Halfmoon Stream Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Halfmoon Stream Observatory clear sky chart from 2005-11-06 to 2024-01-17.

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
23%
23043
18%
74859
6%
22994
36%
22994
18%
49344

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 10thNight
16%
760
18%
2649
5%
757
33%
757
14%
1700
January11th to 20thNight
14%
748
15%
2616
3%
748
30%
748
10%
1821
January21st to endNight
14%
792
20%
2768
4%
792
33%
792
14%
1753
February1st to 10thNight
15%
720
16%
2340
5%
720
29%
720
13%
1609
February11th to 20thNight
11%
702
19%
2153
2%
700
31%
700
14%
1451
February21st to endNight
14%
592
22%
1776
5%
592
36%
592
16%
1188
March1st to 10thNight
12%
720
21%
2160
4%
720
31%
720
15%
1486
March11th to 20thNight
17%
720
17%
1986
5%
720
30%
720
16%
1402
March21st to endNight
19%
792
21%
2170
6%
792
32%
792
19%
1487
April1st to 10thNight
14%
720
17%
1800
3%
720
24%
720
17%
1329
April11th to 20thNight
18%
574
19%
1638
4%
574
29%
574
18%
1103
April21st to endNight
20%
540
14%
1620
4%
540
28%
540
16%
1154
May1st to 10thNight
21%
540
14%
1620
5%
540
30%
540
17%
1147
May11th to 20thNight
19%
532
15%
1594
5%
532
31%
532
17%
1127
May21st to endNight
27%
402
13%
1540
9%
401
39%
401
16%
1017
June1st to 10thNight
27%
360
13%
1260
8%
360
38%
360
15%
873
June11th to 20thNight
34%
360
14%
1260
13%
360
42%
360
21%
800
June21st to endNight
29%
360
10%
1260
7%
360
36%
360
17%
867
July1st to 10thNight
37%
350
12%
1383
11%
350
47%
350
21%
850
July11th to 20thNight
39%
348
14%
1392
16%
348
46%
348
22%
843
July21st to endNight
39%
394
15%
1486
12%
372
49%
372
20%
926
August1st to 10thNight
41%
533
13%
1596
8%
530
46%
530
27%
1027
August11th to 20thNight
38%
532
17%
1596
10%
532
43%
532
26%
1033
August21st to endNight
41%
628
23%
1816
12%
628
47%
628
31%
1124
September1st to 10thNight
37%
720
20%
1872
7%
720
46%
720
36%
1145
September11th to 20thNight
37%
720
24%
1980
12%
720
46%
720
34%
1177
September21st to endNight
33%
720
25%
1980
11%
720
44%
720
28%
1242
October1st to 10thNight
31%
720
20%
2010
9%
720
41%
720
24%
1344
October11th to 20thNight
28%
720
22%
2194
9%
720
42%
720
23%
1401
October21st to endNight
19%
792
16%
2574
5%
792
31%
792
15%
1748
November1st to 10thNight
24%
740
22%
2407
9%
740
40%
740
20%
1531
November11th to 20thNight
23%
760
25%
2470
10%
760
42%
760
18%
1569
November21st to endNight
18%
842
18%
2642
4%
842
34%
842
16%
1710
December1st to 10thNight
14%
850
18%
2791
4%
850
29%
850
14%
1935
December11th to 20thNight
14%
850
17%
3431
3%
849
31%
849
11%
2258
December21st to endNight
11%
890
13%
5029
2%
873
28%
873
7%
3167

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
18%8%36%5%3445%7%37%
74607
Night
18%8%36%5%3445%7%38%
75210
TransparencyDay
47%411%23%14%2
74313
Night
47%311%23%14%2
75039
SeeingDay
24%19%32%18%6%1
14458
Night
23%16%33%22%6%1
23053

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 10thDay
15%9%47%6%34446%38%
1517
11th to 20thDay
20%9%36%5%2445%6%36%
1488
21st to endDay
12%12%37%6%245%46%40%
1585
February1st to 10thDay
18%10%35%5%36%45%6%34%
1620
11th to 20thDay
14%9%47%7%45%45%6%36%
1693
21st to endDay
14%10%48%6%35%5%5%6%34%
1480
March1st to 10thDay
17%10%46%6%35%445%36%
1797
11th to 20thDay
17%8%35%5%34345%41%
1971
21st to endDay
18%9%36%5%2445%5%38%
2182
April1st to 10thDay
21%11%37%5%34445%32%
2160
11th to 20thDay
18%9%25%6%345%5%7%36%
2269
21st to endDay
24%9%46%5%34446%31%
2340
May1st to 10thDay
24%8%36%5%25%45%6%33%
2340
11th to 20thDay
21%8%37%5%34446%36%
2301
21st to endDay
18%7%35%5%345%6%9%36%
2747
June1st to 10thDay
24%7%35%6%35%45%8%31%
2700
11th to 20thDay
20%6%35%5%35%46%7%36%
2700
21st to endDay
24%8%35%5%35%6%6%7%29%
2700
July1st to 10thDay
15%6%25%5%35%6%6%9%38%
2532
11th to 20thDay
14%5%36%6%5%5%5%6%9%37%
2520
21st to endDay
15%5%36%5%35%6%6%10%35%
2731
August1st to 10thDay
14%6%35%5%36%5%6%10%37%
2327
11th to 20thDay
14%7%26%6%445%7%10%36%
2304
21st to endDay
13%6%345%35%5%5%8%44%
2538
September1st to 10thDay
12%5%25%43446%7%48%
2088
11th to 20thDay
13%4245%34346%53%
1980
21st to endDay
16%6%245%2345%8%45%
1980
October1st to 10thDay
17%7%35%6%35%45%6%40%
1949
11th to 20thDay
19%6%25%6%34348%40%
1764
21st to endDay
21%10%36%5%2435%6%35%
1782
November1st to 10thDay
17%8%25%435%447%41%
1671
11th to 20thDay
20%7%2442445%6%41%
1710
21st to endDay
19%9%25%424435%42%
1535
December1st to 10thDay
20%12%45%6%34446%34%
1387
11th to 20thDay
22%8%36%424346%37%
1668
21st to endDay
25%11%35%425%45%5%31%
2551
January1st to 10thNight
16%9%45%5%35%45%6%37%
2649
11th to 20thNight
16%12%47%6%3445%6%32%
2616
21st to endNight
12%8%46%6%45%5%5%7%38%
2768
February1st to 10thNight
16%8%5%6%6%46%5%5%6%32%
2340
11th to 20thNight
13%8%5%8%7%4445%5%37%
2151
21st to endNight
13%11%47%6%34446%39%
1776
March1st to 10thNight
15%13%37%5%35%45%5%37%
2150
11th to 20thNight
16%9%46%6%45%45%6%34%
1985
21st to endNight
18%8%26%6%34445%39%
2170
April1st to 10thNight
21%10%46%5%25%45%5%33%
1800
11th to 20thNight
18%6%36%5%35%5%6%7%35%
1638
21st to endNight
23%9%36%5%3445%6%32%
1620
May1st to 10thNight
21%10%46%5%3445%9%29%
1620
11th to 20thNight
21%6%36%6%46%5%6%8%30%
1593
21st to endNight
18%8%346%45%35%8%35%
1539
June1st to 10thNight
22%8%37%5%45%46%8%30%
1260
11th to 20thNight
16%7%35%5%35%45%9%39%
1260
21st to endNight
22%8%36%5%345%5%8%31%
1260
July1st to 10thNight
15%7%26%5%45%6%6%9%36%
1423
11th to 20thNight
14%6%26%6%445%6%9%38%
1440
21st to endNight
16%6%35%6%36%5%5%8%38%
1574
August1st to 10thNight
12%5%25%6%35%6%5%8%41%
1607
11th to 20thNight
13%7%35%5%36%5%7%8%37%
1596
21st to endNight
13%425%5%3445%7%48%
1816
September1st to 10thNight
13%5%2442445%7%50%
1872
11th to 20thNight
15%6%23323347%52%
1980
21st to endNight
15%7%34434347%46%
1980
October1st to 10thNight
19%5%26%5%35%5%5%6%40%
2010
11th to 20thNight
18%6%25%5%3445%7%42%
2194
21st to endNight
23%9%25%5%34445%35%
2574
November1st to 10thNight
18%7%35%5%2345%6%42%
2407
11th to 20thNight
18%6%35%5%3445%8%40%
2470
21st to endNight
17%8%35%5%34447%40%
2642
December1st to 10thNight
21%10%36%5%3445%5%34%
2791
11th to 20thNight
22%9%345%34345%38%
3531
21st to endNight
24%10%35%423446%35%
5108

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 10thDay
48%29%23%15%1
1518
11th to 20thDay
49%5%11%21%12%2
1488
21st to endDay
45%39%24%17%2
1585
February1st to 10thDay
51%310%20%14%2
1620
11th to 20thDay
50%410%20%14%2
1702
21st to endDay
51%39%20%11%5%
1480
March1st to 10thDay
51%310%18%15%4
1800
11th to 20thDay
45%39%21%17%5%
1971
21st to endDay
48%37%19%17%5%
2182
April1st to 10thDay
54%37%16%15%4
2160
11th to 20thDay
47%39%23%16%2
2269
21st to endDay
55%37%18%13%4
2340
May1st to 10thDay
52%36%21%14%3
2340
11th to 20thDay
51%37%21%16%2
2305
21st to endDay
46%5%15%21%11%2
2747
June1st to 10thDay
53%411%22%9%1
2700
11th to 20thDay
46%411%20%16%2
2700
21st to endDay
54%5%12%18%9%1
2700
July1st to 10thDay
42%5%14%26%12%
2462
11th to 20thDay
44%413%26%11%1
2445
21st to endDay
44%5%13%25%11%1
2578
August1st to 10thDay
42%5%16%29%9%
2314
11th to 20thDay
44%6%14%24%12%
2304
21st to endDay
38%5%12%27%18%1
2538
September1st to 10thDay
35%415%28%17%1
2088
11th to 20thDay
34%39%30%22%3
1980
21st to endDay
39%310%29%17%1
1980
October1st to 10thDay
46%39%25%15%2
1949
11th to 20thDay
45%213%28%11%1
1764
21st to endDay
51%39%21%14%1
1782
November1st to 10thDay
44%313%23%15%2
1671
11th to 20thDay
43%49%23%18%3
1710
21st to endDay
45%315%24%12%1
1535
December1st to 10thDay
53%49%22%11%1
1387
11th to 20thDay
50%28%22%14%4
1668
21st to endDay
56%310%20%9%2
2551
January1st to 10thNight
47%311%24%13%2
2649
11th to 20thNight
53%5%12%18%10%2
2616
21st to endNight
45%48%24%17%2
2768
February1st to 10thNight
51%411%19%13%2
2340
11th to 20thNight
49%38%22%16%2
2153
21st to endNight
47%39%20%16%4
1776
March1st to 10thNight
50%37%21%16%3
2160
11th to 20thNight
50%310%17%16%4
1986
21st to endNight
47%37%20%19%4
2170
April1st to 10thNight
53%36%17%17%3
1800
11th to 20thNight
48%38%23%17%1
1638
21st to endNight
53%311%17%13%3
1620
May1st to 10thNight
53%38%20%14%2
1620
11th to 20thNight
52%48%21%12%3
1594
21st to endNight
49%412%22%12%1
1540
June1st to 10thNight
53%411%23%9%1
1260
11th to 20thNight
46%313%24%12%2
1260
21st to endNight
52%413%20%9%2
1260
July1st to 10thNight
43%5%16%24%11%1
1383
11th to 20thNight
43%416%27%10%
1392
21st to endNight
45%415%25%9%1
1486
August1st to 10thNight
40%6%16%28%9%
1596
11th to 20thNight
43%5%18%22%12%
1596
21st to endNight
37%411%28%18%1
1816
September1st to 10thNight
34%414%32%15%1
1872
11th to 20thNight
34%311%30%20%2
1980
21st to endNight
39%39%31%16%2
1980
October1st to 10thNight
45%310%26%14%1
2010
11th to 20thNight
43%312%30%12%1
2194
21st to endNight
50%311%21%13%1
2574
November1st to 10thNight
43%5%10%26%16%1
2407
11th to 20thNight
43%49%25%17%2
2470
21st to endNight
44%414%21%16%2
2642
December1st to 10thNight
53%39%23%12%1
2791
11th to 20thNight
49%39%21%17%1
3532
21st to endNight
52%212%20%12%1
5108

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 10thDay
30%24%28%14%3
180
11th to 20thDay
31%25%29%10%31
172
21st to endDay
21%29%34%14%2
177
February1st to 10thDay
26%24%31%16%3
340
11th to 20thDay
27%30%31%10%2
392
21st to endDay
23%28%31%14%4
346
March1st to 10thDay
26%28%33%12%1
420
11th to 20thDay
22%31%31%12%31
420
21st to endDay
29%25%26%14%5%1
462
April1st to 10thDay
34%25%26%10%31
420
11th to 20thDay
30%26%26%12%5%1
412
21st to endDay
30%21%31%12%5%1
420
May1st to 10thDay
30%21%33%13%31
423
11th to 20thDay
21%22%36%15%42
447
21st to endDay
21%21%35%18%5%
507
June1st to 10thDay
25%15%33%19%7%1
630
11th to 20thDay
22%14%33%20%10%1
630
21st to endDay
27%11%30%23%7%1
630
July1st to 10thDay
20%12%37%22%8%1
457
11th to 20thDay
20%8%39%21%9%3
444
21st to endDay
16%9%38%26%9%2
488
August1st to 10thDay
16%9%37%28%8%1
446
11th to 20thDay
18%10%30%29%10%2
439
21st to endDay
18%12%31%28%9%2
495
September1st to 10thDay
14%12%34%27%11%2
450
11th to 20thDay
20%13%32%19%11%5%
450
21st to endDay
20%16%32%19%8%5%
450
October1st to 10thDay
20%17%28%23%9%3
435
11th to 20thDay
23%18%33%16%8%3
360
21st to endDay
32%15%34%14%41
396
November1st to 10thDay
23%19%29%21%6%2
365
11th to 20thDay
28%21%31%18%31
370
21st to endDay
27%24%27%17%5%
370
December1st to 10thDay
29%23%30%15%3
237
11th to 20thDay
35%28%27%8%2
180
21st to endDay
32%29%23%14%2
198
January1st to 10thNight
23%23%35%17%3
760
11th to 20thNight
26%23%30%17%3
748
21st to endNight
17%26%35%19%3
792
February1st to 10thNight
23%23%35%18%2
720
11th to 20thNight
23%24%36%14%2
703
21st to endNight
23%24%33%17%3
592
March1st to 10thNight
24%21%38%14%2
720
11th to 20thNight
23%24%32%16%5%
720
21st to endNight
23%20%32%19%5%
792
April1st to 10thNight
29%18%34%16%3
720
11th to 20thNight
24%18%35%19%4
574
21st to endNight
31%16%29%20%4
540
May1st to 10thNight
26%12%33%25%4
540
11th to 20thNight
25%13%39%19%4
532
21st to endNight
24%9%34%28%6%
402
June1st to 10thNight
28%9%31%28%5%
360
11th to 20thNight
19%9%32%31%9%
360
21st to endNight
26%433%32%5%
360
July1st to 10thNight
18%5%33%37%7%
350
11th to 20thNight
17%332%36%11%1
348
21st to endNight
18%333%34%11%1
394
August1st to 10thNight
14%335%38%9%
533
11th to 20thNight
16%5%32%34%12%1
532
21st to endNight
16%7%30%35%11%1
628
September1st to 10thNight
16%7%36%31%10%1
720
11th to 20thNight
19%10%28%26%13%4
720
21st to endNight
21%10%33%25%11%2
720
October1st to 10thNight
22%10%31%25%12%
720
11th to 20thNight
22%13%33%23%8%1
720
21st to endNight
30%16%32%18%4
792
November1st to 10thNight
24%17%30%22%6%1
740
11th to 20thNight
21%19%32%21%6%1
760
21st to endNight
24%24%29%19%4
842
December1st to 10thNight
27%20%33%15%5%
850
11th to 20thNight
26%24%32%16%3
850
21st to endNight
30%22%31%15%2
899
Page generated at 2024-01-14 09:55:01. Version ac07

Copyright 2024 Attilla Danko


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