
2520
16th to endNight
24%13%5%7%6%2434422%
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
15%12%48%6%35%45%6%26%
1432
16th to endDay
14%15%6%9%6%24435%26%
1575
February1st to 15thDay
15%13%7%6%5%36%435%28%
1647
16th to endDay
16%11%46%6%24346%33%
1580
March1st to 15thDay
17%12%46%6%33445%30%
1800
16th to endDay
17%9%47%5%35%446%30%
2222
April1st to 15thDay
19%10%46%6%24445%31%
2151
16th to endDay
20%8%245%33347%34%
2217
May1st to 15thDay
19%8%36%6%36%45%7%29%
2361
16th to endDay
14%5%25%5%35%5%6%7%38%
2617
June1st to 15thDay
12%425%5%3446%6%43%
2520
16th to endDay
10%5%25%6%36%6%8%8%36%
2520
July1st to 15thDay
8%3245%25%6%7%8%44%
2520
16th to endDay
7%425%6%36%6%6%9%41%
2655
August1st to 15thDay
8%425%5%35%6%7%9%41%
2372
16th to endDay
10%4245%346%6%9%41%
2292
September1st to 15thDay
12%32343445%6%48%
2148
16th to endDay
9%5%25%4345%5%8%45%
1837
October1st to 15thDay
14%6%245%23447%43%
1722
16th to endDay
18%7%35%4235%47%37%
1639
November1st to 15thDay
13%10%34423445%41%
1582
16th to endDay
17%9%47%423345%35%
1572
December1st to 15thDay
18%11%48%5%35%325%29%
1440
16th to endDay
22%14%5%7%5%24435%23%
1536
January1st to 15thNight
16%11%47%5%23445%34%
2506
16th to endNight
13%11%8%8%6%24446%29%
2647
February1st to 15thNight
14%13%45%5%14345%36%
2205
16th to endNight
16%10%37%5%24447%34%
1893
March1st to 15thNight
17%9%46%5%35%335%36%
2160
16th to endNight
17%8%36%5%2445%7%33%
2010
April1st to 15thNight
17%7%36%5%2445%6%36%
1797
16th to endNight
18%7%35%42335%6%39%
1743
May1st to 15thNight
18%5%25%435%5%5%7%35%
1588
16th to endNight
10%415%43446%8%45%
1496
June1st to 15thNight
11%42443345%7%49%
1440
16th to endNight
9%4245%36%6%6%9%41%
1440
July1st to 15thNight
6%3145%2446%8%52%
1440
16th to endNight
43233347%7%9%50%
1513
August1st to 15thNight
42145%2446%9%53%
1585
16th to endNight
9%3143335%49%52%
1910
September1st to 15thNight
10%31332335%7%56%
1800
16th to endNight
9%41442446%7%50%
1847
October1st to 15thNight
13%323423346%50%
1906
16th to endNight
20%7%25%423335%41%
2233
November1st to 15thNight
14%7%34424345%46%
2276
16th to endNight
19%8%45%5%23345%37%
2385
December1st to 15thNight
21%9%37%5%23336%30%
2520
16th to endNight
24%14%47%6%3433422%
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
58%413%15%8%
1433
16th to endDay
60%311%16%7%
1575
February1st to 15thDay
57%410%17%8%1
1649
16th to endDay
52%412%21%7%1
1580
March1st to 15thDay
54%413%20%6%
1800
16th to endDay
54%413%20%5%1
2223
April1st to 15thDay
54%39%21%10%
2151
16th to endDay
49%412%18%11%3
2217
May1st to 15thDay
53%412%22%6%
2361
16th to endDay
43%5%12%21%15%1
2621
June1st to 15thDay
39%311%26%17%1
2520
16th to endDay
40%7%12%22%15%2
2520
July1st to 15thDay
34%6%13%27%15%2
2371
16th to endDay
35%6%16%23%14%3
2488
August1st to 15thDay
36%413%28%14%1
2357
16th to endDay
36%5%11%25%16%2
2292
September1st to 15thDay
35%39%26%19%4
2148
16th to endDay
36%49%29%18%1
1837
October1st to 15thDay
39%410%28%14%1
1722
16th to endDay
47%213%23%9%2
1639
November1st to 15thDay
44%310%24%15%2
1582
16th to endDay
51%313%24%7%
1572
December1st to 15thDay
59%213%17%7%
1440
16th to endDay
63%410%13%7%
1536
January1st to 15thNight
52%311%20%10%
2506
16th to endNight
56%313%16%9%
2647
February1st to 15thNight
51%312%21%10%
2214
16th to endNight
49%411%23%9%1
1893
March1st to 15thNight
51%312%19%10%2
2160
16th to endNight
49%413%21%9%1
2010
April1st to 15thNight
47%310%22%13%1
1797
16th to endNight
46%310%23%12%4
1743
May1st to 15thNight
46%411%25%10%
1589
16th to endNight
35%6%15%21%18%3
1498
June1st to 15thNight
34%312%26%19%3
1440
16th to endNight
36%6%13%22%18%2
1440
July1st to 15thNight
29%412%30%19%2
1360
16th to endNight
24%6%15%28%19%4
1417
August1st to 15thNight
25%415%32%19%1
1576
16th to endNight
29%5%13%29%18%5%
1910
September1st to 15thNight
28%210%28%26%3
1800
16th to endNight
31%410%32%17%2
1847
October1st to 15thNight
34%39%29%21%1
1906
16th to endNight
46%210%26%13%1
2233
November1st to 15thNight
40%38%25%18%4
2276
16th to endNight
48%313%22%11%
2385
December1st to 15thNight
55%211%20%8%
2520
16th to endNight
66%29%14%6%
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
24%13%38%18%4
90
16th to endDay
18%12%37%22%7%1
96
February1st to 15thDay
21%25%38%13%1
90
16th to endDay
27%8%39%12%9%2
81
March1st to 15thDay
40%20%21%14%31
90
16th to endDay
31%10%27%19%9%1
237
April1st to 15thDay
23%12%30%22%10%1
270
16th to endDay
21%11%24%27%9%5%
270
May1st to 15thDay
22%10%32%20%10%3
318
16th to endDay
17%11%30%23%13%4
517
June1st to 15thDay
12%7%28%30%15%4
495
16th to endDay
12%9%32%27%12%5%
495
July1st to 15thDay
9%428%29%16%11%
475
16th to endDay
7%424%33%19%9%
515
August1st to 15thDay
7%217%35%22%14%
408
16th to endDay
10%315%29%28%12%
332
September1st to 15thDay
9%5%16%33%24%10%
315
16th to endDay
8%7%21%27%27%8%
262
October1st to 15thDay
11%6%24%33%19%4
162
16th to endDay
27%16%32%20%3
96
November1st to 15thDay
11%13%23%36%10%5%
90
16th to endDay
38%7%33%13%6%
90
December1st to 15thDay
20%28%26%16%6%1
90
16th to endDay
29%29%36%32
96
January1st to 15thNight
22%12%37%21%5%
900
16th to endNight
19%11%35%29%3
960
February1st to 15thNight
21%12%35%24%5%
806
16th to endNight
20%12%34%26%6%
631
March1st to 15thNight
22%11%32%25%7%
720
16th to endNight
19%9%34%26%9%
615
April1st to 15thNight
20%10%34%27%6%
539
16th to endNight
21%8%33%26%9%
540
May1st to 15thNight
20%6%28%32%11%
540
16th to endNight
12%5%28%36%18%
563
June1st to 15thNight
12%325%42%14%
540
16th to endNight
10%428%38%17%
540
July1st to 15thNight
8%118%44%24%2
510
16th to endNight
5%115%46%27%3
564
August1st to 15thNight
48%49%30%4
539
16th to endNight
9%114%38%31%4
573
September1st to 15thNight
11%316%35%28%4
540
16th to endNight
10%5%18%34%26%3
668
October1st to 15thNight
14%6%25%33%17%2
660
16th to endNight
23%11%30%25%9%
704
November1st to 15thNight
18%10%33%25%10%1
700
16th to endNight
22%12%32%25%7%
765
December1st to 15thNight
27%11%31%24%5%
900
16th to endNight
31%10%30%23%3
960
Page generated at 2017-09-19 06:32:33. Version ac04

Copyright 2017 A. Danko


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