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 2005-11-05 to 2017-10-31.

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
24%
14987
17%
47366
6%
14955
36%
14955
19%
31441

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
16%
720
19%
2506
5%
716
34%
716
15%
1589
January16th to endNight
13%
768
17%
2685
3%
768
31%
768
12%
1768
February1st to 15thNight
15%
703
15%
2265
4%
701
29%
701
13%
1563
February16th to endNight
15%
631
19%
1893
4%
631
33%
631
17%
1285
March1st to 15thNight
13%
720
17%
2104
3%
720
28%
720
14%
1504
March16th to endNight
21%
768
19%
2106
6%
768
33%
768
20%
1420
April1st to 15thNight
15%
685
17%
1763
3%
685
25%
685
17%
1297
April16th to endNight
22%
540
15%
1620
4%
540
31%
540
17%
1115
May1st to 15thNight
22%
540
13%
1620
5%
540
32%
540
17%
1153
May16th to endNight
21%
439
11%
1543
6%
438
31%
438
14%
1104
June1st to 15thNight
28%
360
9%
1260
6%
360
36%
360
14%
900
June16th to endNight
34%
360
10%
1260
10%
360
40%
360
21%
824
July1st to 15thNight
40%
340
10%
1349
11%
340
46%
340
21%
844
July16th to endNight
40%
376
12%
1418
11%
354
48%
354
20%
884
August1st to 15thNight
41%
536
13%
1606
7%
533
46%
533
25%
1051
August16th to endNight
43%
596
21%
1742
13%
596
48%
596
33%
1055
September1st to 15thNight
37%
720
19%
1908
8%
720
43%
720
34%
1184
September16th to endNight
39%
717
28%
1980
14%
717
50%
717
34%
1169
October1st to 15thNight
29%
720
21%
2061
8%
720
41%
720
25%
1336
October16th to endNight
20%
768
17%
2458
6%
768
34%
768
18%
1637
November1st to 15thNight
26%
700
20%
2277
10%
700
40%
700
20%
1473
November16th to endNight
23%
738
19%
2448
7%
738
38%
738
16%
1595
December1st to 15thNight
14%
750
17%
2662
4%
750
30%
750
14%
1788
December16th to endNight
12%
792
17%
2832
3%
792
29%
792
12%
1903

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%7%25%5%24446%36%
48377
Night
17%7%35%5%24446%37%
47537
TransparencyDay
47%410%22%13%1
48066
Night
46%311%23%13%1
47366
SeeingDay
23%16%31%19%7%1
6455
Night
22%15%33%22%6%
14988

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%7%45%5%24447%37%
1432
16th to endDay
14%10%27%5%23446%38%
1536
February1st to 15thDay
15%10%36%5%36%336%34%
1594
16th to endDay
13%10%37%5%35%45%6%32%
1580
March1st to 15thDay
20%10%35%5%25%34434%
1845
16th to endDay
17%8%25%42335%5%40%
2115
April1st to 15thDay
19%9%36%5%24445%35%
2185
16th to endDay
21%7%35%5%23446%35%
2340
May1st to 15thDay
26%7%36%424346%30%
2332
16th to endDay
23%7%25%5%2445%8%31%
2577
June1st to 15thDay
27%6%35%5%34346%27%
2700
16th to endDay
21%7%25%5%35%5%5%6%30%
2700
July1st to 15thDay
13%5%25%5%45%5%6%9%36%
2527
16th to endDay
15%5%36%5%35%6%5%9%32%
2645
August1st to 15thDay
15%6%25%5%45%5%6%9%34%
2340
16th to endDay
12%5%13424449%44%
2459
September1st to 15thDay
13%5%25%5%2435%5%46%
2052
16th to endDay
14%423423337%51%
1980
October1st to 15thDay
17%6%25%5%34346%41%
1899
16th to endDay
19%7%35%5%24346%38%
1764
November1st to 15thDay
20%7%24424447%38%
1581
16th to endDay
20%8%25%423335%41%
1509
December1st to 15thDay
21%10%345%23446%34%
1296
16th to endDay
23%11%35%424345%32%
1389
January1st to 15thNight
14%9%3442445%7%38%
2506
16th to endNight
14%9%36%5%35%447%35%
2685
February1st to 15thNight
13%8%47%6%36%5%5%6%32%
2264
16th to endNight
14%10%45%6%23345%37%
1893
March1st to 15thNight
18%11%36%42434434%
2091
16th to endNight
17%6%35%5%34345%40%
2106
April1st to 15thNight
19%8%47%5%2445%5%32%
1763
16th to endNight
21%7%35%5%2445%6%34%
1620
May1st to 15thNight
21%7%36%5%35%35%7%30%
1620
16th to endNight
21%9%35%6%25%36%7%27%
1541
June1st to 15thNight
25%8%35%5%3435%7%27%
1260
16th to endNight
18%6%35%4245%5%9%35%
1260
July1st to 15thNight
14%5%26%6%445%5%8%35%
1429
16th to endNight
15%5%25%6%25%5%48%37%
1514
August1st to 15thNight
12%6%25%436%5%5%8%38%
1617
16th to endNight
11%5%2342445%7%47%
1742
September1st to 15thNight
14%5%24323346%49%
1908
16th to endNight
11%5%23324337%52%
1980
October1st to 15thNight
19%5%14324436%43%
2061
16th to endNight
19%7%25%5%33445%38%
2458
November1st to 15thNight
19%7%25%423446%39%
2277
16th to endNight
17%6%35%434446%39%
2448
December1st to 15thNight
20%10%3442335%435%
2662
16th to endNight
21%12%34323245%34%
2832

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
45%411%23%13%2
1433
16th to endDay
45%311%25%12%1
1536
February1st to 15thDay
51%311%20%12%1
1597
16th to endDay
50%310%20%12%2
1580
March1st to 15thDay
52%39%17%13%2
1855
16th to endDay
44%38%20%18%4
2115
April1st to 15thDay
50%36%19%17%2
2185
16th to endDay
49%39%19%12%4
2340
May1st to 15thDay
54%37%19%13%2
2332
16th to endDay
50%5%12%19%10%1
2581
June1st to 15thDay
57%410%19%8%1
2700
16th to endDay
51%5%10%18%12%
2700
July1st to 15thDay
41%6%13%27%11%
2378
16th to endDay
46%6%13%22%10%1
2478
August1st to 15thDay
45%5%14%25%8%
2327
16th to endDay
36%413%26%18%
2459
September1st to 15thDay
38%411%26%17%1
2052
16th to endDay
33%38%30%22%1
1980
October1st to 15thDay
44%39%26%14%1
1899
16th to endDay
47%310%26%12%
1764
November1st to 15thDay
45%412%22%13%1
1581
16th to endDay
46%312%20%14%1
1509
December1st to 15thDay
50%411%23%9%
1296
16th to endDay
54%39%18%13%
1389
January1st to 15thNight
44%412%24%11%1
2506
16th to endNight
48%38%23%13%1
2685
February1st to 15thNight
50%312%20%11%
2265
16th to endNight
47%310%21%14%2
1893
March1st to 15thNight
53%37%20%12%2
2104
16th to endNight
45%39%19%18%3
2106
April1st to 15thNight
52%35%17%17%2
1763
16th to endNight
50%310%18%13%3
1620
May1st to 15thNight
52%48%18%14%1
1620
16th to endNight
55%411%19%8%1
1543
June1st to 15thNight
55%412%18%6%1
1260
16th to endNight
46%414%22%11%1
1260
July1st to 15thNight
44%416%23%10%
1349
16th to endNight
44%417%24%7%
1418
August1st to 15thNight
41%6%16%25%9%
1606
16th to endNight
35%415%28%15%
1742
September1st to 15thNight
35%313%31%14%1
1908
16th to endNight
32%38%34%19%1
1980
October1st to 15thNight
42%310%27%14%1
2061
16th to endNight
47%311%24%11%
2458
November1st to 15thNight
44%412%23%14%1
2277
16th to endNight
45%411%22%15%1
2448
December1st to 15thNight
50%39%25%10%
2662
16th to endNight
51%210%21%12%
2832

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
8%35%40%13%3
60
16th to endDay
21%28%34%12%3
64
February1st to 15thDay
24%22%32%17%4
240
16th to endDay
16%27%31%17%6%
239
March1st to 15thDay
27%24%32%13%2
270
16th to endDay
23%24%27%16%5%2
288
April1st to 15thDay
27%22%29%14%32
270
16th to endDay
25%23%29%12%6%1
270
May1st to 15thDay
34%13%31%13%5%1
288
16th to endDay
23%17%36%17%4
346
June1st to 15thDay
27%12%28%22%8%
495
16th to endDay
25%9%31%23%7%1
495
July1st to 15thDay
18%9%36%20%12%1
312
16th to endDay
19%6%35%24%11%2
326
August1st to 15thDay
18%7%33%28%10%1
313
16th to endDay
19%10%25%28%12%3
332
September1st to 15thDay
16%9%32%26%11%3
315
16th to endDay
15%10%32%19%12%9%
314
October1st to 15thDay
20%16%27%20%12%4
295
16th to endDay
25%15%37%15%31
288
November1st to 15thDay
23%16%27%22%8%2
235
16th to endDay
25%22%25%19%5%1
240
December1st to 15thDay
31%22%25%17%3
96
16th to endDay
31%32%26%9%
64
January1st to 15thNight
21%22%35%17%3
720
16th to endNight
21%23%34%16%2
768
February1st to 15thNight
18%22%37%18%2
704
16th to endNight
20%22%36%16%4
631
March1st to 15thNight
25%20%35%13%3
720
16th to endNight
20%22%30%20%6%
768
April1st to 15thNight
24%19%35%16%3
685
16th to endNight
26%15%31%20%4
540
May1st to 15thNight
25%10%34%23%5%
540
16th to endNight
26%10%34%22%5%
439
June1st to 15thNight
31%7%26%28%6%
360
16th to endNight
19%435%32%7%
360
July1st to 15thNight
18%5%30%35%10%
340
16th to endNight
17%328%36%13%
376
August1st to 15thNight
13%333%38%11%
536
16th to endNight
14%5%31%33%14%1
596
September1st to 15thNight
18%6%33%29%10%1
720
16th to endNight
15%8%32%26%13%3
717
October1st to 15thNight
23%10%31%22%10%1
720
16th to endNight
23%16%35%18%5%
768
November1st to 15thNight
22%14%30%23%7%1
700
16th to endNight
21%21%29%21%6%
738
December1st to 15thNight
26%20%32%16%4
750
16th to endNight
30%21%31%13%2
792
Page generated at 2017-11-01 17:23:40. Version ac04

Copyright 2017 A. Danko


Halfmoon Stream Observatory Clear Sky Chart |Charts Home