Stokes Starparty
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stokes Starparty clear sky chart from 2005-11-06 to 2024-01-15.

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
29%
23074
19%
74700
9%
23034
41%
23034
19%
48436

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
14%
760
22%
2649
5%
757
35%
757
16%
1641
January11th to 20thNight
18%
737
17%
2577
6%
737
34%
737
13%
1733
January21st to endNight
15%
792
22%
2607
5%
792
34%
792
16%
1635
February1st to 10thNight
16%
720
16%
2340
4%
720
31%
720
15%
1551
February11th to 20thNight
11%
703
19%
2140
3%
700
31%
700
14%
1428
February21st to endNight
14%
592
24%
1776
7%
592
35%
592
14%
1204
March1st to 10thNight
16%
720
20%
2160
6%
720
34%
720
18%
1381
March11th to 20thNight
19%
720
20%
2017
6%
720
33%
720
19%
1335
March21st to endNight
18%
792
21%
2029
5%
792
30%
792
21%
1383
April1st to 10thNight
18%
720
17%
1800
3%
720
27%
720
17%
1294
April11th to 20thNight
22%
711
17%
1775
4%
711
29%
711
22%
1248
April21st to endNight
27%
720
18%
1800
5%
720
34%
720
22%
1261
May1st to 10thNight
24%
514
15%
1594
8%
514
31%
514
15%
1140
May11th to 20thNight
27%
354
20%
1416
12%
354
42%
354
17%
876
May21st to endNight
44%
388
16%
1551
15%
388
51%
388
20%
952
June1st to 10thNight
45%
360
18%
1440
17%
360
55%
360
20%
872
June11th to 20thNight
43%
360
14%
1440
13%
360
54%
360
21%
890
June21st to endNight
49%
360
15%
1440
14%
360
58%
360
25%
818
July1st to 10thNight
54%
350
14%
1400
18%
350
59%
350
22%
838
July11th to 20thNight
55%
348
15%
1392
17%
348
60%
348
22%
833
July21st to endNight
55%
394
18%
1486
18%
372
61%
372
25%
852
August1st to 10thNight
54%
485
17%
1549
13%
483
59%
483
28%
964
August11th to 20thNight
52%
684
15%
1748
9%
684
54%
684
26%
1233
August21st to endNight
49%
792
18%
1980
8%
792
53%
792
30%
1334
September1st to 10thNight
44%
720
21%
1800
8%
720
50%
720
30%
1204
September11th to 20thNight
46%
720
27%
1846
16%
720
53%
720
34%
1148
September21st to endNight
43%
720
25%
1980
17%
720
51%
720
29%
1277
October1st to 10thNight
36%
720
17%
2128
12%
720
43%
720
22%
1426
October11th to 20thNight
33%
720
22%
2160
12%
720
46%
720
25%
1354
October21st to endNight
24%
792
20%
2489
10%
792
38%
792
21%
1630
November1st to 10thNight
31%
740
23%
2407
11%
740
47%
740
24%
1423
November11th to 20thNight
26%
760
24%
2470
11%
760
43%
760
20%
1541
November21st to endNight
25%
760
21%
2608
9%
760
42%
760
20%
1604
December1st to 10thNight
20%
760
17%
2660
7%
760
34%
760
13%
1768
December11th to 20thNight
19%
760
16%
3223
5%
759
33%
759
11%
2085
December21st to endNight
17%
826
12%
4823
5%
817
34%
817
8%
3280

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
16%7%36%5%35%5%5%7%38%
74765
Night
17%7%35%5%3445%7%41%
74997
TransparencyDay
45%7%11%21%14%2
74470
Night
43%6%12%23%15%2
74826
SeeingDay
24%17%28%19%9%3
13782
Night
22%15%29%25%9%1
23085

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
12%9%36%5%35%5%5%6%39%
1517
11th to 20thDay
16%10%46%6%46%45%6%34%
1472
21st to endDay
14%7%45%6%35%5%6%7%38%
1746
February1st to 10thDay
17%8%47%6%35%5%5%7%32%
1620
11th to 20thDay
14%8%36%6%4445%6%39%
1708
21st to endDay
19%10%26%5%3445%6%35%
1480
March1st to 10thDay
13%8%45%6%35%35%8%40%
1797
11th to 20thDay
15%8%46%5%45%45%7%36%
1939
21st to endDay
20%8%36%5%34445%38%
2326
April1st to 10thDay
18%8%36%5%35%45%6%38%
2160
11th to 20thDay
18%6%35%5%44347%41%
2134
21st to endDay
19%6%26%5%45%5%5%6%37%
2160
May1st to 10thDay
23%6%35%5%34447%34%
2378
11th to 20thDay
20%6%35%6%35%5%5%7%36%
2478
21st to endDay
15%5%35%5%35%5%6%9%39%
2725
June1st to 10thDay
16%5%36%5%35%6%6%9%36%
2520
11th to 20thDay
17%6%36%5%45%6%7%9%33%
2520
21st to endDay
13%5%37%6%45%45%9%38%
2520
July1st to 10thDay
13%5%36%6%5%6%6%6%9%37%
2520
11th to 20thDay
11%5%25%5%46%6%7%10%40%
2520
21st to endDay
11%6%36%7%46%5%6%9%38%
2744
August1st to 10thDay
12%5%36%6%47%6%8%8%35%
2377
11th to 20thDay
12%6%27%7%47%6%6%8%36%
2134
21st to endDay
15%6%35%435%5%6%8%42%
2376
September1st to 10thDay
16%6%25%4345%5%6%42%
2160
11th to 20thDay
14%5%2443445%6%50%
2113
21st to endDay
17%6%26%5%35%45%7%40%
1980
October1st to 10thDay
22%6%25%424447%39%
1829
11th to 20thDay
15%7%25%5%3445%8%42%
1800
21st to endDay
23%7%145%345%5%6%36%
1865
November1st to 10thDay
14%7%24423246%51%
1671
11th to 20thDay
19%7%2342445%7%43%
1710
21st to endDay
17%7%345%35%6%5%7%39%
1568
December1st to 10thDay
18%10%36%5%45%5%46%34%
1520
11th to 20thDay
21%8%36%5%2445%6%37%
1906
21st to endDay
20%12%5%8%7%45%5%46%25%
2772
January1st to 10thNight
15%7%345%3446%7%41%
2649
11th to 20thNight
17%8%36%6%35%5%47%35%
2577
21st to endNight
12%8%36%5%345%6%8%41%
2607
February1st to 10thNight
18%8%36%5%35%447%39%
2340
11th to 20thNight
16%7%36%5%45%5%5%8%38%
2138
21st to endNight
18%8%36%6%3445%6%39%
1776
March1st to 10thNight
15%7%35%42445%7%43%
2150
11th to 20thNight
17%7%35%43445%7%42%
2016
21st to endNight
16%7%36%5%345%5%7%40%
2029
April1st to 10thNight
17%7%46%5%45%45%7%36%
1800
11th to 20thNight
18%7%25%5%35%5%47%39%
1775
21st to endNight
20%6%25%4335%5%7%40%
1800
May1st to 10thNight
21%9%45%6%345%45%34%
1594
11th to 20thNight
18%6%25%44446%6%41%
1415
21st to endNight
15%5%25%5%345%5%8%42%
1550
June1st to 10thNight
18%5%25%5%34448%43%
1440
11th to 20thNight
14%6%35%436%5%6%8%41%
1440
21st to endNight
12%425%4245%6%9%47%
1440
July1st to 10thNight
12%5%15%6%345%5%10%44%
1440
11th to 20thNight
12%425%436%6%6%9%44%
1440
21st to endNight
12%3245%35%6%7%9%44%
1574
August1st to 10thNight
11%5%35%4346%6%9%44%
1559
11th to 20thNight
13%7%26%6%36%5%6%8%39%
1748
21st to endNight
15%4246%445%49%43%
1980
September1st to 10thNight
17%425%5%3445%7%46%
1800
11th to 20thNight
15%424433346%52%
1846
21st to endNight
16%5%345%23446%46%
1980
October1st to 10thNight
23%5%24424345%43%
2128
11th to 20thNight
18%6%24423447%46%
2160
21st to endNight
22%8%2431345%6%42%
2489
November1st to 10thNight
13%6%24434446%49%
2407
11th to 20thNight
19%7%3432345%6%45%
2470
21st to endNight
14%6%26%4345%5%7%44%
2608
December1st to 10thNight
19%8%35%5%35%5%5%7%36%
2660
11th to 20thNight
19%9%345%35%5%5%5%37%
3288
21st to endNight
22%10%46%5%34446%32%
4884

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
44%5%10%26%11%3
1518
11th to 20thDay
50%6%12%18%11%3
1472
21st to endDay
44%5%10%23%15%2
1746
February1st to 10thDay
51%5%12%18%13%1
1620
11th to 20thDay
47%5%9%21%16%2
1717
21st to endDay
50%5%9%21%12%3
1480
March1st to 10thDay
43%5%12%23%14%3
1800
11th to 20thDay
46%6%10%22%13%2
1939
21st to endDay
49%5%8%17%17%5%
2326
April1st to 10thDay
47%5%10%20%14%4
2160
11th to 20thDay
44%5%11%21%16%3
2134
21st to endDay
47%5%9%20%14%4
2160
May1st to 10thDay
51%6%9%19%13%3
2378
11th to 20thDay
47%6%10%20%14%2
2482
21st to endDay
42%8%14%20%13%2
2725
June1st to 10thDay
45%8%13%20%14%1
2520
11th to 20thDay
45%9%12%22%11%2
2520
21st to endDay
42%7%12%25%13%
2520
July1st to 10thDay
44%8%12%20%16%2
2450
11th to 20thDay
37%8%16%24%14%1
2445
21st to endDay
42%8%11%20%16%3
2591
August1st to 10thDay
41%9%13%23%13%1
2363
11th to 20thDay
43%9%14%23%11%1
2134
21st to endDay
40%7%11%23%17%3
2376
September1st to 10thDay
42%8%11%21%17%2
2160
11th to 20thDay
36%410%22%24%3
2113
21st to endDay
43%6%10%19%20%2
1980
October1st to 10thDay
45%7%10%20%15%3
1829
11th to 20thDay
40%7%11%24%17%1
1800
21st to endDay
48%6%9%21%14%2
1865
November1st to 10thDay
37%412%25%18%3
1671
11th to 20thDay
41%410%23%18%3
1710
21st to endDay
43%8%12%26%10%2
1568
December1st to 10thDay
50%6%15%16%12%2
1520
11th to 20thDay
47%6%15%22%9%1
1906
21st to endDay
59%8%9%17%8%
2772
January1st to 10thNight
41%5%12%24%15%3
2649
11th to 20thNight
48%6%14%22%9%2
2577
21st to endNight
40%7%10%24%17%2
2607
February1st to 10thNight
46%5%14%21%12%1
2340
11th to 20thNight
45%5%11%19%16%4
2140
21st to endNight
47%47%23%16%3
1776
March1st to 10thNight
41%413%25%13%4
2160
11th to 20thNight
43%5%12%22%16%2
2017
21st to endNight
43%5%11%19%18%4
2029
April1st to 10thNight
48%5%10%20%14%3
1800
11th to 20thNight
45%5%10%20%19%1
1775
21st to endNight
44%6%9%22%15%4
1800
May1st to 10thNight
51%7%8%18%14%2
1594
11th to 20thNight
43%6%13%19%17%2
1416
21st to endNight
39%9%15%23%12%2
1551
June1st to 10thNight
41%6%11%24%18%1
1440
11th to 20thNight
40%8%15%26%11%1
1440
21st to endNight
33%9%16%28%14%
1440
July1st to 10thNight
37%9%14%23%14%3
1400
11th to 20thNight
35%11%15%27%11%1
1392
21st to endNight
32%10%18%20%17%2
1486
August1st to 10thNight
36%8%14%25%15%1
1549
11th to 20thNight
42%10%14%21%12%1
1748
21st to endNight
39%7%12%20%20%2
1980
September1st to 10thNight
39%6%12%26%17%1
1800
11th to 20thNight
34%5%10%23%25%2
1846
21st to endNight
39%6%9%23%23%1
1980
October1st to 10thNight
44%6%10%22%16%1
2128
11th to 20thNight
39%5%13%28%14%1
2160
21st to endNight
43%6%12%24%14%1
2489
November1st to 10thNight
36%5%13%23%21%2
2407
11th to 20thNight
41%5%10%22%19%3
2470
21st to endNight
40%5%14%28%11%1
2608
December1st to 10thNight
47%6%12%22%11%1
2660
11th to 20thNight
47%6%14%18%13%2
3288
21st to endNight
53%6%12%21%8%
4884

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
32%28%24%14%2
180
11th to 20thDay
39%25%29%5%2
168
21st to endDay
27%33%30%6%22
248
February1st to 10thDay
35%31%25%7%2
240
11th to 20thDay
36%25%29%9%1
376
21st to endDay
35%25%27%10%2
346
March1st to 10thDay
28%26%29%14%3
420
11th to 20thDay
28%26%30%12%31
420
21st to endDay
31%26%28%9%5%2
462
April1st to 10thDay
31%24%26%13%5%
420
11th to 20thDay
26%24%26%14%8%1
412
21st to endDay
31%20%30%13%5%1
420
May1st to 10thDay
35%21%23%13%7%2
423
11th to 20thDay
23%21%30%19%6%2
447
21st to endDay
21%10%29%25%13%3
485
June1st to 10thDay
18%15%32%22%12%2
450
11th to 20thDay
20%15%25%26%12%1
450
21st to endDay
16%14%32%27%10%2
450
July1st to 10thDay
16%7%30%24%17%6%
445
11th to 20thDay
12%7%27%33%19%3
444
21st to endDay
14%9%36%27%11%3
488
August1st to 10thDay
12%8%30%29%14%7%
446
11th to 20thDay
14%6%27%31%16%7%
439
21st to endDay
14%11%31%22%15%7%
495
September1st to 10thDay
20%11%26%24%13%6%
450
11th to 20thDay
14%12%29%20%14%11%
450
21st to endDay
22%11%30%21%11%5%
450
October1st to 10thDay
29%10%24%20%13%5%
450
11th to 20thDay
20%18%30%21%9%2
450
21st to endDay
30%17%28%17%7%1
437
November1st to 10thDay
21%21%25%22%10%2
365
11th to 20thDay
28%21%27%17%6%1
370
21st to endDay
29%23%30%14%41
228
December1st to 10thDay
34%25%26%10%5%
180
11th to 20thDay
37%26%26%8%3
180
21st to endDay
30%21%34%11%41
198
January1st to 10thNight
23%23%35%16%2
760
11th to 20thNight
26%21%29%21%3
737
21st to endNight
22%23%35%17%2
792
February1st to 10thNight
26%20%33%19%1
720
11th to 20thNight
27%25%34%13%1
703
21st to endNight
30%22%31%16%2
592
March1st to 10thNight
27%22%32%17%3
720
11th to 20thNight
27%22%31%17%4
720
21st to endNight
24%22%33%16%5%
792
April1st to 10thNight
25%21%33%17%5%
720
11th to 20thNight
23%18%33%20%6%
711
21st to endNight
25%15%29%24%5%
720
May1st to 10thNight
26%13%31%24%6%
514
11th to 20thNight
20%11%36%26%6%1
354
21st to endNight
16%7%27%38%13%1
389
June1st to 10thNight
19%6%24%36%15%1
360
11th to 20thNight
14%6%30%36%13%
360
21st to endNight
11%6%25%44%13%
360
July1st to 10thNight
13%424%37%21%1
350
11th to 20thNight
11%425%43%16%1
348
21st to endNight
12%6%22%43%17%1
394
August1st to 10thNight
9%423%39%22%2
485
11th to 20thNight
14%5%19%36%24%2
684
21st to endNight
15%6%21%35%20%2
792
September1st to 10thNight
17%7%25%33%16%2
720
11th to 20thNight
16%7%25%28%19%5%
720
21st to endNight
18%8%24%30%17%2
720
October1st to 10thNight
25%10%23%26%14%2
720
11th to 20thNight
22%13%27%30%8%
720
21st to endNight
27%15%30%21%7%
792
November1st to 10thNight
19%17%29%25%9%1
740
11th to 20thNight
25%16%28%23%7%1
760
21st to endNight
19%21%31%23%6%1
760
December1st to 10thNight
26%19%30%20%5%
760
11th to 20thNight
24%21%32%21%3
760
21st to endNight
27%20%32%20%2
836
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