Starburst Meadows Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Starburst Meadows Observatory clear sky chart from 2005-11-05 to 2017-04-28.

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
27%
14444
17%
45798
8%
14412
38%
14412
18%
30439

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
17%
720
19%
2506
6%
716
33%
716
15%
1593
January16th to endNight
11%
768
18%
2688
4%
768
30%
768
13%
1752
February1st to 15thNight
14%
704
15%
2246
5%
701
27%
701
12%
1564
February16th to endNight
19%
631
19%
1893
7%
631
36%
631
16%
1290
March1st to 15thNight
16%
720
16%
2123
5%
720
29%
720
14%
1508
March16th to endNight
22%
768
21%
2079
7%
768
33%
768
19%
1376
April1st to 15thNight
21%
712
18%
1790
4%
712
29%
712
20%
1276
April16th to endNight
27%
534
16%
1602
5%
534
36%
534
18%
1098
May1st to 15thNight
29%
495
14%
1485
8%
495
36%
495
16%
1024
May16th to endNight
26%
390
11%
1416
9%
389
33%
389
11%
1039
June1st to 15thNight
32%
330
9%
1320
9%
330
38%
330
11%
961
June16th to endNight
41%
330
8%
1320
10%
330
45%
330
15%
855
July1st to 15thNight
47%
310
10%
1240
15%
310
50%
310
17%
792
July16th to endNight
45%
348
12%
1306
13%
326
54%
326
18%
817
August1st to 15thNight
50%
477
14%
1458
10%
475
53%
475
22%
956
August16th to endNight
51%
583
20%
1633
11%
583
55%
583
30%
1023
September1st to 15thNight
45%
660
19%
1732
10%
660
50%
660
30%
1131
September16th to endNight
46%
657
26%
1815
14%
657
55%
657
34%
1062
October1st to 15thNight
34%
660
21%
1865
11%
660
43%
660
23%
1234
October16th to endNight
24%
704
17%
2274
7%
704
36%
704
19%
1501
November1st to 15thNight
28%
700
21%
2277
12%
700
41%
700
20%
1451
November16th to endNight
22%
720
20%
2340
7%
720
36%
720
16%
1521
December1st to 15thNight
16%
750
16%
2673
4%
750
31%
750
13%
1793
December16th to endNight
15%
773
17%
2717
4%
773
30%
773
12%
1822

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%6%24424447%38%
45894
Night
18%7%2442445%6%39%
45968
Cloud CoverDay
18%6%2442445%7%39%
45904
Night
18%7%24424446%39%
45973
TransparencyDay
44%5%11%22%13%1
45582
Night
45%5%11%22%13%1
45798
SeeingDay
20%17%27%21%9%3
5340
Night
19%22%25%22%9%1
14444

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
17%5%35%435%446%40%
1432
16th to endDay
16%8%24424446%40%
1536
February1st to 15thDay
17%8%25%5%3445%5%34%
1615
16th to endDay
14%10%35%6%25%45%6%35%
1580
March1st to 15thDay
20%9%36%324336%36%
1826
16th to endDay
16%7%36%423335%42%
2142
April1st to 15thDay
19%6%244245%5%6%38%
2157
16th to endDay
21%5%23424346%40%
2306
May1st to 15thDay
24%6%35%5%24446%33%
2137
16th to endDay
21%435%5%25%45%8%34%
2356
June1st to 15thDay
27%6%25%42435%7%30%
2310
16th to endDay
20%6%245%25%5%48%34%
2310
July1st to 15thDay
13%5%245%36%5%6%10%35%
2310
16th to endDay
14%5%235%36%6%7%9%35%
2458
August1st to 15thDay
13%5%25%425%5%6%9%37%
2149
16th to endDay
12%3134245%6%8%45%
2215
September1st to 15thDay
14%424423447%47%
1896
16th to endDay
14%422412336%53%
1815
October1st to 15thDay
19%6%35%5%23335%41%
1763
16th to endDay
19%6%25%424435%41%
1598
November1st to 15thDay
21%5%3332335%6%42%
1581
16th to endDay
22%6%24322335%44%
1615
December1st to 15thDay
22%8%3442433438%
1284
16th to endDay
23%10%45%323345%34%
1503
January1st to 15thNight
15%8%35%33345%6%40%
2506
16th to endNight
16%9%35%5%23445%38%
2688
February1st to 15thNight
14%8%36%6%36%45%5%34%
2245
16th to endNight
15%10%345%3434439%
1893
March1st to 15thNight
19%9%36%424346%34%
2110
16th to endNight
17%5%345%23345%43%
2079
April1st to 15thNight
21%7%245%25%446%36%
1790
16th to endNight
22%5%245%24436%37%
1602
May1st to 15thNight
19%8%25%3346%6%8%32%
1485
16th to endNight
22%8%47%4245%5%6%27%
1414
June1st to 15thNight
25%6%35%5%2445%6%28%
1320
16th to endNight
21%6%2432445%8%36%
1320
July1st to 15thNight
15%5%245%45%5%6%8%34%
1320
16th to endNight
15%5%245%25%5%7%10%35%
1402
August1st to 15thNight
14%5%25%5%345%7%7%39%
1468
16th to endNight
13%41442446%8%45%
1633
September1st to 15thNight
15%6%14332346%48%
1732
16th to endNight
13%313322346%55%
1815
October1st to 15thNight
19%5%24424446%42%
1865
16th to endNight
22%5%25%424445%39%
2274
November1st to 15thNight
18%6%23324446%42%
2277
16th to endNight
18%5%24424346%42%
2340
December1st to 15thNight
22%9%24323345%37%
2673
16th to endNight
22%8%3432335%5%37%
2717

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
16%6%3443445%7%40%
1432
16th to endDay
16%8%2332345%7%40%
1536
February1st to 15thDay
16%9%246%25%447%34%
1615
16th to endDay
14%10%35%5%345%5%5%36%
1580
March1st to 15thDay
20%8%35%424346%36%
1836
16th to endDay
15%7%35%5%23345%43%
2142
April1st to 15thDay
19%5%2442345%7%39%
2157
16th to endDay
20%5%14434446%41%
2306
May1st to 15thDay
23%6%25%5%2345%6%33%
2137
16th to endDay
21%5%25%5%3445%7%35%
2356
June1st to 15thDay
28%5%24334346%32%
2310
16th to endDay
20%4345%3445%7%36%
2310
July1st to 15thDay
13%5%25%5%35%6%6%10%36%
2310
16th to endDay
13%5%245%35%5%7%9%37%
2458
August1st to 15thDay
13%5%24425%5%6%9%40%
2149
16th to endDay
12%313435%5%5%8%46%
2215
September1st to 15thDay
13%414424447%48%
1896
16th to endDay
14%5%13323235%53%
1815
October1st to 15thDay
18%6%26%423345%42%
1763
16th to endDay
19%5%24423345%42%
1598
November1st to 15thDay
20%6%23313446%43%
1581
16th to endDay
22%5%34212335%44%
1615
December1st to 15thDay
23%6%25%32434438%
1284
16th to endDay
23%10%24423346%34%
1503
January1st to 15thNight
15%8%3442345%7%39%
2506
16th to endNight
17%9%34433446%38%
2688
February1st to 15thNight
14%8%35%7%45%5%45%34%
2238
16th to endNight
16%9%35%434345%39%
1893
March1st to 15thNight
20%9%36%434345%35%
2123
16th to endNight
17%6%24423346%43%
2078
April1st to 15thNight
20%7%24425%445%37%
1790
16th to endNight
22%5%245%23446%36%
1602
May1st to 15thNight
20%8%24325%5%6%8%33%
1485
16th to endNight
24%8%46%424446%28%
1414
June1st to 15thNight
26%7%35%5%2445%6%27%
1320
16th to endNight
21%5%1442445%8%35%
1320
July1st to 15thNight
16%425%5%36%5%6%8%35%
1320
16th to endNight
14%5%245%35%5%6%11%34%
1402
August1st to 15thNight
14%5%25%4245%7%7%39%
1468
16th to endNight
14%41342445%8%45%
1633
September1st to 15thNight
15%5%24323436%48%
1732
16th to endNight
13%413313336%54%
1815
October1st to 15thNight
19%5%2432345%6%41%
1865
16th to endNight
21%5%25%333345%39%
2274
November1st to 15thNight
18%6%24324445%43%
2277
16th to endNight
18%6%245%24345%41%
2340
December1st to 15thNight
22%8%24413345%37%
2673
16th to endNight
22%9%34413346%37%
2717

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
43%6%11%23%13%1
1433
16th to endDay
42%5%12%25%13%
1536
February1st to 15thDay
48%6%12%20%11%
1618
16th to endDay
47%5%11%19%13%2
1580
March1st to 15thDay
49%411%19%12%2
1836
16th to endDay
44%38%20%19%4
2142
April1st to 15thDay
44%6%7%20%16%3
2157
16th to endDay
44%5%9%22%15%3
2306
May1st to 15thDay
50%5%8%16%16%2
2137
16th to endDay
48%6%12%18%12%1
2360
June1st to 15thDay
52%5%12%19%8%1
2310
16th to endDay
47%6%10%22%11%1
2310
July1st to 15thDay
39%9%14%25%10%
2161
16th to endDay
40%8%16%22%11%
2291
August1st to 15thDay
38%8%17%24%9%
2135
16th to endDay
33%7%16%25%16%1
2215
September1st to 15thDay
36%6%10%27%18%
1896
16th to endDay
33%49%28%22%1
1815
October1st to 15thDay
45%49%24%14%2
1763
16th to endDay
44%412%24%13%1
1598
November1st to 15thDay
42%413%23%14%1
1581
16th to endDay
44%313%20%16%1
1615
December1st to 15thDay
49%412%20%12%
1284
16th to endDay
52%410%18%12%1
1503
January1st to 15thNight
43%5%12%24%12%1
2506
16th to endNight
47%49%22%14%1
2688
February1st to 15thNight
50%5%11%19%11%1
2246
16th to endNight
47%49%22%12%2
1893
March1st to 15thNight
51%48%20%12%2
2123
16th to endNight
41%5%9%18%19%5%
2079
April1st to 15thNight
48%37%19%17%2
1790
16th to endNight
47%5%10%19%13%3
1602
May1st to 15thNight
46%7%11%16%14%2
1485
16th to endNight
56%6%9%15%10%1
1416
June1st to 15thNight
56%6%10%16%7%1
1320
16th to endNight
46%5%14%20%12%
1320
July1st to 15thNight
42%8%16%21%10%
1240
16th to endNight
42%7%15%23%10%
1306
August1st to 15thNight
39%9%13%25%10%1
1458
16th to endNight
35%6%12%29%15%
1633
September1st to 15thNight
37%5%10%29%15%1
1732
16th to endNight
31%410%31%21%1
1815
October1st to 15thNight
43%49%24%15%2
1865
16th to endNight
45%5%10%24%13%1
2274
November1st to 15thNight
42%5%12%23%15%1
2277
16th to endNight
44%5%12%21%14%1
2340
December1st to 15thNight
49%410%24%11%
2673
16th to endNight
49%5%11%21%11%
2717

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
11%26%30%25%6%
60
16th to endDay
18%23%31%23%3
64
February1st to 15thDay
22%22%34%18%2
231
16th to endDay
20%21%33%20%3
239
March1st to 15thDay
24%27%30%13%3
270
16th to endDay
19%26%33%13%42
288
April1st to 15thDay
22%22%29%17%6%1
270
16th to endDay
21%19%31%14%9%3
259
May1st to 15thDay
26%18%30%13%8%2
228
16th to endDay
20%18%30%21%7%1
267
June1st to 15thDay
25%17%25%21%9%1
255
16th to endDay
20%12%29%25%9%1
255
July1st to 15thDay
14%9%26%26%16%6%
245
16th to endDay
14%12%25%30%15%2
270
August1st to 15thDay
16%11%20%29%18%4
253
16th to endDay
13%9%19%28%18%10%
268
September1st to 15thDay
15%8%20%29%18%7%
255
16th to endDay
18%9%27%22%9%11%
254
October1st to 15thDay
20%16%19%23%13%5%
246
16th to endDay
22%16%32%21%7%
240
November1st to 15thDay
22%21%23%19%10%2
235
16th to endDay
22%25%25%16%7%1
240
December1st to 15thDay
25%17%30%19%7%
84
16th to endDay
34%20%29%14%1
64
January1st to 15thNight
15%33%30%17%3
720
16th to endNight
18%31%31%14%3
768
February1st to 15thNight
17%30%30%18%2
704
16th to endNight
19%27%29%18%4
631
March1st to 15thNight
22%27%28%17%3
720
16th to endNight
17%28%26%19%6%
768
April1st to 15thNight
19%24%31%18%5%
712
16th to endNight
19%23%24%24%6%
534
May1st to 15thNight
19%21%23%25%9%1
495
16th to endNight
25%21%19%24%7%1
390
June1st to 15thNight
22%21%16%27%11%1
330
16th to endNight
22%18%11%34%13%
330
July1st to 15thNight
16%14%13%33%18%2
310
16th to endNight
15%18%13%32%19%
348
August1st to 15thNight
15%11%13%35%22%1
477
16th to endNight
13%10%16%35%20%4
583
September1st to 15thNight
15%10%22%28%19%3
660
16th to endNight
14%13%20%27%19%3
657
October1st to 15thNight
21%15%21%24%14%2
660
16th to endNight
22%18%30%21%6%
704
November1st to 15thNight
17%21%28%23%7%2
700
16th to endNight
17%28%26%19%7%
720
December1st to 15thNight
24%27%27%16%4
750
16th to endNight
24%29%28%15%2
773
Page generated at 2017-04-29 09:45:10. Version ac04

Copyright 2017 A. Danko


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